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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Phase Space Dynamics of a Plasma Wakefield Dechirper for Energy Spread Reduction

Plasma-based accelerators have made impressive progress in recent years. However, the beam energy spread obtained in these accelerators is still at the ~1% level, nearly one order of magnitude larger than what is needed for challenging applications like coherent light sources or colliders. In plasma accelerators, the beam energy spread is mainly dominated by its energy chirp (longitudinally correlated energy spread). Furthermore, we demonstrate that when an initially chirped electron beam from a linac with a proper current profile is sent through a low-density plasma structure, the self-wake of the beam can significantly reduce its energy chirp and the overall energy spread. The resolution-limited energy spectrum measurements show at least a threefold reduction of the beam energy spread from 1.28% to 0.41% FWHM with a dechirping strength of ~1 (MV/m)/(mm pC). Refined time-resolved phase space measurements, combined with high-fidelity three-dimensional particle-in-cell simulations, further indicate the real energy spread after the dechirper is only about 0.13% (FWHM), a factor of 10 reduction of the initial energy spread.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2002

Dynamic Stability of Uncertain Laminated Beams Under Subtangential Loads

Because of the inherent complexity of fiber-reinforced laminated composites, it can be challenging to manufacture composite structures according to their exact design specifications, resulting in unwanted material and geometric uncertainties. In this research, we focus on the deterministic and probabilistic stability analysis of laminated structures subject to subtangential loading, a combination of conservative and nonconservative tangential loads, using the dynamic criterion. Thus a shear-deformable laminated beam element, including warping effects, is derived to study the deterministic and probabilistic response of laminated beams. This twenty-one degrees of freedom element can be used for solving both static and dynamic problems. In the first-order shear deformable model used here we have employed a more accurate method to obtain the transverse shear correction factor. The dynamic version of the principle of virtual work for laminated composites is expressed in its nondimensional form and the element tangent stiffness and mass matrices are obtained using analytical integration The stability is studied by giving the structure a small disturbance about an equilibrium configuration, and observing if the resulting response remains small. In order to study the dynamic behavior by including uncertainties into the problem, three models were developed: Exact Monte Carlo Simulation, Sensitivity Based Monte Carlo Simulation, and Probabilistic FEA. These methods were integrated into the developed finite element analysis. Also, perturbation and sensitivity analysis have been used to study nonconservative problems, as well as to study the stability analysis, using the dynamic criterion.

Goyal, Vijay K.↗
DOE OSTI2024

Dynamically patterning x-ray beam by a femtosecond optical laser

Modern science and technology have greatly benefitted from our ability to precisely manipulate light waves, in both their spatial and temporal degrees of freedom. In the x-ray region, however, spatial control has been virtually static mainly due to stringent requirements for realizing high-performance optical elements. The lack of dynamic spatial control of x-ray beam has prevented researchers from realizing more sophisticated use of the wave field, which has rapidly advanced in the optical region in the past decades. In this study, we propose a practical scheme to dynamically control local x-ray reflectivity of a perfect silicon crystal by a femtosecond optical laser and demonstrate a programmable spatial x-ray modulator. Our modulator aims for spatial manipulation of the x-ray amplitude and is shown to produce arbitrary grayscale patterns with spatial frequencies up to 25 per millimeter. The proposed modulation scheme opens up a platform to enable advanced x-ray sensing and imaging techniques that can fully harness the wave nature of x-rays.

