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All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Hanford Site Composite Analysis Special Analysis: P2R Model Predictive Contaminant Transport Simulations - Sensitivity Case

This environmental calculation file (ECF) documents the methodologies, assumptions, and results of predictive fate and transport simulations using the Plateau-to-River (P2R) model. This ECF supports the reevaluation of the representativeness of solid-waste radionuclide inventory and release rate from three solid waste sites included in the recently completed Hanford Site Composite Analysis (CA) (DOE-RL-2019-52, Composite Analysis for Low-Level Waste Disposal in the Hanford Site Central Plateau (FY 2020)). Specifically, this ECF supports the reevaluation of the representativeness of the base case inventory and radionuclide waste release rates from three solid waste sites (i.e., 218-E-12B, 218-W-3A and 218-W-3AE) and two radionuclides (carbon-14 [C-14] and technetium [Tc-99]). These three waste sites and two radionuclides were identified as being the most significant contributors to groundwater contamination and dose in the CA at time periods after the compliance period. The release rates and footprints of the releases from the vadose zone are implemented in the fate and transport modeling utilizing the HSS package.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1993

Upgrading NASA/DOSE laser ranging system control computers

Laser ranging systems now managed by the NASA Dynamics of the Solid Earth (DOSE) and operated by the Bendix Field Engineering Corporation, the University of Hawaii, and the University of Texas have produced a wealth on interdisciplinary scientific data over the last three decades. Despite upgrades to the most of the ranging station subsystems, the control computers remain a mix of 1970's vintage minicomputers. These encompass a wide range of vendors, operating systems, and languages, making hardware and software support increasingly difficult. Current technology allows replacement of controller computers at a relatively low cost while maintaining excellent processing power and a friendly operating environment. The new controller systems are now being designed using IBM-PC-compatible 80486-based microcomputers, a real-time Unix operating system (LynxOS), and X-windows/Motif IB, and serial interfaces have been chosen. This design supports minimizing short and long term costs by relying on proven standards for both hardware and software components. Currently, the project is in the design and prototyping stage with the first systems targeted for production in mid-1993.

Ricklefs, Randall L.↗
DOE OSTI2024

Effects of Proton Irradiation on the Performance of Skipper CCDs

Skipper CCDs are a mature detector technology that has been suggested for future space telescope instruments requiring sub-electron readout noise in the near-ultraviolet to the near-infrared. While modern skipper CCDs inherit from the radiation-tolerant p-channel detectors developed by LBNL, the effects of high doses of ionizing radiation on skipper CCDs (such as those expected in space) remains largely unmeasured. We report preliminary results on the performance of p-channel skipper CCDs following irradiation with 217-MeV protons at the Northwestern Medicine Proton Center. The total nonionizing energy loss (NIEL) experienced by the detectors exceeds 6 years at the Sun-Earth Lagrange Point 2 (L2). We demonstrate that the skipper amplifier continues to function as expected following this irradiation. Owing to the low readout noise of these detectors, controlled irradiation tests can be used to sensitively characterize the charge transfer inefficiency, dark current, and the density and time constants of charge traps as a function of proton fluence. We conclude with a brief outlook toward future tests of these detectors at other proton and gamma-ray facilities.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Assessment of Baseline Monitoring Data for the Remote-Handled Low-Level Waste Disposal Facility at Idaho National Laboratory

