Science.gov

Sample records for accelerator grid aperture

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

    SciTech Connect

    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.

    2016-02-15

    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.

  2. 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.

  3. Beam optics in a MeV-class multi-aperture multi-grid accelerator for the ITER neutral beam injector.

    PubMed

    Kashiwagi, M; Taniguchi, M; Umeda, N; de Esch, H P L; Grisham, L R; Boilson, D; Hemsworth, R S; Tanaka, M; Tobari, H; Watanabe, K; Inoue, T

    2012-02-01

    In a multi-aperture multi-grid accelerator of the ITER neutral beam injector, the beamlets are deflected due to space charge repulsion between beamlets and beam groups, and also due to magnetic field. Moreover, the beamlet deflection is influenced by electric field distortion generated by grid support structure. Such complicated beamlet deflections and the compensations have been examined utilizing a three-dimensional beam analysis. The space charge repulsion and the influence by the grid support structure were studied in a 1∕4 model of the accelerator including 320 beamlets. Beamlet deflection due to the magnetic field was studied by a single beamlet model. As the results, compensation methods of the beamlet deflection were designed, so as to utilize a metal bar (so-called field shaping plate) of 1 mm thick beneath the electron suppression grid (ESG), and an aperture offset of 1 mm in the ESG.

  4. Ion mobility spectrometer with virtual aperture grid

    SciTech Connect

    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.

  5. Studies of dished accelerator grids for 30-cm ion thrusters

    NASA Technical Reports Server (NTRS)

    Rawlin, V. K.

    1973-01-01

    Eighteen geometrically different sets of dished accelerator grids were tested on five 30-cm thrusters. The geometric variation of the grids included the grid-to-grid spacing, the screen and accelerator hole diameters and thicknesses, the screen and accelerator open area fractions, ratio of dish depth to dish diameter, compensation, and aperture shape. In general, the data taken over a range of beam currents for each grid set included the minimum total accelerating voltage required to extract a given beam current and the minimum accelerator grid voltage required to prevent electron backstreaming.

  6. Studies of dished accelerator grids for 30-cm ion thrusters

    NASA Technical Reports Server (NTRS)

    Rawlin, V. K.

    1973-01-01

    Geometrically different sets of dished accelerator grids were tested on five 30-cm thrusters. The geometric variation of the grids included the grid-to-grid spacing, the screen and accelerator hole diameters and thicknesses, the screen and accelerator open area fractions, ratio of dish depth to the dish diameter, compensation, and aperture shape. In general, the data taken over a range of beam currents for each grid set included the minimum total accelerating voltage required to extract a given beam current and the minimum accelerator grid voltage required to prevent electron backstreaming.

  7. Ion Accelerator With Negatively Biased Decelerator Grid

    NASA Technical Reports Server (NTRS)

    Brophy, John R.

    1994-01-01

    Three-grid ion accelerator in which accelerator grid is biased at negative potential and decelerator grid downstream of accelerator grid biased at smaller negative potential. This grid and bias arrangement reduces frequency of impacts, upon accelerator grid, of charge-exchange ions produced downstream in collisions between accelerated ions and atoms and molecules of background gas. Sputter erosion of accelerator grid reduced.

  8. Tailoring Ion-Thruster Grid Apertures for Greater Efficiency

    NASA Technical Reports Server (NTRS)

    Brophy, John

    2004-01-01

    A report proposes tailoring the diameters of the apertures in the accelerator grid of an ion thruster to reduce the open grid area through which un-ionized propellant gas can escape. The result would be a reduction in the loss of propellant gas and a corresponding increase in propellant efficiency. In a typical ion thruster, the plasma density decreases with radial distance from the centerline, and as a consequence, the diameters of ion beamlets decrease with increasing radial distance. According to the proposal, the apertures, through which the ion beamlets must pass, would be sized to match the diameters (with margin) of the beamlets. The decrease of the aperture diameters with radial distance would result in a significant reduction in the open grid area: In an example based on representative design parameters, the reduction could be as much as 30 percent. In this example, the transparency to un-ionized propellant would decrease from 0.24 to 0.17 and, as a result, the propellant efficiency would increase from 0.91 to 0.96.

  9. Single grid accelerator for an ion thrustor

    NASA Technical Reports Server (NTRS)

    Margosian, P. M.; Nakanishi, S. (Inventor)

    1973-01-01

    A single grid accelerator system for an ion thrustor is discussed. A layer of dielectric material is interposed between this metal grid and the chamber containing an ionized propellant for protecting the grid against sputtering erosion.

  10. Measurement of heat load density profile on acceleration grid in MeV-class negative ion accelerator

    SciTech Connect

    Hiratsuka, Junichi Hanada, Masaya; Kojima, Atsushi; Umeda, Naotaka; Kashiwagi, Mieko; Yoshida, Masafumi; Nishikiori, Ryo; Ichikawa, Masahiro; Watanabe, Kazuhiro; Tobari, Hiroyuki; Miyamoto, Kenji

    2016-02-15

    To understand the physics of the negative ion extraction/acceleration, the heat load density profile on the acceleration grid has been firstly measured in the ITER prototype accelerator where the negative ions are accelerated to 1 MeV with five acceleration stages. In order to clarify the profile, the peripheries around the apertures on the acceleration grid were separated into thermally insulated 34 blocks with thermocouples. The spatial resolution is as low as 3 mm and small enough to measure the tail of the beam profile with a beam diameter of ∼16 mm. It was found that there were two peaks of heat load density around the aperture. These two peaks were also clarified to be caused by the intercepted negative ions and secondary electrons from detailed investigation by changing the beam optics and gas density profile. This is the first experimental result, which is useful to understand the trajectories of these particles.

  11. Application of aluminum and titanium foils in low-energy wide-aperture electron accelerators

    NASA Astrophysics Data System (ADS)

    Bodakin, L. V.; Gusakov, A. I.; Komarov, O. V.; Kosogorov, S. L.; Motovilov, S. A.; Uspenskii, N. A.

    2016-09-01

    We have reported on the results of theoretical and experimental investigations of characteristics of aluminum and titanium foils used in devices to extract electron beams from wide-aperture low-energy accelerators with a high current density. The mechanical properties of foils at different temperatures and the electron beam transmission and absorption coefficients have been compared. The results of analyzing the dependences of the efficiency of the electron beam extraction from accelerators on the type of the electron-optical system, material, and thickness of the foil for various sizes of extraction windows and the same type of the slot support grids have been presented. We have proposed an analytic model for calculating the temperature of the foil in the unit cell of the support grid. The electron transmittance and absorbance, as well as the temperature regimes of the foils, have been calculated using different methods.

  12. Performance of 30-cm ion thrusters with dished accelerator grids

    NASA Technical Reports Server (NTRS)

    Rawlin, V. K.

    1973-01-01

    Thirteen sets of dished accelerator grids were treated on five different 30 cm diameter bombardment thrusters to evaluate the effects of grid geometry variations on thruster discharge chamber performance. The dished grid parameters varied were: grid-to-grid spacing, screen and accelerator grid hole diameter, screen and accelerator open area fraction, compensation for beam divergence losses, and accelerator grid thickness. The effects on discharge chamber performance of main magnetic field changes, magnetic baffle current, cathode pole piece length and cathode position were also investigated.

  13. Three-grid accelerator system for an ion propulsion engine

    NASA Technical Reports Server (NTRS)

    Brophy, John R. (Inventor)

    1994-01-01

    An apparatus is presented for an ion engine comprising a three-grid accelerator system with the decelerator grid biased negative of the beam plasma. This arrangement substantially reduces the charge-exchange ion current reaching the accelerator grid at high tank pressures, which minimizes erosion of the accelerator grid due to charge exchange ion sputtering, known to be the major accelerator grid wear mechanism. An improved method for life testing ion engines is also provided using the disclosed apparatus. In addition, the invention can also be applied in materials processing.

  14. ION ACCELERATION SYSTEM

    DOEpatents

    Luce, J.S.; Martin, J.A.

    1960-02-23

    Well focused, intense ion beams are obtained by providing a multi- apertured source grid in front of an ion source chamber and an accelerating multi- apertured grid closely spaced from and in alignment with the source grid. The longest dimensions of the elongated apertures in the grids are normal to the direction of the magnetic field used with the device. Large ion currents may be withdrawn from the source, since they do not pass through any small focal region between the grids.

  15. Measuring and optimizing the momentum aperture in a particle accelerator.

    PubMed

    Steier, C; Robin, D; Nadolski, L; Decking, W; Wu, Y; Laskar, J

    2002-05-01

    Particle motion in storage rings is confined by various aperture limits, the size of which restricts the performance of the ring in terms of injection efficiency, lifetime, etc. Intrabeam scattering makes particles sweep a large portion of the phase space, where their motion may eventually be resonantly or chaotically excited to large amplitudes leading to collision with the vacuum chamber. We report here the studies performed at the Advanced Light Source (ALS) on the on- and off-momentum particle motion that provides a good understanding of these limitations. Using off-momentum simulations and experiments together with frequency map analysis, we could precisely correlate beam loss areas with resonance locations. The very good agreement between simulations and experiments allowed us to provide guidance for avoiding these dangerous areas. This analysis results in predictive improvements of the momentum aperture, which actually led to a lifetime increase of 25% at the ALS for very high bunch charge.

  16. Grid-enhanced X-ray coded aperture microscopy with polycapillary optics.

    PubMed

    Sowa, Katarzyna M; Last, Arndt; Korecki, Paweł

    2017-03-21

    Polycapillary devices focus X-rays by means of multiple reflections of X-rays in arrays of bent glass capillaries. The size of the focal spot (typically 10-100 μm) limits the resolution of scanning, absorption and phase-contrast X-ray imaging using these devices. At the expense of a moderate resolution, polycapillary elements provide high intensity and are frequently used for X-ray micro-imaging with both synchrotrons and X-ray tubes. Recent studies have shown that the internal microstructure of such an optics can be used as a coded aperture that encodes high-resolution information about objects located inside the focal spot. However, further improvements to this variant of X-ray microscopy will require the challenging fabrication of tailored devices with a well-defined capillary microstructure. Here, we show that submicron coded aperture microscopy can be realized using a periodic grid that is placed at the output surface of a polycapillary optics. Grid-enhanced X-ray coded aperture microscopy with polycapillary optics does not rely on the specific microstructure of the optics but rather takes advantage only of its focusing properties. Hence, submicron X-ray imaging can be realized with standard polycapillary devices and existing set-ups for micro X-ray fluorescence spectroscopy.

  17. Grid-enhanced X-ray coded aperture microscopy with polycapillary optics

    NASA Astrophysics Data System (ADS)

    Sowa, Katarzyna M.; Last, Arndt; Korecki, Paweł

    2017-03-01

    Polycapillary devices focus X-rays by means of multiple reflections of X-rays in arrays of bent glass capillaries. The size of the focal spot (typically 10–100 μm) limits the resolution of scanning, absorption and phase-contrast X-ray imaging using these devices. At the expense of a moderate resolution, polycapillary elements provide high intensity and are frequently used for X-ray micro-imaging with both synchrotrons and X-ray tubes. Recent studies have shown that the internal microstructure of such an optics can be used as a coded aperture that encodes high-resolution information about objects located inside the focal spot. However, further improvements to this variant of X-ray microscopy will require the challenging fabrication of tailored devices with a well-defined capillary microstructure. Here, we show that submicron coded aperture microscopy can be realized using a periodic grid that is placed at the output surface of a polycapillary optics. Grid-enhanced X-ray coded aperture microscopy with polycapillary optics does not rely on the specific microstructure of the optics but rather takes advantage only of its focusing properties. Hence, submicron X-ray imaging can be realized with standard polycapillary devices and existing set-ups for micro X-ray fluorescence spectroscopy.

  18. Grid-enhanced X-ray coded aperture microscopy with polycapillary optics

    PubMed Central

    Sowa, Katarzyna M.; Last, Arndt; Korecki, Paweł

    2017-01-01

    Polycapillary devices focus X-rays by means of multiple reflections of X-rays in arrays of bent glass capillaries. The size of the focal spot (typically 10–100 μm) limits the resolution of scanning, absorption and phase-contrast X-ray imaging using these devices. At the expense of a moderate resolution, polycapillary elements provide high intensity and are frequently used for X-ray micro-imaging with both synchrotrons and X-ray tubes. Recent studies have shown that the internal microstructure of such an optics can be used as a coded aperture that encodes high-resolution information about objects located inside the focal spot. However, further improvements to this variant of X-ray microscopy will require the challenging fabrication of tailored devices with a well-defined capillary microstructure. Here, we show that submicron coded aperture microscopy can be realized using a periodic grid that is placed at the output surface of a polycapillary optics. Grid-enhanced X-ray coded aperture microscopy with polycapillary optics does not rely on the specific microstructure of the optics but rather takes advantage only of its focusing properties. Hence, submicron X-ray imaging can be realized with standard polycapillary devices and existing set-ups for micro X-ray fluorescence spectroscopy. PMID:28322316

  19. Impingement-Current-Erosion Characteristics of Accelerator Grids on Two-Grid Ion Thrusters

    NASA Technical Reports Server (NTRS)

    Barker, Timothy

    1996-01-01

    Accelerator grid sputter erosion resulting from charge-exchange-ion impingement is considered to be a primary cause of failure for electrostatic ion thrusters. An experimental method was developed and implemented to measure erosion characteristics of ion-thruster accel-grids for two-grid systems as a function of beam current, accel-grid potential, and facility background pressure. Intricate accelerator grid erosion patterns, that are typically produced in a short time (a few hours), are shown. Accelerator grid volumetric and depth-erosion rates are calculated from these erosion patterns and reported for each of the parameters investigated. A simple theoretical volumetric erosion model yields results that are compared to experimental findings. Results from the model and experiments agree to within 10%, thereby verifying the testing technique. In general, the local distribution of erosion is concentrated in pits between three adjacent holes and trenches that join pits. The shapes of the pits and trenches are shown to be dependent upon operating conditions. Increases in beam current and the accel-grid voltage magnitude lead to deeper pits and trenches. Competing effects cause complex changes in depth-erosion rates as background pressure is increased. Shape factors that describe pits and trenches (i.e. ratio of the average erosion width to the maximum possible width) are also affected in relatively complex ways by changes in beam current, ac tel-grid voltage magnitude, and background pressure. In all cases, however, gross volumetric erosion rates agree with theoretical predictions.

  20. Improving the Total Impulse Capability of the NSTAR Ion Thruster With Thick-Accelerator-Grid Ion Optics

    NASA Technical Reports Server (NTRS)

    Soulas, George C.

    2001-01-01

    The results of performance tests with thick-accelerator-grid (TAG) ion optics are presented. TAG ion optics utilize a 50 percent thicker accelerator grid to double ion optics' service life. NSTAR ion optics were also tested to provide a baseline performance for comparison. Impingement-limited total voltages for the TAG ion optics were only 0 to 15 V higher than those of the NSTAR ion optics. Electron backstreaming limits for the TAG ion optics were 3 to 9 V higher than those for the NSTAR optics due to the increased accelerator grid thickness for the TAG ion optics. Screen grid ion transparencies for the TAG ion optics were only about 2 percent lower than those for the NSTAR optics, reflecting the lower physical screen grid open area fraction of the TAG ion optics. Accelerator currents for the TAG ion optics were 19 to 43 percent greater than those for the NSTAR ion optics due, in part, to a sudden increase in accelerator current during TAG ion optics' performance tests for unknown reasons and to the lower-than-nominal accelerator aperture diameters. Beam divergence half-angles that enclosed 95 percent of the total beam current and beam divergence thrust correction factors for the TAG ion optics were within 2 degrees and 1 percent, respectively, of those for the NSTAR ion optics.

  1. Physics design of a 100 keV acceleration grid system for the diagnostic neutral beam for international tokamak experimental reactor.

    PubMed

    Singh, M J; De Esch, H P L

    2010-01-01

    This paper describes the physics design of a 100 keV, 60 A H(-) accelerator for the diagnostic neutral beam (DNB) for international tokamak experimental reactor (ITER). The accelerator is a three grid system comprising of 1280 apertures, grouped in 16 groups with 80 apertures per beam group. Several computer codes have been used to optimize the design which follows the same philosophy as the ITER Design Description Document (DDD) 5.3 and the 1 MeV heating and current drive beam line [R. Hemsworth, H. Decamps, J. Graceffa, B. Schunke, M. Tanaka, M. Dremel, A. Tanga, H. P. L. De Esch, F. Geli, J. Milnes, T. Inoue, D. Marcuzzi, P. Sonato, and P. Zaccaria, Nucl. Fusion 49, 045006 (2009)]. The aperture shapes, intergrid distances, and the extractor voltage have been optimized to minimize the beamlet divergence. To suppress the acceleration of coextracted electrons, permanent magnets have been incorporated in the extraction grid, downstream of the cooling water channels. The electron power loads on the extractor and the grounded grids have been calculated assuming 1 coextracted electron per ion. The beamlet divergence is calculated to be 4 mrad. At present the design for the filter field of the RF based ion sources for ITER is not fixed, therefore a few configurations of the same have been considered. Their effect on the transmission of the electrons and beams through the accelerator has been studied. The OPERA-3D code has been used to estimate the aperture offset steering constant of the grounded grid and the extraction grid, the space charge interaction between the beamlets and the kerb design required to compensate for this interaction. All beamlets in the DNB must be focused to a single point in the duct, 20.665 m from the grounded grid, and the required geometrical aimings and aperture offsets have been calculated.

  2. Physics design of a 100 keV acceleration grid system for the diagnostic neutral beam for international tokamak experimental reactor

    NASA Astrophysics Data System (ADS)

    Singh, M. J.; De Esch, H. P. L.

    2010-01-01

    This paper describes the physics design of a 100 keV, 60 A H- accelerator for the diagnostic neutral beam (DNB) for international tokamak experimental reactor (ITER). The accelerator is a three grid system comprising of 1280 apertures, grouped in 16 groups with 80 apertures per beam group. Several computer codes have been used to optimize the design which follows the same philosophy as the ITER Design Description Document (DDD) 5.3 and the 1 MeV heating and current drive beam line [R. Hemsworth, H. Decamps, J. Graceffa, B. Schunke, M. Tanaka, M. Dremel, A. Tanga, H. P. L. De Esch, F. Geli, J. Milnes, T. Inoue, D. Marcuzzi, P. Sonato, and P. Zaccaria, Nucl. Fusion 49, 045006 (2009)]. The aperture shapes, intergrid distances, and the extractor voltage have been optimized to minimize the beamlet divergence. To suppress the acceleration of coextracted electrons, permanent magnets have been incorporated in the extraction grid, downstream of the cooling water channels. The electron power loads on the extractor and the grounded grids have been calculated assuming 1 coextracted electron per ion. The beamlet divergence is calculated to be 4 mrad. At present the design for the filter field of the RF based ion sources for ITER is not fixed, therefore a few configurations of the same have been considered. Their effect on the transmission of the electrons and beams through the accelerator has been studied. The OPERA-3D code has been used to estimate the aperture offset steering constant of the grounded grid and the extraction grid, the space charge interaction between the beamlets and the kerb design required to compensate for this interaction. All beamlets in the DNB must be focused to a single point in the duct, 20.665 m from the grounded grid, and the required geometrical aimings and aperture offsets have been calculated.

  3. High performance auxiliary-propulsion ion thruster with ion-machined accelerator grid

    NASA Technical Reports Server (NTRS)

    Hudson, W. R.; Banks, B. A.

    1975-01-01

    An improvement in thruster performance was achieved by reducing the diameter of the accelerator grid holes. The smaller accelerator grid holes resulted in a reduction in neutral mercury atoms escaping the discharge chamber, which in turn enhanced the discharge propellant utilization from approximately 68 percent to 92 percent. The accelerator grids were fabricated by ion machining with an 8-centimeter-diameter thruster, and the screen grid holes individually focused ion beamlets onto the blank accelerator grid. The resulting accelerator grid holes are less than 1.12 millimeters in diameter, while previously used accelerator grids had hole diameters of 1.69 millimeters. The thruster could be operated with the small-hole accelerator grid at neutralizer potential.

  4. Aperture studies of the BNL colliding beam accelerator with reduced superperiodicity

    SciTech Connect

    Dell, G.F.

    1983-01-01

    Chromatic properties of the Brookhaven CBA (Colliding Beam Accelerator) with one low ..beta.. insertion in each of the three superperiods have been studied using the PATRICIA particle tracking program. Systematic multipoles of order 5 < n less than or equal to 10 as well as random multipoles of order 1 less than or equal to n less than or equal to 10 are, along with random closed orbit errors and sagitta effects, included when determining the aperture of the lattice. 3 references, 6 figures.

  5. Electron Backstreaming Mitigation via a Magnetic Grid

    NASA Technical Reports Server (NTRS)

    Foster, John F.; Roman, Robert F.; Soulas, George C.; Patterson, Michael J.

    2002-01-01

    Electron backstreaming due to accelerator grid hole enlargement has been identified as a failure mechanism that will limit ion thruster service lifetime. Over extended periods of time as accelerator grid apertures enlarge due to erosion, ion thrusters are required to operate at increasingly higher accelerator grid voltages in order to prevent electron backstreaming. These higher voltages give rise to higher grid erosion rates, which in turn accelerates aperture enlargement. Presented here is an approach to mitigate the backflow of electrons into the engine by using a transverse magnetic field.

  6. Sensitivity of 30-cm mercury bombardment ion thruster characteristics to accelerator grid design

    NASA Technical Reports Server (NTRS)

    Rawlin, V. K.

    1978-01-01

    The design of ion optics for bombardment thrusters strongly influences overall performance and lifetime. The operation of a 30 cm thruster with accelerator grid open area fractions ranging from 43 to 24 percent, was evaluated and compared with experimental and theoretical results. Ion optics properties measured included the beam current extraction capability, the minimum accelerator grid voltage to prevent backstreaming, ion beamlet diameter as a function of radial position on the grid and accelerator grid hole diameter, and the high energy, high angle ion beam edge location. Discharge chamber properties evaluated were propellant utilization efficiency, minimum discharge power per beam amp, and minimum discharge voltage.

  7. 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.

  8. The PyZgoubi framework and the simulation of dynamic aperture in fixed-field alternating-gradient accelerators

    NASA Astrophysics Data System (ADS)

    Tygier, S.; Appleby, R. B.; Garland, J. M.; Hock, K.; Owen, H.; Kelliher, D. J.; Sheehy, S. L.

    2015-03-01

    We present PyZgoubi, a framework that has been developed based on the tracking engine Zgoubi to model, optimise and visualise the dynamics in particle accelerators, especially fixed-field alternating-gradient (FFAG) accelerators. We show that PyZgoubi abstracts Zgoubi by wrapping it in an easy-to-use Python framework in order to allow simple construction, parameterisation, visualisation and optimisation of FFAG accelerator lattices. Its object oriented design gives it the flexibility and extensibility required for current novel FFAG design. We apply PyZgoubi to two example FFAGs; this includes determining the dynamic aperture of the PAMELA medical FFAG in the presence of magnet misalignments, and illustrating how PyZgoubi may be used to optimise FFAGs. We also discuss a robust definition of dynamic aperture in an FFAG and show its implementation in PyZgoubi.

  9. Design, fabrication, and operation of dished accelerator grids on a 30-cm ion thruster

    NASA Technical Reports Server (NTRS)

    Rawlin, V. K.; Banks, B. A.; Byers, D. C.

    1972-01-01

    Several closely-space dished accelerator grid systems were fabricated and tested on a 30-cm diameter mercury bombardment thruster and they appear to be a solution to the stringent requirements imposed by the near-term, high-thrust, low specific impulse electric propulsion missions. The grids were simultaneously hydroformed and then simultaneously stress relieved. The ion extraction capability and discharge chamber performance were studied as the total accelerating voltage, the ratio of net-to-total voltage, grid spacing, and dish direction were varied.

  10. Design, fabrication, and operation of dished accelerator grids on a 30-cm ion thruster.

    NASA Technical Reports Server (NTRS)

    Rawlin, V. K.; Banks, B. A.; Byers, D. C.

    1972-01-01

    Several closely-spaced dished accelerator grid systems have been fabricated and tested on a 30-cm diameter mercury bombardment thruster and they appear to be a solution to the stringent requirements imposed by the near-term, high-thrust, low specific impulse electric propulsion missions. The grids were simultaneously hydroformed and then simultaneously stress relieved. The ion extraction capability and discharge chamber performance were studied as the total accelerating voltage, the ratio of net-to-total voltage, grid spacing, and dish direction were varied.

  11. Multiple-grid convergence acceleration of viscous and inviscid flow computations

    NASA Technical Reports Server (NTRS)

    Johnson, G. M.

    1983-01-01

    A multiple-grid algorithm for use in efficiently obtaining steady solution to the Euler and Navier-Stokes equations is presented. The convergence of a simple, explicit fine-grid solution procedure is accelerated on a sequence of successively coarser grids by a coarse-grid information propagation method which rapidly eliminates transients from the computational domain. This use of multiple-gridding to increase the convergence rate results in substantially reduced work requirements for the numerical solution of a wide range of flow problems. Computational results are presented for subsonic and transonic inviscid flows and for laminar and turbulent, attached and separated, subsonic viscous flows. Work reduction factors as large as eight, in comparison to the basic fine-grid algorithm, were obtained. Possibilities for further performance improvement are discussed.

  12. Sustainable Energy in Remote Indonesian Grids. Accelerating Project Development

    SciTech Connect

    Hirsch, Brian; Burman, Kari; Davidson, Carolyn; Elchinger, Michael; Hardison, R.; Karsiwulan, D.; Castermans, B.

    2015-06-30

    Sustainable Energy for Remote Indonesian Grids (SERIG) is a U.S. Department of Energy (DOE) funded initiative to support Indonesia’s efforts to develop clean energy and increase access to electricity in remote locations throughout the country. With DOE support, the SERIG implementation team consists of the National Renewable Energy Laboratory (NREL) and Winrock International’s Jakarta, Indonesia office. Through technical assistance that includes techno-economic feasibility evaluation for selected projects, government-to-government coordination, infrastructure assessment, stakeholder outreach, and policy analysis, SERIG seeks to provide opportunities for individual project development and a collective framework for national replication office.

  13. Charge-exchange erosion studies of accelerator grids in ion thrusters

    NASA Technical Reports Server (NTRS)

    Peng, Xiaohang; Ruyten, Wilhelmus M.; Keefer, Dennis

    1993-01-01

    A particle simulation model is developed to study the charge-exchange grid erosion in ion thrusters for both ground-based and space-based operations. Because the neutral gas downstream from the accelerator grid is different for space and ground operation conditions, the charge-exchange erosion processes are also different. Based on an assumption of now electric potential hill downstream from the ion thruster, the calculations show that the accelerator grid erosion rate for space-based operating conditions should be significantly less than experimentally observed erosion rates from the ground-based tests conducted at NASA Lewis Research Center (LeRC) and NASA Jet Propulsion Laboratory (JPL). To resolve this erosion issue completely, we believe that it is necessary to accurately measure the entire electric potential field downstream from the thruster.

  14. A grid computing-based approach for the acceleration of simulations in cardiology.

    PubMed

    Alonso, José M; Ferrero, José M; Hernández, Vicente; Moltó, Germán; Saiz, Javier; Trénor, Beatriz

    2008-03-01

    This paper combines high-performance computing and grid computing technologies to accelerate multiple executions of a biomedical application that simulates the action potential propagation on cardiac tissues. First, a parallelization strategy was employed to accelerate the execution of simulations on a cluster of personal computers (PCs). Then, grid computing was employed to concurrently perform the multiple simulations that compose the cardiac case studies on the resources of a grid deployment, by means of a service-oriented approach. This way, biomedical experts are provided with a gateway to easily access a grid infrastructure for the execution of these research studies. Emphasis is stressed on the methodology employed. In order to assess the benefits of the grid, a cardiac case study, which analyzes the effects of premature stimulation on reentry generation during myocardial ischemia, has been carried out. The collaborative usage of a distributed computing infrastructure has reduced the time required for the execution of cardiac case studies, which allows, for example, to take more accurate decisions when evaluating the effects of new antiarrhythmic drugs on the electrical activity of the heart.

  15. A tool for accelerating material calculations through the generation of highly efficient k-point grids

    NASA Astrophysics Data System (ADS)

    Mueller, Tim; Wisesa, Pandu

    The calculation of many material properties requires the evaluation of an integral over the Brillouin zone, which is commonly approximated by sampling a regular grid of points, known as k-points, in reciprocal space. We have developed an automated tool for generating k-point grids that significantly accelerates the calculation of material properties compared to commonly used methods. Our tool, which is being made freely available to the public, is capable of generating highly efficient k-point grids in a fraction of a second for any crystalline material. We present an overview of our method, benchmark results, and a discussion of how it can be integrated into a high-throughput computing environment.

  16. Studies of the chromatic properties and dynamic aperture of the BNL colliding-beam accelerator. [PATRICIA particle tracking code

    SciTech Connect

    Dell, G.F.

    1983-01-01

    The PATRICIA particle tracking program has been used to study chromatic effects in the Brookhaven CBA (Colliding Beam Accelerator). The short term behavior of particles in the CBA has been followed for particle histories of 300 turns. Contributions from magnet multipoles characteristic of superconducting magnets and closed orbit errors have been included in determining the dynamic aperture of the CBA for on and off momentum particles. The width of the third integer stopband produced by the temperature dependence of magnetization induced sextupoles in the CBA cable dipoles is evaluated for helium distribution systems having periodicity of one and six. The stopband width at a tune of 68/3 is naturally zero for the system having a periodicity of six and is approx. 10/sup -4/ for the system having a periodicity of one. Results from theory are compared with results obtained with PATRICIA; the results agree within a factor of slightly more than two.

  17. Numerical study of the plasma wall-bias effect on the ion flux through acceleration grid hole

    SciTech Connect

    Park, Seung-Hoon; Chang, C. S.

    2010-07-15

    In the extraction of ion beams from a source plasma through a grid acceleration structure, one of the key improvement issues is the fluence of the ion flux. Theoretical research has usually been focused on the structure of the grid system and the distribution of the electrostatic voltages over the grid layers. In the present work, using a self-consistent computer simulation between the plasma source, sheath potential, and the grid system, the effect of the source-wall biasing on the fluence of the ion flux through a three-grid acceleration system has been examined. It is found that a strongly positive wall-biasing can significantly enhance the ion flux by improving the shape of the plasma sheath potential meniscus at the entrance to the grid hole structure.

  18. In Situ, Time-Resolved Accelerator Grid Erosion Measurements in the NSTAR 8000 Hour Ion Engine Wear Test

    NASA Technical Reports Server (NTRS)

    Sovey, J.

    1997-01-01

    Time-resolved, in situ measurements of the charge exchange ion erosion pattern on the downstream face of the accelerator grid have been made during an ongoin wear test of the NSTAR 30 cm ion thruster.

  19. Further study of the effect of the downstream plasma condition on accelerator grid erosion in an ion thruster

    NASA Technical Reports Server (NTRS)

    Peng, Xiaohang; Ruyten, Wilhelmus M.; Keefer, Dennis

    1992-01-01

    Further numerical results are presented of earlier particle-in-cell/Monte Carlo calculations of accelerator grid erosion in an ion thruster. A comparison between numerical and experimental results suggests that the accelerator grid impingement is primarily due to ions created far downstream from the accelerator grid. In particular, for the same experimental conditions as those of Monheiser and Wilbur at Colorado State University, it is found that a downstream plasma density of 2 x 10 exp 14/cu m is required to give the same ratio of accelerator grid impingement current to beam current (5 percent). For this condition, a potential hill is found in the downstream region of 2.5 V.

  20. Power versus performance tradeoffs of GPU-accelerated backprojection-based synthetic aperture radar image formation

    NASA Astrophysics Data System (ADS)

    Portillo, Ricardo; Arunagiri, Sarala; Teller, Patricia J.; Park, Song J.; Nguyen, Lam H.; Deroba, Joseph C.; Shires, Dale

    2011-06-01

    The continuing miniaturization and parallelization of computer hardware has facilitated the development of mobile and field-deployable systems that can accommodate terascale processing within once prohibitively small size and weight constraints. General-purpose Graphics Processing Units (GPUs) are prominent examples of such terascale devices. Unfortunately, the added computational capability of these devices often comes at the cost of larger demands on power, an already strained resource in these systems. This study explores power versus performance issues for a workload that can take advantage of GPU capability and is targeted to run in field-deployable environments, i.e., Synthetic Aperture Radar (SAR). Specifically, we focus on the Image Formation (IF) computational phase of SAR, often the most compute intensive, and evaluate two different state-of-the-art GPU implementations of this IF method. Using real and simulated data sets, we evaluate performance tradeoffs for single- and double-precision versions of these implementations in terms of time-to-solution, image output quality, and total energy consumption. We employ fine-grain direct-measurement techniques to capture isolated power utilization and energy consumption of the GPU device, and use general and radarspecific metrics to evaluate image output quality. We show that double-precision IF can provide slight image improvement to low-reflective areas of SAR images, but note that the added quality may not be worth the higher power and energy costs associated with higher precision operations.

  1. GPU accelerated cell-based adaptive mesh refinement on unstructured quadrilateral grid

    NASA Astrophysics Data System (ADS)

    Luo, Xisheng; Wang, Luying; Ran, Wei; Qin, Fenghua

    2016-10-01

    A GPU accelerated inviscid flow solver is developed on an unstructured quadrilateral grid in the present work. For the first time, the cell-based adaptive mesh refinement (AMR) is fully implemented on GPU for the unstructured quadrilateral grid, which greatly reduces the frequency of data exchange between GPU and CPU. Specifically, the AMR is processed with atomic operations to parallelize list operations, and null memory recycling is realized to improve the efficiency of memory utilization. It is found that results obtained by GPUs agree very well with the exact or experimental results in literature. An acceleration ratio of 4 is obtained between the parallel code running on the old GPU GT9800 and the serial code running on E3-1230 V2. With the optimization of configuring a larger L1 cache and adopting Shared Memory based atomic operations on the newer GPU C2050, an acceleration ratio of 20 is achieved. The parallelized cell-based AMR processes have achieved 2x speedup on GT9800 and 18x on Tesla C2050, which demonstrates that parallel running of the cell-based AMR method on GPU is feasible and efficient. Our results also indicate that the new development of GPU architecture benefits the fluid dynamics computing significantly.

  2. Application of magnetic pulse compression to the grid system of the ETA/ATA accelerator

    SciTech Connect

    Birx, D.L.; Cook, E.G.; Reginato, L.L.; Schmidt, J.A.; Smith, M.W.

    1982-11-02

    During the past year, several magnetic pulse compression systems have been built and applied to the ETA accelerator. In view of their excellent performance, a non-linear magnetic system has been adopted for the ATA grid drive in place of the spark gap driven Blumlein. The magnetic system will give us a much higher reliability and greater flexibility by being independent of the high pressure gas blown system. A further advantage of this system will be the capability of achieving higher rep-rates in case of a future upgrade. System design and performance under burst mode will be described.

  3. Extended nonlinear chirp scaling algorithm for highly squinted missile-borne synthetic aperture radar with diving acceleration

    NASA Astrophysics Data System (ADS)

    Liu, Rengli; Wang, Yanfei

    2016-04-01

    An extended nonlinear chirp scaling (NLCS) algorithm is proposed to process data of highly squinted, high-resolution, missile-borne synthetic aperture radar (SAR) diving with a constant acceleration. Due to the complex diving movement, the traditional signal model and focusing algorithm are no longer suited for missile-borne SAR signal processing. Therefore, an accurate range equation is presented, named as the equivalent hyperbolic range model (EHRM), which is more accurate and concise compared with the conventional fourth-order polynomial range equation. Based on the EHRM, a two-dimensional point target reference spectrum is derived, and an extended NLCS algorithm for missile-borne SAR image formation is developed. In the algorithm, a linear range walk correction is used to significantly remove the range-azimuth cross coupling, and an azimuth NLCS processing is adopted to solve the azimuth space variant focusing problem. Moreover, the operations of the proposed algorithm are carried out without any interpolation, thus having small computational loads. Finally, the simulation results and real-data processing results validate the proposed focusing algorithm.

  4. Grid-based steered thermodynamic integration accelerates the calculation of binding free energies.

    PubMed

    Fowler, Philip W; Jha, Shantenu; Coveney, Peter V

    2005-08-15

    The calculation of binding free energies is important in many condensed matter problems. Although formally exact computational methods have the potential to complement, add to, and even compete with experimental approaches, they are difficult to use and extremely time consuming. We describe a Grid-based approach for the calculation of relative binding free energies, which we call Steered Thermodynamic Integration calculations using Molecular Dynamics (STIMD), and its application to Src homology 2 (SH2) protein cell signalling domains. We show that the time taken to compute free energy differences using thermodynamic integration can be significantly reduced: potentially from weeks or months to days of wall-clock time. To be able to perform such accelerated calculations requires the ability to both run concurrently and control in realtime several parallel simulations on a computational Grid. We describe how the RealityGrid computational steering system, in conjunction with a scalable classical MD code, can be used to dramatically reduce the time to achieve a result. This is necessary to improve the adoption of this technique and further allows more detailed investigations into the accuracy and precision of thermodynamic integration. Initial results for the Src SH2 system are presented and compared to a reported experimental value. Finally, we discuss the significance of our approach.

  5. Optimization of electrostatic dual-grid beam-deflection system

    NASA Technical Reports Server (NTRS)

    Hudson, W. R.; Lathem, W. C.; Power, J. L.; Banks, B. A.

    1972-01-01

    Tests were performed to minimize accelerator grid erosion of a 5-cm diameter Kaufman ion thruster due to direct beam impingement. Several different screen hole diameters, pillow-shape-square screen holes, and dished screen grids were tried. The optimization was accomplished by copper plating the accelerator grid before testing each grid configuration on a thruster for a 2-hour run. The thruster beam sputtered copper and molybdenum from the accelerator grid where the beam impinged. The observed erosion patterns and measured accelerator currents were used to determine how to modify the accelerator system. The lowest erosion was obtained for a 50-percent open area pillow-shape-square-aperture screen grid, dished 0.043 centimeter convex toward the accelerator grid, which was positioned with the center of the screen grid 0.084 centimeter from the accelerator grid. During this investigation the accelerator current was reduced from 120 to 55 microamperes and was also more uniformly distributed over the area of the accelerator grid.

  6. OpenZika: An IBM World Community Grid Project to Accelerate Zika Virus Drug Discovery

    PubMed Central

    Perryman, Alexander L.; Horta Andrade, Carolina

    2016-01-01

    The Zika virus outbreak in the Americas has caused global concern. To help accelerate this fight against Zika, we launched the OpenZika project. OpenZika is an IBM World Community Grid Project that uses distributed computing on millions of computers and Android devices to run docking experiments, in order to dock tens of millions of drug-like compounds against crystal structures and homology models of Zika proteins (and other related flavivirus targets). This will enable the identification of new candidates that can then be tested in vitro, to advance the discovery and development of new antiviral drugs against the Zika virus. The docking data is being made openly accessible so that all members of the global research community can use it to further advance drug discovery studies against Zika and other related flaviviruses. PMID:27764115

  7. The Impact of Back-Sputtered Carbon on the Accelerator Grid Wear Rates of the NEXT and NSTAR Ion Thrusters

    NASA Technical Reports Server (NTRS)

    Soulas, George C.

    2013-01-01

    A study was conducted to quantify the impact of back-sputtered carbon on the downstream accelerator grid erosion rates of the NASA's Evolutionary Xenon Thruster (NEXT) Long Duration Test (LDT1). A similar analysis that was conducted for the NASA's Solar Electric Propulsion Technology Applications Readiness Program (NSTAR) Life Demonstration Test (LDT2) was used as a foundation for the analysis developed herein. A new carbon surface coverage model was developed that accounted for multiple carbon adlayers before complete surface coverage is achieved. The resulting model requires knowledge of more model inputs, so they were conservatively estimated using the results of past thin film sputtering studies and particle reflection predictions. In addition, accelerator current densities across the grid were rigorously determined using an ion optics code to determine accelerator current distributions and an algorithm to determine beam current densities along a grid using downstream measurements. The improved analysis was applied to the NSTAR test results for evaluation. The improved analysis demonstrated that the impact of back-sputtered carbon on pit and groove wear rate for the NSTAR LDT2 was negligible throughout most of eroded grid radius. The improved analysis also predicted the accelerator current density for transition from net erosion to net deposition considerably more accurately than the original analysis. The improved analysis was used to estimate the impact of back-sputtered carbon on the accelerator grid pit and groove wear rate of the NEXT Long Duration Test (LDT1). Unlike the NSTAR analysis, the NEXT analysis was more challenging because the thruster was operated for extended durations at various operating conditions and was unavailable for measurements because the test is ongoing. As a result, the NEXT LDT1 estimates presented herein are considered preliminary until the results of future post-test analyses are incorporated. The worst-case impact of carbon

  8. The Impact of Back-Sputtered Carbon on the Accelerator Grid Wear Rates of the NEXT and NSTAR Ion Thrusters

    NASA Technical Reports Server (NTRS)

    Soulas, George C.

    2013-01-01

    A study was conducted to quantify the impact of back-sputtered carbon on the downstream accelerator grid erosion rates of the NEXT (NASA's Evolutionary Xenon Thruster) Long Duration Test (LDT1). A similar analysis that was conducted for the NSTAR (NASA's Solar Electric Propulsion Technology Applications Readiness Program) Life Demonstration Test (LDT2) was used as a foundation for the analysis developed herein. A new carbon surface coverage model was developed that accounted for multiple carbon adlayers before complete surface coverage is achieved. The resulting model requires knowledge of more model inputs, so they were conservatively estimated using the results of past thin film sputtering studies and particle reflection predictions. In addition, accelerator current densities across the grid were rigorously determined using an ion optics code to determine accelerator current distributions and an algorithm to determine beam current densities along a grid using downstream measurements. The improved analysis was applied to the NSTAR test results for evaluation. The improved analysis demonstrated that the impact of back-sputtered carbon on pit and groove wear rate for the NSTAR LDT2 was negligible throughout most of eroded grid radius. The improved analysis also predicted the accelerator current density for transition from net erosion to net deposition considerably more accurately than the original analysis. The improved analysis was used to estimate the impact of back-sputtered carbon on the accelerator grid pit and groove wear rate of the NEXT Long Duration Test (LDT1). Unlike the NSTAR analysis, the NEXT analysis was more challenging because the thruster was operated for extended durations at various operating conditions and was unavailable for measurements because the test is ongoing. As a result, the NEXT LDT1 estimates presented herein are considered preliminary until the results of future posttest analyses are incorporated. The worst-case impact of carbon back

  9. Advanced Simulation and Optimization Tools for Dynamic Aperture of Non-scaling FFAGs and Accelerators including Modern User Interfaces

    SciTech Connect

    Mills, F.; Makino, Kyoko; Berz, Martin; Johnstone, C.

    2010-09-01

    With the U.S. experimental effort in HEP largely located at laboratories supporting the operations of large, highly specialized accelerators, colliding beam facilities, and detector facilities, the understanding and prediction of high energy particle accelerators becomes critical to the success, overall, of the DOE HEP program. One area in which small businesses can contribute to the ongoing success of the U.S. program in HEP is through innovations in computer techniques and sophistication in the modeling of high-energy accelerators. Accelerator modeling at these facilities is performed by experts with the product generally highly specific and representative only of in-house accelerators or special-interest accelerator problems. Development of new types of accelerators like FFAGs with their wide choices of parameter modifications, complicated fields, and the simultaneous need to efficiently handle very large emittance beams requires the availability of new simulation environments to assure predictability in operation. In this, ease of use and interfaces are critical to realizing a successful model, or optimization of a new design or working parameters of machines. In Phase I, various core modules for the design and analysis of FFAGs were developed and Graphical User Interfaces (GUI) have been investigated instead of the more general yet less easily manageable console-type output COSY provides.

  10. Performance limits of ion extraction systems with non-circular apertures

    NASA Astrophysics Data System (ADS)

    Shagayda, A.; Madeev, S.

    2016-04-01

    A three-dimensional computer simulation is used to determine the perveance limitations of ion extraction systems with non-circular apertures. The objective of the study is to analyze the possibilities to improve mechanical strength of the ion optics made of carbon-carbon composite materials. Non-circular grid apertures are better suited to the physical structure of carbon-carbon composite materials, than conventionally used circular holes in a hexagonal pattern, because they allow a fewer number of cut fibers. However, the slit-type accelerating systems, usually regarded as the main alternative to the conventional ion optics, have an intolerably narrow range of operating perveance values at which there is no direct ion impingement on the acceleration grid. This paper presents results of comparative analysis of a number of different ion optical systems with non-circular apertures and conventional ion optical systems with circular apertures. It has been revealed that a relatively wide perveance range without direct ion impingement may be obtained with apertures shaped as a square with rounded corners. Numerical simulations show that this geometry may have equivalent perveance range as the traditional geometry with circular apertures while being more mechanically robust. In addition, such important characteristics, as the effective transparency for both the ions and the neutral atoms, the height of the potential barrier reflecting the downstream plasma electrons and the angular divergence of the beamlet also can be very close to these parameters for the optics with circular apertures.

  11. Convergence acceleration of implicit schemes in the presence of high aspect ratio grid cells

    NASA Technical Reports Server (NTRS)

    Buelow, B. E. O.; Venkateswaran, S.; Merkle, C. L.

    1993-01-01

    The performance of Navier-Stokes codes are influenced by several phenomena. For example, the robustness of the code may be compromised by the lack of grid resolution, by a need for more precise initial conditions or because all or part of the flowfield lies outside the flow regime in which the algorithm converges efficiently. A primary example of the latter effect is the presence of extended low Mach number and/or low Reynolds number regions which cause convergence deterioration of time marching algorithms. Recent research into this problem by several workers including the present authors has largely negated this difficulty through the introduction of time-derivative preconditioning. In the present paper, we employ the preconditioned algorithm to address convergence difficulties arising from sensitivity to grid stretching and high aspect ratio grid cells. Strong grid stretching is particularly characteristic of turbulent flow calculations where the grid must be refined very tightly in the dimension normal to the wall, without a similar refinement in the tangential direction. High aspect ratio grid cells also arise in problems that involve high aspect ratio domains such as combustor coolant channels. In both situations, the high aspect ratio cells can lead to extreme deterioration in convergence. It is the purpose of the present paper to address the reasons for this adverse response to grid stretching and to suggest methods for enhancing convergence under such circumstances. Numerical algorithms typically possess a maximum allowable or optimum value for the time step size, expressed in non-dimensional terms as a CFL number or vonNeumann number (VNN). In the presence of high aspect ratio cells, the smallest dimension of the grid cell controls the time step size causing it to be extremely small, which in turn results in the deterioration of convergence behavior. For explicit schemes, this time step limitation cannot be exceeded without violating stability restrictions

  12. Grid Gap Measurement for an NSTAR Ion Thruster

    NASA Technical Reports Server (NTRS)

    Diaz, Esther M.; Soulas, George C.

    2006-01-01

    The change in gap between the screen and accelerator grids of an engineering model NSTAR ion optics assembly was measured during thruster operation with beam extraction. The molybdenum ion optics assembly was mounted onto an engineering model NSTAR ion thruster. The measurement technique consisted of measuring the difference in height of an alumina pin relative to the downstream accelerator grid surface. The alumina pin was mechanically attached to the center aperture of the screen grid and protruded through the center aperture of the accelerator grid. The change in pin height was monitored using a long distance microscope coupled to a digital imaging system. Transient and steady-state hot grid gaps were measured at three power levels: 0.5, 1.5 and 2.3 kW. Also, the change in grid gap was measured during the transition between power levels, and during the startup with high voltage applied just prior to discharge ignition. Performance measurements, such as perveance, electron backstreaming limit and screen grid ion transparency, were also made to confirm that this ion optics assembly performed similarly to past testing. Results are compared to a prior test of 30 cm titanium ion optics.

  13. Grid Erosion Modeling of the NEXT Ion Thruster Optics

    NASA Technical Reports Server (NTRS)

    Ernhoff, Jerold W.; Boyd, Iain D.; Soulas, George (Technical Monitor)

    2003-01-01

    Results from several different computational studies of the NEXT ion thruster optics are presented. A study of the effect of beam voltage on accelerator grid aperture wall erosion shows a non-monotonic, complex behavior. Comparison to experimental performance data indicates improvements in simulation of the accelerator grid current, as well as very good agreement with other quantities. Also examined is the effect of ion optics choice on the thruster life, showing that TAG optics provide better margin against electron backstreaming than NSTAR optics. The model is used to predict the change in performance with increasing accelerator grid voltage, showing that although the current collected on the accel grid downstream face increases, the erosion rate decreases. A study is presented for varying doubly-ionized Xenon current fraction. The results show that performance data is not extremely sensitive to the current fraction.

  14. Grid-based algorithm to search critical points, in the electron density, accelerated by graphics processing units.

    PubMed

    Hernández-Esparza, Raymundo; Mejía-Chica, Sol-Milena; Zapata-Escobar, Andy D; Guevara-García, Alfredo; Martínez-Melchor, Apolinar; Hernández-Pérez, Julio-M; Vargas, Rubicelia; Garza, Jorge

    2014-12-05

    Using a grid-based method to search the critical points in electron density, we show how to accelerate such a method with graphics processing units (GPUs). When the GPU implementation is contrasted with that used on central processing units (CPUs), we found a large difference between the time elapsed by both implementations: the smallest time is observed when GPUs are used. We tested two GPUs, one related with video games and other used for high-performance computing (HPC). By the side of the CPUs, two processors were tested, one used in common personal computers and other used for HPC, both of last generation. Although our parallel algorithm scales quite well on CPUs, the same implementation on GPUs runs around 10× faster than 16 CPUs, with any of the tested GPUs and CPUs. We have found what one GPU dedicated for video games can be used without any problem for our application, delivering a remarkable performance, in fact; this GPU competes against one HPC GPU, in particular when single-precision is used.

