EFFECT OF ELECTRON IRRADIATION ON THE MECHANICAL PROPERTIES OF A COMPOSITE FOIL FOR INFLATABLE SATELLITES
Electron irradiation effect on mechanical properties of composite foil for inflatable satellites
IRRADIATION↗
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Results for “Radiation effects on electronics”
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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Effects of lithium doping on the behavior of silicon and silicon solar cells
Lithium doped silicon solar cells for improved radiation resistance to neutrons, protons, and electrons
Berman, P. A.↗
Comparison of vibration dissociation coupling and radiative heat transfer models for AOTV/AFE flowfields
A series of detailed studies comparing various vibration dissociation coupling models, reaction systems and rates, and radiative heating models has been conducted for the nonequilibrium stagnation region of an AFE/AOTV vehicle. Atomic and molecular nonequilibrium radiation correction factors have been developed and applied to various absorption coefficient step models, and a modified vibration dissociation coupling model has been shown to yield good vibration/electronic temperature and concentration profiles. While results indicate sensitivity to the choice of vibration dissociation coupling model and to the nitrogen electron impact ionization rate, by proper combinations accurate flowfield and radiative heating results can be obtained. These results indicate that nonequilibrium effects significantly affect the flowfield and the radiative heat transfer. However, additional work is needed in ionization chemistry and absorption coefficient modeling.
Carlson, Leland A.↗
Stimulated emission of AKR in regions of a weakly unstable electron velocity distribution
While, according to the cyclotron maser theory, auroral kilometric radiation generates auroral zone instability whose consequent radiation is in many respects consistent with observations, in situ velocity distribution measurements by satellites show only moderate positive gradients which would be only marginally unstable, implying a low radiation level. Numerical simulations are conducted alternatively using an observed electron-velocity distribution and an idealized loss-cone distribution. The expected amplification of X-mode radiation, as well as effects which go beyond the behavior of a simple amplifying medium, emerge in the results.
Kainer, S.↗
Vibrational and Electronic Energy Transfer and Dissociation of Diatomic Molecules by Electron Collisions
At high altitudes and velocities equal to or greater than the geosynchronous return velocity (10 kilometers per second), the shock layer of a hypersonic flight will be in thermochemical nonequilibrium and partially ionized. The amount of ionization is determined by the velocity. For a trans atmospheric flight of 10 kilometers per second and at an altitude of 80 kilometers, a maximum of 1% ionization is expected. At a velocity of 12 - 17 kilometer per second, such as a Mars return mission, up to 30% of the atoms and molecules in the flow field will be ionized. Under those circumstances, electrons play an important role in determining the internal states of atoms and molecules in the flow field and hence the amount of radiative heat load and the distance it takes for the flow field to re-establish equilibrium. Electron collisions provide an effective means of transferring energy even when the electron number density is as low as 1%. Because the mass of an electron is 12,760 times smaller than the reduced mass of N2, its average speed, and hence its average collision frequency, is more than 100 times larger. Even in the slightly ionized regime with only 1% electrons, the frequency of electron-molecule collisions is equal to or larger than that of molecule-molecule collisions, an important consideration in the low density part of the atmosphere. Three electron-molecule collision processes relevant to hypersonic flows will be considered: (1) vibrational excitation/de-excitation of a diatomic molecule by electron impact, (2) electronic excitation/de-excitation, and (3) dissociative recombination in electron-diatomic ion collisions. A review of available data, both theory and experiment, will be given. Particular attention will be paid to tailoring the molecular physics to the condition of hypersonic flows. For example, the high rotational temperatures in a hypersonic flow field means that most experimental data carried out under room temperatures are not applicable. Also, the average electron temperature is expected to be between 10,000 and 20,000 K. Thus only data for low energy electrons are relevant to the model.
Huo, Winifred M.↗
The Environmental Performance at Low Intensity, Low Temperature (LILT) of High Efficiency Triple Junction Solar Cells
A number of JPL missions, either active or in the p l d g stages, require the accurate LILT flew intensity - low temperate) climate of triple-junction solar. Although triple ignition LILT performance was reported as recently as 2002, there has been an evolutionary advance in cell technology by both U.S. space cell manufacturers that, for mission design purposes, effectively obsoletes the earlier data. As a result, JPL initiated a program to develop a database for the LILT performance of the new high performance triple junction solar cells. JPL obtained Emcore Advanced triple Juntion CIC assemblies and Spectrolab Ultra Triple Junction CIC assemblies. These cells were tested at temperature-intensity ranges designed to cover applications between 1 and 5.18 AU solar distances. 1 MeV electron irradiation from 25 E14 to 1 El5 w were performed on the cells to evaluate the combined effect of particulate radiation and LILT conditions. The effect of LILT conditions was observed to incur an increase in the variation of cell performances such that at simulted 5.18 AU conditions the average performance was approximately 30% with the best cells measuring between 32 and 34% efficiency. The 30% average efficiency compares with approximately 25% average efficiency measured on earlier technology triple junction solar cells.
