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NASA NTRS1995

Response of the upper atmosphere to variations in the solar soft x-ray irradiance

Terrestrial far ultraviolet (FUV) airglow emissions have been suggested as a means for remote sensing the structure of the upper atmosphere. The energy which leads to the excitation of FUV airglow emissions is solar irradiance at extreme ultraviolet (EUV) and soft x-ray wavelengths. Solar irradiance at these wavelengths is known to be highly variable; studies of nitric oxide (NO) in the lower thermosphere have suggested a variability of more than an order of magnitude in the solar soft x-ray irradiance. To properly interpret the FUV airflow, the magnitude of the solar energy deposition must be known. Previous analyses have used the electron impact excited Lyman-Birge-Hopfield (LBH) bands of N2 to infer the flux of photoelectrons in the atmosphere and thus to infer the magnitude of the solar irradiance. This dissertation presents the first simultaneous measurements of the FUV airglow, the major atmospheric constituent densities, and the solar EUV and soft x-ray irradiances. The measurements were made on three flights of an identical sounding rocket payload at different levels of solar activity. The linear response in brightness of the LBH bands to variations in solar irradiance is demonstrated. In addition to the N2 LBH bands, atomic oxygen lines at 135.6 and 130.4 nm are also studied. Unlike the LBH bands, these emissions undergo radiative transfer effects in the atmosphere. The OI emission at 135.6 nm is found to be well modeled using a radiative transfer calculation and the known excitation processes. Unfortunately, the assumed processes leading to OI 130.4 nm excitation are found to be insufficient to reproduce the observed variability of this emission. Production of NO in the atmosphere is examined; it is shown that a lower than previously reported variability in the solar soft x-ray irradiance is required to explain the variability of NO.

Bailey, Scott Martin↗

NASA NTRS1999

The ISO View of Star Forming Galaxies

ISO studies of normal galaxies in the local Universe have revealed basic new properties whose significant implications for the star formation process and cosmology are only starting to be understood. This review will touch on the general results of a statistical nature, and provide a quick summary of the profusion of exciting results on individual objects. In the mid-infrared, PHT-S has established that the spectra of star forming galaxies between 6 and-13microns are dominated by the Aromatic Features in Emission (AFE), and show little variation as a function of the heating intensity. The Carriers of the AFE (CAFE) are thus a universal component of dust with standard properties, and contribute between 10 and 25% of the total dust luminosity. In addition to AFE, the spectra show a low-level continuum detectable at wavelengths longer than 3.5microns whose origin is still under investigation. The mid-infrared colors formed as the ratio of flux densities in the 6.75micron and the 15micron bands of ISO-CAM remain essentially constant and near unity for quiescent and mildly active galaxies. As dust heating increases further, the 15micron flux increases steeply compared to 6.75microns, indicating that dust heated to 100K<T<200K becomes a significant component. Such hot dust is presumably located within or just outside HII regions. At the other end of the spectrum, photometry at 120-200microns using ISO-PHOT is starting to constrain the distribution of dust temperatures at the low end of the temperature scale. From LWS data, the far-infrared fine-structure lines of [CII] and [OI], which provide most of the cooling for warm atomic gas, show variations that have remained controversial in their interpretation. In particular, as the galaxy become more active in star formation, its [CII] flux weakens relative to total dust emission while the [OI] does not. This behavior has attracted much interest because it extrapolates to the most active galaxies, making them weaker in [CII] than previously expected. Several explanations for the effect have been advanced, and will be discussed in this review. Spectroscopy with SWS has measured molecular hydrogen in galaxies, providing a powerful handle on the warm molecular gas content. SWS and CAM-CVF studies targeting ionic fine-structure lines have demonstrated their value as diagnostics of the radiation field.

Helou, George↗

NASA NTRS2004

Multivariate Error Covariance Estimates by Monte-Carlo Simulation for Assimilation Studies in the Pacific Ocean

One of the most difficult aspects of ocean state estimation is the prescription of the model forecast error covariances. The paucity of ocean observations limits our ability to estimate the covariance structures from model-observation differences. In most practical applications, simple covariances are usually prescribed. Rarely are cross-covariances between different model variables used. Here a comparison is made between a univariate Optimal Interpolation (UOI) scheme and a multivariate OI algorithm (MvOI) in the assimilation of ocean temperature. In the UOI case only temperature is updated using a Gaussian covariance function and in the MvOI salinity, zonal and meridional velocities as well as temperature, are updated using an empirically estimated multivariate covariance matrix. Earlier studies have shown that a univariate OI has a detrimental effect on the salinity and velocity fields of the model. Apparently, in a sequential framework it is important to analyze temperature and salinity together. For the MvOI an estimation of the model error statistics is made by Monte-Carlo techniques from an ensemble of model integrations. An important advantage of using an ensemble of ocean states is that it provides a natural way to estimate cross-covariances between the fields of different physical variables constituting the model state vector, at the same time incorporating the model's dynamical and thermodynamical constraints as well as the effects of physical boundaries. Only temperature observations from the Tropical Atmosphere-Ocean array have been assimilated in this study. In order to investigate the efficacy of the multivariate scheme two data assimilation experiments are validated with a large independent set of recently published subsurface observations of salinity, zonal velocity and temperature. For reference, a third control run with no data assimilation is used to check how the data assimilation affects systematic model errors. While the performance of the UOI and MvOI is similar with respect to the temperature field, the salinity and velocity fields are greatly improved when multivariate correction is used, as evident from the analyses of the rms differences of these fields and independent observations. The MvOI assimilation is found to improve upon the control run in generating the water masses with properties close to the observed, while the UOI failed to maintain the temperature and salinity structure.

