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Development of a self-assembling ferrofluidic ionic liquid mirror
Abstract
Under the Defense Advanced Research Projects Agency (DARPA) Zenith program, a novel concept has been developed for a self-assembling ferrofluidic ionic liquid mirror (FILM) telescope utilizing a Halbach array of permanent neodymium magnets. The primary mirror will be constructed from two immiscible liquids containing reflective and magnetic nanoparticles (NPs), which will spontaneously phase separate. To maximize reflectivity, minimize wavefront error (WFE), and anchor the reflective layer, the volume of the upper liquid has been minimized. The system is scalable and self-healing and can be deployed without applied acceleration or rotation. The Halbach array overcomes the force of gravity for a ground-based liquid mirror, providing a Kelvin body force potential parallel to the surface of the array. The liquids are held in place and shaped within the mirror by use of the magnetic array, hydrophilic materials, and the high surface tension and high viscosity of the liquid. By tuning the position of the magnet assembly and application of components that tune the effective magnetic field, the liquid surface is forced to adopt the desired optical shape and allows tilting off-axis and slewing with acceptable imaging quality WFE levels.
We report here on the progress of this work in multiple areas including modeling and simulation of the magnetic fluid system optimized for a 0.5 m diameter demonstration mirror and the supporting development of laboratory 0.25 m × 0.25 m flat prototypes of the fluid and magnetic systems. Analytical and finite element models of the ferrofluid and magnetic array have been developed and these results have informed a PDR-level design for a notional build and demonstration of a 0.5 m diameter F/2 spherical mirror with overall root mean squared (RMS) WFE of λ/6 at λ= 550 nm at Zenith which can be slewed to off-zenith pointing angles of up to 10°.
... In the context of adaptive mirror development, electrostatic [27][28][29] and magnetic [30][31][32][33][34] actuators have also been studied. Although ferrofluids are dark and only slightly reflective, significant efforts have been devoted to developing metal liquid-like films that make them reflective and, therefore, applicable to optical systems [30,35]. ...
... This paper assesses the feasibility of the spherical liquid mirror telescope concept as a solution to the LMT limitation to zenith pointing. Although the synthesis of reflective ferrofluids is a necessary condition for the ferrofluid liquid mirror to operate [33][34][35][36][37], this paper focuses only on the ferrohydrodynamic aspects of the problem. The objectives, assumptions, and modeling framework are presented in Sec. 2. The viability of Earth and lunar-based liquid mirror telescopes is explored in Sec. 4 based on optimized solutions. ...
... The Ferrotec EMG-series water-based ferrofluid is used to estimate the properties of the liquid, though different ferrofluids would be used in production. For instance, vacuumcompatible ferrofluids, developed using ionic liquids [35] or silicon oil 1 , would be needed at the surface of the Moon. The EMG series is commercially available and can be easily diluted to specific concentrations. ...
Liquid mirror telescopes exploit the rotation of a reflective fluid to generate diffraction-limited parabolic surfaces. They are economical and scalable but limited to zenith pointing. To expand their field of view, liquid mirror surfaces may be actuated into a spherical cap by means of magnetically susceptible liquids and electromagnetic coils, allowing the optics to rotate without actuating the mirror. However, the practical implementation of the concept remains largely unexplored. This paper adopts a nonlinear ferrohydrodynamic model to explore the technical feasibility of spherical liquid mirror telescopes. Surface deviations for a limited number of coils are extrapolated to determine the magnetic configuration requirements for a given optical wavelength, leading to an expected necessary coil count of 16+-12 for a mirror capable of operation in the visible spectrum, and 13+-10 for one operating in the mid-infrared. Tolerances of 7.3 um for coil positioning, 6.0 A for coil currents, and 9.1 nrad/s for mirror spinning speed are required with coil currents of up to 20 MA to achieve the optical performance metrics using low-density ferrofluids. The results indicate that, although mathematically achievable, the required precision exceeds current technological capabilities, motivating alternative approximations to the problem.
