Sample records for large aperture laser

  1. The role of the solvent viscosity on the spatiotemporal instabilities of large aperture dye lasers

    E-print Network

    Rey Juan Carlos, Universidad

    The role of the solvent viscosity on the spatiotemporal instabilities of large aperture dye lasers for publication 27 May 1998 Local intensity fluctuations in a large aperture dye laser have been measured behavior as the molecular polarization orientation driven by the laser field. © 1998 American Institute

  2. The role of the molecular dynamics in the local intensity instabilities of large aperture dye lasers

    E-print Network

    Rey Juan Carlos, Universidad

    lasers I. Leyvaa) and J. M. Guerra Departamento de O´ ptica, Facultad de Ciencias Fi´sicas Universidad fluctuations of large aperture dye lasers, and find dependencies on solvent viscosity and active molecular size dye lasers are used in a great deal of practical applications, from isotope enrichment to photody

  3. Performance results for Beamlet: A large aperture multipass Nd glass laser

    SciTech Connect

    Campbell, J.H.; Barker, C.E.; VanWonterghem, B.M.; Speck, D.R.; Behrendt, W.C.; Murray, J.R.; Caird, J.A.; Decker, D.E.; Smith, I.C.

    1995-04-11

    The Beamlet laser is a large aperture, flashlamp pumped Nd: glass laser that is a scientific prototype of an advanced Inertial Fusion laser. Beamlet has achieved third harmonic, conversion efficiency of near 80% with its nominal 35cm {times} 35cm square beam at mean 3{omega} fluences in excess of 8 J/cm{sup 2}(3-ns). Beamlet uses an adaptive optics system to correct for aberrations and achieve less than 2 {times} diffraction limited far field spot size.

  4. Specification of large-aperture Nd:phosphate glass laser disks

    Microsoft Academic Search

    Milton J. Shoup; Stephen D. Jacobs; John H. Kelly; Christopher T. Cotton; Samuel F. Morse; Steven A. Kumpan

    1992-01-01

    The purchase of large (15- and 20-cm clear aperture) Brewster-angle laser disks involves the specification of a large number of often conflicting parameters, all of which bear on performance and cost. Furthermore, the laser requirements often approach the state-of-the-art in glass-melting technology and the parameter measurement. This paper enumerates the relevant parameters, the trade-offs made in their selection, and the

  5. Development of large-aperture electro-optical switch for high power laser at CAEP

    NASA Astrophysics Data System (ADS)

    Zhang, Xiongjun; Wu, Dengsheng; Zhang, Jun; Lin, Donghui; Zheng, Jiangang; Zheng, Kuixing

    2015-02-01

    Large-aperture electro-optical switch based on plasma Pockels cell (PPC) is one of important components for inertial confinement fusion (ICF) laser facility. We have demonstrated a single-pulse driven 41 PPC with 400mm400mm aperture for SGIII laser facility. And four 21 PPCs modules with 350mm350mm aperture have been operated in SGII update laser facility. It is different to the PPC of NIF and LMJ for its simple operation to perform Pockels effect. With optimized operation parameters, the PPCs meet the SGII-U laser requirement of four-pass amplification control. Only driven by one high voltage pulser, the simplified PPC system would be provided with less associated diagnostics, and higher reliability. To farther reduce the insert loss of the PPC, research on the large-aperture PPC based on DKDP crystal driven by one pulse is developed. And several single-pulse driven PPCs with 80mm80mm DKDP crystal have been manufactured and operated in laser facilities.

  6. Off-axis multipass amplifier as a large aperture driver stage for fusion lasers.

    PubMed

    Murray, J E; Downs, D C; Hunt, J T; Hermes, G L; Warren, W E

    1981-03-01

    A multipass amplifier configuration is described which has potential as a large aperture, high gain driver stage for fusion laser systems. We avoid the present limitations of large aperture switches by using an off-angle geometry that does not require an optical switch. The saturated gain characteristics of this multipass amplifier are optimized numerically. Three potential problems are investigated experimentally, self-lasing, output beam quality, and amplified spontaneous emission output. The results indicate comparable cost for comparable performance to a linear chain, with some operational advantage for the multipass driver stage. PMID:20309212

  7. Studies on large aperture volume discharge of TEA CO II laser

    NASA Astrophysics Data System (ADS)

    Chen, Yuqi; Zuo, Duluo; Cheng, Zuhai

    2008-03-01

    The studies on large aperture volume discharge of TEA (transversely excited atmospheric) CO II laser are reported. To obtain stable and uniform large aperture volume discharge, the effects of electrode profiles, preionization methods and parameters of discharge circuit have been studied experimentally. For a discharge construction with 70 mm gap and pumped by a 3-stage Marx high voltage pulse generator circuit isolated by resistance with 0.5 ?F capacitance each stage, 150 J pulse energy was obtained from a discharge volume about 4 l.

  8. Large-aperture YCOB crystal growth for frequency conversion in the high average power laser system

    NASA Astrophysics Data System (ADS)

    Fei, Yiting; Chai, Bruce H. T.; Ebbers, C. A.; Liao, Z. M.; Schaffers, K. I.; Thelin, P.

    2006-04-01

    Yttrium calcium oxyborate YCa4O(BO3)3 (YCOB) is a novel non-linear optical crystal possessing good thermal, mechanical and non-linear optical properties. Large-aperture YCOB crystals with 75 mm diameter were grown for high-average power frequency conversion on the mercury laser system. The growth morphology (included facet and spiral growth), cracking and inclusions in the as-grown crystal boule were discussed as the critical problem for large-aperture YCOB crystal growth. This can be minimized through modification of the growth program, including pulling rate, separation procedure, and cooling program. High-average power frequency conversion of the mercury laser using YCOB has been demonstrated, and experimental validation of YCOB material yields 50% conversion at 10 Hz has been achieved.

  9. Large-aperture YCOB crystal growth for frequency conversion in the high average power laser system

    Microsoft Academic Search

    Yiting Fei; Bruce H. T. Chai; C. A. Ebbers; Z. M. Liao; K. I. Schaffers; P. Thelin

    2006-01-01

    Yttrium calcium oxyborate YCa4O(BO3)3 (YCOB) is a novel non-linear optical crystal possessing good thermal, mechanical and non-linear optical properties. Large-aperture YCOB crystals with 75mm diameter were grown for high-average power frequency conversion on the mercury laser system. The growth morphology (included facet and spiral growth), cracking and inclusions in the as-grown crystal boule were discussed as the critical problem for

  10. Wave-Front Control of a Large-Aperture Laser System by Use of a Static Phase Corrector

    NASA Astrophysics Data System (ADS)

    Hernandez-Gomez, Cristina; Collier, John L.; Hawkes, Steve J.; Danson, Colin N.; Edwards, Chris B.; Pepler, Dave A.; Ross, Ian N.; Winstone, Trevor B.

    2000-04-01

    In large-aperture, ultrahigh-intensity laser systems, such as Vulcan at the Rutherford Appleton Laboratory, one of the most important factors that determines the ultimate on-target focused intensity is the wave-front quality of the laser pulse. We report on a wave-front analysis carried out on Vulcan to determine the nature and contribution of the aberrations present in the laser pulse that effectively limited the available on-target intensity. We also report on a significant improvement to the wave-front quality that was achieved by static correction of the main aberration, resulting in an increase of focused intensities by a factor of 4.

  11. Developing Magnetorheological Finishing (MRF) Technology for the Manufacture of Large-Aperture Optics in Megajoule Class Laser Systems

    SciTech Connect

    Menapace, J A

    2010-10-27

    Over the last eight years we have been developing advanced MRF tools and techniques to manufacture meter-scale optics for use in Megajoule class laser systems. These systems call for optics having unique characteristics that can complicate their fabrication using conventional polishing methods. First, exposure to the high-power nanosecond and sub-nanosecond pulsed laser environment in the infrared (>27 J/cm{sup 2} at 1053 nm), visible (>18 J/cm{sup 2} at 527 nm), and ultraviolet (>10 J/cm{sup 2} at 351 nm) demands ultra-precise control of optical figure and finish to avoid intensity modulation and scatter that can result in damage to the optics chain or system hardware. Second, the optics must be super-polished and virtually free of surface and subsurface flaws that can limit optic lifetime through laser-induced damage initiation and growth at the flaw sites, particularly at 351 nm. Lastly, ultra-precise optics for beam conditioning are required to control laser beam quality. These optics contain customized surface topographical structures that cannot be made using traditional fabrication processes. In this review, we will present the development and implementation of large-aperture MRF tools and techniques specifically designed to meet the demanding optical performance challenges required in large-aperture high-power laser systems. In particular, we will discuss the advances made by using MRF technology to expose and remove surface and subsurface flaws in optics during final polishing to yield optics with improve laser damage resistance, the novel application of MRF deterministic polishing to imprint complex topographical information and wavefront correction patterns onto optical surfaces, and our efforts to advance the technology to manufacture large-aperture damage resistant optics.

  12. VOLUME 84, NUMBER 5 P H Y S I C A L R E V I E W L E T T E R S 31 JANUARY 2000 Time Resolved Pattern Evolution in a Large Aperture Laser

    E-print Network

    Rey Juan Carlos, Universidad

    Evolution in a Large Aperture Laser F. Encinas-Sanz, I. Leyva, and J. M. Guerra Departamento de Optica in a broad aperture laser. Nonordered pat- terns yielding to boundary determined regular structures in other pattern forming systems, such as large aperture lasers. In fact, this phenomenon has been

  13. Repetitively pulsed regime of Nd : glass large-aperture laser amplifiers

    SciTech Connect

    Kuzmin, A A; Khazanov, Efim A; Shaykin, A A [Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod (Russian Federation)

    2012-04-30

    A repetitively pulsed operation regime of neodymium glass rod laser amplifiers with apertures of 4.5, 6, 8.5, and 10 cm is analysed using experimental data. The limits of an increase in the pulse repetition rates are determined. Universal dependences are obtained, which help finding a compromise between increasing the repetition rate and enhancing the gain for each particular case. In particular, it is shown that an amplifier 4.5-cm in diameter exhibits a five-fold safety factor with respect to a thermo-mechanical breakdown at a repetition rate of 1 pulse min{sup -1} and stored energy of above 100 J. A strong thermally induced birefringence in two such amplifiers is experimentally reduced to a 'cold' level by employing a 90 Degree-Sign optical rotator.

  14. Wave-front control of a large-aperture laser system by use of a static phase corrector.

    PubMed

    Hernandez-Gomez, C; Collier, J L; Hawkes, S J; Danson, C N; Edwards, C B; Pepler, D A; Ross, I N; Winstone, T B

    2000-04-20

    In large-aperture, ultrahigh-intensity laser systems, such as Vulcan at the Rutherford Appleton Laboratory, one of the most important factors that determines the ultimate on-target focused intensity is the wave-front quality of the laser pulse. We report on a wave-front analysis carried out on Vulcan to determine the nature and contribution of the aberrations present in the laser pulse that effectively limited the available on-target intensity. We also report on a significant improvement to the wave-front quality that was achieved by static correction of the main aberration, resulting in an increase of focused intensities by a factor of 4. PMID:18345093

  15. Industrial large-aperture XeCl laser for surface processing

    NASA Astrophysics Data System (ADS)

    Letardi, Tommaso; Baldesi, Alessandro; Bollanti, Sarah; Bonfigli, Francesca; Di Lazzaro, Paolo; Flora, Francesco; Giordano, Gualtiero; Marinai, Alessandro; Murra, Daniele; Schina, Giovanni; Zheng, Cheng En

    2000-02-01

    In the frame of a large project on new materials technologies for photovoltaic and microelectronic applications (FOTO), the process of amorphous silicon (a-Si) transformation into polycrystalline silicon (poly-Si) by means of laser irradiation has been tested with a long-pulse (160 ns), 8 J/p XeCl source. Following the positive results, a laser source, having design parameters of 10 J/p, 120 ns, 10 Hz, has been designed and built, with the aim of realizing a laboratory line for the production of thin film transistors (TFTs) devices.

  16. Large-aperture CsLiB6O10 frequency doubler for high-energy Nd:glass laser

    NASA Astrophysics Data System (ADS)

    Kiriyama, Hiromitsu; Inoue, Norihiro; Yamakawa, Koichi

    2002-09-01

    We describe the demonstration of the high pulse energy and high efficiency second-harmonic generation (SHG) at 532-nm using large aperture CsLiB6O10 (CLBO) crystals for the first time to our knowledge. A pulsed green energy of 25 J has been generated with 34 J of input 1064-nm Nd:glass laser radiation using a two-stage crystal architecture. High conversion efficiency of 74 % has been attained at fundamental laser intensity of only 370 MW/cm2. This result represents the highest green pulse energy ever reported using the CLBO crystals. We discuss in detail the design and performance of SHG using CLBO crystals.

  17. Laser damage performance of large-aperture fused silica optical components at 351 nm

    NASA Astrophysics Data System (ADS)

    Huang, Wanqing; Han, Wei; Wang, Fang; Xiang, Yong; Li, Fuquan; Feng, Bin; Jing, Feng; Wei, Xiaofeng; Zheng, Wanguo; Zhang, Xiaomin

    2008-12-01

    High power laser facility for ICF will routinely operate at high fluence level. The damage on the large-area FOA optics is a key lifetime limiter. The optics should be checked after each laser shot for damage initiation and growth. On-line monitoring equipments are installed for this purpose. Damage pictures of a fused silica component are successfully taken and the luminance of the pictures could reflect the deterioration of the operational environment. Damage initiation and growth behaviors at 351nm high-fluence laser were observed. Damage density and damage growth are exponential with the shot number and some conclusions could be drawn. These results bring forward demands for future monitoring equipments and more experiments to establish a lifetime model.

  18. HI-CLASS on AEOS: a large-aperture laser radar for space surveillance\\/situational awareness investigations

    Microsoft Academic Search

    Mark A. Kovacs; Gordon L. Dryden; Richard H. Pohle; Kirstie Ayers; Richard A. Carreras; Linda L. Crawford; Russell Taft

    2001-01-01

    The Air Force Research Laboratory\\/Directed Energy Directorate (AFRL\\/DE) via the ALVA (Applications of Lidars for Vehicles with Analysis) program installed in late 2000 a wideband, 12 J 15 Hz CO2 laser radar (ladar) on the 3.67 meter aperture AEOS (Advanced Electro-Optics System) telescope. This system is part of the Maui Space Surveillance System (MSSS), on the summit of Haleakala, Maui,

  19. High energy second-harmonic generation of Nd:glass laser radiation with large aperture CsLiB6O10 crystals

    NASA Astrophysics Data System (ADS)

    Kiriyama, Hiromitsu; Inoue, Norihiro; Yamakawa, Koichi

    2002-09-01

    We have demonstrated the generation of a high-energy green laser pulse using large aperture CsLiB6O10 (CLBO) crystals for the first time to our knowledge. A pulsed energy of 25 J at 532-nm was generated using the 1064-nm incident Nd:glass laser radiation with an energy of 34 J. High conversion efficiency of 74 % at intensities of only 370 MW/cm2 was obtained using a two-stage crystal architecture. This result represents the highest green pulse energy ever reported using the CLBO crystals.

  20. High energy second-harmonic generation of Nd:glass laser radiation with large aperture CsLiB6O10 crystals.

    PubMed

    Kiriyama, Hiromitsu; Inoue, Norihiro; Yamakawa, Koichi

    2002-09-23

    We have demonstrated the generation of a high-energy green laser pulse using large aperture CsLiB6O10 (CLBO) crystals for the first time to our knowledge. A pulsed energy of 25 J at 532-nm was generated using the 1064-nm incident Nd:glass laser radiation with an energy of 34 J. High conversion efficiency of 74 % at intensities of only 370 MW/cm2 was obtained using a two-stage crystal architecture. This result represents the highest green pulse energy ever reported using the CLBO crystals. PMID:19451960

  1. Development of large aperture composite adaptive optics

    NASA Astrophysics Data System (ADS)

    Kmetik, Viliam; Vitovec, Bohumil; Jiran, Lukas; Nemcova, Sarka; Zicha, Josef; Inneman, Adolf; Mikulickova, Lenka; Pavlica, Richard

    2015-01-01

    Large aperture composite adaptive optics for laser applications is investigated in cooperation of Institute of Plasma Physic, Department of Instrumentation and Control Engineering FME CTU and 5M Ltd. We are exploring opportunity of a large-size high-power-laser deformable-mirror production using a lightweight bimorph actuated structure with a composite core. In order to produce a sufficiently large operational free aperture we are developing new technologies for production of flexible core, bimorph actuator and deformable mirror reflector. Full simulation of a deformable-mirrors structure was prepared and validated by complex testing. A deformable mirror actuation and a response of a complicated structure are investigated for an accurate control of the adaptive optics. An original adaptive optics control system and a bimorph deformable mirror driver were developed. Tests of material samples, components and sub-assemblies were completed. A subscale 120 mm bimorph deformable mirror prototype was designed, fabricated and thoroughly tested. A large-size 300 mm composite-core bimorph deformable mirror was simulated and optimized, fabrication of a prototype is carried on. A measurement and testing facility is modified to accommodate large sizes optics.

  2. Low-Cost Large Aperture Telescopes for Optical Communications

    NASA Technical Reports Server (NTRS)

    Hemmati, Hamid

    2006-01-01

    Low-cost, 0.5-1 meter ground apertures are required for near-Earth laser communications. Low-cost ground apertures with equivalent diameters greater than 10 meters are desired for deep-space communications. This presentation focuses on identifying schemes to lower the cost of constructing networks of large apertures while continuing to meet the requirements for laser communications. The primary emphasis here is on the primary mirror. A slumped glass spherical mirror, along with passive secondary mirror corrector and active adaptive optic corrector show promise as a low-cost alternative to large diameter monolithic apertures. To verify the technical performance and cost estimate, development of a 1.5-meter telescope equipped with gimbal and dome is underway.

  3. Very Large Aperture Diffractive Space Telescope

    SciTech Connect

    Hyde, Roderick Allen

    1998-04-20

    A very large (10's of meters) aperture space telescope including two separate spacecraft--an optical primary functioning as a magnifying glass and an optical secondary functioning as an eyepiece. The spacecraft are spaced up to several kilometers apart with the eyepiece directly behind the magnifying glass ''aiming'' at an intended target with their relative orientation determining the optical axis of the telescope and hence the targets being observed. The magnifying glass includes a very large-aperture, very-thin-membrane, diffractive lens, e.g., a Fresnel lens, which intercepts incoming light over its full aperture and focuses it towards the eyepiece. The eyepiece has a much smaller, meter-scale aperture and is designed to move along the focal surface of the magnifying glass, gathering up the incoming light and converting it to high quality images. The positions of the two space craft are controlled both to maintain a good optical focus and to point at desired targets.

  4. Vacuum aperture isolator for retroreflection from laser-irradiated target

    DOEpatents

    Benjamin, Robert F. (Los Alamos, NM); Mitchell, Kenneth B. (Los Alamos, NM)

    1980-01-01

    The disclosure is directed to a vacuum aperture isolator for retroreflection of a laser-irradiated target. Within a vacuum chamber are disposed a beam focusing element, a disc having an aperture and a recollimating element. The edge of the focused beam impinges on the edge of the aperture to produce a plasma which refracts any retroreflected light from the laser's target.

  5. Large Aperture Electrostatic Dust Detector

    SciTech Connect

    C.H. Skinner, R. Hensley, and A.L Roquemore

    2007-10-09

    Diagnosis and management of dust inventories generated in next-step magnetic fusion devices is necessary for their safe operation. A novel electrostatic dust detector, based on a fine grid of interlocking circuit traces biased to 30 or 50 ? has been developed for the detection of dust particles on remote surfaces in air and vacuum environments. Impinging dust particles create a temporary short circuit and the resulting current pulse is recorded by counting electronics. Up to 90% of the particles are ejected from the grid or vaporized suggesting the device may be useful for controlling dust inventories. We report measurements of the sensitivity of a large area (5x5 cm) detector to microgram quantities of dust particles and review its applications to contemporary tokamaks and ITER.

  6. Incoherent aperture beam combining of quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Dahl, Katrin; Raab, Michael; Tholl, Hans Dieter

    2014-10-01

    Quantum cascade lasers can be designed to emit at any desired wavelength in the mid-infrared. When the optical output power of a single quantum cascade laser is too low, the beams of different lasers can be combined, e.g. by incoherent aperture beam combining. For incoherent aperture beam combining the laser beams are arranged side by side on the aperture of the (multi-) laser system and combine in the far field. The technique is neither limited to any number of lasers nor to any laser characteristics. We investigated incoherent aperture beam combining of quantum cascade laser beams in experiment and simulations at different distances from the laser aperture. We present results of combining laser sources of different wavelengths and demonstrate advantages of various beam arrangements.

  7. Design of large aperture focal plane shutter

    NASA Astrophysics Data System (ADS)

    Hu, Jia-wen; Ma, Wen-li; Huang, Jin-long

    2012-09-01

    To satisfy the requirement of large telescope, a large aperture focal plane shutter with aperture size of ?200mm was researched and designed to realize, which could be started and stopped in a relative short time with precise position, and also the blades could open and close at the same time at any orientation. Timing-belts and stepper motors were adopted as the drive mechanism. Velocity and position of the stepper motors were controlled by the PWM pulse generated by DSP. Exponential curve is applied to control the velocity of the stepper motors to make the shutter start and stop in a short time. The closing/open time of shutter is 0.2s, which meets the performance requirements of large telescope properly.

  8. Belt-MRF for large aperture mirrors.

    PubMed

    Ren, Kai; Luo, Xiao; Zheng, Ligong; Bai, Yang; Li, Longxiang; Hu, Haixiang; Zhang, Xuejun

    2014-08-11

    With high-determinacy and no subsurface damage, Magnetorheological Finishing (MRF) has become an important tool in fabricating high-precision optics. But for large mirrors, the application of MRF is restricted by its small removal function and low material removal rate. In order to improve the material removal rate, shorten the processing cycle, we proposed a new MRF concept, named Belt-MRF to expand the application of MRF to large mirrors and made a prototype with a large remove function, using a belt instead of a very large polishing wheel to expand the polishing length. A series of experimental results on Silicon carbide (SiC) and BK 7 specimens and fabrication simulation verified that the Belt-MRF has high material removal rates, stable removal function and high convergence efficiency which makes it a promising technology for processing large aperture optical elements. PMID:25321011

  9. A modular approach toward extremely large apertures

    Microsoft Academic Search

    A. A. Woods Jr.

    1981-01-01

    Modular antenna construction can provide a significant increase in reflector aperture size over deployable reflectors. The modular approach allows reflective mesh surfaces to be supported by a minimum of structure. The kinematics of the selected deployable design approach were validated by the subscale demonstration model. Further design refinements on the module structural\\/joints and design optimization on intermodule joints are needed.

  10. A modular approach toward extremely large apertures

    NASA Astrophysics Data System (ADS)

    Woods, A. A., Jr.

    1981-02-01

    Modular antenna construction can provide a significant increase in reflector aperture size over deployable reflectors. The modular approach allows reflective mesh surfaces to be supported by a minimum of structure. The kinematics of the selected deployable design approach were validated by the subscale demonstration model. Further design refinements on the module structural/joints and design optimization on intermodule joints are needed.

  11. Research on materials for the large aperture space mirror

    NASA Astrophysics Data System (ADS)

    Zhang, Zhuwei; Wang, Bin; Gong, Hui; Gu, Zhenyv; Liu, Yiliang

    2014-11-01

    The properties and developments of materials for large aperture space mirrors, which are pursued for high-resolution earth observation and deep space exploration, are summarized in this paper. All these materials were classified into several kinds depend on their substance and performance. Their advantages and disadvantages in manufacturing large aperture space mirrors were discussed; especially their fabrication, optical machining and application. The trends of development of materials for large space mirrors are overviewed.

  12. Stitching interferometry for cylindrical optics with large angular aperture

    NASA Astrophysics Data System (ADS)

    Peng, Junzheng; Xu, Haifeng; Yu, Yingjie; Chen, Mingyi

    2015-02-01

    Stitching interferometry is an attractive method for measuring optics with large apertures. However, existing stitching algorithms are not suitable for measuring cylindrical optics, because the misalignment aberrations in cylindrical interferometry are more complicated than those in plane, spherical and aspherical measurements. This paper presents a stitching algorithm for measuring cylindrical optics with large angular apertures. With it, we use five aberrations (i.e. piston, tilt, tip, defocus and twist) to describe the possible misalignments of the tested cylindrical surface and to build the cylindrical stitching model. Using this model allows us to calculate the relative misalignment aberrations of subapertures from their overlapped areas, so that the full aperture map of a cylindrical surface is obtained by compensating for these misalignment aberrations. In experiment, a cylindrical lens with an angular aperture over 150 is measured, thus demonstrating the feasibility and validity of the proposed method.

  13. Large diffractive/refractive apertures for space and airborne telescopes

    NASA Astrophysics Data System (ADS)

    MacEwen, Howard A.; Breckinridge, James B.

    2013-05-01

    Recent work, specifically the Lawrence Livermore National Laboratory (LLNL) Eyeglass and the DARPA MOIRE programs, have evaluated lightweight, easily packaged and deployed, diffractive/refractive membrane transmissive lenses as entrance apertures for large space and airborne telescopes. This presentation describes a new, innovative approach to the theory of diffractive and refractive effects in lenses used as telescope entrance apertures and the fabrication of the necessary large membrane optics. Analyses are presented to indicate how a broadband, highly transmissive diffractive / refractive membrane lens can be developed and fabricated, and potential applications in defense and astronomy are briefly discussed.

  14. Large Aperture, Scanning, L-Band SAR

    NASA Technical Reports Server (NTRS)

    Moussessian, Alina; DelCastillo, Linda; Bach, Vinh; Grando, Maurio; Quijano, Ubaldo; Smith, Phil; Zawadzki, Mark

    2011-01-01

    We have developed the first L-band membrane-based active phased array. The antenna is a 16x16 element patch array with dimensions of 2.3mx2.6m. The array uses membrane-compatible Transmit/Receive (T/R) modules for electronic beam steering. We will discuss the antenna design, the fabrication of this large array, the T/R module development, the signal distribution approach and the measured results of the array

  15. ADVANCED TECHNOLOGY LARGE-APERTURE SPACE TELESCOPE (ATLAST)

    E-print Network

    Sirianni, Marco

    = Northrop Grumman Aerospace Systems 8 = Jet Propulsion Laboratory, California Institute of Technology 9ADVANCED TECHNOLOGY LARGE-APERTURE SPACE TELESCOPE (ATLAST): A TECHNOLOGY ROADMAP FOR THE NEXT Aerospace & Technologies Corp. 2 = Marshall Space Flight Center 3 = Goddard Space Flight Center 4 = Space

  16. Scanning measurement system of transmissivity for large aperture optic components

    NASA Astrophysics Data System (ADS)

    Yang, Yi; Yuan, Quan; Shi, Zhendong; Ren, Huan; Ma, Yu-rong; Li, Gao-ping

    2014-09-01

    A scanning measurement system is constructed to measure the transmissivity of each site in large aperture optic components. This system enlarges the beam diameter of light source, and uses a computer-controlled scanning system to measure the transmissivity of optics. The experiments show that the testing accuracy and repeatability of this system both are better than 0.1%.

  17. Sensitivity of synthetic aperture laser optical feedback imaging

    E-print Network

    Glastre, Wilfried; Jacquin, Olivier; Hugon, Olivier; De Chatellus, Hugues Guillet

    2012-01-01

    In this paper we compare the sensitivity of two imaging configurations both based on Laser Optical Feedback Imaging (LOFI). The first one is direct imaging, which uses conventional optical focalisation on target and the second one is made by Synthetic Aperture (SA) Laser, which uses numerical focalisation. We show that SA configuration allows to obtain good resolutions with high working distance and that the drawback of SA imagery is that it has a worse photometric balance in comparison to conventional microscope. This drawback is partially compensated by the important sensitivity of LOFI. Another interest of SA relies on the capacity of getting a 3D information in a single x-y scan.

  18. Laser guide star projection for large telescopes Erez N. Ribak

    E-print Network

    Ribak, Erez

    beam diameter is set by the turbulence distorting the beam going up. Most systems use the light is large, then even for 8 m telescopes and side-mounted laser launchers, the opposite side of the aperture

  19. A 10 cm aperture, high quality TEA CO2 laser

    NASA Astrophysics Data System (ADS)

    Ernst, G. J.

    1982-12-01

    Construction characteristics and performance of a 10 cm aperture, corona-type preionized CO2 laser which features a self-sustained discharge are reported. A mixture of CO2:N2:He gas at a ratio of 1:1:7 yielded an output of 34 J/1. An output of 40 J/1 was obtained with a 1:1:10 mixture ratio, with an overall efficiency of 18%. The system displayed a low self-inductance, thereby giving a high small-signal gain, a homogeneous discharge, and good shot-to-shot reproducibility. A low initial electron density level was indicated by the presence of a several hundreds nanoseconds delay in the current and voltage of the system after the preionization peak. The TEA CO2 laser is noted to have applications in plasma heating and other high-energy laser operations.

  20. The high power large aperture radar method for meteor observations

    NASA Astrophysics Data System (ADS)

    Pellinen-Wannberg, Asta

    2001-11-01

    The high power large aperture (HPLA) radar meteor method is presented. It is compared to the classical meteor radar method in terms of working frequency ranges, beam widths and power densities at meteor altitudes to show the basic differences. The classical meteor radars are sensitive to perpendicular meteor trails. The large aperture radars, with higher working frequencies and higher transmitted power, observe the meteoroid-atmosphere interaction at all look-angles. Due to the narrow beams, these radars mainly observe the population of numerous very small sporadic background particles. Almost no shower-related increase in fluxes has been observed in the EISCAT Geminid, Perseid and Leonid observations. Simultaneously with the meteor mode, the HPLA radars can operate in their usual incoherent scatter modes to observe the electron density variations in the background ionosphere. Thus evolution of sporadic E layers, their average ion composition and their relation to meteor activity can be monitored.

  1. The URAGAN wide-aperture large-area muon hodoscope

    Microsoft Academic Search

    N. S. Barbashina; R. P. Kokoulin; K. G. Kompaniets; G. Mannocchi; A. A. Petrukhin; O. Saavedra; D. A. Timashkov; G. Trinchero; D. V. Chernov; V. V. Shutenko; I. I. Yashin

    2008-01-01

    The URAGAN wide-aperture large-area multilayer muon hodoscope is developed for the NEVOD experimental complex of the Moscow\\u000a Engineering Physics Institute. The hodoscope will be used to study atmospheric and heliospheric processes responsible for\\u000a variations in the muon flux at the Earths surface. The structures of the detector and its system of data acquisition and\\u000a processing are described. The data obtained

  2. Laser aperture diagnostics system for gain and wavefront measurements on NIF/LMJ amplifiers

    SciTech Connect

    Zapata, L. E., LLNL

    1996-12-17

    We are in the midst of constructing an amplifier laboratory (Arnplab) that will be the physics and engineering proving ground for fill sized segmented glass amplifiers of designs that will outfit the National Ignition Facility (NIF) and Laser Megajoule (LMJ) projects. Amplab will demonstrate the cornerstone mechanical, electrical and optical concepts that support the NW and LMJ amplifier schemes. Here we address the optical diagnostics that will be used to characterize optical performance of the amplifiers. We describe, the apparatus that will be used in pulsed measurements of gain distribution and wave-front distortions. The large aperture diagnostic system or LADS, is now being built through a collaborative effort between CEL-V and LLNL. The LADS will provide measurements of gain and wave front distortions over the fill extracting aperture of the NIF and LMJ prototype amplifiers. The LADS will be able to address each of eight apertures via motorized stages and following semi-automated alignment, take data on the aperture of interest. The LADS should be operational in mid-1997 at LLNL and will be used to characterize the optical performance of the very first fill scale prototype 4 x 2 NIF and LMJ amplifiers. It will be transported to Bordeaux, France to make similar measurements during activation of the first 8-aperture LMJ-like facility (LIL) that is planned to start in the near future.

  3. Bridgman growth of large-aperture yttrium calcium oxyborate crystal

    SciTech Connect

    Wu, Anhua, E-mail: wuanhua@mail.sic.ac.cn [Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China)] [Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China); Jiang, Linwen; Qian, Guoxing; Zheng, Yanqing; Xu, Jun; Shi, Erwei [Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China)] [Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China)

    2012-09-15

    Highlights: ? YCOB is a novel non-linear optical crystal possessing good thermal, mechanical and nonlinear optical properties. ? Large size crystal growth is key technology question for YCOB crystal. ? YCOB crystals 3 in. in diameter were grown with modified vertical Bridgman method. ? It is a more effective growth method to obtain large size and high quality YCOB crystal. -- Abstract: Large-aperture yttrium calcium oxyborate YCa{sub 4}O(BO{sub 3}){sub 3} (YCOB) crystals with 3 in. in diameter were grown with modified vertical Bridgman method, and the large crystal plate (63 mm 68 mm 20 mm) was harvested for high-average power frequency conversion system. The crack, facet growth and spiral growth can be effectively controlled in the as-grown crystal, and Bridgman method displays more effective in obtain large size and high quality YCOB crystal plate than Czochralski technique.

  4. Imprinting continuously varying topographical structure onto large-aperture optical surfaces using magnetorheological finishing

    SciTech Connect

    Menapace, J A; Davis, P J; Dixit, S; Campbell, J H; Golini, D; Hachkowski, M R; Nelson, A

    2007-03-07

    Over the past four years we have advanced Magnetorheological Finishing (MRF) techniques and tools to imprint complex continuously varying topographical structures onto large-aperture (430 x 430 mm) optical surfaces. These optics, known as continuous phase plates (CPPs), are important for high-power laser applications requiring precise manipulation and control of beam-shape, energy distribution, and wavefront profile. MRF's unique deterministic-sub-aperture polishing characteristics make it possible to imprint complex topographical information onto optical surfaces at spatial scale-lengths approaching 1 mm and surface peak-to-valleys as high as 22 {micro}m. During this discussion, we will present the evolution of the MRF imprinting technology and the MRF tools designed to manufacture large-aperture 430 x 430 mm CPPs. Our results will show how the MRF removal function impacts and limits imprint fidelity and what must be done to arrive at a high-quality surface. We also present several examples of this imprinting technology for fabrication of phase correction plates and CPPs for use in high-power laser applications.

  5. The COronal Solar Magnetism Observatory (COSMO) Large Aperture Coronagraph

    NASA Astrophysics Data System (ADS)

    Tomczyk, Steve; Gallagher, Dennis; Wu, Zhen; Zhang, Haiying; Nelson, Pete; Burkepile, Joan; Kolinksi, Don; Sutherland, Lee

    2013-04-01

    The COSMO is a facility dedicated to observing coronal and chromospheric magnetic fields. It will be located on a mountaintop in the Hawaiian Islands and will replace the current Mauna Loa Solar Observatory (MLSO). COSMO will provide unique observations of the global coronal magnetic fields and its environment to enhance the value of data collected by other observatories on the ground (e.g. SOLIS, BBO NST, Gregor, ATST, EST, Chinese Giant Solar Telescope, NLST, FASR) and in space (e.g. SDO, Hinode, SOHO, GOES, STEREO, Solar-C, Solar Probe+, Solar Orbiter). COSMO will employ a fleet of instruments to cover many aspects of measuring magnetic fields in the solar atmosphere. The dynamics and energy flow in the corona are dominated by magnetic fields. To understand the formation of CMEs, their relation to other forms of solar activity, and their progression out into the solar wind requires measurements of coronal magnetic fields. The large aperture coronagraph, the Chromospheric and Prominence Magnetometer and the K-Coronagraph form the COSMO instrument suite to measure magnetic fields and the polarization brightness of the low corona used to infer electron density. The large aperture coronagraph will employ a 1.5 meter fuse silica singlet lens, birefringent filters, and a spectropolarimeter to cover fields of view of up to 1 degree. It will observe the corona over a wide range of emission lines from 530.3 nm through 1083.0 nm allowing for magnetic field measurements over a wide range of coronal temperatures (e.g. FeXIV at 530.3 nm, Fe X at 637.4 nm, Fe XIII at 1074.7 and 1079.8 nm. These lines are faint and require the very large aperture. NCAR and NSF have provided funding to bring the large aperture coronagraph to a preliminary design review state by the end of 2013. As with all data from Mauna Loa, the data products from COSMO will be available to the community via the Mauna Loa website: http://mlso.hao.ucar.edu

  6. Producing large-aperture metal-ion beams

    SciTech Connect

    Aksenov, A.I.; Bugaev, S.P.; Emel'yanov, V.A.; Erokhin, G.P.; Pankovets, N.G.; Tolopa, A.M.; Chesnokov, S.M.

    1987-12-01

    A description is given of a pulsed source providing large-aperture beams of ions of various metals with pulse lengths of 100-500 ..mu..sec, repetition frequency 10-50 Hz, ion energy 20-150 keV, and beam current of a few amperes. The source is intended for research in implantation metallurgy. A time of 5-15 min is required to provide about 10/sup 17/ ions/cm/sup 3/ over an area of up to 300 cm/sup 2/.

  7. Design of large aperture, low mass vacuum windows

    SciTech Connect

    Leonhardt, W.J.; Mapes, M.

    1993-01-01

    Large vacuum vessels are employed downstream of fixed targets in High Energy Physics experiments to provide a long path for particles to traverse without interacting with air molecules. These vessels generally have a large aperture opening known as a vacuum window which employs a thin membrane to preserve the vacuum environment yet allows the particles to pass through with a minimal effect on them. Several large windows have been built using a composite of Kevlar/Mylar including circular windows to a diameter of 96.5 cm and rectangular windows up to 193 cm x 86 cm. This paper describes the design, fabrication, testing and operating experience with these windows and relates the actual performance to theoretical predictions.

  8. Design of large aperture, low mass vacuum windows

    SciTech Connect

    Leonhardt, W.J.; Mapes, M.

    1993-07-01

    Large vacuum vessels are employed downstream of fixed targets in High Energy Physics experiments to provide a long path for particles to traverse without interacting with air molecules. These vessels generally have a large aperture opening known as a vacuum window which employs a thin membrane to preserve the vacuum environment yet allows the particles to pass through with a minimal effect on them. Several large windows have been built using a composite of Kevlar/Mylar including circular windows to a diameter of 96.5 cm and rectangular windows up to 193 cm x 86 cm. This paper describes the design, fabrication, testing and operating experience with these windows and relates the actual performance to theoretical predictions.

  9. Design of large aperture, low mass vacuum windows

    SciTech Connect

    Mapes, M.; Leonhardt, W.J. (Brookhaven National Laboratory, Upton, New York 11973 (United States))

    1993-07-01

    Large aperture, low mass, thin vacuum windows are required to minimize beam loss in the beam lines of particle accelerators as the products of nuclear collisions move from upstream targets to downstream detectors. This article describes the design, fabrication, testing, and operating experience of a large rectangular vacuum window, 122 cm[times]61 cm, and two circular windows of 91.4 and 96.5 cm diam. These window designs utilize a composite Kevlar 29 fabric and Mylar laminate as a window material with a typical combined thickness of 0.35 mm. Data for several material thicknesses are also presented. The windows are usually designed to withstand a pressure differential of two to three atmospheres to achieve the required factor of safety. These windows are typically used in the medium vacuum range of 10[sup [minus]4] Torr. The equations used to predict the behavior of the window material will also be discussed.

  10. Development of an efficient large-aperture high damage-threshold sol-gel diffraction grating.

    SciTech Connect

    Ashley, Carol S.; Rambo, Patrick K.; Schwarz, Jens; Dunphy, Darren Robert; Branson, Eric D.; Smith, Ian Craig; Johnson, William Arthur; Reed, Scott T.; Cook, Adam W.

    2005-03-01

    In order to develop the next generation of high peak intensity lasers, new grating technology providing higher damage thresholds and large apertures is required. The current assumption is that this technical innovation will be multilayer dielectric gratings, wherein the uppermost layer of a thin film mirror is etched to create the desired binary phase grating. A variant of this is explored with the upper grating layer being a lower density gelatin-based volume phase grating in either sol-gel or dichromated gelatin. One key benefit is the elimination of the etching step.

  11. Analysis of temporal contrast degradation due to wave front deviation in large aperture ultra-short pulse focusing system

    NASA Astrophysics Data System (ADS)

    Zhu, Ping; Xie, Xinglong; Zhu, Jianqiang; Zhu, Haidong; Yang, Qingwei; Kang, Jun; Guo, Ailin; Gao, Qi

    2014-11-01

    In extremely intense laser system used for plasma physics experiments, temporal contrast is an important property of the ultra-short pulse. In this paper, we theoretically study the temporal contrast degradation due to wave front deviation in large aperture ultra-short pulse focusing system. Two-step focusing fast Fourier transform (FFT) algorithm with the coordinate transform based on Fresnel approximation in space domain and Fourier integral transform method in time domain were used to simulate the focusing process spatially and temporally, in which the spatial distribution of ultra-short pulse temporal contrast characteristics at the focal spot is related to the wave front in large aperture off-axis parabolic mirror focusing optical system. Firstly, temporal contrast degradation due to wave front noise with higher spatial frequency is analyzed and appropriate evaluation parameter for large aperture ultra-short pulse focusing system is put forward from the perspective of temporal contrast. Secondly, the influence of wave front distortion with lower spatial frequency on temporal contrast is revealed comparing different degradation characteristics of various aberrations. At last, a method by controlling and optimizing the wave front to prevent temporal contrast degradation in large aperture ultra-short laser system is proposed, which is of great significance for high temporal contrast petawatt laser facilities.

  12. A Future Large-Aperture UVOIR Space Observatory: Study Overview

    NASA Astrophysics Data System (ADS)

    Postman, Marc; Thronson, Harley A.; Feinberg, Lee; Redding, David; Stahl, H. Philip

    2015-01-01

    The scientific drivers for very high angular resolution coupled with very high sensitivity and wavefront stability in the UV and optical wavelength regime have been well established. These include characterization of exoplanets in the habitable zones of solar type stars, probing the physical properties of the circumgalactic medium around z < 2 galaxies, and resolving stellar populations across a broad range of galactic environments. The 2010 NRC Decadal Survey and the 2013 NASA Science Mission Directorate 30-Year Roadmap identified a large-aperture UVOIR observatory as a priority future space mission. Our joint NASA GSFC/JPL/MSFC/STScI team has extended several earlier studies of the technology and engineering requirements needed to design and build a single filled aperture 10-meter class space-based telescope that can enable these ambitious scientific observations. We present here an overview of our new technical work including a brief summary of the reference science drivers as well as in-depth investigations of the viable telescope architectures, the requirements on thermal control and active wavefront control systems, and the range of possible launch configurations.

  13. Large-Aperture Membrane Active Phased-Array Antennas

    NASA Technical Reports Server (NTRS)

    Karasik, Boris; McGrath, William; Leduc, Henry

    2009-01-01

    Large-aperture phased-array microwave antennas supported by membranes are being developed for use in spaceborne interferometric synthetic aperture radar systems. There may also be terrestrial uses for such antennas supported on stationary membranes, large balloons, and blimps. These antennas are expected to have areal mass densities of about 2 kg/sq m, satisfying a need for lightweight alternatives to conventional rigid phased-array antennas, which have typical areal mass densities between 8 and 15 kg/sq m. The differences in areal mass densities translate to substantial differences in total mass in contemplated applications involving aperture areas as large as 400 sq m. A membrane phased-array antenna includes patch antenna elements in a repeating pattern. All previously reported membrane antennas were passive antennas; this is the first active membrane antenna that includes transmitting/receiving (T/R) electronic circuits as integral parts. Other integral parts of the antenna include a network of radio-frequency (RF) feed lines (more specifically, a corporate feed network) and of bias and control lines, all in the form of flexible copper strip conductors on flexible polymeric membranes. Each unit cell of a prototype antenna (see Figure 1) contains a patch antenna element and a compact T/R module that is compatible with flexible membrane circuitry. There are two membrane layers separated by a 12.7-mm air gap. Each membrane layer is made from a commercially available flexible circuit material that, as supplied, comprises a 127-micron-thick polyimide dielectric layer clad on both sides with 17.5-micron-thick copper layers. The copper layers are patterned into RF, bias, and control conductors. The T/R module is located on the back side of the ground plane and is RF-coupled to the patch element via a slot. The T/R module is a hybrid multilayer module assembled and packaged independently and attached to the membrane array. At the time of reporting the information for this article, an 8 16 passive array (not including T/R modules) and a 2 4 active array (including T/R modules) had been demonstrated, and it was planned to fabricate and test larger arrays.

  14. Development of a large aperture Nb3Sn racetrack quadrupolemagnet

    SciTech Connect

    Ferracin, Paolo; Bartlett, Scott E.; Caspi, Shlomo; Dietderich,Daniel R.; Gourlay, Steven A.; Hannaford, Charles R.; Hafalia, AurelioR.; Lietzke, Alan F.; Mattafirri, Sara; McInturff, Alfred D.; Nyman,Mark; Sabbi, Gianluca

    2005-04-14

    The U.S. LHC Accelerator Research Program (LARP), a collaboration between BNL, FNAL, LBNL, and SLAC, has among its major objectives the development of advanced magnet technology for an LHC luminosity upgrade. The LBNL Superconducting Magnet Group supports this program with a broad effort involving design studies, Nb{sub 3}Sn conductor development, mechanical models, and basic prototypes. This paper describes the development of a large aperture Nb{sub 3}Sn racetrack quadrupole magnet using four racetrack coils from the LBNL Subscale Magnet (SM) Program. The magnet provides a gradient of 95 T/m in a 110 mm bore, with a peak field in the conductor of 11.2 T. The coils are prestressed by a mechanical structure based on a pre-tensioned aluminum shell, and axially supported with aluminum rods. The mechanical behavior has been monitored with strain gauges and the magnetic field has been measured. Results of the test are reported and analyzed.

  15. BLAST: The Balloon-Borne Large Aperture Submillimeter Telescope

    NASA Technical Reports Server (NTRS)

    Devlin, Mark; Ade, Peter; Bock, Jamie; Dicker, Simon; Griffin, Matt; Gunderson, Josh; Halpern, Mark; Hargrave, Peter; Hughes, David; Klein, Jeff

    2004-01-01

    BLAST is the Balloon-borne Large-Aperture Sub-millimeter Telescope. It will fly from a Long Duration Balloon (LDB) platform from Antarctica. The telescope design incorporates a 2 m primary mirror with large-format bolometer arrays operating at 250, 350 and 500 microns. By providing the first sensitive large-area (10 sq. deg.) sub-mm surveys at these wavelengths, BLAST will address some of the most important galactic and cosmological questions regarding the formation and evolution of stars, galaxies and clusters. Galactic and extragalactic BLAST surveys will: (1) identify large numbers of high-redshift galaxies; (2) measure photometric redshifts, rest-frame FIR luminosities and star formation rates thereby constraining the evolutionary history of the galaxies that produce the FIR and sub-mm background; (3) measure cold pre-stellar sources associated with the earliest stages of star and planet formation; (4) make high-resolution maps of diffuse galactic emission over a wide range of galactic latitudes. In addition to achieving the above scientific goals, the exciting legacy of the BLAST LDB experiment will be a catalogue of 3000-5000 extragalactic sub-mm sources and a 100 sq. deg. sub-mm galactic plane survey. Multi-frequency follow-up observations from SIRTF, ASTRO-F, and Herschel, together with spectroscopic observations and sub-arcsecond imaging from ALMA are essential to understand the physical nature of the BLAST sources.

  16. Application of Large Aperture Emats to Weld Inspection

    NASA Astrophysics Data System (ADS)

    Maclauchlan, D. T.; Clark, S. P.; Hancock, J. W.

    2008-02-01

    One of the most significant developments in EMAT operation is the incorporation of phased array techniques. Phased array EMATs enable electronic beam steering and focusing while operating with temporally short pulses for good range resolution. Using phased array EMAT operation, multiple high powered pulsers are combined in the generation of the ultrasonic wave and multiple elements are combined in the reception of the ultrasonic wave, for improved sensitivity. EMATs make it practical to operate with shear horizontal (SH) waves and scan over a metal part's surface. An EMAT generated line force at the surface launches shear horizontal waves with uniform amplitude for beam angles from -90 to 90. Shear horizontal waves also reflect without mode conversion from surfaces that are parallel to the polarization of the shear wave displacements. The combination of these advantages makes phased array EMATs well suited for weld inspection. Recently, BWXT Services has developed a 32 active channel EMAT phased array system for operation up to 5 MHz. In addition, each element can be constructed with several sub-elements, alternating in polarity, to effectively multiply the number of active elements for a restricted range of beam angles. For example by using elements comprised of 4 sub elements, a 128 active element aperture designed for operation with a nominal 60 beam angle provides good beam steering and focusing performance for 45 to 70 beam angles. The large active apertures allow the use of highly focused beams for good defect detection and high resolution imaging of weld defects. Application of this system to weld inspections has verified that good defect detection and imaging is possible. In addition, operation with SH waves has proven to provide improved detection of lack of fusion at the cap and root of the weld for certain weld geometries. The system has also been used to demonstrate the inspection of submerged metal arc welds while welding.

  17. A proposed large deployable space structures experiment for high power, large aperture missions in MEO

    Microsoft Academic Search

    James Winter; Greg Spanjers; D. Cohen; A. Adler; G. Ginet; B. Dichter; J. Granata; K. Denoyer; T. Murphey; P. Wegner; L. Underwood; P. Hausgen; D. Senft

    2004-01-01

    The Air Force Research Laboratory (AFRL) Space Vehicles Directorate has developed the deployable structures experiment (DSX) to research the technologies needed for large space structures and apertures, high-power generation, and survivability in the high radiation environment of a medium earth orbit (MEO). The proposed DSX concept is a combination of four research experiments that coupled together provides DoD with: a)

  18. Large- and Small-Aperture Fixed-Point Cells of Cu, Pt C, and Re C

    NASA Astrophysics Data System (ADS)

    Anhalt, Klaus; Wang, Yunfen; Yamada, Yoshiro; Hartmann, Jrgen

    2008-06-01

    Extending the application of metal (carbide) carbon eutectic fixed-point cells to radiometry, e.g., for measurements in irradiance mode, requires fixed-point cells with large apertures. In order to make large-aperture cells more readily usable in furnace systems with smaller furnace tubes commonly used for small-aperture fixed-point cells, a novel cell design was developed. For each of Cu, Pt C, and Re C fixed points, two types of fixed-point cells were manufactured, the small- and large-aperture cell. For Pt C and Re C, the large-aperture cells were filled with a hyper-eutectic metal carbon mixture; for the small cells, a hypo-eutectic mixture was used for filling. For each material, the small and large cells were compared with respect to radiometric differences. Whereas plateau shape and melting temperature are in good agreement for the small- and large-aperture Cu cells, a larger difference was observed between small- and large-aperture cells of Pt C and Re C, respectively. The origin of these observations, attributed to the temperature distribution inside the furnace, ingot contamination during manufacture, and non-uniform ingot formation for the larger cells, is discussed. The comparison of measurements by a radiation thermometer and filter radiometer of the Re C and Pt C large-aperture cells showed large differences that could be explained only by a strong radiance distribution across the cavity bottom. Further investigations are envisaged to clarify the cause.

  19. The Balloon-borne Large Aperture Submillimeter Telescope: BLAST

    E-print Network

    E. Pascale; P. A. R. Ade; J. J. Bock; E. L. Chapin; J. Chung; M. J. Devlin; S Dicker; M. Griffin; J. O. Gundersen; M. Halpern; P. C. Hargrave; D. H. Hughes; J. Klein; C. J. MacTavish; G. Marsden; P. G. Martin; T. G. Martin; P. Mauskopf; C. B. Netterfield; L. Olmi; G. Patanchon; M. Rex; D. Scott; C. Semisch; N. Thomas; M. D. P. Truch; C. Tucker; G. S. Tucker; M. P. Viero; D. V. Wiebe

    2008-03-27

    The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) is a sub-orbital surveying experiment designed to study the evolutionary history and processes of star formation in local galaxies (including the Milky Way) and galaxies at cosmological distances. The BLAST continuum camera, which consists of 270 detectors distributed between 3 arrays, observes simultaneously in broad-band (30%) spectral-windows at 250, 350, and 500 microns. The optical design is based on a 2m diameter telescope, providing a diffraction-limited resolution of 30" at 250 microns. The gondola pointing system enables raster mapping of arbitrary geometry, with a repeatable positional accuracy of ~30"; post-flight pointing reconstruction to ~5" rms is achieved. The on-board telescope control software permits autonomous execution of a pre-selected set of maps, with the option of manual override. In this paper we describe the primary characteristics and measured in-flight performance of BLAST. BLAST performed a test-flight in 2003 and has since made two scientifically productive long-duration balloon flights: a 100-hour flight from ESRANGE (Kiruna), Sweden to Victoria Island, northern Canada in June 2005; and a 250-hour, circumpolar-flight from McMurdo Station, Antarctica, in December 2006.

  20. Low mass large aperture vacuum window development at CEBAF

    SciTech Connect

    Keppel, C.

    1995-04-01

    Large aperture low mass vacuum windows are being developed for the HMS (High Momentum Spectrometer) and SOS (Short Orbit Spectrometer) spectrometers in Hall C at CEBAF. Because multiple scattering degrades the performance of a spectrometer it is important that the volume be evacuated and that the entrance and exit windows be as low mass as possible. The material used for such windows must be thin and light enough so as to have minimum effect of the beam, and at the same time, be thick and strong enough to operate reliably and safely. To achieve these goals, composite vacuum windows have been constructed of a thin sheet of Mylar with a reinforcing fabric. Reinforcing fabrics such as Kevlar and Spectra are available with tensile strengths significantly greater than that of Mylar. A thin layer of Myler remains necessary since the fabrics cannot achieve any sort of vacuum seal. The design, fabrication, testing, and operating experience with such composite windows for the Hall C spectrometers will be discussed.

  1. Active Optics for a 16-Meter Advanced Technology Large Aperture Space Telescope

    E-print Network

    Sirianni, Marco

    preliminary architecture builds on technologies from the James Webb Space Telescope (JWST), the SpaceActive Optics for a 16-Meter Advanced Technology Large Aperture Space Telescope David C. Redding-optics Advanced Technology Large Aperture Space Telescope, to be launched by the Ares V Heavy Lift Vehicle

  2. Large field-of-view synthetic aperture holography using rotation stages

    NASA Astrophysics Data System (ADS)

    Kim, Sungmin; Im, Yeonsu; Hahn, Joonku

    2014-02-01

    In general, digital holography means a technology to measure an object wave by using a focal plane array (FPA) sensor. Since the limitation of the dimension of the FPA sensor, the field of view obtained by the FPA sensor is usually very narrow. Many methods have been proposed to increase the field of view of measurement. One simple solution is the synthesis of the holograms with small apertures, where each of them is measured by the FPA sensor respectively. If we imagine specific applications such as 360-degree table-top digital holographic display, the large field of view of the object is required to present the three-dimensional contents to the observer who may change his position dynamically. In this paper, we use two-axis rotation stage for acquisition of the object wave with large field of view. In our system, the optics including a laser and a CCD sensor are fixed and the object is mounted on the rotation stage. During the rotation of the object, the holograms are taken sequentially and the object wave over the hemispherical surface in k-space is obtained. The increase of solid angle of the measured hologram means the increase of acquired angular spectrum of interested objects. The resolution of the measurement is closely related with the numerical aperture and the data with fine resolution is expectable. But since it is not easy to match the relative phases of the each hologram, unfortunately the enhancement of the resolution in the reconstructed object wave is negligible.

  3. Improved design of support for large aperture space lightweight mirror

    NASA Astrophysics Data System (ADS)

    Wang, Chao; Ruan, Ping; Liu, Qimin

    2013-08-01

    In order to design a kind of rational large aperture space mirror which can adapt to the space gravity and thermal environment, by taking the choice of material, the lightweight of the mirror and the design of support into account in detail, a double-deck structure with traditional flexible hinge was designed, then the analytical mathematical model of the mirror system was established. The design adopts six supports on back. in order to avoid the constraints, mirror is connected to three middle transition pieces through six flexible hinges, and then the three transition pieces are connected to support plate through another three flexible hinges. However, the initial structure is unable to reach the expected design target and needs to be made further adjustments. By improving and optimizing the original structure, a new type of flexible hinge in the shape of the letter A is designed finally. Compared with the traditional flexible hinge structure, the new structure is simpler and has less influence on the surface figure accuracy of mirror. By using the finite element analysis method, the static and dynamic characteristics as well as the thermal characteristics of the mirror system are analyzed. Analysis results show that the maximum PV value is 37 nm and the maximum RMS value is 10.4 nm when gravity load is applied. Furthermore, the maximum PV value is 46 nm and the maximum RMS value is 10.5 nm under the load case of gravity coupled with 4? uniform temperature rise. The results satisfy the index of optical design. The first order natural frequency of the mirror component is 130 Hz according to the conclusion obtained by modal analytical solution, so the mirror structure has high enough fundamental frequency. And, the structural strength can meet the demand under the overload and the random vibration environment respectively. It indicates that the mirror component structure has enough dynamic, static stiffness and thermal stability, meeting the design requirements.

  4. Time dependence of Fresnel diffraction of ultrashort laser pulses by a circular aperture.

    PubMed

    Jiang, Z; Jacquemin, R; Eberhardt, W

    1997-07-01

    We report on the time dependences of the Fresnel diffraction of ultrashort laser pulses by a circular aperture. The diffraction leads to a pulse delay, time shape change, pulse broadening, and peak power decrease. These effects may have to be taken into account whenever critical thresholds are encountered as, for example, in nonlinear optics or laser fusion. PMID:18259222

  5. In-situ monitoring of surface post-processing in large aperture fused silica optics with Optical Coherence Tomography

    SciTech Connect

    Guss, G M; Bass, I l; Hackel, R P; Mailhiot, C; Demos, S G

    2008-02-08

    Optical Coherence Tomography is explored as a method to image laser-damage sites located on the surface of large aperture fused silica optics during post-processing via CO{sub 2} laser ablation. The signal analysis for image acquisition was adapted to meet the sensitivity requirements for this application. A long-working distance geometry was employed to allow imaging through the opposite surface of the 5-cm thick optic. The experimental results demonstrate the potential of OCT for remote monitoring of transparent material processing applications.

  6. Experimental instrumentation system for the Phased Array Mirror Extendible Large Aperture (PAMELA) test program

    NASA Technical Reports Server (NTRS)

    Boykin, William H., Jr.

    1993-01-01

    Adaptive optics are used in telescopes for both viewing objects with minimum distortion and for transmitting laser beams with minimum beam divergence and dance. In order to test concepts on a smaller scale, NASA MSFC is in the process of setting up an adaptive optics test facility with precision (fraction of wavelengths) measurement equipment. The initial system under test is the adaptive optical telescope called PAMELA (Phased Array Mirror Extendible Large Aperture). Goals of this test are: assessment of test hardware specifications for PAMELA application and the determination of the sensitivities of instruments for measuring PAMELA (and other adaptive optical telescopes) imperfections; evaluation of the PAMELA system integration effort and test progress and recommended actions to enhance these activities; and development of concepts and prototypes of experimental apparatuses for PAMELA.

  7. Large-aperture refractive lenses for momentum-resolved spectroscopy with hard X-rays.

    PubMed

    Fukui, Hiroshi; Simon, Markus; Nazmov, Vladimir; Mohr, Jrgen; Evans-Lutterodt, Kenneth; Stein, Aaron; Baron, Alfred Q R

    2013-07-01

    One-dimensional kinoform and prism refractive lenses with large aperture and high transmittance at 22 keV have been investigated. A 12.0 m focus size (full width at half-maximum) and an effective aperture of 0.85 mm, at a focal length of 705 mm and 21.747 keV, were achieved. PMID:23765301

  8. Large-aperture refractive lenses for momentum-resolved spectroscopy with hard X-rays

    PubMed Central

    Fukui, Hiroshi; Simon, Markus; Nazmov, Vladimir; Mohr, Jrgen; Evans-Lutterodt, Kenneth; Stein, Aaron; Baron, Alfred Q. R.

    2013-01-01

    One-dimensional kinoform and prism refractive lenses with large aperture and high transmittance at 22?keV have been investigated. A 12.0?m focus size (full width at half-maximum) and an effective aperture of 0.85?mm, at a focal length of 705?mm and 21.747?keV, were achieved. PMID:23765301

  9. Fabrication and test of a concave oblate ellipsoid with large relative aperture

    Microsoft Academic Search

    Ke-Xin Li; Li-Yin Yuan; Pei-Ming Hao

    2010-01-01

    Fabrication and test of the concave oblate ellipsoid becomes more difficult as the mirror relative aperture gets larger. The concave oblate ellipsoid discussed in this paper, has a very large relative aperture. Two processing methods are introduced. One is drilling sub-mirror from the mother mirror, the other is processing sub-mirror merely. A novel method to calculate aspheric grinding amount of

  10. Time-gated ballistic imaging using a large aperture switching beam.

    PubMed

    Mathieu, Florian; Reddemann, Manuel A; Palmer, Johannes; Kneer, Reinhold

    2014-03-24

    Ballistic imaging commonly denotes the formation of line-of-sight shadowgraphs through turbid media by suppression of multiply scattered photons. The technique relies on a femtosecond laser acting as light source for the images and as switch for an optical Kerr gate that separates ballistic photons from multiply scattered ones. The achievable image resolution is one major limitation for the investigation of small objects. In this study, practical influences on the optical Kerr gate and image quality are discussed theoretically and experimentally applying a switching beam with large aperture (D = 19 mm). It is shown how switching pulse energy and synchronization of switching and imaging pulse in the Kerr cell influence the gate's transmission. Image quality of ballistic imaging and standard shadowgraphy is evaluated and compared, showing that the present ballistic imaging setup is advantageous for optical densities in the range of 8 < OD < 13. Owing to the spatial transmission characteristics of the optical Kerr gate, a rectangular aperture stop is formed, which leads to different resolution limits for vertical and horizontal structures in the object. Furthermore, it is reported how to convert the ballistic imaging setup into a schlieren-type system with an optical schlieren edge. PMID:24664055

  11. Characterisation of a large aperture steep concave parabolic mirror using SASI based on auto-collimation theory

    NASA Astrophysics Data System (ADS)

    Liu, Bingcai; Li, Bing; Tian, Ailing; Yang, Haoyu; Gao, Fen; Chen, Lei

    2015-01-01

    To characterise a large aperture steep concave parabolic mirror, a new sub-aperture stitching interferometry measurement technology (SASI) based on auto-collimation is proposed. The principle of the stitching process is analysed, and the sub-aperture partitioning for a full aperture of a paraboloid is discussed. Next, the overlapped sampled points between sub-apertures are rectified through sampled points realigned in mesh grids. Finally, two experiments, the SASI based on auto-collimation and the full aperture test, were implemented for a parabolic mirror. The stitching result exhibits good agreement with the full-aperture result.

