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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

Hg-201 (+) CO-Magnetometer for HG-199(+) Trapped Ion Space Atomic Clocks

Local magnetic field strength in a trapped ion atomic clock is measured in real time, with high accuracy and without degrading clock performance, and the measurement is used to compensate for ambient magnetic field perturbations. First and second isotopes of an element are co-located within the linear ion trap. The first isotope has a resonant microwave transition between two hyperfine energy states, and the second isotope has a resonant Zeeman transition. Optical sources emit ultraviolet light that optically pump both isotopes. A microwave radiation source simultaneously emits microwave fields resonant with the first isotope's clock transition and the second isotope's Zeeman transition, and an optical detector measures the fluorescence from optically pumping both isotopes. The second isotope's Zeeman transition provides the measure of magnetic field strength, and the measurement is used to compensate the first isotope's clock transition or to adjust the applied C-field to reduce the effects of ambient magnetic field perturbations.

Burt, Eric A.↗
NASA NTRS2003

Metal Side Reflectors for Trapping Light in QWIPs

Focal-plane arrays of quantum-well infrared photodetectors (QWIPs) equipped with both light-coupling diffraction gratings and metal side reflectors have been proposed, and prototypes are expected to be fabricated soon. The purpose served by the metal side reflectors is to increase quantum efficiency by helping to trap light in the photosensitive material of each pixel. The reasons for using diffraction gratings were discussed in several prior NASA Tech Briefs articles. To recapitulate: In an array of QWIPs, the quantum-well layers are typically oriented parallel to the focal plane and therefore perpendicular or nearly perpendicular to the direction of incidence of infrared light. By virtue of the applicable quantum selection rules, light polarized parallel to the focal plane (as normally incident light is) cannot excite charge carriers and, hence, cannot be detected. Diffraction gratings scatter normally or nearly normally incident light into directions more nearly parallel to the focal plane, so that a significant portion of the light attains a component of polarization normal to the focal plane and, hence, can excite charge carriers. Unfortunately, light scattered in directions parallel or nearly parallel to the focal plane can escape sideways from the QWIP of a given pixel, as illustrated in Figure 1. The escaped light has made only a single pass through the interior photosensitive volume of the QWIP. The quantum efficiency of the QWIP would be increased by trapping light so that it makes multiple passes through the photosensitive volume. As shown in Figure 2, the sides of the QWIP of each pixel would be coated with gold to reflect escaping light back into the interior.

Gunapala, Sarath↗
NASA NTRS2012

Recovering Swift-XRT Energy Resolution through CCD Charge Trap Mapping

The X-ray telescope on board the Swift satellite for gamma-ray burst astronomy has been exposed to the radiation of the space environment since launch in November 2004. Radiation causes damage to the detector, with the generation of dark current and charge trapping sites that result in the degradation of the spectral resolution and an increase of the instrumental background. The Swift team has a dedicated calibration program with the goal of recovering a significant proportion of the lost spectroscopic performance. Calibration observations of supernova remnants with strong emission lines are analysed to map the detector charge traps and to derive position-dependent corrections to the measured photon energies. We have achieved a substantial recovery in the XRT resolution by implementing these corrections in an updated version of the Swift XRT gain file and in corresponding improvements to the Swift XRT HEAsoft software. We provide illustrations of the impact of the enhanced energy resolution, and show that we have recovered most of the spectral resolution lost since launch

Pagani, C.↗
NASA NTRS2012

Calorimetric Low-Temperature Detectors for X-Ray Spectroscopy on Trapped Highly-Charged Heavy Ions

The application of Calorimetric Low-Temperature Detectors (CLTDs) has been proposed at the Heavy-Ion TRAP facility HITRAP which is currently being installed at the Helmholtz Research Center for Heavy Ion Research GSI. This cold ion trap setup will allow the investigation of X-rays from ions practically at rest, for which the excellent energy resolution of CLTDs can be used to its full advantage. However, the relatively low intensities at HITRAP demand larger solid angles and an optimized cryogenic setup. The influence of external magnetic fields has to be taken into account. CLTDs will also be a substantial part of the instrumental equipment at the future Facility for Antiproton and Heavy Ion Research (FAIR), for which a wide variety of high-precision X-ray spectroscopy experiments has been proposed. This contribution will give an overview on the chances and challenges for the application of CLTDs at HITRAP as well as perspectives for future experiments at the FAIR facility.

