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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,117 records · Page 62
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

PROPERTIES OF THE INTERSTELLAR MEDIUM IN STAR-FORMING GALAXIES AT z ∼ 1.4 REVEALED WITH ALMA

We conducted observations of {sup 12}CO(J = 5–4) and dust thermal continuum emission toward 20 star-forming galaxies on the main sequence at z ∼ 1.4 using ALMA to investigate the properties of the interstellar medium. The sample galaxies are chosen to trace the distributions of star-forming galaxies in diagrams of stellar mass versus star formation rate and stellar mass versus metallicity. We detected CO emission lines from 11 galaxies. The molecular gas mass is derived by adopting a metallicity-dependent CO-to-H{sub 2} conversion factor and assuming a CO(5–4)/CO(1–0) luminosity ratio of 0.23. Masses of molecular gas and its fractions (molecular gas mass/(molecular gas mass + stellar mass)) for the detected galaxies are in the ranges of (3.9–12) × 10{sup 10} M{sub ⊙} and 0.25–0.94, respectively; these values are significantly larger than those in local spiral galaxies. The molecular gas mass fraction decreases with increasing stellar mass; the relation holds for four times lower stellar mass than that covered in previous studies, and the molecular gas mass fraction decreases with increasing metallicity. Stacking analyses also show the same trends. Dust thermal emissions were clearly detected from two galaxies and marginally detected from five galaxies. Dust masses of the detected galaxies are (3.9–38) × 10{sup 7} M{sub ⊙}. We derived gas-to-dust ratios and found they are 3–4 times larger than those in local galaxies. The depletion times of molecular gas for the detected galaxies are (1.4–36) × 10{sup 8} yr while the results of the stacking analysis show ∼3 × 10{sup 8} yr. The depletion time tends to decrease with increasing stellar mass and metallicity though the trend is not so significant, which contrasts with the trends in local galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

High Quantum Efficiency Uni-Traveling-Carrier Photodiode for Optical to Microwave Transduction

Modern Quantum Information Systems (QIS) employ optical photons for long distance communication, operating at ambient temperature, between microwave cavities, which house microwave photons used in quantum computing and microwave detection. These optical photons, carried by fiber-optic or free-space links, offer a low-cost, uncooled alternative to bulky, expensive microwave coaxial cables, which are lossy, susceptible to EMI, and a significant thermal conductor to the outside ambient environment. To convert between these two types of photons and implement these optical interconnects, it is necessary to develop a high-performance photodetector for optical to microwave transduction. Freedom Photonics and the University of Virginia have a well-established partnership in developing high-performance photodiodes. In this Phase I effort, we collaborated in designing, fabricating, and testing an advanced, high-speed, high quantum efficiency prototype photodiode for transduction from optical to microwave frequencies. These devices have applications not only in quantum computing and axion detection, but also in other optical-cryogenic interconnect applications, in fields such as radio astronomy and quantum cryptography, as well as in quantum metrology and plasmonics. During this Phase I DOE program, we designed, fabricated, and tested prototype PIN GaAs photodiodes which targeted the performance parameters defined by the program. This process involved identifying a new target wavelength, different from that proposed initially, based on conversations with the Oak Ridge National Lab customer. We designed an epitaxial stack, optimized in theory for ≥95% quantum efficiency at 795 nm, ≥5 GHz, per the target objectives of the program. Additionally, we designed a fabrication process and associated mask plates for top-illuminated, AR-coated devices with device diameters ranging from 50 µm to 800 µm. Using these, we fabricated two 3” wafer quarters of devices, and characterized the devices’ dark current, quantum efficiency, and bandwidth for various device diameters. The prototype devices achieved a quantum efficiency of 89% at the target 795 nm detection wavelength. The bandwidth of the devices proved tricky to characterize, but a 50 µm diameter device shows a 3-dB bandwidth of at least 1.6 GHz, possibly a full 5 GHz, depending on the measurement setup. In the future, we plan to characterize the bandwidth of these devices using an impulse response measurement. All tasks for the Phase I were successfully completed, and sample prototype devices were provided to Oak Ridge National Lab Quantum Information Science researchers. The work performed in Phase I has established a strong foundation for future design and fabrication cycles in Phase II, if granted. The early tests at Oak Ridge National Labs will provide guidance for the required photodiode performance in devices to be supplied in Phase II.

