Electron beam shaping for actively outcoupling radiation from an x-ray regenerative amplifier free-electron laser
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43 PARTICLE ACCELERATORS↗
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Results for “shaped beam”
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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Ion Channel Laser Based on Direct Laser Acceleration of a Shaped Beam Driver (Final Technical Report)
The main focus of our research was to understand the synergies between an electron bunch and a laser pulse when the two co-propagate through the plasma. We have clearly demonstrated using theoretical and computational modeling that the propagation distance of both the bunch and the laser pulse could be extended. The ability of the combined bunch/pulse system to extend the propagation distance and the size of the plasma bubble enables highly-efficient sources of relativistic electrons. As pointed out by the Plasma Decadal Study, such electron sources can be used for generating extremely bright x-rays for a variety of applications can serve as probes and diagnostics for other plasma experiments: high energy density (HED) sciences, inertial confinement fusion (ICF), and potentially Fusion Materials and Technology (FM&T). Development of advanced diagnostics of plasma-based accelerators is yet another key area identified by recent reports. Even broader security and medical applications of compact accelerator-based radiation sources, such as very high energy electron (VHEE) sources for FLASH radiobiology, have been identified by a recent multi-agency panel. A number of key technical issues were considered and successfully resolved during the course of the grant. Those include: beam loading effect of both the driver and witness bunches on the wake, laser channeling by the bunch, and the direct laser acceleration (DLA) of the driver bunch by the laser pulse. To demonstrate clear synergy, we were able to ascertain that the total energy gain of a witness bunch in the wake of the combined bunch/laser complex is large than the sum of the energy gains in the wake of the laser pulse alone, and the driver bunch alone. We have also demonstrated that not only the energy gain is improved, but the energy spread is not sacrificed. To carry out these simulations, we have to develop a range of in-house computational tools, including a fully-3D code WAND-PIC.
43 PARTICLE ACCELERATORS↗
Antenna beam-shaping apparatus Patent
Device for improving efficiency of parabolic horn antenna system for linearly polarized signals
Schuster, D. M.↗
Shaped Beam KU-Band Antenna Design
Antenna systems for a Ku-band synchronous orbit communications satellite were considered. A multiple beam offset feed cluster used in conjunction with an offset parabolic reflector was chosen for the antenna realization. For radiating elements in the feed array, polyrod or dielectric rod radiators fed by waveguide are investigated. Polyrod antennas shrink the cross section of the waveguide required, are fairly directive, and can be tapered to reduce sidelobes. As a consequence, it is thought that mutual coupling effects between adjacent elements will be minimal and the resultant physically small elements will allow greater packing densities for the drive elements in the feed array than would otherwise be possible.
Dudgeon, J. E.↗
Enhancing Direct Exoplanet Spectroscopy with Apodizing and Beam Shaping Optics
Explore the source record for details and available documents.
Benjamin Calvin↗
Paraboloidal Antenna Radiates Fan Or Pencil Beams
Shape of beam determined by type of feed. Theory and experiments show same paraboloidal antenna reflector used to radiate pencil beam or fan beam, depending on configuration of feed. Although pencil-shaped beam desirable in many applications, fan-shaped beam preferred in some scanning-radar and mapping-radar systems. Experiment performed with paraboloidal reflector having focal length of 48 in. (1.22 m) and diameter of 3.65 m. Shows fan beams generated in this way and not seriously distorted by feed offsets tested. Also shows because reflector in near field of feed, fan beam not necessarily focused by placing feed at focal plane.
Huang, John↗
Communications technology
The technologies for optimized, i.e., state of the art, operation of satellite-based communications systems are surveyed. Features of spaceborne active repeater systems, low-noise signal amplifiers, power amplifiers, and high frequency switches are described. Design features and capabilities of various satellite antenna systems are discussed, including multiple beam, shaped reflector shaped beam, offset reflector multiple beam, and mm-wave and laser antenna systems. Attitude control systems used with the antenna systems are explored, along with multiplexers, filters, and power generation, conditioning and amplification systems. The operational significance and techniques for exploiting channel bandwidth, baseband and modulation technologies are described. Finally, interconnectivity among communications satellites by means of RF and laser links is examined, as are the roles to be played by the Space Station and future large space antenna systems.