  12. CAMERA: a compact, automated, laser adaptive optics system for small aperture telescopes

    NASA Astrophysics Data System (ADS)

    Britton, Matthew; Velur, Viswa; Law, Nick; Choi, Philip; Penprase, Bryan E.

    2008-07-01

    CAMERA is an autonomous laser guide star adaptive optics system designed for small aperture telescopes. This system is intended to be mounted permanently on such a telescope to provide large amounts of flexibly scheduled observing time, delivering high angular resolution imagery in the visible and near infrared. The design employs a Shack Hartmann wavefront sensor, a 12x12 actuator MEMS device for high order wavefront compensation, and a solid state 355nm ND:YAG laser to generate a guide star. Commercial CCD and InGaAs detectors provide coverage in the visible and near infrared. CAMERA operates by selecting targets from a queue populated by users and executing these observations autonomously. This robotic system is targeted towards applications that are diffcult to address using classical observing strategies: surveys of very large target lists, recurrently scheduled observations, and rapid response followup of transient objects. This system has been designed and costed, and a lab testbed has been developed to evaluate key components and validate autonomous operations.

  13. Theoretical model to suppress parasitic lasing in large-aperture Ti:sapphire amplifiers using a temporal dual-pulse pump

    NASA Astrophysics Data System (ADS)

    Chu, Yuxi; Liang, Xiaoyan; Yu, Lianghong; Xu, Lu; Li, Ruxin; Xu, Zhizhan

    2014-05-01

    Transverse parasitic lasing (PL) in large-aperture Ti:sapphire (Ti:S) crystals is a critical factor that limits the energy achievable with the chirped-pulse amplification (CPA) technique. We propose a method to suppress PL effects in large-aperture Ti:S amplifiers by using a temporal dual-pulse pump. Theoretical simulations based on the experimental parameters in 2.0 PW Ti:S laser system are performed to predict the transverse gain as a function of pumping time and output energy. By optimizing the temporal profile of the pump beam as well as the time delay between the input seed and pump pulses, we can minimize PL effects in Ti:S crystals. This method is applicable to larger-aperture Ti:S crystals pumped at higher pump fluence and energy, and is potential to develop a ~10 PW laser system.

  14. Experimental demonstration of a self-tracking 16aperture receiver telescope array for laser intersatellite communications

    Microsoft Academic Search

    Andras Kalmar; Klaus H. Kudielka; Walter R. Leeb

    1998-01-01

    An adaptive receive telescope array with 16 apertures has been designed and breadboarded. With respect to size and performance, such a telescope array is well suited for use as receive antenna in a coherent interorbit laser link. The laboratory demonstrator, designed to operate at a wavelength of (lambda) equals 1.064 micrometers, is completely independent of any subsequent receiver and of

  15. Compensation of beamlet repulsion in a large negative ion source with a multi aperture accelerator

    SciTech Connect

    Kashiwagi, M.; Inoue, T.; Hanada, M.; Kamada, M.; Taniguchi, M.; Umeda, N.; Watanabe, K. [Japan Atomic Energy Agency, 801-1, Nukoyama, Naka, 311-0193 (Japan); Grisham, L. R. [Princeton University, Plasma Physics Laboratory, Princeton (United States)

    2009-03-12

    Excess heat loads to accelerator grids limit extension of pulse length in operation of the large negative ion sources with multi aperture accelerator. Part of the heat loads is caused by interception of deflected beamlets due to their space charge repulsion. In this paper, a beamlet steering technique using aperture offset was examined for compensation of the beamlet deflections utilizing a three dimensional beam analysis simulating the D{sup -} negative ion source of JT-60 U. The beamlet deflection was analyzed in detail using fifty beamlets, which were extracted from apertures arranged in a lattice pattern of 10x5. The simulation showed successful compensation of the beamlet deflection by aperture offsets defined according to the thin lens theory. Even if the beam energy was changed, the necessary aperture offset would not be changed maintaining the perveance and a ratio of extraction and acceleration voltage. In JT-60 U, it was shown that the aperture offset of less than 1.0 mm would be enough to compensate the repulsion of all beamlets. When the magnetic field was applied for suppression of co-extracted electrons, necessary aperture offset was estimated to be {+-}0.5 mm for 500 keV D{sup -} ion beam in JT-60 U, in addition to the offset for the space charge repulsion. This result showed good agreements with the previous experimental results and design study of the JT-60 U N-NBI.

  16. Compensation of beamlet repulsion in a large negative ion source with a multi aperture accelerator

    NASA Astrophysics Data System (ADS)

    Kashiwagi, M.; Inoue, T.; Grisham, L. R.; Hanada, M.; Kamada, M.; Taniguchi, M.; Umeda, N.; Watanabe, K.

    2009-03-01

    Excess heat loads to accelerator grids limit extension of pulse length in operation of the large negative ion sources with multi aperture accelerator. Part of the heat loads is caused by interception of deflected beamlets due to their space charge repulsion. In this paper, a beamlet steering technique using aperture offset was examined for compensation of the beamlet deflections utilizing a three dimensional beam analysis simulating the D? negative ion source of JT-60 U. The beamlet deflection was analyzed in detail using fifty beamlets, which were extracted from apertures arranged in a lattice pattern of 105. The simulation showed successful compensation of the beamlet deflection by aperture offsets defined according to the thin lens theory. Even if the beam energy was changed, the necessary aperture offset would not be changed maintaining the perveance and a ratio of extraction and acceleration voltage. In JT-60 U, it was shown that the aperture offset of less than 1.0 mm would be enough to compensate the repulsion of all beamlets. When the magnetic field was applied for suppression of co-extracted electrons, necessary aperture offset was estimated to be 0.5 mm for 500 keV D? ion beam in JT-60 U, in addition to the offset for the space charge repulsion. This result showed good agreements with the previous experimental results and design study of the JT-60 U N-NBI.

  17. Transverse-mode control in vertical-cavity surface-emitting lasers via a patterned phase aperture.

    PubMed

    Achtenhagen, M; Hardy, A; Kapon, E

    2006-12-10

    Transverse-mode discrimination in vertical-cavity surface-emitting lasers that contain a patterned phase aperture is analyzed numerically. The two lowest-order modes are calculated for different aperture shapes and sizes. They are then expanded in Laguerre-Gaussian modes to study the power distribution as well as their beam propagation factor. The mode selection depends on the aperture's size and degree of symmetry. The maximum value for the mode discrimination in the case of a specific phase aperture is determined, and an enhancement by a factor of 3, compared to the case without a phase aperture, is found. PMID:17119600

  18. COMPONENTS OF LASER SYSTEMS: Pumping of the GARPUN wide-aperture excimer laser by counterpropagating electron beams

    NASA Astrophysics Data System (ADS)

    Arlantsev, S. V.; Grigor'yants, E. A.; Vadkovskii, A. D.; Zvorykin, V. D.; Metreveli, G. E.

    1994-03-01

    The transport of high-current electron beams from vacuum diodes to the laser chamber of the GARPUN wide-aperture excimer laser was investigated experimentally and theoretically. The processes involving the transport of fast electrons in argon and krypton in a longitudinal magnetic field were also studied. Pumping by counter-propagating electron beams resulted in the deposition of up to 2.1 kJ of energy into the active medium of the laser, which corresponded to a specific excitation power of ~0.8 MW cm-3 with an inhomogeneity of less than 20% over a 12 cm 18 cm aperture. The efficiency of the energy deposition by electron beams was ~60% and the overall efficiency of the laser pumping system was ~16%.

  19. Large-aperture, tapered fiber-coupled, 10-kHz particle-image velocimetry.

    PubMed

    Hsu, Paul S; Roy, Sukesh; Jiang, Naibo; Gord, James R

    2013-02-11

    We demonstrate the design and implementation of a fiber-optic beam-delivery system using a large-aperture, tapered step-index fiber for high-speed particle-image velocimetry (PIV) in turbulent combustion flows. The tapered fiber in conjunction with a diffractive-optical-element (DOE) fiber-optic coupler significantly increases the damage threshold of the fiber, enabling fiber-optic beam delivery of sufficient nanosecond, 532-nm, laser pulse energy for high-speed PIV measurements. The fiber successfully transmits 1-kHz and 10-kHz laser pulses with energies of 5.3 mJ and 2 mJ, respectively, for more than 25 min without any indication of damage. It is experimentally demonstrated that the tapered fiber possesses the high coupling efficiency (~80%) and moderate beam quality for PIV. Additionally, the nearly uniform output-beam profile exiting the fiber is ideal for PIV applications. Comparative PIV measurements are made using a conventionally (bulk-optic) delivered light sheet, and a similar order of measurement accuracy is obtained with and without fiber coupling. Effective use of fiber-coupled, 10-kHz PIV is demonstrated for instantaneous 2D velocity-field measurements in turbulent reacting flows. Proof-of-concept measurements show significant promise for the performance of fiber-coupled, high-speed PIV using a tapered optical fiber in harsh laser-diagnostic environments such as those encountered in gas-turbine test beds and the cylinder of a combustion engine. PMID:23481818

  20. Laser fabrication of micron-size apertures for electron beam microcolumns

    NASA Astrophysics Data System (ADS)

    Ahn, S. J.; Kim, D. W.; Kim, H. S.; Cho, K. H.; Choi, S. S.

    For electron beam nanolithography and scanning electron microscopy applications, an electrostatic electron lens system called a microcolumn must be assembled. In order to reduce aberrations, laser drilling of the assembled microcolumn system should be highly beneficial. We have drilled micron-size apertures on silicon substrates including molybdenum and tantalum using a 1.064 ?m Nd:YAG laser. In this work, a layer-by-layer evaporation technique using multiple pulse treatment (MPT) is employed in order to minimize melting of the crater wall and maximize the evaporation of the bottom layer of the crater. The machining conditions of an Nd:YAG laser pulsed in the TEM00 mode for ceramic, silicon, and molybdenum diaphragms are optimized. We obtain micron-size apertures for electron beam microcolumn applications such as electron lenses.

  1. Large aperture deformable mirror with a transferred single-crystal silicon membrane actuated using large-stroke PZT Unimorph Actuators

    NASA Technical Reports Server (NTRS)

    Hishinumat, Yoshikazu; Yang, Eui - Hyeok (EH)

    2005-01-01

    We have demonstrated a large aperture (50 mm x 50 mm) continuous membrane deformable mirror (DM) with a large-stroke piezoelectric unimorph actuator array. The DM consists of a continuous, large aperture, silicon membrane 'transferred' in its entirety onto a 20 x 20 piezoelectric unimorph actuator array. A PZT unimorph actuator, 2.5 mm in diameter with optimized PZT/Si thickness and design showed a deflection of 5.7 [m at 20V. An assembled DM showed an operating frequency bandwidth of 30 kHz and influence function of approximately 30%.

  2. The measurement and analysis of wavefront structure from large aperture ICF optics

    SciTech Connect

    Wolfe, C.R.; Lawson, J.K.

    1995-05-30

    This paper discusses the techniques, developed over the past year, for high spatial resolution measurement and analysis of the transmitted and/or reflected wavefront of large aperture ICF optical components. Parts up to 400 mm {times} 750 mm have been measured and include: laser slabs, windows, KDP crystals and lenses. The measurements were performed using state-of-the-art commercial phase shifting interferometers at a wavelength of 633 {mu}m. Both 1 and 2-D Fourier analysis have been used to characterize the wavefront; specifically the Power Spectral Density, (PSD), function was calculated. The PSDs of several precision optical components will be shown. The PSD(V) is proportional to the (amplitude){sup 2} of components of the Fourier frequency spectrum. The PSD describes the scattered intensity and direction as a function of scattering angle in the wavefront. The capability of commercial software is limited to 1-D Fourier analysis only. We are developing our own 2-D analysis capability in support of work to revise specifications for NIF optics. 2-D analysis uses the entire wavefront phase map to construct 2D PSD functions. We have been able to increase the signal-to-noise relative to 1-D and can observe very subtle wavefront structure.

  3. Distributed aperture effect in laser rods with negative lenses A discussion

    NASA Astrophysics Data System (ADS)

    Shie, C.-D.; Peng, K.-S.

    1980-01-01

    The difference between a ray transfer matrix in a lenslike medium and a section of lenslike medium immersed in vacuum is demonstrated. The distributed aperture and useful volume are calculated for a laser rod with negative lenses ground on the ends, using a multiplication of ray transfer matrices and the deductive method used by Barnes and Scalise. The results we obtained are different from their results.

  4. A large single-aperture telescope for submillimeter astronomy

    Microsoft Academic Search

    Wayne Holland; Rob Ivison; William Dent; Eli Atad; Ian Robson; Andy Longmore; Tim Hawarden; Jane Greaves; James Dunlop; Derek Ward-Thompson; Wolfgang Wild

    2006-01-01

    The large submillimeter telescope (LST) is a proposed wide-field, 30m-class telescope operating from a ground-based site in the relatively unexplored 0.2 - 1mm waveband. The telescope will be equipped with imaging and spectroscopic instrumentation to allow astronomers to probe the earliest evolutionary stages of galaxies, stars and planets. It is intended to operate the telescope in the 200mum atmospheric window,

  5. Radiometer design concepts for large aperture microwave radiometer spacecraft

    NASA Technical Reports Server (NTRS)

    Keafer, L. S., Jr.

    1981-01-01

    Concepts involving active and passive microwave systems for soil-moisture monitoring are discussed. It is shown that the first major development efforts should be directed toward the simpler passive design concepts. Subsequently, five passive design concepts for a microwave radiometer spacecraft are outlined and compared. Some common technology needs, such as large space structures and controls, are shown to exist. Also, some peculiar technology needs are identified, such as complicated phasing networks, dielectric lenses, tapered illumination, and reflector-surface irregularity and distortion control techniques. More detailed studies to address these design concepts and assess the associated technology needs are recommended.

  6. Performance predictions for spaceborne, long-lifetime helium dewars containing large-aperture telescopes

    NASA Technical Reports Server (NTRS)

    Hopkins, Richard A.; Nieczkoski, Stephen J.; Volz, Stephen M.

    1990-01-01

    The evolution of design approaches for high-performance superfluid helium dewars containing large-aperture telescopes are discussed. Particular attention is given to thermal-math modeling for the IRAS and the Cosmic Background Explorer (COBE) dewars. Correlation of the recent COBE flight data with the dewar thermal-math model is presented, and apparent predictive deficiencies of the model are discussed.

  7. ATLAST-9.2: A Deployable Large Aperture UVOIR Space Telescope

    Microsoft Academic Search

    William R. Oegerle; L. Feinberg; L. Purves; T. Hyde; H. Thronson; J. Townsend; M. Postman; M. Bolcar; J. Budinoff; B. Dean; M. Clampin; D. Ebbets; Q. Gong; T. Gull; J. Howard; A. Jones; R. Lyon; B. Pasquale; C. Perrygo; S. Smith; P. Thompson; B. Woodgate

    2010-01-01

    We present the results of a study of a deployable version of the Advanced Technology Large Aperture Space Telescope (ATLAST) that could be launched on an Evolved Expendable Launch Vehicle (EELV). ATLAST is a concept for a next-generation UVOIR observatory to follow HST and JWST. The observatory retains significant heritage from JWST, thereby taking advantage of technologies and engineering already

  8. On-board phase and modulus calibration of large aperture synthesis radiometers: study applied to MIRAS

    Microsoft Academic Search

    F. Torres; A. Camps; J. Bara; I. Corbella; R. Ferrero

    1996-01-01

    On-board calibration of bidimensional aperture synthesis radiometers with a large number of antennas by the standard correlated noise injection method is technologically very critical because of the stringent requirements on mass, volume, and phase equalization of the noise distribution network. A novel approach, which makes use of a set of uncorrelated noise sources uniformly distributed in the array, is proposed.

  9. A 16-m Telescope for the Advanced Technology Large Aperture Telescope (ATLAST) Mission

    E-print Network

    Sirianni, Marco

    Abstract The segmented mirror and deployable optics technologies developed for the James Webb Space Telescope enable a 6A 16-m Telescope for the Advanced Technology Large Aperture Telescope (ATLAST) Mission Charles F Study Team Mission Concept Our ATLAST 16-meter telescope Mission Concept will utilize the capabilities

  10. A Large Aperture Infrasound Array for Interferometric Studies Julius T. Fricke1

    E-print Network

    Evers, Lslo G.

    A Large Aperture Infrasound Array for Interferometric Studies Julius T. Fricke1 , Elmer N. Ruigrok 2 , Lslo G. Evers3 , Kees Wapenaar4 , Dick G. Simons5 The traveltime of infrasound through- lation between infrasound receivers (microbarometers). This method is called interferometry

  11. A novel method of calculating far-field patterns of large aperture antennas

    NASA Technical Reports Server (NTRS)

    Bailey, M. C.

    1986-01-01

    A method is described for calculation of the radiation pattern of large aperture antennas. A piece-wise linear approximation of the aperture field using overlapping pyramidal basis functions allows the radiation pattern of an aperture antenna to be calculated as though it were a two-dimensional array. The calculation of radiation pattern data versus theta and phi, suitable for 3-D or contour plot algorithms, is achieved by locating the array in the yz-plane and performing a summation over the aperture field data sampled on a square grid. A FORTRAN subroutine is provided for performing radiation pattern calculations. Numerical results are included to demonstrate the accuracy and convergence of the method. These numerical results indicate that typical accuracies of + or - 0.1 dB for Directivity, + or - dB for the 1st Sidelobe Level, and + - 2dB for the 2nd Sidelobe Level can be obtained with an aperture grid of 45x45 points and requires approximately 0.02 seconds CPU time per far-field data point on a VAX 11/750 with a floating point accelerator.

  12. Tethered Formation Configurations: Meeting the Scientific Objectives of Large Aperture and Interferometric Science

    NASA Technical Reports Server (NTRS)

    Farley, Rodger E.; Quinn, David A.

    2004-01-01

    With the success of the Hubble Space Telescope, it has become apparent that new frontiers of science and discovery are made every time an improvement in imaging resolution is made. For the HST working primarily in the visible and near-visible spectrum, this meant designing, building and launching a primary mirror approximately three meters in diameter. Conventional thinking tells us that accomplishing a comparable improvement in resolution at longer wavelengths for Earth and Space Science applications requires a corresponding increase in the size of the primary mirror. For wavelengths in the sub-millimeter range, a very large telescope with an effective aperture in excess of one kilometer in diameter would be needed to obtain high quality angular resolution. Realistically a single aperture this large is practically impossible. Fortunately such large apertures can be constructed synthetically. Possibly as few as three 3 - 4 meter diameter mirrors flying in precision formation could be used to collect light at these longer wavelengths permitting not only very large virtual aperture science to be carried out, but high-resolution interferometry as well. To ensure the longest possible mission duration, a system of tethered spacecraft will be needed to mitigate the need for a great deal of propellant. A spin-stabilized, tethered formation will likely meet these requirements. Several configurations have been proposed which possibly meet the needs of the Space Science community. This paper discusses two of them, weighing the relative pros and cons of each concept. The ultimate goal being to settle on a configuration which combines the best features of structure, tethers and formation flying to meet the ambitious requirements necessary to make future large synthetic aperture and interferometric science missions successful.

  13. Tethered Formation Configurations: Meeting the Scientific Objectives of Large Aperture and Interferometric Science

    NASA Technical Reports Server (NTRS)

    Farley, Rodger E.; Quinn, David A.; Brodeur, Stephen J. (Technical Monitor)

    2001-01-01

    With the success of the Hubble Space Telescope, it has become apparent that new frontiers of science and discovery are made every time an improvement in imaging resolution is made. For the HST working primarily in the visible and near-visible spectrum, this meant designing, building, and launching a primary mirror approximately three meters in diameter. Conventional thinking tells us that accomplishing a comparable improvement in resolution at longer wavelengths for Earth and Space Science applications requires a corresponding increase in the size of the primary mirror. For wavelengths in the sub-millimeter range, a very large telescope with an effective aperture in excess of one kilometer in diameter would be needed to obtain high quality angular resolution. Realistically a single aperture this large is practically impossible. Fortunately such large apertures can be constructed synthetically. Possibly as few as three 34 meter diameter mirrors flying in precision formation could be used to collect light at these longer wavelengths permitting not only very large virtual aperture science to be carried out, but high-resolution interferometry as well. To ensure the longest possible mission duration, a system of tethered spacecraft will be needed to mitigate the need for a great deal of propellant. A spin-stabilized, tethered formation will likely meet these requirements. Several configurations have been proposed which possibly meet the needs of the Space Science community. This paper discusses two of them, weighing the relative pros and cons of each concept. The ultimate goal being to settle on a configuration which combines the best features of structure, tethers, and formation flying to meet the ambitious requirements necessary to make future large synthetic aperture and interferometric science missions successful.

  14. The application of wavefront coding technology to a large segmented synthetic aperture telescope

    NASA Astrophysics Data System (ADS)

    Feng, Litong; Meng, Junhe; Dun, Xiong; Tao, Yu; Zhu, Lixin; Wu, Xiaojing; Zhang, Zhen; Zhang, Chenzhong; Chen, Xin; Lei, Li; Zhao, Kan

    2010-05-01

    The utilization of a telescope with a large single aperture is limited by the manufacturing technique, cost, volume and weight of a monolithic mirror. In order to solve these problems, the technology of the segmented synthetic aperture was introduced. The primary mirror of a large segmented synthetic aperture telescope consists of several segmented mirrors, whose misalignment errors make the wavefront change drastically and influence the MTF of the optical system badly. The wavefront coding technology (WFC) is an innovative technology that joints the optical design and digital image processing together. By adding a phase mask close to the pupil of an optical system and modulating the wavefront, the WFC system becomes very insensitive to defocus and other aberrations based on defocus. The theoretical analysis of characteristics of the WFC system was done in the form of PSF. The application of WFC to a segmented three mirror anastigmat (TMA) was presented. A space telescope with an effective focal length as 40m, a F number as 10, a field of view as 0.5x0.05 was designed, whose primary mirror consisted of seven segmented mirrors. The influence of defocus and misalignment errors on the telescope was discussed. The imaging process of the WFC system and following image restoration were simulated. As a result, sharp images were obtained and the large segmented synthetic aperture telescope had looser misalignment tolerance and extended depth of focus.

  15. Algorithms for finely adjusting etch depths to improve the diffraction efficiency uniformity of large-aperture BSG

    NASA Astrophysics Data System (ADS)

    Wu, Lixiang; Qiu, Keqiang; Liu, Ying; Fu, Shaojun

    2015-03-01

    Beam sampling gratings (BSGs) employed in high-power laser systems usually have large aperture so that the adequate uniformity of diffraction efficiency is difficult to obtain. We proposed a deterministic method using controllable non-uniform etch to improve the efficiency uniformity of large-aperture BSGs. During the ion beam etching (IBE) process, etch depths are finely adjusted by the dynamic leaf. The motion trajectory of the dynamic leaf is calculated using the fine adjustment algorithm. Simulations are conducted on the basis of a typical example. The simulation predictions show that the cumulative error is 0.067 nm and about 99.1% of depth differences are in the range of the required etch depth tolerance, which suggests that the diffraction efficiency uniformity of BSG is expected to be effectively improved and thus can meet the requirement of a RMS of 5%. As a cost-effective solution, it also has a broad prospect in many optical fabrication fields, especially for the fabrication of large optics.

  16. Fabrication and test of a concave oblate ellipsoid with large relative aperture

    NASA Astrophysics Data System (ADS)

    Li, Ke-xin; Yuan, Li-yin; Hao, Pei-ming

    2010-10-01

    Fabrication and test of the concave oblate ellipsoid becomes more difficult as the mirror relative aperture gets larger. The concave oblate ellipsoid discussed in this paper, has a very large relative aperture. Two processing methods are introduced. One is drilling sub-mirror from the mother mirror, the other is processing sub-mirror merely. A novel method to calculate aspheric grinding amount of the latter method is proposed. As the clear aperture and aperture decenter of the concave oblate ellipsoid in this paper are not large, the former processing method is finally adopted. Two online processing testing methods are proposed. One is reflective auto-collimating test; the other is refractive auto-collimating test. As for the former, a negative power lens is applied to compensate the positive spherical aberration of the concave oblate ellipsoid. The compensator has a negative - negative - positive configuration. As for the latter, the back surface of the spherical is designed to be an auxiliary spherical one. Its compensator is negative- positive- positive compensator. Besides, a high-precision plane is used to realize auto-collimating test. And the form test is selected for its online processing testing. By optical design of the compensator and gradual aberration optimization of its alignment, the test accuracy of the oblate ellipsoid shape can be achieved 1/10? (632.8nm).

  17. Laboratory experiments on synthetic-aperture laser radar with acousto-optic modulators

    NASA Astrophysics Data System (ADS)

    Liu, HuanHuan; Zeng, XiaoDong; Cao, ChangQing; Feng, ZheJun; Fu, Chao

    2009-07-01

    The diffraction limit of laser is smaller than microwave's for its shorter wavelength. Higher spatial resolution will be achieved when laser is applied to the synthetic-aperture radar, called synthetic-aperture laser radar (SAL). Just because of many advantages, in recent years the research on SAL is becoming a hotspot. One of key techniques of SAL is heterodyne detection of signals by means of linear frequency modulation pulse compression (LFM-PC); this paper introduces an experiment based on heterodyne detection with an acousto-optic frequency shifter (AOFS) in our laboratory. Detailed discussion about AOFS is presented. We find that the acousto-optic modulator can considerably influence the transmitted light beam. In particular, when the width of laser beam is larger than the effective width of acousto-optic cell, the transverse distribution of scattering light intensity is inhomogeneous, which will decrease the signal-to-noise ratio of the heterodyne detection. This paper discusses the coupled partial difference equations

  18. Large Aperture "Photon Bucket" Optical Receiver Performance in High Background Environments

    NASA Technical Reports Server (NTRS)

    Vilnrotter, Victor A.; Hoppe, D.

    2011-01-01

    The potential development of large aperture groundbased "photon bucket" optical receivers for deep space communications, with acceptable performance even when pointing close to the sun, is receiving considerable attention. Sunlight scattered by the atmosphere becomes significant at micron wavelengths when pointing to a few degrees from the sun, even with the narrowest bandwidth optical filters. In addition, high quality optical apertures in the 10-30 meter range are costly and difficult to build with accurate surfaces to ensure narrow fields-of-view (FOV). One approach currently under consideration is to polish the aluminum reflector panels of large 34-meter microwave antennas to high reflectance, and accept the relatively large FOV generated by state-of-the-art polished aluminum panels with rms surface accuracies on the order of a few microns, corresponding to several-hundred micro-radian FOV, hence generating centimeter-diameter focused spots at the Cassegrain focus of 34-meter antennas. Assuming pulse-position modulation (PPM) and Poisson-distributed photon-counting detection, a "polished panel" photon-bucket receiver with large FOV will collect hundreds of background photons per PPM slot, along with comparable signal photons due to its large aperture. It is demonstrated that communications performance in terms of PPM symbol-error probability in high-background high-signal environments depends more strongly on signal than on background photons, implying that large increases in background energy can be compensated by a disproportionally small increase in signal energy. This surprising result suggests that large optical apertures with relatively poor surface quality may nevertheless provide acceptable performance for deep-space optical communications, potentially enabling the construction of cost-effective hybrid RF/optical receivers in the future.

  19. Split-aperture laser pulse compressor design tolerant to alignment and line-density differences.

    PubMed

    Rushford, Michael C; Britten, Jerald A; Barty, Christopher P J; Jitsuno, Takahisa; Kondo, Kiminori; Miyanaga, Noriaki; Tanaka, Kazuo A; Kodama, Ryosuke; Xu, Guang

    2008-08-15

    We introduce a four-pass laser pulse compressor design based on two grating apertures with two gratings per aperture that is tolerant to some alignment errors and, importantly, to grating-to-grating period variations. Each half-beam samples each grating in a diamond-shaped compressor that is symmetric about a central bisecting plane. For any given grating, the two half-beams impinge on opposite sides of its surface normal. It is shown that the two split beams have no pointing difference from paired gratings with different periods. Furthermore, no phase shift between half-beams is incurred as long as the planes containing a grating line and the surface normal for each grating of the pair are parallel. For grating pairs satisfying this condition, gratings surfaces need not be on the same plane, as changes in the gap between the two can compensate to bring the beams back in phase. PMID:18709127

  20. A Large Aperture Lidar Observatory for Exploring the Interaction of Our Atmosphere with Space (Invited)

    NASA Astrophysics Data System (ADS)

    Thayer, J. P.; Gardner, C. S.; Swenson, G. R.

    2013-12-01

    The mesopause region has been the subject of intensive study during the past decade because it is recognized as a critical region connecting our sensible atmosphere to the near-space environment. Processes in this region include a host of wave dynamics, heat and constituent transport, turbulence, polar mesospheric cloud formation, and the influx of meteoric material. Moreover, the neutral gas properties above the mesopause from 100 - 200 km altitude are poorly characterized and are influenced by additional processes that include solar EUV absorption / ionization, eddy to molecular diffusion, neutral wind dynamo action, and geomagnetic activity. Thus, this altitude region is a complex confluence of space and atmosphere processes that ultimately determine its properties. Fundamentally these processes are operating in any planetary atmosphere and must be understood in order to advance understanding of habitability and sustainability of a planetary system. While observational and modeling capabilities are evolving, progress in characterizing neutral properties and related processes in the mesopause region and above has been inhibited because they cannot be observed in sufficient detail and at high enough altitudes with existing instrumentation. This is especially true of the neutral atmosphere from 50 - 1000 km, where observations of its properties, dynamics and thermal structure are either sparse or nonexistent. A Large-Aperture Lidar Observatory (LALO) would enable significant progress by providing critical measurements of atmospheric constituents and parameters at greatly enhanced resolution and at much higher altitudes than is possible today. A large telescope in combination with modern high-power lasers, would enable observations of the neutral atmosphere to 1000 km altitude with a sensitivity and resolution approximately 1000 times better than can be achieved with the most powerful lidar systems in operation today. There are no technology barriers to realizing this goal. The knowledge obtained would improve our ability to understand the Earth's atmosphere to its fullest extent and would have a transformational effect on upper atmosphere research in a manner similar to that experienced by ionosphere research with the implementation of large-scale incoherent scatter radars. It would also have direct applications to studies of other planets in our solar system and to the exploration of nearby exoplanets within our galaxy.

  1. The Advanced Technology Large Aperture Space Telescope (ATLAST): Science Drivers and Technology Developments

    NASA Technical Reports Server (NTRS)

    Postman, Marc; Brown, Tom; Sembach, Kenneth; Giavalisco, Mauro; Traub, Wesley; Stapelfeldt, Karl; Calzetti, Daniela; Oegerle, William; Rich, R. Michael; Stahl, H. Phillip; Tumlinson, Jason; Mountain, Matt; Soummer, Remi; Hyde, Tupper

    2011-01-01

    The Advanced Technology Large-Aperture Space Telescope (ATLAST) is a concept for an 8-meter to 16-meter UVOIR space observatory for launch in the 2025-2030 era. ATLAST will allow astronomers to answer fundamental questions at the forefront of modern astrophysics, including "Is there life elsewhere in the Galaxy?" We present a range of science drivers and the resulting performance requirements for ATLAST (8 to 16 milliarcsecond angular resolution, diffraction limited imaging at 0.5 m wavelength, minimum collecting area of 45 square meters, high sensitivity to light wavelengths from 0.1 m to 2.4 m, high stability in wavefront sensing and control). We also discuss the priorities for technology development needed to enable the construction of ATLAST for a cost that is comparable to current generation observatory-class space missions. Keywords: Advanced Technology Large-Aperture Space Telescope (ATLAST); ultraviolet/optical space telescopes; astrophysics; astrobiology; technology development.

  2. Large coded aperture mask for spaceflight hard x-ray images

    Microsoft Academic Search

    Danielle Vigneau; David W. Robinson

    2003-01-01

    The 2.6 square meter coded aperture mask is a vital part of the Burst Alert Telescope on the Swift mission. A random, but known pattern of more than 50,000 lead tiles, each 5 mm square, was bonded to a large honeycomb panel which projects a shadow on the detector array during a gamma ray burst. A two-year development process was

  3. Large excimer lasers for fusion

    SciTech Connect

    Jensen, R.J.

    1986-01-01

    Important goals in DOE and DOD programs require multimegajoule laser pulses. For inertial confinement fusion there is also a requirement to deliver the pulse in about 25 nsec with a very particular power vs time profile - all at high overall efficiency and low cost per joule. After exhaustive consideration of various alternatives, our studies have shown that the most cost effective approach to energy scaling is to increase the size of the final amplifiers up to the 200 to 300 kJ level. This conclusion derives largely from the fact that, at a given complexity, costs increase slowly with increasing part size while output energy should increase dramatically. Extrapolations to low cost by drastic cuts in the unit cost of smaller devices through mass production are considered highly risky. At a minimum the requirement to provide, space, optics and mounts for such systems will remain expensive. In recent years there have been dramatic advances in scaling. The Los Alamos LAM has produced over 10 kJ in a single 1/2 nsec pulse. In this paper we explore the issues involved in scaling to higher energy while still maintaining high efficiencies. In the remainder of this paper we will discuss KrF laser scaling for the fusion mission. We will omit most of the discussion of the laser system design, but address only KrF amplifiers.

  4. Recent Enhancements of the Phased Array Mirror Extendible Large Aperture (PAMELA) Telescope Testbed at MSFC

    NASA Technical Reports Server (NTRS)

    Rakoczy, John; Burdine, Robert (Technical Monitor)

    2001-01-01

    Recent incremental upgrades to the Phased Array Mirror Extendible Large Aperture (PAMELA) telescope testbed have enabled the demonstration of phasing (with a monochromatic source) of clusters of primary mirror segments down to the diffraction limit. PAMELA upgrades include in improved Shack-Hartmann wavefront sensor, passive viscoelastic damping treatments for the voice-coil actuators, mechanical improvement of mirror surface figures, and optical bench baffling. This report summarizes the recent PAMELA upgrades, discusses the lessons learned, and presents a status of this unique testbed for wavefront sensing and control. The Marshall Space Flight Center acquired the Phased Array Mirror Extendible Large Aperture (PAMELA) telescope in 1993 after Kaman Aerospace was unable to complete integration and testing under the limited SDIO and DARPA funding. The PAMELA is a 36-segment, half-meter aperture, adaptive telescope which utilizes a Shack-Hartmann wavefront sensor, inductive coil edge sensors, voice coil actuators, imaging CCD cameras and interferometry for figure alignment, wavefront sensing and control. MSFC originally obtained the PAMELA to supplement its research in the interactions of control systems with flexible structures. In August 1994, complete tip, tilt and piston control was successfully demonstrated using the Shack-Hartmann wavefront sensor and the inductive edge sensors.

  5. Recent Enhancements of the Phased Array Mirror Extendible Large Aperture (PAMELA) Telescope Testbed at MSFC

    NASA Technical Reports Server (NTRS)

    Rakoczy, John; Montgomery, Edward E.; Lindner, Jeff

    2000-01-01

    Recent incremental upgrades to the Phased Array Mirror Extendible Large Aperture (PAMELA) telescope testbed have enabled the demonstration of phasing (with a monochromatic source) of clusters of primary mirror segments down to the diffraction limit. PAMELA upgrades include an improved Shack-Hartmann wavefront sensor, passive viscoelastic damping treatments for the voice-coil actuators, mechanical improvement of mirror surface figures, and optical bench baffling. This report summarizes the recent PAMELA upgrades, discusses the lessons learned, and presents a status of this unique testbed for wavefront sensing and control. The Marshall Space Flight Center acquired the Phased Array Mirror Extendible Large Aperture (PAMELA) telescope in 1993 after Kaman Aerospace was unable to complete integration and testing under the limited SDIO and DARPA funding. The PAMELA is a 36-segment, half-meter aperture, adaptive telescope which utilizes a Shack-Hartmann wavefront sensor, inductive coil edge sensors, voice coil actuators, imaging CCD cameras and interferometry for figure alignment, wavefront sensing and control. MSFC originally obtained the PAMELA to supplement its research in the interactions of control systems with flexible structures. In August 1994, complete tip, tilt and piston control was successfully demonstrated using the Shack-Hartmann wavefront sensor and the inductive edge sensors.

  6. The error analyze of testing the large aperture flat by the Ritchey-Common method

    NASA Astrophysics Data System (ADS)

    Ji, Bo; Xu, Chen; Li, Bo

    2014-11-01

    When polishing and modifying the large aperture flat by the traditional polishing tools, people usually test it by a spherical mirror as a standard surface which been called the Ritchey-Common method, that not only can break through the limitation of the aperture, but also can achieve high precision wave front if the surface of the standard mirror is perfect. However, when doing ultrahigh precision modifying by the modern polishing equipment such as: ion beam polishing, this testing method cannot meet the need of the high precision location, because of the error caused by the nonlinear transformation of the coordinate, the testing result usually cannot been very exactly developed point to point, that restrained the polishing accuracy. Here the error has been studied in order to exactly developing the testing result. At first, in principle, the Ritchey- Common testing path has been analyzed in detail. Secondly, the point to point transfer equation has been deduced, and some feature points have been chosen to help analyze the relationship between the object surface and the image result. Then a program has been written according to the deduced equation, by which the image can be well developed. Finally the error has been compared by using different developing methods in the experiment. The study can solve the nonlinear point to point transfer and location problem caused by the Ritchey-Common testing method, so when manufacturing the large aperture flat, the Ritchey-Common testing method can be used in the ultrahigh precision polishing.

  7. A Full Aperture Backscattering Light Diagnostic System Installed on the Shenguang-III Prototype Laser Facility

    NASA Astrophysics Data System (ADS)

    Xu, Tao; Mei, Yu; Wei, Huiyue; Peng, Xiaoshi; Wang, Feng; Yang, Dong; Liu, Shenye; Yan, Yadong

    2014-06-01

    A full aperture backscattering light diagnostic system (FABLDS) implemented on the Shen Guang-III Prototype Laser Facility is described in the paper. FABLDS measures both stimulated brillouin scattering (SBS) and stimulated Raman scattering (SRS) with a series of optical detectors. Energy sensors record the integrated energy, and streak cameras coupled with spectrometers measure the temporal spectrum of the backscattering light. This paper provides an overview of the FABLDS and detailed descriptions of the optical path. Special components, including off-axis parabolic mirror, spatial filter and optical light filters, are incorporated along the beam path for purifying the scattering light. Several hohlraum targets were employed, including C5H12 gas-filled targets and empty targets in the experiments. Results presented in the paper indicate that the fraction of backscatter light has been obviously shrinked when the laser is smoothed by continuous phase plates (CPP).

  8. Current Aperture III-Nitride Edge-emitting Blue Laser Diode

    NASA Astrophysics Data System (ADS)

    Megalini, Ludovico

    This work presents the first Nitride non polar Current Aperture Edge Emitting Blue Laser Diode (CA-LD) fabricated using the Photo-Electro-Chemical Etching (PECE) technique. The main features of this design are represented by the deep etching of the laser diode ridge through the active region, the controlled etching of the active region by PECE and the increase of the p-contact area with respect to the active region area. Preliminary experiments manifest that CA-LD has similar threshold current density, slope efficiency and peak output power of the more commonly used shallow etch ridge design and it has also shown a reduction in the series resistance down to 40% with respect to the shallow-etch LDs indicating the potential of the CA-LD design in high-efficient, high-power, high-frequency LD applications.

  9. Spatial mode dynamics in wide-aperture quantum-dot lasers

    SciTech Connect

    Mukherjee, Jayanta; McInerney, John G. [Department of Physics and Tyndall National Institute, Optoelectronics Group, National University of Ireland, University College, Cork (Ireland)

    2009-05-15

    We present a systematic theoretical study of spatial mode dynamics in wide-aperture semiconductor quantum-dot lasers within the Maxwell-Bloch formalism. Our opto-electro-thermal model self-consistently captures the essential dynamical coupling between field, polarization, and carrier density in both thermal and nonthermal regimes, providing detailed description of the complex spatiotemporal modal intensity structure and spectra in these novel devices and broad area edge-emitting lasers in general. Using linear stability analysis and high resolution adaptive-grid finite element numerical simulation, we show that in the nonthermal regime, the presence of inhomogeneous broadening in quantum-dot active media leads to suppressed filamentation and enhanced spatial coherence compared to conventional quantum well devices with comparable phase-amplitude coupling (alpha parameter). Increasing the degree of inhomogeneous broadening in the active medium leads to further improvement in spatial coherence. In the thermal regime, there is further suppression of filamentation in the inhomogeneously broadened quantum-dot active medium; however, the spatial coherence aided by inhomogeneous broadening is partly lost due to the effect of temperature on cavity detuning. We propose that device designs based on optimized inhomogeneous broadening of quantum-dot gain medium could ultimately lead to diffraction-limited outputs in the quasi-cw regime which are still very difficult to achieve in conventional wide-aperture designs.

  10. In vivo and in vitro ultrasound beam distortion measurements of a large aperture and a conventional aperture focussed transducer.

    PubMed

    Moshfeghi, M; Waag, R C

    1988-01-01

    Ultrasound focussing through human tissue of thicknesses varying from 10 mm to 35 mm has been measured for two transducers with diameters 50 mm and 19 mm both focussed at 50 mm (f/1 and f/2.6, respectively). Comparisons are made between the two-way focal depth beam patterns obtained in water and those obtained after passage through tissue to study the degrading effects of frequency-dependent attenuation and inhomogeneities, and their dependence on aperture size. The effects of frequency-dependent attenuation is to broaden the beam and shorten the focal distance. Inhomogeneities mainly increase the sidelobe levels and cause deviations from the central beam axis. A direct comparison of the beam patterns of the two transducers after passage through the same tissue samples shows that the resolution is improved by using the larger aperture. The use of the larger transducer in the in vitro measurements on three human liver specimens demonstrated an average improvement in the -6 dB beamwidth, over the smaller transducer, of 42% (standard deviation +/- 3%). The average improvement in the in vivo measurements on ten female breasts was 34% (standard deviation +/- 5%). The measured improvement in water was 52%. Therefore, the measured resolution improvement in tissue is approximately 2/3 of that obtained in water. The results indicate that for an f/1 transducer with a focal depth of 50 mm the upper limit of maximum useful aperture size has not been reached. PMID:3051615

  11. Design of a projection objective with high numeric aperture and large view field

    NASA Astrophysics Data System (ADS)

    Liu, Junbo; Hu, Song; Gao, Hongtao; Zhao, Lixin; Zhu, Xianchang

    2014-08-01

    As the primary facility for the manufacturing of integrated circuit(IC), and MEMS devices [1], the lithographic equipment's improvement is restricted by the projection objective which can decide the capacity of the image transmission of the facility and make the facility be capable of reaching the higher precision or beyond. On the basis of the function, increasing the numeric aperture is coupled with the raising of resolution of the projection objective. In this paper, a design of a projection objective with high numeric aperture and large view field for I-line lithography is proposed. Owning a dual-telecentric structure this optical system owns an angular magnification of -1.25, an effective image field of 9090mm and an image numeric aperture of 0.2. Two aspheric surfaces are adopted in this projection objective to enhance the quality of imaging that will insure the field curvature lower than a half of the DOF, restrict the distortion lower than+/-?/5 and make the MTF approximate the diffraction limits.

  12. Controlling Synchronization in Large Laser Networks

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

    Synchronization in large laser networks with both homogeneous and heterogeneous coupling delay times is examined. The number of synchronized clusters of lasers is established to equal the greatest common divisor of network loops. We experimentally demonstrate up to 16 multicluster phase synchronization scenarios within unidirectional coupled laser networks, whereby synchronization in heterogeneous networks is deduced by mapping to an equivalent homogeneous network. The synchronization in large laser networks is controlled by means of tunable coupling and self-coupling.

  13. Large Coded Aperture Mask for Spaceflight Hard X-ray Images

    NASA Technical Reports Server (NTRS)

    Vigneau, Danielle N.; Robinson, David W.

    2002-01-01

    The 2.6 square meter coded aperture mask is a vital part of the Burst Alert Telescope on the Swift mission. A random, but known pattern of more than 50,000 lead tiles, each 5 mm square, was bonded to a large honeycomb panel which projects a shadow on the detector array during a gamma ray burst. A two-year development process was necessary to explore ideas, apply techniques, and finalize procedures to meet the strict requirements for the coded aperture mask. Challenges included finding a honeycomb substrate with minimal gamma ray attenuation, selecting an adhesive with adequate bond strength to hold the tiles in place but soft enough to allow the tiles to expand and contract without distorting the panel under large temperature gradients, and eliminating excess adhesive from all untiled areas. The largest challenge was to find an efficient way to bond the > 50,000 lead tiles to the panel with positional tolerances measured in microns. In order to generate the desired bondline, adhesive was applied and allowed to cure to each tile. The pre-cured tiles were located in a tool to maintain positional accuracy, wet adhesive was applied to the panel, and it was lowered to the tile surface with synchronized actuators. Using this procedure, the entire tile pattern was transferred to the large honeycomb panel in a single bond. The pressure for the bond was achieved by enclosing the entire system in a vacuum bag. Thermal vacuum and acoustic tests validated this approach. This paper discusses the methods, materials, and techniques used to fabricate this very large and unique coded aperture mask for the Swift mission.

  14. Spacecraft Conceptual Design for the 8-Meter Advanced Technology Large Aperture Space Telescope (ATLAST)

    NASA Technical Reports Server (NTRS)

    Hopkins, Randall C.; Capizzo, Peter; Fincher, Sharon; Hornsby, Linda S.; Jones, David

    2010-01-01

    The Advanced Concepts Office at Marshall Space Flight Center completed a brief spacecraft design study for the 8-meter monolithic Advanced Technology Large Aperture Space Telescope (ATLAST-8m). This spacecraft concept provides all power, communication, telemetry, avionics, guidance and control, and thermal control for the observatory, and inserts the observatory into a halo orbit about the second Sun-Earth Lagrange point. The multidisciplinary design team created a simple spacecraft design that enables component and science instrument servicing, employs articulating solar panels for help with momentum management, and provides precise pointing control while at the same time fast slewing for the observatory.

  15. Compact large-aperture Fabry-Perot interferometer modules for gas spectroscopy at mid-IR

    NASA Astrophysics Data System (ADS)

    Kantojrvi, Uula; Varpula, Aapo; Antila, Tapani; Holmlund, Christer; Mkynen, Jussi; Nsil, Antti; Mannila, Rami; Rissanen, Anna; Antila, Jarkko; Disch, Rolf J.; Waldmann, Torsten A.

    2014-03-01

    VTT has developed Fabry-Prot Interferometers (FPI) for visible and infrared wavelengths since 90's. Here we present two new platforms for mid-infrared gas spectroscopy having a large optical aperture to provide high optical throughput but still enabling miniaturized instrument size. First platform is a tunable filter that replaces a traditional filter wheel, which operates between wavelengths of 4-5 um. Second platform is for correlation spectroscopy where the interferometer provides a comb-like transmission pattern mimicking absorption of diatomic molecules at the wavelength range of 4.7-4.8 um. The Bragg mirrors have 2-4 thin layers of polysilicon and silicon oxide.

  16. Engineering Specification for Large-aperture UVO Space Telescopes Derived from Science Requirements

    NASA Technical Reports Server (NTRS)

    Stahl, H. Philip; Arnold, William; Bevan, Ryan M.; Smith, W. Scott.; Kirk, Charles S.; Postman, Mark

    2013-01-01

    An advanced large aperture UV/optical UVO space telescope is required for the next generation of astrophysics and exoplanet science. The science requirements of proposed exoplanet and astrophysics missions were used to determine the encircled energy, point spread function stability and thermal environment requirements. These requirements then determine the optical wavefront specification for potential telescope assemblies which can fit inside current and planned launch vehicles. The optical wavefront specification becomes the top level of the error budget that is split into various sources that control the structural, thermal and optical design.

  17. System architecture of MMIC-based large aperture arrays for space application

    NASA Technical Reports Server (NTRS)

    Herczfeld, P. R.; Kam, M.; Kunath, R. R.; Bhasin, K. B.; Laprade, N.

    1987-01-01

    The persistent trend to use millimeter-wave frequencies for satellite communications presents the challenge to design large-aperture phased arrays for space applications. These arrays, which comprise 100 to 10,000 elements, are now possible due to the advent of lightwave technology and the availability of monolithic microwave integrated circuits. In this paper, system aspects of optically controlled array design are studied. In particular, two architectures for a 40 GHz array are outlined, and the main system-related issues are examined: power budget, synchronization in frequency and phase, and stochastic effects.

  18. Efficient selection of a single harmonic emission using a multi-color laser field with an aperture-iris diaphragm

    NASA Astrophysics Data System (ADS)

    Wei, Pengfei; Tian, Qili; Zeng, Zhinan; Jiang, Jiaming; Miao, Jing; Zheng, Yinghui; Ge, Xiaochun; Li, Chuang; Li, Ruxin; Xu, Zhizhan

    2014-08-01

    The efficient selection of an almost pure single harmonic emission (the 14th harmonic at 57?nm) from the harmonic comb has been experimentally achieved in an argon gas cell using a multi-color laser field with an aperture-iris diaphragm. When compared with the non-diaphragm case, the purity of the selected single harmonic emission (i.e. the contrast ratio) in the case of using the aperture-iris diaphragm is dramatically increased by approximately order of magnitude. Therefore, the modification of the multi-color laser field by using such an aperture-iris diaphragm before focusing is demonstrated to be an effective way of improving the phase-matching conditions for selective enhancement of the single harmonic emission.

  19. Laser Power Meter Large, bright, backlit LCD

    E-print Network

    Woodall, Jerry M.

    Laser Power Meter FEATURES Large, bright, backlit LCD display Digital accuracy with analog-like movement for laser tuning Works with thermopile and optical sensors Intuitive button-driven user COMPATIBILITY PowerMax thermal sensors Optical sensors FieldMaxII-TO Coherent Laser Measurement and Control

  20. On the Potential of Large Ring Lasers

    E-print Network

    G. E. Stedman; R. B. Hurst; K. U. Schreiber

    2007-07-10

    We describe a new ring laser with area A = 833 m^2 and update performance statistics for several such machines. Anandan & Chaio 1982 judged ring lasers inferior to matter interferometers as possible detectors of gravitational waves. However, we note that geophysically interesting results have been obtained from large ring lasers and that there is still a lot of room for improvements.

  1. A conceptual design of a large aperture microwave radiometer geostationary platform

    NASA Technical Reports Server (NTRS)

    Garn, Paul A.; Garrison, James L.; Jasinski, Rachel

    1992-01-01

    A conceptual design of a Large Aperture Microwave Radiometer (LAMR) Platform has been developed and technology areas essential to the design and on-orbit viability of the platform have been defined. Those technologies that must be developed to the requirement stated here for the LAMR mission to be viable include: advanced radiation resistant solar cells, integrated complex structures, large segmented reflector panels, sub 3 kg/m(exp 2) areal density large antennas, and electric propulsion systems. Technology areas that require further development to enhance the capabilities of the LAMR platform (but are not essential for viability) include: electrical power storage, on-orbit assembly, and on-orbit systems checkout and correction.

  2. THz imaging using Glow Discharge Detector (GDD) focal plane arrays and large aperture quasi optic mirrors

    NASA Astrophysics Data System (ADS)

    Kopeika, N. S.; Abramovich, A.; Joseph, H.; Rozban, D.; Akram, A.; Levanon, A.; Yadid-Pecht, O.; Belenky, A.; Lineykin, S.

    2010-10-01

    The properties of terahertz (THz) radiation are well known. They penetrate well most nonconducting media; there are no known biological hazards, and atmospheric attenuation and scattering is lower than for visual and IR radiation. Recently we have found that common miniature commercial neon glow discharge detector (GDD) lamps costing typically about 30 cents each exhibit high sensitivity to THz radiation, with microsecond order rise times, thus making them excellent candidates for such focal plane arrays. Based on this technology we designed, built and tested 4X4 and 8X8 GDD focal plane arrays. A line vector of 32 GDD pixels is being designed in order to increase the number of pixels in such arrays and thus the image resolution. Unique large aperture quasi optic mirrors were design and tested experimentally in this work. A new technology of light weight large aperture mirrors is proposed in this work. In this case a metal coating on plastic substrate is demonstrated. According to first experiments this technology proves to reliable with minimal deformation in LAB conditions. THz Images at 100 GHz were taken using this new inexpensive technology with good quality and resolution.

  3. Large-aperture, equal-path interferometer for precision measurements of flat transparent surfaces.

    PubMed

    Deck, Leslie L; de Groot, Peter J; Soobitsky, James A

    2014-03-10

    The measurement of flat optical components often presents difficulties because the presence of parallel surfaces generates multiple reflections that confuse conventional laser-based interferometers. These same parts have increasingly demanding surface finish tolerances as technologies improve over time, further complicating the metrology task. Here we describe an interferometric optical system for high-accuracy noncontact evaluation of the form and texture of precision flat surfaces based on an equal-optical-path geometry that uses extended, broadband illumination to reduce the influence of speckle noise, multiple reflections, and coherent artifacts by a factor of 10 when compared to laser-based systems. Combined with a low-distortion, fixed-focus imaging system and 4-Mpixel camera, the 100 mm aperture instrument offers surface height resolutions of 0.1 nm over lateral spatial frequencies extending from 0.01 to 10 cycles/mm. The instrument is vibration resistant for production-line testing of flat optics such as glass hard disks for the data-storage industry and flat-panel-display substrates. PMID:24663410

  4. A CLOSE COMPANION SEARCH AROUND L DWARFS USING APERTURE MASKING INTERFEROMETRY AND PALOMAR LASER GUIDE STAR ADAPTIVE OPTICS

    SciTech Connect

    Bernat, David [Department of Astronomy, Cornell University, Ithaca, NY 14853 (United States); Bouchez, Antonin H.; Cromer, John L.; Dekany, Richard G.; Moore, Anna M. [California Institute of Technology, Pasadena, CA 91125 (United States); Ireland, Michael; Tuthill, Peter [Sydney Institute for Astrophysics, School of Physics, University of Sydney (Australia); Martinache, Frantz [National Astronomical Observatory of Japan, Subaru Telescope, Hilo, HI 96720 (United States); 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 [Palomar Laser Guide Star Adaptive Optics Team, Palomar Observatory, California Institute of Technology, Palomar Mountain, CA 92060 (United States)

    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.

  5. Design of large aperture superferric quadrupole magnets for an in-flight fragment separator

    NASA Astrophysics Data System (ADS)

    Zaghloul, Aziz; Kim, Dogyun; Kim, Jangyoul; Kim, Mijung; Kim, Myeongjin; Yun, Chongcheoul; Kim, Jongwon

    2014-01-01

    Superferric quadrupole magnets to be used for in-flight fragment separator have been designed. A quadrupole magnet triplet for beam focusing is placed in a cryostat together with superconducting correction coils. To maximize acceptance of rare isotope beams produced by projectile fragmentation, it is essential to use large-aperture quadrupole magnets. The pole tip radius is 17 cm in the current design, and we tried to enlarge the aperture with 3D analysis on magnetic fields. In the front end of the separator, where a target and beam dump are located, we plan to use two sets of quadrupole triplets made of high-Tc superconductor (HTS) operating at 20-50 K considering high radiation heat load. The HTS magnet will use warm iron poles. Both low-Tc and high-Tc superconductors are acquired for test winding, and two kinds of dewar and cryostat are under construction to perform the coil and magnet tests. The magnetic design of superferric quadrupole is mainly discussed.

  6. Recent enhancements of the Phased Array Mirror Extendible Large Aperture (PAMELA) telescope testbed at MSFC

    NASA Astrophysics Data System (ADS)

    Rakoczy, John M.; Montgomery, Edward E.; Lindner, Jeffrey L.

    2000-08-01

    Recent incremental upgrades to the Phased Array Mirror Extendible Large Aperture (PAMELA) telescope testbed have enabled the demonstration of phasing (with a monochromatic source) of clusters of primary mirror segments down to the diffraction limit. PAMELA upgrades include an improved Shack-Hartmann wavefront sensor, passive viscoelastic damping treatments for the voice-coil actuators, and mechanical improvement of mirror surface figures. This report summarizes the recent PAMELA upgrades and presents a status of this unique testbed for wavefront sensing and control. The Marshall Space Flight Center acquired the PAMELA telescope in 1993 after Kaman Aerospace was unable to complete integration and testing under the limited SDIO and DARPA funding. The PAMELA is a 36-segment, half-meter aperture, adaptive telescope which utilizes a Shack-Hartmann wavefront sensor, inductive coil edge sensors, voice coil actuators, imaging CCD cameras and interferometry for figure alignment, wavefront sensing and control. MSFC originally obtained the PAMELA to supplement its research in the interactions of control systems with flexible structures. In August 1994, complete tip, tilt and piston control was successfully demonstrated using the Shack-Hartmann wavefront sensor and the inductive edge sensors.

  7. Design of large aperture superferric quadrupole magnets for an in-flight fragment separator

    SciTech Connect

    Zaghloul, Aziz; Kim, Dogyun; Kim, Jangyoul; Kim, Mijung; Kim, Myeongjin; Yun, Chongcheoul; Kim, Jongwon [Rare Isotope Science Project, Institute for Basic Science, Yuseong, Daejeon, 305-811 (Korea, Republic of)

    2014-01-29

    Superferric quadrupole magnets to be used for in-flight fragment separator have been designed. A quadrupole magnet triplet for beam focusing is placed in a cryostat together with superconducting correction coils. To maximize acceptance of rare isotope beams produced by projectile fragmentation, it is essential to use large-aperture quadrupole magnets. The pole tip radius is 17 cm in the current design, and we tried to enlarge the aperture with 3D analysis on magnetic fields. In the front end of the separator, where a target and beam dump are located, we plan to use two sets of quadrupole triplets made of high-Tc superconductor (HTS) operating at 20-50 K considering high radiation heat load. The HTS magnet will use warm iron poles. Both low-Tc and high-Tc superconductors are acquired for test winding, and two kinds of dewar and cryostat are under construction to perform the coil and magnet tests. The magnetic design of superferric quadrupole is mainly discussed.

  8. Development of a Large Aperture Nb3Sn Racetrack Quadrupole Magnet

    SciTech Connect

    Ferracin, Paolo; Bartlett, Scott E.; Caspi, Shlomo; Dietderich, Daniel R.; Gourlay, Steve A.; Hannaford, Charles R.; Hafalia, Aurelio R.; Lietzke, Alan F.; Mattafirri, Sara; McInturff, Alfred D.; Nyman, Mark; Sabbi, Gianluca

    2005-06-01

    The U.S. LHC Accelerator Research Program (LARP), a collaboration between BNL, FNAL, LBNL, and SLAC, has among its major objectives the development of advanced magnet technology for an LHC luminosity upgrade. The LBNL Superconducting Magnet Group supports this program with a broad effort involving design studies, Nb{sub 3}Sn conductor development, mechanical models, and basic prototypes. This paper describes the development of a large aperture Nb{sub 3}Sn racetrack quadrupole magnet using four racetrack coils from the LBNL Subscale Magnet (SM) Program. The magnet provides a gradient of 95 T/m in a 110 mm bore, with a peak field in the conductor of 11.2 T. The coils are pre-stressed by a mechanical structure based on a pre-tensioned aluminum shell, and axially supported with aluminum rods. The mechanical behavior has been monitored with strain gauges and the magnetic field has been measured. Results of the test are reported and analyzed.

  9. THE BALLOON-BORNE LARGE APERTURE SUBMILLIMETER TELESCOPE (BLAST) 2006: CALIBRATION AND FLIGHT PERFORMANCE

    SciTech Connect

    Truch, Matthew D. P.; Devlin, Mark J.; Dicker, Simon R.; Klein, Jeff [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Ade, Peter A. R.; Griffin, Matthew; Hargrave, Peter C.; Mauskopf, Philip; Moncelsi, Lorenzo; Pascale, Enzo [Department of Physics and Astronomy, Cardiff University, 5 The Parade, Cardiff, CF24 3AA (United Kingdom); Bock, James J. [Jet Propulsion Laboratory, Pasadena, CA 91109-8099 (United States); Chapin, Edward L.; Halpern, Mark; Marsden, Gaelen [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1 (Canada); Gundersen, Joshua O. [Department of Physics, University of Miami, 1320 Campo Sano Drive, Coral Gables, FL 33146 (United States); Hughes, David H. [Instituto Nacional de AstrofIsica Optica y Electronica (INAOE), Aptdo. Postal 51 y 72000 Puebla (Mexico); Martin, Peter G. [Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8 (Canada); Netterfield, C. Barth [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4 (Canada); Olmi, Luca [Physics Department, University of Puerto Rico, Rio Piedras Campus, Box 23343, UPR Station, San Juan (Puerto Rico); Patanchon, Guillaume, E-mail: matthew@truch.ne [Universite Paris Diderot, Laboratoire APC, 10 rue Alice Domon et Leonie Duquet 75205 Paris (France)

    2009-12-20

    The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) operated successfully during a 250 hr flight over Antarctica in 2006 December (BLAST06). As part of the calibration and pointing procedures, the red hypergiant star VY CMa was observed and used as the primary calibrator. Details of the overall BLAST06 calibration procedure are discussed. The 1sigma uncertainty on the absolute calibration is accurate to 9.5%, 8.7%, and 9.2% at the 250, 350, and 500 mum bands, respectively. The errors are highly correlated between bands resulting in much lower errors for the derived shape of the 250-500 mum continuum. The overall pointing error is < 5'' rms for the 36'', 42'', and 60'' beams. The performance of optics and pointing systems is discussed.

