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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Exploring the parameter space of MagLIF implosions using similarity scaling. III. Rise-time scaling

Magnetized liner inertial fusion (MagLIF) is a z-pinch magneto-inertial-fusion concept studied at the Z Pulsed Power Facility of Sandia National Laboratories. Two important metrics characterizing current delivery to a z-pinch load are the peak current and the current-rise time, which is roughly the time interval to reach the peak current. It is known that, when driving a z-pinch load with a longer current-rise time, the performance of the z-pinch decreases. However, a theory to understand and quantify this effect is still lacking. Here, in this paper, we utilize a framework based on similarity scaling to analytically investigate the variations in the performance of MagLIF loads when varying the current-rise time, or equivalently, the implosion timescale. To maintain similarity between the implosions, we provide scaling prescriptions of experimental input parameters defining a MagLIF load and derive the expected scaling laws for stagnation conditions and for various performance metrics. We compare predictions of the theory to 2D numerical simulations using the radiation, magneto-hydrodynamic code hydra. For several metrics, we find acceptable agreement between the theory and simulations. Our results show that the voltage φload near the MagLIF load follows a weak scaling law φload ∝$t_{φ}^{-0.12}$ with respect to the characteristic timescale t φ of the voltage source, instead of the ideal φload ∝$t_{φ}^{-1}$ scaling. This occurs because the imploding height of the MagLIF load must increase to preserve end losses. As a consequence of the longer imploding liners, the required total laser preheat energy and delivered electric energy increase. Overall, this study helps understand the trade-offs of the MagLIF design space when considering future pulsed-power generators with shorter and longer current-rise times.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

The Seismic Signature of a High-Energy Density Physics Laboratory and Its Potential for Measuring Time-Dependent Velocity Structure

The Z Machine at Sandia National Laboratories is a pulsed power facility for high-energy density physics experiments that can shock materials to extreme temperatures and pressures through a focused energy release of up to ~ 25 MJ in < 100 nanoseconds. It has been in operation for more than two decades and conducts up to ~ 100 experiments, or “shots,” per year. Based on a set of 74 known shot times from 2018, we determined that Z Machine shots produce detectable ~ 3–17 Hz ground motion 12 km away at the Albuquerque Seismological Laboratory, New Mexico (ANMO), borehole seismograph, with peak signal at ~ 7 Hz. The known shot waveforms were used to create a three-component template, leading to the detection of 2339 Z Machine shots since 1998 through single-station cross-correlation. Local seismic magnitude estimates range from local magnitude (M L ) —2 to —1.3 and indicate that only a small fraction of the shot energy is transmitted by seismic phases observable at 12 km distance. The most recent major facility renovation, which was intended to decrease mechanical dissipation, is associated with an abrupt decrease in observed seismic amplitudes at ANMO despite stable maximum shot energy. The highly repetitive impulsive sources are well suited to coda-wave interferometry to investigate time-dependent velocity structures. Relative velocity variations (dv/v) show an annual cycle with amplitude of ~ 0.2%. Local minima are observed in the late spring, and dv/v increases through the summer monsoon rainfall, possibly reflecting patchy saturation as rainfall infiltrates near the eastern edge of the Albuquerque basin. Importantly, the cumulative results demonstrate that forensic seismology can provide insight into long-term operation of facilities such as pulsed-power laboratories, and that their recurring signals may be valuable for studies of time-dependent structure

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Advancement of hybrid fluid-kinetic modeling for HEDP and ICF science