Borovikov, Anna↗

NASA NTRS1993

Extreme Ultraviolet Emission Spectrum of CO_2 Induced by Electron Impact at 200 eV

We present the extreme ultraviolet (EUV) emission spectrum of CO_2 induced by electronimpact at 200 eV. There are 36 spectral features which are identified with a resolution of 0.5 nmover the wavelength range of 40 to 125 nm. Absolute emission cross sections were obtained for eachof these features. The EUV emission spectrum induced by electron impact consist of atomicmultiplets of CI,II and OI,II,III as well as CO and CO^+ molecular band systems produced bydissociative excitation. The CI (119.4 nm) multiplet is the strongest feature of CI with a peak crosssection of 3.61 x 10^(-19) cm^2 at 200 eV. The strongest feature of OI in the EUV spectrum is theOI (99.0 nm) multiplet with a peak cross section of 3.59 x 10^(-19) cm^2 at 200 eV.

Kanik, I.↗

NASA NTRS2010

The Evolution of Gas in Protoplanetary Systems: The Herschel GASPS Open Time Key Programme

The Gas in Protoplanetary Systems (GASPS) Open Time Key Programme for the Herschel Space Observatory will be the first extensive, systematic survey of gas in circumstellar disks over the critical transition from gas-rich protoplanetary through to gas-poor debris. The brightest spectral lines from disks lie in the far-infrared and arise from radii spanning roughly 10 to 100 AU, where giant planets are expected to form. Herschel is uniquely able to observe this wavelength regime with the sensitivity to allow a large scale survey. We will execute a 2-phase study using the PACS instrument. Phase I is a spectroscopic survey about 250 young stars for fine structure emission lines of [CII] (at 157 microns) and [OI] (at 63 microns). In Phase II, the brightest sources will be followed up with additional PACS spectroscopy ([OI] at 145 microns and some rotational lines of water). We expect that the gas mass sensitivity will be more than an order of magnitude lower than that achieved by ISO and Spitzer or expected for SOFIA. We will also measure the dust continuum to an equivalent mass sensitivity. We will observe several nearby clusters with ages from 1 to 30 Myr, encompassing a wide range of disk masses and stellar luminosities. The sample covers disk evolution from protoplanetary disks through to young debris disks, i.e. the main epoch of planet formation. With this extensive dataset, the GASPS project will: 1) trace gas and dust in the planet formation region across a large multivariate parameter space, 2) provide the first definitive measurement of the gas dissipation timescale in disks, 3) elucidate the evolutionary link between protoplanetary and debris disks, 4) investigate water abundances in the planetforming regions of disks, and 5) provide a huge database of disk observations and models with long-lasting legacy value for follow-up studies.

Roberge, A.↗

NASA NTRS2016

Pilot Field Test: Use of a Compression Garment During a Stand Test After Long-Duration Space Flight

