Exact THD Calculations Applied to Minimize Space Harmonic Content of Winding and Rotor Magnetic Fields
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Energy & Fuels↗
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Results for “Harmonization”
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Orientation dependence of temporal and spectral properties of high-order harmonics in solids [Orientation dependence of high-harmonic temporal and spectral properties in solids]
We investigate the connection between crystal symmetry and temporal and spectral properties of high-order harmonics in solids. We calculate the orientation-dependent harmonic spectrum driven by an intense, linearly polarized infrared laser field, using a momentum-space description of the generation process in terms of strong-field-driven electron dynamics on the band structure. We show that the orientation dependence of both the spectral yield and the subcycle time profile of the harmonic radiation can be understood in terms of the coupling strengths and relative curvatures of the valence band and the low-lying conduction bands. In particular, we show that in some systems this gives rise to a rapid shift of a quarter optical cycle in the timing of harmonics in the secondary plateau as the crystal is rotated relative to the laser polarization. Here, we address recent experimental results in MgO and show that the observed change in orientation dependence for the highest harmonics can be interpreted in the momentum space picture in terms of the contributions of several different conduction bands.
74 ATOMIC AND MOLECULAR PHYSICS↗
Necklace-structured high-harmonic generation for low-divergence, soft x-ray harmonic combs with tunable line spacing
The extreme nonlinear optical process of high-harmonic generation (HHG) makes it possible to map the properties of a laser beam onto a radiating electron wave function and, in turn, onto the emitted x-ray light. Bright HHG beams typically emerge from a longitudinal phased distribution of atomic-scale quantum antennae. Here, we form a transverse necklace-shaped phased array of linearly polarized HHG emitters, where orbital angular momentum conservation allows us to tune the line spacing and divergence properties of extreme ultraviolet and soft x-ray high-harmonic combs. The on-axis HHG emission has extremely low divergence, well below that obtained when using Gaussian driving beams, which further decreases with harmonic order. This work provides a new degree of freedom for the design of harmonic combs—particularly in the soft x-ray regime, where very limited options are available. Such harmonic beams can enable more sensitive probes of the fastest correlated charge and spin dynamics in molecules, nanoparticles, and materials.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Relation of squeezed states between damped harmonic and simple harmonic oscillators
The minimum uncertainty and other relations are evaluated in the framework of the coherent states of the damped harmonic oscillator. It is shown that the coherent states of the damped harmonic oscillator are the squeezed coherent states of the simple harmonic oscillator. The unitary operator is also constructed, and this connects coherent states with damped harmonic and simple harmonic oscillators.
Um, Chung-In↗
High Harmonic Generation Seeding Echo-Enabled Harmonic Generation toward a Storage Ring-Based Tender and Hard X-ray-Free Electron Laser
To align with the global trend of integrating synchrotron light source (SLS) and free electron laser (FEL) facilities on one site, in line with examples such as SPring-8 and SACLA in Japan and ELETTRA and FERMI in Italy, we actively explore FEL options leveraging the ultralow-emittance electron beam of the NSLS-II upgrade. These options show promising potential for synergy with storage ring (SR) operations, thereby significantly enhancing our facility’s capabilities. Echo-enabled harmonic generation (EEHG) is well-suited to SR-based FELs, and has already been demonstrated with the capability of generating extremely narrow bandwidth as well as high brightness, realized using diffraction-limited short pulses in transverse planes and Fourier transform-limited bandwidth in the soft X-ray spectrum. However, regarding a conventional EEHG scheme, the combination of the shortest seed laser wavelength (256 nm) and highest harmonic (200) sets the short wavelength limit to λ = 1.28 nm. To further extend the short wavelength limit down to the tender and hard X-ray region, a vital option is to shorten the seed laser wavelength. Thanks to recent advances in high harmonic generation (HHG), packing 10 9 photons at one harmonic within a few-femtosecond pulse could turn such a novel HHG source into an ideal seeding for EEHG. Thus, compared to the cascaded EEHG, the HHG seeding option could not only lower the cost, but also free the SR space for accommodating more user beamlines. Moreover, to mitigate the SASE background noise on the sample and detector, we combine the HHG seeding EEHG with the crab cavity short pulse scheme for maximum benefit.