  10. Misalignment wavefront detection of large segmented aperture optical system on-orbit

    NASA Astrophysics Data System (ADS)

    Lu, Li-Hong; Zhang, Wei

    2010-05-01

    The optical systems with large collecting aperture and high resolution are the future development directions of optical systems on orbit. The primary mirror of optical system is segmented for its advantages in reducing the difficulty of manufacturing to achieve high imaging resolution. Once on orbit, it needs to correct the misalignment errors in optical system introduced by the effect of various factors. The phase retrieval based on quasi-Newton method nonlinear optimization is proposed to sense the wavefront aberration induced by segmented mirrors in the optical system. And the BFGS method is utilized to seek the optimum value of wavefront aberrations. Then the different defocus impacted on detection accuracy is analyzed. The result of the simulation experiment indicated that once select the suitable defocus, the phase retrieval method can control the wavefront detection error less than 6%.

  11. Thermal design and performance of the balloon-borne large aperture submillimeter telescope for polarimetry BLASTPol

    NASA Astrophysics Data System (ADS)

    Soler, J. D.; Ade, P. A. R.; Angil, F. E.; Benton, S. J.; Devlin, M. J.; Dober, B.; Fissel, L. M.; Fukui, Y.; Galitzki, N.; Gandilo, N. N.; Klein, J.; Korotkov, A. L.; Matthews, T. G.; Moncelsi, L.; Mroczkowski, A.; Netterfield, C. B.; Novak, G.; Nutter, D.; Pascale, E.; Poidevin, F.; Savini, G.; Scott, D.; Shariff, Jamil A.; Thomas, N. E.; Truch, M. D.; Tucker, C. E.; Tucker, G. S.; Ward-Thompson, D.

    2014-07-01

    We present the thermal model of the Balloon-borne Large-Aperture Submillimeter Telescope for Polarimetry (BLASTPol). This instrument was successfully own in two circumpolar flights from McMurdo, Antarctica in 2010 and 2012. During these two flights, BLASTPol obtained unprecedented information about the magnetic field in molecular clouds through the measurement of the polarized thermal emission of interstellar dust grains. The thermal design of the experiment addresses the stability and control of the payload necessary for this kind of measurement. We describe the thermal modeling of the payload including the sun-shielding strategy. We present the in-flight thermal performance of the instrument and compare the predictions of the model with the temperatures registered during the flight. We describe the difficulties of modeling the thermal behavior of the balloon-borne platform and establish landmarks that can be used in the design of future balloon-borne instruments.

  12. Horizon: A Proposal for Large Aperture, Active Optics in Geosynchronous Orbit

    NASA Technical Reports Server (NTRS)

    Chesters, Dennis; Jenstrom, Del

    2000-01-01

    In 1999, NASA's New Millennium Program called for proposals to validate new technology in high-earth orbit for the Earth Observing-3 (NMP EO3) mission to fly in 2003. In response, we proposed to test a large aperture, active optics telescope in geosynchronous orbit. This would flight-qualify new technologies for both Earth and Space science: 1) a future instrument with LANDSAT image resolution and radiometric quality watching continuously from geosynchronous station, and 2) the Next Generation Space Telescope (NGST) for deep space imaging. Six enabling technologies were to be flight-qualified: 1) a 3-meter, lightweight segmented primary mirror, 2) mirror actuators and mechanisms, 3) a deformable mirror, 4) coarse phasing techniques, 5) phase retrieval for wavefront control during stellar viewing, and 6) phase diversity for wavefront control during Earth viewing. Three enhancing technologies were to be flight- validated: 1) mirror deployment and latching mechanisms, 2) an advanced microcontroller, and 3) GPS at GEO. In particular, two wavefront sensing algorithms, phase retrieval by JPL and phase diversity by ERIM International, were to sense optical system alignment and focus errors, and to correct them using high-precision mirror mechanisms. Active corrections based on Earth scenes are challenging because phase diversity images must be collected from extended, dynamically changing scenes. In addition, an Earth-facing telescope in GEO orbit is subject to a powerful diurnal thermal and radiometric cycle not experienced by deep-space astronomy. The Horizon proposal was a bare-bones design for a lightweight large-aperture, active optical system that is a practical blend of science requirements, emerging technologies, budget constraints, launch vehicle considerations, orbital mechanics, optical hardware, phase-determination algorithms, communication strategy, computational burdens, and first-rate cooperation among earth and space scientists, engineers and managers. This manuscript presents excerpts from the Horizon proposal's sections that describe the Earth science requirements, the structural -thermal-optical design, the wavefront sensing and control, and the on-orbit validation.

  13. Edge-facet pumped, multi-aperture, thin-disk laser geometry for very high average power output scaling

    DOEpatents

    Zapata, Luis E.

    2004-12-21

    The average power output of a laser is scaled, to first order, by increasing the transverse dimension of the gain medium while increasing the thickness of an index matched light guide proportionately. Strategic facets cut at the edges of the laminated gain medium provide a method by which the pump light introduced through edges of the composite structure is trapped and passes through the gain medium repeatedly. Spontaneous emission escapes the laser volume via these facets. A multi-faceted disk geometry with grooves cut into the thickness of the gain medium is optimized to passively reject spontaneous emission generated within the laser material, which would otherwise be trapped and amplified within the high index composite disk. Such geometry allows the useful size of the laser aperture to be increased, enabling the average laser output power to be scaled.

  14. ATLAST-9.2: A Deployable Large Aperture UVOIR Space Telescope

    NASA Technical Reports Server (NTRS)

    Oegerle, William R.; Feinberg, L.; Purves, L.; Hyde, T.; Thronson, H.; Townsend, J.; Postman, M.; Bolcar, M.; Budinoff, J.; Dean, B.; Clampin, N.; Ebbets, D.; Gong, Q.; Gull, T.; Howard, J.; Jones, A.; Lyon, R.; Pasquale, B.; Perrygo, C.; Smith, S.; Thompson, P.; Woodgate, B.

    2010-01-01

    We present the results of a study of a deployable version of the Advanced Technology Large Aperture Space Telescope (ATLAST) that could be launched on an Evolved Expendable Launch Vehicle (EELV). ATLAST is a concept for a next-generation UVOIR observatory to follow HST and JWST. The observatory retains significant heritage from JWST, thereby taking advantage of technologies and engineering already developed for that mission. At the same time, we have identified several design changes to the JWST architecture, some of which are required due to the demanding wavefront error requirements at visible wavelengths. The optical telescope assembly has a segmented 9.2-meter aperture and consists of 36 hexagonal glass mirrors, each of which is I.3l5m in size (flat-to-flat). The telescope can be folded to fit in the 6.5m fairing on the planned upgrade to the Delta-IV heavy launch vehicle. Near-real time wavefront sensing and control is performed on-board the telescope using stars in the field of view to deliver diffraction limited imaging performance at 500nm wavelength. The optical design of the telescope provides an 8x20 arcmin FOV in which 4-5 instruments can be accommodated, plus fine guidance and wavefront sensors. Unlike JWST, the OTA sits at the end of a multi-gimbaled arm, allowing pitch and roll motion, and is isolated from the sunshield and spacecraft bus by an active isolation system. Our design permits servicing in order to extend the life of the observatory.

  15. Hybrid Electrostatic/Flextensional Mirror for Lightweight, Large-Aperture, and Cryogenic Space Telescopes

    NASA Technical Reports Server (NTRS)

    Patrick, Brian; Moore, James; Hackenberger, Wesley; Jiang, Xiaoning

    2013-01-01

    A lightweight, cryogenically capable, scalable, deformable mirror has been developed for space telescopes. This innovation makes use of polymer-based membrane mirror technology to enable large-aperture mirrors that can be easily launched and deployed. The key component of this innovation is a lightweight, large-stroke, cryogenic actuator array that combines the high degree of mirror figure control needed with a large actuator influence function. The latter aspect of the innovation allows membrane mirror figure correction with a relatively low actuator density, preserving the lightweight attributes of the system. The principal components of this technology are lightweight, low-profile, high-stroke, cryogenic-capable piezoelectric actuators based on PMN-PT (piezoelectric lead magnesium niobate-lead titanate) single-crystal configured in a flextensional actuator format; high-quality, low-thermal-expansion polymer membrane mirror materials developed by NeXolve; and electrostatic coupling between the membrane mirror and the piezoelectric actuator assembly to minimize problems such as actuator print-through.

  16. Experimental demonstration of a self-tracking 16-aperture receiver telescope array for laser intersatellite communications

    NASA Astrophysics Data System (ADS)

    Kalmar, Andras; Kudielka, Klaus H.; Leeb, Walter R.

    1998-05-01

    An adaptive receive telescope array with 16 apertures has been designed and breadboarded. With respect to size and performance, such a telescope array is well suited for use as receive antenna in a coherent interorbit laser link. The laboratory demonstrator, designed to operate at a wavelength of (lambda) equals 1.064 micrometers, is completely independent of any subsequent receiver and of the data modulation format employed. The telescope array is self-phasing, i.e. the main lobe of the antenna pattern automatically follows the direction of the incident wave. It thus performs non- mechanical fine tracking. Our experimental setup comprises a subtelescope array and a digital control unit employing digital signal processors. Besides inertia-free tracking, the control unit also checks and, if necessary, restores parallel alignment of the subtelescope axes at regular intervals. Space-worthy concepts have been applied wherever possible, although experiments have been performed only in the laboratory. Automatic fine-tracking is achieved within a single subtelescope's field of view (30 (mu) rad) in the frequency range up to 730 Hz.

  17. Optical parametric oscillators for high pulse energy and high average power operation based on large aperture periodically poled KTP and RTA

    NASA Astrophysics Data System (ADS)

    Peltz, M.; Bder, U.; Borsutzky, A.; Wallenstein, R.; Hellstrm, J.; Karlsson, H.; Pasiskevicius, V.; Laurell, F.

    We report on optical parametric oscillators (OPOs) based on large aperture periodically poled KTiOPO4 (PPKTP) and RbTiOAsO4 (PPRTA) pumped with high pulse energy and high average power Q-switched solid-state lasers. The OPOs were pumped with 1064-nm pulses of a diode-pumped Nd:YVO4 laser at 20 kHz repetition rate. The emitted signal wavelengths were 1.72 ?m and 1.58 ?m and the idler wavelengths were 2.79 ?m and 3.26 ?m, respectively. Pumping the PPKTP OPO with 7.2 W and the PPRTA OPO with 8 W average power, 2 W and 1.3 W total OPO output powers were generated. Two-dimensional measurements of the total OPO output power, the signal wavelength and the signal bandwidth in dependence on the crystal location indicated a good uniformity of the quasiphasematching structure over the entire 3-mm-thick crystals. This allowed pumping with larger pump beams and therefore with pulse energies of tens of millijoules. Pumping with different flash-lamp-pumped lasers, good OPO performance and high output pulse energies could be achieved for all pump lasers. Maximum input pulse energies of 56 mJ gave output pulse energies of as much as 18 mJ. The temperature tuning behaviors of both OPOs were measured, showing excellent agreement with calculated temperature tuning curves. New equations for temperature dispersion in RTA are presented. These results show that large-aperture PPKTP and PPRTA crystals are well suited for tunable nanosecond OPO operation with multi-watt average pump power and several tens of millijoules pump pulse energies.

  18. A Future Large-Aperture UVOIR Space Observatory: Key Technologies and Capabilities

    NASA Astrophysics Data System (ADS)

    Stahle, Carl; Clampin, Mark; Balasubramanian, Kunjithapatham; Bolcar, Matthew R.; Feinberg, Lee; Mosier, Gary; Quijada, Manuel; Rauscher, Bernard J.; Redding, David; Shaklan, Stuart; Stahl, H. Philip; Thronson, Harley A.

    2015-01-01

    We present the key technologies and capabilities that will enable a future, large-aperture ultraviolet/optical/infrared (UVOIR) space observatory. These include starlight suppression systems, vibration isolation and control systems, lightweight mirror segments, detector systems, and mirror coatings. These capabilities will provide major advances over current and near-future observatories for sensitivity, angular resolution, and starlight suppression. The goals adopted in our study for the starlight suppression system are 10-10contrast with an inner working angle of 40 milliarcsec and broad bandpass. We estimate that a vibration and isolation control system that achieves a total system vibration isolation of 140 dB for a vibration-isolated mass of ~5000 kg is required to achieve the high wavefront error stability needed for exoplanet coronagraphy. Technology challenges for lightweight mirror segments include diffraction-limited optical quality and high wavefront error stability as well as low cost, low mass, and rapid fabrication. Key challenges for the detector systems include visible-blind, high quantum efficiency UV arrays, photon counting visible and NIR arrays for coronagraphic spectroscopy and starlight wavefront sensing and control, and detectors with deep full wells with low persistence and radiation tolerance to enable transit imaging and spectroscopy at all wavelengths. Finally, mirror coatings with high reflectivity (> 90%), high uniformity (< 1%) and low polarization (< 1%) that are scalable to large diameter mirror substrates will be essential for ensuring that both high throughput UV observations and high contrast observations can be performed by the same observatory.

  19. The Balloon-borne Large-Aperture Submillimeter Telescope for Polarization: BLAST-pol

    E-print Network

    G. Marsden; P. A. R. Ade; S. Benton; J. J. Bock; E. L. Chapin; J. Chung; M. J. Devlin; S. Dicker; L. Fissel; M. Griffin; J. O. Gundersen; M. Halpern; P. C. Hargrave; D. H. Hughes; J. Klein; A. Korotkov; C. J. MacTavish; P. G. Martin; T. G. Martin; T. G. Matthews; P. Mauskopf; L. Moncelsi; C. B. Netterfield; G. Novak; E. Pascale; L. Olmi; G. Patanchon; M. Rex; G. Savini; D. Scott; C. Semisch; N. Thomas; M. D. P. Truch; C. Tucker; G. S. Tucker; M. P. Viero; D. Ward-Thompson; D. V. Wiebe

    2008-09-25

    The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) is a sub-orbital experiment designed to study the process of star formation in local galaxies (including the Milky Way) and in galaxies at cosmological distances. Using a 2-m Cassegrain telescope, BLAST images the sky onto a focal plane, which consists of 270 bolometric detectors split between three arrays, observing simultaneously in 30% wide bands, centered at 250, 350, and 500 microns. The diffraction-limited optical system provides a resolution of 30" at 250 microns. The pointing system enables raster-like scans with a positional accuracy of ~30", reconstructed to better than 5" rms in post-flight analysis. BLAST had two successful flights, from the Arctic in 2005, and from Antarctica in 2006, which provided the first high-resolution and large-area (~0.8-200 deg^2) submillimeter surveys at these wavelengths. As a pathfinder for the SPIRE instrument on Herschel, BLAST shares with the ESA satellite similar focal plane technology and scientific motivation. A third flight in 2009 will see the instrument modified to be polarization-sensitive (BLAST-Pol). With its unprecedented mapping speed and resolution, BLAST-Pol will provide insights into Galactic star-forming nurseries, and give the necessary link between the larger, coarse resolution surveys and the narrow, resolved observations of star-forming structures from space and ground based instruments being commissioned in the next 5 years.

  20. A Future Large-Aperture UVOIR Space Observatory: Key Technologies and Capabilities

    NASA Technical Reports Server (NTRS)

    Bolcar, Matthew Ryan; Stahle, Carl M.; Balasubramaniam, Kunjithapatham; Clampin, Mark; Feinberg, Lee D.; Mosier, Gary E.; Quijada, Manuel A.; Rauscher, Bernard J.; Redding, David C.; Rioux, Norman M.; Shaklan, Stuart B.; Stahl, H. Philip; Thronson, Harley A.

    2015-01-01

    We present the key technologies and capabilities that will enable a future, large-aperture ultravioletopticalinfrared (UVOIR) space observatory. These include starlight suppression systems, vibration isolation and control systems, lightweight mirror segments, detector systems, and mirror coatings. These capabilities will provide major advances over current and near-future observatories for sensitivity, angular resolution, and starlight suppression. The goals adopted in our study for the starlight suppression system are 10-10 contrast with an inner working angle of 20 milliarcsec and broad bandpass. We estimate that a vibration and isolation control system that achieves a total system vibration isolation of 140 dB for a vibration-isolated mass of 5000 kg is required to achieve the high wavefront error stability needed for exoplanet coronagraphy. Technology challenges for lightweight mirror segments include diffraction-limited optical quality and high wavefront error stability as well as low cost, low mass, and rapid fabrication. Key challenges for the detector systems include visible-blind, high quantum efficiency UV arrays, photon counting visible and NIR arrays for coronagraphic spectroscopy and starlight wavefront sensing and control, and detectors with deep full wells with low persistence and radiation tolerance to enable transit imaging and spectroscopy at all wavelengths. Finally, mirror coatings with high reflectivity ( 90), high uniformity ( 1) and low polarization ( 1) that are scalable to large diameter mirror substrates will be essential for ensuring that both high throughput UV observations and high contrast observations can be performed by the same observatory.

  1. Acoustic performance of a large-aperture, seabed, fiber-optic hydrophone array

    NASA Astrophysics Data System (ADS)

    Cranch, G. A.; Crickmore, R.; Kirkendall, C. K.; Bautista, A.; Daley, K.; Motley, S.; Salzano, J.; Latchem, J.; Nash, P. J.

    2004-06-01

    A large-aperture, seabed mounted, fiber-optic hydrophone array has been constructed and characterized. The system is designed for use as a large area surveillance array for deployment in shallow water regions. The underwater portion comprises two arrays of 48 hydrophones separated by a 3 km fiber-optic link, which are connected to a shore station by 40 km of single-mode optical fiber. The hydrophone is based on a fiber-optic Michelson interferometer and the acoustic transduction mechanism is a fiber-wrapped mandrel design. No electrical power is required in the underwater portion. The performance of the system is described, characterized during laboratory measurements and during a recent sea trial. Specifically, measurements of the acoustic resolution, array shape, beam patterns, array gain, and target tracking capability of this array. The system demonstrates self-noise levels up to 20 dB (typically 10 dB) lower than the ambient acoustic noise experienced in the sea trial and array gains close to the theoretical maximum. The system telemetry and electronics have been designed to be expandable to accommodate several hundred hydrophones.

  2. Large-aperture Wide-bandwidth Antireflection-coated Silicon Lenses for Millimeter Wavelengths

    NASA Technical Reports Server (NTRS)

    Datta, R.; Munson, C. D.; Niemack, M. D.; McMahon, J. J.; Britton, J.; Wollack, Edward J.; Beall, J.; Devlin, M. J.; Fowler, J.; Gallardo, P.; Hubmayr, J.; Irwin, K.; Newburgh, L.; Nibarger, J. P.; Page, L.; Quijada, Manuel A.; Schmitt, B. L.; Staggs, S. T.; Thornton, R.; Zhang, L.

    2013-01-01

    The increasing scale of cryogenic detector arrays for submillimeter and millimeter wavelength astrophysics has led to the need for large aperture, high index of refraction, low loss, cryogenic refracting optics. Silicon with n 3.4, low loss, and high thermal conductivity is a nearly optimal material for these purposes but requires an antireflection (AR) coating with broad bandwidth, low loss, low reflectance, and a matched coefficient of thermal expansion. We present an AR coating for curved silicon optics comprised of subwavelength features cut into the lens surface with a custom three-axis silicon dicing saw. These features constitute a metamaterial that behaves as a simple dielectric coating.We have fabricated silicon lenses as large as 33.4 cm in diameter with micromachined layers optimized for use between 125 and 165 GHz. Our design reduces average reflections to a few tenths of a percent for angles of incidence up to 30deg with low cross polarization.We describe the design, tolerance, manufacture, and measurements of these coatings and present measurements of the optical properties of silicon at millimeter wavelengths at cryogenic and room temperatures. This coating and lens fabrication approach is applicable from centimeter to submillimeter wavelengths and can be used to fabricate coatings with greater than octave bandwidth.

  3. Large-Aperture Wide-Bandwidth Anti-Reflection-Coated Silicon Lenses for Millimeter Wavelengths

    NASA Technical Reports Server (NTRS)

    Datta, R.; Munson, C. D.; Niemack, M. D.; McMahon, J. J.; Britton, J.; Wollack, E. J.; Beall, J.; Devlin, M. J.; Fowler, J.; Gallardo, P.; Hubmayr, J.; Irwin, K.; Newburgh, L.; Nibarger, J. P.; Page, L.; Quijada, M. A.; Schmitt, B. L.; Staggs, S. T.; Thornton, R.; Zhang, L.

    2013-01-01

    The increasing scale of cryogenic detector arrays for sub-millimeter and millimeter wavelength astrophysics has led to the need for large aperture, high index of refraction, low loss, cryogenic refracting optics. Silicon with n = 3.4, low loss, and relatively high thermal conductivity is a nearly optimal material for these purposes, but requires an antireflection (AR) coating with broad bandwidth, low loss, low reflectance, and a matched coffecient of thermal expansion. We present an AR coating for curved silicon optics comprised of subwavelength features cut into the lens surface with a custom three axis silicon dicing saw. These features constitute a metamaterial that behaves as a simple dielectric coating. We have fabricated and coated silicon lenses as large as 33.4 cm in diameter with coatings optimized for use between 125-165 GHz. Our design reduces average reflections to a few tenths of a percent for angles of incidence up to 30 deg. with low cross-polarization. We describe the design, tolerance, manufacture, and measurements of these coatings and present measurements of the optical properties of silicon at millimeter wavelengths at cryogenic and room temperatures. This coating and lens fabrication approach is applicable from centimeter to sub-millimeter wavelengths and can be used to fabricate coatings with greater than octave bandwidth.

  4. Electro-Mechanical Simulation of a Large Aperture MOEMS Fabry-Perot Tunable Filter

    NASA Technical Reports Server (NTRS)

    Kuhn, Jonathan L.; Barclay, Richard B.; Greenhouse, Matthew A.; Mott, D. Brent; Satyapal, Shobita; Powers, Edward I. (Technical Monitor)

    2000-01-01

    We are developing a micro-machined electrostatically actuated Fabry-Perot tunable filter with a large clear aperture for application in high through-put wide-field imaging spectroscopy and lidar systems. In the first phase of this effort, we are developing key components based on coupled electro-mechanical simulations. In particular, the movable etalon plate design leverages high coating stresses to yield a flat surface in drum-head tension over a large diameter (12.5 mm). In this approach, the cylindrical silicon movable plate is back etched, resulting in an optically coated membrane that is suspended from a thick silicon support ring. Understanding the interaction between the support ring, suspended membrane, and coating is critical to developing surfaces that are flat to within stringent etalon requirements. In this work, we present the simulations used to develop the movable plate, spring suspension system, and electrostatic actuation mechanism. We also present results from tests of fabricated proof of concept components.

  5. Large-aperture wide-bandwidth antireflection-coated silicon lenses for millimeter wavelengths.

    PubMed

    Datta, R; Munson, C D; Niemack, M D; McMahon, J J; Britton, J; Wollack, E J; Beall, J; Devlin, M J; Fowler, J; Gallardo, P; Hubmayr, J; Irwin, K; Newburgh, L; Nibarger, J P; Page, L; Quijada, M A; Schmitt, B L; Staggs, S T; Thornton, R; Zhang, L

    2013-12-20

    The increasing scale of cryogenic detector arrays for submillimeter and millimeter wavelength astrophysics has led to the need for large aperture, high index of refraction, low loss, cryogenic refracting optics. Silicon with n=3.4, low loss, and high thermal conductivity is a nearly optimal material for these purposes but requires an antireflection (AR) coating with broad bandwidth, low loss, low reflectance, and a matched coefficient of thermal expansion. We present an AR coating for curved silicon optics comprised of subwavelength features cut into the lens surface with a custom three-axis silicon dicing saw. These features constitute a metamaterial that behaves as a simple dielectric coating. We have fabricated silicon lenses as large as 33.4cm in diameter with micromachined layers optimized for use between 125 and 165GHz. Our design reduces average reflections to a few tenths of a percent for angles of incidence up to 30 with low cross polarization. We describe the design, tolerance, manufacture, and measurements of these coatings and present measurements of the optical properties of silicon at millimeter wavelengths at cryogenic and room temperatures. This coating and lens fabrication approach is applicable from centimeter to submillimeter wavelengths and can be used to fabricate coatings with greater than octave bandwidth. PMID:24513939

  6. Large-explosive source, wide-recording aperture, seismic profiling on the Columbia Plateau, Washington

    SciTech Connect

    Jarchow, C.M. (Stanford Univ., CA (United States). Dept. of Geophysics); Catchings, R.D.; Lutter, W.J. (Geological Survey, Menlo Park, CA (United States))

    1994-02-01

    Clear subsurface seismic images have been obtained at low cost on the Columbia Plateau, Washington. The Columbia Plateau is perhaps the most notorious of all bad-data'' areas because large impedance contrasts in surface flood basalts severely degrade the seismic wavefield. This degradation was mitigated in this study via a large-explosive source, wide-recording aperture shooting method. The shooting method emphasizes the wide-angle portion of the wavefield, where Fermat's principle guarantees reverberation will not interfere with the seismic manifestations of crucial geologic interfaces. The basalt diving wave, normally discarded in standard common midpoint (CMP) seismic profiling, can be used to image basalt velocity structure via travel-time inversion. Maximum depth-penetration of the diving wave tightly constrains basalt-sediment interface depth. An arrival observed only at shot-receiver offsets greater than 15 km can be used to determine the velocity and geometry of basement via simultaneous inversion. The results from this study suggest that previous geologic hypotheses and hydrocarbon play concepts for the Columbia Plateau may have been in error.

  7. The Balloon-borne Large-Aperture Submillimeter Telescope for polarization: BLAST-pol

    NASA Astrophysics Data System (ADS)

    Marsden, G.; Ade, P. A. R.; Benton, S.; Bock, J. J.; Chapin, E. L.; Chung, J.; Devlin, M. J.; Dicker, S.; Fissel, L.; Griffin, M.; Gundersen, J. O.; Halpern, M.; Hargrave, P. C.; Hughes, D. H.; Klein, J.; Korotkov, A.; MacTavish, C. J.; Martin, P. G.; Martin, T. G.; Matthews, T. G.; Mauskopf, P.; Moncelsi, L.; Netterfield, C. B.; Novak, G.; Pascale, E.; Olmi, L.; Patanchon, G.; Rex, M.; Savini, G.; Scott, D.; Semisch, C.; Thomas, N.; Truch, M. D. P.; Tucker, C.; Tucker, G. S.; Viero, M. P.; Ward-Thompson, D.; Wiebe, D. V.

    2008-07-01

    The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) is a sub-orbital experiment designed to study the process of star formation in local galaxies (including the Milky Way) and in galaxies at cosmological distances. Using a 2m Cassegrain telescope, BLAST images the sky onto a focal plane, which consists of 270 bolometric detectors split between three arrays, observing simultaneously in 30% wide bands, centered at 250, 350, and 500 ?m. The diffraction-limited optical system provides a resolution of 30" at 250 ?m. The pointing system enables raster-like scans with a positional accuracy of ~30", reconstructed to better than 5" rms in postflight analysis. BLAST had two successful flights, from the Arctic in 2005, and from Antarctica in 2006, which provided the first high-resolution and large-area (~0.8-200 deg2) submillimeter surveys at these wavelengths. As a pathfinder for the SPIRE instrument on Herschel, BLAST shares with the ESA satellite similar focal plane technology and scientific motivation. A third flight in 2009 will see the instrument modified to be polarization-sensitive (BLAST-pol). With its unprecedented mapping speed and resolution, BLAST-pol will provide insights into Galactic star-forming nurseries, and give the necessary link between the larger, coarse resolution surveys and the narrow, resolved observations of star-forming structures from space and ground based instruments being commissioned in the next 5 years.

  8. Advanced Technology Large-Aperture Space Telescope (ATLAST) Appendix G: ATLAST-9.2m Design Study

    E-print Network

    Sirianni, Marco

    ) are required to achieve the ATLAST-9.2m requirements. ATLAST-9.2m draws heavily on James Webb Space TelescopeAdvanced Technology Large-Aperture Space Telescope (ATLAST) 1 Appendix G: ATLAST-9.2m Design Study.........................................................................8 G 2.1 ATLAST 9.2m Optical Telescope Assembly

  9. A New Type of X-ray Condenser Lenses with Large Apertures Fabricated by Rolling of Structured Films

    SciTech Connect

    Simon, M.; Reznikova, E.; Nazmov, V.; Grund, T. [Institut fuer Mikrostrukturtechnik, Forschungszentrum Karlsruhe GmbH Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Last, A. [Institut fuer Mikrostrukturtechnik, Universitaet Karlsruhe Kaiserstrasse 12, 76131 Karlsruhe (Germany)

    2010-04-06

    In order to meet the demand for X-ray lenses with large apertures and, hence, photon flux, a new type of X-ray lenses has been developed: Rolled prismatic X-ray lenses feature a vast number of refracting surfaces to increase transparency and aperture, respectively. Prototypes of such lenses have been fabricated by molding and rolling of a structured polyimide film. In this work, rolled prismatic X-ray lenses are pictured, and results of first tests performed at the ANKA storage ring in Karlsruhe are presented.

  10. Design studies of large aperture, high-resolution Earth science microwave radiometers compatible with small launch vehicles

    NASA Technical Reports Server (NTRS)

    Schroeder, Lyle C.; Bailey, M. C.; Harrington, Richard F.; Kendall, Bruce M.; Campbell, Thomas G.

    1994-01-01

    High-spatial-resolution microwave radiometer sensing from space with reasonable swath widths and revisit times favors large aperture systems. However, with traditional precision antenna design, the size and weight requirements for such systems are in conflict with the need to emphasize small launch vehicles. This paper describes tradeoffs between the science requirements, basic operational parameters, and expected sensor performance for selected satellite radiometer concepts utilizing novel lightweight compactly packaged real apertures. Antenna, feed, and radiometer subsystem design and calibration are presented. Preliminary results show that novel lightweight real aperture coupled with state-of-the-art radiometer designs are compatible with small launch systems, and hold promise for high-resolution earth science measurements of sea ice, precipitation, soil moisture, sea surface temperature, and ocean wind speeds.

  11. Long-wavelength vertical-cavity surface-emitting lasers with selectively etched thin apertures

    NASA Astrophysics Data System (ADS)

    Feezell, Daniel F.

    Long-wavelength vertical-cavity surface-emitting lasers (VCSELs) emitting in the 1300--1600nm wavelength window are attractive light sources for short to mid-range optical fiber communications. These devices target low-loss and low-dispersion minima in standard optical fibers and are expected to provide a low-cost alternative to the existing edge-emitting infrastructure. With low-power consumption, on wafer testing; simple packaging, and high fiber-coupling efficiency, VCSELs are ideal transmitters for CWDM, metro, local area, and storage area networks. Recently, much attention has been devoted to a rich variety of approaches to long-wavelength VCSELs. One underlying problem, however, has been the need to match a reliable high-gain active region with high-index-contrast distributed Bragg reflectors (DBRs) over the full 1300--1600nm wavelength range. One solution to this problem is to utilize well-established InAlGaAs active-region technology coupled with AlGaAsSb DBRs. This combination facilitates monolithic all-epitaxial InP-based devices spanning the entire 1300--1600nm wavelength range. Previously, Dr. Shigeru Nakagawa and Dr. Eric Hall have demonstrated long-wavelength VCSELs with Sb-based technology operating at 1550nm. This dissertation demonstrates the first high-performance InP-based VCSELs with Sb-based DBRs operating at 1310nm, thus solidifying Sb-based technology as a wavelength flexible platform for long-wavelength devices. Also developed is a novel and efficient tunnel-junction aperturing technology for generating extremely low-loss optical and electrical confinement. Lastly, it is shown that the benefits from such an aperturing scheme produce marked improvements in device operation versus previously demonstrated Sb-based VCSELs. The devices from this research generated over 1.6mW single-mode continuous-wave (CW) output power at room temperature (>2mW multi-mode), displayed threshold currents down to 1mA, and operated CW up to 90C. Furthermore, world-record CW differential efficiencies (>60%) for long-wavelength VCSELs were obtained, demonstrating the effectiveness of low-loss selectively etched tunnel-junction apertures. High-speed modulation up to 6.0Gb/s was also demonstrated for the first time in Sb-based VCSELs. Error-free operation at 3.125Gb/s was shown up to 60C, with extinction ratios remaining >8dB. These results clearly demonstrate that all-epitaxial InP-based devices with Sb-based DBRs are a viable option for high-performance long-wavelength VCSELs.

  12. Acoustic characterization of high intensity focused ultrasound fields generated from a transmitter with a large aperture

    NASA Astrophysics Data System (ADS)

    Chen, Tao; Fan, Tingbo; Zhang, Wei; Qiu, Yuanyuan; Tu, Juan; Guo, Xiasheng; Zhang, Dong

    2014-03-01

    Prediction and measurement of the acoustic field emitted from a high intensity focused ultrasound (HIFU) is essential for the accurate ultrasonic treatment. In this study, the acoustic field generated from a strongly focused HIFU transmitter was characterized by a combined experiment and simulation method. The spheroidal beam equation (SBE) was utilized to describe the nonlinear sound propagation. The curve of the source pressure amplitude versus voltage excitation was determined by fitting the measured ratio of the second harmonic to the fundamental component of the focal waveform to the simulation result; finally, the acoustic pressure field generated by the strongly focused HIFU transmitter was predicted by using the SBE model. A commercial fiber optic probe hydrophone was utilized to measure the acoustic pressure field generated from a 1.1 MHz HIFU transmitter with a large half aperture angle of 30. The maximum measured peak-to-peak pressure was up to 72 MPa. The validity of this combined approach was confirmed by the comparison between the measured results and the calculated ones. The results indicate that the current approach might be useful to describe the HIFU field. The results also suggest that this method is not valid for low excitations owing to low sensitivity of the second harmonic.

  13. Subwavelength grating reflectors in MEMS tunable Fabry-Perot infrared filters with large aperture

    NASA Astrophysics Data System (ADS)

    Kurth, Steffen; Hiller, Karla; Meinig, Marco; Besser, Jan; Seifert, Mario; Ebermann, Martin; Neumann, Norbert; Schlachter, Florian; Gessner, Thomas

    2014-02-01

    This paper presents a novel tunable infrared filter applying a subwavelength grating that substitutes the distributed Bragg reflectors (DBRs) in tunable Fabry-Perot (FP) filters to reduce cost and fabrication effort. It consists of uniformly arranged disc resonators which are made of 100 nm thick aluminum at a 200 nm Si3N4 membrane carrier that stands freely after fabrication. The dimensions of the subwavelength structures were optimized based on finite difference time domain (FDTD) analysis. The fabrication sequence consists of silicon MEMS technology steps like deposition and patterning of electrodes and of isolation layers, silicon etching, and wafer bonding, and it includes nano imprint lithography for forming the subwavelength structures at wafer level. The samples have an aperture of 2 mm and are mechanically tuned by electrostatic forces with tuning voltages up to 80 V. They show the typical characteristics of FP filters but with high peak transmittance within a remarkably large wavelength range (T < 50% @ 2.5 ?m 6.5 ?m) spanning over 5 interference orders of the optical resonator. The optical performance was measured by Fourier transform infrared spectrometer and compared to the simulation results. It shows a widely good agreement between calculation and measurement.

  14. Microstrip patch antenna panel for large aperture L-band phased array

    NASA Technical Reports Server (NTRS)

    Chamberlain, Neil; Amaro, Luis; Oakes, Eric; Hodges, Richard; Spitz, Suzanne; Rosen, Paul A.

    2004-01-01

    This paper describes the design and development of a large, lightweight antenna panel for an active phased array operating at L-band. The panel was developed under a JPL program of technology development for space based radar. It utilizes dual-stacked patch elements that are interconnected with corporate feed manifold of striplines. This paper focuses on the electromagnetic design and performance of the radiating elements, with emphasis on scan performance, and also addresses mechanical and thermal aspects of the panel. The element in the array environment has a bandwidth of more than 80MHz centered at 1260MHz and is fed so that it can radiate orthogonal linear polarizations. The envisioned phased array, with a nominal aperture of 50m x 2m, is designed to scan +/-45 degrees in azimuth and +/-20 degrees in elevation. The panel of radiating elements has a mass density of 3.9 kg/m2, which represents approximately 50% of the target 8kg/m2 total panel mass density that includes T/R modules and feed manifolds.

  15. The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) 2005: Calibration and Targeted Sources

    E-print Network

    M. D. P. Truch; P. A. R. Ade; J. J. Bock; E. L. Chapin; M. J. Devlin; S. Dicker; M. Griffin; J. O. Gundersen; M. Halpern; P. C. Hargrave; D. H. Hughes; J. Klein; G. Marsden; P. G. Martin; P. Mauskopf; C. B. Netterfield; L. Olmi; E. Pascale; G. Patanchon; M. Rex; D. Scott; C. Semisch; C. Tucker; G. S. Tucker; M. P. Viero; D. V. Wiebe

    2008-03-31

    The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) operated successfully during a 100-hour flight from northern Sweden in June 2005 (BLAST05). As part of the calibration and pointing procedures, several compact sources were mapped, including solar system, Galactic, and extragalactic targets, specifically Pallas, CRL 2688, LDN 1014, IRAS 20126+4104, IRAS 21078+5211, IRAS 21307+5049, IRAS 22134+5834, IRAS 23011+6126, K3-50, W 75N, and Mrk 231. One additional source, Arp 220, was observed and used as our primary calibrator. Details of the overall BLAST05 calibration procedure are discussed here. The BLAST observations of each compact source are described, flux densities and spectral energy distributions are reported, and these are compared with previous measurements at other wavelengths. The 250, 350, and 500 um BLAST data can provide useful constraints to the amplitude and slope of the submillimeter continuum, which in turn may be useful for the improved calibration of other submillimeter instruments.

  16. Origins of high-frequency scattered waves near PKKP from large aperture seismic array data

    USGS Publications Warehouse

    Earle, P.S.

    2002-01-01

    This article identifies the likely origin of 1-Hz scattered waves in the vicinity of PKKP by comparing measurements of slowness and onset time to ray-theoretical predictions. The measurements are obtained from slant stacks of Large Aperture Seismic Array (LASA) data from 36 earthquakes and six explosions in the range 30??-116??. Three types of scattered waves explain the main features seen in the stacks, including: P scattered to PKP near the Earth's surface (P.PKP), PKKP scattered near its core-mantle-boundary (CMB) reflection point (PK.KP), and SKKP scattered near its CMB reflection point (SK.KP). The LASA stacks image the amplitude and slowness variations of the scattered waves with time. They also show where these waves can be detected and where they are free from contaminating arrivals. SK.KP waves rise above the noise approximately 100 sec before the onset time of the main SKKP arrival near 113??. Observations of PK.KP span 30??-100??. However, at distances greater than 50?? they suffer from P.PKP contamination. At distances less than 40?? the PK.KP last for about 280 sec. This is approximately 130 sec longer than the maximum ray-theoretical prediction for waves scattered at the CMB, indicating a possible combination of near-surface scattering and contributions from the overlying mantle.

  17. Infrasonic interferometry applied to microbaroms observed at the Large Aperture Infrasound Array in the Netherlands

    NASA Astrophysics Data System (ADS)

    Fricke, J. T.; Evers, L. G.; Smets, P. S. M.; Wapenaar, K.; Simons, D. G.

    2014-08-01

    We present the results of infrasonic interferometry applied to microbaroms, obtained from ambient noise. For this purpose the "Large Aperture Infrasound Array" (LAIA) was used, which has been installed in the Netherlands. Preprocessing appeared to be an essential step in enhancing the microbarom signals from ambient noise that strongly influences the results of the interferometry. Both the state of the atmosphere and the noise characteristics are taken into account to assess the strength of the cross correlation. The delay time of the microbaroms between two stations is determined through cross correlating the recordings. By calculating the cross correlations between all 55 station pairs of LAIA, we are able to find the delay time of microbaroms up to a interstation distance of 40.6 km. Using the strength of the cross correlations, we are able to show that the coherence of the microbaroms along the direction of arrival is higher than orthogonal to it. A comparison of the atmospheric state, with a cross correlation, over a period of 10 days, reveals that the infrasound propagation over the array is correlated with the tropospheric temperature and wind. Based on the cross correlations between the three closest stations, we are able to passively estimate the effective sound speed and the wind speed as a function of time.

  18. Study on the method to test large-aperture hyperboloid convex mirror

    NASA Astrophysics Data System (ADS)

    Meng, Xiaohui; Dong, Huiwen; Guo, Wen; Wang, Huijun

    2014-08-01

    There are numerous reflecting optical system designs that call for large-aperture convex surfaces, such as secondary mirror in on-axis three mirror anastigmatic (TMA). Several methods to test high accuracy hyperboloid convex surfaces are introduced separately in this paper. A kind of arrangement is chosen to test a surface with diameter of 420mm, radius of 1371mm, and conic K -2.1229. The CGH compensator for testing is designed, which is made up of illumination lens and hologram test plate with designed residual wavefront aberration less than 0.001? (RMS). The second transmitted method that is equipped with a technical flat surface coating by Ag film in the bottom of surface mirror under test, which form an auto-collimation optical system to eliminate the aberration. The Hindle-Simpson test that requires a larger meniscus lens to compensate the optical aberration, and the designed result of optical test system is less than 0.0016?. Contrasting the CGH compensator and the second transmitted method, the Hindle-Simpson testing method has the advantage of it is easily to manufacture and adjust; meanwhile the test result is stable and has been less affected by the environment. It has been found that the method is rational and reliable, and it can fulfill the requirement of manufacturing and testing process for hyperboloid convex mirrors.

  19. The sensible heat fluxes over irrigated areas in western Turkey determined with a large aperture scintillometer

    NASA Astrophysics Data System (ADS)

    Meijninger, W. M. L.; de Bruin, H. A. R.

    2000-03-01

    As part of an international experiment in which several methods of estimating the actual evapotranspiration were compared, two large aperture scintillometers (LAS) and a small micrometeorological station were installed in the Gediz Basin near Menemen, Turkey during the summer of 1998 by the Meteorology and Air Quality Group of the Wageningen Agricultural University. The instruments will be used to provide "ground-truth" sensible heat fluxes. At the first site, a LAS was set up over a transect of the valley from Belen to Suluklu with a path length of 2700 m. The second LAS (a path length of 670 m) together with a small micrometeorological station was installed in an irrigated cotton field west of the first site. However, due to experimental problems the scintillation method for the second site could not be applied. Instead the variance method, which just as the scintilliation method is based on the Monin-Obukhov similarity theory, was used. The 24 h average sensible heat fluxes of the valley for the entire growing season are presented and special attention is given to the LANDSAT overpass dates June 26 and August 29. The results presented in this paper show that the scintillometer is a robust and reliable "stand-alone" system that is able to provide operational estimates of areal averaged sensible heat fluxes.

  20. [Manufacture tolerance analysis of solid Mach-Zehnder interferometer in large aperture static imaging spectrometer (LASIS)].

    PubMed

    Liu, Qing; Zhou, Jin-Song; Nie, Yun-Feng; L, Qun-Bo

    2014-07-01

    The principle and instrumental structure of large aperture static imaging spectrometer (LASIS) were briefly described in the present paper, the principle of the Mach-Zehnder imaging spectrometer was introduced, and the Mach-Zehnder interferometers' working way in the imaging spectrometer was illustrated. The structure of solid Mach-Zehnder interferometer was analyzed, and discussion was made based on the requirements of field of view (FOV) in image space and single sided interferogram with a small portion around zero path difference (ZPD). The additional optical path difference (OPD) created by manufacturing and matching tolerance of two asymmetrical pentagonal prisms will lead to the displacement of shearing and OPD nonlinearity. It was showed that the additional OPD from non-common optical path structure of solid Mach-Zehnder spectrometer implies more requirements on the manufacture of this element, compared with Sagnac interferometer, for the matching tolerance of two asymmetrical pentagonal prisms to br lower than 0.02 mm. The recovery spectrum error caused by the OPD nonlinearity is lower than 0.2% and can be ignored. PMID:25269324

  1. Structural Feasibility Analysis of a Robotically Assembled Very Large Aperture Optical Space Telescope

    NASA Technical Reports Server (NTRS)

    Wilkie, William Keats; Williams, R. Brett; Agnes, Gregory S.; Wilcox, Brian H.

    2007-01-01

    This paper presents a feasibility study of robotically constructing a very large aperture optical space telescope on-orbit. Since the largest engineering challenges are likely to reside in the design and assembly of the 150-m diameter primary reflector, this preliminary study focuses on this component. The same technology developed for construction of the primary would then be readily used for the smaller optical structures (secondary, tertiary, etc.). A reasonable set of ground and on-orbit loading scenarios are compiled from the literature and used to define the structural performance requirements and size the primary reflector. A surface precision analysis shows that active adjustment of the primary structure is required in order to meet stringent optical surface requirements. Two potential actuation strategies are discussed along with potential actuation devices at the current state of the art. The finding of this research effort indicate that successful technology development combined with further analysis will likely enable such a telescope to be built in the future.

  2. Acoustic characterization of high intensity focused ultrasound fields generated from a transmitter with a large aperture

    SciTech Connect

    Chen, Tao; Fan, Tingbo [Institute of Acoustics, Key Laboratory of Modern Acoustics, MOE, Nanjing University, Nanjing 210093 (China); Jiangsu Province Institute for Medical Equipment Testing, Nanjing 210012 (China); Zhang, Wei [Jiangsu Province Institute for Medical Equipment Testing, Nanjing 210012 (China); Qiu, Yuanyuan [Department of electronic information, Nantong University, Nantong 226019 (China); Tu, Juan, E-mail: juantu@nju.edu.cn, E-mail: dzhang@nju.edu.cn; Guo, Xiasheng [Institute of Acoustics, Key Laboratory of Modern Acoustics, MOE, Nanjing University, Nanjing 210093 (China); Zhang, Dong, E-mail: juantu@nju.edu.cn, E-mail: dzhang@nju.edu.cn [Institute of Acoustics, Key Laboratory of Modern Acoustics, MOE, Nanjing University, Nanjing 210093 (China); Institute of Acoustics, State Key Laboratory of Acoustics, Chinese Academy of Sciences, Beijing 100190 (China)

    2014-03-21

    Prediction and measurement of the acoustic field emitted from a high intensity focused ultrasound (HIFU) is essential for the accurate ultrasonic treatment. In this study, the acoustic field generated from a strongly focused HIFU transmitter was characterized by a combined experiment and simulation method. The spheroidal beam equation (SBE) was utilized to describe the nonlinear sound propagation. The curve of the source pressure amplitude versus voltage excitation was determined by fitting the measured ratio of the second harmonic to the fundamental component of the focal waveform to the simulation result; finally, the acoustic pressure field generated by the strongly focused HIFU transmitter was predicted by using the SBE model. A commercial fiber optic probe hydrophone was utilized to measure the acoustic pressure field generated from a 1.1?MHz HIFU transmitter with a large half aperture angle of 30. The maximum measured peak-to-peak pressure was up to 72?MPa. The validity of this combined approach was confirmed by the comparison between the measured results and the calculated ones. The results indicate that the current approach might be useful to describe the HIFU field. The results also suggest that this method is not valid for low excitations owing to low sensitivity of the second harmonic.

  3. Design of a large-aperture lens antenna usable over a +/- 15 deg scanning sector

    NASA Technical Reports Server (NTRS)

    Parsons, Chester L.; Miller, Lee S.

    1988-01-01

    A lens antenna design is described which requires the formation of both on-axis and far off-axis beams. The aperture is about 100 wavelengths in diameter, and the off-axis beams are displaced +/- 20 beamwidths from the axis. The results are indicative of the much greater scan capabilities of lensatic antennas compared to paraboloidal designs when both have single-aperture nonarray feeds.

  4. Imaging the midcontinent rift beneath Lake Superior using large aperture seismic data

    USGS Publications Warehouse

    Trehu, Anne M.; Morel-a-l'Huissier, Patrick; Meyer, R.; Hajnal, Z.; Karl, J.; Mereu, R. F.; Sexton, J.; Shay, J.; Chan, W. K.; Epili, D.; Jefferson, T.; Shih, X. R.; Wendling, S.; Milkereit, B.; Green, A.; Hutchinson, Deborah R.

    1991-01-01

    We present a detailed velocity model across the 1.1 billion year old Midcontinent Rift System (MRS) in central Lake Superior. The model was derived primarily from onshore-offshore large-aperture seismic and gravity data. High velocities obtained within a highly reflective half-graben that was imaged on coincident seismic reflection data demonstrate the dominantly mafic composition of the graben fill and constrain its total thickness to be at least 30km. Strong wide-angle reflections are observed from the lower crust and Moho, indicating that the crust is thickest (5560km) beneath the axis of the graben. The total crustal thickness decreases rapidly to about 40 km beneath the south shore of the lake and decreases more gradually to the north. Above the Moho is a high-velocity lower crust interpreted to result from syn-rift basaltic intrusion into and/or underplating beneath the Archean lower crust. The lower crust is thickest beneath the axis of the main rift half-graben. A second region of thick lower crust is found approximately 100km north of the axis of the rift beneath a smaller half graben that is interpreted to reflect an earlier stage of rifting. The crustal model presented here resembles recent models of some passive continental margins and is in marked contrast to many models of both active and extinct Phanerozoic continental rift zones. It demonstrates that the Moho is a dynamic feature, since the pre-rift Moho is probably within or above the high-velocity lower crust, whereas the post-rift Moho is defined as the base of this layer. In the absence of major tectonic activity, however, the Moho is very stable, since the large, abrupt variations in crustal thickness beneath the MRS have been preserved for at least a billion years.

  5. HI at z 20: The Large Aperture Experiment to Detect the Dark Ages

    NASA Astrophysics Data System (ADS)

    Greenhill, Lincoln J.; Werthimer, D.; Taylor, G.; Ellingson, S.; LEDA Collaboration

    2012-05-01

    When did the first stars form? Did supermassive black holes form at the same time, earlier, or later? One of the great challenges of cosmology today is the study of these first generation objects. The Large Aperture Experiment to Detect the Dark Ages (LEDA) project seeks to detect, in total-power, emission from neutral Hydrogen (21 cm rest wavelength) in the intergalactic medium about 100 million years after the Big Bang (redshifts 20). Detection would deliver the first observational constraints on models of structure formation and the first pockets of star and black holes formation in the Universe. LEDA will develop and integrate by 2013 signal processing instrumentation into the new first station of the Long Wavelength Array (LWA). This comprises a large-N correlator serving all 512 dipole antennas of the LWA1, leveraging a packetized CASPER architecture and combining FPGAs and GPUs for the F and X stages. Iterative calibration and imaging will rely on warped snapshot imaging and be drawn from a GPU-enabled library (cuWARP) that is designed specifically to support wide-field full polarization imaging with fixed dipole arrays. Calibration techniques will include peeling, correction for ionospheric refraction, direction dependent dipole gains, deconvolution via forward modeling, and exploration of pulsar data analysis to improve performance. Accurate calibration and imaging will be crucial requirements for LEDA, necessary to subtract the bright foreground sky and detect the faint neutral Hydrogen signal. From the computational standpoint, LEDA is a O(100) TeraFlop per second challenge that enables a scalable architecture looking toward development of radio arrays requiring power efficient 10 PetaFlop per second performance. Stage two of the Hydrogen Epoch of Reionization Array (HERA2) is one example.

  6. LCLS X-ray mirror measurements using a large aperture visible light interferometer

    SciTech Connect

    McCarville, T; Soufli, R; Pivovaroff, M

    2011-03-02

    Synchrotron or FEL X-ray mirrors are required to deliver an X-ray beam from its source to an experiment location, without contributing significantly to wave front distortion. Accurate mirror figure measurements are required prior to installation to meet this intent. This paper describes how a 300 mm aperture phasing interferometer was calibrated to <1 nm absolute accuracy and used to mount and measure 450 mm long flats for the Linear Coherent Light Source (LCLS) at Stanford Linear Accelerator Center. Measuring focus mirrors with an interferometer requires additional calibration, because high fringe density introduces systematic errors from the interferometer's imaging optics. This paper describes how these errors can be measured and corrected. The calibration approaches described here apply equally well to interferometers larger than 300 mm aperture, which are becoming more common in optics laboratories. The objective of this effort was to install LCLS flats with < 10 nm of spherical curvature, and < 2 nm rms a-sphere. The objective was met by measuring the mirrors after fabrication, coating and mounting, using a 300 mm aperture phasing interferometer calibrated to an accuracy < 1 nm. The key to calibrating the interferometer accurately was to sample the error using independent geometries that are available. The results of those measurements helped identify and reduce calibration error sources. The approach used to measure flats applies equally well to focus mirrors, provided an additional calibration is performed to measure the error introduced by fringe density. This calibration has been performed on the 300 mm aperture interferometer, and the measurement correction was evaluated for a typical focus mirror. The 300 mm aperture limitation requires stitching figure measurements together for many X-ray mirrors of interest, introducing another possible error source. Stitching is eliminated by applying the calibrations described above to larger aperture instruments. The authors are presently extending this work to a 600 mm instrument. Instruments with 900 mm aperture are now becoming available, which would accommodate the largest mirrors of interest.

  7. Thermal Analysis of the Advanced Technology Large Aperture Space Telescope (ATLAST) 8 Meter Primary Mirror

    NASA Technical Reports Server (NTRS)

    Hornsby, Linda; Stahl, H. Philip; Hopkins, Randall C.

    2010-01-01

    The Advanced Technology Large Aperture Space Telescope (ATLAST) preliminary design concept consists of an 8 meter diameter monolithic primary mirror enclosed in an insulated, optical tube with stray light baffles and a sunshade. ATLAST will be placed in orbit about the Sun-Earth L2 and will experience constant exposure to the sun. The insulation on the optical tube and sunshade serve to cold bias the telescope which helps to minimize thermal gradients. The primary mirror will be maintained at 280K with an active thermal control system. The geometric model of the primary mirror, optical tube, sun baffles, and sunshade was developed using Thermal Desktop(R) SINDA/FLUINT(R) was used for the thermal analysis and the radiation environment was analyzed using RADCAD(R). A XX node model was executed in order to characterize the static performance and thermal stability of the mirror during maneuvers. This is important because long exposure observations, such as extra-solar terrestrial planet finding and characterization, require a very stable observatory wave front. Steady state thermal analyses served to predict mirror temperatures for several different sun angles. Transient analyses were performed in order to predict thermal time constant of the primary mirror for a 20 degree slew or 30 degree roll maneuver. This paper describes the thermal model and provides details of the geometry, thermo-optical properties, and the environment which influences the thermal performance. All assumptions that were used in the analysis are also documented. Parametric analyses are summarized for design parameters including primary mirror coatings and sunshade configuration. Estimates of mirror heater power requirements are reported. The thermal model demonstrates results for the primary mirror heated from the back side and edges using a heater system with multiple independently controlled zones.

  8. Assessing Inter-Sensor Variability and Sensible Heat Flux Derivation Accuracy for a Large Aperture Scintillometer

    PubMed Central

    Rambikur, Evan H.; Chvez, Jos L.

    2014-01-01

    The accuracy in determining sensible heat flux (H) of three Kipp and Zonen large aperture scintillometers (LAS) was evaluated with reference to an eddy covariance (EC) system over relatively flat and uniform grassland near Timpas (CO, USA). Other tests have revealed inherent variability between Kipp and Zonen LAS units and bias to overestimate H. Average H fluxes were compared between LAS units and between LAS and EC. Despite good correlation, inter-LAS biases in H were found between 6% and 13% in terms of the linear regression slope. Physical misalignment was observed to result in increased scatter and bias between H solutions of a well-aligned and poorly-aligned LAS unit. Comparison of LAS and EC H showed little bias for one LAS unit, while the other two units overestimated EC H by more than 10%. A detector alignment issue may have caused the inter-LAS variability, supported by the observation in this study of differing power requirements between LAS units. It is possible that the LAS physical misalignment may have caused edge-of-beam signal noise as well as vulnerability to signal noise from wind-induced vibrations, both having an impact on the solution of H. In addition, there were some uncertainties in the solutions of H from the LAS and EC instruments, including lack of energy balance closure with the EC unit. However, the results obtained do not show clear evidence of inherent bias for the Kipp and Zonen LAS to overestimate H as found in other studies. PMID:24473285

  9. Assessing inter-sensor variability and sensible heat flux derivation accuracy for a large aperture scintillometer.

    PubMed

    Rambikur, Evan H; Chvez, Jos L

    2014-01-01

    The accuracy in determining sensible heat flux (H) of three Kipp and Zonen large aperture scintillometers (LAS) was evaluated with reference to an eddy covariance (EC) system over relatively flat and uniform grassland near Timpas (CO, USA). Other tests have revealed inherent variability between Kipp and Zonen LAS units and bias to overestimate H. Average H fluxes were compared between LAS units and between LAS and EC. Despite good correlation, inter-LAS biases in H were found between 6% and 13% in terms of the linear regression slope. Physical misalignment was observed to result in increased scatter and bias between H solutions of a well-aligned and poorly-aligned LAS unit. Comparison of LAS and EC H showed little bias for one LAS unit, while the other two units overestimated EC H by more than 10%. A detector alignment issue may have caused the inter-LAS variability, supported by the observation in this study of differing power requirements between LAS units. It is possible that the LAS physical misalignment may have caused edge-of-beam signal noise as well as vulnerability to signal noise from wind-induced vibrations, both having an impact on the solution of H. In addition, there were some uncertainties in the solutions of H from the LAS and EC instruments, including lack of energy balance closure with the EC unit. However, the results obtained do not show clear evidence of inherent bias for the Kipp and Zonen LAS to overestimate H as found in other studies. PMID:24473285

  10. Surface accuracy analysis and mathematical modeling of deployable large aperture elastic antenna reflectors

    NASA Astrophysics Data System (ADS)

    Coleman, Michael J.

    One class of deployable large aperture antenna consists of thin light-weight parabolic reflectors. A reflector of this type is a deployable structure that consists of an inflatable elastic membrane that is supported about its perimeter by a set of elastic tendons and is subjected to a constant hydrostatic pressure. A design may not hold the parabolic shape to within a desired tolerance due to an elastic deformation of the surface, particularly near the rim. We can compute the equilibrium configuration of the reflector system using an optimization-based solution procedure that calculates the total system energy and determines a configuration of minimum energy. Analysis of the equilibrium configuration reveals the behavior of the reflector shape under various loading conditions. The pressure, film strain energy, tendon strain energy, and gravitational energy are all considered in this analysis. The surface accuracy of the antenna reflector is measured by an RMS calculation while the reflector phase error component of the efficiency is determined by computing the power density at boresight. Our error computation methods are tailored for the faceted surface of our model and they are more accurate for this particular problem than the commonly applied Ruze Equation. Previous analytical work on parabolic antennas focused on axisymmetric geometries and loads. Symmetric equilibria are not assumed in our analysis. In addition, this dissertation contains two principle original findings: (1) the typical supporting tendon system tends to flatten a parabolic reflector near its edge. We find that surface accuracy can be significantly improved by fixing the edge of the inflated reflector to a rigid structure; (2) for large membranes assembled from flat sheets of thin material, we demonstrate that the surface accuracy of the resulting inflated membrane reflector can be improved by altering the cutting pattern of the flat components. Our findings demonstrate that the proper choice of design parameters can increase the performance of inflatable antennas, opening up new antenna applications where higher resolution and greater sensitivity are desired. These include space applications involving high data rates and high bandwidths, such as lunar surface wireless local networks and orbiting relay satellites. A light-weight inflatable antenna is also an ideal component in aerostat, airship and free balloon systems that supports communication, surveillance and remote sensing applications.

  11. Journal of Atmospheric and Solar-Terrestrial Physics 67 (2005) 11711177 Modelling high-power large-aperture radar meteor trails

    E-print Network

    Oppenheim, Meers

    -aperture radar meteor trails Lars P. Dyrud?, Licia Ray, Meers Oppenheim, Sigrid Close, Kelly Denney Center see high-power large-aperture (HPLA) radar observations of meteor phenomena called head echoes and non demonstrating that meteor trails are unstable to growth of Farley­Buneman gradient-drift (FBGD) waves

  12. Optical design and testing of a fast large-aperture infrared space telescope

    Microsoft Academic Search

    Colin M. Humphries; Yitzhak Nevo; Eli Ettedgui-Atad; John W. Harris

    1992-01-01

    An optical design study for a next generation infrared space telescope has been performed. The concept is that of a passively cooled telescope of minimum aperture 2.5 meter with an F\\/1.2 primary and wavelength coverage from (lambda) equals 2 to at least 40 micrometers , and possibly to 100 micrometers . Compactness, low thermal emission from the optics and structure,

  13. Optical design and testing of a fast, large aperture, infrared space telescope

    Microsoft Academic Search

    C. M. Humphries; Y. Nevo; E. Ettedgui-Atad; J. W. Harris

    1992-01-01

    An optical design study for a next generation infrared space telescope has been performed. The concept is that of a passively cooled telescope of minium aperture 2.5 metre with an F\\/1.2 primary and wavelength coverage from ? = 2 to at least 40 m, and possibly to 100 m. Compactness, low thermal emission from the optics and structure, diffraction limited

  14. Comparison of nxn grille CTF measurement for VESA standard and large-sample aperture methods

    Microsoft Academic Search

    Russell S. Draper; Charles E. Bradford; David A. Fellowes

    2002-01-01

    An alternative method for measuring the contrast transfer function (CTF) of a pixilated display is proposed that reduces the amount of time required to perform a high sample rate-small aperture luminance scan as outlined in the Video Electronics Standards Association (VESA) standard for measuring the contrast of an n X n grille. The alternative method proposed by the Night Vision

  15. Atmospheric-induced wavefront distortion and compensation on large-aperture millimeter-wave telescopes

    Microsoft Academic Search

    Luca Olmi

    2003-01-01

    In the troposphere water vapor plays a fundamental role in radio propagation. The refractivity of water vapor is about 20 times greater in the radio range than in near-infrared or optical regimes. As a consequence, phase fluctuations at frequencies higher than about 1 GHz are predominantly caused by fluctuations in the distribution of water vapor. On filled-aperture telescopes radio seeing

  16. X-ray refractive large aperture rolled prism lenses as condensers for x-ray tubes

    NASA Astrophysics Data System (ADS)

    Vogt, H.; Simon, M.; Last, A.; Marschall, F.; Mohr, J.; Nazmov, V.; Eisenhower, R.; Mettendorf, K. U.