Orthostatic intolerance (OI) is a concern for astronauts returning from long-duration space flight. One countermeasure that has been used to protect against OI after short-duration bed rest and space flight is the use of lower body and abdominal compression garments. However, since the end of the Space Shuttle era we have not been able to test crewmembers during the first 24 hours after landing on Earth. NASA's Pilot Field Test provided us the opportunity to test cardiovascular responses of crewmembers wearing the Russian Kentavr compression garment during a stand test at multiple time points throughout the first 24 hours after landing. HYPOTHESIS We hypothesized that the Kentavr compression garment would prevent an increase in heart rate (HR) >15 bpm during a 3.5-min stand test. METHODS: The Pilot Field Test was conducted up to 3 times during the first 24 hours after crewmembers returned to Earth: (1) either in a tent adjacent to the Soyuz landing site in Kazakhstan (approx.1 hr) or after transportation to the Karaganda airport (approx. 4 hr); (2) during a refueling stop in Scotland (approx.12 hr); and (3) upon return to NASA Johnson Space Center (JSC) (approx.24 hr). We measured HR and arterial pressure (finger photoplethysmography) for 2 min while the crewmember was prone and throughout 3.5 min of quiet standing. Eleven crewmembers consented to participate; however, 2 felt too ill to start the test and 1 stopped 30 sec into the stand portion of the test. Of the remaining 8 crewmembers, 2 did not wear the Russian Kentavr compression garment. Because of inclement weather at the landing site, 5 crewmembers were flown by helicopter to the Karaganda airport before initial testing and received intravenous saline before completing the stand test. One of these crewmembers wore only the portion of the Russian Kentavr compression garment that covered the lower leg and thus lacked thigh and abdominal compression. All crewmembers continued wearing the Russian Kentavr compression garment during the second testing session in Scotland, but none wore it during testing at JSC. RESULTS: The mean Delta HR from the supine to standing position in the 8 crewmembers measured pre-flight or 60 days after return from long-duration space flight was 9.8 bpm. During the first few hours after landing from long-duration space flight, the mean Delta HR of the 6 crewmembers who wore the Russian Kentavr compression garment in Kazakhstan or Karaganda was +14 bpm and the change in mean arterial pressure (Delta MAP) was +0.8 mmHg, while the 2 crewmembers who did not wear the Russian Kentavr compression garment had a Delta HR of +38 bpm and a Delta MAP of +1.1 mmHg. In Scotland, 4 crewmembers wore the Russian Kentavr compression garment and had a Delta HR of +7.4 bpm while the 3 crewmembers who did not wear it had a Delta HR of +25.0 bpm. Seven crewmembers were tested upon return to JSC approx. 24 hr after landing, but none wore the Russian Kentavr compression garment and their Delta HR was 16.0 bpm. CONCLUSIONS: These are the first stand-test data to be collected from long-duration crewmembers during the first 24 hr of re-adaptation to gravity on Earth. The Delta HR measured in crewmembers who completed the stand-test while wearing Kentavr within the first approx.4 hours after returning to Earth was only slightly elevated from pre-flight Delta HR, while the few subjects who did not wear the Russian Kentavr compression garment had a much larger increase in HR in order to maintain arterial pressure throughout 3.5-min of standing. These data demonstrate the effectiveness of a compression garment in preventing large increases in HR during a 3.5 min stand test after long-duration space flight. However, the fact that three crewmembers were too ill to complete the test or was not able to complete 3.5 min of standing despite wearing the Russian Kentavr compression garment indicates that wearing a compression garment does not resolve all problems crewmembers face during the period of re-adaptation immediately after return to Earth's gravity.

Laurie, S. S.↗

NASA NTRS2022

The Dense, Warm Interstellar Medium (D-WIM): Unravelling a New Phase of the ISM A PRIMA FIR Probe Mission Project

We propose a study of the Dense Warm Interstellar Medium (D-WIM) via the two fine structure lines of ionized nitrogen (\NII). This new phase of the interstellar medium (ISM) has density 10 $\cmv \le n(e) \le$ 100 $\cmv$, and has effectively been identified throughout much of the Milky Way and in nearby galaxies. :The unexpected conditiosn in the D-WIM immediately raise important questions both about this phase of the ISM and its relationship to the ISM as a while. These include: what is the structure of the D-WIM -- e.g. filling factor, distribution, and morphology?; what is the origin of the D-WIM?; what supports its ionization and what is its evolution given huge overpressure relative to the $\ge$ 100 times more diffuse Warm Ionized Medium (WIM)?; what is its possible relationship to stars - is it the the remnants of very old HII regions that were produced by clusters of masive stars? The PRIMA survey requires a coverage of a large fraction of the plane, plus selected regions at high galactic latitudes. A sensitivity of 10$^{-9}$ $Wm^{-2}sr^{-1}$ would be highly desirable. A spectral resolution $R$ of 10$^4$ will isolate individual spectral features. $R$ = 10$^3$ would be acceptable to measure the total intensity. This PRIMA survey could be part of a broader survey of the ISM, and include a number of other important ISM tracers such as [CII] 158 \um, [OI] 63 \um\ and [OI] 146 \um, depending on wavelength coverage of the instrument. The sensitivity requirement for study of the D-WIM is likely more stringent than for the other lines, and may require special consideration for successful implementation as well as for determining the area that can be observed.

Lis, Dariusz↗

DOE OSTI2022

On the mechanism of radiation and thermal-induced degradation of the insulation cables in nuclear power plants-the presence of long-lived polyenyl C-centered radicals

Radiolytically and thermally produced long-lived polyenyl C-centered radicals in the nuclear power plants’ insulation cables are detected and measured after more than 45 months of aging since the irradiation and the thermal treatment. Electron Paramagnetic Resonance (EPR) results of the irradiated Cross-linked Polyethylene (XLPE) and Ethylene Propylene Rubber (EthProRu), used as primary insulation materials at Nuclear Power Plants (NPP), clearly demonstrate the presence of polyenyl radicals along with allyl and peroxyl radicals. The yields of these free radicals are dose-rate dependent. EPR results also show the presence of the long-lived polyenyl along with allyl and peroxyl free radicals in the thermally treated XLPE, and EthProRu. These free radicals can cause a major failure in the performance of these cables in NPPs. Besides, the results showed the enhancement in the oxidation reactions due to the migration of copper ions from the conductor to the bulk of the insulation. Further, this study also shows that the oxidation index (OI) and Elongation at Break (EAB) increases and decreases respectively at higher doses and temperatures.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2021

