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At least 1,801 records · Page 100
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

An Interferometric Method of Measuring Reflection Coefficients

A method for determining the reflection coefficients of optical elements, which is based on the use of a reflection interferometer, is proposed. The results of measurements with a He–Ne laser for several samples with different reflectivity levels are presented. Comparison with results of conventional measurements is made. The gain from the use of the reflection interferometer is estimated.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Quantum Key Distribution with Temporal Coding of Time-Bin Qubits

In this study, we demonstrate the possibility of realizing the quantum key distribution system by temporal coding of time-bin qubits that are prepared and measured using unbalanced Mach-Zehnder interferometers. We also show that, to exclude a clear a priori identification of time-bin qubits with equal bases, their encoding with the symbols 0 and 1 can be accomplished by delaying one of them by half the clock interval. The uniqueness of measurements of qutrits in this algorithm is shown to be based on the ability of quantum particles in β-states to interfere with the probability amplitudes at the ports of the system interferometers, as well as the absence of collisions of signaling states of the qutrits in adjacent clock intervals. We describe a method for controlling such collisions, including those that are based on qubits prepared from quasi-one-photon coherent laser states.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2013

X-ray phase-contrast methods

This review is devoted to a comparative description of the methods for forming X-ray phase-contrast images of weakly absorbing (phase) objects. These include the crystal interferometer method, the Talbot interferometer method, diffraction-enhanced X-ray imaging, and the in-line method. The potential of their practical application in various fields of science and technology is discussed. The publications on the development and optimization of X-ray phase-contrast methods and the experimental study of phase objects are analyzed.

36 MATERIALS SCIENCE↗
DOE OSTI2012

On the effect of conductivity of a shock-compressed gas on interferometric recording of parameters of motion of a liner

We report on the results of a study of the acceleration dynamics of an aluminum liner to a velocity of 5.5 km/s using continuous recording of velocity (velocity interferometer system for any reflector (VISAR) and Fabry-Perot interferometer) and motion trajectory (radiointerferometer and resistive transducer) in air and in a helium atmosphere. It is found that for liner velocities exceeding 4.0 and 5.0 km/s, the displacement of the shock wave front is recorded by the radiointerferometer in air and helium, respectively. At these velocities, the conductivities of air and helium behind the shock wave front are estimated.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Neural Network Astronomy as a New Tool for Observing Bright and Compact Objects

We propose a new method for solving an important problem of astronomy that arises in observations with ultrahigh-angular-resolution interferometers. This method is based on the application of the theory of artificial neural networks. We propose and compute a multiparameter model for a celestial object like Sgr A*. For this model we have numerically constructed a number of probable images for neural network training. After neural network training on these images, the quality of its operation has been tested on another series of images from the same model. We have proven that a neural network can recognize and classify celestial objects (also obtained from interferometers) virtually no worse than can be done by a human.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2010

Coupling characterization and noise studies of the optical metrology system onboard the LISA Pathfinder mission

We describe the first investigations of the complete engineering model of the optical metrology system (OMS), a key subsystem of the LISA Pathfinder science mission to space. The latter itself is a technological precursor mission to LISA, a spaceborne gravitational wave detector. At its core, the OMS consists of four heterodyne Mach-Zehnder interferometers, a highly stable laser with an external modulator, and a phase meter. It is designed to monitor and track the longitudinal motion and attitude of two floating test masses in the optical reference frame with (relative) precision in the picometer and nanorad range, respectively. We analyze sensor signal correlations and determine a physical sensor noise limit. The coupling parameters between motional degrees of freedom and interferometer signals are analytically derived and compared to measurements. We also measure adverse cross-coupling effects originating from system imperfections and limitations and describe algorithmic mitigation techniques to overcome some of them. Their impact on system performance is analyzed within the context of the Pathfinder mission.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2010

Real-time heterodyne speckle pattern interferometry using the correlation image sensor

A real-time method for heterodyne speckle pattern interferometry using the correlation image sensor (CIS) is proposed. The CIS demodulates the interference phase of heterodyned speckle wavefronts pixelwise at an ordinary video frame rate. The proposed method neither suffers loss of spatial resolution nor requires a high frame rate. Interferometers for out-of-plane and in-plane deformation are developed with a 200x200 pixel CIS camera. Experimental results confirm that the proposed method realizes real-time imaging of a rough-surfaced object under deformation. The average standard deviations of demodulated phase-difference images for the out-of-plane and in-plane interferometers are 0.33 and 0.13 rad, respectively.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2011