The purpose of this document is to summarize environmental monitoring data collected at the Remote-Handled Low-Level Waste (RHLLW) Disposal Facility during the first four years of facility operations (FY 2019 through FY 2022). This summary provides a “baseline” condition for the facility, which can be used to distinguish contaminant releases from the RHLLW Disposal Facility from pre existing contamination as well as potential future releases from other sources (i.e., upgradient aquifer sources), as specified in the facility monitoring plan. Sufficient data has been collected over the first four years of operation of the RHLLW Disposal Facility to establish baseline conditions for future compliance monitoring of aquifer wells and performance monitoring of vadose zone lysimeters. Except for seven elevated tritium measurements from lysimeter HFEF-South believed to have been impacted by waste disposals, all data was deemed appropriate for establishing baseline concentrations. Monitoring of the aquifer detected indicator analytes gross alpha and gross beta and target analytes tritium and C-14. There were a few C-14 detections prior to an increase in the required detection level (RDL) after the first round of sampling. I-129 and Tc-99 were not detected above RDLs in aquifer samples. Lysimeter samples detected indicator analytes gross alpha and gross beta and target analyte tritium. Target analytes C-14, I-129, and Tc-99 were not detected above RDLs in lysimeter samples. Except for tritium, baseline concentrations of indicator and target analytes measured during the first four years of RHLLW facility operations are expected to represent conditions through the expected 20 year operating period of the facility. Elevated tritium in the aquifer, a result of past discharges of tritium at upgradient facilities, showed a decline over the first four years of operations, and levels are expected to continue to decline with time as a result of dilution and decay. Current tritium levels in lysimeter samples may be elevated due to tritium in the water applied during construction and infiltration testing of the facility. As a result, tritium concentrations in lysimeters may decline with time as a result of dilution and decay. Statistical measures (i.e., mean, standard deviation, and 99% upper confidence level [UCL]) were calculated for all detected analytes using the four years of concentration data. These measures will be used to evaluate future monitoring results and to demonstrate the facility is performing, or not performing, as established in the facility performance assessment (PA). Future monitoring results will also be combined with the baseline data in this report to further establish temporal trends and natural variability in the measurements. Based on the data collected during the baseline period, it is recommended the gross alpha action level for performance monitoring increase from 10 to 20 pCi/L due to several baseline measurements exceeding the preliminary action level of 10. An action level of 20 pCi/L is slightly greater than the 99% UCL, is protective of the aquifer, and would reduce unnecessary sampling. It is also recommended that tritium be added to the lysimeter analyte list for post-baseline period monitoring. Tritium, while not a dose concern, is a good tracer that can provide valuable information on water flow in and around the RHLLW Disposal Facility. Recommendations for a tritium action level are provided if considered necessary.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

Effect of radiation-induced defects on the superfluid density and optical conductivity of overdoped La 2 - x Sr x CuO 4

Using a combination of time-domain THz spectroscopy (TDTS) and mutual inductance measurements, we have investigated the low-energy electrodynamic response of overdoped La$_{2-x}$Sr$_x$CuO$_4$ films that have been exposed to ion irradiation. Films went through three rounds of irradiation (2, 4, and 6 $\times 10^{13}$ ions/cm$^2$) and mututal inductance and TDTS experiments were performed between each step. Together with the as-grown film, this gives four different levels of disorder. The transport scattering rate that is measured directly in the THz experiments is an approximately linear function of the radiation dose at all temperatures. This is consistent with a proportionate increase in elastic scattering from point-like 2D disorder. Here, in the superconducting state we find that the relation between T$_c$, the superfluid density, and the scattering rates are quantitatively at odds with the predictions based on the extant theory of Abrikosov-Gorkov-like pair breaking in a dirty d-wave superconductor. Increasing disorder causes only a small change in T$_c$ for the overdoped films, but the changes to the $\omega \sim 0$ superfluid density are much larger.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS2015

Shields-1, A SmallSat Radiation Shielding Technology Demonstration

The NASA Langley Research Center Shields CubeSat initiative is to develop a configurable platform that would allow lower cost access to Space for materials durability experiments, and to foster a pathway for both emerging and commercial-off-the-shelf (COTS) radiation shielding technologies to gain spaceflight heritage in a relevant environment. The Shields-1 will be Langleys' first CubeSat platform to carry out this mission. Radiation shielding tests on Shields-1 are planned for the expected severe radiation environment in a geotransfer orbit (GTO), where advertised commercial rideshare opportunities and CubeSat missions exist, such as Exploration Mission 1 (EM-1). To meet this objective, atomic number (Z) graded radiation shields (Zshields) have been developed. The Z-shield properties have been estimated, using the Space Environment Information System (SPENVIS) radiation shielding computational modeling, to have ~30% increased shielding effectiveness of electrons, at half the thickness of a corresponding single layer of aluminum. The Shields-1 research payload will be made with the Z-graded radiation shields of varying thicknesses to create dose-depth curves to be compared with baseline materials. Additionally, Shields-1 demonstrates an engineered Z-grade radiation shielding vault protecting the systems' electronic boards. The radiation shielding materials' performances will be characterized using total ionizing dose sensors. Completion of these experiments is expected to raise the technology readiness levels (TRLs) of the tested atomic number (Z) graded materials. The most significant contribution of the Z-shields for the SmallSat community will be that it enables cost effective shielding for small satellite systems, with significant volume constraints, while increasing the operational lifetime of ionizing radiation sensitive components. These results are anticipated to increase the development of CubeSat hardware design for increased mission lifetimes, and enable out of low earth orbit (LEO) missions by using these tested material concepts as shielding for sensitive components and new spaceflight hardware

