scholarly journals Titanium-Based Microbolometers: Control of Spatial Profile of Terahertz Emission in Weak Power Sources

2020 ◽  
Vol 10 (10) ◽  
pp. 3400
Author(s):  
Linas Minkevičius ◽  
Liang Qi ◽  
Agnieszka Siemion ◽  
Domas Jokubauskis ◽  
Aleksander Sešek ◽  
...  
Keyword(s):  
Imaging Techniques ◽  
Dark Field ◽  
Spatial Mode ◽  
Contrast Imaging ◽  
Optical Components ◽  
Broadband Antenna ◽  
Power Sources ◽  
Precise Control ◽  
Imaging And Spectroscopy ◽  
And Control

Terahertz (THz) imaging and spectroscopy set-ups require fine optical alignment or precise control of spatial mode profile. We demonstrate universal, convenient and easy-to-use imaging—resonant and broadband antenna coupled ultrasensitive titanium-based—dedicated to accurately adjust and control spatial mode profiles without additional focusing optical components of weak power THz sources. Versatile operation of the devices is shown using different kinds of THz—electronic multiplier sources, optical THz mixer-based frequency domain and femtosecond optoelectronic THz time-domain spectrometers as well as optically pumped molecular THz laser. Features of the microbolometers within 0.15–0.6 THz range are exposed and discussed, their ability to detect spatial mode profiles beyond the antennas resonances, up to 2.52 THz, are explored. Polarization-sensitive mode control possibilities are examined in details. The suitability of the resonant antenna-coupled microbolometers to resolve low-absorbing objects at 0.3 THz is revealed via direct, dark field and phase contrast imaging techniques as well.

scholarly journals Hard X-ray omnidirectional differential phase and dark-field imaging

2021 ◽  
Vol 118 (9) ◽  
pp. e2022319118
Author(s):  
Hongchang Wang ◽  
Kawal Sawhney
Keyword(s):  
Imaging Techniques ◽  
Dark Field ◽  
X Rays ◽  
Contrast Imaging ◽  
X Ray ◽  
Differential Phase ◽  
Dark Field Imaging ◽  
Spiral Path ◽  
Wide Range ◽  
Phase Images

Ever since the discovery of X-rays, tremendous efforts have been made to develop new imaging techniques for unlocking the hidden secrets of our world and enriching our understanding of it. X-ray differential phase contrast imaging, which measures the gradient of a sample’s phase shift, can reveal more detail in a weakly absorbing sample than conventional absorption contrast. However, normally only the gradient’s component in two mutually orthogonal directions is measurable. In this article, omnidirectional differential phase images, which record the gradient of phase shifts in all directions of the imaging plane, are efficiently generated by scanning an easily obtainable, randomly structured modulator along a spiral path. The retrieved amplitude and main orientation images for differential phase yield more information than the existing imaging methods. Importantly, the omnidirectional dark-field images can be simultaneously extracted to study strongly ordered scattering structures. The proposed method can open up new possibilities for studying a wide range of complicated samples composed of both heavy, strongly scattering atoms and light, weakly scattering atoms.

scholarly journals Symmetric Talbot-Lau neutron grating interferometry and incoherent scattering correction for quantitative dark-field imaging

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Youngju Kim ◽  
Jacopo Valsecchi ◽  
Jongyul Kim ◽  
Seung Wook Lee ◽  
Markus Strobl
Keyword(s):  
Imaging Techniques ◽  
Reference Sample ◽  
Dark Field ◽  
Incoherent Scattering ◽  
The Novel ◽  
Contrast Imaging ◽  
Dark Field Imaging ◽  
Novel Approach ◽  
Set Up ◽  
Field Imaging