    2011-10-01

    At the Institute of Microstructure Technology (IMT) at Karlsruhe Institute of Technology (KIT), refractive X-ray optics are developed. These optics are proposed to be used as condenser optics in X-Ray spectroscopy and microscopy applications with an X-ray tube as a source. To produce the lenses, a thin structured foil with equidistant fins in triangular form is casted from a structured silicon wafer. The foil is then wound around a glass fibre core. Due to this fabrication method, it is possible to produce large-aperture lenses with low absorption in comparison to other types of refractive X-Ray optics, like X-ray lenses with continuous parabolic shape or prism lenses. The first are limited due to their absorption while the latter are limited due to their mechanical stability of the prism columns. The optimisation of the so called X-Ray rolled prism lenses (RXPL) is underway at the institute and involves several parameters. One important property of the lenses is the correct form of the wound foil layers. This determines the number of necessary refractive elements at a given radius, which in turn determines the refracted slope and focal position of the transmitted beam. The spatial extent of the x-ray source is also being accounted for in the lens design. Another important point is the diameter of the winding core, which should be as small as possible due to the fact that the winding core reduces the active area of the lens. The rolling process itself is also revised to produce lenses with the above-mentioned small diameter winding cores and bend foil layers while sustaining a tight- fitting foil bundle. The lenses are studied at different energies and types of X-Ray tubes, as well as synchrotron sources, to gain additional information of the internal structure of the lens after the winding process. In this paper the current status of the lens development and results at X-Ray tube sources for use in diffractometers is presented.

  17. Origins of High-frequency Scattered Waves Near PKKP From Large Aperture Seismic Array Data

    NASA Astrophysics Data System (ADS)

    Earle, P. S.; Vidale, J. E.

    2001-05-01

    Observations of high--frequency ( ~1 Hz) teleseismic scattered waves provide constraints for modelling fine--scale ( ~10 km) core--mantle boundary (CMB) topography and fine--scale mantle heterogeneity. The majority of previous modelling relied on precursors to PKPdf, but here we present an underutilized data set that will aid future research into Earth's fine--scale structure: scattered waves in the vicinity of PKKP. The data set consists of slant stacks generated from Large Aperture Seismic Array (LASA) data from 36 earthquakes and 6 explosions in the range 30o to 129o. Although precursors to PKKP have been studied, we examine stacks in a larger time--distance window and find that waves previously associated with scattering along the PKKP raypath actually originate from near surface scattering of PKP to P (PKP.P). In addition to these near surface contributions, three types of waves scattered at the CMB or in the overlying mantle explain the observed slownesses and onset times, including: forward scattering of PKKP between its P and KKP legs (P.KKP and PKK.P), back scattering of PKKP between its PK and KP legs (PK.KP), and similarly back scattering of SKKP energy between its SK and KP legs (SK.KP). The LASA stacks show where and when these waves are detected and where they are contaminated by the surface--scattered P.PKP. In addition, the stacks image the scattered waves' amplitude and slowness variations with time. P.KKP waves are observed near 128o (just beyond the PKKP ``b'' caustic) and last ~100 s. Close to 113o, SK.KP waves rise above the noise ~100 s before onset time of the main SKKP arrival. Observations of PK.KP span 30o to 100o. However, at distances greater than 50o they suffer from P.PKP contamination. At distances less than 50o PK.KP last for ~300 s. This is ~150 s longer than the maximum ray-theoretical prediction for waves scattered at the CMB, indicating possible contributions from the overlying mantle.

  18. Defining A Risk Analysis Strategy for Exo-Earth Yields from a Future Large Aperture UVOIR Space Telescope

    NASA Astrophysics Data System (ADS)

    Mandell, Avi; Stark, Christopher C.; Roberge, Aki; Domagal-Goldman, Shawn; Stapelfeldt, Karl R.; Robinson, Tyler

    2015-01-01

    The discovery and characterization of Earth-like planets around Sun-like stars using high-contrast imaging is a critical science metric for constraining the requirements on the next-generation large UVOIR space telescope. The dominant driver for the observatory architecture, cost and schedule is the telescope aperture size. Therefore it is important to provide as much constraint as possible on the required aperture size early in the design and planning process.An estimate of the detection yield for Earth-like planets can be calculated using a Monte Carlo simulation of a design reference mission (DRM), allowing the exploration of a variety of mission design and astrophysical parameters. We have developed such a code (Stark et al. 2014); it optimizes the target list and exposure times to maximize mission yield for a specific set of mission parameters. However, many of the important astrophysical quantities and future technical capabilities that feed into these parameters are not well constrained. This leads to a large uncertainty in the final mission architecture needed to achieve a specific exo-Earth yield.In this presentation we discuss the various physical and technological parameters that go into the DRM simulations, and the associated uncertainties based on the current state of research. We then present a strategy for a three-tiered risk assessment using these uncertainties, and conclude with a discussion of the current range in telescope aperture size associated with each risk level.

  19. Large-volume ionization chamber with variable apertures for air-kerma measurements of low-energy radiation sources

    NASA Astrophysics Data System (ADS)

    Culberson, W. S.; DeWerd, L. A.; Anderson, D. R.; Micka, J. A.

    2006-01-01

    This report describes the design and initial measurement results of a large-volume ionization chamber designed to realize the air kerma from therapeutic radiation sources emitting photons with energies up to about 70 keV. The measured ionization current is used to provide absolute source calibrations by the most widely used brachytherapy source strength metric called air-kerma strength. The variable-aperture free-air chamber (VAFAC), named because of its variable aperture stand, will provide insight into the angular dependence of air-kerma strength measurements. Another unique feature of this ionization chamber is its seed holder design that reduces unwanted scatter, ensures vertical positioning, and rotates the seed with a positional accuracy of 0.3. Benchmark experiments show that the VAFAC agrees well with existing National Institute of Standards and Technology standards and is capable of measuring clinical-strength seeds with repeatabilities of less than 2% at the 1? level (k=1).

  20. A Large Sparse Aperture Densified Pupil Hypertelescope Concept for Ground Based Detection of Extra-Solar Earth-Like Planets

    NASA Technical Reports Server (NTRS)

    Gezari, D.; Lyon, R.; Woodruff, R.; Labeyrie, A.; Oegerle, William (Technical Monitor)

    2002-01-01

    A concept is presented for a large (10 - 30 meter) sparse aperture hyper telescope to image extrasolar earth-like planets from the ground in the presence of atmospheric seeing. The telescope achieves high dynamic range very close to bright stellar sources with good image quality using pupil densification techniques. Active correction of the perturbed wavefront is simplified by using 36 small flat mirrors arranged in a parabolic steerable array structure, eliminating the need for large delat lines and operating at near-infrared (1 - 3 Micron) wavelengths with flats comparable in size to the seeing cells.

  1. Design and construction of a large aperture quadrupole electromagnet for ILSE

    SciTech Connect

    Fawley, W.M.; Vella, M.C.; Peters, C.; Stuart, M.; Faltens, A.

    1995-08-01

    We are currently constructing a prototype quadrupole electromagnet for the proposed Induction Linac Systems Experiment (ILSE) at LBNL. ILSE will address many physics and engineering issues relevant to the design of a heavy-ion fusion driver accelerator. The pulsed electromagnet has two layers of current windings and will produce a field gradient of 28 T/m, wi a usable aperture of 6 cm. It operates at a repetition rate of 1 Hz, steady-state. In this paper, we discuss how the interaction of various concerns such as maximum dynamic aperture, short lattice period, field quality, iron yoke weight, heat transfer, and voltage standoff have led to our particular design choices. We also present 2- and 3-D numerical calculations concerning field topography and the results of transport simulations of space-charge dominated ion beams with ILSE parameters.

  2. Large Aperture Polarized Light Source and Novel Liquid Crystal Display Operating Modes

    Microsoft Academic Search

    S. V. Belayev; M. Schadt; M. I. Barnik; J. Fnfschilling; N. V. Malimoneko; K. Schmitt

    1990-01-01

    A wide aperture liquid crystal polarized light source (LC-PLS) is presented which converts unpolarized-into circular- and\\/or linearly polarized light with an efficiency better than 80%. Moreover, new operating modes for electro-optical field-effects on which liquid crystal displays (LCDs) are based are shown to increase the transmission of twisted nematic (TN)-LCDs by a factor of two. Besides, a 25% shift of

  3. Optical design and testing of a fast, large aperture, infrared space telescope

    Microsoft Academic Search

    C. M. Humphries; Y. Nevo; E. Ettedgui-Atad; J. W. Harris

    1992-01-01

    An optical design study for a next generation infrared space telescope has been performed. The concept is that of a passively cooled telescope of minimum aperture 2.5 m with an F\\/1.2 primary and wavelength coverage from 2 to as least 40 microns, and possibly to 100 microns. Compactness, low thermal emission from the optics and structure, diffraction limited imaging at

  4. Damage and fracture in large aperture, fused silica, vacuum spatial filter lenses

    SciTech Connect

    Campbell, J.H.; Edwards, G.J.; Marion, J.E.

    1995-07-07

    Optical damage that results in large scale fracture has been observed in the large, high-fluence, fused-silica, spatial filter lenses on the Nova and Beamlet lasers. In nearly all cases damage occurs on the vacuum side of the lenses and because the vacuum side of the lens is under tensile stress this damage can lead to catastrophic crack growth if the flaw (damage) size exceeds the critical flaw size for SiO{sub 2}. The damaged 52 cm Nova lenses fracture into two and sometimes three large pieces. Although under full vacuum load at the time they fracture, the Nova lenses do not implode. Rather the authors have observed that the pieces lock together and air slowly leaks into the vacuum spatial filter housing through the lens cracks. The Beamlet lenses have a larger aspect ratio and peak tensile stress than Nova. The peak tensile stress at the center of the output surface of the Beamlet lens is 1,490 psi versus 810 psi for Nova. During a recent Beamlet high energy shot, a damage spot on the lens grew to the critical flaw size and the lens imploded. Post shot data indicate the lens probably fractured into 5 to 7 pieces, however, unlike Nova, these pieces did not lock together. Analysis shows that the likely source of damage is contamination from pinhole blow-off or out-gassing of volatile materials within the spatial filter. Contamination degrades the antireflection properties of the sol-gel coating and reduces its damage threshold. By changing the design of the Beamlet lens it may be possible to insure that it fails safe by locking up in much that same manner as the Nova lens.

  5. Fabrication of Efficient, Large Aperture Transmission Diffraction Gratings by Ion-Beam Etching

    Microsoft Academic Search

    H T Nguyen; S R Bryan; J A Britten; M D Perry

    2000-01-01

    The utilization of high-power short pulse laser employing chirped-pulse amplification (CPA) for material processing and inertial confinement research is widely increasing. The performance of these high-power CPA laser system continues to be limited by the ability of the pulse compression gratings to hold up to the high-average-power or high-peak-power of the laser. Pulse compression gratings used in transmission and fabricated

  6. 1030nm Yb-fiber-MOPA-based, multi-aperture high power, high energy uplink laser beacon for deep space communication

    NASA Astrophysics Data System (ADS)

    Engin, Doruk; Burton, John; Darab, Ibraheem; Kimpel, Frank; Mathason, Brian; Gupta, Shantanu

    2014-03-01

    A Yb LMA fiber amplifier based laser transmitter capable of operating with high average power and high energy (~500W, 1mJ) is presented. The prototype, all-fiber, high TRL level laser transmitter is designed to meet all the single aperture requirements of an eight aperture deep space laser beacon system. The high speed FPGA controlled transmitter supports a directly modulated DFB laser and two acousto-optic modulators which are used to implement an open loop pattern dependent -pulse pre-shaping algorithm. Ultra-fast high power diode drivers are used for generating outer nested PPM modulation with Binary PPM (67usec, 33mJ pulses) and for implementing <1usec loss of signal (LOS) protection. Optical performance to be presented will include diffraction limited (M2~1.2) nested PPM optical outputs with >300W average and 9kW peak power with >70% o-o efficiency for the final power stage.

  7. Full aperture backscatter station imager (FABSI) diagnostics system for far-field imaging of laser plasma instabilities on Nova

    SciTech Connect

    Wilke, M.D.; Fernandez, J.C.; Berggren, R.R.; Montgomery, D.; Faulkner, J.; Looney, L.; Jimerson, J. [Los Alamos National Lab., NM (United States); Horton, R.F. [SAIC, Albuquerque, NM (United States)

    1996-06-01

    In ICF, the understanding of laser plasma scattering processes is essential for laser target coupling and in controlling the symmetry of indirect drive implosions. The existing Nova Full Aperture Backscatter Station (FABS) has been useful in understanding laser plasma instabilities occurring in hohlraums by measuring the quantity, spectral distribution and near-field spatial distributions of Brillouin and more recently Raman backscatter. Equally important is an understanding of the farfield spatial intensity distribution which provides information on density, temperature and velocity gradient distributions, and which affect capsule implosion symmetry in hohlraums. Such information could potentially help in understanding processes such as filamentation and saturation mechanism. This paper describes a broad-band, color-corrected far-field imager and associated diagnostics capable of imaging the source of scattered light to better than 25 {micro}m resolution. The imager can either image Brillouin or Raman backscatter through the Nova beam 7 focusing lens or be used like a microscope to image side scatter from other beams.

  8. Atmospheric turbulence measurements by angle of arrival fluctuations and intensity scintillations with large aperture

    Microsoft Academic Search

    Y. Glick; R. Zaibel; G. Bar-Tal; Y. Bar-Sagi

    2000-01-01

    Summary form only given. Atmospheric turbulence was measured using a one station scheme, over a flat beach parallel to the Mediterranean sea shore. A diffusive white target situated at a distance of 1500 m was illuminated with a 5 mJ Q-switched Nd:YAG laser beam at a rep-rate of 500 Hz. The laser spot on the target had a diameter of

  9. 11 nm hard X-ray focus from a large-aperture multilayer Laue lens

    PubMed Central

    Huang, Xiaojing; Yan, Hanfei; Nazaretski, Evgeny; Conley, Raymond; Bouet, Nathalie; Zhou, Juan; Lauer, Kenneth; Li, Li; Eom, Daejin; Legnini, Daniel; Harder, Ross; Robinson, Ian K.; Chu, Yong S.

    2013-01-01

    The focusing performance of a multilayer Laue lens (MLL) with 43.4??m aperture, 4?nm finest zone width and 4.2?mm focal length at 12?keV was characterized with X-rays using ptychography method. The reconstructed probe shows a full-width-at-half-maximum (FWHM) peak size of 11.2?nm. The obtained X-ray wavefront shows excellent agreement with the dynamical calculations, exhibiting aberrations less than 0.3 wave period, which ensures the MLL capable of producing a diffraction-limited focus while offering a sufficient working distance. This achievement opens up opportunities of incorporating a variety of in-situ experiments into ultra high-resolution X-ray microscopy studies. PMID:24356395

  10. Optical design and testing of a fast, large aperture, infrared space telescope

    NASA Technical Reports Server (NTRS)

    Humphries, C. M.; Nevo, Y.; Ettedgui-Atad, E.; Harris, J. W.

    1992-01-01

    An optical design study for a next generation infrared space telescope has been performed. The concept is that of a passively cooled telescope of minimum aperture 2.5 m with an F/1.2 primary and wavelength coverage from 2 to as least 40 microns, and possibly to 100 microns. Compactness, low thermal emission from the optics and structure, diffraction limited imaging at 2 microns, and sensitivity to misalignment aberrations and manufacturing errors were the main considerations for this study. Ray tracing results are presented showing the characteristics of the various designs considered. A preliminary investigation of stray light properties is also given. Special emphasis has been placed on the testing of such a fast primary, and optical systems using a lateral shearing interferometer are described for testing both the primary and the primary/secondary combination.

  11. Alternative Beam Efficiency Calculations for a Large-aperture Multiple-frequency Microwave Radiometer (LAMMR)

    NASA Technical Reports Server (NTRS)

    Schmidt, R. F.

    1979-01-01

    The fundamental definition of beam efficiency, given in terms of a far field radiation pattern, was used to develop alternative definitions which improve accuracy, reduce the amount of calculation required, and isolate the separate factors composing beam efficiency. Well-known definitions of aperture efficiency were introduced successively to simplify the denominator of the fundamental definition. The superposition of complex vector spillover and backscattered fields was examined, and beam efficiency analysis in terms of power patterns was carried out. An extension from single to dual reflector geometries was included. It is noted that the alternative definitions are advantageous in the mathematical simulation of a radiometer system, and are not intended for the measurements discipline where fields have merged and therefore lost their identity.

  12. Design and construction of a large aperture, quadrupole electromagnet prototype for ILSE

    SciTech Connect

    Stuart, M.; Faltens, A.; Fawley, W.M.; Peters, C.; Vella, M.C.

    1995-04-01

    We are currently constructing a prototype quadrupole electromagnet for the proposed Induction Linac Systems Experiment (ILSE) at LBL. ILSE will address many physi and engineering issues relevant to the design of a heavy-ion fusion driver accelerator. The pulsed electromagnet has two layers of current windings and will produce a field gradient exceeding 25 T/m at a repetition rate of 1 Hz steady-state. In this paper, we discuss how the interaction of various concerns such as maximum dynamic aperture, short lattice period, field quality, iron yoke weight, heat transfer, and voltage standoff have led to our particular design choices. We also present 2- and 3-D numerical calculations concerning field topography and the results of transport simulations of space-charge dominated ion beams with ILSE parameters.

  13. Large field F-? laser scanning system

    NASA Astrophysics Data System (ADS)

    Shan, Baozhong; Guo, Baoping; Niu, Hanben

    2009-05-01

    A large field laser scanning system is designed for PID imaging system. According to different deflectors, scanning system methods have optical lens scanning system, polygon mirror scanning system, acousto-optic scanning system and holographic scanning method. To realize large field scanning, a polygon mirror is used as scanner, which has high scanning speed, high resolution and contrast, good gamma characteristic and F-? lens system is used as focusing system in type of scanner before lens. F-? lens is special lens with linear scanning characteristic. F-? lens can focus laser beam and make linear scanning. The scanning performance of F-? lens is usually decided by its focusing characteristics. Designed system can scan object in 356mm length and the resolution achieves 35?m. Ball bearing guide screw system is used to realize scanning in Y direction, the scanning length can be set according to request. Thus, the system can make two dimensional scanning. By evaluating performance of optical system, the system focusing characteristics had achieved the diffraction limit in entire field and satisfies the system's requests. Experiment has been carried on to test the F-? optical focusing system. The experimental results show that diameters of focusing facular at all view field are approximately 35?m, which is identical with theoretical parameter and conforms to F-? characteristic.

  14. Large-acceptance diamond planar refractive lenses manufactured by laser cutting.

    PubMed

    Polikarpov, Maxim; Snigireva, Irina; Morse, John; Yunkin, Vyacheslav; Kuznetsov, Sergey; Snigirev, Anatoly

    2015-01-01

    For the first time, single-crystal diamond planar refractive lenses have been fabricated by laser micromachining in 300 m-thick diamond plates which were grown by chemical vapour deposition. Linear lenses with apertures up to 1 mm and parabola apex radii up to 500 m were manufactured and tested at the ESRF ID06 beamline. The large acceptance of these lenses allows them to be used as beam-conditioning elements. Owing to the unsurpassed thermal properties of single-crystal diamond, these lenses should be suitable to withstand the extreme flux densities expected at the planned fourth-generation X-ray sources. PMID:25537584

  15. Potential of a Future Large Aperture UVOIR Space Observatory for Breakthrough Observations of Star and Planet Formation

    NASA Astrophysics Data System (ADS)

    Danchi, William C.; Grady, Carol A.; Padgett, Deborah

    2015-01-01

    A future large aperture space observatory operating from the UV to the near-infrared with a diameter between 10 and 15 meters will provide a unique opportunity for observations of star and planet formation, from nearby moving groups and associations to star formation in galaxies in the local universe. Our newly formed working group will examine the unique opportunities that such a telescope will give observers in a post-JWST/WFIRST-AFTA era that includes extremely large ground-based observatories such as the TMT, E-ELT, ALMA, and the VLTI. Given a potential suite of instruments for this observatory we will discuss some of the key areas of star and planet formation science where breakthroughs might occur.

  16. Tapered large-core 976nm Yb-doped fiber laser with 10W output power

    NASA Astrophysics Data System (ADS)

    Leich, M.; Jger, M.; Grimm, S.; Hoh, D.; Jetschke, S.; Becker, M.; Hartung, A.; Bartelt, H.

    2014-04-01

    We report on a tapered large-core Yb fiber laser operating at 976 nm emission wavelength. It was realized using a high-numerical aperture large-core fiber with 126 ?m core diameter, which was fabricated by powder-sinter technology and shows a very homogeneous step-index profile. The end of the fiber is tapered down to match a single-mode fiber containing a fiber Bragg grating. Using the benefits of core-pumping and the feedback of the spliced fiber Bragg grating, we achieved efficient pump light absorption and wavelength stable 976 nm lasing with single-mode performance. We could demonstrate 10 W laser power out of a 10 ?m fiber core with a slope efficiency of 31% with respect to the launched pump power. The presented device is well-suited for fiber-coupled pumping of amplifiers for high peak power.

  17. Concept study of an Extremely Large Hyper Telescope (ELHyT) with 1200m sparse aperture for direct imaging at 100 micro-arcsecond resolution

    NASA Astrophysics Data System (ADS)

    Labeyrie, Antoine; Mourard, Denis; Allouche, Fatm; Chakraborthy, Rijuparna; Dejonghe, Julien; Surya, Arun; Bresson, Yves; Aime, Claude; Mary, David; Carlotti, Alexis

    2012-07-01

    The hypertelescope construction initiated in the Southern Alps (Labeyrie et al., this conference) has provided some preliminary operating experience indicating that larger versions, up to perhaps 1200m, are probably feasible at suitable sites. The Arecibo-like architecture of such instruments does not require the large mount and dome which dominate the cost of a 40m ELT. For the same cost, an "Extremely Large Hyper Telescope ( ELHyT) may therefore have a larger collecting area. It may thus in principle reach higher limiting magnitudes, both for seeing-limited and, if equipped with a Laser Guide Star and adaptive phasing, for high-resolution imaging with gain as the size ratio, i.e. about 30 with respect to a 40m ELT. Like the radio arrays of antennas, such instruments can be grown progressively. Also, they can be up-graded with several focal gondolas, independently tracking different sources. Candidate sites have been identified in the Himalaya and the Andes. We describe several design options and compare the science achievable for both instruments, ELTs and ELHyTs. The broad science addressed by an ELHyT covers stellar chromospheres, transiting exoplanets and those requiring a high dynamic range, achieved by array apodization or coronagraphy. With a Laser Guide Star, it extends to faint compact sources beyond the limits of telescopes having a smaller collecting area, supernovae, active galactic nuclei, gamma ray bursts. The sparse content of remote galaxies seen in the Hubble Deep Field appears compatible with the crowding limitations of an ELHyT having 1000 apertures.

  18. Deposition of high quality YBa2Cu3O(7-delta) thin films over large areas by pulsed laser ablation with substrate scanning

    NASA Technical Reports Server (NTRS)

    Davis, M. F.; Wosik, J.; Forster, K.; Deshmukh, S. C.; Rampersad, H. R.

    1991-01-01

    The paper describes thin films deposited in a system where substrates are scanned over areas up to 3.5 x 3.5 cm through the stationary plume of an ablated material defined by an aperture. These YBCO films are deposited on LaAlO3 and SrTiO3 substrates with the thickness of 90 and 160 nm. Attention is focused on the main features of the deposition system: line focusing of the laser beam on the target; an aperture defining the area of the plume; computerized stepper motor-driven X-Y stage translating the heated sampler holder behind the plume-defining aperture in programmed patterns; and substrate mounting block with uniform heating at high temperatures over large areas. It is noted that the high degree of uniformity of the properties in each film batch illustrates that the technique of pulsed laser deposition can be applied to produce large YBCO films of high quality.

  19. Abstract--We have recently completed a large-area, coded-aperture, gamma-ray imager for use in searching for radiation

    E-print Network

    Horn, Berthold K.P.

    Abstract-- We have recently completed a large-area, coded- aperture, gamma-ray imager for use sufficient radiation can reach a large gamma-ray detec- tor from a small source to make detection possible with high-rise buildings beyond three stories are significantly complicated by the extra shield- ing from

  20. Comparison of Turbulent Sensible Heat Flux Determined by Large-Aperture Scintillometer and Eddy Covariance over Urban and Suburban Areas

    NASA Astrophysics Data System (ADS)

    Zhang, He; Zhang, Hongsheng

    2015-01-01

    Field observations of the atmospheric boundary layer were made over urban and suburban areas in the Yangtze River Delta, China. Sensible heat fluxes were obtained by eddy-covariance (EC) systems and large-aperture scintillometers (LASs). The results indicated that (1) the sensible heat flux obtained by LAS was less noisy and slightly larger than that obtained by EC over both urban and suburban surfaces; (2) the values of were higher when the correlation coefficient of vertical wind speed and temperature () was smaller. Lower values of were due to low-frequency trends. The urban values of were smaller than suburban values at low values; (3) the sensible heat flux determined by LAS was improved by use of the Monin-Obukhov similarity theory of the temperature structure parameter over urban and suburban areas, and the improvement is more significant over urban surface areas.

  1. The Advanced Technology Large Aperture Space Telescope (ATLAST): Science Drivers, Technology Developments, and Synergies with Other Future Facilities

    NASA Technical Reports Server (NTRS)

    Postman, Marc; Brown, Tom; Sembach, Kenneth; Giavalisco, Mauro; Traub, Wesley; Stapelfeldt, Karl; Calzetti, Daniela; Oegerle, William; Rich, R. Michael; Stahl, H. Phillip; Tumlinson, Jason; Mountain, Matt; Soummer, Remi; Hyde, Tupper

    2011-01-01

    The Advanced Technology Large-Aperture Space Telescope (ATLAST) is a concept for an 8-meter to 16-meter UVOIR space observatory for launch in the 2025-2030 era. ATLAST will allow astronomers to answer fundamental questions at the forefront of modern astrophysics, including "Is there life elsewhere in the Galaxy?" We present a range of science drivers that define the main performance requirements for ATLAST (8 to 16 milliarcsec angular resolution, diffraction limited imaging at 0.5 m wavelength, minimum collecting area of 45 square meters, high sensitivity to light wavelengths from 0.1 m to 2.4 m, high stability in wavefront sensing and control). We will also discuss the synergy between ATLAST and other anticipated future facilities (e.g., TMT, EELT, ALMA) and the priorities for technology development that will enable the construction for a cost that is comparable to current generation observatory-class space missions.

  2. Transverse Mode Structure and Pattern Formation in Oxide Confined Vertical Cavity Semiconductor Lasers

    SciTech Connect

    Choquette, K.D.; Geib, K.M.; Hegarty, S.P.; Hou, H.Q.; Huyet, G.; McInerney, J.G.; Porta, P.

    1999-07-06

    We analyze the transverse profiles of oxide-confined vertical cavity laser diodes as a function of aperture size. For small apertures we demonstrate that thermal lensing can be the dominant effect in determining the transverse resonator properties. We also analyze pattern formation in lasers with large apertures where we observe the appearance of tilted waves.

  3. Measurement of wavefront structure from large aperture optical components by phase shifting interferometry

    SciTech Connect

    Wolfe, C.R.; Lawson, J.K.; Kellam, M.; Maney, R.T.; Demiris, A.

    1995-05-12

    This paper discusses the results of high spatial resolution measurement of the transmitted or reflected wavefront of optical components using phase shifting interferometry with a wavelength of 6328 {angstrom}. The optical components studied range in size from approximately 50 mm {times} 100 mm to 400 mm {times} 750 mm. Wavefront data, in the form of 3-D phase maps, have been obtained for three regimes of scale length: ``micro roughness``, ``mid-spatial scale``, and ``optical figure/curvature.`` Repetitive wavefront structure has been observed with scale lengths from 10 mm to 100 mm. The amplitude of this structure is typically {lambda}/100 to {lambda}/20. Previously unobserved structure has been detected in optical materials and on the surfaces of components. We are using this data to assist in optimizing laser system design, to qualify optical components and fabrication processes under study in our component development program.

  4. A real-space interactive holographic display based on a large-aperture HOE

    NASA Astrophysics Data System (ADS)

    Khan, Javid; Can, Chi; Greenaway, Alan; Underwood, Ian

    2013-03-01

    We have built a HOE-based display capable of reconstructing arbitrary images, in mid-air at fixed focal depths, that can interact with the viewer in real-time. The display system comprises the HOE, a laser projection subsystem, a Kinect motion sensor and an embedded controller. The HOE functions as a fast converging lens and is A4 page sized (2030cm). We have written a number of simple apps for the display that allow the user to draw in mid-air or to touch icons and buttons that trigger other actions. The reconstructed holographic images are high-resolution, relatively bright and visible under ambient indoor lighting conditions.

  5. New technologies for the actuation and controls of large aperture lightweight quality mirrors

    NASA Technical Reports Server (NTRS)

    Lih, S. S.; Yang, E. H.; Gullapalli, S. N.; Flood, R.

    2003-01-01

    This paper presents a set of candidate components: MEMS based large stroke (>100 microns) ultra lightweight (0.01 gm) discrete inch worm actuator technology, and a distributed actuator technology, in the context of a novel lightweight active flexure-hinged substrate concept that uses the nanolaminate face sheet.

  6. High-resolution adaptive optics scanning laser ophthalmoscope with dual deformable mirrors for large aberration correction

    SciTech Connect

    Chen, D; Jones, S M; Silva, D A; Olivier, S S

    2007-01-25

    Scanning laser ophthalmoscopes with adaptive optics (AOSLO) have been shown previously to provide a noninvasive, cellular-scale view of the living human retina. However, the clinical utility of these systems has been limited by the available deformable mirror technology. In this paper, we demonstrate that the use of dual deformable mirrors can effectively compensate large aberrations in the human retina, making the AOSLO system a viable, non-invasive, high-resolution imaging tool for clinical diagnostics. We used a bimorph deformable mirror to correct low-order aberrations with relatively large amplitudes. The bimorph mirror is manufactured by Aoptix, Inc. with 37 elements and 18 {micro}m stroke in a 10 mm aperture. We used a MEMS deformable mirror to correct high-order aberrations with lower amplitudes. The MEMS mirror is manufactured by Boston Micromachine, Inc with 144 elements and 1.5 {micro}m stroke in a 3 mm aperture. We have achieved near diffraction-limited retina images using the dual deformable mirrors to correct large aberrations up to {+-} 3D of defocus and {+-} 3D of cylindrical aberrations with test subjects. This increases the range of spectacle corrections by the AO systems by a factor of 10, which is crucial for use in the clinical environment. This ability for large phase compensation can eliminate accurate refractive error fitting for the patients, which greatly improves the system ease of use and efficiency in the clinical environment.

  7. Single-frequency oscillation of a wide-aperture krypton laser

    SciTech Connect

    Babin, S A; Khorev, S V [Institute of Automation and Electrometry, Siberian Branch, Russian Academy of Sciences, Novosibirsk (Russian Federation)

    2003-09-30

    The parameters of a high-current krypton discharge in tubes of an increased diameter (5 - 7 mm) are studied and optimised. Increased lasing power on the lines of singly and doubly charged krypton ions is achieved: 14 W (647 - 676 nm) and 6 W (407 - 415 nm). One transverse and one longitudinal mode are selected with efficiencies of 85 and 70 % using a convex - concave resonator and a Fabry - Perot etalon, respectively. The shape of the Lamb dip at the 676-nm line is studied in the single-frequency oscillation mode. It is shown that, in accordance with the theory, the dip broadens by a factor of 2.6 due to Coulomb ion - ion collisions at an achieved electron concentration N{sub e} {approx} 5 x 10{sup 14} cm{sup -3}. (active media. lasers)

  8. Multi-Scale Sensible Heat Fluxes in the Suburban Environment from Large-Aperture Scintillometry and Eddy Covariance

    NASA Astrophysics Data System (ADS)

    Ward, H. C.; Evans, J. G.; Grimmond, C. S. B.

    2014-07-01

    Sensible heat fluxes () are determined using scintillometry and eddy covariance over a suburban area. Two large-aperture scintillometers provide spatially integrated fluxes across path lengths of 2.8 and 5.5 km over Swindon, UK. The shorter scintillometer path spans newly built residential areas and has an approximate source area of 2-4 , whilst the long path extends from the rural outskirts to the town centre and has a source area of around 5-10 . These large-scale heat fluxes are compared with local-scale eddy-covariance measurements. Clear seasonal trends are revealed by the long duration of this dataset and variability in monthly is related to the meteorological conditions. At shorter time scales the response of to solar radiation often gives rise to close agreement between the measurements, but during times of rapidly changing cloud cover spatial differences in the net radiation () coincide with greater differences between heat fluxes. For clear days lags , thus the ratio of to increases throughout the day. In summer the observed energy partitioning is related to the vegetation fraction through use of a footprint model. The results demonstrate the value of scintillometry for integrating surface heterogeneity and offer improved understanding of the influence of anthropogenic materials on surface-atmosphere interactions.

  9. A test of basin-scale acoustic thermometry using a large-aperture vertical array at 3250-km range in the eastern

    E-print Network

    deYoung, Brad

    A test of basin-scale acoustic thermometry using a large- aperture vertical array at 3250-km range, Electrical Engineering and Computer Science Department, University of Michigan, Ann Arbor, Michigan 48109- and basin-scale ocean temperature and heat content variability can be mea- sured using the methods of ocean

  10. OpTIIX: An ISS-Based Testbed Paving the Roadmap Toward a Next Generation Large Aperture UV/Optical Space Telescope

    NASA Technical Reports Server (NTRS)

    Carpenter, Kenneth G.; Etemad, Shar; Seery, Bernard D.; Thronson, Harley; Burdick, Gary M.; Coulter, Dan; Goullioud, Renaud; Green, Joseph J.; Liu, Fengchuan; Ess, Kim; Postman, Marc; Sparks, Williams

    2012-01-01

    The next generation large aperture UV/Optical space telescope will need a diameter substantially larger than even that of JWST in order to address some of the most compelling unanswered scientific quests. These quests include understanding the earliest phases of the Universe and detecting life on exo-planets by studying spectra of their atmospheres. Such 8-16 meter telescopes face severe challenges in terms of cost and complexity and are unlikely to be affordable unless a new paradigm is adopted for their design and construction. The conventional approach is to use monolithic or preassembled segmented mirrors requiring complicated and risky deployments and relying on future heavy-lift vehicles, large fairings and complex geometry. The new paradigm is to launch component modules on relatively small vehicles and then perform in-orbit robotic assembly of those modules. The Optical Testbed and Integration on ISS eXperiment (OpTIIX) is designed to demonstrate, at low cost by leveraging the infrastructure provided by ISS, telescope assembly technologies and end-to-end optical system technologies. The use of ISS as a testbed permits the concentration of resources on reducing the technical risks associated with robotically integrating the components. These include laser metrology and wavefront sensing and control (WFS&C) systems, an imaging instrument, lightweight, low-cost deformable primary mirror segments and the secondary mirror. These elements are then aligned to a diffraction-limited optical system in space. The capability to assemble the optical system and remove and replace components via the existing ISS robotic systems like the Special Purpose Dexterous Manipulator (SPDM), or by the ISS flight crew, allows for future experimentation, as well as repair.

  11. Large scale laser microstructuring of gravure print rollers

    NASA Astrophysics Data System (ADS)

    Hennig, Guido; Selbmann, Karl-Heinz; Pfinninger, Silke; Brendel, Johannes; Brning, Stephan

    2008-02-01

    Application of lasers for print form fabrication plays an increasingly important role in the printing industry due to the high machining rate, the high spatial resolution and the ability of digital modulation. This paper gives an overview of our laser based processes in gravure and embossing with a focus on micro-structuring of gravure print forms by direct laser ablation. The precise large scale micro-fabrication by laser engraving is the fastest and most versatile process for gravure cylinder fabrication (ablation rate up to 1 cm 3/min). Direct laser engraving into metallic cylinders is performed with high power Q-switched Nd:YAG laser systems and fiber lasers at up to 100 kHz repetition rate, tuned for high reproducibility and stability of the mean pulse energy (?2 < 0.6%). Flexible aspect ratios and designs of the cell profile are achieved by fast modulation of the laser beam profile for each single pulse. This allows for optimization of the cell shape to get the best ink transfer interaction on a specific print substrate. New experiments with high power fiber lasers (cw lasers and pulsed MOPA systems > 500W@ 100kHz) resulted in improved cell precision, screen resolution and production efficiency. Future large scale cylinder engraving with ultra short pulse lasers (ps) is discussed.

  12. Performance evaluation of large aperture "polished panel" optical receivers based on experimental data

    NASA Astrophysics Data System (ADS)

    Vilnrotter, V.

    Recent interest in the development of hybrid RF/Optical communications has led to the installation of a polished-panel optical receiver evaluation assembly on the 34-meter research antenna at Deep-Space Station 13 (DSS-13) at NASA's Goldstone Deep Space Communications Complex1. The test setup consists of a custom aluminum panel polished to optical smoothness, and a large-sensor CCD camera designed to image the point-spread function (PSF) generated by the polished aluminum panel. Extensive data has been obtained via real-time tracking and imaging of planets and stars at DSS-13. Both on-source and off-source data were recorded at various elevations, enabling the development of realistic simulations and analytic models to help determine the performance of future deep-space communications systems operating with on-off keying (OOK) or pulse-position-modulated (PPM) signaling formats, and compared with the ultimate quantum bound on detection performance. Experimentally determined PSFs were scaled to provide realistic signal-distributions across a photon-counting detector array when a pulse is received, and uncoded as well as block-coded performance analyzed and evaluated for a well-known class of block codes.

  13. From Monolithics to Tethers to Freeflyers: The Spectrum of Large Aperture Sensing from Space

    NASA Technical Reports Server (NTRS)

    Leitner, Jesse; Quinn, David; Bauer, Frank (Technical Monitor)

    2002-01-01

    As part of NASA's endeavor to push the envelope and go where we have never been before, the Space Science Enterprise has laid out a vision which includes several missions that revolutionize the collection of scientific data from space. Many of the missions designed to meet the objectives of these programs depend heavily on the ability to perform space-based interferometry, which has recently become a rapidly growing field of investigation for both the scientific and engineering communities. While scientists are faced with the challenges of designing high fidelity optical systems capable of making detailed observations, engineers wrestle with the problem of providing s-pace-based platforms that can permit this data gathering to occur. Observational data gathering is desired at's variety of spectral wavelengths and resolutions, calling for interferometers with a range of baseline requirements. Approaches to configuration design are as varied as the missions themselves from large monolithic spacecraft to multiple free-flying small spacecraft and everything in between. As will be discussed, no one approach provides a 'panacea' of solutions rather each has its place in terms of the mission requirements. The purpose here is to identify the advantages and disadvantages of the various approaches, to discuss the driving factors in design selection and determine the relative range of applicability of each design approach.

  14. T/R module development for large aperture L-band phased array

    NASA Technical Reports Server (NTRS)

    Chamberlain, Neil; Andricos, Constantine; Kumley, Kendra; Berkun, Andrew; Hodges, Richard; Spitz, Suzanne

    2004-01-01

    This paper describes a transmit / receive (T/R) module for a large L-band space based radar active phased array being developed at JPL. Electrical performance and construction techniques are described, with emphasis on the former. The T/R modules have a bandwidth of more than 80 MHz centered at 1260MHz and support dual, switched polarizations. Phase and amplitude are controlled by a 6-bit phase shifter and a 6-bit attenuator, respectively. The transmitter power amplifier generates 2.4 W into a nominal 50 ohm load with 36% overall efficiency. The receiver noise figure is 4.4 dB including all front-end losses. The module weighs 32 g and has a footprint of 8 cm x 4.5 cm. Fourteen of these T/R modules were fabricated at the JPL Pick-and-Place Facility and were tested using a computer-controlled measurement facility developed at JPL. Calibrated performance of this set of T/R modules is presented and shows good agreement with design predictions.

  15. Feed System Design Considerations for Large Space Antenna Systems. Part 2: Single Aperture with Overlapping Feeds

    NASA Technical Reports Server (NTRS)

    Jamnejad, V.

    1985-01-01

    Contiguous multiple beams are used to make use of the set of frequency bands at different beams at different geographical locations and achieve the most efficient use of precious frequency allocation. This is feasible only if the interference among cochannel beams is below some acceptable level, by carrier/interference (C/I) ratio. Individual beam patterns of very low sidelobes, which in turn necessitates narrow feed are required. A physically realizable solution to this problem entails either more than one reflector, more complicated optics, or breaking of each feed into a cluster of smaller elements, some of which would then be shared by adjacent beams. The latter, however, requires a complicated beamforming network (BFN) for the proper feeding of the elements. The feedpacking problem is not unique to reflector antennas and exists in lens type antennas as well. The BFN and associated problems are present in the phased array antennas and on a much larger scale. Poor scan capabilities are associated with reflector systems. The scan properties of offset fed reflector systems can be improved by choosing a very large focal length to parent reflector diameter ((F/Dp) ratio, which requires a longer boom to support the feed. In the case of reflectors with cluster feed arrangements, the scan capability for smaller F/Dp ratios is improved by proper adjustment of cluster element excitations. Such a system seems to be appropriate for up to 10 beamwidths scan. For a larger number of beams, systems with wider scan capabilities, such as phased arrays or phased array/reflector combinations, become more appealing.

  16. Three-dimensional shape measurement of large-aperture aspheric mirrors by off-axis null Ronchi test.

    PubMed

    Guo, Chunfeng; Su, Xianyu; Chen, Wenjing; Lei, Baiping; Wu, Fan

    2012-03-20

    An off-axis null Ronchi test is presented to measure the three-dimensional (3D) shape of a large-aperture aspheric mirror. The method designs curved fringe patterns as null sinusoidal gratings by means of phase information and ray tracing. In the process of measurement, the curved fringe patterns are displayed on a transmission-type liquid crystal display (T-LCD) screen, and a CCD camera records the fringe patterns containing the information of deviations of the mirror. The slopes of the deviations of the mirror are obtained by using the recorded fringe patterns. The deviations are restored by integrating, and then the 3D shape of the mirror can be reconstructed. Compared with the classical null Ronchi test, the method can provide enough measured data points and avoid the jagged edges of bands on the null gratings. Moreover, the method can conveniently change period and direction of the curved fringes and accurately control phase shifting. Computer simulations and a preliminary experiment are presented to show the performance of the method. PMID:22441472

  17. The ExaVolt Antenna: A large-aperture, balloon-embedded antenna for ultra-high energy particle detection

    NASA Astrophysics Data System (ADS)

    Gorham, P. W.; Baginski, F. E.; Allison, P.; Liewer, K. M.; Miki, C.; Hill, B.; Varner, G. S.

    2011-12-01

    We describe the scientific motivation, experimental basis, design methodology, and simulated performance of the ExaVolt Antenna (EVA) mission, and planned ultra-high energy (UHE) particle observatory under development for NASA's suborbital super-pressure balloon program in Antarctica. EVA will improve over ANITA's integrated totals - the current state-of-the-art in UHE suborbital payloads - by 1-2 orders of magnitude in a single flight. The design is based on a novel application of toroidal reflector optics which utilizes a super-pressure balloon surface, along with a feed-array mounted on an inner membrane, to create an ultra-large radio antenna system with a synoptic view of the Antarctic ice sheet below it. Radio impulses arise via the Askaryan effect when UHE neutrinos interact within the ice, or via geosynchrotron emission when UHE cosmic rays interact in the atmosphere above the continent. EVA's instantaneous antenna aperture is estimated to be several hundred m 2 for detection of these events within a 150-600 MHz band. For standard cosmogenic UHE neutrino models, EVA should detect of order 30 events per flight in the EeV energy regime. For UHE cosmic rays, of order 15,000 geosynchrotron events would be detected in total, several hundred above 10 EeV, and of order 60 above the GZK cutoff energy.

  18. Lupus I Observations from the 2010 Flight of the Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry

    E-print Network

    Matthews, Tristan G; Angil, Francesco E; Benton, Steven J; Chapin, Edward L; Chapman, Nicholas L; Devlin, Mark J; Fissel, Laura M; Fukui, Yasuo; Gandilo, Natalie N; Gundersen, Joshua O; Hargrave, Peter C; Klein, Jeffrey; Korotkov, Andrei L; Moncelsi, Lorenzo; Mroczkowski, Tony K; Netterfield, Calvin B; Novak, Giles; Nutter, David; Olmi, Luca; Pascale, Enzo; Poidevin, Frdrick; Savini, Giorgio; Scott, Douglas; Shariff, Jamil A; Soler, Juan Diego; Tachihara, Kengo; Thomas, Nicholas E; Truch, Matthew D P; Tucker, Carole E; Tucker, Gregory S; Ward-Thompson, Derek

    2013-01-01

    The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLASTPol) was created by adding polarimetric capability to the BLAST experiment that was flown in 2003, 2005, and 2006. BLASTPol inherited BLAST's 1.8 m primary and its Herschel/SPIRE heritage focal plane that allows simultaneous observation at 250, 350, and 500 {\\mu}m. We flew BLASTPol in 2010 and again in 2012. Both were long duration Antarctic flights. Here we present polarimetry of the nearby filamentary dark cloud Lupus I obtained during the 2010 flight. Despite limitations imposed by the effects of a damaged optical component, we were able to clearly detect submillimeter polarization on degree scales. We compare the resulting BLASTPol magnetic field map with a similar map made via optical polarimetry (The optical data were published in 1998 by J. Rizzo and collaborators.). The two maps partially overlap and are reasonably consistent with one another. We compare these magnetic field maps to the orientations of filaments in Lupus I,...

  19. Spaceborne Microwave Instrument for High Resolution Remote Sensing of the Earth's Surface Using a Large-Aperture Mesh Antenna

    NASA Technical Reports Server (NTRS)

    Njoku, E.; Wilson, W.; Yueh, S.; Freeland, R.; Helms, R.; Edelstein, W.; Sadowy, G.; Farra, D.; West, R.; Oxnevad, K.

    2001-01-01

    This report describes a two-year study of a large-aperture, lightweight, deployable mesh antenna system for radiometer and radar remote sensing of the Earth from space. The study focused specifically on an instrument to measure ocean salinity and Soil moisture. Measurements of ocean salinity and soil moisture are of critical . importance in improving knowledge and prediction of key ocean and land surface processes, but are not currently obtainable from space. A mission using this instrument would be the first demonstration of deployable mesh antenna technology for remote sensing and could lead to potential applications in other remote sensing disciplines that require high spatial resolution measurements. The study concept features a rotating 6-m-diameter deployable mesh antenna, with radiometer and radar sensors, to measure microwave emission and backscatter from the Earth's surface. The sensors operate at L and S bands, with multiple polarizations and a constant look angle, scanning across a wide swath. The study included detailed analyses of science requirements, reflector and feedhorn design and performance, microwave emissivity measurements of mesh samples, design and test of lightweight radar electronic., launch vehicle accommodations, rotational dynamics simulations, and an analysis of attitude control issues associated with the antenna and spacecraft, The goal of the study was to advance the technology readiness of the overall concept to a level appropriate for an Earth science emission.

  20. A combined analogue and digital pulse compression system using large time bandwidth product signals for use in synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Godbole, Pushkar E.

    1989-07-01

    Pulse compression, widely used in modern radar systems, has the advantage in that it allows the use of long duration low-power pulses which facilitate low-power transmission. A synthetic aperture radar (SAR) pulse compression system able to compress very large time bandwidth product signals while still retaining high dynamic range capability and flexibility would be very advantageous. The possibility of implementing the compression in two stages is investigated, in which the first stage compression processing is done by an analog device followed by digital techniques in the second stage. Various signal coding methods were evaluated to determine those most suitable to the two-stage process, and various means of implementing the second stage were compared. A two-stage pulse compression system was then designed and built to generate arbitrarily coded expanded pulses with bandwidths in excess of 200 MHz. Its performance was evaluated in the presence of tone, noise, and jamming. It was shown that the two-stage pulse compression system exhibited greater resistance to quantizer saturation than a comparable digital system. The processing effort required to implement the compression using a digital adaptive matched filter was found to be slightly less than double that of a basic pulse compression system.

  1. Numerical aperture limits on efficient ball lens coupling of laser diodes to single-mode fibers with defocus to balance spherical aberration

    NASA Technical Reports Server (NTRS)

    Wilson, R. Gale

    1994-01-01

    The potential capabilities and limitations of single ball lenses for coupling laser diode radiation to single-mode optical fibers have been analyzed; parameters important to optical communications were specifically considered. These parameters included coupling efficiency, effective numerical apertures, lens radius, lens refractive index, wavelength, magnification in imaging the laser diode on the fiber, and defocus to counterbalance spherical aberration of the lens. Limiting numerical apertures in object and image space were determined under the constraint that the lens perform to the Rayleigh criterion of 0.25-wavelength (Strehl ratio = 0.80). The spherical aberration-defocus balance to provide an optical path difference of 0.25 wavelength units was shown to define a constant coupling efficiency (i.e., 0.56). The relative numerical aperture capabilities of the ball lens were determined for a set of wavelengths and associated fiber-core diameters of particular interest for single-mode fiber-optic communication. The results support general continuing efforts in the optical fiber communications industry to improve coupling links within such systems with emphasis on manufacturing simplicity, system packaging flexibility, relaxation of assembly alignment tolerances, cost reduction of opto-electronic components and long term reliability and stability.

  2. MULTISPECTRAL LASER-INDUCED FLUORESCENCE IMAGING SYSTEM FOR LARGE BIOLOGICAL SAMPLES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Presented is a detailed description of a common aperture, multispectral laser-induced fluorescence imaging system developed to allow detection of fecal matter on agricultural products. With an expanded, 355 nm, Nd:YAG laser beam as the excitation source, fluorescence emission images in the blue, gr...

  3. Resolving the Effects of Aperture and Volume Restriction of the Flow by Semi-Porous Barriers Using Large-Eddy Simulations

    NASA Astrophysics Data System (ADS)

    Chatziefstratiou, Efthalia K.; Velissariou, Vasilia; Bohrer, Gil

    2014-09-01

    The Regional Atmospheric Modelling System (RAMS)-based Forest Large-Eddy Simulation (RAFLES) model is used to simulate the effects of large rectangular prism-shaped semi-porous barriers of varying densities under neutrally buoyant conditions. RAFLES model resolves flows inside and above forested canopies and other semi-porous barriers, and it accounts for barrier-induced drag on the flow and surface flux exchange between the barrier and the air. Unlike most other models, RAFLES model also accounts for the barrier-induced volume and aperture restriction via a modified version of the cut-cell coordinate system. We explicitly tested the effects of the numerical representation of volume restriction, independent of the effects of the drag, by comparing drag-only simulations (where we prescribed neither volume nor aperture restrictions to the flow), restriction-only simulations (where we prescribed no drag), and control simulations where both drag and volume plus aperture restrictions were included. Previous modelling and empirical work have revealed the development of important areas of increased uplift upwind of forward-facing steps, and recirculation zones downwind of backward-facing steps. Our simulations show that representation of the effects of the volume and aperture restriction due to the presence of semi-porous barriers leads to differences in the strengths and locations of increased-updraft and recirculation zones, and the length and strength of impact and adjustment zones when compared to simulation solutions with a drag-only representation. These are mostly driven by differences to the momentum budget of the streamwise wind velocity by resolved turbulence and pressure gradient fields around the front and back edges of the barrier. We propose that volume plus aperture restriction is an important component of the flow system in semi-porous environments such as forests and cities and should be considered by large-eddy simulation (LES).

  4. Large mode-volume, large beta, photonic crystal laser resonator

    SciTech Connect

    Dezfouli, Mohsen Kamandar; Dignam, Marc M. [Department of Physics, Engineering Physics and Astronomy, Queens University, Kingston, ON K7L 3N6 (Canada)

    2014-12-15

    We propose an optical resonator formed from the coupling of 13, L2 defects in a triangular-lattice photonic crystal slab. Using a tight-binding formalism, we optimized the coupled-defect cavity design to obtain a resonator with predicted single-mode operation, a mode volume five times that of an L2-cavity mode and a beta factor of 0.39. The results are confirmed using finite-difference time domain simulations. This resonator is very promising for use as a single mode photonic crystal vertical-cavity surface-emitting laser with high saturation output power compared to a laser consisting of one of the single-defect cavities.

  5. Differential Optical Synthetic Aperture Radar

    DOEpatents

    Stappaerts, Eddy A. (San Ramon, CA)

    2005-04-12

    A new differential technique for forming optical images using a synthetic aperture is introduced. This differential technique utilizes a single aperture to obtain unique (N) phases that can be processed to produce a synthetic aperture image at points along a trajectory. This is accomplished by dividing the aperture into two equal "subapertures", each having a width that is less than the actual aperture, along the direction of flight. As the platform flies along a given trajectory, a source illuminates objects and the two subapertures are configured to collect return signals. The techniques of the invention is designed to cancel common-mode errors, trajectory deviations from a straight line, and laser phase noise to provide the set of resultant (N) phases that can produce an image having a spatial resolution corresponding to a synthetic aperture.

  6. A conceptual design for a Cassegrain-mounted high-resolution optical spectrograph for large-aperture telescopes

    NASA Astrophysics Data System (ADS)

    Froning, Cynthia S.; Osterman, Steven; Burgh, Eric; Beasley, Matthew; Scowen, Paul; Veach, Todd; Jordan, Steven; Ebbets, Dennis; Lieber, Michael; deCino, James; Castilho, Bruno Vaz; Gneiding, Clemens; Csar de Oliveira, Antonio

    2013-09-01

    We present a conceptual design for a high-resolution optical spectrograph appropriate for mounting at Cassegrain on a large aperture telescope. The design is based on our work for the Gemini High Resolution Optical Spectrograph (CUGHOS) project. Our design places the spectrograph at Cassegrain focus to maximize throughput and blue wavelength coverage, delivering R=40,000 resolving power over a continuous 320-1050 nm waveband with throughputs twice those of current instruments. The optical design uses a two-arm, cross-dispersed echelle format with each arm optimized to maximize efficiency. A fixed image slicer is used to minimize optics sizes. The principal challenge for the instrument design is to minimize flexure and degradation of the optical image. To ensure image stability, our opto-mechanical design combines a cost-effective, passively stable bench employing a honeycomb aluminum structure with active flexure control. The active flexure compensation consists of hexapod mounts for each focal plane with full 6-axis range of motion capability to correct for focus and beam displacement. We verified instrument performance using an integrated model that couples the optical and mechanical design to image performance. The full end-to-end modeling of the system under gravitational, thermal, and vibrational perturbations shows that deflections of the optical beam at the focal plane are <29 ?m per exposure under the worst case scenario (<10 ?m for most orientations), with final correction to 5 ?m or better using open-loop active control to meet the stability requirement. The design elements and high fidelity modeling process are generally applicable to instruments requiring high stability under a varying gravity vector.

  7. Design and testing of a large-aperture, high-gain, Brewster{close_quote}s angle zigzag Nd:glass slab amplifier

    Microsoft Academic Search

    M. J. Shoup; J. H. Kelly; D. L. Smith

    1997-01-01

    At the University of Rochester we have constructed and tested a large-aperture, (1.06.5 cm), high-gain (8) Brewster{close_quote}s angle zigzag Nd:glass amplifier with a repetition rate of 2 Hz. This amplifier has a gain uniformity of ±3% and a maximum stress-induced depolarization >2.5%. {copyright} 1997 Optical Society of America

  8. Laser processing system development of large area and high precision

    NASA Astrophysics Data System (ADS)

    Park, Hyeongchan; Ryu, Kwanghyun; Hwang, Taesang

    2013-03-01

    As industry of PCB (Printed Circuit Board) and display growing, this industry requires an increasingly high-precision quality so current cutting process in industry is preferred laser machining than mechanical machining. Now, laser machining is used almost "step and repeat" method in large area, but this method has a problem such as cutting quality in the continuity of edge parts, cutting speed and low productivity. To solve these problems in large area, on-the-fly (stagescanner synchronized system) is gradually increasing. On-the-fly technology is able to process large area with high speed because of stage-scanner synchronized moving. We designed laser-based high precision system with on-the-fly. In this system, we used UV nano-second pulse laser, power controller and scanner with telecentric f-theta lens. The power controller is consisted of HWP(Half Wave Plate), thin film plate polarizer, photo diode, micro step motor and control board. Laser power is possible to monitor real-time and adjust precision power by using power controller. Using this machine, we tested cutting of large area coverlay and sheet type large area PCB by applying on-the-fly. As a result, our developed machine is possible to process large area without the problem of the continuity of edge parts and by high cutting speed than competitor about coverlay.

  9. Dual Polarized UHF\\/VHF Honeycomb Stacked-Patch Feed Array for a Large-Aperture Spaceborne Radar Antenna

    Microsoft Academic Search

    M. Moghaddam; Y. Rahmat-Samii; P. Partridge; L. Van Nieuwstadt; J. Vitaz; M. Haynes; J. Huang; V. Cable

    2007-01-01

    As penetration depth through vegetation and ground becomes more important in active remote sensing applications, there is a shift toward using lower frequencies. To facilitate imaging of ground water, soil moisture and composition, and penetrating through forest canopies, a dual-band synthetic aperture radar (SAR) has been proposed to operate at VHF and UHF frequencies. To accommodate weekly repeat observations from

  10. APT: Aperture Photometry Tool

    NASA Astrophysics Data System (ADS)

    Laher, Russ

    2012-08-01

    Aperture Photometry Tool (APT) is software for astronomers and students interested in manually exploring the photometric qualities of astronomical images. It has a graphical user interface (GUI) which allows the image data associated with aperture photometry calculations for point and extended sources to be visualized and, therefore, more effectively analyzed. Mouse-clicking on a source in the displayed image draws a circular or elliptical aperture and sky annulus around the source and computes the source intensity and its uncertainty, along with several commonly used measures of the local sky background and its variability. The results are displayed and can be optionally saved to an aperture-photometry-table file and plotted on graphs in various ways using functions available in the software. APT is geared toward processing sources in a small number of images and is not suitable for bulk processing a large number of images, unlike other aperture photometry packages (e.g., SExtractor). However, APT does have a convenient source-list tool that enables calculations for a large number of detections in a given image. The source-list tool can be run either in automatic mode to generate an aperture photometry table quickly or in manual mode to permit inspection and adjustment of the calculation for each individual detection. APT displays a variety of useful graphs, including image histogram, and aperture slices, source scatter plot, sky scatter plot, sky histogram, radial profile, curve of growth, and aperture-photometry-table scatter plots and histograms. APT has functions for customizing calculations, including outlier rejection, pixel picking and zapping, and a selection of source and sky models. The radial-profile-interpolation source model, accessed via the radial-profile-plot panel, allows recovery of source intensity from pixels with missing data and can be especially beneficial in crowded fields.

  11. Large-Aperture [O I] 6300 A Photometry of Comet Hale-Bopp: Implications for the Photochemistry of OH

    NASA Technical Reports Server (NTRS)

    Morgenthaler, Jeffrey P.; Harris, Walter M.; Scherb, Frank; Anderson, Christopher M.; Oliversen, Ronald J.; Doane, Nathaniel E.; Combi, Michael R.; Marconi, Maximus L.; Smyth, William H.

    2001-01-01

    Large-aperture photometric observations of comet Hale-Bopp (C/1995 O1) in the forbidden red line of neutral oxygen ([O I] 6300 angstroms) with the 150 mm dual-etalon Fabry-Perot spectrometer that comprises the Wisconsin H-alpha Mapper and a 50 mm dual-etalon Fabry-Perot spectrometer at the McMath-Pierce main telescope from 1997 late February to mid April yield a total metastable O((sup 1)D) production rate of (2.3-5.9) x 10(exp 30)/s. Applying the standard H2O and OH photodissociation branching ratios, we derive a water production rate, Q(H2O), of (2.6-6.1) x 10(exp 31)/s, which disagrees with Q(H2O = 1x10(exp 31)/s determined by independent H2O, OH, and H measurements. Furthermore, our own [O I] 6300 observations of the inner coma (< 30,000 km) using the 3.5 m Wisconsin-Indiana-Yale-NOAO telescope Hydra and Densepak multi-object spectrographs yield Q(H2O) = 1 x 10(exp 31)/s. Using our [O I] 6300 data, which cover spatial scales ranging from 2,000 to 1x10(exp 6) km, and a complementary set of wide-field ground-based OH images, we can constrain the sources of the apparent excess O((sup 1)D) emission to the outer coma, where photodissociation of OH is assumed to be the dominant O((sup 1)D) production mechanism. From production rates of other oxygen-bearing volatiles (e.g., CO and CO2), we can account for at most 30% of the observed excess O((sup 1)D) emission. Since even less O((sup 1)D) should be coming from other sources (e.g., electron excitation of neutral O and distributed nonnuclear sources of H2O), we hypothesize that the bulk of the excess O((sup 1)D) is likely coming from photodissociating OH. Using the experimental OH photo-dissociation cross section of Nee and Lee at Ly-alpha as a guide in modifying the theoretical OH cross sections of van Dishoeck and Dalgarno, we can account for approximately 60% of the observed O((sup 1)D) excess without requiring major modifications to the other OH branching ratios or the total OH photodissociation lifetime.

  12. Estimating Evapotranspiration over Heterogeneously Vegetated Surfaces using Large Aperture Scintillometer, LiDAR, and Airborne Multispectral Imagery

    NASA Astrophysics Data System (ADS)

    Geli, H. M.; Neale, C. M.; Pack, R. T.; Watts, D. R.; Osterberg, J.