Thomsen, D. Laurence, III↗
NASA NTRS1986

Cadmium-induced accumulation of putrescine in oat and bean leaves

The effects of Cd2+ on putrescine (Put), spermidine (Spd), and spermine (Spm) titers were studied in oat and bean leaves. Treatment with Cd2+ for up to 16 hours in the light or dark resulted in a large increase in Put titer, but had little or no effect on Spd or Spm. The activity of arginine decarboxylase (ADC) followed the pattern of Put accumulation, and experiments with alpha-difluoromethylarginine established that ADC was the enzyme responsible for Put increase. Concentrations of Cd2+ as low as 10 micromolar increased Put titer in oat segments. In bean leaves, there was a Cd(2+)-induced accumulation of Put in the free and soluble conjugated fractions, but not in the insoluble fraction. This suggests a rapid exchange between Put that exists in the free form and Put found in acid soluble conjugate forms. It is concluded that Cd2+ can act like certain other stresses (K+ and Mg2+ deficiency, excess NH4+, low pH, salinity, osmotic stress, wilting) to induce substantial increases in Put in plant cells.

NASA Discipline Plant Biology↗
NASA NTRS1993

Time Course of the Response of Myofibrillar and Sarcoplasmic Protein Metabolism to Unweighting of the Soleus Muscle

Contributions of altered in vivo protein synthesis and degradation to unweighting atrophy of the soleus muscle in tail-suspended young female rats were analyzed daily for up to 6 days. Specific changes in myofibrillar and sarcoplasmic proteins were also evaluated to assess their contributions to the loss of total protein. Synthesis of myofibrillar and sarcoplasmic proteins was estimated by intramuscular (IM) injection and total protein by intraperitoneal (IP) injection of flooding doses of H-3-phenylaianine. Total protein loss was greatest during the first 3 days following suspension and was a consequence of the loss of myofibrillar rather than sarcoplasmic proteins. However, synthesis of total myofibrillar and sarcoplasmic proteins diminished in parallel beginning in the first 24 hours. Therefore sarcoplasmic proteins must be spared due to a decrease in their degradation. In contrast, myofibrillar protein degradation increased, thus explaining the elevated degradation of the total pool. Following 72 hours of suspension, protein synthesis remained low, but the rate of myofibrillar protein loss diminished, suggesting a slowing of degradation. These various results show acute loss of protein during unweighting atrophy is a consequence of decreased synthesis and increased degradation of myofibrillar proteins, and sarcoplasmic proteins are spared due to slower degradation, likely explaining the sparing of plasma membrane receptors. Based on other published data, we propose that the slowing of atrophy after the initial response may be attributed to an increased effect of insulin.

Munoz, Kathryn A.↗
NASA NTRS2001

Monte Carlo track structure for radiation biology and space applications

Over the past two decades event by event Monte Carlo track structure codes have increasingly been used for biophysical modelling and radiotherapy. Advent of these codes has helped to shed light on many aspects of microdosimetry and mechanism of damage by ionising radiation in the cell. These codes have continuously been modified to include new improved cross sections and computational techniques. This paper provides a summary of input data for ionizations, excitations and elastic scattering cross sections for event by event Monte Carlo track structure simulations for electrons and ions in the form of parametric equations, which makes it easy to reproduce the data. Stopping power and radial distribution of dose are presented for ions and compared with experimental data. A model is described for simulation of full slowing down of proton tracks in water in the range 1 keV to 1 MeV. Modelling and calculations are presented for the response of a TEPC proportional counter irradiated with 5 MeV alpha-particles. Distributions are presented for the wall and wall-less counters. Data shows contribution of indirect effects to the lineal energy distribution for the wall counters responses even at such a low ion energy.

NASA Center JSC↗
DOE OSTI2026

Thermal Stability and Ion Irradiation Response of Refined Grained V – 4Cr – 4Ti

Since the 1960’s, there has been interest in V-4Cr-4Ti and similar alloys as candidates for low activation structural materials for advanced nuclear reactors. V-4Cr-4Ti was produced using arc melting and subsequently subjected to large strain extrusion machining to produce a multimodal microstructure largely composed of nanocrystalline and ultrafine grain sizes. In-situ thermal stability of the multimodal V-4Cr-4Ti to 800 °C shows the formation of vanadium carbides with negligible grain growth. In-situ dual-beam 16 KeV He+ and 1 MeV Kr2+ ion irradiation performed at 700 °C to a final dose of ~5 displacements per atom show the formation of small He cavities well distributed throughout the system, with preferential clustering at grain boundaries. This work provides insight into how the increased fraction of grain boundaries affect the simultaneous dual beam ion irradiation response of multimodal V – 4 wt.% Cr – 4 wt.% Ti at elevated temperatures. Analysis of the cavities reveal an areal density of 0.024±0.007 cavities/nm2 and swelling of 0.236% after the dual-beam ion irradiation. Nanoindentation shows a ~50% increase in hardening after the ion irradiation at 700 °C.

