Set Of Mirrors Research Articles

ID23-2: an automated and high-performance microfocus beamline for macromolecular crystallography at the ESRF.

ID23-2 is a fixed-energy (14.2 keV) microfocus beamline at the European Synchrotron Radiation Facility (ESRF) dedicated to macromolecular crystallography. The optics and sample environment have recently been redesigned and rebuilt to take full advantage of the upgrade of the ESRF to the fourth generation Extremely Brilliant Source (ESRF-EBS). The upgraded beamline now makes use of two sets of compound refractive lenses and multilayer mirrors to obtain a highly intense (>1013 photons s-1) focused microbeam (minimum size 1.5 µm × 3 µm full width at half-maximum). The sample environment now includes a FLEX-HCD sample changer/storage system, as well as a state-of-the-art MD3Up high-precision multi-axis diffractometer. Automatic data reduction and analysis are also provided for more advanced protocols such as synchrotron serial crystallographic experiments.

Anamorphic beam shaping system designed to optimize irradiance distribution in the Cofiblas process for glass nanofibers production

Glass fibers play a key role as reinforcements in composite materials, where increasing mechanical properties at affordable costs are required in applications such aerospace, automotive and wind turbine manufacturing. The production of glass nanofibers augurs a substantial enhancement of their performance. However, although different techniques are currently used to produce glass, polymer or carbon nanofibers, none of them is practical to continuously produce solid, non-porous and separated glass nanofibers with capability to feasibly scaling up for mass production. The continuous fiberizing by laser melting (Cofiblas), makes possible to obtain ultrafine fibers with virtually infinite length.Here, we provide a deep analysis on the influence of the laser beam shaping system on the performance of the Cofiblas technique. Two different optical systems are compared: the first one consists of a beam-splitter coupled to a set of mirrors and spherical lenses. While the second one, is based on an anamorphic system comprising a simple combination of cylindrical and spherical lenses. Both configurations are evaluated and compared in several sets of experiments with the main target of obtaining continuous glass nanofibers with the smallest diameter. The anamorphic system generates an elliptical Gaussian distribution of the laser beam irradiance, which increases the energy absorbed by the preform. As a result, continuous silica nanofibers with diameters 84.5% smaller are obtained with the anamorphic system, compared with the optical system constituted by spherical lenses.

Distributed active phase-locking of an all-fiber structured laser array by a stochastic parallel gradient descent (SPGD) algorithm.

Coherent beam combining (CBC) of fiber laser array is a promising way to achieve high output power. Phase control is one key point to implement CBC. Appropriate feedback structures should be established to achieve phase control. Most feedback structures of CBC are established after the lasers emit to free space and consist of a set of lenses or mirrors. Those optical elements in free space may hinder array size and integration. In this paper, we demonstrated an all-fiber structured CBC method with distributed phase-locking. By adding an all-fiber measurement loop beside the main laser chain, the phase of main laser chain is appended to the measuring loop. Phases of each main laser chain are locked indirectly though the measurement loops by using stochastic parallel gradient descent (SPGD) algorithm. The principle of distributed phase-locking is also illustrated. Corresponding simulations are carried out and two-channel fiber lasers are coherently combined by this method. The experimental results show that the structure can achieve phase-locking effectively. Stable and distinct interference fringe is observed. Additionally, the structure proposed in this paper is straightforwardly building and expanding.

The Double Vision at the Heart of Luis Correa-Díaz's Americana-Lcd

Luis Correa-Díaz's Americana-lcd examines US popular culture and contemporary politics. The book's engagement with popular culture goes beyond references to movies or rock and roll and incorporates comics by pairing most of the poems with comic strips drawn by the Mexican cartoonist Pavel Ortega. For Hillary Chute, the double narrative of word and image in comics demands a double vision, a back-and-forth between reading and looking. English translations accompany most of the poems, as well. Though translated poems are not trans-medial, translations also demand a back-and-forth between the original and the translation. Both comics and translation, then, are texts with double vision. The book, thus, embeds the poems within a set of mirrors, an intertextual play that is both trans-medial and trans-lingual. Correa-Díaz exploits this double vision throughout the book in other ways as well: among these, he uses irony, puns, and other forms of doubling. The formal and structural double vision of comics, translation, puns, and etc. reinforce the thematic double vision at the heart of Americana-lcd, namely that of the yes/no, or yes/but of the immigrant experience. In this way, Correa-Díaz is able to express love for two countries. In fact, this double vision lets him both praise and blame his adopted country.

