Search NASA⌕ Search

SEARCH · Search NASA

Results for “electron source”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,567 records · Page 87
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Production of C-14 and Stable Ion Beams at the Argonne Tandem Linac Accelerator System with the ECR3 Ion Source

The Argonne Tandem Linac Accelerator System (ATLAS) at Argonne National Laboratory (ANL) paused production of carbon-14 ion beams with the removal of the Tandem Van de Graaff in 2013. Installation of ECR3, an Electron Cyclotron Resonance Ion Source, returned that production capability to ATLAS, with the first C-14 beam delivered in December 2020. Information is presented on C-14 beam current, gas consumption and N-14 filtering techniques using stripping foils at different sections of ATLAS. ECR3 also fulfilled the operational goal of adding flexibility to ATLAS stable beam production capabilities. Beneficial impacts to ATLAS operation, beam development and experimental programs are discussed.

Scott, R. H.↗
DOE OSTI2020

Electronic Population Transfer via Impulsive Stimulated X-Ray Raman Scattering with Attosecond Soft-X-Ray Pulses

Free electron lasers provide a source of X-ray pulses short enough and intense enough to drive nonlinearities in molecular systems. Impulsive interactions driven by these X-ray pulses provide a way to create and probe valence electron motions with high temporal and spatial resolution. Observing these electronic motions is crucial to understand the role of electronic coherence in chemical processes. A simple nonlinear technique for probing electronic motion, impulsive stimulated X-ray Raman scattering (ISXRS), involves a single impulsive interaction to produce a coherent superposition of electronic states. In this work, we demonstrate electronic population transfer via ISXRS using broad bandwidth (5.5 eV full width at half maximum) attosecond X-ray pulses produced by the Linac Coherent Light Source (LCLS). The impulsive excitation is resonantly enhanced by the oxygen 1s → 2π* resonance of nitric oxide (NO), and excited state neutral molecules are probed with a time-delayed UV laser pulse.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2018

Development of a variable-energy, high-intensity, pulsed-mode ion source for low-energy nuclear astrophysics studies

The primary challenge in directly measuring nuclear reaction rates near stellar energies is their small cross sections. The signal-to-background ratio in these complex experiments can be significantly improved by employing high-current (mA-range) beams and novel detection techniques. Therefore, the electron cyclotron resonance ion source at the Laboratory for Experimental Nuclear Astrophysics underwent a complete upgrade of its acceleration column and microwave system to obtain high-intensity, pulsed proton beams. The new column uses a compression design with O-ring seals for vacuum integrity. Its voltage gradient between electrode sections is produced by the parallel resistance of channels of chilled, deionized water. It also incorporates alternating, transverse magnetic fields for electron suppression and an axially adjustable beam extraction system. Following this upgrade, the operational bremsstrahlung radiation levels and high-voltage stability of the source were vastly improved, over 3.5 mA of target beam current was achieved, and an order-of-magnitude increase in normalized brightness was measured. Beam optics calculations, structural design, and further performance results for this source are presented.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Ion beam emittance from an ECRIS

Simulation of ion beam extraction from an Electron Cyclotron Resonance Ion Source (ECRIS) is a fully 3 dimensional problem, even if the extraction geometry has cylindrical symmetry. Because of the strong magnetic flux density, not only the electrons are magnetized but also the Larmor radius of ions is much smaller than the geometrical dimension of the plasma chamber (Ø 64 × 179 mm). If we assume that the influence of collisions is small on the path of particles, we can do particle tracking through the plasma if the initial coordinates of particles are known. We generated starting coordinates of plasma ions by simulation of the plasma electrons, accelerated stochastically by the 14.5 GHz radio frequency power fed to the plasma. With that we were able to investigate the influence of different electron energies on the extracted beam. Using these assumptions, we can reproduce the experimental results obtained 10 years ago, where we monitored the beam profile with the help of viewing targets. Additionally, methods have been developed to investigate arbitrary 2D cuts of the 6D phase space. To this date, we are able to discuss full 4D information. Currently, we extend our analysis tool towards 5D and 6D, respectively.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS2010