We report on the development progress of a hybrid fluid-kinetic code for simulating fluids and plasmas in a wide range of environments, such as laser–matter interactions, inertial confinement fusion, magnetic confinement fusion, and pulsed power. The suite of numerical tools under development utilizes heterogeneous computer architectures and leverages the benefits of particle–based simulation techniques. By working to combine the kinetic particle-in-cell (PIC) model with a particle-based fluid simulation technique, such as smoothed particle hydrodynamics, we are developing a flexible framework capable of accurately modeling complex flows within and between kinetic and fluid regimes. The TriForce code is under development as a C++ framework for parallel, 3D, particle-based, hybrid fluid-kinetic plasma simulations. The fluid half of TriForce will be based upon the meshless smoothed-particle-hydrodynamics (SPH) approach, well-suited for shear, mixing, and turbulence, whereas the kinetic half resembles a traditional particle-in-cell (PIC) code; other particle-based approaches to fluid modeling that do use a mesh are also possible to use and are under investigation. Maxwell’s electromagnetic field equations are solved either via explicit or implicit algorithms or approximated via resistive magnetohydrodynamics (MHD) using an Ohm’s law and resulting induction equation (extended MHD is under development). A primary goal of enabling direct comparisons, from the same code, between results from the variants of MHD and implicit electromagnetic solutions is to improve our fundamental understanding of systems with magnetic fields. The code is under development to recover results from both radiation-MHD and fully kinetic codes in those limits, and is continuing to be developed from other follow-on grants to operate in between where both descriptions may co-exist and interact. For certain applications, it is desired for a simulation to contain fluid ions and electrons as well as kinetic ions and electrons. Typically, it is too computationally intensive to model a full-scale ICF or HEDP experiment fully kinetically since many cycles are expended with very small time steps on modeling the fluid part of a material that is well treated by the fluid approximation. In this case, many traditional PIC particles can be replaced with a single fluid particle representing the thermal part of the distribution function, and there are fewer needed kinetic particles, which describe the non-thermal part and can be sub-cycled relative to the fluid particle advance. Furthermore, a pure fluid code may, depending on the problem, simply lack many physically important details that are beyond the scope of its reduced approximations and assumptions. In this report, we summarize the objectives achieved in the development of the collisional and kinetic half of the code, and the physics problems to which the code has been applied in the areas of advanced and innovative fusion concepts, pulsed power, and magneto-inertial fusion.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Diagnostic constraints on the amount of cold mass in imploded argon pinches on Z

The refurbished Z machine at Sandia National Laboratories has been successfully configured to drive gas-puff Z pinches. A series of experiments using Ar loads produced K-shell yields of 330 ± 9% kJ, with highly reproducible K-shell spectra and power pulses. Using spectroscopic and power data, we are able to constrain the properties of both the cold, non-K-shell radiating mass as well as the hot K-shell component of the pinch plasma. As in previous gas-puff shots on the original version of Z, only about 1/4 to 1/3 of the load mass was heated to temperatures sufficient to produce K-shell x-rays.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Spatiotemporal evolution of high power laser pulses in relativistic magnetized inhomogeneous plasmas

In this work, the spatiotemporal evolution of Gaussian laser pulse propagated through a plasma is investigated in the presence of an external axial magnetic field. The coupled equations of self-focusing and self-compression are obtained via paraxial approximation by taking into account the relativistic nonlinearity. The effect of axial magnetic field on simultaneously relativistic self-focusing and self-compression of the laser pulse is studied for homogeneous and inhomogeneous plasmas. The results show that the simultaneous use of both axial magnetic field and density ramp-up leads to generate pulses with the smallest spot size and shortest compression length.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Impulse Response Functions for Characterizing Pulse-to-Pulse Junction Temperature Behavior in Laser Diode Pulse Trains

A method is proposed for determination of the pulse-to-pulse variation in junction temperature and emission wavelength of a semiconductor laser diode during a train of pulses. Here, this approach, based on impulse response functions, enables predictions for pulse trains with arbitrary pulse-to-pulse variations in output power, pulse width, and pulse delay using a limited set of experimental characterization data. The use of this approach is illustrated by application to a particular device structure.

Deri, Robert J. [Lawrence Livermore National Labor↗
DOE OSTI2018

Charge Composition of Ions in a Cluster Plasma Formed under the Action of a High-Power Laser Pulse

A model describing the ionization of atoms and ions in a cluster under irradiation by a short laser pulse has been constructed. It is shown that the electron-impact ionization weakly affects the final charge composition, and the main mechanism of ion formation in the cluster is the over-barrier ionization by an electric field. The electric field acting on atoms and ions is the result of combined action of the external laser field and the intrinsic electric field of the cluster. The key parameters of the cluster beam and the laser pulse, which determine the properties of the charge composition of the cluster plasma, have been established.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Generation of a Periodic Sequence of High-Power Ultrashort Pulses in a Chain of Coupled Backward-Wave and Traveling-Wave Tubes Operating in the Regimes of Amplification and Nonlinear Kompfner Suppression

We have studied the dynamics of an electronic microwave generator with backward-wave and traveling-wave tubes connected in the feedback circuit and operating in the regimes of amplification and nonlinear Kompfner absorption, respectively. It is shown that radiation generated in such a system can have the form of a periodic sequence of ultrashort pulses. The studied mechanism of pulse generation is analogous to the method of passive mode locking, which is widely used in laser physics.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2013

