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DOE OSTI2026

Search for Double Beta Decays of Xe134 with EXO-200 Phase II

EXO-200 was a leading double beta decay experiment consisting of a single-phase, enriched liquid xenon time projection chamber filled with an admixture of 80.672% ^{136}Xe and 19.098% ^{134}Xe. The detector operated at the Waste Isolation Pilot Plant between 2010 and 2018 and was designed to search for double beta decay of ^{136}Xe. Data were acquired in two phases separated by a period of detector upgrades. We report on the search for 0νββ and 2νββ decay of ^{134}Xe with Phase II EXO-200 data, with median 90% CL exclusion sensitivity to half-life T_{1/2}^{0ν}≥3.7×10^{23} yr and T_{1/2}^{2ν}≥2.6×10^{21} yr, respectively. No statistically significant signal is observed for either decay mode. We set a world-leading lower limit on the half-life of the neutrinoless decay mode of ^{134}Xe of T_{1/2}^{0ν}≥8.7×10^{23} (90% CL) and the second strongest constraint on the two-neutrino decay of T_{1/2}^{2ν}≥2.9×10^{21} (90% CL), a threefold improvement over the EXO-200 Phase I measurement. New constraints are also set for the 2νββ and 0νββ decays of ^{134}Xe to the lowest excited state of ^{134}Ba.

Al Kharusi, S↗

DOE OSTI2020

Analysis of Double-Output CLL Resonant Converter for All-Electric UAV Applications

This paper presents a double-output resonant converter with high-frequency isolation for unmanned aerial vehicle (UAV) applications. The proposed topology is developed by using a full-bridge resonant inverter and double-output half-bridge active rectifiers. For the control system, a phase-shifted pulse width modulation (PS-PWM) method is utilized to adjusts the power flow among the output rectifiers in a wide voltage range regulation with a central control. The theoretical analysis of the converter is explored using the system model under different load conditions with constant frequency. The proposed system is validated with experimental results using 60 V input source and generating 0 - 100 V in each output at a full power of 500 W with 96% maximum efficiency in the laboratory experimental setup.

Asa, Erdem↗

DOE OSTI2023

Single and Double-Sided Jet Impingement Cooling for SiC-Based Power Modules

Efficient thermal management of power electronics systems is crucial for higher reliability. With the miniaturization of systems, high-loss-density electronics require cooling systems that can extract a large amount of heat. This study explored a liquid-jet-impingement-based direct substrate cooling system for single-sided and double-sided cooling to improve heat extraction efficiency and improve the power density by reducing the volume and mass. The cooling system was implemented for a SiC-based direct bonded copper substrate. Numerical simulations were performed to determine the effects of nozzle diameter, the number of nozzles, and nozzle array orientation on single-sided cooling and thermal performance gain over double-sided cooling. A novel manifold design was proposed that reduced the volume and mass of the manifold and still achieved the target power density. The performance of the proposed design was compared with the pin-fin-based cooling system used in the BMW I3 module, and a comparative analysis was done.

Barua, Himel↗

DOE OSTI2022

A Double-Wiebe Function for Reactivity Controlled Compression Ignition Combustion Using Reformate Diesel

Abstract Reactivity controlled compression ignition (RCCI) combustion has previously been proposed as a method to achieve high fuel conversion efficiency and reduce engine emissions. A single-fuel RCCI combustion strategy can have decreased fuel system complexity by using a reformate fuel for port fuel injection and the parent fuel (diesel) for direct injection. This paper presents a one-dimensional computational model of a compression ignition engine with single-fuel RCCI. A Wiebe function is used to predict the combustion process by representing the mass fraction burned (MFB) on a crank angle resolved basis. One single-Wiebe function (SWF) and two double-Wiebe functions(DWFs) were fitted to experimentally derive MFB data using the least-square method. The fitted results were compared with MFBs calculated from experimental data to verify the accuracy. The SWF did not fully capture the MFB curve with high fidelity while the detailed DWF captured the MFB curve within a root mean square error of 1.4%. The reduced double-Wiebe function (RDWF) also resulted in a predicted combustion profile with similar accuracy. Hence, the RDWF was used in a GT-power thermodynamic study to understand the effects of the low-temperature heat release (LTHR) fraction and combustion phasing on combustion characteristics. At optimum phasing of 5–10 crank angle degree after the top dead center, increasing the LTHR fraction from 20% to 60% resulted in the fuel conversion efficiency increasing from 39.5% to 41.1%, thus suggesting that the reformate fuel-based RCCI strategy is viable to unlock improved combustion performance.