TEM↗
DOE OSTI2024

Diesel Oxidation Catalyst Performance with Biodiesel Formulations

Biodiesel (i.e., mono-alkyl esters of long chain fatty acids derived from vegetable oils and animal fats) is a renewable diesel fuel providing life-cycle greenhouse gas emission reductions relative to petroleum-derived diesel. With the expectation that there would be widespread use of biodiesel as a substitute for ultra-low sulfur diesel (ULSD), there have been many studies looking into the effects of biodiesel on engine and aftertreatment, particularly its compatibility to the current aftertreatment technologies. The objective of this study was to generate experimental data to measure the effectiveness of a current technology diesel oxidation catalysts (DOC) to oxidize soy-based biodiesel at various blend levels with ULSD. Biodiesel blends from 0 to 100% were evaluated on an engine using a conventional DOC. In the steady-state performance test where fuel dosing rate was increased at fixed DOC inlet temperature, B20 performed similarly to ULSD at the lowest flow rate or exhaust temperature over 340 degrees C for medium and high flows. B50 blends performed nearly as well under most conditions. Higher blends exhibited reduced thermal efficiency and DOC outlet temperature with increasing dosing rate under most conditions and required exhaust temperatures over 400 degrees C to achieve or nearly achieve performance similar to ULSD. In the steady-state light of test where fuel dosing rate is fixed but exhaust temperature is increased incrementally, B20 generally performed similarly to ULSD at the highest inlet temperature, with only minor deficiencies at lower temperatures. Higher blends exhibited lower thermal efficiency and did not achieve as high DOC outlet temperatures. In the transient light-off test light-off temperature for ULSD was typically less than 225 degrees C, while for B100 it ranged from 290 degrees C to 330 degrees C. Based on the data set, it can be concluded that biodiesel fuels have a higher light-off temperature primarily because of their higher boiling points, with a minor secondary impact of their lower energy content.

ADVANCED PROPULSION SYSTEMS,BIOMASS FUELS↗
NASA NTRS1977

The search for the cause of the low albedo of the moon

The effects of different weathering processes on the albedo of the lunar surface cover is discussed. The surface chemical composition of numerous lunar soil and pulverized rock samples was determined by auger electron spectroscopy. The optical albedo of these samples was also measured. The chemical concentration of iron and titanium is greater on the surface of soil samples than it is on the surface of crushed rock samples with similar bulk composition, whereas the albedo of soil samples is lower than that of the crushed rock samples. A correlation is presented between the surface iron + titanium content and the albedo. Results of solar wind simulation experiments show that irradiation of crushed lunar rock samples with a small dose (corresponding to 3000 years of solar wind) of 2-keV energy protons changed the surface chemistry of the rock to that of the soil. A much larger dose of protons (corresponding to 30,000 years of solar wind) was needed to darken crushed rock to the albedo of the soil of similar bulk chemical composition. The mechanism of darkening by solar wind is discussed, and its effectiveness is compared to that of other darkening processes.

Gold, T.↗
DOE OSTI2022

Hanford Site Composite Analysis Special Analysis: Inventory and Solid Waste Release Modeling for the LLBG Sensitivity Case - UCAQ-22-01 Inventory Discrepancies for 218-E-12B, 218-W-3A, and 218-W-3AE in the Hanford Site Composite Analysis