  15. More IMPATIENT: A Gridding-Accelerated Toeplitz-based Strategy for Non-Cartesian High-Resolution 3D MRI on GPUs

    PubMed Central

    Gai, Jiading; Obeid, Nady; Holtrop, Joseph L.; Wu, Xiao-Long; Lam, Fan; Fu, Maojing; Haldar, Justin P.; Hwu, Wen-mei W.; Liang, Zhi-Pei; Sutton, Bradley P.

    2013-01-01

    Several recent methods have been proposed to obtain significant speed-ups in MRI image reconstruction by leveraging the computational power of GPUs. Previously, we implemented a GPU-based image reconstruction technique called the Illinois Massively Parallel Acquisition Toolkit for Image reconstruction with ENhanced Throughput in MRI (IMPATIENT MRI) for reconstructing data collected along arbitrary 3D trajectories. In this paper, we improve IMPATIENT by removing computational bottlenecks by using a gridding approach to accelerate the computation of various data structures needed by the previous routine. Further, we enhance the routine with capabilities for off-resonance correction and multi-sensor parallel imaging reconstruction. Through implementation of optimized gridding into our iterative reconstruction scheme, speed-ups of more than a factor of 200 are provided in the improved GPU implementation compared to the previous accelerated GPU code. PMID:23682203

  16. More IMPATIENT: A Gridding-Accelerated Toeplitz-based Strategy for Non-Cartesian High-Resolution 3D MRI on GPUs.

    PubMed

    Gai, Jiading; Obeid, Nady; Holtrop, Joseph L; Wu, Xiao-Long; Lam, Fan; Fu, Maojing; Haldar, Justin P; Hwu, Wen-Mei W; Liang, Zhi-Pei; Sutton, Bradley P

    2013-05-01

    Several recent methods have been proposed to obtain significant speed-ups in MRI image reconstruction by leveraging the computational power of GPUs. Previously, we implemented a GPU-based image reconstruction technique called the Illinois Massively Parallel Acquisition Toolkit for Image reconstruction with ENhanced Throughput in MRI (IMPATIENT MRI) for reconstructing data collected along arbitrary 3D trajectories. In this paper, we improve IMPATIENT by removing computational bottlenecks by using a gridding approach to accelerate the computation of various data structures needed by the previous routine. Further, we enhance the routine with capabilities for off-resonance correction and multi-sensor parallel imaging reconstruction. Through implementation of optimized gridding into our iterative reconstruction scheme, speed-ups of more than a factor of 200 are provided in the improved GPU implementation compared to the previous accelerated GPU code.

  17. Negative Transconductance in Apertured Electron Guns

    SciTech Connect

    Harris, J R; O'Shea, P G

    2007-09-21

    Passing an electron beam through an aperture can serve to reduce the beam current or change the transverse beam profile. For a sufficiently intense beam, space charge will drive a radial expansion of the beam, which may cause the current passing through the aperture to increase even though the current arriving at the aperture is decreasing. When a gridded electron gun is used, this may be expressed by stating that the transconductance of the apertured gun is negative. Here we explain this effect, and explore some of the key factors governing when it can occur and influencing its strength.

  18. Improving the growth of Ge/Si islands by modulating the spacing between screen and accelerator grids in ion beam sputtering deposition system

    NASA Astrophysics Data System (ADS)

    Yang, Jie; Zhao, Bo; Wang, Chong; Qiu, Feng; Wang, Rongfei; Yang, Yu

    2016-11-01

    Ge islands were fabricated on Si buffer layer by ion beam sputtering deposition with a spacing between the screen and accelerator grids of either 1 mm or 2 mm. The Si buffer layer exhibits mixed-phase microcrystallinity for samples grown with 1 mm spacing and crystallinity for those with 2 mm spacing. Ge islands are larger and less dense than those grown on the crystalline buffer because of the selective growth mechanism on the microcrystalline buffer. Moreover, the nucleation site of Ge islands formed on the crystalline Si buffer is random. Ge islands grown at different grid-to-grid gaps are characterized by two key factors, namely, divergence half angle of ion beam and crystallinity of buffer layer. High grid-to-grid spacing results in small divergence half angle, thereby enhancing the sputtering energy and redistribution of sputtered atoms. The crystalline volume fraction of the microcrystalline Si buffer was obtained based on the integrated intensity ratio of Raman peaks. The islands show decreased density with decreasing crystalline volume fraction and are difficult to observe at crystalline volume fractions lower than 72%.

  19. Design of the new extraction grid for the NIO1 negative ion source

    NASA Astrophysics Data System (ADS)

    Veltri, P.; Cavenago, M.; Baltador, C.

    2015-04-01

    NIO1 is a compact source of negative ions jointly developed by RFX and INFN, to study the physics of production and acceleration of H- beams. Negative ions, up to 120 mA of current, are extracted from a radiofrequency driven plasma, by means of a gridded electrode (plasma grid, PG) featuring 9 apertures arranged in a 3x3 square lattice. The same aperture pattern is replicated in the following electrodes, allowing ion acceleration up to 60 keV. All electrodes are realized in copper, by electro-deposition technique, leaving empty slots in the metal to place magnets and to flow water for the grid cooling. The first set of electrodes was completed, installed in the source and tested. At the same time, an upgrade of the extraction system was carried out, in order to optimize the beam optics and to explore alternative electrostatic configurations. In particular, the accelerator will be modified by completely replacing the EG grid, exploiting the modularity of NIO1. The new electrode will feature other slots in between apertures, to place additional magnets. This allows testing different magnetic configurations, to optimize electron filtering and residual ion deflection. The present paper describes the theoretical activities driving the design of these new extractors, carried out with most updated numerical codes, and exploiting the synergy with the refined modeling of the 40 A ITER negative ion sources, under development at Consorzio RFX. Beam simulations are performed both with tracing codes (SLACCAD and OPERA) and with particle in cell codes (ACCPIC)

  20. 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).

  1. Simulating ion beam extraction from a single aperture triode acceleration column: A comparison of the beam transport codes IGUN and PBGUNS with test stand data

    SciTech Connect

    Patel, A.; Wills, J. S. C.; Diamond, W. T.

    2008-04-15

    Ion beam extraction from two different ion sources with single aperture triode extraction columns was simulated with the particle beam transport codes PBGUNS and IGUN. For each ion source, the simulation results are compared to experimental data generated on well-equipped test stands. Both codes reproduced the qualitative behavior of the extracted ion beams to incremental and scaled changes to the extraction electrode geometry observed on the test stands. Numerical values of optimum beam currents and beam emittance generated by the simulations also agree well with test stand data.

  2. 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.

  3. 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.

  4. Long pulse acceleration of MeV class high power density negative H{sup −} ion beam for ITER

    SciTech Connect

    Umeda, N. Kojima, A.; Kashiwagi, M.; Tobari, H.; Hiratsuka, J.; Watanabe, K.; Dairaku, M.; Yamanaka, H.; Hanada, M.

    2015-04-08

    R and D of high power density negative ion beam acceleration has been carried out at MeV test facility in JAEA to realize ITER neutral beam accelerator. The main target is H{sup −} ion beam acceleration up to 1 MeV with 200 A/m{sup 2} for 60 s whose pulse length is the present facility limit. For long pulse acceleration at high power density, new extraction grid (EXG) has been developed with high cooling capability, which electron suppression magnet is placed under cooling channel similar to ITER. In addition, aperture size of electron suppression grid (ESG) is enlarged from 14 mm to 16 mm to reduce direct interception on the ESG and emission of secondary electron which leads to high heat load on the upstream acceleration grid. By enlarging ESG aperture, beam current increased 10 % at high current beam and total acceleration grid heat load reduced from 13 % to 10 % of input power at long pulse beam. In addition, heat load by back stream positive ion into the EXG is measured for the first time and is estimated as 0.3 % of beam power, while heat load by back stream ion into the source chamber is estimated as 3.5 ~ 4.0 % of beam power. Beam acceleration up to 60 s which is the facility limit, has achieved at 683 keV, 100 A/m{sup 2} of negative ion beam, whose energy density increases two orders of magnitude since 2011.

  5. Physics design of the HNB accelerator for ITER

    NASA Astrophysics Data System (ADS)

    de Esch, H. P. L.; Kashiwagi, M.; Taniguchi, M.; Inoue, T.; Serianni, G.; Agostinetti, P.; Chitarin, G.; Marconato, N.; Sartori, E.; Sonato, P.; Veltri, P.; Pilan, N.; Aprile, D.; Fonnesu, N.; Antoni, V.; Singh, M. J.; Hemsworth, R. S.; Cavenago, M.

    2015-09-01

    The physics design of the accelerator for the heating neutral beamline on ITER is now finished and this paper describes the considerations and choices which constitute the basis of this design. Equal acceleration gaps of 88 mm have been chosen to improve the voltage holding capability while keeping the beam divergence low. Kerbs (metallic plates around groups of apertures, attached to the downstream surface of the grids) are used to compensate for the beamlet-beamlet interaction and to point the beamlets in the right direction. A novel magnetic configuration is employed to compensate for the beamlet deflection caused by the electron suppression magnets in the extraction grid. A combination of long-range and short-range magnetic fields is used to reduce electron leakage between the grids and limit the transmitted electron power to below 800 kW.

  6. Empirical laws of particle extraction from single-grid source of bipolar ion-electron flow.

    PubMed

    Dudin, S V; Rafalskyi, D V

    2012-11-01

    The present research is devoted to the problem of extraction grid choice for a single-grid source of bipolar ion-electron flow. The paper contains detailed reference information on ion and electron extraction characteristics of 10 different grids with broad range of parameters: aperture width (0.09-0.6 mm), grid transparency (0.19-0.51), thickness (0.036-0.5 mm), and with different aperture geometry. The grids with square, circular, and slit apertures were made with different technologies: laser cutting, welding, weaving, and electrolytic erosion. The general regularities of the ion and electron extraction from the single-grid source are experimentally researched for the cases of dc and RF extraction grid biasing. A conclusion has been made that the maximum extracted ion current at low ion energy (0-200 eV) does not significantly vary for all the grids and does not exceed half of the primary ion current from plasma multiplied by the optical grid transparency. The low-energy limit of efficient ion extraction has been discovered which cannot be overcome by the aperture narrowing. A conclusion is made that the RF extraction mode is superior for all the researched grids since it is characterized by higher extracted ion current at any acceleration voltage for any grid with much more simple and smooth extraction curves behavior in comparison to the dc case as well as absence of arcing, jumps, and hysteresis of the measured curves at any RF voltages. The unique ability of the RF biased single-grid source of simultaneous ion∕electron emission has been studied. The measured maximal attainable ion beam current compensation ratio is always sufficiently higher than 1 and typically varies in the range 2-6. The results obtained in the present paper demonstrate prospective of the single-grid source in space thruster applications and in modern technologies, particularly for ion beam processing of wide bandgap semiconductor devices such as GaN and SiC transistors due to inherent

  7. Improved Antishock Air-Gap Control Algorithm with Acceleration Feedforward Control for High-Numerical Aperture Near-Field Storage System Using Solid Immersion Lens

    NASA Astrophysics Data System (ADS)

    Kim, Jung-Gon; Shin, Won-Ho; Hwang, Hyun-Woo; Jeong, Jun; Park, Kyoung-Su; Park, No-Cheol; Yang, Hyunseok; Park, Young-Pil; Moo Park, Jin; Son, Do Hyeon; Kyo Seo, Jeong; Choi, In Ho

    2010-08-01

    A near-field storage system using a solid immersion lens (SIL) has been studied as a high-density optical disc drive system. The major goal of this research is to improve the robustness of the air-gap controller for a SIL-based near-field recording (NFR) system against dynamic disturbances, such as external shocks. The servo system is essential in near-field (NF) technology because the nanogap distance between the SIL and the disc is 50 nm or less. Also, the air-gap distance must be maintained without collision between the SIL and the disc to detect a stable gap error and read-out signals when an external shock is applied. Therefore, we propose an improved air-gap control algorithm using only an acceleration feedforward controller (AFC) to maintain the air-gap distance without contact for a 4.48 G at 10 ms shock. Thus, the antishock control performance for the SIL-based NF storage system in the presence of external shocks is markedly improved. Furthermore, to enhance the performance of the antishock air-gap control, we use the AFC with a double disturbance observer and a dead-zone nonlinear controller. As a result, the air-gap distance is maintained without contact for a 6.56 G@10 ms shock.

  8. Calculate waveguide aperture susceptance

    NASA Astrophysics Data System (ADS)

    Kwon, J.-K.; Ishii, T. K.

    1982-12-01

    A method is developed for calculating aperture susceptance which makes use of the distribution of an aperture's local fields. This method can be applied to the computation of the aperture susceptance of irises, as well as the calculation of the susceptances of waveguide filters, aperture antennas, waveguide cavity coupling, waveguide junctions, and heterogeneous boundaries such as inputs to ferrite or dielectric loaded waveguides. This method assumes a local field determined by transverse components of the incident wave in the local surface of the cross section in the discontinuity plane which lies at the aperture. The aperture susceptance is calculated by the use of the local fields, the law of energy conservation, and the principles of continuity of the fields. This method requires that the thickness of the aperture structure be zero, but this does not limit the practical usefulness of this local-field method.

  9. Thread Group Multithreading: Accelerating the Computation of an Agent-Based Power System Modeling and Simulation Tool -- C GridLAB-D

    SciTech Connect

    Jin, Shuangshuang; Chassin, David P.

    2014-01-06

    GridLAB-DTM is an open source next generation agent-based smart-grid simulator that provides unprecedented capability to model the performance of smart grid technologies. Over the past few years, GridLAB-D has been used to conduct important analyses of smart grid concepts, but it is still quite limited by its computational performance. In order to break through the performance bottleneck to meet the need for large scale power grid simulations, we develop a thread group mechanism to implement highly granular multithreaded computation in GridLAB-D. We achieve close to linear speedups on multithreading version compared against the single-thread version of the same code running on general purpose multi-core commodity for a benchmark simple house model. The performance of the multithreading code shows favorable scalability properties and resource utilization, and much shorter execution time for large-scale power grid simulations.

  10. Design of the new extraction grid for the NIO1 negative ion source

    SciTech Connect

    Veltri, P. Baltador, C.; Cavenago, M.

    2015-04-08

    NIO1 is a compact source of negative ions jointly developed by RFX and INFN, to study the physics of production and acceleration of H{sup −} beams. Negative ions, up to 120 mA of current, are extracted from a radiofrequency driven plasma, by means of a gridded electrode (plasma grid, PG) featuring 9 apertures arranged in a 3x3 square lattice. The same aperture pattern is replicated in the following electrodes, allowing ion acceleration up to 60 keV. All electrodes are realized in copper, by electro-deposition technique, leaving empty slots in the metal to place magnets and to flow water for the grid cooling. The first set of electrodes was completed, installed in the source and tested. At the same time, an upgrade of the extraction system was carried out, in order to optimize the beam optics and to explore alternative electrostatic configurations. In particular, the accelerator will be modified by completely replacing the EG grid, exploiting the modularity of NIO1. The new electrode will feature other slots in between apertures, to place additional magnets. This allows testing different magnetic configurations, to optimize electron filtering and residual ion deflection. The present paper describes the theoretical activities driving the design of these new extractors, carried out with most updated numerical codes, and exploiting the synergy with the refined modeling of the 40 A ITER negative ion sources, under development at Consorzio RFX. Beam simulations are performed both with tracing codes (SLACCAD and OPERA) and with particle in cell codes (ACCPIC)

  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. Ion beam accelerator system

    NASA Technical Reports Server (NTRS)

    Aston, Graeme (Inventor)

    1984-01-01

    A system is described that combines geometrical and electrostatic focusing to provide high ion extraction efficiency and good focusing of an accelerated ion beam. The apparatus includes a pair of curved extraction grids (16, 18) with multiple pairs of aligned holes positioned to direct a group of beamlets (20) along converging paths. The extraction grids are closely spaced and maintained at a moderate potential to efficiently extract beamlets of ions and allow them to combine into a single beam (14). An accelerator electrode device (22) downstream from the extraction grids, is at a much lower potential than the grids to accelerate the combined beam.

  14. Ion beam accelerator system

    NASA Technical Reports Server (NTRS)

    Aston, G. (Inventor)

    1981-01-01

    A system is described that combines geometrical and electrostatic focusing to provide high ion extraction efficiency and good focusing of an accelerated ion beam. The apparatus includes a pair of curved extraction grids with multiple pairs of aligned holes positioned to direct a group of beamlets along converging paths. The extraction grids are closely spaced and maintained at a moderate potential to efficiently extract beamlets of ions and allow them to combine into a single beam. An accelerator electrode device downstream from the extraction grids is at a much lower potential than the grids to accelerate the combined beam. The application of the system to ion implantation is mentioned.

  15. Ion beamlet vectoring by grid translation

    NASA Technical Reports Server (NTRS)

    Homa, J. M.; Wilbur, P. J.

    1982-01-01

    Ion beamlet vectoring is investigated by collecting deflection and divergence angle data for two-grid systems as a function of the relative displacement of these grids. Results show that at large displacements, accelerator grid impingement becomes a limiting factor and this determines the useful range of beamlet deflection. Beamlet deflection was shown to vary linearly with grid offset angle over this range. Values of deflection-to-offset angle ratio and useful range of deflection are presented as functions of grid-hole geometries, perveance levels, and accelerating voltages. It is found that the divergence of the beamlets is unaffected by deflection over the useful range of beamlet deflection. The grids of a typical dished-grid ion thruster are examined to determine where over the grid surface the grid offsets exceed the useful range, which indicates the regions on the surface where high accelerator grid impingment is probably occurring.

  16. Sub-Aperture Interferometers

    NASA Technical Reports Server (NTRS)

    Zhao, Feng

    2010-01-01

    Sub-aperture interferometers -- also called wavefront-split interferometers -- have been developed for simultaneously measuring displacements of multiple targets. The terms "sub-aperture" and "wavefront-split" signify that the original measurement light beam in an interferometer is split into multiple sub-beams derived from non-overlapping portions of the original measurement-beam aperture. Each measurement sub-beam is aimed at a retroreflector mounted on one of the targets. The splitting of the measurement beam is accomplished by use of truncated mirrors and masks, as shown in the example below

  17. Distributed aperture synthesis.

    PubMed

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

    2010-05-10

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

  18. 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.

  19. Active aperture phased arrays

    NASA Astrophysics Data System (ADS)

    Shenoy, R. P.

    1989-04-01

    Developments towards the realization of active aperture phased arrays are reviewed. The technology and cost aspects of the power amplifier and phase shifter subsystems are discussed. Consideration is given to research concerning T/R modules, MESFETs, side lobe control, beam steering, optical control techniques, and printed circuit antennas. Methods for configuring the array are examined, focusing on the tile and brick configurations. It is found that there is no technological impediment for introducing active aperture phased arrays.

  20. 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.

  1. Efficient Terahertz Wide-Angle NUFFT-Based Inverse Synthetic Aperture Imaging Considering Spherical Wavefront

    PubMed Central

    Gao, Jingkun; Deng, Bin; Qin, Yuliang; Wang, Hongqiang; Li, Xiang

    2016-01-01

    An efficient wide-angle inverse synthetic aperture imaging method considering the spherical wavefront effects and suitable for the terahertz band is presented. Firstly, the echo signal model under spherical wave assumption is established, and the detailed wavefront curvature compensation method accelerated by 1D fast Fourier transform (FFT) is discussed. Then, to speed up the reconstruction procedure, the fast Gaussian gridding (FGG)-based nonuniform FFT (NUFFT) is employed to focus the image. Finally, proof-of-principle experiments are carried out and the results are compared with the ones obtained by the convolution back-projection (CBP) algorithm. The results demonstrate the effectiveness and the efficiency of the presented method. This imaging method can be directly used in the field of nondestructive detection and can also be used to provide a solution for the calculation of the far-field RCSs (Radar Cross Section) of targets in the terahertz regime. PMID:27983618

  2. Efficient Terahertz Wide-Angle NUFFT-Based Inverse Synthetic Aperture Imaging Considering Spherical Wavefront.

    PubMed

    Gao, Jingkun; Deng, Bin; Qin, Yuliang; Wang, Hongqiang; Li, Xiang

    2016-12-14

    An efficient wide-angle inverse synthetic aperture imaging method considering the spherical wavefront effects and suitable for the terahertz band is presented. Firstly, the echo signal model under spherical wave assumption is established, and the detailed wavefront curvature compensation method accelerated by 1D fast Fourier transform (FFT) is discussed. Then, to speed up the reconstruction procedure, the fast Gaussian gridding (FGG)-based nonuniform FFT (NUFFT) is employed to focus the image. Finally, proof-of-principle experiments are carried out and the results are compared with the ones obtained by the convolution back-projection (CBP) algorithm. The results demonstrate the effectiveness and the efficiency of the presented method. This imaging method can be directly used in the field of nondestructive detection and can also be used to provide a solution for the calculation of the far-field RCSs (Radar Cross Section) of targets in the terahertz regime.

  3. 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.

  4. Compensations of beamlet deflections for 1 MeV accelerator of ITER NBI

    NASA Astrophysics Data System (ADS)

    Kashiwagi, Mieko; Taniguchi, Masaki; Umeda, Naotaka; Dairaku, Masayuki; Tobari, Hiroyuki; Yamanaka, Haruhiko; Watanabe, Kazuhiro; Inoue, Takashi; de Esch, H. P. L.; Grisham, Larry R.; Boilson, Deirdre; Hemsworth, Ronald S.; Tanaka, Masanobu

    2013-02-01

    Compensation methods of beamlet deflections have been studied in a three dimensional (3D) beam analysis using OPERA-3d code for 1 MeV accelerator of the ITER neutral beam injector (NBI). The beamlet deflection is caused by i) magnetic field generated by permanent magnets embedded in the extraction grid (EXG) for electron suppression and ii) space charge repulsion between the beamlets and beam groups. Moreover, the beamlet deflection is caused due to electric field distortion formed by a grid support structure. In order to compensate the beamlet deflections due to i) and ii), an aperture offset of 0.6 mm was applied in the electron suppression grid (ESG) and a metal bar with 3 mm in thickness, so-called a kerb, was attached around the aperture area at the back side of the ESG, respectively. Detailed configuration of the compensation methods was also considered so as to suppress the beam spread due to the electric field distortion and to lower electric field concentrations at the edge of the kerb. For the beamlets near the grid support structure, the beamlet deflection due to the space charge repulsion could be negated due to the electric field distortion formed by the grid support structure.

  5. SU-C-BRB-03: Novel Technique to Implement GRID Therapy in a Commercial Treatment Planning System

    SciTech Connect

    Park, H; Mohiuddin, M; Yaldo, D; Tom, B; Worlikar, N

    2015-06-15

    Purpose: Due to the difficulty of creating an accurate multi-aperture block in treatment planning systems (TPS), spatially fractionated radiation therapy (GRID Therapy) is limited to clinical setups using simple monitor unit calculations. In this work, we present a novel approach to accurately model a grid block in a TPS and evaluate its dosimetric accuracy. Methods: An acrylic GRID block was fashioned such that the hole size and spacing were the same dimensions of the brass GRID block (dotDecimal) at isocenter. Holes were non-divergent and drilled 1 cm deep. CT scans (RT Lightspeed, GE Healthcare) of the block were acquired using axial slices with a thickness of 0.625 mm. These were imported into Eclipse (version 11, Varian Medical Systems) and holes were auto-contoured into structures. The GRID block was created in Eclipse by forming apertures around the hole structures using a simple three step process. Treatment plans were created in a water-equivalent phantom using 6 and 10 MV beams, delivered with a linear accelerator (Clinac iX, Varian Medical Systems) and measured using a water tank, film and a diode array. Results: Comparisons of percent depth dose curves and profiles at depths of maximum dose, 5cm, and 10cm for field sizes ranging from 5 cm{sup 2} to 25 cm{sup 2} using water and film were within 3% of their respective positions in Eclipse. GRID plans utilizing various jaw sizes and MLC blocking measured with film and a diode array showed pass rates with an average of 97% using Gamma analysis at 3%/ 3 mm and no lower than 93%. Conclusion: We have developed a simple yet accurate method of incorporating a GRID block into a commercially available TPS and demonstrated that the TPS accurately reflects the dose delivered. This will allow for real-time planning using patient scans and encourage new methods for GRID therapy. Support provided by dotDecimal, Sanford, FL.

  6. 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.

  7. 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.

  8. 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.

  9. Distribution of the background gas in the MITICA accelerator

    NASA Astrophysics Data System (ADS)

    Sartori, E.; Dal Bello, S.; Serianni, G.; Sonato, P.

    2013-02-01

    MITICA is the ITER neutral beam test facility to be built in Padova for the generation of a 40A D- ion beam with a 16×5×16 array of 1280 beamlets accelerated to 1MV. The background gas pressure distribution and the particle flows inside MITICA accelerator are critical aspects for stripping losses, generation of secondary particles and beam non-uniformities. To keep the stripping losses in the extraction and acceleration stages reasonably low, the source pressure should be 0.3 Pa or less. The gas flow in MITICA accelerator is being studied using a 3D Finite Element code, named Avocado. The gas-wall interaction model is based on the cosine law, and the whole vacuum system geometry is represented by a view factor matrix based on surface discretization and gas property definitions. Pressure distribution and mutual fluxes are then solved linearly. In this paper the result of a numerical simulation is presented, showing the steady-state pressure distribution inside the accelerator when gas enters the system at room temperature. The accelerator model is limited to a horizontal slice 400 mm high (1/4 of the accelerator height). The pressure profile at solid walls and through the beamlet axis is obtained, allowing the evaluation and the discussion of the background gas distribution and nonuniformity. The particle flux at the inlet and outlet boundaries (namely the grounded grid apertures and the lateral conductances respectively) will be discussed.

  10. Constructing the ASCI computational grid

    SciTech Connect

    BEIRIGER,JUDY I.; BIVENS,HUGH P.; HUMPHREYS,STEVEN L.; JOHNSON,WILBUR R.; RHEA,RONALD E.

    2000-06-01

    The Accelerated Strategic Computing Initiative (ASCI) computational grid is being constructed to interconnect the high performance computing resources of the nuclear weapons complex. The grid will simplify access to the diverse computing, storage, network, and visualization resources, and will enable the coordinated use of shared resources regardless of location. To match existing hardware platforms, required security services, and current simulation practices, the Globus MetaComputing Toolkit was selected to provide core grid services. The ASCI grid extends Globus functionality by operating as an independent grid, incorporating Kerberos-based security, interfacing to Sandia's Cplant{trademark},and extending job monitoring services. To fully meet ASCI's needs, the architecture layers distributed work management and criteria-driven resource selection services on top of Globus. These services simplify the grid interface by allowing users to simply request ''run code X anywhere''. This paper describes the initial design and prototype of the ASCI grid.

  11. Gridded electron reversal ionizer

    NASA Technical Reports Server (NTRS)

    Chutjian, Ara (Inventor)

    1993-01-01

    A gridded electron reversal ionizer forms a three dimensional cloud of zero or near-zero energy electrons in a cavity within a filament structure surrounding a central electrode having holes through which the sample gas, at reduced pressure, enters an elongated reversal volume. The resultant negative ion stream is applied to a mass analyzer. The reduced electron and ion space-charge limitations of this configuration enhances detection sensitivity for material to be detected by electron attachment, such as narcotic and explosive vapors. Positive ions may be generated by generating electrons having a higher energy, sufficient to ionize the target gas and pulsing the grid negative to stop the electron flow and pulsing the extraction aperture positive to draw out the positive ions.

  12. Configurable Aperture Space Telescope

    NASA Technical Reports Server (NTRS)

    Ennico, Kimberly; Vassigh, Kenny; Bendek, Selman; Young, Zion W; Lynch, Dana H.

    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 strawman mechanical architecture and structural damping analyses, and derive future satlet-based observatory performance requirements. CAST provides an alternative access to visible andor UV wavelength space telescope with 1-meter or larger aperture for NASA SMD Astrophysics and Planetary Science community after the retirement of HST.

  13. 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

  14. 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.

  15. 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.

  16. Adaptive aperture synthesis

    NASA Astrophysics Data System (ADS)

    Johnson, A. M.; Zhang, S.; Mudassar, A.; Love, G. D.; Greenaway, A. H.

    2005-12-01

    High-resolution imaging can be achieved by optical aperture synthesis (OAS). Such an imaging process is subject to aberrations introduced by instrumental defects and/or turbulent media. Redundant spacings calibration (RSC) is a snapshot calibration technique that can be used to calibrate OAS arrays without use of assumptions about the object being imaged. Here we investigate the analogies between RSC and adaptive optics in passive imaging applications.

  17. Grid Work

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Pointwise Inc.'s, Gridgen Software is a system for the generation of 3D (three dimensional) multiple block, structured grids. Gridgen is a visually-oriented, graphics-based interactive code used to decompose a 3D domain into blocks, distribute grid points on curves, initialize and refine grid points on surfaces and initialize volume grid points. Gridgen is available to U.S. citizens and American-owned companies by license.

  18. MAGNETIC GRID

    DOEpatents

    Post, R.F.

    1960-08-01

    An electronic grid is designed employing magnetic forces for controlling the passage of charged particles. The grid is particularly applicable to use in gas-filled tubes such as ignitrons. thyratrons, etc., since the magnetic grid action is impartial to the polarity of the charged particles and, accordingly. the sheath effects encountered with electrostatic grids are not present. The grid comprises a conductor having sections spaced apart and extending in substantially opposite directions in the same plane, the ends of the conductor being adapted for connection to a current source.

  19. Improvement of accelerator of negative ion source on the Large Helical Device

    SciTech Connect

    Kisaki, M. Ikeda, K.; Osakabe, M.; Tsumori, K.; Nakano, H.; Nagaoka, K.; Kaneko, O.; Takeiri, Y.; Geng, S.

    2016-02-15

    To improve the performance of negative-ion based neutral beam injection on the Large Helical Device, the accelerator was modified on the basis of numerical investigations. A field limiting ring was installed on the upper side of a grounded grid (GG) support and a multi-slot GG was adopted instead of a multi-aperture GG. As a result, the voltage holding capability is improved and the heat load on the GG decreases by 40%. In addition, the arc efficiency is improved significantly only by replacing the GG.

  20. Aperture synthesis in space

    NASA Astrophysics Data System (ADS)

    Faucherre, Michel; Greenaway, A. H.; Merkle, F.; Noordam, J. E.; Perryman, M. A. C.

    1989-09-01

    The principles of optical aperture synthesis (OAS), which can yield images of much higher resolution than current ground observations, are essentially those of radio astronomy, and may be used in either space- or ground-based studies of the stellar envelopes around Be stars, the internal dynamics of active galaxies, etc. An account is presently given of possible OAS instrument configurations; it is shown that a large field of view can be achieved, so that the instrument may be calibrated on bright stars during the observation of faint sources. Mission concepts for a 'monostructure' OAS instrument of about 30-m size are examined.

  1. 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.

  2. Minimum description length synthetic aperture radar image segmentation.

    PubMed

    Galland, Frédéric; Bertaux, Nicolas; Réfrégier, Philippe

    2003-01-01

    We present a new minimum description length (MDL) approach based on a deformable partition--a polygonal grid--for automatic segmentation of a speckled image composed of several homogeneous regions. The image segmentation thus consists in the estimation of the polygonal grid, or, more precisely, its number of regions, its number of nodes and the location of its nodes. These estimations are performed by minimizing a unique MDL criterion which takes into account the probabilistic properties of speckle fluctuations and a measure of the stochastic complexity of the polygonal grid. This approach then leads to a global MDL criterion without an undetermined parameter since no other regularization term than the stochastic complexity of the polygonal grid is necessary and noise parameters can be estimated with maximum likelihood-like approaches. The performance of this technique is illustrated on synthetic and real synthetic aperture radar images of agricultural regions and the influence of different terms of the model is analyzed.

  3. 75 FR 6414 - Consumer Interface With the Smart Grid

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-09

    ... efficiency of the electric grid while reducing energy costs to consumers. The ``Smart Grid''--a modernized... energy loads and storage devices such as plug-in electric and hybrid electric vehicles. The Smart Grid... accelerating deployment of smart meters and other components of an advanced electric grid. In many...

  4. Computational study of ion beam extraction phenomena through multiple apertures

    SciTech Connect

    Hu, Wanpeng; Sang, Chaofeng; Tang, Tengfei; Wang, Dezhen; Li, Ming; Jin, Dazhi; Tan, Xiaohua

    2014-03-15

    The process of ion extraction through multiple apertures is investigated using a two-dimensional particle-in-cell code. We consider apertures with a fixed diameter with a hydrogen plasma background, and the trajectories of electrons, H{sup +} and H{sub 2}{sup +} ions in the self-consistently calculated electric field are traced. The focus of this work is the fundamental physics of the ion extraction, and not particular to a specific device. The computed convergence and divergence of the extracted ion beam are analyzed. We find that the extracted ion flux reaching the extraction electrode is non-uniform, and the peak flux positions change according to operational parameters, and do not necessarily match the positions of the apertures in the y-direction. The profile of the ion flux reaching the electrode is mainly affected by the bias voltage and the distance between grid wall and extraction electrode.

  5. Experimental demonstration of tri-aperture Differential Synthetic Aperture Ladar

    NASA Astrophysics Data System (ADS)

    Zhao, Zhilong; Huang, Jianyu; Wu, Shudong; Wang, Kunpeng; Bai, Tao; Dai, Ze; Kong, Xinyi; Wu, Jin

    2017-04-01

    A tri-aperture Differential Synthetic Aperture Ladar (DSAL) is demonstrated in laboratory, which is configured by using one common aperture to transmit the illuminating laser and another two along-track receiving apertures to collect back-scattered laser signal for optical heterodyne detection. The image formation theory on this tri-aperture DSAL shows that there are two possible methods to reconstruct the azimuth Phase History Data (PHD) for aperture synthesis by following standard DSAL principle, either method resulting in a different matched filter as well as an azimuth image resolution. The experimental setup of the tri-aperture DSAL adopts a frequency chirped laser of about 40 mW in 1550 nm wavelength range as the illuminating source and an optical isolator composed of a polarizing beam-splitter and a quarter wave plate to virtually line the three apertures in the along-track direction. Various DSAL images up to target distance of 12.9 m are demonstrated using both PHD reconstructing methods.

  6. Overture: The grid classes

    SciTech Connect

    Brislawn, K.; Brown, D.; Chesshire, G.; Henshaw, W.

    1997-01-01

    Overture is a library containing classes for grids, overlapping grid generation and the discretization and solution of PDEs on overlapping grids. This document describes the Overture grid classes, including classes for single grids and classes for collections of grids.

  7. Fibonacci Grids

    NASA Technical Reports Server (NTRS)

    Swinbank, Richard; Purser, James

    2006-01-01

    Recent years have seen a resurgence of interest in a variety of non-standard computational grids for global numerical prediction. The motivation has been to reduce problems associated with the converging meridians and the polar singularities of conventional regular latitude-longitude grids. A further impetus has come from the adoption of massively parallel computers, for which it is necessary to distribute work equitably across the processors; this is more practicable for some non-standard grids. Desirable attributes of a grid for high-order spatial finite differencing are: (i) geometrical regularity; (ii) a homogeneous and approximately isotropic spatial resolution; (iii) a low proportion of the grid points where the numerical procedures require special customization (such as near coordinate singularities or grid edges). One family of grid arrangements which, to our knowledge, has never before been applied to numerical weather prediction, but which appears to offer several technical advantages, are what we shall refer to as "Fibonacci grids". They can be thought of as mathematically ideal generalizations of the patterns occurring naturally in the spiral arrangements of seeds and fruit found in sunflower heads and pineapples (to give two of the many botanical examples). These grids possess virtually uniform and highly isotropic resolution, with an equal area for each grid point. There are only two compact singular regions on a sphere that require customized numerics. We demonstrate the practicality of these grids in shallow water simulations, and discuss the prospects for efficiently using these frameworks in three-dimensional semi-implicit and semi-Lagrangian weather prediction or climate models.

  8. Grids = Structure.

    ERIC Educational Resources Information Center

    Barrington, Linda; Carter, Jacky

    2003-01-01

    Proposes that narrow columns provide a flexible system of organization for designers. Notes that grids serve the content on the pages, help to develop a layout that will clearly direct the reader to information; and prevent visual monotony. Concludes when grid layouts are used, school publications look as good as professional ones. (PM)

  9. Holographically Correcting Synthetic Aperture Aberrations.

    DTIC Science & Technology

    1987-12-01

    Malacara (20:105-148). The synthetic aperture was aligned in accordance with the synthetic-aperture alignment technique of Gill (8:61-64). The...1987. 20. Malacara , Daniel, ed. Optical Shop Testing. New York: John Wiley & Sons, 1978. 21. Marciniak, Capt Michael. Tutorial Presentation of mV

  10. Long-pulse beam acceleration of MeV-class H(-) ion beams for ITER NB accelerator.

    PubMed

    Umeda, N; Kashiwagi, M; Taniguchi, M; Tobari, H; Watanabe, K; Dairaku, M; Yamanaka, H; Inoue, T; Kojima, A; Hanada, M

    2014-02-01

    In order to realize neutral beam systems in International Thermonuclear Experimental Reactor whose target is to produce a 1 MeV, 200 A/m(2) during 3600 s D(-) ion beam, the electrostatic five-stages negative ion accelerator so-called "MeV accelerator" has been developed at Japan Atomic Energy Agency. To extend pulse length, heat load of the acceleration grids was reduced by controlling the ion beam trajectory. Namely, the beam deflection due to the residual magnetic field of filter magnet was suppressed with the newly developed extractor with a 0.5 mm off-set aperture displacement. The new extractor improved the deflection angle from 6 mrad to 1 mrad, resulting in the reduction of direct interception of negative ions from 23% to 15% of the total acceleration power, respectively. As a result, the pulse length of 130 A/m(2), 881 keV H(-) ion beam has been successfully extended from a previous value of 0.4 s to 8.7 s. This is the first long pulse negative ion beam acceleration over 100 MW/m(2).

  11. Optica aperture synthesis

    NASA Astrophysics Data System (ADS)

    van der Avoort, Casper

    2006-05-01

    Optical long baseline stellar interferometry is an observational technique in astronomy that already exists for over a century, but is truly blooming during the last decades. The undoubted value of stellar interferometry as a technique to measure stellar parameters beyond the classical resolution limit is more and more spreading to the regime of synthesis imaging. With optical aperture synthesis imaging, the measurement of parameters is extended to the reconstruction of high resolution stellar images. A number of optical telescope arrays for synthesis imaging are operational on Earth, while space-based telescope arrays are being designed. For all imaging arrays, the combination of the light collected by the telescopes in the array can be performed in a number of ways. In this thesis, methods are introduced to model these methods of beam combination and compare their effectiveness in the generation of data to be used to reconstruct the image of a stellar object. One of these methods of beam combination is to be applied in a future space telescope. The European Space Agency is developing a mission that can valuably be extended with an imaging beam combiner. This mission is labeled Darwin, as its main goal is to provide information on the origin of life. The primary objective is the detection of planets around nearby stars - called exoplanets- and more precisely, Earth-like exoplanets. This detection is based on a signal, rather than an image. With an imaging mode, designed as described in this thesis, Darwin can make images of, for example, the planetary system to which the detected exoplanet belongs or, as another example, of the dust disk around a star out of which planets form. Such images will greatly contribute to the understanding of the formation of our own planetary system and of how and when life became possible on Earth. The comparison of beam combination methods for interferometric imaging occupies most of the pages of this thesis. Additional chapters will

  12. 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.

  13. Synthetic aperture hitchhiker imaging.

    PubMed

    Yarman, Can Evren; Yazici, Birsen

    2008-11-01

    We introduce a novel synthetic-aperture imaging method for radar systems that rely on sources of opportunity. We consider receivers that fly along arbitrary, but known, flight trajectories and develop a spatio-temporal correlation-based filtered-backprojection-type image reconstruction method. The method involves first correlating the measurements from two different receiver locations. This leads to a forward model where the radiance of the target scene is projected onto the intersection of certain hyperboloids with the surface topography. We next use microlocal techniques to develop a filtered-backprojection-type inversion method to recover the scene radiance. The method is applicable to both stationary and mobile, and cooperative and noncooperative sources of opportunity. Additionally, it is applicable to nonideal imaging scenarios such as those involving arbitrary flight trajectories, and has the desirable property of preserving the visible edges of the scene radiance. We present an analysis of the computational complexity of the image reconstruction method and demonstrate its performance in numerical simulations for single and multiple transmitters of opportunity.

  14. 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.

  15. 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.

  16. Grid oscillators

    NASA Technical Reports Server (NTRS)

    Popovic, Zorana B.; Kim, Moonil; Rutledge, David B.

    1988-01-01

    Loading a two-dimensional grid with active devices offers a means of combining the power of solid-state oscillators in the microwave and millimeter-wave range. The grid structure allows a large number of negative resistance devices to be combined. This approach is attractive because the active devices do not require an external locking signal, and the combining is done in free space. In addition, the loaded grid is a planar structure amenable to monolithic integration. Measurements on a 25-MESFET grid at 9.7 GHz show power-combining and frequency-locking without an external locking signal, with an ERP of 37 W. Experimental far-field patterns agree with theoretical results obtained using reciprocity.

  17. Aperture masking interferometry research simulation

    NASA Astrophysics Data System (ADS)

    Wang, Haitao; Luo, Qiufeng; Fan, Weijun; Zhang, Xian Ling; Tao, Chunkan; Zhu, Yongtian; Zhou, Bifang; Chen, Hanliang

    2004-10-01

    Aperture Masking Interferometry (AMI) is one of the high-resolution astronomical image observation technologies. It is also an important research way to the Optical Aperture Synthesis (OAS). The theory of OAS is simply introduced and AMI simulation method is raised. The mathematics model is built and the interferogram fringes are got. The aperture mask u-v coverage is discussed and one image reconstruction method is done. The reconstructed image result is got with CLEAN method. Shortcoming of this work is also referred and the future research work is mentioned at last.

  18. Grid Computing

    NASA Astrophysics Data System (ADS)

    Foster, Ian

    2001-08-01

    The term "Grid Computing" refers to the use, for computational purposes, of emerging distributed Grid infrastructures: that is, network and middleware services designed to provide on-demand and high-performance access to all important computational resources within an organization or community. Grid computing promises to enable both evolutionary and revolutionary changes in the practice of computational science and engineering based on new application modalities such as high-speed distributed analysis of large datasets, collaborative engineering and visualization, desktop access to computation via "science portals," rapid parameter studies and Monte Carlo simulations that use all available resources within an organization, and online analysis of data from scientific instruments. In this article, I examine the status of Grid computing circa 2000, briefly reviewing some relevant history, outlining major current Grid research and development activities, and pointing out likely directions for future work. I also present a number of case studies, selected to illustrate the potential of Grid computing in various areas of science.

  19. SU-E-T-637: Proton Aperture Quality Assurance Using Computed Tomography

    SciTech Connect

    Reyhan, M; Yue, N; Zou, J

    2015-06-15

    Purpose: To develop an automated algorithm for aperture quality assurance for double scattering proton radiotherapy. Methods: Anterior-Posterior scout images were acquired on a CT scanner for five brass apertures (2 large, 3 small) with 120 kVp and 10mA. A semi-automated algorithm was developed for the QA process. The input includes a user selecting the scout image and the associated patient plan, field and aperture size. The program automatically thresholds the scout image. Next, a connectivity algorithm is used to determine the points associated with the central shape to obtain the contour. To compare with the plan contour, the program converts the detected and plan contours into polar coordinates, interpolates the data to a 1 degree spaced grid, and determines the differences in radial distance at each grid point. Results: The mean and maximum difference and the percentage of points with distance differences less than 1.25 mm (due to the divergent cut of the aperture) between the detected and plan field aperture contours were obtained. A repeatability coefficient was derived based on repeated scanning and processing of three of the apertures. The mean difference for five apertures was 0.44 +/−0.08 mm. The maximum difference in distance was 1.2 +/−0.23 mm for all apertures. The Repeatability Coefficient was +/−0.038 mm, indicating the technique is highly repeatable. The mean percent of points with distance less than 1.25 mm was 97.41 +/−0.35%. Conclusion: Automated CT scout image based proton aperture QA is feasible, saves time, and provides a quantitative metric for proton patient specific aperture QA.

  20. 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.

  1. Microelectrofluidic iris for variable aperture

    NASA Astrophysics Data System (ADS)

    Chang, Jong-hyeon; Jung, Kyu-Dong; Lee, Eunsung; Choi, Minseog; Lee, Seungwan

    2012-03-01

    This paper presents a variable aperture design based on the microelectrofluidic technology which integrates electrowetting and microfluidics. The proposed microelectrofluidic iris (MEFI) consists of two immiscible fluids and two connected surface channels formed by three transparent plates and two spacers between them. In the initial state, the confined aqueous ring makes two fluidic interfaces, on which the Laplace pressure is same, in the hydrophobic surface channels. When a certain voltage is applied between the dielectric-coated control electrode beneath the three-phase contact line (TCL) and the reference electrode for grounding the aqueous, the contact angle changes on the activated control electrode. At high voltage over the threshold, the induced positive pressure difference makes the TCLs on the 1st channel advance to the center and the aperture narrow. If there is no potential difference between the control and reference electrodes, the pressure difference becomes negative. It makes the TCLs on the 1st channel recede and the aperture widen to the initial state. It is expected that the proposed MEFI is able to be widely used because of its fast response, circular aperture, digital operation, high aperture ratio, and possibility to be miniaturized for variable aperture.

  2. Antenna aperture and imaging resolution of synthetic aperture imaging ladar

    NASA Astrophysics Data System (ADS)

    Liu, Liren

    2009-08-01

    In this paper, the azimuth imaging resolutions of synthetic aperture imaging ladar (SAIL) using the antenna telescopes with a circular aperture for reception and a circular plan or a Gaussian beam for transmitting and with a rectangular aperture for reception and a rectangular plane or an elliptic Gaussian beam for transmitting are investigated. The analytic expressions of impulse response for imaging are achieved. The ideal azimuth spot of resolution and its degradation due to the target deviation from the footprint center, the mismatch from the quadratic phase matched filtering, the finite sampling rate and width are discussed. And the range resolution is also studied. Mathematical criteria are all given. As a conclusion, the telescope of rectangular aperture can provide a rectangular footprint more suitable for the SAIL scanning format, and an optimal design of aperture is thus possible for both a high resolution and a wide scan strip. Moreover, an explanation to the resulted azimuth resolution from our laboratory-scaled SAIL is given to verify the developed theory.

  3. Dosimetric characteristics of a newly designed grid block for megavoltage photon radiation and its therapeutic advantage using a linear quadratic model

    SciTech Connect

    Meigooni, Ali S.; Dou Kai; Meigooni, Navid J.; Gnaster, Michael; Awan, Shahid; Dini, Sharifeh; Johnson, Ellis L.

    2006-09-15

    Grid radiation therapy with megavoltage x-ray beam has been proven to be an effective technique for management of large, bulky malignant tumors. The clinical advantage of GRID therapy, combined with conventional radiation therapy, has been demonstrated using a prototype GRID block [Mohiuddin, Curtis, Grizos, and Komarnicky, Cancer 66, 114-118 (1990)]. Recently, a new GRID block design with improved dosimetric properties has become commercially available from Radiation Product Design, Inc. (Albertive, MN). This GRID collimator consists of an array of focused apertures in a cerrobend block arranged in a hexagonal pattern having a circular cross-section with a diameter and center-to-center spacing of 14.3 and 21.1 mm, respectively, in the plane of isocenter. In this project, dosimetric characteristics of the newly redesigned GRID block have been investigated for a Varian 21EX linear accelerator (Varian Associates, Palo Alto, CA). These determinations were performed using radiographic films, thermoluminescent dosimeters in Solid Water trade mark sign phantom materials, and an ionization chamber in water. The output factor, percentage depth dose, beam profiles, and isodose distributions of the GRID radiation as a function of field size and beam energy have been measured using both 6 and 18 MV x-ray beams. In addition, the therapeutic advantage obtained from this treatment modality with the new GRID block design for a high, single fraction of dose has been calculated using the linear quadratic model with {alpha}/{beta} ratios for typical tumor and normal cells. These biological characteristics of the new GRID block design will also be presented.

  4. Radix Representation of Triangular Discrete Grid System

    NASA Astrophysics Data System (ADS)

    Ben, J.; Li, Y. L.; Wang, R.

    2016-11-01

    Discrete Global Grid Systems (DGGSs) are spatial references that use a hierarchical tessellation of cells to partition and address the entire globe. It provides an organizational structure that permits fast integration between multiple sources of large and variable geospatial data. Although many endeavors have been done to describe certain discrete grid systems, there still lack of a uniform mathematical framework for them. This paper simplifies the planar class I aperture 4 triangular discrete grid system into a hierarchical lattice model which is proved to be a radix system in the complex number plane. Mathematical properties of the radix system reveal the discrete grid system is equivalent to the set of complex numbers with special form. The conclusion provides a potential way to build a uniform mathematical framework of DGGS and can be used to design efficient encoding and spatial operation scheme for DGGS.

  5. 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.

  6. A polyvalent harmonic coil testing method for small-aperture magnets.

    PubMed

    Arpaia, Pasquale; Buzio, Marco; Golluccio, Giancarlo; Walckiers, Louis

    2012-08-01

    A method to characterize permanent and fast-pulsed iron-dominated magnets with small apertures is presented. The harmonic coil measurement technique is enhanced specifically for small-aperture magnets by (1) in situ calibration, for facing search-coil production inaccuracy, (2) rotating the magnet around its axis, for correcting systematic effects, and (3) measuring magnetic fluxes by stationary coils at different angular positions for measuring fast pulsed magnets. This method allows a quadrupole magnet for particle accelerators to be characterized completely, by assessing multipole field components, magnetic axis position, and field direction. In this paper, initially the metrological problems arising from testing small-aperture magnets are highlighted. Then, the basic ideas of the proposed method and the architecture of the corresponding measurement system are illustrated. Finally, experimental validation results are shown for small-aperture permanent and fast-ramped quadrupole magnets for the new linear accelerator Linac4 at CERN (European Organization for Nuclear Research).

