Identification of bulk and surface sulfur impurities in Ti O2 by synchrotron x-ray absorption near edge structure

Synchrotron x-ray absorption near edge structure (XANES) measurements of Ti and S K edges, combined with first principles simulations, are used to characterize S-doped Ti O2 prepared by oxidative annealing of Ti S2 at various temperatures. Ti-edge XANES and x-ray powder diffraction data indicate that samples annealed above 300 °C have an anatase Ti O2 crystal structure with no trace of Ti S2 domains. S-edge XANES data reveal that the local structure seen by S atoms evolves gradually, from Ti S2 to a qualitatively different structure, as the annealing temperature is increased from 200 to 500 °C. For samples annealed at 500 °C, the spectrum appears to have features that can be assigned to S on the surface in the form of S O4 and S defects in the bulk (most likely S interstitials) of Ti O2

Potential of Core-Collapse Supernova Neutrino Detection at JUNO

JUNO is an underground neutrino observatory under construction in Jiangmen, China. It uses 20kton liquid scintillator as target, which enables it to detect supernova burst neutrinos of a large statistics for the next galactic core-collapse supernova (CCSN) and also pre-supernova neutrinos from the nearby CCSN progenitors. All flavors of supernova burst neutrinos can be detected by JUNO via several interaction channels, including inverse beta decay, elastic scattering on electron and proton, interactions on C12 nuclei, etc. This retains the possibility for JUNO to reconstruct the energy spectra of supernova burst neutrinos of all flavors. The real time monitoring systems based on FPGA and DAQ are under development in JUNO, which allow prompt alert and trigger-less data acquisition of CCSN events. The alert performances of both monitoring systems have been thoroughly studied using simulations. Moreover, once a CCSN is tagged, the system can give fast characterizations, such as directionality and light curve

Detection of the Diffuse Supernova Neutrino Background with JUNO

As an underground multi-purpose neutrino detector with 20 kton liquid scintillator, Jiangmen Underground Neutrino Observatory (JUNO) is competitive with and complementary to the water-Cherenkov detectors on the search for the diffuse supernova neutrino background (DSNB). Typical supernova models predict 2-4 events per year within the optimal observation window in the JUNO detector. The dominant background is from the neutral-current (NC) interaction of atmospheric neutrinos with 12C nuclei, which surpasses the DSNB by more than one order of magnitude. We evaluated the systematic uncertainty of NC background from the spread of a variety of data-driven models and further developed a method to determine NC background within 15\% with {\it{in}} {\it{situ}} measurements after ten years of running. Besides, the NC-like backgrounds can be effectively suppressed by the intrinsic pulse-shape discrimination (PSD) capabilities of liquid scintillators. In this talk, I will present in detail the improvements on NC background uncertainty evaluation, PSD discriminator development, and finally, the potential of DSNB sensitivity in JUNO

The cadmium tellurium/Silicon(111):Arsenic interface.

The cadmium tellurium/Silicon(111):Arsenic interface

Progress on the commisioning of the Siam Photon source.

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Change in interface magnetism of an exchange-coupled system due to the presence of nonmagnetic spacers

We report on the effect of nonmagnetic spacer layers on the interface magnetism and the exchange bias in the archetypical [Co/CoO]16 system. The separation of the magnetic bilayers by Au layers with various thicknesses dAu≥25 nm leads to a threefold increase of the exchange bias field (Heb). Reflectometry with polarized neutrons does not reveal any appreciable change in the domain population. This result is in agreement with the observation that the granular microstructure within the [Co/CoO] bilayers is independent of dAu. The significant reduction of the magnetic moments in the Co layers can be attributed to interfacial disorder at the Co-Au interfaces. Element-specific x-ray absorption spectroscopy attributes part of the enhancement of Heb to the formation of Co3O4 in the [Co/CoO] bilayers within the multilayers. A considerable proportion of the increase of Heb can be attributed to the loss of magnetization at each of the Co-Au interfaces with increasing dAu. We propose that the interfacial magnetism of ferro- and antiferromagnetic layers can be significantly altered by means of metallic spacer layers thus affecting the exchange bias significantly. This study shows that the magnetism in magnetic multilayers can be engineered by nonmagnetic spacer layers without involving the microstructure of the individual layers