Science.gov

Sample records for beam phase error

  1. Beam-pointing errors of planar-phased arrays.

    NASA Technical Reports Server (NTRS)

    Carver, K. R.; Cooper, W. K.; Stutzman, W. L.

    1973-01-01

    Using both analytical and Monte Carlo techniques, beam-pointing errors of planar-phased arrays are analyzed. The obtained simple formulas for rms pointing errors are applicable to uniform planar arrays with both uniform and Gaussian uncorrelated phase-error distributions and for any arbitrary scan angle.

  2. Influence of nonhomogeneous earth on the rms phase error and beam-pointing errors of large, sparse high-frequency receiving arrays

    NASA Astrophysics Data System (ADS)

    Weiner, M. M.

    1994-01-01

    The performance of ground-based high-frequency (HF) receiving arrays is reduced when the array elements have electrically small ground planes. The array rms phase error and beam-pointing errors, caused by multipath rays reflected from a nonhomogeneous Earth, are determined for a sparse array of elements that are modeled as Hertzian dipoles in close proximity to Earth with no ground planes. Numerical results are presented for cases of randomly distributed and systematically distributed Earth nonhomogeneities where one-half of vertically polarized array elements are located in proximity to one type of Earth and the remaining half are located in proximity to a second type of Earth. The maximum rms phase errors, for the cases examined, are 18 deg and 9 deg for randomly distributed and systematically distributed nonhomogeneities, respectively. The maximum beampointing errors are 0 and 0.3 beam widths for randomly distributed and systematically distributed nonhomogeneities, respectively.

  3. Diffraction study of duty-cycle error in ferroelectric quasi-phase-matching gratings with Gaussian beam illumination

    NASA Astrophysics Data System (ADS)

    Dwivedi, Prashant Povel; Kumar, Challa Sesha Sai Pavan; Choi, Hee Joo; Cha, Myoungsik

    2016-02-01

    Random duty-cycle error (RDE) is inherent in the fabrication of ferroelectric quasi-phase-matching (QPM) gratings. Although a small RDE may not affect the nonlinearity of QPM devices, it enhances non-phase-matched parasitic harmonic generations, limiting the device performance in some applications. Recently, we demonstrated a simple method for measuring the RDE in QPM gratings by analyzing the far-field diffraction pattern obtained by uniform illumination (Dwivedi et al. in Opt Express 21:30221-30226, 2013). In the present study, we used a Gaussian beam illumination for the diffraction experiment to measure noise spectra that are less affected by the pedestals of the strong diffraction orders. Our results were compared with our calculations based on a random grating model, demonstrating improved resolution in the RDE estimation.

  4. Beam-forming Errors in Murchison Widefield Array Phased Array Antennas and their Effects on Epoch of Reionization Science

    NASA Astrophysics Data System (ADS)

    Neben, Abraham R.; Hewitt, Jacqueline N.; Bradley, Richard F.; Dillon, Joshua S.; Bernardi, G.; Bowman, J. D.; Briggs, F.; Cappallo, R. J.; Corey, B. E.; Deshpande, A. A.; Goeke, R.; Greenhill, L. J.; Hazelton, B. J.; Johnston-Hollitt, M.; Kaplan, D. L.; Lonsdale, C. J.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Oberoi, D.; Ord, S. M.; Prabu, T.; Udaya Shankar, N.; Srivani, K. S.; Subrahmanyan, R.; Tingay, S. J.; Wayth, R. B.; Webster, R. L.; Williams, A.; Williams, C. L.

    2016-03-01

    Accurate antenna beam models are critical for radio observations aiming to isolate the redshifted 21 cm spectral line emission from the Dark Ages and the Epoch of Reionization (EOR) and unlock the scientific potential of 21 cm cosmology. Past work has focused on characterizing mean antenna beam models using either satellite signals or astronomical sources as calibrators, but antenna-to-antenna variation due to imperfect instrumentation has remained unexplored. We characterize this variation for the Murchison Widefield Array (MWA) through laboratory measurements and simulations, finding typical deviations of the order of ±10%-20% near the edges of the main lobe and in the sidelobes. We consider the ramifications of these results for image- and power spectrum-based science. In particular, we simulate visibilities measured by a 100 m baseline and find that using an otherwise perfect foreground model, unmodeled beam-forming errors severely limit foreground subtraction accuracy within the region of Fourier space contaminated by foreground emission (the “wedge”). This region likely contains much of the cosmological signal, and accessing it will require measurement of per-antenna beam patterns. However, unmodeled beam-forming errors do not contaminate the Fourier space region expected to be free of foreground contamination (the “EOR window”), showing that foreground avoidance remains a viable strategy.

  5. Phase Errors and the Capture Effect

    SciTech Connect

    Blair, J., and Machorro, E.

    2011-11-01

    This slide-show presents analysis of spectrograms and the phase error of filtered noise in a signal. When the filtered noise is smaller than the signal amplitude, the phase error can never exceed 90{deg}, so the average phase error over many cycles is zero: this is called the capture effect because the largest signal captures the phase and frequency determination.

  6. Correction of Errors in Polarization Based Dynamic Phase Shifting Interferometers

    NASA Astrophysics Data System (ADS)

    Kimbrough, Brad

    2014-10-01

    Polarization based interferometers for single snap-shot measurements allow single frame, quantitative phase acquisition for vibration insensitive measurements of optical surfaces. Application of these polarization based phase sensors requires the test and reference beams of the interferometer to be orthogonally polarized. As with all polarization based interferometers, these systems can suffer from phase dependent errors resulting from systematic polarization aberrations. This type of measurement error presents a particular challenge because it varies in magnitude both spatially and temporally between each measurement. In this article, a general discussion of phase calculation error is presented. We then present an algorithm that is capable of mitigating phase-dependent measurement errors on-the-fly. The algorithm implementation is non-iterative providing sensor frame rate limited phase calculations. Finally, results are presented for both a high numerical aperture system, where the residual error is reduced to the shot noise limit, and a system with significant birefringence in the test arm.

  7. Phase errors and predicted spectral performance of a prototype undulator

    SciTech Connect

    Dejus, R.J.; Vassrman, I.; Moog, E.R.; Gluskin, E.

    1994-08-01

    A prototype undulator has been used to study different magnetic end-configurations and shimming techniques for straightening the beam trajectory. Field distributions obtained by Hall probe measurements were analyzed in terms of trajectory, phase errors, and on-axis brightness for the purpose of correlating predicted spectral intensity with the calculated phase errors. Two device configurations were analyzed. One configuration had a full-strength first magnet at each end and the next-to-last pole was recessed to make the trajectory through the middle of the undulator parallel to the undulator axis. For the second configuration, the first permanent magnet at each end was replaced by a half-strength magnet to reduce the trajectory displacement and the next-to-last pole was adjusted appropriately, and shims were added to straighten the trajectory. Random magnetic field errors can cause trajectory deviations that will affect the optimum angle for viewing the emitted radiation, and care must be taken to select the appropriate angle when calculating the phase errors. This angle may be calculated from the average trajectory angle evaluated at the location of the poles. For the second configuration, we find an rms phase error of less than 3{degrees} and predict 87% of the ideal value of the on-axis brightness for the third harmonic. We have also analyzed the gap dependence of the phase errors and spectral brightness and have found that the rms phase error remain small at all gap settings.

  8. Dose error analysis for a scanned proton beam delivery system

    NASA Astrophysics Data System (ADS)

    Coutrakon, G.; Wang, N.; Miller, D. W.; Yang, Y.

    2010-12-01

    All particle beam scanning systems are subject to dose delivery errors due to errors in position, energy and intensity of the delivered beam. In addition, finite scan speeds, beam spill non-uniformities, and delays in detector, detector electronics and magnet responses will all contribute errors in delivery. In this paper, we present dose errors for an 8 × 10 × 8 cm3 target of uniform water equivalent density with 8 cm spread out Bragg peak and a prescribed dose of 2 Gy. Lower doses are also analyzed and presented later in the paper. Beam energy errors and errors due to limitations of scanning system hardware have been included in the analysis. By using Gaussian shaped pencil beams derived from measurements in the research room of the James M Slater Proton Treatment and Research Center at Loma Linda, CA and executing treatment simulations multiple times, statistical dose errors have been calculated in each 2.5 mm cubic voxel in the target. These errors were calculated by delivering multiple treatments to the same volume and calculating the rms variation in delivered dose at each voxel in the target. The variations in dose were the result of random beam delivery errors such as proton energy, spot position and intensity fluctuations. The results show that with reasonable assumptions of random beam delivery errors, the spot scanning technique yielded an rms dose error in each voxel less than 2% or 3% of the 2 Gy prescribed dose. These calculated errors are within acceptable clinical limits for radiation therapy.

  9. Correlated errors in phase-shifting laser Fizeau interferometry.

    PubMed

    de Groot, Peter J

    2014-07-01

    High-performance data processing algorithms for phase-shifting interferometry accommodate adjustment errors in the phase shift increment as well as harmonic distortions in the interference signal. However, a widely overlooked error source is the combination of these two imperfections. Phase shift tuning errors increase the sensitivity of phase estimation algorithms to second-order and higher harmonics present in Fizeau interference signals. I derive an analytical formula for evaluating these errors more realistically, in part to identify the characteristics of the optimal PSI algorithm. Even for advanced algorithms, it is found that multiple reflections increase the error contribution of detuning by orders of magnitude compared with the two-beam calculation and impose a practical limit of 30% in tuning error for sub-nm metrology in a 4%-4% Fizeau cavity. Consequently, a preferred approach for high precision spherical cavities is to use either wavelength tuning in place of mechanical phase shifting or an iterative solver that accommodates unknown phase shifts as a function of field position. PMID:25089998

  10. Laser Phase Errors in Seeded FELs

    SciTech Connect

    Ratner, D.; Fry, A.; Stupakov, G.; White, W.; /SLAC

    2012-03-28

    Harmonic seeding of free electron lasers has attracted significant attention from the promise of transform-limited pulses in the soft X-ray region. Harmonic multiplication schemes extend seeding to shorter wavelengths, but also amplify the spectral phase errors of the initial seed laser, and may degrade the pulse quality. In this paper we consider the effect of seed laser phase errors in high gain harmonic generation and echo-enabled harmonic generation. We use simulations to confirm analytical results for the case of linearly chirped seed lasers, and extend the results for arbitrary seed laser envelope and phase.

  11. Homodyne laser interferometer involving minimal quadrature phase error to obtain subnanometer nonlinearity.

    PubMed

    Cui, Junning; He, Zhangqiang; Jiu, Yuanwei; Tan, Jiubin; Sun, Tao

    2016-09-01

    The demand for minimal cyclic nonlinearity error in laser interferometry is increasing as a result of advanced scientific research projects. Research shows that the quadrature phase error is the main effect that introduces cyclic nonlinearity error, and polarization-mixing cross talk during beam splitting is the main error source that causes the quadrature phase error. In this paper, a new homodyne quadrature laser interferometer configuration based on nonpolarization beam splitting and balanced interference between two circularly polarized laser beams is proposed. Theoretical modeling indicates that the polarization-mixing cross talk is elaborately avoided through nonpolarizing and Wollaston beam splitting, with a minimum number of quadrature phase error sources involved. Experimental results show that the cyclic nonlinearity error of the interferometer is up to 0.6 nm (peak-to-valley value) without any correction and can be further suppressed to 0.2 nm with a simple gain and offset correction method. PMID:27607285

  12. Quantum Computation with Phase Drift Errors

    NASA Astrophysics Data System (ADS)

    Miquel, César; Paz, Juan Pablo; Zurek, Wojciech Hubert

    1997-05-01

    We numerically simulate the evolution of an ion trap quantum computer made out of 18 ions subject to a sequence of nearly 15 000 laser pulses in order to find the prime factors of N = 15. We analyze the effect of random and systematic phase drift errors arising from inaccuracies in the laser pulses which induce over (under) rotation of the quantum state. Simple analytic estimates of the tolerance for the quality of driving pulses are presented. We examine the use of watchdog stabilization to partially correct phase drift errors concluding that, in the regime investigated, it is rather inefficient.

  13. Dose error analysis for a scanned proton beam delivery system.

    PubMed

    Coutrakon, G; Wang, N; Miller, D W; Yang, Y

    2010-12-01

    All particle beam scanning systems are subject to dose delivery errors due to errors in position, energy and intensity of the delivered beam. In addition, finite scan speeds, beam spill non-uniformities, and delays in detector, detector electronics and magnet responses will all contribute errors in delivery. In this paper, we present dose errors for an 8 × 10 × 8 cm(3) target of uniform water equivalent density with 8 cm spread out Bragg peak and a prescribed dose of 2 Gy. Lower doses are also analyzed and presented later in the paper. Beam energy errors and errors due to limitations of scanning system hardware have been included in the analysis. By using Gaussian shaped pencil beams derived from measurements in the research room of the James M Slater Proton Treatment and Research Center at Loma Linda, CA and executing treatment simulations multiple times, statistical dose errors have been calculated in each 2.5 mm cubic voxel in the target. These errors were calculated by delivering multiple treatments to the same volume and calculating the rms variation in delivered dose at each voxel in the target. The variations in dose were the result of random beam delivery errors such as proton energy, spot position and intensity fluctuations. The results show that with reasonable assumptions of random beam delivery errors, the spot scanning technique yielded an rms dose error in each voxel less than 2% or 3% of the 2 Gy prescribed dose. These calculated errors are within acceptable clinical limits for radiation therapy. PMID:21076200

  14. Aliasing errors in measurements of beam position and ellipticity

    NASA Astrophysics Data System (ADS)

    Ekdahl, Carl

    2005-09-01

    Beam position monitors (BPMs) are used in accelerators and ion experiments to measure currents, position, and azimuthal asymmetry. These usually consist of discrete arrays of electromagnetic field detectors, with detectors located at several equally spaced azimuthal positions at the beam tube wall. The discrete nature of these arrays introduces systematic errors into the data, independent of uncertainties resulting from signal noise, lack of recording dynamic range, etc. Computer simulations were used to understand and quantify these aliasing errors. If required, aliasing errors can be significantly reduced by employing more than the usual four detectors in the BPMs. These simulations show that the error in measurements of the centroid position of a large beam is indistinguishable from the error in the position of a filament. The simulations also show that aliasing errors in the measurement of beam ellipticity are very large unless the beam is accurately centered. The simulations were used to quantify the aliasing errors in beam parameter measurements during early experiments on the DARHT-II accelerator, demonstrating that they affected the measurements only slightly, if at all.

  15. Suppressing phase errors from vibration in phase-shifting interferometry

    SciTech Connect

    Deck, Leslie L.

    2009-07-10

    A general method for reducing the influence of vibrations in phase-shifting interferometry corrects the surface phase map through a spectral analysis of a ''phase-error pattern,'' a plot of the interference intensity versus the measured phase, for each phase-shifted image. The method is computationally fast, applicable to any phase-shifting algorithm and interferometer geometry, has few restrictions on surface shape, and unlike spatial Fourier methods, high density spatial carrier fringes are not required, although at least a fringe of phase departure is recommended. Over a 100x reduction in vibrationally induced surface distortion is achieved for small amplitude vibrations on real data.

  16. Momentum errors in an RF separated beam

    SciTech Connect

    T. Kobilarcik

    2002-09-19

    The purity of an RF separated beam is affected by the difference in mass of the particle types and the momentum bite of the beam. The resulting time-of-flight difference between different types allows separation to occur; the finite momentum bite results in chromatic aberration. Both these features also give rise to a particle type dependent velocity bite, which must also be taken into account. This memo demonstrates a generalizable method for calculating the effect.

  17. Beam line error analysis, position correction, and graphic processing

    NASA Astrophysics Data System (ADS)

    Wang, Fuhua; Mao, Naifeng

    1993-12-01

    A beam transport line error analysis and beam position correction code called ``EAC'' has been enveloped associated with a graphics and data post processing package for TRANSPORT. Based on the linear optics design using TRANSPORT or other general optics codes, EAC independently analyzes effects of magnet misalignments, systematic and statistical errors of magnetic fields as well as the effects of the initial beam positions, on the central trajectory and upon the transverse beam emittance dilution. EAC also provides an efficient way to develop beam line trajectory correcting schemes. The post processing package generates various types of graphics such as the beam line geometrical layout, plots of the Twiss parameters, beam envelopes, etc. It also generates an EAC input file, thus connecting EAC with general optics codes. EAC and the post processing package are small size codes, that are easy to access and use. They have become useful tools for the design of transport lines at SSCL.

  18. Beam Tomography in Longitudinal Phase Space

    NASA Astrophysics Data System (ADS)

    Mane, V.; Wei, J.; Peggs, S.

    1997-05-01

    Longitudinal particle motion in circular accelerators is typically monitored by one dimensional (1-D) profiles. Adiabatic particle motion in 2-D phase space can be reconstructed with tomographic techniques, using 1-D profiles. In this paper, we discuss a filtered backprojection algorithm, with a high pass ramp or Hann filter, for phase space reconstruction. The algorithm uses several projections of the beam at equally spaced angles over half a synchrotron period. A computer program RADON has been developed to process digitized mountain range data and do the phase space reconstruction for the AGS, and later for Relativistic Heavy Ion Collider (RHIC). Analysis has been performed to determine the sensitivity to machine parameters and data acquisition errors. During the Sextant test of RHIC in early 1997, this program has been successfully employed to reconstruct the motion of Au^77+ beam in the AGS.

  19. Error-Induced Beam Degradation in Fermilab's Accelerators

    SciTech Connect

    Yoon, Phil S.; /Rochester U.

    2007-08-01

    In Part I, three independent models of Fermilab's Booster synchrotron are presented. All three models are constructed to investigate and explore the effects of unavoidable machine errors on a proton beam under the influence of space-charge effects. The first is a stochastic noise model. Electric current fluctuations arising from power supplies are ubiquitous and unavoidable and are a source of instabilities in accelerators of all types. A new noise module for generating the Ornstein-Uhlenbeck (O-U) stochastic noise is first created and incorporated into the existing Object-oriented Ring Beam Injection and Tracking (ORBIT-FNAL) package. After being convinced with a preliminary model that the noise, particularly non-white noise, does matter to beam quality, we proceeded to measure directly current ripples and common-mode voltages from all four Gradient Magnet Power Supplies (GMPS). Then, the current signals are Fourier-analyzed. Based upon the power spectra of current signals, we tune up the Ornstein-Uhlnbeck noise model. As a result, we are able to closely match the frequency spectra between current measurements and the modeled O-U stochastic noise. The stochastic noise modeled upon measurements is applied to the Booster beam in the presence of the full space-charge effects. This noise model, accompanied by a suite of beam diagnostic calculations, manifests that the stochastic noise, impinging upon the beam and coupled to the space-charge effects, can substantially enhance the beam degradation process throughout the injection period. The second model is a magnet misalignment model. It is the first time to utilize the latest beamline survey data for building a magnet-by-magnet misalignment model. Given as-found survey fiducial coordinates, we calculate all types of magnet alignment errors (station error, pitch, yaw, roll, twists, etc.) are implemented in the model. We then follow up with statistical analysis to understand how each type of alignment errors are

  20. Chemical Shift Induced Phase Errors in Phase Contrast MRI

    PubMed Central

    Middione, Matthew J.; Ennis, Daniel B.

    2012-01-01

    Phase contrast magnetic resonance imaging (PC-MRI) is subject to numerous sources of error, which decrease clinical confidence in the reported measures. This work outlines how stationary perivascular fat can impart a significant chemical shift induced PC-MRI measurement error using computational simulations, in vitro, and in vivo experiments. This chemical shift error does not subtract in phase difference processing, but can be minimized with proper parameter selection. The chemical shift induced phase errors largely depend on both the receiver bandwidth (BW) and the TE. Both theory and an in vivo comparison of the maximum difference in net forward flow between vessels with and without perivascular fat indicated that the effects of chemically shifted perivascular fat are minimized by the use of high BW (814 Hz/px) and an in-phase TE (HBW-TEIN). In healthy volunteers (N=10) HBW-TEIN significantly improves intrapatient net forward flow agreement compared to low BW (401 Hz/px) and a mid-phase TE as indicated by significantly decreased measurement biases and limits of agreement for the ascending aorta (1.8±0.5 mL vs. 6.4±2.8 mL, P=0.01), main pulmonary artery (2.0±0.9 mL vs. 11.9±5.8 mL, P=0.04), the left pulmonary artery (1.3±0.9 mL vs. 5.4±2.5 mL, P=0.003), and all vessels (1.7±0.8 mL vs. 7.2±4.4 mL, P=0.001). PMID:22488490

  1. Beam masking to reduce cyclic error in beam launcher of interferometer

    NASA Technical Reports Server (NTRS)

    Ames, Lawrence L. (Inventor); Bell, Raymond Mark (Inventor); Dutta, Kalyan (Inventor)

    2005-01-01

    Embodiments of the present invention are directed to reducing cyclic error in the beam launcher of an interferometer. In one embodiment, an interferometry apparatus comprises a reference beam directed along a reference path, and a measurement beam spatially separated from the reference beam and being directed along a measurement path contacting a measurement object. The reference beam and the measurement beam have a single frequency. At least a portion of the reference beam and at least a portion of the measurement beam overlapping along a common path. One or more masks are disposed in the common path or in the reference path and the measurement path to spatially isolate the reference beam and the measurement beam from one another.

  2. Phase error compensation methods for high-accuracy profile measurement

    NASA Astrophysics Data System (ADS)

    Cai, Zewei; Liu, Xiaoli; Peng, Xiang; Zhang, Zonghua; Jiang, Hao; Yin, Yongkai; Huang, Shujun

    2016-04-01

    In a phase-shifting algorithm-based fringe projection profilometry, the nonlinear intensity response, called the gamma effect, of the projector-camera setup is a major source of error in phase retrieval. This paper proposes two novel, accurate approaches to realize both active and passive phase error compensation based on a universal phase error model which is suitable for a arbitrary phase-shifting step. The experimental results on phase error compensation and profile measurement of standard components verified the validity and accuracy of the two proposed approaches which are robust when faced with changeable measurement conditions.

  3. Simulation of Systematic Errors in Phase-Referenced VLBI Astrometry

    NASA Astrophysics Data System (ADS)

    Pradel, N.; Charlot, P.; Lestrade, J.-F.

    2005-12-01

    The astrometric accuracy in the relative coordinates of two angularly-close radio sources observed with the phase-referencing VLBI technique is limited by systematic errors. These include geometric errors and atmospheric errors. Based on simulation with the SPRINT software, we evaluate the impact of these errors in the estimated relative source coordinates for standard VLBA observations. Such evaluations are useful to estimate the actual accuracy of phase-referenced VLBI astrometry.

  4. Self-Nulling Beam Combiner Using No External Phase Inverter

    NASA Technical Reports Server (NTRS)

    Bloemhof, Eric E.

    2010-01-01

    A self-nulling beam combiner is proposed that completely eliminates the phase inversion subsystem from the nulling interferometer, and instead uses the intrinsic phase shifts in the beam splitters. Simplifying the flight instrument in this way will be a valuable enhancement of mission reliability. The tighter tolerances on R = T (R being reflection and T being transmission coefficients) required by the self-nulling configuration actually impose no new constraints on the architecture, as two adaptive nullers must be situated between beam splitters to correct small errors in the coatings. The new feature is exploiting the natural phase shifts in beam combiners to achieve the 180 phase inversion necessary for nulling. The advantage over prior art is that an entire subsystem, the field-flipping optics, can be eliminated. For ultimate simplicity in the flight instrument, one might fabricate coatings to very high tolerances and dispense with the adaptive nullers altogether, with all their moving parts, along with the field flipper subsystem. A single adaptive nuller upstream of the beam combiner may be required to correct beam train errors (systematic noise), but in some circumstances phase chopping reduces these errors substantially, and there may be ways to further reduce the chop residuals. Though such coatings are beyond the current state of the art, the mechanical simplicity and robustness of a flight system without field flipper or adaptive nullers would perhaps justify considerable effort on coating fabrication.

  5. Interferometric phase measurement techniques for coherent beam combining

    NASA Astrophysics Data System (ADS)

    Antier, Marie; Bourderionnet, Jérôme; Larat, Christian; Lallier, Eric; Primot, Jérôme; Brignon, Arnaud

    2015-03-01

    Coherent beam combining of fiber amplifiers provides an attractive mean of reaching high power laser. In an interferometric phase measurement the beams issued for each fiber combined are imaged onto a sensor and interfere with a reference plane wave. This registration of interference patterns on a camera allows the measurement of the exact phase error of each fiber beam in a single shot. Therefore, this method is a promising candidate toward very large number of combined fibers. Based on this technique, several architectures can be proposed to coherently combine a high number of fibers. The first one based on digital holography transfers directly the image of the camera to spatial light modulator (SLM). The generated hologram is used to compensate the phase errors induced by the amplifiers. This architecture has therefore a collective phase measurement and correction. Unlike previous digital holography technique, the probe beams measuring the phase errors between the fibers are co-propagating with the phase-locked signal beams. This architecture is compatible with the use of multi-stage isolated amplifying fibers. In that case, only 20 pixels per fiber on the SLM are needed to obtain a residual phase shift error below λ/10rms. The second proposed architecture calculates the correction applied to each fiber channel by tracking the relative position of the interference finges. In this case, a phase modulator is placed on each channel. In that configuration, only 8 pixels per fiber on the camera is required for a stable close loop operation with a residual phase error of λ/20rms, which demonstrates the scalability of this concept.

  6. Phasing piston error in segmented telescopes.

    PubMed

    Jiang, Junlun; Zhao, Weirui

    2016-08-22

    To achieve a diffraction-limited imaging, the piston errors between the segments of the segmented primary mirror telescope should be reduced to λ/40 RMS. We propose a method to detect the piston error by analyzing the intensity distribution on the image plane according to the Fourier optics principle, which can capture segments with the piston errors as large as the coherence length of the input light and reduce these to 0.026λ RMS (λ = 633nm). This method is adaptable to any segmented and deployable primary mirror telescope. Experiments have been carried out to validate the feasibility of the method. PMID:27557192

  7. Method and apparatus for optical phase error correction

    DOEpatents

    DeRose, Christopher; Bender, Daniel A.

    2014-09-02

    The phase value of a phase-sensitive optical device, which includes an optical transport region, is modified by laser processing. At least a portion of the optical transport region is exposed to a laser beam such that the phase value is changed from a first phase value to a second phase value, where the second phase value is different from the first phase value. The portion of the optical transport region that is exposed to the laser beam can be a surface of the optical transport region or a portion of the volume of the optical transport region. In an embodiment of the invention, the phase value of the optical device is corrected by laser processing. At least a portion of the optical transport region is exposed to a laser beam until the phase value of the optical device is within a specified tolerance of a target phase value.

  8. SAR image quality effects of damped phase and amplitude errors

    NASA Astrophysics Data System (ADS)

    Zelenka, Jerry S.; Falk, Thomas

    The effects of damped multiplicative, amplitude, or phase errors on the image quality of synthetic-aperture radar systems are considered. These types of errors can result from aircraft maneuvers or the mechanical steering of an antenna. The proper treatment of damped multiplicative errors can lead to related design specifications and possibly an enhanced collection capability. Only small, high-frequency errors are considered. Expressions for the average intensity and energy associated with a damped multiplicative error are presented and used to derive graphic results. A typical example is used to show how to apply the results of this effort.

  9. Error analysis in post linac to driver linac transport beam line of RAON

    NASA Astrophysics Data System (ADS)

    Kim, Chanmi; Kim, Eun-San

    2016-07-01

    We investigated the effects of magnet errors in the beam transport line connecting the post linac to the driver linac (P2DT) in the Rare Isotope Accelerator in Korea (RAON). The P2DT beam line is bent by 180-degree to send the radioactive Isotope Separation On-line (ISOL) beams accelerated in Linac-3 to Linac-2. This beam line transports beams with multi-charge state 132Sn45,46,47. The P2DT beam line includes 42 quadrupole, 4 dipole and 10 sextupole magnets. We evaluate the effects of errors on the trajectory of the beam by using the TRACK code, which includes the translational and the rotational errors of the quadrupole, dipole and sextupole magnets in the beam line. The purpose of this error analysis is to reduce the rate of beam loss in the P2DT beam line. The distorted beam trajectories can be corrected by using six correctors and seven monitors.

  10. Compensation of body shake errors in terahertz beam scanning single frequency holography for standoff personnel screening

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Li, Chao; Sun, Zhao-Yang; Zhao, Yu; Wu, Shi-You; Fang, Guang-You

    2016-08-01

    In the terahertz (THz) band, the inherent shake of the human body may strongly impair the image quality of a beam scanning single frequency holography system for personnel screening. To realize accurate shake compensation in imaging processing, it is quite necessary to develop a high-precision measure system. However, in many cases, different parts of a human body may shake to different extents, resulting in greatly increasing the difficulty in conducting a reasonable measurement of body shake errors for image reconstruction. In this paper, a body shake error compensation algorithm based on the raw data is proposed. To analyze the effect of the body shake on the raw data, a model of echoed signal is rebuilt with considering both the beam scanning mode and the body shake. According to the rebuilt signal model, we derive the body shake error estimated method to compensate for the phase error. Simulation on the reconstruction of point targets with shake errors and proof-of-principle experiments on the human body in the 0.2-THz band are both performed to confirm the effectiveness of the body shake compensation algorithm proposed. Project supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. YYYJ-1123).

  11. Laser Phase Errors in Seeded Free Electron Lasers

    SciTech Connect

    Ratner, D.; Fry, A.; Stupakov, G.; White, W.; /SLAC

    2012-04-17

    Harmonic seeding of free electron lasers has attracted significant attention as a method for producing transform-limited pulses in the soft x-ray region. Harmonic multiplication schemes extend seeding to shorter wavelengths, but also amplify the spectral phase errors of the initial seed laser, and may degrade the pulse quality and impede production of transform-limited pulses. In this paper we consider the effect of seed laser phase errors in high gain harmonic generation and echo-enabled harmonic generation. We use simulations to confirm analytical results for the case of linearly chirped seed lasers, and extend the results for arbitrary seed laser envelope and phase.

  12. Detection and correction of wavefront errors caused by slight reference tilt in two-step phase-shifting digital holography.

    PubMed

    Xu, Xianfeng; Cai, Luzhong; Gao, Fei; Jia, Yulei; Zhang, Hui

    2015-11-10

    A simple and convenient method, without the need for any additional optical devices and measurements, is suggested to improve the quality of the reconstructed object wavefront in two-step phase-shifting digital holography by decreasing the errors caused by reference beam tilt, which often occurs in practice and subsequently introduces phase distortion in the reconstructed wave. The effects of reference beam tilt in two-step generalized interferometry is analyzed theoretically, showing that this tilt incurs no error either on the extracted phase shift or on the retrieved real object wave amplitude on the recording plane, but causes great deformation of the recovered object wavefront. A corresponding error detection and correction approach is proposed, and the formulas to calculate the tilt angle and correct the wavefront are deduced. A series of computer simulations to find and remove the wavefront errors caused by reference beam tilt demonstrate the effectiveness of this method. PMID:26560791

  13. First-order approximation error analysis of Risley-prism-based beam directing system.

    PubMed

    Zhao, Yanyan; Yuan, Yan

    2014-12-01

    To improve the performance of a Risley-prism system for optical detection and measuring applications, it is necessary to be able to determine the direction of the outgoing beam with high accuracy. In previous works, error sources and their impact on the performance of the Risley-prism system have been analyzed, but their numerical approximation accuracy was not high. Besides, pointing error analysis of the Risley-prism system has provided results for the case when the component errors, prism orientation errors, and assembly errors are certain. In this work, the prototype of a Risley-prism system was designed. The first-order approximations of the error analysis were derived and compared with the exact results. The directing errors of a Risley-prism system associated with wedge-angle errors, prism mounting errors, and bearing assembly errors were analyzed based on the exact formula and the first-order approximation. The comparisons indicated that our first-order approximation is accurate. In addition, the combined errors produced by the wedge-angle errors and mounting errors of the two prisms together were derived and in both cases were proved to be the sum of errors caused by the first and the second prism separately. Based on these results, the system error of our prototype was estimated. The derived formulas can be implemented to evaluate beam directing errors of any Risley-prism beam directing system with a similar configuration. PMID:25607958

  14. An algorithm based on carrier squeezing interferometry for multi-beam phase extraction in Fizeau interferometer

    NASA Astrophysics Data System (ADS)

    Cheng, Jinlong; Gao, Zhishan; Wang, Kailiang; Yang, Zhongming; Wang, Shuai; Yuan, Qun

    2015-10-01

    Multi-beam interference will exist in the cavity of Fizeau interferometer due to the high reflectivity of test optics. The random phase shift error will be generated by some factors such as the environmental vibration, air turbulence, etc. Both these will cause phase retrieving error. We proposed a non-iterative approach called Carrier Squeezing Multi-beam Interferometry (CSMI) algorithm, which is based on the Carrier squeezing interferometry (CSI) technique to retrieve the phase distribution from multiple-beam interferograms with random phase shift errors. The intensity of multiple-beam interference was decomposed into fundamental wave and high-order harmonics, by using the Fourier series expansion. Multi-beam phase shifting interferograms with linear carrier were rearranged by row or column, to fuse one frame of spatial-temporal fringes. The lobe of the fundamental component related to the phase and the lobes of high-order harmonics and phase shift errors were separated in the frequency domain, so the correct phase was extracted by filtering out the fundamental component. Suppression of the influence from high-order harmonic components, as well as random phase shift error is validated by numerical simulations. Experiments were also executed by using the proposed CSMI algorithm for mirror with high reflection coefficient, showing its advantage comparing with normal phase retrieving algorithms.

  15. Are simple IMRT beams more robust against MLC error? Exploring the impact of MLC errors on planar quality assurance and plan quality for different complexity beams.

    PubMed

    Wang, Jiazhou; Jin, Xiance; Peng, Jiayuan; Xie, Jiang; Chen, Junchao; Hu, Weigang

    2016-01-01

    This study investigated the impact of beam complexities on planar quality assur-ance and plan quality robustness by introducing MLC errors in intensity-modulate radiation therapy. Forty patients' planar quality assurance (QA) plans were enrolled in this study, including 20 dynamic MLC (DMLC) IMRT plans and 20 static MLC (SMLC) IMRT plans. The total beam numbers were 150 and 160 for DMLC and SMLC, respectively. Six different magnitudes of MLC errors were introduced to these beams. Gamma pass rates were calculated by comparing error-free fluence and error-induced fluence. The plan quality variation was acquired by comparing PTV coverage. Eight complexity scores were calculated based on the beam flu-ence and the MLC sequence. The complexity scores include fractal dimension, monitor unit, modulation index, fluence map complexity, weighted average of field area, weighted average of field perimeter, and small aperture ratio (< 5 cm2 and < 50cm2). The Spearman's rank correlation coefficient was calculated to analyze the correlation between these scores and gamma pass rate and plan quality varia-tion. For planar QA, the most significant complexity index was fractal dimension for DMLC (p = -0.40) and weighted segment area for SMLC (p = 0.27) at low magnitude MLC error. For plan quality, the most significant complexity index was weighted segment perimeter for DMLC (p = 0.56) and weighted segment area for SMLC (p= 0.497) at low magnitude MLC error. The sensitivity of planar QA was weakly associated with the field complexity with low magnitude MLC error, but the plan quality robustness was associated with beam complexity. Plans with simple beams were more robust to MLC error. PMID:27167272

  16. Magnetospheric Multiscale (MMS) Mission Commissioning Phase Orbit Determination Error Analysis

    NASA Technical Reports Server (NTRS)

    Chung, Lauren R.; Novak, Stefan; Long, Anne; Gramling, Cheryl

    2009-01-01

    The Magnetospheric MultiScale (MMS) mission commissioning phase starts in a 185 km altitude x 12 Earth radii (RE) injection orbit and lasts until the Phase 1 mission orbits and orientation to the Earth-Sun li ne are achieved. During a limited time period in the early part of co mmissioning, five maneuvers are performed to raise the perigee radius to 1.2 R E, with a maneuver every other apogee. The current baseline is for the Goddard Space Flight Center Flight Dynamics Facility to p rovide MMS orbit determination support during the early commissioning phase using all available two-way range and Doppler tracking from bo th the Deep Space Network and Space Network. This paper summarizes th e results from a linear covariance analysis to determine the type and amount of tracking data required to accurately estimate the spacecraf t state, plan each perigee raising maneuver, and support thruster cal ibration during this phase. The primary focus of this study is the na vigation accuracy required to plan the first and the final perigee ra ising maneuvers. Absolute and relative position and velocity error hi stories are generated for all cases and summarized in terms of the ma ximum root-sum-square consider and measurement noise error contributi ons over the definitive and predictive arcs and at discrete times inc luding the maneuver planning and execution times. Details of the meth odology, orbital characteristics, maneuver timeline, error models, and error sensitivities are provided.

  17. Phase shifter for antenna beam steering

    NASA Astrophysics Data System (ADS)

    Jindal, Ravi; Razban, Tchanguiz

    2016-03-01

    Wide band Array Antenna operates in Ku-band (10.7-12.7 GHz) frequency composed of N×N radiating elements. This antenna aims at the reception of television satellite signals. The goal of this research is to provide better possibility of electronic beam control instead of manual or mechanical control, and design compact and low cost phase shifters to be inserted in the feeding network of this antenna. The electronic control of the phase shifter will allow the control of beam steering. The emphasis of this project will be done at the beginning on the design of a good phase shifter in Ku band. The aim of this research is to define, simulate, release and measure a continuous phase shifter. Better reflection loss, low transmission loss, low Cost of array antennas, large range of phase-shifter, phase flatness and bandwidth will be achieved by providing better gain.

  18. Phase error statistics of a phase-locked loop synchronized direct detection optical PPM communication system

    NASA Technical Reports Server (NTRS)

    Natarajan, Suresh; Gardner, C. S.

    1987-01-01

    Receiver timing synchronization of an optical Pulse-Position Modulation (PPM) communication system can be achieved using a phased-locked loop (PLL), provided the photodetector output is suitably processed. The magnitude of the PLL phase error is a good indicator of the timing error at the receiver decoder. The statistics of the phase error are investigated while varying several key system parameters such as PPM order, signal and background strengths, and PPL bandwidth. A practical optical communication system utilizing a laser diode transmitter and an avalanche photodiode in the receiver is described, and the sampled phase error data are presented. A linear regression analysis is applied to the data to obtain estimates of the relational constants involving the phase error variance and incident signal power.

  19. SYSTEMATIC ERROR REDUCTION: NON-TILTED REFERENCE BEAM METHOD FOR LONG TRACE PROFILER.

    SciTech Connect

    QIAN,S.; QIAN, K.; HONG, Y.; SENG, L.; HO, T.; TAKACS, P.

    2007-08-25

    Systematic error in the Long Trace Profiler (LTP) has become the major error source as measurement accuracy enters the nanoradian and nanometer regime. Great efforts have been made to reduce the systematic error at a number of synchrotron radiation laboratories around the world. Generally, the LTP reference beam has to be tilted away from the optical axis in order to avoid fringe overlap between the sample and reference beams. However, a tilted reference beam will result in considerable systematic error due to optical system imperfections, which is difficult to correct. Six methods of implementing a non-tilted reference beam in the LTP are introduced: (1) application of an external precision angle device to measure and remove slide pitch error without a reference beam, (2) independent slide pitch test by use of not tilted reference beam, (3) non-tilted reference test combined with tilted sample, (4) penta-prism scanning mode without a reference beam correction, (5) non-tilted reference using a second optical head, and (6) alternate switching of data acquisition between the sample and reference beams. With a non-tilted reference method, the measurement accuracy can be improved significantly. Some measurement results are presented. Systematic error in the sample beam arm is not addressed in this paper and should be treated separately.

  20. Nonmechanical beam steering using optical phased arrays

    NASA Astrophysics Data System (ADS)

    Dillon, Thomas E.; Schuetz, Christopher A.; Martin, Richard D.; Mackrides, Daniel G.; Curt, Petersen F.; Bonnett, James; Prather, Dennis W.

    2011-11-01

    Beam steering is an enabling technology for establishment of ad hoc communication links, directed energy for infrared countermeasures, and other in-theater defense applications. The development of nonmechanical beam steering techniques is driven by requirements for low size, weight, and power, and high slew rate, among others. The predominant beam steering technology currently in use relies on gimbal mounts, which are relatively large, heavy, and slow, and furthermore create drag on the airframes to which they are mounted. Nonmechanical techniques for beam steering are currently being introduced or refined, such as those based on liquid crystal spatial light modulators; however, drawbacks inherent to some of these approaches include narrow field of regard, low speed operation, and low optical efficiency. An attractive method that we explore is based on optical phased arrays, which has the potential to overcome the aforementioned issues associated with other mechanical and nonmechanical beam steering techniques. The optical array phase locks a number of coherent optical emitters in addition to applying arbitrary phase profiles across the array, thereby synthesizing beam shapes that can be steered and utilized for a diverse range of applications.

  1. Measurement of four-degree-of-freedom error motions based on non-diffracting beam

    NASA Astrophysics Data System (ADS)

    Zhai, Zhongsheng; Lv, Qinghua; Wang, Xuanze; Shang, Yiyuan; Yang, Liangen; Kuang, Zheng; Bennett, Peter

    2016-05-01

    A measuring method for the determination of error motions of linear stages based on non-diffracting beams (NDB) is presented. A right-angle prism and a beam splitter are adopted as the measuring head, which is fixed on the moving stage in order to sense the straightness and angular errors. Two CCDs are used to capture the NDB patterns that are carrying the errors. Four different types error s, the vertical straightness error and three rotational errors (the pitch, roll and yaw errors), can be separated and distinguished through theoretical analysis of the shift in the centre positions in the two cameras. Simulation results show that the proposed method using NDB can measure four-degrees-of-freedom errors for the linear stage.

  2. Effect of transmitting beam position error on the imaging quality of a Fourier telescope

    NASA Astrophysics Data System (ADS)

    Zhou, Zhi-sheng; Bin, Xiang-Li; Zhang, Wen-xi; Li, Yang; Kong, Xin-xin; Lv, Xiao-yu

    2013-09-01

    The effect of beam position error on the imaging quality of a Fourier telescope is analyzed in this paper. First, the origin of the transmitting beam position error and the error types are discussed. Second, a numerical analysis is performed. To focus on the transmitting beam position error, other noise sources exclusive of the reconstruction process are neglected. The Strehl ratio is set to be the objective function and the transfer function of the position error is constructed. Based on the numerical model, the features of Strehl ratio reduction caused by position error are deduced. Third, simulations are performed to study the position error effect on the imaging quality. A plot of the Strehl ratio versus the different levels of position errors is obtained and the simulation results validate the numerical model to a certain extent. According to the simulation results, a high value of the transmitting beam position error obviously degrades the imaging quality of the system; thus, it is essential to contain the position error within a relatively low level.

  3. Pointing error analysis of Risley-prism-based beam steering system.

    PubMed

    Zhou, Yuan; Lu, Yafei; Hei, Mo; Liu, Guangcan; Fan, Dapeng

    2014-09-01

    Based on the vector form Snell's law, ray tracing is performed to quantify the pointing errors of Risley-prism-based beam steering systems, induced by component errors, prism orientation errors, and assembly errors. Case examples are given to elucidate the pointing error distributions in the field of regard and evaluate the allowances of the error sources for a given pointing accuracy. It is found that the assembly errors of the second prism will result in more remarkable pointing errors in contrast with the first one. The pointing errors induced by prism tilt depend on the tilt direction. The allowances of bearing tilt and prism tilt are almost identical if the same pointing accuracy is planned. All conclusions can provide a theoretical foundation for practical works. PMID:25321377

  4. The effect of electron beam geometric deformation errors on the small-signal characteristic of ECRM

    NASA Astrophysics Data System (ADS)

    Yongjian, Yu

    1993-08-01

    In this paper is studied the effect of electron beam geometric deformation errors on the small — signal characteristics of the TE{mn/o} mode Electron Cyclotron Resonance Maser (ECRM), based on the elliptically cross—sectional e—beam deformation model. As an example, the effect of small geometric deformation errors on the TE{01/o} mode fundamental ECRM coupling coefficient is quantitatively shown.

  5. Developing beam phasing on the Nova laser

    SciTech Connect

    Ehrlich, R.B.; Amendt, P.A.; Dixit, S.N.; Hammel, B.A.; Kalantar, D.H.; Pennington, D.M.; Weiland, T.L.

    1997-03-10

    We are presently adding the capability to irradiate indirectly-driven Nova targets with two rings of illumination inside each end of the hohlraum for studies of time-dependent second Legendre (P2) and time- integrated fourth Legendre (P4) flux asymmetry control. The rings will be formed with specially designed kinoform phase plates (KPPs), which will direct each half of each beam into two separate rings that are nearly uniform azimuthally. The timing and temporal pulse shape of the outer rings will be controlled independently from those of the inner rings, allowing for phasing of the pulse shapes to control time dependent asymmetry. Modifications to the incident beam diagnostics (IBDS) will enable us to verify that acceptable levels of power balance among the contributing segments of each ring have been achieved on each shot. Current techniques for precision beam pointing and timing are expected to be sufficiently accurate for these experiments. We present a design for an affordable retrofit to achieve beam phasing on Nova, results of a simplified demonstration, and calculations highlighting the anticipated benefits.

  6. Some effects of quantization on a noiseless phase-locked loop. [sampling phase errors

    NASA Technical Reports Server (NTRS)

    Greenhall, C. A.

    1979-01-01

    If the VCO of a phase-locked receiver is to be replaced by a digitally programmed synthesizer, the phase error signal must be sampled and quantized. Effects of quantizing after the loop filter (frequency quantization) or before (phase error quantization) are investigated. Constant Doppler or Doppler rate noiseless inputs are assumed. The main result gives the phase jitter due to frequency quantization for a Doppler-rate input. By itself, however, frequency quantization is impractical because it makes the loop dynamic range too small.

  7. Experimental analysis of beam pointing system based on liquid crystal optical phase array

    NASA Astrophysics Data System (ADS)

    Shi, Yubin; Zhang, Jianmin; Zhang, Zhen

    2016-06-01

    In this paper, we propose and demonstrate an elementary non-mechanical beam aiming and steering system with a single liquid crystal optical phase array (LC-OPA) and charge-coupled device (CCD). With the conventional method of beam steering control, the LC-OPA device can realize one dimensional beam steering continuously. An improved beam steering strategy is applied to realize two dimensional beam steering with a single LC-OPA. The whole beam aiming and steering system, including an LC-OPA and a retroreflective target, is controlled by the monitor. We test the feasibility of beam steering strategy both in one dimension and in two dimension at first, then the whole system is build up based on the improved strategy. The experimental results show that the max experimental pointing error is 56 µrad, and the average pointing error of the system is 19 µrad.

  8. Stitching-error reduction in gratings by shot-shifted electron-beam lithography

    NASA Technical Reports Server (NTRS)

    Dougherty, D. J.; Muller, R. E.; Maker, P. D.; Forouhar, S.

    2001-01-01

    Calculations of the grating spatial-frequency spectrum and the filtering properties of multiple-pass electron-beam writing demonstrate a tradeoff between stitching-error suppression and minimum pitch separation. High-resolution measurements of optical-diffraction patterns show a 25-dB reduction in stitching-error side modes.

  9. Numerical phase retrieval from beam intensity measurements in three planes

    NASA Astrophysics Data System (ADS)

    Bruel, Laurent

    2003-05-01

    A system and method have been developed at CEA to retrieve phase information from multiple intensity measurements along a laser beam. The device has been patented. Commonly used devices for beam measurement provide phase and intensity information separately or with a rather poor resolution whereas the MIROMA method provides both at the same time, allowing direct use of the results in numerical models. Usual phase retrieval algorithms use two intensity measurements, typically the image plane and the focal plane (Gerschberg-Saxton algorithm) related by a Fourier transform, or the image plane and a lightly defocus plane (D.L. Misell). The principal drawback of such iterative algorithms is their inability to provide unambiguous convergence in all situations. The algorithms can stagnate on bad solutions and the error between measured and calculated intensities remains unacceptable. If three planes rather than two are used, the data redundancy created confers to the method good convergence capability and noise immunity. It provides an excellent agreement between intensity determined from the retrieved phase data set in the image plane and intensity measurements in any diffraction plane. The method employed for MIROMA is inspired from GS algorithm, replacing Fourier transforms by a beam-propagating kernel with gradient search accelerating techniques and special care for phase branch cuts. A fast one dimensional algorithm provides an initial guess for the iterative algorithm. Applications of the algorithm on synthetic data find out the best reconstruction planes that have to be chosen. Robustness and sensibility are evaluated. Results on collimated and distorted laser beams are presented.

  10. Active and passive compensation of APPLE II-introduced multipole errors through beam-based measurement

    NASA Astrophysics Data System (ADS)

    Chung, Ting-Yi; Huang, Szu-Jung; Fu, Huang-Wen; Chang, Ho-Ping; Chang, Cheng-Hsiang; Hwang, Ching-Shiang

    2016-08-01

    The effect of an APPLE II-type elliptically polarized undulator (EPU) on the beam dynamics were investigated using active and passive methods. To reduce the tune shift and improve the injection efficiency, dynamic multipole errors were compensated using L-shaped iron shims, which resulted in stable top-up operation for a minimum gap. The skew quadrupole error was compensated using a multipole corrector, which was located downstream of the EPU for minimizing betatron coupling, and it ensured the enhancement of the synchrotron radiation brightness. The investigation methods, a numerical simulation algorithm, a multipole error correction method, and the beam-based measurement results are discussed.

  11. Correction of beam errors in high power laser diode bars and stacks

    NASA Astrophysics Data System (ADS)

    Monjardin, J. F.; Nowak, K. M.; Baker, H. J.; Hall, D. R.

    2006-09-01

    The beam errors of an 11 bar laser diode stack fitted with fast-axis collimator lenses have been corrected by a single refractive plate, produced by laser cutting and polishing. The so-called smile effect is virtually eliminated and collimator aberration greatly reduced, improving the fast-axis beam quality of each bar by a factor of up to 5. The single corrector plate for the whole stack ensures that the radiation from all the laser emitters is parallel to a common axis. Beam-pointing errors of the bars have been reduced to below 0.7 mrad.

  12. Correction of phase-error for phase-resolved k-clocked optical frequency domain imaging

    NASA Astrophysics Data System (ADS)

    Mo, Jianhua; Li, Jianan; de Boer, Johannes F.

    2012-01-01

    Phase-resolved optical frequency domain imaging (OFDI) has emerged as a promising technique for blood flow measurement in human tissues. Phase stability is essential for this technique to achieve high accuracy in flow velocity measurement. In OFDI systems that use k-clocking for the data acquisition, phase-error occurs due to jitter in the data acquisition electronics. We presented a statistical analysis of jitter represented as point shifts of the k-clocked spectrum. We demonstrated a real-time phase-error correction algorithm for phase-resolved OFDI. A 50 KHz wavelength-swept laser (Axsun Technologies) based balanced-detection OFDI system was developed centered at 1310 nm. To evaluate the performance of this algorithm, a stationary gold mirror was employed as sample for phase analysis. Furthermore, we implemented this algorithm for imaging of human skin. Good-quality skin structure and Doppler image can be observed in real-time after phase-error correction. The results show that the algorithm can effectively correct the jitter-induced phase error in OFDI system.

  13. Investigation of phase error correction for digital sinusoidal phase-shifting fringe projection profilometry

    NASA Astrophysics Data System (ADS)

    Ma, S.; Quan, C.; Zhu, R.; Tay, C. J.

    2012-08-01

    Digital sinusoidal phase-shifting fringe projection profilometry (DSPFPP) is a powerful tool to reconstruct three-dimensional (3D) surface of diffuse objects. However, a highly accurate profile is often hindered by nonlinear response, color crosstalk and imbalance of a pair of digital projector and CCD/CMOS camera. In this paper, several phase error correction methods, such as Look-Up-Table (LUT) compensation, intensity correction, gamma correction, LUT-based hybrid method and blind phase error suppression for gray and color-encoded DSPFPP are described. Experimental results are also demonstrated to evaluate the effectiveness of each method.

  14. Wide-aperture laser beam measurement using transmission diffuser: errors modeling

    NASA Astrophysics Data System (ADS)

    Matsak, Ivan S.

    2015-06-01

    Instrumental errors of measurement wide-aperture laser beam diameter were modeled to build measurement setup and justify its metrological characteristics. Modeled setup is based on CCD camera and transmission diffuser. This method is appropriate for precision measurement of large laser beam width from 10 mm up to 1000 mm. It is impossible to measure such beams with other methods based on slit, pinhole, knife edge or direct CCD camera measurement. The method is suitable for continuous and pulsed laser irradiation. However, transmission diffuser method has poor metrological justification required in field of wide aperture beam forming system verification. Considering the fact of non-availability of a standard of wide-aperture flat top beam modelling is preferred way to provide basic reference points for development measurement system. Modelling was conducted in MathCAD. Super-Lorentz distribution with shape parameter 6-12 was used as a model of the beam. Using theoretical evaluations there was found that the key parameters influencing on error are: relative beam size, spatial non-uniformity of the diffuser, lens distortion, physical vignetting, CCD spatial resolution and, effective camera ADC resolution. Errors were modeled for 90% of power beam diameter criteria. 12-order Super-Lorentz distribution was primary model, because it precisely meets experimental distribution at the output of test beam forming system, although other orders were also used. The analytic expressions were obtained analyzing the modelling results for each influencing data. Attainability of <1% error based on choice of parameters of expression was shown. The choice was based on parameters of commercially available components of the setup. The method can provide up to 0.1% error in case of using calibration procedures and multiple measurements.

  15. EFFECT OF SOLENOID FIELD ERRORS ON ELECTRON BEAM TEMPERATURES IN THE RHIC ELECTRON COOLER.

    SciTech Connect

    MONTAG,C.KEWISCH,J.

    2003-05-12

    As part of a future upgrade to the Relativistic Heavy Ion Collider (RHIC), electron cooling is foreseen to decrease ion beam emittances. Within the electron cooling section, the ''hot'' ion beam is immersed in a ''cold'' electron beam. The cooling effect is further enhanced by a solenoid field in the cooling section, which forces the electrons to spiral around the field lines with a (Larmor) radius of 10 micrometers, reducing the effective transverse temperature by orders of magnitude. Studies of the effect of solenoid field errors on electron beam temperatures are reported.

  16. Pixelated mask spatial carrier phase shifting interferometry algorithms and associated errors

    SciTech Connect

    Kimbrough, Bradley T

    2006-07-01

    In both temporal and spatial carrier phase shifting interferometry, the primary source of phase calculation error results from an error in the relative phase shift between sample points. In spatial carrier phase shifting interferometry, this phase shifting error is caused directly by the wave front under test and is unavoidable. In order to minimize the phase shifting error, a pix elated spatial carrier phase shifting technique has been developed by 4D technologies. This new technique allows for the grouping of phase shifted pixels together around a single point in two dimensions,minimizing the phase shift change due to the spatial variation in the test wavefront. A formula for the phase calculation error in spatial carrier phase shifting interferometry is derived. The error associated with the use of linear N-point averaging algorithms is presented and compared with those of the pix elated spatial carrier technique.

  17. Active retrodirective arrays for SPS beam pointing. [phase conjugation

    NASA Technical Reports Server (NTRS)

    Chernoff, R.

    1980-01-01

    The basic requirement of the SPS beam pointing system is that it deliver a certain amount of S-band (lambda = 12.5 cm) power to a 9.6 km diameter receiving rectenna on the ground. The power is transmitted from a 1.0 km diameter antenna array on the SPS, which is, for a rectenna at about plus or minus 40 deg. latitude, some 37.5x10 to the 6th power km distant. At the present time ARA's appear to be the best bet to realize this very stringent beam pointing requirement. An active retrodirective array (ARA) transmits a beam towards the apparent source of an illuminating signal called the pilot. The array produces, not merely reflects, RF power. Retrodirectivity is achieved by retransmitting from each element of the array a signal whose phase is the "conjugate" of that received by the element. Phase conjugate circuits and pointing errors in ARA's are described. Results obtained using a 2-element X-band ARA and an 8-element S-band ARA are included.

  18. Signal distortion due to beam-pointing error in a chopper modulated laser system.

    PubMed

    Eklund, H

    1978-01-15

    The detector output has been studied for a long-distance system with a chopped cw laser as transmitter source. It is shown experimentally that the pulse distortion of the detected signal is dependent on the beam-pointing error. Parameters reflecting the pulse distortion are defined. The beam deviation in 1-D is found to be strongly related to these parameters. The result is in agreement with a theoretical model based upon the Fresnel diffraction theory. Possible applications in beam-tracking systems, communications systems, and atmospheric studies are discussed. PMID:20174398

  19. SU-E-T-377: Inaccurate Positioning Might Introduce Significant MapCheck Calibration Error in Flatten Filter Free Beams

    SciTech Connect

    Wang, S; Chao, C; Chang, J

    2014-06-01

    Purpose: This study investigates the calibration error of detector sensitivity for MapCheck due to inaccurate positioning of the device, which is not taken into account by the current commercial iterative calibration algorithm. We hypothesize the calibration is more vulnerable to the positioning error for the flatten filter free (FFF) beams than the conventional flatten filter flattened beams. Methods: MapCheck2 was calibrated with 10MV conventional and FFF beams, with careful alignment and with 1cm positioning error during calibration, respectively. Open fields of 37cmx37cm were delivered to gauge the impact of resultant calibration errors. The local calibration error was modeled as a detector independent multiplication factor, with which propagation error was estimated with positioning error from 1mm to 1cm. The calibrated sensitivities, without positioning error, were compared between the conventional and FFF beams to evaluate the dependence on the beam type. Results: The 1cm positioning error leads to 0.39% and 5.24% local calibration error in the conventional and FFF beams respectively. After propagating to the edges of MapCheck, the calibration errors become 6.5% and 57.7%, respectively. The propagation error increases almost linearly with respect to the positioning error. The difference of sensitivities between the conventional and FFF beams was small (0.11 ± 0.49%). Conclusion: The results demonstrate that the positioning error is not handled by the current commercial calibration algorithm of MapCheck. Particularly, the calibration errors for the FFF beams are ~9 times greater than those for the conventional beams with identical positioning error, and a small 1mm positioning error might lead to up to 8% calibration error. Since the sensitivities are only slightly dependent of the beam type and the conventional beam is less affected by the positioning error, it is advisable to cross-check the sensitivities between the conventional and FFF beams to detect

  20. Optical synthetic-aperture radar processor archietecture with quadratic phase-error correction

    SciTech Connect

    Dickey, F.M.; Mason, J.J. )

    1990-10-15

    Uncompensated phase errors limit the image quality of synthetic-aperture radar. We present an acousto-optic synthetic-aperture radar processor architecture capable of measuring the quadratic phase error. This architecture allows for the error signal to be fed back to the processor to generate the corrected image.

  1. Canceling the momentum in a phase-shifting algorithm to eliminate spatially uniform errors.

    PubMed

    Hibino, Kenichi; Kim, Yangjin

    2016-08-10

    In phase-shifting interferometry, phase modulation nonlinearity causes both spatially uniform and nonuniform errors in the measured phase. Conventional linear-detuning error-compensating algorithms only eliminate the spatially variable error component. The uniform error is proportional to the inertial momentum of the data-sampling weight of a phase-shifting algorithm. This paper proposes a design approach to cancel the momentum by using characteristic polynomials in the Z-transform space and shows that an arbitrary M-frame algorithm can be modified to a new (M+2)-frame algorithm that acquires new symmetry to eliminate the uniform error. PMID:27534475

  2. Ion beam machining error control and correction for small scale optics.

    PubMed

    Xie, Xuhui; Zhou, Lin; Dai, Yifan; Li, Shengyi

    2011-09-20

    Ion beam figuring (IBF) technology for small scale optical components is discussed. Since the small removal function can be obtained in IBF, it makes computer-controlled optical surfacing technology possible to machine precision centimeter- or millimeter-scale optical components deterministically. Using a small ion beam to machine small optical components, there are some key problems, such as small ion beam positioning on the optical surface, material removal rate, ion beam scanning pitch control on the optical surface, and so on, that must be seriously considered. The main reasons for the problems are that it is more sensitive to the above problems than a big ion beam because of its small beam diameter and lower material ratio. In this paper, we discuss these problems and their influences in machining small optical components in detail. Based on the identification-compensation principle, an iterative machining compensation method is deduced for correcting the positioning error of an ion beam with the material removal rate estimated by a selected optimal scanning pitch. Experiments on ϕ10 mm Zerodur planar and spherical samples are made, and the final surface errors are both smaller than λ/100 measured by a Zygo GPI interferometer. PMID:21947039

  3. Steady-state phase error for a phase-locked loop subjected to periodic Doppler inputs

    NASA Technical Reports Server (NTRS)

    Chen, C.-C.; Win, M. Z.

    1991-01-01

    The performance of a carrier phase locked loop (PLL) driven by a periodic Doppler input is studied. By expanding the Doppler input into a Fourier series and applying the linearized PLL approximations, it is easy to show that, for periodic frequency disturbances, the resulting steady state phase error is also periodic. Compared to the method of expanding frequency excursion into a power series, the Fourier expansion method can be used to predict the maximum phase error excursion for a periodic Doppler input. For systems with a large Doppler rate fluctuation, such as an optical transponder aboard an Earth orbiting spacecraft, the method can be applied to test whether a lower order tracking loop can provide satisfactory tracking and thereby save the effect of a higher order loop design.

  4. Autofocus of SAR imagery degraded by ionospheric-induced phase errors

    SciTech Connect

    Jakowatz, C.V. Jr.; Eichel, P.H.; Ghiglia, D.C.

    1989-01-01

    It has been suggested that synthetic aperture radar (SAR) images obtained from platforms such as SEASAT are subject to potential degradation by ionospheric-induced phase errors. This premise is based upon data from various satellite experiments that indicate large levels of phase scintillation in auroral zone data. Current models for phase errors induced by the ionosphere suggest that the phase error power spectrum is power law. This implies that the resulting phase errors contain significant components up to the Nyquist limit. Traditional sub-aperture based autofocus techniques, designed to correct uncompensated platform motion errors, are inadequate due to their inability to estimate higher order error terms. A new non-parametric phase error correction scheme developed at Sandia National Laboratories, however, has been demonstrated to remove phase errors of arbitrary structure. Consequently, our new algorithm is a viable candidate for correcting ionospheric phase errors. In this paper we show examples of SAR images degraded by simulated ionospheric phase errors. These images demonstrate that such errors cause smearing with complicated sidelobe structure. Restoration of these images via the new algorithm illustrates its superiority to classical sub-aperture based autofocus techniques.

  5. Automatic component calibration and error diagnostics for model-based accelerator control. Phase I final report

    SciTech Connect

    Dr. Carl Stern; Dr. Martin Lee

    1999-06-28

    Phase I work studied the feasibility of developing software for automatic component calibration and error correction in beamline optics models. A prototype application was developed that corrects quadrupole field strength errors in beamline models.

  6. Effects and correction of magneto-optic spatial light modulator phase errors in an optical correlator

    NASA Technical Reports Server (NTRS)

    Downie, John D.; Hine, Butler P.; Reid, Max B.

    1992-01-01

    The optical phase errors introduced into an optical correlator by the input and filter plane magnetooptic spatial light modulators have been studied. The magnitude of these phase errors is measured and characterized, their effects on the correlation results are evaluated, and a means of correction by a design modification of the binary phase-only optical-filter function is presented. The efficacy of the phase-correction technique is quantified and is found to restore the correlation characteristics to those obtained in the absence of errors, to a high degree. The phase errors of other correlator system elements are also discussed and treated in a similar fashion.