triple junction↗
Optical Characteristics of Radiated Multifunctional Optical Materials
The performance of optical and electronic materials, and devices are affected significantly in space due to exposure from high energy radiations. We have been investigating the effect of -ray radiations on multifunctional binary and ternary selenide and halide crystals. These materials have shown excellent performance for the wavelength conversion in MWIR and LWIR regions, acousto-optics, and great potential for radiation detection. Crystals with high Z materials such as thallium, mercury and lead based compounds have great potential for the development of a variety of devices and components suitable for space applications. We will report on the characteristics of several halides including mercurous halides (Hg2X2, X= Cl, Br, I), Thallium mercury iodide (Tl4HgI4) and thallium arsenic selenide and thallium gallium selenide, and ternary selenides. These crystals, synthesized with high purity source materials, will be evaluated by studying optical characteristics and measuring resistivity after exposure to a 137Cs -ray source.
Radiation↗
Dynamics of Solar Energetic Particles in Geospace
Solar energetic particles (SEPs) penetrate deep into the geospace and the Earth's atmosphere, initiating nuclear and chemical reactions. These reactions produce secondary hadrons, leptons, and photons, posing radiation hazards at commercial aviation altitudes, particularly during high-latitude flights. During solar particle events, protons with energies above 10 MeV can reach below 100 km altitude, causing ionization that disrupts HF communication and navigation in polar regions. Galactic Cosmic Rays (GCRs) and Solar Energetic Particles (SEPs) pose radiation risks to satellites, astronauts, and ground infrastructure. High-energy particles can lead to single-event effects in spacecraft electronics, such as upsets, latch-ups, and burnouts. These particles also interact with the Earth's atmosphere, generating ionization and secondary particles like hadrons, leptons, and photons, creating hazards for astronauts, especially during extravehicular activities. The work presented in the paper is focused on characterizing the SEP population in geospace in the altitude range starting from that of LEO through MEO and GEO, and up to the magnetopause accounting for the realistic geomagnetic field. The dynamics of SEPs are studied during quiet and geomagnetically active times using Monte Carlo simulations. The paper discusses the variability of the SEP population in geospace in response to geomagnetic activity. The former manifests in the temporal trapping of SEPs in geospace and the suppression of rigidity cutoff during geomagnetic storms.
Valeriy Tenishev↗
The effects of lithium counterdoping on radiation damage and annealing in n(+)p silicon solar cells
Boron-doped silicon n(+)p solar cells were counterdoped with lithium by ion implantation and the resultant n(+)p cells irradiated by 1 MeV electrons. Performance parameters were determined as a function of fluence and a deep level transient spectroscopy (DLTS) study was conducted. The lithium counterdoped cells exhibited significantly increased radiation resistance when compared to boron doped control cells. Isochronal annealing studies of cell performance indicate that significant annealing occurs at 100 C. Isochronal annealing of the deep level defects showed a correlation between a single defect at E sub v + 0.43 eV and the annealing behavior of short circuit current in the counterdoped cells. The annealing behavior was controlled by dissociation and recombination of this defect. The DLTS studies showed that counterdoping with lithium eliminated three deep level defects and resulted in three new defects. The increased radiation resistance of the counterdoped cells is due to the interaction of lithium with oxygen, single vacancies and divacancies. The lithium-oxygen interaction is the most effective in contributing to the increased radiation resistance.