Holographic Optical Lenses Recorded on a Glassy Matrix-Based Photopolymer for Solar Concentrators

Global warming is a very topical issue, therefore the search for new renewable energy sources is considered of fundamental importance. Among these, solar energy offers great possibilities considering that the amount of sunlight hitting the Earth ‘s surface in an hour and a half is enough to meet the world’s electricity consumption for a complete year. Generally, solar concentrators are used to collect the solar radiation and to concentrate it at a single focal point. These devices consist in a set of mirrors or mechanical structures to reduce the area of a photovoltaic cell, which is typically very expensive. Volume transmission phase holographic optical elements could be opportunely designed and realized to obtain a simple, lightweight, compact and inexpensive planar solar concentrator. With the aim of bringing scientific attention to this still developing topic, in this work we critically report a complete investigation on a new photopolymeric material obtained by sol-gel reactions used as possible recording material for volume holographic solar concentrators; as a proof of concept, both terrestrial and extreme environments, such as space, are considered as potential applications.

Design of 4-DOF Voice Coil Motor with Function of Reducing Laser Geometrical Fluctuations

In order to improve the quality of the laser and shorten the optical path of the fast steering mirror (FSM) laser compensation system, this paper proposes a four-degrees-of-freedom (4-DOF) voice coil motor (VCM) with the function of reducing laser geometrical fluctuations. The feature of this paper is the combination of a DC brushed spindle motor and the proposed 4-DOF VCM. A diffuser is installed on the shaft of the DC brushed motor for suppressing the laser speckle. The proposed 4-DOF VCM is combined with a laboratory-designed mirror set, controlling the laser direction to compensate for laser fluctuations. The proposed actuator was designed and verified by using the commercial CAD software SolidWorks and finite element analysis (FEA) software ANSYS. A mathematical model was built to simulate the dynamic response of the proposed 4-DOF VCM in MATLAB Simulink.

IoT Enabled Low Cost Distributed Angle Measurement Fault Detection System for LFR Plants

The advances in renewable solar energy generation have led to the development of Linear Fresnel Reflector (LFR) technology, in which solar energy is focused by means of a set of longitudinal mirrors onto a tubular receiver. The efficiency in the energy generation process is mainly given by the relation between the angle of incidence of incoming sunlight rays and the fixed location of the elevated tubular receiver. In order to maximize efficiency, the tilt angles for each one of the longitudinal mirrors should vary as a function of solar position tracking. The angular variation process is generally based on the use of encoders implementing a closed-loop feedback system to provide information to the controller in relation with actual mirror angular position. An alternative that has recently emerged is the use of inclinometers in order to obtain angular information, providing a cost-effective solution in order to employ angular information for mirror position control. In this work, a low cost monitoring system for LFR plants is presented, based on the use of a distributed configuration to obtain information related to mirror inclination angles. The proposed system is based on the use of accelerometers coupled to low cost wireless transceivers, enabling distributed real time data collection. The system allows fault or damage detection at all monitored mirror sections, avoiding long periods of efficiency loss of the LFR plant. The configuration and location of the wireless sensor nodes has been analyzed by means of deterministic 3D Ray Launching channel modeling, in order to optimize coverage/capacity relations within the scenario under test. The proposed system has been implemented enabling remote LFR facility monitoring by means of cloud-based infrastructure. In addition, the system is highly scalable, allowing the inclusion of other interesting applications such as intruder detection for security.

Dual-axis cubic cavity for drift-compensated multi-wavelength laser stabilisation.

We describe a 'clock control unit' based on a dual-axis cubic cavity (DACC) for the frequency stabilisation of lasers involved in a strontium optical lattice clock. The DACC, which ultimately targets deployment in space applications, provides a short-term stable reference for all auxiliary lasers-i.e. cooling, clear-out, and optical lattice-in a single multi-band cavity. Long-term cavity drift is compensated by a feed-forward scheme exploiting a fixed physical relation to an orthogonal second cavity axis; either by reference to an ultrastable 698 nm clock laser, or by exploiting the differential drift between orthogonal axes extracted by a single laser in common view. Via a change of mirror set in the cavity axis accessed by the clock laser, the system could also provide stabilisation for sub-Hz linewidths at the 698 nm clock wavelength, fulfilling all stabilisation requirements of the clock.