42 ENGINEERING↗
NASA NTRS2023

Cosmological Shocks Around Galaxy Clusters: A Coherent Investigation With DES, SPT & ACT

We search for signatures of cosmological shocks in gas pressure profiles of galaxy clusters using the cluster catalogues from three surveys: the Dark Energy Survey (DES) Year 3, the South Pole Telescope (SPT) SZ survey, and the Atacama Cosmology Telescope (ACT) data releases 4, 5, and 6, and using thermal Sunyaev–Zeldovich (SZ) maps from SPT and ACT. The combined cluster sample contains around 105 clusters with mass and redshift ranges 10 13.7 200m /M ⊙ <10 15.5 and 0.1 < z < 2, and the total sky coverage of the maps is ≈15000deg 2 ⁠. We find a clear pressure deficit at R/R 200m ≈ 1.1 in SZ profiles around both ACT and SPT clusters, estimated at 6σ significance, which is qualitatively consistent with a shock-induced thermal non-equilibrium between electrons and ions. The feature is not as clearly determined in profiles around DES clusters. We verify that measurements using SPT or ACT maps are consistent across all scales, including in the deficit feature. The SZ profiles of optically selected and SZ-selected clusters are also consistent for higher mass clusters. Those of less massive, optically selected clusters are suppressed on small scales by factors of 2–5 compared to predictions, and we discuss possible interpretations of this behaviour. An oriented stacking of clusters – where the orientation is inferred from the SZ image, the brightest cluster galaxy, or the surrounding large-scale structure measured using galaxy catalogues – shows the normalization of the one-halo and two-halo terms vary with orientation. Finally, the location of the pressure deficit feature is statistically consistent with existing estimates of the splashback radius.

galaxies↗
DOE OSTI2025

Sustainable Shape Memory Elastomers with Reduced Melt Viscosity and Enhanced Stiffness

Melt reactive processing of lignin with nitrile rubber is a promising approach to synthesizing shape memory materials. The strong intramolecular interactions in lignin macromolecular structures, caused by π–π stacking in aromatic rings and hydrogen bonding, often result in large phase separation or low miscibility with rubbers. In this study, we investigated the chemical and molecular characteristics, as well as the stiffness and complex viscosity, of modified kraft lignin melt-reacted with an acrylonitrile/butadiene copolymer containing 41% acrylonitrile (NBR41). To enhance the macromolecular compatibility of kraft lignin with NBR41, kraft lignin was cross-linked with poly(propylene glycol) diglycidyl ether (PPDE) and trimethylolpropane triglycidyl ether (TTE), both rich in epoxy reactive groups capable of forming chemical bonds with hydroxyl and carboxyl groups. Here, our findings demonstrate that the modification of kraft lignin with PPDE and TTE resulted in significantly increased stiffness of the composites. The elastic modulus of NBR41-Kraft lignin-PPDE and NBR41-Kraft lignin-TTE increased by 82 and 162%, respectively. Both the yield strength and Young’s modulus of these two samples showed dramatic improvements. Specifically, the yield strength and Young’s modulus of NBR41-Kraft lignin-TTE increased nearly 4 and 3-fold, respectively, compared to the control sample. Interestingly, despite significant improvements in mechanical properties, the viscosity of NBR41-Kraft lignin-PPDE was substantially lower than that of the control sample. At 210 °C and an angular frequency of 1 rad/s, the complex viscosity of NBR41-Kraft lignin was approximately 100.25 ± 4.77 kPa·s, while that of NBR41-Kraft lignin-PPDE was significantly lower at 56 ± 0.93 kPa·s. These findings were validated through Fourier transform infrared spectroscopy, scanning electron microscopy, dynamic mechanical analysis, thermal characterization, rheological tests, and quasi-elastic neutron scattering techniques.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Geochemical Reaction Mechanism Discovery from Molecular Simulation