AbstractWe introduce the application of a symmetric Talbot-Lau neutron grating interferometer which provides a significantly extended autocorrelation length range essential for quantitative dark-field contrast imaging. The highly efficient set-up overcomes the limitation of the conventional Talbot-Lau technique to a severely limited micrometer range as well as the limitation of the other advanced dark-field imaging techniques in the nanometer regime. The novel set-up enables efficient and continuous dark-field contrast imaging providing quantitative small-angle neutron scattering information for structures in a regime from some tens of nanometers to several tens of micrometers. The quantitative analysis enabled in and by such an extended range is demonstrated through application to reference sample systems of the diluted polystyrene particle in aqueous solutions. Here we additionally demonstrate and successfully discuss the correction for incoherent scattering. This correction results to be necessary to achieve meaningful quantitative structural results. Furthermore, we present the measurements, data modelling and analysis of the two distinct kinds of cohesive powders enabled by the novel approach, revealing the significant structural differences of their fractal nature.

scholarly journals Assessment of flow within developing chicken vasculature and biofabricated vascularized tissues using multimodal imaging techniques

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Prasanna Padmanaban ◽  
Ata Chizari ◽  
Tom Knop ◽  
Jiena Zhang ◽  
Vasileios D. Trikalitis ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Imaging Techniques ◽  
Dark Field ◽  
Flow Dynamics ◽  
Laser Speckle ◽  
Shear Stresses ◽  
Imaging Data ◽  
Contrast Imaging ◽  
Flow Shear ◽  
Engineered Tissues

AbstractFluid flow shear stresses are strong regulators for directing the organization of vascular networks. Knowledge of structural and flow dynamics information within complex vasculature is essential for tuning the vascular organization within engineered tissues, by manipulating flows. However, reported investigations of vascular organization and their associated flow dynamics within complex vasculature over time are limited, due to limitations in the available physiological pre-clinical models, and the optical inaccessibility and aseptic nature of these models. Here, we developed laser speckle contrast imaging (LSCI) and side-stream dark field microscopy (SDF) systems to map the vascular organization, spatio-temporal blood flow fluctuations as well as erythrocytes movements within individual blood vessels of developing chick embryo, cultured within an artificial eggshell system. By combining imaging data and computational simulations, we estimated fluid flow shear stresses within multiscale vasculature of varying complexity. Furthermore, we demonstrated the LSCI compatibility with bioengineered perfusable muscle tissue constructs, fabricated via molding techniques. The presented application of LSCI and SDF on perfusable tissues enables us to study the flow perfusion effects in a non-invasive fashion. The gained knowledge can help to use fluid perfusion in order to tune and control multiscale vascular organization within engineered tissues.

scholarly journals Direct imaging and spectroscopy of exoplanets with the ELT/HARMONI high-contrast module

2021 ◽  
Author(s):  
Mathis Houllé ◽  
Arthur Vigan ◽  
Alexis Carlotti ◽  
Élodie Choquet ◽  
Faustine Cantalloube ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Near Infrared ◽  
Direct Detection ◽  
Imaging Techniques ◽  
High Contrast ◽  
Contrast Imaging ◽  
High Contrast Imaging ◽  
Medium Resolution ◽  
Imaging And Spectroscopy ◽  
Integral Field Spectrograph

<p>Combining high-contrast imaging with medium-resolution spectroscopy has recently been shown to significantly boost the direct detection of exoplanets. In this optic, HARMONI, one of the first-light instruments to be mounted on ESO's ELT, will be equipped with a single-conjugated adaptive optics system to reach the diffraction limit of the ELT in H and K bands, a high-contrast module dedicated to exoplanet imaging, and a medium-resolution (up to R = 17 000) optical and near-infrared integral field spectrograph. When combined, these systems will provide unprecedented contrast limits at separations between 50 and 400 mas. We will present in this talk the results of extensive simulations of exoplanet observations with the HARMONI high-contrast module. We used an end-to-end model of the instrument to simulate observations based on realistic observing scenarios and conditions. We then analyzed these observations with the so-called "molecule mapping" technique, which has shown in recent studies its efficiency to disentangle planetary companions from their host star and boost their signal. Although HARMONI has not been fully designed for high-contrast imaging, we will show that it should greatly outperform the current dedicated instruments, such as SPHERE on the VLT. We detect planets above 5σ in 2 hours at contrasts up to 16 mag and separations down to 75 mas in several spectral configurations of the instrument. Simulating planets from population synthesis models, we could image in this amount of time companions as close as 1 AU from a host star at 30 pc and as light as 2 M<sub>Jup</sub>. We show that taking advantage of the combination of high-contrast imaging and medium-resolution spectroscopy through molecule mapping allows us to access much fainter planets (up to 2.5 mag) than the standard high-contrast imaging techniques. We also demonstrate that HARMONI should be available for near-critical exoplanet observations with this method during 60 to 70% of telescope time at the ELT.</p>