Energy & Fuels↗

DOE OSTI2024

Multiphysics Co-Optimization Design and Analysis of Double-Side Cooled Silicon Carbide-Based Power Module: Preprint

With the rapid growth of Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEVs), much more rigorous design targets have been set for automotive power electronics, including high power density, high reliability, and low cost. Novel power module and inverter technologies based on wide bandgap (WEG) semiconductors have been developed to meet these design targets, while providing optimal power semiconductor operating temperature and promising thermomechanical performance. Compared with conventional cooling techniques which are normally applied only on one side of power module, double-side cooling approach is now believed to be the solution to enable high power density and low thermal resistance of WEG semiconductor-based power electronics. In this work, we develop a three-phase power module that is double-sided cooled using dielectric fluid jet impingement. In each phase, four silicon carbide (SiC) power semiconductors are bonded to copper busbars without electrical insulation layers. A finite element analysis (FEA) model is created for thermal and thermomechanical analysis. Based on FEA modeling results, we select particular dimensions for a parametric study to optimize thermal and mechanical performance. Using a multi-objective genetic algorithm (MOGA)-based optimization method, we have minimized the maximum junction temperature and thermal stresses within the power module. The multiphysics co-optimization approach has enabled an efficient design process of power modules with greatly reduced computational cost, as compared to conventional processes that rely on exhaustive numerical simulations and iterations.

ADVANCED PROPULSION SYSTEMS↗

DOE OSTI2025

DESIGN ISSUES AND QUALIFICATION OF HYDROFORMED DOUBLE WALLED EXPANSION JOINTS IN VACUUM SERVICE

The Vacuum Auxiliary System for ITER is devoted to pumping out, venting, and purging the vacuum volumes of the tokamak. Over 5000 clients including the cryostat and vacuum vessel, at 8500 m3 and 1400 m3 respectively, are serviced by approximately 150 pumping stations through 6 km of pipework. The piping and functions provided to the clients include component operation, routing of potentially tritiated gases, and timely leak localization. Expansion joints are used to reduce loadings on pumps and piping stresses but also to qualify in-line components having low allowable design loads. The ITER project utilizes vacuum valves that are not designed to withstand typical piping system loadings and require detailed design and evaluation. Loading scenarios prescribed by governing system specifications must be considered. To maintain allowable design loads for components and to keep piping stresses below code requirements, double walled hydroformed expansion joints have been employed in the design. These are not standard items and require custom fabrication. Installation space constraints and adjacent pipe support attachment location availability at ITER limit standard expansion joint installation guidelines provided by the Expasion Joint Manufacturers Association (EJMA). Careful consideration must be given to the analysis model to ensure proper function and life expectancy of the component. These considerations include accurate accounting of thrust forces, thermal movements, seismic accelerations, equipment and building differential displacements. In addition to displacements, the process internal, external, and interspace pressures affect the qualification and selection of the double walled expansion joints. The calculation results shall confirm that deflections, forces, and moments are reasonable for the size and type required for the system’s demands as evaluated against the manufacturer’s design.

