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At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

Recombinant Spidroins Fully Replicate Primary Mechanical Properties of Natural Spider Silk

Dragline spider silk is among the strongest and toughest bio-based materials, capable of outperforming most synthetic polymers and even some metal alloys.1,2,3,4 These properties have gained spider silk a growing list of potential applications that, coupled with the impracticalities of spider farming, have driven a decades-long effort to produce recombinant spider silk proteins (spidroins) in engineered heterologous hosts.2 However, these efforts have so far been unable to yield synthetic silk fibers with mechanical properties equivalent to natural spider silk, largely due to an inability to stably produce highly repetitive, high molecular weight (MW) spidroins in heterologous hosts.1,5 Here we address these issues by combining synthetic biology techniques with split intein (SI)- mediated ligation for the bioproduction of spidroins with unprecedented MW (556 kDa), containing 192 repeat motifs of the Nephila clavipes MaSp1 dragline spidroin. Fibers spun from these synthetic spidroins display ultimate tensile strength (σ), modulus (E), extensibility (ε), and toughness (UT) of 1.03 +/- 0.11 GPa, 13.7 +/- 3.0 GPa, 18 +/- 6%, and 114 +/- 51 MJ/m3, respectively-equivalent to the performance of natural N. clavipes dragline silk.6 This work demonstrates for the first time that microbially produced synthetic silk fibers can match the performance of natural silk fibers by all common metrics (σ, E, ε, UT), providing a more dependable source of high-strength fibers to replace natural spider silks for mechanically demanding applications. Furthermore, our biosynthetic platform can be potentially expanded for the assembly and production of other protein-based materials with high MW and repetitive sequences that have so far been impossible to synthesize by genetic means alone.

spider silk↗
DOE OSTI2024

Structural and optical characterization of dilute Bi-doped GaN nanostructures grown by molecular beam epitaxy

We have carried out detailed studies on the epitaxy and characterization of dilute Bi-doped GaN nanostructures. A comprehensive investigation of Bi-doped GaN nanowires and quasi-film epitaxial growth conditions has been performed. Scanning electron microscopy studies show that lowering the GaBiN growth temperature causes gradual changes in top c-plane nanowire morphology due to the incremental incorporation of foreign Bi atoms. This trend is further substantiated by the secondary ion mass spectroscopy analysis of a multi-layer Bi-doped GaN quasi-film. However, it is also found that the amount of Bi incorporation into the GaN lattice is relatively independent of the N2 flow rate variation under the growth conditions investigated. Furthermore, room-temperature micro-Raman spectra show that there are additional peaks near 530, 650, and 729 cm−1 wave numbers in the Bi-doped GaN samples, which can primarily be attributed to Bi local vibrational modes, indicative of a small amount of Bi incorporation in the GaN lattice. Moreover, phonon calculations with density functional theory indicate that Bi replacing the N sites is the likely origin of the experimentally measured Raman modes. X-ray photoelectron spectroscopy measurements have also been obtained to deduce the electronic interaction between the Bi dopant atom and the GaN nanostructure. Such one-dimensional nanowires permit the synthesis of dislocation-free highly mismatched alloys due to strain relaxation, allowing efficient light absorption and charge carrier extraction that is relevant for solar energy harvesting and artificial photosynthesis.

Materials Science↗
DOE OSTI2026

Using Density-Corrected DFT to Understand Density-Driven and Functional-Dependent Errors in Ab Initio Simulations of the Hydrated Electron