    2011-12-01

    Estimates of evapotranspiration (ET) over heterogeneous areas is challenging especially in water-limited sparsely vegetated environments. New techniques such as airborne full-waveform LiDAR (Light Detection and Ranging) and high resolution multispectral and thermal imagery can provide enough detail of sparse canopies to improve energy balance model estimations as well as footprint analysis of scintillometer data. The objectives of this study were to estimate ET over such areas and develop methodologies for the use of these airborne data technologies. Because of the associated heterogeneity, this study was conducted over the Cibola National wildlife refuge, southern California on an area dominated with tamarisk (salt cedar) forest (90%) interspersed with arrowweed and bare soil (10%). A set of two large aperture scintillometers (LASs) were deployed over the area to provide estimates of sensible heat flux (HLAS). The LASs were distributed over the area in a way that allowed capturing different surface spatial heterogeneity. Bowen ratio systems were used to provide hydrometeorological variables and surface energy balance fluxes (SEBF) (i.e. Rn, G, H, and LE) measurements. Scintillometer-based estimates of HLAS were improved by considering the effect of the corresponding 3D footprint and the associated displacement height (d) and the roughness length (z0) following Geli et al. (2011). The LiDAR data were acquired using the LASSI Lidar developed at Utah State University (USU). The data was used to obtain 1-m spatial resolution DEM's and vegetation canopy height to improve the HLAS estimates. The BR measurements of Rn and G were combined with LAS estimates, HLAS, to provide estimates of LELASas a residual of the energy balance equation. A thermal remote sensing model namely the two source energy balance (TSEB) of Norman et al. (1995) was applied to provide spatial estimates of SEBF. Four airborne images at 1-4 meter spatial resolution acquired using the USU airborne multispectral system during the 2007-2008 growing season were used. Estimates of LETSEB and HTSEB were compared with those derived based on LAS, HLAS and LELAS, and with those based on BR, HBR and LEBR. The comparison was performed by integrating the spatially estimated fluxes using the BR and the LAS 3D footprint weights.

  13. Large-Aperture [O I] 6300 Photometry of Comet Hale-Bopp: Implications for the Photochemistry of OH

    NASA Astrophysics Data System (ADS)

    Morgenthaler, Jeffrey P.; Harris, Walter M.; Scherb, Frank; Anderson, Christopher M.; Oliversen, Ronald J.; Doane, Nathaniel E.; Combi, Michael R.; Marconi, Maximus L.; Smyth, William H.

    2001-12-01

    Large-aperture photometric observations of comet Hale-Bopp (C/1995 O1) in the forbidden red line of neutral oxygen ([O I] 6300 ) with the 150 mm dual-etalon Fabry-Prot spectrometer that comprises the Wisconsin H? Mapper and a 50 mm dual-etalon Fabry-Prot spectrometer at the McMath-Pierce main telescope from 1997 late February to mid April yield a total metastable O(1D) production rate of (2.3-5.9)1030 s-1. Applying the standard H2O and OH photodissociation branching ratios found in Huebner, Keady, & Lyon and van Dishoeck & Dalgarno, we derive a water production rate, Q(H2O), of (2.6-6.1)1031 s-1, which disagrees with Q(H2O)~11031 s-1 determined by independent H2O, OH, and H measurements. Furthermore, our own [O I] 6300 observations of the inner coma (<30,000 km) using the 3.5 m Wisconsin-Indiana-Yale-NOAO telescope Hydra and Densepak multiobject spectrographs yield Q(H2O)~11031 s-1. Using our [O I] 6300 data, which cover spatial scales ranging from 2,000 to 1106 km, and a complementary set of wide-field ground-based OH images, we can constrain the sources of the apparent excess O(1D) emission to the outer coma, where photodissociation of OH is assumed to be the dominant O(1D) production mechanism. From production rates of other oxygen-bearing volatiles (e.g., CO and CO2), we can account for at most 30% of the observed excess O(1D) emission. Since even less O(1D) should be coming from other sources (e.g., electron excitation of neutral O and distributed nonnuclear sources of H2O), we hypothesize that the bulk of the excess O(1D) is likely coming from photodissociating OH. Using the experimental OH photodissociation cross section of Nee & Lee at Ly? as a guide in modifying the theoretical OH cross sections of van Dishoeck & Dalgarno, we can account for ~60% of the observed O(1D) excess without requiring major modifications to the other OH branching ratios or the total OH photodissociation lifetime.

  14. Large-Area Laser-Lift-Off Processing in Microelectronics

    NASA Astrophysics Data System (ADS)

    Delmdahl, R.; Ptzel, R.; Brune, J.

    Laser lift-off is an enabling technology for microelectronics growth markets such as light emitting diodes, densely packaged semiconductor devices, and flexible displays. For example, thin film transistor structures fabricated on top of polymer layers spun on glass carriers must be delaminated from rigid substrates to create lightweight and rugged flexible displays on polymers. Low-thermal-budget processes are generically required to protect adjacent functional films. Excimer lasers provide short UV wavelength and short pulse duration required for highly-localized energy coupling. The high output power of excimer lasers enables a large processing footprint and the high-throughput rates needed in mass manufacturing.

  15. Continuous-wave operation of a (20\\bar{2}\\bar{1}) InGaN laser diode with a photoelectrochemically etched current aperture

    NASA Astrophysics Data System (ADS)

    Megalini, Ludovico; Becerra, Daniel L.; Farrell, Robert M.; Pourhashemi, A.; Speck, James S.; Nakamura, Shuji; DenBaars, Steven P.; Cohen, Daniel A.

    2015-04-01

    We demonstrated selective and controllable undercut etching of the InGaN/GaN multiple quantum well (MQW) active region of a (20\\bar{2}\\bar{1}) laser diode (LD) structure by photoelectrochemical etching. This technique was used to fabricate current aperture edge-emitting blue laser diodes (CA-LDs), whose performance was compared with that of shallow-etched ridge LDs with a nominally identical epitaxial structure. The threshold current density, threshold voltage, peak output power, and series resistance for the CA-LD (shallow-etched LD) with a 2.5-m-wide active region were 4.4 (8.1) kA/cm2, 6.1 (7.7) V, 96.5 (63.5) mW, and 4.7 (6.0) ? under pulsed conditions and before facet coating, respectively.

  16. Combining Measurements with Three-Dimensional Laser Scanning System and Coded Aperture Gamma-Ray Imaging Systems for International Safeguards Applications

    SciTech Connect

    Boehnen, Chris Bensing [ORNL] [ORNL; Bogard, James S [ORNL] [ORNL; Hayward, Jason P [ORNL] [ORNL; Raffo-Caiado, Ana Claudia [ORNL] [ORNL; Smith, Stephen E [ORNL] [ORNL; Ziock, Klaus-Peter [ORNL] [ORNL

    2010-01-01

    Being able to verify the operator's declaration in regards to technical design of nuclear facilities is an important aspect of every safeguards approach. In addition to visual observation, it is relevant to know if nuclear material is present or has been present in piping and ducts not declared. The possibility of combining different measurement techniques into one tool should optimize the inspection effort and increase safeguards effectiveness. Oak Ridge National Laboratory (ORNL) is engaged in a technical collaboration project involving two U.S. Department of Energy foreign partners to investigate combining measurements from a three-dimensional (3D) laser scanning system and gamma-ray imaging systems. ORNL conducted simultaneous measurements with a coded-aperture gamma-ray imager and the 3D laser scanner in an operational facility with complex configuration and different enrichment levels and quantities of uranium. This paper describes these measurements and their results.

  17. A new look at Fresnel field computation using the Jacobi-Bessel series. [large aperture antenna design

    NASA Technical Reports Server (NTRS)

    Galindo-Israel, V.; Rahmat-Samii, Y.

    1981-01-01

    Computational procedures that would be useful in finding the Fresnel field from a knowledge of the Jacobi-Bessel expansion of the far field are considered. The range of validity of the Fresnel approximation is carefully examined by comparing it with the exact closed form solution for the uniform circular aperture. Also investigated numerically, and in great detail, is the range of validity (over theta) of the Fresnel small angle (FSA) approximation. For moderate sized apertures as small as 10 wavelengths, it is found that the FSA approximation is very accurate to angles as wide as four or more sidelobes (as seen in the far zone). A very efficient computational method is shown to exist for the radiation integral in the form of a single series expansion that is analytically continuous and convergent for a wide range of observation points in three-dimensional space.

  18. Large Signal Resonance and Laser Dilatometer Methods

    NASA Astrophysics Data System (ADS)

    Wolff, A.

    In many piezoelectric devices maximum deformations are desirable. They can only be achieved under high field strengths (1-2 kV mm-1) and cause large mechanical stress amplitudes in the piezoelectric material. This calls for piezoelectric materials with a strong piezoelectric effect that are capable of withstanding both high electric field strengths and large mechanical stresses. Under these large signal conditions, the properties of piezoelectric materials are considerably non-linear and show hysteretic behaviour. As discussed in Chap. 3.3, the non-linear behaviour can be attributed to the motion of non 180 domain walls. Therefore, the non-linearity of the piezoelectric response and the accompanying hysteresis can be described with the aid of Rayleigh's law (Equations (3.48) and (3.49) in Chap. 3.3). The most important aspect of the Rayleigh-like behaviour is the fact that hysteresis and non-linearity in soft piezoelectric ceramics are essentially linked, as can be seen in Fig. 19.7, that is, both hysteresis and non-linearity are results of the same-domain wall pinning processes. Since the hysteretic response is closely related to the electrical and mechanical losses occurring in piezoelectric ceramics or ferroelectric perovskites, in general, the performance of power ceramics can be tested substantially by measuring either the dielectric losses at large field amplitudes or the mechanical losses at large mechanical stress amplitudes. However, to perform these measurements, it is not sufficient to extend simply the standard small-signal capacitance/loss tangent techniques according to IRE or IEEE standards [1] or the impedance measurement techniques as described in Chap. 18 to higher-signal amplitudes. For then the measurement results would be considerably falsified by an overheating of the test samples. With this in mind, pulsed test signals are mostly used [2].

  19. The processing of hexagonally sampled signals with standard rectangular techniques: application to 2-D large aperture synthesis interferometric radiometers

    Microsoft Academic Search

    Adriano Camps; Javier Bara; Ignasi Corbella Sanahuja; Francesc Torres

    1997-01-01

    In Earth observation programs there is a need of passive low frequency (L-band) measurements to monitor soil moisture and ocean salinity with high spatial resolution 10-20 km, a radiometric resolution of 1 K and a revisit time of 1-3 days. Compared to total power radiometers aperture synthesis interferometric radiometers are technologically attractive because of their reduced mass and hardware requirements.

  20. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Optical strength of window materials in wide-aperture repetitively pulsed CO2 lasers

    Microsoft Academic Search

    S. G. Kazantsev

    1998-01-01

    It was established experimentally that irradiation of ionic single crystals by a series of microsecond pulses from a TEA CO2 laser, of 1 --- 15 s duration at a repetition rate in excess of 100 Hz, caused damage at subthreshold intensities as a result of gradual accumulation of thermally induced internal stresses. When the series of pulses were shortened, the

  1. Laser-Induced Production of Large Carbon-Based Toriods

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We report on the production of large carbon-based toroids (CBTs) from fullerencs. The process involves two step laser irradiation of a mixed fullcrene target (76% C-60, 22% C-70). Transmission electron microscopy (11M) clearly identifies toroidal-shaped structures as well as Q-shaped constructs. ...

  2. Plane-polar Fresnel and far-field computations using the Fresnel-Wilcox and Jacobi-Bessel expansions. [for large aperture antennas

    NASA Technical Reports Server (NTRS)

    Rahmat-Samii, Y.; Galindo-Israel, V.

    1981-01-01

    It is pointed out that the computation of the Fresnel fields for large aperture antennas is significant for many applications. The present investigation is concerned with an approach for the effective utilization of the coefficients of the Jacobi-Bessel series for the far-field to obtain an analytically continuous representation of the antenna field which is valid from the Fresnel region into the far field. Attention is given to exact formulations and closed form solutions, Fresnel and Fresnel small angle approximations, aspects of field expansion, the accuracy of the Fresnel and Fresnel small angle approximations, and the Jacobi-Bessel expansion applied to the Fresnel small angle approximation.

  3. Synthetic aperture radar interferometry

    Microsoft Academic Search

    PAUL A. ROSEN; SCOTT HENSLEY; IAN R. JOUGHIN; FUK K. LI; SREN N. MADSEN; ERNESTO RODRGUEZ; RICHARD M. GOLDSTEIN

    2000-01-01

    Synthetic aperture radar interferometry is an imaging technique for measuring the topography of a surface, its changes over time, and other changes in the detailed characteristic of the surface. By exploiting the phase of the coherent radar signal, interferometry has transformed radar remote sensing from a largely interpretive science to a quantitative tool, with applications in cartography, geodesy, land cover

  4. On the feasibility of large-aperture Fresnel lenses for the microfocusing of hard X-rays.

    PubMed

    Jark, Werner; Prenns, Frderic; Matteucci, Marco

    2006-05-01

    Like visible light, X-rays can also be focused by refraction in transmission lenses. For visible light this requires convex lenses while for X-rays one needs to use concave lenses instead. Both lens types can be lightened by the material removal strategy introduced by Fresnel, which results in a lens subdivided into zones. Until now, for the focusing of X-rays, stacks of standard lenses and of Fresnel lenses have mostly been produced. The first are dubbed compound refractive lenses, abbreviated as CRL. State-of-the-art systems of this kind now achieve almost theoretical performance for the focus size and the transmission. On the other hand, the latter Fresnel systems, which promise to provide larger apertures, are still in their infancy. This report discusses systematically the properties of two possible schemes for their realisation. It then compares the optimized apertures of these two schemes with those for CRLs. The best Fresnel lenses in this study are found to provide experimentally more than 50% of the expected refraction efficiency at 8.5 keV photon energy. The photon flux in their focus is then almost identical to that of perfect Be CRLs with the same focal length. This report will also interpret experimental data reported previously for other Fresnel lenses. PMID:16645250

  5. Nuclear-pumped lasers for large-scale applications

    SciTech Connect

    Anderson, R.E.; Leonard, E.M.; Shea, R.E.; Berggren, R.R.

    1988-01-01

    Efficient initiation of large-volume chemical lasers may be achieved by neutron induced reactions which produce charged particles in the final state. When a burst mode nuclear reactor is used as the neutron source, both a sufficiently intense neutron flux and a sufficient short initiation pulse may be possible. Proof-of-principle experiments are planned to demonstrate lasing in a direct nuclear-pumped large-volume system: to study the effects of various neutron absorbing materials on laser performance; to study the effects of long initiation pulse lengths; to determine the performance of large-scale optics and the beam quality that may bo obtained; and to assess the performance of alternative designs of burst systems that increase the neutron output and burst repetition rate. 21 refs., 7 figs., 5 tabs.

  6. Invited review article: Large ring lasers for rotation sensing.

    PubMed

    Schreiber, Karl Ulrich; Wells, Jon-Paul R

    2013-04-01

    Over the last two decades a series of large ring laser gyroscopes have been built having an unparalleled scale factor. These upscaled devices have improved the sensitivity and stability for rotation rate measurements by six orders of magnitude when compared to previous commercial developments. This progress has made possible entirely new applications of ring laser gyroscopes in the fields of geophysics, geodesy, and seismology. Ring lasers are currently the only viable measurement technology, which is directly referenced to the instantaneous rotation axis of the Earth. The sensor technology is rapidly developing. This is evidenced by the first experimentally viable proposals to make terrestrial tests of general relativistic effects such as the frame dragging of the rotating Earth. PMID:23635174

  7. Invited Review Article: Large ring lasers for rotation sensing

    NASA Astrophysics Data System (ADS)

    Schreiber, Karl Ulrich; Wells, Jon-Paul R.

    2013-04-01

    Over the last two decades a series of large ring laser gyroscopes have been built having an unparalleled scale factor. These upscaled devices have improved the sensitivity and stability for rotation rate measurements by six orders of magnitude when compared to previous commercial developments. This progress has made possible entirely new applications of ring laser gyroscopes in the fields of geophysics, geodesy, and seismology. Ring lasers are currently the only viable measurement technology, which is directly referenced to the instantaneous rotation axis of the Earth. The sensor technology is rapidly developing. This is evidenced by the first experimentally viable proposals to make terrestrial tests of general relativistic effects such as the frame dragging of the rotating Earth.

  8. Large aperture at low cost three-dimensional time-of-flight range sensor using scanning micromirrors and synchronous detector switching.

    PubMed

    Bogatscher, Siegwart; Streck, Andreas; Fox, Maik; Meinzer, Sebastian; Heussner, Nico; Stork, Wilhelm

    2014-03-10

    In this article the problem of achieving fast scanning of a time-of-flight range sensor with a large optical receiver aperture at low system cost is targeted. The presented approach to solve this problem consists of a micromirror-based transmitter unit and a receiver unit consisting of a large aperture lens system with a small field of view and a detector array. A concept, which is called synchronous detector switching, is applied to the detector array. Thereby electronic steering of the small receiver field of view is possible. The overall approach is compared to alternative approaches, and the underlying concept of synchronous detector switching is demonstrated experimentally in an implementation of a three-dimensional time-of-flight range sensor. It is theoretically shown that the presented concept is potentially cheaper than the alternative approaches for applications with a field of view of less than 6060. After a discussion of the strengths and limitations of the approach, its effect on broader scientific issues is outlined. PMID:24663413

  9. Aperture Photometry Tool

    NASA Astrophysics Data System (ADS)

    Laher, Russ R.; Gorjian, Varoujan; Rebull, Luisa M.; Masci, Frank J.; Fowler, John W.; Helou, George; Kulkarni, Shrinivas R.; Law, Nicholas M.

    2012-07-01

    Aperture Photometry Tool (APT) is software for astronomers and students interested in manually exploring the photometric qualities of astronomical images. It is a graphical user interface (GUI) designed to allow the image data associated with aperture photometry calculations for point and extended sources to be visualized and, therefore, more effectively analyzed. The finely tuned layout of the GUI, along with judicious use of color-coding and alerting, is intended to give maximal user utility and convenience. Simply mouse-clicking on a source in the displayed image will instantly draw a circular or elliptical aperture and sky annulus around the source and will compute the source intensity and its uncertainty, along with several commonly used measures of the local sky background and its variability. The results are displayed and can be optionally saved to an aperture-photometry-table file and plotted on graphs in various ways using functions available in the software. APT is geared toward processing sources in a small number of images and is not suitable for bulk processing a large number of images, unlike other aperture photometry packages (e.g., SExtractor). However, APT does have a convenient source-list tool that enables calculations for a large number of detections in a given image. The source-list tool can be run either in automatic mode to generate an aperture photometry table quickly or in manual mode to permit inspection and adjustment of the calculation for each individual detection. APT displays a variety of useful graphs with just the push of a button, including image histogram, x and y aperture slices, source scatter plot, sky scatter plot, sky histogram, radial profile, curve of growth, and aperture-photometry-table scatter plots and histograms. APT has many functions for customizing the calculations, including outlier rejection, pixel ""picking"" and ""zapping,"" and a selection of source and sky models. The radial-profile-interpolation source model, which is accessed via the radial-profile-plot panel, allows recovery of source intensity from pixels with missing data and can be especially beneficial in crowded fields.

  10. Homopolar Generator as the Energy Store for a Large Laser

    Microsoft Academic Search

    E. K. Inall; J. L. Hughes

    1968-01-01

    THE homopolar generator1,2 at the Australian National University in Canberra can be connected to deliver 1.5 106 A at more than 800 V for 0.1 s. When light sources capable of handling such power and energy are developed, it will be possible to use the energy to pump a large laser. We have used the generator with its four

  11. Energy extraction from a large-volume HF laser amplifier

    Microsoft Academic Search

    J. M. Hoffman; E. L. Patterson; R. A. Gerber

    1979-01-01

    Energy extraction from a large-volume HF laser amplifier has been measured as a function of input intensity. Both the oscillator and amplifier were operated with similar gas mixtures of H2 and F2, which assured a good spectral match between the oscillator and amplifier. The amplifier input intensity was varied from 10,000 to 20,000,000 W\\/sq cm. An input intensity of 20,000,000

  12. Large-aperture multiple quantum well modulating retroreflector for free-space optical data transfer on unmanned aerial vehicles

    Microsoft Academic Search

    G. Charmaine Gilbreath; William S. Rabinovich; Timothy J. Meehan; Michael J. Vilcheck; Rita Mahon; Ray Burris; Mina Ferraro; Ilene Sokolsky; John A. Vasquez; Chris S. Bovais; Kerry Cochrell; Kim C. Goins; Robin Barbehenn; D. Scott Katzer; Kiki Ikossi-Anastasiou; Marcos J. Montes

    2001-01-01

    We describe progress in the development of a multiple quantum well modulating retroreflector, including a description of recent demonstrations of an infrared data link between a small rotary-wing unmanned airborne vehicle and a ground-based laser interrogator using the device designed and fabricated at the Naval Research Laboratory (NRL). Modulating retroreflector systems couple an optical retroreflector, such as a corner cube,

  13. Combining Measurements with Three-Dimensional Laser Scanning System and Coded Aperture Gamma-Ray Imaging System for International Safeguards Applications

    SciTech Connect

    Boehnen, Chris Bensing [ORNL] [ORNL; Bogard, James S [ORNL] [ORNL; Hayward, Jason P [ORNL] [ORNL; Raffo-Caiado, Ana Claudia [ORNL] [ORNL; Smith, Steven E [ORNL] [ORNL; Ziock, Klaus-Peter [ORNL] [ORNL

    2010-01-01

    Being able to verify the operator's declaration in regard to the technical design of nuclear facilities is an important aspect of every safeguards approach. In addition to visual observation, it is necessary to know if nuclear material is present or has been present in undeclared piping and ducts. The possibility of combining the results from different measurement techniques into one easily interpreted product should optimize the inspection effort and increase safeguards effectiveness. A collaborative effort to investigate the possibility of combining measurements from a three-dimensional (3D) laser scanning system and gamma-ray imaging systems is under way. The feasibility of the concept has been previously proven with different laboratory prototypes of gamma-ray imaging systems. Recently, simultaneous measurements were conducted with a new highly portable, mechanically cooled, High Purity Germanium (HPGe), coded-aperture gamma-ray imager and a 3D laser scanner in an operational facility with complex configuration and different enrichment levels and quantities of uranium. With specially designed software, data from both instruments were combined and a 3D model of the facility was generated that also identified locations of radioactive sources. This paper provides an overview of the technology, describes the measurements, discusses the various safeguards scenarios addressed, and presents results of experiments.

  14. Return Echoes from Medium-Large Footprint Laser Altimeters

    NASA Technical Reports Server (NTRS)

    Blair, J. Bryan; Hofton, Michelle A.; Rabine, David L.

    1999-01-01

    For just over 10 years, NASA Goddard Space Flight Center has been at the forefront of developing return echo laser altimeters and analysis techniques for a variety of both space and airborne applications. In 1991, the Laser Remote Sensing Branch began investigating the use of medium-large diameter footprint return waveforms for measuring vegetation height and structure and sub-canopy topography. Over the last 8 years, using a variety of profiling and scanning laser altimeters (i.e. ATLAS, SLICER, SLA, and LVIS), we have collected return waveforms over a variety of terrestrial surface types. We describe the effects of instrument characteristics and within-footprint surface structure on the shape of the return waveform and suggest several techniques for extracting this information. Specifically for vegetation returns, we describe the effects of canopy parameters such as architecture and closure on the shape of the return waveform. Density profiles, statistics, and examples from a variety of vegetation types will be presented, as well as comparisons with small-footprint laser altimeter data.

  15. Early laser operations at the Large Binocular Telescope Observatory

    NASA Astrophysics Data System (ADS)

    Rahmer, Gustavo; Lefebvre, Michael; Christou, Julian; Raab, Walfried; Rabien, Sebastian; Ziegleder, Julian; Borelli, Jos L.; Gssler, Wolfgang

    2014-08-01

    ARGOS is the GLAO (Ground-Layer Adaptive Optics) Rayleigh-based LGS (Laser Guide Star) facility for the Large Binocular Telescope Observatory (LBTO). It is dedicated for observations with LUCI1 and LUCI2, LBTO's pair of NIR imagers and multi-object spectrographs. The system projects three laser beams from the back of each of the two secondary mirror units, which create two constellations circumscribed on circles of 2 arcmin radius with 120 degree spacing. Each of the six Nd:YAG lasers provides a beam of green (532nm) pulses at a rate of 10kHz with a power of 14W to 18W. We achieved first on-sky propagation on the night of November 5, 2013, and commissioning of the full system will take place during 2014. We present the initial results of laser operations at the observatory, including safety procedures and the required coordination with external agencies (FAA, Space Command, and Military Airspace Manager). We also describe our operational procedures and report on our experiences with aircraft spotters. Future plans for safer and more efficient aircraft monitoring and detection are discussed.

  16. Automatic generation of beam apertures.

    PubMed

    Brewster, L; Mageras, G S; Mohan, R

    1993-01-01

    In order to specify arbitrarily shaped beam apertures for three-dimensional radiation treatment planning, aperture contours (or outlines) are often manually drawn using a beam's eye view display of the target volume and nearby normal structures. This can be a very time consuming process, and can be impractical for multileaf collimation and computer-aided optimization of a large number of fields. A method has been developed that allows automatic generation of aperture shapes that outline the target volume and may spare neighboring structures whenever desired. Margins of user-specified sizes (positive or negative) around the target and normal structures are also incorporated. For a chosen beam orientation, a 3D surface of each anatomic structure of interest is formed and projected onto a plane at the beam's isocenter. The outlines of each projected object are detected by an edge following algorithm, and margins are added. The outlines of normal structures are combined with that of the target volume to obtain the final aperture shape. This is done by overlaying filled versions of the outlines in such a way that regions of the target overlapped by normal structures are cut away, leaving only the target volume region to be irradiated. The remaining target volume outline is again detected to produce an aperture contour. Normal structures may split the aperture into several pieces, so this method detects any number of disjoint aperture contours. The results of the algorithm are illustrated with apertures generated for nasopharynx and prostate tumors, including sparing of normal tissues. PMID:8289714

  17. Experimental verification and theory of CNR gain for an eight-element multiple-aperture coherent laser receiver

    Microsoft Academic Search

    Ronald L. Phillips; Jing Xu; Kevin J. Gamble; Chie L. Gagge; K. Lewis; Giovanni Luvera; Ali Notash; Patrick Thompson; James E. Harvey; R. Glenn Sellar; C. M. Stickley; Larry C. Andrews; Deborah Kelly; John S. Stryjewski

    1997-01-01

    The detection and processing of laser communication signals are drastically affected by the fading induced onto these signals by atmospheric turbulence. One method of reducing this fading is to use an array of detectors in which each of the detector outputs are added together coherently. This requires measuring the phase difference between each of the receivers and co-phasing each of

  18. Development and Testing of a Power Trough System Using a Structurally-Efficient, High-Performance, Large-Aperture Concentrator with Thin Glass Reflector and Focal Point Rotation

    SciTech Connect

    May, E. K.; Forristall, R.

    2005-11-01

    Industrial Solar Technology has assembled a team of experts to develop a large-aperture parabolic trough for the electric power market that moves beyond cost and operating limitations of 1980's designs based on sagged glass reflectors. IST's structurally efficient space frame design will require nearly 50% less material per square meter than a Solel LS-2 concentrator and the new trough will rotate around the focal point. This feature eliminates flexhoses that increase pump power, installation and maintenance costs. IST aims to deliver a concentrator module costing less than $100 per square meter that can produce temperatures up to 400 C. The IST concentrator is ideally suited for application of front surface film reflectors and ensures that US corporations will manufacture major components, except for the high temperature receivers.

  19. On tidal tilt corrections to large ring laser gyroscope observations

    NASA Astrophysics Data System (ADS)

    Tian, Wei

    2014-01-01

    With the fast development of the large ring laser gyroscope (RLG) technology in the last decades, promising applications in geophysics and geodesy (e.g. observations of high-frequency variations of Earth's rotation, Earth's tide tilt and seismic waves) have been realized by various groups with currently running large RLGs. In this letter, we point out that in a large number of previous tilt correction models a significant term is missing. This term is related with the Shida number l2 (called l2-term in the following) and has a contribution, which is comparable with that from high-frequency Earth rotation variations due to ocean tides, to the Sagnac frequency record of RLGs. This term has to be removed (as part of the tilt correction) from the raw data so that RLGs can efficiently be employed as Earth's rotation detectors.

  20. Effect of the photon lifetime on the characteristics of 850-nm vertical-cavity surface-emitting lasers with fully doped distributed Bragg reflectors and an oxide current aperture

    SciTech Connect

    Bobrov, M. A.; Blokhin, S. A., E-mail: blokh@mail.ioffe.ru; Kuzmenkov, A. G.; Maleev, N. A. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation); Blokhin, A. A. [Saint Petersburg State Polytechnical University (Russian Federation); Zadiranov, Yu. M. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation); Nikitina, E. V. [Russian Academy of Sciences, Saint Petersburg Academic UniversityNanotechnology Research and Education Center (Russian Federation); Ustinov, V. M. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

    2014-12-15

    The effect of the photon lifetime in an optical microcavity on the characteristics of 850-nm vertical-cavity surface-emitting lasers (VCSELs) with fully doped distributed Bragg reflectors (DBRs) and an oxide current aperture is studied. The photon lifetime in the microcavity is controlled by varying the upper DBR reflectance. It is found that the speed of VCSELs with a current-aperture diameter of 10 ?m is mainly limited by the self-heating effect, despite an increase in the relaxation-oscillation damping coefficient with increasing photon lifetime in the microcavity. At the same time, the higher level of internal optical loss in lasers with a current-aperture diameter of 1.5 ?m leads to dominance of the effect of relaxation-oscillation damping independently of the radiation output loss. In the case of devices with a current-aperture diameter of 5.5 ?m, both mechanisms limiting the speed operate, which allow an increase in the VCSEL effective modulation frequency from 21 to 24 GHz as the photon lifetime decreases from 3.7 to 0.8 ps.

  1. Laser conoscopy of large-sized optical crystals

    NASA Astrophysics Data System (ADS)

    Kolesnikov, A. I.; Grechishkin, R. M.; Tretiakov, S. A.; Molchanov, V. Ya; Ivanova, A. I.; Kaplunova, E. I.; Vorontsova, E. Yu

    2013-12-01

    Conoscopic interferometry provides a simple method of non-destructive control of the quality of a number of ferro-piezoelectric and optical crystals. Standard optical microscopes, including some commercial instruments, are easily adapted for implementation of conoscopic studies, though limited to small handy samples with a thickness of the order of 0.5 mm. In the present work we show that the usage of wide convergent or divergent conical laser beams in a simple benchtop configuration makes it possible to examine large-sized optical crystals by the method of conoscopy, including samples elongated along the optical axis direction. As distinct from traditional optical microscopy the conoscopic figures obtained with the aid of the laser installment may contain tens and hundreds of isochrome fringes thus increasing the informative capabilities of the method. Large-sized crystals of LiNbO3 (5795 mm), TeO2 prisms (444114mm) were examined experimentally at different angles between the optical axis and normal to the crystal surface. The experimental studies of different optical anomalies are confirmed by calculations based on the theoretical analysis given in a previous work of the authors.

  2. Accelerated aging of 28 Gb s?1 850 nm vertical-cavity surface-emitting laser with multiple thick oxide apertures

    NASA Astrophysics Data System (ADS)

    Kropp, J. R.; Steinle, G.; Schfer, G.; Shchukin, V. A.; Ledentsov, N. N.; Turkiewicz, J. P.; Zoldak, M.

    2015-04-01

    850 nm vertical-cavity surface-emitting lasers with multiple thick oxide apertures suitable for temperature-insensitive error free transmission at 28 Gb s?1 are subjected to accelerated aging at high current densities and chip temperatures. The devices withstand a 20% power change test at a high current density (18 kA c{{m}-2}) at an ambient temperature of 120 {}^\\circ C for 2500 h. At 9095 {}^\\circ C at this current density no degradation was observed up to 5000 h. We performed the studies at further elevated current densities and temperatures and define the acceleration factor as AF={{({{J}stress}/{{J}use})}8}exp [(1.3 eV/{{k}B})(1/{{T}use}-1/{{T}stress})]. The extrapolated lifetime for 20% power drop is estimated as 20 thousand years at 300 K at current density of 18 kA c{{m}-2} which is sufficient for 28 Gb s?1 error-free temperature-insensitive data transmission.

  3. Performance evaluation of a high-sensitivity large-aperture small-animal PET scanner: ClairvivoPET

    Microsoft Academic Search

    Tetsuro Mizuta; Keishi Kitamura; Hiroshi Iwata; Yoshiyuki Yamagishi; Atsushi Ohtani; Kazumi Tanaka; Yoshihiro Inoue

    2008-01-01

    ObjectiveIn this study, we evaluated the performance of a newly commercialized small-animal positron emission tomography (PET) scanner,\\u000a ClairvivoPET, which provides significant advantages in spatial resolution, sensitivity, and quantitative accuracy.\\u000a \\u000a \\u000a \\u000a MethodsThis scanner consists of depth of interaction detector modules with a large axial extent of 151 mm and an external 137Cs source for attenuation correction. Physical performances, resolution, sensitivity, scatter fraction

  4. Goldstone: A Search for Ultra-High Energy Neutrino Interactions in the Moon Using Large-Aperture Radio Antennas

    NSDL National Science Digital Library

    The Goldstone Lunar Ultra-high Energy neutrino experiment (GLUE), a joint project of NASA's Jet Propulsion Lab and UCLA, searches for 10ns microwave pulses from a lunar regolith (meteor ejecta believed to have struck the moon) using two large telescopes. Visitors to this Website can download a detailed, scientific description of the experiment entitled "New Limits on a Diffuse Flux of > 100 EeV Cosmic Neutrinos" (.pdf or .ps), read abstracts and download data (.ps, .pdf, .dvi, HTML), and follow links to photo galleries of experiments in action. Interesting!

  5. Lasers for coherent optical satellite links with large dynamics.

    PubMed

    Chiodo, Nicola; Djerroud, Khelifa; Acef, Ouali; Clairon, Andr; Wolf, Peter

    2013-10-20

    We present the experimental realization of a laser system for ground-to-satellite optical Doppler ranging at the atmospheric turbulence limit. Such a system needs to display good frequency stability (a few parts in 10-14) while allowing large and well-controlled frequency sweeps of 12??GHz at rates exceeding 100??MHz/s. Furthermore it needs to be sufficiently compact and robust for transportation to different astronomical observation sites, where it is to be interfaced with satellite ranging telescopes. We demonstrate that our system fulfills those requirements and should therefore allow operation of ground to low Earth orbit satellite coherent optical links limited only by atmospheric turbulence. PMID:24216589

  6. Functional derivatives applied to error propagation of uncertainties in topography to large-aperture scintillometer-derived heat fluxes

    NASA Astrophysics Data System (ADS)

    Gruber, M. A.; Fochesatto, G. J.; Hartogensis, O. K.; Lysy, M.

    2014-07-01

    Scintillometer measurements allow for estimations of the refractive index structure parameter Cn2 over large areas in the atmospheric surface layer. Turbulent fluxes of heat and momentum are inferred through coupled sets of equations derived from the Monin-Obukhov similarity hypothesis. One-dimensional sensitivity functions have been produced that relate the sensitivity of heat fluxes to uncertainties in single values of beam height over flat terrain. However, real field sites include variable topography. We develop here, using functional derivatives, the first analysis of the sensitivity of scintillometer-derived sensible heat fluxes to uncertainties in spatially distributed topographic measurements. Sensitivity is shown to be concentrated in areas near the center of the beam path and where the underlying topography is closest to the beam height. Relative uncertainty contributions to the sensible heat flux from uncertainties in topography can reach 20% of the heat flux in some cases. Uncertainty may be greatly reduced by focusing accurate topographic measurements in these specific areas. A new two-dimensional variable terrain sensitivity function is developed for quantitative error analysis. This function is compared with the previous one-dimensional sensitivity function for the same measurement strategy over flat terrain. Additionally, a new method of solution to the set of coupled equations is produced that eliminates computational error.

  7. Stability design considerations for mirror support systems in ICF lasers

    SciTech Connect

    Tietbohl, G.L.; Sommer, S.C.

    1996-10-01

    Some of the major components of laser systems used for Inertial Confinement Fusion (ICF) are the large aperture mirrors which direct the path of the laser. These mirrors are typically supported by systems which consist of mirror mounts, mirror enclosures, superstructures, and foundations. Stability design considerations for the support systems of large aperture mirrors have been developed based on the experience of designing and evaluating similar systems at the Lawrence Livermore National Laboratory (LLNL). Examples of the systems developed at LLNL include Nova, the Petawatt laser, Beamlet, and the National Ignition Facility (NIF). The structural design of support systems of large aperture mirrors has typically been controlled by stability considerations in order for the large laser system to meet its performance requirements for alignment and positioning. This paper will discuss the influence of stability considerations and will provide guidance on the structural design and evaluation of mirror support systems in ICF lasers so that this information can be used on similar systems.

  8. The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) 2005: A 4 sq. deg Galactic Plane Survey in Vulpecula (l=59)

    E-print Network

    E. L. Chapin; P. A. R. Ade; J. J. Bock; C. Brunt; M. J. Devlin; S. Dicker; M. Griffin; J. O. Gundersen; M. Halpern; P. C. Hargrave; D. H. Hughes; J. Klein; G. Marsden; P. G. Martin; P. Mauskopf; C. B. Netterfield; L. Olmi; E. Pascale; G. Patanchon; M. Rex; D. Scott; C. Semisch; M. D. P. Truch; C. Tucker; G. S. Tucker; M. P. Viero; D. V. Wiebe

    2007-11-21

    We present the first results from a new 250, 350, and 500 micron Galactic Plane survey taken with the Balloon-borne Large-Aperture Submillimeter Telescope (BLAST) in 2005. This survey's primary goal is to identify and characterize high-mass proto-stellar objects (HMPOs). The region studied here covers 4 sq. deg near the open cluster NGC 6823 in the constellation Vulpecula (l=59). We find 60 compact sources (0) velocities combined with a variety of other velocity and morphological data in the literature. In total, 49 sources are associated with a molecular cloud complex encompassing NGC 6823 (distance ~2.3kpc), 10 objects with the Perseus Arm (~8.5kpc) and one object is probably in the outer Galaxy (~14kpc). Near NGC 6823, the inferred luminosities and masses of BLAST sources span ~40-10^4 L_\\odot, and ~15-700 M_\\odot, respectively. The mass spectrum is compatible with molecular gas masses in other high-mass star forming regions. Several luminous sources appear to be Ultra Compact HII regions powered by early B stars. However, many of the objects are cool, massive gravitationally-bound clumps with no obvious internal radiation from a protostar, and hence excellent HMPO candidates.

  9. Control and data management for a large fusion laser

    Microsoft Academic Search

    J. W. Davis; F. W. Holloway

    1975-01-01

    SHIVA is a powerful (10-kJ 25 TW) neodymium glass laser system to be ; used (in 1977) for target irradiation in fusion research. SHIVA is also a ; development project in that it is pushing the state of the art in laser and ; optical technology. The present design calls for 20 parallel laser amplification ; chains whose light output

  10. High-power coupled large-cavity lasers and multiactive light-emitting diodes

    Microsoft Academic Search

    Guangdi Shen; Peng Lian; Xia Guo; Guohong Wang; Bifeng Cui; Tao Yin; Jianjun Li; Jinyu Du; Guo Gao; Deshu Zou

    2001-01-01

    For increasing laser diode (LD) output power, improving laser beam quality and enhancing the light emitting diode (LED) brightness, the coupled large optical cavity semiconductor lasers and multi-active LEDs with tunneling- regenerated current transport have been presented and experimented. Both the external and differential quantum efficiency and both the LD's output power and LED's brightness are together increasing approximately with

  11. Processing and Application of ICESat Large Footprint Full Waveform Laser Range Data

    Microsoft Academic Search

    V. H. Duong

    2010-01-01

    In the last two decades, laser scanning systems made the transition from scientific research to the commercial market. Laser scanning has a large variety of applications such as digital elevation models, forest inventory and man-made object reconstruction, and became the most required input data for flood plain and hydraulic models. This system is generally called as a discrete laser scanning

  12. Anomalous lasing of high-speed 850?nm InGaAlAs oxide-confined vertical-cavity surface-emitting lasers with a large negative gain-to-cavity wavelength detuning

    SciTech Connect

    Blokhin, S. A., E-mail: blokh@mail.ioffe.ru; Bobrov, M. A.; Maleev, N. A.; Sakharov, A. V.; Ustinov, V. M. [A. F. Ioffe Physical-Technical Institute of the Russian Academy of Sciences, 26 Polytekhnicheskaya Street, Saint Petersburg 194021 (Russian Federation); Kuzmenkov, A. G. [Submicron Heterostructures for Microelectronics, Research and Engineering Center of the Russian Academy of Sciences, 26 Polytekhnicheskaya Street, Saint Petersburg 194021 (Russian Federation); A. F. Ioffe Physical-Technical Institute of the Russian Academy of Sciences, 26 Polytekhnicheskaya Street, Saint Petersburg 194021 (Russian Federation); Blokhin, A. A. [Saint Petersburg State Polytechnical University, 29 Polytekhnicheskaya Street, Saint Petersburg 195251 (Russian Federation); Moser, P.; Lott, J. A. [Zentrum fr Nanophotonik, Technische Universitt Berlin, Hardenbergstrasse 36, Berlin 10623, Federal Republic of Germany (Germany); Bimberg, D. [Zentrum fr Nanophotonik, Technische Universitt Berlin, Hardenbergstrasse 36, Berlin 10623, Federal Republic of Germany (Germany); Electric and Computer Engineering Department, King Abdul-Aziz University, Jeddah 21589 (Saudi Arabia)

    2014-08-11

    The impact of a large negative quantum well gain-to-cavity etalon wavelength detuning on the static and dynamic characteristics of 850?nm InGaAlAs high-speed oxide-confined vertical-cavity surface-emitting lasers (VCSELs) was investigated. Three distinct lasing regimes were revealed in large square aperture (?7??m per side) devices with large detuning including: (1) an anomalous lasing via higher order HermiteGaussian modes at low forward bias current; (2) lasing via the lowest order HermiteGaussian modes at high bias current; and (3) simultaneous lasing via both types of transverse modes at intermediate bias currents. In contrast to conventional multimode VCSELs a two-resonance modulation response was observed for the case of co-lasing via multiple transverse modes with high spectral separation. The reduction in the oxide aperture area resulted in classical lasing via the lowest order modes with a conventional single-resonance frequency response.

  13. Performance of a simplified slit spatial filter for large laser systems.

    PubMed

    Xiong, Han; Yuan, Xiao; Zhang, Xiang; Zou, Kuaisheng

    2014-09-01

    A new-type slit spatial filter system with three lenses was proposed, in which the focal spot was turned into focal line by adding cylindrical lenses to increase focal area and then lower the focal intensity. Its performances on image relay, aperture matching and spatial filtering are comprehended by detailed theoretical calculations and numerical simulation. According to transmission spatial filter in national ignition facility, we present a replaceable slit spatial filter, which can reduce the overall length of laser system, improve the beam quality and suppress or even avoid the pinhole (slit) closure in the spatial filter. PMID:25321597

  14. Large area avalanche photodiode detector array upgrade for a ruby-laser Thomson scattering system

    E-print Network

    Biewer, Theodore

    Large area avalanche photodiode detector array upgrade for a ruby-laser Thomson scattering system T microchannel plate MCP detector was replaced with an array of modular large area avalanche photodiode detectors-laser head, collection optics, a Jarrell-Ash MonoSpec-27 Model 82-499 spectrometer, and avalanche photodiode

  15. Solar Central Receiver with an Irising Aperture

    E-print Network

    Galal, T.; Kulaib, A. M.; Abuzaid, M.

    2010-01-01

    . If the aperture is small, it will be inefficient for periods when the solar isolation is inclined due to spillage. However, if the aperture is large, it will be inefficient for periods when the solar isolation is normal, due to excess heat radiation and convection...

  16. Aperture undersampling using compressive sensing for synthetic aperture stripmap imaging

    NASA Astrophysics Data System (ADS)

    Leier, Stefan; Zoubir, Abdelhak M.

    2014-12-01

    Synthetic aperture imaging is a high-resolution imaging technique employed in radar and sonar applications, which construct a large aperture by constantly transmitting pulses while moving along a scene of interest. In order to avoid azimuth image ambiguities, spatial sampling requirements have to be fulfilled along the aperture trajectory. The latter, however, limits the maximum speed and, therefore, the coverage rate of the imaging system. This paper addresses the emerging field of compressive sensing for stripmap synthetic aperture imaging using transceiver as well as single-transmitter and multi-receiver systems so as to overcome the spatial Nyquist criterion. As a consequence, future imaging systems will be able to significantly reduce their mission time due to an increase in coverage rate. We demonstrate the capability of our proposed compressive sensing approach to at least double the maximum sensor speed based on synthetic data and real data examples. Simultaneously, azimuth image ambiguities are successfully suppressed. The real acoustical measurements are obtained by a small-scale ultrasonic synthetic aperture laboratory system.

  17. Laser-cooling Brings Large Object Near Absolute Zero

    NSDL National Science Digital Library

    Trafton, Anne

    This page showcases research conducted at Massachusetts Institute of Technology on the laser-cooling of macroscopic materials, in order to observe quantum effects. The material--a dime-sized mirror--was suspended with laser beams and cooled to temperatures near 0.8 degrees Kelvin. The site also provides images of the experimental apparatus and the researchers.

  18. Ultrafast Large Area Micropattern Generation in Non-absorbing Polymer Thin-Films by Pulsed Laser Diffraction

    E-print Network

    Ankur Verma; Ashutosh Sharma; Giridhar U. Kulkarni

    2011-01-27

    We report an ultrafast, parallel and beyond-the-master micro-patterning technique for ultrathin (30 nm-400 nm) non-absorbing polymer films by diffraction of a laser light through a two dimensional periodic aperture. The redistribution of laser energy absorbed by the substrate causes self-organization of polymer thin-film in the form of wrinkle like surface relief structures caused by localized melting and freezing of the thin-film. Unlike the conventional laser ablation and laser writing processes, low laser fluence is employed to only passively swell the polymer as a pre-ablative process without the loss of material, and without absorption/reaction with the incident radiation. Self-organization in the thin polymer film aided by the diffraction pattern produces micro-structures made up of thin raised lines. These regular microstructures have far more complex morphologies than the mask geometry and very narrow line widths that can be an order of magnitude smaller than the openings in the mask. The microstructure morphology is easily modulated by changing the film thickness, aperture size and geometry and by changing the diffraction pattern, e.g., by changing the aperture-substrate distance.

  19. PAPER 2004-230 Investigating Fracture Aperture Distributions

    E-print Network

    Schechter, David S.

    to correction. ABSTRACT Fracture aperture is usually estimated by cubic law, which assumes flow between two developed a calibration curve based on existing calibration techniques, which involves area integration at large apertures with a long tail in the small apertures4 . This brought many researchers to think about

  20. Modelling of a reflective waveplate for high-power lasers

    NASA Astrophysics Data System (ADS)

    Heathcote, Robert I.; Buck, Samuel; Clarke, Robert J.; Green, James S.

    2014-09-01

    The polarization state of a laser has a huge bearing on the physics of laser-plasma interactions and it is often desirable to change between linear and circular. For short pulse high power lasers large beam apertures are necessary for transportation. However, in these extreme conditions transmissive birefringent polarization optics become impractical due to their delicacy and their dispersion of the laser bandwidth which will increase the pulse length, which along with large B-integrals, which arises from the transmission of the high-power beams through optics, can be detrimental to the intensity of the laser. It is therefore necessary to consider reflective optics in order to change the polarization. Modelling has been performed at the Central Laser Facility on a design of a large aperture broadband reflective waveplate suitable for short pulse laser systems.

  1. Continuous Earth Rotation Monitoring with the large Ring Laser G

    NASA Astrophysics Data System (ADS)

    Schreiber, Ulrich; Holdaway, John; Gebauer, Andr; Kluegel, Thomas; Wells, Jon-Paul

    2010-05-01

    Over the last decade, ring lasers have found their way back into the research laboratories. By scaling them up in size, they have gained several orders of magnitude over their commercial counterparts, both in sensitivity and stability. Unlike the established space geodetic techniques SLR/LLR and VLBI, ring lasers can be operated autonomous and continuously. While a single ring laser component already provides direct access to the instantaneous axis of rotation of the Earth, it is also susceptible to local perturbations both with respect to platform rotation and instrumental tilt caused by local wind load for example. These instrumental coupling issues are addressed in more detail in a separate paper (Gebauer et al.) in this conference. Currently the laser gyro G at the Geodetic Observatory Wettzell (Germany) can resolve rotation rates as small as 1 pico-rad/s requiring an integration time of less than 2 hours. This opens the door for the research of high frequency variations in Earth rotation. Over the last year we have improved the ring laser technology by as much as a factor of 3 in sensitivity, which makes the domain of ?Omega/Omega ? 10e-9 of Earth rotation accessible to a local rotation sensor. Currently it appears that the micro-seismic background activity of the Earth causes the major part from the observed deviation of the sensor performance with respect to the computed shot noise limit. Recent efforts concentrated on the improvement of the sensor stability against drift effects caused by the aging of the laser gas, scale factor instabilities induced by atmospheric pressure variations and the corresponding temperature changes from adiabatic expansion and compression of the local air around the instrument. Over the last year have introduced a pressure stabilizing vessel enclosing the entire ring laser structure. By monitoring the optical frequency in the ring laser cavity continuously and stabilizing the scale factor in a closed loop system, it became possible to extend the range of sensor stability from the short term (1-3 days) to at least well into the mid-term regime (>40 days) and possible even well beyond that. Once a sufficiently long time-series from ring laser data has become available, we will be able to define the range of temporal stability in more detail. The extension of the regime of stability gives access to geophysical signals at frequencies substantially lower than previously observable with ring lasers. This talk outlines this recent progress in Sagnac interferometry and presents the new data.

  2. Study of laser-induced damage to large core silica fiber by Nd:YAG and Alexandrite lasers

    NASA Astrophysics Data System (ADS)

    Sun, Xiaoguang; Li, Jie; Hokansson, Adam; Whelan, Dan; Clancy, Michael

    2009-02-01

    As a continuation of our earlier study at 2.1 ?m wavelength, we have investigated the laser damage to several types of step-index, large core (1500 ?m) silica fibers at two new wavelengths by high power long pulsed Nd:YAG (1064 nm) and Alexandrite (755 nm) lasers. It was observed that fibers with different designs showed a significant difference in performance at these wavelengths. We will also report a correlation of damage to the fibers between the two laser wavelengths. The performance analyses of different fiber types under the given test conditions will enable optimization of fiber design for specific applications.

  3. Active compensation of large dispersion of femtosecond pulses for precision laser ranging.

    PubMed

    Lee, Sang-Hyun; Lee, Joohyung; Kim, Young-Jin; Lee, Keunwoo; Kim, Seung-Woo

    2011-02-28

    We describe an active way of compensation for large dispersion induced in the femtosecond light pulses travelling in air for laser ranging. The pulse duration is consistently regulated at 250 fs by dispersion control, allowing sub-micrometer resolution in measuring long distances by means of time-of-flight measurement. This method could facilitate more reliable applications of femtosecond pulses for satellite laser ranging, laser altimetry and active LIDAR applications. PMID:21369227

  4. 80-W green KTP laser used in photoselective laser vaporization of the prostrate by frequency doubling of Yb 3+ -doped large-mode area fiber laser

    NASA Astrophysics Data System (ADS)

    Xia, Hongxing; Li, Zhengjia

    2007-05-01

    Photoselective laser vaporization of the prostate (PVP) is the most promising method for the treatment of benign prostatic hyperplasia (BPH), but KTP lasers used in PVP with lamp-pumped are low efficient .To increase the efficiency , we develop a 80-W, 400kHz, linearly polarized green laser based on a frequency-doubled fiber laser. A polarization-maintaining large-mode area (LMA) fiber amplifier generate polarized 1064nm fundamental wave by amplifying the seed signal from a composite Cr 4+:YAG-Nd 3+:YAG crystal fiber laser. The fundamental wave is injected into a KTP crystal with confined temperature management to achieve second harmonic generation (SHG). The overall electrical efficiency to the green portion of the spectrum is 10%.80-W maintenance-free long-lifetime KTP laser obtained can well satisfy the need of PVP.

  5. Large area laser surface micro/nanopatterning by contact microsphere lens arrays

    NASA Astrophysics Data System (ADS)

    Sedao, X.; Derrien, T. J.-Y.; Romer, G. R. B. E.; Pathiraj, B.; Huis in `t Veld, A. J.

    2013-06-01

    Laser surface micro/nanopatterning by particle lens arrays is a well-known technique. Enhanced optical fields can be achieved on a substrate when a laser beam passes through a self-assembled monolayer of silica microspheres placed on the substrate. This enhanced optical field is responsible for ablative material removal from the substrate resulting in a patterned surface. Because of the laser ablation, the microspheres are often ejected from the substrate during laser irradiation. This is a major issue impeding this technique to be used for large area texturing. We explored the possibility to retain the spheres on the substrate surface during laser irradiation. A picosecond laser system (wavelength of 515 nm, pulse duration 6.7 ps, repetition rate 400 kHz) was employed to write patterns through the lens array on a silicon substrate. In this experimental study, the pulse energy was found to be a key factor to realize surface patterning and retain the spheres during the process. When the laser pulse energy is set within the process window, the microspheres stay on the substrate during and after laser irradiation. Periodic patterns of nanoholes can be textured on the substrate surface. The spacing between the nanoholes is determined by the diameter of the microspheres. The depth of the nanoholes varies, depending on the number of laser pulses applied and pulse energy. Large area texturing can be made using overlapping pulses obtained through laser beam scanning.

  6. Overview of recent advances in excimer laser technology at Los Alamos

    SciTech Connect

    Bigio, I.J.; Sze, R.C.; Taylor, A.J.; Gibson, R.B.

    1988-01-01

    From among the areas of excimer laser development at Los Alamos two are selected for further discussion: ultra-high brightness excimer laser systems and discharge-pumped XeF(C..-->..A) lasers operating in the blue-green portion of the spectrum. Two different high brightness systems are described. One is based on small-aperture KrF amplifiers, while the other is based on a large-aperture XeCl amplifier. The XeF(C..-->..A) laser is tunable from 435 to 525 nm, and may one day become a viable alternative to pulsed dye lasers for many applications. 14 refs., 4 figs.

  7. FUNDAMENTAL STUDIES OF IGNITION PROCESSES IN LARGE NATURAL GAS ENGINES USING LASER SPARK IGNITION

    Microsoft Academic Search

    Azer Yalin; Morgan Defoort; Bryan Willson

    2005-01-01

    The current report details project progress made during the first quarterly reporting period of the DOE sponsored project ''Fundamental studies of ignition processes in large natural gas engines using laser spark ignition''. The goal of the overall research effort is to develop a laser ignition system for natural gas engines, with a particular focus on using fiber optic delivery methods.

  8. The laser interferometer system for the large optics diamond turning machine

    SciTech Connect

    Baird, E D; Donaldson, R R; Patterson, S R

    1999-06-29

    The purpose of this report is to describe the Laser Interferometer System designed for the Large Optics Diamond Turning Machine (LODTM). To better understand the laser interferometer system, it is useful to begin with an overview of the LODTM metrology system.

  9. Tracking Hands Above Large Interactive Surfaces with a Low-Cost Scanning Laser Rangefinder

    E-print Network

    used in 3D object scanning. Continuous-wave (CW) phase-measuring systems, often used in robot collisionTracking Hands Above Large Interactive Surfaces with a Low-Cost Scanning Laser Rangefinder Joshua an inexpensive scanning laser rangefinder to measure the real-time position of bare hands in a 2-D plane up

  10. Application of laser velocimetry to unsteady flows in large scale high speed tunnels

    NASA Technical Reports Server (NTRS)

    Owen, F. K.

    1983-01-01

    Flowfield measurements obtained in several large scale, high speed facilities are presented. Sampling bias and seeding problems are addressed and solutions are outlined. The laser velocimeter systems and data reduction procedures which were used in the experiments are also described. The work demonstrated the potential of the laser velocimeter for applications in other than closely controlled, smallscale laboratory situations.

  11. Laser safety training programs for a large and diverse research and development laboratory

    NASA Astrophysics Data System (ADS)

    Stocum, W. E.

    Sandia National Laboratories is a large multiprogram Research and Development laboratory which is operated by a contractor for the US Department of Energy. In the Laboratories, lasers are both the subject of research and the tools that are used in other research, development, and testing activities. Since 1979, laser safety training has been the primary focus of the Laboratories' laser safety program. Approximately 1100 personnel have been trained in formal courses during that time period. The formal course, presented on site by a contractor, consists of two full days of instruction. The course contents include the following topics: Laser technology and safety overview; Federal and ANSI laser standards summaries; Biological effects of laser radiation; Classification of lasers; Laser hazard analysis; Review of ANSI Z136.1 control measures; Laser eye protection. Recent emphasis on regulatory requirements, conduct of operations, and quality management has revealed a need to change the laser safety training curriculum. A new course for users of low power lasers (Class 2 and 3a) is being developed. A refresher course, a management awareness (self-study) course, and major changes in the current course are planned.

  12. Large-aperture fast multilevel Fresnel zone lenses in glass and ultrathin polymer films for visible and near-infrared imaging applications.

    PubMed

    Britten, Jerald A; Dixit, Shamusundar N; DeBruyckere, Michael; Steadfast, Daniel; Hackett, James; Farmer, Brandon; Poe, Garrett; Patrick, Brian; Atcheson, Paul D; Domber, Jeanette L; Seltzer, Aaron

    2014-04-10

    The ability to fabricate 4-level diffractive structures with 1 m critical dimensions has been demonstrated for the creation of fast (?f/3.1 at 633 nm) Fresnel zone lenses (FZLs) with >60% diffraction efficiency into the -1 focusing order and nearly complete suppression of 0 and +1 orders. This is done using tooling capable of producing optics with 800 mm apertures. A 4-level grating fabricated in glass at 300 mm aperture is shown to have <15??nm rms holographic phase error. Glass FZLs have also been used as mandrels for casting zero-thermal-expansion, 20 m thick polymer films created with the 4-level structure as a route to mass replication of efficient diffractive membranes for ultralight segmented space-based telescope applications. PMID:24787399

  13. Time-dependent land uplift and subsidence in the Santa Clara valley, California, from a large interferometric synthetic aperture radar data set

    Microsoft Academic Search

    David A. Schmidt; Roland Brgmann

    2003-01-01

    We invert 115 differential interferograms derived from 47 synthetic aperture radar (SAR) scenes for a time-dependent deformation signal in the Santa Clara valley, California. The time-dependent deformation is calculated by performing a linear inversion that solves for the incremental range change between SAR scene acquisitions. A nonlinear range change signal is extracted from the ERS InSAR data without imposing a

  14. Exciplex laser spatial coherence and its impact on fibre Bragg grating writing in large diameter fibres

    Microsoft Academic Search

    Nathaniel Groothoff; John Canning

    2006-01-01

    The spatial coherence of an ArF exciplex (excimer) laser has been investigated by writing fibre Bragg gratings in photosensitive boron-codoped germanosilicate fibre to analyse the effect of limited spatial coherence on large diameter fibres.

  15. Large scale laser radar for measuring aerosol distribution over a wide area

    Microsoft Academic Search

    Hiroshi Shimizu; Yasuhiro Sasano; Hideaki Nakane; Nobuo Sugimoto; Ichiro Matsui; Nobuo Takeuchi

    1985-01-01

    A large scale laser radar was constructed to measure aerosol distribution over a wide area. It is composed of a high-power YAG laser with an average output energy of 30 W at 1.064 microns and 10 W at 532 nm, a 25-pps repetition rate, and a large (effective diameter 1.5 m) receiving telescope. Three problems which degrade the accuracy of

  16. A smart car for the surface shape measurement of large antenna based on laser tracker

    NASA Astrophysics Data System (ADS)

    Gu, Yonggang; Hu, Jing; Jin, Yi; Zhai, Chao

    2012-09-01

    The geometric accuracy of the surface shape of large antenna is an important indicator of antennas quality. Currently, high-precision measurement of large antenna surface shape can be performed in two ways: photogrammetry and laser tracker. Photogrammetry is a rapid method, but its accuracy is not enough good. Laser tracker can achieve high precision, but it is very inconvenient to move the reflector (target mirror) on the surface of the antenna by hand during the measurement. So, a smart car is designed to carry the reflector in this paper. The car, controlled by wireless, has a small weight and a strong ability for climbing, and there is a holding bracket gripping the reflector and controlling reflector rise up and drop down on the car. During the measurement of laser tracker, the laser beam between laser tracker and the reflector must not be interrupted, so two high-precision three-dimensional miniature electronic compasses, which can real-time monitor the relative angle between the holding bracket and the laser trackers head, are both equipped on the car and the head of laser tracker to achieve automatic alignment between reflector and laser beam. With the aid of the smart car, the measurement of laser tracker has the advantages of high precision and rapidity.

  17. Micro-scanning mirrors for high-power laser applications in laser surgery

    NASA Astrophysics Data System (ADS)

    Sandner, Thilo; Kimme, Simon; Grasshoff, Thomas; Todt, Ulrich; Graf, Alexander; Tulea, Cristian; Lenenbach, Achim; Schenk, Harald

    2014-03-01

    We present two novel micro scanning mirrors with large aperture and HR dielectric coatings suitable for high power laser applications in a miniaturized laser-surgical instrument for neurosurgery to cut skull tissue. An electrostatic driven 2D-raster scanning mirror with 5x7.1mm aperture is used for dynamic steering of a ps-laser beam of the laser cutting process. A second magnetic 2D-beam steering mirror enables a static beam correction of a hand guided laser instrument. Optimizations of a magnetic gimbal micro mirror with 6 mm x 8 mm mirror plate are presented; here static deflections of 3 were reached. Both MEMS devices were successfully tested with a high power ps-laser at 532nm up to 20W average laser power.

  18. Controlling synchronization in large laser networks using number theory

    E-print Network

    Micha Nixon; Moti Fridman; Eitan Ronen; Asher A. Friesem; Nir Davidson; Ido Kanter

    2011-12-18

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

  19. Laser velocimeter measurements in a large transonic wind tunnel

    NASA Technical Reports Server (NTRS)

    Meyers, J. F.; Couch, L. M.; Feller, W. V.; Walsh, M. J.