Weinberg, I.↗
Hot electron preheat effects in two-photon polymerization plastic lattice laser-driven shock-tube experiments on the OMEGA laser
We present simulations of Omega shock tube experiments designed to investigate hot electron preheat effects in 3D-printed, two-photon polymerization (2PP) plastic lattices. Preheat is inferred in the experiments from the expansion of a plastic witness disk embedded in the lattice. Using the Eulerian radiation-hydrodynamics code xRAGE, we model shock propagation and preheat from both radiative and hot electron energy sources to evaluate their relative impact. To simulate the transport of laser-generated hot electrons, the nonlocal electron heat transport model proposed by Schurtz, Nicolaï, and Busquet (SNB) is extended with a hot electron source term and an energy cascade algorithm. We explore how variations in ablator, lattice geometry, and laser drive affect the shock velocity and witness disk expansion. Simulations show that the inclusion of a 5 μm gold layer reduces shock pressure by 60% and shock speeds by 30%–40% but does not significantly reduce the hot electron preheat, and that different lattice geometries lead to enhanced shock velocities—up to 40% faster than in homogeneous foams. However, radiative and conductive preheat from classical mechanisms alone fail to match experiment. By including a hot electron source term, we reproduce experimental observables such as disk expansion rates and spatial radiographic features. We find that a hot electron population corresponding to 4%–8% of the incident laser energy with T hot = 50 keV produces expansion which agrees with the experimental data, suggesting hot electron preheat is the most plausible explanation.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Comparative Effects of Radiation Sterilization Modality on Medical PVC Tubing
As the production volume of single-use, polymer-based medical devices increases each year, so does the need for throughput capacity to sterilize the devices. Around 80% of radiation-sterilized devices are processed using gamma-ray radiation from industrial cobalt-60 sources. Supply chain, security, and disposal concerns are prompting manufacturers and contract sterilizers to explore alternatives to irradiation using cobalt-60 gamma-rays, such as electron beam (E-beam) and X-ray radiation. Advantages of these ‘machine’ sources over radioisotope-based sources are that they do not decay, a characteristic that requires cobalt-60 to be replaced over time, they can be turned off when not in use, and they do not represent the same level of concern regarding misuse. One of the barriers to direct transition from gamma-ray sterilization to E-beam or X-ray sterilization is concern over the relatively unknown effects of sterilization dose of these alternative modalities on the performance of medical device polymers. Commercially available medical devices sterilized with gamma-ray irradiation exhibit acceptable device function, acceptable mechanical performance, and acceptable discoloration. To be viable, alternate sterilization methods must not only achieve acceptable sterilization, but the process must also result in a product with functional, mechanical, and visual effects acceptable to customers and the regulator. Flexible polyvinyl chloride (PVC) is a plastic material that is commonly found in single-use medical devices and is known for its sensitivity to radiation processing. For instance, transparent PVC is known to yellow upon irradiation. To encouraging sterilization alternatives to cobalt-60 gamma-ray, we directly compared the effects of gamma-ray, E-beam, and X-ray radiation exposure at similar sterilization-relevant doses on key properties of medical grade PVC tubing.
cobalt-60↗
Enabling Radiation Tolerant Systems for Space
A hazard to all spacecraft orbiting the Earth is the existence of a harsh environment with its subsequent effects. The effects can provide damaging or even disabling effects on spacecraft and its instruments. One of the most recognized and serious of the different space environments is ionizing radiation and its effects on spacecraft and spacecraft systems. This is increasingly becoming more of an issue for all missions due to the use of lighter composite materials, smaller satellites, and smaller electronics. NASA's Space Environments and Effects (SEE) Program was established to develop new plateaus of technical capability to reduce the cost of NASA's missions and provide leading-edge exploratory and focused technology to promote continued U.S. preeminence in space. The SEE Program has an "Implementation Plan" to develop roadmaps and fund technical tasks to enable radiation systems for space.
Kauffman, Billy↗
Charge carrier mobility of halide perovskite single crystals for ionizing radiation detection
Halide perovskites have recently emerged as promising semiconductor materials for several applications including solar cells, light-emitting diodes (LEDs), and radiation detectors. The charge carrier transport properties, which could be evaluated by the mobility-lifetime (mu-tau or μ-г) product, serve an important role for the development of halide perovskites for radiation detection applications. In this perspective, we firstly explain the charge transport mechanism and the limiting factors that determine the intrinsic charge carrier mobility in halide perovskite single crystals. Then, we overview the techniques and methods that have been employed for evaluating the charge carrier mobility (for both electrons and holes). Lastly, we discuss the discrepancy between the experimentally determined carrier mobility from the literature for halide perovskite single crystals and a perspective on future developments for carrier mobility enhancement is provided.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Revealing the Crystalline Architecture of Semicrystalline Ion Exchange Membranes for the Design of Conductive and Durable Alkaline Anion Exchange Membranes
Alkaline anion exchange membrane (AAEM) fuel cells offer a cost-effective alternative to proton exchange membrane (PEM) fuel cells by eliminating the need for expensive precious metal catalysts. In both PEMs and AAEMs, semicrystalline polymers are a common choice, as the crystalline domains can act as mechanical reinforcements that limit swelling and promote mechanical durability in the material. However, spatially resolved characterization of crystalline organization in ion exchange membranes beyond ensemble-averaged X-ray scattering is underrepresented, likely in part due to ionization damage limitations in soft materials. Here, in this study, we resolve the nanometer-size crystallites in semicrystalline ion exchange membranes by applying cryogenic four-dimensional scanning transmission electron microscopy (cryo-4D-STEM) along with data-processing algorithms designed to optimize signals at a low dose to minimize radiation damage. We investigate the effects of synthesis components, including molecular weight and thermal treatment, on a model system of AAEMs in comparison to Nafion, the most commonly used and commercially successful PEM today. We find that excess water uptake in polymer membranes, a property directly associated with weak mechanical durability and with possible negative impacts on ion conductivity, can be reduced by over 30% by varying the polymer's crystalline morphology through changes in synthesis parameters such as molecular weight and thermal history. Our results indicate that this improvement is correlated with smaller crystalline domains with a more homogeneous distribution. More broadly, these results demonstrate how the crystalline architecture of polymer membranes can be tuned through their chemistry and thermal treatment in order to improve their conductivity and durability for commercial fuel cell performance.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Lunar dust and radiation darkening of Surveyor 3 surfaces
Measured spectral reflectance, evidence obtained from photographs, scanning electron microscopy, and previous work on Surveyor hardware were used to develop an understanding of the observed discoloration and its meaning to future space and lunar operations. Measured reflectance data were analyzed to separate and understand the effects of lunar dust and radiation damage. It was concluded that organic contamination is not a major contributor to the discoloration. Radiation-induced discoloration on the various surfaces was found to be proportional to the degree of solar illumination. Photobleaching of the radiation damage was observed and was responsible for a gradual change in the color of the camera's surface during the evaluation.
