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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Normal-incidence Sb/B{sub 4}C multilayer mirrors for the 80 A < {lambda} < 120 A wavelength range

Periodic and aperiodic Sb/B4C multilayer structures have been theoretically calculated and synthesised for the first time for the application in soft X-ray optics in the 80 A < {lambda} < 120 A range. The reflection spectra of the periodic multilayer mirrors are measured using synchrotron radiation and laser plasma-generated radiation. The experimental spectra are theoretically interpreted with the inclusion of transition layers and substrate roughness. The density of antimony layers is supposedly {rho}{sub (Sb)} = 6.0 g cm{sup -3}, and the thickness of transition layers (if any) in the Sb/B4C multilayer structures does not exceed 10 A. A peak reflectivity of 19 % is attained at a wavelength of 85 A. An aperiodic mirror optimised for maximum uniform reflectivity in the 100 - 120 A range is tested employing the laser plasma radiation source. (x-ray optics)

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Application of conical 90-degree reflectors for solving the problem of mirror alignment in terahertz-range lasers

We report a study of the conical mirrors with an apex angle of 90° in the resonator of the gas-discharge HCN laser with the radiation wavelength of 337 μm (0.89 THz). Experimental results have shown that such mirrors do not require precise alignment. This makes it possible to improve the radiation stability, significantly simplify the construction of laser and reduce the complexity of its maintenance. (laser applications and other topics in quantum electronics)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Control of the phase characteristics of Stokes waves in a Michelson interferometer with SBS mirrors

It is found that, when using stimulated Brillouin scattering (SBS) mirrors (mounted in a ring Michelson interferometer) with counterfocusing, under pumping by pulses with steep (2−3 ns) leading edges and applying Freon FC-75 as an active medium, the phase difference of the Stokes waves on the semitransparent interferometer mirror obeys the dependence Δφ=2ΔkΔl (Δk is the difference in the magnitudes of the pump and Stokes component wave vectors and Δl is the difference in the optical arm lengths). (paper)

42 ENGINEERING↗
DOE OSTI2018

Fibre loop mirror with FBGs for the scanning range stabilisation in a fibre self-sweeping laser

A new scheme is suggested for stabilising scanning range boundaries of a self-sweeping fibre laser with fibre Bragg gratings (FBGs) and a fibre loop mirror. The mechanism for stabilising stop and/or start scanning boundaries is based on the formation of additional selective losses and/or reflection depending on the FBG position relative to the fibre mirror. It is shown that the simultaneous implementation of two selectors reduces fluctuations of the self-sweeping boundaries to several picometres, which is less by one-two orders in magnitude as compared with a case when the FBGs are absent. The approach suggested allows one to enhance predictability of emission wavelength tuning in fibre self-sweeping lasers, which is very important in practical applications. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Comparison of approaches in the manufacture of broadband mirrors for the EUV range: aperiodic and stack structures

We have developed the design and experimentally studied aperiodic and stack broadband Mo/Si mirrors for the purposes of the KORTES project, optimised for uniform reflection in the 17 – 21 nm wavelength range. It is shown that stack structures with an insignificant loss in the reflection coefficient are much more preferable from the point of view of manufacturing and certification, which, in turn, makes it possible to correct the deposition process and to reach the calculated parameters of a multilayer mirror in a small number of iterations. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

VALIDATION OF OBSERVATIONS OBTAINED WITH A LIQUID MIRROR TELESCOPE BY COMPARISON WITH SLOAN DIGITAL SKY SURVEY OBSERVATIONS

The results of a search for peculiar astronomical objects using very low resolution spectra obtained with the NASA Orbital Debris Observatory (NODO) 3 m diameter liquid mirror telescope (LMT) are compared with results of spectra obtained with the Sloan Digital Sky Survey (SDSS). The main purpose of this comparison is to verify whether observations taken with this novel type of telescope are reliable. This comparison is important because LMTs are an inexpensive novel type of telescope that is very useful for astronomical surveys, particularly surveys in the time domain, and validation of the data taken with an LMT by comparison with data from a classical telescope will validate their reliability. We start from a published data analysis that classified as peculiar only 206 of the 18,000 astronomical objects observed with the NODO LMT. A total of 29 of these 206 objects were found in the SDSS. The reliability of the NODO data can be seen through the results of the detailed analysis that, in practice, incorrectly identified less than 0.3% of the 18,000 spectra as peculiar objects, most likely because they are variable stars. We conclude that the LMT gave reliable observations, comparable to those that would have been obtained with a telescope using a glass mirror.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