The Ground-based Experiment of the Prototype of Planetary (& Lunar) Rotation Monitor Telescope

The scientific objective of the Planetary (& Lunar) Rotation Monitor (PRM) telescope is to study the terrestrial planet's (the Moon's) rotation and its interior structure and physics by in-situ observation. In order to verify the brand new principle of observations and the data processing method, the prototype of the telescope is designed and manufactured. The prototype's optical system consists of a commercial telescope and trihedron mirror set placed at the entrance of its light path to realize the capability of observing three fields of view (FOVs) simultaneously. The ground-based validation observation began in 2017, and the images containing the stars from three FOVs were achieved. Star images from different FOVs are initially mixed together, but they can be classified into the three FOVs respectively by calculating the displacement of star images on the CCD plate between two adjacent exposures, to make the observational effect be identical with three independent observations of the three FOVs respectively. After image processing, from the orientation variation of the three FOVs simultaneously in space due to the Earth's rotation, the direction of the rotation axis of the Earth in space can be derived. Its deviation from the theoretical value is about 1″ in average, indicating that the working principle and data processing method are effective. The main errors in observations are discussed, including the atmospheric refraction, the thermal deformation of the commercial telescope tube, the low optical resolution caused by the short focal length, the optical aberration in the multi-FOV observation, etc. It is indicated that the spatial resolution of the telescope can be enhanced with a longer focal length, and the observational reliability can be improved by optimizing the thermal deformation control. Improving the optical design in the simultaneous observation of multiple FOVs will also be helpful to the accuracy enhancement.

Demonstration of >1Tbit/s WDM OWC with wavelength-transparent beam tracking-and-steering capability

Beam tracking-and-steering is crucial for the operation of high-speed, narrow beam, optical wireless communication (OWC) systems. Using a system based on two sets of low-cost cameras for continuous beam tracking and a set of mirrors for steering, we demonstrate here a high-capacity (>1Tbit/s) ten-channel wavelength-division multiplexed (WDM) OWC system based on discrete multitone transmission. The results, which are achieved over a 3.5-m perpendicular distance and across a lateral coverage up to 1.8 m, constitute to the best of our knowledge, the highest aggregate OWC capacity at this coverage.

Large Area Diamond Disk Growth Experiments and Thermomechanical Investigations for the Broadband Brewster Window in DEMO

An electron cyclotron system (ECS) is required in the European DEMO fusion reactor for plasma heating, magnetohydrodynamic control, especially the suppression of neoclassical tearing modes (NTMs), and thermal instability control. Microwave beams of 2 MW, generated by gyrotrons, shall propagate through corrugated HE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> waveguides (WGs) of 63.5-mm inner diameter and finally reach specific locations in the plasma by a dedicated set of mirrors. The deployment of the beam may be done either by angular steering, i.e., tilting moveable mirrors, or by frequency steering, i.e., tuning the gyrotron frequency. In the last option, for long pulse operations, broadband optical grade diamond windows are required as confinement and/or vacuum barriers both at the torus and the gyrotron side. The Brewster-angle window represents a promising solution due to its intrinsic simplicity. However, the WG aperture imposes a minimum Ø180 mm for the disk at the Brewster-angle of 67.2° for diamond. This is an ambitious target, considering 140 mm as the state of the art. First, this article shows the very promising results of diamond growth experiments carried out by Diamond Materials GmbH with the first worldwide free-standing optical grade Ø180-mm disk having an average unpolished thickness of 1.3 mm. For the first time, one side of this large disk was polished and loss tangent measurements were performed at the center and over a large area. Then, the performance of the window featuring these large disks was characterized by a consistent set of thermomechanical analyses in view of the forthcoming window prototyping activity.

Design validation of in-vessel mirrors and beam dump for first plasma operations in ITER

First plasma operation in ITER will start after completing the assembly of the tokamak vessel and the installation of the main sub-systems, but prior to the installation of the blanket modules and the divertor cassettes. Utilization of temporary limiters and divertor replacement structures will provide a poloidal and toroidal reference side position to the plasma edge to protect the vacuum vessel and other components already installed during operations. An additional set of mirrors is required to reflect the power injected from the upper launcher towards the plasma resonance for EC-assisted breakdown of the plasma up to a beam dump needed to trap and absorb the power of the beams after crossing the plasma in order to reduce the stray radiation escaping back into the vacuum chamber down to less than 10% of the total power. The quasi-optical system has been designed, with shape and size of the mirrors compliant with the requirements provided by ITER for their installation, realization and plasma performances, resulting in two standard focussing mirrors and one grating mirror. The beam dump consists of a box with five metal plates, the first providing a spreading of the high incident power and the others coated with absorbing material with thickness distribution studied to gradually reduce the power during the multiple reflections inside the box, avoiding damages to the coating itself. This work focuses on the validation of the quasi-optical design of the mirrors and the assessment of the dump performances, based on a multi-bounces model developed ad-hoc for this purpose. The study includes a tolerance analysis for the beam dump to include the effect of uncertainties in the thickness of the absorbing coating and misalignments of the mirrors, to verify the performances of the dump also when operating in different conditions with respect to the nominal ones.