Generation of Subauroral Longitudinally Extended Emissions Following Intensifications of the Poleward Boundary of the Substorm Bulge and Streamer Production

Observations showing the development of Subauroral Longitudinally Extended Emigerssions on a global scale are presented. It is demonstrated that they occur as a separation of an east-west arc-like band of luminosity that detaches away from the equatorward edge of the auroral distribution following episodes of auroral streamer production. They persist for time intervals on the order of ~30 min and devolve into patchy disjointed segments before they fade. Emissions are seen in both 557.7 nm OI and 391.4 nm N + 2 1NG lines, and 630.0 nm emissions are often observed equatorward. The 391.4 nm emissions are typically weaker and fade away more quickly than the 557.7 nm emissions, suggesting that an auroral precipitation source is initially present but is rapidly depleted as the forms age. All cases are associated with enhanced Subauroral Polarization Stream (SAPS) flows, and one event shows clear association with large-scale Giant Undulations (GUs) and the formation of spur-like forms that fold equatorward under the main oval. A model is proposed for the production of subauroral longitudinally extended forms in which nonlinear growth of SAPS-induced surface waves on the plasmapause results in a disruption of the boundary. It is suggested that hot plasma of plasma sheet origin becomes entrained in the plasmasphere to produce transient precipitation-associated auroral emissions that may decay into STEVE emissions and that cold dense plasma from the plasmasphere becomes entrained onto open drift paths to feed long-lived drainage plumes. This process may occur quasi periodically during intense substorms and storm-time conditions.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2023

Clonality, local population structure, and gametophyte sex ratios in cryptic species of the Sphagnum magellanicum complex

Sphagnum (peatmoss) comprises a moss (Bryophyta) clade with approximately 300-500 species. The genus has unparalleled ecological importance because Sphagnum-dominated peatlands store almost a third of the terrestrial carbon pool and peatmosses engineer the formation and microtopography of peatlands. Genomic resources for Sphagnum are being actively expanded, but many aspects of their biology are still poorly known. Among these are the degree to which Sphagnum species reproduce asexually, and the relative frequencies of male and female gametophytes in these haploid-dominant plants. Here, we assess clonality and gametophyte sex ratios and test hypotheses about the local-scale distribution of clones and sexes in four North American species of the S. magellanicum complex. These four species are difficult to distinguish morphologically and are very closely related. We also assess microbial communities associated with Sphagnum host plant clones and sexes at two sites. 405 samples of the four species, representing 57 populations, were subjected to RADseq. Analyses of population structure and clonality based on the molecular data utilized both phylogenetic and phenetic approaches. Multi-locus genotypes (genets) were identified using the RADseq data. Sexes of sampled ramets were determined using a molecular approach that utilized coverage of loci on the sex chromosomes after the method was validated using a sample of plants that expressed sex phenotypically. Sex ratios were estimated for each species, and populations within species. Differences in fitness between genets was estimated as the numbers of ramets each genet comprised. Degree of clonality (numbers of genets/numbers of ramets [samples]) within species, among sites, and between gametophyte sexes were estimated. Sex ratios were estimated for each species, and populations within species. Sphagnum-associated microbial communities were assessed at two sites in relation to Sphagnum clonality and sex. All four species appear to engage in a mixture of sexual and asexual (clonal) reproduction. A single ramet represents most genets but 2-8 ramets were detected for some genets. Only one genet is represented by ramets in multiple populations; all other genets are restricted to a single population. Within populations ramets of individual genets are spatially clustered, suggesting limited dispersal even within peatlands. Sex ratios are male-biased in S. diabolicum but female-biased in the other three species, although significantly so only in S. divinum. Neither species nor males/females differ in levels of clonal propagation. At St. Regis Lake (NY) and Franklin Bog (VT), microbial community composition is strongly differentiated between the sites, but differences between species, genets, and sexes were not detected. Within S. divinum, however, female gametophytes harbored 2-3 times the number oi of microbial taxa as males. These four Sphagnum species all exhibit a similar reproductive patterns that result from a mixture of sexual and asexual reproduction. The spatial patterns of clonally replicated ramets of genets suggest that these species fall between the so-called phalanx patterns where genets abut one another but do not extensively mix, because of limited ramet fragmentation, and the guerrilla patterns where extensive genet fragmentation and dispersal results in greater mixing of different genets. Although sex ratios in bryophytes are most often female-biased, both male and female biases occur in this complex of closely related species. The association of far greater microbial diversity for female gametophytes in S. divinum, which has a female-biased sex ratio, suggests additional research to determine if levels of microbial diversity are consistently correlated with differing patterns of sex ratio biases.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2021

Numerical Analysis of Fuel Effects on Advanced Compression Ignition Using a Cooperative Fuel Research Engine Computational Fluid Dynamics Model

