Growth and characterization of heteroepitaxial La-substituted BaSnO3_3 films on SrTiO3_3 (001) and SmScO3_3 (110) substrates

Heteroepitaxial growth of BaSnO$_3$ (BSO) and Ba$_{1-x}$La$_x$SnO$_3$ (x = 7 %) (LBSO) thin films on different perovskite single crystal (SrTiO$_3$ (001) and SmScO$_3$ (110)) substrates has been achieved by Pulsed Laser Deposition (PLD) under optimized deposition conditions. X-ray diffraction measurements indicate that the films on either of these substrates are relaxed due to the large mismatch and present a high degree of crystallinity with narrow rocking curves and smooth surface morphology while analytical quantification by proton induced x-ray emission (PIXE) confirms the stoichiometric La transfer from a polyphasic target, producing films with La contents above the bulk solubility limit. The films show degenerate semiconducting behavior on both substrates, with the observed room temperature resistivities, Hall mobilities and carrier concentrations of 4.4 $m \Omega cm$, 10.11 $cm^2 V^{-1} s^{-1}$, and 1.38 $\cdot 10^{20} cm^{-3}$ on SmScO$_3$ and 7.8 $m \Omega cm$, 5.8 $cm^2 V^{-1} s^{-1}$, and 1.36 $\cdot 10^{20} cm^{-3}$ on SrTiO$_3$ ruling out any extrinsic contribution from the substrate. The superior electrical properties observed on the SmScO3 substrate are attributed to reduction in dislocation density from the lower lattice mismatch.Comment: 11 pages, 3 figures, supplementary informations 2 figure

Analysis of a coupled-cavity slow wave structure for a TWT

139-142This paper describes an approach of designing a coupled-cavity slow wave structure (CC-SWS) for a high power traveling wave tube (TWT) using HFSS code, which is a 3-D high frequency electromagnetic simulator. The criteria of deciding the initial design parameters of a cavity are first discussed. Method of computing the dispersion and impedance characteristics of the CC-SWS has been discussed. Analysis was carried out for single and double-slot CC-SWS with coupling slots. Mesh size was optimized for speed and maximum accuracy. The CPU time on Pentium-4, 2.66 GHz system with 1 GB RAM was less then 25 min for three or four cavities. Results of HFSS are matched with the experimental results for a C-band coupled cavity SWS and also compared with the results of analytical method

Thermal analysis of coaxial coupler for a space helix TWT

227-232Thermal and structural analysis of the coaxial coupler for Ku-band 140 W helix space TWT have been carried out using ANSYS software v.10.1 and discussed in the present paper. To evaluate thermal and structural aspects of the coaxial coupler and helix assembly with three APBN support rods, related studies of the coupler assembly with ten turn of helix and output wave guide coupler for the Ku-band 140 W space TWT during extreme case of operation, i.e. at saturation and with perfectly rigid base-plate at 80°C have also been carried out

Thermal analysis of slow wave structure for a space helix travelling wave tube

904-907Thermal analysis of the slow-wave structure for Ku-band 140 W helix space traveling wave tube (TWT) has been carried out using ANSYS software v.10.1. To evaluate the thermal aspects of the helix slow-wave structure with three APBN support rods and barrel assembly, the related studies of the slow-wave structure assembly with six, ten and sixteen turns of helix for the Ku-band 140 W space TWT during extreme case of operation, i.e. at saturation and with perfectly rigid base-plate at 80°C have been carried out. The CPU time on Pentium-4, window XP system with 512 MB RAM is 45 min for six turns, one hour for ten turns and one hour 45 min for sixteen turns of helix. The objective of this analysis is reduced the solution time and to get the same result with higher turns of heli