The hydrated electron, an excess electron in liquid water, plays a crucial role in a plethora of chemical processes, motivating extensive research efforts to characterize its structure, dynamics, and reactivity in solution. Recent theoretical approaches to understanding this intriguing object have involved ab initio simulations based on density functional theory (DFT). Although DFT allows for the study of hydrated electron reactivity and quantum mechanical behavior, it is well-known that anionic systems can suffer from significant density-driven errors (DDEs). Density-corrected DFT (DC-DFT) provides a framework to mitigate such errors; the method reduces DDEs by replacing the self-consistent (SC) density associated with a given density functional with the Hartree–Fock (HF) density. Since HF densities tend to be more localized than DFT SC densities, the DC-DFT scheme significantly improves errors in calculations where the SC density is spuriously delocalized. Here, we investigate how the use of density correction affects the calculated properties of the DFT-simulated (PBEh) hydrated electron, a particularly challenging diffuse anionic system to simulate. First, we analyze charge delocalization in a system consisting of a model octahedral hydrated electron water cluster (the so-called Kevan structure) along with a spatially separated sulfur atom. We show that the use of density correction indeed reduces DDEs in comparison to a standard DFT global hybrid functional. We then propagate molecular dynamics trajectories of the hydrated electron using DC-DFT, where we find that DC further localizes electron density in the cavity region, a signature of reduced charge delocalization. Unfortunately, the decreased radius of gyration of the spin density and corresponding tightening of the local solvation structure from density correction causes predicted observables to deviate further from experimental measurements than when density correction is not employed. Here, we argue that DC’s worse agreement with experiment results from the removal of a fortuitous cancellation of errors that is intrinsic to the PBEh functional. This indicates that the difficulties with DFT to simulate hydrated electrons are primarily due to the inherent approximations in DFT rather than to density-driven errors.

Density functional theory↗
DOE OSTI2022

Assessing MP2 frozen natural orbitals in relativistic correlated electronic structure calculations

The high computational scaling with the basis set size and the number of correlated electrons is a bottleneck limiting applications of coupled cluster algorithms, in particular for calculations based on two- or four-component relativistic Hamiltonians, which often employ uncontracted basis sets. This problem may be alleviated by replacing canonical Hartree–Fock virtual orbitals by natural orbitals (NOs). Here, in this paper, we describe the implementation of a module for generating NOs for correlated wavefunctions and, in particular, second order Møller–Plesset perturbation frozen natural orbitals (MP2FNOs) as a component of our novel implementation of relativistic coupled cluster theory for massively parallel architectures [Pototschnig et al. J. Chem. Theory Comput. 17, 5509, (2021)]. Our implementation can manipulate complex or quaternion density matrices, thus allowing for the generation of both Kramers-restricted and Kramers-unrestricted MP2FNOs. Furthermore, NOs are re-expressed in the parent atomic orbital (AO) basis, allowing for generating coupled cluster singles and doubles NOs in the AO basis for further analysis. By investigating the truncation errors of MP2FNOs for both the correlation energy and molecular properties—electric field gradients at the nuclei, electric dipole and quadrupole moments for hydrogen halides HX (X = F–Ts), and parity-violating energy differences for H 2 Z 2 (Z = O–Se)—we find MP2FNOs accelerate the convergence of the correlation energy in a roughly uniform manner across the Periodic Table. It is possible to obtain reliable estimates for both energies and the molecular properties considered with virtual molecular orbital spaces truncated to about half the size of the full spaces.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Unraveling Adsorbate-Induced Structural Evolution of Iron Carbide Nanoparticles

Iron carbide (Fe x C y ) nanoparticles (NPs) are promising candidates for replacing platinum group metals in industrial applications, such as high-temperature Fischer–Tropsch synthesis. However, due to their amorphous nature, characterization of the active sites has been challenging experimentally and computationally. Here, using a combined density functional theory (DFT), neural network interatomic potential-assisted global optimization, and ensemble learning study, we evaluate dynamic surface changes associated with syngas (H and CO) interactions. For this purpose, we have developed a general procedure that we use to model an experimentally relevant 270-atom Fe 182 C 88 NP using the neural network-assisted stochastic surface walk global optimization algorithm (SSW-NN). Once generated, the Fe 182 C 88 NP active sites and particle morphology are thoroughly characterized before the effects of syngas adsorbate interactions are explored by using DFT and molecular dynamics simulations. Lastly, we explore correlations between geometric and electronic features of the active sites and the adsorption of H (H ads ), using a regularized random forest machine learning algorithm. In doing so, we identified the Fe–C coordination number and p orbital occupancy as the most important descriptors affecting H ads . Furthermore, using a combined ML and quantum chemistry approach, our work demonstrates a general and efficient procedure for generating and probing complex surface phenomena on binary nanoparticles.

