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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Origin of proton irradiation-induced deep acceptors in Al 0.70 Ga 0.30 N

Deep level defect introduction and carrier removal were characterized using steady-state photocapacitance (SSPC), deep level transient spectroscopy (DLTS) and lighted capacitance–voltage for proton irradiated n-type Al 0.70 Ga 0.30 N Schottky diodes grown by metal-organic vapor phase epitaxy on AlN-on-sapphire templates. SSPC observed deep levels in the as-grown diode with zero-phonon transition energies of 2.20, 2.65, 3.10, 3.40, and 4.65 eV relative to the conduction band minimum (E c ), and an additional deep level emerged at 1.20 eV with irradiation. Lighted capacitance–voltage measurements quantified the deep level concentration (N t ) of states detected by SSPC, and it was observed that N t increased with proton fluence only for the 1.2 and 4.65 eV levels. Carrier removal was much larger than the increase in N t of the 1.2 and 4.65 eV deep levels, suggesting that radiation-induced deep level compensators existed beyond what was detected with SSPC. DLTS detected additional, proton-induced deep acceptors at E c —0.55, 0.82, and 1.16 eV, the latter of which is likely the same 1.20 eV deep state observed by SSPC. The concentration of the E c —0.82 eV defect state was large enough to reconcile carrier removal with total deep level introduction. Comparing the E c —0.82 and 1.16 eV deep acceptor levels to previous experimental and theoretical reports suggests that their atomistic origins could be the nitrogen vacancy (V N ) and oxygen substituting on the nitrogen sub-lattice (O N ), respectively. This defect behavior contrasts starkly with GaN, where V N and O N are shallow donors, and demonstrates that the electronic properties of defects can evolve drastically within the AlGaN alloy system ranging from wide bandgap GaN to ultra-wide bandgap AlN.

Armstrong, Andrew Michael [Sandia National Laborat↗
NASA NTRS1985

Photon radiation effects on CdS/CuInSe2 thin film solar cells

The unknown tolerance of CuInSe2 cells to proton irradiation, was tested. It was shown that CdS/CuInSe2 solar cells have an inherent tolerance to irradiation by 1 MeV electrons up to at least 2 x 10 to the 16th power electrons/sq cm. Eleven, unencapsulated, 1 sq cm cells deposited on alumina substrates were irradiated with 1 MeV protons at normal incidence. The cells were exposed to six fluences ranging from 2.5 x 10 to the 10th power protons/sq cm to 5.0 x 10 to the 13th power protons/sq cm. After each interval of exposure, the cells were removed from the radiation chamber to undergo current/voltage characterization. It is shown that none of the cells electrical characteristics exhibited any degradation up to and including a fluence of 1 x 10 to the 11th power protons/sq cm. At fluences greater than this, the damage to the CuInSe2 cells V sub oc and fill factor (FF) was more severe than that exhibited by the Isc. The CuInSe2 cells proved to be approximately a factor of 50 more resistant to 1 MeV proton irradiation than silicon or gallium arsenide cells. Annealing of a CuInSe2 cell at 225 deg C for 6 minutes restored it to within 95% of its initial efficiency.

Dursch, H.↗
NASA NTRS1988

Characterization of production GaAs solar cells for space

The electrical performance of GaAs solar cells was characterized as a function of irradiation with protons and electrons with the underlying goal of producing solar cells suitable for use in space. Proton energies used varied between 50 keV and 10 MeV, and damage coefficients were derived for liquid phase epitaxy GaAs solar cells. Electron energies varied between 0.7 and 2.4 MeV. Cells from recent production runs were characterized as a function of electron and proton irradiation. These same cells were also characterized as a function of solar intensity and operating temperature, both before and after the electron irradiations. The long term stability of GaAs cells during photon exposure was examined. Some cells were found to degrade with photon exposure and some did not. Calibration standards were made for GaAs/Ge solar cells by flight on a high altitude balloon.