Methods to explore reactions using computer simulation are becoming increasingly quantitative, versatile, and robust. In this review, a rationale for how molecular simulation can help build better geochemical kinetics models is first given. We summarize some common methods that geochemists use to simulate reaction mechanisms, specifically classical molecular dynamics and quantum chemical methods and discuss their strengths and weaknesses. Useful tools such as umbrella sampling and metadynamics that enable one to explore reactions are discussed. Several case studies wherein geochemists have used these tools to understand reaction mechanisms are presented, including water exchange and sorption on aqueous species and mineral surfaces, surface charging, crystal growth and dissolution, and electron transfer. The impact that molecular simulation has had on our understanding of geochemical reactivity are highlighted in each case. In the future, it is anticipated that molecular simulation of geochemical reaction mechanisms will become more commonplace as a tool to validate and interpret experimental data, and provide a check on the plausibility of geochemical kinetic models.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1999

Effects of Melt Processing on Evolution of Structure in PEEK

We report on the effects of melt processing temperature on structure formation in Poly(ether-ether-ketone), PEEK. Real time Small Angle X-ray Scattering, SAXS, and thermal analysis are used to follow the melting behavior after various stages of processing. Assignment of peaks to structural entities within the material, the relative perfection of the crystals, and the possibility of their reorganization, are all influenced by the melt processing history. With the advent of high intensity synchrotron sources of X-radiation, polymer scientists gain a research tool which, when used along with thermal analysis, provides additional structural information about the crystals during growth and subsequent melting. PEEK is an engineering thermoplastic polymer with a very high glass transition temperature (145 C) and crystal melting point (337 C). PEEK has been the subject of recent studies by X-ray scattering in which melt and cold crystallization were followed in real-time. X-ray scattering and thermal studies have been used to address the formation of dual endothermic response which has been variously ascribed to lamellar insertion, dual crystal populations, or melting followed by re-crystallization. Another important issue is whether all of the amorphous phase is located in interlamellar regions, or alternatively whether some is located in "pockets" away from the crystalline lamellar stacks. The interpretation of scattering from lamellar stacks varies depending upon whether such amorphous pockets are formed. Some groups believe all of the amorphous phase is interlamellar. This leads to selection of a smaller thickness for the crystals. Other groups suggest that most amorphous phase is not interlamellar, and this leads to the suggestion that the crystal thickness is larger than the amorphous layer within the stacks. To investigate these ideas, we used SAXS and Differential Scanning Calorimetry to compare results of single and dual stage melt crystallization of PEEK using a treatment scheme involving annealing/crystallization at T(sub a1) followed by annealing at T(sub a2) where either T(sub a1) < T(sub a2) or T(sub a1) > T(sub a2). We proposed a model to explain multiple melting endotherms in PPS, treated according to one or two-stage melt or cold crystallization. Key features of this model are that multiple endotherms: (1) are due to reorganization/recrystallization after cold crystallization; and, (2) are dominated by crystal morphology after melt crystallization at high T. In other words, multiple distinct crystal populations are formed by the latter treatment, leading to observation of multiple melting. PEEK 45OG pellets (ICI Americas) were the starting material for this study. Films were compression molded at 400 C, then quenched to ice water. Samples were heated to 375 C in a Mettler FP80 hot stage and held for three min. to erase crystal seeds before cooling them to T(sub a1) = 280 C . Samples were held at T(sub a2) for a period of time, then immediately heated to 360 C. In the second treatment samples were held at T(sub a1) = 31 C for different crystallization times t(sub c) then cooled to 295 C and held 15 min. In situ (SAXS) experiments were performed at the Brookhaven National Synchrotron Light Source with the sample located inside the Mettler hot stage. The system was equipped with a two-dimensional position sensitive detector. The sample to detector distance was 172.7 cm and the X-ray wavelength was 1.54 Angstroms. SAXS data were taken continuously during the isothermal periods and during the heating to 360 C at 5 C/min. Each SAXS scan was collected for 30 sec. Since the samples were isotropic, circular integration was used to increase the signal to noise ratio. After dual stage melt crystallization with T(sub a1) < T(sub a2) the lower melting endotherm arises from holding at T(sub a1). During cooling a broad distribution of crystals forms, and the low-melting tail is perfected during T(sub al). Heating to T(sub a2) melts these imperfect crystals and allows others with greater average long spacing to form in their place. After dual stage crystallization with T(sub a1) > T(sub a2), the amount of space remaining for additional growth at T(sub a2) depends upon the holding time at T(sub a1). The long period of crystals formed at T(sub a2) is smaller than that formed at T(sub a1) due to growth in a now-restricted geometry. Perfection of crystals is seen as an increase of the intensity of the population scattering at higher s, while the intensity of the population scattering at lower s stays constant. During heating from below to above the minor endotherm, we see rapid decrease of the intensity of the X-ray scattering corresponding to the population of crystals scattering in the shoulder. Another important observation is that after the sample is annealed at 295 C, the shoulder intensity is restored once again. The population scattering at higher s remains longer before it disappears in the sample treated to the second stage of melt crystallization, compared to the sample crystallized with a single stage. This could be interpreted as an effect of continued perfection of the less perfect population, which is also reflected in the increased melting temperature of the smaller endotherm as the holding time at 295 C increases. In the corresponding DSC scans we see a shift in the area and the peak temperature of the lower melting endotherm with an increase of the annealing time.

