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The current work reports a detailed calculation of electron impact excitation cross sections for the fine structure transitions of Mo from the manifolds 4d55s, 4d45s2, 4d6, and 4d55p to the manifolds 4d55s, 4d45s2, 4d6, 4d55p, 4d45s5p, 4d55d, 4d56s, 4d45s6s and 4d57s, using the Relativistic Distorted Wave (RDW) approximation for plasma modeling application. Multi-configuration Dirac Fock wave functions are used in the calculations. The oscillator strength and cross-section results are compared with the previous calculations and measurements. A comprehensive collisional radiative (CR) model is developed to characterize laser-induced Molybdenum plasma to ensure that the calculated cross-section can be used for various plasma modeling applications. The current CR model has taken into account the electron impact excitation and de-excitation processes using the calculated consistent cross-sections. The electron-induced processes are dominant kinetic processes in the laser-induced plasma. Furthermore, the diagnostics of the laser-induced Mo plasma is done by coupling the current CR model with the experimental laser-induced breakdown spectroscopic measurements of Mal et al. (Appl. Phys. B 127, 52 (2021)). The plasma parameter, i.e., electron temperature, has been calculated using nine measured intensities of the emission lines of Mo, with wavelengths 406.9, 423.2, 438.1, 453.6, 476.0, 550.6, 553.3, 557.0 and 592.8 nm. The results are also compared with the values reported from the Boltzmann plot at various delay times ranging from 0.5 to 5.0 µs.

This work reports average electron temperature (Te) and electron density (ne) of an atmospheric argon rotating gliding arc (RGA), operated in glow-type mode, under transitional and turbulent flows. Both Te and ne were calculated near the shortest (δ) and longest (Δ) gap between the electrodes, by two different methods using two separate measurements: (1) optical emission spectroscopy (OES) and (2) physical–electrical. Te calculated from (a) collisional radiative model (CRM) (OES) and (b) BOLSIG+ [physical–electrical, reduced electric field (ENo) as input], differed each other by 16%–26% at δ and 6% at Δ. Te was maximum at δ (>2 eV) and minimum near Δ (1.6–1.7 eV). Similarly, the ENo was maximum near the δ (5–8 Td) and minimum near Δ, reaching an asymptotic value (1 Td). By benchmarking Te from CRM, the expected ENo near δ was corrected to 3 Td. The calculated CRM intensity agreed well with that of the measured for most of the emission lines indicating a well optimized model. The average ne near δ and Δ from Stark broadening (OES) was 4.8–8.0×1021 m−3, which is an order higher than the ne calculated through current density (physical–electrical). Te and ne were not affected by gas flow, attributed to the glow-type mode operation. To the best of authors’ knowledge, this work reports for the first time (a) an optimized CRM for RGAs (fine-structure resolved), (b) the poly-diagnostic approach to estimate plasma parameters, and (c) the validation of ENo calculated using physical–electrical measurements.

<p class="p1">In the present work, fabrication and evaluation of low density glass – epoxy (LDGE) composites suitable for absorbing minimum 80 per cent of incident microwave energy in 8 GHz to 12 GHz (X-band) is reported. LDGE composites having different densities were fabricated using a novel method of partially replacing conventional S-glass fabric with low density glass (LDG) layers as the reinforcement materials. Flexural strength, inter laminar shear strength and impact strength of the prepared LDGE composites were evaluated and compared with conventional High density glass-epoxy (HDGE) composites to understand the changes in these properties due to replacement of S-glass fabrics with LDG layers. To convert LDGE structures to radar absorbing structures controlled quantities of milled carbon fibers were impregnated as these conducting milled carbon fibers can act as dielectric lossy materials which could absorb the incident microwave energy by interfacial polarisation. Electromagnetic properties namely loss tangent and reflection loss of carbon fiber impregnated LDGE composites were evaluated in 8 GHz -12 GHz frequency region and compared with HDGE composites. It was observed that both LDGE and HDGE composites have shown loss tangent values more than 1.1 and minimum 80 per cent absorption of incident microwave energy. Thus the results indicates that, LDGE composites can show EM properties on par with HDGE composites. Furthermore these LDGE composite could successfully withstand the low velocity impacts (4.5 m/s) with 50 J incident energy. Due to their ability to show good mechanical properties and light weight, LDGE composites can be used as a replacement for conventional HDGE composites to realise radar absorbing structures.</p>

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