Observing Solar Radio Bursts from the Lunar Surface

Locating low frequency radio observatories on the lunar surface has a number of advantages. Here, we describe the Radio Observatory for Lunar Sortie Science (ROLSS), a concept for a low frequency, radio imaging interferometric array designed to study particle acceleration in the corona and inner heliosphere. ROLSS would be deployed during an early lunar sortie or by a robotic rover as part of an unmanned landing. The prime science mission is to image type II and type III solar radio bursts with the aim of determining the sites at and mechanisms by which the radiating particles are accelerated. Secondary science goals include constraining the density of the lunar ionosphere by searching for a low radio frequency cutoff of the solar radio emissions and constraining the low energy electron population in astrophysical sources. Furthermore, ROLSS serves a pathfinder function for larger lunar radio arrays. Key design requirements on ROLES include the operational frequency and angular resolution. The electron densities in the solar corona and inner heliosphere are such that the relevant emission occurs below 10 MHz, essentially unobservable from Earth's surface due to the terrestrial ionospheric cutoff. Resolving the potential sites of particle acceleration requires an instrument with an angular resolution of at least 2 deg, equivalent to a linear array size of approximately 500 meters. Operations would consist of data acquisition during the lunar day, with regular data downlinks. The major components of the ROLSS array are 3 antenna arms arranged in a Y shape, with a central electronics package (CEP). Each antenna arm is a linear strip of polyimide film (e.g., Kapton (TM)) on which 16 single polarization dipole antennas are located by depositing a conductor (e.g., silver). The arms also contain transmission lines for carrying the radio signals from the science antennas to the CEP.

MacDowall, R. J.↗
NASA NTRS2012

High Angular Resolution Imaging of Solar Radio Bursts from the Lunar Surface

Locating low frequency radio observatories on the lunar surface has a number of advantages, including positional stability and a very low ionospheric radio cutoff. Here, we describe the Radio Observatory on the lunar Surface for Solar studies (ROLSS), a concept for a low frequency, radio imaging interferometric array designed to study particle acceleration in the corona and inner heliosphere. ROLSS would be deployed during an early lunar sortie or by a robotic rover as part of an unmanned landing. The preferred site is on the lunar near side to simplify the data downlink to Earth. The prime science mission is to image type II and type III solar radio bursts with the aim of determining the sites at and mechanisms by which the radiating particles are accelerated. Secondary science goals include constraining the density of the lunar ionosphere by measuring the low radio frequency cutoff of the solar radio emissions or background galactic radio emission, measuring the flux, particle mass, and arrival direction of interplanetary and interstellar dust, and constraining the low energy electron population in astrophysical sources. Furthermore, ROLSS serves a pathfinder function for larger lunar radio arrays. Key design requirements on ROLSS include the operational frequency and angular resolution. The electron densities in the solar corona and inner heliosphere are such that the relevant emission occurs below 10 M Hz, essentially unobservable from Earth's surface due to the terrestrial ionospheric cutoff. Resolving the potential sites of particle acceleration requires an instrument with an angular resolution of at least 2 deg at 10 MHz, equivalent to a linear array size of approximately one kilometer. The major components of the ROLSS array are 3 antenna arms, each of 500 m length, arranged in a Y formation, with a central electronics package (CEP) at their intersection. Each antenna arm is a linear strip of polyimide film (e.g., Kapton(TradeMark)) on which 16 single polarization dipole antennas are located by depositing a conductor (e.g., silver). The arms also contain transmission lines for carrying the radio signals from the science antennas to the CEP. Operations would consist of data acquisition during the lunar day, with data downlinks to Earth one or more times every 24 hours.

MacDowall, Robert J.↗
NASA NTRS2009

The Orbiting Astrophysical Spectrometer In Space (OASIS)

The Orbiting Astrophysical Spectrometer In Space (OASIS) is an Advanced Concept currently understudy at NASA as a mission for the next decade. The goal of the OASIS mission is to identify a local site or sites where galactic cosmic rays (GCR) originate and are accelerated. The mission will allow GCR data to be used to investigate how elements are made and distributed in the galaxy and to improve our understanding of supernovae and the nucleosynthesis of the heavy elements needed for life. OASIS consists of two instruments that provide complementary data on the location and nature of the source(s) through investigating the composition of ultraheavy nuclei and the energy spectrum of electrons. OASIS will measure the relative abundances in the actinide group to determine the age of the r-process material in GCRs. The presence of young r-process material would indicate that GCRs are a sample of the interstellar medium in OB associations. OASIS will follow the electron spectrum to its high-energy end. The energy where this spectrum ends will tell us the distance to the nearest GCR source(s). OASIS will look for spectral features and anisotropy in the high energy electron spectrum that are expected to appear when only a few of the nearest sources can contribute the electron flux. Possibly these measurements will lead to the identification of the nearest cosmic ray electron source.