Clark, Forrest [ORNL] (ORCID:0009000678106843)↗

DOE OSTI2020

Evidence for $\text {W}\text {W}$ production from double-parton interactions in proton–proton collisions at $\sqrt{s} = 13 \,\text {TeV} $ = 13TeV

A search for WW production from double-parton scattering processes using same-charge electron-muon and dimuon events is reported, based on proton-proton collision data collected at a center-of-mass energy of 13 TeV. The analyzed data set corresponds to an integrated luminosity of 77.4 fb$^{-1}$, collected using the CMS detector at the LHC in 2016 and 2017. Multivariate classifiers are used to discriminate between the signal and the dominant background processes. A maximum likelihood fit is performed to extract the signal cross section. This leads to the first evidence for WW production via double-parton scattering, with a significance of 3.9 standard deviations. The measured inclusive cross section is 1.41 $\pm$ 0.28 (stat) $\pm$ 0.28 (syst) pb.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2021

Search for signatures of sterile neutrinos with Double Chooz

We present a search for signatures of neutrino mixing of electron anti-neutrinos with additional hypothetical sterile neutrino flavors using the Double Chooz experiment. The search is based on data from 5 years of operation of Double Chooz, including 2 years in the two-detector configuration. The analysis is based on a profile likelihood, i.e. comparing the data to the model prediction of disappearance in a data-to-data comparison of the two respective detectors. The analysis is optimized for a model of three active and one sterile neutrino. It is sensitive in the typical mass range ${5 \times 10^{-3}}\,\mathrm{eV}^2 \lesssim \varDelta m^2_{41} \lesssim {3 \times 10^{-1}}\,\mathrm{eV}^2$ for mixing angles down to $\sin ^2 2\theta _{14} \gtrsim {0.02}$. No significant disappearance additionally to the conventional disappearance related to $\theta _{13}$ is observed and correspondingly exclusion bounds on the sterile mixing parameter $\theta _{14}$ as a function of $\varDelta m^2_{41}$ are obtained.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

Modeling the Environment-Dependent Kinetics of Oxygen Reduction Reaction – a Continuum Model for Electric Double Layer

Here, for proton-exchange-membrane fuel cells (PEMFCs) to achieve broad commercialization, improved energy-conversion efficiency with minimal Pt-based electrocatalyst is required. Because the sluggish rate of oxygen reduction reaction (ORR) limits the efficiency of PEMFCs, the efficiency improvement requires a better understanding of ORR kinetics and mechanism to design better catalyst. To understand the ORR mechanism, theoretical and experimental analyses have been conducted. While previous studies reasonably explained the catalyst-dependent activity on single crystal catalysts in 0.1 M perchloric acid solution, the explicit effect of electrolyte and related microenvironments is not thoroughly understood. The change in the electrolyte alters the electric-double-layer (EDL) structure and thus the local microenvironment at the electrode/electrolyte interface. Thus, the structure of the EDL should be carefully analyzed to uncover the electrolyte-dependent reaction kinetics. In this talk, we propose a multiscale continuum model to predict the EDL structure and examine the effect of perchloric acid concentration on ORR activity on Pt (111). The model includes Density Potential Functional Theory (DPFT) for electron density and Modified Poisson Boltzmann equation for species’ density and electric potential. Also, the interaction between adsorbents and electric field is taken into account by minimizing the grand potential. After model validation with experimentally measured double-layer capacity data as a function of applied potential and concentration, the effect of the perchloric acid concentration (0.02 M – 0.2 M) on ORR activity is analyzed and discussed. It is shown that the model reproduces the specific activity obtained in the experiments when assuming the oxygen adsorption is limiting the rate, which can be attributed to the large energetic barrier for solvent reorganization. Then, extension of the model to PEMFC ionomer electrolytes will be introduced. Overall, the model framework and findings provide insights into the ORR mechanism and guidance on how to tailor catalyst materials for increased PEMFC performance.