Anspaugh, B. E.↗
NASA NTRS1993

Lifetime prediction of materials exposed to the natural space environment

The goal of this study is to model the lifetime of different types of seal materials based on results obtained from accelerated experiments. A semi-mechanistic approach was taken. Thermal aging data were taken from the literature whereas experiments were conducted at Auburn under this contract for selected environments. The seal materials of interest are Silicone 383, Silicone 650, Viton 835, and Viton 747. The relevant conditions include thermal, oxygen, inert gas, vacuum, and gamma radiation. Compression set data available from NASA were used to examine the thermal effect. Experiments were conducted at Auburn University and at NASA to isolate the role of thermal, oxygen, inert gas, vacuum, gamma irradiation, and proton irradiation. A simple discrete stress relaxation method was developed to determine the relaxation response of the elastomers. Dynamic mechanical thermal analysis was also used to characterize the mechanical response of the specimens. These provide a more meaningful correlation between mechanisms and degradation.

Zee, Ralph↗
NASA NTRS1993

Identification and yield of carbonic acid and formaldehyde in irradiated ices

Carbonic acid, (OH)2CO, was tentatively identified in the IR spectrum of a proton irradiated CO2 + H2O ice mixture. In this report, we present additional evidence for a more definitive identification of (OH)2CO with (1) the infrared spectrum of a residue obtained by proton irradiation of CO2 + D2O ice mixture, and (2) the IR spectra of solid phases of formaldehyde (H2CO), acetone (CH3)2CO, and dimethyl carbonate (OCH3)2CO, which are structurally similar to (OH)2CO. IR characteristics (peak frequencies and complex refractive indices of the compounds in point 2) are also reported. In particular, the integrated absorption coefficients for the C-O band for the compounds in point 2 do not vary by more than 20 percent. Based on these values, we estimate the yields of H2CO and (OH)2CO by proton irradiation or ice mixtures. Both H2CO and (OH)2CO are possible irradiation products of cometary and planetary ices.

Dellorusso, Neil↗
NASA NTRS1977

Io's surface and the histories of the Galilean satellites

Similarities and differences among the Galilean satellites are discussed. A hypothesis is offered that the surface of Io is largely covered by 'evaporite' salts produced by defluidization of Io's interior, migration of salt-saturated solutions to Io's surface, and subsequent H2O loss to space. Laboratory reflectance studies show that evaporites constitute a good match to Io's spectrum in the infrared, in contrast to ices or frosts, the presence of which is not considered likely in view of the absence of near IR ice bands in Io's surface spectrum. Likely coloring agents in the blue include elemental sulfur, which may be produced from sulfates by proton irradiation or other processes, and F-centers produced by irradiation with magnetospheric protons. Preferential irradiation of material in the polar regions may account for Io's peculiar dark polar caps.

Fanale, F. P.↗
DOE OSTI2024

Discerning the effect of various irradiation modes on the corrosion of Zircaloy-4

Using proton irradiation, this study investigates the individual influence of several factors on the corrosion kinetics of Zircaloy-4 in a hydrogenated water environment simulating a Pressurized Water Reactor (PWR). Using both simultaneous irradiation-corrosion and autoclave corrosion, we separately examine: (i) the effect of pre-irradiation on modifying the structure of the material, (ii) the impact of irradiation on creating defects in the growing oxide layer during corrosion, and (iii) the influence of irradiation on increasing the corrosion potential through radiolysis during corrosion. To replicate neutron-irradiated microstructure, two proton pre-irradiation schedules were employed: Schedule 1 (isothermal irradiation at 350 °C to 5 dpa) to simulate high-temperature PWR conditions, and Schedule 2 (two-step process: irradiation to 2.5 dpa at -10 °C followed by 2.5 dpa at 350 °C) to simulate lower temperature PWR and Boiling Water Reactor (BWR) conditions. Long-term autoclave corrosion testing over 360 days at 320 °C revealed no significant difference between unirradiated samples and those pre-irradiated according to either schedule, with all samples exhibiting sub-cubic kinetics within the pre-transition regime. Irradiated samples underwent Simultaneous Irradiation Corrosion (SIC) tests, corroding in 320 °C water while being irradiated with protons. Corrosion was found to accelerate in all SIC-tested samples relative to autoclave conditions, with the greatest increase observed in non-pre-irradiated samples. Pre-irradiation with either schedule resulted in a slower corrosion rate compared to non-pre-irradiated regions under SIC conditions. The degree of radiolysis observed in the SIC tests surpassed typical PWR conditions, approaching levels found in BWRs. Radiolysis products were identified as the primary contributors to accelerated corrosion, corroborated by radiolysis bar tests. Furthermore, these findings underscore the intricate interactions between irradiation, corrosion, and water chemistry in determining Zircaloy-4 corrosion kinetics within nuclear reactor environments.