Growing environmental concerns and demand for a better fuel economy are driving forces that motivate the research for more advanced engines. Multi-mode combustion strategies have gained attention for their potential to provide high thermal efficiency and low emissions for light-duty applications. These strategies target optimizing the engine performance by correlating different combustion modes to load operating conditions. The extension from boosted spark ignition (SI) mode at high loads to advanced compression ignition (ACI) mode at low loads can be achieved by increasing the compression ratio and utilizing intake air heating. Further, in order to enable an accurate control of intake charge condition for ACI mode and rapid mode-switches, it is essential to gain fundamental insights into the autoignition process. Within the scope of ACI, homogeneous charge compression ignition (HCCI) mode is of significant interest. It is known for its potential benefits, operation at low fuel consumption, low NOx, and particulate matter (PM) emissions. In the present work, a virtual Cooperative Fuel Research (CFR) engine model is used to analyze fuel effects on ACI combustion. In particular, the effect of fuel octane sensitivity (S) (at constant Research Octane Number (RON)) on autoignition propensity is assessed under beyond-RON (BRON) and beyond-MON (BMON) ACI conditions. The three-dimensional CFR engine computational fluid dynamics (CFD) model employs a finite-rate chemistry approach with a multi-zone binning strategy to capture autoignition. Two binary blends with Research Octane Number (RON) of 90 are chosen for this study: primary reference fuel (PRF) with S = 0 and toluene–heptane (TH) blend with S = 10.8, representing paraffinic and aromatic gasoline surrogates. Reduced mechanisms for these blends are generated from a detailed gasoline surrogate kinetic mechanism. Simulation results with the reduced mechanisms are validated against experimental data from an in-house CFR engine, with respect to in-cylinder pressure, heat release rate, and combustion phasing. Thereafter, the sensitivity of combustion behavior to ACI operating condition (BRON versus BMON), air-fuel ratio (λ = 2 and 3), and engine speed (600 and 900 rpm) is analyzed for both fuels. It is shown that the sensitivity of a fuel’s autoignition characteristics to λ and engine speed significantly differs at BRON and BMON conditions. Moreover, this sensitivity is found to vary among fuels, despite the same RON. It is also observed that the presence of low-temperature heat release (LTHR) under BRON condition leads to more sequential autoignition and longer combustion duration than BMON condition. Finally, the study indicates that the octane index (OI) fails to capture the trend in the variation of autoignition propensity with S under the BMON condition.

33 ADVANCED PROPULSION SYSTEMS↗

DOE OSTI2022

Upward propagation of gigantic jets revealed by 3D radio and optical mapping

Occasionally, lightning will exit the top of a thunderstorm and connect to the lower edge of space, forming a gigantic jet. Here, we report on observations of a negative gigantic jet that transferred an extraordinary amount of charge between the troposphere and ionosphere (~300 C). It occurred in unusual circumstances, emerging from an area of weak convection. As the discharge ascended from the cloud top, tens of very high frequency (VHF) radio sources were detected from 22 to 45 km altitude, while simultaneous optical emissions (777.4 nm OI emitted from lightning leaders) remained near cloud top (15 to 20 km altitude). This implies that the high-altitude VHF sources were produced by streamers and the streamer discharge activity can extend all the way from near cloud top to the ionosphere. The simultaneous three-dimensional radio and optical data indicate that VHF lightning networks detect emissions from streamer corona rather than the leader channel, which has broad implications to lightning physics beyond that of gigantic jets.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2022

Rethinking PCMI Failures Under Transient Conditions

Under PCMI conditions, the cladding strain is driven by either pellet swelling during normal operation or pellet thermal expansion in transients. The loading in PCMI is displacement controlled because friction between the pellet and the cladding results in a strain compatibility at the pellet/cladding interface. Failure is known to occur under PCMI loading conditions during operation when normal power changes result in release of iodine (and other fission products) causing stress corrosion cracking where the crack-propagation rate is dependent upon the cladding stress but slow relative to strictly mechanical failures. Failures after normal power changes are often referred to as failure by pellet-cladding interaction or PCI to distinguish it from PCMI. Such failures are considered displacement-controlled failures, as noted above, and occur with limited plastic strain. This is different to what is typically thought of as PCMI failure under transient conditions, either Anticipated Operational Occurrences (AOOs) or Reactivity Insertion Accidents (RIAs), which is generally assumed to occur once the cladding reaches a mechanical strain limit. But there are two features in the typical PCMI failure in an RIA that are not consistent with the PCMI assumptions. The first is the ductile shear failure feature in cross section and the second is a large crack opening post failure (e.g., see OI-11 failure in NSRR program). The ductile feature is indicative of a plastic instability that requires very large local strains, and the large crack opening must be the result of a release of energy, both of which are not expected if stress in the cladding was only driven by thermal expansion in the pellet. It is concluded that there must be a mechanism (likely related to rod internal pressure) that eliminates strain compatibility between the pellet and cladding – allowing strain localization to occur in what are known as PCMI transient failures. In some sense, these PCMI failures may actually be early burst failures that occur when thermal expansion causes uniform strains greater than a defined limit and fission gas pressure eliminate the strain compatibility

