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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

A 5 kA pulsed power supply for inductive and plasma loads in large volume plasma device

This paper describes 5 kA, 12 ms pulsed power supply for inductive load of Electron Energy Filter (EEF) in large volume plasma device. The power supply is based upon the principle of rapid sourcing of energy from the capacitor bank (2.8 F/200 V) by using a static switch, comprising of ten Insulated Gate Bipolar Transistors (IGBTs). A suitable mechanism is developed to ensure equal sharing of current and uniform power distribution during the operation of these IGBTs. Safe commutation of power to the EEF is ensured by the proper optimization of its components and by the introduction of over voltage protection (>6 kV) using an indigenously designed snubber circuit. Various time sequences relevant to different actions of power supply, viz., pulse width control and repetition rate, are realized through optically isolated computer controlled interface.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Multi frame synchrotron radiography of pulsed power driven underwater single wire explosions

We present herein the first use of synchrotron-based phase contrast radiography to study pulsed-power driven high energy density physics experiments. Underwater electrical wire explosions have become of interest to the wider physics community due to their ability to study material properties at extreme conditions and efficiently couple stored electrical energy into intense shock waves in water. The latter can be shaped to provide convergent implosions, resulting in very high pressures (1-10 Mbar) produced on relatively small pulsed power facilities (100s of kA-MA). Multiple experiments have explored single-wire explosions in water, hoping to understand the underlying physics and better optimize this energy transfer process; however, diagnostics can be limited. Optical imaging diagnostics are usually obscured by the shock wave itself; and until now, diode-based X-ray radiography has been of relatively low resolution and rather a broad x-ray energy spectrum. Utilising phase contrast imaging capabilities of the ID19 beamline at the European Synchrotron Radiation Facility, we were able to image both the exploding wire and the shock wave. Probing radiation of 20-50 keV radiographed 200 μm tungsten and copper wires, in ~2-cm diameter water cylinders with resolutions of 8 μm and 32 μm. The wires were exploded by a ~30-kA, 500-ns compact pulser, and 128 radiographs, each with a 100-ps X-ray pulse exposure, spaced at 704 ns apart were taken in each experiment. Abel inversion was used to obtain the density profile of the wires, and the results are compared to two dimensional hydrodynamic and one dimensional magnetohydrodynamic simulations.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

Investigating the Performance of SF6 Replacement Gases to Enable the Next Generation of Pulsed Power

High voltage switches are essential components in pulsed power systems, where consistent and reliable performance is crucial—particularly as the field explores alternatives to SF 6 as an insulating gas. This project examines the self-break voltage distributions of various gases, with a focus on the low-voltage discharges observed in the lower tail of these distributions. Experimental results revealed that the specific housing design influenced the self-break behavior. Among the tested gases, air demonstrated a more favorable overall distribution compared to SF 6 , albeit requiring higher operating pressures. However, air also exhibited a greater likelihood of extremely low-voltage dropouts, raising concerns about its suitability as a direct replacement for SF 6 . Notably, all gases tested showed a higher-than-expected probability of low-voltage events when considering the tail of the distribution rather than the bulk behavior.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Commissioning of a modulated pulse-power magnetron sputtering system for depositing niobium thin films

A modulated pulse-power magnetron sputtering system (MPPMS) was commissioned and used to deposit niobium on copper. MPPMS utilizes a modulated pulse train with high peak-to-average energy ratios, thereby increasing the energy density leading to the production of the energetic ions. The MPPMS modulator was designed and constructed based on large voltage/current IGBT modules, which can be externally modulated, produce bi-polar waveforms, and are readily available. A high voltage power supply provides moderate current to the IGBT module to create the precise pulse structure. The MPPMS system was used to deposit ~1 mm thick, niobium film on a copper substrate held at ~77 K to minimize Nb atom surface diffusion and maximize intrinsic film energy. Finally, the Nb film had an average grain size of ~8 nm.