Adsorption↗
DOE OSTI2025

MINE: a new way to design genetics experiments for discovery

Abstract The Maximally Informative Next Experiment or MINE is a new experimental design approach for experiments, such as those in omics, in which the number of effects or parameters p greatly exceeds the number of samples n (p > n). Classical experimental design presumes n > p for inference about parameters and its application to p > n can lead to over-fitting. To overcome p > n, MINE is an ensemble method, which makes predictions about future experiments from an existing ensemble of models consistent with available data in order to select the most informative next experiment. Its advantages are in exploration of the data for new relationships with n < p and being able to integrate smaller and more tractable experiments to replace adaptively one large classic experiment as discoveries are made. Thus, using MINE is model-guided and adaptive over time in a large omics study. Here, MINE is illustrated in two distinct multiyear experiments, one involving genetic networks in Neurospora crassa and a second one involving a genome-wide association study in Sorghum bicolor as a comparison to classic experimental design in an agricultural setting.

Biochemistry & Molecular Biology↗
DOE OSTI2021

Composition and Configuration Dependence of Glass-Transition Temperature in Binary Copolymers and Blends of Polyhydroxyalkanoate Biopolymers

Polyhydroxyalkanoates (PHAs), a promising class of biomaterials, have gained considerable attention to replace petroleum-based plastics owing to their excellent biocompatibility and biodegradability. Homopolymers of PHA suffer from poor tunability in thermal and mechanical properties. Going from homopolymers to copolymers, the design space can be substantially enhanced by combining two or more monomers in different compositions (i.e., relative ratios of the different monomers) and configurations (i.e., relative positions of the different monomers in the polymer backbone) leading to a substantially large chemical space where application-specific optimization for the targeted functionality can be performed. However, this composition and configuration dependence of properties in the vast PHA copolymer chemical space remains largely unexplored. In this contribution, further building on our past work with PHA homopolymers, we systematically explore these chemical trends for glass-transition temperature (Tg) in PHA copolymers and blends. Overall, our molecular dynamics simulations, utilizing a previously validated force field for PHAs, suggest that these trends are largely governed not only by the homopolymer Tg values but also configuration-dependent interchain interactions in the copolymer system. In particular, our results indicate that the configuration-dependent variation in the target property at a fixed composition can be significant in the presence of hydrogen-bond-forming monomers. These qualitative observations are further rationalized by quantitatively analyzing various closely related atomic level descriptors of copolymers and blends such as monomer mobility, number of hydrogen bonds, and pair correlation functions. The findings presented in this work help to develop a deeper atomistic-level understanding of thermomechanical behavior of PHA-based copolymers and can potentially guide the rational design of biopolymers as environmental-friendly functional materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Modeling the Effect of Film Morphology on the Performance of an OLED Device

Organic Light Emitting Diode (OLED) technology is replacing the liquid crystal displays (LCD) in cell phones and is also expected to impact television displays in the future. Dow has an active OLED research program. To complement and ultimately drive this effort, it is necessary to develop efficient computational screening tools for selection and optimization of target molecules. To this end we sought to identify and expand on existing models used by Dow that can better predict the mobility of electrons and holes in organic materials. We focused on N,N'- bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPD), frequently used in academic studies of organic light-emitting diodes; we also studied 4,4'-Bis(N-carbazolyl)-1,1'-biphenyl (CBP), tris(4-carbazoyl-9-ylphenyl)amine (TCTA), and bathophenanthroline (BPhen). We developed a workflow, using a combination of molecular dynamics and quantum chemistry calculations, to predict trends in the electronic structure that correlate with measured electron and hole mobilities of small molecule materials such as NPD for OLEDs, comparing with measurements in the literature and at Dow. This work comprised a first step toward predictive charge carrier mobilities in small-molecule electronic materials with complex morphologies.