36 MATERIALS SCIENCE↗
Second harmonic generation from metamaterials strongly coupled to intersubband transitions in quantum wells
We theoretically analyze the second harmonic generation capacity of two-dimensional periodic metamaterials comprising sub-wavelength resonators strongly coupled to intersubband transitions in quantum wells (QWs) at mid-infrared frequencies. The metamaterial is designed to support a fundamental resonance at ∼30 THz and an orthogonally polarized resonance at the second harmonic frequency (∼60 THz), while the asymmetric quantum well structure is designed to provide a large second order susceptibility. Upon continuous wave illumination at the fundamental frequency we observe second harmonic signals in both the forward and backward directions, with the forward efficiency being larger. We calculate the overall second harmonic conversion efficiency of the forward wave to be ∼1.3 × 10{sup −2} W/W{sup 2}—a remarkably large value, given the deep sub-wavelength dimensions of the QW structure (about 1/15th of the free space wavelength of 10 μm). The results shown in this Letter provide a strategy for designing easily fabricated sources across the entire infrared spectrum through proper choice of QW and resonator designs.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
2017 Algae Harmonization Study: Evaluating the Potential for Future Algal Biofuel Costs, Sustainability, and Resource Assessment from Harmonized Modeling
To present a more unified picture of the long-term future potential for algal biofuels and the goals that must be met to reach that potential, four algae modeling groups collaborated to harmonize respective models for resource assessment (Pacific Northwest National Laboratory), techno-economic analysis (National Renewable Energy Laboratory and Pacific Northwest National Laboratory), and life-cycle analysis (Argonne National Laboratory) of algal biomass production and conversion processes. In contrast to prior harmonization studies that this group has previously conducted, which focused on establishing benchmarks attributed to current performance at the time, the primary intent of the present harmonization study was to project these models to forward-looking targets that must be achieved to reduce fuel costs and greenhouse gas emission profiles to Bioenergy Technologies Office target levels, subject to specific location constraints imposed by resource assessment modeling and thus national-scale fuel output potential (i.e., billion gallons gasoline equivalent per year, or BGGE/yr). In all, while based on a number of aspirational goals not yet demonstrated but plausible to achieve over coming years, the harmonized outputs indicate promising potential for algal biofuels to make a significant contribution to the U.S. fuels market, based on substantial quantities of biomass (104-235 MM tons/yr) projected to be available at costs below 700/ton (generally below 500/ton for freshwater cultivation). While these costs are still significantly higher than terrestrial biomass cost targets, the propensity for capturing high fuel yields and/or high-value tailored coproducts from algal biomass is shown here to provide plausible paths to achieve future targets for cost and sustainability metrics at meaningful volumes.
09 BIOMASS FUELS↗
Beam Energy Dependence of the Third Harmonic of Azimuthal Correlations in Au+Au Collisions at RHIC
In this paper, we present results from a harmonic decomposition of two-particle azimuthal correlations measured with the STAR detector in Au + Au collisions for energies ranging from √sNN = 7.7 to 200 GeV. The third harmonic v$2\atop{3}${ 2 } = , where Φ1 - Φ2 is the angular difference in azimuth, is studied as a function of the pseudorapidity difference between particle pairs Δη = η1-η2 . Nonzero v$2\atop{3}${ 2 } is directly related to the previously observed large- Δη narrow- ΔΦ ridge correlations and has been shown in models to be sensitive to the existence of a low viscosity quark gluon plasma phase. For sufficiently central collisions, v$2\atop{3}${ 2 } persist down to an energy of 7.7 GeV, suggesting that quark gluon plasma may be created even in these low energy collisions. In peripheral collisions at these low energies, however, v$2\atop{3}${ 2 } is consistent with zero. Finally, when scaled by the pseudorapidity density of charged-particle multiplicity per participating nucleon pair, v$2\atop{3}${ 2 } for central collisions shows a minimum near √sNN = 20 GeV .