Pressurized Water Reactor↗
NASA NTRS1976

Investigation of the double exponential in the current-voltage characteristics of silicon solar cells

A theoretical analysis is presented of certain peculiarities of the current-voltage characteristics of silicon solar cells, involving high values of the empirical constant A in the diode equation for a p-n junction. An attempt was made in a lab experiment to demonstrate that the saturation current which is associated with the exponential term qV/A2kT of the I-V characteristic, with A2 roughly equal to 2, originates in the space charge region and that it can be increased, as observed on ATS-1 cells, by the introduction of additional defects through low energy proton irradiation. It was shown that the proton irradiation introduces defects into the space charge region which give rise to a recombination current from this region, although the I-V characteristic is, in this case, dominated by an exponential term which has A = 1.

Wolf, M.↗
NASA NTRS2010

Molecular and Histopathological Changes in Mouse Intestinal Tissue After Proton Exposure

Whole body exposure to protons in mice causes significant apoptosis in the crypts of the small intestine. Increasing numbers of crypts contained more apoptotic lesions as the dose of exposure increased. 16 genes associated with apoptotic pathways were shown to have significantly altered expression as compared to control samples for at least one of the doses of proton exposure 1 gene, Trp53inp1, was significantly up-regulated across all three doses. Those animals exposed to 0.1 Gy of proton irradiation showed greater amounts of significant alterations in gene expression as compared to 1 Gy and 2 Gy exposures. The differences in gene expression changes of low and high dose proton irradiated mice may offer insight into the molecular mechanisms of the possible high sensitivity at low proton doses. RAIDD (CRADD) may be responsible for the hypersensitivity observed in the duodenum of mice exposed to low doses of protons. Caspase-1 may also play a role in the hypersensitivity seen following proton irradiation at a dose of 0.1 Gy. FOXO3A may be involved in the down-regulation of GILZ observed at high doses of proton exposure.

Purgason, Ashley↗
NASA NTRS1993

Results of some initial space qualification testing on triple junction a-Si and CuInSe2 thin film solar cells

A series of environmental tests were completed on one type of triple junction a-Si and two types of CuInSe2 thin film solar cells. The environmental tests include electron irradiation at energies of 0.7, 1.0, and 2.0 MeV, proton irradiation at energies of 0.115, 0.24, 0.3, 0.5, 1.0, and 3.0 MeV, post-irradiation annealing at temperatures between 20 C and 60 C, long term exposure to air mass zero (AM0) photons, measurement of the cells as a function of temperature and illumination intensity, and contact pull strength tests. As expected, the cells are very resistant to electron and proton irradiation. However, when a selected cell type is exposed to low energy protons designed to penetrate to the junction region, there is evidence of more significant damage. A significant amount of recovery was observed after annealing in several of the cells. However, it is not permanent and durable, but merely a temporary restoration, later nullified with additional irradiation. Contact pull strengths measured on the triple junction a-Si cells averaged 667 grams, and pull strengths measured on the Boeing CuInSe2 cells averaged 880 grams. Significant degradation of all cell types was observed after exposure to a 580 hour photon degradation test, regardless of whether the cells had been unirradiated or irradiated (electrons or protons). Although one cell from one manufacturer lost approximately 60 percent of its power after the photon test, several other cells from this manufacturer did not degrade at all.

Mueller, Robert L.↗
NASA NTRS2007

Recovery of Electron/Proton Radiation-Induced Defects in n+p AlInGaP Solar Cell by Minority-Carrier Injection Annealing