This environmental calculation file (ECF) documents the methodologies, assumptions, and results of four sensitivity analyses that reevaluate the representativeness of solid-waste radionuclide inventory and release rate from three solid waste sites included in the recently completed Hanford Site Composite Analysis (CA) (DOE-RL-2019-52, Composite Analysis for Low-Level Waste Disposal in the Hanford Site Central Plateau (FY 2020), Rev. 1) (hereinafter called the CA Update). Specifically, this ECF reevaluates the representativeness of the base case inventory and radionuclide waste release rates from three solid waste sites (i.e., 218-E-12B, 218-W-3A, and 218-W-3AE) and two radionuclides (i.e., carbon-14 [C-14] and technetium-99 [Tc-99]). These three waste sites and two radionuclides were identified as being the most significant contributors to groundwater contamination and dose in the CA Update for the Inner Area boundary at times periods after the compliance period. This ECF first evaluates the representativeness of the C-14 and Tc-99 inventory and second, radionuclide release rates for the three waste sites1. If the inventory and release rates assumed in the CA Update are determined to be not representative, as hypothesized in the CA Update, then this ECF evaluates the impact of more representative inventories and release rates on the transfer of radionuclides to the vadose zone. The four analyses described in this ECF are as follows: 1) 218-E-12B C-14 Inventory and Release Rate Sensitivity Case – Determine the representativeness of the C-14 inventory and associated waste release rate from the 218-E-12B waste site assumed in the CA Update. If the inventory and associated waste release are more appropriately characterized as being different from the assumptions in the CA Update, then update the predicted C-14 release rate and compare the results to the results presented in the CA Update (DOE/RL-2019-52); 2) 218-W-3A C-14 Inventory and Release Rate Sensitivity Case – Determine the representativeness of the C-14 inventory and associated waste release rate from the 218-W-3A waste site assumed in the CA Update. If the inventory and associated waste release are more appropriately characterized as being different from the assumptions in the CA Update, then update the predicted C-14 release rate and compare the results to the results presented in the CA Update (DOE/RL-2019-52); 3) 218-W-3AE Tc-99 Release Rate Sensitivity Case – Determine the representativeness of the Tc-99 inventory and associated waste release rate from the 218-W-3AE waste site assumed in the CA Update. If the inventory and associated waste release are more appropriately characterized as being different from the assumptions in the CA Update, then update the predicted Tc-99 release rate and compare the results to the results presented in the CA Update (DOE/RL-2019-52); 4) 218-W-3AE Tc-99 Release Footprint Sensitivity Case – Determine the representativeness of the Tc-99 waste area footprint for the 218-W-3AE waste site assumed in the CA Update. If the footprint of the waste is more appropriately characterized as being different from the assumptions in the CA Update, then update the predicted Tc-99 release rate and compare the results to the result presented in the CA Update (DOE/RL-2019-52).

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS2008

Enigmatic Isovaline: Investigating the Stability, Racemization, and Formation of a Non-biological Meteoritic Amino Acid

Among the Murchison meteoritic amino acids, isovaline stands out as being both nonbiological (non-protein) and having a relatively high abundance. While approximately equal amounts of D- and L-isovaline have been reported in Murchison and other CM meteorites, the molecule's structure appears to prohibit its racemization in aqueous solutions. We recently have investigated the low-temperature solid-phase chemistry of both isovaline and valine with an eye toward each molecule's formation, stability, and possible interconversions of D and L enantiomers. Ion-irradiated isovaline- and valinecontaining ices were examined by IR spectroscopy and highly-sensitive liquid chromatography/time-of-flight mass spectral methods to assess both amino acid destruction and racemization. Samples were studied in the presence and in the absence of water-ice, and the destruction of both isovaline and valine was measured as a function of radiation dose. In addition, we have undertaken experiments to synthesize isovaline, valine, and their amino acid isomers by solid-phase radiation-chemical pathways other than the oft-invoked Strecker process. This presentation will review and summarize some of our recent findings. -- Our work has been supported by a grant to the Goddard Center for Astrobiology through the NASA Astrobiology Institute. Experiments were performed in the Cosmic Ice Laboratory (RLH, MHM, AL) and the Astrobiology Analytical Laboratory (JPD, DPG) at the NASA Goddard Space Flight Center.

Hudson, Reggie↗
DOE OSTI2024

Monitoring Plan for the Idaho National Laboratory Remote Handled Low Level Waste Disposal Facility