... 14 Figure 3 shows a schematic of the concept. Additional details may be found in Ref. 32. The mirror substrate is a curved (paraboloid) dish to match the required mirror curvature. ...
... Figure 14 shows a schematic of the concept. Additional details may be found in Ref. 32 . ...
... The primary figure control of the ionic ferrofluid is accomplished with a Halbach array. 32 The Halbach array creates a magnetic equipotential surface away from the array and parallel to the top plane of the array. 45 Preliminary ferromagnetic modeling led to the design and construction of a 10″ × 10″ Halbach array prototype with 400 half-inch cubic magnets, as shown in Fig. 15. ...
Astronomy and Space Domain Awareness are limited by the size of available telescope optics, the cost for which scales steeply due to the exquisitely ground and polished primary mirrors, typically made of glass or other lightweight substrates. Liquid mirrors (LMs) may break this unfavorable cost scaling. When rotated at a constant angular velocity, it has been shown that fluid surfaces take the form of a paraboloid, which can function as a primary mirror. However, current LMs cannot slew or tilt off-zenith due to gravity, greatly limiting the viewing area in the sky. To overcome these limitations while also enabling low-cost, very-large-aperture telescopes , the Defense Advanced Research Projects Agency launched the Zenith program. Zenith is developing entirely new LM design-for-build approaches that can create large optical surfaces without rotation and maintain the optical quality during tilt and slew by correcting transient liquid surface aberrations in real time. The development of these new designs is being supported by multi-physics models, materials, surface and field controls, and structures. We discuss key and fundamental aspects of four new design and modeling approaches for this new class of LMs, and the software and simulation tools developed by the Zenith program to design tiltable and size-scalable liquid mirrors.
Astronomy and Space Domain Awareness are limited by the size of available telescope optics, the cost for which scales steeply due to the exquisitely ground and polished primary mirrors, typically made of glass or other light-weight substrates. Liquid mirrors (LMs) may break this unfavorable cost scaling. When rotated at a constant angular velocity, it has been shown that fluid surfaces take the form of a paraboloid, which can function as a primary mirror. However, current LMs cannot slew or tilt off-zenith due to gravity, greatly limiting the viewing area in the sky. To overcome these limitations while also enabling low-cost, very-large-aperture telescopes, DARPA launched the Zenith program. Zenith is developing entirely new LM design-for-build approaches that can create large optical surfaces and maintain optical quality during tilt and slew by correcting transient liquid surface aberrations in real time. The development of these new designs is being supported by multi-physics models, materials, surface and field controls, and structures. This paper discusses key and fundamental aspects of four new design and modeling approaches for this new class of LMs. The software and simulation tools developed by the Zenith program to design tiltable and size-scalable liquid mirrors are also available to the astronomical community as an open-source repository.
The International Liquid Mirror Telescope (ILMT) project is a scientific collaboration in observational astrophysics between the Liège Institute of Astrophysics and Geophysics (Liège University, Belgium), the Aryabatta Research Institute of observational sciencES (ARIES, Nainital, India) and several Canadian universities (British Columbia, Laval, Montréal, Toronto, Victoria and York). Meanwhile, several other institutes have joined the project: the Royal Observatory of Belgium, the National University of Uzbekistan and the Ulugh Beg Astronomical Institute (Uzbekistan) as well as the Poznan Observatory (Poland). The Liège company AMOS (Advanced Mechanical and Optical Systems) has built the telescope structure that has been erected on the ARIES site in Devasthal (Uttarakhand, India). It is the first liquid mirror telescope being dedicated to astronomical observations. First light was obtained on 29th April 2022 and commissioning is being conducted at the present time. In this short article, we describe and illustrate the main components of the ILMT. We also highlight the ILMT papers presented during the third BINA workshop, which discuss various aspects of the ILMT science programs.
