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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 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Connection between asymptotic normalization coefficients and resonance widths of mirror states

Resonance widths are important characteristics of unstable nuclear states playing a crucial role in nuclear structure, nuclear reactions, and nuclear astrophysics. However, often it is difficult or impossible to determine the resonance widths from experiments, especially when required nuclei are unstable or the resonance widths are too small. In this paper, I suggest an indirect method of determination of resonance widths using transfer reactions populating bound states. From this reaction, one can extract the amplitudes of the tails of the bound-state wave functions. These amplitudes are called the asymptotic normalization coefficients (ANCs). The ANC method became one of the benchmarks of the Cyclotron Institute. Once the ANC is experimentally determined, one can find the resonance width of the mirror nuclei using the technique developed in this paper. Mirror nuclei are the ones in which the total number of nucleons is the same but the number of the protons of one of the nuclei is equal to the number of the neutrons of another nucleus. In this paper, 5 different examples of the application of the developed method are presented.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Moving mirror model for quasithermal radiation fields

We analyze the flow of energy and entropy emitted by a class of moving mirror trajectories which provide models for important aspects of the radiation fields produced by black hole evaporation. The mirror radiation fields provide natural, concrete examples of processes that follow thermal distributions for long periods, accompanied by transients which are brief and carry little net energy, yet ultimately represent pure quantum states. In conclusion, a burst of negative energy flux is a generic feature of these fields, but it need not be prominent.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Experimental Search for Neutron to Mirror Neutron Oscillations as an Explanation of the Neutron Lifetime Anomaly

We report an unexplained >4σ discrepancy persists between “beam” and “bottle” measurements of the neutron lifetime. A new model proposed that conversions of neutrons n into mirror neutrons n', part of a dark mirror sector, can increase the apparent neutron lifetime by 1% via a small mass splitting Δm between n and n' inside the 4.6 T magnetic field of the National Institute of Standards and Technology Beam Lifetime experiment. A search for neutron conversions in a 6.6 T magnetic field was performed at the Spallation Neutron Source which excludes this explanation for the neutron lifetime discrepancy.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Trends of Neutron Skins and Radii of Mirror Nuclei from First Principles

The neutron skin of atomic nuclei impacts the structure of neutron-rich nuclei, the equation of state of nucleonic matter, and the size of neutron stars. Here we predict the neutron skin of selected light- and medium-mass nuclei using coupled-cluster theory and the auxiliary field diffusion Monte Carlo method with two- and three-nucleon forces from chiral effective field theory. We find a linear correlation between the neutron skin and the isospin asymmetry in agreement with the liquid-drop model and compare with data. We also extract the linear relationship that describes the difference between neutron and proton radii of mirror nuclei and quantify the effect of charge symmetry breaking terms in the nuclear Hamiltonian. In conclusion, our results for the mirror-difference charge radii and binding energies per nucleon agree with existing data.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Fast automated energy changes at synchrotron radiation beamlines equipped with transfocator or focusing mirrors

Algorithms and procedures to fully automate retuning of synchrotron radiation beamlines over wide energy ranges are discussed. The discussion is based on the implementation at the National Institute of General Medical Sciences and the National Cancer Institute Structural Biology Facility at the Advanced Photon Source. When a user selects a new beamline energy, software synchronously controls the beamline monochromator and undulator to maintain the X-ray beam flux after the monochromator, preserves beam attenuation by determining a new set of attenuator foils, changes, as needed, mirror reflecting stripes and the undulator harmonic, preserves beam focal distance of compound refractive lens focusing by changing the In/Out combination of lenses in the transfocator, and, finally, restores beam position at the sample by on-the-fly scanning of either the Kirkpatrick–Baez mirror angles or the transfocator up/down and inboard/outboard positions. The sample is protected from radiation damage by automatically moving it out of the beam during the energy change and optimization.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Performance of Low-Complexity Spectrally Selective One-Dimensional Mirrors for Photovoltaic Thermal Management

Operation at elevated temperatures is detrimental to the performance of crystalline Si solar modules. One method of reducing module operating temperature is selective reflection of sub-bandgap photons, which can otherwise only be absorbed parasitically. We numerically optimize the design of a series of multilayer photonic mirrors based on real materials using a previously developed optimization routine. Combined ray tracing and finite element simulations reveal the ability of each mirror to increase energy yield and decrease operating temperature. The best design outperforms a conventional glass antireflection coating, contains only nine layers, and maintains performance regardless of geographic location.

