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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Illumination frustums for photoconductive switches

Methods and devices for illuminating a photoconductive switch consisting of an optically actuated photoconductive material situated between two electrodes are described. Light from a light source is coupled to an optical fiber, which is attached to a frustum, the other side of which is proximate to the photoconductive switch. Light from the optical fiber enters the frustum, spreads out, and enters the photoconductive switch via the top-side electrode. Some of the light is absorbed, while the remaining light reflects off the bottom-side electrode, travels back through the photoconductive switch, and any unabsorbed light reenters the frustum. The geometry of the frustum is configured such that most of the light reflects back into the switch itself with only a negligible fraction escaping from the optical fiber, which advantageously results in near total utilization of the light.

Rushford, Michael↗
DOE OSTI2022

Salt Hydrate Eutectic Mixtures for Near-ambient Thermal Energy Storage Applications

In this work, we synthesized and characterized Na2SO4.10H2O – Na2CO3.10H2O eutectic salt hydrate phase change material (PCM) using Differential Scanning Calorimetry (DSC), Attenuated total reflectance infrared spectroscopy (ATR-IR), and X-ray Diffraction (XRD) techniques. The eutectic point of the PCM mixture was predicted based on binary eutectic effect and ion exchange theory. The XRD and ATR-IR results indicate that the eutectic PCM mixture was formed based on only physical mixing without chemical interaction. Moreover, DSC results showed that the eutectic concentration is 50wt% Na2SO4.10H2O – 50wt% Na2CO3.10H2O with melting temperature of 25.18°C and melting enthalpy of 187.46 J/g. Also, 78% of melting enthalpy was recoverable after 10 melt/freeze cycles. This eutectic mixture has the potential to be used in building thermal comfort applications.

Gluesenkamp, Kyle↗
DOE OSTI2021

In Situ ATR-FTIR Study of the Cathode–Electrolyte Interphase: Electrolyte Solution Structure, Transition Metal Redox, and Surface Layer Evolution

We present a study of the lithium nickel manganese cobalt oxide (LiNi 0.6 Mn 0.2 Co 0.2 O 2 , NMC622) cathode-electrolyte interphase (CEI) during galvanostatic charging and discharging using in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) methods to investigate the voltage dependent electrolyte solution structure changes at the interface, transition metal (TM) redox chemistry, and cathode/electrolyte interfacial layer evolution. Furthermore, our in situ cell design provides both reliable electrochemical device testing and strong FTIR vibrational absorption signals near the cathode surface. Specifically, advanced spectral analysis elucidates changes of near-surface Li+ ion (de)solvation by solvent molecules during galvanostatic cycling. Moreover, cathode metal-oxygen vibrational absorptions, sensitive to TM redox behaviors and subsequent local structural variations, were correlated to cathode de-lithiation (and lithiation) and electrolyte solution structure changes. In addition, we have detected the formation and evolution of a CEI surface layer on the NMC622 cathode that contributes to the cell's capacity fade.

25 ENERGY STORAGE↗
DOE OSTI2020

Investigating drivers of microbial activity and respiration in a forested bog

Northern peatlands store nearly one-third of terrestrial carbon (C) stocks while covering only 3% of the global landmass; nevertheless, the drivers of C cycling in these often-waterlogged ecosystems are different from those that control C dynamics in upland forested soils. To explore how multiple abiotic and biotic characteristics of bogs interact to shape microbial activity in a northern, forested bog, we added a labile C tracer ( 13 C-labeled starch) to in situ peat mesocosms and correlated heterotrophic respiration with natural variation in several microbial predictor variables, such as enzyme activity and microbial biomass, as well as with a suite of abiotic variables and proximity to vascular plants aboveground. We found that peat moisture content was positively correlated with respiration and microbial activity, even when moisture levels exceeded total saturation, suggesting that access to organic matter substrates in drier environments may be limiting for microbial activity. Proximity to black spruce trees decreased total and labile heterotrophic respiration. This negative relationship may reflect the influence of tree evapotranspiration and peat shading effects; i.e., microbial activity may decline as peat dries and cools near trees. Here, we isolated the response of heterotrophic respiration to explore the variation in, and interactions among, multiple abiotic and biotic drivers that influence microbial activity. This approach allowed us to reveal the relative influence of individual drivers on C respiration in these globally important C sinks.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