A coupled ferrohydrodynamic interface-tracking model is introduced for the analysis of the equilibrium, linear stability, and modal response of magnetic liquid interfaces in surface tension-dominated axisymmetric multiphase flows. The incompressible viscous mass and momentum balances are solved together with the steady-state Maxwell equations by following a monolithic solution scheme. The method is fully implicit, allowing to reach a steady-state solution in a single time step. In addition, the time-dependent evolution of the interface subject to variable external inputs can also be simulated. The geometry is particularized for the study of the free surface oscillations of a ferrofluid in a cylindrical tank under the influence of an inhomogeneous magnetic field in microgravity. Five regions are used to discretize the simulation domain, which combines analytical and elliptic mappings. Magnetic field-free results are validated by the literature. The modal response of the fluid-magnetic system agrees with measurements from the European Space Agency (ESA) Drop Your Thesis! 2017 The Ferros experiment and improves previous quasi-analytical estimations. This new framework of analysis can be applied to the study of a wide variety of microfluidic and low-gravity fluid systems.
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We present a theoretical model and experimental demonstration of thin liquid film deformations due to a dielectric force distribution established by surface electrodes. We model the spatial electric field produced by a pair of parallel electrodes and use it to evaluate the stress on the liquid–air interface through Maxwell stresses. By coupling this force with the Young–Laplace equation, we obtain the deformation of the interface. To validate our theory, we design an experimental set-up which uses microfabricated electrodes to achieve spatial dielectrophoretic actuation of a thin liquid film, while providing measurements of microscale deformations through digital holographic microscopy. We characterize the deformation as a function of the electrode-pair geometry and film thickness, showing very good agreement with the model. Based on the insights from the characterization of the system, we pattern conductive lines of electrode pairs on the surface of a microfluidic chamber and demonstrate the ability to produce complex two-dimensional deformations. The films can remain in liquid form and be dynamically modulated between different configurations or polymerized to create solid structures with high surface quality.
The management of fluids in space is complicated by the absence of relevant buoyancy forces. This raises significant technical issues for two-phase flow applications. Different approaches have been proposed and tested to induce phase separation in low-gravity; however, further efforts are still required to develop efficient, reliable, and safe devices. The employment of diamagnetic buoyancy is proposed as a complement or substitution of current methods, and as a way to induce the early detachment of gas bubbles from their nucleation surfaces. The governing magnetohydrodynamic equations describing two-phase flows in low-gravity are presented with a focus on bubble dynamics. Numerical simulations are employed to demonstrate the reachability of current magnets under different configurations, compare diamagnetic and Lorentz forces on alkaline electrolytes, and suggest scaling up procedures. The results support the employment of new-generation centimeter-scale neodymium magnets for electrolysis, boiling, and phase separation technologies in space, that would benefit from reduced complexity, mass, and power requirements.
Since their conception, ionic liquids (ILs) have been investigated for an extensive range of applications including in solvent chemistry, catalysis, and electrochemistry. This is due to their designation as designer solvents, whereby the physiochemical properties of an IL can be tuned for specific applications. This has led to significant research activity both by academia and industry from the 1990s, accelerating research in many fields and leading to the filing of numerous patents. However, while ILs have received great interest in the patent literature, only a limited number of processes are known to have been commercialised. This review aims to provide a perspective on the successful commercialisation of IL-based processes, to date, and the advantages and disadvantages associated with the use of ILs in industry.
The potential of a return of human presence to the Moon, raises the possibility of significant lunar infrastructure and with it the possibility of astronomical installations which can make use of the lunar surface as a stable platform and take advantage of the lack of atmosphere. Studies have been done in the US and Canada on the feasibility of such installations, and in particular studies of large lunar liquid mirror telescopes have been performed. We report here on the structural design concepts undertaken for one of these studies.
The NASA Orbital Debris Observatory (NODO) astronomical survey uses a transit 3 m liquid mirror telescope to observe a strip of sky in 20 narrowband filters. In this article, we analyze a subset of data from the 1996 observing season. The catalog consists of 18,000 objects with 10 < V < 19 observed in 10 narrowband filters ranging from 500 to 950 nm. We first demonstrate the reliability of the data by fitting the Bahcall-Soneira model of the Galaxy to the NODO magnitude counts and color counts at various Galactic latitudes. We then perform a hierarchical clustering analysis on the sample to extract 206 objects, out of a total of 18,000, showing peculiar spectral energy distributions. It is a measure of the reliability of the instrument that we extract so few peculiar objects. Although the data and results, per se, may not seem otherwise particularly remarkable, this work constitutes a milestone in optical astronomy, since this is the first article that demonstrates astronomical research with a radically new type of mirror.