    1976-01-01

    A two-component fringe type laser velocimeter operated in the backscatter mode was used to measure the free-stream velocity in an undisturbed flow field in a wind-tunnel test section from Mach 0.2 to Mach 1.0 and to measure the velocity along the stagnating streamline of a hemisphere model from Mach 0.2 to Mach 0.8. Burst signals from the laser velocimeter were processed by high-speed burst counters, and histograms of the number of occurrences of a particular counter output were collected by means of a pulse height analyzer. Arithmetic means of the histograms were calculated, and the results were compared with predicted local gas velocities with allowance for the lag of the scattering particles with respect to the gas flow. The free-stream measurements were accurate to within 2% of the calibration measurements. The stagnation streamline measurements show trends similar to theoretical predictions.

  20. A laser velocimeter system for large-scale aerodynamic testing

    NASA Technical Reports Server (NTRS)

    Reinath, M. S.; Orloff, K. L.; Snyder, P. K.

    1984-01-01

    A unique laser velocimeter was developed that is capable of sensing two orthogonal velocity components from a variable remote distance of 2.6 to 10 m for use in the 40- by 80-Foot and 80- by 120-Foot Wind Tunnels and the Outdoor Aerodynamic Research Facility at Ames Research Center. The system hardware, positioning instrumentation, and data acquisition equipment are described in detail; system capabilities and limitations are discussed; and expressions for systematic and statistical accuracy are developed. Direct and coupled laboratory measurements taken with the system are compared with measurements taken with a laser velocimeter of higher spatial resolution, and sample data taken in the open circuit exhaust flow of a 1/50-scale model of the 80- by 120-Foot Wind Tunnel are presented.

  1. Laser Plasma Particle Accelerators: Large Fields for Smaller Facility Sources

    SciTech Connect

    Geddes, Cameron G.R.; Cormier-Michel, Estelle; Esarey, Eric H.; Schroeder, Carl B.; Vay, Jean-Luc; Leemans, Wim P.; Bruhwiler, David L.; Cary, John R.; Cowan, Ben; Durant, Marc; Hamill, Paul; Messmer, Peter; Mullowney, Paul; Nieter, Chet; Paul, Kevin; Shasharina, Svetlana; Veitzer, Seth; Weber, Gunther; Rubel, Oliver; Ushizima, Daniela; Bethel, Wes; Wu, John

    2009-03-20

    Compared to conventional particle accelerators, plasmas can sustain accelerating fields that are thousands of times higher. To exploit this ability, massively parallel SciDAC particle simulations provide physical insight into the development of next-generation accelerators that use laser-driven plasma waves. These plasma-based accelerators offer a path to more compact, ultra-fast particle and radiation sources for probing the subatomic world, for studying new materials and new technologies, and for medical applications.

  2. Stable discharges in an HF laser with large electrode seperation

    Microsoft Academic Search

    P. D. SLADE; A. Serafetinides

    1978-01-01

    The characteristics of a fast discharge HF chemical laser are described. A Blumlein pulse forming line is used with a resistive cathode (50 ? . cm resistivity germanium). Uniform arc-free discharges have been obtained in gas mixtures of SF6\\/H2\\/Ar, SF6\\/C2H6\\/Ar, and SF6\\/C3H8\\/Ar with electrode separations up to 5.2 cm.

  3. Large ring laser gyroscopes: towards absolute rotation rate sensing

    NASA Astrophysics Data System (ADS)

    Hurst, Robert B.; Rabeendran, Nishanthan; Wells, Jon-Paul R.; Schreiber, K. Ulrich

    2015-01-01

    Ring laser gyroscopes have increased in sensitivity by six orders of magnitude over the last several decades such that they are poised to make valuable contributions to geodesy and terrestrial tests of general relativity. To fully exploit their capabilities, residual (time varying) read out errors arising from backscatter coupling must be physically minimized or otherwise compensated. We present the results of a backscatter correction process for a 12.25 m2 gyroscope with a vast improvement in long term rotational sensitivity.

  4. Comparison of laser-induced surface damage density measurements with small and large beams: toward representativeness

    SciTech Connect

    Lamaignere, Laurent; Dupuy, Gabriel; Donval, Thierry; Grua, Pierre; Bercegol, Herve

    2011-02-01

    Pulsed laser damage density measurements obtained with diverse facilities are difficult to compare, due to the interplay of numerous parameters, such as beam area and pulse geometry, which, in operational large beam conditions, are very different from laboratory measurements. This discrepancy could have a significant impact; if so, one could not even pretend that laser damage density control is a real measurement process. In this paper, this concern is addressed. Tests with large beams of centimeter size on a high-power laser facility have beam performed according to a parametric study and are compared to small beam laboratory tests. It is shown that laser damage densities obtained with large and small beams are equal, within calculated error bars.

  5. Heat assisted magnetic recording (HAMR) with nano-aperture VCSELs for 10 Tb/in2 magnetic storage density

    NASA Astrophysics Data System (ADS)

    Hussain, Sajid; Kundu, Shreya; Bhatia, C. S.; Yang, Hyunsoo; Danner, Aaron J.

    2013-03-01

    We have conducted a thorough experimental analysis of nano-aperture VCSELs for use in heat-assisted magnetic recording (HAMR). To the best of our knowledge, this is the first study to both explore the impact of magnetic media proximity on VCSEL aperture power throughput and to use statistical methods to simultaneously characterize thousands of aperture designs. To achieve areal recording densities beyond 1 Tb/in2, high anisotropy magnetic materials are required to overcome the super-paramagnetic effect. These require high switching fields which are not conventionally available. Heat assisted magnetic recording (HAMR) is a potential technology to reduce the coercivity of the media and thus the required switching field by localized heating to enable writing of bits. The challenges being faced by this technology are to develop a precise method of delivering light to a very small, sub wavelength bit area with sufficient power through a near field aperture, and the fabrication of a laser source which can be integrated with current write heads used in hard disk drives. The focus of our work is to characterize nano-aperture VCSELs and test their potential application to HAMR. We have fabricated 850 nm VCSELs with large arrays of differently shaped nano-apertures in the gold layer on top of each VCSEL. The focusing and transmission characteristics of differently shaped nano-apertures are compared by simulations and experiments. C-shaped and H-shaped nano-apertures have also been fabricated in a gold layer deposited on a SiO2 substrate to observe the effect of close proximity of magnetic media (FePt) on the performance of nano-apertures, and polarization effects have also been characterized.

  6. Variable-aperture screen

    DOEpatents

    Savage, George M. (Richmond, CA)

    1991-01-01

    Apparatus for separating material into first and second portions according to size including a plurality of shafts, a plurality of spaced disks radiating outwardly from each of the shafts to define apertures and linkage interconnecting the shafts for moving the shafts toward or away from one another to vary the size of the apertures while the apparatus is performing the separating function.

  7. Compressed Synthetic Aperture Radar

    Microsoft Academic Search

    Vishal M. Patel; Glenn R. Easley; Dennis M. Healy; Jr.

    2010-01-01

    In this paper, we introduce a new synthetic aperture radar (SAR) imaging modality which can provide a high-resolution map of the spatial distribution of targets and terrain using a significantly reduced number of needed transmitted and\\/or received electromagnetic waveforms. This new imaging scheme, requires no new hardware components and allows the aperture to be compressed. It also presents many new

  8. Rotating Aperture System

    DOEpatents

    Rusnak, Brian (Livermore, CA); Hall, James M. (Livermore, CA); Shen, Stewart (Danville, CA); Wood, Richard L. (Santa Fe, NM)

    2005-01-18

    A rotating aperture system includes a low-pressure vacuum pumping stage with apertures for passage of a deuterium beam. A stator assembly includes holes for passage of the beam. The rotor assembly includes a shaft connected to a deuterium gas cell or a crossflow venturi that has a single aperture on each side that together align with holes every rotation. The rotating apertures are synchronized with the firing of the deuterium beam such that the beam fires through a clear aperture and passes into the Xe gas beam stop. Portions of the rotor are lapped into the stator to improve the sealing surfaces, to prevent rapid escape of the deuterium gas from the gas cell.

  9. The Use of Large Transparent Ceramics in a High Powered, Diode Pumped Solid State Laser

    SciTech Connect

    Yamamoto, R; Bhachu, B; Cutter, K; Fochs, S; Letts, S; Parks, C; Rotter, M; Soules, T

    2007-09-24

    The advent of large transparent ceramics is one of the key enabling technological advances that have shown that the development of very high average power compact solid state lasers is achievable. Large ceramic neodymium doped yttrium aluminum garnet (Nd:YAG) amplifier slabs are used in Lawrence Livermore National Laboratory's (LLNL) Solid State Heat Capacity Laser (SSHCL), which has achieved world record average output powers in excess of 67 kilowatts. We will describe the attributes of using large transparent ceramics, our present system architecture and corresponding performance; as well as describe our near term future plans.

  10. A new route to large area graphene by selective pulsed laser ablation

    Microsoft Academic Search

    A. Roy Barman; S. Dhar; G. Ni; X. Wang; X. Xu; Z. Yi; A. Ariando; B. Oezyilmaz; T. Venkatesan; S. Tripathy

    2010-01-01

    Because of its remarkable electronic properties graphene has a very bright technological future. One of the current challenges is the fabrication of defect free graphene over large areas, a must for device technology. We present a new route for producing a uniform, large area single layer graphene by selectively ablating multilayer graphene by pulsed laser irradiation. An energy density window

  11. Self-similar erbium-doped fiber laser with large normal dispersion

    PubMed Central

    Liu, Hui; Liu, Zhanwei; Lamb, Erin S.; Wise, Frank

    2014-01-01

    We report a large normal dispersion erbium-doped fiber laser with self-similar pulse evolution in the gain fiber. The cavity is stabilized by the local nonlinear attractor in the gain fiber through the use of a narrow filter. Experimental results are accounted for by numerical simulations. This laser produces 3.5 nJ pulses, which can be dechirped to 70 fs with an external grating pair. PMID:24562267

  12. CO2 large-area discharge laser using an unstable-waveguide hybrid resonator

    Microsoft Academic Search

    P. E. Jackson; H. J. Baker; D. R. Hall

    1989-01-01

    A one-dimensional unstable resonator combining free-space and waveguide propagation is used to efficiently extract power from a large-area gain medium in a slab waveguide CO laser. A power of 240 W in a near-diffraction-limited beam has been attained at 12% conversion efficiency from a 38 cm gain length in a compact sealed-off laser head, corresponding to a specific power extraction

  13. CO2 large-area discharge laser using an unstable-waveguide hybrid resonator

    Microsoft Academic Search

    P. E. Jackson; H. J. Baker; D. R. Hall

    1989-01-01

    A one-dimensional unstable resonator combining free-space and waveguide propagation is used to efficiently extract power from a large-area gain medium in a slab waveguide CO2 laser. A power of 240 W in a near-diffraction-limited beam has been attained at 12% conversion efficiency from a 38 cm gain length in a compact sealed-off laser head, corresponding to a specific power extraction

  14. Femtosecond laser-induced asymmetric large scale waves on gold surfaces

    SciTech Connect

    Yong Hwang, Taek; Guo, Chunlei [Institute of Optics, University of Rochester, Rochester, New York 14627 (United States)

    2012-07-09

    With femtosecond (fs) pulse irradiation, we investigate the morphological evolution of a unique type of fs laser-induced periodic surface structure, called nanostructure-covered large scale waves (NC-LSWs), covered by iterating stripe patterns of nanostructures and microstructures with a period of tens of microns. By monitoring the morphological profile of NC-LSWs following fs laser heating of Au, we show that the NC-LSWs are highly asymmetrically formed and propagate on a gold surface. We believe that the selective laser ablation of Au surface and the subsequent mass transfer of liquid Au following nonuniform energy deposition result in the asymmetric NC-LSW propagation on metals.

  15. Distributed aperture synthesis.

    PubMed

    Rabb, David; Jameson, Douglas; Stokes, Andrew; Stafford, Jason

    2010-05-10

    Distributed aperture synthesis is an exciting technique for recovering high-resolution images from an array of small telescopes. Such a system requires optical field values measured at individual apertures to be phased together so that a single, high-resolution image can be synthesized. This paper describes the application of sharpness metrics to the process of phasing multiple coherent imaging systems into a single high-resolution system. Furthermore, this paper will discuss hardware and present the results of simulations and experiments which will illustrate how aperture synthesis is performed. PMID:20588888

  16. Sub-Aperture Interferometers

    NASA Technical Reports Server (NTRS)

    Zhao, Feng

    2010-01-01

    Sub-aperture interferometers -- also called wavefront-split interferometers -- have been developed for simultaneously measuring displacements of multiple targets. The terms "sub-aperture" and "wavefront-split" signify that the original measurement light beam in an interferometer is split into multiple sub-beams derived from non-overlapping portions of the original measurement-beam aperture. Each measurement sub-beam is aimed at a retroreflector mounted on one of the targets. The splitting of the measurement beam is accomplished by use of truncated mirrors and masks, as shown in the example below

  17. Desorption of large organic molecules by laser-induced plasmon excitation

    SciTech Connect

    Lee, I.; Callcott, T.A. (Oak Ridge National Lab., TN (USA) Tennessee Univ., Knoxville, TN (USA). Dept. of Physics and Astronomy); Arakawa, E.T. (Oak Ridge National Lab., TN (USA))

    1991-01-01

    Ejection of large organic molecules from surfaces by laser-induced electronic-excited desorption has attracted considerable interest in recent years. In addition to the importance of this effect for fundamental investigations of the ejection process, this desorption technique has been applied to the study of large, fragile molecules by mass spectrometry. In this paper, we present a new method to induce electronic excitation on the metal surface for the desorption of large organic molecules. 3 refs., 3 figs.

  18. Shock wave absorber having apertured plate

    DOEpatents

    Shin, Y.W.; Wiedermann, A.H.; Ockert, C.E.

    1983-08-26

    The shock or energy absorber disclosed herein utilizes an apertured plate maintained under the normal level of liquid flowing in a piping system and disposed between the normal liquid flow path and a cavity pressurized with a compressible gas. The degree of openness (or porosity) of the plate is between 0.01 and 0.60. The energy level of a shock wave travelling down the piping system thus is dissipated by some of the liquid being jetted through the apertured plate toward the cavity. The cavity is large compared to the quantity of liquid jetted through the apertured plate, so there is little change in its volume. The porosity of the apertured plate influences the percentage of energy absorbed.

  19. Shock wave absorber having apertured plate

    DOEpatents

    Shin, Yong W. (Western Springs, IL); Wiedermann, Arne H. (Chicago Heights, IL); Ockert, Carl E. (Vienna, VA)

    1985-01-01

    The shock or energy absorber disclosed herein utilizes an apertured plate maintained under the normal level of liquid flowing in a piping system and disposed between the normal liquid flow path and a cavity pressurized with a compressible gas. The degree of openness (or porosity) of the plate is between 0.01 and 0.60. The energy level of a shock wave travelling down the piping system thus is dissipated by some of the liquid being jetted through the apertured plate toward the cavity. The cavity is large compared to the quantity of liquid jetted through the apertured plate, so there is little change in its volume. The porosity of the apertured plate influences the percentage of energy absorbed.

  20. Subpicosecond, high-brightness excimer laser systems

    SciTech Connect

    Taylor, A.J.; Gosnell, T.R.; Roberts, J.P.; Lester, C.S.; Gibson, R.B.; Harper, S.E.; Tallman, C.R.

    1988-01-01

    Subpicosecond, high-brightness excimer laser systems are being used to explore the interaction of intense coherent ultraviolet radiation with matter. Applications of current systems include generation of picosecond x-ray pulses, investigation of possible x-ray laser pumping schemes, studies of multiphoton phenomena in atomic species, and time-resolved photochemistry. These systems, based on the amplification of subpicosecond pulses in small aperture (/approximately/1 cm/sup 2/) XeCl or KrF amplifiers, deliver focal spot intensities of /approximately/10/sup 17/ W/cm/sup 2/. Scaling to higher intensities, however, will require an additional large aperture amplifier which preserves near-diffraction-limited beam quality and subpicosecond pulse duration. We describe here both a small aperture KrF system which routinely provides intensities >10/sup 17/ W/cm/sup 2/ to several experiments, and a large aperture XeCl system designed to deliver /approximately/1 J subpicosecond pulses and yield intensities on target in excess of 10/sup 19/W/cm/sup 2/. We also discuss the effects of two-photon absorption on large-aperture, high-brightness excimer lasers. 4 refs., 2 figs.

  1. Variable-aperture screen

    DOEpatents

    Savage, G.M.

    1991-10-29

    Apparatus is described for separating material into first and second portions according to size including a plurality of shafts, a plurality of spaced disks radiating outwardly from each of the shafts to define apertures and linkage interconnecting the shafts for moving the shafts toward or away from one another to vary the size of the apertures while the apparatus is performing the separating function. 10 figures.

  2. LLNL medical and industrial laser isotope separation: large volume, low cost production through advanced laser technologies

    Microsoft Academic Search

    B. Comaskey; K. F. Scheibner; M. Shaw; J. Wilder

    1998-01-01

    The goal of this LDRD project was to demonstrate the technical and economical feasibility of applying laser isotope separation technology to the commercial enrichment (>lkg\\/y) of stable isotopes. A successful demonstration would well position the laboratory to make a credible case for the creation of an ongoing medical and industrial isotope production and development program at LLNL. Such a program

  3. Solar filter for the Mars laser communication demonstration optical receiver

    Microsoft Academic Search

    Brian G. Patrick; Paul Gierow; David Sheikh; W. Tom Roberts

    2004-01-01

    To maximize the cost-effectiveness of the Mars Laser Communication Demonstration (MLCD), the project is pursuing the use of ground-based astronomical telescopes as large-aperture optical receiving antennae. To facilitate communication as the spacecraft approaches solar conjunction, a large membrane filter is being considered to reject approximately 95% of the sun\\

  4. FUNDAMENTAL STUDIES OF IGNITION PROCESSES IN LARGE NATURAL GAS ENGINES USING LASER SPARK IGNITION

    SciTech Connect

    Azer Yalin; Morgan Defoort; Bryan Willson

    2005-01-01

    The current report details project progress made during the first quarterly reporting period of the DOE sponsored project ''Fundamental studies of ignition processes in large natural gas engines using laser spark ignition''. The goal of the overall research effort is to develop a laser ignition system for natural gas engines, with a particular focus on using fiber optic delivery methods. In this report we present our successful demonstration of spark formation using fiber delivery made possible though the use of novel coated hollow fibers. We present results of (high power) experimental characterizations of light propagation using hollow fibers using both a high power research grade laser as well as a more compact laser. Finally, we present initial designs of the system we are developing for future on-engine testing using the hollow fibers.

  5. Investigation of standing wave formation in a human skull for a clinical prototype of a large-aperture, transcranial MR-guided Focused Ultrasound (MRgFUS) phased array: An experimental and simulation study

    PubMed Central

    Song, Junho; Pulkkinen, Aki; Huang, Yuexi; Hynynen, Kullervo

    2014-01-01

    Standing wave formation in an ex vivo human skull was investigated using a clinical prototype of a 30 cm diameter with 15 cm radius of curvature, low frequency (230 kHz), hemispherical transcranial Magnetic Resonance guided Focused Ultrasound (MRgFUS) phased-array. Experimental and simulation studies were conducted with changing aperture size and f-number configurations of the phased array, and qualitatively and quantitatively examined the acoustic pressure variation at the focus due to standing waves. The results demonstrated that the nodes and anti-nodes of standing wave produced by the small aperture array were clearly seen at approximately every 3 mm. The effect of the standing wave became more pronounced as the focus was moved closer to skull base. However, a sharp focus was seen for the full array, and there was no such standing wave pattern in the acoustic plane or near the skull base. This study showed that the fluctuation pressure amplitude would be greatly reduced by using a large-scale, hemispherical phased array with a low f-number. PMID:22049360

  6. Large-Scale Production of Single-Walled Carbon Nanotubes Using Ultrafast Pulses from a Free Electron Laser

    Microsoft Academic Search

    P. C. Eklund; B. K. Pradhan; U. J. Kim; Q. Xiong; J. E. Fischer; A. D. Friedman; B. C. Holloway; M. W. Smith

    2002-01-01

    We report the first use of ultrafast (subpicosecond) laser pulses for large-scale production of single wall carbon nanotubes (SWNT's) by the pulsed laser vaporization (PLV) technique. Very high production rates were achieved; using only 20% of the nominal average power of the 1 kW Jefferson Lab free electron laser (Jlab FEL), carbon soots rich in high quality bundles of SWNT's

  7. Time-dependent land uplift and subsidence in the Santa Clara valley, California, from a large interferometric synthetic aperture radar data set

    NASA Astrophysics Data System (ADS)

    Schmidt, David A.; Brgmann, Roland

    2003-09-01

    We invert 115 differential interferograms derived from 47 synthetic aperture radar (SAR) scenes for a time-dependent deformation signal in the Santa Clara valley, California. The time-dependent deformation is calculated by performing a linear inversion that solves for the incremental range change between SAR scene acquisitions. A nonlinear range change signal is extracted from the ERS InSAR data without imposing a model of the expected deformation. In the Santa Clara valley, cumulative land uplift is observed during the period from 1992 to 2000 with a maximum uplift of 41 18 mm centered north of Sunnyvale. Uplift is also observed east of San Jose. Seasonal uplift and subsidence dominate west of the Silver Creek fault near San Jose with a maximum peak-to-trough amplitude of 35 mm. The pattern of seasonal versus long-term uplift provides constraints on the spatial and temporal characteristics of water-bearing units within the aquifer. The Silver Creek fault partitions the uplift behavior of the basin, suggesting that it acts as a hydrologic barrier to groundwater flow. While no tectonic creep is observed along the fault, the development of a low-permeability barrier that bisects the alluvium suggests that the fault has been active since the deposition of Quaternary units.

  8. Relative intensity noise transfer of large-bandwidth pump lasers in Raman fiber

    E-print Network

    Boyer, Edmond

    Relative intensity noise transfer of large-bandwidth pump lasers in Raman fiber amplifiers Kafing, such incoherent pumping sources must be considered for the purpose of low-noise Raman amplifiers. 2006 Optical transfer for a fiber Raman amplifier when the pump beam has a bandwidth that may be much larger than

  9. Large Eddy Simulation of laser ignition and compressible reacting flow in a rocket-like

    E-print Network

    Paris-Sud XI, Université de

    Large Eddy Simulation of laser ignition and compressible reacting flow in a rocket Toulouse, France c DLR Lampoldshausen, 74239 Hardthausen, Germany Abstract The control of ignition in a rocket engine is a critical problem for combustion cham- ber design. Delayed ignition may lead to high

  10. Holmium:Yttrium-aluminum-garnet laser cystolithotripsy of large bladder calculi

    Microsoft Academic Search

    Joel M. H. Teichman; Vince J. Rogenes; Bradley J. McIver; J. Mansel Harris

    1997-01-01

    ObjectivesPatients with large bladder calculi (4 cm or larger) have traditionally been managed with open cystolithotomy. Endoscopic management with cystolitholapaxy or electrohydraulic lithotripsy risks complications. In an effort to spare patients the morbidity of open cystolithotomy, the results of holmium:yttriumaluminum-garnet (YAG) laser cystolithotripsy for bladder calculi 4 cm or larger were reviewed.

  11. Polarizing aperture stereoscopic cinema camera

    NASA Astrophysics Data System (ADS)

    Lipton, Lenny

    2012-07-01

    The art of stereoscopic cinematography has been held back because of the lack of a convenient way to reduce the stereo camera lenses' interaxial to less than the distance between the eyes. This article describes a unified stereoscopic camera and lens design that allows for varying the interaxial separation to small values using a unique electro-optical polarizing aperture design for imaging left and right perspective views onto a large single digital sensor, the size of the standard 35 mm frame, with the means to select left and right image information. Even with the added stereoscopic capability, the appearance of existing camera bodies will be unaltered.

  12. Large signal nonlinear distortion prediction for a single-mode laser diode under microwave intensity modulation

    Microsoft Academic Search

    1987-01-01

    The large-signal nonlinear distortions from a directly-modulated single-mode GaAlAs laser diode are closely predicted by using a large-signal equivalent circuit model. Criteria for determining intrinsic parameter values are described. The simulations are done in the time domain and then transformed to the frequency domain by FFT. Second harmonics, two-tone third-order intermodulation, multicarrier intermodulation, and intermodulation due to two arbitrarily separated

  13. Radius of Curvature Measurement of Large Optics Using Interferometry and Laser Tracker

    NASA Technical Reports Server (NTRS)

    Hagopian, John; Connelly, Joseph

    2011-01-01

    The determination of radius of curvature (ROC) of optics typically uses either a phase measuring interferometer on an adjustable stage to determine the position of the ROC and the optics surface under test. Alternatively, a spherometer or a profilometer are used for this measurement. The difficulty of this approach is that for large optics, translation of the interferometer or optic under test is problematic because of the distance of translation required and the mass of the optic. Profilometry and spherometry are alternative techniques that can work, but require a profilometer or a measurement of subapertures of the optic. The proposed approach allows a measurement of the optic figure simultaneous with the full aperture radius of curvature.

  14. High-power picosecond laser with 400W average power for large scale applications

    NASA Astrophysics Data System (ADS)

    Du, Keming; Brning, Stephan; Gillner, Arnold

    2012-03-01

    Laser processing is generally known for low thermal influence, precise energy processing and the possibility to ablate every type of material independent on hardness and vaporisation temperature. The use of ultra-short pulsed lasers offers new possibilities in the manufacturing of high end products with extra high processing qualities. For achieving a sufficient and economical processing speed, high average power is needed. To scale the power for industrial uses the picosecond laser system has been developed, which consists of a seeder, a preamplifier and an end amplifier. With the oscillator/amplifier system more than 400W average power and maximum pulse energy 1mJ was obtained. For study of high speed processing of large embossing metal roller two different ps laser systems have been integrated into a cylinder engraving machine. One of the ps lasers has an average power of 80W while the other has 300W. With this high power ps laser fluencies of up to 30 J/cm2 at pulse repetition rates in the multi MHz range have been achieved. Different materials (Cu, Ni, Al, steel) have been explored for parameters like ablation rate per pulse, ablation geometry, surface roughness, influence of pulse overlap and number of loops. An enhanced ablation quality and an effective ablation rate of 4mm3/min have been achieved by using different scanning systems and an optimized processing strategy. The max. achieved volume rate is 20mm3/min.

  15. Optofluidic laser for dual-mode sensitive biomolecular detection with a large dynamic range

    NASA Astrophysics Data System (ADS)

    Wu, Xiang; Oo, Maung Kyaw Khaing; Reddy, Karthik; Chen, Qiushu; Sun, Yuze; Fan, Xudong

    2014-04-01

    Enzyme-linked immunosorbent assay (ELISA) is a powerful method for biomolecular analysis. The traditional ELISA employing light intensity as the sensing signal often encounters large background arising from non-specific bindings, material autofluorescence and leakage of excitation light, which deteriorates its detection limit and dynamic range. Here we develop the optofluidic laser-based ELISA, where ELISA occurs inside a laser cavity. The laser onset time is used as the sensing signal, which is inversely proportional to the enzyme concentration and hence the analyte concentration inside the cavity. We first elucidate the principle of the optofluidic laser-based ELISA, and then characterize the optofluidic laser performance. Finally, we present the dual-mode detection of interleukin-6 using commercial ELISA kits, where the sensing signals are simultaneously obtained by the traditional and the optofluidic laser-based ELISA, showing a detection limit of 1?fg?ml-1 (38?aM) and a dynamic range of 6 orders of magnitude.

  16. Confocal coded aperture imaging

    DOEpatents

    Tobin, Jr., Kenneth William (Harriman, TN); Thomas, Jr., Clarence E. (Knoxville, TN)

    2001-01-01

    A method for imaging a target volume comprises the steps of: radiating a small bandwidth of energy toward the target volume; focusing the small bandwidth of energy into a beam; moving the target volume through a plurality of positions within the focused beam; collecting a beam of energy scattered from the target volume with a non-diffractive confocal coded aperture; generating a shadow image of said aperture from every point source of radiation in the target volume; and, reconstructing the shadow image into a 3-dimensional image of the every point source by mathematically correlating the shadow image with a digital or analog version of the coded aperture. The method can comprise the step of collecting the beam of energy scattered from the target volume with a Fresnel zone plate.

  17. Measurements of Aperture Averaging on Bit-Error-Rate

    NASA Technical Reports Server (NTRS)

    Bastin, Gary L.; Andrews, Larry C.; Phillips, Ronald L.; Nelson, Richard A.; Ferrell, Bobby A.; Borbath, Michael R.; Galus, Darren J.; Chin, Peter G.; Harris, William G.; Marin, Jose A.; Burdge, Geoffrey L.; Wayne, David; Pescatore, Robert

    2005-01-01

    We report on measurements made at the Shuttle Landing Facility (SLF) runway at Kennedy Space Center of receiver aperture averaging effects on a propagating optical Gaussian beam wave over a propagation path of 1,000 in. A commercially available instrument with both transmit and receive apertures was used to transmit a modulated laser beam operating at 1550 nm through a transmit aperture of 2.54 cm. An identical model of the same instrument was used as a receiver with a single aperture that was varied in size up to 20 cm to measure the effect of receiver aperture averaging on Bit Error Rate. Simultaneous measurements were also made with a scintillometer instrument and local weather station instruments to characterize atmospheric conditions along the propagation path during the experiments.

  18. Low-Energy Photoelectrons in Strong-Field Ionization by Laser Pulses with Large Ellipticity

    NASA Astrophysics Data System (ADS)

    Dimitrovski, D.; Maurer, J.; Stapelfeldt, H.; Madsen, L. B.

    2014-09-01

    The 3D photoelectron momentum distributions created by the strong-field ionization of argon atoms and naphthalene molecules with intense, large ellipticity (0.7) femtosecond laser pulses are studied. The experiment reveals the presence of low-energy electrons for randomly oriented naphthalene, but not for argon. Our theory shows that the induced dipole part of the cationic potential facilitates the creation of the low-energy electrons. We establish the conditions in terms of laser pulse parameters and molecular properties for which this type of low-energy electrons can be observed and point to applications thereof.

  19. Breaking and Moving Hotspots in a Large Grain Nb Cavity with a Laser Beam

    SciTech Connect

    Ciovati, G.; Cheng, G.; Flood, R. J.; Jordan, K.; Kneisel, P.; Morrone, M. L.; Turlington, L.; Wilson, K. M.; Zhang, S.; Anlage, S. M.; Gurevich, A. V.; Nemes, G.; Baldwin, C.

    2011-07-25

    Magnetic vortices pinned near the inner surface of SRF Nb cavities are a possible source of RF hotspots, frequently observed by temperature mapping of the cavities outer surface at RF surface magnetic fields of about 100 mT. Theoretically, we expect that the thermal gradient provided by a 10 W green laser shining on the inner cavity surface at the RF hotspot locations can move pinned vortices to different pinning locations. The experimental apparatus to send the beam onto the inner surface of a photoinjector-type large-grain Nb cavity is described. Preliminary results on the changes in thermal maps observed after applying the laser heating are also reported.

  20. Arbitrary-speed quantum gates within large ion crystals through minimum control of laser beams

    E-print Network

    Shi-Liang Zhu; C. Monroe; L. -M. Duan

    2005-08-03

    We propose a scheme to implement arbitrary-speed quantum entangling gates on two trapped ions immersed in a large linear crystal of ions, with minimal control of laser beams. For gate speeds slower than the oscillation frequencies in the trap, a single appropriately-detuned laser pulse is sufficient for high-fidelity gates. For gate speeds comparable to or faster than the local ion oscillation frequency, we discover a five-pulse protocol that exploits only the local phonon modes. This points to a method for efficiently scaling the ion trap quantum computer without shuttling ions.

  1. Low-energy photoelectrons in strong-field ionization by laser pulses with large ellipticity.

    PubMed

    Dimitrovski, D; Maurer, J; Stapelfeldt, H; Madsen, L B

    2014-09-01

    The 3D photoelectron momentum distributions created by the strong-field ionization of argon atoms and naphthalene molecules with intense, large ellipticity (?0.7) femtosecond laser pulses are studied. The experiment reveals the presence of low-energy electrons for randomly oriented naphthalene, but not for argon. Our theory shows that the induced dipole part of the cationic potential facilitates the creation of the low-energy electrons. We establish the conditions in terms of laser pulse parameters and molecular properties for which this type of low-energy electrons can be observed and point to applications thereof. PMID:25238357

  2. Development of Large Concrete Object Geometrical Model Based on Terrestrial Laser Scanning

    NASA Astrophysics Data System (ADS)

    Zaczek-Peplinska, Janina; Popielski, Pawe?; Kasprzak, Adam; Wjcik, Pawe?

    2015-02-01

    The paper presents control periodic measurements of movements and survey of concrete dam on Dunajec River in Ro?nw, Poland. Topographical survey was conducted using laser scanning technique. The goal of survey was data collection and creation of a geometrical model. Acquired cross- and horizontal sections were utilised to create a numerical model of object behaviour at various load depending of changing level of water in reservoir. Modelling was accomplished using finite elements technique. During the project an assessment was conducted to terrestrial laser scanning techniques for such type of research of large hydrotechnical objects such as gravitational water dams. Developed model can be used to define deformations and displacement prognosis.

  3. Polarisation splitting of laser beams by large angles with minimal reflection losses

    SciTech Connect

    Davydov, B L [Institute of Radio Engineering and Electronics, Russian Academy of Sciences, Fryazino, Moscow Region (Russian Federation)

    2006-05-31

    New crystal anisotropic prisms for splitting orthogonally polarised components of laser radiation by large angles with minimal reflection losses caused by the Brewster refraction and total internal reflection of polarised waves from the crystal-air interface are considered and the method for their calculation is described. It is shown that, by assembling glue-free combinations of two or three prisms, thermally stable beamsplitters can be fabricated, which are free from the beam astigmatism and the wave dispersion of the output angles of the beams. The parameters and properties of new beamsplitters are presented in a convenient form in figures and tables. (laser applications and other topics in quantum electronics)

  4. Management of large prostatic adenoma: Lasers versus bipolar transurethral resection of prostate.

    PubMed

    Gupta, Narmada P; Nayyar, Rishi

    2013-07-01

    Transurethral resection of prostate (TURP) has long been the most commonly performed surgical procedure for the management of benign prostate enlargement (BPE), but has several associated limitations. Over the years, laser techniques have developed as major contenders as alternative therapies for BPE. However, simultaneously, TURP has also flourished and with relatively recent development of resection in saline (bipolar TURP), the tussle between laser techniques and TURP has further gained momentum. A systematic search was performed on Medline using the various Medical subject headings related to the surgical management of BPE including TURP, bipolar, lasers, holmium laser enucleation of prostate (HoLEP), photo-selective vaporization of prostate (PVP), etc., All articles types including meta-analysis randomized controlled trials, review articles, guidelines from various urological associations, single center studies from 2002 onward were considered for review. Bipolar TURP, HoLEP, and PVP provide equivalent outcomes for large prostate adenoma (<60 g). For extremely large glands (<150 g), HoLEP is a very efficacious endoscopic alternative to open prostatectomy and has proven long-term results over more than a decade. Bipolar TURP and PVP are attractive with a minimal learning curves and equivalent short term durability. Surgical management of large prostate should be individualized based upon patient's comorbidities and surgeon's expertise. PMID:24082445

  5. Management of large prostatic adenoma: Lasers versus bipolar transurethral resection of prostate

    PubMed Central

    Gupta, Narmada P; Nayyar, Rishi

    2013-01-01

    Transurethral resection of prostate (TURP) has long been the most commonly performed surgical procedure for the management of benign prostate enlargement (BPE), but has several associated limitations. Over the years, laser techniques have developed as major contenders as alternative therapies for BPE. However, simultaneously, TURP has also flourished and with relatively recent development of resection in saline (bipolar TURP), the tussle between laser techniques and TURP has further gained momentum. A systematic search was performed on Medline using the various Medical subject headings related to the surgical management of BPE including TURP, bipolar, lasers, holmium laser enucleation of prostate (HoLEP), photo-selective vaporization of prostate (PVP), etc., All articles types including meta-analysis randomized controlled trials, review articles, guidelines from various urological associations, single center studies from 2002 onward were considered for review. Bipolar TURP, HoLEP, and PVP provide equivalent outcomes for large prostate adenoma (<60 g). For extremely large glands (<150 g), HoLEP is a very efficacious endoscopic alternative to open prostatectomy and has proven long-term results over more than a decade. Bipolar TURP and PVP are attractive with a minimal learning curves and equivalent short term durability. Surgical management of large prostate should be individualized based upon patient's comorbidities and surgeon's expertise. PMID:24082445

  6. 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)

  7. Multiple aperture window and seeker concepts for endo KEW applications

    NASA Astrophysics Data System (ADS)

    Shui, V. H.; Reeves, B. L.; Thyson, N. A.; Mueffelmann, W. H.; Werner, J. S.; Jones, G.

    1992-05-01

    Hypersonic interceptors performing endoatmospheric hit-to-kill missions require very high seeker angle measurement accuracies in very severe aero-thermal environments. Wall jet window/aperture cooling usually leads to significant aero-optic degradation in seeker and hence interceptor performance. This paper describes window/aperture concepts that have the potential of eliminating or significantly reducing the need for coolant injection, together with a multiple aperture sensor concept that can provide a high angle measurement accuracy and a large field of regard, with a small aperture size.

  8. Coded aperture imaging for fluorescent x-rays

    SciTech Connect

    Haboub, A. [Lawrence Berkeley National Laboratories, Berkeley, California 94720 (United States); Lincoln University, Life and Physical Sciences Department, Jefferson City, Missouri 65101 (United States); MacDowell, A. A.; Marchesini, S.; Parkinson, D. Y. [Lawrence Berkeley National Laboratories, Berkeley, California 94720 (United States)

    2014-06-15

    We employ a coded aperture pattern in front of a pixilated charge couple device detector to image fluorescent x-rays (625 KeV) from samples irradiated with synchrotron radiation. Coded apertures encode the angular direction of x-rays, and given a known source plane, allow for a large numerical aperture x-ray imaging system. The algorithm to develop and fabricate the free standing No-Two-Holes-Touching aperture pattern was developed. The algorithms to reconstruct the x-ray image from the recorded encoded pattern were developed by means of a ray tracing technique and confirmed by experiments on standard samples.

  9. Off-axis field approximations for ion traps with apertures

    NASA Astrophysics Data System (ADS)

    Chattopadhyay, Madhurima; Mohanty, Atanu K.

    2009-12-01

    In recent work (Int. J. Mass Spec., vol. 282, pp. 112-122) we have considered the effect of apertures on the fields inside rf traps at points on the trap axis. We now complement and complete that work by considering off-axis fields in axially symmetric (referred to as "3D") and in two dimensional ("2D") ion traps whose electrodes have apertures, i.e., holes in 3D and slits in 2D. Our approximation has two parts. The first, EnoAperture, is the field obtained numerically for the trap under study with apertures artificially closed. We have used the boundary element method (BEM) for obtaining this field. The second part, EdueToAperture, is an analytical expression for the field contribution of the aperture. In EdueToAperture, aperture size is a free parameter. A key element in our approximation is the electrostatic field near an infinite thin plate with an aperture, and with different constant-valued far field intensities on either side. Compact expressions for this field can be found using separation of variables, wherein the choice of coordinate system is crucial. This field is, in turn, used four times within our trap-specific approximation. The off-axis field expressions for the 3D geometries were tested on the quadrupole ion trap (QIT) and the cylindrical ion trap (CIT), and the corresponding expressions for the 2D geometries were tested on the linear ion trap (LIT) and the rectilinear ion trap (RIT). For each geometry, we have considered apertures which are 10%, 30%, and 50% of the trap dimension. We have found that our analytical correction term EdueToAperture, though based on a classical small-aperture approximation, gives good results even for relatively large apertures.

  10. Crystal growth and application of large size YCOB crystal for high power laser

    NASA Astrophysics Data System (ADS)

    Wu, Anhua; Xu, Jun; Zheng, Yanqing; Liang, Xiaoyan

    2014-10-01

    Yttrium calcium oxyborate YCa4O(BO3)3 (YCOB) is a novel non-linear optical crystal possessing good thermal, mechanical and nonlinear optical properties. It is regards the important candidate frequency conversion material for the high-average power laser system. In this work, we described our effort to achieve the successful growth of large size YCOB single crystals, and the crystal quality of large size YCOB crystal grown by the Bridgman method. The OPCPA application of YCOB element was also introduced simply. The results confirmed that Bridgman technology can be used for the growth of large size YCOB crystal as an alternative to Czochralski method.

  11. Laser-assisted ionization-excitation of helium by electron impact at large momentum transfer

    NASA Astrophysics Data System (ADS)

    Bulychev, Andrey A.; Kouzakov, Konstantin A.

    2014-11-01

    Ionization of a helium atom by electron impact in the presence of laser radiation is studied theoretically. The kinematic regime of high impact energy and large momentum transfer is considered. The S-matrix of the process is treated within the first Born and binary-encounter approximations. Triple differential cross sections are calculated for the cases when the residual He+ ion is left both in the ground ( n = 1) and in the first excited ( n = 2) states in the presence of a laser field with frequency ? = 1.55 eV and intensity I = 5 1011 W/cm2. The laser-assisted cross sections corresponding to n = 2 are found to be more sensitive to the electron-electron correlations in helium than the field-free ones.

  12. Apertured paraxial Bessel beams.

    PubMed

    Umul, Yusuf Z

    2010-03-01

    The paraxial Bessel beam is obtained by applying an approximation in the wavenumbers. The scattering of the beams by a circular aperture in an absorbing screen is investigated. The scattered fields are expressed in terms of the Fresnel integrals by evaluating the Kirchhoff diffraction integral in the paraxial approximation. The results are examined numerically. PMID:20208927

  13. Radiometric errors caused by diffraction from circular apertures - Edge effects

    Microsoft Academic Search

    L. P. Boivin

    1977-01-01

    The diffraction corrections associated with a point source and a circular diffracting aperture are calculated for the case where the detector aperture diameter is nearly equal to that of the illuminated area. It is found that the diffraction corrections are relatively large near the center and near the edge, even using white light and detectors with very extended spectral sensitivities.

  14. Preliminary Report On Combined Surgical- And Laser-Treatment Of Large Hemangiomas And Tattoos

    NASA Astrophysics Data System (ADS)

    Ginsbach, G.

    1981-05-01

    As most hemangiomas and tattoos require many sessions to be cured completely by argon-laser or conventional therapy I developed a new combined surgical and laser-therapy method for large hemangiomas and tattoos. This is a three step method. First: The skin lesion is treated by argon-laser with the point by point method, developed by ourself. Second: Under local or general anaesthesia a) the hemangioma is partially excised and undermined letting only the skin which is already treated by argon-laser-beams. Than the hemangioma is exstirpated in toto, the wound closed by running intradermal sutures and a pressure bandage applied, b) the tattoo is abraded as deep as possible, draped by lyofoam. Then a pressure bandage is applied. Third: The hemangioma as well as the tattoo are treated by argon-laser-beams after the operation. This method is safe and effective, gives good results, minimal scars in the case of hemangiomas and tattoos. In this paper the method is described and some cases are illustrated by pre- and postoperational photographs.

  15. A feasibility study into the screening and imaging of hand luggage for threat items at 35 GHz using an active large aperture (1.6 m) security screening imager

    NASA Astrophysics Data System (ADS)

    Bowring, Nicholas J.; O'Reilly, Dean; Salmon, Neil A.; Andrews, David A.; Rezgui, Nacer-Ddine; Harmer, Stuart W.

    2013-10-01

    The feasibility of screening hand luggage for concealed threat items such as Person-Borne Improvised Explosive Devices (PBIED's) both metallic and non-metallic, together with handguns and at millimetre wavelengths is investigated. Previous studies by the authors and others indicate that hand baggage material and fabric is much more transmissive and has less scattering at lower millimetre wave frequencies and the ability to use K-band active imaging with high spatial resolution presents an opportunity to image and hence recognise concealed threats. For this feasibility study, a 1.6 m aperture, 35 GHz security screening imaging system with a spatial resolution of 2.5 cm and a depth of field of around 5 cm is employed, using spatially incoherent illuminating panels to enhance image contrast. In this study, realistic scenarios using backpacks containing a realistic range of threat and non-threat items are scanned, both carried and standalone. This range of items contains large vessels suitable for containing simulated home-made PBIED's and handguns. The comprehensive list of non-threat items includes laptops, bottles, clothing and power supplies. For this study, the range at which imaging data at standoff distances can be acquired is confined to that of the particular system in use, although parameters such as illumination and integration time are optimised. However, techniques for extrapolating towards effective standoff distances using aperture synthesis imagers are discussed. The transmission loss through fabrics and clothing that may form, or be contained in baggage, are reported over range of frequencies ranging from 26 to 110 GHz.

  16. Fabrication of mitigation pits for improving laser damage resistance in dielectric mirrors by femtosecond laser machining

    SciTech Connect

    Wolfe, Justin E.; Qiu, S. Roger; Stolz, Christopher J.

    2011-03-20

    Femtosecond laser machining is used to create mitigation pits to stabilize nanosecond laser-induced damage in multilayer dielectric mirror coatings on BK7 substrates. In this paper, we characterize features and the artifacts associated with mitigation pits and further investigate the impact of pulse energy and pulse duration on pit quality and damage resistance. Our results show that these mitigation features can double the fluence-handling capability of large-aperture optical multilayer mirror coatings and further demonstrate that femtosecond laser macromachining is a promising means for fabricating mitigation geometry in multilayer coatings to increase mirror performance under high-power laser irradiation.

  17. Fabrication of mitigation pits for improving laser damage resistance in dielectric mirrors by femtosecond laser machining.

    PubMed

    Wolfe, Justin E; Qiu, S Roger; Stolz, Christopher J

    2011-03-20

    Femtosecond laser machining is used to create mitigation pits to stabilize nanosecond laser-induced damage in multilayer dielectric mirror coatings on BK7 substrates. In this paper, we characterize features and the artifacts associated with mitigation pits and further investigate the impact of pulse energy and pulse duration on pit quality and damage resistance. Our results show that these mitigation features can double the fluence-handling capability of large-aperture optical multilayer mirror coatings and further demonstrate that femtosecond laser macromachining is a promising means for fabricating mitigation geometry in multilayer coatings to increase mirror performance under high-power laser irradiation. PMID:21460980

  18. Aperture effects in squid jet propulsion.

    PubMed

    Staaf, Danna J; Gilly, William F; Denny, Mark W

    2014-05-01

    Squid are the largest jet propellers in nature as adults, but as paralarvae they are some of the smallest, faced with the inherent inefficiency of jet propulsion at a low Reynolds number. In this study we describe the behavior and kinematics of locomotion in 1 mm paralarvae of Dosidicus gigas, the smallest squid yet studied. They swim with hop-and-sink behavior and can engage in fast jets by reducing the size of the mantle aperture during the contraction phase of a jetting cycle. We go on to explore the general effects of a variable mantle and funnel aperture in a theoretical model of jet propulsion scaled from the smallest (1 mm mantle length) to the largest (3 m) squid. Aperture reduction during mantle contraction increases propulsive efficiency at all squid sizes, although 1 mm squid still suffer from low efficiency (20%) because of a limited speed of contraction. Efficiency increases to a peak of 40% for 1 cm squid, then slowly declines. Squid larger than 6 cm must either reduce contraction speed or increase aperture size to maintain stress within maximal muscle tolerance. Ecological pressure to maintain maximum velocity may lead them to increase aperture size, which reduces efficiency. This effect might be ameliorated by nonaxial flow during the refill phase of the cycle. Our model's predictions highlight areas for future empirical work, and emphasize the existence of complex behavioral options for maximizing efficiency at both very small and large sizes. PMID:24501132

  19. Generalized concepts in large-scale laser isotope separation, with application to deuterium

    Microsoft Academic Search

    J. C. Vanderleeden

    1980-01-01

    Optical laser isotope separation (LIS) and chemical process concepts are developed that arise in the large-scale application of LIS processes with continuous process streams. The discussion applies to one-photon, two-photon and multiphoton LIS and the separation of a multiple-component mixture. It is partly based on a novel reaction chamber which provides throughout its volume a constant energy fluence or power

  20. High-power air-clad large-mode-area photonic crystal fiber laser

    Microsoft Academic Search

    Jens Limpert; T. Schreiber; S. Nolte; H. Zellmer; T. Tunnermann; R. Iliew; F. Lederer; J. Broeng; G. Vienne; A. Petersson; C. Jakobsen

    2003-01-01

    We report on a 2.3 m long air-clad ytterbium-doped large-modearea photonic crystal fiber laser generating up to 80 W output power with a slope efficiency of 78%. Single transverse mode operation is achieved with a mode-field area of 350 µm2. No thermo-optical limitations are observed at the extracted ~35W\\/m, therefore such fibers allow scaling to even higher powers.

  1. Study on 3D laser scanning modeling method for Large-Scale history building

    Microsoft Academic Search

    Xiao-jun Cheng; Hong-fei Zhang; Rui Xie

    2010-01-01

    Digital preservation of excellent history building has become an influence-profound sociality problem. In this paper, taking Wen-Yuan Building(in Tongji University, Shanghai, China) as an example, we introduce a real 3D digital method for Large-Scale history building using 3D laser scanner and total station. Firstly, the building are separated into many station s which are scanned separately in order to get

  2. Intermediate field measurement to characterize the wavefront of high power laser large optics

    NASA Astrophysics Data System (ADS)

    Audo, Frdric; Bouillet, Stphane; Chico, Sandrine; Daurios, Jrme

    2014-09-01

    The French Laser MgaJoule (LMJ) is a high power laser project, dedicated to fusion and plasma experiments. It will include 176 square beams involving thousands of large optical components. The wavefront performances of all those optics are critical to achieve the desired focal spot shape and limit the hot spots that could damage the components. The CEA has developed experimental methods to qualify precisely the quality of the large optical components manufactured for the project and measure the effect of various defects. For specific components (coated or parabola mirrors, lenses or gratings), classical techniques like interferometric setups may fail to measure the wavefront highest spatial frequencies (> 1 mm-1). In order to improve the measurements, we have proposed characterization methods based upon a laser beam diffraction interpretation. They present limits and we need to improve the wavefront measurement for high spatial frequencies (> 1 mm-1). We present in this paper the intermediate field measurement based upon the Talbot effect theory and the Fourier analysis of acquired intensity images. The technique consists in a double pass setup: a plane wave is transmitted through the component twice, to simplify the setup and improve the measurement. Then, intensity images are acquired at different distances with a CCD camera and lead to the wavefront power spectral density. We describe the experimental setup to measure the wavefront of large specific components. We show experimental results. Finally, we discuss about the advantages and the limits of such a method, and we compare it with our previous measurement methods.

  3. Automatic Recognition of Piping System from Large-Scale Terrestrial Laser Scan Data

    NASA Astrophysics Data System (ADS)

    Kawashima, K.; Kanai, S.; Date, H.

    2011-09-01

    Recently, changes in plant equipment have been becoming more frequent because of the short lifetime of the products, and constructing 3D shape models of existing plants (as-built models) from large-scale laser scanned data is expected to make their rebuilding processes more efficient. However, the laser scanned data of the existing plant has massive points, captures tangled objects and includes a large amount of noises, so that the manual reconstruction of a 3D model is very time-consuming and costs a lot. Piping systems especially, account for the greatest proportion of plant equipment. Therefore, the purpose of this research was to propose an algorithm which can automatically recognize a piping system from terrestrial laser scan data of the plant equipment. The straight portion of pipes, connecting parts and connection relationship of the piping system can be recognized in this algorithm. Eigenvalue analysis of the point clouds and of the normal vectors allows for the recognition. Using only point clouds, the recognition algorithm can be applied to registered point clouds and can be performed in a fully automatic way. The preliminary results of the recognition for large-scale scanned data from an oil rig plant have shown the effectiveness of the algorithm.

  4. Aperture Performance Assessment Test

    NASA Astrophysics Data System (ADS)

    Blair, William

    The purpose of this test is severalfold, all relating to the use of various observing strategies with different apertures and how they affect the resulting data quality. We will compare LWRS data taken with and without XOFFsets (e.g. dithering). We will attempt observations with the HIRS aperture, concentrating on LiF1, to see if significant gains in resolution can be made. Finally, additional testing of the MDRS-multiple PKUP per orbit strategy will be performed. It is expected that all of these tests will be performed on the same target in sequence, to minimize the variables and maximize information learned about the different techniques. Multiple runs of this test are anticipated with differing strategies for the detailed sequence of activities.

  5. Aperture center energy showcase

    SciTech Connect

    Torres, J. J.

    2012-03-01

    Sandia and Forest City have established a Cooperative Research and Development Agreement (CRADA), and the partnership provides a unique opportunity to take technology research and development from demonstration to application in a sustainable community. A project under that CRADA, Aperture Center Energy Showcase, offers a means to develop exhibits and demonstrations that present feedback to community members, Sandia customers, and visitors. The technologies included in the showcase focus on renewable energy and its efficiency, and resilience. These technologies are generally scalable, and provide secure, efficient solutions to energy production, delivery, and usage. In addition to establishing an Energy Showcase, support offices and conference capabilities that facilitate research, collaboration, and demonstration were created. The Aperture Center project focuses on establishing a location that provides outreach, awareness, and demonstration of research findings, emerging technologies, and project developments to Sandia customers, visitors, and Mesa del Sol community members.

  6. Multi-transmitter aperture synthesis.

    PubMed

    Rabb, David J; Jameson, Douglas F; Stafford, Jason W; Stokes, Andrew J

    2010-11-22

    Multi-transmitter aperture synthesis is a method in which multiple transmitters can be used to improve resolution and contrast of distributed aperture systems. Such a system utilizes multiple transmitter locations to interrogate a target from multiple look angles thus increasing the angular spectrum content captured by the receiver aperture array. Furthermore, such a system can improve the contrast of sparsely populated receiver arrays by capturing field data in the region between sub-apertures by utilizing multiple transmitter locations. This paper discusses the theory behind multi-transmitter aperture synthesis and provides experimental verification that imagery captured using multiple transmitters will provide increased resolution. PMID:21164838

  7. A New Approach for Structural Monitoring of Large Dams with a Three-Dimensional Laser Scanner

    PubMed Central

    Gonzlez-Aguilera, Diego; Gmez-Lahoz, Javier; Snchez, Jos

    2008-01-01

    Driven by progress in sensor technology, computer methods and data processing capabilities, 3D laser scanning has found a wide range of new application fields in recent years. Particularly, monitoring the static and dynamic behaviour of large dams has always been a topic of great importance, due to the impact these structures have on the whole landscape where they are built. The main goal of this paper is to show the relevance and novelty of the laserscanning methodology developed, which incorporates different statistical and modelling approaches not considered until now. As a result, the methods proposed in this paper have provided the measurement and monitoring of the large Las Cogotas dam (Avila, Spain).

  8. Integrated electrochromic aperture diaphragm

    NASA Astrophysics Data System (ADS)

    Deutschmann, T.; Oesterschulze, E.

    2014-05-01

    In the last years, the triumphal march of handheld electronics with integrated cameras has opened amazing fields for small high performing optical systems. For this purpose miniaturized iris apertures are of practical importance because they are essential to control both the dynamic range of the imaging system and the depth of focus. Therefore, we invented a micro optical iris based on an electrochromic (EC) material. This material changes its absorption in response to an applied voltage. A coaxial arrangement of annular rings of the EC material is used to establish an iris aperture without need of any mechanical moving parts. The advantages of this device do not only arise from the space-saving design with a thickness of the device layer of 50?m. But it also benefits from low power consumption. In fact, its transmission state is stable in an open circuit, phrased memory effect. Only changes of the absorption require a voltage of up to 2 V. In contrast to mechanical iris apertures the absorption may be controlled on an analog scale offering the opportunity for apodization. These properties make our device the ideal candidate for battery powered and space-saving systems. We present optical measurements concerning control of the transmitted intensity and depth of focus, and studies dealing with switching times, light scattering, and stability. While the EC polymer used in this study still has limitations concerning color and contrast, the presented device features all functions of an iris aperture. In contrast to conventional devices it offers some special features. Owing to the variable chemistry of the EC material, its spectral response may be adjusted to certain applications like color filtering in different spectral regimes (UV, optical range, infrared). Furthermore, all segments may be switched individually to establish functions like spatial Fourier filtering or lateral tunable intensity filters.

  9. Aperture Ion Source

    NASA Technical Reports Server (NTRS)

    Herrero, Fred

    2012-01-01

    The aperture ion source was conceived to eliminate distortion in measurements of angular distributions of neutral atoms and molecules that require electron-impact ion sources. The approach simplifies the coupling between ion source and spectrometer while providing virtually distortion-free angular distributions and improved accuracy in the dimensions of the ionization region. Furthermore, it virtually eliminates the volume occupied by the ion source.

  10. Aperture excited dielectric antennas

    NASA Technical Reports Server (NTRS)

    Crosswell, W. F.; Chatterjee, J. S.; Mason, V. B.; Tai, C. T.

    1974-01-01

    The results of a comprehensive experimental and theoretical study of the effect of placing dielectric objects over the aperture of waveguide antennas are presented. Experimental measurements of the radiation patterns, gain, impedance, near-field amplitude, and pattern and impedance coupling between pairs of antennas are given for various Plexiglas shapes, including the sphere and the cube, excited by rectangular, circular, and square waveguide feed apertures. The waveguide excitation of a dielectric sphere is modeled using the Huygens' source, and expressions for the resulting electric fields, directivity, and efficiency are derived. Calculations using this model show good overall agreement with experimental patterns and directivity measurements. The waveguide under an infinite dielectric slab is used as an impedance model. Calculations using this model agree qualitatively with the measured impedance data. It is concluded that dielectric loaded antennas such as the waveguide excited sphere, cube, or sphere-cylinder can produce directivities in excess of that obtained by a uniformly illuminated aperture of the same cross section, particularly for dielectric objects with dimensions of 2 wavelengths or less. It is also shown that for certain configurations coupling between two antennas of this type is less than that for the same antennas without dielectric loading.

  11. Nd:YAG thin-disk laser with large dynamic range unstable resonance

    NASA Astrophysics Data System (ADS)

    Shang, Jianli; Yu, Yi; An, Xiangchao; Gao, Qingsong; Tang, Chun

    2015-02-01

    In this paper, based on the self-reproduction condition of laser wavefront curvature, the influences of disk defocus on laser parameters can be calculated. The laser-pumping overlapping efficiency will decrease by 9%; the magnification will rise to 2.3, and the intra-cavity loss will be high to 30% due to a laser beam size mismatch when each disk has focal length of -100 m in a positive-branch confocal unstable resonator containing four disks with magnification of 1.8. Therefore, the optical conversion efficiency and stability will be reduced significantly. Several methods defocus compensation of are compared, it can be found that inserting variable-focus lens in resonant is useful in large dynamic range. In experiment, the defocus values are measured in different pumping power. A lens group, used for compensate components according to the single pass probe, is carefully designed. Under this compensation, the pulse energy can be maintained in 10 J from 1 Hz to 100 Hz. The output power can be improved 2.33 times compared to non-compensation condition.

  12. 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.

  13. DFB laser based on single mode large effective area heavy concentration EDF.

    PubMed

    Li, Qi; Yan, Fengping; Peng, Wanjing; Feng, Ting; Feng, Suchun; Tan, Siyu; Liu, Peng; Ren, Wenhua

    2012-10-01

    A ? phase shifted distributed feedback (DFB) laser based on single mode large effective area heavy concentration erbium-doped fiber (EDF) has been demonstrated. The homemade EDF was fabricated by the modified chemical-vapor deposition (MCVD) technique, and the 13cm long ? phase shifted fiber grating was written in the intracore of the EDF. The erbium-doped concentration is 4.19 10(25) ions/m(3), the mode field diameter of the fiber is 12.2801 um at 1550 nm, the absorption coefficients of the fiber are 34.534 dB/m at 980 nm and 84.253 dB/m at 1530 nm. The threshold of the DFB laser is 66 mW, and the measured maximum output power is 43.5 mW at 450 mW pump power that corresponding to the slope efficiency of 11.5%. The signal-to-noise ratio (SNR) of the operating laser at 200 mW input power is 55 dB, and the DFB laser has a Lorentz linewidth of 9.8 kHz at the same input pump power. PMID:23188334

  14. Large-scale numerical simulation of laser propulsion by parallel computing

    NASA Astrophysics Data System (ADS)

    Zeng, Yaoyuan; Zhao, Wentao; Wang, Zhenghua

    2013-05-01

    As one of the most significant methods to study laser propelled rocket, the numerical simulation of laser propulsion has drawn an ever increasing attention at present. Nevertheless, the traditional serial simulation model cannot satisfy the practical needs because of insatiable memory overhead and considerable computation time. In order to solve this problem, we study on a general algorithm for laser propulsion design, and bring about parallelization by using a twolevel hybrid parallel programming model. The total computing domain is decomposed into distributed data spaces, and each partition is assigned to a MPI process. A single step of computation operates in the inter loop level, where a compiler directive is used to split MPI process into several OpenMP threads. Finally, parallel efficiency of hybrid program about two typical configurations on a China-made supercomputer with 4 to 256 cores is compared with pure MPI program. And, the hybrid program exhibits better performance than the pure MPI program on the whole, roughly as expected. The result indicates that our hybrid parallel approach is effective and practical in large-scale numerical simulation of laser propulsion.

  15. Automatic alignment technology in high power laser system

    NASA Astrophysics Data System (ADS)

    Zhang, Xin; Dai, Wan-jun; Wang, Yuan-cheng; Lian, Bo; Yang, Ying; Yuan, Qiang; Deng, Xue-wei; Zhao, Jun-pu; Zhou, Wei

    2015-02-01

    The high power solid laser system is becoming larger and higher energy that requires the beam automatic alignment faster and higher precision to ensure safety running of laser system and increase the shooting success rate. This paper take SGIII laser facility for instance, introduce the basic principle of automatic alignment of large laser system. The automatic alignment based on digital image processing technology which use the imaging of seven-classes spatial filter pinholes for feedback to working. Practical application indicates that automatic alignment system of cavity mirror in SGIII facility can finish the work in 210 seconds of four bundles and will not exceed 270 seconds of all six bundles. The alignment precision promoted to 2.5% aperture from 8% aperture. The automatic alignment makes it possible for fast and safety running of lager laser system.

