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Sample records for lass large aperture

  1. A study of strange and strangeonium states produced in LASS (Large Aperture Superconducting Solenoid)

    SciTech Connect

    Aston, D.; Awaji, N.; Bienz, T.; Bird, F.; D'Amore, J.; Dunwoodie, W.; Endorf, R.; Fujii, K.; Hayashii, H.; Iwata, S.

    1986-01-01

    Results are presented from the analysis of several final states from a high-sensitivity (4 ev/nb) study of inelastic K/sup -/p interactions at 11 GeV/c carried out in the LASS Spectrometer at SLAC. New information is reported on leading and underlying K* states, and the strangeonium states produced by hypercharge exchange exchange are compared and contrasted with those observed in radiative decays of the J/psi. 8 refs., 15 figs.

  2. The LASS (Larger Aperture Superconducting Solenoid) spectrometer

    SciTech Connect

    Aston, D.; Awaji, N.; Barnett, B.; Bienz, T.; Bierce, R.; Bird, F.; Bird, L.; Blockus, D.; Carnegie, R.K.; Chien, C.Y.

    1986-04-01

    LASS is the acronym for the Large Aperture Superconducting Solenoid spectrometer which is located in an rf-separated hadron beam at the Stanford Linear Accelerator Center. This spectrometer was constructed in order to perform high statistics studies of multiparticle final states produced in hadron reactions. Such reactions are frequently characterized by events having complicated topologies and/or relatively high particle multiplicity. Their detailed study requires a spectrometer which can provide good resolution in momentum and position over almost the entire solid angle subtended by the production point. In addition, good final state particle identification must be available so that separation of the many kinematically-overlapping final states can be achieved. Precise analyses of the individual reaction channels require high statistics, so that the spectrometer must be capable of high data-taking rates in order that such samples can be acquired in a reasonable running time. Finally, the spectrometer must be complemented by a sophisticated off-line analysis package which efficiently finds tracks, recognizes and fits event topologies and correctly associates the available particle identification information. This, together with complicated programs which perform specific analysis tasks such as partial wave analysis, requires a great deal of software effort allied to a very large computing capacity. This paper describes the construction and performance of the LASS spectrometer, which is an attempt to realize the features just discussed. The configuration of the spectrometer corresponds to the data-taking on K and K interactions in hydrogen at 11 GeV/c which took place in 1981 and 1982. This constitutes a major upgrade of the configuration used to acquire lower statistics data on 11 GeV/c K p interactions during 1977 and 1978, which is also described briefly.

  3. Large aperture diffractive space telescope

    DOEpatents

    Hyde, Roderick A.

    2001-01-01

    A large (10's of meters) aperture space telescope including two separate spacecraft--an optical primary objective lens 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 objective lens 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 objective lens, 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 which may be either earth bound or celestial.

  4. Large aperture scanning airborne lidar

    NASA Technical Reports Server (NTRS)

    Smith, J.; Bindschadler, R.; Boers, R.; Bufton, J. L.; Clem, D.; Garvin, J.; Melfi, S. H.

    1988-01-01

    A large aperture scanning airborne lidar facility is being developed to provide important new capabilities for airborne lidar sensor systems. The proposed scanning mechanism allows for a large aperture telescope (25 in. diameter) in front of an elliptical flat (25 x 36 in.) turning mirror positioned at a 45 degree angle with respect to the telescope optical axis. The lidar scanning capability will provide opportunities for acquiring new data sets for atmospheric, earth resources, and oceans communities. This completed facility will also make available the opportunity to acquire simulated EOS lidar data on a near global basis. The design and construction of this unique scanning mechanism presents exciting technological challenges of maintaining the turning mirror optical flatness during scanning while exposed to extreme temperatures, ambient pressures, aircraft vibrations, etc.

  5. the Large Aperture GRB Observatory

    SciTech Connect

    Bertou, Xavier

    2009-04-30

    The Large Aperture GRB Observatory (LAGO) aims at the detection of high energy photons from Gamma Ray Bursts (GRB) using the single particle technique (SPT) in ground based water Cherenkov detectors (WCD). To reach a reasonable sensitivity, high altitude mountain sites have been selected in Mexico (Sierra Negra, 4550 m a.s.l.), Bolivia (Chacaltaya, 5300 m a.s.l.) and Venezuela (Merida, 4765 m a.s.l.). We report on the project progresses and the first operation at high altitude, search for bursts in 6 months of preliminary data, as well as search for signal at ground level when satellites report a burst.

  6. Large aperture Fresnel telescopes/011

    SciTech Connect

    Hyde, R.A., LLNL

    1998-07-16

    At Livermore we`ve spent the last two years examining an alternative approach towards very large aperture (VLA) telescopes, one based upon transmissive Fresnel lenses rather than on mirrors. Fresnel lenses are attractive for VLA telescopes because they are launchable (lightweight, packagable, and deployable) and because they virtually eliminate the traditional, very tight, surface shape requirements faced by reflecting telescopes. Their (potentially severe) optical drawback, a very narrow spectral bandwidth, can be eliminated by use of a second (much smaller) chromatically-correcting Fresnel element. This enables Fresnel VLA telescopes to provide either single band ({Delta}{lambda}/{lambda} {approximately} 0.1), multiple band, or continuous spectral coverage. Building and fielding such large Fresnel lenses will present a significant challenge, but one which appears, with effort, to be solvable.

  7. Eyeglass. 1. Very large aperture diffractive telescopes.

    PubMed

    Hyde, R A

    1999-07-01

    The Eyeglass is a very large aperture (25-100-m) space telescope consisting of two distinct spacecraft, separated in space by several kilometers. A diffractive lens provides the telescope s large aperture, and a separate, much smaller, space telescope serves as its mobile eyepiece. Use of a transmissive diffractive lens solves two basic problems associated with very large aperture space telescopes; it is inherently launchable (lightweight, packagable, and deployable) it and virtually eliminates the traditional, very tight surface shape tolerances faced by reflecting apertures. The potential drawback to use of a diffractive primary (very narrow spectral bandwidth) is eliminated by corrective optics in the telescope s eyepiece; the Eyeglass can provide diffraction-limited imaging with either single-band (Deltalambda/lambda approximately 0.1), multiband, or continuous spectral coverage. PMID:18323902

  8. 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.

  9. Large Advanced Space Systems (LASS) computer-aided design program additions

    NASA Technical Reports Server (NTRS)

    Farrell, C. E.

    1982-01-01

    The LSS preliminary and conceptual design requires extensive iteractive analysis because of the effects of structural, thermal, and control intercoupling. A computer aided design program that will permit integrating and interfacing of required large space system (LSS) analyses is discussed. The primary objective of this program is the implementation of modeling techniques and analysis algorithms that permit interactive design and tradeoff studies of LSS concepts. Eight software modules were added to the program. The existing rigid body controls module was modified to include solar pressure effects. The new model generator modules and appendage synthesizer module are integrated (interfaced) to permit interactive definition and generation of LSS concepts. The mass properties module permits interactive specification of discrete masses and their locations. The other modules permit interactive analysis of orbital transfer requirements, antenna primary beam n, and attitude control requirements.

  10. 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 ν 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.

  11. 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 φ200mm 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.

  12. Large aperture adaptive optics for intense lasers

    NASA Astrophysics Data System (ADS)

    Deneuville, François; Ropert, Laurent; Sauvageot, Paul; Theis, Sébastien

    2015-05-01

    ISP SYSTEM has developed a range of large aperture electro-mechanical deformable mirrors (DM) suitable for ultra short pulsed intense lasers. The design of the MD-AME deformable mirror is based on force application on numerous locations thanks to electromechanical actuators driven by stepper motors. DM design and assembly method have been adapted to large aperture beams and the performances were evaluated on a first application for a beam with a diameter of 250mm at 45° angle of incidence. A Strehl ratio above 0.9 was reached for this application. Simulations were correlated with measurements on optical bench and the design has been validated by calculation for very large aperture (up to Ø550mm). Optical aberrations up to Zernike order 5 can be corrected with a very low residual error as for actual MD-AME mirror. Amplitude can reach up to several hundreds of μm for low order corrections. Hysteresis is lower than 0.1% and linearity better than 99%. Contrary to piezo-electric actuators, the μ-AME actuators avoid print-through effects and they permit to keep the mirror shape stable even unpowered, providing a high resistance to electro-magnetic pulses. The MD-AME mirrors can be adapted to circular, square or elliptical beams and they are compatible with all dielectric or metallic coatings.

  13. A large aperture electro-optic deflector

    NASA Astrophysics Data System (ADS)

    Bosco, A.; Boogert, S. T.; Boorman, G. E.; Blair, G. A.

    2009-05-01

    An electro-optic laser beam deflector with a clear optical aperture of 8.6 mm has been designed, realized, and tested. The electro-optic material used to implement the device was a MgO:LiNbO3 crystal. The exceptionally large aperture makes the device suitable for applications where fast scanning of high power laser beams is needed. The measured deflection angle was 120 μrad/kV for a total length of electro-optic material of 90 mm. A mode quality analysis of the laser beam revealed that the M2 of the laser is affected by less than 4% during scan operation when maximum driving voltage is applied.

  14. 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.

  15. 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.

  16. Large aperture ac interferometer for optical testing.

    PubMed

    Moore, D T; Murray, R; Neves, F B

    1978-12-15

    A 20-cm clear aperture modified Twyman-Green interferometer is described. The system measures phase with an AC technique called phase-lock interferometry while scanning the aperture with a dual galvanometer scanning system. Position information and phase are stored in a minicomputer with disk storage. This information is manipulated with associated software, and the wavefront deformation due to a test component is graphically displayed in perspective and contour on a CRT terminal. PMID:20208642

  17. Testing the large aperture optical components by the sub-aperture stitching interferometer

    NASA Astrophysics Data System (ADS)

    He, Yong; Wang, Zhao-xuan; Wang, Qing; Ji, Bo

    2008-03-01

    Nowadays many large aperture optical components are widely used in the high-tech area, how to test them become more and more important. Here describes a new method to test the large aperture optical components using the small aperture interferometer, deduce how to get the aperture number and the concrete process of the stitching parameter in a systematic way, finally get the best plan to choose the sub-aperture of the square and circular optical plane. To specify the stability of the method we operate an experiment, the result shows that the stitching accuracy can reach λ/10, it meet the need of the inertia constraint fusion etc, that is good enough to be used in the high-tech area.

  18. Study on test metrology of large aperture optical system wavefront

    NASA Astrophysics Data System (ADS)

    Liu, Zhiying; Fu, Yuegang; Gao, Tianyuan; Wang, Zhijian

    2009-05-01

    Large aperture optical system test has been a key problem for a long time. It could be solved by sub-aperture stitching method after the sub-apertures are tested. Sub-aperture stitching technology is a feasible method for testing large diameter optical system with small diameter interferometer sub-aperture stitching. Auto-collimating component will be needed with interferometer stitching method. Auto-collimating component is defined that the image could be kept stable when the optical component rotates about any axis in space. And the beam could be back along original optical path. By this means, auto collimation could be realized. The auto-collimating component is smaller than the test system. The whole wavefront of large aperture system could be tested through the method that the auto-collimating component moves along the guide rail and rotates about optical axis. A right angle roof prism is chosen as the auto-collimating component due to its character of easier manufacture. The active matrix, characteristic orientation and extreme axial is deduced with dynamic optics. The sub-aperture stitching testing process is simulated by ZEMAX in detail. The test result by stitching method is compared with that by directive test method for large aperture optical system. It is shown that the relative test error is less than 4.3λ 0/00. The sub -aperture stitching test method is verified.

  19. Eyeglass: A Very Large Aperture Diffractive Space Telescope

    SciTech Connect

    Hyde, R; Dixit, S; Weisberg, A; Rushford, M

    2002-07-29

    Eyeglass is a very large aperture (25-100 meter) space telescope consisting of two distinct spacecraft, separated in space by several kilometers. A diffractive lens provides the telescope's large aperture, and a separate, much smaller, space telescope serves as its mobile eyepiece. Use of a transmissive diffractive lens solves two basic problems associated with very large aperture space telescopes; it is inherently fieldable (lightweight and flat, hence packagable and deployable) and virtually eliminates the traditional, very tight, surface shape tolerances faced by reflecting apertures. The potential drawback to use of a diffractive primary (very narrow spectral bandwidth) is eliminated by corrective optics in the telescope's eyepiece. The Eyeglass can provide diffraction-limited imaging with either single-band, multiband, or continuous spectral coverage. Broadband diffractive telescopes have been built at LLNL and have demonstrated diffraction-limited performance over a 40% spectral bandwidth (0.48-0.72 {micro}m). As one approach to package a large aperture for launch, a foldable lens has been built and demonstrated. A 75 cm aperture diffractive lens was constructed from 6 panels of 1 m thick silica; it achieved diffraction-limited performance both before and after folding. This multiple panel, folding lens, approach is currently being scaled-up at LLNL. We are building a 5 meter aperture foldable lens, involving 72 panels of 700 {micro}m thick glass sheets, diffractively patterned to operate as coherent f/50 lens.

  20. A review of large aperture Schlieren photography technique

    NASA Astrophysics Data System (ADS)

    Xu, Song-bo; Xie, Yong-jun; Chen, Lei

    2016-01-01

    Schlieren photography is a visual process to display the flow of fluids of varying density. It is widely used in wind tunnel tests to photograph the flow of air around objects. To achieve schlieren images with high sensitivity and high resolution, and satisfy the requirements of the large-scale wind tunnel tests, it is urgent to develop schlieren photographers with large aperture primary mirrors. However, the application of large aperture primary mirrors may bring many challenges in the design of the schlieren system. First, the surface figure of large aperture primary mirrors is difficult to control so that the support structure may need more strategical design. Second, because the schlieren system works under some severe environments of the wind tunnel test including the air disturbance, wind-induced ground vibration and high ambient pressure, it has to withstand serious instability risks to ensure a good schlieren image quality. In this work, the current status of the development in the large aperture schlieren systems is reviewed. Several advanced methods, for example, active damping control technique, focal spot monitoring technique, 18-points whilffletree support technique, etc.., are introduced to deal with the challenges of the large aperture schlieren system. This work aims at improving the technical development of large aperture schlieren photographer, which may contribute to the acquisition of the high sensitive and high resolution schlieren images and the improvement of the testing capability in wind tunnel experiments.

  1. 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.

  2. Large Aperture, Scanning, L-Band SAR

    NASA Technical Reports Server (NTRS)

    Moussessian, Alina; Del Castillo, 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.

  3. Enhancing efficiency of single, large-aperture antennas

    NASA Technical Reports Server (NTRS)

    Cohen, M.; Grimes, D. E.; Littlepage, R. S.

    1971-01-01

    Numerical analysis method provides means of describing energy distribution in focal plane of parabolic surface in terms of phase and wavelength. Two approaches for enhancing antenna efficiency include single, large reflector focused to feeding element, and array of smaller apertures whose individual outputs are summed.

  4. Fabrication and applications of large aperture diffractive optics

    SciTech Connect

    Dixit, S; Britten, J B; Hyde, R; Rushford, M; Summers, L; Toeppen, J

    2002-02-19

    Large aperture diffractive optics are needed in high power laser applications to protect against laser damage during operation and in space applications to increase the light gathering power and consequently the signal to noise. We describe the facilities we have built for fabricating meter scale diffractive optics and discuss several examples of these.

  5. Operational aspects of the Main Injector large aperture quadrupole (WQB)

    SciTech Connect

    Chou, W.; Bartelson, L.; Brown, B.; Capista, D.; Crisp, J.; DiMarco, J.; Fitzgerald, J.; Glass, H.; Harding, D.; Johnson, D.; Kashikhin, V.; /Fermilab

    2007-06-01

    A two-year Large Aperture Quadrupole (WQB) Project was completed in the summer of 2006 at Fermilab. [1] Nine WQBs were designed, fabricated and bench-tested by the Technical Division. Seven of them were installed in the Main Injector and the other two for spares. They perform well. The aperture increase meets the design goal and the perturbation to the lattice is minimal. The machine acceptance in the injection and extraction regions is increased from 40{pi} to 60{pi} mm-mrad. This paper gives a brief report of the operation and performance of these magnets. Details can be found in Ref [2].

  6. Imaging with Concave Large-Aperture Therapeutic Ultrasound Arrays Using Conventional Synthetic-Aperture Beamforming

    PubMed Central

    Wan, Yayun; Ebbini, Emad S.

    2009-01-01

    Several dual-mode ultrasound array (DMUA) systems are being investigated for potential use in image-guided surgery. In therapeutic mode, DMUAs generate pulsed or continuous-wave (CW) high-intensity focused ultrasound (HIFU) beams capable of generating localized therapeutic effects within the focal volume. In imaging mode, pulse-echo data can be collected from the DMUA elements to obtain B-mode images or other forms of feedback on the state of the target tissue before, during, and after the application of the therapeutic HIFU beam. Therapeutic and technological constraints give rise to special characteristics of therapeutic arrays. Specifically, DMUAs have concave apertures with low f-number values and are typically coarsely sampled using directive elements. These characteristics necessitate pre- and post-beamforming signal processing of echo data to improve the spatial and contrast resolution and maximize the image uniformity within the imaging field of view (IxFOV). We have recently developed and experimentally validated beamforming algorithms for concave large-aperture DMUAs with directive elements. Experimental validation was performed using a 1 MHz, 64-element, concave spherical aperture with 100 mm radius of curvature. The aperture was sampled in the lateral direction using elongated elements 1−λ×33.3‒ with 1.333‒−λ center-to-center spacing (λ is the wavelength). This resulted in f-number values of 0.8 and 2 in the azimuth and elevation directions, respectively. In this paper, we present a new DMUA design approach based on different sampling of the shared concave aperture to improve image quality while maintaining therapeutic performance. A pulse-wave (PW) simulation model using a modified version of the Field II program is used in this study. The model is used in generating pulse-echo data for synthetic-aperture (SA) beamforming for forming images of a variety of targets, e.g., wire arrays and speckle-generating cyst phantoms. To provide

  7. Self-Referencing Hartmann Test for Large-Aperture Telescopes

    NASA Technical Reports Server (NTRS)

    Korechoff, Robert P.; Oseas, Jeffrey M.

    2010-01-01

    A method is proposed for end-to-end, full aperture testing of large-aperture telescopes using an innovative variation of a Hartmann mask. This technique is practical for telescopes with primary mirrors tens of meters in diameter and of any design. Furthermore, it is applicable to the entire optical band (near IR, visible, ultraviolet), relatively insensitive to environmental perturbations, and is suitable for ambient laboratory as well as thermal-vacuum environments. The only restriction is that the telescope optical axis must be parallel to the local gravity vector during testing. The standard Hartmann test utilizes an array of pencil beams that are cut out of a well-corrected wavefront using a mask. The pencil beam array is expanded to fill the full aperture of the telescope. The detector plane of the telescope is translated back and forth along the optical axis in the vicinity of the nominal focal plane, and the centroid of each pencil beam image is recorded. Standard analytical techniques are then used to reconstruct the telescope wavefront from the centroid data. The expansion of the array of pencil beams is usually accomplished by double passing the beams through the telescope under test. However, this requires a well-corrected, autocollimation flat, the diameter or which is approximately equal to that of the telescope aperture. Thus, the standard Hartmann method does not scale well because of the difficulty and expense of building and mounting a well-corrected, large aperture flat. The innovation in the testing method proposed here is to replace the large aperture, well-corrected, monolithic autocollimation flat with an array of small-aperture mirrors. In addition to eliminating the need for a large optic, the surface figure requirement for the small mirrors is relaxed compared to that required of the large autocollimation flat. The key point that allows this method to work is that the small mirrors need to operate as a monolithic flat only with regard to

  8. Temperature characteristic of 808nm VCSELs with large aperture

    NASA Astrophysics Data System (ADS)

    Feng, Yuan; Feng, Dawei; Hao, Yongqin; Wang, Yong; Yan, Changling; Lu, Peng; Li, Yang

    2015-03-01

    In order to study the output characteristics of 808nm vertical cavity surface emitting laser(VCSEL) with large aperture at different temperature, 808nm VCSEL with 500μm emitting diameter are fabricated with Reticular Electrode Structure(RES). Lasing wavelength, optical power and the threshold current are measured by changing the temperature of heat sink. And an output power of 0.42W is achieved at 1.3A at room temperature under continuous wave operation. The central wavelength is 803.32nm, and the full width at half maximum is 0.16nm, the temperature shift is 0.06nm/°, the thermal resistance is 0.098°/mW. The testing results show that 808nm VCSEL with large aperture is good temperature characteristic.

  9. Mission definition for a large-aperture microwave radiometer spacecraft

    NASA Technical Reports Server (NTRS)

    Keafer, L. S., Jr.

    1981-01-01

    An Earth-observation measurements mission is defined for a large-aperture microwave radiometer spacecraft. This mission is defined without regard to any particular spacecraft design concept. Space data application needs, the measurement selection rationale, and broad spacecraft design requirements and constraints are described. The effects of orbital parameters and image quality requirements on the spacecraft and mission performance are discussed. Over the land the primary measurand is soil moisture; over the coastal zones and the oceans important measurands are salinity, surface temperature, surface winds, oil spill dimensions and ice boundaries; and specific measurement requirements have been selected for each. Near-all-weather operation and good spatial resolution are assured by operating at low microwave frequencies using an extremely large aperture antenna in a low-Earth-orbit contiguous mapping mode.

  10. Phase retrieval in situ measurement for large aperture parabolic mirror

    NASA Astrophysics Data System (ADS)

    Ding, Lingyan; Wu, Yulie; Li, Shengyi; Liao, Yang; Shu, Yong

    2010-10-01

    Phase retrieval is a promising method for in-situ metrology and has been applied to spherical mirror surface metrology successfully. To meet the requirement of in-situ measurement in manufacturing large aperture parabolic mirror, a new method using phase retrieval technology is developed. In this method, an approximately parallel beam is used to illuminate the large parabolic mirror. The beam is produced by a point light source far away from the tested mirror. Then, intensity of diffraction patterns near the focus is measured by CCD. The experiment of testing a parabolic mirror with aperture 400mm and radius of curvature at vertex 2789.7mm is described. And some advices of improving the setup are presented. Errors brought by the approximately parallel beam are compensated by an algorithm derived from GS iterative algorithm. Phase retrieval result is consistent with that measured by interferometer sub-aperture stitching in error distribution, PV value and RMS value. The experiment shows that this method features simple optical path, good anti-vibration ability and acceptable accuracy.

  11. A Future Large-Aperture UVOIR Space Observatory: Reference Designs

    NASA Technical Reports Server (NTRS)

    Thronson, Harley; Rioux, Norman; Feinberg, Lee; Stahl, H. Philip; Redding, Dave; Jones, Andrew; Sturm, James; Collins, Christine; Liu, Alice

    2015-01-01

    Our joint NASA GSFC/JPL/MSFC/STScI study team has used community-provided science goals to derive mission needs, requirements, and candidate mission architectures for a future large-aperture, non-cryogenic UVOIR space observatory. We describe the feasibility assessment of system thermal and dynamic stability for supporting coronagraphy. The observatory is in a Sun-Earth L2 orbit providing a stable thermal environment and excellent field of regard. Reference designs include a 36-segment 9.2 m aperture telescope that stows within a five meter diameter launch vehicle fairing. Performance needs developed under the study are traceable to a variety of reference designs including options for a monolithic primary mirror.

  12. A future large-aperture UVOIR space observatory: reference designs

    NASA Astrophysics Data System (ADS)

    Rioux, Norman; Thronson, Harley; Feinberg, Lee; Stahl, H. Philip; Redding, Dave; Jones, Andrew; Sturm, James; Collins, Christine; Liu, Alice

    2015-09-01

    Our joint NASA GSFC/JPL/MSFC/STScI study team has used community-provided science goals to derive mission needs, requirements, and candidate mission architectures for a future large-aperture, non-cryogenic UVOIR space observatory. We describe the feasibility assessment of system thermal and dynamic stability for supporting coronagraphy. The observatory is in a Sun-Earth L2 orbit providing a stable thermal environment and excellent field of regard. Reference designs include a 36-segment 9.2 m aperture telescope that stows within a five meter diameter launch vehicle fairing. Performance needs developed under the study are traceable to a variety of reference designs including options for a monolithic primary mirror.

  13. Large-aperture broadband sapphire windows for common aperture, target acquisition, tracking, and surveillance systems

    NASA Astrophysics Data System (ADS)

    Askinazi, Joel

    1997-06-01

    State of the art optical sensing systems performing target acquisition/tracking and surveillance functions are being designed to incorporate a number of sensors into one package. These include visual and MWIR cameras, FLIRs, and laser range finders. These combined systems are being configured to view through a common aperture window. Typical window diameters are to eleven inches, but some surveillance applications have windows approaching twenty inches in diameter. These sensor windows typically operate in hostile environments including very high pressure differentials, large thermal gradients, and severe rain and sand abrasion. EMI/EMC protection and de-icing capabilities are also commonly required. For airborne applications and to minimize thermal gradients, thinner, lightweight, high strength windows are also necessary. Sapphire is an ideal window material to satisfy these requirements due to its high strength, UV-MWIR bandpass, minimal optical scatter, excellent index of refraction homogeneity and very high scratch/impact resistance. Associated optical fabrication, grid lithography and optical coating processes have been developed at Hughes Danbury for sapphire windows. This paper addresses the development of a family of large aperture, broadband sapphire windows which also provide EMI/EMC protection and de-icing capabilities. The resulting design configuration and performance characteristics are also addressed. Future technology development requirements are also discussed.

  14. Silicon Powder Filters for Large-Aperture Cryogenic Receivers

    NASA Astrophysics Data System (ADS)

    Boone, Fletcher; Essinger-Hileman, T.; Bennett, C. L.; Marriage, T.; Xu, Z.

    2014-01-01

    Upcoming experiments probing for the existence of B-mode polarization in the cosmic microwave background (CMB) will require large arrays of background-limited detectors. This will necessitate the use of cryogenic receivers with large-aperture vacuum windows and correspondingly large low-pass infrared-blocking filters to minimize thermal load. Large-diameter filters composed of absorptive dielectrics are difficult to conductively cool adequately, and thus tend to heat up and re-radiate towards the focal plane. Reflective metal-mesh filters are challenging to manufacture at such large apertures and with feature sizes small enough to effectively block 300K thermal radiation. In order to overcome these difficulties, we have developed a novel type of thermal filter that scatters, rather than reflects or absorbs, unwanted infrared radiation. Comprised of ultra-pure silicon powder distributed within a polymethylpentene (PMP) substrate, these filters are not absorptive in the infrared while being transparent to microwaves, and are comparatively straightforward to produce. By adjusting the size of the silicon particles, the frequency cut-off of these low-pass filters is fully tunable. Small scale (70mm diameter, 3mm thickness) prototypes have exhibited <10% transmission throughout the infrared spectrum and <1% transmission at the peak of the 300K blackbody spectrum, while maintaining an estimated 97% transmission in the microwave regime.

  15. U-turn alternative to the large aperture switch

    SciTech Connect

    Vann, C.S.

    1994-03-09

    The primary alternative laser architecture is the U-turn design. The U-turn has significantly different cost and performance risks than the full-aperture switch, which makes it a highly desirable alternative. The U-turn was conceived at LLNL in 1992. A similar concept, the L-turn had already been discovered by the French at CEL-V. Both concepts are based on the multipass glass amplifier design, but the full-aperture Pockels cell and polarizer are replaced with smaller and less expensive optics. Eliminating the large switch and polarizer not only reduces component costs, it also provides options for shortening the laser which, in turn, could reduce the size and cost of the laser building. Efficient use of the amplifier aperture (small vignetting allowance) requires that the U-turn have a long transport spatial filter; however, this is not a disadvantage if a long spatial filter is already required for image relaying to the frequency converter. Given a long spatial filter, the U-turn is potentially more efficient because losses in the switch and polarizer are avoided.

  16. Extracting spatial information from large aperture exposures of diffuse sources

    NASA Technical Reports Server (NTRS)

    Clarke, J. T.; Moos, H. W.

    1981-01-01

    The spatial properties of large aperture exposures of diffuse emission can be used both to investigate spatial variations in the emission and to filter out camera noise in exposures of weak emission sources. Spatial imaging can be accomplished both parallel and perpendicular to dispersion with a resolution of 5-6 arc sec, and a narrow median filter running perpendicular to dispersion across a diffuse image selectively filters out point source features, such as reseaux marks and fast particle hits. Spatial information derived from observations of solar system objects is presented.

  17. Large aperture spatial heterodyne imaging spectrometer: Principle and experimental results

    NASA Astrophysics Data System (ADS)

    Xiangli, Bin; Cai, Qisheng; Du, Shusong

    2015-12-01

    A large aperture spatial heterodyne imaging spectrometer (LASHIS) is proposed. It is a kind of pushbroom Fourier transform ultraspectral imager with no moving parts. This imaging spectrometer, based on a Sagnac lateral shearing interferometer combined with a pair of gratings, has the advantages of high spectral resolution, high throughput and robustness. The principle of LASHIS and its spectral retrieval method are introduced. The processing chain to convert raw images to ultraspectral datacube is also described. Experimental results demonstrate the high resolving power of LASHIS with the emission spectrum of a low pressure sodium lamp.

  18. 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

  19. Large-aperture interferometer using local reference beam

    NASA Technical Reports Server (NTRS)

    Howes, W. L.

    1982-01-01

    A large-aperture interferometer was devised by adding a local-reference-beam-generating optical system to a schlieren system. Two versions of the interferometer are demonstrated, one employing 12.7 cm (5 in.) diameter schlieren optics, the other employing 30.48 cm (12 in.) diameter parabolic mirrors in an off-axis system. In the latter configuration a cylindrical lens is introduced near the light source to correct for astigmatism. A zone plate is a satisfactory decollimating element in the reference-beam arm of the interferometer. Attempts to increase the flux and uniformity of irradiance in the reference beam by using a diffuser are discussed.

  20. 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.

  1. 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.

  2. Simulating aperture masking at the Large Binocular Telescope

    NASA Astrophysics Data System (ADS)

    Stürmer, Julian; Quirrenbach, Andreas

    2012-07-01

    Preliminary investigations for an Aperture Masking Experiment at the Large Binocular Telescope (LBT) and its application to stellar surface imaging are presented. An algorithm is implemented which generates non redundant aperture masks for the LBT. These masks are adapted to the special geometrical conditions at the LBT. At the same time, they are optimized to provide a uniform UV-coverage. It is also possible to favor certain baselines to adapt the UV-coverage to observational requirements. The optimization is done by selecting appropriate masks among a large number (order 109) of randomized realizations of non-redundant (NR) masks. Using results of numerical simulations of the surface of red supergiants, interferometric data is generated as it would be available with these masks at the LBT while observing Betelgeuse. An image reconstruction algorithm is used to reconstruct images from Squared Visibility and Closure Phase data. It is shown that a number of about 15 holes per mask is sufficient to retrieve detailed images. Additionally, noise is added to the data in order to simulate the influence of measurement errors e.g. photon noise. Both the position and the shape of surface structures are hardly influenced by this noise. However, the flux of these details changes significantly.

  3. Optimal strategy for fabrication of large aperture aspheric surfaces.

    PubMed

    Feng, Yunpeng; Cheng, Haobo; Wang, Tan; Dong, Zhichao; Tam, Hon-Yuen

    2014-01-01

    Aspheric surfaces are widely used because of their desirable characteristics. Such a surface can obtain nearly perfect imaging quality with fewer optical elements and reduce the size and mass of optical systems. Various machine systems have been developed based on modern deterministic polishing technologies for large aperture aspheric surfaces. Several factors affect the final precision of large aperture aspheric surfaces, such as the velocity limit of the machine and the path design. Excess velocity, which will be truncated automatically by the computer numerical control system, may cause the dwell time to deviate from the desired time. When a path designed on a two-dimensional surface map with equidistant pitch is projected onto an aspheric surface, the pitch changes as a result of the varied curvature of the aspheric surface. This may affect the removal map and cause some ripple errors. A multiregion distribution strategy, which includes velocity checking, is proposed in this study to avoid exceeding the velocity limits. The strategy can be used to modify local errors and edge effects. A three-dimensional spiral path generation method is also presented using an iterative method to ensure uniformity in the space length of the adjacent circle of the spiral path. This process can reduce the ripple error caused by the overlapping of tool paths. A polishing experiment was conducted, and the results proved the validity of the proposed strategies. PMID:24514001

  4. 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.

  5. Optical system design for lens with large relative aperture

    NASA Astrophysics Data System (ADS)

    Zhang, Kaisheng; Zhang, Zhi; Zhang, Zhaohui; Wang, Zefeng; Yan, Aqi; Fei, Jiaqi; Mei, Chao; Zhang, Gaopeng

    2015-10-01

    As the space remote sensing technology progresses, the developing trend of telescope is larger and larger aperture, higher and higher resolution. An Optical system with the relative aperture of 1:2 is introduced. The primary optical properties are: focal length of 120mm, F number of 2, field angle of 7.4°. It has the advantages of large high resolution, small size and excellent image quality. Several kinds of aberration curves and the MTF curve are given. Its imaging quality is nearly diffraction limited so that the spatial frequency is greater than 70lp/mm when its modulated transfer function (MTF) value of the optical system is equal to 0.8,and the optical system distortion is less than 1%. At last, the stray light is analyzed and the baffle of the telescope is designed. The solid model of the Optical system was constructed in Tracepro software, the point sources transmittance (PST) cure was given at different off-axis angle between 7.4°~80° the analysis result indicates that the PST values are less than 10-6 when off-axis angle are larger than soar critical angle. So the system is suitable for observation or photography of deep sky objects.

  6. Expression and prognostic significance of a new tumor metastasis suppressor gene LASS2 in human bladder carcinoma.

    PubMed

    Wang, Haifeng; Wang, Jiansong; Zuo, Yigang; Ding, Mingxia; Yan, Ruping; Yang, Delin; Ke, Changxin

    2012-09-01

    The LASS2 gene has been identified as a new tumor metastasis suppressor gene and has been seen to correlate with the degree of invasion and recurrence in carcinomas of prostate, breast, liver, ovarian, and pancreas. However, expression and prognostic significance of LASS2 in human bladder carcinoma are largely unknown. In this study, the protein expression of LASS2 in 80 patients with different stages was detected by immunohistochemical staining. The prognostic value of LASS2 in bladder cancers can also be assessed by a long-term follow-up investigation. The mRNA expression level of the LASS2 gene was examined using real-time quantitative PCR (qPCR) in human bladder carcinoma and paired non-tumor bladder tissues, which were obtained from 30 patients who underwent total cystectomy. We found that patients with LASS2-negative bladder cancer were linked to poor clinical prognosis. The expression of LASS2 mRNA was significantly correlated with clinical stage (P < 0.001), depth of tumor invasion (P < 0.001), and recurrence (P < 0.001). Thus, LASS2 expression may be correlated with the development and progression of human bladder carcinoma and may be a prognostic indicator for this carcinoma. PMID:21755371

  7. 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

  8. Factors affecting the performance of large-aperture microphone arrays.

    PubMed

    Silverman, Harvey F; Patterson, William R; Sachar, Joshua

    2002-05-01

    Large arrays of microphones have been proposed and studied as a possible means of acquiring data in offices, conference rooms, and auditoria without requiring close-talking microphones. When such an array essentially surrounds all possible sources, it is said to have a large aperture. Large-aperture arrays have attractive properties of spatial resolution and signal-to-noise enhancement. This paper presents a careful comparison of theoretical and measured performance for an array of 256 microphones using simple delay-and-sum beamforming. This is the largest currently functional, all digital-signal-processing array that we know of. The array is wall-mounted in the moderately adverse environment of a general-purpose laboratory (8 m x 8 m x 3 m). The room has a T60 reverberation time of 550 ms. Reverberation effects in this room severely impact the array's performance. However, the width of the main lobe remains comparable to that of a simplified prediction. Broadband spatial resolution shows a single central peak with 10 dB gain about 0.4 m in diameter at the -3 dB level. Away from that peak, the response is approximately flat over most of the room. Optimal weighting for signal-to-noise enhancement degrades the spatial resolution minimally. Experimentally, we verify that signal-to-noise gain is less than proportional to the square root of the number of microphones probably due to the partial correlation of the noise between channels, to variation of signal intensity with polar angle about the source, and to imperfect correlation of the signal over the array caused by reverberations. We show measurements of the relative importance of each effect in our environment. PMID:12051434

  9. Factors affecting the performance of large-aperture microphone arrays

    NASA Astrophysics Data System (ADS)

    Silverman, Harvey F.; Patterson, William R.; Sachar, Joshua

    2002-05-01

    Large arrays of microphones have been proposed and studied as a possible means of acquiring data in offices, conference rooms, and auditoria without requiring close-talking microphones. When such an array essentially surrounds all possible sources, it is said to have a large aperture. Large-aperture arrays have attractive properties of spatial resolution and signal-to-noise enhancement. This paper presents a careful comparison of theoretical and measured performance for an array of 256 microphones using simple delay-and-sum beamforming. This is the largest currently functional, all digital-signal-processing array that we know of. The array is wall-mounted in the moderately adverse environment of a general-purpose laboratory (8 m×8 m×3 m). The room has a T60 reverberation time of 550 ms. Reverberation effects in this room severely impact the array's performance. However, the width of the main lobe remains comparable to that of a simplified prediction. Broadband spatial resolution shows a single central peak with 10 dB gain about 0.4 m in diameter at the -3 dB level. Away from that peak, the response is approximately flat over most of the room. Optimal weighting for signal-to-noise enhancement degrades the spatial resolution minimally. Experimentally, we verify that signal-to-noise gain is less than proportional to the square root of the number of microphones probably due to the partial correlation of the noise between channels, to variation of signal intensity with polar angle about the source, and to imperfect correlation of the signal over the array caused by reverberations. We show measurements of the relative importance of each effect in our environment.

  10. Large-aperture, high-damage-threshold optics for beamlet

    SciTech Connect

    Campbell, J.H.; Atherton, L.J.; DeYoreo, J.J.

    1996-06-01

    Beamlet serves as a test bed for the proposed National Ignition Facility (NIF) laser design and components. Therefore, its optics are similar in size and quality to those proposed for the NIF. In general, the optics in the main laser cavity and transport section of Beamlet are larger and have higher damage thresholds than the optics manufactured for any of the previous laser systems. In addition, the quality of the Beamlet optical materials is higher, leading to better wavefront quality, higher optical transmission, and lower-intensity modulation of the output laser beam than, for example, that typically achieved on Nova. In this article, the authors discuss the properties and characteristics of the large-aperture optics used on Beamlet.

  11. Optical simulation of large aperture spatial heterodyne imaging spectrometer

    NASA Astrophysics Data System (ADS)

    Cai, Qisheng; Xiangli, Bin; Fang, Yu

    2016-05-01

    Large aperture spatial heterodyne imaging spectrometer (LASHIS) is a new pushbroom Fourier transform ultraspectral imager with no moving parts. It is based on a Sagnac interferometer combined with a pair of gratings. In this paper, the basic principle of LASHIS is reviewed and an optical LASHIS model is set up in ZEMAX. Three interference images are presented, one is calculated according to the basic theory, one is simulated using the optical model in ZEMAX, and the other is generated by the experimental device set up in our laboratory. These three interference images show a good agreement with each other that demonstrate the correctness of the optical model. Using this model, we can simulate the interference image quickly. This image gives a visualized evaluation of the system performance, and it will be more convenient for system design or tolerance analysis of LASHIS.

  12. Advances in optical materials for large aperture lasers

    SciTech Connect

    Stokowski, S.E.; Lowdermilk, W.H.; Marchi, F.T.; Swain, J.E.; Wallerstein, E.P.; Wirtenson, G.R.

    1981-12-15

    Lawrence Livermore National Laboratory (LLNL) is using large aperture Nd: glass lasers to investigate the feasibility of inertial confinement fusion. In our experiments high power laser light is focussed onto a small (100 to 500 micron) target containing a deuterium-tritium fuel mixture. During the short (1 to 5 ns) laser pulse the fuel is compressed and heated, resulting in fusion reactions. The generation and control of the powerful laser pulses for these experiments is a challenging scientific and engineering task, which requires the development of new optical materials, fabrication techniques, and coatings. LLNL with the considerable cooperation and support from the optical industry, where most of the research and development and almost all the manufacturing is done, has successfully applied several new developments in these areas.

  13. Large-aperture interferometer with local reference beam

    NASA Technical Reports Server (NTRS)

    Howes, W. L.

    1984-01-01

    A large-aperture interferometer was devised by adding a local-reference-beam-generating optical system to a schlieren system. Two versions of the interferometer are demonstrated, one employing 12.7 cm (5 in.) diameter schlieren optics, the other employing 30.48 cm (12 in.) diameter parabolic mirrors in an off-axis system. In the latter configuration a cylindrical lens is introduced near the light source to correct for astigmatism. A zone plate is a satisfactory decollimating element in the reference-beam arm of the interferometer. Attempts to increase the flux and uniformity of irradiance in the reference beam by using a diffuser are discussed. Previously announced in STAR as N83-13979

  14. 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.

  15. APPLICATION OF LARGE APERTURE EMATS TO WELD INSPECTION

    SciTech Connect

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

    2008-02-28

    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 deg. to 90 deg. 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 deg. beam angle provides good beam steering and focusing performance for 45 deg. to 70 deg. 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.

  16. MOIRE: ground demonstration of a large aperture diffractive transmissive telescope

    NASA Astrophysics Data System (ADS)

    Atcheson, Paul; Domber, Jeanette; Whiteaker, Kevin; Britten, Jerald A.; Dixit, Shamasundar N.; Farmer, Brandon

    2014-08-01

    The desire to field space-based telescopes with apertures in excess of 10 meter diameter is forcing the development of extreme lightweighted large optomechanical structures. Sparse apertures, shell optics, and membrane optics are a few of the approaches that have been investigated and demonstrated. Membrane optics in particular have been investigated for many years. The MOIRE approach in which the membrane is used as a transmissive diffractive optical element (DOE) offers a significant relaxation in the control requirements on the membrane surface figure, supports extreme lightweighting of the primary collecting optic, and provides a path for rapid low cost production of the primary optical elements. Successful development of a powered meter-scale transmissive membrane DOE was reported in 2012. This paper presents initial imaging results from integrating meter-scale transmissive DOEs into the primary element of a 5- meter diameter telescope architecture. The brassboard telescope successfully demonstrates the ability to collect polychromatic high resolution imagery over a representative object using the transmissive DOE technology. The telescope includes multiple segments of a 5-meter diameter telescope primary with an overall length of 27 meters. The object scene used for the demonstration represents a 1.5 km square complex ground scene. Imaging is accomplished in a standard laboratory environment using a 40 nm spectral bandwidth centered on 650 nm. Theoretical imaging quality for the tested configuration is NIIRS 2.8, with the demonstration achieving NIIRS 2.3 under laboratory seeing conditions. Design characteristics, hardware implementation, laboratory environmental impacts on imagery, image quality metrics, and ongoing developments will be presented.

  17. NST: Thermal Modeling for a Large Aperture Solar Telescope

    NASA Astrophysics Data System (ADS)

    Coulter, Roy

    2011-05-01

    Late in the 1990s the Dutch Open Telescope demonstrated that internal seeing in open, large aperture solar telescopes can be controlled by flushing air across the primary mirror and other telescope structures exposed to sunlight. In that system natural wind provides a uniform air temperature throughout the imaging volume, while efficiently sweeping heated air away from the optics and mechanical structure. Big Bear Solar Observatory's New Solar Telescope (NST) was designed to realize that same performance in an enclosed system by using both natural wind through the dome and forced air circulation around the primary mirror to provide the uniform air temperatures required within the telescope volume. The NST is housed in a conventional, ventilated dome with a circular opening, in place of the standard dome slit, that allows sunlight to fall only on an aperture stop and the primary mirror. The primary mirror is housed deep inside a cylindrical cell with only minimal openings in the side at the level of the mirror. To date, the forced air and cooling systems designed for the NST primary mirror have not been implemented, yet the telescope regularly produces solar images indicative of the absence of mirror seeing. Computational Fluid Dynamics (CFD) analysis of the NST primary mirror system along with measurements of air flows within the dome, around the telescope structure, and internal to the mirror cell are used to explain the origin of this seemingly incongruent result. The CFD analysis is also extended to hypothetical systems of various scales. We will discuss the results of these investigations.

  18. Design considerations for a large aperture high field superconducting dipole

    SciTech Connect

    Harfoush, F.; Ankenbrandt, C.; Harrison, M.; Kerby, J.; Koepke, K.; Mantsch, P.; Nicol, T.; Riddiford, A.; Theilacker, J.

    1989-03-01

    The final phase of the Fermilab upgrade proposal calls for a new ring of superconducting magnets to be placed in the existing Main Accelerator tunnel. The goal of this design study is to specify a high field dipole (HFD) that is capable of supporting fixed target operation (ramping, resonant extraction) at a field of 6.6T (1.5 Tev) and colliding beam physics at 8.0T (1.8 Tev). The magnetic field quality at high field is set by the large amplitude orbits associated with resonant extraction. The field quality must therefore be at least as good as the existing Tevatron magnets which fulfill these criteria. The high fields and large aperture of this magnet result in large forces on the coil and collar assemblies. Therefore, the cold mass design must be able to sustain these forces while providing sufficient cooling to the coils during 4.2 K fixed target operation, and a minimum heat load during 1.8 K collider operation. The design work is still in progress but a cosine-theta, cold-iron dipole with a 70mm inner diameter coil has been tentatively adopted. This report presents details on the conductor and cable parameters, coil cross-section, projected manufacturing tolerances, iron yoke design, and cold mass assembly. 4 refs., 5 figs., 1 tab.

  19. Cavity-excited Huygens' metasurface antennas for near-unity aperture illumination efficiency from arbitrarily large apertures.

    PubMed

    Epstein, Ariel; Wong, Joseph P S; Eleftheriades, George V

    2016-01-01

    One of the long-standing problems in antenna engineering is the realization of highly directive beams using low-profile devices. In this paper, we provide a solution to this problem by means of Huygens' metasurfaces (HMSs), based on the equivalence principle. This principle states that a given excitation can be transformed to a desirable aperture field by inducing suitable electric and (equivalent) magnetic surface currents. Building on this concept, we propose and demonstrate cavity-excited HMS antennas, where the single-source-fed cavity is designed to optimize aperture illumination, while the HMS facilitates the current distribution that ensures phase purity of aperture fields. The HMS breaks the coupling between the excitation and radiation spectra typical to standard partially reflecting surfaces, allowing tailoring of the aperture properties to produce a desirable radiation pattern, without incurring edge-taper losses. The proposed low-profile design yields near-unity aperture illumination efficiencies from arbitrarily large apertures, offering new capabilities for microwave, terahertz and optical radiators. PMID:26790605

  20. Cavity-excited Huygens' metasurface antennas for near-unity aperture illumination efficiency from arbitrarily large apertures

    NASA Astrophysics Data System (ADS)

    Epstein, Ariel; Wong, Joseph P. S.; Eleftheriades, George V.

    2016-01-01

    One of the long-standing problems in antenna engineering is the realization of highly directive beams using low-profile devices. In this paper, we provide a solution to this problem by means of Huygens' metasurfaces (HMSs), based on the equivalence principle. This principle states that a given excitation can be transformed to a desirable aperture field by inducing suitable electric and (equivalent) magnetic surface currents. Building on this concept, we propose and demonstrate cavity-excited HMS antennas, where the single-source-fed cavity is designed to optimize aperture illumination, while the HMS facilitates the current distribution that ensures phase purity of aperture fields. The HMS breaks the coupling between the excitation and radiation spectra typical to standard partially reflecting surfaces, allowing tailoring of the aperture properties to produce a desirable radiation pattern, without incurring edge-taper losses. The proposed low-profile design yields near-unity aperture illumination efficiencies from arbitrarily large apertures, offering new capabilities for microwave, terahertz and optical radiators.

  1. Cavity-excited Huygens' metasurface antennas for near-unity aperture illumination efficiency from arbitrarily large apertures

    PubMed Central

    Epstein, Ariel; Wong, Joseph P. S.; Eleftheriades, George V.

    2016-01-01

    One of the long-standing problems in antenna engineering is the realization of highly directive beams using low-profile devices. In this paper, we provide a solution to this problem by means of Huygens' metasurfaces (HMSs), based on the equivalence principle. This principle states that a given excitation can be transformed to a desirable aperture field by inducing suitable electric and (equivalent) magnetic surface currents. Building on this concept, we propose and demonstrate cavity-excited HMS antennas, where the single-source-fed cavity is designed to optimize aperture illumination, while the HMS facilitates the current distribution that ensures phase purity of aperture fields. The HMS breaks the coupling between the excitation and radiation spectra typical to standard partially reflecting surfaces, allowing tailoring of the aperture properties to produce a desirable radiation pattern, without incurring edge-taper losses. The proposed low-profile design yields near-unity aperture illumination efficiencies from arbitrarily large apertures, offering new capabilities for microwave, terahertz and optical radiators. PMID:26790605

  2. Subarray partitions of large aperture planar towed arrays

    NASA Astrophysics Data System (ADS)

    Watson, Jennifer A.; Baggeroer, Arthur B.; Zurk, Lisa M.; Tracey, Brian H.

    2002-05-01

    The current focus of passive detection and localization is in littoral regions where acoustic propagation becomes complicated by severe bottom interaction. The resultant high-transmission loss motivates the need for high-array gain for effective performance over long ranges. Large planar seismic arrays, with aperture dimensions upwards of 3 km×0.5 km, have potential to achieve high gain and good resolution when using matched field processing. In realistic environments, however, large arrays are suceptible to signal gain degradation mechanisms, particularly due to spatial decorrelation of the signal and non-stationary environments. One approach to overcoming this is partitioning the array. Subarray processing reduces stationarity requirements and extracts optimum coherent gain, thus achieving higher gain than that of smaller arrays. This work examines criteria for partitioning planar arrays to perform localization using MFP. Trade-offs between spatial resolution, array gain, and resilience to motion will be quantified and discussed. Performance of different subarray geometries will be presented using adaptive and conventional MFP. [Work sponsored by DARPA under Air Force Contract No. F1962800-00-C-0002. Opinions, interpretations, conclusions, and recommendations are those of the authors and are not necessarily endorsed by the Department of Defense. AB's work was supported by ONR through the SECNAV CNO Chair.

  3. Multidirectional curved integral imaging with large depth by additional use of a large-aperture lens.

    PubMed

    Shin, Dong-Hak; Lee, Byoungho; Kim, Eun-Soo

    2006-10-01

    We propose a curved integral imaging system with large depth achieved by the additional use of a large-aperture lens in a conventional large-depth integral imaging system. The additional large-aperture lens provides a multidirectional curvature effect and improves the viewing angle. The proposed system has a simple structure due to the use of well-fabricated, unmodified flat devices. To calculate the proper elemental images for the proposed system, we explain a modified computer-generated pickup technique based on an ABCD matrix and analyze an effective viewing zone in the proposed system. From experiments, we show that the proposed system has an improved viewing angle of more than 7 degrees compared with conventional integral imaging. PMID:16983427

  4. Error analysis of large aperture static interference imaging spectrometer

    NASA Astrophysics Data System (ADS)

    Li, Fan; Zhang, Guo

    2015-12-01

    Large Aperture Static Interference Imaging Spectrometer is a new type of spectrometer with light structure, high spectral linearity, high luminous flux and wide spectral range, etc ,which overcomes the contradiction between high flux and high stability so that enables important values in science studies and applications. However, there're different error laws in imaging process of LASIS due to its different imaging style from traditional imaging spectrometers, correspondingly, its data processing is complicated. In order to improve accuracy of spectrum detection and serve for quantitative analysis and monitoring of topographical surface feature, the error law of LASIS imaging is supposed to be learned. In this paper, the LASIS errors are classified as interferogram error, radiometric correction error and spectral inversion error, and each type of error is analyzed and studied. Finally, a case study of Yaogan-14 is proposed, in which the interferogram error of LASIS by time and space combined modulation is mainly experimented and analyzed, as well as the errors from process of radiometric correction and spectral inversion.

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

    NASA Astrophysics Data System (ADS)

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

    2008-07-01

    The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) is a suborbital 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 three arrays, observes simultaneously in broadband (30%) spectral windows at 250, 350, and 500 μm. The optical design is based on a 2 m diameter telescope, providing a diffraction-limited resolution of 30'' at 250 μm. The gondola pointing system enables raster mapping of arbitrary geometry, with a repeatable positional accuracy of ~30''; postflight pointing reconstruction to lesssim5'' rms is achieved. The onboard telescope control software permits autonomous execution of a preselected 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 hr flight from ESRANGE (Kiruna), Sweden to Victoria Island, northern Canada in 2005 June; and a 250 hr, circumpolar flight from McMurdo Station, Antarctica, in 2006 December.

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

    NASA Astrophysics Data System (ADS)

    Semisch, Christopher; BLAST Collaboration

    2007-12-01

    The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) is a sub-orbital survey-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 250µm, 350µm, and 500µm. The optical design is based on a 2m diameter Cassegrain telescope, providing a diffraction-limited resolution of 30" at 250µm. The gondola pointing system enables raster-like maps of arbitrary geometry, with a repeatable positional accuracy of 30"; post-flight pointing reconstruction to < 5" rms is also achieved. The on-board telescope control software permits autonomous execution of a pre-selected set of maps, with the option of manual intervention. Since a test-flight in 2003, BLAST has 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.

