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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 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Benchmarking collective effects of electron interactions in a wiggler with OPAL-FEL

OPAL-FEL is a recently developed tool for the modeling of particle accelerators containing wigglers or undulators. It extends the well established 3D electrostatic particle-tracking code OPAL, by merging it with the finite-difference time-domain electromagnetic solver MITHRA. We present results of two benchmark cases where OPAL-FEL simulations are compared to experimental results. Both experiments concern electron beamlines where the longitudinal phase space is modulated with a short magnetic wiggler. Good agreement was found in both the space charge and radiation dominated regimes.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Observation of a massive phason in a charge-density-wave insulator

The lowest-lying fundamental excitation of an incommensurate charge density wave (CDW) material is widely believed to be a massless phason -- a collective modulation of the phase of the CDW order parameter. However, as first pointed out by Lee and Fukuyama, long-range Coulomb interactions should push the phason energy up to the plasma energy of the CDW condensate, resulting in a massive phason and a fully gapped spectrum. Whether such behavior occurs in a CDW system has been unresolved for more than four decades. Using time-domain THz emission spectroscopy, we investigate this issue in the material (TaSe 4 ) 2 I, a classical example of a quasi-one-dimensional CDW insulator. Upon transient photoexcitation at low temperatures, we find the material strikingly emits coherent, narrow-band THz radiation. The frequency, polarization and temperature-dependence of the emitted radiation imply the existence of a phason that acquires mass by coupling to long-range Coulomb interaction. Our observations constitute the first direct evidence of the massive "Lee-Fukuyama" phason and highlight the potential applicability of fundamental collective modes of correlated materials as compact and robust sources of THz radiation.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Observation of nonlocal Josephson effect on double InAs nanowires

Short-range coherent coupling of two Josephson junctions (JJs) are predicted to generate a supercurrent in one JJ nonlocally modulated by the phase difference in the other. We report on observation of the nonlocal Josephson effect on double InAs nanowires as experimental evidence of the coherent coupling. We measure one JJ sharing one superconducting electrode with the other JJ and observe switching current oscillation as a control of the nonlocal phase difference. Our result will contribute to engineer novel superconducting phenomena with the short-range coherent coupling.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Suppression of ITG turbulence due to spectral shift during biasing induced H-mode on HBT-EP

Investigations of biasing induced H-mode discharges on HBT-EP show that the edge turbulence is consistent with the ion temperature gradient) mode and have allowed for the controlled observation of the effect of applied flow shear on the turbulence. Measurements of the radial wavenumber spectrum of floating potentials at the edge show that the turbulence intensity decreases with increasing shift in the spectrum average ⟨ k r ⟩ when increasing amounts of bias probe voltage (and increasing amounts of flow shear) is applied. This is in agreement with the spectral shift model [Staebler et al., Phys. Rev. Lett. 110, 055003 2013] for turbulence suppression via sheared flow. A shift in the wavenumber spectrum occurs at applied electrode voltages and currents below the threshold needed for an L–H transition, and a dithering transition is obtained when biasing near the threshold. Suppression of blob-filament turbulence in the scrape-off layer (SOL) precedes the L–H transition, with the SOL turbulence remaining low throughout the dithering phase, despite the modulation of turbulence levels in the nearby edge. This demonstrates that the SOL turbulence “decouples” from the edge turbulence. The spectral shift in the measured radial wavenumber is corroborated by the direct measurement of eddy tilt angle using a novel time delay analysis technique first developed for Doppler reflectometry [Pinzon et al., Plasma Phys. Controlled Fusion 61, 105009 (2019)] but adapted here for floating potential measurements.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

A novel high frequency, high bandwidth, three phase Mach–Zehnder optical data link

In inertial confinement fusion, hydrogen isotopes are fused together under high pressures and temperatures. Typically, the duration of these experiments is incredibly short, on the order of around 60–150 ps. Due to the high radiation environment, a detector’s signal is typically data linked far distances to a protected location. The diagnostic challenge for fusion reaction history measurements is to measure signals of interest maximizing dynamic range while also maintaining time resolution on the order of 10 ps. In this work, we present a new experimental optical data link used to efficiently transport diagnostic signals over great distances to the recording system while not restricting the dynamic range. The concept of a three phase Mach–Zehnder modulator system is introduced as well as a description of the physical prototype. The initial results from testing at the OMEGA facility show that this system is a viable method for signal transportation.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

Improved Frequency-Domain Steady-State Modeling of the Dual-Active-Bridge Converter Considering Finite ZVS Transition Time Effects

This article presents an improved analytical modeling (IAM) approach for the dual-active-bridge (DAB) converter in the frequency-domain. Specifically, finite transition times are incorporated into the improved modeling that are significant in DAB converters operated at high frequency. The IAM approach is first motivated by comparing traditional frequency-domain modeling against realistic simulation results in LTspice. Next, the IAM approach is mathematically developed in an iterative fashion, where the conventional frequency-domain approach is used as the initialization of the operational behavior of the converter. Subsequent iterations of the IAM algorithm incorporate finite rise- and falltimes of device output capacitances based on detailed switching behavior analyses, which may considerably perturb the desired modulation parameters (i.e., phase shift and zero states). While the initially proposed IAM approach demonstrates advantages over ideal modeling, it is still shown to exhibit errors when applied to device transitions with significant nonlinearity in parasitic output capacitance. To account for this, a three-slope approximation to the switching transition is then motivated and developed, which enables significantly improved steady-state prediction accuracy. Simulation and experimental results confirm unacceptable inaccuracies associated with the conventional frequency-domain modeling across a wide range of operating conditions, alongside enhanced accuracy provided by the proposed modeling approach.

