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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

An Airy beam as a self-similar solution to the problem of slit laser beam propagation in a linear medium and in a photorefractive crystal with diffusion nonlinearity

We have analysed self-similar solutions to the propagation problem of a slit beam with a plane wavefront in a linear medium and in a photorefractive crystal with diffusion nonlinearity. It is shown that in the latter case, despite the presence of the nonlinear term in the wave equation, the linear superposition principle holds true for the solutions of this class due to saturation. At the same time, the mirror symmetry violation of the wave equation for the transverse coordinate in the nonlinear case and the requirement to the spatial localisation modify one of the localised partial solutions (Airy beam) to the corresponding linear problem and prohibit the existence of other solutions of this class. (laser beams)

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Experimental investigation of beam-ion losses induced by magnetic perturbations using the light ion beam probe technique in the ASDEX Upgrade tokamak

The impact of externally applied magnetic perturbations (MPs) on fast-ion losses has been investigated by means of the light ion beam probe (LIBP) technique in the ASDEX Upgrade tokamak. The LIBP technique allows to experimentally infer the fast-ion orbit displacement induced by MPs via first-orbit losses using scintillator based fast-ion loss detector (FILD) measurements. The fast-ion orbit displacement against different applied MP spectra has been studied. These shots were conducted in ELM mitigated H-mode plasmas. A rigid rotation of the MP coils was applied with a frequency of 1 Hz, with an n = 2 configuration and changing the differential phase between the upper and lower set of coils (ΔΦ ul ) on a shot-to-shot basis. Beam sources Q7 (tangential) and Q8 (radial) were used to probe different fast-ion orbits with FILD1. The measured fast-ion orbit displacement ranges from 3 to 20 mm approximately, and no qualitative difference is observed between ions from beam sources Q7 and Q8. The minimum is found for a ΔΦ ul ~ 50°, which is shifted with respect to the minimum of the plasma boundary displacement, found at ΔΦ ul ~ 0°. A first attempt to validate the orbit following code ASCOT—including the plasma response calculated with the MARS-F code—against these experimental measurements is performed. Finally, while the dependence of the first-orbit fast-ion displacement with ΔΦ ul does not match the experimental measurements, these simulations do capture other features such as the order of magnitude of the orbit displacement and the importance of the toroidal spectrum of the applied perturbation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Beam-induced wakefield observation in X -band choke-mode cavities

The X-band choke-mode structure is currently being studied as an alternative design for the accelerating structure of the compact linear collider (CLIC) main linac. The geometry of the choke-mode structure is designed to ensure the strong suppression of the beam-induced long-range transverse wakefield and therefore maintain the stability and quality of the beam in the CLIC main linac. Experiments conducted at the ArgonneWakefield Accelerator Facility are presented in this study to verify the design of the wakefield suppressor. The beam-induced radio frequency (rf) signals in a three-cell choke-mode structure were measured, and measured results show good agreement with the simulation results. The measured results also show strong damping in high-order dipolar modes with a quality factor Q of 10 to 20. The difference between the frequencies of the first and second dipole modes is about 3 GHz, which validates the special design of the cancelling dipole modes at the time of the succeeding bunch (0.5 ns).

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

Suppression of Alfven Modes on the National Spherical Torus Experiment Upgrade with Outboard Beam Injection [Suppression of Alfven Modes on the NSTX-U with Outboard Beam Injection]

In this paper we present data from experiments on the National Spherical Torus Experiment Upgrade, where it is shown for the first time that small amounts of high pitch-angle beam ions can strongly suppress the counterpropagating global Alfven eigenmodes (GAE). GAE have been implicated in the redistribution of fast ions and modification of the electron power balance in previous experiments on NSTX. The ability to predict the stability of Alfven modes, and developing methods to control them, is important for fusion reactors like the International Tokamak Experimental Reactor, which are heated by a large population of nonthermal, super-Alfvenic ions consisting of fusion generated alpha's and beam ions injected for current profile control. We present a qualitative interpretation of these observations using an analytic model of the Doppler-shifted ion-cyclotron resonance drive responsible for GAE instability which has an important dependence on k(perpendicular to rho L). A quantitative analysis of this data with the HYM stability code predicts both the frequencies and instability of the GAE prior to, and suppression of the GAE after the injection of high pitch-angle beam ions.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Measurement and modeling of beam transport in the FODO line of the Spallation Neutron Source Beam Test Facility

Ongoing studies at the Spallation Neutron Source (SNS) Beam Test Facility (BTF) seek to understand and model bunch dynamics in a high-power LINAC front-end. The BTF has recently been upgraded with a reconfiguration from a U-shaped line to a Straight line. We report the current state of model benchmarking, with a focus on RMS beam sizes within the FODO line. The beam measurement is obtained via three camera/screen pairs in the FODO line. This presentation discusses the methodology and results of this measurement.