  7. Intracavity Herriott-cell testbed for large-aperture femtosecond optics

    NASA Astrophysics Data System (ADS)

    Rácz, Péter; Nagy, Benedek J.; Ferencz, Kárpát; Dombi, Péter

    2014-12-01

    We demonstrate a versatile test method of large-aperture femtosecond mirrors inside a long-cavity Ti:sapphire laser oscillator. The Herriott-cell inside the cavity is utilized for the purpose of carrying out full-aperture testing. The method is highly sensitive to the homogeneity of mirror reflectivity and group delay dispersion over the whole mirror surface and it is suitable for testing both high reflector and chirped mirrors starting from 2” size up to arbitrarily large apertures.

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

    NASA Astrophysics Data System (ADS)

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

    2009-01-01

    The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) is a suborbital 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 three arrays, observes simultaneously in broadband (30%) spectral windows at 250, 350, and 500 microns. The optical design is based on a 2 m 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"; postflight pointing reconstruction to <5" rms is achieved. The onboard telescope control software permits autonomous execution of a preselected set of maps, with the option of manual override. On this poster, 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 2005 June; and a 250 hour, circumpolar flight from McMurdo Station, Antarctica in 2006 December. The BLAST collaboration acknowledges the support of NASA through grants NAG5-12785, NAG5-13301, and NNGO-6GI11G, the Canadian Space Agency (CSA), the Science and Technology Facilities Council (STFC), Canada's Natural Sciences and Engineering Research Council (NSERC), the Canada Foundation for Innovation, the Ontario Innovation Trust, the Puerto Rico Space Grant Consortium, the Fondo Institucional para la Investigacion of the University of Puerto Rico, and the National Science Foundation Office of Polar Programs.

  9. Large-pitch steerable synthetic transmit aperture imaging (LPSSTA)

    NASA Astrophysics Data System (ADS)

    Li, Ying; Kolios, Michael C.; Xu, Yuan

    2016-04-01

    A linear ultrasound array system usually has a larger pitch and is less costly than a phased array system, but loses the ability to fully steer the ultrasound beam. In this paper, we propose a system whose hardware is similar to a large-pitch linear array system, but whose ability to steer the beam is similar to a phased array system. The motivation is to reduce the total number of measurement channels M (the product of the number of transmissions, nT, and the number of the receive channels in each transmission, nR), while maintaining reasonable image quality. We combined adjacent elements (with proper delays introduced) into groups that would be used in both the transmit and receive processes of synthetic transmit aperture imaging. After the M channels of RF data were acquired, a pseudo-inversion was applied to estimate the equivalent signal in traditional STA to reconstruct a STA image. Even with the similar M, different choices of nT and nR will produce different image quality. The images produced with M=N2/15 in the selected regions of interest (ROI) were demonstrated to be comparable with a full phased array, where N is the number of the array elements. The disadvantage of the proposed system is that its field of view in one delay-configuration is smaller than a standard full phased array. However, by adjusting the delay for each element within each group, the beam can be steered to cover the same field of view as the standard fully-filled phased array. The LPSSTA system might be useful for 3D ultrasound imaging.

  10. Intense THz Pulses with large ponderomotive potential generated from large aperture photoconductive antennas.

    PubMed

    Ropagnol, X; Khorasaninejad, M; Raeiszadeh, M; Safavi-Naeini, S; Bouvier, M; Côté, C Y; Laramée, A; Reid, M; Gauthier, M A; Ozaki, T

    2016-05-30

    We report the generation of free space terahertz (THz) pulses with energy up to 8.3 ± 0.2 µJ from an encapsulated interdigitated ZnSe Large Aperture Photo-Conductive Antenna (LAPCA). An aperture of 12.2 cm2 is illuminated using a 400 nm pump laser with multi-mJ energies at 10 Hz repetition rate. The calculated THz peak electric field is 331 ± 4 kV/cm with a spectrum characterized by a median frequency of 0.28 THz. Given its relatively low frequency, this THz field will accelerate charged particles efficiently having very large ponderomotive energy of 15 ± 1 eV for electrons in vacuum. The scaling of the emission is studied with respect to the dimensions of the antenna, and it is observed that the capacitance of the LAPCA leads to a severe decrease in and distortion of the biasing voltage pulse, fundamentally limiting the maximum applied bias field and consequently the maximum energy of the radiated THz pulses. In order to demonstrate the advantages of this source in the strong field regime, an open-aperture Z-scan experiment was performed on n-doped InGaAs, which showed significant absorption bleaching. PMID:27410061

  11. Optical system of large relative aperture and wide field using aspheric corrector for detecting

    NASA Astrophysics Data System (ADS)

    Ming, Ming; Wang, Jianli; Zhang, Jingxu

    2009-05-01

    The magnitude requirement of space target detecting determines that the image of detecting telescope should have several performances: small spots, small 80% encircled energy diameter and good MTF(Modulation transfer function). So the aperture and field of view of optical system have some demands accordingly. The larger aperture, the more energy that telescope collects and higher magnitude the telescope detects; the wider field of view, the more extensive range which the telescope searches. Now most of ground telescopes whose apertures are from 500mm to 1000mm is on-axis optical system, so wide field of view becomes the most importance problem. To obtain large relative aperture and wide field of view, the paper introduces a catadioptric telescope with small aperture aspheric refractive corrector, whose conic surface will be used to remove the aberrations due to large relative aperture and wide field of view. As to the optical system, there is only one aspheric refractive corrector, and it is relatively easy for manufacturing because of its concave figure and normal material. The paper gives the example, and optimizes this optical system with ZEMAX program. And then the paper provides a specific analysis program for testing the aspheric refractive corrector. The aperture of this optical system is 750mm, and its relative aperture is 0.82, and the field of view is 3.6° diameter(diagonal). Its structure is simple and the image quality is also very good.

  12. 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.

  13. The scaling relationship between telescope cost and aperture size for very large telescopes

    NASA Technical Reports Server (NTRS)

    van Belle, Gerard T.; Meinel, Aden Baker; Meinel, Marjorie Pettit

    2004-01-01

    Cost data for ground-based telescopes of the last century are analyzed for trends in the relationship between aperture size and cost. We find that for apertures built prior to 1980, costs scaled as aperture size to the 2.8 power, which is consistent with the precious finding of Meinel (1978). After 1980, 'traditional' monolithic mirror telescope costs have scaled as aperture to the 2.5 power. The large multiple mirror telescopes built or in construction during this time period (Keck, LBT, GTC) appear to deviate from this relationship with significant cost savings as a result, although it is unclear what power law such structures follow. We discuss the implications of the current cost-aperture size data on the proposed large telescope projects of the next ten to twenty years. Structures that naturally tend towards the 2.0 power in the cost-aperture relationship will be the favorable choice for future extremely large apertures; out expectation is that space-based structures will ultimately gain economic advantage over ground-based ones.

  14. Reflective Schmidt-Cassegrain system for large-aperture telescopes.

    PubMed

    Brychikhin, M N; Chkhalo, N I; Eikhorn, Ya O; Malyshev, I V; Pestov, A E; Plastinin, Yu A; Polkovnikov, V N; Rizvanov, A A; Salashchenko, N N; Strulya, I L; Toropov, M N

    2016-06-01

    A reflective modification of the Schmidt-Cassegrain system was built and tested. Ultraviolet (UV) and soft x-ray applications are discussed. The system consists of a planoid mirror with an aspheric profile and prime concave and secondary convex spherical mirrors. Spherical aberration in a wide field of view and astigmatism are compensated by the aspheric profile of the planoid. The main parameters of the scheme are as follows: an entrance aperture of 180 mm, a focal ratio F/3.2, an angular resolution better than 3'' (corresponding to a pixel size of a back-side illuminated CCD), a field of view of ±1.5° (2ω=3°) and a flat image field with a diameter of 30.4 mm. Due to the absence of chromatic aberrations and wide field of view, the scheme is of considerable interest for hyperspectral instruments. In particular, the operating range of the instruments can be expanded into vacuum UV and UV regions. PMID:27411199

  15. 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%.

  16. Synthesis of a large communications aperture using small antennas

    NASA Technical Reports Server (NTRS)

    Resch, George M.; Cwik, T. W.; Jamnejad, V.; Logan, R. T.; Miller, R. B.; Rogstad, Dave H.

    1994-01-01

    In this report we compare the cost of an array of small antennas to that of a single large antenna assuming both the array and single large antenna have equal performance and availability. The single large antenna is taken to be one of the 70-m antennas of the Deep Space Network. The cost of the array is estimated as a function of the array element diameter for three different values of system noise temperature corresponding to three different packaging schemes for the first amplifier. Array elements are taken to be fully steerable paraboloids and their cost estimates were obtained from commercial vendors. Array loss mechanisms and calibration problems are discussed. For array elements in the range 3 - 35 m there is no minimum in the cost versus diameter curve for the three system temperatures that were studied.

  17. 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

  18. Zinc selenide-based large aperture photo-controlled deformable mirror.

    PubMed

    Quintavalla, Martino; Bonora, Stefano; Natali, Dario; Bianco, Andrea

    2016-06-01

    Realization of large aperture deformable mirrors with a large density of actuators is important in many applications, and photo-controlled deformable mirrors (PCDMs) represent an innovation. Herein we show that PCDMs are scalable realizing a 2-inch aperture device based on a polycrystalline zinc selenide (ZnSe) as the photoconductive substrate and a thin polymeric reflective membrane. ZnSe is electrically characterized and analyzed through a model that we previously introduced. The PCDM is then optically tested, demonstrating its capabilities in adaptive optics. PMID:27244417

  19. Eyeglass Large Aperture, Lightweight Space Optics FY2000 - FY2002 LDRD Strategic Initiative

    SciTech Connect

    Hyde, R

    2003-02-10

    A series of studies by the Air Force, the National Reconnaissance Office and NASA have identified the critical role played by large optics in fulfilling many of the space related missions of these agencies. Whether it is the Next Generation Space Telescope for NASA, high resolution imaging systems for NRO, or beam weaponry for the Air Force, the diameter of the primary optic is central to achieving high resolution (imaging) or a small spot size on target (lethality). While the detailed requirements differ for each application (high resolution imaging over the visible and near-infrared for earth observation, high damage threshold but single-wavelength operation for directed energy), the challenges of a large, lightweight primary optic which is space compatible and operates with high efficiency are the same. The advantage of such large optics to national surveillance applications is that it permits these observations to be carried-out with much greater effectiveness than with smaller optics. For laser weapons, the advantage is that it permits more tightly focused beams which can be leveraged into either greater effective range, reduced laser power, and/or smaller on-target spot-sizes; weapon systems can be made either much more effective or much less expensive. This application requires only single-wavelength capability, but places an emphasis upon robust, rapidly targetable optics. The advantages of large aperture optics to astronomy are that it increases the sensitivity and resolution with which we can view the universe. This can be utilized either for general purpose astronomy, allowing us to examine greater numbers of objects in more detail and at greater range, or it can enable the direct detection and detailed examination of extra-solar planets. This application requires large apertures (for both light-gathering and resolution reasons), with broad-band spectral capability, but does not emphasize either large fields-of-view or pointing agility. Despite

  20. Annular sub-aperture stitching interferometry for testing of large aspherical surfaces

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-kun; Wang, Li-hui; Zheng, Li-gong; Deng, Wei-jie; Zhang, Xue-jun

    2008-03-01

    Annular subaperture stitching interferometric technology can test large-aperture, high numerical aperture aspheric surfaces with high resolution, low cost and high efficiency without auxiliary null optics. In this paper, the basic principle and theory of the stitching method are introduced, the reasonable mathematical model and effective splicing algorithm are established based on simultaneous least-squares method and Zernike polynomial fitting. The translation errors are eliminated from each subaperture through the synthetical optimization stitching mode, it keeps the error from transmitting and accumulating. The numerical simulations have been carried on by this method. As results, the surface map of the full aperture after stitching is consistent to the input surface map, the difference of PV error and RMS error between them is -0.0074 λ and -0.00052 λ (λ is 632.8nm), respectively; the relative error of PV and RMS is -0.53% and -0.31%; and the PV and RMS of residual error of the full aperture phase distribution is 0.027 λ and 0.0023 λ, respectively. The results conclude that this splicing model and algorithm are accurate and feasible. So it provides another quantitive measurement for test aspheric surfaces especially for large aperture aspheres besides null-compensation.

  1. Large Aperture Scanning Lidar Based on Holographic Optical Elements

    NASA Technical Reports Server (NTRS)

    Schwemmer, Geary K.; Miller, David O.; Wilkerson, Thomas D.; Andrus, Ionio; Guerra, David V.; Einaudi, Franco (Technical Monitor)

    2001-01-01

    Lidar remote sensing instruments can make a significant contribution to satisfying many of the required measurements of atmospheric and surface parameters for future spaceborne platforms, including topographic altimeters, atmospheric profiles of, wind, humidity, temperature, trace molecules, aerosols, and clouds. It is highly desirable to have wide measurement swaths for rapid coverage rather than just the narrow ribbon of data that is obtained with a nadir only observation. For most applications global coverage is required, and for wind measurements scanning or pointing is required in order to retrieve the full 3-D wind vector from multiple line-of-sight Doppler measurements. Conventional lidar receivers make up a substantial portion of the instrument's size and weight. Wide angle scanning typically requires a large scanning mirror in front of the receiver telescope, or pointing the entire telescope and aft optics assembly, Either of these methods entails the use of large bearings, motors, gearing and their associated electronics. Spaceborne instruments also need reaction wheels to counter the torque applied to the spacecraft by these motions. NASA has developed simplified conical scanning telescopes using Holographic Optical Elements (HOEs) to reduce the size, mass, angular momentum, and cost of scanning lidar systems. NASA has developed two operating lidar systems based on 40 cm diameter HOEs. The first such system, named Prototype Holographic Atmospheric Scanner for Environmental Remote Sensing (PHASERS) was a joint development between NASA Goddard Space Flight Center (GSFC) and the University of Maryland College Park. PHASERS is based on a reflection HOE for use at the doubled Nd:YAG laser wavelength of 532 nm and has recently undergone a number of design changes in a collaborative effort between GSFC and Saint Anselm College in New Hampshire. The next step was to develop IR transmission HOEs for use with the Nd:YAG fundamental in the Holographic Airborne

  2. Large Aperture Scanning Lidar Based on Holographic Optical Elements

    NASA Technical Reports Server (NTRS)

    Schwemmer, Geary K.; Miller, David O.; Wilkerson, Thomas D.; Andrus, Ionio; Guerra, David V.; Einaudi, Franco (Technical Monitor)

    2001-01-01

    Lidar remote sensing instruments can make a significant contribution to satisfying many of the required measurements of atmospheric and surface parameters for future spaceborne platforms, including topographic altimeters, atmospheric profiles of, wind, humidity, temperature, trace molecules, aerosols, and clouds. It is highly desirable to have wide measurement swaths for rapid coverage rather than just the narrow ribbon of data that is obtained with a nadir only observation. For most applications global coverage is required, and for wind measurements scanning or pointing is required in order to retrieve the full 3-D wind vector from multiple line-of-sight Doppler measurements. Conventional lidar receivers make up a substantial portion of the instrument's size and weight. Wide angle scanning typically requires a large scanning mirror in front of the receiver telescope, or pointing the entire telescope and aft optics assembly, Either of these methods entails the use of large bearings, motors, gearing and their associated electronics. Spaceborne instruments also need reaction wheels to counter the torque applied to the spacecraft by these motions. NASA has developed simplified conical scanning telescopes using Holographic Optical Elements (HOEs) to reduce the size, mass, angular momentum, and cost of scanning lidar systems. NASA has developed two operating lidar systems based on 40 cm diameter HOEs. The first such system, named Prototype Holographic Atmospheric Scanner for Environmental Remote Sensing (PHASERS) was a joint development between NASA Goddard Space Flight Center (GSFC) and the University of Maryland College Park. PHASERS is based on a reflection HOE for use at the doubled Nd:YAG laser wavelength of 532 nm and has recently undergone a number of design changes in a collaborative effort between GSFC and Saint Anselm College in New Hampshire. The next step was to develop IR transmission HOEs for use with the Nd:YAG fundamental in the Holographic Airborne

  3. π/K/p identification with a large-aperture ring-imaging cherenkov counter

    NASA Astrophysics Data System (ADS)

    Adams, M.; Bastin, A.; Coutrakon, G.; Glass, H.; Jaffe, D.; Kirz, J.; McCarthy, R.; Hubbard, J. R.; Mangeot, Ph.; Mullie, J.; Peisert, A.; Tichit, J.; Bouclier, R.; Charpak, G.; Santiard, J. C.; Sauli, F.; Crittenden, J.; Hsiung, Y.; Kaplan, D.; Brown, C.; Childress, S.; Finley, D.; Ito, A.; Jonckheere, A.; Jöstlein, H.; Lederman, L.; Orava, R.; Smith, S.; Sugano, K.; Ueno, K.; Maki, A.; Hemmi, Y.; Miyake, K.; Nakamura, T.; Sasao, N.; Sakai, Y.; Gray, R.; Plaag, R.; Rothberg, J.; Rutherfoord, J.; Young, K.

    1983-11-01

    The operating large aperture ring-imaging Cherenkov detector from the FNAL experiment E605 is described. Cherenkov ultraviolet photons are detected with a multi-step avalanche chamber using a He/TEA gas mixture and π/K/p separation is obtained from 50 to 200 GeV/ c.

  4. Large aperture vibrating wire monitor with two mechanically coupled wires for beam halo measurements

    SciTech Connect

    Arutunian, S. G.; Avetisyan, A. E.; Davtyan, M. M.; Harutyunyan, G. S.; Vasiniuk, I. E.; Chung, M.; Scarpine, V.

    2014-03-01

    Development of a new type of Vibrating Wire Monitor (VWM), which has two mechanically coupled wires (vibrating and target), is presented. The new monitor has a much larger aperture size than the previous model of the VWM, and thus allows us to measure transverse beam halos more effectively. A prototype of such a large aperture VWM with a target wire length of 60 mm was designed, manufactured, and bench-tested. Initial beam measurements have been performed at the Fermilab High Intensity Neutrino Source (HINS) facility, and key results are presented.

  5. A systematic investigation of large-scale diffractive coded aperture designs

    NASA Astrophysics Data System (ADS)

    Gottesman, Stephen R.; Shrekenhamer, Abraham; Isser, Abraham; Gigioli, George

    2012-10-01

    One obstacle to optimizing performance of large-scale coded aperture systems operating in the diffractive regime has been the lack of a robust, rapid, and efficient method for generating diffraction patterns that are projected by the system onto the focal plane. We report on the use of the 'Shrekenhamer Transform' for a systematic investigation of various types of coded aperture designs operating in the diffractive mode. Each design is evaluated in terms of its autocorrelation function for potential use in future imaging applications. The motivation of our study is to gain insight into more efficient optimization methods of image reconstruction algorithms.

  6. 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.

  7. 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.

  8. 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 4×1 PPC with 400mm×400mm aperture for SGIII laser facility. And four 2×1 PPCs modules with 350mm×350mm 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 80mm×80mm DKDP crystal have been manufactured and operated in laser facilities.

  9. 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.

  10. The development of large-aperture test system of infrared camera and visible CCD camera

    NASA Astrophysics Data System (ADS)

    Li, Yingwen; Geng, Anbing; Wang, Bo; Wang, Haitao; Wu, Yanying

    2015-10-01

    Infrared camera and CCD camera dual-band imaging system is used in many equipment and application widely. If it is tested using the traditional infrared camera test system and visible CCD test system, 2 times of installation and alignment are needed in the test procedure. The large-aperture test system of infrared camera and visible CCD camera uses the common large-aperture reflection collimator, target wheel, frame-grabber, computer which reduces the cost and the time of installation and alignment. Multiple-frame averaging algorithm is used to reduce the influence of random noise. Athermal optical design is adopted to reduce the change of focal length location change of collimator when the environmental temperature is changing, and the image quality of the collimator of large field of view and test accuracy are also improved. Its performance is the same as that of the exotic congener and is much cheaper. It will have a good market.

  11. Initial Technology Assessment for the Large-Aperture UV-Optical-Infrared (LUVOIR) Mission Concept Study

    NASA Technical Reports Server (NTRS)

    Bolcar, Matthew R.; Feinberg, Lee; France, Kevin; Rauscher, Bernard J.; Redding, David; Schiminovich, David

    2016-01-01

    The NASA Astrophysics Division's 30-Year Roadmap prioritized a future large-aperture space telescope operating in the ultra-violet/optical/infrared wavelength regime. The Association of Universities for Research in Astronomy envisioned a similar observatory, the High Definition Space Telescope. And a multi-institution group also studied the Advanced Technology Large Aperture Space Telescope. In all three cases, a broad science case is outlined, combining general astrophysics with the search for biosignatures via direct-imaging and spectroscopic characterization of habitable exoplanets. We present an initial technology assessment that enables such an observatory that is currently being studied for the 2020 Decadal Survey by the Large UV/Optical/Infrared (LUVOIR) surveyor Science and Technology Definition Team. We present here the technology prioritization for the 2016 technology cycle and define the required technology capabilities and current state-of-the-art performance. Current, planned, and recommended technology development efforts are also reported.

  12. Research on 2x1 plasma electrode electro-optical switch with large aperture

    NASA Astrophysics Data System (ADS)

    Zhang, Xiong Jun; Zheng, Kui Xing; Feng, B.; Wu, D. S.; Lu, J. P.; Tian, X. L.; Jin, F.; Sui, Zhan; Wei, Xiaofeng; Zhang, Xiaomin

    2005-01-01

    In conceptual design of the prototype for SG-III facility, a full aperture electro-optical switch was placed between the cavity mirror and the main amplifier to isolate the reflected beams. The beam on the cavity mirror is 240mm×240mm square. Pockells cells of conversional design with coaxial ring electrodes can not scale to such large square aperture. In the 1980s, a plasma electrode Pockels cell (PEPC) concept was invented at LLNL. It uses transparent plasma electrode formed through gas discharge as the electrodes to apply the voltage across switching crystal to rotate the polarization of a transmitted laser beam. And it can be scaled to large aperture with thin crystal. So the switch which would be used in SG-III is based on this technology. The technical integration line as a prototype of SG-III laser is actually a 4×2 beam bundle. And the full aperture optical switch is mechanically designed four apertures as a removable unit, and electrically two 2×1 PEPC putting together. So we built a 2×1 PEPC to develop the technology first. The 2×1 PEPC is a sandwich structure made of an insulating mid plane between a pair of plasma chambers. The frame of both plasma chambers are machining in duralumin. Each chamber is installed with a planar magnetic cathode and four segments spherical anodes made from stainless steel. The cathode and anode are insulated from the housing with a special shell made from plastic, and plasma is insulated from the housing by an 80-μm-thick anodic coating on the duralumin. The two plasma chambers are separated by a mid plane of glass frame with two square holes. The two holes are filled by two electro-optical crystals with a 240-mm square aperture. With the optimized operating pressure and the electrical parameters, a very good homogeneity and low resistivity plasma electrode is obtained. Finally we tested its switching performance to simulate the case that it will be used in the SG-III prototype facility. It works with a quarter wave

  13. Large-aperture prism-array lens for high-energy X-ray focusing.

    PubMed

    Zhang, Weiwei; Liu, Jing; Chang, Guangcai; Shi, Zhan; Li, Ming; Ren, Yuqi; Zhang, Xiaowei; Yi, Futing; Liu, Peng; Sheng, Weifan

    2016-09-01

    A new prism-array lens for high-energy X-ray focusing has been constructed using an array of different prisms obtained from different parabolic structures by removal of passive parts of material leading to a multiple of 2π phase variation. Under the thin-lens approximation the phase changes caused by this lens for a plane wave are exactly the same as those caused by a parabolic lens without any additional corrections when they have the same focal length, which will provide good focusing; at the same time, the total transmission and effective aperture of this lens are both larger than those of a compound kinoform lens with the same focal length, geometrical aperture and feature size. This geometry can have a large aperture that is not limited by the feature size of the lens. Prototype nickel lenses with an aperture of 1.77 mm and focal length of 3 m were fabricated by LIGA technology, and were tested using CCD camera and knife-edge scan method at the X-ray Imaging and Biomedical Application Beamline BL13W1 at Shanghai Synchrotron Radiation Facility, and provided a focal width of 7.7 µm and a photon flux gain of 14 at an X-ray energy of 50 keV. PMID:27577761

  14. Partial feedback unstable resonator on small scale supersonic large aperture chemical laser

    NASA Astrophysics Data System (ADS)

    Wang, Hongyan; Wang, Rui; Li, Lei

    2015-05-01

    There is always a challenge on large aperture medium power laser's resonator design, stable resonator would supports significant higher order transverse modes, folded and telescope stable resonator are too complex and not preferred by engineers, unstable resonator need rather large round trip gain to compensate its high geometric out-coupling, which is difficult for this kind of laser since its gain length is limited due to the power level and large aperture. Partial feedback unstable resonator had been proposed to tackle this difficulty since the early days of laser development, however, the debates of its effect never stopped even with those distinguished optical resonator scientists such as Siegman, Anan'ev, and Weber. Recently integrated partial feedback unstable resonator design had been successfully demonstrated on a medium size chemical oxygen iodine laser. In this paper, we carry this resonator configuration on a small scale discharge driven supersonic nozzle array Hydrogen Fluoride chemical laser, a typical large aperture short gain length device. With magnification equals 4/3, we successfully get ten Watts level ring beam output.

  15. Active polishing technology for large aperture aspherical mirror and ultra thin mirror

    NASA Astrophysics Data System (ADS)

    Cui, Xaingqun; Gao, Bilie; Li, Xinnan

    2006-02-01

    Some results on active polishing technology for large aperture aspherical mirrors and ultra thin mirrors, which have been developed in recent years in Nanjing Institute of Astronomical Optics and Technology, CAS, are presented in this paper. There are two polishing methods developed for the large aperture ultra thin mirrors with two different trial mirrors respectively. One is a hexagonal mirror with diagonal size of 1100mm, and thickness of 25mm by no-separate support method specially for polish the sub-mirror of Schmidt corrector of LAMOST, which is a national large scientific project of China. Another is a circular mirror with 1035mm in diameter and 26mm in thickness by active support method. The active stressed polishing technology developed for large aperture aspherical mirror with fast f ratio, and a paraboloidal mirror with a diameter of 910mm and an f ratio 2 as was successfully polished. The computer controlled polishing is also different from the normal way in the system. Some complicated aspects were added. The results showed the final surface accuracy of all these trial mirrors is better than expected requirements for normal application in astronomical telescopes.

  16. Large aperture and polarizer-free liquid crystal lenses for ophthalmic applications

    NASA Astrophysics Data System (ADS)

    Lin, Yi-Hsin; Chen, Hung-Shan; Chang, Chia-Ming; Wang, Yu-Jen

    2014-10-01

    Large aperture and polarizer-free liquid crystal lenses (LC lenses) based on a double-layered structure for ophthalmic applications are demonstrated. The polarizer-free LC lens functions as both of a positive lens and a negative lens with large aperture size of 10mm. The lens power is electrically and continuously tunable ranging from -1.32 Diopter to 1.83 Diopter. To demonstrate the polarization independency, the wavefronts of the LC lenses under different polarized light were measured and discussed. The detail operations of the applied voltage and frequency are also discussed. The imaging performance of the LC lens is also evaluated. This study provide a detail understanding of the polarizer-free LC lenses based on a double-layered structure.

  17. 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.

  18. High-power narrow-band terahertz generation using large-aperture photoconductors

    SciTech Connect

    Park, S.G.; Weiner, A.M.; Melloch, M.R. . School of Electrical and Computer Engineering); Siders, C.W.; Siders, J.L.W.; Taylor, A.J. )

    1999-08-01

    Large-aperture biased photoconductive emitters which can generate high-power narrow-band terahertz (THz) radiation are developed. These emitters avoid saturation at high fluence excitation and achieve enhanced peak power spectral density by employing a thick layer of short-lifetime low-temperature-grown GaAs (LT-GaAs) photoconductor and multiple-pulse excitation. THz waveforms are calculated from the saturation theory of large-aperture photoconductors, and a comparison is made between theory and measurement. A direct comparison of the multiple-pulse saturation properties of THz emission from semi-insulating GaAs and LT-GaAs emitters reveals a strong dependence on the carrier lifetime. In particular, the data demonstrate that saturation is avoided only when the interpulse spacing is longer than the carrier lifetime.

  19. Comparison of full-aperture interferometry to sub-aperture stitched interferometry for a large diameter fast mirror

    NASA Technical Reports Server (NTRS)

    Catanzaro, B.; Thomas, J.; Cohen, E.

    2001-01-01

    The Herschel Space Observatory (formerly known as FIRST) consists of a 3.5 m space telescope. Stitching sub aperture interferograms may offer considerable cost savings during testing of the flight telescope as compared to other techniques. A comparative demonstration is presented of interferogram stitching techniques that enable a composite map of a 3-D surface to be assembled from a sequence of sub-aperture measurements. This paper describes the fundamental procedures for stitching together component data sets and demonstrates such techniques with real data sets.

  20. 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.

  1. Fabrication of large aperture kinoform phase plates in fused silica for smoothing focal plane intensity profiles

    SciTech Connect

    Rushford, M.; Dixit, S.; Thomas, I.; Perry, M.

    1996-04-26

    We have fabricated large aperture (40-cm) kinoform phase plates for producing super-Gaussian focal plane intensity profiles. The continuous phase screen, designed using a new iterative procedure, was fabricated in fused silica as a 16-level, one-wave deep rewrapped phase profile using a lithographic process and wet etching in buffered hydrofluoric acid. The observed far-field contains 94% of the incident energy inside the desired spot.

  2. Fast inspection of bulk and surface defects of large aperture optics in high power lasers

    NASA Astrophysics Data System (ADS)

    Zhao, Yuan'an; Hu, Guohang; Liu, Shijie; Yi, Kui; Shao, Jianda

    2015-05-01

    Laser induced damage for nanosecond pulse duration is attributed to the existence of defects. The growth and polishing, as well as coating deposition, may induce versatile kinds of defects, including dig, scratch and inclusion. It is special important to get the information of the defects, such as size and location, which is the basis to know the origin of the defects and figures out effective techniques to eliminate it. It is quite easy to get the information of the defects with micron-level resolution, but it is time-consuming and is not suitable for fast inspection of the large aperture (hundreds of millimeters). In this work, on-the-fly image capture technique was employed to realize fast inspection of large aperture optics. A continuous green laser was employed as illumination source to enhance and enlarge the image of bulk defects. So it could detect the submicron-scale defects. A transmission microscopy with white light illumination was employed to detect the surface defect. Its field of view was about 2.8mm×1.6mm. The sample was raster scanned driving by a stepper motor through the stationary illumination laser and digital camera, and the speed to scan the sample was about 10mm/s. The results of large aperture optics proved the functions of this fast inspection technique.

  3. Application of Modern Aperture Integration (AI) and Geometrical Theory of Diffraction (GTD) Techniques for Analysis of Large Reflector Antennas

    NASA Technical Reports Server (NTRS)

    Rudduck, R. C.

    1985-01-01

    The application of aperture integration (AI) and geometrical theory of diffraction (GTO) techniques to analyze large reflector antennas is outlined. The following techniques were used: computer modeling, validation of analysis and computer codes, computer aided design modifications, limitation on the conventional aperture integration (AIC) method, extended aperture integration (AIE) method, the AIE method for feed scattering calculations, near field probing predictions for 15 meter model, limitation on AIC for surface tolerance effects, aperture integration on the surface (AIS) method, and AIC and GTD calculations for compact range reflector.

  4. An Engineering Design Reference Mission for a Future Large-Aperture UVOIR Space Observatory

    NASA Astrophysics Data System (ADS)

    Thronson, Harley A.; Bolcar, Matthew R.; Clampin, Mark; Crooke, Julie A.; Redding, David; Rioux, Norman; Stahl, H. Philip

    2016-01-01

    From the 2010 NRC Decadal Survey and the NASA Thirty-Year Roadmap, Enduring Quests, Daring Visions, to the recent AURA report, From Cosmic Birth to Living Earths, multiple community assessments have recommended development of a large-aperture UVOIR space observatory capable of achieving a broad range of compelling scientific goals. Of these priority science goals, the most technically challenging is the search for spectroscopic biomarkers in the atmospheres of exoplanets in the solar neighborhood. Here we present an engineering design reference mission (EDRM) for the Advanced Technology Large-Aperture Space Telescope (ATLAST), which was conceived from the start as capable of breakthrough science paired with an emphasis on cost control and cost effectiveness. An EDRM allows the engineering design trade space to be explored in depth to determine what are the most demanding requirements and where there are opportunities for margin against requirements. Our joint NASA GSFC/JPL/MSFC/STScI study team has used community-provided science goals to derive mission needs, requirements, and candidate mission architectures for a future large-aperture, non-cryogenic UVOIR space observatory. The ATLAST observatory is designed to operate at a Sun-Earth L2 orbit, which provides a stable thermal environment and excellent field of regard. Our reference designs have emphasized a serviceable 36-segment 9.2 m aperture telescope that stows within a five-meter diameter launch vehicle fairing. As part of our cost-management effort, this particular reference mission builds upon the engineering design for JWST. Moreover, it is scalable to a variety of launch vehicle fairings. Performance needs developed under the study are traceable to a variety of additional reference designs, including options for a monolithic primary mirror.

  5. Research on the support structure of the primary mirror of large-aperture telescope

    NASA Astrophysics Data System (ADS)

    Wang, Yang; Zhang, Jingxu

    2007-12-01

    Large-aperture telescope can be used in surveying battlefield, researching landform, searching object, real-time monitoring, imaging, detecting and identifying spatial targets and so on. A large-aperture telescope for achieving high resolution power is designed to monitor spatial target and image in real time. Real-time monitoring plays an important role in military conflicts. The orbit parameter of object, quantity, geometrical shape parameter and so on can be obtained by detect spatial target. With the development of optical technology, people require larger aperture in optics-electronic (O-E) system. By increasing optical aperture, the ability of collecting light and resolution power in the system can be enhanced. But the support structure of the primary mirror of large-aperture telescope will be a very difficult problem. With the increase of primary mirror aperture, the weight of the primary mirror will become larger than before. The root mean square (rms) of the primary mirror is affected by many factors, such as deadweight, deformation of heat, environment and so on. Due to the primary mirror of telescope is an important component of telescope system. By reducing the weight of primary mirror, precision of the system is ensured. During the designing phase, one can consider the supporting project of the primary mirror synthetically and analyze it roundly according to technical requirement of optical system and the effect factors. The final structural design can be reasonable. In an astronomical telescope, the surface of reflector is an important part for collecting dark radiation of celestial bodies. Its surface shape will have an effect on collecting efficiency of telescope radiant energy directly. So the rms must be very high. Optical system of large aperture, small wavelength and small focus can receive maximal light intensity. For ground-based optical astronomical telescope, the design proposed in the paper can satisfy the requirement of the possible

  6. 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.

  7. Development of Large-Aperture, Light-Weight Fresnel Lenses for Gossamer Space Telescopes

    SciTech Connect

    Sham, D; Hyde, R; Weisberg, A; Early, J; Rushford, M; Britten, J

    2002-04-29

    In order to examine more distant astronomical objects, with higher resolution, future space telescopes require objectives with significantly larger aperture than presently available. NASA has identified a progression in size from the 2.4m aperture objective currently used in the HUBBLE space telescope[l,2], to 25m and greater in order to observe, e.g., extra-solar planets. Since weight is a crucial factor for any object sent into space, the relative weight of large optics over a given area must be reduced[3]. The areal mass density of the primary mirror for the Hubble space telescope is {approx}200 kg/m{sup 2}. This is expected to be reduced to around 15 kg/m{sup 2} for the successor to Hubble--the next generation space telescope (NGST)[4]. For future very large aperture telescopes needed for extra-solar planet detection, the areal mass density must be reduced even further. For example, the areal mass density goal for the Gossamer space telescopes is < 1 kg/m{sup 2}. The production of lightweight focusing optics at >10m size is also an enabling technology for many other applications such as Earth observation, power beaming, and optical communications.

  8. 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.

  9. End-to-End Assessment of a Large Aperture Segmented Ultraviolet Optical Infrared (UVOIR) Telescope Architecture

    NASA Technical Reports Server (NTRS)

    Feinberg, Lee; Rioux, Norman; Bolcar, Matthew; Liu, Alice; Guyon, Oliver; Stark, Chris; Arenberg, Jon

    2016-01-01

    Key challenges of a future large aperture, segmented Ultraviolet Optical Infrared (UVOIR) Telescope capable of performing a spectroscopic survey of hundreds of Exoplanets will be sufficient stability to achieve 10^-10 contrast measurements and sufficient throughput and sensitivity for high yield Exo-Earth spectroscopic detection. Our team has collectively assessed an optimized end to end architecture including a high throughput coronagraph capable of working with a segmented telescope, a cost-effective and heritage based stable segmented telescope, a control architecture that minimizes the amount of new technologies, and an Exo-Earth yield assessment to evaluate potential performance. These efforts are combined through integrated modeling, coronagraph evaluations, and Exo-Earth yield calculations to assess the potential performance of the selected architecture. In addition, we discusses the scalability of this architecture to larger apertures and the technological tall poles to enabling it.

  10. Simulation analysis of on-orbit adjustment and compensation for large aperture optical system

    NASA Astrophysics Data System (ADS)

    Liu, Jianfeng; Li, Bo; Sun, Dewei; Ruan, Ningjuan; Zhou, Feng

    2014-09-01

    With the uprating requirements of space remote sensing, the aperture of the optical remote sensor is getting larger and larger. The influences of both the support of optical elements and gravity deformation on the optical system are difficult to conquer. Therefore, it is necessary to compensate the descending optical performance which is caused by the surface error of primary mirror by means of adjusting the position parameters of the optical elements on-orbit. A large aperture coaxial three-mirror optical system is introduced in the paper. Matlab and MetroPro are used to simulate the surface error of the primary mirror. The surface error of the primary mirror is compensated by adjusting the position freedoms of the secondary mirror. The results show that the adjustment of the position freedoms of the secondary mirror can compensate both the coma and some astigmatism of the primary mirror, but not the spherical aberration.

  11. Source-Search Sensitivity of a Large-Area, Coded-Aperture, Gamma-Ray Imager

    SciTech Connect

    Ziock, K P; Collins, J W; Craig, W W; Fabris, L; Lanza, R C; Gallagher, S; Horn, B P; Madden, N W; Smith, E; Woodring, M L

    2004-10-27

    We have recently completed a large-area, coded-aperture, gamma-ray imager for use in searching for radiation sources. The instrument was constructed to verify that weak point sources can be detected at considerable distances if one uses imaging to overcome fluctuations in the natural background. The instrument uses a rank-19, one-dimensional coded aperture to cast shadow patterns onto a 0.57 m{sup 2} NaI(Tl) detector composed of 57 individual cubes each 10 cm on a side. These are arranged in a 19 x 3 array. The mask is composed of four-centimeter thick, one-meter high, 10-cm wide lead blocks. The instrument is mounted in the back of a small truck from which images are obtained as one drives through a region. Results of first measurements obtained with the system are presented.

  12. ATLAST-9.2m: a Large-Aperture Deployable Space Telescope

    NASA Technical Reports Server (NTRS)

    Oergerle, William; Feinberg, Lee D.; Purves, Lloyd R.; Hyde, T. Tupper; Thronson, Harley A.; Townsend, Jacqueline A.; Postman, Marc; Bolear, Matthew R.; Budinoff, Jason G.; Dean, Bruce H.; Clampin, Mark C.; Ebbets, Dennis C.; Gong, Qian; Gull, Theodore R.; Howard, Joseph M.; Jones, Andrew L.; Lyon, Richard G.; Pasquale, Bert A.; Perrygo, Charles; Smith, Jeffrey S.; Thompson, Patrick L.; Woodgate, Bruce E.

    2010-01-01

    We present results of a study of a deployable version of the Advanced Technology Large-Aperture Space Telescope (ATLAST), designed to operate in a Sun-Earth L2 orbit. The primary mirror of the segmented 9.2-meter aperture has 36 hexagonal 1.315 m (flat to flat) glass mirrors. The architecture and folding of the telescope is similar to JWST, allowing it to fit into the 6.5 m fairing of a modest upgrade to the Delta-IV Heavy version of the Evolved Expendable Launch Vehicle (EELV). We discuss the overall observatory design, optical design, instruments, stray light, wavefront sensing and control, pointing and thermal control, and in-space servicing options.

  13. Detection of and compensation for blocked elements using large coherent apertures: ex vivo studies

    NASA Astrophysics Data System (ADS)

    Jakovljevic, Marko; Bottenus, Nick; Kuo, Lily; Kumar, Shalki; Dahl, Jeremy; Trahey, Gregg

    2016-04-01

    When imaging with ultrasound through the chest wall, it is not uncommon for parts of the array to get blocked by ribs, which can limit the acoustic window and significantly impede visualization of the structures of interest. With the development of large-aperture, high-element-count, 2-D arrays and their potential use in transthoracic imaging, detecting and compensating for the blocked elements is becoming increasingly important. We synthesized large coherent 2-D apertures and used them to image a point target through excised samples of canine chest wall. Blocked elements are detected based on low amplitude of their signals. As a part of compensation, blocked elements are turned off on transmit (Tx) and receive (Rx), and point-target images are created using: coherent summation of the remaining channels, compounding of intercostal apertures, and adaptive weighting of the available Tx/Rx channel-pairs to recover the desired k-space response. The adaptive compensation method also includes a phase aberration correction to ensure that the non-blocked Tx/Rx channel pairs are summed coherently. To evaluate the methods, we compare the point-spread functions (PSFs) and near-field clutter levels for the transcostal and control acquisitions. Specifically, applying k-space compensation to the sparse aperture data created from the control acquisition reduces sidelobes from -6.6 dB to -12 dB. When applied to the transcostal data in combination with phase-aberration correction, the same method reduces sidelobes only by 3 dB, likely due to significant tissue induced acoustic noise. For the transcostal acquisition, turning off blocked elements and applying uniform weighting results in maximum clutter reduction of 5 dB on average, while the PSF stays intact. Compounding reduces clutter by about 3 dB while the k-space compensation increases clutter magnitude to the non-compensated levels.

  14. High resolution beamforming on large aperture vertical line arrays: Processing synthetic data

    NASA Astrophysics Data System (ADS)

    Tran, Jean-Marie Q.; Hodgkiss, William S.

    1990-09-01

    This technical memorandum studies the beamforming of large aperture line arrays deployed vertically in the water column. The work concentrates on the use of high resolution techniques. Two processing strategies are envisioned: (1) full aperture coherent processing which offers in theory the best processing gain; and (2) subaperture processing which consists in extracting subapertures from the array and recombining the angular spectra estimated from these subarrays. The conventional beamformer, the minimum variance distortionless response (MVDR) processor, the multiple signal classification (MUSIC) algorithm and the minimum norm method are used in this study. To validate the various processing techniques, the ATLAS normal mode program is used to generate synthetic data which constitute a realistic signals environment. A deep-water, range-independent sound velocity profile environment, characteristic of the North-East Pacific, is being studied for two different 128 sensor arrays: a very long one cut for 30 Hz and operating at 20 Hz; and a shorter one cut for 107 Hz and operating at 100 Hz. The simulated sound source is 5 m deep. The full aperture and subaperture processing are being implemented with curved and plane wavefront replica vectors. The beamforming results are examined and compared to the ray-theory results produced by the generic sonar model.

  15. 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.

  16. Pulse power requirements for large aperture optical switches based on plasma electrode Pockels cells

    SciTech Connect

    Rhodes, M.A.; Taylor, J.

    1992-06-01

    We discuss very large-aperture optical switches (greater than 30 [times] 30 cm) as an enabling technology for inertial confinement fusion drivers based on multipass laser amplifiers. Large-scale laser fusion drivers such as the Nova laser have been based on single-pass amplifier designs in part because of the unavailability of a suitable large-aperture switch. We are developing an optical switch based on a Pockels cell employing plasma-electrodes. A plasma-electrode Pockels cell (PEPC) is a longitudinal-mode Pockels cell in which a plasma discharge is formed on each side of an electro-optic crystal (typically KDP or deuterated KDP, often designated KD*P). The plasmas formed on either side of the crystal act as transparent electrodes for a switching-pulse and are intended to allow uniform charging of the entire crystal. The switching-pulse is a nominally rectangular high-voltage pulse equal to the half-wave voltage V[sub x] ( 8 kV for KD*P or 17 kV for KDP) and is applied across the crystal via the plasma-electrodes. When the crystal is charged to V[sub x], the polarization of an incoming, linearly polarized, laser beam is rotated by 90[degree]. When used in conjunction with an appropriate, passive polarizer, an optical switch is thus realized. A switch with a clear aperture of 37 [times] 37 cm is now in construction for the Beamlet laser which will serve as a test bed for this switch as well as other technologies required for an advanced NOVA laser design. In this paper, we discuss the unique power electronics requirements of PEPC optical switches.

  17. Pulse power requirements for large aperture optical switches based on plasma electrode Pockels cells

    SciTech Connect

    Rhodes, M.A.; Taylor, J.

    1992-06-01

    We discuss very large-aperture optical switches (greater than 30 {times} 30 cm) as an enabling technology for inertial confinement fusion drivers based on multipass laser amplifiers. Large-scale laser fusion drivers such as the Nova laser have been based on single-pass amplifier designs in part because of the unavailability of a suitable large-aperture switch. We are developing an optical switch based on a Pockels cell employing plasma-electrodes. A plasma-electrode Pockels cell (PEPC) is a longitudinal-mode Pockels cell in which a plasma discharge is formed on each side of an electro-optic crystal (typically KDP or deuterated KDP, often designated KD*P). The plasmas formed on either side of the crystal act as transparent electrodes for a switching-pulse and are intended to allow uniform charging of the entire crystal. The switching-pulse is a nominally rectangular high-voltage pulse equal to the half-wave voltage V{sub x} ( 8 kV for KD*P or 17 kV for KDP) and is applied across the crystal via the plasma-electrodes. When the crystal is charged to V{sub x}, the polarization of an incoming, linearly polarized, laser beam is rotated by 90{degree}. When used in conjunction with an appropriate, passive polarizer, an optical switch is thus realized. A switch with a clear aperture of 37 {times} 37 cm is now in construction for the Beamlet laser which will serve as a test bed for this switch as well as other technologies required for an advanced NOVA laser design. In this paper, we discuss the unique power electronics requirements of PEPC optical switches.

  18. Large-aperture MOEMS Fabry-Perot interferometer for miniaturized spectral imagers

    NASA Astrophysics Data System (ADS)

    Rissanen, Anna; Langner, Andreas; Viherkanto, Kai; Mannila, Rami

    2015-02-01

    VTT's optical MEMS Fabry-Perot interferometers (FPIs) are tunable optical filters, which enable miniaturization of spectral imagers into small, mass producible hand-held sensors with versatile optical measurement capabilities. FPI technology has also created a basis for various hyperspectral imaging instruments, ranging from nanosatellites, environmental sensing and precision agriculture with UAVs to instruments for skin cancer detection. Until now, these application demonstrations have been mostly realized with piezo-actuated FPIs fabricated by non-monolithical assembly method, suitable for achieving very large optical apertures and with capacity to small-to-medium volumes; however large-volume production of MEMS manufacturing supports the potential for emerging spectral imaging applications also in large-volume applications, such as in consumer/mobile products. Previously reported optical apertures of MEMS FPIs in the visible range have been up to 2 mm in size; this paper presents the design, successful fabrication and characterization of MEMS FPIs for central wavelengths of λ = 500 nm and λ = 650 nm with optical apertures up to 4 mm in diameter. The mirror membranes of the FPI structures consist of ALD (atomic layer deposited) TiO2-Al2O3 λ/4- thin film Bragg reflectors, with the air gap formed by sacrificial polymer etching in O2 plasma. The entire fabrication process is conducted below 150 °C, which makes it possible to monolithically integrate the filter structures on other ICdevices such as detectors. The realized MEMS devices are aimed for nanosatellite space application as breadboard hyperspectral imager demonstrators.

  19. End-to-End Assessment of a Large Aperture Segmented Ultraviolet Optical Infrared (UVOIR) Telescope Architecture

    NASA Technical Reports Server (NTRS)

    Feinberg, Lee; Bolcar, Matt; Liu, Alice; Guyon, Olivier; Stark,Chris; Arenberg, Jon

    2016-01-01

    Key challenges of a future large aperture, segmented Ultraviolet Optical Infrared (UVOIR) Telescope capable of performing a spectroscopic survey of hundreds of Exoplanets will be sufficient stability to achieve 10-10 contrast measurements and sufficient throughput and sensitivity for high yield Exo-Earth spectroscopic detection. Our team has collectively assessed an optimized end to end architecture including a high throughput coronagraph capable of working with a segmented telescope, a cost-effective and heritage based stable segmented telescope, a control architecture that minimizes the amount of new technologies, and an Exo-Earth yield assessment to evaluate potential performance.

  20. 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.

  1. 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.

  2. Spacecraft conceptual design for the 8-meter Advanced Technology Large Aperture Space Telescope (ATLAST)

    NASA Astrophysics Data System (ADS)

    Hopkins, Randall C.; Capizzo, Peter; Fincher, Sharon; Hornsby, Linda S.; Jones, David; Mosier, Gary; Stahl, H. Philip; Thomas, Dan; Thompson, Kevin S.

    2010-07-01

    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.

  3. Electro-optic harmonic conversion switch for large-aperture multipass laser systems

    SciTech Connect

    Henesian, M.A.; Goldhar, J.; Haas, R.A.

    1984-08-01

    The authors have demonstrated electro-optically tuned second-harmonic generation using Type I KDP inside a plasma-electrode discharge cell. An axial voltage of +/- 52 kV is required to switch a 1.064-..mu..m beam by conversion to 0.53 ..mu..m, in agreement with theory. Electro-optically tuned harmonic generation may be combined with a recently developed transparent plasma electrode to produce a large-aperture switch for multipass laser systems. 7 references, 4 figures, 1 table.

  4. Simple mathematical model for designing laser diode focusing optics with a large numerical aperture

    NASA Astrophysics Data System (ADS)

    Sun, Haiyin

    2014-10-01

    A simple mathematical model is derived for conveniently designing laser diode focusing optics with a large numerical aperture. The astigmatism of laser diode beams and the lens truncation effects are considered in the model. The linearly polarized nature of laser diode beams is also included. Two design examples using this model are presented. Design results show that the lens truncation will increase the size of the focused spot and the value of the M2 factor, and the lens truncation caused a focal shift, which is not enough to correct laser diode beam astigmatism.

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

    NASA Astrophysics Data System (ADS)

    Kantojärvi, Uula; Varpula, Aapo; Antila, Tapani; Holmlund, Christer; Mäkynen, Jussi; Näsilä, Antti; Mannila, Rami; Rissanen, Anna; Antila, Jarkko; Disch, Rolf J.; Waldmann, Torsten A.

    2014-03-01

    VTT has developed Fabry-Pérot 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.

  6. 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.

  7. 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.

  8. Designs for a large-aperture telescope to map the CMB 10× faster.

    PubMed

    Niemack, Michael D

    2016-03-01

    Current large-aperture cosmic microwave background (CMB) telescopes have nearly maximized the number of detectors that can be illuminated while maintaining diffraction-limited image quality. The polarization-sensitive detector arrays being deployed in these telescopes in the next few years will have roughly 10⁴ detectors. Increasing the mapping speed of future instruments by at least an order of magnitude is important to enable precise probes of the inflationary paradigm in the first fraction of a second after the big bang and provide strong constraints on cosmological parameters. The CMB community has begun planning a next generation "Stage IV" CMB project that will be comprised of multiple telescopes with between 10⁵-10⁶ detectors to pursue these goals. This paper introduces the new crossed Dragone telescope and receiver optics designs that increase the usable diffraction-limited field-of-view, and therefore the mapping speed, by an order of magnitude compared to the upcoming generation of large-aperture instruments. Polarization systematics and engineering considerations are presented, including a preliminary receiver model to demonstrate that these designs will enable high efficiency illumination of >10⁵ detectors in a next generation CMB telescope. PMID:26974631

  9. Radiometric calibration method for large aperture infrared system with broad dynamic range.

    PubMed

    Sun, Zhiyuan; Chang, Songtao; Zhu, Wei

    2015-05-20

    Infrared radiometric measurements can acquire important data for missile defense systems. When observation is carried out by ground-based infrared systems, a missile is characterized by long distance, small size, and large variation of radiance. Therefore, the infrared systems should be manufactured with a larger aperture to enhance detection ability and calibrated at a broader dynamic range to extend measurable radiance. Nevertheless, the frequently used calibration methods demand an extended-area blackbody with broad dynamic range or a huge collimator for filling the system's field stop, which would greatly increase manufacturing costs and difficulties. To overcome this restriction, a calibration method based on amendment of inner and outer calibration is proposed. First, the principles and procedures of this method are introduced. Then, a shifting strategy of infrared systems for measuring targets with large fluctuations of infrared radiance is put forward. Finally, several experiments are performed on a shortwave infrared system with Φ400  mm aperture. The results indicate that the proposed method cannot only ensure accuracy of calibration but have the advantage of low cost, low power, and high motility. Hence, it is an effective radiometric calibration method in the outfield. PMID:26192499

  10. Optimization analysis of primary mirror in large aperture telescope based on workbench

    NASA Astrophysics Data System (ADS)

    Feng, Zhengsen; Wang, Guomin

    2015-10-01

    With the diameter increasing for large aperture telescope primary mirror, the gravity caused by the increased of surface size will directly affect the quality of optical imaging, the adjustment of large aperture primary mirror will be frequent according to the requirement of observation. As the angle and the azimuth's transformation of primary mirror influences the surface shape accuracy immediately, the rational design of the primary mirror supporting structure is of crucial importance. Now the general method is to use ANSYS APDL programming, which is inconvenient and complex to fit for the different components, the calculation require much time and the analysis is lack of efficient. Taking the diameter of 1.12 m telescope primary mirror as the research objection, the paper combine the actual design parameters of SONG telescope, respectively using ANSYS WORKBENCH to employ the primary mirror axial and lateral support model in finite element method, the optimal solution is obtained by optimization design and the change rule of mirror surface deformation under inclined condition is studied. The optimization results according with the requirements of the primary mirror comprehensive error proves that the optimization analysis method is available and applicable.