47 OTHER INSTRUMENTATION↗
NASA NTRS1993

Z-DNA binding protein from chicken blood nuclei

A protein (Z alpha) that appears to be highly specific for the left-handed Z-DNA conformer has been identified in chicken blood nuclear extracts. Z alpha activity is measured in a band-shift assay by using a radioactive probe consisting of a (dC-dG)35 oligomer that has 50% of the deoxycytosines replaced with 5-bromodeoxycytosine. In the presence of 10 mM Mg2+, the probe converts to the Z-DNA conformation and is bound by Z alpha. The binding of Z alpha to the radioactive probe is specifically blocked by competition with linear poly(dC-dG) stabilized in the Z-DNA form by chemical bromination but not by B-form poly(dC-dG) or boiled salmon-sperm DNA. In addition, the binding activity of Z alpha is competitively blocked by supercoiled plasmids containing a Z-DNA insert but not by either the linearized plasmid or by an equivalent amount of the parental supercoiled plasmid without the Z-DNA-forming insert. Z alpha can be crosslinked to the 32P-labeled brominated probe with UV light, allowing us to estimate that the minimal molecular mass of Z alpha is 39 kDa.

NASA Discipline Exobiology↗
DOE OSTI2024

3D printed lignin/polymer composite with enhanced mechanical and anti-thermal-aging performance

Lignin is the most abundant natural aromatic polymer globally but is still underutilized as a renewable material, even with its versatile properties. One approach to using lignin is to incorporate it in polymer composites, but this application is often limited by the poor mechanical performance of the resultant composite due to the poor interfacial adhesion. Following the structure–property relationship, stronger interactions were designed to be enhanced by alternating the functional groups of lignin. Here, this study applied a demethylation method to hardwood lignin (Ori-Lig) to introduce more phenolic hydroxyl groups. Research studies with rheology behavior and molecular simulations demonstrated that an increased phenolic hydroxyl content could improve the adhesion between the modified lignin (OH-Lig) and the polymer matrix at the interface. The tensile performance of the samples from the fused depositional modeling (FDM) 3D printing technique was also improved due to the improved interfacial adhesion. Specifically, by adding 10 wt% of the modified lignin, the tensile strength of the 3D printed samples could reach 46.1 MPa (40.2 MPa of Polyamide 12, PA12), and Young’s Modulus could be improved to 1.73 GPa (1.48 GPa of PA12). OH-Lig also improved anti-aging performance so that the tensile strength of the OH-Lig composite after thermo-aging (100 h at 140 °C) remained ~48MPa. The enhanced mechanical performance with anti-aging properties indicated that the OH-Lig composite may replace PA12 to reduce the use of petrol-based materials. This work showed the method of purposefully designing and modifying lignin structures to fulfill the interaction requirements between lignin and polymer matrix. The as-prepared lignin could be used to prepare functional composites to achieve improved mechanical performance and targeted functions at the same time.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Toward Consistent High-Fidelity Quantum Learning on Unstable Devices via Efficient In-Situ Calibration