In Liquid Infrared Scattering Scanning Near-Field Optical Microscopy for Chemical and Biological Nanoimaging

Imaging biological systems with simultaneous intrinsic chemical specificity and nanometer spatial resolution in their typical native liquid environment has remained a long-standing challenge. In this paper we demonstrate a general approach of chemical nanoimaging in liquid based on infrared scattering scanning near-field optical microscopy (IR $s$-SNOM). It is enabled by combining AFM operation in a fluid cell with evanescent IR illumination via total internal reflection, which provides spatially confined excitation for minimized IR water absorption, reduced far-field background, and enhanced directional signal emission and sensitivity. We demonstrate in-liquid IR $s$-SNOM vibrational nanoimaging and conformational identification of catalase nano-crystals and spatio-spectral analysis of biomimetic peptoid sheets with monolayer sensitivity and chemical specificity at the few zeptomole level. This work establishes the principles of in-liquid and in-situ IR $s$-SNOM spectroscopic chemical nano-imaging and its general applicability to biomolecular, cellular, catalytic, electrochemical, or other interfaces and nano-systems in liquids or solutions.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2022

Spectroscopic Investigation of Catalyst Inks and Thin Films Toward the Development of Ionomer Quality Control

As the production of polymer electrolyte fuel cells expands, novel quality control methods must be invented or adapted in order to support expected rates of production. Ensuring the quality of deposited catalyst layers is an essential step in the fuel cell manufacturing process, as the efficiency of a fuel cell is reliant on the catalyst layer being uniform at both the target platinum loading and the target ionomer content. Implementing a quality control method that is sensitive to these aspects is imperative, as wasting precious metals and other catalyst materials is expensive, and represents a potential barrier to entry into the field for manufacturers experimenting with novel deposition processes. In this work, we analyzed catalyst inks to determine if their ionomer content could be quantized spectroscopically. Attenuated total reflection (ATR) Fourier transform infrared spectroscopic technique was investigated producing a signal proportional to the ionomer content. ATR spectroscopy was able to quantitatively differentiate samples in which the ionomer to carbon mass ratio (I/C) varied between 0.9 and 3.0. The I/C ratio was correlated to the measured ATR signal near the CF 2 vibrational bands located between 1100 cm −1 and 1400 cm −1 . The experimental results obtained constitute a step toward the development of novel quality control methodologies for catalyst inks utilized by the fuel cell industry.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2020

Impact of divertor material on neutral recycling and discharge fueling in DIII-D

We report that experiments with the lower divertor of DIII-D during the Metal Rings Campaign (MRC) show that the fraction F of atomic D in the total recycling flux is material-dependent and varies through the ELM cycle, which may affect divertor fueling. Between ELMs, F C ~ 10% and FW ~ 40%, consistent with expectations if all atomic recycling is due to reflections. During ELMs, F C increases to 50% and F W to 60%. In contrast, the total D recycling coefficient including atoms and molecules R stays close to unity near the strike point where the surface is saturated with D. During ELMs, R can deviate from unity, increasing during high energy ELM-ion deposition (net D release) and decreasing at the end of the ELM which leads to ability of the target to trap the ELM-deposited D. The increase of R > 1 in response to an increase in ion impact energy Ei has been studied with small divertor target samples using Divertor Materials Evaluation System (DiMES). An electrostatic bias was applied to DiMES to change E i by 90 eV. On all studied materials including C, Mo, uncoated and W-coated TZM (>99% Mo, Ti, and Zr alloy), W, and W fuzz, an increase of E i transiently increased the D yield (and R) by ~10%. On C there was also an increase in the molecular D 2 yield, probably due to ion-induced D 2 desorption. Despite the measured increase in F on W compared to C, attached H-mode shots with OSP on W during MRC did not demonstrate a higher pedestal density. About 8% increase in the edge density could be seen only in attached L-mode scenarios. The difference can be explained by higher D trapping in the divertor and lower divertor fueling efficiency in H- versus L-mode.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

Structure of Complex Liquid–Liquid Extraction Organic Phases for Rare Earth Separations