  7. A polyvalent harmonic coil testing method for small-aperture magnets

    NASA Astrophysics Data System (ADS)

    Arpaia, Pasquale; Buzio, Marco; Golluccio, Giancarlo; Walckiers, Louis

    2012-08-01

    A method to characterize permanent and fast-pulsed iron-dominated magnets with small apertures is presented. The harmonic coil measurement technique is enhanced specifically for small-aperture magnets by (1) in situ calibration, for facing search-coil production inaccuracy, (2) rotating the magnet around its axis, for correcting systematic effects, and (3) measuring magnetic fluxes by stationary coils at different angular positions for measuring fast pulsed magnets. This method allows a quadrupole magnet for particle accelerators to be characterized completely, by assessing multipole field components, magnetic axis position, and field direction. In this paper, initially the metrological problems arising from testing small-aperture magnets are highlighted. Then, the basic ideas of the proposed method and the architecture of the corresponding measurement system are illustrated. Finally, experimental validation results are shown for small-aperture permanent and fast-ramped quadrupole magnets for the new linear accelerator Linac4 at CERN (European Organization for Nuclear Research).

  8. Apodized apertures for solar coronagraphy

    NASA Astrophysics Data System (ADS)

    Aime, C.

    2007-05-01

    Aims:We propose the principle of a new solar telescope that makes it possible to observe the solar corona very close to the solar limb, without the help of a Lyot coronagraph. The result is obtained using a strongly apodized aperture. Methods: We obtain the theoretical form of the diffraction halo produced by the solar disk at the level of the corona for a perfect diffraction-limited telescope, for raw and apodized apertures. The problem is first solved at one dimension for which a complete set of analytical expressions can be derived, including the effect of the center-to-limb solar variation. Formal equations are written for the two-dimensional case, and it is shown that the expression may take the form of a 1D integral. Nevertheless, the problem is difficult to solve. An analytic expression can be worked out using the line spread function, which is shown to give a valid approximation of the problem, in excellent agreement with a numerical computation that uses the exact integral. Results: We show for the raw aperture that the diffraction halo is very strong and decreases slowly as ρ-1. We propose as a solution to this problem an apodized aperture based on the generalized prolate spheroidal functions (GPSF). Such an apodized aperture may reduce the diffraction halo enough to permit a direct observation of the solar corona very close to the solar limb. A signal-to-noise ratio analysis is given. Conclusions: Different strengths of apodization may be used, but very strong apodizations are indeed mandatory. A good choice seems to be a GPSF aperture with the prolate coefficient c on the order of 10. It could reduce the halo of diffraction by a factor 105 (at the cost of an intensity throughput of 10% and a reduction in the classical resolution by a factor of about 1.6) and permit observation of the corona very close to the solar limb.

  9. Coded-Aperture Transaxial Tomography Using Modular Gamma Cameras

    NASA Astrophysics Data System (ADS)

    Roney, Timothy Joseph

    Imaging in nuclear medicine involves the injection of a radioactive tracer into the body and subsequent detection of the radiation emanating from an organ of interest. Single -photon emission computed tomography (SPECT) is the branch of nuclear medicine that yields three-dimensional maps of the distribution of a tracer, most commonly as a series of two-dimensional slices. One major drawback to transaxial tomographic imaging in SPECT today is the rotation required of a gamma camera to collect the tomographic data set. Transaxial SPECT usually involves a large, single-crystal scintillation camera and an aperture (collimator) that together only satisfy a small portion of the spatial sampling requirements simultaneously. It would be very desirable to have a stationary data-collection apparatus that allows all spatial sampling in the data set to occur simultaneously. Aperture or detector motion (or both) is merely an inconvenience in most imaging situations where the patient is stationary. However, aperture or detector motion (or both) enormously complicate the prospect of tomograhically recording dynamic events, such as the beating heart, with radioactive pharmaceuticals. By substituting a set of small modular detectors for the large single-crystal detector, we can arrange the usable detector area in such a way as to collect all spatial samples simultaneously. The modular detectors allow for the possibility of using other types of stationary apertures. We demonstrate the capabilities of one such aperture, the pinhole array. The pinhole array is one of many kinds of collimators known as coded apertures. Coded apertures differ from conventional apertures in nuclear medicine in that they allow for overlapping projections of the object on the detector. Although overlapping projections is not a requirement when using pinhole arrays, there are potential benefits in terms of collection efficiency. There are also potential drawbacks in terms of the position uncertainty of

  10. A finite difference-time domain technique for modeling narrow apertures in conducting scatterers

    NASA Technical Reports Server (NTRS)

    Demarest, Kenneth R.

    1987-01-01

    The finite difference-time domain (FDTD) technique has proven to be a valuable tool for the calculation of the transient and steady state scattering characteristics of relatively complex scatterer and source configurations. In spite of its usefulness, it exhibits serious deficiencies when used to analyze geometries that contain fine detail. An FDTD technique is described that utilizes Babinet's principle to decouple the regions on both sides of the aperture. The result is an FDTD technique that is capable of modeling apertures that are much smaller than the spatial grid used in the analysis and yet is not perturbed by numerical noise when used in the 'scattered field' mode. Numerical results are presented that show the field penetration through cavity-backed apertures that are much smaller than the spatial grid used during the solution.

  11. 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.

  12. Synthetic Aperture Radar Oceanographic Investigations.

    DTIC Science & Technology

    1987-03-01

    Shuchman, P.G. Teleki, S.V. Hsiao, O.H. Shemdin , and W.E. Brown, Synthetic Aperture Radar Imaging of Ocean Waves : Comparison with Wave Measurements, J... Shemdin , Synthetic Aperture Radar Imaging of Ocean Waves during the Marineland Experiment, IEEE J. Oceanic Eg., OE-8, pp. 83-90, 1983. 12. R.A...If the surface reflectivity is assumed to be spatially un- section. are computed from the wave height spectrum as correlated, i.e. follows . (x. Y. t

  13. Investigation of ion beam space charge compensation with a 4-grid analyzer

    SciTech Connect

    Ullmann, C. Adonin, A.; Berezov, R.; Fils, J.; Hollinger, R.; Kester, O.; Chauvin, N.; Delferrière, O.; Senée, F.; Tuske, O.

    2016-02-15

    Experiments to investigate the space charge compensation of pulsed high-current heavy ion beams are performed at the GSI ion source text benches with a 4-grid analyzer provided by CEA/Saclay. The technical design of the 4-grid analyzer is revised to verify its functionality for measurements at pulsed high-current heavy ion beams. The experimental investigation of space charge compensation processes is needed to increase the performance and quality of current and future accelerator facilities. Measurements are performed directly downstream a triode extraction system mounted to a multi-cusp ion source at a high-current test bench as well as downstream the post-acceleration system of the high-current test injector (HOSTI) with ion energies up to 120 keV/u for helium and argon. At HOSTI, a cold or hot reflex discharge ion source is used to change the conditions for the measurements. The measurements were performed with helium, argon, and xenon and are presented. Results from measurements with single aperture extraction systems are shown.

  14. Investigation of ion beam space charge compensation with a 4-grid analyzer

    NASA Astrophysics Data System (ADS)

    Ullmann, C.; Adonin, A.; Berezov, R.; Chauvin, N.; Delferrière, O.; Fils, J.; Hollinger, R.; Kester, O.; Senée, F.; Tuske, O.

    2016-02-01

    Experiments to investigate the space charge compensation of pulsed high-current heavy ion beams are performed at the GSI ion source text benches with a 4-grid analyzer provided by CEA/Saclay. The technical design of the 4-grid analyzer is revised to verify its functionality for measurements at pulsed high-current heavy ion beams. The experimental investigation of space charge compensation processes is needed to increase the performance and quality of current and future accelerator facilities. Measurements are performed directly downstream a triode extraction system mounted to a multi-cusp ion source at a high-current test bench as well as downstream the post-acceleration system of the high-current test injector (HOSTI) with ion energies up to 120 keV/u for helium and argon. At HOSTI, a cold or hot reflex discharge ion source is used to change the conditions for the measurements. The measurements were performed with helium, argon, and xenon and are presented. Results from measurements with single aperture extraction systems are shown.

  15. Design and Simulation of a Rotating Aperture & Vacuum System for Neutron Imaging

    SciTech Connect

    Fitsos, P; Hall, J; Rusnak, B; Shen, S

    2006-02-27

    The development of a high-energy (10Mev) neutron imaging system at Lawrence Livermore National Laboratory (LLNL) depends on a precision engineered rotating aperture and vacuum system for generating neutrons that are used for imaging dense objects. This subsystem is part of a larger system which includes a linear accelerator that creates a deuteron beam, a scintillator detector, imaging optics and a high resolution CCD camera. The rotating aperture vacuum system has been successfully simulated and tested. Results show the feasibility of the design and point toward ways to improve the design by minimizing the rotating aperture gap.

  16. Particle-in-Cell Modeling of Magnetized Argon Plasma Flow Through Small Mechanical Apertures

    SciTech Connect

    Adam B. Sefkow and Samuel A. Cohen

    2009-04-09

    Motivated by observations of supersonic argon-ion flow generated by linear helicon-heated plasma devices, a three-dimensional particle-in-cell (PIC) code is used to study whether stationary electrostatic layers form near mechanical apertures intersecting the flow of magnetized plasma. By self-consistently evaluating the temporal evolution of the plasma in the vicinity of the aperture, the PIC simulations characterize the roles of the imposed aperture and applied magnetic field on ion acceleration. The PIC model includes ionization of a background neutral-argon population by thermal and superthermal electrons, the latter found upstream of the aperture. Near the aperture, a transition from a collisional to a collisionless regime occurs. Perturbations of density and potential, with mm wavelengths and consistent with ion acoustic waves, propagate axially. An ion acceleration region of length ~ 200-300 λD,e forms at the location of the aperture and is found to be an electrostatic double layer, with axially-separated regions of net positive and negative charge. Reducing the aperture diameter or increasing its length increases the double layer strength.

  17. 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.

  18. 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.

  19. 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.

  20. Safe Grid

    NASA Technical Reports Server (NTRS)

    Chow, Edward T.; Stewart, Helen; Korsmeyer, David (Technical Monitor)

    2003-01-01

    The biggest users of GRID technologies came from the science and technology communities. These consist of government, industry and academia (national and international). The NASA GRID is moving into a higher technology readiness level (TRL) today; and as a joint effort among these leaders within government, academia, and industry, the NASA GRID plans to extend availability to enable scientists and engineers across these geographical boundaries collaborate to solve important problems facing the world in the 21 st century. In order to enable NASA programs and missions to use IPG resources for program and mission design, the IPG capabilities needs to be accessible from inside the NASA center networks. However, because different NASA centers maintain different security domains, the GRID penetration across different firewalls is a concern for center security people. This is the reason why some IPG resources are been separated from the NASA center network. Also, because of the center network security and ITAR concerns, the NASA IPG resource owner may not have full control over who can access remotely from outside the NASA center. In order to obtain organizational approval for secured remote access, the IPG infrastructure needs to be adapted to work with the NASA business process. Improvements need to be made before the IPG can be used for NASA program and mission development. The Secured Advanced Federated Environment (SAFE) technology is designed to provide federated security across NASA center and NASA partner's security domains. Instead of one giant center firewall which can be difficult to modify for different GRID applications, the SAFE "micro security domain" provide large number of professionally managed "micro firewalls" that can allow NASA centers to accept remote IPG access without the worry of damaging other center resources. The SAFE policy-driven capability-based federated security mechanism can enable joint organizational and resource owner approved remote

  1. Datums, Ellipsoids, Grids, and Grid Reference Systems

    DTIC Science & Technology

    1992-01-01

    Tunisie Grid, Sud Algerie Grid, Sud Maroc Grid, and Sud Tunisie Grid. 4-1.1.8 The...REFERENCES ON THE SUD ALGERIE AND SUD TUNISIE GRIDS 6-8.5.2 When oil reference boxes cannot be accommodated in the margin, the excess is shown in expanses...GIVING REFERENCES ON THE SUD ALGERIE AND SUD TUNISIE GRIDS 6-21 DMA TM 8358.1 I CHAPTER 7 GRIDS ON MAPS AT 1:250,000 AND 1:500,000 SCALE 7.1 GENERAL.

  2. Synthetic-aperture chirp confocal imaging.

    PubMed

    Chien, Wei-Chen; Dilworth, D S; Liu, Elson; Leith, E N

    2006-01-20

    An imaging system that combines synthetic-aperture imaging, holography, and an optical chirp with confocal imaging is described and analyzed. Comparisons are made with synthetic-aperture radar systems. Adaptation of several synthetic-aperture radar techniques to the optical counterparts is suggested.

  3. Modernization of electron accelerator with a large cross section beam for radiation effects on materials

    NASA Astrophysics Data System (ADS)

    Vorobyov, M. S.; Denisov, V. V.; Koval, N. N.; Sulakshin, S. A.; Shugurov, V. V.; Yakovlev, V. V.

    2017-01-01

    The results of the work on the creation of an automated wide-aperture electron accelerator with a grid plasma cathode based on the low-pressure arc discharge and outputting of a large section beam (750×150 mm) in the atmosphere through a outlet foil window. The distinctive feature of such electron accelerator is a weak correlation of beam parameters, as well as a high current beam extraction efficiency to air, reaching ≈ (80 ÷ 90)% of the current in the accelerating gap at an accelerating voltage of 200 kV, beam current amplitude in the atmosphere up to 30A, frequency and pulse duration up to 50 s-1 and 100 μs, respectively. The electron source provides a stable continuous operation for tens of hours in a repetitively pulsed modes at the maximum average beam power in the atmosphere is ≈5 kW. Examples of applications of such accelerator in the radiation-stimulated technology are given, showing the prospects of its using in scientific and technological purposes.

  4. Spatially fractionated radiotherapy (GRID) using helical tomotherapy.

    PubMed

    Zhang, Xin; Penagaricano, Jose; Yan, Yulong; Liang, Xiaoying; Morrill, Steven; Griffin, Robert J; Corry, Peter; Ratanatharathorn, Vaneerat

    2016-01-08

    Spatially fractionated radiotherapy (GRID) was designed to treat large tumors while sparing skin, and it is usually delivered with a linear accelerator using a commercially available block or multileaf collimator (LINAC-GRID). For deep-seated (skin to tumor distance (> 8 cm)) tumors, it is always a challenge to achieve adequate tumor dose coverage. A novel method to perform GRID treatment using helical tomotherapy (HT-GRID) was developed at our institution. Our approach allows treating patients by generating a patient-specific virtual GRID block (software-generated) and using IMRT technique to optimize the treatment plan. Here, we report our initial clinical experience using HT-GRID, and dosimetric comparison results between HT-GRID and LINAC-GRID. This study evaluates 10 previously treated patients who had deep-seated bulky tumors with complex geometries. Five of these patients were treated with HT-GRID and replanned with LINAC-GRID for comparison. Similarly, five other patients were treated with LINAC-GRID and replanned with HT-GRID for comparison. The prescription was set such that the maximum dose to the GTV is 20 Gy in a single fraction. Dosimetric parameters compared included: mean GTV dose (DGTV mean), GTV dose inhomogeneity (valley-to-peak dose ratio (VPR)), normal tissue doses (DNmean), and other organs-at-risk (OARs) doses. In addition, equivalent uniform doses (EUD) for both GTV and normal tissue were evaluated. In summary, HT-GRID technique is patient-specific, and allows adjustment of the GRID pattern to match different tumor sizes and shapes when they are deep-seated and cannot be adequately treated with LINAC-GRID. HT-GRID delivers a higher DGTV mean, EUD, and VPR compared to LINAC-GRID. HT-GRID delivers a higher DNmean and lower EUD for normal tissue compared to LINAC-GRID. HT-GRID plans also have more options for tumors with complex anatomical relationships between the GTV and the avoidance OARs (abutment or close proximity).

  5. 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.

  6. 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.

  7. Large Aperture Scintillometer Intercomparison Study

    NASA Astrophysics Data System (ADS)

    Kleissl, J.; Gomez, J.; Hong, S.-H.; Hendrickx, J. M. H.; Rahn, T.; Defoor, W. L.

    2008-07-01

    Two field studies with six large aperture scintillometers (LASs) were performed using horizontal and slant paths. The accuracy of this novel and increasingly popular technique for measuring sensible heat fluxes was quantified by comparing measurements from different instruments over nearly identical transects. Random errors in LAS measurements were small, since correlation coefficients between adjacent measurements were greater than 0.995. However, for an ideal set-up differences in linear regression slopes of up to 21% were observed with typical inter-instrument differences of 6%. Differences of 10% are typical in more realistic measurement scenarios over homogeneous natural vegetation and different transect heights and locations. Inaccuracies in the optics, which affect the effective aperture diameter, are the most likely explanation for the observed differences.

  8. Synthetic Aperture Radar Simulation Study

    DTIC Science & Technology

    1984-03-01

    multilook are discussed. A chapter is devoted to elevation and planimetric data bases. In addition, six- teen pictures of SAR images from Hughes Aircraft, as...scans. Figure 5.4-1 is a photograph ot two SAR displays. The tirst display is made up ot six subscans and has a multilook ot one. Note that tading is...dentfi by block number) * Synthetic Aperture Radar ( SAR ) Simulation Study Radar Simulation Data Bases 5/~t. 4th.- Computer Image Generation Display 20

  9. Design of a nonscaling fixed field alternating gradient accelerator

    NASA Astrophysics Data System (ADS)

    Trbojevic, D.; Courant, E. D.; Blaskiewicz, M.

    2005-05-01

    We present a design of nonscaling fixed field alternating gradient accelerators (FFAG) minimizing the dispersion action function H. The design is considered both analytically and via computer modeling. We present the basic principles of a nonscaling FFAG lattice and discuss optimization strategies so that one can accelerate over a broad range of momentum with reasonable apertures. Acceleration schemes for muons are discussed.

  10. Sparse-aperture adaptive optics

    NASA Astrophysics Data System (ADS)

    Tuthill, Peter; Lloyd, James; Ireland, Michael; Martinache, Frantz; Monnier, John; Woodruff, Henry; ten Brummelaar, Theo; Turner, Nils; Townes, Charles

    2006-06-01

    Aperture masking interferometry and Adaptive Optics (AO) are two of the competing technologies attempting to recover diffraction-limited performance from ground-based telescopes. However, there are good arguments that these techniques should be viewed as complementary, not competitive. Masking has been shown to deliver superior PSF calibration, rejection of atmospheric noise and robust recovery of phase information through the use of closure phases. However, this comes at the penalty of loss of flux at the mask, restricting the technique to bright targets. Adaptive optics, on the other hand, can reach a fainter class of objects but suffers from the difficulty of calibration of the PSF which can vary with observational parameters such as seeing, airmass and source brightness. Here we present results from a fusion of these two techniques: placing an aperture mask downstream of an AO system. The precision characterization of the PSF enabled by sparse-aperture interferometry can now be applied to deconvolution of AO images, recovering structure from the traditionally-difficult regime within the core of the AO-corrected transfer function. Results of this program from the Palomar and Keck adaptive optical systems are presented.

  11. Linear Accelerators

    NASA Astrophysics Data System (ADS)

    Sidorin, Anatoly

    2010-01-01

    In linear accelerators the particles are accelerated by either electrostatic fields or oscillating Radio Frequency (RF) fields. Accordingly the linear accelerators are divided in three large groups: electrostatic, induction and RF accelerators. Overview of the different types of accelerators is given. Stability of longitudinal and transverse motion in the RF linear accelerators is briefly discussed. The methods of beam focusing in linacs are described.

  12. GridMan: A grid manipulation system

    NASA Technical Reports Server (NTRS)

    Eiseman, Peter R.; Wang, Zhu

    1992-01-01

    GridMan is an interactive grid manipulation system. It operates on grids to produce new grids which conform to user demands. The input grids are not constrained to come from any particular source. They may be generated by algebraic methods, elliptic methods, hyperbolic methods, parabolic methods, or some combination of methods. The methods are included in the various available structured grid generation codes. These codes perform the basic assembly function for the various elements of the initial grid. For block structured grids, the assembly can be quite complex due to a large number of clock corners, edges, and faces for which various connections and orientations must be properly identified. The grid generation codes are distinguished among themselves by their balance between interactive and automatic actions and by their modest variations in control. The basic form of GridMan provides a much more substantial level of grid control and will take its input from any of the structured grid generation codes. The communication link to the outside codes is a data file which contains the grid or section of grid.

  13. 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.

  14. Penning discharge ion source with self-cleaning aperture

    DOEpatents

    Gavin, Basil F.; MacGill, Robert A.; Thatcher, Raymond K.

    1982-01-01

    An ion source of the Penning discharge type having a self-cleaning aperture is provided by a second dynode (24) with an exit aperture (12) in a position opposite a first dynode 10a, from which the ions are sputtered, two opposing cathodes (14, 16), each with an anode (18, 20) for accelerating electrons emitted from the cathodes into a cylindrical space defined by the first and second dynode. A support gas maintained in this space is ionized by the electrons. While the cathodes are supplied with a negative pulse to emit electrons, the first dynode is supplied with a negative pulse (e.g., -300 V) to attract atoms of the ionized gas (plasma). At the same time, the second dynode may also be supplied with a small voltage that is negative with respect to the plasma (e.g., -5 V) for tuning the position of the plasma miniscus for optimum extraction geometry. When the negative pulse to the first dynode is terminated, the second dynode is driven strongly negative (e.g., -600 V) thereby allowing heavy sputtering to take place for a short period to remove virtually all of the atoms deposited on the second dynode from material sputtered off the first dynode. An extractor (22) immediately outside the exit aperture of the second dynode is maintained at ground potential during this entire period of sputtering while the anode, dynode and cathode reference voltage is driven strongly positive (about +20 kV to +30 kV) so that ions accelerated through the aperture will be at ground potential. In that manner, material from the first dynode deposited on the second dynode will be sputtered, in time, to add to the ion beam. Atoms sputtered from the second dynode which do not become ionized and exit through the slit will be redeposited on the first dynode, and hence recycled for further ion beam generation during subsequent operating cycles.

  15. Penning discharge ion source with self-cleaning aperture

    DOEpatents

    Gavin, B.F.; MacGill, R.A.; Thatcher, R.K.

    1980-11-10

    An ion source of the Penning discharge type having a self-cleaning aperture is provided by a second dynode with an exit aperture in a position opposite a first dynode, from which the ions are sputtered, two opposing cathodes, each with an anode for accelerating electrons emitted from the cathodes into a cylindrical space defined by the first and second dynode. A support gas maintained in this space is ionized by the electrons. While the cathodes are supplied with a negative pulse to emit electrons, the first dynode is supplied with a negative pulse (e.g., -300 V) to attract atoms of the ionized gas (plasma). At the same time, the second dynode may also be supplied with a small voltage that is negative with respect to the plasma (e.g., -5 V) for tuning the position of the plasma miniscus for optimum extraction geometry. When the negative pulse to the first dynode is terminated, the second dynode is driven strongly negative (e.g., -600 V) thereby allowing heavy sputtering to take place for a short period to remove virtually all of the atoms deposited on the second dynode from material sputtered off the first dynode. An extractor immediately outside the exit aperture of the second dynode is maintained at ground potential while the anode, dynode, and cathode reference voltage is driven strongly positive (about +20 kV to +30 kV) so that ions accelerated through the aperture will be at ground potential. Material from the first dynode deposited on the second dynode will be sputtered, in time, to add to the ion beam.

  16. Data Grid Management Systems

    NASA Technical Reports Server (NTRS)

    Moore, Reagan W.; Jagatheesan, Arun; Rajasekar, Arcot; Wan, Michael; Schroeder, Wayne

    2004-01-01

    The "Grid" is an emerging infrastructure for coordinating access across autonomous organizations to distributed, heterogeneous computation and data resources. Data grids are being built around the world as the next generation data handling systems for sharing, publishing, and preserving data residing on storage systems located in multiple administrative domains. A data grid provides logical namespaces for users, digital entities and storage resources to create persistent identifiers for controlling access, enabling discovery, and managing wide area latencies. This paper introduces data grids and describes data grid use cases. The relevance of data grids to digital libraries and persistent archives is demonstrated, and research issues in data grids and grid dataflow management systems are discussed.

  17. Dual aperture multispectral Schmidt objective

    NASA Astrophysics Data System (ADS)

    Minott, P. O.

    1984-04-01

    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.

  18. 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.

  19. 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.

  20. 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

  1. Can Accelerators Accelerate Learning?

    NASA Astrophysics Data System (ADS)

    Santos, A. C. F.; Fonseca, P.; Coelho, L. F. S.

    2009-03-01

    The 'Young Talented' education program developed by the Brazilian State Funding Agency (FAPERJ) [1] makes it possible for high-schools students from public high schools to perform activities in scientific laboratories. In the Atomic and Molecular Physics Laboratory at Federal University of Rio de Janeiro (UFRJ), the students are confronted with modern research tools like the 1.7 MV ion accelerator. Being a user-friendly machine, the accelerator is easily manageable by the students, who can perform simple hands-on activities, stimulating interest in physics, and getting the students close to modern laboratory techniques.

  2. PARTICLE ACCELERATOR

    DOEpatents

    Teng, L.C.

    1960-01-19

    ABS>A combination of two accelerators, a cyclotron and a ring-shaped accelerator which has a portion disposed tangentially to the cyclotron, is described. Means are provided to transfer particles from the cyclotron to the ring accelerator including a magnetic deflector within the cyclotron, a magnetic shield between the ring accelerator and the cyclotron, and a magnetic inflector within the ring accelerator.

  3. Ion accelerator systems for high power 30 cm thruster operation

    NASA Technical Reports Server (NTRS)

    Aston, G.

    1982-01-01

    Two and three-grid accelerator systems for high power ion thruster operation were investigated. Two-grid translation tests show that over compensation of the 30 cm thruster SHAG grid set spacing the 30 cm thruster radial plasma density variation and by incorporating grid compensation only sufficient to maintain grid hole axial alignment, it is shown that beam current gains as large as 50% can be realized. Three-grid translation tests performed with a simulated 30 cm thruster discharge chamber show that substantial beamlet steering can be reliably affected by decelerator grid translation only, at net-to-total voltage ratios as low as 0.05.

  4. NWTC Transmission and Grid Integration (Revised) (Fact Sheet)

    SciTech Connect

    Not Available

    2010-04-01

    The rapid growth of alternative power sources, especially wind power, is creating challenges that affect the existing electric grid. To keep up with this rapid growth, researchers in the Transmission and Grid Integration Group provide scientific, engineering, and analytical expertise to help advance alternative energy and accelerate its integration into the nation's electrical grid. For example, we evaluate U.S. wind energy resources and collect and analyze data about the impact of wind development on the electrical grid. Researchers in the Transmission and Grid Integration Group offer assistance to utility industry partners in the following integration areas.

  5. Advanced Multiple Aperture Seeing Profiler

    NASA Astrophysics Data System (ADS)

    Ren, Deqing; Zhao, Gang

    2016-10-01

    Measurements of the seeing profile of the atmospheric turbulence as a function of altitude are crucial for solar astronomical site characterization, as well as the optimized design and performance estimation of solar Multi-Conjugate Adaptive Optics (MCAO). Knowledge of the seeing distribution, up to 30 km, with a potential new solar observation site, is required for future solar MCAO developments. Current optical seeing profile measurement techniques are limited by the need to use a large facility solar telescope for such seeing profile measurements, which is a serious limitation on characterizing a site's seeing conditions in terms of the seeing profile. Based on our previous work, we propose a compact solar seeing profiler called the Advanced Multiple Aperture Seeing Profile (A-MASP). A-MASP consists of two small telescopes, each with a 100 mm aperture. The two small telescopes can be installed on a commercial computerized tripod to track solar granule structures for seeing profile measurement. A-MASP is extreme simple and portable, which makes it an ideal system to bring to a potential new site for seeing profile measurements.

  6. Hand aperture patterns in prehension.

    PubMed

    Bongers, Raoul M; Zaal, Frank T J M; Jeannerod, Marc

    2012-06-01

    Although variations in the standard prehensile pattern can be found in the literature, these alternative patterns have never been studied systematically. This was the goal of the current paper. Ten participants picked up objects with a pincer grip. Objects (3, 5, or 7cm in diameter) were placed at 30, 60, 90, or 120cm from the hands' starting location. Usually the hand was opened gradually to a maximum immediately followed by hand closing, called the standard hand opening pattern. In the alternative opening patterns the hand opening was bumpy, or the hand aperture stayed at a plateau before closing started. Two participants in particular delayed the start of grasping with respect to start of reaching, with the delay time increasing with object distance. For larger object distances and smaller object sizes, the bumpy and plateau hand opening patterns were used more often. We tentatively concluded that the alternative hand opening patterns extended the hand opening phase, to arrive at the appropriate hand aperture at the appropriate time to close the hand for grasping the object. Variations in hand opening patterns deserve attention because this might lead to new insights into the coordination of reaching and grasping.

  7. Multiple arrested synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Shuster, J. S.

    1981-05-01

    This report contains the formulation and analysis of an airborne synthetic aperture rate scheme which employs a multiplicity of antennas with the displaced phase center antenna technique to detect slowly moving targets embedded in a severe clutter environment. The radar is evaluated using the target to clutter power ratio as the measure of performance. Noise is ignored in the analysis. An optimization scheme which maximizes this ratio is employed to obtain the optimum processor weighting. The performance of the MASAR processor with optimum weights is compared against that using target weights (composed of the target signal) and that using binomial weights (which, effectively, form an n-pulse canceller). Both the target and the clutter are modeled with the electric field backscattering coefficient. The target is modeled simply as a deterministically moving point scatterer with the same albedo as a point of clutter. The clutter is modeled as a homogeneous, isotropic, two dimensional, spatiotemporal random field for which only the correlation properties are required. The analysis shows that this radar, with its optimum weighting scheme, is a promising synthetic aperture concept for the detection of slowly moving targets immersed in strong clutter environments.

  8. 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.

  9. A Roadmap for caGrid, an Enterprise Grid Architecture for Biomedical Research

    PubMed Central

    Saltz, Joel; Hastings, Shannon; Langella, Stephen; Oster, Scott; Kurc, Tahsin; Payne, Philip; Ferreira, Renato; Plale, Beth; Goble, Carole; Ervin, David; Sharma, Ashish; Pan, Tony; Permar, Justin; Brezany, Peter; Siebenlist, Frank; Madduri, Ravi; Foster, Ian; Shanbhag, Krishnakant; Mead, Charlie; Hong, Neil Chue

    2012-01-01

    caGrid is a middleware system which combines the Grid computing, the service oriented architecture, and the model driven architecture paradigms to support development of interoperable data and analytical resources and federation of such resources in a Grid environment. The functionality provided by caGrid is an essential and integral component of the cancer Biomedical Informatics Grid (caBIG™) program. This program is established by the National Cancer Institute as a nationwide effort to develop enabling informatics technologies for collaborative, multi-institutional biomedical research with the overarching goal of accelerating translational cancer research. Although the main application domain for caGrid is cancer research, the infrastructure provides a generic framework that can be employed in other biomedical research and healthcare domains. The development of caGrid is an ongoing effort, adding new functionality and improvements based on feedback and use cases from the community. This paper provides an overview of potential future architecture and tooling directions and areas of improvement for caGrid and caGrid-like systems. This summary is based on discussions at a roadmap workshop held in February with participants from biomedical research, Grid computing, and high performance computing communities. PMID:18560123

  10. A roadmap for caGrid, an enterprise Grid architecture for biomedical research.

    PubMed

    Saltz, Joel; Hastings, Shannon; Langella, Stephen; Oster, Scott; Kurc, Tahsin; Payne, Philip; Ferreira, Renato; Plale, Beth; Goble, Carole; Ervin, David; Sharma, Ashish; Pan, Tony; Permar, Justin; Brezany, Peter; Siebenlist, Frank; Madduri, Ravi; Foster, Ian; Shanbhag, Krishnakant; Mead, Charlie; Chue Hong, Neil

    2008-01-01

    caGrid is a middleware system which combines the Grid computing, the service oriented architecture, and the model driven architecture paradigms to support development of interoperable data and analytical resources and federation of such resources in a Grid environment. The functionality provided by caGrid is an essential and integral component of the cancer Biomedical Informatics Grid (caBIG) program. This program is established by the National Cancer Institute as a nationwide effort to develop enabling informatics technologies for collaborative, multi-institutional biomedical research with the overarching goal of accelerating translational cancer research. Although the main application domain for caGrid is cancer research, the infrastructure provides a generic framework that can be employed in other biomedical research and healthcare domains. The development of caGrid is an ongoing effort, adding new functionality and improvements based on feedback and use cases from the community. This paper provides an overview of potential future architecture and tooling directions and areas of improvement for caGrid and caGrid-like systems. This summary is based on discussions at a roadmap workshop held in February with participants from biomedical research, Grid computing, and high performance computing communities.

  11. Door assembly with shear layer control aperture

    NASA Technical Reports Server (NTRS)

    Kahn, William C. (Inventor); Johnston, John T. (Inventor); Fluegel, Kyle G. (Inventor)

    1996-01-01

    There is described a vehicle door assembly with shear layer control for controlling the airflow in and around an aperture in the vehicle fuselage. The vehicle door assembly consists of an upper door and a lower door, both slidably mounted to the exterior surface of the vehicle fuselage. In addition, an inner door is slidably mounted beneath the upper door. Beneath the inner door is an aperture assembly having an aperture opening positionable to be substantially flush with the exterior surface of the vehicle fuselage. Also provided are means for positioning the aperture assembly in an upward and downward direction in relation to the vehicle fuselage.

  12. Advanced optics experiments using nonuniform aperture functions

    NASA Astrophysics Data System (ADS)

    Wood, Lowell T.

    2013-05-01

    A method to create instructive, nonuniform aperture functions using spatial frequency filtering is described. The diffraction from a single slit in the Fresnel limit and the interference from a double slit in the Fraunhofer limit are spatially filtered to create electric field distributions across an aperture to produce apodization, inverse apodization or super-resolution, and apertures with phase shifts across their widths. The diffraction effects from these aperture functions are measured and calculated. The excellent agreement between the experimental results and the calculated results makes the experiment ideal for use in an advanced undergraduate or graduate optics laboratory to illustrate experimentally several effects in Fourier optics.

  13. 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.

  14. 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

  15. 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.

  16. Enhanced Optical Transmission with Coaxial Apertures

    NASA Astrophysics Data System (ADS)

    Haftel, Michael; Schlockermann, Carl; Orbons, Shannon; Roberts, Ann; Jamieson, David; Freeman, Darren; Luther-Davies, Barry

    2007-03-01

    Recently it has been shown that ``cylindrical'' surface plasmons (CSP's) on cylindrical interfaces of coaxial ring apertures produce a new form of extraordinary optical transmission (EOT) that extends to ever increasing wavelengths as the dielectric ring narrows. Using analytic and FDTD calculations we present some of the consequences of CSP's on EOT as well as experimental confirmation of such effects. We find that EOT, even with cylindrical apertures, is aided by the increase in cutoff wavelength due to CSP's, which is a consequence of the mode structure of individual apertures. CSP effects also explain most of the long-wavelength features of transmission spectra measured for CR apertures. We also show that CSP's can be ``spoofed'' at low frequencies by coaxial apertures in metamaterials consisting of a (macroscopic) periodic dielectric structure embedded in a perfect conductor. F. I. Baida et al., Phys. Rev. B 67, 155314 (2003); M.I Haftel et al., Appl. Phys. Lett. 88, 193104 (2006).

  17. 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.

  18. 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.

  19. Parallel grid population

    DOEpatents

    Wald, Ingo; Ize, Santiago

    2015-07-28

    Parallel population of a grid with a plurality of objects using a plurality of processors. One example embodiment is a method for parallel population of a grid with a plurality of objects using a plurality of processors. The method includes a first act of dividing a grid into n distinct grid portions, where n is the number of processors available for populating the grid. The method also includes acts of dividing a plurality of objects into n distinct sets of objects, assigning a distinct set of objects to each processor such that each processor determines by which distinct grid portion(s) each object in its distinct set of objects is at least partially bounded, and assigning a distinct grid portion to each processor such that each processor populates its distinct grid portion with any objects that were previously determined to be at least partially bounded by its distinct grid portion.

  20. 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.

  1. Scientific Grid computing.

    PubMed

    Coveney, Peter V

    2005-08-15

    We introduce a definition of Grid computing which is adhered to throughout this Theme Issue. We compare the evolution of the World Wide Web with current aspirations for Grid computing and indicate areas that need further research and development before a generally usable Grid infrastructure becomes available. We discuss work that has been done in order to make scientific Grid computing a viable proposition, including the building of Grids, middleware developments, computational steering and visualization. We review science that has been enabled by contemporary computational Grids, and associated progress made through the widening availability of high performance computing.

  2. Finding Optimal Apertures in Kepler Data

    NASA Astrophysics Data System (ADS)

    Smith, Jeffrey C.; Morris, Robert L.; Jenkins, Jon M.; Bryson, Stephen T.; Caldwell, Douglas A.; Girouard, Forrest R.

    2016-12-01

    With the loss of two spacecraft reaction wheels precluding further data collection for the Kepler primary mission, even greater pressure is placed on the processing pipeline to eke out every last transit signal in the data. To that end, we have developed a new method to optimize the Kepler Simple Aperture Photometry (SAP) photometric apertures for both planet detection and minimization of systematic effects. The approach uses a per cadence modeling of the raw pixel data and then performs an aperture optimization based on signal-to-noise ratio and the Kepler Combined Differential Photometric Precision (CDPP), which is a measure of the noise over the duration of a reference transit signal. We have found the new apertures to be superior to the previous Kepler apertures. We can now also find a per cadence flux fraction in aperture and crowding metric. The new approach has also been proven to be robust at finding apertures in K2 data that help mitigate the larger motion-induced systematics in the photometry. The method further allows us to identify errors in the Kepler and K2 input catalogs.

  3. Measurement of beam divergence of 30-centimeter dished grids

    NASA Technical Reports Server (NTRS)

    Danilowicz, R. L.; Rawlin, V. K.; Banks, B. A.; Wintucky, E. G.

    1973-01-01

    The beam divergence of a 30-centimeter diameter thruster with dished grids was calculated from current densities measured with a probe rake containing seventeen planar molybdenum probes. The measured data were analyzed as a function of a number of parameters. The most sensitive parameters were the amount of compensation of the accelerator grid and the ratio of net to total accelerating voltage. The thrust losses were reduced by over 5 percent with the use of compensated grids alone, and by variation of other parameters the overall thrust losses due to beam divergence were reduced to less than 2 percent.

  4. Measurement of beam divergence of 30-centimeter dished grids

    NASA Technical Reports Server (NTRS)

    Danilowicz, R. L.; Rawlin, V. K.; Banks, B. A.; Wintucky, E. G.

    1973-01-01

    The beam divergence of a 30-centimeter diameter thrustor with dished grids was calculated from current densities measured with a probe rake containing seventeen planar molybdenum probes. The measured data were analyzed as a function of a number of parameters. The most sensitive parameters were the amount of compensation of the accelerator grid and the ratio of net to total accelerating voltage. The thrust losses were reduced by over 5 percent with the use of compensated grids alone, and by variation of other parameters the overall thrust losses due to beam divergence were reduced to less than 2 percent.

  5. Walking through Apertures in Individuals with Stroke

    PubMed Central

    Higuchi, Takahiro

    2017-01-01

    Objective Walking through a narrow aperture requires unique postural configurations, i.e., body rotation in the yaw dimension. Stroke individuals may have difficulty performing the body rotations due to motor paralysis on one side of their body. The present study was therefore designed to investigate how successfully such individuals walk through apertures and how they perform body rotation behavior. Method Stroke fallers (n = 10), stroke non-fallers (n = 13), and healthy controls (n = 23) participated. In the main task, participants walked for 4 m and passed through apertures of various widths (0.9–1.3 times the participant’s shoulder width). Accidental contact with the frame of an aperture and kinematic characteristics at the moment of aperture crossing were measured. Participants also performed a perceptual judgment task to measure the accuracy of their perceived aperture passability. Results and Discussion Stroke fallers made frequent contacts on their paretic side; however, the contacts were not frequent when they penetrated apertures from their paretic side. Stroke fallers and non-fallers rotated their body with multiple steps, rather than a single step, to deal with their motor paralysis. Although the minimum passable width was greater for stroke fallers, the body rotation angle was comparable among groups. This suggests that frequent contact in stroke fallers was due to insufficient body rotation. The fact that there was no significant group difference in the perceived aperture passability suggested that contact occurred mainly due to locomotor factors rather than perceptual factors. Two possible explanations (availability of vision and/or attention) were provided as to why accidental contact on the paretic side did not occur frequently when stroke fallers penetrated the apertures from their paretic side. PMID:28103299

  6. Parallel optical nanolithography using nanoscale bowtie apertures

    NASA Astrophysics Data System (ADS)

    Uppuluri, Sreemanth M. V.

    Over the past two decades various branches of science and engineering have developed techniques for producing nanoscopic light sources for different applications such as imaging, detection and fabrication. These areas include near-field scanning optical microscopy (NSOM), surface-enhanced Raman scattering and detection (SERS), plasmonics and so on. In particular nanolithography techniques have been developed to produce feature sizes in the sub-100 nm length scales. These processes include variations of standard photolithography process to achieve high resolution, optical fiber-based near-field lithography, surface plasmon assisted nanolithography, interference optical lithography and so on. This work presents a study of the viability of using nanoscale bowtie apertures for nanolithography. Bowtie apertures exhibit a unique property of supporting a propagating TE10 mode at wavelengths of light in the visible and near-UV regimes. The energy of this mode is concentrated in the gap region of the aperture and thus these apertures have the potential to produce high intensity nanoscale light spots that can be used for nano-patterning applications. We demonstrate this capability of nanoscale bowtie apertures by patterning photoresist to obtain resolution less than 100 nm. Initially we present the results from static lithography experiments and show that the ridge apertures of different shapes -- C, H and bowtie produce holes in the photoresist of dimensions around 50-60 nm. Subsequently we address the issues involved in using these apertures for nano directwriting. We show that chromium thin-films offer a viable solution to produce high quality metal films of surface roughness less than 1 nm over an area of 25 mum2. This is indeed important to achieve intimate contact between the apertures and the photoresist surface. We also explain ways to decrease friction between the mask and photoresist surfaces during nano direct-writing. In addition, to decrease the contact force

  7. Passive microwave imaging by aperture synthesis technology

    NASA Astrophysics Data System (ADS)

    Lang, Liang; Zhang, Zuyin; Guo, Wei; Gui, Liangqi

    2007-11-01

    In order to verify the theory of aperture synthesis at low expense, two-channel ka-band correlation radiometer which is basic part of synthetic aperture radiometer is designed firstly before developing the multi-channel synthetic aperture radiometer. The performance of two-channel correlation radiometer such as stability and coherence of visibility phase are tested in the digital correlation experiment. Subsequently all required baselines are acquired by moving the antenna pair sequentially, corresponding samples of the visibility function are measured and the image of noise source is constructed using an inverse Fourier transformation.

  8. Dynamic Power Grid Simulation

    SciTech Connect

    Top, Philip; Woodward, Carol; Smith, Steve; Banks, Lawrence; Kelley, Brian

    2015-09-14

    GridDyn is a part of power grid simulation toolkit. The code is designed using modern object oriented C++ methods utilizing C++11 and recent Boost libraries to ensure compatibility with multiple operating systems and environments.

  9. Method of grid generation

    DOEpatents

    Barnette, Daniel W.

    2002-01-01

    The present invention provides a method of grid generation that uses the geometry of the problem space and the governing relations to generate a grid. The method can generate a grid with minimized discretization errors, and with minimal user interaction. The method of the present invention comprises assigning grid cell locations so that, when the governing relations are discretized using the grid, at least some of the discretization errors are substantially zero. Conventional grid generation is driven by the problem space geometry; grid generation according to the present invention is driven by problem space geometry and by governing relations. The present invention accordingly can provide two significant benefits: more efficient and accurate modeling since discretization errors are minimized, and reduced cost grid generation since less human interaction is required.

  10. Transient simulation of ram accelerator flowfields

    NASA Astrophysics Data System (ADS)

    Drabczuk, Randall P.; Rolader, G.; Dash, S.; Sinha, N.; York, B.

    1993-01-01

    This paper describes the development of an advanced computational fluid dynamic (CFD) simulation capability in support of the USAF Armament Directorate ram accelerator research initiative. The state-of-the-art CRAFT computer code has been specialized for high fidelity, transient ram accelerator simulations via inclusion of generalized dynamic gridding, solution adaptive grid clustering, and high pressure thermo-chemistry. Selected ram accelerator simulations are presented that serve to exhibit the CRAFT code capabilities and identify some of the principle research/design Issues.

  11. Transient simulation of ram accelerator flowfields

    NASA Astrophysics Data System (ADS)

    Sinha, N.; York, B. J.; Dash, S. M.; Drabczuk, R.; Rolader, G. E.

    1992-10-01

    This paper describes the development of an advanced computational fluid dynamic (CFD) simulation capability in support of the U.S. Air Force Armament Directorate's ram accelerator research initiative. The state-of-the-art CRAFT computer code has been specialized for high fidelity, transient ram accelerator simulations via inclusion of generalized dynamic gridding, solution adaptive grid clustering, high pressure thermochemistry, etc. Selected ram accelerator simulations are presented which serve to exhibit the CRAFT code's capabilities and identify some of the principal research/design issues.

  12. Control of aperture closure during reach-to-grasp movements in Parkinson's disease.

    PubMed

    Rand, M K; Smiley-Oyen, A L; Shimansky, Y P; Bloedel, J R; Stelmach, G E

    2006-01-01

    This study examined whether the pattern of coordination between arm-reaching toward an object (hand transport) and the initiation of aperture closure for grasping is different between PD patients and healthy individuals, and whether that pattern is affected by the necessity to quickly adjust the reach-to-grasp movement in response to an unexpected shift of target location. Subjects reached for and grasped a vertical dowel, the location of which was indicated by illuminating one of the three dowels placed on a horizontal plane. In control conditions, target location was fixed during the trial. In perturbation conditions, target location was shifted instantaneously by switching the illumination to a different dowel during the reach. The hand distance from the target at which the subject initiated aperture closure (aperture closure distance) was similar for both the control and perturbation conditions within each group of subjects. However, that distance was significantly closer to the target in the PD group than in the control group. The timing of aperture closure initiation varied considerably across the trials in both groups of subjects. In contrast, aperture closure distance was relatively invariant, suggesting that aperture closure initiation was determined by spatial parameters of arm kinematics rather than temporal parameters. The linear regression analysis of aperture closure distance showed that the distance was highly predictable based on the following three parameters: the amplitude of maximum grip aperture, hand velocity, and hand acceleration. This result implies that a control law, the arguments of which include the above parameters, governs the initiation of aperture closure. Further analysis revealed that the control law was very similar between the subject groups under each condition as well as between the control and perturbation conditions for each group. Consequently, the shorter aperture closure distance observed in PD patients apparently is a

  13. Parallel unstructured grid generation

    NASA Technical Reports Server (NTRS)

    Loehner, Rainald; Camberos, Jose; Merriam, Marshal

    1991-01-01

    A parallel unstructured grid generation algorithm is presented and implemented on the Hypercube. Different processor hierarchies are discussed, and the appropraite hierarchies for mesh generation and mesh smoothing are selected. A domain-splitting algorithm for unstructured grids which tries to minimize the surface-to-volume ratio of each subdomain is described. This splitting algorithm is employed both for grid generation and grid smoothing. Results obtained on the Hypercube demonstrate the effectiveness of the algorithms developed.

  14. IPG Power Grid Overview

    NASA Technical Reports Server (NTRS)

    Hinke, Thomas

    2003-01-01

    This presentation will describe what is meant by grids and then cover the current state of the IPG. This will include an overview of the middleware that is key to the operation of the grid. The presentation will then describe some of the future directions that are planned for the IPG. Finally the presentation will conclude with a brief overview of the Global Grid Forum, which is a key activity that will contribute to the successful availability of grid components.

  15. Future accelerators (?)

    SciTech Connect

    John Womersley

    2003-08-21

    I describe the future accelerator facilities that are currently foreseen for electroweak scale physics, neutrino physics, and nuclear structure. I will explore the physics justification for these machines, and suggest how the case for future accelerators can be made.

  16. AstroGrid-PL

    NASA Astrophysics Data System (ADS)

    Stachowski, Greg; Kundera, Tomasz; Ciecielag, Paweł; AstroGridPL Team

    2016-06-01

    We summarise the achievements AstroGrid-PL project, which aims to provide an infrastructure grid computing, distributed storage and Virtual Observatory services to the Polish astronomical community. It was developed from 2011-2015 as a domain grid component within the large PLGrid Plus project for scientific computing in Poland.

  17. GridKit

    SciTech Connect

    Peles, Slaven

    2016-11-06

    GridKit is a software development kit for interfacing power systems and power grid application software with high performance computing (HPC) libraries developed at National Labs and academia. It is also intended as interoperability layer between different numerical libraries. GridKit is not a standalone application, but comes with a suite of test examples illustrating possible usage.