14 SOLAR ENERGY↗
DOE OSTI2023

Design and Assembly of a Large-Aperture Nb 3 Sn Cos-Theta Dipole Coil With Stress Management in Dipole Mirror Configuration

The stress-management cos-theta (SMCT) coil is a new concept which has been proposed and is being developed at Fermilab in the framework of US Magnet Development Program (US-MDP) for high-field and/or large-aperture accelerator magnets based on low-temperature and high-temperature superconductors. The SMCT structure is used to reduce large coil deformations under the Lorentz forces and, thus, the excessively large strains and stresses in the coil. A large-aperture Nb 3 Sn SMCT dipole coil has been developed and fabricated at Fermilab to demonstrate and test the SMCT concept including coil design, fabrication technology and performance. The first SMCT coil has been assembled with 60-mm aperture Nb 3 Sn coil inside a dipole mirror configuration and will be tested separately and in series with the insert coil. Here this paper summarizes the large-aperture SMCT coil design and parameters and reports the coil fabrication steps and its assembly in dipole mirror configuration.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Quench Performance of a Large-Aperture Nb 3 Sn Cos-Theta Coil With Stress Management in Dipole Mirror Configurations

A 123-mm-aperture Nb 3 Sn cos-theta (CT) dipole coil with stress management (SM) has been developed at Fermilab to demonstrate and test the SM concept, including coil design, fabrication technology, and performance. The first SMCT1 coil has been fabricated and assembled together with a 60-mm-aperture Nb 3 Sn coil inside a dipole mirror structure and tested separately and in series with the inner coil. This article summarizes the design, parameters, and quench performance of the SMCT1 coil in a dipole mirror configuration.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Controllability Study of Propagating Mode Content by an Angle-Adjustable Mirror of a Miter-Bend in EC H&CD Transmission Line

A miter-bend-type mode converter, which has an angle-adjustable mirror, is proposed to control the transmission mode content in the electron cyclotron heating and current drive transmission line. This component excites the higher order mode by injecting a tilted radio frequency beam into a waveguide using the angle-adjustable mirror. A mock-up model of the converter was developed to evaluate the principle of the mode conversion.The experimental result of the mock-up representing the ratio of LP 01 mode and LP 11 mode was successfully controlled by 10% as the theoretical prediction.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Repair of a Mirror Coating on a Large Optic for High Laser Damage Applications using Ion Milling and Over-Coating Methods.

When an optical coating is damaged, deposited incorrectly, or is otherwise unsuitable, the conventional method to restore the optic often entails repolishing the optic surface, which can incur a large cost and long lead time. We propose three alternative options to repolishing, including (i) burying the unsuitable coating under another optical coating, (ii) using ion milling to etch the unsuitable coating completely from the optic surface, and then recoating the optic, and (iii) using ion milling to etch through a number of unsuitable layers, leaving the rest of the coating intact, and then recoating the layers that were etched. Repairs were made on test optics with dielectric mirror coatings according to the above three options. The mirror coatings to be repaired were quarter wave stacks of HfO 2 and SiO 2 layers for high reflection at 1054 nm at 45° incidence in P-polarization. One of the coating layers was purposely deposited incorrectly as Hf metal instead of HfO 2 to evaluate the ability of each repair method to restore the coating’s high laser-induced damage threshold (LIDT) of 64.0 J/cm 2 . Finally, the repaired coating with the highest resistance to laser-induced damage was achieved using repair method (ii) with an LIDT of 49.0 – 61.0 J/cm 2 .

42 ENGINEERING↗
DOE OSTI2013

Potential of the neutron lloyd's mirror interferometer for the search for new interactions

We discuss the potential of the neutron Lloyd's mirror interferometer in a search for new interactions at small scales. We consider three hypothetical interactions that may be tested using the interferometer. The chameleon scalar field proposed to solve the enigma of accelerating expansion of the Universe produces interaction between particles and matter. The axion-like spin-dependent coupling between a neutron and nuclei or/and electrons may result in a P- and T-noninvariant interaction with matter. Hypothetical non-Newtonian gravitational interactions mediates an additional short-range potential between neutrons and bulk matter. These interactions between the neutron and the mirror of a Lloyd-type neutron interferometer cause a phase shift of neutron waves. We estimate the sensitivity and systematic effects of possible experiments.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Dissipation of Energy of an AC Electric Field in a Semi-Infinite Electron Plasma with Mirror Boundary Conditions

