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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 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

High efficiency normal conducting linac for environmental water remediation

A continuous wave (CW) electron accelerator for the treatment of industrial streams including an electron beam source, a modified high efficiency slot coupled cavity, at least one focusing magnet positioned surrounding the accelerator to contain the beam in the accelerator, an efficient radio frequency power supply means for supplying power of a radio frequency to the cavity to induce a TM01 accelerating mode in the cavity, an electron beam spreader or raster, a fixed magnet array or two-dimensional scanning magnet for deflecting the accelerated beam into a desired shape, and an exit window for extracting the deflected electron beam. The accelerator includes a graded-beta cavity to enable use with a low-power pulsed electron source. The accelerator benefits from a low wall-power loss accelerating cavity that is energized with efficient RF sources, enabling it to be operated in continuous wave mode.

Hannon, Fay↗
DOE OSTI2017

Small-Size High-Current Generators for X-Ray Backlighting

The paper deals with the soft X-ray backlighting based on the X-pinch as a powerful tool for physical studies of fast processes. Proposed are the unique small-size pulsed power generators operating as a low-inductance capacitor bank. These pulse generators provide the X-pinch-based soft X-ray source (hν = 1–10 keV) of micron size at 2–3 ns pulse duration. The small size and weight of pulse generators allow them to be transported to any laboratory for conducting X-ray backlighting of test objects with micron space resolution and nanosecond exposure time. These generators also allow creating synchronized multi-frame radiographic complexes with frame delay variation in a broad range.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1992

High-efficiency, high-output-power antiguide laser diode arrays

Antiguide laser arrays have been fabricated and operated up to peak pulsed powers of 7.7 W in a beam with a full-width at half-maximum in the main lobe of 0.7 deg. Up to 0.7 W of continuous wave power is emitted into a radiation pattern 2.5 times the diffraction limit. By varying the temperature of the array to vary the operating wavelength of the device, the threshold gain condition of the array modes is altered, allowing thermal tuning of the far field of the device.

Mehuys, D.↗
NASA NTRS2011

Comparison Between MAD-IPA Thrust Stand Measurements and Performance Modeling

The high specific impulse values associated with electric propulsion (EP) that allow for higher payload fractions than conventional, chemical propulsion are achieved by the acceleration of ionized propellant (plasma) by electromagnetic body forces. The lifetime of many EP devices is limited by electrode erosion caused by direct plasma-electrode interaction, while the efficiency is often limited by, among other thruster-specific factors, the available power in space. The efficiency can be increased during higher power operation since the amount of power required to ionize the propellant is fixed and decreases as a percentage of the increased input power. Pulsed inductive plasma accelerators [1-3] are a potentially elegant solution to the problems of high power demands and electrode erosion. The former is addressed in the pulsed nature of these devices, which allows for instantaneous operation on the order of megawatts while requiring a continuous supply on the order of only kilowatts, while the latter is addressed by inductive coupling of the thruster to ionized propellant. These devices operate by rapidly (on the order of microseconds) discharging stored energy at a given pulse repetition rate through a coil creating time-varying magnetic and electric fields that cause ionization, current formation and acceleration of propellant away from the coil. While the inductive (contact-less) nature of the energy transfer from the thruster to the propellant alleviates the problem of erosion and enables the use of in-situ and storable propellants incompatible with metallic electrodes, it places high voltage demands (on the order of tens of kilovolts) on the energy storage system to achieve propellant ionization.

Hallock, Ashley K.↗
DOE OSTI2016

Repetitive operation of an L-band magnetically insulated transmission line oscillator with metal array cathode

We present the repetitive operation research results of an L-band magnetically insulated transmission line oscillator with metal array cathode (MAC-MILO) in this paper. To ensure a more uniform emission of electrons emitted from the cathode, metal plates with different outer radii and thicknesses are periodically arranged in longitudinal direction on the cathode substrate to act as emitters. The higher order mode depressed MILO (HDMILO) structure is applied to ensure stability of the tube. Comparison experiments are carried out between velvet cathode and MAC MILO driven by a 20 GW/40 Ω/40 ns/20 Hz pulse power system. Experimental results reveal that the MAC has much lower outgassing rate, much longer life time, and higher repetitive stability. The MAC-MILO could work stably with a rep-rate up to 20 Hz at a power level of 550 MW when employing a 350 kV/35 kA electric pulse. The TE{sub 11} mode radiation pattern in the farfield region reveals the tube works steadily on the dominant mode. More than 2000 shots have been tested in repetitive mode without any obvious degradation of the detected microwave parameters.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1990