We demonstrate the impact of rapid mixing of the precursors in a time scale of milliseconds on the
reaction rate and magnetic properties of co-precipitated magnetite with a custom-made mixer. The
mixed volume is directed into a desk-top AC susceptometer to monitor the magnetic response from
the growing particles in real-time. These measurements indicate that the reaction is mostly
completed within a minute. The obtained superparamagnetic nanoparticles exhibit a narrow size
distribution and large magnetization (87 Am2 kg�1). Transmission electron micrographs suggest
that rapid mixing is the key for better crystallinity and a more uniform morphology leading to the
observed magnetization values.
In space a ferro-magnetic liquid can be confined in a region through
electromagnetic forces. The surface of the liquid can be used as a
concave mirror for astronomical purposes. A description of the technique
and of the problems related is given, together with some cases studied
for different classes of telescopes.
This paper reports the preparation of magnetic fluids consisting of magnetite nanoparticles dispersed in an ionic liquid. Different additives were used in order to stabilize the fluids. Colloidal stability was checked by magnetic sedimentation, centrifugation and direct observation. The results of these tests showed that a true ferrofluid was only obtained when the nanoparticles were coated with a layer of surfactant compatible with the ionic liquid. These experiments also showed that stability could not be reached just by electrostatic repulsion. The conclusions of the stability tests were confirmed by calculations of the interparticle energies of interaction. The rheological behaviour of the magnetic fluids upon magnetic field application was also investigated. The experimental magnetoviscous response was fitted by a microstructural model. The model considered that the fluids consisted of two populations of particles, one with a magnetic core diameter of 9 nm, and another with a larger diameter. Upon field application chain-like structures are supposed to be induced. According to estimations particles of 9 nm are too small to aggregate upon field application. The results of the calculations showed that the intensity of the magnetoviscous response depends on the concentration and size of the large particles, and on the thickness of the surfactant layers.
We discuss a new technology that promises large, inexpensive mirrors. We argue that it should be possible to tilt a rotating viscous liquid by perhaps as much as a few tens of degrees. The tilted liquid parabolic surface is used as the support for a thin reflecting metallic film. It may also be possible to use it to support an ultrathin glass mirror. We demonstrate two critical steps: that a viscous liquid mirror can be tilted and that an optical-quality metallic film can be deposited on a liquid. The advent of astronomically useful tilted floating-mirror telescopes is contingent on the development of high-viscosity, high-reflectivity liquids. It is a good omen that we already have identified two classes of such liquids; however, there remain technical challenges to overcome before such liquids can be used in viable telescopes.
We present a new class of large liquid mirrors that use a ferrofluid covered by a reflecting layer of nanoparticles. The surface of the mirror is shaped by several concentric loops of current carrying coils. We first validate our theoretical models by comparing the theoretical predictions to interferometric measurements of a small prototype, finding agreement between data and theory. We then compute with Monte Carlo simulations models for f/2 mirrors having diameters varying between 15 and 44 m. Although much work remains to be done before a functional large mirror is actually built, our first exploration of the concept indicates that it is technologically feasible, thus warranting further work.
This paper discusses an innovative low-cost deformable mirror made of a magnetic liquid (ferrofluid) whose surface is actuated by an hexagonal array of small current carrying coils. Predicted and experimental performances of a 37-actuator ferrofluid deformable mirror are presented along with wavefront correction examples. We show the validity of the model used to compute the actuators currents to obtain a desired wavefront shape. We demonstrate that the ferrofluid deformable mirror can correct a 11 µm low order aberrated wavefront to a residual RMS error of 0.05 µm corresponding to a Strehl ratio of 0.82.