Georgiev, Georgi↗
DOE OSTI2018

The Effect of Aging on the Delamination Fracture Energy of Glass Solar Reflectors

Thin metal and metal oxide films deposited on glass or polymer substrates have been widely applied to manufacture front surfaced solar reflectors such as those used in the concentrated solar power (CSP) systems due to the facts that they are highly transparent, resistant to ultraviolet (UV) light and abrasion, and chemically inert. However, the reliable operation over long periods of outdoor exposure of such solar reflectors depends on the adequate adhesion between each layer to prevent delamination and subsequent failure. We report results from measurements of the delamination fracture energy (DFE) of the weakest interface in both as-deposited and aged reflectors, where the reflector construction consists of a glass/copper/silver/oxide stack. In this study, DFE was measured using a width-tapered beam method and the test results showed that the weakest interface of this solar reflector is the copper-glass interface, with a delamination fracture energy of approximately 4.4 J/m 2 . In order to verify the test results, finite element (FE) simulations were run using the commercial software package ABAQUS 6.14 based on the cohesive zone model (CZM). In the simulations, the DFE derived from the delamination measurement was treated as an input and the delamination forces from the FE simulations were compared to the experimental results. The good agreement between the tested and simulated delamination force indicated that this width-tapered beam method is accurate even for very small DFE, making it appropriate to test the DFE of front surfaced glass solar reflectors. Additionally, in order to study the aging effect on the DFE, accelerated aging tests were conducted using samples with different protective coatings, one group of samples with alumina ( Al 2 O 3 ) protective coating and the other group with titania ( TiO 2 ) protective coating. The DFE after 50 and 100 hours of accelerated aging were measured. The test results showed that the copper-glass interface would still be the weakest interface for all samples after aging, and the DFE for samples with Al 2 O 3 protective coating was unchanged whereas the copper-glass interface was found to undergo statistically significant change after both 50 and 100 hours of aging for samples with TiO 2 protective coating. We found that DFE at the copper/glass interface decreased after 50 hours of aging then increased after 100 hours of aging. The origin of this non-monotonic response of TiO 2 coated reflectors under accelerated aging conditions is unknown.