Complex, multicomponent liquids with hierarchical structure and phase transitions are encountered in many natural and industrial processes, including in chemical separations. One notable example is aggregation and organic phase splitting in liquid–liquid extraction (LLE) of metal ions. While these two phenomena that have long been closely associated, a mechanistic link between mesoscale structure and the capacity-limiting organic phase splitting remains elusive due to complexity of these systems. Here, in this study, we combine small-angle X-ray scattering (SAXS), X-ray photon correlation spectroscopy (XPCS), and molecular dynamics simulation to reveal a comprehensive picture of structure at the nano- and mesoscale in these complex solutions. For the representative case of rare earth extraction from an acidic aqueous phase by a malonamide extractant in dodecane, we investigate a wide range of process-relevant extractant and acid concentrations to provide a complete picture of how aggregation depends on composition. We decompose organic phase structure from SAXS into two contributions, which together can capture the scattering at all compositions: composition fluctuations described by the Ornstein–Zernike equation at low wavenumber Q, and nanostructure modeled by a “pre-peak” at intermediate Q. The former contains information about the thermodynamics of demixing, while the latter reflects nanoscopic self-assembly of the extractant and extracted solutes. While fluctuations have typically not been considered in the literature, we find they in fact dominate the total structure for nearly all practical conditions. As only the fluctuations have a strong temperature response, we confirm this attribution with temperature-dependent SAXS measurements, including for extracted europium nitrate complexes. SAXS and XPCS measurements near the critical point find static and dynamic scaling consistent with theory. Overall, this new paradigm for understanding LLE organic phases connects composition, nanoscale, and mesoscale structuring to phase behavior, providing both a comprehensive picture of solution structure and a quantitative link between aggregation and third phase formation.

Peroutka, Allison A. [Argonne National Laboratory ↗
DOE OSTI2020

High-resolution optical micro-spectroscopy extending from the near-infrared to the vacuum-ultraviolet

Optical characterization of small samples over a wide spectral range with rapid data acquisition is essential for the analysis of many material systems, such as 2D van der Waals layers and their heterostructures. In this paper, we present the design and implementation of a tabletop micro-spectroscopy system covering the near-infrared to the vacuum-ultraviolet (1.2 eV–6.8 eV or ~1.0 μm to 185 nm) using mostly off-the-shelf components. It can measure highly reproducible local reflectance spectra with a total integration time of a few minutes and a full-width-half-maximum spot size of 2.7 by 5.6 μm. For precise positioning, the design also allows simultaneous monitoring of the measurement location and the wide-field image of the sample. We demonstrate ultra-broadband reflectance spectra of exfoliated thin flakes of several wide-gap 2D materials, including ZnPS 3 , hexagonal BN, and Ca(OH) 2 .

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

A refraction correction for buried interfaces applied to in situ grazing-incidence X-ray diffraction studies on Pd electrodes

In situ characterization of electrochemical systems can provide deep insights into the structure of electrodes under applied potential. Grazing-incidence X-ray diffraction (GIXRD) is a particularly valuable tool owing to its ability to characterize the near-surface structure of electrodes through a layer of electrolyte, which is of paramount importance in surface-mediated processes such as catalysis and adsorption. Corrections for the refraction that occurs as an X-ray passes through an interface have been derived for a vacuum–material interface. In this work, a more general form of the refraction correction was developed which can be applied to buried interfaces, including liquid–solid interfaces. Furthermore, the correction is largest at incidence angles near the critical angle for the interface and decreases at angles larger and smaller than the critical angle. Effective optical constants are also introduced which can be used to calculate the critical angle for total external reflection at the interface. This correction is applied to GIXRD measurements of an aqueous electrolyte–Pd interface, demonstrating that the correction allows for the comparison of GIXRD measurements at multiple incidence angles. This work improves quantitative analysis of d-spacing values from GIXRD measurements of liquid–solid systems, facilitating the connection between electrochemical behavior and structure under in situ conditions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Comparison of total emitted solar-induced chlorophyll fluorescence (SIF) and top-of-canopy (TOC) SIF in estimating photosynthesis