We describe a new technology for the fabrication of inexpensive high-quality mirrors. We begin by chemically producing a large number of metallic nanoparticles coated with organic ligands. The particles are then spread on a liquid substrate where they self-assemble to give optical quality reflective surfaces. Since liquid surfaces can be modified by a variety of means (e.g., rotation, electromagnetic fields), this opens the possibility of making a new class of versatile and inexpensive optical elements that can have complex shapes and that can be modified within short time scales. Interferometric measurements show optical quality surfaces. We have obtained reflectivity curves that show 80% peak reflectivities. We are confident that we can improve the reflectivity curves because theoretical models predict higher values. We expect nanoengineered liquid mirrors to be useful for scientific and engineering applications. The technology is interesting for large optics, such as large rotating parabolic mirrors, because of its low cost. Furthermore, because the surfaces of ferrofluids can be shaped with magnetic fields, one can generate complex, time-varying surfaces that are difficult to make with conventional techniques.
We propose and demonstrate a novel liquid deformable mirror, based on electrocapillary actuation, for high-order wavefront correction. The device consists of a two-dimensional array of vertically oriented microchannels filled with two immiscible liquids, an aqueous electrolyte, and a viscous dielectric liquid, where the dielectric liquid overfills the top end of the channel and forms a thin layer on top. To remedy the poor reflectivity of pure liquids, a free-floating reflective membrane or a dye-coated liquid can be used. The proposed device offers several advantages for adaptive optics applications. These advantages include a high number of actuators, high stroke dynamic range, low power dissipation, fast response time, an initially flat surface, and low cost. However, the device is mainly suitable for dynamic wavefront correction and is limited by its orientation.
Astronomy and Space Domain Awareness are limited by the size of available telescope optics, the cost for which scales steeply due to the exquisitely ground and polished primary mirrors, typically made of glass or other light-weight substrates. Liquid mirrors (LMs) may break this unfavorable cost scaling. When rotated at a constant angular velocity, it has been shown that fluid surfaces take the form of a paraboloid, which can function as a primary mirror. However, current LMs cannot slew or tilt off-zenith due to gravity, greatly limiting the viewing area in the sky. To overcome these limitations while also enabling low-cost, very-large-aperture telescopes, DARPA launched the Zenith program. Zenith is developing entirely new LM design-for-build approaches that can create large optical surfaces and maintain optical quality during tilt and slew by correcting transient liquid surface aberrations in real time. The development of these new designs is being supported by multi-physics models, materials, surface and field controls, and structures. This paper discusses key and fundamental aspects of four new design and modeling approaches for this new class of LMs. The software and simulation tools developed by the Zenith program to design tiltable and size-scalable liquid mirrors are also available to the astronomical community as an open-source repository.
Injection-induced electro-convection (EC) of dielectric liquids is a fundamental problem in electrohydrodynamics. However, most previous studies with this type of EC assume that the liquid is perfectly insulating. By perfectly insulating, we mean an ideal liquid with zero conductivity, and in this situation, the free charges in the bulk liquid originate entirely from the injection of ions. In this study, we perform a numerical analysis with the EC of dielectric liquids with a certain residual conductivity based on a dissociation–injection model. The
spatiotemporal distributions of the flow field, electric field, and positive/negative charge density in the parallel plate configuration are solved utilizing the finite volume method. It is found that the residual conductivity inhibits the onset of EC flow, as well as the strength of the flow field. The flow features and bifurcations are studied in various scenarios with three different injection strengths in the strong, medium, and weak regimes. Three distinct bifurcation sequences with abundant features are observed by continually increasing or decreasing the electric Reynolds number. The present study shows that the residual conductivity significantly affects the bifurcation process and the corresponding critical point of EC flows.