Growth of hematite on (0001) and {1102} sapphire substrates

1990 ◽  
Vol 48 (4) ◽  
pp. 376-377
Author(s):  
Lisa A. Tietz ◽  
Scott R. Summerfelt ◽  
C. Barry Carter
Keyword(s):  
Imaging Techniques ◽  
Chemical Vapor ◽  
Interface Energy ◽  
Dark Field ◽  
Cation Sublattice ◽  
Sapphire Substrates ◽  
Dark Field Imaging ◽  
Weak Beam ◽  
Pressure Chemical ◽  
Interface Structures

Defects in thin films are often introduced at the substrate-film interface during the early stages of growth. The interface structures of semiconductor heterojunctions have been extensively studied because of the electrical activity of defects in these materials. Much less attention has been paid to the structure of oxide-oxide heterojunctions. In this study, the structures of the interfaces formed between hematite (α-Fe2O3) and two orientations of sapphire (α-Al2O3) are examined in relationship to the defects introduced into the hematite film. In such heterojunctions, the oxygen sublattice is expected to have a strong influence on the epitaxy; however, defects which involve only the cation sublattice may be introduced at the interface with little increase in interface energy.Oxide heterojunctions were produced by depositing small quantities of hematite directly onto electrontransparent sapphire substrates using low-pressure chemical vapor deposition. Prior to deposition, the ionthinned substrates were chemically cleaned and annealed at 1400°C to give “clean”, crystalline surfaces. Hematite was formed by the reaction of FeCl3 vapor with water vapor at 1150°C and 1-2 Torr. The growth of the hematite and the interface structures formed on (0001) and {102} substrates have been studied by bright-field, strong- and weak-beam dark-field imaging techniques.

Recent applications of TEM to the study of interfaces

1990 ◽  
Vol 48 (4) ◽  
pp. 308-309
Author(s):  
C. Barry Carter
Keyword(s):  
High Resolution ◽  
Sample Preparation ◽  
Grain Boundaries ◽  
Diffuse Scattering ◽  
Imaging Techniques ◽  
Amorphous Material ◽  
Contrast Imaging ◽  
Current State ◽  
Actual Nature ◽  
High Resolution Images

This paper will review the current state of understanding of interface structure and highlight some of the future needs and problems which must be overcome. The study of this subject can be separated into three different topics: 1) the fundamental electron microscopy aspects, 2) material-specific features of the study and 3) the characteristics of the particular interfaces. The two topics which are relevant to most studies are the choice of imaging techniques and sample preparation. The techniques used to study interfaces in the TEM include high-resolution imaging, conventional diffraction-contrast imaging, and phase-contrast imaging (Fresnel fringe images, diffuse scattering). The material studied affects not only the characteristics of the interfaces (through changes in bonding, etc.) but also the method used for sample preparation which may in turn have a significant affect on the resulting image. Finally, the actual nature and geometry of the interface must be considered. For example, it has become increasingly clear that the plane of the interface is particularly important whenever at least one of the adjoining grains is crystalline.A particularly productive approach to the study of interfaces is to combine different imaging techniques as illustrated in the study of grain boundaries in alumina. In this case, the conventional imaging approach showed that most grain boundaries in ion-thinned samples are grooved at the grain boundary although the extent of this grooving clearly depends on the crystallography of the surface. The use of diffuse scattering (from amorphous regions) gives invaluable information here since it can be used to confirm directly that surface grooving does occur and that the grooves can fill with amorphous material during sample preparation (see Fig. 1). Extensive use of image simulation has shown that, although information concerning the interface can be obtained from Fresnel-fringe images, the introduction of artifacts through sample preparation cannot be lightly ignored. The Fresnel-fringe simulation has been carried out using a commercial multislice program (TEMPAS) which was intended for simulation of high-resolution images.