Absorption of the electromagnetic energy in a semi-infinite electron plasma is calculated for an arbitrary degree of the electron gas degeneracy. Absorption is determined by solving the boundary-value problem on the oscillations of electron plasma in a half-space with mirror boundary conditions for electrons. The Vlasov−Boltzmann kinetic equation with the Bhatnagar–Gross–Krook collision integral for the electron distribution function and Maxwell’s equation for the electric field are employed. The electron distribution function and the electric field inside plasma are searched for in the form of expansions in the eigenfunctions of the initial set of equations. The expansion coefficients are found for the case of mirror boundary conditions. The contribution of the plasma surface to absorption is analyzed. Cases with different degrees of electron gas degeneracy are considered. It is shown that absorption of the electromagnetic energy near the surface depends substantially on the ratio between the electric field frequency and the volumetric electron collision frequency.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Semiconductor Heterolasers with Double-Mirror Two-Dimensional Bragg Resonators

A double-mirror two-dimensional Bragg resonator design based on structures of planar geometry, which is typical of both band-to-band and quantum-cascade heterolasers, is suggested. The distinguishing feature of this design is the coupling between longitudinal and transverse energy flows in two-dimensional Bragg mirrors. The eigenmode spectrum of the structure is described. It is shown that the proposed design can be used for synchronizing radiation emitted in lasers and laser arrays.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Remote Mirror Security

The Remote Mirror Security project is a git hook used to evaluate a remote repository from which changes are mirrored and enforce a security policy before accepting changes.

Mendoza, ThomasA.↗
DOE OSTI2024

Temporal contrast degradation from mid-spatial-frequency surface error on stretcher mirrors

Temporal contrast degradation due to mid-spatial-frequency error in chirped-pulse amplification stretcher optics is studied. Third-order cross-correlation measurements reveal a temporal peak that appears when using two different mirrors processed by magnetorheological finishing, despite an improvement in rms roughness compared to a third unprocessed mirror. Simulations based on measured power spectral density show how the actual impact on contrast is different from measurements using a typical bandwidth-limited third-order cross correlator. Furthermore, strategies are proposed to avoid this type of contrast degradation while exploiting computer numerically controlled polishing techniques for enhancement of surface figure and roughness.

47 OTHER INSTRUMENTATION↗
DOE OSTI2019

Design and alignment of an all-spherical unobscured four-mirror image relay for an ultra-broadband sub-petawatt laser

We describe the design and alignment of an unobscured reflective image relay for use in an ultra-broadband half-petawatt laser system in development at the University of Rochester’s Laboratory for Laser Energetics. The design consists of four spherical mirrors in an unobscured configuration. We show the theoretical basis for such a four-mirror design using first-order optical matrix methods and nodal aberration theory. We also describe the process of aligning this design in a test bed and show the results of this alignment method. We were able to achieve a diffraction-limited nominal design. Furthermore, upon aligning the design in our test bed, we were able to successfully align the design to achieve our target wavefront error of less than 0.3 waves p–v and 0.07 waves rms at the central laser-operating wavelength of 910 nm.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

Cascaded Plasma Mirrors for Enhanced Relativistic Harmonic Generation

Relativistic harmonic generation is a waveform-dependent process that can be enhanced by multi-color driving pulses. We experimentally demonstrate higher-efficiency harmonics from a plasma mirror cascade, where an initial plasma mirror produces the multi-color beam.

Edwards, M. R.↗
DOE OSTI2019

Thermal behavior characterization of a kilowatt-power-level cryogenically cooled Yb:YAG active mirror laser amplifier

We present an analysis of the thermal behavior of a high-energy kilowatt-average-power diode-pumped cryogenically cooled Yb:YAG active mirror laser amplifier based on measurements and simulations. Maps of the temperature distribution of the laser material at pump powers up to 1 kW were obtained for the first time by spatially and spectrally resolving the fluorescence induced by a scanning probe beam. The wavefront distortion resulting from the front surface deformation and the overall deformation of the gain medium assembly were measured using a Mach–Zehnder interferometer. The measured deformations agree well with the results of thermomechanical modeling using finite element method simulations, and with the results of focal length shift measurements. The relative contributions to the optical path difference (OPD) of the mechanical deformations, refractive index changes, and electronic contribution are discussed. We propose that the Cr 4+ :YAG cladding plays a significant role in both the temperature distribution and the overall OPD changes. Moreover, the pump-induced mechanical deformations of the assembly dominate the OPD changes in this kilowatt-average-pump-power cryogenically cooled Yb:YAG active mirror laser.

36 MATERIALS SCIENCE↗