  11. A Large Aperture, High Energy Laser System for Optics and Optical Component Testing

    SciTech Connect

    Nostrand, M C; Weiland, T L; Luthi, R L; Vickers, J L; Sell, W D; Stanley, J A; Honig, J; Auerbach, J; Hackel, R P; Wegner, P J

    2003-11-01

    A large aperture, kJ-class, multi-wavelength Nd-glass laser system has been constructed at Lawrence Livermore National Lab which has unique capabilities for studying a wide variety of optical phenomena. The master-oscillator, power-amplifier (MOPA) configuration of this ''Optical Sciences Laser'' (OSL) produces 1053 nm radiation with shaped pulse lengths which are variable from 0.1-100 ns. The output can be frequency doubled or tripled with high conversion efficiency with a resultant 100 cm{sup 2} high quality output beam. This facility can accommodate prototype hardware for large-scale inertial confinement fusion lasers allowing for investigation of integrated system issues such as optical lifetime at high fluence, optics contamination, compatibility of non-optical materials, and laser diagnostics.

  12. 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

    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.

  13. Large aperture tunable-focus liquid lens using shape memory alloy spring.

    PubMed

    Hasan, Nazmul; Kim, Hanseup; Mastrangelo, Carlos H

    2016-06-13

    A tunable-focus large aperture liquid lens is constructed using shape memory alloy (SMA) springs as actuators. The lens mainly consists of a shallow liquid-filled cylindrical cavity bound by a thin compressible annular rim and encapsulated by a flexible circular membrane on the top of the rim and a rigid circular plate at the rim bottom. The lens optical power is adjusted by a controlled compression of the annular rim via actuation of the three shape-memory alloy (SMA) springs. Since the volume of the cavity liquid is constant, the rim compression bulges the flexible membrane outward thus reducing its radius of curvature and the lens focal length. The fabricated tunable lens demonstrated an optical power range of 0-4 diopters utilizing a driving voltage less than 3V. Lens optical wavefront profiling was done using a Shack-Hartmann sensor displaying a RMS wave front error of 0.77 µm and 1.68 µm at 0 D and + 4 D. The aperture diameter and thickness of the fabricated lens are 34 mm and 9 mm, respectively, while weighing 16.7 g. PMID:27410350

  14. Advanced Technology Large-Aperture Space Telescope: Science Drivers and Technology Developments

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    The Advanced Technology Large-Aperture Space Telescope (ATLAST) is a concept for an 8- to 16-m ultraviolet optical near Infrared space observatory for launch in the 2025 to 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-marcsec angular resolution, diffraction limited imaging at 0.5 micron wavelength, minimum collecting area of 45 sq m, high sensitivity to light wavelengths from 0.1 to 2.4 micron, 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 that of current generation observatory-class space missions.

  15. 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.

  16. Data correction techniques for the airborne large-aperture static image spectrometer based on image registration

    NASA Astrophysics Data System (ADS)

    Zhang, Geng; Shi, Dalian; Wang, Shuang; Yu, Tao; Hu, Bingliang

    2015-01-01

    We propose an approach to correct the data of the airborne large-aperture static image spectrometer (LASIS). LASIS is a kind of stationary interferometer which compromises flux output and device stability. It acquires a series of interferograms to reconstruct the hyperspectral image cube. Reconstruction precision of the airborne LASIS data suffers from the instability of the plane platform. Usually, changes of plane attitudes, such as yaws, pitches, and rolls, can be precisely measured by the inertial measurement unit. However, the along-track and across-track translation errors are difficult to measure precisely. To solve this problem, we propose a co-optimization approach to compute the translation errors between the interferograms using an image registration technique which helps to correct the interferograms with subpixel precision. To demonstrate the effectiveness of our approach, experiments are run on real airborne LASIS data and our results are compared with those of the state-of-the-art approaches.

  17. 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

  18. OASIS 1.0: Very Large-Aperture High-Power Lidar for Exploring Geospace

    NASA Astrophysics Data System (ADS)

    Chu, X.; Smith, J. A.; Chen, C.; Zhao, J.; Yu, Z.; Gardner, C. S.

    2015-12-01

    A new initiative, namely OASIS (the Observatory for Atmosphere Space Interaction Studies), has called for a very large-aperture high-power (VLAHP) lidar as its first step forward to acquire the unprecedented measurement capabilities for exploring the space-atmosphere interaction region (SAIR). Currently, there exists a serious observational gap of the Earth's neutral atmosphere above 100 km. Information on neutral winds and temperatures and on the plasma-neutral coupling in the SAIR, especially between 100 and 200 km, is either sparse or nonexistent. Fully exploring the SAIR requires measurements of the neutral atmosphere to complement radar observations of the plasma. Lidar measurements of neutral winds, temperatures and species can enable these explorations. Many of these topics will be addressed with the VLAHP lidar. Discoveries of thermospheric neutral Fe, Na and K layers up to nearly 200 km at McMurdo, Antarctica and other locations on Earth, have opened a new door to observing the neutral thermosphere with ground-based instruments. These neutral metal layers provide the tracers for resonance Doppler lidars to directly measure the neutral temperatures and winds in the thermosphere, thus enabling the VLAHP lidar dream! Because the thermospheric densities of these metal atoms are many times smaller than the layer peak densities near 90 km, high power-aperture product lidars, like the VLAHP lidar, are required to derive scientifically useful measurements. Furthermore, several key technical challenges for VLAHP lidar have been largely resolved in the last a few years through the successful development of Fe and Na Doppler lidars at Boulder. By combining Rayleigh and Raman with resonance lidar techniques and strategically operating the VLAHP lidar next to incoherent scatter radar and other complementary instruments, the VLAHP lidar will enable new cutting-edge exploration of the geospace. These new concepts and progresses will be introduced in this paper.

  19. Topology optimization-based lightweight primary mirror design of a large-aperture space telescope.

    PubMed

    Liu, Shutian; Hu, Rui; Li, Quhao; Zhou, Ping; Dong, Zhigang; Kang, Renke

    2014-12-10

    For the large-aperture space telescope, the lightweight primary mirror design with a high-quality optical surface is a critical and challenging issue. This work presents a topology optimization-based design procedure for a lightweight primary mirror and a new mirror configuration of a large-aperture space telescope is obtained through the presented design procedure. Inspired by the topology optimization method considering cast constraints, an optimization model for the configuration design of the mirror back is proposed, through which the distribution and the heights of the stiffeners on the mirror back can be optimized simultaneously. For the purpose of minimizing the optical surface deviation due to self-weight and polishing pressure loadings, the objective function is selected as to maximize the mirror structural stiffness, which can be achieved by minimizing the structural compliance. The total mass of the primary mirror is assigned as the constraint. In the application example, results of the optimized design topology for two kinds of mass constraints are presented. Executing the design procedure for specific requirements and postprocessing the topology obtained of the structure, a new mirror configuration with tree-like stiffeners and a multiple-arch back in double directions is proposed. A verification model is constructed to evaluate the design results and the finite element method is used to calculate the displacement of the mirror surface. Then the RMS deviation can be obtained after fitting the deformed surface by Zernike polynomials. The proposed mirror is compared with two classical mirrors in the optical performance, and the comparison results demonstrate the superiority of the new mirror configuration. PMID:25608076

  20. 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.

  1. Performance of a Fieldable Large-Area, Coded-Aperture, Gamma Imager

    SciTech Connect

    Habte Ghebretatios, Frezghi; Cunningham, Mark F; Fabris, Lorenzo; Ziock, Klaus-Peter

    2007-01-01

    We recently developed a fieldable large-area, coded-aperture, gamma imager (the Large Area Imager - LAI). The instrument was developed to detect weak radiation sources in a fluctuating natural background. Ideally, the efficacy of the instrument is determined using receiver-operator statistics generated from measurement data in terms of probability of detection versus probability of false alarm. However, due to the impracticality of hiding many sources in public areas, it is difficult to measure the data required to generate receiver-operator characteristic (ROC) curves. Instead, we develop a high statistics "model source" from measurements of a real point source and then inject the model source into data collected from the world at large where, presumably, no source exists. In this paper we have applied this "source injection" technique to evaluate the performance of the LAI. We plotted ROC curves obtained for different source locations from the imager and for different source strengths when the source is injected at 50 m from the imager. The result shows that this prototype instrument provides excellent performance for a 1-mCi source at a distance of 50 m from the imager in a single pass at 25 mph.

  2. Large-aperture two-dimensional x-ray refractive mosaic lenses.

    PubMed

    Nazmov, Vladimir; Reznikova, Elena; Mohr, Juergen; Saile, Volker; Tajiri, Hiroo; Voigt, Anja

    2016-09-01

    Lenses with high numerical aperture are required for images with very high spatial resolution, which is difficult to realize in the x-ray range because of low-refraction-index decrement and relatively high absorption of x-rays in the material. However, such an aperture can be realized by means of a mosaic lens, as shown in this work. PMID:27607293

  3. 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 33.4 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 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

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. The Advanced Technology Large-Aperture Space Telescope (ATLAST) Technology Roadmap

    NASA Technical Reports Server (NTRS)

    Stahle, Carl; Balasubramanian, K.; Bolcar, M.; Clampin, M.; Feinberg, L.; Hartman, K.; Mosier, C.; Quijada, M.; Rauscher, B.; Redding, D.; Shaklan, S.; Stahl, P.; Thronson, H.

    2014-01-01

    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 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.

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

    SciTech Connect

    Jarchow, C.M. . Dept. of Geophysics); Catchings, R.D.; Lutter, W.J. )

    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.

  10. Application of image entropy evaluation function for the leveling of large aperture components in auto defects detecting

    NASA Astrophysics Data System (ADS)

    Cao, Pin; Liu, Dong; Zhao, Peng; Yang, Yong-ying; Wang, Shi-tong

    2012-10-01

    In large aperture component's dark-field scattering defects imaging system, the component's size is large and part with a wedge. When the component is in the completely level position, the surface defects image can be clearly acquired by a high magnification microscope. Otherwise, fuzzy defects image would be gained because of defocusing which makes digital identification can't be able to be done. For the problem of leveling large aperture, wedge component, this paper proposes a method that using image information entropy as focusing evaluation function for leveling large aperture components. Firstly, in three different points of component surface acquiring multi-images by the same continuous steps. Then calculating the images' entropy and fitting a curve to it. Based on minimum image information entropy value criterion, the focal plane can be found and each point's defocusingamount of the fist acquisition position can be gained. Relay on the relation model of acquisition points, adjust points and defocusingamount that has been built, each adjust point's adjustment can be got. The component's level position can be achieved by adjusting the adjust points. In the experiment that using a high magnification (of 16) microscope scans over the whole surface of the component with the size of 430mm×430mm. The image microscope is always in the depth of focus which shows that the leveling precision has achieved 20μm. Until now, this method has been successfully used in large aperture component's dark-field scattering defects imaging system.

  11. 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.; Last, A.

    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.

  12. 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.

  13. Strangeonia and kin; new results from kaon hadroproduction with LASS

    SciTech Connect

    Aston, D.; Bienz, T.; Bird, F.; Dunwoodie, W.; Johnson, W.B.; Kunz, P.; Kwon, Y.; Leith, D.W.G.S.; Levinson, L.; Ratcliff, B.N.; Rensing, P.; Schultz, D.; Shapiro, S.; Sinervo, P.K.; Tarnopolsky, G.; Toge, N.; Waite, A.; Williams, S. ); Awaji, N.; Fujii, K.; Hayashii, H.; Iwata, S.; Kajikawa, R.; Matsui, T.; Miyamoto, A.; Ozaki, H.; Pak, C.O.; Shimomura, T.; Sugiyama,

    1989-12-01

    Recent results from a high statistics study of strangeonium mesons produced in LASS by an 11 GeV/c K{sup -} beam are reviewed and compared with the quark model. New data from a variety of final states (K*{ovr K*}, {phi}{phi}, {phi}{pi}{sup 0}) produced by hypercharge exchange are described, and compared with results from other hadroproduction modes and from J/{psi} decay. 17 refs., 12 figs.

  14. 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.

  15. Large field distributed aperture laser semiactive angle measurement system design with imaging fiber bundles.

    PubMed

    Xu, Chunyun; Cheng, Haobo; Feng, Yunpeng; Jing, Xiaoli

    2016-09-01

    A type of laser semiactive angle measurement system is designed for target detecting and tracking. Only one detector is used to detect target location from four distributed aperture optical systems through a 4×1 imaging fiber bundle. A telecentric optical system in image space is designed to increase the efficiency of imaging fiber bundles. According to the working principle of a four-quadrant (4Q) detector, fiber diamond alignment is adopted between an optical system and a 4Q detector. The structure of the laser semiactive angle measurement system is, we believe, novel. Tolerance analysis is carried out to determine tolerance limits of manufacture and installation errors of the optical system. The performance of the proposed method is identified by computer simulations and experiments. It is demonstrated that the linear region of the system is ±12°, with measurement error of better than 0.2°. In general, this new system can be used with large field of view and high accuracy, providing an efficient, stable, and fast method for angle measurement in practical situations. PMID:27607276

  16. [Modeling and simulation of effect of optical distortion on the large aperture static imaging spectrometer].

    PubMed

    Lü, Qun-bo; Xiangli, Bin; Yao, Tao; Jing, Juan-juan; Wang, Zhong-hou

    2010-01-01

    As a new type Fourier transform imaging spectrometry, large aperture static imaging spectrometry (LASIS) has come forth in recent years, which has many advantages such as simple principle, high stability and so on. However, the requirement for the optical system design of LASIS was very harsh. As one of the optical aberrations, optical distortion degrades the data quality acquired by LASIS, consequently limits its applications. According to the analysis of the data acquisition principle of LASIS, the data model with the effect of optical distortion was presented, which could be used for LASIS performance pre-evaluation. Finally, the computer simlulation of the data model was achieved with supposed parameters. The simulation results indicated that the relative error more than 5% was induced in the recovery spectrum, and approximate 8 nm spectral line deviation was occurred at the long wavelength region. The results show that the 4% optical distortion was inapplicable for LASIS although it is acceptant for common optical imaging system. PMID:20302101

  17. 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.

  18. Performance of large-aperture optical switches for high-energy inertial-confinement fusion lasers

    SciTech Connect

    Rhodes, M.A.; Woods, B.; DeYoreo, J.J.; Roberts, D.; Atherton, L.J.

    1995-08-20

    We describe the design and performance of large-aperture ({lt}30 cm {times} 30 cm) optical switches that have demonstrated, for the first time to our knowledge, active switching of a high-energy ({lt}5 kJ) optical pulse in an inertial-confinement fusion laser. These optical switches, which consist of a plasma-electrode Pockels cell (PEPC) and a passive polarizer, permit the design of efficient, multipass laser amplifiers. In a PEPC, plasma discharges on the faces of a thin (1-cm) electro-optic crystal (KDP or KD{bold |}P) act as highly conductive and transparent electrodes. These plasma electrodes facilitate rapid ({lt}100 ns) and uniform charging of the crystal to the half-wave voltage and discharging back to 0 V. We discuss the operating principles, design, optical performance, and technical issues of a 32 cm {times} 32 cm prototype PEPC with both KDP and KD{bold |}P crystals, and a 37 cm {times} 37 cm PEPC with a KDP crystal for the Beamlet laser. This PEPC recently switched a 6-kJ, 3-ns pulse in a four-pass cavity.

  19. Improving 351-nm Damage Performance of Large-Aperture Fused Silica and DKDP Optics

    SciTech Connect

    Burnham, A K; Hackel, L; Wegner, P; Parham, T; Hrubesh, L; Penetrante, B; Whitman, P; Demos, S; Menapace, J; Runkel, M; Fluss, M; Feit, M; Key, M; Biesiada, T

    2002-01-07

    A program to identify and eliminate the causes of UV laser-induced damage and growth in fused silica and DKDP has developed methods to extend optics lifetimes for large-aperture, high-peak-power, UV lasers such as the National Ignition Facility (NIF). Issues included polish-related surface damage initiation and growth on fused silica and DKDP, bulk inclusions in fused silica, pinpoint bulk damage in DKDP, and UV-induced surface degradation in fused silica and DKDP in a vacuum. Approaches included an understanding of the mechanism of the damage, incremental improvements to existing fabrication technology, and feasibility studies of non-traditional fabrication technologies. Status and success of these various approaches are reviewed. Improvements were made in reducing surface damage initiation and eliminating growth for fused silica by improved polishing and post-processing steps, and improved analytical techniques are providing insights into mechanisms of DKDP damage. The NIF final optics hardware has been designed to enable easy retrieval, surface-damage mitigation, and recycling of optics.

  20. 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.

  1. 8 Meter Advanced Technology Large-Aperture Space Telescope (ATLAST-8m)

    NASA Technical Reports Server (NTRS)

    Stahl, H. Philip

    2010-01-01

    ATLAST-8m (Advanced Technology Large Aperture Space Telescope) is a proposed 8-meter monolithic UV/optical/NIR space observatory (wavelength range 110 to 2500 nm) to be placed in orbit at Sun-Earth L2 by NASA's planned Ares V heavy lift vehicle. Given its very high angular resolution (15 mas @ 500 nm), sensitivity and performance stability, ATLAST-8m is capable of achieving breakthroughs in a broad range of astrophysics including: Is there life elsewhere in the Galaxy? An 8-meter UVOIR observatory has the performance required to detect habitability (H2O, atmospheric column density) and biosignatures (O2, O3, CH4) in terrestrial exoplanet atmospheres, to reveal the underlying physics that drives star formation, and to trace the complex interactions between dark matter, galaxies, and intergalactic medium. The ATLAST Astrophysics Strategic Mission Concept Study developed a detailed point design for an 8-m monolithic observatory including optical design; structural design/analysis including primary mirror support structure, sun shade and secondary mirror support structure; thermal analysis; spacecraft including structure, propulsion, GN&C, avionics, power systems and reaction wheels; mass and power budgets; and system cost. The results of which were submitted by invitation to NRC's 2010 Astronomy & Astrophysics Decadal Survey.

  2. 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.

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

    SciTech Connect

    Chen, Tao; Fan, Tingbo; Zhang, Wei; Qiu, Yuanyuan; Tu, Juan E-mail: dzhang@nju.edu.cn; Guo, Xiasheng; Zhang, Dong E-mail: dzhang@nju.edu.cn

    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.

  4. A procedure for combining rotating-coil measurements of large-aperture accelerator magnets

    NASA Astrophysics Data System (ADS)

    Köster, Oliver; Fiscarelli, Lucio; Russenschuck, Stephan

    2016-05-01

    The rotating search coil is a precise and widely used tool for measuring the magnetic field harmonics of accelerator magnets. This paper deals with combining several such multipole measurements, in order to cover magnet apertures largely exceeding the diameter of the available search coil. The method relies on the scaling laws for multipole coefficients and on the method of analytic continuation along zero-homotopic paths. By acquiring several measurements of the integrated magnetic flux density at different transverse positions within the bore of the accelerator magnet, the uncertainty on the field harmonics can be reduced at the expense of tight tolerances on the positioning. These positioning tolerances can be kept under control by mounting the rotating coil and its motor-drive unit on precision alignment stages. Therefore, the proposed technique is able to yield even more precise results for the higher-order field components than a dedicated rotating search coil of larger diameter. Moreover, the versatility of the measurement bench is enhanced by avoiding the construction of rotating search coils of different measurement radii.

  5. 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 0.001λ (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 0.0016λ. 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.

  6. Tracking marine mammals and ships with small and large-aperture hydrophone arrays

    NASA Astrophysics Data System (ADS)

    Gassmann, Martin

    Techniques for passive acoustic tracking in all three spatial dimensions of marine mammals and ships were developed for long-term acoustic datasets recorded continuously over months using custom-designed arrays of underwater microphones (hydrophones) with spacing ranging from meters to kilometers. From the three-dimensional tracks, the acoustical properties of toothed whales and ships, such as sound intensity and directionality, were estimated as they are needed for the passive acoustic abundance estimation of toothed whales and for a quantitative description of the contribution of ships to the underwater soundscape. In addition, the tracks of the toothed whales reveal their underwater movements and demonstrate the potential of the developed tracking techniques to investigate their natural behavior and responses to sound generated by human activity, such as from ships or military SONAR. To track the periodically emitted echolocation sounds of toothed whales in an acoustically refractive environment in the upper ocean, a propagation-model based technique was developed for a hydrophone array consisting of one vertical and two L-shaped subarrays deployed from the floating instrument platform R/P FLIP. The technique is illustrated by tracking a group of five shallow-diving killer whales showing coordinated behavior. The challenge of tracking the highly directional echolocation sounds of deep-diving (< 1 km) toothed whales, in particular Cuvier's beaked whales, was addressed by embedding volumetric small-aperture (≈ 1 m element spacing) arrays into a large-aperture (≈ 1 km element spacing) seafloor array to reduce the minimum number of required receivers from five to two. The capabilities of this technique are illustrated by tracking several groups of up to three individuals over time periods from 10 min to 33 min within an area of 20 km2 in the Southern California Bight. To track and measure the underwater radiated sound of ships, a frequency domain beamformer was

  7. 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 (55–60km) 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.

  8. 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.

  9. 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

  10. Three-dimensional digital holographic aperture synthesis for rapid and highly-accurate large-volume metrology

    NASA Astrophysics Data System (ADS)

    Crouch, Stephen; Kaylor, Brant M.; Barber, Zeb W.; Reibel, Randy R.

    2015-09-01

    Currently large volume, high accuracy three-dimensional (3D) metrology is dominated by laser trackers, which typically utilize a laser scanner and cooperative reflector to estimate points on a given surface. The dependency upon the placement of cooperative targets dramatically inhibits the speed at which metrology can be conducted. To increase speed, laser scanners or structured illumination systems can be used directly on the surface of interest. Both approaches are restricted in their axial and lateral resolution at longer stand-off distances due to the diffraction limit of the optics used. Holographic aperture ladar (HAL) and synthetic aperture ladar (SAL) can enhance the lateral resolution of an imaging system by synthesizing much larger apertures by digitally combining measurements from multiple smaller apertures. Both of these approaches only produce two-dimensional imagery and are therefore not suitable for large volume 3D metrology. We combined the SAL and HAL approaches to create a swept frequency digital holographic 3D imaging system that provides rapid measurement speed for surface coverage with unprecedented axial and lateral resolution at longer standoff ranges. The technique yields a "data cube" of Fourier domain data, which can be processed with a 3D Fourier transform to reveal a 3D estimate of the surface. In this paper, we provide the theoretical background for the technique and show experimental results based on an ultra-wideband frequency modulated continuous wave (FMCW) chirped heterodyne ranging system showing ~100 micron lateral and axial precisions at >2 m standoff distances.

  11. Coherent polarization stabilization in large-aperture rectangular post bottom-emitting vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Wang, W.; Ning, Y. Q.; Tian, Z. H.; Zhang, X.; Shi, J. J.; Wang, Z. F.; Zhang, L. S.; Zhang, Y.; Liu, Y.; Qin, L.; Wang, L. J.

    2011-03-01

    The output characteristics of large-aperture rectangular post bottom-emitting vertical-cavity surface-emitting lasers (VCSELs) were investigated. It was shown that the output power of the rectangle VCSELs can be up to 660 mW at a current of 5 A. Both H-polarization (horizontal) and V-polarization (vertical) demonstrated a coherent stabilization over the entire range of operation current, and coherent spectrum blue-shift of H-polarization light occurred with respect to V-polarization light at three different injected currents. The polarization states of output light were stabilized in the two orthogonal directions and H-polarization was the most principal polarization which was parallel to the longer side of the rectangular aperture. From the relationship between polarization ratio and aspect ratio of the oxidation confinement aperture (OCA), it was found that the highest polarization ratio (about 2:1) took place when the appropriate aspect ratio was 5:3, which meant better polarization stabilization in large-aperture VCSELs.

  12. Determining suitability of Large Aperture Scintillometer for validating remote sensing based evapotranspiration maps

    NASA Astrophysics Data System (ADS)

    Paul, G.; Gowda, P. H.; Howell, T. A.; Basu, S.; Colaizzi, P. D.; Marek, T.

    2013-12-01

    Scintillation method is a relatively new technique for measuring the sensible heat and water fluxes over land surfaces. Path integrating capabilities of scintillometer over heterogeneous landscapes make it a potential tool for comparing the energy fluxes derived from remote sensing based energy balance algorithms. For this reason, scintillometer-derived evapotranspiration (ET) fluxes are being used to evaluate remote sensing based energy balance algorithms for their ability to estimate ET fluxes. However, LAS' (Large Aperture Scintillometer) ability to derive ET fluxes is not thoroughly tested. The objective of this study was to evaluate LAS- and Surface Energy Balance System (SEBS)-derived fluxes against lysimetric data to determine LAS' suitability for validating remote sensing based evapotranspiration (ET) maps. The study was conducted during the Bushland Evapotranspiration and Agricultural Remote sensing EXperiment - 2008 (BEAREX-08) at the USDA-ARS Conservation and Production Research Laboratory (CPRL), Bushland, Texas. SEBS was coded in a GIS environment to retrieve ET fluxes from the high resolution imageries acquired using airborne multispectral sensors. The CPRL has four large weighing lysimeters (3 m long x 3 m wide x 2.4 m deep), each located in the middle of approximately 5 ha fields, arranged in a block pattern. The two lysimeter fields located on the east (NE and SE) were managed under irrigated conditions, and the other two lysimeters on the west (NW and SW) were under dryland management. Each lysimeter field was equipped with an automated weather station that provided measurements for net radiation (Rn), Ts, soil heat flux (Go), Ta, relative humidity, and wind speed. During BEAREX08, the NE and SE fields were planted to cotton on May 21, and the NW and SW dryland lysimeters fields were planted to cotton on June 5. One LAS each was deployed across two large dryland lysimeter fields (NW and SW) and two large irrigated lysimeter fields (NE and SE). The

  13. 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

  14. [Research of spectrum signal-to-noise ratio of large aperture static imaging spectrometer].

    PubMed

    Wang, Shuang; Li, Li-Bo; Pi, Hai-Feng

    2014-03-01

    The process of acquiring hyperspectral data cube of a Large Aperture Static Imaging Spectrometer (LASIS) includes several vital and essential steps, such as interferometer modulation, rectangular convolution sampling by pixels of detector and spectra retrieving. In this process, how to precisely evaluate the Signal-Noise Ratio (SNR) of spectra and how to wholly establish a related evaluation model were both generally very complicated. After a full consideration of the transmission process, utilizing the theory of rectangular convolution sampling and the spectral retrieving method regarding the computation of real part of the discrete Fourier transform of interferogram, formulas of both spectral signal and spectral noise were deduced theoretically, and then a evaluation model regarding the spectral SNR of LASIS was established. By using this model and other design factors of LASIS involving the wavenumber related optical transmittance, the interferometer beam splitter efficiency, the detector quantum efficiency and the main circuit noise, a simulation of spectral SNR was implemented. The simulation result was compared with the measurement result of the SNR of a LASIS instrument. The SNR lines and trends of the two match each other basically in single spectral band. The average deviation between them is proved to be 3.58%. This comparison result demonstrates the feasibility and effectiveness of the evaluation model. This SNR evaluation model consisting of the main technical aspects of typical LASIS instrument from the input spectral radiation to the output spectrum data is possible to be applied widely in practical design and implement of LASIS, as well as may provide valuable reference on SNR calculation and evaluation for other imaging spectrometers. PMID:25208427

  15. 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.

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

    PubMed Central

    Rambikur, Evan H.; Chávez, José 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

  17. ExoEarth Yield Estimates for a Future Large Aperture Direct Imaging Mission

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    ExoEarth yield is a critical science metric that will constrain the required aperture of a future exoplanet-imaging mission. I will present a numerically efficient method for maximizing the yield of exoEarth candidates by simultaneously optimizing the exposure time of every star, number of visits per star, and delay time between visits, while maximally adapting the target list to the mission's capabilities. This method can potentially double the exoEarth candidate yield compared to previous methods. I will show how the yield scales with mission parameters, including aperture size and high level coronagraph parameters, and address the impact of astrophysical uncertainties on exoEarth yield.

  18. Test results of a single aperture 10 tesla dipole model magnet for the Large Hadron Collider

    SciTech Connect

    Yamamoto, Akira; Shintomi, Takakazu; Kimura, Nobuhiro

    1996-07-01

    A single aperture dipole magnet has been developed with a design magnetic field of 10 tesla by using Nb-Ti/Cu conductor to be operated at 1.8 K in pressurized super fluid helium. The magnet features double shell coil design by using high keystone Rutherford cable and compact non-magnetic steel collars to be adaptable in split/symmetric coil/collar design for twin aperture dipoles. A design central magnetic field of 10 tesla has been successfully achieved in excitation at 1.95 K in pressurized superfluid helium. Test results of the magnet with a summary of the design and fabrication will be presented.

  19. [Design of a dual-channel Mach-Zehnder lateral shearing interferometer for the large aperture static imaging spectrometer].

    PubMed

    Fu, Qiang; Xiangli, Bin; Lü, Qun-bo; Jing, Juan-juan

    2012-02-01

    Large aperture static imaging spectrometry (LASIS) is a kind of joint temporally and spatially modulated Fourier transform imaging spectrometry. In such instruments, lateral shearing interferometer is a key element, the most frequently used type of which is the Sagnac interferometer. In this configuration, one half of the light entering the interferometer backtracks and causes a great decrease in energy efficiency. The present paper proposes a modified Mach-Zehnder lateral shearing interferometer structure to tackle this problem. With the ability to produce the same lateral shear, it features the advantage of dual channel output. We present a ray tracing procedure to induce the general expression of the lateral shear as well as analyze the contributions of error sources to the shear accuracy. The results serve as a new idea for the design of large aperture static imaging spectrometers and can be used to instruct the design and optimization of this kind of imaging spectrometer. PMID:22512210

  20. A novel measurement scheme for the radial group delay of large-aperture ultra-short laser pulses

    NASA Astrophysics Data System (ADS)

    Wu, Fenxiang; Xu, Yi; Li, Zhaoyang; Li, Wenkai; Lu, Jun; Wang, Cheng; Li, Yanyan; Liu, Yanqi; Lu, Xiaoming; Peng, Yujie; Wang, Ding; Leng, Yuxin; Li, Ruxin

    2016-05-01

    In femtosecond high-peak-power laser system, the radial group delay (RGD) of the pulse front introduced by conventional lens-based beam expanders can significantly decrease the achievable focal intensity, especially when it is larger than the pulse duration. In order to quantitatively analyze and compensate the RGD, a novel measurement scheme based on self-reference and second-order cross-correlation technology is proposed and applied to measure the RGD of the large-aperture ultra-short laser pulses directly. The measured result of the RGD in a 200 TW Ti:sapphire laser system is in good agreement with the theoretical calculation. To our knowledge, it is the first time to realize the direct RGD measurement of large-aperture ultra-short laser pulses.

  1. 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.

  2. 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.

  3. A high-resolution detecting system based on machine vision for defects on large aperture and super-smooth surface

    NASA Astrophysics Data System (ADS)

    Yang, Yongying; Zhao, Limin; Wang, Shitong; Cao, Pin; Liu, Dong; Li, Lu; Yan, Lu; Li, Chen; Xie, Shibing; Li, Yang; Chen, Yangjie

    2015-02-01

    The high-resolution detecting system based on machine vision for defects on large aperture and super-smooth surface uses a novel ring telecentric lighting optical system detecting the defects on the sample all round and without blind spots. The scattering light induced by surface defects enters the adaptive and highly zoom microscopic scattering dark-field imaging system for defect detecting and then forms digital images. Sub-aperture microscopic scanning sampling and fast stitching on the surface is realized by using precise multi-axis shifting guided scanning system and a standard comparison board based upon binary optics is used to implement fast calibration of micron-dimension defects detected actually. The pattern recognition technology of digital image processing which can automatically output digitalized surface defects statements after scaling is established to comprehensively evaluate defects. This system which can reach micron-dimension defect resolution can achieve detections of large aperture components of 850 mm × 500 mm, solve the durable problem of subjective uncertainty brought in by human visual detection of defects and achieve quantitative detection of defects with machine vision.

  4. Effect of Internal Aperture Variability on Tracer Transport in Large Discrete Fracture Networks (DFN)

    NASA Astrophysics Data System (ADS)

    Makedonska, N.; Painter, S. L.; Hyman, J.; Karra, S.; Gable, C. W.; Viswanathan, H. S.

    2015-12-01

    Aperture variability within individual fractures is usually neglected in modeling flow and transport through fractured media. Typically, individual fractures are assumed to be homogeneous. However, in reality, individual fractures are heterogeneous, which may affect flow and transport in fractured media. The relative importance of including in-fracture variability in flow and transport modeling has been under debate for a long time. Previous studies have shown flow channeling on an individual fracture with internal variability, where the fracture is considered isolated from the rest of the fracture network. Although these studies yield some clear insights into the process, the boundary conditions are impractical for field-scale networks, where the realistic boundary conditions are determined by fracture connections in the network. Therefore, flow in a single fracture is controlled not only by in-fracture variability but also by boundary conditions. In order to address the question of the importance of in-fracture variability, the internal heterogeneity of every individual fracture is incorporated into a three-dimensional fracture network, represented by a composition of intersecting fractures. The new DFN simulation capability, dfnWorks, is used to generate a kilometer scale DFNs similar to the Forsmark, Sweden site. In our DFN model, the in-fracture aperture variability is scattered over each cell of the computational mesh along the fracture, representing by a stationary Gaussian random field with various correlation lengths. The Lagrangian particle tracking is conducted in multiple DFN realizations and the flow-dependent Lagrangian parameters, non-reacting travel time, τ, and cumulative reactivity parameter, β, are obtained along particles streamlines. It is shown that early particle travel times are more sensitive to in-fracture aperture variability than tails of travel time distributions, where no significant effect of the aperture variations and spatial

  5. Operation of a DC large aperture volume-production H sup minus source

    SciTech Connect

    Kwan, J.W.; Ackerman, G.D.; Anderson, O.A.; Chan, C.F.; Cooper, W.S.; deVries, G.J.; Leung, K.N.; Lietzke, A.F.; Steele, W.F.

    1989-04-01

    In testing a multicusp volume-production H{sup {minus}} ion source (20 cm diameter, 23 cm long), we optimized the gas pressure, the plasma electrode bias potential and the magnetic filter. At the optimum pressure of 9 mT, the H{sup {minus}} beam output increased linearly with discharge power. The maximum H{sup {minus}} beam, measured with a current transformer downstream of the accelerator, was 100 mA while using a 6.67 cm{sup 2} aperture. Presently we are limited by overheating of the cathodes by the plasma ions. Under similar discharge conditions the maximum H{sup {minus}} current density was found to vary as a{sup {minus}0.7} where a is the aperture radius. Results from emittance measurements showed that the effective H{sup {minus}} ion temperature increased with a for a {gt} 0.8 cm. Thus the brightness of the beam decreased with increasing aperture radius. Operating the source with cesium would increase the H{sup {minus}} output however our accelerator must be improved to avoid breakdowns caused by the cesium contamination. 8 refs., 6 figs.

  6. 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.

  7. Optical Design for the Optimum Solid Immersion Lens with High Numerical Aperture and Large Tolerance

    NASA Astrophysics Data System (ADS)

    Choi, Narak; Shim, Seongbo; Milster, Tom D.; Kim, Jaisoon

    2007-06-01

    Super hemispherical solid immersion lens system becomes a matter of interest due to its high numerical aperture (NA) gain. However, because of the instability of the aplanatic condition, even small amount of alignment error can easily lower the optical performance. To overcome the instability while maintaining high NA gain, we suggest an optimum solid immersion lens (opti-SIL) system which combines the advantages of both super hemispherical SIL (hyper-SIL) and hemispherical SIL (hemi-SIL). Exemplary designs and simulation results of the tolerance analysis show that opti-SIL system has much higher tolerances to various performance-lowering factors than hyper-SIL, even with relatively small NA resignation.

  8. Computation of scalar far-field patterns of large-aperture antennas

    NASA Technical Reports Server (NTRS)

    Omalley, T. A.

    1976-01-01

    In computer programs used for evaluating the performance of high-gain antennas, efficient numerical methods for calculating the far-field patterns must be used since the majority of computer time and storage requirements may be attributed to this phase of the program. The numerical method most frequently used is the Fast Fourier Transform (FFT), which computes the far field as the Fourier transform of the field distribution in the antenna aperture. A new numerical method that in many applications is superior to the FFT in terms of reducing computer time and storage requirements is described.

  9. Near-Space TOPSAR Large-Scene Full-Aperture Imaging Scheme Based on Two-Step Processing.

    PubMed

    Zhang, Qianghui; Wu, Junjie; Li, Wenchao; Huang, Yulin; Yang, Jianyu; Yang, Haiguang

    2016-01-01

    Free of the constraints of orbit mechanisms, weather conditions and minimum antenna area, synthetic aperture radar (SAR) equipped on near-space platform is more suitable for sustained large-scene imaging compared with the spaceborne and airborne counterparts. Terrain observation by progressive scans (TOPS), which is a novel wide-swath imaging mode and allows the beam of SAR to scan along the azimuth, can reduce the time of echo acquisition for large scene. Thus, near-space TOPS-mode SAR (NS-TOPSAR) provides a new opportunity for sustained large-scene imaging. An efficient full-aperture imaging scheme for NS-TOPSAR is proposed in this paper. In this scheme, firstly, two-step processing (TSP) is adopted to eliminate the Doppler aliasing of the echo. Then, the data is focused in two-dimensional frequency domain (FD) based on Stolt interpolation. Finally, a modified TSP (MTSP) is performed to remove the azimuth aliasing. Simulations are presented to demonstrate the validity of the proposed imaging scheme for near-space large-scene imaging application. PMID:27472341

  10. Technology development for the Advanced Technology Large Aperture Space Telescope (ATLAST) as a candidate large UV-Optical-Infrared (LUVOIR) surveyor

    NASA Astrophysics Data System (ADS)

    Bolcar, Matthew R.; Balasubramanian, Kunjithapatham; Clampin, Mark; Crooke, Julie; Feinberg, Lee; Postman, Marc; Quijada, Manuel; Rauscher, Bernard; Redding, David; Rioux, Norman; Shaklan, Stuart; Stahl, H. Philip; Stahle, Carl; Thronson, Harley

    2015-09-01

    The Advanced Technology Large Aperture Space Telescope (ATLAST) team has identified five key technologies to enable candidate architectures for the future large-aperture ultraviolet/optical/infrared (LUVOIR) space observatory envisioned by the NASA Astrophysics 30-year roadmap, Enduring Quests, Daring Visions. The science goals of ATLAST address a broad range of astrophysical questions from early galaxy and star formation to the processes that contributed to the formation of life on Earth, combining general astrophysics with direct-imaging and spectroscopy of habitable exoplanets. The key technologies are: internal coronagraphs, starshades (or external occulters), ultra-stable large-aperture telescopes, detectors, and mirror coatings. Selected technology performance goals include: 1x10-10 raw contrast at an inner working angle of 35 milli-arcseconds, wavefront error stability on the order of 10 pm RMS per wavefront control step, autonomous on-board sensing and control, and zero-read-noise single-photon detectors spanning the exoplanet science bandpass between 400 nm and 1.8 μm. Development of these technologies will provide significant advances over current and planned observatories in terms of sensitivity, angular resolution, stability, and high-contrast imaging. The science goals of ATLAST are presented and flowed down to top-level telescope and instrument performance requirements in the context of a reference architecture: a 10-meter-class, segmented aperture telescope operating at room temperature (~290 K) at the sun-Earth Lagrange-2 point. For each technology area, we define best estimates of required capabilities, current state-of-the-art performance, and current Technology Readiness Level (TRL) - thus identifying the current technology gap. We report on current, planned, or recommended efforts to develop each technology to TRL 5.

  11. Technology Development for the Advanced Technology Large Aperture Space Telescope (ATLAST) as a Candidate Large UV-Optical-Infrared (LUVOIR) Surveyor

    NASA Technical Reports Server (NTRS)

    Bolcar, Matthew R.; Balasubramanian, Kunjithapatha; Clampin, Mark; Crooke, Julie; Feinberg, Lee; Postman, Marc; Quijada, Manuel; Rauscher, Bernard; Redding, David; Rioux, Norman; Shaklan, Stuart; Stahl, H. Philip; Stahle, Carl; Thronson, Harley

    2015-01-01

    The Advanced Technology Large Aperture Space Telescope (ATLAST) team has identified five key technologies to enable candidate architectures for the future large-aperture ultraviolet/optical/infrared (LUVOIR) space observatory envisioned by the NASA Astrophysics 30-year roadmap, Enduring Quests, Daring Visions. The science goals of ATLAST address a broad range of astrophysical questions from early galaxy and star formation to the processes that contributed to the formation of life on Earth, combining general astrophysics with direct-imaging and spectroscopy of habitable exoplanets. The key technologies are: internal coronagraphs, starshades (or external occulters), ultra-stable large-aperture telescopes, detectors, and mirror coatings. Selected technology performance goals include: 1x10?10 raw contrast at an inner working angle of 35 milli-arcseconds, wavefront error stability on the order of 10 pm RMS per wavefront control step, autonomous on-board sensing & control, and zero-read-noise single-photon detectors spanning the exoplanet science bandpass between 400 nm and 1.8 µm. Development of these technologies will provide significant advances over current and planned observatories in terms of sensitivity, angular resolution, stability, and high-contrast imaging. The science goals of ATLAST are presented and flowed down to top-level telescope and instrument performance requirements in the context of a reference architecture: a 10-meter-class, segmented aperture telescope operating at room temperature (290 K) at the sun-Earth Lagrange-2 point. For each technology area, we define best estimates of required capabilities, current state-of-the-art performance, and current Technology Readiness Level (TRL) - thus identifying the current technology gap. We report on current, planned, or recommended efforts to develop each technology to TRL 5.

  12. 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.

  13. 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.

  14. Amplification of femtosecond pulses to above 1 J with large aperture Cr:LiSrAIF{sub 6} amplifiers

    SciTech Connect

    Ditmire, T.; Perry, M.D.

    1995-01-01

    The authors have developed a chirped pulse amplification system capable of producing femtosecond pulses with energy above one joule. This is accomplished by using a large aperture, flashlamp pumped Cr-LiSrAlF{sub 6} (Cr:LiSAF) amplifier. Optimum design of the 19 mm diameter amplifier results in a single pass gain of 5 with good beam quality. This amplifier produces 1.05 J pulses after compression with a width of < 125 fs at a repetition rate of 0.05 Hz.

  15. Large-aperture deformable mirror correction of tiled-grating wavefront error

    NASA Astrophysics Data System (ADS)

    Kruschwitz, B. E.; Jungquist, R.; Qiao, J.; Abbey, S.; Dean, S. E.; Maywar, D. N.; Moore, M. D.; Waxer, L. J.; Wilson, M. E.

    2006-06-01

    When tiling three gratings, with each individually exhibiting astigmatism and power due to holographic errors and coating stress, the resulting wavefront aberrations contain high-frequency components as well as the fundamental frequency, which is nearly three cycles across the aperture in the tiling direction. A deformable mirror (DM) that was designed to compensate for much slower errors (e.g., those arising from distortion in amplifier disks) is being used to compensate for this tiling-induced error. This investigation studies the effectiveness of compensating only the fundamental frequency of the tiled aberration, and shows that this provides a significant improvement that is adequate for a range of expected aberrations. Limitations of the DM correction technique are also studied.

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

    SciTech Connect

    Kuzmin, A A; Khazanov, Efim A; Shaykin, A A

    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.

  17. Astrometric plates obtained at the primary focus of large aperture reflectors

    NASA Technical Reports Server (NTRS)

    Markos, A.

    1984-01-01

    Coma, astigmatism, and great differences in stellar magnitudes between photographed object and reference stars constitute the main sources of errors in measuring positional plates. These three sources of error can easily be eliminated by the method used at the Klet Observatory for obtaining precise observations of faint objects. The astrometric plates are taken by the method of two diaphragms. The first diaphragm, with a small central aperture; is located in front of the photographic plate. The second diaphragm is situated in front of the mirror. By a very short (of the order of tens of seconds) exposure a sufficient number of reference stars can be obtained throughout the entire plate. The stars are very well defined to the very edge of the plate and are easy to measure. Moreover, this method makes it possible to use plates of larger dimensions than usual so that it is always possible to find the necessary reference stars.

  18. 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.

  19. 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.

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

    SciTech Connect

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

    2000-09-14

    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 out of bulk fused silica have intrinsically the highest laser damage threshold when compared with metal or multilayer dielectric gratings that work in reflection. LLNL has developed processing capability to produce high efficiency fused silica transmission gratings at sizes useful to future Petawatt-class systems, and has demonstrated high efficiency at smaller aperture. This report shows that fused silica diffraction exhibiting >95% efficiency into the -1 diffraction order in transmission (90{sup o} deflection of the incident light, at an incidence angle of 45{sup o} to the grating face). The microstructure of this grating consisted of grooves ion-beam etched to a depth of 1.6 microns with a pitch of 0.75 microns, using a holographically produced photoresist mask that was subsequently stripped away in significance to the fabrication of the small scale high efficiency grating was the development of the processing technology and infrastructure for production of such gratings at up to 65 cm diameter. LLNL is the currently the only location in the world with the ability to coat, interferometrically expose, and ion etch diffractive optics at this aperture. Below, we describe the design, fabrication, performance and, the scaleup process for a producing a high-efficiency transmission grating on a 65 cm fused silica substrate.

  1. Analysis of fratricide effect observed with GeMS and its relevance for large aperture astronomical telescopes

    NASA Astrophysics Data System (ADS)

    Otarola, Angel; Neichel, Benoit; Wang, Lianqi; Boyer, Corinne; Ellerbroek, Brent; Rigaut, François

    2013-12-01

    Large aperture ground-based telescopes require Adaptive Optics (AO) to correct for the distortions induced by atmospheric turbulence and achieve diffraction limited imaging quality. These AO systems rely on Natural and Laser Guide Stars (NGS and LGS) to provide the information required to measure the wavefront from the astronomical sources under observation. In particular one such LGS method consists in creating an artificial star by means of fluorescence of the sodium atoms at the altitude of the Earth's mesosphere. This is achieved by propagating one or more lasers, at the wavelength of the Na D2a resonance, from the telescope up to the mesosphere. Lasers can be launched from either behind the secondary mirror or from the perimeter of the main aperture. The so-called central- and side-launch systems, respectively. The central-launch system, while helpful to reduce the LGS spot elongation, introduces the so-called "fratricide" effect. This consists of an increase in the photon-noise in the AO Wave Front Sensors (WFS) sub-apertures, with photons that are the result of laser photons back-scattering from atmospheric molecules (Rayleigh scattering) and atmospheric aerosols (dust and/or cirrus clouds ice particles). This affects the performance of the algorithms intended to compute the LGS centroids and subsequently compute and correct the turbulence-induced wavefront distortions. In the frame of the Thirty Meter Telescope (TMT) project and using actual LGS WFS data obtained with the Gemini Multi-Conjugate Adaptive Optics System (Gemini MCAO a.k.a. GeMS), we show results from an analysis of the temporal variability of the observed fratricide effect, as well as comparison of the absolute magnitude of fratricide photon-flux level with simulations using models that account for molecular (Rayleigh) scattering and photons backscattered from cirrus clouds.

  2. Distributed Bragg reflector ring oscillators: A large aperture source of high single-mode optical power

    SciTech Connect

    Dzurko, K.M.; Hardy, A.; Scifres, D.R.; Welch, D.F.; Waarts, R.G.; Lang, R.J. )

    1993-06-01

    Distributed Bragg reflector (DBR) ring oscillators are the first monolithic semiconductor lasers containing broad-area active regions which operate in a single mode to several times their threshold current. Orthogonally oriented diffraction gratings surrounding an unpatterned active region select a single spatial and temporal mode of oscillation. This paper presents both analytic and experimental verification of single mode operation for active dimensions up to 368 [times] 1000 [mu]m. Threshold current densities under 200 A/cm[sup 2] and total differential efficiencies greater than 60% have been measured. DBR ring oscillators have demonstrated over 1 W of single frequency output power, 460 mW of spatially coherent, single frequency output power, and nearly circular diffraction limited output to 4 [times] I[sub th]. The performance potential of these devices is enormous, considering that the output apertures are nearly two orders of magnitude wider than conventional single mode sources which generate up to 0.2 W of coherent output.

  3. 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.

  4. A fundamental mode Nd:GdVO4 laser pumped by a large aperture 808 nm VCSEL

    NASA Astrophysics Data System (ADS)

    Hao, Y. Q.; Ma, J. L.; Yan, C. L.; Liu, G. J.; Ma, X. H.; Gong, J. F.; Feng, Y.; Wei, Z. P.; Wang, Y. X.; Zhao, Y. J.

    2013-05-01

    A fundamental mode Nd:GdVO4 laser pumped by a vertical cavity surface emitting laser (VCSEL) is experimentally demonstrated. The VCSEL has a circular output-beam which makes it easier for it to be directly coupled to a Nd:GdVO4 microcrystal. In our research, a large aperture 808 nm VCSEL, with a multi-ring-shaped aperture (MRSA) and an almost Gaussian-shaped far-field profile, is used as the pumping source. Experimental results for the Nd:GdVO4 laser pumped by the VCSEL are presented. The maximum output peak power of 0.754 W is obtained under a pump peak power of 1.3 W, and the corresponding opto-optic conversion efficiency is 58.1%. The average slope efficiency is 65.8% from the threshold pump power of 0.2 W to the pump power of 1.3 W. The laser beam quality factors are measured to be {M}x2=1.2 0 and {M}y2=1.1 5.

  5. Subwavelength-thick lenses with high numerical apertures and large efficiency based on high-contrast transmitarrays

    NASA Astrophysics Data System (ADS)

    Arbabi, Amir; Horie, Yu; Ball, Alexander J.; Bagheri, Mahmood; Faraon, Andrei

    2015-05-01

    Flat optical devices thinner than a wavelength promise to replace conventional free-space components for wavefront and polarization control. Transmissive flat lenses are particularly interesting for applications in imaging and on-chip optoelectronic integration. Several designs based on plasmonic metasurfaces, high-contrast transmitarrays and gratings have been recently implemented but have not provided a performance comparable to conventional curved lenses. Here we report polarization-insensitive, micron-thick, high-contrast transmitarray micro-lenses with focal spots as small as 0.57 λ. The measured focusing efficiency is up to 82%. A rigorous method for ultrathin lens design, and the trade-off between high efficiency and small spot size (or large numerical aperture) are discussed. The micro-lenses, composed of silicon nano-posts on glass, are fabricated in one lithographic step that could be performed with high-throughput photo or nanoimprint lithography, thus enabling widespread adoption.

  6. Subwavelength-thick lenses with high numerical apertures and large efficiency based on high-contrast transmitarrays.

    PubMed

    Arbabi, Amir; Horie, Yu; Ball, Alexander J; Bagheri, Mahmood; Faraon, Andrei

    2015-01-01

    Flat optical devices thinner than a wavelength promise to replace conventional free-space components for wavefront and polarization control. Transmissive flat lenses are particularly interesting for applications in imaging and on-chip optoelectronic integration. Several designs based on plasmonic metasurfaces, high-contrast transmitarrays and gratings have been recently implemented but have not provided a performance comparable to conventional curved lenses. Here we report polarization-insensitive, micron-thick, high-contrast transmitarray micro-lenses with focal spots as small as 0.57 λ. The measured focusing efficiency is up to 82%. A rigorous method for ultrathin lens design, and the trade-off between high efficiency and small spot size (or large numerical aperture) are discussed. The micro-lenses, composed of silicon nano-posts on glass, are fabricated in one lithographic step that could be performed with high-throughput photo or nanoimprint lithography, thus enabling widespread adoption. PMID:25947118

  7. A cryogenic rotation stage with a large clear aperture for the half-wave plates in the Spider instrument

    NASA Astrophysics Data System (ADS)

    Bryan, Sean; Ade, Peter; Amiri, Mandana; Benton, Steven; Bihary, Richard; Bock, James; Bond, J. Richard; Chiang, H. Cynthia; Contaldi, Carlo; Crill, Brendan; Dore, Olivier; Elder, Benjamin; Filippini, Jeffrey; Fraisse, Aurelien; Gambrel, Anne; Gandilo, Natalie; Gudmundsson, Jon; Hasselfield, Matthew; Halpern, Mark; Hilton, Gene; Holmes, Warren; Hristov, Viktor; Irwin, Kent; Jones, William; Kermish, Zigmund; Lawrie, Craig; MacTavish, Carrie; Mason, Peter; Megerian, Krikor; Moncelsi, Lorenzo; Montroy, Thomas; Morford, Tracy; Nagy, Johanna; Netterfield, C. Barth; Padilla, Ivan; Rahlin, Alexandra S.; Reintsema, Carl; Riley, Daniel C.; Ruhl, John; Runyan, Marcus; Saliwanchik, Benjamin; Shariff, Jamil; Soler, Juan; Trangsrud, Amy; Tucker, Carole; Tucker, Rebecca; Turner, Anthony; Wen, Shyang; Wiebe, Donald; Young, Edward

    2016-01-01

    We describe the cryogenic half-wave plate rotation mechanisms built for and used in Spider, a polarization-sensitive balloon-borne telescope array that observed the cosmic microwave background at 95 GHz and 150 GHz during a stratospheric balloon flight from Antarctica in January 2015. The mechanisms operate at liquid helium temperature in flight. A three-point contact design keeps the mechanical bearings relatively small but allows for a large (305 mm) diameter clear aperture. A worm gear driven by a cryogenic stepper motor allows for precise positioning and prevents undesired rotation when the motors are depowered. A custom-built optical encoder system monitors the bearing angle to an absolute accuracy of ±0.1∘. The system performed well in Spider during its successful 16 day flight.