Christl, Mark J.↗
DOE OSTI2017

Radioactive source calibration test of the CMS Hadron Endcap Calorimeter test wedge with Phase I upgrade electronics

The Phase I upgrade of the CMS Hadron Endcap Calorimeters consists of new photodetectors (Silicon Photomultipliers in place of Hybrid Photo-Diodes) and front-end electronics. The upgrade will eliminate the noise and the calibration drift of the Hybrid Photo-Diodes and enable the mitigation of the radiation damage of the scintillators and the wavelength shifting fibers with a larger spectral acceptance of the Silicon Photomultipliers. The upgrade also includes increased longitudinal segmentation of the calorimeter readout, which allows pile-up mitigation and recalibration due to depth-dependent radiation damage. As a realistic operational test, the responses of the Hadron Endcap Calorimeter wedges were calibrated with a $^{60}$Co radioactive source with upgrade electronics. The test successfully established the procedure for future source calibrations of the Hadron Endcap Calorimeters. Lastly we describe the instrumentation details and the operational experiences related to the sourcing test.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2026

Arabidopsis cytochrome b 5 proteins support fatty acid ω-3 but not ω-6 desaturation

Fatty acids are primary components of lipids, which serve as major energy sources in cells and play essential roles in membrane structure, signaling, and metabolic regulation (Shanklin and Cahoon 1998). The degree of fatty acid unsaturation critically influences lipid physicochemical properties, thereby affecting membrane fluidity and biological function (Nguyen et al. 2019). In Arabidopsis thaliana, fatty acid desaturation occurs via 2 parallel pathways: the “prokaryotic pathway” in plastids, involving glycosylglycerides, such as monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), and phospholipid phosphatidylglycerol (PG); and the “eukaryotic pathway” in the endoplasmic reticulum (ER), involving phosphatidylcholine (PC) (Lou et al. 2014) (Supplementary Figure S1). Seven fatty acid desaturases (FADs) in Arabidopsis differentially desaturate each glycerolipid class in the plastid and ER (Nguyen et al. 2019). FAD2, an ER-resident ω-6 fatty acid desaturase, catalyzes the conversion of oleic acid (18:1) to linoleic acid (18:2), which can be further desaturated to α-linolenic acid (18:3) by FAD3, an ER-resident ω-3 fatty acid desaturase. In plastids, FAD6 catalyzes the desaturation of 18:1/16:1 to produce 18:2/16:2, while FAD7 and FAD8 redundantly convert 18:2/16:2 to 18:3/16:3 (Li-Beisson et al. 2013; Nguyen et al. 2019). Additionally, fatty acids synthesized in the ER can also be reimported into plastids to their site of de novo synthesis (Xu et al. 2010). All FADs require reducing power, in the form of 2 electrons, for catalysis, but the sources of the electrons vary between their subcellular localizations. In the ER, FAD2 and FAD3 receive electrons from a cytochrome b 5 (CB5)-based electron transfer chain comprising cytochrome b 5 reductase (CBR) and CB5. In contrast, ferredoxin serves as the electron donor for plastid-localized FAD6, FAD7, and FAD8 (Ohlrogge and Browse 1995; Andreu et al. 2007). While the relative contributions of the 2 pathways to total cellular desaturation products vary across tissues and species, most polyunsaturated FA biosynthesis in seeds occurs via ER-resident FAD2 and FAD3 (Miquel and Browse 1992; Ohlrogge and Browse 1995).

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Near-Threshold Photoemission from Graphene-Coated Cu(110)

In this article, the brightness of electron beams emitted from photocathode sources plays a critical role in determining the performance of x-ray free-electron lasers and ultrafast electron-diffraction applications. In order to achieve the maximum brightness, the electrons need to be emitted from a photocathode with the lowest-possible mean transverse energy (MTE). Recent investigations have shown that capping a Cu(110) photocathode with a monolayer of graphene can protect the quantum efficiency (QE) from long-term exposure to varying vacuum conditions. However, there have been no studies that investigate the effects that a monolayer of graphene has on the MTE. Here, we report on measurements of a graphene-coated Cu(110) single crystal near the photoemission threshold for room and liquid-nitrogen temperatures. At room temperature, a minimum MTE of 25 meV is measured at 295 nm. At liquid-nitrogen temperatures, a minimum MTE of 9 meV is measured at the photoemission threshold of 290 nm.