36 MATERIALS SCIENCE↗
DOE OSTI2016

The kinematics of C iv in star-forming galaxies at z ∼ 1.2

We present the first statistical sample of rest-frame far-UV spectra of star-forming galaxies at z ∼ 1. These spectra are unique in that they cover the high-ionization C iv λλ1548, 1550 doublet. We also detect low-ionization features such as Si ii λ1526, Fe ii λ1608, Al ii λ1670, Ni ii λλ1741, 1751, and Si ii λ1808, and intermediate-ionization features from Al iii λλ1854, 1862. Comparing the properties of absorption lines of lower- and higher-ionization states provides a window into the multiphase nature of circumgalactic gas. Our sample is drawn from the DEEP2 survey and spans the redshift range 1.01 ≤ z ≤ 1.35 (〈z〉=1.25). By isolating the interstellar C iv absorption from the stellar P Cygni wind profile, we find that 69% of the C iv profiles are blueshifted with respect to the systemic velocity. Furthermore, C iv shows a small but significant blueshift relative to Fe ii (offset of the best-fit linear regression −76 ± 26 km s{sup −1}). At the same time, the C iv blueshift is on average comparable to that of Mg ii λλ2796, 2803. At this point, in explaining the larger blueshift of C iv absorption at the ∼3σ level, we cannot distinguish between the faster motion of highly ionized gas relative to gas traced by Fe ii and filling in on the red side from resonant C iv emission. We investigate how far-UV interstellar absorption kinematics correlate with other galaxy properties using stacked spectra. These stacking results show a direct link between C iv absorption and the current star formation rate, though we only observe small velocity differences among different ionization states tracing the outflowing interstellar medium.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

STAR FORMATION IN THE EARLY UNIVERSE: BEYOND THE TIP OF THE ICEBERG

We present late-time Hubble Space Telescope (HST) imaging of the fields of six Swift gamma-ray bursts (GRBs) lying at 5.0 {approx}< z {approx}< 9.5. Our data include very deep observations of the field of the most distant spectroscopically confirmed burst, GRB 090423, at z = 8.2. Using the precise positions afforded by their afterglows, we can place stringent limits on the luminosities of their host galaxies. In one case, that of GRB 060522 at z 5.11, there is a marginal excess of flux close to the GRB position which may be a detection of a host at a magnitude J{sub AB} Almost-Equal-To 28.5. None of the others are significantly detected, meaning that all the hosts lie below L* at their respective redshifts, with star formation rates (SFRs) {approx}< 4 M{sub Sun} yr{sup -1} in all cases. Indeed, stacking the five fields with WFC3-IR data, we conclude a mean SFR <0.17 M{sub Sun} yr{sup -1} per galaxy. These results support the proposition that the bulk of star formation, and hence integrated UV luminosity, at high redshifts arises in galaxies below the detection limits of deep-field observations. Making the reasonable assumption that GRB rate is proportional to UV luminosity at early times allows us to compare our limits with expectations based on galaxy luminosity functions (LFs) derived from the Hubble Ultra-Deep Field and other deep fields. We infer that an LF, which is evolving rapidly toward steeper faint-end slope ({alpha}) and decreasing characteristic luminosity (L*), as suggested by some other studies, is consistent with our observations, whereas a non-evolving LF shape is ruled out at {approx}> 90% confidence. Although it is not yet possible to make stronger statements, in the future, with larger samples and a fuller understanding of the conditions required for GRB production, studies like this hold great potential for probing the nature of star formation, the shape of the galaxy LF, and the supply of ionizing photons in the early universe.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Geometric magnetic frustration in RE{sub 2}O{sub 2}S oxysulfides (RE = Sm, Eu and Gd)

Graphical abstract: Stacked planes in the <001> direction of an oxysulfide structure, showing the triangular nets formed by rare earth cations, which moments present geometric magnetic frustration. - Highlights: • We prepared monophasic RE{sub 2}O{sub 2}S Oxysulfides (RE = Sm, Eu and Gd). • RE{sub 2}O{sub 2}S compounds were characterized regarding structural and magnetic properties. • Mössbauer spectra were obtained for Eu{sub 2}O{sub 2}S and Gd{sub 2}O{sub 2}S at different temperatures. • Oxysulfides present geometric magnetic frustration of the rare-earth sublattice. - Abstract: RE{sub 2}O{sub 2}S oxysulfides (with RE = Sm, Eu and Gd) were prepared and characterized regarding their structural and magnetic properties. The compounds crystallized in the trigonal symmetry (space group P-3m/D{sub 3}{sup 3}d), with the lattice parameter varying linearly with the ionic radius of the RE cation. All these oxysulfides are magnetically frustrated and only the gadolinium sample showed magnetic order down to 3 K. The magnetic frustration is attributed to the spatial distribution of cations over the lattice, where the RE’s magnetic moments occupy the sites forming a triangular plane lattice, perpendicular to the direction. This geometric magnetic frustration was firstly recognized for these oxysulfides.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Lyman Alpha Emitting Galaxies at 2 < z < 3: Towards a Calibrated Probe of Dark Energy