  18. Chimera Grid Tools

    NASA Technical Reports Server (NTRS)

    Chan, William M.; Rogers, Stuart E.; Nash, Steven M.; Buning, Pieter G.; Meakin, Robert

    2005-01-01

    Chimera Grid Tools (CGT) is a software package for performing computational fluid dynamics (CFD) analysis utilizing the Chimera-overset-grid method. For modeling flows with viscosity about geometrically complex bodies in relative motion, the Chimera-overset-grid method is among the most computationally cost-effective methods for obtaining accurate aerodynamic results. CGT contains a large collection of tools for generating overset grids, preparing inputs for computer programs that solve equations of flow on the grids, and post-processing of flow-solution data. The tools in CGT include grid editing tools, surface-grid-generation tools, volume-grid-generation tools, utility scripts, configuration scripts, and tools for post-processing (including generation of animated images of flows and calculating forces and moments exerted on affected bodies). One of the tools, denoted OVERGRID, is a graphical user interface (GUI) that serves to visualize the grids and flow solutions and provides central access to many other tools. The GUI facilitates the generation of grids for a new flow-field configuration. Scripts that follow the grid generation process can then be constructed to mostly automate grid generation for similar configurations. CGT is designed for use in conjunction with a computer-aided-design program that provides the geometry description of the bodies, and a flow-solver program.

  19. 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.

  20. An empirical explanation of aperture effects.

    PubMed

    Sung, Kyongje; Wojtach, William T; Purves, Dale

    2009-01-06

    The perceived direction of a moving line changes, often markedly, when viewed through an aperture. Although several explanations of this remarkable effect have been proposed, these accounts typically focus on the percepts elicited by a particular type of aperture and offer no biological rationale. Here, we test the hypothesis that to contend with the inherently ambiguous nature of motion stimuli the perceived direction of objects moving behind apertures of different shapes is determined by a wholly empirical strategy of visual processing. An analysis of moving line stimuli generated by objects projected through apertures shows that the directions of motion subjects report in psychophysical testing is accounted for by the frequency of occurrence of the 2D directions of stimuli generated by simulated 3D sources. The completeness of these predictions supports the conclusion that the direction of perceived motion is fully determined by accumulated behavioral experience with sources whose physical motions cannot be conveyed by image sequences as such.

  1. 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.

  2. 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.

  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. 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.

  5. Eyeglass. 1. Very large aperture diffractive telescopes

    SciTech Connect

    Hyde, R.A.

    1999-07-01

    The Eyeglass is a very large aperture (25{endash}100-m) space telescope consisting of two distinct spacecraft, separated in space by several kilometers. A diffractive lens provides the telescope{close_quote}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{close_quote}s eyepiece; the Eyeglass can provide diffraction-limited imaging with either single-band ({Delta}{lambda}/{lambda}{approximately}0.1), multiband, or continuous spectral coverage. {copyright} 1999 Optical Society of America

  6. Active multi-aperture imaging through turbulence

    NASA Astrophysics Data System (ADS)

    Miller, Nicholas J.; Widiker, Jeffrey J.; McManamon, Paul F.; Haus, Joseph W.

    2012-06-01

    We describe our Innovative Multi Aperture Gimbaless Electro-Optical (IMAGE) testbed which uses coherent detection of the complex field reflected off a diffuse target with seven hexagonally arranged apertures. The seven measured optical fields are then phased with a digital optimization algorithm to synthesize a composite image whose angular resolution exceeds that of a single aperture. This same post-detection phasing algorithm also corrects aberrations induced by imperfect optics and a turbulent atmospheric path. We present the coherent imaging sub-aperture design used in the IMAGE array as well as the design of a compact range used to perform scaled tests of the IMAGE array. We present some experimental results of imaging diffuse targets in the compact range with two phase screens which simulates a ~7[Km] propagation path through distributed atmospheric turbulence.

  7. 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.

  8. Measured Radiation and Background Levels During Transmission of Megawatt Electron Beams Through Millimeter Apertures

    SciTech Connect

    Alarcon, Ricardo; Balascuta, S.; Benson, Stephen V.; Bertozzi, William; Boyce, James R.; Cowan, Ray; Douglas, David R.; Evtushenko, Pavel; Fisher, P.; Ihloff, Ernest E.; Kalantarians, Narbe; Kelleher, Aidan Michael; Krossler, W. J.; Legg, Robert A.; Long, Elena; Milner, Richard; Neil, George R.; Ou, Longwu; Schmookler, Barack Abraham; Tennant, Christopher D.; Tschalar, C.; Williams, Gwyn P.; Zhang, Shukui

    2013-11-01

    We report measurements of photon and neutron radiation levels observed while transmitting a 0.43 MW electron beam through millimeter-sized apertures and during beam-off, but accelerating gradient RF-on, operation. These measurements were conducted at the Free-Electron Laser (FEL) facility of the Jefferson National Accelerator Laboratory (JLab) using a 100 MeV electron beam from an energy-recovery linear accelerator. The beam was directed successively through 6 mm, 4 mm, and 2 mm diameter apertures of length 127 mm in aluminum at a maximum current of 4.3 mA (430 kW beam power). This study was conducted to characterize radiation levels for experiments that need to operate in this environment, such as the proposed DarkLight Experiment. We find that sustained transmission of a 430 kW continuous-wave (CW) beam through a 2 mm aperture is feasible with manageable beam-related backgrounds. We also find that during beam-off, RF-on operation, multipactoring inside the niobium cavities of the accelerator cryomodules is the primary source of ambient radiation when the machine is tuned for 130 MeV operation.

  9. 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.

  10. The CMS integration grid testbed

    SciTech Connect

    Graham, Gregory E.

    2004-08-26

    The CMS Integration Grid Testbed (IGT) comprises USCMS Tier-1 and Tier-2 hardware at the following sites: the California Institute of Technology, Fermi National Accelerator Laboratory, the University of California at San Diego, and the University of Florida at Gainesville. The IGT runs jobs using the Globus Toolkit with a DAGMan and Condor-G front end. The virtual organization (VO) is managed using VO management scripts from the European Data Grid (EDG). Gridwide monitoring is accomplished using local tools such as Ganglia interfaced into the Globus Metadata Directory Service (MDS) and the agent based Mona Lisa. Domain specific software is packaged and installed using the Distribution After Release (DAR) tool of CMS, while middleware under the auspices of the Virtual Data Toolkit (VDT) is distributed using Pacman. During a continuous two month span in Fall of 2002, over 1 million official CMS GEANT based Monte Carlo events were generated and returned to CERN for analysis while being demonstrated at SC2002. In this paper, we describe the process that led to one of the world's first continuously available, functioning grids.

  11. Effect of speed manipulation on the control of aperture closure during reach-to-grasp movements.

    PubMed

    Rand, Miya K; Squire, Linda M; Stelmach, George E

    2006-09-01

    This study investigates coordination between hand transport and grasp movement components by examining a hypothesis that the hand location, relative to the object, in which aperture closure is initiated remains relatively constant under a wide range of transport speed. Subjects made reach-to-grasp movements to a dowel under four speed conditions: slow, comfortable, fast but comfortable, and maximum (i.e., as fast as possible). The distance traveled by the wrist after aperture reached its maximum (aperture closure distance) increased with an increase of transport speed across the speed conditions. This finding rejected the hypothesis and suggests that the speed of hand transport is taken into account in aperture closure initiation. Within each speed condition, however, the closure distance exhibited relatively small variability across trials, even though the total distance traveled by the wrist during the entire transport movement varied from trial to trial. The observed stability in aperture closure distance across trials implies that the hand distance to the object plays an important role in the control law governing the initiation of aperture closure. Further analysis showed that the aperture closure distance depended on the amplitude of peak aperture as well as hand velocity and acceleration. To clarify the form of the above control law, we analyzed four different mathematical models, in which a decision to initiate grasp closure is made as soon as a specific movement parameter (wrist distance to target or transport time) crosses a threshold that is either a constant value or a function of the above-mentioned other movement-related parameters. Statistical analysis performed across all movement conditions revealed that the control law model (according to which grasp initiation is made when hand distance to target becomes less than a certain linear function of aperture amplitude, hand velocity, and hand acceleration) produced significantly smaller residual errors

  12. FermiGrid

    SciTech Connect

    Yocum, D.R.; Berman, E.; Canal, P.; Chadwick, K.; Hesselroth, T.; Garzoglio, G.; Levshina, T.; Sergeev, V.; Sfiligoi, I.; Sharma, N.; Timm, S.; /Fermilab

    2007-05-01

    As one of the founding members of the Open Science Grid Consortium (OSG), Fermilab enables coherent access to its production resources through the Grid infrastructure system called FermiGrid. This system successfully provides for centrally managed grid services, opportunistic resource access, development of OSG Interfaces for Fermilab, and an interface to the Fermilab dCache system. FermiGrid supports virtual organizations (VOs) including high energy physics experiments (USCMS, MINOS, D0, CDF, ILC), astrophysics experiments (SDSS, Auger, DES), biology experiments (GADU, Nanohub) and educational activities.

  13. Grid Architecture 2

    SciTech Connect

    Taft, Jeffrey D.

    2016-01-01

    The report describes work done on Grid Architecture under the auspices of the Department of Electricity Office of Electricity Delivery and Reliability in 2015. As described in the first Grid Architecture report, the primary purpose of this work is to provide stakeholder insight about grid issues so as to enable superior decision making on their part. Doing this requires the creation of various work products, including oft-times complex diagrams, analyses, and explanations. This report provides architectural insights into several important grid topics and also describes work done to advance the science of Grid Architecture as well.

  14. Role of vision in aperture closure control during reach-to-grasp movements.

    PubMed

    Rand, Miya K; Lemay, Martin; Squire, Linda M; Shimansky, Yury P; Stelmach, George E

    2007-08-01

    We have previously shown that the distance from the hand to the target at which finger closure is initiated during the reach (aperture closure distance) depends on the amplitude of peak aperture, as well as hand velocity and acceleration. This dependence suggests the existence of a control law according to which a decision to initiate finger closure during the reach is made when the hand distance to target crosses a threshold that is a function of the above movement-related parameters. The present study examined whether the control law is affected by manipulating the visibility of the hand and the target. Young adults made reach-to-grasp movements to a dowel under conditions in which the target or the hand or both were either visible or not visible. Reaching for and grasping a target when the hand and/or target were not visible significantly increased transport time and widened peak aperture. Aperture closure distance was significantly lengthened and wrist peak velocity was decreased only when the target was not visible. Further analysis showed that the control law was significantly different between the visibility-related conditions. When either the hand or target was not visible, the aperture closure distance systematically increased compared to its value for the same amplitude of peak aperture, hand velocity, and acceleration under full visibility. This implies an increase in the distance-related safety margin for grasping when the hand or target is not visible. It has been also found that the same control law can be applied to all conditions, if variables describing hand and target visibility were included in the control law model, as the parameters of the task-related environmental context, in addition to the above movement-related parameters. This suggests that that the CNS utilizes those variables for controlling grasp initiation based on a general control law.

  15. Aperture Engineering for Impulse Radiating Antennas

    NASA Astrophysics Data System (ADS)

    Tyo, J. S.

    The past several years have seen the development of an improved understanding of the role of aperture design for impulse radiating antennas (IRAs). The understanding began with the emergence of the concept of prompt aperture efficiency for ultra-wideband (UWB) antennas. This emergence allowed us to concentrate on ways to shape the aperture and control the field distribution within the aperture in order to maximize the prompt response from IRAs. In many high voltage UWB applications it is impossible to increase the radiated fields by increasing the source power. This is because in such instances the sources are already at the limits of linear electromagnetics. In these cases, we would like to come up with methods to improve the radiated field without altering the input impedance of the IRA. In this paper we will explore several such methods including the position of the feed arms to maximize field uniformity, the shaping of the aperture to increase radiated fields by reducing the aperture size, the relative sizing of the reflector (or lens) and the feed horn, and actually reorienting the currents on the reflector by controlling the direction of current flow. One common thread appears in all of these studies, that is the influence of Dr. Carl Baum on the direction and development of the work.

  16. Hydrogen ionic plasma generated using Al plasma grid

    NASA Astrophysics Data System (ADS)

    Oohara, W.; Anegawa, N.; Egawa, M.; Kawata, K.; Kamikawa, T.

    2016-08-01

    Negative hydrogen ions are produced in the apertures of a plasma grid made of aluminum under the irradiation of positive ions, generating an ionic plasma consisting of positive and negative ions. The saturation current ratio obtained using a Langmuir probe reflects the existence ratio of electrons and is found to increase in connection with the diffusion of the ionic plasma. The local increment of the current ratio suggests the collapse of negative ions and the replacement of detached electrons.

  17. Apparent apertures from ground penetrating radar data and their relation to heterogeneous aperture fields

    NASA Astrophysics Data System (ADS)

    Shakas, A.; Linde, N.

    2017-03-01

    Considering fractures with heterogeneous aperture distributions, we explore the reliability of constant-aperture estimates derived from ground penetrating radar (GPR) reflection data. We generate geostatistical fracture aperture realizations that are characterized by the same mean-aperture and variance, but different Hurst exponents and cutoff lengths. For each of the 16 classes of heterogeneity considered, we generate 1000 fracture realizations from which we compute GPR reflection data using our recent effective-dipole forward model. We then use each (noise-contaminated) dataset individually to invert for a single 'apparent' aperture, i.e., we assume that the fracture aperture is homogeneous. We find that the inferred 'apparent' apertures are only reliable when fracture heterogeneity is non-fractal (the Hurst exponent is close to 1) and the scale of the dominant aperture heterogeneities is larger than the first Fresnel zone. These results are a direct consequence of the non-linear character of the thin-bed reflection coefficients. As fracture heterogeneity is ubiquitous and often fractal, our results suggest that robust field-based inference of fracture aperture can only be achieved by accounting for the non-linear response of fracture heterogeneity on GPR data.

  18. Which grids are Hamiltonian

    SciTech Connect

    Hedetniemi, S. M.; Hedetniemi, S. T.; Slater, P. J.

    1980-01-01

    A complete grid G/sub m,n/ is a graph having m x n pertices that are connected to form a rectangular lattice in the plane, i.e., all edges of G/sub m,n/ connect vertices along horizontal or vertical lines. A grid is a subgraph of a complete grid. As an illustration, complete grids describe the basic pattern of streets in most cities. This paper examines the existence of Hamiltonian cycles in complete grids and complete grids with one or two vertices removed. It is determined for most values of m,n greater than or equal to 1, which grids G/sub m,n/ - (u) and G/sub m,n/ - (u,v) are Hamiltonian. 12 figures. (RWR)

  19. Understanding The Smart Grid

    SciTech Connect

    2007-11-15

    The report provides an overview of what the Smart Grid is and what is being done to define and implement it. The electric industry is preparing to undergo a transition from a centralized, producer-controlled network to a decentralized, user-interactive one. Not only will the technology involved in the electric grid change, but the entire business model of the industry will change too. A major objective of the report is to identify the changes that the Smart Grid will bring about so that industry participants can be prepared to face them. A concise overview of the development of the Smart Grid is provided. It presents an understanding of what the Smart Grid is, what new business opportunities or risks might come about due to its introduction, and what activities are already taking place regarding defining or implementing the Smart Grid. This report will be of interest to the utility industry, energy service providers, aggregators, and regulators. It will also be of interest to home/building automation vendors, information technology vendors, academics, consultants, and analysts. The scope of the report includes an overview of the Smart Grid which identifies the main components of the Smart Grid, describes its characteristics, and describes how the Smart Grid differs from the current electric grid. The overview also identifies the key concepts involved in the transition to the Smart Grid and explains why a Smart Grid is needed by identifying the deficiencies of the current grid and the need for new investment. The report also looks at the impact of the Smart Grid, identifying other industries which have gone through a similar transition, identifying the overall benefits of the Smart Grid, and discussing the impact of the Smart Grid on industry participants. Furthermore, the report looks at current activities to implement the Smart Grid including utility projects, industry collaborations, and government initiatives. Finally, the report takes a look at key technology

  20. 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

  1. Navigation in Grid Space with the NAS Grid Benchmarks

    NASA Technical Reports Server (NTRS)

    Frumkin, Michael; Hood, Robert; Biegel, Bryan A. (Technical Monitor)

    2002-01-01

    We present a navigational tool for computational grids. The navigational process is based on measuring the grid characteristics with the NAS Grid Benchmarks (NGB) and using the measurements to assign tasks of a grid application to the grid machines. The tool allows the user to explore the grid space and to navigate the execution at a grid application to minimize its turnaround time. We introduce the notion of gridscape as a user view of the grid and show how it can be me assured by NGB, Then we demonstrate how the gridscape can be used with two different schedulers to navigate a grid application through a rudimentary grid.

  2. Directional synthetic aperture flow imaging.

    PubMed

    Jensen, Jørgen Arendt; Nikolov, Svetoslav Ivanov

    2004-09-01

    A method for flow estimation using synthetic aperture imaging and focusing along the flow direction is presented. The method can find the correct velocity magnitude for any flow angle, and full color flow images can be measured using only 32 to 128 pulse emissions. The approach uses spherical wave emissions with a number of defocused elements and a linear frequency-modulated pulse (chirp) to improve the signal-to-noise ratio. The received signals are dynamically focused along the flow direction and these signals are used in a cross-correlation estimator for finding the velocity magnitude. The flow angle is manually determined from the B-mode image. The approach can be used for both tissue and blood velocity determination. The approach was investigated using both simulations and a flow system with a laminar flow. The flow profile was measured with a commercial 7.5 MHz linear array transducer. A plastic tube with an internal diameter of 17 mm was used with an EcoWatt 1 pump generating a laminar, stationary flow. The velocity profile was measured for flow angles of 90 and 60 degrees. The RASMUS research scanner was used for acquiring radio frequency (RF) data from 128 elements of the array, using 8 emissions with 11 elements in each emission. A 20-micros chirp was used during emission. The RF data were subsequently beamformed off-line and stationary echo canceling was performed. The 60-degree flow with a peak velocity of 0.15 m/s was determined using 16 groups of 8 emissions, and the relative standard deviation was 0.36% (0.65 mm/s). Using the same setup for purely transverse flow gave a standard deviation of 1.2% (2.1 mm/s). Variation of the different parameters revealed the sensitivity to number of lines, angle deviations, length of correlation interval, and sampling interval. An in vivo image of the carotid artery and jugular vein of a healthy 29-year-old volunteer was acquired. A full color flow image using only 128 emissions could be made with a high

  3. Efficient generation of generalized Monkhorst-Pack grids through the use of informatics

    NASA Astrophysics Data System (ADS)

    Wisesa, Pandu; McGill, Kyle A.; Mueller, Tim

    2016-04-01

    We present a method for rapidly generating efficient k -point grids for Brillouin zone integration by using a database of precalculated grids. Benchmark results on 102 randomly selected materials indicate that for well-converged calculations, the grids generated by our method have fewer than half as many irreducible k -points as Monkhorst-Pack grids generated using a more conventional method, significantly accelerating the calculation of properties of crystalline materials.

  4. Phase dependence of transport-aperture coordination variability reveals control strategy of reach-to-grasp movements.

    PubMed

    Rand, Miya K; Shimansky, Y P; Hossain, Abul B M I; Stelmach, George E

    2010-11-01

    Based on an assumption of movement control optimality in reach-to-grasp movements, we have recently developed a mathematical model of transport-aperture coordination (TAC), according to which the hand-target distance is a function of hand velocity and acceleration, aperture magnitude, and aperture velocity and acceleration (Rand et al. in Exp Brain Res 188:263-274, 2008). Reach-to-grasp movements were performed by young adults under four different reaching speeds and two different transport distances. The residual error magnitude of fitting the above model to data across different trials and subjects was minimal for the aperture-closure phase, but relatively much greater for the aperture-opening phase, indicating considerable difference in TAC variability between those phases. This study's goal is to identify the main reasons for that difference and obtain insights into the control strategy of reach-to-grasp movements. TAC variability within the aperture-opening phase of a single trial was found minimal, indicating that TAC variability between trials was not due to execution noise, but rather a result of inter-trial and inter-subject variability of motor plan. At the same time, the dependence of the extent of trial-to-trial variability of TAC in that phase on the speed of hand transport was sharply inconsistent with the concept of speed-accuracy trade-off: the lower the speed, the larger the variability. Conversely, the dependence of the extent of TAC variability in the aperture-closure phase on hand transport speed was consistent with that concept. Taking into account recent evidence that the cost of neural information processing is substantial for movement planning, the dependence of TAC variability in the aperture-opening phase on task performance conditions suggests that it is not the movement time that the CNS saves in that phase, but the cost of neuro-computational resources and metabolic energy required for TAC regulation in that phase. Thus, the CNS

  5. Grid enabled Service Support Environment - SSE Grid

    NASA Astrophysics Data System (ADS)

    Goor, Erwin; Paepen, Martine

    2010-05-01

    The SSEGrid project is an ESA/ESRIN project which started in 2009 and is executed by two Belgian companies, Spacebel and VITO, and one Dutch company, Dutch Space. The main project objectives are the introduction of a Grid-based processing on demand infrastructure at the Image Processing Centre for earth observation products at VITO and the inclusion of Grid processing services in the Service Support Environment (SSE) at ESRIN. The Grid-based processing on demand infrastructure is meant to support a Grid processing on demand model for Principal Investigators (PI) and allow the design and execution of multi-sensor applications with geographically spread data while minimising the transfer of huge volumes of data. In the first scenario, 'support a Grid processing on demand model for Principal Investigators', we aim to provide processing power close to the EO-data at the processing and archiving centres. We will allow a PI (non-Grid expert user) to upload his own algorithm, as a process, and his own auxiliary data from the SSE Portal and use them in an earth observation workflow on the SSEGrid Infrastructure. The PI can design and submit workflows using his own processes, processes made available by VITO/ESRIN and possibly processes from other users that are available on the Grid. These activities must be user-friendly and not requiring detailed knowledge about the underlying Grid middleware. In the second scenario we aim to design, implement and demonstrate a methodology to set up an earth observation processing facility, which uses large volumes of data from various geographically spread sensors. The aim is to provide solutions for problems that we face today, like wasting bandwidth by copying large volumes of data to one location. We will avoid this by processing the data where they are. The multi-mission Grid-based processing on demand infrastructure will allow developing and executing complex and massive multi-sensor data (re-)processing applications more

  6. Securing smart grid technology

    NASA Astrophysics Data System (ADS)

    Chaitanya Krishna, E.; Kosaleswara Reddy, T.; Reddy, M. YogaTeja; Reddy G. M., Sreerama; Madhusudhan, E.; AlMuhteb, Sulaiman

    2013-03-01

    In the developing countries electrical energy is very important for its all-round improvement by saving thousands of dollars and investing them in other sector for development. For Growing needs of power existing hierarchical, centrally controlled grid of the 20th Century is not sufficient. To produce and utilize effective power supply for industries or people we should have Smarter Electrical grids that address the challenges of the existing power grid. The Smart grid can be considered as a modern electric power grid infrastructure for enhanced efficiency and reliability through automated control, high-power converters, modern communications infrastructure along with modern IT services, sensing and metering technologies, and modern energy management techniques based on the optimization of demand, energy and network availability and so on. The main objective of this paper is to provide a contemporary look at the current state of the art in smart grid communications as well as critical issues on smart grid technologies primarily in terms of information and communication technology (ICT) issues like security, efficiency to communications layer field. In this paper we propose new model for security in Smart Grid Technology that contains Security Module(SM) along with DEM which will enhance security in Grid. It is expected that this paper will provide a better understanding of the technologies, potential advantages and research challenges of the smart grid and provoke interest among the research community to further explore this promising research area.

  7. Development of a large aperture Nb3Sn racetrack quadrupolemagnet

    SciTech Connect

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

    2005-04-14

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

  8. A new pad-based neutron detector for stereo coded aperture thermal neutron imaging

    NASA Astrophysics Data System (ADS)

    Dioszegi, I.; Yu, B.; Smith, G.; Schaknowski, N.; Fried, J.; Vanier, P. E.; Salwen, C.; Forman, L.

    2014-09-01

    A new coded aperture thermal neutron imager system has been developed at Brookhaven National Laboratory. The cameras use a new type of position-sensitive 3He-filled ionization chamber, in which an anode plane is composed of an array of pads with independent acquisition channels. The charge is collected on each of the individual 5x5 mm2 anode pads, (48x48 in total, corresponding to 24x24 cm2 sensitive area) and read out by application specific integrated circuits (ASICs). The new design has several advantages for coded-aperture imaging applications in the field, compared to the previous generation of wire-grid based neutron detectors. Among these are its rugged design, lighter weight and use of non-flammable stopping gas. The pad-based readout occurs in parallel circuits, making it capable of high count rates, and also suitable to perform data analysis and imaging on an event-by-event basis. The spatial resolution of the detector can be better than the pixel size by using a charge sharing algorithm. In this paper we will report on the development and performance of the new pad-based neutron camera, describe a charge sharing algorithm to achieve sub-pixel spatial resolution and present the first stereoscopic coded aperture images of thermalized neutron sources using the new coded aperture thermal neutron imager system.

  9. Understanding the Grid

    SciTech Connect

    2016-01-14

    The electric power grid has been rightly celebrated as the single most important engineering feat of the 20th century. The grid powers our homes, offices, hospitals, and schools; and, increasingly, it powers our favorite devices from smartphones to HDTVs. With those and other modern innovations and challenges, our grid will need to evolve. Grid modernization efforts will help the grid make full use of today’s advanced technologies and serve our needs in the 21st century. While the vast majority of upgrades are implemented by private sector energy companies that own and operate the grid, DOE has been investing in technologies that are revolutionizing the way we generate, store and transmit power.

  10. 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.

  11. High numerical aperture focusing of singular beams

    NASA Astrophysics Data System (ADS)

    Normatov, Alexander; Spektor, Boris; Shamir, Joseph

    2009-02-01

    Rigorous vector analysis of high numerical aperture optical systems encounters severe difficulties. While existing analytic methods, based on the Richards-Wolf approach, allow focusing of nearly planar incident wavefronts, these methods break down for beams possessing considerable phase jumps, such as beams containing phase singularities. This work was motivated by the need to analyze a recently introduced metrological application of singular beams that demonstrated an experimental sensitivity of 20nm under a moderate numerical aperture of 0.4. One of the possibilities to obtain even better sensitivity is by increasing the numerical aperture of the optical system. In this work we address the issue of high numerical aperture focusing of the involved singular beams. Our solution exploits the superposition principle to evaluate the three dimensional focal distribution of the electromagnetic field provided the illuminating wavefront can be described as having piecewise quasi constant phase. A brief overview of singular beam microscopy is followed by deeper discussion of the involved high numerical aperture focusing issue. Further, a few examples of different singular beam focal field distributions are presented.

  12. SAGA: A Simple API for Grid Applications -- High-Level ApplicationProgramming on the Grid

    SciTech Connect

    Goodale, Tom; Jha, Shantenu; Kaiser, Hartmut; Kielmann, Thilo; Kleijer, Pascal; von Laszewski, Gregor; Lee, Craig; Merzky, Andre; Rajic,Hrabri; Shalf, John

    2006-05-31

    Grid technology has matured considerably over the past fewyears. Progress in both implementation and standardization is reaching alevel of robustness that enables production quality deployments of gridservices in the academic research community with heightened interest andearly adoption in the industrial community. Despite this progress, gridapplications are far from ubiquitous, and new applications require anenormous amount of programming effort just to see first light. A keyimpediment to accelerated deployment of grid applications is the scarcityof high-level application programming abstractions that bridge the gapbetween existing grid middle-ware and application-level needs. The SimpleAPI for Grid Applications (SAGA [1]) is a GGF standardization effort thataddresses this particular gap by providing a simple, stable, and uniformprogramming interface that integrates the most common grid programmingabstractions. These most common abstractions were identified through theanalysis of several existing and emerging Grid applications. In thisarticle, we present the SAGA effort, describe its relationship to otherGrid API efforts within the GGF community, and introduce the first draftof the API using some application programming examples.

  13. Challenges facing production grids

    SciTech Connect

    Pordes, Ruth; /Fermilab

    2007-06-01

    Today's global communities of users expect quality of service from distributed Grid systems equivalent to that their local data centers. This must be coupled to ubiquitous access to the ensemble of processing and storage resources across multiple Grid infrastructures. We are still facing significant challenges in meeting these expectations, especially in the underlying security, a sustainable and successful economic model, and smoothing the boundaries between administrative and technical domains. Using the Open Science Grid as an example, I examine the status and challenges of Grids operating in production today.

  14. Enhanced Elliptic Grid Generation

    NASA Technical Reports Server (NTRS)

    Kaul, Upender K.

    2007-01-01

    An enhanced method of elliptic grid generation has been invented. Whereas prior methods require user input of certain grid parameters, this method provides for these parameters to be determined automatically. "Elliptic grid generation" signifies generation of generalized curvilinear coordinate grids through solution of elliptic partial differential equations (PDEs). Usually, such grids are fitted to bounding bodies and used in numerical solution of other PDEs like those of fluid flow, heat flow, and electromagnetics. Such a grid is smooth and has continuous first and second derivatives (and possibly also continuous higher-order derivatives), grid lines are appropriately stretched or clustered, and grid lines are orthogonal or nearly so over most of the grid domain. The source terms in the grid-generating PDEs (hereafter called "defining" PDEs) make it possible for the grid to satisfy requirements for clustering and orthogonality properties in the vicinity of specific surfaces in three dimensions or in the vicinity of specific lines in two dimensions. The grid parameters in question are decay parameters that appear in the source terms of the inhomogeneous defining PDEs. The decay parameters are characteristic lengths in exponential- decay factors that express how the influences of the boundaries decrease with distance from the boundaries. These terms govern the rates at which distance between adjacent grid lines change with distance from nearby boundaries. Heretofore, users have arbitrarily specified decay parameters. However, the characteristic lengths are coupled with the strengths of the source terms, such that arbitrary specification could lead to conflicts among parameter values. Moreover, the manual insertion of decay parameters is cumbersome for static grids and infeasible for dynamically changing grids. In the present method, manual insertion and user specification of decay parameters are neither required nor allowed. Instead, the decay parameters are

  15. A grid amplifier

    NASA Technical Reports Server (NTRS)

    Kim, Moonil; Weikle, Robert M., II; Hacker, Jonathan B.; Delisio, Michael P.; Rutledge, David B.; Rosenberg, James J.; Smith, R. P.

    1991-01-01

    A 50-MESFET grid amplifier is reported that has a gain of 11 dB at 3.3 GHz. The grid isolates the input from the output by using vertical polarization for the input beam and horizontal polarization for the transmitted output beam. The grid unit cell is a two-MESFET differential amplifier. A simple calibration procedure allows the gain to be calculated from a relative power measurement. This grid is a hybrid circuit, but the structure is suitable for fabrication as a monolithic wafer-scale integrated circuit, particularly at millimeter wavelengths.

  16. Unstructured surface grid generation

    NASA Technical Reports Server (NTRS)

    Samareh-Abolhassani, Jamshid

    1993-01-01

    Viewgraphs on unstructured surface grid generation are presented. Topics covered include: requirements for curves, surfaces, solids, and text; surface approximation; triangulation; advancing; projection; mapping; and parametric curves.

  17. New multigrid approach for three-dimensional unstructured, adaptive grids

    NASA Technical Reports Server (NTRS)

    Parthasarathy, Vijayan; Kallinderis, Y.

    1994-01-01

    A new multigrid method with adaptive unstructured grids is presented. The three-dimensional Euler equations are solved on tetrahedral grids that are adaptively refined or coarsened locally. The multigrid method is employed to propagate the fine grid corrections more rapidly by redistributing the changes-in-time of the solution from the fine grid to the coarser grids to accelerate convergence. A new approach is employed that uses the parent cells of the fine grid cells in an adapted mesh to generate successively coaser levels of multigrid. This obviates the need for the generation of a sequence of independent, nonoverlapping grids as well as the relatively complicated operations that need to be performed to interpolate the solution and the residuals between the independent grids. The solver is an explicit, vertex-based, finite volume scheme that employs edge-based data structures and operations. Spatial discretization is of central-differencing type combined with a special upwind-like smoothing operators. Application cases include adaptive solutions obtained with multigrid acceleration for supersonic and subsonic flow over a bump in a channel, as well as transonic flow around the ONERA M6 wing. Two levels of multigrid resulted in reduction in the number of iterations by a factor of 5.

  18. New multigrid approach for three-dimensional unstructured, adaptive grids

    NASA Astrophysics Data System (ADS)

    Parthasarathy, Vijayan; Kallinderis, Y.

    1994-05-01

    A new multigrid method with adaptive unstructured grids is presented. The three-dimensional Euler equations are solved on tetrahedral grids that are adaptively refined or coarsened locally. The multigrid method is employed to propagate the fine grid corrections more rapidly by redistributing the changes-in-time of the solution from the fine grid to the coarser grids to accelerate convergence. A new approach is employed that uses the parent cells of the fine grid cells in an adapted mesh to generate successively coarser levels of multigrid. This obviates the need for the generation of a sequence of independent, nonoverlapping grids as well as the relatively complicated operations that need to be performed to interpolate the solution and the residuals between the independent grids. The solver is an explicit, vertex-based, finite volume scheme that employs edge-based data structures and operations. Spatial discretization is of central-differencing type combined with special upwind-like smoothing operators. Application cases include adaptive solutions obtained with multigrid acceleration for supersonic and subsonic flow over a bump in a channel, as well as transonic flow around the ONERA M6 wing. Two levels of multigrid resulted in reduction in the number of iterations by a factor of 5.

  19. New multigrid approach for three-dimensional unstructured, adaptive grids

    NASA Astrophysics Data System (ADS)

    Parthasarathy, Vijayan; Kallinderis, Y.

    1994-05-01

    A new multigrid method with adaptive unstructured grids is presented. The three-dimensional Euler equations are solved on tetrahedral grids that are adaptively refined or coarsened locally. The multigrid method is employed to propagate the fine grid corrections more rapidly by redistributing the changes-in-time of the solution from the fine grid to the coarser grids to accelerate convergence. A new approach is employed that uses the parent cells of the fine grid cells in an adapted mesh to generate successively coaser levels of multigrid. This obviates the need for the generation of a sequence of independent, nonoverlapping grids as well as the relatively complicated operations that need to be performed to interpolate the solution and the residuals between the independent grids. The solver is an explicit, vertex-based, finite volume scheme that employs edge-based data structures and operations. Spatial discretization is of central-differencing type combined with a special upwind-like smoothing operators. Application cases include adaptive solutions obtained with multigrid acceleration for supersonic and subsonic flow over a bump in a channel, as well as transonic flow around the ONERA M6 wing. Two levels of multigrid resulted in reduction in the number of iterations by a factor of 5.

  20. Analysis of secondary particle behavior in multiaperture, multigrid accelerator for the ITER neutral beam injector.

    PubMed

    Mizuno, T; Taniguchi, M; Kashiwagi, M; Umeda, N; Tobari, H; Watanabe, K; Dairaku, M; Sakamoto, K; Inoue, T

    2010-02-01

    Heat load on acceleration grids by secondary particles such as electrons, neutrals, and positive ions, is a key issue for long pulse acceleration of negative ion beams. Complicated behaviors of the secondary particles in multiaperture, multigrid (MAMuG) accelerator have been analyzed using electrostatic accelerator Monte Carlo code. The analytical result is compared to experimental one obtained in a long pulse operation of a MeV accelerator, of which second acceleration grid (A2G) was removed for simplification of structure. The analytical results show that relatively high heat load on the third acceleration grid (A3G) since stripped electrons were deposited mainly on A3G. This heat load on the A3G can be suppressed by installing the A2G. Thus, capability of MAMuG accelerator is demonstrated for suppression of heat load due to secondary particles by the intermediate grids.

  1. 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.

  2. 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.

  3. Distributed Apertures in Laminar Flow Laser Turrets.

    DTIC Science & Technology

    1981-09-01

    t r by Oe" Vmbat) High Energy Lasers Aperture Arrays Laser Turrets Aero-Optics 20. Aeft*ACT (CieOuu en revere siea of 400arind OE#1 by.*f Week.1a...ciation to Mom and Dad for their love and resolve which encourages the author to fulfill his potential. 11 I. INTRODUCTION Propagation of laser energy ...is the true measure of the "goodness" of a system of one or more apertures. PIB FPIB A (11) Power projected is found by use of the relation for the on

  4. 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.

  5. 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.

  6. Comparison of calculated with measured dynamic aperture

    SciTech Connect

    Zimmermann, F.

    1994-06-01

    The measured dynamic aperture of the HERA proton ring and the value expected from simulation studies agree within a factor of 2. A better agreement is achieved if a realistic tune modulation is included in the simulation. The approximate threshold of tune-modulation induced diffusion can be calculated analytically. Its value is in remarkable agreement with the dynamic aperture measured. The calculation is based on parameters of resonances through order 11 which are computed using differential-algebra methods and normal-form algorithms. Modulational diffusion in conjunction with drifting machine parameters appears to be the most important transverse diffusion process.

  7. Sub-aperture stitching test of a cylindrical mirror with large aperture

    NASA Astrophysics Data System (ADS)

    Xue, Shuai; Chen, Shanyong; Shi, Feng; Lu, Jinfeng

    2016-09-01

    Cylindrical mirrors are key optics of high-end equipment of national defense and scientific research such as high energy laser weapons, synchrotron radiation system, etc. However, its surface error test technology develops slowly. As a result, its optical processing quality can not meet the requirements, and the developing of the associated equipment is hindered. Computer Generated-Hologram (CGH) is commonly utilized as null for testing cylindrical optics. However, since the fabrication process of CGH with large aperture is not sophisticated yet, the null test of cylindrical optics with large aperture is limited by the aperture of the CGH. Hence CGH null test combined with sub-aperture stitching method is proposed to break the limit of the aperture of CGH for testing cylindrical optics, and the design of CGH for testing cylindrical surfaces is analyzed. Besides, the misalignment aberration of cylindrical surfaces is different from that of the rotational symmetric surfaces since the special shape of cylindrical surfaces, and the existing stitching algorithm of rotational symmetric surfaces can not meet the requirements of stitching cylindrical surfaces. We therefore analyze the misalignment aberrations of cylindrical surfaces, and study the stitching algorithm for measuring cylindrical optics with large aperture. Finally we test a cylindrical mirror with large aperture to verify the validity of the proposed method.

  8. Monte Carlo simulation of ion-neutral charge exchange collisions and grid erosion in an ion thruster

    NASA Technical Reports Server (NTRS)

    Peng, Xiaohang; Ruyten, Wilhelmus M.; Keefer, Dennis

    1991-01-01

    A combined particle-in-cell (PIC)/Monte Carlo simulation model has been developed in which the PIC method is used to simulate the charge exchange collisions. It is noted that a number of features were reproduced correctly by this code, but that its assumption of two-dimensional axisymmetry for a single set of grid apertures precluded the reproduction of the most characteristic feature of actual test data; namely, the concentrated grid erosion at the geometric center of the hexagonal aperture array. The first results of a three-dimensional code, which takes into account the hexagonal symmetry of the grid, are presented. It is shown that, with this code, the experimentally observed erosion patterns are reproduced correctly, demonstrating explicitly the concentration of sputtering between apertures.

  9. Security for grids

    SciTech Connect

    Humphrey, Marty; Thompson, Mary R.; Jackson, Keith R.

    2005-08-14

    Securing a Grid environment presents a distinctive set of challenges. This paper groups the activities that need to be secured into four categories: naming and authentication; secure communication; trust, policy, and authorization; and enforcement of access control. It examines the current state of the art in securing these processes and introduces new technologies that promise to meet the security requirements of Grids more completely.

  10. Internet 2 Access Grid.

    ERIC Educational Resources Information Center

    Simco, Greg

    2002-01-01

    Discussion of the Internet 2 Initiative, which is based on collaboration among universities, businesses, and government, focuses on the Access Grid, a Computational Grid that includes interactive multimedia within high-speed networks to provide resources to enable remote collaboration among the research community. (Author/LRW)

  11. Geometric grid generation

    NASA Technical Reports Server (NTRS)

    Ives, David

    1995-01-01

    This paper presents a highly automated hexahedral grid generator based on extensive geometrical and solid modeling operations developed in response to a vision of a designer-driven one day turnaround CFD process which implies a designer-driven one hour grid generation process.

  12. LINEAR ACCELERATOR

    DOEpatents

    Colgate, S.A.

    1958-05-27

    An improvement is presented in linear accelerators for charged particles with respect to the stable focusing of the particle beam. The improvement consists of providing a radial electric field transverse to the accelerating electric fields and angularly introducing the beam of particles in the field. The results of the foregoing is to achieve a beam which spirals about the axis of the acceleration path. The combination of the electric fields and angular motion of the particles cooperate to provide a stable and focused particle beam.

  13. Silicon ball grid array chip carrier

    DOEpatents

    Palmer, David W.; Gassman, Richard A.; Chu, Dahwey

    2000-01-01

    A ball-grid-array integrated circuit (IC) chip carrier formed from a silicon substrate is disclosed. The silicon ball-grid-array chip carrier is of particular use with ICs having peripheral bond pads which can be reconfigured to a ball-grid-array. The use of a semiconductor substrate such as silicon for forming the ball-grid-array chip carrier allows the chip carrier to be fabricated on an IC process line with, at least in part, standard IC processes. Additionally, the silicon chip carrier can include components such as transistors, resistors, capacitors, inductors and sensors to form a "smart" chip carrier which can provide added functionality and testability to one or more ICs mounted on the chip carrier. Types of functionality that can be provided on the "smart" chip carrier include boundary-scan cells, built-in test structures, signal conditioning circuitry, power conditioning circuitry, and a reconfiguration capability. The "smart" chip carrier can also be used to form specialized or application-specific ICs (ASICs) from conventional ICs. Types of sensors that can be included on the silicon ball-grid-array chip carrier include temperature sensors, pressure sensors, stress sensors, inertia or acceleration sensors, and/or chemical sensors. These sensors can be fabricated by IC processes and can include microelectromechanical (MEM) devices.

  14. 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.

  15. 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.

  16. 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…

  17. 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.

  18. 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…

  19. Demonstration of synthetic aperture imaging ladar

    NASA Astrophysics Data System (ADS)

    Buell, W.; Marechal, N.; Buck, J.; Dickinson, R.; Kozlowski, D.; Wright, T.; Beck, S.

    2005-05-01

    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. This paper details our laboratory-scale SAIL testbed, digital signal processing techniques, and image results. A number of fine-resolution, well-focused SAIL images are shown including both retro-reflecting and diffuse scattering targets. A general digital signal processing solution to the laser waveform instability problem is described and demonstrated, involving both new algorithms and hardware elements. These algorithms are primarily data-driven, without a priori knowledge of waveform and sensor position, representing a crucial step in developing a robust imaging system. These techniques perform well on waveform errors, but not on external phase errors such as turbulence or vibration. As a first step towards mitigating phase errors of this type, we have developed a balanced, quadrature phase, laser vibrometer to work in conjunction with our SAIL system to measure and compensate for relative line of sight motion between the target and transceiver. We describe this system and present a comparison of the vibrometer-measured phase error with the phase error inferred from the SAIL data.

  20. 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.

  1. Dynamic aperture of the recycler ring

    SciTech Connect

    Xiao, Meiqin; Sen, Tanaji

    2000-11-15

    This report describes the dynamic aperture tracking for the Recycler Ring based on the latest modified lattice Ver 20. The purpose of the calculation is to check the optical properties of the lattice with the replacement of the high beta straight section (HB30) by a low beta straight section (LB30) for stochastic cooling.

  2. Millimeter-wave diode-grid phase shifters

    NASA Technical Reports Server (NTRS)

    Lam, Wayne W.; Stolt, Kjell S.; Jou, Christina F.; Luhmann, Neville C., Jr.; Chen, Howard Z.

    1988-01-01

    Monolithic diode grids have been fabricated on 2-cm square gallium-arsenide wafers with 1600 Schottky-barrier varactor diodes. Shorted diodes are detected with a liquid-crystal technique, and the bad diodes are removed with an ultrasonic probe. A small-aperture reflectometer that uses wavefront division interference was developed to measure the reflection coefficient of the grids. A phase shift of 70 deg with a 7-dB loss was obtained at 93 GHz when the bias on the diode grid was changed from -3 V to 1 V. A simple transmission-line grid model, together with the measured low-frequency parameters for the diodes, was shown to predict the measured performance over the entire capacitive bias range of the diodes, as well as over the complete reactive tuning range provided by a reflector behind the grid, and over a wide range of frequencies from 33 GHz to 141 GHz. This shows that the transmission-line model and the measured low-frequency diode parameters can be used to design an electronic beam-steering array and to predict its performance. An electronic beam-steering array made of a pair of grids using state-of-the-art diodes with 5-ohm series resistances would have a loss of 1.4 dB at 90 GHz.

  3. Optimization Of A Computational Grid

    NASA Technical Reports Server (NTRS)

    Pearce, Daniel G.

    1993-01-01

    In improved method of generation of computational grid, grid-generation process decoupled from definition of geometry. Not necessary to redefine boundary. Instead, continuous boundaries in physical domain specified, and then grid points in computational domain mapped onto continuous boundaries.

  4. Acceleration switch

    DOEpatents

    Abbin, Jr., Joseph P.; Devaney, Howard F.; Hake, Lewis W.

    1982-08-17

    The disclosure relates to an improved integrating acceleration switch of the type having a mass suspended within a fluid filled chamber, with the motion of the mass initially opposed by a spring and subsequently not so opposed.

  5. Acceleration switch

    DOEpatents

    Abbin, J.P. Jr.; Devaney, H.F.; Hake, L.W.

    1979-08-29

    The disclosure relates to an improved integrating acceleration switch of the type having a mass suspended within a fluid filled chamber, with the motion of the mass initially opposed by a spring and subsequently not so opposed.

  6. ION ACCELERATOR

    DOEpatents

    Bell, J.S.

    1959-09-15

    An arrangement for the drift tubes in a linear accelerator is described whereby each drift tube acts to shield the particles from the influence of the accelerating field and focuses the particles passing through the tube. In one embodiment the drift tube is splii longitudinally into quadrants supported along the axis of the accelerator by webs from a yoke, the quadrants. webs, and yoke being of magnetic material. A magnetic focusing action is produced by energizing a winding on each web to set up a magnetic field between adjacent quadrants. In the other embodiment the quadrants are electrically insulated from each other and have opposite polarity voltages on adjacent quadrants to provide an electric focusing fleld for the particles, with the quadrants spaced sufficienily close enough to shield the particles within the tube from the accelerating electric field.

  7. Berkeley Proton Linear Accelerator

    DOE R&D Accomplishments Database

    Alvarez, L. W.; Bradner, H.; Franck, J.; Gordon, H.; Gow, J. D.; Marshall, L. C.; Oppenheimer, F. F.; Panofsky, W. K. H.; Richman, C.; Woodyard, J. R.

    1953-10-13

    A linear accelerator, which increases the energy of protons from a 4 Mev Van de Graaff injector, to a final energy of 31.5 Mev, has been constructed. The accelerator consists of a cavity 40 feet long and 39 inches in diameter, excited at resonance in a longitudinal electric mode with a radio-frequency power of about 2.2 x 10{sup 6} watts peak at 202.5 mc. Acceleration is made possible by the introduction of 46 axial "drift tubes" into the cavity, which is designed such that the particles traverse the distance between the centers of successive tubes in one cycle of the r.f. power. The protons are longitudinally stable as in the synchrotron, and are stabilized transversely by the action of converging fields produced by focusing grids. The electrical cavity is constructed like an inverted airplane fuselage and is supported in a vacuum tank. Power is supplied by 9 high powered oscillators fed from a pulse generator of the artificial transmission line type.

  8. Three-dimensional adaptive grid-embedding Euler technique

    NASA Astrophysics Data System (ADS)

    Davis, Roger L.; Dannenhoffer, John F., III

    1994-06-01

    A new three-dimensional adaptive-grid Euler procedure is presented that automatically detects high-gradient regions in the flow and locally subdivides the computational grid in these regions to provide a uniform, high level of accuracy over the entire domain. A tunable, semistructured data system is utilized that provides global topological unstructured-grid flexibility along with the efficiency of a local, structured-grid system. In addition, this structure data allows for the flow solution algorithm to be executed on a wide variety of parallel/vector computing platforms. An explicit, time-marching, control volume procedure is used to integrate the Euler equations to a steady state. In addition, a multiple-grid procedure is used throughout the embedded-grid regions as well as on subgrids coarser than the initial grid to accelerate convergence and properly propagate disturbance waves through refined-grid regions. Upon convergence, high flow gradient regions, where it is assumed that large truncation errors in the solution exist, are detected using a combination of directional refinement vectors that have large components in areas of these gradients. The local computational grid is directionally subdivided in these regions and the flow solution is reinitiated. Overall convergence occurs when a prespecified level of accuracy is reached. Solutions are presented that demonstrate the efficiency and accuracy of the present procedure.

  9. LINEAR ACCELERATOR

    DOEpatents

    Christofilos, N.C.; Polk, I.J.

    1959-02-17

    Improvements in linear particle accelerators are described. A drift tube system for a linear ion accelerator reduces gap capacity between adjacent drift tube ends. This is accomplished by reducing the ratio of the diameter of the drift tube to the diameter of the resonant cavity. Concentration of magnetic field intensity at the longitudinal midpoint of the external sunface of each drift tube is reduced by increasing the external drift tube diameter at the longitudinal center region.

  10. 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%.