47 OTHER INSTRUMENTATION↗
NASA NTRS2007

Dual-Beam Atom Laser Driven by Spinor Dynamics

An atom laser now undergoing development simultaneously generates two pulsed beams of correlated Rb-87 atoms. (An atom laser is a source of atoms in beams characterized by coherent matter waves, analogous to a conventional laser, which is a source of coherent light waves.) The pumping mechanism of this atom laser is based on spinor dynamics in a Bose-Einstein condensate. By virtue of the angular-momentum conserving collisions that generate the two beams, the number of atoms in one beam is correlated with the number of atoms in the other beam. Such correlations are intimately linked to entanglement and squeezing in atomic ensembles, and atom lasers like this one could be used in exploring related aspects of Bose-Einstein condensates, and as components of future sensors relying on atom interferometry. In this atom-laser apparatus, a Bose-Einstein condensate of about 2 x 10(exp 6) Rb-87 atoms at a temperature of about 120 micro-K is first formed through all-optical means in a relatively weak singlebeam running-wave dipole trap that has been formed by focusing of a CO2-laser beam. By a technique that is established in the art, the trap is loaded from an ultrahigh-vacuum magnetooptical trap that is, itself, loaded via a cold atomic beam from an upstream two-dimensional magneto-optical trap that resides in a rubidium-vapor cell that is differentially pumped from an adjoining vacuum chamber, wherein are performed scientific observations of the beams ultimately generated by the atom laser.

Thompson, Robert↗
DOE OSTI2016

Influence of laser induced hot electrons on the threshold for shock ignition of fusion reactions

The effects of Hot Electrons (HEs) generated by the nonlinear Laser-Plasma Interaction (LPI) on the dynamics of Shock Ignition Inertial Confinement Fusion targets are investigated. The coupling between the laser beam, plasma dynamics and hot electron generation and propagation is described with a radiative hydrodynamics code using an inline model based on Paraxial Complex Geometrical Optics [Colaïtis et al., Phys. Rev. E 92, 041101 (2015)]. Two targets are considered: the pure-DT HiPER target and a CH-DT design with baseline spike powers of the order of 200–300 TW. In both cases, accounting for the LPI-generated HEs leads to non-igniting targets when using the baseline spike powers. While HEs are found to increase the ignitor shock pressure, they also preheat the bulk of the imploding shell, notably causing its expansion and contamination of the hotspot with the dense shell material before the time of shock convergence. The associated increase in hotspot mass (i) increases the ignitor shock pressure required to ignite the fusion reactions and (ii) significantly increases the power losses through Bremsstrahlung X-ray radiation, thus rapidly cooling the hotspot. These effects are less prominent for the CH-DT target where the plastic ablator shields the lower energy LPI-HE spectrum. Simulations using higher laser spike powers of 500 TW suggest that the CH-DT capsule marginally ignites, with an ignition window width significantly smaller than without LPI-HEs, and with three quarters of the baseline target yield. The latter effect arises from the relation between the shock launching time and the shell areal density, which becomes relevant in presence of a LPI-HE preheating.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Scaling of induction-cell transverse impedance: effect on accelerator design

The strength of the dangerous beam breakup (BBU) instability in linear induction accelerators (LIAs) is characterized by the transverse coupling impedance Z ⊥ . This note addresses the dimensional scaling of Z ⊥ , which is important when comparing new LIA designs to existing accelerators with known i BBU growth. Moreover, it is shown that the scaling of Z ⊥ with the accelerating gap size relates BBU growth directly to high-voltage engineering considerations. It is proposed to firmly establish this scaling though a series of AMOS calculations.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

Heavy ion beam physics at Facility for Rare Isotope Beams

The Facility for Rare Isotope Beams (FRIB) will be the world's premier rare-isotope beam facility. Experiments with the majority (~80%) of the isotope predicted to exist will become available. The FRIB facility is based on a superconducting (SC) heavy ion linac with output energy above 200 MeV/u for any ions at beam power of 400 kW. FRIB includes a target facility for in-flight production of rare isotopes. A three-stage fragment separator will be used to prepare fast rare isotope beams with high-purity for nuclear physics experiments. The installation work of the accelerator and experimental systems is approaching completion and multi-stage beam commissioning activities started in summer 2017 with expected project completion in early 2022. In conclusion, the commencement of operation for users' experiments is planned immediately following the project completion.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

de Gennes Narrowing and Relationship between Structure and Dynamics in Self-Organized Ion-Beam Nanopatterning