Cantonwine, Paul↗

DOE OSTI2021

Room temperature plasma-etching and surface passivation of far-ultraviolet Al mirrors using electron beam generated plasmas

The development of optical systems operating in the far ultraviolet range (FUV, λ=100-200 nm) is limited by the efficiency of passivated aluminum (Al) mirrors. Although it is presently possible to obtain high-reflectivity FUV mirrors through physical vapor deposition, the process involves deposition with substrates at high temperatures, which is technically challenging for large optical elements. A novel passivation procedure for bare Al mirrors is reported. The treatment consisted of using a low-temperature electron-beam generated plasma produced in a gas mixture of Ar and SF6 to etch away the native oxide layer from the Al film, while simultaneously promoting the generation of a thin aluminum tri-fluoride (AlF3) layer on the Al surface. In the first section we analyze the effect of varying both ion energy and SF6 concentration on the FUV reflectance, thickness, composition, and surface morphology of the resulting AlF3 protective layers. In the second section, the reflectivity of samples is optimized at selected important FUV wavelengths for astronomical observations. Notably, samples attained state-of-the-art reflectances of 75% at 108.5 nm (He Lyman γ), 91% at 121.6 nm (H Lyman α), 90% at 130.4 nm (OI), and of 95% at 155.0 nm (C IV). The stability over time of these passivated mirrors is also investigated.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2020

Materials Data on K5Au(IO)2 by Materials Project

K5Au(OI)2 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. there are three inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a distorted linear geometry to two equivalent O2- and four equivalent I1- atoms. Both K–O bond lengths are 2.80 Å. There are a spread of K–I bond distances ranging from 3.58–3.87 Å. In the second K1+ site, K1+ is bonded in a distorted linear geometry to two equivalent O2- and four equivalent I1- atoms. There are one shorter (2.70 Å) and one longer (2.76 Å) K–O bond lengths. There are two shorter (3.60 Å) and two longer (3.74 Å) K–I bond lengths. In the third K1+ site, K1+ is bonded in a distorted linear geometry to two equivalent O2- and four equivalent I1- atoms. Both K–O bond lengths are 2.82 Å. All K–I bond lengths are 3.66 Å. Au1+ is bonded in a linear geometry to two equivalent O2- atoms. Both Au–O bond lengths are 2.06 Å. O2- is bonded to five K1+ and one Au1+ atom to form corner-sharing OK5Au octahedra. The corner-sharing octahedra tilt angles range from 0–12°. I1- is bonded in a 10-coordinate geometry to ten K1+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Rb3Bi7Pb3(IO)10 by Materials Project