Atomic resolution Z-contrast imaging of bulk crystal surfaces in Scanning Reflection Electron Microscopy

1990 ◽  
Vol 48 (4) ◽  
pp. 414-415
Author(s):  
Z. L. Wang ◽  
J. Bentley
Keyword(s):  
Electron Microscopy ◽  
Elastic Scattering ◽  
Dark Field ◽  
Contrast Imaging ◽  
Crystal Lattices ◽  
Small Probe ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Image Position ◽  
Z Contrast

The success of obtaining atomic-number-sensitive (Z-contrast) images in scanning transmission electron microscopy (STEM) has shown the feasibility of imaging composition changes at the atomic level. This type of image is formed by collecting the electrons scattered through large angles when a small probe scans across the specimen. The image contrast is determined by two scattering processes. One is the high angle elastic scattering from the nuclear sites,where ϕNe is the electron probe function centered at bp = (Xp, yp) after penetrating through the crystal; F denotes a Fourier transform operation; D is the detection function of the annular-dark-field (ADF) detector in reciprocal space u. The other process is thermal diffuse scattering (TDS), which is more important than the elastic contribution for specimens thicker than about 10 nm, and thus dominates the Z-contrast image. The TDS is an average “elastic” scattering of the electrons from crystal lattices of different thermal vibrational configurations,

Switched Reluctance Motor for Electric Submersible Pump

2021 ◽  
Vol 1 (2) ◽  
Author(s):  
Robert Adams ◽  
Jinjiang Xiao ◽  
Michael Cross ◽  
Max Deffenbaugh
Keyword(s):  
State Space ◽  
Performance Feedback ◽  
Motor System ◽  
Reverse Direction ◽  
Submersible Pump ◽  
Pump System ◽  
Switched Reluctance ◽  
Precise Control ◽  
And Control ◽  
Electric Submersible Pump

Switched reluctance motors may be advantageous when used as the primary motor for an electric submersible pump system.  They are less susceptible to jamming failures due to their high starting torque and ability to reverse direction.  Driving these motors requires well-timed pulse waveforms and precise control of the motor based on its rotational position.  In general, voltage-based sensing and control systems at the surface see highly unpredictable waveforms with excessive ringing behaviour due to the impedance characteristics of the long cabling between the surface controller and the downhole motor system.  In this work, a system is detailed which monitors the current waveforms on the motor coil excitation conductors at the surface as a source of motor performance feedback and control.  State-space modelling of the system shows stable current waveforms at the surface controller for both short and long interconnect cable systems.  A laboratory demonstration of the surface controller, interconnect cabling, and motor system is shows excellent agreement with the current and voltage waveforms predicted by the state-space system model.

scholarly journals High-fidelity photometry and astrometry of high-contrast imaged companions using LOCI processing.

2013 ◽  
Vol 8 (S299) ◽  
pp. 44-45
Author(s):  
Jérôme Maire ◽  
Jonathan Gagné ◽  
David Lafrenière ◽  
James R. Graham ◽  
René Doyon
Keyword(s):  
Contrast Ratio ◽  
Angular Separation ◽  
Speckle Noise ◽  
High Contrast ◽  
Contrast Imaging ◽  
High Contrast Imaging ◽  
Suppression Technique ◽  
Imaging And Spectroscopy ◽  
And Migration ◽  
Imaging Performance

RésuméDirect imaging and spectroscopy of exoplanets is a key element for understanding planet formation and migration. Such direct detections and characterizations remains technologically challenging, since a very high contrast ratio and small angular separation are involved, and futhermore speckle noise limits the high-contrast imaging performance. We further discuss a speckle subtraction and suppression technique that fully takes advantage of spectral and time-domain information on quasi-static speckles to measure the highest-fidelity photometry as well as accurate astrometry of detected companions.

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