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Sample records for observatory laser guide

  1. Sodium laser guide star results at the Lick Observatory

    SciTech Connect

    Friedman, H.; Erbert, G.; Kuklo, T.

    1995-10-01

    Results of return signal level and guide star spot size for a sodium laser guide star recently installed at the Lick Observatory are presented. Operational characteristics of frequency stability, amplitude stability, and pointing accuracy are discussed.

  2. Measurements of the Lick Observatory Sodium Laser Guide Star

    SciTech Connect

    Gavel, D. T., LLNL

    1998-03-01

    The Lick Observatory guide star laser has provided a beacon sufficient to close the adaptive optics loop and produce corrected images during runs in 1996 and 1997. This report summarizes measurements of the wavefront quality of the outgoing beam, photoreturn signal from the sodium beacon, and radiance distribution of the guide star on the sky, and follows with an analysis of the impact of the laser on adaptive optics system performance.

  3. Performance of laser guide star adaptive optics at Lick Observatory

    SciTech Connect

    Olivier, S.S.; An, J.; Avicola, K.

    1995-07-19

    A sodium-layer laser guide star adaptive optics system has been developed at Lawrence Livermore National Laboratory (LLNL) for use on the 3-meter Shane telescope at Lick Observatory. The system is based on a 127-actuator continuous-surface deformable mirror, a Hartmann wavefront sensor equipped with a fast-framing low-noise CCD camera, and a pulsed solid-state-pumped dye laser tuned to the atomic sodium resonance line at 589 nm. The adaptive optics system has been tested on the Shane telescope using natural reference stars yielding up to a factor of 12 increase in image peak intensity and a factor of 6.5 reduction in image full width at half maximum (FWHM). The results are consistent with theoretical expectations. The laser guide star system has been installed and operated on the Shane telescope yielding a beam with 22 W average power at 589 nm. Based on experimental data, this laser should generate an 8th magnitude guide star at this site, and the integrated laser guide star adaptive optics system should produce images with Strehl ratios of 0.4 at 2.2 {mu}m in median seeing and 0.7 at 2.2 {mu}m in good seeing.

  4. Remote Operations of Laser Guide Star Systems: Gemini Observatory.

    NASA Astrophysics Data System (ADS)

    Oram, Richard J.; Fesquet, Vincent; Wyman, Robert; D'Orgeville, Celine

    2011-03-01

    The Gemini North telescope, equipped with a 14W laser, has been providing Laser Guide Star Adaptive Optics (LGS AO) regular science queue observations for worldwide astronomers since February 2007. The new 55W laser system for MCAO was installed on the Gemini South telescope in May 2010. In this paper, we comment on how Gemini Observatory developed regular remote operation of the Laser Guide Star Facility and high-power solid-state laser as routine normal operations. Fully remote operation of the LGSF from the Hilo base facility HBF was initially trialed and then optimized and became the standard operating procedure (SOP) for LGS operation in December 2008. From an engineering perspective remote operation demands stable, well characterized and base-lined equipment sets. In the effort to produce consistent, stable and controlled laser parameters (power, wavelength and beam quality) we completed a failure mode effect analysis of the laser system and sub systems that initiated a campaign of hardware upgrades and procedural improvements to the routine maintenance operations. Finally, we provide an overview of normal operation procedures during LGS runs and present a snapshot of data accumulated over several years that describes the overall LGS AO observing efficiency at the Gemini North telescope.

  5. Adaptive optics and laser guide stars at Lick observatory

    SciTech Connect

    Brase, J.M.

    1994-11-15

    For the past several years LLNL has been developing adaptive optics systems for correction of both atmospheric turbulence effects and thermal distortions in optics for high-power lasers. Our early work focused on adaptive optics for beam control in laser isotope separation and ground-based free electron lasers. We are currently developing innovative adaptive optics and laser systems for sodium laser guide star applications at the University of California`s Lick and Keck Observeratories. This talk will describe our adaptive optics technology and some of its applications in high-resolution imaging and beam control.

  6. Laser Guide Star Based Astrophysics at Lick Observatory

    SciTech Connect

    Max, C; Gavel, D.; Friedman, H.; Olivier, S.; Macintosh, B.; Brase, J.; Avicola, K.; Gibbard, S.; An, J.

    2000-03-10

    The resolution of ground-based telescopes is typically limited to {approx}1 second of arc because of the blurring effects of atmospheric turbulence. Adaptive optics (AO) technology senses and corrects for the optical distortions due to turbulence hundreds of times per second using high-speed sensors, computers, deformable mirror, and laser technology. The goal of this project is to make AO systems widely useful astronomical tools providing resolutions up to an order of magnitude better than current, ground-based telescopes. Astronomers at the University of California Lick Observatory at Mt. Hamilton now routinely use the LLNL developed AO system for high resolution imaging of astrophysical objects. We report here on the instrument development progress and on the science observations made with this system during this 3-year ERI project.

  7. Light pollution generated by laser guide star at Canarian Observatories

    NASA Astrophysics Data System (ADS)

    Chueca, Sergio; Fuensalida, Jesus J.

    2004-11-01

    A new generation of instrument using a launching laser is been developed to correct the atmospheric image blurring and to establish optical communication with space. Then, light pollution generated by laser will be a serious operational problem in next years. This laser could affect astronomical works of adjacent telescopes when the laser lay across the field of view of the observing telescope, this is a kind of light pollution. This could be avoided with an adequate operational politic to detect possible interference between the laser and the astronomical telescopes. In this paper is analysed the mathematical probability of a cross-event happen.

  8. Near infra-red astronomy with adaptive optics and laser guide stars at the Keck Observatory

    SciTech Connect

    Max, C.E.; Gavel, D.T.; Olivier, S.S.

    1995-08-03

    A laser guide star adaptive optics system is being built for the W. M. Keck Observatory`s 10-meter Keck II telescope. Two new near infra-red instruments will be used with this system: a high-resolution camera (NIRC 2) and an echelle spectrometer (NIRSPEC). The authors describe the expected capabilities of these instruments for high-resolution astronomy, using adaptive optics with either a natural star or a sodium-layer laser guide star as a reference. They compare the expected performance of these planned Keck adaptive optics instruments with that predicted for the NICMOS near infra-red camera, which is scheduled to be installed on the Hubble Space Telescope in 1997.

  9. Initial results from the Lick Observatory Laser Guide Star Adaptive Optics System

    SciTech Connect

    Olivier, S.S.; An, J.; Avicola, K.

    1995-11-08

    A prototype adaptive optics system has been installed and tested on the 3 m Shane telescope at Lick Observatory. The adaptive optics system performance, using bright natural guide stars, is consistent with expectations based on theory. A sodium-layer laser guide star system has also been installed and tested on the Shane telescope. Operating at 15 W, the laser system produces a 9th magnitude guide star with seeing-limited size at 589 nm. Using the laser guide star, the adaptive optics system has reduced the wavefront phase variance on scales above 50 cm by a factor of 4. These results represent the first continuous wavefront phase correction using a sodium-layer laser guide star. Assuming tip-tilt is removed using a natural guide star, the measured control loop performance should produce images with a Strehl ratio of 0.4 at 2.2 {mu}m in 1 arc second seeing. Additional calibration procedures must be implemented in order to achieve these results with the prototype Lick adaptive optics system.

  10. Improved performance of the laser guide star adaptive optics system at Lick Observatory

    SciTech Connect

    An, J R; Avicola, K; Bauman, B J; Brase, J M; Campbell, E W; Carrano, C; Cooke, J B; Freeze, G J; Friedman, H W; Max, C E; Gates, E L; Gavel, D T; Kanz, V K; Kuklo, T C; Macintosh, B A; Newman, M J; Olivier, S S; Pierce, E L; Waltjen, K E; Watson, A

    1999-07-20

    Results of experiments with the laser guide star adaptive optics system on the 3-meter Shane telescope at Lick Observatory have demonstrated a factor of 4 performance improvement over previous results. Stellar images recorded at a wavelength of 2 {micro}m were corrected to over 40% of the theoretical diffraction-limited peak intensity. For the previous two years, this sodium-layer laser guide star system has corrected stellar images at this wavelength to {approx}10% of the theoretical peak intensity limit. After a campaign to improve the beam quality of the laser system, and to improve calibration accuracy and stability of the adaptive optics system using new techniques for phase retrieval and phase-shifting diffraction interferometry, the system performance has been substantially increased. The next step will be to use the Lick system for astronomical science observations, and to demonstrate this level of performance with the new system being installed on the 10-meter Keck II telescope.

  11. First significant image improvement from a sodium-layer laser guide star adaptive optics system at Lick Observatory

    SciTech Connect

    Olivier, S.S.; Max, C.E.; Friedman, H.W.; An, J.; Avicola, K.; Beeman, B.V.; Bissinger, H.D.; Brase, J.M.; Erbert, G.V.; Gavel, D.T.; Kanz, K.; Macintosh, B.; Neeb, K.P.; Waltjen, K.E.

    1997-07-14

    Atmospheric turbulence severely limits the resolution of ground-based telescopes. Adaptive optics can correct for the aberrations caused by the atmosphere, but requires a bright wavefront reference source in close angular proximity to the object being imaged. Since natural reference stars of the necessary brightness are relatively rare, methods of generating artificial reference beacons have been under active investigation for more than a decade. In this paper, we report the first significant image improvement achieved using a sodium-layer laser guide star as a wavefront reference for a high- order adaptive optics system. An artificial beacon was created by resonant scattering from atomic sodium in the mesosphere, at an altitude of 95 km. Using this laser guide star, an adaptive optics system on the 3 m Shane Telescope at Lick Observatory produced a factor of 2.4 increase in peak intensity and a factor of 2 decrease in full width at half maximum of a stellar image, compared with image motion compensation alone. The Strehl ratio when using the laser guide star as the reference was 65% of that obtained with a natural guide star, and the image full widths at half maximum were identical, 0.3 arc sec, using either the laser or the natural guide star. This sodium-layer laser guide star technique holds great promise for the world`s largest telescopes. 24 refs., 4 figs., 1 tab.

  12. Active beam shaping in multiple laser guide stars

    NASA Astrophysics Data System (ADS)

    Jones, Katharine J.

    2012-10-01

    Adaptive beam shaping is a critical part of multiple Laser Guide Stars (LGS) for Multiple Conjugate Adaptive Optics (MCAO) for ground-based astronomical telescopes. There are two kinds of Laser Guide Stars: Na Laser Guide Stars (at 589 nm and 92 km altitude) and Rayleigh Laser Guide Stars (at 532 nm and 20 km altitude). Multiple Conjugate Adaptive Optics (MCAO) corrects for each "layer" of atmosphere independently. Multiple Laser Guide Stars are being developed to achieve a measure of tilt and increase the isoplanatic patch. Multiple Laser Guide Stars are being combined with Multiple Conjugate Optics in the Large Binocular Telescope (LBT): more than one Laser Guide Star (4-5) and two different wavelengths: 589 nm and 532 nm. Other observatories have multiple Laser Guide Stars but only one wavelength: 589 nm or 532 nm. Because Laser Guide Stars are launched into the atmosphere, adaptive beam shaping will be carried out before the laser is launched and will be different depending on which laser is being used, presumably to effect the tightest beam which can be achieved at the power level which is required to provide the requisite return to gound-based wavefront sensors. A complete range of devices are used. Beam attenuation and divergnece will take place. Multiple Laser Guide Stars of major observatories (SOR, LBT, MMT, ESO VLT and Gemini South) will be evaluated for effective adaptive beam shaping and impact on performance

  13. Matera Laser Ranging Observatory (MLRO): An overview

    NASA Technical Reports Server (NTRS)

    Varghese, Thomas K.; Decker, Winfield M.; Crooks, Henry A.; Bianco, Giuseppe

    1993-01-01

    The Agenzia Spaziale Italiana (ASI) is currently under negotiation with the Bendix Field Engineering Corporation (BFEC) of the Allied Signal Aerospace Company (ASAC) to build a state-of-the-art laser ranging observatory for the Centro di Geodesia Spaziale, in Matera, Italy. The contract calls for the delivery of a system based on a 1.5 meter afocal Cassegrain astronomical quality telescope with multiple ports to support a variety of experiments for the future, with primary emphasis on laser ranging. Three focal planes, viz. Cassegrain, Coude, and Nasmyth will be available for these experiments. The open telescope system will be protected from dust and turbulence using a specialized dome which will be part of the building facilities to be provided by ASI. The fixed observatory facility will be partitioned into four areas for locating the following: laser, transmit/receive optics, telescope/dome enclosure, and the operations console. The optical tables and mount rest on a common concrete pad for added mechanical stability. Provisions will be in place for minimizing the effects of EMI, for obtaining maximum cleanliness for high power laser and transmit optics, and for providing an ergonomic environment fitting to a state-of-the-art multipurpose laboratory. The system is currently designed to be highly modular and adaptable for scaling or changes in technology. It is conceived to be a highly automated system with superior performance specifications to any currently operational system. Provisions are also made to adapt and accommodate changes that are of significance during the course of design and integration.

  14. Guide star targeting success for the HEAO-B observatory

    NASA Technical Reports Server (NTRS)

    Farrenkopf, R. L.; Hoffman, D. P.

    1977-01-01

    The statistics associated with the successful selection and acquisition of guide stars as attitude benchmarks for use in reorientation maneuvers of the HEAO-B observatory are considered as a function of the maneuver angle, initial attitude uncertainties, and the pertinent celestial region. Success likelihoods in excess of 0.99 are predicted assuming anticipated gyro and star tracker error sources. The maneuver technique and guide star selection constraints are described in detail. The results presented are specialized numerically to the HEAO-B observatory. However, the analytical techniques developed are considered applicable to broader classes of spacecraft requiring celestial targeting.

  15. Daytime School Guided Visits to an Astronomical Observatory in Brazil

    ERIC Educational Resources Information Center

    Colombo, Pedro Donizete, Jr.; Silva, Cibelle Celestino; Aroca, Silvia Calbo

    2010-01-01

    This article analyzes the activity "Daytime School Guided Visits" at an astronomical observatory in Brazil with pupils from primary school. The adopted research methodology relied on questionnaire applications and semistructured interviews. The objectives were to identify the influences of the visits on learning of astronomical concepts and on…

  16. Recent Science and Engineering Results with the Laser Guidestar Adaptive Optics System at Lick Observatory

    SciTech Connect

    Gavel, D T; Gates, E; Max, C; Olivier, S; Bauman, B; Pennington, D; Macintosh, B; Patience, J; Brown, C; Danforth, P; Hurd, R; Severson, S; Lloyd, J

    2002-10-17

    The Lick Observatory laser guide star adaptive optics system has undergone continual improvement and testing as it is being integrated as a facility science instrument on the Shane 3 meter telescope. Both Natural Guide Star (NGS) and Laser Guide Star (LGS) modes are now used in science observing programs. We report on system performance results as derived from data taken on both science and engineering nights and also describe the newly developed on-line techniques for seeing and system performance characterization. We also describe the future enhancements to the Lick system that will enable additional science goals such as long-exposure spectroscopy.

  17. Multi-task guiding system of the Mt. Suhora Observatory

    NASA Astrophysics Data System (ADS)

    Krzesinski, J.; Wojcik, K.

    1993-12-01

    A short description of the computer controlled guiding system using images from a sensitive TV camera is presented. The system works with a 0.6/7.5 m telescope of Mt. Suhora Observatory and can accept input from any standard video camera. The IBM 286-486 or compatible personal computer equipped with a SVGA graphic card and framegrabber card is used as a control unit. The program works under a DOS operating system. An effect of guiding on the classic photoelectric photometry and CCD image quality is discussed.

  18. Laser guide star measurements at Lawrence Livermore National Laboratory

    SciTech Connect

    Friedman, H.; Avicola, K.; Bissinger, H.; Brase, J.; Duff, J.; Gavel, D.; Horton, J.; Max, C.; Olivier, S.; Rapp, D.; Salmon, T.; Smauley, D.; Waltjen, K.

    1993-02-01

    Recent studies from the Laser Guide Star Project at Lawrence Livermore National Laboratory are presented. Photometry of the return signal has shown that the photon return is approximately 10 photons/cm{sup 2}ms at the pupil of the receiving telescope in agreement with a detailed model of the sodium interaction. Wavefronts of the laser guide star have also been measured with a Shack-Hartmann technique and power spectra have been shown to agree with those of nearby natural stars. Plans for closed loop demonstrations using the laser guide star at LLNL and nearby Lick Observatory are discussed.

  19. Compliance guide for laser products

    SciTech Connect

    Not Available

    1985-09-01

    Manufacturers of products subject to performance standards under the Radiation Control for Health and Safety Act of 1968 are required to furnish various reports to the Center for Devices and Radiological Health (FDA). The guide is for use by manufacturers of lasers and laser products in preparing Initial Reports and Model Change Reports on Lasers and Products Containing Lasers. The publication incorporates changes from the 1985 amendments to the standard and supersedes previous editions.

  20. Diffractively Coupled, Refractively Guided Lasers

    NASA Technical Reports Server (NTRS)

    Katz, Joseph; Cser, Jim; Marshall, William K.

    1987-01-01

    Semiconductor-laser arrays more reliable, more powerful, and easier to make. Improved design intended to eliminate undesired electromagnetic modes and mode shifts sometimes occuring in gain-guided variety. Reflected from mirror/window at end of common resonator section of laser, energy refracted from each laser enters adjacent laser. Mutual coupling establishes phase relationships among lasers. Monolithic laser array made by standard epitaxial techniques. Made in part with polymeric materials to mitigate some deleterious effects of all-expitaxial processing. Potential applications include optical communications, ranging, printing, and recording.

  1. Design and performance of a laser guide star system for the Keck II telescope

    SciTech Connect

    Friedman, H. W., LLNL

    1998-05-18

    A laser system to generate sodium-layer guide stars has been designed, built and delivered to the Keck Observatory in Hawaii. The system uses frequency doubled YAG lasers to pump liquid dye lasers and produces 20 W of average power. The design and performance results of this laser system are presented.

  2. The Central laser facility at the Pierre Auger Observatory

    SciTech Connect

    Arqueros, F.; Bellido, J.; Covault, C.; D'Urso, D.; Di Giulio, C.; Facal, P.; Fick, B.; Guarino, F.; Malek, M.; Matthews, J.A.J.; Matthews, J.; Meyhandan, R.; Monasor, M.; Mostafa, M.; Petrinca, P.; Roberts, M.; Sommers, P.; Travnicek, P.; Valore, L.; Verzi, V.; Wiencke, Lawrence; /Utah U.

    2005-07-01

    The Central Laser Facility is located near the middle of the Pierre Auger Observatory in Argentina. It features a UV laser and optics that direct a beam of calibrated pulsed light into the sky. Light scattered from this beam produces tracks in the Auger optical detectors which normally record nitrogen fluorescence tracks from cosmic ray air showers. The Central Laser Facility provides a ''test beam'' to investigate properties of the atmosphere and the fluorescence detectors. The laser can send light via optical fiber simultaneously to the nearest surface detector tank for hybrid timing analyses. We describe the facility and show some examples of its many uses.

  3. OCDR guided laser ablation device

    DOEpatents

    Dasilva, Luiz B.; Colston, Jr., Bill W.; James, Dale L.

    2002-01-01

    A guided laser ablation device. The device includes a mulitmode laser ablation fiber that is surrounded by one or more single mode optical fibers that are used to image in the vicinity of the laser ablation area to prevent tissue damage. The laser ablation device is combined with an optical coherence domain reflectometry (OCDR) unit and with a control unit which initializes the OCDR unit and a high power laser of the ablation device. Data from the OCDR unit is analyzed by the control unit and used to control the high power laser. The OCDR images up to about 3 mm ahead of the ablation surface to enable a user to see sensitive tissue such as a nerve or artery before damaging it by the laser.

  4. Smithsonian Astrophysical Observatory laser tracking systems

    NASA Technical Reports Server (NTRS)

    Pearlman, M. R.; Lanham, N. W.; Lehr, C. G.; Wohn, J.

    1977-01-01

    The four SAO laser satellite-ranging systems, located in Brazil, Peru, Australia, and Arizona, have been in operation for more than five years and have provided ranging data at accuracy levels of a meter or better. The paper examines system hardware (laser transmitter, the electronics, mount, photoreceiver, minicomputer, and station timing) and software (prediction program, calibration programs, and data handling and quick-look programs) and also considers calibration, station operation, and system performance.

  5. Design of a fieldable laser system for a sodium guide star

    SciTech Connect

    Friedman, H.; Erbert, G.; Kuklo, T.; Salmon, T.; Smauley, D.; Thompson, G.; Wong, Nan

    1994-03-17

    The design and background data for a sodium layer laser guide star system to be installed on the 3 meter telescope at Lick Observatory is presented. A 30 W dye laser at 589 nm and 10 kHz will be mounted on the telescope and will be pumped by fiber coupled frequency doubled YAG laser located in a separate room.

  6. Wavefront Measurement for Laser-Guiding Diagnostic

    SciTech Connect

    University of Chicago; Lawrence Berkeley National Laboratory; Shiraishi, S.; Gonsalves, A. J.; Lin, C.; Nakamura, K.; Osterhoff, J.; Sokollik, T.; Tilborg, J. van; Geddes, C. G. R.; Schroeder, C. B.; Toth, Cs.; Esarey, E.; Leemans, W. P.

    2010-06-01

    The wavefront of a short laser pulse after interaction in a laser-plasma accelerator (LPA) was measured to diagnose laser-guiding quality. Experiments were performed on a 100 TW class laser at the LOASIS facility of LBNL using a hydrogenfilled capillary discharge waveguide. Laser-guiding with a pre-formed plasma channel allows the laser pulse to propagate over many Rayleigh lengths at high intensity and is crucial to accelerate electrons to the highest possible energy. Efficient coupling of laser energy into the plasma is realized when the laser and the channel satisfy a matched guiding condition, in which the wavefront remains flat within the channel. Using a wavefront sensor, the laser-guiding quality was diagnosed based on the wavefront of the laser pulse exiting the plasma channel. This wavefront diagnostic will contribute to achieving controlled, matched guiding in future experiments.

  7. Wavefront Measurement for Laser-Guiding Diagnostic

    SciTech Connect

    Shiraishi, S.; Gonsalves, A. J.; Lin, C.; Nakamura, K.; Osterhoff, J.; Sokollik, T.; van Tilborg, J.; Geddes, C. G. R.; Schroeder, C. B.; Toth, Cs.; Esarey, E.; Leemans, W. P.

    2010-11-04

    The wavefront of a short laser pulse after interaction in a laser-plasma accelerator (LPA) was measured to diagnose laser-guiding quality. Experiments were performed on a 100 TW class laser at the LOASIS facility of LBNL using a hydrogen-filled capillary discharge waveguide. Laser-guiding with a pre-formed plasma channel allows the laser pulse to propagate over many Rayleigh lengths at high intensity and is crucial to accelerate electrons to the highest possible energy. Efficient coupling of laser energy into the plasma is realized when the laser and the channel satisfy a matched guiding condition, in which the wavefront remains flat within the channel. Using a wavefront sensor, the laser-guiding quality was diagnosed based on the wavefront of the laser pulse exiting the plasma channel. This wavefront diagnostic will contribute to achieving controlled, matched guiding in future experiments.

  8. Image improvement from a sodium-layer laser guide star adaptive optics system

    SciTech Connect

    Max, C. E., LLNL

    1997-06-01

    A sodium-layer laser guide star beacon with high-order adaptive optics at Lick Observatory produced a factor of 2.4 intensity increase and a factor of 2 decrease in full width at half maximum for an astronomical point source, compared with image motion compensation alone. Image full widths at half maximum were identical for laser and natural guide stars (0.3 arc seconds). The Strehl ratio with the laser guide star was 65% of that with a natural guide star. This technique should allow ground-based telescopes to attain the diffraction limit, by correcting for atmospheric distortions.

  9. The Central Raman Laser Facility at the Pierre Auger Observatory

    NASA Astrophysics Data System (ADS)

    medina, C.; Mayotte, E.; Wiencke, L. R.; Rizi, V.; Grillo, A.

    2013-12-01

    We describe the newly upgraded Central Raman Laser Facility (CRLF) located close to the center of the Piere Auger observatory (PAO) in Argentina. The CRLF features a Raman Lidar receiver, a 335 nm wavelength solid state laser, a robotic beam energy calibration system, and a weather station, all powered by solar energy and operated autonomously using a single board computer. The system optics are arranged to direct the laser beam into the atmosphere in steered and vertical modes with adjustable polarization settings,and it is measured in a bi-static configuration by the 4 fluorescence stations of the Pierre Auger observatory. Additionally the system optics can be easily switched to provide a fixed vertical beam that is measured by a Raman Lidar receiver in mono-static configuration,allowing an independent measurement of the aerosol optical depth τ(z,t) and other properties of the atmosphere. A description of the CLRF's installation, hardware and software integration, initial operations and examples of data collected, will also be presented.

  10. LIGO - The Laser Interferometer Gravitational-Wave Observatory

    NASA Technical Reports Server (NTRS)

    Abramovici, Alex; Althouse, William E.; Drever, Ronald W. P.; Gursel, Yekta; Kawamura, Seiji; Raab, Frederick J.; Shoemaker, David; Sievers, Lisa; Spero, Robert E.; Thorne, Kip S.

    1992-01-01

    The goal of the Laser Interferometer Gravitational-Wave Observatory (LIGO) Project is to detect and study astrophysical gravitational waves and use data from them for research in physics and astronomy. LIGO will support studies concerning the nature and nonlinear dynamics for gravity, the structures of black holes, and the equation of state of nuclear matter. It will also measure the masses, birth rates, collisions, and distributions of black holes and neutron stars in the universe and probe the cores of supernovae and the very early universe. The technology for LIGO has been developed during the past 20 years. Construction will begin in 1992, and under the present schedule, LIGO's gravitational-wave searches will begin in 1998.

  11. Direct observation of laser guided corona discharges

    NASA Astrophysics Data System (ADS)

    Wang, Tie-Jun; Wei, Yingxia; Liu, Yaoxiang; Chen, Na; Liu, Yonghong; Ju, Jingjing; Sun, Haiyi; Wang, Cheng; Lu, Haihe; Liu, Jiansheng; Chin, See Leang; Li, Ruxin; Xu, Zhizhan

    2015-12-01

    Laser based lightning control holds a promising way to solve the problem of the long standing disaster of lightning strikes. But it is a challenging project due to insufficient understanding of the interaction between laser plasma channel and high voltage electric filed. In this work, a direct observation of laser guided corona discharge is reported. Laser filament guided streamer and leader types of corona discharges were observed. An enhanced ionization took place in the leader (filament) through the interaction with the high voltage discharging field. The fluorescence lifetime of laser filament guided corona discharge was measured to be several microseconds, which is 3 orders of magnitude longer than the fluorescence lifetime of laser filaments. This work could be advantageous towards a better understanding of laser assisted leader development in the atmosphere.

  12. Direct observation of laser guided corona discharges

    PubMed Central

    Wang, Tie-Jun; Wei, Yingxia; Liu, Yaoxiang; Chen, Na; Liu, Yonghong; Ju, Jingjing; Sun, Haiyi; Wang, Cheng; Lu, Haihe; Liu, Jiansheng; Chin, See Leang; Li, Ruxin; Xu, Zhizhan

    2015-01-01

    Laser based lightning control holds a promising way to solve the problem of the long standing disaster of lightning strikes. But it is a challenging project due to insufficient understanding of the interaction between laser plasma channel and high voltage electric filed. In this work, a direct observation of laser guided corona discharge is reported. Laser filament guided streamer and leader types of corona discharges were observed. An enhanced ionization took place in the leader (filament) through the interaction with the high voltage discharging field. The fluorescence lifetime of laser filament guided corona discharge was measured to be several microseconds, which is 3 orders of magnitude longer than the fluorescence lifetime of laser filaments. This work could be advantageous towards a better understanding of laser assisted leader development in the atmosphere. PMID:26679271

  13. Direct observation of laser guided corona discharges.

    PubMed

    Wang, Tie-Jun; Wei, Yingxia; Liu, Yaoxiang; Chen, Na; Liu, Yonghong; Ju, Jingjing; Sun, Haiyi; Wang, Cheng; Lu, Haihe; Liu, Jiansheng; Chin, See Leang; Li, Ruxin; Xu, Zhizhan

    2015-01-01

    Laser based lightning control holds a promising way to solve the problem of the long standing disaster of lightning strikes. But it is a challenging project due to insufficient understanding of the interaction between laser plasma channel and high voltage electric filed. In this work, a direct observation of laser guided corona discharge is reported. Laser filament guided streamer and leader types of corona discharges were observed. An enhanced ionization took place in the leader (filament) through the interaction with the high voltage discharging field. The fluorescence lifetime of laser filament guided corona discharge was measured to be several microseconds, which is 3 orders of magnitude longer than the fluorescence lifetime of laser filaments. This work could be advantageous towards a better understanding of laser assisted leader development in the atmosphere. PMID:26679271

  14. Consistency analysis on laser signal in laser guided weapon simulation

    NASA Astrophysics Data System (ADS)

    Yin, Ruiguang; Zhang, Wenpan; Guo, Hao; Gan, Lin

    2015-10-01

    The hardware-in-the-loop simulation is widely used in laser semi-active guidance weapon experiments, the authenticity of the laser guidance signal is the key problem of reliability. In order to evaluate the consistency of the laser guidance signal, this paper analyzes the angle of sight, laser energy density, laser spot size, atmospheric back scattering, sun radiation and SNR by comparing the different working state between actual condition and hardware-in-the-loop simulation. Based on measured data, mathematical simulation and optical simulation result, laser guidance signal effects on laser seeker are determined. By using Monte Carlo method, the laser guided weapon trajectory and impact point distribution are obtained, the influence of the systematic error are analyzed. In conclusion it is pointed out that the difference between simulation system and actual system has little influence in normal guidance, has great effect on laser jamming. The research is helpful to design and evaluation of laser guided weapon simulation.

  15. Implementation of the Chicago sum frequency laser at Palomar laser guide star test bed

    NASA Astrophysics Data System (ADS)

    Velur, Viswa; Kibblewhite, Edward J.; Dekany, Richard G.; Troy, Mitchell; Petrie, Hal L.; Thicksten, Robert P.; Brack, Gary; Trin, Thang; Cheselka, Matthew

    2004-10-01

    Work is underway at the University of Chicago and Caltech Optical Observatories to implement a sodium laser guide star adaptive optics system for the 200 inch Hale telescope at Palomar Observatory. The Chicago sum frequency laser (CSFL) consists of two pulsed, diode-pumped, mode-locked Nd:YAG lasers working at 1.064 micron and 1.32 micron wavelengths. Light from the two laser beams is mixed in a non-linear crystal to produce radiation centered at 589 nm with a spectral width of 1.0 GHz (FWHM) to match that of the Sodium-D2 line. Currently the 1.064 micron and 1.32 micron lasers produce 14 watts and 8 watts of TEM-00 power respectively. The laser runs at 500 Hz rep. rate with 10% duty cycle. This pulse format is similar to that of the MIT-Lincoln labs and allows range gating of unwanted Rayleigh scatter down an angle of 60 degrees to zenith angle. The laser system will be kept in the Coude lab and will be projected up to a laser launch telescope (LLT) bore-sited to the Hale telescope. The beam-transfer optics, which conveys the laser beam from the Coude lab to the LLT, consists of motorized mirrors that are controlled in real time using quad-cell positioning systems. This needs to be done to prevent laser beam wander due to deflections of the telescope while tracking. There is a central computer that monitors the laser beam propagation up to the LLT, the interlocks and safety system status, laser status and actively controls the motorized mirrors. We plan to install a wide-field visible camera (for high flying aircraft) and a narrow field of view (FoV) IR camera (for low-flying aircraft) as part of our aircraft avoidance system.

  16. Laser-guide-stars used for cophasing broad capture ranges

    NASA Astrophysics Data System (ADS)

    Martinez, P.; Janin-Potiron, P.

    2016-08-01

    Context. Segmented primary mirrors are indispensable to master the steady increase in spatial resolution. Phasing optics systems must reduce segment misalignments to guarantee the high optical quality required for astronomical science programs. Aims: Modern telescopes routinely use adaptive optics systems to compensate for the atmosphere and use laser-guide-stars to create artificial stars as bright references in the field of observation. Because multiple laser-guide-star adaptive optics are being implemented in all major observatories, we propose to use man-made stars not only for adaptive optics, but for phasing optics. Methods: We propose a method called the doublet-wavelength coherence technique (DWCT), exploiting the D lines of sodium in the mesosphere using laser guide-stars. The signal coherence properties are then used. Results: The DWCT capture range exceeds current abilities by a factor of 100. It represents a change in paradigm by improving the phasing optics capture range from micrometric to millimetric. It thereby potentially eliminates the need of a man-made mechanical pre-phasing step. Conclusions: Extremely large telescopes require hundreds of segments, several of which need to be substituted on a daily basis to be recoated. The DWCT relaxes mechanical integration requirements and speeds up integration and re-integration process.

  17. Multiple laser guide stars (LGS) for multiple conjugate adaptive optics (MCAO)

    NASA Astrophysics Data System (ADS)

    Jones, Katharine J.

    2012-10-01

    For wavefront sensing and control, the most extensive use of Mult-Conjugate Adaptive Optics (MCAO) systems for extended-path aberration compensation lies with the use of multiple Laser Guide Stars (LGS) for Multi-Conjugate Adaptive Optics (MCAO). Ground-based adaptive optics systems were initially developed by the Starfire Optical Range (SOR) in 1983. Both Rayleigh guide stars and Na guide stars have been developed. More recently, both laser systems, Na LGS at 93 km and Rayleigh guide stars at 20 km, are being combined in the Large Binocular Telescope (LBT) for multiple LGS for Multiple Conjugate Adaptive Optics (MCAO) (M. Hart et al, 2011). Each side of the LBT has 3 Rayleigh LGS which are projected into two triangular constellations. A sodium LGS will be added to each aperture using the same launch optics as the Rayleigh beacons. This will combine low altitude Rayleigh LGS and high altitude Na laser guide stars into a uniquely powerful tomographic wavefront sensing system for Multi-Conjugate Adaptive Optics. Other observatories have used either Rayleigh guide stars or Na guide stars. ESO VLT has 4 Na LGS. MMT has 5 Rayleigh guide stars. Gemini Multi-Conjugate Adaptive Optics System (GEMS) has 5 Na LGS. The many multiple LGS MCAO observatories will be compared for effective design and projected performance.

  18. AFIRE: fiber Raman laser for laser guide star adaptive optics

    NASA Astrophysics Data System (ADS)

    Bonaccini Calia, D.; Hackenberg, W.; Chernikov, S.; Feng, Y.; Taylor, L.

    2006-06-01

    Future adaptive optics systems will benefit from multiple sodium laser guide stars in achieving satisfactory sky coverage in combination with uniform and high-Strehl correction over a large field of view. For this purpose ESO is developing with industry AFIRE, a turn-key, rack-mounted 589-nm laser source based on a fiber Raman laser. The fiber laser will deliver the beam directly at the projector telescope. The required output power is in the order of 10 W in air per sodium laser guide star, in a diffraction-limited beam and with a bandwidth of < 2 GHz. This paper presents the design and first demonstration results obtained with the AFIRE breadboard. 4.2W CW at 589nm have so far been achieved with a ~20% SHG conversion efficiency.

  19. Laser Guiding for GeV Laser-Plasma Accelerators

    SciTech Connect

    Leemans, Wim; Esarey, Eric; Geddes, Cameron; Schroeder, C.B.; Toth, Csaba

    2005-06-06

    Guiding of relativistically intense laser beams in preformed plasma channels is discussed for development of GeV-class laser accelerators. Experiments using a channel guided laser wakefield accelerator (LWFA) at LBNL have demonstrated that near mono-energetic 100 MeV-class electron beams can be produced with a 10 TW laser system. Analysis, aided by particle-in-cell simulations, as well as experiments with various plasma lengths and densities, indicate that tailoring the length of the accelerator, together with loading of the accelerating structure with beam, is the key to production of mono-energetic electron beams. Increasing the energy towards a GeV and beyond will require reducing the plasma density and design criteria are discussed for an optimized accelerator module. The current progress and future directions are summarized through comparison with conventional accelerators, highlighting the unique short term prospects for intense radiation sources based on laser-driven plasma accelerators.

  20. Laser guiding for GeV laser-plasma accelerators.

    PubMed

    Leemans, Wim; Esarey, Eric; Geddes, Cameron; Schroeder, Carl; Tóth, Csaba

    2006-03-15

    Guiding of relativistically intense laser beams in preformed plasma channels is discussed for development of GeV-class laser accelerators. Experiments using a channel guided laser wakefield accelerator at Lawrence Berkeley National Laboratory (LBNL) have demonstrated that near mono-energetic 100 MeV-class electron beams can be produced with a 10 TW laser system. Analysis, aided by particle-in-cell simulations, as well as experiments with various plasma lengths and densities, indicate that tailoring the length of the accelerator, together with loading of the accelerating structure with beam, is the key to production of mono-energetic electron beams. Increasing the energy towards a GeV and beyond will require reducing the plasma density and design criteria are discussed for an optimized accelerator module. The current progress and future directions are summarized through comparison with conventional accelerators, highlighting the unique short-term prospects for intense radiation sources based on laser-driven plasma accelerators. PMID:16483950

  1. Image improvement from a sodium-layer laser guide star adaptive optics system

    SciTech Connect

    Max, C.E.; Olivier, S.S.; Friedman, H.W.

    1997-09-12

    A sodium-layer laser guide star beacon with high-order adaptive optics at Lick Observatory (Mount Hamilton, California) produced a factor of 2.4 intensity increase and a factor of 2 decrease in full width at half maximum for an astronomical point source, compared with image motion compensation alone. The image full widths at half maximum were identical for laser and natural guide stars (0.3 arc second). The Strehl ratio with the laser guide star was 65 percent of that with a natural guide star. This technique should allow ground-based telescopes to attain the diffraction limit, by correcting for atmospheric distortions. 21 refs., 4 figs., 1 tab.

  2. Coupling coefficient of gain-guided lasers

    NASA Technical Reports Server (NTRS)

    Katz, J.; Kapon, E.; Lindsey, C.; Margalit, S.; Yariv, A.

    1984-01-01

    An analytical model is presented for the coupling coefficient for two gain-guided coupled waveguides, e.g., semiconductor laser arrays. A common parabolic gain distribution is assumed for the lasers, and the effective dielectric constant distribution is approximated in terms of the bulk refraction index, wavelength, power filling factor, and the antiguiding factor. The fundamental mode is then formulated and used in an integral for the coupling coefficient. The dependence of the coefficient of various waveguide parameters is described.

  3. Guided transmission for 10 micron tunable lasers

    NASA Technical Reports Server (NTRS)

    Yu, C.; Sabzali, A.; Yekrangian, A.

    1986-01-01

    Performance characteristics are reported for two types of IR tunable laser guided transmission, one of which incorporates a CO2 laser, metallic piping or fiber-optics, and a detector system, while the other employs a tunable diode laser, fiber-optics, and a detector system. While existing technology furnishes low loss, rugged, near-single mode piping, fiber-optics exhibits appreciably higher loss, and its multimode fibers are fragile and chemically unstable. Studies have accordingly concentrated on such relevant fiber parameters as loss, toxicity, hygroscopicity, refractive index, flexibility, and thermal behavior at low temperature.

  4. Water jet guided laser versus saw dicing

    NASA Astrophysics Data System (ADS)

    Dushkina, Natalia M.; Wagner, Frank R.; Boillat, Christophe; Buchilly, Jean-Marie; Richerzhagen, Bernold

    2003-07-01

    The incessantly growing demands for higher speed of the wireless telecommunications and more compact devices require using of thin compound semiconductor wafers. The dicing is the very last process of the wafer manufacturing. At this stage the IC pattern is completely built up and the wafer has the highest value. Therefore, the goal of the singulation process is to provide the highest possible throughput. The conventional saw techniques "struggle" at their speed limits, while the conventional laser is not an appropriate dicing tool due to the strong thermal effect and big heat affected zones. The water-jet guided laser technology provides cool laser dicing since the laser is coupled in a fine stable water-jet and conducted to the work piece by means of total internal reflection like through an optical fiber, as the relatively low water pressure (10 - 30 MPa) of the tiny jet with diameter 40 - 100 μm results in a negligible force on the sample. This technology provides higher cutting speeds and burr-free kerf quality. By means of the Laser MicroJet, wafers as thin as 25 μm could be diced in streets of 50 μm width, with almost 100% wafer throughput. Here we compare the water-jet guided laser cutting with conventional techniques for dicing of thin semiconductor wafers. The results for Silicon and GaAs/Ge wafers are discussed in terms of speed, kerf quality and die fracture strength.

  5. Plasma channel guided laser wakefield accelerator

    NASA Astrophysics Data System (ADS)

    Geddes, Cameron Guy Robinson

    2005-11-01

    High quality electron beams (several 109 electrons above 80 MeV energy with percent energy spread and low divergence) have been produced for the first time in a compact, high gradient, all-optical laser accelerator by extending the interaction distance using a pre-formed plasma density channel to guide the drive laser pulse. Laser-driven accelerators, in which particles are accelerated by the electric field of a plasma wave (wake) driven by the radiation pressure of an intense laser, have over the past decade demonstrated accelerating fields thousands of times greater than those achievable in conventional radio-frequency accelerators. This has spurred interest in them as compact next-generation sources of energetic electrons and radiation. To date, however, acceleration distances have been severely limited by the lack of a controllable method for extending the propagation distance of the focused laser pulse. The ensuing short acceleration distance resulted in low-energy beams with 100 percent electron energy spread, which has limited potential applications. Optical guiding of relativistically intense (>1018 W/cm 2) laser pulses over distances greater than 10 diffraction lengths is demonstrated herein using plasma channels, which have a density minimum on the axis of propagation, formed by hydrodynamic shock. Laser modes with peak powers of up to 4 TW---twice the self-guiding threshold---were guided without aberration by tuning the plasma density profile. The transmitted optical spectrum showed that the pulse remained in the channel over the entire length, and no accelerated electrons were observed at these powers. Simulations indicated that a large plasma wave was driven by the 4 TW pulse, indicating a possible dark current free structure for a laser wakefield accelerator using controlled injection. The presence of a large plasma wave was verified by increasing laser power and observing electron acceleration. At a guided drive pulse power of 9 TW (500 mJ in 50 fs

  6. Synchronization of Geodetic Observatories thanks to Time Transfer by Laser Link

    NASA Astrophysics Data System (ADS)

    Belli, Alexandre; Exertier, Pierre; Samain, Etienne; Vernotte, François

    2015-08-01

    Since 2008, the Time Transfer by Laser Link experiment (T2L2) onboard Jason-2 at 1336 km allows the clock synchronization by an optical link between ground clocks (generally H-maser) and the space instrument. The space segment includes roughly a detector, a timer, a frequency reference (Ultra Stable Oscillator, USO, provided by the DORIS system) and a Laser Reflector Array. Taking into account the current precision and accuracy of the laser ranging technology and the specifications of the space instrument, the stability of the ground to space time transfer is established at a few picoseconds (ps) over 100 seconds. The combination of any two ground stations (from the International Laser Ranging network) referred to their H-maser clock provides, in common view, a very stable ground to ground time transfer of 10 ps over the common pass (around 10 minutes). The accuracy, of around 100 ps between two time calibrated observatories, is demonstrated thanks to several experiments and a rigourous error budget. However, several geodetic observatories reveal to have a time shift of hundreds of nanoseconds, between their local time reference system and UTC. In order to provide geodetic observatories with a unique time reference frame we used the T2L2 instrument to transfer time in the non-common view mode, all around the international laser network.We show that T2L2 is able to provide accurate frequencies, which are deduced from the ground to space time transfers over each laser station at a few 10-13. Thanks to this monitoring of the frequency variations of the onboard oscillator, we established a physical model to be integrated over 10,000 seconds (around one orbital revolution). This model is built by considering all observatories, weighted by the accuracy of their ground clock. The Grasse geodetic observatory is used to calibrate the model because it is bring back to UTC thanks to a permanent GPS link calibrated tothe Paris Observatory (UTC(OP)). By applying this model, we

  7. Compact Fiber Laser for 589nm Laser Guide Star Generation

    NASA Astrophysics Data System (ADS)

    Pennington, D.; Drobshoff, D.; Mitchell, S.; Brown, A.

    Laser guide stars are crucial to the broad use of astronomical adaptive optics, because they facilitate access to a large fraction of possible locations on the sky. Lasers tuned to the 589 nm atomic sodium resonance can create an artificial beacon at altitudes of 95-105 km, thus coming close to reproducing the light path of starlight. The deployment of multiconjugate adaptive optics on large aperture telescopes world-wide will require the use of three to nine sodium laser guide stars in order to achieve uniform correction over the aperture with a high Strehl value. Current estimates place the minimum required laser power at > 10 W per laser for a continuous wave source, though a pulsed format, nominally 6?s in length at ~ 16.7 kHz, is currently preferred as it would enable tracking the laser through the Na layer to mitigate spot elongation. The lasers also need to be compact, efficient, robust and turnkey. We are developing an all-fiber laser system for generating a 589 nm source for laser-guided adaptive optics. Fiber lasers are more compact and insensitive to alignment than their bulk laser counterparts, and the heat-dissipation characteristics of fibers, coupled with the high efficiencies demonstrated and excellent spatial mode characteristics, make them a preferred candidate for many high power applications. Our design is based on sum-frequency mixing an Er/Yb:doped fiber laser operating at 1583 nm with a 938 nm Nd:silica fiber laser in a periodically poled crystal to generate 589 nm. We have demonstrated 14 W at 1583 nm with an Er/Yb:doped fiber laser, based on a Koheras single frequency fiber oscillator amplified in an IPG Photonics fiber amplifier. The Nd:silica fiber laser is a somewhat more novel device, since the Nd3+ ions must operate on the resonance transition (i.e. 4F3/2-4I9/2), while suppressing ASE losses at the more conventional 1088 nm transition. Optimization of the ratio of the fiber core and cladding permits operation of the laser at room

  8. Guide star lasers for adaptive optics

    NASA Astrophysics Data System (ADS)

    Roberts, William Thomas, Jr.

    Exploitation of the imaging capabilities of the new generation of ground-based astronomical telescopes relies heavily on Adaptive Optics (AO). Current AO system designs call for sodium guide star lasers capable of producing at least eight Watts of power tuned to the peak of the sodium D2 line, with a high duty cycle to avoid saturation, and with 0.5-1.0 GHz spectral broadening. This work comprises development and testing of six candidate laser systems and materials which may afford a path to achieving these goals. An end-pumped CW dye laser producing 4.0 Watts of tuned output power was developed and used to obtain the first accurate measurement of sodium layer scattering efficiency. Methods of optimizing the laser output through improving pump overlap efficiency and reducing the number of intracavity scattering surfaces are covered. The 1181 nm fluorescence peak of Mn5+ ion in Ba5 (PO4)3Cl could be tuned and doubled to reach 589 nm. While efforts to grow this crystal were under way, the Mn5+ ion in natural apatite (Ca5(PO4)3F) was studied as a potential laser material. Fluorescence saturation measurements and transmission saturation are presented, as well as efforts to obtain CW lasing in natural apatite. A Q-switched laser color-center laser in LiF : F-2 was developed and successfully tuned and doubled to the sodium D 2 line. Broad-band lasing of 80 mW and tuned narrow-band lasing of 35 mW at 1178 nm were obtained with 275 mW of input pump power at 1064 nm. The measured thermal properties of this material indicate its potential for scaling to much higher power. A Q-switched intracavity Raman laser was developed in which CaWO 4 was used to shift a Nd:YAG laser, the frequency-doubled output of which was centered at 589.3 nm. To obtain light at 589.0 nm, a compositionally tuned pump laser of Nd : Y3Ga1.1Al3.9O 12 was produced which generated the desired shift, but was inhomogeneous broadened, limiting the tunable power of the material. Finally, temperature tuning of

  9. MLRS - A lunar/artificial satellite laser ranging facility at the McDonald Observatory

    NASA Technical Reports Server (NTRS)

    Shelus, P. J.

    1985-01-01

    Experience from lunar and satellite laser ranging experiments carried out at McDonald Observatory has been used to design the McDonald Laser Ranging Station (MLRS). The MLRS is a dual-purpose installation designed to obtain observations from the LAGEOS satellite and lunar targets. The instruments used at the station include a telescope assembly 0.76 meters in diameter; a Q-switched doubled neodymium YAG laser with a pulse rate of three nanoseconds; and a GaAs photodetector with Fabry-Perot interferometric filter. A functional diagram of the system is provided. The operating parameters of the instruments are summarized in a table.

  10. The Laser Interferometer Gravitational-Wave Observatory: Lasers at the Frontiers of Astrophysics

    NASA Astrophysics Data System (ADS)

    Reitze, David

    2005-04-01

    The Laser Interferometric Gravitational-Wave Observatory (LIGO) is poised to open a new window on the universe - the detection of gravitational waves from distant large-scale astrophysical sources. Gravitational waves were predicted by Einstein almost 90 years ago but never been observed directly despite a number of experiments over the last 40 years. While there exists strong indirect evidence for gravitational waves, it is only with the construction of large-scale high precision interferometers that direct detection of gravitational waves is possible. Gravitational waves are miniscule dynamic strains applied to space-time by motion of massive astrophysical objects. A passing gravitational wave will expand and contract the distance between two mirrors (`test masses') in the arms of an interferometer. Direct observation of gravitational waves presents a formidable challenge, because the magnitude of the dynamic strain is expected to be infinitesimal, less than one part in 10-22. The astrophysical motivation for detecting gravitational waves is compelling. Unlike the visible sky, the gravitational wave `sky' is completely unexplored. The LIGO detectors and its partner GEO600 in Europe have the sensitivity to observe gravitational waves not only in our own galaxy, but in neighboring galaxies, thus opening an absolutely unique window into these phenomena. In the first part of the presentation, we will give an overview of gravitational waves - what they are and where they come from -- and describe in general terms the techniques that gravitational wave astrophysicists use to hunt for them. In the second part of the presentation, we describe the LIGO interferometers emphasizing the critical role that lasers and optics play in its operation.

  11. Electromagnetically Induced Guiding of Counter-propagating Lasers in Plasmas

    SciTech Connect

    First Author = G. Shvets; A. Pukhov

    1998-05-01

    The interaction of counter-propagating laser pulses in a plasma is considered. When the frequencies of the two lasers are close, nonlinear modification of the refraction index results in the mutual focusing of the two beams. A short (of order the plasma period) laser pulse can also be nonlinearly focused by a long counter-propagating beam which extends over the entire guiding length. This phenomenon of electromagnetically induced guiding can be utilized in laser-driven plasma accelerators.

  12. Laser guide star adaptive optics: Present and future

    SciTech Connect

    Olivier, S.S.; Max, C.E.

    1993-03-01

    Feasibility demonstrations using one to two meter telescopes have confirmed the utility of laser beacons as wavefront references for adaptive optics systems. Laser beacon architectures suitable for the new generation of eight and ten meter telescopes are presently under study. This paper reviews the concept of laser guide star adaptive optics and the progress that has been made by groups around the world implementing such systems. A description of the laser guide star program at LLNL and some experimental results is also presented.

  13. Analytical model for ring heater thermal compensation in the Advanced Laser Interferometer Gravitational-wave Observatory.

    PubMed

    Ramette, Joshua; Kasprzack, Marie; Brooks, Aidan; Blair, Carl; Wang, Haoyu; Heintze, Matthew

    2016-04-01

    Advanced laser interferometer gravitational-wave detectors use high laser power to achieve design sensitivity. A small part of this power is absorbed in the interferometer cavity mirrors where it creates thermal lenses, causing aberrations in the main laser beam that must be minimized by the actuation of "ring heaters," which are additional heater elements that are aimed to reduce the temperature gradients in the mirrors. In this article we derive the first, to the best of our knowledge, analytical model of the temperature field generated by an ideal ring heater. We express the resulting optical aberration contribution to the main laser beam in this axisymmetric case. Used in conjunction with wavefront measurements, our model provides a more complete understanding of the thermal state of the cavity mirrors and will allow a more efficient use of the ring heaters in the Advanced Laser Interferometer Gravitational-wave Observatory. PMID:27139664

  14. Laser beam riding guided system principle and design research

    NASA Astrophysics Data System (ADS)

    Qu, Zhou; Jin, Yi; Xu, Zhou; Xing, Hao

    2016-01-01

    With the development of science and technology, precision-strike weapons has been considered to be important for winning victory in military field. Laser guidance is a major method to execute precision-strike in modern warfare. At present, the problems of primary stage of Laser guidance has been solved with endeavors of countries. Several technical aspects of laser-beam riding guided system have been mature, such as atmosphere penetration of laser beam, clutter inhibition on ground, laser irradiator, encoding and decoding of laser beam. Further, laser beam quality, equal output power and atmospheric transmission properties are qualified for warfare situation. Riding guidance instrument is a crucial element of Laser-beam riding guided system, and is also a vital element of airborne, vehicle-mounted and individual weapon. The optical system mainly consist of sighting module and laser-beam guided module. Photoelectric detector is the most important sensing device of seeker, and also the key to acquire the coordinate information of target space. Currently, in consideration of the 1.06 u m of wavelength applied in all the semi-active laser guided weapons systems, lithium drifting silicon photodiode which is sensitive to 1.06 u m of wavelength is used in photoelectric detector. Compared to Solid and gas laser, diode laser has many merits such as small volume, simple construction, light weight, long life, low lost and easy modulation. This article introduced the composition and operating principle of Laser-beam riding guided system based on 980 nm diode laser, and made a analysis of key technology; for instance, laser irradiator, modulating disk of component, laser zooming system. Through the use of laser diode, Laser-beam riding guided system is likely to have smaller shape and very light.

  15. Laser guide stars and adaptive optics for astronomy

    SciTech Connect

    Max, C.E.

    1992-07-15

    Five papers are included: feasibility experiment for sodium-alyer laser guide stars at LLNL; system design for a high power sodium beacon laser; sodium guide star adaptive optics system for astronomical imaging in the visible and near-infrared; high frame-rate, large field wavefront sensor; and resolution limits for ground-based astronomical imaging. Figs, tabs, refs.

  16. Adaptive Optics with Sodium Laser Guide Stars

    NASA Astrophysics Data System (ADS)

    Lloyd-Hart, M.; Angel, J. R. P.; Jacobsen, B.; Wittman, D.; McCarthy, D.; Martinez, T.

    1994-12-01

    Adaptive optics requires a reference source of light in the sky to measure wavefront aberration introduced by atmospheric turbulence. Natural stars are ideal for this purpose, but the density of bright stars is not sufficient to provide complete sky coverage. The problem can be overcome with an artificial beacon generated from resonant backscattering off mesospheric sodium atoms exited by a low-power laser tuned to the D2 resonance. Recent experiments at the Multiple Mirror Telescope (MMT) have demonstrated for the first time that an adaptive optics system using a sodium laser guide beacon can be used to improve the imaging quality of the telescope. A beacon of mv = 10.4 was used to control the relative image motion between two of the six apertures of the MMT, while a natural star was used to measure the absolute tilt. A factor of two improvement in the K-band Strehl ratio was measured, and the resolution improved from 0(\\?.58) to 0(\\?.41) . The experiment demonstrated all the features needed for correction of telescopes of 6.5 to 8-m diameter to the diffraction limit in the near infrared with a single sodium laser beacon.

  17. Dynamics of laser-guided alternating current high voltage discharges

    NASA Astrophysics Data System (ADS)

    Daigle, J.-F.; Théberge, F.; Lassonde, P.; Kieffer, J.-C.; Fujii, T.; Fortin, J.; Châteauneuf, M.; Dubois, J.

    2013-10-01

    The dynamics of laser-guided alternating current high voltage discharges are characterized using a streak camera. Laser filaments were used to trigger and guide the discharges produced by a commercial Tesla coil. The streaking images revealed that the dynamics of the guided alternating current high voltage corona are different from that of a direct current source. The measured effective corona velocity and the absence of leader streamers confirmed that it evolves in a pure leader regime.

  18. Laser system design for the generation of a sodium-layer laser guide star

    SciTech Connect

    Friedman, H.W.

    1993-01-01

    The design considerations for a laser system used to generate a sodium-layer guide star are presented. Laser technology developed for the Atomic Vapor Laser Isotope Separation (AVLIS) Program is shown to be directly relevant to this problem and results of a demonstration using the AVLIS laser to generate such a guide star are shown. The design of a compact laser suitable for use at a large telescope such as the Keck is also presented.

  19. Arm locking for space-based laser interferometry gravitational wave observatories

    NASA Astrophysics Data System (ADS)

    Yu, Yinan; Mitryk, Shawn; Mueller, Guido

    2014-09-01

    Laser frequency stabilization is a critical part of the interferometry measurement system of space-based gravitational wave observatories such as the Laser Interferometer Space Antenna (LISA). Arm locking as a proposed frequency stabilization technique transfers the stability of the long arm lengths to the laser frequency. The arm locking sensor synthesizes an adequately filtered linear combination of the interspacecraft phase measurements to estimate the laser frequency noise, which can be used to control the laser frequency. At the University of Florida we developed the hardware-based University of Florida LISA Interferometer Simulator to study and verify laser frequency noise reduction and suppression techniques under realistic LISA-like conditions. These conditions include the variable Doppler shifts among the spacecraft, LISA-like signal travel times, optical transponders, realistic laser frequency, and timing noise. We review the different types of arm locking sensors and discuss their expected performance in LISA. The presented results are supported by results obtained during experimental studies of arm locking under relevant LISA-like conditions. We measured the noise suppression as well as initial transients and frequency pulling in the presence of Doppler frequency errors. This work has demonstrated the validity and feasibility of arm locking in LISA.

  20. Sodium Laser Guide Star Adaptive Optics Imaging Polarimetry of Herbig Ae/Be Stars

    SciTech Connect

    Perrin, M D; Graham, J R; Lloyd, J P; Kalas, P; Gates, E L; Gavel, D T; Pennington, D M; Max, C E

    2004-01-08

    The future of high-resolution ground-based optical and infrared astronomy requires the successful implementation of laser guide star adaptive optics systems. We present the first science results from the Lick Observatory sodium beacon laser guide star system. By coupling this system to a near-infrared (J;H;Ks bands) dual-channel imaging polarimeter, we achieve very high sensitivity to light scattered in the circumstellar enviroment of Herbig Ae/Be stars on scales of 100-300 AU. Observations of LkH{alpha} 198 reveal a highly polarized, biconical nebula 10 arcseconds in diameter (6000 AU) . We also observe a polarized jet-like feature associated with the deeply embedded source LkH{alpha} 198-IR. The star LkH{alpha} 233 presents a narrow, unpolarized dark lane dividing its characteristic butterfly-shaped polarized reflection nebulosity. This linear structure is oriented perpendicular to an optical jet and bipolar cavity and is consistent with the presence of an optically thick circumstellar disk blocking our direct view of the star. These data suggest that the evolutionary picture developed for the lower-mass T Tauri stars is also relevant to the Herbig Ae/Be stars and demonstrate the ability of laser guide star adaptive optics systems to obtain scientific results competitive with natural guide star adaptive optics or space-based telescopes.

  1. Electromagnetically induced guiding of counterpropagating lasers in plasmas

    SciTech Connect

    Shvets, G.; Pukhov, A.

    1999-01-01

    The interaction of counterpropagating laser pulses in a plasma is considered. When the frequencies of the two lasers are close, nonlinear modification of the refraction index results in the mutual focusing of the two beams. A short (of order of the plasma period) laser pulse can also be nonlinearly focused by a long counterpropagating beam which extends over the entire guiding length. This phenomenon of electromagnetically induced guiding can be utilized in laser-driven plasma accelerators. {copyright} {ital 1999} {ital The American Physical Society}

  2. Coupling mechanism of gain-guided integrated semiconductor laser arrays

    NASA Technical Reports Server (NTRS)

    Kapon, E.; Lindsey, C.; Margalit, S.; Yariv, A.; Katz, J.

    1984-01-01

    It is shown that a gain-guided laser array couples via propagating fields rather than the evanescent mode coupling typically responsible for directional coupling in passive (directional couplers) and active (laser array) devices. It is shown that these phase-locked modes exhibit an interference pattern, in the junction plane, which arises from the curvature of the phase fronts of optical fields of the interacting lasers. The experimental results are interpreted with the aid of a simple theoretical model, and the effect of the observed mode pattern on the coupling of gain-guided lasers is discussed.

  3. The study of laser beam riding guided system based on 980nm diode laser

    NASA Astrophysics Data System (ADS)

    Qu, Zhou; Xu, Haifeng; Sui, Xin; Yang, Kun

    2015-10-01

    With the development of science and technology, precision-strike weapons has been considered to be important for winning victory in military field. Laser guidance is a major method to execute precision-strike in modern warfare. At present, the problems of primary stage of Laser guidance has been solved with endeavors of countries. Several technical aspects of laser-beam riding guided system have been mature, such as atmosphere penetration of laser beam, clutter inhibition on ground, laser irradiator, encoding and decoding of laser beam. Further, laser beam quality, equal output power and atmospheric transmission properties are qualified for warfare situation. Riding guidance instrument is a crucial element of Laser-beam riding guided system, and is also a vital element of airborne, vehicle-mounted and individual weapon. The optical system mainly consist of sighting module and laser-beam guided module. Photoelectric detector is the most important sensing device of seeker, and also the key to acquire the coordinate information of target space. Currently, in consideration of the 1.06 u m of wavelength applied in all the semi-active laser guided weapons systems, lithium drifting silicon photodiode which is sensitive to 1.06 u m of wavelength is used in photoelectric detector. Compared to Solid and gas laser, diode laser has many merits such as small volume, simple construction, light weight, long life, low lost and easy modulation. This article introduced the composition and operating principle of Laser-beam riding guided system based on 980 nm diode laser, and made a analysis of key technology; for instance, laser irradiator, modulating disk of component, laser zooming system. Through the use of laser diode, Laser-beam riding guided system is likely to have smaller shape and very light.

  4. Cryogenic far-infrared laser absorptivity measurements of the Herschel Space Observatory telescope mirror coatings.

    PubMed

    Fischer, Jacqueline; Klaassen, Tjeerd; Hovenier, Niels; Jakob, Gerd; Poglitsch, Albrecht; Sternberg, Oren

    2004-07-01

    Far-infrared laser calorimetry was used to measure the absorptivity, and thus the emissivity, of aluminum-coated silicon carbide mirror samples produced during the coating qualification run of the Herschel Space Observatory telescope to be launched by the European Space Agency in 2007. The samples were measured at 77 K to simulate the operating temperature of the telescope in its planned orbit about the second Lagrangian point, L2, of the Earth-Sun system. Together, the telescope's equilibrium temperature in space and the emissivity of the mirror surfaces will determine the far-infrared-submillimeter background and thus the sensitivity of two of the three astronomical instruments aboard the observatory if stray-light levels can be kept low relative to the mirror emission. Absorptivities of both clean and dust-contaminated samples were measured at 70, 118, 184, and 496 microm. Theoretical fits to the data predict absorptivities of 0.2-0.4% for the clean sample and 0.2-0.8% for the dusty sample, over the spectral range of the Herschel Space Observatory instruments. PMID:15250543

  5. Laser guiding at>1018 W/cm2 in plasma channels formed by theignitor heater method

    SciTech Connect

    Geddes, C.G.R.; Toth, C.; vanTilborg, J.; Leemans, W.P.

    2004-05-01

    Experiments explore guiding of intense laser pulses, optimization using channel formation beams and gas jet targets, and the interplay of channel guiding and relativistic self guiding. Impact on laser wakefield particle acceleration is being assessed.

  6. Guiding of relativistic laser pulses by preformed plasmachannels

    SciTech Connect

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

    2004-12-10

    Guiding of relativistically intense (>1018 W/cm2) laser pulses over more than 10 diffraction lengths has been demonstrated using plasma channels formed by hydrodynamic shock. Pulses up to twice the self guiding threshold power were guided without aberration by tuning the guide profile. Transmitted spectra and mode images showed the pulse remained in the channel over the entire length. Experiments varying guided mode power and simulations show a large plasma wave was driven.Operating just below the trapping threshold produces a dark current free structure suitable for controlled injection.

  7. The Laser Guide Star System for Adaptive Optics at Subaru Telescope

    NASA Astrophysics Data System (ADS)

    Hayano, Y.; Saito, Y.; Ito, M.; Saito, N.; Akagawa, K.; Takazawa, A.; Ito, M.; Wada, S.; Takami, H.; Iye, M.

    -power laser beam with no suffer from the non-linear scatter effect, i.e. stimulated Brillouin scatter, in the PCF. The laser launching telescope (LLT) has an output clear aperture as 50 cm. It is classical Cassegrain type optical configuration with tertiary mirror to insert the laser beam from the side. The wavefront error is designed to be 60 to 70nm. The LLT is a copy product what European Southern Observatory has been designed for the laser guide star system at Very Large Telescope. We succeeded to launch the laser beam to the sky on October 12, 2006. After several tests on the sky, we succeeded to get an image of the laser guide star with the size of more than 10 arc second. The larger size of the laser guide star is caused by the large optical aberration on the primary mirror of LLT due to the heat stress generated at the trigonal support points. We are making a plan to repair this problem during June and the second laser launching test will start around this summer.

  8. Robust remote-pumping sodium laser for advanced LIDAR and guide star applications

    NASA Astrophysics Data System (ADS)

    Ernstberger, Bernhard; Enderlein, Martin; Friedenauer, Axel; Schwerdt, Robin; Wei, Daoping; Karpov, Vladimir; Leisching, Patrick; Clements, Wallace R. L.; Kaenders, Wilhelm G.

    2015-10-01

    The performance of large ground-based optical telescopes is limited due to wavefront distortions induced by atmospheric turbulence. Adaptive optics systems using natural guide stars with sufficient brightness provide a practical way for correcting the wavefront errors by means of deformable mirrors. Unfortunately, the sky coverage of bright stars is poor and therefore the concept of laser guide stars was invented, creating an artificial star by exciting resonance fluorescence from the mesospheric sodium layer about 90 km above the earth's surface. Until now, mainly dye lasers or sumfrequency mixing of solid state lasers were used to generate laser guide stars. However, these kinds of lasers require a stationary laser clean room for operation and are extremely demanding in maintenance. Under a development contract with the European Southern Observatory (ESO) and W. M. Keck Observatory (WMKO), TOPTICA Photonics AG and its partner MPB Communications have finalized the development of a next-generation sodium guide star laser system which is available now as a commercial off-the-shelf product. The laser is based on a narrow-band diode laser, Raman fiber amplifier (RFA) technology and resonant second-harmonic generation (SHG), thus highly reliable and simple to operate and maintain. It emits > 22 W of narrow-linewidth (≈ 5 MHz) continuous-wave radiation at sodium resonance and includes a re-pumping scheme for boosting sodium return flux. Due to the SHG resonator acting as spatial mode filter and polarizer, the output is diffraction-limited with RMS wavefront error < λ/25. Apart from this unique optical design, a major effort has been dedicated to integrating all optical components into a ruggedized system, providing a maximum of convenience and reliability for telescope operators. The new remote-pumping architecture allows for a large spatial separation between the main part of the laser and the compact laser head. Together with a cooling-water flow of less than 5 l

  9. Wide baseline optical interferometry with Laser Guide Stars

    SciTech Connect

    Gavel, D. T., LLNL

    1998-03-01

    Laser guide stars have been used successfully as a reference source for adaptive optics systems. We present a possible method for utilizing laser beacons as sources for interferometric phasing. The technique would extend the sky coverage for wide baseline interferometers and allow interferometric measurement and imaging of dim objects.

  10. Laser systems for the generation of sodium layer guide stars

    SciTech Connect

    Friedman, H.; Erbert, G.; Kuklo, T.; Salmon, T.; Thompson, G.; Wong, N.; Malik, J.

    1996-03-05

    Laser generated guide stars in the mesosphere at 90 km provide an effective beacon for adaptive optics schemes which compensate the effects of atmospheric turbulence. This report discusses the attributes of the laser systems which are desirable from a point of view of overall adaptive optics system performance and operation ease.

  11. Desing of a Laser Guide Star System for the Keck II Telescope

    SciTech Connect

    Friedman, H.W.; Erbert, G.V.; Kuklo, T.; Thompson, G.R.; Wong, N.J.; Gavel, D.T.; Salmon, J.T.; Feldman, M.

    1997-09-11

    A laser guide star system similar to that deployed at the Lick Observatory has been designed for the Keck II 10 m telescope on Mauna Kea, Hawaii. The subaperature size on the primary is comparable to that at Lick, and at the same observational wavelength centered about the K band, so that the average power requirements of the laser system are also comparable, at about 20 W. One major difference is that the seeing at Mauna Kea is about a factor of two better than at Lick so that the spot diameter requirements are smaller and this can give rise to reduced back scatter resulting from saturation effects in the sodium layer. To reduce the peak flux in the sodium layer and obtain a smaller spot diameter, the output beam diameter has been increased along with the repetition rate of the laser. As with the Lick laser system, a dye laser is pumped by a series of frequency doubled YAG lasers which are remotely located and coupled to the dye laser on the telescope by optical fibers. The laser system has a full set of beam control optics as well as launch telescope and safety systems. A computer system couples the laser system to the User Interface and Supervisory Control system of the main telescope. The laser system is due to be shipped to Keck during the fall of 1997 where it will be integrated with the telescope at Mauna Kea. The Adaptive Optics and Optics Bench systems will be integrated first and be ready for integration with the laser in the summer of 1998. 1 ref., 8 figs.

  12. Guiding effect of quantum wells in semiconductor lasers

    SciTech Connect

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

    2013-05-31

    The guiding effect of InGaAs quantum wells in GaAs- and InP-based semiconductor lasers has been studied theoretically and experimentally. The results demonstrate that such waveguides can be effectively used in laser structures with a large refractive index difference between the quantum well material and semiconductor matrix and a large number of quantum wells (e.g. in InP-based structures). (semiconductor lasers. physics and technology)

  13. Indication of Local Laser Pump Depletion via Transmitted Self-Guided Laser Light

    SciTech Connect

    Pak, A. E.; Marsh, K. A.; Ralph, J. E.; Lu, W.; Clayton, C. E.; Joshi, C.