36 MATERIALS SCIENCE↗
DOE OSTI2015

An ultrafast nanotip electron gun triggered by grating-coupled surface plasmons

We demonstrate multiphoton photoelectron emission from gold nanotips induced by nanofocusing surface plasmons, resonantly excited on the tip shaft by a grating coupler. The tip is integrated into an electron gun assembly, which facilitates control over the spatial emission sites and allows us to disentangle direct grating emission from plasmon-triggered apex emission. The nanoscale source size of this electron gun concept enables highly coherent electron pulses with applications in ultrafast electron imaging and diffraction.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2026

Energy response characterization of current-mode MeV Cherenkov aerogel detectors

Current-mode Cherenkov aerogel detectors have been used to measure time resolved spectra of MeV radiographic x-ray sources and have been considered to replace gas Cherenkov systems. The simulations of the Cherenkov response of aerogel detectors have uncertainties in how to model the complex structure of aerogels. Data from three sites—the Idaho electron beam, the Los Alamos Site electron beam and microtron sources at Los Alamos—have been used to calibrate the relative energy response of 15 aerogels, varying in density from 10 to 430 mg/cm 3 , from incident electrons with energies from 1 to 12 MeV. Detector simulations need to introduce density variation in the aerogels to match the collected data.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1985

Positive ion composition and derived particle heating in the lower auroral ionosphere

Two E11a rocket flights in salvo B (launched on November 16, 1980) and A2 (launched on November 30, 1980), which provide positive ion composition, total and partial ion density, and electron density in the altitude range 60-170 km above Kiruna under conditions of moderate and strong magnetic disturbance, are examined. It is shown that the ionization sources are predominantly precipitating electrons in salvo B and precipitating protons in salvo A2. Under winter-time auroral conditions the characteristics of the positive ion composition are large NO(+)/O2(+) density ratios, with maximum values of 20 at 118 km in salvo B and 100 at 100 km in salvo A2, respectively. The transition from NO(+) to proton hydrates is found at an altitude of 79 km in salvo B and 76 km in salvo A2. The calculated O(+) and N(+) densities are in good agreement with model calculations and from these calculations it is concluded that 28(+) is mainly N2(+) above 110 km in salvo B and above 105 km in salvo A2, and Si(+) below these altitudes. By altitude integration of the ion-electron pair production, the energy flux of precipitating particles is found to have values of 0.85 mW/sq m and 1.0 mW/sq m in salvoes B and A2, respectively.

Kopp, E.↗
DOE OSTI2015

Cryogenic Considerations for Superconducting Magnet Design for the Material Plasma Exposure eXperiment

In order to determine long term performance of plasma facing components such as diverters and first walls for fusion devices, next generation plasma generators are needed. A Material Plasma Exposure eXperiment (MPEX) has been proposed to address this need through the generation of plasmas in front of the target with electron temperatures of 1-15 eV and electron densities of 1020 to 1021 m-3. Heat fluxes on target diverters could reach 20 MW/m2. In order generate this plasma, a unique radio frequency helicon source and heating of electrons and ions through Electron Bernstein Wave (EBW) and Ion Cyclotron Resonance Heating (ICRH) has been proposed. MPEX requires a series of magnets with non-uniform central fields up to 2 T over a 5m length in the heating and transport region and 1 T uniform central field over a 1-m length on a diameter of 1.3 m. Given the field requirements, superconducting magnets are under consideration for MPEX. In order to determine the best construction method for the magnets, the cryogenic refrigeration has been analyzed with respect to cooldown and operational performance criteria for open-cycle and closed-cycle systems, capital and operating costs of these system, and maturity of supporting technology such as cryocoolers. These systems will be compared within the context of commercially available magnet constructions to determine the most economical method for MPEX operation. The current state of the MPEX magnet design including details on possible superconducting magnet configurations will be presented.