  8. The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLAST-Pol): Instrument and 2010 Science Campaign

    NASA Astrophysics Data System (ADS)

    Gandilo, Natalie; BLAST-Pol Collaboration

    2012-01-01

    The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLAST-Pol) is a 1.8-m telescope that observes polarized dust emission with a resolution of 1'. BLAST-Pol images the sky onto a focal plane that consists of 270 feed-horn coupled bolometers at 250, 350, and 500 microns. In January 2011, BLAST-Pol completed a successful 9.5-day flight over Antarctica. Eight science targets were observed, and a second flight is planned for December 2012. I will give an overview of the instrument performance during the first science campaign and present preliminary maps. BLAST-Pol maps will provide an excellent dataset for studying the role of magnetic fields in star formation.

  9. 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. Philip; 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.

  10. A cryogenic rotation stage with a large clear aperture for the half-wave plates in the Spider instrument.

    PubMed

    Bryan, Sean; Ade, Peter; Amiri, Mandana; Benton, Steven; Bihary, Richard; Bock, James; Bond, J Richard; Chiang, H Cynthia; Contaldi, Carlo; Crill, Brendan; Dore, Olivier; Elder, Benjamin; Filippini, Jeffrey; Fraisse, Aurelien; Gambrel, Anne; Gandilo, Natalie; Gudmundsson, Jon; Hasselfield, Matthew; Halpern, Mark; Hilton, Gene; Holmes, Warren; Hristov, Viktor; Irwin, Kent; Jones, William; Kermish, Zigmund; Lawrie, Craig; MacTavish, Carrie; Mason, Peter; Megerian, Krikor; Moncelsi, Lorenzo; Montroy, Thomas; Morford, Tracy; Nagy, Johanna; Netterfield, C Barth; Padilla, Ivan; Rahlin, Alexandra S; Reintsema, Carl; Riley, Daniel C; Ruhl, John; Runyan, Marcus; Saliwanchik, Benjamin; Shariff, Jamil; Soler, Juan; Trangsrud, Amy; Tucker, Carole; Tucker, Rebecca; Turner, Anthony; Wen, Shyang; Wiebe, Donald; Young, Edward

    2016-01-01

    We describe the cryogenic half-wave plate rotation mechanisms built for and used in Spider, a polarization-sensitive balloon-borne telescope array that observed the cosmic microwave background at 95 GHz and 150 GHz during a stratospheric balloon flight from Antarctica in January 2015. The mechanisms operate at liquid helium temperature in flight. A three-point contact design keeps the mechanical bearings relatively small but allows for a large (305 mm) diameter clear aperture. A worm gear driven by a cryogenic stepper motor allows for precise positioning and prevents undesired rotation when the motors are depowered. A custom-built optical encoder system monitors the bearing angle to an absolute accuracy of ±0.1(∘). The system performed well in Spider during its successful 16 day flight. PMID:26827333

  11. A survey of near-field testing methods for large aperture antennas and future trends

    NASA Technical Reports Server (NTRS)

    Newell, A. C.

    1983-01-01

    In recent years, a near-field antenna measurements have progressed from theoretical concepts to a wide variety of operational measurement systems. The current status of this work is summarized and its possible application to large space antennas is discussed.

  12. Co-expression of LASS2 and TGF-β1 predicts poor prognosis in hepatocellular carcinoma

    PubMed Central

    Ruan, Haoyu; Wang, Ting; Yang, Chen; Jin, Guangzhi; Gu, Dishui; Deng, Xuan; Wang, Cun; Qin, Wenxin; Jin, Haojie

    2016-01-01

    Longevity assurance homolog 2 of yeast LAG1 (LASS2) has been reported to act as an important tumor suppressor in the development of human cancers. However, little is known about the prognostic value of LASS2 in hepatocellular carcinoma (HCC) . In the present study, we analyzed correlation between LASS2 and TGF-β1 levels, and evaluated their prognostic values in HCC patients. We first analyzed the expression of LASS2 and TGF-β1 in two independent cohorts (test cohort: 184 HCC patients; validation cohort: 118 HCC patients) using immunohistochemistry (IHC). Kaplan-Meier survival and Cox regression analyses were executed to evaluate the prognosis of HCC. The results of IHC analysis revealed a positive correlation between the expression of LASS2 and TGF-β1. HCC Patients with low expression of LASS2 and TGF-β1 had shorter overall survival (OS) and time to recurrence (TTR) than patients with high expression of LASS2 and TGF-β1. Furthermore, combination of LASS2 and TGF-β1 was an independent and significant risk factor for OS and TTR. In conclusion, low expression of LASS2 and TGF-β1 contributes to the aggressiveness and poor prognosis of HCC, and may represent a novel prognostic biomarker for HCC patients. PMID:27581744

  13. Co-expression of LASS2 and TGF-β1 predicts poor prognosis in hepatocellular carcinoma.

    PubMed

    Ruan, Haoyu; Wang, Ting; Yang, Chen; Jin, Guangzhi; Gu, Dishui; Deng, Xuan; Wang, Cun; Qin, Wenxin; Jin, Haojie

    2016-01-01

    Longevity assurance homolog 2 of yeast LAG1 (LASS2) has been reported to act as an important tumor suppressor in the development of human cancers. However, little is known about the prognostic value of LASS2 in hepatocellular carcinoma (HCC) . In the present study, we analyzed correlation between LASS2 and TGF-β1 levels, and evaluated their prognostic values in HCC patients. We first analyzed the expression of LASS2 and TGF-β1 in two independent cohorts (test cohort: 184 HCC patients; validation cohort: 118 HCC patients) using immunohistochemistry (IHC). Kaplan-Meier survival and Cox regression analyses were executed to evaluate the prognosis of HCC. The results of IHC analysis revealed a positive correlation between the expression of LASS2 and TGF-β1. HCC Patients with low expression of LASS2 and TGF-β1 had shorter overall survival (OS) and time to recurrence (TTR) than patients with high expression of LASS2 and TGF-β1. Furthermore, combination of LASS2 and TGF-β1 was an independent and significant risk factor for OS and TTR. In conclusion, low expression of LASS2 and TGF-β1 contributes to the aggressiveness and poor prognosis of HCC, and may represent a novel prognostic biomarker for HCC patients. PMID:27581744

  14. Quantitative comparison of terahertz emission from (100) InAs surfaces and a GaAs large-aperture photoconductive switch at high fluences.

    PubMed

    Reid, Matthew; Fedosejevs, Robert

    2005-01-01

    InAs has previously been reported to be an efficient emitter of terahertz radiation at low excitation fluences by use of femtosecond laser pulses. The scaling and saturation of terahertz emission from a (100) InAs surface as a function of excitation fluence is measured and quantitatively compared with the emission from a GaAs large-aperture photoconductive switch. We find that, although the instantaneous peak radiated terahertz field from (100) InAs exceeds the peak radiated signals from a GaAs large-aperture photoconductive switch biased at 1.6 kV/cm, the pulse duration is shorter. For the InAs source the total energy radiated is less than can be obtained from a GaAs large-aperture photoconductive switch. PMID:15662896

  15. Preliminary evaluation of sensible heat flux measurements from a large aperture scintillometer using lysimetric data

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The path integrating capabilities of scintillometers over several kilometers make it a potential tool that can bridge the gap between primary point based observations (lysimeters, Bowen ratio, or eddy covariance) and the demand for large-scale spatially averaged surface fluxes. Further, the spatial...

  16. 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.

  17. 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.

  18. Research of active panel technology for large aperture millimeter-wave/sub-millimeter-wave telescope

    NASA Astrophysics Data System (ADS)

    Wu, Xuhao; Cui, Xiangqun

    2010-05-01

    As Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) project was completed successfully, indicating the key technology of active optics has been mastered by the Chinese astronomical community, experts of Nanjing Institute of Astronomical Optics and Technology (NIAOT), builders of this project, started to consider how to use the technology developed in large optical telescope such as LAMOST to improve the performance of millimeterwave / sub-millimeter-wave telescope. In order to do more research work about active optics of millimeter submillimeter band and improve the performance of Delingha 13.7m millimeter-wave telescope, researchers of NIAOT intend to upgrade the reflect panel accuracy of this telescope. This paper will introduce the preliminary work of the accuracy-upgrading task, numerical simulation of the 13.7m telescope. In this presentation, the primary reflector finite element model (FEM) construction, gravity and thermal deformation, and modal analyze are described. The result shows that the gravity and thermal distortion of the reflector are contributed mostly by the back-structure and the active support for the panels is very necessary to restrain this kind of distortion.

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

    NASA Astrophysics Data System (ADS)

    Lillie, Charles F.; Dailey, D. R.; Polidan, R. S.

    2010-01-01

    Future space observatories will require increasingly large telescopes to study the earliest stars and galaxies, as well as faint nearby objects. Technologies now under development will enable telescopes much larger than the 6.5-meter diameter James Webb Space Telescope (JWST) to be developed at comparable costs. Current segmented mirror and deployable optics technology enables the 6.5 meter JWST telescope to be folded for launch in the 5-meter diameter Ariane 5 payload fairing, and deployed autonomously after reaching orbit. Late in the next decade, when the Ares V Cargo Launch Vehicle payload fairing becomes operational, even larger telescope can be placed in orbit. In this paper we present our concept for a 16-meter JWST derivative, chord-fold telescope which could be stowed in the 10-m diameter Ares V fairing, plus a description of the new technologies that enable ATLAST to be developed at an affordable price.

  20. Design of large aperture four group elements mid-wave infrared zoom lens

    NASA Astrophysics Data System (ADS)

    Ji, Yiqun; Shi, Rongbao; He, Hucheng; Shen, Weimin

    2012-10-01

    Zoom lens with variable focal length is well fit for researching objectives far and near. Design of zoom lens working at mid-wave infrared wavelength (7.7-10.3_m) and its view field 10 degrees is presented. Determination of the initial configuration of the variable and the compensate groups are discussed according to the mechanism compensate curves. The compensate group is determined with positive power. Its focal length changes during a large scope, which is from 300mm to 100mm. And the corresponding F number variables from 3.75 to 1.25. So the residual aberration needs to be carefully corrected. The optimized zoom lens is composed of four group elements, and its performance reaches diffraction limited at each focal position.

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

    NASA Astrophysics Data System (ADS)

    Matthews, Tristan G.; Ade, Peter A. R.; Angilè, 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, Frédérick; 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

    2014-04-01

    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 μm. 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, and we find that the dominant filament in the cloud is approximately perpendicular to the large-scale field, while secondary filaments appear to run parallel to the magnetic fields in their vicinities. This is similar to what is observed in Serpens South via near-IR polarimetry, and consistent with what is seen in MHD simulations by F. Nakamura and Z. Li.

  2. Study on the Stressed Mirror Polishing with a Continuous Polishing Machine for Large Aperture Off-axis Aspheric Mirrors

    NASA Astrophysics Data System (ADS)

    Li, Xin-nan; Zhang, Hai-ying; Cui, Xiang-qun; Jiang, Zi-bo; Zheng, Yi; Liu, Xing-tao; Ni, Hou-kun

    2012-10-01

    A special stressed annular polishing technique is proposed to mill the off-axis aspheric sub-mirrors of a large segmented mirror with an annular polishing machine. Based on the basic principle of stressed annular polishing technique, a set of special stressing mechanisms are designed to convert milling the aspheric surfaces of sub-mirrors with different off-axis distances into milling the spherical surfaces with identical radii of curvature, so that they can be pol- ished simultaneously on a continuous polishing machine. It took about contin- uous 40 hours to polish a scaled-down mirror of the planning Chinese Future Giant Telescope (CFGT) using this technique. This mirror has the 330 mm di- ameter, 3.6 m off-axis distance, and the 21.6 m radius of curvature, and its max- imum asphericity is 16 micron. The experiment shows that this method has a high effciency, suits batch manufacturing, especially the batch manufacturing of aspheric sub-mirrors of the segmented primary mirror of an extremely large aperture telescope.

  3. LUPUS I observations from the 2010 flight of the Balloon-borne large aperture submillimeter telescope for polarimetry

    SciTech Connect

    Matthews, Tristan G.; Chapman, Nicholas L.; Novak, Giles; Ade, Peter A. R.; Hargrave, Peter C.; Nutter, David; Angilè, Francesco E.; Devlin, Mark J.; Klein, Jeffrey; Benton, Steven J.; Fissel, Laura M.; Gandilo, Natalie N.; Netterfield, Calvin B.; Chapin, Edward L.; Fukui, Yasuo; Gundersen, Joshua O.; Korotkov, Andrei L.; Moncelsi, Lorenzo; Mroczkowski, Tony K.; Olmi, Luca; and others

    2014-04-01

    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 μm. 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, and we find that the dominant filament in the cloud is approximately perpendicular to the large-scale field, while secondary filaments appear to run parallel to the magnetic fields in their vicinities. This is similar to what is observed in Serpens South via near-IR polarimetry, and consistent with what is seen in MHD simulations by F. Nakamura and Z. Li.

  4. Processing method and process modeling of large aperture transparent magnesium aluminate spinel domes

    NASA Astrophysics Data System (ADS)

    Yu, Jian; McWilliams, Brandon; Kilczewski, Steven; Gilde, Gary; Lidie, Ashley; Sands, James

    2009-05-01

    Polycrystalline spinel serves as an alternative to materials such as sapphire and magnesium fluoride that are currently being used in electromagnetic window applications such as missile domes, where high strength, high hardness and high transmittance in the visible and infrared spectra are required. The cubic crystal lattice of spinel imparts an isotropy to the bulk optical property, which eliminates optical distortion due to birefringence that occurs in sapphire and other non-cubic materials. The current study is to find a reliable manufacturing process to produce large magnesium aluminate spinel domes from powder consolidation efficiently. A binder-less dry ball milling process was used to deflocculate the spinel powder to increase its fluidity in an effort to ease the shape-forming. Dry ball milling time trials were conducted at several intervals to determine the appropriate level of time required to break up both the hard and soft agglomerates associated with the virgin spinel powder. The common problems encountered in dry powder shape-forming are crack growth and delamination of the green body during cold isostatic pressing (CIPing). The cracking and the delamination are due to the buildup of stress gradients on the green body that are created by the frictional force between the powder and the die wall or mold wall. To understand the stresses during the CIPing process, a finite element analysis of stresses on the green body was conducted. The simulation was used to evaluate the effect of die tooling and process characteristics on the development of stress gradients in the green body dome. Additionally, the effect of friction between the die wall and powder was examined by the simulation. It was found that by mitigating the frictional forces, cracking and delamination on the green body could be eliminated. A stepped-pressure CIPing technique was developed to reduce stress gradient build-up during CIPing. Also, oleic acid lubricant was applied to the die wall to

  5. Large-aperture continuous-phase diffractive optical element for beam transform

    NASA Astrophysics Data System (ADS)

    Tan, Qiaofeng; Yan, Yingbai; Jin, Guofan; Wu, Minxian

    1999-11-01

    Beam transform, such as to obtain uniform focal spot with flat top, steep edge, low side lobes and high light efficiency, can be realized well by diffractive optical element (DOE). The DOE has many advantages, such as high light efficiency and strong phase distribution design flexibility. To increase the light efficiency and decrease large-angle scattering, continuous phase DOE should be used. The phase design is competed by a kind of multi-resolution hybrid algorithm based on hill-climbing and simulated annealing, which exploits sufficiently strong convergence ability of the hill climbing and global optimization potential of the simulated annealing. A kind of phase distribution with good geometrical structure and diameter 80 mm is obtained by choosing disturbance function, receipt and refused probability and so on. The simulated results show that the light efficiency is more than 95 percent, and the non-uniformity is less than 5 percent. Because the etching depth is direct proportion to the exposure time, to obtain continuous phase DOE, a kind of hollowed-out mask, namely gray-scale mask is used to control exposure time of each are. The mask is manufactured by linear cutting machine. The continuous phase DOE with diameter 80mm is fabricated by ion-etching with the mask. Finally, the tolerance of manufacturing error including depth error and alignment error are analyzed.

  6. 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.

  7. 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.

  8. Performance Evaluation of Large Aperture 'Polished Panel' Optical Receivers Based on Experimental Data

    NASA Technical Reports Server (NTRS)

    Vilnrotter, Victor

    2013-01-01

    Recent interest in hybrid RF/Optical communications has led to the development and 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 Communications Complex. 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 realtime 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 with photon-counting detection, and compared with the ultimate quantum bound on detection performance for these modulations. 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.

  9. Neutral density estimation derived from meteoroid measurements using high-power, large-aperture radar

    NASA Astrophysics Data System (ADS)

    Li, A.; Close, S.

    2016-07-01

    We present a new method to estimate the neutral density of the lower thermosphere/upper mesosphere given deceleration measurements from meteoroids as they enter Earth's atmosphere. By tracking the plasma (referred to as head echoes) surrounding the ablating meteoroid, we are able to measure the range and velocity of the meteoroid in 3-D. This is accomplished at Advanced Research Projects Agency Long-Range Tracking and Instrumentation Radar (ALTAIR) with the use of four additional receiving horns. Combined with the momentum and ablation equations, we can feed large quantities of data into a minimization function which estimates the associated constants related to the ablation process and, more importantly, the density ratios between successive layers of the atmosphere. Furthermore, if we take statistics of the masses and bulk densities of the meteoroids, we can calculate the neutral densities and its associated error by the ratio distribution on the minimum error statistic. A standard deviation of approximately 10% can be achieved, neglecting measurement error from the radar. Errors in velocity and deceleration compound this uncertainty, which in the best case amounts to an additional 4% error. The accuracy can be further improved if we take increasing amounts of measurements, limited only by the quality of the ranging measurements and the probability of knowing the median of the distribution. Data analyzed consist mainly of approximately 500 meteoroids over a span of 20 min on two separate days. The results are compared to the existing atmospheric model NRLMSISE-00, which predicts lower density ratios and static neutral densities at these altitudes.

  10. Large aperture kinoform phase plates in fused silica for spatial beam smoothing on Nova and the Beamlet Lasers

    SciTech Connect

    Rushford, M.C.; Dixit, S.N.; Thomas, I.M.; Martin, A.M.; Perry, M.D.

    1997-03-01

    It is now widely recognized that spatial beam smoothing (homogenization) is essential in coupling the laser energy to the inertial confinement fusion (ICF) targets. For the indirect drive approach to ICF, it is desirable to distribute the laser energy into a uniformly speckled profile that has a flat-top super-Gaussian envelope (8th power or higher) and contains greater than 95% of the energy inside the super-Gaussian profile. Spatial smoothing is easily achieved by introducing a binary random phase plate (RPP) in the beam. This produces a homogenized far-field pattern which consists of an overall envelope function determined by the RPP element superimposed with a fine scale speckle pattern arising due to the interference among the various RPP elements. Although easy to fabricate and currently in routine use in many fusion laboratories, the binary RPPs do not meet the ICF requirements stated above since the far-field intensity profile is restricted to essentially an Airy function containing only 84% (an upper limit) of the energy inside the central spot. Approaches using lenslet arrays (refractive or diffractive) have limited use since they operate in the quasi-far-field and have a short depth of focus. The limitations of the RPPs can be overcome by relaxing the binary phase constraint. We have recently presented 5 continuously varying phase screens for tailoring the focal plane irradiance profiles. Called kinoform phase plates (KPPs), these phase screens offer complete flexibility in tailoring the focal plane envelope and, at the same time, increasing the energy efficiency inside the focal spot. In this paper we discuss the design and fabrication of such kinoform phase plates in fused silica for spatial beam smoothing on the Nova and the Beamlet lasers. Since the phase plates are used at the end of the laser chain, KPPs on Nova and Beamlet have to be fabricated on large aperture optics (65-cm diameter and 40-cm square substrates respectively). The following

  11. Constraining lowermost mantle structure with PcP/P amplitude ratios from large aperture arrays

    NASA Astrophysics Data System (ADS)

    Ventosa, S.; Romanowicz, B. A.

    2015-12-01

    Observations of weak short-period teleseismic body waves help to resolve lowermost mantle structure at short wavelengths, which is essential for understanding mantle dynamics and the interactions between the mantle and core. Their limited amount and uneven distribution are however major obstacles to solve for volumetric structure of the D" region, topography of the core-mantle boundary (CMB) and D" discontinuity, and the trade-offs among them. While PcP-P differential travel times provide important information, there are trade-offs between velocity structure and core-mantle boundary topography, which PcP/P amplitude ratios can help resolve, as long as lateral variations in attenuation and biases due to focusing are small or can be corrected for. Dense broadband seismic networks help to improve signal-to-noise ratio (SNR) of the target phases and signal-to-interference ratio (SIR) of other mantle phases when the slowness difference is large enough. To improve SIR and SNR of teleseismic PcP data, we have introduced the slant-stacklet transform to define coherent-guided filters able to separate and enhance signals according to their slowness, time of arrival and frequency content. We thus obtain optimal PcP/P amplitude ratios in the least-square sense using two short sliding windows to match the P signal with a candidate PcP signal. This method allows us to dramatically increase the amount of high-quality observations of short-period PcP/P amplitude ratios by allowing for smaller events and wider epicentral distance and depth ranges.We present the results of measurement of PcP/P amplitude ratios, sampling regions around the Pacific using dense arrays in North America and Japan. We observe that short-period P waves traveling through slabs are strongly affected by focusing, in agreement with the bias we have observed and corrected for due to mantle heterogeneities on PcP-P travel time differences. In Central America, this bias is by far the stronger anomaly we observe

  12. MRF Applications: On the Road to Making Large-Aperture Ultraviolet Laser Resistant Continuous Phase Plates for High-Power Lasers

    SciTech Connect

    Menapace, J A; Davis, P J; Steele, W A; Hachkowski, M R; Nelson, A; Xin, K

    2006-10-26

    Over the past two years we have developed MRF tools and procedures to manufacture large-aperture (430 X 430 mm) continuous phase plates (CPPs) that are capable of operating in the infrared portion (1053 nm) of high-power laser systems. This is accomplished by polishing prescribed patterns of continuously varying topographical features onto finished plano optics using MRF imprinting techniques. We have been successful in making, testing, and using large-aperture CPPs whose topography possesses spatial periods as low as 4 mm and surface peak-to-valleys as high as 8.6 {micro}m. Combining this application of MRF technology with advanced MRF finishing techniques that focus on ultraviolet laser damage resistance makes it potentially feasible to manufacture large-aperture CPPs that can operate in the ultraviolet (351 nm) without sustaining laser-induced damage. In this paper, we will discuss the CPP manufacturing process and the results of 351-nm/3-nsec equivalent laser performance experiments conducted on large-aperture CPPs manufactured using advanced MRF protocols.

  13. 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.

  14. Performance of large aperture tapered fiber phase conjugate mirror with high pulse energy and 1-kHz repetition rate.

    PubMed

    Zhao, Zhigang; Dong, Yantao; Pan, Sunqiang; Liu, Chong; Chen, Jun; Tong, Lixin; Gao, Qingsong; Tang, Chun

    2012-01-16

    A large aperture fused silica tapered fiber phase conjugate mirror is presented with a maximum 70% stimulated Brillouin scattering (SBS) reflectivity, which is obtained with 1 kHz repetition rate, 15 ns pulse width and 38 mJ input pulse energy. To the best of our knowledge, this is the highest SBS reflectivity ever reported by using optical fiber as a phase conjugate mirror for such high pulse repetition rate (1 kHz) and several tens of millijoule (mJ) input pulse energy. The influences of fiber end surface quality and pump pulse widths on SBS reflectivity are investigated experimentally. The results show that finer fiber end surface quality and longer input pulse widths are preferred for obtaining higher SBS reflectivity with higher input pulse energy. Double passing amplification experiments are also performed. 52 mJ pulse energy is achieved at 1 kHz repetition rate, with a reflected SBS pulse width of 1.5 ns and a M(2) factor of 2.3. The corresponding peak power reaches 34.6 MW. Obvious beam quality improvement is observed. PMID:22274534

  15. Low stress ion-assisted coatings on fused silica substrates for large aperture laser pulse compression gratings

    NASA Astrophysics Data System (ADS)

    Smith, Douglas J.; McCullough, Mike; Smith, Claire; Mikami, Takuya; Jitsuno, Takahisa

    2008-10-01

    Large aperture laser pulse compressor designs use several diffraction gratings in series and sometimes tiled together to compress an amplified 1 to 10 ns pulse to 0.1 to 10 ps. The wavefront of the compressed pulse must be well controlled to allow focusing to a small spot on a target. Traditionally, multilayer dielectric gratings (MLDG) have been fabricated onto high thermal expansion substrates such as BK7 glass to prevent crazing and excessive bending due to tensile coating stress when operated in high vacuum. However, the high CTE of the BK7 can cause wavefront distortion and changes in the period of the grating. This work uses ion-assisted deposition of HfO2/SiO2 films to increase the compressive stress in MLD layers to allow use of silica substrates in the compressor vacuum environment. Stress, coating uniformity, and damage results are reported. The process was scaled to full size (91cm × 42cm) MLD gratings for use in the Osaka University LFEX laser system. Diffracted wavefront results from the full scale gratings is presented.

  16. A scalable multi-chip architecture to realise large-format microshutter arrays for coded aperture applications

    NASA Astrophysics Data System (ADS)

    McNie, Mark E.; King, David O.; Smith, Gilbert W.; Stone, Steven M.; Brown, Alan G.; Gordon, Neil T.; Slinger, Christopher W.; Cannon, Kevin; Riches, Stephen; Rogers, Stanley

    2009-08-01

    Coded aperture imaging has been used for astronomical applications for several years. Typical implementations used a fixed mask pattern and are designed to operate in the X-Ray or gamma ray bands. Recently applications have emerged in the visible and infra red bands for low cost lens-less imaging systems and system studies have shown that considerable advantages in image resolution may accrue from the use of multiple different images of the same scene - requiring a reconfigurable mask. Previously we reported on the realization of a 2x2cm single chip mask in the mid-IR based on polysilicon micro-opto-electro-mechanical systems (MOEMS) technology and its integration with ASIC drive electronics using conventional wire bonding. The MOEMS architecture employs interference effects to modulate incident light - achieved by tuning a large array of asymmetric Fabry-Perot optical cavities via an applied voltage and uses a hysteretic row/column scheme for addressing. In this paper we present the latest transmission results in the mid-IR band (3-5μm) and report on progress in developing a scalable architecture based on a tiled approach using multiple 2 x 2cm MOEMS chips with associated control ASICs integrated using flip chip technology. Initial work has focused on a 2 x 2 tiled array as a stepping stone towards an 8 x 8 array.

  17. Seasonal variability of turbulent fluxes over a vegetated subtropical coastal wetland measured by large aperture scintillometry and eddy covariance

    NASA Astrophysics Data System (ADS)

    Guyot, Adrien; Gray, Michael; Riesenkamp, Michiel; Lockington, David; McGowan, Hamish

    2016-04-01

    Subtropical coastal wetlands are particularly susceptible to the impacts of climate variability: their recharge rates strongly depend on rainfall, and the occurrence of prolonged droughts or wet periods have direct consequences for wetland health and bio-diversity. There is therefore a need to close the water budget of these ecosystems and this requires the quantification of rates of evaporation/evapotranspiration. However, few studies have documented land-atmosphere exchanges over wetlands for which water level varies considerably during a typical annual cycle. Here, we present a year of turbulent flux observations over a wetland on the subtropical coast of eastern Australia. Large Aperture Scintillometry and Eddy Covariance are used to derive sensible heat fluxes. Latent heat fluxes are also derived through an energy balance for both instruments' observations and also directly through Eddy Covariance. Careful sensitivity analysis of the instrumental footprints, seasonal variations of land surface parameters such as roughness length and displacement height are examined and subsequent uncertainties in the derived turbulent fluxes are discussed. Finally we show how these observations can also help better understand hydrological processes at the catchment scale.

  18. Comparison of full-aperture interferometry to subaperture stitched interferometry for a large-diameter fast mirror

    NASA Astrophysics Data System (ADS)

    Catanzaro, Brian E.; Thomas, James A.; Cohen, Eri J.

    2001-11-01

    The Herschel Space Observatory (formerly known as FIRST) consists of a 3.5 m space telescope. Stitching sub aperture interferograms may offer considerable cost savings during testing of the flight telescope as compared to other techniques. A comparative demonstration is presented of interferogram stitching techniques that enable a composite map of a 3-D surface to be assembled from a sequence of sub-aperture measurements. This paper describes the fundamental procedures for stitching together component data sets and demonstrates such techniques with real data sets. A set of 14 sub-aperture measurements was made of a 2 m diameter all-composite mirror developed as part of the Herschel Space Observatory program and two different stitching software packages were employed to stitch together the sub-aperture surface maps. The software packages differ fundamentally in the way the sub-aperture maps are three-dimensionally stitched, one employing a local technique and the other using a global technique. The processed results from both algorithms are compared with each other and with a full-aperture reference measurement made of the same test optic. A summary of the results is presented and potential modifications and enhancements to the stitching techniques are discussed.

  19. 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).

  20. Modeling the global micrometeor input function in the upper atmosphere observed by high power and large aperture radars

    NASA Astrophysics Data System (ADS)

    Janches, Diego; Heinselman, Craig J.; Chau, Jorge L.; Chandran, Amal; Woodman, Ronald

    2006-07-01

    We report initial results of an effort to model the diurnal and seasonal variability of the meteor rate detected by high power and large aperture (HPLA) radars. The model uses Monte Carlo simulation techniques and at present assumes that most of the detected particles originate from three radiant distributions with the most dominant concentrated around the Earth's apex. The other two sources are centered 80° in ecliptic longitude to each side of the apex and are commonly known as helion and antihelion. To reproduce the measurements, the apex source flux was set to provide ˜70% of the total number of particles while the other ˜30% is provided by the combined contribution of the two remaining sources. The results of the model are in excellent agreement with observed diurnal curves obtained at different seasons and locations using the 430 MHz Arecibo radar in Puerto Rico, the 50 MHz Jicamarca radar in Perú, and the 1.29 GHz Sondrestrom radar in Greenland. To obtain agreement with the observed diurnal and seasonal variability of the meteor rate, an empirical atmospheric filtering effect was introduced in the simulation which prevents meteors with low-elevation radiants (≤20°) from being detected by the radars at mesospheric altitudes. The filtering effect is probably produced by a combination of factors related to the interaction of the meteor with the air molecules such as electron production and/or the ablation at higher altitudes. On the basis of these results we calculate the micrometeor global, diurnal, and seasonal input in the upper atmosphere.

  1. Estimation of turbulent sensible heat and momentum fluxes over a heterogeneous urban area using a large aperture scintillometer

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Hyun; Lee, Jun-Ho; Kim, Bo-Young

    2015-08-01

    The accurate determination of surface-layer turbulent fluxes over urban areas is critical to understanding urban boundary layer (UBL) evolution. In this study, a remote-sensing technique using a large aperture scintillometer (LAS) was investigated to estimate surface-layer turbulent fluxes over a highly heterogeneous urban area. The LAS system, with an optical path length of 2.1 km, was deployed in an urban area characterized by a complicated land-use mix (residential houses, water body, bare ground, etc.). The turbulent sensible heat ( Q H) and momentum fluxes (τ) were estimated from the scintillation measurements obtained from the LAS system during the cold season. Three-dimensional LAS footprint modeling was introduced to identify the source areas ("footprint") of the estimated turbulent fluxes. The analysis results showed that the LAS-derived turbulent fluxes for the highly heterogeneous urban area revealed reasonable temporal variation during daytime on clear days, in comparison to the land-surface process-resolving numerical modeling. A series of sensitivity tests indicated that the overall uncertainty in the LAS-derived daytime Q H was within 20%-30% in terms of the influence of input parameters and the nondimensional similarity function for the temperature structure function parameter, while the estimation errors in τ were less sensitive to the factors of influence, except aerodynamic roughness length. The 3D LAS footprint modeling characterized the source areas of the LAS-derived turbulent fluxes in the heterogeneous urban area, revealing that the representative spatial scales of the LAS system deployed with the 2.1 km optical path distance ranged from 0.2 to 2 km2 (a "micro- a scale"), depending on local meteorological conditions.

  2. Determining meteoroid bulk densities using a plasma scattering model with high-power large-aperture radar data

    NASA Astrophysics Data System (ADS)

    Close, Sigrid; Volz, Ryan; Loveland, Rohan; Macdonell, Alex; Colestock, Patrick; Linscott, Ivan; Oppenheim, Meers

    2012-09-01

    We present an improved technique for calculating bulk densities of low-mass (<1 g) meteoroids using a scattering model applied to the high-density plasma formed around the meteoroid as it enters Earth’s atmosphere. These plasmas, referred to as head echoes, travel at or near the speed of the meteoroid, thereby allowing the determination of the ballistic coefficient (mass divided by physical cross-section), which depends upon speed and deceleration. Concurrently, we apply a scattering model to the returned signal strength of the head echo in order to correlate radar-cross-section (RCS) to plasma density and meteoroid mass. In this way, we can uniquely solve for the meteoroid mass, radius and bulk density independently. We have applied this new technique to head echo data collected in 2007 and 2008 simultaneously at VHF (160 MHz) and UHF (422 MHz) at ALTAIR, which is a high-power large-aperture radar located on the Kwajalein Atoll. These data include approximately 20,000 detections with dual-frequency, dual-polarization, and monopulse (i.e. angle) returns. From 2000 detections with the smallest monopulse errors, we find a mean meteoroid bulk density of 0.9 g/cm3 with observations spanning almost three orders of magnitude from 0.01 g/cm3 to 8 g/cm3. Our results show a clear dependence between meteoroid bulk density and altitude of head echo formation, as well as dependence between meteoroid bulk density and 3D speed. The highest bulk densities are detected at the lowest altitudes and lowest speeds. Additionally, we stipulate that the approximations used to derive the ballistic parameter, in addition to neglecting fragmentation, suggest that the traditional ballistic parameter must be used with caution when determining meteoroid parameters.

  3. 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; César 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 μm per exposure under the worst case scenario (<10 μm for most orientations), with final correction to 5 μm 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.

  4. Design and prototype tests of a large-aperture 37-53 MHz ferrite-tuned booster synchrotron cavity

    SciTech Connect

    Mark S. Champion et al.

    2001-07-12

    The Booster synchrotron at Fermilab employs eighteen 37-53 MHz ferrite-tuned double-gap coaxial radiofrequency cavities for acceleration of protons from 400 MeV to 8 GeV. The cavities have an aperture of 2.25 inches and operate at 55 kV per cavity. Future high duty factor operation of the Booster will be problematic due to unavoidable beam loss at the cavities resulting in excessive activation. The power amplifiers, high maintenance items, are mounted directly to the cavities in the tunnel. A proposed replacement for the Booster, the Proton Driver, will utilize the Booster radiofrequency cavities and requires not only a larger aperture, but also higher voltage. A research and development program is underway at Fermilab to modify the Booster cavities to provide a 5-inch aperture and a 20% voltage increase. A prototype has been constructed and high power tests have bee completed. The cavity design and test results is presented.

  5. Thermo-optical simulation and experiment for the assessment of single, hollow, and large aperture retroreflector for lunar laser ranging

    NASA Astrophysics Data System (ADS)

    Araki, Hiroshi; Kashima, Shingo; Noda, Hirotomo; Kunimori, Hiroo; Chiba, Kouta; Mashiko, Hitomi; Kato, Hiromasa; Otsubo, Toshimichi; Matsumoto, Yoshiaki; Tsuruta, Seiitsu; Asari, Kazuyoshi; Hanada, Hideo; Yasuda, Susumu; Utsunomiya, Shin; Takino, Hideo

    2016-06-01

    A single aperture and hollow retroreflector [corner-cube mirror (CCM)] that in principle has no internal optical path difference is a key instrument for achieving lunar laser ranging one order or more accurate than the current level (~2 cm). We are developing CCM whose aperture is 20 cm with optimized dihedral angles. The 20-cm CCM yields two times peak height for returned laser pulse compared with Apollo 15's retroreflector. Two investigations were conducted to confirm the feasibility of the 20-cm aperture CCM. The first is thermo-optical simulation and evaluation of the 20-cm CCM in the lunar thermal environment. Through this simulation, it has turned out for the first time that 20-cm aperture CCM made of single-crystal Si or "ultra-low expansion glass-ceramics" such as CCZ-EX® (OHARA Inc.) can be used for CCM with no thermal control, if the perfectly fixed point of CCM is limited to one. The second is annealing and shear loading experiments of single-crystal silicon (Si) samples. Through these experiments, high-temperature annealing from 100 to 1000 °C is confirmed to be effective for the enhancement of the adhesive strength between optically contacted surfaces with no optical damage in roughness and accuracy, indicating that this annealing process would enhance the rigidity of CCM fabricated by the optically contacted plates.

  6. Campaign-Style Titanite LASS: Implications for Crustal Flow, Phase Transformations and Titanite Closure

    NASA Astrophysics Data System (ADS)

    Hacker, Bradley R.; Garber, Joshua M.; Kylander-Clark, Andrew RC; Andersen, Torgeir B.

    2016-04-01

    LASS (laser-ablation split-stream ICP MS) U-Pb and trace-element data were measured in titanite from >250 samples of quartzofeldspathic gneiss and leucosomes across the ultrahigh-pressure (UHP) Western Gneiss Region of Norway to understand deformation and metamorphism of continental crust during subduction and exhumation. Titanite is unstable at pressures > 1.5 GPa, and, indeed, most yielded post-UHP dates, concommitant with titanite breakdown during subduction. A number of titanites sampled across large areas, however, have pre-UHP U-Pb dates, indicating that the titanites survived their excursion to and return from mantle depths metastably. Pre-UHP titanites have trace-element concentrations reflective of their host-rock composition and indicative of magmatic growth from an LREE-enriched melt. In contrast, re- and neocrystallized titanites that grew during exhumation have heterogeneous trace-element signatures and elevated fluorine concentrations, indicating that preservation of pre-UHP titanite was governed by reduced H2O activity. These U-Pb and trace-element data from titanite over a broad area have three important implications. Titanite grains can remain closed to complete Pb loss during regional metamorphism at temperatures as high as 750°C and pressures as high as 3 GPa, implying that thermally mediated volume diffusion was not the principal factor controlling resetting of the U-Pb system. Phase transformations in--and deformation of--quartzofeldspathic rocks can be inhibited at the same conditions; much of the WGR remained untransformed, drier, and stronger even as the rocks were subducted to and exhumed from mantle depths.

  7. 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.

  8. 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.

  9. Manufacture of Large-Aperture Diffractive Optics and Ultrathin Optics for High-Power Laser and Space Applications

    SciTech Connect

    Britten, J A

    2002-01-18

    We have developed equipment and technology for fabricating submicron pitch, high-efficiency diffraction gratings over meter-scale apertures that are used for pulse compression in ultrafast systems around the world. We have also developed wet-etch figuring (WEF) to generate arbitrary continuous contours on ultrathin glass substrates in a closed loop process. The current and future states of these technologies will be discussed.

  10. Development of design technique for vacuum insulation in large size multi-aperture multi-grid accelerator for nuclear fusion.

    PubMed

    Kojima, A; Hanada, M; Tobari, H; Nishikiori, R; Hiratsuka, J; Kashiwagi, M; Umeda, N; Yoshida, M; Ichikawa, M; Watanabe, K; Yamano, Y; Grisham, L R

    2016-02-01

    Design techniques for the vacuum insulation have been developed in order to realize a reliable voltage holding capability of multi-aperture multi-grid (MAMuG) accelerators for fusion application. In this method, the nested multi-stage configuration of the MAMuG accelerator can be uniquely designed to satisfy the target voltage within given boundary conditions. The evaluation of the voltage holding capabilities of each acceleration stages was based on the previous experimental results about the area effect and the multi-aperture effect. Since the multi-grid effect was found to be the extension of the area effect by the total facing area this time, the total voltage holding capability of the multi-stage can be estimated from that per single stage by assuming the stage with the highest electric field, the total facing area, and the total apertures. By applying these consideration, the analysis on the 3-stage MAMuG accelerator for JT-60SA agreed well with the past gap-scan experiments with an accuracy of less than 10% variation, which demonstrated the high reliability to design MAMuG accelerators and also multi-stage high voltage bushings. PMID:26932032

  11. Development of design technique for vacuum insulation in large size multi-aperture multi-grid accelerator for nuclear fusion

    NASA Astrophysics Data System (ADS)

    Kojima, A.; Hanada, M.; Tobari, H.; Nishikiori, R.; Hiratsuka, J.; Kashiwagi, M.; Umeda, N.; Yoshida, M.; Ichikawa, M.; Watanabe, K.; Yamano, Y.; Grisham, L. R.

    2016-02-01

    Design techniques for the vacuum insulation have been developed in order to realize a reliable voltage holding capability of multi-aperture multi-grid (MAMuG) accelerators for fusion application. In this method, the nested multi-stage configuration of the MAMuG accelerator can be uniquely designed to satisfy the target voltage within given boundary conditions. The evaluation of the voltage holding capabilities of each acceleration stages was based on the previous experimental results about the area effect and the multi-aperture effect. Since the multi-grid effect was found to be the extension of the area effect by the total facing area this time, the total voltage holding capability of the multi-stage can be estimated from that per single stage by assuming the stage with the highest electric field, the total facing area, and the total apertures. By applying these consideration, the analysis on the 3-stage MAMuG accelerator for JT-60SA agreed well with the past gap-scan experiments with an accuracy of less than 10% variation, which demonstrated the high reliability to design MAMuG accelerators and also multi-stage high voltage bushings.

  12. The asialoglycoprotein receptor suppresses the metastasis of hepatocellular carcinoma via LASS2-mediated inhibition of V-ATPase activity.

    PubMed

    Gu, Dishui; Jin, Haojie; Jin, Guangzhi; Wang, Cun; Wang, Ning; Hu, Fangyuan; Luo, Qin; Chu, Wei; Yao, Ming; Qin, Wenxin

    2016-08-28

    The asialoglycoprotein receptor (ASGR), which is expressed mainly in hepatocytes, is downregulated in poorly differentiated hepatocellular carcinoma (HCC). Here we investigated the role of ASGR1 in HCC metastasis as well as the possible underlying molecular mechanisms. We found that ASGR1 was downregulated in HCC tissue compared with adjacent non-tumorous liver tissue and that lower ASGR1 expression was associated with higher TNM stage and poorer prognosis in HCC patients. ASGR1 overexpression inhibited hepatoma cell migration and invasion in vitro and in vivo, while ASGR1 knockdown had the opposite effects. Furthermore, ASGR1 interacted directly with human longevity assurance homolog 2 of yeast LAG1 (LASS2). Knockdown of LASS2 attenuated the inhibitory effects of ASGR1 on hepatoma cell migration and invasion in vitro. ASGR1 decreased V-ATPase activity in hepatoma cells, and this was reversed by LASS2 knockdown. Finally, HCC patients with low LASS2 levels had poor prognosis, while those with high ASGR1 and LASS2 levels had better prognosis. Thus, ASGR1 may act as a potential metastasis suppressor in HCC, and the combination of ASGR1 and LASS2 may help predict the prognosis of HCC patients. PMID:27241665

  13. A study program on large aperture electronic scanning phased array antennas for the shuttle imaging microwave system

    NASA Technical Reports Server (NTRS)

    1974-01-01

    Fundamental phased array theory and performance parameters are discussed in terms of their application to microwave radiometry, and four scanning phased arrays representing current examples of state-of-the-art phased array technology are evaluated for potential use as components of the multispectral antenna system for the space shuttle imaging microwave system (SIMS). A discussion of problem areas, both in performance and fabrication is included, with extrapolations of performance characteristics for phased array antennas of increased sizes up to 20 m by 20 m. The possibility of interlacing two or more phased arrays to achieve a multifrequency aperture is considered, and, finally, a specific antenna system is recommended for use with SIMS.

  14. Instrument Design of the Large Aperture Solar UV Visible and IR Observing Telescope (SUVIT) for the SOLAR-C Mission

    NASA Astrophysics Data System (ADS)

    Suematsu, Y.; Katsukawa, Y.; Shimizu, T.; Ichimoto, K.; Takeyama, N.

    2012-12-01

    We present an instrumental design of one major solar observation payload planned for the SOLAR-C mission: the Solar Ultra-violet Visible and near IR observing Telescope (SUVIT). The SUVIT is designed to provide high-angular-resolution investigation of the lower solar atmosphere, from the photosphere to the uppermost chromosphere, with enhanced spectroscopic and spectro-polarimetric capability in wide wavelength regions from 280 nm (Mg II h&k lines) to 1100 nm (He I 1083 nm line) with 1.5 m class aperture and filtergraphic and spectrographic instruments.

  15. Design and performance of the new cathode readout proportional chambers in LASS

    SciTech Connect

    Aiken, G.; Aston, D.; Dunwoodie, W.

    1980-10-01

    The design and construction of a new proportional chamber system for the LASS spectrometer are discussed. This system consists of planar and cylindrical chambers employing anode wire and cathode strip readout techniques. The good timing characteristics of anode readout combine with the excellent spatial resolution of cathode readout to provide powerful and compact detectors. Preliminary resolution data are presented along with operating characteristics of the various devices.

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

    NASA Astrophysics Data System (ADS)

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

    2001-12-01

    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, HI. This ladar adopts the technology successfully demonstrated by the first generation HI-CLASS (High Performance CO2) Ladar Surveillance Sensor) operating on the nearby 0.6 meter aperture Laser Beam Director (LBD) and developed under the Field Ladar Demonstration program, jointly sponsored by AFRL/DE and the Army's Space and Missile Defense Command. The moderate power (approximately 180 watts) HI-CLASS/AEOS system generates multiple, coherent waveforms for precision satellite tracking and characterization of space objects for 1 m2 targets at ranges out to 10,000 km. This system also will be used to track space objects smaller than30 cm at ranges to 2,000 km. A third application of this system is to provide data for developing satellite identification, characterization, health and status techniques. This paper will discuss the operating characteristics and innovative features of the new system. The paper will also review recent results in support of AF needs, demonstrations, experiments, as well as planned activities that directly support applications in the DoD, scientific, and commercial arenas.

  17. Performance of a prototype for a large-aperture multipass Nd:glass laser for inertial confinement fusion

    SciTech Connect

    Van Wonterghem, B.M.; Murray, J.R.; Campbell, J.H.; Speck, D.R.; Barker, C.E.; Smith, I.C.; Browning, D.F.; Behrendt, W.C.

    1997-07-01

    The Beamlet is a single-beam prototype of future multibeam megajoule-class Nd:glass laser drivers for inertial confinement fusion. It uses a multipass main amplifier, adaptive optics, and efficient, high-fluence frequency conversion to the third harmonic. The Beamlet amplifier contains Brewster-angle glass slabs with a clear aperture of 39 cm{times}39 cm and a full-aperture plasma-electrode Pockels cell switch. It has been successfully tested over a range of pulse lengths from 1{endash}10 ns up to energies at 1.053 {mu}m of 5.8 kJ at 1 ns and 17.3 kJ at 10 ns. A 39-actuator deformable mirror corrects the beam quality to a Strehl ratio of as much as 0.4. The 1.053-{mu}m output has been converted to the third harmonic at efficiencies as high as 80{percent} and fluences as high as 8.7 J/cm{sup 2} for 3-ns pulses. {copyright} 1997 Optical Society of America

  18. Comparison of CNES spherical and NASA hemispherical large aperture integrating sources. I - Using a laboratory transfer spectroradiometer. II - Using the SPOT-2 satellite instruments

    NASA Technical Reports Server (NTRS)

    Guenther, B.; Mclean, J.; Leroy, M.; Henry, P.

    1990-01-01

    CNES spherical and NASA hemispherical large aperture calibration sources are examined using a laboratory transfer spectroradiometer and SPOT-2 instruments. The sources, collected at Matra in France during October 1987, are compared in terms of absolute calibration, linearity, and uniformity. The laboratory transfer spectroradiometer data reveal that the calibration results correspond to within about 7 percent absolute accuracy level and the linearity of the CNES source with lamp level is good. It is observed using the satellite data that both sources have an excellent uniformity over a 4 deg field of view.

  19. 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.

  20. Large-scale and non-contact surface topography measurement using scanning ion conductance microscopy and sub-aperture stitching technique

    NASA Astrophysics Data System (ADS)

    Zhuang, Jian; Guo, Renfei; Li, Fei; Yu, Dehong

    2016-08-01

    In this paper, we propose a large-scale and non-contact surface topography measurement method using a non-contact scanning probe microscopy (SPM) technique, scanning ion conductance microscopy (SICM), combined with the sub-aperture stitching technique. The phase correlation techniques were first applied to the three-dimensional (3D) images measured by the SICM to acquire an initially coarse stitching position. Then the tip–tilt compensated sub-aperture stitching algorithm is utilized to eliminate tilts and translations among adjacent images and expand the lateral measuring range of the existing hopping mode SICM system. This SICM and the stitching based method has been used to measure some large-scale samples (micrometer to millimeter scale) in a non-contact, quantitative and high resolution way. Simulation and experimental results on these samples verify the feasibility of this method and the effectiveness of the stitching algorithm. A measuring range of 1.08 mm  ×  0.55 mm and a lateral resolution of 100 nm or even higher were obtained in these experiments. Compared with atomic force microscopy (AFM), the non-contact feature of the proposed method ensures less damage to the surface topography. The non-optical feature makes the data stitching simpler than the existing optical microscopic methods, which need consider how to compensate the vignetting effect caused by the inhomogeneity of light.

  1. Repression of the miR-93-enhanced sensitivity of bladder carcinoma to chemotherapy involves the regulation of LASS2

    PubMed Central

    Liu, Jingyu; Wang, Haifeng; Wang, Yan; Li, Zhenkun; Pan, Yi; Liu, Qiying; Yang, Mingying; Wang, Jiansong

    2016-01-01

    The aberrant expression of miRNA has an important function in bladder cancer (BC). Previous studies indicate that LASS2 is involved in the development of sensitivity to chemotherapy in cancer cells. In the present study, the miRNAs related to LASS2 were selected by using miRNA profiling to distinguish chemo-resistant and chemo-sensitive tumor specimens from patients. Higher levels of miR-93 were observed in the cisplatin-resistant BC cell line RT4, compared to the cell line T24. The role of miR-93 in chemo-sensitivity was demonstrated both in cell culture and mouse tumor xenograft models. We found that inhibiting miR-93 promoted cisplatin-induced apoptosis due to the accumulation of DNA damage. A reporter gene assay was performed, and the results showed miR-93 was not a target of the 3′ untranslated region of LASS2, but had an altered protein expression level. Inhibitors of miR-93 could also enhance the chemo-sensitivity of tumor cells transfected with si-LASS2, but the effect was very slight. These findings suggest that miR-93 plays an important role in the chemo-sensitivity of BC, and may be involved in regulating the LASS2 gene. PMID:27099514

  2. Achieving high focusing power for a large-aperture liquid crystal lens with novel hole-and-ring electrodes.

    PubMed

    Chiu, Chi-Wei; Lin, Yu-Cheng; Chao, Paul C-P; Fuh, Andy Y-G

    2008-11-10

    Aiming to equip commercial camera modules, such as the optical imaging systems with a CMOS sensor module in 3 Mega pixels, an ultra thin liquid crystal lens with designed hole-and-ring electrodes is proposed in this study to achieve high focusing power. The LC lens with proposed electrodes improves the central intensity of electric field which leads to better focusing quality. The overall thickness of the LC lens can be as thin as 1.2 mm and the shortest focal length of the 4 mm-aperture lens occurs at 20 cm under an applied voltage of 30 V at 1 KHz. The inner ring electrode requires only 40% of applied voltage of the external hole electrode. The applied voltages for this internal ring and external hole electrodes can simply be realized by a pre-designed parallel resistance pair and a single voltage source. Experiments are conducted for validation and it shows that the designed LC lens owns good image clearness and contrast at the focal plane. The proposed design reduces the thickness of LC lens and is capable of achieving relative higher focusing power than past studies with lower applied voltage. PMID:19582020

  3. Optical sparse aperture imaging.

    PubMed

    Miller, Nicholas J; Dierking, Matthew P; Duncan, Bradley D

    2007-08-10

    The resolution of a conventional diffraction-limited imaging system is proportional to its pupil diameter. A primary goal of sparse aperture imaging is to enhance resolution while minimizing the total light collection area; the latter being desirable, in part, because of the cost of large, monolithic apertures. Performance metrics are defined and used to evaluate several sparse aperture arrays constructed from multiple, identical, circular subapertures. Subaperture piston and/or tilt effects on image quality are also considered. We selected arrays with compact nonredundant autocorrelations first described by Golay. We vary both the number of subapertures and their relative spacings to arrive at an optimized array. We report the results of an experiment in which we synthesized an image from multiple subaperture pupil fields by masking a large lens with a Golay array. For this experiment we imaged a slant edge feature of an ISO12233 resolution target in order to measure the modulation transfer function. We note the contrast reduction inherent in images formed through sparse aperture arrays and demonstrate the use of a Wiener-Helstrom filter to restore contrast in our experimental images. Finally, we describe a method to synthesize images from multiple subaperture focal plane intensity images using a phase retrieval algorithm to obtain estimates of subaperture pupil fields. Experimental results from synthesizing an image of a point object from multiple subaperture images are presented, and weaknesses of the phase retrieval method for this application are discussed. PMID:17694146

  4. Location of Body Wave Microseism Sources Using Three-Component Data From a Large Aperture Seismic Array in China

    NASA Astrophysics Data System (ADS)

    Liu, Q.; Koper, K. D.; Burlacu, R.; Ni, S.; Wang, F.