Kilbourne, Caroline↗
NASA NTRS2013

Design and Testing of a Shell-Flow Hollow-Fiber Venting Gas Trap

A Venting Gas Trap (VGT) was designed, built, and tested at NASA Johnson Space Center to eliminate dissolved and free gas from the circulating coolant loop of the Orion Environmental Control Life Support System. The VGT was downselected from two different designs. The VGT has robust operation, and easily met all the Orion requirements, especially size and weight. The VGT has a novel design with the gas trap made of a five-layer spiral wrap of porous hydrophobic hollow fibers that form a cylindrically shaped curtain terminated by a dome-shaped distal plug. Circulating coolant flows into the center of the cylindrical curtain and flows between the hollow fibers, around the distal plug, and exits the VGT outlet. Free gas is forced by the coolant flow to the distal plug and brought into contact with hollow fibers. The proximal ends of the hollow fibers terminate in a venting chamber that allows for rapid venting of the free gas inclusion, but passively limits the external venting from the venting chamber through two small holes in the event of a long-duration decompression of the cabin. The VGT performance specifications were verified in a wide range of flow rates, bubble sizes, and inclusion volumes. Long-duration and integrated Orion human tests of the VGT are also planned for the coming year.

Bue, Grant C.↗
NASA NTRS2013

A Comparison between High-Energy Radiation Background Models and SPENVIS Trapped-Particle Radiation Models

We have been assessing the effects of background radiation in low-Earth orbit for the next generation of X-ray and Cosmic-ray experiments, in particular for International Space Station orbit. Outside the areas of high fluxes of trapped radiation, we have been using parameterizations developed by the Fermi team to quantify the high-energy induced background. For the low-energy background, we have been using the AE8 and AP8 SPENVIS models to determine the orbit fractions where the fluxes of trapped particles are too high to allow for useful operation of the experiment. One area we are investigating is how the fluxes of SPENVIS predictions at higher energies match the fluxes at the low-energy end of our parameterizations. I will summarize our methodology for background determination from the various sources of cosmogenic and terrestrial radiation and how these compare to SPENVIS predictions in overlapping energy ranges.

high-energy radiation↗
NASA NTRS2013

Next Generation JPL Ultra-Stable Trapped Ion Atomic Clocks

Over the past decade, trapped ion atomic clock development at the Jet Propulsion Laboratory (JPL) has focused on two directions: 1) new atomic clock technology for space flight applications that require strict adherence to size, weight, and power requirements, and 2) ultra-stable atomic clocks, usually for terrestrial applications emphasizing ultimate performance. In this paper we present a new ultra-stable trapped ion clock designed, built, and tested in the second category. The first new standard, L10, will be delivered to the Naval Research Laboratory for use in characterizing DoD space clocks.

Naval Research Laboratory (NRL)↗
NASA NTRS1960

Distribution of Trapped Radiation in the Geomagnetic Field

The altitude dependence (360 to 2090 km) of the intensity of geomagnetically trapped radiation as measured with Explorer I (satellite 1958a) is given for a number of geographic locations. It is found that all intensity data in the vicinity of the magnetic dip equator and over the full range of longitude and of altitude can be represented satisfactorily by a single function of the scalar magnetic field intensity B. The value of B at the lower boundary of the inner zone of trapped radiation is a monotonically increasing function of magnetic dip latitude; such data from all available geographic locations are well represented by a single curve.