42 ENGINEERING↗
DOE OSTI2023

Hall interchange instability as a seed for helical magneto-Rayleigh–Taylor instabilities in magnetized liner inertial fusion Z-Pinches scaled from Z-Machine parameters to a next generation pulsed power facility

Magnetized liner inertial fusion (MagLIF) is a magneto-inertial-fusion concept that is studied on the 20-MA, 100-ns rise time Z Pulsed Power Facility at Sandia National Laboratories. Given the relative success of the platform, there is a wide interest in studying the scaled performance of this concept at a next-generation pulsed-power facility that may produce peak currents upward of 60 MA. An important aspect that requires more research is the instability dynamics of the imploding MagLIF liner, specifically how instabilities are initially seeded. It has been shown in magnetized 1-MA thin-foil liner Z-pinch implosion simulations that a Hall interchange instability (HII) effect can provide an independent seeding mechanism for helical magneto-Rayleigh–Taylor instabilities. Here in this paper, we explore this instability at higher peak currents for MagLIF using 2D discontinuous Galerkin PERSEUS simulations, an extended magneto-hydrodynamics code, which includes Hall physics. Our simulations of scaled MagLIF loads show that the growth rate of the HII is invariant to the peak current, suggesting that studies at 20-MA are directly relevant to 60-MA class machines.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Generation of high power pulsed terahertz radiation using a plasmonic photoconductive emitter array with logarithmic spiral antennas

An array of 3 × 3 plasmonic photoconductive terahertz emitters with logarithmic spiral antennas is fabricated on a low temperature (LT) grown GaAs substrate and characterized in response to a 200 fs optical pump from a Ti:sapphire mode-locked laser at 800 nm wavelength. A microlens array is used to split and focus the optical pump beam onto the active area of each plasmonic photoconductive emitter element. Pulsed terahertz radiation with record high power levels up to 1.9 mW in the 0.1–2 THz frequency range is measured at an optical pump power of 320 mW. The record high power pulsed terahertz radiation is enabled by the use of plasmonic contact electrodes, enhancing the photoconductor quantum efficiencies, and by increasing the overall device active area, mitigating the carrier screening effect and thermal breakdown at high optical pump power levels.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Experimental platform for investigations of high-intensity laser plasma interactions in the magnetic field of a pulsed power generator

An experimental platform for the studying of high-intensity laser plasma interactions in strong magnetic fields has been developed based on the 1 MA Zebra pulsed power generator coupled with the 50-TW Leopard laser. The Zebra generator produces 100-300 T longitudinal and transverse magnetic fields with different types of loads. The Leopard laser creates plasma at intensity of 1019 W/cm2 in the magnetic field of coil loads. Focusing and targeting systems are integrated in the vacuum chamber of the pulsed power generator and protected from the plasma debris and strong mechanical shock. The first experiments with plasma at laser intensity >2x1018 W/cm2 demonstrated collimation of the laser produced plasma in the axial magnetic field strength >100 T.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

An Experimental Platform for Pulsed-Power Driven Magnetic Reconnection

We describe a versatile pulsed-power driven platform for magnetic reconnection experiments, based on exploding wire arrays driven in parallel [Suttle, L. G. et al. PRL, 116, 225001]. This platform produces inherently magnetised plasma flows for the duration of the generator current pulse (250 ns), resulting in a long-lasting reconnection layer. The layer exists for long enough to allow evolution of complex processes such as plasmoid formation and movement to be diagnosed by a suite of high spatial and temporal resolution laser-based diagnostics. We can access a wide range of magnetic reconnection regimes by changing the wire material or moving the electrodes inside the wire arrays. We present results with aluminium and carbon wires, in which the parameters of the inflows and the layer which forms are significantly different. By moving the electrodes inside the wire arrays, we change how strongly the inflows are driven. This enables us to study both symmetric reconnection in a range of different regimes, and asymmetric reconnection.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

