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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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At least 217 records · Page 12

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DOE OSTI2011

First results from two particle azimuthal correlations at ALICE

Analysis of the leading particle correlations in p+p data taken by the ALICE experiment at centre of mass energies {radical}(s) = 0.9 and 7 TeV is presented. Per trigger normalized associated particle yield as a function of pair relative azimuthal angle {Delta}{phi} is used to determine the jet-fragmentation transverse momentum j{sub T}. The resulting values are compared to similar measurements at lower centre of mass energies done at RHIC and ISR. Furthermore we study the distribution of the transverse momentum component of associated particles with respect to leading particle, p{sub out}. This quantity is related to di-jet acoplanarity. We present an analytic formula which estimates a background component of measured p{sub out} coming from uncorrelated pairs.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2014

Controlling spin-dependent tunneling by bandgap tuning in epitaxial rocksalt MgZnO films

Widespread application of magnetic tunnel junctions (MTJs) for information storage has so far been limited by the complicated interplay between tunnel magnetoresistance (TMR) ratio and the product of resistance and junction area (RA). An intricate connection exists between TMR ratio, RA value and the bandgap and crystal structure of the barrier, a connection that must be unravelled to optimise device performance and enable further applications to be developed. In this paper, we demonstrate a novel method to tailor the bandgap of an ultrathin, epitaxial Zn-doped MgO tunnel barrier with rocksalt structure. This structure is attractive due to its good Δ 1 spin filtering effect, and we show that MTJs based on tunable MgZnO barriers allow effective balancing of TMR ratio and RA value. Finally, in this way spin-dependent transport properties can be controlled, a key challenge for the development of spintronic devices.

36 MATERIALS SCIENCE↗

DOE OSTI2011

Gluon saturation and energy dependence of hadron multiplicity in pp and AA collisions at the LHC

The recent results in {radical}(s)=2.76 TeV Pb+Pb collisions at the Large Hadron Collider (LHC) reported by the ALICE collaboration shows that the power-law energy-dependence of charged hadron multiplicity in Pb+Pb collisions is significantly different from p+p collisions. We show that this different energy-dependence can be explained by inclusion of a strong angular-ordering in the gluon-decay cascade within the color glass condensate (or gluon saturation) approach. This effect is more important in nucleus-nucleus collisions where the saturation scale is larger than 1 GeV. Our prescription gives a good description of the LHC data both in p+p and Pb+Pb collisions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2012

High performance electrical, magnetic, electromagnetic and electrooptical devices enabled by three dimensionally ordered nanodots and nanorods

Novel articles and methods to fabricate same with self-assembled nanodots and/or nanorods of a single or multicomponent material within another single or multicomponent material for use in electrical, electronic, magnetic, electromagnetic and electrooptical devices is disclosed. Self-assembled nanodots and/or nanorods are ordered arrays wherein ordering occurs due to strain minimization during growth of the materials. A simple method to accomplish this when depositing in-situ films is also disclosed. Device applications of resulting materials are in areas of superconductivity, photovoltaics, ferroelectrics, magnetoresistance, high density storage, solid state lighting, non-volatile memory, photoluminescence, thermoelectrics and in quantum dot lasers.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

DOE OSTI2013

High performance superconducting devices enabled by three dimensionally ordered nanodots and/or nanorods

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2011

High performance devices enabled by epitaxial, preferentially oriented, nanodots and/or nanorods

Novel articles and methods to fabricate same with self-assembled nanodots and/or nanorods of a single or multicomponent material within another single or multicomponent material for use in electrical, electronic, magnetic, electromagnetic, superconducting and electrooptical devices is disclosed. Self-assembled nanodots and/or nanorods are ordered arrays wherein ordering occurs due to strain minimization during growth of the materials. A simple method to accomplish this when depositing in-situ films is also disclosed. Device applications of resulting materials are in areas of superconductivity, photovoltaics, ferroelectrics, magnetoresistance, high density storage, solid state lighting, non-volatile memory, photoluminescence, thermoelectrics and in quantum dot lasers.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Design and implementation of a portable diagnostic system for Thomson scattering and optical emission spectroscopy measurements