Thompson, Trent↗
DOE OSTI2016

Large dynamic range beam diagnostics and beam dynamics studies for high current electron LINACs

As described in the previous reports we have been working on an apodized optical system for transverse beam profile measurements by means of imaging. The key issues of LDR imaging is properly managing diffraction effects within the optical system, which is proposed to accomplish by means of amplitude apodization. Shortly before the time of the last progress report we have finished manufacturing of several apodizing elements. We have completed mechanical design of our first apodized imaging system and have built its prototype on an optical bench. Since testing diagnostic equipment with beam is costly and is not always possible due to limited beam availability, it has been our intention to make as much preliminary testing and characterization on a test bench in the laboratory.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

An examination of different representations of the electrostatic field and potential of an intense relativistic electron beam in a cylindrical conductor and their implications on foil focusing of an elliptical beam

Knowledge of the electrostatic field and potential of an intense relativistic electron beam (IREB) in a cylindrical conductor is essential for understanding the transport of IREBs including the interaction of a grounded conducting foil with the beam. Different representations of the electrostatic field or potential exist in the literature. The different representations are compared and an extension to foil focusing of elliptical beams is discussed.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Beam Dynamics Simulations of Transient Beam Loading Effects in the 10GeV EIC Electron Storage Ring

We report on beam dynamics studies of transient beam loading effects in the 10 GeV EIC electron storage ring [1]. The studies are carried out with time-dependent Vlasov-Fokker-Planck simulations performed with the parallel, particle tracking code SPACE [2], which allows to follow self-consistently the dynamics of h bunches, where h in the number of RF buckets, in arbitrary multi-bunch configurations. The specific goal of the numerical simulations is to determine stable RF cavity settings under heavy beam loading. We also study the option to operate with a passive, third-harmonic cavity (3HC) system for bunch lengthening, addressing both stability and the performance limitation due to a gap in the uniform filling pattern for ion clearing.

43 PARTICLE ACCELERATORS↗
DOE OSTI2026

Comments on the paper “Eliminating beam-induced depolarizing effects in the hydrogen jet target for high-precision proton beam polarimetry at the Electron-Ion Collider” (Part I)

A critical review of the methodology used in F. Rathmann et al., Phys. Rev. Accel. Beams 29, 021001 (2026), to evaluate beam-induced depolarization of the Atomic Polarized Hydrogen Gas Jet (HJET) target at the Electron–Ion Collider (EIC) is presented. It is shown that several key assumptions underlying that analysis—including the introduction of a photon emission threshold, the application of Fermi’s Golden Rule to coherent hyperfine transitions, the interpretation of power broadening as a physical linewidth increase, and the treatment of spatial magnetic fields—are either incorrect or internally inconsistent. As a consequence, the predicted large depolarization effects are demonstrated to be artifacts of the adopted methodology rather than genuine physical phenomena. A consistent quantum-mechanical treatment based on the time-dependent Schrödinger equation shows that beam-induced depolarization probabilities at the EIC are negligibly small.

43 PARTICLE ACCELERATORS↗
NASA NTRS1972

Smoke Plume Analysis Using Fan-beam and Single-beam Radiometers

Smoke plume data were taken using the stacks of the Mills Road Steam Plant on Redstone Arsenal, Huntsville, Alabama. The fan-beam unit was placed approximately 235 meters east of the Mills Road Steam Plant, and the single-beam unit was placed approximately 80 meters north of the fan-beam unit. Results of the smoke plume measurements indicate that the smoke plume is a periodic process near the mouth of the smokestack. The usefulness of the system is limited because of inaccurate and cumbersome positioning methods and base line constraints due to cable length. It is recommended that the radiometers be mounted on pedestals which have both azimuth and elevation positions determined by digitally controlled stepper drive motors. It is also recommended that a time multiplex system be used to transmit data from the radiometers to the electronics van.