An experimental platform for pulsed-power driven magnetic reconnection

We describe a versatile pulsed-power driven platform for magnetic reconnection experiments, based on the exploding wire arrays driven in parallel [Suttle et al., Phys. Rev. Lett. 116, 225001 (2016)]. This platform produces inherently magnetised plasma flows for the duration of the generator current pulse (250 ns), resulting in a long-lasting reconnection layer. The layer exists for long enough to allow the evolution of complex processes such as plasmoid formation and movement to be diagnosed by a suite of high spatial and temporal resolution laser-based diagnostics. We can access a wide range of magnetic reconnection regimes by changing the wire material or moving the electrodes inside the wire arrays. We present results with aluminium and carbon wires, in which the parameters of the inflows and the layer that forms are significantly different. By moving the electrodes inside the wire arrays, we change how strongly the inflows are driven. This enables us to study both symmetric reconnection in a range of different regimes and asymmetric reconnection.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Solid-state resistor for pulsed power machines

A flexible solid-state resistor comprises a string of ceramic resistors that can be used to charge the capacitors of a linear transformer driver (LTD) used in a pulsed power machine. The solid-state resistor is able to absorb the energy of a switch prefire, thereby limiting LTD cavity damage, yet has a sufficiently low RC charge time to allow the capacitor to be recharged without disrupting the operation of the pulsed power machine.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Implementing and diagnosing magnetic flux compression on the Z pulsed power accelerator

We report on the progress made to date for a Laboratory Directed Research and Development (LDRD) project aimed at diagnosing magnetic flux compression on the Z pulsed-power accelerator (0-20 MA in 100 ns). Each experiment consisted of an initially solid Be or Al liner (cylindrical tube), which was imploded using the Z accelerator's drive current (0-20 MA in 100 ns). The imploding liner compresses a 10-T axial seed field, B z ( 0 ) , supplied by an independently driven Helmholtz coil pair. Assuming perfect flux conservation, the axial field amplification should be well described by B z ( t ) = B z ( 0 ) x [ R ( 0 ) / R ( t )] 2 , where R is the liner's inner surface radius. With perfect flux conservation, B z ( t ) and dB z / dt values exceeding 10 4 T and 10 12 T/s, respectively, are expected. These large values, the diminishing liner volume, and the harsh environment on Z, make it particularly challenging to measure these fields. We report on our latest efforts to do so using three primary techniques: (1) micro B-dot probes to measure the fringe fields associated with flux compression, (2) streaked visible Zeeman absorption spectroscopy, and (3) fiber-based Faraday rotation. We also mention two new techniques that make use of the neutron diagnostics suite on Z. These techniques were not developed under this LDRD, but they could influence how we prioritize our efforts to diagnose magnetic flux compression on Z in the future. The first technique is based on the yield ratio of secondary DT to primary DD reactions. The second technique makes use of the secondary DT neutron time-of-flight energy spectra. Both of these techniques have been used successfully to infer the degree of magnetization at stagnation in fully integrated Magnetized Liner Inertial Fusion (MagLIF) experiments on Z [P. F. Schmit et al. , Phys. Rev. Lett. 113 , 155004 (2014); P. F. Knapp et al. , Phys. Plasmas, 22 , 056312 (2015)]. Finally, we present some recent developments for designing and fabricating novel micro B-dot probes to measure B z ( t ) inside of an imploding liner. In one approach, the micro B-dot loops were fabricated on a printed circuit board (PCB). The PCB was then soldered to off-the-shelf 0.020- inch-diameter semi-rigid coaxial cables, which were terminated with standard SMA connectors. These probes were recently tested using the COBRA pulsed power generator (0-1 MA in 100 ns) at Cornell University. In another approach, we are planning to use new multi-material 3D printing capabilities to fabricate novel micro B-dot packages. In the near future, we plan to 3D print these probes and then test them on the COBRA generator. With successful operation demonstrated at 1-MA, we will then make plans to use these probes on a 20-MA Z experiment.