  7. Sensitivity analysis and optimization method for the fabrication of one-dimensional beam-splitting phase gratings

    PubMed Central

    Pacheco, Shaun; Brand, Jonathan F.; Zaverton, Melissa; Milster, Tom; Liang, Rongguang

    2015-01-01

    A method to design one-dimensional beam-spitting phase gratings with low sensitivity to fabrication errors is described. The method optimizes the phase function of a grating by minimizing the integrated variance of the energy of each output beam over a range of fabrication errors. Numerical results for three 1x9 beam splitting phase gratings are given. Two optimized gratings with low sensitivity to fabrication errors were compared with a grating designed for optimal efficiency. These three gratings were fabricated using gray-scale photolithography. The standard deviation of the 9 outgoing beam energies in the optimized gratings were 2.3 and 3.4 times lower than the optimal efficiency grating. PMID:25969268

  8. Analysis of the effects of mismatched errors on coherent beam combining based on a self-imaging waveguide

    NASA Astrophysics Data System (ADS)

    Tao, R.; Wang, X.; Zhou, Pu; Si, Lei

    2016-01-01

    A theoretical model of coherent beam combining (CBC) based on a self-imaging waveguide (SIW) is built and the effects of mismatched errors on SIW-based CBC are simulated and analysed numerically. With the combination of the theoretical model and the finite difference beam propagation method, two main categories of errors, assembly and nonassembly errors, are numerically studied to investigate their effect on the beam quality by using the M2 factor. The optimisation of the SIW and error control principle of the system is briefly discussed. The generalised methodology offers a good reference for investigating waveguide-based high-power coherent combining of fibre lasers in a comprehensive way.

  9. Model studies of the beam-filling error for rain-rate retrieval with microwave radiometers

    NASA Technical Reports Server (NTRS)

    Ha, Eunho; North, Gerald R.

    1995-01-01

    Low-frequency (less than 20 GHz) single-channel microwave retrievals of rain rate encounter the problem of beam-filling error. This error stems from the fact that the relationship between microwave brightness temperature and rain rate is nonlinear, coupled with the fact that the field of view is large or comparable to important scales of variability of the rain field. This means that one may not simply insert the area average of the brightness temperature into the formula for rain rate without incurring both bias and random error. The statistical heterogeneity of the rain-rate field in the footprint of the instrument is key to determining the nature of these errors. This paper makes use of a series of random rain-rate fields to study the size of the bias and random error associated with beam filling. A number of examples are analyzed in detail: the binomially distributed field, the gamma, the Gaussian, the mixed gamma, the lognormal, and the mixed lognormal ('mixed' here means there is a finite probability of no rain rate at a point of space-time). Of particular interest are the applicability of a simple error formula due to Chiu and collaborators and a formula that might hold in the large field of view limit. It is found that the simple formula holds for Gaussian rain-rate fields but begins to fail for highly skewed fields such as the mixed lognormal. While not conclusively demonstrated here, it is suggested that the notionof climatologically adjusting the retrievals to remove the beam-filling bias is a reasonable proposition.

  10. The effect of exit beam phase aberrations on parallel beam coherent x-ray reconstructions

    SciTech Connect

    Hruszkewycz, S. O.; Fuoss, P. H.; Harder, R.; Xiao, X.

    2010-12-15

    Diffraction artifacts from imperfect x-ray windows near the sample are an important consideration in the design of coherent x-ray diffraction measurements. In this study, we used simulated and experimental diffraction patterns in two and three dimensions to explore the effect of phase imperfections in a beryllium window (such as a void or inclusion) on the convergence behavior of phasing algorithms and on the ultimate reconstruction. A predictive relationship between beam wavelength, sample size, and window position was derived to explain the dependence of reconstruction quality on beryllium defect size. Defects corresponding to this prediction cause the most damage to the sample exit wave and induce signature error oscillations during phasing that can be used as a fingerprint of experimental x-ray window artifacts. The relationship between x-ray window imperfection size and coherent x-ray diffractive imaging reconstruction quality explored in this work can play an important role in designing high-resolution in situ coherent imaging instrumentation and will help interpret the phasing behavior of coherent diffraction measured in these in situ environments.

  11. The effect of exit beam phase aberrations on parallel beam coherent x-ray reconstructions.

    SciTech Connect

    Hruszkewycz, S. O.; Harder, R.; Xiao, X.; Fuoss, P. H.

    2010-12-01

    Diffraction artifacts from imperfect x-ray windows near the sample are an important consideration in the design of coherent x-ray diffraction measurements. In this study, we used simulated and experimental diffraction patterns in two and three dimensions to explore the effect of phase imperfections in a beryllium window (such as a void or inclusion) on the convergence behavior of phasing algorithms and on the ultimate reconstruction. A predictive relationship between beam wavelength, sample size, and window position was derived to explain the dependence of reconstruction quality on beryllium defect size. Defects corresponding to this prediction cause the most damage to the sample exit wave and induce signature error oscillations during phasing that can be used as a fingerprint of experimental x-ray window artifacts. The relationship between x-ray window imperfection size and coherent x-ray diffractive imaging reconstruction quality explored in this work can play an important role in designing high-resolution in situ coherent imaging instrumentation and will help interpret the phasing behavior of coherent diffraction measured in these in situ environments.

  12. Experimental analysis of beam aiming and pointing system with phased only spatial light modulators

    NASA Astrophysics Data System (ADS)

    Shi, Yubin; Feng, Guobin; Si, Lei

    2015-05-01

    In this paper, an advanced non-mechanical beam aiming and pointing system is presented. Traditional beam steering is based on the mechanical systems. In the complex and expensive systems, beam jittering and many other problems are major limitations. However, beam steering with optical phased array (OPA) devices can realize agile beam control with random access pointing and high efficiency. Our system is mainly based on phased only spatial light modulators (SLM), which can realize beam steering non-mechanically. Based on the conventional one dimensional beam steering method of SLM, two dimensional beam steering method was presented at first in order to demonstrate the feasibility of the whole system. Then the whole system was tested. Our beam steering system can steer beam to a target which was moving at the speed of 3.8mrad/s within the field of view. The RMS error of the system was 0.0246mrad in one dimension, and 0.139mrad in two dimension respectively. Meanwhile the whole process was recorded by another camera in order to show the results.

  13. Sparse Auto-Calibration for Radar Coincidence Imaging with Gain-Phase Errors

    PubMed Central

    Zhou, Xiaoli; Wang, Hongqiang; Cheng, Yongqiang; Qin, Yuliang

    2015-01-01

    Radar coincidence imaging (RCI) is a high-resolution staring imaging technique without the limitation of relative motion between target and radar. The sparsity-driven approaches are commonly used in RCI, while the prior knowledge of imaging models needs to be known accurately. However, as one of the major model errors, the gain-phase error exists generally, and may cause inaccuracies of the model and defocus the image. In the present report, the sparse auto-calibration method is proposed to compensate the gain-phase error in RCI. The method can determine the gain-phase error as part of the imaging process. It uses an iterative algorithm, which cycles through steps of target reconstruction and gain-phase error estimation, where orthogonal matching pursuit (OMP) and Newton’s method are used, respectively. Simulation results show that the proposed method can improve the imaging quality significantly and estimate the gain-phase error accurately. PMID:26528981

  14. Radar coincidence imaging with phase error using Bayesian hierarchical prior modeling

    NASA Astrophysics Data System (ADS)

    Zhou, Xiaoli; Wang, Hongqiang; Cheng, Yongqiang; Qin, Yuliang

    2016-01-01

    Radar coincidence imaging (RCI) is a high-resolution imaging technique without the limitation of relative motion between target and radar. In sparsity-driven RCI, the prior knowledge of imaging model requires to be known accurately. However, the phase error generally exists as a model error, which may cause inaccuracies of the model and defocus the image. The problem is formulated using Bayesian hierarchical prior modeling, and the self-calibration variational message passing (SC-VMP) algorithm is proposed to improve the performance of RCI with phase error. The algorithm determines the phase error as part of the imaging process. The scattering coefficient and phase error are iteratively estimated using VMP and Newton's method, respectively. Simulation results show that the proposed algorithm can estimate the phase error accurately and improve the imaging quality significantly.

  15. Superconducting resonator used as a beam phase detector.

    SciTech Connect

    Sharamentov, S. I.; Pardo, R. C.; Ostroumov, P. N.; Clifft, B. E.; Zinkann, G. P.; Physics

    2003-05-01

    Beam-bunch arrival time has been measured for the first time by operating superconducting cavities, normally part of the linac accelerator array, in a bunch-detecting mode. The very high Q of the superconducting cavities provides high sensitivity and allows for phase-detecting low-current beams. In detecting mode, the resonator is operated at a very low field level comparable to the field induced by the bunched beam. Because of this, the rf field in the cavity is a superposition of a 'pure' (or reference) rf and the beam-induced signal. A new method of circular phase rotation (CPR), allowing extraction of the beam phase information from the composite rf field was developed. Arrival time phase determination with CPR is better than 1{sup o} (at 48 MHz) for a beam current of 100 nA. The electronics design is described and experimental data are presented.

  16. Highly efficient electron vortex beams generated by nanofabricated phase holograms

    SciTech Connect

    Grillo, Vincenzo; Mafakheri, Erfan; Frabboni, Stefano

    2014-01-27

    We propose an improved type of holographic-plate suitable for the shaping of electron beams. The plate is fabricated by a focused ion beam on a silicon nitride membrane and introduces a controllable phase shift to the electron wavefunction. We adopted the optimal blazed-profile design for the phase hologram, which results in the generation of highly efficient (25%) electron vortex beams. This approach paves the route towards applications in nano-scale imaging and materials science.

  17. Refracting type laser beam scanner with minimum across-scan error

    NASA Astrophysics Data System (ADS)

    Khattak, Anwar S.

    1993-11-01

    An economical refracting type laser beam scanning device, exhibiting a minimum across-scan error without corrective measures, is described. The main structural assembly of the device consists of a rotating prism, a fixed spherical lens, and a fixed convex spherical auxiliary reflector (SAR). Trigonometric equations are developed to determine the radius of curvature of the SAR and the size of the exit pupil. Resolution analyses are presented for a specific set of design parameters.

  18. A review of setup error in supine breast radiotherapy using cone-beam computed tomography.

    PubMed

    Batumalai, Vikneswary; Holloway, Lois; Delaney, Geoff P

    2016-01-01

    Setup error in breast radiotherapy (RT) measured with 3-dimensional cone-beam computed tomography (CBCT) is becoming more common. The purpose of this study is to review the literature relating to the magnitude of setup error in breast RT measured with CBCT. The different methods of image registration between CBCT and planning computed tomography (CT) scan were also explored. A literature search, not limited by date, was conducted using Medline and Google Scholar with the following key words: breast cancer, RT, setup error, and CBCT. This review includes studies that reported on systematic and random errors, and the methods used when registering CBCT scans with planning CT scan. A total of 11 relevant studies were identified for inclusion in this review. The average magnitude of error is generally less than 5mm across a number of studies reviewed. The common registration methods used when registering CBCT scans with planning CT scan are based on bony anatomy, soft tissue, and surgical clips. No clear relationships between the setup errors detected and methods of registration were observed from this review. Further studies are needed to assess the benefit of CBCT over electronic portal image, as CBCT remains unproven to be of wide benefit in breast RT. PMID:27311516

  19. Random and systematic beam modulator errors in dynamic intensity modulated radiotherapy

    NASA Astrophysics Data System (ADS)

    Parsai, Homayon; Cho, Paul S.; Phillips, Mark H.; Giansiracusa, Robert S.; Axen, David

    2003-05-01

    This paper reports on the dosimetric effects of random and systematic modulator errors in delivery of dynamic intensity modulated beams. A sliding-widow type delivery that utilizes a combination of multileaf collimators (MLCs) and backup diaphragms was examined. Gaussian functions with standard deviations ranging from 0.5 to 1.5 mm were used to simulate random positioning errors. A clinical example involving a clival meningioma was chosen with optic chiasm and brain stem as limiting critical structures in the vicinity of the tumour. Dose calculations for different modulator fluctuations were performed, and a quantitative analysis was carried out based on cumulative and differential dose volume histograms for the gross target volume and surrounding critical structures. The study indicated that random modulator errors have a strong tendency to reduce minimum target dose and homogeneity. Furthermore, it was shown that random perturbation of both MLCs and backup diaphragms in the order of σ = 1 mm can lead to 5% errors in prescribed dose. In comparison, when MLCs or backup diaphragms alone was perturbed, the system was more robust and modulator errors of at least σ = 1.5 mm were required to cause dose discrepancies greater than 5%. For systematic perturbation, even errors in the order of +/-0.5 mm were shown to result in significant dosimetric deviations.

  20. Channel calibration for digital array radar in the presence of amplitude-phase and mutual coupling errors

    NASA Astrophysics Data System (ADS)

    Li, Weixing; Zhang, Yue; Lin, Jianzhi; Chen, Zengping

    2015-10-01

    Amplitude-phase errors and mutual coupling errors among multi-channels in digital array radar (DAR) will seriously deteriorate the performance of signal processing such as digital beam-forming (DBF) and high resolution direction finding. In this paper, a combined algorithm for error calibration in DAR has been demonstrated. The algorithm firstly estimates the amplitude-phase errors of each channel using interior calibration sources with the help of the calibration network. Then the signals from far field are received and the amplitude-phase errors are compensated. According to the subspace theories, the relationship between the principle eigenvectors and distorted steering vectors is expressed, and the cost function containing the mutual coupling matrix (MCM) and incident directions is established. Making use of the properties of MCM of uniform linear array, Gauss-Newton method is implied to iteratively compute the MCM and the direction of arrival (DOA). Simulation results have shown the effectiveness and performance of proposed algorithm. Based on an 8-elements DAR test-bed, experiments are carried out in anechoic chamber. The results illustrate that the algorithm is feasible in actual systems.

  1. Phased laser array for generating a powerful laser beam

    DOEpatents

    Holzrichter, John F.; Ruggiero, Anthony J.

    2004-02-17

    A first injection laser signal and a first part of a reference laser beam are injected into a first laser element. At least one additional injection laser signal and at least one additional part of a reference laser beam are injected into at least one additional laser element. The first part of a reference laser beam and the at least one additional part of a reference laser beam are amplified and phase conjugated producing a first amplified output laser beam emanating from the first laser element and an additional amplified output laser beam emanating from the at least one additional laser element. The first amplified output laser beam and the additional amplified output laser beam are combined into a powerful laser beam.

  2. Per-beam, planar IMRT QA passing rates do not predict clinically relevant patient dose errors

    SciTech Connect

    Nelms, Benjamin E.; Zhen Heming; Tome, Wolfgang A.

    2011-02-15

    Purpose: The purpose of this work is to determine the statistical correlation between per-beam, planar IMRT QA passing rates and several clinically relevant, anatomy-based dose errors for per-patient IMRT QA. The intent is to assess the predictive power of a common conventional IMRT QA performance metric, the Gamma passing rate per beam. Methods: Ninety-six unique data sets were created by inducing four types of dose errors in 24 clinical head and neck IMRT plans, each planned with 6 MV Varian 120-leaf MLC linear accelerators using a commercial treatment planning system and step-and-shoot delivery. The error-free beams/plans were used as ''simulated measurements'' (for generating the IMRT QA dose planes and the anatomy dose metrics) to compare to the corresponding data calculated by the error-induced plans. The degree of the induced errors was tuned to mimic IMRT QA passing rates that are commonly achieved using conventional methods. Results: Analysis of clinical metrics (parotid mean doses, spinal cord max and D1cc, CTV D95, and larynx mean) vs IMRT QA Gamma analysis (3%/3 mm, 2/2, 1/1) showed that in all cases, there were only weak to moderate correlations (range of Pearson's r-values: -0.295 to 0.653). Moreover, the moderate correlations actually had positive Pearson's r-values (i.e., clinically relevant metric differences increased with increasing IMRT QA passing rate), indicating that some of the largest anatomy-based dose differences occurred in the cases of high IMRT QA passing rates, which may be called ''false negatives.'' The results also show numerous instances of false positives or cases where low IMRT QA passing rates do not imply large errors in anatomy dose metrics. In none of the cases was there correlation consistent with high predictive power of planar IMRT passing rates, i.e., in none of the cases did high IMRT QA Gamma passing rates predict low errors in anatomy dose metrics or vice versa. Conclusions: There is a lack of correlation between

  3. Error analysis of the phase-shifting technique when applied to shadow moire

    SciTech Connect

    Han, Changwoon; Han Bongtae

    2006-02-20

    An exact solution for the intensity distribution of shadow moire fringes produced by a broad spectrum light is presented. A mathematical study quantifies errors in fractional fringe orders determined by the phase-shifting technique, and its validity is corroborated experimentally. The errors vary cyclically as the distance between the reference grating and the specimen increases. The amplitude of the maximum error is approximately 0.017 fringe, which defines the theoretical limit of resolution enhancement offered by the phase-shifting technique.

  4. Radio metric errors due to mismatch and offset between a DSN antenna beam and the beam of a troposphere calibration instrument

    NASA Technical Reports Server (NTRS)

    Linfield, R. P.; Wilcox, J. Z.

    1993-01-01

    Two components of the error of a troposphere calibration measurement were quantified by theoretical calculations. The first component is a beam mismatch error, which occurs when the calibration instrument senses a conical volume different from the cylindrical volume sampled by a Deep Space Network (DSN) antenna. The second component is a beam offset error, which occurs if the calibration instrument is not mounted on the axis of the DSN antenna. These two error sources were calculated for both delay (e.g., VLBI) and delay rate (e.g., Doppler) measurements. The beam mismatch error for both delay and delay rate drops rapidly as the beamwidth of the troposphere calibration instrument (e.g., a water vapor radiometer or an infrared Fourier transform spectrometer) is reduced. At a 10-deg elevation angle, the instantaneous beam mismatch error is 1.0 mm for a 6-deg beamwidth and 0.09 mm for a 0.5-deg beam (these are the full angular widths of a circular beam with uniform gain out to a sharp cutoff). Time averaging for 60-100 sec will reduce these errors by factors of 1.2-2.2. At a 20-deg elevation angle, the lower limit for current Doppler observations, the beam-mismatch delay rate error is an Allan standard deviation over 100 sec of 1.1 x 10(exp -14) with a 4-deg beam and 1.3 x 10(exp -l5) for a 0.5-deg beam. A 50-m beam offset would result in a fairly modest (compared to other expected error sources) delay error (less than or equal to 0.3 mm for 60-sec integrations at any elevation angle is greater than or equal to 6 deg). However, the same offset would cause a large error in delay rate measurements (e.g., an Allan standard deviation of 1.2 x 10(exp -14) over 100 sec at a 20-deg elevation angle), which would dominate over other known error sources if the beamwidth is 2 deg or smaller. An on-axis location is essential for accurate troposphere calibration of delay rate measurements. A half-power beamwidth (for a beam with a tapered gain profile) of 1.2 deg or smaller is

  5. The effects of betatron phase advances on beam-beam and its compensation in RHIC

    SciTech Connect

    Luo, Y.; Fischer, W.; Gu, X.; Tepikian, S.; Trbojevic, D.

    2011-03-28

    In this article we perform simulation studies to investigate the effects of betatron phase advances between the beam-beam interaction points on half-integer resonance driving term, second order chromaticty and dynamic aperture in RHIC. The betatron phase advances are adjusted with artificial matrices inserted in the middle of arcs. The lattices for the 2011 RHIC polarized proton (p-p) run and 2010 RHIC Au-Au runs are used in this study. We also scan the betatron phase advances between IP8 and the electron lens for the proposed Blue ring lattice with head-on beam-beam compensation.

  6. Overview of Phase Space Manipulations of Relativistic Electron Beams

    SciTech Connect

    Xiang, Dao; /SLAC

    2012-08-31

    Phase space manipulation is a process to rearrange beam's distribution in 6-D phase space. In this paper, we give an overview of the techniques for tailoring beam distribution in 2D, 4D, and 6D phase space to meet the requirements of various applications. These techniques become a new focus of accelerator physics R&D and very likely these advanced concepts will open up new opportunities in advanced accelerators and the science enabled by them.

  7. Optical beam forming techniques for phased array antennas

    NASA Technical Reports Server (NTRS)

    Wu, Te-Kao; Chandler, C.

    1993-01-01

    Conventional phased array antennas using waveguide or coax for signal distribution are impractical for large scale implementation on satellites or spacecraft because they exhibit prohibitively large system size, heavy weight, high attenuation loss, limited bandwidth, sensitivity to electromagnetic interference (EMI) temperature drifts and phase instability. However, optical beam forming systems are smaller, lighter, and more flexible. Three optical beam forming techniques are identified as applicable to large spaceborne phased array antennas. They are (1) the optical fiber replacement of conventional RF phased array distribution and control components, (2) spatial beam forming, and (3) optical beam splitting with integrated quasi-optical components. The optical fiber replacement and the spatial beam forming approaches were pursued by many organizations. Two new optical beam forming architectures are presented. Both architectures involve monolithic integration of the antenna radiating elements with quasi-optical grid detector arrays. The advantages of the grid detector array in the optical process are the higher power handling capability and the dynamic range. One architecture involves a modified version of the original spatial beam forming approach. The basic difference is the spatial light modulator (SLM) device for controlling the aperture field distribution. The original liquid crystal light valve SLM is replaced by an optical shuffling SLM, which was demonstrated for the 'smart pixel' technology. The advantages are the capability of generating the agile beams of a phased array antenna and to provide simultaneous transmit and receive functions. The second architecture considered is the optical beam splitting approach. This architecture involves an alternative amplitude control for each antenna element with an optical beam power divider comprised of mirrors and beam splitters. It also implements the quasi-optical grid phase shifter for phase control and grid

  8. Direct focusing error correction with ring-wide TBT beam position data

    SciTech Connect

    Yang, M.J.; /Fermilab

    2011-03-01

    Turn-By-Turn (TBT) betatron oscillation data is a very powerful tool in studying machine optics. Hundreds and thousands of turns of free oscillations are taken in just few tens of milliseconds. With beam covering all positions and angles at every location TBT data can be used to diagnose focusing errors almost instantly. This paper describes a new approach that observes focusing error collectively over all available TBT data to find the optimized quadrupole strength, one location at a time. Example will be shown and other issues will be discussed. The procedure presented clearly has helped to reduce overall deviations significantly, with relative ease. Sextupoles, being a permanent feature of the ring, will need to be incorporated into the model. While cumulative effect from all sextupoles around the ring may be negligible on turn-to-turn basis it is not so in this transfer line analysis. It should be noted that this procedure is not limited to looking for quadrupole errors. By modifying the target of minimization it could in principle be used to look for skew quadrupole errors and sextupole errors as well.

  9. Correction of magnetooptic device phase errors in optical correlators through filter design modifications

    NASA Technical Reports Server (NTRS)

    Downie, John D.; Reid, Max B.; Hine, Butler P.

    1991-01-01

    We address the problem of optical phase errors in an optical correlator introduced by the input and filter plane spatial light modulators. Specifically, we study a laboratory correlator with magnetooptic spatial light modulator (MOSLM) devices. We measure and characterize the phase errors, analyze their effects on the correlation process, and discuss a means of correction through a design modification of the binary phase-only optical filter function. The phase correction technique is found to produce correlation results close to those of an error-free correlator.

  10. Fringe order error in multifrequency fringe projection phase unwrapping: reason and correction.

    PubMed

    Zhang, Chunwei; Zhao, Hong; Zhang, Lu

    2015-11-10

    A multifrequency fringe projection phase unwrapping algorithm (MFPPUA) is important to fringe projection profilometry, especially when a discontinuous object is measured. However, a fringe order error (FOE) may occur when MFPPUA is adopted. An FOE will result in error to the unwrapped phase. Although this kind of phase error does not spread, it brings error to the eventual 3D measurement results. Therefore, an FOE or its adverse influence should be obviated. In this paper, reasons for the occurrence of an FOE are theoretically analyzed and experimentally explored. Methods to correct the phase error caused by an FOE are proposed. Experimental results demonstrate that the proposed methods are valid in eliminating the adverse influence of an FOE. PMID:26560763

  11. Coarse-Frequency-Comb Multiple-Beam Interferometry: Phase Assessment Using Common Phase Shifting Procedures

    NASA Astrophysics Data System (ADS)

    Schwider, J.

    2010-04-01

    interferometry in combination with frequency comb illumination. Through the use of a set of properly selected wavelengths the resulting interference pattern will become on the one hand more and more cosine-type with increasing enhancement factors and on the other hand it will be shown how the nonlinear relationship of the intensity distribution on the phase in the multiple beam interferometer can be overcome. Typical systematic errors show a periodicity with 4-times the fringe frequency of the interference pattern. By using the averaging of the measuring results of two measurements having a phase offset of π/4 it is possible to reduce this error by at least one order of magnitude. The impact of the nonlinear intensity profile of multiple beam fringes in transmitted light can in addition be reduced through inverted intensity values in the common phase shifting equations. It will be shown that in this way repeatability values can be obtained of 1.2 A˚ peak to valley and 0.12 A˚ rms.

  12. Effect of Field Errors in Muon Collider IR Magnets on Beam Dynamics

    SciTech Connect

    Alexahin, Y.; Gianfelice-Wendt, E.; Kapin, V.V.; /Fermilab

    2012-05-01

    In order to achieve peak luminosity of a Muon Collider (MC) in the 10{sup 35} cm{sup -2}s{sup -1} range very small values of beta-function at the interaction point (IP) are necessary ({beta}* {le} 1 cm) while the distance from IP to the first quadrupole can not be made shorter than {approx}6 m as dictated by the necessity of detector protection from backgrounds. In the result the beta-function at the final focus quadrupoles can reach 100 km making beam dynamics very sensitive to all kind of errors. In the present report we consider the effects on momentum acceptance and dynamic aperture of multipole field errors in the body of IR dipoles as well as of fringe-fields in both dipoles and quadrupoles in the ase of 1.5 TeV (c.o.m.) MC. Analysis shows these effects to be strong but correctable with dedicated multipole correctors.

  13. Motion-induced phase error estimation and correction in 3D diffusion tensor imaging.

    PubMed

    Van, Anh T; Hernando, Diego; Sutton, Bradley P

    2011-11-01

    A multishot data acquisition strategy is one way to mitigate B0 distortion and T2∗ blurring for high-resolution diffusion-weighted magnetic resonance imaging experiments. However, different object motions that take place during different shots cause phase inconsistencies in the data, leading to significant image artifacts. This work proposes a maximum likelihood estimation and k-space correction of motion-induced phase errors in 3D multishot diffusion tensor imaging. The proposed error estimation is robust, unbiased, and approaches the Cramer-Rao lower bound. For rigid body motion, the proposed correction effectively removes motion-induced phase errors regardless of the k-space trajectory used and gives comparable performance to the more computationally expensive 3D iterative nonlinear phase error correction method. The method has been extended to handle multichannel data collected using phased-array coils. Simulation and in vivo data are shown to demonstrate the performance of the method. PMID:21652284

  14. Simulation-aided investigation of beam hardening induced errors in CT dimensional metrology

    NASA Astrophysics Data System (ADS)

    Tan, Ye; Kiekens, Kim; Welkenhuyzen, Frank; Angel, J.; De Chiffre, L.; Kruth, Jean-Pierre; Dewulf, Wim

    2014-06-01

    Industrial x-ray computed tomography (CT) systems are being increasingly used as dimensional measuring machines. However, micron level accuracy is not always achievable, as of yet. The measurement accuracy is influenced by many factors, such as the workpiece properties, x-ray voltage, filter, beam hardening, scattering and calibration methods (Kruth et al 2011 CIRP Ann. Manuf. Technol. 60 821-42, Bartscher et al 2007 CIRP Ann. Manuf. Technol. 56 495-8, De Chiffre et al 2005 CIRP Ann. Manuf. Technol. 54 479-82, Schmitt and Niggemann 2010 Meas. Sci. Technol. 21 054008). Since most of these factors are mutually correlated, it remains challenging to interpret measurement results and to identify the distinct error sources. Since simulations allow isolating the different affecting factors, they form a useful complement to experimental investigations. Dewulf et al (2012 CIRP Ann. Manuf. Technol. 61 495-8) investigated the influence of beam hardening correction parameters on the diameter of a calibrated steel pin in different experimental set-ups. It was clearly shown that an inappropriate beam hardening correction can result in significant dimensional errors. This paper confirms these results using simulations of a pin surrounded by a stepped cylinder: a clear discontinuity in the measured diameter of the inner pin is observed where it enters the surrounding material. The results are expanded with an investigation of the beam hardening effect on the measurement results for both inner and outer diameters of the surrounding stepped cylinder. Accuracy as well as the effect on the uncertainty determination is discussed. The results are compared with simulations using monochromatic beams in order to have a benchmark which excludes beam hardening effects and x-ray scattering. Furthermore, based on the above results, the authors propose a case-dependent calibration artefact for beam hardening correction and edge offset determination. In the final part of the paper, the

  15. Beam-phase monitoring with non-destructive pickup

    SciTech Connect

    Bogaty, J.; Clifft, B.E.

    1995-08-01

    An intensity and phase-sensitive capacitive pickup was installed at the entrance to the PII linac. This device is based on an extension of the design of the Beam Current Monitor developed as part of the ATLAS radiation safety system. The purpose of the pickup is to allow the arrival phase of the beam from the ECR source at the entrance to the PII linac to be set to a standard which reproduces previous tune conditions and establishes a standard. The new pickups and associated electronics demonstrated sensitivity well below 1 electrical nanoamp but can handle beam currents of many electrical microamps as well. In addition to phase information, beam current is also measured by the units thus providing a continuous, non-intercepting current readout as well. From the very first use of PII, we established a few {open_quotes}reference tunes{close_quotes} for the linac and scaled those tunes for any other beam desired. For such scaling to work properly, the velocity and phase of the beam from the ion source must be fixed and reproducible. In last year`s FWP the new ATLAS Master Oscillator System was described. The new system has the ability of easily adjusting the beam arrival phase at the entrance to each of the major sections of the facility - PII, Booster, ATLAS. Our present techniques for establishing the beam arrival phase at the entrance of each of the linac sections are cumbersome and, sometimes, intellectually challenging. The installation of these capacitative pickups at the entrance to each of the linac sections will make the determination and setting of the beam arrival phase direct, simple, and dynamic. This should dramatically shorten our setup time for {open_quotes}old-tune{close_quotes} configurations and increase useful operating hours. Permanent electronics for the PII entrance pickup is under construction.

  16. Soliton-guided phase shifter and beam splitter

    SciTech Connect

    Steiglitz, Ken

    2010-03-15

    We propose, analyze, and study numerically a phase shifter for light wave packets trapped by Kerr solitons in a nonlinear medium. We also study numerically a previously proposed soliton-guided nonpolarizing beam splitter.

  17. Blind phase error suppression for color-encoded digital fringe projection profilometry

    NASA Astrophysics Data System (ADS)

    Ma, S.; Zhu, R.; Quan, C.; Li, B.; Tay, C. J.; Chen, L.

    2012-04-01

    Color-encoded digital fringe projection profilometry (CDFPP) has the advantage of fast speed, non-contact and full-field testing. It is one of the most important dynamic three-dimensional (3D) profile measurement techniques. However, due to factors such as color cross-talk and gamma distortion of electro-optical devices, phase errors arise when conventional phase-shifting algorithms with fixed phase shift values are utilized to retrieve phases. In this paper, a simple and effective blind phase error suppression approach based on isotropic n-dimensional fringe pattern normalization (INFPN) and carrier squeezing interferometry (CSI) is proposed. It does not require pre-calibration for the gamma and color-coupling coefficients or the phase shift values. Simulation and experimental works show that our proposed approach is able to effectively suppress phase errors and achieve accurate measurement results in CDFPP.

  18. Compact and phase-error-robust multilayered AWG-based wavelength selective switch driven by a single LCOS.

    PubMed

    Sorimoto, Keisuke; Tanizawa, Ken; Uetsuka, Hisato; Kawashima, Hitoshi; Mori, Masahiko; Hasama, Toshifumi; Ishikawa, Hiroshi; Tsuda, Hiroyuki

    2013-07-15

    A novel liquid crystal on silicon (LCOS)-based wavelength selective switch (WSS) is proposed, fabricated, and demonstrated. It employs a multilayered arrayed waveguide grating (AWG) as a wavelength multiplex/demultiplexer. The LCOS deflects spectrally decomposed beams channel by channel and switches them to desired waveguide layers of the multilayered AWG. In order to obtain the multilayered AWG with high yield, phase errors of the AWG is externally compensated for by an additional phase modulation with the LCOS. This additional phase modulation is applied to the equivalent image of the facet of the AWG, which is projected by a relay lens. In our previously-reported WSS configuration, somewhat large footprint and increased cost were the drawbacks, since two LCOSs were required: one LCOS was driven for the inter-port switching operation, and the other was for the phase-error compensation. In the newly proposed configuration, on the other hand, both switching and compensation operations are performed using a single LCOS. This reduction of the component count is realized by introducing the folded configuration with a reflector. The volume of the WSS optics is 80 × 100 × 60 mm3, which is approximately 40% smaller than the previous configuration. The polarization-dependent loss and inter-channel crosstalk are less than 1.5 dB and -21.0 dB, respectively. An error-free transmission of 40-Gbit/s NRZ-OOK signal through the WSS is successfully demonstrated. PMID:23938561

  19. Phase conjugation of a quantum-degenerate atomic fermion beam.

    PubMed

    Search, Chris P; Meystre, Pierre

    2003-09-01

    We discuss the possibility of phase conjugation of an atomic Fermi field via nonlinear wave mixing in an ultracold gas. It is shown that for a beam of fermions incident on an atomic phase-conjugate mirror, a time-reversed backward propagating fermionic beam is generated similar to the case in nonlinear optics. By adopting an operational definition of the phase, we show that it is possible to infer the presence of the phase-conjugate field by the loss of the interference pattern in an atomic interferometer. PMID:14525466

  20. Phase error suppression by low-pass filtering for synthetic aperture imaging ladar

    NASA Astrophysics Data System (ADS)

    Sun, Zhiwei; Hou, Peipei; Zhi, Ya'nan; Sun, Jianfeng; Zhou, Yu; Xu, Qian; Lu, Zhiyong; Liu, Liren

    2014-09-01

    Compared to synthetic aperture radar (SAR), synthetic aperture imaging ladar (SAIL) is more sensitive to the phase errors induced by atmospheric turbulence, undesirable line-of-sight translation-vibration and waveform phase error, because the light wavelength is about 3-6 orders of magnitude less than that of the radio frequency. This phase errors will deteriorate the imaging results. In this paper, an algorithm based on low-pass filtering to suppress the phase error is proposed. In this algorithm, the azimuth quadratic phase history with phase error is compensated, then the fast Fourier transform (FFT) is performed in azimuth direction, after the low-pass filtering, the inverse FFT is performed, then the image is reconstructed simultaneously in the range and azimuth direction by the two-dimensional (2D) FFT. The highfrequency phase error can be effectively eliminated hence the imaging results can be optimized by this algorithm. The mathematical analysis by virtue of data-collection equation of side-looking SAIL is presented. The theoretical modeling results are also given. In addition, based on this algorithm, a principle scheme of optical processor is proposed. The verified experiment is performed employing the data obtained from a SAIL demonstrator.

  1. A multimode DLL with trade-off between multiphase and static phase error

    NASA Astrophysics Data System (ADS)

    Dandan, Zhang; Wenrui, Zhu; Wei, Li; Zhihong, Huang; Lijiang, Gao; Haigang, Yang

    2014-05-01

    A multimode DLL with trade-off between multiphase and static phase error is presented. By adopting a multimode control circuit to regroup the delay line, a better static phase error performance can be achieved while reducing the number of output phases. The DLL accomplishes three operation modes: mode1 with a four-phase output, mode2 with a two-phase output and a better static phase error performance, and mode3 with only a one-phase output but the best static phase error performance. The proposed DLL has been fabricated in 0.13 μm CMOS technology and measurement results show that the static phase errors of mode1, mode2 and mode3 are -18.2 ps, 11.8 ps and -6:44 ps, respectively, at 200 MHz. The measured RMS and peak-to-peak jitters of mode1, mode2 and mode3 are 2.0 ps, 2.2 ps, 2.1 ps and 10 ps, 9.3 ps, 10 ps respectively.

  2. Beam-Switch Transient Effects in the RF Path of the ICAPA Receive Phased Array Antenna

    NASA Technical Reports Server (NTRS)

    Sands, O. Scott

    2003-01-01

    When the beam of a Phased Array Antenna (PAA) is switched from one pointing direction to another, transient effects in the RF path of the antenna are observed. Testing described in the report has revealed implementation-specific transient effects in the RF channel that are associated with digital clocking pulses that occur with transfer of data from the Beam Steering Controller (BSC) to the digital electronics of the PAA under test. The testing described here provides an initial assessment of the beam-switch phenomena by digitally acquiring time series of the RF communications channel, under CW excitation, during the period of time that the beam switch transient occurs. Effects are analyzed using time-frequency distributions and instantaneous frequency estimation techniques. The results of tests conducted with CW excitation supports further Bit-Error-Rate (BER) testing of the PAA communication channel.

  3. Cone Beam Computed Tomography Number Errors and Consequences for Radiotherapy Planning: An Investigation of Correction Methods

    SciTech Connect

    Poludniowski, Gavin G.; Evans, Philip M.; Webb, Steve

    2012-09-01

    Purpose: The potential of keV cone beam computed tomography (CBCT) for guiding adaptive replanning is well-known. There are impediments to this, one being CBCT number accuracy. The purpose of this study was to investigate CBCT number correction methods and the affect of residual inaccuracies on dose deposition. Four different correction strategies were applied to the same patient data to compare performance and the sophistication of correction-method needed for acceptable dose errors. Methods and Materials: Planning CT and CBCT reconstructions were used for 12 patients (6 brain, 3 prostate, and 3 bladder cancer patients). All patients were treated using Elekta linear accelerators and XVI imaging systems. Two of the CBCT number correction methods investigated were based on an algorithm previously proposed by the authors but only previously applied to phantoms. Two further methods, based on an approach previously suggested in the research literature, were also examined. Dose calculations were performed using scans of a 'worst' subset of patients using the Pinnacle{sup 3} version 9.0 treatment planning system and the patients' clinical plans. Results: All mean errors in CBCT number were <50 HU, and all correction methods performed well or adequately in dose calculations. The worst single dose discrepancy identified for any of the examined methods or patients was 3.0%. Mean errors in the doses to treatment volumes or organs at risk were negatively correlated with the mean error in CT number. That is, a mean CT number that was too large, averaged over the entire CBCT volume, implied an underdosing in a volume-of-interest and vice versa. Conclusions: Results suggest that (1) the correction of CBCT numbers to within a mean error of 50 HU in the scan volume provides acceptable discrepancies in dose (<3%) and (2) this is achievable with even quite unsophisticated correction methods.

  4. Poster — Thur Eve — 08: Rotational errors with on-board cone beam computed tomography

    SciTech Connect

    Ali, E. S. M.; Webb, R.; Nyiri, B.

    2014-08-15

    The focus of this study is on the Elekta XVI on-board cone beam computed tomography (CBCT) system. A rotational mismatch as large as 0.5° is observed between clockwise (CW) and counter-clockwise (CCW) CBCT scans. The error could affect non-isocentric treatments (e.g., lung SBRT and acoustic neuroma), as well as off-axis organs-at-risk. The error is caused by mislabeling of the projections with a lagging gantry angle, which is caused by the finite image acquisition time and delays in the imaging system. A 30 cm diameter cylindrical phantom with 5 mm diameter holes is used for the scanning. CW and CCW scans are acquired for five gantry speeds (360 to 120 deg./min.) on six linacs from three generations (MLCi, MLCi2, and Agility). Additional scans are acquired with different x-ray pulse widths for the same mAs. In the automated CBCT analysis (using ImageJ), the CW/CCW mismatch in a series of line profiles is identified and used to calculate the rotational error. Results are consistent among all linacs and indicate that the error varies linearly with gantry speed. The finite width of the x-ray pulses is a major but predictable contributor to the delay causing the error. For 40 ms pulses, the delay is 34 ± 1 ms. A simple solution applied in our clinic is adjusting the gantry angle offset to make the CCW one-minute scans correct. A more involved approach we are currently investigating includes adjustments of pulse width and mA, resulting in focal spot changes, with potential impact on image quality.

  5. Low-phase-error offset-compensated switched-capacitor integrator

    NASA Technical Reports Server (NTRS)

    Ki, W.-H.; Temes, G. C.

    1990-01-01

    A modification of the offset-compensated switched-capacitor integrator is described. The resulting circuit has a reduced delay and low gain distortion. It also retains the simplicity and low phase errors of earlier schemes.

  6. The Pancharatnam-Berry phase in polarization singular beams

    NASA Astrophysics Data System (ADS)

    Kumar, Vijay; Viswanathan, Nirmal K.

    2013-04-01

    Space-variant inhomogeneously polarized field formed due to superposition of orthogonally polarized Gaussian (LG00) and Laguerre-Gaussian (LG01) beams results in polarization singular beams with different morphology structures such as lemon, star and dipole patterns around the C-point in the beam cross-section. The Pancharatnam-Berry phase plays a critical role in the formation and characteristics of these spatially inhomogeneous fields. We present our experimental results wherein we measure the variable geometric phase by tracking the trajectory of the component vortices in the beam cross-section, by interfering with selective polarization states and by tracking different latitudes on the Poincaré sphere without the effect of a dynamic phase.

  7. Controllable Airy-like beams induced by tunable phase patterns

    NASA Astrophysics Data System (ADS)

    Li, D.; Qian, Y.

    2016-01-01

    We propose and experimentally observe a novel family of Airy-like beams. First, we theoretically investigate the physical generation of our proposed controllable Airy-like beams by introducing a rotation angle factor into the phase function, which can regulate and flexibly control the beam wavefront. Meanwhile we can also readily control the main lobes of these beams to follow appointed parabolic trajectories using the rotation angle factor. We also demonstrate that the controllable Airy-like beams lack the properties of being diffraction-free and self-healing. The experiments are performed and the results are in accord with the theoretical simulations. We believe that the intriguing characteristics of our proposed Airy-like beams could provide more degrees of freedom, and are likely to give rise to new applications and lend versatility to the emerging field.

  8. Simulation of phase noise for coherent beam combination

    NASA Astrophysics Data System (ADS)

    Hu, Qi-qi; Huang, Zhi-meng; Tang, Xuan; Luo, Yong-quan; Zhang, Da-yong

    2015-02-01

    Active coherent beam combination has been a hot area of research for several years. Particular algorithm module is used to stabilize the phase difference between beamlets, and make them coherent. The phase noise increases with the raising power of laser output. Under low power condition, we simulate the phase noise of high power laser amplifier by the Arbitrary Function Generators (AFGs), and send them to the phase modulators to destabilize the phase, to test the performance of the phase lock algorithm. The experimental results show the feasibility.

  9. Stabilization of signal beam intensity for fault-tolerant automatic routing with double phase conjugate mirrors

    NASA Astrophysics Data System (ADS)

    Kato, Hayato; Okamoto, Atsushi; Bunsen, Masatoshi

    2004-06-01

    We have proposed a fault-tolerant automatic routing method with two photorefractive double phase conjugate mirrors (DPCMs) for free space optical communication by now. In this method, a signal beam can be all-optically and automatically switched from a main line to a backup line when the main line is shut off by obstacles. The optical link between a transmitter and a receiver is kept without any electronic devices and complex optical configuration because the adequate communication line is automatically selected by two DPCMs which are generated by the signal beam and support beams in one photorefractive crystal. In this report, we equalize the signal beam intensities on the main line and the backup line to increase the reliability of communication. If a coupling strength ratio between two DPCMs is inappropriate, the signal beam intensities on both lines become inequality and this induces the increase of the bit error rate in beam detection. Therefore, it is necessary to adjust the signal beam intensities by changing the coupling strength ratio between two DPCMs. We show that the signal beam intensities on both lines can be equalized completely by using the optimum coupling strength ratio between two DPCMs, e.g. about 1.28 in BaTiO3 crystal.

  10. Simple Array Beam-Shaping Using Phase-Only Adjustments.

    SciTech Connect

    Doerry, Armin W.

    2015-07-01

    Conventional beam-shaping for array antennas is accomplished via an amplitude-taper on the elemental radiators. It is well known that proper manipulation of the elemental phases can also shape the antenna far-field pattern. A fairly simple transformation from a desired amplitude-taper to a phase-taper can yield nearly equivalent results.

  11. Method of error analysis for phase-measuring algorithms applied to photoelasticity.

    PubMed

    Quiroga, J A; González-Cano, A

    1998-07-10

    We present a method of error analysis that can be applied for phase-measuring algorithms applied to photoelasticity. We calculate the contributions to the measurement error of the different elements of a circular polariscope as perturbations of the Jones matrices associated with each element. The Jones matrix of the real polariscope can then be calculated as a sum of the nominal matrix and a series of contributions that depend on the errors associated with each element separately. We apply this method to the analysis of phase-measuring algorithms for the determination of isoclinics and isochromatics, including comparisons with real measurements. PMID:18285900

  12. A log-likelihood-gain intensity target for crystallographic phasing that accounts for experimental error.

    PubMed

    Read, Randy J; McCoy, Airlie J

    2016-03-01

    The crystallographic diffraction experiment measures Bragg intensities; crystallographic electron-density maps and other crystallographic calculations in phasing require structure-factor amplitudes. If data were measured with no errors, the structure-factor amplitudes would be trivially proportional to the square roots of the intensities. When the experimental errors are large, and especially when random errors yield negative net intensities, the conversion of intensities and their error estimates into amplitudes and associated error estimates becomes nontrivial. Although this problem has been addressed intermittently in the history of crystallographic phasing, current approaches to accounting for experimental errors in macromolecular crystallography have numerous significant defects. These have been addressed with the formulation of LLGI, a log-likelihood-gain function in terms of the Bragg intensities and their associated experimental error estimates. LLGI has the correct asymptotic behaviour for data with large experimental error, appropriately downweighting these reflections without introducing bias. LLGI abrogates the need for the conversion of intensity data to amplitudes, which is usually performed with the French and Wilson method [French & Wilson (1978), Acta Cryst. A35, 517-525], wherever likelihood target functions are required. It has general applicability for a wide variety of algorithms in macromolecular crystallography, including scaling, characterizing anisotropy and translational noncrystallographic symmetry, detecting outliers, experimental phasing, molecular replacement and refinement. Because it is impossible to reliably recover the original intensity data from amplitudes, it is suggested that crystallographers should always deposit the intensity data in the Protein Data Bank. PMID:26960124

  13. A log-likelihood-gain intensity target for crystallographic phasing that accounts for experimental error

    PubMed Central

    Read, Randy J.; McCoy, Airlie J.

    2016-01-01

    The crystallographic diffraction experiment measures Bragg intensities; crystallo­graphic electron-density maps and other crystallographic calculations in phasing require structure-factor amplitudes. If data were measured with no errors, the structure-factor amplitudes would be trivially proportional to the square roots of the intensities. When the experimental errors are large, and especially when random errors yield negative net intensities, the conversion of intensities and their error estimates into amplitudes and associated error estimates becomes nontrivial. Although this problem has been addressed intermittently in the history of crystallographic phasing, current approaches to accounting for experimental errors in macromolecular crystallography have numerous significant defects. These have been addressed with the formulation of LLGI, a log-likelihood-gain function in terms of the Bragg intensities and their associated experimental error estimates. LLGI has the correct asymptotic behaviour for data with large experimental error, appropriately downweighting these reflections without introducing bias. LLGI abrogates the need for the conversion of intensity data to amplitudes, which is usually performed with the French and Wilson method [French & Wilson (1978 ▸), Acta Cryst. A35, 517–525], wherever likelihood target functions are required. It has general applicability for a wide variety of algorithms in macromolecular crystallography, including scaling, characterizing anisotropy and translational noncrystallographic symmetry, detecting outliers, experimental phasing, molecular replacement and refinement. Because it is impossible to reliably recover the original intensity data from amplitudes, it is suggested that crystallographers should always deposit the intensity data in the Protein Data Bank. PMID:26960124

  14. Power Spectrum of Uplink Array Signals with Random Phase and Delay Errors

    NASA Technical Reports Server (NTRS)

    Vilnrotter, Victor A.

    2011-01-01

    Link Array signals emanating from different antennas must be compensated for Doppler and delay in order to achieve the N(sup 2) array gain predicted by theory. However compensation is never perfect, leaving residual errors that cause losses in array gain and degradation in signal quality. Here we develop a mathematical model for Uplink Array signals in the presence of phase and delay errors, similar to well-known multipath analyses but with features unique to this problem. The resulting losses and distortions are described, and the power spectral density of the array signal derived first conditioned on a given error vector, then averaged over distributions deemed suitable for Uplink Array applications. The impact of phase and delay errors on array gain and signal distortion are addressed, and the maximum data throughput is quantified in terms of the assumed error statistics.

  15. Neural network calibration of a snapshot birefringent Fourier transform spectrometer with periodic phase errors.

    PubMed

    Luo, David; Kudenov, Michael W

    2016-05-16

    Systematic phase errors in Fourier transform spectroscopy can severely degrade the calculated spectra. Compensation of these errors is typically accomplished using post-processing techniques, such as Fourier deconvolution, linear unmixing, or iterative solvers. This results in increased computational complexity when reconstructing and calibrating many parallel interference patterns. In this paper, we describe a new method of calibrating a Fourier transform spectrometer based on the use of artificial neural networks (ANNs). In this way, it is demonstrated that a simpler and more straightforward reconstruction process can be achieved at the cost of additional calibration equipment. To this end, we provide a theoretical model for general systematic phase errors in a polarization birefringent interferometer. This is followed by a discussion of our experimental setup and a demonstration of our technique, as applied to data with and without phase error. The technique's utility is then supported by comparison to alternative reconstruction techniques using fast Fourier transforms (FFTs) and linear unmixing. PMID:27409947

  16. A phase-space beam position monitor for synchrotron radiation

    PubMed Central

    Samadi, Nazanin; Bassey, Bassey; Martinson, Mercedes; Belev, George; Dallin, Les; de Jong, Mark; Chapman, Dean

    2015-01-01

    The stability of the photon beam position on synchrotron beamlines is critical for most if not all synchrotron radiation experiments. The position of the beam at the experiment or optical element location is set by the position and angle of the electron beam source as it traverses the magnetic field of the bend-magnet or insertion device. Thus an ideal photon beam monitor would be able to simultaneously measure the photon beam’s position and angle, and thus infer the electron beam’s position in phase space. X-ray diffraction is commonly used to prepare monochromatic beams on X-ray beamlines usually in the form of a double-crystal monochromator. Diffraction couples the photon wavelength or energy to the incident angle on the lattice planes within the crystal. The beam from such a monochromator will contain a spread of energies due to the vertical divergence of the photon beam from the source. This range of energies can easily cover the absorption edge of a filter element such as iodine at 33.17 keV. A vertical profile measurement of the photon beam footprint with and without the filter can be used to determine the vertical centroid position and angle of the photon beam. In the measurements described here an imaging detector is used to measure these vertical profiles with an iodine filter that horizontally covers part of the monochromatic beam. The goal was to investigate the use of a combined monochromator, filter and detector as a phase-space beam position monitor. The system was tested for sensitivity to position and angle under a number of synchrotron operating conditions, such as normal operations and special operating modes where the photon beam is intentionally altered in position and angle at the source point. The results are comparable with other methods of beam position measurement and indicate that such a system is feasible in situations where part of the synchrotron beam can be used for the phase-space measurement. PMID:26134798

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

    NASA Astrophysics Data System (ADS)

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

    1999-11-01

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

  18. Balancing the Lifetime and Storage Overhead on Error Correction for Phase Change Memory

    PubMed Central

    An, Ning; Wang, Rui; Gao, Yuan; Yang, Hailong; Qian, Depei

    2015-01-01

    As DRAM is facing the scaling difficulty in terms of energy cost and reliability, some nonvolatile storage materials were proposed to be the substitute or supplement of main memory. Phase Change Memory (PCM) is one of the most promising nonvolatile memory that could be put into use in the near future. However, before becoming a qualified main memory technology, PCM should be designed reliably so that it can ensure the computer system’s stable running even when errors occur. The typical wear-out errors in PCM have been well studied, but the transient errors, that caused by high-energy particles striking on the complementary metal-oxide semiconductor (CMOS) circuit of PCM chips or by resistance drifting in multi-level cell PCM, have attracted little focus. In this paper, we propose an innovative mechanism, Local-ECC-Global-ECPs (LEGE), which addresses both soft errors and hard errors (wear-out errors) in PCM memory systems. Our idea is to deploy a local error correction code (ECC) section to every data line, which can detect and correct one-bit errors immediately, and a global error correction pointers (ECPs) buffer for the whole memory chip, which can be reloaded to correct more hard error bits. The local ECC is used to detect and correct the unknown one-bit errors, and the global ECPs buffer is used to store the corrected value of hard errors. In comparison to ECP-6, our method provides almost identical lifetimes, but reduces approximately 50% storage overhead. Moreover, our structure reduces approximately 3.55% access latency overhead by increasing 1.61% storage overhead compared to PAYG, a hard error only solution. PMID:26158524

  19. Beam Position and Phase Monitor - Wire Mapping System

    SciTech Connect

    Watkins, Heath A; Shurter, Robert B.; Gilpatrick, John D.; Kutac, Vincent G.; Martinez, Derwin

    2012-04-10

    The Los Alamos Neutron Science Center (LANSCE) deploys many cylindrical beam position and phase monitors (BPPM) throughout the linac to measure the beam central position, phase and bunched-beam current. Each monitor is calibrated and qualified prior to installation to insure it meets LANSCE requirements. The BPPM wire mapping system is used to map the BPPM electrode offset, sensitivity and higher order coefficients. This system uses a three-axis motion table to position the wire antenna structure within the cavity, simulating the beam excitation of a BPPM at a fundamental frequency of 201.25 MHz. RF signal strength is measured and recorded for the four electrodes as the antenna position is updated. An effort is underway to extend the systems service to the LANSCE facility by replacing obsolete electronic hardware and taking advantage of software enhancements. This paper describes the upgraded wire positioning system's new hardware and software capabilities including its revised antenna structure, motion control interface, RF measurement equipment and Labview software upgrades. The main purpose of the wire mapping system at LANSCE is to characterize the amplitude response versus beam central position of BPPMs before they are installed in the beam line. The wire mapping system is able to simulate a beam using a thin wire and measure the signal response as the wire position is varied within the BPPM aperture.

  20. Shaping the beam profile of an elliptical Gaussian beam by an elliptical phase aperture

    NASA Astrophysics Data System (ADS)

    Wen, Wei; Wu, Gaofeng; Song, Kehui; Dong, Yiming

    2013-03-01

    Based on the generalized Collins integral formula, an analytical paraxial propagation formula for an elliptical Gaussian beam (EGB) passing through an astigmatic ABCD optical system with an elliptical phase aperture is derived by use of a tensor method. As an application example, we study the propagation properties of an EGB passing through an elliptical aperture in free space. It is found that the elliptical phase aperture can be used for shaping the beam profile of an EGB, which is useful in many applications, such as free space optical communication and material thermal processing. The elliptical phase aperture induced changes of the propagation factors of an EGB are also analyzed.

  1. Simultaneous phase-shifting interferometry: immune to azimuth error of fast-axes in retarder array.

    PubMed

    Zheng, Donghui; Chen, Lei; Li, Jinpeng; Gu, Chenfeng; Zhu, Wenhua; Han, Zhigang

    2015-11-20

    Simultaneous phase-shifting interferometry based on a 2×2 retarder array with random fast-axes (RARF-SPSI) is proposed for real-time wavefront measurements. The retarder array is used as the phase-shift component, where the phase retardances are π/2, π, 3π/2, and 2π and the four fast-axes of the four retarders can be somewhat random. In this paper, the mathematical model of RARF-SPSI is built by using a Stokes vector and a Mueller matrix, the phase demodulation method through solving equations is derived, and the coefficient matrix of the equations that is associated with the azimuth of the fast-axes is calculated by Fourier analysis. Then the corresponding simulation analysis is executed. In the experiment, four simultaneous phase-shifting interferograms are captured and the phase distribution under test is demodulated through the proposed method. Compared with the four-bucket phase-shifting algorithm adopted in traditional simultaneous phase-shifting interferometry, the ripple error is suppressed well. The advantage of the proposed RARF-SPSI is that there is no need to calibrate the fast-axes of the phase-shift component before measuring; in other words, the phase demodulation error caused by the azimuth error of fast-axes is eliminated. PMID:26836541

  2. Error Analysis of Cine Phase Contrast MRI Velocity Measurements used for Strain Calculation

    PubMed Central

    Jensen, Elisabeth R.; Morrow, Duane A.; Felmlee, Joel P.; Odegard, Gregory M.; Kaufman, Kenton R.

    2014-01-01

    Cine Phase Contrast (CPC) MRI offers unique insight into localized skeletal muscle behavior by providing the ability to quantify muscle strain distribution during cyclic motion. Muscle strain is obtained by temporally integrating and spatially differentiating CPC-encoded velocity. The aim of this study was to quantify measurement accuracy and precision and to describe error propagation into displacement and strain. Using an MRI-compatible jig to move a B-gel phantom within a 1.5T MRI bore, CPC-encoded velocities were collected. The three orthogonal encoding gradients (through plane, frequency, and phase) were evaluated independently in post-processing. Two systematic error types were corrected: eddy current-induced bias and calibration-type error. Measurement accuracy and precision were quantified before and after removal of systematic error. Through plane- and frequency-encoded data accuracy were within 0.4mm/s after removal of systematic error – a 70% improvement over the raw data. Corrected phase-encoded data accuracy was within 1.3mm/s. Measured random error was between 1 to 1.4mm/s, which followed the theoretical prediction. Propagation of random measurement error into displacement and strain was found to depend on the number of tracked time segments, time segment duration, mesh size, and dimensional order. To verify this, theoretical predictions were compared to experimentally calculated displacement and strain error. For the parameters tested, experimental and theoretical results aligned well. Random strain error approximately halved with a two-fold mesh size increase, as predicted. Displacement and strain accuracy were within 2.6mm and 3.3%, respectively. These results can be used to predict the accuracy and precision of displacement and strain in user-specific applications. PMID:25433567

  3. Phase errors in diffraction-limited imaging: contrast limits for sparse aperture masking

    NASA Astrophysics Data System (ADS)

    Ireland, M. J.

    2013-08-01

    Bispectrum phase, closure phase and their generalization to kernel phase are all independent of pupil-plane phase errors to first order. This property, when used with sparse aperture masking behind adaptive optics, has been used recently in high-contrast observations at or inside the formal diffraction limit of large telescopes. Finding the limitations to these techniques requires an understanding of spatial and temporal third-order phase effects, as well as effects such as time-variable dispersion when coupled with the non-zero bandwidths in real observations. In this paper, formulae describing many of these errors are developed, so that a comparison can be made to fundamental noise processes of photon noise and background noise. I show that the current generation of aperture-masking observations of young solar-type stars, taken carefully in excellent observing conditions, are consistent with being limited by temporal phase noise and photon noise. This has relevance for plans to combine pupil remapping with spatial filtering. Finally, I describe calibration strategies for kernel phase, including the optimized calibrator weighting as used for LkCa15, and the restricted kernel phase POISE (phase observationally independent of systematic errors) technique that avoids explicit dependence on calibrators.

  4. Correction of phase extraction error in phase-shifting interferometry based on Lissajous figure and ellipse fitting technology.

    PubMed

    Liu, Fengwei; Wu, Yongqian; Wu, Fan

    2015-04-20

    The accuracy of phase-shifting interferometers (PSI) is crippled by nonlinearity of the phase shifter and instability of the environment such as vibration and air turbulence. A general algorithm, utilizing Lissajous figures and ellipse fitting, of correcting the phase extraction error in the phase shifting interferometry is described in this paper. By plotting N against D, where N and D represent the numerator and denominator terms of the phase extraction function (i.e. an arctangent function) respectively, a Lissajous ellipse is created. Once the parameters of the ellipse are determined by ellipse fitting, one can transform the ellipse to a unit circle (ETC). Through this process the phase extraction error caused by random phase shift errors can be corrected successfully. Proposed method is non-iterated, adapts to all phase shifting algorithms (PSAs), and has high accuracy. Some factors that may affect the performance of proposed method are discussed in numerical simulations. Optical experiments are implemented to validate the effectiveness of proposed algorithm. PMID:25969117

  5. Improved beam smoothing with SSD using generalized phase modulation

    SciTech Connect

    Rothenberg, J.E.

    1997-01-01

    The smoothing of the spatial illumination of an inertial confinement fusion target is examined by its spatial frequency content. It is found that the smoothing by spectral dispersion method, although efficient for glass lasers, can yield poor smoothing at low spatial frequency. The dependence of the smoothed spatial spectrum on the characteristics of phase modulation and dispersion is examined for both sinusoidal and more general phase modulation. It is shown that smoothing with non-sinusoidal phase modulation can result in spatial spectra which are substantially identical to that obtained with the induced spatial incoherence or similar method where random phase plates are present in both methods and identical beam divergence is assumed.

  6. Optical pupil relay design for SILEX - Optimising wavefront error and transmit/receive beams co-alignment

    NASA Astrophysics Data System (ADS)

    Jonas, Reginald P.

    1992-06-01

    This paper describes some of the key parameters that have been considered for the European Satellite Interorbital Link EXperiment (SILEX) optical relay lens design. Particular attention has been given to the specific requirement of transmit/receive beams co-alignment. The method of evaluating co-alignment errors is described and the effect of manufacturing tolerances and environmental long term stability on the co-alignment error investigated.

  7. Phase errors elimination in compact digital holoscope (CDH) based on a reasonable mathematical model

    NASA Astrophysics Data System (ADS)

    Wen, Yongfu; Qu, Weijuan; Cheng, Cheeyuen; Wang, Zhaomin; Asundi, Anand

    2015-03-01

    In the compact digital holoscope (CDH) measurement process, theoretically, we need to ensure the distances between the reference wave and object wave to the hologram plane exactly match. However, it is not easy to realize in practice due to the human factors. This can lead to a phase error in the reconstruction result. In this paper, the strict theoretical analysis of the wavefront interference is performed to demonstrate the mathematical model of the phase error and then a phase errors elimination method is proposed based on the advanced mathematical model, which has a more explicit physical meaning. Experiments are carried out to verify the performance of the presented method and the results indicate that it is effective and allows the operator can make operation more flexible.

  8. Phase errors in high line density CGH used for aspheric testing: beyond scalar approximation.

    PubMed

    Peterhänsel, S; Pruss, C; Osten, W

    2013-05-20

    One common way to measure asphere and freeform surfaces is the interferometric Null test, where a computer generated hologram (CGH) is placed in the object path of the interferometer. If undetected phase errors are present in the CGH, the measurement will show systematic errors. Therefore the absolute phase of this element has to be known. This phase is often calculated using scalar diffraction theory. In this paper we discuss the limitations of this theory for the prediction of the absolute phase generated by different implementations of CGH. Furthermore, for regions where scalar approximation is no longer valid, rigorous simulations are performed to identify phase sensitive structure parameters and evaluate fabrication tolerances for typical gratings. PMID:23736387

  9. Phase Error Correction in Time-Averaged 3D Phase Contrast Magnetic Resonance Imaging of the Cerebral Vasculature

    PubMed Central

    MacDonald, M. Ethan; Forkert, Nils D.; Pike, G. Bruce; Frayne, Richard

    2016-01-01

    Purpose Volume flow rate (VFR) measurements based on phase contrast (PC)-magnetic resonance (MR) imaging datasets have spatially varying bias due to eddy current induced phase errors. The purpose of this study was to assess the impact of phase errors in time averaged PC-MR imaging of the cerebral vasculature and explore the effects of three common correction schemes (local bias correction (LBC), local polynomial correction (LPC), and whole brain polynomial correction (WBPC)). Methods Measurements of the eddy current induced phase error from a static phantom were first obtained. In thirty healthy human subjects, the methods were then assessed in background tissue to determine if local phase offsets could be removed. Finally, the techniques were used to correct VFR measurements in cerebral vessels and compared statistically. Results In the phantom, phase error was measured to be <2.1 ml/s per pixel and the bias was reduced with the correction schemes. In background tissue, the bias was significantly reduced, by 65.6% (LBC), 58.4% (LPC) and 47.7% (WBPC) (p < 0.001 across all schemes). Correction did not lead to significantly different VFR measurements in the vessels (p = 0.997). In the vessel measurements, the three correction schemes led to flow measurement differences of -0.04 ± 0.05 ml/s, 0.09 ± 0.16 ml/s, and -0.02 ± 0.06 ml/s. Although there was an improvement in background measurements with correction, there was no statistical difference between the three correction schemes (p = 0.242 in background and p = 0.738 in vessels). Conclusions While eddy current induced phase errors can vary between hardware and sequence configurations, our results showed that the impact is small in a typical brain PC-MR protocol and does not have a significant effect on VFR measurements in cerebral vessels. PMID:26910600

  10. Phase-modulated beams technique for thin photorefractive films characterization

    NASA Astrophysics Data System (ADS)

    Barmenkov, Yu. O.; Kir'yanov, A. V.; Starodumov, A. N.; Kozhevnikov, N. M.; Lemmetyinen, H.

