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At least 1,549 records · Page 86

Status and challenges in enabling the lithium metal electrode for high-energy and low-cost rechargeable batteries

Enabling the reversible lithium metal electrode is essential for surpassing the energy content of today’s lithium-ion cells. Although lithium metal cells for niche applications have been developed already, efforts are underway to create rechargeable lithium metal batteries that can significantly advance vehicle electrification and grid energy storage. In this Perspective, we focus on three tasks to guide and further advance the reversible lithium metal electrode. First, we summarize the state of research and commercial efforts in terms of four key performance parameters, and identify additional performance parameters of interest. We then advocate for the use of limited lithium (≤30 μm) to ensure early identification of technical challenges associated with stable and dendrite-free cycling and a more rapid transition to commercially relevant designs. Finally, we provide a cost target and outline material costs and manufacturing methods that could allow lithium metal cells to reach 100 US$ kWh–1.

25 ENERGY STORAGE↗

Zero-dimensional to three-dimensional nanojoining: current status and potential applications

We report that the continuing miniaturization of microelectronics is pushing advanced manufacturing into nanomanufacturing. Nanojoining is a bottom-up assembly technique that enables functional nanodevice fabrication with dissimilar nanoscopic building blocks and/or molecular components. Various conventional joining techniques have been modified and re-invented for joining nanomaterials. Our review surveys recent progress in nanojoining methods, as compared to conventional joining processes. Examples of nanojoining are given and classified by the dimensionality of the joining materials. At each classification, nanojoining is reviewed and discussed according to materials specialties, low dimensional processing features, energy input mechanisms and potential applications. The preparation of new intermetallic materials by reactive nanoscale multilayer foils based on self-propagating high-temperature synthesis is highlighted. This review will provide insight into nanojoining fundamentals and innovative applications in power electronics packaging, plasmonic devices, nanosoldering for printable electronics, 3D printing and space manufacturing.

36 MATERIALS SCIENCE↗

EXFOR – a global experimental nuclear reaction data repository: Status and new developments

Members of the International Network of Nuclear Reaction Data Centres (NRDC) have collaborated since the 1960s on the worldwide collection, compilation and dissemination of experimental nuclear reaction data. New publications are systematically complied, and all agreed data assembled and incorporated within the EXFOR database. Here, recent upgrades to achieve greater completeness of the contents are described, along with reviews and adjustments of the compilation rules for specific types of data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

The Majorana Demonstrator Status and Preliminary Results

The MAJORANA Collaboration is using an array of high-purity Ge detectors to search for neutrinoless double-beta decay in 76 Ge. Searches for neutrinoless double-beta decay are understood to be the only viable experimental method for testing the Majorana nature of the neutrino. Observation of this decay would imply violation of lepton number, that neutrinos are Majorana in nature, and provide information on the neutrino mass. The MAJORANA DEMONSTRATOR comprises 44.1 kg of p-type point-contact Ge detectors (29.7 kg enriched in 76 Ge) surrounded by a low-background shield system. The experiment achieved a high efficiency of converting raw Ge material to detectors and an unprecedented detector energy resolution of 2.5 keV FWHM at Q ββ . The MAJORANA collaboration began taking physics data in 2016. Here, this paper summarizes key construction aspects of the Demonstrator and shows preliminary results from initial data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Status of the Muon G − 2 Experiment

The Muon g−2 Experiment at Fermi National Accelerator Laboratory was designed to measure the anomalous magnetic moment of the muon, aµ, with a precision of 140 parts-per-billion; a four-fold improvement over the former BNL measurement. The Fermilab experiment was motivated by the about 3.5 standard deviation between the experiment and the Standard Model calculation of aµ which could be a hint of new physics. The experiment at Fermilab relies on the well-established storage ring technique using magic momentum muons but employs new detector systems and a higher rate of muons per injection cycle to achieve the significant improvement in precision. A first result from the Run-1 data taking period has achieved an uncertainty of 0.46 parts-per-million and confirmed the BNL discrepancy, further increasing the tension with the Standard Model to 4.2 σ. The experimental technique, key aspects of the measurement, and the data analysis of Run-1 will be summarized.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