Cuccia, C. Louis↗
ACTS on-orbit multibeam antenna pattern measurements
The Advanced Communication Technology (ACTS) is a key to NASA's goal of developing high-risk, advanced communications technology using multiple frequency bands to support the nation's future communication needs. Using the multiple, dynamic hopping spot beams and advanced on board switching and processing systems, ACTS will open a new era in communications satellite technology. One of the key technologies to be validated as part of the ACTS program is the multibeam antenna (MBA) with rapidly reconfigurable hopping and fixed spot beams to serve users equipped with small-aperture terminals within the coverage areas. The MBA test program is designed to evaluate the on-orbit ACTS antenna performance. The main parameters measured are beam shape, beam center location and gain.
Acosta, R.↗
Parametric study of high-energy ring-shaped electron beams from a laser wakefield accelerator
Abstract Laser wakefield accelerators commonly produce on-axis, low-divergence, high-energy electron beams. However, a high charge, annular shaped beam can be trapped outside the bubble and accelerated to high energies. Here we present a parametric study on the production of low-energy-spread, ultra-relativistic electron ring beams in a two-stage gas cell. Ring-shaped beams with energies higher than 750 MeV are observed simultaneously with on axis, continuously injected electrons. Often multiple ring shaped beams with different energies are produced and parametric studies to control the generation and properties of these structures were conducted. Particle tracking and particle-in-cell simulations are used to determine properties of these beams and investigate how they are formed and trapped outside the bubble by the wake produced by on-axis injected electrons. These unusual femtosecond duration, high-charge, high-energy, ring electron beams may find use in beam driven plasma wakefield accelerators and radiation sources.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
System and method for grain refinement and general control of grain morphology in laser additive manufacturing
The present disclosure relates to a system for forming a material layer that may make use of an optical light source for generating an optical beam, and a beam shaping subsystem configured to shape the optical beam to generate a complex beam intensity profile. The complex shaped beam may be used to selectively melt at least portions of a bed of powder particles residing on a substrate during formation of the material layer, as the optical light source is moved. A computer may be used to control the optical light source. The complex beam intensity profile enables control over the microstructure of grains formed during melting of the powder particles as the material layer is formed.
Roehling, Tien↗
Efficient six-dimensional phase space reconstructions from experimental measurements using generative machine learning
Next-generation accelerator concepts, which hinge on the precise shaping of beam distributions, demand equally precise diagnostic methods capable of reconstructing beam distributions within six-dimensional position-momentum spaces. However, the characterization of intricate features within six-dimensional beam distributions using current diagnostic techniques necessitates a substantial number of measurements, using many hours of valuable beam time. Novel phase space reconstruction techniques are needed to reduce the number of measurements required to reconstruct detailed, high-dimensional beam features in order to resolve complex beam phenomena and as a feedback in precision beam shaping applications. In this study, we present a novel approach to reconstructing detailed six-dimensional phase space distributions from experimental measurements using generative machine learning and differentiable beam dynamics simulations. We demonstrate that this approach can be used to resolve six-dimensional phase space distributions from scratch, using basic beam manipulations and as few as 20 two-dimensional measurements of the beam profile. We also demonstrate an application of the reconstruction method in an experimental setting at the Argonne Wakefield Accelerator, where it is able to reconstruct the beam distribution and accurately predict previously unseen measurements 75× faster than previous methods.
43 PARTICLE ACCELERATORS↗
Generation of structured coherent extreme ultraviolet beams from an MgO crystal
Short wavelength high-harmonic sources are undergoing intense development for applications in spectroscopy and microscopy. Despite recent progress in peak and average power, spatial control over coherent extreme ultraviolet (XUV) beams remains a formidable challenge due to the lack of suitable optical elements for beam shaping and control. In this work, we demonstrate a robust and precise approach that structures XUV high-order harmonics in space as they are emitted from a nanostructured MgO crystal. Our demonstration paves the way for bridging the numerous applications of shaped light beams from the visible to the short wavelengths, with potential uses for applications in microscopy and nanoscale machining.
36 MATERIALS SCIENCE↗
Measuring Liquid Drops In Gas Flow
Nonintrusive optical technique enables measurement of drops of water ingested through aircraft-engine nacelle. Drops photographed by light of laser beam directed across nacelle inlet. Beam shaped by beam expander and slit into sheet 9 mm thick. Exposure time only 10 ns- length of laser pulse, and drop motion therefore frozen in each of series of photographs. Fluorescent dye added to water improves edge definition of photographic images of drops; scattered laser light and its interference effects filtered out and only light at fluorescence wavelength photographed. Technique used in research on ingestion of water from heavy rain or wheel spray, but adapts to any droplet-laden gas stream.