    2009-01-22

    In recent experiments it has been shown that an ultra-intense, ultra-short laser pulse can be self-guided over tens of Rayleigh lengths in an underdense plasma where {tau}(FWHM of the laser pulse) is on the order of the plasma wavelength ({lambda}{sub p}). Using an imaging spectrograph, the frequency of the transmitted laser pulse was spatially and spectrally resolved at the exit of 3, 5, and 8 mm long plasmas. The mechanism of laser pump depletion was studied by observing the amount that the transmitted laser pulse's spectrum was red shifted in wavelength through the interaction with the self-guiding plasma wave.

  14. Status of the GRAAL system development: very wide-field correction with 4 laser guide-stars

    NASA Astrophysics Data System (ADS)

    Paufique, J.; Argomedo, J.; Arsenault, R.; Conzelmann, R.; Donaldson, R.; Hubin, N.; Jochum, L.; Jost, A.; Kiekebusch, M.; Kolb, J.; Kuntschner, H.; Le Louarn, M.; Madec, P.-Y.; Siebenmorgen, R.; Tordo, S.

    2012-07-01

    We recall the design and present the development status of GRAAL, the Ground-layer adaptive optics assisted by Laser, which will deliver wide-field (10 arcmin), enhanced images to the HAWK-I instrument on the VLT, with an improved seeing. GRAAL is an adaptive optics module, part of the Adaptive optics facility (AOF), using four Laser- and one natural guide-stars to measure the turbulence, and correcting for it by deforming the adaptive secondary mirror of a Unit telescope in the Paranal observatory. GRAAL is in the laboratory in Europe and the integration of its laser guide-star optics is completed. The first wave-front sensor camera will be ready for its integration in the coming weeks, allowing the first system tests to start.

  15. Improving sodium laser guide star brightness by polarization switching

    PubMed Central

    Fan, Tingwei; Zhou, Tianhua; Feng, Yan

    2016-01-01

    Optical pumping with circularly polarized light has been used to enhance the brightness of sodium laser guide star. But the benefit is reduced substantially due to the precession of sodium atoms in geomagnetic field. Switching the laser between left and right circular polarization at the Larmor frequency is proposed to improve the return. With ESO’s laser guide star system at Paranal as example, numerical simulation shows that the return flux is increased when the angle between geomagnetic field and laser beam is larger than 60°, as much as 50% at 90°. The proposal is significant since most astronomical observation is at angle between 60° and 90° and it only requires a minor addition to the delivery optics of present laser system. PMID:26797503

  16. Improving sodium laser guide star brightness by polarization switching.

    PubMed

    Fan, Tingwei; Zhou, Tianhua; Feng, Yan

    2016-01-01

    Optical pumping with circularly polarized light has been used to enhance the brightness of sodium laser guide star. But the benefit is reduced substantially due to the precession of sodium atoms in geomagnetic field. Switching the laser between left and right circular polarization at the Larmor frequency is proposed to improve the return. With ESO's laser guide star system at Paranal as example, numerical simulation shows that the return flux is increased when the angle between geomagnetic field and laser beam is larger than 60°, as much as 50% at 90°. The proposal is significant since most astronomical observation is at angle between 60° and 90° and it only requires a minor addition to the delivery optics of present laser system. PMID:26797503

  17. Laser guide star experiment at Lawrence Livermore National Laboratory

    SciTech Connect

    Max, C.E.; Friedman, H.W.; Brase, J.B.; Avicola, K.; Bissinger, H.; Gavel, D.T.; Horton, J.A.; Morris, J.R.; Olivier, S.S.; Presta, R.W.; Rapp, D.A.; Salmon, T.J.; Waltjen, K.

    1993-01-01

    An overview of the Laser Guide Star feasibility experiment at Lawrence Livermore National Laboratory is presented. The goal of the project is to demonstrate a closed-loop adaptive optics system using a sodium-layer laser guide star to correct wavefront aberrations caused by atmospheric turbulence. The laser beam is projected upwards from a beam director located 5 meters from a half-meter telescope and forms a spot about 2 meters in diameter in the mesospheric sodium layer at an altitude of about 95 km. The laser beam is approximately fifth magnitude and is visible to the unaided eye at the top of the Rayleigh-scattered laser beam. A Shack-Hartmann wave front sensor measures the aberrated wave front and a continuous sheet deformable mirrow will correct the wave front in a closed loop control system at a bandwidth fast enough to follow changes in the atmosphere. In this paper, the authors present an overview of the methodology for the design of the experiment and the requirements of the laser source. The long term goal of this effort is to develop laser guide stars and adaptive optics for large astronomical telescopes and to this end, a summary of laser issues relevant to future sites is presented.

  18. Polarization competition in quasi-index-guided laser diodes

    SciTech Connect

    Amann, M.; Stegmueller, B.

    1988-03-15

    The mechanism of polarization competition in laser diodes with a lateral quasi-index-guiding (QIG) structure is analyzed generally by way of the effective index approximation using a simplified QIG laser model. The influence of the relevant waveguide parameters on the polarization-dependent threshold current of QIG laser diodes is investigated in detail by example of lambda = 1.3-..mu..m ridge-waveguide lasers. Thereby, it is found that for intermediate values of the effective index step, the TM mode exhibits a higher gain and lower threshold current, whereas for pure gain guiding or strong index guiding, the TE mode prevails. This behavior, which compares excellently to published experimental results, is proven as a basic feature of the two-dimensional waveguiding mechanism in QIG devices. Accordingly, the effect of stress-induced anisotropy of the optical gain has been found to be of minor importance as the origin for TM-polarized QIG lasers made from lattice-matched heterostructures. It is further demonstrated that, for certain device parameters, the QIG lasers with a small effective index step exhibit somewhat higher threshold currents than the purely gain-guided devices of identical geometry.

  19. Guide for preparing initial reports and model change reports on lasers and products containing lasers

    SciTech Connect

    Not Available

    1985-09-01

    Manufacturers of products subject to performance standards under the Radiation Control for Health and Safety Act of 1968 are required to furnish various reports to the Center for Devices and Radiological Health (FDA). The guide is for use by manufacturers of lasers and products containing lasers in preparating initial and model change reports. The format of the guide incorporates changes from the 1985 amendments to the standard and supersedes previous editions. Much of the instructional material for use in completing this form has been moved to the companion publication Compliance Guide for Laser Products.

  20. MRI-guided laser ablation of neuroendocrine tumor hepatic metastases

    PubMed Central

    Perälä, Jukka; Klemola, Rauli; Kallio, Raija; Li, Chengli; Vihriälä, Ilkka; Salmela, Pasi I; Tervonen, Osmo

    2014-01-01

    Background Neuroendocrine tumors (NET) represent a therapeutically challenging and heterogeneous group of malignancies occurring throughout the body, but mainly in the gastrointestinal system. Purpose To describe magnetic resonance imaging (MRI)-guided laser ablation of NET liver metastases and assess its role within the current treatment options and methods. Material and Methods Two patients with NET tumor hepatic metastases were treated with MRI-guided interstitial laser ablation (LITT). Three tumors were treated. Clinical follow-up time was 10 years. Results Both patients were successfully treated. There were no local recurrences at the ablation site during the follow-up. Both patients had survived at 10-year follow-up. One patient is disease-free. Conclusion MRI-guided laser ablation can be used to treat NET tumor liver metastases but combination therapy and a rigorous follow-up schedule are recommended. PMID:24778794

  1. Sodium laser guide star system at Lawrence Livermore National Laboratory: System description and experimental results

    SciTech Connect

    Avicola, K.; Brase, J.; Morris, J.

    1994-03-02

    The architecture and major system components of the sodium-layer kw guide star system at LLNL will be described, and experimental results reported. The subsystems include the laser system, the beam delivery system including a pulse stretcher and beam pointing control, the beam director, and the telescope with its adaptive-optics package. The laser system is one developed for the Atomic Vapor Laser Isotope Separation (AVLIS) Program. This laser system can be configured in various ways in support of the AVLIS program objectives, and was made available to the guide star program at intermittent times on a non-interference basis. The first light transmitted into the sky was in July of 1992, at a power level of 1. 1 kW. The laser pulse width is about 32 ns, and the pulse repetition rate was 26 kHz for the 1. 1 kW configuration and 13 kHz for a 400 W configuration. The laser linewidth is tailored to match the sodium D{sub 2} absorption line, and the laser system has active control of beam pointing and wavefront quality. Because of the short pulse length the sodium transition is saturated and the laser power is not efficiently utilized. For this reason a pulse stretcher was developed, and the results of this effort will be reported. The beam is delivered via an evacuated pipe from the laser building to the guide star site, a distance of about 100 meters, and then launched vertically. A beam director provides the means to track the sky in the full AO system, but was not used in the experiments reported here. The return signal is collected by a 1/2 meter telescope with the AO package. This telescope is located 5 meters from the km launch tube. Smaller packages for photometry, wavefront measurement, and spot image and motion analysis have been used. Although the unavailability of the AVLIS laser precluded a full AO system demonstration, data supporting feasibility and providing input to the system design for a Lick Observatory AO system was obtained.

  2. 75 FR 76015 - Compliance Policy Guide Sec. 393.200 Laser(s) as Medical Devices for Facelift, Wrinkle Removal...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-07

    ... the Federal Register of August 9, 2010 (75 FR 48180 at 48233), FDA included the Compliance Policy... HUMAN SERVICES Food and Drug Administration Compliance Policy Guide Sec. 393.200 Laser(s) as Medical... Administration (FDA) is announcing the withdrawal of Compliance Policy Guide Sec. 393.200 Laser(s) as...

  3. The laser guide star program for the LBT

    NASA Astrophysics Data System (ADS)

    Rabien, S.; Ageorges, N.; Angel, R.; Brusa, G.; Brynnel, J.; Busoni, L.; Davies, R.; Deysenroth, M.; Esposito, S.; Gässler, W.; Genzel, R.; Green, R.; Haug, M.; Lloyd Hart, M.; Hölzl, G.; Masciadri, E.; Pogge, R.; Quirrenbach, A.; Rademacher, M.; Rix, H. W.; Salinari, P.; Schwab, C.; Stalcup, T., Jr.; Storm, J.; Strüder, L.; Thiel, M.; Weigelt, G.; Ziegleder, J.

    2008-07-01

    Laser guide star adaptive optics and interferometry are currently revolutionizing ground-based near-IR astronomy, as demonstrated at various large telescopes. The Large Binocular Telescope from the beginning included adaptive optics in the telescope design. With the deformable secondary mirrors and a suite of instruments taking advantage of the AO capabilities, the LBT will play an important role in addressing major scientific questions. Extending from a natural guide star based system, towards a laser guide stars will multiply the number of targets that can be observed. In this paper we present the laser guide star and wavefront sensor program as currently being planned for the LBT. This program will provide a multi Rayleigh guide star constellation for wide field ground layer correction taking advantage of the multi object spectrograph and imager LUCIFER in a first step. The already foreseen upgrade path will deliver an on axis diffraction limited mode with LGS AO based on tomography or additional sodium guide stars to even further enhance the scientific use of the LBT including the interferometric capabilities.

  4. Smithsonian Astrophysical Observatory's minicomputer vs. the laser. [computer predictions for laser tracking stations

    NASA Technical Reports Server (NTRS)

    Cherniack, J. R.

    1973-01-01

    Review of some of the problems encountered in replacing a CDC 6400, that was used for supplying a network of laser tracking stations with predictions, by an 8K Data General 1200 minicomputer with a teletype for I/O. Before the replacement, the predictions were expensive to compute and to transmit, and were clumsy logistically. The achieved improvements are described, along with every step it took to accomplish them, and the incurred costs.

  5. A sodium laser guide star coupling efficiency measurement method

    NASA Astrophysics Data System (ADS)

    Feng, Lu; Shen, Zhi-Xia; Xue, Suijian; Li, Yang-Peng; Jin, Kai; Otarola, Angel; Bo, Yong; Zuo, Jun-Wei; Bian, Qi; Wei, Kai; Hu, Jing-Yao

    2016-09-01

    A large telescope's adaptive optics (AO) system requires one or more bright artificial laser guide stars to improve its sky coverage. The recent advent of a high power sodium laser is perfect for such application. However, besides the output power, other parameters of the laser also have a significant impact on the brightness of the generated sodium laser guide star, mostly in non-linear relationships. When tuning and optimizing these parameters it is necessary to tune based on a laser guide star generation performance metric. Although return photon fluxis widely used, variability of the atmosphere and sodium layer makes it difficult to compare results from different sites or even within a short time period for the same site. A new metric, coupling efficiency, is adopted in our field tests. In this paper, we will introduce our method for measuring the coupling efficiency of a 20W class pulse sodium laser for AO application during field tests that were conducted during 2013–2015.

  6. Sodium-layer laser-guide-star experimental results

    SciTech Connect

    Avicola, K.; Brase, J.M.; Morris, J.R.

    1994-02-01

    The authors describe a series of experiments to characterize the sodium-layer guide star that was formed with the highpower laser developed for the Lawrence Livermore National Laboratory Atomic Vapor Laser Isotope Separation program. An emission spot size of 3.0 m was measured, with an implied laser irradiance spot diameter of 2.0 m. The rms spot motion at the higher laser powers, with active beam-pointing control, was less than 0.5 arcsec and had little effect on the observed spot size under these conditions. The authors measured the resonant backscatter from the sodium layer as a function of laser power to obtain a saturation curve. With a transmitted power of 1100 W and an atmospheric transmission of 0.6, the irradiance from the guide star at the ground was 10 (photons/cm{sup 2})/ms, corresponding to a visual magnitude of 5.1. The implications for the performance of wave-front sensors with a laser guide star of this magnitude and resulting closed-loop adaptive-optics performance are discussed. 13 refs., 9 figs.

  7. Diffused guides for distributed-feedback lasers

    NASA Technical Reports Server (NTRS)

    Elachi, C.

    1975-01-01

    Proposed waveguide is hollow cylindrical pipe. Inside channel surface is infused with gas or metal molecules, forming periodic cross sections along entire length. Light is scattered at periodic infusions, resulting in distributed feedback. Configuration is suited for capillary gas lasers.

  8. [Laser navigation guided cleft lip repair].

    PubMed

    Bing, Shi

    2016-06-01

    A new method using the ideal mid-facial line as the navigating reference was introduced to improve the outcome of cleft lip repair. Using the verticle coordinate crossing the middle point of the intercanthus line, surgeons could observe and correct the distortion of the fine structures in labial-nasal area. This laser projecting mid-facial-line navigation was repeatable, while not interfere the operating. In conclusion, generalizing laser navigation is a valuable supplementary for cleft lip repair. PMID:27526442

  9. Transurethral ultrasound-guided laser-induced prostatectomy

    NASA Astrophysics Data System (ADS)

    Babayan, Richard K.; Roth, Robert A.

    1991-07-01

    A transurethral ultrasound-guided Nd:YAG laser delivery system has been developed for use as an alternative approach to the treatment of benign prostatic hyperplasia. The TULIP system has been extensively tested in canine models and is currently undergoing FDA trials in humans.

  10. Laser Electro-Optic Technology. Florida Vocational Program Guide.

    ERIC Educational Resources Information Center

    University of South Florida, Tampa. Dept. of Adult and Vocational Education.

    This program guide identifies primary considerations in the organization, operation, and evaluation of a laser electro-optic technology program. An occupational description and program content are presented. A curriculum framework specifies the exact course title, course number, levels of instruction, major course content, laboratory activities,…

  11. Laser Electro-Optic Engineering Technology. Florida Vocational Program Guide.

    ERIC Educational Resources Information Center

    University of South Florida, Tampa. Dept. of Adult and Vocational Education.

    This program guide identifies particular considerations in the organization, operation, and evaluation of laser electro-optic engineering technology programs. Contents include an occupational description and information on the following: program content, including a curriculum framework that details major concepts and intended outcomes and a list…

  12. Tesla coil discharges guided by femtosecond laser filaments in air

    NASA Astrophysics Data System (ADS)

    Brelet, Yohann; Houard, Aurélien; Arantchouk, Leonid; Forestier, Benjamin; Liu, Yi; Prade, Bernard; Carbonnel, Jérôme; André, Yves-Bernard; Mysyrowicz, André

    2012-04-01

    A Tesla coil generator was designed to produce high voltage pulses oscillating at 100 kHz synchronisable with a nanosecond temporal jitter. Using this compact high voltage generator, we demonstrate reproducible meter long discharges in air at a repetition rate of 1 Hz. Triggering and guiding of the discharges are performed in air by femtosecond laser filaments.

  13. Observing techniques for astronomical laser guide star adaptive optics

    SciTech Connect

    Max, C.E.; Macintosh, B.; Olivier, S.S.; Gavel, D.T.; Friedman, H.W.

    1998-05-01

    We discuss astronomical observing requirements and their implementation using sodium-layer laser guide star adaptive optics. Specific issues requiring implementation include the ability to place the astronomical object at different locations within the field of view; reliable subtraction of Rayleigh-scattered light; efficient focusing; and stable point-spread-function characterization.

  14. Laser needle guide for the sonic flashlight.

    PubMed

    Wang, David; Wu, Bing; Stetten, George

    2005-01-01

    We have extended the real-time tomographic reflection display of the Sonic Flashlight to a laser guidance system that aims to improve safety and accuracy of needle insertion, especially for deep procedures. This guidance system is fundamentally different from others currently available. Two low-intensity lasers are mounted on opposite sides of a needle aimed parallel to the needle. The needle is placed against a notch in the Sonic Flashlight mirror such that the laser beams reflect off the mirror to create bright red spots on the flat panel display. Due to diffuse reflection from these spots, the virtual image created by the flat panel display contains the spots, identifying the projected destination of the needle at its actual location in the tissue. We have implemented our design and validated its performance, identifying several areas for potential improvement. PMID:16685901

  15. Experimental studies of laser guiding in plasma channels

    SciTech Connect

    Volfbeyn, P.; Leemans, W.P.

    1998-07-01

    The authors present results of experimental investigations of laser guiding in plasma channels. A new technique for plasma channel creation, the Ignitor-Heater scheme is proposed and experimentally tested in hydrogen and nitrogen. It makes use of two laser pulses. The Ignitor, an ultrashort (< 100 fs) laser pulse, is brought to a line focus using a cylindrical lens to ionize the gas. The Heater pulse (160 ps long) is used subsequently to heat the existing spark via inverse Bremsstrahlung. The hydrodynamic shock expansion creates a partially evacuated plasma channel with a density minimum on axis. Such a channel has properties of an optical waveguide. This technique allows, creation of plasma channels in low atomic number gases, such as hydrogen, which is of importance for guiding of highly intense laser pulses. The channel density was diagnosed with time resolved longitudinal interferometry. From these measurements the plasma temperature was inferred. The guiding properties of the channels were tested by injecting a > 5 {times} 10{sup 17} W/cm{sup 2}, 75 fs laser pulse.

  16. Recent developments in aircraft protection systems for laser guide star operations

    NASA Astrophysics Data System (ADS)

    Stomski, Paul J.; Murphy, Thomas W.; Campbell, Randy

    2012-07-01

    The astronomical community's use of high power laser guide star adaptive optics (LGS-AO) systems presents a potential hazard to aviation. Historically, the most common and trusted means of protecting aircraft and their occupants has been the use of safety observers (aka spotters) armed with shut-off switches. These safety observers watch for aircraft at risk and terminate laser propagation before the aircraft can be adversely affected by the laser. Efforts to develop safer and more cost-effective automated aircraft protection systems for use by the astronomical community have been inhibited by both technological and regulatory challenges. This paper discusses recent developments in these two areas. Specifically, with regard to regulation and guidance we discuss the 2011 release of AS-6029 by the SAE as well as the potential impact of RTCA DO-278A. With regard to the recent developments in the technology used to protect aircraft from laser illumination, we discuss the novel Transponder Based Aircraft Detection (TBAD) system being installed at W. M. Keck Observatory (WMKO). Finally, we discuss our strategy for evaluating TBAD compliance with the regulations and for seeking appropriate approvals for LGS operations at WMKO using a fully automated, flexibly configured, multi-tier aircraft protection system incorporating this new technology.

  17. 25 W Raman-fiber-amplifier-based 589 nm laser for laser guide star.

    PubMed

    Feng, Yan; Taylor, Luke R; Calia, Domenico Bonaccini

    2009-10-12

    We report on a 25 W continuous wave narrow linewidth (< 2.3 MHz) 589 nm laser by efficient (> 95%) coherent beam combination of two narrow linewidth (< 1.5 MHz) Raman fiber amplifiers with a Mach-Zehnder interferometer scheme and frequency doubling in an external resonant cavity with an efficiency of 86%. The results demonstrate the narrow linewidth Raman fiber amplifier technology as a promising solution for developing laser for sodium laser guide star adaptive optics. PMID:20372636

  18. Guiding cold atoms in a hollow laser beam

    NASA Astrophysics Data System (ADS)

    Xu, Xinye; Minogin, V. G.; Lee, Kwanil; Wang, Yuzhu; Jhe, Wonho

    1999-12-01

    The theory of atom guiding in a far blue-detuned hollow laser beam (HLB) is developed for the dipole interaction scheme described by a three-level Λ model. The complete kinetic description of atomic motion based on the Fokker-Planck equation for the atomic distribution function is presented. The dipole gradient force, radiation pressure force, and momentum diffusion tensor are then derived. It is found that even for a far-detuned laser beam, the optical potential for a three-level Λ atom is not generally reduced to a sum of two independent potentials associated with the two two-level interactions in the Λ scheme. The theory developed here is also compared with the experimental guiding of cold 85Rb atoms in the HLB. The experimental results are found to be in good agreement with the Monte Carlo simulations based on the three-level Λ model. We observe that the guiding efficiency depends strongly on the intensity and the detuning of the HLB and the initial temperature of atoms. In particular, the experimental results show that, at small detunings, the guiding efficiency is deteriorated strongly by the radiation pressure force. The Monte Carlo simulations also indicate that the efficiency of guiding versus detuning depends strongly on the direction of the HLB propagation with respect to that of atomic motion. Under optimal conditions, the guiding efficiency was found to be about 20%.

  19. Performance results on the laser portion of the Keck laser guide star system

    SciTech Connect

    Cooke, J B; Danforth, P M; Erbert, G V; Feldman, M; Friedman, H W; Gavel, D T; Jenkins, S L; Jones, H E; Kanz, V K; Kuklo, T; Newman, M J; Pierce, E L; Presta, R W; Salmon, J T; Thompson, G R; Wong, N J

    1998-09-29

    The Laser Guide Star (LGS) system for the Keck II, 10 m telescope consists of two separate but interconnected systems, the laser and the adaptive optics bench. The laser portion of the LGSl is a set of five frequency doubled YAG lasers pumping a master oscillator-power amplifier dye chain to produce up to 30 W of 589 p at 26 kHz of tuned light. Presently the laser system has been set up at the Keck facility in Waimea, HI and is undergoing test and evaluation. When it will be set up on the Keck II telescope, the pump lasers, dye master oscillator and associated control equipment will be located on the dome floor and the dye laser amplifiers, beam control system and diagnostics will be mounted directly on the telescope as shown in Fig. 1, Extensive use of fiber optics for both transmission of the oscillator pulse and the pump laser light has been used.

  20. Laser Triggered Electron Injection into a Channel Guided Wakefield Accelerator

    NASA Astrophysics Data System (ADS)

    Nakamura, K.; Filip, C.

    2005-10-01

    Laser-plasma accelerators have demonstrated the generation of narrow energy spread (˜ few %) electron beams with considerable amount of charge (>100 pC). Stability of laser-plasma accelerators, as in the conventional accelerators, requires highly synchronized injection of electrons into the structured accelerating field. The Colliding Pulse Method[1] with pre-formed plasma channel guiding [2] can result in jitter-free injection in a dark-current-free accelerating structure. We report on experimental progress of laser triggered injection of electrons into a laser wakefield, where an intense laser pulse is guided by a pre-formed plasma channel. The experiments use the multi-beam, multi-terawatt Ti:Al2O3 laser at LOASIS facility of LBNL. The ignitor-heater method is used to first produce a pre-formed plasma channel in a hydrogen gas jet. Two counter propagating beams (wakefield driver:100-500mJ-50fs, injector:50-300mJ-50fs) then are focused onto the entrance of the channel. Preliminary results indicate that electron beam properties are affected by the second beam. Details of the experiment will be presented. [1]G.Fubiani, et al, Phys. Rev. E 70, 016402 (2004). [2]C.G.R. Geddes et al, Nature 431, 538 (2004). This work is supported by DoE under contract DE-AC02-05CH11231.

  1. Research aims at development of laser-guided electron beam

    NASA Astrophysics Data System (ADS)

    Kozicharow, E.

    1985-02-01

    The U.S. Department of Defense is conducting a technology development program that may result in the stationing of a laser-guided electron beam weapon, at ionospheric altitudes of 80-600 km, for the interception and destruction of Soviet ICBMs at ranges of more than 1000 miles. This research program is pursuing the principle of ion-focused propagation, which resolves the problem of atmospheric beam scattering by ionizing a channel in the atmospheric medium with a laser. Also discussed is the development status of space-based particle beams and lasers, ground-based laser systems employing orbiting mirror platforms for beam aiming, and nuclear device-powered directed energy weapons.

  2. Photon Return On-Sky Test of Pulsed Sodium Laser Guide Star with D2b Repumping

    NASA Astrophysics Data System (ADS)

    Jin, Kai; Wei, Kai; Feng, Lu; Bo, Yong; Zuo, JunWei; Li, Min; Fu, HanChu; Dai, XiaoLin; Bian, Qi; Yao, Ji; Xu, Chang; Wang, ZhiChao; Peng, QingJun; Xue, XiangHui; Cheng, XueWu; Rao, ChangHui; Xu, ZuYan; Zhang, YuDong

    2015-08-01

    Sodium laser guide star (LGS) system has become one of the critical components in modern astronomical adaptive optics system (AOS), especially for the next-generation extremely large telescopes, such as the Thirty Meter Telescope and the European Extremely Large Telescope. Since the wavefront detection performance of AOS is directly related to the brightness of LGS, it is important for AOS to maximize its photon generation efficiency by all means. Sodium D2b line repumping is such a technique that can greatly increase the returned photons for either sodium continuous wave (CW) laser or pulsed laser. This technique has been studied theoretically and field tested with a 20 W CW laser by European Southern Observatory team. However, field test results of a 20 W class pulsed laser with D2b repumping have not been reported yet. In this paper, our latest field test results with theoretical comparison of D2b repumping with a 20 W quasi-continuous wave (QCW) pulsed laser will be presented. With a linearly polarized beam, approximate 40% photon return enhancement was achieved when 10% of laser power was detuned to D2b line, which agreed well with results from a rate equation-based Monte Carlo photon return simulation program. Both experiment and simulation results indicate that with a higher laser intensity projected at the sodium layer, the D2b repumping will be more effective.

  3. Precise Gravity Measurements for Lunar Laser Ranging at Apache Point Observatory

    NASA Astrophysics Data System (ADS)

    Crossley, D. J.; Murphy, T.; Boy, J.; De Linage, C.; Wheeler, R. D.; Krauterbluth, K.

    2012-12-01

    Lunar Laser Ranging (LLR) at Apache Point Observatory began in 2006 under the APOLLO project using a 3.5 m telescope on a 2780 m summit in New Mexico. Recent improvements in the technical operations are producing uncertainties at the few-mm level in the 1.5 x 10^13 cm separation of the solar orbits of the Earth and Moon. This level of sensitivity permits a number of important aspects of gravitational theory to be tested. Among these is the Equivalence Principle that determines the universality of free fall, tests of the time variation of the Gravitational Constant G, deviations from the inverse square law, and preferred frame effects. In 2009 APOLLO installed a superconducting gravimeter (SG) on the concrete pier under the main telescope to further constrain the deformation of the site as part of an initiative to improve all aspects of the modeling process. We have analyzed more than 3 years of high quality SG data that provides unmatched accuracy in determining the local tidal gravimetric factors for the solid Earth and ocean tide loading. With on-site gravity we have direct measurements of signals such as polar motion, and can compute global atmospheric and hydrological loading for the site using GLDAS and local hydrology models that are compared with the SG observations. We also compare the SG residuals with satellite estimates of seasonal ground gravity variations from the GRACE mission. Apache Point is visited regularly by a team from the National Geospatial-Intelligence Agency to provide absolute gravity values for the calibration of the SG and to determine secular gravity changes. Nearby GPS location P027 provides continuous position information from the Plate Boundary Observatory of Earthscope that is used to correlate gravity/height variations at the site. Unusual aspects of the data processing include corrections for the telescope azimuth that appear as small offsets at the 1 μGal level and can be removed by correlating the azimuth data with the SG

  4. New process for screen cutting: water-jet guided laser

    NASA Astrophysics Data System (ADS)

    Perrottet, Delphine; Amorosi, Simone; Richerzhagen, Bernold

    2005-07-01

    Today's OLED manufacturers need high-precision, fast tools to cut the metal screens used to deposit the electroluminescent layers onto the substrate. Conventional methods -tching and dry laser cutting - are not satisfying regarding the demands of high-definition OLED displays. A new micro machining technology, the water jet guided laser - a hybrid of laser and water jet technologies that has been actively used in recent years in the electronic and semiconductor field - is now available to OLED manufacturers. This technology represents a significant improvement in screen, mask and stencil cutting, as it combines high precision and high speed. It is able to cut small apertures with totally clean edges (no dross or slag), as the water jet removes the particles and a thin water film is maintained on the material surface during the process. Because the water jet cools the material between the laser pulses, the cut material is free of any thermal stress. The water jet guided laser is also a very fast process: as an example, rectangular slots can be cut in 30 to 50 microns thick stainless steel or nickel at a rate between 25'000 and 30'000 holes per hour.

  5. Guiding of laser beams in plasmas by electromagnetic cascade compression

    NASA Astrophysics Data System (ADS)

    Kalmykov, S.; Shvets, G.

    2006-10-01

    The near-resonant beatwave excitation of an electron plasma wave (EPW) can be employed for generating trains of few- femtosecond electromagnetic pulses in rarefied plasmas. The EPW produces a co-moving index grating that induces a laser phase modulation at the difference frequency. As a result, the cascade of sidebands red- and blue-shifted 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. In the 3D cylindrical geometry, the frequency-downshifted EPW not only modulates the laser phase, but also causes the pulse to self-focus [P. Gibbon, Phys. Fluids B 2, 2196 (1990)]. After self-focusing, the laser beam inevitably diverges. Remarkably, the longitudinal beatnote compression can compensate the intensity drop due to diffraction. Thus, a train of high intensity radiation spikes with continually evolving longitudinal profile can be self- guided over several Rayleigh lengths in homogeneous plasma. 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 show that achieving GeV energy is possible under realistic experimental conditions.

  6. 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.

  7. 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.

  8. Fluorescence enhancing mechanism of optical repumping in sodium atoms for brighter laser guide star.

    PubMed

    Lihang, Li; Wang, Hongyan; Hua, Weihong; Ning, Yu; Xu, Xiaojun

    2016-04-01

    With quantum Bloch equations and sodium cell based experiment, we systematically resolved optical repumping mechanism of sodium atoms, a path to brighter sodium laser guide star (SLGS) that would be accepted by worldwide observatories. Besides the former studies, we detailed the population distribution of sodium atoms with and without repumping, which makes the repumping mechanism easy to understand. Experimental results based on a buffer gas free sodium cell and a single frequency laser implies that the optimum repumping frequency offset is 1712 MHz, and the repumping power fraction should be 10-18%. The light intensity depended character of repumping is also carried out. We learned that future SLGS pumped by higher effective light intensity would benefit more from repumping. To the best of our knowledge, this is the first systematic investigation of repumping mechanism using a single mode sum-frequency laser, which gives thorough support for previous numerical work and shows that the lab bench experiment could be used as an intermediate link between theoretical modeling and on-sky test. PMID:27136991

  9. High-gain reverse guide field free electron lasers

    SciTech Connect

    Tsui, K.H.

    1995-10-01

    Electron beam trajectories under circularly polarized external wigglers in free electron laser devices with axial guide fields are reconsidered by introducing the self-fields of the electron beam. The competition between the self-fields and the wiggler field plus the action of the guide field are not only responsible for the known positive guide field singularity, but also the new reverse guide field singularity. The physics of the new reverse field singularity relies on the fact that an azimuthal magnetic field uniform in {ital z} is able to generate steady-state helical beam orbits just as if it were a transverse wiggler. According to this theory, the handness of the circularly polarized microwave should depend on the guide field configuration. High-gain strong pump equations coupled to these trajectories are used to account for the Massachusetts Institute of Technology reverse guide field results [Phys. Rev. Lett. {bold 67}, 3082 (1991)]. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  10. Microfluidics-Based Laser Guided Cell-Micropatterning System

    PubMed Central

    Erdman, Nick; Schmidt, Lucas; Qin, Wan; Yang, Xiaoqi; Lin, Yongliang; DeSilva, Mauris N; Gao, Bruce Z.

    2014-01-01

    The ability to place individual cells into an engineered microenvironment in a cell-culture model is critical for the study of in vivo-relevant cell-cell and cell-extracellular matrix interactions. Microfluidics provides a high-throughput modality to inject various cell types into a microenvironment. Laser guided systems provide the high spatial and temporal resolution necessary for single-cell micropatterning. Combining these two techniques, the authors designed, constructed, tested, and evaluated 1) a novel removable microfluidics-based cell-delivery biochip and 2) a combined system that uses the novel biochip coupled with a laser guided cell-micropatterning system to place individual cells into both 2D and 3D arrays. Cell-suspensions of chick forebrain neurons and glial cells were loaded into their respective inlet reservoirs and traversed the microfluidic channels until reaching the outlet ports. Individual cells were trapped and guided from the outlet of a microfluidic channel to a target site on the cell-culture substrate. At the target site, 2D and 3D pattern arrays were constructed with micron-level accuracy. Single-cell manipulation was accomplished at a rate of 150 μm/s in the radial plane and 50 μm/s in the axial direction of the laser beam. Results demonstrated that a single-cell can typically be patterned in 20-30 seconds, and that highly accurate and reproducible cellular arrays and systems can be achieved through coupling the microfluidics-based cell-delivery biochip with the laser guided system. PMID:25190714

  11. Guiding-center equations for electrons in ultraintense laser fields

    SciTech Connect

    Moore, J.E.; Fisch, N.J. )

    1994-05-01

    The guiding-center equations are derived for electrons in arbitrarily intense laser fields also subject to external fields and ponderomotive forces. Exhibiting the relativistic mass increase of the oscillating electrons, a simple frame-invariant equation is shown to govern the behavior of the electrons for sufficiently weak background fields and ponderomotive forces. The parameter regime for which such a formulation is valid is made precise, and some predictions of the equation are checked by numerical simulation.

  12. Guiding-center equations for electrons in ultraintense laser fields

    SciTech Connect

    Moore, J.E.; Fisch, N.J.

    1994-01-01

    The guiding-center equations are derived for electrons in arbitrarily intense laser fields also subject to external fields and ponderomotive forces. Exhibiting the relativistic mass increase of the oscillating electrons, a simple frame-invariant equation is shown to govern the behavior of the electrons for sufficiently weak background fields and ponderomotive forces. The parameter regime for which such a formulation is valid is made precise, and some predictions of the equation are checked by numerical simulation.

  13. Effects of laser beam propagation and saturation on the spatial shape of sodium laser guide stars.

    PubMed

    Marc, Fabien; Guillet de Chatellus, Hugues; Pique, Jean-Paul

    2009-03-30

    The possibility to produce diffraction-limited images by large telescopes through Adaptive Optics is closely linked to the precision of measurement of the position of the guide star on the wavefront sensor. In the case of laser guide stars, many parameters can lead to a strong distortion on the shape of the LGS spot. Here we study the influence of both the saturation of the sodium layer excited by different types of lasers, the spatial quality of the laser mode at the ground and the influence of the atmospheric turbulence on the upward propagation of the laser beam. Both shape and intensity of the LGS spot are found to depend strongly on these three effects with important consequences on the precision on the wavefront analysis. PMID:19333251

  14. ARGOS: the laser guide star system for the LBT

    NASA Astrophysics Data System (ADS)

    Rabien, S.; Ageorges, N.; Barl, L.; Beckmann, U.; Blümchen, T.; Bonaglia, M.; Borelli, J. L.; Brynnel, J.; Busoni, L.; Carbonaro, L.; Davies, R.; Deysenroth, M.; Durney, O.; Elberich, M.; Esposito, S.; Gasho, V.; Gässler, W.; Gemperlein, H.; Genzel, R.; Green, R.; Haug, M.; Hart, M. L.; Hubbard, P.; Kanneganti, S.; Masciadri, E.; Noenickx, J.; Orban de Xivry, G.; Peter, D.; Quirrenbach, A.; Rademacher, M.; Rix, H. W.; Salinari, P.; Schwab, C.; Storm, J.; Strüder, L.; Thiel, M.; Weigelt, G.; Ziegleder, J.

    2010-07-01

    ARGOS is the Laser Guide Star adaptive optics system for the Large Binocular Telescope. Aiming for a wide field adaptive optics correction, ARGOS will equip both sides of LBT with a multi laser beacon system and corresponding wavefront sensors, driving LBT's adaptive secondary mirrors. Utilizing high power pulsed green lasers the artificial beacons are generated via Rayleigh scattering in earth's atmosphere. ARGOS will project a set of three guide stars above each of LBT's mirrors in a wide constellation. The returning scattered light, sensitive particular to the turbulence close to ground, is detected in a gated wavefront sensor system. Measuring and correcting the ground layers of the optical distortions enables ARGOS to achieve a correction over a very wide field of view. Taking advantage of this wide field correction, the science that can be done with the multi object spectrographs LUCIFER will be boosted by higher spatial resolution and strongly enhanced flux for spectroscopy. Apart from the wide field correction ARGOS delivers in its ground layer mode, we foresee a diffraction limited operation with a hybrid Sodium laser Rayleigh beacon combination.

  15. Experimental research on water-jet guided laser processing

    NASA Astrophysics Data System (ADS)

    Li, Ling; Wang, Yang; Yang, Lijun; Chu, Jiecheng

    2007-01-01

    The water-jet guided laser processing is a new compound micro-machining process in which the laser beam passes through the water-jet by full reflection onto the workpiece. In this paper, a new key component:the coupling unit was designed and which would form a long, slim, high-pressure and stable water-jet. The couple unit made the fluid field in the chamber symmetry; the coupling quality of the laser beam and the water-jet could be easily detected by CCD camera. For its excellent surface quality, the nozzle with a \\fgr 0.18mm hole got better machining effect than other nozzles. Aiming at finding optimum machining parameters, experiments were carried out. The results showed the attenuation of laser energy bore relation to water-jet stability. The energy intensity distributed over the water-jet cross section nearly homogeneous and the laser energy nearly did not decrease in long working distance. When water-jet pressure was high, efficient cooling of the workpiece prevented burrs, cracks and heat affected zone from forming. During cutting Si wafer process, nearly no cracking was found; Adjusting reasonable laser parameters grooving 65Mn, the machining accuracy would combine with the speed.

  16. Return flux budget of polychromatic laser guide stars.

    PubMed

    Guillet de Chatellus, Hugues; Pique, Jean-Paul; Moldovan, Ioana Cristina

    2008-02-01

    The polychromatic laser guide star (PLGS) is one of the solutions proposed to extend the sky coverage by large telescopes to 100% by enabling a complete knowledge of all perturbation orders of the wavefront. The knowledge of the tip-tilt is deduced from the monitoring of the chromatic components of the PLGS, from 330 nm to the visible or near infrared. Here we study the original scheme to create the PLGS by resonant excitation of the mesospheric sodium by two pulsed lasers (tens of kilohertz repetition rate, tens of watts average power, tens of nanoseconds pulse duration), at 589 and 569 nm, respectively. The efficiency of this process is investigated numerically by means of both Bloch equation and rate equation models. The influence of numerous laser parameters is studied. In the best case, having optimized all laser parameters, the return flux at 330 nm should not exceed 7x10(4) photons/s/m2 for 2x18 W laser average power at the mesosphere. This maximum is obtained for a modeless laser whose spot diameter corresponds to 4 times the diffraction limit. For a diffraction-limited spot, the return flux falls down to 4x10(4)photons/s/m2. PMID:18246174

  17. Optical guiding and beam bending in free-electron lasers

    SciTech Connect

    Scharlemann, E.T.

    1987-01-01

    The electron beam in a free-electron laser (FEL) can act as an optical fiber, guiding or bending the optical beam. The refractive and gain effects of the bunched electron beam can compensate for diffraction, making possible wigglers that are many Rayleigh ranges (i.e., characteristic diffraction lengths) long. The origin of optical guiding can be understood by examining gain and refractive guiding in a fiber with a complex index of refraction, providing a mathematical description applicable also to the FEL, with some extensions. In the exponential gain regime of the FEL, the electron equations of motion must be included, but a self-consistent description of exponential gain with diffraction fully included becomes possible. The origin of the effective index of refraction of an FEL is illustrated with a simple example of bunched, radiating dipoles. Some of the properties of the index of refraction are described. The limited experimental evidence for optical beam bending is summarized. The evidence does not yet provide conclusive proof of the existence of optical guiding, but supports the idea. Finally, the importance of refractive guiding for the performance of a high-gain tapered-wiggler FEL amplifier is illustrated with numerical simulations.

  18. Laser Research and Development Studies for Laser Guide Star Systems

    SciTech Connect

    Pennington, D.; Beach, R.; Ebbers, C.; Erbert, G.; Nguyen, H.; Page, R.; Payne, S.; Perry, M.

    2000-02-23

    In this paper we consider two CW solid state laser approaches to a 589 nm LGS system. Both are based on the technique of sum-frequency generation, but differ in the cavity architecture. Both technologies are very promising and are worth of further consideration. This preliminary proposal is intended to encompass both designs. A down select shall be performed early in the project execution to focus on the most promising option. The two design options consist of: (1) A dual-frequency resonator with intra-cavity doubling in LB0 offers the promise of a simple architecture and may scale more easily to high power. This design has been shown to be highly reliable, efficient and high power when used in frequency-doubled Nd:YAG lasers for programs at LLNL and in commercial products. The challenge in this design is the demonstration of a high power13 18 nm oscillator with adequate suppression of the 1064 nm line. (2) A MOPA based design uses commercial low power oscillators to produce both wavelengths, then amplifies the wavelengths before doubling. This design requires the demonstration of a 1318 nm amplifier, though the design is scaled from a kW CW amplifier already delivered to a customer at a different wavelength. The design must also demonstrate high power scaling of sum-frequency generation in the relatively new nonlinear material, PPLN. The first step in the process would be to further evaluate the two conceptual options for technical feasibility, cost and constructability. Then a down selection to one design would be conducted. Finally, R&D on that design would then proceed. Minimal testing should be required for this selection. The majority of the funding received would be allocated to development of the design selected.

  19. On Sky Validation of the Polychromatic Laser Guide Star Concept

    NASA Astrophysics Data System (ADS)

    Girard, J.

    2005-10-01

    The atmospheric turbulence affects image quality and causes angular resolution losses at the focus of large ground based optical telescopes. Real time adaptive optics (AO) corrects wave front distortions measured with at least one bright reference source located within a tiny isoplanatic angle from the science object. At visible wavelengths, the probability to find one such natural star is ridiculously small. The laser guide star (LGS) solves the problem but the overall wavefront slope (referred here as tilt) remains undetermined. The Polychromatic Laser Guide Star will allow the use of AO with full sky coverage. Based on the tilt chromaticity, a multicolor reference spot is created in the upper atmosphere and the differential tilt is measured between two wavelengths to retrieve the tilt itself. In the present thesis, I describe ATTILA, an experiment designed to prove the feasibility of the concept in astronomical conditions. Observations carried on at Observatoire de Haute Provence on natural stars allowed us to establish the proportionality law that links the tilt and the differential tilt for the first time. A temporal monitoring of the two signals shows a good correlation. The accuracy obtained on the slope (about one Airy disk ) let us be optimistic for the future full ELP-OA demonstrator with lasers. This work required an in-depth characterization of a detector featuring the novel EMCCD technology as well as the implementation and tests of pendular seismometers dedicated to measure telescope angular vibrations.

  20. ISIS topside-sounder Plasma-wave investigations as guides to desired Virtual Wave Observatory (VWO) data search capabilities

    NASA Astrophysics Data System (ADS)

    Benson, R. F.; Fung, S. F.

    2008-12-01

    Many plasma-wave phenomena, observed by space-borne radio sounders, cannot be properly explained in terms of wave propagation in a cold plasma consisting of mobile electrons and infinitely massive positive ions. These phenomena include signals known as plasma resonances. The principal resonances at the harmonics of the electron cyclotron frequency, the plasma frequency, and the upper-hybrid frequency are well explained by the warm-plasma propagation of sounder-generated electrostatic waves. Other resonances have been attributed to sounder-stimulated plasma instability and non-linear effects, eigenmodes of cylindrical electromagnetic plasma oscillations, and plasma memory processes. Data from the topside sounders of the International Satellites for Ionospheric Studies (ISIS) program played a major role in these interpretations. A data transformation and preservation effort at the Goddard Space Flight Center has produced digital ISIS topside ionograms and a metadata search program that has enabled some recent discoveries pertaining to the physics of these plasma resonances. For example, data records were obtained that enabled the long-standing question (several decades) of the origin of the plasma resonance at the fundamental electron cyclotron frequency to be explained [Muldrew, Radio Sci., 2006]. These data-search capabilities, and the science enabled by them, will be presented as a guide to desired data search capabilities to be included in the Virtual Wave Observatory (VWO).

  1. ISIS Topside-Sounder Plasma-Wave Investigations as Guides to Desired Virtual Wave Observatory (VWO) Data Search Capabilities

    NASA Technical Reports Server (NTRS)

    Benson, Robert F.; Fung, Shing F.

    2008-01-01

    Many plasma-wave phenomena, observed by space-borne radio sounders, cannot be properly explained in terms of wave propagation in a cold plasma consisting of mobile electrons and infinitely massive positive ions. These phenomena include signals known as plasma resonances. The principal resonances at the harmonics of the electron cyclotron frequency, the plasma frequency, and the upper-hybrid frequency are well explained by the warm-plasma propagation of sounder-generated electrostatic waves, Other resonances have been attributed to sounder-stimulated plasma instability and non-linear effects, eigenmodes of cylindrical electromagnetic plasma oscillations, and plasma memory processes. Data from the topside sounders of the International Satellites for Ionospheric Studies (ISIS) program played a major role in these interpretations. A data transformation and preservation effort at the Goddard Space Flight Center has produced digital ISIS topside ionograms and a metadata search program that has enabled some recent discoveries pertaining to the physics of these plasma resonances. For example, data records were obtained that enabled the long-standing question (several decades) of the origin of the plasma resonance at the fundamental electron cyclotron frequency to be explained [Muldrew, Radio Sci., 2006]. These data-search capabilities, and the science enabled by them, will be presented as a guide to desired data search capabilities to be included in the Virtual Wave Observatory (VWO).

  2. Assembly and test results of the AOF laser guide star units at ESO

    NASA Astrophysics Data System (ADS)

    Hackenberg, W.; Bonaccini Calia, D.; Buzzoni, B.; Comin, M.; Dupuy, C.; Gago, F.; Guidolin, I. M.; Guzman, R.; Holzloehner, R.; Kern, L.; Kirchbauer, J.-.; Lewis, S.; Lizon, J.-.; McLay, S.; Pfrommer, T.; Quattri, M.; Quentin, J.; Ridings, R.

    2014-08-01

    The Four Laser Guide Star Facility (4LGSF) is part of the ESO Adaptive Optics Facility, in which one of the VLT telescopes, UT4, is transformed in an adaptive telescope-equipped with a deformable secondary mirror, two adaptive optics systems at the Nasmyth focii and four sodium laser guide star modular units. In this paper we present the design, the assembly and validation test performed so far in Europe on the first laser guide star unit.

  3. Analysis of Capillary Guided Laser Plasma Accelerator Experiments at LBNL

    SciTech Connect

    Nakamura, K.; Esarey, E.; Leemans, W. P.; Gonsalves, A. J.; Panasenko, D.; Toth, Cs.; Geddes, C. G. R.; Schroeder, C. B.; Lin, C.

    2009-01-22

    Laser wakefield acceleration experiments were carried out by using a hydrogen-filled capillary discharge waveguide. For a 15 mm long, 200 {mu}m diameter capillary, quasi-monoenergetic e-beams up to 300 MeV were observed. By de-tuning discharge delay from optimum guiding performance, self-trapping was found to be stabilized. For a 33 mm long, 300 {mu}m capillary, a parameter regime with high energy electron beams, up to 1 GeV, was found. In this regime, the electron beam peak energy was correlated with the amount of trapped electrons.

  4. Analysis of Capillary Guided Laser Plasma Accelerator Experiments at LBNL

    SciTech Connect

    Advanced Light Source; Nakamura, Kei; Gonsalves, Anthony; Panasenko, Dmitriy; Lin, Chen; Toth, Csaba; Geddes, Cameron; Schroeder, Carl; Esarey, Eric; Leemans, Wim

    2008-09-29

    Laser wakefield acceleration experiments were carried out by using a hydrogen-filledcapillary discharge waveguide. For a 15 mm long, 200 mu m diameter capillary, quasi-monoenergetic e-beams up to 300 MeV were observed. By de-tuning discharge delay from optimum guiding performance, self-trapping was found to be stabilized. For a 33 mm long, 300 mu m capillary, a parameter regime with high energy electron beams, up to 1 GeV, was found. In this regime, the electron beam peak energy was correlated with the amount of trapped electrons.

  5. Transurethral ultrasound-guided laser prostatectomy: initial Luebeck experince

    NASA Astrophysics Data System (ADS)

    Thomas, Stephen; Spitzenpfeil, Elisabeth; Knipper, Ansgar; Jocham, Dieter

    1994-02-01

    Transurethral ultrasound guided laser prostatectomy is one of the most promising alternative invasive treatment modalities for benign prostatic hyperplasia. The principle feature is an on- line 3-D controlling of Nd:YAG laser denaturation of the periurethral tissue. Necrotic tissue is not removed, but sloughs away with the urinary stream within weeks. The bleeding hazard during and after the operation is minimal. By leaving the bladder neck untouched, sexual function is not endangered. Thirty-one patients with symptomatic BPH were treated with the TULIP system and followed up for at least 12 weeks. Suprapubic bladder drainage had to be maintained for a mean time of 37 days. Conventional TURP was performed in four patients due to chronic infection, recurrent bleeding, and poor results. Our initial experience with the TULIP system shows it to be very efficient and safe. A longer follow up of a larger patient population is necessary to compare the therapeutic efficiency to conventional transurethral resection.

  6. Laser-assisted guiding of electric discharges around objects

    PubMed Central

    Clerici, Matteo; Hu, Yi; Lassonde, Philippe; Milián, Carles; Couairon, Arnaud; Christodoulides, Demetrios N.; Chen, Zhigang; Razzari, Luca; Vidal, François; Légaré, François; Faccio, Daniele; Morandotti, Roberto

    2015-01-01

    Electric breakdown in air occurs for electric fields exceeding 34 kV/cm and results in a large current surge that propagates along unpredictable trajectories. Guiding such currents across specific paths in a controllable manner could allow protection against lightning strikes and high-voltage capacitor discharges. Such capabilities can be used for delivering charge to specific targets, for electronic jamming, or for applications associated with electric welding and machining. We show that judiciously shaped laser radiation can be effectively used to manipulate the discharge along a complex path and to produce electric discharges that unfold along a predefined trajectory. Remarkably, such laser-induced arcing can even circumvent an object that completely occludes the line of sight. PMID:26601188

  7. Laser-assisted guiding of electric discharges around objects.

    PubMed

    Clerici, Matteo; Hu, Yi; Lassonde, Philippe; Milián, Carles; Couairon, Arnaud; Christodoulides, Demetrios N; Chen, Zhigang; Razzari, Luca; Vidal, François; Légaré, François; Faccio, Daniele; Morandotti, Roberto

    2015-06-01

    Electric breakdown in air occurs for electric fields exceeding 34 kV/cm and results in a large current surge that propagates along unpredictable trajectories. Guiding such currents across specific paths in a controllable manner could allow protection against lightning strikes and high-voltage capacitor discharges. Such capabilities can be used for delivering charge to specific targets, for electronic jamming, or for applications associated with electric welding and machining. We show that judiciously shaped laser radiation can be effectively used to manipulate the discharge along a complex path and to produce electric discharges that unfold along a predefined trajectory. Remarkably, such laser-induced arcing can even circumvent an object that completely occludes the line of sight. PMID:26601188

  8. Laser induced electron acceleration in an ion-channel guiding

    SciTech Connect

    Esmaeilzadeh, Mahdi; Taghavi, Amin; Hanifpour, Maryam

    2011-09-15

    Direct electron acceleration by a propagating laser pulse of circular polarization in an ion-channel guiding is studied by developing a relativistic three-dimensional single particle code. The electron chaotic dynamic is also studied using time series, power spectrum, and Liapunov exponent. It is found that the electron motion is regular (non-chaotic) for laser pulse with short time duration, while for long enough time duration, the electron motion may be chaotic. In the case of non-chaotic motion, the electron can gain and retain very high energy in the presence of ion-channel before reaching the steady-state, whereas in the case of chaotic motion, the electron gains energy and then loses it very rapidly in an unpredictable manner.

  9. A novel laser angioplasty guided hollow fiber using mid-infrared laser

    NASA Astrophysics Data System (ADS)

    Yoshihashi-Suzuki, Sachiko; Yamada, Shinya; Sato, Izuru; Awazu, Kunio

    2006-02-01

    We have proposed selective removal of cholesterol ester by infrared laser of wavelength with 5.75 μm irradiation; the wavelength of 5.75 μm correspond with the ester bond C=O stretching vibration. The flexible laser guiding line and a compact light source are required for our proposal. We used a compact mid-infrared tunable laser by difference frequency generation; DFG laser was developed for substitute light source of free electron laser. In the present work, first, we have developed hollow optical fiber with a diamond lens-tip to deliver DFG laser in the blood vessel and evaluated the transmission of DFG laser from 5.5 μm to 7.5 μm. The transmission of 5.75 μm is about 65%, the DFG beam was focused on the tip of fiber by diamond lens-tip. Secondly, we performed the selective removal experiment of cholesterol ester using the hollow optical fiber with diamond lens-tip and DFG laser. The sample used a two layer model, cholesterol oleate and gelatin. The cholesterol oleate was decomposed by 5.75 μm DFG irradiation with 3.8 W/cm2.

  10. Time transfer between the Goddard Optical Research Facility and the U.S. Naval Observatory using 100 picosecond laser pulses

    NASA Technical Reports Server (NTRS)

    Alley, C. O.; Rayner, J. D.; Steggerda, C. A.; Mullendore, J. V.; Small, L.; Wagner, S.

    1983-01-01

    A horizontal two-way time comparison link in air between the University of Maryland laser ranging and time transfer equipment at the Goddard Optical Research Facility (GORF) 1.2 m telescope and the Time Services Division of the U.S. Naval Observatory (USNO) was established. Flat mirrors of 25 cm and 30 cm diameter respectively were placed on top of the Washington Cathedral and on a water tower at the Beltsville Agricultural Research Center. Two optical corner reflectors at the USNO reflect the laser pulses back to the GORF. Light pulses of 100 ps duration and an energy of several hundred microjoules are sent at the rate of 10 pulses per second. The detection at the USNO is by means of an RCA C30902E avalanche photodiode and the timing is accomplished by an HP 5370A computing counter and an HP 1000 computer with respect to a 10 pps pulse train from the Master Clock.

  11. From Dye Laser Factory to Portable Semiconductor Laser: Four Generations of Sodium Guide Star Lasers for Adaptive Optics in Astronomy and Space Situational Awareness

    NASA Astrophysics Data System (ADS)

    d'Orgeville, C.; Fetzer, G.

    This presentation recalls the history of sodium guide star laser systems used in astronomy and space situational awareness adaptive optics, analysing the impact that sodium laser technology evolution has had on routine telescope operations. While it would not be practical to describe every single sodium guide star laser system developed to date, it is possible to characterize their evolution in broad technology terms. The first generation of sodium lasers used dye laser technology to create the first sodium laser guide stars in Hawaii, California, and Spain in the late 1980's and 1990's. These experimental systems were turned into the first laser guide star facilities to equip medium-to-large diameter adaptive optics telescopes, opening a new era of LGS AO-enabled diffraction-limited imaging from the ground. Although they produced exciting scientific results, these laser guide star facilities were large, power-hungry and messy. In the USA, a second-generation of sodium lasers was developed in the 2000's that used cleaner, yet still large and complex, solid-state laser technology. These are the systems in routine operation at the 8-10m class astronomical telescopes and 4m-class satellite imaging facilities today. Meanwhile in Europe, a third generation of sodium lasers was being developed using inherently compact and efficient fiber laser technology, and resulting in the only commercially available sodium guide star laser system to date. Fiber-based sodium lasers will be deployed at two astronomical telescopes and at least one space debris tracking station this year. Although highly promising, these systems remain significantly expensive and they have yet to demonstrate high performance in the field. We are proposing to develop a fourth generation of sodium lasers: based on semiconductor technology, these lasers could provide the final solution to the problem of sodium laser guide star adaptive optics for all astronomy and space situational awareness applications.

  12. Study of optimal wavefront sensing with elongated laser guide stars

    NASA Astrophysics Data System (ADS)

    Thomas, S. J.; Adkins, S.; Gavel, D.; Fusco, T.; Michau, V.

    2008-06-01

    Over the past decade, adaptive optics (AO) has become an established method for overcoming the effects of atmospheric turbulence on both astronomical imaging and spectroscopic observations. These systems are now beginning to make extensive use of laser guide star (LGS) techniques to improve performance and provide increased sky coverage. Sodium LGS AO employs one or more lasers at 589-nm wavelength to produce an artificial guide star through excitation of sodium atoms in the mesosphere (90 km altitude). Because of its dependence on the abundance and distribution of sodium atoms in the mesosphere, this approach has its own unique set of difficulties not seen with natural stars. The sodium layer exhibits time-dependent variations in density and altitude, and since it is at a finite range, the LGS images become elongated due to the thickness of the layer and the offset between the laser projection point and the subapertures of a Shack-Hartmann wavefront sensor (SHWFS). Elongation causes the LGS image to be spread out resulting in a decrease in the signal-to-noise ratio which, in turn, leads to an increase in SHWFS measurement error and therefore an increased error in wavefront phase reconstruction. To address the problem of elongation, and also to provide a higher level of readout performance and reduced readout noise, a new type of charge-coupled device (CCD) is now under development for Shack-Hartmann wavefront sensing called the polar coordinate CCD. In this device, discrete imaging arrays are provided in each SHWFS subaperture and the size, shape and orientation of each discrete imaging array are adjusted to optimally sample the LGS image. The device is referred to as the polar coordinate CCD because the location of each imager is defined by a polar coordinate system centred on the laser guide star projection point. This concept is especially suited to Extremely Large Telescopes (ELTs) where the effect of perspective elongation is a significant factor. In this

  13. Laser micromachining in microelectronic industry by water-jet-guided laser

    NASA Astrophysics Data System (ADS)

    Sibailly, Ochelio; Wagner, Frank; Richerzhagen, Bernold

    2004-07-01

    The water jet guided laser technology (laser Microjet«) has been developed since 10 years now and is used for several applications in the semiconductor industry. In this unique laser cutting technique, a thin stable water jet is used as a waveguide for a high-power Nd:YAG laser, that may be frequency doubled or tripled. This presentation gives an overview of the semiconductor machining applications of this technique and relates the different applications to alternative techniques and the different functions of the water jet. The water jet cools the sample when the laser is not emitting, it expels the melt very efficiently, and it avoids that the few generated particles can attach to the wafer surface. The strengths of Laser Microjet« machining are free shape cutting and cutting of thin wafers. In free shape cutting the system leads to much better results in terms of fracture strength and process simplicity than the classical laser cutting methods. In thin wafer cutting astonishing cutting speeds are obtained at very good cut quality (200 mm/s in 50 micron thick wafers). Due to the free shape cutting possibilities drilling and slotting with aspect ratios of up to 5 is also possible resulting in the same edge quality as standard cutting.

  14. Adaptive interferometric velocity measurements using a laser guide star

    NASA Astrophysics Data System (ADS)

    Czarske, J.; Radner, H.; Büttner, L.

    2015-07-01

    We have harnessed the power of programmable photonics devices for an interferometric measurement technique. Laser interferometers are widely used for flow velocity measurements, since they offer high temporal and spatial resolutions. However, often optical wavefront distortions deteriorate the measurement properties. In principle, adaptive optics enables the correction of these disturbances. One challenge is to generate a suitable reference signal for the closed loop operation of the adaptive optics. An adaptive Mach Zehnder interferometer is presented to measure through a dynamic liquid-gas phase boundary, which can lead to a misalignment of the interfering laser beams. In order to generate the reference signal for the closed loop control, the Fresnel reflex of the phase boundary is used as Laser Guide Star (LGS) for the first time to the best of the authors' knowledge. The concept is related to the generation of artificial stars in astronomy, where the light transmitted by the atmosphere is evaluated. However, the adaptive interferometric flow velocity measurements at real world experiments require a different concept, since only the reflected light can be evaluated. The used LGS allows to measure the wavefront distortions induced by the dynamic phase boundary. Two biaxial electromagnetically driven steering mirrors are employed to correct the wavefront distortions. This opens up the possibility for accurate flow measurements through a dynamic phase boundary using only one optical access. Our work represents a paradigm shift in interferometric velocity measurement techniques from using static to dynamic optical elements.

  15. Photometric observations of a polychromatic laser guide star.

    PubMed

    Foy, R; Tallon, M; Tallon-Bosc, I; Thiébaut, E; Vaillant, J; Foy, F C; Robert, D; Friedman, H; Biraben, F; Grynberg, G; Gex, J P; Mens, A; Migus, A; Weulersse, J M; Butler, D J

    2000-12-01

    We report the photometric observation of a polychromatic laser guide star (PLGS) using the AVLIS laser at the Lawrence Livermore National Laboratory (LLNL). The process aims at providing a measurement of the tilt of the incoming wave front at a telescope induced by atmospheric turbulence. It relies on the two-photon coherent excitation of the 4D5/2 energy level of sodium atoms in the mesosphere. We used two laser beams at 589 and 569 nm, with a maximum total average output power of approximately 350 W. For the purpose of photometric calibration, a natural star was observed simultaneously through the same instrument as the PLGS at the focus of the LLNL 50-cm telescope. Photometric measurements of the 330-nm return flux confirm our previous theoretical studies that the PLGS process should allow us at a later stage to correct for the tilt at wavelengths as short as approximately 1 microm at good astronomical sites. They show also that, at saturation of two-photon coherent absorption in the mesosphere, the backscattered flux increases by a factor of approximately 2 when the pulse repetition rate decreases by a factor of 3 at constant average power. This unexpected behavior is briefly discussed. PMID:11140483

  16. A Monte Carlo simulation for predicting photon return from sodium laser guide star

    NASA Astrophysics Data System (ADS)

    Feng, Lu; Kibblewhite, Edward; Jin, Kai; Xue, Suijian; Shen, Zhixia; Bo, Yong; Zuo, Junwei; Wei, Kai

    2015-10-01

    Sodium laser guide star is an ideal source for astronomical adaptive optics system correcting wave-front aberration caused by atmospheric turbulence. However, the cost and difficulties to manufacture a compact high quality sodium laser with power higher than 20W is not a guarantee that the laser will provide a bright enough laser guide star due to the physics of sodium atom in the atmosphere. It would be helpful if a prediction tool could provide the estimation of photon generating performance for arbitrary laser output formats, before an actual laser were designed. Based on rate equation, we developed a Monte Carlo simulation software that could be used to predict sodium laser guide star generating performance for arbitrary laser formats. In this paper, we will describe the model of our simulation, its implementation and present comparison results with field test data.

  17. Large scale Tesla coil guided discharges initiated by femtosecond laser filamentation in air

    NASA Astrophysics Data System (ADS)

    Arantchouk, L.; Point, G.; Brelet, Y.; Prade, B.; Carbonnel, J.; André, Y.-B.; Mysyrowicz, A.; Houard, A.

    2014-07-01

    The guiding of meter scale electric discharges produced in air by a Tesla coil is realized in laboratory using a focused terawatt laser pulse undergoing filamentation. The influence of the focus position, the laser arrival time, or the gap length is studied to determine the best conditions for efficient laser guiding. Discharge parameters such as delay, jitter, and resistance are characterized. An increase of the discharge length by a factor 5 has been achieved with the laser filaments, corresponding to a mean breakdown field of 2 kV/cm for a 1.8 m gap length. Consecutive guided discharges at a repetition rate of 10 Hz are also reported.

  18. Experimental assessment of the matched filter for laser guide star wavefront sensing.

    PubMed

    Conan, Rodolphe; Lardière, Olivier; Herriot, Glen; Bradley, Colin; Jackson, Kate

    2009-02-20

    Laser guide star wavefront sensing comes with several limitations. When imaged with a Shack-Hartmann wavefront sensor, the laser guide star is seen as extended sources elongated in the directions given by the lenslet locations and the laser axis. A test bed has been built in the Adaptive Optics Laboratory of the University of Victoria that reproduces this effect as seen on extremely large telescopes. A new wavefront sensing algorithm, the matched filter, has been implemented and its performance assessed with the test bed. Its ability to mitigate laser guide star aberrations by tracking the sodium layer fluctuations in a closed loop adaptive optics system is shown. PMID:23567582

  19. High-Precision Lunar Ranging and Gravitational Parameter Estimation With the Apache Point Observatory Lunar Laser-ranging Operation

    NASA Astrophysics Data System (ADS)

    Johnson, Nathan H.

    This dissertation is concerned with several problems of instrumentation and data analysis encountered by the Apache Point Observatory Lunar Laser-ranging Operation. Chapter 2 considers crosstalk between elements of a single-photon avalanche photodiode detector. Experimental and analytic methods were developed to determine crosstalk rates, and empirical findings are presented. Chapter 3 details electronics developments that have improved the quality of data collected by detectors of the same type. Chapter 4 explores the challenges of estimating gravitational parameters on the basis of ranging data collected by this and other experiments and presents resampling techniques for the derivation of standard errors for estimates of such parameters determined by the Planetary Ephemeris Program (PEP), a solar-system model and data-fitting code. Possible directions for future work are discussed in Chapter 5. A manual of instructions for working with PEP is presented as an appendix.

  20. Guiding of intense laser pulse in uniform plasmas and preformed plasma channels

    SciTech Connect

    Wang Jingwei; Lei, A. L.; Wang Xin; Yu Wei; Yu, M. Y.; Senecha, V. K.; Wang, X. G.; Murakami, M.; Mima, K.

    2010-10-15

    Guiding of laser pulse in uniform plasmas and preformed plasma channels is investigated. The self-guiding mechanisms for these two cases are quite different. It is found that an intense laser pulse can be steadily self-guided in underdense plasmas with nearly a constant spot size if the self-consistently generated electron cavity has a sufficiently steep density gradient at the edge. In a preformed plasma channel, however, laser guiding is maintained mainly by the balance between the light diffraction and focusing. The latter is induced by the wall plasmas which greatly reduce the local dielectric constant. It is shown that the self-guiding of a laser pulse in uniform plasmas requires tens of terawatts power, but those that are in preformed channels can be realized with only a terawatt power.

  1. Development of laser guide stars and adaptive optics for large astronomical telescopes

    SciTech Connect

    Max, C.E.; Avicola, K.; Bissinger, H.; Brase, J.M.; Gavel, D.T.; Friedman, H.; Morris, J.R.; Olivier, S.S.; Rapp, D.; Salmon, J.T.; Waltjen, K.

    1992-06-29

    We describe a feasibility experiment to demonstrate high-order adaptive optics using a sodium-layer laser guide star. We use the copper-vapor-pumped dye lasers developed for LLNL's atomic Vapor Laser Isotope Separation program to create the laser guide star. Closed-loop adaptive corrections will be accomplished using a 69-subaperture adaptive optics system on a one-meter telescope at LLNL. The laser bream is projected upwards from a beam director approximately 5 meters away from the main telescope, and is expected to form a spot 1-2 meters in diameter at the atmospheric sodium layer (95 km altitude). We describe the overall system architecture and adaptive optics components, and analyze the expected performance. Our long-term goal is to develop sodium-layer laser guide stars and adaptive optics for large astronomical telescopes. We discuss preliminary design trade-offs for the Keck Telescope at Mauna Kea.

  2. Development of laser guide stars and adaptive optics for large astronomical telescopes

    SciTech Connect

    Max, C.E.; Avicola, K.; Bissinger, H.; Brase, J.M.; Gavel, D.T.; Friedman, H.; Morris, J.R.; Olivier, S.S.; Rapp, D.; Salmon, J.T.; Waltjen, K.

    1992-06-29

    We describe a feasibility experiment to demonstrate high-order adaptive optics using a sodium-layer laser guide star. We use the copper-vapor-pumped dye lasers developed for LLNL`s atomic Vapor Laser Isotope Separation program to create the laser guide star. Closed-loop adaptive corrections will be accomplished using a 69-subaperture adaptive optics system on a one-meter telescope at LLNL. The laser bream is projected upwards from a beam director approximately 5 meters away from the main telescope, and is expected to form a spot 1-2 meters in diameter at the atmospheric sodium layer (95 km altitude). We describe the overall system architecture and adaptive optics components, and analyze the expected performance. Our long-term goal is to develop sodium-layer laser guide stars and adaptive optics for large astronomical telescopes. We discuss preliminary design trade-offs for the Keck Telescope at Mauna Kea.

