[en] A novel one-dimensional chainlike organic-inorganic polymer [Cu(en)₂]₃[Cu(en)₂(H₂O)]₂{[Cu₄(GeW₉O₃₄)₂][Cu(en)₂]}· 9.5H₂O (en=ethylenediamine) has been synthesized by hydrothermal reaction in good yield, and characterized by elemental analysis, IR, TG-DTA, EPR, magnetic properties, and single-crystal X-ray diffraction. The diffraction analysis reveals that the polymer represents the first high-dimensional organic-inorganic hybrid based on the sandwich-type polyoxometalates linked by transition-metal coordination cations. (author)

[en] The pitch angle scattering rates of deuterium beam ions in low density, nearly MHD-quiescent plasmas are measured using an imaging neutral particle analyzer (INPA) in DIII-D. The INPA is a scintillator-based diagnostic that provides energy and radially resolved measurements of confined fast ions. The main purpose of this study is to validate this novel diagnostic system during classical fast ion behavior. The pitch angle scattering rate is manipulated by varying the electron temperature using electron cyclotron heating (ECH) and by changing Zeff through neon gas puffing. To compare with the experimental data, a series of synthetic INPA images are simulated through the following steps: (1) the time evolution of the fast ion distribution is obtained by the NUBEAM module of the TRANSP code; (2) the neutral flux towards the INPA is estimated by the FIDASIM code; (3) the INPASIM code simulates the neutral-foil interaction and traces the ions to the strike position of the INPA phosphor. Preliminary results show agreement within 25% error in signals produced by the probing beam. In addition, a sensitivity study on the INPA phase space was performed by artificially varying the pitch angle scattering rate (through Zeff) to observed the change in signal detected. It was found that in general, the signal levels decreased as the pitch angle scattering rates increased and vice versa.

[en] Fast ion loss detector (FILD) measurements indicate intermittent bursts of losses associated with Alfvén Eigenmode (AE) induced critical-gradient transport. During the current ramp phase of a DIII-D inner wall limited, oval shaped, L-mode plasma with reversed-shear magnetic safety factor profile, the total AE activity increases with neutral beam injected (NBI) power. A mix of both frequency sweeping reversed-shear Alfvén eigenmodes (RSAEs) and near-constant frequency toroidicity induced Alfvén eigenmodes (TAEs) are also observed. As the beam power increases from 2.4 to 9.2 MW, the frequency and amplitude of fast-ion fluctuations increases, and a skewed tail emerges in the distribution of loss events. The addition of electron cyclotron heating changes the types of AEs present, increases the measured fast-ion density, and alters loss behavior [2]. New fluctuation measurements from an upgraded bank of FILD, fast-ion D-alpha, and imaging neutral particle analyzer diagnostics will be presented. In theory, intermittency is associated with the domino effect, where avalanches of global redistribution and losses can occur when many overlapping modes provide a channel for particle transport over a larger portion of phase space [3]. Quantification of intermittent transport is important for model validation, particularly for simplified critical gradient transport models that do not account for time dynamics. Furthermore, these experiments suggest that losses can be altered, or perhaps ‘smeared out’ using active control to manipulate AE mode activity.

[en] A new 17-channel soft X-ray diagnostic system was developed for a study of magnetohydrodynamics (MHD) fluctuations and installed on the Large Helical Device (LHD). The Absolute X-ray Ultraviolet Photodiodes (AXUV diode) with a large sensitivity area 10 mm × 10 mm were adopted as the detectors. The sightlines were designed to cover the whole plasma with 3.8 cm space separation and the expected radial resolution was 7 cm at the equatorial plane of LHD. The toroidally elongated pin hole (25 mm × 7 mm) was used to increase the signal to noise ratio and a Be foil of 15 μm in thickness was used to shut the visible light. The detector array was placed inside the vertically elongated section of the LHD vacuum vessel, being shielded by an aluminum box. In the experimental campaign of LHD, this fiscal year 2011, various kinds of MHD fluctuations excited in core and edge plasma regions have clearly been detected by this newly installed diagnostic system. The characteristic behaviors of the ELM activity in H-mode plasmas and the “Fishbone”-like instabilities induced by the perpendicular neutral beam injection (NBI) were derived from the soft X-ray data. (author)

[en] Recent DIII-D experiments show that small variations in neutral beam modulation period, even with constant time averaged power input, can have a dramatic impact on the beam driven Alfven eigenmode spectrum and resultant fast ion transport. Neutral beam modulation is a common technique used in fusion experiments for regulation of injected power and various diagnostic applications, however, the period is often chosen arbitrarily or to accommodate hardware constraints without regard for the physics implications. When one beam is temporarily turned off or replaced by an unlike beam (different geometry or injection voltage), a bump-on-tail like distribution in velocity space is transiently created that can provide free energy for instability drive. The persistence of the bump-on tail feature depends on, among other things, the modulation period. Continuous modulation which is fast compared to the slowing down time creates a more persistent velocity space inversion while slow modulation transiently creates a bump-on-tail associated with each beam pulse before filling in. For heating scenarios where different modulated beams are interleaved, the time-dependent mix also depends heavily on the modulation period.