Investigating the relationship between structure and dynamical processes is a central goal in condensed matter physics. Perhaps the most noted relationship between the two is the phenomenon of de Gennes narrowing, in which relaxation times in liquids are proportional to the scattering structure factor. Here, a similar relationship is discovered during the self-organized ion-beam nanopatterning of silicon using coherent x-ray scattering. However, in contrast to the exponential relaxation of fluctuations in classic de Gennes narrowing, the dynamic surface exhibits a wide range of behaviors as a function of the length scale, with a compressed exponential relaxation at lengths corresponding to the dominant structural motif—self-organized nanoscale ripples. These behaviors are reproduced in simulations of a nonlinear model describing the surface evolution. Our team suggests that the compressed exponential behavior observed here is due to the morphological persistence of the self-organized surface ripple patterns which form and evolve during ion-beam nanopatterning.

36 MATERIALS SCIENCE↗
NASA NTRS2000

On the Dynamics of Two Dimensional Array Beam Scanning Via Coupled Oscillators

This presentation will begin with a description of the previous published work contributing to the results reported here. The previously developed one dimensional continuum model will be generalized to two dimensions and a Green's function for the resulting differential equation will be obtained as an eigenfunction expansion. This will be used to obtain dynamic solutions relevant to the steering of the radiated beam. Finally, some remarks concerning limitations on the interoscillator phase difference will be provided.

Pogorzelski, R. J.↗
DOE OSTI2018

Calculations of Beam-Beam Effect and Luminosity for Crab Dynamics Simulations in JLEIC

Crab crossing is an integral part of the Jefferson Lab Electron-Ion Collider (JLEIC) design to achieve high luminosity while meeting the detection and physics pro-gram requirements. The crab crossing scheme provides a head-on beam-beam collision for beams with a nonzero crossing angle. Simulations of crabbing dynamics currently do not include beam-beam effects. We describe a framework for accurate simulation of beam-beam effects on crabbing dynamics by applying a numerical calculation of the Bassetti-Erskine analytic solution to symplectic particle tracking codes. The numerical calculation is benchmarked against the analytic solution by calculating the luminosity reduction for several colliding beam scenarios. Benchmarking results show good agreement be-tween the numerical calculation and analytic solution, paving the way for implementation of the beam-beam kick to Elegant tracking simulations.

Huang, He↗
DOE OSTI2021

Nanoscale dynamics during self-organized ion beam patterning of Si. I. Ar + bombardment

X-ray photon correlation spectroscopy (XPCS) is used to investigate the fluctuation dynamics during self- organized nanopatterning of silicon by Ar + bombardment at 65° polar angle. Rich structure is observed in the development of the correlation dynamics as seen in the evolving correlation time τ(q || ) and fluctuation relaxation exponent n(q || ). Furthermore, on length scales of the ripple structure, local structure becomes ever more long lived as coarsening progresses. In addition, τ (q || ) develops a peak on length scales corresponding to the ripple wavelength. As patterning progresses, correlation times become asymmetric between the positive and negative directions, suggesting the possibility of different dynamics on the slopes facing toward and away from the ion beam. Relaxation exponents show evolution from linear dynamics at early times to compressed exponential relaxation at low wave numbers and stretched exponential relaxation at high wave numbers. Compressed exponential behavior is reminiscent of stress relaxation processes observed in glasses.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1990

Modeling of composite beams and plates for static and dynamic analysis

A rigorous theory and corresponding computational algorithms was developed for a variety of problems regarding the analysis of composite beams and plates. The modeling approach is intended to be applicable to both static and dynamic analysis of generally anisotropic, nonhomogeneous beams and plates. Development of a theory for analysis of the local deformation of plates was the major focus. Some work was performed on global deformation of beams. Because of the strong parallel between beams and plates, the two were treated together as thin bodies, especially in cases where it will clarify the meaning of certain terminology and the motivation behind certain mathematical operations.