This monitoring plan for Idaho National Laboratory’s Remote-Handled Low Level Waste Disposal Facility was developed to meet the requirements for monitoring low-level waste disposal facilities according to the U.S. Department of Energy (DOE) Order 435.1, “Radioactive Waste Management,” and the guidance provided in the associated technical standard “Disposal Authorization Statement and Tank Closure Documentation” (DOE-STD-5002-2017). The purpose of this monitoring plan is to document a monitoring strategy that includes (1) compliance monitoring activities to demonstrate compliance with regulatory standards/limits and (2) performance monitoring to build confidence the facility is performing as demonstrated in the facility performance assessment (PA) (DOE-ID 2018a), composite analysis (CA) (DOE ID 2012), and CA addendum (DOE-ID 2018b). The de minimus impact to the aquifer predicted by the PA suggests that aquifer compliance monitoring should be augmented with performance monitoring of the drainage course materials and sedimentary interbeds in the vadose zone beneath the facility to provide a more effective means of identifying performance deviations. The monitoring approach delineated in this document was informed by the systems evaluation of natural and engineered facility features presented in the PA, an assessment of aquifer baseline conditions (INL 2017d), the dose analysis conducted in support of the PA and CA, and monitoring data collected during the first four years of facility operations (baseline monitoring phase) (INL 2023b). This plan provides monitoring locations, sampling frequencies, and sampling methods; recommendations for data evaluation; and a description of the monitoring plan implementation. Collected data will be used to demonstrate facility compliance and to identify conditions that are not consistent with the key assumptions made by the PA and CA.

12 - MGMT OF RADIOACTIVE AND NON-RADIOACTIVE WASTE↗
NASA NTRS1995

Radiation Safety Issues in High Altitude Commercial Aircraft

The development of a global economy makes the outlook for high speed commercial intercontinental flight feasible, and the development of various configurations operating from 20 to 30 km have been proposed. In addition to the still unresolved issues relating to current commercial operations (12-16 km), the higher dose rates associated with the higher operating altitudes makes il imperative that the uncertainties in the atmospheric radiation environment and the associated health risks be re-examined. Atmospheric radiation associated with the galactic cosmic rays forms a background level which may, under some circumstances, exceed newly recommended allowable exposure limits proposed on the basis of recent evaluations of the A -bomb survivor data (due to increased risk coefficients). These larger risk coefficients, within the context of the methodology for estimating exposure limits, are resulting in exceedingly low estimated allowable exposure limits which may impact even present day flight operations and was the reason for the CEC workshop in Luxembourg (1990). At higher operating altitudes, solar particles events can produce exposures many orders of magnitude above background levels and pose significant health risks to the most sensitive individuals (such as during pregnancy). In this case the appropriate quality factors are undefined, and some evidence exists which indicates that the quality factor for stochastic effects is a substantial underestimate.

Wilson, John W.↗
NASA NTRSDate not supplied

Overview of Community Response Testing Campaign with NASA's X-59 Aircraft

Prohibition of civil supersonic flight over land became federal regulation in 1973, currently codified in 14 CFR Part 91.817. Of concern, the sonic booms that result when aircraft travel at supersonic speeds were deemed an untenable source of noise affecting populations directly under and near flight paths. Over the past fifty years, research in aircraft design and shaping has led to the prospect of low-noise supersonic flight. As part of its Quesst mission, NASA is building an experimental aircraft, the X-59, to demonstrate this capability. After completing flight test and design validation phases, NASA will field a national community testing campaign in order to collect data on how people perceive the sound from low-noise supersonic flight. The collected data will be provided to national and international regulators as they consider replacing the overland speed limit with a noise-based limit. This presentation provides an overview of the community test campaign, and identifies some of the key objectives, plans, and anticipated challenges.

X-59↗
DOE OSTI2021

Nanoscale friction of CVD single-layer MoS 2 with controlled defect formation

Two-dimensional (2D) layered nanomaterials such as graphene, molybdenum disulfide (MoS 2 ), or tungsten disulfide offer a promising solution in areas of solid-state lubrication, due to their excellent mechanical properties as well as low friction. However, defects can influence their friction and reduce their superior tribological properties. Thus, it is crucial to understand the effects of defects on sliding behavior in 2D nanomaterials, to foster a functional strategy for utilizing 2D nanomaterials as solid-state tribological films. In this study, frictional effects of defects, grain boundaries, and atomic-scale structural defects were explored on chemical vapor deposition (CVD) grown single layer MoS 2 . Selective patterning of defects into MoS 2 was accomplished via controlled irradiation of helium ions with varying ion doses. The friction of MoS 2 was characterized by friction force microscopy (FFM) and was found that friction depends on the defect formation controlled by helium ion irradiation. This approach offers a correlation between surface topography, defects and friction. Understanding the relative friction of MoS 2 in the presence of different levels of defects is foundational to studying tribological properties of a single layer MoS 2 at both nanoscales and macroscales.

36 MATERIALS SCIENCE↗