Rb3Pb3Bi7(OI)10 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are three inequivalent Rb1+ sites. In the first Rb1+ site, Rb1+ is bonded in a 7-coordinate geometry to two O2- and five I1- atoms. There are one shorter (3.01 Å) and one longer (3.03 Å) Rb–O bond lengths. There are a spread of Rb–I bond distances ranging from 3.54–3.86 Å. In the second Rb1+ site, Rb1+ is bonded in a 2-coordinate geometry to two O2- and three I1- atoms. There are one shorter (2.91 Å) and one longer (3.08 Å) Rb–O bond lengths. There are a spread of Rb–I bond distances ranging from 3.59–4.05 Å. In the third Rb1+ site, Rb1+ is bonded in a distorted single-bond geometry to one O2- and four I1- atoms. The Rb–O bond length is 2.74 Å. There are a spread of Rb–I bond distances ranging from 3.76–4.22 Å. There are three inequivalent Pb2+ sites. In the first Pb2+ site, Pb2+ is bonded in a single-bond geometry to one O2- and two I1- atoms. The Pb–O bond length is 2.27 Å. There are one shorter (3.26 Å) and one longer (3.57 Å) Pb–I bond lengths. In the second Pb2+ site, Pb2+ is bonded in a distorted single-bond geometry to one O2- and three I1- atoms. The Pb–O bond length is 2.19 Å. There are a spread of Pb–I bond distances ranging from 3.10–3.56 Å. In the third Pb2+ site, Pb2+ is bonded in a 2-coordinate geometry to two O2- and three I1- atoms. There are one shorter (2.31 Å) and one longer (2.38 Å) Pb–O bond lengths. There are a spread of Pb–I bond distances ranging from 3.19–3.75 Å. There are seven inequivalent Bi3+ sites. In the first Bi3+ site, Bi3+ is bonded in a 3-coordinate geometry to three O2- and two I1- atoms. There are two shorter (2.17 Å) and one longer (2.19 Å) Bi–O bond lengths. There are one shorter (3.34 Å) and one longer (3.75 Å) Bi–I bond lengths. In the second Bi3+ site, Bi3+ is bonded in a 3-coordinate geometry to three O2- and two I1- atoms. There are a spread of Bi–O bond distances ranging from 2.16–2.19 Å. There are one shorter (3.34 Å) and one longer (3.39 Å) Bi–I bond lengths. In the third Bi3+ site, Bi3+ is bonded in a 4-coordinate geometry to three O2- and two equivalent I1- atoms. There are a spread of Bi–O bond distances ranging from 2.22–2.52 Å. There are one shorter (3.35 Å) and one longer (3.66 Å) Bi–I bond lengths. In the fourth Bi3+ site, Bi3+ is bonded in a 2-coordinate geometry to two O2- and two I1- atoms. There are one shorter (2.06 Å) and one longer (2.18 Å) Bi–O bond lengths. There are one shorter (3.05 Å) and one longer (3.52 Å) Bi–I bond lengths. In the fifth Bi3+ site, Bi3+ is bonded in a distorted L-shaped geometry to two O2- and one I1- atom. There are one shorter (2.06 Å) and one longer (2.13 Å) Bi–O bond lengths. The Bi–I bond length is 3.49 Å. In the sixth Bi3+ site, Bi3+ is bonded in a distorted water-like geometry to two O2- and two I1- atoms. There are one shorter (2.07 Å) and one longer (2.12 Å) Bi–O bond lengths. There are one shorter (3.07 Å) and one longer (3.57 Å) Bi–I bond lengths. In the seventh Bi3+ site, Bi3+ is bonded in a distorted L-shaped geometry to two O2- and one I1- atom. There are one shorter (2.07 Å) and one longer (2.15 Å) Bi–O bond lengths. The Bi–I bond length is 3.17 Å. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to three Bi3+ and one I1- atom. The O–I bond length is 3.59 Å. In the second O2- site, O2- is bonded in a 3-coordinate geometry to three Bi3+ and one I1- atom. The O–I bond length is 3.36 Å. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Rb1+, one Pb2+, and one Bi3+ atom. In the fourth O2- site, O2- is bonded in a distorted water-like geometry to two Bi3+ and one I1- atom. The O–I bond length is 3.23 Å. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to one Pb2+ and one Bi3+ atom. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to one Rb1+, two Bi3+, and one I1- atom. The O–I bond length is 3.57 Å. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to one Rb1+, one Pb2+, and one Bi3+ atom. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to two Rb1+ and one I1- atom. The O–I bond length is 1.95 Å. In the ninth O2- site, O2- is bonded in a distorted water-like geometry to two Bi3+ and one I1- atom. The O–I bond length is 3.87 Å. In the tenth O2- site, O2- is bonded in a 3-coordinate geometry to one Pb2+ and two Bi3+ atoms. There are ten inequivalent I1- sites. In the first I1- site, I1- is bonded in a distorted single-bond geometry to one Bi3+ atom. In the second I1- site, I1- is bonded in a 2-coordinate geometry to two Bi3+ atoms. In the third I1- site, I1- is bonded in a 4-coordinate geometry to one Rb1+, one Pb2+, and two Bi3+ atoms. In the fourth I1- site, I1- is bonded in a 5-coordinate geometry to one Pb2+, four Bi3+, and two O2- atoms. In the fifth I1- site, I1- is bonded in a 3-coordinate geometry to two equivalent Rb1+ and one Pb2+ atom. In the sixth I1- site, I1- is bonded in a 3-coordinate geometry to one Rb1+, one Bi3+, and one O2- atom. In the seventh I1- site, I1- is bonded in a 6-coordinate geometry to three Rb1+, one Pb2+, one Bi3+, and one O2- atom. In the eighth I1- site, I1- is bonded in a 5-coordinate geometry to three Rb1+ and two Pb2+ atoms. In the ninth I1- site, I1- is bonded in a 1-coordinate geometry to one O2- atom. In the tenth I1- site, I1- is bonded in a 6-coordinate geometry to two Rb1+, two equivalent Pb2+, one Bi3+, and one O2- atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Sr(IO)2 by Materials Project