We report many studies have shown that solar-induced fluorescence (SIF) has a good potential to predict gross primary production (GPP) of vegetation. What we measured by remote sensing or near-surface platforms is top-of-canopy (TOC) SIF (SIF toc ), which is not necessarily equal or proportional to total emitted SIF (SIF tot ) from the entire canopy due to the (re)absorption and scattering effects. However, photosynthesis, the process that plants use to fix carbon from the atmosphere, occurs at the entire vertical canopy. Here, by using the recollision theory, we calculated SIF tot at 760 nm from the measured SIF toc , hyperspectral reflectance (R), canopy interception (i) and leaf albedo (ω l ). Among them, both SIF toc and R can be obtained from concurrent TOC spectral measurements; i and ω l in the near-infrared region can be estimated from the open access datasets with a good accuracy. Our result confirms that the measured SIF toc only accounts for a small fraction of SIF tot : the above-the-canopy sensor can only “see” on average 22.9% of SIF tot at Harvard Forest. SIF tot has the following advantages over SIF toc in estimating GPP: (1) SIF tot improves the diurnal estimate of canopy GPP, especially capable to capture the midday depression of photosynthesis which may cause the large discrepancies between SIF toc and GPP on a diurnal basis, (2) SIF tot produces a stronger correlation with GPP from plants with complex canopy structure or under sky conditions with more diffuse irradiance, and (3) the SIF tot -GPP relationship shows a stronger resilience to environmental stresses. The fluorescence escape ratio (f esc ), the ratio between SIF toc multiplied by π and SIF tot , is mostly determined by the sun-canopy-sensor geometry and leaf inclination distribution. The effect of LAI and the leaf chlorophyll concentration on f esc is marginal at the 760 nm wavelength. Our results suggest that converting SIF toc into SIF tot provides a better tool to understand and estimate GPP.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2026

Point-scale organic-matter decomposition in streambeds is weakly associated with reach-scale respiration

Stream and river ecosystems play a central role in the movement and decomposition of particulate organic matter, serving as a conduit between terrestrial hillslopes and coastal environments. Microbial-catalyzed decomposition generates simpler organic molecules that fuel respiration, often in the sediments of these ecosystems. However, the degree of connection between sediment-associated respiration (ER??d) and organic-matter decomposition remains poorly understood. How that relationship compares to decomposition’s relationship with whole ecosystem (ERtot) and water column (ERwc) respiration is also not clear. We examined the link between particulate organic matter decomposition—using cellulose-based cotton strips as a standardized substrate—and all three components of respiration across 48 sites in the environmentally diverse Yakima River Basin (Washington State, USA). We hypothesized that decomposition within sediments would be most strongly related to ERsed, but decomposition rates were more closely associated with ERtot, with little connection to ERsed or ERwc. This suggests that particulate organic matter decomposition within stream/river sediments reflects integrated system respiration rather than processes confined to sediments or the water column alone. Further, across the basin, decomposition rates nearly spanned the previously reported global range for streams and rivers and were best explained by total dissolved nitrogen (TDN), sediment grain size, and aridity of the upstream drainage area. These results highlight the strong influence of land cover and basin-scale biophysical variation on sediment-associated decomposition processes and indicate that mechanistic models of organic matter decomposition in streams/rivers should account for coupled sediment–water–land interactions.

Stegen, James C. (ORCID:0000000191357424)↗
DOE OSTI2021

Spatially co-registered wide-field nonlinear optical imaging of living and complex biosystems in a total internal reflection geometry

Nonlinear optical microscopy that leverages an objective based total internal reflection (TIR) excitation scheme is an attractive means for rapid, wide-field imaging with enhanced surface sensitivity. Through select combinations of distinct modalities, one can, in principle, access complementary chemical and structural information for various chemical species near interfaces. Here, we report a successful implementation of such a wide-field nonlinear optical microscope system, which combines coherent anti-Stokes Raman scattering (CARS), two-photon fluorescence (TPF), second harmonic generation (SHG), and sum frequency generation (SFG) modalities on the same platform. The intense optical fields needed to drive these high order nonlinear optical processes are achieved through the use of femtosecond pulsed light in combination with the intrinsic field confinement induced by TIR over a large field of view. The performance of our multimodal microscope was first assessed through the experimental determination of its chemical fidelity, intensity and polarization dependences, and spatial resolution using a set of well-defined model systems. Subsequently, its unique capabilities were validated through imaging complex biological systems, including Hydrangea quercifolia pollen grains and Pantoea sp. YR343 bacterial cells. Specifically, the spatial distribution of different molecular groups in the former was visualized via vibrational contrast mechanisms of CARS, whereas co-registered TPF imaging allowed the identification of spatially localized intrinsic fluorophores. We further demonstrate the feasibility of our microscope for wide-field CARS imaging on live cells through independent characterization of cell viability using spatially co-registered TPF imaging. Overall, this approach to TIR enabled wide-field imaging is expected to provide new insights into bacterial strains and their interactions with other species in the rhizosphere in a time-resolved and chemically selective manner.