ITER ECH Transmission Line System Design and Status

The electron cyclotron (EC) heating & current drive (H&CD) system on ITER provides plasma heating by generating, transmitting, and launching high-intensity, high-frequency (170 GHz) electromagnetic wave energy steerable across the plasma cross-section. The transmission line (TL) subsystem connects the Matching Optics Unit (MOU) on each of the 24 gyrotrons to the 32 feed points in the four upper launchers and the 24 feed points in the equatorial launcher. Each TL must be able to operate at up to 1.2 MW of input power for up to 1 hour pulse lengths. The TL system contains 50 mm water-cooled corrugated waveguide, 90o miter bends, 140o miter bends, polarizer miter bend pairs, switches, expansion units, pumpouts, DC breaks, MOU-TL adapters, Radio Frequency (RF) loads, and isolation shutter valves. A detailed finite element analysis has been used to verify the thermo-mechanical performance of each component. The microwave performance has been analyzed using a 2-D electromagnetic code combined with a Monte Carlo code. This approach allows the impact of manufacturing and installation tolerances to be assessed and optimized to provide a high probability of achieving the system performance requirements. Prototypes of the waveguide and TL components have been fabricated and tested at high-power. Production contracts are now being issued for fabrication and delivery of the waveguide and components to ITER.

Hanson, Gregory↗

dCache project status and update

The dCache project delivers an open-source, massively scalable, distributed storage system deployed internationally to satisfy today’s scientists’ ever-demanding storage requirements. Its multifaceted approach supports different use cases with the same storage, from high throughput data ingest, data sharing over wide area networks, efficient access from HPC clusters, and longterm data persistence on tertiary storage. Even though dCache was initially developed for HEP experiments, today, it is used by various scientific communities, including astrophysics, biomed, and life science, each with their specific requirements. To match the needs of these new communities and keep up with the scaling demands of existing experiments, dCache is permanently evolving. With this contribution, we would like to highlight the recent developments in dCache regarding integration with CERN Tape Archive (CTA), advanced metadata handling, token-based authorization support, bulk API for QoS transitions, REST API to control interaction with the tape system, and future development directions.

Mkrtchyan, Tigran [DESY]↗

Status of Mercury and Imp: Two Monte Carlo Transport Codes Developed Using Shared Infrastructure at Lawrence Livermore National Laboratory

The Monte Carlo Transport Project at Lawrence Livermore National Laboratory develops two Monte Carlo transport codes used in production by a sizable internal user community. Mercury is a Monte Carlo particle transport code used to model the interaction of neutrons, gammas, and light ions with a material. Imp is an implicit Monte Carlo thermal x-ray photon transport code used to model the interaction of x-ray photons with a material. This paper describes the two codes and highlights recent developments.

Pozulp, Michael↗

Status of GPU capabilities within the Shift Monte Carlo radiation transport code

Shift is a general-purpose Monte Carlo (MC) radiation transport code for fission, fusion, and national security applications. Shift has been adapted to efficiently run on GPUs in order to leverage leadership-class supercomputers. This work presents Shift’s current GPU capabilities. These include core radiation transport capabilities for eigenvalue and fixed-source simulations, and support for non-uniform domain decomposition, Doppler broadening, free-gas elastic scattering, general-purpose geometry, hybrid MC/deterministic transport, and depletion. Transport results demonstrate a 2–5× GPU-to-CPU speedup on a per-node basis for an eigenvalue problem on the Frontier supercomputer and a 28× speedup for a fixed-source problem on the Summit supercomputer.

Biondo, Elliott [ORNL] (ORCID:0000000290881360)↗

Status of neutron diagnostics on the experimental advanced superconducting tokamak

Neutron diagnostics have become a significant means to study energetic particles in high power auxiliary heating plasmas on the Experimental Advanced Superconducting Tokamak (EAST). Several kinds of neutron diagnostic systems have been implemented for time-resolved measurements of D-D neutron flux, fluctuation, emission profile, and spectrum. All detectors have been calibrated in laboratory, and in situ calibration using {sup 252}Cf neutron source in EAST is in preparation. A new technology of digitized pulse signal processing is adopted in a wide dynamic range neutron flux monitor, compact recoil proton spectrometer, and time of flight spectrometer. Improvements will be made continuously to the system to achieve better adaptation to the EAST’s harsh γ-ray and electro-magnetic radiation environment.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Status of the new SNS injector and external antenna ion source