Development of Glass-Tube-Pair Type Doppler Probe Array for 1D Profile Measurement of Two Component Ion-Flow Vector

We developed a new glass-tube-pair type Doppler probe array for 1D ion velocity vector and temperature measurement. It needs just two parallel glass-tube insertion, realizing low plasma perturbation and 1D ion flow vector measurement on a single discharge. Using four mirrors and optical fibers for one measurement point, this system can measure ion local light emissions of each measurement volume from four different directions, enabling us to measure local ion flow vector and temperature. All set of mirrors and optical fibers are aligned in the two parallel glass tubes for 1D measurement by a single discharge. This system measured successfully ion outflow speed of two merging tokamak plasmas, about 80% of poloidal Alfvén speed in agreement with recent reconnection experiments and theory.

Feasibility study of an efficient method to measure depth profile of particle ions using a wedge-shaped acrylic block

The depth-profile measurement of particle ions is a time- and labor-consuming task, and thus an efficient method is desired. To solve this problem, we propose a new method to measure depth profiles and test it for carbon ions. In our method, we use a thin silver-activated zinc sulfide (ZnS(Ag)) scintillator plate set against the inner top side of a black box and irradiate a uniform carbon-ion beam to this plate from the upper side. On the ZnS(Ag) plate, a wedge-shaped acrylic block is set to absorb the carbon ions depending on the plate’s position. The scintillation light’s image is reflected by a surface mirror set below the ZnS(Ag) plate and then detected by a cooled charge-coupled device (CCD) camera from the side. We irradiate carbon ions for 6 s and measure the ZnS(Ag) image that is partially attenuated by the wedge-shaped acrylic block. By setting the profile on the measured image, we could estimate the depth profile of the carbon-ion beam, although a quenching of the scintillator is observed around the Bragg peak area. We conclude that our proposed method is promising for efficiently measuring the depth profile of particle ions.

Remarks on Using One-Way Mirror Supervision Method to Train Psychoanalytic Psychotherapists

The one-way mirror method of supervision is an excellent method to train psychotherapists. Its positive influences on training candidates and patients are well-documented in previous studies. Based on his personal experiences as an observer of psychoanalytic psychotherapy sessions from behind a mirror, the author recognized particular materials, dynamics and defenses both in the patients and the trainees, brought out by the one-way mirror setting. The advantages of this supervision method and the materials, defenses and dynamics that this setting instigated in patients and therapists are explored separately. The importance of the supervisory relationship in dealing with such issues is elaborated.

Mid-infrared interference coatings with excess optical loss below 10 ppm.

We present high-reflectivity substrate-transferred single-crystal GaAs/AlGaAs interference coatings at a center wavelength of 4.54 μm with record-low excess optical loss below 10 parts per million. These high-performance mirrors are realized via a novel microfabrication process that differs significantly from the production of amorphous multilayers generated via physical vapor deposition processes. This new process enables reduced scatter loss due to the low surface and interfacial roughness, while low background doping in epitaxial growth ensures strongly reduced absorption. We report on a suite of optical measurements, including cavity ring-down, transmittance spectroscopy, and direct absorption tests to reveal the optical losses for a set of prototype mirrors. In the course of these measurements, we observe a unique polarization-orientation-dependent loss mechanism which we attribute to elastic anisotropy of these strained epitaxial multilayers. A future increase in layer count and a corresponding reduction of transmittance will enable optical resonators with a finesse in excess of 100 000 in the mid-infrared spectral region, allowing for advances in high resolution spectroscopy, narrow-linewidth laser stabilization, and ultrasensitive measurements of various light-matter interactions.

In Situ Underwater Average Flow Velocity Estimation Using a Low-cost Video Velocimeter

AbstractThe development of a low-cost Video Velocimeter (VIV) to estimate underwater bulk flow velocity is described. The instrument utilizes a simplified particle image correlation technique to reconstruct an average flow velocity vector from video recordings of ambient particles. The VIV uses a single camera with a set of mirrors that splits the view into two stereoscopic views, allowing estimation of the flow velocity vector. The VIV was validated in a controlled flume using ambient seawater, and subsequently field tested together with an acoustic Doppler velocimeter with both mounted close to the coastal seafloor. When used in non-turbulent flow, the instrument can estimate mean flow velocity parallel to the front face of the instrument with root-mean-squared errors of the main flow within 10% of the ±20 cm/s measurement range when compared to an ADV. The predominant feature of the VIV is that it is a cost-effective method to estimate flow velocity in complex benthic habitats where velocity parallel to the sea floor is of interest.