47 OTHER INSTRUMENTATION↗
DOE OSTI2023

Sorption‐Induced Fiber Optic Plasmonic Gas Sensing via Small Grazing Angle of Incidence

Abstract Sensing technologies based on plasmonic nanomaterials are of interest for various chemical, biological, environmental, and medical applications. In this work, an incorporation strategy of colloidal plasmonic nanoparticles (pNPs) in microporous polymer for realizing distinct sorption‐induced plasmonic sensing is reported. This approach is demonstrated by introducing tin‐doped indium oxide pNPs into a polymer of intrinsic microporosity (PIM‐1). The composite film (pNPs‐polymer) provides distinct and tunable optical features on the fiber optic (FO) platform that can be used as a signal transducer for gas sensing (e.g., CO 2 ) under atmospheric conditions. The resulting pNPs‐polymer composite demonstrates high sensitivity response on FO in the evanescent field configuration, provided by the dramatic response of modes above the total‐internal‐reflection angle. Furthermore, by varying the pNPs content in the polymer matrix, the optical behavior of the pNPs‐polymer composite film can be tuned to affect the operational wavelength by over several hundred nanometers and the sensitivity of the sensor in the near‐infrared range. It is also shown that the pNPs‐polymer composite film exhibits remarkable stability over a period of more than 10 months by mitigating the physical aging issue of the polymer.

Kim, Ki‐Joong↗
DOE OSTI2022

Tunable, Homoepitaxial Hyperbolic Metamaterials Enabled by High Mobility CdO

We report propagating light exhibits hyperbolicity in strongly anisotropic materials where the principal components of the dielectric tensor are opposite in sign. While hyperbolicity occurs naturally in anisotropic polar dielectrics, wherein optical phonons along orthogonal crystal axes are nondegenerate, such optical anisotropy can also be engineered in hyperbolic metamaterials (HMMs): thin film superlattices of alternating dielectric and metallic layers. Contrasted with the severely limited tunability of natural hyperbolic materials, the hyperbolic behavior of HMMs can be tailored significantly both through superlattice design and material selection. However, so far HMMs have suffered from high optical losses, hindering their performance. In this report, broadly tunable (λ = 2–5 µm) Type I and II hyperbolic modes with low losses (quality (Q)-factors up to 19.7) are observed through attenuated total reflectance measurements of monolithic, homoepitaxial superlattices of high- and low-doped cadmium oxide (CdO). Further, the low losses offered by CdO enable the first demonstration of real-space imaging of hyperbolic plasmon polaritons in nanoresonators by scattering-type scanning near-field optical microscopy—previously only possible for hyperbolic phonon polariton materials. Tunable, low-loss CdO HMMs promise designability for applications such as on-chip photonics, super-resolution imaging (hyperlensing), enhanced emission, novel emitter designs, and possibly quantum nanophotonic and time variant metasurfaces.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Mechanistic Study of Controlled Zinc Electrodeposition Behaviors Facilitated by Nanoscale Electrolyte Additives at the Electrode Interface

