Search

Molecular (DME) 2Tm(SC 6F 5) 3and tetrametallic (DME) 4(μ 2-SPh) 8Tm 4(SPh) 4have been isolated in high yield and characterized by conventional methods. The fluorinated thiolate has an eight-coordinate Tm(III) ion bound to three sulfur atoms from the thiolates, four oxygen donors from the THF ligands, and a relatively weak dative Tm−F interaction with a 2.842(3)Å Tm−F separation. The benzenethiolate compound crystallizes as a tetramer with an alternating number (3, 2, 3) of thiolates connecting the nearly linear array of Tm(III) ions. Emission properties of both thiolates and the chalcogen-rich cluster (THF) 6Tm 4Se 9(SC 6F 5) 2have been established. The Ph compound is significantly more emissive than either of the fluorinated species. [ABSTRACT FROM AUTHOR]

Dust events are recorded in the SST-1 tokamak with fast visible imaging and infrared imaging systems. The events are analyzed from the image sequences with an in-house developed dust tracking routine in MATLAB called FINDUST. Specific operating scenarios for dust observation and their deleterious effects on discharge evolution are identified. A clear correlation of the dust events frequency and strength with the successful start-up and discharge evolution is observed over eight consecutive experimental campaigns in SST-1. It has been seen that the electron cyclotron resonance heating (ECRH) generated pre-ionization slab annular-plasma around the fundamental layer is most likely to generate dust, while the strongest effect of the ECRH fundamental layer on the plasma facing components is seen when the confined plasma column disrupts by some means while the ECRH pulse is still ON. [ABSTRACT FROM AUTHOR]

Intensity fluctuations are investigated using the fast camera imaging technique in the slab annular plasma as a function of magnetic shear and connection length in the spherical tokamak QUEST. Note that here QUEST is operated as a simple magnetized torus with a tight aspect ratio. Slab annular plasmas feature open magnetic field lines and can mimic the tokamak edge-scrape off layer (SOL)-like plasma attributes reasonably well. Three magnetic shear regimes are realized using three poloidal magnetic field (PF) coil pairs. A whole range of connection lengths (∼∞ ≥ Lc ≥ 5.5 m) is scanned by varying the PF strength for a given toroidal field for each magnetic shear regime. For the first time a systematic study of the effect of magnetic shear and field line pitch together on edge-SOL-like plasma fluctuations is being reported. Slab plasmas with intermediate magnetic shear are observed to be more susceptible to generate distinct blobs when Lc is reduced by increasing the PF strength. A distinct coherent mode appears only at the lowest magnetic shear slab featuring a deep potential well. Such mode is not apparent at other magnetic shear cases even at the same Lc. Finally, with a combination of PF coil pairs, both the features of intermediate and low magnetic shear slabs are shown to be realizable simultaneously. Significantly stronger blobs are observed with such combination of PF mirror ratios in the presence of a coherent mode. This study may provide better insight into the effect of magnetic configuration in the tokamak edge and SOL turbulence and can help in searching for better tools to control cross-field convective intermittent transport in tokamaks. [ABSTRACT FROM AUTHOR]

The feasibility of inferring the plasma parameters of a Penning discharge in helium, from the experimentally observed intensities of a number of spectral lines in the visible wavelength region, is explored. The collisional-radiative model of ADAS (atomic data analysis structure) code and database has been used for this analysis. The electron density, electron temperature, ground-state atom and ion densities and also the 2 3S metastable state density are the parameters thus estimated. The results are encouraging. The derived plasma parameters are then used to obtain the intensities of a few lines in the vacuum ultraviolet (VUV) region. This has been compared with the observed VUV spectral lines, recorded simultaneously with the visible lines, using a VUV spectrometer for which intensity calibration was not available, to arrive at calibration factors. It is expected that this approach might provide an alternative to the 'branching ratio' method for calibration in the VUV region once the analysis is improved and the possible re-absorption of certain lines is accounted for. [ABSTRACT FROM AUTHOR]