Electron-impact ionization and electron attachment cross sections of radicals important in transient gaseous discharges

Electron-impact ionization and electron attachment cross sections of radicals and excited molecules were measured using an apparatus that consists of an electron beam, a molecular beam and a laser beam. The information obtained is needed for the pulse power applications in the areas of high power gaseous discharge switches, high energy lasers, particle beam experiments, and electromagnetic pulse systems. The basic data needed for the development of optically-controlled discharge switches were also investigated. Transient current pulses induced by laser irradiation of discharge media were observed and applied for the study of electron-molecule reaction kinetics in gaseous discharges.

Lee, Long C.↗
DOE OSTI2015

Investigation of a metallic photonic crystal high power microwave mode converter

It is demonstrated that an L band metallic photonic crystal TEM-TE{sub 11} mode converter is suitable for narrow band high power microwave application. The proposed mode converter is realized by partially filling metallic photonic crystals along azimuthal direction in a coaxial transmission line for phase-shifting. A three rows structure is designed and simulated by commercial software CST Microwave Studio. Simulation results show that its conversion efficiency is 99% at the center frequency 1.58 GHz. Over the frequency range of 1.56-1.625 GHz, the conversion efficiency exceeds 90 %, with a corresponding bandwidth of 4.1 %. This mode converter has a gigawatt level power handling capability which is suitable for narrow band high power microwave application. Using magnetically insulated transmission line oscillator(MILO) as a high power microwave source, particle-in-cell simulation is carried out to test the performance of the mode converter. The expected TE{sub 11} mode microwave output is obtained and the MILO works well. Mode conversion performance of the converter is tested by far-field measurement method. And the experimental result confirms the validity of our design. Then, high power microwave experiment is carried out on a Marx-driven Blumlein water line pulsed power accelerator. Microwave frequency, radiated pattern and power are measured in the far-field region and the results agree well with simulation results. The experiment also reveals that no microwave breakdown or pulse shortening took place in the experimental setup.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Investigating the effective range of vacuum ultraviolet-mediated breakdown in high-power microwave metamaterials

Metamaterials and periodic structures operating under high-power excitations are susceptible to breakdown. It was recently demonstrated that a localized breakdown created in a given region of a periodic structure can facilitate breakdown in other regions of the structure where the intensity of the incident electromagnetic fields may not be high enough to cause breakdown under normal circumstances. It was also demonstrated that this phenomenon is due to the generation of vacuum ultraviolet radiation at the location of the initial discharge, which propagates to the neighboring regions (e.g., other unit cells in a periodic structure) and facilitates the generation of a discharge at a lower incident power level. In this paper, we present the results of an experimental study conducted to determine the effective range of this physical phenomenon for periodic structures that operate in air and in pure nitrogen gas at atmospheric pressure levels. It is demonstrated that when breakdown is induced in a periodic structure using a high-power pulse with a frequency of 9.382 GHz, duration of 0.8 μs, and peak power level of 25 kW, this phenomenon is highly likely to happen in radii of approximately 16–17 mm from the location of the initial discharge under these test conditions. The results of this study are significant in designing metamaterials and periodic structures for high-power microwave applications as they suggest that a localized discharge created in such a periodic structure with a periodicity less than 16–17 mm can spread over a large surface and result in a distributed discharge.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Post-compression of long-wave infrared 2 picosecond sub-terawatt pulses in bulk materials

We have experimentally demonstrated the post-compression of a long-wave infrared (9.2 μm) 150 GW peak power pulse from 2 ps to less than 500 fs using a sequence of two bulk materials with negative group velocity dispersion (GVD). The compression resulted in up to 1.6-fold increase of the peak power and up to 2.8-fold increase of the intensity in the center of a quasi-Gaussian beam. The partial decoupling of the self-phase modulation and chirp compensation stages by using two materials with significantly different ratios of nonlinear refractive index to GVD provides accurate optimization of the compression mechanism and promises a viable path to scaling peak powers to supra-terawatt levels. During the preparatory study, we measured, for the first time to our knowledge, the nonlinear refractive indices of NaCl, KCl, and BaF 2 for picosecond pulses in the long-wave infrared region.

