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DOE OSTI2021

Double band inversion in the topological phase transition of Ge 1-x Sn x alloys

Abstract We use first-principles simulation and alchemical mixing approximation to reveal the unique double band inversion and topological phase transition in Ge Sn alloys. Wave function parity, spatial charge distribution and surface state spectrum analyses suggest that the band inversion in Ge Sn is relayed by its first valence band. As the system evolves from Ge to -Sn, its conduction band moves down, and inverts with the first and the second valence bands consecutively. The first band inversion makes the system nontrivial, while the second one does not change the topological invariant of the system. Both of the band inversions yield surface modes spanning the individual inverted gaps, but only the surface mode in the upper gap associates with the nontrivial nature of tensile-strained -Sn.

Physics↗

DOE OSTI2023

OLCF Summit Supercomputer GPU Snapshots During Double-Bit Errors and Normal Operations

As we move into the exascale era, the power and energy footprints of high-performance computing (HPC) systems have grown significantly larger. Due to the harsh power and thermal conditions the system, components are exposed to extreme operating conditions. Operation of such modern HPC systems requires deep insights into long term system behavior to maintain its efficiency as well as its longevity. To help the HPC community to gain such insights, we provide double-bit errors using system telemetry data and logs collected from the Summit supercomputer, equipped with 27,648 Tesla V100 GPUs with 2nd-generation high-bandwidth memory (HBM2). The dataset relies on Nvidia XID records internally collected by GPU firmware at the time of failure occurrence, on the reboot-time logs of each Summit node, on node-level job scheduler records collected after each job termination, and on a 1Hz data rate from the baseboard management controllers (BMCs) of each Summit compute node using the OpenBMC event subscription protocol. Technical details can be found in the paper Oles et. al “Understanding GPU Memory Corruption at Extreme Scale: The Summit Case Study” ICS’24 (https://doi.org/10.1145/3650200.3656615).

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2025

Polarization-separated double-imaging spectroscopy for weakly-ionized plasma diagnostics

Laser Thomson scattering, which provides thermal properties of electrons, has been extensively utilized in plasma diagnostics. However, being a non-resonant linear light scattering technique, it often encounters several challenges in weakly-ionized plasma diagnostics due to spectral overlap with different scatterings induced from other existing species, including Mie, Rayleigh, and rotational Raman scatterings. To address this challenge, we propose an imaging spectroscopy technique, polarization-separated double-imaging spectroscopy (PoDIS), which selectively separates specific scatterings based on their polarization characteristics. Using an atmospheric plasma jet as a plasma source for demonstration, we show that PoDIS can effectively separate rotational Raman and Thomson scatterings from a superimposed spectrum without prior knowledge or assumptions about the thermal properties of neutrals or electrons. This separation enables independent fitting of the rotational Raman and Thomson scattering spectra, allowing for precise determination of the thermal properties of neutral particles and electrons separately.

Bak, Junhwi [Texas A&M University, College Station↗

DOE OSTI2020

Mid-infrared frequency doubling using strip-loaded silicon nitride on epitaxial barium titanate thin film waveguides

Broadband mid-infrared (mid-IR) frequency doubling was demonstrated using nonlinear barium titanate (BTO) thin films. The device has a strip-loaded waveguide structure consisting of top silicon nitride (SiN) strips and an underneath BTO guiding layer. The epitaxial BTO was deposited on a strontium titanate (STO) substrate by pulsed-laser deposition. Through a SiN grating coupler, the pumping mid-IR light at wavelength λ = 3.30 − 3.45 µ m was coupled into the nonlinear BTO layer, where the spectrum of the near-infrared (NIR) second-harmonic generation was characterized. The developed BTO waveguides provide a platform for mid-IR nonlinear integrated photonics and on-chip quantum optics.

42 ENGINEERING↗

DOE OSTI2020

EGS Collab Experiment 1: 3D Seismic Velocity Model and Updated Microseismic Catalog from Double-Difference Seismic Tomography

This package contains a 3D Seismic velocity model and an updated microseismic catalog obtained for a double-difference seismic tomography study. The 3D_seismic_velocity_model text file contains x (m), y(m), z(m), P-wave velocity (km/s), P-wave velocity quality indicator (1 for well-constrained; 0 for poorly constrained), S-wave velocity (km/s), and S-wave velocity quality indicator (1 for well-constrained; 0 for poorly constrained). The Updated_MEQ_catalog text file contains event origin time, x(m), y(m), z(m), error in x (m), error in y (m), error in z (m), and RMS misfit (millisecond). The 3D_seismic_P-wave_velocity_model animation file shows slices of the 3D P-wave velocity model. The 3D_seismic_S-wave_velocity_model animation file shows slices of the 3D S-wave velocity model. The Interactive_MEQ_location_comparison API file is an interactive visualization of the updated microseismic event locations and the original seismic catalog. The visualization allows users to view and compare the event locations by dragging, rotating, and zooming in. An updated version of 3D_seismic_velocity_model and associated animations were included, which were calculated with a more strict assumption for quality indicators.