    2000-04-01

    The phase-modulated beams technique is developed for nonlinear thin photorefractive films characterization. In the Raman-Nath diffraction approximation, the formulas are deduced, allowing us to measure the amplitude of phase grating recorded in a film and its nonlinear refractive index n2. The method is applied for studying Langmuir-Blodgett multilayer thin (˜0.6 μm) films of Bacteriorhodopsin at wavelength 633 nm.

  11. BEAM POSITION AND PHASE MONITORS FOR THE LANSCE LINAC

    SciTech Connect

    McCrady, Rodney C.; Gilpatrick, John D.; Power, John F.

    2011-01-01

    New beam-position and phase monitors are under development for the linac at the Los Alamos Neutron Science Center (LANSCE). Transducers have been designed and are being fabricated. We are considering many options for the electronic instrumentation to process the signals and provide position and phase data with the necessary precision and flexibility to serve the various required functions. We'll present the various options under consideration for instrumentation along with the advantages and shortcomings of these options.

  12. BEAM POSITION AND PHASE MONITORS FOR THE LANSCE LINAC

    SciTech Connect

    McCrady, Rodney C.; Gilpatrick, John D.; Watkins, Heath A.

    2012-04-11

    New beam-position and phase monitors are under development for the linac at the Los Alamos Neutron Science Center (LANSCE.) Transducers have been designed and are being installed. We are considering many options for the electronic instrumentation to process the signals and provide position and phase data with the necessary precision and flexibility to serve the various required functions. We'll present the various options under consideration for instrumentation along with the advantages and shortcomings of these options.

  13. Characteristics of medication errors made by students during the administration phase: a descriptive study.

    PubMed

    Wolf, Zane Robinson; Hicks, Rodney; Serembus, Joanne Farley

    2006-01-01

    Faculty concentrate on teaching nursing students about safe medication administration practices and on challenging them to develop skills for calculating drug dose and intravenous flow rate problems. In spite of these efforts, students make medication errors and little is known about the attributes of these errors. Therefore, this descriptive, retrospective, secondary analysis study examined the characteristics of medication errors made by nursing students during the administration phase of the medication use process as reported to the MEDMARX, a database operated by the United States Pharmacopeia through the Patient Safety Program. Fewer than 3% of 1,305 student-made medication errors occurring in the administration process resulted in patient harm. Most were omission errors, followed by errors of giving the wrong dose (amount) of a drug. The most prevalent cause of the errors was students' performance deficits, whereas inexperience and distractions were leading contributing factors. The antimicrobial therapeutic class of drugs and the 10 subcategories within this class were the most commonly reported medications involved. Insulin was the highest-frequency single medication reported. Overall, this study shows that students' administration errors may be more frequent than suspected. Faculty might consider curriculum revisions that incorporate medication use safety throughout each course in nursing major courses. PMID:16459288

  14. Breast Patient Setup Error Assessment: Comparison of Electronic Portal Image Devices and Cone-Beam Computed Tomography Matching Results

    SciTech Connect

    Topolnjak, Rajko; Sonke, Jan-Jakob; Nijkamp, Jasper; Rasch, Coen; Minkema, Danny; Remeijer, Peter; Vliet-Vroegindeweij, Corine van

    2010-11-15

    Purpose: To quantify the differences in setup errors measured with the cone-beam computed tomography (CBCT) and electronic portal image devices (EPID) in breast cancer patients. Methods and Materials: Repeat CBCT scan were acquired for routine offline setup verification in 20 breast cancer patients. During the CBCT imaging fractions, EPID images of the treatment beams were recorded. Registrations of the bony anatomy for CBCT to planning CT and EPID to digitally reconstructed-radiographs (DRRs) were compared. In addition, similar measurements of an anthropomorphic thorax phantom were acquired. Bland-Altman and linear regression analysis were performed for clinical and phantom registrations. Systematic and random setup errors were quantified for CBCT and EPID-driven correction protocols in the EPID coordinate system (U, V), with V parallel to the cranial-caudal axis and U perpendicular to V and the central beam axis. Results: Bland-Altman analysis of clinical EPID and CBCT registrations yielded 4 to 6-mm limits of agreement, indicating that both methods were not compatible. The EPID-based setup errors were smaller than the CBCT-based setup errors. Phantom measurements showed that CBCT accurately measures setup error whereas EPID underestimates setup errors in the cranial-caudal direction. In the clinical measurements, the residual bony anatomy setup errors after offline CBCT-based corrections were {Sigma}{sub U} = 1.4 mm, {Sigma}{sub V} = 1.7 mm, and {sigma}{sub U} = 2.6 mm, {sigma}{sub V} = 3.1 mm. Residual setup errors of EPID driven corrections corrected for underestimation were estimated at {Sigma}{sub U} = 2.2mm, {Sigma}{sub V} = 3.3 mm, and {sigma}{sub U} = 2.9 mm, {sigma}{sub V} = 2.9 mm. Conclusion: EPID registration underestimated the actual bony anatomy setup error in breast cancer patients by 20% to 50%. Using CBCT decreased setup uncertainties significantly.

  15. Phase-diversity phase-sensitive amplification in fiber loop with polarization beam splitter

    NASA Astrophysics Data System (ADS)

    Inoue, K.

    2015-10-01

    In this paper, we propose a parametric amplification scheme based on phase-sensitive amplification in an optical fiber. The proposed system consists of a nonlinear fiber and a dispersive medium in a loop configuration with a polarization beam splitter, where phase-sensitive amplification occurs bi-directionally. The dispersive medium shifts the relative phase between signal and pump lights, due to which the amplified signal light is always obtained regardless of the signal input phase, i.e., a phase-diversity operation is achieved, while the output phase is digitized as in conventional phase-sensitive amplifiers.

  16. X-Ray cone-beam phase tomography formulas based on phase-attenuation duality.

    PubMed

    Wu, Xizeng; Liu, Hong

    2005-08-01

    We present a detailed derivation of the phase-retrieval formula based on the phase-attenuation duality that we recently proposed in previous brief communication. We have incorporated the effects of x-ray source coherence and detector resolution into the phase-retrieval formula as well. Since only a single image is needed for performing the phase retrieval by means of this new approach, we point out the great advantages of this new approach for implementation of phase tomography. We combine our phase-retrieval formula with the Feldkamp-Davis-Kresss (FDK) cone-beam reconstruction algorithm to provide a three-dimensional phase tomography formula for soft tissue objects of relatively small sizes, such as small animals or human breast. For large objects we briefly show how to apply Katsevich's cone-beam reconstruction formula to the helical phase tomography as well. PMID:19498608

  17. Performance modeling of the effects of aperture phase error, turbulence, and thermal blooming on tiled subaperture systems

    NASA Astrophysics Data System (ADS)

    Leakeas, Charles L.; Capehart, Shay R.; Bartell, Richard J.; Cusumano, Salvatore J.; Whiteley, Matthew R.

    2011-06-01

    Laser weapon systems comprised of tiled subapertures are rapidly emerging in importance in the directed energy community. Performance models of these laser weapon systems have been developed from numerical simulations of a high fidelity wave-optics code called WaveTrain which is developed by MZA Associates. System characteristics such as mutual coherence, differential jitter, and beam quality rms wavefront error are defined for a focused beam on the target. Engagement scenarios are defined for various platform and target altitudes, speeds, headings, and slant ranges along with the natural wind speed and heading. Inputs to the performance model include platform and target height and velocities, Fried coherence length, Rytov number, isoplanatic angle, thermal blooming distortion number, Greenwood and Tyler frequencies, and atmospheric transmission. The performance model fit is based on power-in-the-bucket (PIB) values against the PIB from the simulation results for the vacuum diffraction-limited spot size as the bucket. The goal is to develop robust performance models for aperture phase error, turbulence, and thermal blooming effects in tiled subaperture systems.

  18. A hybrid method for synthetic aperture ladar phase-error compensation

    NASA Astrophysics Data System (ADS)

    Hua, Zhili; Li, Hongping; Gu, Yongjian

    2009-07-01

    As a high resolution imaging sensor, synthetic aperture ladar data contain phase-error whose source include uncompensated platform motion and atmospheric turbulence distortion errors. Two previously devised methods, rank one phase-error estimation algorithm and iterative blind deconvolution are reexamined, of which a hybrid method that can recover both the images and PSF's without any a priori information on the PSF is built to speed up the convergence rate by the consideration in the choice of initialization. To be integrated into spotlight mode SAL imaging model respectively, three methods all can effectively reduce the phase-error distortion. For each approach, signal to noise ratio, root mean square error and CPU time are computed, from which we can see the convergence rate of the hybrid method can be improved because a more efficient initialization set of blind deconvolution. Moreover, by making a further discussion of the hybrid method, the weight distribution of ROPE and IBD is found to be an important factor that affects the final result of the whole compensation process.

  19. Propagation of laser beam parameters through pure phase transmittances

    NASA Astrophysics Data System (ADS)

    Piquero, G.; Mejías, P. M.; Martínez-Herrero, R.

    1996-02-01

    The propagation laws of the intensity moments of a laser beam through ABCD optical systems are generalized to include pure phase transmittances. This is done by representing the behaviour of such transmittances by means of a 4 × 4 matrix, M, which can be handled, to some extent, as the ABCD-matrices associated with ordinary first-order optical systems. This formalism enables the application of ABCD propagation formulae to cascaded optical systems containing pure phase transmittances. Matrix M is used to determine the intensity moments at the output of two special quartic phase transmittances, namely, a circular spherically aberrated lens and a pair of orthogonal cylindrical (also aberrated) lenses.

  20. Nanowire growth by an electron beam induced massive phase transformation

    SciTech Connect

    Sood, Shantanu; Kisslinger, Kim; Gouma, Perena

    2014-11-15

    Tungsten trioxide nanowires of a high aspect ratio have been synthesized in-situ in a TEM under an electron beam of current density 14A/cm² due to a massive polymorphic reaction. Sol-gel processed pseudocubic phase nanocrystals of tungsten trioxide were seen to rapidly transform to one dimensional monoclinic phase configurations, and this reaction was independent of the substrate on which the material was deposited. The mechanism of the self-catalyzed polymorphic transition and accompanying radical shape change is a typical characteristic of metastable to stable phase transformations in nanostructured polymorphic metal oxides. A heuristic model is used to confirm the metastable to stable growth mechanism. The findings are important to the control electron beam deposition of nanowires for functional applications starting from colloidal precursors.

  1. Nanowire growth by an electron beam induced massive phase transformation

    DOE PAGESBeta

    Sood, Shantanu; Kisslinger, Kim; Gouma, Perena

    2014-11-15

    Tungsten trioxide nanowires of a high aspect ratio have been synthesized in-situ in a TEM under an electron beam of current density 14A/cm² due to a massive polymorphic reaction. Sol-gel processed pseudocubic phase nanocrystals of tungsten trioxide were seen to rapidly transform to one dimensional monoclinic phase configurations, and this reaction was independent of the substrate on which the material was deposited. The mechanism of the self-catalyzed polymorphic transition and accompanying radical shape change is a typical characteristic of metastable to stable phase transformations in nanostructured polymorphic metal oxides. A heuristic model is used to confirm the metastable to stablemore » growth mechanism. The findings are important to the control electron beam deposition of nanowires for functional applications starting from colloidal precursors.« less

  2. Single beam Fourier transform digital holographic quantitative phase microscopy

    SciTech Connect

    Anand, A. Chhaniwal, V. K.; Mahajan, S.; Trivedi, V.; Faridian, A.; Pedrini, G.; Osten, W.; Dubey, S. K.; Javidi, B.

    2014-03-10

    Quantitative phase contrast microscopy reveals thickness or height information of a biological or technical micro-object under investigation. The information obtained from this process provides a means to study their dynamics. Digital holographic (DH) microscopy is one of the most used, state of the art single-shot quantitative techniques for three dimensional imaging of living cells. Conventional off axis DH microscopy directly provides phase contrast images of the objects. However, this process requires two separate beams and their ratio adjustment for high contrast interference fringes. Also the use of two separate beams may make the system more vulnerable to vibrations. Single beam techniques can overcome these hurdles while remaining compact as well. Here, we describe the development of a single beam DH microscope providing whole field imaging of micro-objects. A hologram of the magnified object projected on to a diffuser co-located with a pinhole is recorded with the use of a commercially available diode laser and an arrayed sensor. A Fourier transform of the recorded hologram directly yields the complex amplitude at the image plane. The method proposed was investigated using various phase objects. It was also used to image the dynamics of human red blood cells in which sub-micrometer level thickness variation were measurable.

  3. Magnitude and clinical relevance of translational and rotational patient setup errors: A cone-beam CT study

    SciTech Connect

    Guckenberger, Matthias . E-mail: guckenberg_m@klinik.uni-wuerzburg.de; Meyer, Juergen; Vordermark, Dirk; Baier, Kurt; Wilbert, Juergen; Flentje, Michael

    2006-07-01

    Purpose: To establish volume imaging using an on-board cone-beam CT (CB-CT) scanner for evaluation of three-dimensional patient setup errors. Methods and Materials: The data from 24 patients were included in this study, and the setup errors using 209 CB-CT studies and 148 electronic portal images were analyzed and compared. The effect of rotational errors alone, translational errors alone, and combined rotational and translational errors on target coverage and sparing of organs at risk was investigated. Results: Translational setup errors using the CB-CT scanner and an electronic portal imaging device differed <1 mm in 70.7% and <2 mm in 93.2% of the measurements. Rotational errors >2{sup o} were recorded in 3.7% of pelvic tumors, 26.4% of thoracic tumors, and 12.4% of head-and-neck tumors; the corresponding maximal rotational errors were 5{sup o}, 8{sup o}, and 6{sup o}. No correlation between the magnitude of translational and rotational setup errors was observed. For patients with elongated target volumes and sharp dose gradients to adjacent organs at risk, both translational and rotational errors resulted in considerably decreased target coverage and highly increased doses to the organs at risk compared with the initial treatment plan. Conclusions: The CB-CT scanner has been successfully established for the evaluation of patient setup errors, and its feasibility in day-to-day clinical practice has been demonstrated. Our results have indicated that rotational errors are of clinical significance for selected patients receiving high-precision radiotherapy.

  4. High rates of phasing errors in highly polymorphic species with low levels of linkage disequilibrium.

    PubMed

    Bukowicki, Marek; Franssen, Susanne U; Schlötterer, Christian

    2016-07-01

    Short read sequencing of diploid individuals does not permit the direct inference of the sequence on each of the two homologous chromosomes. Although various phasing software packages exist, they were primarily tailored for and tested on human data, which differ from other species in factors that influence phasing, such as SNP density, amounts of linkage disequilibrium (LD) and sample sizes. Despite becoming increasingly popular for other species, the reliability of phasing in non-human data has not been evaluated to a sufficient extent. We scrutinized the phasing accuracy for Drosophila melanogaster, a species with high polymorphism levels and reduced LD relative to humans. We phased two D. melanogaster populations and compared the results to the known haplotypes. The performance increased with size of the reference panel and was highest when the reference panel and phased individuals were from the same population. Full genomic SNP data and inclusion of sequence read information also improved phasing. Despite humans and Drosophila having similar switch error rates between polymorphic sites, the distances between switch errors were much shorter in Drosophila with only fragments <300-1500 bp being correctly phased with ≥95% confidence. This suggests that the higher SNP density cannot compensate for the higher recombination rate in D. melanogaster. Furthermore, we show that populations that have gone through demographic events such as bottlenecks can be phased with higher accuracy. Our results highlight that statistically phased data are particularly error prone in species with large population sizes or populations lacking suitable reference panels. PMID:26929272

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

    PubMed

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

    2016-01-10

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

  6. Optics for Phase Ionization Cooling of Muon Beams

    SciTech Connect

    R.P. Johnson; S.A. Bogacz; Y.S. Derbenev

    2006-06-26

    The realization of a muon collider requires a reduction of the 6D normalized emittance of an initially generated muon beam by a factor of more than 106. Analytical and simulation studies of 6D muon beam ionization cooling in a helical channel filled with pressurized gas or liquid hydrogen absorber indicate that a factor of 106 is possible. Further reduction of the normalized 4D transverse emittance by an additional two orders of magnitude is envisioned using Parametric-resonance Ionization Cooling (PIC). To realize the phase shrinkage effect in the parametric resonance method, one needs to design a focusing channel free of chromatic and spherical aberrations. We report results of our study of a concept of an aberration-free wiggler transport line with an alternating dispersion function. Resonant beam focusing at thin beryllium wedge absorber plates positioned near zero dispersion points then provides the predicted PIC effect.

  7. The effects of digitizing rate and phase distortion errors on the shock response spectrum

    NASA Technical Reports Server (NTRS)

    Wise, J. H.

    1983-01-01

    Some of the methods used for acquisition and digitization of high-frequency transients in the analysis of pyrotechnic events, such as explosive bolts for spacecraft separation, are discussed with respect to the reduction of errors in the computed shock response spectrum. Equations are given for maximum error as a function of the sampling rate, phase distortion, and slew rate, and the effects of the characteristics of the filter used are analyzed. A filter is noted to exhibit good passband amplitude, phase response, and response to a step function is a compromise between the flat passband of the elliptic filter and the phase response of the Bessel filter; it is suggested that it be used with a sampling rate of 10f (5 percent).

  8. Environment-assisted error correction of single-qubit phase damping

    NASA Astrophysics Data System (ADS)

    Trendelkamp-Schroer, Benjamin; Helm, Julius; Strunz, Walter T.

    2011-12-01

    Open quantum system dynamics of random unitary type may in principle be fully undone. Closely following the scheme of environment-assisted error correction proposed by Gregoratti and Werner [J. Mod. Opt.10.1080/09500340308234541 50, 915 (2003)], we explicitly carry out all steps needed to invert a phase-damping error on a single qubit. Furthermore, we extend the scheme to a mixed-state environment. Surprisingly, we find cases for which the uncorrected state is closer to the desired state than any of the corrected ones.

  9. Optimization of finite-size errors in finite-temperature calculations of unordered phases

    NASA Astrophysics Data System (ADS)

    Iyer, Deepak; Srednicki, Mark; Rigol, Marcos

    2015-06-01

    It is common knowledge that the microcanonical, canonical, and grand-canonical ensembles are equivalent in thermodynamically large systems. Here, we study finite-size effects in the latter two ensembles. We show that contrary to naive expectations, finite-size errors are exponentially small in grand canonical ensemble calculations of translationally invariant systems in unordered phases at finite temperature. Open boundary conditions and canonical ensemble calculations suffer from finite-size errors that are only polynomially small in the system size. We further show that finite-size effects are generally smallest in numerical linked cluster expansions. Our conclusions are supported by analytical and numerical analyses of classical and quantum systems.

  10. Optimization of finite-size errors in finite-temperature calculations of unordered phases

    NASA Astrophysics Data System (ADS)

    Iyer, Deepak; Srednicki, Mark; Rigol, Marcos

    It is common knowledge that the microcanonical, canonical, and grand canonical ensembles are equivalent in thermodynamically large systems. Here, we study finite-size effects in the latter two ensembles. We show that contrary to naive expectations, finite-size errors are exponentially small in grand canonical ensemble calculations of translationally invariant systems in unordered phases at finite temperature. Open boundary conditions and canonical ensemble calculations suffer from finite-size errors that are only polynomially small in the system size. We further show that finite-size effects are generally smallest in numerical linked cluster expansions. Our conclusions are supported by analytical and numerical analyses of classical and quantum systems.

  11. Quantitative, comparable coherent anti-Stokes Raman scattering (CARS) spectroscopy: correcting errors in phase retrieval

    NASA Astrophysics Data System (ADS)

    Camp, Charles H., Jr.; Lee, Young Jong; Cicerone, Marcus T.

    2016-04-01

    Coherent anti-Stokes Raman scattering (CARS) microspectroscopy has demonstrated significant potential for biological and materials imaging. To date, however, the primary mechanism of disseminating CARS spectroscopic information is through pseudocolor imagery, which explicitly neglects a vast majority of the hyperspectral data. Furthermore, current paradigms in CARS spectral processing do not lend themselves to quantitative sample-to-sample comparability. The primary limitation stems from the need to accurately measure the so-called nonresonant background (NRB) that is used to extract the chemically-sensitive Raman information from the raw spectra. Measurement of the NRB on a pixel-by-pixel basis is a nontrivial task; thus, reference NRB from glass or water are typically utilized, resulting in error between the actual and estimated amplitude and phase. In this manuscript, we present a new methodology for extracting the Raman spectral features that significantly suppresses these errors through phase detrending and scaling. Classic methods of error-correction, such as baseline detrending, are demonstrated to be inaccurate and to simply mask the underlying errors. The theoretical justification is presented by re-developing the theory of phase retrieval via the Kramers-Kronig relation, and we demonstrate that these results are also applicable to maximum entropy method-based phase retrieval. This new error-correction approach is experimentally applied to glycerol spectra and tissue images, demonstrating marked consistency between spectra obtained using different NRB estimates, and between spectra obtained on different instruments. Additionally, in order to facilitate implementation of these approaches, we have made many of the tools described herein available free for download.

  12. Phase error analysis and compensation for phase shifting profilometry with projector defocusing.

    PubMed

    Zheng, Dongliang; Da, Feipeng; Kemao, Qian; Seah, Hock Soon

    2016-07-20

    Phase shifting profilometry (PSP) using binary fringe patterns with projector defocusing is promising for high-speed 3D shape measurement. To obtain a high-quality phase, the projector usually requires a high defocusing level, which leads to a drastic fall in fringe contrast. Due to its convenience and high speed, PSP using squared binary patterns with small phase shifting algorithms and slight defocusing is highly desirable. In this paper, the phase accuracies of the classical phase shifting algorithms are analyzed theoretically, and then compared using both simulation and experiment. We also adapt two algorithms for PSP using squared binary patterns, which include a Hilbert three-step PSP and a double three-step PSP. Both algorithms can increase phase accuracy, with the latter featuring additional invalid point detection. The adapted algorithms are also compared with the classical algorithms. Based on our analysis and comparison results, proper algorithm selection can be easily made according to the practical requirement. PMID:27463929

  13. Error detection and correction for a multiple frequency quaternary phase shift keyed signal

    NASA Astrophysics Data System (ADS)

    Hopkins, Kevin S.

    1989-06-01

    A multiple frequency quaternary phased shift (MFQPSK) signaling system was developed and experimentally tested in a controlled environment. In order to insure that the quality of the received signal is such that information recovery is possible, error detection/correction (EDC) must be used. Various EDC coding schemes available are reviewed and their application to the MFQPSK signal system is analyzed. Hamming, Golay, Bose-Chaudhuri-Hocquenghem (BCH), Reed-Solomon (R-S) block codes as well as convolutional codes are presented and analyzed in the context of specific MFQPSK system parameters. A computer program was developed in order to compute bit error probabilities as a function of signal to noise ratio. Results demonstrate that various EDC schemes are suitable for the MFQPSK signal structure, and that significant performance improvements are possible with the use of certain error correction codes.

  14. Wavelength error analysis in a multiple-beam Fizeau laser wavemeter having a linear diode array readout

    NASA Technical Reports Server (NTRS)

    Robinson, D. M.; Fales, C. L., Jr.; Skolaut, M. W., Jr.

    1985-01-01

    An estimate of the wavelength accuracy of a laser wavemeter is performed for a system consisting of a multiple-beam Fizeau interferometer and a linear photosensor array readout. The analysis consists of determining the fringe position errors which result when various noise sources are included in the fringe forming and detection process. Two methods of estimating the fringe centers are considered: (1) maximum pixel current location, and (2) average pixel location for two detectors with nearly equal output currents. Wavelength error results for these two methods are compared for some typical wavemeter parameters.

  15. Simplified formula for mean cycle-slip time of phase-locked loops with steady-state phase error.

    NASA Technical Reports Server (NTRS)

    Tausworthe, R. C.

    1972-01-01

    Previous work shows that the mean time from lock to a slipped cycle of a phase-locked loop is given by a certain double integral. Accurate numerical evaluation of this formula for the second-order loop is extremely vexing because the difference between exponentially large quantities is involved. The presented article demonstrates a method in which a much-reduced precision program can be used to obtain the mean first-cycle slip time for a loop of arbitrary degree tracking at a specified SNR and steady-state phase error. It also presents a simple approximate formula that is asymptotically tight at higher loop SNR.

  16. Quantifying error of lidar and sodar Doppler beam swinging measurements of wind turbine wakes using computational fluid dynamics

    DOE PAGESBeta

    Lundquist, J. K.; Churchfield, M. J.; Lee, S.; Clifton, A.

    2015-02-23

    Wind-profiling lidars are now regularly used in boundary-layer meteorology and in applications such as wind energy and air quality. Lidar wind profilers exploit the Doppler shift of laser light backscattered from particulates carried by the wind to measure a line-of-sight (LOS) velocity. The Doppler beam swinging (DBS) technique, used by many commercial systems, considers measurements of this LOS velocity in multiple radial directions in order to estimate horizontal and vertical winds. The method relies on the assumption of homogeneous flow across the region sampled by the beams. Using such a system in inhomogeneous flow, such as wind turbine wakes ormore » complex terrain, will result in errors. To quantify the errors expected from such violation of the assumption of horizontal homogeneity, we simulate inhomogeneous flow in the atmospheric boundary layer, notably stably stratified flow past a wind turbine, with a mean wind speed of 6.5 m s-1 at the turbine hub-height of 80 m. This slightly stable case results in 15° of wind direction change across the turbine rotor disk. The resulting flow field is sampled in the same fashion that a lidar samples the atmosphere with the DBS approach, including the lidar range weighting function, enabling quantification of the error in the DBS observations. The observations from the instruments located upwind have small errors, which are ameliorated with time averaging. However, the downwind observations, particularly within the first two rotor diameters downwind from the wind turbine, suffer from errors due to the heterogeneity of the wind turbine wake. Errors in the stream-wise component of the flow approach 30% of the hub-height inflow wind speed close to the rotor disk. Errors in the cross-stream and vertical velocity components are also significant: cross-stream component errors are on the order of 15% of the hub-height inflow wind speed (1.0 m s−1) and errors in the vertical velocity measurement exceed the actual

  17. Quantifying error of lidar and sodar Doppler beam swinging measurements of wind turbine wakes using computational fluid dynamics

    SciTech Connect

    Lundquist, J. K.; Churchfield, M. J.; Lee, S.; Clifton, A.

    2015-02-23

    Wind-profiling lidars are now regularly used in boundary-layer meteorology and in applications such as wind energy and air quality. Lidar wind profilers exploit the Doppler shift of laser light backscattered from particulates carried by the wind to measure a line-of-sight (LOS) velocity. The Doppler beam swinging (DBS) technique, used by many commercial systems, considers measurements of this LOS velocity in multiple radial directions in order to estimate horizontal and vertical winds. The method relies on the assumption of homogeneous flow across the region sampled by the beams. Using such a system in inhomogeneous flow, such as wind turbine wakes or complex terrain, will result in errors.

    To quantify the errors expected from such violation of the assumption of horizontal homogeneity, we simulate inhomogeneous flow in the atmospheric boundary layer, notably stably stratified flow past a wind turbine, with a mean wind speed of 6.5 m s-1 at the turbine hub-height of 80 m. This slightly stable case results in 15° of wind direction change across the turbine rotor disk. The resulting flow field is sampled in the same fashion that a lidar samples the atmosphere with the DBS approach, including the lidar range weighting function, enabling quantification of the error in the DBS observations. The observations from the instruments located upwind have small errors, which are ameliorated with time averaging. However, the downwind observations, particularly within the first two rotor diameters downwind from the wind turbine, suffer from errors due to the heterogeneity of the wind turbine wake. Errors in the stream-wise component of the flow approach 30% of the hub-height inflow wind speed close to the rotor disk. Errors in the cross-stream and vertical velocity components are also significant: cross-stream component errors are on the order of 15% of the hub-height inflow wind speed (1.0 m s−1) and errors in the vertical velocity measurement

  18. Idling error and SWAP/MOVE operation in RezQu architecture for phase qubits

    NASA Astrophysics Data System (ADS)

    Galiautdinov, Andrei; Korotkov, Alexander

    2011-03-01

    We analyze several basic operations in the RezQu architecture for superconducting phase qubits recently proposed by John Martinis, concentrating on the idling error, generation of single-excitation states, and the single-excitation transfer (which we call MOVE) between a phase qubit and its memory. We show that the idling error is negligible, being proportional to the sixth power of the coupling strength. We also show that in the rotating wave approximation the MOVE operation, which is simpler than the usual SWAP, can be realized perfectly using a tune/detune pulse with four adjustable parameters. The pulse consists of the front ramp (with proper shaping), a constant near-resonant overshoot, and an arbitrary rear ramp. This work was supported by NSA and IARPA under ARO grant No. W911NF-10-1-0334.

  19. Sparsity-based moving target localization using multiple dual-frequency radars under phase errors

    NASA Astrophysics Data System (ADS)

    Al Kadry, Khodour; Ahmad, Fauzia; Amin, Moeness G.

    2015-05-01

    In this paper, we consider moving target localization in urban environments using a multiplicity of dual-frequency radars. Dual-frequency radars offer the benefit of reduced complexity and fast computation time, thereby permitting real-time indoor target localization and tracking. The multiple radar units are deployed in a distributed system configuration, which provides robustness against target obscuration. We develop the dual-frequency signal model for the distributed radar system under phase errors and employ a joint sparse scene reconstruction and phase error correction technique to provide accurate target location and velocity estimates. Simulation results are provided that validate the performance of the proposed scheme under both full and reduced data volumes.

  20. Error catastrophe and phase transition in the empirical fitness landscape of HIV

    NASA Astrophysics Data System (ADS)

    Hart, Gregory R.; Ferguson, Andrew L.

    2015-03-01

    We have translated clinical sequence databases of the p6 HIV protein into an empirical fitness landscape quantifying viral replicative capacity as a function of the amino acid sequence. We show that the viral population resides close to a phase transition in sequence space corresponding to an "error catastrophe" beyond which there is lethal accumulation of mutations. Our model predicts that the phase transition may be induced by drug therapies that elevate the mutation rate, or by forcing mutations at particular amino acids. Applying immune pressure to any combination of killer T-cell targets cannot induce the transition, providing a rationale for why the viral protein can exist close to the error catastrophe without sustaining fatal fitness penalties due to adaptive immunity.

  1. Parameter dimension of turbulence-induced phase errors and its effects on estimation in phase diversity

    NASA Technical Reports Server (NTRS)

    Thelen, Brian J.; Paxman, Richard G.

    1994-01-01

    The method of phase diversity has been used in the context of incoherent imaging to estimate jointly an object that is being imaged and phase aberrations induced by atmospheric turbulence. The method requires a parametric model for the phase-aberration function. Typically, the parameters are coefficients to a finite set of basis functions. Care must be taken in selecting a parameterization that properly balances accuracy in the representation of the phase-aberration function with stability in the estimates. It is well known that over parameterization can result in unstable estimates. Thus a certain amount of model mismatch is often desirable. We derive expressions that quantify the bias and variance in object and aberration estimates as a function of parameter dimension.

  2. Analytical solution of two-phase spherical Stefan problem by heat polynomials and integral error functions

    NASA Astrophysics Data System (ADS)

    Kharin, Stanislav N.; Sarsengeldin, Merey M.; Nouri, Hassan

    2016-08-01

    On the base of the Holm model, we represent two phase spherical Stefan problem and its analytical solution, which can serve as a mathematical model for diverse thermo-physical phenomena in electrical contacts. Suggested solution is obtained from integral error function and its properties which are represented in the form of series whose coefficients have to be determined. Convergence of solution series is proved.

  3. Beam Phase Space of an Intense Ion Beam in a Neutralizing Plasma

    NASA Astrophysics Data System (ADS)

    Seidl, Peter A.; Bazouin, Guillaume; Beneytout, Alice; Lidia, Steven M.; Vay, Jean-Luc; Grote, David P.

    2011-10-01

    The Neutralized Drift Compression Experiment (NDCX-I) generates high intensity ion beams to explore warm dense matter physics. Transverse final focusing is accomplished with an 8-Tesla, 10-cm long pulsed solenoid magnet combined with a background neutralizing plasma to effectively cancel the space charge field of the ion beam. We report on phase space measurements of the beam before the neutralization channel and of the focused ion beam at the target plane. These are compared to WARP particle-in-cell simulations of the ion beam propagation through the focusing system and neutralizing plasma. Due to the orientation of the plasma sources with respect to the focusing magnet, the plasma distribution within the final focusing lens is strongly affected by the magnetic field, an effect which can influence the peak intensity at the target and which is included in the model of the experiment. Work performed under auspices of U.S. DoE by LLNL, LBNL under Contracts DE-AC52-07NA27344, DE-AC02-05CH1123.

  4. Phase and synchronous detector theory as applied to beam position and intensity measurements

    SciTech Connect

    Gilpatrick, J.D.

    1995-05-01

    A popular signal processing technique for beam position measurements uses the principle of amplitude-to-phase (AM/PM) conversion and phase detection. This technique processes position-sensitive beam-image-current probe-signals into output signals that are proportional to the beam`s position. These same probe signals may be summed and processed in a different fashion to provide output signals that are proportional to the peak beam current which is typically referred to as beam intensity. This paper derives the transfer functions for the AM/PM beam position and peak beam current processors.

  5. Suppression of backreflection error in resonator integrated optic gyro by the phase difference traversal method.

    PubMed

    Wang, Junjie; Feng, Lishuang; Wang, Qiwei; Jiao, Hongchen; Wang, Xiao

    2016-04-01

    The phase difference traversal (PDT) method is proposed to suppress the backreflection-induced error in resonator integrated optic gyro (RIOG). Theoretical analysis shows that the backreflection-induced zero-bias fluctuation is periodical and sine/cosine-like. By forcing the phase difference between the CW and CCW incident light to traverse the interval [0, 2π] repeatedly and rapidly enough, the fluctuation can be low-pass filtered and, hence, the backreflection-induced error can be effectively suppressed. A RIOG apparatus is built up, with multi-wave hybrid phase modulation to traverse the phase difference and in-phase modulation to set the operation point. A short-term bias stability of 0.0055 deg/s and a long-term bias stability of 0.013 deg/s are successfully demonstrated which, to the best of our knowledge, are the best results reported to date for the buried-type silica waveguide ring resonator-based RIOG. PMID:27192293

  6. Tailoring phase-space in neutron beam extraction

    NASA Astrophysics Data System (ADS)

    Weichselbaumer, S.; Brandl, G.; Georgii, R.; Stahn, J.; Panzner, T.; Böni, P.

    2015-09-01

    In view of the trend towards smaller samples and experiments under extreme conditions it is important to deliver small and homogeneous neutron beams to the sample area. For this purpose, elliptic and/or Montel mirrors are ideally suited as the phase space of the neutrons can be defined far away from the sample. Therefore, only the useful neutrons will arrive at the sample position leading to a very low background. We demonstrate the ease of designing neutron transport systems using simple numeric tools, which are verified using Monte-Carlo simulations that allow taking into account effects of gravity and finite beam size. It is shown that a significant part of the brilliance can be transferred from the moderator to the sample. Our results may have a serious impact on the design of instruments at spallation sources such as the European Spallation Source (ESS) in Lund, Sweden.

  7. Laser-beam apodization with a graded random phase window.

    PubMed

    Haas, R A; Summers, M A; Linford, G J

    1986-10-01

    Experiments and analysis indicate that graded random phase modulation can be used to apodize a laser beam. In the case of an obscuration or a hard edge it can prevent the formation of Fresnel-diffraction ripples. For example, here the interaction of a 1-microm-wavelength laser beam with a central obscuration of half-width a = 100 microm is studied theoretically. It is found that if the exit surface of a window, placed immediately downstream of the obstacle, is randomly modulated with a Gaussian amplitude transverse correlation length l = 50 microm and a mean-square amplitude that decreases exponentially from a peak height of ~1 microm(2) away from the center of the obscuration with transverse scale length L = 500 microm, then the Fresnel-diffraction ripples normally produced by the obscuration are eliminated. The scaling of these results is also discussed. The calculations are in general agreement with experimental results. PMID:19738707

  8. Quality improvement of partially coherent symmetric-intensity beams caused by quartic phase distortions.

    PubMed

    Martínez-Herrero, R; Mejías, P M; Piquero, G

    1992-12-01

    The effects that quartic phase distortions produce in the beam-quality parameter of partially coherent symmetric-intensitybeams are studied. An analytical expression for the beam-quality parameter at the output plane of a pure phase plate with quartic phase aberration has been derived. Explicit conditions to improve the beam quality are provided, and the corresponding optimized beam-quality value that can be attained for a given field has been determined. PMID:19798272

  9. Experimental generation of Hermite-Gauss and Ince-Gauss beams through kinoform phase holograms

    NASA Astrophysics Data System (ADS)

    Mellado-Villaseñor, Gabriel; Aguirre-Olivas, Dilia; Sánchez-de-la-Llave, David; Arrizón, Victor

    2015-08-01

    We generate Hermite-Gauss and Ince-Gauss beams by using kinoform phase holograms encoded onto a liquid crystal display. The phase transmittance of this holograms coincide with the phases of such beams. Scale versions of the desired beams appear at the Fourier domain of the KPHs. When an appropriated pupil size is employed, the method synthesizes HG and IG beams with relatively high accuracy and high efficiency. It is noted that experimental and numerical results are agreement with the theory.

  10. Single-beam phase retrieval with partially coherent light illumination

    NASA Astrophysics Data System (ADS)

    Zhou, Meiling; Min, Junwei; Gao, Peng; Liang, Yansheng; Lei, Ming; Yao, Baoli

    2016-01-01

    A single-beam phase retrieval method with partially coherent illumination is proposed. By using an obverse and reverse iterative (ORI) algorithm, objects can be reconstructed within less time by recording a sequence of diffraction patterns at different axial planes under partially coherent light illumination. Partially coherent light illumination reduces coherent noise and the number of diffraction patterns needed for reconstruction. Thus, the whole process is fast and has high immunity to external perturbation due to the reference-less configuration. Both simulation and experimental results are presented to demonstrate the feasibility of the proposed approach.

  11. Simulation of oxide phases formation under pulsed electron beam

    NASA Astrophysics Data System (ADS)

    Kryukova, O. N.; Maslov, A. L.

    2016-04-01

    This paper presents the mathematical model of evolution phase composition in the TiNi+Si system under impulsive electron beam. It was assumed that the initial coating contains small concentration of molecular oxygen. This model is one-demensional, and takes into account the phenomena of diffusion, chemical reactions, and thermal effects of chemical reactions. Results of the numerical modeling had show that the oxide of titanium and triple solution TiNiSi formed in significant amounts, and triple solution preferentially forms in the substrate. Other oxides must be formed in trace amounts.

  12. Analysis of counting errors in the phase/Doppler particle analyzer

    NASA Technical Reports Server (NTRS)

    Oldenburg, John R.

    1987-01-01

    NASA is investigating the application of the Phase Doppler measurement technique to provide improved drop sizing and liquid water content measurements in icing research. The magnitude of counting errors were analyzed because these errors contribute to inaccurate liquid water content measurements. The Phase Doppler Particle Analyzer counting errors due to data transfer losses and coincidence losses were analyzed for data input rates from 10 samples/sec to 70,000 samples/sec. Coincidence losses were calculated by determining the Poisson probability of having more than one event occurring during the droplet signal time. The magnitude of the coincidence loss can be determined, and for less than a 15 percent loss, corrections can be made. The data transfer losses were estimated for representative data transfer rates. With direct memory access enabled, data transfer losses are less than 5 percent for input rates below 2000 samples/sec. With direct memory access disabled losses exceeded 20 percent at a rate of 50 samples/sec preventing accurate number density or mass flux measurements. The data transfer losses of a new signal processor were analyzed and found to be less than 1 percent for rates under 65,000 samples/sec.

  13. Effect of initial phase on error in electron energy obtained using paraxial approximation for a focused laser pulse in vacuum

    SciTech Connect

    Singh, Kunwar Pal; Arya, Rashmi; Malik, Anil K.

    2015-09-14

    We have investigated the effect of initial phase on error in electron energy obtained using paraxial approximation to study electron acceleration by a focused laser pulse in vacuum using a three dimensional test-particle simulation code. The error is obtained by comparing the energy of the electron for paraxial approximation and seventh-order correction description of the fields of Gaussian laser. The paraxial approximation predicts wrong laser divergence and wrong electron escape time from the pulse which leads to prediction of higher energy. The error shows strong phase dependence for the electrons lying along the axis of the laser for linearly polarized laser pulse. The relative error may be significant for some specific values of initial phase even at moderate values of laser spot sizes. The error does not show initial phase dependence for a circularly laser pulse.

  14. SITE project. Phase 1: Continuous data bit-error-rate testing

    NASA Astrophysics Data System (ADS)

    Fujikawa, Gene; Kerczewski, Robert J.

    1992-09-01

    The Systems Integration, Test, and Evaluation (SITE) Project at NASA LeRC encompasses a number of research and technology areas of satellite communications systems. Phase 1 of this project established a complete satellite link simulator system. The evaluation of proof-of-concept microwave devices, radiofrequency (RF) and bit-error-rate (BER) testing of hardware, testing of remote airlinks, and other tests were performed as part of this first testing phase. This final report covers the test results produced in phase 1 of the SITE Project. The data presented include 20-GHz high-power-amplifier testing, 30-GHz low-noise-receiver testing, amplitude equalization, transponder baseline testing, switch matrix tests, and continuous-wave and modulated interference tests. The report also presents the methods used to measure the RF and BER performance of the complete system. Correlations of the RF and BER data are summarized to note the effects of the RF responses on the BER.

  15. SITE project. Phase 1: Continuous data bit-error-rate testing

    NASA Technical Reports Server (NTRS)

    Fujikawa, Gene; Kerczewski, Robert J.

    1992-01-01

    The Systems Integration, Test, and Evaluation (SITE) Project at NASA LeRC encompasses a number of research and technology areas of satellite communications systems. Phase 1 of this project established a complete satellite link simulator system. The evaluation of proof-of-concept microwave devices, radiofrequency (RF) and bit-error-rate (BER) testing of hardware, testing of remote airlinks, and other tests were performed as part of this first testing phase. This final report covers the test results produced in phase 1 of the SITE Project. The data presented include 20-GHz high-power-amplifier testing, 30-GHz low-noise-receiver testing, amplitude equalization, transponder baseline testing, switch matrix tests, and continuous-wave and modulated interference tests. The report also presents the methods used to measure the RF and BER performance of the complete system. Correlations of the RF and BER data are summarized to note the effects of the RF responses on the BER.

  16. The backward phase flow and FBI-transform-based Eulerian Gaussian beams for the Schroedinger equation

    SciTech Connect

    Leung Shingyu; Qian Jianliang

    2010-11-20

    We propose the backward phase flow method to implement the Fourier-Bros-Iagolnitzer (FBI)-transform-based Eulerian Gaussian beam method for solving the Schroedinger equation in the semi-classical regime. The idea of Eulerian Gaussian beams has been first proposed in . In this paper we aim at two crucial computational issues of the Eulerian Gaussian beam method: how to carry out long-time beam propagation and how to compute beam ingredients rapidly in phase space. By virtue of the FBI transform, we address the first issue by introducing the reinitialization strategy into the Eulerian Gaussian beam framework. Essentially we reinitialize beam propagation by applying the FBI transform to wavefields at intermediate time steps when the beams become too wide. To address the second issue, inspired by the original phase flow method, we propose the backward phase flow method which allows us to compute beam ingredients rapidly. Numerical examples demonstrate the efficiency and accuracy of the proposed algorithms.

  17. Space telemetry degradation due to Manchester data asymmetry induced carrier tracking phase error

    NASA Technical Reports Server (NTRS)

    Nguyen, Tien M.

    1991-01-01

    The deleterious effects that the Manchester (or Bi-phi) data asymmetry has on the performance of phase-modulated residual carrier communication systems are analyzed. Expressions for the power spectral density of an asymmetric Manchester data stream, the interference-to-carrier signal power ratio (I/C), and the error probability performance are derived. Since data asymmetry can cause undesired spectral components at the carrier frequency, the I/C ratio is given as a function of both the data asymmetry and the telemetry modulation index. Also presented are the data asymmetry and asymmetry-induced carrier tracking loop and the system bit-error rate to various parameters of the models.

  18. Using Lambert W function and error function to model phase change on microfluidics

    NASA Astrophysics Data System (ADS)

    Bermudez Garcia, Anderson

    2014-05-01

    Solidification and melting modeling on microfluidics are solved using Lambert W's function and error's functions. Models are formulated using the heat's diffusion equation. The generic posed case is the melting of a slab with time dependent surface temperature, having a micro or nano-fluid liquid phase. At the beginning the solid slab is at melting temperature. A slab's face is put and maintained at temperature greater than the melting limit and varying in time. Lambert W function and error function are applied via Maple to obtain the analytic solution evolution of the front of microfluidic-solid interface, it is analytically computed and slab's corresponding melting time is determined. It is expected to have analytical results to be useful for food engineering, cooking engineering, pharmaceutical engineering, nano-engineering and bio-medical engineering.

  19. Detailed calculation of spectral noise caused by measurement errors of Mach-Zehnder interferometer optical path phases in a spatial heterodyne spectrometer with a phase shift scheme.

    PubMed

    Takada, Kazumasa; Seino, Mitsuyoshi; Chiba, Akito; Okamoto, Katsunari

    2013-04-20

    We calculate the root mean square (rms) value of the spectral noise caused by optical path phase measurement errors in a spatial heterodyne spectrometer (SHS) featuring a complex Fourier transformation. In our calculation the deviated phases of each Mach-Zehnder interferometer in the in-phase and quadrature states are treated as statistically independent random variables. We show that the rms value is proportional to the rms error of the phase measurement and that the proportionality coefficient is given analytically. The relationship enables us to estimate the potential performance of the SHS such as the sidelobe suppression ratio for a given measurement error. PMID:23669661

  20. Errors incurred in a plane-wave-type expansion of a Gaussian beam. [in laser force calculations on light scattering aerosol experiments

    NASA Technical Reports Server (NTRS)

    Kattawar, G. W.

    1980-01-01

    The multipole expansion obtained by Morita et al. (1968) of the Gaussian laser beam used to levitate an aerosol particle in order that its complete phase matrix may be measured is compared with that of Tsai and Pogorzelski (1975) in order to demonstrate the effect of the incorrect expansion used by Morita. Errors incurred by the use of an equation in which one side satisfies the scalar wave equation while the other side does not and can be reduced to a plane wave amplitude are calculated as functions of the inverse of the wave number times the beam waist, the wave number times the radial spherical coordinate and the angular spherical coordinate. Errors on the order of a few percent, considered undetectable are obtained in the squared-field amplitudes due to the expansion, however, they are found to become significant (several tens of percent) when the angle is zero. It is concluded that the expansion of Morita should only be used in the regions where the spherical angle is less than 0.01 and its product with the wave number and the radial spherical coordinate is less than unity.

  1. Axially symmetric loop phase-conjugation scheme with broadband longitudinally dispersed light beams

    SciTech Connect

    Odintsov, Vladimir I

    2004-07-31

    A loop phase-conjugation scheme based on an axially symmetric four-wave interaction of focused light beams is proposed. It is shown that, when a longitudinal dispersion is introduced into the light beams, this scheme allows a phase conjugation of spatially coherent broadband radiation. The region of coherent interaction of focused longitudinally dispersed light beams is estimated. (nonlinear optical phenomena)

  2. Effects on flat-beam generation from space-charge force and beamline errors

    SciTech Connect

    Sun, Y.-E.; Kim, K.-J.; Piot, P.; /Fermilab

    2005-05-01

    The transformation of a round, angular-momentum-dominated electron beam produced in a photoinjector into a flat beam using a transformer composed of three skew-quadrupoles [1] has been developed theoretically [2, 3] and experimentally [4]. In this paper, we present numerical and analytical studies of space-charge forces, and evaluate the corresponding limits on the ratio of vertical-to-horizontal emittances. We also investigate the sensitivities of flat-beam emittances on the quadrupole misalignments in each of the six degrees of freedom.

  3. Bit error rate testing of fiber optic data links for MMIC-based phased array antennas

    NASA Technical Reports Server (NTRS)

    Shalkhauser, K. A.; Kunath, R. R.; Daryoush, A. S.

    1990-01-01

    The measured bit-error-rate (BER) performance of a fiber optic data link to be used in satellite communications systems is presented and discussed. In the testing, the link was measured for its ability to carry high burst rate, serial-minimum shift keyed (SMSK) digital data similar to those used in actual space communications systems. The fiber optic data link, as part of a dual-segment injection-locked RF fiber optic link system, offers a means to distribute these signals to the many radiating elements of a phased array antenna. Test procedures, experimental arrangements, and test results are presented.

  4. Positioning Errors of Pencil-beam Interferometers for Long TraceProfilers

    SciTech Connect

    Yashchuk, Valeriy V.

    2006-07-12

    We analyze the random noise and the systematic errors of the positioning of the interference patterns in the long trace profilers (LTP). The analysis, based on linear regression methods, allows the estimation of the contributions to the positioning error of a number of effects, including non-uniformity of the detector photo-response and pixel pitch, read-out and dark signal noise, ADC resolution, as well as signal shot noise. The dependence of the contributions on pixel size and on total number of pixels involved in positioning is derived analytically. The analysis, when applied to the LTP II available at the ALS optical metrology laboratory, has shown that the main source for the random positioning error of the interference pattern is the read-out noise estimated to be {approx}0.2 rad. The photo-diode-array photo-response and pixel pitch non-uniformity determine the magnitude of the systematic positioning error and are found to be {approx}0.3 rad for each of the effects. Recommendations for an optimal fitting strategy, detector selection and calibration are provided. Following these recommendations will allow the reduction of the error of LTP interference pattern positioning to a level adequate for the slope measurement with 0.1-rad accuracy.

  5. Simultaneous optical image compression and encryption using error-reduction phase retrieval algorithm

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Liu, Zhengjun; Liu, Shutian

    2015-12-01

    We report a simultaneous image compression and encryption scheme based on solving a typical optical inverse problem. The secret images to be processed are multiplexed as the input intensities of a cascaded diffractive optical system. At the output plane, a compressed complex-valued data with a lot fewer measurements can be obtained by utilizing error-reduction phase retrieval algorithm. The magnitude of the output image can serve as the final ciphertext while its phase serves as the decryption key. Therefore the compression and encryption are simultaneously completed without additional encoding and filtering operations. The proposed strategy can be straightforwardly applied to the existing optical security systems that involve diffraction and interference. Numerical simulations are performed to demonstrate the validity and security of the proposal.

  6. Silicon ion irradiation effects on the magnetic properties of ion beam synthesized CoPt phase

    SciTech Connect

    Balaji, S.; Amirthapandian, S.; Panigrahi, B. K.; Mangamma, G.; Kalavathi, S.; Gupta, Ajay; Nair, K. G. M.

    2012-06-05

    Ion beam mixing of Pt/Co bilayers using self ion (Pt{sup +}) beam results in formation of CoPt phase. Upon ion beam annealing the ion mixed samples using 4 MeV Si{sup +} ions at 300 deg. C, diffusion of Co towards the Pt/Co interface is observed. The Si{sup +} ion beam rotates the magnetization of the CoPt phase from in plane to out of plane of the film.

  7. Realization of a phase bunching effect for minimization of beam phase width in a central region of an AVF cyclotron

    NASA Astrophysics Data System (ADS)

    Miyawaki, Nobumasa; Fukuda, Mitsuhiro; Kurashima, Satoshi; Okumura, Susumu; Kashiwagi, Hirotsugu; Nara, Takayuki; Ishibori, Ikuo; Yoshida, Ken-ichi; Yokota, Watalu; Nakamura, Yoshiteru; Arakawa, Kazuo; Kamiya, Tomihiro

    2011-04-01

    A phase bunching effect has been achieved for the first time using a rising slope of the dee voltage waveform produced at the first acceleration gap between the RF shielding cover of the inflector and the puller in the new central region of the JAEA AVF cyclotron. The feasibility of the phase bunching effect in the central region for a two-dee system with a span angle of 86° in three acceleration harmonic modes was assessed by a simple geometrical analysis of particle trajectories and a three-dimensional beam orbit simulation using the calculated electric field and a measured magnetic field. The simulation indicated that the initial beam phase width of 40 RF degrees is compressed to 11 RF degrees (about 28% of the initial phase width) in the second harmonic mode. A phase width of 1.5 RF degrees FWHM for a 260 MeV 20Ne7+ beam accelerated in the second harmonic mode was observed when using a 4 mm phase slit gap. The phase width reduction was considerably enhanced by the bunching effect, compared with the beam phase width of 7.3 RF degrees FWHM in the same harmonic mode for a 10 MeV H+ beam accelerated in the original central region. The ratio of the beam current for the 1.5 RF degrees FWHM phase width with 4 mm phase slit gap restriction to the full beam current without the phase slit was drastically improved to 80%, while the beam current was less than 1% of the full beam when narrowing the phase slit gap to obtain the 7.3 RF degrees FWHM phase width in the original central region.

  8. The study of the structural stability of the spiral laser beams propagation through inhomogeneous phase medium

    NASA Astrophysics Data System (ADS)

    Zinchik, Alexander A.; Muzychenko, Yana B.

    2015-06-01

    This paper discusses theoretical and experimental results of the investigation of light beams that retain their intensity structure during propagation and focusing. Spiral laser beams are a family of laser beams that preserve the structural stability up to scale and rotation with the propagation. Properties of spiral beams are of practical interest for laser technology, medicine and biotechnology. Researchers use a spiral beams for movement and manipulation of microparticles. Functionality laser manipulators can be significantly enhanced by using spiral beams whose intensity remains invariable. It is well known, that these beams has non-zero orbital angular momentum. Spiral beams have a complicated phase distribution in cross section. In this paper we investigate the structural stability of the laser beams having a spiral phase structure by passing them through an inhomogeneous phase medium. Laser beam is passed through a medium is characterized by a random distribution of phase in the range 0..2π. The modeling was performed using VirtualLab 5.0 (manufacturer LightTrans GmbH). Compared the intensity distribution of the spiral and ordinary laser beam after the passage of the inhomogeneous medium. It is shown that the spiral beams exhibit a significantly better structural stability during the passage phase heterogeneous environments than conventional laser beams. The results obtained in the simulation are tested experimentally. Experimental results show good agreement with the theoretical results.

  9. Impacts of double-ended beam-pointing error on system performance

    NASA Astrophysics Data System (ADS)

    Horkin, Phil R.

    2000-05-01

    Optical Intersatellite links have been investigated for many years, but to date have enjoyed few spaceborne applications. The literature is rich in articles describing system issues such as jitter and pointing effects, but this author believes that simplifications generally made lead to significant errors. Simplifications made, for example, due to the complexity of joint distribution functions are easily overcome with widely available computer tools. Satellite- based data transport systems must offer similar Quality of Service (QoS) parameters as fiber-based transport. The movement to packet-based protocols adds additional constraints not often considered in past papers. BER may no longer be the dominant concern; packet loss, misdelivery, or severely corrupted packets can easily dominate the error budgets. The aggregation of static and dynamic pointing errors on both ends of such a link dramatically reduces the QoS. The approach described in this paper provides the terminal designer the methodology to analytically balance the impacts of these error sources against implementation solutions.

  10. Phase conjugation upon SBS of a focused laser speckle beam

    SciTech Connect

    Bogachev, V A; Kochemasov, G G; Starikov, F A

    2008-09-30

    The phase conjugation (PC) of a focused Gaussian laser beam with a partial spatial coherence of the wave front is studied numerically and theoretically upon SBS within the framework of a three-dimensional nonstationary SBS model, which takes into account transient processes and SBS saturation. The dependences of the PC coefficient h on the laser radiation power are obtained for different excesses of the angular divergence over the diffraction limit {xi}. It is found that for the given reflectance of laser radiation from the SBS mirror, the PC coefficient monotonically decreases with increasing the divergence. For example, under the near threshold SBS conditions, h decreases from 70% to 30%, when {xi} increases from 1 to 10. For the given divergence, the PC coefficient increases with increasing the reflectance and approaches the ideal one (h > 90%) upon deep SBS saturation, when the reflectance exceeds 90%-95%. (nonlinear optical phenomena)

  11. Time-delayed directional beam phased array antenna

    DOEpatents

    Fund, Douglas Eugene; Cable, John William; Cecil, Tony Myron

    2004-10-19

    An antenna comprising a phased array of quadrifilar helix or other multifilar antenna elements and a time-delaying feed network adapted to feed the elements. The feed network can employ a plurality of coaxial cables that physically bridge a microstrip feed circuitry to feed power signals to the elements. The cables provide an incremental time delay which is related to their physical lengths, such that replacing cables having a first set of lengths with cables having a second set of lengths functions to change the time delay and shift or steer the antenna's main beam. Alternatively, the coaxial cables may be replaced with a programmable signal processor unit adapted to introduce the time delay using signal processing techniques applied to the power signals.

  12. Efficient generation of Hermite-Gauss and Ince-Gauss beams through kinoform phase elements.

    PubMed

    Aguirre-Olivas, Dilia; Mellado-Villaseñor, Gabriel; Sánchez-de-la-Llave, David; Arrizón, Victor

    2015-10-01

    We discuss the generation of Hermite-Gauss and Ince-Gauss beams employing phase elements whose transmittances coincide with the phase modulations of such beams. A scaled version of the desired field appears, distorted by marginal optical noise, at the element's Fourier domain. The motivation to perform this study is that, in the context of the proposed approach, the desired beams are generated with the maximum possible efficiency. A disadvantage of the method is the distortion of the desired beams by the influence of several nondesired beam modes generated by the phase elements. We evaluate such distortion employing the root mean square deviation as a figure of merit. PMID:26479622

  13. Analysis of errors detected in external beam audit dosimetry program at Mexican radiotherapy centers

    NASA Astrophysics Data System (ADS)

    Álvarez-Romero, José T.; Tovar-Muñoz, Víctor M.

    2012-10-01

    Presented and analyzed are the causes of deviation observed in the pilot postal dosimetry audit program to verify the absorbed dose to water Dw in external beams of teletherapy 60Co and/or linear accelerators in Mexican radiotherapy centers, during the years 2007-2011.

  14. Creating Ruddlesden-Popper phases by hybrid molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Haislmaier, Ryan C.; Stone, Greg; Alem, Nasim; Engel-Herbert, Roman

    2016-07-01

    The synthesis of a 50 unit cell thick n = 4 Srn+1TinO3n+1 (Sr5Ti4O13) Ruddlesden-Popper (RP) phase film is demonstrated by sequentially depositing SrO and TiO2 layers in an alternating fashion using hybrid molecular beam epitaxy (MBE), where Ti was supplied using titanium tetraisopropoxide (TTIP). A detailed calibration procedure is outlined for determining the shuttering times to deposit SrO and TiO2 layers with precise monolayer doses using in-situ reflection high energy electron diffraction (RHEED) as feedback. Using optimized Sr and TTIP shuttering times, a fully automated growth of the n = 4 RP phase was carried out over a period of >4.5 h. Very stable RHEED intensity oscillations were observed over the entire growth period. The structural characterization by X-ray diffraction and high resolution transmission electron microscopy revealed that a constant periodicity of four SrTiO3 perovskite unit cell blocks separating the double SrO rocksalt layer was maintained throughout the entire film thickness with a very little amount of planar faults oriented perpendicular to the growth front direction. These results illustrate that hybrid MBE is capable of layer-by-layer growth with atomic level precision and excellent flux stability.

  15. Method of phase space beam dilution utilizing bounded chaos generated by rf phase modulation

    NASA Astrophysics Data System (ADS)

    Pham, Alfonse N.; Lee, S. Y.; Ng, K. Y.

    2015-12-01

    This paper explores the physics of chaos in a localized phase-space region produced by rf phase modulation applied to a double rf system. The study can be exploited to produce rapid particle bunch broadening exhibiting longitudinal particle distribution uniformity. Hamiltonian models and particle-tracking simulations are introduced to understand the mechanism and applicability of controlled particle diffusion. When phase modulation is applied to the double rf system, regions of localized chaos are produced through the disruption and overlapping of parametric resonant islands and configured to be bounded by well-behaved invariant tori to prevent particle loss. The condition of chaoticity and the degree of particle dilution can be controlled by the rf parameters. The method has applications in alleviating adverse space-charge effects in high-intensity beams, particle bunch distribution uniformization, and industrial radiation-effects experiments.

  16. Correction of timing errors in photomultiplier tubes used in phase-modulation fluorometry.

    PubMed

    Lakowicz, J R; Cherek, H; Balter, A

    1981-09-01

    The measurement of fluorescence lifetimes is known to be hindered by the wavelength-dependent and photocathode area-dependent time response of photomultiplier tubes. A simple and direct method is described to minimize these effects in photomultiplier tubes used for phase-modulation fluorometry. Reference fluorophores of known lifetime were used in place of the usual scattering reference. The emission wavelengths of the reference and sample were matched by either filters or a monochromator, and the use of a fluorophore rather than a scatterer decreases the differences in spatial distribution of light emanating from the reference and sample. Thus photomultiplier tube artifacts are minimized. Five reference fluorophores were selected on the basis of availability, ease of solution preparation, and constancy of lifetime with temperature and emission wavelength. These compounds are p-terphenyl, PPO, PPD, POPOP and dimethyl POPOP. These compounds are dissolved in ethanol to give standard solutions that can be used over the temperature range from -55 to +55 degrees C. Purging with inert gas is not necessary. The measured phase and modulation of the reference solution is used, in conjunction with the known reference lifetime, to calculate the actual phase and modulation of the excitation beam. The use of standard fluorophores does not require separate experiments to quantify photomultiplier effects, and does not increase the time required for the measurement of fluorescence lifetimes. Examples are presented which demonstrate the elimination of artifactual photomultiplier effects in measurements of the lifetimes of NADH (0.4 ns) and indole solutions quenched by iodide. In addition, the use of these reference solutions increases the accuracy of fluorescence lifetime measurements ranging to 30 ns. We judge this method to provide more reliable lifetime measurements by the phase and modulation method. The test solutions and procedures we describe may be used by other

  17. Complex phase error and motion estimation in synthetic aperture radar imaging

    NASA Astrophysics Data System (ADS)

    Soumekh, M.; Yang, H.

    1991-06-01

    Attention is given to a SAR wave equation-based system model that accurately represents the interaction of the impinging radar signal with the target to be imaged. The model is used to estimate the complex phase error across the synthesized aperture from the measured corrupted SAR data by combining the two wave equation models governing the collected SAR data at two temporal frequencies of the radar signal. The SAR system model shows that the motion of an object in a static scene results in coupled Doppler shifts in both the temporal frequency domain and the spatial frequency domain of the synthetic aperture. The velocity of the moving object is estimated through these two Doppler shifts. It is shown that once the dynamic target's velocity is known, its reconstruction can be formulated via a squint-mode SAR geometry with parameters that depend upon the dynamic target's velocity.

  18. Correction of vignetting and distortion errors induced by two-axis light beam steering

    PubMed Central

    Gao, Liang; Tkaczyk, Tomasz S.

    2012-01-01

    A mirror facet’s angle correction approach is presented for eliminating pupil plane distortions and sub-field image vignetting in the image mapping spectrometry (IMS). The two-axis light reflection problem on the image mapper is solved and a rigorous analytical solution is provided. The cellular fluorescence imaging experiment demonstrates that, with an angle-corrected image mapper, the acquired image quality of spectral channels has been significantly improved compared to previous IMS images. The proposed mathematical model can also be used in solving general two-axis beam steering problems for instruments with active optical mirrors. PMID:24976654

  19. Growth and phase velocity of self-modulated beam-driven plasma waves

    SciTech Connect

    Benedetti, Carlo; Esarey, Eric; Gruener, Florian; Leemans, Wim

    2011-09-20

    A long, relativistic particle beam propagating in an overdense plasma is subject to the self-modulation instability. This instability is analyzed and the growth rate is calculated, including the phase relation. The phase velocity of the wake is shown to be significantly less than the beam velocity. These results indicate that the energy gain of a plasma accelerator driven by a self-modulated beam will be severely limited by dephasing. In the long-beam, strongly-coupled regime, dephasing is reached in a homogeneous plasma in less than four e-foldings, independent of beam-plasma parameters.