  3. Feasibility experiment for sodium-layer laser guide stars at the Lawrence Livermore National Laboratory

    SciTech Connect

    Max, C.; Avicola, K.; Bissinger, H.; Brase, J.; Gavel, D.; Friedman, H.; Morris, J.; Oliver, S.; Salmon, J.T.; Waltjen, K.

    1992-03-09

    We are developing a feasibility experiment to demonstrate closed-loop adaptive optics using a sodium-layer laser guide star. We will use the copper-vapor-pumped dye lasers developed for LLNL's Atomic Vapor Laser Isotope Separation Program to create the laser guide star. Closed-loop adaptive corrections will be accomplished using a 69-subaperture adaptive optics system on a one-meter telescope at LLNL. The laser beam will be projected upwards from a beam director approximately 5 meters away from the main telescope, and is expected to form a spot about a meter in diameter at the atmospheric sodium layer (at an altitude of 95 km). Details of the adaptive optics components and an analysis of the expected performance will be presented in companion papers for this Workshop. Here we summarize the overall architecture and system objectives. The long-term goal of our effort is to develop laser guide stars and adaptive optics for large astronomical telescopes.

  4. Laser spectroscopy of atoms guided by evanescent waves in micron-sized hollow optical fibers

    SciTech Connect

    Ito, H.; Nakata, T.; Sakaki, K.; Ohtsu, M.; Lee, K.I.; Jhe, W.

    1996-06-01

    We report the first laser spectroscopic experiments on the Rb beam guided by blue-detuned evanescent waves in micron-sized hollow fibers. The two-step photoionization spectra show the long-range dispersive properties of dipole interaction between guided atoms and evanescent waves. A large enhancement factor of 20in in the transmitted atomic flux is obtained at optimal conditions and the total guidance efficiency is estimated to be above 40{percent}. The state- and species-selective guide with proper frequency detunings of the guide laser realizes in-line spatial separation of two stable Rb isotopes. {copyright} {ital 1996 The American Physical Society.}

  5. Reporting guide for laser-light shows and displays (21 CFR 1002)

    SciTech Connect

    Not Available

    1988-05-01

    The guide is to be used for reporting laser-light shows or displays incorporating Class IIIb or Class IV lasers only. Separate reports are not required for shows or displays that incorporate Class I, IIa, II, or IIIa laser-projection systems. Such show descriptions must be included in the user instructions and the report for the laser projector. Laser projectors used in any light shows or displays regardless of the class of the projector must be certified by the manufacturer and reported using the guide titled, Guide for Preparing Initial Reports and Model Change Reports on Lasers and Products Containing Lasers, HHS Publication FDA 86-8259. These guides assist manufacturers in providing the information that the Center for Devices and Radiological Health (CDRH) needs to determine how laser-light-shown projections and laser-light shows comply with the Federal standard for laser products (21 CDR 1040.10 and 1040.11) and with the conditions of an approved variance.

  6. Split atmospheric tomography using laser and natural guide stars.

    PubMed

    Gilles, Luc; Ellerbroek, Brent L

    2008-10-01

    Laser guide star (LGS) atmospheric tomography is described in the literature as integrated minimum-variance tomographic wavefront reconstruction from a concatenated wavefront-sensor measurement vector consisting of many high-order, tip/tilt (TT)-removed LGS measurements, supplemented by a few low-order natural guide star (NGS) components essential to estimating the TT and tilt anisoplanatism (TA) modes undetectable by the TT-removed LGS wavefront sensors (WFSs). The practical integration of these NGS WFS measurements into the tomography problem is the main subject of this paper. A split control architecture implementing two separate control loops driven independently by closed-loop LGS and NGS measurements is proposed in this context. Its performance is evaluated in extensive wave optics Monte Carlo simulations for the Thirty Meter Telescope (TMT) LGS multiconjugate adaptive optics (MCAO) system, against the delivered performance of the integrated control architecture. Three iterative algorithms are analyzed for atmospheric tomography in both cases: a previously proposed Fourier domain preconditioned conjugate gradient (FDPCG) algorithm, a simple conjugate gradient (CG) algorithm without preconditioning, and a novel layer-oriented block Gauss-Seidel conjugate gradient algorithm (BGS-CG). Provided that enough iterations are performed, all three algorithms yield essentially identical closed-loop residual RMS wavefront errors for both control architectures, with the caveat that a somewhat smaller number of iterations are required by the CG and BGS-CG algorithms for the split approach. These results demonstrate that the split control approach benefits from (i) a simpler formulation of minimum-variance atmospheric tomography allowing for algorithms with reduced computational complexity and cost (processing requirements), (ii) a simpler, more flexible control of the NGS-controlled modes, and (iii) a reduced coupling between the LGS- and NGS-controlled modes. Computation

  7. Comparative Study of Remote Fiber Laser and Water-Jet Guided Laser Cutting of Thin Metal Sheets

    NASA Astrophysics Data System (ADS)

    Hock, Klaus; Adelmann, Benedikt; Hellmann, Ralf

    This article presents a comparison between remote laser cutting with a fiber laser and water-jet guided laser cutting using a 532 nm solid state laser. Complex contours are processed in stainless steel and brass sheets (thickness ≤ 100 μm), respectively. Results for achievable quality and productivity as well as possible applications for both systems are shown and discussed. We sustained dross free cuts with almost no heat affected zone and small kerf width for the water-jet guided process, whereas small dross, notable heat affected zone and varying kerf width where observed for remote cutting. However, process times for the water-jet guided process where considerably higher than those for remote cutting.

  8. Laser ablation of basal cell carcinomas guided by confocal microscopy

    NASA Astrophysics Data System (ADS)

    Sierra, Heidy; Cordova, Miguel; Nehal, Kishwer; Rossi, Anthony; Chen, Chih-Shan Jason; Rajadhyaksha, Milind

    2016-02-01

    Laser ablation offers precise and fast removal of superficial and early nodular types of basal cell carcinomas (BCCs). Nevertheless, the lack of histological confirmation has been a limitation. Reflectance confocal microscopy (RCM) imaging combined with a contrast agent can offer cellular-level histology-like feedback to detect the presence (or absence) of residual BCC directly on the patient. We conducted an ex vivo bench-top study to provide a set of effective ablation parameters (fluence, number of passes) to remove superficial BCCs while also controlling thermal coagulation post-ablation to allow uptake of contrast agent. The results for an Er:YAG laser (2.9 um and pulse duration 250us) show that with 6 passes of 25 J/cm2, thermal coagulation can be effectively controlled, to allow both the uptake of acetic acid (contrast agent) and detection of residual (or absence) BCCs. Confirmation was provided with histological examination. An initial in vivo study on 35 patients shows that the uptake of contrast agent aluminum chloride) and imaging quality is similar to that observed in the ex vivo study. The detection of the presence of residual tumor or complete clearance was confirmed in 10 wounds with (additional) histology and in 25 lesions with follow-up imaging. Our results indicate that resolution is sufficient but further development and use of appropriate contrast agent are necessary to improve sensitivity and specificity. Advances in RCM technology for imaging of lateral and deep margins directly on the patient may provide less invasive, faster and less expensive image-guided approaches for treatment of BCCs.

  9. Design of an infrared camera based aircraft detection system for laser guide star installations

    SciTech Connect

    Friedman, H.; Macintosh, B.

    1996-03-05

    There have been incidents in which the irradiance resulting from laser guide stars have temporarily blinded pilots or passengers of aircraft. An aircraft detection system based on passive near infrared cameras (instead of active radar) is described in this report.

  10. Laser Guiding at Relativistic Intensities and Wakefield ParticleAcceleration in Plasma Channels

    SciTech Connect

    Geddes, C.G.R.; Toth, Cs.; van Tilborg, J.; Esarey, E.; Schroeder, C.B.; Bruhwiler, D.; Nieter, C.; Cary, J.; Leemans, W.P.

    2005-05-01

    High quality electron beams with hundreds of picoCoulombs ofcharge inpercent energy spread above 80 MeV were produced for the firsttime in high gradient laser wakefield accelerators by guiding the drivelaser pulse.

  11. Follow the yellow-orange rabbit: a CCD optimized for wavefront sensing a pulsed sodium laser guide star

    NASA Astrophysics Data System (ADS)

    Beletic, James W.

    2004-09-01

    Most large telescopes are now implementing sodium laser guide star (LGS) adaptive optics (AO) systems. Most of these systems plan to use the Shack-Hartmann approach for wavefront sensing. In these systems, the laser spots that are imaged in the Shack-Hartmann subapertures suffer spot elongation due to the 10 km extent of the sodium layer. The spot elongation extends radially from the projection point, and increases linearly with the distance the subaperture is separated from the laser. For 8-meter class telescopes with laser projection behind the secondary mirror, the spot elongation is ~1 arc sec at the edge of the pupil, and does not significantly affect the performance of the AO system. However, for the coming generation of extremely large telescopes, sodium LGS spot elongation will significantly degrade the quality of wavefront measurement. Attention should now be given to the development of technologies that can reduce or eliminate the spot elongation problem. The laser spot elongation can be greatly reduced by projecting the sodium laser in a series of short (1-3 µsec) pulses. The Lawrence Livermore National Laboratory (LLNL) has been funded to develop a pulsed fiber laser. In parallel, a new kind of wavefront sensor detector must be developed to properly sense the pulsed laser return. In this paper, we present our project that will develop a novel CCD which is optimized for sensing the return from a pulsed sodium LGS. Our CCD design uses custom pixel morphology that aligns the pixels of each subaperture with the radial extension of the LGS spot. This pixel geometry will allow each subaperture to follow the yellow-orange rabbit (i.e. the 589 nm laser pulse) as it traverses the sodium layer, providing optimal sampling of a limited number of detected photons. This CCD will attain photon-noise limited performance at high frame rates, using MOSFET amplifiers that exist today (2-3 electrons noise). However, we seek even lower noise amplifiers, and as part of

  12. A laser guide star wavefront sensor bench demonstrator for TMT.

    PubMed

    Lardiere, Olivier; Conan, Rodolphe; Bradley, Colin; Jackson, Kate; Herriot, Glen

    2008-04-14

    Sodium laser guide stars (LGSs) allow, in theory, Adaptive Optics (AO) systems to reach a full sky coverage, but they have their own limitations. The artificial star is elongated due to the sodium layer thickness, and the temporal and spatial variability of the sodium atom density induces changing errors on wavefront measurements, especially with Extremely Large Telescopes (ELTs) for which the LGS elongation is larger. In the framework of the Thirty-Meter-Telescope project (TMT), the AO-Lab of the University of Victoria (UVic) has built an LGS-simulator test bed in order to assess the performance of new centroiding algorithms for LGS Shack-Hartmann wavefront sensors (SH-WFS). The design of the LGS-bench is presented, as well as laboratory SH-WFS images featuring 29x29 radially elongated spots, simulated for a 30-m pupil. The errors induced by the LGS variations, such as focus and spherical aberrations, are characterized and discussed. This bench is not limited to SH-WFS and can serve as an LGS-simulator test bed to any other LGS-AO projects for which sodium layer fluctuations are an issue. PMID:18542656

  13. Nonlinear study of an ion-channel guiding free-electron laser

    SciTech Connect

    Ouyang, Zhengbiao; Zhang, Shi-Chang

    2015-04-15

    A nonlinear model and simulations of the output power of an ion-channel guiding free-electron laser (FEL) are presented in this paper. Results show that the nonlinear output power of an ion-channel guiding FEL is comparable to that of an axial guide magnetic field FEL. Compared to an axial guide magnetic field FEL, an ion-channel guiding FEL substantially weakens the negative effect of the electron-beam energy spread on the output power due to its advantageous focusing mechanism on the electron motion.

  14. Laser-guided placement of the tibial guide in the transtibial technique for anterior cruciate ligament reconstruction.

    PubMed

    Takahashi, Toshiaki; Takeda, Haruhiko; Watanabe, Seiji; Yamamoto, Haruyasu

    2009-02-01

    In anterior cruciate ligament (ACL) reconstruction, it is important to determine the location and direction of the femoral bone tunnel when using the transtibial technique. Accurately identifying the anatomic location at which to make the femoral bone tunnel for double-bundle ACL reconstruction is not a straightforward procedure. We describe a new method in which the centrum of the femoral tunnel is marked with an awl and a laser beam-guided technique is used to place the tibial pin. This procedure allows us to mark the desired location of the femoral tunnel before drilling the tibial bone tunnel when using the transtibial technique. This is the first report of a laser-guided technique used in arthroscopic surgery. We used a laser beam to determine the location of the femoral tunnel--the anatomic site needed to perform the intra-articular drilling in the tibia. In this technique, a laser pointer is set at the tibial guide, which reflects the laser beam and illuminates the point where the femoral bone tunnel should be made. Our method offers an easy and accurate way to reconfirm the tibial placement before drilling. PMID:19171283

  15. Competency-Based Curriculum Guide for Laser Technology. September 1980-June 1981.

    ERIC Educational Resources Information Center

    Fioroni, John J.

    This document contains materials developed by a project to provide a competency-based curriculum guide for laser technology at the community college level. An abstract of the final report is included. Next, the 17 job competencies determined as necessary to meet the job description of laser technician are listed. A career ladder and qualifications…

  16. Systematic design and analysis of laser-guide-star adaptive-optics systems for large telescopes

    SciTech Connect

    Gavel, D.T.; Morris, J.R.; Vernon, R.G.

    1994-02-01

    The authors discuss the design of laser-guided adaptive-optics systems for the large, 8-10-m-class telescopes. Through proper choice of system components and optimized system design, the laser power that is needed at the astronomical site can be kept to a minimum. 37 refs., 9 figs., 3 tabs.

  17. Installation of two high-sensitivity laser strainmeters in a new underground geodynamical observatory (GEODYN) at Canfranc (Spain)

    NASA Astrophysics Data System (ADS)

    Crescentini, L.; Botta, V.; Amoruso, A.; Bettini, A.

    2012-04-01

    High-sensitivity wide-band strain measurements allow an advanced study of different geodynamic phenomena, both local and global, in a spectrum ranging from short period seismic waves to tectonic deformation. Among the latest results produced by the few high-sensitivity wide-band laser interferometers operating allover the world, the analysis of the strain recorded by the Gran Sasso (Italy) laser interferometers before and after the 2009 L'Aquila earthquake allowed putting tight constraints on earthquake nucleation processes and other pre-seismic phenomena, and detecting the slow diffusive propagation of an aseismic rupture during the first hours following the main event.The Gran Sasso interferometers are operating since several years, proving their high reliability. An improved version of the Gran Sasso interferometers have been recently installed in the Canfranc (Spain) underground Laboratory (LSC). The LSC is located at depth in one of the most seismically active areas in Western Europe, at the Pyrenean chain that marks the boundary between the European plate and the Iberian microplate. These features make it particularly suitable and interesting for hosting an advanced integrated geodynamic observatory (GEODYN), of which the interferometers are part. The first tests on strain data evidence a much lower noise level with respect that the Gran Sasso installations, expecially in the frequency band 0.0001 to 0.1 Hz, suggesting the capability of producing clear records of low-frequency seismic waves, Earth free oscillations, and possible local aseismic stress release. We will give a technical description of the installation, show some examples of recordings, and discuss the local distortion of the deformation field, as obtained by comparing Earth tide predictions and observations.

  18. Advancing adaptive optics technology: Laboratory turbulence simulation and optimization of laser guide stars

    NASA Astrophysics Data System (ADS)

    Rampy, Rachel A.

    optimizing the laser beacons used to bring AO correction to parts of the sky that lack a naturally bright light source for measuring atmospheric distortion. Long pulse length laser guide stars (LGS) that use fluorescence from the D 2 transition in mesospheric sodium are valuable both due to their high altitude, and because they permit Rayleigh blanking and fratricide avoidance in multiple LGS systems. Bloch equation simulations of sodium-light interactions in Mathematica show that certain spectral formats and pulse lengths (on the order of 30 μs), with high duty cycles (20-50%), should be able to achieve photon returns within 10% of what is seen from continuous wave (CW) excitation. Utilizing this recently developed code (called LGSBloch), I investigated the time dependent characteristics of sodium fluorescence. I then identified the optimal format for the new LGS that will be part of the upgrade to the AO system on the Shane 3 meter telescope at the Lick Observatory. I discuss these results, along with their general applicability to other LGS systems, and provide a brief description of the potential benefits of uplink correction. Predictions from the LGSBloch simulation package are compared to data from currently operating LGS systems. For a CW LGS, the return flux measurements and theory show reasonable agreement, but for short pulse lasers, such as those at the Lick and Keck Observatories, the code seems to be overestimating the data by a factor of 2--3. Several tactics to explicate this discrepancy are explored, such as verifying parameters involved in the measurements and including greater detail in the modeling. Although these efforts were unsuccessful at removing the discrepancy, they illuminated other facets of the problem that deserve further consideration. Use of the sophisticated LGSBloch model has allowed detailed study of the evolution of the energy level populations and other physical effects (e.g. Larmor precession, atomic recoil, and collisions). This has

  19. Variable Curvature Mirrors for ELT Laser Guide Star refocusing systems

    NASA Astrophysics Data System (ADS)

    Challita, Zalpha; Hugot, Emmanuel; Ferrari, Marc; Madec, Fabrice; Le Mignant, David; Cuby, Jean-Gabriel

    2011-09-01

    The future generation of Extremely Large Telescopes will require a complex combination of technologies for adaptive optics (AO) systems assisted by laser guide stars (LGS). In this context, LGS defocusing is one of the system issues that can be tackled using active refocusing mirrors such as Variable Curvature Mirrors (VCM). Indeed, the distance from the LGS spot to the telescope pupil ranges from about 80 to 200 km, depending on the Sodium layer altitude and the elevation of the telescope, and induces a large defocusing at the LGS wave-front sensor focal plane. To compensate for that, we propose an original concept including a VCM specifically designed to keep a focused spot on the wave-front sensor: the mirror is made of a thin meniscus bend using a pressure applied on its back face. Due to the large defocusing, the LGS-VCM must be able to change its shape from F/12.5 to F/5, leading to more than 1 mm sag. The VCM benefits of a specific shape with a variable radial thickness distribution, allowing keeping an optical quality better than λ/5 over this very large range of deformation. The work presented here details the analytical development leading to the specific geometry of the active component, the results of finite element analysis and the expected performances in terms of surface error versus the range of refocalisation. Two prototypes have been manufactured to compare the real behaviour of the mirror and the simulations data. Results obtained on the prototypes show that the deformation of the VCM is very close to the simulation, and leads to a realistic concept.

  20. Noise-like pulse in a gain-guided soliton fiber laser.

    PubMed

    Zhao, L M; Tang, D Y; Wu, J; Fu, X Q; Wen, S C

    2007-03-01

    We report on the operation of a passively mode-locked fiber ring laser made of purely positive dispersion fibers and mode-locked by using the nonlinear polarization rotation technique. It was experimentally found that apart from the gain-guided soliton operation the laser can also emit a kind of noise-like pulse. We show numerically that the noise-like pulse emission is caused by the peak power clamping effect of the laser cavity on the gain-guided soliton. PMID:19532451

  1. Noise-like pulse in a gain-guided soliton fiber laser

    NASA Astrophysics Data System (ADS)

    Zhao, L. M.; Tang, D. Y.; Wu, J.; Fu, X. Q.; Wen, S. C.

    2007-03-01

    We report on the operation of a passively mode-locked fiber ring laser made of purely positive dispersion fibers and mode-locked by using the nonlinear polarization rotation technique. It was experimentally found that apart from the gain-guided soliton operation the laser can also emit a kind of noise-like pulse. We show numerically that the noise-like pulse emission is caused by the peak power clamping effect of the laser cavity on the gain-guided soliton.

  2. Guided wave generation and sensing system using a single laser source and optical fibers

    NASA Astrophysics Data System (ADS)

    Lee, Hyeonseok; Park, Hyun-Jun; Sohn, Hoon; Kwon, Il-bum

    2010-04-01

    Structural health monitoring (SHM) techniques based on guided waves have been of great interests to many researchers. Among various SHM devices used for guided wave generation and sensing, lead zirconate titanate (PZT) transducers and fiber Bragg grating (FBG) sensors have been widely used because of their light weight, non-intrusive nature and compactness. To best take advantage of their merits, combination of PZT-based guided wave excitation and FBG-based sensing has been attempted by a few researchers. However, the PZT-based actuation and the FBG-based sensing are basically two independent systems in the past studies. This study proposes an integrated PZT/FBG system using a single laser source. Since power and data delivery is based on optical fibers, it may alleviate problems associated with conventional wire cables such as electromagnetic interference (EMI) and power/data attenuation. The experimental procedure for the proposed system is as follows. First, a tunable laser is used as the common power source for guided wave generation and sensing. The tunable laser beam is modulated and amplified to contain an arbitrary waveform. Then, it is transmitted to the PZT transducer node through an optical fiber for guided wave actuation. The transmitted laser beam is also used with the FBG sensor to measure high-speed strain changes induced by guided waves. Feasibility of the proposed technique has been experimentally demonstrated using aluminum plates. The results show that the proposed system could properly generate and sense the guided waves compared to the conventional methods.

  3. Transendoscopic application of CO2 laser irradiation using the OmniGuide fiber

    NASA Astrophysics Data System (ADS)

    Tate, Lloyd P., Jr.; Elce, Yvonne A.

    2005-04-01

    Transendoscopic laser surgery has been performed in large animals since 1984. It is used to treat many upper respiratory disorders, as well as urogenital diseases. Initially, the Nd:YAG laser was the laser of choice until the early 1990's, when smaller, more compact diode lasers entered the veterinary field. In the mid 1980's, several attempts were made to transmit CO2 laser energy transendoscopically. True success was not obtained until 2004 when the OmniGuide CO2 Laser Hollow Light Guide (fiber) was fabricated. Although there is attenuation of energy, this very flexible fiber allows the CO2 laser to be used transendoscopically for incision and ablation of tissue. Both healing and recuperation time are reduced, compared to other wavelengths transmitted through solid quartz fiber. The OmniGuide fiber can be coupled to the output ports of CO2 lasers commonly used in veterinary medicine. Transendoscopic application of the CO2 laser is advantageous in that there is no endoscopic white-out, no volume heating of tissue, and it provides accurate means of performing upper respiratory surgery in the standing large animal.

  4. A study on laser-based ultrasonic technique by the use of guided wave tomographic imaging

    SciTech Connect

    Park, Junpil Lim, Juyoung; Cho, Younho; Krishnaswamy, Sridhar

    2015-03-31

    Guided wave tests are impractical for investigating specimens with limited accessibility and coarse surfaces or geometrically complicated features. A non-contact setup with a laser ultrasonic transmitter and receiver is the classic attractive for guided wave inspection. The present work was done to develop a non-contact guided-wave tomography technique by laser ultrasonic technique in a plate-like structure. A method for Lam wave generation and detection in an aluminum plate with a pulse laser ultrasonic transmitter and a Michelson interferometer receiver has been developed. In the images obtained by laser scanning, the defect shape and area showed good agreement with the actual defect. The proposed approach can be used as a non-contact-based online inspection and monitoring technique.

  5. Controlled fundamental supermode operation of phase-locked arrays of gain-guided diode lasers

    NASA Technical Reports Server (NTRS)

    Kapon, E.; Margalit, S.; Yariv, A.; Katz, J.

    1984-01-01

    Uniform semiconductor laser arrays tend to oscillate in a superposition of their supermodes, thus leading to large beam divergence and spectral spread. Discrimination among the supermodes in phase-locked arrays is discussed theoretically. It is shown that supermode discrimination in gain-guided arrays, in favor of the fundamental supermode, is made possible by the near-field interference patterns which result from the complex optical fields of the gain-guided lasers. A fundamental supermode operation is demonstrated, for the first time, in GaAlAs/GaAs gain-guided laser arrays. This is achieved by control of the current (gain) profile across the array by means of individual laser contacts.

  6. Advancing adaptive optics technology: Laboratory turbulence simulation and optimization of laser guide stars

    NASA Astrophysics Data System (ADS)

    Rampy, Rachel A.

    optimizing the laser beacons used to bring AO correction to parts of the sky that lack a naturally bright light source for measuring atmospheric distortion. Long pulse length laser guide stars (LGS) that use fluorescence from the D 2 transition in mesospheric sodium are valuable both due to their high altitude, and because they permit Rayleigh blanking and fratricide avoidance in multiple LGS systems. Bloch equation simulations of sodium-light interactions in Mathematica show that certain spectral formats and pulse lengths (on the order of 30 μs), with high duty cycles (20-50%), should be able to achieve photon returns within 10% of what is seen from continuous wave (CW) excitation. Utilizing this recently developed code (called LGSBloch), I investigated the time dependent characteristics of sodium fluorescence. I then identified the optimal format for the new LGS that will be part of the upgrade to the AO system on the Shane 3 meter telescope at the Lick Observatory. I discuss these results, along with their general applicability to other LGS systems, and provide a brief description of the potential benefits of uplink correction. Predictions from the LGSBloch simulation package are compared to data from currently operating LGS systems. For a CW LGS, the return flux measurements and theory show reasonable agreement, but for short pulse lasers, such as those at the Lick and Keck Observatories, the code seems to be overestimating the data by a factor of 2--3. Several tactics to explicate this discrepancy are explored, such as verifying parameters involved in the measurements and including greater detail in the modeling. Although these efforts were unsuccessful at removing the discrepancy, they illuminated other facets of the problem that deserve further consideration. Use of the sophisticated LGSBloch model has allowed detailed study of the evolution of the energy level populations and other physical effects (e.g. Larmor precession, atomic recoil, and collisions). This has

  7. Laser altimetry simulator. Version 3.0: User's guide

    NASA Technical Reports Server (NTRS)

    Abshire, James B.; Mcgarry, Jan F.; Pacini, Linda K.; Blair, J. Bryan; Elman, Gregory C.

    1994-01-01

    A numerical simulator of a pulsed, direct detection laser altimeter has been developed to investigate the performance of space-based laser altimeters operating over surfaces with various height profiles. The simulator calculates the laser's optical intensity waveform as it propagates to and is reflected from the terrain surface and is collected by the receiver telescope. It also calculates the signal and noise waveforms output from the receiver's optical detector and waveform digitizer. Both avalanche photodiode and photomultiplier detectors may be selected. Parameters of the detected signal, including energy, the 50 percent rise-time point, the mean timing point, and the centroid, can be collected into histograms and statistics calculated after a number of laser firings. The laser altimeter can be selected to be fixed over the terrain at any altitude. Alternatively, it can move between laser shots to simulate the terrain profile measured with the laser altimeter.

  8. Scribing of GaN wafer for white LED by water-jet-guided laser

    NASA Astrophysics Data System (ADS)

    Nilsson, Thomas; Wagner, Frank; Housh, R.; Richerzhagen, Bernold

    2004-06-01

    In 1993, a laser light guiding water jet was successfully developed at the Institute of Applied Optics (EPFL, Lausanne, Switzerland; patented as Laser Microjet. The laser beam is focused into a nozzle from which a thin low-pressure water jet is emitted. The laser beam is injected in the water jet and guided in it by total internal reflection at the water/air interface similarly to a standard optical fiber. Normally a pulsed laser is used, so the continuous water jet is able to immediately cool the cut, reducing efficiently the heat-affected zone. The result is a very narrow, parallel, burr-free, clean cut, without detectable thermal damage. LED manufacturing is one example where thin layers need to be removed from well-defined regions on a wafer without damaging the neighboring structures. Compared with diamond saw cutting for which chipping and delaminating of the wafer cannot be avoided due to the strong shear forces; or compared with conventional laser cutting where low power irradiation of nearby functional structures occurs, the laser Microjet offers better edge quality and high precision. Compared to the main competitor, etching techniques combined with subsequent sawing of the substrate, the water jet guided laser is faster at similar edge quality.

  9. An Operations and Maintenance Overview of the Gemini North Artificial Guide Star Laser

    NASA Astrophysics Data System (ADS)

    Wyman, R.; Boccas, M.; D'Orgeville, C.; White, K.

    This is an overview of technical issues, and operational and maintenance activities for the Gemini North Guide Star Laser system that are specific to the laser itself, which currently operates in support of Laser Guide Star Adaptive Optics (LGS AO) science observations. Discussion will detail various issues with laser pump diode failures, failure analysis and reliability as well as techniques in spectral temperature tuning and laser diode procurements. Wavelength stability has been a major issue for operation of the laser and continuous monitoring of the laser is required to maintain power and wavelength within specification. Current investigation in to the problem will be reviewed along with the methods of managing the issue. The sum frequency generation PPSLT crystal will be discussed with respect to performance, maintenance and future testing plans to commission spare crystals in the laser system should they be needed. Various improvements in software and hardware will be briefly discussed along with an overview of diagnostics tools that are in place or being developed. Since the completion of science commissioning the operations model we follow to prepare and maintain the laser for LGS AO science observations has allowed for very good uptime. During this time it has been an intensive training for those operating the system and some of the experience will be discussed along with the current laser operations support model.

  10. Optimization of an Image-Guided Laser-Induced Choroidal Neovascularization Model in Mice

    PubMed Central

    Sun, Ye; Fu, Zhongjie; Liu, Chi-Hsiu; Evans, Lucy; Tian, Katherine; Saba, Nicholas; Fredrick, Thomas; Morss, Peyton; Chen, Jing; Smith, Lois E. H.

    2015-01-01

    The mouse model of laser-induced choroidal neovascularization (CNV) has been used in studies of the exudative form of age-related macular degeneration using both the conventional slit lamp and a new image-guided laser system. A standardized protocol is needed for consistent results using this model, which has been lacking. We optimized details of laser-induced CNV using the image-guided laser photocoagulation system. Four lesions with similar size were consistently applied per eye at approximately double the disc diameter away from the optic nerve, using different laser power levels, and mice of various ages and genders. After 7 days, the mice were sacrificed and retinal pigment epithelium/choroid/sclera was flat-mounted, stained with Isolectin B4, and imaged. Quantification of the area of the laser-induced lesions was performed using an established and constant threshold. Exclusion criteria are described that were necessary for reliable data analysis of the laser-induced CNV lesions. The CNV lesion area was proportional to the laser power levels. Mice at 12-16 weeks of age developed more severe CNV than those at 6-8 weeks of age, and the gender difference was only significant in mice at 12-16 weeks of age, but not in those at 6-8 weeks of age. Dietary intake of omega-3 long-chain polyunsaturated fatty acid reduced laser-induced CNV in mice. Taken together, laser-induced CNV lesions can be easily and consistently applied using the image-guided laser platform. Mice at 6-8 weeks of age are ideal for the laser-induced CNV model. PMID:26161975

  11. Upper limit power for self-guided propagation of intense lasers in plasma

    SciTech Connect

    Wang Weimin; Hu Zhidan; Chen Liming; Li Yutong; Sheng Zhengming; Zhang Jie; Zeng Ming; Liu Yue; Kawata, Shigeo; Zheng Chunyang; Mori, Warren B.

    2012-10-29

    It is shown that there is an upper-limit laser power for self-focusing of a laser pulse in plasma in addition to the well-known lower-limit critical power set by the relativistic effect. This upper limit is caused by the transverse ponderomotive force of the laser, which tends to expel plasma electrons from the laser propagating area. Furthermore, there is a lower-limit plasma density for a given laser spot size, below which self-focusing does not occur for any laser power. Both the lower-limit density and the upper-limit power are derived theoretically and verified by two-dimensional and three-dimensional particle-in-cell simulations. It is also found that plasma channels may be unfavorable for stable guiding of lasers above the upper-limit power.

  12. Femtosecond laser guiding of a high-voltage discharge and the restoration of dielectric strength in air and nitrogen

    SciTech Connect

    Leonov, S. B.; Firsov, A. A.; Shurupov, M. A.; Michael, J. B.; Shneider, M. N.; Miles, R. B.; Popov, N. A.

    2012-12-15

    The use of a low energy, high peak intensity (>100 TW/cm{sup 2}) femtosecond laser pulse is investigated for guiding and control of a sub-microsecond high voltage discharge. Study of the laser induced plasma channel and measurements of the field required for breakdown in air and nitrogen at atmospheric pressure are presented. Direct imaging of the dynamics of the discharge breakdown shows effective laser guiding. The effectiveness of laser guiding is shown to be critically dependent on the laser focusing geometry, timing, and location relative to the electrodes.

  13. Femtosecond laser guiding of a high-voltage discharge and the restoration of dielectric strength in air and nitrogen

    NASA Astrophysics Data System (ADS)

    Leonov, S. B.; Firsov, A. A.; Shurupov, M. A.; Michael, J. B.; Shneider, M. N.; Miles, R. B.; Popov, N. A.

    2012-12-01

    The use of a low energy, high peak intensity (>100 TW/cm2) femtosecond laser pulse is investigated for guiding and control of a sub-microsecond high voltage discharge. Study of the laser induced plasma channel and measurements of the field required for breakdown in air and nitrogen at atmospheric pressure are presented. Direct imaging of the dynamics of the discharge breakdown shows effective laser guiding. The effectiveness of laser guiding is shown to be critically dependent on the laser focusing geometry, timing, and location relative to the electrodes.

  14. Self-Guiding of Ultrashort Relativistically Intense Laser Pulses to the Limit of Nonlinear Pump Depletion

    SciTech Connect

    Ralph, J. E.; Marsh, K. A.; Pak, A. E.; Lu, W.; Clayton, C. E.; Fang, F.; Joshi, C.; Tsung, F. S.; Mori, W. B.

    2009-01-22

    A study of self-guiding of ultra short, relativistically intense laser pulses is presented. Here, the laser pulse length is on the order of the nonlinear plasma wavelength and the normalized vector potential is greater than one. Self-guiding of ultrashort laser pulses over tens of Rayliegh lengths is possible when driving a highly nonlinear wake. In this case, self-guiding is limited by nonlinear pump depletion. Erosion of the pulse due to diffraction at the head of the laser pulse is minimized for spot sizes close to the blow-out radius. This is due to the slowing of the group velocity of the photons at the head of the laser pulse. Using an approximately 10 TW Ti:Sapphire laser with a pulse length of approximately 50 fs, experimental results are presented showing self-guiding over lengths exceeding 30 Rayliegh lengths in various length Helium gas jets. Fully explicit 3D PIC simulations supporting the experimental results are also presented.

  15. Laser active imaging-guided anti-tank missile system small-scale integration design

    NASA Astrophysics Data System (ADS)

    Yan, Mingliang; Shan, Xiangqian; Qu, Zhou

    2010-10-01

    At present, the domestic and international third-generation anti-tank missiles, laser-guided missiles are mostly divided into active laser-guided and laser semi-active guidance, this guidance system, there are vulnerable to electronic interference, can not be fully realized after launching deficiencies. Article based on this, an in-depth understanding of imaging-guided laser-active working principle, based on the pairs of third-generation anti-tank missile guidance system, boldly proposed to improve the anti-tank missiles, laser-active small-scale integration of imaging guidance system design, the main purpose is to improve a certain type of The optical target missile, TV angle measurement, laser-guided instruction transmission means, so that anti-tank missiles to achieve forward-looking, the next obstacle avoidance TV and multi-functional integration of the entire after launching smart missiles, and in theory be able to study the new antitank missiles play a certain reference.

  16. A guide to developing a laser standard operating procedure

    SciTech Connect

    Barat, K.

    1996-10-01

    The American National Standard Institute standard Z136.1 Safe Use of Lasers calls for the preparation of a standard operating procedure (SOP) with the use of class 3b and class 4 lasers. However, the ANSI Z 136.1 standard does not recommend or suggest a format for the SOP. The goal of this article is to outline, explain and suggest an SOP format that could be applied by a laser safety officer to a varied number of situations and laser uses.

  17. Guiding of high intensity ultrashort laser pulses in plasma channels produced with the dual laser pulse ignitor-heater technique

    SciTech Connect

    Volfbeyn, P.; Leemans, W.P.

    1998-07-01

    The authors present results of experimental investigations of laser guiding in plasma channels. A new technique for plasma channel creation, the Ignitor-Heater scheme is proposed and experimentally tested in hydrogen and nitrogen. It makes use of two laser pulses. The Ignitor, an ultrashort (< 100 fs) laser pulse, is brought to a line focus using a cylindrical lens to ionize the gas. The Heater pulse (160 ps long) is used subsequently to heat the existing spark via inverse Bremsstrahlung. The hydrodynamic shock expansion creates a partially evacuated plasma channel with a density minimum on axis. Such a channel has properties of an optical waveguide. This technique allows creation of plasma channels in low atomic number gases, such as hydrogen, which is of importance for guiding of highly intense laser pulses. The channel density was diagnosed with time resolved longitudinal interferometry. From these measurements the plasma temperature was inferred. The guiding properties of the channels were tested by injecting a > 5 {times} 10{sup 17} W/cm{sup 2}, 75 fs laser pulse.

  18. Arecibo Observatory for All

    ERIC Educational Resources Information Center

    Bartus, P.; Isidro, G. M.; La Rosa, C.; Pantoja, C. A.

    2007-01-01

    We describe new materials available at the Arecibo Observatory for visitors with visual impairments. These materials include a guide in Braille that describes the telescope, explains some basic terms used in radio astronomy, and lists frequently asked questions. We have also designed a tactile model of the telescope. Our interest is in enabling…

  19. Integrated guided wave generation and sensing using a single laser source and optical fibers

    NASA Astrophysics Data System (ADS)

    Lee, Hyeonseok; Park, Hyun-Jun; Sohn, Hoon; Kwon, Il-Bum

    2010-10-01

    This study proposes an integrated lead zirconate titanate/fiber Bragg grating (PZT/FBG) system that can generate and measure guided waves for structural health monitoring (SHM) using a common laser source and optical cables. Among various SHM devices used for guided wave generation and sensing, PZT transducers and FBG sensors have been widely used because of their light weight, non-intrusive nature and compactness. To take the best advantage of the merits of these SHM devices, a combination of PZT-based guided wave generation and FBG-based sensing has been attempted by some researchers. However, the existing hybrid approaches have two independent systems: a wave generation system using electrical devices and a sensing system with optical devices. We have developed a fully integrated PZT/FBG system that uses a single laser source and optical cables. This system can alleviate problems associated with conventional electrical cables, such as electromagnetic interference, signal attenuation and vulnerability to noise. A tunable laser, the common power source for guided wave generation and sensing, is modulated and amplified to excite PZT. This laser is also used with FBG sensors for measuring high-speed strain changes induced by guided waves. The feasibility of this system has been experimentally demonstrated using an aluminum plate.

  20. Current status of the laser guide star adaptive optics system for Subaru Telescope

    NASA Astrophysics Data System (ADS)

    Hayano, Yutaka; Takami, Hideki; Guyon, Olivier; Oya, Shin; Hattori, Masayuki; Saito, Yoshihiko; Watanabe, Makoto; Murakami, Naoshi; Minowa, Yosuke; Ito, Meguru; Colley, Stephen; Eldred, Michael; Golota, Taras; Dinkins, Matthew; Kashikawa, Nobunari; Iye, Masanori

    2008-07-01

    The current status and recent results, since last SPIE conference at Orlando in 2006, for the laser guide star adaptive optics system for Subaru Telescope is presented. We had a first light using natural guide star and succeed to launch the sodium laser beam in October 2006. The achieved Strehl ratio on the 10th magnitude star was around 0.5 at K band. We confirmed that the full-width-half-maximum of the stellar point spread function is smaller than 0.1 arcsec even at the 0.9 micrometer wavelehgth. The size of the artificial guide star by the laser beam tuned at the wavelength of 589 nm was estimated to be 10 arcsec. The obtained blurred artificial guide star is caused by the wavefront error on the laser launching telescope. After the first light and first launch, we found that we need to modify and to fix the components, which are temporarily finished. Also components, which were postponed to fabricate after the first light, are required to build newly. All components used by the natural guide star adaptive optics system are finalized recently and we are ready to go on the sky. Next engineering observation is scheduled in August, 2008.

  1. Centroid gain compensation in Shack-Hartmann adaptive optics systems with natural or laser guide star

    PubMed

    Veran; Herriot

    2000-08-01

    In an adaptive optics system with an undersampled Shack-Hartmann wave-front sensor (WFS), variations in seeing, laser guide star quality, and sodium layer thickness and range distance all combine to vary WFS centroid gain across the pupil during an exposure. While using the minimum of 4 pixels per WFS subaperture improves frame rate and read noise, the WFS centroid gain uncertainty may introduce static aberrations and degrade servo loop phase margin. We present a novel method to estimate and compensate WFS gains of each subaperture individually in real time for both natural and laser guide stars. PMID:10935871

  2. Self-guided laser wakefield acceleration beyond 1 GeV using ionization-induced injection.

    PubMed

    Clayton, C E; Ralph, J E; Albert, F; Fonseca, R A; Glenzer, S H; Joshi, C; Lu, W; Marsh, K A; Martins, S F; Mori, W B; Pak, A; Tsung, F S; Pollock, B B; Ross, J S; Silva, L O; Froula, D H

    2010-09-01

    The concepts of matched-beam, self-guided laser propagation and ionization-induced injection have been combined to accelerate electrons up to 1.45 GeV energy in a laser wakefield accelerator. From the spatial and spectral content of the laser light exiting the plasma, we infer that the 60 fs, 110 TW laser pulse is guided and excites a wake over the entire 1.3 cm length of the gas cell at densities below 1.5 × 10(18) cm(-3). High-energy electrons are observed only when small (3%) amounts of CO2 gas are added to the He gas. Computer simulations confirm that it is the K-shell electrons of oxygen that are ionized and injected into the wake and accelerated to beyond 1 GeV energy. PMID:20867526

  3. Lick sodium laser guide star: performance during the 1998 LGS observing campaign

    SciTech Connect

    Bauman, B; Friedman, H; Gavel, D T

    1999-07-19

    The performance of a sodium laser guide star adaptive optics system depends crucially on the characteristics of the laser guide star in the sodium layer. System performance is quite sensitive to sodium layer spot radiance, that is, return per unit sterradian on the sky, hence we have been working to improve projected beam quality via improvements to the laser and changes to the launched beam format. The laser amplifier was reconfigured to a ''bounce-beam'' geometry, which considerably improves wavefront quality and allows a larger round instead of square launch beam aperture. The smaller beacon makes it easier to block the unwanted Rayleigh light and improves the accuracy of Hartmann sensor wavefront measurements in the A0 system. We present measurements of the beam quality and of the resulting sodium beacon and compare to similar measurements from last year.

  4. Direct analysis of gain-guided phase-locked semiconductor laser arrays

    NASA Technical Reports Server (NTRS)

    Marshall, W. K.; Katz, J.

    1986-01-01

    A method for analyzing arbitrary one-dimensional waveguides is described and applied to find the lateral modes of gain-guided laser arrays directly, without the need for a coupled-mode approximation. Detailed results are given for a four-element array for which experimental results are available, and the effect of varying device parameters on the relative gains of the modes is considered. The results show differences between gain-guided and real-index guided arrays which are not evident in prior analyses.

  5. Semiconductor laser having a non-absorbing passive region with beam guiding

    NASA Technical Reports Server (NTRS)

    Botez, Dan (Inventor)

    1986-01-01

    A laser comprises a semiconductor body having a pair of end faces and including an active region comprising adjacent active and guide layers which is spaced a distance from the end face and a passive region comprising adjacent non-absorbing guide and mode control layers which extends between the active region and the end face. The combination of the guide and mode control layers provides a weak positive index waveguide in the lateral direction thereby providing lateral mode control in the passive region between the active region and the end face.

  6. Feasibility experiment for sodium-layer laser guide stars at the Lawrence Livermore National Laboratory

    SciTech Connect

    Max, C.; Avicola, K.; Bissinger, H.; Brase, J.; Gavel, D.; Friedman, H.; Morris, J.; Oliver, S.; Salmon, J.T.; Waltjen, K.

    1992-03-09

    We are developing a feasibility experiment to demonstrate closed-loop adaptive optics using a sodium-layer laser guide star. We will use the copper-vapor-pumped dye lasers developed for LLNL`s Atomic Vapor Laser Isotope Separation Program to create the laser guide star. Closed-loop adaptive corrections will be accomplished using a 69-subaperture adaptive optics system on a one-meter telescope at LLNL. The laser beam will be projected upwards from a beam director approximately 5 meters away from the main telescope, and is expected to form a spot about a meter in diameter at the atmospheric sodium layer (at an altitude of 95 km). Details of the adaptive optics components and an analysis of the expected performance will be presented in companion papers for this Workshop. Here we summarize the overall architecture and system objectives. The long-term goal of our effort is to develop laser guide stars and adaptive optics for large astronomical telescopes.

  7. Design, layout, and early results of a feasibility experiment for sodium-layer laser-guide-star adaptive optics

    SciTech Connect

    Max, C.E.; Avicola, K.; Brase, J.M.

    1994-02-01

    The authors describe the design and the early results of a feasibility experiment for sodium-layer laser-guide-star adaptive optics. Copper-vapor-laser-pumped dye lasers from Lawrence Livermore National Laboratory`s Atomic Vapor Laser Isotope Separation program are used to create the guide star. The laser beam is projected upward from a beam director that is located {approximately}5 m from a 0.5-m telescope and forms an irradiance spot {approximately} 2 m in diameter at the atmospheric-sodium layer (at an altitude of 95 km). The laser guide star is approximately fifth magnitude and is visible to the naked eye at the top of the Rayleigh-scattered laser beam. To date, the authors have made photometric measurements and open-loop wave-front-sensor measurements of the laser guide star. They give an overview of the experiment`s design and the laser systems, describe the experimental setup, show preliminary photometric and open-loop wave-front-sensor data on the guide star, and present predictions of closed-loop adaptive-optics performance based on these experimental data. The long-term goal of this effort is to develop laser guide stars and adaptive optics for use with large astronomical telescopes. 26 refs., 17 figs., 2 tabs.

  8. Observation of strong correlation between quasimonoenergetic electron beam generation by laser wakefield and laser guiding inside a preplasma cavity.

    PubMed

    Hosokai, Tomonao; Kinoshita, Kenichi; Ohkubo, Takeru; Maekawa, Akira; Uesaka, Mitsuru; Zhidkov, Alexei; Yamazaki, Atsushi; Kotaki, Hideyuki; Kando, Masaki; Nakajima, Kazuhisa; Bulanov, Sergei V; Tomassini, Paolo; Giulietti, Antonio; Giulietti, Danilo

    2006-03-01

    We use a one-shot measurement technique to study effects of laser prepulses on the electron laser wakefield acceleration driven by relativistically intense laser pulses (lambda=790 nm, 11 TW, 37 fs) in dense helium gas jets. A quasimonoenergetic electron bunch with an energy peak approximately 11.5 MeV[DeltaE/E approximately 10% (FWHM)] and with a narrow-cone angle (0.04pi mm mrad) of ejection is detected at a plasma density of 8 x 10(19) cm(-3). A strong correlation between the generation of monoenergetic electrons and optical guiding of the pulse in a thin channel produced by picosecond laser prepulses is observed. This generation mechanism is well corroborated by two-dimensional particle-in-cell simulations. PMID:16605668

  9. Experimental studies of laser guiding and wake excitation in plasma channels

    NASA Astrophysics Data System (ADS)

    Volfbeyn, Pavel

    1998-12-01

    This thesis presents results of experimental investigations of laser guiding in plasma channels. A new technique for plasma channel creation, the Ignitor- Heater scheme was proposed and experimentally tested in hydrogen and nitrogen. It made use of two laser pulses. The Ignitor, an ultrashort (<100 fs) laser pulse, was brought to a line focus using a cylindrical lens to ionize the gas. The Heater pulse (100-200 ps long) was used subsequently to heat the existing spark via inverse Bremsstrahlung. The hydrodynamic shock expansion created a partially evacuated plasma channel with a density minimum on axis. Such a channel has properties of an optical waveguide. This technique allowed, for the first time, creation of plasma channels in low atomic number gases, such as hydrogen, which is of importance for guiding of highly intense laser pulses. The channel density was diagnosed with time resolved longitudinal interferometry. From these measurements the plasma temperature was inferred. The guiding properties of the channels were tested by injecting a 5 × 1017 W/cm2, 75fs laser pulse. The guiding properties and transmission and coupling efficiency were studied as a function of relative position of the channel and the injection pulse focus. Whereas entrance coupling efficiency into the channel was lower than expected, channel coupling to continuum losses were found to be in good agreement with analytical predictions. We speculate that increased coupling efficiency can be achieved through better mode matching into the channel. Analytic and numerical one dimensional (1-D), nonrelativistic theory of laser pulse propagation in underdense plasma was presented, in the context of laser wakefield acceleration. The relation between the laser pulse energy depletion, longitudinal laser pulse shape distortion, and changes in the group velocity and center wavelength was explored. 1-D theory was extended to treat the case of a laser exciting a wake in a hollow plasma channel, by making

  10. Improved laser triggering and guiding of meqavolt discharges with dual fs-ns pulses

    SciTech Connect

    Mejean, Guillaume; Ackermann, Roland; Kasparian, Jerome; Salmon, Estelle; Yu Jin; Wolf, Jean-Pierre; Rethmeier, Kay; Kalkner, Wilfried; Rohwetter, Philipp; Stelmaszczyk, Kamil; Woeste, Ludger

    2006-01-09

    We demonstrate that the capacity of ultrashort high-power laser pulses to trigger and guide high-voltage discharges can be significantly enhanced by a subsequent visible nanosecond laser pulse. The femtosecond pulse induces a bundle of filaments, which creates a conducting channel of low density and cold plasma connecting the electrodes. The subsequent laser pulse photodetaches electrons from O{sub 2}{sup -} ions in the electrode leader. The resulting electrons allow efficient heating by Joule effect in a retroaction loop, resulting in a 5% reduction of the breakdown voltage.

  11. Series production of next-generation guide-star lasers at TOPTICA and MPBC

    NASA Astrophysics Data System (ADS)

    Enderlein, Martin; Friedenauer, Axel; Schwerdt, Robin; Rehme, Paul; Wei, Daoping; Karpov, Vladimir; Ernstberger, Bernhard; Leisching, Patrick; Clements, Wallace R. L.; Kaenders, Wilhelm G.

    2014-07-01

    Large telescopes equipped with adaptive optics require high power 589-nm continuous-wave sources with emission linewidths of ~5 MHz. These guide-star lasers should be highly reliable and simple to operate and maintain for many years at the top of a mountain facility. After delivery of the first 20-W systems to our lead customer ESO, TOPTICA and MPBC have begun series production of next-generation sodium guide-star lasers. The chosen approach is based on ESO's patented narrow-band Raman fiber amplifier (RFA) technology [1]. A master oscillator signal from a TOPTICA 50-mW, 1178-nm diode laser, with stabilized emission frequency and linewidth of ~ 1 MHz, is amplified in an MPBC polarization-maintaining (PM) RFA pumped by a high-power 1120-nm PM fiber laser. With efficient stimulated Brillouin scattering suppression, an unprecedented 40 W of narrow-band RFA output has been obtained. This is spatially mode-matched into a patented resonant-cavity frequency doubler providing also the repumper light [2]. With a diffraction-limited output beam and doubling efficiencies < 80%, all ESO design goals have been easily fulfilled. Together with a wall-plug efficiency of < 3%, including all system controls, and a cooling liquid flow of only 5 l/min, the modular, turn-key, maintenance-free and compact system design allows a direct integration with a launch telescope. With these fiber-based guide star lasers, TOPTICA for the first time offers a fully engineered, off-the-shelf guide star laser system for ground-based optical telescopes. Here we present a comparison of test results of the first batch of laser systems, demonstrating the reproducibility of excellent optical characteristics.

  12. Analysis of optical klystron wave guide free electron laser with betatron oscillation effects

    NASA Astrophysics Data System (ADS)

    Jain, Deepi; Mishra, G.

    2014-12-01

    In this paper, we analyze the effect of the betatron oscillation on spontaneous emission and gain spectrum of an optical klystron wave guide free electron laser. The analysis also includes the effects of length mismatch of the two undulator sections of the klystron configuration. We observe that intensity and gain can be change with length mismatch parameter without changing the central emission frequency.

  13. Laser guiding at relativistic intensities and wakefield particle acceleration in plasma channels

    SciTech Connect

    Geddes, C.G.R.; Toth, Cs.; van Tilborg, J.; Esarey, E.; Schroeder, C.B.; Bruhwiler, D.; Cary, J.; Leemans, W.P.

    2004-08-01

    Electron beams with hundreds of picoCoulombs of charge in percent energy spread at above 80 MeV, and with few milliradian divergence, have been produced for the first time in a high gradient laser wakefield accelerator by guiding the drive laser pulse. Channels formed by hydrodynamic shock were used to guide acceleration relevant laser intensities of at least 1E18W/cm2 at the guide output over more than 10 Rayleigh lengths at LBNL's l'OASIS facility (10TW, 2E19W/cm2). The pondermotive force of the laser pulse drove an intense plasma wave, producing acceleration gradients on the order of 100 GV/m. Electrons were trapped from the background plasma and accelerated. By extending the acceleration length using the guiding channel, the energy of the electron beam was greatly increased, and bunches of small energy spread and low emittance were formed. Experiments varying gas jet length as well assimilations indicate that the high quality beams were formed when beam loading turned off injection after an initial load, producing an isolated bunch, and when that bunch was subsequently accelerated to the dephasing length at which point it rotated in phase space to produce low energy spread.

  14. Laser System Technician. A Catalog of Performance Objectives and Performance Guides.

    ERIC Educational Resources Information Center

    Florida State Dept. of Education, Tallahassee. Div. of Vocational, Adult, and Community Education.

    This Vocational-Technical Education Consortium of States (V-TECS) catalog contains the state-of-the-art tasks and standards of performance for the occupation of laser system technician. It provides the curriculum specialist or instructor with the foundation for instructional development. Performance objectives and performance guides are provided…

  15. Performance of capillary discharge guided laser plasma wakefieldaccelerator

    SciTech Connect

    Nakamura, Kei; Esarey, Eric; Geddes, Cameron G.R.; Gonsalves,Anthony J.; Leemans, Wim P.; Panasenko, Dmitriy; Schroeder, Carl B.; Toth, Csaba; Hooker, S.M.

    2007-06-25

    A GeV-class laser-driven plasma-based wakefield acceleratorhas been realized at the Lawrence Berkeley National Laboratory (LBNL).The device consists of the 40TW high repetition rate Ti:sapphire LOASISlaser system at LBNL and a gas-filled capillary discharge waveguidedeveloped at Oxford University. The operation of the capillary dischargeguided laser plasma wakefield accelerator with a capillaryof 225 mu mdiameter and 33 mm in length was analyzed in detail. The input intensitydependence suggests that excessive self-injection causes increased beamloading leading to broadband lower energy electron beam generation. Thetrigger versus laser arrival timing dependence suggests that the plasmachannel parameters can be tuned to reduce beam divergence.

  16. Laser to single-mode-fiber coupling: A laboratory guide

    NASA Technical Reports Server (NTRS)

    Ladany, I.

    1992-01-01

    All the information necessary to achieve reasonably efficient coupling of semiconductor lasers to single mode fibers is collected from the literature, reworked when necessary, and presented in a mostly tabular form. Formulas for determining the laser waist radius and the fiber mode radius are given. Imaging relations connecting these values with the object and image distances are given for three types of lenses: ball, hemisphere, and Gradient Index (GRIN). Sources for these lenses are indicated, and a brief discussion is given about ways of reducing feedback effects.

  17. Sky coverage modeling for the whole sky for laser guide star multiconjugate adaptive optics.

    PubMed

    Wang, Lianqi; Andersen, David; Ellerbroek, Brent

    2012-06-01

    The scientific productivity of laser guide star adaptive optics systems strongly depends on the sky coverage, which describes the probability of finding natural guide stars for the tip/tilt wavefront sensor(s) to achieve a certain performance. Knowledge of the sky coverage is also important for astronomers planning their observations. In this paper, we present an efficient method to compute the sky coverage for the laser guide star multiconjugate adaptive optics system, the Narrow Field Infrared Adaptive Optics System (NFIRAOS), being designed for the Thirty Meter Telescope project. We show that NFIRAOS can achieve more than 70% sky coverage over most of the accessible sky with the requirement of 191 nm total rms wavefront. PMID:22695611

  18. Astronomical observatories

    NASA Technical Reports Server (NTRS)

    Ponomarev, D. N.

    1983-01-01

    The layout and equipment of astronomical observatories, the oldest scientific institutions of human society are discussed. The example of leading observatories of the USSR allows the reader to familiarize himself with both their modern counterparts, as well as the goals and problems on which astronomers are presently working.

  19. Ondrejov Observatory

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    The Ondrejov Observatory is located 20 miles from Prague in the village of Ondrejov. It was established in 1898 as a private observatory and donated to the state of Czechoslovakia in 1928. Since 1953 it has been part of the Astronomical Institute, Academy of Sciences of the Czech Republic; there are 40 astronomers....

  20. Amateur Observatories

    NASA Astrophysics Data System (ADS)

    Gavin, M.

    1997-08-01

    A roundup of amateur observatories in this country and abroad, with construction and location details, concluding with a detailed description and architect's drawing of the author's own observatory at Worcester Park, Surrey. The text of the 1996 Presidential Address to the British Astronomical Association.

  1. Microsurgery of the retina with a needle-guided 193-nm excimer laser.

    PubMed

    Lewis, A; Palanker, D; Hemo, I; Pe'er, J; Zauberman, H

    1992-07-01

    This article presents a method used to guide the beam from an argon fluoride excimer laser to make it suitable for microsurgical purposes and confine it to areas that can be varied in dimension from 1 micron to tens or hundreds of microns. This approach guides the excimer laser beam with an articulated mechanical arm and confines it with variable-diameter tapered tubes, possibly allowing the use of this laser in in vitro retinal surgery with endolaser techniques. Currently, because of the lack of a delivery and focusing system for the 193-nm argon fluoride beam and its absorption by biologic liquids, this laser is used exclusively in ophthalmology for topical applications, such as corneal sculpting. This new method resolves these problems in a unique way with impressive results. Specifically, it was shown that, with this needle-guided excimer laser, it is possible to remove retinal tissue accurately without detectable damage to surrounding cells. Applications of this new technique in retinal surgery are discussed. PMID:1634334

  2. Calibration method for a vision guiding-based laser-tracking measurement system

    NASA Astrophysics Data System (ADS)

    Shao, Mingwei; Wei, Zhenzhong; Hu, Mengjie; Zhang, Guangjun

    2015-08-01

    Laser-tracking measurement systems (laser trackers) based on a vision-guiding device are widely used in industrial fields, and their calibration is important. As conventional methods typically have many disadvantages, such as difficult machining of the target and overdependence on the retroreflector, a novel calibration method is presented in this paper. The retroreflector, which is necessary in the normal calibration method, is unnecessary in our approach. As the laser beam is linear, points on the beam can be obtained with the help of a normal planar target. In this way, we can determine the function of a laser beam under the camera coordinate system, while its corresponding function under the laser-tracker coordinate system can be obtained from the encoder of the laser tracker. Clearly, when several groups of functions are confirmed, the rotation matrix can be solved from the direction vectors of the laser beams in different coordinate systems. As the intersection of the laser beams is the origin of the laser-tracker coordinate system, the translation matrix can also be determined. Our proposed method not only achieves the calibration of a single laser-tracking measurement system but also provides a reference for the calibration of a multistation system. Simulations to evaluate the effects of some critical factors were conducted. These simulations show the robustness and accuracy of our method. In real experiments, the root mean square error of the calibration result reached 1.46 mm within a range of 10 m, even though the vision-guiding device focuses on a point approximately 5 m away from the origin of its coordinate system, with a field of view of approximately 200 mm  ×  200 mm.

  3. Thoracic Pedicle Screw Placement Guide Plate Produced by Three-Dimensional (3-D) Laser Printing.

    PubMed

    Chen, Hongliang; Guo, Kaijing; Yang, Huilin; Wu, Dongying; Yuan, Feng

    2016-01-01

    BACKGROUND The aim of this study was to evaluate the accuracy and feasibility of an individualized thoracic pedicle screw placement guide plate produced by 3-D laser printing. MATERIAL AND METHODS Thoracic pedicle samples of 3 adult cadavers were randomly assigned for 3-D CT scans. The 3-D thoracic models were established by using medical Mimics software, and a screw path was designed with scanned data. Then the individualized thoracic pedicle screw placement guide plate models, matched to the backside of thoracic vertebral plates, were produced with a 3-D laser printer. Screws were placed with assistance of a guide plate. Then, the placement was assessed. RESULTS With the data provided by CT scans, 27 individualized guide plates were produced by 3-D printing. There was no significant difference in sex and relevant parameters of left and right sides among individuals (P>0.05). Screws were placed with assistance of guide plates, and all screws were in the correct positions without penetration of pedicles, under direct observation and anatomic evaluation post-operatively. CONCLUSIONS A thoracic pedicle screw placement guide plate can be produced by 3-D printing. With a high accuracy in placement and convenient operation, it provides a new method for accurate placement of thoracic pedicle screws. PMID:27194139

  4. Thoracic Pedicle Screw Placement Guide Plate Produced by Three-Dimensional (3-D) Laser Printing

    PubMed Central

    Chen, Hongliang; Guo, Kaijing; Yang, Huilin; Wu, Dongying; Yuan, Feng

    2016-01-01

    Background The aim of this study was to evaluate the accuracy and feasibility of an individualized thoracic pedicle screw placement guide plate produced by 3-D laser printing. Material/Methods Thoracic pedicle samples of 3 adult cadavers were randomly assigned for 3-D CT scans. The 3-D thoracic models were established by using medical Mimics software, and a screw path was designed with scanned data. Then the individualized thoracic pedicle screw placement guide plate models, matched to the backside of thoracic vertebral plates, were produced with a 3-D laser printer. Screws were placed with assistance of a guide plate. Then, the placement was assessed. Results With the data provided by CT scans, 27 individualized guide plates were produced by 3-D printing. There was no significant difference in sex and relevant parameters of left and right sides among individuals (P>0.05). Screws were placed with assistance of guide plates, and all screws were in the correct positions without penetration of pedicles, under direct observation and anatomic evaluation post-operatively. Conclusions A thoracic pedicle screw placement guide plate can be produced by 3-D printing. With a high accuracy in placement and convenient operation, it provides a new method for accurate placement of thoracic pedicle screws. PMID:27194139

  5. Design of a fieldable laser system for a sodium-layer guide star

    SciTech Connect

    Friedman, H.W.; Erbert, G.V.; Kuklo, T.C.; Salmon, T.; Smauley, D.A.; Thompson, G.R.; Wong, N.

    1994-12-31

    A laser system to generate a sodium-layer guide star has been designed that incorporates state-of-the-art, solid-state pump lasers and well-developed dye lasers as the frequency tunable converter. With the use of efficient quartz fibers, the pump laser and dye master oscillator can be located far from the telescope, allowing simple thermal management and providing a stable environment for the coherent part of the laser system. The remainder of the system, consisting of single-pass dye amplifiers, is mounted directly on the telescope, thereby eliminating complex and inefficient beam-transport configurations. A key feature of this laser system is the scalability to higher powers, which will be required for observation wavelengths in the visible region. Most of the cost and complexity exist in this {open_quotes}front end{close_quotes} of the system. Adding another dye laser amplifier, which can be accommodated on the same laser table, and adding more pump lasers in the equipment area can raise the output power level to the hundred-watt range.

  6. Optical guiding of terawatt laser pulses in the plasma waveguide

    NASA Astrophysics Data System (ADS)

    Alexeev, I.; Fan, J.; Kim, K. Y.; Nikitin, S.; Milchberg, H. M.

    1999-11-01

    We report coupling and guiding of pulses of peak power 0.5 TW in 1.5 cm long preformed plasma waveguides generated in a high repetition rate argon gas jet. Greater than 50 percent coupling was measured in the injection of 50 mJ, 100 fs pulses, giving guided intensities up to 10^17 W/cm^2. For short delays between waveguide generation and pulse injection, refraction-induced pulse shortening occurred, with this effect reduced either by increasing the delay between waveguide generation and injection or by injecting a prepulse into the waveguide. We will also describe recent experiments which attempt to reduce the avalanche ionization threshold for the gases in which the waveguide is generated. This work is supported by the US Department of Energy (DEF G0297 ER 41039) and the National Science Foundation (PHY-9515509).

  7. Guiding of intense femtosecond laser pulses in fully ionized plasma channels

    NASA Astrophysics Data System (ADS)

    Downer, M. C.

    2002-11-01

    Plasma waveguides capable of guiding relativistically intense fs laser pulses without optical distortion are essential to developing GeV-scale laser wakefield accelerators, coherent short-wavelength sources and lenses for fourth-generation x-ray sources. Various approaches to guiding terawatt pulses through preformed plasma fibers inside gas-filled solid capillaries [1], and in laser-generated cylindrical shock waves [2] will be compared. We report the first implementation of a laser-generated waveguide in a Helium plasma, which provides full ionization and minimization of ionization-induced distortions of the guided pulse up to relativistic guided intensity. 80 fs laser pulses were guided at near-relativistic intensity (0.2 x 10^18 W/cm^2) over 60 Rayleigh ranges (1.5 cm) with > 50% throughput, 20 Hz repetition rate and no detectable distortion of their spectrum or 16 micron-diameter TEM_00 mode structure [3]. Channels were generated by the method developed by Milchberg et al. [2], in which a filament of He gas (300-700 Torr) was ionized and heated by a powerful line-focused Nd:YAG laser pulse. To enable waveguide formation in Helium, the method was modified by slightly (0.1%) pre-ionizing the helium to seed inverse bremsstrahlung absorption, and by lengthening (100 to 400 ps) and strengthening (0.3 to 1 J) the channel-forming laser pulse. Recent femtosecond time-resolved pump-probe experiments inside the Helium channel will be reported. The issues involved, and current progress, in upgrading performance to fully relativistic guided intensity (10^18 W/cm^2) will be discussed. [1] Ehrlich et al., Phys. Rev. Lett. 77, 4186 (1996); Hosokai et al., Opt. Lett. 25, 10 (2000); Spence et al., Phys. Rev. E 63, 015401 (2001). [2] C. G. Durfee, III and H. M. Milchberg, Phys. Rev. Lett. 71, 2409 (1993); J. Fan, et al. Appl. Phys. Lett. 73, 3064 (1998). [3] E. W. Gaul et al., Appl. Phys. Lett. 77, 4112 (2000).

  8. Status of ARGOS - The Laser Guide Star System for the LBT

    NASA Astrophysics Data System (ADS)

    Raab, Walfried; Rabien, Sebastian; Gaessler, Wolfgang; Esposito, Simone; Antichi, Jacopo; Lloyd-Hart, Michael; Barl, Lothar; Beckmann, Udo; Bonaglia, Marco; Borelli, Jose; Brynnel, Joar; Buschkamp, Peter; Busoni, Lorenzo; Carbonaro, Luca; Christou, Julian; Connot, Claus; Davies, Richard; Deysenroth, Matthias; Durney, Olivier; Green, Richard; Gemperlein, Hans; Gasho, Victor; Haug, Marcus; Hubbard, Pete; Ihle, Sebastian; Kulas, Martin; Loose, Christina; Lehmitz, Michael; Noenickx, Jamison; Nussbaum, Edmund; Orban De Xivry, Gilles; Quirrenbach, Andreas; Peter, Diethard; Rahmer, Gustavo; Rademacher, Matt; Storm, Jesper; Schwab, Christian; Vaitheeswaran, Vidhya; Ziegleder, Julian

    2013-12-01

    ARGOS is an innovative multiple laser guide star adaptive optics system for the Large Binocular Telescope (LBT), designed to perform effective GLAO correction over a very wide field of view. The system is using high powered pulsed green (532 nm) lasers to generate a set of three guide stars above each of the LBT mirrors. The laser beams are launched through a 40 cm telescope and focused at an altitude of 12 km, creating laser beacons by means of Rayleigh scattering. The returning scattered light, primarily sensitive to the turbulences close to the ground, is detected by a gated wavefront sensor system. The derived ground layer correction signals are directly driving the adaptive secondary mirror of the LBT. ARGOS is especially designed for operation with the multiple object spectrograph Luci, which will benefit from both, the improved spatial resolution, as well as the strongly enhanced flux. In addition to the GLAO Rayleigh beacon system, ARGOS was also designed for a possible future upgrade with a hybrid sodium laser - Rayleigh beacon combination, enabling diffraction limited operation. The ARGOS laser system has undergone extensive tests during Summer 2012 and is scheduled for installation at the LBT in Spring 2013. The remaining sub-systems will be installed during the course of 2013. We report on the overall status of the ARGOS system and the results of the sub-system characterizations carried out so far.

  9. Aero-thermal simulations of the TMT Laser Guide Star Facility

    NASA Astrophysics Data System (ADS)

    Vogiatzis, Konstantinos; Boyer, Corinne; Wei, Kai; Tang, Jinlong; Ellerbroek, Brent

    2014-08-01

    The Laser Guide Star Facility (LGSF) system of the Thirty Meter Telescope (TMT) will generate the artificial laser guide stars required by the TMT Adaptive Optics (AO) systems. The LGSF uses multiple sodium lasers to generate and project several asterisms from a laser launch telescope located behind the TMT secondary mirror. The laser beams are transported from a location below the primary mirror to the launch telescope using conventional optics to relay the beams along the telescope structure. The beams and relay optics are enclosed into hermetic ducts for safety reasons and to protect the optics against the environment. A Computational Solid Fluid Dynamics (CSFD) model of the LGSF ducts has been developed. It resolves the duct thickness, laser beam transfer lenses, mirrors and their framework for most of the laser beam path that is subject to significant temperature gradients and/or large vertical change. It also resolves the air inside the duct and its thermal interaction with the aforementioned components through conjugate heat transfer. The thermal interaction of the laser beam with the optics is also captured. The model provides guidance to the LGSF design team and a first estimate of the laser beam stability performance and requirement compliance. As the telescope structure design has evolved in the recent years, a new optical path has been proposed for the LGSF. Both the original and the new optical paths are compared against optical, mechanical and other telescope performance related criteria. The optical performance criteria include a first order analysis of the optical turbulence generated within the ducts. In this study simulations of the thermal environment within the ducts of the two candidate paths are performed and conclusions are drawn.