The goal of this project was to establish the physical properties of Ly{alpha} emitting galaxies from redshifts of 2 to 3 in order to better calibrate the use of LAEs as probes of the large scale structure of the universe for upcoming dark energy experiments, such as the Hobby Eberly Telescope Dark Energy Experiment (HETDEX). We have obtained narrow-band imaging of the Extended Chandra Deep Field South (ECDF-S) in two different narrow-band filters centered at Lyα at z=2.1 and 3.1. The resulting of samples of LAEs were used to determine the LAE luminosity function, equivalent width distribution and clustering properties (bias) of LAEs at these redshifts. While the results from the ECDF-S appear robust, they are based on a single field. To explore the effects of cosmic variance and galaxy environment on the physical properties of LAEs, we have also obtained narrow-band data at both redshifts (z = 2:1 and 3:1) in three additional fields (SDSS 1030+-05, the Extended Hubble Deep Field South, and CW 1255+01). The narrow-band imaging data has been reduced and LAE catalogs are being generated. We have calculated preliminary luminosity functions, equivalent width distributions, and clustering properties. We have also obtained follow-up spectroscopy in the optical (using VLT/FORS) and in the near-infrared (using Magellan/MMIRS). Since individual LAEs have too little S/N to enable meaningful fits for stellar population parameters, our previous work has analyzed stacked Spectral Energy Distributions (SEDs). SED fitting was performed on several subsets of LAEs selected by their rest-UV luminosity, UV spectral slope, Ly alpha luminosity, Equivalent Width, or rest-optical (IRAC) luminosity.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Star Formation Activity of Barred Spiral Galaxies

We study the star formation activity of nearby galaxies with bars using a sample of late-type galaxies at 0.02⩽z⩽0.05489 and M{sub r}<−19.5 from the Sloan Digital Sky Survey. We compare the physical properties of strongly and weakly barred galaxies with those of non-barred galaxies that have stellar mass and redshift distributions similar to barred galaxies. We find that the star formation activity of strongly barred galaxies probed by starburstiness, g−r, NUV−r, and mid-infrared [3.4]–[12] colors is, on average, lower than that of non-barred galaxies. However, weakly barred galaxies do not show such a difference between barred and non-barred galaxies. The amounts of atomic and molecular gas in strongly barred galaxies are smaller than those in non-barred galaxies, and the gas metallicity is higher in strongly barred galaxies than in non-barred galaxies. The gas properties of weakly barred galaxies again show no difference from those of non-barred galaxies. We stack the optical spectra of barred and non-barred galaxies in several mass bins and fit to the stacked spectra with a spectral fitting code, STARLIGHT. We find no significant difference in stellar populations between barred and non-barred galaxies for both strongly and weakly barred galaxies. Our results are consistent with the idea that the star formation activity of barred galaxies was enhanced in the past along with significant gas consumption, and is currently lower than or similar to that of non-barred galaxies. The past star formation enhancement depends on the strength of bars.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Mechanistic insights into rubidium ion adsorption at the quartz (101) surface from quantum chemical metadynamics

Ion sorption extent and mechanism depend in part on the mineral surface termination, which can be highly complex. Variations in surface functional groups, particularly with defect density and surface roughness, influence mineral reactivity towards solutes. In this work, we investigate the adsorption of a rubidium cation (Rb + ) at pristine and defect quartz (101) surface sites using well-tempered metadynamics, based on simulations with the quantum chemical density-functional tight-binding (DFTB) method. We compare the relative energetics of Rb + adsorption across selected sites for each surface, with nanosecond-level sampling, highlighting similarities between vicinal and geminal silanol sites. We find that the positive Rb + partial atomic charge can increase by as much as 0.5e as it approaches the surface, with implications for modulation of ion adsorption strength and extent at the quartz (101) surface with surface vacancies, silanol coverage, and charge.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1973