In the near-term noisy intermediate-scale quantum (NISQ) era, high noise will significantly reduce the fidelity of quantum computing. What's worse, recent works reveal that the noise on quantum devices is not stable, that is, the noise is dynamically changing over time. This leads to an imminent challenging problem: At run-time, is there a way to efficiently achieve a consistent high-fidelity quantum system on unstable devices? To study this problem, we take quantum learning (a.k.a., variational quantum algorithm) as a vehicle, which has a wide range of applications, such as combinatorial optimization and machine learning. A straightforward approach is to optimize a variational quantum circuit (VQC) with a parameter-shift approach on the target quantum device before using it; however, the optimization has an extremely high time cost, which is not practical at run-time. To address the pressing issue, in this paper, we proposed a novel quantum pulse-based noise adaptation framework, namely QuPAD. In the proposed framework, first, we identify that the CNOT gate is the fidelity bottleneck of the conventional VQC, and we employ a more robust parameterized multi-qubit gate (i.e., Rzx gate) to replace CNOT gate. Second, by benchmarking Rzx gate with different parameters, we build a fitting function for each coupling qubit pair, such that the deviation between the theoretic output of Rzx gate and its on-device output under a given pulse amplitude and duration can be efficiently predicted. On top of this, an evolutionary algorithm is devised to identify the pulse amplitude and duration of each Rzx gate (i.e., calibration) and find the quantum circuits with high fidelity. Experiments show that the runtime on quantum devices of QuPAD with 8–10 qubits is less than 15 minutes, which is up to 270 x faster than the parameter-shift approach. In addition, compared to the vanilla VQC as a baseline, QuPAD can achieve 59.33% accuracy gain on a classification task, and average 66.34% closer to ground state energy for molecular simulation.

Hu, Zhirui↗
DOE OSTI2024

Molecular basis for dual functions in pilus assembly modulated by the lid of a pilus-specific sortase

The biphasic assembly of Gram-positive pili begins with the covalent polymerization of distinct pilins catalyzed by a pilus-specific sortase, followed by the cell wall anchoring of the resulting polymers mediated by the housekeeping sortase. In Actinomyces oris, the pilus-specific sortase SrtC2 not only polymerizes FimA pilins to assemble type 2 fimbriae with CafA at the tip, but it can also act as the anchoring sortase, linking both FimA polymers and SrtC1-catalyzed FimP polymers (type 1 fimbriae) to peptidoglycan when the housekeeping sortase SrtA is inactive. To date, the structure-function determinants governing the unique substrate specificity and dual enzymatic activity of SrtC2 have not been illuminated. Here, we present the crystal structure of SrtC2 solved to 2.10-Å resolution. SrtC2 harbors a canonical sortase fold and a lid typical for class C sortases and additional features specific to SrtC2. Structural, biochemical, and mutational analyses of SrtC2 reveal that the extended lid of SrtC2 modulates its dual activity. Specifically, we demonstrate that the polymerizing activity of SrtC2 is still maintained by alanine-substitution, partial deletion, and replacement of the SrtC2 lid with the SrtC1 lid. Strikingly, pilus incorporation of CafA is significantly reduced by these mutations, leading to compromised polymicrobial interactions mediated by CafA. In a srtA mutant, the partial deletion of the SrtC2 lid reduces surface anchoring of FimP polymers, and the lid-swapping mutation enhances this process, while both mutations diminish surface anchoring of FimA pili. Evidently, the extended lid of SrtC2 enables the enzyme the cell wall-anchoring activity in a substrate-selective fashion.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Metagenomics harvested genus-specific single-stranded DNA-annealing proteins improve and expand recombineering in Pseudomonas species

The widespread Pseudomonas genus comprises a collection of related species with remarkable abilities to degrade plastics and polluted wastes and to produce a broad set of valuable compounds, ranging from bulk chemicals to pharmaceuticals. Pseudomonas possess characteristics of tolerance and stress resistance making them valuable hosts for industrial and environmental biotechnology. However, efficient and high-throughput genetic engineering tools have limited metabolic engineering efforts and applications. To improve their genome editing capabilities, we first employed a computational biology workflow to generate a genus-specific library of potential single-stranded DNA-annealing proteins (SSAPs). Assessment of the library was performed in different Pseudomonas using a high-throughput pooled recombinase screen followed by Oxford Nanopore NGS analysis. Among different active variants with variable levels of allelic replacement frequency (ARF), efficient SSAPs were found and characterized for mediating recombineering in the four tested species. New variants yielded higher ARFs than existing ones in Pseudomonas putida and Pseudomonas aeruginosa, and expanded the field of recombineering in Pseudomonas taiwanensisand Pseudomonas fluorescens. These findings will enhance the mutagenesis capabilities of these members of the Pseudomonas genus, increasing the possibilities for biotransformation and enhancing their potential for synthetic biology applications.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1999

