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Chen, Y. C.

Publications and source records attributed to Chen, Y. C..

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

The Present and Future of QCD: QCD Town Meeting White Paper – An Input to the 2023 NSAC Long Range Plan

It is currently understood that there are four fundamental forces in nature: gravitational, electromagnetic, weak and strong forces. The strong force governs the interactions between quarks and gluons, elementary particles whose interactions give rise to the vast majority of visible mass in the universe. The mathematical description of the strong force is provided by the non-Abelian gauge theory Quantum Chromodynamics (QCD). While QCD is an exquisite theory, constructing the nucleons and nuclei from quarks, and furthermore explaining the behavior of quarks and gluons at all energies, remain to be complex and challenging problems. Such challenges, along with the desire to understand all visible matter at the most fundamental level, position the study of QCD as a central thrust of research in nuclear science. Experimental insight into the strong force can be gained using large particle accelerator facilities, which are necessary to probe the very short distance scales over which quarks and gluons interact. The Long Range Plans (LRPs) exercise of 1989 and 1996 led directly to the construction of two world-class facilities: the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab (JLab) that is focused on studying how the structure of hadrons emerges from QCD (cold QCD research), and the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Lab (BNL) that aims at the discovery and study of a new state of matter, the quark-gluon plasma (QGP), at extremely high temperatures (hot QCD research). These past investments have produced major advances. Nucleons and nuclei are being studied with increasing precision with a unified description of the partonic structure utilizing multi-dimensional imaging. Significant progress has been made, paving the way towards a complete picture of how quarks and gluons give rise to the mass, spin, and momentum of the nucleon. In hot QCD, the QGP is created in the collisions of nuclei at RHIC and the Large Hadron Collider (LHC) and is observed to behave like a fluid with very low specific shear viscosity; the current goals are to understand how the fluid behavior emerges from QCD and to characterize the temperature (and chemical potential) dependence of the properties of the QGP. As this White Paper is written, current experimental programs at CEBAF, RHIC and the LHC continue to provide exciting near term opportunities to capitalize on the investments in experimental equipment and accelerator operations. Most importantly, the QCD community looks forward to the construction of the Electron Ion Collider (EIC) as a major new facility to push forward QCD research in the next decades, with significant focus on exploring the properties of gluons, the mediators of the strong force.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

High-precision measurement of the W boson mass with the CDF II detector

The mass of the W boson, a mediator of the weak force between elementary particles, is tightly constrained by the symmetries of the standard model of particle physics. The Higgs boson was the last missing component of the model. After observation of the Higgs boson, a measurement of the W boson mass provides a stringent test of the model. We measure the W boson mass, M W , using data corresponding to 8.8 inverse femtobarns of integrated luminosity collected in proton-antiproton collisions at a 1.96 tera–electron volt center-of-mass energy with the CDF II detector at the Fermilab Tevatron collider. A sample of approximately 4 million W boson candidates is used to obtain M W = 80,433.5 ± 6.4 stat ± 6.9 syst = 80,433.5 ± 9.4 MeV/c 2 , the precision of which exceeds that of all previous measurements combined (stat, statistical uncertainty; syst, systematic uncertainty; MeV, mega–electron volts; c, speed of light in a vacuum). This measurement is in significant tension with the standard model expectation.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