Materials at Extreme Conditions [Slides]

The area of warm, dense matter (WDM) has received considerable attention recently due its identification with an assortment of environments as diverse as the interiors of exoplanets, the atmospheres of stars, inertial confinement fusion capsules, and the plasma from laser interactions with materials from clusters to nanostructures that span temperatures from a few thousand (~ 1 eV) to a few million (~ 100 eV) degrees Kelvin and densities from a few hundredths solid (~ 10 21 atoms/cm 3 ) to hundreds of times compressed solid (~ 10 26 atoms/cm 3 ). The WDM regime, which resembles a transient "soup" of atoms, molecules, ions, and free electrons, presents a particularly difficult challenge although one being met by high-energy-density physics (HEDP) experiments, involving high-powered lasers and pulse-power devices, as well as through the development of sophisticated theoretical and computation physics techniques. While the nuclei conform to a classical treatment within molecular dynamics simulations, the electrons require a quantum mechanical treatment of a large collection of atoms, periodically replicated in space. The electronic structure calculations, which closely resemble those of atomic and molecular physics for large molecules or clusters, generally utilize Density Functional Theory (DFT) approaches. From these simulations, we extract various properties such as equation-of-state, transport coefficients, and opacities, which characterize the particular regime. We discuss various theoretical procedures and examine several representative environments from planetary interiors to hot, dense plasmas.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Optimization of nanosecond transient plasma ignition for clean combustion

Based on a previously developed, retrofittable nanosecond pulsed TPS ignition prototype, transient plasma ignition technology is evaluated for higher energy efficiency and lower emission by optimizing pulse power conditions using advanced diagnostic-based approaches. Combustion performances of a TPS ignition electrode powered by nanosecond voltage pulses of two different rising times (i.e. 4 ns and 8 ns) but the same full-width-half-maximum (FWHM) of 6 ns were compared for single-shot and high-repetition-rate ignitions. The use of faster risetime reduces the voltage amplitude criterion for combustion ignition under a single-shot, stoichiometric fuel-air condition, resulting in higher energy efficiency. In addition, it was demonstrated that high-frequency bursts of pulses positively affect the combustion process; four-consecutive pulsed plasma ignition at a pulse repletion rate (PRR) of 1 kHz needs only half of the voltage to achieve combustion, and increasing the PRR from 1 kHz to 10 kHz improves the energy efficiency by a factor of >1.3. A prototype of retrofittable nanosecond pulsed ignition system was developed and tested in a newly built testing/diagnostic platform, paving the way for ultimate optimization of the TPS prototype for low cost, highly efficient, and low emission combustion.

02 PETROLEUM↗
DOE OSTI2021

RG217 V2-V2 Coaxial Cable Acceptance Test

The ECSE Solid State Pulsed Power unit is a high current, high power solid-state pulse modulator. The RG217 V2-V2 Coaxial Cable Assembly is the interface cable between the Solid State Pulser and the load. This document covers the testing procedure for the RG217 V2-V2 Coaxial Cable Assembly. This assembly is comprised of RG217 Coaxial Cable with a LRU Connector on either end. This test procedure verifies the cable is undamaged and assembled correctly, the correct cable connectors are installed properly onto the cable, and that the entire assembly meets conductivity and holdoff voltage requirements. This procedure will verify that the RG217 Coaxial Cable Assembly meets all assembly and functional requirements. In particular, this procedure verifies the Cable Shield and Center Conductor meet conductivity requirements by testing their resistances. Additionally, this procedure ensures the RG217 Coaxial Cable Assembly meets holdoff voltage requirements by applying high voltage and verifying the RG217 Coaxial Cable Assembly does not experience any breakdowns or arcing.

42 ENGINEERING↗
DOE OSTI2021

RG217 V2-V2 Coaxial Cable Soldering Procedure

The ECSE Solid State Pulsed Power unit is a high-current, high power solid-state pulse modulator. The RG217 V2-V2 Coaxial Cable Assembly is the interface cable between the Solid State Pulser and the load. This document covers the soldering procedure for the RG217 V2-V2 Coaxial Cable Assembly. This assembly is comprised of RG217 Coaxial Cable with a LRU Connector on either end. This soldering procedure describes the process used to solder cable tips properly onto the cable center conductor.

42 ENGINEERING↗