Fuel particle and impurity influxes have been investigated for ADITYA-U tokamak plasma operated with toroidal belt limiter using PMT based spectroscopic diagnostic system installed on machine. The influxes of hydrogen and impurity ions are estimated using various lines of sight (LoS) terminating on the graphite limiter and stainless steel wall to understand their contributions in recycled particle and impurities into the main plasma. It is found that the influxes of neutral hydrogen and oxygen are around 4 times higher in case of LoS terminating on the limiter than the wall while carbon influxes from the both LoSs are comparable. The comparable integrated particle influxes from both LoSs indicate the important role of the wall in the recycling and presence of the impurities in the plasma. The particle confinement time (τ p ) and recycling coefficient (R) are also estimated to quantify those from the estimated particle influxes. The τ p values vary between 8 to 25 ms when plasma electron density is in the range of 2.0 -3.2 × 10 19 m −3 . Analysis of recycling coefficient, R suggests that the Plasma Facing Component (PFC) acts as the particle sink at the beginning of the plasma operational campaign. The R values tend to become more than one as the campaign progresses suggesting that the PFC acting as the particle source.

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A capacitive coupled radio frequency (RF) plasma system has been developed for producing tungsten coated graphite tiles using plasma assisted chemical vapor deposition (PACVD) technique. To characterize the deposition chamber for optimal plasma parameters, small amount of air is released into the hydrogen plasma purposefully to measure its gas temperature using spectral bands of nitrogen molecule. Optical emission spectra in the wavelength range 350 to 900 nm have been recorded with a miniature spectrometer. Molecular spectral bands of N 2 (B 3 g -A 3 + u ) have been observed and identified as three bands from the nitrogen 1PS (Δν = 2, 3 & 4). These bands are simulated using MATLAB code developed in-house by considering Boltzmann distribution of particles in the vibrational states. The experimental spectra have been modelled with the simulated spectrum through the best-fit technique by iterating the latter one with different temperature values. Boltzmann plot method is also utilized to evaluate plasma gas temperature using identified vibrational bands. The estimated temperature using spectral modelling method matches fairly well with Boltzmann plot method. The estimated vibrational temperatures are in the range of ∼7000 -8000 K, an order higher than the room temperature ∼300 K.

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The ternary chalcopyrite compounds and related structures are well known for their noteworthy electronic and optical properties. The interaction between monovalent and trivalent atoms has a significant influence on their electronic as well as optical behavior. In the present work, a density functional theory based first-principles calculation is performed to investigate the structural, electronic, lattice dynamical, and optical properties of rhombohedral CuRhX2 (X = S, Se, Te) compounds. The electronic band structure of these compounds depicts semiconducting nature with an indirect bandgap of 1.8, 1.17, and 0.75 eV for CuRhS2, CuRhSe2, and CuRhTe2, respectively. There is a greater hole mobility and p-type conductivity in these compounds due to strong p-d hybridization. The phonon dispersion curves of these compounds confirm their dynamical stability as there is no imaginary frequency for any of the phonon modes in the entire Brillouin zone (BZ). Furthermore, we discuss mode compatibility at the zone center of the BZ and other high symmetry points of the BZ. The Raman spectra of CuRhX2 demonstrate two Raman active modes, namely, the Eg and A1g. The frequency of Raman active modes Eg and A1g decreases due to the increase in Rh–X bond length. The static dielectric constants fall in the range of 8.7–10.4. The absorption coefficient of these compounds is in the range of 1.5–2.0 eV depending upon the ionic radii of chalcogen atoms. Thus, it can be deduced that these systems can be efficiently used in solar energy converters in the UV as well as in the visible region.

The decrease in the physical dimensions of the devices have sought the attention of research community due to quick response, high sensitivity and sturdiness of the devices. These devices in the form of nano resonators have been extensively used as sensors to detect the entity at submicron level as well as to identify the properties of matter at submicron level. With the process like chemical vapour deposition, lithography technique as well as mechanical exfoliation techniques, it has become possible to produce materials which are 2D in nature. The excellent mechanical and electrical properties of graphene as well as its complete plain geometry advocate it as an ideal material for the development of sensors used for identifying the object at nano level. Here an attempt is made to analyse the vibration characterization of graphene resonator in the form of membrane to understand the shift in the frequency by adsorbing the mass and change in the temperature. The tobacco mosaic virus is considered as a mass adsorbed onto the graphene nano ribbon based membrane. Along with the adsorption of the mass, the effect of variation in temperature is also introduced to observe the shift in the natural frequency of the graphene membrane based resonator.

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