Alterations of p53 in tumorigenic human bronchial epithelial cells correlate with metastatic potential

The cellular and molecular mechanisms of radiation-induced lung cancer are not known. In the present study, alterations of p53 in tumorigenic human papillomavirus-immortalized human bronchial epithelial (BEP2D) cells induced by a single low dose of either alpha-particles or 1 GeV/nucleon (56)Fe were analyzed by PCR-single-stranded conformation polymorphism (SSCP) coupled with sequencing analysis and immunoprecipitation assay. A total of nine primary and four secondary tumor cell lines, three of which were metastatic, together with the parental BEP2D and primary human bronchial epithelial (NHBE) cells were studied. The immunoprecipitation assay showed overexpression of mutant p53 proteins in all the tumor lines but not in NHBE and BEP2D cells. PCR-SSCP and sequencing analysis found band shifts and gene mutations in all four of the secondary tumors. A G-->T transversion in codon 139 in exon 5 that replaced Lys with Asn was detected in two tumor lines. One mutation each, involving a G-->T transversion in codon 215 in exon 6 (Ser-->lle) and a G-->A transition in codon 373 in exon 8 (Arg-->His), was identified in the remaining two secondary tumors. These results suggest that p53 alterations correlate with tumorigenesis in the BEP2D cell model and that mutations in the p53 gene may be indicative of metastatic potential.

Non-NASA Center↗
DOE OSTI2025

Algae Asphalt to Enhance Pavement Sustainability and Performance at Subzero Temperatures

This paper evaluates the potential of algae-derived biobinders as sustainable alternatives for pavement construction. It specifically examines the physicochemical and rheological properties of biomodified binders and their potential to offset carbon emissions when used as partial replacements for conventional petroleum-based asphalt binders. Biosequestration of CO 2 using microalgal cell factories is a promising way of recycling CO 2 into biomass via photosynthesis. Our study demonstrates that incorporating algae-derived binders into asphalt can significantly reduce carbon emissions. Each 1% increase in algae-based biobinder leads to an approximate 4.5% decrease in net carbon emissions. This indicates that a blend containing about 22% biobinder has the potential to achieve carbon neutrality. Blends with higher proportions may even result in net-negative emissions, highlighting a promising strategy for environmentally responsible road construction. In terms of performance, the study shows that certain algae-derived biobinders significantly enhance the cracking resistance of asphalt, particularly under subzero temperatures, by improving its stress-relief capacity. A key contribution of this work is the introduction of polarizability as a novel molecular-level parameter for assessing the compatibility of algae-derived bio-oils with asphalt. By capturing the electronic responsiveness of bio-oil molecules, polarizability serves as a predictive indicator of their interaction potential with asphalt components, providing a new dimension for evaluating the binder performance at the molecular scale. Among the tested materials, the biobinder derived from Haematococcus pluvialis demonstrated particularly strong improvements in resistance to permanent deformation under repeated loading conditions analogous to traffic-induced stress, as well as enhanced resistance to moisture-induced damage. In conclusion, these findings advance the chemistry-driven design of biomass-based binders and highlight a promising pathway toward the development of low-carbon, high-performance, and sustainable infrastructure materials.