Parikh, Pradip G.↗
Simulation of electrostatic turbulence in the plasma sheet boundary layer with electron currents and bean-shaped ion beams
Plasma data from ISEE-1 show the presence of electron currents as well as energetic ion beams in the plasma sheet boundary layer. Broadband electrostatic noise and low-frequency electromagnetic bursts are detected in the plasma sheet boundary layer, especially in the presence of strong ion flows, currents, and steep spacial gradients in the fluxes of few-keV electrons and ions. Particle simulations have been performed to investigate electrostatic turbulence driven by a cold electron beam and/or ion beams with a bean-shaped velocity distribution. The simulation results show that the counterstreaming ion beams as well as the counterstreaming of the cold electron beam and the ion beam excite ion acoustic waves with a given Doppler-shifted real frequency. However, the effect of the bean-shaped ion velocity distributions reduces the growth rates of ion acoustic instability. The simulation results also show that the slowing down of the ion bean is larger at the larger perpendicular velocity. The wave spectra of the electric fields at some points of the simulations show turbulence generated by growing waves.
Nishikawa, K.-I.↗
Partial-Wave Representations of Laser Beams for Use in Light-Scattering Calculations
In the framework of generalized Lorenz-Mie theory, laser beams are described by sets of beam-shape coefficients. The modified localized approximation to evaluate these coefficients for a focused Gaussian beam is presented. A new description of Gaussian beams, called standard beams, is introduced. A comparison is made between the values of the beam-shape coefficients in the framework of the localized approximation and the beam-shape coefficients of standard beams. This comparison leads to new insights concerning the electromagnetic description of laser beams. The relevance of our discussion is enhanced by a demonstration that the localized approximation provides a very satisfactory description of top-hat beams as well.
Gouesbet, Gerard↗
Improved Gaussian Beam-Scattering Algorithm
The localized model of the beam-shape coefficients for Gaussian beam-scattering theory by a spherical particle provides a great simplification in the numerical implementation of the theory. We derive an alternative form for the localized coefficients that is more convenient for computer computations and that provides physical insight into the details of the scattering process. We construct a FORTRAN program for Gaussian beam scattering with the localized model and compare its computer run time on a personal computer with that of a traditional Mie scattering program and with three other published methods for computing Gaussian beam scattering. We show that the analytical form of the beam-shape coefficients makes evident the fact that the excitation rate of morphology-dependent resonances is greatly enhanced for far off-axis incidence of the Gaussian beam.
Lock, James A.↗
Polarization/Spatial Combining of Laser-Diode Pump Beams
A breadboard version of an optical beam combiner is depicted which make it possible to use the outputs of any or all of four multimode laser diodes to pump a non-planar ring oscillator (NPRO) laser. The output of each laser diode has a single-mode profile in the meridional plane containing an axis denoted the 'fast' axis and a narrower multimode profile in the orthogonal meridional plane, which contains an axis denoted the 'slow' axis and a narrower multimode profile in the orthogonal meridional plane, which contains an axis denoted the 'slow' axis. One of the purposes served by the beam-combining optics is to reduce the fast-axis numerical aperture (NA) of the laser-diode output to match the NA of the optical fiber. Along the slow axis, the unmodified laser-diode NA is already well matched to the fiber optic NA, so no further slow-axis beam shaping is needed. In this beam combiner, the laser-diode outputs are collimated by aspherical lenses, then half-wave plates and polarizing beam splitters are used to combine the four collimated beams into two beams. Spatial combination of the two beams and coupling into the optical fiber is effected by use of anamorphic prisms, mirrors, and a focusing lens. The anamorphic prisms are critical elements in the NA-matching scheme, in that they reduce the fast-axis beam width to 1/6 of its original values. Inasmuch as no slow-axis beam shaping is needed, the collimating and focusing lenses are matched for 1:1 iumaging. Because these lenses are well corrected for infinite conjugates the combiner offers diffraction-limited performance along both the fast and slow axes.
Gelsinger, Paul↗