    2015-12-01

    From September 2013 through October 2014 up to 100 Guralp CMG-3 broadband seismometers were deployed in the WT-Array (WTA) in northwest China. The aperture of WTA is about 700 km, with an average station spacing of approximately 50 km. Here, we process continuous, three-component WTA data to detect and locate body wave microseism sources in four distinct period bands: 1.0-2.5 s, 2.5-5 s, 5-10 s, and 10-20 s. We back-project vertical component data through a 1D reference Earth model (AK135) to a global grid of hypothetical source locations, assuming P-wave (30o-90o), PP-wave (60o-180o), and S-wave (30o-75o) propagation. At the same time, we rotate the horizontals and back-project the radial and transverse components of the wavefield. For each frequency band, grid point, and assumed origin time, the array power is calculated from the amplitude of a windowed, filtered, and tapered time domain beam constructed with fourth-root stacking. We find strong P-wave and S-wave noise sources in the North Pacific and North Atlantic Oceans. Shorter period sources (2.5-5 s) are mainly observed in the North Pacific Ocean, while both short and long period (2.5-20 s) sources are observed in the North Atlantic Ocean. Median power plots for each month during September 2013 through October 2014 show distinct seasonal variations. The energy peaks in the North Atlantic are visible from November to March and strong energy is also observed in the North Pacific from October to April. We also observe PP-waves in the Southern Ocean, especially for May-August 2014. Using classical f-k analysis and plane-wave propagation, we are able to confirm the back-projection results. To improve our understanding of body wave microseism generation, we compare the observed P, S, and PP wave microseism locations with the predictions of significant wave height and wave-wave interactions derived from the WAVEWATCH III ocean model.From September 2013 through October 2014 up to 100 Guralp CMG-3 broadband

  5. Experimental and numerical investigation of ADP square crystal with large aperture in the new Final Optics Assembly under the non-critical phase matching

    NASA Astrophysics Data System (ADS)

    Sun, Fuzhong; Zhang, Peng; Bai, Qingshun; Lu, Lihua; Xiang, Yong

    2016-04-01

    This paper presented a new Final Optics Assembly (FOA) of ammonium dihydrogen phosphate (ADP) square crystal with large aperture under the non-critical phase matching (NCPM), which controlled by the constant temperature water, and the temperature distribution was analyzed by simulation and experiment. Firstly, thermal analysis was carried out, as well as the temperature distribution of the cavity only heated under different velocities was analyzed. Then, the temperature distributions of ADP square crystal in the cavity were achieved using the Finite Volume Method (FVM), and this prediction was validated by the experiment results when the velocity is 0.1 m/s and 0.5 m/s. Finally, the optimal FHG conversion efficiency was obtained and the comparison of different heating methods was also highlighted.

  6. The effect of air flow on the temperature distribution and the harmonic conversion efficiency of the ADP crystal with large aperture in the temperature control scheme

    NASA Astrophysics Data System (ADS)

    Sun, Fuzhong; Zhang, Peng; Lu, Lihua; Xiang, Yong; Bai, Qingshun

    2016-03-01

    This paper presented a temperature control scheme for ammonium dihydrogen phosphate (ADP) crystal of Ф80 mm in diameter, and the influence of the air flow was also studied. This research aims to obtain the high energy, high frequency laser with large aperture under the non-critical phase matching (NCPM). Firstly, thermal analysis was carried out to investigate the air flow property in the cavity, as well as the effect of ambient temperature was analyzed. Secondly, the temperature distributions of air flow were achieved using the Finite Volume Method (FVM), and this prediction was validated by the experiment results. Finally, the effect of air flow in the cavity was obtained from the heating method, and the variation of harmonic conversion efficiency caused by the ambient temperature was also highlighted.

  7. Planarization of amorphous silicon thin film transistors for high-aperture-ratio and large-area active-matrix liquid crystal displays

    NASA Astrophysics Data System (ADS)

    Lan, Je-Hsiung

    The reduction of the backlight power consumption and the improvement of the display image uniformity for future large-area and high-resolution active-matrix liquid- crystal displays (AM-LCDs) are very important. One possible method to achieve the former goal is to increase the pixel electrode aperture-ratio. This can be realized by overlapping the pixel electrode with both gate/data buslines. While for the latter, reduction of the RC-delay by using a low resistance gate metal line is the key. Both of these approaches can be realized by using planarization technology. In this dissertation, the planarization technology based on low dielectric constant organic polymer, benzocyclobutene (BCB), is demonstrated, and this technology has been successfully applied to hydrogenated amorphous-silicon (a-Si:H) thin-film transistor (TFT) arrays and thick metal gate buslines/electrodes. Through the planarization technology, a high-aperture-ratio (HAR) pixel electrode structure has been fabricated. The parasitic capacitance and crosstalk issues in the HAR pixel electrode have been studied through interconnect analysis and circuit simulation. The impact of the parasitic capacitance on display performances, such as feedthrough voltage, vertical crosstalk, pixel electrode aperture-ratio, pixel charging behavior, and gate busline RC-delay issues, has been thoroughly discussed. Some key issues during the process integration of the HAR pixel electrode structure have been addressed. These include the BCB contact via formation, the patterning of the ITO pixel electrodes on BCB layer, the selection of Ar plasma treatment conditions for BCB surface, and the optical transmittance evaluation of the ITO/BCB double-layer structure. In addition, the BCB passivation effects on back-channel etched type a-Si:H TFTs have been investigated. It is found that there is no degradation in the TFT electrical performance and reliability after the BCB passivation. Finally, the planarization technology is

  8. A 2x2 multi-chip reconfigurable MOEMS mask: a stepping stone to large format microshutter arrays for coded aperture applications

    NASA Astrophysics Data System (ADS)

    McNie, Mark E.; Brown, Alan G.; King, David O.; Smith, Gilbert W.; Gordon, Neil T.; Riches, Stephen; Rogers, Stanley

    2010-08-01

    Coded aperture imaging has been used for astronomical applications for several years. Typical implementations used a fixed mask pattern and are designed to operate in the X-Ray or gamma ray bands. Recently applications have emerged in the visible and infra red bands for low cost lens-less imaging systems and system studies have shown that considerable advantages in image resolution may accrue from the use of multiple different images of the same scene - requiring a reconfigurable mask. Previously reported work focused on realising a 2x2cm single chip mask in the mid-IR based on polysilicon micro-optoelectro- mechanical systems (MOEMS) technology and its integration with ASIC drive electronics using conventional wire bonding. It employs interference effects to modulate incident light - achieved by tuning a large array of asymmetric Fabry-Perot optical cavities via an applied voltage and uses a hysteretic row/column scheme for addressing. In this paper we report on the latest results in the mid-IR for the single chip reconfigurable MOEMS mask, trials in scaling up to a mask based on a 2x2 multi-chip array and report on progress towards realising a large format mask comprising 44 MOEMS chips. We also explore the potential of such large, transmissive IR spatial light modulator arrays for other applications and in the current and alternative architectures.

  9. Synthetic Aperture Radiometer Systems

    NASA Technical Reports Server (NTRS)

    LeVine, David M.

    1999-01-01

    Aperture synthesis is a new technology for passive microwave remote sensing from space which has the potential to overcome the limitations set in the past by antenna size. This is an interferometric technique in which pairs of small antennas and signal processing are used to obtain the resolution of a single large antenna. The technique has been demonstrated successfully at L-band with the aircraft prototype instrument, ESTAR. Proposals have been submitted to demonstrate this technology in space (HYDROSTAR and MIRAS).

  10. miR-9 promotes cell proliferation and inhibits apoptosis by targeting LASS2 in bladder cancer.

    PubMed

    Wang, Haifeng; Zhang, Wei; Zuo, Yigang; Ding, Mingxia; Ke, Changxing; Yan, Ruping; Zhan, Hui; Liu, Jingyu; Wang, Jiansong

    2015-12-01

    MicroRNA-9 upregulation was reported in several tumors. However, its function and mechanism in human bladder cancer remains obscure. The present study aims to identify the expression pattern, biological roles and potential mechanism of miR-9 in human bladder cancers. We found that expression level of miR-9 in bladder cancer tissues was higher than normal tissues. miR-9 mimic transfection was performed in T24 and 5637 cells with low miR-9 expression, and miR-9 inhibitor was employed in BIU-87 cell line with high endogenous expression. miR-9 increased cell proliferation, cell cycle progression, invasion and chemoresistance, with upregulation of cyclin D1, MMP9, Bcl-2, and survivin and downregulation of E-cadherin. Using luciferase reporter assay, we confirmed that LASS2 was a direct target of miR-9 in bladder cancer cells. Transfection of miR-9 mimic downregulated LASS2 expression. LASS2 transfection downregulated Bcl-2 and survivin expression, which were induced by miR-9 mimic in both cell lines. In conclusion, these results indicate that miR-9 upregulation might be associated with malignant phenotype of bladder cancer. miR-9 promotes chemoresistance of bladder cancer cells by target LASS2. PMID:26150338

  11. Precision large field scanning system for high numerical aperture lenses and application to femtosecond micromachining of ophthalmic materials

    NASA Astrophysics Data System (ADS)

    Brooks, D. R.; Brown, N. S.; Savage, D. E.; Wang, C.; Knox, W. H.; Ellis, J. D.

    2014-06-01

    A precision, large stroke (nearly 1 cm) scanning system was designed, built, and calibrated for micromachining of ophthalmic materials including hydrogels and cornea (excised and in vivo). This system comprises a flexure stage with an attached objective on stacked vertical and horizontal translation stages. This paper outlines the design process leading to our most current version including the specifications that were used in the design and the drawbacks of other methods that were previously used. Initial measurements of the current version are also given. The current flexure was measured to have a 27 Hz natural frequency with no load.

  12. Large aperture Fizeau interferometer commissioning and preliminary measurements of a long x-ray mirror at European X-ray Free Electron Laser

    NASA Astrophysics Data System (ADS)

    Vannoni, M.; Freijo Martín, I.

    2016-05-01

    The European XFEL (X-ray Free Electron Laser) is a large facility under construction in Hamburg, Germany. It will provide a transversally fully coherent x-ray radiation with outstanding characteristics: high repetition rate (up to 2700 pulses with a 0.6 ms long pulse train at 10 Hz), short wavelength (down to 0.05 nm), short pulse (in the femtoseconds scale), and high average brilliance (1.6 ṡ 1025 (photons s-1 mm-2 mrad-2)/0.1% bandwidth). The beam has very high pulse energy; therefore, it has to be spread out on a relatively long mirror (about 1 m). Due to the very short wavelength, the mirrors need to have a high quality surface on their entire length, and this is considered very challenging even with the most advanced polishing methods. In order to measure the mirrors and to characterize their interaction with the mechanical mount, we equipped a metrology laboratory with a large aperture Fizeau interferometer. The system is a classical 100 mm diameter commercial Fizeau, with an additional expander providing a 300 mm diameter beam. Despite the commercial nature of the system, special care has been taken in the polishing of the reference flats and in the expander quality. We report the first commissioning of the instrument, its calibration, and performance characterization, together with some preliminary results with the measurement of a 950 mm silicon substrate. The intended application is to characterize the final XFEL mirrors with nanometer accuracy.

  13. Refurbishment and Testing of the 1970's Era LASS Solenoid Coils for JLab's Hall D

    SciTech Connect

    Anumagalla, Ravi; Biallas, George; Brindza, Paul; Carstens, Thomas; Creel, Jonathan; Egiyan, Hovanes; Martin, Floyd; Qiang, Yi; Spiegel, Scot; Stevens, Mark; Wissmann, Mark; Wolin, Elliott

    2012-07-01

    JLab refurbished the LASS1, 1.85 m bore Solenoid, consisting of four superconducting coils to act as the principal analysis magnet for nuclear physics in the newly constructed, Hall D at Jefferson Lab. The coils, built in 1971 at Stanford Linier Accelerator Center and used a second time at the MEGA Experiment at Los Alamos, had electrical shorts and leaks to the insulating vacuum along with deteriorated superinsulation & instrumentation. Root cause diagnosis of the problems and the repair methods are described along with the measures used to qualify the vessels and piping within the Laboratory's Pressure Safety Program (mandated by 10CFR851). The extraordinary refrigerator operational methods used to utilize the obsolete cryogenic apparatus gathered for the off-line, single coil tests are described.

  14. Commissioning and Testing the 1970's Era LASS Solenoid Magnet in JLab's Hall D

    SciTech Connect

    Ballard, Joshua T.; Biallas, George H.; Brown, G.; Butler, David E.; Carstens, Thomas J.; Chudakov, Eugene A.; Creel, Jonathan D.; Egiyan, Hovanes; Martin, F.; Qiang, Yi; Smith, Elton S.; Stevens, Mark A.; Spiegel, Scot L.; Whitlatch, Timothy E.; Wolin, Elliott J.; Ghoshal, Probir K.

    2015-06-01

    JLab refurbished and reconfigured the LASS1, 1.85m bore Solenoid and installed it as the principal analysis magnet for nuclear physics in the newly constructed, Hall D at Jefferson Lab. The magnet contains four superconducting coils within an iron yoke. The magnet was built in the early1970's at Stanford Linear Accelerator Center and used a second time at Los Alamos National Laboratory. The coils were extensively refurbished and individually tested by JLab. A new Cryogenic Distribution Box provides cryogens and their control valving, current distribution bus, and instrumentation pass-through. A repurposed CTI 2800 refrigerator system and new transfer line complete the system. We describe the re-configuration, the process and problems of re-commissioning the magnet and the results of testing the completed magnet.

  15. Long-Term Evaluation of the Scintec Boundary-Layer Scintillometer and the Wageningen Large-Aperture Scintillometer: Implications for Scintillometer Users

    NASA Astrophysics Data System (ADS)

    Van Kesteren, B.; Beyrich, F.; Hartogensis, O. K.; Braam, M.

    2015-08-01

    We compare the structure parameter of the refractive index, , measured simultaneously with two large-aperture scintillometers: the WagLAS (Wageningen University, Wageningen, the Netherlands) and the BLS900 (Scintec, Rottenburg, Germany). A 3.5-year dataset shows a bias in of about 17 % between the instruments. Analysis of these data reveals firstly that the logarithmic amplifiers in the WagLAS exhibit a strong dependence on temperature, resulting in an overestimation of of up to 35 % for temperatures 0 . Secondly, high-pass filtering of the WagLAS and BLS900 intensity data artificially reduces for crosswinds 2 (error 25 and 5 % respectively). Thirdly, the BLS900 increasingly underestimates (up to 10-15 %) with increasing signal saturation. We demonstrate that Scintec's data processing relies too heavily on the assumption that the intensity data obey a log-normal distribution, which they do not in the case of saturation. Fourthly, both instruments ignore the dissipation range of the refractive-index spectrum, which leads to an overestimation of of up to 30 % for friction velocity 0.2 . Implications of these findings are discussed and placed into perspective for other scintillometer users. Furthermore, we present a tool for revealing saturation and other violations of Rytov theory for any given scintillometer type, including microwave scintillometers.

  16. Evolving Design Criteria for Very Large Aperture Space Based Telescopes and Their Influence on the Need for Integrated Tools in the Optimization Process

    NASA Technical Reports Server (NTRS)

    Arnold, William R., Sr.

    2015-01-01

    the aperture grows, the primary takes up the majority of the mass and volume and the established rules need to be adjusted. For example, a small change in lowest frequency requirement can change the cost by millions of dollars. The paper uses numerous trade studies created during the software development phase of the Arnold Mirror Modeler to illustrate the influences of system specifications on the design space. The future telescopes will require better performance, stability and documented feasibility to meet the hurdles of today's budget and schedules realities. AMTD is developing the tools, but the basic system planning mentality also has to adopt to the requirements of these very large and complex physical structures.

  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, Fatmé; 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. 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.

  19. Source locations of teleseismic P, SV, and SH waves observed in microseisms recorded by a large aperture seismic array in China

    NASA Astrophysics Data System (ADS)

    Liu, Qiaoxia; Koper, Keith D.; Burlacu, Relu; Ni, Sidao; Wang, Fuyun; Zou, Changqiao; Wei, Yunhao; Gal, Martin; Reading, Anya M.

    2016-09-01

    Transversely polarized seismic waves are routinely observed in ambient seismic energy across a wide range of periods, however their origin is poorly understood because the corresponding source regions are either undefined or weakly constrained, and nearly all models of microseism generation incorporate a vertically oriented single force as the excitation mechanism. To better understand the origin of transversely polarized energy in the ambient seismic wavefield we make the first systematic attempt to locate the source regions of teleseismic SH waves observed in microseismic (2.5-20 s) noise. We focus on body waves instead of surface waves because the source regions can be constrained in both azimuth and distance using conventional array techniques. To locate microseismic sources of SH waves (as well as SV and P waves) we continuously backproject the vertical, radial, and transverse components of the ambient seismic wavefield recorded by a large-aperture array deployed in China during 2013-2014. As expected, persistent P wave sources are observed in the North Atlantic, North Pacific, and Indian Oceans, mainly at periods of 2.5-10 s, in regions with the strong ocean wave interactions needed to produce secondary microseisms. SV waves are commonly observed to originate from locations indistinguishable from the P wave sources, but with smaller signal-to-noise ratios. We also observe SH waves with about half or less the signal-to-noise ratio of SV waves. SH source regions are definitively located in deep water portions of the Pacific, away from the sloping continental shelves that are thought to be important for the generation of microseismic Love waves, but nearby regions that routinely generate teleseismic P waves. The excitation mechanism for the observed SH waves may therefore be related to the interaction of P waves with small-wavelength bathymetric features, such as seamounts and basins, through some sort of scattering process.

  20. Diagnostic for dynamic aperture

    SciTech Connect

    Morton, P.L.; Pellegrin, J.L.; Raubenheimer, T.; Rivkin, L.; Ross, M.; Ruth, R.D.; Spence, W.L.

    1985-04-01

    In large accelerators and low beta colliding beam storage rings, the strong sextupoles, which are required to correct the chromatic effects, produce strong nonlinear forces which act on particles in the beam. In addition in large hadron storage rings the superconducting magnets have significant nonlinear fields. To understand the effects of these nonlinearities on the particle motion there is currently a large theoretical effort using both analytic techniques and computer tracking. This effort is focused on the determination of the 'dynamic aperture' (the stable acceptance) of both present and future accelerators and storage rings. A great deal of progress has been made in understanding nonlinear particle motion, but very little experimental verification of the theoretical results is available. In this paper we describe 'dynamic tracking', a method being studied at the SPEAR storage ring, which can be used to obtain experimental results which are in a convenient form to be compared with the theoretical predictions.

  1. An analysis on the influence of spatial scales on sensible heat fluxes in the north Tibetan Plateau based on Eddy covariance and large aperture scintillometer data

    NASA Astrophysics Data System (ADS)

    Sun, Genhou; Hu, Zeyong; Sun, Fanglin; Wang, Jiemin; Xie, Zhipeng; Lin, Yun; Huang, Fangfang

    2016-05-01

    The influence of spatial scales on surface fluxes is an interesting but not fully investigated question. This paper presents an analysis on the influence of spatial scales on surface fluxes in the north Tibetan Plateau based on eddy covariance (EC) and large aperture scintillometer (LAS) data at site Nagqu/BJ, combined with the land surface temperature (LST) and normalized difference vegetation index (NDVI) of moderate-resolution imaging spectroradiometer (MODIS). The analysis shows that sensible heat fluxes calculated with LAS data (H_LAS) agree reasonably well with sensible heat fluxes calculated with EC data (H_EC) in the rain and dry seasons. The difference in their footprints due to the wind direction is an important reason for the differences in H_EC and H_LAS. The H_LAS are statistically more consistent with H_EC when their footprints overlap than when their footprints do not. A detailed analysis on H_EC and H_LAS changes with net radiation and wind direction in rain and dry season indicates that the spatial heterogeneity in net radiation created by clouds contributes greatly to the differences in H_EC and H_LAS in short-term variations. A significant relationship between the difference in footprint-weighted averages of LST and difference in H_EC and H_LAS suggests that the spatial heterogeneity in LST at two spatial scales is a reason for the differences in H_EC and H_LAS and that LST has a positive correlation with the differences in H_EC and H_LAS. A significant relationship between the footprint-weighted averages of NDVI and the ratio of sensible heat fluxes at two spatial scales to net radiation (H/Rn) in the rain season supports the analysis that the spatial heterogeneity in canopy at two spatial scales is another reason for differences in H_EC and H_LAS and that canopy has a negative correlation with (H/Rn). An analysis on the influence of the difference in aerodynamic roughness lengths at two spatial scales on sensible heat fluxes shows that the

  2. A comparison of detection sensitivity between ALTAIR and Arecibo meteor observations: Can high power and large aperture radars detect low velocity meteor head-echoes

    NASA Astrophysics Data System (ADS)

    Janches, Diego; Close, Sigrid; Fentzke, Jonathan T.

    2008-01-01

    Meteor head-echo observations using High Power and Large Aperture (HPLA) radars have been routinely used for micrometeor studies for over a decade. The head-echo is a signal from the radar-reflective plasma region traveling with the meteoroid and its detection allows for very precise determination of instantaneous meteor altitude, velocity and deceleration. Unlike specular meteor radars (SMR), HPLA radars are diverse instruments when compared one to another. The operating frequencies range from 46 MHz to 1.29 GHz while the antenna configurations changes from 18,000 dipoles in a 300 m×300 m square array, phase arrays of dipoles to single spherical or parabolic dishes of various dimensions. Hunt et al. [Hunt, S.M., Oppenheim, M., Close, S., Brown, P.G., McKeen, F., Minardi, M., 2004. Icarus 168, 34-42] and Close et al. [Close, S., Brown, P., Campbell-Brown, M., Oppenheim, M., Colestock, P., 2007. Icarus, doi: 10.1016/j.icarus.2006.09.07] recently showed, by utilizing a head-echo plasma-based model, the presence of instrumental biases in the ALTAIR VHF radar system against detecting meteors produced by very small particles (<1 μg) moving at slow (˜20 km/s) velocities due to the low head echo radar cross-section (RCS) associated with these particles. In this paper we apply the same methodology to the Arecibo 430 MHz radar and compare the results with those presented by Close et al. [Close, S., Brown, P., Campbell-Brown, M., Oppenheim, M., Colestock, P., 2007. Icarus, doi: 10.1016/j.icarus.2006.09.07]. We show that, if the methodology applied by Hunt et al. [Hunt, S.M., Oppenheim, M., Close, S., Brown, P.G., McKeen, F., Minardi, M., 2004. Icarus 168, 34-42] and Close et al. [Close, S., Brown, P., Campbell-Brown, M., Oppenheim, M., Colestock, P., 2007. Icarus, doi: 10.1016/j.icarus.2006.09.07] is accurate, for particles at least 1 μg or heavier, while the bias may exist for the ALTAIR measurements, it does not exist in the Arecibo data due to its greater sensitivity.

  3. ABCD matrix for apertured spherical waves.

    PubMed

    Wang, S; Bernabeu, E; Alda, J

    1991-05-01

    An ABCD matrix for describing the hard aperture under a large Fresnel number is defined in this Technical Note based on Li and Wolf's formula. It is useful for analyzing focal shifts of complicated optical systems with hard apertures. PMID:20700324

  4. New Aperture Partitioning Element

    NASA Astrophysics Data System (ADS)

    Griffin, S.; Calef, B.; Williams, S.

    Postprocessing in an optical system can be aided by adding an optical element to partition the pupil into a number of segments. When imaging through the atmosphere, the recorded data are blurred by temperature-induced variations in the index of refraction along the line of sight. Using speckle imaging techniques developed in the astronomy community, this blurring can be corrected to some degree. The effectiveness of these techniques is diminished by redundant baselines in the pupil. Partitioning the pupil reduces the degree of baseline redundancy, and therefore improves the quality of images that can be obtained from the system. It is possible to implement the described approach on an optical system with a segmented primary mirror, but not very practical. This is because most optical systems do not have segmented primary mirrors, and those that do have relatively low bandwidth positioning of segments due to their large mass and inertia. It is much more practical to position an active aperture partitioning element at an aft optics pupil of the optical system. This paper describes the design, implementation and testing of a new aperture partitioning element that is completely reflective and reconfigurable. The device uses four independent, annular segments that can be positioned with a high degree of accuracy without impacting optical wavefront of each segment. This mirror has been produced and is currently deployed and working on the 3.6 m telescope.

  5. 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 µm 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 µm 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

  6. Thermal emission by a subwavelength aperture

    NASA Astrophysics Data System (ADS)

    Joulain, Karl; Ezzahri, Younès; Carminati, Rémi

    2016-04-01

    We calculate, by means of fluctuational electrodynamics, the thermal emission of an aperture separating from the outside, vacuum or a material at temperature T. We show that thermal emission is very different whether the aperture size is large or small compared to the thermal wavelength. Subwavelength apertures separating vacuum from the outside have their thermal emission strongly decreased compared to classical blackbodies which have an aperture much larger than the wavelength. A simple expression of their emissivity can be calculated and their total emissive power scales as T8 instead of T4 for large apertures. Thermal emission of disk of materials with a size comparable to the wavelength is also discussed. It is shown in particular that emissivity of such a disk is increased when the material can support surface waves such as phonon polaritons.

  7. Spectroscopie Raman et Rayleigh stimulée des mélasses optiques unidimensionnelles (partie II)

    NASA Astrophysics Data System (ADS)

    Courtois, Jean-Yves

    Dans la première partie de cet article, nous nous sommes attachés à décrire dans le détail les caractéristiques générales des processus de diffusion Raman et Rayleigh stimulée se produisant dans les milieux atomiques et moléculaires traditionnels, de manière à bien faire ressortir les spécificités des propriétés optiques non linéaires des mélasses optiques, dont l'étude fait l'objet de cette seconde partie. L'origine de ces spécificités réside dans une particularité des atomes refroidis par laser, à savoir l'intime corrélation entre degrés de liberté internes et externes dans leur réponse non linéaire. Cette caractéristique est en fait inhérente au processus de ralentissement : d'une part la force exercée par les faisceaux lasers sur les atomes (pression de radiation et redistribution de photons) dépend fortement de l'état atomique interne, et d'autre part cet état est modifié de façon très sélective en position ou en vitesse par les ondes lasers de refroidissement (déplacements lumineux et pompage optique). Elle sous-tend toute la richesse et l'originalité du comportement non linéaire des mélasses optiques, mais aussi toute la complexité de leur modélisation théorique, qui requiert une description globale de l'évolution des degrés de liberté internes et externes des atomes sous l'action des champs lasers. Afin de mettre en évidence le lien entre ces corrélations et les propriétés non linéaires des atomes froids, nous concentrerons notre étude d'une part sur les mélasses linbot lin qui constituent un cas de couplage entre état interne et position des atomes localisés au fond des puits du potentiel associé aux déplacements lumineux (paragr. 4), et d'autre part sur les mélasses σ^+-σ- qui correspondent quant à elles à un couplage entre état interne et vitesse atomiques (paragr. 5).

  8. Detrital zircon LASS-ICP-MS petrochronologic depth profiling for determining source-to-sink relationships in the Central Alps.

    NASA Astrophysics Data System (ADS)

    Anfinson, O. A.; Stockli, D. F.; Stockli, L.; Malusa', M. G.

    2015-12-01

    Laser Ablation-Split Stream Depth Profiling (LASS-DP) ICP-MS petrochronology of detrital zircon (DZ) from Oligocene-Miocene strata in the Molasse and Northern Apennines showcases, in the light of the well-constrained depositional history of these successions, the advantages of this novel approach compared to traditional single and split-stream detrital zircon techniques in elucidating sediment provenance and source-to-sink relationships. While DZ U-Pb data from Oligocene-Miocene strata deposited in both the Molasse and Northern Apennines document shifts in the relative abundance of Cadomian, Caledonian, Variscan and Alpine aged detrital zircon, the source regions remain ambiguous due to non-diagnostic crystallization ages, leading to minimal zircon age variability. In contrast, DZ LASS-DP-ICP-MS petrochronology allows for the simultaneous recovery of multiple U-Pb ages and corresponding geochemical data, and thus dramatically increases our ability to resolve the petrogenetic history of individual DZ grains. The technique shows the immense power of determining the growth history of single DZ grains (rim to core relationships) and identifying/resolving the presence and age of thin magmatic/metamorphic overgrowths. Rupelian turbidites in the Apenninic foredeep exhibit a DZ population with consistent <5 mm Cretaceous metamorphic overgrowths that would likely not be resolved as a coherent population in polished sections. LASS-DP ICP-MS analysis of Caledonian and Variscan detrital zircon populations from the Molasse Basin show a distinct shift in rim-core age pairs in individual zircons that point to the erosion of different source during progressive Alpine unroofing. The geochemical data confirm a crustally derived magmatic source for the majority of the detrital zircon grains within the basin. While this technique, in comparison to traditional polished mounts, might underrepresent older core ages, this slight bias is clearly offset by the better definition and

  9. Single-pulse driven, large-aperture 2×1 array plasma-electrodes optical switch for SG-II upgrading facility

    NASA Astrophysics Data System (ADS)

    Zhang, Jun; Wu, Dengsheng; Zheng, Jiangang; Zheng, Kuixing; Zhu, Qihua; Zhang, Xiongjun

    2014-12-01

    We demonstrate the design and performance of an optical switch that has been constructed for the SG-II upgrading facility. The device is a longitudinal, potassium di-hydrogen phosphate (KDP), 360 mm×360 mm aperture, and 2×1 array electro-optical switch driven by a 20 kV output switching-voltage pulse generator through two plasma electrodes produced at the rise edge of the switching-voltage pulse. The results show that the temporal responses and the spatial performance of the optical switch fulfill the operation requirements of the SG-II upgrading facility.

  10. Debuncher Momentum Aperture Measurements

    SciTech Connect

    O'Day, S.

    1991-01-01

    During the November 1990 through January 1991 {bar p} studies period, the momentum aperture of the beam in the debuncher ring was measured. The momentum aperture ({Delta}p/p) was found to be 4.7%. The momentum spread was also measured with beam bunch rotation off. A nearly constant particle population density was observed for particles with {Delta}p/p of less than 4.3%, indicating virtually unobstructed orbits in this region. The population of particles with momenta outside this aperture was found to decrease rapidly. An absolute or 'cut-off' momentum aperture of {Delta}p/p = 5.50% was measured.

  11. Variable-aperture screen

    DOEpatents

    Savage, George M.

    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.

  12. Rotating Aperture System

    DOEpatents

    Rusnak, Brian; Hall, James M.; Shen, Stewart; Wood, Richard L.

    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.

  13. Evolving design criteria for very large aperture space-based telescopes and their influence on the need for intergrated tools in the optimization process

    NASA Astrophysics Data System (ADS)

    Arnold, William R.

    2015-09-01

    NASA's Advanced Mirror Technology Development (AMTD) program has been developing the means to design and build the future generations of space based telescopes. With the nearing completion of the James Webb Space Telescope (JWST), the astrophysics community is already starting to define the requirements for follow on observatories. The restrictions of available launch vehicles and the possibilities of planned future vehicles have fueled the competition between monolithic primaries (with better optical quality) and segmented primaries (with larger apertures, but with diffraction, costs and figure control issues). Regardless of the current shroud sizes and lift capacities, these competing architectures share the need for rapid design tools. As part of the AMTD program a number of tools have been developed and tested to speed up the design process. Starting with the Arnold Mirror Modeler (which creates Finite Element Models (FEM) for structural analysis) and now also feeds these models into thermal stability analyses. They share common file formats and interchangeable results. During the development of the program, numerous trade studies were created for 4 meter and 8 meter monolithic primaries, complete with support systems. Evaluation of these results has led to a better understanding of how the specification drives the results. This paper will show some of the early trade studies for typical specification requirements such as lowest mirror bending frequency and suspension system lowest frequency. The results use representative allowable stress values for each mirror substrate material and construction method and generic material properties. These studies lead to some interesting relationships between feasible designs and the realities of actually trying to build these mirrors. Much of the traditional specifications were developed for much smaller systems, where the mass and volume of the primary where a small portion of the overall satellite. JWST shows us that as

  14. Evolving Design Criteria for Very Large Aperture Space-Based Telescopes and Their Influence on the Need for Integrated Tools in the Optimization Process

    NASA Technical Reports Server (NTRS)

    Arnold, William R., Sr.

    2015-01-01

    NASA's Advanced Mirror Technology Development (AMTD) program has been developing the means to design and build the future generations of space based telescopes. With the nearing completion of the James Webb Space Telescope (JWST), the astrophysics community is already starting to define the requirements for follow on observatories. The restrictions of available launch vehicles and the possibilities of planned future vehicles have fueled the competition between monolithic primaries (with better optical quality) and segmented primaries (with larger apertures, but with diffraction, costs and figure control issues). Regardless of the current shroud sizes and lift capacities, these competing architectures share the need for rapid design tools. As part of the AMTD program a number of tools have been developed and tested to speed up the design process. Starting with the Arnold Mirror Modeler (which creates Finite Element Models (FEM) for structural analysis) and now also feeds these models into thermal stability analyses. They share common file formats and interchangeable results. During the development of the program, numerous trade studies were created for 4 meter and 8 meter monolithic primaries, complete with support systems. Evaluation of these results has led to a better understanding of how the specification drives the results. This paper will show some of the early trade studies for typical specification requirements such as lowest mirror bending frequency and suspension system lowest frequency. The results use representative allowable stress values for each mirror substrate material and construction method and generic material properties. These studies lead to some interesting relationships between feasible designs and the realities of actually trying to build these mirrors. Much of the traditional specifications were developed for much smaller systems, where the mass and volume of the primary where a small portion of the overall satellite. JWST shows us that as

  15. Synthetic aperture methods for angular scatter imaging

    NASA Astrophysics Data System (ADS)

    Guenther, Drake A.; Ranganathan, Karthik; McAllister, Michael J.; Rigby, K. W.; Walker, William F.

    2004-04-01

    Angular scatter offers a new source of tissue contrast and an opportunity for tissue characterization in ultrasound imaging. We have previously described the application of the translating apertures algorithm (TAA) to coherently acquire angular scatter data over a range of scattering angles. While this approach works well at the focus, it suffers from poor depth of field (DOF) due to a finite aperture size. Furthermore, application of the TAA with large focused apertures entails a tradeoff between spatial resolution and scattering angle resolution. While large multielement apertures improve spatial resolution, they encompass many permutations of transmit/receive element pairs. This results in the simultaneous interrogation of multiple scattering angles, limiting angular resolution. We propose a synthetic aperture imaging scheme that achieves both high spatial resolution and high angular resolution. In backscatter acquisition mode, we transmit successively from single transducer elements, while receiving on the same element. Other scattering angles are interrogated by successively transmitting and receiving on different single elements chosen with the appropriate spatial separation between them. Thus any given image is formed using only transmit/receive element pairs at a single separation. This synthetic aperture approach minimizes averaging across scattering angles, and yields excellent angular resolution. Likewise, synthetic aperture methods allow us to build large effective apertures to maintain a high spatial resolution. Synthetic dynamic focusing and dynamic apodization are applied to further improve spatial resolution and DOF. We present simulation results and experimental results obtained using a GE Logiq 700MR system modified to obtain synthetic aperture TAA data. Images of wire targets exhibit high DOF and spatial resolution. We also present a novel approach for combining angular scatter data to effectively reduce grating lobes. With this approach we have

  16. Optica aperture synthesis

    NASA Astrophysics Data System (ADS)

    van der Avoort, Casper

    2006-05-01

    aperture mask, these optical paths are stated to be homothetic. In short, these two types will be addressed as the Michelson or the Homothetic type. The other two types are addressed as Densified and Staircase. The first one is short for densified pupil imaging, an imaging technique very similar to the Homothetic type, be it that the natural course of light after the aperture mask is altered. However, the combination of the beams of light is again in focus. The Staircase method is an alternative to the co-axial Michelson method and lends its name from the fact that a staircase-shaped mirror is placed in an intermediate focal plane after each telescope in the array, before combining the beams of light co-axially. This addition allows stellar imaging as with the Michelson type, with the advantage of covering a large field-of-view. The details of these methods will intensively be discussed in this thesis, but the introduction of them at this point allows a short list of results, found by comparing them for equal imaging tasks. Homothetic imagers are best suited for covering a wide field-of-view, considering the information content of the interferometric signals these arrays produce. The large number of detectors does not seem to limit the imaging performance in the presence of noise, due to the high ratio of coherent versus incoherent information in the detector signal. The imaging efficiency of a Michelson type array is also high, although -considering only polychromatic wide-field imaging tasks- the ratio of coherent versus incoherent information in the detected signals is very low. This results in very large observation times needed to produce images comparable to those obtained with a Homothetic array. A detailed presentation of the characteristics of the detected signals in a co-axial Michelson array reveal that such signals, obtained by polychromatic observation of extended sources, have fringe envelope functions that do not allow Fourier-spectroscopy to obtain high

  17. 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

  18. Broadband synthetic aperture geoacoustic inversion.

    PubMed

    Tan, Bien Aik; Gerstoft, Peter; Yardim, Caglar; Hodgkiss, William S

    2013-07-01

    A typical geoacoustic inversion procedure involves powerful source transmissions received on a large-aperture receiver array. A more practical approach is to use a single moving source and/or receiver in a low signal to noise ratio (SNR) setting. This paper uses single-receiver, broadband, frequency coherent matched-field inversion and exploits coherently repeated transmissions to improve estimation of the geoacoustic parameters. The long observation time creates a synthetic aperture due to relative source-receiver motion. This approach is illustrated by studying the transmission of multiple linear frequency modulated (LFM) pulses which results in a multi-tonal comb spectrum that is Doppler sensitive. To correlate well with the measured field across a receiver trajectory and to incorporate transmission from a source trajectory, waveguide Doppler and normal mode theory is applied. The method is demonstrated with low SNR, 100-900 Hz LFM pulse data from the Shallow Water 2006 experiment. PMID:23862809

  19. Measurement of the surface form error of large aperture plane optical surfaces with a polarization phase-shifting liquid reference reflection Fizeau interferometer.

    PubMed

    Chatterjee, Sanjib; Kumar, Y Pavan; Singh, Rishipal; Singh, Sarvendra

    2016-01-10

    A polarization phase-shifting liquid reference reflection Fizeau interferometer has been proposed. A polarization cyclic path optical configuration along with a concave telescope mirror is used to produce a pair of expanded, collimated p and s polarized beams with a small angular separation between them. The collimated beams are deflected along a vertical direction toward a Fizeau interferometer cavity formed between a liquid surface that acts as a reference surface and a plane test surface. Either the p or s polarized beam is allowed to strike the liquid surface normally and the orientation of the test surface is adjusted to reflect the other beam, having orthogonal linear polarization, in the direction of the normally reflected reference beam from the liquid surface. A combination of a quarter-wave plate and linear polarizer is used to apply polarization phase shift between the test and reference beams, and quantitative surface form error is measured by applying phase-shifting interferometry. A method for elimination of the residual system aberration is discussed. Results obtained for an optically polished BK-7 disk of clear aperture diameter ≈160  mm are presented. PMID:26835767

  20. Finding Large Aperture Fractures in Geothermal Resource Areas Using a Three-Component Long-Offset Surface Seismic Survey, PSInSAR and Kinematic Structural Analysis

    SciTech Connect

    Teplow, William J.; Warren, Ian

    2015-08-12

    The DOE cost-share program applied innovative and cutting edge seismic surveying and processing, permanent scatter interferometry-synthetic aperture radar (PSInSAR) and structural kinematics to the exploration problem of locating and mapping largeaperture fractures (LAFs) for the purpose of targeting geothermal production wells. The San Emidio geothermal resource area, which is under lease to USG, contains production wells that have encountered and currently produce from LAFs in the southern half of the resource area (Figure 2). The USG lease block, incorporating the northern extension of the San Emidio geothermal resource, extends 3 miles north of the operating wellfield. The northern lease block was known to contain shallow thermal waters but was previously unexplored by deep drilling. Results of the Phase 1 exploration program are described in detail in the Phase 1 Final Report (Teplow et al., 2011). The DOE cost shared program was completed as planned on September 30, 2014. This report summarizes results from all of Phase 1 and 2 activities.

  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. 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

  3. Shock wave absorber having apertured plate

    DOEpatents

    Shin, Yong W.; Wiedermann, Arne H.; Ockert, Carl E.

    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.

  4. 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.

  5. Differential Synthetic Aperture Ladar

    SciTech Connect

    Stappaerts, E A; Scharlemann, E

    2005-02-07

    We report a differential synthetic aperture ladar (DSAL) concept that relaxes platform and laser requirements compared to conventional SAL. Line-of-sight translation/vibration constraints are reduced by several orders of magnitude, while laser frequency stability is typically relaxed by an order of magnitude. The technique is most advantageous for shorter laser wavelengths, ultraviolet to mid-infrared. Analytical and modeling results, including the effect of speckle and atmospheric turbulence, are presented. Synthetic aperture ladars are of growing interest, and several theoretical and experimental papers have been published on the subject. Compared to RF synthetic aperture radar (SAR), platform/ladar motion and transmitter bandwidth constraints are especially demanding at optical wavelengths. For mid-IR and shorter wavelengths, deviations from a linear trajectory along the synthetic aperture length have to be submicron, or their magnitude must be measured to that precision for compensation. The laser coherence time has to be the synthetic aperture transit time, or transmitter phase has to be recorded and a correction applied on detection.

  6. Confocal coded aperture imaging

    DOEpatents

    Tobin, Jr., Kenneth William; Thomas, Jr., Clarence E.

    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.

  7. 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.

  8. Apodizer aperture for lasers

    DOEpatents

    Jorna, Siebe; Siebert, Larry D.; Brueckner, Keith A.

    1976-11-09

    An aperture attenuator for use with high power lasers which includes glass windows shaped and assembled to form an annulus chamber which is filled with a dye solution. The annulus chamber is shaped such that the section in alignment with the axis of the incident beam follows a curve which is represented by the equation y = (r - r.sub.o).sup.n.

  9. Coded aperture computed tomography

    NASA Astrophysics Data System (ADS)

    Choi, Kerkil; Brady, David J.

    2009-08-01

    Diverse physical measurements can be modeled by X-ray transforms. While X-ray tomography is the canonical example, reference structure tomography (RST) and coded aperture snapshot spectral imaging (CASSI) are examples of physically unrelated but mathematically equivalent sensor systems. Historically, most x-ray transform based systems sample continuous distributions and apply analytical inversion processes. On the other hand, RST and CASSI generate discrete multiplexed measurements implemented with coded apertures. This multiplexing of coded measurements allows for compression of measurements from a compressed sensing perspective. Compressed sensing (CS) is a revelation that if the object has a sparse representation in some basis, then a certain number, but typically much less than what is prescribed by Shannon's sampling rate, of random projections captures enough information for a highly accurate reconstruction of the object. This paper investigates the role of coded apertures in x-ray transform measurement systems (XTMs) in terms of data efficiency and reconstruction fidelity from a CS perspective. To conduct this, we construct a unified analysis using RST and CASSI measurement models. Also, we propose a novel compressive x-ray tomography measurement scheme which also exploits coding and multiplexing, and hence shares the analysis of the other two XTMs. Using this analysis, we perform a qualitative study on how coded apertures can be exploited to implement physical random projections by "regularizing" the measurement systems. Numerical studies and simulation results demonstrate several examples of the impact of coding.

  10. Synthetic Aperture Radar Interferometry

    NASA Technical Reports Server (NTRS)

    Rosen, P. A.; Hensley, S.; Joughin, I. R.; Li, F.; Madsen, S. N.; Rodriguez, E.; Goldstein, R. M.

    1998-01-01

    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 characteristics of the surface. This paper reviews the techniques of interferometry, systems and limitations, and applications in a rapidly growing area of science and engineering.

  11. Phasing rectangular apertures.

    PubMed

    Baker, K L; Homoelle, D; Utterback, E; Jones, S M

    2009-10-26

    Several techniques have been developed to phase apertures in the context of astronomical telescopes with segmented mirrors. Phasing multiple apertures, however, is important in a wide range of optical applications. The application of primary interest in this paper is the phasing of multiple short pulse laser beams for fast ignition fusion experiments. In this paper analytic expressions are derived for parameters such as the far-field distribution, a line-integrated form of the far-field distribution that could be fit to measured data, enclosed energy or energy-in-a-bucket and center-of-mass that can then be used to phase two rectangular apertures. Experimental data is taken with a MEMS device to simulate the two apertures and comparisons are made between the analytic parameters and those derived from the measurements. Two methods, fitting the measured far-field distribution to the theoretical distribution and measuring the ensquared energy in the far-field, produced overall phase variance between the 100 measurements of less than 0.005 rad(2) or an RMS displacement of less than 12 nm. PMID:19997175

  12. Temporal Aperture Modulation

    NASA Technical Reports Server (NTRS)

    Proctor, R. J.

    1981-01-01

    The two types of modulation techniques useful to X-ray imaging are reviewed. The use of optimum coded temporal aperature modulation is shown, in certain cases, to offer an advantage over a spatial aperture modulator. Example applications of a diffuse anisotropic X-ray background experiment and a wide field of view hard X-ray imager are discussed.

  13. Full-aperture wavefront reconstruction from annular subaperture interferometric data by use of Zernike annular polynomials and a matrix method for testing large aspheric surfaces

    SciTech Connect

    Hou Xi; Wu Fan; Yang Li; Wu Shibin; Chen Qiang

    2006-05-20

    We propose a more accurate and efficient reconstruction method used in testing large aspheric surfaces with annular subaperture interferometry. By the introduction of the Zernike annular polynomials that are orthogonal over the annular region, the method proposed here eliminates the coupling problem in the earlier reconstruction algorithm based on Zernike circle polynomials. Because of the complexity of recurrence definition of Zernike annular polynomials, a general symbol representation of that in a computing program is established. The program implementation for the method is provided in detail. The performance of the reconstruction algorithm is evaluated in some pertinent cases, such as different random noise levels, different subaperture configurations, and misalignments.

  14. Coded aperture imaging for fluorescent x-rays

    SciTech Connect

    Haboub, A.; MacDowell, A. A.; Marchesini, S.; Parkinson, D. Y.

    2014-06-15

    We employ a coded aperture pattern in front of a pixilated charge couple device detector to image fluorescent x-rays (6–25 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.

  15. Design of scanning spherical trireflector antennas with high aperture efficiency

    NASA Technical Reports Server (NTRS)

    Shen, Bing; Stutzman, Warren L.

    1993-01-01

    It is frequently desirable to scan the main beam of a large antenna system without moving the main aperture structure. Spherical reflectors have excellent potential in this application. However, they are not commonly used because of poor aperture efficiency and high side lobes in traditional implementations. This paper introduces a new dual-subreflector feed system design which does not require oversizing the spherical main reflector to accommodate scan and yet permits a controlled aperture illumination. The design yields high aperture efficiency, low cross-polarization, and low side lobes.

  16. Multiple aperture window and seeker concepts for endo KEW applications

    SciTech Connect

    Shui, V.H.; Reeves, B.L.; Thyson, N.A.; Mueffelmann, W.H.; Werner, J.S.; Jones, G. Loral Infrared and Imaging Systems, Lexington, MA U.S. Army, Strategic Defense Command, Huntsville, AL )

    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. 15 refs.

  17. 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.

  18. Genetic apertures: an improved sparse aperture design framework.

    PubMed

    Salvaggio, Philip S; Schott, John R; McKeown, Donald M

    2016-04-20

    The majority of optical sparse aperture imaging research in the remote sensing field has been confined to a small set of aperture layouts. While these layouts possess some desirable properties for imaging, they may not be ideal for all applications. This work introduces an optimization framework for sparse aperture layouts based on genetic algorithms as well as a small set of fitness functions for incoherent sparse aperture image quality. The optimization results demonstrate the merits of existing designs and the opportunity for creating new sparse aperture layouts. PMID:27140086

  19. The slant-stacklet transform and its application to teleseismic PcP-P data recorded at large aperture seismic array

    NASA Astrophysics Data System (ADS)

    Ventosa, S.; Romanowicz, B. A.

    2015-12-01

    In most high-resolution studies of the Earth's Deep Interior, the limited amount and uneven distribution of high-quality observations of short-period teleseismic body waves are major obstacles. Dense broadband seismic networks help to overcome major challenges of low signal-to-noise ratio (SNR) of the target phases and of signal-to-interference ratio (SIR) of other (often stronger) mantle phases when the slowness difference is large enough. Intuitive delay-and-sum (i.e. slant-stack) approaches are routinely applied to combine data of many spatially close stations to improve data quality. Alternative methods developed in the context of image processing, such as Radon transform-based methods, have proven useful in exploration seismology to facilitate enhancement and separation of signals according to their slowness and time of arrival. In this spirit, we have introduced the slant-stacklet transform to define coherency-guided filters able to exploit signals that would have been otherwise rejected because of low SNR or SIR. As an illustration, this method allows us to dramatically increase the amount of high-quality PcP observations using dense arrays in North America and Japan, sampling Central America, the western Pacific and Alaska/western Canada with unprecedented resolution and accuracy. After mantle corrections, the main signal left in these regions is relatively long wavelength in these regions of fast velocities around the Pacific, except at the western border of the Pacific large-low shear-velocity province (LLSVP) where we observe a rapid reduction of Vp velocity over a distance of about 10˚. This is just one step to further increase lowermost mantle imaging using P waves, much more information from PcP and other complementary signals (e.g. PdP) around the globe are needed to resolve volumetric structure, topography of the core-mantle boundary and D" discontinuity, and the trade-offs between them, in order to improve our understanding of the interaction

  20. 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.

  1. Configurable Aperture Space Telescope

    NASA Technical Reports Server (NTRS)

    Ennico, Kimberly; Bendek, Eduardo

    2015-01-01

    In December 2014, we were awarded Center Innovation Fund to evaluate an optical and mechanical concept for a novel implementation of a segmented telescope based on modular, interconnected small sats (satlets). The concept is called CAST, a Configurable Aperture Space Telescope. With a current TRL is 2 we will aim to reach TLR 3 in Sept 2015 by demonstrating a 2x2 mirror system to validate our optical model and error budget, provide straw man mechanical architecture and structural damping analyses, and derive future satlet-based observatory performance requirements. CAST provides an alternative access to visible and/or UV wavelength space telescope with 1-meter or larger aperture for NASA SMD Astrophysics and Planetary Science community after the retirement of HST

  2. Multispectral Dual-Aperture Schmidt Objective

    NASA Technical Reports Server (NTRS)

    Minott, P. O.

    1983-01-01

    Off-axis focal planes make room for beam splitters. System includes two off-axis primary spherical reflectors, each concentric with refractive corrector at aperature. Off-axis design assures large aperture required for adequate spatial resolution. Separate images have precise registration, used for multispectral resource mapping or remote sensing.

  3. 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 50μm. 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.

  4. 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.

  5. Implementation of swept synthetic aperture imaging

    NASA Astrophysics Data System (ADS)

    Bottenus, Nick; Jakovljevic, Marko; Boctor, Emad; Trahey, Gregg E.

    2015-03-01

    Ultrasound imaging of deep targets is limited by the resolution of current ultrasound systems based on the available aperture size. We propose a system to synthesize an extended effective aperture in order to improve resolution and target detectability at depth using a precisely-tracked transducer swept across the region of interest. A Field II simulation was performed to demonstrate the swept aperture approach in both the spatial and frequency domains. The adaptively beam-formed system was tested experimentally using a volumetric transducer and an ex vivo canine abdominal layer to evaluate the impact of clutter-generating tissue on the resulting point spread function. Resolution was improved by 73% using a 30.8 degree sweep despite the presence of varying aberration across the array with an amplitude on the order of 100 ns. Slight variations were observed in the magnitude and position of side lobes compared to the control case, but overall image quality was not significantly degraded as compared by a simulation based on the experimental point spread function. We conclude that the swept aperture imaging system may be a valuable tool for synthesizing large effective apertures using conventional ultrasound hardware.

  6. 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

  7. Class of near-perfect coded apertures

    NASA Technical Reports Server (NTRS)

    Cannon, T. M.; Fenimore, E. E.

    1977-01-01

    Coded aperture imaging of gamma ray sources has long promised an improvement in the sensitivity of various detector systems. The promise has remained largely unfulfilled, however, for either one of two reasons. First, the encoding/decoding method produces artifacts, which even in the absence of quantum noise, restrict the quality of the reconstructed image. This is true of most correlation-type methods. Second, if the decoding procedure is of the deconvolution variety, small terms in the transfer function of the aperture can lead to excessive noise in the reconstructed image. It is proposed to circumvent both of these problems by use of a uniformly redundant array (URA) as the coded aperture in conjunction with a special correlation decoding method.

  8. The aperture problem in contoured stimuli

    PubMed Central

    Kane, David; Bex, Peter J.; Dakin, Steven C.