HIGH-STRENGTH LIGHTWEIGHT ENGINES FOR HEAVY-DUTY DIESEL TRUCKS

This project with Cummins supports the development of next generation heavy duty diesel engines that can achieve a 50% or better Break Thermal Efficiency (BTE). The fuel efficiency roadmap for the 50% BTE engine considers six main areas for efficiency improvement in the baseline engine, several of which involve making more efficient use of thermal energy (heat) in the engine. Increased operating temperatures and improved thermal management are expected to enable significant increases in $power$ $density$, thus resulting in greater power output for the same sized engine or engine downsizing (or light weighting) for the same power output. However, it has become apparent that several key components will be exposed to temperatures beyond the capabilities of current engine and exhaust materials, requiring the availability of the next generation of high temperature materials to allow the engine to reach the targeted efficiencies, commercially viable durability, and emission targets. The objective of this project was to identify and/or develop key materials, and evaluate their critical properties to enable the design and development of a lightweight, higher efficiency engine, with enhanced temperature capability and reduced heat-loss to the atmosphere in order to facilitate waste heat recovery and improved efficiency. An increase in the temperature capability of exhaust manifold materials, and piston materials were identified as having a positive influence on the efficiency of the next generation diesel engines. Since the current materials (High SiMo cast irons used in exhaust manifolds, and 4140 steel in pistons) are already operating near their limits of their temperature and strength capabilities, it was determined that new materials with the right combination of properties are required for these components. Oxidation and constrained thermal fatigue tests were used to down-select CF8C plus (CF8CP), a cast austenitic stainless steel, for exhaust manifolds capable of operating at higher temperatures. A prototype exhaust manifold was fabricated using CF8CP and successfully tested in a marine engine. A functionally graded multiple-layer thermal barrier coating system was designed with four layers of mixed bondcoat alloy (NiCoCrAlYHfSi) and yttria stabilized zirconia (YSZ) and was shown to reduce the effective thermal conductivity of the coating-substrate (steel and Ti-6Al-4V) system. The graded alloy and YSZ mixture were intended to achieve better match of thermal expansion coefficient (CTE) and minimize thermal stresses. Such coatings can increase the temperature capability of pistons fabricated from steel and Ti-alloys. Effect of oil additives and friction conformal contact friction tests showed there was a 15-30% reduction in friction by the polymer-graphite composite coating compared to the uncoated steel piston. Standalone Mn-P coating had little beneficial impact. Changing the oil from CJ-4 to PC-11 had little impact on the friction behavior in boundary lubrication. Wear behavior was tested under a point contact configuration with a high contact pressure. The candidate CK-4 oil showed similar or slightly better lubricity compared to the CJ-4 oil while the candidate FA-4 oil decisively increased the piston skirt wear. Although both coatings prevented scuffing failure observed for the uncoated steel skirt in a base oil without an additive package, they surprisingly caused a higher piston wear rate when tested in any of the fully formulated engine oil. The detrimental impact was attributed to the Mn-P film, either as a standalone coating, or a coating interlayer. The porous and brittle Mn-P film was broken during the wear test and the released hard Mn-P grains are suspected to cause third-body abrasion to accelerate the wear process. This work also evaluated the feasibility of developing an improved high temperature, low mass, cost-neutral turbocharger compressor wheel for heavy-duty engine applications from TiAl using additive manufacturing, utilizing its unique ability to fabricate high strength, low weight structures. This work has shown that the phase transforming nature of the TiAl alloys enable obtaining equiaxed microstructures in the as-built state without the need for tedious beam parameter manipulations. The HIPed structures have good RT tensile properties that will enable them to be surface machined to the required tolerance that can 2 then be heat treated to obtain the desired microstructures. Additionally, the negligible residual stresses stemming from the high build chamber temperatures ensure the parts are formed without cracks (one of the major issues in traditional manufacturing of these intermetallics).

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2017

Observation of the Y (4140) structure in the J/ψΦ mass spectrum in B±→ J/ψΦK ± decays

Here, the observation of the $Y(4140)$ structure in $B^\pm\rightarrow J/\psi\,\phi K^\pm$ decays produced in $\bar{p} p $ collisions at $\sqrt{s}=1.96~TeV$ is reported with a statistical significance greater than 5 standard deviations. A fit to the $J/\psi\,\phi$ mass spectrum is performed assuming the presence of a Breit-Wigner resonance. The fit yields a signal of $19^{+6}_{-5}$ resonance events, and resonance mass and width of $4143.4^{+2.9}_{-3.0}(\mathrm{stat})\pm0.6(\mathrm{syst}) ~MeVcc$ and $15.3^{+10.4}_{-6.1}(\mathrm{stat})\pm2.5(\mathrm{syst})~MeVcc$ respectively. The parameters of this resonance-like structure are consistent with values reported from an earlier CDF analysis.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

THz and Sub-THz Capabilities of a Table-Top Radiation Source Driven by an RF Thermionic Electron Gun