A diagnostic system, which has a design goal of high-portability, has been designed at Oak Ridge National Laboratory (ORNL). This project aims at providing measurements of key plasma parameters (ne, Te, ni, Ti) for fusion-relevant devices, utilizing Thomson scattering (TS) and optical emission spectroscopy (OES). The innovative design employs mostly commercial off-the-shelf instrumentation and a traveling team of researchers to conduct measurements at various magnetic-confinement plasma devices. The TS diagnostic uses a Quantel Q-smart 1500 Nd:YAG laser with a 2ω harmonic generator to produce up to 850 mJ of 532 nm laser pulses at 10 Hz. Collection optics placed at the detection port consists of an 11 × 3 optical fiber bundle, where the TS diagnostic uses an 11 × 1 subset array of the fibers, the OES diagnostic uses another 11 fibers, and the remaining fibers are available to the host institution. The detection system is comprised of two separate IsoPlane-320 spectrometers with triple-grating turrets of various line spacing and two PI-MAX 4 intensified CCD detectors, used simultaneously to measure a broad range of ion, impurity, and electron parameters. The self-contained diagnostic package also includes a data processing and storage system. The design and initial implementation of the TS-OES diagnostic system are described. The experiments from the proof-of-principle operation of the portable package on a high density (∼2.5 × 1022 m−3) and low-temperature (∼5 eV) electrothermal arc source at ORNL are also discussed.

Kafle, N. (ORCID:000000028144787X)↗

DOE OSTI2010

The ALICE experiment at the LHC First Physics Results

ALICE is one of the experiments at the LHC. The excellent performance of the detector has been demonstrated with the measurement and analysis of the first proton-proton collisions provided by the LHC on November 2009. We review the first physics results and the general status of the project. We also review the activities of the Mexican group participating in ALICE project.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Refurbishment of a used in-vacuum undulator from the National Synchrotron Light Source for the National Synchrotron Light Source-II ring

The National Synchrotron Light Source (NSLS) ceased operation in September 2014 and was succeeded by NSLS-II. There were four in-vacuum undulators (IVUs) in operation at NSLS. The most recently constructed IVU for NSLS was the mini-gap undulator (MGU-X25, to be renamed IVU18 for NSLS-II), which was constructed in 2006. This device was selected to be reused for the New York Structural Biology Consortium Microdiffraction beamline at NSLS-II. At the time of construction, IVU18 was a state-of-the-art undulator designed to be operated as a cryogenic permanent-magnet undulator. Due to the more stringent field quality and impedance requirements of the NSLS-II ring, the transition region was redesigned. The control system was also updated to NSLS-II specifications. As a result, this paper reports the details of the IVU18 refurbishment activities including additional magnetic measurement and tuning.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Synthesis, engineering, and theory of 2D van der Waals magnets

The recent discovery of magnetism in monolayers of two-dimensional van der Waals materials has opened new venues in materials science and condensed matter physics. Until recently, two-dimensional magnetism remained elusive: Spontaneous magnetic order is a routine instance in three-dimensional materials but it is not a priori guaranteed in the two-dimensional world. Since the 2016 discovery of antiferromagnetism in monolayer FePS 3 by two groups and the subsequent demonstration of ferromagnetic order in monolayer CrI 3 and bilayer Cr 2 Ge 2 Te 6 , the field changed dramatically. Within several years of scientific discoveries focused on 2D magnets, novel opportunities have opened up in the field of spintronics, namely spin pumping devices, spin transfer torque, and tunneling. In this review, we describe the state of the art of the nascent field of magnetic two-dimensional materials focusing on synthesis, engineering, and theory aspects. Finally, we also discuss challenges and some of the many different promising directions for future work, highlighting unique applications that may extend even to other realms, including sensing and data storage.