Carroll, W. F.↗
Connecting radiation-driven changes in structural, thermal, and mechanical properties in several medical device polymers
Stemming from security threats and shortages in supply, a recent push has emerged to develop alternatives to radioisotope Cobalt-60 gamma radiation for sterilization of polymeric medical products, including electron beam (e-beam) and X-ray machine-based sources. However, before large-scale implementation, the effects of these non-isotope-based methods must be thoroughly investigated from several perspectives, involving their potential detrimental effects on the structural, thermal, and mechanical properties of polymers in medical devices. This paper investigates such effects in commonly used medical device polymers, including polypropylene homopolymer (PPH), polyolefin elastomer (POE), low-density polyethylene (LDPE), acrylonitrile butadiene styrene (ABS), and chlorobutyl rubber (CIIR). To connect radiation-driven changes in polymer structural and thermal properties and corresponding changes in mechanical properties, several characterization techniques were utilized, including gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). We found that the tensile strength of X-ray irradiated PPH, as well as X-ray, e-beam, and gamma irradiated CIIR decreases due to chain scission, which is corroborated by GPC and DMA. The GPC results of LDPE suggest chain scission, but interestingly without a corresponding decline in tensile strength. By comparison, POE and ABS appear to undergo further crosslinking with increasing irradiation dose, which generally strengthens them. Importantly, in the vast majority of the cases, there were small to no changes in properties upon changing radiation technologies (at a given dose), i.e., no radiation source dependence. However, in a few specific cases, radiation method dependencies did arise, for instance, in terms of the molecular weight of PPH being significantly increased upon X-ray irradiation, while the melting temperature, glass transition temperature, and elongation at break reduced compared to gamma. Overall, this study provides valuable insight into radiation-driven chemical and structural changes in polymers that produce changes in physical and functional properties.
36 MATERIALS SCIENCE↗
The effects of charged particle and UV radiation on the stability of silvered and aluminized FEP Teflon second surface mirrors
Determining solar absorptance stability of metallized Teflon second surface mirror thermal control coatings as function of electron, proton, and UV radiation dosage
Wappaus, W. A.↗
Radiation Testing Electronics with Heavy Ions-The Best Way to Hit a Target Moving Ever Exponentially Faster
In 1972, when engineers at Hughes Aircraft Corporation discovered that errors in their satellite avionics were being caused by cosmic rays (so-called single-event effects, or SEE), Moore's Law was only 7 years old. Now, more than 45 years on, the scaling that drove Moore's Law for its first 35 years has reached its limits. However, electronics technology continues to evolve exponentially and SEE remain a formidable issue for use of electronics in space. SEE occur when a single ionizing particle passes through a sensitive volume in an active semiconductor device and generates sufficient charge to cause anomalous behavior or failure in the device. Because SEE can occur at any time during the mission, the emphasis of SEE risk management methodologies is ensuring that all SEE modes in a device under test are detected by the test. Because a particle's probability of causing an SEE generally increases as the particle becomes more ionizing, heavy-ion beams have been and remain the preferred tools for elucidating SEE vulnerabilities. In this talk we briefly discuss space radiation environments and SEE mechanisms, describe SEE test methodologies and discuss current and future challenges for use of heavy-ion beams for SEE testing in an era when the continued validity of Moore's law depends on innovation rather than CMOS scaling.
space radiation environments↗