Instrumental phase-based method for Fourier transform spectrometer measurements processing

Phase correction is a critical procedure for most space-borne Fourier transform spectrometers (FTSs) whose accuracy (owing to often poor signal-to-noise ratio, SNR) can be jeopardized from many uncontrollable environmental conditions. This work considers the phase correction in an FTS working under significant temperature change during the measurement and affected by mechanical disturbances. The implemented method is based on the identification of an instrumental phase that is dependent on the interferometer temperature and on the extraction of a linear phase component through a least-squares approach. The use of an instrumental phase parameterized with the interferometer temperature eases the determination of the linear phase that can be extracted using only a narrow spectral region selected to be immune from disturbances. The procedure, in this way, is made robust against phase errors arising from instrumental effects, a key feature to reduce the disturbances through spectra averaging. The method was specifically developed for the Mars IR Mapper spectrometer, that was designed for operation onboard a rover on the Mars surface; the validation was performed using ground and in-flight measurements of the Fourier transform IR spectrometer planetary Fourier spectrometer, onboard the MarsExpress mission. The symmetrization has been exploited also for the spectra calibration, highlighting the issues deriving from the cases of relevant beamsplitter emission. The applicability of this procedure to other instruments is conditional to the presence in the spectra of at least one spectral region with a large SNR along with a negligible (or known) beamsplitter emission. For the PFS instrument, the processing of data with relevant beamsplitter emission has been performed exploiting the absorption carbon dioxide bands present in Martian spectra.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Interferometric investigation and simulation of refractive index in glass matrixes containing nanoparticles of varying sizes

The relationship between refractive index and nanoparticle radii of cadmium selenide (CdSe) nanoparticles embedded within glass matrixes was investigated experimentally and by simulations. A homemade automated Michelson interferometer arrangement employing a rotating table and a He-Ne laser source at a wavelength of 632.8 nm determined the refractive index versus nanoparticle radii of embedded cadmium selenide (CdSe) nanoparticles. The refractive index was found to decrease linearly with nanoparticle radius increase. However, one sample showed a step increase in refractive index; on spectroscopic analysis, it was found that its resonant wavelength matched that of the He-Ne source wavelength. The simulations showed that two conditions caused the step increase in refractive index: low plasma frequency and matched sample and source resonances. This simple interferometer setup defines a new method of determining the radii of nanoparticles embedded in substrates and enables refractive index tailoring by modification of exact annealing conditions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

All-fiber interferometry: design and analysis

This paper presents a design procedure for a fiber interferometer, the optical system, and its associated electronic control. Analog and digital circuits were optimized to achieve an inexpensive and compact system. The lock-in amplifier required for phase control was designed using a field programmable gate array that was also configured to carry out the required phase stepping. The interferometer was built into two stages. The first stage used only one wavelength to measure samples with step heights in the hundreds of nanometers, with improvements in accuracy through averaging of data. The next stage included two measurement wavelengths to extend the measurement range to a few hundreds of micrometers. The paper conducts a systematic study of sources of errors. A least squares method that minimizes measurement time but retains accuracy has been used to measure height.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

THE HYDROGEN EPOCH OF REIONIZATION ARRAY DISH. I. BEAM PATTERN MEASUREMENTS AND SCIENCE IMPLICATIONS

The Hydrogen Epoch of Reionization Array (HERA) is a radio interferometer aiming to detect the power spectrum of 21 cm fluctuations from neutral hydrogen from the epoch of reionization (EOR). Drawing on lessons from the Murchison Widefield Array and the Precision Array for Probing the EOR, HERA is a hexagonal array of large (14 m diameter) dishes with suspended dipole feeds. The dish not only determines overall sensitivity, but also affects the observed frequency structure of foregrounds in the interferometer. This is the first of a series of four papers characterizing the frequency and angular response of the dish with simulations and measurements. In this paper, we focus on the angular response (i.e., power pattern), which sets the relative weighting between sky regions of high and low delay and thus apparent source frequency structure. We measure the angular response at 137 MHz using the ORBCOMM beam mapping system of Neben et al. We measure a collecting area of 93 m{sup 2} in the optimal dish/feed configuration, implying that HERA-320 should detect the EOR power spectrum at z ∼ 9 with a signal-to-noise ratio of 12.7 using a foreground avoidance approach with a single season of observations and 74.3 using a foreground subtraction approach. Finally, we study the impact of these beam measurements on the distribution of foregrounds in Fourier space.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Delay spectrum with phase-tracking arrays: extracting the H i power spectrum from the epoch of reionization