    2010-01-01

    A moving object elicits responses from V1 neurons tuned to a broad range of locations, directions, and spatiotemporal frequencies. Global pooling of such signals can overcome their intrinsic ambiguity in relation to the object’s direction/speed (the “aperture problem”); here we examine the role of low-spatial frequencies (SF) and second-order statistics in this process. Subjects made a 2AFC fine direction-discrimination judgement of ‘naturally’ contoured stimuli viewed rigidly translating behind a series of small circular apertures. This configuration allowed us to manipulate the scene in several ways; by randomly switching which portion of the stimulus was presented behind each aperture or by occluding certain spatial frequency bands. We report that global motion integration is (a) largely insensitive to the second-order statistics of such stimuli and (b) is rigidly broadband even in the presence of a disrupted low SF component. PMID:19810794

  9. New LGS for large aperture telescope

    NASA Astrophysics Data System (ADS)

    Lukin, Vladimir; Bolbasova, Lidia

    2007-10-01

    The image quality is analyzed of an extraterrestrial object formed by astronomical optical system through the turbulent atmosphere. Relative increase the Strehl parameter is calculated under adaptive correction based on the laser guide star technique. The efficiency of adaptive correction of distortions for different type of the guide sources is compared. A special wave front sensor is applied, which operates using the broad laser beam as a reference wave. The calculations are performed for different models of the vertical variations of the structural parameter of the refractive index of the turbulent atmosphere. The wave front sensor was used, which enables to reconstruct the continuous phase of the reference wave. As the estimates show, the parameters of the formed field are quite close to that plane wave. So the higher correction and big increase of the Strehl parameter are obtained, that is indirect evidence of the good correction of the higher mode components, which are badly corrected using the traditional techniques for formation of LGS by means of a focused laser beam. As comparative calculations for different models of vertical variations of the structural parameter of the refractive index have shown, there are serious differences in the behaviors of the correlation radii for the plane and spherical waves.

  10. Large Aperture Multiplexed Diffractive Lidar Optics

    NASA Technical Reports Server (NTRS)

    Rallison, Richard D.; Schwemmer, Geary K. (Technical Monitor)

    1999-01-01

    We have delivered only 2 or 3 UV Holographic Optical Elements (HOEs) thus far and have fallen short of the intended goal in size and in dual wavelength function. Looking back, it has been fortuitous that we even made anything work in the UV region. It was our good fortune to discover that the material we work with daily was adequate for use at 355 nm, if well rinsed during processing. If we had stuck to our original plan of etching in small pieces of fused silica, we would still be trying to make the first small section in our ion mill, which is not yet operational. The original plan was far too ambitious and would take another 2 years to complete beginning where we left off this time. In order to make a HOE for the IR as well as the UV we will likely have to learn to sensitize some film to the 1064 line and we have obtained sensitizer that is reported to work in that region already. That work would also take an additional year to complete.

  11. 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.

  12. Aperture shape optimization for IMRT treatment planning

    NASA Astrophysics Data System (ADS)

    Cassioli, A.; Unkelbach, J.

    2013-01-01

    We propose an algorithm for aperture shape optimization (ASO) for step and shoot delivery of intensity-modulated radiotherapy. The method is an approach to direct aperture optimization (DAO) that exploits gradient information to locally optimize the positions of the leafs of a multileaf collimator. Based on the dose-influence matrix, the dose distribution is locally approximated as a linear function of the leaf positions. Since this approximation is valid only in a small interval around the current leaf positions, we use a trust-region-like method to optimize the leaf positions: in one iteration, the leaf motion is confined to the beamlets where the leaf edges are currently positioned. This yields a well-behaved optimization problem for the leaf positions and the aperture weights, which can be solved efficiently. If, in one iteration, a leaf is moved to the edge of a beamlet, the leaf motion can be confined to the neighboring beamlet in the next iteration. This allows for large leaf position changes over the course of the algorithm. In this paper, the ASO algorithm is embedded into a column-generation approach to DAO. After a new aperture is added to the treatment plan, we use the ASO algorithm to simultaneously optimize aperture weights and leaf positions for the new set of apertures. We present results for a paraspinal tumor case, a prostate case and a head and neck case. The computational results indicate that, using this approach, treatment plans close to the ideal fluence map optimization solution can be obtained.

  13. Differential Optical Synthetic Aperture Radar

    DOEpatents

    Stappaerts, Eddy A.

    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.

  14. 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.

  15. Compounding in synthetic aperture imaging.

    PubMed

    Hansen, Jens Munk; Jensen, Jørgen Arendt

    2012-09-01

    A method for obtaining compound images using synthetic aperture data is investigated using a convex array transducer. The new approach allows spatial compounding to be performed for any number of angles without reducing the frame rate or temporal resolution. This important feature is an intrinsic property of how the compound images are constructed using synthetic aperture data and an improvement compared with how spatial compounding is obtained using conventional methods. The synthetic aperture compound images are created by exploiting the linearity of delay-and-sum beamformation for data collected from multiple spherical emissions to synthesize multiple transmit and receive apertures, corresponding to imaging the tissue from multiple directions. The many images are added incoherently, to produce a single compound image. Using a 192-element, 3.5-MHz, λ-pitch transducer, it is demonstrated from tissue-phantom measurements that the speckle is reduced and the contrast resolution improved when applying synthetic aperture compound imaging. At a depth of 4 cm, the size of the synthesized apertures is optimized for lesion detection based on the speckle information density. This is a performance measure for tissue contrast resolution which quantifies the tradeoff between resolution loss and speckle reduction. The speckle information density is improved by 25% when comparing synthetic aperture compounding to a similar setup for compounding using dynamic receive focusing. The cystic resolution and clutter levels are measured using a wire phantom setup and compared with conventional application of the array, as well as to synthetic aperture imaging without compounding. If the full aperture is used for synthetic aperture compounding, the cystic resolution is improved by 41% compared with conventional imaging, and is at least as good as what can be obtained using synthetic aperture imaging without compounding. PMID:23007781

  16. Agile multiple aperture imager receiver development

    NASA Astrophysics Data System (ADS)

    Lees, David E. B.; Dillon, Robert F.

    1990-02-01

    A variety of unconventional imaging schemes have been investigated in recent years that rely on small, unphased optical apertures (subaperture) to measure properties of an incoming optical wavefront and recover images of distant objects without using precisely figured, large aperture optical elements. Such schemes offer several attractive features. They provide the potential to create very lare effective aperture that are expandable over time and can be launched into space in small pieces. Since the subapertures are identical in construction, they may be mass producible at potentially low cost. A preliminary design for a practical low cost optical receiver is presented. The multiple aperture design has high sensitivity, wide field-of-view, and is lightweight. A combination of spectral, temporal, and spatial background suppression are used to achieve daytime operation at low signal levels. Modular packaging to make the number of receiver subapertures conveniently scalable is also presented. The design is appropriate to a ground-base proof-of-concept experiment for long range active speckle imaging.

  17. The saga of the LEP dynamic aperture

    NASA Astrophysics Data System (ADS)

    Verdier, A.

    1999-05-01

    The large electron-positron collider LEP at CERN provides a beautiful example of our conceptual limits concerning the problem of dynamic aperture (short term stability of the transverse oscillations of particle trajectories) in circular machines. For the operation at 45 GeV (Z0 peak) the dynamic aperture did not pose any problem although its measurement gave a value much smaller than that predicted up to the end of 1993. After this date the measurements gave the same result as predicted but it was not possible to trace back the origin of the discrepancy. At high energy (the maximum operating energy foreseen is 100 GeV) the beam emittance increases with the square of the beam energy. Therefore, low emittance optics were proposed. These optics suffer from large anharmonicities because of the increased sextupole strengths. This led to an unexpected limitation of the beam lifetime.

  18. 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.

  19. Spectroscopie Raman et Rayleigh stimulée des mélasses optiques unidimensionnelles (partie I)

    NASA Astrophysics Data System (ADS)

    Courtois, Jean-Yves

    stimulated Raman lines are homogeneously broadened, and that a stimulated Rayleigh structure appears on the spectra because of the probe-induced time modulation of the cooling force, which induces a modulation of the atomic momentum distribution. In the latter situation, the Raman structures are inhomogeneously broadened, and a recoil-induced resonance is predicted in the center of the spectrum. Its shape corresponds to the derivative of a Gaussian curve and its width is directly proportional to the Doppler width of the molasses. Finally, Section 6 presents a short review about the recent developments in the field of nonlinear spectroscopy of optical molasses. Cet article s'inscrit dans le double contexte de la spectroscopie non linéaire des milieux atomiques et de la physique du refroidissement d'atomes neutres par laser. Il présente une étude détaillée des spectres de transmission d'une onde sonde interagissant avec une mélasse optique unidimensionnelle. Plus précisément, nous montrons que dans chacun des deux cas modèles des mélasses “linperp lin” et “σ^+-σ^-” (ainsi dénommées par référence à la configuration de polarisation des deux faisceaux lasers à l'origine du mécanisme de refroidissement), les spectres pompes-sonde présentent des structures résonnantes pouvant s'interpréter en termes de diffusion Raman ou Rayleigh stimulée, et apportant un grand nombre d'informations sur les propriétés physiques des mélasses optiques. Cet article s'articule autour de deux grandes parties. Destinée à faire ultérieurement ressortir la spécificité des processus de diffusion stimulée se produisant dans les mélasses optiques, la première est consacrée à une présentation générale des processus Raman et Rayleigh stimulés se produisant dans les milieux atomiques et moléculaires conventionnels. L'effet Raman stimulé, lié à l'existence de centres diffuseurs ayant des états d'énergies et de populations différentes, fait l'objet du

  20. New Techniques of LASS-ICPMS Depth Profiling Applied to Detrital Zircon from the Central Alps-Apennines System

    NASA Astrophysics Data System (ADS)

    Anfinson, O. A.; Smye, A.; Stockli, D. F.

    2014-12-01

    Detrital zircon U-Pb age dating has become a widely used tool for determining sediment provenance in basins and orogenic systems. While traditional LA-ICPMS zircon geochronology is powerful, it has limitations when source regions are characterized by monotonous or non-diagnostic crystallization ages or by major sediment recycling and homogenization, leading to minimal zircon age variability. In the central Alps of Switzerland and Italy, for example, similar Cadomian, Caledonian, and Variscan zircons dominate with only minor Alpine ages. Samples collected from Oligocene-Miocene strata deposited in both the northern (Swiss Molasse) and southern (Apenninic foredeep) Alpine foreland basins document shifts in the relative abundance of Cadomian, Caledonian, Variscan and Alpine aged detrital zircon, but the exact source region and genesis of the grains remains poorly constrained based on zircon U-Pb age data alone. Laser Ablation Split Stream (LASS)-ICPMS depth profiling of detrital zircon allows for the simultaneous recovery of multiple ages and of chemical/petrogenetic data from single zircons, and has the potential to shed additional light on provenance. This study applies this approach to Oligocene-Miocene strata of the Swiss Molasse Basin and Apenninic foredeep. Recent advances in LA-ICPMS sample cell technology allow for reliable recovery of age and trace element data during progressive ablation into zircons. Decreased washout (<.3 sec) reduces vertical signal smearing during ablation and penetration into unpolished, tape-mounted grains. In contrast to traditional polished mount zircon spot-analysis, depth-profiling of unpolished grains minimizes zonal mixing given that ablation pits are commonly oriented perpendicular to growth zones. Split-stream analysis of U-Pb isotopic data and REE/trace element abundances during ablation improves petrochronologic resolution to the further elucidated the growth history and genesis of individual zircon grains. Results from the

  1. Dynamic Aperture Measurements at the Advanced Light Source

    SciTech Connect

    Decking, W.; Robin, D.

    1999-03-12

    A large dynamic aperture for a storage ring is of importance for long lifetimes and a high injection efficiency. Measurements of the dynamic aperture of the third generation synchrotron light source Advanced Light Source (ALS) using beam excitation with kicker magnets are presented. The experiments were done for various accelerator conditions, allowing us to investigate the influence of different working points, chromaticities, insertion devices, etc.. The results are compared both with tracking calculations and a simple model for the dynamic aperture yielding good agreements. This gives us confidence in the predictability of the nonlinear accelerator model. This is especially important for future ALS upgrades as well as new storage ring designs.

  2. Interferometric synthetic aperture microscopy

    NASA Astrophysics Data System (ADS)

    Ralston, Tyler S.; Marks, Daniel L.; Scott Carney, P.; Boppart, Stephen A.

    2007-02-01

    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 light-sample 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.

  3. Interferometric synthetic aperture microscopy

    NASA Astrophysics Data System (ADS)

    Ralston, Tyler S.

    State-of-the-art interferometric microscopies have problems representing objects that lie outside of the focus because the defocus and diffraction effects are not accounted for in the processing. These problems occur because of the lack of comprehensive models to include the scattering effects in the processing. In this dissertation, a new modality in three-dimensional (3D) optical microscopy, Interferometric Synthetic Aperture Microscopy (ISAM), is introduced to account for the scattering effects. Comprehensive models for interferometric microscopy, such as optical coherence tomography (OCT) are developed, for which forward, adjoint, normal, and inverse operators are formulated. Using an accurate model for the probe beam, the resulting algorithms demonstrate accurate linear estimation of the susceptibility of an object from the interferometric data. Using the regularized least squares solution, an ISAM reconstruction of underlying object structure having spatially invariant resolution is obtained from simulated and experimental interferometric data, even in regions outside of the focal plane of the lens. Two-dimensional (2D) and 3D interferometric data is used to resolve objects outside of the confocal region with minimal loss of resolution, unlike in OCT. Therefore, high-resolution details are recovered from outside of the confocal region. Models and solutions are presented for the planar-scanned, the rotationally scanned, and the full-field illuminated geometry. The models and algorithms presented account for the effects of a finite beam width, the source spectrum, the illumination and collection fields, as well as defocus, diffraction and dispersion effects.

  4. Sparse aperture endoscope

    DOEpatents

    Fitch, Joseph P.

    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.

  5. 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.

  6. Lucky imaging and aperture synthesis with low-redundancy apertures.

    PubMed

    Ward, Jennifer E; Rhodes, William T; Sheridan, John T

    2009-01-01

    Lucky imaging, used with some success in astronomical and even horizontal-path imaging, relies on fleeting conditions of the atmosphere that allow momentary improvements in image quality, at least in portions of an image. Aperture synthesis allows a larger aperture and, thus, a higher-resolution imaging system to be synthesized through the superposition of image spatial-frequency components gathered by cooperative combinations of smaller subapertures. A combination of lucky imaging and aperture synthesis strengthens both methods for obtaining improved images through the turbulent atmosphere. We realize the lucky imaging condition appropriate for aperture synthesis imaging for a pair of rectangular subapertures and demonstrate that this condition occurs when the signal energy associated with bandpass spatial-frequency components achieves its maximum value. PMID:19107157

  7. Fast-neutron, coded-aperture imager

    NASA Astrophysics Data System (ADS)

    Woolf, Richard S.; Phlips, Bernard F.; Hutcheson, Anthony L.; Wulf, Eric A.

    2015-06-01

    This work discusses a large-scale, coded-aperture imager for fast neutrons, building off a proof-of concept instrument developed at the U.S. Naval Research Laboratory (NRL). The Space Science Division at the NRL has a heritage of developing large-scale, mobile systems, using coded-aperture imaging, for long-range γ-ray detection and localization. The fast-neutron, coded-aperture imaging instrument, designed for a mobile unit (20 ft. ISO container), consists of a 32-element array of 15 cm×15 cm×15 cm liquid scintillation detectors (EJ-309) mounted behind a 12×12 pseudorandom coded aperture. The elements of the aperture are composed of 15 cm×15 cm×10 cm blocks of high-density polyethylene (HDPE). The arrangement of the aperture elements produces a shadow pattern on the detector array behind the mask. By measuring of the number of neutron counts per masked and unmasked detector, and with knowledge of the mask pattern, a source image can be deconvolved to obtain a 2-d location. The number of neutrons per detector was obtained by processing the fast signal from each PMT in flash digitizing electronics. Digital pulse shape discrimination (PSD) was performed to filter out the fast-neutron signal from the γ background. The prototype instrument was tested at an indoor facility at the NRL with a 1.8-μCi and 13-μCi 252Cf neutron/γ source at three standoff distances of 9, 15 and 26 m (maximum allowed in the facility) over a 15-min integration time. The imaging and detection capabilities of the instrument were tested by moving the source in half- and one-pixel increments across the image plane. We show a representative sample of the results obtained at one-pixel increments for a standoff distance of 9 m. The 1.8-μCi source was not detected at the 26-m standoff. In order to increase the sensitivity of the instrument, we reduced the fastneutron background by shielding the top, sides and back of the detector array with 10-cm-thick HDPE. This shielding configuration led

  8. Miniature synthetic-aperture radar system

    NASA Astrophysics Data System (ADS)

    Stockton, Wayne; Stromfors, Richard D.

    1990-11-01

    Loral Defense Systems-Arizona has developed a high-performance synthetic-aperture radar (SAR) for small aircraft and unmanned aerial vehicle (UAV) reconnaissance applications. This miniature radar, called Miniature Synthetic-Aperture Radar (MSAR), is packaged in a small volume and has low weight. It retains key features of large SAR systems, including high-resolution imaging and all-weather operation. The operating frequency of MSAR can optionally be selected to provide foliage penetration capability. Many imaging radar configurations can be derived using this baseline system. MSAR with a data link provides an attractive UAV sensor. MSAR with a real-time image formation processor is well suited to installations where onboard processing and immediate image analysis are required. The MSAR system provides high-resolution imaging for short-to-medium range reconnaissance applications.

  9. Study on key techniques for synthetic aperture ladar system

    NASA Astrophysics Data System (ADS)

    Cao, Changqing; Zeng, Xiaodong; Feng, Zhejun; Zhang, Wenrui; Su, Lei

    2008-03-01

    The spatial resolution of a conventional imaging LADAR system is constrained by the diffraction limit of the telescope aperture. The purpose of this work is to investigate Synthetic Aperture Imaging LADAR (SAIL), which employs aperture synthesis with coherent laser radar to overcome the diffraction limit and achieve fine-resolution, long range, two-dimensional imaging with modest aperture diameters. Because of many advantages, LADAR based on synthetic aperture theory is becoming research hotspot and practicality. Synthetic Aperture LADAR (SAL) technology satisfies the critical need for reliable, long-range battlefield awareness. An image that takes radar tens of seconds to produce can be produced in a few thousands of a second at optical frequencies. While radar waves respond to macroscopic features such as corners, edges, and facets, laser waves interact with microscopic surface characteristics, which results in imagery that appears more familiar and is more easily interpreted. SAL could provide high resolution optical/infrared imaging. In the present paper we have tried to answer three questions: (1) the process of collecting the samples over the large "synthetic" aperture; (2) differences between SAR and SAL; (3) the key techniques for SAL system. The principle and progress of SAL are introduced and a typical SAL system is described. Beam stabilization, chirp laser, and heterodyne detection, which are among the most challenging aspects of SAL, are discussed in detail.

  10. Interferometric Synthetic Aperture Microscopy (ISAM)

    NASA Astrophysics Data System (ADS)

    Adie, Steven G.; Shemonski, Nathan D.; Ralston, Tyler S.; Carney, P. Scott; Boppart, Stephen A.

    The trade-off between transverse resolution and depth-of-field, and the mitigation of optical aberrations, are long-standing problems in optical imaging. The deleterious impact of these problems on three-dimensional tomography increases with numerical aperture (NA), and so they represent a significant impediment for real-time cellular resolution tomography over the typical imaging depths achieved with OCT. With optical coherence microscopy (OCM), which utilizes higher-NA optics than OCT, the depth-of-field is severely reduced, and it has been postulated that aberrations play a major role in reducing the useful imaging depth in OCM. Even at lower transverse resolution, both these phenomena produce artifacts that degrade the imaging of fine tissue structures. Early approaches to the limited depth-of-field problem in time-domain OCT utilized dynamic focusing. In spectral-domain OCT, this focus-shifting approach to data acquisition leads to long acquisition times and large datasets. Adaptive optics (AO) has been utilized to correct optical aberrations, in particular for retinal OCT, but in addition to requiring elaborate and expensive setups, the real-time optimization requirements at the time of imaging, and the correction of spatially varying effects of aberrations throughout an imaged volume, remain as significant challenges. This chapter presents computed imaging solutions for the reconstruction of sample structure when imaging with ideal and aberrated Gaussian beams.

  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. 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 μm. 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, Ω, 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

  13. Superresolution and Synthetic Aperture Radar

    SciTech Connect

    DICKEY,FRED M.; ROMERO,LOUIS; DOERRY,ARMIN W.

    2001-05-01

    Superresolution concepts offer the potential of resolution beyond the classical limit. This great promise has not generally been realized. In this study we investigate the potential application of superresolution concepts to synthetic aperture radar. The analytical basis for superresolution theory is discussed. The application of the concept to synthetic aperture radar is investigated as an operator inversion problem. Generally, the operator inversion problem is ill posed. A criterion for judging superresolution processing of an image is presented.

  14. Conical Rotating Aperture Geometries In Digital Radiography

    NASA Astrophysics Data System (ADS)

    Rudin, Stephen; Bednarek, Daniel R.; Wong, Roland

    1981-11-01

    Applications of conical rotating aperture (RA) geometries to digital radiography are described. Two kinds of conical RA imaging systems are the conical scanning beam and the conical scanning grid assemblies. These assemblies comprise coaxial conical surface(s) the axis of which is collinear with the x-ray focal spot. This geometry allows accurate alignment and continuous focusing of the slits or the grid lines. Image receptors which use solid state photodiode arrays are described for each type of conical RA system: multiple linear arrays for the conical scanning beam assembly and multiple area arrays for the conical scanning grid assembly. The digital rotating-aperture systems combine the wide dynamic range characteristics of solid state detectors with the superior scatter-rejection advantages of scanned beam approaches. The high scanning-beam velocities attainable by the use of rotating apertures should make it possible to obtain digital images for those procedures such as chest radiography which require large fields of view and short exposure times.

  15. Feasibility of Swept Synthetic Aperture Ultrasound Imaging.

    PubMed

    Bottenus, Nick; Long, Will; Zhang, Haichong K; Jakovljevic, Marko; Bradway, David P; Boctor, Emad M; Trahey, Gregg E

    2016-07-01

    Ultrasound image quality is often inherently limited by the physical dimensions of the imaging transducer. We hypothesize that, by collecting synthetic aperture data sets over a range of aperture positions while precisely tracking the position and orientation of the transducer, we can synthesize large effective apertures to produce images with improved resolution and target detectability. We analyze the two largest limiting factors for coherent signal summation: aberration and mechanical uncertainty. Using an excised canine abdominal wall as a model phase screen, we experimentally observed an effective arrival time error ranging from 18.3 ns to 58 ns (root-mean-square error) across the swept positions. Through this clutter-generating tissue, we observed a 72.9% improvement in resolution with only a 3.75 dB increase in side lobe amplitude compared to the control case. We present a simulation model to study the effect of calibration and mechanical jitter errors on the synthesized point spread function. The relative effects of these errors in each imaging dimension are explored, showing the importance of orientation relative to the point spread function. We present a prototype device for performing swept synthetic aperture imaging using a conventional 1-D array transducer and ultrasound research scanner. Point target reconstruction error for a 44.2 degree sweep shows a reconstruction precision of 82.8 μm and 17.8 μm in the lateral and axial dimensions respectively, within the acceptable performance bounds of the simulation model. Improvements in resolution, contrast and contrast-to-noise ratio are demonstrated in vivo and in a fetal phantom. PMID:26863653

  16. 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. Borisov, S. V.; Voronov, S. A.; Malakhov, V. V.

    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.

  17. Aperture combined Raman laser

    SciTech Connect

    Woods, C.; Tang, K.; Howton, C.; Muller, D.; Hunter, R.O. Jr.

    1983-01-01

    Excimer lasers, while able to produce large powers and energies, are limited to a few discrete wavelengths. Efficient Raman shifting promises the availability of a much broader wavelength range. A method was developed which both Raman shifts and allows for multiple pump beams.

  18. Metamaterial Apertures for Computational Imaging

    NASA Astrophysics Data System (ADS)

    Hunt, John; Driscoll, Tom; Mrozack, Alex; Lipworth, Guy; Reynolds, Matthew; Brady, David; Smith, David R.

    2013-01-01

    By leveraging metamaterials and compressive imaging, a low-profile aperture capable of microwave imaging without lenses, moving parts, or phase shifters is demonstrated. This designer aperture allows image compression to be performed on the physical hardware layer rather than in the postprocessing stage, thus averting the detector, storage, and transmission costs associated with full diffraction-limited sampling of a scene. A guided-wave metamaterial aperture is used to perform compressive image reconstruction at 10 frames per second of two-dimensional (range and angle) sparse still and video scenes at K-band (18 to 26 gigahertz) frequencies, using frequency diversity to avoid mechanical scanning. Image acquisition is accomplished with a 40:1 compression ratio.

  19. 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.

  20. A flat laser array aperture

    NASA Astrophysics Data System (ADS)

    Papadakis, Stergios J.; Ricciardi, Gerald F.; Gross, Michael C.; Krill, Jerry A.

    2010-04-01

    We describe a design concept for a flat (or conformal) thin-plate laser phased-array aperture. The aperture consists of a substrate supporting a grid of single-mode optical waveguides fabricated from a linear electro-optic material. The waveguides are coupled to a single laser source or detector. An arrangement of electrodes provides for two-dimensional beam steering by controlling the phase of the light entering the grid. The electrodes can also be modulated to simultaneously provide atmospheric turbulence modulation for long-range free-space optical communication. An approach for fabrication is also outlined.

  1. Mosaic of coded aperture arrays

    DOEpatents

    Fenimore, Edward E.; Cannon, Thomas M.

    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.

  2. Multi-aperture digital coherent combining for free-space optical communication receivers.

    PubMed

    Geisler, David J; Yarnall, Timothy M; Stevens, Mark L; Schieler, Curt M; Robinson, Bryan S; Hamilton, Scott A

    2016-06-13

    Space-to-ground optical communication systems can benefit from reducing the size, weight, and power profiles of space terminals. One way of reducing the required power-aperture product on a space platform is to implement effective, but costly, single-aperture ground terminals with large collection areas. In contrast, we present a ground terminal receiver architecture in which many small less-expensive apertures are efficiently combined to create a large effective aperture while maintaining excellent receiver sensitivity. This is accomplished via coherent detection behind each aperture followed by digitization. The digitized signals are then combined in a digital signal processing chain. Experimental results demonstrate lossless coherent combining of four lasercom signals, at power levels below 0.1 photons/bit/aperture. PMID:27410287

  3. High resolution non-iterative aperture synthesis.

    PubMed

    Kraczek, Jeffrey R; McManamon, Paul F; Watson, Edward A

    2016-03-21

    The maximum resolution of a multiple-input multiple-output (MIMO) imaging system is determined by the size of the synthetic aperture. The synthetic aperture is determined by a coordinate shift using the relative positions of the illuminators and receive apertures. Previous methods have shown non-iterative phasing for multiple illuminators with a single receive aperture for intra-aperture synthesis. This work shows non-iterative phasing with both multiple illuminators and multiple receive apertures for inter-aperture synthesis. Simulated results show that piston, tip, and tilt can be calculated using inter-aperture phasing after intra-aperture phasing has been performed. Use of a fourth illuminator for increased resolution is shown. The modulation transfer function (MTF) is used to quantitatively judge increased resolution. PMID:27136816

  4. Dynamic aperture measurement on Aladdin

    SciTech Connect

    Bridges, J.; Cho, Y.; Chou, W.; Crosbie, E.; Kramer, S.; Kustom, R.; Voss, D.; Teng, L.; Kleman, K.; Otte, R.; Trzeciak, W.; Symon, K.; Wisconsin Univ., Stoughton, WI . Synchrotron Radiation Center; Wisconsin Univ., Madison, WI . Dept. of Physics)

    1989-01-01

    The sextupole-induced non-linear transverse beam dynamics in the synchrotron radiation storage ring Aladdin is studied. Specifically, the dynamic aperture is measured as function of the sextupole strength. The results agree reasonably well with computer simulations. 1 ref., 8 figs., 1 tab.

  5. Future of synthetic aperture radar

    NASA Technical Reports Server (NTRS)

    Barath, F. T.

    1978-01-01

    The present status of the applications of Synthetic Aperture Radars (SARs) is reviewed, and the technology state-of-the art as represented by the Seasat-A and SIR-A SARs examined. The potential of SAR applications, and the near- and longer-term technology trends are assessed.

  6. SEASAT Synthetic Aperture Radar Data

    NASA Technical Reports Server (NTRS)

    Henderson, F. M.

    1981-01-01

    The potential of radar imagery from space altitudes is discussed and the advantages of radar over passive sensor systems are outlined. Specific reference is made to the SEASAT synthetic aperture radar. Possible applications include oil spill monitoring, snow and ice reconnaissance, mineral exploration, and monitoring phenomena in the urban environment.

  7. Multiple-Aperture-Based Solar Seeing Profiler

    NASA Astrophysics Data System (ADS)

    Ren, Deqing; Zhao, Gang; Zhang, Xi; Dou, Jiangpei; Chen, Rui; Zhu, Yongtian; Yang, Feng

    2015-09-01

    Characterization of day-time atmospheric turbulence profiles up to 30 km above the telescope is crucial for designs and performance estimations of future solar multiconjugate adaptive optics (MCAO) systems. Recently, the S-DIMM+ method has been successfully used to measure the vertical profile of turbulence. However, to measure profile up to 30 km employing the S-DIMM+ method, a telescope with a diameter of at least 1.0 m is needed, which restricts the usage of S-DIMM+, since large telescopes are scarce and their time is limited. To solve this problem, we introduce the multiple-aperture seeing profiler (MASP), which consists of two portable small telescopes instead of a single large aperture. Numerical simulations are carried out to evaluate the performance of MASP. We find that for one layer case, MASP can retrieve the seeing with error ~5% using 800 frames of wavefront sensor (WFS) data, which is quite similar to the results of a telescope with diameter of 1120 mm. We also simulate profiles with four turbulence layers, and find that our MASP can effectively retrieve the strengths and heights of the four turbulence layers. Since previous measurements at Big Bear Solar Observatory showed that day-time turbulence profile typically consists of four layers, the MASP we introduced is sufficient for actual seeing measurement.

  8. Fresnel diffraction of aperture with rough edge

    NASA Astrophysics Data System (ADS)

    Cui, Yuwei; Zhang, Wei; Wang, Junhong; Zhang, Meina; Teng, Shuyun

    2015-06-01

    The Fresnel diffraction of an aperture with a rough edge is studied in this paper. Circular and elliptical apertures with sinusoidal and random edges are chosen as examples to investigate the influence of the aperture edge on the diffraction. The numerical calculation results indicate intuitively the variations of the transverse and longitude diffraction intensity distributions with the edge parameters of the aperture. The data files of aperture models are obtained through the numerical calculations, and the aperture samples are obtained with the help of a liquid crystal light modulator (LCLM). Thus, the practical experiments of the diffractions of apertures with rough edges are carried out. The measured results are consistent with the calculated ones. The approximate analytic expressions of the diffraction by the modified aperture are deduced on the basis of the Fresnel diffraction theory and the statistic optics, and the reasonable explanations for the influence of edge parameters on the diffraction are given through the theoretical analysis.

  9. Alternative aperture stop position designs for SIRTF

    NASA Technical Reports Server (NTRS)

    Davis, Paul K.; Dinger, Ann S.

    1990-01-01

    Three designs of the Space Infrared Telescope Facility (SIRTF) for a 100,000 high earth orbit are considered with particular attention given to the evaluation of the aperture stop position. The choice of aperture stop position will be based on stray light considerations which are being studied concurrently. It is noted that there are advantages in cost, mass, and astronomical aperture to placing the aperture stop at or near the primary mirror, if the stray light circumstances allow.

  10. Development of the Synthetic Aperture Radiometer ESTAR and the Next Generation

    NASA Technical Reports Server (NTRS)

    LeVine, David M.; Haken, Michael; Swift, Calvin T.

    2004-01-01

    ESTAR is a research instrument built to develop the technology of aperture synthesis for passive remote sensing of Earth from space. Aperture synthesis is an interferometric technology that addresses the problem of putting large antenna apertures in space to achieve the spatial resolution needed for remote sensing at long wavelengths ESTAR was a first step (synthesis only across track and only at horizontal polarization). The development has progressed to a new generation instrument that is dual polarized and does aperture synthesis in two dimensions. Among the plans for the future is technology to combine active and passive remote sensing.

  11. Sub-aperture stitching with scanning pentaprism testing optical wave-front

    NASA Astrophysics Data System (ADS)

    Wang, Lihua; Yang, Wei; Li, Lei; Wu, Shibin; Lin, Zhaohen

    2010-05-01

    This paper describes a pentaprism scanning combined with sub-aperture stitching interference method to test large aperture optical system wave-front. This method uses pentaprism scanning and interferometer testing sub-aperture optical system wave-front, after testing all the sub-aperture wave-front and then using average error stitching algorithm to reconstruction full-aperture optical system wave-front. It makes use of the pentaprism easily to adjust and interferometer's high-precision characteristic. Analyzed the mechanical precision of turntable and electric guide, when the turntable sway angle is less than 8', location accuracy is less than 1.194' and the electric guide linearity is less than 8'location accuracy is less than 83.3μm, can meet the testing requirements. We used 40mm sub-aperture testing 312mm full aperture wave-front PV is 0.2197λ and RMS is 0.0536λ. Compared the stitching results with Zygo interferometer directly full aperture testing verified the accuracy of the method and provides a new idea for testing a large aperture optical wave-front.

  12. VSATs - Very small aperture terminals

    NASA Astrophysics Data System (ADS)

    Everett, John L.

    The present volume on very small aperture terminals (VSATs) discusses antennas, semiconductor devices, and traveling wave tubes and amplifiers for VSAT systems, VSAT low noise downconverters, and modems and codecs for VSAT systems. Attention is given to multiaccess protocols for VSAT networks, protocol software in Ku-band VSAT network systems, system design of VSAT data networks, and the policing of VSAT networks. Topics addressed include the PANDATA and PolyCom systems, APOLLO - a satellite-based information distribution system, data broadcasting within a satellite television channel, and the NEC NEXTAR VSAT system. Also discussed are small aperture military ground terminals, link budgets for VSAT systems, capabilities and experience of a VSAT service provider, and developments in VSAT regulation.

  13. Aperture masking behind AO systems

    NASA Astrophysics Data System (ADS)

    Ireland, Michael J.

    2012-07-01

    Sparse Aperture-Mask Interferometry (SAM or NRM) behind Adaptive Optics (AO) has now come of age, with more than a dozen astronomy papers published from several 5-10m class telescopes around the world. I will describe the reasons behind its success in achieving relatively high contrasts ( 1000:1 at lambda/ D) and repeatable binary astronomy at the diffraction limit, even when used behind laser-guide star adaptive optics. Placed within the context of AO calibration, the information in an image can be split into pupil-plane phase, Fourier amplitude and closure-phase. It is the closure-phase observable, or its generalisation to Kernel phase, that is immune to pupil-plane phase errors at first and second-order and has been the reason for the technique's success. I will outline the limitations of the technique and the prospects for aperture-masking and related techniques in the future.

  14. Characterization of a dense aperture array for radio astronomy

    NASA Astrophysics Data System (ADS)

    Torchinsky, S. A.; Olofsson, A. O. H.; Censier, B.; Karastergiou, A.; Serylak, M.; Picard, P.; Renaud, P.; Taffoureau, C.

    2016-05-01

    EMBRACE@Nançay is a prototype instrument consisting of an array of 4608 densely packed antenna elements creating a fully sampled, unblocked aperture. This technology is proposed for the Square Kilometre Array and has the potential of providing an extremely large field of view making it the ideal survey instrument. We describe the system, calibration procedures, and results from the prototype.

  15. Multiple aperture imager component development

    NASA Astrophysics Data System (ADS)

    Lees, David E.; Henshaw, Philip D.

    1991-03-01

    This final report presents results of an experimental and analytical effort to develop multiple aperture imagers built from unphased, direct-detection subapertures. An object was imaged using wave length shift instead of object motion to create multiple speckle pattern realizations. An analysis of subaperture geometry effects of autocorrelation estimate was performed. Experimental measurements of detector modulator transfer function were made. Finally, a new algorithm to reconstruct imagery with improved signal-to-noise ratio was developed.

  16. ESTAR - A synthetic aperture microwave radiometer for measuring soil moisture

    NASA Technical Reports Server (NTRS)

    Le Vine, D. M.; Griffis, A.; Swift, C. T.; Jackson, T. J.

    1992-01-01

    The measurement of soil moisture from space requires putting relatively large microwave antennas in orbit. Aperture synthesis, an interferometric technique for reducing the antenna aperture needed in space, offers the potential for a practical means of meeting these requirements. An aircraft prototype, electronically steered thinned array L-band radiometer (ESTAR), has been built to develop this concept and to demonstrate its suitability for the measurement of soil moisture. Recent flights over the Walnut Gulch Watershed in Arizona show good agreement with ground truth and with measurements with the Pushbroom Microwave Radiometer (PBMR).

  17. Synthetic aperture radar processing with polar formatted subapertures

    SciTech Connect

    Doerry, A.W.

    1994-10-01

    Synthetic Aperture Radar (SAR) uses the motion of a small real antenna to synthesize a larger aperture, and thereby achieve very fine azimuth resolution. Efficient SAR image formation requires modelling the radar echo and compensating (focusing) the delay and phase for various positions in the target scene. Polar-Format processing is one successful algorithm developed to process large scenes at fine resolutions, but is still limited, especially at resolutions near a wavelength. This paper shows how using tiers of subapertures can overcome the limitations of Polar-Format processing and increase the focused scene size substantially while using only efficient vector multiplies and Fast Fourier Transforms.

  18. Coherent sub-aperture ultraviolet imagery

    NASA Astrophysics Data System (ADS)

    Morton, R. G.; Connally, W. J.; Avicola, K.; Monjo, D.; Olson, T.

    1989-09-01

    Laboratory targets have been imaged by a multi-sub-aperture, coherent receiver technique in which a common local oscillator illuminates the sub-aperture array to preserve both phase and intensity information. The target, receiver and range dimensions were chosen such that each sub-aperture was smaller than the speckle size. Various targets were illuminated by microsecond pulses from an e-beam pumped XeF power amplifier, which was seeded by a coherent ultraviolet beam generated with a frequency doubled visible dye laser. Data is presented showing comparisons between the coherent multi-sub-aperture approach and conventional, full aperture photography of the same traget(s).

  19. 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

  20. Controlled-aperture wave-equation migration

    SciTech Connect

    Huang, L.; Fehler, Michael C.; Sun, H.; Li, Z.

    2003-01-01

    We present a controlled-aperture wave-equation migration method that no1 only can reduce migration artiracts due to limited recording aperlurcs and determine image weights to balance the efl'ects of limited-aperture illumination, but also can improve thc migration accuracy by reducing the slowness perturbations within thc controlled migration regions. The method consists of two steps: migration aperture scan and controlled-aperture migration. Migration apertures for a sparse distribution of shots arc determined using wave-equation migration, and those for the other shots are obtained by interpolation. During the final controlled-aperture niigration step, we can select a reference slowness in c;ontrollecl regions of the slowness model to reduce slowncss perturbations, and consequently increase the accuracy of wave-equation migration inel hods that makc use of reference slownesses. In addition, the computation in the space domain during wavefield downward continuation is needed to be conducted only within the controlled apertures and therefore, the computational cost of controlled-aperture migration step (without including migration aperture scan) is less than the corresponding uncontrolled-aperture migration. Finally, we can use the efficient split-step Fourier approach for migration-aperture scan, then use other, more accurate though more expensive, wave-equation migration methods to perform thc final controlled-apertio.ee migration to produce the most accurate image.

  1. Reconstruction of coded aperture images

    NASA Technical Reports Server (NTRS)

    Bielefeld, Michael J.; Yin, Lo I.

    1987-01-01

    Balanced correlation method and the Maximum Entropy Method (MEM) were implemented to reconstruct a laboratory X-ray source as imaged by a Uniformly Redundant Array (URA) system. Although the MEM method has advantages over the balanced correlation method, it is computationally time consuming because of the iterative nature of its solution. Massively Parallel Processing, with its parallel array structure is ideally suited for such computations. These preliminary results indicate that it is possible to use the MEM method in future coded-aperture experiments with the help of the MPP.

  2. Aperture scanning Fourier ptychographic microscopy

    PubMed Central

    Ou, Xiaoze; Chung, Jaebum; Horstmeyer, Roarke; Yang, Changhuei

    2016-01-01

    Fourier ptychographic microscopy (FPM) is implemented through aperture scanning by an LCOS spatial light modulator at the back focal plane of the objective lens. This FPM configuration enables the capturing of the complex scattered field for a 3D sample both in the transmissive mode and the reflective mode. We further show that by combining with the compressive sensing theory, the reconstructed 2D complex scattered field can be used to recover the 3D sample scattering density. This implementation expands the scope of application for FPM and can be beneficial for areas such as tissue imaging and wafer inspection. PMID:27570705

  3. TELESCOPES: Astronomers Overcome 'Aperture Envy'.

    PubMed

    Irion, R

    2000-07-01

    Many users of small telescopes are disturbed by the trend of shutting down smaller instruments in order to help fund bigger and bolder ground-based telescopes. Small telescopes can thrive in the shadow of giant new observatories, they say--but only if they are adapted to specialized projects. Telescopes with apertures of 2 meters or less have unique abilities to monitor broad swaths of the sky and stare at the same objects night after night, sometimes for years; various teams are turning small telescopes into robots, creating networks that span the globe and devoting them to survey projects that big telescopes don't have a prayer of tackling. PMID:17832960

  4. Dual aperture multispectral Schmidt objective

    NASA Technical Reports Server (NTRS)

    Minott, P. O. (Inventor)

    1984-01-01

    A dual aperture, off-axis catadioptic Schmidt objective is described. It is formed by symmetrically aligning two pairs of Schmidt objectives on opposite sides of a common plane (x,z). Each objective has a spherical primary mirror with a spherical focal plane and center of curvature aligned along an optic axis laterally spaced apart from the common plane. A multiprism beamsplitter with buried dichroic layers and a convex entrance and concave exit surfaces optically concentric to the center of curvature may be positioned at the focal plane. The primary mirrors of each objective may be connected rigidly together and may have equal or unequal focal lengths.

  5. Ionospheric effects on synthetic aperture radar at VHF

    SciTech Connect

    Fitzgerald, T.J.

    1997-02-01

    Synthetic aperture radars (SAR) operated from airplanes have been used at VHF because of their enhanced foliage and ground penetration compared to radars operated at UHF. A satellite-borne VHF SAR would have considerable utility but in order to operate with high resolution it would have to use both a large relative bandwidth and a large aperture. The presence of the ionosphere in the propagation path of the radar will cause a deterioration of the imaging because of dispersion over the bandwidth and group path changes in the imaged area over the collection aperture. In this paper we present calculations of the effects of a deterministic ionosphere on SAR imaging for a radar operated with a 100 MHz bandwidth centered at 250 MHz and over an angular aperture of 23{degrees}. The ionosphere induces a point spread function with an approximate half-width of 150 m in the slant-range direction and of 25 m in the cross-range direction compared to the nominal resolution of 1.5 m in both directions.

  6. Resonant Effects in Nanoscale Bowtie Apertures

    NASA Astrophysics Data System (ADS)

    Ding, Li; Qin, Jin; Guo, Songpo; Liu, Tao; Kinzel, Edward; Wang, Liang

    2016-06-01

    Nanoscale bowtie aperture antennas can be used to focus light well below the diffraction limit with extremely high transmission efficiencies. This paper studies the spectral dependence of the transmission through nanoscale bowtie apertures defined in a silver film. A realistic bowtie aperture is numerically modeled using the Finite Difference Time Domain (FDTD) method. Results show that the transmission spectrum is dominated by Fabry-Pérot (F-P) waveguide modes and plasmonic modes. The F-P resonance is sensitive to the thickness of the film and the plasmonic resonant mode is closely related to the gap distance of the bowtie aperture. Both characteristics significantly affect the transmission spectrum. To verify these numerical results, bowtie apertures are FIB milled in a silver film. Experimental transmission measurements agree with simulation data. Based on this result, nanoscale bowtie apertures can be optimized to realize deep sub-wavelength confinement with high transmission efficiency with applications to nanolithography, data storage, and bio-chemical sensing.

  7. DAVINCI a Dilute Aperture Coronagraph

    NASA Astrophysics Data System (ADS)

    Shao, Michael

    2009-01-01

    The motivation for DAVINCI was originally to make use of the technology developed for space interferometers like SIM to build a coronagraph from four 1.1m telescopes that was dramatically lower in cost than a 4 5m filled aperture offaxis coronagraph. Our initial studies through team X have shown this cost savings to be real. But a more careful analysis showed that DAVINCI would have an inner working angle of 35mas a factor of 2 smaller than a 2 lambda/D 4 meter coronagraph or 70m external occulter, resulting in a 10X increase in the number of potential Earth-Clone targets. DAVINCI uses a nulling interferometer as a coronagraph, a nulling interferometer is one the few coronagraph architectures that are compatible with segmented and dilute aperture telescopes. Combined with a post coronagraph wavefront sensor several ultra-demanding tolerances of conventional coronagraphs can be relaxed by factors of 100. The post coronagraph wavefront sensor is also much less affected by local and exozodi background than wavefront sensors that use the science camera as the wavefront sensor. The post coronagraph interferometer is also used on ground based extreme AO coronagraphs, GPI, and P1640.

  8. Synthetic aperture sonar image statistics

    NASA Astrophysics Data System (ADS)

    Johnson, Shawn F.

    Synthetic Aperture Sonar (SAS) systems are capable of producing photograph quality seafloor imagery using a lower frequency than other systems of comparable resolution. However, as with other high-resolution sonar systems, SAS imagery is often characterized by heavy-tailed amplitude distributions which may adversely affect target detection systems. The constant cross-range resolution with respect to range that results from the synthetic aperture formation process provides a unique opportunity to improve our understanding of system and environment interactions, which is essential for accurate performance prediction. This research focused on the impact of multipath contamination and the impact of resolution on image statistics, accomplished through analyses of data collected during at-sea experiments, analytical modeling, and development of numerical simulations. Multipath contamination was shown to have an appreciable impact on image statistics at ranges greater than the water depth and when the levels of the contributing multipath are within 10 dB of the direct path, reducing the image amplitude distribution tails while also degrading image clarity. Image statistics were shown to depend strongly upon both system resolution and orientation to seafloor features such as sand ripples. This work contributes to improving detection systems by aiding understanding of the influences of background (i.e. non-target) image statistics.

  9. Diffraction smoothing aperture for an optical beam

    DOEpatents

    Judd, O'Dean P.; Suydam, Bergen R.

    1976-01-01

    The disclosure is directed to an aperture for an optical beam having an irregular periphery or having perturbations imposed upon the periphery to decrease the diffraction effect caused by the beam passing through the aperture. Such apertures are particularly useful with high power solid state laser systems in that they minimize the problem of self-focusing which frequently destroys expensive components in such systems.

  10. Prototype development of a Geostationary Synthetic Thinned Aperture Radiometer, GeoSTAR

    NASA Technical Reports Server (NTRS)

    Tanner, A. B.; Wilson, W. J.; Kangaslahti, P. P.; Lambrigsten, B. H.; Dinardo, S. J.; Piepmeier, J. R.; Ruf, C. S.; Rogacki, S.; Gross, S. M.; Musko, S.

    2004-01-01

    Preliminary details of a 2-D synthetic aperture radiometer prototype operating from 50 to 55 GHz will be presented. The laboratory prototype is being developed to demonstrate the technologies and system design needed to do millimeter-wave atmospheric soundings with high spatial resolution from Geostationary orbit. The concept is to deploy a large thinned aperture Y-array on a geostationary satellite, and to use aperture synthesis to obtain images of the Earth without the need for a large mechanically scanned antenna. The laboratory prototype consists of a Y-array of 24 horn antennas, MMIC receivers, and a digital cross-correlation sub-system.

  11. High Contrast Imaging with an Arbitrary Aperture: Active Correction of Aperture Discontinuities

    NASA Astrophysics Data System (ADS)

    Pueyo, Laurent; Norman, Colin; Soummer, Remi; Perrin, Marshall; N'Diaye, Mamadou; Choquet, Elodie

    2013-12-01

    We discuss the application of a new method to achieve high-contrast images with Extremely Large Telescopes. Our approach relies on using two sequential Deformable Mirrors to compensate for the large amplitude excursions in the telescope aperture due to secondary support structures and/or segment gaps. In this configuration the parameter landscape of Deformable Mirror Surfaces that yield high contrast Point Spread Functions is not linear, and non-linear methods are needed to find the true minimum in the optimization topology. We solve the highly non-linear Monge-Ampere equation that is the fundamental equation describing the physics of phase induced amplitude modulation. We determine the optimum configuration for our two sequential Deformable Mirror system and show that high-throughput and high contrast solutions can be achieved using realistic surface deformations that are accessible using existing technologies. We name this process Active Compensation of Aperture Discontinuities (ACAD). We quantify the performances of this technique on various ELTs geometries. We illustrate its application when seeking to maintain high contrast in the configuration for which some of the primary mirror's segments might be missing.

  12. Ion mobility spectrometer with virtual aperture grid

    DOEpatents

    Pfeifer, Kent B.; Rumpf, Arthur N.

    2010-11-23

    An ion mobility spectrometer does not require a physical aperture grid to prevent premature ion detector response. The last electrodes adjacent to the ion collector (typically the last four or five) have an electrode pitch that is less than the width of the ion swarm and each of the adjacent electrodes is connected to a source of free charge, thereby providing a virtual aperture grid at the end of the drift region that shields the ion collector from the mirror current of the approaching ion swarm. The virtual aperture grid is less complex in assembly and function and is less sensitive to vibrations than the physical aperture grid.

  13. High-contrast imaging with an arbitrary aperture: Active compensation of aperture discontinuities

    SciTech Connect

    Pueyo, Laurent; Norman, Colin

    2013-06-01

    We present a new method to achieve high-contrast images using segmented and/or on-axis telescopes. Our approach relies on using two sequential deformable mirrors (DMs) to compensate for the large amplitude excursions in the telescope aperture due to secondary support structures and/or segment gaps. In this configuration the parameter landscape of DM surfaces that yield high-contrast point-spread functions is not linear, and nonlinear methods are needed to find the true minimum in the optimization topology. We solve the highly nonlinear Monge-Ampere equation that is the fundamental equation describing the physics of phase-induced amplitude modulation. We determine the optimum configuration for our two sequential DM system and show that high-throughput and high-contrast solutions can be achieved using realistic surface deformations that are accessible using existing technologies. We name this process Active Compensation of Aperture Discontinuities (ACAD). We show that for geometries similar to the James Webb Space Telescope, ACAD can attain at least 10{sup –7} in contrast and an order of magnitude higher for both the future extremely large telescopes and on-axis architectures reminiscent of the Hubble Space Telescope. We show that the converging nonlinear mappings resulting from our DM shapes actually damp near-field diffraction artifacts in the vicinity of the discontinuities. Thus, ACAD actually lowers the chromatic ringing due to diffraction by segment gaps and struts while not amplifying the diffraction at the aperture edges beyond the Fresnel regime. This outer Fresnel ringing can be mitigated by properly designing the optical system. Consequently, ACAD is a true broadband solution to the problem of high-contrast imaging with segmented and/or on-axis apertures. We finally show that once the nonlinear solution is found, fine tuning with linear methods used in wavefront control can be applied to further contrast by another order of magnitude. Generally speaking

  14. Finite-aperture tapered unstable resonator lasers

    NASA Astrophysics Data System (ADS)

    Bedford, Robert George

    The development of high power, high brightness semiconductor lasers is important for applications such as efficient pumping of fiber amplifiers and free space communication. The ability to couple directly into the core of a single-mode fiber can vastly increase the absorption of pump light. Further, the high mode-selectivity provided by unstable resonators accommodates single-mode operation to many times the threshold current level. The objective of this dissertation is to investigate a more efficient semiconductor-based unstable resonator design. The tapered unstable resonator laser consists of a single-mode ridge coupled to a tapered gain region. The ridge, aided by spoiling grooves, provides essential preparation of the fundamental mode, while the taper provides significant amplification and a large output mode. It is shown a laterally finite taper-side mirror (making the laser a "finite-aperture tapered unstable resonator laser") serves to significantly improve differential quantum efficiency. This results in the possibility for higher optical powers while still maintaining single-mode operation. Additionally, the advent of a detuned second order grating allows for a low divergent, quasicircular output beam emitted from the semiconductor surface, easing packaging tolerances, and making two dimensional integrated arrays possible. In this dissertation, theory, design, fabrication, and characterization are presented. Material theory is introduced, reviewing gain, carrier, and temperature effects on field propagation. Coupled-mode and coupled wave theory is reviewed to allow simulation of the passive grating. A numerical model is used to investigate laser design and optimization, and effects of finite-apertures are explored. A microfabrication method is introduced to create the FATURL in InAlGaAs/-InGaAsP/InP material emitting at about 1410 nm. Fabrication consists of photolithography, electron-beam lithography, wet etch and dry etching processes, metal and

  15. 4D Light Field Imaging System Using Programmable Aperture

    NASA Technical Reports Server (NTRS)

    Bae, Youngsam

    2012-01-01

    Complete depth information can be extracted from analyzing all angles of light rays emanated from a source. However, this angular information is lost in a typical 2D imaging system. In order to record this information, a standard stereo imaging system uses two cameras to obtain information from two view angles. Sometimes, more cameras are used to obtain information from more angles. However, a 4D light field imaging technique can achieve this multiple-camera effect through a single-lens camera. Two methods are available for this: one using a microlens array, and the other using a moving aperture. The moving-aperture method can obtain more complete stereo information. The existing literature suggests a modified liquid crystal panel [LC (liquid crystal) panel, similar to ones commonly used in the display industry] to achieve a moving aperture. However, LC panels cannot withstand harsh environments and are not qualified for spaceflight. In this regard, different hardware is proposed for the moving aperture. A digital micromirror device (DMD) will replace the liquid crystal. This will be qualified for harsh environments for the 4D light field imaging. This will enable an imager to record near-complete stereo information. The approach to building a proof-ofconcept is using existing, or slightly modified, off-the-shelf components. An SLR (single-lens reflex) lens system, which typically has a large aperture for fast imaging, will be modified. The lens system will be arranged so that DMD can be integrated. The shape of aperture will be programmed for single-viewpoint imaging, multiple-viewpoint imaging, and coded aperture imaging. The novelty lies in using a DMD instead of a LC panel to move the apertures for 4D light field imaging. The DMD uses reflecting mirrors, so any light transmission lost (which would be expected from the LC panel) will be minimal. Also, the MEMS-based DMD can withstand higher temperature and pressure fluctuation than a LC panel can. Robotics need

  16. Adaptive Full Aperture Wavefront Sensor Study

    NASA Technical Reports Server (NTRS)

    Robinson, William G.