30 DIRECT ENERGY CONVERSION↗

DOE OSTI2022

Fault Diagnosis of Double Pitch Time-Sharing Meshing Toothed Conveyor Chain Transmission System Based on Neural Network

With the rapid development of industry, the production and demand of automobiles have increased significantly. The generation of cars often requires tens of thousands of processes, consisting of hundreds of assembly lines to complete. Chain conveyors are widely used in the transportation of automobile assembly lines. The existing conveyor chains are roller chains. With the improvement of the requirements for conveyor reliability, synchronization, and environmental friendliness, the characteristics of roller conveyor chains restrict the further development of chain conveyors. It is urgent to study a new conveyor chain system to improve the synchronization, reliability, and environmental friendliness of chain conveyors on hundreds of assembly lines. In this paper, the mathematical modeling, meshing analysis, reliability, and environmental friendliness of the parameters of the components of the double pitch time-sharing meshing toothed conveyor chain system are studied. In addition, a novel fault diagnosis method of double pitch time-sharing meshing toothed conveyor chain transmission system based on neural network model is proposed in this paper.

Ding, Song↗

DOE OSTI2021

Single-shot, double-pulse determination of the detonation energy in nanosecond-laser ablation using the blast model

We demonstrate a novel single-shot method to determine the detonation energy of laser-induced plasma and investigate its performance. This approach can be used in cases where there are significant shot-to-shot variations in ablation conditions, such as laser fluctuations, target inhomogeneity, or multiple filamentation with ultrashort pulses. The Sedov blast model is used to fit two time-delayed shadowgrams measured with a double-pulse laser. We find that the reconstruction of detonation parameters is insensitive to the choice of interpulse delay in double-pulse shadowgraphy. In contrast, the initial assumption of expansion dimensionality has a large impact on the reconstructed detonation energy. The method allows for a reduction in the uncertainties of blast wave energy measurements as a diagnostic technique employed in various laser ablation applications.

42 ENGINEERING↗

DOE OSTI2026

SEGUID v2: Extending SEGUID checksums for circular, linear, single- and double-stranded biological sequences

Background Synthetic biology involves combining different DNA fragments, each containing functional biological parts, to address specific problems. Fundamental gene-function research often requires cloning and propagating DNA fragments, such as those from the iGEM Parts Registry or Addgene, typically distributed as circular plasmids. Addgene’s repository alone offers around 150,000 plasmids. To ensure data integrity, cryptographic checksums can be calculated for the sequences. Each sequence has a unique checksum, making checksums useful for validation and quick lookups of associated annotations. For example, the SEGUID checksum uniquely identifies protein sequences with a 27-character string. Objectives The original SEGUID, while effective for protein sequences and single-stranded DNA (ssDNA), is not suitable for circular DNA since there is no natural starting position nor for double-stranded DNA (dsDNA) since two separate sequences are present. Challenges include how to uniquely represent linear dsDNA, circular ssDNA, and circular dsDNA. To meet these needs, we propose SEGUID v2, which extends the original SEGUID to handle additional types of sequences. Conclusions SEGUID v2 produces orientation and rotation invariant checksums for single-stranded, double-stranded, possibly staggered, linear, and circular DNA and RNA sequences. Customizable alphabets allow for other types of sequences. In contrast to the original SEGUID, which uses Base64, SEGUID v2 uses Base64url to encode the SHA-1 hash. This ensures SEGUID v2 checksums can be used as-is in filenames, regardless of platform, and in URLs, with minimal friction. Availability SEGUID v2 is readily available for major programming languages, distributed under the MIT license. JavaScript package seguid is available on npm, Python package seguid on PyPi, R package seguid on CRAN, and a Tcl script on GitHub. These tools, along with documentation, examples, and an online SEGUID Calculator , can be found at https://www.seguid.org .