[en] A novel one-dimensional (1D) coordination polymer [{Cu(2,2'-bpy)}₆(Mo₆O₂₂)][GeMo₁₂O₄₀].H₂O (2,2'-bpy=2,2'-bipyridine), which represents the first example of 1D organic-inorganic hybrid based on a Keggin-type heteropolyanion [GeMo₁₂O₄₀]^4- and an unprecedented isopolyanion [Mo₆O₂₂]^8-, has been hydrothermally synthesized and characterized by single crystal X-ray diffraction. Crystal data: C₆₀H₅₀Cu₆GeMo₁₈N₁₂O₆₃, monoclinic, P2₁/c, a=13.9344(3), b=20.0329(3), c=17.2151(3) A; β=94.0220(10)^o, V=4793.70(15) A³, T=293(2) K; Z=2. - Graphical abstract: A novel polyoxometalate [{Cu(2,2'-bpy)}₆(Mo₆O₂₂)][GeMo₁₂O₄₀].H₂O, which represents the first example of 1D organic-inorganic hybrid based on a Keggin-type heteropolyanion [GeMo₁₂O₄₀]^4- and an unprecedented isopolyanion [Mo₆O₂₂]^8-

[en] In this study, ordered meso-macroporous titania–silica–polyoxometalate (HPW/SiO₂–TiO₂) material was prepared in one-pot by evaporation-induced self-assembly (EISA) method, with non-ionic surfactant (P123) and monodisperse polystyrene microspheres applied as co-structure-directing agents. And the oxidative desulfurization (ODS) application of as-synthesized hierarchical nanocomposite materials was tested in model fuel. The characterization results of catalyst suggested that Keggin-type polyoxometalate was successfully incorporated into the ordered meso-macroporous SiO₂–TiO₂ framework. Moreover, the effect of Lewis acid center of the HPW/SiO₂–TiO₂ catalyst on ODS process was investigated. The optimum proportion of titanium and silicon ratio on catalyst was found to be 1:1, which exhibited remarkable catalytic performance on aromatic sulfur compounds at mild conditions. It revealed that Lewis acid sites played an important role in selectively adsorb DBT and its derivatives. What’s More, the combination of Lewis acid sites and ordered meso/macroporous architecture of catalyst will further facilitated the mass transport in ODS process. No decrease in the activity was observed after six runs, indicating a good stability of as-prepared catalyst.

[en] Amphiphilic polyoxometalate was successfully immobilized on the surface of amino-functional ordered meso/macroporous silica materials by the precipitation method and used as a catalyst for oxidative desulfurization (ODS). The as-prepared catalyst exhibited highly ordered meso/macroporous structure with the amphiphilic polyoxometalate covered on the amino-functional SiO₂. The nanocomposite was used as catalyst in ODS process which can remove dibenzothiophene (DBT) in model fuel within 2 h. Moreover, the recyclability of catalysts was carried out and it was related to the increasing amino group on surface of catalyst. (paper)

[en] The recently developed imaging neutral particle analyzer (INPA) on DIII-D enables fast ion velocityspace tomography of unprecedented fidelity, as well as resolution of local phase space dynamics under the action of classical and non-classical transport mechanisms. The INPA itself measures charge-exchanged energetic neutrals by viewing an “active” neutral beam through essentially a 1D pinhole camera with a rear collimating slit that defines the neutral particle collection sightlines. The incident neutrals are ionized by stripping foils and the local tokamak magnetic field acts as a magnetic spectrometer to disperse ions on the scintillator.

[en] Although the stability of ellipticity, toroidal and reversed-shear Alfven eigenmodes (EAE, TAE, RSAE) is relatively well understood, less is known about the stability of lower-frequency modes such as the beta-induced Alfven eigenmode (BAE), the beta-induced Alfven-acoustic eigenmode (BAAE), and the energetic-particle geodesic acoustic mode (EGAM). Because they are often unstable in present devices and are implicated in fast-ion transport, understanding their stability is vital. To that end, a database of ~1000 beam-heated discharges has been assembled. Modes are classified based on electron cyclotron emission, beam emission spectroscopy, magnetics, and interferometer data.