  10. Design and evaluation of a fiberoptic fluorescence guided laser recanalization system.

    PubMed

    Garrand, T J; Stetz, M L; O'Brien, K M; Gindi, G R; Sumpio, B E; Deckelbaum, L I

    1991-01-01

    Current angioplasty techniques for recanalization of totally occluded arteries are limited by the inability to cross the occlusion and by the risk of perforation. A fiberoptic fluorescence guided laser recanalization system was developed and evaluated in vitro for recanalization of 17 human femoral or tibial totally occluded arterial segments (length 1.9-6.8 cm, diameter 2.5-6.0 mm). A 400 or 600 micron silica fiber was coupled to a helium-cadmium laser (lambda = 325 nm) for fluorescence excitation and to a holmium: YAG laser (lambda = 2.1 micron) for tissue ablation. Fluorescence was recorded during recanalization after every other holmium laser pulse. During recanalization, each arterial segment was bent 30-90 degrees with respect to the fiber to simulate arterial tortuosity. Ablation continued with fiber advancement as long as the fluorescence confirmed that the target tissue was atherosclerotic. Arterial spectra were classified as normal or atherosclerotic by an on-line computerized fluorescence classification algorithm (sensitivity 93%, specificity 95%). Normal fluorescence necessitated redirection of the fiber greater than 30 times per segment to continue recanalization. Fifteen of 17 totally occluded arteries had multiple recanalization channels created following total energy delivery of 40-1,016 Joules per segment with no angiographic or histologic evidence of laser perforation. Two heavily calcified arterial occlusions were not recanalized due to inhibition of holmium: YAG laser ablation by the recording of normal fluorescence spectra. Therefore, this fluorescence guided laser recanalization system appears safe and effective for recanalization of totally occluded arteries and merits in vivo evaluation. However, the lower sensitivity of fluorescence detection of heavily calcified plaques may limit the efficacy (but not safety) of fluorescence guided recanalization of heavily calcified occlusions. PMID:2034008

  11. Laser-Guided Neuronal Tracing in Brain Explants

    PubMed Central

    Klug, Achim

    2016-01-01

    Short Abstract We describe a technique to label neurons and their processes via anterograde or retrograde tracer injections into brain nuclei using an in-vitro preparation. We modified an existing method of in-vitro tracer electroporation by taking advantage of fluorescently labeled mouse mutants and basic optical equipment in order to increase labeling accuracy. Long Abstract We present a technique which combines an in-vitro tracer injection protocol, which uses a series of electrical and pressure pulses to increase dye uptake through electroporation in brain explants with targeted laser illumination and matching filter goggles during the procedure. The described technique of in-vitro electroporation by itself yields relatively good visual control for targetting certain areas of the brain. By combining it with laser excitation of fluorescent genetic markers and their read-out through band-passing filter goggles, which can pick up the emissions of the genetically labeled cells/nuclei and the fluorescent tracing dye, a researcher can substantially increase the accuracy of injections by finding the area of interest and controlling for the dye-spread/uptake in the injection area much more efficiently. In addition, the laser illumination technique allows to study the functionality of a given neurocircuit by providing information about the type of neurons projecting to a certain area in cases where the GFP expression is linked to the type of transmitter expressed by a subpopulation of neurons. PMID:26649948

  12. On-Sky Tests of a High-Power Pulsed Laser for Sodium Laser Guide Star Adaptive Optics

    NASA Astrophysics Data System (ADS)

    Otarola, Angel; Hickson, Paul; Gagné, Ronald; Bo, Yong; Zuo, Junwei; Xie, Shiyong; Feng, Lu; Rochester, Simon; Budker, Dmitry; Shen, Shixia; Xue, Suijian; Min, Li; Wei, Kai; Boyer, Corinne; Ellerbroek, Brent; Hu, Jingyao; Peng, Qinjun; Xu, Zuyan

    2016-03-01

    We present results of on-sky tests performed in the summer of 2013 to characterize the performance of a prototype high-power pulsed laser for adaptive optics. The laser operates at a pulse repetition rate (PRR) of 600-800Hz, with a 6% duty cycle. Its coupling efficiency was found to be, in the best test case (using 18W of transmitted power), 231±14 photons s‑1 sr‑1 atom‑1 W‑1 m2 when circular polarization was employed and 167±17 photons s‑1 sr‑1 atom‑1 W‑1 m2 with linear polarization. No improvement was seen when D2b repumping was used, but this is likely due to the relatively large laser guide star (LGS) diameter, typically 10 arcsec or more, which resulted in low irradiance levels. Strong relaxation oscillations were present in the laser output, which have the effect of reducing the coupling efficiency. To better understand the results, a physical modeling was performed using the measured pulse profiles and parameters specific to these tests. The model results, for a 10 arcsec angular size LGS spot, agree well with the observations. When extrapolating the physical model for a sub-arcsecond angular size LGS (typical of what is needed for a successful astronomical guide star), the model predicts that this laser would have a coupling efficiency of 130 photons s‑1 sr‑1 atom‑1 W‑1 m2, using circular polarization and D2b repumping, for a LGS diameter of 0.6 arcsec Full Width at Half Maximum (FWHM), and free of relaxation oscillations in the 589 nm laser light.

  13. Near-IR Image-Guided Laser Ablation of Demineralization on Tooth Occlusal Surfaces

    PubMed Central

    Tom, Henry; Chan, Kenneth H.; Darling, Cynthia L.; Fried, Daniel

    2016-01-01

    Introduction Studies have shown that reflectance images at near-IR wavelengths coincident with higher water absorption are well-suited for image-guided laser ablation of carious lesions since the contrast between sound and demineralized enamel is extremely high and interference from stains is minimized. The objective of this study was to demonstrate that near-IR reflectance images taken at a wavelength range of 1,500–1,700 nm can be used to guide a 9.3 μm CO2 laser for the selective ablation of early demineralization on tooth occlusal surfaces. Methods The occlusal surfaces of ten sound human molars were used in this in vitro study. Shallow simulated caries lesions with random patterns and varying depth and position were produced on tooth occlusal surfaces. Sequential near-IR reflectance images at 1,500–1,700 nm were used to guide the laser for the selective removal of the demineralized enamel. Digital microscopy and polarization sensitive optical coherence tomography (PS-OCT) were used to assess selectivity. Results Images taken before and after lesion removal suggest that the demineralized areas were removed with high selectivity. Although the estimated volume of tissue ablated was typically higher than the initial lesion volume measured with PS-OCT, the volume of enamel removed by the laser correlated well with the initial lesion volume. Conclusion Sequential near-IR reflectance images at 1,500–1,700 nm can be used to guide a 9.3 μm CO2 laser for the selective ablation of early demineralization on tooth occlusal surfaces. PMID:26763111

  14. Electromagnetically Induced Guiding and Superradiant Amplification of Counter-Propagating Lasers in Plasma

    SciTech Connect

    Fisch, N.J.; Shvets, G.

    1998-08-01

    The interaction of counter-propagating laser pulses in a plasma in considered. When the frequencies of the two lasers are close, nonlinear modification of the refraction index results in the mutual focusing of the two beams. A short (of order the plasma period) laser pulse can be nonlinearly focused by a long counter-propagating beam which extends over the entire guiding length. It is also demonstrated that a short (< 1/ omega (sub p)) laser pulse can be superradiantly amplified by a counter-propagating long low-intensity pump while remaining ultra-short. Particle-in-Cell simulations indicate that pump depletion can be as high as 40%. This implies that the long pump is efficiently compressed in time without frequency chirping and pulse stretching, making the superradiant amplification an interesting alternative to the conventional method of producing ultra-intense pulses by the chirped-pulse amplification.

  15. Intrinsic corrections to optical guiding in a free electron laser

    NASA Astrophysics Data System (ADS)

    Chen, Yu-Jiuan; Scharlemann, E. T.; Sessler, A. M.

    1988-10-01

    The effect on optical guiding of the undulations of an electron beam in an FEL is investigated, and a model for a fully saturated FEL amplifier with no remaining gain is developed. The density of the electrom beam in the model fully includes the effects of both transverse and longitudinal undulation of the beam. The longitudinal density modulation is expressed in terms of the Bessel functions of ζ, where ζ = {a w2}/{2(1 + a w2}) is the shift of the electron phase in the electron bucket caused by its longitudinal undulation. The transverse density modulation is evaluated to second order in the ratio of undulation amplitude δr to beam radial scale length rb. The radiation field from the modeled beam is calculated in terms of spatial modes proportional to exp[i( k + δk + lkw) z - i ωt], where l is an arbitrary integer. Here, δk is the change of the wavenumber of the radiation caused by the electron bunches. Radially radiating modes with intensity on the order of ( {δk}/{k w)ζ 2} are found. Optical guiding is found to be modified by the transverse undulations of the beam at second order in {δr}/{r b}, and by the longitudinal undulations to first order in {δk}/{k w}. For the usual FEL parameters, the correction is quite small.

  16. Imaging performance analysis of adaptive optical telescopes using laser guide stars.

    PubMed

    Welsh, B M

    1991-12-01

    The use of laser guide stars in conjunction with adaptive optical telescopes offers the possibility of nearly diffraction-limited imaging performance from large, ground-based telescopes. We investigate the expected imaging performance of an adaptive telescope, using laser guide stars created in the mesospheric sodium (Na) layer. A 2-3-m class telescope is analyzed for the case of a single, on-axis guide star at an altitude of 92 km (the nominal height of the mesospheric Na layer). We analyze an annular telescope pupil with approximately 15 wave-front sensor subapertures and mirror actuators spanning the pupil diameter. The imaging performance is quantified in terms of the pupil-averaged rms wave-front error, the optical transfer function, the point spread function, the Strehl ratio, and finally the angular resolution. The performance analysis takes into account the degradation caused by the limitation of the wave-front sensor as well as the deformable mirror. These limitations include the finite spacing and size of the wave-front sensor subapertures and the spacing and influence function of the mirror actuators. The effects of anisoplanatism and shot noise are also included in the analysis. The results of the investigation indicate that a 3-m adaptive telescope using a single Na guide star is capable of achieving a Strehl ratio of 0.57 and an angular resolution nearly matching that of diffraction-limited performance (0.05 arcsec). This performance is achieved assuming that r(0) = 20 cm and a 5-W laser is used to create the guide star. The effect of variations in seeing conditions and guide star brightness is also investigated. PMID:20717316

  17. Taosi Observatory

    NASA Astrophysics Data System (ADS)

    Sun, Xiaochun

    Taosi observatory is the remains of a structure discovered at the later Neolithic Taosi site located in Xiangfen County, Shanxi Province, in north-central China. The structure is a walled enclosure on a raised platform. Only rammed-earth foundations of the structure remained. Archaeoastronomical studies suggest that this structure functioned as an astronomical observatory. Historical circumstantial evidence suggests that it was probably related to the legendary kingdom of Yao from the twenty-first century BC.

  18. Design of guided-mode resonance mirrors for short laser cavities.

    PubMed

    Kondo, Tomohiro; Ura, Shogo; Magnusson, Robert

    2015-08-01

    A guided-mode resonance mirror (GMRM) consists of a waveguide grating integrated on an optical buffer layer on a high-reflection substrate. An incident free-space wave at the resonance wavelength is once coupled by the grating to a guided mode and coupled again by the same grating back to free space. The reflection characteristics of a GMRM are numerically calculated and theoretically analyzed. It is predicted that notch filtering or flat reflection spectra are obtained depending on the optical buffer layer thickness. Design of short cavities using a GMRM is discussed for potential application in surface-mount packaging of diode lasers onto a photonic circuit board. PMID:26367288

  19. Hydrogen isotope correction for laser instrument measurement bias at low water vapor concentration using conventional isotope analyses: application to measurements from Mauna Loa Observatory, Hawaii.

    PubMed

    Johnson, L R; Sharp, Z D; Galewsky, J; Strong, M; Van Pelt, A D; Dong, F; Noone, D

    2011-03-15

    The hydrogen and oxygen isotope ratios of water vapor can be measured with commercially available laser spectroscopy analyzers in real time. Operation of the laser systems in relatively dry air is difficult because measurements are non-linear as a function of humidity at low water concentrations. Here we use field-based sampling coupled with traditional mass spectrometry techniques for assessing linearity and calibrating laser spectroscopy systems at low water vapor concentrations. Air samples are collected in an evacuated 2 L glass flask and the water is separated from the non-condensable gases cryogenically. Approximately 2 µL of water are reduced to H(2) gas and measured on an isotope ratio mass spectrometer. In a field experiment at the Mauna Loa Observatory (MLO), we ran Picarro and Los Gatos Research (LGR) laser analyzers for a period of 25 days in addition to periodic sample collection in evacuated flasks. When the two laser systems are corrected to the flask data, they are strongly coincident over the entire 25 days. The δ(2)H values were found to change by over 200‰ over 2.5 min as the boundary layer elevation changed relative to MLO. The δ(2)H values ranged from -106 to -332‰, and the δ(18)O values (uncorrected) ranged from -12 to -50‰. Raw data from laser analyzers in environments with low water vapor concentrations can be normalized to the international V-SMOW scale by calibration to the flask data measured conventionally. Bias correction is especially critical for the accurate determination of deuterium excess in dry air. PMID:21290447

  20. CONTROL OF LASER RADIATION PARAMETERS. GENERATION OF ULTRASHORT PULSES: Mode locking in linear injection laser arrays with gain-guided waveguides

    NASA Astrophysics Data System (ADS)

    Nakwaski, W.

    1990-12-01

    The problem of mode locking in linear arrays of lasers with gain-guided waveguides is considered on the basis of a theoretical analysis of Basov, Belenov, and Letokhov for diffraction-coupled lasers and also using the Vaĭnshteĭn approximation for diffraction losses. A simple calculation procedure, enabling an easy determination of the maximum wavelength difference between adjacent elements of gain-guided arrays, is proposed.

  1. Multimodal scanning laser ophthalmoscopy for image guided treatment of age-related macular degeneration

    NASA Astrophysics Data System (ADS)

    Hammer, Daniel X.; Ferguson, R. D.; Patel, Ankit H.; Iftimia, Nicusor V.; Mujat, Mircea; Husain, Deeba

    2009-02-01

    Subretinal neovascular membranes (SRNM) are a deleterious complication of laser eye injury and retinal diseases such as age-related macular degeneration (AMD), choroiditis, and myopic retinopathy. Photodynamic therapy (PDT) and anti-vascular endothelial growth factor (VEGF) drugs are approved treatment methods. PDT acts by selective dye accumulation, activation by laser light, and disruption and clotting of the new leaky vessels. However, PDT surgery is currently not image-guided, nor does it proceed in an efficient or automated manner. This may contribute to the high rate of re-treatment. We have developed a multimodal scanning laser ophthalmoscope (SLO) for automated diagnosis and image-guided treatment of SRNMs associated with AMD. The system combines line scanning laser ophthalmoscopy (LSLO), fluorescein angiography (FA), indocyanine green angiography (ICGA), PDT laser delivery, and retinal tracking in a compact, efficient platform. This paper describes the system hardware and software design, performance characterization, and automated patient imaging and treatment session procedures and algorithms. Also, we present initial imaging and tracking measurements on normal subjects and automated lesion demarcation and sizing analysis of previously acquired angiograms. Future pre-clinical testing includes line scanning angiography and PDT treatment of AMD subjects. The automated acquisition procedure, enhanced and expedited data post-processing, and innovative image visualization and interpretation tools provided by the multimodal retinal imager may eventually aid in the diagnosis, treatment, and prognosis of AMD and other retinal diseases.

  2. High contrast optical imaging methods for image guided laser ablation of dental caries lesions

    NASA Astrophysics Data System (ADS)

    LaMantia, Nicole R.; Tom, Henry; Chan, Kenneth H.; Simon, Jacob C.; Darling, Cynthia L.; Fried, Daniel

    2014-02-01

    Laser based methods are well suited for automation and can be used to selectively remove dental caries to minimize the loss of healthy tissues and render the underlying enamel more resistant to acid dissolution. The purpose of this study was to determine which imaging methods are best suited for image-guided ablation of natural non-cavitated carious lesions on occlusal surfaces. Multiple caries imaging methods were compared including near-IR and visible reflectance and quantitative light fluorescence (QLF). In order for image-guided laser ablation to be feasible, chemical and physical modification of tooth surfaces due to laser irradiation cannot greatly reduce the contrast between sound and demineralized dental hard tissues. Sound and demineralized surfaces of 48 extracted human molar teeth with non-cavitated lesions were examined. Images were acquired before and after laser irradiation using visible and near-IR reflectance and QLF at several wavelengths. Polarization sensitive-optical coherence tomography was used to confirm that lesions were present. The highest contrast was attained at 1460-nm and 1500-1700-nm, wavelengths coincident with higher water absorption. The reflectance did not decrease significantly after laser irradiation for those wavelengths.

  3. High contrast optical imaging methods for image guided laser ablation of dental caries lesions

    PubMed Central

    LaMantia, Nicole R.; Tom, Henry; Chan, Kenneth H.; Simon, Jacob C.; Darling, Cynthia L.; Fried, Daniel

    2014-01-01

    Laser based methods are well suited for automation and can be used to selectively remove dental caries to minimize the loss of healthy tissues and render the underlying enamel more resistant to acid dissolution. The purpose of this study was to determine which imaging methods are best suited for image-guided ablation of natural non-cavitated carious lesions on occlusal surfaces. Multiple caries imaging methods were compared including near-IR and visible reflectance and quantitative light fluorescence (QLF). In order for image-guided laser ablation to be feasible, chemical and physical modification of tooth surfaces due to laser irradiation cannot greatly reduce the contrast between sound and demineralized dental hard tissues. Sound and demineralized surfaces of 48 extracted human molar teeth with non-cavitated lesions were examined. Images were acquired before and after laser irradiation using visible and near-IR reflectance and QLF at several wavelengths. Polarization sensitive-optical coherence tomography was used to confirm that lesions were present. The highest contrast was attained at 1460-nm and 1500–1700-nm, wavelengths coincident with higher water absorption. The reflectance did not decrease significantly after laser irradiation for those wavelengths. PMID:24791129

  4. GeV electron beams from cm-scale channel guided laser wakefieldaccelerator

    SciTech Connect

    Nakamura,K.; Nagler, B.; Toth, Cs.; Geddes, C.G.R.; Schroeder,C.; Esarey, E.; Leemans, W.P.; Gonsalves, A.J.; Hooker, S.M.

    2007-02-20

    Laser-wakefield accelerators (LWFA) can produce electricfields of order 10-100 GV/m suitable for acceleration of electrons torelativistic energies. The wakefields are excited by a relativisticallyintense laser pulse propagating through a plasma and have a phasevelocity determined by the group velocity of the light pulse. Twoimportant effects that can limit the acceleration distanceand hence thenet energy gain obtained by an electron are diffraction of the drivelaser pulse and particle-wake dephasing. Diffraction of a focusedultra-short laser pulse can be overcome by using preformed plasmachannels. The dephasing limit can be increased by operating at a lowerplasma density, since this results in an increase in the laser groupvelocity. Here we present detailed results on the generation of GeV-classelectron beams using an intense femtosecond laser beamand a 3.3 cm longpreformed discharge-based plasma channel [W.P. Leemans et al., NaturePhysics 2, 696-699 (2006)]. The use of a discharge-based waveguidepermitted operation at an order ofmagnitude lower density and 15 timeslonger distance than in previous experiments that relied on laserpreformed plasma channels. Laser pulses with peak power ranging from10-50 TW were guided over more than 20 Rayleigh ranges and high-qualityelectron beams with energy up to 1 GeV were obtained by channelling a 40TW peak power laser pulse. The dependence of the electron beamcharacteristics on capillary properties, plasma density,and laserparameters are discussed.

  5. Combination of fiber-guided pulsed erbium and holmium laser radiation for tissue ablation under water

    NASA Astrophysics Data System (ADS)

    Pratisto, Hans; Frenz, Martin; Ith, Michael; Altermatt, Hans J.; Jansen, E. Duco; Weber, Heinz P.

    1996-07-01

    Because of the high absorption of near-infrared laser radiation in biological tissue, erbium lasers and holmium lasers emitting at 3 and 2 mu m, respectively, have been proven to have optimal qualities for cutting or welding and coagulating tissue. To combine the advantages of both wavelengths, we realized a multiwavelength laser system by simultaneously guiding erbium and holmium laser radiation by means of a single zirconium fluoride (ZrF4) fiber. Laser-induced channel formation in water and poly(acrylamide) gel was investigated by the use of a time-resolved flash-photography setup, while pressure transients were recorded simultaneously with a needle hydrophone. The shapes and depths of vapor channels produced in water and in a submerged gel after single erbium and after combination erbium-holmium radiation delivered by means of a 400- mu m ZrF4 fiber were measured. Transmission measurements were performed to determine the amount of pulse energy available for tissue ablation. The effects of laser wavelength and the delay time between pulses of different wavelengths on the photomechanical and photothermal responses of meniscal tissue were evaluated in vitro by the use of histology. It was observed that the use of a short (200- mu s, 100-mJ) holmium laser pulse as a prepulse to generate a vapor bubble through which the ablating erbium laser pulse can be transmitted (delay time, 100 mu s) increases the cutting depth in meniscus from 450 to 1120 mu m as compared with the depth following a single erbium pulse. The results indicate that a combination of erbium and holmium laser radiation precisely and efficiently cuts tissue under water with 20-50- mu m collateral tissue damage. wave, cavitation, channel formation, infrared-fiber-delivery system, tissue damage, cartilage.

  6. Performance of keck adaptive optics with sodium laser guide star

    SciTech Connect

    Gavel, D.T.; Olivier, S.; Brase, J.

    1996-03-08

    The Keck telescope adaptive optics system is designed to optimize performance in he 1 to 3 micron region of observation wavelengths (J, H, and K astronomical bands). The system uses a 249 degree of freedom deformable mirror, so that the interactuator spacing is 56 cm as mapped onto the 10 meter aperture. 56 cm is roughly equal to r0 at 1.4 microns, which implies the wavefront fitting error is 0.52 ({lambda}/2{pi})({ital d}/{ital r}{sub 0}){sup 5/6} = 118 nm rms. This is sufficient to produce a system Strehl of 0.74 at 1.4 microns if all other sources of error are negligible, which would be the case with a bright natural guidestar and very high control bandwidth. Other errors associated with the adaptive optics will however contribute to Strehl degradation, namely, servo bandwidth error due to inability to reject all temporal frequencies of the aberrated wavefront, wavefront measurement error due to finite signal-to-noise ratio in the wavefront sensor, and, in the case of a laser guidestar, the so-called cone effect where rays from the guidestar beacon fail to sample some of the upper atmosphere turbulence. Cone effect is mitigated considerably by the use of the very high altitude sodium laser guidestar (90 km altitude), as opposed to Rayleigh beacons at 20 km. However, considering the Keck telescope`s large aperture, this is still the dominating wavefront error contributor in the current adaptive optics system design.

  7. Positioning method for a visual guiding system in a laser welding machine

    NASA Astrophysics Data System (ADS)

    He, Tao; Fan, Youqing; Xie, Yulang; Wu, Qinghua

    2013-10-01

    Combined with the development of guiding systems in laser welding, a visual guidance based positioning method for coaxial installation with a laser welding head is researched. A system calibrating method has been researched and designed, which is to install calibration cylinder in the part fixing a machined part, and test the calibration cylinder center coordinates works calibration of the system. A localization method based on template matching and characteristics of the target image are extracted as target image for templates, guiding two localizations both coarse positioning and fine positioning. Coarse positioning can reduce the influence of other information on the target image. Fine positioning is the second location of targets on the basis of the coarse positioning, reducing the information and keeping effect information of target image characteristics. And the method of sub-pixel localization based on least square method is fixed the center position of the target.

  8. An ion guide laser ion source for isobar-suppressed rare isotope beams

    SciTech Connect

    Raeder, Sebastian Ames, Friedhelm; Bishop, Daryl; Bricault, Pierre; Kunz, Peter; Mjøs, Anders; Heggen, Henning; Institute of Applied Physics, TU Darmstadt, Schlossgartenstr. 7, 64289 Darmstadt ; Lassen, Jens Teigelhöfer, Andrea; Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2

    2014-03-15

    Modern experiments at isotope separator on-line (ISOL) facilities like ISAC at TRIUMF often depend critically on the purity of the delivered rare isotope beams. Therefore, highly selective ion sources are essential. This article presents the development and successful on-line operation of an ion guide laser ion source (IG-LIS) for the production of ion beams free of isobaric contamination. Thermionic ions from the hot ISOL target are suppressed by an electrostatic potential barrier, while neutral radio nuclides effusing out are resonantly ionized by laser radiation within a quadrupole ion guide behind this barrier. The IG-LIS was developed through detailed thermal and ion optics simulation studies and off-line tests with stable isotopes. In a first on-line run with a SiC target a suppression of surface-ionized Na contaminants in the ion beam of up to six orders of magnitude was demonstrated.

  9. Laser Wakefield Acceleration at Reduced Density in the Self-Guided Regime

    SciTech Connect

    Ralph, J E; Albert, F; Glenzer, S H; Palastro, J P; Pollock, B B; Shaw, J L; Till, A; Froula, D H; Clayton, C E; Lu, W; Mori, W B; Pak, A E; Joshi, C; Martin, S; Silva, L O

    2009-11-18

    Experiments conducted using a 200TW 60 fs laser have demonstrated up to 720 MeV electrons in the self-guided laser wakefield regime using pure Helium gas jet targets. Charge and energy of the accelerated electrons was measured using an electron spectrometer with a 0.5T magnet and charge callibrated image plates. The self-trapped charge in a helium plasma was shown to fall off with decreasing electron density with a threshold at 2.5 x 10{sup 18} (cm{sup -3}) below which no charge is trapped. Self-guiding however is shown to continue below this density limitation over distances of 14 mm with an exit spot size of 25{micro}m. Simulations show that injection of electrons at these densities can be assisted through ionization induced trapping in a mix of Helium with 3% Oxygen.

  10. Thermo-mechanical simulation of guided waves in pipes excited by laser pulses

    NASA Astrophysics Data System (ADS)

    Lim, Hyeong Uk; Hong, Jung-Wuk

    2013-04-01

    Ultrasonic guided waves have been widely utilized for the structural health monitoring (SHM) of structural components such as plates and pipes. In particular, the noncontact excitation of the pipe surfaces using laser pulses has shown several advantages in experiments by eliminating the bonding process of the dielectric patches on the curved surfaces and the complicated interpretation of the temperature effect on the bonding layers. However, the numerical simulation of the methodology requires thermo-mechanical coupling and large-scale computation. Therefore, the numerical efficiency of the spatial partitioning by deploying thermo-mechanical elements and mechanical elements is investigated. Then, the laser excitation on the surface is modeled in the form of heat flux, and the generated wave forms are observed. The formation and propagation of the guided waves are also represented numerically.

  11. An ion guide laser ion source for isobar-suppressed rare isotope beams.

    PubMed

    Raeder, Sebastian; Heggen, Henning; Lassen, Jens; Ames, Friedhelm; Bishop, Daryl; Bricault, Pierre; Kunz, Peter; Mjøs, Anders; Teigelhöfer, Andrea

    2014-03-01

    Modern experiments at isotope separator on-line (ISOL) facilities like ISAC at TRIUMF often depend critically on the purity of the delivered rare isotope beams. Therefore, highly selective ion sources are essential. This article presents the development and successful on-line operation of an ion guide laser ion source (IG-LIS) for the production of ion beams free of isobaric contamination. Thermionic ions from the hot ISOL target are suppressed by an electrostatic potential barrier, while neutral radio nuclides effusing out are resonantly ionized by laser radiation within a quadrupole ion guide behind this barrier. The IG-LIS was developed through detailed thermal and ion optics simulation studies and off-line tests with stable isotopes. In a first on-line run with a SiC target a suppression of surface-ionized Na contaminants in the ion beam of up to six orders of magnitude was demonstrated. PMID:24689577

  12. Effects of the irradiation of a finite number of laser beams on the implosion of a cone-guided target

    NASA Astrophysics Data System (ADS)

    Yanagawa, T.; Sakagami, H.; Nagatomo, H.; Sunahara, A.

    2016-03-01

    In direct drive laser fusion, the non-uniformity of the laser absorption on the target surface caused by the irradiation of a finite number of laser beams is a sever problem. GekkoXII laser at Osaka University has twelve laser beams and is irradiated to the target with a dodecahedron orientation, in which the distribution of the laser absorption on the target surface becomes non-uniform. Furthermore, in the case of a cone-guided target, the laser irradiation orientation is more limited. In this paper, we conducted implosion simulations of the cone- guided target based on GekkoXII irradiation orientation and compared the case of using the twelve beams and nine beams where the three beams irradiating the cone region are cut. The implosion simulations were conducted by a three-dimensional pure hydro code.

  13. 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

  14. Free-running modes for gain-guided diode laser arrays

    NASA Astrophysics Data System (ADS)

    Hadley, G. Ronald; Hohimer, John P.; Owyoung, A.

    1987-06-01

    A numerical model for directly calculating the eigenmodes of multiple-stripe gain-guided diode laser arrays is presented which includes the effects of both carrier diffusion and heating in the active region. Comprehensive calculations of the eigenmodes of a CW gain-guided array using this model are directly compared to experimental observations on commercial ten-stripe arrays. These numerical and experimental results show that, contrary to popular wisdom, gain-guided arrays are characterized by a large number of eigenmodes, not limited to the number of elements in the array. In addition, the results show the importance of including the refractive index perturbation arising from junction heating, which dramatically alters both the character and the gain of the array modes.

  15. Optical coherence tomography-guided laser microsurgery for blood coagulation with continuous-wave laser diode

    NASA Astrophysics Data System (ADS)

    Chang, Feng-Yu; Tsai, Meng-Tsan; Wang, Zu-Yi; Chi, Chun-Kai; Lee, Cheng-Kuang; Yang, Chih-Hsun; Chan, Ming-Che; Lee, Ya-Ju

    2015-11-01

    Blood coagulation is the clotting and subsequent dissolution of the clot following repair to the damaged tissue. However, inducing blood coagulation is difficult for some patients with homeostasis dysfunction or during surgery. In this study, we proposed a method to develop an integrated system that combines optical coherence tomography (OCT) and laser microsurgery for blood coagulation. Also, an algorithm for positioning of the treatment location from OCT images was developed. With OCT scanning, 2D/3D OCT images and angiography of tissue can be obtained simultaneously, enabling to noninvasively reconstruct the morphological and microvascular structures for real-time monitoring of changes in biological tissues during laser microsurgery. Instead of high-cost pulsed lasers, continuous-wave laser diodes (CW-LDs) with the central wavelengths of 450 nm and 532 nm are used for blood coagulation, corresponding to higher absorption coefficients of oxyhemoglobin and deoxyhemoglobin. Experimental results showed that the location of laser exposure can be accurately controlled with the proposed approach of imaging-based feedback positioning. Moreover, blood coagulation can be efficiently induced by CW-LDs and the coagulation process can be monitored in real-time with OCT. This technology enables to potentially provide accurate positioning for laser microsurgery and control the laser exposure to avoid extra damage by real-time OCT imaging.

  16. Optical coherence tomography-guided laser microsurgery for blood coagulation with continuous-wave laser diode

    PubMed Central

    Chang, Feng-Yu; Tsai, Meng-Tsan; Wang, Zu-Yi; Chi, Chun-Kai; Lee, Cheng-Kuang; Yang, Chih-Hsun; Chan, Ming-Che; Lee, Ya-Ju

    2015-01-01

    Blood coagulation is the clotting and subsequent dissolution of the clot following repair to the damaged tissue. However, inducing blood coagulation is difficult for some patients with homeostasis dysfunction or during surgery. In this study, we proposed a method to develop an integrated system that combines optical coherence tomography (OCT) and laser microsurgery for blood coagulation. Also, an algorithm for positioning of the treatment location from OCT images was developed. With OCT scanning, 2D/3D OCT images and angiography of tissue can be obtained simultaneously, enabling to noninvasively reconstruct the morphological and microvascular structures for real-time monitoring of changes in biological tissues during laser microsurgery. Instead of high-cost pulsed lasers, continuous-wave laser diodes (CW-LDs) with the central wavelengths of 450 nm and 532 nm are used for blood coagulation, corresponding to higher absorption coefficients of oxyhemoglobin and deoxyhemoglobin. Experimental results showed that the location of laser exposure can be accurately controlled with the proposed approach of imaging-based feedback positioning. Moreover, blood coagulation can be efficiently induced by CW-LDs and the coagulation process can be monitored in real-time with OCT. This technology enables to potentially provide accurate positioning for laser microsurgery and control the laser exposure to avoid extra damage by real-time OCT imaging. PMID:26568136

  17. Keele Observatory

    NASA Astrophysics Data System (ADS)

    Theodorus van Loon, Jacco; Albinson, James; Bagnall, Alan; Bryant, Lian; Caisley, Dave; Doody, Stephen; Johnson, Ian; Klimczak, Paul; Maddison, Ron; Robinson, StJohn; Stretch, Matthew; Webb, John

    2015-08-01

    Keele Observatory was founded by Dr. Ron Maddison in 1962, on the hill-top campus of Keele University in central England, hosting the 1876 Grubb 31cm refractor from Oxford Observatory. It since acquired a 61cm research reflector, a 15cm Halpha solar telescope and a range of other telescopes. Run by a group of volunteering engineers and students under directorship of a Keele astrophysicist, it is used for public outreach as well as research. About 4,000 people visit the observatory every year, including a large number of children. We present the facility, its history - including involvement in the 1919 Eddington solar eclipse expedition which proved Albert Einstein's theory of general relativity - and its ambitions to erect a radio telescope on its site.

  18. Suppression of Weibel Instabilities in Advanced Fast Ignition Laser Fusion Pellets by Two Cone-Guided Relativistic Laser Beams

    NASA Astrophysics Data System (ADS)

    Stefan, V.

    2007-11-01

    I propose utilization of two cone-guided relativistic laser beams in antiparallel interaction with the fusion pellet as a novel approach for the suppression of Weibel instabilities in the core of advanced fast ignition pellets.ootnotetextM. Tabak, J. Hammer, M.E. Glinsky, W.L. Kruer, S. C. Wilks, J. Woodworth, E. M. Campbell, and M.D. Perry, Phys. Plasmas 1 (5), 1626 (1994). The propagation of generated suprathermal electron beam toward the core may lead to the appearance of colossal (˜10MG), small scale (L˜velocity of light/local electron plasma frequencyootnotetextV. Stefan, Suppression of Weibel Instabilities by High-Harmonic Electron Bernstein Modes in Advanced Fast Ignition Laser Fusion Pellets.APS-2006. October 30-November 3, 2006; Philadelphia, Pennsylvania. magnetic fields. This would suppress the transport of magnetic fields into the core of the pellet and may eliminate the difficulties in the nonlinear-relativistic treatment of magnetized core plasma.

  19. Near-infrared image-guided laser ablation of dental decay

    PubMed Central

    Tao, You-Chen; Fried, Daniel

    2009-01-01

    Image-guided laser ablation systems are now feasible for dentistry with the recent development of nondestructive high-contrast imaging modalities such as near-IR (NIR) imaging and optical coherence tomography (OCT) that are capable of discriminating between sound and demineralized dental enamel at the early stages of development. Our objective is to demonstrate that images of demineralized tooth surfaces have sufficient contrast to be used to guide a CO2 laser for the selective removal of natural and artificial caries lesions. NIR imaging and polarization-sensitive optical coherence tomography (PS-OCT) operating at 1310-nm are used to acquire images of natural lesions on extracted human teeth and highly patterned artificial lesions produced on bovine enamel. NIR and PS-OCT images are analyzed and converted to binary maps designating the areas on the samples to be removed by a CO2 laser to selectively remove the lesions. Postablation NIR and PS-OCT images confirmed preferential removal of demineralized areas with minimal damage to sound enamel areas. These promising results suggest that NIR and PS-OCT imaging systems can be integrated with a CO2 laser ablation system for the selective removal of dental caries. PMID:19895146

  20. Near-infrared image-guided laser ablation of dental decay

    NASA Astrophysics Data System (ADS)

    Tao, You-Chen; Fried, Daniel

    2009-09-01

    Image-guided laser ablation systems are now feasible for dentistry with the recent development of nondestructive high-contrast imaging modalities such as near-IR (NIR) imaging and optical coherence tomography (OCT) that are capable of discriminating between sound and demineralized dental enamel at the early stages of development. Our objective is to demonstrate that images of demineralized tooth surfaces have sufficient contrast to be used to guide a CO2 laser for the selective removal of natural and artificial caries lesions. NIR imaging and polarization-sensitive optical coherence tomography (PS-OCT) operating at 1310-nm are used to acquire images of natural lesions on extracted human teeth and highly patterned artificial lesions produced on bovine enamel. NIR and PS-OCT images are analyzed and converted to binary maps designating the areas on the samples to be removed by a CO2 laser to selectively remove the lesions. Postablation NIR and PS-OCT images confirmed preferential removal of demineralized areas with minimal damage to sound enamel areas. These promising results suggest that NIR and PS-OCT imaging systems can be integrated with a CO2 laser ablation system for the selective removal of dental caries.

  1. Mesospheric sodium structure variability on horizontal scales relevant to laser guide star asterisms

    NASA Astrophysics Data System (ADS)

    Pfrommer, Thomas; Hickson, Paul

    2012-07-01

    Adaptive optics (AO) systems of modern telescopes use laser guide stars, produced by resonant excitation of sodium atoms in the mesosphere at around 92 km. Wavefront sensor subapertures, if sufficiently far away from the primary mirror center, resolve the internal structure of the sodium layer. The variability of this structure is caused by the influence of gravity waves and wind shear turbulence. The relevance of such dynamics to AO has been investigated over the past four years. A high-resolution lidar system, employed at the 6-m liquid mirror telescope, which is located near Vancouver, Canada, has been used to study mesospheric dynamics, such as the temporal behavior of the mean altitude. The main results from this study have been published elsewhere and will be summarized here. Along with the temporal variability, the mean altitude on horizontal scales of order IOs of meters has been studied by introducing a tip/tilt stage in the experimental setup. This enables us to swap the laser pulse within a 1 arcmin field of view. The horizontal mean altitude structure function has been measured on 10 observing nights between July and August 2011. Results reveal severe structural differences and a strong horizontal anisotropy. Individual laser beacons in a laser guide star asterism will therefore have at the same time significantly different focus heights. By propagating this 2d structure function to the entrance pupil of a 39 m telescope, we derive a differential focus wavefront error map.

  2. High-quality electron beams from a laser wakefield accelerator using plasma-channel guiding.

    PubMed

    Geddes, C G R; Toth, C S; Van Tilborg, J; Esarey, E; Schroeder, C B; Bruhwiler, D; Nieter, C; Cary, J; Leemans, W P

    2004-09-30

    Laser-driven accelerators, in which particles are accelerated by the electric field of a plasma wave (the wakefield) driven by an intense laser, have demonstrated accelerating electric fields of hundreds of GV m(-1) (refs 1-3). These fields are thousands of times greater than those achievable in conventional radio-frequency accelerators, spurring interest in laser accelerators as compact next-generation sources of energetic electrons and radiation. To date, however, acceleration distances have been severely limited by the lack of a controllable method for extending the propagation distance of the focused laser pulse. The ensuing short acceleration distance results in low-energy beams with 100 per cent electron energy spread, which limits potential applications. Here we demonstrate a laser accelerator that produces electron beams with an energy spread of a few per cent, low emittance and increased energy (more than 10(9) electrons above 80 MeV). Our technique involves the use of a preformed plasma density channel to guide a relativistically intense laser, resulting in a longer propagation distance. The results open the way for compact and tunable high-brightness sources of electrons and radiation. PMID:15457252

  3. High quality electron beams from a plasma channel guided laser wakefield accelerator

    SciTech Connect

    Geddes, C.G.R.; Toth, Cs.; van Tilborg, J.; Esarey, E.; Schroeder, C.B.; Bruhwiler, D.; Nieter, C.; Cary, J.; Leemans, W.P.

    2004-07-08

    Laser driven accelerators, in which particles are accelerated by the electric field of a plasma wave driven by an intense laser, have demonstrated accelerating electric fields of hundreds of GV/m. These fields are thousands of times those achievable in conventional radiofrequency (RF) accelerators, spurring interest in laser accelerators as compact next generation sources of energetic electrons and radiation. To date however, acceleration distances have been severely limited by lack of a controllable method for extending the propagation distance of the focused laser pulse. The ensuing short acceleration distance results in low energy beams with 100% electron energy spread, limiting applications. Here we demonstrate that a relativistically intense laser can be guided by a preformed plasma density channel and that the longer propagation distance can result in electron beams of percent energy spread with low emittance and increased energy, containing >10{sup 9} electrons above 80 MeV. The preformed plasma channel technique forms the basis of a new class of accelerators, combining beam quality comparable to RF accelerators with the high gradients of laser accelerators to produce compact tunable high brightness electron and radiation sources.

  4. Plasma Parameter of a Capillary Discharge-Produced Plasma Channel to Guide an Ultrashort Laser Pulse

    SciTech Connect

    Higashiguchi, Takeshi; Terauchi, Hiromitsu; Bai, Jin-xiang; Yugami, Noboru

    2009-01-22

    We have observed the optical guiding of a 100-fs laser pulse with the laser intensity in the range of 10{sup 16} W/cm{sup 2} using a 1.5-cm long capillary discharge-produced plasma channel for compact electron acceleration applications. The optical pulse propagation using the plasma channel is achieved with the electron densities of 10{sup 17}-10{sup 18} cm{sup -3} and the electron temperatures of 0.5-4 eV at a discharge time delay of around 150 ns and a discharge current of 500 A with a pulse duration of 100-150 ns. An energy spectrum of the accelerated electrons from a laser-plasma acceleration scheme showed a peak at 1.3 MeV with a maximum energy tail of 1.6 MeV.

  5. Intelligent Image Analysis for Image-Guided Laser Hair Removal and Skin Therapy

    NASA Technical Reports Server (NTRS)

    Walker, Brian; Lu, Thomas; Chao, Tien-Hsin

    2012-01-01

    We present the development of advanced automatic target recognition (ATR) algorithms for the hair follicles identification in digital skin images to accurately direct the laser beam to remove the hair. The ATR system first performs a wavelet filtering to enhance the contrast of the hair features in the image. The system then extracts the unique features of the targets and sends the features to an Adaboost based classifier for training and recognition operations. The ATR system automatically classifies the hair, moles, or other skin lesion and provides the accurate coordinates of the intended hair follicle locations. The coordinates can be used to guide a scanning laser to focus energy only on the hair follicles. The intended benefit would be to protect the skin from unwanted laser exposure and to provide more effective skin therapy.

  6. Tip-tilt reconstruction with a single dim natural guide star in multiconjugate adaptive optics with laser guide stars

    NASA Astrophysics Data System (ADS)

    Femenã­A, Bruno

    2005-12-01

    A solution to the problem of detecting the tip-tilt modes in multiconjugate adaptive optics (MCAO) with laser guide stars (LGS) is presented. This solution requires the presence of only a single relatively dim natural guide star (NGS) within the reconstructed field of view (FoV). The dim NGS is used for the reconstruction of the tip-tilt modes on the entire FoV, while the tomographic reconstruction of second-order and higher-order modes is made possible by having an LGS constellation with LGSs at different heights. Due to the relatively low brightness required for the tip-tilt NGS and the large corrected FoV (as compared with the case of conventional adaptive optics) the presented solution provides a means to achieve near-diffraction-limited performance of a 10-m-class telescope in the near infrared over a large portion of the sky. Sky coverage calculations assuming median seeing conditions indicate that this technique could be applied to 75% (95%) of the sky, achieving corrections with an average Strehl ratio -0.42(-0.33) in the 2.2 μm K band across the 1.5 - reconstructed FoV.

  7. MR-Guided Laser-Induced Thermotherapy of the Infratemporal Fossa and Orbit in Malignant Chondrosarcoma via a Modified Technique

    SciTech Connect

    Vogl, Thomas J.; Mack, Martin G.; Straub, Ralf; Eichler, Katrin; Zangos, Stephan

    2001-12-15

    A 76-year-old patient presented with a recurrent mass of a malignant chondrosarcoma in the right infratemporal fossa and in the left maxillary sinus with orbital invasion. The patient was treated with a palliative intention with MR-guided laser-induced thermotherapy using a modified applicator technique. Following treatment clinical symptoms improved and MRI revealed complete laser-induced tumor necrosis.

  8. Detection of superficial esophageal squamous cell neoplasia by chromoendoscopy-guided confocal laser endomicroscopy

    PubMed Central

    Huang, Jin; Yang, Yun-Sheng; Lu, Zhong-Sheng; Wang, Shuang-Fang; Yang, Jing; Yuan, Jing

    2015-01-01

    AIM: To evaluate the diagnostic potential of Lugol’s chromoendoscopy-guided confocal laser endomicroscopy (CLE) in detecting superficial esophageal squamous cell neoplasia (ESCN). METHODS: Between December 2008 and September 2010, a total of 52 patients were enrolled at the Chinese PLA General Hospital in Beijing, China. First, Lugol’s chromoendoscopy-guided CLE was performed in these patients and the CLE in vivo histological diagnosis was recorded. Then, chromoendoscopy-guided biopsy was performed in the same patients by another endoscopist who was blinded to the CLE findings. Based on the biopsy and CLE diagnosis, en bloc endoscopic resection was performed. The CLE in vivo diagnosis and the histological diagnosis of biopsy of ESCN were compared, using a histological examination of the endoscopic resection specimens as the standard reference. RESULTS: A total of 152 chromoendoscopy-guided biopsies were obtained from 56 lesions. In the 56 lesions of 52 patients, a total of 679 CLE images were obtained vs 152 corresponding biopsies. The sensitivity, specificity, negative predictive value and positive predictive value of chromoendoscopy-guided CLE compared with biopsy were 95.7% vs 82% (P < 0.05), 90% vs 70% (P < 0.05), 81.8% vs 46.7% (P < 0.05), and 97.8% vs 92.7% (P > 0.05), respectively. There was a significant improvement in sensitivity, specificity, negative predictive value, and accuracy when comparing chromoendoscopy-guided CLE with biopsy. CONCLUSION: Lugol’s chromoendoscopy-guided CLE is a real-time, non-invasive endoscopic diagnostic technology; the accuracy of the detection of superficial ESCN is equivalent to or may be superior to biopsy histology. PMID:26078575

  9. Robo-AO: Initial results from the first autonomous laser guide star adaptive optics instrument

    NASA Astrophysics Data System (ADS)

    Riddle, R. L.; Baranec, C.; Law, N. M.; Ramaprakash, A. N.; Tendulkar, S.; Hogstrom, K.; Bui, K.; Burse, M.; Chordia, P.; Das, H.; Dekany, R.; Kulkarni, S.; Punnadi, S.; Smith, R.

    2014-12-01

    Large surveys are discovering thousands of objects which require further characterization at high angular resolution. The demands on space-based observatories and large telescopes with AO systems leave them generally unavailable for large high angular resolution surveys. To address this gap, we have developed Robo-AO, the first robotic laser AO system, as an economical and efficient imaging instrument for 1-3 m class telescopes. Observations of over 200 stellar objects per night have routinely been performed, with target-to-target observation overheads of less than 1.5 minutes. Scientific programs of several thousands of targets can be executed in mere weeks, and Robo-AO has already completed the three largest AO surveys to date.

  10. Laser guiding due to transverse frequency chirp and plasma inhomogeneity: Relevance to laser wakefield acceleration

    NASA Astrophysics Data System (ADS)

    Bandhu Pathak, Vishwa; Vieira, Jorge; Fonseca, Ricardo; Silva, Luis

    2012-10-01

    Multi-dimensional particle-in-cell (PIC) simulations using OSIRIS show that the transverse frequency chirp can induce pulse front tilt (PFT) in the laser as it propagates. The PFT leads to transverse inhomogeneity in the electron density at the laser front such that the laser drifts in the transverse direction followed by its wake and the injected/self-injected electron beam inside the blowout region. We further investigate the effect of the chirp and transverse plasma inhomogeneities (linear density gradient and parabolic plasma channel) on the transverse drift by developing an analytical model based on a variational principle approach. Theory and simulations predict a linear dependence of the frequency chirp on the transverse drift. In the presence of a linear density gradient the laser drifts towards the decreasing plasma density. We show that an appropriate transverse chirp can balance the drift, and can reduce/nullify the injected electron beam pointing angle. In extreme scenarios, dispersion effects due to transverse chirp can filament the laser generating multiple bubble in the same transverse plane.

  11. Laser Station Design for the Global Light System for the Planned JEM-EUSO Extreme Universe Observatory

    NASA Astrophysics Data System (ADS)

    Geier, Christine; Burg, Martin; Bigler, Colton; Wiencke, Lawrence

    2014-03-01

    The JEM-EUSO Global Light System (GLS) will provide ground-based calibration and monitoring for the JEM-EUSO detector planned for the International Space Station (ISS). JEM-EUSO will use the atmosphere as a giant calorimeter to measure Ultra High Energy Cosmic Rays (UHECRs). The GLS will include twelve ground stations. All twelve will have calibration xenon flash bulbs and six will have steered lasers. The GLS laser stations will generate optical signatures by creating light tracks across the JEM-EUSO field of view. The lasers and xenon flashers will be used to benchmark the JEM-EUSO instrument during its mission since energy, duration and orientation of those sources can be controlled. In this presentation, we will describe a project to design and build a working prototype of a GLS laser station. In order to meet the specifications set forth in the design requirements, our design incorporates remote operation capability, solar power, and a controlled internal climate. These components are in addition to the laser and calibration system and steering mechanism. All components will be combined in a robust, durable design that can be deployed and operated in remote locations across the globe.

  12. Particle-free semiconductor cutting using the water jet guided laser

    NASA Astrophysics Data System (ADS)

    Perrottet, Delphine; Spiegel, Akos; Wagner, Frank; Housh, Roy; Richerzhagen, Bernold; Manley, John

    2005-04-01

    For many years, wafer cutting has posed a challenge to laser-based cutting techniques because of the brittle nature of semiconductors and the exacting requirements for cleanliness. Since conventional laser cutting generates a strong heat-affected zone and a large amount of particles, abrasive sawing is currently the standard process for semiconductor wafer dicing. However, abrasive sawing can no longer fulfill the demands of new, emerging types of semiconductor devices like those based on thin wafers and compound semiconductors. New separation methods are investigated here. The water jet guided laser is a relatively recent technology that offers not only a significantly reduced heat-affected zone but also a cleaner wafer surface. This is due, first, to the water jet, which cools the material between the laser pulses and removes a significant amount of molten material generated by laser ablation. However, the system has recently been upgraded by adding a device that covers the entire wafer surface with a well-controlled thin water film throughout the cutting process. The few generated particles are thus kept in suspension and will not deposit on the wafer surface.

  13. Laser treatment of cutaneous lesions with image-guided fine spot-scanning irradiation

    NASA Astrophysics Data System (ADS)

    Nitta, Isami; Zhao, Xuefeng; Kanno, Akihiro; Kan, Yasushi; Yoshimasa, Takezawa; Maruyama, Tomohiro; Maeda, Yoshitaka

    2007-11-01

    We propose a new laser irradiation method for the treatment of cutaneous lesions in plastic surgery. In general, lasers with a spot size of 1 to 10 mm are used in irradiation on diseased skin. Although the target absorbs more light energy according to the theory of selective photothermolysis, the surrounding tissue, however, is still somewhat damaged. In proposed method, an f-theta lens, which is assembled by a shrink fitter, focuses the irradiation laser beam to a very fine spot with the size of 125 μm. Guided by the captured object-image, such laser beam is conducted by a pair of galvanometer-driven mirrors to irradiate only the desired tissue target without thermal damage to surrounding tissue. Moreover, an optical coherence tomography, whose probe is capable of wide field of view, can be used to provide the guidance information for the best treatment. The usefulness of the developed laser therapy apparatus was demonstrated by performing an experiment on the removal of tattoo pigment.

  14. Magnetic resonance-guided laser interstitial thermal therapy: report of a series of pediatric brain tumors.

    PubMed

    Tovar-Spinoza, Zulma; Choi, Hoon

    2016-06-01

    OBJECTIVE Magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) is a novel, minimally invasive treatment that has multiple advantages in pediatric use and broad applicability for different types of lesions. Here, the authors report the preliminary results of the first series of pediatric brain tumors treated with MRgLITT at Golisano Children's Hospital in Syracuse, New York. METHODS Pediatric brain tumors treated with MRgLITT between February 2012 and August 2014 at Golisano Children's Hospital were evaluated retrospectively. Medical records, radiological findings, surgical data, complications, and results of tumor volumetric analyses were reviewed. The Visualase thermal laser system (Medtronic) was used in all MRgLITT procedures. RESULTS This series included 11 patients with 12 tumors (pilocytic astrocytoma, ependymoma, medulloblastoma, choroid plexus xanthogranuloma, subependymal giant cell astrocytoma, and ganglioglioma). A single laser and multiple overlapping ablations were used for all procedures. The mean laser dose was 10.23 W, and the mean total ablation time was 68.95 seconds. The mean initial target volume was 6.79 cm(3), and the mean immediate post-ablation volume was 7.86 cm(3). The mean hospital stay was 3.25 days, and the mean follow-up time was 24.5 months. Tumor volume decreased in the first 3 months after surgery (n = 11; p = 0.007) and continued to decrease by the 4- to 6-month followup (n = 11; mean volume 2.61 cm(3); p = 0.009). Two patients experienced post-ablation complications: transient right leg weakness in one patient, and transient hemiparesis, akinetic mutism, and eye movement disorder in the other. CONCLUSIONS Magnetic resonance-guided laser interstitial thermal therapy is an effective first- or second-line treatment for select pediatric brain tumors. Larger multiinstitutional clinical trials are necessary to evaluate its use for different types of lesions to further standardize practices. PMID:26849811

  15. Guided Wave Sensing In a Carbon Steel Pipe Using a Laser Vibrometer System

    NASA Astrophysics Data System (ADS)

    Ruíz Toledo, Abelardo; Salazar Soler, Jordi; Chávez Domínguez, Juan Antonio; García Hernández, Miguel Jesús; Turó Peroy, Antoni

    2010-05-01

    Non-Destructive Evaluation (NDE) techniques have achieved a great development during the last decades as a valuable tool for material characterization, manufacturing control and structural integrity tests. Among these tools, the guided wave technology has been rapidly extended because it reduces inspection time and costs compared to the ordinary point by point testing in large structures, as well as because of the possibility of inspecting under insulation and coating conditions. This fast development has motivated the creation of several inspection and material characterization systems including different technologies which can be combined with this technique. Different measurements systems based on laser techniques have been presented in order to inspect pipes, plates and diverse structures. Many of them are experimental systems of high cost and complexity which combine the employment of a laser for generation of waves in the structure and an interferometer for detection. Some of them employ air-coupled ultrasound generation transducers, with high losses in air and which demand high energy for exciting waves in materials of high stiffness. The combined employment of a commercial vibrometer system for Lamb wave sensing in plates has been successfully shown in the literature. In this paper we present a measurement system based on the combined employment of a piezoelectric wedge transducer and a laser vibrometer to sense guided acoustic waves in carbon steel pipes. The measurement system here presented is mainly compounded of an angular wedge transducer, employed to generate the guided wave and a commercial laser vibrometer used in the detection process. The wedge transducer is excited by means of a signal function generator whose output signal has been amplified with a power signal amplifier. A high precision positioning system is employed to place the laser beam at different points through the pipe surface. The signal detected by the laser vibrometer system is

  16. Design and Performance of Raman Fiber Amplifier Based 589-nm Guide Star Lasers for ESO VLT and Their Suitability for Future ELT AO Systems

    NASA Astrophysics Data System (ADS)

    Karpov, V.; Protopopov, V.; Clements, W.; Kaenders, W. G.; Friedenauer, A.; Ernstberger, B.; Hackenberg, W.; Lewis, St. A.; Bonaccini Calia, D.

    2011-09-01

    Large telescopes equipped with adaptive optics require 20-25W CW 589-nm light sources with emission linewidths of ˜5MHz. Towards this goal, ESO has been working for a number of years on the development of laser sources based on high-power narrow-band 1178-nm Raman fiber amplifiers (RFA) with subsequent frequency doubling to 589nm, demonstrating field tested lasers and powers beyond 50W CW. We present the design and performance of the guide star lasers being developed by industrial partners Toptica and MPBC, under contract from ESO, for deployment at the ESO VLT. The laser is designed and robustly engineered specifically for deployment on telescope facilities. The laser design is based on ESO's patented narrow-band RFA. The linearly-polarized, fiber-coupled emission of a Toptica CW diode laser, emitting 20mW at 1178nm, serves as master oscillator signal with stabilized emission frequency and controllable spectral linewidth up to a few MHz. The narrow-band seed signal is amplified in a polarization-maintaining (PM) Raman fiber amplifier developed by MPBC. The amplifier is pumped by a high-power 1120-nm PM fiber laser. With efficient suppression of stimulated Brillouin scattering, an unprecedented 40W of narrow-band RFA output has been obtained. The RFA output is then mode-matched into a resonant cavity doubler with a free spectral range exactly matching the sodium D2a to D2b separation. This allows simultaneous generation of an additional frequency component (D2b line) in the output beam to re-pump the electronic population of sodium atoms, thereby increasing the return flux. We have demonstrated doubling efficiencies >80%, resulting in CW output powers at 589nm easily exceeding the design goal of 20W. Fiber lasers provide excellent output beam quality and are turn-key, maintenance-free, reliable, ruggedized devices whose compactness allows installation directly on the launch telescope structure. They are therefore well suited for LGS applications, also considering

  17. Grand Observatory

    NASA Technical Reports Server (NTRS)

    Young, Eric W.

    2002-01-01

    Various concepts have been recently presented for a 100 m class astronomical observatory. The science virtues of such an observatory are many: resolving planets orbiting around other stars, resolving the surface features of other stars, extending our temporal reach back toward the beginning (at and before stellar and galactic development), improving on the Next Generation Space Telescope, and other (perhaps as yet) undiscovered purposes. This observatory would be a general facility instrument with wide spectral range from at least the near ultraviolet to the mid infrared. The concept espoused here is based on a practical, modular design located in a place where temperatures remain (and instruments could operate) within several degrees of absolute zero with no shielding or cooling. This location is the bottom of a crater located near the north or south pole of the moon, most probably the South Polar Depression. In such a location the telescope would never see the sun or the earth, hence the profound cold and absence of stray light. The ideal nature of this location is elaborated herein. It is envisioned that this observatory would be assembled and maintained remotely through the use of expert robotic systems. A base station would be located above the crater rim with (at least occasional) direct line-of-sight access to the earth. Certainly it would be advantageous, but not absolutely essential, to have humans travel to the site to deal with unexpected contingencies. Further, observers and their teams could eventually travel there for extended observational campaigns. Educational activities, in general, could be furthered thru extended human presence. Even recreational visitors and long term habitation might follow.

  18. A tomographic algorithm to determine tip-tilt information from laser guide stars

    NASA Astrophysics Data System (ADS)

    Reeves, A. P.; Morris, T. J.; Myers, R. M.; Bharmal, N. A.; Osborn, J.

    2016-06-01

    Laser Guide Stars (LGS) have greatly increased the sky-coverage of Adaptive Optics (AO) systems. Due to the up-link turbulence experienced by LGSs, a Natural Guide Star (NGS) is still required, preventing full sky-coverage. We present a method of obtaining partial tip-tilt information from LGSs alone in multi-LGS tomographic LGS AO systems. The method of LGS up-link tip-tilt determination is derived using a geometric approach, then an alteration to the Learn and Apply algorithm for tomographic AO is made to accommodate up-link tip-tilt. Simulation results are presented, verifying that the technique shows good performance in correcting high altitude tip-tilt, but not that from low altitudes. We suggest that the method is combined with multiple far off-axis tip-tilt NGSs to provide gains in performance and sky-coverage over current tomographic AO systems.

  19. GeV Electron Beams from a Capillary Discharge Guided Laser Plasma Accelerator

    SciTech Connect

    Nakamura, Kei; Gonsalves, Anthony; Panasenko, Dmitriy; Lin, Chen; Toth, Csaba; Geddes, Cameron; Schroeder, Carl; Esarey, Eric; Leemans, Wim

    2010-07-08

    Laser plasma acceleration (LPA) up to 1 GeV has been realized at Lawrence Berkeley National Laboratory by using a capillary discharge waveguide. In this paper, the capillary discharge guided LPA system including a broadband single-shot electron spectrometer is described. The spectrometer was designed specifically for LPA experiments and has amomentumacceptance of 0.01 - 1.1 GeV/c with a percent level resolution. Experiments using a 33 mm long, 300 mu m diameter capillary demonstrated the generation of high energy electron beams up to 1 GeV. By de-tuning discharge delay from optimum guiding performance, selftrapping and acceleration were found to be stabilized producing 460 MeV electron beams.

  20. Analysis of dual-end-pumped Nd3+-doped index-crossover gain guided-index antiguided fiber laser

    NASA Astrophysics Data System (ADS)

    Shen, Xiao; Wei, Wei; Zou, Hui; Zhang, Liaolin

    2016-05-01

    A dual-end pumped Nd3+-doped index-crossover gain guided-index antiguided (IGG-IAG) fiber laser is analyzed in theory. Pump light propagation and output laser characteristics are both explored by solving the related rate equations. Simulation results show that pump power confined in the IGG-IAG fiber core is larger and more uniform than that of the gain-guided and index-antiguided(GG-IAG) fiber, and the optimum fiber length and the output power of the IGG-IAG fiber laser are both larger than that of GG-IAG fiber laser. The relationship between threshold pump power and doped concentration, fiber length, fiber radius is researched respectively. The analysis results give out a method for the optimal design of the IGG-IAG fiber laser.

  1. Magnetic Resonance-Guided Focal Laser-Induced Interstitial Thermal Therapy in a Canine Prostate Model

    PubMed Central

    Stafford, R. Jason; Shetty, Anil; Elliott, Andrew M.; Klumpp, Sherry A.; McNichols, Roger J.; Gowda, Ashok; Hazle, John D.; Ward, John F.

    2014-01-01

    Purpose To evaluate a newly FDA-cleared closed-loop, magnetic resonance (MR)-guided laser-induced interstitial thermal therapy (LITT) system for targeted ablation of prostate tissue in order to assess targeting ability, lesion generation and feasibility. Materials and Methods Mongrel dogs with (n = 2) and without (n = 5) canine transmissible venereal tumors in the prostate were imaged with a 1.5-T MR imaging scanner. Real-time 3D MR imaging was used to accurately position water-cooled 980-nm laser applicators to pre-determined targets within the canine prostates. Destruction of targeted tissue was guided with MR temperature imaging in real time for precise control of thermal ablation. MR predictions of thermal damage were correlated with findings from post-treatment images and compared to histopathology. Results Template-based targeting using MR guidance allowed the laser applicator to be placed within a mean of 1.1 mm (SD = 0.7 mm) of the target location. The mean width and length of the ablation zone by MR were 13.7 mm (SD = 1.3 mm) and 19.0 mm (SD = 4.2 mm) using single and compound exposures. The thermal damage predicted by MR correlated with the thermal damage determined by post-treatment imaging with a slope near unity and excellent correlation (R2 = 0.94). Conclusions This LITT system provided rapid and localized heating of tissue with minimal collateral thermal spread or injury. Combined with real-time monitoring and template-based planning, MR-guided LITT is an attractive modality for prostate cancer focal therapy. PMID:20727549

  2. Conceptual design for a user-friendly adaptive optics system at Lick Observatory

    SciTech Connect

    Bissinger, H.D.; Olivier, S.; Max, C.

    1996-03-08

    In this paper, we present a conceptual design for a general-purpose adaptive optics system, usable with all Cassegrain facility instruments on the 3 meter Shane telescope at the University of California`s Lick Observatory located on Mt. Hamilton near San Jose, California. The overall design goal for this system is to take the sodium-layer laser guide star adaptive optics technology out of the demonstration stage and to build a user-friendly astronomical tool. The emphasis will be on ease of calibration, improved stability and operational simplicity in order to allow the system to be run routinely by observatory staff. A prototype adaptive optics system and a 20 watt sodium-layer laser guide star system have already been built at Lawrence Livermore National Laboratory for use at Lick Observatory. The design presented in this paper is for a next- generation adaptive optics system that extends the capabilities of the prototype system into the visible with more degrees of freedom. When coupled with a laser guide star system that is upgraded to a power matching the new adaptive optics system, the combined system will produce diffraction-limited images for near-IR cameras. Atmospheric correction at wavelengths of 0.6-1 mm will significantly increase the throughput of the most heavily used facility instrument at Lick, the Kast Spectrograph, and will allow it to operate with smaller slit widths and deeper limiting magnitudes. 8 refs., 2 figs.

  3. Experimental study of self-trapping in capillary discharge guided laser wakefield acceleration

    SciTech Connect

    Panasenko, D.; Esarey, E.; Geddes, C. G. R.; Gonsalves, A. J.; Leemans, W. P.; Lin, C.; Nakamura, K.; Schroeder, C. B.; Toth, C.

    2009-05-04

    Laser wakefield acceleration experiments were carried out using hydrogen-filled capillary discharge waveguides. For a 33 mm long, 300 mu m capillary, parameter regimes with high energy electron beams (up to 1 GeV) and stable 0.5 GeV were found. In the high energy regime, the electron beam peak energy was correlated with the number of trapped electrons. For a 15 mm long, 200 mu m diameter capillary, quasi-monoenergetic e beams up to 300 MeV were observed. By de-tuning discharge delay from optimum guiding performance, self-trapping was found to be stabilized.

  4. Magnetic Resonance-Guided Laser Induced Thermal Therapy for Glioblastoma Multiforme: A Review

    PubMed Central

    Norred, Sarah E.; Johnson, Jacqueline Anne

    2014-01-01

    Magnetic resonance-guided laser induced thermotherapy (MRgLITT) has become an increasingly relevant therapy for tumor ablation due to its minimally invasive approach and broad applicability across many tissue types. The current state of the art applies laser irradiation via cooled optical fiber applicators in order to generate ablative heat and necrosis in tumor tissue. Magnetic resonance temperature imaging (MRTI) is used concurrently with this therapy to plan treatments and visualize tumor necrosis. Though application in neurosurgery remains in its infancy, MRgLITT has been found to be a promising therapy for many types of brain tumors. This review examines the current use of MRgLITT with regard to the special clinical challenge of glioblastoma multiforme and examines the potential applications of next-generation nanotherapy specific to the treatment of glioblastoma. PMID:24527455

  5. Suppression of Rayleigh scattering noise in sodium laser guide stars by hyperfine depolarization of fluorescence.

    PubMed

    Guillet de Chatellus, Hugues; Moldovan, Ioana; Fesquet, Vincent; Pique, Jean-Paul

    2006-11-27

    We propose what we believe is a novel method for enabling the complete suppression of noise due to Rayleigh scattering in sodium laser guide star systems by means of selective discrimination between Rayleigh and fluorescence signals based on polarization properties. We show that, contrary to the nearly 100% polarized Rayleigh scattering, fluorescence from the D(2) sodium line is strongly depolarized under excitation by a modeless laser. This offers the possibility of completely cancelling the effects of the Rayleigh scattering background while preserving the fluorescence signal to about 40% of its maximal value, leading to an improvement of the signal-to-noise ratio by several orders of magnitude. Both theoretical and experimental data confirm this new proposal. PMID:19529568

  6. US-Guided Femoral and Sciatic Nerve Blocks for Analgesia During Endovenous Laser Ablation

    SciTech Connect

    Yilmaz, Saim Ceken, Kagan; Alimoglu, Emel; Sindel, Timur

    2013-02-15

    Endovenous laser ablation may be associated with significant pain when performed under standard local tumescent anesthesia. The purpose of this study was to investigate the efficacy of femoral and sciatic nerve blocks for analgesia during endovenous ablation in patients with lower extremity venous insufficiency. During a 28-month period, ultrasound-guided femoral or sciatic nerve blocks were performed to provide analgesia during endovenous laser ablation in 506 legs and 307 patients. The femoral block (n = 402) was performed at the level of the inguinal ligament, and the sciatic block at the posterior midthigh (n = 124), by injecting a diluted lidocaine solution under ultrasound guidance. After the blocks, endovenous laser ablations and other treatments (phlebectomy or foam sclerotherapy) were performed in the standard fashion. After the procedures, a visual analogue pain scale (1-10) was used for pain assessment. After the blocks, pain scores were 0 or 1 (no pain) in 240 legs, 2 or 3 (uncomfortable) in 225 legs, and 4 or 5 (annoying) in 41 legs. Patients never experienced any pain higher than score 5. The statistical analysis revealed no significant difference between the pain scores of the right leg versus the left leg (p = 0.321) and between the pain scores after the femoral versus sciatic block (p = 0.7). Ultrasound-guided femoral and sciatic nerve blocks may provide considerable reduction of pain during endovenous laser and other treatments, such as ambulatory phlebectomy and foam sclerotherapy. They may make these procedures more comfortable for the patient and easier for the operator.