  20. Propagation of Gaussian beams through a modified von Karman phase screen

    NASA Astrophysics Data System (ADS)

    Whitfield, Erica M.; Banerjee, Partha P.; Haus, Joseph W.

    2012-10-01

    Gaussian beam propagation through a thin screen and an extended random media has been studied using a beam propagation method. We use the modified von Karman spectrum model to describe the phase screen statistics. The scintillation index is analyzed as a function of the structure constant, phase screen location, the initial width and curvature of the Gaussian beam, etc. The numerical simulations are extended using a pair of Gaussian beams. We examine the interference of the beams and measure the fringe visibility at the target. The results are correlated with the scintillation index.

  1. Growth and phase velocity of self-modulated beam-driven plasma waves.

    PubMed

    Schroeder, C B; Benedetti, C; Esarey, E; Grüner, F J; Leemans, W P

    2011-09-30

    A long, relativistic particle beam propagating in an overdense plasma is subject to the self-modulation instability. This instability is analyzed and the growth rate is calculated, including the phase relation. The phase velocity of the wake is shown to be significantly less than the beam velocity. These results indicate that the energy gain of a plasma accelerator driven by a self-modulated beam will be severely limited by dephasing. In the long-beam, strongly coupled regime, dephasing is reached in a homogeneous plasma in less than four e foldings, independent of beam-plasma parameters. PMID:22107202

  2. Growth and Phase Velocity of Self-Modulated Beam-Driven Plasma Waves

    SciTech Connect

    Schroeder, C. B.; Benedetti, C.; Esarey, E.; Leemans, W. P.; Gruener, F. J.

    2011-09-30

    A long, relativistic particle beam propagating in an overdense plasma is subject to the self-modulation instability. This instability is analyzed and the growth rate is calculated, including the phase relation. The phase velocity of the wake is shown to be significantly less than the beam velocity. These results indicate that the energy gain of a plasma accelerator driven by a self-modulated beam will be severely limited by dephasing. In the long-beam, strongly coupled regime, dephasing is reached in a homogeneous plasma in less than four e foldings, independent of beam-plasma parameters.

  3. Relative position determination of a lunar rover using the biased differential phase delay of same-beam VLBI

    NASA Astrophysics Data System (ADS)

    Chen, Ming; Liu, Qinghui; Wu, Yajun; Zhao, Rongbing; Dai, Zhiqiang

    2011-12-01

    When only data transmission signals with a bandwidth of 1 MHz exist in the rover, the position can be obtained using the differential group delay data of the same-beam very long baseline interferometry (VLBI). The relative position between a lunar rover and a lander can be determined with an error of several hundreds of meters. When the guidance information of the rover is used to determine relative position, the rover's wheel skid behavior and integral movement may influence the accuracy of the determined position. This paper proposes a new method for accurately determining relative position. The differential group delay and biased differential phase delay are obtained from the same-beam VLBI observation, while the modified biased differential phase delay is obtained using the statistic mean value of the differential group delay and the biased phase delay as basis. The small bias in the modified biased phase delay is estimated together with other parameters when the relative position of the rover is calculated. The effectiveness of the proposed method is confirmed using the same-beam VLBI observation data of SELENE. The radio sources onboard the rover and the lander are designed for same-beam VLBI observations. The results of the simulations of the differential delay of the same-beam VLBI observation between the rover and the lander show that the differential delay is sensitive to relative position. An approach to solving the relative position and a strategy for tracking are also introduced. When the lunar topography data near the rover are used and the observations are scheduled properly, the determined relative position of the rover may be nearly as accurate as that solved using differential phase delay data.

  4. Combining the switched-beam and beam-steering capabilities in a 2-D phased array antenna system

    NASA Astrophysics Data System (ADS)

    Tsai, Yi-Che; Chen, Yin-Bing; Hwang, Ruey-Bing

    2016-01-01

    This paper presents the development, fabrication, and measurement of a novel beam-forming system consisting of 16 subarray antennas, each containing four aperture-coupled patch antennas, and the application of this system in smart wireless communication systems. The beam patterns of each of the subarray antennas can be switched toward one of nine zones over a half space by adjusting the specific phase delay angles among the four antenna elements. Furthermore, when all subarrays are pointed at the same zone, slightly continuous beam steering in around 1° increments can be achieved by dynamically altering the progressive phase delay angle among the subarrays. Phase angle calibration was implemented by coupling each transmitter output and down converter into the in-phase/quadrature baseband to calculate the correction factor to the weight. In addition, to validate the proposed concepts and the fabricated 2-D phased array antenna system, this study measured the far-field radiation patterns of the aperture-coupled patch array integrated with feeding networks and a phase-calibration system to carefully verify its spatially switched-beam and beam-steering characteristics at a center frequency of 2.4 GHz which can cover the industrial, scientific, and medical band and some long-term evolution applications. In addition, measured results were compared with calculated results, and agreement between them was observed.

  5. On detector linearity and precision of beam shift detection for quantitative differential phase contrast applications.

    PubMed

    Zweck, Josef; Schwarzhuber, Felix; Wild, Johannes; Galioit, Vincent

    2016-09-01

    Differential phase contrast is a STEM imaging mode where minute sideways deflections of the electron probe are monitored, usually by using a position sensitive device (Chapman, 1984 [1]; Lohr et al., 2012 [2]) or, alternatively in some cases, a fast camera (Müller et al., 2012 [3,4]; Yang et al., 2015 [5]; Pennycook et al., 2015 [6]) as a pixelated detector. While traditionally differential phase contrast electron microscopy was mainly focused on investigations of micro-magnetic domain structures and their specific features, such as domain wall widths, etc. (Chapman, 1984 [1]; Chapman et al., 1978, 1981, 1985 [7-9]; Sannomiya et al., 2004 [10]), its usage has recently been extended to mesoscopic (Lohr et al., 2012, 2016 [2,12]; Bauer et al., 2014 [11]; Shibata et al., 2015 [13]) and nano-scale electric fields (Shibata et al., 2012 [14]; Mueller et al., 2014 [15]). In this paper, the various interactions which can cause a beam deflection are reviewed and expanded by two so far undiscussed mechanisms which may be important for biological applications. As differential phase contrast microscopy strongly depends on the ability to detect minute beam deflections we first treat the linearity problem for an annular four quadrant detector and then determine the factors which limit the minimum measurable deflection angle, such as S/N ratio, current density, dwell time and detector geometry. Knowing these factors enables the experimenter to optimize the set-up for optimum performance of the microscope and to get a clear figure for the achievable field resolution error margins. PMID:27376783

  6. Twist phase-induced polarization changes in electromagnetic Gaussian Schell-model beams

    NASA Astrophysics Data System (ADS)

    Cai, Y.; Korotkova, O.

    2009-08-01

    Electromagnetic Gaussian Schell-model (EGSM) beam with twist phase (i.e., twisted EGSM beam) is introduced as an extension of its scalar version based on the unified theory of coherence and polarization. We show how analytical paraxial propagation formulae of isotropic and anisotropic EGSM beams passing through a general astigmatic ABCD optical system can be modified in the presence of the twist phase. Numerical examples demonstrate that the twist phase affects the spectral density, the state of coherence, and the degree of polarization of EGSM beams on propagation.

  7. Arbitrary polarized beams generated and detected by one phase-only LC-SLM

    NASA Astrophysics Data System (ADS)

    Chen, Dong; Qi, Junli; Wang, Weihua; Chen, Yu; Gu, Guohua; Chu, Delin; Zhang, Qianghua; Deng, Haifei; Zhao, Sugui; Han, Jiajia; Wang, Rongfei

    2014-09-01

    Arbitrary polarized beams, including homogeneously polarized beams and cylindrical vector beams, have been generated by an experimental setup with one phase-only liquid crystal spatial light modulator, and a four-path method was demonstrated to measure the polarization degree of detected beams. Besides, another method was proposed to measure the polarization directions of cylindrical vector beams. The polarized states can be calculated by controlling the spatial light modulator and optical intensity obtained from a CCD. The generation setup and detection methods have simple structure and low cost, and they are available for multi wavelength input beams, and the detection methods can realize real-time and on-line measurement.

  8. Effects of errors in velocity tilt on maximum longitudinal compression during neutralized drift compression of intense beam pulses: I. general description

    SciTech Connect

    Kaganovich, Igor D.; Massidda, Scottt; Startsev, Edward A.; Davidson, Ronald C.; Vay, Jean-Luc; Friedman, Alex

    2012-06-21

    Neutralized drift compression offers an effective means for particle beam pulse compression and current amplification. In neutralized drift compression, a linear longitudinal velocity tilt (head-to-tail gradient) is applied to the non-relativistic beam pulse, so that the beam pulse compresses as it drifts in the focusing section. The beam current can increase by more than a factor of 100 in the longitudinal direction. We have performed an analytical study of how errors in the velocity tilt acquired by the beam in the induction bunching module limit the maximum longitudinal compression. It is found that the compression ratio is determined by the relative errors in the velocity tilt. That is, one-percent errors may limit the compression to a factor of one hundred. However, a part of the beam pulse where the errors are small may compress to much higher values, which are determined by the initial thermal spread of the beam pulse. It is also shown that sharp jumps in the compressed current density profile can be produced due to overlaying of different parts of the pulse near the focal plane. Examples of slowly varying and rapidly varying errors compared to the beam pulse duration are studied. For beam velocity errors given by a cubic function, the compression ratio can be described analytically. In this limit, a significant portion of the beam pulse is located in the broad wings of the pulse and is poorly compressed. The central part of the compressed pulse is determined by the thermal spread. The scaling law for maximum compression ratio is derived. In addition to a smooth variation in the velocity tilt, fast-changing errors during the pulse may appear in the induction bunching module if the voltage pulse is formed by several pulsed elements. Different parts of the pulse compress nearly simultaneously at the target and the compressed profile may have many peaks. The maximum compression is a function of both thermal spread and the velocity errors. The effects of the

  9. Generation of optical crystals and quasicrystal beams: Kaleidoscopic patterns and phase singularity

    SciTech Connect

    Chen, Y. F.; Liang, H. C.; Lin, Y. C.; Tzeng, Y. S.; Su, K. W.; Huang, K. F.

    2011-05-15

    We explore the feasibility of the generation of pseudonondiffracting optical beams related to crystal and quasicrystal structures. It is experimentally confirmed that optical crystal and quasicrystal beams can be remarkably generated with a collimated light to illuminate a high-precision mask with multiple apertures regularly distributed on a ring. We also found that exotic kaleidoscopic patterns can be exhibited with the high-order quasicrystal beams. More importantly, the structures of phase singularities in optical quasicrystal beams are manifested.

  10. Experimental generation of Mathieu-Gauss beams with a phase-only spatial light modulator.

    PubMed

    Hernández-Hernández, R J; Terborg, R A; Ricardez-Vargas, I; Volke-Sepúlveda, K

    2010-12-20

    We present a novel method for the efficient generation of even, odd, and helical Mathieu-Gauss beams of arbitrary order and ellipticity by means of a phase-only spatial light modulator (SLM). Our method consists of displaying the phase of the desired beam in the SLM; the reconstructed field is obtained on-axis following a spatial filtering process with an annular aperture. The propagation invariance and topological properties of the generated beams are investigated numerically and experimentally. PMID:21173824

  11. Effect of beam broadening on the VHF Doppler mini-radar simple method for correcting wind velocity errors

    NASA Astrophysics Data System (ADS)

    Candusso, J.-P.; Crochet, M.

    2001-01-01

    A Doppler VHF mini-radar has been developed at LSEET (Laboratoire de Sondages de l'Environnement Terrestre) to permit investigations at low altitudes, where classical large ST-VHF profilers are blind in the first kilometers of the atmosphere, and UHF boundary layer radars are disturbed by precipitations, birds and insects echoes. Due to a small size of the antenna array, beam broadening effects are important and can provide errors in the atmospheric parameter estimation (reflectivity and wind velocity). A simple overlapping correction method based on the decomposition of the power spectrum is employed to retrieve wind velocity profiles. Measurements from a high-resolution ST radar are used as a benchmark which allows data comparisons and evaluation of this new method.

  12. The Gouy phase anomaly for harmonic and time-domain paraxial Gaussian beams

    NASA Astrophysics Data System (ADS)

    Nowack, Robert L.; Kainkaryam, Sribharath M.

    2011-02-01

    The Gouy phase anomaly resulting from the focusing of wave solutions is illustrated using 2-D paraxial Gaussian beams. For harmonic Gaussian beams, this gives rise to a continuous variation of the Gouy phase as a function of propagation distance. This is in contrast to the discontinuous phase anomaly at caustics for ray solutions. However, as the beam-width of a Gaussian beam at a focus gets smaller, the Gouy phase anomaly becomes more concentrated near the focus and approaches that of the ray solution. The Gouy phase for a harmonic Gaussian beam is first illustrated in a homogeneous medium, and then in a quadratic velocity waveguide where the beam can pass through multiple focus points. However for multiple focus points, care must be taken to ensure that the phase remains continuous. Finally, an example is shown of the Gouy phase for a time-domain signal using a Gabor wavelet. This is validated using the finite difference method, and illustrates the progressive phase advance of a time-domain signal modifying the pulse shape with distance. Intuitively, as a wave solution gets `squeezed' at a focus, it `squirts' forward by slightly increasing its apparent speed in the propagation direction and modifying the pulse shape. However, this is a phase advance and not a group or energy advance and does not violate causality. Nonetheless, this could potentially influence the interpretation of travel-times using correlation techniques when using sources that generate beamed signals, for example from transducer sources in the laboratory.

  13. Developing an Error Model for Ionospheric Phase Distortions in L-Band SAR and InSAR Data

    NASA Astrophysics Data System (ADS)

    Meyer, F. J.; Agram, P. S.

    2014-12-01

    Many of the recent and upcoming spaceborne SAR systems are operating in the L-band frequency range. The choice of L-band has a number of advantages especially for InSAR applications. These include deeper penetration into vegetation, higher coherence, and higher sensitivity to soil moisture. While L-band SARs are undoubtedly beneficial for a number of earth science disciplines, their signals are susceptive to path delay effects in the ionosphere. Many recent publications indicate that the ionosphere can have detrimental effects on InSAR coherence and phase. It has also been shown that the magnitude of these effects strongly depends on the time of day and geographic location of the image acquisition as well as on the coincident solar activity. Hence, in order to provide realistic error estimates for geodetic measurements derived from L-band InSAR, an error model needs to be developed that is capable of describing ionospheric noise. With this paper, we present a global ionospheric error model that is currently being developed in support of NASA's future L-band SAR mission NISAR. The system is based on a combination of empirical data analysis and modeling input from the ionospheric model WBMOD, and is capable of predicting ionosphere-induced phase noise as a function of space and time. The error model parameterizes ionospheric noise using a power spectrum model and provides the parameters of this model in a global 1x1 degree raster. From the power law model, ionospheric errors in deformation estimates can be calculated. In Polar Regions, our error model relies on a statistical analysis of ionospheric-phase noise in a large number of SAR data from previous L-band SAR missions such as ALOS PALSAR and JERS-1. The focus on empirical analyses is due to limitations of WBMOD in high latitude areas. Outside of the Polar Regions, the ionospheric model WBMOD is used to derive ionospheric structure parameters for as a function of solar activity. The structure parameters are

  14. Effects of Random Circuit Fabrication Errors on Small Signal Gain and on Output Phase In a Traveling Wave Tube

    NASA Astrophysics Data System (ADS)

    Rittersdorf, I. M.; Antonsen, T. M., Jr.; Chernin, D.; Lau, Y. Y.

    2011-10-01

    Random fabrication errors may have detrimental effects on the performance of traveling-wave tubes (TWTs) of all types. A new scaling law for the modification in the average small signal gain and in the output phase is derived from the third order ordinary differential equation that governs the forward wave interaction in a TWT in the presence of random error that is distributed along the axis of the tube. Analytical results compare favorably with numerical results, in both gain and phase modifications as a result of random error in the phase velocity of the slow wave circuit. Results on the effect of the reverse-propagating circuit mode will be reported. This work supported by AFOSR, ONR, L-3 Communications Electron Devices, and Northrop Grumman Corporation.

  15. Biometrics based key management of double random phase encoding scheme using error control codes

    NASA Astrophysics Data System (ADS)

    Saini, Nirmala; Sinha, Aloka

    2013-08-01

    In this paper, an optical security system has been proposed in which key of the double random phase encoding technique is linked to the biometrics of the user to make it user specific. The error in recognition due to the biometric variation is corrected by encoding the key using the BCH code. A user specific shuffling key is used to increase the separation between genuine and impostor Hamming distance distribution. This shuffling key is then further secured using the RSA public key encryption to enhance the security of the system. XOR operation is performed between the encoded key and the feature vector obtained from the biometrics. The RSA encoded shuffling key and the data obtained from the XOR operation are stored into a token. The main advantage of the present technique is that the key retrieval is possible only in the simultaneous presence of the token and the biometrics of the user which not only authenticates the presence of the original input but also secures the key of the system. Computational experiments showed the effectiveness of the proposed technique for key retrieval in the decryption process by using the live biometrics of the user.

  16. A line scanned light-sheet microscope with phase shaped self-reconstructing beams.

    PubMed

    Fahrbach, Florian O; Rohrbach, Alexander

    2010-11-01

    We recently demonstrated that Microscopy with Self-Reconstructing Beams (MISERB) increases both image quality and penetration depth of illumination beams in strongly scattering media. Based on the concept of line scanned light-sheet microscopy, we present an add-on module to a standard inverted microscope using a scanned beam that is shaped in phase and amplitude by a spatial light modulator. We explain technical details of the setup as well as of the holograms for the creation, positioning and scaling of static light-sheets, Gaussian beams and Bessel beams. The comparison of images from identical sample areas illuminated by different beams allows a precise assessment of the interconnection between beam shape and image quality. The superior propagation ability of Bessel beams through inhomogeneous media is demonstrated by measurements on various scattering media. PMID:21164769

  17. Semiconductor diode laser having an intracavity spatial phase controller for beam control and switching

    DOEpatents

    Hohimer, J.P.

    1994-06-07

    A high-power broad-area semiconductor laser having a intracavity spatial phase controller is disclosed. The integrated intracavity spatial phase controller is easily formed by patterning an electrical contact metallization layer when fabricating the semiconductor laser. This spatial phase controller changes the normally broad far-field emission beam of such a laser into a single-lobed near-diffraction-limited beam at pulsed output powers of over 400 mW. Two operating modes, a thermal and a gain operating mode, exist for the phase controller, allowing for steering and switching the beam as the modes of operation are switched, and the emission beam may be scanned, for example, over a range of 1.4 degrees or switched by 8 degrees. More than one spatial phase controller may be integrated into the laser structure. 6 figs.

  18. Semiconductor diode laser having an intracavity spatial phase controller for beam control and switching

    DOEpatents

    Hohimer, John P.

    1994-01-01

    A high-power broad-area semiconductor laser having a intracavity spatial phase controller is disclosed. The integrated intracavity spatial phase controller is easily formed by patterning an electrical contact metallization layer when fabricating the semiconductor laser. This spatial phase controller changes the normally broad far-field emission beam of such a laser into a single-lobed near-diffraction-limited beam at pulsed output powers of over 400 mW. Two operating modes, a thermal and a gain operating mode, exist for the phase controller, allowing for steering and switching the beam as the modes of operation are switched, and the emission beam may be scanned, for example, over a range of 1.4 degrees or switched by 8 degrees. More than one spatial phase controller may be integrated into the laser structure.

  19. Hermite-Gaussian beams with self-forming spiral phase distribution

    NASA Astrophysics Data System (ADS)

    Zinchik, Alexander A.; Muzychenko, Yana B.

    2014-05-01

    Spiral laser beams is a family of laser beams that preserve the structural stability up to scale and rotate with the propagation. Properties of spiral beams are of practical interest for laser technology, medicine and biotechnology. Researchers use a spiral beams for movement and manipulation of microparticles. Spiral beams have a complicated phase distribution in cross section. This paper describes the results of analytical and computer simulation of Hermite-Gaussian beams with self-forming spiral phase distribution. In the simulation used a laser beam consisting of the sum of the two modes HG TEMnm and TEMn1m1. The coefficients n1, n, m1, m were varied. Additional phase depending from the coefficients n, m, m1, n1 imposed on the resulting beam. As a result, formed the Hermite Gaussian beam phase distribution which takes the form of a spiral in the process of distribution. For modeling was used VirtualLab 5.0 (manufacturer LightTrans GmbH).

  20. The effects of receiver tracking phase error on the performance of the concatenated Reed-Solomon/Viterbi channel coding system

    NASA Technical Reports Server (NTRS)

    Liu, K. Y.

    1981-01-01

    Analytical and experimental results are presented of the effects of receiver tracking phase error, caused by weak signal conditions on either the uplink or the downlink or both, on the performance of the concatenated Reed-Solomon (RS) Viterbi channel coding system. The test results were obtained under an emulated S band uplink and X band downlink, two way space communication channel in the telecommunication development laboratory of JPL with data rates ranging from 4 kHz to 20 kHz. It is shown that, with ideal interleaving, the concatenated RS/Viterbi coding system is capable of yielding large coding gains at very low bit error probabilities over the Viterbi decoded convolutional only coding system. Results on the effects of receiver tracking phase errors on the performance of the concatenated coding system with antenna array combining are included.

  1. Amplitude and phase beam characterization using a two-dimensional wavefront sensor

    SciTech Connect

    Neal, D.R.; Alford, W.J.; Gruetzner, J.K.; Warren, M.E.

    1996-09-01

    We have developed a two-dimensional Shack-Hartman wavefront sensor that uses binary optic lenslet arrays to directly measure the wavefront slope (phase gradient) and amplitude of the laser beam. This sensor uses an array of lenslets that dissects the beam into a number of samples. The focal spot location of each of these lenslets (measured by a CCD camera) is related to the incoming wavefront slope over the lenslet. By integrating these measurements over the laser aperture, the wavefront or phase distribution can be determined. Since the power focused by each lenslet is also easily determined, this allows a complete measurement of the intensity and phase distribution of the laser beam. Furthermore, all the information is obtained in a single measurement. Knowing the complete scalar field of the beam allows the detailed prediction of the actual beam`s characteristics along its propagation path. In particular, the space- beamwidth product M{sup 2}, can be obtained in a single measurement. The intensity and phase information can be used in concert with information about other elements in the optical train to predict the beam size, shape, phase and other characteristics anywhere in the optical train. We present preliminary measurements of an Ar{sup +} laser beam and associated M{sup 2} calculations.

  2. Longitudinal phase-space coating of beam in a storage ring

    NASA Astrophysics Data System (ADS)

    Bhat, C. M.

    2014-06-01

    In this Letter, I report on a novel scheme for beam stacking without any beam emittance dilution using a barrier rf system in synchrotrons. The general principle of the scheme called longitudinal phase-space coating, validation of the concept via multi-particle beam dynamics simulations applied to the Fermilab Recycler, and its experimental demonstration are presented. In addition, it has been shown and illustrated that the rf gymnastics involved in this scheme can be used in measuring the incoherent synchrotron tune spectrum of the beam in barrier buckets and in producing a clean hollow beam in longitudinal phase space. The method of beam stacking in synchrotrons presented here is the first of its kind.

  3. Phase Space Tomography: A Simple, Portable and Accurate Technique to Map Phase Spaces of Beams with Space Charge

    SciTech Connect

    Stratakis, D.; Kishek, R. A.; Bernal, S.; Walter, M.; Haber, I.; Fiorito, R.; Thangaraj, J. C. T.; Quinn, B.; Reiser, M.; O'Shea, P. G.; Li, H.

    2006-11-27

    In order to understand the charged particle dynamics, e.g. the halo formation, emittance growth, x-y energy transfer and coupling, knowledge of the actual phase space is needed. Other the past decade there is an increasing number of articles who use tomography to map the beam phase space and measure the beam emittance. These studies where performed at high energy facilities where the effect of space charge was neglible and therefore not considered in the analysis. This work extends the tomography technique to beams with space charge. In order to simplify the analysis linear forces where assumed. By carefully modeling the tomography process using the particle-in-cell code WARP we test the validity of our assumptions and the accuracy of the reconstructed phase space. Finally, we report experimental results of phase space mapping at the University of Maryland Electron Ring (UMER) using tomography.

  4. Nonparaxial multi-Gaussian beam models and measurement models for phased array transducers.

    PubMed

    Zhao, Xinyu; Gang, Tie

    2009-01-01

    A nonparaxial multi-Gaussian beam model is proposed in order to overcome the limitation that paraxial Gaussian beam models lose accuracy in simulating the beam steering behavior of phased array transducers. Using this nonparaxial multi-Gaussian beam model, the focusing and steering sound fields generated by an ultrasonic linear phased array transducer are calculated and compared with the corresponding results obtained by paraxial multi-Gaussian beam model and more exact Rayleigh-Sommerfeld integral model. In addition, with help of this novel nonparaxial method, an ultrasonic measurement model is provided to investigate the sensitivity of linear phased array transducers versus steering angles. Also the comparisons of model predictions with experimental results are presented to certify the accuracy of this provided measurement model. PMID:18774152

  5. Coherent-phase or random-phase acceleration of electron beams in solar flares

    NASA Technical Reports Server (NTRS)

    Aschwanden, Markus J.; Benz, Arnold O.; Montello, Maria L.

    1994-01-01

    Time structures of electron beam signatures at radio wavelengths are investigated to probe correlated versus random behavior in solar flares. In particular we address the issue whether acceleration and injection of electron beams is coherently modulated by a single source, or whether the injection is driven by a stochastic (possibly spatially fragmented) process. We analyze a total of approximately = 6000 type III bursts observed by Ikarus (Zurich) in the frequency range of 100-500 MHz, during 359 solar flares with simultaneous greater than or = 25 keV hard X-ray emission, in the years 1890-1983. In 155 flares we find a total of 260 continuous type III groups, with an average number of 13 +/- 9 bursts per group, a mean duration of D = 12 +/- 14 s, a mean period of P = 2.0 +/- 1.2 s, with the highest burst rate at a frequency of nu = 310 +/- 120 MHz. Pulse periods have been measured between 0.5 and 10 s, and can be described by an exponential distribution, i.e., N(P) varies as e (exp -P/1.0s). The period shows a frequency dependence of P(nu)=46(exp-0.6)(sub MHz)s for different flares, but is invariant during a particular flare. We measure the mean period P and its standard deviation sigma (sub p) in each type III group, and quantify the degree of periodicity (or phase-coherence) by the dimensionless parameter sigma (sub p)P. The representative sample of 260 type III burst groups shows a mean periodicity of sigma (sub p/P) = 0.37 +/- 0.12, while Monte Carlo simulations of an equivalent set of truly random time series show a distinctly different value of sigma (sub p)P = 0.93 +/- 0.26. This result indicates that the injection of electron beams is coherently modulated by a particle acceleration source which is either compact or has a global organization on a timescale of seconds, in contrast to an incoherent acceleration source, which is stochastic either in time or space. We discuss the constraints on the size of the acceleration region resulting from electron beam

  6. Phasing surface emitting diode laser outputs into a coherent laser beam

    DOEpatents

    Holzrichter, John F.

    2006-10-10

    A system for generating a powerful laser beam includes a first laser element and at least one additional laser element having a rear laser mirror, an output mirror that is 100% reflective at normal incidence and <5% reflective at an input beam angle, and laser material between the rear laser mirror and the output mirror. The system includes an injector, a reference laser beam source, an amplifier and phase conjugater, and a combiner.

  7. Adaptive optimisation of a generalised phase contrast beam shaping system

    NASA Astrophysics Data System (ADS)

    Kenny, F.; Choi, F. S.; Glückstad, J.; Booth, M. J.

    2015-05-01

    The generalised phase contrast (GPC) method provides versatile and efficient light shaping for a range of applications. We have implemented a generalised phase contrast system that used two passes on a single spatial light modulator (SLM). Both the pupil phase distribution and the phase contrast filter were generated by the SLM. This provided extra flexibility and control over the parameters of the system including the phase step magnitude, shape, radius and position of the filter. A feedback method for the on-line optimisation of these properties was also developed. Using feedback from images of the generated light field, it was possible to dynamically adjust the phase filter parameters to provide optimum contrast.

  8. The influence of radio altimeter errors on pilot performance during the final approach and landing phase of an RPV mission

    NASA Technical Reports Server (NTRS)

    Howard, J. C.

    1975-01-01

    Due to the fact that remotely piloted vehicles (RPV's) are currently being flown from fixed base control centers, kinesthetic and real world peripheral vision cues are absent. The absence of these cues complicates the piloting task, particularly during the final approach and landing phase of a mission. The pilot's task is futher complicated by errors in the displayed altitude information. To determine the influence of these errors on pilot performance during the final approach and landing phase of a mission, an experiment was conducted in which pilot subjects were asked to fly a fixed base simulation of a Piper PA-30 aircraft, using degraded altitude information. For this experiment, the chevron component of the display configuration was driven by a radio altimeter. Four altimeters were used, each with a different error characteristic, but within the range specified for the Sperry series of radio altimeters. Results indicate that for range of errors considered, there is no significant difference in landing performance that can be attributed to errors in altitude information.

  9. Optical simulation of laser beam phase-shaping focusing optimization in biological tissues

    NASA Astrophysics Data System (ADS)

    Gomes, Ricardo; Vieira, Pedro; Coelho, João. M. P.

    2013-11-01

    In this paper we report the development of an optical simulator that can be used in the development of methodologies for compensate/decrease the light scattering effect of most biological tissues through phase-shaping methods. In fact, scattering has long been a major limitation for the medical applications of lasers where in-depth tissues concerns due to the turbid nature of most biological media in the human body. In developing the simulator, two different approaches were followed: one using multiple identical beams directed to the same target area and the other using a phase-shaped beam. In the multiple identical beams approach (used mainly to illustrate the limiting effect of scattering on the beam's propagation) there was no improvement in the beam focus at 1 mm compared to a single beam layout but, in phase-shaped beam approach, a 8x improvement on the radius of the beam at the same depth was achieved. The models were created using the optical design software Zemax and numerical algorithms created in Matlab programming language to shape the beam wavefront. A dedicated toolbox allowed communication between both programs. The use of the two software's proves to be a simple and powerful solution combining the best of the two and allowing a significant potential for adapting the simulations to new systems and thus allow to assess their response and define critical engineering parameters prior to laboratorial implementation.

  10. Quantifying Errors in Flow Measurement Using Phase Contrast Magnetic Resonance Imaging: Comparison of Several Boundary Detection Methods

    PubMed Central

    Jiang, Jing; Kokeny, Paul; Ying, Wang; Magnano, Chris; Zivadinov, Robert; Haacke, E. Mark

    2014-01-01

    Quantifying flow from phase-contrast MRI (PC-MRI) data requires that the vessels of interest be segmented. This estimate of the vessel area will dictate the type and magnitude of the error sources that affect the flow measurement. These sources of errors are well understood and mathematical expressions have been derived for them in previous work. However, these expressions contain many parameters that render them difficult to use for making practical error estimates. In this work, some realistic assumptions were made that allow for the simplification of such expressions in order to make them more useful. These simplified expressions were then used to numerically simulate the effect of segmentation accuracy and provide some criteria that if met, would keep errors in flow quantification below 10% or 5%. Four different segmentation methods were used on simulated and phantom MRA data to verify the theoretical results. Numerical simulations showed that including partial volumed edge pixels in vessel segmentation provides less error than missing them. This was verified with MRA simulations, as the best performing segmentation method generally included such pixels. Further, it was found that to obtain a flow error of less than 10% (5%), the vessel should be at least 4 (5) pixels in diameter, have an SNR of at least 10:1 and a peak velocity to saturation cut-off velocity ratio of at least 5:3. PMID:25460329

  11. Determination of the misalignment error of a compound zero-order waveplate using the spectroscopic phase shifting method

    NASA Astrophysics Data System (ADS)

    Zheng, Quan; Han, Zhigang; Chen, Lei

    2016-09-01

    The spectroscopic phase shifting method was proposed to determine the misalignment error of a compound zero-order waveplate. The waveplate, which is composed of two separate multi-order quartz waveplates, was measured by a polarizer-waveplate-analyser setup with a spectrometer as the detector. The theoretical relationship between the misalignment error and the azimuth of the polarized light that emerged from the waveplate was studied by comparing two forms of the Jones matrix of the waveplate. Four spectra were obtained to determine the wavelength-dependent azimuth using a phase shifting algorithm when the waveplate was rotated to four detection angles. The misalignment error was ultimately solved from the wavelength-dependent azimuth by the Levenberg-Marquardt method. Experiments were conducted at six misalignment angles. The measured results of the misalignment angle agree well with their nominal values, indicating that the spectroscopic phase shifting method can be a reliable way to measure the misalignment error of a compound zero-order waveplate.

  12. Anisotropic pure-phase plates for quality improvement of partially coherent, partially polarized beams.

    PubMed

    Martínez-Herrero, Rosario; Mejías, Pedro M; Piquero, Gemma

    2003-03-01

    From a theoretical point of view, the use of anisotropic pure-phase plates (APP) is considered in order to improve the quality parameter of certain partially coherent, partially polarized beams. It is shown that, to optimize the beam-quality parameter, the phases of the two Cartesian components of the field at the output of the APP plate should be identical and should exhibit a quadratic dependence on the radial polar coordinate. PMID:12630845

  13. Anisotropic pure-phase plates for quality improvement of partially coherent, partially polarized beams

    NASA Astrophysics Data System (ADS)

    MartíNez-Herrero, Rosario; MejíAs, Pedro M.; Piquero, Gemma

    2003-03-01

    From a theoretical point of view, the use of anisotropic pure-phase plates (APP) is considered in order to improve the quality parameter of certain partially coherent, partially polarized beams. It is shown that, to optimize the beam-quality parameter, the phases of the two Cartesian components of the field at the output of the APP plate should be identical and should exhibit a quadratic dependence on the radial polar coordinate.

  14. Laser beam collimation using a phase conjugate Twyman-Green interferometer

    NASA Technical Reports Server (NTRS)

    Shukla, R. P.; Dokhanian, M.; George, M. C.; Venkateswarlu, Putcha

    1991-01-01

    This paper presents an improved technique for testing laser beam collimation using a phase conjugate Twyman-Green interferometer. The technique is useful for measuring laser beam divergence. It is possible using this technique to detect the defocusing of the order of one micrometer for a well corrected collimating lens. A relation is derived for the defocusing that can be detected by the phase conjugate interferometer.

  15. Optical phased array using high-contrast grating all-pass filters for fast beam steering

    NASA Astrophysics Data System (ADS)

    Yang, Weijian; Sun, Tianbo; Rao, Yi; Chan, Trevor; Megens, Mischa; Yoo, Byung-Wook; Horsley, David A.; Wu, Ming C.; Chang-Hasnain, Connie J.

    2013-03-01

    A novel 8x8 optical phased array based on high-contrast grating (HCG) all-pass filters (APFs) is experimentally demonstrated with high speed beam steering. Highly efficient phase tuning is achieved by micro-electro-mechanical actuation of the HCG to tune the cavity length of the APFs. Using APF phase-shifters allows a large phase shift with an actuation range of only tens of nanometers. The ultrathin HCG further ensures a high tuning speed (0.626 MHz). Both one-dimensional and two-dimensional HCGs are demonstrated as the actuation mirrors of the APF arrays with high beam steering performance.

  16. Spot Scanning Proton Beam Therapy for Prostate Cancer: Treatment Planning Technique and Analysis of Consequences of Rotational and Translational Alignment Errors

    SciTech Connect

    Meyer, Jeff; Bluett, Jaques; Amos, Richard

    2010-10-01

    Purpose: Conventional proton therapy with passively scattered beams is used to treat a number of tumor sites, including prostate cancer. Spot scanning proton therapy is a treatment delivery means that improves conformal coverage of the clinical target volume (CTV). Placement of individual spots within a target is dependent on traversed tissue density. Errors in patient alignment perturb dose distributions. Moreover, there is a need for a rational planning approach that can mitigate the dosimetric effect of random alignment errors. We propose a treatment planning approach and then analyze the consequences of various simulated alignment errors on prostate treatments. Methods and Materials: Ten control patients with localized prostate cancer underwent treatment planning for spot scanning proton therapy. After delineation of the clinical target volume, a scanning target volume (STV) was created to guide dose coverage. Errors in patient alignment in two axes (rotational and yaw) as well as translational errors in the anteroposterior direction were then simulated, and dose to the CTV and normal tissues were reanalyzed. Results: Coverage of the CTV remained high even in the setting of extreme rotational and yaw misalignments. Changes in the rectum and bladder V45 and V70 were similarly minimal, except in the case of translational errors, where, as a result of opposed lateral beam arrangements, much larger dosimetric perturbations were observed. Conclusions: The concept of the STV as applied to spot scanning radiation therapy and as presented in this report leads to robust coverage of the CTV even in the setting of extreme patient misalignments.

  17. Forming and steering of symmetrical multiple laser beams in optical phased array

    NASA Astrophysics Data System (ADS)

    Liu, Xiang; Zhang, Jian; Wu, Liying; Gan, Yu; Wang, Dong; Ge, Jiajia

    2010-04-01

    Multi-beam technology is one of the key technologies in optical phased array systems for multi-object treatment and multi-task operation. A multi-beam forming and steering method was proposed. This method uses isosceles triangle multilevel phase grating (ITMPG) to form multiple beams simultaneously. Phase profile of the grating is a quantized isosceles triangle with stairs. By changing the phase difference corresponding to the triangle height, multiple beams can be steered symmetrically. It took 34 ms to calculate a set of parameters for one ITMPG, namely one steering. A liquid crystal spatial light modulator was used for the experiment, which formed 6 gratings. The distortion of which had been compensated with the accuracy of 0.0408 λ. Each grating included 16 phase elements with the same period. Steering angle corresponded to the triangle height, which is the phase difference. Relative diffraction efficiency for multiple beams was greater than 81%, intensity nonuniformity was less than 0.134, and the deflection resolution was 2.263 mrad. Experimental results demonstrate that the proposed method can be used to form and steer symmetrical multiple beams simultaneously with the same intensity and high diffraction efficiency in the far field, the deflection resolution is related to the reciprocal of grating period.

  18. Nanoengineering of Ruddlesden-Popper phases using molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Haeni, Jeffrey Hewlett

    Epitaxial films including superlattices of the A n+1BnO3 n+1 Ruddlesden-Popper homologous series with A=Sr and Ba and B=Ti and Ru have been grown by reactive molecular beam epitaxy (MBE) on (LaAlO3)0.3--(SrAl0.5Ta 0.5O3)0.7 (LSAT), SrTiO3, DyScO 3 and Si substrates. The strict composition control necessary for the synthesis of these phases was achieved through the use of reflection high-energy electron diffraction (RHEED) intensity oscillations. The first five members of the Srn+1 TinO3n+1 and the Sr n+1RunO3 n+1 Ruddlesden-Popper homologous series, i.e., Sr 2TiO4, Sr3Ti2O7, Sr 4Ti3O10, Sr5Ti4O13 , and Sr6Ti5O16, and Sr2RuO 4, Sr3Ru2O7, Sr4Ru 3O10, Sr5Ru4O13, and Sr 6Ru5O16, respectively, were grown with layer-by-layer deposition. Dielectric measurements indicate that the dielectric constant tensor coefficient epsilon33 of the Srn +1TinO3n +1 series increases from a minimum of 44 +/- 4 in the n = 1 (Sr2TiO4) film to a maximum of 263 +/- 2 in the n = infinity (SrTiO3) film. XPS measurements on Sr2TiO4/SrTiO3 heterostructures indicate a type II interface between the two materials, with a valence band offset of -0.40 +/- 0.1 eV, and a conduction band offset of -0.2 +/- 0.1 eV. Epitaxial SrTiO3 thin films grown on DyScO3 and LSAT substrates show dramatically different dielectric properties, as measured with interdigitated electrodes. The film on DyScO3 is under biaxial tensile strain and shows significant room temperature tunability and a sharp Curie-Weiss peak at 293 K. Under biaxial compressive strain, the SrTiO 3 exhibits negligible room temperature tunability. Epitaxial SrTiO3/BaTiO3 short period superlattices were grown with nearly atomically-abrupt interfaces that are maintained even after annealing to high temperature. In addition, cross-sectional TEM reveals that all superlattice periods grown are coherently strained to the underlying (001) SrTiO3 and (001) LSAT substrates. Epitaxial SrRuO3 layers were grown on Si (100) on which a thin epitaxial (Ba,Sr)O/SrSi2

  19. Propagation of the power-exponent-phase vortex beam in paraxial ABCD system.

    PubMed

    Lao, Guanming; Zhang, Zhaohui; Zhao, Daomu

    2016-08-01

    The general analytical formula for the propagation of the power-exponent-phase vortex (PEPV) beam through a paraxial ABCD optical system is derived. On that basis the evolution of the intensity distribution of such a beam in free space and the focusing system is investigated. In addition, some experiments are carried out, which verify the theoretical predictions. Both of the theoretical and experimental results show that the beam's profile can be modulated by the topological charge and the power order of the PEPV beam. PMID:27505774

  20. Continuous Beam Steering From a Segmented Liquid Crystal Optical Phased Array

    NASA Technical Reports Server (NTRS)

    Titus, Charles M.; Pouch, John; Nguyen, Hung; Miranda, Felix; Bos, Philip J.

    2002-01-01

    Optical communications to and from deep space probes will require beams possessing divergence on the order of a microradian, and must be steered with sub-microradian precision. Segmented liquid crystal spatial phase modulators, a type of optical phased array, are considered for this ultra-high resolution beam steering. It is shown here that in an ideal device of this type, there are ultimately no restrictions on the angular resolution. Computer simulations are used to obtain that result, and to analyze the influence of beam truncation and substrate flatness on the performance of this type of device.

  1. Continuous Beam Steering From A Segmented Liquid Crystal Optical Phased Array

    NASA Technical Reports Server (NTRS)

    Pouch, John; Nguyen, Hung; Miranda, Felix; Titus, Charles M.; Bos, Philip J.

    2002-01-01

    Optical communications to and from deep space probes will require beams possessing divergence on the order of a microradian, and must be steered with sub-microradian precision. Segmented liquid crystal spatial phase modulators, a type of optical phased array, are considered for this ultra-high resolution beam steering. It is shown here that in an ideal device of this type, there are ultimately no restrictions on the angular resolution. Computer simulations are used to obtain that result, and to analyze the influence of beam truncation and substrate flatness on the performance of this type of device.

  2. Spatially varying geometric phase in classically entangled vector beams of light

    NASA Astrophysics Data System (ADS)

    King-Smith, Andrew; Leary, Cody

    We present theoretical results describing a spatially varying geometric (Pancharatnam) phase present in vector modes of light, in which the polarization and transverse spatial mode degrees of freedom exhibit classical entanglement. We propose an experimental setup capable of characterizing this effect, in which a vector mode propagates through a Mach-Zehnder interferometer with a birefringent phase retarder present in one arm. Since the polarization state of a classically entangled light beam exhibits spatial variation across the transverse mode profile, the phase retarder gives rise to a spatially varying geometric phase in the beam propagating through it. When recombined with the reference beam from the other interferometer arm, the presence of the geometric phase is exhibited in the resulting interference pattern. We acknowledge funding from the Research Corporation for Science Advancement by means of a Cottrell College Science Award.

  3. Semiconductor diode laser having an intracavity spatial phase controller for beam control and switching

    SciTech Connect

    Hohimer, J.P.

    1992-12-31

    A high-power broad-area semiconductor laser having a intracavity spatial phase controller is disclosed. The integrated intracavity spatial phase controller is easily formed by patterning an electrical contact metallization layer when fabricating the semiconductor laser. This spatial phase controller changes the normally broad far-field emission bean, of such a laser into a single-lobed near-diffraction-limited beam at pulsed output powers of over 400 mW. Two operating modes, a thermal and a gain operating mode, exist for the phase controller, allowing for steering and switching the beam as the modes of operation are switched, and the emission beam may be scanned, for example, over a range of 1.4 degrees or switched by 8 degrees. More than one spatial phase controller may be integrated into the laser structure.

  4. Adaptive optimisation of a generalised phase contrast beam shaping system

    PubMed Central

    Kenny, F.; Choi, F.S.; Glückstad, J.; Booth, M.J.

    2015-01-01

    The generalised phase contrast (GPC) method provides versatile and efficient light shaping for a range of applications. We have implemented a generalised phase contrast system that used two passes on a single spatial light modulator (SLM). Both the pupil phase distribution and the phase contrast filter were generated by the SLM. This provided extra flexibility and control over the parameters of the system including the phase step magnitude, shape, radius and position of the filter. A feedback method for the on-line optimisation of these properties was also developed. Using feedback from images of the generated light field, it was possible to dynamically adjust the phase filter parameters to provide optimum contrast. PMID:26089573

  5. Report for simultaneous, multiple independently steered beam study for Airborne Electronically Steerable Phased Array (AESPA) program

    NASA Technical Reports Server (NTRS)

    1978-01-01

    Design concepts of an array for the formation of multiple, simultaneous, independently pointed beams for satellite communication links were investigated through tradeoffs of various approaches which were conceived as possible solutions to the problem. After the preferred approach was selected, a more detailed design was configured and is presented as a candidate system that should be given further consideration for development leading to a preliminary design. This array uses an attenuator and a phase shifter with every element. The aperture excitation necessary to form the four beams is calculated and then placed across the array using these devices. Pattern analysis was performed for two beam and four beam cases with numerous patterns being presented. Parameter evaluation shown includes pointing accuracy and beam shape, sidelobe characteristics, gain control, and beam normalization. It was demonstrated that a 4 bit phase shifter and a 6 bit, 30 dB attenuator were sufficient to achieve adequate pattern performances. The phase amplitude steered multibeam array offers the flexibility of 1 to 4 beams with an increase in gain of 6 dB if only one beam is selected.

  6. Design of Transversal Phase Space Meter for Atomic Hydrogen Beam Source

    NASA Astrophysics Data System (ADS)

    Belov, A. S.

    2016-02-01

    For optimization of polarized atomic beam sources apparatus it is important to have detailed information about characteristics of sources of hydrogen atoms, especially, taking into account present intensity limitations of polarized atomic beam sources. Usually, longitudinal velocity distribution of hydrogen atoms produced by RF dissociator is measured while transversal phase space of unpolarized atomic hydrogen beams was not measured up to now. In this work we report and discuss a design of transversal phase space meter for pulsed atomic hydrogen beam source. The meter design is based on “two slits” method which is well known from ion beam technique. Specific feature of the meter are movable sensitive detector of hydrogen atoms and molecules.

  7. Analysis of laser beam quality degradation caused by quartic phase aberrations.

    PubMed

    Siegman, A E

    1993-10-20

    Simple formulas are derived for the degradation in the beam-quality factor, M(2), of an arbitrary laser beam caused by quartic phase distortions such as those that might occur in a spherically aberrated optical component, a thermally aberrated laser output window, or a divergent beam emerging from a high-index dielectric medium as in a wide-stripe, unstable-resonator diode laser. A new formula for the defocus correction that is needed to collimate optimally a beam with quartic phase aberration is also derived. Analytical results and numerical examples are given for both radially aberrated and one-dimensionaltransversely aberrated cases, and a simple experimental measurement of the beam-quality degradation produced by a thin plano-convex lens is shown to be in good agreement with the theory. PMID:20856411

  8. Transformation of phase dislocations under acousto-optic interaction of optical and acoustical Bessel beams

    NASA Astrophysics Data System (ADS)

    Belyi, V. N.; Khilo, P. A.; Kazak, N. S.; Khilo, N. A.

    2016-07-01

    The generation of wavefront phase dislocations of vortex Bessel light beams under acousto-optic (AO) diffraction in uniaxial crystals has been investigated. For the first time the process of AO interaction is studied with participation of Bessel acoustic beams instead of plane waves. A mathematical description of AO interaction is provided, which supposes the satisfaction of two types of phase-matching condition. The acousto-optic processes of transferring optical singularities onto the wavefront of BLBs are investigated and the generation of high-order optical vortices is considered at the interaction of optical and acoustical Bessel beams. The change of Bessel function order or phase dislocation order is explained as a result of the spin–orbital interaction under acousto-optic diffraction of vortex Bessel beams.

  9. Simplex method in problems of light-beam phase control.

    PubMed

    Chesnokov, S S; Davletshina, I V

    1995-12-20

    The possibility of the application of the simplex method to problems of wave-front control for light beams propagating in a nonlinear medium is investigated. A numerical analysis of simplex-method effectiveness in comparison with the gradient procedure of hill climbing is carried out. The regimes of stationary and nonstationary wind refraction are considered. The simplest optimization of the simplex size and the control basis is done. PMID:21068958

  10. Electronically controlled optical beam-steering by an active phased array of metallic nanoantennas.

    PubMed

    DeRose, C T; Kekatpure, R D; Trotter, D C; Starbuck, A; Wendt, J R; Yaacobi, A; Watts, M R; Chettiar, U; Engheta, N; Davids, P S

    2013-02-25

    An optical phased array of nanoantenna fabricated in a CMOS compatible silicon photonics process is presented. The optical phased array is fed by low loss silicon waveguides with integrated ohmic thermo-optic phase shifters capable of 2π phase shift with ∼ 15 mW of applied electrical power. By controlling the electrical power to the individual integrated phase shifters fixed wavelength steering of the beam emitted normal to the surface of the wafer of 8° is demonstrated for 1 × 8 phased arrays with periods of both 6 and 9 μm. PMID:23482053

  11. Assessment of residual error in liver position using kV cone-beam computed tomography for liver cancer high-precision radiation therapy

    SciTech Connect

    Hawkins, Maria A.; Brock, Kristy K.; Eccles, Cynthia; Moseley, Douglas; Jaffray, David; Dawson, Laura A. . E-mail: laura.dawson@rmp.uhn.on.ca

    2006-10-01

    Purpose: To evaluate the residual error in liver position using breath-hold kilovoltage (kV) cone-beam computed tomography (CT) following on-line orthogonal megavoltage (MV) image-guided breath-hold liver cancer conformal radiotherapy. Methods and Materials: Thirteen patients with liver cancer treated with 6-fraction breath-hold conformal radiotherapy were investigated. Before each fraction, orthogonal MV images were obtained during exhale breath-hold, with repositioning for offsets >3 mm, using the diaphragm for cranio-caudal (CC) alignment and vertebral bodies for medial-lateral (ML) and anterior posterior (AP) alignment. After repositioning, repeat orthogonal MV images, orthogonal kV fluoroscopic movies, and kV cone-beam CTs were obtained in exhale breath-hold. The cone-beam CT livers were registered to the planning CT liver to obtain the residual setup error in liver position. Results: After repositioning, 78 orthogonal MV image pairs, 61 orthogonal kV image pairs, and 72 kV cone-beam CT scans were obtained. Population random setup errors ({sigma}) in liver position were 2.7 mm (CC), 2.3 mm (ML), and 3.0 mm (AP), and systematic errors ({sigma}) were 1.1 mm, 1.9 mm, and 1.3 mm in the superior, medial, and posterior directions. Liver offsets >5 mm were observed in 33% of cases; offsets >10 mm and liver deformation >5 mm were observed in a minority of patients. Conclusions: Liver position after radiation therapy guided with MV orthogonal imaging was within 5 mm of planned position in the majority of patients. kV cone-beam CT image guidance should improve accuracy with reduced dose compared with orthogonal MV image guidance for liver cancer radiation therapy.

  12. Worst error analysis of batch filter and sequential filter in the approach phase of spacecraft navigation problems

    NASA Technical Reports Server (NTRS)

    Nishimura, T.

    1974-01-01

    The worst error performance of the sequential filter is compared with the performance of the batch filter which is still in general use in the deep space tracking. An approach phase of a spacecraft on a typical mission to the planet Mars is considered. The estimated parameters include the position and the speed of the spacecraft, nongravitational acceleration acting on the spacecraft, and the locations of the tracking stations.

  13. Different setup errors assessed by weekly cone-beam computed tomography on different registration in nasopharyngeal carcinoma treated with intensity-modulated radiation therapy

    PubMed Central

    Su, Jiqing; Chen, Wen; Yang, Huiyun; Hong, Jidong; Zhang, Zijian; Yang, Guangzheng; Li, Li; Wei, Rui

    2015-01-01

    The study aimed to investigate the difference of setup errors on different registration in the treatment of nasopharyngeal carcinoma based on weekly cone-beam computed tomography (CBCT). Thirty nasopharyngeal cancer patients scheduled to undergo intensity-modulated radiotherapy (IMRT) were prospectively enrolled in the study. Each patient had a weekly CBCT before radiation therapy. In the entire study, 201 CBCT scans were obtained. The scans were registered to the planning CT to determine the difference of setup errors on different registration sites. Different registration sites were represented by bony landmarks. Nasal septum and pterygoid process represent head, cervical vertebrae 1–3 represent upper neck, and cervical vertebrae 4–6 represent lower neck. Patient positioning errors were recorded in the right–left (RL), superior–inferior (SI), and anterior–posterior (AP) directions over the course of radiotherapy. Planning target volume margins were calculated from the systematic and random errors. In this study, we can make a conclusion that there are setup errors in RL, SI, and AP directions of nasopharyngeal carcinoma patients undergoing IMRT. In addition, the head and neck setup error has the difference, with statistical significance, while patient setup error of neck is greater than that of head during the course of radiotherapy. In our institution, we recommend a planning target volume margin of 3.0 mm in RL direction, 1.3 mm in SI direction, and 2.6 mm in AP direction for nasopharyngeal cancer patients undergoing IMRT with weekly CBCT scans. PMID:26396530

  14. Phase-preserving beam expander for biomedical X-ray imaging.

    PubMed

    Martinson, Mercedes; Samadi, Nazanin; Bassey, Bassey; Gomez, Ariel; Chapman, Dean

    2015-05-01

    The BioMedical Imaging and Therapy beamlines at the Canadian Light Source are used by many researchers to capture phase-based imaging data. These experiments have so far been limited by the small vertical beam size, requiring vertical scanning of biological samples in order to image their full vertical extent. Previous work has been carried out to develop a bent Laue beam-expanding monochromator for use at these beamlines. However, the first attempts exhibited significant distortion in the diffraction plane, increasing the beam divergence and eliminating the usefulness of the monochromator for phase-related imaging techniques. Recent work has been carried out to more carefully match the polychromatic and geometric focal lengths in a so-called `magic condition' that preserves the divergence of the beam and enables full-field phase-based imaging techniques. The new experimental parameters, namely asymmetry and Bragg angles, were evaluated by analysing knife-edge and in-line phase images to determine the effect on beam divergence in both vertical and horizontal directions, using the flat Bragg double-crystal monochromator at the beamline as a baseline. The results show that by using the magic condition, the difference between the two monochromator types is less than 10% in the diffraction plane. Phase fringes visible in test images of a biological sample demonstrate that this difference is small enough to enable in-line phase imaging, despite operating at a sub-optimal energy for the wafer and asymmetry angle that was used. PMID:25931100

  15. Subluminous phase velocity of a focused laser beam and vacuum laser acceleration.

    PubMed

    Pang, J; Ho, Y K; Yuan, X Q; Cao, N; Kong, Q; Wang, P X; Shao, L; Esarey, E H; Sessler, A M

    2002-12-01

    It has been found that for a focused laser beam propagating in free space, there exists, surrounding the laser beam axis, a subluminous wave phase velocity region. Relativistic electrons injected into this region can be trapped in the acceleration phase and remain in phase with the laser field for sufficiently long times, thereby receiving considerable energy from the field. Optics placed near the laser focus are not necessary, thus allowing high intensities and large energy gains. Important features of this process are examined via test particle simulations. The resulting energy gains are in agreement with theoretical estimates based on acceleration by the axial laser field. PMID:12513421

  16. Efficient phase-matching for difference frequency generation with pump of Bessel laser beams.

    PubMed

    Liu, Pengxiang; Shi, Wei; Xu, Degang; Zhang, Xinzheng; Zhang, Guizhong; Yao, Jianquan

    2016-01-25

    A type of phase matching for difference frequency generation with Bessel-type pump beams is proposed. In this geometry, the phase matching is achieved in a cone around the laser path by properly controlling the beam profile. An experimental case that 1.5THz generation with ~2μm lasers pumped bulk GaAs crystal is considered. Calculations of the energy conversion characteristics are performed based on a semi-analytical model. The results indicate that this configuration could relax the phase matching condition in a wide range of nonlinear crystals and pump wavelengths. PMID:26832473

  17. ATHEANA: {open_quotes}a technique for human error analysis{close_quotes} entering the implementation phase

    SciTech Connect

    Taylor, J.; O`Hara, J.; Luckas, W.

    1997-02-01

    Probabilistic Risk Assessment (PRA) has become an increasingly important tool in the nuclear power industry, both for the Nuclear Regulatory Commission (NRC) and the operating utilities. The NRC recently published a final policy statement, SECY-95-126, encouraging the use of PRA in regulatory activities. Human reliability analysis (HRA), while a critical element of PRA, has limitations in the analysis of human actions in PRAs that have long been recognized as a constraint when using PRA. In fact, better integration of HRA into the PRA process has long been a NRC issue. Of particular concern, has been the omission of errors of commission - those errors that are associated with inappropriate interventions by operators with operating systems. To address these concerns, the NRC identified the need to develop an improved HRA method, so that human reliability can be better represented and integrated into PRA modeling and quantification. The purpose of the Brookhaven National Laboratory (BNL) project, entitled `Improved HRA Method Based on Operating Experience` is to develop a new method for HRA which is supported by the analysis of risk-significant operating experience. This approach will allow a more realistic assessment and representation of the human contribution to plant risk, and thereby increase the utility of PRA. The project`s completed, ongoing, and future efforts fall into four phases: (1) Assessment phase (FY 92/93); (2) Analysis and Characterization phase (FY 93/94); (3) Development phase (FY 95/96); and (4) Implementation phase (FY 96/97 ongoing).

  18. A dynamic plasmonic manipulation technique assisted by phase modulation of an incident optical vortex beam.

    PubMed

    Yuan, G H; Wang, Q; Tan, P S; Lin, J; Yuan, X-C

    2012-09-28

    A novel phase modulation method for dynamic manipulation of surface plasmon polaritons (SPPs) with a phase engineered optical vortex (OV) beam illuminating on nanoslits is experimentally demonstrated. Because of the unique helical phase carried by an OV beam, dynamic control of SPP multiple focusing and standing wave generation is realized by changing the OV beam's topological charge constituent with the help of a liquid-crystal spatial light modulator. Measurement of SPP distributions with near-field scanning optical microscopy showed an excellent agreement with numerical predictions. The proposed phase modulation technique for manipulating SPPs features has seemingly dynamic and reconfigurable advantages, with profound potential for development of SPP coupling, routing, multiplexing and high-resolution imaging devices on plasmonic chips. PMID:22948098

  19. Qubits in phase space: Wigner-function approach to quantum-error correction and the mean-king problem

    SciTech Connect

    Paz, Juan Pablo; Roncaglia, Augusto Jose; Saraceno, Marcos

    2005-07-15

    We analyze and further develop a method to represent the quantum state of a system of n qubits in a phase-space grid of NxN points (where N=2{sup n}). The method, which was recently proposed by Wootters and co-workers (Gibbons et al., Phys. Rev. A 70, 062101 (2004).), is based on the use of the elements of the finite field GF(2{sup n}) to label the phase-space axes. We present a self-contained overview of the method, we give insights into some of its features, and we apply it to investigate problems which are of interest for quantum-information theory: We analyze the phase-space representation of stabilizer states and quantum error-correction codes and present a phase-space solution to the so-called mean king problem.

  20. Steady-state probability density function of the phase error for a DPLL with an integrate-and-dump device

    NASA Technical Reports Server (NTRS)

    Simon, M.; Mileant, A.

    1986-01-01

    The steady-state behavior of a particular type of digital phase-locked loop (DPLL) with an integrate-and-dump circuit following the phase detector is characterized in terms of the probability density function (pdf) of the phase error in the loop. Although the loop is entirely digital from an implementation standpoint, it operates at two extremely different sampling rates. In particular, the combination of a phase detector and an integrate-and-dump circuit operates at a very high rate whereas the loop update rate is very slow by comparison. Because of this dichotomy, the loop can be analyzed by hybrid analog/digital (s/z domain) techniques. The loop is modeled in such a general fashion that previous analyses of the Real-Time Combiner (RTC), Subcarrier Demodulator Assembly (SDA), and Symbol Synchronization Assembly (SSA) fall out as special cases.

  1. Evolution of the ring Airy Gaussian beams with a spiral phase in the Kerr medium

    NASA Astrophysics Data System (ADS)

    Chen, Bo; Chen, Chidao; Peng, Xi; Peng, Yulian; Zhou, Meiling; Deng, Dongmei; Guo, Hong

    2016-05-01

    Nonlinear optical phenomena are of great practical interest in optics. The evolution of ring Airy Gaussian beams with a spiral phase in the nonlinear Kerr medium is investigated using the nonlinear Schrödinger equation. Numerical simulations indicate that the distribution factor b can influence the formation of the ring Airy Gaussian beams. Results show that the beams can be oscillating, and the light filament can be achieved under appropriate laser input power. On the other hand, the evolution of the ring Airy Gaussian beams with a spiral phase in the nonlinear Kerr medium can be implemented, and the numerical simulations of the holographic generation of the ring Airy Gaussian vortex beams propagated in the medium demonstrate that the vortex can be preserved along the propagation. The Poynting vector shows that the energy flow of the ring Airy Gaussian beams flows in the opposite direction on both sides of the focus plane; however, for beams with a spiral phase, the flow direction remains the same; the energy flow can rotate in opposite directions on both sides of the focal plane.

  2. Tomographic measurement of the phase space distribution of a space-charge-dominated beam

    NASA Astrophysics Data System (ADS)

    Stratakis, Diktys

    Many applications of accelerators, such as free electron lasers, pulsed neutron sources, and heavy ion fusion, require a good quality beam with high intensity. In practice, the achievable intensity is often limited by the dynamics at the low-energy, space-charge dominated end of the machine. Because low-energy beams can have complex distribution functions, a good understanding of their detailed evolution is needed. To address this issue, we have developed a simple and accurate tomographic method to map the beam phase using quadrupole magnets, which includes the effects from space charge. We extend this technique to use also solenoidal magnets which are commonly used at low energies, especially in photoinjectors, thus making the diagnostic applicable to most machines. We simulate our technique using a particle in cell code (PIC), to ascertain accuracy of the reconstruction. Using this diagnostic we report a number of experiments to study and optimize injection, transport and acceleration of intense space charge dominated beams. We examine phase mixing, by studying the phase-space evolution of an intense beam with a transversely nonuniform initial density distribution. Experimental measurements, theoretical predictions and PIC simulations are in good agreement each other. Finally, we generate a parabolic beam pulse to model those beams from photoinjectors, and combine tomography with fast imaging techniques to investigate the time-sliced parameters of beam current, size, energy spread and transverse emittance. We found significant differences between the slice emittance profiles and slice orientation as the beam propagates downstream. The combined effect of longitudinal nonuniform profiles and fast imaging of the transverse phase space provided us with information about correlations between longitudinal and transverse dynamics that we report within this dissertation.

  3. Electron-beam synthesis of fuel in the gas phase

    NASA Astrophysics Data System (ADS)

    Ponomarev, A. V.; Holodkova, E. M.; Ershov, B. G.

    2012-09-01

    Electron-beam synthesis of liquid fuel from gaseous alkanes was upgraded for formation of conventional and alternative fuel from biomass or pyrolysis oil. Bio-feedstock conversion algorithm includes two consecutive stages: (1) initial macromolecules' transformation to low-molecular-weight intermediates; (2) transformation of these intermediates to stable fuel in gaseous alkanes' atmosphere. Radicals originated from alkanes participate in alkylation/hydrogenation of biomass intermediates. Chemical fixation of gaseous alkanes is amplified in the presence of biomass derivatives due to suppression of gas regeneration reactions, higher molar mass of reagents and lower volatility of radiolytic intermediates.

  4. Demonstration of the frequency offset errors introduced by an incorrect setting of the Zeeman/magnetic field adjustment on the cesium beam frequency standard

    NASA Technical Reports Server (NTRS)

    Kaufmann, D. C.