Hodges, Dewey H.↗
DOE OSTI2016

High-Voltage Breakdown Penalties for the Beam-Breakup Instability

The strength of the dangerous beam breakup (BBU) instability in linear induction accelerators (LIAs) is determined by the transverse coupling impedance Z ⊥ of the induction cell cavity. For accelerating gap width w less than the beam pipe radius b, the transverse impedance is theoretically proportional to w/b, favoring narrow gaps to suppress BBU. On the other hand, cells with narrow gaps cannot support high accelerating gradients, because of electrical breakdown and shorting of the gap. Thus, there is an engineering trade-off between BBU growth and accelerating gradient, which must be considered for next generation LIAs now being designed. In this article this tradeoff is explored, using a simple pillbox cavity as an illustrative example. For this model, widening the gap to reduce the probability of breakdown increases BBU growth, unless higher magnetic focusing fields are used to further suppress the instability.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Radiation defect dynamics in GaAs studied by pulsed ion beams

Gallium arsenide under ion bombardment at room temperature and above exhibits pronounced dynamic annealing that remains poorly understood. Here, we use a pulsed beam method to study radiation defect dynamics in GaAs in the temperature range of 20–100 °C irradiated with 500 keV Xe ions. Results show that, with increasing temperature, the defect relaxation time constant monotonically decreases from ~5.2 to ~0.4 ms. A change in the dominant dynamic annealing process occurs at a critical temperature of ~60 °C, as evidenced by a change in the activation energy. A comparison with the other semiconductors studied by the pulsed beam method (Si, Ge, and 4H-SiC) reveals that both the high-temperature activation energy and the temperature below which dynamic annealing becomes negligible scale with the melting point.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Beam-, Target- and Double- Spin Asymmetry Measurements in Deeply Virtual π 0 , π + and π - Meson Production

This thesis presents measurements of spin asymmetries in single pion electroproduction from the EG1-DVCS experiment carried out at the Thomas Jefferson National Accelerator Facility in 2009 with use of the CEBAF Large Acceptance Spectrometer. The experiment made use of a 6 GeV longitudinally polarised electron beam and (dynamically) longitudinally polarised targets of 14 NH 3 and 14 ND 3 (giving access to protons and deuterons), providing the means to measure three spin asymmetries: beam-, target-, and double-spin. Deeply Virtual Meson Production for the π 0 , π + and π - channels were studied for the kinematic range of Q 2 > 1 GeV 2 and W > 2 GeV. The collection of measurements includes the analysis of numerous reconstruction topologies, as well as making use of different target materials. These are the world's first charged pion spin asymmetry measurements in this kinematic regime. The sPlot maximum likelihood fit based background subtraction technique was implemented in the data analysis, showing strong agreement with a traditional and commonly used cuts-based approach. This novel technique was thoroughly tested to develop implementation and execution. The results obtained will provide a reference point for future analyses at the upgraded experimental facility and motivate the use of the sPlot technique. These measurements will provide insight into the structure of nucleons through their interpretation in relation to Generalised Parton Distributions which describe substructure correlations between longitudinal momentum and transverse position of partons. In particular, here the spin asymmetries dependence on t , the squared four-momentum transfer to the target nucleon, carries information on the spatial parton distributions in the transverse plane.

Murdoch, Gavin↗
DOE OSTI2025

Pulsar Movement Animation and its Corresponding Signal Visualization for Timing Source

The global positioning system, widely used for synchronization in energy systems, faces vulnerabilities, while Pulsars—natural cosmic clocks—offer long-term stability as potential backup timing sources. Existing research lacks sufficient exploration of Pulsar signal animation under astrophysical factors, limiting practical applications. This study establishes a mathematical model based on the rotation dynamics of dual-beam Pulsars and implements dynamic signal visualization through MATLAB. The model dynamically illustrates the relative motion between Pulsar beams and observers via timeline calculations, beam intensity modeling, and rotation matrix derivation. A case study on the millisecond Pulsar J1939+2134 reveals that observer angles influence signal peak timing, while beam widths determine signal duration, highlighting the critical role of parameter calibration for timing accuracy. Open-source code and animation results are publicly shared, providing tools for interdisciplinary research. This study validates the feasibility of Pulsar-based timing in energy systems, offering new insights to enhance synchronization robustness.

Wu, Ori [ORNL] (ORCID:0000000326723410)↗