15 GEOTHERMAL ENERGY↗

DOE OSTI2025

Geometry-driven modeling of electron localization in InAs/GaAs double quantum dots

The coupled electronic states in two-dimensional (2D) and three-dimensional (3D) double quantum dot (DQD) systems are investigated using a phenomenological model applied to InAs/GaAs heterostructures. The single-band k • p effective potential approach previously proposed by our group is employed to numerically calculate the energy spectrum and spatial localization of a single electron, serving as an indicator of the coupling strength within the binary system. For identical quantum dots (QDs) in a DQD, the electronic states exhibit ideal coherence. We systematically vary the DQD geometry and the strength of the confinement potential (via an applied electric field) to examine the effects of symmetry breaking and the sensitivity of electron localization in both identical and nearly identical DQDs. Our results show that coherence in DQDs is highly sensitive to these subtle variations. This sensitivity can be harnessed to detect changes in the surrounding environment, such as fluctuations in chemical or electrical properties that affect the DQD system.

electron localization↗

DOE OSTI2023

A symmetry algebra in double-scaled SYK

The double-scaled limit of the Sachdev-Ye-Kitaev (SYK) model takes the number of fermions and their interaction number to infinity in a coordinated way. In this limit, two entangled copies of the SYK model have a bulk description of sorts known as the “chord Hilbert space”. We analyze a symmetry algebra acting on this Hilbert space, generated by the two Hamiltonians together with a two-sided operator known as the chord number. This algebra is a deformation of the JT gravitational algebra, and it contains a subalgebra that is a deformation of the \mathfrak{sl}_2 𝔰 𝔩 2 near-horizon symmetries. The subalgebra has finite-dimensional unitary representations corresponding to matter moving around in a discrete Einstein-Rosen bridge. In a semiclassical limit the discreteness disappears and the subalgebra simplifies to \mathfrak{sl}_2 𝔰 𝔩 2 , but with a non-standard action on the boundary time coordinate. One can make the action of \mathfrak{sl}_2 𝔰 𝔩 2 algebra more standard at the cost of extending the boundary circle to include some “fake” portions. Such fake portions also accommodate certain subtle states that survive the semi-classical limit, despite oscillating on the scale of discreteness. We discuss applications of this algebra, including sub-maximal chaos, the traversable wormhole protocol, and a two-sided OPE.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2022

Longitudinal double-spin asymmetries of inclusive jet and dijet production at STAR

The STAR experiment probes the gluon helicity distribution \Delta g(x, Q^2) Δ g ( x , Q 2 ) using collisions of longitudinally polarized protons at \sqrt{s} = 200 s = 200 ~GeV and \sqrt{s} = 510 s = 510 ~GeV. \Delta g(x, Q^2) Δ g ( x , Q 2 ) can be accessed through the double-spin asymmetries A_{LL} A L L in gluon-dominated hard scattering processes via inclusive jet and dijet production. This proceedings report on recent measurements of A_{LL} A L L for inclusive jets and dijets in the mid-pseudorapidity ( |\eta| < 1 | η | < 1 ) and dijets in the intermediate pseudrapidity ( -0.8 < \eta < 1.8 − 0.8 < η < 1.8 ) regions. These measurements provide sensitivity to \Delta g(x, Q^2) Δ g ( x , Q 2 ) for gluon momentum fractions x x from \simeq 0.5 ≃ 0.5 down to \simeq 0.004 ≃ 0.004 . The results are in good agreement with previous STAR measurements and recent theoretical evaluations of prior world data.

Zurek, Maria↗

DOE OSTI2022

Longitudinal double helicity asymmetry $A_{LL}$ from direct photon, jet and charged pion production in polarized $\vec{p}+\vec{p}$ collisions

Understanding the proton spin composition from the quarks and gluons spin polarization and their motion is important to test various kinds of sum rules and nonperturbative properties of hadrons. At the Relativistic Heavy Ion Collider (RHIC), we collide longitudinally polarized proton beams and measure the double helicity asymmetry A_{LL} A L L , which is an important physical quantity for extracting the polarized parton distribution functions (PDFs) of the proton. Direct photon, jet and charged pion production are good channels to probe the gluon spin polarization inside the proton, with the ability to probe also the sign of the gluon spin. Direct photon production is the theoretically ``cleanest’’ channel, with little fragmentation contribution, but limited by statistics. On the other hand, jet and charged pion production have more statistics, but include more hard processes and hadronization effects. I will present the recent measurements of direct photon, jet and charged pion A_{LL} A L L s at PHENIX and show their complementary roles in extracting the gluon spin.