    1976-01-01

    The fine frequency setting of a cesium beam frequency standard is accomplished by adjusting the C field control with the appropriate Zeeman frequency applied to the harmonic generator. A novice operator in the field, even when using the correct Zeeman frequency input, may mistakenly set the C field to any one of seven major Beam I peaks (fingers) represented by the Ramsey curve. This can result in frequency offset errors of as much as 2.5 parts in ten to the tenth. The effects of maladjustment are demonstrated and suggestions are discussed on how to avoid the subtle traps associated with C field adjustments.

  5. Compact Simultaneous-beam Optical Strain Measurement System, Phase 5

    NASA Technical Reports Server (NTRS)

    Lant, Christian T.

    1994-01-01

    Recent advances on the laser speckle strain measurement system under development at NASA Lewis Research Center have resulted in a compact, easy-to-use measurement package having many performance improvements over previous systems. NASA has developed this high performance optical strain measurement system for high temperature material testing applications. The system is based on I. Yamaguchi's two-beam speckle-shift strain measurement theory, and uses a new optical design that allows simultaneous recording of laser speckle patterns. This design greatly improves system response over previous implementations of the two-beam speckle-shift technique. The degree of immunity to transient rigid body motions is no longer dependent on the data transfer rate. The system automatically calculates surface strains at a frequency of about 5 Hz using a high speed digital signal processor in a personal computer. This system is fully automated, and can be operated remotely. This report describes the designs and methods used by the system, and shows low temperature strain test results obtained from small diameter tungsten-rhenium and palladium-chrome wires.

  6. Beam hardening effects in grating-based x-ray phase-contrast imaging

    SciTech Connect

    Chabior, Michael; Donath, Tilman; David, Christian; Bunk, Oliver; Schuster, Manfred; Schroer, Christian; Pfeiffer, Franz

    2011-03-15

    Purpose: In this work, the authors investigate how beam hardening affects the image formation in x-ray phase-contrast imaging and consecutively develop a correction algorithm based on the results of the analysis. Methods: The authors' approach utilizes a recently developed x-ray imaging technique using a grating interferometer capable of visualizing the differential phase shift of a wave front traversing an object. An analytical description of beam hardening is given, highlighting differences between attenuation and phase-contrast imaging. The authors present exemplary beam hardening artifacts for a number of well-defined samples in measurements at a compact laboratory setup using a polychromatic source. Results: Despite the differences in image formation, the authors show that beam hardening leads to a similar reduction of image quality in phase-contrast imaging as in conventional attenuation-contrast imaging. Additionally, the authors demonstrate that for homogeneous objects, beam hardening artifacts can be corrected by a linearization technique, applicable to all kinds of phase-contrast methods using polychromatic sources. Conclusions: The evaluated correction algorithm is shown to yield good results for a number of simple test objects and can thus be advocated in medical imaging and nondestructive testing.

  7. Interfractional and intrafractional errors assessed by daily cone-beam computed tomography in nasopharyngeal carcinoma treated with intensity-modulated radiation therapy: a prospective study

    PubMed Central

    Lu, Heming; Lin, Hui; Feng, Guosheng; Chen, Jiaxin; Shu, Liuyang; Pang, Qiang; Cheng, Jinjian; Peng, Luxing; Wu, Danling; Liao, Chaolong; Mo, Ying

    2012-01-01

    This prospective study was to assess interfractional and intrafractional errors and to estimate appropriate margins for planning target volume (PTV) by using daily cone-beam computed tomography (CBCT) guidance in nasopharyngeal carcinoma (NPC). Daily pretreatment and post-treatment CBCT scans were acquired separately after initial patient setup and after the completion of each treatment fraction in 10 patients treated with IMRT. Online corrections were made before treatment if any translational setup error was found. Interfractional and intrafractional errors were recorded in the right–left (RL), superior–inferior (SI) and anterior–posterior (AP) directions. For the translational shifts, interfractional errors >2 mm occurred in 21.7% of measurements in the RL direction, 12.7% in the SI direction and 34.1% in the AP direction, respectively. Online correction resulted in 100% of residual errors ≤2 mm in the RL and SI directions, and 95.5% of residual errors ≤2 mm in the AP direction. No residual errors >3 mm occurred in the three directions. For the rotational shifts, a significant reduction was found in the magnitudes of residual errors compared with those of interfractional errors. A margin of 4.9 mm, 4.0 mm and 6.3 mm was required in the RL, SI and AP directions, respectively, when daily CBCT scans were not performed. With daily CBCT, the margins were reduced to 1.2 mm in all directions. In conclusion, daily CBCT guidance is an effective modality to improve the accuracy of IMRT for NPC. The online correction could result in a 70–81% reduction in margin size. PMID:22843373

  8. Transformation of the optical vortex light beams in holographic elements with embedded phase singularities

    NASA Astrophysics Data System (ADS)

    Sviridova, S. V.; Bekshaev, A. Y.

    2012-01-01

    Transformations of spatial characteristics of optical vortex (OV) light beams at passing through a computer-generated hologram (CGH) that imparts an additional phase singularity ("fork" hologram) are investigated. The spatial structure of the diffracted beam is studied for different combinations of the incident OV order m, embedded topological charge of the CGH q and the diffraction order n. Variations of the intensity distribution are investigated experimentally. Due to the incident beam displacement with respect to the CGH optical axis, the diffracted beam profile is deformed, rotates in the azimuthal direction in agreement with the internal energy circulation and its 'center of gravity' is displaced orthogonally to the incident beam displacement. The results are compared with theoretical predictions based on two models of the incident OV beam. As, in experiment, the incident beam was created from the Gaussian beam passed another fork hologram, the Kummer beam model seems presumably more relevant but the standard Laguerre-Gaussian model in some cases fits the experimental data quite well.

  9. Transformation of the optical vortex light beams in holographic elements with embedded phase singularities

    NASA Astrophysics Data System (ADS)

    Sviridova, S. V.; Bekshaev, A. Y.

    2011-09-01

    Transformations of spatial characteristics of optical vortex (OV) light beams at passing through a computer-generated hologram (CGH) that imparts an additional phase singularity ("fork" hologram) are investigated. The spatial structure of the diffracted beam is studied for different combinations of the incident OV order m, embedded topological charge of the CGH q and the diffraction order n. Variations of the intensity distribution are investigated experimentally. Due to the incident beam displacement with respect to the CGH optical axis, the diffracted beam profile is deformed, rotates in the azimuthal direction in agreement with the internal energy circulation and its 'center of gravity' is displaced orthogonally to the incident beam displacement. The results are compared with theoretical predictions based on two models of the incident OV beam. As, in experiment, the incident beam was created from the Gaussian beam passed another fork hologram, the Kummer beam model seems presumably more relevant but the standard Laguerre-Gaussian model in some cases fits the experimental data quite well.

  10. Modulation of auroral electrojet currents using dual HF beams with ELF phase offset

    NASA Astrophysics Data System (ADS)

    Golkowski, M.; Cohen, M.; Moore, R. C.

    2012-12-01

    The modulation of naturally occuring ionospheric currents with high power radio waves in the high frequency (HF, 3-10 MHz) band is a well known technique for generation of extremely low frequency (ELF, 3-3000 Hz) and very low frequency (VLF, 3-30 kHz) waves. We use the heating facility of the High Frequency Active Auroral Research Program (HAARP) to investigate the effect of using dual HF beams with an ELF/VLF phase offset between the modulation waveforms. Experiments with offset HF beams confirm the model of independent ELF/VLF sources. Experiments with co-located HF beams exhibit interaction between the first and second harmonics of the modulated tones when square and sine wave modulation waveforms are employed. Using ELF/VLF phase offsets for co-loacted beams is also shown to be a potential diagnostic for the D-region ionospheric profile.

  11. Stable radio frequency phase delivery by rapid and endless post error cancellation.

    PubMed

    Wu, Zhongle; Dai, Yitang; Yin, Feifei; Xu, Kun; Li, Jianqiang; Lin, Jintong

    2013-04-01

    We propose and demonstrate a phase stabilization method for transfer and downconvert radio frequency (RF) signal from remote antenna to center station via a radio-over-fiber (ROF) link. Different from previous phase-locking-loop-based schemes, we post-correct any phase fluctuation by mixing during the downconversion process at the center station. A rapid and endless operation is predicted. The ROF technique transfers the received RF signal directly, which will reduce the electronic complexity at the antenna end. The proposed scheme is experimentally demonstrated, with a phase fluctuation compression factor of about 200. The theory and performance are also discussed. PMID:23546256

  12. Measuring uncertainty in dose delivered to the cochlea due to setup error during external beam treatment of patients with cancer of the head and neck

    SciTech Connect

    Yan, M.; Lovelock, D.; Hunt, M.; Mechalakos, J.; Hu, Y.; Pham, H.; Jackson, A.

    2013-12-15

    Purpose: To use Cone Beam CT scans obtained just prior to treatments of head and neck cancer patients to measure the setup error and cumulative dose uncertainty of the cochlea. Methods: Data from 10 head and neck patients with 10 planning CTs and 52 Cone Beam CTs taken at time of treatment were used in this study. Patients were treated with conventional fractionation using an IMRT dose painting technique, most with 33 fractions. Weekly radiographic imaging was used to correct the patient setup. The authors used rigid registration of the planning CT and Cone Beam CT scans to find the translational and rotational setup errors, and the spatial setup errors of the cochlea. The planning CT was rotated and translated such that the cochlea positions match those seen in the cone beam scans, cochlea doses were recalculated and fractional doses accumulated. Uncertainties in the positions and cumulative doses of the cochlea were calculated with and without setup adjustments from radiographic imaging. Results: The mean setup error of the cochlea was 0.04 ± 0.33 or 0.06 ± 0.43 cm for RL, 0.09 ± 0.27 or 0.07 ± 0.48 cm for AP, and 0.00 ± 0.21 or −0.24 ± 0.45 cm for SI with and without radiographic imaging, respectively. Setup with radiographic imaging reduced the standard deviation of the setup error by roughly 1–2 mm. The uncertainty of the cochlea dose depends on the treatment plan and the relative positions of the cochlea and target volumes. Combining results for the left and right cochlea, the authors found the accumulated uncertainty of the cochlea dose per fraction was 4.82 (0.39–16.8) cGy, or 10.1 (0.8–32.4) cGy, with and without radiographic imaging, respectively; the percentage uncertainties relative to the planned doses were 4.32% (0.28%–9.06%) and 10.2% (0.7%–63.6%), respectively. Conclusions: Patient setup error introduces uncertainty in the position of the cochlea during radiation treatment. With the assistance of radiographic imaging during setup

  13. Controlling multipolar surface plasmon excitation through the azimuthal phase structure of electron vortex beams

    NASA Astrophysics Data System (ADS)

    Ugarte, Daniel; Ducati, Caterina

    2016-05-01

    We have theoretically studied how the azimuthal phase structure of an electron vortex beam excites surface plasmons on metal particles of different geometries as observed in electron energy loss spectroscopy (EELS). We have developed a semiclassical approximation combining a ring-shaped beam and the dielectric formalism. Our results indicate that for the case of total orbital angular momentum transfer, we can manipulate surface plasmon multipole excitation and even attain an enhancement factor of several orders of magnitude. Since electron vortex beams interact with particles mostly through effects due to azimuthal symmetry, i.e., in the plane perpendicular to the electron beam, anisotropy information (longitudinal and transversal) of the sample may be derived in EELS studies by comparing nonvortex and vortex beam measurements.

  14. Phase-conjugation and self-oscillation with copropagating cross-polarized beams

    NASA Astrophysics Data System (ADS)

    Vallet, M.; Pinard, M.; Grynberg, G.

    1991-03-01

    We present the result of an experiment on optical phase conjugation made with a probe beam propagating in the same direction as the forward pump beam but having an orthogonal polarization. Using the difference of polarization, we separate the reflected beam from the backward pump beam. Is is shown that the amplitude of the reflected beam is the sum of two components, one proportional to the conjugate of the probe and one proportional to the amplitude of the probe. The experiment is done in sodium vapor and reflectivities larger than 350% have been observed near the D 1 transition. Weaker reflectivities due to a less efficient optical pumping are obtained near the D 2 line. We also describe the characteristics of the cw oscillation that appears between the Na cell and a mirror.

  15. Detection of Procedural Errors with Stainless Steel and NiTi Instruments by Undergraduate Students Using Conventional Radiograph and Cone Beam Computed Tomography

    PubMed Central

    Alves, Regis Augusto Aleixo; Souza, João Batista; Gonçalves Alencar, Ana Helena; Pécora, Jesus Djalma; Estrela, Carlos

    2013-01-01

    Introduction This study investigated procedural errors made during root canal preparation using stainless steel and nickel-titanium (NiTi) instruments by undergraduate students, using two diagnostic imaging methods. Materials and Methods Sixty human molars were divided into three groups (n=20; group 1: K-Flexofile, group 2: K3, and group 3: BioRace). The root canals were filled with gutta-percha and AH Plus. Periapical radiographs and cone beam computed tomography (CBCT) images were obtained to detect procedural errors made by undergraduate students during root canal preparation. Two examiners evaluated the presence or absence of fractured instruments, perforations and canal transportations. The agreement between observers was assessed using the kappa coefficient. The Kolmogorov-Smirnov, Fisher exact, ANOVA and Tukey tests were used for statistical analysis. The level of significance was set at 5%. Results There were no significant differences in detecting procedural errors between two- and three-dimensional diagnostic imaging methods. There were no significant differences in procedural errors between stainless steel and NiTi instruments. Mean preparation time was recorded in minutes, and results were significantly different between the three groups. NiTi instruments had the lowest mean preparation time. Conclusion Both periapical radiographs and CBCT identified procedural errors, however, three-dimensional images offered more diagnostic resources. The frequency of procedural errors was low for any of the endodontic instruments despite being used by inexperienced operators. PMID:24171022

  16. Beam quality changes of radially and azimuthally polarized fields propagating through quartic phase plates

    NASA Astrophysics Data System (ADS)

    Martínez-Herrero, R.; Piquero, G.; Mejías, P. M.

    2008-02-01

    In terms of the so-called irradiance moments of a light field, the beam quality change, Δ Q, of radially and azimuthally polarized beams caused by propagation through a quartic phase plate (as occurs, for example, in strongly pumped laser rods used in high-power solid-state lasers) is studied. Analytical expressions for Δ Q are given, and a comparison between the scalar and vectorial regimes is also shown. The results are applied to several cases of interest.

  17. Study of phase transitions in NbN ultrathin films under composite ion beam irradiation

    NASA Astrophysics Data System (ADS)

    Prikhodko, K.; Gurovich, B.; Dement'eva, M.

    2016-04-01

    This work demonstrates implementation of Selective Displacement of Atoms (SDA) technique to change the crystal structure and atomic composition of thin superconductive film of NbN under low dose composite ion beam irradiation. All structure investigations were performed using High Resolution Transmission Electron Microscopy (HRTEM) technique by the analysis of Fourier transformation of bright field HRTEM images. It was found that composite ion beam irradiation induces the formation of niobium oxynitrides phases.

  18. Longitudinal phase space manipulation of an ultrashort electron beam via THz IFEL interaction

    SciTech Connect

    Moody, J. T.; Li, R. K.; Musumeci, P.; Scoby, C. M.; To, H.

    2012-12-21

    A scheme where a laser locked THz source is used to manipulate the longitudinal phase space of an ultrashort electron beam using an IFEL interaction is investigated. The efficiency of THz source based on the pulse front tilt optical rectification scheme is increased by cryogenic cooling to achieve sufficient THz power for compression and synchronization. Start-to-end simulations describing the evolution of the beam from the cathode to the compression point after the undulator are presented.

  19. Coherent beam combination using self-phase locked stimulated Brillouin scattering phase conjugate mirrors with a rotating wedge for high power laser generation.

    PubMed

    Park, Sangwoo; Cha, Seongwoo; Oh, Jungsuk; Lee, Hwihyeong; Ahn, Heekyung; Churn, Kil Sung; Kong, Hong Jin

    2016-04-18

    The self-phase locking of a stimulated Brillouin scattering-phase conjugate mirror (SBS-PCM) allows a simple and scalable coherent beam combination of existing lasers. We propose a simple optical system composed of a rotating wedge and a concave mirror to overcome the power limit of the SBS-PCM. Its phase locking ability and the usefulness on the beam-combination laser are demonstrated experimentally. A four-beam combination is demonstrated using this SBS-PCM scheme. The relative phases between the beams were measured to be less than λ/24.7. PMID:27137299

  20. A Monte Carlo simulation framework for electron beam dose calculations using Varian phase space files for TrueBeam Linacs

    SciTech Connect

    Rodrigues, Anna; Yin, Fang-Fang; Wu, Qiuwen; Sawkey, Daren

    2015-05-15

    Purpose: To develop a framework for accurate electron Monte Carlo dose calculation. In this study, comprehensive validations of vendor provided electron beam phase space files for Varian TrueBeam Linacs against measurement data are presented. Methods: In this framework, the Monte Carlo generated phase space files were provided by the vendor and used as input to the downstream plan-specific simulations including jaws, electron applicators, and water phantom computed in the EGSnrc environment. The phase space files were generated based on open field commissioning data. A subset of electron energies of 6, 9, 12, 16, and 20 MeV and open and collimated field sizes 3 × 3, 4 × 4, 5 × 5, 6 × 6, 10 × 10, 15 × 15, 20 × 20, and 25 × 25 cm{sup 2} were evaluated. Measurements acquired with a CC13 cylindrical ionization chamber and electron diode detector and simulations from this framework were compared for a water phantom geometry. The evaluation metrics include percent depth dose, orthogonal and diagonal profiles at depths R{sub 100}, R{sub 50}, R{sub p}, and R{sub p+} for standard and extended source-to-surface distances (SSD), as well as cone and cut-out output factors. Results: Agreement for the percent depth dose and orthogonal profiles between measurement and Monte Carlo was generally within 2% or 1 mm. The largest discrepancies were observed within depths of 5 mm from phantom surface. Differences in field size, penumbra, and flatness for the orthogonal profiles at depths R{sub 100}, R{sub 50}, and R{sub p} were within 1 mm, 1 mm, and 2%, respectively. Orthogonal profiles at SSDs of 100 and 120 cm showed the same level of agreement. Cone and cut-out output factors agreed well with maximum differences within 2.5% for 6 MeV and 1% for all other energies. Cone output factors at extended SSDs of 105, 110, 115, and 120 cm exhibited similar levels of agreement. Conclusions: We have presented a Monte Carlo simulation framework for electron beam dose calculations for

  1. Implication of spot position error on plan quality and patient safety in pencil-beam-scanning proton therapy

    SciTech Connect

    Yu, Juan; Beltran, Chris J. Herman, Michael G.

    2014-08-15

    Purpose: To quantitatively and systematically assess dosimetric effects induced by spot positioning error as a function of spot spacing (SS) on intensity-modulated proton therapy (IMPT) plan quality and to facilitate evaluation of safety tolerance limits on spot position. Methods: Spot position errors (PE) ranging from 1 to 2 mm were simulated. Simple plans were created on a water phantom, and IMPT plans were calculated on two pediatric patients with a brain tumor of 28 and 3 cc, respectively, using a commercial planning system. For the phantom, a uniform dose was delivered to targets located at different depths from 10 to 20 cm with various field sizes from 2{sup 2} to 15{sup 2} cm{sup 2}. Two nominal spot sizes, 4.0 and 6.6 mm of 1 σ in water at isocenter, were used for treatment planning. The SS ranged from 0.5 σ to 1.5 σ, which is 2–6 mm for the small spot size and 3.3–9.9 mm for the large spot size. Various perturbation scenarios of a single spot error and systematic and random multiple spot errors were studied. To quantify the dosimetric effects, percent dose error (PDE) depth profiles and the value of percent dose error at the maximum dose difference (PDE [ΔDmax]) were used for evaluation. Results: A pair of hot and cold spots was created per spot shift. PDE[ΔDmax] is found to be a complex function of PE, SS, spot size, depth, and global spot distribution that can be well defined in simple models. For volumetric targets, the PDE [ΔDmax] is not noticeably affected by the change of field size or target volume within the studied ranges. In general, reducing SS decreased the dose error. For the facility studied, given a single spot error with a PE of 1.2 mm and for both spot sizes, a SS of 1σ resulted in a 2% maximum dose error; a SS larger than 1.25 σ substantially increased the dose error and its sensitivity to PE. A similar trend was observed in multiple spot errors (both systematic and random errors). Systematic PE can lead to noticeable hot

  2. Human subthalamic nucleus-medial frontal cortex theta phase coherence is involved in conflict and error related cortical monitoring.

    PubMed

    Zavala, Baltazar; Tan, Huiling; Ashkan, Keyoumars; Foltynie, Thomas; Limousin, Patricia; Zrinzo, Ludvic; Zaghloul, Kareem; Brown, Peter

    2016-08-15

    The medial prefrontal cortex (mPFC) is thought to control the shift from automatic to controlled action selection when conflict is present or when mistakes have been recently committed. Growing evidence suggests that this process involves frequency specific communication in the theta (4-8Hz) band between the mPFC and the subthalamic nucleus (STN), which is the main target of deep brain stimulation (DBS) for Parkinson's disease. Key in this hypothesis is the finding that DBS can lead to impulsivity by disrupting the correlation between higher mPFC oscillations and slower reaction times during conflict. In order to test whether theta band coherence between the mPFC and the STN underlies adjustments to conflict and to errors, we simultaneously recorded mPFC and STN electrophysiological activity while DBS patients performed an arrowed flanker task. These recordings revealed higher theta phase coherence between the two sites during the high conflict trials relative to the low conflict trials. These differences were observed soon after conflicting arrows were displayed, but before a response was executed. Furthermore, trials that occurred after an error was committed showed higher phase coherence relative to trials that followed a correct trial, suggesting that mPFC-STN connectivity may also play a role in error related adjustments in behavior. Interestingly, the phase coherence we observed occurred before increases in theta power, implying that the theta phase and power may influence behavior at separate times during cortical monitoring. Finally, we showed that pre-stimulus differences in STN theta power were related to the reaction time on a given trial, which may help adjust behavior based on the probability of observing conflict during a task. PMID:27181763

  3. Modified read-out system of the beam phase measurement system for CSNS

    NASA Astrophysics Data System (ADS)

    Bai, Jiao-Ni; Zeng, Lei; Wang, Biao; Li, Peng; Li, Fang; Xu, Tao-Guang; Li, Zi-Gao

    2013-10-01

    The customized beam phase measurement system can meet the requirement of beam loss control of the radio-frequency quadrupole (RFQ). However, its read-out part cannot satisfy the requirement of China Spallation Neutron Source (CSNS). CSNS uses the Experimental Physics and Industrial Control System (EPICS) as its control system. So it is necessary to develop the EPICS read-out system consisting of EPICS IOC databases, driver support and OPIs. The new system has been successfully tested in the RFQ. In the future, it will be applied to the beam diagnostics of CSNS.

  4. Generation of equal-intensity coherent optical beams by binary geometrical phase on metasurface

    NASA Astrophysics Data System (ADS)

    Wang, Zheng-Han; Jiang, Shang-Chi; Xiong, Xiang; Peng, Ru-Wen; Wang, Mu

    2016-06-01

    We report here the design and realization of a broadband, equal-intensity optical beam splitter with a dispersion-free binary geometric phase on a metasurface with unit cell consisting of two mirror-symmetric elements. We demonstrate experimentally that two identical beams can be efficiently generated with incidence of any polarization. The efficiency of the device reaches 80% at 1120 nm and keeps larger than 70% in the range of 1000-1400 nm. We suggest that this approach for generating identical, coherent beams have wide applications in diffraction optics and in entangled photon light source for quantum communication.

  5. Phase-space analysis of charged and optical beam transport: Wigner rotation angle

    NASA Technical Reports Server (NTRS)

    Dattoli, G.; Torre, Amalia

    1994-01-01

    The possibility of using the phase space formalism to establish a correspondence between the dynamical behavior of squeezed states and optical or charged beams, propagating through linear systems, has received a great deal of attention during the last years. In this connection, it has been indicated how optical experiments may be conceived to measure the Wigner rotation angle. In this paper we address the topic within the context of the paraxial propagation of optical or charged beams and suggest a possible experiment for measuring the Wigner angle using an electron beam passing through quadrupoles and drift sections. The analogous optical system is also discussed.

  6. Development of a fast scintillator based beam phase measurement system for compact superconducting cyclotrons

    SciTech Connect

    Bhattacharjee, Tanushyam; Kanti Dey, Malay; Dhara, Partha; Roy, Suvodeep; Debnath, Jayanta; Balakrishna Bhole, Rajendra; Dutta, Atanu; Pradhan, Jedidiah; Pal, Sarbajit; Pal, Gautam; Roy, Amitava; Chakrabarti, Alok

    2013-05-15

    In an isochronous cyclotron, measurements of central phase of the ion beam with respect to rf and the phase width provide a way to tune the cyclotron for maximum energy gain per turn and efficient extraction. We report here the development of a phase measurement system and the measurements carried out at the Variable Energy Cyclotron Centre's (VECC's) K= 500 superconducting cyclotron. The technique comprises detecting prompt {gamma}-rays resulting from the interaction of cyclotron ion beam with an aluminium target mounted on a radial probe in coincidence with cyclotron rf. An assembly comprising a fast scintillator and a liquid light-guide inserted inside the cyclotron was used to detect the {gamma}-rays and to transfer the light signal outside the cyclotron where a matching photo-multiplier tube was used for light to electrical signal conversion. The typical beam intensity for this measurement was a few times 10{sup 11} pps.

  7. Nonlinear theory of beam-wave interaction in the pasotron with a phase-mixed electron beam

    SciTech Connect

    Bliokh, Yu.P.; Nusinovich, G.S.

    2006-02-15

    The nonlinear theory describing the interaction processes in traveling-wave-amplifier (TWT) and backward-wave-oscillator (BWO) configurations of pasotrons is developed. It is shown that space charge forces in electron bunches formed in the process of beam-wave interaction in the pasotron play a role completely different from that in linear-beam devices with a strong magnetic focusing of electron beams. While in the latter devices the space charge forces limit the device efficiency due to saturation of the axial bunching, in the pasotron they do not destroy electron bunches but cause the radial expansion of them, which may increase device efficiency. The role of these forces is compared with the ion focusing and the radial electric field of the wave, and it is shown that, under certain conditions, it may dominate. The efficiency of the pasotron-TWT with a phase-mixed beam well focused at the entrance may exceed 50%. In the pasotron-BWO, the efficiency is lower (up to 26% in the case studied), but it can grow as the equivalent of the Pierce gain parameter increases.

  8. The effects of receiver tracking phase error on the performance of the concatenated Reed-Solomon Viterbi channel coding system

    NASA Technical Reports Server (NTRS)

    Liu, K. Y.; Woo, K. T.

    1980-01-01

    In connection with attempts to achieve very low error probabilities, Odenwalder (1970) proposed a concatenated coding system using the Viterbi-decoded convolutional codes as the inner code and Reed-Solomon (RS) codes as the outer code. Analytical and experimental results are presented concerning the effects of the receiver tracking phase error on the performance of the concatenated RS/Viterbi channel coding system. On the basis of these results it is concluded that certain problems regarding communication operations on deep-space missions can be alleviated by employing the RS/Viterbi coding system. In one-way communication, an employment of RS/Viterbi coding will also provide greater data protection than the Viterbi-decoded convolutional-only coding system.

  9. Experimental measurement of the 4-d transverse phase space map of a heavy ion beam

    SciTech Connect

    Hopkins, H S

    1997-12-01

    The development and employment of a new diagnostic instrument for characterizing intense, heavy ion beams is reported on. This instrument, the ''Gated Beam Imager'' or ''GBI'' was designed for use on Lawrence Livermore National Laboratory Heavy Ion Fusion Project's ''Small Recirculator'', an integrated, scaled physics experiment and engineering development project for studying the transport and control of intense heavy ion beams as inertial fusion drivers in the production of electric power. The GBI allows rapid measurement and calculation of a heavy ion beam's characteristics to include all the first and second moments of the transverse phase space distribution, transverse emittance, envelope parameters and beam centroid. The GBI, with appropriate gating produces a time history of the beam resulting in a 4-D phase-space and time ''map'' of the beam. A unique capability of the GBI over existing diagnostic instruments is its ability to measure the ''cross'' moments between the two transverse orthogonal directions. Non-zero ''cross'' moments in the alternating gradient lattice of the Small Recirculator are indicative of focusing element rotational misalignments contributing to beam emittance growth. This emittance growth, while having the same effect on the ability to focus a beam as emittance growth caused by non-linear effects, is in principle removable by an appropriate number of focusing elements. The instrument uses the pepperpot method of introducing a plate with many pinholes into the beam and observing the images of the resulting beamlets as they interact with a detector after an appropriate drift distance. In order to produce adequate optical signal and repeatability, the detector was chosen to be a microchannel plate (MCP) with a phosphor readout screen. The heavy ions in the pepperpot beamlets are stopped in the MCP's thin front metal anode and the resulting secondary electron signal is amplified and proximity-focused onto the phosphor while maintaining

  10. Experimental measurement of the 4-D transverse phase space map of a heavy ion beam

    NASA Astrophysics Data System (ADS)

    Hopkins, Harvey Small

    The development and employment of a new diagnostic instrument for characterizing intense, heavy ion beams is reported on. This instrument, the 'Gated Beam Imager' or 'GBI' was designed for use on Lawrence Livermore National Laboratory Heavy Ion Fusion Project's 'Small Recirculator', an integrated, scaled physics experiment and engineering development project for studying the transport and control of intense heavy ion beams as inertial fusion drivers in the production of electric power. The GBI allows rapid measurement and calculation of a heavy ion beam's characteristics to include all the first and second moments of the transverse phase space distribution, transverse emittance, envelope parameters and beam centroid. The GBI, with appropriate gating produces a time history of the beam resulting in a 4-D phase-space and time 'map' of the beam. A unique capability of the GBI over existing diagnostic instruments is its ability to measure the 'cross' moments between the two transverse orthogonal directions. Non- zero 'cross' moments in the alternating gradient lattice of the Small Recirculator are indicative of focusing element rotational misalignments contributing to beam emittance growth. This emittance growth, while having the same effect on the ability to focus a beam as emittance growth caused by non-linear effects, is in principle removable by an appropriate number of focusing elements. The instrument uses the pepperpot method of introducing a plate with many pinholes into the beam and observing the images of the resulting beamlets as they interact with a detector after an appropriate drift distance. In order to produce adequate optical signal and repeatability, the detector was chosen to be a microchannel plate (MCP) with a phosphor readout screen. The heavy ions in the pepperpot beamlets are stopped in the MCP's thin front metal anode and the resulting secondary electron signal is amplified and proximity-focused onto the phosphor while maintaining the spatial

  11. Evolution of electron beam phase space distribution in a high-gain FEL

    SciTech Connect

    Webb,S.D.; Litvinenko, V. N.

    2009-08-23

    FEL-based coherent electron cooling (CEC) offers a new avenue to achieve high luminosities in high energy colliders such as RHIC, LHC, and eRHIC. Traditional treatments consider the FEL as an amplifier of optical waves with specific initial conditions, focusing on the resulting field. CEC requires knowledge of the phase space distribution of the electron beam in the FEL. We present 1D analytical results for the phase space distribution of an electron beam with an arbitrary initial current profile, and discuss approaches of expanding to 3D results.

  12. Phase-contrast tomography with low-intensity beams

    SciTech Connect

    Rehacek, J.; Hradil, Z.; Zawisky, M.; Dubus, F.; Bonse, U.

    2005-02-01

    In newly developed neutron phase tomography, wave properties of neutrons are exploited for the nondestructive testing of the internal structure of matter. We show how limitations due to small available intensities of present neutron sources can be overcome by using an advanced maximum-likelihood reconstruction algorithm. Unlike the standard filtered back-projection, the developed procedure gives reasonable results also when used on very noisy data or data consisting of only a few measured projections. This is demonstrated by means of simulations and also experimentally. The proposed method leads to considerably shorter measuring times and/or increased precision.

  13. An Error Analysis of the Phased Array Antenna Pointing Algorithm for STARS Flight Demonstration No. 2

    NASA Technical Reports Server (NTRS)

    Carney, Michael P.; Simpson, James C.

    2005-01-01

    STARS is a multicenter NASA project to determine the feasibility of using space-based assets, such as the Tracking and Data Relay Satellite System (TDRSS) and Global Positioning System (GPS), to increase flexibility (e.g. increase the number of possible launch locations and manage simultaneous operations) and to reduce operational costs by decreasing the need for ground-based range assets and infrastructure. The STARS project includes two major systems: the Range Safety and Range User systems. The latter system uses broadband communications (125 kbps to 500 kbps) for voice, video, and vehicle/payload data. Flight Demonstration #1 revealed the need to increase the data rate of the Range User system. During Flight Demo #2, a Ku-band antenna will generate a higher data rate and will be designed with an embedded pointing algorithm to guarantee that the antenna is pointed directly at TDRS. This algorithm will utilize the onboard position and attitude data to point the antenna to TDRS within a 2-degree full-angle beamwidth. This report investigates how errors in aircraft position and attitude, along with errors in satellite position, propagate into the overall pointing vector.

  14. A Novel Three-Phase UPS Inverter Driven by Error-Tracking-Mode PWM Scheme

    NASA Astrophysics Data System (ADS)

    Ohshima, Masaaki; Nakamura, Fuminori; Tamai, Shinzo; Yamamoto, Yuushin; Yoshida, Kouichi

    With prevalence of information technology into our modern society and advance of automation technology in modern production process, the UPS market is assumed to make sustainable expansion. Error-Tracking-Mode PWM scheme offers novel constantly-sampled current-regulated switching algorithm to voltage-source power converters. This paper proposes a UPS in which Error-Tracking-Mode PWM scheme is applied to the current minor loop. The upper voltage control loop (ac-AVR) is developed afresh, that makes best of the PWM attributes. The equivalent output impedance of the UPS is derived theoretically for not only small signal but also large signal operation, that value can be arbitrarily specified by the ac-AVR parameters. A 3 kVA experimental setup was designed and fabricated, which has demonstrated the theoretical characteristics satisfactorily. The paper discusses the experimental results in detail. The authors believe that the paper presents a clue to realize independent and autonomic operation of dispersed PWM converters.

  15. Bit-error-rate testing of fiber optic data links for MMIC-based phased array antennas

    NASA Technical Reports Server (NTRS)

    Shalkhauser, K. A.; Kunath, R. R.; Daryoush, A. S.

    1990-01-01

    The measured bit-error-rate (BER) performance of a fiber optic data link to be used in satellite communications systems is presented and discussed. In the testing, the link was measured for its ability to carry high burst rate, serial-minimum shift keyed (SMSK) digital data similar to those used in actual space communications systems. The fiber optic data link, as part of a dual-segment injection-locked RF fiber optic link system, offers a means to distribute these signals to the many radiating elements of a phased array antenna. Test procedures, experimental arrangements, and test results are presented.

  16. Resonator fiber optic gyro with high backscatter-error suppression using two independent phase-locked lasers

    NASA Astrophysics Data System (ADS)

    Wu, Jiangfeng; Smiciklas, Marc; Strandjord, Lee K.; Qiu, Tiequn; Ho, Waymon; Sanders, Glen A.

    2015-09-01

    A resonator fiber optic gyro was constructed using separate lasers for counter-rotating waves to overcome interference between optical backscatter and signal light that causes dead-zone behavior and scale factor nonlinearity. This approach enabled a 2 MHz frequency separation between waves in the resonator; eliminating the intended backscatter error. The two lasers were phase-locked to prevent increased gyro noise due to laser frequency noise. Dead-band-free operation near zero-rate, scale factor linearity of 25 ppm and stability of 11 ppm were demonstrated - the closest results to navigation-grade performance reported to date. The approach is also free of impractical frequency shifter technology.

  17. Potential errors in measuring the phase difference between chest flow and mouth flow.

    PubMed

    Mishima, M; Kawakami, K; Sugiura, N; Fukunaga, T; Sakai, N; Hirai, T; Kuno, K

    1993-01-01

    We have previously reported that the phase difference between chest and mouth flows was a useful indicator of obstructive lung disease. In this paper, we calculated the effects of (i) airway reactance, (ii) extrathoracic airway shunt impedance, (iii) heating and humidification of the inspired air, (iv) abdominal gas volume, and (v) respiratory quotient on the measurement of the phase difference between chest flow (Vc) and mouth flow (Vm) using computer simulations. When the airway impedance was approximated as simple airway resistance, the phase difference (theta r) was calculated to be 0.8% less than the phase difference (theta s) calculated from the airway impedance (Za), including airway inertance and shunt compliance, in the normal lung. theta s became larger than theta r when the peripheral resistance increased, but did not exceed 5%. The extrathoracic airway shunt impedance effect did not exceed 0.1%, regardless of the respiratory frequency, airway impedance or thoracic gas volume. The influence of heating and humidification of the inspired air on the phase difference was calculated to be within 5%. The effect of abdominal gas was highly dependent on the abdominal gas volume and the respiratory pattern, but was calculated to be within 5%. The influence of the respiratory quotient was calculated to be negligible. As a result, it was concluded that none of the factors discussed above are an obstacle to the clinical application of this method for the evaluation of pathological changes in obstructive airway disorders. PMID:8280667

  18. RESONATORS, MODES, BEAMS: Gain saturation of laser beams and production and decay of phase dislocations

    NASA Astrophysics Data System (ADS)

    Malyutin, A. A.

    2006-02-01

    The distortion of the distribution of initially pure laser modes caused by the gain saturation is simulated numerically. It is shown that the gain saturation results in a considerable enrichment of the modal spectrum of radiation accompanied by the production and decay of phase dislocations in the far-field domain and at the output of an astigmatic π/2-mode converter.

  19. Emittance and Phase Space Exchange for Advanced Beam Manipulation and Diagnostics

    SciTech Connect

    Xiang, Dao; Chao, Alex; /SLAC

    2012-04-27

    Alternative chicane-type beam lines are proposed for exact emittance exchange between transverse phase space (x,x') and longitudinal phase space (z,{delta}), where x is the transverse position, x' is the transverse divergence, and z and {delta} are relative longitudinal position and energy deviation with respect to the reference particle. Methods to achieve exact phase space exchanges, i.e., mapping x to z, x' to {delta}, z to x, and {delta} to x', are suggested. Schemes to mitigate and completely compensate for the thick-lens effect of the transverse cavity on emittance exchange are studied. Some applications of the phase space exchange for advanced beam manipulation and diagnostics are discussed.

  20. Study of the transverse beam motion in the DARHT Phase II accelerator

    SciTech Connect

    Chen, Yu-Jiuan; Fawley, W M; Houck, T L

    1998-08-20

    The accelerator for the second-axis of the Dual Axis Radiographic Hydrodynamic Test (DARHT) facility will accelerate a 4-kA, 3-MeV, 2--µs long electron current pulse to 20 MeV. The energy variation of the beam within the flat-top portion of the current pulse is (plus or equal to) 0.5%. The performance of the DARHT Phase II radiographic machine requires the transverse beam motion to be much less than the beam spot size which is about 1.5 mm diameter on the x-ray converter. In general, the leading causes of the transverse beam motion in an accelerator are the beam breakup instability (BBU) and the corkscrew motion. We have modeled the transverse beam motion in the DARHT Phase II accelerator with various magnetic tunes and accelerator cell configurations by using the BREAKUP code. The predicted sensitivity of corkscrew motion and BBU growth to different tuning algorithms will be presented.

  1. Phase shift errors in the theory and practice of surface intensity measurements

    NASA Technical Reports Server (NTRS)

    Mcgary, M. C.; Crocker, M. J.

    1982-01-01

    The surface acoustical intensity method (sometimes known as the microphone-accelerometer cross-spectral method) is a relatively new noise source/path identification tool. Several researchers have had difficulties implementing this method because of instrumentation phase mis-match. A simple technique for measuring and correcting instrumentation phase mis-match has been developed. This new technique has been tested recently on a noise source identification problem of practical interest. The results of the experiments indicate that the surface acoustic intensity method produces reliable data and can be applied to a variety of noise source/path problems.

  2. Phase-preserving beam expander for biomedical X-ray imaging

    PubMed Central

    Martinson, Mercedes; Samadi, Nazanin; Bassey, Bassey; Gomez, Ariel; Chapman, Dean

    2015-01-01

    The BioMedical Imaging and Therapy beamlines at the Canadian Light Source are used by many researchers to capture phase-based imaging data. These experiments have so far been limited by the small vertical beam size, requiring vertical scanning of biological samples in order to image their full vertical extent. Previous work has been carried out to develop a bent Laue beam-expanding monochromator for use at these beamlines. However, the first attempts exhibited significant distortion in the diffraction plane, increasing the beam divergence and eliminating the usefulness of the monochromator for phase-related imaging techniques. Recent work has been carried out to more carefully match the polychromatic and geometric focal lengths in a so-called ‘magic condition’ that preserves the divergence of the beam and enables full-field phase-based imaging techniques. The new experimental parameters, namely asymmetry and Bragg angles, were evaluated by analysing knife-edge and in-line phase images to determine the effect on beam divergence in both vertical and horizontal directions, using the flat Bragg double-crystal monochromator at the beamline as a baseline. The results show that by using the magic condition, the difference between the two monochromator types is less than 10% in the diffraction plane. Phase fringes visible in test images of a biological sample demonstrate that this difference is small enough to enable in-line phase imaging, despite operating at a sub-optimal energy for the wafer and asymmetry angle that was used. PMID:25931100

  3. Determination of absolute interferometric phase using the beam-amplitude ratio technique

    SciTech Connect

    Bickel, D.L.; Hensley, W.H.

    1996-03-01

    Determination of the absolute phase difference (i.e., not modulo 2{pi}) is a key problem in interferometric synthetic aperture radar (IFSAR) for topographic mapping. One way of solving this problem requires use of a technique different from the basic interferometry to resolve a `coarse` angle measurement that lies within the IFSAR ambiguity angle. The method investigated in this paper involves taking advantage of the difference in the amplitude ratio versus elevation angle that occurs when the elevation beams of the two IFSAR antennas are pointed in slightly different directions. The performance of the technique is a function of the angular separation of the two beams, the elevation beamwidth, and the symmetry of the two beam-amplitude patterns. The performance required of the technique is set by the ambiguity angle of the interferometer. This paper presents an analysis of the beam-amplitude ratio technique and shows experimental results.

  4. New asymmetric propagation invariant beams obtained by amplitude and phase modulation in frequency space

    PubMed Central

    Mendoza-Hernández, J.; Arroyo Carrasco, M.L.; Méndez Otero, M.M.; Chávez-Cerda, S.; Iturbe Castillo, M.D.

    2014-01-01

    In this paper, we demonstrate, numerically and experimentally that using the mask-lens setup used by Durnin to generate Bessel beams Durnin [Phys. Rev. Lett. 58, 1499 (1987)], it is possible to generate different kinds of propagation invariant beams. A modification in the amplitude or phase of the field that illuminates the annular slit is proposed that corresponds to modulation in frequency space. In particular, we characterize the new invariant beams that were obtained by modulating the amplitude of the annular mask and when the incident field was modulated with a one-dimensional quadratic or cubic phase. Experimental results using an amplitude mask are shown in order to corroborate the numerical predictions. PMID:25705088

  5. Generation of nondiffracting quasi-circular polarization beams using an amplitude modulated phase hologram.

    PubMed

    Yuan, G H; Wei, S B; Yuan, X-C

    2011-08-01

    We propose an approach to the generation of nondiffracting quasi-circularly polarized beams by a highly focusing azimuthally polarized beam using an amplitude modulated spiral phase hologram. Numerical verifications are implemented in the calculation of the electromagnetic fields and Poynting vector field near the focus based on the vector diffraction theory, and the polarization of the wavefront near the focal plane is analyzed in detail by calculating the Stokes polarization parameters. It is found that the electric field, magnetic field, and Poynting vector field can simultaneously be uniform and nondiverging over a relatively long axial range of ~7.23λ. In the transverse plane, the ellipticity and azimuthal angle of the local polarization ellipse varies from point to point. No polarization singularity and phase singularity are found at the beam center, which makes the bright spot possible. PMID:21811334

  6. Cone-beam differential phase-contrast laminography with x-ray tube source

    NASA Astrophysics Data System (ADS)

    Fu, J.; Biernath, T.; Willner, M.; Amberger, M.; Meiser, J.; Kunka, D.; Mohr, J.; Herzen, J.; Bech, M.; Pfeiffer, F.

    2014-06-01

    We report on an x-ray cone-beam differential phase-contrast computed laminography (DPC-CL) method for tomographic reconstruction of thin and lamellar objects. We describe the specific scan geometry of DPC-CL, which consists of a Talbot-Lau grating interferometer and a lab-based x-ray tube source, and derive a filtered back-projection (FBP) reconstruction algorithm. The experimental results of a flat sphere phantom and a piece of ham demonstrate the validity of the proposed technique. The existing DPC-CL methods are based on synchrotron sources and the parallel-beam geometry. In contrast, our approach adopts a more accessible x-ray tube source and a cone-beam geometry. Therefore it significantly widens the application range of phase-contrast laminography, particularly in practical laboratory settings, beyond applications at large-scale synchrotron facilities.

  7. Phase conjugation of mode scrambled optical beams Application to spatial recovery and interbeam temporal information exchange

    NASA Astrophysics Data System (ADS)

    Yahalom, Ram; Kyuma, Kazuo; Yariv, Amnon

    1987-03-01

    Coupling of temporal information between two beams is demonstrated using a combination of a multimode fiber and a photorefractive passive phase conjugation mirror. It is shown that the polarization and spatial properties are fully recovered but temporal information is exchanged. The theoretical explanation for these phenomena and possible applications are discussed.

  8. Arbitrary shaping of on-axis amplitude of femtosecond Bessel beams with a single phase-only spatial light modulator.

    PubMed

    Ouadghiri-Idrissi, Ismail; Giust, Remo; Froehly, Luc; Jacquot, Maxime; Furfaro, Luca; Dudley, John M; Courvoisier, Francois

    2016-05-30

    Arbitrary shaping of the on-axis intensity of Bessel beams requires spatial modulation of both amplitude and phase. We develop a non-iterative direct space beam shaping method to generate Bessel beams with high energy throughput from direct space with a single phase-only spatial light modulator. For this purpose, we generalize the approach of Bolduc et al. to non-uniform input beams. We point out the physical limitations imposed on the on-axis intensity profile for unidirectional beams. Analytical, numerical and experimental results are provided. PMID:27410077

  9. Spindle error motion measurement using concentric circle grating and phase modulation interferometers

    NASA Astrophysics Data System (ADS)

    Aketagawa, M.; Madden, M.; Uesugi, S.; Kumagai, T.; Maeda, Y.; Okuyama, E.

    2012-11-01

    In the conventional methods to measure radial, axial and angular motions of spindles, complicated artifacts with relative large volume (such as two balls linked with a cylinder) are required. Small volume artifact is favorable from the viewpoint of the accurate and practical measurement of the spindle motion. This paper describes a concurrent measurement of spindle radial, axial and angular motions using concentric circle grating and phase modulation interferometers. In the measurement, the concentric circle grating with fine pitch is installed on top of the spindle of interest. The grating is a reference artifact in the method. Three optical sensors are fixed over the concentric circle grating, and observe the proper positions of the grating. The optical sensor consists of a frequency modulated laser diode as a light source, and two interferometers. One interferometer observes an interference fringe between reflected light form a fixed mirror and 0-th order diffraction light from the grating to measure the axial motion. Another interferometer observes an interference fringe between +/-2nd diffraction lights from the grating to measure the radial motion. Using three optical sensors, three radial displacements and three axial displacements of the proper observed position of the grating can be measured. From these measured displacements, radial, axial and angular motions of the spindle can be calculated concurrently. In the paper, a measurement instrument, a novel fringe interpolation technique by sinusoidal phase modulation and experimental results are discussed.

  10. Theory of third-harmonic generation using Bessel beams, and self-phase-matching

    SciTech Connect

    Tewari, S.P.; Huang, H.; Boyd, R.W. ||

    1996-09-01

    Taking Bessel beams ({ital J}{sub 0} beam) as a representation of a conical beam, and a slowly varying envelope approximation (SVEA) we obtain the results for the theory of third-harmonic generation from an atomic medium. We demonstrate how the phenomenon of self-phase-matching is contained in the transverse-phase-matching integral of the theory. A method to calculate the transverse-phase-matching integral containing four Bessel functions is described which avoids the computer calculations of the Bessel functions. In order to consolidate the SVEA result an alternate method is used to obtain the exact result for the third-harmonic generation. The conditions are identified in which the exact result goes over to the result of the SVEA. The theory for multiple Bessel beams is also discussed which has been shown to be the source of the wide width of the efficiency curve of the third-harmonic generation observed in experiments. {copyright} {ital 1996 The American Physical Society.}

  11. Coherent beam combining of pulsed fibre amplifiers with active phase control

    SciTech Connect

    Wang, X L; Zhou, Pu; Ma, Y X; Ma, H T; Xu, X J; Liu, Z J; Zhao, Y J

    2011-12-31

    Coherent beam combining of pulsed fibre lasers is a promising method for power scaling while simultaneously maintaining good beam quality. We propose and demonstrate a scalable architecture for coherent beam combining of all-fibre pulsed amplifiers with active phase control using the stochastic parallel gradient descent (SPGD) algorithm. A low-pass filter is introduced to eliminate the fluctuation of the metric function caused by pulsed lasers and to extract the exact phase noise signal. Active control is thereby based on the SPGD algorithm, resulting in stable coherent beam combining at the receiving plane even in a turbulent environment. Experimental results show that the fringe visibility of the long exposure pattern increases from 0 to 0.4, and the power encircled in the main-lobe increases by 1.6 times when the system evolves from the open-loop phase-locking scheme to the closed-loop scheme. This architecture can be easily scaled up to a higher power by increasing the number of amplifying channels and the power of a single amplifier.

  12. Fully integrated hybrid silicon free-space beam steering source with 32-channel phased array

    NASA Astrophysics Data System (ADS)

    Hulme, J. C.; Doylend, J. K.; Heck, M. J. R.; Peters, J. D.; Davenport, M. L.; Bovington, J. T.; Coldren, L. A.; Bowers, J. E.

    2014-03-01

    Free-space beam steering using optical phased arrays is a promising method for implementing free-space communication links and Light Detection and Ranging (LIDAR) without the sensitivity to inertial forces and long latencies which characterize moving parts. Implementing this approach on a silicon-based photonic integrated circuit adds the additional advantage of working with highly developed CMOS processing techniques. In this work we discuss our progress in the development of a fully integrated 32 channel PIC with a widely tunable diode laser, a waveguide phased array, an array of fast phase modulators, an array of hybrid III-V/silicon amplifiers, surface gratings, and a graded index lens (GRIN) feeding an array of photodiodes for feedback control. The PIC has been designed to provide beam steering across a 15°x5° field of view with 0.6°x0.6° beam width and background peaks suppressed 15 dB relative to the main lobe within the field of view for arbitrarily chosen beam directions. Fabrication follows the hybrid silicon process developed at UCSB with modifications to incorporate silicon diodes and a GRIN lens.

  13. Beam Position and Phase Monitors Characterized and Installed in the LANSCE CCL

    SciTech Connect

    Gilpatrick, John D; Kutac, Vincent G.; Martinez, Derwin; McCrady, Rodney C.; O'Hara, James F.; Olivas, Felix R.; Shurter, Robert B.; Watkins, Heath A.

    2012-04-11

    The Los Alamos Neutron Science Center - Risk Mitigation Project is in the process of replacing older Coupled-Cavity-Linac (CCL) Beam-Position Monitors (BPMs) with newer Beam Position and Phase Monitors (BPPMs) and their associated electronics and cable plants. In many locations, these older BPMs include a separate Delta-T loop for measuring the beam's central phase and energy. Thirty-one BPPMs have been installed and many have monitored the charged particle beam. The installation of these newer BPPMs is the first step to installing complete BPPM measurement systems. Prior to the installation, a characterization of each BPPM took place. The characterization procedure includes a mechanical inspection, a vacuum testing, and associated electrical tests. The BPPM electrical tests for all four electrodes include contact resistance measurements, Time Domain Reflectometer (TDR) measurements, relative 201.25-MHz phase measurements, and finally a set of position-sensitive mapping measurements were performed which included associated fitting routines. This paper will show these data for a typical characterized BPPM.

  14. Measuring Dirac CP-violating phase with intermediate energy beta beam facility

    NASA Astrophysics Data System (ADS)

    Bakhti, P.; Farzan, Y.

    2014-02-01

    Taking the established nonzero value of , we study the possibility of extracting the Dirac CP-violating phase by a beta beam facility with a boost factor . We compare the performance of different setups with different baselines, boost factors, and detector technologies. We find that an antineutrino beam from He decay with a baseline of km has a very promising CP-discovery potential using a 500 kton water Cherenkov detector. Fortunately this baseline corresponds to the distance between FermiLAB to Sanford underground research facility in South Dakota.

  15. Analyzing the propagation behavior of scintillation index and bit error rate of a partially coherent flat-topped laser beam in oceanic turbulence.

    PubMed

    Yousefi, Masoud; Golmohammady, Shole; Mashal, Ahmad; Kashani, Fatemeh Dabbagh

    2015-11-01

    In this paper, on the basis of the extended Huygens-Fresnel principle, a semianalytical expression for describing on-axis scintillation index of a partially coherent flat-topped (PCFT) laser beam of weak to moderate oceanic turbulence is derived; consequently, by using the log-normal intensity probability density function, the bit error rate (BER) is evaluated. The effects of source factors (such as wavelength, order of flatness, and beam width) and turbulent ocean parameters (such as Kolmogorov microscale, relative strengths of temperature and salinity fluctuations, rate of dissipation of the mean squared temperature, and rate of dissipation of the turbulent kinetic energy per unit mass of fluid) on propagation behavior of scintillation index, and, hence, on BER, are studied in detail. Results indicate that, in comparison with a Gaussian beam, a PCFT laser beam with a higher order of flatness is found to have lower scintillations. In addition, the scintillation index and BER are most affected when salinity fluctuations in the ocean dominate temperature fluctuations. PMID:26560913

  16. Phase-modulated decoupling and error suppression in qubit-oscillator systems

    NASA Astrophysics Data System (ADS)

    Green, Todd; Biercuk, Michael

    2015-03-01

    A key requirement for scalable QIP is the ability to controllably produce high-fidelity multi-particle entanglement on demand. This is accomplished in experimental systems using a variety of techniques, but a prominent approach relies on the realization of an indirect interaction between basic quantum systems mediated by bosonic oscillator modes. A significant source of infidelity in these experiments is the presence of residual qubit-oscillator entanglement at the conclusion of an interaction period. We demonstrate how the exclusive use of discrete phase shifts in the field moderating the qubit-oscillator interaction - easily implemented with modern synthesizers - is sufficient to both ensure multiple oscillator modes are decoupled and to suppress the effects of fluctuations in the driving field. We present detailed example protocols tailored to the execution of Molmer-Sorensen entangling gates in trapped ion systems and demonstrate that our approach allows multiqubit gate implementation with a significant reduction in technical complexity relative to previously deomstrated protocols.

  17. Application of a transverse phase-space measurement technique for high-brightness, H{sup {minus}} beams to the GTA H{sup {minus}} beam

    SciTech Connect

    Johnson, K.F.; Garcia, R.C.; Rusthoi, D.P.; Sander, O.R.; Sandoval, D.P.; Shinas, M.A.; Smith, M.; Yuan, V.W.; Connolly, R.C.

    1995-05-01

    The Ground Test Accelerator (GTA) had the objective Of Producing a high-brightness, high-current H-beam. The major components were a 35 keV injector, a Radio Frequency Quadrupole (RFQ), an intertank matching section (IMS), and a drift tube linac (DTL), consisting of 10 modules. A technique for measuring the transverse phase-space of high-power density beams has been developed and tested. This diagnostic has been applied to the GTA H-beam. Experimental results are compared to the slit and collector technique for transverse phase-space measurements and to simulations.

  18. Influence of beam-loaded effects on phase-locking in the high power microwave oscillator

    SciTech Connect

    Li, Zhenghong; Zhou, Zhigang; Qiu, Rong

    2014-06-15

    Owing to the power limitation of a single device, much more attentions are focused on developing high power microwave (HPM) oscillators that can be phase-locked to the external signal in the recent HPM researches. Although the phase-locking is proved to be feasible in the conventional devices (such as magnetrons), challenges still exist in the HPM devices due to beam-loaded effects, which are more obvious in HPM devices because of its high current and the low Q-factor of the device. A simple structured HPM oscillator (Bitron) is introduced to study such effects on the phase-locking in the HPM oscillator. The self-consistent analysis is carried out to study such effects together with particle in cell simulations. Then the modified Adler equation is established for the phase-locking HPM oscillator. Finally, conditions for the phase-locking in the HPM oscillator are given.

  19. On Zero Steady-State Error Voltage Control of Single-Phase PWM Inverters With Different Load Types

    SciTech Connect

    Dong, Dong; Timothy, Thacker; Burgos, Rolando; Wang, Fei; Boroyevich, Dushan

    2011-01-01

    This paper comprehensively investigates and compares different multiloop linear control schemes for single-phase pulsewidth modulation inverters, both in stationary and synchronous (d-q) frames, by focusing on their steady-state error under different loading conditions. Specifically, it is shown how proportional plus resonant (P + R) control and load current feedback (LCF) control can, respectively, improve the steady-state and transient performance of the inverter, leading to the proposal of a PID + R + LCF control scheme. Furthermore, the LCF control and capacitive current feedback control schemes are shown to be subject to stability issues under second and higher order filter loads. Additionally, the equivalence between the stationary frame and d-q frame controllers is discussed depending on the orthogonal term generation method, and a d-q frame voltage control strategy is proposed eliminating the need for the generation of this orthogonal component. This is achieved while retaining all the advantages of operating in the synchronous d-q frame, i.e., zero steady-state error and ease of implementation. All theoretical findings are validated experimentally using a 1.5 kW laboratory prototype.

  20. SU-D-19A-04: Parameter Characterization of Electron Beam Monte Carlo Phase Space of TrueBeam Linacs

    SciTech Connect

    Rodrigues, A; Yin, F; Wu, Q; Sawkey, D

    2014-06-01

    Purpose: For TrueBeam Monte Carlo simulations, Varian does not distribute linac head geometry and material compositions, instead providing a phase space file (PSF) for the users. The PSF has a finite number of particle histories and can have very large file size, yet still contains inherent statistical noises. The purpose of this study is to characterize the electron beam PSF with parameters. Methods: The PSF is a snapshot of all particles' information at a given plane above jaws including type, energy, position, and directions. This study utilized a preliminary TrueBeam PSF, of which validation against measurement is presented in another study. To characterize the PSF, distributions of energy, position, and direction of all particles are analyzed as piece-wise parameterized functions of radius and polar angle. Subsequently, a pseudo PSF was generated based on this characterization. Validation was assessed by directly comparing the true and pseudo PSFs, and by using both PSFs in the down-stream MC simulations (BEAMnrc/DOSXYZnrc) and comparing dose distributions for 3 applicators at 15 MeV. Statistical uncertainty of 4% was limited by the number of histories in the original PSF. Percent depth dose (PDD) and orthogonal (PRF) profiles at various depths were evaluated. Results: Preliminary results showed that this PSF parameterization was accurate, with no visible differences between original and pseudo PSFs except at the edge (6 cm off axis), which did not impact dose distributions in phantom. PDD differences were within 1 mm for R{sub 7} {sub 0}, R{sub 5} {sub 0}, R{sub 3} {sub 0}, and R{sub 1} {sub 0}, and PRF field size and penumbras were within 2 mm. Conclusion: A PSF can be successfully characterized by distributions for energy, position, and direction as parameterized functions of radius and polar angles; this facilitates generating sufficient particles at any statistical precision. Analyses for all other electron energies are under way and results will be

  1. Low crosstalk optical hierarchical authentication with a fixed random phase lock based on two beams interference

    NASA Astrophysics Data System (ADS)

    Lu, Dajiang; He, Wenqi; Peng, Xiang

    2015-09-01

    We propose a novel method to achieve the purpose of hierarchical authentication based on two beams interference. In this method, different target images indicating different authentication levels are analytically encoded into corresponding phase-only masks (phase keys) and amplitude-only masks (amplitude keys) with the help of a random phase mask, which is created in advance and acts as the fixed lock of this authentication system. For the authentication process, a legal user can obtain a specified target image at the output plane if his/her phase key, and amplitude key, which should be settled close against the fixed internal phase lock, are respectively illuminated by two coherent beams. By comparing the target image with all the standard certification images in the database, the system can thus verify the user's identity. In simple terms, this system can not only confirm the legality of a user but also distinguish his/her identity level. Moreover, in despite of the internal phase lock of this system being fixed, the crosstalk between different pairs of keys hold by different users is low. Theoretical analysis and numerical simulation are both provided to demonstrate the validity of this method.

  2. Phase-transition oscillations induced by a strongly focused laser beam

    NASA Astrophysics Data System (ADS)

    Devailly, Clémence; Crauste-Thibierge, Caroline; Petrosyan, Artyom; Ciliberto, Sergio

    2015-11-01

    We report the observation of a surprising phenomenon consisting in a oscillating phase transition which appears in a binary mixture when this is enlightened by a strongly focused infrared laser beam. The mixture is poly-methyl-meth-acrylate (PMMA)-3-octanone, which has an upper critical solution temperature at Tc=306.6 K and volume fraction ϕc=12.8 % [Crauste et al., arXiv:1310.6720, 2013]. We describe the dynamical properties of the oscillations, which are produced by a competition between various effects: the local accumulation of PMMA produced by the laser beam, thermophoresis, and nonlinear diffusion. We show that the main properties of this kind of oscillations can be reproduced in the Landau theory for a binary mixture in which a local driving mechanism, simulating the laser beam, is introduced.

  3. Phase-transition oscillations induced by a strongly focused laser beam.

    PubMed

    Devailly, Clémence; Crauste-Thibierge, Caroline; Petrosyan, Artyom; Ciliberto, Sergio

    2015-11-01

    We report the observation of a surprising phenomenon consisting in a oscillating phase transition which appears in a binary mixture when this is enlightened by a strongly focused infrared laser beam. The mixture is poly-methyl-meth-acrylate (PMMA)-3-octanone, which has an upper critical solution temperature at T(c)=306.6K and volume fraction ϕ(c)=12.8% [Crauste et al., arXiv:1310.6720, 2013]. We describe the dynamical properties of the oscillations, which are produced by a competition between various effects: the local accumulation of PMMA produced by the laser beam, thermophoresis, and nonlinear diffusion. We show that the main properties of this kind of oscillations can be reproduced in the Landau theory for a binary mixture in which a local driving mechanism, simulating the laser beam, is introduced. PMID:26651700

  4. Characterization of holographically generated beams via phase retrieval based on Wigner distribution projections.

    PubMed

    Rodrigo, José A; Alieva, Tatiana; Cámara, Alejandro; Martínez-Matos, O; Cheben, Pavel; Calvo, María L

    2011-03-28

    In this work, we propose a robust and versatile approach for the characterization of the complex field amplitude of holographically generated coherent-scalar paraxial beams. For this purpose we apply an iterative algorithm that allows recovering the phase of the generated beam from the measurement of its Wigner distribution projections. Its performance is analyzed for beams of different symmetry: Laguerre-Gaussian, Hermite-Gaussian and spiral ones, which are obtained experimentally by a computer generated hologram (CGH) implemented on a programmable spatial light modulator (SLM). Using the same method we also study the quality of their holographic recording on a highly efficient photopolymerizable glass. The proposed approach is useful for the creation of adaptive CGH that takes into account the peculiarities of the SLM, as well as for the quality control of the holographic data storage. PMID:21451630

  5. Geometrical Optics of Beams with Vortices: Berry Phase and Orbital Angular Momentum Hall Effect

    SciTech Connect

    Bliokh, Konstantin Yu.

    2006-07-28

    We consider propagation of a paraxial beam carrying the spin angular momentum (polarization) and intrinsic orbital angular momentum (IOAM) in a smoothly inhomogeneous isotropic medium. It is shown that the presence of IOAM can dramatically enhance and rearrange the topological phenomena that previously were considered solely in connection to the polarization of transverse waves. In particular, the appearance of a new type of Berry phase that describes the parallel transport of the beam structure along a curved ray is predicted. We derive the ray equations demonstrating the splitting of beams with different values of IOAM. This is the orbital angular momentum Hall effect, which resembles the Magnus effect for optical vortices. Unlike the spin Hall effect of photons, it can be much larger in magnitude and is inherent to waves of any nature. Experimental means to detect the phenomena are discussed.

