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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 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Comparative study of X-ray emission from plasma focus relative to different preionization schemes

A 2.7-kJ Mather-type plasma focus has been investigated for X-ray emission with preionization produced by an α-source, a β-source, and a shunt resistor. Time-resolved and time integrated measurements are carried out using a PIN-diode-based X-ray spectrometer and pinhole camera. The β-source ({sub 28}Ni{sup 63}) assisted preionization enhances the X-ray emission up to 25%, while preionization induced by depleted uranium ({sub 92}U{sup 238}) increases both Cu-K{sub α} and total X-ray yield of about 100%. The preionization caused by the optimum shunt resistor enhances the Cu-K{sub α} and total X-ray yield of about 53%. It is found that preionization also broadens the working pressure range for the high X-ray yield and improves the shot-to-shot reproducibility of the system. Pinhole images reveal that the X-ray emission from the anode tip is dominant owing to impact of electron bombardment, while the X-ray emission from hot spots is also visible.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Dose Measurements in a 20-J Repetitive Plasma Focus

In this article, the results of X-ray dose measurements executed using thermoluminescent dosimeters in experiments with a very small (20 J) repetitive plasma focus device named SORENA-1 are presented and analyzed. The working gas in these experiments was Argon. Also, pinch formation in experiments with this device has been observed. This device has been designed and constructed in Plasma and Nuclear Fusion Research School of Nuclear Science and Technology Research Institute of Iran. From these results, it is concluded that we can do experiments with this device using Ar as working gas all over the working days of year, and a good symmetry for measured dose around the device has been seen.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2019

Localized States near a Thin Layer with the Nonlinear Properties Separating Nonlinear Focusing and Defocusing Media

Based on the nonlinear Schrödinger equation, new types of localized states near the contact of defocusing and self-focusing media with the Kerr nonlinearity separated by a thin defect layer with the similar nonlinearity have been described. The occurrence of the localized states of two types is demonstrated. The dispersion relations between the excitation localization energy and characteristics of the media and defect layer have been obtained. The localization energy levels for particular cases have been obtained in the explicit analytical form.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

On the Mechanism of Absorption and Restoration of Radiation Transmission in the Channel of Small-Scale Self-Focusing of a Short Laser Pulse in Neodymium Glass

When diagnosing a small-scale self-focusing (SSSF) channel of a 0.5-ns laser pulse with an intensity of 3–5 GW/cm{sup 2} in neodymium glasses, an absorption jump was detected (with a front of ≈0.5 ns) at wavelengths of 1.06 and 0.66 μm in addition to filament-like damage typical of SSSF, spectral broadening, and laser radiation scattering. The absorption coefficient reached 0.15 cm{sup –1}, and transmission in the medium was restored during 15–35 ns for phosphate glass and 5–10 ns for silicate glass. The physical bases of this effect of the appearance and relaxation of absorption in glasses have not been previously presented. An analysis of the experimental data showed that the absorption jump is due to the fast population of the {sup 4}I{sub 11/2} level of Nd{sup 3+} ions in glasses when nonlinear processes occur in the SSSF channel such as stimulated Raman scattering and broadening of the laser pulse spectrum. The relaxation time of the population at the {sup 4}I{sub 11/2} level and the restoration of transmission in glasses after the termination of the laser pulse are determined by the characteristic sizes of the Nd{sup 3+} ions excitation regions arising in the samples upon interference of the laser and scattered radiation, as well as the thermophysical characteristics of the glasses.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Correlation of the neutron yield from the plasma focus upon variations in the magnetic field energy of the discharge circuit

The relation between neutron yield Y and magnetic field energy variations ΔW in the discharge circuit has been studied for a Mather-type plasma-focus camera. The activation technique (activation of silver isotopes) has been used to measure the integral yield of DD neutrons from the source. The time dependence of the neutron yield has been recorded by scintillation detectors. For the device used in the investigations, the neutron yield exhibits a linear dependence on variations in the magnetic field energy ΔW in the discharge circuit at the instant of neutron generation. It is also found that this dependence is related to the initial deuteron pressure in the discharge chamber.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Effect of External Longitudinal Electric Field on Tracking Force upon the Interaction of a Relativistic Electron Beam with the Ion Channel in the Ion Focusing Regime