SMALL-SCALE PRESSURE-BALANCED STRUCTURES DRIVEN BY MIRROR-MODE WAVES IN THE SOLAR WIND

Recently, small-scale pressure-balanced structures (PBSs) have been studied with regard to their dependence on the direction of the local mean magnetic field B{sub 0} . The present work continues these studies by investigating the compressive wave mode forming small PBSs, here for B{sub 0} quasi-perpendicular to the x-axis of Geocentric Solar Ecliptic coordinates (GSE-x). All the data used were measured by WIND in the quiet solar wind. From the distribution of PBSs on the plane determined by the temporal scale and angle θ{sub xB} between the GSE-x and B{sub 0} , we notice that at θ{sub xB} = 115° the PBSs appear at temporal scales ranging from 700 s to 60 s. In the corresponding temporal segment, the correlations between the plasma thermal pressure P{sub th} and the magnetic pressure P{sub B}, as well as that between the proton density N{sub p} and the magnetic field strength B, are investigated. In addition, we use the proton velocity distribution functions to calculate the proton temperatures T and T{sub ∥}. Minimum Variance Analysis is applied to find the magnetic field minimum variance vector B{sub N} . We also study the time variation of the cross-helicity σ{sub c} and the compressibility C{sub p} and compare these with values from numerical predictions for the mirror mode. In this way, we finally identify a short segment that has T > T{sub ∥}, proton β ≅ 1, both pairs of P{sub th}-P{sub B} and N{sub p}-B showing anti-correlation, and σ{sub c} ≈ 0 with C{sub p} > 0. Although the examination of σ{sub c} and C{sub p} is not conclusive, it provides helpful additional information for the wave mode identification. Additionally, B{sub N} is found to be highly oblique to B{sub 0} . Thus, this work suggests that a candidate mechanism for forming small-scale PBSs in the quiet solar wind is due to mirror-mode waves.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

The blob crashes into the mirror: modeling the exceptional γ-ray flaring activity of 3C 454.3 in 2010 November

3C 454.3 is a prominent flat-spectrum radio quasar that in recent years attracted considerable attention because of its variable high-energy emissions. In this paper, we focus on the exceptional flaring activity of 3C 454.3 that was detected by AGILE and by Fermi-LAT in 2010 November. In the light of the time-varying data ranging from the radio, optical, and X-ray up to GeV γ-ray bands, we discuss a theoretical framework addressing all data in their overall evolution. For two weeks, the source has shown a plateau of enhanced GeV emission preceding a sudden major flare lasting about three days before decaying. The γ-ray flare onset is abrupt (about six hours), and is characterized by a prominent 'Compton dominance' with the GeV flux exceeding the pre-flare values by a factor of four to five. During this episode, the optical and X-ray fluxes increased by a factor of around two. Within the standard framework of a jet launched with a Lorentz bulk factor Γ ∼ 10 from a central black hole, we explore the yields of two alternatives. Case 1, with high-energy emission originating within the broad line region (BLR); and Case 2, with most of it produced outside at larger distances of a few parsecs. We show that Case 1 has considerable problems in explaining the whole set of multifrequency data. Case 2, instead, leads to a consistent and interesting interpretation based on the enhanced inverse Compton radiation that is produced as the jet crashes onto a mirror cloud positioned at parsec scales. This model explains the γ-ray versus optical/X-ray behavior of 3C 454.3, including the otherwise puzzling phenomena such as the prominent 'rphan' optical flare, and the enhanced line emission with no appreciable γ-ray counterpart that preceded the GeV γ-ray flare. It also accounts for the delayed onset of the latter on top of the long plateau. Our modeling of the exceptional 3C 454.3 γ-ray flare shows that while emission inside the canonical BLR is problematic, major and rapid variations can be produced at parsec scales with moderate bulk Lorentz factors Γ ≈ 15. Our 'crashed mirror' model is also applicable to other blazar flares marked by large Compton dominance of the emitted radiation such as the flare of PKS 1830–211 in 2010 October.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Centrifugal-mirror confinement with strong azimuthal magnetic field

