Synthesis and crystal structure of Bis(2-phenylpyridine-C,N’)-bis(acetonitrile) iridium(III)hexafluorophosphate showing three anion/cation couples in the asymmetric unit

The title compound bis(2-phenylpyridine-C,N’)-bis(acetonitrile)iridium(III)hexafluorophosphate, a six-coordinate iridium(III) complex, crystallizes in the P-1 space group. Iridium is in a distorted octahedral (n = 6) coordination with the N,C’ atoms of two phenylpyridine and the N atoms of two acetonitrile ligands. The peculiarity of this structure is that three independent moieties of the title compound and three PF6− anions, to counterbalance the charge, are observed in the asymmetric unit and this is a rather uncommon fact among the Cambridge Crystallographic Database (CSD) entries. The three couples are almost identical conformers with very similar torsional angles. The packing, symmetry, and space group were accurately analyzed and described also by means of Hirshfeld surface analysis, which is able to underline subtle differences among the three anion/cation couples in the asymmetric unit. The driving force of the packing is the clustering of the aromatic rings and the maximization of acetonitrile:PF6− interactions. The asymmetry of the cluster is the cause of the unusual number of moieties in the asymmetric unit

On the rehydration of organic layered double hydroxides to form low-ordered carbon/LDH nanocomposites

Low-ordered carbon/layered double hydroxide (LDH) nanocomposites were prepared by rehydration of the oxides produced by calcination of an organic LDH. While the memory effect is a widely recognized effect on oxides produced by inorganic LDH, it is unprecedented from the calcination/rehydration of organic ones. Different temperatures (400, 600, and 1100 °C) were tested on the basis of thermogravimetric data. Water, instead of a carbonate solution, was used for the rehydration, with CO2 available from water itself and/or air to induce a slower process with an easier and better intercalation of the carbonaceous species. The samples were characterized by X-ray powder diffraction (XRPD), infrared in reflection mode (IR), and Raman spectroscopies and scanning electron microscopy (SEM). XRPD indicated the presence of carbonate LDH, and of residuals of unreacted oxides. IR confirmed that the prevailing anion is carbonate, coming from the water used for the rehydration and/or air. Raman data indicated the presence of low-ordered carbonaceous species moieties and SEM and XRPD the absence of separated bulky graphitic sheets, suggesting an intimate mixing of the low ordered carbonaceous phase with reconstructed LDH. Organic LDH gave better memory effect after calcination at 400 °C. Conversely, the carbonaceous species are observed after rehydration of the sample calcined at 600 °C with a reduced memory effect, demonstrating the interference of the carbonaceous phase with LDH reconstruction and the bonding with LDH layers to form a low-ordered carbon/LDH nanocomposite

Verification/validation and physics model extension in high fidelity 3D RF full wave simulations on Petra-M

This paper reports the recent progress towards a whole-device scale RF actuator simulation. Our approach is to combine progresses made by open source scientific and math software communities for meshing, FEM assembly, and linear solvers to construct an integrated FEM fullwave simulation framework (the Petra-M FEM framework). The goal is to bring in engineering CAD level geometrical detail to our wave simulation capability, and advanced RF wave physics models, such as RF rectified sheath models and non-local hot plasma effects. In Petra-M, the high harmonic fast wave (HHFW) propagation was fully resolved in a 3D NSTX-U torus. In the NSTX-U simulation, the ratio between wavelength to the device size reaches 15, which is in the range required for resolving the ICRF wave fields in ITER. Verification and validation of the RF wave field computed by Petra-M through the international/multi-institutional efforts has been a major research focus, which yields an excellent code benchmark agreement between Petra-M, TOPICA and RAPLCIASOL. The spectral analysis of 3D wave field has been performed to interrogate the wave field behavior, which shows the consistency with the wave theory. RF rectified potential model was incorporated in our wave field solver. We developed a new non-linear iteration algorithm, which allows for using both the thick sheath (asymptotic) model and non-linear sheath impedance models seamlessly. The 3D RF sheath simulation on the WEST ICRF antenna indicates that the sheath potential tends to concentrate near the corner of antenna box, which is consistent with experimental observation of RF induced heat load pattern