  7. Laser guide star wavefront sensing for ground-layer adaptive optics on extremely large telescopes.

    PubMed

    Clare, Richard M; Le Louarn, Miska; Béchet, Clementine

    2011-02-01

    We propose ground-layer adaptive optics (GLAO) to improve the seeing on the 42 m European Extremely Large Telescope. Shack-Hartmann wavefront sensors (WFSs) with laser guide stars (LGSs) will experience significant spot elongation due to off-axis observation. This spot elongation influences the design of the laser launch location, laser power, WFS detector, and centroiding algorithm for LGS GLAO on an extremely large telescope. We show, using end-to-end numerical simulations, that with a noise-weighted matrix-vector-multiply reconstructor, the performance in terms of 50% ensquared energy (EE) of the side and central launch of the lasers is equivalent, the matched filter and weighted center of gravity centroiding algorithms are the most promising, and approximately 10×10 undersampled pixels are optimal. Significant improvement in the 50% EE can be observed with a few tens of photons/subaperture/frame, and no significant gain is seen by adding more than 200 photons/subaperture/frame. The LGS GLAO is not particularly sensitive to the sodium profile present in the mesosphere nor to a short-timescale (less than 100 s) evolution of the sodium profile. The performance of LGS GLAO is, however, sensitive to the atmospheric turbulence profile. PMID:21283238

  8. Nature defect evaluation of laser welded thin plate using laser guide wave

    NASA Astrophysics Data System (ADS)

    Song, Kyung Seok; Kim, Jae Yeol

    2007-07-01

    The longitudinal, shear and surface waves have been used to an Ultrasonic wave exploration method to identify internal defects but it has technical difficulties to detect defects in a limited space with having several millimeters board thickness. It is applicable to use Lamb wave, a kind of induction ultrasonic wave that has a relatively high inspection efficiency and defect detection sensitiveness compare to perpendicular or square explorations in terms of the internal defect detection in these kinds of thin board. The Lamb wave is a special type of induction ultrasonic wave to propagate to a board and it is effective to inspect such as board structure, cell structure, etc. Recently a laser is being used to generate Lamb wave but it not being widely utilized because of difficulties in receiving and selective generation in various modes Lamb wave generating and a low S/N ratio, wide range of generating frequency band when a laser is used. This paper aims to study that the defect exploration method to specimen's thickness, using an characteristic of an ultrasonic wave generating in ablation area and thermoelasticity area, has been applied to using a way of receiving it by Air-Coupled Transducer and transmitting it by an ultrasonic wave and a way of non-contact receiving and transmitting ultrasonic wave using a laser. The longitudinal, shear waves have been used in 60mm thickness specimen and Lamb wave in 3mm to run artificial defect detection test. In this way, the usefulness of non-contact laser ultrasonic wave has been verified. To confirm the possibility of implementation on natural defect existing at real welding part, thickness in 3mm SM45C and STS304 artificial defect specimen has been made and defect detection test using Lamb wave has been executed. Detected signal by signal treatment has been expressed in visual not RF signal. By doing so the convenience of defect detection has been attempted and the effectiveness of defect signal visualization using Lamb

  9. Ice Observatory

    NASA Astrophysics Data System (ADS)

    blugerman, n.

    2015-10-01

    My project is to make ice observatories to perceive astral movements as well as light phenomena in the shape of cosmic rays and heat, for example.I find the idea of creating an observation point in space, that in time will change shape and eventually disappear, in consonance with the way we humans have been approaching the exploration of the universe since we started doing it. The transformation in the elements we use to understand big and small transformations, within the universe elements.

  10. Virtual Observatories

    NASA Astrophysics Data System (ADS)

    Genova, Françoise

    2011-06-01

    Astronomy has been at the forefront among scientific disciplines for the sharing of data, and the advent of the World Wide Web has produced a revolution in the way astronomers do science. The recent development of the concept of Virtual Observatory builds on these foundations. This is one of the truly global endeavours of astronomy, aiming at providing astronomers with seamless access to data and tools, including theoretical data. Astronomy on-line resources provide a rare example of a world-wide, discipline-wide knowledge infrastructure, based on internationally agreed interoperability standards.

  11. Simulation and analysis of laser guide star adaptive optics systems for the eight to ten meter class telescopes

    SciTech Connect

    Gavel, D.T.; Olivier, S.S.

    1994-03-01

    This paper discusses the design and analysis of laser-guided adaptive optic systems for the large, 8--10 meter class telescopes. We describe a technique for calculating the expected modulation transfer function and the point spread function for a closed loop adaptive optics system, parameterized by the degree of correction and the seeing conditions. The results agree closely with simulations and experimental data, and validate well known scaling law models even at low order correction. Scaling law.model analysis of a proposed adaptive optics system at the Keck telescope leads to the conclusion that a single laser guide star beacon will be adequate for diffraction limited imaging at wavelengths between 1 and 3 am with reasonable coverage of the sky. Cone anisoplanatism will dominate wavefront correction error at the visible wavelengths unless multiple laser guide stars are used.

  12. Intraoperative real-time MRI-guided stereotactic biopsy followed by laser thermal ablation for progressive brain metastases after radiosurgery.

    PubMed

    Torcuator, Roy G; Hulou, M Maher; Chavakula, Vamsidhar; Jolesz, Ferenc A; Golby, Alexandra J

    2016-02-01

    Stereotactic radiosurgery is one of the treatment options for brain metastases. However, there are patients who will progress after radiosurgery. One of the potential treatments for this subset of patients is laser ablation. Image-guided stereotactic biopsy is important to determine the histopathological nature of the lesion. However, this is usually based on preoperative, static images, which may affect the target accuracy during the actual procedure as a result of brain shift. We therefore performed real-time intraoperative MRI-guided stereotactic aspiration and biopsies on two patients with symptomatic, progressive lesions after radiosurgery followed immediately by laser ablation. The patients tolerated the procedure well with no new neurologic deficits. Intraoperative MRI-guided stereotactic biopsy followed by laser ablation is safe and accurate, providing real-time updates and feedback during the procedure. PMID:26596402

  13. Discovery of a 66 mas Ultracool Binary with Laser Guide Star Adaptive Optics

    SciTech Connect

    Siegler, N; Close, L; Burgasser, A; Cruz, K; Marois, C; Macintosh, B; Barman, T

    2007-02-02

    We present the discovery of 2MASS J21321145+1341584AB as a closely separated (0.066'') very low-mass field dwarf binary resolved in the near-infrared by the Keck II Telescope using laser guide star adaptive optics. Physical association is deduced from the angular proximity of the components and constraints on their common proper motion. We have obtained a near-infrared spectrum of the binary and find that it is best described by an L5{+-}0.5 primary and an L7.5{+-}0.5 secondary. Model-dependent masses predict that the two components straddle the hydrogen burning limit threshold with the primary likely stellar and the secondary likely substellar. The properties of this sytem - close projected separation (1.8{+-}0.3AU) and near unity mass ratio - are consistent with previous results for very low-mass field binaries. The relatively short estimated orbital period of this system ({approx}7-12 yr) makes it a good target for dynamical mass measurements. Interestingly, the system's angular separation is the tightest yet for any very low-mass binary published from a ground-based telescope and is the tightest binary discovered with laser guide star adaptive optics to date.

  14. Wavefront sensor for the Large Binocular Telescope laser guide star facility

    NASA Astrophysics Data System (ADS)

    Busoni, L.; Esposito, S.; Rabien, S.; Haug, M.; Ziegleder, J.; Hölzl, G.

    2008-07-01

    A laser guide star facility is currently being planned for the LBT. The first step of the program aims at the implementation of a ground layer adaptive optics (GLAO) system tailored on the wide-field imager / multi-object spectrograph LUCIFER having a 4x4' FoV. The current design is based on multiple Rayleigh guide stars arranged in a 2-5 arcmin angular radius constellation. A future update path toward small-field diffraction limited performances is foreseen using a hybrid system of sodium and Rayleigh beacons promising lower power requirements for the sodium laser. In this paper we present the estimated performances for both the GLAO and the hybrid implementations and we introduce the wavefront sensors opto-mechanical design . Simulations of the GLAO system show an expected gain in FWHM and encircled energy of 1.5-3 (depending on atmospheric turbulence profiles) with a FWHM variation over LUCIFER FoV below 10% and point out the role of such a GLAO system as PSF stabilizer both over the FoV and with respect to seeing temporal variations. Results of simulations for the hybrid configurations will be presented.

  15. Investigation of resistive guiding of fast electrons in ultra-intense laser-solid interactions

    NASA Astrophysics Data System (ADS)

    Green, James; Booth, Nicola; Robinson, Alex; Lancaster, Kate; Murphy, Chris; Ridgers, Chris

    2015-11-01

    A key issue in realising the development of a number of high-intensity laser-plasma applications is the critical problem of fast electron divergence. Previous experimental measurements have indicated that the electron divergence angle is considerable at relativistic intensities (> 1018 Wcm-2) and that self-pinching of the electron beam will not be sufficient to produce the collimated propagation that is required for applications such as WDM studies or bright, short-pulse X-ray sources. A number of concepts have been proposed to improve fast electron collimation, with one promising approach being to exploit resistivity gradients inside targets to magnetically guide fast electrons. Here we present experimental work using a novel conical target geometry that uses a high/low Z interface to produce such guiding. A range of target designs have been tested using the Vulcan Petawatt laser to investigate improvements in fast electron transport and collimation. Preliminary results will be presented from a number of complementary diagnostics in order to assess the degree and robustness of the focusing mechanism.

  16. EUS-Guided Needle-Based Confocal Laser Endomicroscopy: A Novel Technique With Emerging Applications

    PubMed Central

    Koduru, Pramoda; Joshi, Virendra; Karstensen, John G.; Saftoiu, Adrian; Vilmann, Peter; Giovannini, Marc

    2015-01-01

    Endoscopic ultrasound (EUS) has emerged as an excellent tool for imaging the gastrointestinal tract, as well as surrounding structures. EUS-guided fine-needle aspiration (EUS-FNA) has become the standard of care for the tissue sampling of a variety of masses and lymph nodes within and around the gut, providing further diagnostic and staging information. Confocal laser endomicroscopy (CLE) is a novel endoscopic method that enables imaging at a subcellular level of resolution during endoscopy, allowing up to 1000-fold magnification of tissue and providing an optical biopsy. A new procedure that has been developed in the past few years is needle-based confocal laser endomicroscopy (nCLE), which involves a mini-CLE probe that can be passed through a 1 9-gauge needle during EUS-FNA. This enables the real-time visualization of tissue at a microscopic level, with the potential to further improve the diagnostic accuracy of EUS-FNA. The device has been studied in animals as well as in humans, and the results so far have been promising. Recently, this method has also been used for the visualization of regulatory proteins and receptors in the pancreas, setting a cornerstone for nCLE in molecular imaging. The aim of this article is to review the role of EUS-guided nCLE in modern endoscopy and its implications in molecular imaging. PMID:27099595

  17. Modeling low order aberrations in laser guide star adaptive optics systems.

    PubMed

    Clare, Richard M; van Dam, Marcos A; Bouchez, Antonin H

    2007-04-16

    When using a laser guide star (LGS) adaptive optics (AO) system, quasi-static aberrations are observed between the measured wavefronts from the LGS wavefront sensor (WFS) and the natural guide star (NGS) WFS. These LGS aberrations, which can be as much as 1200 nm RMS on the Keck II LGS AO system, arise due to the finite height and structure of the sodium layer. The LGS aberrations vary significantly between nights due to the difference in sodium structure. In this paper, we successfully model these LGS aberrations for the Keck II LGS AO system. We use this model to characterize the LGS aberrations as a function of pupil angle, elevation, sodium structure, uplink tip/tilt error, detector field of view, the number of detector pixels, and seeing. We also employ the model to estimate the LGS aberrations for the Palomar LGS AO system, the planned Keck I and the Thirty Meter Telescope (TMT) LGS AO systems. The LGS aberrations increase with increasing telescope diameter, but are reduced by central projection of the laser compared to side projection. PMID:19532717

  18. MRI-guided prostate focal laser ablation therapy using a mechatronic needle guidance system

    NASA Astrophysics Data System (ADS)

    Cepek, Jeremy; Lindner, Uri; Ghai, Sangeet; Davidson, Sean R. H.; Trachtenberg, John; Fenster, Aaron

    2014-03-01

    Focal therapy of localized prostate cancer is receiving increased attention due to its potential for providing effective cancer control in select patients with minimal treatment-related side effects. Magnetic resonance imaging (MRI)-guided focal laser ablation (FLA) therapy is an attractive modality for such an approach. In FLA therapy, accurate placement of laser fibers is critical to ensuring that the full target volume is ablated. In practice, error in needle placement is invariably present due to pre- to intra-procedure image registration error, needle deflection, prostate motion, and variability in interventionalist skill. In addition, some of these sources of error are difficult to control, since the available workspace and patient positions are restricted within a clinical MRI bore. In an attempt to take full advantage of the utility of intraprocedure MRI, while minimizing error in needle placement, we developed an MRI-compatible mechatronic system for guiding needles to the prostate for FLA therapy. The system has been used to place interstitial catheters for MRI-guided FLA therapy in eight subjects in an ongoing Phase I/II clinical trial. Data from these cases has provided quantification of the level of uncertainty in needle placement error. To relate needle placement error to clinical outcome, we developed a model for predicting the probability of achieving complete focal target ablation for a family of parameterized treatment plans. Results from this work have enabled the specification of evidence-based selection criteria for the maximum target size that can be confidently ablated using this technique, and quantify the benefit that may be gained with improvements in needle placement accuracy.

  19. Methods for correcting tilt anisoplanatism in laser-guide-star-based multiconjugate adaptive optics.

    PubMed

    Ellerbroek, B L; Rigaut, F

    2001-10-01

    Multiconjugate adaptive optics (MCAO) is a technique for correcting turbulence-induced phase distortions in three dimensions instead of two, thereby greatly expanding the corrected field of view of an adaptive optics system. This is accomplished with use of multiple deformable mirrors conjugate to distinct ranges in the atmosphere, with actuator commands computed from wave-front sensor (WFS) measurements from multiple guide stars. Laser guide stars (LGSs) must be used (at least for the forseeable future) to achieve a useful degree of sky coverage in an astronomical MCAO system. Much as a single LGS cannot be used to measure overall wave-front tilt, a constellation of multiple LGSs at a common range cannot detect tilt anisoplanatism. This error alone will significantly degrade the performance of a MCAO system based on a single tilt-only natural guide star (NGS) and multiple tilt-removed LGSs at a common altitude. We present a heuristic, low-order model for the principal source of tilt anisoplanatism that suggests four possible approaches to eliminating this defect in LGS MCAO: (i) tip/tilt measurements from multiple NGS, (ii) a solution to the LGS tilt uncertainty problem, (iii) additional higher-order WFS measurements from a single NGS, or (iv) higher-order WFS measurements from both sodium and Rayleigh LGSs at different ranges. Sample numerical results for one particular MCAO system configuration indicate that approach (ii), if feasible, would provide the highest degree of tilt anisoplanatism compensation. Approaches (i) and (iv) also provide very useful levels of performance and do not require unrealistically low levels of WFS measurement noise. For a representative set of parameters for an 8-m telescope, the additional laser power required for approach (iv) is on the order of 2 W per Rayleigh LGS. PMID:11583271

  20. Near-GeV acceleration of electrons by a nonlinear plasma wave driven by a self-guided laser pulse.

    PubMed

    Kneip, S; Nagel, S R; Martins, S F; Mangles, S P D; Bellei, C; Chekhlov, O; Clarke, R J; Delerue, N; Divall, E J; Doucas, G; Ertel, K; Fiuza, F; Fonseca, R; Foster, P; Hawkes, S J; Hooker, C J; Krushelnick, K; Mori, W B; Palmer, C A J; Phuoc, K Ta; Rajeev, P P; Schreiber, J; Streeter, M J V; Urner, D; Vieira, J; Silva, L O; Najmudin, Z

    2009-07-17

    The acceleration of electrons to approximately 0.8 GeV has been observed in a self-injecting laser wakefield accelerator driven at a plasma density of 5.5x10(18) cm(-3) by a 10 J, 55 fs, 800 nm laser pulse in the blowout regime. The laser pulse is found to be self-guided for 1 cm (>10zR), by measurement of a single filament containing >30% of the initial laser energy at this distance. Three-dimensional particle in cell simulations show that the intensity within the guided filament is amplified beyond its initial focused value to a normalized vector potential of a0>6, thus driving a highly nonlinear plasma wave. PMID:19659287

  1. A low-noise transimpedance amplifier for the detection of “Violin-Mode” resonances in advanced Laser Interferometer Gravitational wave Observatory suspensions

    SciTech Connect

    Lockerbie, N. A.; Tokmakov, K. V.

    2014-11-15

    This paper describes the design and performance of an extremely low-noise differential transimpedance amplifier, which takes its two inputs from separate photodiodes. The amplifier was planned to serve as the front-end electronics for a highly sensitive shadow-displacement sensing system, aimed at detecting very low-level “Violin-Mode” (VM) oscillations in 0.4 mm diameter by 600 mm long fused-silica suspension fibres. Four such highly tensioned fibres support the 40 kg test-masses/mirrors of the Advanced Laser Interferometer Gravitational wave Observatory interferometers. This novel design of amplifier incorporates features which prevent “noise-gain peaking” arising from large area photodiode (and cable) capacitances, and which also usefully separate the DC and AC photocurrents coming from the photodiodes. In consequence, the differential amplifier was able to generate straightforwardly two DC outputs, one per photodiode, as well as a single high-gain output for monitoring the VM oscillations—this output being derived from the difference of the photodiodes’ two, naturally anti-phase, AC photocurrents. Following a displacement calibration, the amplifier's final VM signal output was found to have an AC displacement responsivity at 500 Hz of (9.43 ± 1.20) MV(rms) m{sup −1}(rms), and, therefore, a shot-noise limited sensitivity to such AC shadow- (i.e., fibre-) displacements of (69 ± 13) picometres/√Hz at this frequency, over a measuring span of ±0.1 mm.

  2. A low-noise transimpedance amplifier for the detection of "Violin-Mode" resonances in Advanced Laser Interferometer Gravitational wave Observatory suspensions.

    PubMed

    Lockerbie, N A; Tokmakov, K V

    2014-11-01

    This paper describes the design and performance of an extremely low-noise differential transimpedance amplifier, which takes its two inputs from separate photodiodes. The amplifier was planned to serve as the front-end electronics for a highly sensitive shadow-displacement sensing system, aimed at detecting very low-level "Violin-Mode" (VM) oscillations in 0.4 mm diameter by 600 mm long fused-silica suspension fibres. Four such highly tensioned fibres support the 40 kg test-masses/mirrors of the Advanced Laser Interferometer Gravitational wave Observatory interferometers. This novel design of amplifier incorporates features which prevent "noise-gain peaking" arising from large area photodiode (and cable) capacitances, and which also usefully separate the DC and AC photocurrents coming from the photodiodes. In consequence, the differential amplifier was able to generate straightforwardly two DC outputs, one per photodiode, as well as a single high-gain output for monitoring the VM oscillations-this output being derived from the difference of the photodiodes' two, naturally anti-phase, AC photocurrents. Following a displacement calibration, the amplifier's final VM signal output was found to have an AC displacement responsivity at 500 Hz of (9.43 ± 1.20) MV(rms) m(-1)(rms), and, therefore, a shot-noise limited sensitivity to such AC shadow- (i.e., fibre-) displacements of (69 ± 13) picometres/√Hz at this frequency, over a measuring span of ±0.1 mm. PMID:25430131

  3. A low-noise transimpedance amplifier for the detection of "Violin-Mode" resonances in advanced Laser Interferometer Gravitational wave Observatory suspensions

    NASA Astrophysics Data System (ADS)

    Lockerbie, N. A.; Tokmakov, K. V.

    2014-11-01

    This paper describes the design and performance of an extremely low-noise differential transimpedance amplifier, which takes its two inputs from separate photodiodes. The amplifier was planned to serve as the front-end electronics for a highly sensitive shadow-displacement sensing system, aimed at detecting very low-level "Violin-Mode" (VM) oscillations in 0.4 mm diameter by 600 mm long fused-silica suspension fibres. Four such highly tensioned fibres support the 40 kg test-masses/mirrors of the Advanced Laser Interferometer Gravitational wave Observatory interferometers. This novel design of amplifier incorporates features which prevent "noise-gain peaking" arising from large area photodiode (and cable) capacitances, and which also usefully separate the DC and AC photocurrents coming from the photodiodes. In consequence, the differential amplifier was able to generate straightforwardly two DC outputs, one per photodiode, as well as a single high-gain output for monitoring the VM oscillations—this output being derived from the difference of the photodiodes' two, naturally anti-phase, AC photocurrents. Following a displacement calibration, the amplifier's final VM signal output was found to have an AC displacement responsivity at 500 Hz of (9.43 ± 1.20) MV(rms) m-1(rms), and, therefore, a shot-noise limited sensitivity to such AC shadow- (i.e., fibre-) displacements of (69 ± 13) picometres/√Hz at this frequency, over a measuring span of ±0.1 mm.

  4. An automated airplane detection system for the safeguard against airplane illumination from the laser guide star beacons at the MMT

    NASA Astrophysics Data System (ADS)

    Snyder, Miguel; Lloyd-Hart, Michael

    2007-09-01

    Laser beams for guide star generation are a potential hazard for aircraft. At the MMT telescope located on Mt. Hopkins in Southern Arizona, a constellation of five Rayleigh guide stars is created with a total of 25 W of projected power at 532 nm wavelength. We report operational results from an automatic system deployed at the MMT that is designed to detect aircraft and shut down the lasers if a collision with the beams appears likely. The system, building on a previous prototype, uses a wide-angle CCD camera mounted with a minimally unobstructed view to the optical support structure at the top of the telescope. A computer program reads the camera once every two seconds and calculates the difference between adjacent image pairs. The anti-collision beacons required on all aircraft by the Federal Aviation Administration appear as streaks in the field. If an airplane is detected, it is located in the field relative to the laser beam and its path is projected. If aircraft are detected near or appear that they will approach the beam, the laser's safety shutter is closed and warning messages are sent to the laser operator. Failsafe operation is assured by a "heart beat" signal continuously sent from the detection system to the laser controller, and by the fact that the safety shutter must be energized to open. In the event of a power failure, the system must be manually reset by the Laser Safety Officer before the laser beam can again be propagated.

  5. Scientific goals for the MMT's multi-laser-guided adaptive optics

    NASA Astrophysics Data System (ADS)

    Lloyd-Hart, Michael; Stalcup, Thomas; Baranec, Christoph; Milton, N. Mark; Rademacher, Matthew; Snyder, Miguel; Meyer, Michael; Eisenstein, Daniel

    2006-06-01

    The MMT's five Rayleigh laser guide star system has successfully demonstrated open loop wavefront sensing for both ground-layer and laser tomography adaptive optics (AO). Closed loop correction is expected for the first time in the autumn of 2006. The program is moving into its second phase: construction of a permanent facility to feed AO instruments now used with the telescope's existing natural star AO system. The new facility will preserve the thermal cleanliness afforded by the system's adaptive secondary mirror. With the present laser power of 4 W in each of the Rayleigh beacons, we will first offer ground-layer correction over a 2 arcmin field in J, H, and K bands, with expected image quality routinely 0.2 arcsec or better. Later, we will also offer imaging and spectroscopy from 1.5 to 4.8 μm with a tomographically corrected diffraction limited beam. The development of these techniques will lead to a facility all-sky capability at the MMT for both ground-layer and diffraction-limited imaging, and will be a critical advance in the tools necessary for extremely large telescopes of the future, particularly the Giant Magellan Telescope. We describe the present state of system development, planned progress to completion, and highlight the early scientific applications.

  6. Impact of sodium laser guide star fratricide on multi-conjugate adaptive optics systems.

    PubMed

    Wang, Lianqi; Otarola, Angel; Ellerbroek, Brent

    2010-11-01

    Laser beams projected from the ground to form sodium layer laser guide stars (LGSs) for adaptive optics (AO) systems experience scattering and absorption that reduce their intensity as they propagate upward through the atmosphere. Some fraction of the scattered light will be collected by the other wavefront sensors and causes additional background in parts of the pupil. This cross-talk between different LGS wavefront sensors is referred to as the fratricide effect. In this paper we quantify the magnitude of four different sources of scattering/absorption and backscattering, and we evaluate their impact on performance with various zenith angles and turbulence profiles for one particular AO system. The resulting wavefront error for the Thirty Meter Telescope (TMT) multi-conjugate AO (MCAO) system, NFIRAOS, is on the order of 5 to 20 nm RMS, provided that the mean background from the fratricide effect can be calibrated and subtracted with an accuracy of 80%. We also present the impact on system performance of momentary variations in LGS signal levels due to variations in cirrus absorption or laser power, and we show that this affects the performance more than does an equal variation in the level of the fratricide. PMID:21045880

  7. Robo-AO: Initial results from the first autonomous laser guide star adaptive optics instrument

    NASA Astrophysics Data System (ADS)

    Riddle, R.; Baranec, C.; Law, N. M.; Ramaprakash, A. N.; Tendulkar, S.; Hogstrom, K.; Bui, K.; Burse, M.; Chordia, P.; Das, H.; Dekany, R.; Kulkarni, S.; Punnadi, S.; Smith, R.

    2014-03-01

    Large surveys, such as the Kepler mission and Palomar Transient Factory, are discovering upwards of thousands of objects which require further characterization at angular resolutions significantly finer than normally allowed by atmospheric seeing. The demands on precious space-based observatories (i.e. Hubble Space Telescope) and large telescopes with adaptive optics (AO) systems (i.e. Keck, VLT, Gemini) leave them generally unavailable for high angular resolution surveys of more than a few hundred targets at a time. To address the gap between scientific objects and available telescopes, we have developed Robo-AO, the first robotic laser AO system, as an economical and efficient imaging instrument for the more readily available 1-3 m class telescopes. The Robo-AO system system demonstrates angular resolutions approaching the visible diffraction limit of the Palomar 60-inch telescope. Observations of over 200 stellar objects per night have routinely been performed, with target-to-target observation overheads of less than 1.5 minutes. Scientific programs requiring high-resolution follow-up characterization of several thousands of targets can thus be executed in mere weeks, and Robo-AO has already completed the three largest AO surveys to date.

  8. Real-Time Magnetic Resonance-Guided Stereotactic Laser Amygdalohippocampotomy for Mesial Temporal Lobe Epilepsy

    PubMed Central

    Willie, Jon T.; Laxpati, Nealen G.; Drane, Daniel L.; Gowda, Ashok; Appin, Christina; Hao, Chunhai; Brat, Daniel J.; Helmers, Sandra L.; Saindane, Amit; Nour, Sherif G.; Gross, Robert E.

    2014-01-01

    Background Open surgery effectively treats mesial temporal lobe epilepsy (MTLE), but carries risks of neurocognitive deficits, which may be reduced with minimally invasive alternatives. Objective To describe technical and clinical outcomes of stereotactic laser amygdalohippocampotomy (SLAH) with real-time magnetic resonance thermal imaging (MRTI) guidance. Methods Under general anesthesia and utilizing standard stereotactic methods, 13 adult patients with intractable MTLE (with and without mesial temporal sclerosis, MTS) prospectively underwent insertion of a saline-cooled fiber-optic laser applicator into amygdalohippocampal structures from an occipital trajectory. Computer-controlled laser ablation was performed during continuous MRTI followed by confirmatory contrast-enhanced anatomic imaging and volumetric reconstruction. Clinical outcomes were determined from seizure diaries. Results A mean 60% volume of the amygdalohippocampal complex was ablated in 13 patients (9 with MTS) undergoing 15 procedures. Median hospitalization was one day. With follow-up ranging from 5-26 (median 14) months, 77% (10/13) of patients achieved meaningful seizure reduction, of which 54% (7/13) were free of disabling seizures. Of patients with preoperative MTS, 67% (6/9) achieved seizure freedom. All recurrences were observed by<6 months. Variances in ablation volume and length did not account for individual clinical outcomes. Whereas no complications of laser therapy itself were observed, one significant complication, a visual field defect, resulted from deviated insertion of a stereotactic aligning rod, which was corrected prior to ablation. Conclusion Real-time MR-guided SLAH is a technically novel, safe, and effective alternative to open surgery. Further evaluation with larger cohorts over time is warranted. PMID:24618797

  9. Endoscopic laser range scanner for minimally invasive, image guided kidney surgery

    NASA Astrophysics Data System (ADS)

    Friets, Eric; Bieszczad, Jerry; Kynor, David; Norris, James; Davis, Brynmor; Allen, Lindsay; Chambers, Robert; Wolf, Jacob; Glisson, Courtenay; Herrell, S. Duke; Galloway, Robert L.

    2013-03-01

    Image guided surgery (IGS) has led to significant advances in surgical procedures and outcomes. Endoscopic IGS is hindered, however, by the lack of suitable intraoperative scanning technology for registration with preoperative tomographic image data. This paper describes implementation of an endoscopic laser range scanner (eLRS) system for accurate, intraoperative mapping of the kidney surface, registration of the measured kidney surface with preoperative tomographic images, and interactive image-based surgical guidance for subsurface lesion targeting. The eLRS comprises a standard stereo endoscope coupled to a steerable laser, which scans a laser fan beam across the kidney surface, and a high-speed color camera, which records the laser-illuminated pixel locations on the kidney. Through calibrated triangulation, a dense set of 3-D surface coordinates are determined. At maximum resolution, the eLRS acquires over 300,000 surface points in less than 15 seconds. Lower resolution scans of 27,500 points are acquired in one second. Measurement accuracy of the eLRS, determined through scanning of reference planar and spherical phantoms, is estimated to be 0.38 +/- 0.27 mm at a range of 2 to 6 cm. Registration of the scanned kidney surface with preoperative image data is achieved using a modified iterative closest point algorithm. Surgical guidance is provided through graphical overlay of the boundaries of subsurface lesions, vasculature, ducts, and other renal structures labeled in the CT or MR images, onto the eLRS camera image. Depth to these subsurface targets is also displayed. Proof of clinical feasibility has been established in an explanted perfused porcine kidney experiment.

  10. Rapid embedded wire heating via resistive guiding of laser-generated fast electrons as a hydrodynamic driver

    SciTech Connect

    Robinson, A. P. L.; Schmitz, H.; Pasley, J.

    2013-12-15

    Resistively guiding laser-generated fast electron beams in targets consisting of a resistive wire embedded in lower Z material should allow one to rapidly heat the wire to over 100 eV over a substantial distance without strongly heating the surrounding material. On the multi-ps timescale, this can drive hydrodynamic motion in the surrounding material. Thus, ultra-intense laser solid interactions have the potential as a controlled driver of radiation hydrodynamics in solid density material. In this paper, we assess the laser and target parameters needed to achieve such rapid and controlled heating of the embedded wire.

  11. Guiding and focusing of fast electron beams produced by ultra-intense laser pulse using a double cone funnel target

    SciTech Connect

    Zhang, Wen-shuai; Cai, Hong-bo; Zhu, Shao-ping

    2015-10-15

    A novel double cone funnel target design aiming at efficiently guiding and focusing fast electron beams produced in high intensity (>10{sup 19 }W/cm{sup 2}) laser-solid interactions is investigated via two-dimensional particle-in-cell simulations. The forward-going fast electron beams are shown to be directed and focused to a smaller size in comparison with the incident laser spot size. This plasma funnel attached on the cone target guides and focuses electrons in a manner akin to the control of liquid by a plastic funnel. Such device has the potential to add substantial design flexibility and prevent inefficiencies for important applications such as fast ignition. Two reasons account for the collimation of fast electron beams. First, the sheath electric fields and quasistatic magnetic fields inside the vacuum gap of the double cone provide confinement of the fast electrons in the laser-plasma interaction region. Second, the interface magnetic fields inside the beam collimator further guide and focus the fast electrons during the transport. The application of this technique to cone-guided fast ignition is considered, and it is shown that it can enhance the laser energy deposition in the compressed fuel plasma by a factor of 2 in comparison with the single cone target case.

  12. Guiding and focusing of fast electron beams produced by ultra-intense laser pulse using a double cone funnel target

    NASA Astrophysics Data System (ADS)

    Zhang, Wen-shuai; Cai, Hong-bo; Zhu, Shao-ping

    2015-10-01

    A novel double cone funnel target design aiming at efficiently guiding and focusing fast electron beams produced in high intensity (>1019 W/cm2) laser-solid interactions is investigated via two-dimensional particle-in-cell simulations. The forward-going fast electron beams are shown to be directed and focused to a smaller size in comparison with the incident laser spot size. This plasma funnel attached on the cone target guides and focuses electrons in a manner akin to the control of liquid by a plastic funnel. Such device has the potential to add substantial design flexibility and prevent inefficiencies for important applications such as fast ignition. Two reasons account for the collimation of fast electron beams. First, the sheath electric fields and quasistatic magnetic fields inside the vacuum gap of the double cone provide confinement of the fast electrons in the laser-plasma interaction region. Second, the interface magnetic fields inside the beam collimator further guide and focus the fast electrons during the transport. The application of this technique to cone-guided fast ignition is considered, and it is shown that it can enhance the laser energy deposition in the compressed fuel plasma by a factor of 2 in comparison with the single cone target case.

  13. Guided conversion to enhance cation detection in water using laser-induced breakdown spectroscopy

    SciTech Connect

    Lu Yuan; Li Ying; Wu Jianglai; Zhong Shilei; Zheng Ronger

    2010-05-01

    A novel approach, named guided conversion enhancement, has been established to improve the laser-induced breakdown spectroscopy (LIBS) sensitivity of cation detection in water. Two processes were involved in this approach: the main part was replacement reaction that converted the cations in water to solid granules on the surface of an immersed metallic sheet; the other was electric assistance that increased local cation concentration and strengthened the reaction. With the aid of replacement reaction and an electric field, a detection limit of 16 ppb was achieved for copper cation (Cu{sup 2+}) detection in a water solution of CuSO4. The obtained results suggest that this approach has significant potential to be developed as an effective method for underwater cation detection.

  14. Tissue differentiation using laser-induced shock waves by detection of acoustic transients through an optical wave-guide

    NASA Astrophysics Data System (ADS)

    Tschepe, Johannes; Ahrens, Thomas; Helfmann, Juergen; Mueller, Gerhard J.; Gapontsev, Valentin P.

    1993-05-01

    Some physical phenomena which occur during the fragmentation of calculi by laser induced optical break down are presented. With in vitro experiments it could be shown that the energy of the laser induced plasma and of the cavitation bubble (induced by the plasma) depends by the nature of the tissue. The laser induced plasma and the cavitation bubble generate shock waves. These sound waves are transferred via the laser fiber and detected with a piezo- electrical sensor at the proximal end. The acoustic signal contains information on the potential energy of the bubble, which depends on the energy of the plasma. The possibility of measuring the energy dependent acoustic transients allows to distinguish between hard and soft tissue and by this it is suitable for controlling the laser lithotripsy process. The transmission of acoustic transients through silica glass fibers is investigated by theoretical calculations. It shows the feasibility of silica glass fibers as an acoustic wave guide.

  15. Multi-laser-guided adaptive optics for the Large Binocular Telescope

    NASA Astrophysics Data System (ADS)

    Lloyd-Hart, M.; Angel, R.; Green, R.; Stalcup, T.; Milton, N. M.; Powell, K.

    2007-09-01

    We describe the conceptual design of an advanced laser guide star facility (LGSF) for the Large Binocular Telescope (LBT), to be built in collaboration with the LBT's international partners. The highest priority goal for the facility is the correction of ground-layer turbulence, providing partial seeing compensation in the near IR bands over a 4' field. In the H band, GLAO is projected to improve the median seeing from 0.55" to 0.2". The new facility will build on the LBT's natural guide star AO system, integrated into the telescope with correction by adaptive secondary mirrors, and will draw on Arizona's experience in the construction of the first multi-laser adaptive optics (AO) system at the 6.5 m MMT. The LGSF will use four Rayleigh beacons at 532 nm, projected to an altitude of 25 km, on each of the two 8.4 m component telescopes. Initial use of the system for ground layer correction will deliver image quality well matched to the LBT's two LUCIFER near IR instruments. They will be used for direct imaging over a 4'×4' field and will offer a unique capability in high resolution multi-object spectroscopy. The LGSF is designed to include long-term upgrade paths. Coherent imaging at the combined focus of the two apertures will be exploited by the LBT Interferometer in the thermal IR. Using the same launch optics, an axial sodium or Rayleigh beacon can be added to each constellation, for tomographic wavefront reconstruction and diffraction limited imaging over the usual isoplanatic patch. In the longer term, a second DM conjugated to high altitude is foreseen for the LBT's LINC-NIRVANA instrument, which would extend the coherent diffraction-limited field to an arcminute in diameter with multi-conjugate AO.

  16. Daytime Observations with ELTs in the Thermal Infrared Using Laser Guide Star Adaptive Optics

    NASA Astrophysics Data System (ADS)

    Beckers, J. M.

    2011-09-01

    Using Magneto-Optical Filters (MOFs; also called FADOFs = Faraday Anomalous Dispersion Optical Filters) it is possible to clearly see Sodium Laser Guide Stars in the daytime sky. This makes it possible to use ELT Adaptive Optics systems for diffraction limited observations 24 hours/day. Because of the bright daytime sky this LGS AO application is only of astronomical interest in the mid-infrared wavelength region (4 - 25 microns wavelengths) where the thermal radiation of the atmosphere-telescope system dominates the scattering of sunlight thus making the day- and night- sky background comparable. Incorporating MOFs in the LGS wavefront sensor thus would more than double the ELT observing time for mid-infrared astronomy and would make sources in almost the entire sky available for observation at any time of the year. Even though the AO would increase the brightness of point-sources, it would not compete with the James Webb Space Telescope in terms of detectability. The gain with respect to the JWST lies in the 5 to 6 times better linear angular resolution. The contrast gain in brightness at near-IR wavelengths is sufficient to give sufficient natural guide stars there for tip-tilt control. MOFs have been shown to function with Na lasers in LIDAR applications (see Beckers and Cacciani, Experimental Astronomy 11, 133, 2001). The main complication associated with incorporating MOFs in ELT AO system is likely the requirement to make the telescope and its enclosure robust in the daytime environment. I refer to SPIE Proceedings 6986 (2008) for a recent reference on this topic.

  17. Haystack Observatory

    NASA Technical Reports Server (NTRS)

    1972-01-01

    Radio astronomy programs comprise three very-long-baseline interferometer projects, ten spectral line investigations, one continuum mapping in the 0.8 cm region, and one monitoring of variable sources. A low-noise mixer was used in mapping observations of 3C273 at 31 GHz and in detecting of a new methyl alcohol line at 36,169 MHz in Sgr B2. The new Mark 2 VLBI recording terminal was used in galactic H2O source observations using Haystack and the Crimean Observatory, USSR. One feature in W29 appears to have a diameter of 0.3 millisec of arc and a brightness temperature of 1.4 x 10 to the 15th power K. Geodetic baseline measurements via VLBI between Green Bank and Haystack are mutually consistent within a few meters. Radar investigations of Mercury, Venus, Mars, and the Moon have continued. The favorable opposition of Mars and improvements in the radar permit measurements on a number of topographic features with unprecedented accuracy, including scarps and crater walls. The floor of Mare Serenitatis slopes upward towards the northeast and is also the location of a strong gravitational anomaly.

  18. Guiding and collimation of laser-accelerated proton beams using thin foils followed with a hollow plasma channel

    NASA Astrophysics Data System (ADS)

    Xiao, K. D.; Zhou, C. T.; Qiao, B.; He, X. T.

    2015-09-01

    It is proposed that guided and collimated proton acceleration by intense lasers can be achieved using an advanced target—a thin foil followed by a hollow plasma channel. For the advanced target, the laser-accelerated hot electrons can be confined in the hollow channel at the foil rear side, which leads to the formation of transversely localized, Gaussian-distributed sheath electric field and resultantly guiding of proton acceleration. Further, due to the hot electron flow along the channel wall, a strong focusing transverse electric field is induced, taking the place of the original defocusing one driven by hot electron pressure in the case of a purely thin foil target, which results in collimation of proton beams. Two-dimensional particle-in-cell simulations show that collimated proton beams with energy about 20 MeV and nearly half-reduced divergence of 26° are produced at laser intensities 1020 W/cm2 by using the advanced target.

  19. Adaptive optics with four laser guide stars: correction of the cone effect in large telescopes.

    PubMed

    Viard, Elise; Le, Louarn Miska; Hubin, Norbert

    2002-01-01

    We study the performance of an adaptive optics (AO) system with four laser guide stars (LGSs) and a natural guide star (NGS). The residual cone effect with four LGSs is obtained by a numerical simulation. This method allows the adaptive optics system to be extended toward the visible part of the spectrum without tomographic reconstruction of three-dimensional atmospheric perturbations, resolving the cone effect in the visible. Diffraction-limited images are obtained with 17-arc ms precision in median atmospheric conditions at wavelengths longer than 600 nm. The gain achievable with such a system operated on an existing AO system is studied. For comparison, performance in terms of achievable Strehl ratio is also computed for a reasonable system composed of a 40 x 40 Shack-Hartmann wave-front sensor optimized for the I band. Typical errors of a NGS wave front are computed by use of analytical formulas. With the NGS errors and the cone effect, the Strehl ratio can reach 0.45 at 1.25 microm under good-seeing conditions with the Nasmyth Adaptive Optics System (NAOS; a 14 x 14 subpupil wave-front sensor) at the Very Large Telescope and 0.8 with a 40 x 40 Shack-Hartmann wave-front sensor. PMID:11900425

  20. Intrinsic corrections to optical guiding in a free-electron laser: Beam Research Program

    NASA Astrophysics Data System (ADS)

    Chen, Yu-Jiuan; Scharlemann, E. T.; Sessler, A. M.

    The effect on optical guiding of the undulations of an electron beam in a free electron laser (FEL) is investigated. A model for a fully saturated FEL amplifier with no remaining gain is developed. The density of the electron beam includes the effects of both transverse and longitudinal undulation. The longitudinal density modulation is expressed in terms of the Bessel functions of zeta, where zeta = a(sub w)/2(1 + a(sub w)) is the shift of the electron phase in the electron bucket caused by its longitudinal undulation. The transverse density modulation is evaluated to second order in the ratio of undulation amplitude delta r to beam radial scale length r(sub b). The radiation field is calculated in terms of spatial modes proportional to exp(i(k + delta k + lk(sub w)z - iwt)), where l is an arbitrary integer. Here, delta k is the change of the wavenumber of the radiation caused by the electron bunches. Radially radiating modes with intensity on the order of (delta k/k(sub w))zeta sup 2 are found. Optical guiding is modified by the transverse undulations of the beam at second order in delta r(sub b), and by the longitudinal undulations to first order in delta k/k (sub w). For the usual FEL parameters, the correction is quite small.

  1. Selective removal of esthetic composite restorations with spectral guided laser ablation

    PubMed Central

    Yi, Ivana; Chan, Kenneth H.; Tsuji, Grant H.; Staninec, Michal; Darling, Cynthia L.; Fried, Daniel

    2016-01-01

    Dental composites are used for a wide range of applications such as fillings for cavities, adhesives for orthodontic brackets, and closure of gaps (diastemas) between teeth by esthetic bonding. Anterior restorations are used to replace missing, diseased and unsightly tooth structure for both appearance and function. When these restorations must be replaced, they are difficult to remove mechanically without causing excessive removal or damage to enamel because dental composites are color matched to teeth. Previous studies have shown that CO2 lasers have high ablation selectivity and are well suited for removal of composite on occlusal surfaces while minimizing healthy tissue loss. A spectral feedback guidance system may be used to discriminate between dental composite and dental hard tissue for selective ablation of composite material. The removal of composite restorations filling diastemas is more challenging due to the esthetic concern for anterior teeth. The objective of this study is to determine if composite spanning a diastema between anterior teeth can be removed by spectral guided laser ablation at clinically relevant rates with minimal damage to peripheral healthy tissue and with higher selectivity than a high speed dental hand-piece. PMID:26997742

  2. Human retinal imaging using visible-light optical coherence tomography guided by scanning laser ophthalmoscopy

    PubMed Central

    Yi, Ji; Chen, Siyu; Shu, Xiao; Fawzi, Amani A.; Zhang, Hao F.

    2015-01-01

    We achieved human retinal imaging using visible-light optical coherence tomography (vis-OCT) guided by an integrated scanning laser ophthalmoscopy (SLO). We adapted a spectral domain OCT configuration and used a supercontinuum laser as the illumating source. The center wavelength was 564 nm and the bandwidth was 115 nm, which provided a 0.97 µm axial resolution measured in air. We characterized the sensitivity to be 86 dB with 226 µW incidence power on the pupil. We also integrated an SLO that shared the same optical path of the vis-OCT sample arm for alignment purposes. We demonstrated the retinal imaging from both systems centered at the fovea and optic nerve head with 20° × 20° and 10° × 10° field of view. We observed similar anatomical structures in vis-OCT and NIR-OCT. The contrast appeared different from vis-OCT to NIR-OCT, including slightly weaker signal from intra-retinal layers, and increased visibility and contrast of anatomical layers in the outer retina. PMID:26504622

  3. In vivo testing of laser optoacoustic system for image-guided biopsy of prostate

    NASA Astrophysics Data System (ADS)

    Oraevsky, Alexander; Ermilov, Sergey; Mehta, Ketan; Miller, Tom; Bell, Brent; Orihuela, Eduardo; Motamedi, Massoud

    2006-02-01

    We have developed and used a laser optoacoustic imaging system with transrectal probe (LOIS-P) for detection of mechanical lesions in canine prostates in vivo. LOIS images have been acquired with a 128-channel transrectal probe and a 32-channel data acquisition system. Optoacoustic images showed a strong contrast enhancement for a blood containing lesion, when compared with ultrasound images. Our studies demonstrated that sufficient optoacoustic contrast exists between blood containing lesion and prostate tissue, although the lesion has been undetectable with ultrasound. The imaging results have been compared with visual examination of surgically excised prostates. Although axial resolution of the wide-band transducers employed in the transrectal probe provides good axial resolution of 0.5 mm, the convex arc geometry of the this array of transducers provides lateral resolution degrading with depth in tissue. A two step algorithm has been developed to improve the lateral resolution of deeply located objects. This algorithm employs optoacoustic image reconstruction based on radial back-projection to determine location and shape of the target object, then a procedure, we call Maximum Angular Amplitude Probability (MAAP), to determine true brightness of the object and simultaneously remove arc-shaped artifacts associated with radial back-projection. A laser optoacoustic imaging system (LOIS-P) with transrectal probe operating in backward detection mode empowered with the new image reconstruction algorithm seems promising as a modality for detection of prostate cancer and guiding prostate biopsy.

  4. Selective removal of esthetic composite restorations with spectral guided laser ablation

    NASA Astrophysics Data System (ADS)

    Yi, Ivana; Chan, Kenneth H.; Tsuji, Grant H.; Staninec, Michal; Darling, Cynthia L.; Fried, Daniel

    2016-02-01

    Dental composites are used for a wide range of applications such as fillings for cavities, adhesives for orthodontic brackets, and closure of gaps (diastemas) between teeth by esthetic bonding. Anterior restorations are used to replace missing, diseased and unsightly tooth structure for both appearance and function. When these restorations must be replaced, they are difficult to remove mechanically without causing excessive removal or damage to enamel because dental composites are color matched to teeth. Previous studies have shown that CO2 lasers have high ablation selectivity and are well suited for removal of composite on occlusal surfaces while minimizing healthy tissue loss. A spectral feedback guidance system may be used to discriminate between dental composite and dental hard tissue for selective ablation of composite material. The removal of composite restorations filling diastemas is more challenging due to the esthetic concern for anterior teeth. The objective of this study is to determine if composite spanning a diastema between anterior teeth can be removed by spectral guided laser ablation at clinically relevant rates with minimal damage to peripheral healthy tissue and with higher selectivity than a high speed dental handpiece.

  5. Integration and laboratory characterization of the ARGOS laser guide star wavefront sensors

    NASA Astrophysics Data System (ADS)

    Busoni, Lorenzo; Bonaglia, Marco; Carbonaro, Luca; Mazzoni, Tommaso; Antichi, Jacopo; Esposito, Simone; Orban De Xivry, Gilles; Rabien, Sebastian

    2013-12-01

    The integration status of the ARGOS wavefront sensors is presented. ARGOS is the laser guide star AO program for the LBT. It will implement a Ground Layer AO correction for the instruments LUCI, an infrared imaging and spectrograph camera, using 3 pulsed low-altitudes Rayleigh beacons for each LBT's eye. It profits of the LBT's adaptive secondary mirrors and of FLAO's pyramid unit for NGS sensing. Each LGS is independently stabilized for on-sky jitter and range-gated using custom Pockels cells and then sensed by a 15x15 SH sensor. The 3 pupil images are reimaged on a single lenslet array and a single detector. In the WFS are also installed 3 patrol cameras for the acquisition of the laser beacons, a system for the stabilization of the pupil images on the lenslet array and an internal source for calibration purposes. The two units are now completing the integration phase in Arcetri premises. We describe the characterization of the units and the closed-loop test realized using a deformable MEMS mirror.

  6. Optical Tube Assemblies for the ESO VLT Four Laser Guide Star Facility

    NASA Astrophysics Data System (ADS)

    Henselmans, R.; Nijkerk, D.; Lemmen, M.; Doelman, N.; Rijnveld, N.; Kamphues, F.

    2011-09-01

    ESO is implementing a new Adaptive Optics facility (AOF) on the Unit Telescope 4 (UT4) of the Very Large Telescope (VLT). For increased sky coverage, Four Laser Guide Star Facilities (4LGSF) will be installed. TNO is developing the Optical Tube Asssemblies (OTAs) for the 4LGSF.The OTAs are Galilean 20x beam expanders, expanding a ˜15 mm input beam to a steerable ˜300 mm output beam with a wavefront quality requirement of <50 nm rms. The allowed defocus under the influence of the changing environmental air temperature (0-15°C, -0.7°C/hr gradient) is only 0.2 waves. The thermal behaviour of the system has been analyzed by combining optical, lumped mass and FE analyses. The design is passively athermalized over a large temperature range as well as under the influence of thermal gradients. Extensive thermal and high power laser testing has shown the system performs as required. This poster describes the design and test results.

  7. Human retinal imaging using visible-light optical coherence tomography guided by scanning laser ophthalmoscopy.

    PubMed

    Yi, Ji; Chen, Siyu; Shu, Xiao; Fawzi, Amani A; Zhang, Hao F

    2015-10-01

    We achieved human retinal imaging using visible-light optical coherence tomography (vis-OCT) guided by an integrated scanning laser ophthalmoscopy (SLO). We adapted a spectral domain OCT configuration and used a supercontinuum laser as the illumating source. The center wavelength was 564 nm and the bandwidth was 115 nm, which provided a 0.97 µm axial resolution measured in air. We characterized the sensitivity to be 86 dB with 226 µW incidence power on the pupil. We also integrated an SLO that shared the same optical path of the vis-OCT sample arm for alignment purposes. We demonstrated the retinal imaging from both systems centered at the fovea and optic nerve head with 20° × 20° and 10° × 10° field of view. We observed similar anatomical structures in vis-OCT and NIR-OCT. The contrast appeared different from vis-OCT to NIR-OCT, including slightly weaker signal from intra-retinal layers, and increased visibility and contrast of anatomical layers in the outer retina. PMID:26504622

  8. Efficient excitation of a mesospheric sodium laser guide star by intermediate-duration pulses

    SciTech Connect

    Morris, J.R.

    1994-02-01

    Calculations of backscatter emission of meosopheric sodium atoms in a laser guide star that is excited by pulses ranging from 30-ns to 0.9-{mu}s duration are described. The efficient use of such pulses at saturating irradiance values is shown to require {approximately} 3 GHz of spectral broadening to provide access to the full absorption spectrum of the D{sub 2} line. The broadening is provided by frequency modulation. A set of density matrices was used to account for all 24 hyperfine states and inhomogeneous Doppler broadening. At the broadband (3-GHz) saturation irradiance of 4 W/cm{sup 2}, both linearly and circularly polarized laser beams are shown to produce emission rates exceeding 60% of the maximum possible rate-equation rate for the 0.9-{mu}s pulses. As expected, circular polarization produced more backscatter than did linear polarization, but the enhancement never exceeded 1/3 in the calculations that are reported. A brief estimate of state precession in the Earth`s magnetic field suggests that achieving even this enhancement will require that the time scale for optical pumping be held to less than 1 {mu}s, which will require the use of irradiances greater than 0.7 W/cm{sup 2} and spectral coverage of the full 3-GHz hyperfine-plus-Doppler absorption profile, at least until most of the population is pumped out of the F = 1 ground states. 46 refs., 24 figs., 5 tabs.

  9. 1.5T MRI-guided trans-perineal laser ablation of locally recurrent prostate adenocarcinoma

    NASA Astrophysics Data System (ADS)

    McPhail, E. Frederick; Mynderse, Lance A.; Callstrom, Matthew R.; Gorny, Krzysztof R.; McNichols, Roger J.; Atwell, Thomas D.; Gettman, Matthew T.; Amrami, Kimberly K.; Kawashima, Akira; Woodrum, David A.

    2010-02-01

    Introduction: Biochemical recurrence of prostate cancer after definitive therapy with radical prostatectomy (RP) is known to occur between 25-30%. We present the first known case of 1.5T MRI guided ablation using laser interstitial thermal therapy (LITT) for locally recurrent prostate cancer following RP. Methods: The patient elected to undergo MRI-guided LITT of the biopsy proven cancer recurrence using an FDAapproved MRI compatible, 980nm, 15-watt laser system with MR thermometry. Under T2-weighted MR(1.5T Siemens) imaging, guidance and targeting of the lesions with trans-perineal placement of laser applicators. Multiple cycles of laser energy were used to ablate the tumor. A MRI-compatible urethral cooling catheter was placed to prevent urethral thermal damage. Results: Intra-procedural temperature mapping allowed continuous monitoring of the ablation zone and permitted ablation control until tumor coverage was achieved. Additionally, the protective cooling effects of the urethral cooling catheter could also be seen with the temperature mapping. Post-ablation gadolinium and T2 weighted MR imaging demonstrated an ablation defect encompassing the recurrent tumor with no residual hyper-enhancing nodules. Three month follow-up shows no residual or recurrent tumor seen on MR imaging. Conclusion: This represents the first known, successful, MRI-guided, LITT procedures at 1.5T for locally recurrent prostate adenocarcinoma following RP.

  10. The Thirty Meter Telescope (TMT): An International Observatory

    NASA Astrophysics Data System (ADS)

    Sanders, Gary H.

    2013-06-01

    The Thirty Meter Telescope (TMT) will be the first truly global ground-based optical/infrared observatory. It will initiate the era of extremely large (30-meter class) telescopes with diffraction limited performance from its vantage point in the northern hemisphere on Mauna Kea, Hawaii, USA. The astronomy communities of India, Canada, China, Japan and the USA are shaping its science goals, suite of instrumentation and the system design of the TMT observatory. With large and open Nasmyth-focus platforms for generations of science instruments, TMT will have the versatility and flexibility for its envisioned 50 years of forefront astronomy. The TMT design employs the filled-aperture finely-segmented primary mirror technology pioneered with the W.M. Keck 10-meter telescopes. With TMT's 492 segments optically phased, and by employing laser guide star assisted multi-conjugate adaptive optics, TMT will achieve the full diffraction limited performance of its 30-meter aperture, enabling unprecedented wide field imaging and multi-object spectroscopy. The TMT project is a global effort of its partners with all partners contributing to the design, technology development, construction and scientific use of the observatory. TMT will extend astronomy with extremely large telescopes to all of its global communities.

  11. Issues in the design and optimization of adaptive optics and laser guide stars for the Keck Telescopes

    SciTech Connect

    Max, C.E.; Gavel, D.T.; Olivier, S.S.

    1994-03-01

    We discuss issues in optimizing the design of adaptive optics and laser guide star systems for the Keck Telescope. The initial tip-tilt system will use Keck`s chopping secondary mirror. We describe design constraints, choice of detector, and expected performance of this tip-tilt system as well as its sky coverage. The adaptive optics system is being optimized for wavelengths of I-2.2{mu}m. We are studying adaptive optics concepts which use a wavefront sensor with varying numbers of subapertures, so as to respond to changing turbulence conditions. The goal is to be able to ``gang together`` groups of deformable mirror subapertures under software control, when conditions call for larger subapertures. We present performance predictions as a function of sky coverage and the number of deformable mirror degrees of freedom. We analyze the predicted brightness several candidate laser guide star systems, as a function of laser power and pulse format. These predictions are used to examine the resulting Strehl as a function of observing wavelength and laser type. We discuss laser waste heat and thermal management issues, and conclude with an overview of instruments under design to take advantage of the Keck adaptive optics system.

  12. ELPOA: toward the tilt measurement from a polychromatic laser guide star

    NASA Astrophysics Data System (ADS)

    Foy, Renaud; Pique, Jean-Paul; Petit, Alain D.; Chevrou, Patrick; Michau, Vincent; Grynberg, Gilbert; Migus, Arnold; Ageorges, Nancy; Bellanger, Veronique; Biraben, Francois; Deron, Ruy; Fews, Hayden; Foy, Francoise-Claude; Hoegemann, Claudia; Laubscher, Markus; Mueller, Daniel; d'Orgeville, Celine; Peillet, Olivier; Redfern, Mike; Schoeck, Matthias; Segonds, Patricia; Soden, Richard; Tallon, Michel; Thiebaut, Eric; Tokovinin, Andrei A.; Vaillant, Jerome; Weulersse, Jean-Marc

    2000-07-01

    Adaptive optics at astronomical telescopes aims at correcting in real time the phase corrugations of incoming wavefronts caused by the turbulent atmosphere, as early proposed by Babcock. Measuring the phase errors requires a bright source, which is located within the isoplanatic patch of the program source. The probability that such a reference source exists is a function of the wavelength of the observation, of the required image quality (Strehl ratio), of the turbulence optical properties, and of the direction of the observation. Several papers have addressed the problem of the sky coverage as a function of these parameters (see e.g.: Le Louarn et al). It turns out that the sky coverage is disastrously low in particular in the short (visible) wavelength range where, unfortunately, the gain in spatial resolution brought by adaptive optics is the largest. Foy and Labeyrie have proposed to overcome this difficulty by creating an artificial point source in the sky in the direction of the observation relying on the backscattered light due to a laser beam. This laser guide star (hereafter referred to as LGS) can be bright enough to allow us to accurately measure the wavefront phase errors, except for two modes which are the piston (which is not relevant in this case) and the tilt. Pilkington has emphasized that the round trip time of the laser beam to the mesosphere, where the LGS is most often formed, is significantly shorter than the typical tilt coherence time; then the inverse-return- of-light principle causes deflections of the outgoing and the ingoing beams to cancel. The apparent direction of the LGS is independent of the tilt. Therefore the tilt cannot be measured only from the LGS. Until now, the way to overcome this difficulty has been to use a natural guide star to sense the tilt. Although the tilt is sensed through the entire telescope pupil, one cannot use a faint source because approximately equals 90% of the variance of the phase error is in the tilt

  13. The Four-Laser Guide Star Facility (4LGSF) for the ESO VLT Adaptive Optics Facility (AOF)

    NASA Astrophysics Data System (ADS)

    Hackenberg, W.; Bonaccini Calia, D.; Lewis, S.; Holzlohner, R.; Buzzoni, B.; Comin, M.; Dupuy, C.; Guidolin, I. M.; Kern, L.; Quattri, M.; Quentin, J.; Ridings, R.; Argomedo, J.; Arsenault, R.; Conzelmann, R.; Delabre, B.; Donaldson, R.; Downing, M.; Duchateau, M.; Hubin, N.; Igl, G.; Jochum, L.; Jolley, P.; Jost, A.; Kiekebusch, M.; Kolb, J.; Kuntschner, H.; Lizon, J.-L.; Le Louarn, M.; Madec, P.-Y.; Manescau, A.; Paufique, J.; Pirard, J.-F.; Reyes, J.; Silber, A.; Soenke, C.; Stroebele, S.; Stuik, R.; Tordo, S.; Vernet, E.; Collazos, R. Guzman

    2011-09-01

    The 4LGSF is to be installed as a subsystem of the ESO Adaptive Optics Facility (AOF) on Unit Telescope 4 (UT4) of the VLT, to provide the AO systems GALACSI/MUSE and GRAAL/HAWK-I with four sodium laser guide stars. The 4LGSF will deploy four modular LGS Units at the UT4 Centrepiece. Two key aspects of the 4LGSF design are: (i) new industrial laser source (fibre lasers) with reduced volume, reduced need of maintenance, higher reliability, simpler operation and optimised spectral format for highly efficient sodium excitation, (ii) modular structure of the four LGS Units, composed of the laser and laser launch telescope, capable to operate independently of the others. The final design of the 4LGSF is now complete and the project has entered the manufacturing, assembly, integration and test phase. Furthermore, modular LGS units containing the laser emitter integrated on the launch telescope have already been demonstrated at ESO in the past years, and results will be presented. We believe that having the laser sources as an integral part of a modular unit together with the launching system offers many advantages at the system level, including the avoidance of beam relays, retaining the flexibility to use as many LGS as required independently, and the possibility of building redundancy into the system. We believe that many of these 4LGSF concepts can serve for ELT multi-LGS-assisted adaptive telescope designs and provide a valuable experience in advance of the E-ELT.

  14. The U.S. National Virtual Observatory

    NASA Astrophysics Data System (ADS)

    Hanisch, Robert

    The U.S. National Virtual Observatory project is a development effort aimed at implementing the framework for an eventual Virtual Observatory facility. Project activities include the development of metadata standards resource and service registries table and image access protocols interfaces to the computational grid and access to VO resources for education and public outreach. Select science prototypes are used to guide technical development and demonstrate the capabilities of the VO framework for enhancing research. The US NVO project works closely with international VO partners through the International Virtual Observatory Alliance. The US NVO project is funded by the National Science Foundation under Cooperative Agreement AST0122449 with The Johns Hopkins University.

  15. Compared performance of different centroiding algorithms for high-pass filtered laser guide star Shack-Hartmann wavefront sensors

    NASA Astrophysics Data System (ADS)

    Lardière, Olivier; Conan, Rodolphe; Clare, Richard; Bradley, Colin; Hubin, Norbert

    2010-07-01

    Variations of the sodium layer altitude and atom density profile induce errors on laser-guide-star (LGS) adaptive optics systems. These errors must be mitigated by (i), optimizing the LGS wavefront sensor (WFS) and the centroiding algorithm, and (ii), by adding a high-pass filter on the LGS path and a low-bandwidth natural-guide-star WFS. In the context of the ESO E-ELT project, five centroiding algorithms, namely the centre-of-gravity (CoG), the weighted CoG, the matched filter, the quad-cell and the correlation, have been evaluated in closedloop on the University of Victoria LGS wavefront sensing test bed. Each centroiding algorithm performance is compared for a central versus side-launch laser, different fields of view, pixel sampling, and LGS flux.

  16. CT-guided percutaneous laser disc decompression with Ceralas D, a diode laser with 980-nm wavelength and 200-microm fiber optics.

    PubMed

    Gevargez, A; Groenemeyer, D W; Czerwinski, F

    2000-01-01

    The aim of this study was to evaluate the compact, portable Ceralas-D diode laser (CeramOptec; 980 + 30 nm wavelength, 200-microm optical fiber) concerning clinical usefulness, handling, and clinical results in the CT-guided treatment of herniated lumbar discs. The positioning of the canula in intradiscal space, the placement of the laser fiber into the disc through the lying canula, and the vaporization itself were carried out under CT-guidance. Due to the thin fiber optic, it was possible to use a thin 23-gauge canula. The laser procedure was performed in 0.1- to 1-s shots with 1-s pulse pause and 4-W power output. A total of 1650-2300 J was applied on each percutaneous laser disc decompression (PLDD). Results in 26 patients were established with a visual-analogue scale (VAS). On the follow-up examinations, 46% of the patients were absolutely pain free ( > 85 % VAS) and fully active in everyday life after 4 postoperative weeks. Thirty-one percent of patients were relieved of the leg pain but had occasional back pain without sensorimotor impairment. Fifteen percent sensed a slight alleviation ( > 50% VAS) of the radiate pain. Eight percent did not experience radicular or pseudo-radicular pain alleviation (< 25% VAS). Cerales-D proves to be an efficient tool for CT-guided PLDD on non-sequestered herniated lumbar discs. PMID:10939481

  17. Guiding glaucoma laser surgery using Fourier-domain optical coherence tomography at 1.3 μm

    NASA Astrophysics Data System (ADS)

    Bayleyegn, Masreshaw D.; Makhlouf, Houssine; Crotti, Caroline; Plamann, Karsten; Dubois, Arnaud

    2012-06-01

    Glaucoma is a disease of the optic nerve that is usually associated with an increased internal pressure of the eye and can lead to a decreased vision and eventually blindness. It is the second leading cause of blindness worldwide with more than 80 million people affected and approximately 6 million blind. The standard clinical treatment for glaucoma, after unsuccessful administration of eyedrops and other treatments, is performing incisional surgery. However, due to post-surgical complications like scarring and wound healing, this conventional method has a global success rate of only about 60%. In comparison, as femtosecond laser surgery may be performed in volume and is a priori less invasive and less susceptible of causing scarring, glaucoma laser surgery could be a novel technique to supplement the conventional glaucoma surgery. We have been working on the development of a new tool for glaucoma treatment that uses an optimized femtosecond laser source centered at 1.65 μm wavelength for making the surgery and an imaging system based on optical coherence tomography (OCT) for guiding the laser surgery. In this proceeding, we present the results obtained so far on the development and utilization of Fourier-domain OCT imaging system working at 1.3 μm center wavelength for guiding the laser incision. Cross-sectional OCT image of pathological human cornea showing the Schlemm's canal, where the surgery is intended to be done, is presented. By coupling OCT imaging system with the laser incision system, we also demonstrate real-time imaging of femtosecond laser incision of cornea.

  18. Prolongation of the lifetime of guided discharges triggered in atmospheric air by femtosecond laser filaments up to 130 μs

    NASA Astrophysics Data System (ADS)

    Arantchouk, L.; Honnorat, B.; Thouin, E.; Point, G.; Mysyrowicz, A.; Houard, A.

    2016-04-01

    The triggering and guiding of electric discharges produced in atmospheric air by a compact 100 kV Marx generator is realized in laboratory using an intense femtosecond laser pulse undergoing filamentation. We describe here an approach allowing extending the lifetime of the discharges by injecting a current with an additional circuit. Laser guiding discharges with a length of 8.5 cm and duration of 130 μs were obtained.

  19. Pyramid wavefront sensing with a laser guide star for an ELT

    NASA Astrophysics Data System (ADS)

    Le Roux, Brice

    2010-07-01

    The wavefront sensor [WFS] is a key element of an Adaptive Optics [AO] system. It gives access to a direct measurement of the turbulent phase, its curvature or its slope, from which the mirror voltages are computed. The ability of the system to correct efficiently the atmospheric turbulence is strongly dependent on the performance of the WFS in estimating the turbulent phase. The Shack-Hartmann [SH] WFS has been for a long time the standard used in AO systems. In 1996, it has been proposed1 a new generation WFS, the pyramid WFS. It is a focal plane WFS, based on the principle of a Foucault knife-edge. It has been demonstrated that it provides a consistent gain with respect to the Shack-Hartmann.2,5-7 More recently, improvements were proposed to increase the pyramid performance.3, 4 On the framework of the developpement of extremely large telescopes, the interest of a pyramid wave front sensor appears clearly. But its behaviour with laser guide stars [LGS], most probably necessary in any Extremely Large Telescope [ELT], is still relatively unknown. Some WFS dedicated to LGS wave front sensing has already been proposed8,9 but a full study of the pyramid WFS behaviour is still necessary. This work's aim is to bring answers to this topic.

  20. Simulation of a prebunched free-electron laser with planar wiggler and ion channel guiding

    SciTech Connect

    Rouhani, M. H.; Maraghechi, B.

    2010-02-15

    A one-dimensional and nonlinear simulation of a free-electron laser with a prebunched electron beam, a planar wiggler, and ion-channel guiding is presented. Using Maxwell's equations and full Lorentz force equation of motion for the electron beam, a set of coupled nonlinear differential equations is derived in slowly varying amplitude and wave number approximation and is solved numerically. This set of equations describes self-consistently the longitudinal dependence of radiation amplitude, growth rates, space-charge amplitude, and wave numbers together with the evolution of the electron beam. Because of using full Lorentz force equation of motion, it is possible to treat the injection of the beam into the wiggler. The electron beam is assumed cold, propagates with a relativistic velocity, ions are assumed immobile, and slippage is ignored. The effect of prebunched electron beam on saturation is studied. Ion-channel density is varied and the results for groups I and II orbits are compared with the case when the ion channel is absent. It is found that by using an ion channel/a prebunched electron beam growth rate can be increased, saturation length can be decreased, and the saturated amplitude of the radiation can be increased.

  1. Active optics: variable curvature mirrors for ELT laser guide star refocusing systems

    NASA Astrophysics Data System (ADS)

    Challita, Zalpha; Hugot, Emmanuel; Madec, Fabrice; Ferrari, Marc; Le Mignant, David; Vivès, Sébastien; Cuby, Jean-Gabriel

    2011-10-01

    The future generation of Extremely Large Telescopes will require a complex combination of technologies for adaptive optics (AO) systems assisted by laser guide stars (LGS). In this context, the distance from the LGS spot to the telescope pupil ranges from about 80 to 200 km, depending on the Sodium layer altitude and the elevation of the telescope. This variation leads to a defocusing effect on the LGS wave-front sensor which needs to be compensated. We propose an active mirror able to compensate for this variation, based on an original optical design including this active optics component. This LGS Variable Curvature Mirror (LGS-VCM) is a 120 mm spherical active mirror able to achieve 820 μm deflection sag with an optical quality better than 150 nm RMS, allowing the radius of curvature variation from F/12 to F/2. Based on elasticity theory, the deformation of the metallic mirror is provided by an air pressure applied on a thin meniscus with a variable thickness distribution. In this article, we detail the analytical development leading to the specific geometry of the active component, the results of finite element analysis and the expected performances in terms of surface error versus the range of refocalisation. Three prototypes have been manufactured to compare the real behavior of the mirror and the simulations data. Results obtained on the prototypes are detailed, showing that the deformation of the VCM is very close to the simulation, and leads to a realistic active concept.

