The time- and space-resolved emission profiles of LiI and LiII emission lines from the laser-blow-off plumes of a multilayered LiF–C thin film have been studied using spectroscopic technique. The evolution features were analyzed in different ambient environments ranging from high vacuum to 3mbars of argon pressures and at various fluences of the ablating laser. During the evolution of the plume, a transition region was found to exist between 4 and 6mm. Here, the plume dynamics changed from free expansion to collisional regime, where the plume experienced viscous force of the medium. The enhancement observed in neutral lines, in comparison with ionic lines, is explained in terms of the yield difference in electron impact excitation and ionization processes. Substantial difference in the arrival time distribution of the plume species was observed for LiI and LiII lines at high ambient pressures. Three expansion models are invoked to explain the evolution of the plume in different ambient conditions. The laser fluence was found to control the ratio of ions and neutrals.

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A new experimental set-up which consists of a pulse magnetic field system has been developed to capture the different phases of expanding plasma plume across the transverse magnetic field, varying from 0 to 0.57 T. Two internally synchronized ICCD cameras mounted in the orthogonal direction have been used to record the two directional projections (across and along the magnetic field directions) of the plasma plume. The plume takes the conventional ellipsoidal shape in the absence of a magnetic field. Well-defined cavity-like structures have been observed in a plane perpendicular to the field direction, which are dominant at the early stage of the plasma and comparatively lower magnetic fields. As the time evolves, the cavity changes to jet/cone-like structures which in turn change to slab-like structures with a further increase in time delay. On the other hand, well separated intensity columns (striation-like structures) appeared in a plane parallel to the magnetic field direction, which are more apparent at a higher magnetic field. Based on the projections of plume images in two perpendicular planes, the three dimensional structure of the plasma plume is modeled as an elliptical cylinder-like structure. The time dependence of dynamics and geometry of the plasma plume in the presence of a magnetic field are correlated with the expansion in diamagnetic and non-diamagnetic regimes. The validity of plasma instability, which is responsible for observed striation-like structures, is also discussed.

The effect of the atomic mass of the ablating target on the formation and expansion of the interaction region in laterally colliding plasmas has been studied. Fast imaging and optical emission spectroscopy have been utilized as diagnostic tools to investigate the characteristic features of the seed plasma as well as interaction zone formed by different target materials (i.e., carbon, aluminium, and nickel). The present results reveal that dynamical, spectral, and geometrical features of the induced interaction zone depend on the mass of the ablated species and spatial separation between the interacting plumes. It has been observed that a sharp, intense, and more directional interaction zone is formed by the interaction of heavier plume species in comparison to that observed for a lighter atomic mass target. Further, the difference in the plasma parameters in seed and interaction regions are explained from the analysis of emission from both the regions for aluminium plasma.

Abstract. The ITER Ion Cyclotron Heating and Current Drive system (IC H&CD) is designed to deliver 20MW to a broad range of plasma scenarios between 40 and 55MHz, during very long pulses. It consists of two broadband equatorial port plug antennas, their pre-matching and matching systems, transmission lines, Radio Frequency (RF) Sources and High Voltage Power Supplies. The overall project schedule has been revised and agreed by ITER Council; it re-integrates the second antenna and its power supplies in construction baseline and sets the dates for progressive installation with DT phase planned in 2035. Recent progress on ICRF subsystems is reported, covering design evolution, qualification of test articles and specific R&D results in domestic agencies, suppliers, associated laboratories and IO.