Improved measurements of ICRF antenna input impedance at ASDEX Upgrade during ICRF coupling studies

A new set of diagnostics has been implemented on ASDEX Upgrade to measure the input impedance of the ICRF antennas, in the form of a voltage and current probe pair installed on each feeding line of every antenna. Besides allowing the measurement of the reflection coefficient Γ of each antenna port, the probes have two advantages: first, they are located close to the antenna ports (∼3 m) and thus the measurements are not affected by the uncertainties due to the transmission and matching network; second, they are independent of matching conditions. These diagnostics have been used to study the behavior of the ASDEX Upgrade antennas while changing the plasma shape (low to high triangularity) and applying magnetic perturbations (MPs) via saddle coils. Scans in the separatrix position Rsep were also performed. Upper triangularity δo was increased from 0.1 to 0.3 (with the lower triangularity δu kept roughly constant at 0.45) and significant decreases in |Γ| (up to ∼30%, markedly improving antenna coupling) and moderate changes in phase (up to ∼5°) of Γ on each feeding line were observed approximately at δo ≥ 0.29. During MPs (in ∼0.5 s pulses with a coil current of 1 kA), a smaller response was observed: 6% - 7% in |Γ|, with changes in phase of ∼5° apparently due to Rsep scans only. As |Γ| is usually in the range 0.8 - 0.9, this still leads to a significant increase in possible coupled power. Numerical simulations of the antenna behavior were carried out using the FELICE code; the simulation results are in qualitative agreement with experimental measurements. The results presented here complement the studies on the influence of gas injection and MPs on the ICRF antenna performance presented in [4]

ICRH-related impurity source and control across experiments in H, D, T plasmas at JET-ILW

The experimental and theoretical analysis were focused on experiments conducted to assess the effect of plasma isotopes, protium (H), deuterium (D), and tritium (T) on ion cyclotron resonance heating (ICRH) related plasma wall interactions. Comparison of L-mode discharges with N = 1 3He and N = 1 H minority ICRH heating scenarios were done for different isotopes. For the selected pulses, the behaviour of high-Z, mid-Z and low-Z intrinsic impurity and radiated power behaviour was investigated based on data from VUV, visible spectroscopy, and bolometry diagnostic at Joint European Torus. It was found that for N = 1 3He scenario during radiofrequency antennas operation, core W, Ni content, Be source and the radiated power are higher for pi/2 in comparison to dipole antenna phasing. Lowest core Ni, W content and radiated power is clearly observed for H plasmas in comparison to D and T, where for this ICRH scenario behaviour was similar. However, lower Be photon flux is observed for T in comparison to D plasmas. Be sputtering by He particles is responsible for such an effect. Additionally, several computer simulations were conducted using the COREDIV code. The difference in the electron temperature was due to the difference in the isotope masses. Increased temperature in the central plasma in the case of T plasmas leads to higher radiation in the central plasma in comparison to H plasmas. As a result, the power across separatrix is lower and the temperature on the divertor plate decreases with the increase of the isotope mass. At these temperatures on the divertor plate, W is not sputtered by the main plasma ions H, D and T and by He. For the N = 1 H ICRH scenario clear difference between D and T plasma was observed with higher metallic impurity content for T plasma in comparison to D. Impurity content in the plasmas is found to be sensitive to the power balance between the antenna straps. Its minimum is observed for the maximum of P cen/P tot

Characterizations and first plasma operation of the WEST load-resilient actively cooled ICRF launchers

The paper discusses the characterization of the three high power steady-state and load-resilient ICRF launchers of WEST before their installation in the tokamak. These launchers have been characterized and validated in low-power experiments (milliwatt range) as well as in experiments at the nominal RF voltages and currents in the TITAN vacuum chamber (~30 kV and 915 A peak). The successful commissioning of two of the launchers during the WEST C3 campaign at ~1 MW power level is illustrated. Manual and real-time controlled impedance-matching of the launchers are discussed, as well as the validation of their load-resilience. Furthermore, several redundant and complementary protection systems have been validated and are reviewed in the paper