Duckworth, Robert C↗
DOE OSTI2015

X-Ray Comb Generation from Nuclear-Resonance-Stabilized X-Ray Free-Electron Laser Oscillator for Fundamental Physics and Precision Metrology

An x-ray free-electron laser oscillator (XFELO) is a next-generation x-ray source, similar to free-electron laser oscillators at VUV and longer wavelengths but using crystals as high-reflectivity x-ray mirrors. Each output pulse from an XFELO is fully coherent with high spectral purity. The temporal coherence length can further be increased drastically, from picoseconds to microseconds or even longer, by phase-locking successive XFELO output pulses, using the narrow nuclear resonance lines of nuclei such as Fe-57 as a reference. We show that the phase fluctuation due to the seismic activities is controllable and that due to spontaneous emission is small. The fluctuation of electron-bunch spacing contributes mainly to the envelope fluctuation but not to the phase fluctuation. By counting the number of standing-wave maxima formed by the output of the nuclear-resonance-stabilized (NRS) XFELO over an optically known length, the wavelength of the nuclear resonance can be accurately measured, possibly leading to a new length or frequency standard at x-ray wavelengths. A NRS-XFELO will be an ideal source for experimental x-ray quantum optics as well as other fundamental physics. The technique can be refined for other, narrower resonances such as Ta-181 or Sc-45.

Adams, B. W.↗
NASA NTRS2000

Deep Space Systems Technology Program Future Deliveries

NASA is in a period of frequent launches of low cost deep space missions with challenging performance needs. The modest budgets of these missions make it impossible for each to develop its own technology, therefore, efficient and effective development and insertion of technology for these missions must be approached at a higher level than has been done in the past. The Deep Space Systems Technology Program (DSST), often referred to as X2000, has been formed to address this need. The program is divided into a series of "Deliveries" that develop and demonstrate a set of spacecraft system capabilities with broad applicability for use by multiple missions. The First Delivery Project, to be completed in 2001, will provide a one MRAD-tolerant flight computer, power switching electronics, efficient radioisotope power source, and a transponder with services at 8.4 GHz and 32 GHz bands. Plans call for a Second Delivery in late 2003 to enable complete deep space systems in the 10 to 50 kg class, and a Third Delivery built around Systems on a Chip (extreme levels of electronic and microsystems integration) around 2006. Formulation of Future Deliveries (past the First Delivery) is ongoing and includes plans for such developments as highly miniaturized digital/analog/power electronics, optical communications, multifunctional structures, miniature lightweight propulsion, advanced thermal control techniques, highly efficient radioisotope power sources, and a unified flight ground software architecture to support the needs of future highly intelligent space systems. All developments are targeted at broad applicability and reuse, and will be commercialized within the US.

Salvo, Christopher G.↗
DOE OSTI2016

Microstructural analysis of recycled concrete using X-ray microtomography

This paper reports an investigation of the recycled concrete (RC) microstructure using synchrotron microtomography (μCT) at the Advanced Light Source combined with Scanning Electron Microscopy analysis. The study evaluated the influence of 50% of recycled concrete aggregate (RCA) and its water absorption compensation on the RC microstructure. The following variables were studied: a) the compressive strength of the original concrete used to obtain the RCA (40 and 80 MPa) and b) the initial moisture condition of the RCA (Saturated Surface Dry and Oven Dry). The microtomographic images showed the mixtures cast with RCA in the dry condition developed an evident macropore network surrounding the RCA particle that was not observed in the mixtures using RCA in the SSD condition. SEM images confirmed the initial findings from μCT and showed that the thickness of the interfacial transition zone in RC is in the same order of magnitude as the reference concrete.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Effect of THz-bandwidth incoherent laser radiation on bulk damage in potassium dihydrogen phosphate crystals

Abstract The laser-damage performance characteristics of potassium dihydrogen phosphate (KDP) samples under exposure to a distinctive broadband incoherent laser pulse are investigated. A laser system providing such pulses is intended to explore improved energy-coupling efficiency on the target in direct-drive inertial confinement fusion experiments and provides incoherent bandwidths as large as 10 THz in a nanosecond pulse. A consequence of this bandwidth is very rapid fluctuations in intensity capable of reaching maxima much larger than the average intensity within the pulse. A custom damage-test station has been built to perform measurements with broadband incoherent pulses in order to determine what effect these fast and high-intensity oscillations have on laser damage. A set of experiments under different bandwidth and beam configurations shows the effect to be minimal when probing bulk damage in KDP. Modeling indicates this behavior is supported by long electron-relaxation times compared to the source-field fluctuations, following excitation of individual electrons in the conduction band. The results help better understand the laser-induced–damage mechanisms in KDP, and its ability to operate in broadband temporally incoherent high-energy lasers that may be particularly suitable for future laser-fusion energy systems.

36 MATERIALS SCIENCE↗