2D materials↗

DOE OSTI2011

HybridStore: A Cost-Efficient, High-Performance Storage System Combining SSDs and HDDs

Unlike the use of DRAM for caching or buffering, certain idiosyncrasies of NAND Flash-based solid-state drives (SSDs) make their integration into existing systems non-trivial. Flash memory suffers from limits on its reliability, is an order of magnitude more expensive than the magnetic hard disk drives (HDDs), and can sometimes be as slow as the HDD (due to excessive garbage collection (GC) induced by high intensity of random writes). Given these trade-offs between HDDs and SSDs in terms of cost, performance, and lifetime, the current consensus among several storage experts is to view SSDs not as a replacement for HDD but rather as a complementary device within the high-performance storage hierarchy. We design and evaluate such a hybrid system called HybridStore to provide: (a) HybridPlan: improved capacity planning technique to administrators with the overall goal of operating within cost-budgets and (b) HybridDyn: improved performance/lifetime guarantees during episodes of deviations from expected workloads through two novel mechanisms: write-regulation and fragmentation busting. As an illustrative example of HybridStore s ef cacy, HybridPlan is able to nd the most cost-effective storage con guration for a large scale workload of Microsoft Research and suggest one MLC SSD with ten 7.2K RPM HDDs instead of fourteen 7.2K RPM HDDs only. HybridDyn is able to reduce the average response time for an enterprise scale random-write dominant workload by about 71% as compared to a HDD-based system.

Kim, Youngjae↗

DOE OSTI2010

Integrated Power Adapter: Isolated Converter with Integrated Passives and Low Material Stress

ADEPT Project: CPES at Virginia Tech is developing an extremely efficient power converter that could be used in power adapters for small, lightweight laptops and other types of mobile electronic devices. Power adapters convert electrical energy into useable power for an electronic device, and they currently waste a lot of energy when they are plugged into an outlet to power up. CPES at Virginia Tech is integrating high-density capacitors, new magnetic materials, high-frequency integrated circuits, and a constant-flux transformer to create its efficient power converter. The high-density capacitors enable the power adapter to store more energy. The new magnetic materials also increase energy storage, and they can be precisely dispensed using a low-cost ink-jet printer which keeps costs down. The high-frequency integrated circuits can handle more power, and they can handle it more efficiently. And, the constant-flux transformer processes a consistent flow of electrical current, which makes the converter more efficient.

Agile Delivery of Electrical Power Technology↗

DOE OSTI2011

Identified particle studies at the LHC with the ALICE experiment

In this article, we discuss the first results from the analysis of pp collisions at LHC energies with the ALICE detector. We concentrate on the studies of identified particles, with a focus on the detector performance and the baryon transport analyses.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2021

RKKY Exchange Bias Mediated Ultrafast All-Optical Switching of a Ferromagnet

The discovery of ultrafast helicity-independent all-optical switching (HI-AOS), as well as picosecond all-electrical switching of a ferrimagnet, has inspired the ultrafast spintronics community to explore ultrafast switching of a ferromagnet to achieve practical ultrafast storage and memory devices. Two explored mechanisms of HI-AOS of a ferromagnet in ferromagnet-ferrimagnet heterostructure are: a) exploiting the indirect exchange coupling with and b) injection of non-local spin current originated from a switching ferrimagnet. Here, in this manuscript, exchange mediated HI-AOS of a Ruderman–Kittel–Kasuya–Yosida (RKKY) exchange coupled “[Co/Pt]-multilayers/Pt spacer/CoGd” heterostructure is demonstrated. The authors have measured layer-resolved static magnetic properties, single-shot HI-AOS, and magnetization dynamics of the ferromagnetic Co/Pt multilayers (MLs), that are ferromagnetically or antiferromagnetically coupled with ferrimagnetic CoGd layers. Time-resolved magnetization dynamics reveal a 3.5 ps switching time of the Co/Pt MLs, which is the fastest switching of a ferromagnet reported to date. Employing an extended microscopic three-temperature model, the temporal dynamics of the exchange coupled ferromagnet–ferrimagnet heterostructure are simulated, qualitatively and quantitatively explaining the experimental switching phenomena. This work experimentally as well as theoretically establishes the mechanism of exchange mediated all-optical switching of ferromagnet-ferrimagnet heterostructures, which can be integrated with a magnetic tunnel junction for efficient reading after ultrafast energy-efficient switching.