Pereira, Humberto↗

DOE OSTI2025

Bi-stability and period-doubling cascade of frequency combs in exceptional-point lasers

Abstract Recent studies have demonstrated that a laser can self-generate frequency combs when tuned near an exceptional point (EP), where two cavity modes coalesce. These EP combs induce periodic modulation of the population inversion in the gain medium, and their repetition rate is independent of the laser cavity’s free spectral range. In this work, we perform a stability analysis that reveals two notable properties of EP combs, bi-stability and a period-doubling cascade. The period-doubling cascade enables halving of the repetition rate while maintaining the comb’s total bandwidth, presenting opportunities for the design of highly compact frequency comb generators.

exceptional points↗

DOE OSTI2020

CT analysis of double shell targets

We are more accurately determining the initial conditions of our double shell targets used for ICF: Fusion has the capability to provide clean, safe energy; We are studying double shell capsules to determine if ignition is possible; We have taken CT scans of the initial target and analyzed these scans for roundness; We are developing a method to analyze these scans.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2020

Optimizing the Accelerated Recursive Doubling Algorithm for Block Tridiagonal Systems of Equations

The need to solve block tridiagonal systems with hundreds or thousands of right-hand sides for the same block tridiagonal matrix is common in a variety of disciplines. To meet this need, the Accelerated Recursive Doubling Algorithm was developed. After a right-hand side independent phase, the algorithm allows for the quick, online calculation of solutions for different right-hand sides. In this work, we present methods to optimize the Accelerated Recursive Doubling Algorithm in memory usage and computation time in a hybrid parallelization model. The right-hand side independent phase of the naïve implementation takes ≥ 11/3 the amount of memory required to store the tridiagonal matrix, while our implementation reduces the fraction to ≈ 5/3 . The right-hand side dependent phase of the naïve implementation takes ≥ 6 times the amount of memory required to store the right-hand side, while our implementation reduces the fraction to ≈ 3. The computation time for the independent phase is reduced to ≈ 2/3 times that of the naïve implementation, while the computation time for the dependent phase is reduced to ≈ 5/9 . With increasing numbers of shared-memory threads q on every distributed processing element, we have O(q) theoretical speedup.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2021

Research in Neutrinoless Double-Beta Decay (Final Report)

The research objective of the supported work was to search for neutrinoless double-beta decay in 76 Ge and investigate and identify backgrounds to a double-beta decay search. Understanding the neutrino mass generation mechanism, the absolute neutrino mass scale, the neutrino mass spectrum, and the possible Majorana nature of neutrinos are some of the future discoveries of the next generation neutrino experiments. The Majorana collaboration operated the Demonstrator experiment comprising 44 kg (30 kg enriched in 76 Ge) of Ge detectors in total split between two modules contained in a low background shield at the Sanford Underground Research Facility in Lead, South Dakota. Observation of 0νββ would have profound implications for the Standard Model of particle physics by demonstrating that neutrinos are Majorana particles, that lepton number is not conserved, and it would provide a measure of the effective Majorana neutrino mass. The decay rate of 0νββ is incredibly small and may only produce a few signature events in a detector per year. Therefore, observation of this rare process demands a careful study and implementation of signal processing, detector design, and new levels of background suppression.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2021

Symmetry requirements for double shell capsules with aluminum ablators

Double shell targets present a promising avenue to obtain robust neutron yield on current laser facilities. The nature of the target, like current single shell designs, requires a symmetric implosion of an outer ablator to obtain a symmetric fuel volume that will lead to alpha heating and thermonuclear burn. Due to using aluminum as an ablator material and requiring different convergence than single shell symmetry studies at various energies are required. This paper moves forward from previous experiments conducted at 1MJ to show implosion symmetry at 1.25 and 1.5MJ. Symmetry in these experiments is sufficient to merit experiments using double shells to study the platform further. Additional studies are carried out on the outer shell symmetry impacts, showing that mitigating mode growth on the outer ablator is of great importance.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2021

Double Sided LGAD Design Studies

We summarize TCAD design studies for double sided thick buried layer Low Gain Avalanche Diodes (LGADs). These thick double sided devices introduce new features that require overall optimization. We describe both the parameterized and full process simulation and discuss how the results affect the range of process and LGAD physical parameters.

74 ATOMIC AND MOLECULAR PHYSICS↗