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Soft X-Ray Second Harmonic Generation as an Interfacial Probe
Nonlinear optical processes at soft x-ray wavelengths have remained largely unexplored due to the lack of available light sources with the requisite intensity and coherence. Here we report the observation of soft x-ray second harmonic generation near the carbon K edge (~284 eV) in graphite thin films generated by high intensity, coherent soft x-ray pulses at the FERMI free electron laser. Our experimental results and accompanying first-principles theoretical analysis highlight the effect of resonant enhancement above the carbon K edge and show the technique to be interfacially sensitive in a centrosymmetric sample with second harmonic intensity arising primarily from the first atomic layer at the open surface. Here, this technique and the associated theoretical framework demonstrate the ability to selectively probe interfaces, including those that are buried, with elemental specificity, providing a new tool for a range of scientific problems.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
3rd harmonic magnetometry assessment of NbTiN-based SIS structures
In the quest for alternative superconducting materials to bring accelerator cavity performance beyond the bulk niobium (Nb) intrinsic limits, a promising concept proposes that superconductor-insulator-superconductor (SIS) thin film structures can delay magnetic flux penetration in accelerator cavities to higher fields [1]. NbTiN is a candidate superconductor for such structures. We have demonstrated high quality NbTiN and AlN deposited by reactive direct current magnetron sputtering (DCMS), both for individual layers and multilayers. Interface quality has been assessed for bi-layer stacks with various NbTiN and AlN thicknesses from 500 and 30 nm down to 3 and 1 nm. These SIS structures show continued sharp interfaces. The Hfp enhancement of the films was examined with 3rd harmonic magnetometry. The system was designed and built in an ongoing collaboration with CEA Saclay. It can measure 1? to 2? samples on a temperature controlled stage. This contribution presents the assessment of the first penetration field enhancement with 3rd harmonic magnetometry for standalone films and multilayer nanostructures.
Valente, Anne-Marie↗
Controlling the polarization and vortex charge of attosecond high-harmonic beams via simultaneous spin–orbit momentum conservation
Optical interactions are governed by both spin and angular momentum conservation laws, which serve as a tool for controlling light–matter interactions or elucidating electron dynamics and structure of complex systems. Here, we uncover a form of simultaneous spin and orbital angular momentum conservation and show, theoretically and experimentally, that this phenomenon allows for unprecedented control over the divergence and polarization of extreme-ultraviolet vortex beams. High harmonics with spin and orbital angular momenta are produced, opening a novel regime of angular momentum conservation that allows for manipulation of the polarization of attosecond pulses—from linear to circular—and for the generation of circularly polarized vortices with tailored orbital angular momentum, including harmonic vortices with the same topological charge as the driving laser beam. As a result, our work paves the way to ultrafast studies of chiral systems using high-harmonic beams with designer spin and orbital angular momentum.
High-harmonic generation↗
On the eigenstructure of spherical harmonic equations for radiative transport
The spherical harmonic equations for radiative transport are a linear, hyperbolic set of balance laws that describe the state of a system of particles as they advect through and collide with a material medium. For regimes in which the collisionality of the system is light to moderate, significant qualitative differences have been observed between solutions, based on whether the angular approximation used to derive the equations occurs in a subspace of even or odd degree. This difference can be traced back to the eigenstructure of the coefficient matrices in the advection operator of the hyperbolic system. In this paper, we use classical properties of the spherical harmonics to examine this structure. In particular, we show how elements in the null space of the coefficient matrices depend on the parity of the spherical harmonic approximation and we relate these results to observed differences in even and odd expansions.
Garrett, Charles K.↗
High-harmonic generation from an atomically thin semiconductor [Observation of high harmonics from an atomically thin semiconductor]
High-harmonic generation (HHG) in bulk solids permits the exploration of materials in a new regime of strong fields and attosecond timescales. The generation process has been discussed in the context of strongly driven electron dynamics in single-particle bands. Two-dimensional materials exhibit distinctive electronic properties compared to the bulk that could significantly modify the HHG process, including different symmetries, access to individual valleys and enhanced many-body interactions. Here we demonstrate non-perturbative HHG from a monolayer MoS 2 crystal, with even and odd harmonics extending to the 13th order. The even orders are predominantly polarized perpendicular to the pump and are compatible with the anomalous transverse intraband current arising from the material’s Berry curvature, while the weak parallel component suggests the importance of interband transitions. The odd harmonics exhibit a significant enhancement in efficiency per layer compared to the bulk, which is attributed to correlation effects. In conclusion, the combination of strong many-body Coulomb interactions and widely tunable electronic properties in two-dimensional materials offers a new platform for attosecond physics.