Design features and experimental results are presented for a sub-mm wave source [1] based on APS RF thermionic electron gun. The setup includes compact alpha-magnet, quadrupoles, sub-mm-wave radiators, and THz optics. The sub-THz radiator is a planar, oversized structure with gratings. Source upgrade for generation frequencies above 1 THz is discussed. The THz radiator will use a short-period undulator having 1 T field amplitude, ~20 cm length, and integrated with a low-loss oversized waveguide. Both radiators are integrated with a miniature horn antenna and a small ~90°-degree in-vacuum bending magnet. The electron beamline is designed to operate different modes including conversion to a flat beam interacting efficiently with the radiator. The source can be used for cancer diagnostics, surface defectoscopy, and non-destructive testing. Sub-THz experiment demonstrated a good potential of a robust, table-top system for generation of a narrow bandwidth THz radiation. This setup can be considered as a prototype of a compact, laser-free, flexible source capable of generation of long trains of Sub-THz and THz pulses with repetition rates not available with laser-driven sources.

Smirnov, Alexei V.↗
DOE OSTI2017

Measurement of the D + -meson production cross section at low transverse momentum in p p ¯ collisions at s = 1.96 TeV

We report on a measurement of the D + -meson production cross section as a function of transverse momentum (p T ) in proton-antiproton (p$\bar{p}$) collisions at 1.96 TeV center-of-mass energy, using the full data set collected by the Collider Detector at Fermilab in Tevatron Run II and corresponding to 10 fb -1 of integrated luminosity. We use D + →K - π + π + decays fully reconstructed in the central rapidity region |y|<1 with transverse momentum down to 1.5 GeV/c, a range previously unexplored in p$\bar{p}$ collisions. Inelastic p$\bar{p}$ scattering events are selected online using minimally biasing requirements followed by an optimized offline selection. The K - π + π + mass distribution is used to identify the D + signal, and the D + transverse impact-parameter distribution is used to separate prompt production, occurring directly in the hard-scattering process, from secondary production from b-hadron decays. We obtain a prompt D + signal of 2950 candidates corresponding to a total cross section σ(D + ,1.5 T <14.5 GeV/c,|y|<1)=71.9±6.8(stat)±9.3(syst) μb. While the measured cross sections are consistent with theoretical estimates in each p T bin, the shape of the observed p T spectrum is softer than the expectation from quantum chromodynamics. The results are unique in p$\bar{p}$ collisions and can improve the shape and uncertainties of future predictions.

(K-↗
NASA NTRS1998

160-190 GHz Monolithic Low Noise Amplifiers

This paper presents the results of two 160-190 GHz monolithic low noise amplifiers (LNAs) fabricated with 0.07-microns pseudomorphic (PM) InAlAs/InGaAs/InP HEMT technology using a reactive ion etch (RIE) via hole process. A peak small signal gain of 9 dB was measured at 188 GHz for the first LNA with a 3-dB bandwidth from 164 to 192 GHz while the second LNA has achieved over 6-dB gain from 142 to 180 GHz. The same design (second LNA) was also fabricated with 0.08-micron gate and a wet etch process, showing a small signal gain of 6 dB with noise figure 6 dB. All the measurement results were obtained via on-wafer probing. The LNA noise measurement at 170 GHz is also the first attempt at this frequency.

Kok, Y. L.↗
NASA NTRS1993

A constrained joint source/channel coder design and vector quantization of nonstationary sources

The emergence of broadband ISDN as the network for the future brings with it the promise of integration of all proposed services in a flexible environment. In order to achieve this flexibility, asynchronous transfer mode (ATM) has been proposed as the transfer technique. During this period a study was conducted on the bridging of network transmission performance and video coding. The successful transmission of variable bit rate video over ATM networks relies on the interaction between the video coding algorithm and the ATM networks. Two aspects of networks that determine the efficiency of video transmission are the resource allocation algorithm and the congestion control algorithm. These are explained in this report. Vector quantization (VQ) is one of the more popular compression techniques to appear in the last twenty years. Numerous compression techniques, which incorporate VQ, have been proposed. While the LBG VQ provides excellent compression, there are also several drawbacks to the use of the LBG quantizers including search complexity and memory requirements, and a mismatch between the codebook and the inputs. The latter mainly stems from the fact that the VQ is generally designed for a specific rate and a specific class of inputs. In this work, an adaptive technique is proposed for vector quantization of images and video sequences. This technique is an extension of the recursively indexed scalar quantization (RISQ) algorithm.