The U.S. Spallation Neutron Source (SNS) now operates with 1.2 MW of beam power on target with the near-term goal of delivering 1.4 MW and a longer-term goal of delivering >2 MW required by the planned Proton Power Upgrade (PPU) and Second Target Station (STS) projects. In early 2018 we plan to replace the entire 2.5 MeV injector configuration which includes the ion source, the Low Energy Beam Transport (LEBT) and the Radio Frequency Quadrupole accelerator (RFQ) with one which is currently being tested on a research accelerator called the Beam Test Facility (BTF) located at the SNS facility. This report first provides a description of the new injector: the ion source and the cage enclosure, the new LEBT support structure and the new RFQ. Since fall of 2016, this system has been tested extensively with regard to output beam current, beam persistence, emittance and energy. The results of these experiments employing both internal and external antenna ion sources will be summarized here showing the system to be capable of supporting SNS 1.4 MW operations with a significant margin as well as potentially meeting facility upgrade requirements. This represents a significant performance upgrade over the current SNS front end system with the compromised RFQ and will replace that system in early 2018.

Welton, Robert F.↗

Status of h-BN quasi-bulk crystals and high efficiency neutron detectors

III-nitrides have fomented a revolution in the lighting industry and are poised to make a huge impact in the field of power electronics. In the III-nitride family, the crystal growth and use of hexagonal BN (h-BN) as an ultrawide bandgap (UWBG) semiconductor are much less developed. Bulk crystals of h-BN produced by the high-temperature/high-pressure and the metal flux solution methods possess very high crystalline and optical qualities but are impractical to serve as substrates or for device implementation as their sizes are typically in millimeters. The development of crystal growth technologies for producing thick epitaxial films (or quasi-bulk or semi-bulk crystals) in large wafer sizes with high crystalline quality is a prerequisite for utilizing h-BN as an UWBG electronic material. Compared to traditional III-nitrides, BN has another unique application as solid-state neutron detectors, which however, also require the development of quasi-bulk crystals to provide high detection efficiencies because the theoretical efficiency (ηi) relates to the detector thickness (d) by ηi=1−e−dλ, where λ denotes the thermal neutron absorption length which is 47 μm (237 μm) for 10B-enriched (natural) h-BN. We provide an overview and recent progress toward the development of h-BN quasi-bulk crystals via hydride vapor phase epitaxy (HVPE) growth and the attainment of thermal neutron detectors based on 100 μm thick 10B-enriched h-BN with a record efficiency of 60%. The thermal neutron detection efficiency was shown to enhance at elevated temperatures. Benchmarking the crystalline and optical qualities of h-BN quasi-bulk crystals with the state-of-the-art mm-sized bulk crystal flakes and 0.5 μm thick epitaxial films identified that reducing the density of native defects such as vacancies remains the most critical task for h-BN quasi-bulk crystal growth by HVPE.

Physics↗

Microscopy Instrumentation and Nanopositioning at NSLS-II: Current Status and Future Directions

The development of ultra-brilliant synchrotron facilities and recent advances in the fabrication of efficient nano-focusing optics have stimulated rapid development and applications of the focused beams used to elucidate nanoscale phenomena in many areas of science and technology. Various nano-focusing optics, including Kirkpatrick- Baez (KB) and elliptical mirrors, Fresnel zone plates (ZP), compound refractive and kinoform lenses, and multilayer Laue lenses (MLL), are routinely used to achieve nano-focusing. The latest experiments utilizing KB mirrors have demonstrated focal spot size of 13 nm with the ZPs and MLLs being able to focus hard X-rays to 10 nm and below. When the focused beam size is reduced to below 100 nm, there is a need to develop a dedicated system tailored for a specific application, which satisfies stringent mechanical, vibrational, and thermal characteristics to successfully enable nano-scale imaging. Multiple degrees of motion, including their positioning accuracy, resonance frequencies, and amount of heat being dissipated, have to be thoroughly considered in order to efficiently perform nano-focusing experiments.

47 OTHER INSTRUMENTATION↗