43 PARTICLE ACCELERATORS↗
NASA NTRS1971

Observation of Pulsed Gamma Rays with Energies Greater than 250 keV from the Crab Nebula Pulsar NP 0532

Data from a balloon flight experiment using an Na I scintillation spectrometer were analyzed for gamma ray pulsation. The payload was carried to a nominal atmospheric depth of 3.5 g/cm2. A superposed epoch analysis was performed on a 12,000 second portion of the data spanning a total time interval of 16,700 seconds at float altitude. A positive pulsed contribution was observed at the expected apparent frequency of NP 0532 having the typical double pulse structure. The results indicate a time-averaged pulse photon flux of 0.00144 + or - 0.00057 photons/sq cm/sec in the energy interval from 250 keV to 2.3 MeV. This represents a time-averaged pulsed power of 0.000649 + or - 0.000257 keV/sq cm/sec/keV. The ratio of interpulse to main pulse was found to be 2.4 + or - 1.9. The analysis indicates a positive photon flux from 250 keV to 725 keV of 0.00120 + or - 0.00052 photons/sq cm/sec.

Orwig, L. E.↗
DOE OSTI2018

Narrowing transient testing pulse widths to enhance LWR RIA experiment design in the TREAT facility

The Transient Reactor Test (TREAT) Facility provided thousands of transient irradiations and plays a crucial role in nuclear-heated safety research. The facility’s flexible design and multi-mission nature saw historic experiments for numerous reactor fuels and transient types but was never specifically adapted to address very-brief pulse transients akin to postulated Light Water Reactor (LWR) Reactivity Initiated Accidents (RIA). Since the behaviors of fuel under these conditions depends strongly on energy input duration and resulting cladding time/temperature response under pellet cladding mechanical interactions, this three-year project was conceived to investigate new pulse-narrowing capabilities. Kinetic models showed incremental improvements for minor facility enhancements including increased reactivity step insertions (to initiate the power pulse) and slightly-increased transient rod drive speed for pulse termination (“clipping”). Replacing peak fuel assemblies, repositioning non-transient control rods to hold down the “hot side” of the core, and balancing against required excess reactivity needs, the limiting fuel assembly power can be reduced by ~20 %. Furthermore, this is a remarkable discovery of latent capability in TREAT, not only in enabling the subject capabilities for reduced pulse widths, but also significantly “uprating” the core’s transient energy capacity. Incremental improvements can likely enhance TREAT’s capability into BWR-relevant missions; briefer PWR pulse shapes can only be achieved with an advanced clipping system. Helium-3 ( 3 He) was found to offer the greatest benefits for clipping design and overall performance. A unique concept showed great promise for enabling a 3 He-based system with a reasonable cost; this design concept will likely become the focal point of future work.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2015

Patterned graphene ablation and two-photon functionalization by picosecond laser pulses in ambient conditions

Direct laser writing is a technology with excellent prospects for mask-less processing of carbon-based nanomaterials, because of the wide range of photoinduced reactions that can be performed on large surfaces with submicron resolution. In this paper, we demonstrate the use of picoseconds laser pulses for one-step ablation and functionalization of graphene. Varying the parameters of power, pulse frequency, and speed, we demonstrated the ablation down to 2 μm width and up to mm-long lines as well as functionalization with spatial resolution less than 1 μm with linear speeds in the range of 1 m/s. Raman and atomic-force microscopy studies were used to indicate the difference in modified graphene states and correlation to the changes in optical properties.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

R&D Program for HEP High-Power Targets at Fermilab

A high-power target system is a key beam element to complete future High Energy Physics (HEP) experiments. In the recent past, major accelerator facilities have been limited in beam power not by their accelerators, but by the beam intercepting device survivability. The target must then endure high power pulsed beam, leading to high cycle thermal stresses/pressures and thermal shocks. The increased beam power will also create significant challenges such as corrosion and radiation damage that can cause harmful effects on the material and degrade their mechanical and thermal properties during irradiation. This can eventually lead to the failure of the material and drastically reduce the lifetime of targets and beam intercepting devices. In order to operate reliable beam-intercepting devices in the framework of energy and intensity increase projects of the future, it is essential to develop a strong R&D program and have synergy with various expertise. After presenting the high power targetry challenges facing next generation multi-MW accelerators, we will give an overview of Fermilab’s R&D program in support of High Power Targetry development. The RaDIATE collaboration (Radiation Damage In Accelerator Target Environment), managed by Fermilab, also draws on existing expertise in related fields to execute a coordinated strategy for high power targetry R&D between the 14 international member institutions.