Yoshida, Sekiko↗
NASA NTRS2017

Mercury Trapped Ion Frequency Standard for Ultra-Stable Reference Applications

An atomic clock including an ion trap assembly, a C-field coil positioned for generating a first magnetic field in the interrogation region of the ion trap assembly, a compensation coil positioned for generating a second magnetic field in the interrogation region, wherein the combination of the first and second magnetic fields produces an ion number-dependent second order Zeeman shift (Zeeman shift) in the resonance frequency that is opposite in sign to an ion number-dependent second order Doppler shift (Doppler shift) in the resonance frequency, the C-field coil has a radius selected using data indicating how changes in the radius affect an ion-number-dependent shift in the resonance frequency, such that a difference in magnitude between the Doppler shift and the Zeeman shift is controlled or reduced, and the resonance frequency, including the adjustment by the Zeeman shift, is used to obtain the frequency standard.

Burt, Eric A.↗
NASA NTRS2016

Modeling and Simulation of Trapping Mechanisms of Granular Media in Space

This paper describes the modeling and simulation of trapped granular media, within the context of the Granular Imager project. We describe the physics of trapped granular media in space, and the methodologies used to stably confine and shape such a medium using electromagnetic fields. The numerical models have also been validated with results in the literature, obtaining excellent agreement. The results of the numerical tests indicate that it is possible, with structural arrangements of rings and plates at different levels of electrostatic potential, to stably confine one or more charged particles, when driven by voltages that can be modulated in time and space.

Quadrelli, Marco B.↗
NASA NTRSDate not supplied

Rayleigh-Scattering-Based Measurement of 'trapped waves' in High-speed Jets

Recently reported research by others identified a system of waves in the near-exit region of high-speed jets that are different from the well-known Kelvin-Helmholtz waves. In an experimental study, Rayleigh-scattering-based measurement of density fluctuations associated with these waves was used. Simultaneously, a microphone placed near the exit of the jet measured pressure fluctuations associated with the ‘trapped waves’. The pressure fluctuations were observed as a series of peaks in the spectra. Measurements were acquired in high subsonic and under-expanded screeching supersonic flows from a 1-inch diameter convergent nozzle in a free jet facility. The Rayleigh measurement volume was translated throughout the flow field while the microphone was held fixed just outside the flow near the nozzle exit. Even though the signal-to-noise ratio for the Rayleigh data was poor, cross-correlation of density fluctuations with the microphone signal provided some insight into the propagation characteristics of the trapped waves as well as the screech component.

Rayleigh scattering↗
NASA NTRS2004

Comparison of high-energy trapped particle environments at the Earth and Jupiter

The "Van Allen belts" of the trapped energetic particles in the Earth's magnetosphere were discovered by the Explorer I satellite in 1958. In addition, in 1959, it was observed that UHF radio emissions from Jupiter probably had a similar source -- the Jovian radiation belts. In this paper, the global characteristics of these two planets' trapped radiation environments and respective magnetosphere are compared and state-of-the-art models used to generate estimates of high-energy electron and proton populations - the dominate particles in these environments.

Garrett, Henry B.↗
NASA NTRS2021

Trapped Waves and Screech Tones With Various Rectangular Nozzles

This report documents experimental observations made on ‘trapped waves’ occurring with various convergent, rectangular nozzles. Most of the data pertain to three nozzles of aspect ratios (AR) 2, 4 and 8, each having an equivalent diameter of 2.12 in. The trapped waves, manifesting as a series of peaks in the near field pressure fluctuation spectra, are seen with all three nozzles. The number of spectral peaks detected on the major axis is larger than that detected on the minor axis by a factor approximately equal to the AR. These spectral peaks occur in high subsonic conditions and persist into the supersonic regime. Screech tones seem to appear as a continuation of these spectral peaks, i.e., with increasing Mach number it is as if one of these peaks gets amplified and turns into the screech tone. This trend is clearer at smaller AR and gets somewhat obscured at higher AR. Screech frequency variation with Mach number is documented for these and other rectangular nozzles, covering an AR range of 1-16. For larger AR (≥ 3), screech frequency is found to scale on the narrow dimension of the nozzle. Screech staging behavior is more pronounced for smaller AR cases. The screech frequency data for the AR=1 (square) case involves multiple stages similar to that of a round nozzle.