One practical challenge for the centrifugal-mirror confinement concept is the large radial voltage necessary to drive supersonic azimuthal rotation. In principle, the addition of a strong azimuthal field could reduce the required voltage, since the simple azimuthal E x B drift would be replaced by more rapid azimuthal trapped-particle precession. Also, if the mirror ratio is large enough, newly ionized ions are accelerated to the necessary parallel velocities in their first bounce orbit, both confining and significantly heating them. Unfortunately, MHD analysis shows that the centrifugal-force-confining plasma current is purely azimuthal. This implies that only the axial magnetic field contributes to the confining magnetic pressure, severely limiting the usefulness of the azimuthal magnetic field in a beta-limited plasma scenario.

Grad-Shafranov↗
DOE OSTI2013

The inverse problem of bimorph mirror tuning on a beamline

One of the challenges of tuning bimorph mirrors with many electrodes is that the calculated focusing voltages can be different by more than the safety limit (such as 500 V for the mirrors used at 17-ID at the Advanced Photon Source) between adjacent electrodes. A study of this problem at 17-ID revealed that the inverse problem of the tuning in situ, using X-rays, became ill-conditioned when the number of electrodes was large and the calculated focusing voltages were contaminated with measurement errors. Increasing the number of beamlets during the tuning could reduce the matrix condition number in the problem, but obtaining voltages with variation below the safety limit was still not always guaranteed and multiple iterations of tuning were often required. Applying Tikhonov regularization and using the L-curve criterion for the determination of the regularization parameter made it straightforward to obtain focusing voltages with well behaved variations. Some characteristics of the tuning results obtained using Tikhonov regularization are given in this paper.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Diaboloidal mirrors: algebraic solution and surface shape approximations

A new type of optical element that can focus a cylindrical wave to a point focus (or vice versa) is analytically described. Such waves are, for example, produced in a beamline where light is collimated in one direction and then doubly focused by a single optic. A classical example in X-ray optics is the collimated two-crystal monochromator, with toroidal mirror refocusing. The element here replaces the toroid, and in such a system provides completely aberration free, point-to-point imaging of rays from the on-axis source point. We present an analytic solution for the mirror shape in its laboratory coordinate system with zero slope at the centre, and approximate solutions, based on bending an oblique circular cone and a bent right circular cylinder, that may facilitate fabrication and metrology.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Multilayer X-ray mirrors for the (4.4-5)-nm carbon-window spectral region

Cr/C-based multilayer X-ray mirrors intended for the reflection of X-ray radiation in the 'carbon-window' spectral region ({lambda} = 4.4-5 nm) are fabricated and studied. The structures are formed by magnetron sputtering at different deposition parameters. Under normal incidence, record reflection coefficients up to 15% are reached. The structural parameters of the mirrors are investigated by reflectometry at wavelengths of 0.154 and 4.47 nm.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Fiber laser cleaning of metal mirror surfaces for optical diagnostic systems of the ITER

The results of experimental studies into efficiency of removal of films with a complex composition from metal mirrors by pulsed fiber laser irradiation are presented. It is shown that the initial reflectivity of optical elements can be restored by the selection of modes of irradiation impacting the surface with the sputtered film. Effective cleaning is performed by radiation with a power density lower than 10{sup 7} W/cm{sup 2}. The removal of contaminations at such a relatively low power density occurs in a solid phase, owing to which the thermal effect on the mirror is insignificant.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Development of a laser cleaning method for the first mirror surface of the charge exchange recombination spectroscopy diagnostics on ITER