    1997-01-01

    This grant and the work described was in support of a Seven Segment Demonstrator (SSD) and review of wavefront sensing techniques proposed by the Government and Contractors for the Next Generation Space Telescope (NGST) Program. A team developed the SSD concept. For completeness, some of the information included in this report has also been included in the final report of a follow-on contract (H-27657D) entitled "Construction of Prototype Lightweight Mirrors". The original purpose of this GTRI study was to investigate how various wavefront sensing techniques might be most effectively employed with large (greater than 10 meter) aperture space based telescopes used for commercial and scientific purposes. However, due to changes in the scope of the work performed on this grant and in light of the initial studies completed for the NGST program, only a portion of this report addresses wavefront sensing techniques. The wavefront sensing techniques proposed by the Government and Contractors for the NGST were summarized in proposals and briefing materials developed by three study teams including NASA Goddard Space Flight Center, TRW, and Lockheed-Martin. In this report, GTRI reviews these approaches and makes recommendations concerning the approaches. The objectives of the SSD were to demonstrate functionality and performance of a seven segment prototype array of hexagonal mirrors and supporting electromechanical components which address design issues critical to space optics deployed in large space based telescopes for astronomy and for optics used in spaced based optical communications systems. The SSD was intended to demonstrate technologies which can support the following capabilities: Transportation in dense packaging to existing launcher payload envelopes, then deployable on orbit to form a space telescope with large aperture. Provide very large (greater than 10 meters) primary reflectors of low mass and cost. Demonstrate the capability to form a segmented primary or

  17. Multifocal interferometric synthetic aperture microscopy

    PubMed Central

    Xu, Yang; Chng, Xiong Kai Benjamin; Adie, Steven G.; Boppart, Stephen A.; Scott Carney, P.

    2014-01-01

    There is an inherent trade-off between transverse resolution and depth of field (DOF) in optical coherence tomography (OCT) which becomes a limiting factor for certain applications. Multifocal OCT and interferometric synthetic aperture microscopy (ISAM) each provide a distinct solution to the trade-off through modification to the experiment or via post-processing, respectively. In this paper, we have solved the inverse problem of multifocal OCT and present a general algorithm for combining multiple ISAM datasets. Multifocal ISAM (MISAM) uses a regularized combination of the resampled datasets to bring advantages of both multifocal OCT and ISAM to achieve optimal transverse resolution, extended effective DOF and improved signal-to-noise ratio. We present theory, simulation and experimental results. PMID:24977909

  18. Multifocal interferometric synthetic aperture microscopy.

    PubMed

    Xu, Yang; Chng, Xiong Kai Benjamin; Adie, Steven G; Boppart, Stephen A; Carney, P Scott

    2014-06-30

    There is an inherent trade-off between transverse resolution and depth of field (DOF) in optical coherence tomography (OCT) which becomes a limiting factor for certain applications. Multifocal OCT and interferometric synthetic aperture microscopy (ISAM) each provide a distinct solution to the trade-off through modification to the experiment or via post-processing, respectively. In this paper, we have solved the inverse problem of multifocal OCT and present a general algorithm for combining multiple ISAM datasets. Multifocal ISAM (MISAM) uses a regularized combination of the resampled datasets to bring advantages of both multifocal OCT and ISAM to achieve optimal transverse resolution, extended effective DOF and improved signal-to-noise ratio. We present theory, simulation and experimental results. PMID:24977909

  19. Synthetic aperture interferometry: error analysis

    SciTech Connect

    Biswas, Amiya; Coupland, Jeremy

    2010-07-10

    Synthetic aperture interferometry (SAI) is a novel way of testing aspherics and has a potential for in-process measurement of aspherics [Appl. Opt.42, 701 (2003)].APOPAI0003-693510.1364/AO.42.000701 A method to measure steep aspherics using the SAI technique has been previously reported [Appl. Opt.47, 1705 (2008)].APOPAI0003-693510.1364/AO.47.001705 Here we investigate the computation of surface form using the SAI technique in different configurations and discuss the computational errors. A two-pass measurement strategy is proposed to reduce the computational errors, and a detailed investigation is carried out to determine the effect of alignment errors on the measurement process.

  20. A novel approach to correct the coded aperture misalignment for fast neutron imaging

    NASA Astrophysics Data System (ADS)

    Zhang, F. N.; Hu, H. S.; Zhang, T. K.; Jia, Q. G.; Wang, D. M.; Jia, J.

    2015-12-01

    Aperture alignment is crucial for the diagnosis of neutron imaging because it has significant impact on the coding imaging and the understanding of the neutron source. In our previous studies on the neutron imaging system with coded aperture for large field of view, "residual watermark," certain extra information that overlies reconstructed image and has nothing to do with the source is discovered if the peak normalization is employed in genetic algorithms (GA) to reconstruct the source image. Some studies on basic properties of residual watermark indicate that the residual watermark can characterize coded aperture and can thus be used to determine the location of coded aperture relative to the system axis. In this paper, we have further analyzed the essential conditions for the existence of residual watermark and the requirements of the reconstruction algorithm for the emergence of residual watermark. A gamma coded imaging experiment has been performed to verify the existence of residual watermark. Based on the residual watermark, a correction method for the aperture misalignment has been studied. A multiple linear regression model of the position of coded aperture axis, the position of residual watermark center, and the gray barycenter of neutron source with twenty training samples has been set up. Using the regression model and verification samples, we have found the position of the coded aperture axis relative to the system axis with an accuracy of approximately 20 μm. Conclusively, a novel approach has been established to correct the coded aperture misalignment for fast neutron coded imaging.

  1. A novel approach to correct the coded aperture misalignment for fast neutron imaging

    SciTech Connect

    Zhang, F. N.; Hu, H. S. Wang, D. M.; Jia, J.; Zhang, T. K.; Jia, Q. G.

    2015-12-15

    Aperture alignment is crucial for the diagnosis of neutron imaging because it has significant impact on the coding imaging and the understanding of the neutron source. In our previous studies on the neutron imaging system with coded aperture for large field of view, “residual watermark,” certain extra information that overlies reconstructed image and has nothing to do with the source is discovered if the peak normalization is employed in genetic algorithms (GA) to reconstruct the source image. Some studies on basic properties of residual watermark indicate that the residual watermark can characterize coded aperture and can thus be used to determine the location of coded aperture relative to the system axis. In this paper, we have further analyzed the essential conditions for the existence of residual watermark and the requirements of the reconstruction algorithm for the emergence of residual watermark. A gamma coded imaging experiment has been performed to verify the existence of residual watermark. Based on the residual watermark, a correction method for the aperture misalignment has been studied. A multiple linear regression model of the position of coded aperture axis, the position of residual watermark center, and the gray barycenter of neutron source with twenty training samples has been set up. Using the regression model and verification samples, we have found the position of the coded aperture axis relative to the system axis with an accuracy of approximately 20 μm. Conclusively, a novel approach has been established to correct the coded aperture misalignment for fast neutron coded imaging.

  2. A novel approach to correct the coded aperture misalignment for fast neutron imaging.

    PubMed

    Zhang, F N; Hu, H S; Zhang, T K; Jia, Q G; Wang, D M; Jia, J

    2015-12-01

    Aperture alignment is crucial for the diagnosis of neutron imaging because it has significant impact on the coding imaging and the understanding of the neutron source. In our previous studies on the neutron imaging system with coded aperture for large field of view, "residual watermark," certain extra information that overlies reconstructed image and has nothing to do with the source is discovered if the peak normalization is employed in genetic algorithms (GA) to reconstruct the source image. Some studies on basic properties of residual watermark indicate that the residual watermark can characterize coded aperture and can thus be used to determine the location of coded aperture relative to the system axis. In this paper, we have further analyzed the essential conditions for the existence of residual watermark and the requirements of the reconstruction algorithm for the emergence of residual watermark. A gamma coded imaging experiment has been performed to verify the existence of residual watermark. Based on the residual watermark, a correction method for the aperture misalignment has been studied. A multiple linear regression model of the position of coded aperture axis, the position of residual watermark center, and the gray barycenter of neutron source with twenty training samples has been set up. Using the regression model and verification samples, we have found the position of the coded aperture axis relative to the system axis with an accuracy of approximately 20 μm. Conclusively, a novel approach has been established to correct the coded aperture misalignment for fast neutron coded imaging. PMID:26724035

  3. Error analysis of sub-aperture stitching interferometry

    NASA Astrophysics Data System (ADS)

    Jia, Xin; Xu, Fuchao; Xie, Weimin; Xing, Tingwen

    2012-10-01

    Large-aperture optical elements are widely employed in high-power laser system, astronomy, and outer-space technology. Sub-aperture stitching is an effective way to extend the lateral and vertical dynamic range of a conventional interferometer. With the aim to provide the accuracy of equipment, this paper simulates the arithmetic to analyze the errors. The Selection of stitching mode and setting of the number of subaperture is given. According to the programmed algorithms simulation stitching is performed for testing the algorithm. In this paper, based on the Matlab we simulate the arithmetic of Sub-aperture stitching. The sub-aperture stitching method can also be used to test the free formed surface. The freeformed surface is created by Zernike polynomials. The accuracy has relationship with the errors of tilting, positioning. Through the stitching the medium spatial frequency of the surface can be tested. The results of errors analysis by means of Matlab are shown that how the tilting and positioning errors to influence the testing accuracy. The analysis of errors can also be used in other interferometer systems.

  4. Synthetic tracked aperture ultrasound imaging: design, simulation, and experimental evaluation.

    PubMed

    Zhang, Haichong K; Cheng, Alexis; Bottenus, Nick; Guo, Xiaoyu; Trahey, Gregg E; Boctor, Emad M

    2016-04-01

    Ultrasonography is a widely used imaging modality to visualize anatomical structures due to its low cost and ease of use; however, it is challenging to acquire acceptable image quality in deep tissue. Synthetic aperture (SA) is a technique used to increase image resolution by synthesizing information from multiple subapertures, but the resolution improvement is limited by the physical size of the array transducer. With a large F-number, it is difficult to achieve high resolution in deep regions without extending the effective aperture size. We propose a method to extend the available aperture size for SA-called synthetic tracked aperture ultrasound (STRATUS) imaging-by sweeping an ultrasound transducer while tracking its orientation and location. Tracking information of the ultrasound probe is used to synthesize the signals received at different positions. Considering the practical implementation, we estimated the effect of tracking and ultrasound calibration error to the quality of the final beamformed image through simulation. In addition, to experimentally validate this approach, a 6 degree-of-freedom robot arm was used as a mechanical tracker to hold an ultrasound transducer and to apply in-plane lateral translational motion. Results indicate that STRATUS imaging with robotic tracking has the potential to improve ultrasound image quality. PMID:27088108

  5. A systematic review of aperture shapes

    NASA Astrophysics Data System (ADS)

    Schultz, A. B.; Frazier, T. V.

    The paper discusses the application of apodization to reflecting telescopes. The diffraction pattern of a telescope, which is the image of a star, can be changed considerably by using different aperture shapes in combination with appropriately shaped occulting masks on the optical axis. Aperture shapes studied were the circular, square, and hexagonal. Polaris (α-UMin) was used as the test system.

  6. New military uses for synthetic aperture radar (SAR)

    NASA Astrophysics Data System (ADS)

    Reamer, Richard E.; Stockton, Wayne; Stromfors, Richard D.

    1993-02-01

    Loral Defense Systems-Arizona, holder of the original patent for the invention of Synthetic Aperture Radar (SAR), developed SAR to meet the military's need for an all-weather, day/night sensor that could produce high quality reconnaissance imagery in adverse weather and restricted visibility conditions. These features, and the ability to image large areas with fine resolution in a relatively short period of time make this sensor useful for many military applications. To date, however, SARs for military use have been hampered by the fact that they've been large, complex, and expensive. Additionally, they have been mounted on special purpose, single mission aircraft which are costly to operate. That situation has changed. A small, modular SAR, called Miniature Synthetic Aperture Radar (MSAR) developed by Loral can be mounted with relative ease on Unmanned Aerial Vehicles (UAV) or on multi-mission aircraft such as the F-16, F/A-18, or on the F-14.

  7. Micro Ring Grating Spectrometer with Adjustable Aperture

    NASA Technical Reports Server (NTRS)

    Park, Yeonjoon (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor); Choi, Sang H. (Inventor)

    2012-01-01

    A spectrometer includes a micro-ring grating device having coaxially-aligned ring gratings for diffracting incident light onto a target focal point, a detection device for detecting light intensity, one or more actuators, and an adjustable aperture device defining a circular aperture. The aperture circumscribes a target focal point, and directs a light to the detection device. The aperture device is selectively adjustable using the actuators to select a portion of a frequency band for transmission to the detection device. A method of detecting intensity of a selected band of incident light includes directing incident light onto coaxially-aligned ring gratings of a micro-ring grating device, and diffracting the selected band onto a target focal point using the ring gratings. The method includes using an actuator to adjust an aperture device and pass a selected portion of the frequency band to a detection device for measuring the intensity of the selected portion.

  8. Variable aperture collimator for high energy radiation

    DOEpatents

    Hill, Ronald A.

    1984-05-22

    An apparatus is disclosed providing a variable aperture energy beam collimator. A plurality of beam opaque blocks are in sliding interface edge contact to form a variable aperture. The blocks may be offset at the apex angle to provide a non-equilateral aperture. A plurality of collimator block assemblies may be employed for providing a channel defining a collimated beam. Adjacent assemblies are inverted front-to-back with respect to one another for preventing noncollimated energy from emerging from the apparatus. An adjustment mechanism comprises a cable attached to at least one block and a hand wheel mechanism for operating the cable. The blocks are supported by guide rods engaging slide brackets on the blocks. The guide rods are pivotally connected at each end to intermediate actuators supported on rotatable shafts to change the shape of the aperture. A divergent collimated beam may be obtained by adjusting the apertures of adjacent stages to be unequal.

  9. Fresnel Lenses for Wide-Aperture Optical Receivers

    NASA Technical Reports Server (NTRS)

    Hemmati, Hamid

    2004-01-01

    Wide-aperture receivers for freespace optical communication systems would utilize Fresnel lenses instead of conventional telescope lenses, according to a proposal. Fresnel lenses weigh and cost much less than conventional lenses having equal aperture widths. Plastic Fresnel lenses are commercially available in diameters up to 5 m large enough to satisfy requirements for aperture widths of the order of meters for collecting sufficient light in typical long-distance free-space optical communication systems. Fresnel lenses are not yet suitable for high-quality diffraction-limited imaging, especially in polychromatic light. However, optical communication systems utilize monochromatic light, and there is no requirement for high-quality imaging; instead, the basic requirement for an optical receiver is to collect the incoming monochromatic light over a wide aperture and concentrate the light onto a photodetector. Because of lens aberrations and diffraction, the light passing through any lens is focused to a blur circle rather than to a point. Calculations for some representative cases of wide-aperture non-diffraction-limited Fresnel lenses have shown that it should be possible to attain blur-circle diameters of less than 2 mm. Preferably, the blur-circle diameter should match the width of the photodetector. For most high-bandwidth communication applications, the required photodetector diameters would be about 1 mm. In a less-preferable case in which the blur circle was wider than a single photodetector, it would be possible to occupy the blur circle with an array of photodetectors. As an alternative to using a single large Fresnel lens, one could use an array of somewhat smaller lenses to synthesize the equivalent aperture area. Such a configuration might be preferable in a case in which a single Fresnel lens of the requisite large size would be impractical to manufacture, and the blur circle could not be made small enough. For example one could construct a square array

  10. 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 light—via the C-shaped aperture—while providing a nanometric hotspot determined by the sharpness of the tip itself. PMID:23676841

  11. Planetary Remote Sensing Science Enabled by MIDAS (Multiple Instrument Distributed Aperture Sensor)

    NASA Technical Reports Server (NTRS)

    Pitman, Joe; Duncan, Alan; Stubbs, David; Sigler, Robert; Kendrick, Rick; Chilese, John; Lipps, Jere; Manga, Mike; Graham, James; dePater, Imke

    2004-01-01

    The science capabilities and features of an innovative and revolutionary approach to remote sensing imaging systems, aimed at increasing the return on future space science missions many fold, are described. Our concept, called Multiple Instrument Distributed Aperture Sensor (MIDAS), provides a large-aperture, wide-field, diffraction-limited telescope at a fraction of the cost, mass and volume of conventional telescopes, by integrating optical interferometry technologies into a mature multiple aperture array concept that addresses one of the highest needs for advancing future planetary science remote sensing.

  12. Buckling-induced retraction of spherical shells: A study on the shape of aperture

    NASA Astrophysics Data System (ADS)

    Lin, Sen; Xie, Yi Min; Li, Qing; Huang, Xiaodong; Zhou, Shiwei

    2015-06-01

    Buckling of soft matter is ubiquitous in nature and has attracted increasing interest recently. This paper studies the retractile behaviors of a spherical shell perforated by sophisticated apertures, attributed to the buckling-induced large deformation. The buckling patterns observed in experiments were reproduced in computational modeling by imposing velocity-controlled loads and eigenmode-affine geometric imperfection. It was found that the buckling behaviors were topologically sensitive with respect to the shape of dimple (aperture). The shell with rounded-square apertures had the maximal volume retraction ratio as well as the lowest energy consumption. An effective experimental procedure was established and the simulation results were validated in this study.

  13. The impact of different aperture distribution models and critical stress criteria on equivalent permeability in fractured rocks

    NASA Astrophysics Data System (ADS)

    Bisdom, Kevin; Bertotti, Giovanni; Nick, Hamidreza M.

    2016-05-01

    Predicting equivalent permeability in fractured reservoirs requires an understanding of the fracture network geometry and apertures. There are different methods for defining aperture, based on outcrop observations (power law scaling), fundamental mechanics (sublinear length-aperture scaling), and experiments (Barton-Bandis conductive shearing). Each method predicts heterogeneous apertures, even along single fractures (i.e., intrafracture variations), but most fractured reservoir models imply constant apertures for single fractures. We compare the relative differences in aperture and permeability predicted by three aperture methods, where permeability is modeled in explicit fracture networks with coupled fracture-matrix flow. Aperture varies along single fractures, and geomechanical relations are used to identify which fractures are critically stressed. The aperture models are applied to real-world large-scale fracture networks. (Sub)linear length scaling predicts the largest average aperture and equivalent permeability. Barton-Bandis aperture is smaller, predicting on average a sixfold increase compared to matrix permeability. Application of critical stress criteria results in a decrease in the fraction of open fractures. For the applied stress conditions, Coulomb predicts that 50% of the network is critically stressed, compared to 80% for Barton-Bandis peak shear. The impact of the fracture network on equivalent permeability depends on the matrix hydraulic properties, as in a low-permeable matrix, intrafracture connectivity, i.e., the opening along a single fracture, controls equivalent permeability, whereas for a more permeable matrix, absolute apertures have a larger impact. Quantification of fracture flow regimes using only the ratio of fracture versus matrix permeability is insufficient, as these regimes also depend on aperture variations within fractures.

  14. Smov Fos/fgs Fine Alignment (small Apertures)

    NASA Astrophysics Data System (ADS)

    Kinney, Anne

    1994-01-01

    The goal is to measure the precise aperture locations and sizes. The analysis of the observations will result in database changes to the table of aperture locations. Precise aperture locations will be determined by performing a raster step and dwell sequence in the FOS apertures along the edges of the apertures. An aperture map is required at each step of the dwell sequence. This test has to be conducted for both the RED and BLUE detectors.

  15. Smov Fos/fgs Fine Alignment (small Apertures) Revitalized

    NASA Astrophysics Data System (ADS)

    Kinney, Anne

    1994-01-01

    The goal is to measure the precise aperture locations and sizes. The analysis of the observations will result in database changes to the table of aperture locations. Precise aperture locations will be determined by performing a raster step and dwell sequence in the FOS apertures along the edges of the apertures. An aperture map is required at each step of the dwell sequence. This test has to be conducted for both the RED and BLUE detectors.

  16. Zircon U-Pb and trace element zoning characteristics in an anatectic granulite domain: Insights from LASS-ICP-MS depth profiling

    NASA Astrophysics Data System (ADS)

    Marsh, Jeffrey H.; Stockli, Daniel F.

    2015-12-01

    Understanding the geochemical characteristics of metamorphic zircon, and how they may be modified by recrystallization processes, is fundamental to defining the timescales of tectonic processes affecting continental lithosphere. We utilize laser ablation split-stream (LASS)-ICP-MS depth-profiling analysis to obtain a continuous rim-to-core record of the U-Pb ages and trace-element composition preserved within variably recrystallized zircon from different rock types within a well-studied granulite domain in the western Grenville Province, Canada. Detailed analysis of the depth-resolved signal enables definition of chemically distinct (homogeneous) internal domains and heterogeneous intervening zones that can generally be correlated with textural features observed in CL. Three age populations have been distinguished within the ~ 35 μm deep profiles that correlate well with the established timing of protolith formation, granulite-facies metamorphism, and amphibolite-facies shearing, respectively. The U-Pb isotopic system and Th/U ratios in much of the crystal interiors have undergone considerable modification, as evidenced by a linear correlation between 207Pb/206Pb age and Th/U ratio. Interior and rim domains commonly contain blurred or faded oscillatory zoning patterns, suggesting that solid-state recrystallization is at least partially responsible for the modified U-Th-Pb composition. A number of systematic trends in trace element composition are also observed between interior domains and recrystallized rims, including 1) decreased Th/U (to ~ 0.1), 2) tighter clustering of Hf concentrations, 3) decreased total REE, 4) unchanged Eu anomalies, and 5) a widened spread of HREE enrichment values (YbN/GdN). Both YbN/GdN vs. Th/U and U/Ce vs. Th plots show increasing degree of compositional differentiation from protolith zircon as a function of metamorphic reworking processes (i.e. sample type). The transition zones between interior and rim domains exhibit textural

  17. Longwave infrared (LWIR) coded aperture dispersive spectrometer.

    PubMed

    Fernandez, C; Guenther, B D; Gehm, M E; Brady, D J; Sullivan, M E

    2007-04-30

    We describe a static aperture-coded, dispersive longwave infrared (LWIR) spectrometer that uses a microbolometer array at the detector plane. The two-dimensional aperture code is based on a row-doubled Hadamard mask with transmissive and opaque openings. The independent column code nature of the matrix makes for a mathematically well-defined pattern that spatially and spectrally maps the source information to the detector plane. Post-processing techniques on the data provide spectral estimates of the source. Comparative experimental results between a slit and coded aperture for emission spectroscopy from a CO(2) laser are demonstrated. PMID:19532832

  18. Scalar wave diffraction from a circular aperture

    SciTech Connect

    Cerjan, C.

    1995-01-25

    The scalar wave theory is used to evaluate the expected diffraction patterns from a circular aperture. The standard far-field Kirchhoff approximation is compared to the exact result expressed in terms of oblate spheroidal harmonics. Deviations from an expanding spherical wave are calculated for circular aperture radius and the incident beam wavelength using suggested values for a recently proposed point diffractin interferometer. The Kirchhoff approximation is increasingly reliable in the far-field limit as the aperture radius is increased, although significant errors in amplitude and phase persist.

  19. Three dimensional digital holographic aperture synthesis.

    PubMed

    Crouch, Stephen; Kaylor, Brant M; Barber, Zeb W; Reibel, Randy R

    2015-09-01

    Aperture synthesis techniques are applied to temporally and spatially diverse digital holograms recorded with a fast focal-plane array. Because the technique fully resolves the downrange dimension using wide-bandwidth FMCW linear-chirp waveforms, extremely high resolution three dimensional (3D) images can be obtained even at very long standoff ranges. This allows excellent 3D image formation even when targets have significant structure or discontinuities, which are typically poorly rendered with multi-baseline synthetic aperture ladar or multi-wavelength holographic aperture ladar approaches. The background for the system is described and system performance is demonstrated through both simulation and experiments. PMID:26368474

  20. The Application of Aperture Synthesis to the Remote Sensing of Sea Surface Salinity From Space

    NASA Technical Reports Server (NTRS)

    LeVine, David M.

    1998-01-01

    Sea surface salinity is measured optimally at the long wavelength end of the microwave spectrum in order to maximize radiometric sensitivity to changes in salinity. Long wavelengths (e.g. L-band) mean large antennas in space, and because of the technological challenge associated with putting large scanning antennas in orbit, no system currently exists to measure salinity. Aperture synthesis is an interferometric technique to make deployment of large antenna apertures in space feasible. It uses pairs of small antennas and signal processing to achieve the resolution of a single large aperture. Aperture synthesis has been demonstrated successfully for remote sensing by the aircraft prototype radiometer, ESTAR. ESTAR is an L-band instrument which employs aperture synthesis in the cross track dimension. Recent measurements with ESTAR of the fresh water outflow from the Delaware River are in good agreement (about 1 psu) with shipboard thermosalinograph measurements. Synthetic aperture radiometers are currently being developed for remote sensing from space. HYDROSTAR is an instrument for remote sensing from space based on the design of ESTAR. It employs aperture synthesis in one dimension and is being proposed as a pathfinder instrument to make global maps of soil moisture and sea surface salinity and to demonstrate the feasibility of aperture synthesis for remote sensing from space. Instruments which use remote sensing in two dimensions are currently being developed by the European Space Agency. These instruments include additional channels (frequencies and polarizations) and may be able to achieve radiometric sensitivity and spatial resolution to meet the diverse needs of the coastal zone and open ocean oceanographic communities.

  1. An aperture-matched compact range feed horn design

    NASA Technical Reports Server (NTRS)

    Heedy, D. J.; Burnside, W. D.

    1985-01-01

    The moment method and the uniform geometrical theory of diffraction are used to obtain two separate solutions for the E-plane far field pattern of an aperture-matched horn antenna. This particular horn antenna consists of a standard pyramidal horn with the following modifications: a rolled edge section attached to the aperture edges and a curved throat section. The resulting geometry provides significantly better performance in terms of the pattern, impedance, and frequency characteristics than normally obtainable. The moment method is used to calculate the E-plane pattern and voltage standing-wave ratio (VSWR) of the antenna. However, at higher frequencies, the moment method requires large amounts of computation time. On the other hand, the uniform geometrical theory of diffraction provides a quick and efficient high frequency solution for the E-plane field pattern. This procedure has been successfully applied to design a compact range feed horn.

  2. A Computational Model for Aperture Control in Reach-to-Grasp Movement Based on Predictive Variability

    PubMed Central

    Takemura, Naohiro; Fukui, Takao; Inui, Toshio

    2015-01-01

    In human reach-to-grasp movement, visual occlusion of a target object leads to a larger peak grip aperture compared to conditions where online vision is available. However, no previous computational and neural network models for reach-to-grasp movement explain the mechanism of this effect. We simulated the effect of online vision on the reach-to-grasp movement by proposing a computational control model based on the hypothesis that the grip aperture is controlled to compensate for both motor variability and sensory uncertainty. In this model, the aperture is formed to achieve a target aperture size that is sufficiently large to accommodate the actual target; it also includes a margin to ensure proper grasping despite sensory and motor variability. To this end, the model considers: (i) the variability of the grip aperture, which is predicted by the Kalman filter, and (ii) the uncertainty of the object size, which is affected by visual noise. Using this model, we simulated experiments in which the effect of the duration of visual occlusion was investigated. The simulation replicated the experimental result wherein the peak grip aperture increased when the target object was occluded, especially in the early phase of the movement. Both predicted motor variability and sensory uncertainty play important roles in the online visuomotor process responsible for grip aperture control. PMID:26696874

  3. Experimental determination of the coefficients of the hydraulic resistance of apertures in the rotary disks

    NASA Astrophysics Data System (ADS)

    Shvets, I. T.; Dyban, Ye. P.; Selyavin, G. F.; Stradomskiy, M. V.

    1988-01-01

    Following are some conclusions reached in the determination of the haydraulic resistance of apertures in rotary disks: (1) rotation of disk exerts a substantial influence on condition of course of air through apertures. In the large ratios of the velocity of the rotation of the mean flow rate in the aperture (order u/c = 2.5) the value of the coefficient of flow rate for the apertures with the sharp entering edges decreases approximately 6 times; (2) with sufficient high u/c (more than 4) effect of form of entering edges it is possible not to consider; (3) rounding of trailing edges virtually does not have effect on conditions of air flow through apertures in rotary disks; (4) coefficient of flow rate of apertures of square form investigated in work is close to coefficient of expenditure of cylindrical channels (with identical hydraulic radii); (5) relative depth of aperture in the range of relations 0.96 less than l/d less than 6.04 virtually does not have effect on dependence of value of coefficient of flow rate from rotation; (6) on the basis of analysis of experimental data in work empirical dependence of coefficients of flow rate and hydraulic resistance on parameters K and K, are obtained. The ratios indicated are valid for the disk, which rotates in the housing with the value relative to the axial clearance between the disk and the housing of more than 1.5.

  4. Realization of a video-rate distributed aperture millimeter-wave imaging system using optical upconversion

    NASA Astrophysics Data System (ADS)

    Schuetz, Christopher; Martin, Richard; Dillon, Thomas; Yao, Peng; Mackrides, Daniel; Harrity, Charles; Zablocki, Alicia; Shreve, Kevin; Bonnett, James; Curt, Petersen; Prather, Dennis

    2013-05-01

    Passive imaging using millimeter waves (mmWs) has many advantages and applications in the defense and security markets. All terrestrial bodies emit mmW radiation and these wavelengths are able to penetrate smoke, fog/clouds/marine layers, and even clothing. One primary obstacle to imaging in this spectrum is that longer wavelengths require larger apertures to achieve the resolutions desired for many applications. Accordingly, lens-based focal plane systems and scanning systems tend to require large aperture optics, which increase the achievable size and weight of such systems to beyond what can be supported by many applications. To overcome this limitation, a distributed aperture detection scheme is used in which the effective aperture size can be increased without the associated volumetric increase in imager size. This distributed aperture system is realized through conversion of the received mmW energy into sidebands on an optical carrier. This conversion serves, in essence, to scale the mmW sparse aperture array signals onto a complementary optical array. The side bands are subsequently stripped from the optical carrier and recombined to provide a real time snapshot of the mmW signal. Using this technique, we have constructed a real-time, video-rate imager operating at 75 GHz. A distributed aperture consisting of 220 upconversion channels is used to realize 2.5k pixels with passive sensitivity. Details of the construction and operation of this imager as well as field testing results will be presented herein.

  5. Shaped Apertures in Photoresist Films Enhance the Lifetime and Mechanical Stability of Suspended Lipid Bilayers

    PubMed Central

    Kalsi, Sumit; Powl, Andrew M.; Wallace, B.A.; Morgan, Hywel; de Planque, Maurits R.R.

    2014-01-01

    Planar lipid bilayers suspended in apertures provide a controlled environment for ion channel studies. However, short lifetimes and poor mechanical stability of suspended bilayers limit the experimental throughput of bilayer electrophysiology experiments. Although bilayers are more stable in smaller apertures, ion channel incorporation through vesicle fusion with the suspended bilayer becomes increasingly difficult. In an alternative bilayer stabilization approach, we have developed shaped apertures in SU8 photoresist that have tapered sidewalls and a minimum diameter between 60 and 100 μm. Bilayers formed at the thin tip of these shaped apertures, either with the painting or the folding method, display drastically increased lifetimes, typically >20 h, and mechanical stability, being able to withstand extensive perturbation of the buffer solution. Single-channel electrical recordings of the peptide alamethicin and of the proteoliposome-delivered potassium channel KcsA demonstrate channel conductance with low noise, made possible by the small capacitance of the 50 μm thick SU8 septum, which is only thinned around the aperture, and unimpeded proteoliposome fusion, enabled by the large aperture diameter. We anticipate that these shaped apertures with micrometer edge thickness can substantially enhance the throughput of channel characterization by bilayer lipid membrane electrophysiology, especially in combination with automated parallel bilayer platforms. PMID:24739164

  6. Synthetic aperture elastography: a GPU based approach

    NASA Astrophysics Data System (ADS)

    Verma, Prashant; Doyley, Marvin M.

    2014-03-01

    Synthetic aperture (SA) ultrasound imaging system produces highly accurate axial and lateral displacement estimates; however, low frame rates and large data volumes can hamper its clinical use. This paper describes a real-time SA imaging based ultrasound elastography system that we have recently developed to overcome this limitation. In this system, we implemented both beamforming and 2D cross-correlation echo tracking on Nvidia GTX 480 graphics processing unit (GPU). We used one thread per pixel for beamforming; whereas, one block per pixel was used for echo tracking. We compared the quality of elastograms computed with our real-time system relative to those computed using our standard single threaded elastographic imaging methodology. In all studies, we used conventional measures of image quality such as elastographic signal to noise ratio (SNRe). Specifically, SNRe of axial and lateral strain elastograms computed with real-time system were 36 dB and 23 dB, respectively, which was numerically equal to those computed with our standard approach. We achieved a frame rate of 6 frames per second using our GPU based approach for 16 transmits and kernel size of 60 × 60 pixels, which is 400 times faster than that achieved using our standard protocol.

  7. Synthetic Aperture Radar Missions Study Report

    NASA Technical Reports Server (NTRS)

    Bard, S.

    2000-01-01

    This report reviews the history of the LightSAR project and summarizes actions the agency can undertake to support industry-led efforts to develop an operational synthetic aperture radar (SAR) capability in the United States.

  8. Contour-Mapping Synthetic-Aperture Radar

    NASA Technical Reports Server (NTRS)

    Goldstein, R. M.; Caro, E. R.; Wu, C.

    1985-01-01

    Airborne two-antenna synthetic-aperture-radar (SAR) interferometric system provides data processed to yield terrain elevation as well as reflectedintensity information. Relative altitudes of terrain points measured to within error of approximately 25 m.

  9. Optical Transmission Properties of Dielectric Aperture Arrays

    NASA Astrophysics Data System (ADS)

    Yang, Tao

    Optical detection devices such as optical biosensors and optical spectrometers are widely used in many applications for the functions of measurements, inspections and analysis. Due to the large dimension of prisms and gratings, the traditional optical devices normally occupy a large space with complicated components. Since cheaper and smaller optical devices are always in demand, miniaturization has been kept going for years. Thanks to recent fabrication advances, nanophotonic devices such as semiconductor laser chips have been growing in number and diversity. However, the optical biosensor chips and the optical spectrometer chips are seldom reported in the literature. For the reason of improving system integration, the study of ultra-compact, low-cost, high-performance and easy-alignment optical biosensors and optical spectrometers are imperative. This thesis is an endeavor in these two subjects and will present our research work on studying the optical transmission properties of dielectric aperture arrays and developing new optical biosensors and optical spectrometers. The first half of the thesis demonstrates that the optical phase shift associated with the surface plasmon (SP) assisted extraordinary optical transmission (EOT) in nano-hole arrays fabricated in a metal film has a strong dependence on the material refractive index value in close proximity to the holes. A novel refractive index sensor based on detecting the EOT phase shift is proposed by building a model. This device readily provides a 2-D biosensor array platform for non-labeled real-time detection of a variety of organic and biological molecules in a sensor chip format, which leads to a high packing density, minimal analyte volumes, and a large number of parallel channels while facilitating high resolution imaging and supporting a large space-bandwidth product (SBP). Simulation (FDTD Solutions, Lumerical Solutions Inc) results indicate an achievable sensitivity limit of 4.37x10-9 refractive index

  10. High contrast imaging with an arbitrary aperture: active correction of aperture discontinuities: fundamental limits and practical trade- offs

    NASA Astrophysics Data System (ADS)

    Pueyo, Laurent; Norman, Colin; Soummer, Rémi; Perrin, Marshall; N'Diaye, Mamadou; Choquet, Élodie; Hoffmann, Jordan; Carlotti, Alexis; Mawet, Dimitri

    2014-08-01

    We present a new method to achieve high-contrast images using segmented and/or on-axis telescopes. Our approach relies on using two sequential Deformable Mirrors to compensate for the large amplitude excursions in the telescope aperture due to secondary support structures and / or segment gaps. We solve the highly non-linear Monge-Ampere equation that is the fundamental equation describing the physics of phase induced amplitude modulation. We determine the optimum configuration for our two sequential Deformable Mirror system and show that high-throughput and high contrast solutions can be achieved using realistic surface deformations that are accessible using existing technologies. We name this process Active Compensation of Aperture Discontinuities (ACAD). We show that for geometries similar to JWST, ACAD can attain at least 10-7 in contrast and an order of magnitude higher for future Extremely Large Telescopes, even when the pupil features a "missing segment" . Because the converging non-linear mappings resulting from our Deformable Mirror shapes damps near-field diffraction artifacts in the vicinity of the discontinuities this solution is particularly appealing in terms of spectral bandwidth. We present preliminary results that illustrate the performances of ACAD in the presence of diffraction for apertures for with secondary support structures of varying width and argue that the ultimate contrast achieved can by combining ACAD with modern wavefront control algorithms.

  11. Coded apertures for efficient pyroelectric motion tracking.

    PubMed

    Gopinathan, U; Brady, D; Pitsianis, N

    2003-09-01

    Coded apertures may be designed to modulate the visibility between source and measurement spaces such that the position of a source among N resolution cells may be discriminated using logarithm of N measurements. We use coded apertures as reference structures in a pyroelectric motion tracking system. This sensor system is capable of detecting source motion in one of the 15 cells uniformly distributed over a 1.6m x 1.6m domain using 4 pyroelectric detectors. PMID:19466102

  12. Motion-adaptive compressive coded apertures

    NASA Astrophysics Data System (ADS)

    Harmany, Zachary T.; Oh, Albert; Marcia, Roummel; Willett, Rebecca

    2011-09-01

    This paper describes an adaptive compressive coded aperture imaging system for video based on motion-compensated video sparsity models. In particular, motion models based on optical flow and sparse deviations from optical flow (i.e. salient motion) can be used to (a) predict future video frames from previous compressive measurements, (b) perform reconstruction using efficient online convex programming techniques, and (c) adapt the coded aperture to yield higher reconstruction fidelity in the vicinity of this salient motion.

  13. Resonant Effects in Nanoscale Bowtie Apertures

    PubMed Central

    Ding, Li; Qin, Jin; Guo, Songpo; Liu, Tao; Kinzel, Edward; Wang, Liang

    2016-01-01

    Nanoscale bowtie aperture antennas can be used to focus light well below the diffraction limit with extremely high transmission efficiencies. This paper studies the spectral dependence of the transmission through nanoscale bowtie apertures defined in a silver film. A realistic bowtie aperture is numerically modeled using the Finite Difference Time Domain (FDTD) method. Results show that the transmission spectrum is dominated by Fabry-Pérot (F-P) waveguide modes and plasmonic modes. The F-P resonance is sensitive to the thickness of the film and the plasmonic resonant mode is closely related to the gap distance of the bowtie aperture. Both characteristics significantly affect the transmission spectrum. To verify these numerical results, bowtie apertures are FIB milled in a silver film. Experimental transmission measurements agree with simulation data. Based on this result, nanoscale bowtie apertures can be optimized to realize deep sub-wavelength confinement with high transmission efficiency with applications to nanolithography, data storage, and bio-chemical sensing. PMID:27250995

  14. Resonant Effects in Nanoscale Bowtie Apertures.

    PubMed

    Ding, Li; Qin, Jin; Guo, Songpo; Liu, Tao; Kinzel, Edward; Wang, Liang

    2016-01-01

    Nanoscale bowtie aperture antennas can be used to focus light well below the diffraction limit with extremely high transmission efficiencies. This paper studies the spectral dependence of the transmission through nanoscale bowtie apertures defined in a silver film. A realistic bowtie aperture is numerically modeled using the Finite Difference Time Domain (FDTD) method. Results show that the transmission spectrum is dominated by Fabry-Pérot (F-P) waveguide modes and plasmonic modes. The F-P resonance is sensitive to the thickness of the film and the plasmonic resonant mode is closely related to the gap distance of the bowtie aperture. Both characteristics significantly affect the transmission spectrum. To verify these numerical results, bowtie apertures are FIB milled in a silver film. Experimental transmission measurements agree with simulation data. Based on this result, nanoscale bowtie apertures can be optimized to realize deep sub-wavelength confinement with high transmission efficiency with applications to nanolithography, data storage, and bio-chemical sensing. PMID:27250995

  15. Application of a geocentrifuge and sterolithographically fabricated apertures to multiphase flow in complex fracture apertures.

    SciTech Connect

    Glenn E. McCreery; Robert D. Stedtfeld; Alan T. Stadler; Daphne L. Stoner; Paul Meakin

    2005-09-01

    A geotechnical centrifuge was used to investigate unsaturated multiphase fluid flow in synthetic fracture apertures under a variety of flow conditions. The geocentrifuge subjected the fluids to centrifugal forces allowing the Bond number to be systematically changed without adjusting the fracture aperture of the fluids. The fracture models were based on the concept that surfaces generated by the fracture of brittle geomaterials have a self-affine fractal geometry. The synthetic fracture surfaces were fabricated from a transparent epoxy photopolymer using sterolithography, and fluid flow through the transparent fracture models was monitored by an optical image acquisition system. Aperture widths were chosen to be representative of the wide range of geological fractures in the vesicular basalt that lies beneath the Idaho Nation Laboratory (INL). Transitions between different flow regimes were observed as the acceleration was changed under constant flow conditions. The experiments showed the transition between straight and meandering rivulets in smooth walled apertures (aperture width = 0.508 mm), the dependence of the rivulet width on acceleration in rough walled fracture apertures (average aperture width = 0.25 mm), unstable meandering flow in rough walled apertures at high acceleration (20g) and the narrowing of the wetted region with increasing acceleration during the penetration of water into an aperture filled with wetted particles (0.875 mm diameter glass spheres).

  16. SU-E-J-20: Adaptive Aperture Morphing for Online Correction for Prostate Cancer Radiotherapy

    SciTech Connect

    Sandhu, R; Qin, A; Yan, D

    2014-06-01

    Purpose: Online adaptive aperture morphing is desirable over translational couch shifts to accommodate not only the target position variation but also anatomic changes (rotation, deformation, and relation of target to organ-atrisks). We proposed quick and reliable method for adapting segment aperture leaves for IMRT treatment of prostate. Methods: The proposed method consists of following steps: (1) delineate the contours of prostate, SV, bladder and rectum on kV-CBCT; (2) determine prostate displacement from the rigid body registration of the contoured prostate manifested on the reference CT and the CBCT; (3) adapt the MLC segment apertures obtained from the pre-treatment IMRT planning to accommodate the shifts as well as anatomic changes. The MLC aperture adaptive algorithm involves two steps; first move the whole aperture according to prostate translational/rotational shifts, and secondly fine-tune the aperture shape to maintain the spatial relationship between the planning target contour and the MLC aperture to the daily target contour. Feasibility of this method was evaluated retrospectively on a seven-field IMRT treatment of prostate cancer patient by comparing dose volume histograms of the original plan and the aperture-adjusted plan, with/without additional segments weight optimization (SWO), on two daily treatment CBCTs selected with relative large motion and rotation. Results: For first daily treatment, the prostate rotation was significant (12degree around lateral-axis). With apertureadjusted plan, the D95 to the target was improved 25% and rectum dose (D30, D40) was reduced 20% relative to original plan on daily volumes. For second treatment-fraction, (lateral shift = 6.7mm), after adjustment target D95 improved by 3% and bladder dose (D30, maximum dose) was reduced by 1%. For both cases, extra SWO did not provide significant improvement. Conclusion: The proposed method of adapting segment apertures is promising in treatment position correction

  17. An optical technology study on large aperture telescopes

    NASA Technical Reports Server (NTRS)

    Korsch, D.

    1985-01-01

    The difficult and crucial problem of selecting a suitable telescope concept for an advanced space observatory was examined. To this end two and four mirror telescopes were analyzed and compared. Both configurations are very practical and structurally similar. Parabolic primary and spherical primary four mirror telescope were compared with respect to their performance and the alignment sensitivities of the three correction mirrors. A 1 meter class afocal telescope system with lag angle compensation, to be used in a LIDAR experiment, was examined.

  18. Large-Aperture, Three Mirror Telescopes for Near-Earth

    NASA Astrophysics Data System (ADS)

    Ackermann, M.; McGraw, J.

    In this era when Space Situational Awareness (SSA) is a national priority and optical-infrared telescopic sensor development is underway, cost-benefit analyses of competing approaches are necessary and appropriate. The DOD is presently investing in a new three-mirror telescope for SSA. At the same time, the Air Force, various universities and private research organizations are either studying or building wide-field telescopes with similar capabilities, but in most cases, at a significantly lower cost. Much of the expense for the DOD system appears driven by certain design choices which were advertised as necessary to fulfill the mission. Design details which would allow an independent analysis have not been published and no public comparison with other approaches is known to exist. Most telescope designs however, can be closely approximated from their optical configuration and imaging performance specifications. An optical designer will tell you that field curvature is one of the five monochromatic aberrations which they try to eliminate. The fact that one DOD development effort considers field curvature a design feature immediately draws attention to the project. This coupled with the paucity of published information and the very high development cost makes this program irresistible for comparison with competing approaches. This paper examines the likely design and performance of a proxy telescope intended to find NEOs, compares and contrasts that telescope with similar, but lower cost on-going projects, and examines the predictable impacts of reproducing such a telescope and placing multiple copies around the globe. The study primarily concentrates on performance measured in terms of search rate in square degrees per hour vs. object visual magnitude. Other considerations such as cost, transportability, availability of replacement components and ease of installation are also considered.

  19. MICRONERVA: A Novel Approach to Large Aperture Astronomical Spectroscopy

    NASA Astrophysics Data System (ADS)

    Hall, Ryan; Plavchan, Peter; Geneser, Claire; Giddens, Frank; Spangler, Sophia

    2016-06-01

    MICRONERVA (MICRO Novel Exoplanet Radial Velocity Array) is a project to measure precise spectroscopic radial velocities. The cost of telescopes are a strong function of diameter, and light gathering power as opposed to angular resolution is the fundamental driver for telescope design for many spectroscopic science applications. By sacrificing angular resolution, many multiple smaller fiber-fed telescopes can be combined to synthesize the light gathering power of a larger diameter telescope at a lower effective cost. For our MICRONERVA prototype, based upon the larger MINERVA project, we will attempt to demonstrate that an array of four 8-inch CPC Celestron telescopes can be automated with sufficient active guiding precision for robust nightly robotic operations. The light from each telescope is coupled into single mode fibers, which are conveniently matched to the point spread function of 8-inch telescopes, which can be diffraction limited at red wavelengths in typical seeing at good observing sites. Additionally, the output from an array of single mode fibers provides stable output illumination of a spectrograph, which is a critical requirement of future precise radial velocity instrumentation. All of the hardware from the system is automated using Python programs and ASCOM and MaxIm DL software drivers. We will present an overview of the current status of the project and plans for future work. The detection of exoplanets using the techniques of MICRONERVA could potentially enable cost reductions for many types of spectroscopic research.

  20. The design of a large aperture high field dipole

    SciTech Connect

    Harfoush, F.; Harrison, M.; Kerby, J.; Koepke, K.; Mantsch, P.; Nicol, T.; Riddiford, A.; Theilacker, J.

    1989-12-01

    The impetus for this design report originated in the Snowmass 88 meeting where the subject of higher energies within the constraints of the existing Tevatron tunnel enclosure was investigated. It was determined that beam transport to the fixed target experimental areas was possible up to an energy of {approximately}1.5 Tev. Collider operation was feasible at somewhat higher energies (1.8 Tev), primarily limited by the ability to design a single turn beam abort system within the constraints of the straight section length. A new accelerator in the existing tunnel would, of necessity, have a similar though not identical lattice and straight section layout to the present Tevatron. Thus when issues arose in the magnet design requiring input from the accelerator standpoint we have assumed a Tevatron like machine. The possibility of using these high field magnets as elements in the existing Tevatron to create new warm space,' for another Interaction Region for example, also emphasizes compatibility with the present machine. 16 refs., 62 figs., 23 tabs.

  1. Deployable large aperture optics system for remote sensing applications.

    SciTech Connect

    Sumali, Anton Hartono; Martin, Jeffrey W.; Main, John A.; Macke, Benjamin T.; Massad, Jordan Elias; Chaplya, Pavel Mikhail

    2004-04-01

    This report summarizes research into effects of electron gun control on piezoelectric polyvinylidene fluoride (PVDF) structures. The experimental apparatus specific to the electron gun control of this structure is detailed, and the equipment developed for the remote examination of the bimorph surface profile is outlined. Experiments conducted to determine the optimum electron beam characteristics for control are summarized. Clearer boundaries on the bimorphs control output capabilities were determined, as was the closed loop response. Further controllability analysis of the bimorph is outlined, and the results are examined. In this research, the bimorph response was tested through a matrix of control inputs of varying current, frequency, and amplitude. Experiments also studied the response to electron gun actuation of piezoelectric bimorph thin film covered with multiple spatial regions of control. Parameter ranges that yielded predictable control under certain circumstances were determined. Research has shown that electron gun control can be used to make macrocontrol and nanocontrol adjustments for PVDF structures. The control response and hysteresis are more linear for a small range of energy levels. Current levels needed for optimum control are established, and the generalized controllability of a PVDF bimorph structure is shown.

  2. Optical slicing of large scenes by synthetic aperture integral imaging

    NASA Astrophysics Data System (ADS)

    Navarro, Héctor; Saavedra, Genaro; Molina, Ainhoa; Martínez-Corral, Manuel; Martínez-Cuenca, Raúl; Javidi, Bahram

    2010-04-01

    Integral imaging (InI) technology was created with the aim of providing the binocular observers of monitors, or matrix display devices, with auto-stereoscopic images of 3D scenes. However, along the last few years the inventiveness of researches has allowed to find many other interesting applications of integral imaging. Examples of this are the application of InI in object recognition, the mapping of 3D polarization distributions, or the elimination of occluding signals. One of the most interesting applications of integral imaging is the production of views focused at different depths of the 3D scene. This application is the natural result of the ability of InI to create focal stacks from a single input image. In this contribution we present new algorithm for this optical slicing application, and show that it is possible the 3D reconstruction with improved lateral resolution.

  3. Design of a neutron penumbral-aperture microscope with 10-. mu. m resolution

    SciTech Connect

    Ress, D.; Lerche, R.A.; Ellis, R.J.; Lane, S.M.

    1990-05-01

    We are currently designing a 10-{mu}m resolution neutron penumbral-aperture microscope to diagnose high-convergence targets at the Nova laser facility. To achieve such high resolution, the new microscope will require substantial improvements in three areas. First, we have designed thick penumbral apertures with extremely sharp cutoffs over a useful ({approx}100 {mu}m) field of view; fabrication of such apertures appears feasible using gold electroplating techniques. Second, the limited field of view and required close proximity of the aperture to the target (2 cm) necessitates a durable mounting and alignment system with {plus}25 {mu}m accuracy. Finally, a neutron detector containing 160,000 scintillator elements is required; readout and optimization of this large array are outstanding issues. 5 refs., 3 figs.

  4. Transmission enhancement through deep subwavelength apertures using connected split ring resonators.

    PubMed

    Ates, Damla; Cakmak, Atilla Ozgur; Colak, Evrim; Zhao, Rongkuo; Soukoulis, C M; Ozbay, Ekmel

    2010-02-15

    We report astonishingly high transmission enhancement factors through a subwavelength aperture at microwave frequencies by placing connected split ring resonators in the vicinity of the aperture. We carried out numerical simulations that are consistent with our experimental conclusions. We experimentally show higher than 70,000-fold extraordinary transmission through a deep subwavelength aperture with an electrical size of lambda/31 x lambda/12 (width x length), in terms of the operational wavelength. We discuss the physical origins of the phenomenon. Our numerical results predict that even more improvements of the enhancement factors are attainable. Theoretically, the approach opens up the possibility for achieving very large enhancement factors by overcoming the physical limitations and thereby minimizes the dependence on the aperture geometries. PMID:20389408

  5. Microstrip Yagi Antenna with Dual Aperture-Coupled Feed

    NASA Technical Reports Server (NTRS)

    Pogorzelski, Ronald; Venkatesan, Jaikrishna

    2008-01-01

    A proposed microstrip Yagi antenna would operate at a frequency of 8.4 GHz (which is in the X band) and would feature a mechanically simpler, more elegant design, relative to a prior L-band microstrip Yagi antenna. In general, the purpose of designing a microstrip Yagi antenna is to combine features of a Yagi antenna with those of a microstrip patch to obtain an antenna that can be manufactured at low cost, has a low profile, and radiates a directive beam that, as plotted on an elevation plane perpendicular to the antenna plane, appears tilted away from the broadside. Such antennas are suitable for flush mounting on surfaces of diverse objects, including spacecraft, aircraft, land vehicles, and computers. Stated somewhat more precisely, what has been proposed is a microstrip antenna comprising an array of three Yagi elements. Each element would include four microstrip-patch Yagi subelements: one reflector patch, one driven patch, and two director patches. To obtain circular polarization, each driven patch would be fed by use of a dual offset aperture-coupled feed featuring bow-tie-shaped apertures. The selection of the dual offset bow-tie aperture geometry is supported by results found in published literature that show that this geometry would enable matching of the impedances of the driven patches to the 50-Omega impedance of the microstrip feedline while maintaining a desirably large front-to-back lobe ratio.

