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This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data for the site US-CF4 CAF-LTAR Boyd South. This is the FLUXNET version of the carbon flux data for the site US-CF4 CAF-LTAR Boyd South produced by applying the standard ONEFlux (1F) software.
CF4 is Silicon tetrafluoride-like structured and crystallizes in the monoclinic C2/c space group. The structure is zero-dimensional and consists of four carbon tetrafluoride molecules. C4+ is bonded in a tetrahedral geometry to four equivalent F1- atoms. All C–F bond lengths are 1.34 Å. F1- is bonded in a single-bond geometry to one C4+ atom.
CsB(CF4)2 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. Cs1+ is bonded in a 12-coordinate geometry to twelve F1- atoms. There are a spread of Cs–F bond distances ranging from 3.07–3.43 Å. B3+ is bonded in a water-like geometry to two equivalent F1- atoms. Both B–F bond lengths are 1.42 Å. There are two inequivalent C2+ sites. In the first C2+ site, C2+ is bonded in a trigonal non-coplanar geometry to three F1- atoms. There is two shorter (1.38 Å) and one longer (1.39 Å) C–F bond length. In the second C2+ site, C2+ is bonded in a trigonal non-coplanar geometry to three F1- atoms. There is one shorter (1.38 Å) and two longer (1.39 Å) C–F bond length. There are five inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one Cs1+ and one C2+ atom. In the second F1- site, F1- is bonded in a single-bond geometry to one Cs1+ and one C2+ atom. In the third F1- site, F1- is bonded in a single-bond geometry to two equivalent Cs1+ and one B3+ atom. In the fourth F1- site, F1- is bonded in a single-bond geometry to two equivalent Cs1+ and one C2+ atom. In the fifth F1- site, F1- is bonded in a single-bond geometry to one Cs1+ and one C2+ atom.
(CF3)2TeF2 is Ammonia-derived structured and crystallizes in the monoclinic C2/c space group. The structure is zero-dimensional and consists of twelve fluoro tellurohypofluorite molecules and twenty-four fluoroform molecules.
AsH6(CF)2SbF6 crystallizes in the orthorhombic Ibca space group. The structure is zero-dimensional and consists of eight AsH6(CF)2 clusters and eight SbF6 clusters. In each AsH6(CF)2 cluster, C4+ is bonded to one As3- and three H1+ atoms to form distorted corner-sharing CAsH3 tetrahedra. The C–As bond length is 1.91 Å. There is one shorter (1.09 Å) and two longer (1.10 Å) C–H bond length. As3- is bonded in a distorted tetrahedral geometry to two equivalent C4+ and two equivalent F1- atoms. Both As–F bond lengths are 1.73 Å. There are three inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one C4+ atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C4+ atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one C4+ atom. F1- is bonded in a single-bond geometry to one As3- atom. In each SbF6 cluster, Sb3- is bonded in an octahedral geometry to six F1- atoms. There are a spread of Sb–F bond distances ranging from 1.91–1.94 Å. There are three inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one Sb3- atom. In the second F1- site, F1- is bonded in a single-bond geometry to one Sb3- atom. In the third F1- site, F1- is bonded in a single-bond geometry to one Sb3- atom.
Tantalum (Ta) has promise as a structural material for micromechanical sensors and actuators. Anisotropic etching of alpha (α) phase Ta is required for micromachining applications. Uniform thickness and etch across a full wafer are desirable features. An experimental investigation is conducted to study plasma etching rate and anisotropy in etching α -Ta in relation to pressure and gas flow ratio. A comparatively low toxicity gas, carbon tetrafluoride (CF4), and argon (Ar) are used. Spectrometry by optical emission spectrometry (OES) and residual gas analysis (RGA) are employed to characterize the plasma to gain insight into the etch mechanisms. At low flow, the etch rate is slow due to an inadequate supply of the etching gas, CF4. The etch rate is also slowed at high flow due to a reduced CF4 residence time. Flow and pressure conditions to achieve a good etch rate and vertical sidewalls are identified and explained by means of a full factorial experiment coupled with emission spectra. Finally, with these conditions, uniform etching of 2.5 μm thick α-Ta across a 4-inch wafer is demonstrated.