Sayood, Khalid↗
NASA NTRS1993

Improved Hall-Effect Sensors For Magnetic Memories

High-electron-mobility sensor films deposited on superlattice buffer (strain) layers. Improved Hall-effect sensors offer combination of adequate response and high speed needed for use in micromagnet/Hall-effect random-access memories. Hall-effect material chosen for use in sensors is InAs.

Wu, Jiin-Chuan↗
NASA NTRS1993

Every Good Virtue You Ever Wanted in a Q-switched Solid-state Laser and More: Monolithic, Diode-pumped, Self-q-switched, Highly Reproducible, Diffraction-limited Nd:yag Laser

The applications of Q-switched lasers are well known, for example, laser radar, laser remote sensing, satellite orbit determination, Moon orbit and 'moon quake' determination, satellite laser communication, and many nonlinear optics applications. Most of the applications require additional properties of the Q-switched lasers, such as single-axial and/or single-transverse mode, high repetition rate, stable pulse shape and pulse width, or ultra compact and rugged oscillators. Furthermore, space based and airborne lasers for lidar and laser communication applications require efficient, compact, lightweight, long-lived, and stable-pulsed laser sources. Diode-pumped solid-state lasers (DPSSL) have recently shown the potential for satisfying all of these requirements. We will report on the operating characteristics of a diode-pumped, monolithic, self-Q-switched Cr,Nd:YAG laser where the chromium ions act as a saturable absorber for the laser emission at 1064 nm. The pulse duration is 3.5 ns and the output is highly polarized with an extinction ratio of 700:1. It is further shown that the output is single-longitudinal-mode with transform-limited spectral line width without pulse-to-pulse mode competition. Consequently, the pulse-to-pulse intensity fluctuation is less than the instrument resolution of 0.25 percent. This self-stabilization mechanism is because the lasing mode bleaches the distributed absorber and establishes a gain-loss grating similar to that used in the distributed feedback semiconductor lasers. A repetition rate above 5 KHz has also been demonstrated. For higher power, this laser can be used for injection seeding an amplifier (or amplifier chain) or injection locking of a power oscillator pumped by diode lasers. We will discuss some research directions on the master oscillator for higher output energy per pulse as well as how to scale the output power of the diode-pumped amplifier(s) to multi-kilowatt average power.

Chen, Y. C.↗
NASA NTRS1993

Studies and simulations of the DigiCipher system

During this period the development of simulators for the various high definition television (HDTV) systems proposed to the FCC was continued. The FCC has indicated that it wants the various proposers to collaborate on a single system. Based on all available information this system will look very much like the advanced digital television (ADTV) system with major contributions only from the DigiCipher system. The results of our simulations of the DigiCipher system are described. This simulator was tested using test sequences from the MPEG committee. The results are extrapolated to HDTV video sequences. Once again, some caveats are in order. The sequences used for testing the simulator and generating the results are those used for testing the MPEG algorithm. The sequences are of much lower resolution than the HDTV sequences would be, and therefore the extrapolations are not totally accurate. One would expect to get significantly higher compression in terms of bits per pixel with sequences that are of higher resolution. However, the simulator itself is a valid one, and should HDTV sequences become available, they could be used directly with the simulator. A brief overview of the DigiCipher system is given. Some coding results obtained using the simulator are looked at. These results are compared to those obtained using the ADTV system. These results are evaluated in the context of the CCSDS specifications and make some suggestions as to how the DigiCipher system could be implemented in the NASA network. Simulations such as the ones reported can be biased depending on the particular source sequence used. In order to get more complete information about the system one needs to obtain a reasonable set of models which mirror the various kinds of sources encountered during video coding. A set of models which can be used to effectively model the various possible scenarios is provided. As this is somewhat tangential to the other work reported, the results are included as an appendix.

Sayood, K.↗
NASA NTRS1993

The proposed HDTV schemes and the NASA network

Results of the simulation of high definition television (HDTV) techniques in the context of their application to transmit HDTV sequences over the NASA network are presented. Various tradeoffs involved in selecting the different services available on the NASA network are discussed. The possibility of transmitting an HDTV-like signal over the CCSDS network is investigated. Some suitable approaches are suggested.

Chen, Y. C.↗