Nuclear analysis of the DEMO divertor survey visible high-resolution spectrometer

Spectroscopic measurements have been recently proposed in DEMO for divertor detachment control. In its current design, the DEMO Divertor Survey Visible High-Resolution Spectrometer is foreseen to perform spectroscopy measurements by integrating three optical subsystems into an equatorial port (EP). Behind the first wall, light travels through a set of metallic mirrors and ducts before it reaches the closure plate of the EP. This paper presents a nuclear analysis performed with the Monte Carlo simulation program MCNP6 for two alternative configurations of the system. The results show that the configuration with 5 mirrors per transmission line is very effective to reduce the neutron streaming through the port. However, it will not be possible, with the current design, to introduce standard electronics along the spectroscopy ducts, as the dose rate limits for non-critical electronic components are exceeded in both configurations. In the plasma-facing mirrors, the heat loads are below 2 mW/cm3, which shows that the strategy of recessing the first mirrors and placing them behind small-diameter openings is effective to decrease the loads in the mirrors. FISPACT simulations for different materials show that material transmutation in the mirrors will be negligible throughout the DEMO reactor lifetime.

Design optimization of the Upper Steering Mirror Assembly (USMA) for ITER ECHUL in view of disruptive events

Four Electron Cyclotron Heating Upper Launchers (ECHUL) will be used at ITER to counteract magneto-hydrodynamic plasma instabilities by targeting them with up to 20 MW of mm-wave power at 170 GHz. The millimeter waves are guided through a set of fixed mirrors (M1, M2 and M3) and the front steering mirror set (M4), aiming at the correct location in the plasma for suppression of the q = 3/2 and q = 2/1 Neoclassical Tearing Modes (NTMs). At the M4 reflecting mirror surfaces, part of the mm-wave power is converted into heat by ohmic dissipation, totaling ca. 25 kW of absorbed power and reaching a peak power density of up to 1.8 MW/m2 in each of the 4 beam center spots.The latest in-vessel mm-wave mirrors Components Load Specification (CLS) data imposes an increase of the electromagnetically induced loads relative to those anticipated in earlier designs, resulting in higher mechanical load on the Crossed Flexure Pivot (CFP) due to Vertical Displacements Events (VDEs). The present paper reports the main design optimizations as well as the finite elements analyses carried out with the objective to: 1) reduce the electromagnetic loads on the components due to induced Eddy currents, 2) dissipate the thermal loads coming from the beams themselves and the plasma following the design requirements in terms of coolant temperature rise, pressure drop and admissible corrosion rate values, 3) assure the components structural integrity enforcing the ITER Structural Design Code for the In-Vessel Components (SDC-IC).

Conscious perception and perceptual echoes: a binocular rivalry study.

Alpha rhythms (∼10Hz) in the human brain are classically associated with idling activities, being predominantly observed during quiet restfulness with closed eyes. However, recent studies demonstrated that alpha (∼10Hz) rhythms can directly relate to visual stimulation, resulting in oscillations, which can last for as long as one second. This alpha reverberation, dubbed perceptual echoes (PE), suggests that the visual system actively samples and processes visual information within the alpha-band frequency. Although PE have been linked to various visual functions, their underlying mechanisms and functional role are not completely understood. In this study, we investigated the relationship between conscious perception and the generation and the amplitude of PE. Specifically, we displayed two coloured Gabor patches with different orientations on opposite sides of the screen, and using a set of dichoptic mirrors, we induced a binocular rivalry between the two stimuli. We asked participants to continuously report which one of two Gabor patches they consciously perceived, while recording their EEG signals. Importantly, the luminance of each patch fluctuated randomly over time, generating random sequences from which we estimated two impulse-response functions (IRFs) reflecting the PE generated by the perceived (dominant) and non-perceived (suppressed) stimulus, respectively. We found that the alpha power of the PE generated by the consciously perceived stimulus was comparable with that of the PE generated during monocular vision (control condition) and higher than the PE induced by the suppressed stimulus. Moreover, confirming previous findings, we found that all PEs propagated as a travelling wave from posterior to frontal brain regions, irrespective of conscious perception. All in all our results demonstrate a correlation between conscious perception and PE, suggesting that the synchronization of neural activity plays an important role in visual sampling and conscious perception.