We report the first X-ray coherent diffractive imaging experiment on molecule-doped helium nanodroplets. It complements previous work, where we reported single-shot X-ray coherent diffractive imaging studies of Xe dopant clusters formed in 4He and 3He droplets. These noble gas clusters were used to visualize the impact of rotational excitation of the droplets on the spatial distribution of atomic dopants within the droplets, and to study the differences and connections between quantum and classical droplet rotational motion. Here, we expand our studies to the molecular dopants CF4, CHF3, CH3CN, and SF6, imaged with 1.5 keV photons. We find multiple Bragg spots in the diffraction patterns of molecule-doped droplets with radii of approximately 600 nm, which provide evidence that molecules form elongated clusters with preferential alignment along the angular momentum axis of the 4He droplets, in agreement with our previous results on the aggregation of Xe clusters on quantum vortices. Real-space reconstructions of molecular dopant cluster density profiles are obtained for droplets with smaller radii of approximately 300 nm. The diffuse images suggest the formation of low-density, potentially porous, molecular clusters upon aggregation at T = 0.4 K in 4He droplets. In the normal fluid 3He droplets, molecules aggregate into loose clusters on the droplets' equator, similar to previous observations for Xe atoms. Time-of-flight mass spectra reveal that the doped helium nanodroplet moieties fragment extensively into constituent atomic ions, producing only a small fraction of molecular fragment ions. The findings are discussed in the context of previously proposed schemes to use He droplets as potential tamper materials for ultrafast X-ray imaging experiments.
C4F7N [2,3,3,3-tetrafluoro-2-(trifluoromethyl)propanenitrile]/CO2 gas mixtures are being developed as an eco-friendly electrical insulator to replace SF6, the most potent greenhouse industrial gaseous dielectric. However, recent studies have reported complicated and often conflicting decomposition pathways for C4F7N/CO2 gas mixtures, which has raised concerns. In this work, the decomposition characteristics of C4F7N/CO2 gas mixtures were studied comprehensively by both designed computations and experiments. Computations were performed starting from fundamental propositions of C4F7N/CO2 decompositions, which were further experimentally verified by pyrolysis, long-term thermal aging with/without catalytic materials (industrial-grade molecular sieves 4A), and electrical decomposition by spark discharge. The results of both computations and experiments suggest that in an ideal thermal decomposition, C4F7N is likely to decompose into C2F6 and small fluoronitriles first at high temperatures. The generation of C3F6 and C2N2 from C4F7N thermal decomposition at lower temperatures appears because of the catalytic effect of incompatible materials, for example, the industrial-grade molecular sieves 4A that we tested. The electron impact dissociation of C4F7N plays an important role in C4F7N electrical decomposition, leading to additional formation of distinctive small molecules of CF4 and C2N2 of low concentrations. It was pointed out based on a real arcing test in a load disconnector that the decomposition of C4F7N gas mixtures in real applications will be at a much moderate and manageable rate than what was obtained from the highly accelerated laboratory tests presented in this work. The signatures of decomposition products extracted in this study provide invaluable guidance for developing decomposition-based diagnosis and fixation of decomposition byproducts toward SF6-free power grids.
Cr(CH2)6(CF4)2 is Fluorite structured and crystallizes in the cubic Fm-3m space group. The structure is zero-dimensional and consists of eight carbon tetrafluoride molecules and four hexamethylchromium(vi) molecules.
The µWELL-PICOSEC detector, which is based on Resistive Micro-Well (µRWELL) technology, is a novel concept for fast timing gaseous detectors that can provide timing resolution in the tens of picosecond range, making it ideal candidate for time-of-flight (TOF) technology for particle identification (PID) in particle physics experiments as well as for future medical instrumentation. The µRWELL-PICOSEC concept is based on a Cerenkov radiator that produces Cerenkov photons from high energetic charged particles, a photocathode layer that converts the Cerenkov photons into primary electrons, a µRWELL amplification layer that multiply the electrons through amplification in a CF4-based gas mixture and a pad-segmentation anode readout coupled with fast timing electronics to provide fast signal. Beam tests were carried out at the CERN SPS H4 beamline in summer 2023 and 2024. Preliminary results show timing performance of the order of 23 ps achievable with µRWELL-PICOSEC prototype. and position scan of the 100-pads of a multi-channel prototype was also performed to study time response uniformity of large area detector. In this talk, after a brief overview of the PICOSEC technology, we will present recent results with different single channel µRWELL-PICOSEC prototype designs and also the position scan results of the 100-pads large prototype to study timing response uniformity for large area µRWELL-PICOSEC detector. Finally, we will discuss the ongoing R&D effort to further improve the timing resolution and allow good position capabilities through charge sharing for large area.