14 SOLAR ENERGY↗
DOE OSTI2020

Octet: A coherent qubit control system for trapped-ion quantum computers

This is firmware and software designed for a Zynq UltraScale+ RFSoC chip made by Xilinx, specifically targeted to laser-based individual addressing of trapped ion qubits via a multi-channel AOM. The design features 8 dual-tone outputs with frequencies up to 409 MHz that can be controlled statically or dynamically via on-chip cubic spline interpolation engines that allow one to generate sequences of output waveforms with fast modulation of frequency, phase, amplitude, and z-rotations that are smooth/discrete and can run simultaneously across all parameters/tones. It also features global phase alignment on all tones regardless of frequency and the ability to return to a known phase/frequency at any later time on a per-tone basis without the need for manual bookkeeping. Acoustic and optical cross-talk can also be destructively canceled by adding neighboring outputs with variable amplitude/phase/delay. Each tone can be optionally frequency locked to an external RF source. SAND2020-12703 M Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

Lobser, Daniel↗
DOE OSTI2023

Implementing an electronic sideband offset lock for isotope shift spectroscopy in radium

We demonstrate laser frequency stabilization with at least 6 GHz of offset tunability using an in-phase/quadrature (IQ) modulator to generate electronic sidebands (ESB) on a titanium sapphire laser at 714 nm and we apply this technique to perform isotope shift spectroscopy of 226 Ra and 225 Ra. By locking the laser to a single resonance of a high finesse optical cavity and adjusting the lock offset, we determine the frequency difference between the magneto-optical trap (MOT) transitions in the two isotopes to be 2630.0 ± 0.3 MHz, a factor of 29 more precise than the previously available data. Using the known value of the hyperfine splitting of the 3 P 1 level, we calculate the isotope shift for the 1 S 0 to 3 P 1 transition to be 2267.0 ± 2.2 MHz, a factor of 8 more precise than the best available value. Our technique could be applied to countless other atomic systems to provide unprecedented precision in isotope shift spectroscopy and other relative frequency comparisons.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

A Novel High Frequency, High Bandwidth, Three Phase Mach Zehnder Optical Data Link [Slides]

Inertial Confinement Fusion (ICF) produces high yield, high bandwidth signals that must be sent over large distances. A three phase Mach Zehnder modulator system helps resolve many of the issues faced with measuring these signals. This setup requires a three step reconstruction program. The testing results from OMEGA show this setup was successful and is ready for fielding at Inertial Confinement Fusion, including the National Ignition Facility (NIF).

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Next-Generation Modular Flexible Low-Cost SiC-based High-Frequency-Link Transformer (Final Technical Report)

This project, led by the small business NextWatt LLC, led to the design and development of a novel high-frequency-link (HFL) transformer that yields reduce number of semiconductor devices compared to conventional solid-state transformers (SSTs). The HFL transformer is based on SiC device technology and nanocrystalline-core-based magnetics techniology. The control actuation of the SiC devices are algorithmically implemented in digital signal processor (DSP) platform. The overall HFL transformer technology is conceived and developed using a modular approach. During the course of the project the novel technology and its experimental performances at the module, multi-phase, and cascaded multi-phase levels have been demonstrated to the sponsor U.S. Department of Energy (DOE).

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS1971

Linear modulator Final report

Design, operation, and alignment of single channel breadboard modulator, demodulator, and phase locked loops for double sideband signals

Source record↗
NASA NTRS1972

A study of compressed spatially non-Gaussian optical pulses from mode-locked lasers.

The effect of the grating-induced phase and spatial modulations by multiple transverse modes simultaneously present in mode-locked laser pulses is investigated. Our analysis shows that the dispersions of the grating pair become strongly dependent on wavelength because of the energy exchanges occurring among transverse modes. As a result, the maximum-intensity trace at the output of the grating is shown to be curved and the grating-induced pulse-compression rate is shown to vary significantly across the beam cross section. Also, a discussion is presented relating our analysis to existing experimental data on the wavelength-dependent chirping rates of mode-locked laser beams.

Kim, D. M.↗
NASA NTRS1972

Spectral analysis program. Volume 1: User's guide

The spectral analysis program (SAP) was developed to provide the Manned Spacecraft Center with the capability of computing the power spectrum of a phase or frequency modulated high frequency carrier wave. Previous power spectrum computational techniques were restricted to relatively simple modulating signals because of excessive computational time, even on a high speed digital computer. The present technique uses the recently developed extended fast Fourier transform and represents a generalized approach for simple and complex modulating signals. The present technique is especially convenient for implementation of a variety of low-pass filters for the modulating signal and bandpass filters for the modulated signal.

Hayden, W. L.↗
NASA NTRS1974

Wideband infrared receiver backend

The design, operation, and configuration of the receiver backend for a wideband infrared tracking receiver are described. A squaring loop is incorporated into the receiver design to enable it to track the Doppler shifted carrier which is Phase Shift Keyed modulated. The receiver has a 400 MHz instantaneous bandwidth and tracks signals whose carrier frequency at the backend input is between 200 and 900 MHz with frequency variation rates greater than 20 MHz/second. The output data is compatible with MECL 3 logic.

Flattau, T.↗
NASA NTRS1974

TDRSS telecommunications study, phase 2

Providing an extension to parametric analysis of the telecommunications support capability of the Tracking and Data Relay Satellite System (TDRSS), this phase considers candidate modulation waveforms which could meet the shuttle telecommunications requirements and also be compatible with the TDRSS single access S-band service. In addition, it considers the feasibility of modifying a single access S-band user transponder for operation with conventional STDN signals emanating from remotely located ground stations.

Cahn, C. R.↗