  11. Control of aperture closure initiation during trunk-assisted reach-to-grasp movements.

    PubMed

    Rand, Miya K; Van Gemmert, Arend W A; Hossain, Abul B M I; Shimansky, Yury P; Stelmach, George E

    2012-06-01

    The present study investigated how the involvement and direction of trunk movement during reach-to-grasp movements affect the coordination between the transport and grasping components. Seated young adults made prehensile movements in which the involvement of the trunk was varied; the trunk was not involved, moved forward (flexion), or moved backward (extension) in the sagittal plane during the reach to the object. Each of the trunk movements was combined with an extension or flexion motion of the arm during the reach. Regarding the relationship between the trunk and arm motion for arm transport, the onset of wrist motion relative to that of the trunk was delayed to a greater extent for the trunk extension than for the trunk flexion. The variability of the time period from the peak of wrist velocity to the peak of trunk velocity was also significantly greater for trunk extension compared to trunk flexion. These findings indicate that trunk flexion was better integrated into the control of wrist transport than trunk extension. In terms of the temporal relationship between wrist transport and grip aperture, the relationship between the time of peak wrist velocity and the time of peak grip aperture did not change or become less steady across conditions. Therefore, the stability of temporal coordination between wrist transport and grip aperture was maintained despite the variation of the pattern of intersegmental coordination between the arm and the trunk during arm transport. The transport-aperture coordination was further assessed in terms of the control law according to which the initiation of aperture closure during the reach occurs when the hand crosses a hand-to-target distance threshold for grasp initiation, which is a function of peak aperture, wrist velocity and acceleration, trunk velocity and acceleration, and trunk-to-target distance at the time of aperture closure initiation. The participants increased the hand-to-target distance threshold for grasp

  12. Direct Replacement of Arbitrary Grid-Overlapping by Non-Structured Grid

    NASA Technical Reports Server (NTRS)

    Kao, Kai-Hsiung; Liou, Meng-Sing

    1994-01-01

    A new approach that uses nonstructured mesh to replace the arbitrarily overlapped structured regions of embedded grids is presented. The present methodology uses the Chimera composite overlapping mesh system so that the physical domain of the flowfield is subdivided into regions which can accommodate easily-generated grid for complex configuration. In addition, a Delaunay triangulation technique generates nonstructured triangular mesh which wraps over the interconnecting region of embedded grids. It is designed that the present approach, termed DRAGON grid, has three important advantages: eliminating some difficulties of the Chimera scheme, such as the orphan points and/or bad quality of interpolation stencils; making grid communication in a fully conservative way; and implementation into three dimensions is straightforward. A computer code based on a time accurate, finite volume, high resolution scheme for solving the compressible Navier-Stokes equations has been further developed to include both the Chimera overset grid and the nonstructured mesh schemes. For steady state problems, the local time stepping accelerates convergence based on a Courant - Friedrichs - Leury (CFL) number near the local stability limit. Numerical tests on representative steady and unsteady supersonic inviscid flows with strong shock waves are demonstrated.

  13. Sparse grid techniques for particle-in-cell schemes

    NASA Astrophysics Data System (ADS)

    Ricketson, L. F.; Cerfon, A. J.

    2017-02-01

    We propose the use of sparse grids to accelerate particle-in-cell (PIC) schemes. By using the so-called ‘combination technique’ from the sparse grids literature, we are able to dramatically increase the size of the spatial cells in multi-dimensional PIC schemes while paying only a slight penalty in grid-based error. The resulting increase in cell size allows us to reduce the statistical noise in the simulation without increasing total particle number. We present initial proof-of-principle results from test cases in two and three dimensions that demonstrate the new scheme’s efficiency, both in terms of computation time and memory usage.

  14. Decentral Smart Grid Control

    NASA Astrophysics Data System (ADS)

    Schäfer, Benjamin; Matthiae, Moritz; Timme, Marc; Witthaut, Dirk

    2015-01-01

    Stable operation of complex flow and transportation networks requires balanced supply and demand. For the operation of electric power grids—due to their increasing fraction of renewable energy sources—a pressing challenge is to fit the fluctuations in decentralized supply to the distributed and temporally varying demands. To achieve this goal, common smart grid concepts suggest to collect consumer demand data, centrally evaluate them given current supply and send price information back to customers for them to decide about usage. Besides restrictions regarding cyber security, privacy protection and large required investments, it remains unclear how such central smart grid options guarantee overall stability. Here we propose a Decentral Smart Grid Control, where the price is directly linked to the local grid frequency at each customer. The grid frequency provides all necessary information about the current power balance such that it is sufficient to match supply and demand without the need for a centralized IT infrastructure. We analyze the performance and the dynamical stability of the power grid with such a control system. Our results suggest that the proposed Decentral Smart Grid Control is feasible independent of effective measurement delays, if frequencies are averaged over sufficiently large time intervals.

  15. An investigation of the RCS (radar cross section) computation of grid cavities

    SciTech Connect

    Sabihi, Ahmad

    2014-12-10

    In this paper, the aperture of a cavity is covered by a metallic grid net. This metallic grid is to reduce RCS deduced by impinging radar ray on the aperture. A radar ray incident on a grid net installed on a cavity may create six types of propagation. 1-Incident rays entering inside the cavity and backscattered from it.2-Incidebnt rays on the grid net and created reection rays as an array of scatterers. These rays may create a wave with phase difference of 180 degree with respect to the exiting rays from the cavity.3-Incident rays on the grid net create surface currents owing on the net and make travelling waves, which regenerate the magnetic and electric fields. These fields make again propagated waves against incident ones.4-Creeping waves.5-Diffracted rays due to leading edges of net’s elements.6-Mutual impedance among elements of the net could be effective on the resultant RCS. Therefore, the author compares the effects of three out of six properties to a cavity without grid net. This comparison shows that RCS prediction of cavity having a grid net is much more reduced than that of without one.

  16. The open science grid

    SciTech Connect

    Pordes, R.; /Fermilab

    2004-12-01

    The U.S. LHC Tier-1 and Tier-2 laboratories and universities are developing production Grids to support LHC applications running across a worldwide Grid computing system. Together with partners in computer science, physics grid projects and active experiments, we will build a common national production grid infrastructure which is open in its architecture, implementation and use. The Open Science Grid (OSG) model builds upon the successful approach of last year's joint Grid2003 project. The Grid3 shared infrastructure has for over eight months provided significant computational resources and throughput to a range of applications, including ATLAS and CMS data challenges, SDSS, LIGO, and biology analyses, and computer science demonstrators and experiments. To move towards LHC-scale data management, access and analysis capabilities, we must increase the scale, services, and sustainability of the current infrastructure by an order of magnitude or more. Thus, we must achieve a significant upgrade in its functionalities and technologies. The initial OSG partners will build upon a fully usable, sustainable and robust grid. Initial partners include the US LHC collaborations, DOE & NSF Laboratories and Universities & Trillium Grid projects. The approach is to federate with other application communities in the U.S. to build a shared infrastructure open to other sciences and capable of being modified and improved to respond to needs of other applications, including CDF, D0, BaBar, and RHIC experiments. We describe the application-driven, engineered services of the OSG, short term plans and status, and the roadmap for a consortium, its partnerships and national focus.

  17. Trends in life science grid: from computing grid to knowledge grid

    PubMed Central

    Konagaya, Akihiko

    2006-01-01

    Background Grid computing has great potential to become a standard cyberinfrastructure for life sciences which often require high-performance computing and large data handling which exceeds the computing capacity of a single institution. Results This survey reviews the latest grid technologies from the viewpoints of computing grid, data grid and knowledge grid. Computing grid technologies have been matured enough to solve high-throughput real-world life scientific problems. Data grid technologies are strong candidates for realizing "resourceome" for bioinformatics. Knowledge grids should be designed not only from sharing explicit knowledge on computers but also from community formulation for sharing tacit knowledge among a community. Conclusion Extending the concept of grid from computing grid to knowledge grid, it is possible to make use of a grid as not only sharable computing resources, but also as time and place in which people work together, create knowledge, and share knowledge and experiences in a community. PMID:17254294

  18. Grid Connected Functionality

    DOE Data Explorer

    Baker, Kyri; Jin, Xin; Vaidynathan, Deepthi; Jones, Wesley; Christensen, Dane; Sparn, Bethany; Woods, Jason; Sorensen, Harry; Lunacek, Monte

    2016-08-04

    Dataset demonstrating the potential benefits that residential buildings can provide for frequency regulation services in the electric power grid. In a hardware-in-the-loop (HIL) implementation, simulated homes along with a physical laboratory home are coordinated via a grid aggregator, and it is shown that their aggregate response has the potential to follow the regulation signal on a timescale of seconds. Connected (communication-enabled), devices in the National Renewable Energy Laboratory's (NREL's) Energy Systems Integration Facility (ESIF) received demand response (DR) requests from a grid aggregator, and the devices responded accordingly to meet the signal while satisfying user comfort bounds and physical hardware limitations.

  19. Cathode-less gridded ion thrusters for small satellites

    NASA Astrophysics Data System (ADS)

    Aanesland, Ane; Rafalskyi, Dmytro

    2015-09-01

    We present here a new gridded ion thruster, called Neptune, that operates with only one Radio Frequency (RF) power source for ionization, ion acceleration and beam neutralization in addition to solid iodine as propellant. Thus significant simplifications, over excising gridded thrusters, might allow downscaling to satellites as small as 6 kg. The combined acceleration and neutralization is achieved by applying an RF voltage to the grid system via a blocking capacitor. As for similar RF capacitive systems, a self-bias is formed such that ions are continuously accelerated while electrons are emitted in brief instants within the RF sheath collapse. Moreover, the RF nature of the acceleration system leads to a higher space charge limited current extracted across the grids compared to classical DC operated systems. Measurements of the ion and electron energy distribution functions in the plasma plume show that in addition to the directed beam of ions, the electrons are also anisotropic resulting in a flowing plasma, rather than a beam of positive ions. Experimental characterization of this RF accelerated plume is detailed. This work received financial state aid managed by the ANR as part of the program ``Investissements d'avenir'' under the reference ANR-11-IDEX-0003-02 (Project MINIATURE).

  20. Stability of non-linear integrable accelerator

    SciTech Connect

    Batalov, I.; Valishev, A.; /Fermilab

    2011-09-01

    The stability of non-linear Integrable Optics Test Accelerator (IOTA) model developed in [1] was tested. The area of the stable region in transverse coordinates and the maximum attainable tune spread were found as a function of non-linear lens strength. Particle loss as a function of turn number was analyzed to determine whether a dynamic aperture limitation present in the system. The system was also tested with sextupoles included in the machine for chromaticity compensation. A method of evaluation of the beam size in the linear part of the accelerator was proposed.

  1. Fractal characteristics of fracture roughness and aperture data

    SciTech Connect

    Kumar, S.; Bodvarsson, G.S.; Boernge, J.

    1991-05-01

    In this study mathematical expressions are developed for the characteristics of apertures between rough surfaces. It has shown that the correlation between the opposite surfaces influences the aperture properties and different models are presented for these different surface correlations. Fracture and apertures profiles measured from intact fractures are evaluated and it is found that they qualitatively follow the mathematically predicted trends.

  2. 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.

  3. 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

  4. Accelerating the Design of Space Vehicles

    NASA Technical Reports Server (NTRS)

    Laufenberg, Larry (Editor)

    2003-01-01

    One of NASA's key goals is to increase the safety and reduce the cost of space transportation. Thus, a key element of NASA's new Integrated Space Transportation Plan is to develop new propulsion, structures, and operations for future generations of reusable launch vehicles (RLVs). As part of this effort to develop the next RLV, the ClCT Program's Computing, Networking, and Information Systems (CNIS) Project is developing and demonstrating collaborative software technologies that use the collective power of the NASA Grid to accelerate spacecraft design. One of these technologies, called AeroDB, automates the execution and monitoring of computational fluid dynamics (CFD) parameter studies on the NASA Grid. About the NASA Grid The NASA Grid, or Information Power Grid,. is being developed to leverage the distributed resources of NASA's many computers. instruments, simulators, and data storage systems. The goal is to use these combined resources to sdve difficult NASA challenges, such as iimulating the entire flight of a space vehicle from ascent to descent.To realize the vision of the NASA Grid, the CNIS Project is developing the software framework and protocols for building domain-specific environments and interfaces, new Grid services based on emerging industry standards, and advanced networking and computing testbeds to support new Grid-based applications such as AeroDB.

  5. Simultaneous beam sampling and aperture shape optimization for SPORT

    SciTech Connect

    Zarepisheh, Masoud; Li, Ruijiang; Xing, Lei; Ye, Yinyu

    2015-02-15

    Purpose: Station parameter optimized radiation therapy (SPORT) was recently proposed to fully utilize the technical capability of emerging digital linear accelerators, in which the station parameters of a delivery system, such as aperture shape and weight, couch position/angle, gantry/collimator angle, can be optimized simultaneously. SPORT promises to deliver remarkable radiation dose distributions in an efficient manner, yet there exists no optimization algorithm for its implementation. The purpose of this work is to develop an algorithm to simultaneously optimize the beam sampling and aperture shapes. Methods: The authors build a mathematical model with the fundamental station point parameters as the decision variables. To solve the resulting large-scale optimization problem, the authors devise an effective algorithm by integrating three advanced optimization techniques: column generation, subgradient method, and pattern search. Column generation adds the most beneficial stations sequentially until the plan quality improvement saturates and provides a good starting point for the subsequent optimization. It also adds the new stations during the algorithm if beneficial. For each update resulted from column generation, the subgradient method improves the selected stations locally by reshaping the apertures and updating the beam angles toward a descent subgradient direction. The algorithm continues to improve the selected stations locally and globally by a pattern search algorithm to explore the part of search space not reachable by the subgradient method. By combining these three techniques together, all plausible combinations of station parameters are searched efficiently to yield the optimal solution. Results: A SPORT optimization framework with seamlessly integration of three complementary algorithms, column generation, subgradient method, and pattern search, was established. The proposed technique was applied to two previously treated clinical cases: a head and

  6. Surface grid generation for multi-block structured grids

    NASA Astrophysics Data System (ADS)

    Spekreijse, S. P.; Boerstoel, J. W.; Kuyvenhoven, J. L.; van der Marel, M. J.

    A new grid generation technique for the computation of a structured grid on a generally curved surface in 3D is discussed. The starting assumption is that the parameterization of the surface exists, i.e. a smooth geometrical shape function exists which maps the parametric space (the unit square) one-to-one on the surface. The grid generation system computes a grid on the surface with as boundary conditions the following data specified along the four edges of the surface: (1) the position of the boundary grid points, (2) the grid line slopes at the boundary grid points, (3) the first grid cell lengths at the boundary grid points. The fourth-order elliptic biharmonic equations are used to compute the two families of grid lines in the parametric space. After that, each grid point in the parametric space is found as the intersection point between two individual grid lines, one from each family. The grid points on the surface are finally found by mapping the grid points in the parametric space on the surface via the geometrical shape function. Results are shown for an O-type 2D Euler grid, a C-type 2D Navier-Stokes grid and on some curved surfaces in 3D space.

  7. Grid Computing Education Support

    SciTech Connect

    Steven Crumb

    2008-01-15

    The GGF Student Scholar program enabled GGF the opportunity to bring over sixty qualified graduate and under-graduate students with interests in grid technologies to its three annual events over the three-year program.

  8. Space Development Grid Portal

    NASA Technical Reports Server (NTRS)

    Vaziri, Arsi

    2004-01-01

    This viewgraph presentation provides information on the development of a portal to provide secure and distributed grid computing for Payload Operations Integrated Center and Mission Control Center ground services.

  9. Implementing Production Grids

    NASA Technical Reports Server (NTRS)

    Johnston, William E.; Ziobarth, John (Technical Monitor)

    2002-01-01

    We have presented the essence of experience gained in building two production Grids, and provided some of the global context for this work. As the reader might imagine, there were a lot of false starts, refinements to the approaches and to the software, and several substantial integration projects (SRB and Condor integrated with Globus) to get where we are today. However, the point of this paper is to try and make it substantially easier for others to get to the point where Information Power Grids (IPG) and the DOE Science Grids are today. This is what is needed in order to move us toward the vision of a common cyber infrastructure for science. The author would also like to remind the readers that this paper primarily represents the actual experiences that resulted from specific architectural and software choices during the design and implementation of these two Grids. The choices made were dictated by the criteria laid out in section 1. There is a lot more Grid software available today that there was four years ago, and various of these packages are being integrated into IPG and the DOE Grids. However, the foundation choices of Globus, SRB, and Condor would not be significantly different today than they were four years ago. Nonetheless, if the GGF is successful in its work - and we have every reason to believe that it will be - then in a few years we will see that the 28 functions provided by these packages will be defined in terms of protocols and MIS, and there will be several robust implementations available for each of the basic components, especially the Grid Common Services. The impact of the emerging Web Grid Services work is not yet clear. It will likely have a substantial impact on building higher level services, however it is the opinion of the author that this will in no way obviate the need for the Grid Common Services. These are the foundation of Grids, and the focus of almost all of the operational and persistent infrastructure aspects of Grids.

  10. Random array grid collimator

    DOEpatents

    Fenimore, E.E.

    1980-08-22

    A hexagonally shaped quasi-random no-two-holes touching grid collimator. The quasi-random array grid collimator eliminates contamination from small angle off-axis rays by using a no-two-holes-touching pattern which simultaneously provides for a self-supporting array increasng throughput by elimination of a substrate. The presentation invention also provides maximum throughput using hexagonally shaped holes in a hexagonal lattice pattern for diffraction limited applications. Mosaicking is also disclosed for reducing fabrication effort.

  11. Near-Body Grid Adaption for Overset Grids

    NASA Technical Reports Server (NTRS)

    Buning, Pieter G.; Pulliam, Thomas H.

    2016-01-01

    A solution adaption capability for curvilinear near-body grids has been implemented in the OVERFLOW overset grid computational fluid dynamics code. The approach follows closely that used for the Cartesian off-body grids, but inserts refined grids in the computational space of original near-body grids. Refined curvilinear grids are generated using parametric cubic interpolation, with one-sided biasing based on curvature and stretching ratio of the original grid. Sensor functions, grid marking, and solution interpolation tasks are implemented in the same fashion as for off-body grids. A goal-oriented procedure, based on largest error first, is included for controlling growth rate and maximum size of the adapted grid system. The adaption process is almost entirely parallelized using MPI, resulting in a capability suitable for viscous, moving body simulations. Two- and three-dimensional examples are presented.

  12. Exploring Hypersonic, Unstructured-Grid Issues through Structured Grids

    NASA Technical Reports Server (NTRS)

    Mazaheri, Ali R.; Kleb, Bill

    2007-01-01

    Pure-tetrahedral unstructured grids have been shown to produce asymmetric heat transfer rates for symmetric problems. Meanwhile, two-dimensional structured grids produce symmetric solutions and as documented here, introducing a spanwise degree of freedom to these structured grids also yields symmetric solutions. The effects of grid skewness and other perturbations of structured-grids are investigated to uncover possible mechanisms behind the unstructured-grid solution asymmetries. By using controlled experiments around a known, good solution, the effects of particular grid pathologies are uncovered. These structured-grid experiments reveal that similar solution degradation occurs as for unstructured grids, especially for heat transfer rates. Non-smooth grids within the boundary layer is also shown to produce large local errors in heat flux but do not affect surface pressures.

  13. Using Grid Benchmarks for Dynamic Scheduling of Grid Applications

    NASA Technical Reports Server (NTRS)

    Frumkin, Michael; Hood, Robert

    2003-01-01

    Navigation or dynamic scheduling of applications on computational grids can be improved through the use of an application-specific characterization of grid resources. Current grid information systems provide a description of the resources, but do not contain any application-specific information. We define a GridScape as dynamic state of the grid resources. We measure the dynamic performance of these resources using the grid benchmarks. Then we use the GridScape for automatic assignment of the tasks of a grid application to grid resources. The scalability of the system is achieved by limiting the navigation overhead to a few percent of the application resource requirements. Our task submission and assignment protocol guarantees that the navigation system does not cause grid congestion. On a synthetic data mining application we demonstrate that Gridscape-based task assignment reduces the application tunaround time.

  14. Beyond grid security

    NASA Astrophysics Data System (ADS)

    Hoeft, B.; Epting, U.; Koenig, T.

    2008-07-01

    While many fields relevant to Grid security are already covered by existing working groups, their remit rarely goes beyond the scope of the Grid infrastructure itself. However, security issues pertaining to the internal set-up of compute centres have at least as much impact on Grid security. Thus, this talk will present briefly the EU ISSeG project (Integrated Site Security for Grids). In contrast to groups such as OSCT (Operational Security Coordination Team) and JSPG (Joint Security Policy Group), the purpose of ISSeG is to provide a holistic approach to security for Grid computer centres, from strategic considerations to an implementation plan and its deployment. The generalised methodology of Integrated Site Security (ISS) is based on the knowledge gained during its implementation at several sites as well as through security audits, and this will be briefly discussed. Several examples of ISS implementation tasks at the Forschungszentrum Karlsruhe will be presented, including segregation of the network for administration and maintenance and the implementation of Application Gateways. Furthermore, the web-based ISSeG training material will be introduced. This aims to offer ISS implementation guidance to other Grid installations in order to help avoid common pitfalls.

  15. Grid generation strategies for turbomachinery configurations

    NASA Technical Reports Server (NTRS)

    Lee, K. D.; Henderson, T. L.

    1991-01-01

    Turbomachinery flow fields involve unique grid generation issues due to their geometrical and physical characteristics. Several strategic approaches are discussed to generate quality grids. The grid quality is further enhanced through blending and adapting. Grid blending smooths the grids locally through averaging and diffusion operators. Grid adaptation redistributes the grid points based on a grid quality assessment. These methods are demonstrated with several examples.

  16. Large aperture compound lenses made of lithium

    NASA Astrophysics Data System (ADS)

    Cremer, J. T.; Piestrup, M. A.; Beguiristain, H. R.; Gary, C. K.; Pantell, R. H.

    2003-04-01

    We have measured the intensity profile and transmission of x rays focused by a series of biconcave parabolic unit lenses fabricated in lithium. For specified focal length and photon energy lithium compound refractive lenses (CRL) have a larger transmission, aperture size, and gain compared to aluminum, kapton, and beryllium CRLs. The lithium compound refractive lens was composed of 335 biconcave, parabolic unit lenses each with an on-axis radius of curvature of 0.95 mm. Two-dimensional focusing was obtained at 8.0 keV with a focal length of 95 cm. The effective aperture of the CRL was measured to be 1030 μm with on-axis (peak) transmissions of 27% and an on-axis intensity gain of 18.9.

  17. Compact high precision adjustable beam defining aperture

    DOEpatents

    Morton, Simon A; Dickert, Jeffrey

    2013-07-02

    The present invention provides an adjustable aperture for limiting the dimension of a beam of energy. In an exemplary embodiment, the aperture includes (1) at least one piezoelectric bender, where a fixed end of the bender is attached to a common support structure via a first attachment and where a movable end of the bender is movable in response to an actuating voltage applied to the bender and (2) at least one blade attached to the movable end of the bender via a second attachment such that the blade is capable of impinging upon the beam. In an exemplary embodiment, the beam of energy is electromagnetic radiation. In an exemplary embodiment, the beam of energy is X-rays.

  18. 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''.

  19. 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.

  20. Polarization-sensitive interferometric synthetic aperture microscopy

    PubMed Central

    South, Fredrick A.; Liu, Yuan-Zhi; Xu, Yang; Shemonski, Nathan D.; Carney, P. Scott; Boppart, Stephen A.

    2015-01-01

    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. PMID:26648593

  1. Acceleration Studies

    NASA Technical Reports Server (NTRS)

    Rogers, Melissa J. B.

    1993-01-01

    Work to support the NASA MSFC Acceleration Characterization and Analysis Project (ACAP) was performed. Four tasks (analysis development, analysis research, analysis documentation, and acceleration analysis) were addressed by parallel projects. Work concentrated on preparation for and implementation of near real-time SAMS data analysis during the USMP-1 mission. User support documents and case specific software documentation and tutorials were developed. Information and results were presented to microgravity users. ACAP computer facilities need to be fully implemented and networked, data resources must be cataloged and accessible, future microgravity missions must be coordinated, and continued Orbiter characterization is necessary.

  2. Arc Length Based Grid Distribution For Surface and Volume Grids

    NASA Technical Reports Server (NTRS)

    Mastin, C. Wayne

    1996-01-01

    Techniques are presented for distributing grid points on parametric surfaces and in volumes according to a specified distribution of arc length. Interpolation techniques are introduced which permit a given distribution of grid points on the edges of a three-dimensional grid block to be propagated through the surface and volume grids. Examples demonstrate how these methods can be used to improve the quality of grids generated by transfinite interpolation.

  3. 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

  4. Infrared interferometer with a scanned aperture.

    PubMed

    Edwin, R P

    1975-08-01

    A Twyman-Green interferometer operating at a 3.39-microm wavelength has been built in which the collimator aperture was scanned by a laser beam. The scanning was produced by reflecting the laser beam from a mirror supported by four piezoelectric elements and oscillated about two orthogonal axes. The radiation transmitted by the interferometer was measured by a stationary detector of small area. The complete system offers a cheap and efficient alternative to conventional ir interferometers.

  5. Synthetic aperture ladar concept for infrastructure monitoring

    NASA Astrophysics Data System (ADS)

    Turbide, Simon; Marchese, Linda; Terroux, Marc; Bergeron, Alain

    2014-10-01

    Long range surveillance of infrastructure is a critical need in numerous security applications, both civilian and military. Synthetic aperture radar (SAR) continues to provide high resolution radar images in all weather conditions from remote distances. As well, Interferometric SAR (InSAR) and Differential Interferometric SAR (D-InSAR) have become powerful tools adding high resolution elevation and change detection measurements. State of the art SAR systems based on dual-use satellites are capable of providing ground resolutions of one meter; while their airborne counterparts obtain resolutions of 10 cm. D-InSAR products based on these systems could produce cm-scale vertical resolution image products. Deformation monitoring of railways, roads, buildings, cellular antennas, power structures (i.e., power lines, wind turbines, dams, or nuclear plants) would benefit from improved resolution, both in the ground plane and vertical direction. The ultimate limitation to the achievable resolution of any imaging system is its wavelength. State-of-the art SAR systems are approaching this limit. The natural extension to improve resolution is to thus decrease the wavelength, i.e. design a synthetic aperture system in a different wavelength regime. One such system offering the potential for vastly improved resolution is Synthetic Aperture Ladar (SAL). This system operates at infrared wavelengths, ten thousand times smaller than radar wavelengths. This paper presents a laboratory demonstration of a scaled-down infrastructure deformation monitoring with an Interferometric Synthetic Aperture Ladar (IFSAL) system operating at 1.5 μm. Results show sub-millimeter precision on the deformation applied to the target.

  6. Performance Limits for Synthetic Aperture Radar

    DTIC Science & Technology

    2006-02-01

    LIMITATION OF ABSTRACT Same as Report ( SAR ) 18. NUMBER OF PAGES 70 19a. NAME OF RESPONSIBLE PERSON a. REPORT unclassified b. ABSTRACT...second edition Armin W. Doerry SAR Applications Department Sandia National Laboratories PO Box 5800 Albuquerque, NM 87185-1330...ABSTRACT The performance of a Synthetic Aperture Radar ( SAR ) system depends on a variety of factors, many which are interdependent in some manner. It is

  7. The Benefits of Grid Networks

    ERIC Educational Resources Information Center

    Tennant, Roy

    2005-01-01

    In the article, the author talks about the benefits of grid networks. In speaking of grid networks the author is referring to both networks of computers and networks of humans connected together in a grid topology. Examples are provided of how grid networks are beneficial today and the ways in which they have been used.

  8. Substrate effect on aperture resonances in a thin metal film.

    PubMed

    Kang, J H; Choe, Jong-Ho; Kim, D S; Park, Q-Han

    2009-08-31

    We present a simple theoretical model to study the effect of a substrate on the resonance of an aperture in a thin metal film. The transmitted energy through an aperture is shown to be governed by the coupling of aperture waveguide mode to the incoming and the outgoing electromagnetic waves into the substrate region. Aperture resonance in the energy transmission thus depends critically on the refractive index of a substrate. We explain the substrate effect on aperture resonance in terms of destructive interference among evanescent modes or impedance mismatch. Our model shows an excellent agreement with a rigorous FDTD calculation and is consistent with previous experimental observations.

  9. Synthetic aperture radar processing with tiered subapertures

    SciTech Connect

    Doerry, A.W.

    1994-06-01

    Synthetic Aperture Radar (SAR) is used to form images that are maps of radar reflectivity of some scene of interest, from range soundings taken over some spatial aperture. Additionally, the range soundings are typically synthesized from a sampled frequency aperture. Efficient processing of the collected data necessitates using efficient digital signal processing techniques such as vector multiplies and fast implementations of the Discrete Fourier Transform. Inherent in image formation algorithms that use these is a trade-off between the size of the scene that can be acceptably imaged, and the resolution with which the image can be made. These limits arise from migration errors and spatially variant phase errors, and different algorithms mitigate these to varying degrees. Two fairly successful algorithms for airborne SARs are Polar Format processing, and Overlapped Subaperture (OSA) processing. This report introduces and summarizes the analysis of generalized Tiered Subaperture (TSA) techniques that are a superset of both Polar Format processing and OSA processing. It is shown how tiers of subapertures in both azimuth and range can effectively mitigate both migration errors and spatially variant phase errors to allow virtually arbitrary scene sizes, even in a dynamic motion environment.

  10. Diffraction contrast imaging using virtual apertures.

    PubMed

    Gammer, Christoph; Burak Ozdol, V; Liebscher, Christian H; Minor, Andrew M

    2015-08-01

    Two methods on how to obtain the full diffraction information from a sample region and the associated reconstruction of images or diffraction patterns using virtual apertures are demonstrated. In a STEM-based approach, diffraction patterns are recorded for each beam position using a small probe convergence angle. Similarly, a tilt series of TEM dark-field images is acquired. The resulting datasets allow the reconstruction of either electron diffraction patterns, or bright-, dark- or annular dark-field images using virtual apertures. The experimental procedures of both methods are presented in the paper and are applied to a precipitation strengthened and creep deformed ferritic alloy with a complex microstructure. The reconstructed virtual images are compared with conventional TEM images. The major advantage is that arbitrarily shaped virtual apertures generated with image processing software can be designed without facing any physical limitations. In addition, any virtual detector that is specifically designed according to the underlying crystal structure can be created to optimize image contrast.

  11. Restoring Aperture Profile At Sample Plane

    SciTech Connect

    Jackson, J L; Hackel, R P; Lungershausen, A W

    2003-08-03

    Off-line conditioning of full-size optics for the National Ignition Facility required a beam delivery system to allow conditioning lasers to rapidly raster scan samples while achieving several technical goals. The main purpose of the optical system designed was to reconstruct at the sample plane the flat beam profile found at the laser aperture with significant reductions in beam wander to improve scan times. Another design goal was the ability to vary the beam size at the sample to scan at different fluences while utilizing all of the laser power and minimizing processing time. An optical solution was developed using commercial off-the-shelf lenses. The system incorporates a six meter relay telescope and two sets of focusing optics. The spacing of the focusing optics is changed to allow the fluence on the sample to vary from 2 to 14 Joules per square centimeter in discrete steps. More importantly, these optics use the special properties of image relaying to image the aperture plane onto the sample to form a pupil relay with a beam profile corresponding almost exactly to the flat profile found at the aperture. A flat beam profile speeds scanning by providing a uniform intensity across a larger area on the sample. The relayed pupil plane is more stable with regards to jitter and beam wander. Image relaying also reduces other perturbations from diffraction, scatter, and focus conditions. Image relaying, laser conditioning, and the optical system designed to accomplish the stated goals are discussed.

  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. Coded-aperture imaging in nuclear medicine

    NASA Technical Reports Server (NTRS)

    Smith, Warren E.; Barrett, Harrison H.; Aarsvold, John N.

    1989-01-01

    Coded-aperture imaging is a technique for imaging sources that emit high-energy radiation. This type of imaging involves shadow casting and not reflection or refraction. High-energy sources exist in x ray and gamma-ray astronomy, nuclear reactor fuel-rod imaging, and nuclear medicine. Of these three areas nuclear medicine is perhaps the most challenging because of the limited amount of radiation available and because a three-dimensional source distribution is to be determined. In nuclear medicine a radioactive pharmaceutical is administered to a patient. The pharmaceutical is designed to be taken up by a particular organ of interest, and its distribution provides clinical information about the function of the organ, or the presence of lesions within the organ. This distribution is determined from spatial measurements of the radiation emitted by the radiopharmaceutical. The principles of imaging radiopharmaceutical distributions with coded apertures are reviewed. Included is a discussion of linear shift-variant projection operators and the associated inverse problem. A system developed at the University of Arizona in Tucson consisting of small modular gamma-ray cameras fitted with coded apertures is described.

  14. The AdaptiSPECT Imaging Aperture

    PubMed Central

    Chaix, Cécile; Moore, Jared W.; Van Holen, Roel; Barrett, Harrison H.; Furenlid, Lars R.

    2015-01-01

    In this paper, we present the imaging aperture of an adaptive SPECT imaging system being developed at the Center for Gamma Ray Imaging (AdaptiSPECT). AdaptiSPECT is designed to automatically change its configuration in response to preliminary data, in order to improve image quality for a particular task. In a traditional pinhole SPECT imaging system, the characteristics (magnification, resolution, field of view) are set by the geometry of the system, and any modification can be accomplished only by manually changing the collimator and the distance of the detector to the center of the field of view. Optimization of the imaging system for a specific task on a specific individual is therefore difficult. In an adaptive SPECT imaging system, on the other hand, the configuration can be conveniently changed under computer control. A key component of an adaptive SPECT system is its aperture. In this paper, we present the design, specifications, and fabrication of the adaptive pinhole aperture that will be used for AdaptiSPECT, as well as the controls that enable autonomous adaptation. PMID:27019577

  15. Synthetic aperture imaging in ultrasound calibration

    NASA Astrophysics Data System (ADS)

    Ameri, Golafsoun; Baxter, John S. H.; McLeod, A. Jonathan; Jayaranthe, Uditha L.; Chen, Elvis C. S.; Peters, Terry M.

    2014-03-01

    Ultrasound calibration allows for ultrasound images to be incorporated into a variety of interventional applica­ tions. Traditional Z- bar calibration procedures rely on wired phantoms with an a priori known geometry. The line fiducials produce small, localized echoes which are then segmented from an array of ultrasound images from different tracked probe positions. In conventional B-mode ultrasound, the wires at greater depths appear blurred and are difficult to segment accurately, limiting the accuracy of ultrasound calibration. This paper presents a novel ultrasound calibration procedure that takes advantage of synthetic aperture imaging to reconstruct high resolution ultrasound images at arbitrary depths. In these images, line fiducials are much more readily and accu­ rately segmented, leading to decreased calibration error. The proposed calibration technique is compared to one based on B-mode ultrasound. The fiducial localization error was improved from 0.21mm in conventional B-mode images to 0.15mm in synthetic aperture images corresponding to an improvement of 29%. This resulted in an overall reduction of calibration error from a target registration error of 2.00mm to 1.78mm, an improvement of 11%. Synthetic aperture images display greatly improved segmentation capabilities due to their improved resolution and interpretability resulting in improved calibration.

  16. High resolution beamforming for small aperture arrays

    NASA Astrophysics Data System (ADS)

    Clark, Chris; Null, Tom; Wagstaff, Ronald A.

    2003-04-01

    Achieving fine resolution bearing estimates for multiple sources using acoustic arrays with small apertures, in number of wavelengths, is a difficult challenge. It requires both large signal-to-noise ratio (SNR) gains and very narrow beam responses. High resolution beamforming for small aperture arrays is accomplished by exploiting acoustical fluctuations. Acoustical fluctuations in the atmosphere are caused by wind turbulence along the propagation path, air turbulence at the sensor, source/receiver motion, unsteady source level, and fine scale temperature variations. Similar environmental and source dependent phenomena cause fluctuations in other propagation media, e.g., undersea, optics, infrared. Amplitude fluctuations are exploited to deconvolve the beam response functions from the beamformed data of small arrays to achieve high spatial resolution, i.e., fine bearing resolution, and substantial SNR gain. Results are presented for a six microphone low-frequency array with an aperture of less than three wavelengths. [Work supported by U.S. Army Armament Research Development and Engineering Center.

  17. Coded-aperture imaging in nuclear medicine

    NASA Astrophysics Data System (ADS)

    Smith, Warren E.; Barrett, Harrison H.; Aarsvold, John N.

    1989-11-01

    Coded-aperture imaging is a technique for imaging sources that emit high-energy radiation. This type of imaging involves shadow casting and not reflection or refraction. High-energy sources exist in x ray and gamma-ray astronomy, nuclear reactor fuel-rod imaging, and nuclear medicine. Of these three areas nuclear medicine is perhaps the most challenging because of the limited amount of radiation available and because a three-dimensional source distribution is to be determined. In nuclear medicine a radioactive pharmaceutical is administered to a patient. The pharmaceutical is designed to be taken up by a particular organ of interest, and its distribution provides clinical information about the function of the organ, or the presence of lesions within the organ. This distribution is determined from spatial measurements of the radiation emitted by the radiopharmaceutical. The principles of imaging radiopharmaceutical distributions with coded apertures are reviewed. Included is a discussion of linear shift-variant projection operators and the associated inverse problem. A system developed at the University of Arizona in Tucson consisting of small modular gamma-ray cameras fitted with coded apertures is described.

  18. Smart Grid Integration Laboratory

    SciTech Connect

    Troxell, Wade

    2011-12-22

    The initial federal funding for the Colorado State University Smart Grid Integration Laboratory is through a Congressionally Directed Project (CDP), DE-OE0000070 Smart Grid Integration Laboratory. The original program requested in three one-year increments for staff acquisition, curriculum development, and instrumentation all which will benefit the Laboratory. This report focuses on the initial phase of staff acquisition which was directed and administered by DOE NETL/ West Virginia under Project Officer Tom George. Using this CDP funding, we have developed the leadership and intellectual capacity for the SGIC. This was accomplished by investing (hiring) a core team of Smart Grid Systems engineering faculty focused on education, research, and innovation of a secure and smart grid infrastructure. The Smart Grid Integration Laboratory will be housed with the separately funded Integrid Laboratory as part of CSU's overall Smart Grid Integration Center (SGIC). The period of performance of this grant was 10/1/2009 to 9/30/2011 which included one no cost extension due to time delays in faculty hiring. The Smart Grid Integration Laboratory's focus is to build foundations to help graduate and undergraduates acquire systems engineering knowledge; conduct innovative research; and team externally with grid smart organizations. Using the results of the separately funded Smart Grid Workforce Education Workshop (May 2009) sponsored by the City of Fort Collins, Northern Colorado Clean Energy Cluster, Colorado State University Continuing Education, Spirae, and Siemens has been used to guide the hiring of faculty, program curriculum and education plan. This project develops faculty leaders with the intellectual capacity to inspire its students to become leaders that substantially contribute to the development and maintenance of Smart Grid infrastructure through topics such as: (1) Distributed energy systems modeling and control; (2) Energy and power conversion; (3) Simulation of

  19. Performance of the first short model 150 mm aperture Nb$_3$Sn Quadrupole MQXFS for the High- Luminosity LHC upgrade

    SciTech Connect

    Chlachidze, G.; et al.

    2016-08-30

    The US LHC Accelerator Research Program (LARP) and CERN combined their efforts in developing Nb3Sn magnets for the High-Luminosity LHC upgrade. The ultimate goal of this collaboration is to fabricate large aperture Nb3Sn quadrupoles for the LHC interaction regions (IR). These magnets will replace the present 70 mm aperture NbTi quadrupole triplets for expected increase of the LHC peak luminosity by a factor of 5. Over the past decade LARP successfully fabricated and tested short and long models of 90 mm and 120 mm aperture Nb3Sn quadrupoles. Recently the first short model of 150 mm diameter quadrupole MQXFS was built with coils fabricated both by the LARP and CERN. The magnet performance was tested at Fermilab’s vertical magnet test facility. This paper reports the test results, including the quench training at 1.9 K, ramp rate and temperature dependence studies.

  20. Filled aperture concepts for the Terrestrial Planet Finder

    NASA Astrophysics Data System (ADS)

    Ridgway, Stephen T.

    2003-02-01

    Filled aperture telescopes can deliver a real, high Strehl image which is well suited for discrimination of faint planets in the vicinity of bright stars and against an extended exo-zodiacal light. A filled aperture offers a rich variety of PSF control and diffraction suppression techniques. Filled apertures are under consideration for a wide spectral range, including visible and thermal-IR, each of which offers a significant selection of biomarker molecular bands. A filled aperture visible TPF may be simpler in several respects than a thermal-IR nuller. The required aperture size (or baseline) is much smaller, and no cryogenic systems are required. A filled aperture TPF would look and act like a normal telescope - vendors and users alike would be comfortable with its design and operation. Filled aperture telescopes pose significant challenges in production of large primary mirrors, and in very stringent wavefront requirements. Stability of the wavefront control, and hence of the PSF, is a major issue for filled aperture systems. Several groups have concluded that these and other issues can be resolved, and that filled aperture options are competitive for a TPF precursor and/or for the full TPF mission. Ball, Boeing-SVS and TRW have recently returned architecture reviews on filled aperture TPF concepts. In this paper, I will review some of the major considerations underlying these filled aperture concepts, and suggest key issues in a TPF Buyers Guide.

  1. Particle acceleration

    NASA Technical Reports Server (NTRS)

    Vlahos, L.; Machado, M. E.; Ramaty, R.; Murphy, R. J.; Alissandrakis, C.; Bai, T.; Batchelor, D.; Benz, A. O.; Chupp, E.; Ellison, D.

    1986-01-01

    Data is compiled from Solar Maximum Mission and Hinothori satellites, particle detectors in several satellites, ground based instruments, and balloon flights in order to answer fundamental questions relating to: (1) the requirements for the coronal magnetic field structure in the vicinity of the energization source; (2) the height (above the photosphere) of the energization source; (3) the time of energization; (4) transistion between coronal heating and flares; (5) evidence for purely thermal, purely nonthermal and hybrid type flares; (6) the time characteristics of the energization source; (7) whether every flare accelerates protons; (8) the location of the interaction site of the ions and relativistic electrons; (9) the energy spectra for ions and relativistic electrons; (10) the relationship between particles at the Sun and interplanetary space; (11) evidence for more than one acceleration mechanism; (12) whether there is single mechanism that will accelerate particles to all energies and also heat the plasma; and (13) how fast the existing mechanisms accelerate electrons up to several MeV and ions to 1 GeV.

  2. Plasma accelerator

    DOEpatents

    Wang, Zhehui; Barnes, Cris W.

    2002-01-01

    There has been invented an apparatus for acceleration of a plasma having coaxially positioned, constant diameter, cylindrical electrodes which are modified to converge (for a positive polarity inner electrode and a negatively charged outer electrode) at the plasma output end of the annulus between the electrodes to achieve improved particle flux per unit of power.

  3. Accelerated Achievement

    ERIC Educational Resources Information Center

    Ford, William J.

    2010-01-01

    This article focuses on the accelerated associate degree program at Ivy Tech Community College (Indiana) in which low-income students will receive an associate degree in one year. The three-year pilot program is funded by a $2.3 million grant from the Lumina Foundation for Education in Indianapolis and a $270,000 grant from the Indiana Commission…

  4. ACCELERATION INTEGRATOR

    DOEpatents

    Pope, K.E.

    1958-01-01

    This patent relates to an improved acceleration integrator and more particularly to apparatus of this nature which is gyrostabilized. The device may be used to sense the attainment by an airborne vehicle of a predetermined velocitv or distance along a given vector path. In its broad aspects, the acceleration integrator utilizes a magnetized element rotatable driven by a synchronous motor and having a cylin drical flux gap and a restrained eddy- current drag cap deposed to move into the gap. The angular velocity imparted to the rotatable cap shaft is transmitted in a positive manner to the magnetized element through a servo feedback loop. The resultant angular velocity of tae cap is proportional to the acceleration of the housing in this manner and means may be used to measure the velocity and operate switches at a pre-set magnitude. To make the above-described dcvice sensitive to acceleration in only one direction the magnetized element forms the spinning inertia element of a free gyroscope, and the outer housing functions as a gimbal of a gyroscope.

  5. Coherent synthetic imaging using multi-aperture scanning Fourier ptychography

    NASA Astrophysics Data System (ADS)

    Xie, Zongliang; Ma, Haotong; Qi, Bo; Ren, Ge

    2016-10-01

    The high resolution is what the synthetic aperture technique quests for. In this paper, we propose an approach of coherent synthetic imaging with sparse aperture systems using multi-aperture scanning Fourier ptychography algorithm, which can further improve the resolution of sparse aperture systems. The reported technique first acquires a series of raw images by scanning a sparse aperture system and then the captured images are used to synthesize a larger spectrum in the frequency domain using aperture-scanning Fourier ptychography algorithm. The system's traveling circumvent its diffraction limit so that a super-resolution image can be obtained. Numerical simulation demonstrates the validity. The technique proposed in this paper may find wide applications in synthetic aperture imaging and astronomy.

  6. Imaging performance of annular apertures. II - Line spread functions

    NASA Technical Reports Server (NTRS)

    Tschunko, H. F. A.

    1978-01-01

    Line images formed by aberration-free optical systems with annular apertures are investigated in the whole range of central obstruction ratios. Annular apertures form lines images with central and side line groups. The number of lines in each line group is given by the ratio of the outer diameter of the annular aperture divided by the width of the annulus. The theoretical energy fraction of 0.889 in the central line of the image formed by an unobstructed aperture increases for centrally obstructed apertures to 0.932 for the central line group. Energy fractions for the central and side line groups are practically constant for all obstruction ratios and for each line group. The illumination of rectangular secondary apertures of various length/width ratios by apertures of various obstruction ratios is discussed.

  7. Rank minimization code aperture design for spectrally selective compressive imaging.

    PubMed

    Arguello, Henry; Arce, Gonzalo R

    2013-03-01

    A new code aperture design framework for multiframe code aperture snapshot spectral imaging (CASSI) system is presented. It aims at the optimization of code aperture sets such that a group of compressive spectral measurements is constructed, each with information from a specific subset of bands. A matrix representation of CASSI is introduced that permits the optimization of spectrally selective code aperture sets. Furthermore, each code aperture set forms a matrix such that rank minimization is used to reduce the number of CASSI shots needed. Conditions for the code apertures are identified such that a restricted isometry property in the CASSI compressive measurements is satisfied with higher probability. Simulations show higher quality of spectral image reconstruction than that attained by systems using Hadamard or random code aperture sets.

  8. Accelerator target

    DOEpatents

    Schlyer, D.J.; Ferrieri, R.A.; Koehler, C.

    1999-06-29

    A target includes a body having a depression in a front side for holding a sample for irradiation by a particle beam to produce a radioisotope. Cooling fins are disposed on a backside of the body opposite the depression. A foil is joined to the body front side to cover the depression and sample therein. A perforate grid is joined to the body atop the foil for supporting the foil and for transmitting the particle beam therethrough. A coolant is circulated over the fins to cool the body during the particle beam irradiation of the sample in the depression. 5 figs.

  9. Accelerator target

    DOEpatents

    Schlyer, David J.; Ferrieri, Richard A.; Koehler, Conrad

    1999-01-01

    A target includes a body having a depression in a front side for holding a sample for irradiation by a particle beam to produce a radioisotope. Cooling fins are disposed on a backside of the body opposite the depression. A foil is joined to the body front side to cover the depression and sample therein. A perforate grid is joined to the body atop the foil for supporting the foil and for transmitting the particle beam therethrough. A coolant is circulated over the fins to cool the body during the particle beam irradiation of the sample in the depression.

  10. Can Clouds replace Grids? Will Clouds replace Grids?

    NASA Astrophysics Data System (ADS)

    Shiers, J. D.

    2010-04-01

    The world's largest scientific machine - comprising dual 27km circular proton accelerators cooled to 1.9oK and located some 100m underground - currently relies on major production Grid infrastructures for the offline computing needs of the 4 main experiments that will take data at this facility. After many years of sometimes difficult preparation the computing service has been declared "open" and ready to meet the challenges that will come shortly when the machine restarts in 2009. But the service is not without its problems: reliability - as seen by the experiments, as opposed to that measured by the official tools - still needs to be significantly improved. Prolonged downtimes or degradations of major services or even complete sites are still too common and the operational and coordination effort to keep the overall service running is probably not sustainable at this level. Recently "Cloud Computing" - in terms of pay-per-use fabric provisioning - has emerged as a potentially viable alternative but with rather different strengths and no doubt weaknesses too. Based on the concrete needs of the LHC experiments - where the total data volume that will be acquired over the full lifetime of the project, including the additional data copies that are required by the Computing Models of the experiments, approaches 1 Exabyte - we analyze the pros and cons of Grids versus Clouds. This analysis covers not only technical issues - such as those related to demanding database and data management needs - but also sociological aspects, which cannot be ignored, neither in terms of funding nor in the wider context of the essential but often overlooked role of science in society, education and economy.

  11. Bringing Federated Identity to Grid Computing

    SciTech Connect

    Teheran, Jeny

    2016-03-04

    The Fermi National Accelerator Laboratory (FNAL) is facing the challenge of providing scientific data access and grid submission to scientific collaborations that span the globe but are hosted at FNAL. Users in these collaborations are currently required to register as an FNAL user and obtain FNAL credentials to access grid resources to perform their scientific computations. These requirements burden researchers with managing additional authentication credentials, and put additional load on FNAL for managing user identities. Our design integrates the existing InCommon federated identity infrastructure, CILogon Basic CA, and MyProxy with the FNAL grid submission system to provide secure access for users from diverse experiments and collab orations without requiring each user to have authentication credentials from FNAL. The design automates the handling of certificates so users do not need to manage them manually. Although the initial implementation is for FNAL's grid submission system, the design and the core of the implementation are general and could be applied to other distributed computing systems.