It has been shown that, in the presence of a longitudinal external electric field, the magnitude of the tracking or detracking force that emerges during the acceleration or deceleration of a beam propagating along a preliminarily created ion channel in the ion-focusing regime can be commensurate with the force of the interaction of a relativistic electron beam with the ion plasma channel.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Ion-Optical System of an Ion Source with Energy Focusing in the Formed Beam

Ways to reduce ion beam intensity losses in a mass spectrometric ion source, which are caused by chromatic aberration of its immersion ion-optical system, are considered. These losses are rather significant in forming a beam from ions with a large energy spread. The reduction of aberration losses is especially important when ion sources are used jointly with mass analyzers with energy focusing. It is shown that these losses can be reduced significantly by using a new type of ion-optical system of the ion source, which includes achromatic elements. A special method for calculating such elements is given. Computer simulations have shown high efficiency of such elements in the ion-optical path of ion sources of mass spectrometers.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Filamentation and Self-Focusing of Electron Beams in Vacuum and Gas Diodes

In this paper, we experimentally studied pulsed electron beams with a high local density. The conditions in which the energy density cumulation is observed during the interaction of electrons with the anode are shown to develop in vacuum and gas diodes at nanosecond and subnanosecond durations of a beam current pulse and a decrease in the interelectrode gap. The average electron energy in filamentation and self-focusing of an electron beam in a vacuum diode of an accelerator at a current of ~2 kA and a no-load voltage of ~400 kV was established to be 50–100 keV while the energy density was 10{sup 9}–10{sup 10} J/cm{sup 3}. It is confirmed that the beam current density in a gas diode can exceed 1 kA/cm{sup 2}. It is hypothesized that superdense electron beams in vacuum and gas diodes are formed as a result of avalanche multiplication of runaway electrons in the cathode–anode gap plasma.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Fully three-dimensional simulation and modeling of a dense plasma focus

A dense plasma focus (DPF) is a pulsed-power machine that electromagnetically accelerates and cylindrically compresses a shocked plasma in a Z-pinch. The pinch results in a brief (~ 100 ns) pulse of X-rays, and, for some working gases, also a pulse of neutrons. A great deal of experimental research has been done into the physics of DPF reactions, and there exist mathematical models describing its behavior during the different time phases of the reaction. Two of the phases, known as the inverse pinch and the rundown, are approximately governed by magnetohydrodynamics, and there are a number of well-established codes for simulating these phases in two dimensions or in three dimensions under the assumption of axial symmetry. There has been little success, however, in developing fully three-dimensional simulations. In this work we present three-dimensional simulations of DPF reactions and demonstrate that three-dimensional simulations predict qualitatively and quantitatively different behavior than their two-dimensional counterparts. One of the most important quantities to predict is the time duration between the formation of the gas shock and Z-pinch, and the three-dimensional simulations more faithfully represent experimental results for this time duration and are essential for accurate prediction of future experiments.

Dense plasma focus, magnetohydrodynamics, simulati↗
DOE OSTI2016

Dense Plasma Focus Modeling

The mechanisms for pinch formation in Dense Plasma Focus (DPF) devices, with the generation of high-energy ions beams and subsequent neutron production over a relatively short distance, are not fully understood. Here we report on high-fidelity 2D and 3D numerical magnetohydrodynamic (MHD) simulations using the LA-COMPASS code to study the pinch formation dynamics and its associated instabilities and neutron production.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Station 6: Focused Experiments

This station, the second of four on the inside portion of the exhibit, explains focused experiments at Los Alamos. The station consists of a title monitor, main monitor, pushbuton monitor, and tabletop.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2026

Automation of Laser Plasma Focused Ion Beam Microscopy for Next-Gen Energy Materials