  6. Two-Dimensional Aperture Coding for Magnetic Sector Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Russell, Zachary E.; Chen, Evan X.; Amsden, Jason J.; Wolter, Scott D.; Danell, Ryan M.; Parker, Charles B.; Stoner, Brian R.; Gehm, Michael E.; Brady, David J.; Glass, Jeffrey T.

    2015-02-01

    In mass spectrometer design, there has been a historic belief that there exists a fundamental trade-off between instrument size, throughput, and resolution. When miniaturizing a traditional system, performance loss in either resolution or throughput would be expected. However, in optical spectroscopy, both one-dimensional (1D) and two-dimensional (2D) aperture coding have been used for many years to break a similar trade-off. To provide a viable path to miniaturization for harsh environment field applications, we are investigating similar concepts in sector mass spectrometry. Recently, we demonstrated the viability of 1D aperture coding and here we provide a first investigation of 2D coding. In coded optical spectroscopy, 2D coding is preferred because of increased measurement diversity for improved conditioning and robustness of the result. To investigate its viability in mass spectrometry, analytes of argon, acetone, and ethanol were detected using a custom 90-degree magnetic sector mass spectrometer incorporating 2D coded apertures. We developed a mathematical forward model and reconstruction algorithm to successfully reconstruct the mass spectra from the 2D spatially coded ion positions. This 2D coding enabled a 3.5× throughput increase with minimal decrease in resolution. Several challenges were overcome in the mass spectrometer design to enable this coding, including the need for large uniform ion flux, a wide gap magnetic sector that maintains field uniformity, and a high resolution 2D detection system for ion imaging. Furthermore, micro-fabricated 2D coded apertures incorporating support structures were developed to provide a viable design that allowed ion transmission through the open elements of the code.

  7. Multiple instrument distributed aperture sensor (MIDAS) evolved design concept

    NASA Astrophysics Data System (ADS)

    Stubbs, David; Duncan, Alan; Pitman, Joseph T.; Sigler, Robert; Kendrick, Rick; Smith, Eric H.; Mason, James

    2004-10-01

    An innovative approach to future space telescopes that enables order of magnitude increased science return for astronomical, Earth-observing and planetary science missions is described. Our concept, called Multiple Instrument Distributed Aperture Sensor (MIDAS), provides a large-aperture, wide-field, diffraction-limited telescope at a fraction of the cost, mass and volume of conventional space telescopes. MIDAS integrates many optical interferometry advances as an evolution of over a decade of technology development in distributed aperture optical imaging systems. Nine collector telescopes are integrated into MIDAS as the primary remote sensing science payload, supporting a collection of six back-end science instruments tailored to a specific mission. By interfacing to multiple science instruments, enabling sequential and concurrent functional modes, we expand the potential science return of future space science missions many fold. Passive imaging modes with MIDAS enable remote sensing at diffraction-limited resolution sequentially by each science instrument, as well as in somewhat lower resolution by multiple science instruments acting concurrently on the image, such as in different wavebands. Our MIDAS concept inherently provides nanometer-resolution hyperspectral passive imaging without the need for any moving parts in the science instruments. For Earth-observing and planetary science missions, the MIDAS optical design provides high-resolution imaging at high altitudes for long dwell times, thereby enabling real-time, wide-area remote sensing of dynamic planetary surface characteristics. In its active remote sensing modes, using an integrated solid-state laser source, MIDAS enables surface illumination, active spectroscopy, LIDAR, vibrometery, and optical communications. Our concept is directly scalable to telescope synthetic apertures of 5m, limited by launch vehicle fairing diameter, and above 5m diameter achieved by means of autonomous deployments or manned

  8. Two-dimensional aperture coding for magnetic sector mass spectrometry.

    PubMed

    Russell, Zachary E; Chen, Evan X; Amsden, Jason J; Wolter, Scott D; Danell, Ryan M; Parker, Charles B; Stoner, Brian R; Gehm, Michael E; Brady, David J; Glass, Jeffrey T

    2015-02-01

    In mass spectrometer design, there has been a historic belief that there exists a fundamental trade-off between instrument size, throughput, and resolution. When miniaturizing a traditional system, performance loss in either resolution or throughput would be expected. However, in optical spectroscopy, both one-dimensional (1D) and two-dimensional (2D) aperture coding have been used for many years to break a similar trade-off. To provide a viable path to miniaturization for harsh environment field applications, we are investigating similar concepts in sector mass spectrometry. Recently, we demonstrated the viability of 1D aperture coding and here we provide a first investigation of 2D coding. In coded optical spectroscopy, 2D coding is preferred because of increased measurement diversity for improved conditioning and robustness of the result. To investigate its viability in mass spectrometry, analytes of argon, acetone, and ethanol were detected using a custom 90-degree magnetic sector mass spectrometer incorporating 2D coded apertures. We developed a mathematical forward model and reconstruction algorithm to successfully reconstruct the mass spectra from the 2D spatially coded ion positions. This 2D coding enabled a 3.5× throughput increase with minimal decrease in resolution. Several challenges were overcome in the mass spectrometer design to enable this coding, including the need for large uniform ion flux, a wide gap magnetic sector that maintains field uniformity, and a high resolution 2D detection system for ion imaging. Furthermore, micro-fabricated 2D coded apertures incorporating support structures were developed to provide a viable design that allowed ion transmission through the open elements of the code. PMID:25510933

  9. LASS U-Th-Pb monazite and rutile geochronology of felsic high-pressure granulites (Rhodope, N Greece): Effects of fluid, deformation and metamorphic reactions in local subsystems

    NASA Astrophysics Data System (ADS)

    Wawrzenitz, Nicole; Krohe, Alexander; Baziotis, Ioannis; Mposkos, Evripidis; Kylander-Clark, Andrew R. C.; Romer, Rolf L.

    2015-09-01

    The specific chemical composition of monazite in shear zones is controlled by the syndeformation dissolution-precipitation reactions of the rock-forming minerals. This relation can be used for dating deformation, even when microfabric characteristics like shape preferred orientation or intracrystalline deformation of monazite itself are missing. Monazite contemporaneously formed in and around the shear zones may have different compositions. These depend on the local chemical context rather than reflecting successive crystallization episodes of monazite. This is demonstrated in polymetamorphic, mylonitic high-pressure (HP) garnet-kyanite granulites of the Alpine Sidironero Complex (Rhodope UHP terrain, Northern Greece). The studied mylonitic rocks escaped from regional migmatization at 40-36 Ma and from subsequent shearing through cooling until 36 Ma. In-situ laser-ablation split-stream inductively-coupled plasma mass spectrometry (LASS) analyses have been carried out on monazite from micro-scale shear zones, from pre-mylonitic microlithons as well as of monazite inclusions in relictic minerals complimented by U-Pb data on rutile and Rb-Sr data of biotite. Two major metamorphic episodes, Mesozoic and Cenozoic, are constrained. Chemical compositions, isotopic characteristics and apparent ages systematically vary among monazite of four different microfabric domains (I-IV). Within three pre-mylonitic domains (inclusions in (I) pre-mylonitic kyanite and (II) garnet porphyroclasts, and (III) in pre-mylonitic microlithons) monazite yields ages of ca. 130-150 Ma for HP-granulite metamorphism, in line with previous geochronological results in the area. Patchy alteration of the pre-mylonitic monazite by intra-grain dissolution-precipitation processes variably increased negative Eu anomaly and reduced the HREE contents. The apparent age of this altered monazite is reduced. Monazite in the syn-mylonitic shear bands (IV) differs in chemical composition from unaltered and

  10. Bi-metal coated aperture SNOM probes

    NASA Astrophysics Data System (ADS)

    Antosiewicz, Tomasz J.; Wróbel, Piotr; Szoplik, Tomasz

    2011-05-01

    Aperture probes of scanning near-field optical microscopes (SNOM) offer resolution which is limited by a sum of the aperture diameter at the tip of a tapered waveguide probe and twice the skin depth in metal used for coating. An increase of resolution requires a decrease of the aperture diameter. However, due to low energy throughput of such probes aperture diameters usually are larger than 50 nm. A groove structure at fiber core-metal coating interface for photon-to-plasmon conversion enhances the energy throughput 5-fold for Al coated probes and 30-fold for Au coated probes due to lower losses in the metal. However, gold coated probes have lower resolution, first due to light coupling from the core to plasmons at the outside of the metal coating, and second due to the skin depth being larger than for Al. Here we report on the impact of a metal bilayer of constant thickness for coating aperture SNOM probes. The purpose of the bilayer of two metals of which the outer one is aluminum and the inner is a noble metal is to assure low losses, hence larger transmission. Using body-of-revolution finite-difference time-domain simulations we analyze properties of probes without corrugations to measure the impact of using a metal bilayer and choose an optimum bi-metal configuration. Additionally we investigate how this type of metalization works in the case of grooved probes.

  11. Solar energy apparatus with apertured shield

    NASA Technical Reports Server (NTRS)

    Collings, Roger J. (Inventor); Bannon, David G. (Inventor)

    1989-01-01

    A protective apertured shield for use about an inlet to a solar apparatus which includesd a cavity receiver for absorbing concentrated solar energy. A rigid support truss assembly is fixed to the periphery of the inlet and projects radially inwardly therefrom to define a generally central aperture area through which solar radiation can pass into the cavity receiver. A non-structural, laminated blanket is spread over the rigid support truss in such a manner as to define an outer surface area and an inner surface area diverging radially outwardly from the central aperture area toward the periphery of the inlet. The outer surface area faces away from the inlet and the inner surface area faces toward the cavity receiver. The laminated blanket includes at least one layer of material, such as ceramic fiber fabric, having high infra-red emittance and low solar absorption properties, and another layer, such as metallic foil, of low infra-red emittance properties.

  12. Nonlinear synthetic aperture radar imaging using a harmonic radar

    NASA Astrophysics Data System (ADS)

    Gallagher, Kyle A.; Mazzaro, Gregory J.; Ranney, Kenneth I.; Nguyen, Lam H.; Martone, Anthony F.; Sherbondy, Kelly D.; Narayanan, Ram M.

    2015-05-01

    This paper presents synthetic aperture radar (SAR) images of linear and nonlinear targets. Data are collected using a linear/nonlinear step frequency radar. We show that it is indeed possible to produce SAR images using a nonlinear radar. Furthermore, it is shown that the nonlinear radar is able to reduce linear clutter by at least 80 dB compared to a linear radar. The nonlinear SAR images also show the system's ability to detect small electronic devices in the presence of large linear clutter. The system presented here has the ability to completely ignore a 20-inch trihedral corner reflector while detecting a RF mixer with a dipole antenna attached.

  13. Interferometric synthetic aperture radar studies of Alaska volcanoes

    USGS Publications Warehouse

    Lu, Zhiming; Wicks, C., Jr.; Power, J.; Dzurisin, D.; Thatcher, W.; Masterlark, Timothy

    2002-01-01

    Interferometric synthetic aperture radar (InSAR) imaging is a recently developed geodetic technique capable of measuring ground-surface deformation with centimeter to subcentimeter vertical precision and spatial resolution of tens-of-meter over a relatively large region (???104 km2). The spatial distribution of surface deformation data, derived from InSAR images, enables the construction of detailed mechanical models to enhance the study of magmatic and tectonic processes associated with volcanoes. This paper summarizes our recent InSAR studies of several Alaska volcanoes, which include Okmok, Akutan, Kiska, Augustine, Westdahl, and Peulik volcanoes.

  14. Role of the aperture in Z-scan experiments: A parametric study

    NASA Astrophysics Data System (ADS)

    Rashidian Vaziri, M. R.

    2015-11-01

    In close-aperture Z-scan experiments, a small aperture is conventionally located in the far-field thereby enabling the detection of slight changes in the laser beam profile due to the Kerr-lensing effect. In this work, by numerically solving the Fresnel-Kirchhoff diffraction integrals, the amount of transmitted power through apertures has been evaluated and a parametric study on the role of the various parameters that can influence this transmitted power has been done. In order to perform a comprehensive analysis, we have used a nonlinear phase shift optimized for nonlocal nonlinear media in our calculations. Our results show that apertures will result in the formation of symmetrical fluctuations on the wings of Z-scan transmittance curves. It is further shown that the appearance of these fluctuations can be ascribed to the natural diffraction of the Gaussian beam as it propagates up to the aperture plane. Our calculations reveal that the nonlocal parameter variations can shift the position of fluctuations along the optical axis, whereas their magnitude depends on the largeness of the induced nonlinear phase shift. It is concluded that since the mentioned fluctuations are produced by the natural diffraction of the Gaussian beam itself, one must take care not to mistakenly interpret them as noise and should not expect to eliminate them from experimental Z-scan transmittance curves by using apertures with different sizes.

  15. Test of film thickness based on annular sub-aperture stitching interference

    NASA Astrophysics Data System (ADS)

    Yang, Li-hong; Su, Jun-hong; Chen, Zhi-li

    2010-10-01

    The technology of annular sub-aperture stitching interference used in film thickness testing is an efficient route with the characters of high-resolution and low-cost, which don't need compensation with auxiliary components. In this contribution, the interference methods of film thickness testing and principles of annular sub-aperture stitching are introduced, and then a model of annular sub-aperture stitching is established on the interference phase of thin film; finally, Sub-aperture spatial phases are unwrapped by fast Fourier transform (FFT) algorithms, and based on this, annular image is obtained by Zernike polynomial fitting algorithm and stitching objective function. The processing algorithms program are written and simulated by a computer. A variety of affecting the accuracy of splicing factors of the errors are analyzed in detail, and the solutions are given to reduce the errors, and proposed changes to the existing experimental platform. The results show that the PV value and the RMS value of phase residuals of full aperture splicing are 0.0092λ and 0.0036λ before and after stitching respectively, and it achieves a large aperture high-precision detection of film thickness.

  16. Deterministic measurement and correction of the pad shape in full-aperture polishing processes

    NASA Astrophysics Data System (ADS)

    Liao, D.; Zhang, Q.; Xie, R.; Chen, X.; Zhao, S.; Wang, J.

    2015-11-01

    Full-aperture polishing is a significant process in fabricating large optical flats because it restrains Mid-Spatial Frequency errors and removes material quickly on the whole optic surface. Nevertheless, optical flats fabricated by full-aperture polishing generally fail to meet the stringent requirement of surface figure, which has to be corrected by sub-aperture polishing processes. Surface figure of optical flats in full-aperture polishing processes is primarily dependent on the pressure distribution uniformity which correlates intensively with the lap shape. At present, practical and precise means are urgently desired for measuring and correcting the lap shape, especially the polyurethane pad lap. In the study, we present a novel method for deterministic measurement of the pad shape. The method obtains the height of the pad at spirally distributed locations implemented by the revolution of the pad and translation of the laser displacement sensor. The pad shape in terms of matrixes whose elements representing the heights at the corresponding locations is then calculated by interpolation algorithm based on the obtained data. Further, we propose a method for deterministic correction of the pad shape utilizing a small conditioning tool. The dwell time algorithm and implementation strategy for the dwell time are provided for common full-aperture polishers. These solutions for the deterministic measurement and correction of the pad shape have been validated on a full-aperture polisher with polyurethane pad. The polishing experiments revealed that the optic surface figure was obviously improved.

  17. Wave-front aberrations analysis by Zernike polynomials based on the annular sub-aperture stitching system

    NASA Astrophysics Data System (ADS)

    Duan, Lei; Hui, Mei; Deng, Jiayuan; Gong, Cheng; Zhao, Yuejin

    2012-11-01

    Annular sub-aperture stitching method was developed for testing large-aperture aspheric surfaces without using of any compensating element for measurement. It is necessary to correct measurement of aspheric optical aberrations and create mathematical description to describe wave-front aberrations. Zernike polynomials are suitable to describe wave aberration functions and data fitting of experimental measurements for the annular sub-aperture stitching system. This paper uses Zernike polynomials to describe the wave-front aberrations of full wave-front and reconstructed wave-front by annular sub-aperture stitching algorithm. At the same time, the imaging quality of the aspheric optical element can be contrasted. The stitching result shows good agreement with the full aperture result.

  18. Synthetic aperture radar capabilities in development

    SciTech Connect

    Miller, M.

    1994-11-15

    The Imaging and Detection Program (IDP) within the Laser Program is currently developing an X-band Synthetic Aperture Radar (SAR) to support the Joint US/UK Radar Ocean Imaging Program. The radar system will be mounted in the program`s Airborne Experimental Test-Bed (AETB), where the initial mission is to image ocean surfaces and better understand the physics of low grazing angle backscatter. The Synthetic Aperture Radar presentation will discuss its overall functionality and a brief discussion on the AETB`s capabilities. Vital subsystems including radar, computer, navigation, antenna stabilization, and SAR focusing algorithms will be examined in more detail.

  19. Fast decoding algorithms for coded aperture systems

    NASA Astrophysics Data System (ADS)

    Byard, Kevin

    2014-08-01

    Fast decoding algorithms are described for a number of established coded aperture systems. The fast decoding algorithms for all these systems offer significant reductions in the number of calculations required when reconstructing images formed by a coded aperture system and hence require less computation time to produce the images. The algorithms may therefore be of use in applications that require fast image reconstruction, such as near real-time nuclear medicine and location of hazardous radioactive spillage. Experimental tests confirm the efficacy of the fast decoding techniques.

  20. PDII- Additional discussion of the dynamic aperture

    SciTech Connect

    Norman M. Gelfand

    2002-07-23

    This note is in the nature of an addition to the dynamic aperture calculations found in the report on the Proton Driver, FERMILAB-TM-2169. A extensive discussion of the Proton Driver lattice, as well as the nomenclature used to describe it can be found in TM-2169. Basically the proposed lattice is a racetrack design with the two arcs joined by two long straight sections. The straight sections are dispersion free. Tracking studies were undertaken with the objective of computing the dynamic aperture for the lattice and some of the results have been incorporated into TM-2169. This note is a more extensive report of those calculations.

  1. Processing for spaceborne synthetic aperture radar imagery

    NASA Technical Reports Server (NTRS)

    Lybanon, M.

    1973-01-01

    The data handling and processing in using synthetic aperture radar as a satellite-borne earth resources remote sensor is considered. The discussion covers the nature of the problem, the theory, both conventional and potential advanced processing techniques, and a complete computer simulation. It is shown that digital processing is a real possibility and suggests some future directions for research.

  2. Multiple aperture seeker design for endoatmospheric intercepts

    NASA Astrophysics Data System (ADS)

    Werner, Jennifer; Shui, Ven; Reeves, Barry

    1993-06-01

    An IR optical seeker concept developed by Loral Infrared and Imaging Systems to meet the endoatmospheric requirements for hit-to-kill intercepts is presented. The seeker works in conjunction with an uncooled window concept developed by Textron Defense Systems. The combination of the compact seeker design with an uncooled window aperture provides an adequate solution with minimal complexity.

  3. Interferometric Synthetic Aperture Microwave Radiometers : an Overview

    NASA Technical Reports Server (NTRS)

    Colliander, Andreas; McKague, Darren

    2011-01-01

    This paper describes 1) the progress of the work of the IEEE Geoscience and Remote Sensing Society (GRSS) Instrumentation and Future Technologies Technical Committee (IFT-TC) Microwave Radiometer Working Group and 2) an overview of the development of interferometric synthetic aperture microwave radiometers as an introduction to a dedicated session.

  4. Dynamic metamaterial aperture for microwave imaging

    NASA Astrophysics Data System (ADS)

    Sleasman, Timothy; F. Imani, Mohammadreza; Gollub, Jonah N.; Smith, David R.

    2015-11-01

    We present a dynamic metamaterial aperture for use in computational imaging schemes at microwave frequencies. The aperture consists of an array of complementary, resonant metamaterial elements patterned into the upper conductor of a microstrip line. Each metamaterial element contains two diodes connected to an external control circuit such that the resonance of the metamaterial element can be damped by application of a bias voltage. Through applying different voltages to the control circuit, select subsets of the elements can be switched on to create unique radiation patterns that illuminate the scene. Spatial information of an imaging domain can thus be encoded onto this set of radiation patterns, or measurements, which can be processed to reconstruct the targets in the scene using compressive sensing algorithms. We discuss the design and operation of a metamaterial imaging system and demonstrate reconstructed images with a 10:1 compression ratio. Dynamic metamaterial apertures can potentially be of benefit in microwave or millimeter wave systems such as those used in security screening and through-wall imaging. In addition, feature-specific or adaptive imaging can be facilitated through the use of the dynamic aperture.

  5. Partially redundant apertures for infrared stellar imaging

    NASA Astrophysics Data System (ADS)

    Aitken, G. J. M.; Corteggiani, J. P.; Gay, J.

    1981-06-01

    Spectral-bandwidth constraints to ensure controlled amounts of redundancy are established for a class of two-dimensional partially redundant arrays (PRA's). In the IR, where speckle statistics are poor, the telescope-atmosphere modulation transfer function is determined solely by the PRA geometry. Signal-to-noise-ratio estimates, an optimum aperture criterion, and a six-element PRA example are presented.

  6. Radiation safety considerations in proton aperture disposal.

    PubMed

    Walker, Priscilla K; Edwards, Andrew C; Das, Indra J; Johnstone, Peter A S

    2014-04-01

    Beam shaping in scattered and uniform scanned proton beam therapy (PBT) is made commonly by brass apertures. Due to proton interactions, these devices become radioactive and could pose safety issues and radiation hazards. Nearly 2,000 patient-specific devices per year are used at Indiana University Cyclotron Operations (IUCO) and IU Health Proton Therapy Center (IUHPTC); these devices require proper guidelines for disposal. IUCO practice has been to store these apertures for at least 4 mo to allow for safe transfer to recycling contractors. The devices require decay in two staged secure locations, including at least 4 mo in a separate building, at which point half are ready for disposal. At 6 mo, 20-30% of apertures require further storage. This process requires significant space and manpower and should be considered in the design process for new clinical facilities. More widespread adoption of pencil beam or spot scanning nozzles may obviate this issue, as apertures then will no longer be necessary. PMID:24562073

  7. Vowel Aperture and Syllable Segmentation in French

    ERIC Educational Resources Information Center

    Goslin, Jeremy; Frauenfelder, Ulrich H.

    2008-01-01

    The theories of Pulgram (1970) suggest that if the vowel of a French syllable is open then it will induce syllable segmentation responses that result in the syllable being closed, and vice versa. After the empirical verification that our target French-speaking population was capable of distinguishing between mid-vowel aperture, we examined the…

  8. Dynamic metamaterial aperture for microwave imaging

    SciTech Connect

    Sleasman, Timothy; Imani, Mohammadreza F.; Gollub, Jonah N.; Smith, David R.

    2015-11-16

    We present a dynamic metamaterial aperture for use in computational imaging schemes at microwave frequencies. The aperture consists of an array of complementary, resonant metamaterial elements patterned into the upper conductor of a microstrip line. Each metamaterial element contains two diodes connected to an external control circuit such that the resonance of the metamaterial element can be damped by application of a bias voltage. Through applying different voltages to the control circuit, select subsets of the elements can be switched on to create unique radiation patterns that illuminate the scene. Spatial information of an imaging domain can thus be encoded onto this set of radiation patterns, or measurements, which can be processed to reconstruct the targets in the scene using compressive sensing algorithms. We discuss the design and operation of a metamaterial imaging system and demonstrate reconstructed images with a 10:1 compression ratio. Dynamic metamaterial apertures can potentially be of benefit in microwave or millimeter wave systems such as those used in security screening and through-wall imaging. In addition, feature-specific or adaptive imaging can be facilitated through the use of the dynamic aperture.

  9. Aperture synthesis imaging from the moon

    NASA Technical Reports Server (NTRS)

    Burns, Jack O.

    1991-01-01

    Four candidate imaging aperture synthesis concepts are described for possible emplacement on the moon beginning in the next decade. These include an optical interferometer with 10 microarcsec resolution, a submillimeter array with 6 milliarcsec resolution, a moon-earth VLBI experiment, and a very low frequency interferometer in lunar orbit.

  10. Perceiving Affordances for Fitting through Apertures

    ERIC Educational Resources Information Center

    Ishak, Shaziela; Adolph, Karen E.; Lin, Grace C.

    2008-01-01

    Affordances--possibilities for action--are constrained by the match between actors and their environments. For motor decisions to be adaptive, affordances must be detected accurately. Three experiments examined the correspondence between motor decisions and affordances as participants reached through apertures of varying size. A psychophysical…

  11. Clutter free synthetic aperture radar correlator

    NASA Technical Reports Server (NTRS)

    Jain, A.

    1977-01-01

    A synthetic aperture radar correlation system including a moving diffuser located at the image plane of a radar processor is described. The output of the moving diffuser is supplied to a lens whose impulse response is at least as wide as that of the overall processing system. A significant reduction in clutter results is given.

  12. Design and performance of a distributed aperture millimeter-wave imaging system using optical upconversion

    NASA Astrophysics Data System (ADS)

    Martin, Richard; Schuetz, Christopher A.; Dillon, Thomas E.; Chen, Caihua; Samluk, Jesse; Stein, E. Lee, Jr.; Mirotznik, Mark; Prather, Dennis W.

    2009-05-01

    Passive imaging using millimeter waves (mmWs) has many advantages and applications in the defense and security markets. All terrestrial bodies emit mmW radiation and these wavelengths are able to penetrate smoke, blowing dust or sand, fog/clouds/marine layers, and even clothing. One primary obstacle to imaging in this spectrum is that longer wavelengths require larger apertures to achieve the resolutions typically desired in surveillance applications. As a result, lens-based focal plane systems tend to require large aperture optics, which severely limit the minimum achievable volume and weight of such systems. To overcome this limitation, a distributed aperture detection scheme is used in which the effective aperture size can be increased without the associated volumetric increase in imager size. However, such systems typically require high frequency (~ 30 - 300 GHz) signal routing and down conversion as well as large correlator banks. Herein, we describe an alternate approach to distributed aperture mmW imaging using optical upconversion of the mmW signal onto an optical carrier. This conversion serves, in essence, to scale the mmW sparse aperture array signals onto a complementary optical array. The optical side bands are subsequently stripped from the optical carrier and optically recombined to provide a real-time snapshot of the mmW signal. In this paper, the design tradeoffs of resolution, bandwidth, number of elements, and field of view inherent in this type of system will be discussed. We also will present the performance of a 30 element distributed aperture proof of concept imaging system operating at 35 GHz.

  13. Multi-aperture foveated imaging.

    PubMed

    Carles, Guillem; Chen, Shouqian; Bustin, Nicholas; Downing, James; McCall, Duncan; Wood, Andrew; Harvey, Andrew R

    2016-04-15

    Foveated imaging, such as that evolved by biological systems to provide high angular resolution with a reduced space-bandwidth product, also offers advantages for man-made task-specific imaging. Foveated imaging systems using exclusively optical distortion are complex, bulky, and high cost, however. We demonstrate foveated imaging using a planar array of identical cameras combined with a prism array and superresolution reconstruction of a mosaicked image with a foveal variation in angular resolution of 5.9:1 and a quadrupling of the field of view. The combination of low-cost, mass-produced cameras and optics with computational image recovery offers enhanced capability of achieving large foveal ratios from compact, low-cost imaging systems. PMID:27082366

  14. Prototype Development of a Geostationary Synthetic Thinned Aperture Radiometer, GeoSTAR

    NASA Technical Reports Server (NTRS)

    Tanner, Alan B.; Wilson, William J.; Kangaslahti, Pekka P.; Lambrigsten, Bjorn H.; Dinardo, Steven J.; Piepmeier, Jeffrey R.; Ruf, Christopher S.; Rogacki, Steven; Gross, S. M.; Musko, Steve

    2004-01-01

    Preliminary details of a 2-D synthetic aperture radiometer prototype operating from 50 to 58 GHz will be presented. The instrument is being developed as a laboratory testbed, and the goal of this work is to demonstrate the technologies needed to do atmospheric soundings with high spatial resolution from Geostationary orbit. The concept is to deploy a large sparse aperture Y-array from a geostationary satellite, and to use aperture synthesis to obtain images of the earth without the need for a large mechanically scanned antenna. The laboratory prototype consists of a Y-array of 24 horn antennas, MMIC receivers, and a digital cross-correlation sub-system. System studies are discussed, including an error budget which has been derived from numerical simulations. The error budget defines key requirements, such as null offsets, phase calibration, and antenna pattern knowledge. Details of the instrument design are discussed in the context of these requirements.

  15. High power 808 nm vertical cavity surface emitting laser with multi-ring-shaped-aperture structure

    NASA Astrophysics Data System (ADS)

    Hao, Y. Q.; Shang, C. Y.; Feng, Y.; Yan, C. L.; Zhao, Y. J.; Wang, Y. X.; Wang, X. H.; Liu, G. J.

    2011-02-01

    The carrier conglomeration effect has been one of the main problems in developing electrically pumped high power vertical cavity surface emitting laser (VCSEL) with large aperture. We demonstrate a high power 808 nm VCSEL with multi-ring-shaped-aperture (MRSA) to weaken the carrier conglomeration effect. Compared with typical VCSEL with single large aperture (SLA), the 300-μm-diameter VCSEL with MRSA has more uniform near field and far field patterns. Moreover, MRSA laser exhibits maximal CW light output power 0.3 W which is about 3 times that of SLA laser. And the maximal wall-plug efficiency of 17.4% is achieved, higher than that of SLA laser by 10%.

  16. RF Performance of Membrane Aperture Shells

    NASA Technical Reports Server (NTRS)

    Flint, Eirc M.; Lindler, Jason E.; Thomas, David L.; Romanofsky, Robert

    2007-01-01

    This paper provides an overview of recent results establishing the suitability of Membrane Aperture Shell Technology (MAST) for Radio Frequency (RF) applications. These single surface shells are capable of maintaining their figure with no preload or pressurization and minimal boundary support, yet can be compactly roll stowed and passively self deploy. As such, they are a promising technology for enabling a future generation of RF apertures. In this paper, we review recent experimental and numerical results quantifying suitable RF performance. It is shown that candidate materials possess metallic coatings with sufficiently low surface roughness and that these materials can be efficiently fabricated into RF relevant doubly curved shapes. A numerical justification for using a reflectivity metric, as opposed to the more standard RF designer metric of skin depth, is presented and the resulting ability to use relatively thin coating thickness is experimentally validated with material sample tests. The validity of these independent film sample measurements are then confirmed through experimental results measuring RF performance for reasonable sized doubly curved apertures. Currently available best results are 22 dBi gain at 3 GHz (S-Band) for a 0.5m aperture tested in prime focus mode, 28dBi gain for the same antenna in the C-Band (4 to 6 GHz), and 36.8dBi for a smaller 0.25m antenna tested at 32 GHz in the Ka-Band. RF range test results for a segmented aperture (one possible scaling approach) are shown as well. Measured antenna system actual efficiencies (relative to the unachievable) ideal for these on axis tests are generally quite good, typically ranging from 50 to 90%.

  17. Data management approach to search and rescue synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Green, John E.; Rogers, George W.

    1997-06-01

    The NASA sponsored Search and Rescue Synthetic Aperture Radar (SAR) program seeks to use foliage penetrating synthetic aperture radar (SAR) to locate light plane crashes in remote areas. In addition to the hardware and pattern recognition issues, data management is recognized as a significant part of the overall problem. A single NASA/JPL AIRSAR polarimetric image in P, L, and C bands takes approximately 524 megabytes of storage. Algorithmic development efforts, as well as an eventual operational system, will likely require maintaining a large database of SAR imagery, as well as derived features and associated geographical information. The need for this much data is driven in large part by the complexity of the detection problem. A simple classification/detection algorithm does not currently seem feasible. Rather, a data driven approach that can incorporate local background characteristics as well as geographical information seems to be called for. This in turn makes data management a key issue. This paper presents a comprehensive data management framework suitable for the SAR problem, as well as other similar massive data set management problems.

  18. Deployable Wide-Aperture Array Antennas

    NASA Technical Reports Server (NTRS)

    Fink, Patrick W.; Dobbins, Justin A.; Lin, Greg Y.; Chu, Andrew; Scully, Robert C.

    2005-01-01

    Inexpensive, lightweight array antennas on flexible substrates are under development to satisfy a need for large-aperture antennas that can be stored compactly during transport and deployed to full size in the field. Conceived for use aboard spacecraft, antennas of this type also have potential terrestrial uses . most likely, as means to extend the ranges of cellular telephones in rural settings. Several simple deployment mechanisms are envisioned. One example is shown in the figure, where the deployment mechanism, a springlike material contained in a sleeve around the perimeter of a flexible membrane, is based on a common automobile window shade. The array can be formed of antenna elements that are printed on small sections of semi-flexible laminates, or preferably, elements that are constructed of conducting fabric. Likewise, a distribution network connecting the elements can be created from conventional technologies such as lightweight, flexible coaxial cable and a surface mount power divider, or preferably, from elements formed from conductive fabrics. Conventional technologies may be stitched onto a supporting flexible membrane or contained within pockets that are stitched onto a flexible membrane. Components created from conductive fabrics may be attached by stitching conductive strips to a nonconductive membrane, embroidering conductive threads into a nonconductive membrane, or weaving predetermined patterns directly into the membrane. The deployable antenna may comprise multiple types of antenna elements. For example, thin profile antenna elements above a ground plane, both attached to the supporting flexible membrane, can be used to create a unidirectional boresight radiation pattern. Or, antenna elements without a ground plane, such as bow-tie dipoles, can be attached to the membrane to create a bidirectional array such as that shown in the figure. For either type of antenna element, the dual configuration, i.e., elements formed of slots in a conductive

  19. Modeling AXAF Obstructions with the Generalized Aperture Program.

    NASA Astrophysics Data System (ADS)

    Nguyen, D.; Gaetz, T.; Jerius, D.; Stern, I.

    The generalized aperture program is designed to simulate the effects on the incident photon stream of physical obstructions, such as thermal baffles and pre- and post-collimators. It can handle a wide variety of aperture shapes, and has provisions to allow alterations of the photons by the apertures. The philosophy behind the aperture program is that a geometrically complicated aperture may be modeled by a combination of geometrically simpler apertures. This is done by incorporating a language, lua, to lay out the apertures. User provided call-back functions enable the modeling of the interactions of the incident photon with the apertures. This approach allows for maximum flexibility, since the geometry and interactions of obstructions can be specified by the user at run time.

  20. Method of forming aperture plate for electron microscope

    NASA Technical Reports Server (NTRS)

    Heinemann, K. (Inventor)

    1974-01-01

    An electron microscope is described with an electron source a condenser lens having either a circular aperture for focusing a solid cone of electrons onto a specimen or an annular aperture for focusing a hollow cone of electrons onto the specimen. It also has objective lens with an annular objective aperture, for focusing electrons passing through the specimen onto an image plane. A method of making the annular objective aperture using electron imaging, electrolytic deposition and ion etching techniques is included.

  1. Multiple Instrument Distributed Aperture Sensor (MIDAS) for planetary remote sensing

    NASA Astrophysics Data System (ADS)

    Pitman, Joseph T.; Duncan, Alan; Stubbs, David; Sigler, Robert D.; Kendrick, Richard L.; Smith, Eric H.; Mason, James E.; Delory, Gregory; Lipps, Jere H.; Manga, Michael; Graham, James R.; de Pater, Imke; Reiboldt, Sarah; Marcus, Philip; Bierhaus, Edward; Dalton, James B.; Fienup, James R.; Yu, Jeffrey W.

    2004-12-01

    An innovative approach that enables greatly increased return from planetary science remote sensing missions is described. Our concept, called Multiple Instrument Distributed Aperture Sensor (MIDAS), provides a large-aperture, wide-field telescope at a fraction of the cost, mass and volume of conventional space telescopes, by integrating advanced optical interferometry technologies. All optical assemblies are integrated into MIDAS as the primary remote sensing science payload, thereby reducing the cost, resources, complexity, integration and risks of a set of back-end science instruments (SI"s) tailored to a specific mission, such as advanced SI"s now in development for future planetary remote sensing missions. MIDAS interfaces to multiple SI"s for redundancy and to enable synchronized concurrent science investigations, such as with multiple highly sensitive spectrometers. Passive imaging modes with MIDAS enable high resolution remote sensing at the diffraction limit of the overall synthetic aperture, sequentially by each science instrument as well as in somewhat lower resolution by multiple science instruments acting concurrently on the image, such as in different wavebands. Our MIDAS concept inherently provides nanometer-resolution hyperspectral passive imaging without the need for any moving parts in the science instruments. In its active remote sensing modes using an integrated laser subsystem, MIDAS enables LIDAR, vibrometry, illumination, various active laser spectroscopies such as ablative, breakdown, fluorescence, Raman and time-resolved spectroscopy. The MIDAS optical design also provides high-resolution imaging for long dwell times at high altitudes, thereby enabling real-time, wide-area remote sensing of dynamic changes in planet surface processes. These remote sensing capabilities significantly enhance astrobiologic, geologic, atmospheric, and similar scientific objectives for planetary exploration missions.

  2. Multiple instrument distributed aperture sensor (MIDAS) science payload concept

    NASA Astrophysics Data System (ADS)

    Stubbs, David M.; Duncan, Alan L.; Pitman, Joe T.; Sigler, Robert D.; Kendrick, Richard L.; Chilese, John F.; Smith, Eric H.

    2004-10-01

    We describe the Multiple Instrument Distributed Aperture Sensor (MIDAS) concept, an innovative approach to future planetary science mission remote sensing that enables order of magnitude increased science return. MIDAS provides a large-aperture, wide-field, diffraction-limited telescope at a fraction of the cost, mass and volume of conventional space telescopes, by integrating advanced optical interferometry technologies. All telescope optical assemblies are integrated into MIDAS as the primary remote sensing science payload, thereby reducing the cost, resources, complexity, I&T and risks of a set of back-end science instruments (SI's) tailored to a specific mission. MIDAS interfaces to multiple science instruments, enabling sequential and concurrent functional modes, thereby expanding the potential planetary science return many fold. Passive imaging modes with MIDAS enable remote sensing at diffraction-limited resolution sequentially by each science instrument, or at lower resolution by multiple science instruments acting concurrently on the image, such as in different wavebands. Our MIDAS concept inherently provides nanometer-resolution hyperspectral passive imaging without the need for any moving parts in the science instruments. For planetary science missions, the MIDAS optical design provides high-resolution imaging for long dwell times at high altitudes, thereby enabling real-time, wide-area remote sensing of dynamic surface characteristics. In its active remote sensing modes, using an integrated solid-state laser source, MIDAS enables LIDAR, vibrometry, surface illumination, and various active or ablative spectroscopies. Our concept is scalable to apertures well over 10m, achieved by autonomous deployments or manned assembly in space. MIDAS is a proven candidate for future planetary science missions, enabled by our continued investments in focused MIDAS technology development areas. In this paper we present the opto-mechanical design for a 1.5m MIDAS point

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

    DOEpatents

    Benjamin, Robert F.; Mitchell, Kenneth B.

    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.

  4. Dual aperture dipole magnet with second harmonic component

    DOEpatents

    Praeg, W.F.

    1983-08-31

    An improved dual aperture dipole electromagnet includes a second-harmonic frequency magnetic guide field winding which surrounds first harmonic frequency magnetic guide field windings associated with each aperture. The second harmonic winding and the first harmonic windings cooperate to produce resultant magnetic waveforms in the apertures which have extended acceleration and shortened reset portions of electromagnet operation.

  5. Dual aperture dipole magnet with second harmonic component

    DOEpatents

    Praeg, Walter F.

    1985-01-01

    An improved dual aperture dipole electromagnet includes a second-harmonic frequency magnetic guide field winding which surrounds first harmonic frequency magnetic guide field windings associated with each aperture. The second harmonic winding and the first harmonic windings cooperate to produce resultant magnetic waveforms in the apertures which have extended acceleration and shortened reset portions of electromagnet operation.

  6. Fabrication of Nanoscale Oxide Aperture under the Influence of Electron Beam Exposure

    NASA Astrophysics Data System (ADS)

    Jung, M. Y.; Kim, D. W.; Choi, Seong S.

    2004-03-01

    Recently there have been tremendous interests about near field optical lithographic techniques for the next generation gigabyte information storage devices. The near field optical lithographic technique will circumvent the classical diffraction limit and can provide the sub-wavelength size patterns less than 100 nm and the parallel data processing has been examined. Therefore, several parallel processing techniques such as multi-cantilever array and the nano-size aperture array have been previously reported. In this work, the nano-fabrication technique for the sub-wavelength size aperture array is presented. Initially, the (50× 50) dot array was patterned on the SiO2 thermally grown on Si (100) substrate. Each dot has (5× 5) μ m^2 pattern size. The anisotropic TMAH etching of the Si substrate was performed and followed by anisotropic stress-dependent thermal oxidation at 1000 r C and backside Si etching using TMAH solution. The opening of the nano-size aperture on the oxide pyramid array was carried out using water-diluted (50:1) HF solution. The uniformity of the (50× 50) nano-size aperture array was examined carefully on the four corners of the array patterns. The average diameter of the aperture was ˜ 260 nm and its deviation was found to be ˜ 10%. The opening rate of the nano-oxide aperture presented the slightly higher that the expected data. The increased opening rate was attributed to the large amount of electron accumulation during FE-SEM measurements. The increased opening rate can be attributed to the Fermi level shift from electron accumulation on the nanoscale aperture area..

  7. Polarization-sensitive interferometric synthetic aperture microscopy

    NASA Astrophysics Data System (ADS)

    South, Fredrick A.; Liu, Yuan-Zhi; Xu, Yang; Shemonski, Nathan D.; Carney, P. Scott; Boppart, Stephen A.

    2015-11-01

    Three-dimensional optical microscopy suffers from the well-known compromise between transverse resolution and depth-of-field. This is true for both structural imaging methods and their functional extensions. Interferometric synthetic aperture microscopy (ISAM) is a solution to the 3D coherent microscopy inverse problem that provides depth-independent transverse resolution. We demonstrate the extension of ISAM to polarization sensitive imaging, termed polarization-sensitive interferometric synthetic aperture microscopy (PS-ISAM). This technique is the first functionalization of the ISAM method and provides improved depth-of-field for polarization-sensitive imaging. The basic assumptions of polarization-sensitive imaging are explored, and refocusing of birefringent structures is experimentally demonstrated. PS-ISAM enables high-resolution volumetric imaging of birefringent materials and tissue.

  8. A Germanium-Based, Coded Aperture Imager

    SciTech Connect

    Ziock, K P; Madden, N; Hull, E; William, C; Lavietes, T; Cork, C

    2001-10-31

    We describe a coded-aperture based, gamma-ray imager that uses a unique hybrid germanium detector system. A planar, germanium strip detector, eleven millimeters thick is followed by a coaxial detector. The 19 x 19 strip detector (2 mm pitch) is used to determine the location and energy of low energy events. The location of high energy events are determined from the location of the Compton scatter in the planar detector and the energy is determined from the sum of the coaxial and planar energies. With this geometry, we obtain useful quantum efficiency in a position-sensitive mode out to 500 keV. The detector is used with a 19 x 17 URA coded aperture to obtain spectrally resolved images in the gamma-ray band. We discuss the performance of the planar detector, the hybrid system and present images taken of laboratory sources.

  9. Performance limits for Synthetic Aperture Radar.

    SciTech Connect

    Doerry, Armin Walter

    2006-02-01

    The performance of a Synthetic Aperture Radar (SAR) system depends on a variety of factors, many which are interdependent in some manner. It is often difficult to ''get your arms around'' the problem of ascertaining achievable performance limits, and yet those limits exist and are dictated by physics, no matter how bright the engineer tasked to generate a system design. This report identifies and explores those limits, and how they depend on hardware system parameters and environmental conditions. Ultimately, this leads to a characterization of parameters that offer optimum performance for the overall SAR system. For example, there are definite optimum frequency bands that depend on weather conditions and range, and minimum radar PRF for a fixed real antenna aperture dimension is independent of frequency. While the information herein is not new to the literature, its collection into a single report hopes to offer some value in reducing the ''seek time''.

  10. Frequency scanning from subwavelength aperture array.

    PubMed

    Yang, Rui; Zhang, Jiawei; Wang, Hui

    2014-06-15

    Resonant transmission of microwaves is demonstrated through subwavelength holes on a semicircular radiator. Split ring resonators, offering a perfect control of the emitting apertures, are applied to determine the radiation direction and the resonant frequency. Full wave simulation shows that our design is capable of achieving wide angular scanning beams without causing any other main lobe, and the steerable beams could be easily controlled through tuning the excitation frequency. PMID:24978511

  11. Analytic inversion in synthetic aperture radar.

    PubMed Central

    Rothaus, O S

    1994-01-01

    A method of processing synthetic aperture radar signals that avoids some of the approximations currently in use that appear to be responsible for severe phase distortions is described. As a practical matter, this method requires N3 numerical operations, as opposed to the N2 ln N currently the case, but N3 is now easily managed, for N in the range of interest. PMID:11607485

  12. Real-time interferometric synthetic aperture microscopy.

    PubMed

    Ralston, Tyler S; Marks, Daniel L; Carney, P Scott; Boppart, Stephen A

    2008-02-18

    An interferometric synthetic aperture microscopy (ISAM) system design with real-time 2D cross-sectional processing is described in detail. The system can acquire, process, and display the ISAM reconstructed images at frame rates of 2.25 frames per second for 512 X 1024 pixel images. This system provides quantitatively meaningful structural information from previously indistinguishable scattering intensities and provides proof of feasibility for future real-time ISAM systems. PMID:18542337

  13. Variable-Aperture Reciprocating Reed Valve

    NASA Technical Reports Server (NTRS)

    Lindner, Jeffrey L. (Inventor); Myers, W. Neill (Inventor); Kelley, Anthony R. (Inventor); Yang, Hong Q. (Inventor)

    2015-01-01

    A variable-aperture reciprocating reed valve includes a valve body defining a through hole region having a contoured-profile portion. A semi-rigid plate is affixed on one side thereof to the valve body to define a cantilever extending across the through hole region. At least one free edge of the cantilever opposes the contoured-profile portion of the through hole region in a non-contact relationship.

  14. Addressing Three Fallacies About Synthetic Aperture Radar

    NASA Astrophysics Data System (ADS)

    Atwood, Don; Garron, Jessica

    2013-12-01

    Synthetic aperture radar (SAR) has long been recognized as a valuable tool for real-time environmental analysis and understanding of the Earth's geophysical properties. With its ability to see through clouds and to image day and night in all seasons, it can provide high-resolution data when optical sensors cannot. This capability has enabled SAR scientists to delineate flooding events, assess earthquake damage, map forest fires, rescue trapped icebreakers, and identify the extent of oil spills.

  15. Exploiting Decorrelations In Synthetic-Aperture Radar

    NASA Technical Reports Server (NTRS)

    Zebker, Howard A.; Villasenor, John D.

    1994-01-01

    Temporal decorrelation between synthetic-aperture-radar data acquired on subsequent passes along same or nearly same trajectory serves as measure of change in target scene. Based partly on mathematical models of statistics of correlations between first- and second-pass radar echoes. Also based partly on Fourier-transform relations between radar-system impulse response and decorrelation functions particularly those expressing decorrelation effects of rotation and horizontal shift of trajectories between two passes.

  16. Complementary lattice arrays for coded aperture imaging

    NASA Astrophysics Data System (ADS)

    Ding, Jie; Noshad, Mohammad; Tarokh, Vahid

    2016-05-01

    In this work, we consider complementary lattice arrays in order to enable a broader range of designs for coded aperture imaging systems. We provide a general framework and methods that generate richer and more flexible designs than existing ones. Besides this, we review and interpret the state-of-the-art uniformly redundant arrays (URA) designs, broaden the related concepts, and further propose some new design methods.

  17. Effective wavelength scaling of rectangular aperture antennas.

    PubMed

    Chen, Yuanyuan; Yu, Li; Zhang, Jiasen; Gordon, Reuven

    2015-04-20

    We investigate the resonances of aperture antennas from the visible to the terahertz regime, with comparison to comprehensive simulations. Simple piecewise analytic behavior is found for the wavelength scaling over the entire spectrum, with a linear regime through the visible and near-IR. This theory will serve as a useful and simple design tool for applications including biosensors, nonlinear plasmonics and surface enhanced spectroscopies. PMID:25969079

  18. Aperture modulated, translating bed total body irradiation

    SciTech Connect

    Hussain, Amjad; Villarreal-Barajas, Jose Eduardo; Dunscombe, Peter; Brown, Derek W.

    2011-02-15

    Purpose: Total body irradiation (TBI) techniques aim to deliver a uniform radiation dose to a patient with an irregular body contour and a heterogeneous density distribution to within {+-}10% of the prescribed dose. In the current article, the authors present a novel, aperture modulated, translating bed TBI (AMTBI) technique that produces a high degree of dose uniformity throughout the entire patient. Methods: The radiation beam is dynamically shaped in two dimensions using a multileaf collimator (MLC). The irregular surface compensation algorithm in the Eclipse treatment planning system is used for fluence optimization, which is performed based on penetration depth and internal inhomogeneities. Two optimal fluence maps (AP and PA) are generated and beam apertures are created to deliver these optimal fluences. During treatment, the patient/phantom is translated on a motorized bed close to the floor (source to bed distance: 204.5 cm) under a stationary radiation beam with 0 deg. gantry angle. The bed motion and dynamic beam apertures are synchronized. Results: The AMTBI technique produces a more homogeneous dose distribution than fixed open beam translating bed TBI. In phantom studies, the dose deviation along the midline is reduced from 10% to less than 5% of the prescribed dose in the longitudinal direction. Dose to the lung is reduced by more than 15% compared to the unshielded fixed open beam technique. At the lateral body edges, the dose received from the open beam technique was 20% higher than that prescribed at umbilicus midplane. With AMTBI the dose deviation in this same region is reduced to less than 3% of the prescribed dose. Validation of the technique was performed using thermoluminescent dosimeters in a Rando phantom. Agreement between calculation and measurement was better than 3% in all cases. Conclusions: A novel, translating bed, aperture modulated TBI technique that employs dynamically shaped MLC defined beams is shown to improve dose uniformity

  19. RFI at L-band in Synthetic Aperture Radiometers

    NASA Technical Reports Server (NTRS)

    LeVine, David M.; Haken, M.; Wang, James R. (Technical Monitor)

    2003-01-01

    The spectral window at 1.413 GHz (L-band), set aside for passive use only, is critical for passive remote sensing of the earth from space. It is the largest spectral window available in the long wavelength end of the microwave spectrum where measurements are needed to monitor parameters of the surface such as soil moisture and sea surface salinity. The sensitivity to these parameters is rapidly lost at higher frequencies and is compromised by the ionosphere and antenna size at lower frequencies. Instruments for remote sensing from space in this spectral window are being developed by NASA (Aquarius) and ESA (SMOS) and are expected to be in orbit in a few years (2006). Although the band at 1.413 GHz is protected for passive use, RFI is a common problem. For example, the synthetic aperture radiometer, ESTAR (L-band, Horizontal polarization), has frequently experienced problems with RFI. During the Southern Great Plains Experiments (1997 and 1999), ESTAR experienced RFI significant enough to warrant changes in flight lines. The largest sources of RFI were identified as originating in airports and a likely source is air traffic control radar. In experiments in the vicinity of Richmond, VA, RFI in the form of periodic spikes was recorded, again suggestive of radar. However, in most cases the sources of the RFI are unknown. RFI is a sufficiently common problem that the first step in processing ESTAR data is a screening for RFI (a filter is used to detect large, rapid changes in brightness). Recently, measurements have been made with a new synthetic aperture radiometer, 2D-STAR. Examples of RFI observed simultaneously with ESTAR and the new synthetic aperture radiometer will be presented. 2D-STAR is an airborne instrument designed to develop the technology of aperture synthesis in two dimensions. It employs dual polarized patch antennas arranged in a cross configuration (+). Synthesis in two dimensions offers the potential for optimal thinning, but because of the wide

  20. Phase-Slip Avalanches in the Superflow of {sup 4}He through Arrays of Nanosize Apertures

    SciTech Connect

    Pekker, David; Barankov, Roman; Goldbart, Paul M.

    2007-04-27

    In response to recent experiments by the Berkeley group, we construct a model of superflow through an array of nanosize apertures that incorporates two basic ingredients: (1) disorder associated with each aperture having its own random critical velocity, and (2) effective interaperture coupling, mediated through the bulk superfluid. As the disorder becomes weak there is a transition from a regime where phase slips are largely independent to a regime where interactions lead to system-wide avalanches of phase slips. We explore the flow dynamics in both regimes, and make connections to the experiments.