A high efficient In0.48Ga0.52P/In0.01Ga0.99As/Ge triple junction solar cell has been developed for application in space and terrestrial concentrator PV system [1-3]. Recently, a high conversion efficiency of 31.5% (AM1.5G) has been obtained in InGaP/(In)GaAs/Ge triple junction solar cell, and as a new top cell material of triple junction cells, (Al)InGaP [1] has been proposed to improve the open-circuit voltage (Voc) because it shows a higher Voc of 1.5V while maintaining the same short-circuit current (ISC) as a conventional InGaP top cell under AM1.5G conditions as seen in figure 1 (a). Moreover, the spectral response of 1.96eV AlInGaP cell with a thickness of 2.5..m shows a higher response in the long wavelength region, compared with that of 1.87eV InGaP cell with 0.6..m thickness, as shown in figure 1 (b). Its development will realize next generation multijunction (MJ) solar cells such as a lattice mismatched AlInGaP/InGaAs/Ge 3-junction and lattice matched AlInGaP/GaAs/InGaAsN/Ge 4-junction solar cells. Figure 2 shows the super high-efficiency MJ solar cell structures and wide band spectral response by MJ solar cells under AM1.5G conditions. For realizing high efficient MJ space solar cells, the higher radiation-resistance under the electron or proton irradiation is required. The irradiation studies for a conventional top cell InGaP have been widely done [4-6], but little irradiation work has been performed on AlInGaP solar cells. Recently, we made the first reports of 1 MeV electron or 30 keV proton irradiation effects on AlInGaP solar cells, and evaluated the defects generated by the irradiation [7,8]. The present study describes the recovery of 1 MeV electron / 30 keV proton irradiation-induced defects in n+p- AlInGaP solar cells by minority-carrier injection enhanced annealing or isochronal annealing. The origins of irradiation-induced defects observed by deep level transient spectroscopy (DLTS) measurements are discussed.

Lee, H. S.↗
NASA NTRS1991

Proton and electron damage coefficients for GaAs/Ge solar cells

A series of electron and proton irradiations of GaAs/Ge solar cells has been carried out for the purpose of deriving radiation damage coefficients for GaAs/Ge solar cells. The electron irradiations were performed at energies of 0.6, 1.0, 2.4, and 12 MeV. The proton irradiation energies used were 0.05, 0.2, 0.3, 0.5, 1.0, 3.0, and 9.5 MeV. I-V characteristics were measured before and after each irradiation. Omnidirectional damage coefficients were calculated for both electrons and protons incident on GaAs/Ge solar cells. The calculations were carried out for infinite backshielding on the cells and for eight different thicknesses of coverglass.

Anspaugh, Bruce E.↗
NASA NTRS2016

Radiation Tolerance Studies of Long Wavelength Infrared InAs/GaSb Detectors

In this work we investigated the effect of proton irradiation on the performance of long wavelength infrared (LWIR) InAs/GaSb photodiodes (λ(sub c) = 10.2µm) based on the complementary barrier infrared detector (CBIRD) design. We found that irradiation with 68MeV protons up to the total ionizing dose TID = 200 kRad results in only small (about 15%) decrease of the Quantum Efficiency and does not increase the operational bias of the photodiodes. However, the irradiation causes a significant increase of the dark current from j(sub d) = 5x10(exp -5) A/sq cm at V(sub b) = 0.1V and T = 80K to j(sub d) = 6x10(exp -3) A/sq cm at TID = 200 kRad. This change in the dark current mechanism can be attributed to the onset of surface leakage current, generated by the trap assisted tunneling processes in the proton displacement damage areas near the device sidewalls.

InAs/GaSb photodiodes↗
NASA NTRS1989

Atomic oxygen resistant protective coatings for the Hubble Space Telescope solar array in low earth orbit

The Hubble Space Telescope back-up solar array (BSFR-ATOX) was designed with atomic oxygen resistant materials to replace the original high efficiency cell (HEC) array. Pending qualification of the BSFR-ATOX array, protective coatings for application to the existing HEC array were evaluated. Three polysiloxane-type coating materials, SWS V-10, DC-100, and CV-1144 were evaluated with respect to atomic oxygen resistance, outgassing, contamination potential, stability under UV irradiation, electron-proton irradiation, thermal cycling, and long-term storage after application. Atomic oxygen testing included characterization of the atomic oxygen plasma using comparison of Kapton reaction to existing flight data, residual gas analysis, and temperature measurements. Results from these tests show DC-100 as a greater contamination concern if used in the vicinity of sensitive optical surfaces, i.e., solar cell cover glasses. The SWS V-10 and CV-1144 coatings met all acceptance criteria.