Ji, Zhongling↗

DOE OSTI2020

Design and Analysis of a Double Wall, Water Cooled Window for Accelerator Based Mo-99 Production

The electron accelerator based Mo-99 production technique requires the use of Rhodotrons to generate 38 MeV, 6.32 mA pulsed electron beams. The introduction of the pulsed beam structure has introduced fatigue concerns in the vacuum-helium windows that did not exist previously for electron beam production via linear accelerators. Previous analysis has shown that temperature fluctuations of approximately 100°C above and below the steady state operating temperature of ~500°C will occur within the windows. A water cooled window will eliminate this concern by reducing the primary mechanical stress due to the 300-psig helium pressure load as well as the secondary thermally induced stress. Although a water cooled window was considered years ago, the complexities of adding an additional water line was unattractive until now. A double wall, water cooled window has been designed and analyzed for this reason. The water cooled window design is shown to decrease the helium-side window temperature to as low as 125°C, while the vacuum-side window is maintained at 161°C at a water flow rate of 3.2 GPM. These low steady state temperatures reduce the thermal stress of the helium-side window significantly. Also, the primary mechanical stress has been reduced by roughly 50% due to the reduced pressure gradient across the helium-side window (150-psig water and 300-psig helium). Considering a Mo-99 production loss of roughly 1%, the water cooled window is a drastic improvement over the previous helium cooled designs and should be greatly considered for future upgrades and redesign.

43 PARTICLE ACCELERATORS↗

DOE OSTI2020

Hanford Double Shell Waste Tank Corrosion Studies (Final Report FY2019)

During fiscal year (FY) 2019, the Savannah River National Laboratory (SRNL) focused on four primary tasks for Hanford Double Shell Tanks (DSTs) corrosion studies. The first task, New Limits, was a continuation from the electrochemical work started in FY16, to expand electrochemical testing to elevated temperatures and elevated hydroxide concentrations and evaluate how these factors will influence pitting corrosion. Using the pitting factor (PF) equation, these new conditions were validated to provide a conservative estimate for the susceptibility of pitting corrosion on legacy carbon steel. The second task, Secondary Liner Corrosion, focused on Vapor Space Corrosion (VSC) and immersion testing studies using two commercially available vapor corrosion inhibitors (VCIs). For this FY, the VCI strategy was applied mid-experiment to determine performance on weathered coupons. The third task, Long-Term Open Circuit Potential (OCP) Drift, was performed using simplified simulated chemistries to evaluate change in pitting corrosion risk due to evolution of corrosion potential for mill-scale and freshly polished 600-grit surfaces. Finally, the fourth task, Microbiologically-Influenced Corrosion (MIC) studies, was focused on the study of leak detection pit (LDP) water sent from the Hanford tank farm for determination of bacteria that can be conducive to corrosion using commercially available kits: BART TM and MICkit® 5. In addition, this FY, a secondary task was added which was a continuation of the study of the Quartz-enhanced Photoacoustic Spectroscopy (QEPAS) system. Work was started but was ultimately not pursued. A summary of each task performed is presented below.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2020

DUNE’s Potential to Search for Neutrinoless Double Beta Decay

Neutrinoless double beta decay is a forbidden process by the standard model due to a violation of lepton number and could be piece of the matter/anti-matter asymmetry puzzle. Its rarity makes it very difficult to search for, but if found could aid in figuring out the mass hierarchy. The idea is to take advantage of DUNE's size and capabilities to attempt to detect the decay by doping the liquid argon with Xenon, a candidate isotope for this decay. Thus, we need to know whether this search is feasible within DUNE’s framework

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2020

Design, Optimization, and In-Depth Understanding of Front and Rear Junction Screen-Printed Double-Side Passivated Contacts Solar Cells

Investigate the efficiency potential of n-type screen-printed poly-Si based double-side tunnel oxide passivated contacts (DS-TOPCon) silicon solar cells Establish key material/device parameters and technologies to attain practically achievable DS-TOPCon cell efficiency by Quokka 2D Develop fundamental understanding of underlying mechanisms governing cell operation in front junction (FJ) and rear junction (RJ) cell designs to explain why RJ is a better choice for DS-TOPCon structure

