First-principles investigation of Nox and Sox adsorption on anatase-supported BaO and Pt overlayers

Cataloged from PDF version of article.We present a density functional theory investigation of the adsorption properties of NO and NO2 as well as SO2 and SO3 on BaO and Pt overlayers on anatase TiO2(001) surface. Mono layers, bilayers, and trilayers of BaO grow without strain-induced large scale reconstructions. While the bilayer and trilayer preserve, to a large extent, the NO2 adsorption characteristics of the clean BaO(100) surface, the effect of the support is evident in SO2 and SO3 adsorption energies, which are somewhat reduced with respect to the clean BaO(100) surface. When a Pt(100) layer is added on the TiO2 surface, four stable adsorption geometries are identified in the case of NO while NO2 is found to adsorb in only two configurations

Multiabsorber Transition-Edge Sensors for X-Ray Astronomy

We are developing arrays of position-sensitive microcalorimeters for future x-ray astronomy applications. These position-sensitive devices commonly referred to as hydras consist of multiple x-ray absorbers, each with a different thermal coupling to a single-transition-edge sensor microcalorimeter. Their development is motivated by a desire to achieve very large pixel arrays with some modest compromise in performance. We report on the design, optimization, and first results from devices with small pitch pixels (<75 m) being developed for a high-angular and energy resolution imaging spectrometer for Lynx. The Lynx x-ray space telescope is a flagship mission concept under study for the National Academy of Science 2020 decadal survey. Broadband full-width-half-maximum (FWHM) resolution measurements on a 9-pixel hydra have demonstrated E(FWHM) = 2.23 0.14 eV at Al-K, E(FWHM) = 2.44 0.29 eV at Mn-K, and E(FWHM) = 3.39 0.23 eV at Cu-K. Position discrimination is demonstrated to energies below <1 keV and the device performance is well-described by a finite-element model. Results from a prototype 20-pixel hydra with absorbers on a 50-m pitch have shown E(FWHM) = 3.38 0.20 eV at Cr-K1. We are now optimizing designs specifically for Lynx and extending the number of absorbers up to 25/hydra. Numerical simulation suggests optimized designs could achieve 3 eV while being compatible with the bandwidth requirements of the state-of-the art multiplexed readout schemes, thus making a 100,000 pixel microcalorimeter instrument a realistic goal

Thermal Fluctuation Noise in Mo/Au Superconducting Transition-Edge Sensor Microcalorimeters

In many superconducting transition-edge sensor (TES) microcalorimeters, the measured electrical noise exceeds theoretical estimates based on a thermal model of a single body thermally connected to a heat bath. Here, we report on noise and complex impedance measurements of a range of designs of TESs made with a Mo/Au bilayer. We have fitted the measured data using a two-body model, where the x-ray absorber and the TES are connected by an internal thermal conductance Gae. We find that the so-called excess noise measured in these devices is consistent with the noise generated from the internal thermal fluctuations between the x-ray absorber and the TES. Our fitted parameters are consistent with the origin of Gae being from the finite thermal conductance of the TES itself. These results suggest that even in these relatively low resistance Mo/Au TESs, the internal thermal conductance of the TES may add significant additional noise and could account for all the measured excess noise. Furthermore, we find that around regions of the superconducting transition with rapidly changing derivative of resistance with respect to temperature, an additional noise mechanism may dominate. These observations may lead to a greater understanding of TES devices and allow the design of TES microcalorimeters with improved performance

Internal Thermal Fluctuation Noise in Mo/Au TES's

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The Impact of Transition Edge Sensor Design on Achievable Performance Uniformity of Kilo-Pixel Arrays

Future astronomy missions using x-ray transition-edge sensor (TES) microcalorimeters, such as X-IFU on Athena, will require large arrays of 1000s of pixels fabricated on a single wafer. To wire out so many pixels the current array designs have pixels with different rotational orientations. Fabrication is done in multiple layers and so, dependent on method, there is potential for spatial misalignment between layers. Because of the variation of orientation of pixels, misalignment may not impact each pixel equally. This has the potential to degrade the achievable uniformity of performance across an array. How well aligned do different layers need to be? How does sensitivity to misalignment depend on choice of pixel design

First-principles investigation of NO x and SO x adsorption on anatase-supported BaO and Pt overlayers

We present a density functional theory investigation of the adsorption properties of NO and NO 2 as well as SO 2 and SO 3 on BaO and Pt overlayers on anatase TiO 2(001) surface. Monolayers, bilayers, and trilayers of BaO grow without strain-induced large scale reconstructions. While the bilayer and trilayer preserve, to a large extent, the NO 2 adsorption characteristics of the clean BaO(100) surface, the effect of the support is evident in SO 2 and SO 3 adsorption energies, which are somewhat reduced with respect to the clean BaO(100) surface. When a Pt(100) layer is added on the TiO 2 surface, four stable adsorption geometries are identified in the case of NO while NO 2 is found to adsorb in only two configurations. © 2012 American Chemical Society

Comparative estimation of diagnostic informativity of a fine-needle aspiration biopsy and pathomorphological investigation of nodal thyroidal tumors

Objective. Comparative estimation of diagnostic informativity of a fine-needle aspiration biopsy (FNAB) and pathohistological investigation of nodal thyroidal tumors. Маterials and methods. Retrospective analysis of the FNAB and the thyroidal pathohistology results was conducted in 171 patients before and after thyroidectomy, performed for nodal thyroidal tumors. Results. In accordance to the FNAB results a benign thyroidal affection was revealed in 131 (76.6%) patients and a malignant one - in 12 (7%). The method sensitivity has constituted 83.3%, and specificity - 98,5%. In 28 (16.4%) patients the FNAB results were uncertain. In 4 (14.3%) of 28 patients while further pathohistological investigation doing, a malignant affection of a thyroid gland was revealed (follicular cancer - in 1, papillary - in 1, follicular form of papillary cancer - in 1, Hurthle-cellular and papillary cancer - in 1). In 24 (85.7%) of 28 patients a benign thyroidal affection was revealed. In this group the FNAB sensitivity have constituted 65-99%, specificity - 98.5%. As a result of pathohistological investigation a benign thyroidal affection in 153 (89.5%) of 171 patients and malignant - in 18 (10.5%) were revealed. Conclusion. In preoperative diagnosis of nodal thyroidal tumors the uncertain FNAB results rate in preoperative diagnosis of nodal thyroid tumors, in accordance to our data, have constituted 16.4%, what restricts possibilities of this method in verification of malignant thyroidal affections. That is why the operation must not be indicated, basing on the FNAB data only, and molecular-genetic markers ought to be analyzed in this group of patients

TES Pixel Optimization for the ATHENA X-IFU Instrument

ATHENA is a European led x-ray observatory due for launch in the early 2030s. The X-ray Integral Field Unit (X-IFU) instrument on ATHENA will have an array of 3168 TES microcalorimeters, 2.5 eV resolution (at 7 keV), 5 arc second angular resolution and a 5 arc minute field of view. As one example, will allow unprecedented views of composition and dynamics of galaxy clusters