  12. Large-aperture high-resolution x-ray collimator for the Solar Maximum Mission.

    PubMed

    Nobles, R A; Acton, L W; Joki, E G; Leibacher, J W; Peterson, R C

    1980-09-01

    A description is presented of a flight-qualified large-aperture 12 x 12-sec of arc angular resolution multigrid x-ray collimator developed for the Solar Maximum Mission (SMM) flat crystal spectrometer. This collimator, designed for the 1.4-22.4-A wavelength range, utilizes an optical bench/metering structure to align and support prealigned grid subassemblies. One advantage of this scheme is to provide ready access to the grid subassemblies for inspection and/or servicing. The optical bench is a lightweight, rigid, and stable aluminum honeycomb structure. Aluminum is a viable material choice in this application because of the good thermal control expected in the SMM instrument package. The grids are of a compound and bimetallic design, having 63.5-microm square holes on an 88.9-microm spacing in 8-microm thick gold, which is in turn supported by a 76-microm thick Invar grid having 600-microm square holes on a 739-microm spacing. The small apertures in the gold provide the 12-sec of arc collimation with the Invar grids providing wide angle off-axis blocking out to an ~35-min of arc view angle. The collimator has seven individual channels, four of a 5.1- x 10-cm area and three of a 1.3- x 10-cm area. Laboratory measurements gave an average angular resolution of 12.5-sec of arc FWHM with 0.259 transmission for the large area channels and 12.0 sec of arc and 0.200 transmission for the small area channels. A hypothetical perfectly aligned collimator would have 12.5-sec of arc resolution and 0.300 transmission. A thermal filter composed of two layers of ~1000-A thick aluminum prevents solar heating of the front collimator grids by absorbing longer wavelength radiation while passing most of the x radiation in the band of interest. The filter was flight qualified by passing a protoflight acoustic test environment of 147-dB total sound level, 20-microN/M(2) reference, for 1-min duration.

  13. EXOTIC MAGNETS FOR ACCELERATORS.

    SciTech Connect

    WANDERER, P.

    2005-09-18

    Over the last few years, several novel magnet designs have been introduced to meet the requirements of new, high performance accelerators and beam lines. For example, the FAIR project at GSI requires superconducting magnets ramped at high rates ({approx} 4 T/s) in order to achieve the design intensity. Magnets for the RIA and FAIR projects and for the next generation of LHC interaction regions will need to withstand high doses of radiation. Helical magnets are required to maintain and control the polarization of high energy protons at RHIC. In other cases, novel magnets have been designed in response to limited budgets and space. For example, it is planned to use combined function superconducting magnets for the 50 GeV proton transport line at J-PARC to satisfy both budget and performance requirements. Novel coil winding methods have been developed for short, large aperture magnets such as those used in the insertion region upgrade at BEPC. This paper will highlight the novel features of these exotic magnets.

  14. Complex Volume Grid Generation Through the Use of Grid Reusability

    NASA Technical Reports Server (NTRS)

    Alter, Stephen J.

    1997-01-01

    This paper presents a set of surface and volume grid generation techniques which reuse existing surface and volume grids. These methods use combinations of data manipulations to reduce grid generation time, improve grid characteristics, and increase the capabilities of existing domain discretization software. The manipulation techniques utilize physical and computational domains to produce basis function on which to operate and modify grid character and smooth grids using Trans-Finite Interpolation, a vector interpolation method and parametric re-mapping technique. With these new techniques, inviscid grids can be converted to viscous grids, multiple zone grid adaption can be performed to improve CFD solver efficiency, and topological changes to improve modeling of flow fields can be done simply and quickly. Examples of these capabilities are illustrated as applied to various configurations.

  15. TFSSRA - THICK FREQUENCY SELECTIVE SURFACE WITH RECTANGULAR APERTURES

    NASA Technical Reports Server (NTRS)

    Chen, J. C.

    1994-01-01

    Thick Frequency Selective Surface with Rectangular Apertures (TFSSRA) was developed to calculate the scattering parameters for a thick frequency selective surface with rectangular apertures on a skew grid at oblique angle of incidence. The method of moments is used to transform the integral equation into a matrix equation suitable for evaluation on a digital computer. TFSSRA predicts the reflection and transmission characteristics of a thick frequency selective surface for both TE and TM orthogonal linearly polarized plane waves. A model of a half-space infinite array is used in the analysis. A complete set of basis functions with unknown coefficients is developed for the waveguide region (waveguide modes) and for the free space region (Floquet modes) in order to represent the electromagnetic fields. To ensure the convergence of the solutions, the number of waveguide modes is adjustable. The method of moments is used to compute the unknown mode coefficients. Then, the scattering matrix of the half-space infinite array is calculated. Next, the reference plane of the scattering matrix is moved half a plate thickness in the negative z-direction, and a frequency selective surface of finite thickness is synthesized by positioning two plates of half-thickness back-to-back. The total scattering matrix is obtained by cascading the scattering matrices of the two half-space infinite arrays. TFSSRA is written in FORTRAN 77 with single precision. It has been successfully implemented on a Sun4 series computer running SunOS, an IBM PC compatible running MS-DOS, and a CRAY series computer running UNICOS, and should run on other systems with slight modifications. Double precision is recommended for running on a PC if many modes are used or if high accuracy is required. This package requires the LINPACK math library, which is included. TFSSRA requires 1Mb of RAM for execution. The standard distribution medium for this program is one 5.25 inch 360K MS-DOS format diskette. It is also

  16. NREL Smart Grid Projects

    SciTech Connect

    Hambrick, J.

    2012-01-01

    Although implementing Smart Grid projects at the distribution level provides many advantages and opportunities for advanced operation and control, a number of significant challenges must be overcome to maintain the high level of safety and reliability that the modern grid must provide. For example, while distributed generation (DG) promises to provide opportunities to increase reliability and efficiency and may provide grid support services such as volt/var control, the presence of DG can impact distribution operation and protection schemes. Additionally, the intermittent nature of many DG energy sources such as photovoltaics (PV) can present a number of challenges to voltage regulation, etc. This presentation provides an overview a number of Smart Grid projects being performed by the National Renewable Energy Laboratory (NREL) along with utility, industry, and academic partners. These projects include modeling and analysis of high penetration PV scenarios (with and without energy storage), development and testing of interconnection and microgrid equipment, as well as the development and implementation of advanced instrumentation and data acquisition used to analyze the impacts of intermittent renewable resources. Additionally, standards development associated with DG interconnection and analysis as well as Smart Grid interoperability will be discussed.

  17. An Adaptive Unstructured Grid Method by Grid Subdivision, Local Remeshing, and Grid Movement

    NASA Technical Reports Server (NTRS)

    Pirzadeh, Shahyar Z.

    1999-01-01

    An unstructured grid adaptation technique has been developed and successfully applied to several three dimensional inviscid flow test cases. The approach is based on a combination of grid subdivision, local remeshing, and grid movement. For solution adaptive grids, the surface triangulation is locally refined by grid subdivision, and the tetrahedral grid in the field is partially remeshed at locations of dominant flow features. A grid redistribution strategy is employed for geometric adaptation of volume grids to moving or deforming surfaces. The method is automatic and fast and is designed for modular coupling with different solvers. Several steady state test cases with different inviscid flow features were tested for grid/solution adaptation. In all cases, the dominant flow features, such as shocks and vortices, were accurately and efficiently predicted with the present approach. A new and robust method of moving tetrahedral "viscous" grids is also presented and demonstrated on a three-dimensional example.

  18. Transmissivity Reduction Of Fracture Due To Silica Precipitation Is Faster For Variable Aperture

    NASA Astrophysics Data System (ADS)

    Pandey, S. N.; Chaudhuri, A.; Kelkar, S.; Rajaram, H.

    2013-12-01

    Geothermal energy have certain ecological benefits as it does not disturb the local ecosystem. It is also able to generate power with minimum operating cost. The extraction of geothermal energy has grown significantly in the past few decades. One of the major challenges for reservoir scale modeling of geothermal system is to describe the exact configuration of aperture fields. Hence the sustainability of geothermal power plant and future estimation of power production is affected during continuous evolution by geochemical and geomechanical processes. The formation of scale due to precipitation of silica in the wells and the fault creates major problem in the sustainability of the geothermal heat extraction. In this study we simulated the reduction of fracture transmissivity due to precipitation by 3-D simulation of coupled thermo-hydro-chemical (THC) processes a simple geothermal system with a horizontal fault, which connects the injection and production wells to facilitate the cold water circulation. The variability of aperture within the fracture/fault is more realistic and it is known that the reduction of effective transmissivity is accelerated by the heterogeneity of the aperture field. The objective of the study is to understand the results of aperture field heterogeneity on the power production. For comparison among different heterogeneous cases, the initial effective transmissivity has been taken same for each. Using numerical simulation of flow between the wells, the same initial effective transmissivity (i.e. same pressure drop between the wells for same mass flow rate) was attained through iteration. The values of standard deviations were taken in the range of 0 to 0.4. Temperature dependent kinetic rate laws were used for the reactive transport modeling. Here the numerical simulations were performed for injection concentration as the solubility at the temperature in the production well. This extreme case is based on the assumption that there is no

  19. Particle Accelerators in China

    NASA Astrophysics Data System (ADS)

    Zhang, Chuang; Fang, Shouxian

    As the special machines that can accelerate charged particle beams to high energy by using electromagnetic fields, particle accelerators have been widely applied in scientific research and various areas of society. The development of particle accelerators in China started in the early 1950s. After a brief review of the history of accelerators, this article describes in the following sections: particle colliders, heavy-ion accelerators, high-intensity proton accelerators, accelerator-based light sources, pulsed power accelerators, small scale accelerators, accelerators for applications, accelerator technology development and advanced accelerator concepts. The prospects of particle accelerators in China are also presented.

  20. How vein sealing boosts fracture widening rates - The buckling-enhanced aperture growth mechanism for syn-tectonic veins

    NASA Astrophysics Data System (ADS)

    Nüchter, Jens-Alexander

    2017-01-01

    The paper introduces the mechanism of buckling-enhanced aperture growth for syn-tectonic veins that formed in simple-shear dominated kinematic frameworks in the middle or lower crust. Apart from the well understood concepts of fracture widening driven by effective tensile stresses, buckling-enhanced fracture aperture growth relates widening to active outward buckling of more viscous incipient cement layers precipitated as hydrothermal minerals for the pore fluid on the walls of juvenile syn-tectonic veins, driven by fracture-parallel compressive creep strain in the host rocks. Thus, the mechanism proposed here follows similar principles as tectonic folding, although important differences exist. Inspired by the structural record of low-aspect ratio veins exposed in HP/LT metamorphic rocks cropping out on south Evia island, Greece, generic numerical models are calculated to study development of buckling instabilities in such incompletely cemented veins and their impact on aperture growth rates. The models indicate (1) that aperture growth rates increase with increasing viscosity contrast between the host rocks and the cement layers, (2) an increase in the thickness of the cement layers cause acceleration of aperture growth, (3) that support of restraining forces at the vein tips offered by the host rocks against buckling of the cement layers cause fully compressive states of stress ahead the fracture tips, and (4) that fracture aperture growth is possible against fully compressive fracture-normal stresses. The buckling-enhanced vein aperture growth mechanism yields important implications for the maintenance and decay of fracture-bound permeability and for the mechanical state of the middle and lower crust in seismically active regions.

  1. The physics of light transmission through subwavelength apertures and aperture arrays

    NASA Astrophysics Data System (ADS)

    Weiner, J.

    2009-06-01

    The passage of light through apertures much smaller than the wavelength of the light has proved to be a surprisingly subtle phenomenon. This report describes how modern developments in nanofabrication, coherent light sources and numerical vector field simulations have led to the upending of early predictions from scalar diffraction theory and classical electrodynamics. Optical response of real materials to incident coherent radiation at petahertz frequencies leads to unexpected consequences for transmission and extinction of light through subwavelength aperture arrays. This paper is a report on progress in our understanding of this phenomenon over the past decade.

  2. Modern Grid Initiative Distribution Taxonomy Final Report

    SciTech Connect

    Schneider, Kevin P.; Chen, Yousu; Chassin, David P.; Pratt, Robert G.; Engel, David W.; Thompson, Sandra E.

    2008-11-01

    This is the final report for the development of a toxonomy of prototypical electrical distribution feeders. Two of the primary goals of the Department of Energy's (DOE) Modern Grid Initiative (MGI) are 'to accelerate the modernization of our nation's electricity grid' and to 'support demonstrations of systems of key technologies that can serve as the foundation for an integrated, modern power grid'. A key component to the realization of these goals is the effective implementation of new, as well as existing, 'smart grid technologies'. Possibly the largest barrier that has been identified in the deployment of smart grid technologies is the inability to evaluate how their deployment will affect the electricity infrastructure, both locally and on a regional scale. The inability to evaluate the impacts of these technologies is primarily due to the lack of detailed electrical distribution feeder information. While detailed distribution feeder information does reside with the various distribution utilities, there is no central repository of information that can be openly accessed. The role of Pacific Northwest National Laboratory (PNNL) in the MGI for FY08 was to collect distribution feeder models, in the SynerGEE{reg_sign} format, from electric utilities around the nation so that they could be analyzed to identify regional differences in feeder design and operation. Based on this analysis PNNL developed a taxonomy of 24 prototypical feeder models in the GridLAB-D simulations environment that contain the fundamental characteristics of non-urban core, radial distribution feeders from the various regions of the U.S. Weighting factors for these feeders are also presented so that they can be used to generate a representative sample for various regions within the United States. The final product presented in this report is a toolset that enables the evaluation of new smart grid technologies, with the ability to aggregate their effects to regional and national levels. The

  3. Fusion Data Grid Service

    NASA Astrophysics Data System (ADS)

    Shasharina, Svetlana; Wang, Nanbor

    2004-11-01

    Simulations and experiments in the fusion and plasma physics community generate large datasets at remote sites. Visualization and analysis of these datasets are difficult because of the incompatibility among the various data formats adopted by simulation, experiments, and analysis tools, and the large sizes of analyzed data. Grids and Web Services technologies are capable of providing solutions for such heterogeneous settings, but need to be customized to the field-specific needs and merged with distributed technologies currently used by the community. This paper describes how we are addressing these issues in the Fusion Grid Service under development. We also present performance results of relevant data transfer mechanisms including binary SOAP, DIME, GridFTP and MDSplus and CORBA. We will describe the status of data converters (between HDF5 and MDSplus data types), developed in collaboration with MIT (J. Stillerman). Finally, we will analyze bottlenecks of MDSplus data transfer mechanism (work performed in collaboration with General Atomics (D. Schissel and M. Qian).

  4. Information Power Grid Posters

    NASA Technical Reports Server (NTRS)

    Vaziri, Arsi

    2003-01-01

    This document is a summary of the accomplishments of the Information Power Grid (IPG). Grids are an emerging technology that provide seamless and uniform access to the geographically dispersed, computational, data storage, networking, instruments, and software resources needed for solving large-scale scientific and engineering problems. The goal of the NASA IPG is to use NASA's remotely located computing and data system resources to build distributed systems that can address problems that are too large or complex for a single site. The accomplishments outlined in this poster presentation are: access to distributed data, IPG heterogeneous computing, integration of large-scale computing node into distributed environment, remote access to high data rate instruments,and exploratory grid environment.

  5. Compact accelerator

    DOEpatents

    Caporaso, George J.; Sampayan, Stephen E.; Kirbie, Hugh C.

    2007-02-06

    A compact linear accelerator having at least one strip-shaped Blumlein module which guides a propagating wavefront between first and second ends and controls the output pulse at the second end. Each Blumlein module has first, second, and third planar conductor strips, with a first dielectric strip between the first and second conductor strips, and a second dielectric strip between the second and third conductor strips. Additionally, the compact linear accelerator includes a high voltage power supply connected to charge the second conductor strip to a high potential, and a switch for switching the high potential in the second conductor strip to at least one of the first and third conductor strips so as to initiate a propagating reverse polarity wavefront(s) in the corresponding dielectric strip(s).

  6. Laser acceleration

    NASA Astrophysics Data System (ADS)

    Tajima, T.; Nakajima, K.; Mourou, G.

    2017-02-01

    The fundamental idea of Laser Wakefield Acceleration (LWFA) is reviewed. An ultrafast intense laser pulse drives coherent wakefield with a relativistic amplitude robustly supported by the plasma. While the large amplitude of wakefields involves collective resonant oscillations of the eigenmode of the entire plasma electrons, the wake phase velocity ˜ c and ultrafastness of the laser pulse introduce the wake stability and rigidity. A large number of worldwide experiments show a rapid progress of this concept realization toward both the high-energy accelerator prospect and broad applications. The strong interest in this has been spurring and stimulating novel laser technologies, including the Chirped Pulse Amplification, the Thin Film Compression, the Coherent Amplification Network, and the Relativistic Mirror Compression. These in turn have created a conglomerate of novel science and technology with LWFA to form a new genre of high field science with many parameters of merit in this field increasing exponentially lately. This science has triggered a number of worldwide research centers and initiatives. Associated physics of ion acceleration, X-ray generation, and astrophysical processes of ultrahigh energy cosmic rays are reviewed. Applications such as X-ray free electron laser, cancer therapy, and radioisotope production etc. are considered. A new avenue of LWFA using nanomaterials is also emerging.

  7. BICEP's acceleration

    SciTech Connect

    Contaldi, Carlo R.

    2014-10-01

    The recent Bicep2 [1] detection of, what is claimed to be primordial B-modes, opens up the possibility of constraining not only the energy scale of inflation but also the detailed acceleration history that occurred during inflation. In turn this can be used to determine the shape of the inflaton potential V(φ) for the first time — if a single, scalar inflaton is assumed to be driving the acceleration. We carry out a Monte Carlo exploration of inflationary trajectories given the current data. Using this method we obtain a posterior distribution of possible acceleration profiles ε(N) as a function of e-fold N and derived posterior distributions of the primordial power spectrum P(k) and potential V(φ). We find that the Bicep2 result, in combination with Planck measurements of total intensity Cosmic Microwave Background (CMB) anisotropies, induces a significant feature in the scalar primordial spectrum at scales k∼ 10{sup -3} Mpc {sup -1}. This is in agreement with a previous detection of a suppression in the scalar power [2].

  8. GridPV Toolbox

    SciTech Connect

    Broderick, Robert; Quiroz, Jimmy; Grijalva, Santiago; Reno, Matthew; Coogan, Kyle

    2014-07-15

    Matlab Toolbox for simulating the impact of solar energy on the distribution grid. The majority of the functions are useful for interfacing OpenDSS and MATLAB, and they are of generic use for commanding OpenDSS from MATLAB and retrieving GridPV Toolbox information from simulations. A set of functions is also included for modeling PV plant output and setting up the PV plant in the OpenDSS simulation. The toolbox contains functions for modeling the OpenDSS distribution feeder on satellite images with GPS coordinates. Finally, example simulations functions are included to show potential uses of the toolbox functions.

  9. The Configurable Aperture Space Telescope (CAST)

    NASA Astrophysics Data System (ADS)

    Ennico, Kimberly; Bendek, Eduardo A.; Lynch, Dana H.; Vassigh, Kenny K.; Young, Zion

    2016-07-01

    The Configurable Aperture Space Telescope, CAST, is a concept that provides access to a UV/visible-infrared wavelength sub-arcsecond imaging platform from space, something that will be in high demand after the retirement of the astronomy workhorse, the 2.4 meter diameter Hubble Space Telescope. CAST allows building large aperture telescopes based on small, compatible and low-cost segments mounted on autonomous cube-sized satellites. The concept merges existing technology (segmented telescope architecture) with emerging technology (smartly interconnected modular spacecraft, active optics, deployable structures). Requiring identical mirror segments, CAST's optical design is a spherical primary and secondary mirror telescope with modular multi-mirror correctors placed at the system focal plane. The design enables wide fields of view, up to as much as three degrees, while maintaining aperture growth and image performance requirements. We present a point design for the CAST concept based on a 0.6 meter diameter (3 x 3 segments) growing to a 2.6 meter diameter (13 x 13 segments) primary, with a fixed Rp=13,000 and Rs=8,750 mm curvature, f/22.4 and f/5.6, respectively. Its diffraction limited design uses a two arcminute field of view corrector with a 7.4 arcsec/mm platescale, and can support a range of platescales as fine as 0.01 arcsec/mm. Our paper summarizes CAST, presents a strawman optical design and requirements for the underlying modular spacecraft, highlights design flexibilities, and illustrates applications enabled by this new method in building space observatories.

  10. Optimization of synthetic aperture image quality

    NASA Astrophysics Data System (ADS)

    Moshavegh, Ramin; Jensen, Jonas; Villagomez-Hoyos, Carlos A.; Stuart, Matthias B.; Hemmsen, Martin Christian; Jensen, Jørgen Arendt

    2016-04-01

    Synthetic Aperture (SA) imaging produces high-quality images and velocity estimates of both slow and fast flow at high frame rates. However, grating lobe artifacts can appear both in transmission and reception. These affect the image quality and the frame rate. Therefore optimization of parameters effecting the image quality of SA is of great importance, and this paper proposes an advanced procedure for optimizing the parameters essential for acquiring an optimal image quality, while generating high resolution SA images. Optimization of the image quality is mainly performed based on measures such as F-number, number of emissions and the aperture size. They are considered to be the most contributing acquisition factors in the quality of the high resolution images in SA. Therefore, the performance of image quality is quantified in terms of full-width at half maximum (FWHM) and the cystic resolution (CTR). The results of the study showed that SA imaging with only 32 emissions and maximum sweep angle of 22 degrees yields a very good image quality compared with using 256 emissions and the full aperture size. Therefore the number of emissions and the maximum sweep angle in the SA can be optimized to reach a reasonably good performance, and to increase the frame rate by lowering the required number of emissions. All the measurements are performed using the experimental SARUS scanner connected to a λ/2-pitch transducer. A wire phantom and a tissue mimicking phantom containing anechoic cysts are scanned using the optimized parameters for the transducer. Measurements coincide with simulations.

  11. Observation of acceleration and deceleration in gigaelectron-volt-per-metre gradient dielectric wakefield accelerators

    PubMed Central

    O'Shea, B. D.; Andonian, G.; Barber, S. K.; Fitzmorris, K. L.; Hakimi, S.; Harrison, J.; Hoang, P. D.; Hogan, M. J.; Naranjo, B.; Williams, O. B.; Yakimenko, V.; Rosenzweig, J. B.

    2016-01-01

    There is urgent need to develop new acceleration techniques capable of exceeding gigaelectron-volt-per-metre (GeV m−1) gradients in order to enable future generations of both light sources and high-energy physics experiments. To address this need, short wavelength accelerators based on wakefields, where an intense relativistic electron beam radiates the demanded fields directly into the accelerator structure or medium, are currently under intense investigation. One such wakefield based accelerator, the dielectric wakefield accelerator, uses a dielectric lined-waveguide to support a wakefield used for acceleration. Here we show gradients of 1.347±0.020 GeV m−1 using a dielectric wakefield accelerator of 15 cm length, with sub-millimetre transverse aperture, by measuring changes of the kinetic state of relativistic electron beams. We follow this measurement by demonstrating accelerating gradients of 320±17 MeV m−1. Both measurements improve on previous measurements by and order of magnitude and show promise for dielectric wakefield accelerators as sources of high-energy electrons. PMID:27624348

  12. Observation of acceleration and deceleration in gigaelectron-volt-per-metre gradient dielectric wakefield accelerators.

    PubMed

    O'Shea, B D; Andonian, G; Barber, S K; Fitzmorris, K L; Hakimi, S; Harrison, J; Hoang, P D; Hogan, M J; Naranjo, B; Williams, O B; Yakimenko, V; Rosenzweig, J B

    2016-09-14

    There is urgent need to develop new acceleration techniques capable of exceeding gigaelectron-volt-per-metre (GeV m(-1)) gradients in order to enable future generations of both light sources and high-energy physics experiments. To address this need, short wavelength accelerators based on wakefields, where an intense relativistic electron beam radiates the demanded fields directly into the accelerator structure or medium, are currently under intense investigation. One such wakefield based accelerator, the dielectric wakefield accelerator, uses a dielectric lined-waveguide to support a wakefield used for acceleration. Here we show gradients of 1.347±0.020 GeV m(-1) using a dielectric wakefield accelerator of 15 cm length, with sub-millimetre transverse aperture, by measuring changes of the kinetic state of relativistic electron beams. We follow this measurement by demonstrating accelerating gradients of 320±17 MeV m(-1). Both measurements improve on previous measurements by and order of magnitude and show promise for dielectric wakefield accelerators as sources of high-energy electrons.

  13. Observation of acceleration and deceleration in gigaelectron-volt-per-metre gradient dielectric wakefield accelerators

    DOE PAGES

    O’Shea, B. D.; Andonian, G.; Barber, S. K.; ...

    2016-09-14

    There is urgent need to develop new acceleration techniques capable of exceeding gigaelectron-volt-per-metre (GeV m–1) gradients in order to enable future generations of both light sources and high-energy physics experiments. To address this need, short wavelength accelerators based on wakefields, where an intense relativistic electron beam radiates the demanded fields directly into the accelerator structure or medium, are currently under intense investigation. One such wakefield based accelerator, the dielectric wakefield accelerator, uses a dielectric lined-waveguide to support a wakefield used for acceleration. Here we show gradients of 1.347±0.020 GeV m–1 using a dielectric wakefield accelerator of 15 cm length, withmore » sub-millimetre transverse aperture, by measuring changes of the kinetic state of relativistic electron beams. We follow this measurement by demonstrating accelerating gradients of 320±17 MeV m–1. As a result, both measurements improve on previous measurements by and order of magnitude and show promise for dielectric wakefield accelerators as sources of high-energy electrons.« less

  14. Observation of acceleration and deceleration in gigaelectron-volt-per-metre gradient dielectric wakefield accelerators

    SciTech Connect

    O’Shea, B. D.; Andonian, G.; Barber, S. K.; Fitzmorris, K. L.; Hakimi, S.; Harrison, J.; Hoang, P. D.; Hogan, M. J.; Naranjo, B.; Williams, O. B.; Yakimenko, V.; Rosenzweig, J. B.

    2016-09-14

    There is urgent need to develop new acceleration techniques capable of exceeding gigaelectron-volt-per-metre (GeV m–1) gradients in order to enable future generations of both light sources and high-energy physics experiments. To address this need, short wavelength accelerators based on wakefields, where an intense relativistic electron beam radiates the demanded fields directly into the accelerator structure or medium, are currently under intense investigation. One such wakefield based accelerator, the dielectric wakefield accelerator, uses a dielectric lined-waveguide to support a wakefield used for acceleration. Here we show gradients of 1.347±0.020 GeV m–1 using a dielectric wakefield accelerator of 15 cm length, with sub-millimetre transverse aperture, by measuring changes of the kinetic state of relativistic electron beams. We follow this measurement by demonstrating accelerating gradients of 320±17 MeV m–1. As a result, both measurements improve on previous measurements by and order of magnitude and show promise for dielectric wakefield accelerators as sources of high-energy electrons.

  15. Synthetic aperture radar autofocus via semidefinite relaxation.

    PubMed

    Liu, Kuang-Hung; Wiesel, Ami; Munson, David C

    2013-06-01

    The autofocus problem in synthetic aperture radar imaging amounts to estimating unknown phase errors caused by unknown platform or target motion. At the heart of three state-of-the-art autofocus algorithms, namely, phase gradient autofocus, multichannel autofocus (MCA), and Fourier-domain multichannel autofocus (FMCA), is the solution of a constant modulus quadratic program (CMQP). Currently, these algorithms solve a CMQP by using an eigenvalue relaxation approach. We propose an alternative relaxation approach based on semidefinite programming, which has recently attracted considerable attention in other signal processing problems. Experimental results show that our proposed methods provide promising performance improvements for MCA and FMCA through an increase in computational complexity.

  16. Dual-sided coded-aperture imager

    DOEpatents

    Ziock, Klaus-Peter

    2009-09-22

    In a vehicle, a single detector plane simultaneously measures radiation coming through two coded-aperture masks, one on either side of the detector. To determine which side of the vehicle a source is, the two shadow masks are inverses of each other, i.e., one is a mask and the other is the anti-mask. All of the data that is collected is processed through two versions of an image reconstruction algorithm. One treats the data as if it were obtained through the mask, the other as though the data is obtained through the anti-mask.

  17. Synthetic aperture radar in geosynchronous orbit

    NASA Technical Reports Server (NTRS)

    Tomiyasu, K.

    1978-01-01

    Radar images of the earth were taken with a synthetic aperture radar (SAR) from geosynchronous orbital ranges by utilizing satellite motion relative to a geostationary position. A suitable satellite motion was obtained by having an orbit plane inclined relative to the equatorial plane and by having an eccentric orbit. Potential applications of these SAR images are topography, water resource management and soil moisture determination. Preliminary calculations show that the United States can be mapped with 100 m resolution cells in about 4 hours. With the use of microwave signals the mapping can be performed day or night, through clouds and during adverse weather.

  18. Combined synthetic aperture radar/Landsat imagery

    NASA Technical Reports Server (NTRS)

    Marque, R. E.; Maurer, H. E.

    1978-01-01

    This paper presents the results of investigations into merging synthetic aperture radar (SAR) and Landsat multispectral scanner (MSS) images using optical and digital merging techniques. The unique characteristics of airborne and orbital SAR and Landsat MSS imagery are discussed. The case for merging the imagery is presented and tradeoffs between optical and digital merging techniques explored. Examples of Landsat and airborne SAR imagery are used to illustrate optical and digital merging. Analysis of the merged digital imagery illustrates the improved interpretability resulting from combining the outputs from the two sensor systems.

  19. Aperture correction for a sphere interferometer

    NASA Astrophysics Data System (ADS)

    Arnold Nicolaus, R.; Bönsch, Gerhard

    2009-12-01

    Considerations have been made to derive a correction for the diameter measurements of a sphere by means of a special sphere interferometer. This correction is caused by the finite diameter of the light source acting as the entrance 'pinhole' aperture in the light collimating system. The finite diameter has the effect that the wave which is incident on the sphere is a superposition of spherical waves which are slightly inclined with respect to each other. The resulting correction is essential for high accuracy dimensional measurements of silicon spheres to determine the Avogadro constant—a new determination of which is a contribution to a new definition of the kilogram.

  20. Synthetic aperture radar for disaster monitoring

    NASA Astrophysics Data System (ADS)

    Dunkel, R.; Saddler, R.; Doerry, A. W.

    2011-06-01

    Synthetic Aperture Radar (SAR) is well known to afford imaging in darkness and through clouds, smoke, and other obscurants. As such, it is particularly useful for mapping and monitoring a variety of natural and man-made disasters. A portfolio of SAR image examples has been collected using General Atomics Aeronautical Systems, Inc.'s (GA-ASI's) Lynx® family of Ku-Band SAR systems, flown on both operational and test-bed aircraft. Images are provided that include scenes of flooding, ice jams in North Dakota, agricultural field fires in southern California, and ocean oil slicks from seeps off the coast of southern California.

  1. Essential Grid Workflow Monitoring Elements

    SciTech Connect

    Gunter, Daniel K.; Jackson, Keith R.; Konerding, David E.; Lee,Jason R.; Tierney, Brian L.

    2005-07-01

    Troubleshooting Grid workflows is difficult. A typicalworkflow involves a large number of components networks, middleware,hosts, etc. that can fail. Even when monitoring data from all thesecomponents is accessible, it is hard to tell whether failures andanomalies in these components are related toa given workflow. For theGrid to be truly usable, much of this uncertainty must be elim- inated.We propose two new Grid monitoring elements, Grid workflow identifiersand consistent component lifecycle events, that will make Gridtroubleshooting easier, and thus make Grids more usable, by simplifyingthe correlation of Grid monitoring data with a particular Gridworkflow.

  2. Distributed Accounting on the Grid

    NASA Technical Reports Server (NTRS)

    Thigpen, William; Hacker, Thomas J.; McGinnis, Laura F.; Athey, Brian D.

    2001-01-01

    By the late 1990s, the Internet was adequately equipped to move vast amounts of data between HPC (High Performance Computing) systems, and efforts were initiated to link together the national infrastructure of high performance computational and data storage resources together into a general computational utility 'grid', analogous to the national electrical power grid infrastructure. The purpose of the Computational grid is to provide dependable, consistent, pervasive, and inexpensive access to computational resources for the computing community in the form of a computing utility. This paper presents a fully distributed view of Grid usage accounting and a methodology for allocating Grid computational resources for use on a Grid computing system.

  3. Enabling Campus Grids with Open Science Grid Technology

    NASA Astrophysics Data System (ADS)

    Weitzel, Derek; Bockelman, Brian; Fraser, Dan; Pordes, Ruth; Swanson, David

    2011-12-01

    The Open Science Grid is a recognized key component of the US national cyber-infrastructure enabling scientific discovery through advanced high throughput computing. The principles and techniques that underlie the Open Science Grid can also be applied to Campus Grids since many of the requirements are the same, even if the implementation technologies differ. We find five requirements for a campus grid: trust relationships, job submission, resource independence, accounting, and data management. The Holland Computing Center's campus grid at the University of Nebraska-Lincoln was designed to fulfill the requirements of a campus grid. A bridging daemon was designed to bring non-Condor clusters into a grid managed by Condor. Condor features which make it possible to bridge Condor sites into a multi-campus grid have been exploited at the Holland Computing Center as well.

  4. Efficient twin aperture magnets for the future circular e+ /e_ collider

    NASA Astrophysics Data System (ADS)

    Milanese, A.

    2016-11-01

    We report preliminary designs for the arc dipoles and quadrupoles of the FCC-ee double-ring collider. After recalling cross sections and parameters of warm magnets used in previous large accelerators, we focus on twin aperture layouts, with a magnetic coupling between the gaps, which minimizes construction cost and reduces the electrical power required for operation. We also indicate how the designs presented may be further optimized so as to optimally address any further constraints related to beam physics, vacuum system, and electric power consumption.

  5. First Test Results of the 150 mm Aperture IR Quadrupole Models for the High Luminosity LHC

    SciTech Connect

    Ambrosio, G.; Chlachidze, G.; Wanderer, P.; Ferracin, P.; Sabbi, G.

    2016-10-06

    The High Luminosity upgrade of the LHC at CERN will use large aperture (150 mm) quadrupole magnets to focus the beams at the interaction points. The high field in the coils requires Nb3Sn superconductor technology, which has been brought to maturity by the LHC Accelerator Re-search Program (LARP) over the last 10 years. The key design targets for the new IR quadrupoles were established in 2012, and fabrication of model magnets started in 2014. This paper discusses the results from the first single short coil test and from the first short quadrupole model test. Remaining challenges and plans to address them are also presented and discussed.

  6. Advanced concepts for acceleration

    SciTech Connect

    Keefe, D.

    1986-07-01

    Selected examples of advanced accelerator concepts are reviewed. Such plasma accelerators as plasma beat wave accelerator, plasma wake field accelerator, and plasma grating accelerator are discussed particularly as examples of concepts for accelerating relativistic electrons or positrons. Also covered are the pulsed electron-beam, pulsed laser accelerator, inverse Cherenkov accelerator, inverse free-electron laser, switched radial-line accelerators, and two-beam accelerator. Advanced concepts for ion acceleration discussed include the electron ring accelerator, excitation of waves on intense electron beams, and two-wave combinations. (LEW)

  7. A dual-sided coded-aperture radiation detection system

    NASA Astrophysics Data System (ADS)

    Penny, R. D.; Hood, W. E.; Polichar, R. M.; Cardone, F. H.; Chavez, L. G.; Grubbs, S. G.; Huntley, B. P.; Kuharski, R. A.; Shyffer, R. T.; Fabris, L.; Ziock, K. P.; Labov, S. E.; Nelson, K.

    2011-10-01

    We report the development of a large-area, mobile, coded-aperture radiation imaging system for localizing compact radioactive sources in three dimensions while rejecting distributed background. The 3D Stand-Off Radiation Detection System (SORDS-3D) has been tested at speeds up to 95 km/h and has detected and located sources in the millicurie range at distances of over 100 m. Radiation data are imaged to a geospatially mapped world grid with a nominal 1.25- to 2.5-m pixel pitch at distances out to 120 m on either side of the platform. Source elevation is also extracted. Imaged radiation alarms are superimposed on a side-facing video log that can be played back for direct localization of sources in buildings in urban environments. The system utilizes a 37-element array of 5×5×50 cm 3 cesium-iodide (sodium) detectors. Scintillation light is collected by a pair of photomultiplier tubes placed at either end of each detector, with the detectors achieving an energy resolution of 6.15% FWHM (662 keV) and a position resolution along their length of 5 cm FWHM. The imaging system generates a dual-sided two-dimensional image allowing users to efficiently survey a large area. Imaged radiation data and raw spectra are forwarded to the RadioNuclide Analysis Kit (RNAK), developed by our collaborators, for isotope ID. An intuitive real-time display aids users in performing searches. Detector calibration is dynamically maintained by monitoring the potassium-40 peak and digitally adjusting individual detector gains. We have recently realized improvements, both in isotope identification and in distinguishing compact sources from background, through the installation of optimal-filter reconstruction kernels.

  8. Accelerators and the Accelerator Community

    SciTech Connect

    Malamud, Ernest; Sessler, Andrew

    2008-06-01

    In this paper, standing back--looking from afar--and adopting a historical perspective, the field of accelerator science is examined. How it grew, what are the forces that made it what it is, where it is now, and what it is likely to be in the future are the subjects explored. Clearly, a great deal of personal opinion is invoked in this process.

  9. Unlocking the smart grid

    SciTech Connect

    Rokach, Joshua Z.

    2010-10-15

    The country has progressed in a relatively short time from rotary dial phones to computers, cell phones, and iPads. With proper planning and orderly policy implementation, the same will happen with the Smart Grid. Here are some suggestions on how to proceed. (author)

  10. NSTAR Smart Grid Pilot

    SciTech Connect

    Rabari, Anil; Fadipe, Oloruntomi

    2014-03-31

    NSTAR Electric & Gas Corporation (“the Company”, or “NSTAR”) developed and implemented a Smart Grid pilot program beginning in 2010 to demonstrate the viability of leveraging existing automated meter reading (“AMR”) deployments to provide much of the Smart Grid functionality of advanced metering infrastructure (“AMI”), but without the large capital investment that AMI rollouts typically entail. In particular, a central objective of the Smart Energy Pilot was to enable residential dynamic pricing (time-of-use “TOU” and critical peak rates and rebates) and two-way direct load control (“DLC”) by continually capturing AMR meter data transmissions and communicating through customer-sited broadband connections in conjunction with a standardsbased home area network (“HAN”). The pilot was supported by the U.S. Department of Energy’s (“DOE”) through the Smart Grid Demonstration program. NSTAR was very pleased to not only receive the funding support from DOE, but the guidance and support of the DOE throughout the pilot. NSTAR is also pleased to report to the DOE that it was able to execute and deliver a successful pilot on time and on budget. NSTAR looks for future opportunities to work with the DOE and others in future smart grid projects.

  11. The surveillance error grid.

    PubMed

    Klonoff, David C; Lias, Courtney; Vigersky, Robert; Clarke, William; Parkes, Joan Lee; Sacks, David B; Kirkman, M Sue; Kovatchev, Boris

    2014-07-01

    Currently used error grids for assessing clinical accuracy of blood glucose monitors are based on out-of-date medical practices. Error grids have not been widely embraced by regulatory agencies for clearance of monitors, but this type of tool could be useful for surveillance of the performance of cleared products. Diabetes Technology Society together with representatives from the Food and Drug Administration, the American Diabetes Association, the Endocrine Society, and the Association for the Advancement of Medical Instrumentation, and representatives of academia, industry, and government, have developed a new error grid, called the surveillance error grid (SEG) as a tool to assess the degree of clinical risk from inaccurate blood glucose (BG) monitors. A total of 206 diabetes clinicians were surveyed about the clinical risk of errors of measured BG levels by a monitor. The impact of such errors on 4 patient scenarios was surveyed. Each monitor/reference data pair was scored and color-coded on a graph per its average risk rating. Using modeled data representative of the accuracy of contemporary meters, the relationships between clinical risk and monitor error were calculated for the Clarke error grid (CEG), Parkes error grid (PEG), and SEG. SEG action boundaries were consistent across scenarios, regardless of whether the patient was type 1 or type 2 or using insulin or not. No significant differences were noted between responses of adult/pediatric or 4 types of clinicians. Although small specific differences in risk boundaries between US and non-US clinicians were noted, the panel felt they did not justify separate grids for these 2 types of clinicians. The data points of the SEG were classified in 15 zones according to their assigned level of risk, which allowed for comparisons with the classic CEG and PEG. Modeled glucose monitor data with realistic self-monitoring of blood glucose errors derived from meter testing experiments plotted on the SEG when compared to

  12. 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.

  13. KAOS: kilo-aperture optical spectrograph

    NASA Astrophysics Data System (ADS)

    Barden, Samuel C.; Dey, Arjun; Boyle, Brian; Glazebrook, Karl

    2004-09-01

    A design is described for a potential new facility capable of taking detailed spectroscopy of millions of objects in the Universe to explore the complexity of the Universe and to answer fundamental questions relating to the equation of state of dark energy and to how the Milky Way galaxy formed. The specific design described is envisioned for implementation on the Gemini 8-meter telescopes. It utilizes a 1.5° field of view and samples that field with up to ~5000 apertures. This Kilo-Aperture Optical Spectrograph (KAOS) is mounted at prime focus with a 4-element corrector, atmospheric dispersion compensator (ADC), and an Echidna-style fiber optic positioner. The ADC doubles as a wobble plate, allowing fast guiding that cancels out the wind buffeting of the telescope. The fibers, which can be reconfigured in less than 10 minutes, feed to an array of 12 spectrographs located in the pier of the telescope. The spectrographs are capable of provided spectral resolving powers of a few thousand up to about 40,000.

  14. Very large aperture optics for space applications

    NASA Astrophysics Data System (ADS)

    Horwath, T. G.; Smith, J. P.; Johnson, M. T.

    1994-09-01

    A new type of space optics technology is presented which promises the realization of very large apertures (tens of meters), while packagable into lightweight, small volume containers compatible with conventional launch vehicles. This technology makes use of thin foils of circular shape which are uniformly mass loaded around the perimeter. Once unfurled and set into rapid rotation about the transversal axis, the foil is stretched into a perfectly flat plane by the centrifugal forces acting on the peripheral masses. The simplest applications of this novel technology are optically flat reflectors, using metallized foils of Mylar, Kevlar, or Kapton. Other more complex optical components can be realized by use of binary optics techniques, such as depositing holograms by selective local microscale removal of the reflective surface. Electrostatic techniques, in conjunction with an auxiliary foil, under local, distributed real-time control of the optical parameters, allow implementation of functions like beam steering and focal length adjustments. Gas pressurization allows stronger curvatures and thus smaller focal ratios for non-imaging applications. Limits on aperture are imposed primarily by manufacturing capabilities. Applications of such large optics in space are numerous. They range from military, such as space based lasers, to the civilian ones of power beaming, solar energy collection, and astronomy. This paper examines this simple and innovative concept in detail, discusses deployment and attitude control issues and presents approaches for realization.

  15. The SKA New Instrumentation: Aperture Arrays

    NASA Astrophysics Data System (ADS)

    van Ardenne, A.; Faulkner, A. J.; de Vaate, J. G. bij

    The radio frequency window of the Square Kilometre Array is planned to cover the wavelength regime from cm up to a few meters. For this range to be optimally covered, different antenna concepts are considered enabling many science cases. At the lowest frequency range, up to a few GHz, it is expected that multi-beam techniques will be used, increasing the effective field-of-view to a level that allows very efficient detailed and sensitive exploration of the complete sky. Although sparse narrow band phased arrays are as old as radio astronomy, multi-octave sparse and dense arrays now being considered for the SKA, requiring new low noise design, signal processing and calibration techniques. These new array techniques have already been successfully introduced as phased array feeds upgrading existing reflecting telescopes and for new telescopes to enhance the aperture efficiency as well as greatly increasing their field-of-view (van Ardenne et al., Proc IEEE 97(8):2009) by [1]. Aperture arrays use phased arrays without any additional reflectors; the phased array elements are small enough to see most of the sky intrinsically offering a large field of view.

  16. Multi-shot compressed coded aperture imaging

    NASA Astrophysics Data System (ADS)

    Shao, Xiaopeng; Du, Juan; Wu, Tengfei; Jin, Zhenhua

    2013-09-01

    The classical methods of compressed coded aperture (CCA) still require an optical sensor with high resolution, although the sampling rate has broken the Nyquist sampling rate already. A novel architecture of multi-shot compressed coded aperture imaging (MCCAI) using a low resolution optical sensor is proposed, which is mainly based on the 4-f imaging system, combining with two spatial light modulators (SLM) to achieve the compressive imaging goal. The first SLM employed for random convolution is placed at the frequency spectrum plane of the 4-f imaging system, while the second SLM worked as a selecting filter is positioned in front of the optical sensor. By altering the random coded pattern of the second SLM and sampling, a couple of observations can be obtained by a low resolution optical sensor easily, and these observations will be combined mathematically and used to reconstruct the high resolution image. That is to say, MCCAI aims at realizing the super resolution imaging with multiple random samplings by using a low resolution optical sensor. To improve the computational imaging performance, total variation (TV) regularization is introduced into the super resolution reconstruction model to get rid of the artifacts, and alternating direction method of multipliers (ADM) is utilized to solve the optimal result efficiently. The results show that the MCCAI architecture is suitable for super resolution computational imaging using a much lower resolution optical sensor than traditional CCA imaging methods by capturing multiple frame images.

  17. Integrated feeds for electronically reconfigurable apertures

    NASA Astrophysics Data System (ADS)

    Nicholls, Jeffrey Grant

    With the increasing ubiquity of wireless technology, the need for lower-profile, electronically reconfigurable, highly-directive beam-steering antennas is increasing. This thesis proposes a new electronic beam-steering antenna architecture which combines the full-space beam-steering properties of reflectarrays and transmitarrays with the low-profile feeding characteristics of leaky-wave antennas. Two designs are developed: an integrated feed reflectarray and an integrated feed transmitarray, both of which integrate a leaky-wave feed directly next to the reconfigurable aperture itself. The integrated feed transmitarray proved to be the better architecture due to its simpler design and better performance. A 6-by-6 element array was fabricated and experimentally verified, and full-space (both azimuth and elevation) beam-steering was demonstrated at angles up to 45 degrees off broadside. In addition to the reduction in profile, the integrated feed design enables robust fixed control of the amplitude distribution across the aperture, a characteristic not as easily attained in typical reflectarrays/transmitarrays.

  18. Design of Octupole Channel for Integrable Optics Test Accelerator

    SciTech Connect

    Antipov, Sergey; Carlson, Kermit; Castellotti, Riccardo; Valishev, Alexander; Wesseln, Steven

    2016-06-01

    We present the design of octupole channel for Integrable Optics Test Accelerator (IOTA). IOTA is a test accelerator at Fermilab, aimed to conduct research towards high-intensity machines. One of the goals of the project is to demonstrate high nonlinear betatron tune shifts while retaining large dynamic aperture in a realistic accelerator design. At the first stage the tune shift will be attained with a special channel of octupoles, which creates a variable octupole potential over a 1.8 m length. The channel consists of 18 identical air-cooled octupole magnets. The magnets feature a simple low-cost design, while meeting the requirements on maximum gradient - up to 1.4 kG/cm³, and field quality - strength of harmonics below 1%. Numerical simulations show that the channel is capable of producing a nonlinear tune shift of 0.08 without restriction of dynamic aperture of the ring.

  19. Ultrafast silicon nanoplasmonic grid-gate transistor

    NASA Astrophysics Data System (ADS)

    Greig, S. R.; Elezzabi, A. Y.

    2015-03-01

    We present the detailed investigation of an ultrafast silicon based nanoplasmonic three terminal device. The device operates on the principle of ponderomotive acceleration of two-photon absorption generated electrons within a nanoplasmonic waveguide structure. Due to high spatial mode confinement, high spatial asymmetry, and high enhancement of the nanoplasmonic electric field, electrons are accelerated to high kinetic energies and are directed towards the copper anode generating an output current. Application of a negative grid voltage modulates an effective energy barrier that restricts the number of electrons reaching the anode, thus reducing the output current. Operating at electric field strengths up to 1×107 V/cm generates a 150 fs output current pulse of 628 mA/μm. Careful consideration of the materials used facilitates monolithic integration with current complementary-metal-oxide-semiconductor nanoelectronics devices.

  20. New physics and applications of apertures in thin metal films

    NASA Astrophysics Data System (ADS)

    Gordon, Reuven; Al-Balushi, Ahmed A.; Kotnala, Abhay; Gelfand, Ryan F.; Wheaton, Skylar; Chen, Shuwen; Jin, Shilong

    2014-08-01

    The nanoplasmonic properties of apertures in metal films have been studied extensively; however, we have recently discovered surprising new features of this simple system with applications to super-focusing and super-scattering. Furthermore, apertures allow for optical tweezers that can hold onto particles of the order of 1 nm; I will briefly highlight our work using these apertures to study protein - small molecule interactions and protein - DNA binding.

  1. Experimental investigations of 3 mm aperture PPLN structures

    NASA Astrophysics Data System (ADS)

    Kolker, D.; Pronyushkina, A.; Boyko, A.; Kostyukova, N.; Trashkeev, S.; Nuyshkov, B.; Shur, V.

    2017-01-01

    We are reporting about investigation of domestic 3 mm aperture periodically polled lithium niobate (PPLN) structures for cascaded mid-IR OPO. Wide aperture periodically poled MgO-doped lithium niobate (LiNbO3) structures at multigrating, fan-out and multi fan-out configuration were prepared at “Labfer LTD”. Laser source based on such structures can be used for special applications. Four different PPLN structures were investigated and effective aperture for effective pumping was defined.