Burns, H. D.↗
NASA NTRS2014

Single-event Effect Report for EPC Series eGaN FETs: Proton Testing for SEE and TNID Effects

Previous testing of the Enhanced Power Conversion (EPC) eGaN FETs showed sensitivity to destructive single-event effects (SEE) effects to heavy ions. The presence of tungsten plugs in the gate area raises concerns that the device may be vulnerable to SEE from protons. Irradiation of biased and unbiased devices with heavy ion has results in some damage suspected of being due to total non-ionizing dose (TNID). Proton irradiation is a better radiation type to study this effect. This study presents the results of testing device with protons for SEE and TNID. No SEE in the EPC2012 device, the most sensitive device to SEE, were seen with 53 MeV protons at several angles. The devices continued to function after 1.5 Mrad (Si) of proton dose with only a slight shift in parameters. These results suggest that gross TNID will not be a factor in using these devices nor suffer from SEE due to protons. However, the device should be tested at with 500 MeV protons to guarantee to immunity proton SEE.

Scheick, Leif↗
NASA NTRS2023

Formation of Amino Acids and Carboxylic Acids in Weakly Reducing Planetary Atmospheres by Solar Energetic Particles from the Young Sun

Life most likely started during the Hadean Eon; however, the environmental conditions which contributed to the complexity of its chemistry are poorly known. A better understanding of various environmental conditions, including global (heliospheric) and local (atmospheric, surface, and oceanic), along with the internal dynamic conditions of the early Earth, are required to understand the onset of abiogenesis. Herein, we examine the contributions of galactic cosmic rays (GCRs) and solar energetic particles (SEPs) associated with superflares from the young Sun to the formation of amino acids and carboxylic acids in weakly reduced gas mixtures representing the early Earth’s atmosphere. We also compare the products with those introduced by lightning events and solar ultraviolet light (UV). In a series of laboratory experiments, we detected and characterized the formation of amino acids and carboxylic acids via proton irradiation of a mixture of carbon dioxide, methane, nitrogen, and water in various mixing ratios. These experiments show the detection of amino acids after acid hydrolysis when 0.5% (v/v) of initial methane was introduced to the gas mixture. In the set of experiments with spark discharges (simulation of lightning flashes) performed for the same gas mixture, we found that at least 15% methane was required to detect the formation of amino acids, and no amino acids were detected in experiments via UV irradiation, even when 50% methane was used. Carboxylic acids were formed in non-reducing gas mixtures (0% methane) by proton irradiation and spark discharges. Hence, we suggest that GCRs and SEP events from the young Sun represent the most effective energy sources for the prebiotic formation of biologically important organic compounds from weakly reducing atmospheres. Since the energy flux of space weather, which generated frequent SEPs from the young Sun in the first 600 million years after the birth of the solar system, was expected to be much greater than that of GCRs, we conclude that SEP-driven energetic protons are the most promising energy sources for the prebiotic production of bioorganic compounds in the atmosphere of the Hadean Earth.

Kensei Kobayashi↗
NASA NTRS2009

Altered Gene Expressions and Cytogenetic Repair Efficiency in Cells with Suppressed Expression of XPA after Proton Exposure

Cellular responses to damages from ionizing radiation (IR) exposure are influenced not only by the genes involved in DNA double strand break (DSB) repair, but also by non- DSB repair genes. We demonstrated previously that suppressed expression of several non-DSB repair genes, such as XPA, elevated IR-induced cytogenetic damages. In the present study, we exposed human fibroblasts that were treated with control or XPA targeting siRNA to 250 MeV protons (0 to 4 Gy), and analyzed chromosome aberrations and expressions of genes involved in DNA repair. As expected, after proton irradiation, cells with suppressed expression of XPA showed a significantly elevated frequency of chromosome aberrations compared with control siRNA treated (CS) cells. Protons caused more severe DNA damages in XPA knock-down cells, as 36% cells contained multiple aberrations compared to 25% in CS cells after 4Gy proton irradiation. Comparison of gene expressions using the real-time PCR array technique revealed that expressions of p53 and its regulated genes in irradiated XPA suppressed cells were altered similarly as in CS cells, suggesting that the impairment of IR induced DNA repair in XPA suppressed cells is p53-independent. Except for XPA, which was more than 2 fold down regulated in XPA suppressed cells, several other DNA damage sensing and repair genes (GTSE1, RBBP8, RAD51, UNG and XRCC2) were shown a more than 1.5 fold difference between XPA knock-down cells and CS cells after proton exposure. The possible involvement of these genes in the impairment of DNA repair in XPA suppressed cells will be further investigated.

Zhang, Ye↗