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Su, D.

Publications and source records attributed to Su, D..

7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Doubling off-axis electron cyclotron current drive efficiency via velocity space engineering

For the first time, experiments on the DIII-D tokamak have demonstrated electron cyclotron current drive with more than double the conventional efficiency by tailoring the wave–particle interactions in velocity space using a novel ‘top launch’ geometry. Steering the EC waves to propagate nearly parallel to the resonance drives current more efficiently by (1) selective damping on electrons with higher parallel velocity v ||, and (2) longer absorption path to compensate for inherently weaker absorption at higher v ||. Experiments using a fixed-injection top launch system find an optimal velocity space interaction for maximum current drive efficiency at ρ ~ 0.5 where the ease of drawing out a high v || electron tail is balanced by sufficient absorption.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

On the irreversible sodiation of tin disulfide

Tin disulfide is considered as a promising electrode material for sodium-ion batteries because of its two-dimensional layered structural characteristics allowing the intercalation of Na ions. Understanding the underlying reaction mechanisms and the decisive step of the reaction reversibility is critical for its applications. Herein, we investigate the sodiation and desodiation processes of SnS 2 by employing in situ transmission electron microscopy (TEM). After the initial intercalation reaction, a rock-salt Na y SnS 2 phase with disordering Na and Sn cations is observed, followed with a conversion reaction and an alloying reaction. Additionally, the disordering reaction occurs along <1-10> direction of pristine SnS 2 phase which is correlated with local bonding rearrangements induced by the exchange of Sn and Na cations. In-situ TEM studies and first-principles calculations indicate that the original 2D SnS 2 structure could not be recovered during desodiation. Instead, the disordered Na y SnS 2 phase is finally formed, which indicates that the irreversible disordering transition is the determining step of irreversible cycling. This work probes the structural evolution of sodiation, providing a fundamental understanding of the electrochemical properties of metal sulfides and inspiring rational designs of high performance electrodes for sodium-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2020

Study of CMOS strip sensor for future silicon tracker

Monolithic silicon sensors developed with High-Voltage CMOS (HV-CMOS) processes have become highly attractive for charged particle tracking. Compared with the standard CMOS sensors, HV-CMOS sensors can provide larger and deeper depletion regions that lead to larger signals and faster charge collection. They can provide high position resolution, low material budget, high radiation hardness and low cost that are desirable for high performance tracking in harsh collision environment. Various studies have been conducted to explore the technology feasibility for the large-area tracking systems at future collider experiments. CHESS (CMOS HV/HR Evaluation for Strip Sensor) sensor series have been developed as an alternative solution to the conventional silicon micro-strip detectors for the ATLAS inner tracker upgrade. The first prototype (named CHESS1) was to evaluate the diode geometry and the in-pixel analog electronics. Obtained test results were used to optimize the second prototype (named CHESS2). CHESS2 was implemented with a full digital readout architecture and realized as a full reticle sized monolithic sensor. Here, the basic characteristics of the CHESS2 prototype sensors and their performance in response to different input signals are presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