The detection of redshifted 21 cm emission from the epoch of reionization (EoR) is a challenging task owing to strong foregrounds that dominate the signal. In this paper, we propose a general method, based on the delay spectrum approach, to extract H i power spectra that are applicable to tracking observations using an imaging radio interferometer ('Delay Spectrum with Imaging Arrays'). Our method is based on modeling the H i signal taking into account the impact of wide field effects such as the w-term, which are then used as appropriate weights in cross-correlating the measured visibilities. Our method is applicable to any radio interferometer that tracks a phase center and could be utilized for arrays such as the Murchison Widefield Array (MWA), Low Frequency Array (LOFAR), Giant Meterwave Radio Telescope (GMRT), Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER), and HERA. In the literature the delay spectrum approach has been implemented for near-redundant baselines using drift scan observations. In this paper we explore the scheme for non-redundant tracking arrays. This is the first application of delay spectrum methodology to such data to extract the H i signal. We analyze 3 hr of MWA tracking data on the EoR1 field. We present both two-dimensional (k{sub ∥},k{sub ⊥}) and one-dimensional (k) power spectra from the analysis. Our results are in agreement with the findings of other pipelines developed to analyze the MWA EoR data.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Detecting triple systems with gravitational wave observations

The Laser Interferometer Gravitational Wave Observatory (LIGO) has recently discovered gravitational waves (GWs) emitted by merging black hole binaries. We examine whether future GW detections may identify triple companions of merging binaries. Such a triple companion causes variations in the GW signal due to: (1) the varying path length along the line of sight during the orbit around the center of mass; (2) relativistic beaming, Doppler, and gravitational redshift; (3) the variation of the “light”-travel time in the gravitational field of the triple companion; and (4) secular variations of the orbital elements. We find that the prospects for detecting a triple companion are the highest for low-mass compact object binaries which spend the longest time in the LIGO frequency band. In particular, for merging neutron star binaries, LIGO may detect a white dwarf or M-dwarf perturber at a signal-to-noise ratio of 8, if it is within 0.4 R{sub ⊙} distance from the binary and the system is within a distance of 100 Mpc. Stellar mass (supermassive) black hole perturbers may be detected at a factor 5 × (10{sup 3}×) larger separations. Such pertubers in orbit around a merging binary emit GWs at frequencies above 1 mHz detectable by the Laser Interferometer Space Antenna in coincidence.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Improved Constraints on the Disk around MWC 349A from the 23 m LBTI

We present new spatially resolved observations of MWC 349A from the Large Binocular Telescope Interferometer (LBTI), a 23 m baseline interferometer made up of two, co-mounted 8 m telescopes. MWC 349A is a B[e] star with an unknown evolutionary state. Proposed scenarios range from a young stellar object, to a B[e] supergiant, to a tight binary system. Radio continuum and recombination line observations of this source revealed a sub-arcsecond bipolar outflow surrounding an ∼100 mas circumstellar disk. Follow-up infrared studies detected the disk, and suggested that it may have skew and an inner clearing. Our new infrared interferometric observations, which have more than twice the resolution of previously published data sets, support the presence of both skew and a compact infrared excess. They rule out inner clearings with radii greater than ∼14 mas. We show the improvements in disk parameter constraints provided by LBTI, and discuss the inferred disk parameters in the context of the posited evolutionary states for MWC 349A.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

( Fermi Fermi)-LAT observations of the LIGO event GW150914

The Fermi Large Area Telescope (LAT) has an instantaneous field of view (FoV) covering ∼1/5 of the sky and it completes a survey of the entire sky in high-energy gamma-rays every 3 hr. It enables searches for transient phenomena over timescales from milliseconds to years. Among these phenomena could be electromagnetic counterparts to gravitational wave (GW) sources. In this paper, we present a detailed study of the LAT observations relevant to Laser Interferometer Gravitational-wave Observatory (LIGO) event GW150914, which is the first direct detection of gravitational waves and has been interpreted as being due to the coalescence of two stellar-mass black holes. The localization region for GW150914 was outside the LAT FoV at the time of the GW signal. However, as part of routine survey observations, the LAT observed the entire LIGO localization region within ∼70 minutes of the trigger and thus enabled a comprehensive search for a γ-ray counterpart to GW150914. The study of the LAT data presented here did not find any potential counterparts to GW150914, but it did provide limits on the presence of a transient counterpart above 100 MeV on timescales of hours to days over the entire GW150914 localization region.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