47 OTHER INSTRUMENTATION↗
DOE OSTI2018

Dynamics of Power Pulses in a Research Reactor with Neptunium Nuclear Fuel

The current trend in neutron-aided scientific research presupposes the development of new high-intensity pulsed sources. One variant of such an installation could be a pulsed reactor with a fissile-isotope core – {sup 237}Np. The present work is devoted to a study of the dynamics of power pulses of a neptunium reactor taking account of fast temperature feedback during pulse buildup. The problem is reduced to a simple model of a single frequency oscillator combined with the equation of single point kinetics of a reactor neglecting delayed neutrons. It is shown that on the basis of such an approximation, owing to feedback on the temperature of a fuel element the estimated energy of accidental power pulses decreases by almost a factor of 10 compared with a calculation neglecting fast feedback.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1993

INPIStron switched pulsed power for dense plasma pinches

The inverse plasma switch INPIStron was employed for 10kJ/40kV capacitor bank discharge system to produce focused dense plasmas in hypocycloidal-pinch (HCP) devices. A single unit and an array of multiple HCP's were coupled as the load of the pulsed power circuit. The geometry and switching plasma dynamics were found advantageous and convenient for commutating the large current pulse from the low impedance transmission line to the low impedance plasma load. The pulse power system with a single unit HCP, the system A, was used for production of high temperature plasma focus and its diagnostics. The radially running down plasma dynamics, revealed in image converter photographs, could be simulated by a simple snow-plow model with a correction for plasma resistivity. The system B with an array of 8-HCP units which forms a long coaxial discharge chamber was used for pumping a Ti-sapphire laser. The intense UV emission from the plasma was frequency shifted with dye-solution jacket to match the absorption band of the Ti crystal laser near 500 nm. An untuned laser pulse energy of 0.6 J/pulse was obtained for 6.4 kJ/40 kV discharge, or near 103 times of the explosion limit of conventional flash lamps. For both systems the advantages of the INPIStron were well demonstrated: a single unit is sufficient for a large current (greater than 50 kA) without increasing the system impedance, highly reliable and long life operation and implied scalability for the high power ranges above I(sub peak) = 1 MA and V(sub hold) = 100 kV.

Han, Kwang S.↗
DOE OSTI2016

Measuring 20-100 T B-fields using Zeeman splitting of sodium emission lines on a 500 kA pulsed power machine

We have shown that Zeeman splitting of the sodium (Na) D-lines at 5890 and 5896 Å can be used to measure the magnetic field (B-field) produced in high current pulsed power experiments. We have measured the B-field next to a return current conductor in a hybrid X-pinch experiment near a peak current of about 500 kA. Na is deposited on the conductor and then is desorbed and excited by radiation from the hybrid X-pinch. The D-line emission spectrum implies B-fields of about 20 T with a return current post of 4 mm diameter or up to 120 T with a return current wire of 0.455 mm diameter. These measurements were consistent or lower than the expected B-field, thereby showing that basic Zeeman splitting can be used to measure the B-field in a pulsed-power-driven high-energy-density (HED) plasma experiment. We hope to extend these measurement techniques using suitable ionized species to measurements within HED plasmas.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1999

Pulse Power Capability Of High Energy Density Capacitors Based on a New Dielectric Material

A new dielectric composite consisting of a polymer coated onto a high-density metallized Kraft has been developed for application in high energy density pulse power capacitors. The polymer coating is custom formulated for high dielectric constant and strength with minimum dielectric losses. The composite can be wound and processed using conventional wound film capacitor manufacturing equipment. This new system has the potential to achieve 2 to 3 J/cu cm whole capacitor energy density at voltage levels above 3.0 kV, and can maintain its mechanical properties to temperatures above 150 C. The technical and manufacturing development of the composite material and fabrication into capacitors are summarized in this paper. Energy discharge testing, including capacitance and charge-discharge efficiency at normal and elevated temperatures, as well as DC life testing were performed on capacitors manufactured using this material. TPL (Albuquerque, NM) has developed the material and Aerovox (New Bedford, MA) has used the material to build and test actual capacitors. The results of the testing will focus on pulse power applications specifically those found in electro-magnetic armor and guns, high power microwave sources and defibrillators.