  2. Tomographic Processing of Synthetic Aperture Radar Signals for Enhanced Resolution

    DTIC Science & Technology

    1989-11-01

    digital signal processing view of strip-mapping synthetic aperture radar," M.S. thesis , University of Illinois, Urbana, IL,1988." [571 David C. Munson...TOMOGRAPHIC PROCESSING OF 1 SYNTHETIC APERTURE I RADAR SIGNALS FOR ENHANCED RESOLUTION,I * Jerald Lee Bauck DTIC ELECTE JAN2419901D I I UNIVERSITY OF ILLINOIS...NC 27709-2211 ELEMENT NO. NO. NO CCESSION NO. 11i. TITLE (Include Security Classification) TOMOGRAPHIC PROCESSING OF SYNTHETIC APERTURE RADlAR SIGNALS

  3. Impact accelerations

    NASA Technical Reports Server (NTRS)

    Vongierke, H. E.; Brinkley, J. W.

    1975-01-01

    The degree to which impact acceleration is an important factor in space flight environments depends primarily upon the technology of capsule landing deceleration and the weight permissible for the associated hardware: parachutes or deceleration rockets, inflatable air bags, or other impact attenuation systems. The problem most specific to space medicine is the potential change of impact tolerance due to reduced bone mass and muscle strength caused by prolonged weightlessness and physical inactivity. Impact hazards, tolerance limits, and human impact tolerance related to space missions are described.

  4. Stripline kicker for integrable optics test accelerator

    SciTech Connect

    Antipov, Sergey A.; Didenko, Alexander; Lebedev, Valeri; Valishev, Alexander

    2016-06-30

    We present a design of a stripline kicker for Integrable Optics Test Accelerator (IOTA). For its experimental program IOTA needs two full-aperture kickers, capable to create an arbitrary controllable kick in 2D. For that reason their strengths are variable in a wide range of amplitudes up to 16 mrad, and the pulse length 100 ns is less than a revolution period for electrons. In addition, the kicker should have a physical aperture of 40 mm for a proposed operation with proton beam, and an outer size of 70 mm to fit inside existing quadrupole magnets to save space in the ring. Computer simulations using CST Microwave Studio show high field uniformity and wave impedance close to 50 {\\Omega}.

  5. Accelerator system for neutron radiography

    SciTech Connect

    Rusnak, B; Hall, J

    2000-09-21

    The field of x-ray radiography is well established for doing non-destructive evaluation of a vast array of components, assemblies, and objects. While x-rays excel in many radiography applications, their effectiveness diminishes rapidly if the objects of interest are surrounded by thick, high-density materials that strongly attenuate photons. Due to the differences in interaction mechanisms, neutron radiography is highly effective in imaging details inside such objects. To obtain a high intensity neutron source suitable for neutron imaging a 9-MeV linear accelerator is being evaluated for putting a deuteron beam into a high-pressure deuterium gas cell. As a windowless aperture is needed to transport the beam into the gas cell, a low-emittance is needed to minimize losses along the high-energy beam transport (HEBT) and the end station. A description of the HEBT, the transport optics into the gas cell, and the requirements for the linac will be presented.

  6. Equil: A Global Grid System

    NASA Astrophysics Data System (ADS)

    Hahn, Sebastian; Reimer, Christioph; Paulik, Christoph; Wagner, Wolfgang

    2016-08-01

    Geophysical parameters derived from space-borne Earth Observation Systems are either assigned to discrete points on a fixed Earth grid (e.g. regular lon/lat grid) or located on orbital point nodes with a customized arrangement, often in-line with the instrument's measurement geometry. The driving factors of the choice and structure of a spatial reference system (i.e. the grid) are typically spatial resolution, instrument geometry, measurement technique or application.In this study we propose a global grid system, the so- called Equil grid, and demonstrate its realization and structure. An exemplary Equil grid with a base sampling distance of 12.5 km is compared against two other grids commonly used in the domain of remote sensing of soil moisture. The simple nearly-equidistant grid design makes it interesting for a wide range of other geophysical parameters as well.

  7. Functionalized apertures for the detection of chemical and biological materials

    DOEpatents

    Letant, Sonia E.; van Buuren, Anthony W.; Terminello, Louis J.; Thelen, Michael P.; Hope-Weeks, Louisa J.; Hart, Bradley R.

    2010-12-14

    Disclosed are nanometer to micron scale functionalized apertures constructed on a substrate made of glass, carbon, semiconductors or polymeric materials that allow for the real time detection of biological materials or chemical moieties. Many apertures can exist on one substrate allowing for the simultaneous detection of numerous chemical and biological molecules. One embodiment features a macrocyclic ring attached to cross-linkers, wherein the macrocyclic ring has a biological or chemical probe extending through the aperture. Another embodiment achieves functionalization by attaching chemical or biological anchors directly to the walls of the apertures via cross-linkers.

  8. Diffraction from oxide confinement apertures in vertical-cavity lasers

    SciTech Connect

    Roos, P.A.; Carlsten, J.L.; Kilper, D.C.; Lear, K.L.

    1999-08-01

    Direct measurement of scattered fields from oxide confinement apertures in vertical-cavity lasers is presented. Diffraction fringes associated with each transverse lasing mode are detected in the far field from devices with varying oxide aperture dimensions and with quantum efficiencies as high as 48{percent}. The diffracted pattern symmetries match the rectangular symmetry of the oxide apertures present in the devices and fringe locations are compared to Fraunhofer theory. The fraction of power diffracted from the lasing mode remains roughly constant as a function of relative pump rate, but is shown to depend on both transverse mode order and oxide aperture size. {copyright} {ital 1999 American Institute of Physics.}

  9. 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.

  10. Current Grid operation and future role of the Grid

    NASA Astrophysics Data System (ADS)

    Smirnova, O.

    2012-12-01

    Grid-like technologies and approaches became an integral part of HEP experiments. Some other scientific communities also use similar technologies for data-intensive computations. The distinct feature of Grid computing is the ability to federate heterogeneous resources of different ownership into a seamless infrastructure, accessible via a single log-on. Like other infrastructures of similar nature, Grid functioning requires not only technologically sound basis, but also reliable operation procedures, monitoring and accounting. The two aspects, technological and operational, are closely related: weaker is the technology, more burden is on operations, and other way around. As of today, Grid technologies are still evolving: at CERN alone, every LHC experiment uses an own Grid-like system. This inevitably creates a heavy load on operations. Infrastructure maintenance, monitoring and incident response are done on several levels, from local system administrators to large international organisations, involving massive human effort worldwide. The necessity to commit substantial resources is one of the obstacles faced by smaller research communities when moving computing to the Grid. Moreover, most current Grid solutions were developed under significant influence of HEP use cases, and thus need additional effort to adapt them to other applications. Reluctance of many non-HEP researchers to use Grid negatively affects the outlook for national Grid organisations, which strive to provide multi-science services. We started from the situation where Grid organisations were fused with HEP laboratories and national HEP research programmes; we hope to move towards the world where Grid will ultimately reach the status of generic public computing and storage service provider and permanent national and international Grid infrastructures will be established. How far will we be able to advance along this path, depends on us. If no standardisation and convergence efforts will take place

  11. Photofabricated Wire-Grid Polarizers

    NASA Technical Reports Server (NTRS)

    Siegel, Peter H.; Dengler, Robert J.

    1992-01-01

    Freestanding metallic grids for use as polarizers for electromagnetic radiation at millimeter and submillimeter wavelengths made by simple modification of designs of freestanding square- and nearly-square cell metallic grids, according to proposal. Cross wires provide mechanical support, but distance between cross wires made greater than one wavelength so cross wires have little effect on polarizing characteristics of grid. Possible to fabricate grids commercially for frequencies up to several terahertz.

  12. Applications of algebraic grid generation

    NASA Technical Reports Server (NTRS)

    Eiseman, Peter R.; Smith, Robert E.

    1990-01-01

    Techniques and applications of algebraic grid generation are described. The techniques are univariate interpolations and transfinite assemblies of univariate interpolations. Because algebraic grid generation is computationally efficient, the use of interactive graphics in conjunction with the techniques is advocated. A flexible approach, which works extremely well in an interactive environment, called the control point form of algebraic grid generation is described. The applications discussed are three-dimensional grids constructed about airplane and submarine configurations.

  13. Ion accelerator system mounting design and operating characteristics for a 5 kW 30-cm xenon ion engine

    NASA Technical Reports Server (NTRS)

    Aston, Graeme; Brophy, John R.

    1987-01-01

    Results from a series of experiments to determine the effect of accelerator grid mount geometry on the performance of the J-series ion optics assembly are described. Three mounting schemes, two flexible and one rigid, are compared for their relative ion extraction capability over a range of total accelerating voltages. The largest ion beam current, for the maximum total voltage investigated, is shown to occur using one of the flexible grid mounting geometries. However, at lower total voltages and reduced engine input power levels, the original rigid J-series ion optics accelerator grid mounts result in marginally better grid system performance at the same cold interelectrode gap.

  14. A grid spacing control technique for algebraic grid generation methods

    NASA Technical Reports Server (NTRS)

    Smith, R. E.; Kudlinski, R. A.; Everton, E. L.

    1982-01-01

    A technique which controls the spacing of grid points in algebraically defined coordinate transformations is described. The technique is based on the generation of control functions which map a uniformly distributed computational grid onto parametric variables defining the physical grid. The control functions are smoothed cubic splines. Sets of control points are input for each coordinate directions to outline the control functions. Smoothed cubic spline functions are then generated to approximate the input data. The technique works best in an interactive graphics environment where control inputs and grid displays are nearly instantaneous. The technique is illustrated with the two-boundary grid generation algorithm.

  15. Grid Interaction Technical Team Roadmap

    SciTech Connect

    2013-06-01

    The mission of the Grid Interaction Technical Team (GITT) is to support a transition scenario to large scale grid-connected vehicle charging with transformational technology, proof of concept and information dissemination. The GITT facilitates technical coordination and collaboration between vehicle-grid connectivity and communication activities among U.S. DRIVE government and industry partners.

  16. Cloud Computing for the Grid: GridControl: A Software Platform to Support the Smart Grid

    SciTech Connect

    2012-02-08

    GENI Project: Cornell University is creating a new software platform for grid operators called GridControl that will utilize cloud computing to more efficiently control the grid. In a cloud computing system, there are minimal hardware and software demands on users. The user can tap into a network of computers that is housed elsewhere (the cloud) and the network runs computer applications for the user. The user only needs interface software to access all of the cloud’s data resources, which can be as simple as a web browser. Cloud computing can reduce costs, facilitate innovation through sharing, empower users, and improve the overall reliability of a dispersed system. Cornell’s GridControl will focus on 4 elements: delivering the state of the grid to users quickly and reliably; building networked, scalable grid-control software; tailoring services to emerging smart grid uses; and simulating smart grid behavior under various conditions.

  17. Advanced methods in synthetic aperture radar imaging

    NASA Astrophysics Data System (ADS)

    Kragh, Thomas

    2012-02-01

    For over 50 years our world has been mapped and measured with synthetic aperture radar (SAR). A SAR system operates by transmitting a series of wideband radio-frequency pulses towards the ground and recording the resulting backscattered electromagnetic waves as the system travels along some one-dimensional trajectory. By coherently processing the recorded backscatter over this extended aperture, one can form a high-resolution 2D intensity map of the ground reflectivity, which we call a SAR image. The trajectory, or synthetic aperture, is achieved by mounting the radar on an aircraft, spacecraft, or even on the roof of a car traveling down the road, and allows for a diverse set of applications and measurement techniques for remote sensing applications. It is quite remarkable that the sub-centimeter positioning precision and sub-nanosecond timing precision required to make this work properly can in fact be achieved under such real-world, often turbulent, vibrationally intensive conditions. Although the basic principles behind SAR imaging and interferometry have been known for decades, in recent years an explosion of data exploitation techniques enabled by ever-faster computational horsepower have enabled some remarkable advances. Although SAR images are often viewed as simple intensity maps of ground reflectivity, SAR is also an exquisitely sensitive coherent imaging modality with a wealth of information buried within the phase information in the image. Some of the examples featured in this presentation will include: (1) Interferometric SAR, where by comparing the difference in phase between two SAR images one can measure subtle changes in ground topography at the wavelength scale. (2) Change detection, in which carefully geolocated images formed from two different passes are compared. (3) Multi-pass 3D SAR tomography, where multiple trajectories can be used to form 3D images. (4) Moving Target Indication (MTI), in which Doppler effects allow one to detect and

  18. Dusty-Plasma Particle Accelerator

    NASA Technical Reports Server (NTRS)

    Foster, John E.

    2005-01-01

    A dusty-plasma apparatus is being investigated as means of accelerating nanometer- and micrometer-sized particles. Applications for the dusty-plasma particle accelerators fall into two classes: Simulation of a variety of rapidly moving dust particles and micrometeoroids in outer-space environments that include micrometeoroid streams, comet tails, planetary rings, and nebulae and Deposition or implantation of nanoparticles on substrates for diverse industrial purposes that could include hardening, increasing thermal insulation, altering optical properties, and/or increasing permittivities of substrate materials. Relative to prior apparatuses used for similar applications, dusty-plasma particle accelerators offer such potential advantages as smaller size, lower cost, less complexity, and increased particle flux densities. A dusty-plasma particle accelerator exploits the fact that an isolated particle immersed in plasma acquires a net electric charge that depends on the relative mobilities of electrons and ions. Typically, a particle that is immersed in a low-temperature, partially ionized gas, wherein the average kinetic energy of electrons exceeds that of ions, causes the particle to become negatively charged. The particle can then be accelerated by applying an appropriate electric field. A dusty-plasma particle accelerator (see figure) includes a plasma source such as a radio-frequency induction discharge apparatus containing (1) a shallow cup with a biasable electrode to hold the particles to be accelerated and (2) a holder for the substrate on which the particles are to impinge. Depending on the specific design, a pair of electrostatic-acceleration grids between the substrate and discharge plasma can be used to both collimate and further accelerate particles exiting the particle holder. Once exposed to the discharge plasma, the particles in the cup quickly acquire a negative charge. Application of a negative voltage pulse to the biasable electrode results in the

  19. A Large, Free-Standing Wire Grid for Microwave Variable-delay Polarization Modulation

    NASA Technical Reports Server (NTRS)

    Voellmer, George

    2008-01-01

    One technique for mapping the polarization signature of the cosmic microwave background uses large, polarizing grids in reflection. We present the system requirements, the fabrication, assembly, and alignment procedures, and the test results for the polarizing grid component of a 50 cm clear aperture, Variable-delay Polarization Modulator (VPM). This grid is being built and tested at the Goddard Space Flight Center as part of the Polarimeter for Observing Inflationary Cosmology at the Reionization Epoch (POINCARE). VPMs modulate the polarized component of a radiation source by splitting the incoming beam into two orthogonal polarization components using a free-standing wire grid. The path length difference between these components is varied with a translating mirror, and then they are recombined. This precision instrumentation technique can be used to encode and demodulate the cosmic microwave background's polarization signature. For the demonstration instrument, 64 micrometer diameter tungsten wires are being assembled into a 200 pm pitch, free-standing wire grid with a 50 cm clear aperture, and an expected overall flatness better than 30 micrometers. A rectangular, aluminum stretching frame holds the wires with sufficient tension to achieve a minimum resonant frequency of 185 Hz, allowing VPM mirror translation frequencies of several Hz. A lightly loaded, flattening ring with a 50 cm inside diameter rests against the wires and brings them into accurate planarity.

  20. Shuttle computational grid generation

    NASA Technical Reports Server (NTRS)

    Ing, Chang

    1987-01-01

    The well known Karman-Trefftz conformal transformation, consisting of repeated applications of the same basic formula, were found to be quite successful to body, wing, and wing-body cross sections. This grid generation technique is extended to cross sections of more complex forms, and also more automatic. Computer programs were written for the selection of hinge points on cross section with angular shapes, the Karman-Trefftz tranformation of arbitrary shapes, and the special transform of hinge point on the imaginary axis. A feasibility study is performed for the future application of conformal mapping grid generation to complex three dimensional configurations. Examples such as Orbiter vehicle section and a few others were used.

  1. Smart Grid Demonstration Project

    SciTech Connect

    Miller, Craig; Carroll, Paul; Bell, Abigail

    2015-03-11

    The National Rural Electric Cooperative Association (NRECA) organized the NRECA-U.S. Department of Energy (DOE) Smart Grid Demonstration Project (DE-OE0000222) to install and study a broad range of advanced smart grid technologies in a demonstration that spanned 23 electric cooperatives in 12 states. More than 205,444 pieces of electronic equipment and more than 100,000 minor items (bracket, labels, mounting hardware, fiber optic cable, etc.) were installed to upgrade and enhance the efficiency, reliability, and resiliency of the power networks at the participating co-ops. The objective of this project was to build a path for other electric utilities, and particularly electrical cooperatives, to adopt emerging smart grid technology when it can improve utility operations, thus advancing the co-ops’ familiarity and comfort with such technology. Specifically, the project executed multiple subprojects employing a range of emerging smart grid technologies to test their cost-effectiveness and, where the technology demonstrated value, provided case studies that will enable other electric utilities—particularly electric cooperatives— to use these technologies. NRECA structured the project according to the following three areas: Demonstration of smart grid technology; Advancement of standards to enable the interoperability of components; and Improvement of grid cyber security. We termed these three areas Technology Deployment Study, Interoperability, and Cyber Security. Although the deployment of technology and studying the demonstration projects at coops accounted for the largest portion of the project budget by far, we see our accomplishments in each of the areas as critical to advancing the smart grid. All project deliverables have been published. Technology Deployment Study: The deliverable was a set of 11 single-topic technical reports in areas related to the listed technologies. Each of these reports has already been submitted to DOE, distributed to co-ops, and

  2. Accelerator system and method of accelerating particles

    NASA Technical Reports Server (NTRS)

    Wirz, Richard E. (Inventor)

    2010-01-01

    An accelerator system and method that utilize dust as the primary mass flux for generating thrust are provided. The accelerator system can include an accelerator capable of operating in a self-neutralizing mode and having a discharge chamber and at least one ionizer capable of charging dust particles. The system can also include a dust particle feeder that is capable of introducing the dust particles into the accelerator. By applying a pulsed positive and negative charge voltage to the accelerator, the charged dust particles can be accelerated thereby generating thrust and neutralizing the accelerator system.

  3. Very high numerical aperture light transmitting device

    DOEpatents

    Allison, Stephen W.; Boatner, Lynn A.; Sales, Brian C.

    1998-01-01

    A new light-transmitting device using a SCIN glass core and a novel calcium sodium cladding has been developed. The very high index of refraction, radiation hardness, similar solubility for rare earths and similar melt and viscosity characteristics of core and cladding materials makes them attractive for several applications such as high-numerical-aperture optical fibers and specialty lenses. Optical fibers up to 60 m in length have been drawn, and several simple lenses have been designed, ground, and polished. Preliminary results on the ability to directly cast optical components of lead-indium phosphate glass are also discussed as well as the suitability of these glasses as a host medium for rare-earth ion lasers and amplifiers.

  4. Automated change detection for synthetic aperture sonar

    NASA Astrophysics Data System (ADS)

    G-Michael, Tesfaye; Marchand, Bradley; Tucker, J. D.; Sternlicht, Daniel D.; Marston, Timothy M.; Azimi-Sadjadi, Mahmood R.

    2014-05-01

    In this paper, an automated change detection technique is presented that compares new and historical seafloor images created with sidescan synthetic aperture sonar (SAS) for changes occurring over time. The method consists of a four stage process: a coarse navigational alignment; fine-scale co-registration using the scale invariant feature transform (SIFT) algorithm to match features between overlapping images; sub-pixel co-registration to improves phase coherence; and finally, change detection utilizing canonical correlation analysis (CCA). The method was tested using data collected with a high-frequency SAS in a sandy shallow-water environment. By using precise co-registration tools and change detection algorithms, it is shown that the coherent nature of the SAS data can be exploited and utilized in this environment over time scales ranging from hours through several days.

  5. Optical aperture synthesis with electronically connected telescopes.

    PubMed

    Dravins, Dainis; Lagadec, Tiphaine; Nuñez, Paul D

    2015-04-16

    Highest resolution imaging in astronomy is achieved by interferometry, connecting telescopes over increasingly longer distances and at successively shorter wavelengths. Here, we present the first diffraction-limited images in visual light, produced by an array of independent optical telescopes, connected electronically only, with no optical links between them. With an array of small telescopes, second-order optical coherence of the sources is measured through intensity interferometry over 180 baselines between pairs of telescopes, and two-dimensional images reconstructed. The technique aims at diffraction-limited optical aperture synthesis over kilometre-long baselines to reach resolutions showing details on stellar surfaces and perhaps even the silhouettes of transiting exoplanets. Intensity interferometry circumvents problems of atmospheric turbulence that constrain ordinary interferometry. Since the electronic signal can be copied, many baselines can be built up between dispersed telescopes, and over long distances. Using arrays of air Cherenkov telescopes, this should enable the optical equivalent of interferometric arrays currently operating at radio wavelengths.

  6. Saturation of the Large Aperture Scintillometer

    NASA Astrophysics Data System (ADS)

    Kohsiek, W.; Meijninger, W. M. L.; Debruin, H. A. R.; Beyrich, F.

    2006-10-01

    The saturation aspects of a large aperture (0.3 m) scintillometer operating over a 10-km path were investigated. Measurements were made over mainly forested, hilly terrain with typical maximum sensible heat fluxes of 300-400 W m -2, and over flat terrain with mainly grass, and typical maximum heat fluxes of 100-150 W m-2. Scintillometer-based fluxes were compared with eddy-correlation observations. Two different schemes for calculating the reduction of scintillation caused by saturation were applied: one based on the work of Hill and Clifford, the other based on Frehlich and Ochs. Without saturation correction, the scintillation fluxes were lower than the eddy-correlation fluxes; the saturation correction according to Frehlich and Ochs increased the scintillometer fluxes to an unrealistic level. Correcting the fluxes after the theory of the Hill and Clifford gave satisfying results

  7. Bistatic synthetic aperture radar using two satellites

    NASA Technical Reports Server (NTRS)

    Tomiyasu, K.

    1978-01-01

    The paper demonstrates the feasibility of a bistatic synthetic aperture radar (BISAR) utilizing two satellites. The proposed BISAR assumes that the direction of the two narrow antenna beams are programmed to coincide over the desired area to be imaged. Functionally, the transmitter and receiver portions can be interchanged between the two satellites. The two satellites may be in one orbit plane or two different orbits such as geosynchronous and low-earth orbits. The pulse repetition frequency and imaging geometry are constrained by contours of isodops and isodels. With two images of the same area viewed from different angles, it is possible in principle to derive three-dimensional stereo images. Applications of BISAR include topography, water resource management, and soil moisture determination.. Advantages of BISAR over a monostatic SAR are mentioned, including lower transmitter power and greater ranges in incidence angle and coverage.

  8. High numerical aperture multilayer Laue lenses

    SciTech Connect

    Morgan, Andrew J.; Prasciolu, Mauro; Andrejczuk, Andrzej; Krzywinski, Jacek; Meents, Alke; Pennicard, David; Graafsma, Heinz; Barty, Anton; Bean, Richard J.; Barthelmess, Miriam; Oberthuer, Dominik; Yefanov, Oleksandr; Aquila, Andrew; Chapman, Henry N.; Bajt, Saša

    2015-06-01

    The ever-increasing brightness of synchrotron radiation sources demands improved X-ray optics to utilise their capability for imaging and probing biological cells, nanodevices, and functional matter on the nanometer scale with chemical sensitivity. Here we demonstrate focusing a hard X-ray beam to an 8 nm focus using a volume zone plate (also referred to as a wedged multilayer Laue lens). This lens was constructed using a new deposition technique that enabled the independent control of the angle and thickness of diffracting layers to microradian and nanometer precision, respectively. This ensured that the Bragg condition is satisfied at each point along the lens, leading to a high numerical aperture that is limited only by its extent. We developed a phase-shifting interferometric method based on ptychography to characterise the lens focus. The precision of the fabrication and characterisation demonstrated here provides the path to efficient X-ray optics for imaging at 1 nm resolution.

  9. Analysis of synthetic aperture radar imagery

    NASA Technical Reports Server (NTRS)

    Blanchard, B. J.

    1977-01-01

    Some problems faced in applications of radar measurements in hydrology are: (1) adequate calibration of the radar systems and direct digital data will be required in order that repeatable data can be acquired for hydrologic applications; (2) quantitative hydrologic research on a large scale will be prohibitive with aircraft mounted synthetic aperture radar systems due to the system geometry; (3) spacecraft platforms appear to be the best platforms for radar systems when conducting research over watersheds larger than a few square kilometers; (4) experimental radar systems should be designed to avoid use of radomes; and (5) cross polarized X and L band data seem to discriminate between good and poor hydrologic cover better than like polarized data.

  10. Shutter/aperture settings for aerial photography

    NASA Technical Reports Server (NTRS)

    Lockwood, H. E.; Perry, L.

    1976-01-01

    Determination of aerial camera shutter and aperture settings to produce consistently high-quality aerial photographs is a task complicated by numerous variables. Presented in this article are brief discussions of each variable and specific data which may be used for the systematic control of each. The variables discussed include sunlight, aircraft altitude, subject and season, film speed, and optical system. Data which may be used as a base reference are included, and encompass two sets of sensitometric specifications for two film-chemistry processes along with camera-aircraft parameters, which have been established and used to produce good exposures. Information contained here may be used to design and implement an exposure-determination system for aerial photography.

  11. Wireless Communications in Smart Grid

    NASA Astrophysics Data System (ADS)

    Bojkovic, Zoran; Bakmaz, Bojan

    Communication networks play a crucial role in smart grid, as the intelligence of this complex system is built based on information exchange across the power grid. Wireless communications and networking are among the most economical ways to build the essential part of the scalable communication infrastructure for smart grid. In particular, wireless networks will be deployed widely in the smart grid for automatic meter reading, remote system and customer site monitoring, as well as equipment fault diagnosing. With an increasing interest from both the academic and industrial communities, this chapter systematically investigates recent advances in wireless communication technology for the smart grid.

  12. Dynamic aperture effects due to linear coupling

    SciTech Connect

    Parzen, G.

    1991-01-01

    The coupling introduced by the random a{sub 1} can produce considerable distortion of the betatron motion. For a given initial x{sub o}, x{sub o}{prime}, y{sub o}, y{sub o}{prime}, the maximum x and the maximum y for the subsequent motion can be considerably larger when coupling is present. The maximum x and y can be used as a measure of the betatron distortion. One effect of this betatron distortion shows up in the dynamic aperture, in a loss in the stability limit, A{sub SL}, found by tracking. The betatron distortion causes the particle to move further out in the magnets, where it sees stronger non-linear fields. Previous tracking showed a loss in A{sub SL} due to random a{sub 1} and b{sub 1}. It was noticed then that the loss in A{sub SL} was associated with a betatron motion distortion which was primarily a linear effect. For a given initial x, x{prime}, y, y{prime} the x{sub max} and y{sub max} in the high-{Beta} magnets were considerably larger for those random a{sub 1} distributions which produced the smaller A{sub SL}. The studies described in this report show that the stability limit, A{sub SL}, depends on the starting location around the ring. This variation in A{sub SL} around the ring can be correlated with the variation in the betatron distortion for particles starting at different places around the ring. It is proposed that the average of the A{sub SL} found by starting at each of the QF, the focusing quadrupoles in the arcs, can be taken as a measure of the dynamic aperture. It is found that the average A{sub SL} is reduced by about 15% by the random a{sub 1} multipoles expected in RHIC.

  13. TRMM Gridded Text Products

    NASA Technical Reports Server (NTRS)

    Stocker, Erich Franz

    2007-01-01

    NASA's Tropical Rainfall Measuring Mission (TRMM) has many products that contain instantaneous or gridded rain rates often among many other parameters. However, these products because of their completeness can often seem intimidating to users just desiring surface rain rates. For example one of the gridded monthly products contains well over 200 parameters. It is clear that if only rain rates are desired, this many parameters might prove intimidating. In addition, for many good reasons these products are archived and currently distributed in HDF format. This also can be an inhibiting factor in using TRMM rain rates. To provide a simple format and isolate just the rain rates from the many other parameters, the TRMM product created a series of gridded products in ASCII text format. This paper describes the various text rain rate products produced. It provides detailed information about parameters and how they are calculated. It also gives detailed format information. These products are used in a number of applications with the TRMM processing system. The products are produced from the swath instantaneous rain rates and contain information from the three major TRMM instruments: radar, radiometer, and combined. They are simple to use, human readable, and small for downloading.

  14. 3D Structured Grid Adaptation

    NASA Technical Reports Server (NTRS)

    Banks, D. W.; Hafez, M. M.

    1996-01-01

    Grid adaptation for structured meshes is the art of using information from an existing, but poorly resolved, solution to automatically redistribute the grid points in such a way as to improve the resolution in regions of high error, and thus the quality of the solution. This involves: (1) generate a grid vis some standard algorithm, (2) calculate a solution on this grid, (3) adapt the grid to this solution, (4) recalculate the solution on this adapted grid, and (5) repeat steps 3 and 4 to satisfaction. Steps 3 and 4 can be repeated until some 'optimal' grid is converged to but typically this is not worth the effort and just two or three repeat calculations are necessary. They also may be repeated every 5-10 time steps for unsteady calculations.

  15. Frequency Diversity for Improving Synthetic Aperture Radar Imaging

    DTIC Science & Technology

    2009-03-01

    xiii List of Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvi I. Introduction ...Improving Synthetic Aperture Radar Imaging I. Introduction 1.1 Research Motivation Synthetic aperture radar (SAR) is an active radio frequency (RF) imaging...PFA) begins with introduction of the linear frequency modulated (LFM) waveform. LFM is the most common waveform used in general radar applications [25

  16. Fraunhofer Diffraction Patterns from Apertures Illuminated with Nonparallel Light.

    ERIC Educational Resources Information Center

    Klingsporn, Paul E.

    1979-01-01

    Discusses several aspects of Fraunhofer diffraction patterns from apertures illuminated by diverging light. Develops a generalization to apertures of arbitrary shape which shows that the sizes of the pattern are related by a simple scale factor. Uses the Abbe theory of image formation by diffraction to discuss the intensity of illumination of the…

  17. Phenomenology of electromagnetic coupling: Conductors penetrating an aperture

    SciTech Connect

    Wright, D.B.; King, R.J.

    1987-06-01

    The purpose of this study was to investigate the coupling effects of penetrating conductors through free-standing apertures. This penetrating conductor and aperture arrangement are referred to as a modified aperture. A penetrating conductor is defined here to be a thin, single wire bent twice at 90 angles. The wire was inserted through a rectangular aperture in a metal wall. Vertical segments on both sides of the wall coupled energy from one region to the other. Energy was incident upon the modified aperture from what is referred to as the exterior region. The amount of coupling was measured by a D sensor on the other (interior) side of the wall. This configuration of an aperture in a metal wall was used as opposed to an aperture in a cavity in order to simplify the interpretation of resulting data. The added complexity of multiple cavity resonances was therefore eliminated. Determining the effects of penetrating conductors on aperture coupling is one of several topics being investigated as part of on-going research at Lawrence Livermore National Laboratory on the phenomenology of electromagnetic coupling. These phenomenology studies are concerned with the vulnerability of electronic systems to high intensity electromagnetic fields. The investigation is relevant to high altitude EMP (HEMP), enhanced HEMP (EHEMP), and high power microwave (HPM) coupling.

  18. Possible Influence of Aperture Heating on VIRGO Radiometry on SOHO

    NASA Astrophysics Data System (ADS)

    Frohlich, C.

    2010-12-01

    The early increase, first observed by the PMO6V radiometer on VIRGO/SOHO, indicates that aperture heating may be a problem for solar radiometry, not only in space, but also on ground. Heating of the precision aperture in front of the receiver cavity increases the irradiance in proportion to the incoming solar radiation and the emitted radiation from the aperture is added to the irradiance measured. Similar effects are also observed in ACRIMs and the HF on NIMBUS-7 and seem to be inherent to radiometers with the precision aperture directly in front of the cavity and the view limiting one at some distance in front. With this arrangement the precision aperture is illuminated during the measurement phase only and the measured irradiance increased accordingly. In TIM on SORCE the precision aperture is in front of the radiometer and the cavity entrance area determines the view angle. This avoids the influence of aperture heating and it may explain - at least part of - the fact that TIM measures lower values than the classical radiometers. Experimentally this effect is very difficult to determine directly and the result of thermal-model calculations and air-vacuum ratios with different amount of aperture heating are used to learn more about the magnitude of this effect. An estimate of this effect for the PMO6V/VIRGO instrument is presented.

  19. The sonar aperture and its neural representation in bats.

    PubMed

    Heinrich, Melina; Warmbold, Alexander; Hoffmann, Susanne; Firzlaff, Uwe; Wiegrebe, Lutz

    2011-10-26

    As opposed to visual imaging, biosonar imaging of spatial object properties represents a challenge for the auditory system because its sensory epithelium is not arranged along space axes. For echolocating bats, object width is encoded by the amplitude of its echo (echo intensity) but also by the naturally covarying spread of angles of incidence from which the echoes impinge on the bat's ears (sonar aperture). It is unclear whether bats use the echo intensity and/or the sonar aperture to estimate an object's width. We addressed this question in a combined psychophysical and electrophysiological approach. In three virtual-object playback experiments, bats of the species Phyllostomus discolor had to discriminate simple reflections of their own echolocation calls differing in echo intensity, sonar aperture, or both. Discrimination performance for objects with physically correct covariation of sonar aperture and echo intensity ("object width") did not differ from discrimination performances when only the sonar aperture was varied. Thus, the bats were able to detect changes in object width in the absence of intensity cues. The psychophysical results are reflected in the responses of a population of units in the auditory midbrain and cortex that responded strongest to echoes from objects with a specific sonar aperture, regardless of variations in echo intensity. Neurometric functions obtained from cortical units encoding the sonar aperture are sufficient to explain the behavioral performance of the bats. These current data show that the sonar aperture is a behaviorally relevant and reliably encoded cue for object size in bat sonar.

  20. Wave-Coherence Measurements Using Synthetic-Aperture Radar

    DTIC Science & Technology

    2000-09-30

    3473-3482, 1997. PUBLICATIONS Walker, D.T., Lyzenga, D.R. & Renouf , M.A. Characterizing wave coherence with satellite-based synthetic aperture radar...Res. (2000). Walker, D.T., Lyzenga, D.R. & Renouf , M.A. Characterizing wave coherence with satellite-based synthetic aperture radar. Proceedings of

  1. Synthetic aperture design for increased SAR image rate

    SciTech Connect

    Bielek, Timothy P.; Thompson, Douglas G.; Walker, Bruce C.

    2009-03-03

    High resolution SAR images of a target scene at near video rates can be produced by using overlapped, but nevertheless, full-size synthetic apertures. The SAR images, which respectively correspond to the apertures, can be analyzed in sequence to permit detection of movement in the target scene.

  2. Progress in Grid Generation: From Chimera to DRAGON Grids

    NASA Technical Reports Server (NTRS)

    Liou, Meng-Sing; Kao, Kai-Hsiung

    1994-01-01

    Hybrid grids, composed of structured and unstructured grids, combines the best features of both. The chimera method is a major stepstone toward a hybrid grid from which the present approach is evolved. The chimera grid composes a set of overlapped structured grids which are independently generated and body-fitted, yielding a high quality grid readily accessible for efficient solution schemes. The chimera method has been shown to be efficient to generate a grid about complex geometries and has been demonstrated to deliver accurate aerodynamic prediction of complex flows. While its geometrical flexibility is attractive, interpolation of data in the overlapped regions - which in today's practice in 3D is done in a nonconservative fashion, is not. In the present paper we propose a hybrid grid scheme that maximizes the advantages of the chimera scheme and adapts the strengths of the unstructured grid while at the same time keeps its weaknesses minimal. Like the chimera method, we first divide up the physical domain by a set of structured body-fitted grids which are separately generated and overlaid throughout a complex configuration. To eliminate any pure data manipulation which does not necessarily follow governing equations, we use non-structured grids only to directly replace the region of the arbitrarily overlapped grids. This new adaptation to the chimera thinking is coined the DRAGON grid. The nonstructured grid region sandwiched between the structured grids is limited in size, resulting in only a small increase in memory and computational effort. The DRAGON method has three important advantages: (1) preserving strengths of the chimera grid; (2) eliminating difficulties sometimes encountered in the chimera scheme, such as the orphan points and bad quality of interpolation stencils; and (3) making grid communication in a fully conservative and consistent manner insofar as the governing equations are concerned. To demonstrate its use, the governing equations are

  3. Mean Performance Optimization of an Orbiting Distributed Aperture by Warped Aperture Image Plane Comparisons

    DTIC Science & Technology

    2002-09-01

    7-6 v Page 7.4 Viewing Geometry Effects on Io(ξ, η) . . . . . . . . . . . . . 7-10 7.5 Optimized Formations for Inertial... Effects of Each Aligning Rotation on Receiver Loci . . . . . . . . . 7-11 7.6. Effects of Each Aligning Rotation on Io(ξ, η)? . . . . . . . . . . . . 7-11...this solution to include the effects of non-ideal viewing geometries. xvi MEAN PERFORMANCE OPTIMIZATION OF AN ORBITING DISTRIBUTED APERTURE BY WARPED

  4. GridTool: A surface modeling and grid generation tool

    NASA Technical Reports Server (NTRS)

    Samareh-Abolhassani, Jamshid

    1995-01-01

    GridTool is designed around the concept that the surface grids are generated on a set of bi-linear patches. This type of grid generation is quite easy to implement, and it avoids the problems associated with complex CAD surface representations and associated surface parameterizations. However, the resulting surface grids are close to but not on the original CAD surfaces. This problem can be alleviated by projecting the resulting surface grids onto the original CAD surfaces. GridTool is designed primary for unstructured grid generation systems. Currently, GridTool supports VGRID and FELISA systems, and it can be easily extended to support other unstructured grid generation systems. The data in GridTool is stored parametrically so that once the problem is set up, one can modify the surfaces and the entire set of points, curves and patches will be updated automatically. This is very useful in a multidisciplinary design and optimization process. GridTool is written entirely in ANSI 'C', the interface is based on the FORMS library, and the graphics is based on the GL library. The code has been tested successfully on IRIS workstations running IRIX4.0 and above. The memory is allocated dynamically, therefore, memory size will depend on the complexity of geometry/grid. GridTool data structure is based on a link-list structure which allows the required memory to expand and contract dynamically according to the user's data size and action. Data structure contains several types of objects such as points, curves, patches, sources and surfaces. At any given time, there is always an active object which is drawn in magenta, or in their highlighted colors as defined by the resource file which will be discussed later.

  5. Smart Grid Risk Management

    NASA Astrophysics Data System (ADS)

    Abad Lopez, Carlos Adrian

    Current electricity infrastructure is being stressed from several directions -- high demand, unreliable supply, extreme weather conditions, accidents, among others. Infrastructure planners have, traditionally, focused on only the cost of the system; today, resilience and sustainability are increasingly becoming more important. In this dissertation, we develop computational tools for efficiently managing electricity resources to help create a more reliable and sustainable electrical grid. The tools we present in this work will help electric utilities coordinate demand to allow the smooth and large scale integration of renewable sources of energy into traditional grids, as well as provide infrastructure planners and operators in developing countries a framework for making informed planning and control decisions in the presence of uncertainty. Demand-side management is considered as the most viable solution for maintaining grid stability as generation from intermittent renewable sources increases. Demand-side management, particularly demand response (DR) programs that attempt to alter the energy consumption of customers either by using price-based incentives or up-front power interruption contracts, is more cost-effective and sustainable in addressing short-term supply-demand imbalances when compared with the alternative that involves increasing fossil fuel-based fast spinning reserves. An essential step in compensating participating customers and benchmarking the effectiveness of DR programs is to be able to independently detect the load reduction from observed meter data. Electric utilities implementing automated DR programs through direct load control switches are also interested in detecting the reduction in demand to efficiently pinpoint non-functioning devices to reduce maintenance costs. We develop sparse optimization methods for detecting a small change in the demand for electricity of a customer in response to a price change or signal from the utility

  6. 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.

  7. Microfabricated high-bandpass foucault aperture for electron microscopy

    DOEpatents

    Glaeser, Robert; Cambie, Rossana; Jin, Jian

    2014-08-26

    A variant of the Foucault (knife-edge) aperture is disclosed that is designed to provide single-sideband (SSB) contrast at low spatial frequencies but retain conventional double-sideband (DSB) contrast at high spatial frequencies in transmission electron microscopy. The aperture includes a plate with an inner open area, a support extending from the plate at an edge of the open area, a half-circle feature mounted on the support and located at the center of the aperture open area. The radius of the half-circle portion of reciprocal space that is blocked by the aperture can be varied to suit the needs of electron microscopy investigation. The aperture is fabricated from conductive material which is preferably non-oxidizing, such as gold, for example.

  8. Measurements of Aperture Averaging on Bit-Error-Rate

    NASA Technical Reports Server (NTRS)

    Bastin, Gary L.; Andrews, Larry C.; Phillips, Ronald L.; Nelson, Richard A.; Ferrell, Bobby A.; Borbath, Michael R.; Galus, Darren J.; Chin, Peter G.; Harris, William G.; Marin, Jose A.; Burdge, Geoffrey L.; Wayne, David; Pescatore, Robert

    2005-01-01

    We report on measurements made at the Shuttle Landing Facility (SLF) runway at Kennedy Space Center of receiver aperture averaging effects on a propagating optical Gaussian beam wave over a propagation path of 1,000 in. A commercially available instrument with both transmit and receive apertures was used to transmit a modulated laser beam operating at 1550 nm through a transmit aperture of 2.54 cm. An identical model of the same instrument was used as a receiver with a single aperture that was varied in size up to 20 cm to measure the effect of receiver aperture averaging on Bit Error Rate. Simultaneous measurements were also made with a scintillometer instrument and local weather station instruments to characterize atmospheric conditions along the propagation path during the experiments.

  9. Accelerator simulation activities at the SSCL

    SciTech Connect

    Bourianoff, G.

    1992-11-01

    This paper will attempt to summarize the activities related to accelerator simulation at the SSC laboratory during the recent past. Operational simulations including injection, extraction, and correction, performance prediction of a specified lattice design, in particular, the effect of higher-order multipoles on linear aperture and the effect of power supply ripple on emittance growth in the collider, and lastly, the development and application of advanced techniques to particle tracking, e.g., parallel processing and mapping techniques will be discussed in this paper.

  10. Characterization of fracture aperture for groundwater flow and transport

    NASA Astrophysics Data System (ADS)

    Sawada, A.; Sato, H.; Tetsu, K.; Sakamoto, K.

    2007-12-01

    This paper presents experiments and numerical analyses of flow and transport carried out on natural fractures and transparent replica of fractures. The purpose of this study was to improve the understanding of the role of heterogeneous aperture patterns on channelization of groundwater flow and dispersion in solute transport. The research proceeded as follows: First, a precision plane grinder was applied perpendicular to the fracture plane to characterize the aperture distribution on a natural fracture with 1 mm of increment size. Although both time and labor were intensive, this approach provided a detailed, three dimensional picture of the pattern of fracture aperture. This information was analyzed to provide quantitative measures for the fracture aperture distribution, including JRC (Joint Roughness Coefficient) and fracture contact area ratio. These parameters were used to develop numerical models with corresponding synthetic aperture patterns. The transparent fracture replica and numerical models were then used to study how transport is affected by the aperture spatial pattern. In the transparent replica, transmitted light intensity measured by a CCD camera was used to image channeling and dispersion due to the fracture aperture spatial pattern. The CCD image data was analyzed to obtain the quantitative fracture aperture and tracer concentration data according to Lambert-Beer's law. The experimental results were analyzed using the numerical models. Comparison of the numerical models to the transparent replica provided information about the nature of channeling and dispersion due to aperture spatial patterns. These results support to develop a methodology for defining representative fracture aperture of a simplified parallel fracture model for flow and transport in heterogeneous fractures for contaminant transport analysis.

  11. XUV coherent diffraction imaging in reflection geometry with low numerical aperture.

    PubMed

    Zürch, Michael; Kern, Christian; Spielmann, Christian

    2013-09-09

    We present an experimental realization of coherent diffraction imaging in reflection geometry illuminating the sample with a laser driven high harmonic generation (HHG) based XUV source. After recording the diffraction pattern in reflection geometry, the data must be corrected before the image can be reconstructed with a hybrid-input-output (HIO) algorithm. In this paper we present a detailed investigation of sources of spoiling the reconstructed image due to the nonlinear momentum transfer, errors in estimating the angle of incidence on the sample, and distortions by placing the image off center in the computation grid. Finally we provide guidelines for the necessary parameters to realize a satisfactory reconstruction within a spatial resolution in the range of one micron for an imaging scheme with a numerical aperture NA < 0.03.

  12. Acceleration modules in linear induction accelerators

    NASA Astrophysics Data System (ADS)

    Wang, Shao-Heng; Deng, Jian-Jun

    2014-05-01

    The Linear Induction Accelerator (LIA) is a unique type of accelerator that is capable of accelerating kilo-Ampere charged particle current to tens of MeV energy. The present development of LIA in MHz bursting mode and the successful application into a synchrotron have broadened LIA's usage scope. Although the transformer model is widely used to explain the acceleration mechanism of LIAs, it is not appropriate to consider the induction electric field as the field which accelerates charged particles for many modern LIAs. We have examined the transition of the magnetic cores' functions during the LIA acceleration modules' evolution, distinguished transformer type and transmission line type LIA acceleration modules, and re-considered several related issues based on transmission line type LIA acceleration module. This clarified understanding should help in the further development and design of LIA acceleration modules.

  13. 47 CFR 25.134 - Licensing provisions for Very Small Aperture Terminal (VSAT) and C-band Small Aperture Terminal...

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... network using a code division multiple access (CDMA) technique, N is the maximum number of co-frequency... Terminal (VSAT) and C-band Small Aperture Terminal (CSAT) networks. 25.134 Section 25.134 Telecommunication...) and C-band Small Aperture Terminal (CSAT) networks. (a)(1) [Reserved] (2) Large Networks of...

  14. Grid crusher apparatus and method

    SciTech Connect

    McDaniels, J.D. Jr.

    1994-01-11

    A grid crusher apparatus and method are provided for a nuclear fuel rod consolidation system. Spacer grids are crushed within a basket which is then placed in a storage canister. The grid crusher apparatus has a ram assembly and a basket driving mechanism. The ram assembly has a sleeve ram and a central ram. The sleeve ram surrounds the central ram which is longitudinally movable within the sleeve ram. The central ram protrudes from the sleeve ram at a ram contact end and is retractable upon application of a preselected force to the central ram so that the central ram is flush with the sleeve ram at the ram contact end. The basket driving mechanism is configured to move the basket containing a spacer grid towards the ram contact end so that the spacer grid is crushed within the basket. The spacer grid is crushed by the combination of successive forces from the central ram and the sleeve ram, respectively. Essentially, the central portion of the spacer grid is crushed first, and then the remaining outer portion of the spacer grid is crushed to complete the crushing action of the spacer grid. The foregoing process is repeated for other spacer grids until the basket reaches a predetermined allowable capacity, and then the basket is stored in a storage canister. 11 figs.

  15. Evaluating the Information Power Grid using the NAS Grid Benchmarks

    NASA Technical Reports Server (NTRS)

    VanderWijngaartm Rob F.; Frumkin, Michael A.

    2004-01-01

    The NAS Grid Benchmarks (NGB) are a collection of synthetic distributed applications designed to rate the performance and functionality of computational grids. We compare several implementations of the NGB to determine programmability and efficiency of NASA's Information Power Grid (IPG), whose services are mostly based on the Globus Toolkit. We report on the overheads involved in porting existing NGB reference implementations to the IPG. No changes were made to the component tasks of the NGB can still be improved.

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

    SciTech Connect

    Mukherjee, Jayanta; McInerney, John G.

    2009-05-15

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

  17. 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

  18. The Volume Grid Manipulator (VGM): A Grid Reusability Tool

    NASA Technical Reports Server (NTRS)

    Alter, Stephen J.

    1997-01-01

    This document is a manual describing how to use the Volume Grid Manipulation (VGM) software. The code is specifically designed to alter or manipulate existing surface and volume structured grids to improve grid quality through the reduction of grid line skewness, removal of negative volumes, and adaption of surface and volume grids to flow field gradients. The software uses a command language to perform all manipulations thereby offering the capability of executing multiple manipulations on a single grid during an execution of the code. The command language can be input to the VGM code by a UNIX style redirected file, or interactively while the code is executing. The manual consists of 14 sections. The first is an introduction to grid manipulation; where it is most applicable and where the strengths of such software can be utilized. The next two sections describe the memory management and the manipulation command language. The following 8 sections describe simple and complex manipulations that can be used in conjunction with one another to smooth, adapt, and reuse existing grids for various computations. These are accompanied by a tutorial section that describes how to use the commands and manipulations to solve actual grid generation problems. The last two sections are a command reference guide and trouble shooting sections to aid in the use of the code as well as describe problems associated with generated scripts for manipulation control.

  19. Experience in grid optimization

    NASA Technical Reports Server (NTRS)

    Mastin, C. W.; Soni, B. K.; Mcclure, M. D.

    1987-01-01

    Two optimization methods for solving a variational problem in grid generation are described and evaluated. The smoothness, cell volumes, and orthogonality of the variational integrals are examined. The Jacobi-Newton iterative method is compared to the Fletcher-Reeves conjugate gradient method. It is observed that a combination of the Jacobi-Newton iteration and the direct solution of the variational problem produces an algorithm which is easy to program and requires less storage and computer time/iteration than the conjugate gradient method.

  20. TASMANIAN Sparse Grids Module

    SciTech Connect

    and Drayton Munster, Miroslav Stoyanov

    2013-09-20

    Sparse Grids are the family of methods of choice for multidimensional integration and interpolation in low to moderate number of dimensions. The method is to select extend a one dimensional set of abscissas, weights and basis functions by taking a subset of all possible tensor products. The module provides the ability to create global and local approximations based on polynomials and wavelets. The software has three components, a library, a wrapper for the library that provides a command line interface via text files ad a MATLAB interface via the command line tool.