  6. Developmental Status of Beam Position and Phase Monitor for PEFP Proton Linac

    NASA Astrophysics Data System (ADS)

    Park, Sungju; Park, Jangho; Yu, Inha; Kim, Dotae; Hwang, Jung-Yun; Nam, Sanghoon

    2004-11-01

    The PEFP (Proton Engineering Frontier Project) at the KAERI (Korea Atomic Energy Research Institute) is building a high-power proton linear accelerator aiming to generate 100-MeV proton beams with 20-mA peak current. (Pulse width and max. repetition rate of 1 ms and 120 Hz respectively.) We have developed the Beam Position and Phase Monitor (BPPM) for the machine that features the button-type PU, the full-analog processing electronics, and the EPICS-based control system. The beam responses of the button-type PU have been obtained using the MAGIC (Particle-In-Cell) code. The processing electronics has been developed in collaboration with Bergoz Instrumentation. In this article, we report the present status of the system developments except the control system.

  7. Temperature-fluctuation-sensitive accumulative effect of the phase measurement errors in low-coherence interferometry in characterizing arrayed waveguide gratings.

    PubMed

    Zhao, Changyun; Wei, Bing; Yang, Longzhi; Wang, Gencheng; Wang, Yuehai; Jiang, Xiaoqing; Li, Yubo; Yang, Jianyi

    2015-09-20

    We investigate the accumulative effect of the phase measurement errors in characterizing optical multipath components by low-coherence interferometry. The accumulative effect is caused by the fluctuation of the environment temperature, which leads to the variation of the refractive index of the device under test. The resulting phase measurement errors accumulate with the increasing of the phase difference between the two interferometer arms. Our experiments were carried out to demonstrate that the accumulative effect is still obvious even though the thermo-optical coefficient of the device under test is quite small. Shortening the measurement time to reduce the fluctuation of the environment temperature can effectively restrain the accumulative effect. The experiments show that when the scanning speed increases to 4.8 mm/s, the slope of the phase measurement errors decreases to 5.52×10(-8), which means the accumulative effect can be ignored. PMID:26406502

  8. Phase-only shaping algorithm for Gaussian-apodized Bessel beams.

    PubMed

    Durfee, Charles G; Gemmer, John; Moloney, Jerome V

    2013-07-01

    Gaussian-apodized Bessel beams can be used to create a Bessel-like axial line focus at a distance from the focusing lens. For many applications it is desirable to create an axial intensity profile that is uniform along the Bessel zone. In this article, we show that this can be accomplished through phase-only shaping of the wavefront in the far field where the beam has an annular ring structure with a Gaussian cross section. We use a one-dimensional transform to map the radial input field to the axial Bessel field and then optimized the axial intensity with a Gerchberg-Saxton algorithm. By separating out the quadratic portion of the shaping phase the algorithm converges more rapidly. PMID:23842364

  9. TIME-DEPENDENT PHASE SPACE MEASUREMENTS OF THE LONGITUDINALLY COMPRESSING BEAM IN NDCX-I

    SciTech Connect

    LBNL; Lidia, S.M.; Bazouin, G.; Seidl, P.A.

    2011-03-15

    The Neutralized Drift Compression Experiment (NDCXI) generates high intensity ion beams to explore Warm Dense Matter physics. A {approx}150 kV, {approx}500 ns modulating voltage pulse is applied to a {approx}300 kV, 5-10 {mu}s, 25 mA K+ ion beam across a single induction gap. The velocity modulated beam compresses longitudinally during ballistic transport along a space charge neutralizing plasma transport line, resulting in {approx}3A peak current with {approx}2-3 ns pulse durations (FWHM) at the target plane. Transverse final focusing is accomplished with a {approx}8 T, 10 cm long pulsed solenoid magnet. Time-dependent electrostatic focusing in the induction gap, and chromatic aberrations in the final focus optics limit the peak fluenceat the target plane for the compressed beam pulse. We report on time-dependent phase space measurements of the compressed pulse in the ballistic transport beamline, and measurement of the time-dependent radial impulses derived from the interaction of the beam and the induction gap voltage. We present results of start-to-end simulations to benchmark the experiments. Fast correction strategies are discussed with application to both NDCX-I and the soon to be commissioned NDCX-II accelerators.

  10. Space charge and beam stability issues of the Fermilab proton driver in Phase I

    SciTech Connect

    K. Y. Ng

    2001-08-24

    Issues concerning beam stability of the proposed Fermilab Proton Driver are studied in its Phase I. Although the betatron tune shifts are dominated by space charge, these shifts are less than 0.25 and will therefore not drive the symmetric and antisymmetric modes of the beam envelope into instability. The longitudinal space charge force is large and inductive inserts may be needed to compensate for the distortion of the rf potential. Although the longitudinal impedance is space charge dominated, it will not drive any microwave instability, unless the real part of the impedance coming from the inductive inserts and wall resistivity of the beam tube are large enough. The design of the beam tube is therefore very important in order to limit the flow of eddy current and keep wall resistivity low. The transverse impedance is also space charge dominated. With the Proton Driver operated at an imaginary transition gamma, however, Landau damping will never be canceled and beam stability can be maintained with negative chromaticities.

  11. Experimental Characterization of the Transverse Phase Space of a 60-MeV Electron Beam Through a Compressor Chicane

    SciTech Connect

    Zhou, F.; Kabel, A.; Rosenzweig, J.; Agustsson, R.; Andonian, G.; Cline, D.; Murokh, A.; Yakimenko, V.; /UCLA /SLAC /Brookhaven

    2007-02-12

    Space charge and coherent synchrotron radiation may deteriorate electron beam quality when the beam passes through a magnetic bunch compressor. This paper presents the transverse phase-space tomographic measurements for a compressed beam at 60 MeV, around which energy the first stage of magnetic bunch compression takes place in most advanced linacs. Transverse phase-space bifurcation of a compressed beam is observed at that energy, but the degree of the space charge-induced bifurcation is appreciably lower than the one observed at 12 MeV.

  12. Experiments with active phase matching of parallel-amplified multiline HF laser beams by a phase-locked Mach-Zehnder interferometer

    NASA Astrophysics Data System (ADS)

    Coffer, J. G.; Bernard, J. M.; Chodzko, R. A.; Turner, E. B.; Gross, R. W. F.; Warren, W. R.

    1983-01-01

    Active phase matching of multiline HF laser beams by means of a phase-locked Mach-Zehnder interferometer was demonstrated by locking the interferometer to the central interference fringe at zero optical path length difference. The central fringe could be found by varying the spectral content of the input beam. Laser amplification in one leg of the interferometer decreased fringe visibility without adversely affecting locking. Single-line fringe patterns produced by an array spectrometer (while the interferometer was operated in its scanning mode) were analyzed to show that no significant dispersion occurred in the amplifier. The techniques developed have potential for measuring dispersion mismatch between larger parallel amplifiers. These experiments demonstrated in principle that a number of multiline HF amplified beams can be recombined and phase-matched to produce a high beam quality output beam.

  13. Projection phase contrast microscopy with a hard x-ray nanofocused beam: Defocus and contrast transfer

    SciTech Connect

    Salditt, T.; Giewekemeyer, K.; Fuhse, C.; Krueger, S. P.; Tucoulou, R.; Cloetens, P.

    2009-05-01

    We report a projection phase contrast microscopy experiment using hard x-ray pink beam undulator radiation focused by an adaptive mirror system to 100-200 nm spot size. This source is used to illuminate a lithographic test pattern with a well-controlled range of spatial frequencies. The oscillatory nature of the contrast transfer function with source-to-sample distance in this holographic imaging scheme is quantified and the validity of the weak phase object approximation is confirmed for the experimental conditions.

  14. Overview of results from phase I of the Beam Energy Scan program at RHIC

    NASA Astrophysics Data System (ADS)

    McDonald, Daniel

    2015-05-01

    The first phase of the Beam Energy Scan (BES) program at the Relativistic Heavy Ion Collider (RHIC) was successfully completed during the years 2010, 2011 and 2014, with Au+Au collisions at center-of-mass energies (√sNN) of 7.7, 11.5, 14.5, 19.6, 27, and 39 GeV. The BES has three distinct goals: search for the turning off of the signatures of the Quark Gluon Plasma (QGP), search for the first-order phase transition, and search for the critical point. We report several interesting results that address each of these goals of the BES program.

  15. Spiral phase plates for the generation of high-order Laguerre-Gaussian beams with non-zero radial index

    NASA Astrophysics Data System (ADS)

    Ruffato, G.; Carli, M.; Massari, M.; Romanato, F.

    2015-03-01

    The work of design, fabrication and characterization of spiral phase plates for the generation of Laguerre-Gaussian (LG) beams with non-null radial index is presented. Samples were fabricated by electron beam lithography on polymethylmethacrylate layers over glass substrates. The optical response of these phase optical elements was measured and the purity of the experimental beams was investigated in terms of Laguerre-Gaussian modes contributions. The farfield intensity pattern was compared with theoretical models and numerical simulations, while the expected phase features were confirmed by interferometric analyses. The high quality of the output beams confirms the applicability of these phase plates for the generation of high-order Laguerre-Gaussian beams. A novel application consisting in the design of computer-generated holograms encoding information for light beams carrying phase singularities is shown. A numerical code based on iterative Fourier transform algorithm has been developed for the computation of the phase pattern of phase-only diffractive optical element for illumination under LG beams. Numerical analysis and preliminary experimental results confirm the applicability of these devices as high-security optical elements.

  16. Optical beam steering using surface micromachined gratings and optical phased arrays

    NASA Astrophysics Data System (ADS)

    Burns, David M.; Bright, Victor M.; Gustafson, Steven C.; Watson, Edward A.

    1997-07-01

    Two categories of optical beam steering micro-electro- mechanical systems (MEMS) were investigated: variable blaze gratings (VBGs) and linear optical phased arrays. All devices were surface micromachined using the multi-user MEMS processes (MUMPs). VBGs use an adjustable blaze angle to direct the majority of reflected light into a selectable diffraction order. Diffraction efficiencies greater than 50% were demonstrated. Linear optical phased arrays use a single row of piston micromirrors to create a far-field pattern with a steerable main lobe along one axis. All devices were constructed of polysilicon and gold and were actuated with electrostatic force. Electrostatic actuation provides high speed operation at a very low drive power. These optical beam steering devices discussed in this work are less optically efficient than a single pivoting mirror, but they require no post-fabrication assembly and can handle large beam diameters. Also, the low individual mass of the elements in surface micromachined VBGs and optical phased arrays yield faster system response times than a single macroscale pivoting mirror.

  17. Control of phased-array antennas

    NASA Astrophysics Data System (ADS)

    Samoilenko, V. I.; Shishov, Iu. A.

    Principles and algorithms for the control of phased arrays are described. Particular consideration is given to algorithms for the control of phase distribution, adaptive arrays, beam-steerable arrays, the design of phase shifters, the compensation of beam-pointing errors, and the calibration of high-gain antenna pointing.

  18. Two-dimensional phase unwrapping to help characterize an electromagnetic beam for quasi-optical mode converter design.

    PubMed

    Perkins, Michael P; Vernon, Ronald J

    2008-12-10

    An improved two-dimensional phase unwrapping procedure is discussed that uses a weighted least-squares algorithm, a congruence operation, and a filter to unwrap the phase distribution of an electromagnetic beam. These improvements make possible several advances for mirror designs used in gyrotron quasi-optical mode converters. The improved phase unwrapping procedure is demonstrated by applying it to a measured beam and a simulated beam that are used to design mirrors. The unwrapping procedure produces a smooth unwrapped phase that does not change the characteristics of the beam. The smooth unwrapped phase distribution is also used to find an estimate for the wavenumber vector distribution that is needed to design the mirrors. PMID:19079470

  19. The backward phase flow and FBI-transform-based Eulerian Gaussian beams for the Schrödinger equation

    NASA Astrophysics Data System (ADS)

    Leung, Shingyu; Qian, Jianliang

    2010-11-01

    We propose the backward phase flow method to implement the Fourier-Bros-Iagolnitzer (FBI)-transform-based Eulerian Gaussian beam method for solving the Schrödinger equation in the semi-classical regime. The idea of Eulerian Gaussian beams has been first proposed in [12]. In this paper we aim at two crucial computational issues of the Eulerian Gaussian beam method: how to carry out long-time beam propagation and how to compute beam ingredients rapidly in phase space. By virtue of the FBI transform, we address the first issue by introducing the reinitialization strategy into the Eulerian Gaussian beam framework. Essentially we reinitialize beam propagation by applying the FBI transform to wavefields at intermediate time steps when the beams become too wide. To address the second issue, inspired by the original phase flow method, we propose the backward phase flow method which allows us to compute beam ingredients rapidly. Numerical examples demonstrate the efficiency and accuracy of the proposed algorithms.

  20. Error localization in RHIC by fitting difference orbits

    SciTech Connect

    Liu C.; Minty, M.; Ptitsyn, V.

    2012-05-20

    The presence of realistic errors in an accelerator or in the model used to describe the accelerator are such that a measurement of the beam trajectory may deviate from prediction. Comparison of measurements to model can be used to detect such errors. To do so the initial conditions (phase space parameters at any point) must be determined which can be achieved by fitting the difference orbit compared to model prediction using only a few beam position measurements. Using these initial conditions, the fitted orbit can be propagated along the beam line based on the optics model. Measurement and model will agree up to the point of an error. The error source can be better localized by additionally fitting the difference orbit using downstream BPMs and back-propagating the solution. If one dominating error source exist in the machine, the fitted orbit will deviate from the difference orbit at the same point.

  1. Cherenkov phase-matching in Raman-seeded four-wave mixing by a femtosecond Bessel beam

    NASA Astrophysics Data System (ADS)

    Blonskyi, I.; Kadan, V.; Dmitruk, I.; Korenyuk, P.

    2012-06-01

    It is demonstrated experimentally that the angle vs. wavelength dependence of the emission generated by multi-step four-wave mixing process seeded by stimulated Raman scattering in water under femtosecond Bessel beam excitation is determined by the longitudinal phase-matching from IR to near UV. It is shown that if on-axis phase velocity of the pump Bessel beam is equal to the phase velocity of the Stokes axial wave, then, similar to Cherenkov radiation, all the other anti-Stokes beams too acquire that axial velocity.

  2. Influence of Head Motion on the Accuracy of 3D Reconstruction with Cone-Beam CT: Landmark Identification Errors in Maxillofacial Surface Model

    PubMed Central

    Song, Jin-Myoung; Cho, Jin-Hyoung

    2016-01-01

    Purpose The purpose of this study was to investigate the influence of head motion on the accuracy of three-dimensional (3D) reconstruction with cone-beam computed tomography (CBCT) scan. Materials and Methods Fifteen dry skulls were incorporated into a motion controller which simulated four types of head motion during CBCT scan: 2 horizontal rotations (to the right/to the left) and 2 vertical rotations (upward/downward). Each movement was triggered to occur at the start of the scan for 1 second by remote control. Four maxillofacial surface models with head motion and one control surface model without motion were obtained for each skull. Nine landmarks were identified on the five maxillofacial surface models for each skull, and landmark identification errors were compared between the control model and each of the models with head motion. Results Rendered surface models with head motion were similar to the control model in appearance; however, the landmark identification errors showed larger values in models with head motion than in the control. In particular, the Porion in the horizontal rotation models presented statistically significant differences (P < .05). Statistically significant difference in the errors between the right and left side landmark was present in the left side rotation which was opposite direction to the scanner rotation (P < .05). Conclusions Patient movement during CBCT scan might cause landmark identification errors on the 3D surface model in relation to the direction of the scanner rotation. Clinicians should take this into consideration to prevent patient movement during CBCT scan, particularly horizontal movement. PMID:27065238

  3. SU-E-J-103: Setup Errors Analysis by Cone-Beam CT (CBCT)-Based Imaged-Guided Intensity Modulated Radiotherapy for Esophageal Cancer

    SciTech Connect

    Yang, H; Wang, W; Hu, W; Chen, X; Wang, X; Yu, C

    2014-06-01

    Purpose: To quantify setup errors by pretreatment kilovolt cone-beam computed tomography(KV-CBCT) scans for middle or distal esophageal carcinoma patients. Methods: Fifty-two consecutive middle or distal esophageal carcinoma patients who underwent IMRT were included this study. A planning CT scan using a big-bore CT simulator was performed in the treatment position and was used as the reference scan for image registration with CBCT. CBCT scans(On-Board Imaging v1. 5 system, Varian Medical Systems) were acquired daily during the first treatment week. A total of 260 CBCT scans was assessed with a registration clip box defined around the PTV-thorax in the reference scan based on(nine CBCTs per patient) bony anatomy using Offline Review software v10.0(Varian Medical Systems). The anterior-posterior(AP), left-right(LR), superiorinferior( SI) corrections were recorded. The systematic and random errors were calculated. The CTV-to-PTV margins in each CBCT frequency was based on the Van Herk formula (2.5Σ+0.7σ). Results: The SD of systematic error (Σ) was 2.0mm, 2.3mm, 3.8mm in the AP, LR and SI directions, respectively. The average random error (σ) was 1.6mm, 2.4mm, 4.1mm in the AP, LR and SI directions, respectively. The CTV-to-PTV safety margin was 6.1mm, 7.5mm, 12.3mm in the AP, LR and SI directions based on van Herk formula. Conclusion: Our data recommend the use of 6 mm, 8mm, and 12 mm for esophageal carcinoma patient setup in AP, LR, SI directions, respectively.

  4. Spiral phase plates with radial discontinuities for the generation of multiring orbital angular momentum beams: fabrication, characterization, and application

    NASA Astrophysics Data System (ADS)

    Ruffato, Gianluca; Massari, Michele; Carli, Marta; Romanato, Filippo

    2015-11-01

    A design of spiral phase plates for the generation of multiring beams carrying orbital angular momentum (OAM) is presented. Besides the usual helical profile, these phase plates present radial π-discontinuities in correspondence of the zeros of the associated Laguerre polynomials. Samples were fabricated by electron beam lithography over glass substrates coated with a polymethylmethacrylate resist layer. The optical response was analyzed and the purity of the generated beams was investigated in terms of Laguerre-Gaussian modes contributions. The far-field intensity pattern was compared with theoretical models and numerical simulations, while the expected phase features were confirmed by interferometric analysis with a Mach-Zehnder setup. The high quality of the output beams confirms the applicability of these phase plates for the generation of high-order OAM beams with nonzero radial index. An application consisting of the design of computer-generated holograms encoding information for light beams carrying phase singularities is presented and described. A numerical code based on an iterative Fourier transform algorithm has been developed for the computation of phase-only diffractive optical element for illumination under OAM beams. Numerical analysis and preliminary experimental results confirm the applicability of these devices as high-security optical elements for anticounterfeiting applications.

  5. Generalized propagation law of laser beam parameters through thin pure-phase transmittances

    NASA Astrophysics Data System (ADS)

    Piquero, Gemma; Mejias, Pedro M.; Martinez-Herrero, Rosario

    1996-11-01

    As is well-known, pure-phase transmittances are not, in general, first-order optical systems. It thus seems that a simple ABCD-propagation law cannot be applied to this kind of transmittance. In other words, such optical elements could not be characterized by an overall ABCD matrix. The aim of the present contribution is to overcome this trouble. In fact, the propagation laws of the intensity moments of a laser beam through ABCD optical systems are generalized to include pure phase transmittances. This is done by representing the behavior of such transmittances by means of a 4 by 4 matrix, M, which can be handled, to some extent, as the ABCD-matrices associated with ordinary first-order optical systems. This formalism enables the application of ABCD propagation formulae to cascaded optical systems containing pure phase transmittances. Matrix M is applied, in particular, to determine the intensity moments and the beam quality parameter at the output of special quartic phase transmittances, namely, thin and thick spherically aberrated lenses.

  6. Ion beam-induced amorphous-to-tetragonal phase transformation and grain growth of nanocrystalline zirconia

    SciTech Connect

    Lian, Jie; Zhang, Jiaming; Namavar, Fereydoon; Zhang, Yanwen; Lu, Fengyuan; Haider, Hani; Garvin, Kevin; Weber, William J.; Ewing, Rodney C.

    2009-05-26

    Nanocrystalline zirconia has recently attracted extensive research interest due to its unique mechanical, thermal and electrical properties as compared to bulk zirconia counterparts, and it is of particular importance to control the phase stability of different polymorphs (amorphous, cubic, tetragonal and monoclinic phases) at different size regimes. In this paper, we performed ion beam bombardments on bilayers (amorphous and cubic) of pure nano-zirconia using 1 MeV Kr2+ irradiation. Transmission electron microscopy (TEM) analysis reveals that amorphous zirconia transforms to a tetragonal structure under irradiation at room temperature, suggesting that the tetragonal phase is more energetically favorable under these conditions. The final grain size of the tetragonal zirconia can be controlled by irradiation conditions. The irradiation-induced nanograins of tetragonal ZrO2 are stable at ambient conditions and maintain their physical integrity over a long period of time after irradiation. These results demonstrated that ion-beam modification methods provide the means to control the phase stability and structure of zirconia polymorphs.

  7. Two dimensional thermo-optic beam steering using a silicon photonic optical phased array

    NASA Astrophysics Data System (ADS)

    Mahon, Rita; Preussner, Marcel W.; Rabinovich, William S.; Goetz, Peter G.; Kozak, Dmitry A.; Ferraro, Mike S.; Murphy, James L.

    2016-03-01

    Components for free space optical communication terminals such as lasers, amplifiers, and receivers have all seen substantial reduction in both size and power consumption over the past several decades. However, pointing systems, such as fast steering mirrors and gimbals, have remained large, slow and power-hungry. Optical phased arrays provide a possible solution for non-mechanical beam steering devices that can be compact and lower in power. Silicon photonics is a promising technology for phased arrays because it has the potential to scale to many elements and may be compatible with CMOS technology thereby enabling batch fabrication. For most free space optical communication applications, two-dimensional beam steering is needed. To date, silicon photonic phased arrays have achieved two-dimensional steering by combining thermo-optic steering, in-plane, with wavelength tuning by means of an output grating to give angular tuning, out-of-plane. While this architecture might work for certain static communication links, it would be difficult to implement for moving platforms. Other approaches have required N2 controls for an NxN element phased array, which leads to complexity. Hence, in this work we demonstrate steering using the thermo-optic effect for both dimensions with a simplified steering mechanism requiring only two control signals, one for each steering dimension.

  8. Study of Optical Phase Lock Loops and the Applications in Coherent Beam Combining and Coherence Cloning

    NASA Astrophysics Data System (ADS)

    Liang, Wei

    Optical Phase-Lock loops (OPLLs) have potential applications in phase coherent optics including frequency synthesis, clock distribution and recovery, jitter and noise reduction, etc. However, most implemented OPLLs are based on solid state lasers, fiber lasers, or specially designed semiconductor lasers, whose bulky size and high cost inhibit the applications of OPLLs. Semiconductor lasers have the advantages of low cost, small size, and high efficiency. In this thesis, I report on a study of OPLLs using commercial SCLs, and explore their novel applications in coherent beam combining and coherence cloning. In chapter 1-3, I will first introduce the theory of OPLLs and presents the experimental study of OPLLs made of different commercial SCLs. To improve the performance of OPLLs, electronic compensations using filter designs are also discussed and studied. In chapter 4-5, I will study the application of OPLLs in coherent beam combining. Using OPLLs, an array of slave lasers can be phase locked to the same master laser at the same frequency, their outputs can then be coherently combined. The phase variations of the element beams due to the optical path-length variations in fibers can be further corrected for by using multi-level OPLLs. This approach eliminates the use of the optical phase/frequency shifters conventionally required in a coherent beam combining system. In the proof of principle experiment, we have combined two lasers with a combining efficiency of 94% using the filled-aperture combining configuration. Furthermore, I will discuss the scalability of a cascaded filled-aperture combining system for the combination of a large number of lasers. OPLLs can also be used to reduce the phase noise of SCLs by locking them to a low noise master laser. In chapter 6, I will describe the theory of coherence cloning using OPLLs and present the experimental measurements of the linewidths and frequency noises of a low noise fiber laser, a free-running and locked slave

  9. Structure-phase states evolution in Al-Si alloy under electron-beam treatment and high-cycle fatigue

    SciTech Connect

    Konovalov, Sergey Alsaraeva, Krestina Gromov, Victor Semina, Olga; Ivanov, Yurii

    2015-10-27

    By methods of scanning and transmission electron diffraction microscopy the analysis of structure-phase states and defect substructure of silumin subjected to high-intensity electron beam irradiation in various regimes and subsequent fatigue loading up to failure was carried out. It is revealed that the sources of fatigue microcracks are silicon plates of micron and submicron size are not soluble in electron beam processing. The possible reasons of the silumin fatigue life increase under electron-beam treatment are discussed.

  10. Generation of acoustic self-bending and bottle beams by phase engineering

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Li, Tongcang; Zhu, Jie; Zhu, Xuefeng; Yang, Sui; Wang, Yuan; Yin, Xiaobo; Zhang, Xiang

    2014-07-01

    Directing acoustic waves along curved paths is critical for applications such as ultrasound imaging, surgery and acoustic cloaking. Metamaterials can direct waves by spatially varying the material properties through which the wave propagates. However, this approach is not always feasible, particularly for acoustic applications. Here we demonstrate the generation of acoustic bottle beams in homogeneous space without using metamaterials. Instead, the sound energy flows through a three-dimensional curved shell in air leaving a close-to-zero pressure region in the middle, exhibiting the capability of circumventing obstacles. By designing the initial phase, we develop a general recipe for creating self-bending wave packets, which can set acoustic beams propagating along arbitrary prescribed convex trajectories. The measured acoustic pulling force experienced by a rigid ball placed inside such a beam confirms the pressure field of the bottle. The demonstrated acoustic bottle and self-bending beams have potential applications in medical ultrasound imaging, therapeutic ultrasound, as well as acoustic levitations and isolations.

  11. Focusing field of the radial vector beams with multi-vortex phases

    NASA Astrophysics Data System (ADS)

    Huang, Shuai; Wang, Xiaolei; Zhu, Zhuqing; Gong, Liping; Zhu, Bowen; Song, Lipei

    2016-05-01

    Based on vector diffraction theory, which was described originally by Richards and Wolf, we calculate the focusing fields of the radial vector beams loading two, three and four vortex phases. The calculations and simulations show that one, two and three optical dark-holes could be generated in the focusing field by a high numerical aperture for the two, three and four vortex phases, respectively. In addition, the distances between the optical dark-holes are positively correlated with the distances between vortex phases. Based on this study, the generation of the optical dark-hole and the manipulation of the dark-hole's distance may be used in the capture and manipulation of multiple particles.

  12. Improvement in underwater phase measurement of an amplitude-modulated laser beam by polarimetric techniques.

    PubMed

    Bartolini, L; De Dominicis, L; Fornetti, G; Francucci, M; Guarneri, M; Poggi, C; Ricci, R

    2007-06-01

    The phase of the amplitude-modulated radiation reflected by a Lambertian target immersed in water was measured by using a linearly and circularly polarized sounding laser beam. Different values of the water extinction coefficient in the range of 0.06 - 2 m(-1) were realized by adding skim milk as a scattering element. It is shown that very efficient rejection of optical noise, resulting in reliable phase measurements, is accomplished with a cross-polarized and copolarized detection scheme for linear and circular polarization, respectively. The experiment demonstrates that phase measurements are very sensitive to optical noise suppression and that, as far as single scattering is the main involved mechanism, significant improvements can be achieved by adopting a polarization control on both the transmitter and the receiver stages of the apparatus. PMID:17546135

  13. Phase Contrast Cone Beam Tomography with an X-Ray Grating Interferometer

    NASA Astrophysics Data System (ADS)

    Jerjen, I.; Revol, V.; Kottler, C.; Luethi, Th.; Sennhauser, U.; Kaufmann, R.; Urban, C.

    2010-04-01

    We report on our recent developments of reconstruction algorithms for Differential Phase Contrast X-ray Computed Tomography (DPC CT). DPC images provide information about the real and imaginary part of the refractive index which is an advantage when objects with poor absorption but good phase contrast are inspected. In order to promote DPC CT for industrial applications we developed an adapted Feldkamp algorithm which allows reconstructing the three-dimensional image of the refractive index of an object from the DPC projections obtained with our large field of view, high energy grating interferometer set up in a cone beam geometry. We present slice images of a test object and show different ways of visualization of the phase and absorption information.

  14. Controllable high-quality electron beam generation by phase slippage effect in layered targets

    SciTech Connect

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

    2014-11-15

    The bubble structure generated by laser-plasma interactions changes in size depending on the local plasma density. The self-injection electrons' position with respect to wakefield can be controlled by tailoring the longitudinal plasma density. A regime to enhance the energy of the wakefield accelerated electrons and to improve the beam quality is proposed and achieved using layered plasmas with increasing densities. Both the wakefield size and the electron bunch duration are significantly contracted in this regime. The electrons remain in the strong acceleration phase of the wakefield, while their energy spread decreases because of their tight spatial distribution. An electron beam of 0.5 GeV with less than 1% energy spread is obtained through 2.5D particle-in-cell simulations.

  15. Angular beam width of a slit-diffracted wave with noncollinear group and phase velocities

    NASA Astrophysics Data System (ADS)

    Lock, Edwin H.

    2012-12-01

    Taking magnetostatic surface wave diffraction as an example, this paper theoretically investigates the 2D diffraction pattern arising in the far-field region of a ferrite slab in the case of a plane wave with noncollinear group and phase velocities incident on a wide, arbitrarily oriented slit in an opaque screen. A universal analytical formula for the angular width of a diffracted beam is derived, which is valid for magnetostatic and other types of waves in anisotropic media and structures (including metamaterials) in 2D geometries. It is shown that the angular width of a diffracted beam in an anisotropic medium can not only take values greater or less than \\lambda _0/D (where \\lambda _0 is the incident wavelength, and D is the slit width), but can also be zero under certain conditions.

  16. Coherent beam combining using a 2D internally sensed optical phased array.

    PubMed

    Roberts, Lyle E; Ward, Robert L; Sutton, Andrew J; Fleddermann, Roland; de Vine, Glenn; Malikides, Emmanuel A; Wuchenich, Danielle M R; McClelland, David E; Shaddock, Daniel A

    2014-08-01

    Coherent combination of multiple lasers using an optical phased array (OPA) is an effective way to scale optical intensity in the far field beyond the capabilities of single fiber lasers. Using an actively phase locked, internally sensed, 2D OPA we demonstrate over 95% fringe visibility of the interfered beam, λ/120 RMS output phase stability over a 5 Hz bandwidth, and quadratic scaling of intensity in the far field using three emitters. This paper presents a new internally sensed OPA architecture that employs a modified version of digitally enhanced heterodyne interferometry (DEHI) based on code division multiplexing to measure and control the phase of each emitter. This internally sensed architecture can be implemented with no freespace components, offering improved robustness to shock and vibration exhibited by all-fiber devices. To demonstrate the concept, a single laser is split into three channels/emitters, each independently controlled using separate electro-optic modulators. The output phase of each channel is measured using DEHI to sense the small fraction of light that is reflected back into the fiber at the OPA's glass-air interface. The relative phase between emitters is used to derive the control signals needed to stabilize their relative path lengths and maintain coherent combination in the far field. PMID:25090317

  17. Numerical simulation of gas-solid two-phase flow in U-beam separator

    NASA Astrophysics Data System (ADS)

    Zhou, X. Y.; Zhang, H. Z.; Chen, X. P.; Ruan, J. M.; Dou, H. S.

    2015-01-01

    Numerical simulation is carried out for gas-solid two-phase flow in a U-beam separator. In this study, the U-beam is altered with the inlet fins in order to improve the performance of the separator. The inlet fin angle of the separator are 30°, 35°, 40°, 45°, 50°, 55 ° and 60°. The governing equations are the Reynolds-Averaged Navier-Stokes equation with the standard k-epsilon model and the discrete phase model (DPM) describing the discrete two - phase flow as well as stochastic tracking model. Results show that the pressure drop deviation with fins is within 3% from those without fins. It is found that there is a maximum separation efficiency at the fin angle of 35°. Fin induces generation of a stagnation region which could collect particles and lead to change of vortical structures. The fin induced flow also causes the turbulent intensity inside the baffle to decrease to facilitate separation.

  18. Theory of laser beam apodization with a graded random phase window.

    PubMed

    Haas, R A

    1988-07-01

    Analysis indicates that graded random phase modulation can be used to apodize a laser beam. In the case of an obscuration or hard edge, it can prevent the formation of Fresnel diffraction ripples. For example, suppose laser radiation of wavelength lambda interacts with a central obscuration of halfwidth a followed immediately by a window. If the exit surface of the window is randomly modulated with a Gaussian amplitude transverse correlation length l and a mean square amplitude t 2(r) that decreases smoothly from a peak height at the obstacle of ~(2) with a transverse scale length L > a > l, then the Fresnel diffraction ripples normally produced by the obscuration are eliminated. Following the apodizer the laser beam consists of two components. One is widely scattered with mean intensity I (s). The other is essentially tunscattered and apodized with mean intensity I (a). The scattered light has an angular divergence proportional to lambda/l. The apodizer intensity transmission is T(a) = exp[-alpha(2)t (2)(r)], where alpha = 2pir(n - 1)/lambda and n is the window refractive index. Tayloring t (2)(r) can produce desired apodization profiles for hard edges and obscurations. Interference between the scattered and unscattered radiation produces intensity fluctuations on the laser beam that have the characteristics of laser speckle. The magnitude of these fluctuations is greatest near the apodizer and at the edge of the apodized beam. The local intensity probability density of the fluctuations is approximately the modified Rician density. Using this distribution the probability of intensity fluctuations exceeding a given value I/I (a) is calculated for several values of r = I (a)/I (s). It is found that for high power applications minimization of optical damage requires r greater, similar 100. This may be achieved by minimizing the correlation length l of the apodizer surface modulation, spatial filtering the beam, and/or placing optical components a sufficient distance

  19. Transcranial phase aberration correction using beam simulations and MR-ARFI

    SciTech Connect

    Vyas, Urvi Kaye, Elena; Pauly, Kim Butts

    2014-03-15

    Purpose: Transcranial magnetic resonance-guided focused ultrasound surgery is a noninvasive technique for causing selective tissue necrosis. Variations in density, thickness, and shape of the skull cause aberrations in the location and shape of the focal zone. In this paper, the authors propose a hybrid simulation-MR-ARFI technique to achieve aberration correction for transcranial MR-guided focused ultrasound surgery. The technique uses ultrasound beam propagation simulations with MR Acoustic Radiation Force Imaging (MR-ARFI) to correct skull-caused phase aberrations. Methods: Skull-based numerical aberrations were obtained from a MR-guided focused ultrasound patient treatment and were added to all elements of the InSightec conformal bone focused ultrasound surgery transducer during transmission. In the first experiment, the 1024 aberrations derived from a human skull were condensed into 16 aberrations by averaging over the transducer area of 64 elements. In the second experiment, all 1024 aberrations were applied to the transducer. The aberrated MR-ARFI images were used in the hybrid simulation-MR-ARFI technique to find 16 estimated aberrations. These estimated aberrations were subtracted from the original aberrations to result in the corrected images. Each aberration experiment (16-aberration and 1024-aberration) was repeated three times. Results: The corrected MR-ARFI image was compared to the aberrated image and the ideal image (image with zero aberrations) for each experiment. The hybrid simulation-MR-ARFI technique resulted in an average increase in focal MR-ARFI phase of 44% for the 16-aberration case and 52% for the 1024-aberration case, and recovered 83% and 39% of the ideal MR-ARFI phase for the 16-aberrations and 1024-aberration case, respectively. Conclusions: Using one MR-ARFI image and noa priori information about the applied phase aberrations, the hybrid simulation-MR-ARFI technique improved the maximum MR-ARFI phase of the beam's focus.

  20. Relative phase interactions of two copropagating laser beams in underdense plasmas at different intensities and spot sizes

    SciTech Connect

    Mahdy, A. I.

    2010-06-15

    The mutual interactions of two copropagating laser beams at a relative phase are studied using a two-dimensional fluid code. The interactions are investigated in underdense plasma at selected beam configurations and beam parameters for two separate nonlinearities, i.e., the ponderomotive and the relativistic nonlinearity. The selected beam configurations are introduced by different initial transverse spot size perturbations (finite and infinite) and different initial transversal intensity distributions (nonuniform and uniform) over those spot sizes and the selected beam parameters are given by different initial beam intensities relevant to each nonlinearity. In the ponderomotive nonlinearity, simulation results show that no mutual interactions are demonstrated between the copropagating beams regardless of the initial beam configurations and parameters. In nonlinear relativistic simulations, the mutual interactions between the beams are clearly observed, a mutual repulsion is formed in the presence of initial intensities that are nonuniformly distributed over finite spot sizes, and an effective strongly modulated mutual attraction takes places in the presence of initial intensities that are uniformly distributed over infinite spot sizes. Moreover, it is found in these simulations that increasing the initial beam intensities improves the attraction properties between the copropagationg beams.

  1. Coherent beam combiner for a high power laser

    DOEpatents

    Dane, C. Brent; Hackel, Lloyd A.

    2002-01-01

    A phase conjugate laser mirror employing Brillouin-enhanced four wave mixing allows multiple independent laser apertures to be phase locked producing an array of diffraction-limited beams with no piston phase errors. The beam combiner has application in laser and optical systems requiring high average power, high pulse energy, and low beam divergence. A broad range of applications exist in laser systems for industrial processing, especially in the field of metal surface treatment and laser shot peening.

  2. Diffraction-free optical beam propagation with near-zero phase variation in extremely anisotropic metamaterials

    NASA Astrophysics Data System (ADS)

    Sun, Lei; Yang, Xiaodong; Wang, Wei; Gao, Jie

    2015-03-01

    Extremely anisotropic metal-dielectric multilayer metamaterials are designed to have the effective permittivity tensor of a transverse component (parallel to the interfaces of the multilayer) with zero real part and a longitudinal component (normal to the interfaces of the multilayer) with ultra-large imaginary part at the same wavelength, including the optical nonlocality analysis based on the transfer-matrix method. The diffraction-free deep-subwavelength optical beam propagation with near-zero phase variation in the designed multilayer stack due to the near-flat iso-frequency contour is demonstrated and analyzed, including the effects of the multilayer period and the material loss.

  3. Topics on RF beam control of a synchrotron

    SciTech Connect

    Zhang, S.Y.; Weng, W.T.

    1992-07-13

    In this paper, several typical situations of longitudinal motion in synchrotron design and operation are studied. The study is based on a unified beam dynamic model of synchrotron oscillation under phase and radial feedbacks. Cases studied include frequency error, lock-in range, bunch excursion, phase manipulation, injection and field errors.

  4. Molecular beam epitaxy of single phase GeMnTe with high ferromagnetic transition temperature.

    PubMed

    Hassan, M; Springholz, G; Lechner, R T; Groiss, H; Kirchschlager, R; Bauer, G

    2011-05-15

    Ferromagnetic Ge(1-x)Mn(x)Te is a promising candidate for diluted magnetic semiconductors because solid solutions exist over a wide range of compositions up to x(Mn)≈0.5, where a maximum in the total magnetization occurs. In this work, a systematic study of molecular beam epitaxy of GeMnTe on (1 1 1) BaF(2) substrates is presented, in which the Mn concentration as well as growth conditions were varied over a wide range. The results demonstrate that single phase growth of GeMnTe can be achieved only in a narrow window of growth conditions, whereas at low as well as high temperatures secondary phases or even phase separation occurs. The formation of secondary phases strongly reduces the layer magnetization as well as the Curie temperatures. Under optimized conditions, single phase GeMnTe layers are obtained with Curie temperatures as high as 200 K for Mn concentrations close to the solubility limit of x(Mn)=50%. PMID:21776175

  5. Fully phase multiple information encoding based on superposition of two beams and Fresnel-transform domain

    NASA Astrophysics Data System (ADS)

    Abuturab, Muhammad Rafiq

    2015-12-01

    A novel asymmetric multiple information encoding using superposition of two beams and Fresnel transform, is proposed. In this scheme, each channel of individual user image is separately phase encoded and then modulated by random phase mask. The three modulated user channels are independently multiplied to produce three complex user channels. They are individually multiplied with three channels of carrier image and Fresnel transformed, and then phase- and amplitude truncated to produce first set of three encrypted channels and three asymmetric keys. Now each channel of secret image is normalized, phase-only masked, and then independently multiplied by corresponding modulated user channels. The three resultant channels are separately multiplied to construct three complex secret channels. Afterward, the three encrypted channels are multiplied with corresponding three complex secret channels and Fresnel transformed, and then phase- and amplitude truncated to obtain second set of three encrypted channels and three asymmetric keys. The wavelengths and propagation distances of two Fresnel transforms, and two asymmetric keys are common keys to all authorized-users, while two individual keys are provided to each authorized-user. The encryption process is implemented digitally while the decryption process can be performed optoelectronically. The proposed method is asymmetric, noniterative and larger multiplexing capacity without any cross-talk noise effects. Owing to the individual user image based method, high robustness against existing attacks can be achieved. Numerical simulation results demonstrate that the proposed method is feasible and efficient.

  6. A study of respiration-correlated cone-beam CT scans to correct target positioning errors in radiotherapy of thoracic cancer

    SciTech Connect

    Santoro, J. P.; McNamara, J.; Yorke, E.; Pham, H.; Rimner, A.; Rosenzweig, K. E.; Mageras, G. S.

    2012-10-15

    Purpose: There is increasingly widespread usage of cone-beam CT (CBCT) for guiding radiation treatment in advanced-stage lung tumors, but difficulties associated with daily CBCT in conventionally fractionated treatments include imaging dose to the patient, increased workload and longer treatment times. Respiration-correlated cone-beam CT (RC-CBCT) can improve localization accuracy in mobile lung tumors, but further increases the time and workload for conventionally fractionated treatments. This study investigates whether RC-CBCT-guided correction of systematic tumor deviations in standard fractionated lung tumor radiation treatments is more effective than 2D image-based correction of skeletal deviations alone. A second study goal compares respiration-correlated vs respiration-averaged images for determining tumor deviations. Methods: Eleven stage II-IV nonsmall cell lung cancer patients are enrolled in an IRB-approved prospective off-line protocol using RC-CBCT guidance to correct for systematic errors in GTV position. Patients receive a respiration-correlated planning CT (RCCT) at simulation, daily kilovoltage RC-CBCT scans during the first week of treatment and weekly scans thereafter. Four types of correction methods are compared: (1) systematic error in gross tumor volume (GTV) position, (2) systematic error in skeletal anatomy, (3) daily skeletal corrections, and (4) weekly skeletal corrections. The comparison is in terms of weighted average of the residual GTV deviations measured from the RC-CBCT scans and representing the estimated residual deviation over the treatment course. In the second study goal, GTV deviations computed from matching RCCT and RC-CBCT are compared to deviations computed from matching respiration-averaged images consisting of a CBCT reconstructed using all projections and an average-intensity-projection CT computed from the RCCT. Results: Of the eleven patients in the GTV-based systematic correction protocol, two required no correction

  7. Phase composition in NiTi near-surface layers after electron beam treatment and its variation depending on beam energy density

    SciTech Connect

    Ostapenko, Marina G.; Meisner, Ludmila L.; Lotkov, Aleksandr I. E-mail: egu@ispms.tsc.ru; Gudimova, Ekaterina Y. E-mail: egu@ispms.tsc.ru

    2014-11-14

    In the work, we study the mechanisms of structural phase state formation in NiTi surface layers after low-energy pulsed electron beam irradiation depending on the electron beam energy density. It is revealed that after electron beam treatment of the NiTi specimens at energy densities E{sub 1} = 15 J/cm{sup 2}, E{sub 2} = 20 J/cm{sup 2}, and E{sub 3} = 30 J/cm{sup 2}, a series of effects is observed: the absence of the Ti2Ni phase and the presence of new peaks correspond to the B19′ martensite phase with monoclinic structure. Estimation of the relative volume content of the B2 and B19′ phases from the total intensity of their peaks shows that the percentage of the martensite phase increases from ∼5 vol.% in the NiTi specimen irradiated at E{sub 1} = 15 J/cm{sup 2} to ∼80 vol.% in the NiTi specimen irradiated at E{sub 3} = 30 J/cm{sup 2}. It is found that in the NiTi specimens irradiated at E ≤ 20 J/cm{sup 2}, the layer that contains a martensite phase resides not on the surface but at some depth from it.

  8. Development of system using beam's eye view images to measure respiratory motion tracking errors in image-guided robotic radiosurgery system.

    PubMed

    Inoue, Mitsuhiro; Shiomi, Hiroya; Iwata, Hiromitsu; Taguchi, Junichi; Okawa, Kohei; Kikuchi, Chie; Inada, Kosaku; Iwabuchi, Michio; Murai, Taro; Koike, Izumi; Tatewaki, Koshi; Ohta, Seiji; Inoue, Tomio

    2015-01-01

    The accuracy of the CyberKnife Synchrony Respiratory Tracking System (SRTS) is considered to be patient-dependent because the SRTS relies on an individual correlation between the internal tumor position (ITP) and the external marker position (EMP), as well as a prediction method to compensate for the delay incurred to adjust the position of the linear accelerator (linac). We aimed to develop a system for obtaining pretreatment statistical measurements of the SRTS tracking error by using beam's eye view (BEV) images, to enable the prediction of the patient-specific accuracy. The respiratory motion data for the ITP and the EMP were derived from cine MR images obtained from 23 patients. The dynamic motion phantom was used to reproduce both the ITP and EMP motions. The CyberKnife was subsequently operated with the SRTS, with a CCD camera mounted on the head of the linac. BEV images from the CCD camera were recorded during the tracking of a ball target by the linac. The tracking error was measured at 15 Hz using in-house software. To assess the precision of the position detection using an MR image, the positions of test tubes (determined from MR images) were compared with their actual positions. To assess the precision of the position detection of the ball, ball positions measured from BEV images were compared with values measured using a Vernier caliper. The SRTS accuracy was evaluated by determining the tracking error that could be identified with a probability of more than 95% (Ep95). The detection precision of the tumor position (determined from cine MR images) was < 0.2 mm. The detection precision of the tracking error when using the BEV images was < 0.2mm. These two detection precisions were derived from our measurement system and were not obtained from the SRTS. The median of Ep95 was found to be 1.5 (range, 1.0-3.5) mm. The difference between the minimum and maximum Ep95 was 2.5mm, indicating that this provides a better means of evaluating patient-specific SRTS

  9. Sub-nanometer periodic nonlinearity error in absolute distance interferometers.

    PubMed

    Yang, Hongxing; Huang, Kaiqi; Hu, Pengcheng; Zhu, Pengfei; Tan, Jiubin; Fan, Zhigang

    2015-05-01

    Periodic nonlinearity which can result in error in nanometer scale has become a main problem limiting the absolute distance measurement accuracy. In order to eliminate this error, a new integrated interferometer with non-polarizing beam splitter is developed. This leads to disappearing of the frequency and/or polarization mixing. Furthermore, a strict requirement on the laser source polarization is highly reduced. By combining retro-reflector and angel prism, reference and measuring beams can be spatially separated, and therefore, their optical paths are not overlapped. So, the main cause of the periodic nonlinearity error, i.e., the frequency and/or polarization mixing and leakage of beam, is eliminated. Experimental results indicate that the periodic phase error is kept within 0.0018°. PMID:26026510

  10. Beam combinable, kilowatt, all-fiber amplifier based on phase-modulated laser gain competition.

    PubMed

    Naderi, Nader A; Flores, Angel; Anderson, Brian M; Dajani, Iyad

    2016-09-01

    We report power scaling results of a highly efficient narrow-linewidth monolithic Yb-doped fiber amplifier seeded with two signals, operating at 1038 and 1064 nm. With the appropriate seed power ratio applied, this technique was shown to suppress stimulated Brillouin scattering in conjunction with phase modulation, while generating the output power in predominantly the longer wavelength signal. Notably, the integration of laser gain competition with pseudo-random bit sequence phase modulation, set at a clock rate of 2.5 GHz and utilizing an optimized pattern to match the shortened effective nonlinear length, yielded 1 kW of output power. The beam quality was measured to be near the diffraction limit with no sign of transverse mode instability. Furthermore, the coherent beam combination performance of the amplifier provided a 90% combining efficiency with no indication of spectral broadening when compared to the single-tone case. Overall, the power scaling results represent a significant reduction in spectral linewidth compared to that of commercially available narrow-linewidth Yb-doped fiber amplifiers. PMID:27607948

  11. Structural and Magnetic Phase Transitions in Manganese Arsenide Thin-Films Grown by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Jaeckel, Felix Till

    Phase transitions play an important role in many fields of physics and engineering, and their study in bulk materials has a long tradition. Many of the experimental techniques involve measurements of thermodynamically extensive parameters. With the increasing technological importance of thin-film technology there is a pressing need to find new ways to study phase transitions at smaller length-scales, where the traditional methods are insufficient. In this regard, the phase transitions observed in thin-films of MnAs present interesting challenges. As a ferromagnetic material that can be grown epitaxially on a variety of technologically important substrates, MnAs is an interesting material for spintronics applications. In the bulk, the first order transition from the low temperature ferromagnetic alpha-phase to the beta-phase occurs at 313 K. The magnetic state of the beta-phase has remained controversial. A second order transition to the paramagnetic gamma-phase takes place at 398 K. In thin-films, the anisotropic strain imposed by the substrate leads to the interesting phenomenon of coexistence of alpha- and beta-phases in a regular array of stripes over an extended temperature range. In this dissertation these phase transitions are studied in films grown by molecular beam epitaxy on GaAs (001). The films are confirmed to be of high structural quality and almost purely in the A0 orientation. A diverse set of experimental techniques, germane to thin-film technology, is used to probe the properties of the film: Temperature-dependent X-ray diffraction and atomic-force microscopy (AFM), as well as magnetotransport give insights into the structural properties, while the anomalous Hall effect is used as a probe of magnetization during the phase transition. In addition, reflectance difference spectroscopy (RDS) is used as a sensitive probe of electronic structure. Inductively coupled plasma etching with BCl3 is demonstrated to be effective for patterning MnAs. We show

  12. Field error lottery

    SciTech Connect

    Elliott, C.J.; McVey, B. ); Quimby, D.C. )

    1990-01-01

    The level of field errors in an FEL is an important determinant of its performance. We have computed 3D performance of a large laser subsystem subjected to field errors of various types. These calculations have been guided by simple models such as SWOOP. The technique of choice is utilization of the FELEX free electron laser code that now possesses extensive engineering capabilities. Modeling includes the ability to establish tolerances of various types: fast and slow scale field bowing, field error level, beam position monitor error level, gap errors, defocusing errors, energy slew, displacement and pointing errors. Many effects of these errors on relative gain and relative power extraction are displayed and are the essential elements of determining an error budget. The random errors also depend on the particular random number seed used in the calculation. The simultaneous display of the performance versus error level of cases with multiple seeds illustrates the variations attributable to stochasticity of this model. All these errors are evaluated numerically for comprehensive engineering of the system. In particular, gap errors are found to place requirements beyond mechanical tolerances of {plus minus}25{mu}m, and amelioration of these may occur by a procedure utilizing direct measurement of the magnetic fields at assembly time. 4 refs., 12 figs.

  13. Luminosity Loss due to Beam Distortion and the Beam-Beam Instability

    SciTech Connect

    Wu, Juhao; Raubenheimer, T.O.; Chao, A.W.; Seryi, A.; Sramek, C.K.; /Rice U.

    2005-06-30

    In a linear collider, sources of emittance dilution such as transverse wakefields or dispersive errors will couple the vertical phase space to the longitudinal position within the beam (the so-called ''banana effect''). When the Intersection Point (IP) disruption parameter is large, these beam distortions will be amplified by a single bunch kink instability which will lead to luminosity loss. We study this phenomena both analytically using linear theory and via numerical simulation. In particular, we examine the dependence of the luminosity loss on the wavelength of the beam distortions and the disruption parameter. This analysis may prove useful when optimizing the vertical disruption parameter for luminosity operation with given beam distortions.

  14. Measuring Cyclic Error in Laser Heterodyne Interferometers

    NASA Technical Reports Server (NTRS)

    Ryan, Daniel; Abramovici, Alexander; Zhao, Feng; Dekens, Frank; An, Xin; Azizi, Alireza; Chapsky, Jacob; Halverson, Peter

    2010-01-01

    An improved method and apparatus have been devised for measuring cyclic errors in the readouts of laser heterodyne interferometers that are configured and operated as displacement gauges. The cyclic errors arise as a consequence of mixing of spurious optical and electrical signals in beam launchers that are subsystems of such interferometers. The conventional approach to measurement of cyclic error involves phase measurements and yields values precise to within about 10 pm over air optical paths at laser wavelengths in the visible and near infrared. The present approach, which involves amplitude measurements instead of phase measurements, yields values precise to about .0.1 microns . about 100 times the precision of the conventional approach. In a displacement gauge of the type of interest here, the laser heterodyne interferometer is used to measure any change in distance along an optical axis between two corner-cube retroreflectors. One of the corner-cube retroreflectors is mounted on a piezoelectric transducer (see figure), which is used to introduce a low-frequency periodic displacement that can be measured by the gauges. The transducer is excited at a frequency of 9 Hz by a triangular waveform to generate a 9-Hz triangular-wave displacement having an amplitude of 25 microns. The displacement gives rise to both amplitude and phase modulation of the heterodyne signals in the gauges. The modulation includes cyclic error components, and the magnitude of the cyclic-error component of the phase modulation is what one needs to measure in order to determine the magnitude of the cyclic displacement error. The precision attainable in the conventional (phase measurement) approach to measuring cyclic error is limited because the phase measurements are af-

  15. Monte Carlo simulation of TrueBeam flattening-filter-free beams using Varian phase-space files: Comparison with experimental data

    SciTech Connect

    Belosi, Maria F.; Fogliata, Antonella E-mail: afc@iosi.ch; Cozzi, Luca; Clivio, Alessandro; Nicolini, Giorgia; Vanetti, Eugenio; Rodriguez, Miguel; Sempau, Josep; Krauss, Harald; Khamphan, Catherine; Fenoglietto, Pascal; Puxeu, Josep; Fedele, David; Mancosu, Pietro; Brualla, Lorenzo

    2014-05-15

    Purpose: Phase-space files for Monte Carlo simulation of the Varian TrueBeam beams have been made available by Varian. The aim of this study is to evaluate the accuracy of the distributed phase-space files for flattening filter free (FFF) beams, against experimental measurements from ten TrueBeam Linacs. Methods: The phase-space files have been used as input in PRIMO, a recently released Monte Carlo program based on thePENELOPE code. Simulations of 6 and 10 MV FFF were computed in a virtual water phantom for field sizes 3 × 3, 6 × 6, and 10 × 10 cm{sup 2} using 1 × 1 × 1 mm{sup 3} voxels and for 20 × 20 and 40 × 40 cm{sup 2} with 2 × 2 × 2 mm{sup 3} voxels. The particles contained in the initial phase-space files were transported downstream to a plane just above the phantom surface, where a subsequent phase-space file was tallied. Particles were transported downstream this second phase-space file to the water phantom. Experimental data consisted of depth doses and profiles at five different depths acquired at SSD = 100 cm (seven datasets) and SSD = 90 cm (three datasets). Simulations and experimental data were compared in terms of dose difference. Gamma analysis was also performed using 1%, 1 mm and 2%, 2 mm criteria of dose-difference and distance-to-agreement, respectively. Additionally, the parameters characterizing the dose profiles of unflattened beams were evaluated for both measurements and simulations. Results: Analysis of depth dose curves showed that dose differences increased with increasing field size and depth; this effect might be partly motivated due to an underestimation of the primary beam energy used to compute the phase-space files. Average dose differences reached 1% for the largest field size. Lateral profiles presented dose differences well within 1% for fields up to 20 × 20 cm{sup 2}, while the discrepancy increased toward 2% in the 40 × 40 cm{sup 2} cases. Gamma analysis resulted in an agreement of 100% when a 2%, 2 mm criterion

  16. Analysis of beam loss mechanism in the Project X linac

    SciTech Connect

    Carneiro, J.-P.; Lebedev, V.; Nagaitsev, S.; Ostiguy, J.-F.; Solyak, N.; /Fermilab

    2011-03-01

    Minimization of the beam losses in a multi-MW H{sup -} linac such as ProjectX to a level below 1 W/m is a challenging task. The impact of different mechanism of beam stripping, including stripping in electric and magnetic fields, residual gas, blackbody radiation and intra-beam stripping, is analyzed. Other sources of beam losses are misalignements of beamline elements and errors in RF fields and phases. We present in this paper requirements for dynamic errors and correction schemes to keep beam losses under control.

  17. Structural phase states in NiTi near-surface layers modified by electron and ion beams

    SciTech Connect

    Meisner, Ludmila Meisner, Stanislav; Mironov, Yurii Kashin, Oleg Lotkov, Aleksandr; Kudryashov, Andrey

    2014-11-14

    The paper considers the effects arising on X-ray diffraction patterns taken in different diffraction geometries and how these effects can be interpreted to judge structural states in NiTi near-surface regions after electron and ion beam treatment. It is shown that qualitative and quantitative analysis of phase composition, lattice parameters of main phases, elastic stress states, and their in-depth variation requires X-ray diffraction patterns in both symmetric Bragg–Brentano and asymmetric Lambot–Vassamilleta geometries with variation in X-ray wavelengths and imaging conditions (with and with no β-filter). These techniques of structural phase analysis are more efficient when the thickness of modified NiTi surface layers is 1–10 μm (after electron beam treatment) and requires special imaging conditions when the thickness of modified NiTi surface layers is no greater than 1 μm (after ion beam treatment)

  18. On-shot laser beam diagnostics for high-power laser facility with phase modulation imaging

    NASA Astrophysics Data System (ADS)

    Pan, X.; Veetil, S. P.; Liu, C.; Tao, H.; Jiang, Y.; Lin, Q.; Li, X.; Zhu, J.

    2016-05-01

    A coherent-modulation-imaging-based (CMI) algorithm has been employed for on-shot laser beam diagnostics in high-power laser facilities, where high-intensity short-pulsed lasers from terawatt to petawatt are designed to realize inertial confinement fusion (ICF). A single-shot intensity measurement is sufficient for wave-front reconstruction, both for the near-field and far-field at the same time. The iterative reconstruction process is computationally very efficient and was completed in dozens of seconds by the additional use of a GPU device to speed it up. The compact measurement unit—including a CCD and a piece of pre-characterized phase plate—makes it convenient for focal-spot intensity prediction in the target chamber. It can be placed almost anywhere in high-power laser facilities to achieve near-field wave-front diagnostics. The feasibility of the method has been demonstrated by conducting a series of experiments with diagnostic beams and seed pulses with deactivated amplifiers in our high-power laser system.

  19. Proton beam lithography in negative tone liquid phase PDMS polymer resist

    NASA Astrophysics Data System (ADS)

    Huszank, Robert; Rajta, István; Cserháti, Csaba

    2015-04-01

    In this work we investigated the applicability of liquid PDMS polymer as a negative resist material for direct proton beam writing technique. We irradiated the polymer in liquid phase, spin-coated on different substrate materials creating various microstructures. PDMS pre-polymer was cross-linked just by PBW. As the cross-linking process increases, the irradiated area becomes more solid. The rate of the solidification strongly depends on the deposited ion dose. The effects of fluence, beam current, substrate type and developer solvent was investigated. Furthermore, at the irradiated areas the adhesion, the wettability and Young's modulus also changes due to the chemical change of the PDMS polymer. This effect makes the possibility to form microstructures in PDMS with tunable adhesion and wettability properties. In practical viewpoint, the PDMS resist can also have some advantages compared to other resists such as easy stripping, very fast developing (as the un-cross-linked PDMS is soluble in many organic solvents), not sensitive to light, high current or high fluence.

  20. Bismuth-induced phase control of GaAs nanowires grown by molecular beam epitaxy

    SciTech Connect

    Lu, Zhenyu; Chen, Pingping E-mail: luwei@mail.sitp.ac.cn; Shi, Suixing; Yao, Luchi; Zhou, Xiaohao; Lu, Wei E-mail: luwei@mail.sitp.ac.cn; Zhang, Zhi; Zhou, Chen; Zou, Jin

    2014-10-20

    In this work, the crystal structure of GaAs nanowires grown by molecular beam epitaxy has been tailored only by bismuth without changing the growth temperature and V/III flux ratio. The introduction of bismuth can lead to the formation of zinc-blende GaAs nanowires, while the removal of bismuth changes the structure into a 4H polytypism before it turns back to the wurtzite phase eventually. The theoretical calculation shows that it is the steadiest for bismuth to adsorb on the GaAs(111){sub B} surface compared to the liquid gold catalyst surface and the interface between the gold catalyst droplet and the nanowire, and these adsorbed bismuth could decrease the diffusion length of adsorbed Ga and hence the supersaturation of Ga in the gold catalyst droplet.

  1. Probing transverse coherence of x-ray beam with 2-D phase grating interferometer

    PubMed Central

    Marathe, Shashidhara; Shi, Xianbo; Wojcik, Michael J.; Kujala, Naresh G.; Divan, Ralu; Mancini, Derrick C.; Macrander, Albert T.; Assoufid, Lahsen

    2014-01-01

    Transverse coherence of the x-ray beam from a bending magnet source was studied along multiple directions using a 2-D π/2 phase grating by measuring interferogram visibilities at different distances behind the grating. These measurements suggest that the preferred measuring orientation of a 2-D checkerboard grating is along the diagonal directions of the square blocks, where the interferograms have higher visibility and are not sensitive to the deviation of the duty cycle of the grating period. These observations are verified by thorough wavefront propagation simulations. The accuracy of the measured coherence values was also validated by the simulation and analytical results obtained from the source parameters. In addition, capability of the technique in probing spatially resolved local transverse coherence is demonstrated. PMID:24977503

  2. Probing transverse coherence of x-ray beam with 2-D phase grating interferometer.

    PubMed

    Marathe, Shashidhara; Shi, Xianbo; Wojcik, Michael J; Kujala, Naresh G; Divan, Ralu; Mancini, Derrick C; Macrander, Albert T; Assoufid, Lahsen

    2014-06-16

    Transverse coherence of the x-ray beam from a bending magnet source was studied along multiple directions using a 2-D π/2 phase grating by measuring interferogram visibilities at different distances behind the grating. These measurements suggest that the preferred measuring orientation of a 2-D checkerboard grating is along the diagonal directions of the square blocks, where the interferograms have higher visibility and are not sensitive to the deviation of the duty cycle of the grating period. These observations are verified by thorough wavefront propagation simulations. The accuracy of the measured coherence values was also validated by the simulation and analytical results obtained from the source parameters. In addition, capability of the technique in probing spatially resolved local transverse coherence is demonstrated. PMID:24977503

  3. Correction for ‘artificial’ electron disequilibrium due to cone-beam CT density errors: implications for on-line adaptive stereotactic body radiation therapy of lung

    NASA Astrophysics Data System (ADS)

    Disher, Brandon; Hajdok, George; Wang, An; Craig, Jeff; Gaede, Stewart; Battista, Jerry J.