Automation can revolutionize the use of ultrafast laser ablation and plasma-focused ion beam (PFIB) techniques for high-throughput, reproducible cross-sectioning and various sample preparation in materials characterization. As these methods become essential for analyzing complex energy materials and next-generation devices, efficient, standardized workflows are needed to minimize variability and enhance precision. This work highlights our advancements in developing automated processes for sample preparation that integrates machine learning, workflow optimization, and large-scale data acquisition to improve efficiency and scalability in applications such as electrolyzers, photovoltaic cells, and microelectronics. To streamline cross-sectioning and lamella fabrication, we have implemented fully automated workflows that standardize laser ablation and PFIB milling sequences. These workflows incorporate pre-programmed protocols for material removal, alignment, and thinning, reducing user intervention and ensuring consistency across different sample types. Machine learning algorithms further enhance automation by predicting optimal milling strategies and adapting parameters based on material properties and sectioning requirements. This approach significantly improves throughput while maintaining the structural integrity of prepared samples for high-resolution imaging and analysis, including transmission electron microscopy. Beyond sample preparation, our automation platform enables the acquisition of large, high-resolution datasets through serial sectioning, image alignment, and 3D reconstruction. These automated routines facilitate multi-scale characterization, capturing structural and compositional details from the nanoscale to the device level. By reducing variability and increasing efficiency, our automated approach enhances defect analysis, failure diagnostics, and process optimization, accelerating advancements in materials research and device engineering.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Effects of Focused Ion Beam Lithography on La 2– x Sr x CuO 4 Single Crystals

Focused ion beam (FIB) milling is a mask-free lithography technique that allows the precise shaping of 3D materials on the micron and sub-micron scale. The recent discovery of electronic nematicity in La 2–x Sr x CuO 4 (LSCO) thin films triggered the search for the same phenomenon in bulk LSCO crystals. With this motivation, we have systematically explored FIB patterning of bulk LSCO crystals into micro-devices suitable for longitudinal and transverse resistivity measurements. We found that several detrimental factors can affect the result, ultimately compromising the possibility of effectively using FIB milling to fabricate sub-micrometer LSCO devices, especially in the underdoped regime.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Tin–Lead Liquid Metal Alloy Source for Focused Ion Beams

Focused Ion Beam (FIB) systems are increasingly utilized in nanotechnology for nanostructuring, surface modification, doping, and rapid prototyping. Recently, their potential for quantum applications has been explored, leveraging FIB’s direct-write capabilities for in situ single ion implantation, which is crucial for fabricating single photon emitters. Color centers in diamond can function as qubits and are of particular interest due to their capacity to store and transmit quantum information. While Group-IV color centers exhibit high brightness, they require low temperatures to retain coherence. However, lead-vacancy in diamond (PbV) operates at the higher end (4 K) of this temperature spectrum due to larger ground-state splitting, making them particularly interesting. In this context, our study presents results for lead (Pb)-containing alloys with eutectic points below 600 °C and results on using tantalum (Ta) and titanium (Ti) as emitter materials for a Pb liquid metal alloy ion source. We show that a standard FIB system is able to resolve the different Pb isotopes and achieve nanoscale spot sizes, as required for quantum information science applications.

color center↗
DOE OSTI2017

Gravitational Focusing and the Star Cluster Initial Mass Function

We discuss the possibility that gravitational focusing is responsible for the power-law mass function of star clusters N(logM)∝M{sup −1}. This power law can be produced asymptotically when the mass accretion rate of an object depends upon the mass of the accreting body, as M-dot ∝M{sup 2}. Although Bondi–Hoyle–Lyttleton accretion formally produces this dependence on mass in a uniform medium, realistic environments are much more complicated. However, numerical simulations in SPH that allow for sink formation yield such an asymptotic power-law mass function. We perform pure N-body simulations to isolate the effects of gravity from those of gas physics and to show that clusters naturally result with the power-law mass distribution. We also consider the physical conditions necessary to produce clusters on appropriate timescales. Our results help support the idea that gravitationally dominated accretion is the most likely mechanism for producing the cluster mass function.

79 ASTRONOMY AND ASTROPHYSICS↗