  16. Wind Scanner: A full-scale Laser Facility for Wind and Turbulence Measurements around large Wind Turbines

    E-print Network

    Wind Scanner: A full-scale Laser Facility for Wind and Turbulence Measurements around large Wind Turbines Torben Mikkelsen, Jakob Mann and Michael Courtney Wind Energy Department, Risø National Laboratory:Torben.Mikkelsen@Risoe.dk Summary RIS? DTU has started to build a newly designed laser-based lidar scanning facility for remote wind

  17. Element Antenna Design for a Two-dimensional Aperture Synthetic Millimeter-wave radiometer

    Microsoft Academic Search

    Dongmo Zhao; Jungang Miao; Fang Li; Zhiping Li

    2006-01-01

    An aperture synthetic radiometer makes use a large number of, sparsely distributed, radiometers to achieve high resolution (special and radiometric) measurements. Each element radiometer has its own element antennas, the specifications of which strongly influence the final performance of the aperture synthetic radiometer. Therefore, in designing element antennas, one must consider the restrictions posed by the aperture synthetic radiometer requirements

  18. Large-area high-power VCSEL pump arrays optimized for high-energy lasers

    NASA Astrophysics Data System (ADS)

    Wang, Chad; Geske, Jonathan; Garrett, Henry; Cardellino, Terri; Talantov, Fedor; Berdin, Glen; Millenheft, David; Renner, Daniel; Klemer, Daniel

    2012-06-01

    Practical, large-area, high-power diode pumps for one micron (Nd, Yb) as well as eye-safer wavelengths (Er, Tm, Ho) are critical to the success of any high energy diode pumped solid state laser. Diode efficiency, brightness, availability and cost will determine how realizable a fielded high energy diode pumped solid state laser will be. 2-D Vertical-Cavity Surface-Emitting Laser (VCSEL) arrays are uniquely positioned to meet these requirements because of their unique properties, such as low divergence circular output beams, reduced wavelength drift with temperature, scalability to large 2-D arrays through low-cost and high-volume semiconductor photolithographic processes, high reliability, no catastrophic optical damage failure, and radiation and vacuum operation tolerance. Data will be presented on the status of FLIR-EOC's VCSEL pump arrays. Analysis of the key aspects of electrical, thermal and mechanical design that are critical to the design of a VCSEL pump array to achieve high power efficient array performance will be presented.

  19. An all-optronic synthetic aperture lidar

    NASA Astrophysics Data System (ADS)

    Turbide, Simon; Marchese, Linda; Terroux, Marc; Babin, Franois; Bergeron, Alain

    2012-09-01

    Synthetic Aperture Radar (SAR) is a mature technology that overcomes the diffraction limit of an imaging system's real aperture by taking advantage of the platform motion to coherently sample multiple sections of an aperture much larger than the physical one. Synthetic Aperture Lidar (SAL) is the extension of SAR to much shorter wavelengths (1.5 ?m vs 5 cm). This new technology can offer higher resolution images in day or night time as well as in certain adverse conditions. It could be a powerful tool for Earth monitoring (ship detection, frontier surveillance, ocean monitoring) from aircraft, unattended aerial vehicle (UAV) or spatial platforms. A continuous flow of high-resolution images covering large areas would however produce a large amount of data involving a high cost in term of post-processing computational time. This paper presents a laboratory demonstration of a SAL system complete with image reconstruction based on optronic processing. This differs from the more traditional digital approach by its real-time processing capability. The SAL system is discussed and images obtained from a non-metallic diffuse target at ranges up to 3m are shown, these images being processed by a real-time optronic SAR processor origiinally designed to reconstruct SAR images from ENVISAT/ASAR data.

  20. Preclinical Assessment of a 980-nm Diode Laser Ablation System in a Large Animal Tumor Model

    PubMed Central

    Ahrar, Kamran; Gowda, Ashok; Javadi, Sanaz; Borne, Agatha; Fox, Matthew; McNichols, Roger; Ahrar, Judy U.; Stephens, Clifton; Stafford, R. Jason

    2010-01-01

    Purpose To characterize the performance of a 980-nm diode laser ablation system in an in vivo tumor model. Materials and Methods This study was approved by the Institutional Animal Care and Use Committee. The ablation system consisted of a 15-W, 980-nm diode laser, flexible diffusing tipped fiber optic, and 17-gauge internally cooled catheter. Ten immunosuppressed dogs were inoculated subcutaneously with canine transmissible venereal tumor fragments in eight dorsal locations. Laser ablations were performed at 79 sites where inoculations were successful (99%) using powers of 10 W, 12.5 W, and 15 W, with exposure times between 60 and 180 seconds. In 20 cases, multiple overlapping ablations were performed. After the dogs were euthanized, the tumors were harvested, sectioned along the applicator track, measured and photographed. Measurements of ablation zone were performed on gross specimen. Histopathology and viability staining was performed using hematoxylin and eosin (H&E) and nicotinamide adenine dinucleotide hydrogen (NADH) staining. Results Gross pathology confirmed well-circumscribed ablation zone with sharp boundaries between thermally ablated tumor in the center surrounded by viable tumor tissue. When a single applicator was used, the greatest ablation diameters ranged from 12 mm at the lowest dose (10 W, 60 sec) to 26 mm at the highest dose (15 W, 180 sec). Multiple applicators created ablation zones of up to 42 mm in greatest diameter (with the lasers operating at 15 W for 120 sec). Conclusions The new 980-nm diode laser and internally cooled applicator effectively creates large ellipsoid thermal ablations in less than 3 minutes. PMID:20346883

  1. Monolithic Ge-on-Si lasers for large-scale electronic-photonic integration

    NASA Astrophysics Data System (ADS)

    Liu, Jifeng; Kimerling, Lionel C.; Michel, Jurgen

    2012-09-01

    A silicon-based monolithic laser source has long been envisioned as a key enabling component for large-scale electronic-photonic integration in future generations of high-performance computation and communication systems. In this paper we present a comprehensive review on the development of monolithic Ge-on-Si lasers for this application. Starting with a historical review of light emission from the direct gap transition of Ge dating back to the 1960s, we focus on the rapid progress in band-engineered Ge-on-Si lasers in the past five years after a nearly 30-year gap in this research field. Ge has become an interesting candidate for active devices in Si photonics in the past decade due to its pseudo-direct gap behavior and compatibility with Si complementary metal oxide semiconductor (CMOS) processing. In 2007, we proposed combing tensile strain with n-type doping to compensate the energy difference between the direct and indirect band gap of Ge, thereby achieving net optical gain for CMOS-compatible diode lasers. Here we systematically present theoretical modeling, material growth methods, spontaneous emission, optical gain, and lasing under optical and electrical pumping from band-engineered Ge-on-Si, culminated by recently demonstrated electrically pumped Ge-on-Si lasers with >1 mW output in the communication wavelength window of 1500-1700 nm. The broad gain spectrum enables on-chip wavelength division multiplexing. A unique feature of band-engineered pseudo-direct gap Ge light emitters is that the emission intensity increases with temperature, exactly opposite to conventional direct gap semiconductor light-emitting devices. This extraordinary thermal anti-quenching behavior greatly facilitates monolithic integration on Si microchips where temperatures can reach up to 80 C during operation. The same band-engineering approach can be extended to other pseudo-direct gap semiconductors, allowing us to achieve efficient light emission at wavelengths previously considered inaccessible.

  2. Fiber Bragg grating in large-mode-area fiber for high power fiber laser applications.

    PubMed

    Mohammed, Waleed; Gu, Xijia

    2010-10-01

    Fiber Bragg gratings (FBGs) are indispensable components in the design of monolithic high-power fiber lasers. As the laser power scales up, the adoption of larger-mode-area fibers with high V numbers poses new challenges for FBG design and fabrication. In this paper, we present the simulation, fabrication, and measurement of the FBGs inscribed on large-mode-area fibers. The simulation used the T-matrix approach to calculate the spectral response of the FBG that matched well with the measured spectra. The observed fringes in the reflection spectrum are explained by the interference between the low-order modes that were also confirmed with the simulation. Some unique features of the FBG and their potential applications are discussed. PMID:20885465

  3. Multispectral laser-induced fluorescence imaging system for large biological samples

    NASA Astrophysics Data System (ADS)

    Kim, Moon S.; Lefcourt, Alan M.; Chen, Yud-Ren

    2003-07-01

    A laser-induced fluorescence imaging system developed to capture multispectral fluorescence emission images simultaneously from a relatively large target object is described. With an expanded, 355-nm Nd:YAG laser as the excitation source, the system captures fluorescence emission images in the blue, green, red, and far-red regions of the spectrum centered at 450, 550, 678, and 730 nm, respectively, from a 30-cm-diameter target area in ambient light. Images of apples and of pork meat artificially contaminated with diluted animal feces have demonstrated the versatility of fluorescence imaging techniques for potential applications in food safety inspection. Regions of contamination, including sites that were not readily visible to the human eye, could easily be identified from the images.

  4. Asymmetric dihedral angle offsets for large-size lunar laser ranging retroreflectors

    NASA Astrophysics Data System (ADS)

    Otsubo, Toshimichi; Kunimori, Hiroo; Noda, Hirotomo; Hanada, Hideo; Araki, Hiroshi; Katayama, Masato

    2011-08-01

    The distribution of two-dimensional velocity aberration is off-centered by 5 to 6 microradians in lunar laser ranging, due to the stable measurement geometry in the motion of the Earth and the Moon. The optical responses of hollow-type retroreflectors are investigated through numerical simulations, especially focusing on large-size, single-reflector targets that can ultimately minimize the systematic error in future lunar laser ranging. An asymmetric dihedral angle offset, i.e. setting unequal angles between the three back faces, is found to be effective for retroreflectors that are larger than 100 mm in diameter. Our numerical simulation results reveal that the optimized return energy increases approximately 3.5 times more than symmetric dihedral angle cases, and the optimized dihedral angle offsets are 0.65-0.8 arcseconds for one angle, and zeroes for the other two angles.

  5. 3D reconstruction of large target by range gated laser imaging

    NASA Astrophysics Data System (ADS)

    Li, Sining; Yan, Xu; Wang, Wei; Zhang, Dayong; Lu, Wei

    2014-11-01

    We have developed a whole set of range gated laser imaging system with ~3km maximum acquisition distance, the system uses a Nd:YAG electro-optical Q-switched 532nm laser as transmitter, a double micro channel plate as gated sensor, all the components are controlled by the a trigger control unit with accuracy of subnanosecond. A imaging scheme is designed for imaging the large building ~500m away, and a sequence of images are obtained in the experiment, which are the basic data for 3D reconstruction; to improve the range resolution, we study the temporal distribution of intensity of the received signal, and use centroid algorithm for data processing. We compare the 3D image with the theoretical model, and the results are corresponding.

  6. The proceedings of the 1st international workshop on laboratory astrophysics experiments with large lasers

    SciTech Connect

    Remington, B.A.; Goldstein, W.H. [eds.] [eds.

    1996-08-09

    The world has stood witness to the development of a number of highly sophisticated and flexible, high power laser facilities (energies up to 50 kJ and powers up to 50 TW), driven largely by the world-wide effort in inertial confinement fusion (ICF). The charter of diagnosing implosions with detailed, quantitative measurements has driven the ICF laser facilities to be exceedingly versatile and well equipped with diagnostics. Interestingly, there is considerable overlap in the physics of ICF and astrophysics. Both typically involve compressible radiative hydrodynamics, radiation transport, complex opacities, and equations of state of dense matter. Surprisingly, however, there has been little communication between these two communities to date. With the recent declassification of ICF in the USA, and the approval to commence with construction of the next generation ``superlasers``, the 2 MJ National Ignition Facility in the US, and its equivalent, the LMJ laser in France, the situation is ripe for change. . Given the physics similarities that exist between ICF and astrophysics, one strongly suspects that there should exist regions of overlap where supporting research on the large lasers could be beneficial to the astrophysics community. As a catalyst for discussions to this end, Lawrence Livermore National Laboratory sponsored this workshop. Approximately 100 scientists attended from around the world, representing eight countries: the USA, Canada, UK, France, Germany, Russia, Japan, and Israel. A total of 30 technical papers were presented. The two day workshop was divided into four sessions, focusing on nonlinear hydrodynamics, radiative hydrodynamics, radiation transport, and atomic physics-opacities. Copies of the presentations are contained in these proceedings.

  7. Metal optics in CO2 laser fusion systems

    Microsoft Academic Search

    W. H. Reichelt; D. J. Blevins; W. C. Turner

    1977-01-01

    Large-aperture, short-pulsed CO2 laser systems have been developed to investigate the feasibility of laser-driven fusion. Metal mirrors play an important role in such systems as they are compatible with the existing materials limitations of energetic pulses; electroplated copper seems to be the best configuration for mirror structure. Fabrication techniques such as single-point diamond turning are cost- and time-effective, and applicable

  8. Coded Aperture Imaging for Fluorescent X-rays-Biomedical Applications

    SciTech Connect

    Haboub, Abdel; MacDowell, Alastair; Marchesini, Stefano; Parkinson, Dilworth

    2013-06-01

    Employing a coded aperture pattern in front of a charge couple device pixilated detector (CCD) allows for imaging of fluorescent x-rays (6-25KeV) being emitted from samples irradiated with x-rays. Coded apertures encode the angular direction of x-rays and allow for a large Numerical Aperture x- ray imaging system. The algorithm to develop the self-supported coded aperture pattern of the Non Two Holes Touching (NTHT) pattern was developed. The algorithms to reconstruct the x-ray image from the encoded pattern recorded were developed by means of modeling and confirmed by experiments. Samples were irradiated by monochromatic synchrotron x-ray radiation, and fluorescent x-rays from several different test metal samples were imaged through the newly developed coded aperture imaging system. By choice of the exciting energy the different metals were speciated.

  9. Intense-laser generated fast electron transport in a large preplasma created by a long pulse laser

    Microsoft Academic Search

    T. Yabuuchi; M. S. Wei; B. S. Paradkar; J. A. King; F. N. Beg; R. B. Stephens; M. Hatakeyama; N. Nakanii; H. Habara; K. Mima; K. A. Tanaka

    2009-01-01

    Understanding the generation and transport of fast electrons from intense laser-matter interactions is crucial for the Fast Ignition scheme. It has been shown that the plasma associated with the intrinsic prepulse of the intense laser light affects the fast electron generation as well as the fast electron transport. A short pulse laser experiment investigating these effects was carried out with

  10. Exploiting multi-scale parallelism for large scale numerical modelling of laser wakefield accelerators

    NASA Astrophysics Data System (ADS)

    Fonseca, R. A.; Vieira, J.; Fiuza, F.; Davidson, A.; Tsung, F. S.; Mori, W. B.; Silva, L. O.

    2013-12-01

    A new generation of laser wakefield accelerators (LWFA), supported by the extreme accelerating fields generated in the interaction of PW-Class lasers and underdense targets, promises the production of high quality electron beams in short distances for multiple applications. Achieving this goal will rely heavily on numerical modelling to further understand the underlying physics and identify optimal regimes, but large scale modelling of these scenarios is computationally heavy and requires the efficient use of state-of-the-art petascale supercomputing systems. We discuss the main difficulties involved in running these simulations and the new developments implemented in the OSIRIS framework to address these issues, ranging from multi-dimensional dynamic load balancing and hybrid distributed/shared memory parallelism to the vectorization of the PIC algorithm. We present the results of the OASCR Joule Metric program on the issue of large scale modelling of LWFA, demonstrating speedups of over 1 order of magnitude on the same hardware. Finally, scalability to over 106 cores and sustained performance over 2 P Flops is demonstrated, opening the way for large scale modelling of LWFA scenarios.

  11. Huygens--Fresnel--Kirchhoff wave-front diffraction formulation: paraxial and exact Gaussian laser beams

    SciTech Connect

    Kraus, H.G. (Idaho National Engineering Laboratory, EG G Idaho Incorporated, P.O. Box 1625, Idaho Falls, Idaho 83415 (US))

    1990-01-01

    The Huygens--Fresnel diffraction integral has been formulated for incident Gaussian laser beams by using the Kirchhoff obliquity factor with the wave front instead of the aperture plane as the surface of integration. Accurate numerical-integration calculations were used to investigate the Fresnel field diffraction region for the much-studied case of a circular aperture. It is shown that the classical aperture-plane formulation becomes inaccurate when the wave front, as truncated at the aperture, has any degree of curvature to it, whereas the newly developed wave-front formulation produces accurate results for as much as one aperture diameter behind the aperture plane. The wave-front diffraction integral was developed for both the classical paraxial and the recently developed exact solutions to the scalar wave equation for a Gaussian beam. Detailed comparisons of these two diffraction solutions show that they are essentially identical for the typical laboratory laser. The typical laboratory laser is defined as having a wavelength in the near-infrared-through-visible range, a beam diameter as large as several millimeters, and a beam divergence angle as large as several milliradians.

  12. Large-Spot Material Interactions with a High-Power Solid-State Laser Beam

    SciTech Connect

    Boley, C D; Fochs, S N; Rubenchik, A M

    2008-08-06

    We study the material interactions produced by the beam of a 25-kW solid-state laser, in experiments characterized by relatively large spot sizes ({approx}3 cm) and the presence of airflow. The targets are iron or aluminum slabs, of thickness 1 cm. In the experiments with iron, we show that combustion plays an important role in heating the material. In the experiments with aluminum, we observe a sharp transition from no melting to complete melt-through as the intensity on target increases. A layer of paint greatly reduces the requirements for melt-through. We explain these effects and incorporate them into an overall computational model.

  13. Large-solid-angle illuminators for extreme ultraviolet lithography with laser plasmas

    SciTech Connect

    Kubiak, G.D.; Tichenor, D.A. [Sandia National Labs., Livermore, CA (United States); Sweatt, W.C.; Chow, W.W. [Sandia National Labs., Albuquerque, NM (United States)

    1995-06-01

    Laser Plasma Sources (LPSS) of extreme ultraviolet radiation are an attractive alternative to synchrotron radiation sources for extreme ultraviolet lithography (EUVL) due to their modularity, brightness, and modest size and cost. To fully exploit the extreme ultraviolet power emitted by such sources, it is necessary to capture the largest possible fraction of the source emission half-sphere while simultaneously optimizing the illumination stationarity and uniformity on the object mask. In this LDRD project, laser plasma source illumination systems for EUVL have been designed and then theoretically and experimentally characterized. Ellipsoidal condensers have been found to be simple yet extremely efficient condensers for small-field EUVL imaging systems. The effects of aberrations in such condensers on extreme ultraviolet (EUV) imaging have been studied with physical optics modeling. Lastly, the design of an efficient large-solid-angle condenser has been completed. It collects 50% of the available laser plasma source power at 14 nm and delivers it properly to the object mask in a wide-arc-field camera.

  14. A Faraday isolator with a square optical aperture

    NASA Astrophysics Data System (ADS)

    Mironov, ?vgeniy ?.; Starobor, ?lexey V.; Voitovich, ?lexander V.; Palashov, ?leg V.

    2015-03-01

    A Faraday isolator with a square magneto-optical element is proposed and investigated. It is shown that the device has better isolation ratio and higher level of maximal operating power over conventional isolators with a round aperture when used in high-power laser systems with a square profile of beam intensity distribution.

  15. Large Aperture Systems: 2000-2004

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This custom bibliography from the NASA Scientific and Technical Information Program lists a sampling of records found in the NASA Aeronautics and Space Database. The scope of this topic includes technologies for next generation astronomical telescopes and detectors. This area of focus is one of the enabling technologies as defined by NASA s Report of the President s Commission on Implementation of United States Space Exploration Policy, published in June 2004.

  16. Time-of-flight detection of monoatomic ions generated by femtosecond laser ablation from large molecules

    NASA Astrophysics Data System (ADS)

    Kato, Toshiyuki; Kobayashi, Tohru; Kurata-Nishimura, Mizuki; Okamura-Oho, Yuko; Sano, Takuma; Oyama, Rieko; Matsumura, Yonehiro; Yamamoto, Hiroshi; Hayashizaki, Yoshihide; Matsuo, Yukari; Kawai, Jun

    2008-03-01

    Single-shot femtosecond laser ablation (fsLA) was applied to large molecules to analyze elemental composition through out wide range of mass-to-charge ratio. Molecular samples such as Eu-DNA and cosmetic powders were atomized and ionized simultaneously by the single-shot fsLA and positive atomic ions were detected using a reflectron time-of-flight (TOF) mass spectrometer. The ratios among the signal intensity of the detected stable isotopes including 151,153Eu and 182-184,186W were consistent with the respective natural abundances of the isotopes. The results demonstrate the feasibility of the fsLA-TOF method as a high-throughput analytical technique for elemental microanalysis of large molecular samples in small quantities.

  17. A low-noise large dynamic-range readout suitable for laser spectroscopy with photodiodes

    NASA Astrophysics Data System (ADS)

    Pullia, A.; Sanvito, T.; Potenza, M. A.; Zocca, F.

    2012-10-01

    An original low-noise large dynamic-range readout system for optical light spectroscopy with PIN diodes is presented. The front-end circuit is equipped with a smart device for automatic cancellation of the large dc offset brought about by the photodiode current. This device sinks away the exact amount of dc current from the preamplifier input, yielding auto zeroing of the output-voltage offset, while introducing the minimum electronic noise possible. As a result the measurement dynamic-range is maximized. Moreover, an auxiliary inspection point is provided which precisely tracks the dc component of the photodiode current. This output allows for precise beam alignment and may also be used for diagnostic purposes. The excellent gain stability and linearity make the circuit perfectly suited for optical-light pulse spectroscopy. Applications include particle sizing in the 100 nm range, two-dimensional characterization of semiconductor detectors, ultra-precise characterization of laser beam stability, confocal microscopy.

  18. Scanning reflection and transmission photometer for large high power laser optics

    SciTech Connect

    Thomas, N.L.; Robinson, W.L.; Wirtenson, G.R.; Wallerstein, E.P.

    1981-12-11

    The Nova OTR (overall transmittance/reflectance) photometer operates at 1.064 nm, 528 nm, or 351 nm in order to closely simulate 1st, 2nd and 3rd harmonic frequencies of the Nova fusion laser. The optic is scanned on a large XY carriage while reflectance or transmittance data is taken on-the-fly. The system is controlled by an LSI 11/23 computer which processes the data and prints out the results in hard copy form, or stores data on a memory disk. The detectors are temperature controlled to within +- 0.01/sup 0/C which aids in achieving of an absolute accuracy of +- 0.1 to +- 0.5% of full scale, depending on the operating point. The photometer is capable of scanning a large optic (1 meter in diameter) in 20 to 30 minutes.

  19. Laser-driven, magnetized quasi-perpendicular collisionless shocks on the Large Plasma Device

    SciTech Connect

    Schaeffer, D. B., E-mail: dschaeffer@physics.ucla.edu; Everson, E. T.; Bondarenko, A. S.; Clark, S. E.; Constantin, C. G.; Vincena, S.; Van Compernolle, B.; Tripathi, S. K. P.; Gekelman, W.; Niemann, C. [Department of Physics and Astronomy, University of California - Los Angeles, Los Angeles, California 90095 (United States); Winske, D. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2014-05-15

    The interaction of a laser-driven super-Alfvnic magnetic piston with a large, preformed magnetized ambient plasma has been studied by utilizing a unique experimental platform that couples the Raptor kJ-class laser system [Niemann et al., J. Instrum. 7, P03010 (2012)] to the Large Plasma Device [Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)] at the University of California, Los Angeles. This platform provides experimental conditions of relevance to space and astrophysical magnetic collisionless shocks and, in particular, allows a detailed study of the microphysics of shock formation, including piston-ambient ion collisionless coupling. An overview of the platform and its capabilities is given, and recent experimental results on the coupling of energy between piston and ambient ions and the formation of collisionless shocks are presented and compared to theoretical and computational work. In particular, a magnetosonic pulse consistent with a low-Mach number collisionless shock is observed in a quasi-perpendicular geometry in both experiments and simulations.

  20. Large format imaging detectors for x-ray free-electron-lasers

    NASA Astrophysics Data System (ADS)

    Hartmann, Robert; Epp, Sascha; Gorke, Hubert; Hartmann, Andreas; Hauser, Gnther; Herrmann, Sven; Holl, Peter; Kimmel, Nils; Meidinger, Norbert; Reich, Christian; Rolles, Daniel; Soltau, Heike; Strder, Lothar; Ullrich, Joachim; Weidenspointner, Georg

    2011-06-01

    New generation synchrotron light sources, the X-ray free electron lasers, require a two dimensional focal plane instrumentation to perform X-ray imaging from below 100eV up to 25keV. The instruments have to face the accelerator bunch structure and energy bandwidth which is different for existing (FLASH, Hamburg and LCLS, Menlo Park) and future photon sources (SACLA, Harima and XFEL, Hamburg). Within the frame of the Center for Free Electron Laser Science (CFEL), a joint effort of the Max-Planck Society, DESY and the University of Hamburg, the MPI semiconductor laboratory developed, produced and operated large area X-ray CCD detectors with a format of nearly 60cm2 image area. They show outstanding characteristics: a high readout speed due to a complete parallel signal processing, high and homogeneous quantum efficiency, low signal noise, radiation hardness and a high pixel charge handling capacitance. We will present measurement results which demonstrate the X-ray spectroscopic and imaging capabilities of the fabricated devices. We will also report on the concept and the anticipated properties of the full, large scale system. The implementation of the detector into an experimental chamber to perform measurements e.g. of macromolecules in order to determine their structure at atomic resolutions will be shown.

  1. Efficient synthetic aperture imaging from a circular aperture with possible application to catheter-based imaging.

    PubMed

    O'Donnell, M; Thomas, L J

    1992-01-01

    Phased-array imaging, including complete dynamic focus, is explored for imaging using a circular aperture. Based on the constraints of catheter-based systems, an efficient synthetic aperture method has been developed for imaging using a single wire connection between the imaging array and external electronics. The method employs a highly sampled array with an element pitch small compared to the acoustic wavelength. On any given firing of the array, however, a large number of channels are electrically connected on both transmission and reception. From firing to firing, one element is dropped and one new element is included, in analogy to a classic linear array system. Using an optimal filtering approach for synthetic aperture reconstruction, a dynamically focused image exhibiting diffraction limited resolution is produced. The results of detailed simulations are presented demonstrating the capabilities of the method. In addition, the prospects for real-time implementation of the reconstruction are discussed. PMID:18267647

  2. Resolution enhancing using cantilevered tip-on-aperture silicon probe in scanning near-field optical microscopy.

    PubMed

    Chang, Won-Seok; Bauerdick, Sven; Jeong, Mun Seok

    2008-09-01

    Scanning near-field optical microscopy (SNOM) achieves a resolution beyond the diffraction limit of conventional optical microscopy systems by utilizing subwavelength aperture probe scanning. A problem associated with SNOM is that the light throughput decreases markedly as the aperture diameter decreases. Apertureless scanning near-field optical microscopes obtain a much better resolution by concentrating the light field near the tip apex. However, a far-field illumination by a focused laser beam generates a large background scattering signal. Both disadvantages are overcome using the tip-on-aperture (TOA) approach, as presented in previous works. In this study, a finite difference time domain analysis of the degree of electromagnetic field enhancement is performed to verify the efficiency of TOA probes. For plasmon enhancement, silver is deposited on commercially available cantilevered SNOM tips with 20 nm thicknesses. To form the aperture and TOA in the probes, electron beam-induced deposition and focused ion beam machining were applied at the end of the sharpened tip. The results show that cantilevered TOA probes were highly efficient for improvements of the resolution of optical and topological measurement of nanostructures. PMID:18579310

  3. Fabrication of Cantilevered Tip-on-Aperture Probe for Enhancing Resolution of Scanning Near-Field Optical Microscopy System

    NASA Astrophysics Data System (ADS)

    Chang, Won-Seok; Jeong, Mun Seok; Kim, Dae-Chul; Kim, Jeongyong

    2007-08-01

    The scanning near-field optical microscopy (SNOM) system achieves a resolution beyond the diffraction limit of the conventional optical microscopy system by subwavelength aperture probe scanning. The problem is that the light throughput decreases very markedly with decreasing aperture diameter. Apertureless scanning near-field optical microscopes obtain a much better resolution by concentrating light field near the tip apex. However, far-field illumination by a focused laser beam generates a large background scattering signal. Both disadvantages are overcome using the tip-on-aperture (TOA) approach presented in previous works. In this study, the fabrication of a cantilevered tip for SNOM and scanning force microscopy (SFM) has been described. The nano-probes are batch-fabricated on a silicon wafer. The Si3N4 has excellent optical transparent characteristics, higher Youngs modulus and yield strength so that it should provide a better probe for SNOM and SFM. For this purpose, a Si3N4 thin film was deposited using low-pressure chemical vapor deposition (LPCVD). To form the aperture and TOA in the probe, we applied focused ion beam (FIB) machining at the end of the sharpened tip. For verification of the efficiency of the micromachined TOA probes, numerical analysis using the finite-difference time domain (FDTD) analysis and experimental measurement using an inverted microscope based the SNOM system were performed.

  4. Multiple Differential Aperture Microscopy

    SciTech Connect

    Chung, Jin-Seok [ORNL; Isa, Saliman Anavami [ORNL; Greene, Virgil [ORNL; Broadwater, Ombreyan Q [ORNL; Liu, W. [Argonne National Laboratory (ANL); Ice, Gene E [ORNL

    2007-01-01

    Differential-aperture X-ray microscopy (DAXM) is a powerful approach to 3D tomography with particular relevance to X-ray microdiffraction. With DAXM, scattering from submicron volumes can be resolved. However, the method is intrinsically a scanning technique where every resolved volume element (voxel) requires at least one area-detector readout. Previous applications of DAXM have used a single wire for knife-edge step profiling. Here, we demonstrate a way to accelerate DAXM measurements using multiple wires. A proof-of-principle experiment with a three-wire prototype showed that the speed of measurements can be tripled, but careful calibrations of wires will be required to maintain the spatial accuracy. In addition, related possibilities for accelerating measurements are briefly discussed.

  5. Wave-front analysis method of circular aperture sampling for collimation testing.

    PubMed

    Zhang, Mingli; Liu, Liren; Wan, Lingyu; Luan, Zhu

    2005-05-10

    A new type of wave-front analysis method for the collimation testing of laser beams is proposed. A concept of wave-front height is defined, and, on this basis, the wave-front analysis method of circular aperture sampling is introduced. The wave-front height of the tested noncollimated wave can be estimated from the distance between two identical fiducial diffraction planes of the sampled wave, and then the divergence is determined. The design is detailed, and the experiment is demonstrated. The principle and experiment results of the method are presented. Owing to the simplicity of the method and its low cost, it is a promising method for checking the collimation of a laser beam with a large divergence. PMID:15943321

  6. Material Measurements Using Groundplane Apertures

    NASA Technical Reports Server (NTRS)

    Komisarek, K.; Dominek, A.; Wang, N.

    1995-01-01

    A technique for material parameter determination using an aperture in a groundplane is studied. The material parameters are found by relating the measured reflected field in the aperture to a numerical model. Two apertures are studied which can have a variety of different material configurations covering the aperture. The aperture cross-sections studied are rectangular and coaxial. The material configurations involved combinations of single layer and dual layers with or without a resistive exterior resistive sheet. The resistivity of the resistive sheet can be specified to simulate a perfect electric conductor (PEC) backing (0 Ohms/square) to a free space backing (infinity Ohms/square). Numerical parameter studies and measurements were performed to assess the feasibility of the technique.

  7. Initiation, Growth and Mitigation of UV Laser Induced Damage in Fused Silica

    SciTech Connect

    Rubenchik, A M; Feit, M D

    2001-12-21

    Laser damage of large fused silica optics initiates at imperfections. Possible initiation mechanisms are considered. We demonstrate that a model based on nanoparticle explosions is consistent with the observed initiation craters. Possible mechanisms for growth upon subsequent laser irradiation, including material modification and laser intensification, are discussed. Large aperture experiments indicate an exponential increase in damage size with number of laser shots. Physical processes associated with this growth and a qualitative explanation of self-accelerated growth is presented. Rapid growth necessitates damage growth mitigation techniques. Several possible mitigation techniques are mentioned, with special emphasis on CO{sub 2} processing. Analysis of material evaporation, crack healing, and thermally induced stress are presented.

  8. Development of large scale production of Nd-doped phosphate glasses for megajoule-scale laser systems

    SciTech Connect

    Ficini, G. [Centre d`Etudes de Limeil-Valenton, Villeneuve, St. Georges (France); Campbell, J.H. [Lawrence Livermore National Lab., CA (United States)

    1996-05-01

    Nd-doped phosphate glasses are the preferred gain medium for high-peak-power lasers used for Inertial Confinement Fusion research because they have excellent energy storage and extraction characteristics. In addition, these glasses can be manufactured defect-free in large sizes and at relatively low cost. To meet the requirements of the future mega-joule size lasers, advanced laser glass manufacturing methods are being developed that would enable laser glass to be continuously produced at the rate of several thousand large (790 x 440 x 44 mm{sup 3}) plates of glass per year. This represents more than a 10 to 100-fold improvement in the scale of the present manufacturing technology.

  9. Aperture synthesis using orbiting telescopes

    NASA Technical Reports Server (NTRS)

    Kuiper, T. B. H.; Synnott, S. P.; Linfield, R. P.; Resch, G. M.; Tubbs, E. F.

    1985-01-01

    A study was carried out to determine the feasibility, with current technology, of performing aperture synthesis using two telescopes orbiting the earth in coordinated orbits separated by approximately 10 m to 1 km. The objective was to determine whether there is a practical alternative to a very large, deployed, servo-controlled submillimeter telescope (i.e., the Large Deployable Reflector) for obtaining high-resolution submillimeter images of astronomical sources. It is found that suitable classes of orbits exist which can provide good UV coverage over the entire sky and the real-time correlation of wideband signals can be performed in orbit using current technology. The most difficult task appears to be the real-time determination of the orientation of the baseline vector in a stable coordinate system. A plausible scheme has been identified for the determination of an arbitrary direction to within 0.003 arcsec in an astrometric coordinate system. This scheme not only makes submillimeter interferometric image reconstruction possible but should also have numerous other applications.

  10. Conceptual design of a large E-beam-pumped KrF laser for ICF commercial applications

    Microsoft Academic Search

    D. B. Harris; L. M. Waganer; D. S. Zuckerman; D. A. Bowers

    1986-01-01

    Two types of KrF lasers appear attractive as a driver for an ICF electric power plant. The original concept uses large electron-beam-pumped amplifiers and pure angular multiplexing to deliver short, shaped pulses to the target. A recently conceived alternate concept uses many small, long-pulse e-beam sustained discharge lasers which transfer their energy through the forward Raman process to a multiplexed

  11. Diffraction of a Laser Beam.

    ERIC Educational Resources Information Center

    Jodoin, Ronald E.

    1979-01-01

    Investigates the effect of the nonuniform irradiance across a laser beam on diffraction of the beam, specifically the Fraunhofer diffraction of a laser beam with a Gaussian irradiance profile as it passes through a circular aperture. (GA)

  12. Bore-sight calibration of the profile laser scanner using a large size exterior calibration field

    NASA Astrophysics Data System (ADS)

    Koska, Bronislav; K?emen, Tom; troner, Martin

    2014-10-01

    The bore-sight calibration procedure and results of a profile laser scanner using a large size exterior calibration field is presented in the paper. The task is a part of Autonomous Mapping Airship (AMA) project which aims to create s surveying system with specific properties suitable for effective surveying of medium-wide areas (units to tens of square kilometers per a day). As is obvious from the project name an airship is used as a carrier. This vehicle has some specific properties. The most important properties are high carrying capacity (15 kg), long flight time (3 hours), high operating safety and special flight characteristics such as stability of flight, in terms of vibrations, and possibility to flight at low speed. The high carrying capacity enables using of high quality sensors like professional infrared (IR) camera FLIR SC645, high-end visible spectrum (VIS) digital camera and optics in the visible spectrum and tactical grade INSGPS sensor iMAR iTracerRT-F200 and profile laser scanner SICK LD-LRS1000. The calibration method is based on direct laboratory measuring of coordinate offset (lever-arm) and in-flight determination of rotation offsets (bore-sights). The bore-sight determination is based on the minimization of squares of individual point distances from measured planar surfaces.

  13. Development and utilization of a laser velocimeter system for a large transonic wind tunnel

    NASA Technical Reports Server (NTRS)

    Freedman, R. J.; Greissing, J. P.

    1982-01-01

    The need for measurements of the velocity flow field about spinner propeller nacelle configurations at Mach numbers to 0.8 was met by a specially developed laser velocimeter system. This system, which uses an argon ion laser and 4 beam 2 color optics, was required to operate in the hostile environment associated with the operation of a large transonic wind tunnel. To overcome the conditions present in locating the sensitive optics in close proximity to the wind tunnel, an isolation system was developed. The system protects the velocimeter from the high vibrations, elevated temperatures, destructive acoustic pressures and low atmospheric pressures attendant with the operation of the wind tunnel. The system was utilized to map the flow field in front of, behind and in between the rotating blades of an advanced swept blade propeller model at a Mach number of 0.8. The data collected by the system will be used to correlate and verify computer analyses of propeller nacelle flow fields and propeller performance.

  14. Fracture-aperture alteration induced by calcite precipitation

    NASA Astrophysics Data System (ADS)

    Jones, T.; Detwiler, R. L.

    2013-12-01

    Mineral precipitation significantly alters the transport properties of fractured rock. Chemical solubility gradients that favor precipitation induce mineral growth, which decreases the local aperture and alters preferential flow paths. Understanding the resulting development of spatial heterogeneities is necessary to predict the evolution of transport properties in the subsurface. We present experimental results that quantify the relationship between mineral precipitation and aperture alteration in a transparent analog fracture, 7.62cm x 7.62cm, with a uniform aperture of ~200 ?m. Prior to flow experiments, a pump circulated a super-saturated calcite solution over the bottom glass, coating the glass surface with calcite. This method of seeding resulted in clusters of calcite crystals with large reactive surface area and provided micro-scale variability in the aperture field. A continuous flow syringe pump injected a reactive fluid into the fracture at 0.5 ml/min. The fluid was a mixture of sodium bicarbonate (NaHCO3, 0.02M) and calcium chloride (CaCl2 0.0004M) with a saturation index, ?, of 8.51 with respect to calcite. A strobed LED panel backlit the fracture and a high-resolution CCD camera monitored changes in transmitted light intensity. Light transmission techniques provided a quantitative measurement of fracture aperture over the flow field. Results from these preliminary experiments showed growth near the inlet of the fracture, with decreasing precipitation rates in the flow direction. Over a period of two weeks, the fracture aperture decreased by 17% within the first 4mm of the inlet. Newly precipitated calcite bridged individual crystal clusters and smoothed the reacting surface. This observation is an interesting contradiction to the expectation of surface roughening induced by mineral growth. Additionally, the aperture decreased uniformly across the width of the fracture due to the initial aperture distribution. Future experiments of precipitation within variable-aperture fields will investigate the dependency of growth patterns on heterogeneous aperture distributions. (a) Aperture strain (?b/bi) after 14 days. Precipitation is concentrated near the inlet and decreases in the flow direction. (b) Width-averaged profiles of the initial and final aperture field show changes in aperture and smoothing that results from calcite precipitation between the initial discrete crystals.

  15. Time-resolved pattern evolution in a large-aperture class A laser Nonlinear Dynamics and Chaos Group. Universidad Rey Juan Carlos, 28933 Mostoles, Madrid, Spain

    E-print Network

    Rey Juan Carlos, Universidad

    and Chaos Group. Universidad Rey Juan Carlos, 28933 Mostoles, Madrid, Spain J. M. Guerra Departamento de Optica, Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, 28040 Madrid, Spain Received 15

  16. Tunable fiber laser using fiber Bragg gratings integrated carbon fiber composite with large tuning range

    NASA Astrophysics Data System (ADS)

    Liaw, Shien-Kuei; Shin, Chow-Shing; Wu, Wen-Fang

    2014-12-01

    A wide-tuning range linear cavity C+L band tunable fiber laser is proposed in this paper. By using 3-point bending device to facilitate wavelength tuning of fiber Bragg gratings (FBGs), a scheme with two parallel strain-tunable FBGs (TFBGs) is demonstrated in L band operation. A large tuning range of over 22.5 nm with 0.1 nm precise resolution for each TFBG is obtained. The overlapping tuning range for two TFBGs is from 1564 to 1600.5 nm with 2 dB power variation. Using 10 M Erbium-doped fiber (EDF) and 100 mW pumping power, the stable lasing output power is measured at 1582.0 nm with threshold pump power and side mode suppression ratio (SMSR) of 10 mW and 50 dB, respectively. And the measured slope efficiency is 11.5% corresponding to quantum efficiency of 12.3%.

  17. Large-Scale Hollow Retroreflectors for Lunar Laser Ranging at Goddard Space Flight Center

    NASA Astrophysics Data System (ADS)

    Preston, Alix M.

    2012-05-01

    Laser ranging to the retroreflector arrays placed on the lunar surface by the Apollo astronauts and the Soviet Luna missions have dramatically increased our understanding of gravitational physics along with Earth and Moon geophysics, geodesy, and dynamics. Although the precision of the range measurements has historically been limited by the ground station capabilities, advances in the APOLLO instrument at the Apache Point facility in New Mexico is beginning to be limited by errors associated with the lunar arrays. We report here on efforts at Goddard Space Flight Center to develop the next generation of lunar retroreflectors. We will describe a new facility that is being used to design, assemble, and test large-scale hollow retroreflectors. We will also describe results from investigations into various bonding techniques used to assemble the open corner cubes and mirror coatings that have dust mitigation properties.

  18. Laser radar-based measuring systems for large scale assembly applications

    NASA Astrophysics Data System (ADS)

    Kaisto, Ilkka P.; Kostamovaara, Juha T.; Manninen, Markku; Myllylae, Risto A.

    1993-02-01

    Long term research on pulsed time-of-flight laser distance measurement has opened new dimensions in measurement applications, from large scale assembly in shipbuilding to precast concrete element production, leading to improved quality control and more efficient manufacturing. The ACMAN 3-D coordinate meters measure the coordinate values of a point in terms of radial distance and two angles directly from natural surfaces. The accuracy of coordinate values is 1 mm (1-sigma) in the measurement range of 3 - 30 m. The functions of the automatic ACMAN 200 include pointing with a red beam, automatic searching and measuring of marked target points and shape measurement by scanning. Coaxial optics of measuring, pointing and aiming provide the optimal measurement geometry. ACMAN 3-D coordinate meters are integrated into the ACMAN 1000 and ACMAN 2000 series dimension control systems.

  19. Large-Scale Hollow Retroreflectors for Lunar Laser Ranging at Goddard Space Flight Center

    NASA Technical Reports Server (NTRS)

    Preston, Alix

    2012-01-01

    Laser ranging to the retroreflector arrays placed on the lunar surface by the Apollo astronauts and the Soviet Luna missions have dramatically increased our understanding of gravitational physics along with Earth and Moon geophysics, geodesy, and dynamics. Although the precision of the range measurements has historically been limited by the ground station capabilities, advances in the APOLLO instrument at the Apache Point facility in New Mexico is beginning to be limited by errors associated with the lunar arrays. We report here on efforts at Goddard Space Flight Center to develop the next generation of lunar retroreflectors. We will describe a new facility that is being used to design, assemble, and test large-scale hollow retroreflectors. We will also describe results from investigations into various bonding techniques used to assemble the open comer cubes and mirror coatings that have dust mitigation properties.

  20. Large-scale in vivo femtosecond laser neurosurgery screen reveals small-molecule enhancer of regeneration

    PubMed Central

    Samara, Chrysanthi; Rohde, Christopher B.; Gilleland, Cody L.; Norton, Stephanie; Haggarty, Stephen J.; Yanik, Mehmet Fatih

    2010-01-01

    Discovery of molecular mechanisms and chemical compounds that enhance neuronal regeneration can lead to development of therapeutics to combat nervous system injuries and neurodegenerative diseases. By combining high-throughput microfluidics and femtosecond laser microsurgery, we demonstrate for the first time large-scale in vivo screens for identification of compounds that affect neurite regeneration. We performed thousands of microsurgeries at single-axon precision in the nematode Caenorhabditis elegans at a rate of 20seconds per animal. Following surgeries, we exposed the animals to a hand-curated library of approximately one hundred small molecules and identified chemicals that significantly alter neurite regeneration. In particular, we found that the PKC kinase inhibitor staurosporine strongly modulates regeneration in a concentration- and neuronal type-specific manner. Two structurally unrelated PKC inhibitors produce similar effects. We further show that regeneration is significantly enhanced by the PKC activator prostratin. PMID:20937901

  1. Triple-clad large-pitch fibers for compact high-power pulsed fiber laser systems.

    PubMed

    Gaida, Christian; Stutzki, Fabian; Jansen, Florian; Otto, Hans-Jrgen; Eidam, Tino; Jauregui, Cesar; de Vries, Oliver; Limpert, Jens; Tnnermann, Andreas

    2014-01-15

    We present a novel ytterbium (Yb)-doped large-pitch fiber design with significantly increased pump absorption and higher energy storage/gain per unit length, which enables high-peak-power fiber laser systems with smaller footprints. Up to now index matching between core and surrounding material in microstructured fibers was achieved by co-doping the active core region with fluorine. Here we carry out the index matching by passively doping the cladding with germanium, thus raising its index of refraction. Hence, the fluorine in the core can be omitted, which leads to an effective increase of the core doping concentration, while detrimental effects such as photo-darkening and lifetime quenching are avoided by maintaining the bulk Yb concentration. Experiments and simulations show that a gain higher than 50 dB/m and an output average power higher than 100 W with excellent beam quality are feasible even with a fiber length of only 40 cm. PMID:24562108

  2. Percutaneous laser-induced interstitial thermotherapy (LITT) for the treatment of very large uterine leiomyomas

    NASA Astrophysics Data System (ADS)

    Chapman, Roxana

    1997-05-01

    The success of treating tumors of the liver under local anaesthesia and ultrasound and computered tomography control by mens of the diode laser of 810 nm wavelength with fiber splitter and multiple fibers suggested this form of LITT might be suitable for the treatment of very large leiomyomas where laparoscopy was not possible. The immediate effect of LITT was to produce a large volume of coagulation within the myomas, to destroy the oestrogen receptors and to coagulate the surrounding blood vessels. After one month the coagulated volume had been converted into a jelly-like substance and the zone surrounding this had started to degenerate because of the destruction of its blood vessels which had resulted in local tissue anoxia. Three months later the central coagulum and surrounding zone had been partially absorbed and the whole volume of myoma treated had shrunk to a quarter of the original size. It has thus been shown that a minimally invasive method for the destruction of very large uterine leiomyomas can be safely performed, but further research is required before its general adoption.

  3. Sparse aperture endoscope

    DOEpatents

    Fitch, Joseph P. (Livermore, CA)

    1999-07-06

    An endoscope which reduces the volume needed by the imaging part thereof, maintains resolution of a wide diameter optical system, while increasing tool access, and allows stereographic or interferometric processing for depth and perspective information/visualization. Because the endoscope decreases the volume consumed by imaging optics such allows a larger fraction of the volume to be used for non-imaging tools, which allows smaller incisions in surgical and diagnostic medical applications thus produces less trauma to the patient or allows access to smaller volumes than is possible with larger instruments. The endoscope utilizes fiber optic light pipes in an outer layer for illumination, a multi-pupil imaging system in an inner annulus, and an access channel for other tools in the center. The endoscope is amenable to implementation as a flexible scope, and thus increases the utility thereof. Because the endoscope uses a multi-aperture pupil, it can also be utilized as an optical array, allowing stereographic and interferometric processing.

  4. Sparse aperture endoscope

    DOEpatents

    Fitch, J.P.

    1999-07-06

    An endoscope is disclosed which reduces the volume needed by the imaging part, maintains resolution of a wide diameter optical system, while increasing tool access, and allows stereographic or interferometric processing for depth and perspective information/visualization. Because the endoscope decreases the volume consumed by imaging optics such allows a larger fraction of the volume to be used for non-imaging tools, which allows smaller incisions in surgical and diagnostic medical applications thus produces less trauma to the patient or allows access to smaller volumes than is possible with larger instruments. The endoscope utilizes fiber optic light pipes in an outer layer for illumination, a multi-pupil imaging system in an inner annulus, and an access channel for other tools in the center. The endoscope is amenable to implementation as a flexible scope, and thus increases it's utility. Because the endoscope uses a multi-aperture pupil, it can also be utilized as an optical array, allowing stereographic and interferometric processing. 7 figs.

  5. Interferometric synthetic aperture microscopy

    PubMed Central

    Ralston, Tyler S.; Marks, Daniel L.; Carney, P. Scott; Boppart, Stephen A.

    2014-01-01

    State-of-the-art methods in high-resolution three-dimensional optical microscopy require that the focus be scanned through the entire region of interest. However, an analysis of the physics of the lightsample interaction reveals that the Fourier-space coverage is independent of depth. Here we show that, by solving the inverse scattering problem for interference microscopy, computed reconstruction yields volumes with a resolution in all planes that is equivalent to the resolution achieved only at the focal plane for conventional high-resolution microscopy. In short, the entire illuminated volume has spatially invariant resolution, thus eliminating the compromise between resolution and depth of field. We describe and demonstrate a novel computational image-formation technique called interferometric synthetic aperture microscopy (ISAM). ISAM has the potential to broadly impact real-time three-dimensional microscopy and analysis in the fields of cell and tumour biology, as well as in clinical diagnosis where in vivo imaging is preferable to biopsy. PMID:25635181

  6. Precise and high-throughput femtopulse laser mask repair of large defects

    NASA Astrophysics Data System (ADS)

    White, Roy; LeClaire, Jeff; Robinson, Tod; Dinsdale, Andrew; Bozak, Ron; Lee, David A.

    2006-10-01

    As mask complexity has increased and design rules continued to shrink, the manufacturing cost per mask has steadily increased as well. Studies also show that defects are the number one issue for mask yield. Smaller defects are typically addressed through process development, or through photomask repair. The occurrence of large defects often may only be further reduced through use of expensive clean room improvements, like SMIF handling systems. The impact of each large defect therefore increases while the feasibility in their repair decreases as they can span a large number of adjoining densely packed patterns. The presence of sub-resolution features such as scatter bars and the increasing use of embedded phase-shifting masks also complicates the timely repair of such defects. Existing mask repair techniques such as nanomachining, electron beam, or focused ion beam are challenged to produce high yield repairs on such large defects within a reasonable timeframe. Often very complex repairs may in fact take longer than a rewrite of the mask! Deep UV (DUV) femtosecond pulse laser mask repair provides a unique solution to this defect repair need. Methods and results are discussed for the process optimization for the removal of large (5?m) area repair on both Cr and MoSi absorber films on quartz. Additionally, high repair throughput results are shown for unknown contamination removal, and reproduction of >=1 ?m complex unconnected patterns in a single repair run lasting a matter of minutes. Closed-loop CD feedback in-situ with the iterative repair process for such structures can readily result in an edge placement control within +/-15 nm. Prior iterative CD closed-loop repairs on specific structures have reliably yielded results within +/-10 nm, as confirmed by AIMS CD error, even after aggressive mask wet clean. The nanometer scale dimensional resolution and repeatability of such repairs is shown with the use of sub-pixel resolution automated pattern reconstruction using integrated high-NA DUV microscope imaging.

  7. Improved Accuracy for Interferometric Radar Images Using Polarimetric Radar and Laser Altimetry Data

    E-print Network

    Evans, Brian L.

    Improved Accuracy for Interferometric Radar Images Using Polarimetric Radar and Laser Altimetry and under most weather conditions. Both interferometric and stereo synthetic aperture radar (SAR) data can be used to determine topography over large areas, but interferometric SAR (INSAR) data provides the best

  8. COMPONENTS OF LASER SYSTEMS AND PROCESSES OCCURRING IN THEM: Fast-response system for stabilization of the axis of the angular distribution of laser radiation

    NASA Astrophysics Data System (ADS)

    Vinogradov, E. G.; Glebova, S. N.; Pavlov, N. V.; Razhenkov, E. T.

    1988-09-01

    A fast-acting system for stabilization of the axis of the angular distribution of radiation from a continuous-flow CO2 laser is considered. The results of a simulation experiment are reported: they show that it is possible to suppress, by 24-28 dB, fluctuations of the position of the axis in the spectral range 0-20 Hz. This makes the proposed system a promising method for large-aperture laser beams.

  9. Near-term feasibility demonstration of laser power beaming

    SciTech Connect

    Friedman, H.W.

    1994-01-01

    A mission to recharge batteries of satellites in geostationary orbits (geosats) may be a commercially viable application which could be achieved with laser systems somewhat larger than present state-of-the-art. The lifetime of batteries on geosats is limited by repetitive discharge cycles which occur when the satellites are eclipsed by the earth during the spring and fall equinoxes. By coupling high power lasers with modern, large aperture telescopes and laser guide star adaptive optics systems, present day communications satellites could be targeted. It is important that a near term demonstration of laser power beaming be accomplished using lasers in the kilowatt range so that issues associated with high average power be addressed. The Laser Guide Star Facility at LLNL has all the necessary subsystems needed for such a near term demonstration, including high power lasers for both the power beam and guide star, beam directors and satellite tracking system.

  10. Gradient polymer-disposed liquid crystal single layer of large nematic droplets for modulation of laser light.

    PubMed

    Hadjichristov, Georgi B; Marinov, Yordan G; Petrov, Alexander G

    2011-06-01

    The light modulating ability of gradient polymer-disposed liquid crystal (PDLC) single layer of large droplets formed by nematic E7 in UV-cured polymer NOA65 is studied. Operating at relatively low voltages, such PDLC film with a of thickness 10-25??m and droplet size up to 50??m exhibits a good contrast ratio and is capable of producing a large phase shift for the propagating coherent light. For a linearly polarized He-Ne laser (?=633?nm), an electrically commanded phase shift as large as ?/2 can be obtained by the large-droplet region of the film. The electrically produced phase shift and its spatial profile controlled by the thickness of the gradient PDLC single layers of large nematic droplets can be useful for tunable spatial light modulators and other devices for active control of laser light. PMID:21629309

  11. Bistatic synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Yates, Gillian

    Synthetic aperture radar (SAR) allows all-weather, day and night, surface surveillance and has the ability to detect, classify and geolocate objects at long stand-off ranges. Bistatic SAR, where the transmitter and the receiver are on separate platforms, is seen as a potential means of countering the vulnerability of conventional monostatic SAR to electronic countermeasures, particularly directional jamming, and avoiding physical attack of the imaging platform. As the receiving platform can be totally passive, it does not advertise its position by RF emissions. The transmitter is not susceptible to jamming and can, for example, operate at long stand-off ranges to reduce its vulnerability to physical attack. This thesis examines some of the complications involved in producing high-resolution bistatic SAR imagery. The effect of bistatic operation on resolution is examined from a theoretical viewpoint and analytical expressions for resolution are developed. These expressions are verified by simulation work using a simple 'point by point' processor. This work is extended to look at using modern practical processing engines for bistatic geometries. Adaptations of the polar format algorithm and range migration algorithm are considered. The principal achievement of this work is a fully airborne demonstration of bistatic SAR. The route taken in reaching this is given, along with some results. The bistatic SAR imagery is analysed and compared to the monostatic imagery collected at the same time. Demonstrating high-resolution bistatic SAR imagery using two airborne platforms represents what I believe to be a European first and is likely to be the first time that this has been achieved outside the US (the UK has very little insight into US work on this topic). Bistatic target characteristics are examined through the use of simulations. This also compares bistatic imagery with monostatic and gives further insight into the utility of bistatic SAR.

  12. Nonlinear laser lithography for indefinitely large-area nanostructuring with femtosecond pulses

    NASA Astrophysics Data System (ADS)

    ktem, Blent; Pavlov, Ihor; Ilday, Serim; Kalayc?o?lu, Hamit; Rybak, Andrey; Yava?, Seydi; Erdo?an, Mutlu; Ilday, F. mer

    2013-11-01

    Dynamical systems based on the interplay of nonlinear feedback mechanisms are ubiquitous in nature. Well-understood examples from photonics include mode locking and a broad class of fractal optics, including self-similarity. In addition to the fundamental interest in such systems, fascinating technical functionalities that are difficult or even impossible to achieve with linear systems can emerge naturally from them if the right control tools can be applied. Here, we demonstrate a method that exploits positive nonlocal feedback to initiate, and negative local feedback to regulate, the growth of ultrafast laser-induced metal-oxide nanostructures with unprecedented uniformity, at high speed, low cost and on non-planar or flexible surfaces. The nonlocal nature of the feedback allows us to stitch the nanostructures seamlessly, enabling coverage of indefinitely large areas with subnanometre uniformity in periodicity. We demonstrate our approach through the fabrication of titanium dioxide and tungsten oxide nanostructures, but it can also be extended to a large variety of other materials.

  13. Fusion of image and laser-scanning data in a large-scale 3D virtual environment

    NASA Astrophysics Data System (ADS)

    Shih, Jhih-Syuan; Lin, Ta-Te

    2013-05-01

    Construction of large-scale 3D virtual environment is important in many fields such as robotic navigation, urban planning, transportation, and remote sensing, etc. Laser scanning approach is the most common method used in constructing 3D models. This paper proposes an automatic method to fuse image and laser-scanning data in a large-scale 3D virtual environment. The system comprises a laser-scanning device installed on a robot platform and the software for data fusion and visualization. The algorithms of data fusion and scene integration are presented. Experiments were performed for the reconstruction of outdoor scenes to test and demonstrate the functionality of the system. We also discuss the efficacy of the system and technical problems involved in this proposed method.

  14. Acousto-optic laser scanning for multi-site photo-stimulation of single neurons in vitro

    NASA Astrophysics Data System (ADS)

    Losavio, Bradley E.; Iyer, Vijay; Patel, Saumil; Saggau, Peter

    2010-08-01

    To study the complex synaptic interactions underpinning dendritic information processing in single neurons, experimenters require methods to mimic presynaptic neurotransmitter release at multiple sites with no physiological damage. We show that laser scanning systems built around large-aperture acousto-optic deflectors and high numerical aperture objective lenses provide the sub-millisecond, sub-micron precision necessary to achieve physiological, exogenous synaptic stimulation. Our laser scanning systems can produce the sophisticated spatio-temporal patterns of synaptic input that are necessary to investigate single-neuron dendritic physiology.

  15. Femtosecond laser-induced damage threshold of electron-beam deposited materials for broadband high-reflective coatings on large optics

    NASA Astrophysics Data System (ADS)

    Hervy, Adrien; Chriaux, Gilles; Gallais, Laurent; Mouricaud, Daniel; Djidel, Slimane

    2014-09-01

    In new laser facilities, broadband ultra-short pulses need to be transported in large and energetic beams to the experiment chambers through high performance optical components. We studied laser resistance of electronbeam- deposited materials in order to design meter scale high reflective optics according to petawatt-system requirements. We report intrinsic laser resistance of several dielectric materials, spectral performances of high reflective coatings and their laser induced damage threshold at different pulse durations from 150ps to 11fs.

  16. Percutaneous Pneumatic and Laser Lithotripsy as a Possible Therapeutic Strategy for Bilateral Large Calculi in a Horseshoe Kidney

    Microsoft Academic Search

    Chikashi Seto; Kohji Satoh; Hiroshi Morishita; Kazuto Komatsu; Mikio Namiki

    2004-01-01

    This report concerns a case of bilateral large calculi in a horseshoe kidney. Three sessions of percutaneous nephrolithotripsy for the calculi successfully disintegrated and removed the fragments without any complications. For complete stone removal we used pneumatic and laser lithotriptors which were passed, respectively, through a rigid nephroscope and a flexible pyeloscope. It is emphasized that the selection of the

  17. Mapping Boreal Wetlands Using Spaceborne Synthetic Aperture Radar

    Microsoft Academic Search

    E. Podest; K. C. McDonald; T. Bohn; D. Lettenmaier

    2006-01-01

    Carbon and methane emissions from wetlands and lakes can have a large impact on global climate. These ecosystems are dominant features in the northern high latitudes hence the importance of assessing their spatial and temporal extent to improve upon global net carbon exchange estimates. Spaceborne synthetic aperture radar (SAR) is an effective tool for this purpose since large inaccessible areas

  18. SYNTHETIC APERTURE SONAR: A TOOL IN UNDERWATER ARCHAEOLOGY

    Microsoft Academic Search

    Roy E Hansen; Helge S Telle

    The principle of synthetic aperture sonar (SAS) is coherent combination of successive pings such that the along-track resolution is improved. The along-track resolution in SAS images become range and frequency independent. SAS technology is efficient - it provides high resolution and large area coverage simultaneously. This makes SAS an ideal tool in search for small objects over large areas. The

  19. High-energy laser weapons: technology overview

    NASA Astrophysics Data System (ADS)

    Perram, Glen P.; Marciniak, Michael A.; Goda, Matthew

    2004-09-01

    High energy laser (HEL) weapons are ready for some of today"s most challenging military applications. For example, the Airborne Laser (ABL) program is designed to defend against Theater Ballistic Missiles in a tactical war scenario. Similarly, the Tactical High Energy Laser (THEL) program is currently testing a laser to defend against rockets and other tactical weapons. The Space Based Laser (SBL), Advanced Tactical Laser (ATL) and Large Aircraft Infrared Countermeasures (LAIRCM) programs promise even greater applications for laser weapons. This technology overview addresses both strategic and tactical roles for HEL weapons on the modern battlefield and examines current technology limited performance of weapon systems components, including various laser device types, beam control systems, atmospheric propagation, and target lethality issues. The characteristics, history, basic hardware, and fundamental performance of chemical lasers, solid state lasers and free electron lasers are summarized and compared. The elements of beam control, including the primary aperture, fast steering mirror, deformable mirrors, wavefront sensors, beacons and illuminators will be discussed with an emphasis on typical and required performance parameters. The effects of diffraction, atmospheric absorption, scattering, turbulence and thermal blooming phenomenon on irradiance at the target are described. Finally, lethality criteria and measures of weapon effectiveness are addressed. The primary purpose of the presentation is to define terminology, establish key performance parameters, and summarize technology capabilities.