Lidar Observations of Raman Scattering from S02 in a Power Plant Stack Plume

LIDAR techniques have been successfully applied to the detection of the Raman backscatter from S02 in the plume of a 200 megawatt coal-burning electrical- generating plant from a distance of 210 meters. The LIDAR system used consists of a 61-centimeter-diameter, f /4 Newtonian telescope and a 1.0-1.5-joules per pulse, 1-pulse-per-second ruby laser. Narrow band interference filters are used to select the 7546-angstrom v (sub 1) vibrational line of S02. The signal from a photomultiplier tube was sequentially applied to each 254-nanosecond-wide channel of a 15-cihannel photon counting system, resulting in a direct correlation between channel number and range increment. Photon counts were accumulated from the backscatter of a number of laser pulses (typically 50 or 100), and the accumulated counts per channel printed on paper tape. One sequence of measurements was made during a two-hour period while the plant electrical output was being reduced by approximately 50 percent. Although the Raman system had not been quantitatively calibrated, the LIDAR data correlated well with the varying plant electrical output. N2 scattering observations were also made and an approximate quantitative S02 concentration obtained by ratioing the S02 data to N2 data. This ratio compared well to the in-situ measurements made during the same period by Environmental Protection Agency sampling instruments.

Brumfield, M. L.↗
DOE OSTI2020

Outside the Lyman-break box: detecting Lyman continuum emitters at 3.5 < z < 5.1 with CLAUDS

ABSTRACT Identifying non-contaminated sample of high-redshift galaxies with escaping Lyman continuum (LyC) flux is important for understanding the sources and evolution of cosmic reionization. We present CLAUDS (CFHT Large Area u-band deep survey) u-band photometry of the COSMOS field to probe LyC radiation from spectroscopically confirmed galaxies at $z$ ≥ 3.5 and outside the standard Lyman-break galaxy colour-selection expectations. Complementary to the CLAUDS data, we use Subaru multifilter photometry, Hubble Space Telescope (HST) multifilter imaging, and the spectroscopic surveys D10K, VUDS, and 3D-HST. We present a sample of Lyman continuum galaxy (LCG) candidates in the redshift range 3.5 ≲ $z$ ≲ 5.1. Here, we introduce 5 LCG candidates, where two are flagged quality 1 and three quality 2. The estimated $f_{\rm esc}^{\rm abs}$ for quality 1 candidates are in the range $\sim 5 - 73{{\ \rm per\ cent}}$ and $\sim 30 - 93{{\ \rm per\ cent}}$. These estimates are based on our derived parameters from individual galaxies as inputs to a range of BPASS models as well as mean intergalactic medium (IGM) and maximal intergalactic and circumgalactic media (IGM+CGM) transmission. We conclude that our search for LCGs is most likely biased to lines of sight with low H i densities or free from Lyman limit systems. Our two best LCG candidates have EW (Lyα) ≤ 50 Å and we find no correlation or anticorrelation between EW (Lyα), $f_{\rm esc}^{\rm abs}$, and Robs, the ratio of ionizing to non-ionizing observed flux in the measured passbands. Stacking candidates without solid LyC detections (S/N < 3) results in an estimated $f_{\rm esc}^{\rm abs}$ from galaxies not greater than $1{{\ \rm per\ cent}}$.

Meštrić, U.↗
DOE OSTI2023

Cosmological shocks around galaxy clusters: A coherent investigation with DES, SPT & ACT

We search for signatures of cosmological shocks in gas pressure profiles of galaxy clusters using the cluster catalogs from three surveys: the Dark Energy Survey (DES) Year 3, the South Pole Telescope (SPT) SZ survey, and the Atacama Cosmology Telescope (ACT) data releases 4, 5, and 6, and using thermal Sunyaev-Zeldovich (SZ) maps from SPT and ACT. The combined cluster sample contains around $10^5$ clusters with mass and redshift ranges $10^{13.7} < M_{\rm 200m}/M_\odot < 10^{15.5}$ and $0.1 < z < 2$, and the total sky coverage of the maps is $\approx 15,000 \,\,{\rm deg}^2$. We find a clear pressure deficit at $R/R_{\rm 200m}\approx 1.1$ in SZ profiles around both ACT and SPT clusters, estimated at $6\sigma$ significance, which is qualitatively consistent with a shock-induced thermal non-equilibrium between electrons and ions. The feature is not as clearly determined in profiles around DES clusters. We verify that measurements using SPT or ACT maps are consistent across all scales, including in the deficit feature. The SZ profiles of optically selected and SZ-selected clusters are also consistent for higher mass clusters. Those of less massive, optically selected clusters are suppressed on small scales by factors of 2-5 compared to predictions, and we discuss possible interpretations of this behavior. An oriented stacking of clusters -- where the orientation is inferred from the SZ image, the brightest cluster galaxy, or the surrounding large-scale structure measured using galaxy catalogs -- shows the normalization of the one-halo and two-halo terms vary with orientation. Finally, the location of the pressure deficit feature is statistically consistent with existing estimates of the splashback radius.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Spectroscopic Confirmation of Five Galaxy Clusters at z > 1.25 in the 2500 deg 2 SPT-SZ Survey