36 MATERIALS SCIENCE↗
Microwave Imaging Reflectometry for the study of Edge Harmonic Oscillations on DIII-D [Microwave Imaging Reflectometry (MIR) for the study of Edge Harmonic Oscillations (EHOs) on DIII-D]
Quiescent H-mode (QH) is an ELM free mode of operation in which edge-localized harmonic oscillations (EHOs) are believed to enhance particle transport, thereby stabilizing ELMs and preventing damage to the divertor and plasma facing components. Microwave Imaging Reflectometer (MIR) enabling direct comparison between the measured and simulated 2D images of density fluctuations near the edge can determine the 2D structure of density oscillation which can help to explain the physics behind EHO modes. MIR data sometimes indicates a counter-propagation between higher (n>1) and dominant (n=1) harmonics of coherent EHOs in the steep gradient regions of the pedestal. To preclude diagnostic artifacts, we have performed forward modeling that includes possible optical misalignments to show that offsets between transmitting and receiving antennas do not account for this feature. We have also simulated the non-uniform rotation of the EHO structure, which induces multiple harmonics that are properly characterized in the synthetic diagnostic. Excluding these possible explanations for the data, the counter-propagation observed in MIR data, which is not corroborated by external Mirnov coil array measurements, may be due to subtleties of the eigenmode structure, such as an inversion radius consistent with a magnetic island. Similar effects are observed in analysis of internal ECE-Imaging and BES data. Furthermore, the identification of a non-ideal structure motivates further exploration of nonlinear models of this instability.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Geomagnetic main field analysis at the core-mantle boundary - Spherical harmonics compared with harmonic splines
An optimum truncation level, N, in a spherical-harmonic analysis of the geomagnetic main field at the core-mantle boundary is determined by harmonic-spline analysis. Specifically, that value of N is found at which the two analyses are closest in a well defined sense and, for that value of N, the 'closeness' of two models is determined. Depending slightly on the definition of closeness, optimum N is found to be either 10 or 11. For those values the two analyses give remarkably similar results, showing that the conveniences of spherical harmonics can be retained with little penalty.
Benton, E. R.↗
Maximizing Earth Science Observations with Data Harmonization: Harmonized Landsat/Sentinel-2
In August 2021, NASA released science quality harmonized Landsat/Sentinel-2 products for both cloud-based access and direct download from the Land Processes Distributed Active Archive Center (LP DAAC). These 30-meter products, HLSS30 (Sentinel-2 component) and HLSL30 (Landsat component) are placed on the same grid and are generated and distributed fully in the cloud. Similarly, ESA is prototyping harmonized Landsat Sentinel-2 products at 10-meter resolution. The data production and science teams from NASA and ESA will present technical details on the data production system, data product status and availability, and the benefit of harmonizing instruments with similar sensing characteristics between the agencies.
Earth Science↗
Observation of second harmonic generation in doped polymeric carbon monoxide
Abstract not provided
Pravica, Michael G.↗
Four-harmonic buncher for radioactive and stable beams switching at the ATLAS facility [Four-harmonic buncher for radioactive and stable beams combination at the ATLAS facility]
Here, the Argonne Tandem Linac Accelerator System (ATLAS) is planning an upgrade to a multi-user facility to simultaneously accelerate both stable beams from an ECR ion source and radioactive beams from an Electron Beam Ion Source charge breeder. The ATLAS Multi-User Upgrade will need to provide high transmission of ion beams with a mass-to-charge ratio up to 7 as it enables more options to alternate radioactive and stable beams. Currently, the bunching is provided with a lumped circuit multi-harmonic buncher, which cannot effectively operate at the required amplitude of the saw-tooth voltage for ions with mass-to-charge ratio of 7 due to thermal issues. RadiaBeam Systems in collaboration with Argonne National Laboratory has designed a four-harmonic coaxial resonator buncher with the ATLAS fundamental frequency of 12.125 MHz, and a compact, less than 2-m-long, footprint, capable of providing the required voltage of 6.2 kV. This device allows fast and reliable pre-bunching of DC ion beams with the capability of fast switching of heavy-ion radioactive and stable beams for delivery to multiple users. In this paper, we will discuss the RF and engineering design considerations of this buncher.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