  2. Laser-cooled cesium atoms confined in a fiber-guided magic-wavelength dipole trap

    NASA Astrophysics Data System (ADS)

    Yoon, Taehyun; Haapamaki, Christopher; Flannery, Jeremy; Bappi, Golam; Al Maruf, Rubayet; Alshehri, Omar; Bajcsy, Michal

    2016-05-01

    Strong light-matter interactions crucial for the achievement of optical nonlinearities with small photon numbers can be implemented by confining both photons and an atomic ensemble inside a hollow-core optical waveguide. We have developed an experimental setup trapping cesium atoms in a magneto-optical trap (MOT) and loading them into a hollow-core photonic crystal fiber (HCPCF) where they are transversely confined by a red-detuned optical dipole trap that is also guided by the fiber. This dipole trap is realized at cesium's `magic wavelength' (935.6nm), which results in a state-insensitive trap and suppression of the radially varying AC-Stark shift for the confined atomic cloud. This was not possible with rubidium atoms used the previous experiments in this platform since rubidium does not have a convenient magic wavelength for the red-detuned dipole trap. We report our procedure to load and probe the laser-cooled atoms inside the HCPCF and discuss the outlooks of this system for implementing nonlinear optics with single photons. We also describe our progress on integrating cavities into the HCPCF that could potentially allow transforming the fiber into a cQED system in the strong coupling regime.

  3. The Physics of the SODIUM Laser Guide Stat: Predicting and Enhancing the Photon Returns of Sodium Guide Stars for Different Laser Technologies

    NASA Astrophysics Data System (ADS)

    Kibblewhite, E.

    We have written a detailed Monte Carlo code to determine the photon return from the sodium layer for different types of laser. The code captures the effects of magnetic field, radiation pressure, collision lifetime distribution and spin-exchange relaxation time on the multi-level sodium atom for CW and pulsed laser formats. We compare these results with those obtained from the Optical Bloch equations for a two level atom and from experimental data, where available. We discuss the effect of saturation and optimal pulse and spectral format of lasers for different applications.

  4. A Catalog of Performance Objectives and Performance Guides for Laser Systems Technician for the Job Titles of Laser Technician D.O.T. 019.181-010, Laser Systems Technician D.O.T.-N/A.

    ERIC Educational Resources Information Center

    Pennsylvania State Dept. of Education, Harrisburg. Bureau of Vocational and Technical Education.

    This catalog lists and describes the tasks performed by a laser technician and standards for their performance. Each duty contains performance objectives for related tasks. Included in the objectives are standards that must be met and conditions for performance of the tasks. Performance guides provided for each objective identify the conditions…

  5. Loading Rate-Dependent Elastoviscoplasticity in San Andreas Fault Observatory at Depth (SAFOD) Fault Gouge: Implications for Repeating Earthquakes and Fault Zone-Guided Waves

    NASA Astrophysics Data System (ADS)

    Kohli, A. H.; Lockner, D. A.

    2015-12-01

    Deformation experiments on phyllosilicate-rich fault gouges reveal velocity-strengthening behavior and monotonic strength evolution in response to perturbations in slip velocity below ~10-4 ms-1. Fault gouge from the actively creeping zones at the San Andreas Fault Observatory at Depth (SAFOD) exhibits similar monotonic strength evolution and has been described in terms of rate-state friction-velocity dependence and ageing behavior. While these parameters provide phenomenological descriptions of gouge rheology on relatively short timescales, they are commonly applied in numerical simulations of repeating earthquakes within the SAF creeping section, often being adjusted arbitrarily in order to match seismological observations. With first assuming a deformation constitutive law, we performed comprehensive microstructural and mechanical characterization of fault gouge from the SAFOD Central Deforming Zone (CDZ). An in-situ displacement sensor was developed to provide direct measurements of gouge deformation under various loading conditions, including constant and variable strain rate and constant and variable shear stress. Constant and variable strain-rate tests confirm previous observations of low shear strength and reveal viscoplastic deformation below the frictional yield strength. Variable loading rate tests demonstrate an apparent yield stress for viscoplastic behavior at low loading rates, and a transition to elastic behavior with increasing loading rate up to 0.02 MPas-1. The elastic response of the gouge constrains the static shear modulus ~500 MPa, providing a lower bound of ~450 ms-1 for the shear velocity of the SAFOD fault core. Our microstructural and mechanical characterization of the gouge is consistent with the physical interpretation of an elastically perfect elastoviscoplastic solid. Parameterizing this model with our experimental data demonstrates general agreement with the observed loading rate-dependence of the gouge and provides a physical

  6. Experimental observations and simulations on relativistic self-guiding of an ultra-intense laser pulse in underdense plasmas

    SciTech Connect

    Chiron, A.; Bonnaud, G.; Dulieu, A.; Miquel, J.L.; Malka, G.; Louis-Jacquet, M.; Mainfray, G.

    1996-04-01

    The experimental images of the sidescattered light from a plasma, created by the multiterawatt laser pulse propagating in a hydrogen gas jet, exhibit clear dependence on both gas jet pressure and laser power. Two- and three-dimensional simulations of wave propagation, in presence of the relativistic electron mass increase and the ponderomotive expel of electrons, have been performed to reproduce the Thomson radiation from the plasma electrons. They show electron cavitation induced by the beam focusing, self-focusing, self-guiding, smoothing of the beam nonuniformities and, at larger power, beam filamentation. A bremsstrahlung model with account of the ionization, heating, expansion, and recombination dynamics of the gas, provides the plasma emission background. Both Thomson emission and bremsstrahlung are required to recover the experimental emission patterns. Among the interpretations, a scenario of laser self-guiding over five Rayleigh lengths can be found for 10 TW laser power and 5{times}10{sup 18} cm{sup {minus}3} electron density, which surprisingly disappears at larger powers and densities. {copyright} {ital 1996 American Institute of Physics.}

  7. Serial removal of caries lesions from tooth occlusal surfaces using near-IR image-guided IR laser ablation

    NASA Astrophysics Data System (ADS)

    Chan, Kenneth H.; Tom, Henry; Darling, Cynthia L.; Fried, Daniel

    2015-02-01

    Previous studies have established that caries lesions can be imaged with high contrast without the interference of stains at near-IR wavelengths greater than 1300-nm. It has been demonstrated that computer controlled laser scanning systems utilizing IR lasers operating at high pulse repetition rates can be used for serial imaging and selective removal of caries lesions. In this study, we report our progress towards the development of algorithms for generating rasterized ablation maps from near-IR reflectance images for the removal of natural lesions from tooth occlusal surfaces. An InGaAs camera and a filtered tungsten-halogen lamp producing near-IR light in the range of 1500-1700-nm were used to collect crosspolarization reflectance images of tooth occlusal surfaces. A CO2 laser operating at a wavelength of 9.3- μm with a pulse duration of 10-15-μs was used for image-guided ablation.

  8. Pulse evolution and plasma-wave phase velocity in channel-guided laser-plasma accelerators.

    PubMed

    Benedetti, C; Rossi, F; Schroeder, C B; Esarey, E; Leemans, W P

    2015-08-01

    The self-consistent laser evolution of an intense, short-pulse laser exciting a plasma wave and propagating in a preformed plasma channel is investigated, including the effects of pulse steepening and energy depletion. In the weakly relativistic laser intensity regime, analytical expressions for the laser energy depletion, pulse self-steepening rate, laser intensity centroid velocity, and phase velocity of the plasma wave are derived and validated numerically. PMID:26382537

  9. Development of a fiber-guided laser ultrasonic system resilient to high temperature and gamma radiation for nuclear power plant pipe monitoring

    NASA Astrophysics Data System (ADS)

    Yang, Jinyeol; Lee, Hyeonseok; Lim, Hyung Jin; Kim, Nakhyeon; Yeo, Hwasoo; Sohn, Hoon

    2013-08-01

    This study develops an embeddable optical fiber-guided laser ultrasonic system for structural health monitoring (SHM) of pipelines exposed to high temperature and gamma radiation inside nuclear power plants (NPPs). Recently, noncontact laser ultrasonics is gaining popularity among the SHM community because of its advantageous characteristics such as (a) scanning capability, (b) immunity against electromagnetic interference (EMI) and (c) applicability to high-temperature surfaces. However, its application to NPP pipelines has been hampered because pipes inside NPPs are often covered by insulators and/or target surfaces are not easily accessible. To overcome this problem, this study designs embeddable optical fibers and fixtures so that laser beams used for ultrasonic inspection can be transmitted between the laser sources and the target pipe. For guided-wave generation, an Nd:Yag pulsed laser coupled with an optical fiber is used. A high-power pulsed laser beam is guided through the optical fiber onto a target structure. Based on the principle of laser interferometry, the corresponding response is measured using a different type of laser beam guided by another optical fiber. All devices are especially designed to sustain high temperature and gamma radiation. The robustness/resilience of the proposed measurement system installed on a stainless steel pipe specimen has been experimentally verified by exposing the specimen to high temperature of up to 350 °C and optical fibers to gamma radiation of up to 125 kGy (20 kGy h-1).

  10. Wavefront-guided versus standard laser in situ keratomileusis to correct low to moderate myopia.

    PubMed

    Nuijts, Rudy M M A; Nabar, Vaishaly A; Hament, Willem J; Eggink, Fred A G J

    2002-11-01

    To evaluate the 6-month refractive outcomes of wavefront-guided laser in situ keratomileusis (LASIK) (Zyoptix, Bausch & Lomb) versus standard LASIK (PlanoScan, Bausch & Lomb). Department of Ophthalmology, University Hospital Maastricht, Maastricht, The Netherlands. In a prospective randomized study, 12 patients with myopia had Zyoptix wavefront-guided LASIK in 1 eye and PlanoScan LASIK in the contralateral eye. The safety, efficacy, predictability, stability, optical zone size, and ablation depth were evaluated. The mean preoperative spherical equivalent (SE) of the subjective manifest refraction was -3.88 diopters (D) +/- 1.92 (SD) (Zyoptix) and -4.35 +/- 2.11 D (PlanoScan). Six months postoperatively, 8% of PlanoScan patients and 16% of Zyoptix patients gained at least 2 lines of best corrected visual acuity; the safety index was 1.12 in the Zyoptix group and 1.08 in the PlanoScan group. An SE of +/-1.00 D and +/-0.50 D was achieved by 100% and 92%, respectively, in both groups. There were 2 undercorrections in the Zyoptix group and 1 undercorrection in the PlanoScan group. In the Zyoptix group, 100% had a UCVA of 20/40 and 67% of 20/20 and in the PlanoScan group, 100% and 83%, respectively. The efficacy index was 0.87 and 0.93 in the Zyoptix group and PlanoScan group, respectively. The mean optical zone 6 months postoperatively was 6.16 +/- 0.34 mm in the PlanoScan group and 6.23 +/- 0.41 mm in the Zyoptix group (P =.67). The ablation depth per diopter of defocus equivalent was 13.5 +/- 4.6 microm/D and 8.6 +/- 4.4 microm/D, respectively (P =.01).An excellent safety index was achieved with the Zyoptix and PlanoScan treatments. The efficacy index was marginally lower for Zyoptix treatments as a result of 2 undercorrections. The ablation depth in the Zyoptix group per diopter of defocus equivalent was significantly lower than in the PlanoScan group. Further refinements in defining the ablation algorithms may increase the efficacy index. PMID:12457662

  11. Concept for image-guided vitreo-retinal fs-laser surgery: adaptive optics and optical coherence tomography for laser beam shaping and positioning

    NASA Astrophysics Data System (ADS)

    Matthias, Ben; Brockmann, Dorothee; Hansen, Anja; Horke, Konstanze; Knoop, Gesche; Gewohn, Timo; Zabic, Miroslav; Krüger, Alexander; Ripken, Tammo

    2015-03-01

    Fs-lasers are well established in ophthalmic surgery as high precision tools for corneal flap cutting during laser in situ keratomileusis (LASIK) and increasingly utilized for cutting the crystalline lens, e.g. in assisting cataract surgery. For addressing eye structures beyond the cornea, an intraoperative depth resolved imaging is crucial to the safety and success of the surgical procedure due to interindividual anatomical disparities. Extending the field of application even deeper to the posterior eye segment, individual eye aberrations cannot be neglected anymore and surgery with fs-laser is impaired by focus degradation. Our demonstrated concept for image-guided vitreo-retinal fs-laser surgery combines adaptive optics (AO) for spatial beam shaping and optical coherence tomography (OCT) for focus positioning guidance. The laboratory setup comprises an adaptive optics assisted 800 nm fs-laser system and is extended by a Fourier domain optical coherence tomography system. Phantom structures are targeted, which mimic tractional epiretinal membranes in front of excised porcine retina within an eye model. AO and OCT are set up to share the same scanning and focusing optics. A Hartmann-Shack sensor is employed for aberration measurement and a deformable mirror for aberration correction. By means of adaptive optics the threshold energy for laser induced optical breakdown is lowered and cutting precision is increased. 3D OCT imaging of typical ocular tissue structures is achieved with sufficient resolution and the images can be used for orientation of the fs-laser beam. We present targeted dissection of the phantom structures and its evaluation regarding retinal damage.

  12. Update on Optical Design of Adaptive Optics System at Lick Observatory

    SciTech Connect

    Bauman, B J; Gavel, D T; Waltjen, K E; Freeze, G J; Hurd, R L; Gates, E I; Max, C E; Olivier, S S; Pennington, D M

    2001-07-31

    In 1999, we presented our plan to upgrade the adaptive optics (AO) system on the Lick Observatory Shane telescope (3m) from a prototype instrument pressed into field service to a facility instrument. This paper updates the progress of that plan and details several important improvements in the alignment and calibration of the AO bench. The paper also includes a discussion of the problems seen in the original design of the tip/tilt (t/t) sensor used in laser guide star mode, and how these problems were corrected with excellent results.

  13. A ground-layer adaptive optics system with multiple laser guide stars.

    PubMed

    Hart, M; Milton, N M; Baranec, C; Powell, K; Stalcup, T; McCarthy, D; Kulesa, C; Bendek, E

    2010-08-01

    To determine the influence of the environment on star formation, we need to study the process in the extreme conditions of massive young star clusters ( approximately 10(4) solar masses) near the centre of our own Galaxy. Observations must be carried out in the near infrared because of very high extinction in visible light within the Galactic plane. We need high resolution to identify cluster members from their peculiar motions, and because most such clusters span more than 1', efficient observation demands a wide field of view. There is at present no space-based facility that meets all these criteria. Ground-based telescopes can in principle make such observations when fitted with ground-layer adaptive optics (GLAO), which removes the optical aberration caused by atmospheric turbulence up to an altitude of approximately 500 m (refs 7-10). A GLAO system that uses multiple laser guide stars has been developed at the 6.5-m MMT telescope, in Arizona. In previous tests, the system improved the resolution of the telescope by 30-50%, limited by wavefront error in the optics, but that was insufficient to allow rapid determination of cluster membership. Here we report observations of the core of the globular cluster M3 made after commissioning a sensor to monitor and remove slowly varying aberration in the optics. In natural seeing of 0.7'', the point spread function at 2.2-mum wavelength was sharpened uniformly to 0.3'' over a field of at least 2'. The wide-field resolution was enhanced by a factor of two to three over previous work, with better uniformity, and extends to a wavelength of 1.2 mum. Entire stellar clusters may be examined in a single pointing, and cluster membership can be determined from two such observations separated by just one year. PMID:20686568

  14. MAPPING THE CLUMPY STRUCTURES WITHIN SUBMILLIMETER GALAXIES USING LASER-GUIDE STAR ADAPTIVE OPTICS SPECTROSCOPY

    SciTech Connect

    Menendez-Delmestre, Karin; Goncalves, Thiago S.; Blain, Andrew W.; Swinbank, Mark; Smail, Ian; Ivison, Rob J.; Chapman, Scott C.

    2013-04-20

    We present the first integral-field spectroscopic observations of high-redshift submillimeter-selected galaxies (SMGs) using Laser-Guide Star Adaptive Optics. We target H{alpha} emission of three SMGs at redshifts z {approx} 1.4-2.4 with the OH-Suppressing Infrared Imaging Spectrograph on Keck. The spatially resolved spectroscopy of these galaxies reveals unresolved broad-H{alpha} line regions (FWHM >1000 km s{sup -1}) likely associated with an active galactic nucleus (AGN) and regions of diffuse star formation traced by narrow-line H{alpha} emission (FWHM {approx}< 500 km s{sup -1}) dominated by multiple H{alpha}-bright stellar clumps, each contributing 1%-30% of the total clump-integrated H{alpha} emission. We find that these SMGs host high star formation rate surface densities, similar to local extreme sources, such as circumnuclear starbursts and luminous infrared galaxies. However, in contrast to these local environments, SMGs appear to be undergoing such intense activity on significantly larger spatial scales as revealed by extended H{alpha} emission over 4-16 kpc. H{alpha} kinematics show no evidence of ordered global motion as would be found in a disk, but rather large velocity offsets ({approx}few Multiplication-Sign 100 km s{sup -1}) between the distinct stellar clumps. Together with the asymmetric distribution of the stellar clumps around the AGN in these objects, it is unlikely that we are unveiling a clumpy disk structure as has been suggested in other high-redshift populations of star-forming galaxies. The SMG clumps in this sample may correspond to remnants of originally independent gas-rich systems that are in the process of merging, hence triggering the ultraluminous SMG phase.

  15. MASS OF THE SOUTHERN BLACK HOLE IN NGC 6240 FROM LASER GUIDE STAR ADAPTIVE OPTICS

    SciTech Connect

    Medling, Anne M.; Max, Claire E.; Ammons, S. Mark; Davies, Richard I.; Engel, Hauke; Canalizo, Gabriela E-mail: max@ucolick.org E-mail: hauke@mpe.mpg.de

    2011-12-10

    NGC 6240 is a pair of colliding disk galaxies, each with a black hole in its core. We have used laser guide star adaptive optics on the Keck II telescope to obtain high-resolution ({approx}0.''06) near-infrared integral-field spectra of the region surrounding the supermassive black hole in the south nucleus of this galaxy merger. We use the K-band CO absorption bandheads to trace stellar kinematics. We obtain a spatial resolution of about 20 pc and thus directly resolve the sphere of gravitational influence of the massive black hole. We explore two different methods to measure the black hole mass. Using a Jeans Axisymmetric Multi-Gaussian mass model, we investigate the limit that a relaxed mass distribution produces all of the measured velocity dispersion, and find an upper limit on the black hole mass at 2.0 {+-} 0.2 Multiplication-Sign 10{sup 9} M{sub Sun }. When assuming the young stars whose spectra we observe remain in a thin disk, we compare Keplerian velocity fields to the measured two-dimensional velocity field and fit for a mass profile containing a black hole point mass plus a radially varying spherical component, which suggests a lower limit for the black hole mass of 8.7 {+-} 0.3 Multiplication-Sign 10{sup 8} M{sub Sun }. Our measurements of the stellar velocity dispersion place this active galactic nucleus within the scatter of the M{sub BH}-{sigma}{sub *} relation. As NGC 6240 is a merging system, this may indicate that the relation is preserved during a merger at least until the final coalescence of the two nuclei.

  16. First clinical application of a liquid-core light guide connected to an Er:YAG laser for oral treatment of leukoplakia.

    PubMed

    Meister, Jörg; Franzen, Rene; Eyrich, Gerold; Bongartz, Jens; Gutknecht, Norbert; Hering, Peter

    2010-09-01

    For medical applications, erbium lasers are usually equipped with articulated mirror arms or special glass fibers. However, only with mirror arms is it so far possible to transmit high average powers or pulse energies in the region of 1 J to achieve suitable energy densities for fast tissue preparation. An alternative to the glass fiber systems mentioned above are liquid-core light guides. An extremely flexible liquid-core light guide was used to connect a dental Er:YAG laser system to an especially adapted dental laser applicator. The core liquid was continuously circulated during laser irradiation to transmit pulse energies up to 1.1 J. A modified laser handpiece was used for exemplary clinical treatment. The experimental setup with the highly flexible light guide was completed successfully, and its ease of handling for a dental surgeon was demonstrated in the clinical treatment of leukoplakia of the oral cheek mucosa. Complete ablation of the epithelium with the laser was performed. One year postoperatively, the patient remains disease-free. This article describes the technical realization of a liquid-core light guide system for medical applications. We report about the first successful clinical treatment of oral hyperkeratosis using this new light guide technology. PMID:20393767

  17. Gain-guided soliton fiber laser with high-quality rectangle spectrum for ultrafast time-stretch microscopy.

    PubMed

    Hu, Song; Yao, Jian; Liu, Meng; Luo, Ai-Ping; Luo, Zhi-Chao; Xu, Wen-Cheng

    2016-05-16

    The ultrafast time-stretch microscopy has been proposed to enhance the temporal resolution of a microscopy system. The optical source is a key component for ultrafast time-stretch microscopy system. Herein, we reported on the gain-guided soliton fiber laser with high-quality rectangle spectrum for ultrafast time-stretch microscopy. By virtue of the excellent characteristics of the gain-guided soliton, the output power and the 3-dB bandwidth of the stable mode-locked soliton could be up to 3 mW and 33.7 nm with a high-quality rectangle shape, respectively. With the proposed robust optical source, the ultrafast time-stretch microscopy with the 49.6 μm resolution and a scan rate of 11 MHz was achieved without the external optical amplification. The obtained results demonstrated that the gain-guided soliton fiber laser could be used as an alternative high-quality optical source for ultrafast time-stretch microscopy and will introduce some applications in fields such as biology, chemical, and optical sensing. PMID:27409899

  18. Guiding and collimation of laser-accelerated proton beams using thin foils followed with a hollow plasma channel

    SciTech Connect

    Xiao, K. D.; Zhou, C. T.; Qiao, B.; He, X. T.

    2015-09-15

    It is proposed that guided and collimated proton acceleration by intense lasers can be achieved using an advanced target—a thin foil followed by a hollow plasma channel. For the advanced target, the laser-accelerated hot electrons can be confined in the hollow channel at the foil rear side, which leads to the formation of transversely localized, Gaussian-distributed sheath electric field and resultantly guiding of proton acceleration. Further, due to the hot electron flow along the channel wall, a strong focusing transverse electric field is induced, taking the place of the original defocusing one driven by hot electron pressure in the case of a purely thin foil target, which results in collimation of proton beams. Two-dimensional particle-in-cell simulations show that collimated proton beams with energy about 20 MeV and nearly half-reduced divergence of 26° are produced at laser intensities 10{sup 20 }W/cm{sup 2} by using the advanced target.

  19. Improving Self-Guiding of an Ultra-Intense Laser by Tailoring the Longitudinal Profile of the Leading Edge

    NASA Astrophysics Data System (ADS)

    Mori, Warren; Tzoufras, Michail; Tsung, Frank; Sahai, Aakash

    2013-10-01

    Self-guiding of an ultra-intense laser pulse requires the refractive index to build up rapidly to a sufficient value before the main body of the pulse passes by. For short single-frequency pulses this occurs within a plasma period and a large portion of the leading edge is subject to diffraction. Nevertheless, if the body of the pulse survives long enough, the concomitant changes in its spectral content result in highly localized absorption, such that a large amount of the energy of the leading edge of the pulse is absorbed before it can diffract. To illustrate these mechanisms and optimize laser wakefield accelerators we propose a pulse profile with a ``bulbous bow,'' that is a lower-intensity low-energy precursor, that can produce the necessary buildup for the index of refraction to guide the body of the laser. The wake-field behind such a pulse is more stable, contains more energy, is sustained longer, and the corresponding de-phasing length is extended.

  20. A Miniature Forward-imaging B-scan Optical Coherence Tomography Probe to Guide Real-time Laser Ablation

    PubMed Central

    Li, Zhuoyan; Shen, Jin H.; Kozub, John A.; Prasad, Ratna; Lu, Pengcheng; Joos, Karen M.

    2014-01-01

    Background and Objective Investigations have shown that pulsed lasers tuned to 6.1 μm in wavelength are capable of ablating ocular and neural tissue with minimal collateral damage. This study investigated whether a miniature B-scan forward-imaging optical coherence tomography (OCT) probe can be combined with the laser to provide real-time visual feedback during laser incisions. Study Design/Methods and Materials A miniature 25-gauge B-scan forward-imaging OCT probe was developed and combined with a 250 μm hollow-glass waveguide to permit delivery of 6.1 μm laser energy. A gelatin mixture and both porcine corneal and retinal tissues were simultaneously imaged and lased (6.1 μm, 10 Hz, 0.4-0.7 mJ) through air. The ablation studies were observed and recorded in real time. The crater dimensions were measured using OCT imaging software (Bioptigen, Durham, NC). Histological analysis was performed on the ocular tissues. Results The combined miniature forward-imaging OCT and mid-infrared laser-delivery probe successfully imaged real-time tissue ablation in gelatin, corneal tissue, and retinal tissue. Application of a constant number of 60 pulses at 0.5 mJ/pulse to the gelatin resulted in a mean crater depth of 123 ± 15 μm. For the corneal tissue, there was a significant correlation between the number of pulses used and depth of the lased hole (Pearson correlation coefficient = 0.82; P = 0.0002). Histological analysis of the cornea and retina tissues showed discrete holes with minimal thermal damage. Conclusions A combined miniature OCT and laser -delivery probe can monitor real-time tissue laser ablation. With additional testing and improvements, this novel instrument has the future possibility of effectively guiding surgeries by simultaneously imaging and ablating tissue. PMID:24648326

  1. The Orbiting Carbon Observatory (OCO)

    NASA Technical Reports Server (NTRS)

    Miller, Charles E.

    2005-01-01

    CO2 is the principal human generated driver of climate change. Accurate forecasting of future climate requires an improved understanding of the global carbon cycle and its interaction with the climate system. The Orbiting Carbon Observatory (OCO) will make global, space-based observations of atmospheric CO2 with the precision, resolution, and coverage needed to understand sources and sinks. OCO data will provide critical information for decision makers including the scientific basis for policy formulation, guide for carbon management strategies and treaty monitoring.

  2. Gain-guided index-antiguided fiber with a Fabry-Perot layer for large mode area laser amplifiers.

    PubMed

    Lai, Chih-Hsien; Chen, Hsuan-Yu; Du, Cheng-Han; Chiou, Yih-Peng

    2015-02-23

    We propose a modified gain-guided index-antiguided (GGIAG) fiber structure for large mode area laser amplifiers, in which a thin dielectric layer is placed between the low-index core and the high-index cladding. The introduced dielectric layer functions as a Fabry-Perot etalon. By letting the resonant wavelength of the Fabry-Perot layer coincide with the signal wavelength, the signal is gain-guided in the fiber core. Moreover, the pump is confined in the low-index core owing to the antiresonant reflection originated from the Fabry-Perot layer. Numerical results indicate that the leakage loss of the pump can be minified over two orders of magnitude in the proposed structure, and thus the end-pumping efficiency could be enhanced significantly. PMID:25836427

  3. The Polychromatic Laser Guide Star for tilt measurement: progress report of the demonstrator at Observatoire de Haute Provence

    NASA Astrophysics Data System (ADS)

    Foy, Renaud; Éric, Pierre; Eysseric, Jérôme; Foy, Françoise; Fusco, Thierry; Girard, Julien; Le Van Suu, Auguste; Perruchot, Sandrine; Richaud, Pierre; Richaud, Yoann; Rondeau, Xavier; Tallon, Michel; Thiébaut, Éric; Boër, Michel

    2007-09-01

    The Polychromatic Laser Guide Star aims at providing for the tilt measurement from a LGS without any natural guide star. Thus it allows adaptive optics to provide us with a full sky coverage. This is critical in particular to extend adaptive optics to the visible range, where isoplanatism is so small that the probability is negligible to find a natural star to measure the tilt. We report new results obtained within the framework of the Polychromatic LGS programme ELP-OA. Natural stars have been used to mimic the PLGS, in order to check the feasibility of using the difference in the tilt at two wavelengths to derive the tilt itself. We report results from the ATTILA experiment obtained at the 1.52 m telescope at Observatoire de Haute-Provence. Tilts derived from the differential tilts are compared with direct tilt measurements. The accuracy of the measurements is currently ~ 1.5 Airy disk rms at 550 nm. These results prove the feasibility of the Polychromatic Laser Guide Star programme ELP-OA. New algorithms based on inverse problems under development within our programme would lead to smaller error bars by 1 magnitude, as soon as they will run fast enough. We describe the ELP-OA demonstrator which we are setting up at the same telescope, with a special emphasis on the optimization of the excitation process, which definitely has to rely on the two-photon excitation of sodium atoms in the mesosphere. We will describe the implementation at the telescope, including the projector device, the focal instrumentation and the NdYAG pumped dye lasers.

  4. Transendoscopic application of CO II laser irradiation using the OmniGuide fiber to treat dorsal displacement of the soft palate in the horse

    NASA Astrophysics Data System (ADS)

    Tate, Lloyd P., Jr.

    2006-02-01

    Transendoscopic laser surgery has been performed in horses since 1984. It is used to treat many upper respiratory disorders, as well as urogenital diseases. Initially, the Nd:YAG laser was the laser of choice until the early 1990s, when smaller, more compact diode lasers entered the veterinary field. In the mid 1980s, several attempts were made to transmit CO II laser energy transendoscopically. True success was not obtained until 2004 when the OmniGuide CO II Fiber was fabricated. Although there is attenuation of energy, this very flexible fiber allows the CO II laser to be used transendoscopically for incision and ablation of tissue. Intermittent dorsal displacement of the soft palate has more recently been treated using a diode laser and contact fiber to scarify the caudal border of the soft palate. This procedure was initially reported as being performed in combination with a myectomy. The CO II laser's fiber was used in eight cases. It offered no touch technique and allowed improved visualization of the target tissue. Both healing and recuperation time were reduced, compared to other wavelengths transmitted through solid quartz fiber. The OmniGuide Fiber can be coupled to the output port of CO II lasers commonly used in veterinary medicine. Transendoscopic application of the CO II laser is advantageous in that there is no endoscopic white-out, no volume heating of tissue, and it provides an accurate means of performing upper respiratory surgery in the standing horse.

  5. Gain-guided broad area quantum cascade lasers emitting 23.5 W peak power at room temperature.

    PubMed

    Sergachev, Ilia; Maulini, Richard; Bismuto, Alfredo; Blaser, Stephane; Gresch, Tobias; Muller, Antoine

    2016-08-22

    We report gain-guided broad area quantum cascade lasers at 4.55 μm. The devices were processed in a buried heterostructure configuration with a current injector section much narrower than the active region. They demonstrate 23.5 W peak power at a temperature of 20°C and duty cycle of 1%, while their far field consists of a single symmetric lobe centered on the optical axis. These experimental results are supported well by 2D numerical simulations of electric currents and optical fields in a device cross-section. PMID:27557186

  6. Confocal microscopy to guide Erbium:yttrium aluminum garnet laser ablation of basal cell carcinoma: an ex vivo feasibility study

    PubMed Central

    Larson, Bjorg A.; Chen, Chih-Shan Jason; Rajadhyaksha, Milind

    2013-01-01

    Abstract. For the removal of superficial and nodular basal cell carcinomas (BCCs), laser ablation provides certain advantages relative to other treatment modalities. However, efficacy and reliability tend to be variable because tissue is vaporized such that none is available for subsequent histopathological examination for residual BCC (and to confirm complete removal of tumor). Intra-operative reflectance confocal microscopy (RCM) may provide a means to detect residual tumor directly on the patient and guide ablation. However, optimization of ablation parameters will be necessary to control collateral thermal damage and preserve sufficient viability in the underlying layer of tissue, so as to subsequently allow labeling of nuclear morphology with a contrast agent and imaging of residual BCC. We report the results of a preliminary study of two key parameters (fluence, number of passes) vis-à-vis the feasibility of labeling and RCM imaging in human skin ex vivo, following ablation with an erbium:yttrium aluminum garnet laser. PMID:24045654

  7. Lasers.

    ERIC Educational Resources Information Center

    Schewe, Phillip F.

    1981-01-01

    Examines the nature of laser light. Topics include: (1) production and characteristics of laser light; (2) nine types of lasers; (3) five laser techniques including holography; (4) laser spectroscopy; and (5) laser fusion and other applications. (SK)

  8. Laser-guided direct writing for three-dimensional tissue engineering: Analysis and application of radiation forces

    NASA Astrophysics Data System (ADS)

    Nahmias, Yaakov Koby

    Tissue Engineering aims for the creation of functional tissues or organs using a combination of biomaterials and living cells. Artificial tissues can be implanted in patients to restore tissue function that was lost due to trauma, disease, or genetic disorder. Tissue equivalents may also be used to screen the effects of drugs and toxins, reducing the use of animals in research. One of the principle limitations to the size of engineered tissue is oxygen and nutrient transport. Lacking their own vascular bed, cells embedded in the engineered tissue will consume all available oxygen within hours while out branching blood vessels will take days to vascularize the implanted tissue. Establishing capillaries within the tissue prior to implantation can potentially eliminate this limitation. One approach to establishing capillaries within the tissue is to directly write endothelial cells with micrometer accuracy as it is being built. The patterned endothelial cells will then self-assemble into vascular structures within the engineering tissue. The cell patterning technique known as laser-guided direct writing can confine multiple cells in a laser beam and deposit them as a steady stream on any non-absorbing surface with micrometer scale accuracy. By applying the generalized Lorenz-Mie theory for light scattering on laser-guided direct writing we were able to accurately predict the behavior of with various cells and particles in the focused laser. In addition, two dimensionless parameters were identified for general radiation-force based system design. Using laser-guided direct writing we were able to direct the assembly of endothelial vascular structures with micrometer accuracy in two and three dimensions. The patterned vascular structures provided the backbone for subsequent in vitro liver morphogenesis. Our studies show that hepatocytes migrate toward and adhere to endothelial vascular structures in response to endothelial-secreted hepatocyte growth factor (HGF). Our

  9. Echocardiography-guided percutaneous per-ventricular laser ablation of ventricular septum: in vivo study in a canine model.

    PubMed

    He, Guangbin; Sun, Chao; Zhang, Xiangkong; Zuo, Lei; Qin, Haiying; Zheng, Minjuan; Zhou, Xiaodong; Liu, Liwen

    2016-05-01

    Surgical myectomy and ethanol ablation are established intervention strategies for left ventricular outflow obstruction in hypertrophic cardiomyopathy. Safety and efficacy limitations of these interventions call for a minimally invasive, potentially safer, and more efficacious strategy. In this study, we aimed to evaluate the feasibility of echocardiography-guided percutaneous per-ventricular laser ablation of a ventricular septum in a canine model. Six domestic dogs were chosen for the study. A 21G needle was inserted into the right ventricle with its tip reaching the targeted basal to mid-septum, after which laser ablation was performed as follows: 1-W laser for 3 min (180 J) at the basal segment and 5 min (300 J) at middle segment of the septum, respectively. Echocardiography, blood chemistry tests, and pathology examination were performed to assess the results of laser ablation. No death or major complications, i.e., tamponade, pericardial effusion, or ventricular fibrillation, occurred. The laser-ablated areas were well demarcated in the results of the pathological examination. The diameters of the ablated regions were 4.42 ± 0.57 and 5.28 ± 0.83 mm for 3 and 5 min ablation, respectively. Pre-ablation and post-ablation, cardiac enzymes were found to increase significantly while no significant differences were found among M-mode, 2D (LVEF), pulsed-wave (PW) Doppler, and tissue Doppler imaging (TDI) measurements. Contrast echocardiography confirmed the perfusion defects in the ablated regions. Microscopically, the ablated myocardium showed coagulative changes and a sparse distribution of disappearing nuclei and an increase in eosinophil number were observed. Our study suggests that percutaneous and per-ventricular laser ablation of the septum is feasible, potentially safe and efficacious, and warrants further investigation and validation. PMID:26861985

  10. High-brightness power delivery for fiber laser pumping: simulation and measurement of low-NA fiber guiding

    NASA Astrophysics Data System (ADS)

    Yanson, Dan; Levy, Moshe; Peleg, Ophir; Rappaport, Noam; Shamay, Moshe; Dahan, Nir; Klumel, Genady; Berk, Yuri; Baskin, Ilya

    2015-02-01

    Fiber laser manufacturers demand high-brightness laser diode pumps delivering optical pump energy in both a compact fiber core and narrow angular content. A pump delivery fiber of a 105 μm core and 0.22 numerical aperture (NA) is typically used, where the fiber NA is under-filled to ease the launch of laser diode emission into the fiber and make the fiber tolerant to bending. At SCD, we have developed multi-emitter fiber-coupled pump modules that deliver 50 W output from a 105 μm, 0.15 NA fiber at 915, 950 and 976 nm wavelengths enabling low-NA power delivery to a customer's fiber laser network. In this work, we address the challenges of coupling and propagating high optical powers from laser diode sources in weakly guiding step-index multimode fibers. We present simulations of light propagation inside the low-NA multimode fiber for different launch conditions and fiber bend diameters using a ray-racing tool and demonstrate how these affect the injection of light into cladding-bounded modes. The mode filling at launch and source NA directly limit the bend radius at which the fiber can be coiled. Experimentally, we measure the fiber bend loss using our 50 W fiber-coupled module and establish a critical bend diameter in agreement with our simulation results. We also employ thermal imaging to investigate fiber heating caused by macro-bends and angled cleaving. The low mode filling of the 0.15 NA fiber by our brightness-enhanced laser diodes allows it to be coiled with diameters down to 70 mm at full operating power despite the low NA and further eliminates the need for mode-stripping at fiber combiners and splices downstream from our pump modules.

  11. A Fluorescence-Guided Laser Ablation System for Removal of Residual Cancer in a Mouse Model of Soft Tissue Sarcoma

    PubMed Central

    Lazarides, Alexander L.; Whitley, Melodi J.; Strasfeld, David B.; Cardona, Diana M.; Ferrer, Jorge M.; Mueller, Jenna L.; Fu, Henry L.; DeWitt, Suzanne Bartholf; Brigman, Brian E.; Ramanujam, Nimmi; Kirsch, David G.; Eward, William C.

    2016-01-01

    The treatment of soft tissue sarcoma (STS) generally involves tumor excision with a wide margin. Although advances in fluorescence imaging make real-time detection of cancer possible, removal is limited by the precision of the human eye and hand. Here, we describe a novel pulsed Nd:YAG laser ablation system that, when used in conjunction with a previously described molecular imaging system, can identify and ablate cancer in vivo. Mice with primary STS were injected with the protease-activatable probe LUM015 to label tumors. Resected tissues from the mice were then imaged and treated with the laser using the paired fluorescence-imaging/ laser ablation device, generating ablation clefts with sub-millimeter precision and minimal underlying tissue damage. Laser ablation was guided by fluorescence to target tumor tissues, avoiding normal structures. The selective ablation of tumor implants in vivo improved recurrence-free survival after tumor resection in a cohort of 14 mice compared to 12 mice that received no ablative therapy. This prototype system has the potential to be modified so that it can be used during surgery to improve recurrence-free survival in patients with cancer. PMID:26877775

  12. Wavefront-Guided Laser in Situ Keratomileusis (Lasik) versus Wavefront-Guided Photorefractive Keratectomy (Prk): A Prospective Randomized Eye-to-Eye Comparison (An American Ophthalmological Society Thesis)

    PubMed Central

    Manche, Edward E.; Haw, Weldon W.

    2011-01-01

    Purpose To compare the safety and efficacy of wavefront-guided laser in situ keratomileusis (LASIK) vs photorefractive keratectomy (PRK) in a prospective randomized clinical trial. Methods A cohort of 68 eyes of 34 patients with −0.75 to −8.13 diopters (D) of myopia (spherical equivalent) were randomized to receive either wavefront-guided PRK or LASIK in the fellow eye using the VISX CustomVue laser. Patients were evaluated at 1 day, 1 week, and months 1, 3, 6, and 12. Results At 1 month, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), 5% and 25% contrast sensitivity, induction of higher-order aberrations (HOAs), and subjective symptoms of vision clarity, vision fluctuation, ghosting, and overall self-assessment of vision were worse (P<0.05) in the PRK group. By 3 months, these differences had resolved (P>0.05). At 1 year, mean spherical equivalent was reduced 94% to −0.27 ± 0.31 D in the LASIK group and reduced 96% to −0.17 ± 0.41 D in the PRK group. At 1 year, 91% of eyes were within ±0.50 D and 97 % were within ±1.0 D in the PRK group. At 1 year, 88% of eyes were within ±0.50 D and 97% were within ±1.0 D in the LASIK group. At 1 year, 97% of eyes in the PRK group and 94% of eyes in the LASIK group achieved an UCVA of 20/20 or better (P=0.72). Refractive stability was achieved in both PRK and LASIK groups after 1 month. There were no intraoperative or postoperative flap complications in the LASIK group. There were no instances of corneal haze in the PRK group. Conclusions Wavefront-guided LASIK and PRK are safe and effective at reducing myopia. At 1 month postoperatively, LASIK demonstrates an advantage over PRK in UCVA, BSCVA, low-contrast acuity, induction of total HOAs, and several subjective symptoms. At postoperative month 3, these differences between PRK and LASIK results had resolved. PMID:22253488

  13. Turning a remotely controllable observatory into a fully autonomous system

    NASA Astrophysics Data System (ADS)

    Swindell, Scott; Johnson, Chris; Gabor, Paul; Zareba, Grzegorz; Kubánek, Petr; Prouza, Michael

    2014-08-01

    We describe a complex process needed to turn an existing, old, operational observatory - The Steward Observatory's 61" Kuiper Telescope - into a fully autonomous system, which observers without an observer. For this purpose, we employed RTS2,1 an open sourced, Linux based observatory control system, together with other open sourced programs and tools (GNU compilers, Python language for scripting, JQuery UI for Web user interface). This presentation provides a guide with time estimates needed for a newcomers to the field to handle such challenging tasks, as fully autonomous observatory operations.

  14. Stimulated-Brillouin-scattering-suppressed high-power single-frequency polarization-maintaining Raman fiber amplifier with longitudinally varied strain for laser guide star.

    PubMed

    Zhang, Lei; Hu, Jinmeng; Wang, Jianhua; Feng, Yan

    2012-11-15

    An up to 44 W, 1 MHz linewidth, 1178 nm CW laser is obtained by Raman amplification of a distributed feedback diode laser in a variably strained polarization-maintaining fiber with a record-high optical efficiency of 52%, pumped by a linearly polarized 1120 nm fiber laser. A polarization extinction ratio of 30 dB is achieved due to the all-polarization-maintaining configuration and the polarization dependence of Raman gain. The strain distribution is designed according to the signal power evolution along the fiber. A 20 times reduction in the effective stimulated Brillouin scattering coefficient is achieved. A 24.3 W 589 nm laser is generated by an external resonant doubling cavity with an optical efficiency of 68.5%. The laser is locked to 589.1591 nm for a laser guide star. PMID:23164917

  15. INTERMAGNET and magnetic observatories

    USGS Publications Warehouse

    Love, Jeffrey J.; Chulliat, Arnaud

    2012-01-01

    A magnetic observatory is a specially designed ground-based facility that supports time-series measurement of the Earth’s magnetic field. Observatory data record a superposition of time-dependent signals related to a fantastic diversity of physical processes in the Earth’s core, mantle, lithosphere, ocean, ionosphere, magnetosphere, and, even, the Sun and solar wind.

  16. The Norwegian Naval Observatories

    NASA Astrophysics Data System (ADS)

    Pettersen, Bjørn Ragnvald

    2007-07-01

    Archival material has revealed milestones and new details in the history of the Norwegian Naval Observatories. We have identified several of the instrument types used at different epochs. Observational results have been extracted from handwritten sources and an extensive literature search. These allow determination of an approximate location of the first naval observatory building (1842) at Fredriksvern. No physical remains exist today. A second observatory was established in 1854 at the new main naval base at Horten. Its location is evident on military maps and photographs. We describe its development until the Naval Observatory buildings, including archives and instruments, were completely demolished during an allied air bomb raid on 23 February 1945. The first director, C.T.H. Geelmuyden, maintained scientific standards at the the Observatory between 1842 and 1870, and collaborated with university astronomers to investigate, develop, and employ time-transfer by telegraphy. Their purpose was accurate longitude determination between observatories in Norway and abroad. The Naval Observatory issued telegraphic time signals twice weekly to a national network of sites, and as such served as the first national time-service in Norway. Later the Naval Observatory focused on the particular needs of the Navy and developed into an internal navigational service.

  17. Beijing Ancient Observatory

    NASA Astrophysics Data System (ADS)

    Shi, Yunli

    The Beijing Ancient Observatory is now the only complete example of an observatory from the seventeenth century in the world. It is a monument to the prosperity of astronomy in traditional China. Its instruments are emblems of the encounter and amalgamation of Chinese and European Science in the seventeenth and eighteenth centuries.

  18. Svetloe Radio Astronomical Observatory

    NASA Technical Reports Server (NTRS)

    Smolentsev, Sergey; Rahimov, Ismail

    2013-01-01

    This report summarizes information about the Svetloe Radio Astronomical Observatory activities in 2012. Last year, a number of changes took place in the observatory to improve some technical characteristics and to upgrade some units to their required status. The report provides an overview of current geodetic VLBI activities and gives an outlook for the future.

  19. Zelenchukskaya Radio Astronomical Observatory

    NASA Technical Reports Server (NTRS)

    Smolentsev, Sergey; Dyakov, Andrei

    2013-01-01

    This report summarizes information about Zelenchukskaya Radio Astronomical Observatory activities in 2012. Last year a number of changes took place in the observatory to improve some technical characteristics and to upgrade some units to the required status. The report provides an overview of current geodetic VLBI activities and gives an outlook for the future.

  20. Studies in fiber guided excimer laser surgery for cutting and drilling bone and meniscus.

    PubMed

    Dressel, M; Jahn, R; Neu, W; Jungbluth, K H

    1991-01-01

    Our experiments on transmitting high-power excimer laser pulses through optical fibers and our investigations on excimer laser ablation of hard tissue show the feasibility of using the excimer laser as an additional instrument in general and accident surgery involving minimal invasive surgery. By combining XeCl-excimer lasers and tapered fused silica fibers we obtained output fluences up to 32 J/cm2 and ablation rates of 3 microns/pulse of hard tissue. This enables us to cut bone and cartilage in a period of time which is suitable for clinical operations. Various experiments were carried out on cadavers in order to optimize the parameters of the excimer laser and fibers: e.g., wavelength, pulse duration, energy, repetition rate, fiber core diameter. The surfaces of the cut tissue are comparable to cuts with conventional instruments. No carbonisation was observed. The temperature increase is below 40 degrees C in the tissue surrounding the laser spot. The healing rate of an excimer laser cut is not slower than mechanical treatments; the quality is comparable. PMID:1661360

  1. Strasbourg's "Academy" observatory

    NASA Astrophysics Data System (ADS)

    Heck, André

    2011-08-01

    The observing post located on the roof of Strasbourg's 19th-century "Academy" is generally considered as the second astronomical observatory of the city: a transitional facility between the (unproductive) turret lantern at the top of the Hospital Gate and the German (Wilhelminian) Observatory. The current paper reviews recent findings from archives (blueprints, inventories, correspondence, decrees and other documents) shedding some light on this observatory of which virtually nothing was known to this day. While being, thanks to Chrétien Kramp (1760-1826), an effective attempt to establish an actual observatory equipped with genuine instrumentation, the succession of political regimes in France and the continual bidding for moving the university to other locations, together with the faltering of later scholars, torpedoed any significant scientific usage of the place. A meridian instrument with a Cauchoix objective doublet was however recovered by the German observatory and is still existing.

  2. Quality inspection guided laser processing of irregular shape objects by stereo vision measurement: application in badminton shuttle manufacturing

    NASA Astrophysics Data System (ADS)

    Qi, Li; Wang, Shun; Zhang, Yixin; Sun, Yingying; Zhang, Xuping

    2015-11-01

    The quality inspection process is usually carried out after first processing of the raw materials such as cutting and milling. This is because the parts of the materials to be used are unidentified until they have been trimmed. If the quality of the material is assessed before the laser process, then the energy and efforts wasted on defected materials can be saved. We proposed a new production scheme that can achieve quantitative quality inspection prior to primitive laser cutting by means of three-dimensional (3-D) vision measurement. First, the 3-D model of the object is reconstructed by the stereo cameras, from which the spatial cutting path is derived. Second, collaborating with another rear camera, the 3-D cutting path is reprojected to both the frontal and rear views of the object and thus generates the regions-of-interest (ROIs) for surface defect analysis. An accurate visual guided laser process and reprojection-based ROI segmentation are enabled by a global-optimization-based trinocular calibration method. The prototype system was built and tested with the processing of raw duck feathers for high-quality badminton shuttle manufacture. Incorporating with a two-dimensional wavelet-decomposition-based defect analysis algorithm, both the geometrical and appearance features of the raw feathers are quantified before they are cut into small patches, which result in fully automatic feather cutting and sorting.

  3. Bone Repair on Fractures Treated with Osteosynthesis, ir Laser, Bone Graft and Guided Bone Regeneration: Histomorfometric Study

    NASA Astrophysics Data System (ADS)

    dos Santos Aciole, Jouber Mateus; dos Santos Aciole, Gilberth Tadeu; Soares, Luiz Guilherme Pinheiro; Barbosa, Artur Felipe Santos; Santos, Jean Nunes; Pinheiro, Antonio Luiz Barbosa

    2011-08-01

    The aim of this study was to evaluate, through the analysis of histomorfometric, the repair of complete tibial fracture in rabbits fixed with osteosynthesis, treated or not with infrared laser light (λ780 nm, 50 mW, CW) associated or not to the use of hydroxyapatite and guided bone regeneration (GBR). Surgical fractures were created, under general anesthesia (Ketamina 0,4 ml/Kg IP and Xilazina 0,2 ml/Kg IP), on the dorsum of 15 Oryctolagus rabbits that were divided into 5 groups and maintained on individual cages, at day/night cycle, fed with solid laboratory pelted diet and had water ad libidum. On groups II, III, IV and V the fracture was fixed with wire osteosynthesis. Animals of groups III and V were grafted with hydroxyapatite and GBR technique used. Animals of groups IV and V were irradiated at every other day during two weeks (16 J/cm2, 4×4 J/cm2). Observation time was that of 30 days. After animal death (overdose of general anesthetics) the specimes were routinely processed to wax and underwent histological analysis by light microscopy. The histomorfometric analysis showed an increased bone neoformation, increased collagen deposition, less reabsorption and inflammation when laser was associated to the HATCP. It is concluded that IR laser light was able to accelerate fracture healing and the association with HATCP and GBR resulted on increased deposition of CHA.

  4. Nonlinear theory of a free electron laser with a helical wiggler and an axial guide magnetic field

    NASA Astrophysics Data System (ADS)

    Ginzburg, N. S.; Peskov, N. Yu.

    2013-09-01

    A 1D nonlinear theory of a free electron laser (FEL) with a helical wiggler and an axial guide magnetic field is developed based on averaged equations of the electron motion. By averaging we separated two different cases of the e-beam/rf-wave interaction. The first one corresponds to the traditional wiggler synchronism (resonance) of rf wave with the electrons moving along stationary helical trajectories. The second one corresponds to combination resonances distinguishing by excitation of oscillation of the electrons near the stationary helical trajectory. Comparative analysis of the FEL operation in different regimes has been studied under the traditional wiggler synchronism condition. It was shown that FELs operated far from cyclotron resonance (including a reversed guide field orientation) possess low sensitivity to the initial velocity spread in the driving beam resulting in high electron efficiency. In contrast, under the weak guide field (the gyrofrequency is less than the bounce frequency) of a conventional orientation, the FEL efficiency is restricted by a significant increase in the transverse velocity of the electrons during the interaction with the rf wave that results in violation of the synchronism conditions and is accompanied by electron current losses. An additional mechanism of FEL efficiency enhancement under the conventional guide field orientation in the conditions when the gyrofrequency is higher than the bounce frequency, based on the dependence of the effective mass of the oscillating electrons on their energy, was demonstrated. Results of the theoretical analysis are compared with the results of experimental studies of FEL oscillators. The specific features of energy extraction from the electron beam under condition of an abnormal Doppler effect in the case of the combination resonance are described. This regime is beneficial to increase radiation frequency keeping wiggler period and electron energies.

  5. Guided post-acceleration of laser-driven ions by a miniature modular structure

    NASA Astrophysics Data System (ADS)

    Kar, Satyabrata; Ahmed, Hamad; Prasad, Rajendra; Cerchez, Mirela; Brauckmann, Stephanie; Aurand, Bastian; Cantono, Giada; Hadjisolomou, Prokopis; Lewis, Ciaran L. S.; Macchi, Andrea; Nersisyan, Gagik; Robinson, Alexander P. L.; Schroer, Anna M.; Swantusch, Marco; Zepf, Matt; Willi, Oswald; Borghesi, Marco

    2016-04-01

    All-optical approaches to particle acceleration are currently attracting a significant research effort internationally. Although characterized by exceptional transverse and longitudinal emittance, laser-driven ion beams currently have limitations in terms of peak ion energy, bandwidth of the energy spectrum and beam divergence. Here we introduce the concept of a versatile, miniature linear accelerating module, which, by employing laser-excited electromagnetic pulses directed along a helical path surrounding the laser-accelerated ion beams, addresses these shortcomings simultaneously. In a proof-of-principle experiment on a university-scale system, we demonstrate post-acceleration of laser-driven protons from a flat foil at a rate of 0.5 GeV m-1, already beyond what can be sustained by conventional accelerator technologies, with dynamic beam collimation and energy selection. These results open up new opportunities for the development of extremely compact and cost-effective ion accelerators for both established and innovative applications.

  6. Remote Control Southern Hemisphere SSA Observatory

    NASA Astrophysics Data System (ADS)

    Ritchie, I.; Pearson, M.; Sang, J.

    2013-09-01

    EOS Space Systems (EOSSS) is a research and development company which has developed custom observatories, camera and telescope systems for space surveillance since 1996, as well as creating several evolutions of systems control software for control of observatories and laser tracking systems. Our primary reserach observatory is the Space Reserach Centre (SRC) at Mount Stromlo Asutralia. The current SRC control systems are designed such that remote control can be offered for real time data collection, noise filtering and flexible session management. Several imaging fields of view are available simultaneously for tracking orbiting objects, with real time imaging to Mag 18. Orbiting objects can have the centroids post processed into orbital determination/ orbital projection (OD/OP) elements. With or without laser tracking of orbiting objects, they can be tracked in terminator conditions and their OD/OP data created, then enhanced by proprietary methods involving ballistic coefficient estimation and OD convergence pinning, using a priori radar elements. Sensors in development include a thermal imager for satellite thermal signature detection. Extending laser tracking range by use of adaptive optics beam control is also in development now. This Southern Hemisphere observatory is in a unique position to facilitate the study of space debris, either stand-alone or as part of a network such as Falcon. Current national and international contracts will enhance the remote control capabilities further, creating a resource ready to go for a wide variety of SSA missions.

  7. Water-jet guided laser: possibilities and potential for singulation of electronic packages

    NASA Astrophysics Data System (ADS)

    Wagner, Frank R.; Spiegel, Akos; Vago, Nandor; Richerzhagen, Bernold

    2002-06-01

    Singulation of packages is an important step in the manufacturing of IC devices. Presently, the most widely used technique is abrasive sawing. Due to the combination of different materials used in packages such as copper and mold compound, the saw rapidly blunts and also conventional laser cutting by a water-jet with the high precision and speed of a laser cut and is now applied into electronic package singulation.

  8. Magnetic resonance imaging-guided interstitial application of laser aided by fiber optic temperature sensing

    NASA Astrophysics Data System (ADS)

    Farahani, Keyvan; Shellock, Frank G.; Lufkin, Robert B.; Castro, Dan J.

    1992-04-01

    In order to further understand signal variations observed on magnetic resonance imaging scans of interstitial laser heating, a commercial multichannel fluoroptic thermometer, equipped with fiber optic sensors, was employed in conjunction with the laser/MRI phototherapy system. Three calibrated fiber optic sensors of the thermometer were used to measure temperature changes in ex-vivo sheep's brain at various distances directly across from the beam of a Nd:YAG laser emitted from a bare fiber. Laser was operated at 5 W for 220 sec. Temperature was measured every 10 seconds and MR images were acquired during and after laser irradiation until temperature in all probes returned to the equilibrium level of prelaser irradiation. Image contrast analysis of the heated region showed that MRI signal variations, during heating and cooling periods, correlated well with the changes in temperature. It is concluded that direct thermometry of MRI-monitored laser application will aid in understanding the effects of high focal heating on the MRI signal.

  9. RESOLVING THE DYNAMICAL MASS OF A z {approx} 1.3 QUASI-STELLAR OBJECT HOST GALAXY USING SINFONI AND LASER GUIDE STAR ASSISTED ADAPTIVE OPTICS

    SciTech Connect

    Inskip, K. J.; Jahnke, K.; Rix, H.-W.; Van de Ven, G.

    2011-10-01

    Recent studies of the tight scaling relations between the masses of supermassive black holes (BHs) and their host galaxies have suggested that in the past BHs constituted a larger fraction of their host galaxies' mass. However, these arguments are limited by selection effects and difficulties in determining robust host galaxy masses at high redshifts. Here we report the first results of a new, complementary diagnostic route: we directly determine a dynamical host galaxy mass for the z = 1.3 luminous quasar J090543.56+043347.3 through high spatial resolution (0.''47, 4 kpc FWHM) observations of the host galaxy gas kinematics over 30 x 40 kpc using the European Southern Observatory/Very Large Telescope/SINFONI with laser guide star adaptive optics. Combining our result of M{sub dyn} = 2.05{sup +1.68}{sub -0.74} x 10{sup 11} M{sub sun} (within a radius 5.25 {+-} 1.05 kpc) with M{sub BH,MgII} = 9.02 {+-} 1.43 x 10{sup 8} M{sub sun}, M{sub BH,H{alpha}} = 2.83{sup +1.93}{sub -1.13} x 10{sup 8} M{sub sun}, we find that the ratio of BH mass to host galaxy dynamical mass for J090543.56+043347.3 matches the present-day relation for M{sub BH} versus M{sub Bulge,Dyn}, well within the IR scatter, and deviating at most by a factor of two from the mean. J090543.56+043347.3 displays clear signs of an ongoing tidal interaction and of spatially extended star formation at a rate of 50-100 M{sub sun} yr{sup -1}, above the cosmic average for a galaxy of this mass and redshift. We argue that its subsequent evolution may move J090543.56+043347.3 even closer to the z = 0 relation for M{sub BH} versus M{sub Bulge,Dyn}. Our results support the picture in which any substantive evolution in these relations must occur prior to z {approx} 1.3. Having demonstrated the power of this modeling approach, we are currently analyzing similar data on seven further objects to better constrain such evolution.

  10. The Virtual Observatory: I

    NASA Astrophysics Data System (ADS)

    Hanisch, R. J.

    2014-11-01

    The concept of the Virtual Observatory arose more-or-less simultaneously in the United States and Europe circa 2000. Ten pages of Astronomy and Astrophysics in the New Millennium: Panel Reports (National Academy Press, Washington, 2001), that is, the detailed recommendations of the Panel on Theory, Computation, and Data Exploration of the 2000 Decadal Survey in Astronomy, are dedicated to describing the motivation for, scientific value of, and major components required in implementing the National Virtual Observatory. European initiatives included the Astrophysical Virtual Observatory at the European Southern Observatory, the AstroGrid project in the United Kingdom, and the Euro-VO (sponsored by the European Union). Organizational/conceptual meetings were held in the US at the California Institute of Technology (Virtual Observatories of the Future, June 13-16, 2000) and at ESO Headquarters in Garching, Germany (Mining the Sky, July 31-August 4, 2000; Toward an International Virtual Observatory, June 10-14, 2002). The nascent US, UK, and European VO projects formed the International Virtual Observatory Alliance (IVOA) at the June 2002 meeting in Garching, with yours truly as the first chair. The IVOA has grown to a membership of twenty-one national projects and programs on six continents, and has developed a broad suite of data access protocols and standards that have been widely implemented. Astronomers can now discover, access, and compare data from hundreds of telescopes and facilities, hosted at hundreds of organizations worldwide, stored in thousands of databases, all with a single query.

  11. Interaction of a self-focused laser beam with a DT fusion target in a plasma-loaded cone-guided ICF scheme

    NASA Astrophysics Data System (ADS)

    Saedjalil, N.; Mehrangiz, M.; Jafari, S.; Ghasemizad, A.

    2016-06-01

    In this paper, the interaction of a self-focused laser beam with a DT fusion target in a plasma-loaded cone-guided ICF scheme has been presented. We propose here to merge a plasma-loaded cone with the precompressed DT target in order to strongly focus the incident laser beam on the core to improve the fusion gain. The WKB approximation is used to derive a differential equation that governs the evolution of beamwidth of the incident laser beam with the distance of propagation in the plasma medium. The effects of initial plasma and laser parameters, such as initial plasma electron temperature, initial radius of the laser beam, initial laser beam intensity and plasma density, on self-focusing and defocusing of the Gaussian laser beam have been studied. Numerical results indicate that with increasing the plasma frequency (or plasma density) in the cone, the laser beam will be self-focused noticeably, while for a thinner laser beam (with small radius), it will diverge as propagate in the cone. By evaluating the energy deposition of the relativistic electron ignitors in the fuel, the importance of electron transportation in the cone-attached shell was demonstrated. Moreover, by lessening the least energy needed for ignition, the electrons coupling with the pellet enhances. Therefore, it increases the fusion efficiency. In this scheme, with employing a plasma-loaded cone, the fusion process improves without needing an ultrahigh-intensity laser beam in a conventional ICF.

  12. Short periodical oscillations of pole coordinates determined by the Main Astronomical Observatory of the UAS from the Lageos laser ranging data in the MERIT campaign

    NASA Astrophysics Data System (ADS)

    Kosek, W.; Kolaczek, B.; Nurutdinov, K. Kh.; Taradii, V. K.; Tsesis, M. L.

    Pole coordinate variations in the MERIT campaign were computed from Lageos laser ranging data by the Kiev Geodynamics Program on the basis of pure numerical integration techniques, and they were compared with the pole coordinate variations computed by the Center for Space Researches (CSR), U.S.A. Short periodical variations of the pole coordinate variations have been analyzed.

  13. Intervention Planning Using a Laser Navigation System for CT-Guided Interventions: A Phantom and Patient Study

    PubMed Central

    Lee, Clara; Bolck, Jan; Naguib, Nagy N.N.; Schulz, Boris; Eichler, Katrin; Aschenbach, Rene; Wichmann, Julian L.; Vogl, Thomas. J.; Zangos, Stephan

    2015-01-01

    Objective To investigate the accuracy, efficiency and radiation dose of a novel laser navigation system (LNS) compared to those of free-handed punctures on computed tomography (CT). Materials and Methods Sixty punctures were performed using a phantom body to compare accuracy, timely effort, and radiation dose of the conventional free-handed procedure to those of the LNS-guided method. An additional 20 LNS-guided interventions were performed on another phantom to confirm accuracy. Ten patients subsequently underwent LNS-guided punctures. Results The phantom 1-LNS group showed a target point accuracy of 4.0 ± 2.7 mm (freehand, 6.3 ± 3.6 mm; p = 0.008), entrance point accuracy of 0.8 ± 0.6 mm (freehand, 6.1 ± 4.7 mm), needle angulation accuracy of 1.3 ± 0.9° (freehand, 3.4 ± 3.1°; p < 0.001), intervention time of 7.03 ± 5.18 minutes (freehand, 8.38 ± 4.09 minutes; p = 0.006), and 4.2 ± 3.6 CT images (freehand, 7.9 ± 5.1; p < 0.001). These results show significant improvement in 60 punctures compared to freehand. The phantom 2-LNS group showed a target point accuracy of 3.6 ± 2.5 mm, entrance point accuracy of 1.4 ± 2.0 mm, needle angulation accuracy of 1.0 ± 1.2°, intervention time of 1.44 ± 0.22 minutes, and 3.4 ± 1.7 CT images. The LNS group achieved target point accuracy of 5.0 ± 1.2 mm, entrance point accuracy of 2.0 ± 1.5 mm, needle angulation accuracy of 1.5 ± 0.3°, intervention time of 12.08 ± 3.07 minutes, and used 5.7 ± 1.6 CT-images for the first experience with patients. Conclusion Laser navigation system improved accuracy, duration of intervention, and radiation dose of CT-guided interventions. PMID:26175571

  14. Long-lived laser-induced microwave plasma guides in the atmosphere: Self-consistent plasma-dynamic analysis and numerical simulations

    SciTech Connect

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

    2010-08-15

    A detailed model of plasma dynamics, which self-consistently integrates plasma-kinetic, Navier-Stokes, electron heat conduction, and electron-vibration energy transfer equations, is used to quantify the limitations on the lifetime of microwave plasma waveguides induced in the atmosphere through filamentation with high-intensity ultrashort laser pulses further sustained by long laser pulses. We demonstrate that a near-infrared or midinfrared laser pulse can tailor plasma decay in the wake of a filament, efficiently suppressing, through electron temperature increase, the attachment of electrons to neutral species and dissociative recombination, thus substantially increasing the plasma-guide lifetime and facilitating long-distance transmission of microwaves.

  15. The Penllergare Observatory

    NASA Astrophysics Data System (ADS)

    Birks, J. L.

    2005-12-01

    This rather picturesque and historically important Victorian observatory was built by the wealthy John Dillwyn Llewelyn near to his mansion, some four miles north-west of Swansea, Wales. He had many scientific interests, in addition to astronomy, and was a notable pioneer of photography in Wales. Together with his eldest daughter, Thereza, (who married the grandson of the fifth Astronomer Royal, Nevil Maskelyne), he took some early photographs of the Moon from this site. This paper describes the construction of the observatory, and some of those primarily involved with it. Despite its having undergone restoration work in 1982, the state of the observatory is again the cause for much concern.

  16. Development and Evaluation of a Registration Methodology for Information-Guided Precision Robotic Laser Neurosurgery System

    NASA Astrophysics Data System (ADS)

    Nakamura, Ryoichi; Hara, Mikiko; Omori, Shigeru; Uematsu, Miyuki; Umezu, Mitsuo; Muragaki, Yoshihiro; Iseki, Hiroshi

    To establish safe, precise, and minimally invasive surgery, Computer Aided Surgery (CAS) systems, such as intra-operative imaging and navigation system to detect the location of the target of therapy, and surgical robot system, are very powerful tools. There is strong need to combine these CAS systems for fusion of advanced diagnosis and treatment technologies. In this paper, we introduce our new method to register the intraoperative imaging information, robotic surgery system, and patient using surgical navigation system. Using our Open-MRI navigation system and laser surgery system for neurosurgery, we can make registration between these system and patient precisely. The experimental result shows that the error on the registration between image data and the laser surgery system is low enough to fulfill the requirement of laser surgery system in the use of high-resolution image data. This system realizes the safe, precise and minimally invasive neurosurgery by the combination of intra-operative diagnosis and advanced therapeutic device.

  17. Effects of electromagnetic wiggler and ion channel guiding on equilibrium orbits and waves propagation in a free electron laser

    NASA Astrophysics Data System (ADS)

    Amri, Hassan Ehsani; Mohsenpour, Taghi

    2016-02-01

    In this paper, an analysis of equilibrium orbits for electrons by a simultaneous solution of the equation of motion and the dispersion relation for electromagnetic wave wiggler in a free-electron laser (FEL) with ion-channel guiding has been presented. A fluid model has been used to investigate interactions among all possible waves. The dispersion relation has been derived for electrostatic and electromagnetic waves with all relativistic effects included. This dispersion relation has been solved numerically. For group I and II orbits, when the transverse velocity is small, only the FEL instability is found. In group I and II orbits with relatively large transverse velocity, new couplings between other modes are found.

  18. Percutaneous transluminal laser guide wire recanalization of chronic subclavian artery occlusion in symptomatic coronary-subclavian steal syndrome.

    PubMed

    Eggebrecht, H; Naber, C K; Oldenburg, O; Herrmann, J; Haude, M; Erbel, R; Baumgart, D

    2000-12-01

    Treatment of subclavian artery stenosis by percutaneous balloon angioplasty and adjunctive stent placement was shown to be safe and efficacious, but it may be limited in tight stenoses and long occlusions. We describe the case of a patient who experienced progressive angina pectoris associated with signs of cerebrovertebral insufficiency 9 yr after bypass surgery, including left internal mammary artery (LIMA) grafting to the left anterior descending coronary artery. Angiography showed reversed flow through the LIMA graft into the subclavian artery and a 4-cm occlusion beginning at the origin of the left subclavian artery, representing a rare coronary-subclavian steal syndrome. After a conventional approach failed, recanalization was performed successfully using laser guide wire angioplasty with adjunctive stent placement in a combined radial and femoral approach. PMID:11108691

  19. Ti:Sapphire micro-structures by femtosecond laser inscription: Guiding and luminescence properties

    NASA Astrophysics Data System (ADS)

    Ren, Yingying; Jiao, Yang; Vázquez de Aldana, Javier R.; Chen, Feng

    2016-08-01

    We report on the fabrication of buried cladding waveguides with different diameters in a Ti:Sapphire crystal by femtosecond laser inscription. The propagation properties are studied, showing that the cladding waveguides could support near- to mid-infrared waveguiding at both TE and TM polarizations. Confocal micro-photoluminescence experiments reveal that the original fluorescence properties in the waveguide region are very well preserved, while it suffers from a strong quenching at the centers of laser induced filaments. Broadband waveguide fluorescence emissions with high efficiency are realized, indicating the application of the cladding waveguides in Ti:Sapphire as compact broadband luminescence sources in biomedical fields.

  20. Wave guided laser wake-field acceleration in splash plasma channels

    NASA Astrophysics Data System (ADS)

    MIZUTA, Yoshio; HOSOKAI, Tomonao; MASUDA, Shinichi; ZHIDKOV, Alexei; NAKANII, Nobuhiko; JIN, Zhan; NAKAHARA, Hiroki; KOHARA, Tomohiro; IWASA, Kenta; KANDO, Masaki; BULANOV, Sergei; KODAMA, Ryosuke

    2016-03-01

    A transient plasma micro optics (plasma channel and focusing plasma optics- TPMO) in the LWFA provides controllable electron self-injections that result in production of higher quality bunches. In recent study of the TPMO, the deep, straight and short-lived plasma channels [splash plasma channel] were produced by picosecond and sub-picosecond laser pulses in the ponderomotive force dominant regime. Various techniques were used to characterize those channels in argon gas jets irradiated by moderate intensity, ∼1015-16 W/cm2, laser pulses with their durations from sub-picoseconds.