The launch of the James Webb Space Telescope (JWST) will open up a new window for observations at the highest redshifts, reaching out to . However, even with this new facility, the first stars will remain out of reach, as they are born in small minihalos with luminosities too faint to be detected even by the longest exposure times. In this paper, we investigate the basic properties of the Ultimately Large Telescope, a facility that can detect Population III star formation regions at high redshift. Observations will take place in the near-infrared and therefore a Moon-based facility is proposed. An instrument needs to reach magnitudes as faint as 39 mag AB , corresponding to a primary mirror size of about 100 m in diameter. Assuming JWST NIRCam filters, we estimate that Population III sources will have unique signatures in a color–color space and can be identified unambiguously.
Permanent magnet arrays offer several attributes attractive for the development of a low-cost portable MRI scanner for brain imaging. They offer the potential for a relatively lightweight, low to mid-field system with no cryogenics, a small fringe field, and no electrical power requirements or heat dissipation needs. The cylindrical Halbach array, however, requires external shimming or mechanical adjustments to produce B
0
fields with standard MRI homogeneity levels (e.g., 0.1 ppm over field of view), particularly when constrained or truncated geometries are needed, such as a head-only magnet where the magnet length is constrained by the shoulders. For portable scanners using rotation of the magnet for spatial encoding with generalized projections, the spatial pattern of the field is important since it acts as the encoding field. In either a static or rotating magnet, it will be important to be able to optimize the field pattern of cylindrical Halbach arrays in a way that retains construction simplicity. To achieve this, we present a method for designing an optimized cylindrical Halbach magnet using the genetic algorithm (GA) to achieve either homogeneity (for standard MRI applications) or a favorable spatial encoding field pattern (for rotational spatial encoding applications). We compare the chosen designs against a standard, fully populated sparse Halbach design, and evaluate optimized spatial encoding fields using point-spread-function and image simulations. We validate the calculations by comparing to the measured field of a constructed magnet. The experimentally implemented design produced fields in good agreement with the predicted fields, and the GA was successful in improving the chosen metrics. For the uniform target field, an order of magnitude homogeneity improvement was achieved compared to the un-optimized, fully populated design. For the rotational encoding design, the resolution uniformity is improved by 95% compared to a uniformly populated design.
MOEMS-based electrostatic micro-deformable mirrors (MDM) are promising for future AO systems. Original complete polymer mirrors have been designed and realized. Specific control-command strategy is presented and tested; electrostatic MDM are well-suited for open-loop operation.
If uncorrected, the Coriolis force due to the rotation of the Earth causes significant aberration of images produced by large liquid-mirror telescopes. We show that this problem can be eliminated by a fixed compensating tilt of the liquid-mirror rotation axis. The required tilt angle, which is a function of latitude and the mirror rotation rate, is on the order of 10" for current telescopes. This result removes the last fundamental obstacle to achieving diffraction-limited performance with large liquid mirrors.
Liquid propellants can be collected in a zero-g environment by use of the concept of dielectrophoresis, i.e., the induced motion of electrically neutral bodies in a nominiform electric field. A brief analysis of the field forces is presented, and liquid collection experiments in simulated and actual zero-g environments are described, including tests in aircraft flying ballistic trajectories. Two dielectrophoretic propellant collection systems for a 250,000-lb liquid-hydrogen/liquid-oxygen space vehicle are described and compared with a typical auxiliary propulsion system for propellant settling. Results indicate that the dielectrophoretic systems are lighter and will pro vide collecting forces of nearly the same magnitude. The use of the high vollages (10⁶v) required for a dielectrophoretic system on a large vehicle is discussed, and additional applications of the concept are considered. This system appears to offer a lightweight, low-power method of collecting propellant in zero g with forces on the order of 10⁻⁴-I0⁻²g. Propellant boiloff losses can be decreased by (formula presented) by collecting the propellant off the lank walls with dielectrophoretic forces. © 1965 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.
The Large Zenith Telescope is a 6 m optical telescope employing a
rotating primary mirror coated with a film of liquid mercury. Located at
an altitude of 400 m in the Coast Mountains of southwestern British
Columbia, this telescope began regular operation in 2005 October.