Algae↗
DOE OSTI2020

Renewable Ammonia as An Energy Fuel for Ocean Exploration and Transportation

Renewable power generated from wave energy has faced technological and cost barriers to entry into utility-scale electricity markets. As an alternative, the production of chemical fuels, such as ammonia (NH3) which has high energy density (11.5 MJ/L) and facile storage properties, may open wave energy to new markets including ocean exploration and transportation. The electrochemical method has been studied to synthesize NH3 from air and water at ambient conditions. Based on some recent work on the electrochemical synthesis of NH3, it is possible to achieve an overall conversion efficiency of 10% from wave energy to NH3 through an electrochemical reaction between air and water. If all the recoverable wave energy in the United States (1170 TWh/yr) is used to produce renewable NH3 fuel replacing hydrocarbon fuels, this can help reduce over 300 million tons of CO2 emission every year. Several potential application scenarios at sea have been proposed for renewable NH3 fuel including production and storage for marine shipping and seasonal energy storage for Arctic exploration. Liquefied NH3 has much higher energy density, both gravimetric and volumetric, than a variety of batteries but the energy efficiency of NH3 is lower than modern batteries such as Li-ion. The Levelized cost of storing NH3 prepared using electric energy is less than $0.2/kWh and the storage time can exceed 10,000 hours which indicates that NH3 can be a promising energy storage solution to make use of abundant wave energy. However, there are some safety and environmental concerns involved in the usage of NH3 at sea. The challenges in the electrochemical catalyst for the NH3 synthesis and how molecular simulation may help to screen electrocatalyst with high efficiency and selectivity were also briefly discussed.

Liu, Jian↗
DOE OSTI2024

Analysis and Grading of the Test Performance of PS Modules for the CMS Phase-II Outer Tracker Upgrade

The Outer Tracker detector of the Compact Muon Solenoid (CMS) experiment provides information about the trajectory of charged particles produced in proton-proton collisions at the Large Hadron Collider (LHC). During the High Luminosity LHC upgrade, scheduled for the late 2020s, the Outer Tracker will be replaced with new modules capable of transmitting data to the L1 Trigger. These modules are being assembled at several facilities around the world, including Fermilab, necessitating coordinated standards of module quality. Here I discuss the development of POTATO (Phase-II Outer Tracker Analyzer of Test Outputs), a C++ software which provides a standardized procedure for analyzing and grading test results of the Outer Tracker modules. The particular focus of this paper is on the analysis and grading of the PS (pixel-strip) modules in POTATO.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Ultra-short pulse generation from mid-IR to THz range using plasma wakes and relativistic ionization fronts

In this work, we discuss numerical and experimental results on frequency downshifting and upshifting of a 10 μ m infrared (IR) laser to cover the entire wavelength (frequency) range from λ = 1 to 150 μ m ( ν = 300–2 THz) using two different plasma techniques. The first plasma technique utilizes frequency downshifting of the drive laser pulse in a nonlinear plasma wake. Based on this technique, we have proposed and demonstrated that in a tailored plasma structure, multi-millijoule energy, single-cycle, long-wavelength IR (3–20 μ m) pulses can be generated by using an 810 nm Ti:sapphire drive laser. Here, we extend this idea to the THz frequency regime. We show that sub-joule, terawatts, single-cycle terahertz (2–12 THz or 150–25 μ m) pulses can be generated by replacing the drive laser with a picosecond 10 μ m CO 2 laser and a different shaped plasma structure. The second plasma technique employs frequency upshifting by colliding a CO 2 laser with a rather sharp relativistic ionization front created by ionization of a gas in less than half cycle (17 fs) of the CO 2 laser. Even though the electrons in the ionization front carry no energy, the frequency of the CO 2 laser can be upshifted due to the relativistic Doppler effect as the CO 2 laser pulse enters the front. The wavelength can be tuned from 1 to 10 μ m by simply changing the electron density of the front. While the upshifted light with 5 < λ ( μ m ) < 10 propagates in the forward direction, that with 1 < λ ( μ m ) < 5 is back-reflected. These two plasma techniques seem extremely promising for covering the entire molecular fingerprint region.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