  1. Tilt angular anisoplanatism and a full-aperture tilt-measurement technique with a laser guide star.

    PubMed

    Belen'kii, M S

    2000-11-20

    A method is presented for sensing atmospheric wave-front tilt from a laser guide star (LGS) by observing a laser beacon with auxiliary telescopes. The analysis is performed with a LGS scatter model and Zernike polynomial expansion of wave-front distortions. It is shown that integration of the LGS image over its angular extent and the position of the auxiliary telescope in an array reduce the tilt sensing error associated with the contribution from the downward path. This allows us to single out only the wave-front tilt of the transmitted beam on the uplink path that corresponds to the tilt for the scientific object. The tilt angular correlation is analyzed in the atmosphere with a finite turbulence outer scale. The tilt correlation angle depends on the angular size of the telescope and the outer scale of turbulence. The tilt sensing error increases with the auxiliary telescope diameter, suggesting that an auxiliary telescope must be small. The Strehl ratio associated with the contribution from the downward path is in the range from 0.1 to 0.9 when the relative telescope diameter D/r(0) varies from 4 to 93 and the turbulence outer scale is in the 10-150-m range. Tilt correction increases the Strehl ratio compared with the uncorrected image for all the system parameters and seeing conditions considered. The method discussed gives a higher performance than the conventional technique, which uses an off-axis natural guide star. A scheme for measuring tilt with a beam projected from a small aperture is described. This scheme allows us to avoid phosphorescence of the main optical train for a sodium LGS. PMID:18354615

  2. Global Health Observatory (GHO)

    MedlinePlus

    ... repository Reports Country statistics Map gallery Standards Global Health Observatory (GHO) data Monitoring health for the SDGs ... relevant web pages on the theme. Monitoring the health goal: indicators of overall progress Mortality and global ...

  3. Observatory Improvements for SOFIA

    NASA Technical Reports Server (NTRS)

    Peralta, Robert A.; Jensen, Stephen C.

    2012-01-01

    The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a joint project between NASA and Deutsches Zentrum fuer Luft- und Raumfahrt (DLR), the German Space Agency. SOFIA is based in a Boeing 747 SP and flown in the stratosphere to observe infrared wavelengths unobservable from the ground. In 2007 Dryden Flight Research Center (DFRC) inherited and began work on improving the plane and its telescope. The improvements continue today with upgrading the plane and improving the telescope. The Observatory Verification and Validation (V&V) process is to ensure that the observatory is where the program says it is. The Telescope Status Display (TSD) will provide any information from the on board network to monitors that will display the requested information. In order to assess risks to the program, one must work through the various threats associate with that risk. Once all the risks are closed the program can work towards improving the observatory.

  4. Big Bear Solar Observatory

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    Big Bear Solar Observatory (BBSO) is located at the end of a causeway in a mountain lake more than 2 km above sea level. The site has more than 300 sunny days a year and a natural inversion caused by the lake which makes for very clean images. BBSO is the only university observatory in the US making high-resolution observations of the Sun. Its daily images are posted at http://www.bbso.njit.e...

  5. Maintenance management at La Silla Paranal Observatory

    NASA Astrophysics Data System (ADS)

    Montano, Nelson

    2008-07-01

    From the beginning of the VLT project, the European Southern Observatory (ESO) considered the application of a competent maintenance strategy a fundamental aspect for future operations of the Paranal Observatory. For that purpose, a special maintenance philosophy was developed during the project stage and applied during the initial years of operations. The merging of the La Silla and Paranal Observatories in 2005 added a new managerial challenge to the regular operational requirements (high availability and reliability) which motivated ESO Management to develop a stronger strategy for the operations of the new merged Observatory. Part of the new strategy considered the creation of a dedicated department for the management of all maintenance activities, separating this support from the traditional scheme where the Engineering Department had the responsibility for the entire technical support to operations. In order to keep a competent level of maintenance operations for the new unified Observatory, the La Silla Paranal (LSP) Maintenance Department has been using a well known maintenance management model used in various industrial applications as a guide. Today the operations of the Maintenance Department are concentrated on developing and implementing practices regarding concepts such as Maintenance Tactics, Planning, Data Management, Performance Indicators and Material Management. In addition to that, advances related to Reliability Analysis been taken in order to reach a superior level of excellence. The results achieved by the LSP Maintenance Department are reflected in a reduced rate of functional failures, allowing uninterrupted operations of the Observation sites.

  6. Ultrasound-guided interstitial laser photocoagulation of an autonomous thyroid nodule: the introduction of a novel alternative.

    PubMed

    Døssing, Helle; Bennedbaek, Finn Noe; Hegedüs, Laszlo

    2003-09-01

    Radioiodine ((131)I) and surgery are the standard therapeutic options for the solitary autonomous thyroid nodule (AFTN). Percutaneous ethanol injection (PEI) has proven to be an effective technique and possible alternative to the conventional treatment options. However, PEI is not devoid of side effects and often necessitates multiple treatment sessions. We present a case of a 17-year-old female successfully treated with ultrasound (US)-guided percutaneous interstitial laser photocoagulation (ILP) for an AFTN. Initially, she had a serum thyrotropin (TSH) of 0.01 mU/L and normal peripheral thyroid hormone levels. Scintigraphically it was a hot nodule with suppression of extranodular uptake, and ultrasonographically it was a solitary solid 8.2-mL nodule. One treatment session (3 W for 650 seconds [1950 J]) normalized serum thyrotropin (TSH) level within 2 months and decreased the nodule volume to 4.9 mL (40% reduction) without further alterations during an additional 9 months of follow-up. Side effects were transient thyrotoxicosis and local pain as seen with PEI. To our knowledge, this is the first reported case of ILP used in a patient with a pretoxic thyroid nodule. US-guided thermic tissue coagulation with ILP could become a useful alternative for the AFTN in patients who cannot or will not undergo surgery or treatment with (131)I. PMID:14588105

  7. Guided-wave-based damage detection in a composite T-joint using 3D scanning laser Doppler vibrometer

    NASA Astrophysics Data System (ADS)

    Kolappan Geetha, Ganesh; Roy Mahapatra, D.; Srinivasan, Gopalakrishnan

    2012-04-01

    Composite T-joints are commonly used in modern composite airframe, pressure vessels and piping structures, mainly to increase the bending strength of the joint and prevents buckling of plates and shells, and in multi-cell thin-walled structures. Here we report a detailed study on the propagation of guided ultrasonic wave modes in a composite T-joint and their interactions with delamination in the co-cured co-bonded flange. A well designed guiding path is employed wherein the waves undergo a two step mode conversion process, one is due to the web and joint filler on the back face of the flange and the other is due to the delamination edges close to underneath the accessible surface of the flange. A 3D Laser Doppler Vibrometer is used to obtain the three components of surface displacements/velocities of the accessible face of the flange of the T-joint. The waves are launched by a piezo ceramic wafer bonded on to the back surface of the flange. What is novel in the proposed method is that the location of any change in material/geometric properties can be traced by computing a frequency domain power flow along a scan line. The scan line can be chosen over a grid either during scan or during post-processing of the scan data off-line. The proposed technique eliminates the necessity of baseline data and disassembly of structure for structural interrogation.

  8. A near-infrared tip-tilt sensor for the Keck I laser guide star adaptive optics system

    NASA Astrophysics Data System (ADS)

    Wizinowich, Peter; Smith, Roger; Biasi, Roberto; Cetre, Sylvain; Dekany, Richard; Femenia-Castella, Bruno; Fucik, Jason; Hale, David; Neyman, Chris; Pescoller, Dietrich; Ragland, Sam; Stomski, Paul; Andrighettoni, Mario; Bartos, Randy; Bui, Khanh; Cooper, Andrew; Cromer, John; van Dam, Marcos; Hess, Michael; James, Ean; Lyke, Jim; Rodriguez, Hector; Stalcup, Thomas

    2014-07-01

    The sky coverage and performance of laser guide star (LGS) adaptive optics (AO) systems is limited by the natural guide star (NGS) used for low order correction. This limitation can be dramatically reduced by measuring the tip and tilt of the NGS in the near-infrared where the NGS is partially corrected by the LGS AO system and where stars are generally several magnitudes brighter than at visible wavelengths. We present the design of a near-infrared tip-tilt sensor that has recently been integrated with the Keck I telescope's LGS AO system along with some initial on-sky results. The implementation involved modifications to the AO bench, real-time control system, and higher level controls and operations software that will also be discussed. The tip-tilt sensor is a H2RG-based near-infrared camera with 0.05 arc second pixels. Low noise at high sample rates is achieved by only reading a small region of interest, from 2×2 to 16×16 pixels, centered on an NGS anywhere in the 100 arc second diameter field. The sensor operates at either Ks or H-band using light reflected by a choice of dichroic beamsplitters located in front of the OSIRIS integral field spectrograph.

  9. Manastash Ridge Observatory Autoguider Upgrade

    NASA Astrophysics Data System (ADS)

    Lozo, Jason; Huehnerhoff, Joseph; Armstrong, John; Davila, Adrian; Johnson, Courtney; McMaster, Alex; Olinger, Kyle

    2016-06-01

    The Astronomy Undergraduate Engineering Group (AUEG) at the University of Washington has designed and manufactured a novel autoguider system for the 0.8-meter telescope at the Manastash Ridge Observatory in Ellensburg, Washington. The system uses a pickoff mirror placed in the unused optical path, directing the outer field to the guide camera via a system of axi-symmetrically rotating relay mirrors (periscope). This allows the guider to sample nearly 7 times the area that would be possible with the same fixed detector. This system adds closed loop optical feedback to the tracking capabilities of the telescope. When tuned the telescope will be capable of acheiving 0.5 arcsecond tracking or better. Dynamic focusing of the primary optical path will also be an included feature of this system. This unique guider will be a much needed upgrade to the telescope allowing for increased scientific capability.

  10. Efficacious insect and disease control with laser-guided air-assisted sprayer

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Efficacy of a newly developed air-assisted variable-rate sprayer was investigated for the control of arthropod pests and plant diseases in six commercial fields. The sprayer was integrated with a high-speed laser scanning sensor, a custom-designed signal processing program, an automatic flow control...

  11. Image-guided genomic analysis of tissue response to laser-induced thermal stress

    NASA Astrophysics Data System (ADS)

    Mackanos, Mark A.; Helms, Mike; Kalish, Flora; Contag, Christopher H.

    2011-05-01

    The cytoprotective response to thermal injury is characterized by transcriptional activation of ``heat shock proteins'' (hsp) and proinflammatory proteins. Expression of these proteins may predict cellular survival. Microarray analyses were performed to identify spatially distinct gene expression patterns responding to thermal injury. Laser injury zones were identified by expression of a transgene reporter comprised of the 70 kD hsp gene and the firefly luciferase coding sequence. Zones included the laser spot, the surrounding region where hsp70-luc expression was increased, and a region adjacent to the surrounding region. A total of 145 genes were up-regulated in the laser irradiated region, while 69 were up-regulated in the adjacent region. At 7 hours the chemokine Cxcl3 was the highest expressed gene in the laser spot (24 fold) and adjacent region (32 fold). Chemokines were the most common up-regulated genes identified. Microarray gene expression was successfully validated using qRT- polymerase chain reaction for selected genes of interest. The early response genes are likely involved in cytoprotection and initiation of the healing response. Their regulatory elements will benefit creating the next generation reporter mice and controlling expression of therapeutic proteins. The identified genes serve as drug development targets that may prevent acute tissue damage and accelerate healing.

  12. Guided post-acceleration of laser-driven ions by a miniature modular structure

    PubMed Central

    Kar, Satyabrata; Ahmed, Hamad; Prasad, Rajendra; Cerchez, Mirela; Brauckmann, Stephanie; Aurand, Bastian; Cantono, Giada; Hadjisolomou, Prokopis; Lewis, Ciaran L. S.; Macchi, Andrea; Nersisyan, Gagik; Robinson, Alexander P. L.; Schroer, Anna M.; Swantusch, Marco; Zepf, Matt; Willi, Oswald; Borghesi, Marco

    2016-01-01

    All-optical approaches to particle acceleration are currently attracting a significant research effort internationally. Although characterized by exceptional transverse and longitudinal emittance, laser-driven ion beams currently have limitations in terms of peak ion energy, bandwidth of the energy spectrum and beam divergence. Here we introduce the concept of a versatile, miniature linear accelerating module, which, by employing laser-excited electromagnetic pulses directed along a helical path surrounding the laser-accelerated ion beams, addresses these shortcomings simultaneously. In a proof-of-principle experiment on a university-scale system, we demonstrate post-acceleration of laser-driven protons from a flat foil at a rate of 0.5 GeV m−1, already beyond what can be sustained by conventional accelerator technologies, with dynamic beam collimation and energy selection. These results open up new opportunities for the development of extremely compact and cost-effective ion accelerators for both established and innovative applications. PMID:27089200

  13. Image-guided genomic analysis of tissue response to laser-induced thermal stress

    PubMed Central

    Mackanos, Mark A.; Helms, Mike; Kalish, Flora; Contag, Christopher H.

    2011-01-01

    The cytoprotective response to thermal injury is characterized by transcriptional activation of “heat shock proteins” (hsp) and proinflammatory proteins. Expression of these proteins may predict cellular survival. Microarray analyses were performed to identify spatially distinct gene expression patterns responding to thermal injury. Laser injury zones were identified by expression of a transgene reporter comprised of the 70 kD hsp gene and the firefly luciferase coding sequence. Zones included the laser spot, the surrounding region where hsp70-luc expression was increased, and a region adjacent to the surrounding region. A total of 145 genes were up-regulated in the laser irradiated region, while 69 were up-regulated in the adjacent region. At 7 hours the chemokine Cxcl3 was the highest expressed gene in the laser spot (24 fold) and adjacent region (32 fold). Chemokines were the most common up-regulated genes identified. Microarray gene expression was successfully validated using qRT- polymerase chain reaction for selected genes of interest. The early response genes are likely involved in cytoprotection and initiation of the healing response. Their regulatory elements will benefit creating the next generation reporter mice and controlling expression of therapeutic proteins. The identified genes serve as drug development targets that may prevent acute tissue damage and accelerate healing. PMID:21639585

  14. Observations of large-scale fluid transport by laser-guided plankton aggregationsa)

    NASA Astrophysics Data System (ADS)

    Wilhelmus, Monica M.; Dabiri, John O.

    2014-10-01

    Diel vertical migration of plankton has been proposed to affect global ocean circulation to a degree comparable to winds and tides. This biomixing process has never been directly observed, however, due to the inability to predict its occurrence in situ or to reproduce it in a laboratory setting. Furthermore, it has been argued that the energy imparted to the ocean by plankton migrations occurs at the scale of individual organisms, which is too small to impact ocean mixing. We describe the development of a multi-laser guidance system that leverages the phototactic abilities of plankton to achieve controllable vertical migrations concurrently with laser velocimetry of the surrounding flow. Measurements in unstratified fluid show that the hydrodynamic interactions between neighboring swimmers establish an alternate energy transfer route from the small scales of individually migrating plankton to significantly larger scales. Observations of laser-induced vertical migrations of Artemia salina reveal the appearance of a downward jet, which triggers a Kelvin-Helmholtz instability that results in the generation of eddy-like structures with characteristic length scales much larger than the organisms. The measured energy spectrum is consistent with these findings and indicates energy input at large scales, despite the small individual size of the organisms. These results motivate the study of biomixing in the presence of stratification to assess the contribution of migrating zooplankton to local and global ocean dynamics. The laser control methodology developed here enables systematic study of the relevant processes.

  15. Guided post-acceleration of laser-driven ions by a miniature modular structure.

    PubMed

    Kar, Satyabrata; Ahmed, Hamad; Prasad, Rajendra; Cerchez, Mirela; Brauckmann, Stephanie; Aurand, Bastian; Cantono, Giada; Hadjisolomou, Prokopis; Lewis, Ciaran L S; Macchi, Andrea; Nersisyan, Gagik; Robinson, Alexander P L; Schroer, Anna M; Swantusch, Marco; Zepf, Matt; Willi, Oswald; Borghesi, Marco

    2016-01-01

    All-optical approaches to particle acceleration are currently attracting a significant research effort internationally. Although characterized by exceptional transverse and longitudinal emittance, laser-driven ion beams currently have limitations in terms of peak ion energy, bandwidth of the energy spectrum and beam divergence. Here we introduce the concept of a versatile, miniature linear accelerating module, which, by employing laser-excited electromagnetic pulses directed along a helical path surrounding the laser-accelerated ion beams, addresses these shortcomings simultaneously. In a proof-of-principle experiment on a university-scale system, we demonstrate post-acceleration of laser-driven protons from a flat foil at a rate of 0.5 GeV m(-1), already beyond what can be sustained by conventional accelerator technologies, with dynamic beam collimation and energy selection. These results open up new opportunities for the development of extremely compact and cost-effective ion accelerators for both established and innovative applications. PMID:27089200

  16. A tip/tilt mirror with large dynamic range for the ESO VLT Four Laser Guide Star Facility

    NASA Astrophysics Data System (ADS)

    Rijnveld, N.; Henselmans, R.; Nijland, B.

    2011-09-01

    One of the critical elements in the Four Laser Guide Star Facility (4LGSF) for the ESO Very Large Telescope (VLT) is the Optical Tube Assembly (OTA), consisting of a stable 20x laser beam expander and an active tip/tilt mirror, the Field Selector Mechanism (FSM). This paper describes the design and performance testing of the FSM. The driving requirement for the FSM is its large stroke of +/-6.1 mrad, in combination with less than 1.5 μrad RMS absolute accuracy. The FSM design consists of a Zerodur mirror, bonded to a membrane spring and strut combination to allow only tip and tilt. Two spindle drives actuate the mirror, using a stiffness based transmission to increase resolution. Absolute accuracy is achieved with two differential inductive sensor pairs. A prototype of the FSM is realized to optimize the control configuration and measure its performance. Friction in the spindle drive is overcome by creating a local velocity control loop between the spindle drives and the shaft encoders. Accuracy is achieved by using a cascaded low bandwidth control loop with feedback from the inductive sensors. The pointing jitter and settling time of the FSM are measured with an autocollimator. The system performance meets the strict requirements, and is ready to be implemented in the first OTA.

  17. The importance of corona generation and leader formation during laser filament guided discharges in air

    NASA Astrophysics Data System (ADS)

    Schmitt-Sody, Andreas; French, David; White, William; Lucero, Adrian; Roach, William P.; Hasson, Victor

    2015-03-01

    Images taken with an intensified CCD camera show the dynamics during filament guided discharge events. The images reveal that filament initiated corona plays a role in the presented results. Furthermore, the images show the formation of leaders, propagating and eventually bridging the gap between the high voltage (HV) electrodes. Analysis of the images and comparison to oscilloscope traces of voltage and current dynamics reveal the origin of the delay between the filament and HV discharge and allows for a probability of discharge analysis.

  18. Treatment of a supratentorial primitive neuroectodermal tumor using magnetic resonance-guided laser-induced thermal therapy.

    PubMed

    Jethwa, Pinakin R; Lee, Jason H; Assina, Rachid; Keller, Irwin A; Danish, Shabbar F

    2011-11-01

    Supratentorial primitive neuroectodermal tumors (PNETs) are rare tumors that carry a poorer prognosis than those arising from the infratentorial compartment (such as medulloblastoma). The overall prognosis for these patients depends on several factors including the extent of resection, age at diagnosis, CSF dissemination, and site in the supratentorial space. The authors present the first case of a patient with a newly diagnosed supratentorial PNET in which cytoreduction was achieved with MR-guided laser-induced thermal therapy. A 10-year-old girl presented with left-sided facial weakness and a large right thalamic mass extending into the right midbrain. The diagnosis of supratentorial PNET was made after stereotactic biopsy. Therapeutic options for this lesion were limited because of the risks of postoperative neurological deficits with resection. The patient underwent MR-guided laser-induced thermal ablation of her tumor. Under real-time MR thermometry, thermal energy was delivered to the tumor at a core temperature of 90°C for a total of 960 seconds. The patient underwent follow-up MR imaging at regular intervals to evaluate the tumor response to the thermal ablation procedure. Initial postoperative scans showed an increase in the size of the lesion as well as the amount of the associated edema. Both the size of the lesion and the edema stabilized by 1 week and then decreased below preablation levels at the 3-month postsurgical follow-up. There was a slight increase in the size of the lesion and associated edema at the 6-month follow-up scan, presumably due to concomitant radiation she received as part of her postoperative care. The patient tolerated the procedure well and has had resolution of her symptoms since surgery. Further study is needed to assess the role of laser-induced thermal therapy for the treatment of intracranial tumors. As such, it is a promising tool in the neurosurgical armamentarium. Postoperative imaging has shown no evidence of definitive

  19. Creating Griffith Observatory

    NASA Astrophysics Data System (ADS)

    Cook, Anthony

    2013-01-01

    Griffith Observatory has been the iconic symbol of the sky for southern California since it began its public mission on May 15, 1935. While the Observatory is widely known as being the gift of Col. Griffith J. Griffith (1850-1919), the story of how Griffith’s gift became reality involves many of the people better known for other contributions that made Los Angeles area an important center of astrophysics in the 20th century. Griffith began drawing up his plans for an observatory and science museum for the people of Los Angeles after looking at Saturn through the newly completed 60-inch reflector on Mt. Wilson. He realized the social impact that viewing the heavens could have if made freely available, and discussing the idea of a public observatory with Mt. Wilson Observatory’s founder, George Ellery Hale, and Director, Walter Adams. This resulted, in 1916, in a will specifying many of the features of Griffith Observatory, and establishing a committee managed trust fund to build it. Astronomy popularizer Mars Baumgardt convinced the committee at the Zeiss Planetarium projector would be appropriate for Griffith’s project after the planetarium was introduced in Germany in 1923. In 1930, the trust committee judged funds to be sufficient to start work on creating Griffith Observatory, and letters from the Committee requesting help in realizing the project were sent to Hale, Adams, Robert Millikan, and other area experts then engaged in creating the 200-inch telescope eventually destined for Palomar Mountain. A Scientific Advisory Committee, headed by Millikan, recommended that Caltech Physicist Edward Kurth be put in charge of building and exhibit design. Kurth, in turn, sought help from artist Russell Porter. The architecture firm of John C. Austin and Fredrick Ashley was selected to design the project, and they adopted the designs of Porter and Kurth. Philip Fox of the Adler Planetarium was enlisted to manage the completion of the Observatory and become its

  20. Goddard Geophysical and Astronomical Observatory

    NASA Technical Reports Server (NTRS)

    Figueroa, Ricardo

    2013-01-01

    This report summarizes the technical parameters and the technical staff of the VLBI system at the fundamental station GGAO. It also gives an overview about the VLBI activities during the report year. The Goddard Geophysical and Astronomical Observatory (GGAO) consists of a 5-meter radio telescope for VLBI, a new 12-meter radio telescope for VLBI2010 development, a 1-meter reference antenna for microwave holography development, an SLR site that includes MOBLAS-7, the NGSLR development system, and a 48" telescope for developmental two-color Satellite Laser Ranging, a GPS timing and development lab, a DORIS system, meteorological sensors, and a hydrogen maser. In addition, we are a fiducial IGS site with several IGS/IGSX receivers. GGAO is located on the east coast of the United States in Maryland. It is approximately 15 miles NNE of Washington, D.C. in Greenbelt, Maryland.

  1. MRI-guided laser thermal therapy in the prostate: preliminary results

    NASA Astrophysics Data System (ADS)

    McNichols, Roger J.; Gowda, Ashok; Stafford, R. J.; Price, Roger E.; Hazle, John D.

    2004-07-01

    Minimally invasive thermal therapies for the treatment of prostate cancer offer potential to reduce cost, treatment time, and patient trauma. A drawback to such therapies is that it is often difficult or impossible to know the exact volume of which is being destroyed. In this work, we report on the use of magnetic resonance (MR) thermal imaging to provide real-time feedback control over laser interstitial thermal therapy (LITT) in an in vivo canine prostate model.

  2. How to guide lubricants - Tailored laser surface patterns on stainless steel

    NASA Astrophysics Data System (ADS)

    Grützmacher, Philipp G.; Rosenkranz, Andreas; Gachot, Carsten

    2016-05-01

    In this experimental study, periodic line-like structures with different periodicities (5, 10, 19, and 300 μm) and structural depths (approximately 1 and 4 μm) were fabricated on stainless steel samples (AISI-304) by short-pulse laser interference and ultrashort-pulse laser patterning. A detailed characterization of the resulting surface topography was performed by white light interferometry and scanning electron microscopy. The spreading dynamics of additive-free synthetic polyalphaolefine oil on a polished reference sample are compared to laser patterned surfaces. These studies are conducted using a newly developed test rig, which allowed for controlled temperature gradients and a precise recording of the spreading dynamics of lubricants on sample surfaces. It could be demonstrated that the spreading velocity parallel to the surface pattern is higher for all samples which can be explained by increased capillary forces and liquid pinning induced by the surface patterning. Furthermore, a decline of the spreading velocity over time for all samples and orientations is clearly visible which can be traced back to a viscosity increase induced by the temperature gradient and a reduced droplet volume. For parallel orientation, the experimental findings are in good agreement with the Lucas-Washburn equation and established models.

  3. NASA'S Great Observatories

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Why are space observatories important? The answer concerns twinkling stars in the night sky. To reach telescopes on Earth, light from distant objects has to penetrate Earth's atmosphere. Although the sky may look clear, the gases that make up our atmosphere cause problems for astronomers. These gases absorb the majority of radiation emanating from celestial bodies so that it never reaches the astronomer's telescope. Radiation that does make it to the surface is distorted by pockets of warm and cool air, causing the twinkling effect. In spite of advanced computer enhancement, the images finally seen by astronomers are incomplete. NASA, in conjunction with other countries' space agencies, commercial companies, and the international community, has built observatories such as the Hubble Space Telescope, the Compton Gamma Ray Observatory, and the Chandra X-ray Observatory to find the answers to numerous questions about the universe. With the capabilities the Space Shuttle provides, scientist now have the means for deploying these observatories from the Shuttle's cargo bay directly into orbit.

  4. Everyday astronomy @ Sydney Observatory

    NASA Astrophysics Data System (ADS)

    Parello, S. L.

    2008-06-01

    Catering to a broad range of audiences, including many non-English speaking visitors, Sydney Observatory offers everything from school programmes to public sessions, day care activities to night observing, personal interactions to web-based outreach. With a history of nearly 150 years of watching the heavens, Sydney Observatory is now engaged in sharing the wonder with everybody in traditional and innovative ways. Along with time-honoured tours of the sky through two main telescopes, as well as a small planetarium, Sydney Observatory also boasts a 3D theatre, and offers programmes 363 days a year - rain or shine, day and night. Additionally, our website neversleeps, with a blog, YouTube videos, and night sky watching podcasts. And for good measure, a sprinkling of special events such as the incomparable Festival of the Stars, for which most of northern Sydney turns out their lights. Sydney Observatory is the oldest working observatory in Australia, and we're thrilled to be looking forward to our 150th Anniversary next year in anticipation of the International Year of Astronomy immediately thereafter.

  5. Changes in disc herniation after CT-guided Percutaneous Laser Disc Decompression (PLDD): MR findings

    NASA Astrophysics Data System (ADS)

    Brat, Hugues G.; Bouziane, Tarik; Lambert, Jean; Divano, Luisa

    2004-09-01

    The aim of Percutaneous Laser Disc Decompression (PLDD) is to vaporize a small portion of the nucleus pulposus. Clinical efficacy of this technique is largely proven. However, time-evolution of intervertebral disc and its hernia after PLDD is not known. This study analyses changes in disc herniation and its native intervertebral disc at a mean follow-up of 7.5 months after PLDD in asymptomatic patients. Main observations at MRI are appearance of a high signal on T2WI in the hernia in 59%, shrinking of the hernia in 66% and overall stability of disc height.

  6. WFIRST Observatory Performance

    NASA Technical Reports Server (NTRS)

    Kruk, Jeffrey W.

    2012-01-01

    The WFIRST observatory will be a powerful and flexible wide-field near-infrared facility. The planned surveys will provide data applicable to an enormous variety of astrophysical science. This presentation will provide a description of the observatory and its performance characteristics. This will include a discussion of the point spread function, signal-to-noise budgets for representative observing scenarios and the corresponding limiting sensitivity. Emphasis will be given to providing prospective Guest Observers with information needed to begin thinking about new observing programs.

  7. Yellowstone Volcano Observatory

    USGS Publications Warehouse

    Venezky, Dina Y.; Lowenstern, Jacob

    2008-01-01

    Eruption of Yellowstone's Old Faithful Geyser. Yellowstone hosts the world's largest and most diverse collection of natural thermal features, which are the surface expression of magmatic heat at shallow depths in the crust. The Yellowstone system is monitored by the Yellowstone Volcano Observatory (YVO), a partnership among the U.S. Geological Survey (USGS), Yellowstone National Park, and the University of Utah. YVO is one of five USGS Volcano Hazards Program observatories that monitor U.S. volcanoes for science and public safety. Learn more about Yellowstone and YVO at http://volcanoes.usgs.gov/yvo.

  8. Wavefront sensor testing in hypersonic flows using a laser-spark guide star

    NASA Astrophysics Data System (ADS)

    Neal, Daniel R.; Armstrong, Darrell J.; Hedlund, Eric; Lederer, Melissa; Collier, Arnold S.; Spring, Charles; Gruetzner, James K.; Hebner, Gregory A.; Mansell, Justin D.

    1997-11-01

    The flight environment of next-generation theater missile defense interceptors involves hypersonic speeds that place severe aero-thermodynamic loads on missile components including the windows used for optical seekers. These heating effects can lead to significant boresight error and aberration. Ground-based tests are required to characterize these effects. We have developed methods to measure aberrations in seeker windows using a Shack-Hartmann wavefront sensor. Light from a laser or other source with a well known wavefront is passed through the window and falls on the sensor. The sensor uses an array of micro-lenses to generate a grid of focal spots on a CCD detector. The positions of the focal spots provide a measure of the wavefront slope over each micro-lens. The wavefront is reconstructed by integrating the slopes, and analyzed to characterize aberrations. During flight, optical seekers look upstream through a window at 'look angles' angles near 0 degrees relative to the free stream flow. A 0 degree angle corresponds to large angles approaching 90 degrees when measured relative to the normal of the window, and is difficult to simulate using conventional techniques to illuminate the wavefront sensor during wind tunnel tests. For this reason, we developed a technique using laser- induced optical breakdown that allows arbitrary look angles down to 0 degrees.

  9. Clinical outcomes of wavefront-guided laser in situ keratomileusis to treat moderate-to-high astigmatism

    PubMed Central

    Schallhorn, Steven C; Venter, Jan A; Hannan, Stephen J; Hettinger, Keith A

    2015-01-01

    Purpose The purpose of this study was to evaluate the refractive and visual outcomes of wavefront-guided laser in situ keratomileusis (LASIK) in eyes with myopic astigmatism and cylindrical component ≥2.0 diopter (D). Methods In this retrospective study, 611 eyes that underwent LASIK for simple or compound myopic astigmatism were analyzed. Preoperative refractive cylinder ranged from −2.00 D to −6.00 D (mean −2.76±0.81 D), and the sphere was between 0.00 D and −9.75 D (mean −2.79±2.32 D). Predictability, visual outcomes, and vector analysis of changes in refractive astigmatism were evaluated. Results At 3 months after LASIK, 83.8% of eyes had uncorrected distance visual acuity of 20/20 or better, 90.3% had manifest spherical equivalent within ±0.50 D, and 79.1% had residual refractive cylinder within ±0.50 D of intended correction. The mean correction ratio for refractive cylinder was 0.92±0.14, the mean error of angle was −0.45°±2.99°, and the mean error vector was 0.37±0.38 D. A statistically significant correlation was found between the error of magnitude (arithmetic difference in the magnitudes between surgically induced refractive correction and intended refractive correction) and the intended refractive correction (r=0.26, P<0.01). Conclusion Wavefront-guided LASIK for the correction of myopic astigmatism is safe, effective, and predictable. PMID:26203219

  10. Percutaneous Ultrasound-Guided Laser Ablation with Contrast-Enhanced Ultrasonography for Hyperfunctioning Parathyroid Adenoma: A Preliminary Case Series

    PubMed Central

    Jiang, Tianan; Chen, Fen; Zhou, Xiang; Hu, Ying; Zhao, Qiyu

    2015-01-01

    The study was to evaluate the safety and effectiveness of ultrasound-guided percutaneous laser ablation (pLA) as a nonsurgical treatment for primary parathyroid adenoma. Surgery was contraindicated in, or refused by, the included patients. No lesion enhancement on contrast-enhanced ultrasound immediately after pLA was considered “complete ablation.” Nodule size, serum calcium, and parathyroid hormone level were compared before and after pLA. Complete ablation was achieved in all 21 patients with 1 (n = 20) or 2 (n = 1) sessions. Nodule volume decreased from 0.93 ± 0.58 mL at baseline to 0.53 ± 0.38 and 0.48 ± 0.34 mL at 6 and 12 months after pLA (P < 0.05). At 1 day, 6 months, and 12 months after pLA, serum PTH decreased from 15.23 ± 3.00 pmol/L at baseline to 7.41 ± 2.79, 6.95 ± 1.78, and 6.90 ± 1.46 pmol/L, serum calcium decreased from 3.77 ± 0.77 mmol/L at baseline to 2.50 ± 0.72, 2.41 ± 0.37, and 2.28 ± 0.26 mmol/L, respectively (P < 0.05). At 12 months, treatment success (normalization of PTH and serum calcium) was achieved in 81%. No serious complications were observed. Ultrasound-guided pLA with contrast-enhanced ultrasound is a viable alternative to surgery for primary parathyroid adenoma. PMID:26788059

  11. Percutaneous Ultrasound-Guided Laser Ablation with Contrast-Enhanced Ultrasonography for Hyperfunctioning Parathyroid Adenoma: A Preliminary Case Series.

    PubMed

    Jiang, Tianan; Chen, Fen; Zhou, Xiang; Hu, Ying; Zhao, Qiyu

    2015-01-01

    The study was to evaluate the safety and effectiveness of ultrasound-guided percutaneous laser ablation (pLA) as a nonsurgical treatment for primary parathyroid adenoma. Surgery was contraindicated in, or refused by, the included patients. No lesion enhancement on contrast-enhanced ultrasound immediately after pLA was considered "complete ablation." Nodule size, serum calcium, and parathyroid hormone level were compared before and after pLA. Complete ablation was achieved in all 21 patients with 1 (n = 20) or 2 (n = 1) sessions. Nodule volume decreased from 0.93 ± 0.58 mL at baseline to 0.53 ± 0.38 and 0.48 ± 0.34 mL at 6 and 12 months after pLA (P < 0.05). At 1 day, 6 months, and 12 months after pLA, serum PTH decreased from 15.23 ± 3.00 pmol/L at baseline to 7.41 ± 2.79, 6.95 ± 1.78, and 6.90 ± 1.46 pmol/L, serum calcium decreased from 3.77 ± 0.77 mmol/L at baseline to 2.50 ± 0.72, 2.41 ± 0.37, and 2.28 ± 0.26 mmol/L, respectively (P < 0.05). At 12 months, treatment success (normalization of PTH and serum calcium) was achieved in 81%. No serious complications were observed. Ultrasound-guided pLA with contrast-enhanced ultrasound is a viable alternative to surgery for primary parathyroid adenoma. PMID:26788059

  12. Tip-tilt compensation: Resolution limits for ground-based telescopes using laser guide star adaptive optics. Revision 2

    SciTech Connect

    Olivier, S.S.; Max, C.E.; Gavel, D.T.; Brase, J.M.

    1992-10-08

    The angular resolution of long-exposure images from ground-based telescopes equipped with laser guide star adaptive optics systems is fundamentally limited by the the accuracy with which the tip-tilt aberrations introduced by the atmosphere can be corrected. Assuming that a natural star is used as the tilt reference, the residual error due to tilt anisoplanatism can significantly degrade the long-exposure resolution even if the tilt reference star is separated from the object being imaged by a small angle. Given the observed distribution of stars in the sky, the need to find a tilt reference star quite close to the object restricts the fraction of the sky over which long-exposure images with diffraction limited resolution can be obtained. In this paper, the authors present a comprehensive performance analysis of tip-tilt compensation systems that use a natural star as a tilt reference, taking into account properties of the atmosphere and of the Galactic stellar populations, and optimizing over the system operating parameters to determine the fundamental limits to the long-exposure resolution. Their results show that for a ten meter telescope on Mauna Kea, if the image of the tilt reference star is uncorrected, about half the sky can be imaged in the V band with long-exposure resolution less than 60 milli-arc-seconds (mas), while if the image of the tilt reference star is fully corrected, about half the sky can be imaged in the V band with long-exposure resolution less than 16 mas. Furthermore, V band images long-exposure resolution of less than 16 mas may be obtained with a ten meter telescope on Mauna Kea for unresolved objects brighter than magnitude 22 that are fully corrected by a laser guide star adaptive optics system. This level of resolution represents about 70% of the diffraction limit of a ten meter telescope in the V band and is more than a factor of 45 better than the median seeing in the V band on Mauna Kea.

  13. Kinetic description of a free electron laser with an electromagnetic-wave wiggler and ion-channel guiding by using the Einstein coefficient technique

    NASA Astrophysics Data System (ADS)

    Mehdian, H.; AbasiRostami, S.; Hasanbeigi, A.

    2016-04-01

    A theoretical study of electron trajectories and gain in a free electron laser (FEL) with an electromagnetic-wave wiggler and ion-channel guiding is presented based on the Einstein coefficient method. The laser gain in the low-gain regime is obtained for the case of a cold tenuous relativistic electron beam, where the beam plasma frequency is much less than the radiation frequency propagating in this configuration. The resulting gain equation is analyzed numerically over a wide range of system parameters.

  14. Note: Characterization of the plasma parameters of a capillary discharge-produced plasma channel waveguide to guide an intense laser pulse

    SciTech Connect

    Higashiguchi, Takeshi; Yugami, Noboru; Hikida, Masafumi; Terauchi, Hiromitsu; Bai Jinxiang; Kikuchi, Takashi; Tao Yezheng

    2010-04-15

    We demonstrated the production of an optical waveguide in a capillary discharge-produced plasma using a cylindrical capillary. Plasma parameters of its waveguide were characterized by use of both a Nomarski laser interferometer and a hydrogen plasma line spectrum. A space-averaged maximum temperature of 3.3 eV with electron densities of the order of 10{sup 17} cm{sup -3} was observed at a discharge time of 150 ns and a maximum discharge current of 400 A. An ultrashort, intense laser pulse was guided by use of this plasma channel.

  15. Magnetic Resonance Imaging-Guided Focused Laser Interstitial Thermal Therapy for Intracranial Lesions: Single-Institution Series

    PubMed Central

    Hawasli, Ammar H.; Bagade, Swapnil; Shimony, Joshua S.; Miller-Thomas, Michelle

    2013-01-01

    BACKGROUND: Surgical treatments for deep-seated intracranial lesions have been limited by morbidities associated with resection. Real-time magnetic resonance imaging–guided focused laser interstitial thermal therapy (LITT) offers a minimally invasive surgical treatment option for such lesions. OBJECTIVE: To review treatments and results of patients treated with LITT for intracranial lesions at Washington University School of Medicine. METHODS: In a review of 17 prospectively recruited LITT patients (34-78 years of age; mean, 59 years), we report demographics, treatment details, postoperative imaging characteristics, and peri- and postoperative clinical courses. RESULTS: Targets included 11 gliomas, 5 brain metastases, and 1 epilepsy focus. Lesions were lobar (n = 8), thalamic/basal ganglia (n = 5), insular (n = 3), and corpus callosum (n = 1). Mean target volume was 11.6 cm3, and LITT produced 93% target ablation. Patients with superficial lesions had shorter intensive care unit stays. Ten patients experienced no perioperative morbidities. Morbidities included transient aphasia, hemiparesis, hyponatremia, deep venous thrombosis, and fatal meningitis. Postoperative magnetic resonance imaging showed blood products within the lesion surrounded by new thin uniform rim of contrast enhancement and diffusion restriction. In conjunction with other therapies, LITT targets often showed stable or reduced local disease. Epilepsy focus LITT produced seizure freedom at 8 months. Preliminary overall median progression-free survival and survival from LITT in tumor patients were 7.6 and 10.9 months, respectively. However, this small cohort has not been followed for a sufficient length of time, necessitating future outcomes studies. CONCLUSION: Early peri- and postoperative clinical data demonstrate that LITT is a safe and viable ablative treatment option for intracranial lesions, and may be considered for select patients. ABBREVIATION: LITT, laser interstitial thermal therapy

  16. CT-guided Percutaneous Laser Disc Decompression (PLDD): prospective clinical outcome

    NASA Astrophysics Data System (ADS)

    Brat, Hugues G.; Bouziane, Tarik; Lambert, Jean; Divano, Luisa

    2004-09-01

    Percutaneous Laser Disc Decompression (PLDD) is a minimal invasive and effective treatment for contained lumbar disc hernias with correspondent radicular pain. This prospective study evaluates clinical efficacy of patients treated with PLDD under CT-fluoroscopic guidance. An independent observer assessed clinical outcome in a series of 40 consecutive patients at a mean follow-up of 7.5 months after treatment. According to Mac Nab criteria, 80% of patients experienced a good response to PLDD, 12.5% a fair response and 7.5% a poor response. 37 patients (92.5%) were back at work after 3 weeks. This technique could represent an alternative and secure treatment to conventional surgery for contained disc hernias.

  17. Torun Radio Astronomy Observatory

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    Torun Center for Astronomy is located at Piwnice, 15 km north of Torun, Poland. A part of the Faculty of Physics and Astronomy of the Nicolaus Copernicus University, it was created by the union of Torun Radio Astronomy Observatory (TRAO) and the Institute of Astronomy on 1 January 1997....

  18. Strasbourg's "First" astronomical observatory

    NASA Astrophysics Data System (ADS)

    Heck, André

    2011-08-01

    The turret lantern located at the top of the Strasbourg Hospital Gate is generally considered as the first astronomical observatory of the city, but such a qualification must be treated with caution. The thesis of this paper is that the idea of a tower-observatory was brought back by a local scholar, Julius Reichelt (1637-1717), after he made a trip to Northern Europe around 1666 and saw the "Rundetårn" (Round Tower) recently completed in Copenhagen. There, however, a terrace allowed (and still allows) the full viewing of the sky, and especially of the zenith area where the atmospheric transparency is best. However, there is no such terrace in Strasbourg around the Hospital Gate lantern. Reichelt had also visited Johannes Hevelius who was then developing advanced observational astronomy in Gdansk, but nothing of the kind followed in Strasbourg. Rather, the Hospital Gate observatory was built essentially for the prestige of the city and for the notoriety of the university, and the users of this observing post did not make any significant contributions to the progress of astronomical knowledge. We conclude that the Hospital Gate observatory was only used for rudimentary viewing of bright celestial objects or phenomena relatively low on the horizon.

  19. Armenian Virtual Observatory

    NASA Astrophysics Data System (ADS)

    Mickaelian, A. M.

    2015-07-01

    Vast amount of information continuously accumulated in astronomy requires finding new solutions for its efficient storage, use and dissemination, as well as accomplishing new research projects. Virtual Observatories (VOs) have been created in a number of countries to set up a new environment for these tasks. Based on them, the International Virtual Observatory Alliance (IVOA) was created in 2002, which unifies 19 VO projects, including Armenian Virtual Observatory (ArVO) founded in 2005. ArVO is a project of Byurakan Astrophysical Observatory (BAO) aimed at construction of a modern system for data archiving, extraction, acquisition, reduction, use and publication. ArVO technical and research projects are presented, including the Global Spectroscopic Database, which is being built based on Digitized First Byurakan Survey (DFBS). Quick optical identification of radio, IR or X-ray sources will be possible by plotting their positions in the DFBS or other spectroscopic plate and matching all available data. Accomplishment of new projects by combining data is so important that the International Council of Scientific Unions (ICSU) recently created World Data System (WDS) for unifying data coming from all science areas, and BAO has also joined it.

  20. High Energy Astronomy Observatory

    NASA Technical Reports Server (NTRS)

    1980-01-01

    An overview of the High Energy Astronomy Observatory 2 contributions to X-ray astronomy is presented along with a brief description of the satellite and onboard telescope. Observations relating to galaxies and galactic clusters, black holes, supernova remnants, quasars, and cosmology are discussed.

  1. Poznan acute Astronomical Observatory

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    This Poznan acute Astronomical Observatory is a unit of the Adam Mickiewicz University, located in Poznan acute, Poland. From its foundation in 1919, it has specialized in astrometry and celestial mechanics (reference frames, dynamics of satellites and small solar system bodies). Recently, research activities have also included planetary and stellar astrophysics (asteroid photometry, catalysmic b...

  2. Record low-threshold index-guided InGaAs/GaAlAs vertical-cavity surface-emitting laser with a native oxide confinement structure

    NASA Astrophysics Data System (ADS)

    Hayashi, Y.; Mukaihara, T.; Hatori, N.; Ohnoki, N.; Matsutani, A.; Koyama, F.; Iga, K.

    1995-03-01

    An index-guided InGaAs/GaAlAs vertical-cavity surface-emitting laser with a native oxide confinement structure has been proposed and fabricated. A record threshold current of 70 micro A was achieved with a 5 micron-diameter core device. The proposed structure provides strong electrical and optical confinements. Also a reduction in nonradiative recombination and an improvement in the thermal resistance can be expected.

  3. Theoretical and experimental study of hybrid unstable-guided resonator for diffusion-cooled CO2 laser

    NASA Astrophysics Data System (ADS)

    Serri, Laura; Fantini, Vincenzo; De Silvestri, Sandro; Magni, Vittorio C.

    1996-08-01

    Diffusion cooled carbon-dioxide laser sources allow nowadays to produce more than two kilowatt output power with weights, dimensions and costs reduced with respect to the traditional fast axial flow sources of the same power level. In particular, they can be easily integrated in traditional as well as in robot-laser workstations. These kinds of sources are characterized by two large area water cooled coaxial or planar electrodes with small spacing (few millimeters) in order to guarantee a good mixture cooling. Consequently the discharge geometry results 'optically hard:' a thin ring or a thin rectangle. In this communication we present theoretical and experimental results concerning the design and development of the optical resonator and of the external optical chain for a carbon-dioxide laser prototype. The work was done in the frame of a national project. The prototype is a diffusion cooled, rf excited slab source with 1 kW output power. The surface of each electrode is 110 by 700 mm and their spacing is 2 mm. For this geometry a hybrid unstable-guided resonator has been adopted. The main problem of this configuration is that the extracted beam is elliptical and astigmatic, and therefore needs to be manipulated before the working point where high optical quality is required for material processing. A particular computer code has been developed to calculate the resonator modes and the calculated profiles of the beam have been compared with the measured ones with and without external optical chain. The good agreement of the results confirms that the criteria adopted for the simulation are correct and that the code developed can be successfully employed in the design stage. This is particularly significant for this class of sources because an extensive experimental study of different optical combinations of the resonator mirrors can become expensive. In fact the mirrors have large dimensions (about 110 by 40 mm) and non standard curvature radii. Moreover they need

  4. Effect of Myopic Defocus on Visual Acuity after Phakic Intraocular Lens Implantation and Wavefront-guided Laser in Situ Keratomileusis.

    PubMed

    Kamiya, Kazutaka; Shimizu, Kimiya; Igarashi, Akihito; Kawamorita, Takushi

    2015-01-01

    This study aimed to investigate the effect of myopic defocus on visual acuity after phakic intraocular lens (IOL) implantation and wavefront-guided laser in situ keratomileusis (wfg-LASIK). Our prospective study comprised thirty eyes undergoing posterior chamber phakic IOL implantation and 30 eyes undergoing wfg-LASIK. We randomly measured visual acuity under myopic defocus after cycloplegic and non-cycloplegic correction. We also calculated the modulation transfer function by optical simulation and estimated visual acuity from Campbell &Green's retinal threshold curve. Visual acuity in the phakic IOL group was significantly better than that in the wfg-LASIK group at myopic defocus levels of 0, -1, and -2 D (p < 0.001, p < 0.001, and p = 0.02, Mann-Whitney U-test), but not at a defocus of -3 D (p = 0.30). Similar results were also obtained in a cycloplegic condition. Decimal visual acuity values at a myopic defocus of 0, -1, -2, and -3 D by optical simulation were estimated to be 1.95, 1.21, 0.97, and 0.75 in the phakic IOL group, and 1.39, 1.11, 0.94, and 0.71 in the wfg-LASIK group, respectively. From clinical and optical viewpoints, phakic IOL implantation was superior to wfg-LASIK in terms of the postoperative visual performance, even in the presence of low to moderate myopic regression. PMID:25994984

  5. A CLOSE COMPANION SEARCH AROUND L DWARFS USING APERTURE MASKING INTERFEROMETRY AND PALOMAR LASER GUIDE STAR ADAPTIVE OPTICS

    SciTech Connect

    Bernat, David; Bouchez, Antonin H.; Cromer, John L.; Dekany, Richard G.; Moore, Anna M.; Ireland, Michael; Tuthill, Peter; Martinache, Frantz; Angione, John; Burruss, Rick S.; Guiwits, Stephen R.; Henning, John R.; Hickey, Jeff; Kibblewhite, Edward; McKenna, Daniel L.; Petrie, Harold L.; Roberts, Jennifer; Shelton, J. Chris; Thicksten, Robert P.; Trinh, Thang

    2010-06-01

    We present a close companion search around 16 known early L dwarfs using aperture masking interferometry with Palomar laser guide star adaptive optics (LGS AO). The use of aperture masking allows the detection of close binaries, corresponding to projected physical separations of 0.6-10.0 AU for the targets of our survey. This survey achieved median contrast limits of {Delta}K {approx} 2.3 for separations between 1.2 {lambda}/D-4{lambda}/D and {Delta}K {approx} 1.4 at 2/3 {lambda}/D. We present four candidate binaries detected with moderate-to-high confidence (90%-98%). Two have projected physical separations less than 1.5 AU. This may indicate that tight-separation binaries contribute more significantly to the binary fraction than currently assumed, consistent with spectroscopic and photometric overluminosity studies. Ten targets of this survey have previously been observed with the Hubble Space Telescope as part of companion searches. We use the increased resolution of aperture masking to search for close or dim companions that would be obscured by full aperture imaging, finding two candidate binaries. This survey is the first application of aperture masking with LGS AO at Palomar. Several new techniques for the analysis of aperture masking data in the low signal-to-noise regime are explored.

  6. Efficient reconstruction method for ground layer adaptive optics with mixed natural and laser guide stars.

    PubMed

    Wagner, Roland; Helin, Tapio; Obereder, Andreas; Ramlau, Ronny

    2016-02-20

    The imaging quality of modern ground-based telescopes such as the planned European Extremely Large Telescope is affected by atmospheric turbulence. In consequence, they heavily depend on stable and high-performance adaptive optics (AO) systems. Using measurements of incoming light from guide stars, an AO system compensates for the effects of turbulence by adjusting so-called deformable mirror(s) (DMs) in real time. In this paper, we introduce a novel reconstruction method for ground layer adaptive optics. In the literature, a common approach to this problem is to use Bayesian inference in order to model the specific noise structure appearing due to spot elongation. This approach leads to large coupled systems with high computational effort. Recently, fast solvers of linear order, i.e., with computational complexity O(n), where n is the number of DM actuators, have emerged. However, the quality of such methods typically degrades in low flux conditions. Our key contribution is to achieve the high quality of the standard Bayesian approach while at the same time maintaining the linear order speed of the recent solvers. Our method is based on performing a separate preprocessing step before applying the cumulative reconstructor (CuReD). The efficiency and performance of the new reconstructor are demonstrated using the OCTOPUS, the official end-to-end simulation environment of the ESO for extremely large telescopes. For more specific simulations we also use the MOST toolbox. PMID:26906596

  7. Identifying clouds over the Pierre Auger Observatory using infrared satellite data

    SciTech Connect

    Abreu, Pedro; et al.,

    2013-12-01

    We describe a new method of identifying night-time clouds over the Pierre Auger Observatory using infrared data from the Imager instruments on the GOES-12 and GOES-13 satellites. We compare cloud identifications resulting from our method to those obtained by the Central Laser Facility of the Auger Observatory. Using our new method we can now develop cloud probability maps for the 3000 km^2 of the Pierre Auger Observatory twice per hour with a spatial resolution of ~2.4 km by ~5.5 km. Our method could also be applied to monitor cloud cover for other ground-based observatories and for space-based observatories.

  8. Impact of laser-structured biomaterial interfaces on guided cell responses

    PubMed Central

    Fadeeva, Elena; Deiwick, Andrea; Chichkov, Boris; Schlie-Wolter, Sabrina

    2014-01-01

    To achieve a perfect integration of biomaterials into the body, tissue formation in contact with the interface has to be controlled. In this connection, a selective cell control is required: fibrotic encapsulation has to be inhibited, while tissue guidance has to be stimulated. As conventional biomaterials do not fulfil this specification, functionalization of the biointerface is under development to mimic the natural environment of the cells. One approach focuses on the fabrication of defined surface topographies. Thereby, ultrashort pulse laser ablation is very beneficial, owing to a large variety of fabricated structures, reduced heat-affected zones, high precision and reproducibility. We demonstrate that nanostructures in platinum and microstructures in silicon selectively control cell behaviour: inhibiting fibroblasts, while stimulating neuronal attachment and differentiation. However, the control of fibroblasts strongly correlates with the created size dimensions of the surface structures. These findings suggest favourable biomaterial interfaces for electronic devices. The mechanisms which are responsible for selective cell control are poorly understood. To give an insight, cell behaviour in dependence of biomaterial interfaces is discussed—including basic research on the role of the extracellular matrix. This knowledge is essential to understand such specific cell responses and to optimize biomaterial interfaces for future biomedical applications. PMID:24501676

  9. PROPER MOTIONS OF THE ARCHES CLUSTER WITH KECK LASER GUIDE STAR ADAPTIVE OPTICS: THE FIRST KINEMATIC MASS MEASUREMENT OF THE ARCHES

    SciTech Connect

    Clarkson, W. I.; Ghez, A. M.; Morris, M. R.; Yelda, S.; Lu, J. R.; Stolte, A.; McCrady, N.; Do, T.

    2012-06-01

    We report the first detection of the intrinsic velocity dispersion of the Arches cluster-a young ({approx}2 Myr), massive (10{sup 4} M{sub Sun }) starburst cluster located only 26 pc in projection from the Galactic center. This was accomplished using proper motion measurements within the central 10'' Multiplication-Sign 10'' of the cluster, obtained with the laser guide star adaptive optics system at Keck Observatory over a three-year time baseline (2006-2009). This uniform data set results in proper motion measurements that are improved by a factor {approx}5 over previous measurements from heterogeneous instruments. By careful, simultaneous accounting of the cluster and field contaminant distributions as well as the possible sources of measurement uncertainties, we estimate the internal velocity dispersion to be 0.15 {+-} 0.01 mas yr{sup -1}, which corresponds to 5.4 {+-} 0.4 km s{sup -1} at a distance of 8.4 kpc. Projecting a simple model for the cluster onto the sky to compare with our proper motion data set, in conjunction with surface density data, we estimate the total present-day mass of the cluster to be M(r < 1.0 pc) = 1.5{sup +0.74}{sub -0.60} Multiplication-Sign 10{sup 4} M{sub Sun }. The mass in stars observed within a cylinder of radius R (for comparison to photometric estimates) is found to be M(R < 0.4 pc) = 0.90{sup +0.40}{sub -0.35} Multiplication-Sign 10{sup 4} M{sub Sun} at formal 3{sigma} confidence. This mass measurement is free from assumptions about the mass function of the cluster, and thus may be used to check mass estimates from photometry and simulation. Photometric mass estimates assuming an initially Salpeter mass function ({Gamma}{sub 0} = 1.35, or {Gamma} {approx} 1.0 at present, where dN/d(log M){proportional_to}M{sup {Gamma}}) suggest a total cluster mass M{sub cl} {approx} (4-6) Multiplication-Sign 10{sup 4} M{sub Sun} and projected mass ({approx} 2 {<=} M(R < 0.4 pc) {<=} 3) Multiplication-Sign 10{sup 4} M{sub Sun }. Photometric

  10. NASA's Great Observatories: Paper Model.

    ERIC Educational Resources Information Center

    National Aeronautics and Space Administration, Washington, DC.

    This educational brief discusses observatory stations built by the National Aeronautics and Space Administration (NASA) for looking at the universe. This activity for grades 5-12 has students build paper models of the observatories and study their history, features, and functions. Templates for the observatories are included. (MVL)

  11. ShaneAO: an enhanced adaptive optics and IR imaging system for the Lick Observatory 3-meter telescope

    NASA Astrophysics Data System (ADS)

    Kupke, Renate; Gavel, Donald; Roskosi, Constance; Cabak, Gerald; Cowley, David; Dillon, Daren; Gates, Elinor L.; McGurk, Rosalie; Norton, Andrew; Peck, Michael; Ratliff, Christopher; Reinig, Marco

    2012-07-01

    The Lick Observatory 3-meter telescope has a history of serving as a testbed for innovative adaptive optics techniques. In 1996, it became one of the first astronomical observatories to employ laser guide star (LGS) adaptive optics as a facility instrument available to the astronomy community. Work on a second-generation LGS adaptive optics system, ShaneAO, is well underway, with plans to deploy on telescope in 2013. In this paper we discuss key design features and implementation plans for the ShaneAO adaptive optics system. Once again, the Shane 3-m will host a number of new techniques and technologies vital to the development of future adaptive optics systems on larger telescopes. Included is a woofer-tweeter based wavefront correction system incorporating a voice-coil actuated, low spatial and temporal bandwidth, high stroke deformable mirror in conjunction with a high order, high bandwidth MEMs deformable mirror. The existing dye laser, in operation since 1996, will be replaced with a fiber laser recently developed at Lawrence Livermore National Laboratories. The system will also incorporate a high-sensitivity, high bandwidth wavefront sensor camera. Enhanced IR performance will be achieved by replacing the existing PICNIC infrared array with an Hawaii 2RG. The updated ShaneAO system will provide opportunities to test predictive control algorithms for adaptive optics. Capabilities for astronomical spectroscopy, polarimetry, and visible-light adaptive optical astronomy will be supported.

  12. ESO's Two Observatories Merge

    NASA Astrophysics Data System (ADS)

    2005-02-01

    On February 1, 2005, the European Southern Observatory (ESO) has merged its two observatories, La Silla and Paranal, into one. This move will help Europe's prime organisation for astronomy to better manage its many and diverse projects by deploying available resources more efficiently where and when they are needed. The merged observatory will be known as the La Silla Paranal Observatory. Catherine Cesarsky, ESO's Director General, comments the new development: "The merging, which was planned during the past year with the deep involvement of all the staff, has created unified maintenance and engineering (including software, mechanics, electronics and optics) departments across the two sites, further increasing the already very high efficiency of our telescopes. It is my great pleasure to commend the excellent work of Jorge Melnick, former director of the La Silla Observatory, and of Roberto Gilmozzi, the director of Paranal." ESO's headquarters are located in Garching, in the vicinity of Munich (Bavaria, Germany), and this intergovernmental organisation has established itself as a world-leader in astronomy. Created in 1962, ESO is now supported by eleven member states (Belgium, Denmark, Finland, France, Germany, Italy, The Netherlands, Portugal, Sweden, Switzerland, and the United Kingdom). It operates major telescopes on two remote sites, all located in Chile: La Silla, about 600 km north of Santiago and at an altitude of 2400m; Paranal, a 2600m high mountain in the Atacama Desert 120 km south of the coastal city of Antofagasta. Most recently, ESO has started the construction of an observatory at Chajnantor, a 5000m high site, also in the Atacama Desert. La Silla, north of the town of La Serena, has been the bastion of the organization's facilities since 1964. It is the site of two of the most productive 4-m class telescopes in the world, the New Technology Telescope (NTT) - the first major telescope equipped with active optics - and the 3.6-m, which hosts HARPS

  13. Multi-GeV electron beams from capillary discharge guided sub-petawatt class laser pulses in the self-trapping regime

    NASA Astrophysics Data System (ADS)

    Leemans, Wim

    2014-10-01

    Laser plasma accelerators (LPAs) can produce acceleration gradients on the order of tens to hundreds of GV/m, making them attractive as compact particle accelerators. During the past decade, quasi-monochromatic electron beams at the 1 GeV energy level have been produced using laser pulses at the 40-50 TW peak power level. With the availability of petawatt class lasers, beams up to 2 GeV have been produced from 7 cm long gas cells at UT Austin using 150 J laser pulses and at the 1 GeV level with tails extending to 3 GeV at the GIST facility in Korea. In this talk we present experimental results using the 1 Hz petawatt class BELLA laser at LBNL of the generation of multi-GeV electron beams with center energy up to 4.2 GeV, 6% rms energy spread, charge approximately 10 pC and an rms divergence around 0.3 mrad. The beams were produced from 9 cm long capillary discharge waveguide structure with a plasma density of ~ 7 ×1017cm-3 , powered by laser pulses with peak power up to 0.3 PW. Preformed plasma waveguides allow the use of lower laser power compared to unguided plasma structures to achieve the same beam energy. Detailed comparison between experiment and simulation indicates the importance of the near-field laser transverse mode quality on guiding and acceleration in the LPA. By tuning the plasma density, regimes were found where laser beams with a top hat near-field profile were guided well, and where high energy electron beams can be produced, with narrow divergence [ <0.8 mrad (FWHM)], and relatively small integrated energy spread (<10%). Provided that the slice energy spread and emittance are sufficiently low, electron beams with this energy could power x-ray free electron lasers. Future experiments will aim at increasing the beam energy to the 10 GeV level. Work supported by Office of Science, Office of HEP, US DOE Contract DE-AC02-05CH11231.

  14. Blue laser imaging endoscopy system for the early detection and characterization of colorectal lesions: a guide for the endoscopist

    PubMed Central

    Togashi, Kazutomo; Nemoto, Daiki; Utano, Kenichi; Isohata, Noriyuki; Kumamoto, Kensuke; Endo, Shungo; Lefor, Alan K.

    2016-01-01

    Blue laser imaging is a new system for image-enhanced endoscopy using laser light. Blue laser imaging utilizes two monochromatic lasers (410 and 450 nm) instead of xenon light. A 410 nm laser visualizes vascular microarchitecture, similar to narrow band imaging, and a 450 nm laser provides white light by excitation. According to three recently published reports, the diagnostic ability of polyp characterization using blue laser imaging compares favorably with narrow band imaging. No published data are available to date regarding polyp detection with blue laser imaging. However, blue laser imaging has the possibility to increase the detection of colorectal polyps by depicting brighter and clearer endoscopic images, even at a distant view, compared with first-generation image-enhanced endoscopy. A clinical trial to compare the detection between blue laser imaging and xenon light is warranted. PMID:26770267

  15. Alaska Volcano Observatory

    USGS Publications Warehouse

    Venezky, Dina Y.; Murray, Tom; Read, Cyrus

    2008-01-01

    Steam plume from the 2006 eruption of Augustine volcano in Cook Inlet, Alaska. Explosive ash-producing eruptions from Alaska's 40+ historically active volcanoes pose hazards to aviation, including commercial aircraft flying the busy North Pacific routes between North America and Asia. The Alaska Volcano Observatory (AVO) monitors these volcanoes to provide forecasts of eruptive activity. AVO is a joint program of the U.S. Geological Survey (USGS), the Geophysical Institute of the University of Alaska Fairbanks (UAFGI), and the State of Alaska Division of Geological and Geophysical Surveys (ADGGS). AVO is one of five USGS Volcano Hazards Program observatories that monitor U.S. volcanoes for science and public safety. Learn more about Augustine volcano and AVO at http://www.avo.alaska.edu.

  16. Mount Wilson Observatory

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    Mount Wilson Observatory, located in the San Gabriel Mountains near Pasadena, California, was founded in 1904 by George Ellery Hale with financial support from Andrew Carnegie. In the 1920s and 1930s, working at the 2.5 m Hooker telescope, Edwin Hubble made two of the most important discoveries in the history of astronomy: first, that `nebulae' are actually island universes—galaxies—each with bil...

  17. Arcetri Astrophysical Observatory

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    The Arcetri Astrophysical Observatory, a government research institute founded in 1972, is located close to the villa where Galileo spent the last 11 years of his life. Under the directorship of Giorgio Abetti (1921-53) it became the growth point of Italian astrophysics with emphasis on solar physics; a tradition continued by his successor Guglielmo Righini (1953-78). Since 1978 the activities ha...

  18. Megalithic observatory Kokino

    NASA Astrophysics Data System (ADS)

    Cenev, Gj.

    2006-05-01

    In 2001, on the footpath of a mountain peak, near the village of Kokino, archeologist Jovica Stankovski discovered an archeological site from The Bronze Age. The site occupies a large area and is scaled in two levels. Several stone seats (thrones) are dominant in this site and they are pointing towards the east horizon. The high concentration of the movable archeological material found on the upper platform probably indicates its use in a function containing still unknown cult activities. Due to precise measurements and a detailed archaeoastronomical analysis of the site performed in the past three years by Gjore Cenev, physicist from the Planetarium in Skopje, it was shown that the site has characteristics of a sacred site, but also of a Megalithic Observatory. The markers found in this observatory point on the summer and winter solstices and spring and autumn equinoxes. It can be seen that on both sides of the solstice markers, that there are markers for establishing Moon's positions. The markers are crafted in such a way that for example on days when special rites were performed (harvest rites for example) the Sun filled a narrow space of the marker and special ray lighted the man sitting on only one of the thrones, which of course had a special meaning. According to the positions of the markers that are used for Sun marking, especially on the solstice days, it was calculated that this observatory dates from 1800 B.C.

  19. Sierra Remote Observatories

    NASA Astrophysics Data System (ADS)

    Ringwald, Fred; Morgan, G. E.; Barnes, F. S., III; Goldman, D. S.; Helm, M. R.; Mortfield, P.; Quattrocchi, K. B.; Van Vleet, L.

    2009-05-01

    We report the founding of a new facility for astrophotography and small-telescope science. Sierra Remote Observatories are eight small observatories at 4610' altitude in the Sierra Nevada Mountains of California. The sky brightness during New Moon typically rates 3 on the Bortle scale. Typical seeing is 1.2", with a one-sigma range between 1.0" and 1.6", measured during 2007 June-September. All eight observatories are operated by remote control over the Internet, from as far away as Toronto and South Carolina. The telescopes range in aperture from 106 mm to 16 inches. Color images have so far been published in several magazines (Astronomy, Practical Astronomer, and Sky & Telescope) and on NASA's Astronomy Picture of the Day website. Science programs include time-resolved photometry of cataclysmic variables including the discovery of a 3.22-hour periodicity in the light curve of the nova-like V378 Pegasi, the serendipitous discovery of a previously undesignated spherical bubble in Cygnus, the discovery of three asteroids, and monitoring of Comet Lulin.

  20. The Russian Virtual Observatory

    NASA Astrophysics Data System (ADS)

    Dluzhnevskaya, O. B.; Malkov, O. Yu.; Kilpio, A. A.; Kilpio, E. Yu.; Kovaleva, D. A.; Sat, L. A.

    The Russian Virtual Observatory (RVO) will be an integral component of the International Virtual Observatory (IVO). The RVO has the main goal of integrating resources of astronomical data accumulated in Russian observatories and institutions (databases, archives, digitized glass libraries, bibliographic data, a remote access system to information and technical resources of telescopes etc.), and providing transparent access for scientific and educational purposes to the distributed information and data services that comprise its content. Another goal of the RVO is to provide Russian astronomers with on-line access to the rich volumes of data and metadata that have been, and will continue to be, produced by astronomical survey projects. Centre for Astronomical Data (CAD), among other Russian institutions, has had the greatest experience in collecting and distributing astronomical data for more than 20 years. Some hundreds of catalogs and journal tables are currently available from the CAD repository. More recently, mirrors of main astronomical data resources (VizieR, ADS, etc) are now maintained in CAD. Besides, CAD accumulates and makes available for the astronomical community information on principal Russian astronomical resources.

  1. Targeted multifunctional gold-based nanoshells for magnetic resonance-guided laser ablation of head and neck cancer.

    PubMed

    Melancon, Marites P; Lu, Wei; Zhong, Meng; Zhou, Min; Liang, Gan; Elliott, Andrew M; Hazle, John D; Myers, Jeffrey N; Li, Chun; Stafford, R Jason

    2011-10-01

    Image-guided thermal ablation of tumors is becoming a more widely accepted minimally invasive alternative to surgery for patients who are not good surgical candidates, such as patients with advanced head and neck cancer. In this study, multifunctional superparamagnetic iron oxide coated with gold nanoshell (SPIO@Au NS) that have both optical and magnetic properties was conjugated with the targeting agent, C225 monoclonal antibody, against epidermal growth factor receptor (EGFR). C225-SPIO@Au NS have an average a diameter of 82 ± 4.4 nm, contain 142 ± 15 antibodies per nanoshell, have an absorption peak in the near infrared (~800 nm), and have transverse relaxivity (r(2)) of 193 and 353 mM(-1) s(-1) versus Feridex™ of 171 and 300 mM(-1) s(-1), using 1.5 T and 7 T MR scanners, respectively. Specific targeting of the synthesized C225-SPIO@Au NS was tested in vitro using A431 cells and oral cancer cells, FaDu, OSC19, and HN5, all of which overexpress EGFR. Selective binding was achieved using C225-SPIO@Au NS but not with the non-targeting PEG-SPIO@Au NS and blocking group (excess of C225 + C225-SPIO@Au NS). In vivo biodistribution on mice bearing A431 tumors also showed selective targeting of C225-SPIO@Au NS compared with the non-targeting and blocking groups. The selective photothermal ablation of the nanoshells shows that without laser treatment there were no cell death and among the groups that were treated with laser at a power of 36 W/cm(2) for 3 min, only the cells treated with C225-SPIO@Au NS had cell killing (p < 0.001). In summary, successful synthesis and characterization of targeted C225-SPIO@Au NS demonstrating both superparamagnetic and optical properties has been achieved. We have shown both in vitro and in vivo that these nanoshells are MR-active and can be selectively heated up for simultaneous imaging and photothermal ablation therapy. PMID:21745689

  2. Lights Will Guide You : Sample Preparation and Applications for Integrated Laser and Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Karreman, M. A.