14 SOLAR ENERGY↗

DOE OSTI2020

Double Quarter Wave Crab Cavity Wire Stretching Measurement at BNL

The Double Quarter Wave (DQW) crab cavity is one out of the two crab cavities within Work Package 4 of the LHC (Large Hadron Collider) Hi-Lumi Program, and the RF design of the cavity was originally supported by the US LHC Accelerator Research Program (LARP) and later the LHC Accelerator Upgrade Program (AUP) funded by the DOE High Energy Physics Office in the Office of Science. Brookhaven National Laboratory (BNL) has delivered the successful DQW crab cavity RF design, and worked actively with all. The wire stretching measurement was completed on the prototype DQW crab cavity for operation practice and calibration of the measurement system. Four locations were defined to be on the electrical center plane of the crab cavity, and survey of the wire indicated all are on the same plane. The successful measurement validated the wire stretching system built at Brookhaven National Lab. The offset of the four wire locations to the fitted plane provided the error of the measurement.

43 PARTICLE ACCELERATORS↗

DOE OSTI2021

Hanford Double Shell Waste Tank Corrosion Studies FY2020 (Final Report)

For fiscal year (FY) 2020, the Savannah River National Laboratory (SRNL) focused on three experimental tasks related to Hanford Double Shell Tank (DST) chemistry and integrity. The first task focused on understanding risk of corrosion due to formation of either continuous layers or discrete patches of deposits on the tanks’ inner sidewalls and bottoms. The second task studied vapor space corrosion (VSC) of the secondary liner using two commercially available vapor corrosion inhibitors (VCIs) at manufacturer recommended dosages. Finally, the third task investigated the long-term open circuit potential (OCP) drift for mill-scale coupons, coupons with polished surfaces, and partial mill-scale coupons that were exposed to tank waste simulants. Additional tests were performed to evaluate the OCP drift as a function of the quantity and composition of organic compounds added to the simulant. A test that was included in the matrix that established the new chemistry limits for tank corrosion, but was previously unreported, was presented and reviewed as well.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2021

Summary of Summer Project: Evaluating New Double Perovskite Halide Scintillators for Radiation Detection Applications

Project Outline: • Experimental validation of machine learning based prediction models; • Evaluating double perovskite halides (chlorides, some bromides) – A 2 bb'X 6 :Ce; A = Br + , Cs + ; B = Na + , K + ; B' = RE 3+ ; X = Cl - , Br - ; • Performing single crystal growth and characterization (physical, optical, scintillation properties).

61 RADIATION PROTECTION AND DOSIMETRY↗

DOE OSTI2021

Pathways for a compact double-quarter wave cavity with low peak surface fields and large deflecting kick

This paper describes the parameter choices necessary to obtain a compact Double Quarter Wave (DQW) cavity with low peak surface fields – electric and magnetic – and large deflecting kick. The work is motivated by the space limitations and demanding crabbing voltage required for the crabbing system of the Electron-Ion Collider (EIC) and focuses on the optimization of the 197 MHz crab cavities for the EIC’s hadron ring. For a crabbing voltage of 11.5 MV, the optimized cavity is less than one meter long, showing a maximum peak surface magnetic field of 70 mT and a maximum peak surface electric field of 45 MV/m.

43 PARTICLE ACCELERATORS↗

DOE OSTI2021

Design of double- and multi-bend achromat lattices with large dynamic aperture and approximate invariants

A numerical method to design nonlinear double- and multi-bend achromat (DBA and MBA) lattices with approximate invariants of motion is investigated. The search for such nonlinear lattices is motivated by Fermilab’s Integrable Optics Test Accelerator (IOTA), whose design is based on an integrable Hamiltonian system with two invariants of motion. While it may not be possible to design an achromatic lattice for a dedicated synchrotron light source storage ring with one or more exact invariants of motion, it is possible to tune the sextupoles and octupoles in existing DBA and MBA lattices to produce approximate invariants. In our procedure, the lattice is tuned while minimizing the turn-by-turn fluctuations of the Courant-Snyder actions J x and J y at several distinct amplitudes, while simultaneously minimizing diffusion of the on-energy betatron tunes. The resulting lattices share some important features with integrable ones, such as a large dynamic aperture, trajectories confined to invariant tori, robustness to resonances and errors, and a large amplitude-dependent tune-spread. Compared to the nominal NSLS-II lattice, the single- and multi-bunch instability thresholds are increased and the bunch-by-bunch feedback gain can be reduced.

43 PARTICLE ACCELERATORS↗