LOCALIZATION AND BROADBAND FOLLOW-UP OF THE GRAVITATIONAL-WAVE TRANSIENT GW150914

A gravitational-wave (GW) transient was identified in data recorded by the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) detectors on 2015 September 14. The event, initially designated G184098 and later given the name GW150914, is described in detail elsewhere. By prior arrangement, preliminary estimates of the time, significance, and sky location of the event were shared with 63 teams of observers covering radio, optical, near-infrared, X-ray, and gamma-ray wavelengths with ground- and space-based facilities. In this Letter we describe the low-latency analysis of the GW data and present the sky localization of the first observed compact binary merger. We summarize the follow-up observations reported by 25 teams via private Gamma-ray Coordinates Network circulars, giving an overview of the participating facilities, the GW sky localization coverage, the timeline, and depth of the observations. As this event turned out to be a binary black hole merger, there is little expectation of a detectable electromagnetic (EM) signature. Nevertheless, this first broadband campaign to search for a counterpart of an Advanced LIGO source represents a milestone and highlights the broad capabilities of the transient astronomy community and the observing strategies that have been developed to pursue neutron star binary merger events. Detailed investigations of the EM data and results of the EM follow-up campaign are being disseminated in papers by the individual teams.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

A decam search for an optical counterpart to the LIGO gravitational-wave event GW151226

We report the results of a Dark Energy Camera optical follow-up of the gravitational-wave (GW) event GW151226, discovered by the Advanced Laser Interferometer Gravitational-wave Observatory detectors. Our observations cover 28.8 deg{sup 2} of the localization region in the i and z bands (containing 3% of the BAYESTAR localization probability), starting 10 hr after the event was announced and spanning four epochs at 2–24 days after the GW detection. We achieve 5σ point-source limiting magnitudes of i≈21.7 and z≈21.5, with a scatter of 0.4 mag, in our difference images. Given the two-day delay, we search this area for a rapidly declining optical counterpart with ≳3σ significance steady decline between the first and final observations. We recover four sources that pass our selection criteria, of which three are cataloged active galactic nuclei. The fourth source is offset by 5.8 arcsec from the center of a galaxy at a distance of 187 Mpc, exhibits a rapid decline by 0.5 mag over 4 days, and has a red color of i−z≈0.3 mag. These properties could satisfy a set of cuts designed to identify kilonovae. However, this source was detected several times, starting 94 days prior to GW151226, in the Pan-STARRS Survey for Transients (dubbed as PS15cdi) and is therefore unrelated to the GW event. Given its long-term behavior, PS15cdi is likely a Type IIP supernova that transitioned out of its plateau phase during our observations, mimicking a kilonova-like behavior. We comment on the implications of this detection for contamination in future optical follow-up observations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Radio follow-up of gravitational-wave triggers during advanced LIGO O1

We present radio follow-up observations carried out with the Karl G. Jansky Very Large Array during the first observing run (O1) of the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO). A total of three gravitational-wave triggers were followed-up during the ≈4 months of O1, from 2015 September to 2016 January. Two of these triggers, GW150914 and GW151226, are binary black hole (BH) merger events of high significance. A third trigger, G194575, was subsequently declared as an event of no interest (i.e., a false alarm). Our observations targeted selected optical transients identified by the intermediate Palomar Transient Factory in the Advanced LIGO error regions of the three triggers, and a limited region of the gravitational-wave localization area of G194575 not accessible to optical telescopes due to Sun constraints, where a possible high-energy transient was identified. No plausible radio counterparts to GW150914 and GW151226 were found, in agreement with expectations for binary BH mergers. We show that combining optical and radio observations is key to identifying contaminating radio sources that may be found in the follow-up of gravitational-wave triggers, such as emission associated with star formation and active galactic nuclei. We discuss our results in the context of the theoretical predictions for radio counterparts to gravitational-wave transients, and describe our future plans for the radio follow-up of Advanced LIGO (and Virgo) triggers.

79 ASTRONOMY AND ASTROPHYSICS↗

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