Equipped with a four-element Richardson prime-focus corrector and
thinned 2048×2048 pixel drift-scanning CCD imaging camera, it is
used for astronomical survey observations and also serves as an
engineering test facility for further development of liquid-mirror
technology. Built at a cost of less than $1 million dollars, it achieves
an image quality and sensitivity comparable to that of a conventional
telescope of equal aperture and is limited primarily by the astronomical
quality of the site.
Liquid mirror optical telescopes use rotating mercury to form precise
paraboloidal primary reflectors. These telescopes, which represent an
inexpensive alternative to traditional telescopes, to date have been
limited in their sky coverage to a small viewing area (typically 1/4 sq.
deg) centered on the zenith. We propose to increase the sky coverage
area of a mercury optical telescope by at least two orders of magnitude,
using the same concept as that employed in the 305 m diameter radio
telescope at Arecibo, Puerto Rico, which has a spherical primary
reflector. We have shown that it should be possible to deflect a 2.65 m
diameter f/1.9 rotating mercury paraboloid into a precise spherical
shape, by using ferrofluid mercury in a carefully tailored magnetic
field. The 10 deg x 10 deg sky coverage of such a telescope could make
it the instrument of choice in a number of astronomical observing
programs.
Two liquid-mirror telescopes with 1.2 and 1 m diameters are used to
search for optical phenomena in the sky with timescales less than 2 min.
A total of 130 hr of usable data was obtained, but no events were
observed. It is concluded that optical flashes and flares are rare
events.
Liquid mirrors promise to give very large telescopes at low cost making
them ideal instruments for cosmological studies. The concept, past work,
recent observations, and present unpublished optical shop tests are
briefly reviewed. Tests on a 1.5-m liquid mirror indicate an excellent
image and surface quality. Imagery and Ronchi tests indicate that a
point-spread function having a FWHM of the order of 0.3 arcsecond can be
obtained. In particular, bars having a width of 0.5 arcsecond and a
separation of 1 arcsecond between their centers are clearly and cleanly
resolved. Simple improvements should improve image quality even further.
The mirror has a thin mercury layer that decreases costs and renders it
less sensitive to vibrations and disturbances due to the wind.
This book, a translation of the original Russian edition published in 1976, deals with the behaviour of liquids in zero gravity conditions, or conditions close to this. The interest in zero gravity problems stems from space flights. The problems involved, however, contain hardly anything truly novel, their specific properties being due to surface tension. Problems of fluid mechanics taking surface tension into account have been studied for well over a century in connection with cases in which capillary forces become significant. The book is devoted to an analysis of the problems of fluid mechanics under zero gravity from the viewpoint of applied mathematics. (D.W.T.)
Surface films of organically coated silver nanoparticles, when supported by a liquid substrate, exhibit properties of interest for the fabrication of a new class of liquid mirrors. The development of such mirrors clearly requires the optimization of film reflectivity and stability. The present article reports the dependence of film reflectivity on the choice and concentration of the organic ligand employed to protect against particle coalescence. In the specific case of the aromatic amines considered in this study, the choice of ligand is found to have little effect on the resulting optical properties of the films. Each ligand is, however, found to have an optimal concentration to be employed during particle coating. Characterisation of the films by thermogravimetry, elemental analysis and atomic adsorption measurements indicates a very high silver content, reaching about 98% by weight. X-ray photoelectron spectra reveal that the remaining organic component consists primarily of the stabilising ligand. The unexpectedly high silver content of these films eliminates the optimization of this parameter as a possible route to improved reflectivity.
By taking advantage of both the magnetic strength and the astounding simplicity of the magnetic properties of oriented rare earth cobalt material, new designs have been developed for a number of devices. In this article on multipole magnets, special emphasis is put on quadrupoles because of their frequent use and because the aperture fields achievable (1.2–1.4 T) are rather large. This paper also lays the foundation for future papers on: (a) linear arrays for use as “plasma buckets” or undulators for the production of synchrotron radiation; (b) structures for the production of solenoidal fields; and (c) three-dimensional structures such as helical undulators or multipoles.