Pellemoine, Frederique [Fermilab]↗
NASA NTRS1990

Pulsed coherent solid-state 1.06-micron and 2.1-micron laser radar systems for remote velocity measurement

A low average power, pulsed, solid-state, 1.06-micron coherent laser radar (CLR) for range and velocity measurements of atmospheric and hard targets has been developed. The system has been operating at a field test site near Boulder, CO since September, 1988. Measurements have been taken on moving targets such as atmospheric aerosol particles, belt sanders, spinning disks, and various stationary targets. The field measurements have shown that this system exhibits excellent velocity measurement performance. A fast-tuning CW Nd:YAG oscillator has also been developed which has a frequency tuning range of greater than 30 GHz (which spans a target radial velocity range of over 16 km/s) and a tuning speed greater than 30 GHz/ms.

Henderson, Sammy W.↗
DOE OSTI2023

High Power Targetry R&D and support for future generation accelerator

A high-power target system is a key beam element to complete future High Energy Physics (HEP) experiments. The target endures high power pulsed beam, leading to high cycle thermal stresses/pressures and thermal shocks. The increased beam power will also create significant challenges such as corrosion and radiation damage that can cause harmful effects on the material and degrade their mechanical and thermal properties during irradiation. This can eventually lead to the failure of the material and drastically reduce the lifetime of targets and beam intercepting devices. Designing a reliable target is already a challenge for MW class facilities today and has led several major accelerator facilities to operate at lower power due to target concerns. With present plans to increase beam power for next generation accelerator facilities in the next decade and the multi-year time-scale to acquire the knowledge on material behavior under such extreme environment, timely R&D of robust high-power targets is critical to fully secure the physics benefits of ambitious accelerator power upgrades. The next generation of high-power targets for future accelerators will use more complex geometries, novel materials, and new concepts allowing better high heat flux cooling methods. Advanced numerical simulations need to be developed to satisfy the physical design requirements of reliable beam-intercepting devices. In parallel, radiation hardened beam instrumentation irradiation methods for high-power targets must be further developed. Additional irradiation facilities are needed since only a few facilities worldwide offer beams for target testing, and the beam provided may not be appropriate for the specific facility or project. Thus, a comprehensive research and development program must be implemented to address the challenges that multi-MW targets face.

Pellemoine, F.↗
NASA NTRS2022

Plasma Activated Water for Crewed Transit and Planetary Habitation: A Study of Gas Type, Electrode Material, and Power Supply Selection and the Impact on the Final Frontier - FY21 CIF

An in-depth study of plasma activated water (PAW) generation was conducted to link changes in power supply, electrode material, input gas, and treatment time to the resulting reaction chemistry. These changes in chemistry can help tailor PAW for different space applications. An AC, DC, and nanosecond (ns) pulsed power supply were each used to generate PAW with stainless steel, copper, tungsten, or platinum (Pt) electrodes while utilizing air, nitrogen (N2), carbon dioxide (CO2), helium (He), or argon (Ar) as the feed gas. Tap or deionized (DI) water was treated for 1 to 15 minutes, and the generated PAW was tested for changes in pH, conductivity, oxidation reduction potential, nitrates (NO3-), ammonium (NH4+), and peroxide. Calculations showed that the production of reactive nitrogen species was the leading cause of pH and conductivity changes. The DC generated air plasma was able to reduce the pH of DI water and generate NO3‑. The pulsed supply, operating at 20% of the input power of the DC supply, lowered the pH generated NO3‑. When a simulated Martian gas mixture of 95% CO2 and 5% N2 was used as the feed gas, NO3‑ was generated with the DC and pulsed supplies, respectively. Mixing PAW with plasma generated ash from inedible biomass allowed pH control, thus enhancing PAW’s potential use for sanitation applications. The large shift in pH was used to study sanitation effects of Escherichia coli (E. coli) reduction and Staphylococcus aureus (S. aureus), in which log reductions were found to be negligible. Additionally, the plasma generated ash in combination with PAW was also implemented in 10-day microgreen growth trials, in which PAW and ash resulted in quicker emergence of the microgreens compared to the standard growth conditions and comparable dry masses to Hoagland’s nutrient solution treated samples.

plasma activated water (PAW)↗