Dodd, J. L.↗
NASA NTRS1981

Effective path length corrections in beam-beam scattering experiments

The effect of the change of scattering geometry with scattering angle in beam-beam experiments is investigated. Atomic (molecular) target distributions associated with static gas, orifice, tube, capillary array (with and without further collimation), and jet sources have been considered in model calculations for a number of commonly used electron scattering geometries. The relationship between scattering intensity, cross section, and the geometrical integral called 'effective path length' is derived. Volume correction factors (the reciprocal of effective path length) have been calculated for sample cases to illustrate the effect of various beam and scattering geometry characteristics. The validity of the model calculation has been experimentally verified. Most of the commonly used scattering geometries require significant correction of the scattering intensity distributions, but with proper planning scattering geometries can be designed such that the intensity and the cross section angular distribution are identical within 1%.

Brinkmann, R. T.↗
NASA NTRS1989

Far field beam pattern of one MW combined beam of laser diode array amplifiers for space power transmission

The far-field beam pattern and the power-collection efficiency are calculated for a multistage laser-diode-array amplifier consisting of about 200,000 5-W laser diode arrays with random distributions of phase and orientation errors and random diode failures. From the numerical calculation it is found that the far-field beam pattern is little affected by random failures of up to 20 percent of the laser diodes with reference of 80 percent receiving efficiency in the center spot. The random differences in phases among laser diodes due to probable manufacturing errors is allowed to about 0.2 times the wavelength. The maximum allowable orientation error is about 20 percent of the diffraction angle of a single laser diode aperture (about 1 cm). The preliminary results indicate that the amplifier could be used for space beam-power transmission with an efficiency of about 80 percent for a moderate-size (3-m-diameter) receiver placed at a distance of less than 50,000 km.

Kwon, Jin H.↗
NASA NTRS1993

Gaussian-Beam/Physical-Optics Design Of Beam Waveguide

In iterative method of designing wideband beam-waveguide feed for paraboloidal-reflector antenna, Gaussian-beam approximation alternated with more nearly exact physical-optics analysis of diffraction. Includes curved and straight reflectors guiding radiation from feed horn to subreflector. For iterative design calculations, curved mirrors mathematically modeled as thin lenses. Each distance Li is combined length of two straight-line segments intersecting at one of flat mirrors. Method useful for designing beam-waveguide reflectors or mirrors required to have diameters approximately less than 30 wavelengths at one or more intended operating frequencies.

Veruttipong, Watt↗
NASA NTRS1995

A Coupled Layerwise Analysis of the Thermopiezoelectric Response of Smart Composite Beams Beams

Thermal effects are incorporated into previously developed discrete layer mechanics for piezoelectric composite beam structures. The updated mechanics explicitly account for the complete coupled thermoelectromechanical response of smart composite beams. This unified representation leads to an inherent capability to model both the sensory and actuator responses of piezoelectric composite beams in a thermal environment. Finite element equations are developed and numerical results are presented to demonstrate the capability of the current formulation to represent the behavior of both sensory and active smart structures under thermal loadings.

Lee, H.-J.↗
DOE OSTI2012

First Beam Waist Measurements in the Final Focus Beam Line at the KEK Accelerator Test Facility

The ATF2 project is the final focus system prototype for the ILC and CLIC linear collider projects, with a purpose to reach a 37 nm vertical beam size at the interaction point using compact optics based on a novel scheme of local chromaticity correction. Construction of all components and installation were completed at the end of 2008. An initial commissioning phase followed in 2009, using larger than nominal {beta} functions at the interaction point, corresponding to reduced demagnification factors in comparison to the design, to limit effects from higher-order optical aberrations and hence simplify beam tuning procedures while key instrumentation was being tested and calibrated. In this paper, first measurements of dispersion and Twiss parameters are presented based on scanning the beam during this period with a set of tungsten wires located just behind the interaction point, using two complementary analysis methods.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Beam experiments towards high-intensity beams in RHIC

Proton bunch intensities in RHIC are planned to be increased from 2 {center_dot} 10{sup 11} to 3 {center_dot} 10{sup 11} protons per bunch to increase the luminosity, together with head-on beam-beam compensation using electron lenses. To study the feasibility of the intensity increase, beam experiments are being performed. Recent experimental results are presented.

43 PARTICLE ACCELERATORS↗