In this paper, we present spectroscopic confirmation of five galaxy clusters at 1.25 < z < 1.5, discovered in the 2500 deg 2 South Pole Telescope Sunyaev–Zel’dovich (SZ) survey. These clusters, taken from a mass-limited sample with a nearly redshift-independent selection function, have multiwavelength follow-up imaging data from the X-ray to near-IR and currently form the most homogeneous massive high-redshift cluster sample known. We identify 44 member galaxies, along with 25 field galaxies, among the five clusters, and describe the full set of observations and data products from Magellan/LDSS3 multiobject spectroscopy of these cluster fields. We briefly describe the analysis pipeline and present ensemble analyses of cluster member galaxies that demonstrate the reliability of the measured redshifts. We report z = 1.259, 1.288, 1.316, 1.401, and 1.474 for the five clusters from a combination of absorption-line (Ca ii H&K doublet—λλ3968, 3934) and emission-line ([O ii] λλ3727, 3729) spectral features. Moreover, the calculated velocity dispersions yield dynamical cluster masses in good agreement with the SZ masses for these clusters. We discuss the velocity and spatial distributions of passive and [O ii]-emitting galaxies in these clusters, showing that they are consistent with velocity segregation and biases observed in lower redshift South Pole Telescope clusters. We identify modest [O ii] emission and pronounced CN and Hδ absorption in a stacked spectrum of 28 passive galaxies with Ca ii H&K-derived redshifts. Lastly, this work increases the number of spectroscopically confirmed SZ-selected galaxy clusters at z > 1.25 from three to eight, further demonstrating the efficacy of SZ selection for the highest redshift massive clusters and enabling detailed study of these systems.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2026

Design and Commissioning of a Deuterium-Tritium Gas Delivery System for Muon Catalyzed Fusion in a Diamond Anvil Cell

We report the design, commissioning, and operation of deuterium-deuterium (DD) and deuterium-tritium (DT) gas delivery systems developed to load a diamond anvil cell (DAC) beam target for muon-catalyzed fusion (muCF). The DAC approach enables DT fuel to be compressed to GPa pressures at more than twice the liquid density and heated from cryogenic temperatures through 500 K, opening access to a substantially expanded parameter range for muCF kinetics and yield measurements. In this approach, DT is cryo-condensed to a liquid in a minichamber and then compressed in the DAC using a helium-driven pneumatic membrane, achieving high pressures in a millimeter-scale DT sample volume. A DD gas delivery system was designed and used to validate the experimental apparatus, measure the gas quantities needed for filling, develop operational experience, and collect kinetics and yield data with DD targets. The DT gas delivery system adds tritium-specific capabilities for inventory minimization, secondary containment, and activity monitoring. The DT system integrates depleted uranium storage beds and a liquid helium cryogenic condenser used for pressure building and cryopumping. High-purity delivery is provided by a rapid-response palladium permeator. The system is housed in a helium-atmosphere glovebox held at negative pressure with continuous cleanup. We present the process and instrumentation design, a failure modes and effects analysis (FMEA), and data from the experiment's in situ Raman spectrometer, which provides direct confirmation of target loading and composition through the optically clear diamond anvils. The 2024 and 2025 DT campaigns achieved repeatable target fills and operation with no measurable tritium releases to the stack, demonstrating safe, high-purity DT loading at novel density-temperature conditions for muCF studies.

Koukina, Elena [Acceleron Fusion]↗