    2013-06-01

    Cone-beam computed tomography (CBCT) has rapidly become a clinically useful imaging modality for image-guided radiation therapy. Unfortunately, CBCT images of the thorax are susceptible to artefacts due to scattered photons, beam hardening, lag in data acquisition, and respiratory motion during a slow scan. These limitations cause dose errors when CBCT image data are used directly in dose computations for on-line, dose adaptive radiation therapy (DART). The purpose of this work is to assess the magnitude of errors in CBCT numbers (HU), and determine the resultant effects on derived tissue density and computed dose accuracy for stereotactic body radiation therapy (SBRT) of lung cancer. Planning CT (PCT) images of three lung patients were acquired using a Philips multi-slice helical CT simulator, while CBCT images were obtained with a Varian On-Board Imaging system. To account for erroneous CBCT data, three practical correction techniques were tested: (1) conversion of CBCT numbers to electron density using phantoms, (2) replacement of individual CBCT pixel values with bulk CT numbers, averaged from PCT images for tissue regions, and (3) limited replacement of CBCT lung pixels values (LCT) likely to produce artificial lateral electron disequilibrium. For each corrected CBCT data set, lung SBRT dose distributions were computed for a 6 MV volume modulated arc therapy (VMAT) technique within the Philips Pinnacle treatment planning system. The reference prescription dose was set such that 95% of the planning target volume (PTV) received at least 54 Gy (i.e. D95). Further, we used the relative depth dose factor as an a priori index to predict the effects of incorrect low tissue density on computed lung dose in regions of severe electron disequilibrium. CT number profiles from co-registered CBCT and PCT patient lung images revealed many reduced lung pixel values in CBCT data, with some pixels corresponding to vacuum (-1000 HU). Similarly, CBCT data in a plastic lung

  4. Correction for 'artificial' electron disequilibrium due to cone-beam CT density errors: implications for on-line adaptive stereotactic body radiation therapy of lung.

    PubMed

    Disher, Brandon; Hajdok, George; Wang, An; Craig, Jeff; Gaede, Stewart; Battista, Jerry J

    2013-06-21

    Cone-beam computed tomography (CBCT) has rapidly become a clinically useful imaging modality for image-guided radiation therapy. Unfortunately, CBCT images of the thorax are susceptible to artefacts due to scattered photons, beam hardening, lag in data acquisition, and respiratory motion during a slow scan. These limitations cause dose errors when CBCT image data are used directly in dose computations for on-line, dose adaptive radiation therapy (DART). The purpose of this work is to assess the magnitude of errors in CBCT numbers (HU), and determine the resultant effects on derived tissue density and computed dose accuracy for stereotactic body radiation therapy (SBRT) of lung cancer. Planning CT (PCT) images of three lung patients were acquired using a Philips multi-slice helical CT simulator, while CBCT images were obtained with a Varian On-Board Imaging system. To account for erroneous CBCT data, three practical correction techniques were tested: (1) conversion of CBCT numbers to electron density using phantoms, (2) replacement of individual CBCT pixel values with bulk CT numbers, averaged from PCT images for tissue regions, and (3) limited replacement of CBCT lung pixels values (LCT) likely to produce artificial lateral electron disequilibrium. For each corrected CBCT data set, lung SBRT dose distributions were computed for a 6 MV volume modulated arc therapy (VMAT) technique within the Philips Pinnacle treatment planning system. The reference prescription dose was set such that 95% of the planning target volume (PTV) received at least 54 Gy (i.e. D95). Further, we used the relative depth dose factor as an a priori index to predict the effects of incorrect low tissue density on computed lung dose in regions of severe electron disequilibrium. CT number profiles from co-registered CBCT and PCT patient lung images revealed many reduced lung pixel values in CBCT data, with some pixels corresponding to vacuum (-1000 HU). Similarly, CBCT data in a plastic lung

  5. SweepSAR: Beam-forming on Receive Using a Reflector-Phased Array Feed Combination for Spaceborne SAR

    NASA Technical Reports Server (NTRS)

    Freeman, A.; Krieger, G.; Rosen, P.; Younis, M.; Johnson, W. T. K.; Huber, S.; Jordan, R.; Moreira, A.

    2012-01-01

    In this paper, an alternative approach is described that is suited for longer wavelength SARs in particular, employing a large, deployable reflector antenna and a much simpler phased array feed. To illuminate a wide swath, a substantial fraction of the phased array feed is excited on transmit to sub-illuminate the reflector. Shorter transmit pulses are required than for conventional SAR. On receive, a much smaller portion of the phased array feed is used to collect the return echo, so that a greater portion of the reflector antenna area is used. The locus of the portion of the phased array used on receive is adjusted using an analog beam steering network, to 'sweep' the receive beam(s) across the illuminated swath, tracking the return echo. This is similar in some respects to the whiskbroom approach to optical sensors, hence the name: SweepSAR.SweepSAR has advantages over conventional SAR in that it requires less transmit power, and if the receive beam is narrow enough, it is relatively immune to range ambiguities. Compared to direct radiating arrays with digital beam- forming, it is much simpler to implement, uses currently available technologies, is better suited for longer wavelength systems, and does not require extremely high data rates or onboard processing.

  6. Phase and group velocity of focused, pulsed Gaussian beams in the presence and absence of primary aberrations

    NASA Astrophysics Data System (ADS)

    Major, Balázs; Horváth, Zoltán L.; Porras, Miguel A.

    2015-06-01

    This work presents a study on the phase- and group-velocity variations of focused, pulsed Gaussian beams during the propagation through the focal region along the optical axis. In the aberration-free case, it is discussed how the wavelength dependence of beam properties alters the group velocity, and how a chromatic aberration-like effect can arise even when focusing is performed with an element that does not have chromatic aberration. It is also examined what effects primary spherical aberration, astigmatism, coma, curvature of field and distortion, along with chromatic aberration, have on the phase- and group-velocity changes occurring during propagation through focus.

  7. 3D Algebraic Iterative Reconstruction for Cone-Beam X-Ray Differential Phase-Contrast Computed Tomography

    PubMed Central

    Fu, Jian; Hu, Xinhua; Velroyen, Astrid; Bech, Martin; Jiang, Ming; Pfeiffer, Franz

    2015-01-01

    Due to the potential of compact imaging systems with magnified spatial resolution and contrast, cone-beam x-ray differential phase-contrast computed tomography (DPC-CT) has attracted significant interest. The current proposed FDK reconstruction algorithm with the Hilbert imaginary filter will induce severe cone-beam artifacts when the cone-beam angle becomes large. In this paper, we propose an algebraic iterative reconstruction (AIR) method for cone-beam DPC-CT and report its experiment results. This approach considers the reconstruction process as the optimization of a discrete representation of the object function to satisfy a system of equations that describes the cone-beam DPC-CT imaging modality. Unlike the conventional iterative algorithms for absorption-based CT, it involves the derivative operation to the forward projections of the reconstructed intermediate image to take into account the differential nature of the DPC projections. This method is based on the algebraic reconstruction technique, reconstructs the image ray by ray, and is expected to provide better derivative estimates in iterations. This work comprises a numerical study of the algorithm and its experimental verification using a dataset measured with a three-grating interferometer and a mini-focus x-ray tube source. It is shown that the proposed method can reduce the cone-beam artifacts and performs better than FDK under large cone-beam angles. This algorithm is of interest for future cone-beam DPC-CT applications. PMID:25775480

  8. Beam-path conditioning for high-power laser systems

    SciTech Connect

    Stephens, T.; Johnson, D.; Languirand, M.

    1990-01-01

    Heating of mirrors and windows by high-power radiation from a laser transmitter produces turbulent density gradients in the gas near the optical surfaces. If the gradients are left uncontrolled, the resulting phase errors reduce the intensity on the target and degrade the signal returned to a receiver. Beam path conditioning maximizes the efficiency of the optical system by alleviating thermal turbulence within the beam path. Keywords: High power radiation, Beam path, Optical surface, Laser beams, Reprints. (JHD)

  9. Stefan problem for a finite liquid phase and its application to laser or electron beam welding

    SciTech Connect

    Kasuya, T.; Shimoda, N.

    1997-10-01

    An exact solution of a heat conduction problem with the effect of latent heat of solidification (Stefan problem) is derived. The solution of the one dimensional Stefan problem for a finite liquid phase initially existing in a semi-infinite body is applied to evaluate temperature fields produced by laser or electron beam welding. The solution of the model has not been available before, as Carslaw and Jaeger [{ital Conduction of Heat in Solids}, 2nd ed. (Oxford University Press, New York, 1959)] pointed out. The heat conduction calculations are performed using thermal properties of carbon steel, and the comparison of the Stefan problem with a simplified linear heat conduction model reveals that the solidification rate and cooling curve over 1273 K significantly depend on which model (Stefan or linear heat conduction problem) is applied, and that the type of the thermal model applied has little meaning for cooling curve below 1273 K. Since the heat conduction problems with a phase change arise in many important industrial fields, the solution derived in this study is ready to be used not only for welding but also for other industrial applications. {copyright} {ital 1997 American Institute of Physics.}

  10. Calibration artefacts in radio interferometry - III. Phase-only calibration and primary beam correction

    NASA Astrophysics Data System (ADS)

    Grobler, T. L.; Stewart, A. J.; Wijnholds, S. J.; Kenyon, J. S.; Smirnov, O. M.

    2016-09-01

    This is the third installment in a series of papers in which we investigate calibration artefacts. Calibration artefacts (also known as ghosts or spurious sources) are created when we calibrate with an incomplete model. In the first two papers of this series, we developed a mathematical framework which enabled us to study the ghosting mechanism itself. An interesting concomitant of the second paper was that ghosts appear in symmetrical pairs. This could possibly account for spurious symmetrization. Spurious symmetrization refers to the appearance of a spurious source (the antighost) symmetrically opposite an unmodelled source around a modelled source. The analysis in the first two papers indicates that the antighost is usually very faint, in particular, when a large number of antennas are used. This suggests that spurious symmetrization will mainly occur at an almost undetectable flux level. In this paper, we show that phase-only calibration produces an antighost that is N-times (where N denotes the number of antennas in the array) as bright as the one produced by phase and amplitude calibration and that this already bright ghost can be further amplified by the primary beam correction.

  11. Transformation of optical-vortex beams by holograms with embedded phase singularity

    NASA Astrophysics Data System (ADS)

    Bekshaev, A. Ya.; Orlinska, O. V.

    2010-04-01

    Spatial characteristics of diffracted beams produced by the "fork" holograms from incident circular Laguerre-Gaussian modes are studied theoretically. The complex amplitude distribution of a diffracted beam is described by models of the Kummer beam or of the hypergeometric-Gaussian beam. Physically, in most cases its structure is formed under the influence of the divergent spherical wave originating from the discontinuity caused by the hologram's groove bifurcation. Presence of this wave is manifested by the ripple structure in the near-field beam pattern and by the power-law amplitude decay at the beam periphery. Conditions when the divergent wave is not excited are discussed. The diffracted beam carries a screw wavefront dislocation (optical vortex) whose order equals to algebraic sum of the incident beam azimuthal index and the topological charge of the singularity imparted by the hologram. The input beam singularity can be healed when the above sum is zero. In such cases the diffracted beam can provide better energy concentration in the central intensity peak than the Gaussian beam whose initial distribution coincides with the Gaussian envelope of the incident beam. Applications are possible for generation of optical-vortex beams with prescribed properties and for analyzing the optical-vortex beams in problems of information processing.

  12. Phase I Trial of Bortezomib and Concurrent External Beam Radiation in Patients With Advanced Solid Malignancies

    SciTech Connect

    Pugh, Thomas J.; Chen Changhu; Rabinovitch, Rachel; Eckhardt, S. Gail; Rusthoven, Kyle E.; Swing, Robyn; Raben, David

    2010-10-01

    Purpose: To determine the maximal tolerated dose of bortezomib with concurrent external beam radiation therapy in patients with incurable solid malignant tumors requiring palliative therapy. Methods and Materials: An open label, dose escalation, phase I clinical trial evaluated the safety of three dose levels of bortezomib administered intravenously (1.0 mg/m{sup 2}, 1.3 mg/m{sup 2}, and 1.6 mg/m{sup 2}/ dose) once weekly with concurrent radiation in patients with histologically confirmed solid tumors and a radiographically appreciable lesion suitable for palliative radiation therapy. All patients received 40 Gy in 16 fractions to the target lesion. Dose-limiting toxicity was the primary endpoint, defined as any grade 4 hematologic toxicity, any grade {>=}3 nonhematologic toxicity, or any toxicity requiring treatment to be delayed for {>=}2 weeks. Results: A total of 12 patients were enrolled. Primary sites included prostate (3 patients), head and neck (3 patients), uterus (1 patient), abdomen (1 patient), breast (1 patient), kidney (1 patient), lung (1 patient), and colon (1 patient). The maximum tolerated dose was not realized with a maximum dose of 1.6 mg/m{sup 2}. One case of dose-limiting toxicity was appreciated (grade 3 urosepsis) and felt to be unrelated to bortezomib. The most common grade 3 toxicity was lymphopenia (10 patients). Common grade 1 to 2 events included nausea (7 patients), infection without neutropenia (6 patients), diarrhea (5 patients), and fatigue (5 patients). Conclusions: The combination of palliative external beam radiation with concurrent weekly bortezomib therapy at a dose of 1.6 mg/m{sup 2} is well tolerated in patients with metastatic solid tumors. The maximum tolerated dose of once weekly bortezomib delivered concurrently with radiation therapy is greater than 1.6 mg/m{sup 2}.

  13. Optical BEAMTAP beam-forming and jammer-nulling system for broadband phased-array antennas.

    PubMed

    Kriehn, G; Kiruluta, A; Silveira, P E; Weaver, S; Kraut, S; Wagner, K; Weverka, R T; Griffiths, L

    2000-01-10

    We present an approach to receive-mode broadband beam forming and jammer nulling for large adaptive antenna arrays as well as its efficient and compact optical implementation. This broadband efficient adaptive method for true-time-delay array processing (BEAMTAP) algorithm decreases the number of tapped delay lines required for processing an N-element phased-array antenna from N to only 2, producing an enormous savings in delay-line hardware (especially for large broadband arrays) while still providing the full NM degrees of freedom of a conventional N-element time-delay-and-sum beam former that requires N tapped delay lines with M taps each. This allows the system to adapt fully and optimally to an arbitrarily complex spatiotemporal signal environment that can contain broadband signals of interest, as well as interference sources and narrow-band and broadband jammers--all of which can arrive from arbitrary angles onto an arbitrarily shaped array--thus enabling a variety of applications in radar, sonar, and communication. This algorithm is an excellent match with the capabilities of radio frequency (rf) photonic systems, as it uses a coherent optically modulated fiber-optic feed network, gratings in a photorefractive crystal as adaptive weights, a traveling-wave detector for generating time delay, and an acousto-optic device to control weight adaptation. Because the number of available adaptive coefficients in a photorefractive crystal is as large as 10(9), these photonic systems can adaptively control arbitrarily large one- or two-dimensional antenna arrays that are well beyond the capabilities of conventional rf and real-time digital signal processing techniques or alternative photonic techniques. PMID:18337889

  14. Ion separation in imperfect fields of the quadrupole mass analyzer Part I. Ion beam dynamics in the phase-space

    NASA Astrophysics Data System (ADS)

    Titov, Vladimir V.

    1995-01-01

    The theoretical aspects of ion separation in imperfect fields of the quadrupole mass analyzer are discussed by applying analysis of the beam dynamics in a phase-space. The analytical method which uses an approximate solution of the Hill equation with a small heterogeneous part which indicates that the trap mechanism of ion separation is conditioned by the properties of characteristic solutions is improved. These solutions are reduced to an approximate solution in the form of a general solution of a homogeneous Mathieu equation with combined factors taking into account a small heterogeneous part which defines the region of beam capture (acceptance) in a phase-space. The estimation criterion of simulation accuracy is the relative deviation of an operating point on the Mathieu diagram from the top of a stability triangle. The infringement of independence principle of ion oscillations about each of the positional axes caused by distortions increases the cross-sectional area of the beam. The beam is cut out by the mass analyzer aperture. This causes transmission losses which depend on phase. Therefore, the ion current at the mass analyzer exit is amplitude modulated by the frequency of the alternate component of field. The maximum current is at zero phase. The modulation depth is proportional to the relative value of the distortions.

  15. Interaction-Point Phase-Space Characterization using Single-Beam and Luminous-Region Measurements at PEP-II

    SciTech Connect

    Kozanecki, W; Bevan, A.J.; Viaud, B.F.; Cai, Y.; Fisher, A.S.; O'Grady, C.; Lindquist, B.; Roodman, A.; J.M.Thompson, M.Weaver; /SLAC

    2008-09-09

    We present an extensive experimental characterization of the e{sup {+-}} phase space at the interaction point of the SLAC PEP-II B-Factory, that combines a detailed mapping of luminous-region observables using the BABAR detector, with stored-beam measurements by accelerator techniques.

  16. Interface kinetics in phase-field models: Isothermal transformations in binary alloys and step dynamics in molecular-beam epitaxy

    NASA Astrophysics Data System (ADS)

    Boussinot, G.; Brener, Efim A.

    2013-08-01

    We present a unified description of interface kinetic effects in phase-field models for isothermal transformations in binary alloys and steps dynamics in molecular-beam-epitaxy. The phase-field equations of motion incorporate a kinetic cross-coupling between the phase field and the concentration field. This cross-coupling generalizes the phenomenology of kinetic effects and was omitted until recently in classical phase-field models. We derive general expressions (independent of the details of the phase-field model) for the kinetic coefficients within the corresponding macroscopic approach using a physically motivated reduction procedure. The latter is equivalent to the so-called thin-interface limit but is technically simpler. It involves the calculation of the effective dissipation that can be ascribed to the interface in the phase-field model. We discuss in detail the possibility of a nonpositive definite matrix of kinetic coefficients, i.e., a negative effective interface dissipation, although being in the range of stability of the underlying phase-field model. Numerically we study the step-bunching instability in molecular-beam-epitaxy due to the Ehrlich-Schwoebel effect, present in our model due to the cross-coupling. Using the reduction procedure we compare the results of the phase-field simulations with the analytical predictions of the macroscopic approach.

  17. Interface kinetics in phase-field models: isothermal transformations in binary alloys and step dynamics in molecular-beam epitaxy.

    PubMed

    Boussinot, G; Brener, Efim A

    2013-08-01

    We present a unified description of interface kinetic effects in phase-field models for isothermal transformations in binary alloys and steps dynamics in molecular-beam-epitaxy. The phase-field equations of motion incorporate a kinetic cross-coupling between the phase field and the concentration field. This cross-coupling generalizes the phenomenology of kinetic effects and was omitted until recently in classical phase-field models. We derive general expressions (independent of the details of the phase-field model) for the kinetic coefficients within the corresponding macroscopic approach using a physically motivated reduction procedure. The latter is equivalent to the so-called thin-interface limit but is technically simpler. It involves the calculation of the effective dissipation that can be ascribed to the interface in the phase-field model. We discuss in detail the possibility of a nonpositive definite matrix of kinetic coefficients, i.e., a negative effective interface dissipation, although being in the range of stability of the underlying phase-field model. Numerically we study the step-bunching instability in molecular-beam-epitaxy due to the Ehrlich-Schwoebel effect, present in our model due to the cross-coupling. Using the reduction procedure we compare the results of the phase-field simulations with the analytical predictions of the macroscopic approach. PMID:24032848

  18. Kinetic Description of Intense Beam Propagation Through a Periodic Focusing Field for Uniform Phase-Space Density

    SciTech Connect

    Ronald C. Davidson; Hong Qin; Stephan I. Tzenov; Edward A. Startsev

    2003-02-26

    The Vlasov-Maxwell equations are used to investigate the nonlinear evolution of an intense sheet beam with distribution function f{sub b}(x,x{prime},s) propagating through a periodic focusing lattice k{sub x}(s+S) = k{sub x}(s), where S = const is the lattice period. The analysis considers the special class of distribution functions with uniform phase-space density f{sub b}(x,x{prime},s) = A = const inside of the simply connected boundary curves, x{prime}{sub +}(x,s) and x{prime}{sub -}(x,s), in the two-dimensional phase space (x,x{prime}). Coupled nonlinear equations are derived describing the self-consistent evolution of the boundary curves, x{prime}{sub +}(x,s) and x{prime}{sub -}(x,s), and the self-field potential {psi}(x,s) = e{sub b}{phi}(x,s)/{gamma}{sub b}m{sub b}{beta}{sub g}{sup 2}c{sup 2}. The resulting model is shown to be exactly equivalent to a (truncated) warm-fluid description with zero heat flow and triple-adiabatic equation-of-state with scalar pressure P{sub b}(x,s) = const x [n{sub b}(x,s)]. Such a fluid model is amenable to direct analysis by transforming to Lagrangian variables following the motion of a fluid element. Specific examples of periodically focused beam equilibria are presented, ranging from a finite-emittance beam in which the boundary curves in phase space (x,x{prime}) correspond to a pulsating parallelogram, to a cold beam in which the number density of beam particles, n{sub b}(x,s), exhibits large-amplitude periodic oscillations. For the case of a sheet beam with uniform phase-space density, the present analysis clearly demonstrates the existence of periodically focused beam equilibria without the undesirable feature of an inverted population in phase space that is characteristic of the Kapchinskij-Vladimirskij beam distribution.

  19. Phase and Structural States Formed in Titanium Nickelide Subsurface Layers Exposed to High-Current Pulsed Electron Beams

    NASA Astrophysics Data System (ADS)

    Neyman, A. A.; Meisner, L. L.; Lotkov, A. I.; Semin, V. O.

    2015-06-01

    The behavior of the non-equilibrium states formed in the subsurface layers of a titanium nickelide-based alloy exposed to electron beams operated in the pulsed surface layer melting mode is investigated experimentally. Using methods of an x-ray diffraction analysis, and optical, scanning, and transmission electron microscopies, an 8-10 μm thick surface layer is shown to exhibit В2 phase-based structure undergoing inhomogeneous lattice microstrain. The core layer located at a depth of 10-20 μm below the irradiated surface contains a small amount (up to 5 vol.%) of a phase with В19' martensite structure along with a slightly distorted lattice and unmelted Ti2Ni phase particles. Electron beam treatment brings about changes in the chemical composition of the surface-modified layer which becomes enriched in titanium owing to the dissolution of the Ti2Ni phase particles therein. Transmission electron microscopy has not revealed martensite phases in the modified layer. The electron beam exposure of the titanium nickelide surface is assumed to give rise to nonequilibrium highly distorted bcc structure.

  20. An Exploratory Statistical Analysis of a Planet Approach-Phase Guidance Scheme Using Angular Measurements with Significant Error

    NASA Technical Reports Server (NTRS)

    Friedlander, Alan L.; Harry, David P., III

    1960-01-01

    An exploratory analysis of vehicle guidance during the approach to a target planet is presented. The objective of the guidance maneuver is to guide the vehicle to a specific perigee distance with a high degree of accuracy and minimum corrective velocity expenditure. The guidance maneuver is simulated by considering the random sampling of real measurements with significant error and reducing this information to prescribe appropriate corrective action. The instrumentation system assumed includes optical and/or infrared devices to indicate range and a reference angle in the trajectory plane. Statistical results are obtained by Monte-Carlo techniques and are shown as the expectation of guidance accuracy and velocity-increment requirements. Results are nondimensional and applicable to any planet within limits of two-body assumptions. The problem of determining how many corrections to make and when to make them is a consequence of the conflicting requirement of accurate trajectory determination and propulsion. Optimum values were found for a vehicle approaching a planet along a parabolic trajectory with an initial perigee distance of 5 radii and a target perigee of 1.02 radii. In this example measurement errors were less than i minute of arc. Results indicate that four corrections applied in the vicinity of 50, 16, 15, and 1.5 radii, respectively, yield minimum velocity-increment requirements. Thrust devices capable of producing a large variation of velocity-increment size are required. For a vehicle approaching the earth, miss distances within 32 miles are obtained with 90-percent probability. Total velocity increments used in guidance are less than 3300 feet per second with 90-percent probability. It is noted that the above representative results are valid only for the particular guidance scheme hypothesized in this analysis. A parametric study is presented which indicates the effects of measurement error size, initial perigee, and initial energy on the guidance

  1. The calculation of the diffraction of the laser beams with a phase singularity on the micro-axicons with using high-performance computing

    NASA Astrophysics Data System (ADS)

    A, Savelyev D.; N, Khonina S.

    2014-03-01

    We analyze the diffraction of the laser beam with a vortex phase singularity on the basis of the finite-difference time-domain method (FDTD). It is shown that, when incident beam has phase singularity, increase of the micro-axicon radius leads to extension of the light needle consisting of longitudinal electric field component. The numerical investigations held of the near-field diffraction for the most common and easily implemented types of polarization of the incident beam - linear and circular.

  2. MIMO based optical phased array technology with electronic beam steering for laser radar applications

    NASA Astrophysics Data System (ADS)

    Sharma, Neha; Zmuda, Henry

    2010-04-01

    This paper will address the analysis and design of an electronically scanned phased array laser radar (ladar) system utilizing the techniques of multi-input multi-output (MIMO) array design. MIMO radar is has attracted much attention recently from both researchers and practitioners alike due to its significant potential for advancing the state-of-the-art RF radar technology. The laser radar architecture presented stands to gain significant inroads on the ability to apply RF array processing methods to laser radar systems in several ways. Specifically, using MIMO array design concepts, it is shown that the resolution of the ladar array can substantially exceed the diffraction limited resolution of a conventional array. Additionally, the use of array methods provides the capability to electronically steer the aperture, thus avoiding the mechanical beam scanning methods generally encountered in laser radar systems. Finally, by using an array of radiators, an increase in total radiated power is achieved, relieving the power burden on a single laser. The problems traditionally encountered in applying conventional array techniques to laser/detector arrays, for example, the inability to achieve half-wavelength spacing or the surfacing of source coherence issues, actually work to one's advantage when viewed in the MIMO paradigm. It is anticipated that the successful implementation of this system will significantly advance the state-of-the-art of laser radar capabilities for high speed imaging, target detection, tracking, and signature analysis.

  3. Tuning method for phase shifters with very low first field integral errors for the European X-ray Free Electron Laser

    NASA Astrophysics Data System (ADS)

    Li, Yuhui; Pflueger, Joachim

    2015-03-01

    For the long gap tunable undulator systems of the European XFEL, 91 phase shifters are needed. They need to fulfil stringent and demanding field integral tolerances if their strengths, i.e., their magnetic gaps, are changed. In order to avoid additional correctors, their first field integral errors must not exceed ±0.004 Tmm for self-amplified spontaneous emission operation at 1 Å. For longer wavelengths there are slightly relaxed requirements. In addition, a good field range of ±0.5 mm is required. Phase shifters are manufactured by using state of the art techniques such as measurement and sorting of magnets, measurement and sorting of subassemblies, etc. In spite of these efforts, inhomogeneities of the permanent magnet material as well as mechanic manufacturing errors, which cannot be avoided and lead to violations of the demanding first field integral specifications. Therefore, a fast and robust shimming technique was developed for the serial production of these devices. It is based on measured signatures of shims with different geometries and uses symmetry properties of shims placed on different positions and poles with different polarity. In this paper, the specifications for the phase shifters in the European XFEL are derived first. Then the method is described in detail and results are presented, which demonstrate that all requirements can be fulfilled.

  4. Experimental two-phase flow measurement using ultra fast limited-angle-type electron beam X-ray computed tomography

    NASA Astrophysics Data System (ADS)

    Bieberle, M.; Fischer, F.; Schleicher, E.; Koch, D.; Menz, H.-J.; Mayer, H.-G.; Hampel, U.

    2009-09-01

    An experimental evaluation of a novel limited-angle-type ultra fast electron beam X-ray computed tomography approach for the visualization and measurement of a gas-liquid two-phase flow is reported here. With this method, a simple linear electron beam scan is used to produce instantaneous radiographic views of a two-phase flow in a pipe segment of a flow loop. Electron beam scanning can be performed very rapidly, thus a frame rate of 5 kHz is achieved. Radiographic projections are recorded by a very fast detector arc made of zink-cadmium-telluride elements. This detector records the X-ray radiation passing through the object with a sampling rate of 1 MHz. The reconstruction of slice images from the recorded detector data is a limited-angle problem since in our scanning geometry the object’s Radon space is only incompletely sampled. It was investigated here, whether this technology is able to produce accurate gas fraction data from bubbly two-phase flow. Experiments were performed both on a Perspex phantom with known geometry and an experimental flow loop operated under vacuum conditions in an electron beam processing box.

  5. Generation of phase - matched coherent point source in plasma media by propagated X-ray laser seeded beam

    NASA Astrophysics Data System (ADS)

    Pikuz, T.; Faenov, A.; Magnitskiy, S.; Nagorskiy, N.; Tanaka, M.; Ishino, M.; Nishikino, M.; Kando, M.; Kato, Y.; Kawachi, T.

    2016-03-01

    There is a significant interest in developing the coherent table-top X-ray lasers. Advent of plasma-based transient collisional excitation x-ray laser and particular, injection of coherent seeded beam, especially high-order harmonics, has tremendously improved the spatial coherence of such lasers, what allowed them to be the same widely used as synchrotron sources. Here we report experimental founding of unknown interference structure in a spatial profile of the output beam of the two-stage plasma X-ray laser. That allowed us experimental and theoretical discovering a new phenomenon consisted in a generation of phase-matched coherent point source in a laser plasma media by propagated X-ray laser seeded beam. This phenomenon could extend the applications of such x-ray lasers. For explanation of the observed phenomenon a new method of solving the standard system of Maxwell-Bloch equations has been developed. It was found that the interference pattern in the output laser beam was formed due to an emergence of phase-matched coherent virtual point source in the XRL amplifier and could be treated as the first observation of mirage phenomenon, analogous to the optical mirage, but in X-rays. The obtained results bring new comprehension into the physical nature of amplification of X-ray radiation in laser-induced plasma amplifiers and opening new opportunities for X-ray interferometry, holography and other applications, which requiring multiple rigidly phased sources of coherent radiation.

  6. Symmetry control using beam phasing in ~0.2 NIF scale high temperature Hohlraum experiment on OMEGA

    SciTech Connect

    Delamater, Norman D; Wilson, Goug C; Kyrala, George A; Seifter, Achim; Hoffman, N M; Dodd, E; Glebov, V

    2009-01-01

    Results are shown from recent experiments at the Omega laser facility, using 40 Omega beams driving the hohlraum with 3 cones from each side and up to 19.5 kJ of laser energy. Beam phasing is achieved by decreasing the energy separately in each of the three cones, by 3 kJ, for a total drive energy of 16.5kJ. This results in a more asymmetric drive, which will vary the shape of the imploded symmetry capsule core from round to oblate or prolate in a systematic and controlled manner. These results would be the first demonstration of beam phasing for implosions in such 'high temperature' (275 eV) hohlraums at Omega. Dante measurements confirmed the predicted peak drive temperatures of 275 eV. Implosion core time dependent x-ray images were obtained from framing camera data which show the expected change in symmetry due to beam phasing and which also agree well with post processed hydro code calculations. Time resolved hard x-ray data has been obtained and it was found that the hard x-rays are correlated mainly with the low angle 21{sup o} degree cone.

  7. Delayed-Phase Cone-Beam CT Improves Detectability of Intrahepatic Cholangiocarcinoma During Conventional Transarterial Chemoembolization

    SciTech Connect

    Schernthaner, Ruediger Egbert; Lin, MingDe; Duran, Rafael; Chapiro, Julius; Wang, Zhijun; Geschwind, Jean-François

    2015-08-15

    PurposeTo evaluate the detectability of intrahepatic cholangiocarcinoma (ICC) on dual-phase cone-beam CT (DPCBCT) during conventional transarterial chemoembolization (cTACE) compared to that of digital subtraction angiography (DSA) with respect to pre-procedure contrast-enhanced magnetic resonance imaging (CE-MRI) of the liver.MethodsThis retrospective study included 17 consecutive patients (10 male, mean age 64) with ICC who underwent pre-procedure CE-MRI of the liver, and DSA and DPCBCT (early-arterial phase (EAP) and delayed-arterial phase (DAP)) just before cTACE. The visibility of each ICC lesion was graded by two radiologists on a three-rank scale (complete, partial, and none) on DPCBCT and DSA images, and then compared to pre-procedure CE-MRI.ResultsOf 61 ICC lesions, only 45.9 % were depicted by DSA, whereas EAP- and DAP-CBCT yielded a significantly higher detectability rate of 73.8 % and 93.4 %, respectively (p < 0.01). Out of the 33 lesions missed on DSA, 18 (54.5 %) and 30 (90.9 %) were revealed on EAP- and DAP-CBCT images, respectively. DSA depicted only one lesion that was missed by DPCBCT due to streak artifacts caused by a prosthetic mitral valve. DAP-CBCT identified significantly more lesions than EAP-CBCT (p < 0.01). Conversely, EAP-CBCT did not detect lesions missed by DAP-CBCT. For complete lesion visibility, DAP-CBCT yielded significantly higher detectability (78.7 %) compared to EAP (31.1 %) and DSA (21.3 %) (p < 0.01).ConclusionDPCBCT, and especially the DAP-CBCT, significantly improved the detectability of ICC lesions during cTACE compared to DSA. We recommend the routine use of DAP-CBCT in patients with ICC for per-procedure detectability and treatment planning in the setting of TACE.

  8. Refractive Errors

    MedlinePlus

    ... and lens of your eye helps you focus. Refractive errors are vision problems that happen when the ... cornea, or aging of the lens. Four common refractive errors are Myopia, or nearsightedness - clear vision close ...

  9. Magnitude of observer error using cone beam CT for prostate interfraction motion estimation: effect of reducing scan length or increasing exposure

    PubMed Central

    Harris, Emma J; Hansen, Vibeke N; Thomas, Karen; South, Christopher; Hafeez, Shaista; Huddart, Robert; Dearnaley, David P

    2015-01-01

    Objective: Cone beam CT (CBCT) enables soft-tissue registration to planning CT for position verification in radiotherapy. The aim of this study was to determine the interobserver error (IOE) in prostate position verification using a standard CBCT protocol, and the effect of reducing CBCT scan length or increasing exposure, compared with standard imaging protocol. Methods: CBCT images were acquired using a novel 7 cm length image with standard exposure (1644 mAs) at Fraction 1 (7), standard 12 cm length image (1644 mAs) at Fraction 2 (12) and a 7 cm length image with higher exposure (2632 mAs) at Fraction 3 (7H) on 31 patients receiving radiotherapy for prostate cancer. Eight observers (two clinicians and six radiographers) registered the images. Guidelines and training were provided. The means of the IOEs were compared using a Kruzkal–Wallis test. Levene's test was used to test for differences in the variances of the IOEs and the independent prostate position. Results: No significant difference was found between the IOEs of each image protocol in any direction. Mean absolute IOE was the greatest in the anteroposterior direction. Standard deviation (SD) of the IOE was the least in the left–right direction for each of the three image protocols. The SD of the IOE was significantly less than the independent prostate motion in the anterior–posterior (AP) direction only (1.8 and 3.0 mm, respectively: p = 0.017). IOEs were within 1 SD of the independent prostate motion in 95%, 77% and 96% of the images in the RL, SI and AP direction. Conclusion: Reducing CBCT scan length and increasing exposure did not have a significant effect on IOEs. To reduce imaging dose, a reduction in CBCT scan length could be considered without increasing the uncertainty in prostate registration. Precision of CBCT verification of prostate radiotherapy is affected by IOE and should be quantified prior to implementation. Advances in knowledge: This study shows the importance

  10. A high-speed, high-efficiency phase controller for coherent beam combining based on SPGD algorithm

    SciTech Connect

    Huang, Zh M; Liu, C L; Li, J F; Zhang, D Y

    2014-04-28

    A phase controller for coherent beam combining (CBC) of fibre lasers has been designed and manufactured based on a stochastic parallel gradient descent (SPGD) algorithm and a field programmable gate array (FPGA). The theoretical analysis shows that the iteration rate is higher than 1.9 MHz, and the average compensation bandwidth of CBC for 5 or 20 channels is 50 kHz or 12.5 kHz, respectively. The tests show that the phase controller ensures reliable phase locking of lasers: When the phases of five lasers are locked by the improved control strategy with a variable gain, the energy encircled in the target is increased by 23 times than that in the single output, the phase control accuracy is better than λ/20, and the combining efficiency is 92%. (control of laser radiation parameters)

  11. Tight focusing of a higher-order radially polarized beam transmitting through multi-zone binary phase pupil filters.

    PubMed

    Guo, Hanming; Weng, Xiaoyu; Jiang, Man; Zhao, Yanhui; Sui, Guorong; Hu, Qi; Wang, Yang; Zhuang, Songlin

    2013-03-11

    When the pupil filters are used to improve the performance of the imaging system, the conversion efficiency is a critical characteristic for real applications. Here, in order to take full advantage of the subwavelength focusing property of the radially polarized higher-order Laguerre-Gaussian (LG) beam, we introduce the multi-zone binary phase pupil filters into the imaging system to deal with the problem that the focal spot is split along the z axis for the small size parameter of the incident LG beam. We provide an easy-to-perform procedure for the design of multi-zone binary phase pupil filters, where the zone numbers of π phase are uncertain when the optimizing procedure starts. Based on this optimizing procedure, we successfully find the set of optimum structures of a seventeen-belt binary phase pupil filters and generate the excellent focal spot, where the depth of focus, the focal spot transverse size, the Strehl ratio, and the sidelobe intensity are 9.53λ, 0.41λ, 41.75% and 16.35% in vacuum, respectively. Most importantly, even allowing the power loss of the incident LG beam truncated by the pupil of the imaging system, the conversion efficiency is still as high as 37.3%. Theoretical calculations show that we succeed to have sufficient conversion efficiency while utilizing the pupil filters to decrease the focal spot and extend the depth of focus. PMID:23482107

  12. Localization and migration of phase singularities in the edge-diffracted optical-vortex beams

    NASA Astrophysics Data System (ADS)

    Bekshaev, Aleksandr; Chernykh, Aleksey; Khoroshun, Anna; Mikhaylovskaya, Lidiya

    2016-02-01

    When a circularly-symmetric light beam with optical vortex (OV) diffracts at an opaque screen with the sharp edge, the OV core is displaced from the beam axis and, in case of the m-charged incident OV, decomposed into |m| single-charged ones. By means of numerical simulations and based on examples of incident beams with topological charges |m| = 1, 2, 3 we show that, while the screen edge monotonously advances towards the beam axis, the OVs in the diffracted beam cross section move away from the incident beam axis along spiral-like trajectories. The trajectories contain fine structure details that reflect the nature and peculiar spatial configuration of the diffracting beam. For the Kummer beams’ diffraction, the trajectories contain self-crossings and regions of ‘backward’ rotation (loops); in the case of Laguerre-Gaussian beams, the trajectories are smoother. The numerical results are supported by analytical approximations and conform to experiments. The general shape of the trajectories and their local behavior show high sensitivity to the diffraction conditions (spatial structure of the diffracting beam, its disposition with respect to the screen edge, etc), which can be used in diverse metrological applications.

  13. Phase transformation studies in unirradiated and proton beam irradiated Ni-Ti alloy between 25 and 100°C

    NASA Astrophysics Data System (ADS)

    Ayub, Rana; Afzal, Naveed; Ahmad, R.

    2012-06-01

    The stress-induced phase transformation characteristics of unirradiated and proton beam irradiated NiTi alloy were investigated at different tests temperatures. The wire-shaped NiTi specimens were irradiated by 2 MeV proton beam for 30 min at room temperature to a flux of 1019 protons/m2 s. Engineering stress-strain (S-S) curves of both unirradiated and irradiated specimens were obtained using a materials testing machine at 25, 50, 75 and 100°C. The results indicate a single-stage phase transformation from austenite to martensite (B2-B19‧) in unirraidated specimens at all the test temperatures. In contrast, in the case of the irradiated specimens, a two-stage austenite-rhombohedral-martensite (B2-R-B19‧) phase transformation is observed at 25 and 50°C. The B2-R-B19‧ phase transformation, however, is found to change into B2-B19‧ transformation at 75 and 100°C. The stress required to initiate the B19‧ phase transformation (σMS) and the plateau range are found to be lower in irradiated specimens compared with those of the unirradiated specimens. The results obtained are discussed on the basis of the formation of Ni4Ti3 precipitates in irradiated specimens and their consequences on the phase transformations.

  14. Experimental Demonstration of Longitudinal Beam Phase-Space Linearizer in a Free-Electron Laser Facility by Corrugated Structures

    NASA Astrophysics Data System (ADS)

    Deng, Haixiao; Zhang, Meng; Feng, Chao; Zhang, Tong; Wang, Xingtao; Lan, Taihe; Feng, Lie; Zhang, Wenyan; Liu, Xiaoqing; Yao, Haifeng; Shen, Lei; Li, Bin; Zhang, Junqiang; Li, Xuan; Fang, Wencheng; Wang, Dan; Couprie, Marie-emmanuelle; Lin, Guoqiang; Liu, Bo; Gu, Qiang; Wang, Dong; Zhao, Zhentang

    2014-12-01

    Removal of the undesired time-energy correlations in the electron beam is of paramount importance for efficient lasing of a high-gain free-electron laser. Recently, it has been theoretically and experimentally demonstrated that the longitudinal wakefield excited by the electrons themselves in a corrugated structure allows for precise control of the electron beam phase space. In this Letter, we report the first utilization of a corrugated structure as a beam linearizer in the operation of a seeded free-electron laser driven by a 140 MeV linear accelerator, where a gain of ˜10 000 over spontaneous emission was achieved at the second harmonic of the 1047 nm seed laser, and a free-electron laser bandwidth narrowing by 50% was observed, in good agreement with the theoretical expectations.

  15. Power combination of two phase-locked high power microwave beams from a new coaxial microwave source based on dual beams

    SciTech Connect

    Li, Yangmei; Zhang, Xiaoping Zhang, Jiande; Dang, Fangchao; Yan, Xiaolu

    2014-10-15

    The new coaxial high power microwave source based on dual beams has demonstrated two phase-locked output microwave beams generated by its two sub-sources. In order to achieve a single higher output power, we present a three-port waveguide-based power combiner to combine the two microwave beams. Particle-in-cell simulation results show that when the diode voltage is 675 kV and the guiding magnetic field is 0.8 T, a combined microwave with an average power of about 4.0 GW and a frequency of 9.74 GHz is generated; the corresponding power conversion efficiency is 29%. The combination effect of the combiner is further validated in the diode voltage range from 675 kV to 755 kV as well as in the pulse regime. The simulations indicate that the maximum surface axial electric field strength of the electrodynamic structure is 720 kV/cm, which is relatively low corresponding to an output power of 4.0 GW. The stable combined output suggests the probability of long-pulse operation for the combined source.

  16. An interferometer-based phase control system

    NASA Technical Reports Server (NTRS)

    Ott, J. H.; Rice, J. S.

    1981-01-01

    A system for focusing and pointing the SPS power beam is discussed. The system is ground based and closed loop. One receiving antenna is required on earth. A conventional uplinked data channel transmits an 8-bit phase error correction back to the SPS for sequential calibration of each power module. Beam pointing resolution is better than 140 meters at the rectenna.

  17. An interferometer-based phase control system

    NASA Technical Reports Server (NTRS)

    Ott, J. H.; Rice, J. S.

    1980-01-01

    A system for focusing and pointing the SPS power beam is discussed. The system is ground based and closed loop. One receiving antenna is required on Earth. A conventional uplink data channel transmits an 8-bit phase error correlation back to the SPS for sequential calibration of each power module. Beam pointing resolution is better than 140 meters at the Rectenna.

  18. Real-time monitoring of thermal and mechanical tissue response to modulated phased-array HIFU beams in vivo

    NASA Astrophysics Data System (ADS)

    Liu, Dalong; Ballard, John R.; Haritonova, Alyona; Choi, Jeungwan; Bischof, John; Ebbini, Emad S.

    2012-10-01

    An integrated system employing real-time ultrasound thermography and strain imaging in monitoring tissue response to phased-array heating patterns has been developed. The imaging system is implemented on a commercially available scanner (SonixRP) at frame rates > 500 fps with limited frame sizes covering the vicinity of the HIFU focal spot. These frame rates are sufficient to capture tissue motion and deformation even in the vicinity of large arteries. With the high temporal and spatial resolution of our strain imaging system, we are able to capture and separate tissue strains due to natural motion (breathing and pulsation) from HIFU induced strains (thermal and mechanical). We have collected in vivo strain imaging during sub-therapeutic and therapeutic HIFU exposure in swine and rat model. A 3.5-MHz phased array was used to generate sinusoidally-modulated pHIFU beams at different intensity levels and durations near blood vessels of different sizes (e.g. femoral in the swine and rat models). The results show that our approach is capable of characterizing the thermal and mechanical tissue response to sub-therapeutic pHIFU beam. For therapeutic pHIFU beams, the approach is still capable of localizing the therapeutic beam, but the results at the focal spot are complicated by bubble generation.

  19. Stokes parameters of phase-locked partially coherent flat-topped array laser beams propagating through turbulent atmosphere

    NASA Astrophysics Data System (ADS)

    Golmohammady, Sh; Ghafary, B.

    2016-06-01

    In this study, generalized Stokes parameters of a phase-locked partially coherent flat-topped array beam based on the extended Huygens–Fresnel principle and the unified theory of coherence and polarization have been reported. Analytical formulas for 2  ×  2 cross-spectral density matrix elements, and consequently Stokes parameters of a phase-locked partially coherent flat-topped array beam propagating through the turbulent atmosphere have been formulated. Effects of many physical attributes such as wavelength, turbulence strength, flatness order and other source parameters on the Stokes parameters, and therefore spectral degree of polarization upon propagation have been studied thoroughly. The behaviour of the spectral degree of coherence of a delineated beam for different source conditions has been investigated. It can be shown that four generalized Stokes parameters increase by raising the flatness order at the same propagation distance. Increasing the number of beams leads to a decrease in the Stokes parameters to zero slowly. The results are of utmost importance for optical communications.

  20. DETERMINING PHASE-SPACE PROPERTIES OF THE LEDA RFQ OUTPUT BEAM

    SciTech Connect

    W. LYSENKO; ET AL

    2000-08-01

    Quadruple scans were used to characterize the LEDA RFQ beam. Experimental data were fit to computer simulation models for the rms beam size. The codes were found to be inadequate in accurately reproducing details of the wire scanner data. When this discrepancy is resolved, we plan to fit using all the data in wire scanner profiles, not just the rms value.

  1. Influence of thermal defocusing on the quality of phase conjugation of Gaussian beams by stimulated Brillouin scattering

    SciTech Connect

    Kir'yanov, Yu F; Kochemasov, G G; Maslov, N V; Shestakova, I V

    1998-01-31

    A numerical investigation is reported of the influence of the thermal self-interaction of a Gaussian pump beam on the quality of phase conjugation by stimulated Brillouin scattering (SBS). A laser pulse is assumed to be sufficiently long to apply the equalised pressure approximation in calculating the acoustic field. All the calculations are carried out in a three-dimensional formulation for focused beams making use of an approximation linear in respect of the pump intensity. It is confirmed that the growth of thermal perturbations increases the SBS threshold and lowers the phase conjugation quality. A comparison of the calculated and published experimental results shows that they are in satisfactory quantitative agreement. (nonlinear optical phenomena and devices)

  2. 6D phase space electron beam analysis and machine sensitivity studies for ELI-NP GBS

    NASA Astrophysics Data System (ADS)

    Giribono, A.; Bacci, A.; Curatolo, C.; Drebot, I.; Palumbo, L.; Petrillo, V.; Rossi, A. R.; Serafini, L.; Vaccarezza, C.; Vannozzi, A.; Variola, A.

    2016-09-01

    The ELI-NP Gamma Beam Source (GBS) is now under construction in Magurele-Bucharest (RO). Here an advanced source of gamma photons with unprecedented specifications of brilliance (>1021), monochromaticity (0.5%) and energy tunability (0.2-19.5 MeV) is being built, based on Inverse Compton Scattering in the head-on configuration between an electron beam of maximum energy 750 MeV and a high quality high power ps laser beam. These requirements make the ELI-NP GBS an advanced and challenging gamma ray source. The electron beam dynamics analysis and control regarding the machine sensitivity to the possible jitter and misalignments are presented. The effects on the beam quality are illustrated providing the basis for the alignment procedure and jitter tolerances.

  3. Combined Phase SpaceCharacterization at the PEP-II IP using Single-beam and Luminous-region Measurements

    SciTech Connect

    Bevan, A.; Kozanecki, W.; Viaud, B.; Cai, Y.; Fisher, A.; O'Grady, C.; Thompson, J.; Weaver, M.; /SLAC

    2006-06-23

    We present a novel method to characterize the e{sup {+-}} phase space at the IP of the SLAC B-factory, that combines single-beam measurements with a detailed mapping of luminous-region observables. Transverse spot sizes are determined in the two rings with synchrotron-light monitors and extrapolated to the IP using measured lattice functions. The specific luminosity, which is proportional to the inverse product of the overlap IP beam sizes, is continuously monitored using radiative/Bhabha events. The spatial variation of the luminosity and of the transverse-boost distribution of the colliding e{sup {+-}}, are measured using e{sup +}e{sup -} {yields} {mu}{sup +}{mu}{sup -} events reconstructed in the BABAR detector. The combination of these measurements provide constraints on the emittances, horizontal and vertical spot sizes, angular divergences and {beta} functions of both beams at the IP during physics data-taking. Preliminary results of this combined spot-size analysis are confronted with independent measurements of IP {beta}-functions and overlap IP beam sizes at low beam current.

  4. Direct observation of the topological charge of a terahertz vortex beam generated by a Tsurupica spiral phase plate

    SciTech Connect

    Miyamoto, K.; Suizu, K.; Akiba, T.; Omatsu, T.

    2014-06-30

    A terahertz (THz) spiral phase plate with high transmission (>90% after Fresnel correction) and low dispersion has been developed based on the Tsurupica olefin polymer. Direct observations of the topological charge (both magnitude and sign) of a THz vortex beam are performed by using a THz camera with tilted lens focusing and radial defect introduction. The vortex outputs with a topological charge of ±1 (or ±2) are obtained at a frequency of 2 (or 4) THz.

  5. Real-Time Correction of Rigid-Body-Motion-Induced Phase Errors for Diffusion-Weighted Steady State Free Precession Imaging

    PubMed Central

    O’Halloran, R; Aksoy, M; Aboussouan, E; Peterson, E; Van, A; Bammer, R

    2014-01-01

    Purpose Diffusion contrast in diffusion-weighted steady state free precession MRI is generated through the constructive addition of signal from many coherence pathways. Motion-induced phase causes destructive interference which results in loss of signal magnitude and diffusion contrast. In this work, a 3D navigator-based real-time correction of the rigid-body-motion-induced phase errors is developed for diffusion-weighted steady state free precession MRI. Methods The efficacy of the real-time prospective correction method in preserving phase coherence of the steady-state is tested in 3D phantom experiments and 3D scans of healthy human subjects. Results In nearly all experiments, the signal magnitude in images obtained with proposed prospective correction was higher than the signal magnitude in images obtained with no correction. In the human subjects the mean magnitude signal in the data was up to 30 percent higher with prospective motion correction than without. Prospective correction never resulted in a decrease in mean signal magnitude in either the data or in the images. Conclusions The proposed prospective motion correction method is shown to preserve the phase coherence of the steady state in diffusion-weighted steady state free precession MRI, thus mitigating signal magnitude losses that would confound the desired diffusion contrast. PMID:24715414

  6. A simple method used to evaluate phase-change materials based on focused-ion beam technique

    NASA Astrophysics Data System (ADS)

    Peng, Cheng; Wu, Liangcai; Rao, Feng; Song, Zhitang; Lv, Shilong; Zhou, Xilin; Du, Xiaofeng; Cheng, Yan; Yang, Pingxiong; Chu, Junhao

    2013-05-01

    A nanoscale phase-change line cell based on focused-ion beam (FIB) technique has been proposed to evaluate the electrical property of the phase-change material. Thanks to the FIB-deposited SiO2 hardmask, only one etching step has been used during the fabrication process of the cell. Reversible phase-change behaviors are observed in the line cells based on Al-Sb-Te and Ge-Sb-Te films. The low power consumption of the Al-Sb-Te based cell has been explained by theoretical calculation accompanying with thermal simulation. This line cell is considered to be a simple and reliable method in evaluating the application prospect of a certain phase-change material.

  7. High-contrast grating MEMS optical phase-shifters for two-dimensional free-space beam steering

    NASA Astrophysics Data System (ADS)

    Megens, Mischa; Yoo, Byung-Wook; Chan, Trevor; Yang, Weijian; Sun, Tianbo; Chang-Hasnain, Connie J.; Wu, Ming C.; Horsley, David A.

    2014-02-01

    We report an optical phased array (OPA) for two-dimensional free-space beam steering. The array is composed of tunable MEMS all-pass filters (APFs) based on polysilicon high contrast grating (HCG) mirrors. The cavity length of each APF is voltage controlled via an electrostatically-actuated HCG top mirror and a fixed DBR bottom mirror. The HCG mirrors are composed of only a single layer of polysilicon, achieving >99% reflectivity through the use of a subwavelength grating patterned into the polysilicon surface. Conventional metal-coated MEMS mirrors must be thick (1-50 μm) to prevent warpage arising from thermal and residual stress. The single material construction used here results in a high degree of flatness even in a thin 350 nm HCG mirror. Relative to beamsteering systems based on a single rotating MEMS mirror, which are typically limited to bandwidths below 50 kHz, the MEMS OPA described here has the advantage of greatly reduced mass and therefore achieves a bandwidth over 500 kHz. The APF structure affords large (~2π) phase shift at a small displacement (< 50 nm), an order-of-magnitude smaller than the displacement required in a single-mirror phase-shifter design. Precise control of each all-pass-filter is achieved through an interferometric phase measurement system, and beam steering is demonstrated using binary phase patterns.

  8. Production of a Biomimetic Fe(I)-S Phase on Pyrite by Atomic-Hydrogen Beam-Surface Reactive Scattering

    PubMed Central

    Che, Li; Gardenghi, David J.; Szilagyi, Robert K.; Minton, Timothy K.

    2011-01-01

    Molecular beam-surface scattering and X-ray absorption spectroscopic experiments were employed to study the reaction of deuterium atoms with a pyrite, FeS2 (100), surface and to investigate the electronic and geometric structures of the resulting Fe-S phases. Incident D atoms, produced by a radio frequency plasma and expanded in an effusive beam, were directed at a pyrite surface held at various temperatures from ambient up to 200 °C. During exposure to the D-atom beam, D2S products were released with a thermal distribution of molecular speeds, indicating that the D atoms likely reacted in thermal equilibrium with the surface. The yield of D2S from the surface decreased approximately exponentially with exposure duration, suggesting that the surface accessible sulfur atoms were depleted, thus leaving an iron-rich surface. This conclusion is consistent with X-ray absorption measurements of the exposed surfaces, which indicated the formation of a layered structure, with elemental iron as the outermost layer on top of a formally Fe(I)-S phase as an intermediate layer and a formally Fe(II)-S2 bulk pyrite layer at lower depths. The reduced Fe(I)-S phase is particularly remarkable because of its similarity to the catalytically active sites of small molecule metalloenzymes, such as FeFe-hydrogenases and MoFe-nitrogenases. PMID:21526811

  9. Tailoring the optimal control cost function to a desired output: application to minimizing phase errors in short broadband excitation pulses

    NASA Astrophysics Data System (ADS)

    Skinner, Thomas E.; Reiss, Timo O.; Luy, Burkhard; Khaneja, Navin; Glaser, Steffen J.

    2005-01-01

    The de facto standard cost function has been used heretofore to characterize the performance of pulses designed using optimal control theory. The freedom to choose new, creative quality factors designed for specific purposes is demonstrated. While the methodology has more general applicability, its utility is illustrated by comparison to a consistently chosen example—broadband excitation. The resulting pulses are limited to the same maximum RF amplitude used previously and tolerate the same variation in RF homogeneity deemed relevant for standard high-resolution NMR probes. Design criteria are unchanged: transformation of Iz → Ix over resonance offsets of ±20 kHz and RF variability of ±5%, with a peak RF amplitude equal to 17.5 kHz. However, the new cost effectively trades a small increase in residual z magnetization for improved phase in the transverse plane. Compared to previous broadband excitation by optimized pulses (BEBOP), significantly shorter pulses are achievable, with only marginally reduced performance. Simulations transform Iz to greater than 0.98 Ix, with phase deviations of the final magnetization less than 2°, over the targeted ranges of resonance offset and RF variability. Experimental performance is in excellent agreement with the simulations.

  10. Beam diagnostics

    SciTech Connect

    Bogaty, J.; Clifft, B.E.; Zinkann, G.P.; Pardo, R.C.

    1995-08-01

    The ECR-PII injector beam line is operated at a fixed ion velocity. The platform high voltage is chosen so that all ions have a velocity of 0.0085c at the PII entrance. If a previous tune configuration for the linac is to be used, the beam arrival time must be matched to the previous tune as well. A nondestructive beam-phase pickup detector was developed and installed at the entrance to the PII linac. This device provides continuous phase and beam current information and allows quick optimization of the beam injected into PII. Bunches traverse a short tubular electrode thereby inducing displacement currents. These currents are brought outside the vacuum interface where a lumped inductance resonates electrode capacitance at one of the bunching harmonic frequencies. This configuration yields a basic sensitivity of a few hundred millivolts signal per microampere of beam current. Beam-induced radiofrequency signals are summed against an offset frequency generated by our master oscillator. The resulting kilohertz difference frequency conveys beam intensity and bunch phase information which is sent to separate processing channels. One channel utilizes a phase locked loop which stabilizes phase readings if beam is unstable. The other channel uses a linear full wave active rectifier circuit which converts kilohertz sine wave signal amplitude to a D.C. voltage representing beam current. A prototype set of electronics is now in use with the detector and we began to use the system in operation to set the arrival beam phase. A permanent version of the electronics system for the phase detector is now under construction. Additional nondestructive beam intensity and phase monitors at the {open_quotes}Booster{close_quotes} and {open_quotes}ATLAS{close_quotes} linac sections are planned as well as on some of the high-energy beam lines. Such a monitor will be particularly useful for FMA experiments where the primary beam hits one of the electric deflector plates.

  11. Simulated performance of the superconducting section of the APT linac under various fault and error conditions

    SciTech Connect

    Gray, E.R.; Nath, S.; Wangler, T.P.

    1997-08-01

    The current design for the production of tritium uses both normal-conducting (NC) and superconducting (SC) structures. To evaluate the performance of the superconducting part of the linac which constitutes more than 80% of the accelerator, studies have been made to include the effects of various error and fault conditions. Here, the authors present the simulation results of studies such as effects of rf phase and amplitude errors, cavity/klystron failure, quadrupole misalignment errors, quadrupole gradient error, and beam-input mismatches.

  12. Rheological properties of styrene-butadiene rubber filled with electron beam modified surface treated dual phase fillers

    NASA Astrophysics Data System (ADS)

    Shanmugharaj, A. M.; Bhowmick, Anil K.

    2004-01-01

    The rheological properties of styrene-butadiene rubber (SBR) loaded with dual phase filler were measured using Monsanto Processability Tester (MPT) at three different temperatures (100°C, 110°C and 130°C) and four different shear rates (61.3, 306.3, 613, and 1004.5 s -1). The effect of electron beam modification of dual phase filler in absence and presence of trimethylol propane triacrylate (TMPTA) or triethoxysilylpropyltetrasulphide (Si-69) on melt flow properties of SBR was also studied. The viscosity of all the systems decreases with shear rate indicating their pseudoplastic or shear thinning nature. The higher shear viscosity for the SBR loaded with the electron beam modified filler is explained in terms of variation in structure of the filler upon electron beam irradiation. Die swell of the modified filler loaded SBR is slightly higher than that of the unmodified filler loaded rubber, which is explained by calculating normal stress difference for the systems. Activation energy of the modified filler loaded SBR systems is also slightly higher than that of the control filler loaded SBR system.

  13. Effect of crosslinking agent functionality and curing beam intensity on the phase separation kinetics of a photopolymerizing PDLC

    NASA Astrophysics Data System (ADS)

    Crawford, Nathan; Dadmun, Mark

    2004-03-01

    Polymer dispersed liquid crystals (PDLC's) are used to construct a variety of electro-optical devices, including privacy windows and holographic diffraction gratings. The final morphology of a given PDLC device depends not only on the initial syrup composition but also the polymerization and phase separation rate. In this work we report time-resolved light scattering results that monitor the phase separation kinetics of PDLC syrups undergoing photo-polymerization. Both the intensity of the curing beam and the composition of the syrups were allowed to vary. The presence of an intensity maximum at a given wave vector, q, during the early stages of polymerization appear to support spinodal decomposition (SD) as the phase separation mechanism. This process is analyzed to provide quantification of the interphase periodic distance and the mobility of the components in this process.

  14. Phase Space Generation for Proton and Carbon Ion Beams for External Users’ Applications at the Heidelberg Ion Therapy Center

    PubMed Central

    Tessonnier, Thomas; Marcelos, Tiago; Mairani, Andrea; Brons, Stephan; Parodi, Katia

    2016-01-01

    In the field of radiation therapy, accurate and robust dose calculation is required. For this purpose, precise modeling of the irradiation system and reliable computational platforms are needed. At the Heidelberg Ion Therapy Center (HIT), the beamline has been already modeled in the FLUKA Monte Carlo (MC) code. However, this model was kept confidential for disclosure reasons and was not available for any external team. The main goal of this study was to create efficiently phase space (PS) files for proton and carbon ion beams, for all energies and foci available at HIT. PSs are representing the characteristics of each particle recorded (charge, mass, energy, coordinates, direction cosines, generation) at a certain position along the beam path. In order to achieve this goal, keeping a reasonable data size but maintaining the requested accuracy for the calculation, we developed a new approach of beam PS generation with the MC code FLUKA. The generated PSs were obtained using an infinitely narrow beam and recording the desired quantities after the last element of the beamline, with a discrimination of primaries or secondaries. In this way, a unique PS can be used for each energy to accommodate the different foci by combining the narrow-beam scenario with a random sampling of its theoretical Gaussian beam in vacuum. PS can also reproduce the different patterns from the delivery system, when properly combined with the beam scanning information. MC simulations using PS have been compared to simulations, including the full beamline geometry and have been found in very good agreement for several cases (depth dose distributions, lateral dose profiles), with relative dose differences below 0.5%. This approach has also been compared with measured data of ion beams with different energies and foci, resulting in a very satisfactory agreement. Hence, the proposed approach was able to fulfill the different requirements and has demonstrated its capability for application to

  15. Dual-axis beam correction for an array of single-mode diode laser emitters using a laser-written custom phase-plate.

    PubMed

    Trela, Natalia; Baker, Howard J; Wendland, Jozef J; Hall, Denis R

    2009-12-21

    A single optical component for a diode laser bar combines fast-axis smile and lens error correction with slow-axis collimation. Produced by laser-machining/polishing, it provides 0.9 mm focal length, 200 microm pitch slow-axis collimation on the same surface that corrects fast-axis errors. Custom fabrication enables fill-factor optimization for the 49 single-mode beams and gives parallel collimation with rms pointing errors of 3% and 6% of the far-field divergence for the fast- and slow-axis array respectively. Sub-micron pitch mismatch between the slow-axis lens and emitter arrays, and beam pointing changes by thermal expansion of the laser bar are detected. PMID:20052066

  16. Two-beam ultrabroadband coherent anti-Stokes Raman spectroscopy for high resolution gas-phase multiplex imaging

    SciTech Connect

    Bohlin, Alexis; Kliewer, Christopher J.

    2014-01-20

    We propose and develop a method for wideband coherent anti-Stokes Raman spectroscopy (CARS) in the gas phase and demonstrate the single-shot measurement of N{sub 2}, H{sub 2}, CO{sub 2}, O{sub 2}, and CH{sub 4}. Pure-rotational and vibrational O-, Q-, and S- branch spectra are collected simultaneously, with high spectral and spatial resolution, and within a single-laser-shot. The relative intensity of the rotational and vibrational signals can be tuned arbitrarily using polarization techniques. The ultrashort 7 fs pump and Stokes pulses are automatically overlapped temporally and spatially using a two-beam CARS technique, and the crossed probe beam allows for excellent spatial sectioning of the probed location.

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

    SciTech Connect

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

    1997-03-01

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

  18. Residual stress measurement in thin films using a slitting method with geometric phase analysis under a dual beam (FIB/SEM) system

    NASA Astrophysics Data System (ADS)

    Zhu, Ronghua; Xie, Huimin; Dai, Xianglu; Zhu, Jianguo; Jin, Aizi

    2014-09-01

    Stress generated during thin film deposition is a critical issue for many applications. In general, the possible origins of the residual stress include intrinsic and extrinsic stresses. Since high residual stresses can cause detrimental effects on the film, such as delamination and wrinkle, it is of great importance to quantify the residual stress for the optimal design and the evaluation of its mechanical behavior. In this study, a method combining focused ion beam (FIB) milling and geometric phase analysis (GPA) is developed to assess the residual stress of thin films. The procedures of the residual stress measurement using this method include grating fabrication and slot milling by FIB, high-resolution scanning electron microscope (SEM) imaging of the grating before and after stress relaxation, and deformation analysis by GPA. The residual stress can be inferred from the released deformation using the reference displacements of the finite element model. As an application, this method was utilized to measure the residual stress in a TiAlSiN film, and the measured result is in good agreement with that obtained by the curvature method. In order to analyze the measurement error, the influence factors of Ga+ bombardment and the deposited platinum layer on the stress calculation are also discussed in detail.

