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Nucleation is important in processing of good quality diamond crystals and textured thin films by microwave plasma enhanced chemical vapor deposition (MPECVD) for applications in quantum devices and systems. Bias-enhanced nucleation (BEN) is one approach for diamond nucleation in situ during MPECVD. However, the mechanism of diamond nucleation by BEN is not well understood. This paper describes results on the nucleation of diamond within a carbon film upon application of electric field during the BEN-facilitated MPECVD process. The nature of the diamond film and nuclei formed is characterized by SEM (scanning electron microscopy), Raman spectroscopy, and high-resolution transmission electron microscopy (HRTEM). The HRTEM images and associated diffraction patterns of the nucleation layer show that the diamond nuclei are formed within the carbon film close to the Si (100) substrate surface under the influence of microwaves and electric fields that lead to formation of the textured diamond film and crystal upon further growth. These results are expected to develop diamond films of optimum quality containing a nitrogen-vacancy center for application in quantum systems. 

A sealant is required for the solid oxide fuel cell (SOFC) to maintain hermeticity at high operating temperatures, keep fuel and oxidant from mixing, and avoid shorting of the cell stack. Glass and glass–ceramic materials are widely used as a sealant because their properties can be tailored to meet the stringent requirements of SOFC stack, but they are susceptible to cracking. In contrast, a promising concept of self‐repairable glass for seals is pursued for making reliable seals that can self‐repair cracks at the SOFC operating temperatures. This concept is studied through measuring crack‐healing kinetics and independent measurement of glass viscosity for relating to the observed self‐repair. The cracks on the glass surface are created using a Vickers indenter to achieve a well‐defined crack geometry, and then the glass is exposed to elevated temperatures for different length of times to study the crack‐healing kinetics. The crack‐healing kinetics is compared with the predictions of our theoretical model and found to be in good agreement. In addition, glass viscosity is extracted from the healing kinetics and compared with the independent measurement of viscosity measured from the dilatometry and sintering data to further validate the crack‐healing theoretical model. These results are presented and discussed.

 

The next core-collapse supernova in the Milky Way or its satellites will represent a once-in-a-generation opportunity to obtain detailed information about the explosion of a star and provide significant scientific insight for a variety of fields because of the extreme conditions found within. Supernovae in our galaxy are not only rare on a human timescale but also happen at unscheduled times, so it is crucial to be ready and use all available instruments to capture all possible information from the event. The first indication of a potential stellar explosion will be the arrival of a bright burst of neutrinos. Its observation by multiple detectors worldwide can provide an early warning for the subsequent electromagnetic fireworks, as well as signal to other detectors with significant backgrounds so they can store their recent data. The supernova early warning system (SNEWS) has been operating as a simple coincidence between neutrino experiments in automated mode since 2005. In the current era of multi-messenger astronomy there are new opportunities for SNEWS to optimize sensitivity to science from the next galactic supernova beyond the simple early alert. This document is the product of a workshop in June 2019 towards design of SNEWS 2.0, an upgraded SNEWS with enhanced capabilities exploiting the unique advantages of prompt neutrino detection to maximize the science gained from such a valuable event.

 

The nature of dark matter and properties of neutrinos are among the most pressing issues in contemporary particle physics. The dual-phase xenon time-projection chamber is the leading technology to cover the available parameter space for weakly interacting massive particles, while featuring extensive sensitivity to many alternative dark matter candidates. These detectors can also study neutrinos through neutrinoless double-beta decay and through a variety of astrophysical sources. A next-generation xenon-based detector will therefore be a true multi-purpose observatory to significantly advance particle physics, nuclear physics, astrophysics, solar physics, and cosmology. This review article presents the science cases for such a detector.