    2013-03-01

    Correlative microscopy is the combined use of two different forms of microscopy in the study of a specimen, allowing for the exploitation of the advantages of both imaging tools. The integrated Laser and Electron Microscope (iLEM), developed at Utrecht University, combines a fluorescence microscope (FM) and a transmission electron microscope (TEM) in a single set-up. The region of interest in the specimen is labeled or tagged with a fluorescent probe and can easily be identified within a large field of view with the FM. Next, this same area is retraced in the TEM and can be studied at high resolution. The iLEM demands samples that can be imaged with both FM and TEM. Biological specimen, typically composed of light elements, generate low image contrast in the TEM. Therefore, these samples are often ‘contrasted’ with heavy metal stains. FM, on the other hand, images fluorescent samples. Sample preparation for correlative microscopy, and iLEM in particular, is complicated by the fact that the heavy metals stains employed for TEM quench the fluorescent signal of the probe that is imaged with FM. The first part of this thesis outlines preparation procedures for biological material yielding specimen that can be imaged with the iLEM. Here, approaches for the contrasting of thin sections of cells and tissue are introduced that do not affect the fluorescence signal of the probe that marks the region of interest. Furthermore, two novel procedures, VIS2FIXH and VIS2FIX­FS are described that allow for the chemical fixation of thin sections of cryo-immobilized material. These procedures greatly expedite the sample preparation process, and open up novel possibilities for the immuno-labeling of difficult antigens, eg. proteins and lipids that are challenging to preserve. The second part of this thesis describes applications of iLEM in research in the field of life and material science. The iLEM was employed in the study of UVC induced apoptosis (programmed cell death) of

  3. Characterization of Adaptive Optics at Keck Observatory

    SciTech Connect

    van Dam, M A; Macintosh, B A

    2003-07-24

    In this paper, the adaptive optics (AO) system at Keck Observatory is characterized. The AO system is described in detail. The physical parameters of the lenslets, CCD and deformable mirror, the calibration procedures and the signal processing algorithms are explained. Results of sky performance tests are presented: the AO system is shown to deliver images with an average Strehl ratio of up to 0.37 at 1.59 {micro}m using a bright guide star. An error budget that is consistent with the observed image quality is presented.

  4. Effect of Myopic Defocus on Visual Acuity after Phakic Intraocular Lens Implantation and Wavefront-guided Laser in Situ Keratomileusis

    PubMed Central

    Kamiya, Kazutaka; Shimizu, Kimiya; Igarashi, Akihito; Kawamorita, Takushi

    2015-01-01

    This study aimed to investigate the effect of myopic defocus on visual acuity after phakic intraocular lens (IOL) implantation and wavefront-guided laser in situ keratomileusis (wfg-LASIK). Our prospective study comprised thirty eyes undergoing posterior chamber phakic IOL implantation and 30 eyes undergoing wfg-LASIK. We randomly measured visual acuity under myopic defocus after cycloplegic and non-cycloplegic correction. We also calculated the modulation transfer function by optical simulation and estimated visual acuity from Campbell & Green’s retinal threshold curve. Visual acuity in the phakic IOL group was significantly better than that in the wfg-LASIK group at myopic defocus levels of 0, –1, and –2 D (p < 0.001, p < 0.001, and p = 0.02, Mann-Whitney U-test), but not at a defocus of –3 D (p = 0.30). Similar results were also obtained in a cycloplegic condition. Decimal visual acuity values at a myopic defocus of 0, −1, −2, and -3 D by optical simulation were estimated to be 1.95, 1.21, 0.97, and 0.75 in the phakic IOL group, and 1.39, 1.11, 0.94, and 0.71 in the wfg-LASIK group, respectively. From clinical and optical viewpoints, phakic IOL implantation was superior to wfg-LASIK in terms of the postoperative visual performance, even in the presence of low to moderate myopic regression. PMID:25994984

  5. Distributed Kalman filtering compared to Fourier domain preconditioned conjugate gradient for laser guide star tomography on extremely large telescopes.

    PubMed

    Gilles, Luc; Massioni, Paolo; Kulcsár, Caroline; Raynaud, Henri-François; Ellerbroek, Brent

    2013-05-01

    This paper discusses the performance and cost of two computationally efficient Fourier-based tomographic wavefront reconstruction algorithms for wide-field laser guide star (LGS) adaptive optics (AO). The first algorithm is the iterative Fourier domain preconditioned conjugate gradient (FDPCG) algorithm developed by Yang et al. [Appl. Opt.45, 5281 (2006)], combined with pseudo-open-loop control (POLC). FDPCG's computational cost is proportional to N log(N), where N denotes the dimensionality of the tomography problem. The second algorithm is the distributed Kalman filter (DKF) developed by Massioni et al. [J. Opt. Soc. Am. A28, 2298 (2011)], which is a noniterative spatially invariant controller. When implemented in the Fourier domain, DKF's cost is also proportional to N log(N). Both algorithms are capable of estimating spatial frequency components of the residual phase beyond the wavefront sensor (WFS) cutoff frequency thanks to regularization, thereby reducing WFS spatial aliasing at the expense of more computations. We present performance and cost analyses for the LGS multiconjugate AO system under design for the Thirty Meter Telescope, as well as DKF's sensitivity to uncertainties in wind profile prior information. We found that, provided the wind profile is known to better than 10% wind speed accuracy and 20 deg wind direction accuracy, DKF, despite its spatial invariance assumptions, delivers a significantly reduced wavefront error compared to the static FDPCG minimum variance estimator combined with POLC. Due to its nonsequential nature and high degree of parallelism, DKF is particularly well suited for real-time implementation on inexpensive off-the-shelf graphics processing units. PMID:23695321

  6. Study of electron acceleration and x-ray radiation as a function of plasma density in capillary-guided laser wakefield accelerators

    SciTech Connect

    Ju, J.; Döpp, A.; Cros, B.; Svensson, K.; Genoud, G.; Wojda, F.; Burza, M.; Persson, A.; Lundh, O.; Wahlström, C.-G.; Ferrari, H.

    2013-08-15

    Laser wakefield electron acceleration in the blow-out regime and the associated betatron X-ray radiation were investigated experimentally as a function of the plasma density in a configuration where the laser is guided. Dielectric capillary tubes were employed to assist the laser keeping self-focused over a long distance by collecting the laser energy around its central focal spot. With a 40 fs, 16 TW pulsed laser, electron bunches with tens of pC charge were measured to be accelerated to an energy up to 300 MeV, accompanied by X-ray emission with a peak brightness of the order of 10{sup 21} ph/s/mm{sup 2}/mrad{sup 2}/0.1%BW. Electron trapping and acceleration were studied using the emitted X-ray beam distribution to map the acceleration process; the number of betatron oscillations performed by the electrons was inferred from the correlation between measured X-ray fluence and beam charge. A study of the stability of electron and X-ray generation suggests that the fluctuation of X-ray emission can be reduced by stabilizing the beam charge. The experimental results are in good agreement with 3D particle-in-cell (PIC) simulation.

  7. Phantom Study of a New Laser-Etched Needle for Improving Visibility During Ultrasonography-Guided Lumbar Medial Branch Access With Novices

    PubMed Central

    2016-01-01

    Objective To compare the visibility and procedural parameters between a standard spinal needle and a new laser-etched needle (LEN) in real-time ultrasonography guided lumbar medial branch access in a phantom of the lumbosacral spine. Methods We conducted a prospective single-blinded observational study at a rehabilitation medicine center. A new model of LEN was manufactured with a standard 22-gauge spinal needle and a laser etching machine. Thirty-two inexperienced polyclinic medical students performed ultrasonography-guided lumbar medial branch access using both a standard spinal needle and a LEN with scanning protocol. The outcomes included needle visibility score, needle elapsed time, first-pass success rate, and number of needle sticks. Results The LEN received significantly better visibility scores and shorter needle elapsed time compared to the standard spinal needle. First-pass success rate and the number of needle sticks were not significantly different between needles. Conclusion A new LEN is expected to offer better visibility and enable inexperienced users to perform an ultrasonography-guided lumbar medial branch block more quickly. However, further study of variables may be necessary for clinical application. PMID:27606263

  8. Distributed Observatory Management

    NASA Astrophysics Data System (ADS)

    Godin, M. A.; Bellingham, J. G.

    2006-12-01

    A collection of tools for collaboratively managing a coastal ocean observatory have been developed and used in a multi-institutional, interdisciplinary field experiment. The Autonomous Ocean Sampling Network program created these tools to support the Adaptive Sampling and Prediction (ASAP) field experiment that occurred in Monterey Bay in the summer of 2006. ASAP involved the day-to-day participation of a large group of researchers located across North America. The goal of these investigators was to adapt an array of observational assets to optimize data collection and analysis. Achieving the goal required continual interaction, but the long duration of the observatory made sustained co-location of researchers difficult. The ASAP team needed a remote collaboration tool, the capability to add non-standard, interdisciplinary data sets to the overall data collection, and the ability to retrieve standardized data sets from the collection. Over the course of several months and "virtual experiments," the Ocean Observatory Portal (COOP) collaboration tool was created, along with tools for centralizing, cataloging, and converting data sets into common formats, and tools for generating automated plots of the common format data. Accumulating the data in a central location and converting the data to common formats allowed any team member to manipulate any data set quickly, without having to rely heavily on the expertise of data generators to read the data. The common data collection allowed for the development of a wide range of comparison plots and allowed team members to assimilate new data sources into derived outputs such as ocean models quickly. In addition to the standardized outputs, team members were able to produce their own specialized products and link to these through the collaborative portal, which made the experimental process more interdisciplinary and interactive. COOP was used to manage the ASAP vehicle program from its start in July 2006. New summaries were

  9. Astronomical publications of Melbourne Observatory

    NASA Astrophysics Data System (ADS)

    Andropoulos, Jenny Ioanna

    2014-05-01

    During the second half of the 19th century and the first half of the 20th century, four well-equipped government observatories were maintained in Australia - in Melbourne, Sydney, Adelaide and Perth. These institutions conducted astronomical observations, often in the course of providing a local time service, and they also collected and collated meteorological data. As well, some of these observatories were involved at times in geodetic surveying, geomagnetic recording, gravity measurements, seismology, tide recording and physical standards, so the term "observatory" was being used in a rather broad sense! Despite the international renown that once applied to Williamstown and Melbourne Observatories, relatively little has been written by modern-day scholars about astronomical activities at these observatories. This research is intended to rectify this situation to some extent by gathering, cataloguing and analysing the published astronomical output of the two Observatories to see what contributions they made to science and society. It also compares their contributions with those of Sydney, Adelaide and Perth Observatories. Overall, Williamstown and Melbourne Observatories produced a prodigious amount of material on astronomy in scientific and technical journals, in reports and in newspapers. The other observatories more or less did likewise, so no observatory of those studied markedly outperformed the others in the long term, especially when account is taken of their relative resourcing in staff and equipment.

  10. Portable coastal observatories

    USGS Publications Warehouse

    Frye, Daniel; Butman, Bradford; Johnson, Mark; von der Heydt, Keith; Lerner, Steven

    2000-01-01

    Ocean observational science is in the midst of a paradigm shift from an expeditionary science centered on short research cruises and deployments of internally recording instruments to a sustained observational science where the ocean is monitored on a regular basis, much the way the atmosphere is monitored. While satellite remote sensing is one key way of meeting the challenge of real-time monitoring of large ocean regions, new technologies are required for in situ observations to measure conditions below the ocean surface and to measure ocean characteristics not observable from space. One method of making sustained observations in the coastal ocean is to install a fiber optic cable from shore to the area of interest. This approach has the advantage of providing power to offshore instruments and essentially unlimited bandwidth for data. The LEO-15 observatory offshore of New Jersey (yon Alt et al., 1997) and the planned Katama observatory offshore of Martha's Vineyard (Edson et al., 2000) use this approach. These sites, along with other cabled sites, will play an important role in coastal ocean science in the next decade. Cabled observatories, however, have two drawbacks that limit the number of sites that are likely to be installed. First, the cable and the cable installation are expensive and the shore station needed at the cable terminus is often in an environmentally sensitive area where competing interests must be resolved. Second, cabled sites are inherently limited geographically to sites within reach of the cable, so it is difficult to cover large areas of the coastal ocean.

  11. The PS1 Observatory

    NASA Astrophysics Data System (ADS)

    Kaiser, Nick; Morgan, J.; Pier, E.; Chambers, K.

    2007-12-01

    The Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) will use gigapixel cameras on multi-aperture telescopes to survey the sky in the visible and near-infrared bands. The first surveys will begin in 2008 using a single telescope system (PS1) has been deployed on Haleakala, Maui. This facility is currently undergoing commissioning tests. The PS1 telescope is a 1.8-m f/4 Richey-Chretien design that employs three 50 cm diameter correcting lens. The optical system produces a 3 degree diameter field of view at the focal plane. Images will be recorded on a 1.4 gigapixel CCD camera (described in an accompanying poster presentation). The survey programs will be conducted using g, r, i, and z filters which closely approximate the band-pass and response of those used in the Sloan Digital Sky Survey. These filters will be supplemented with a y band filter further to the infrared of z and a wide w filter for solar system observations. The images from the PS1 camera are supplemented by an Imaging Sky Probe that will provide co-pointed photometric calibration images of each target field. An all-sky camera at the observatory monitors sky conditions and transparency. The operation of the PS1 telescope is supported by the Observatory, Telescope, and Instrument Software (OTIS) system. The OTIS software interfaces the telescope control software provided by the vendor and the CCD camera computer systems. OTIS also records and archives environmental metadata from the dome and the observatory weather station.

  12. Image-guided removal of occlusal caries lesions with a λ= 9.3-μm CO2 laser using near-IR transillumination

    NASA Astrophysics Data System (ADS)

    Chung, Leon C.; Tom, Henry; Chan, Kenneth H.; Simon, Jacob C.; Fried, Daniel; Darling, Cynthia L.

    2015-02-01

    Previous studies have shown that near-IR transillumination is well suited for imaging deep occlusal lesions. The purpose of this study was to determine if near-IR images can be used to guide a CO2 laser for the selective removal of natural occlusal lesions on extracted teeth. Near-IR occlusal transillumination images of extracted human teeth with natural occlusal caries lesions were acquired using an InGaAs camera and near-IR light at wavelengths from 1290 to 1470-nm from a filtered tungsten halogen source. A CO2 laser operating at 9.3-μm with a pulse duration of 10-15-μs and a pulse repetition rate of 100-300-Hz was used for caries removal. Optical Coherence tomography was used to confirm lesion presence and serial scans were used to assess selective removal. Teeth were also sectioned for histological examination using polarized light microscopy. This study suggests that near-infrared transillumination is a promising method for the image guided laser ablation of occlusal caries lesions but the use of serial near-IR transillumination imaging for monitoring lesion removal was limited.

  13. ESO's Two Observatories Merge

    NASA Astrophysics Data System (ADS)

    2005-02-01

    On February 1, 2005, the European Southern Observatory (ESO) has merged its two observatories, La Silla and Paranal, into one. This move will help Europe's prime organisation for astronomy to better manage its many and diverse projects by deploying available resources more efficiently where and when they are needed. The merged observatory will be known as the La Silla Paranal Observatory. Catherine Cesarsky, ESO's Director General, comments the new development: "The merging, which was planned during the past year with the deep involvement of all the staff, has created unified maintenance and engineering (including software, mechanics, electronics and optics) departments across the two sites, further increasing the already very high efficiency of our telescopes. It is my great pleasure to commend the excellent work of Jorge Melnick, former director of the La Silla Observatory, and of Roberto Gilmozzi, the director of Paranal." ESO's headquarters are located in Garching, in the vicinity of Munich (Bavaria, Germany), and this intergovernmental organisation has established itself as a world-leader in astronomy. Created in 1962, ESO is now supported by eleven member states (Belgium, Denmark, Finland, France, Germany, Italy, The Netherlands, Portugal, Sweden, Switzerland, and the United Kingdom). It operates major telescopes on two remote sites, all located in Chile: La Silla, about 600 km north of Santiago and at an altitude of 2400m; Paranal, a 2600m high mountain in the Atacama Desert 120 km south of the coastal city of Antofagasta. Most recently, ESO has started the construction of an observatory at Chajnantor, a 5000m high site, also in the Atacama Desert. La Silla, north of the town of La Serena, has been the bastion of the organization's facilities since 1964. It is the site of two of the most productive 4-m class telescopes in the world, the New Technology Telescope (NTT) - the first major telescope equipped with active optics - and the 3.6-m, which hosts HARPS

  14. NASA's Heliophysics System Observatory

    NASA Astrophysics Data System (ADS)

    Clarke, Steven

    2016-04-01

    NASA formulates and implements a national research program for understanding the Sun and its interactions with the Earth and the solar system and how these phenomena impact life and society. This research provides theory, data, and modeling development services to national and international space weather efforts utilizing a coordinated and complementary fleet of spacecraft, called the Heliophysics System Observatory (HSO), to understand the Sun and its interactions with Earth and the solar system, including space weather. This presentation will focus on NASA's role in space weather research and the contributions the agency continues to provide to the science of space weather, leveraging inter-agency and international collaborations for the benefit of society.

  15. Next Generation Virtual Observatories

    NASA Astrophysics Data System (ADS)

    Fox, P.; McGuinness, D. L.

    2008-12-01

    Virtual Observatories (VO) are now being established in a variety of geoscience disciplines beyond their origins in Astronomy and Solar Physics. Implementations range from hydrology and environmental sciences to solid earth sciences. Among the goals of VOs are to provide search/ query, access and use of distributed, heterogeneous data resources. With many of these goals being met and usage increasing, new demands and requirements are arising. In particular there are two of immediate and pressing interest. The first is use of VOs by non-specialists, especially for information products that go beyond the usual data, or data products that are sought for scientific research. The second area is citation and attribution of artifacts that are being generated by VOs. In some sense VOs are re-publishing (re-packaging, or generating new synthetic) data and information products. At present only a few VOs address this need and it is clear that a comprehensive solution that includes publishers is required. Our work in VOs and related semantic data framework and integration areas has lead to a view of the next generation of virtual observatories which the two above-mentioned needs as well as others that are emerging. Both of the needs highlight a semantic gap, i.e. that the meaning and use for a user or users beyond the original design intention is very often difficult or impossible to bridge. For example, VOs created for experts with complex, arcane or jargon vocabularies are not accessible to the non-specialist and further, information products the non-specialist may use are not created or considered for creation. In the second case, use of a (possibly virtual) data or information product (e.g. an image or map) as an intellectual artifact that can be accessed as part of the scientific publication and review procedure also introduces terminology gaps, as well as services that VOs may need to provide. Our supposition is that formalized methods in semantics and semantic web

  16. Strasbourg Observatory Archives Revisited

    NASA Astrophysics Data System (ADS)

    Heck, A.

    2002-12-01

    Official talks in France and Germany after World War I were generally of hatred and revenge. Strasbourg Observatory had just changed nationality (from Prussian to French) for the first time (this would happen again at the outbreak of WWII and after the conflict). Documents show that astronomers did not share the general attitude. For example the inventory book started in German was continued in French after 1918. It is moving to see those different handwritings in two different languages on the same pages -- making of that book a unique document in various respects, but also reminding us that the native language of the region was in fact Alsacian.

  17. Acquirement of the observatory code of Langkawi National Observatory

    NASA Astrophysics Data System (ADS)

    Loon, Chin Wei; Zainuddin, Mohd. Zambri; Ahmad, Nazhatulshima; Shukor, Muhammad Shamim; Tahar, Muhammad Redzuan

    2015-04-01

    Observatory code was assigned by The International Astronomical Union (IAU) Minor Planet Center (MPC) for a permanent observatory that intended to do astrometric CCD-observing program of minor planet or comets in solar system. The purpose of acquiring an observatory code is to document specific details about a particular observation site and the types of instruments used within the observatory. In addition, many astronomical centers and stations worldwide will know there is an active observatory at the particular location and international cooperation program in astronomy observation is possible. The Langkawi National Observatory has initiated an observation program to monitor minor planet, specifically those Near Earth Objects (NEOs) that may bring potentially hazardous to the Earth. In order to fulfil the requirement that stated by MPC for undertaking astrometric CCD-observing program, an observatory code was required. The instruments and methods that applied to obtain the observatory code will be discussed. The Langkawi National Observatory is now coded as O43 and listed in the MPC system, the single worldwide location for receipt and distribution of positional measurements of minor planets, comets and outer irregular natural satellites of major planets.

  18. The Asiago Observatory's reflectogoniometer

    NASA Astrophysics Data System (ADS)

    Fornasier, S.; Pernechele, C.; Barbieri, C.

    1999-09-01

    We present the Asiago Astrophysical Observatory reflectogoniometer, a useful instrument which allows to perform laboratory studies of transmitted and diffuse light. In particular the instrument allows a complete characterization of the Bidirectional Reflectance Function (BDRF) for spherical shape samples and of the Transmittance Function for plane samples. The instrument is placed in an optical laboratory of the Asiago Astrophysical Observatory. Data are acquired by a CCD camera, equipped with its own frame grabber card, and analysed by a pc. Image calibration, i.e. the procedure that converts the value of each pixel of a CCD frame in a radiometric quantity, follows the standard sequence used for remote sensing application (bias, dark, flat fielding, distortion corrections, reflectogoniometric calibration, using a reflectometric standard), and it is implemented in a data reduction pipeline. The instrument tests performed until now have confirm that the imaging-goniophotometer is an instrument suitable for the quick characterization of diffusing surfaces in all the tree possible configuration: transmittance measurements (translucent plates), partial reflectance measurements (diffusing sheets), and bidirectional function characterization (coatings and paints). The goniophotometer may have different astronomical and industrial applications: it can be used for the characterization of absorbance properties of paints for baffling in spatial missions, of diffusive properties of flat field panels, of trasmittance properties of different glasses type and of reflective properties of rocks surfaces, like, for example, meteorites samples.

  19. Wendelstein Observatory Operations Software

    NASA Astrophysics Data System (ADS)

    Gössl, C. A.; Snigula, J. M.; Munzert, T.

    2014-05-01

    LMU München operates an astrophysical observatory on Mt. Wendelstein which has been equipped with a modern 2m-class telescope recently. The new Fraunhofer telescope is starting science operations now with a 64 Mpixel, 0.5°×0.5° FoV wide field camera and will successively be equipped with a three channel optical/NIR camera and two fibre coupled spectrographs (IFU spectrograph VIRUSW already in operation at the 2.7m McDonald, Texas and an upgraded Echelle spectrograph FOCES formerly operated at Calar Alto oberservatory, Spain). All instruments will be mounted simultaneously and can be activated within a minute. The observatory also operates a small 40cm telescope with a CCD-camera and a simple fibre coupled spectrograph for students lab and photometric monitoring as well as a large number of support equipment like a meteo station, allsky cameras, a multitude of webcams, in addition to a complex building control system environment. Here we describe the ongoing effort to build a centralised controlling interface for all. This includes remote/robotic operation, visualisation via browser technologies, and data processing and archiving.

  20. Wendelstein Observatory control software

    NASA Astrophysics Data System (ADS)

    Gössl, Claus; Snigula, Jan; Kodric, Mihael; Riffeser, Arno; Munzert, Tobias

    2014-07-01

    LMU München operates an astrophysical observatory on Mt. Wendelstein1 which has been equipped with a modern 2m-class telescope2, 3 recently. The new Fraunhofer telescope has started science operations in autumn 2013 with a 64 Mpixel, 0:5 x 0:5 square degree FoV wide field camera,4 and will successively be equipped with a 3 channel optical/NIR camera5 and 2 fibre coupled spectrographs (IFU spectrograph VIRUSW6 already in operation at the 2.7 McDonald, Texas and an upgraded Echelle spectrograph FOCES7, 8 formerly operated at Calar Alto oberservatory, Spain). All instruments will be mounted simultaneously and can be activated within a minute. The observatory also operates a small 40cm telescope with a CCD-camera and a simple fibre coupled spectrograph for students lab and photometric monitoring as well as a large number of support equipment like a meteo station, allsky cameras, a multitude of webcams, in addition to a complex building control system environment. Here we describe the ongoing effort to build a centralised controlling interface for all hardware. This includes remote/robotic operation, visualisation via web browser technologies, and data processing and archiving.

  1. Flaw Inspection of Aluminum Pipes by Non-Contact Visualization of Circumferential Guided Waves using Laser Ultrasound Generation and an Air-Coupled Sensor

    NASA Astrophysics Data System (ADS)

    Urabe, K.; Takatsubo, J.; Toyama, N.; Yamamoto, T.; Tsuda, H.

    2014-06-01

    Our group had previously proposed a generation laser scanning system for visualizing ultrasound propagation on an object as an animate image, which provided visible and quick flaw inspection. Recently, we improved this system to make it completely non-contact by employing an air-coupled ultrasound transducer as a receiver instead of a contact transducer, and demonstrated the successful visualization of Lamb waves propagating on aluminum and carbon fiber reinforced plastic plates, as well as the detection of flaws. In this research, we applied this system to the non-contact visualization of circumferential guided waves on aluminum pipes. It was shown that circumferential guided waves propagating in opposite directions could be visualized separately, and that a flaw such as a slit or thinning on the inside surface of the pipe could be successfully detected even when it existed outside the scanning area.

  2. Stratospheric Observatory for Infrared Astronomy

    NASA Astrophysics Data System (ADS)

    Hamidouche, M.; Young, E.; Marcum, P.; Krabbe, A.

    2010-12-01

    We present one of the new generations of observatories, the Stratospheric Observatory For Infrared Astronomy (SOFIA). This is an airborne observatory consisting of a 2.7-m telescope mounted on a modified Boeing B747-SP airplane. Flying at an up to 45,000 ft (14 km) altitude, SOFIA will observe above more than 99 percent of the Earth's atmospheric water vapor allowing observations in the normally obscured far-infrared. We outline the observatory capabilities and goals. The first-generation science instruments flying on board SOFIA and their main astronomical goals are also presented.

  3. GPM Core Observatory Launch Animation

    NASA Video Gallery

    This animation depicts the launch of the Global Precipitation Measurement (GPM) Core Observatory satellite from Tanegashima Space Center, Japan. The launch is currently scheduled for Feb. 27, 2014....

  4. A new MOS mask cutter facility at Gemini/Cerro Tololo observatories

    NASA Astrophysics Data System (ADS)

    Wyman, Robert T.; Trancho, Gelys; Tighe, Roberto

    2010-07-01

    The installation and commissioning of a new laser cutter facility in La Serena, Chile is a cooperative effort between Gemini Observatory and the Cerro Tololo Inter-American Observatory. This system enables the cutting of aluminum and carbon fiber slit masks for three multi-object spectrographs operating in Chile: GMOS-S, Flamingos-2, and Goodman spectrograph. Selection of the new laser cutter tool was based on slit mask specifications developed for two materials. Prior to the commissioning all slit mask production was performed at Gemini's Northern base facility with a similar laser cutter system. The new facility supports two observatories and enhances the capabilities for both. This paper will discuss the observatory arrangement with respect to mask data tracking and handling. The laser system and facility will be discussed along with mask cutting performance, process development and manufacturing methods.

  5. Performance of adaptive optics at Lick Observatory

    SciTech Connect

    Olivier, S.S.; An, J.; Avicola, K.

    1994-03-01

    A prototype adaptive optics system has been developed at Lawrence Livermore National Laboratory (LLNL) for use at Lick Observatory. This system is based on an ITEX 69-actuator continuous-surface deformable mirror, a Kodak fast-framing intensified CCD camera, and a Mercury VME board containing four Intel i860 processors. The system has been tested using natural reference stars on the 40-inch Nickel telescope at Lick Observatory yielding up to a factor of 10 increase in image peak intensity and a factor of 6 reduction in image full width at half maximum (FWHM). These results are consistent with theoretical expectations. In order to improve performance, the intensified CCD camera will be replaced by a high-quantum-efficiency low-noise fast CCD camera built for LLNL by Adaptive Optics Associates using a chip developed by Lincoln Laboratory, and the 69-actuator deformable mirror will be replaced by a 127-actuator deformable mirror developed at LLNL. With these upgrades, the system should perform well in median seeing conditions on the 120-inch Shane telescope for observing wavelengths longer than {approximately}1 {mu}m and using natural reference stars brighter than m{sub R} {approximately} 10 or using the laser currently being developed at LLNL for use at Lick Observatory to generate a sodium-layer reference star.

  6. Search of Binary Jupiter-Trojan Asteroids with Laser Guide Star AO systems: a moon around 624 Hektor

    NASA Astrophysics Data System (ADS)

    Marchis, Franck; Berthier, J.; Wong, M. H.; Descamps, P.; Hestroffer, D.; Colas, F.; de Pater, I.; Vachier, F.

    2006-09-01

    In 2006, we initiated a search for multiple asteroids in Jupiter Trojan L4 population with Laser Guide Star Adaptive Optics (LGS AO) technology on 8-10m class telescopes. To maximize the chance of detecting companion, we prioritized Trojan asteroids that could be member of collisional families in our search (see the PeTrA project and Beaugé and Roig (A&A, 2001)). Our first night was performed on July 17 2006 UT with the Keck LGS AO system. Twenty targets up to the 18th magnitude in R band were observed mostly in Kp broadband filter with an angular resolution 0.06 arcsec. Images of 624 Hektor, our brightest target (predicted V=14.4) revealed the presence of a moonlet companion (Marchis et al., IAU, 2006, provisional designation S/2006(624)1) located at 0.36” ( 1150 km) from the primary with a peak SNR 25. The resolved primary has a bilobated shape, but it is unclear if the primary is a contact or separated binary. It can be approximated as an ellipse with major and minor axes 2a = 350 km and 2b = 210 km (108 and 65 milli-arcseconds). The pole solution λ=329°, β=-25° in ecliptic B1950 (Magnusson 1989, and updated table) is in agreement with the observations. Based on the integrated brightness ratio between the moonlet and the primary of about 6.5, the diameter of S/2006(624)1 is estimated to be about 15 km. Additional observations will be recorded using the Keck and Gemini LGS AO system in Aug-Sept. 2006 aiming to estimate the orbit of the moonlet. The conditions of observations seem optimal since the system will be seen pole-on during this period. 624 Hektor is the first binary asteroid found in the L4 point and the first Trojan possessing a moonlet companion. The result of this campaign of observations, including Aug-Sept. observations, will be discussed.

  7. Nd: YAG interstitial laser phototherapy guided by magnetic resonance imaging in an ex vivo model: Dosimetry of laser-MR-tissue interaction

    SciTech Connect

    Anzai, Y.; Lufkin, R.B.; Saxton, R.E.; Fetterman, H.; Farahani, K.; Layfield, L.J.; Jolesz, F.C.; Hanafee, W.H.; Castro, D.J. )

    1991-07-01

    Interstitial laser phototherapy (ILP) is a promising technique in which laser energy is delivered percutaneously to various depths of tumors. This technique will become clinically useful only when efficient, sensitive, and noninvasive monitoring systems are developed. In this study, the spatial distribution of ILP in bovine liver tissue, induced by a Nd: YAG laser with an interstitial sapphire-frosted contact probe, was evaluated by magnetic resonance imaging (MRI). Tissue was exposed to three energy densities of the Nd:YAG laser by a reproducible method of dosimetry. Thermal profiles were measured with a probe inserted 5 mm from the laser tip. T1-weighted magnetic resonance images were taken after the laser exposure. Tissue specimens were then evaluated for standard quantification of laser-induced damages. A linear correlation between the level of laser energy, induced temperature change, lesion size on T1 magnetic resonance image, and volume of histological damage was observed. Further improvement of this technique of dosimetry in an in vivo model should allow the development of software for MRI which will correlate the above parameters and render this technique of ILP clinically useful.

  8. On-the-fly cross flow laser guided separation of aerosol particles based on size, refractive index and density-theoretical analysis.

    PubMed

    Lall, A A; Terray, A; Hart, S J

    2010-12-20

    Laser separation of particles is achieved using forces resulting from the momentum exchange between particles and photons constituting the laser radiation. Particles can experience different optical forces depending on their size and/or optical properties, such as refractive index. Thus, particles can move at different speeds in the presence of an optical force, leading to spatial separations. In this paper, we present a theoretical analysis on laser separation of non-absorbing aerosol particles moving at speeds (1-10 cm/sec) which are several orders of magnitude greater than typical particle speeds used in previous studies in liquid medium. The calculations are presented for particle deflection by a loosely focused Gaussian 1064 nm laser, which simultaneously holds and deflects particles entrained in flow perpendicular to their direction of travel. The gradient force holds the particles against the viscous drag for a short period of time. The scattering force simultaneously pushes the particles, perpendicular to the flow, during this period. Our calculations show particle deflections of over 2500 µm for 15 µm aerosol particles, and a separation of over 1500 µm between 5 µm and 10 µm particles when the laser is operated at 10 W. We show that a separation of about 421 µm can be achieved between two particles of the same size (10 µm) but having a refractive index difference of 0.1. Density based separations are also possible. Two 10 µm particles with a density difference of 600 kg/m3 can be separated by 193 µm. Examples are shown for separation distances between polystyrene, poly(methylmethacrylate), silica and water particles. These large laser guided deflections represent a novel achievement for optical separation in the gas phase. PMID:21196954

  9. Observatory ends scientific investigations

    NASA Astrophysics Data System (ADS)

    Bell, Peter M.

    The Orbiting Astronomical Observatory (OAO-3), which was instrumental in the discovery of the first suspected black hole, wound up its scientific investigation at the end of 1980. Spacecraft science operations were terminated after 8½ years of operation. Named Copernicus, OAO-3 performed consistently beyond design specifications and 7½ years beyond project requirements. Its performance profile, according to the NASA-Goddard engineers and scientists, was ‘astonishing.’While formal scientific investigations were ended December 31, a series of engineering tests are still being made until February 15. At that time, all contact with the spacecraft will end. Project engineers are uncertain whether Copernicus will orient itself permanently toward the sun, begin a permanent orbital tumbling action, or a variation of both.

  10. The Sudbury Neutrino Observatory

    NASA Astrophysics Data System (ADS)

    Bellerive, A.; Klein, J. R.; McDonald, A. B.; Noble, A. J.; Poon, A. W. P.

    2016-07-01

    This review paper provides a summary of the published results of the Sudbury Neutrino Observatory (SNO) experiment that was carried out by an international scientific collaboration with data collected during the period from 1999 to 2006. By using heavy water as a detection medium, the SNO experiment demonstrated clearly that solar electron neutrinos from 8B decay in the solar core change into other active neutrino flavors in transit to Earth. The reaction on deuterium that has equal sensitivity to all active neutrino flavors also provides a very accurate measure of the initial solar flux for comparison with solar models. This review summarizes the results from three phases of solar neutrino detection as well as other physics results obtained from analyses of the SNO data.

  11. Orbiting Carbon Observatory

    NASA Technical Reports Server (NTRS)

    Miller, Charles E.

    2005-01-01

    Human impact on the environment has produced measurable changes in the geological record since the late 1700s. Anthropogenic emissions of CO2 today may cause the global climate to depart for its natural behavior for many millenia. CO2 is the primary anthropogenic driver of climate change. The Orbiting Carbon Observatory goals are to help collect measurements of atmospheric CO2, answering questions such as why the atmospheric CO2 buildup varies annually, the roles of the oceans and land ecosystems in absorbing CO2, the roles of North American and Eurasian sinks and how these carbon sinks respond to climate change. The present carbon cycle, CO2 variability, and climate uncertainties due atmospheric CO2 uncertainties are highlighted in this presentation.

  12. The virtual observatory registry

    NASA Astrophysics Data System (ADS)

    Demleitner, M.; Greene, G.; Le Sidaner, P.; Plante, R. L.

    2014-11-01

    In the Virtual Observatory (VO), the Registry provides the mechanism with which users and applications discover and select resources-typically, data and services-that are relevant for a particular scientific problem. Even though the VO adopted technologies in particular from the bibliographic community where available, building the Registry system involved a major standardisation effort, involving about a dozen interdependent standard texts. This paper discusses the server-side aspects of the standards and their application, as regards the functional components (registries), the resource records in both format and content, the exchange of resource records between registries (harvesting), as well as the creation and management of the identifiers used in the system based on the notion of authorities. Registry record authors, registry operators or even advanced users thus receive a big picture serving as a guideline through the body of relevant standard texts. To complete this picture, we also mention common usage patterns and open issues as appropriate.

  13. Global geodetic observatories

    NASA Astrophysics Data System (ADS)

    Boucher, Claude; Pearlman, Mike; Sarti, Pierguido

    2015-01-01

    Global geodetic observatories (GGO) play an increasingly important role both for scientific and societal applications, in particular for the maintenance and evolution of the reference frame and those applications that rely on the reference frame for their viability. The International Association of Geodesy (IAG), through the Global Geodetic Observing System (GGOS), is fully involved in coordinating the development of these systems and ensuring their quality, perenniality and accessibility. This paper reviews the current role, basic concepts, and some of the critical issues associated with the GGOs, and advocates for their expansion to enhance co-location with other observing techniques (gravity, meteorology, etc). The historical perspective starts with the MERIT campaign, followed by the creation of international services (IERS, IGS, ILRS, IVS, IDS, etc). It provides a basic definition of observing systems and observatories and the build up of the international networks and the role of co-locations in geodesy and geosciences and multi-technique processing and data products. This paper gives special attention to the critical topic of local surveys and tie vectors among co-located systems in sites; the agreement of space geodetic solutions and the tie vectors now place one of the most significant limitations on the quality of integrated data products, most notably the ITRF. This topic focuses on survey techniques, extrapolation to instrument reference points, computation techniques, systematic biases, and alignment of the individual technique reference frames into ITRF. The paper also discusses the design, layout and implementation of network infrastructure, including the role of GGOS and the benefit that would be achieved with better standardization and international governance.

  14. Sudbury Neutrino Observatory

    NASA Astrophysics Data System (ADS)

    Beier, E. W.

    1992-03-01

    This document is a technical progress report on work performed at the University of Pennsylvania during the current year on the Sudbury Neutrino Observatory project. The motivation for the experiment is the measurement of neutrinos emitted by the sun. The Sudbury Neutrino Observatory (SNO) is a second generation dedicated solar neutrino experiment which will extend the results of our work with the Kamiokande II detector by measuring three reactions of neutrinos rather than the single reaction measured by the Kamiokande experiment. The collaborative project includes physicists from Canada, the United Kingdom, and the United States. Full funding for the construction of this facility was obtained in Jan. 1990, and its construction is estimated to take five years. The motivation for the SNO experiment is to study the fundamental properties of neutrinos, in particular the mass and mixing parameters, which remain undetermined after decades of experiments in neutrino physics utilizing accelerators and reactors as sources of neutrinos. To continue the study of neutrino properties it is necessary to use the sun as a neutrino source. The long distance to the sun makes the search for neutrino mass sensitive to much smaller mass than can be studied with terrestrial sources. Furthermore, the matter density in the sun is sufficiently large to enhance the effects of small mixing between electron neutrinos and mu or tau neutrinos. This experiment, when combined with the results of the radiochemical Cl-37 and Ga-71 experiments and the Kamiokande II experiment, should extend our knowledge of these fundamental particles, and as a byproduct, improve our understanding of energy generation in the sun.

  15. Global Ionosphere Radio Observatory

    NASA Astrophysics Data System (ADS)

    Galkin, I. A.; Reinisch, B. W.; Huang, X. A.

    2014-12-01

    The Global Ionosphere Radio Observatory (GIRO) comprises a network of ground-based high-frequency vertical sounding sensors, ionosondes, with instrument installations in 27 countries and a central Lowell GIRO Data Center (LGDC) for data acquisition and assimilation, including 46 real-time data streams as of August 2014. The LGDC implemented a suite of technologies for post-processing, modeling, analysis, and dissemination of the acquired and derived data products, including: (1) IRI-based Real-time Assimilative Model, "IRTAM", that builds and publishes every 15-minutes an updated "global weather" map of the peak density and height in the ionosphere, as well as a map of deviations from the classic IRI climate; (2) Global Assimilative Model of Bottomside Ionosphere Timelines (GAMBIT) Database and Explorer holding 15 years worth of IRTAM computed maps at 15 minute cadence;. (3) 17+ million ionograms and matching ionogram-derived records of URSI-standard ionospheric characteristics and vertical profiles of electron density; (4) 10+ million records of the Doppler Skymaps showing spatial distributions over the GIRO locations and plasma drifts; (5) Data and software for Traveling Ionospheric Disturbance (TID) diagnostics; and (6) HR2006 ray tracing software mated to the "realistic" IRTAM ionosphere. In cooperation with the URSI Ionosonde Network Advisory Group (INAG), the LGDC promotes cooperative agreements with the ionosonde observatories of the world to accept and process real-time data of HF radio monitoring of the ionosphere, and to promote a variety of investigations that benefit from the global-scale, prompt, detailed, and accurate descriptions of the ionospheric variability.

  16. Ancient "Observatories" - A Relevant Concept?

    NASA Astrophysics Data System (ADS)

    Belmonte, Juan Antonio

    It is quite common, when reading popular books on astronomy, to see a place referred to as "the oldest observatory in the world". In addition, numerous books on archaeoastronomy, of various levels of quality, frequently refer to the existence of "prehistoric" or "ancient" observatories when describing or citing monuments that were certainly not built with the primary purpose of observing the skies. Internet sources are also guilty of this practice. In this chapter, the different meanings of the word observatory will be analyzed, looking at how their significances can be easily confused or even interchanged. The proclaimed "ancient observatories" are a typical result of this situation. Finally, the relevance of the concept of the ancient observatory will be evaluated.

  17. Design and early results of the sodium-layer laser guide star adaptive optics experiment at the Lawrence Livermore National Laboratory

    SciTech Connect

    Gavel, D.T.; Max, C.E.; Avicola, K.

    1993-07-30

    Adaptive optic systems promise to give diffraction limited performance to ground based telescopes operating at visible and near infrared wavelengths. However, because of the short spatial scale of atmospheric turbulence, the corrected field of view is limited to only a few arc seconds in the visible, to perhaps 10 arc seconds at L band (3.5 {mu}). A bright point source must be in this field of view as a wavefront reference, but the number density of natural stars is too small for full sky coverage at imaging wavelengths less than 3{mu}. A sufficiently bright point source can be artificially generated by a laser however, and investigations into the use of laser beacons has been proceeding for some time now. Our experiments at Livermore have concentrated on the formation of guide stars in the sodium mesospheric layer at 90 km altitude. We have also designed and built adaptive optics systems that use both artificial and natural guide stars. Experimental results to date have shown great promise for the practicality of this technique in astronomy.

  18. Klimovskaya: A new geomagnetic observatory

    NASA Astrophysics Data System (ADS)

    Soloviev, A. A.; Sidorov, R. V.; Krasnoperov, R. I.; Grudnev, A. A.; Khokhlov, A. V.

    2016-05-01

    In 2011 Geophysical Center RAS (GC RAS) began to deploy the Klimovskaya geomagnetic observatory in the south of Arkhangelsk region on the territory of the Institute of Physiology of Natural Adaptations, Ural Branch, Russian Academy of Sciences (IPNA UB RAS). The construction works followed the complex of preparatory measures taken in order to confirm that the observatory can be constructed on this territory and to select the optimal configuration of observatory structures. The observatory equipping stages are described in detail, the technological and design solutions are described, and the first results of the registered data quality control are presented. It has been concluded that Klimovskaya observatory can be included in INTERMAGNET network. The observatory can be used to monitor and estimate geomagnetic activity, because it is located at high latitudes and provides data in a timely manner to the scientific community via the web-site of the Russian-Ukrainian Geomagnetic Data Center. The role of ground observatories such as Klimovskaya remains critical for long-term observations of secular variation and for complex monitoring of the geomagnetic field in combination with low-orbiting satellite data.

  19. The Solar Dynamics Observatory

    NASA Technical Reports Server (NTRS)

    Pesnell, William D.

    2008-01-01

    The Solar Dynamics Observatory (SDO) is the first Space Weather Mission in NASA's Living With a Star Program. SDO's main goal is to understand, driving towards a predictive capability, those solar variations that influence life on Earth and humanity's technological systems. The past decade has seen an increasing emphasis on understanding the entire Sun, from the nuclear reactions at the core to the development and loss of magnetic loops in the corona. SDO's three science investigations (HMI, AIA, and EVE) will determine how the Sun's magnetic field is generated and structured, how this stored magnetic energy is released into the heliosphere and geospace as the solar wind, energetic particles, and variations in the solar irradiance. SDO will return full-disk Dopplergrams, full-disk vector magnetograms, full-disk images at nine EIUV wavelengths, and EUV spectral irradiances, all taken at a rapid cadence. This means you can 'observe the database' to study events, but we can also move forward in producing quantitative models of what the Sun is doing today. SDO is scheduled to launch in 2008 on an Atlas V rocket from the Kennedy Space Center, Cape Canaveral, Florida. The satellite will fly in a 28 degree inclined geosynchronous orbit about the longitude of New Mexico, where a dedicated Ka-band ground station will receive the 150 Mbps data flow. How SDO data will transform the study of the Sun and its affect on Space Weather studies will be discussed.

  20. Morphologic and histologic changes in canine temporomandibular joint tissues following arthroscopic guided neodymium:YAG laser exposure

    SciTech Connect

    Bradrick, J.P.; Eckhauser, M.L.; Indresano, A.T. )

    1989-11-01

    A neodymium:yttrium aluminum garnet (Nd:YAG) laser beam was introduced by a quartz fiber passed arthroscopically into the superior joint space of the temporomandibular joints (TMJ) of five mongrel dogs, with one joint serving as a control without laser wounds. Immediate postoperative death and examination of the disc grossly and histologically revealed different patterns for contact and noncontact burn wounds. The wounds exhibited signs of thermal coagulation necrosis similar to those reported in other tissues. The potential implications of the adaptation of the Nd:YAG laser to TMJ arthroscopic surgery are discussed.

  1. RFA-based 589-nm guide star lasers for ESO VLT: a paradigm shift in performance, operational simplicity, reliability, and maintenance

    NASA Astrophysics Data System (ADS)

    Friedenauer, Axel; Karpov, Vladimir; Wei, Daoping; Hager, Manfred; Ernstberger, Bernhard; Clements, Wallace R. L.; Kaenders, Wilhelm G.

    2012-07-01

    Large telescopes equipped with adaptive optics require 20-25W CW 589-nm sources with emission linewidths of ~5 MHz. These Guide Star (GS) lasers should also be highly reliable and simple to operate and maintain for many years at the top of a mountain facility. Under contract from ESO, industrial partners TOPTICA and MPBC are nearing completion of the development of GS lasers for the ESO VLT, with delivery of the first of four units scheduled for December 2012. We report on the design and performance of the fully-engineered Pre-Production Unit (PPU), including system reliability/availability analysis, the successfully-concluded qualification testing, long-term component and system level tests and long-term maintenance and support planning. The chosen approach is based on ESO's patented narrow-band Raman Fiber Amplifier (EFRA) technology. A master oscillator signal from a linearly-polarized TOPTICA 20-mW, 1178-nm CW diode laser, with stabilized emission frequency and controllable linewidth up to a few MHz, is amplified in an MPBC polarization-maintaining (PM) RFA pumped by a high-power 1120-nm PM fiber laser. With efficient stimulated Brillouin scattering suppression, an unprecedented 40W of narrow-band RFA output has been obtained. This is then mode-matched into a resonant-cavity doubler with a free-spectral-range matching the sodium D2a to D2b separation, allowing simultaneous generation of an additional frequency component (D2b line) to re-pump the sodium atom electronic population. With this technique, the return flux can be increased without having to resort to electro-optical modulators and without the risk of introducing optical wave front distortions. The demonstrated output powers with doubling efficiencies >80% at 589 nm easily exceed the 20W design goal and require less than 700 W of electrical power. In summary, the fiber-based guide star lasers provide excellent beam quality and are modular, turn-key, maintenance-free, reliable, efficient, and ruggedized

  2. Prussian blue/serum albumin/indocyanine green as a multifunctional nanotheranostic agent for bimodal imaging guided laser mediated combinatorial phototherapy.

    PubMed

    Sahu, Abhishek; Lee, Jong Hyun; Lee, Hye Gyeong; Jeong, Yong Yeon; Tae, Giyoong

    2016-08-28

    Developing novel nanotheranostic agent using only clinically approved materials is highly desirable and challenging. In this study, we combined three clinically approved materials, Prussian blue (PB), serum albumin (BSA), and indocyanine green (ICG), by a simple and biocompatible method to prepare a multifunctional theranostic PB-BSA-ICG nanoparticle. The multifunctional nanoparticle system could provide dual mode magnetic resonance (MR) and near infrared (NIR) fluorescence imaging as well as combined photothermal and photodynamic (PTT-PDT) therapy in response to a single NIR laser. This nanoparticle showed an excellent stability in physiological solutions and could suppress the photo-instability of ICG. In the absence of light, the nanoparticles showed no cytotoxicity, but significant cell death was induced through combined PTT-PDT effect after irradiation with NIR laser light. A high tumor accumulation and minimal nonspecific uptake by other major organs of PB-BSA-ICG nanoparticle were observed in vivo, analyzed by T1-weighted MR and NIR fluorescence bimodal imaging in tumor xenograft mice after intravenous injection. The nanoparticles efficiently suppressed the tumor growth through combinatorial phototherapy with no tumor recurrence upon a single NIR laser irradiation. These results demonstrated that PB-BSA-ICG is potentially an interesting nanotheranostic agent for imaging guided cancer therapy by overcoming the limitations of each technology and enhancing the therapeutic efficiency as well as reducing side effects. PMID:27349352

  3. Architecture of Chinese Virtual Observatory

    NASA Astrophysics Data System (ADS)

    Cui, Chen-Zhou; Zhao, Yong-Heng

    2004-06-01

    Virtual Observatory (VO) is brought forward under the background of progresses of astronomical technologies and information technologies. VO architecture design embodies the combination of above two technologies. As an introduction of VO, principle and workflow of Virtual Observatory are given firstly. Then the latest progress on VO architecture is introduced. Based on the Grid technology, layered architecture model and service-oriented architecture model are given for Chinese Virtual Observatory. In the last part of the paper, some problems on architecture design are discussed in detail.

  4. Development of Mykolaiv Virtual Observatory

    NASA Astrophysics Data System (ADS)

    Mazhaev, A.; Protsyuk, Yu.

    Results obtained in 2010-2013 on the development of astronomical databases and web services are presented. Mykolaiv Virtual Observatory (MVO) is a part of the Ukrainian Virtual Observatory (UkrVO). At present, MVO consists of three major databases containing data on: astrometric catalogues, photographic plates, CCD observations. The databases facilitate the process of data mining and provide easy access to the textual and graphic information on the results of observations and their reduction obtained during the whole history of Nikolaev Astronomical Observatory (NAO).

  5. OSO-6 Orbiting Solar Observatory

    NASA Technical Reports Server (NTRS)

    1972-01-01

    The description, development history, test history, and orbital performance analysis of the OSO-6 Orbiting Solar Observatory are presented. The OSO-6 Orbiting Solar Observatory was the sixth flight model of a series of scientific spacecraft designed to provide a stable platform for experiments engaged in the collection of solar and celestial radiation data. The design objective was 180 days of orbital operation. The OSO-6 has telemetered an enormous amount of very useful experiment and housekeeping data to GSFC ground stations. Observatory operation during the two-year reporting period was very successful except for some experiment instrument problems.

  6. An MRI guided system for prostate laser ablation with treatment planning and multi-planar temperature monitoring

    NASA Astrophysics Data System (ADS)

    Xu, Sheng; Agarwal, Harsh; Bernardo, Marcelino; Seifabadi, Reza; Turkbey, Baris; Partanen, Ari; Negussie, Ayele; Glossop, Neil; Choyke, Peter; Pinto, Peter; Wood, Bradford J.

    2016-03-01

    Prostate cancer is often over treated with standard treatment options which impact the patients' quality of life. Laser ablation has emerged as a new approach to treat prostate cancer while sparing the healthy tissue around the tumor. Since laser ablation has a small treatment zone with high temperature, it is necessary to use accurate image guidance and treatment planning to enable full ablation of the tumor. Intraoperative temperature monitoring is also desirable to protect critical structures from being damaged in laser ablation. In response to these problems, we developed a navigation platform and integrated it with a clinical MRI scanner and a side firing laser ablation device. The system allows imaging, image guidance, treatment planning and temperature monitoring to be carried out on the same platform. Temperature sensing phantoms were developed to demonstrate the concept of iterative treatment planning and intraoperative temperature monitoring. Retrospective patient studies were also conducted to show the clinical feasibility of the system.

  7. THE 2011 FEBRUARY 15 X2 FLARE, RIBBONS, CORONAL FRONT, AND MASS EJECTION: INTERPRETING THE THREE-DIMENSIONAL VIEWS FROM THE SOLAR DYNAMICS OBSERVATORY AND STEREO GUIDED BY MAGNETOHYDRODYNAMIC FLUX-ROPE MODELING

    SciTech Connect

    Schrijver, Carolus J.; Title, Alan M.; Aulanier, Guillaume; Pariat, Etienne; Delannee, Cecile E-mail: title@lmsal.com E-mail: etienne.pariat@obspm.fr

    2011-09-10

    The 2011 February 15 X2.2 flare and associated Earth-directed halo coronal mass ejection were observed in unprecedented detail with high resolution in spatial, temporal, and thermal dimensions by the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory, as well as by instruments on the two STEREO spacecraft, then at near-quadrature relative to the Sun-Earth line. These observations enable us to see expanding loops from a flux-rope-like structure over the shearing polarity-inversion line between the central {delta}-spot groups of AR 11158, developing a propagating coronal front ('EIT wave'), and eventually forming the coronal mass ejection moving into the inner heliosphere. The observations support the interpretation that all of these features, including the 'EIT wave', are signatures of an expanding volume traced by loops (much larger than the flux rope only), surrounded by a moving front rather than predominantly wave-like perturbations; this interpretation is supported by previously published MHD models for active-region and global scales. The lateral expansion of the eruption is limited to the local helmet-streamer structure and halts at the edges of a large-scale domain of connectivity (in the process exciting loop oscillations at the edge of the southern polar coronal hole). The AIA observations reveal that plasma warming occurs within the expansion front as it propagates over quiet Sun areas. This warming causes dimming in the 171 A (Fe IX and Fe X) channel and brightening in the 193 and 211 A (Fe XII-XIV) channels along the entire front, while there is weak 131 A (Fe VIII and Fe XXI) emission in some directions. An analysis of the AIA response functions shows that sections of the front running over the quiet Sun are consistent with adiabatic warming; other sections may require additional heating which MHD modeling suggests could be caused by Joule dissipation. Although for the events studied here the effects of volumetric expansion are much

  8. The 2011 February 15 X2 Flare, Ribbons, Coronal Front, and Mass Ejection: Interpreting the Three-dimensional Views from the Solar Dynamics Observatory and STEREO Guided by Magnetohydrodynamic Flux-rope Modeling

    NASA Astrophysics Data System (ADS)

    Schrijver, Carolus J.; Aulanier, Guillaume; Title, Alan M.; Pariat, Etienne; Delannée, Cecile

    2011-09-01

    The 2011 February 15 X2.2 flare and associated Earth-directed halo coronal mass ejection were observed in unprecedented detail with high resolution in spatial, temporal, and thermal dimensions by the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory, as well as by instruments on the two STEREO spacecraft, then at near-quadrature relative to the Sun-Earth line. These observations enable us to see expanding loops from a flux-rope-like structure over the shearing polarity-inversion line between the central δ-spot groups of AR 11158, developing a propagating coronal front ("EIT wave"), and eventually forming the coronal mass ejection moving into the inner heliosphere. The observations support the interpretation that all of these features, including the "EIT wave," are signatures of an expanding volume traced by loops (much larger than the flux rope only), surrounded by a moving front rather than predominantly wave-like perturbations; this interpretation is supported by previously published MHD models for active-region and global scales. The lateral expansion of the eruption is limited to the local helmet-streamer structure and halts at the edges of a large-scale domain of connectivity (in the process exciting loop oscillations at the edge of the southern polar coronal hole). The AIA observations reveal that plasma warming occurs within the expansion front as it propagates over quiet Sun areas. This warming causes dimming in the 171 Å (Fe IX and Fe X) channel and brightening in the 193 and 211 Å (Fe XII-XIV) channels along the entire front, while there is weak 131 Å (Fe VIII and Fe XXI) emission in some directions. An analysis of the AIA response functions shows that sections of the front running over the quiet Sun are consistent with adiabatic warming; other sections may require additional heating which MHD modeling suggests could be caused by Joule dissipation. Although for the events studied here the effects of volumetric expansion are much

  9. History of the Marseille Observatory

    NASA Astrophysics Data System (ADS)

    Prévot, Marie-Louise; Caplan, James

    The Marseille Observatory was founded in 1702 by the Jesuit order. It was located near the Vieux Port until the 1860s, when it was taken over as an annex to the Paris Observatory, directed by Le Verrier, and moved to its present location on the Plateau Longchamp. It again became independent in 1873. For information on the early history of the observatory we are largely indebted to F.X. von Zach, who spent several years in Marseille, and who was a good friend of J. Thulis, director from 1801 to 1810. Some aspects of the foundation and early history of the observatory, and of the lives of some of the astronomers who worked there, are presented and illustrated. Our collection of old instruments and documents are described.

  10. Haystack Observatory Technology Development Center

    NASA Technical Reports Server (NTRS)

    Beaudoin, Chris; Corey, Brian; Niell, Arthur; Cappallo, Roger; Whitney, Alan

    2013-01-01

    Technology development at MIT Haystack Observatory were focused on four areas in 2012: VGOS developments at GGAO; Digital backend developments and workshop; RFI compatibility at VLBI stations; Mark 6 VLBI data system development.

  11. Islamic Astronomical Instruments and Observatories

    NASA Astrophysics Data System (ADS)

    Heidarzadeh, Tofigh

    This chapter is a brief survey of astronomical instruments being used and developed in Islamic territories from the eighth to the fifteenth centuries as well as a concise account of major observatories and observational programs in this period.

  12. The Infrared Space Observatory (ISO)

    NASA Technical Reports Server (NTRS)

    Helou, George; Kessler, Martin F.

    1995-01-01

    ISO, scheduled to launch in 1995, will carry into orbit the most sophisticated infrared observatory of the decade. Overviews of the mission, instrument payload and scientific program are given, along with a comparison of the strengths of ISO and SOFIA.

  13. Sofia Observatory Performance and Characterization

    NASA Technical Reports Server (NTRS)

    Temi, Pasquale; Miller, Walter; Dunham, Edward; McLean, Ian; Wolf, Jurgen; Becklin, Eric; Bida, Tom; Brewster, Rick; Casey, Sean; Collins, Peter; Jakob, Holger; Killebrew, Jana; Lampater, Ulrich; Mandushev, Georgi; Marcum, Pamela; Meyer, Allan; Pfueller, Enrico; Reinacher, Andreas; Roeser, Hans-Peter; Savage, Maureen; Teufel, Stefan; Wiedemann, Manuel

    2012-01-01

    The Stratospheric Observatory for Infrared Astronomy (SOFIA) has recently concluded a set of engineering flights for Observatory performance evaluation. These in-flight opportunities have been viewed as a first comprehensive assessment of the Observatory's performance and will be used to address the development activity that is planned for 2012, as well as to identify additional Observatory upgrades. A series of 8 SOFIA Characterization And Integration (SCAI) flights have been conducted from June to December 2011. The HIPO science instrument in conjunction with the DSI Super Fast Diagnostic Camera (SFDC) have been used to evaluate pointing stability, including the image motion due to rigid-body and flexible-body telescope modes as well as possible aero-optical image motion. We report on recent improvements in pointing stability by using an Active Mass Damper system installed on Telescope Assembly. Measurements and characterization of the shear layer and cavity seeing, as well as image quality evaluation as a function of wavelength have been performed using the HIPO+FLITECAM Science Instrument configuration (FLIPO). A number of additional tests and measurements have targeted basic Observatory capabilities and requirements including, but not limited to, pointing accuracy, chopper evaluation and imager sensitivity. SCAI activities included in-flight partial Science Instrument commissioning prior to the use of the instruments as measuring engines. This paper reports on the data collected during the SCAI flights and presents current SOFIA Observatory performance and characterization.

  14. Endoscopic cystoventriculostomy and ventriculo-cysternostomy using a 2.0 micron fiber guided cw laser in children with hydrocephalus

    NASA Astrophysics Data System (ADS)

    Ludwig, Hans C.; Kruschat, Thomas; Knobloch, Torsten; Rostasy, Kevin M.; Teichmann, Heinrich O.; Buchfelder, Michael

    2005-08-01

    Preterm infants have a high incidence of post hemorrhagic or post infectious hydrocephalus often associated with ventricular or arachnoic cysts which carry a high risk of entrapment of cerebrospinal fluid (CSF). In these cases fenestration and opening of windows within the separating membranes are neurosurgical options. In occlusive hydrocephalus caused by aquaeductal stenosis 3rd ventriculostomy is the primary choice of the operative procedures. Although Nd:YAG and diode lasers have already been used in neuroendoscopic procedures, neurosurgeons avoid the use of high energy lasers in proximity to vital structures because of potential side effects. We have used a recently developed diode pumped solid state (DPSS) laser emitting light at a wavelength of 2.0 micron (Revolix TM LISA laser products, Katlenburg, Germany), which can be delivered through silica fibres towards endoscopic targets. From July 2002 until May 2005 22 endoscopic procedures in 20 consecutive patients (age 3 months to 12 years old) were performed. Most children suffered from complex post hemorrhagic and post infectious hydrocephalus, in whom ventriculoperitoneal shunt devices failed to restore a CSF equilibrium due to entrapment of CSF pathways by the cysts. We used two different endoscopes, a 6 mm Neuroendoscope (Braun Aesculap, Melsungen, Germany) and a 4 mm miniature Neuroscope (Storz, Tuttlingen, Germany). The endoscopes were connected to a standard camera and TV monitor, the laser energy was introduced through a 365 micron core diameter bare ended silica fibre (PercuFib, LISA laser products, Katlenburg, Germany) through the endoscope's working channel. The continuous wave laser was operated at power levels from 5 to 15 Watt in continuous and chopped mode. The frequency of the laser in chopped mode was varied between 5 and 20 Hz. All patients tolerated the procedure well. No immediate or long term side effects were noted. In 3 patients with cystic compression of the 4th ventricle, insertion of

  15. Impact of the thermal lens effect in atmospheric pressure DBD-plasma columns on coaxially guided laser beams

    NASA Astrophysics Data System (ADS)

    Hoffmeister, J.; Brückner, S.; Gerhard, C.; Wieneke, S.; Viöl, W.

    2014-12-01

    The combination of laser and low-temperature plasmas is of growing interest for micro-structuring purposes for a wide range of materials. This combination can be used for a reduction of the ablation threshold as well as an improvement of the machining quality in various laser material processing applications. The plasma involved in such combination, however, leads to a thermally generated influence on the laser beam quality. In this paper, a DBD-based argon plasma as typically used in low-temperature laser plasma hybrid arrangements was investigated by interferometric and beam profile measurements. The radial temperature profile as well as the beam propagation characteristics in terms of focal shift and effective pointing stability was determined. Due to the argon plasma, a temperature increase ΔT by up to 25 K, and thus a thermal lens was observed within the light path of the laser beam featuring an increase in refractive index Δn by maximum 2.86 × 10-5. In the given setup, the plasma-induced thermal lens caused a focal shift by up to 4 mm. Further, the lateral focus position was deviated by a maximum of about 30 µm, which is in the order of magnitude of the beam waist radius.

  16. Air-guided photonic-crystal-fiber pulse-compression delivery of multimegawatt femtosecond laser output for nonlinear-optical imaging and neurosurgery

    NASA Astrophysics Data System (ADS)

    Lanin, Aleksandr A.; Fedotov, Il'ya V.; Sidorov-Biryukov, Dmitrii A.; Doronina-Amitonova, Lyubov V.; Ivashkina, Olga I.; Zots, Marina A.; Sun, Chi-Kuang; Ömer Ilday, F.; Fedotov, Andrei B.; Anokhin, Konstantin V.; Zheltikov, Aleksei M.

    2012-03-01

    Large-core hollow photonic-crystal fibers (PCFs) are shown to enable a fiber-format air-guided delivery of ultrashort infrared laser pulses for neurosurgery and nonlinear-optical imaging. With an appropriate dispersion precompensation, an anomalously dispersive 15-μm-core hollow PCF compresses 510-fs, 1070-nm light pulses to a pulse width of about 110 fs, providing a peak power in excess of 5 MW. The compressed PCF output is employed to induce a local photodisruption of corpus callosum tissues in mouse brain and is used to generate the third harmonic in brain tissues, which is captured by the PCF and delivered to a detector through the PCF cladding.

  17. Report on the lunar ranging at McDonald Observatory, 1 February - 31 May 1976

    NASA Technical Reports Server (NTRS)

    Palm, C. S.; Wiant, J. R.

    1976-01-01

    The four spring lunations produced 105 acquisitions, including the 2000th range measurement made at McDonald Observatory. Statistics were normal for the spring months. Laser and electronics problems are noted. The Loran-C station delay was corrected. Preliminary doubles data is shown. New magnetic tape data formats are presented. R and D efforts include a new laser modification design.

  18. The Carl Sagan solar and stellar observatories as remote observatories

    NASA Astrophysics Data System (ADS)

    Saucedo-Morales, J.; Loera-Gonzalez, P.

    In this work we summarize recent efforts made by the University of Sonora, with the goal of expanding the capability for remote operation of the Carl Sagan Solar and Stellar Observatories, as well as the first steps that have been taken in order to achieve autonomous robotic operation in the near future. The solar observatory was established in 2007 on the university campus by our late colleague A. Sánchez-Ibarra. It consists of four solar telescopes mounted on a single equatorial mount. On the other hand, the stellar observatory, which saw the first light on 16 February 2010, is located 21 km away from Hermosillo, Sonora at the site of the School of Agriculture of the University of Sonora. Both observatories can now be remotely controlled, and to some extent are able to operate autonomously. In this paper we discuss how this has been accomplished in terms of the use of software as well as the instruments under control. We also briefly discuss the main scientific and educational objectives, the future plans to improve the control software and to construct an autonomous observatory on a mountain site, as well as the opportunities for collaborations.

  19. Increased sky coverage with optimal correction of tilt and tilt-anisoplanatism modes in laser-guide-star multiconjugate adaptive optics.

    PubMed

    Correia, Carlos; Véran, Jean-Pierre; Herriot, Glen; Ellerbroek, Brent; Wang, Lianqi; Gilles, Luc

    2013-04-01

    Laser-guide-star multiconjugate adaptive optics (MCAO) systems require natural guide stars (NGS) to measure tilt and tilt-anisoplanatism modes. Making optimal use of the limited number of photons coming from such, generally dim, sources is mandatory to obtain reasonable sky coverage, i.e., the probability of finding asterisms amenable to NGS wavefront (WF) sensing for a predefined WF error budget. This paper presents a Strehl-optimal (minimum residual variance) spatiotemporal reconstructor merging principles of modal atmospheric tomography and optimal stochastic control theory. Simulations of NFIRAOS, the first light MCAO system for the thirty-meter telescope, using ~500 typical NGS asterisms, show that the minimum-variance (MV) controller delivers outstanding results, in particular for cases with relatively dim stars (down to magnitude 22 in the H-band), for which low-temporal frame rates (as low as 16 Hz) are required to integrate enough flux. Over all the cases tested ~21 nm rms median improvement in WF error can be achieved with the MV compared to the current baseline, a type-II controller based on a double integrator. This means that for a given level of tolerable residual WF error, the sky coverage is increased by roughly 10%, a quite significant figure. The improvement goes up to more than 20% when compared with a traditional single-integrator controller. PMID:23595319

  20. GEOSCOPE Observatory Recent Developments

    NASA Astrophysics Data System (ADS)

    Leroy, N.; Pardo, C.; Bonaime, S.; Stutzmann, E.; Maggi, A.

    2010-12-01

    The GEOSCOPE observatory consists of a global seismic network and a data center. The 31 GEOSCOPE stations are installed in 19 countries, across all continents and on islands throughout the oceans. They are equipped with three component very broadband seismometers (STS1 or STS2) and 24 or 26 bit digitizers, as required by the Federation of Seismic Digital Network (FDSN). In most stations, a pressure gauge and a thermometer are also installed. Currently, 23 stations send data in real or near real time to GEOSCOPE Data Center and tsunami warning centers. In 2009, two stations (SSB and PPTF) have been equipped with warpless base plates. Analysis of one year of data shows that the new installation decreases long period noise (20s to 1000s) by 10 db on horizontal components. SSB is now rated in the top ten long period stations for horizontal components according to the LDEO criteria. In 2010, Stations COYC, PEL and RER have been upgraded with Q330HR, Metrozet electronics and warpless base plates. They have been calibrated with the calibration table CT-EW1 and the software jSeisCal and Calex-EW. Aluminum jars are now installed instead of glass bells. A vacuum of 100 mbars is applied in the jars which improves thermal insulation of the seismometers and reduces moisture and long-term corrosion in the sensor. A new station RODM has just been installed in Rodrigues Island in Mauritius with standard Geoscope STS2 setup: STS2 seismometer on a granite base plate and covered by cooking pot and thermal insulation, it is connected to Q330HR digitizer, active lightning protection, Seiscomp PC and real-time internet connection. Continuous data of all stations are collected in real time or with a delay by the GEOSCOPE Data Center in Paris where they are validated, archived and made available to the international scientific community. Data are freely available to users by different interfaces according data types (see : http://geoscope.ipgp.fr) - Continuous data in real time coming