  19. X–ray absorption, phase and dark–field tomography through a beam tracking approach

    PubMed Central

    Vittoria, Fabio A.; Endrizzi, Marco; Diemoz, Paul C.; Zamir, Anna; Wagner, Ulrich H.; Rau, Christoph; Robinson, Ian K.; Olivo, Alessandro

    2015-01-01

    We present a development of the beam–tracking approach that allows its implementation in computed tomography. One absorbing mask placed before the sample and a high resolution detector are used to track variations in the beam intensity distribution caused by the sample. Absorption, refraction, and dark–field are retrieved through a multi–Gaussian interpolation of the beam. Standard filtered back projection is used to reconstruct three dimensional maps of the real and imaginary part of the refractive index, and of the dark–field signal. While the method is here demonstrated using synchrotron radiation, its low coherence requirements suggest a possible implementation with laboratory sources. PMID:26541117

  20. Growth and phase transition characteristics of pure M-phase VO{sub 2} epitaxial film prepared by oxide molecular beam epitaxy

    SciTech Connect

    Fan, L. L.; Chen, S.; Wu, Y. F.; Chen, F. H.; Chu, W. S.; Chen, X.; Zou, C. W.; Wu, Z. Y.

    2013-09-23

    VO{sub 2} epitaxial film with large size has been prepared by oxide-molecular beam epitaxy method on Al{sub 2}O{sub 3} (0001) substrate. The VO{sub 2} film shows a perfect crystal orientation, uniformity, and distinct metal-insulator phase transition (MIT) characteristics. It is observed that the MIT character is closely associated with the crystal defects such as oxygen vacancies. By controlling the growth condition, the MIT temperature can be tuned through modifying the content of oxygen vacancies. The role of the oxygen vacancies on the phase transition behavior of this VO{sub 2} film is discussed in the framework of the hybridization theory and the valence state of vanadium.

  1. An orbit fit program for localizing errors in RHIC

    SciTech Connect

    Liu, C.; Minty, M.; Ptitsyn, V.

    2011-11-01

    Many errors in an accelerator are evidenced as transverse kicks to the beam which distort the beam trajectory. Therefore, the information of the errors are imprinted in the distorted orbits, which are different from what would be predicted by the optics model. In this note, we introduce an algorithm for fitting the orbit based on an on-line optics model. By comparing the measured and fitted orbits, we first present results validating the algorithm. We then apply the algorithm and localize the location of the elusive source of vertical diurnal variations observed in RHIC. The difference of two trajectories (linear accelerator) or closed orbits (storage ring) should match exactly a betatron oscillation, which is predictable by the optics model, in an ideal machine. However, in the presence of errors, the measured trajectory deviates from prediction since the model is imperfect. Comparison of measurement to model can be used to detect such errors. To do so the initial conditions (phase space parameters at any point) must be determined which can be done by comparing the difference orbit to prediction using only a few beam position monitors (BPMs). The fitted orbit can be propagated along the beam line based on the optics model. Measurement and model will agree up to the point of an error. The error source can be better localized by additionally fitting the difference orbit using downstream BPMs and back-propagating the solution. If one dominating error source exist in the machine, the fitted orbit will deviate from the difference orbit at the same point.

  2. Distribution of high-stability 100.04  GHz millimeter wave signal over 60  km optical fiber with fast phase-error-correcting capability.

    PubMed

    Sun, Dongning; Dong, Yi; Shi, Hongxiao; Xia, Zongyang; Liu, Zhangweiyi; Wang, Siwei; Xie, Weilin; Hu, Weisheng

    2014-05-15

    We demonstrate a phase-stabilized remote distribution of 100.04 GHz millimeter wave signal over 60 km optical fiber. The phase error of the remote millimeter wave signal induced by fiber transmission delay variations is detected by dual-heterodyne phase error transfer and corrected with a feedback system based on a fast response acousto-optic frequency shifter. The phase noise within the bandwidth of 300 Hz is effectively suppressed; thus, the fast transmission delay variations can be compensated. The residual phase noise of the remote 100.04 GHz signal reaches -56  dBc/Hz at 1 Hz frequency offset from the carrier, and long-term stability of 1.6×10(-16) at 1000 s averaging time is achieved. The fast phase-noise-correcting capability is evaluated by vibrating part of the transmission fiber link. PMID:24978219

  3. Medication Errors

    MedlinePlus

    ... to reduce the risk of medication errors to industry and others at FDA. Additionally, DMEPA prospectively reviews ... List of Abbreviations Regulations and Guidances Guidance for Industry: Safety Considerations for Product Design to Minimize Medication ...

  4. Medication Errors

    MedlinePlus

    Medicines cure infectious diseases, prevent problems from chronic diseases, and ease pain. But medicines can also cause harmful reactions if not used ... You can help prevent errors by Knowing your medicines. Keep a list of the names of your ...

  5. An estimate of the error caused by the elongation of the wavelength in a focused beam in free-space electromagnetic parameters measurement

    SciTech Connect

    Zhang, Yunpeng; Li, En Guo, Gaofeng; Xu, Jiadi; Wang, Chao

    2014-09-15

    A pair of spot-focusing horn lens antenna is the key component in a free-space measurement system. The electromagnetic constitutive parameters of a planar sample are determined using transmitted and reflected electromagnetic beams. These parameters are obtained from the measured scattering parameters by the microwave network analyzer, thickness of the sample, and wavelength of a focused beam on the sample. Free-space techniques introduced by most papers consider the focused wavelength as the free-space wavelength. But in fact, the incident wave projected by a lens into the sample approximates a Gaussian beam, thus, there has an elongation of the wavelength in the focused beam and this elongation should be taken into consideration in dielectric and magnetic measurement. In this paper, elongation of the wavelength has been analyzed and measured. Measurement results show that the focused wavelength in the vicinity of the focus has an elongation of 1%–5% relative to the free-space wavelength. Elongation's influence on the measurement result of the permittivity and permeability has been investigated. Numerical analyses show that the elongation of the focused wavelength can cause the increase of the measured value of the permeability relative to traditionally measured value, but for the permittivity, it is affected by several parameters and may increase or decrease relative to traditionally measured value.

  6. Transverse phase-space evolution in non-stationary charged particle beams

    SciTech Connect

    Bohn, C.L.

    1992-10-01

    The transverse dynamics of a nonrelativistic, mismatched, one- dimensional sheet beam propagating through a continuous, linear focusing channel is investigated. The investigation is based on the Fokker-Planck equation in which the relaxation rate and diffusion coefficient are calculated from a simple model of turbulence resulting from charge redistribution.

  7. Transverse phase-space evolution in non-stationary charged particle beams

    SciTech Connect

    Bohn, C.L.

    1992-01-01

    The transverse dynamics of a nonrelativistic, mismatched, one- dimensional sheet beam propagating through a continuous, linear focusing channel is investigated. The investigation is based on the Fokker-Planck equation in which the relaxation rate and diffusion coefficient are calculated from a simple model of turbulence resulting from charge redistribution.

  8. Synthesis of dynamic phase profile by the correlation technique for spatial control of optical beams in multiplexing and switching

    NASA Astrophysics Data System (ADS)

    Bugaychuk, Svitlana A.; Gnatovskyy, Vladimir O.; Sidorenko, Andrey V.; Pryadko, Igor I.; Negriyko, Anatoliy M.

    2015-11-01

    New approach for the correlation technique, which is based on multiple periodic structures to create a controllable angular spectrum, is proposed and investigated both theoretically and experimentally. The transformation of an initial laser beam occurs due to the actions of consecutive phase periodic structures, which may differ by their parameters. Then, after the Fourier transformation of a complex diffraction field, the output diffraction orders will be changed both by their intensities and by their spatial position. The controllable change of output angular spectrum is carried out by a simple control of the parameters of the periodic structures. We investigate several simple examples of such management.

  9. Comparative Study of Solid-Phase Crystallization of Amorphous Silicon Deposited by Hot-Wire CVD, Plasma-Enhanced CVD, and Electron-Beam Evaporation

    SciTech Connect

    Stradins, P.; Kunz, O.; Young, D. L.; Yan, Y.; Jones, K. M.; Xu, Y.; Reedy, R. C.; Branz, H. M.; Aberle, A. G.; Wang, Q.

    2007-01-01

    Solid-phase crystallization (SPC) rates are compared in amorphous silicon films prepared by three different methods: hot-wire chemical vapor deposition (HWCVD), plasma-enhanced chemical vapor deposition (PECVD), and electron-beam physical vapor deposition (e-beam). Random SPC proceeds approximately 5 and 13 times slower in PECVD and e-beam films, respectively, as compared to HWCVD films. Doping accelerates random SPC in e-beam films but has little effect on the SPC rate of HWCVD films. In contrast, the crystalline growth front in solid-phase epitaxy experiments propagates at similar speed in HWCVD, PECVD, and e-beam amorphous Si films. This strongly suggests that the observed large differences in random SPC rates originate from different nucleation rates in these materials while the grain growth rates are relatively similar. The larger grain sizes observed for films that exhibit slower random SPC support this suggestion.

  10. An interferometer based phase control system

    NASA Technical Reports Server (NTRS)

    Ott, J. H.; Rice, J. S.

    1980-01-01

    An interferometer based phase control system for focusing and pointing the solar power satellite (SPS) power beam is discussed. The system is ground based and closed loop. One receiving antenna is required on Earth. A conventional uplink data channel transmits an 8 bit phase error correction back to the SPS for sequential calibration of each power module. Beam pointing resolution is better than 140 meters at the rectenna.

  11. Interferometer-based phase control system

    SciTech Connect

    Ott, J.H.; Rice, J.S.

    1980-01-01

    An interferometer-based phase control system for focusing and pointing the SPS power beam is discussed. The system is ground based and closed loop. One receiving antenna is required on earth. A conventional uplink data channel transmits an 8-bit phase error correction back to the SPS for sequential calibration of each power module. Beam pointing resolution is better than 140 meters at the Rectenna. 1 ref.

  12. Heating and ionization of stellar chromospheres by nonthermal proton beams: Implications for impulsive phase, redshifted Lyman-alpha radiation in stellar flares

    NASA Technical Reports Server (NTRS)

    Brosius, Jeffrey W.; Robinson, Richard D.; Maran, Stephen P.

    1995-01-01

    We investigate the physical basis for the timescale of impulsive-phase, redshifted Lyman-alpha emission in stellar flares on the assumption that it is determined by energy losses in a nonthermal proton beam that is penetrating the chromosphere from above. The temporal evolution of ionization and heating in representative model chromospheres subjected to such beams is calculated. The treatment of 'stopping' of beam protons takes into account their interactions with (1) electrons bound in neutral hydrogen, (2) nuclei of neutral hydrogen, (3) free electrons, and (4) ambient thermal protons. We find that, for constant incident beam flux, the system attains an equilibrium with the beam energy input to the chromosphere balanced by radiative losses. In equilibrium, the beam penetration depth is constant, and erosion of the chromosphere ceases. If the redshifted, impulsive-phase stellar flare Lyman-alpha emission is produced by downstreaming hydrogen formed through charge exchange between beam protons and ambient hydrogen, then the emission should end when the beam no longer reaches neutral hydrogen. The durations of representative emission events calculated on this assumption range from 0.1 to 14 s. The stronger the beam, the shorter the timescale over which the redshifted Lyman-alpha emission can be observed.

  13. Electrical performance of phase change memory cells with Ge3Sb2Te6 deposited by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Boschker, Jos E.; Boniardi, Mattia; Redaelli, Andrea; Riechert, Henning; Calarco, Raffaella

    2015-01-01

    Here, we report on the electrical characterization of phase change memory cells containing a Ge3Sb2Te6 (GST) alloy grown in its crystalline form by Molecular Beam Epitaxy (MBE). It is found that the high temperature growth on the amorphous substrate results in a polycrystalline film exhibiting a rough surface with a grain size of approximately 80-150 nm. A detailed electrical characterization has been performed, including I-V characteristic curves, programming curves, set operation performance, crystallization activation at low temperature, and resistance drift, in order to determine the material related parameters. The results indicate very good alignment of the electrical parameters with the current state-of-the-art GST, deposited by physical vapor deposition. Such alignment enables a possible employment of the MBE deposition technique for chalcogenide materials in the phase change memory technology, thus leading to future studies of as-deposited crystalline chalcogenides as integrated in electrical vehicles.

  14. Oblique incidence effect on steering efficiency of liquid crystal polarization gratings used for optical phased array beam steering amplification

    NASA Astrophysics Data System (ADS)

    Xiangjie, Zhao; Jiazhu, Duan; Dayong, Zhang; Cangli, Liu; Yongquan, Luo

    2016-07-01

    A liquid crystal polarization grating (LCPG) is proposed that amplifies the steering angle of a liquid crystal optical phased array for non-mechanical beam steering, taking advantage of its high steering efficiency under normal incidence. However, oblique incidence may play an important role in the overall steering efficiency. The effect of oblique incidence on steering efficiency of a LCPG was analyzed by numerically solving the extended Jones matrix and considering propagation crosstalk. The results indicate that the outgoing laser beam is amplitude-modulated under the effect of oblique incidence and behaves as a sinusoidal-modulated amplitude grating, which diffracts certain energies to non-blazed orders. Over-oblique incidence may even eliminate the steering effect of the incident beam. The modulation depth of the induced amplitude grating was found to be proportional to the product of sinusoidal value of oblique incidence angle and the LC layer thickness, and inversely proportional to the periodic pitch length of the LCPG. Both in-plane incidence and out-of-plane incidence behave similarly to influence the steering efficiency. Finally, the overall steering efficiency for cascaded LCPGs was analyzed and a difference of up to 11 % steering efficiency can be induced between different LCPG configurations, even without considering the over-oblique incidence effect. Both the modulation depth and final steering efficiency can be optimized by varying the LC birefringence and layer thickness.

  15. Beam quality improvement of pulsed Nd:YAG lasers using Brillouin phase conjugation

    NASA Astrophysics Data System (ADS)

    Eichler, Hans J.; Haase, Andreas; Hermann, S.; Menzel, Ralf; Schumann, D.

    1993-04-01

    Using phaseconjugating mirrors (PCMs) the beam quality of solid state lasers can be improved by compensating the thermal lens of the rods at high average powers. Oscillators with one PCM as a highly reflecting mirror and double-pass amplifiers with PCMs have been investigated. PCMs are realized by stimulated Brillouin scattering (SBS). Nd:YAG and Nd,Cr:GSGG oscillators have been built with pulse repetition rates up to 45 Hz. Stable TEM00-mode operation has been obtained. Average output powers of 10 watts for 15 ns Q-switched pulses of a Nd:YAG laser and 7 watts for Nd,Cr:GSGG have been achieved. In a double pass Nd:YAG amplifier the thermal lens was compensated leading to a nearly diffraction limited beam with a maximum output power of 40 watts.

  16. High-efficiency beam manipulation combining geometric phase with anisotropic Huygens surface

    NASA Astrophysics Data System (ADS)

    Zhao, Wenyu; Jiang, Huan; Liu, Bingyi; Song, Jie; Jiang, Yongyuan

    2016-05-01

    Conventional geometric metasurfaces relying on space-variant metal antennas for beam manipulation suffer from strong Ohmic loss and incomplete polarization conversion. The efficiency is often limited to rather small values, especially when operating in transmission mode. Here, we tackle this challenge by deliberately constructing an equivalent sheet with anisotropic surface electric and magnetic polarizabilities using cross-shaped dielectric antennas. An incident circularly polarized light can be almost fully converted to a transmitted light of opposite helicity with an unprecedented efficiency up to 98%. Such a transmissive metasurface possessing the merits of high-efficiency, non-dispersion, and robust against variations can serve as an outstanding candidate for flat optics, such as anomalous refraction and beam focusing.

  17. Rapid phase-correlated rescanning irradiation improves treatment time in carbon-ion scanning beam treatment under irregular breathing

    NASA Astrophysics Data System (ADS)

    Mori, Shinichiro; Furukawa, Takuji

    2016-05-01

    To shorten treatment time in pencil beam scanning irradiation, we developed rapid phase-controlled rescanning (rPCR), which irradiates two or more isoenergy layers in a single gating window. Here, we evaluated carbon-ion beam dose distribution with rapid and conventional PCR (cPCR). 4 dimensional computed tomography (4DCT) imaging was performed on 12 subjects with lung or liver tumors. To compensate for intrafractional range variation, the field-specific target volume (FTV) was calculated using 4DCT within the gating window (T20–T80). We applied an amplitude-based gating strategy, in which the beam is on when the tumor is within the gating window defined by treatment planning. Dose distributions were calculated for layered phase-controlled rescanning under an irregular respiratory pattern, although a single 4DCT data set was used. The number of rescannings was eight times. The prescribed doses were 48 Gy(RBE)/1 fr (where RBE is relative biological effectiveness) delivered via four beam ports to the FTV for the lung cases and 45 Gy(RBE)/2 fr delivered via two beam ports to the FTV for the liver cases. In the liver cases, the accumulated dose distributions showed an increased magnitude of hot/cold spots with rPCR compared with cPCR. The results of the dose assessment metrics for the cPCR and rPCR were very similar. The D 95, D max, and D min values (cPCR/rPCR) averaged over all the patients were 96.3  ±  0.9%/96.0  ±  1.2%, 107.3  ±  3.6%/107.1  ±  2.9%, and 88.8  ±  3.2%/88.1  ±  3.1%, respectively. The treatment times in cPCR and rPCR were 110.7 s and 53.5 s, respectively. rPCR preserved dose conformation under irregular respiratory motion and reduced the total treatment time compared with cPCR.

  18. Rapid phase-correlated rescanning irradiation improves treatment time in carbon-ion scanning beam treatment under irregular breathing.

    PubMed

    Mori, Shinichiro; Furukawa, Takuji

    2016-05-21

    To shorten treatment time in pencil beam scanning irradiation, we developed rapid phase-controlled rescanning (rPCR), which irradiates two or more isoenergy layers in a single gating window. Here, we evaluated carbon-ion beam dose distribution with rapid and conventional PCR (cPCR). 4 dimensional computed tomography (4DCT) imaging was performed on 12 subjects with lung or liver tumors. To compensate for intrafractional range variation, the field-specific target volume (FTV) was calculated using 4DCT within the gating window (T20-T80). We applied an amplitude-based gating strategy, in which the beam is on when the tumor is within the gating window defined by treatment planning. Dose distributions were calculated for layered phase-controlled rescanning under an irregular respiratory pattern, although a single 4DCT data set was used. The number of rescannings was eight times. The prescribed doses were 48 Gy(RBE)/1 fr (where RBE is relative biological effectiveness) delivered via four beam ports to the FTV for the lung cases and 45 Gy(RBE)/2 fr delivered via two beam ports to the FTV for the liver cases. In the liver cases, the accumulated dose distributions showed an increased magnitude of hot/cold spots with rPCR compared with cPCR. The results of the dose assessment metrics for the cPCR and rPCR were very similar. The D 95, D max, and D min values (cPCR/rPCR) averaged over all the patients were 96.3  ±  0.9%/96.0  ±  1.2%, 107.3  ±  3.6%/107.1  ±  2.9%, and 88.8  ±  3.2%/88.1  ±  3.1%, respectively. The treatment times in cPCR and rPCR were 110.7 s and 53.5 s, respectively. rPCR preserved dose conformation under irregular respiratory motion and reduced the total treatment time compared with cPCR. PMID:27100312

  19. Beam test characterization of CMS silicon pixel detectors for the phase-1 upgrade

    NASA Astrophysics Data System (ADS)

    Korol, I.

    2015-10-01

    The Silicon Pixel Detector forms the innermost part of the CMS tracking system and is critical to track and vertex reconstruction. Being in close proximity to the beam interaction point, it is exposed to the highest radiation levels in the silicon tracker. In order to preserve the tracking performance with the LHC luminosity increase which is foreseen for the next years, the CMS collaboration has decided to build a new pixel detector with four barrel layers mounted around a reduced diameter beam pipe, as compared to the present three layer pixel detector in the central region. A new digital version of the front-end readout chip has been designed and tested; it has increased data buffering and readout link speed to maintain high efficiency at increasing occupancy. In addition, it offers lower charge thresholds that will improve the tracking efficiency and position resolution. Single chip modules have been evaluated in the DESY electron test beam in terms of charge collection, noise, tracking efficiency and position resolution before and after irradiation with 24 GeV protons from the CERN Proton Synchroton equivalent to the fluence expected after 500 fb-1 of integrated luminosity in the fourth layer of the pixel tracker. High efficiency and an excellent position resolution have been observed which are well maintained even after the proton irradiation. The results are well described by the CMS pixel detector simulation.

  20. Formation of structure, phase composition and properties of electro explosion resistant coatings using electron-beam processing

    SciTech Connect

    Romanov, Denis A. E-mail: kos2906@mail.ru E-mail: gromov@physics.sibsiu.ru Sosnin, Kirill V. E-mail: kos2906@mail.ru E-mail: gromov@physics.sibsiu.ru Budovskikh, Evgenij A. E-mail: kos2906@mail.ru E-mail: gromov@physics.sibsiu.ru Gromov, Viktor E. E-mail: kos2906@mail.ru E-mail: gromov@physics.sibsiu.ru Semin, Alexander P. E-mail: kos2906@mail.ru E-mail: gromov@physics.sibsiu.ru

    2014-11-14

    For the first time, the high intensity electron beam modification of electroexplosion composite coatings of MoCu, MoCCu, WCu, WCCu and TiB{sub 2}Cu systems was done. The studies of phase and elemental composition, defective structure conditions of these coatings were carried out. The regimes of electron-beam processing making possible to form the dense, specular luster surface layers having a submicrocrystalline structure were revealed. It was established that electron-beam processing of elecroexplosion spraying of layer of elecroexplosion spraying carried out in the regime of melting results in the formation of structurally and contrationally homogeneous surface layer. Investigation of the effect of electron-beam processing of electroexplosion electroerosion resistant coatings on their tribological properties (wear resistanse and coefficient of friction) and electroerosion resistance was done. It was shown that all the examined costings demonstrate the increase of electroerosion resistance in spark erosion up to 10 times.

  1. Pattern manipulation via on-chip phase modulation between orbital angular momentum beams

    SciTech Connect

    Li, Huanlu; Strain, Michael J.; Meriggi, Laura; Sorel, Marc; Chen, Lifeng; Zhu, Jiangbo; Cicek, Kenan; Wang, Jianwei; Thompson, Mark G.; Cai, Xinlun; Yu, Siyuan

    2015-08-03

    An integrated approach to thermal modulation of relative phase between two optical vortices with opposite chirality has been demonstrated on a silicon-on-insulator substrate. The device consists of a silicon-integrated optical vortex emitter and a phase controlled 3 dB coupler. The relative phase between two optical vortices can be actively modulated on chip by applying a voltage on the integrated heater. The phase shift is shown to be linearly proportional to applied electrical power, and the rotation angle of the interference pattern is observed to be inversely proportional to topological charge. This scheme can be used in lab-on-chip, communications and sensing applications. It can be intentionally implemented with other modulation elements to achieve more complicated applications.

  2. Skylab water balance error analysis

    NASA Technical Reports Server (NTRS)

    Leonard, J. I.

    1977-01-01

    Estimates of the precision of the net water balance were obtained for the entire Skylab preflight and inflight phases as well as for the first two weeks of flight. Quantitative estimates of both total sampling errors and instrumentation errors were obtained. It was shown that measurement error is minimal in comparison to biological variability and little can be gained from improvement in analytical accuracy. In addition, a propagation of error analysis demonstrated that total water balance error could be accounted for almost entirely by the errors associated with body mass changes. Errors due to interaction between terms in the water balance equation (covariances) represented less than 10% of the total error. Overall, the analysis provides evidence that daily measurements of body water changes obtained from the indirect balance technique are reasonable, precise, and relaible. The method is not biased toward net retention or loss.

  3. A multi-center inter-manufacturer study of the temporal stability of phase-contrast velocity mapping background offset errors

    PubMed Central

    2012-01-01

    Background Phase-contrast velocity images often contain a background or baseline offset error, which adds an unknown offset to the measured velocities. For accurate flow measurements, this offset must be shown negligible or corrected. Some correction techniques depend on replicating the clinical flow acquisition using a uniform stationary phantom, in order to measure the baseline offset at the region of interest and subtract it from the clinical study. Such techniques assume that the background offset is stable over the time of a patient scan, or even longer if the phantom scans are acquired later, or derived from pre-stored background correction images. There is no published evidence regarding temporal stability of the background offset. Methods This study assessed the temporal stability of the background offset on 3 different manufacturers’ scanners over 8 weeks, using a retrospectively-gated phase-contrast cine acquisition with fixed parameters and at a fixed location, repeated 5 times in rapid succession each week. A significant offset was defined as 0.6 cm/s within 50 mm of isocenter, based upon an accuracy of 10% in a typical cardiac shunt measurement. Results Over the 5 repeated cine acquisitions, temporal drift in the baseline offset was insignificant on two machines (0.3 cm/s, 0.2 cm/s), and marginally insignificant on the third machine (0.5 cm/s) due to an apparent heating effect. Over a longer timescale of 8 weeks, insignificant drift (0.4 cm/s) occurred on one, with larger drifts (0.9 cm/s, 0.6 cm/s) on the other machines. Conclusions During a typical patient study, background drift was insignificant. Extended high gradient power scanning with work requires care to avoid drift on some machines. Over the longer term of 8 weeks, significant drift is likely, preventing accurate correction by delayed phantom corrections or derivation from pre-stored background offset data. PMID:23083397

  4. Beam lifetime and limitations during low-energy RHIC operation

    SciTech Connect

    Fedotov, A.V.; Bai, M.; Blaskiewicz, M.; Fischer, W.; Kayran, D.; Montag, C.; Satogata, T.; Tepikian, S.; Wang, G.

    2011-03-28

    The low-energy physics program at the Relativistic Heavy Ion Collider (RHIC), motivated by a search for the QCD phase transition critical point, requires operation at low energies. At these energies, large nonlinear magnetic field errors and large beam sizes produce low beam lifetimes. A variety of beam dynamics effects such as Intrabeam Scattering (IBS), space charge and beam-beam forces also contribute. All these effects are important to understand beam lifetime limitations in RHIC at low energies. During the low-energy RHIC physics run in May-June 2010 at beam {gamma} = 6.1 and {gamma} = 4.1, gold beam lifetimes were measured for various values of space-charge tune shifts, transverse acceptance limitation by collimators, synchrotron tunes and RF voltage. This paper summarizes our observations and initial findings.

  5. 3D tracking and phase-contrast imaging by twin-beams digital holographic microscope in microfluidics

    NASA Astrophysics Data System (ADS)

    Miccio, L.; Memmolo, P.; Finizio, A.; Paturzo, M.; Merola, F.; Grilli, S.; Ferraro, P.

    2012-06-01

    A compact twin-beam interferometer that can be adopted as a flexible diagnostic tool in microfluidic platforms is presented. The devise has two functionalities, as explained in the follow, and can be easily integrated in microfluidic chip. The configuration allows 3D tracking of micro-particles and, at same time, furnishes Quantitative Phase-Contrast maps of tracked micro-objects by interference microscopy. Experimental demonstration of its effectiveness and compatibility with biological field is given on for in vitro cells in microfluidic environment. Nowadays, several microfluidic configuration exist and many of them are commercially available, their development is due to the possibility for manipulating droplets, handling micro and nano-objects, visualize and quantify processes occurring in small volumes and, clearly, for direct applications on lab-on-a chip devices. In microfluidic research field, optical/photonics approaches are the more suitable ones because they have various advantages as to be non-contact, full-field, non-invasive and can be packaged thanks to the development of integrable optics. Moreover, phase contrast approaches, adapted to a lab-on-a-chip configurations, give the possibility to get quantitative information with remarkable lateral and vertical resolution directly in situ without the need to dye and/or kill cells. Furthermore, numerical techniques for tracking of micro-objects needs to be developed for measuring velocity fields, trajectories patterns, motility of cancer cell and so on. Here, we present a compact holographic microscope that can ensure, by the same configuration and simultaneously, accurate 3D tracking and quantitative phase-contrast analysis. The system, simple and solid, is based on twin laser beams coming from a single laser source. Through a easy conceptual design, we show how these two different functionalities can be accomplished by the same optical setup. The working principle, the optical setup and the mathematical

  6. Ion beam induced cubic to monoclinic phase transformation of nanocrystalline yttria

    NASA Astrophysics Data System (ADS)

    Shivaramu, N. J.; Lakshminarasappa, B. N.; Nagabhushana, K. R.; Singh, Fouran

    2016-07-01

    Sol gel derived nanocrystalline yttria pellets are irradiated with 120 MeV Ag9+ ions for fluence in the range 1 × 1012-3 × 1013 ions cm-2. Pristine and irradiated samples are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy. XRD pattern of pristine Y2O3 nanocrystal reveal cubic structure. A new XRD peak at 30.36° is observed in pellet irradiated with 1 × 1013 ions cm-2. The peak at 30.36° is corresponding to (4 0 2 bar) plane of monoclinic phase. The diffraction intensity of (4 0 2 bar) plane increases with Ag9+ ion fluence. Raman spectrum of pristine pellet show bands corresponding to cubic phase. And, ion irradiated sample show new peaks at 410, 514 and 641 cm-1 corresponding monoclinic phase. HR-TEM and SAED pattern of ion irradiated sample confirmed the presence of monoclinic phase. Hence, it is confirmed that, 120 MeV Ag9+ ions induce phase transformation in nanocrystalline Y2O3.

  7. Phasing of several gain channels for coherent and spectral combining of laser beams

    SciTech Connect

    Pyrkov, Yu N; Trikshev, A I; Tsvetkov, V B

    2012-09-30

    A system for maintaining a constant phase difference between several laser channels is designed and an algorithm of its operation under a slow (with a characteristic time of no less than 100 ms) variation in the radiation phase in a channel is developed. Different possible regimes of operation of the measurement system and versions for phase difference maintaining are analysed and an optimal algorithm is elaborated. Long-term stable operation of the system under thermal and mechanical effects on the active medium is experimentally demonstrated by the example of a seven-channel fibre amplifier with a working wavelength of 1.064 {mu}m. (optical fibres, lasers and amplifiers. properties and applications)

  8. Multiple-access phased array antenna simulator for a digital beam-forming system investigation

    NASA Technical Reports Server (NTRS)

    Kerczewski, Robert J.; Yu, John; Walton, Joanne C.; Perl, Thomas D.; Andro, Monty; Alexovich, Robert E.

    1992-01-01

    Future versions of data relay satellite systems are currently being planned by NASA. Being given consideration for implementation are on-board digital beamforming techniques which will allow multiple users to simultaneously access a single S-band phased array antenna system. To investigate the potential performance of such a system, a laboratory simulator has been developed at NASA's Lewis Research Center. This paper describes the system simulator, and in particular, the requirements, design and performance of a key subsystem, the phased array antenna simulator, which provides realistic inputs to the digital processor including multiple signals, noise, and nonlinearities.

  9. Multiple-access phased array antenna simulator for a digital beam forming system investigation

    NASA Technical Reports Server (NTRS)

    Kerczewski, Robert J.; Yu, John; Walton, Joanne C.; Perl, Thomas D.; Andro, Monty; Alexovich, Robert E.

    1992-01-01

    Future versions of data relay satellite systems are currently being planned by NASA. Being given consideration for implementation are on-board digital beamforming techniques which will allow multiple users to simultaneously access a single S-band phased array antenna system. To investigate the potential performance of such a system, a laboratory simulator has been developed at NASA's Lewis Research Center. This paper describes the system simulator, and in particular, the requirements, design, and performance of a key subsystem, the phased array antenna simulator, which provides realistic inputs to the digital processor including multiple signals, noise, and nonlinearities.

  10. Investigation of Fiber Optics Based Phased Locked Diode Lasers

    NASA Technical Reports Server (NTRS)

    Burke, Paul D.; Gregory, Don A.

    1997-01-01

    Optical power beaming requires a high intensity source and a system to address beam phase and location. A synthetic aperture array of phased locked sources can provide the necessary power levels as well as a means to correct for phase errors. A fiber optic phase modulator with a master oscillator and power amplifier (MOPA) using an injection-locking semiconductor optical amplifier has proven to be effective in correcting phase errors as large as 4pi in an interferometer system. Phase corrections with the piezoelectric fiber stretcher were made from 0 - 10 kHz, with most application oriented corrections requiring only 1 kHz. The amplifier did not lose locked power output while the phase was changed, however its performance was below expectation. Results of this investigation indicate fiber stretchers and amplifiers can be incorporated into a MOPA system to achieve successful earth based power beaming.

  11. Shape error analysis for reflective nano focusing optics

    SciTech Connect

    Modi, Mohammed H.; Idir, Mourad

    2010-06-23

    Focusing performance of reflective x-ray optics is determined by surface figure accuracy. Any surface imperfection present on such optics introduces a phase error in the outgoing wave fields. Therefore converging beam at the focal spot will differ from the desired performance. Effect of these errors on focusing performance can be calculated by wave optical approach considering a coherent wave field illumination of optical elements. We have developed a wave optics simulator using Fresnel-Kirchhoff diffraction integral to calculate the mirror pupil function. Both analytically calculated and measured surface topography data can be taken as an aberration source to outgoing wave fields. Simulations are performed to study the effect of surface height fluctuations on focusing performances over wide frequency range in high, mid and low frequency band. The results using real shape profile measured with long trace profilometer (LTP) suggest that the shape error of {lambda}/4 PV (peak to valley) is tolerable to achieve diffraction limited performance. It is desirable to remove shape error of very low frequency as 0.1 mm{sup -1} which otherwise will generate beam waist or satellite peaks. All other frequencies above this limit will not affect the focused beam profile but only caused a loss in intensity.

  12. Quantum error correction beyond qubits

    NASA Astrophysics Data System (ADS)

    Aoki, Takao; Takahashi, Go; Kajiya, Tadashi; Yoshikawa, Jun-Ichi; Braunstein, Samuel L.; van Loock, Peter; Furusawa, Akira

    2009-08-01

    Quantum computation and communication rely on the ability to manipulate quantum states robustly and with high fidelity. To protect fragile quantum-superposition states from corruption through so-called decoherence noise, some form of error correction is needed. Therefore, the discovery of quantum error correction (QEC) was a key step to turn the field of quantum information from an academic curiosity into a developing technology. Here, we present an experimental implementation of a QEC code for quantum information encoded in continuous variables, based on entanglement among nine optical beams. This nine-wave-packet adaptation of Shor's original nine-qubit scheme enables, at least in principle, full quantum error correction against an arbitrary single-beam error.

  13. A phase screen model for simulating numerically the propagation of a laser beam in rain

    SciTech Connect

    Lukin, I P; Rychkov, D S; Falits, A V; Lai, Kin S; Liu, Min R

    2009-09-30

    The method based on the generalisation of the phase screen method for a continuous random medium is proposed for simulating numerically the propagation of laser radiation in a turbulent atmosphere with precipitation. In the phase screen model for a discrete component of a heterogeneous 'air-rain droplet' medium, the amplitude screen describing the scattering of an optical field by discrete particles of the medium is replaced by an equivalent phase screen with a spectrum of the correlation function of the effective dielectric constant fluctuations that is similar to the spectrum of a discrete scattering component - water droplets in air. The 'turbulent' phase screen is constructed on the basis of the Kolmogorov model, while the 'rain' screen model utiises the exponential distribution of the number of rain drops with respect to their radii as a function of the rain intensity. Theresults of the numerical simulation are compared with the known theoretical estimates for a large-scale discrete scattering medium. (propagation of laser radiation in matter)

  14. Development of a phase contrast imaging system based on a yttrium aluminum garnet laser with folded beam for observations of density fluctuations in compact helical system

    SciTech Connect

    Matsuo, K.; Uchida, N.; Kawakubo, M.; Iguchi, H.; Okamura, S.; Matsuoka, K.; Akiyama, T.

    2008-10-15

    A near-infrared laser phase contrast optical system incorporating a folded beam was developed in order to measure the distribution of density fluctuations in a high-temperature plasma. The coherent light source used was an yttrium aluminum garnet laser stabilized by a ring oscillator. The probe beam system separates and reflects the incident and exiting beams with a polarizer and a fully reflective mirror with a waveplate. This system was employed with a compact helical system to detect fluctuations at the plasma edge.

  15. Modulation of auroral electrojet currents using dual modulated HF beams with ELF phase offset, a potential D-region ionospheric diagnostic

    NASA Astrophysics Data System (ADS)

    GołKowski, M.; Cohen, M. B.; Moore, R. C.

    2013-05-01

    Experiments at the ionospheric heating facility of the High Frequency Active Auroral Research Program (HAARP) are performed employing dual HF beams amplitude modulated at ELF/VLF with a phase offset between the two modulation waveforms. The amplitude of the observed ELF/VLF waves is strongly dependent on the imposed ELF/VLF phase offset, the modulation waveform, and the orientation of the HF beams. Data from two ground stations are interpreted using simulations of modulated heating power envelopes as well as a comprehensive model of ionospheric ELF/VLF generation. It is found that two colocated vertical beams HF beams excite a single ionospheric ELF/VLF source, but independent ELF/VLF sources can be induced in the ionospheric region above the heater if the HF beams are offset from zenith to intersect at their 3 dB points. Furthermore, the use of two vertical HF beams with ELF phase offset is found to be a potential diagnostic method for the ionospheric D region.

  16. Generating high-current monoenergetic proton beams by a circularly polarized laser pulse in the phase-stable acceleration regime.

    PubMed

    Yan, X Q; Lin, C; Sheng, Z M; Guo, Z Y; Liu, B C; Lu, Y R; Fang, J X; Chen, J E

    2008-04-01

    A new ion acceleration method, namely, phase-stable acceleration, using circularly-polarized laser pulses is proposed. When the initial target density n(0) and thickness D satisfy a(L) approximately (n(0)/n(c))D/lambda(L) and D>l(s) with a(L), lambda(L), l(s), and n(c) the normalized laser amplitude, the laser wavelength in vacuum, the plasma skin depth, and the critical density of the incident laser pulse, respectively, a quasiequilibrium for the electrons is established by the light pressure and the space charge electrostatic field at the interacting front of the laser pulse. The ions within the skin depth of the laser pulse are synchronously accelerated and bunched by the electrostatic field, and thereby a high-intensity monoenergetic proton beam can be generated. The proton dynamics is investigated analytically and the results are verified by one- and two-dimensional particle-in-cell simulations. PMID:18517963

  17. Phase-space moment-equation model of highly relativistic electron-beams in plasma-wakefield accelerators

    SciTech Connect

    Robson, R.E.; Mehrling, T.; Osterhoff, J.

    2015-05-15

    We formulate a new procedure for modelling the transverse dynamics of relativistic electron beams with significant energy spread when injected into plasma-based accelerators operated in the blow-out regime. Quantities of physical interest, such as the emittance, are furnished directly from solution of phase space moment equations formed from the relativistic Vlasov equation. The moment equations are closed by an Ansatz, and solved analytically for prescribed wakefields. The accuracy of the analytic formulas is established by benchmarking against the results of a semi-analytic/numerical procedure which is described within the scope of this work, and results from a simulation with the 3D quasi-static PIC code HiPACE.

  18. Coherence and polarization of electromagnetic beams modulated by random phase screens and their changes through complex ABCD optical systems.

    PubMed

    Hanson, Steen G; Wang, Wei; Jakobsen, Michael L; Takeda, Mitsuo

    2008-09-01

    The change of coherence and polarization of an electromagnetic beam modulated by a random anisotropic phase screen passing through any optical system is found within the framework of complex ABCD-matrix theory This means that the formalism can treat imaging and Fourier transform and free-space optical systems, as well as fractional Fourier transform systems, with finite-size limiting apertures of Gaussian transmission shape. Thus, the current paper shall be considered as a continuation, extension, and generalization of a previous work by Shirai and Wolf [J. Opt. Soc. Am. A21, 1907 (2004)]. It will be shown that the inclusion of apertures in the optical system strongly influences not only the propagation of spatial coherence but also the degree of polarization of a propagating field. Analytical expressions of coherence and polarization propagation will be given in terms of the matrix elements for any complex optical system. PMID:18758562

  19. High precision 6.8GHz phase locking of coherent laser beams for optical lattice experiment

    NASA Astrophysics Data System (ADS)

    Ding, Xun; Sang, Linlin; Zhang, Chen; Jin, Ge; Jiang, Xiao

    2013-12-01

    With the optical phase lock loop (OPLL) we made, we can achieve phase locking at frequency differences ranging from 0.5GHz to 7.5 GHz. This OPLL is fully applicable in atomic physics experiments, mostly in coherent lasers frequency locking. Two kinds of modulation modes were brought to ensure the frequency range and precision: the fast feedback current as the injection current and the slow feedback current to adjust the piezo-electric transducer. This device has been put into an optical lattice platform to lock a laser used for cooling and trapping atoms. The beat signal has a -3dB band width of 1Hz at 6.834GHz, corresponding to the hyperfine splitting of the ground state 87Rb atom.

  20. Some Aspects of the Two Beam Performance of DCI

    SciTech Connect

    Krishnagopal, S.; Siemann, R.H.

    1991-09-01

    The results of beam-beam simulations that model DCI operating as an e{sup +}e{sup -} collider are reported. The simulation techniques, including a new procedure for incorporating synchrotron radiation, are described. Phase advance errors between the interaction points explain the beam-beam limit at the operating point q{sub x} = q{sub y} = 0.725 (q denotes the fractional part of the tune). The effects of radiation damping are also studied near that operating point. Simulation and experiments disagree in a second operating region, q{sub x} = q{sub y} {approx} 0.795, indicating additional physics outside the scope of our model.

  1. Quasi-phase matching and quantum control of high harmonic generation in waveguides using counterpropagating beams

    DOEpatents

    Zhang, Xiaoshi; Lytle, Amy L.; Cohen, Oren; Kapteyn, Henry C.; Murnane, Margaret M.

    2010-11-09

    All-optical quasi-phase matching (QPM) uses a train of counterpropagating pulses to enhance high-order harmonic generation (HHG) in a hollow waveguide. A pump pulse enters one end of the waveguide, and causes HHG in the waveguide. The counterpropagation pulses enter the other end of the waveguide and interact with the pump pulses to cause QPM within the waveguide, enhancing the HHG.

  2. Sb-induced phase control of InAsSb nanowires grown by molecular beam epitaxy.

    PubMed

    Zhuang, Q D; Anyebe, Ezekiel A; Chen, R; Liu, H; Sanchez, Ana M; Rajpalke, Mohana K; Veal, Tim D; Wang, Z M; Huang, Y Z; Sun, H D

    2015-02-11

    For the first time, we report a complete control of crystal structure in InAs(1-x)Sb(x) NWs by tuning the antimony (Sb) composition. This claim is substantiated by high-resolution transmission electron microscopy combined with photoluminescence spectroscopy. The pure InAs nanowires generally show a mixture of wurtzite (WZ) and zinc-blende (ZB) phases, where addition of a small amount of Sb (∼2-4%) led to quasi-pure WZ InAsSb NWs, while further increase of Sb (∼10%) resulted in quasi-pure ZB InAsSb NWs. This phase transition is further evidenced by photoluminescence (PL) studies, where a dominant emission associated with the coexistence of WZ and ZB phases is present in the pure InAs NWs but absent in the PL spectrum of InAs0.96Sb0.04 NWs that instead shows a band-to-band emission. We also demonstrate that the Sb addition significantly reduces the stacking fault density in the NWs. This study provides new insights on the role of Sb addition for effective control of nanowire crystal structure. PMID:25559370

  3. Displacement damage in bit error ratio performance of on-off keying, pulse position modulation, differential phase shift keying, and homodyne binary phase-shift keying-based optical intersatellite communication system.

    PubMed

    Liu, Yun; Zhao, Shanghong; Gong, Zizheng; Zhao, Jing; Dong, Chen; Li, Xuan

    2016-04-10

    Displacement damage (DD) effect induced bit error ratio (BER) performance degradations in on-off keying (OOK), pulse position modulation (PPM), differential phase-shift keying (DPSK), and homodyne binary phase shift keying (BPSK) based systems were simulated and discussed under 1 MeV neutron irradiation to a total fluence of 1×1012  n/cm2 in this paper. Degradation of main optoelectronic devices included in communication systems were analyzed on the basis of existing experimental data. The system BER degradation was subsequently simulated and the variations of BER with different neutron irradiation location were also achieved. The result shows that DD on an Er-doped fiber amplifier (EDFA) is the dominant cause of system degradation, and a BPSK-based system performs better than the other three systems against DD. In order to improve radiation hardness of communication systems against DD, protection and enhancement of EDFA are required, and the use of a homodyne BPSK modulation scheme is a considered choice. PMID:27139876

  4. Characterization of the in-line x-ray phase contrast imaging beam line developed at ALLS and based on laser driven betatron radiation

    NASA Astrophysics Data System (ADS)

    Fourmaux, S.; Otani, K.; Saraf, A.; MacLean, S.; Wesolowski, M. J.; Babyn, P. S.; Hallin, E.; Krol, A.; Kieffer, J. C.

    2015-05-01

    The 200TW ALLS laser system (30 fs, 5J) is used to accelerate electrons through laser wakefield and generate betatron emission in the 10keV range. Single shot phase contrast images of a series of nylon fibers with diameter ranging from 10μm to 400μm have been obtained in different geometries and are interpreted with a comprehensive model of x-ray propagation integrating the properties and geometries of the imaging beam line. A simple figure of merit, which can give indication on the interface sharpness of a phase object, is used to assess the quality of the imaging beam line.

  5. Cell identification using single beam lensless imaging with pseudo-random phase encoding.

    PubMed

    Javidi, Bahram; Rawat, Siddharth; Komatsu, Satoru; Markman, Adam

    2016-08-01

    In this Letter, we propose a novel compact optical system for automated cell identification. Our system employs pseudo-random encoding of the light modulated by the cells under inspection to capture the unique opto-biological signature of the micro-organisms by an image sensor and without using a microscope objective lens to magnify the object beam. The proposed instrument can be fabricated using a compact light source, a thin diffuser, and an image sensor connected to computational hardware; thus, it can be compact and cost effective. Experiments are presented using the proposed system to identify and classify various micro-objects and demonstrate proof of concept. The captured opto-biological signature pattern can be attributed to the micro-object's morphology, size, sub-cellular complex structure, index of refraction, internal material composition, etc. Using the captured signature of the micro-object, we extract statistical features such as mean, variance, skewness, kurtosis, entropy, and correlation coefficients for cell identification using the random forest classifier. For comparison, similar identification experiments were repeated with a digital shearing interferometer. To the best of our knowledge, this is the first report on automated cell identification using the proposed approach. PMID:27472644

  6. Flow measurement by cardiovascular magnetic resonance: a multi-centre multi-vendor study of background phase offset errors that can compromise the accuracy of derived regurgitant or shunt flow measurements

    PubMed Central

    2010-01-01

    Aims Cardiovascular magnetic resonance (CMR) allows non-invasive phase contrast measurements of flow through planes transecting large vessels. However, some clinically valuable applications are highly sensitive to errors caused by small offsets of measured velocities if these are not adequately corrected, for example by the use of static tissue or static phantom correction of the offset error. We studied the severity of uncorrected velocity offset errors across sites and CMR systems. Methods and Results In a multi-centre, multi-vendor study, breath-hold through-plane retrospectively ECG-gated phase contrast acquisitions, as are used clinically for aortic and pulmonary flow measurement, were applied to static gelatin phantoms in twelve 1.5 T CMR systems, using a velocity encoding range of 150 cm/s. No post-processing corrections of offsets were implemented. The greatest uncorrected velocity offset, taken as an average over a 'great vessel' region (30 mm diameter) located up to 70 mm in-plane distance from the magnet isocenter, ranged from 0.4 cm/s to 4.9 cm/s. It averaged 2.7 cm/s over all the planes and systems. By theoretical calculation, a velocity offset error of 0.6 cm/s (representing just 0.4% of a 150 cm/s velocity encoding range) is barely acceptable, potentially causing about 5% miscalculation of cardiac output and up to 10% error in shunt measurement. Conclusion In the absence of hardware or software upgrades able to reduce phase offset errors, all the systems tested appeared to require post-acquisition correction to achieve consistently reliable breath-hold measurements of flow. The effectiveness of offset correction software will still need testing with respect to clinical flow acquisitions. PMID:20074359

  7. Evidence of liquid phase during laser-induced periodic surface structures formation induced by accumulative ultraviolet picosecond laser beam

    SciTech Connect

    Huynh, T. T. D.; Petit, A.; Semmar, N.

    2015-11-09

    Laser-induced periodic surface structures (LIPSS) were formed on Cu/Si or Cu/glass thin films using Nd:YAG laser beam (40 ps, 10 Hz, and 30 mJ/cm{sup 2}). The study of ablation threshold is always achieved over melting when the variation of the number of pulses increases from 1 to 1000. But the incubation effect is leading to reduce the threshold of melting as increasing the number of laser pulse. Also, real time reflectivity signals exhibit typical behavior to stress the formation of a liquid phase during the laser-processing regime and helps to determine the threshold of soft ablation. Atomic Force Microscopy (AFM) analyses have shown the topology of the micro-crater containing regular spikes with different height. Transmission Electron Microscopy (TEM) allows finally to show three distinguished zones in the close region of isolated protrusions. The central zone is a typical crystallized area of few nanometers surrounded by a mixed poly-crystalline and amorphous area. Finally, in the region far from the protrusion zone, Cu film shows an amorphous structure. The real time reflectivity, AFM, and HR-TEM analyses evidence the formation of a liquid phase during the LIPSS formation in the picosecond regime.

  8. Detailed analyses of dynamic and static errors in neutron radiography testing

    SciTech Connect

    Joo, H.; Glickstein, S.S.

    1999-01-01

    Neutron radiography systems are being used for real-time visualization of the dynamic behavior as well as time-averaged measurements of spatial vapor fraction distributions for two phase fluids. The extraction of quantitative data on vapor-liquid flow fields is a significant advance in the methodology of fundamental two-phase flow experimentation. The data in the form of video images are typically recorded on videotape at 30 frames per second. Image analysis of the video pictures is used to extract time-dependent or time-averaged data. The determination of the average vapor fraction requires averaging of the logarithm of time-dependent intensity measurements of the neutron beam (gray scale distribution of the image) that passes through the fluid. This could be significantly different than averaging the intensity of the transmitted beam and then taking the logarithm of that term. This is termed the dynamic error (error in the time-averaged vapor fractions due t the inherent time-dependence of the measured data) and is separate from the static error (statistical sampling uncertainty). The results provide insight into the characteristics of these errors and help to quantify achievable bounds on the limits of these errors. The static error was determined by the uncertainties of measured beam intensities. It was found that the maximum static error increases as liquid thickness increases and can be reduced by increasing the neutron source strength. The dynamic error increased with large fluctuations in the local vapor fractions and with increasing liquid thickness. Detailed analyses of both sources of errors are discussed.

  9. Distributed phased array architecture study

    NASA Technical Reports Server (NTRS)

    Bourgeois, Brian

    1987-01-01

    Variations in amplifiers and phase shifters can cause degraded antenna performance, depending also on the environmental conditions and antenna array architecture. The implementation of distributed phased array hardware was studied with the aid of the DISTAR computer program as a simulation tool. This simulation provides guidance in hardware simulation. Both hard and soft failures of the amplifiers in the T/R modules are modeled. Hard failures are catastrophic: no power is transmitted to the antenna elements. Noncatastrophic or soft failures are modeled as a modified Gaussian distribution. The resulting amplitude characteristics then determine the array excitation coefficients. The phase characteristics take on a uniform distribution. Pattern characteristics such as antenna gain, half power beamwidth, mainbeam phase errors, sidelobe levels, and beam pointing errors were studied as functions of amplifier and phase shifter variations. General specifications for amplifier and phase shifter tolerances in various architecture configurations for C band and S band were determined.

  10. X-ray micro-beam techniques and phase contrast tomography applied to biomaterials

    NASA Astrophysics Data System (ADS)

    Fratini, Michela; Campi, Gaetano; Bukreeva, Inna; Pelliccia, Daniele; Burghammer, Manfred; Tromba, Giuliana; Cancedda, Ranieri; Mastrogiacomo, Maddalena; Cedola, Alessia

    2015-12-01

    A deeper comprehension of the biomineralization (BM) process is at the basis of tissue engineering and regenerative medicine developments. Several in-vivo and in-vitro studies were dedicated to this purpose via the application of 2D and 3D diagnostic techniques. Here, we develop a new methodology, based on different complementary experimental techniques (X-ray phase contrast tomography, micro-X-ray diffraction and micro-X-ray fluorescence scanning technique) coupled to new analytical tools. A qualitative and quantitative structural investigation, from the atomic to the micrometric length scale, is obtained for engineered bone tissues. The high spatial resolution achieved by X-ray scanning techniques allows us to monitor the bone formation at the first-formed mineral deposit at the organic-mineral interface within a porous scaffold. This work aims at providing a full comprehension of the morphology and functionality of the biomineralization process, which is of key importance for developing new drugs for preventing and healing bone diseases and for the development of bio-inspired materials.

  11. Phase 1 Study of Dose Escalation in Hypofractionated Proton Beam Therapy for Non-Small Cell Lung Cancer

    SciTech Connect

    Gomez, Daniel R.; Gillin, Michael; Liao, Zhongxing; Wei, Caimiao; Lin, Steven H.; Swanick, Cameron; Alvarado, Tina; Komaki, Ritsuko; Cox, James D.; Chang, Joe Y.

    2013-07-15

    Background: Many patients with locally advanced non-small cell lung cancer (NSCLC) cannot undergo concurrent chemotherapy because of comorbidities or poor performance status. Hypofractionated radiation regimens, if tolerable, may provide an option to these patients for effective local control. Methods and Materials: Twenty-five patients were enrolled in a phase 1 dose-escalation trial of proton beam therapy (PBT) from September 2010 through July 2012. Eligible patients had histologically documented lung cancer, thymic tumors, carcinoid tumors, or metastatic thyroid tumors. Concurrent chemotherapy was not allowed, but concurrent treatment with biologic agents was. The dose-escalation schema comprised 15 fractions of 3 Gy(relative biological effectiveness [RBE])/fraction, 3.5 Gy(RBE)/fraction, or 4 Gy(RBE)/fraction. Dose constraints were derived from biologically equivalent doses of standard fractionated treatment. Results: The median follow-up time for patients alive at the time of analysis was 13 months (range, 8-28 months). Fifteen patients received treatment to hilar or mediastinal lymph nodes. Two patients experienced dose-limiting toxicity possibly related to treatment; 1 received 3.5-Gy(RBE) fractions and experienced an in-field tracheoesophageal fistula 9 months after PBT and 1 month after bevacizumab. The other patient received 4-Gy(RBE) fractions and was hospitalized for bacterial pneumonia/radiation pneumonitis 4 months after PBT. Conclusion: Hypofractionated PBT to the thorax delivered over 3 weeks was well tolerated even with significant doses to the lungs and mediastinal structures. Phase 2/3 trials are needed to compare the efficacy of this technique with standard treatment for locally advanced NSCLC.

  12. Dynamic and static error analyses of neutron radiography testing

    SciTech Connect

    Joo, H.; Glickstein, S.S.

    1999-03-01

    Neutron radiography systems are being used for real-time visualization of the dynamic behavior as well as time-averaged measurements of spatial vapor fraction distributions for two phase fluids. The data in the form of video images are typically recorded on videotape at 30 frames per second. Image analysis of he video pictures is used to extract time-dependent or time-averaged data. The determination of the average vapor fraction requires averaging of the logarithm of time-dependent intensity measurements of the neutron beam (gray scale distribution of the image) that passes through the fluid. This could be significantly different than averaging the intensity of the transmitted beam and then taking the logarithm of that term. This difference is termed the dynamic error (error in the time-averaged vapor fractions due to the inherent time-dependence of the measured data) and is separate from the static error (statistical sampling uncertainty). Detailed analyses of both sources of errors are discussed.

  13. Nanoscale dimensional focused ion beam repair of quartz defects on 90-nm node alternating aperture phase shift masks

    NASA Astrophysics Data System (ADS)

    Robinson, Tod E.; Graupera, Anthony; Morrison, Troy B.; Ramstein, Marcus

    2004-08-01

    The effort to produce perfect dimension repairs of quartz bump defects on Alternating-Aperture Phase Shift Masks (AAPSM) has been brought to a new level with process developments to meet 90 nm technology node specifications. Decreasing photomask line and space dimensions pushes performance requirements for a mask repair system in terms of fine control in difficult to access structures on the mask surface. New repair strategies using a recently improved focused ion beam mask repair system for different defect types are discussed, along with their relative effectiveness. These strategies are then applied to the repair of full height extension and bridging defects in a line and space array. The role of quartz topography and its optical effects, Cr edge bias, and the combination of both strategies in a quartz bump repair are discussed. Additionally, effective process controls in repair are also discussed, along with analysis of metrology data received from a stylus nano-profilometer (SNP) system, and their relationship to potential imaging on the wafer by examination of AIMS data at a high numerical aperture. Several possible mask repair process flows are also reviewed in light of this work.

  14. Active fiber-based retroreflector providing phase-retracing anti-parallel laser beams for precision spectroscopy.

    PubMed

    Beyer, A; Maisenbacher, L; Matveev, A; Pohl, R; Khabarova, K; Chang, Y; Grinin, A; Lamour, T; Shi, T; Yost, D C; Udem, Th; Hänsch, T W; Kolachevsky, N

    2016-07-25

    We present an active fiber-based retroreflector providing high quality phase-retracing anti-parallel Gaussian laser beams for precision spectroscopy of Doppler sensitive transitions. Our design is well-suited for a number of applications where implementing optical cavities is technically challenging and corner cubes fail to match the demanded requirements, most importantly retracing wavefronts and preservation of the laser polarization. To illustrate the performance of the system, we use it for spectroscopy of the 2S-4P transition in atomic hydrogen and demonstrate an average suppression of the first order Doppler shift to 4 parts in 106 of the full collinear shift. This high degree of cancellation combined with our cryogenic source of hydrogen atoms in the metastable 2S state is sufficient to enable determinations of the Rydberg constant and the proton charge radius with competitive uncertainties. Advantages over the usual Doppler cancellation based on corner cube type retroreflectors are discussed as well as an alternative method using a high finesse cavity. PMID:27464193

  15. Optical multiple-image encryption based on the chaotic structured phase masks under the illumination of a vortex beam in the gyrator domain.

    PubMed

    Liansheng, Sui; Bei, Zhou; Xiaojuan, Ning; Ailing, Tian

    2016-01-11

    A novel multiple-image encryption scheme using the nonlinear iterative phase retrieval algorithm in the gyrator transform domain under the illumination of an optical vortex beam is proposed. In order to increase the randomness, the chaotic structured phase mask based on the logistic map, Fresnel zone plate and radial Hilbert mask is proposed. With the help of two chaotic phase masks, each plain image is encoded into two phase-only masks that are considered as the private keys by using the iterative phase retrieval process in the gyrator domain. Then, the second keys of all plain images are modulated into the ciphertext, which has the stationary white noise distribution. Due to the use of the chaotic structured phase masks, the problem of axis alignment in the optical setup can easily be solved. Two private keys are directly relative to the plain images, which makes that the scheme has high resistance against various potential attacks. Moreover, the use of the vortex beam that can integrates more system parameters as the additional keys into one phase mask can improve the security level of the cryptosystem, which makes the key space enlarged widely. Simulation results are given to verify the feasibility and robustness of the proposed encryption scheme. PMID:26832280

  16. PARTICLE BEAM TRACKING CIRCUIT

    DOEpatents

    Anderson, O.A.

    1959-05-01

    >A particle-beam tracking and correcting circuit is described. Beam induction electrodes are placed on either side of the beam, and potentials induced by the beam are compared in a voltage comparator or discriminator. This comparison produces an error signal which modifies the fm curve at the voltage applied to the drift tube, thereby returning the orbit to the preferred position. The arrangement serves also to synchronize accelerating frequency and magnetic field growth. (T.R.H.)

  17. Dependence of tracking error characteristics of in-line-type differential push-pull methods on arrangement error of segmented gratings

    NASA Astrophysics Data System (ADS)

    Shinoda, Masahisa; Nakai, Kenya

    2011-09-01

    We present the validity of in-line-type differential push-pull methods using segmented gratings with respect to arrangement errors by numerical calculation for the first time. In these differential push-pull methods, the segmented gratings for generating subspots are divided into more than two regions, each with a specific width and a specific phase value, and are ideally arranged on the optical axis. We calculate tracking error signals in these methods with respect to the arrangement errors against the optical axis under parameter conditions of the widths of the segmented regions of the gratings. The obtained results show that the grating with a simpler configuration with two regions reveals good compatibility between DVD-recordable (DVD-R) and DVD-random access memory (DVD-RAM) compared with those with three or four regions, when the arrangement error is less than 10% of the radius of the incident laser beam.

  18. Optical beam shaping and diffraction free waves: A variational approach

    NASA Astrophysics Data System (ADS)

    Gemmer, John A.; Venkataramani, Shankar C.; Durfee, Charles G.; Moloney, Jerome V.

    2014-08-01

    We investigate the problem of shaping radially symmetric annular beams into desired intensity patterns along the optical axis. Within the Fresnel approximation, we show that this problem can be expressed in a variational form equivalent to the one arising in phase retrieval. Using the uncertainty principle we prove various rigorous lower bounds on the functional; these lower bounds estimate the L2 error for the beam shaping problem in terms of the design parameters. We also use the method of stationary phase to construct a natural ansatz for a minimizer in the short wavelength limit. We illustrate the implications of our results by applying the method of stationary phase coupled with the Gerchberg-Saxton algorithm to beam shaping problems arising in the remote delivery of beams and pulses.

  19. [Diagnostic Errors in Medicine].

    PubMed

    Buser, Claudia; Bankova, Andriyana

    2015-12-01

    The recognition of diagnostic errors in everyday practice can help improve patient safety. The most common diagnostic errors are the cognitive errors, followed by system-related errors and no fault errors. The cognitive errors often result from mental shortcuts, known as heuristics. The rate of cognitive errors can be reduced by a better understanding of heuristics and the use of checklists. The autopsy as a retrospective quality assessment of clinical diagnosis has a crucial role in learning from diagnostic errors. Diagnostic errors occur more often in primary care in comparison to hospital settings. On the other hand, the inpatient errors are more severe than the outpatient errors. PMID:26649954

  20. Optical modeling for a laser phased-array directed energy system

    NASA Astrophysics Data System (ADS)

    Hughes, Gary B.; Lubin, Philip; Griswold, Janelle; Cook, Brianna; Bozzini, Durante; O'Neill, Hugh; Meinhold, Peter; Suen, Jonathan; Bible, Johanna; Riley, Jordan; Johansson, Isabella E.; Pryor, Mark; Kangas, Miikka

    2014-09-01

    We present results of optical simulations for a laser phased array directed energy system. The laser array consists of individual optical elements in a square or hexagonal array. In a multi-element array, the far-field beam pattern depends on both mechanical pointing stability and on phase relationships between individual elements. The simulation incorporates realistic pointing and phase errors. Pointing error components include systematic offsets to simulate manufacturing and assembly variations. Pointing also includes time-varying errors that simulate structural vibrations, informed from random vibration analysis of the mechanical design. Phase errors include systematic offsets, and time-varying errors due to both mechanical vibration and temperature variation in the fibers. The optical simulation is used to determine beam pattern and pointing jitter over a range of composite error inputs. Results are also presented for a 1 m aperture array with 10 kW total power, designed as a stand-off system on a dedicated asteroid diversion/capture mission that seeks to evaporate the surface of the target at a distance of beyond 10 km. Phase stability across the array of λ/10 is shown to provide beam control that is sufficient to vaporize the surface of a target at 10 km. The model is also a useful tool for characterizing performance for phase controller design in relation to beam formation and pointing.