  1. Adventures in Computational Grids

    NASA Technical Reports Server (NTRS)

    Walatka, Pamela P.; Biegel, Bryan A. (Technical Monitor)

    2002-01-01

    Sometimes one supercomputer is not enough. Or your local supercomputers are busy, or not configured for your job. Or you don't have any supercomputers. You might be trying to simulate worldwide weather changes in real time, requiring more compute power than you could get from any one machine. Or you might be collecting microbiological samples on an island, and need to examine them with a special microscope located on the other side of the continent. These are the times when you need a computational grid.

  2. 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

  3. Sequential beamforming for synthetic aperture imaging.

    PubMed

    Kortbek, Jacob; Jensen, Jørgen Arendt; Gammelmark, Kim Løkke

    2013-01-01

    Synthetic aperture sequential beamforming (SASB) is a novel technique which allows to implement synthetic aperture beamforming on a system with a restricted complexity, and without storing RF-data. The objective is to improve lateral resolution and obtain a more depth independent resolution compared to conventional ultrasound imaging. SASB is a two-stage procedure using two separate beamformers. The initial step is to construct and store a set of B-mode image lines using a single focal point in both transmit and receive. The focal points are considered virtual sources and virtual receivers making up a virtual array. The second stage applies the focused image lines from the first stage as input data, and take advantage of the virtual array in the delay and sum beamforming. The size of the virtual array is dynamically expanded and the image is dynamically focused in both transmit and receive and a range independent lateral resolution is obtained. The SASB method has been investigated using simulations in Field II and by off-line processing of data acquired with a commercial scanner. The lateral resolution increases with a decreasing F#. Grating lobes appear if F#≤2 for a linear array with λ-pitch. The performance of SASB with the virtual source at 20mm and F#=1.5 is compared with conventional dynamic receive focusing (DRF). The axial resolution is the same for the two methods. For the lateral resolution there is improvement in FWHM of at least a factor of 2 and the improvement at -40dB is at least a factor of 3. With SASB the resolution is almost constant throughout the range. For DRF the FWHM increases almost linearly with range and the resolution at -40dB is fluctuating with range. The theoretical potential improvement in SNR of SASB over DRF has been estimated. An improvement is attained at the entire range, and at a depth of 80mm the improvement is 8dB.

  4. Progress on plasma accelerators

    SciTech Connect

    Chen, P.

    1986-05-01

    Several plasma accelerator concepts are reviewed, with emphasis on the Plasma Beat Wave Accelerator (PBWA) and the Plasma Wake Field Accelerator (PWFA). Various accelerator physics issues regarding these schemes are discussed, and numerical examples on laboratory scale experiments are given. The efficiency of plasma accelerators is then revealed with suggestions on improvements. Sources that cause emittance growth are discussed briefly.

  5. Recursive Bayesian synthetic aperture geoacoustic inversion in the presence of motion dynamics.

    PubMed

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

    2014-09-01

    A low signal to noise ratio (SNR), single source/receiver, broadband, frequency-coherent matched-field inversion procedure recently has been proposed. It exploits coherently repeated transmissions to improve estimation of the geoacoustic parameters. The long observation time improves the SNR and creates a synthetic aperture due to relative source-receiver motion. To model constant velocity source/receiver horizontal motion, waveguide Doppler theory for normal modes is necessary. However, the inversion performance degrades when source/receiver acceleration exists. Furthermore processing a train of pulses all at once does not take advantage of the natural incremental acquisition of data along with the ability to assess the temporal evolution of parameter uncertainty. Here a recursive Bayesian estimation approach is developed that coherently processes the data pulse by pulse and incrementally updates estimates of parameter uncertainty. It also approximates source/receiver acceleration by assuming piecewise constant but linearly changing source/receiver velocities. When the source/receiver acceleration exists, it is shown that modeling acceleration can reduce further the parameter estimation biases and uncertainties. The method is demonstrated in simulation and in the analysis of low SNR, 100-900 Hz linear frequency modulated (LFM) pulses from the Shallow Water 2006 experiment.

  6. 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.

  7. 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.

  8. Empower your Smart Grid Transformation

    DTIC Science & Technology

    2016-06-13

    TWITTER: #seiwebinar © 2011 Carnegie Mellon University Empower your Smart Grid Transformation David White SGMM Project Manager 10 March 2011 Report...2011 2. REPORT TYPE 3. DATES COVERED 00-00-2011 to 00-00-2011 4. TITLE AND SUBTITLE Empower your Smart Grid Transformation 5a. CONTRACT NUMBER...and a core development team member for the SEI Smart Grid Maturity Model (SGMM), a business tool to assist utilities with planning and tracking

  9. A multigrid method for steady Euler equations on unstructured adaptive grids

    NASA Technical Reports Server (NTRS)

    Riemslagh, Kris; Dick, Erik

    1993-01-01

    A flux-difference splitting type algorithm is formulated for the steady Euler equations on unstructured grids. The polynomial flux-difference splitting technique is used. A vertex-centered finite volume method is employed on a triangular mesh. The multigrid method is in defect-correction form. A relaxation procedure with a first order accurate inner iteration and a second-order correction performed only on the finest grid, is used. A multi-stage Jacobi relaxation method is employed as a smoother. Since the grid is unstructured a Jacobi type is chosen. The multi-staging is necessary to provide sufficient smoothing properties. The domain is discretized using a Delaunay triangular mesh generator. Three grids with more or less uniform distribution of nodes but with different resolution are generated by successive refinement of the coarsest grid. Nodes of coarser grids appear in the finer grids. The multigrid method is started on these grids. As soon as the residual drops below a threshold value, an adaptive refinement is started. The solution on the adaptively refined grid is accelerated by a multigrid procedure. The coarser multigrid grids are generated by successive coarsening through point removement. The adaption cycle is repeated a few times. Results are given for the transonic flow over a NACA-0012 airfoil.

  10. Tissue harmonic synthetic aperture ultrasound imaging.

    PubMed

    Hemmsen, Martin Christian; Rasmussen, Joachim Hee; Jensen, Jørgen Arendt

    2014-10-01

    Synthetic aperture sequential beamforming (SASB) and tissue harmonic imaging (THI) are combined to improve the image quality of medical ultrasound imaging. The technique is evaluated in a comparative study against dynamic receive focusing (DRF). The objective is to investigate if SASB combined with THI improves the image quality compared to DRF-THI. The major benefit of SASB is a reduced bandwidth between the probe and processing unit. A BK Medical 2202 Ultraview ultrasound scanner was used to acquire beamformed RF data for offline evaluation. The acquisition was made interleaved between methods, and data were recorded with and without pulse inversion for tissue harmonic imaging. Data were acquired using a Sound Technology 192 element convex array transducer from both a wire phantom and a tissue mimicking phantom to investigate spatial resolution and penetration. In vivo scans were also performed for a visual comparison. The spatial resolution for SASB-THI is on average 19% better than DRI-THI, and the investigation of penetration showed equally good signal-to-noise ratio. In vivo B-mode scans were made and compared. The comparison showed that SASB-THI reduces the artifact and noise interference and improves image contrast and spatial resolution.

  11. Multistatic synthetic aperture radar image formation.

    PubMed

    Krishnan, V; Swoboda, J; Yarman, C E; Yazici, B

    2010-05-01

    In this paper, we consider a multistatic synthetic aperture radar (SAR) imaging scenario where a swarm of airborne antennas, some of which are transmitting, receiving or both, are traversing arbitrary flight trajectories and transmitting arbitrary waveforms without any form of multiplexing. The received signal at each receiving antenna may be interfered by the scattered signal due to multiple transmitters and additive thermal noise at the receiver. In this scenario, standard bistatic SAR image reconstruction algorithms result in artifacts in reconstructed images due to these interferences. In this paper, we use microlocal analysis in a statistical setting to develop a filtered-backprojection (FBP) type analytic image formation method that suppresses artifacts due to interference while preserving the location and orientation of edges of the scene in the reconstructed image. Our FBP-type algorithm exploits the second-order statistics of the target and noise to suppress the artifacts due to interference in a mean-square sense. We present numerical simulations to demonstrate the performance of our multistatic SAR image formation algorithm with the FBP-type bistatic SAR image reconstruction algorithm. While we mainly focus on radar applications, our image formation method is also applicable to other problems arising in fields such as acoustic, geophysical and medical imaging.

  12. FASS: the full aperture seeing sensor

    NASA Astrophysics Data System (ADS)

    Guesalaga, A.; Perera, S.; Osborn, J.; Sarazin, M.; Neichel, B.; Wilson, R.

    2016-07-01

    We describe a novel technique atmospheric turbulence monitoring called FASS (full aperture seeing sensor) based on a low noise CCD detector. The method uses a Fourier processing approach that estimates the spatial frequency distribution of the scintillation images. This frequency approach samples the propagated images along pupil rings, making the frequency transformation circular, avoiding distortions due to the finite nature of the data. It is shown that aspects such as detector exposure time, opto-mechanical stability, detailed modelling of propagation, noise and star chromaticity, must be carefully addressed during the design and calibration stages. Although only ground conjugation results are presented in this article, the technique is expected to operate in the generalized mode guaranteeing sufficiently large speckles (larger than the detector pixels). Pixel gains and offsets are effectively corrected, so they don't significantly influence the accuracy of the profile estimation. Temporal correlations are also shown to provide complementary information not only on the layer wind velocity, but a coarse estimation of their altitude. Factors limiting the accuracy of the method, such as chromaticity, turbulence strength, exposure time and vibrations are discussed. The method provides excellent performance in simulations and encouraging preliminary results from on-sky images acquired and Paranal, Chile. Comparison to coetaneous profiles estimated with the Durham Stereo-SCIDAR instrument (DSS) are analysed.

  13. Synthetic-Aperture Silhouette Imaging (SASI)

    NASA Astrophysics Data System (ADS)

    Paxman, R.

    2016-09-01

    The problem of ground-based fine-resolution imaging of geosynchronous satellites continues to be an important unsolved space-surveillance problem. We are investigating a passive-illumination approach that is radically different from amplitude, intensity, or heterodyne interferometry approaches. The approach, called Synthetic-Aperture Silhouette Imaging (SASI), produces a fine-resolution image of the satellite silhouette. When plane-wave radiation emanating from a bright star is occluded by a GEO satellite, then the light is diffracted and a moving diffraction pattern (shadow) is cast on the surface of the earth. With prior knowledge of the satellite orbit and star location, the track of the moving shadow can be predicted with high precision. A linear array of inexpensive hobby telescopes can be deployed roughly perpendicular to the shadow track to collect a time history of the star intensity as the shadow passes by. A phase-retrieval algorithm, using the strong constraint that the occlusion of the satellite is a binary-valued silhouette, allows us to retrieve the missing phase and reconstruct a fine-resolution image of the silhouette. Silhouettes are highly informative, providing diagnostic information about deployment of antennas and solar panels, enabling satellite pose estimation, and revealing the presence and orientation of neighboring satellites in rendezvous and proximity operations.

  14. Role of hysteresis in stomatal aperture dynamics

    NASA Astrophysics Data System (ADS)

    Ramos, Antônio M. T.; Prado, Carmen P. C.

    2013-01-01

    Stomata are pores responsible for gas exchange in leaves. Several experiments indicate that stomata synchronize into clusters or patches. The patches’ coordination may produce oscillations in stomatal conductance. Previous studies claim to reproduce some experimental results. However, none was able to explain the variety of behavior observed in the stomatal dynamics. Recently, Ferraz and Prado suggested a realistic geometry of vein distribution. Although it reproduces the patches, no oscillation was observed and the patches remain static. Without exploring significant details, the authors stated that hysteresis in stomatal aperture could explain several experimental features. In this paper, the hysteresis hypothesis is further explored through the concept of hysteretic operators. We have shown that the hysteresis assumption is sufficient to obtain dynamical patches and oscillations in stomatal conductance. The robustness of this hypothesis is tested by using different hysteresis operators. The model analysis reveals a dependence between the period of oscillation in stomatal conductance and the water deficit between the leaf and the environment. This underlying feature of the model might inspire further experiments to test this hypothesis.

  15. High numerical aperture multilayer Laue lenses

    PubMed Central

    Morgan, Andrew J.; Prasciolu, Mauro; Andrejczuk, Andrzej; Krzywinski, Jacek; Meents, Alke; Pennicard, David; Graafsma, Heinz; Barty, Anton; Bean, Richard J.; Barthelmess, Miriam; Oberthuer, Dominik; Yefanov, Oleksandr; Aquila, Andrew; Chapman, Henry N.; Bajt, Saša

    2015-01-01

    The ever-increasing brightness of synchrotron radiation sources demands improved X-ray optics to utilise their capability for imaging and probing biological cells, nanodevices, and functional matter on the nanometer scale with chemical sensitivity. Here we demonstrate focusing a hard X-ray beam to an 8 nm focus using a volume zone plate (also referred to as a wedged multilayer Laue lens). This lens was constructed using a new deposition technique that enabled the independent control of the angle and thickness of diffracting layers to microradian and nanometer precision, respectively. This ensured that the Bragg condition is satisfied at each point along the lens, leading to a high numerical aperture that is limited only by its extent. We developed a phase-shifting interferometric method based on ptychography to characterise the lens focus. The precision of the fabrication and characterisation demonstrated here provides the path to efficient X-ray optics for imaging at 1 nm resolution. PMID:26030003

  16. Motion measurement for synthetic aperture radar

    SciTech Connect

    Doerry, Armin W.

    2015-01-01

    Synthetic Aperture Radar (SAR) measures radar soundings from a set of locations typically along the flight path of a radar platform vehicle. Optimal focusing requires precise knowledge of the sounding source locations in 3-D space with respect to the target scene. Even data driven focusing techniques (i.e. autofocus) requires some degree of initial fidelity in the measurements of the motion of the radar. These requirements may be quite stringent especially for fine resolution, long ranges, and low velocities. The principal instrument for measuring motion is typically an Inertial Measurement Unit (IMU), but these instruments have inherent limi ted precision and accuracy. The question is %22How good does an IMU need to be for a SAR across its performance space?%22 This report analytically relates IMU specifications to parametric requirements for SAR. - 4 - Acknowledgements Th e preparation of this report is the result of a n unfunded research and development activity . Although this report is an independent effort, it draws heavily from limited - release documentation generated under a CRADA with General Atomics - Aeronautical System, Inc. (GA - ASI), and under the Joint DoD/DOE Munitions Program Memorandum of Understanding. Sandia National Laboratories is a multi - program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of En ergy's National Nuclear Security Administration under contract AC04-94AL85000.

  17. High-aperture cryogenic light microscopy.

    PubMed

    Le Gros, M A; McDermott, G; Uchida, M; Knoechel, C G; Larabell, C A

    2009-07-01

    We report here the development of instruments and protocols for carrying out high numerical aperture immersion light microscopy on cryogenic specimens. Imaging by this modality greatly increases the lifetimes of fluorescence probes, including those commonly used for protein localization studies, while retaining the ability to image the specimen with high fidelity and spatial resolution. The novel use of a cryogenic immersion fluid also minimizes the refractive index mismatch between the sample and lens, leading to a more efficient coupling of the light from the sample to the image forming system. This enhancement is applicable to both fluorescence and transmitted light microscopy techniques. The design concepts used for the cryogenic microscope can be applied to virtually any existing light-based microscopy technique. This prospect is particularly exciting in the context of 'super-resolution' techniques, where enhanced fluorescence lifetime probes are especially useful. Thus, using this new modality it is now possible to observe dynamic events in a live cell, and then rapidly vitrify the specimen at a specific time point prior to carrying out high-resolution imaging. The techniques described can be used in conjunction with other imaging modalities in correlated studies. We have also developed instrumentation to perform cryo-light imaging together with soft X-ray tomography on the same cryo-fixed specimen as a means of carrying out high content, quantifiable correlated imaging analyses. These methods are equally applicable to correlated light and electron microscopy of frozen biological objects.

  18. High numerical aperture multilayer Laue lenses

    DOE PAGES

    Morgan, Andrew J.; Prasciolu, Mauro; Andrejczuk, Andrzej; ...

    2015-06-01

    The ever-increasing brightness of synchrotron radiation sources demands improved X-ray optics to utilise their capability for imaging and probing biological cells, nanodevices, and functional matter on the nanometer scale with chemical sensitivity. Here we demonstrate focusing a hard X-ray beam to an 8 nm focus using a volume zone plate (also referred to as a wedged multilayer Laue lens). This lens was constructed using a new deposition technique that enabled the independent control of the angle and thickness of diffracting layers to microradian and nanometer precision, respectively. This ensured that the Bragg condition is satisfied at each point along themore » lens, leading to a high numerical aperture that is limited only by its extent. We developed a phase-shifting interferometric method based on ptychography to characterise the lens focus. The precision of the fabrication and characterisation demonstrated here provides the path to efficient X-ray optics for imaging at 1 nm resolution.« less

  19. Optical aperture synthesis with electronically connected telescopes

    PubMed Central

    Dravins, Dainis; Lagadec, Tiphaine; Nuñez, Paul D.

    2015-01-01

    Highest resolution imaging in astronomy is achieved by interferometry, connecting telescopes over increasingly longer distances and at successively shorter wavelengths. Here, we present the first diffraction-limited images in visual light, produced by an array of independent optical telescopes, connected electronically only, with no optical links between them. With an array of small telescopes, second-order optical coherence of the sources is measured through intensity interferometry over 180 baselines between pairs of telescopes, and two-dimensional images reconstructed. The technique aims at diffraction-limited optical aperture synthesis over kilometre-long baselines to reach resolutions showing details on stellar surfaces and perhaps even the silhouettes of transiting exoplanets. Intensity interferometry circumvents problems of atmospheric turbulence that constrain ordinary interferometry. Since the electronic signal can be copied, many baselines can be built up between dispersed telescopes, and over long distances. Using arrays of air Cherenkov telescopes, this should enable the optical equivalent of interferometric arrays currently operating at radio wavelengths. PMID:25880705

  20. A synthetic aperture acoustic prototype system

    NASA Astrophysics Data System (ADS)

    Luke, Robert H.; Bishop, Steven S.; Chan, Aaron M.; Gugino, Peter M.; Donzelli, Thomas P.; Soumekh, Mehrdad

    2015-05-01

    A novel quasi-monostatic system operating in a side-scan synthetic aperture acoustic (SAA) imaging mode is presented. This research project's objectives are to explore the military utility of outdoor continuous sound imaging of roadside foliage and target detection. The acoustic imaging method has several military relevant advantages such as being immune to RF jamming, superior spatial resolution as compared to 0.8-2.4 GHz ground penetrating radar (GPR), capable of standoff side and forward-looking scanning, and relatively low cost, weight and size when compared to GPR technologies. The prototype system's broadband 2-17 kHz LFM chirp transceiver is mounted on a manned all-terrain vehicle. Targets are positioned within the acoustic main beam at slant ranges of two to seven meters and on surfaces such as dirt, grass, gravel and weathered asphalt and with an intervening metallic chain link fence. Acoustic image reconstructions and signature plots result in means for literal interpretation and quantifiable analyses.

  1. Radar aperture synthesis observations of asteroids

    NASA Technical Reports Server (NTRS)

    De Pater, Imke; Palmer, Patrick; Mitchell, David L.; Ostro, Steven J.; Yeomens, Donald K.; Snyder, Lewis E.

    1994-01-01

    We report of Goldstone-VLA, radar aperture-synthesis observations of the mainbelt asteroids 324 Bamberga and 7 Iris and the near-Earth asteroids 1991 EE and 4179 Toutatis. Simultaneous resolution of echoes in both angle and Doppler frequency provide new constraints on the mainbelt asteroids' pole directions: Bamberga's spin vector is within 40 deg of the south ecliptic pole, and the twofold ambiguity in Iris' pole direction (P. Magnusson, 1989) is resolved in favor of the ecliptic coordinates lambda = 15 deg, beta = +25 deg. For Bamberga, monostatic and bistatic radar echoes and VLA thermal-emission measurements, also reported here, are consistent with radiometric estimates of Bamberga's size and with the hypothesis that the asteroid is overlain by a regolith having a porosity of approximately 50%. Our near-Earth asteroid measurements required the development of new on-line VLA software that allows imaging of objects that are in the telescope's `near field.' This software has been successfully tested on Toutatis at a distance of 0.06 AU and will be essential for VLA observations of Earth-approaching comets.

  2. SU-E-T-348: Effect of Treatment Table and Immobilization Devices On Surface Dose When Using a GRID Technique

    SciTech Connect

    Gajdos, S; Donaghue, J

    2015-06-15

    Purpose: To determine the increase of surface dose of MLC-designed GRID therapy in the presence of immobilization devices and treatment table. Methods: To create a GRID field, our facility utilizes an MLC consisting of four millimeter wide leaves. The field is designed to have aperture sizes of 0.8 cm X 0.8 cm with inter-aperture distance of 3.2 cm. Gafchromic EBT3 film was placed between the surface of a solid water phantom and the immobilization device. The treatment table was also present within the beam path. The devices consist of carbon fiber exterior shell. A piece of film was also placed at maximal depth for the photon energy of 10 MV. Image files were converted to dose per a calibration curve based on the selected red channel. The surface dose to maximum dose was established by comparing the ratio of seven centrally located aperture regions-of-interest and four adjacent inter-aperture regions-of-interest were measured with the available software tools. Results: With no devices present in beam path, the ratio of surface dose to maximum dose was 11.5% ± 0.3% for aperture region and 7.0% ± 0.1% for inter-aperture region. When devices are present, the ratio of surface dose to maximum dose was 45.2% ± 0.5% and 33.8% ± 1.1%, respectively. Due to the presence of devices, the surface dose increases in aperture region by 3.8 times or in the inter-aperture region by 4.7 times. Conclusion: The purpose of using GRID technique is to deliver a single fractional dose in range of 15–20 Gy to a bulky lesion while also preserving skin tolerance. The increase of surface dose due to devices placed in beam path may increase the chance of skin toxicity in GRID therapy. Care should be used to determine best manageable patient immobilization while considering skin dose especially for posteriorly located lesions.

  3. Smart Grid Enabled EVSE

    SciTech Connect

    None, None

    2015-01-12

    The combined team of GE Global Research, Federal Express, National Renewable Energy Laboratory, and Consolidated Edison has successfully achieved the established goals contained within the Department of Energy’s Smart Grid Capable Electric Vehicle Supply Equipment funding opportunity. The final program product, shown charging two vehicles in Figure 1, reduces by nearly 50% the total installed system cost of the electric vehicle supply equipment (EVSE) as well as enabling a host of new Smart Grid enabled features. These include bi-directional communications, load control, utility message exchange and transaction management information. Using the new charging system, Utilities or energy service providers will now be able to monitor transportation related electrical loads on their distribution networks, send load control commands or preferences to individual systems, and then see measured responses. Installation owners will be able to authorize usage of the stations, monitor operations, and optimally control their electricity consumption. These features and cost reductions have been developed through a total system design solution.

  4. Does the electric power grid need a room temperature superconductor?

    NASA Astrophysics Data System (ADS)

    Malozemoff, A. P.

    2013-11-01

    Superconductivity can revolutionize electric power grids, for example with high power underground cables to open urban power bottlenecks and fault current limiters to solve growing fault currents problems. Technology based on high temperature superconductor (HTS) wire is beginning to meet these critical needs. Wire performance is continually improving. For example, American Superconductor has recently demonstrated long wires with up to 500 A/cm-width at 77 K, almost doubling its previous production performance. But refrigeration, even at 77 K, is a complication, driving interest in discovering room temperature superconductors (RTS). Unfortunately, short coherence lengths and accelerated flux creep will make RTS applications unlikely. Existing HTS technology, in fact, offers a good compromise of relatively high operating temperature but not so high as to incur coherence-length and flux-creep limitations. So - no, power grids do not need RTS; existing HTS wire is proving to be what grids really need.

  5. Measurement and simulation of apertures on Z hohlraums

    SciTech Connect

    Chrien, R.E.; Matuska, W. Jr.; Swenson, F.J.

    1998-12-01

    The authors have performed aperture measurements and simulations for vacuum hohlraums heated by wire array implosions. A low-Z plastic coating is often applied to the aperture to create a high ablation pressure which retards the expansion of the gold hohlraum wall. However, this interface is unstable and may be subjects to the development of highly nonlinear perturbations (jets) as a result of shocks converging near the edge of the aperture. These experiments have been simulated using Lagrangian and Eulerian radiation hydrodynamics codes.

  6. Electromagnetic Formation Flight (EMFF) for Sparse Aperture Arrays

    NASA Technical Reports Server (NTRS)

    Kwon, Daniel W.; Miller, David W.; Sedwick, Raymond J.

    2004-01-01

    Traditional methods of actuating spacecraft in sparse aperture arrays use propellant as a reaction mass. For formation flying systems, propellant becomes a critical consumable which can be quickly exhausted while maintaining relative orientation. Additional problems posed by propellant include optical contamination, plume impingement, thermal emission, and vibration excitation. For these missions where control of relative degrees of freedom is important, we consider using a system of electromagnets, in concert with reaction wheels, to replace the consumables. Electromagnetic Formation Flight sparse apertures, powered by solar energy, are designed differently from traditional propulsion systems, which are based on V. This paper investigates the design of sparse apertures both inside and outside the Earth's gravity field.

  7. Terahertz interferometric synthetic aperture tomography for confocal imaging systems.

    PubMed

    Heimbeck, M S; Marks, D L; Brady, D; Everitt, H O

    2012-04-15

    Terahertz (THz) interferometric synthetic aperture tomography (TISAT) for confocal imaging within extended objects is demonstrated by combining attributes of synthetic aperture radar and optical coherence tomography. Algorithms recently devised for interferometric synthetic aperture microscopy are adapted to account for the diffraction-and defocusing-induced spatially varying THz beam width characteristic of narrow depth of focus, high-resolution confocal imaging. A frequency-swept two-dimensional TISAT confocal imaging instrument rapidly achieves in-focus, diffraction-limited resolution over a depth 12 times larger than the instrument's depth of focus in a manner that may be easily extended to three dimensions and greater depths.

  8. OGC and Grid Interoperability in enviroGRIDS Project

    NASA Astrophysics Data System (ADS)

    Gorgan, Dorian; Rodila, Denisa; Bacu, Victor; Giuliani, Gregory; Ray, Nicolas

    2010-05-01

    EnviroGRIDS (Black Sea Catchment Observation and Assessment System supporting Sustainable Development) [1] is a 4-years FP7 Project aiming to address the subjects of ecologically unsustainable development and inadequate resource management. The project develops a Spatial Data Infrastructure of the Black Sea Catchment region. The geospatial technologies offer very specialized functionality for Earth Science oriented applications as well as the Grid oriented technology that is able to support distributed and parallel processing. One challenge of the enviroGRIDS project is the interoperability between geospatial and Grid infrastructures by providing the basic and the extended features of the both technologies. The geospatial interoperability technology has been promoted as a way of dealing with large volumes of geospatial data in distributed environments through the development of interoperable Web service specifications proposed by the Open Geospatial Consortium (OGC), with applications spread across multiple fields but especially in Earth observation research. Due to the huge volumes of data available in the geospatial domain and the additional introduced issues (data management, secure data transfer, data distribution and data computation), the need for an infrastructure capable to manage all those problems becomes an important aspect. The Grid promotes and facilitates the secure interoperations of geospatial heterogeneous distributed data within a distributed environment, the creation and management of large distributed computational jobs and assures a security level for communication and transfer of messages based on certificates. This presentation analysis and discusses the most significant use cases for enabling the OGC Web services interoperability with the Grid environment and focuses on the description and implementation of the most promising one. In these use cases we give a special attention to issues such as: the relations between computational grid and

  9. High-contrast imaging with an arbitrary aperture: active correction of aperture discontinuities

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

    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. 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 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" . We show that the converging non-linear mappings resulting from our Deformable Mirror 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 strut's while not amplifying the diffraction at the aperture edges beyond the Fresnel regime and illustrate the broadband properties of ACAD in the case of the pupil configuration corresponding to the Astrophysics Focused Telescope Assets. Since details about these telescopes are not yet available to the broader astronomical community, our test case is based on a geometry mimicking the actual one, to the best of our knowledge.

  10. High-contrast Imaging with an Arbitrary Aperture: Active Compensation of Aperture Discontinuities

    NASA Astrophysics Data System (ADS)

    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 10-7 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, the

  11. 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

  12. From the grid to the smart grid, topologically

    NASA Astrophysics Data System (ADS)

    Pagani, Giuliano Andrea; Aiello, Marco

    2016-05-01

    In its more visionary acceptation, the smart grid is a model of energy management in which the users are engaged in producing energy as well as consuming it, while having information systems fully aware of the energy demand-response of the network and of dynamically varying prices. A natural question is then: to make the smart grid a reality will the distribution grid have to be upgraded? We assume a positive answer to the question and we consider the lower layers of medium and low voltage to be the most affected by the change. In our previous work, we analyzed samples of the Dutch distribution grid (Pagani and Aiello, 2011) and we considered possible evolutions of these using synthetic topologies modeled after studies of complex systems in other technological domains (Pagani and Aiello, 2014). In this paper, we take an extra important step by defining a methodology for evolving any existing physical power grid to a good smart grid model, thus laying the foundations for a decision support system for utilities and governmental organizations. In doing so, we consider several possible evolution strategies and apply them to the Dutch distribution grid. We show how increasing connectivity is beneficial in realizing more efficient and reliable networks. Our proposal is topological in nature, enhanced with economic considerations of the costs of such evolutions in terms of cabling expenses and economic benefits of evolving the grid.

  13. NAS Grid Benchmarks: A Tool for Grid Space Exploration

    NASA Technical Reports Server (NTRS)

    Frumkin, Michael; VanderWijngaart, Rob F.; Biegel, Bryan (Technical Monitor)

    2001-01-01

    We present an approach for benchmarking services provided by computational Grids. It is based on the NAS Parallel Benchmarks (NPB) and is called NAS Grid Benchmark (NGB) in this paper. We present NGB as a data flow graph encapsulating an instance of an NPB code in each graph node, which communicates with other nodes by sending/receiving initialization data. These nodes may be mapped to the same or different Grid machines. Like NPB, NGB will specify several different classes (problem sizes). NGB also specifies the generic Grid services sufficient for running the bench-mark. The implementor has the freedom to choose any specific Grid environment. However, we describe a reference implementation in Java, and present some scenarios for using NGB.

  14. Accelerator Physics Challenges for the NSLS-II Project

    SciTech Connect

    Krinsky,S.

    2009-05-04

    The NSLS-II is an ultra-bright synchrotron light source based upon a 3-GeV storage ring with a 30-cell (15 super-period) double-bend-achromat lattice with damping wigglers used to lower the emittance below 1 nm. In this paper, we discuss the accelerator physics challenges for the design including: optimization of dynamic aperture; estimation of Touschek lifetime; achievement of required orbit stability; and analysis of ring impedance and collective effects.

  15. 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

  16. Magnetically tunable broadband transmission through a single small aperture.

    PubMed

    Bi, Ke; Liu, Wenjun; Guo, Yunsheng; Dong, Guoyan; Lei, Ming

    2015-07-22

    Extraordinary transmission through a small aperture is of great interest. However, it faces a limitation that most of approaches can not realize the tunable transmission property, which is not benefit for the miniaturization of the microwave system. Here, we demonstrate a magnetically tunable broadband transmission through a small aperture. By placing two ferrite rods symmetrically on both sides of a single small aperture, the strongly localized electromagnetic fields are effectively coupled to the two ferrite rods. Both the simulated and experimental results indicate that such structure not only realizes a nearly total transmission through a small aperture, but also obtains a magnetically tunable property. This work offers new opportunities for the miniaturization of the microwave system.

  17. Synthetic aperture radar signal processing: Trends and technologies

    NASA Technical Reports Server (NTRS)

    Curlander, John C.

    1993-01-01

    An overview of synthetic aperture radar (SAR) technology is presented in vugraph form. The following topics are covered: an SAR ground data system; SAR signal processing algorithms; SAR correlator architectures; and current and future trends.

  18. Ambiguity Of Doppler Centroid In Synthetic-Aperture Radar

    NASA Technical Reports Server (NTRS)

    Chang, Chi-Yung; Curlander, John C.

    1991-01-01

    Paper discusses performances of two algorithms for resolution of ambiguity in estimated Doppler centroid frequency of echoes in synthetic-aperture radar. One based on range-cross-correlation technique, other based on multiple-pulse-repetition-frequency technique.

  19. Synthetic aperture radar range - Azimuth ambiguity design and constraints

    NASA Technical Reports Server (NTRS)

    Mehlis, J. G.

    1980-01-01

    Problems concerning the design of a system for mapping a planetary surface with a synthetic aperture radar (SAR) are considered. Given an ambiguity level, resolution, and swath width, the problems are related to the determination of optimum antenna apertures and the most suitable pulse repetition frequency (PRF). From the set of normalized azimuth ambiguity ratio curves, the designer can arrive at the azimuth antenna length, and from the sets of normalized range ambiguity ratio curves, he can arrive at the range aperture length or pulse repetition frequency. A procedure based on this design method is shown in an example. The normalized curves provide results for a SAR using a uniformly or cosine weighted rectangular antenna aperture.

  20. Photonic spin-controlled multifunctional shared-aperture antenna array

    NASA Astrophysics Data System (ADS)

    Maguid, Elhanan; Yulevich, Igor; Veksler, Dekel; Kleiner, Vladimir; Brongersma, Mark L.; Hasman, Erez

    2016-06-01

    The shared-aperture phased antenna array developed in the field of radar applications is a promising approach for increased functionality in photonics. The alliance between the shared-aperture concepts and the geometric phase phenomenon arising from spin-orbit interaction provides a route to implement photonic spin-control multifunctional metasurfaces. We adopted a thinning technique within the shared-aperture synthesis and investigated interleaved sparse nanoantenna matrices and the spin-enabled asymmetric harmonic response to achieve helicity-controlled multiple structured wavefronts such as vortex beams carrying orbital angular momentum. We used multiplexed geometric phase profiles to simultaneously measure spectrum characteristics and the polarization state of light, enabling integrated on-chip spectropolarimetric analysis. The shared-aperture metasurface platform opens a pathway to novel types of nanophotonic functionality.

  1. Magnetically tunable broadband transmission through a single small aperture

    PubMed Central

    Bi, Ke; Liu, Wenjun; Guo, Yunsheng; Dong, Guoyan; Lei, Ming

    2015-01-01

    Extraordinary transmission through a small aperture is of great interest. However, it faces a limitation that most of approaches can not realize the tunable transmission property, which is not benefit for the miniaturization of the microwave system. Here, we demonstrate a magnetically tunable broadband transmission through a small aperture. By placing two ferrite rods symmetrically on both sides of a single small aperture, the strongly localized electromagnetic fields are effectively coupled to the two ferrite rods. Both the simulated and experimental results indicate that such structure not only realizes a nearly total transmission through a small aperture, but also obtains a magnetically tunable property. This work offers new opportunities for the miniaturization of the microwave system. PMID:26198543

  2. An Adaptive Homomorphic Aperture Photometry Algorithm for Merging Galaxies

    NASA Astrophysics Data System (ADS)

    Huang, J. C.; Hwang, C. Y.

    2017-03-01

    We present a novel automatic adaptive aperture photometry algorithm for measuring the total magnitudes of merging galaxies with irregular shapes. First, we use a morphological pattern recognition routine for identifying the shape of an irregular source in a background-subtracted image. Then, we extend the shape of the source by using the Dilation image operation to obtain an aperture that is quasi-homomorphic to the shape of the irregular source. The magnitude measured from the homomorphic aperture would thus have minimal contamination from the nearby background. As a test of our algorithm, we applied our technique to the merging galaxies observed by the Sloan Digital Sky Survey and the Canada–France–Hawaii Telescope. Our results suggest that the adaptive homomorphic aperture algorithm can be very useful for investigating extended sources with irregular shapes and sources in crowded regions.

  3. Highly uniform parallel microfabrication using a large numerical aperture system

    NASA Astrophysics Data System (ADS)

    Zhang, Zi-Yu; Zhang, Chen-Chu; Hu, Yan-Lei; Wang, Chao-Wei; Li, Jia-Wen; Su, Ya-Hui; Chu, Jia-Ru; Wu, Dong

    2016-07-01

    In this letter, we report an improved algorithm to produce accurate phase patterns for generating highly uniform diffraction-limited multifocal arrays in a large numerical aperture objective system. It is shown that based on the original diffraction integral, the uniformity of the diffraction-limited focal arrays can be improved from ˜75% to >97%, owing to the critical consideration of the aperture function and apodization effect associated with a large numerical aperture objective. The experimental results, e.g., 3 × 3 arrays of square and triangle, seven microlens arrays with high uniformity, further verify the advantage of the improved algorithm. This algorithm enables the laser parallel processing technology to realize uniform microstructures and functional devices in the microfabrication system with a large numerical aperture objective.

  4. High-aperture diffractive lens for holographic printer

    NASA Astrophysics Data System (ADS)

    Zherdev, A. Y.; Odinokov, S. B.; Lushnikov, D. S.; Shishova, M. V.; Gurylev, O. A.; Kaytukov, C. B.

    2016-10-01

    The optical scheme of holographic printer for obtaining of holographic stereograms with an increasing field of view is proposed. Conventional holographic printers allow obtaining holographic stereograms with the field of view up to 90°. Proposed scheme allows increasing field of view up to 120°. The optical scheme is based on a diffuser and a diffraction optical element, the high-aperture diffractive lens. The experience of using the composite holographic lens and the amplitude diffractive lens based on a binary Fresnel zone plate as a high-aperture diffractive lens is described. Samples of high-aperture diffractive lens with f-number f/0.3 are obtained and investigated. Samples of holographic stereograms are obtained using samples of high-aperture diffractive lens.

  5. Role of Sucrose in Emerging Mechanisms of Stomatal Aperture Regulation.

    SciTech Connect

    Outlaw, W. H.

    2000-09-15

    Focused on the second of 2 hypotheses that were proposed for testing that transpiration rate determines the extent to which suc accumulates in the GC wall providing a mechanism for regulating stomatal aperture size.

  6. Detection of small, slow ground targets using Synthetic Aperture Radar

    NASA Technical Reports Server (NTRS)

    Chen, Curtis; Chapin, Elaine; Rosen, Paul

    2005-01-01

    Synthetic aperture radar (SAR) along-track interferometry (ATI) is a technique for sensing Earth-surface motion. The technique involves interferometrically combining data from two radar images acquired from phase centers separated along the platform flight track.

  7. Accelerators-Limitations of Technology A Summary of the Snowmass Accelerator Working Group Reports

    NASA Astrophysics Data System (ADS)

    Tigner, Maury

    1983-04-01

    Hadron colliders and accelerators in the 20 TeV energy range turned out to be the majority interest among active members of the Accelerator Row Group. While other types of accelerator and other energy ranges were discussed, largely on the basis of work done else-where, our primary creative activities at this summer study focused on the hadron facility. Examining both the economic and accelerator physics dimensions of such a facility, we were able to give some hope to the idea that a well designed and concentrated R/D program, elaborating much further on technologies we now possess, might bring a 20 TeV facility within our national reach. The central challenges for this R/D program appear to be 1. Achievement of virtual automation of superconducting magnet, accelerator housing and other accelerator component manufacture and installation. 2. Achievement of a thorough understanding of the field vs. cost relation for superconducting magnets. 3. Achievement of a thorough understanding of the luminosity-aperture-energy relation.

  8. The Open Science Grid

    SciTech Connect

    Pordes, Ruth; Kramer, Bill; Olson, Doug; Livny, Miron; Roy, Alain; Avery, Paul; Blackburn, Kent; Wenaus, Torre; Wurthwein, Frank; Gardner, Rob; Wilde, Mike; /Chicago U. /Indiana U.

    2007-06-01

    The Open Science Grid (OSG) provides a distributed facility where the Consortium members provide guaranteed and opportunistic access to shared computing and storage resources. OSG provides support for and evolution of the infrastructure through activities that cover operations, security, software, troubleshooting, addition of new capabilities, and support for existing and engagement with new communities. The OSG SciDAC-2 project provides specific activities to manage and evolve the distributed infrastructure and support its use. The innovative aspects of the project are the maintenance and performance of a collaborative (shared & common) petascale national facility over tens of autonomous computing sites, for many hundreds of users, transferring terabytes of data a day, executing tens of thousands of jobs a day, and providing robust and usable resources for scientific groups of all types and sizes. More information can be found at the OSG web site: www.opensciencegrid.org.

  9. Multi-aperture viewing: perception of figures through very small apertures.

    PubMed

    Mateeff, S; Popov, D; Hohnsbein, J

    1993-12-01

    A new phenomenon of viewing objects through multiple apertures is reported. When a solid figure is hidden behind a sieve of very small apertures (pinholes), only its general shape may be perceived. Outline figures may be entirely invisible behind the sieve. Motion of the figure markedly improves the visibility of the outline figures and of the small details and edges of the solid figures. Two experiments are presented. The first demonstrates that the size of a dark stimulus moving behind a rear-illuminated row of holes is perceived with an accuracy that may be considerably better (i.e. the error is smaller) than the interhole distance. The results of the second experiment show that the visibility of an outline figure, a ring, is significantly better when the figure smoothly moves than when presented at random positions behind a two-dimensional sieve. Changing the velocity within the range of 5.18-10.36 deg/sec does not affect the visibility of the figure while it moves; however, a lower rate of discrete presentation leads to significantly better visibility. An explanation of the phenomenon is presented in terms of integration of information about the relative positions of the covered/uncovered holes, with a possible involvement of motion analyzing mechanisms.

  10. Autofocus algorithm for synthetic aperture radar imaging with large curvilinear apertures

    NASA Astrophysics Data System (ADS)

    Bleszynski, E.; Bleszynski, M.; Jaroszewicz, T.

    2013-05-01

    An approach to autofocusing for large curved synthetic aperture radar (SAR) apertures is presented. Its essential feature is that phase corrections are being extracted not directly from SAR images, but rather from reconstructed SAR phase-history data representing windowed patches of the scene, of sizes sufficiently small to allow the linearization of the forward- and back-projection formulae. The algorithm processes data associated with each patch independently and in two steps. The first step employs a phase-gradient-type method in which phase correction compensating (possibly rapid) trajectory perturbations are estimated from the reconstructed phase history for the dominant scattering point on the patch. The second step uses phase-gradient-corrected data and extracts the absolute phase value, removing in this way phase ambiguities and reducing possible imperfections of the first stage, and providing the distances between the sensor and the scattering point with accuracy comparable to the wavelength. The features of the proposed autofocusing method are illustrated in its applications to intentionally corrupted small-scene 2006 Gotcha data. The examples include the extraction of absolute phases (ranges) for selected prominent point targets. They are then used to focus the scene and determine relative target-target distances.

  11. Grid generation using classical techniques

    NASA Technical Reports Server (NTRS)

    Moretti, G.

    1980-01-01

    A brief historical review of conformal mapping and its applications to problems in fluid mechanics and electromagnetism is presented. The use of conformal mapping as a grid generator is described. The philosophy of the 'closed form' approach and its application to a Neumann problem is discussed. Karman-Trefftz mappings and grids for ablated, three dimensional bodies are also discussed.

  12. Some Observations on Grid Convergence

    NASA Technical Reports Server (NTRS)

    Salas, manuel D.

    2006-01-01

    It is claimed that current practices in grid convergence studies, particularly in the field of external aerodynamics, are flawed. The necessary conditions to properly establish grid convergence are presented. A theoretical model and a numerical example are used to demonstrate these ideas.

  13. Intelligent automated surface grid generation

    NASA Technical Reports Server (NTRS)

    Yao, Ke-Thia; Gelsey, Andrew

    1995-01-01

    The goal of our research is to produce a flexible, general grid generator for automated use by other programs, such as numerical optimizers. The current trend in the gridding field is toward interactive gridding. Interactive gridding more readily taps into the spatial reasoning abilities of the human user through the use of a graphical interface with a mouse. However, a sometimes fruitful approach to generating new designs is to apply an optimizer with shape modification operators to improve an initial design. In order for this approach to be useful, the optimizer must be able to automatically grid and evaluate the candidate designs. This paper describes and intelligent gridder that is capable of analyzing the topology of the spatial domain and predicting approximate physical behaviors based on the geometry of the spatial domain to automatically generate grids for computational fluid dynamics simulators. Typically gridding programs are given a partitioning of the spatial domain to assist the gridder. Our gridder is capable of performing this partitioning. This enables the gridder to automatically grid spatial domains of wide range of configurations.

  14. LAPS Grid generation and adaptation

    NASA Astrophysics Data System (ADS)

    Pagliantini, Cecilia; Delzanno, Gia Luca; Guo, Zehua; Srinivasan, Bhuvana; Tang, Xianzhu; Chacon, Luis

    2011-10-01

    LAPS uses a common-data framework in which a general purpose grid generation and adaptation package in toroidal and simply connected domains is implemented. The initial focus is on implementing the Winslow/Laplace-Beltrami method for generating non-overlapping block structured grids. This is to be followed by a grid adaptation scheme based on Monge-Kantorovich optimal transport method [Delzanno et al., J. Comput. Phys,227 (2008), 9841-9864], that equidistributes application-specified error. As an initial set of applications, we will lay out grids for an axisymmetric mirror, a field reversed configuration, and an entire poloidal cross section of a tokamak plasma reconstructed from a CMOD experimental shot. These grids will then be used for computing the plasma equilibrium and transport in accompanying presentations. A key issue for Monge-Kantorovich grid optimization is the choice of error or monitor function for equi-distribution. We will compare the Operator Recovery Error Source Detector (ORESD) [Lapenta, Int. J. Num. Meth. Eng,59 (2004) 2065-2087], the Tau method and a strategy based on the grid coarsening [Zhang et al., AIAA J,39 (2001) 1706-1715] to find an ``optimal'' grid. Work supported by DOE OFES.

  15. Transmission of High-Power Electron Beams Through Small Apertures

    SciTech Connect

    Tschalaer, Christoph; Alarcon, Ricardo O.; Balascuta, S.; Benson, Stephen V.; Bertozzi, William; Boyce, James R.; Cowan, Ray Franklin; Douglas, David R.; Evtushenko, Pavel; Fisher, Peter H.; Ihloff, Ernest E.; Kalantarians, Narbe; Kelleher, Aidan Michael; Legg, Robert A.; Milner, Richard; Neil, George R.; Ou, Longwu; Schmookler, Barak Abraham; Tennant, Christopher D.; Williams, Gwyn P.; Zhang, Shukui

    2013-11-01

    Tests were performed to pass a 100 MeV, 430 kWatt c.w. electron beam from the energy-recovery linac at the Jefferson Laboratory's FEL facility through a set of small apertures in a 127 mm long aluminum block. Beam transmission losses of 3 p.p.m. through a 2 mm diameter aperture were maintained during a 7 hour continuous run.

  16. Apodised aperture using rotation of plane of polarization

    DOEpatents

    Simmons, W.W.; Leppelmeier, G.W.; Johnson, B.C.

    1975-09-01

    An apodised aperture based on the rotation of plane of polarization producing desirable characteristics on a transmitted light beam such as beam profiling in high flux laser amplifier chains is described. The apodised aperture is made with a lossless element by using one or more polarizers and/or analyzers and magneto-optical Faraday means for selectively rotating the plane of polarized radiation over the cross section to effect the desired apodisation. (auth)

  17. Aperture efficiency of integrated-circuit horn antennas

    NASA Technical Reports Server (NTRS)

    Guo, Yong; Lee, Karen; Stimson, Philip; Potter, Kent; Rutledge, David

    1991-01-01

    The aperture efficiency of silicon integrated-circuit horn antennas has been improved by optimizing the length of the dipole probes and by coating the entire horn walls with gold. To make these measurements, a new thin-film power-density meter was developed for measuring power density with accuracies better than 5 percent. The measured aperture efficiency improved from 44 percent to 72 percent at 93 GHz. This is sufficient for use in many applications which now use machined waveguide horns.

  18. Multifrequency Aperture-Synthesizing Microwave Radiometer System (MFASMR). Volume 1

    NASA Technical Reports Server (NTRS)

    Wiley, C. A.; Chang, M. U.

    1981-01-01

    Background material and a systems analysis of a multifrequency aperture - synthesizing microwave radiometer system is presented. It was found that the system does not exhibit high performance because much of the available thermal power is not used in the construction of the image and because the image that can be formed has a resolution of only ten lines. An analysis of image reconstruction is given. The system is compared with conventional aperture synthesis systems.

  19. Receiver for solar energy collector having improved aperture aspect

    DOEpatents

    McIntire, William R.

    1984-01-01

    A secondary concentrator for use in receiver systems for linear focusing primary concentrators is provided with reflector wings at each end. The wings increase the capture of light rays reflected from areas adjacent the rim of a primary concentrator, increasing the apparent aperture size of the absorber as viewed from the rim of the primary concentrator. The length, tilt, and curvature of the wing reflectors can be adjusted to provide an absorber having a desired aperture aspect.

  20. Phase Centers of Subapertures in a Tapered Aperture Array.

    SciTech Connect

    Doerry, Armin W.; Bickel, Douglas L.

    2015-11-01

    Antenna apertures that are tapered for sidelobe control can also be parsed into subapertures for Direction of Arrival (DOA) measurements. However, the aperture tapering complicates phase center location for the subapertures, knowledge of which is critical for proper DOA calculation. In addition, tapering affects subaperture gains, making gain dependent on subaperture position. Techniques are presented to calculate subaperture phase center locations, and algorithms are given for equalizing subapertures’ gains. Sidelobe characteristics and mitigation are also discussed.