A set of optical diagnostics is expected for measuring the plasma characteristics in ITER. Optical elements located inside discharge chambers are exposed to an intense radiation load, sputtering due to collisions with energetic atoms formed in the charge transfer processes, and contamination due to recondensation of materials sputtered from different parts of the construction of the chamber. Removing the films of the sputtered materials from the mirrors with the aid of pulsed laser radiation is an efficient cleaning method enabling recovery of the optical properties of the mirrors. In this work, we studied the efficiency of removal of metal oxide films by pulsed radiation of a fiber laser. Optimization of the laser cleaning conditions was carried out on samples representing metal substrates polished with optical quality with deposition of films on them imitating the chemical composition and conditions expected in ITER. It is shown that, by a proper selection of modes of radiation exposure to the surface with a deposited film, it is feasible to restore the original high reflection characteristics of optical elements.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Manifestation of Nonuniversality of Lepton Interactions in Spontaneously Violated Mirror Symmetry

Data from the LHCb experiments are indicative of a substantial distinction between the B → K (or K*) + e{sup +}e{sup −} and B → K (or K*) + μ{sup +}μ{sup −} branching ratios (April 2017). The branching ratio for the e+e− channel is substantially greater than that for the μ{sup +}μ{sup −} channel, whereas Standard Model (SM) calculations require that they be equal to each other. The above distinction may suggest the existence of a new interaction changing generations and discriminating between leptons that has couplings that are much greater than and are inverse in strength to the SM fermion couplings to the Higgs boson. Under conditions of spontaneously violated mirror symmetry, the coupling of SM particles to the second Higgs scalar that is inevitably present there and which is in principle heavy possesses precisely these properties. An inverse character of this coupling and its strength are not an additional hypothesis but a necessary condition for qualitatively reproducing, in addition, the observed charged-lepton mass hierarchy and the structure of weak lepton mixing—the Pontecorvo–Maki–Nakagawa–Sakata (PMNS) matrix. Within the mirror model being considered, all properties of the new interaction, including its inverse character, are due to the hierarchical character of the quark and charged-lepton mass spectrum.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Beryllium as a Material for Thermally Stable X-Ray Mirrors

Thermophysical and mechanical characteristics of beryllium are compared with the corresponding characteristics of promising materials that are used for fabrication of precision mirrors working under high-intensity electromagnetic irradiation. Advantages and prospects for application of beryllium in the third- and fourth-generation synchrotrons are discussed. An original method for fabrication of ultrasmooth surfaces of beryllium substrates is presented, and limiting roughnesses are reported. Reflectances at a wavelength of 13.5 nm are determined for a multilayer Mo/Si mirror deposited on the beryllium substrate. Prospects for improving quality of polishing of beryllium substrates are discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Influence of Thermal Annealing on the Properties of Multilayer Mo/Be Mirrors

The influence of thermal action on X-ray optics performance and structure of films and transition regions in multilayer Mo/Be mirrors optimized for a reflection maximum in the interval 11.2–11.4 nm at normal incidence has been considered. The annealing temperature reached 300°C and the annealing time was 1 and 4 h. It has been shown that after thermal annealing in vacuum for 1 h at 300°C, the reflection coefficient rises; however, when the annealing time grows to 4 h, it drops. Grains in molybdenum films become finer, and the profiles of transition regions change from exponential to linear. The period of multilayer mirrors has remained the same under all annealing conditions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Ion polished Cr/Sc attosecond multilayer mirrors for high water window reflectivity

Recent advances in the development of attosecond soft X-ray sources ranging into the water window spectral range, between the 1s states of carbon and oxygen (284 eV–543 eV), are also driving the development of suited broadband multilayer optics for steering and shaping attosecond pulses. The relatively low intensity of current High Harmonic Generation (HHG) soft X-ray sources calls for an efficient use of photons, thus the development of low-loss multilayer optics is of uttermost importance. Here, we report about the realization of broadband Cr/Sc attosecond multilayer mirrors with nearly atomically smooth interfaces by an optimized ion beam deposition and assisted interface polishing process. This yields to our knowledge highest multilayer mirror reflectivity at 300 eV near normal incidence. The results are verified by transmission electron microscopy (TEM) and soft/hard X-ray reflectometry.

36 MATERIALS SCIENCE↗