Sr(OI)2 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are four inequivalent Sr sites. In the first Sr site, Sr is bonded in a 9-coordinate geometry to four O and four I atoms. There are a spread of Sr–O bond distances ranging from 2.50–2.53 Å. There are a spread of Sr–I bond distances ranging from 3.43–3.71 Å. In the second Sr site, Sr is bonded in a 9-coordinate geometry to four O and five I atoms. There are a spread of Sr–O bond distances ranging from 2.51–2.53 Å. There are a spread of Sr–I bond distances ranging from 3.47–3.83 Å. In the third Sr site, Sr is bonded in a 9-coordinate geometry to four O and four I atoms. There are a spread of Sr–O bond distances ranging from 2.51–2.53 Å. There are a spread of Sr–I bond distances ranging from 3.43–3.70 Å. In the fourth Sr site, Sr is bonded in a 9-coordinate geometry to four O and five I atoms. There are a spread of Sr–O bond distances ranging from 2.50–2.53 Å. There are a spread of Sr–I bond distances ranging from 3.46–3.85 Å. There are eight inequivalent O sites. In the first O site, O is bonded in a 3-coordinate geometry to two equivalent Sr and one O atom. The O–O bond length is 1.38 Å. In the second O site, O is bonded in a 3-coordinate geometry to two equivalent Sr and one O atom. The O–O bond length is 1.37 Å. In the third O site, O is bonded in a 3-coordinate geometry to two equivalent Sr and one O atom. The O–O bond length is 1.38 Å. In the fourth O site, O is bonded in a 3-coordinate geometry to two equivalent Sr and one O atom. The O–O bond length is 1.37 Å. In the fifth O site, O is bonded in a 3-coordinate geometry to two equivalent Sr and one O atom. In the sixth O site, O is bonded in a 3-coordinate geometry to two equivalent Sr and one O atom. In the seventh O site, O is bonded in a 3-coordinate geometry to two equivalent Sr and one O atom. In the eighth O site, O is bonded in a 3-coordinate geometry to two equivalent Sr and one O atom. There are eight inequivalent I sites. In the first I site, I is bonded in a distorted water-like geometry to two Sr and one I atom. The I–I bond length is 3.31 Å. In the second I site, I is bonded in a 2-coordinate geometry to three Sr and one I atom. The I–I bond length is 3.27 Å. In the third I site, I is bonded in a distorted water-like geometry to two Sr and one I atom. The I–I bond length is 3.28 Å. In the fourth I site, I is bonded in a 2-coordinate geometry to three Sr and one I atom. The I–I bond length is 3.30 Å. In the fifth I site, I is bonded in a distorted rectangular see-saw-like geometry to two Sr and two I atoms. The I–I bond length is 2.88 Å. In the sixth I site, I is bonded in a 4-coordinate geometry to two Sr and two I atoms. The I–I bond length is 2.88 Å. In the seventh I site, I is bonded in a distorted rectangular see-saw-like geometry to two Sr and two I atoms. In the eighth I site, I is bonded in a 4-coordinate geometry to two Sr and two I atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Sr(IO)2 by Materials Project

Sr(OI)2 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are four inequivalent Sr sites. In the first Sr site, Sr is bonded to four O and three I atoms to form distorted edge-sharing SrI3O4 pentagonal bipyramids. There are a spread of Sr–O bond distances ranging from 2.47–2.50 Å. There are a spread of Sr–I bond distances ranging from 3.35–3.51 Å. In the second Sr site, Sr is bonded in a 2-coordinate geometry to four O and five I atoms. There are a spread of Sr–O bond distances ranging from 2.48–2.72 Å. There are a spread of Sr–I bond distances ranging from 3.40–4.02 Å. In the third Sr site, Sr is bonded in a 2-coordinate geometry to four O and four I atoms. There are a spread of Sr–O bond distances ranging from 2.48–2.70 Å. There are a spread of Sr–I bond distances ranging from 3.43–3.65 Å. In the fourth Sr site, Sr is bonded in a 4-coordinate geometry to four O and four I atoms. There are a spread of Sr–O bond distances ranging from 2.46–2.52 Å. There are a spread of Sr–I bond distances ranging from 3.31–3.94 Å. There are eight inequivalent O sites. In the first O site, O is bonded in a 3-coordinate geometry to two equivalent Sr and one O atom. The O–O bond length is 1.38 Å. In the second O site, O is bonded in a T-shaped geometry to two equivalent Sr and one O atom. The O–O bond length is 1.40 Å. In the third O site, O is bonded in a distorted T-shaped geometry to two equivalent Sr and one O atom. The O–O bond length is 1.42 Å. In the fourth O site, O is bonded in a 3-coordinate geometry to two equivalent Sr and one O atom. The O–O bond length is 1.37 Å. In the fifth O site, O is bonded in a 3-coordinate geometry to two equivalent Sr and one O atom. In the sixth O site, O is bonded in a 4-coordinate geometry to two equivalent Sr, one O, and one I atom. The O–I bond length is 2.36 Å. In the seventh O site, O is bonded in a 4-coordinate geometry to two equivalent Sr, one O, and one I atom. The O–I bond length is 2.34 Å. In the eighth O site, O is bonded in a distorted T-shaped geometry to two equivalent Sr and one O atom. There are eight inequivalent I sites. In the first I site, I is bonded in a 4-coordinate geometry to three Sr and one I atom. The I–I bond length is 3.34 Å. In the second I site, I is bonded in a distorted single-bond geometry to one Sr, one O, and one I atom. The I–I bond length is 3.17 Å. In the third I site, I is bonded in a distorted single-bond geometry to one Sr, one O, and one I atom. In the fourth I site, I is bonded in a 2-coordinate geometry to three Sr and one I atom. In the fifth I site, I is bonded in a distorted bent 120 degrees geometry to two Sr and one I atom. The I–I bond length is 3.29 Å. In the sixth I site, I is bonded in a 2-coordinate geometry to two Sr and one I atom. The I–I bond length is 3.29 Å. In the seventh I site, I is bonded in a 2-coordinate geometry to two Sr and one I atom. In the eighth I site, I is bonded in a distorted bent 120 degrees geometry to two Sr and one I atom.

36 MATERIALS SCIENCE↗