Winsor, Paul↗
DOE OSTI2015

High power pulsed magnetron sputtering: A method to increase deposition rate

High power pulsed magnetron sputtering (HPPMS) is a state-of-the-art physical vapor deposition technique with several industrial applications. One of the main disadvantages of this process is its low deposition rate. In this work, the authors report a new magnetic field configuration, which produces deposition rates twice that of conventional magnetron's dipole magnetic field configuration. Three different magnet pack configurations are discussed in this paper, and an optimized magnet pack configuration for HPPMS that leads to a higher deposition rate and nearly full-face target erosion is presented. The discussed magnetic field produced by a specially designed magnet assembly is of the same size as the conventional magnet assembly and requires no external fields. Comparison of deposition rates with different power supplies and the electron trapping efficiency in complex magnetic field arrangements are discussed.

42 ENGINEERING↗
DOE OSTI2024

Radiatively cooled magnetic reconnection experiments driven by pulsed power

We present evidence for strong radiative cooling in a pulsed-power-driven magnetic reconnection experiment. Two aluminum exploding wire arrays, driven by a 20 MA peak current, 300 ns rise time pulse from the Z machine (Sandia National Laboratories), generate strongly driven plasma flows (MA≈7) with anti-parallel magnetic fields, which form a reconnection layer (SL≈120) at the mid-plane. The net cooling rate far exceeds the Alfvénic transit rate (τcool−1/τA−1≫1), leading to strong cooling of the reconnection layer. We determine the advected magnetic field and flow velocity using inductive probes positioned in the inflow to the layer, and inflow ion density and temperature from analysis of visible emission spectroscopy. A sharp decrease in x-ray emission from the reconnection layer, measured using filtered diodes and time-gated x-ray imaging, provides evidence for strong cooling of the reconnection layer after its initial formation. X-ray images also show localized hotspots, regions of strong x-ray emission, with velocities comparable to the expected outflow velocity from the reconnection layer. These hotspots are consistent with plasmoids observed in 3D radiative resistive magnetohydrodynamic simulations of the experiment. X-ray spectroscopy further indicates that the hotspots have a temperature (170 eV) much higher than the bulk layer (≤75 eV) and inflow temperatures (about 2 eV) and that these hotspots generate the majority of the high-energy (>1 keV) emission.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Implementation of Talbot–Lau x-ray deflectometry in the pulsed power environment using a copper X-pinch backlighter

A Talbot–Lau x-ray deflectometer can map electron density gradients in high energy density plasmas, as well as provide information about plasma elemental composition through single-image x-ray refraction and attenuation measurements. A new adaptation to a pulsed power environment used backlighting from copper X-pinches, allowing for electron density mapping of a low-Z object. Even though the X-pinch backlighter is not properly optimized for emitting x-rays in terms of source size and photon fluence, Moire fringe patterns with contrast up to 14% and fringe shift due to refraction on a beryllium object are obtained. Due to the proximity of the deflectometer with the X-pinch (~6 cm), it is shown that a protective filter is required to avoid damage in the closest (i.e., source) grating due to both plasma debris and mechanical shock. Regarding grating survival, these did not show any damage due to the intense magnetic field or heating induced by plasma radiation. Electron density on beryllium was measured with a difference lower than 16%. The areal electron density mapping of the sample was limited by source size characteristics, in similarity to transmission radiography. These results show the potential of plasma electron density as well as material mapping through Talbot–Lau x-ray deflectometry in a pulsed power environment.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