A phenomenological treatment is given for the fluid dynamics and thermodynamics of strongly polarizable magnetic fluid continua in the presence of nonuniform magnetic fields. Examples of the fluids treated here have only recently been synthesized in the laboratory. It is found that vorticity may be generated by thermomagnetic interaction even in the absence of viscosity and this leads to the development of augmented Bernoulli relationships. An illustration of a free‐surface problem of static equilibrium is confirmed by experiment and information is obtained regarding a fluid's magnetic susceptibility. Another illustration elucidates the mechanism of an energy conversion technique. Finally, an analytical solution is found for the problem of source flow with heat addition in order to display the thermomagnetic and magnetomechanical effects attendant to simultaneous heat addition and fluid motion in the presence of a magnetic field.
Context.We give a progress report on tiltable, nanoengineered, rotating liquid mirrors, which were discussed in previous papers.Aims.We want to develop the technology, improve reflectivities and user-friendliness. The ultimate goal is to demonstrate high-quality liquid mirrors that can be tilted by a few tens of degrees.Methods.We coated hydrophilic liquid substrates that have poor reflectivities with a reflective layer of self-assembling metallic nanoparticles. We analyzed the wavefronts of 1-m diameter mirrors with Ronchi tests, knife-edge tests and point-spread functions (PSFs).Results.There is significant improvement over previous work where the reflecting layer was deposited on hydrophobic oils. While previous work only demonstrated tilted low-reflectivity mirrors, we now test a high-reflectivity 1-m diameter liquid mirror tilted by 45 arcmin.Conclusions.It is considerably easier to coat hydrophilic liquids than hydrophobic ones. We have reached a significant milestone by demonstrating a tilted, highly reflective, liquid mirror. Although this is still an immature technology, it is near the stage where it could be used in astronomy. The remaining technical challenges, for which we propose solutions, are not fundamental and could be overcome with additional work. This will be a worthwhile undertaking, considering the very low cost of liquid mirrors.
It is shown that a previously unknown class of magnetization patterns exists in planar structures which have the unique property that all the flux escapes from one surface with none leaving the other side. A simple case is a constant amplitude rotating vector magnetization where the sense of rotation dictates which surface has no flux. More complicated magnetization patterns are elucidated. The likelihood that the one-sided flux phenomenon occurs partially in the normal write, the contact-printing and the print-through processes of tape recording is discussed. It is concluded that significant improvements in tape recording performance would ensue if means could be found to enhance the effect.
The force on a macroscopic polarizable body in an inhomogenous electromagnetic field is calculated for three simple exactly solvable situations. Comparing different approaches we pinpoint possible pitfalls and resolve recent confusion about the force density in ferrofluids. Comment: 8 pages, 3 figures, submitted to Am. J. Phys
Carbon Dioxide Removal by Ionic Liquid System (CDRILS): Impacts of trace contaminants and ground prototype testing
- Kamire
Overview of DARPA's liquid mirror telescope program, and open-source liquid optic modeling tools
- M Nayak
- S Basu
- M Julian
- K Iyer
Nayak, M., Basu, S., Julian, M. and Iyer, K., "Overview of DARPA's liquid mirror telescope program, and
open-source liquid optic modeling tools," Proceedings SPIE 13100-116, (2024).
Carbon Dioxide Removal by Ionic Liquid System (CDRILS): Impacts of trace contaminants and ground prototype testing
- R Kamire
- P Henson
- S F Yates
- E Rahislic
- M Triezenberg
- B Dotson
- S Skomurski
- J Ford
- E Pope
- K Pedersen
Kamire, R., Henson, P., Yates, S. F., Rahislic, E., Triezenberg, M., Dotson, B., Skomurski, S., Ford, J., Pope, E.
and Pedersen, K., "Carbon Dioxide Removal by Ionic Liquid System (CDRILS): Impacts of trace contaminants
and ground prototype testing," 51st International Conference on Environmental Systems, ICES-2022-289, St.
Paul, MN, (2022). https://hdl.handle.net/2346/89801