36 MATERIALS SCIENCE↗

DOE OSTI2011

Strange quark suppression and strange hadron production in pp collisions at energies available at the BNL Relativistic Heavy Ion Collider and the CERN Large Hadron Collider

The parton and hadron cascade model PACIAE based on PYTHIA is utilized to systematically investigate strange particle production in pp collisions at energies available at the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC). Globally speaking, the PACIAE results of the strange particle rapidity density at midrapidity and the transverse momentum distribution are better than those of PYTHIA (default) in comparison with STAR and ALICE experimental data. This may represent the importance of the parton and hadron rescatterings, as well as the reduction mechanism of strange quark suppression, added in the PACIAE model. The K/{pi} ratios as a function of reaction energy in pp collisions from CERN Super Proton Synchrotron (SPS) to LHC energies are also analyzed in this paper.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2018

Magneto-ionic control of magnetism using a solid-state proton pump

Voltage-gated ion transport as a means of manipulating magnetism electrically could enable ultralow-power memory, logic and sensor technologies. Earlier work made use of electric-field-driven O 2– displacement to modulate magnetism in thin films by controlling interfacial or bulk oxidation states. However, elevated temperatures are required and chemical and structural changes lead to irreversibility and device degradation. Here we show reversible and non-destructive toggling of magnetic anisotropy at room temperature using a small gate voltage through H + pumping in all-solid-state heterostructures. We achieve 90° magnetization switching by H + insertion at a Co/GdO x interface, with no degradation in magnetic properties after >2,000 cycles. We then demonstrate reversible anisotropy gating by hydrogen loading in Pd/Co/Pd heterostructures, making metal–metal interfaces susceptible to voltage control. The hydrogen storage metals Pd and Pt are high spin–orbit coupling materials commonly used to generate perpendicular magnetic anisotropy, Dzyaloshinskii–Moriya interaction, and spin–orbit torques in ferromagnet/heavy-metal heterostructures. Furthermore, our work provides a platform for voltage-controlled spin–orbitronics.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2010

First results from the HMPID detector in the ALICE experiment at LHC

The ALICE experiment is dedicated to the study of heavy-ion collisions at LHC energies. ALICE has a high-quality hadron identification system in the central region e.g. a Inner Tracking System, a large Time-Projection-Chamber, a Time-Of-Flight and the High Momentum Particle Identification Detector (HMPID). The ALICE HMPID detector has been designed to identify charged hadrons ({rho}, K, p) in the momentum range 1<p<5 GeV/c. Despite its limited geometrical acceptance, less than 10% of the central ALICE barrel, the HMPID detector has successfully accumulated enough statistics during the first proton-proton runs at LHC, to allow the detector alignment and to evaluate the calibration parameters needed to estimate its performance. Preliminary HMPID results from p-p collisions at {radical}(s) = 7 TeV and its future contribution to the ALICE physics programme, will be presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2011

Heavy-flavour production in hot quark matter

Recent results from the RHIC facility and first measurements from the ALICE experiment at the CERN-Large Hadron Collider (LHC) on open heavy-flavour are presented. We focus on RHIC measurements of single electrons and jetlike heavy-flavour particle correlations. First D meson signals from 7 TeV proton-proton collisions from ALICE are discussed. Next-to-leading-order QCD processes, such as gluon splitting, become important at LHC energies and its contribution can be accesses by the measurement of the charm content in jets.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