Nanoparticle organic hybrid materials (NOHMs) are liquid-like materials composed of an inorganic core to which a polymeric canopy is ionically tethered. NOHMs have unique properties including negligible vapor pressure, high oxidative thermal stability, and the ability to bind to reactive species of interest due to the tunability of their polymeric canopy. This makes them promising multifunctional materials for a wide range of energy and environmental technologies, including electrolyte additives for electrochemical energy storage (e.g., flow batteries) and the electrochemical conversion of CO 2 to chemicals and fuels. Due to their unique transport behaviors in fluid systems, an understanding of the near-electrode surface behavior of NOHMs in electrolyte solutions and their effect on electrochemical reactions is still lacking. In this work, the complexation of zinc (Zn) by NOHMs with an ionically tethered polyetheramine canopy (HPE) (NOHM-I-HPE) was studied using attenuated total reflectance Fourier transform infrared and Carbon-13 nuclear magnetic resonance spectroscopy. Additionally, various electrochemical techniques were employed to discern the role of NOHM-I-HPE during zinc electrodeposition, and the results were compared to those of the electrochemical system containing untethered HPE polymers. Our findings confirmed that NOHM-I-HPE and HPE reversibly complex zinc in the aqueous electrolyte. NOHM-I-HPE and HPE were found to block some of the electrode active sites, reducing the overall current density during electrodeposition, while facilitating the formation of smooth zinc deposits, as revealed by surface imaging and diffraction techniques. Observed variations in the current density responses and the degree of passivation created by the NOHM-I-HPE and HPE adsorbed on the electrode surface revealed that their different packing behaviors at the electrode–electrolyte interface influence the zinc deposition mechanism. The presence of the nanoparticle and ordering offered by the NOHMs as well as the structured conformation of the polymeric canopy allowed the formation of void spaces and free volumes for enhanced transport behaviors. Furthermore, these findings provided insights into how structured electrolyte additives such as NOHMs can allow for advancements in electrolyte design for controlled deposition of metal species from energy-dense electrolytes or for other electrochemical reactions.

25 ENERGY STORAGE↗
DOE OSTI2021

A 1D Lyman-alpha profile camera for plasma edge neutral studies on the DIII-D tokamak

A one dimensional, absolutely calibrated pinhole camera system was installed on the DIII-D tokamak to measure edge Lyman-alpha (Ly-α) emission from hydrogen isotopes, which can be used to infer neutral density and ionization rate profiles. The system is composed of two cameras, each providing a toroidal fan of 20 lines of sight, viewing the plasma edge on the inboard and outboard side of DIII-D. The cameras’ views lie in a horizontal plane 77 cm below the midplane. At its tangency radius, each channel provides a radial resolution of ~2 cm full width at half maximum (FWHM) with a total coverage of 22 cm. Each camera consists of a rectangular pinhole, Ly-α reflective mirror, narrow-band Ly-α transmission filter, and a 20 channel AXUV photodetector. The combined mirror and transmission filter have a FWHM of 5 nm, centered near the Ly-α wavelength of 121.6nm and is capable of rejecting significant, parasitic carbon-III (C-III) emission from intrinsic plasma impurities. To provide a high spatial resolution measurement in a compact footprint, the camera utilizes advanced engineering and manufacturing techniques including 3D printing, high stability mirror mounts, and a novel alignment procedure. Absolutely calibrated, spatially resolved Ly-α brightness measurements utilize a bright, isolated line with low parasitic surface reflections and enable quantitative comparison to modeling to study divertor neutral leakage, main chamber fueling, and radial particle transport.

Ionization Rate↗
DOE OSTI2021

A 1D Lyman-alpha Profile Camera for Plasma Edge Neutral Studies on the DIII-D Tokamak

A one dimensional, absolutely calibrated pinhole camera system was installed on the DIII-D tokamak to measure edge Lyman-alpha (Ly-a) emission from hydrogenic isotopes which can be used to infer neutral density and ionization rate proles. The system is composed of two cameras, each providing a toroidal fan of twenty lines of sight, viewing the plasma edge on the inboard and outboard side of DIII-D. The cameras' views lie in a horizontal plane 77 cm below the midplane. At its tangency radius, each channel provides a radial resolution of approximately 2 cm full width at half maximum (FWHM) with a total coverage of 22 cm. Each camera consists of a rectangular pinhole, Ly-a reflective mirror, narrow-band Ly-a transmission fiter, and a 20 channel AXUV photodetector. The combined mirror and transmission fiter have a FWHM of 5 nm, centered near the Ly-a wavelength of 121.6 nm and is capable of rejecting significant, parasitic carbon-III (C-III) emission from intrinsic plasma impurities. To provide a high spatial resolution measurement in a compact footprint, the camera utilizes advanced engineering and manufacturing techniques including 3D printing, high stability mirror mounts, and a novel alignment procedure. Absolutely calibrated, spatially resolved Ly-a brightness measurements utilize a bright, isolated line with low parasitic surface reflections and enable quantitative comparison to modeling to study divertor neutral leakage, main chamber fueling and radial particle transport.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