nozzles↗
NASA NTRS2021

Electron Energy Interplay in the Geomagnetic Trap Below the Auroral Acceleration Region

This publication addresses the collisional superthermal electron dynamics below the auroral acceleration region (AAR). This region is the portion of an auroral field line with a field-aligned electric field that leads to the formation of precipitating monoenergetic keV electron fluxes that produce the discrete auroral displays observable from the ground. It is assumed that these precipitating electron fluxes are monoenergetic and accelerated through a potential drop, V, such that these electrons are peaked at an energy E0 = eV, where e is the electron charge. Monoenergetic electrons precipitating into the upper atmosphere degrade to lower energies via many different collisional processes and produce the secondary electron population with energies of 10–100s eV which escapes back to magnetospheric altitudes and becomes geomagnetically trapped between the AAR and the upper ionosphere. The secondary electrons in this geomagnetic trap transfer energy via elastic Coulomb collisions to the thermal electrons. That energy is then returned to the topside ionosphere as heat flux carried by the electron thermal conduction which is essential to maintaining the topside electron temperature.

George V Khazanov↗
NASA NTRSDate not supplied

Comparison of the NAIRAS Trajectory Dose Model With ISS Measurements: Effects of Trapped Particles and Solar Energetic Particle Events.

The NAIRAS(Nowcast of Aerospace Ionizing RAdiation system) model was initially developed for fast computation of GCR and SEP events in the Earth's atmosphere. It was recently improved for computing the effects of trapped particles and its domain of validity was extended to the near space environments, which notably includes the international space station (ISS). To validate the new capabilities of the model, we compared its outputs with some measurements made in the ISS. Historical data contained several SEP events while newer measurements made with the ARMAS instrument flying in the experience bay of KIBO show the influence of trapped particles and GCR over the total dose received.

Guillaume Gronoff↗
NASA NTRS2024

The Peregrine Ion Trap Mass Spectrometer (PITMS) Investigation Development and Pre-Flight Planning

The Peregrine Ion Trap Mass Spectrometer (PITMS) is a mass spectrometer instrument that operated during the Astrobotic Peregrine Mission-1 as part of the NASA Commercial Lunar Payload Services (CLPS) initiative. This paper describes the instrument and investigation design, development, and planning conducted by the PITMS team consisting of a successful partnership between NASA Goddard Space Flight Center (GSFC), The Open University (OU), NASA, and ESA. PITMS was designed to measure the abundance and temporal variability of volatile species in the near-surface lunar exosphere from a landed platform on the lunar surface. The PITMS instrument consisted of an ESA-provided Exospheric Mass Spectrometer (EMS; including sensor, electronics, controller, power supply boards) and a GSFC wrapper that provided structural elements, thermal control, and a deployable dust cover. PITMS was designed to operate as a passive sampler, where ambient gases would enter PITMS through an aperture, diffuse around the mass analyzer cavity, become ionized by electron impact and trapped in a radiofrequency field, then sequentially released to a detector to build a mass spectrum. PITMS was capable of measuring species with a massto-charge ratio (m/z) from 10 to 150 Da, with a mass resolution of approximately 0.5 amu. The PITMS science investigation was planned to be operated by GSFC with an international team of scientists. Though the mission did not achieve its lunar landing, information about the PITMS instrument and planning is provided to be able to understand and effectively use data that will be forthcoming from the investigation.

Barbara Cohen↗
NASA NTRS2024

‘Trapped Wave’ Resonances in Jets From Plug Nozzles

An experimental study is conducted investigating the characteristics of ‘trapped wave’ (TW) resonance tones occurring with nozzles having a center plug. The pressure fluctuation spectral peaks due to these ‘guided’ or ‘trapped’ waves when the nozzle contains a center plug occur at nondimensional frequencies that are an order of magnitude larger than those noted with simple round nozzles. It appears that the exit gap width of the plug nozzle is the characteristic length-scale that dictates the corresponding TW frequencies. The results of this study further our understanding of this phenomenon as it relates to other complex nozzle geometries.

instability↗