  20. Very high numerical aperture light transmitting device

    DOEpatents

    Allison, Stephen W. (Knoxville, TN); Boatner, Lynn A. (Oak Ridge, TN); Sales, Brian C. (Knoxville, TN)

    1998-01-01

    A new light-transmitting device using a SCIN glass core and a novel calcium sodium cladding has been developed. The very high index of refraction, radiation hardness, similar solubility for rare earths and similar melt and viscosity characteristics of core and cladding materials makes them attractive for several applications such as high-numerical-aperture optical fibers and specialty lenses. Optical fibers up to 60 m in length have been drawn, and several simple lenses have been designed, ground, and polished. Preliminary results on the ability to directly cast optical components of lead-indium phosphate glass are also discussed as well as the suitability of these glasses as a host medium for rare-earth ion lasers and amplifiers.

  1. Scan mirrors relay for high resolution laser scanning systems

    NASA Astrophysics Data System (ADS)

    Kessler, David

    2014-09-01

    Two dimensional beam deflection is often required in medical laser scanning systems such as OCT or confocal microscopy. Commonly two linear galvo mirrors are used for performance in terms of their large apertures and scan angles. The galvo mirrors are placed at the vicinity of entrance pupil of the scan lens with a "displacement distance" separating them. This distance limits the scan fields and/or reduces the effective aperture of the scan lens. Another option is to use a beam or pupil relay, and image one galvo mirror onto the other. However, beam (or pupil) relays are notoriously complicated, expensive and can add significant aberrations. This paper discusses a simple, all reflective, diffraction limited, color corrected, beam relay, capable of large scan angles and large deflecting mirrors. The design is based on a unique combination of an Offner configuration with a Schmidt aspheric corrector. The design is highly corrected up to large scan mirrors and large scan angles down to milliwaves of aberrations. It allows significantly larger scan field and or scan lenses with higher numerical aperture as compared with scanners using galvos separated by the displacement distance. While this relay is of exceptionally high performance, it has one element located where the beam is focused which may present a problem for high power lasers. Thus modifications of the above design are introduced where the beam is focused in mid air thus making it usable for high power systems such including laser marking and fabrication systems.

  2. Multibeam synthetic aperture radar for global oceanography

    NASA Technical Reports Server (NTRS)

    Jain, A.

    1979-01-01

    A single-frequency multibeam synthetic aperture radar concept for large swath imaging desired for global oceanography is evaluated. Each beam iilluminates a separate range and azimuth interval, and images for different beams may be separated on the basis of the Doppler spectrum of the beams or their spatial azimuth separation in the image plane of the radar processor. The azimuth resolution of the radar system is selected so that the Doppler spectrum of each beam does not interfere with the Doppler foldover due to the finite pulse repetition frequency of the radar system.

  3. Iterative phase noise estimation and suppression for CO-OFDM systems with large laser linewidth

    NASA Astrophysics Data System (ADS)

    Yang, Chuanchuan; He, Changhong; Wang, Ziyu

    2011-12-01

    In order to further improve the laser phase noise tolerance of coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems, an iterative phase noise suppression algorithm is proposed in this paper, which is powerful in mitigating the laser phase noise induced intercarrier interference (ICI) even when laser linewidth achieves 2 MHz. Compared with the existing ICI suppression method, the performance gain brought by the proposal is significant when the laser linewidth is larger than 1.5 MHz. The BER floor which can not be avoided by using the existing phase noise suppression methods can be reduced effectively by employing the new iterative algorithm.

  4. Large-Scale Production of Carbon Nanotubes Using the Jefferson Lab Free Electron Laser

    NASA Technical Reports Server (NTRS)

    Holloway, Brian C.

    2003-01-01

    We report on our interdisciplinary program to use the Free Electron Laser (FEL) at the Thomas Jefferson National Accelerator Facility (J-Lab) for high-volume pulsed laser vaporization synthesis of carbon nanotubes. Based in part on the funding of from this project, a novel nanotube production system was designed, tested, and patented. Using this new system nanotube production rates over 100 times faster than conventional laser systems were achieved. Analysis of the material produced shows that it is of as high a quality as the standard laser-based materials.

  5. Spin-lasers: From threshold reduction to large-signal analysis

    SciTech Connect

    Lee, Jeongsu; Bearden, Sean; Wasner, Evan; uti?, Igor, E-mail: zigor@buffalo.edu [Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260 (United States)

    2014-07-28

    Lasers in which spin-polarized carriers are injected provide paths to different practical room temperature spintronic devices, not limited to magnetoresistive effects. Unlike the conventional understanding of spintronic devices, an optimal performance of such spin-lasers can arise for finite, not infinite, spin relaxation time. By considering spin-relaxation times of both electrons and holes, we elucidate advantages of spin-lasers over their conventional (spin-unpolarized) counterparts. In addition to the steady-state threshold reduction, spin-lasers can improve transient operation leading to shorter turn-on delay times, reduced ringing of emitted light, and an enhanced bandwidth.

  6. Orienting the camera and firing lasers to enhance large scale particle image velocimetry for streamflow monitoring

    NASA Astrophysics Data System (ADS)

    Tauro, Flavia; Porfiri, Maurizio; Grimaldi, Salvatore

    2014-09-01

    Large scale particle image velocimetry (LSPIV) is a nonintrusive methodology for continuous surface flow monitoring in natural environments. Recent experimental studies demonstrate that LSPIV is a promising technique to estimate flow discharge in riverine systems. Traditionally, LSPIV implementations are based on the use of angled cameras to capture extended fields of view; images are then orthorectified and calibrated through the acquisition of ground reference points. As widely documented in the literature, the identification of ground reference points and image orthorectification are major hurdles in LSPIV. Here we develop an experimental apparatus to address both of these issues. The proposed platform includes a laser system for remote frame calibration and a low-cost camera that is maintained orthogonal with respect to the water surface to minimize image distortions. We study the feasibility of the apparatus on two complex natural riverine environments where the acquisition of ground reference points is prevented and illumination and seeding density conditions are challenging. While our results confirm that velocity estimations can be severely affected by inhomogeneously seeded surface tracers and adverse illumination settings, they demonstrate that LSPIV implementations can benefit from the proposed apparatus. Specifically, the presented system opens novel avenues in the development of stand-alone platforms for remote surface flow monitoring.

  7. Laser Speckle Flowmetry Method for Measuring Spatial and Temporal Hemodynamic Alterations Throughout Large Microvascular Networks

    PubMed Central

    Meisner, Joshua K.; Sumer, Suna; Murrell, Kelsey P.; Higgins, Timothy J.; Price, Richard J.

    2012-01-01

    Objectives 1) Develop and validate laser speckle flowmetry (LSF) as a quantitative tool for individual microvessel hemodynamics in large networks. 2) Use LSF to determine if structural differences in the dorsal skinfold microcirculation (DSFWC) of C57BL/6 and BALB/c mice impart differential network hemodynamic responses to occlusion. Methods We compared LSF velocity measurements to known/measured velocities in vitro using capillary tube tissue phantoms and in vivo using mouse DSFWCs and cremaster muscles. Hemodynamic changes induced by feed arteriole occlusion were measured using LSF in DSFWCs implanted on C57BL/6 and BALB/c. Results In vitro, we found that the normalized speckle intensity (NSI) versus velocity linear relationship (R2?0.97) did not vary with diameter or hematocrit and can be shifted to meet an expected operating range. In vivo, DSFWC and cremaster muscle preparations (R2=0.92 and 0.95, respectively) demonstrated similar linear relationships between NSI and centerline velocity. Stratification of arterioles into predicted collateral pathways revealed significant differences between C57BL/6 and BALB/c strains in response to feed arteriole occlusion. Conclusions These data demonstrate the applicability of LSF to intravital microscopy microcirculation preparations for determining both relative and absolute hemodynamics on a network-wide scale while maintaining the resolution of individual microvessels. PMID:22591575

  8. Power scaling of Ti:Sapphire amplifiers: Design of a high average power Temto-Petawatt laser

    Microsoft Academic Search

    A. J. Bayramian; J. P. Armstrong; G. K. Beer; R. W. Campbell; R. R. Cross; A. C. Erlandson; B. L. Freitas; R. A. Kent; J. A. Menapace; W. A. Molander; K. I. Schaffers; C. W. Siders; S. B. Sutton; J. B. Tassano; S. Telford; C. A. Ebbers; J. A. Caird; C. P. J. Barty

    2008-01-01

    A large-aperture high-average-power gas-cooled Ti:sapphire slab pumped by the Mercury laser is the final amplifier in a chirped pulse amplification chain capable of producing a compressed peak power >1 petawatt and peak intensity >1023 W\\/cm2.

  9. Laser conditioning methods fo hafnia silica multiplayer mirrors

    SciTech Connect

    Stolz, C.J.; Sheehan, L.M.; Maricle, S.M. Schwartz, S.; Kozlowski, M.R.; Jennings, R.T.; Hue, J.

    1998-01-06

    Large aperture multilayer hafnia silica high reflector coatings at 1064 nm, deposited by reactive electron-beam deposition, were prepared to examine different laser conditioning methods for manufacturing high fluence optics in the National Ignition Facility. Laser conditioning is a process where the damage threshold of the coating is increased or the damage that is created is minimized so that it does not grow upon further irradiation. Two laser conditioning methods were examined for coatings deposited from only oxide starting materials. Off-line laser conditioning consists of raster scanning a mirror past a 1 mm diameter Gaussian beam over the entire clear aperture; a process that takes approximately 24 hours per scan. On-line laser conditioning consisted of a large aperture 300 mm x 300 mm beam from the Beamlet laser that irradiated the entire full clear aperture of a series of mirrors; a process that was limited by a 2-4 hour shot rate. In both cases a six-step process was used with the mirror first irradiated at a low fluence, then successively higher fluences increased in equal increments up to the peak laser operating fluence. Mirrors that were only partially laser conditioned damaged catastrophically while fully conditioned mirrors survived fluences exceeding the safe operating Beamlet fluence. An alternative off-line laser conditioning method was examined for coatings deposited from hafnia or metallic hafnium sources. Single-step laser conditioning consists of off-line raster scanning an optic at the peak operating fluence, thus decreasing the laser conditioning cost by reducing the number of scans and required laser conditioning stations to process all the mirrors for the National Ignition Facility. Between pulses the optic is stepped approximately one fourth of the l/e* Gaussian beam diameter so each area of the coating is irradiated by different segments of the beam starting at a low fluence at the outer edge of the beam diameter and increasing to the peak fluence in the center of the beam. The one-step conditioning results appear positive, but the influence of the coating improvements due to the metallic hafnium process on laser conditioning is undefined.

  10. Sensitivity function analysis of gravitational wave detection with single-laser and large-momentum-transfer atomic sensors

    NASA Astrophysics Data System (ADS)

    Tang, Biao; Zhang, Bao-Cheng; Zhou, Lin; Wang, Jin; Zhan, Ming-Sheng

    2015-03-01

    Recently, a configuration using atomic interferometers (AIs) had been suggested for the detection of gravitational waves. A new AI with some additional laser pulses for implementing large momentum transfer was also put forward, in order to reduce the effect of shot noise and laser frequency noise. We use a sensitivity function to analyze all possible configurations of the new AI and to distinguish how many momenta are transferred in a specific configuration. By analyzing the new configuration, we further explore a detection scheme for gravitational waves, in particular, that ameliorates laser frequency noise. We find that the amelioration occurs in such a scheme, but novelly, in some cases, the frequency noise can be canceled completely by using a proper data processing method. Supported by the National Natural Science Foundation of China.

  11. Hard X-ray generation and plasma filament formation under interaction of femtosecond laser pulses with large molecular clusters

    NASA Astrophysics Data System (ADS)

    Gordienko, Vyacheslav M.; Dzhidzhoev, Murat S.; Zhvaniya, Irina A.; Platonenko, Viktor T.; Trubnikov, Dmitriy N.; Fedorov, Denis O.

    2013-03-01

    We have demonstrated that the efficiency of hard X-ray generation (with energy 2 - 4 keV) from the femtosecond laser excitation (intensity I 1016 W/cm2, pulse energy E 5 mJ) of large molecular clusters (SF6, CF3I) can reach 10-6 (with yield 109 photons/J). It was shown that at maximal X-ray yield, the plasma filament is essentially non-uniform and has a multifocal structure. It was observed that the amplitude of the central and trailing spectral components of the chirped laser pulse decreases after its interaction with the cluster target as a result of efficient laser energy absorption under self-focusing conditions.

  12. Laser induced bulk damage of KDP crystals prepared by rapid growth

    NASA Astrophysics Data System (ADS)

    Zhao, Yuan'an; Wang, Yueliang; Hu, Guohang; Shao, Jianda; Chang, Junxiu; Liu, Xiaofeng; Li, Dawei; Yao, Yuangen; Lin, Xiuqin; Zheng, Guozong

    2014-09-01

    Laser damage of TYPE-I KDP plate was investigated. High-purity large-aperture KDP crystals used for second harmonic frequency generation in high power laser systems were prepared by rapid growth. The different parts of the KDP boule, spanning the growth history including early, middle and late growth stages, were examined for their bulk defect properties and laser damage behaviors. Ultra-microscopy was employed to analyze the preexisting laser scattering defects, and the correlations between scattering and laser damage initiations/ growth were identified. The laser damage fluence was dominated by the defect scale or the scattering intensity. Simulation of thermal response of the defects under laser radiation indicated the micro-explosion occurrence. Thermal annealing and laser conditioning were applied to reduce defect density and improve laser damage resistance. Based on the above techniques, laser induced damage threshold (LIDT) of 400 mm aperture TYPE-I crystal plate exceeded 22J/cm2 (1064nm, 3ns), which met the requirements of the high power laser systems.

  13. Mosaic of coded aperture arrays

    DOEpatents

    Fenimore, Edward E. (Los Alamos, NM); Cannon, Thomas M. (Los Alamos, NM)

    1980-01-01

    The present invention pertains to a mosaic of coded aperture arrays which is capable of imaging off-axis sources with minimum detector size. Mosaics of the basic array pattern create a circular on periodic correlation of the object on a section of the picture plane. This section consists of elements of the central basic pattern as well as elements from neighboring patterns and is a cyclic version of the basic pattern. Since all object points contribute a complete cyclic version of the basic pattern, a section of the picture, which is the size of the basic aperture pattern, contains all the information necessary to image the object with no artifacts.

  14. Guiding and triggering of large-scale electrical discharges using ultrashort pulse lasers

    Microsoft Academic Search

    D. Comtois; C. Y. Chien; P. Couture; A. Desparois; T. W. Johnston; Z. Jiang; J.-C. Kieffer; B. La Fontaine; F. Martin; R. Mawassi; H. P. Mercure; H. Pepin; C. Potvin; F. A. M. Rizk; F. Vidal

    1999-01-01

    Summary form only given. The possibility of channeling lightning discharges is of enormous scientific and economic value but presents great technical challenges. The use of lasers to trigger and guide such discharges is an area of intense international research. Recent advances in ultra-short pulse lasers have opened new possibilities of achieving this goal. We have demonstrated the propagation of high

  15. Accurate measurement of large optical frequency differences with a mode-locked laser

    Microsoft Academic Search

    J. Reichert; R. Holzwarth; T. W. Hnsch

    1999-01-01

    We have used the comb of optical frequencies emitted by a mode-locked laser as a ruler to measure differences of as much as 20 THz between laser frequencies. This is to our knowledge the largest gap measured with a frequency comb, with high potential for further improvements. To check the accuracy of this approach we show that the modes are

  16. Optical properties of plastically bent large-diameter sapphire fiber tips for laser tissue ablations

    NASA Astrophysics Data System (ADS)

    Tong, Limin

    2000-10-01

    Aiming to facilitate laser surgery applications, six 0.75mm- diameter 90mm-length sapphire fiber tips were plastically bent by means of CO2 lasers with bending radii from 1.7mm to 3.6mm and bending angles of 15-120 degree(s). The average bending loss caused by the bending process of the tips is about 0.03dB with the minimum loss less than 0.02dB, the damage thresholds of these tips are higher than 160MW/cm2 for Nd:YAG laser pulses at 1.06micrometers and 2MW/cm2 for CuBr laser pulses at 510.6nm. Satisfactory optical properties of these sapphire fiber tips show that they are promising for use in laser surgery applications such as tissue ablations. 16

  17. Conceptual design of a large E-beam-pumped KrF laser for ICF commercial applications

    SciTech Connect

    Harris, D.B.; Waganer, L.M.; Zuckerman, D.S.; Bowers, D.A.

    1986-11-01

    Two types of KrF lasers appear attractive as a driver for an ICF electric power plant. The original concept uses large electron-beam-pumped amplifiers and pure angular multiplexing to deliver short, shaped pulses to the target. A recently conceived alternate concept uses many small, long-pulse e-beam sustained discharge lasers which transfer their energy through the forward Raman process to a multiplexed set of beams to deliver the energy to target. Preliminary comparisons of the two systems indicate that the original concept has both a lower cost and a lower system efficiency, and both concepts appear to be nearly equally attractive as an ICF driver for an electric power plant. This paper examines a 4.8 MJ, 5 Hz KrF laser system designed using the original concept. The laser uses 24 main amplifiers arranged in eight sets of three amplifiers each. This layout optimizes both the optical system and the gas flow system, and uses a simple target illumination scheme that provides neutron shielding to allow hands-on maintenance in the laser hall.

  18. Application of Ruze Equation for Inflatable Aperture Antennas

    NASA Technical Reports Server (NTRS)

    Welch, Bryan W.

    2008-01-01

    Inflatable aperture reflector antennas are an emerging technology that NASA is investigating for potential uses in science and exploration missions. As inflatable aperture antennas have not been proven fully qualified for space missions, they must be characterized properly so that the behavior of the antennas can be known in advance. To properly characterize the inflatable aperture antenna, testing must be performed in a relevant environment, such as a vacuum chamber. Since the capability of having a radiofrequency (RF) test facility inside a vacuum chamber did not exist at NASA Glenn Research Center, a different methodology had to be utilized. The proposal to test an inflatable aperture antenna in a vacuum chamber entailed performing a photogrammetry study of the antenna surface by using laser ranging measurements. A root-mean-square (rms) error term was derived from the photogrammetry study to calculate the antenna surface loss as described by the Ruze equation. However, initial testing showed that problems existed in using the Ruze equation to calculate the loss due to errors on the antenna surface. This study utilized RF measurements obtained in a near-field antenna range and photogrammetry data taken from a laser range scanner to compare the expected performance of the test antenna (via the Ruze equation) with the actual RF patterns and directivity measurements. Results showed that the Ruze equation overstated the degradation in the directivity calculation. Therefore, when the photogrammetry study is performed on the test antennas in the vacuum chamber, a more complex equation must be used in light of the fact that the Ruze theory overstates the loss in directivity for inflatable aperture reflector antennas.

  19. Separation of the electron and proton cosmic-ray components by means of a calorimeter in the PAMELA satellite-borne experiment for the case of particle detection within a large aperture

    SciTech Connect

    Karelin, A. V., E-mail: karelin@hotbox.ru; Borisov, S. V.; Voronov, S. A.; Malakhov, V. V. [National Research Nuclear University MEPhI (Russian Federation)

    2013-06-15

    The PAMELA satellite-borne experiment is designed to study cosmic rays over a broad energy range. The apparatus has been in near-Earth cosmic space from June 2006 to the present time. It is equipped with a magnetic spectrometer for determining the sign of the particle charge and rigidity. In solving some problems, however, information from the magnetic spectrometer becomes inaccessible, so that it is necessary to employ a calorimeter to separate the electron and nuclear cosmic-ray components. A procedure for separating these components for particles arriving off the magnetic-spectrometer aperture is considered.

  20. Plasmonic nanofocusing with a metallic pyramid and an integrated C-shaped aperture

    PubMed Central

    Lindquist, Nathan C.; Johnson, Timothy W.; Nagpal, Prashant; Norris, David J.; Oh, Sang-Hyun

    2013-01-01

    We demonstrate the design, fabrication and characterization of a near-field plasmonic nanofocusing probe with a hybrid tip-plus-aperture design. By combining template stripping with focused ion beam lithography, a variety of aperture-based near-field probes can be fabricated with high optical performance. In particular, the combination of large transmission through a C-shaped aperture aligned to the sharp apex (<10?nm radius) of a template-stripped metallic pyramid allows the efficient delivery of lightvia the C-shaped aperturewhile providing a nanometric hotspot determined by the sharpness of the tip itself. PMID:23676841

  1. INTERACTION OF LASER RADIATION WITH MATTER: Large-scale structures produced on metal surfaces by multiple laser pulses

    NASA Astrophysics Data System (ADS)

    Kirichenko, N. A.

    2009-05-01

    A mathematical model is constructed to describe the formation of inhomogeneous surface structures 10-50 ?m in height on metal surfaces exposed to repetitive laser pulses with the following parameters: pulse duration of ~20 ns, pulse repetition rate of ~10 kHz, pulse intensity in the range 107108 W cm-2 and beam diameter from 50 to 100 ?m. The model takes into account melting of the metal and melt flow over a distorted surface. The surface profile amplitude evaluated in the model agrees with experimental data.

  2. Fundamental Studies of Ignition Process in Large Natural Gas Engines Using Laser Spark Ignition

    SciTech Connect

    Azer Yalin; Bryan Willson

    2008-06-30

    Past research has shown that laser ignition provides a potential means to reduce emissions and improve engine efficiency of gas-fired engines to meet longer-term DOE ARES (Advanced Reciprocating Engine Systems) targets. Despite the potential advantages of laser ignition, the technology is not seeing practical or commercial use. A major impediment in this regard has been the 'open-path' beam delivery used in much of the past research. This mode of delivery is not considered industrially practical owing to safety factors, as well as susceptibility to vibrations, thermal effects etc. The overall goal of our project has been to develop technologies and approaches for practical laser ignition systems. To this end, we are pursuing fiber optically coupled laser ignition system and multiplexing methods for multiple cylinder engine operation. This report summarizes our progress in this regard. A partial summary of our progress includes: development of a figure of merit to guide fiber selection, identification of hollow-core fibers as a potential means of fiber delivery, demonstration of bench-top sparking through hollow-core fibers, single-cylinder engine operation with fiber delivered laser ignition, demonstration of bench-top multiplexing, dual-cylinder engine operation via multiplexed fiber delivered laser ignition, and sparking with fiber lasers. To the best of our knowledge, each of these accomplishments was a first.

  3. Controlling the nonlinear intracavity dynamics of large He-Ne laser gyroscopes

    E-print Network

    Cuccato, Davide; Belfi, Jacopo; Beverini, Nicol; Ortolan, Antonello; Di Virgilio, Angela

    2013-01-01

    A model based on Lamb's theory of gas lasers is applied to a He-Ne ring laser gyroscope in order to estimate and remove the laser dynamics contribution from the rotation measurements. The intensities of the counter-propagating laser beams exiting one cavity mirror are continuously observed together with a monitor of the laser population inversion. These observables, once properly calibrated with a dedicated procedure, allow us to estimate cold cavity and active medium parameters driving the main part of the nonlinearities of the system. The parameters identification and noise subtraction procedure has been verified by means of a Monte Carlo study of the system, and experimentally tested on the G-Pisa ring laser oriented with the normal to the ring plane almost parallel to the Earth rotation axis. In this configuration the Earth rotation-rate provides the maximum Sagnac effect while the contribution of the orientation error is reduced at minimum. After the subtraction of laser dynamics by a Kalman filter, the ...

  4. Sparse-aperture adaptive optics

    Microsoft Academic Search

    Peter Tuthill; James Lloyd; Michael Ireland; Frantz Martinache; John Monnier; Henry Woodruff; Theo ten Brummelaar; Nils Turner; Charles Townes

    2006-01-01

    Aperture masking interferometry and Adaptive Optics (AO) are two of the competing technologies attempting to recover diffraction-limited performance from ground-based telescopes. However, there are good arguments that these techniques should be viewed as complementary, not competitive. Masking has been shown to deliver superior PSF calibration, rejection of atmospheric noise and robust recovery of phase information through the use of closure

  5. Large energy soliton erbium-doped fiber laser with a graphene-polymer composite mode locker

    E-print Network

    Han Zhang; Qiaoliang Bao; Dingyuan Tang; Luming Zhao; Kianping Loh

    2009-09-30

    Due to its unique electronic property and the Pauli Blocking Principle, atomic layer graphene possesses wavelength-independent ultrafast saturable absorption, which can be exploited for the ultrafast photonics application. Through chemical functionalization, a graphene-polymer nanocomposite membrane was fabricated and firstly used to mode lock a fiber laser. Stable mode locked solitons with 3 nJ pulse energy, 700 fs pulse width at the 1590 nm wavelength have been directly generated from the laser. We show that graphene-polymer nanocomposites could be an attractive saturable absorber for high power fiber laser mode locking.

  6. Vacuum isostatic micro/macro molding of PTFE materials for laser beam shaping in environmental applications: large scale UV laser water purification

    NASA Astrophysics Data System (ADS)

    Lizotte, Todd; Ohar, Orest

    2009-08-01

    Accessibility to fresh clean water has determined the location and survival of civilizations throughout the ages [1]. The tangible economic value of water is demonstrated by industry's need for water in fields such as semiconductor, food and pharmaceutical manufacturing. Economic stability for all sectors of industry depends on access to reliable volumes of good quality water. As can be seen on television a nation's economy is seriously affected by water shortages through drought or mismanagement and as such those water resources must therefore be managed both for the public interest and the economic future. For over 50 years ultraviolet water purification has been the mainstay technology for water treatment, killing potential microbiological agents in water for leisure activities such as swimming pools to large scale waste water treatment facilities where the UV light photo-oxidizes various pollutants and contaminants. Well tailored to the task, UV provides a cost effective way to reduce the use of chemicals in sanitization and anti-biological applications. Predominantly based on low pressure Hg UV discharge lamps, the system is plagued with lifetime issues (~1 year normal operation), the last ten years has shown that the technology continues to advance and larger scale systems are turning to more advanced lamp designs and evaluating solidstate UV light sources and more powerful laser sources. One of the issues facing the treatment of water with UV lasers is an appropriate means of delivering laser light efficiently over larger volumes or cross sections of water. This paper examines the potential advantages of laser beam shaping components made from isostatically micro molding microstructured PTFE materials for integration into large scale water purification and sterilization systems, for both lamps and laser sources. Applying a unique patented fabrication method engineers can form micro and macro scale diffractive, holographic and faceted reflective structures into fused and semi-fused PTFE materials and compounds for use in UV Reactors. The materials unique attributes provide an unusual but effective hybrid element, by combining Lambertian diffusion and spectral reflective attributes. This paper will provide examples of the applications where this technology could be applied and typical constructions. An overview of UV sources commonly used in water treatment, including high power UV lasers and solid state UV light sources will be discussed. The paper will summarize how beam shaping elements produced in PTFE materials would provide further benefits to the emerging water disinfection or treatment market.

  7. High numerical aperture tabletop soft x-ray diffraction microscopy with 70-nm resolution

    PubMed Central

    Sandberg, Richard L.; Song, Changyong; Wachulak, Przemyslaw W.; Raymondson, Daisy A.; Paul, Ariel; Amirbekian, Bagrat; Lee, Edwin; Sakdinawat, Anne E.; La-O-Vorakiat, Chan; Marconi, Mario C.; Menoni, Carmen S.; Murnane, Margaret M.; Rocca, Jorge J.; Kapteyn, Henry C.; Miao, Jianwei

    2008-01-01

    Light microscopy has greatly advanced our understanding of nature. The achievable resolution, however, is limited by optical wavelengths to ?200 nm. By using imaging and labeling technologies, resolutions beyond the diffraction limit can be achieved for specialized specimens with techniques such as near-field scanning optical microscopy, stimulated emission depletion microscopy, and photoactivated localization microscopy. Here, we report a versatile soft x-ray diffraction microscope with 70- to 90-nm resolution by using two different tabletop coherent soft x-ray sourcesa soft x-ray laser and a high-harmonic source. We also use field curvature correction that allows high numerical aperture imaging and near-diffraction-limited resolution of 1.5?. A tabletop soft x-ray diffraction microscope should find broad applications in biology, nanoscience, and materials science because of its simple optical design, high resolution, large depth of field, 3D imaging capability, scalability to shorter wavelengths, and ultrafast temporal resolution. PMID:18162534

  8. Solid state lasers III; Proceedings of the Meeting, Los Angeles, CA, Jan. 20-22, 1992

    NASA Astrophysics Data System (ADS)

    Quarles, Gregory J.

    The present volume on solid state lasers discusses components, systems, and applications of eye-safe lasers, pulsed-laser technology, diode and advanced pumping, high-power laser technology, and practical applications of ultrahigh-energy lasers. Attention is given to diode-pumped erbium glass lasers, 2.0-micron laser applications, engineering aspects of solid state phase-conjugate lasers, a Ti:sapphire laser with long-pulse lamp pumping, and a rotating pipe geometry glass laser. Topics addressed include picosecond sources for subcentimeter laser ranging, the effect of ionic and particular platinum on the performance of large-aperture Nd:phosphate glass rod amplifiers, thermal stress fracture in slab lasers, and the implementation of pulse shaping on the OMEGA laser system. Also discussed are all-solid-state diode-pumped eyesafe lasers, energy transport in the modern disk amplifier, the production of turnable coherent gamma rays from accelerated positronium, and X-ray laser research at the Nova laser.

  9. Imaging algorithms for a strip-map synthetic aperture sonar: minimizing the effects of aperture errors and aperture undersampling

    Microsoft Academic Search

    Peter T. Gough; David W. Hawkins

    1997-01-01

    Imaging the sea floor using high-precision synthetic aperture sonar (SAS) techniques is at the stage where the efficiency and the robustness of the various imaging algorithms are of concern. There have been several block processing algorithms developed for relatively narrow-band-, narrow swath-, and narrow beamwidth synthetic aperture systems mainly for use by the synthetic aperture radar (SAR) community. These algorithms

  10. Refined Motion Compensation for Highly Squinted Spotlight Syn-thetic Aperture Radar

    E-print Network

    in the presence of a large squint angle. 1 Introduction Advanced synthetic aperture radar (SAR) systems are conRefined Motion Compensation for Highly Squinted Spotlight Syn- thetic Aperture Radar Minh PhuongCom directly after range compression. The first-order MoCom corrects an incorrect velocity in azi- muth

  11. WFPC2 aperture photometry and PSF modelling

    E-print Network

    N. R. Tanvir; D. R. T. Robinson; T. von Hippel

    1995-03-22

    Since the WFPC-2 undersamples the PSF, aperture photometry can produce results which are competetive with profile fitting in many situations. This article reports and investigation of aperture corrections using both real data and PSF models.

  12. REVIEW ARTICLE Interferometric Synthetic Aperture Radar

    E-print Network

    Kansas, University of

    REVIEW ARTICLE Interferometric Synthetic Aperture Radar Christopher T. Allen Department of Electrical Engineering and Computer Science and Radar Systems and Remote Sensing Laboratory University of Kansas Abstract. This paper provides a brief review of interferometric synthetic aperture radar (In

  13. Robust frequency stabilization of multiple spectroscopy lasers with large and tunable offset frequencies.

    PubMed

    Nevsky, A; Alighanbari, S; Chen, Q-F; Ernsting, I; Vasilyev, S; Schiller, S; Barwood, G; Gill, P; Poli, N; Tino, G M

    2013-11-15

    We have demonstrated a compact, robust device for simultaneous absolute frequency stabilization of three diode lasers whose carrier frequencies can be chosen freely relative to the reference. A rigid ULE multicavity block is employed, and, for each laser, the sideband locking technique is applied. A small lock error, computer control of frequency offset, wide range of frequency offset, simple construction, and robust operation are the useful features of the system. One concrete application is as a stabilization unit for the cooling and trapping lasers of a neutral-atom lattice clock. The device significantly supports and improves the clock's operation. The laser with the most stringent requirements imposed by this application is stabilized to a line width of 70 Hz, and a residual frequency drift less than 0.5 Hz/s. The carrier optical frequency can be tuned over 350 MHz while in lock. PMID:24322162

  14. Large-area nanoimprinting on various substrates by reconfigurable maskless laser direct writing

    Microsoft Academic Search

    Daeho Lee; Heng Pan; Alex Sherry; Seung Hwan Ko; Ming-Tsang Lee; Eunpa Kim; Costas P Grigoropoulos

    2012-01-01

    Laser-assisted, one-step direct nanoimprinting of metal and semiconductor nanoparticles (NPs) was investigated to fabricate submicron structures including mesh, line, nanopillar and nanowire arrays. Master molds were fabricated with high-speed (200 mm s?1) laser direct writing (LDW) of negative or positive photoresists on Si wafers. The fabrication was completely free of lift-off or reactive ion etching processes. Polydimethylsiloxane (PDMS) stamps fabricated

  15. Asymptotic theory of a large fiber-laser array passive phase locking.

    PubMed

    Napartovich, Anatoly P; Elkin, Nikolay N; Vysotsky, Dmitry V

    2014-11-01

    Coherent laser beam combining is a potentially attractive way to increase the combined beam brightness beyond the technological limits to single-mode fiber lasers. Passive phase locking (PPL) does not need external management and leads to strong simplification of the system. A specific feature of fiber amplifiers and lasers is that they possess optical path differences of the magnitude of many wavelengths. The involved problem in the PPL approach is to specify an ultimate limit to the phase-locked laser-array size. Earlier studies confirm the stabilizing role of gain saturation on beam-combining efficiency. The purpose of our study is to decipher the desired effect of nonlinearity on the combining efficiency in two architectures of a globally coupled fiber-laser array: (I)an array of amplifiers in ring resonator configuration with spatially filtered feedback; (II)an array of lasers also with external feedback. The external-cavity feedback in both systems results in global coupling, i.e., each element is coherently coupled to all the others. A semi-analytical approach based on the probability theory is developed to calculate the probability density for the efficiency as a function of system parameters in both ensembles. Comparison between (I) and (II) arrays indicates that the II-type arrays demonstrate better characteristics while scaling the array size. PMID:25402934

  16. Simulation and Realization of a Focus Shifting Unit using a Tunable Lens for 3D Laser Material Processing

    NASA Astrophysics Data System (ADS)

    Eberle, G.; Chiron, V.; Wegener, K.

    3D laser microprocessing using current market available technologies reveals itself to be a cost intensive and complex undertaking which is mostly due to the control architecture and use of moving components. Recent market appearance of electronically tunable lenses exhibiting NIR transmission, large aperture, high damage threshold and fast response times are available for laser based applications. Hence, enabling usage in the field of laser microprocessing. This paper thus introduces the functional principle of electrically tunable lenses, setup arrangement for 3D laser microprocessing, computational simulation of system parameters and comparison with experimental results.

  17. Permeability of Self-Affine Aperture Fields Laurent Talon

    E-print Network

    Permeability of Self-Affine Aperture Fields Laurent Talon and Harold Auradou Univ. Pierre et Marie (Dated: April 18, 2010) We introduce a model that allows for the prediction of the permeability of self. In the lubrication approximation, the permeability shows three different scaling regimes. For fractures with a large

  18. Large-mode-area infrared guiding in ultrafast laser written waveguides in sulfur-based chalcogenide glasses.

    PubMed

    D'Amico, C; Cheng, G; Mauclair, C; Troles, J; Calvez, L; Nazabal, V; Caillaud, C; Martin, G; Arezki, B; LeCoarer, E; Kern, P; Stoian, R

    2014-06-01

    Current demands in astrophotonics impose advancing optical functions in infrared domains within embedded refractive index designs. We demonstrate concepts for large-mode-area guiding in ultrafast laser photowritten waveguides in bulk Sulfur-based chalcogenide glasses. If positive index contrasts are weak in As2S3, Ge doping increases the matrix rigidity and allows for high contrast (10(-3)) positive refractive index changes. Guiding with variable mode diameter and large-mode-area light transport is demonstrated up to 10 ?m spectral domain using transverse slit-shaped and evanescently-coupled multicore traces. PMID:24921505

  19. Far field characterization of diffracting circular apertures

    Microsoft Academic Search

    Christian Obermller; Khaled Karrai

    1995-01-01

    The far field angular intensity distribution I(?) of the ?=633 nm radiation transmitted through diffracting circular apertures is measured for diameters ranging between 60 and 500 nm. The circular apertures are located at the apex of aluminum coated tapered optical fiber tips. I(?) depends sensitively on the aperture diameters down to ?\\/6. This property is used to determine the optical

  20. SYNTHETIC APERTURE RADAR AUTOFOCUS VIA SEMIDEFINITE RELAXATION

    E-print Network

    Wiseman, Yair

    1 SYNTHETIC APERTURE RADAR AUTOFOCUS VIA SEMIDEFINITE RELAXATION Kuang-Hung Liu, Student Member in Synthetic Aperture Radar imaging amounts to estimating unknown phase errors caused by unknown platform relaxation. I. INTRODUCTION Synthetic aperture radar (SAR) offers a means of producing high

  1. Lunar Laser Ranging Experiment for Japanese SELENE-2 landing mission

    NASA Astrophysics Data System (ADS)

    Noda, H.; Kunimori, H.; Araki, H.; Fuse, T.; Hanada, H.; Katayama, M.; Otsubo, T.; Sasaki, S.; Tazawa, S.; Tsuruta, S.; Funazaki, K.; Taniguchi, H.; Murata, K.

    2012-04-01

    We present the development status of the Lunar Laser Ranging experiment proposed to Japanese SELENE-2 lunar landing mission. The Lunar Laser Ranging measures the distance between laser link stations on the Earth and retroreflectors on the Moon, by detecting the time of flight of photons of high-powered laser emitted from the ground station. Since the Earth-Moon distance contains information of lunar orbit, lunar solid tides, and lunar orientation and rotation, we can estimate the inner structure of the Moon through orientation, rotation and tide. Retroreflectors put by the Apollo and Luna missions in 1970's are arrays of many small Corner Cube Prisms (CCP). Because of the tilt of these arrays from the Earth direction due to the optical libration, the returned laser pulse is broaden, causing the main range error of more than 1.5 cm ([1]). Therefore retroreflectors with larger single aperture are necessary for more accurate ranging, and we propose a large single retroreflector of hollow-type with 15 cm aperture. Larger aperture up to 20 cm might be favorable if more mass is permitted for payloads. To cancel the velocity aberration, a large, single aperture retroreflector needs small amount of offset angle between the reflecting planes to spoil the return beam pattern. This angle offset, called Dihedral Angle Offset (DAO) must be optimized to be less than 1 second of arc with 0.1 seconds of arc accuracy to accumulate more photons [2, 3]. The realization of such small DAO is challenging with current technology, therefore the development of fabrication method is important. As for the mirror material, some ceramic products (ZPF: Zero-expansion Pore-free ceramics or SiC: silicon carbide) are under consideration in terms of weight, hardness and handling. The thermal quality of the material can be evaluated by both the thermal conductivity and the coefficient of thermal expansion. The method to fasten three planes each other with precise DAO must be developed.

  2. Large Scale Laser Two-Photon Polymerization Structuring for Fabrication of Artificial Polymeric Scaffolds for Regenerative Medicine

    NASA Astrophysics Data System (ADS)

    Malinauskas, M.; Purlys, V.; ukauskas, A.; Rutkauskas, M.; Danilevi?ius, P.; Paipulas, D.; Bi?kauskait?, G.; Bukelskis, L.; Baltriukien?, D.; irmenis, R.; Gaidukevi?iut?, A.; Bukelskien?, V.; Gadonas, R.; Sirvydis, V.; Piskarskas, A.

    2010-11-01

    We present a femtosecond Laser Two-Photon Polymerization (LTPP) system of large scale three-dimensional structuring for applications in tissue engineering. The direct laser writing system enables fabrication of artificial polymeric scaffolds over a large area (up to cm in lateral size) with sub-micrometer resolution which could find practical applications in biomedicine and surgery. Yb:KGW femtosecond laser oscillator (Pharos, Light Conversion. Co. Ltd.) is used as an irradiation source (75 fs, 515 nm (frequency doubled), 80 MHz). The sample is mounted on wide range linear motor driven stages having 10 nm sample positioning resolution (XYALS130-100, ZALS130-50, Aerotech, Inc.). These stages guarantee an overall travelling range of 100 mm into X and Y directions and 50 mm in Z direction and support the linear scanning speed up to 300 mm/s. By moving the sample three-dimensionally the position of laser focus in the photopolymer is changed and one is able to write complex 3D (three-dimensional) structures. An illumination system and CMOS camera enables online process monitoring. Control of all equipment is automated via custom made computer software "3D-Poli" specially designed for LTPP applications. Structures can be imported from computer aided design STereoLihography (stl) files or programmed directly. It can be used for rapid LTPP structuring in various photopolymers (SZ2080, AKRE19, PEG-DA-258) which are known to be suitable for bio-applications. Microstructured scaffolds can be produced on different substrates like glass, plastic and metal. In this paper, we present microfabricated polymeric scaffolds over a large area and growing of adult rabbit myogenic stem cells on them. Obtained results show the polymeric scaffolds to be applicable for cell growth practice. It exhibit potential to use it for artificial pericardium in the experimental model in the future.

  3. Large Scale Laser Two-Photon Polymerization Structuring for Fabrication of Artificial Polymeric Scaffolds for Regenerative Medicine

    SciTech Connect

    Malinauskas, M.; Purlys, V.; Zukauskas, A.; Rutkauskas, M.; Danilevicius, P.; Paipulas, D.; Bickauskaite, G.; Gadonas, R.; Piskarskas, A. [Vilnius University, Physics Faculty, Department of Quantum Electronics, Laser Research Center, Sauletekio ave. 10, LT-10223 Vilnius (Lithuania); Bukelskis, L.; Baltriukiene, D.; Bukelskiene, V. [Institute of Biochemistry, Vivarium, Mokslininkuo str. 12, LT-08662 Vilnius (Lithuania); Sirmenis, R. [Vilnius University Hospital Santariskiuo Klinikos, Santariskiuo g. 2, LT-08661 Vilnius (Lithuania); Gaidukeviciute, A. [Institute of Electronic Structure and Laser, Foundation for Research and Technology Hellas, Vassilika Vouton, 711 10 Heraklion, Crete (Greece); Sirvydis, V. [Vilnius University, Faculty of Medicine, Heart Surgery Center, Santariskiuo 2, LT-08661, Vilnius (Lithuania)

    2010-11-10

    We present a femtosecond Laser Two-Photon Polymerization (LTPP) system of large scale three-dimensional structuring for applications in tissue engineering. The direct laser writing system enables fabrication of artificial polymeric scaffolds over a large area (up to cm in lateral size) with sub-micrometer resolution which could find practical applications in biomedicine and surgery. Yb:KGW femtosecond laser oscillator (Pharos, Light Conversion. Co. Ltd.) is used as an irradiation source (75 fs, 515 nm (frequency doubled), 80 MHz). The sample is mounted on wide range linear motor driven stages having 10 nm sample positioning resolution (XY--ALS130-100, Z--ALS130-50, Aerotech, Inc.). These stages guarantee an overall travelling range of 100 mm into X and Y directions and 50 mm in Z direction and support the linear scanning speed up to 300 mm/s. By moving the sample three-dimensionally the position of laser focus in the photopolymer is changed and one is able to write complex 3D (three-dimensional) structures. An illumination system and CMOS camera enables online process monitoring. Control of all equipment is automated via custom made computer software ''3D-Poli'' specially designed for LTPP applications. Structures can be imported from computer aided design STereoLihography (stl) files or programmed directly. It can be used for rapid LTPP structuring in various photopolymers (SZ2080, AKRE19, PEG-DA-258) which are known to be suitable for bio-applications. Microstructured scaffolds can be produced on different substrates like glass, plastic and metal. In this paper, we present microfabricated polymeric scaffolds over a large area and growing of adult rabbit myogenic stem cells on them. Obtained results show the polymeric scaffolds to be applicable for cell growth practice. It exhibit potential to use it for artificial pericardium in the experimental model in the future.

  4. Optimum synthetic-aperture imaging of extended astronomical objects.

    PubMed

    van der Avoort, Casper; Pereira, Silvania F; Braat, Joseph J M; den Herder, Jan-Willem

    2007-04-01

    In optical aperture-synthesis imaging of stellar objects, different beam combination strategies are used and proposed. Coaxial Michelson interferometers are very common and a homothetic multiaxial interferometer is recently realized in the Large Binocular Telescope. Laboratory experiments have demonstrated the working principles of two new approaches: densified pupil imaging and wide field-of-view (FOV) coaxial imaging using a staircase-shaped mirror. We develop a common mathematical formulation for direct comparison of the resolution and noise sensitivity of these four telescope configurations for combining beams from multiple apertures for interferometric synthetic aperture, wide-FOV imaging. Singular value decomposition techniques are used to compare the techniques and observe their distinct signal-to-noise ratio behaviors. We conclude that for a certain chosen stellar object, clear differences in performance of the imagers are identifiable. PMID:17361290

  5. Experimental demonstration of a stripmap holographic aperture ladar system.

    PubMed

    Stafford, Jason W; Duncan, Bradley D; Dierking, Matthew P

    2010-04-20

    By synthesizing large effective apertures through the translation of a smaller imaging sensor and the subsequent proper phasing and correlation of detected signals in postprocessing, holographic aperture ladar (HAL) systems seek to increase the resolution of remotely imaged targets. The stripmap HAL process was demonstrated in the laboratory, for the first time to our knowledge. Our results show that the stripmap HAL transformation can precisely account for off-axis transmitter induced phase migrations. This in turn allows multiple pupil plane field segments, sequentially collected across a synthetic aperture, to be coherently mosaiced together. As a direct consequence, we have been able to confirm the capability of the HAL method to potentially provide substantial increases in longitudinal cross-range resolution. The measurement and sampling of complex pupil plane field segments, as well as target related issues arising from short laboratory ranges, have also been addressed. PMID:20411005

  6. Clustering of optically trapped large diameter plasmonic gold nanoparticles by laser beam of hybrid-TEM11* mode

    NASA Astrophysics Data System (ADS)

    Kumar, Ranjeet; Mehta, Dalip Singh; Shakher, Chandra

    2011-01-01

    Multiple trapping and clustering of gold nanoparticles (Au-NPs) of 254- and 150-nm diameter was affected using optical tweezers near the plasmon excitation wavelength. To ensure that the gradient force exceeded the sum of multiply-enhanced destabilizing absorption and scattering forces originating from plasmon excitation, embedded intensity gradient regions of a spatially featured asymmetric (SFA) laser beam were exploited. Thus, an intra-cavity generated SFA beam, also referred as hybrid TEM11* mode, is an intermediate between pure TEM00 and TEM11 beams and was directly obtained from a diode-pumped solid state (Nd:YAG) laser resonator without introducing any external beam modulation devices. The parabolic Gaussian-ray model of a tightly focused laser beam was adopted to evaluate the radiation forces including the volume-correction factor raised from fractional polarization of such large diameter Au-NPs under laser illumination. Temperature rise of Au-NPs and its dissipation profile in surrounding medium has also been presented. This multiple trapping and clustering of Au-NPs at plasmon excitation wavelength using sufficiently low power could be realized due to embedded intensity gradients of the SFA beam. The study might be useful for understanding the light-matter interaction, improving the sensitivity of diagnostics, and safety and efficacy of therapeutic nanotechnologies in medicine, photothermolysis, and surface-enhanced Raman spectroscopy, etc.

  7. The development of a laser safety program for a large academic research institution using Texas A&M University as a model

    E-print Network

    Johnson, Douglas Allen

    1995-01-01

    This thesis presents a model for developing a laser safety program for a large academic research institution. It is based on the standards and requirements of the 1993 American National Standards Institute document Z136.1, The Safe Use of Lasers...

  8. Broadband standoff detection of large molecules by mid-infrared active coherent laser spectrometry.

    PubMed

    Macleod, Neil A; Molero, Francisco; Weidmann, Damien

    2015-01-26

    A widely tunable active coherent laser spectrometer (ACLaS) has been demonstrated for standoff detection of broadband absorbers in the 1280 to 1318 cm-1 spectral region using an external cavity quantum cascade laser as a mid-infrared source. The broad tuning range allows detection and quantification of vapor phase molecules, such as dichloroethane, ethylene glycol dinitrate, and tetrafluoroethane. The level of confidence in molecular mixing ratios retrieved from interfering spectral measurements is assessed in a quantitative manner. A first qualitative demonstration of condensed phase chemical detection on nitroacetanilide has also been conducted. Detection performances of the broadband ACLaS have been placed in the context of explosive detection and compared to that obtained using distributed feedback quantum cascade lasers. PMID:25835851

  9. Microscopic mechanisms of laser spallation and ablation of metal targets from large-scale molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Wu, Chengping; Zhigilei, Leonid V.

    2014-01-01

    The microscopic mechanisms of femtosecond laser ablation of an Al target are investigated in large-scale massively parallel atomistic simulations performed with a computational model combining classical molecular dynamics technique with a continuum description of the laser excitation and subsequent relaxation of conduction band electrons. The relatively large lateral size of the computational systems used in the simulations enables a detailed analysis of the evolution of multiple voids generated in a sub-surface region of the irradiated target in the spallation regime, when the material ejection is driven by the relaxation of laser-induced stresses. The nucleation, growth, and coalescence of voids take place within a broad (100 nm) region of the target, leading to the formation of a transient foamy structure of interconnected liquid regions and eventual separation (or spallation) of a thin liquid layer from the bulk of the target. The thickness of the spalled layer is decreasing from the maximum of 50 nm while the temperature and ejection velocity are increasing with increasing fluence. At a fluence of 2.5 times the spallation threshold, the top part of the target reaches the conditions for an explosive decomposition into vapor and small clusters/droplets, marking the transition to the phase explosion regime of laser ablation. This transition is signified by a change in the composition of the ablation plume from large liquid droplets to a mixture of vapor-phase atoms and clusters/droplets of different sizes. The clusters of different sizes are spatially segregated in the expanding ablation plume, where small/medium size clusters present in the middle of the plume are followed by slower (velocities of less than 3 km/s) large droplets consisting of more than 10,000 atoms. The similarity of some of the characteristics of laser ablation of Al targets (e.g., evolution of voids in the spallation regime and cluster size distributions in the phase explosion regime) to the ones observed in earlier simulations performed for different target materials points to the common mechanical and thermodynamic origins of the underlying processes.

  10. Dynamically variable spot size laser system

    NASA Technical Reports Server (NTRS)

    Gradl, Paul R. (Inventor); Hurst, John F. (Inventor); Middleton, James R. (Inventor)

    2012-01-01

    A Dynamically Variable Spot Size (DVSS) laser system for bonding metal components includes an elongated housing containing a light entry aperture coupled to a laser beam transmission cable and a light exit aperture. A plurality of lenses contained within the housing focus a laser beam from the light entry aperture through the light exit aperture. The lenses may be dynamically adjusted to vary the spot size of the laser. A plurality of interoperable safety devices, including a manually depressible interlock switch, an internal proximity sensor, a remotely operated potentiometer, a remotely activated toggle and a power supply interlock, prevent activation of the laser and DVSS laser system if each safety device does not provide a closed circuit. The remotely operated potentiometer also provides continuous variability in laser energy output.

  11. Laser amplifier based on a neodymium glass rod 150 mm in diameter

    NASA Astrophysics Data System (ADS)

    Shaykin, A. A.; Fokin, A. P.; Soloviev, A. A.; Kuzmin, A. A.; Shaikin, I. A.; Burdonov, K. F.; Charukhchev, A. V.; Khazanov, E. A.

    2014-05-01

    A unique large-aperture neodymium glass rod amplifier is experimentally studied. The small-signal gain distribution is measured at different pump energies. The aperture-averaged gain is found to be 2.3. The stored energy (500 J), the maximum possible pump pulse repetition rate, and the depolarisation in a single pulse and in a series of pulses with a repetition rate of one pulse per five minutes are calculated based on the investigations performed. It is shown that the use of this amplifier at the exit of the existing laser can increase the output pulse energy from 300 to 600 J.

  12. Meeting thin film design and production challenges for laser damage resistant optical coatings at the Sandia Large Optics Coating Operation

    NASA Astrophysics Data System (ADS)

    Bellum, John; Kletecka, Damon; Rambo, Patrick; Smith, Ian; Kimmel, Mark; Schwarz, Jens; Geissel, Matthias; Copeland, Guild; Atherton, Briggs; Smith, Douglas; Smith, Claire; Khripin, Constantine

    2009-10-01

    Sandia's Large Optics Coating Operation provides laser damage resistant optical coatings on meter-class optics required for the ZBacklighter Terawatt and Petawatt lasers. Deposition is by electron beam evaporation in a 2.3 m 2.3 m 1.8 m temperature controlled vacuum chamber. Ion assisted deposition (IAD) is optional. Coating types range from antireflection (AR) to high reflection (HR) at S and P polarizations for angle of incidence (AOI) from 0 to 47. This paper reports progress in meeting challenges in design and deposition of these high laser induced damage threshold (LIDT) coatings. Numerous LIDT tests (NIF-MEL protocol, 3.5 ns laser pulses at 1064 nm and 532 nm) on the coatings confirm that they are robust against laser damage. Typical LIDTs are: at 1064 nm, 45 AOI, Ppol, 79 J/cm2 (IAD 32 layer HR coating) and 73 J/cm2 (non-IAD 32 layer HR coating); at 1064 nm, 32 AOI, 82 J/cm2 (Ppol) and 55 J/cm2 (Spol ) (non-IAD 32 layer HR coating); and at 532 nm, Ppol, 16 J/cm2 (25 AOI) and 19 J/cm2 (45 AOI) (IAD 50 layer HR coating). The demands of meeting challenging spectral, AOI and LIDT performances are highlighted by an HR coating required to provide R > 99.6% reflectivity in Ppol and Spol over AOIs from 24 to 47 within ~ 1% bandwidth at both 527 nm and 1054 nm. Another issue is coating surface roughness. For IAD of HR coatings, elevating the chamber temperature to ~ 120 C and turning the ion beam off during the pause in deposition between layers reduce the coating surface roughness compared to runs at lower temperatures with the ion beam on continuously. Atomic force microscopy and optical profilometry confirm the reduced surface roughness for these IAD coatings, and tests show that their LIDTs remain high.

  13. A laser-sheet flow visualization technique for the large wind tunnels of the National Full-Scale Aerodynamics Complex

    NASA Technical Reports Server (NTRS)

    Reinath, M. S.; Ross, J. C.

    1990-01-01

    A flow visualization technique for the large wind tunnels of the National Full Scale Aerodynamics Complex (NFAC) is described. The technique uses a laser sheet generated by the NFAC Long Range Laser Velocimeter (LRLV) to illuminate a smoke-like tracer in the flow. The LRLV optical system is modified slightly, and a scanned mirror is added to generate the sheet. These modifications are described, in addition to the results of an initial performance test conducted in the 80- by 120-Foot Wind Tunnel. During this test, flow visualization was performed in the wake region behind a truck as part of a vehicle drag reduction study. The problems encountered during the test are discussed, in addition to the recommended improvements needed to enhance the performance of the technique for future applications.

  14. Substrate influence on NMOS transistors in large-area laser crystallized isolated Si layers

    Microsoft Academic Search

    D. Herbst; M. A. Bosch; S. K. Tewksbury

    1983-01-01

    Metal-gate NMOS transistors have been fabricated in isolated silicon layers prepared in high-temperature biased laser crystallization. The transistor parameters are strongly influenced by the substrate material, in our case simultaneously processed silica and silicon wafers. Stress built up in the silicon layer strongly affects the carrier mobility and may also significantly influence the threshold voltage, the kink voltage, as well

  15. Laser Metrology Sensing and Control for Large Segmented-Mirror Telescopes

    NASA Technical Reports Server (NTRS)

    Zhao, Feng; Rao, Shanti; Ksendzov, Alex; Kadogawa, Hiroshi

    2006-01-01

    Described an optical hexapod metrology concept: a) Can work together with edge sensors; b) Can measure M1 - M2 distance and M1 global curvature. Swept-frequency laser metrology system: a) Absolute optical path length measurement (approx.1 micron); b) Relative optical path length measurement (approx.nm) Air turbulence is a concern for ground-based telescopes and needs further study.

  16. A novel DWDM method to design a 100-kW Laser

    NASA Astrophysics Data System (ADS)

    Basu, Santanu

    2010-02-01

    In this paper, I will present the design analysis of a novel concept that may be used to generate a diffraction-limited beam from an aperture so that as much as 450 kW of laser power can be efficiently deposited on a diffraction-limited spot at a range. The laser beam will be comprised of many closely spaced wavelength channels as in a DWDM. The technique relies on the ability of an angular dispersion amplifier to multiplex a large number of high power narrow frequency lasers, wavelengths of which may be as close as 0.4 nm.

  17. Spatial decoherence of pulsed broad-area vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Peeters, Michael; Verschaffelt, Guy; Thienpont, Hugo; Mandre, Shyam K.; Fischer, Ingo; Grabherr, Martin

    2005-11-01

    We report a strong reduction of spatial coherence of the emission of large aperture vertical-cavity surface-emitting lasers when they are driven by microsecond electrical pulses. We give evidence that this is due to a breakdown of the modal emission of these lasers. The spatial decoherence manifests itself in the formation of a Gaussian far field intensity distribution. The coherence radius we extract is 1.4 micrometer under these operating conditions, irrespective of the Fresnel number of the vertical-cavity surface-emitting laser. Finally, the spatial coherence properties can be varied by changing the pulse duration or pulse amplitude.

  18. Production of extended plasma channels in atmospheric air by amplitude-modulated UV radiation of GARPUN-MTW Ti : sapphire-KrF laser. Part 1. Regenerative amplification of subpicosecond pulses in a wide-aperture electron beam pumped KrF amplifier

    SciTech Connect

    Zvorykin, V D; Ionin, Andrei A; Levchenko, A O; Mesyats, Gennadii A; Seleznev, L V; Sinitsyn, D V; Smetanin, Igor V; Sunchugasheva, E S; Ustinovskii, N N; Shutov, A V [P N Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

    2013-04-30

    Regenerative amplification of single and multiple ultrashort subpicosecond UV pulses in a wide-aperture KrF amplifier with an unstable confocal resonator was investigated on the GARPUN-MTW hybrid laser system. Amplitude-modulated 100-ns long UV radiation pulses with an energy of several tens of joules were obtained at the output of the system. The pulses were a combination of a quasi-stationary oscillation pulse and a train of amplified ultrashort pulses (USPs) with a peak power of 0.2-0.3 TW, which exceeded the power of free-running lasing pulse by three orders of magnitude. The population inversion recovery time in the active KrF laser medium was estimated: {tau}{sub c} {<=} 2.0 ns. Trains of USPs spaced at an interval {Delta}t Almost-Equal-To {tau}{sub c} were shown to exhibit the highest amplification efficiency. The production of amplitude-modulated UV pulses opens up the way to the production and maintenance of extended plasma channels in atmospheric air. (extreme light fields and their applications)

  19. The application and research of the multi-receiving telescopes technology in laser ranging to space targets

    NASA Astrophysics Data System (ADS)

    Wu, Zhibo; Zhang, Haifeng; Zhang, Zhongping; Deng, Huarong; Li, Pu; Meng, Wendong; Cheng, Zhien; Shen, Lurun; Tang, Zhenhong

    2014-11-01

    Laser ranging technology can directly measure the distance between space targets and ground stations with the highest measurement precision and will play an irreplaceable role in orbit check and calibrating microwave measurement system. The precise orbit determination and accurate catalogue of space targets can also be realized by laser ranging with multi-stations. Among space targets, most of ones are inactive targets and space debris, which should be paid the great attentions for the safety of active spacecrafts. Because of laser diffuse reflection from the surface of targets, laser ranging to space debris has the characteristics of wide coverage and weak strength of laser echoes, even though the powerful laser system is applied. In order to increase the receiving ability of laser echoes, the large aperture telescope should be adopted. As well known, some disadvantages for one set of large aperture telescope, technical development difficulty and system running and maintenance complexity, will limit its flexible applications. The multi-receiving telescopes technology in laser ranging to space targets is put forward to realize the equivalent receiving ability produced by one larger aperture telescope by way of using multi-receiving telescopes, with the advantages of flexibility and maintenance. The theoretical analysis of the feasibility and key technologies of multi-receiving telescopes technology in laser ranging to space targets are presented in this paper. The experimental measurement system based on the 60cm SLR system and 1.56m astronomical telescopes with a distance of about 50m is established to provide the platform for researching on the multi-receiving telescopes technology. The laser ranging experiments to satellites equipped with retro-reflectors are successfully performed by using the above experimental system and verify the technical feasibility to increase the ability of echo detection. And the multi-receiving telescopes technology will become a novel effective way to improve the detection ability of laser ranging to space debris.

  20. 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 temperature by minimizing the 1088 nm gain, along with induced bend loss. A 938 nm seed beam is provided by a 0.2 W diode laser, frequency broadened to 400 MHz by DC modulating the diode. This seeds a two stage double-clad, Nd:doped fiber amplifier, producing 16 W of 938 nm light with M2~ 1.05. Over 3.5 W at 589 nm in continuous wave (CW) format has been generated by sumfrequency mixing the two lasers in periodically poled potassium dihydrogen phosphate (PPKTP). To convert the system to a pulsed format, we added amplitude modulators after both the 1583 nm and 938 nm oscillators and a pre-amplifier in each line to restore the average power to the level prior to modulation. Frequency mixing is simplified by using a pulsed format as the higher peak power facilitates more efficient conversion. To date we have demonstrated 3.8 W at 589 nm in periodically poled stoichiometric lithium tantalate (PPSLT) using a 1 ?s pulse length and a 10% duty cycle. Additional bandwidth, pre-compensation for square pulse distortion (SPD) and polarization maintaining amplifier fiber is currently being implemented to enable scaling to higher output power and lower repetition rate. Details of these experiments, system design and performance will be presented.