Electrical Engineering

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Electron beam analysis of pseudospark sourced electron gun

Pseudospark discharge based plasma cathode has capability to provide high current density electron beam during discharge process. In this paper an effort has been made to simulate the breakdown processes in the pseudospark discharge based plasma cathode electron gun. The two-dimensional plasma simulation codes VORPAL and OOPIC-Pro have been used and results are compared. The peak discharge current in the plasma cathode electron gun is found to be dependent on aperture size, hollow cathode dimensions, anode voltage and seed electrons energy. The effect of these design parameters on the peak anode current has been analysed by both the codes and results matches well within 10% variation. For the seed electron generation an electron beam trigger source is used to control the discharge process in the hollow cathode cavity. The time span of trigger source has been varied from 1-100 ns to analyze the effect on the peak anode current. © Published under licence by IOP Publishing Ltd.

Fulltext

Journal of Physics: Conference Series

Comparative simulation studies of plasma cathode electron (PCE) gun

The homogeneous boundary value problem arising in the propagation of electromagnetic waves guided by an open tape helix modelled to be of infinitesimal tape thickness and infinite tape-material conductivity is shown to be inherently ill posed. It is demonstrated how the ill posed problem may be regularised using the mollification method. The regularised boundary value problem is then solved to yield the approximate dispersion equation which takes the form of the solvability condition for an infinite system of linear homogeneous algebraic equations viz., the determinant of the infinite-order coefficient matrix is zero. For the numerical computation of the dispersion characteristic, all the entries of the symmetrically truncated version of the coefficient matrix are estimated by summing an adequate number of the rapidly converging (after regularisation) series for them. The tape-current distribution is estimated from the null-space vector of the truncated coefficient matrix corresponding to a specified root of the dispersion equation. A comparison of the numerical results with those for the anisotropically conducting model (that neglects the component of the tape-current density perpendicular to the winding direction) of the tape helix reveals that the propagation characteristic computed on the basis of the anisotropically conducting model could be substantially in error even for moderately wide tapes. © 2012 The Institution of Engineering and Technology.

IET Microwaves, Antennas and Propagation

Perfectly conducting tape-helix model for guided electromagnetic wave propagation

In this abstract, the impact of the gate and substrate biasing on the 3D current crowding behavior in the drain extended devices has been correlated with the shape of the NWell. Role of am-bipolar current flow in an optimized device structure for designing an efficient ESD protection device has been discussed by utilizing the self ballasting mechanisms under high current injection. © 2012 IEEE.

International Conference on Simulation of Semiconductor Processes and Devices, SISPAD

Physics of optimized high current ESD performance of drain extended NMOS (De-NMOS)

Two series of polycatenar molecules consisting of a π-conjugated rigid core derived from 3-hexen-1,5-diyne coupled to different types of benzoic acid derivatives have been prepared and their potential as multifunctional materials has been investigated. The size ratio between the rigid core and the benzoate-derived groups, which vary in bulk, is crucial to address self-organization, thus indicating the delicate balance of forces involved in liquid crystalline (LC) behaviour. LC nematic, crystalline or LC columnar behaviour is observed depending on the structure of the benzoate moiety. Hexagonal two-dimensional columnar organization is attained for mesogens with benzoate-derived groups bearing six and nine alkoxylic tails. The stacking unit of the columnar organizations is different depending on the total number of tails, twelve or eighteen, with two molecules and half a molecule per columnar stratum, respectively. Macroscopic properties related to molecular structure, such as luminescence, chirality and electroactivity, have also been studied. Luminescent behaviour is observed for all mesogenic materials, which show higher Stokes shifts than in solution. In addition, supramolecular chirality in the mesophase has been observed for a chiral mesogen. Finally, the photoconducting behaviour of two of the columnar materials has been evaluated. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2012.

New Journal of Chemistry

A linear conjugated core for functional columnar liquid crystals

An objective comparison of three different thermal non-destructive evaluation (NDE) techniques - pulsed thermography (PT), lock-in (LI) thermography, and frequency modulated thermal wave imaging (FMTWI), has been carried out on a CFRP sample. The matched energy comparison shows that on the basis of computed SNR, the shallow defects are better detected by PT, while deeper defects are detected equally by all techniques. © 2012 American Institute of Physics.

AIP Conference Proceedings

An objective comparison of pulsed, lock-in, and frequency modulated thermal wave imaging

In this paper, the development of large volume double ring Penning plasma discharge source for efficient light emissions is reported. The developed Penning discharge source consists of two cylindrical end cathodes of stainless steel having radius 6 cm and a gap 5.5 cm between them, which are fitted in the top and bottom flanges of the vacuum chamber. Two stainless steel anode rings with thickness 0.4 cm and inner diameters 6.45 cm having separation 2 cm are kept at the discharge centre. Neodymium (Nd2Fe14B) permanent magnets are physically inserted behind the cathodes for producing nearly uniform magnetic field of ∼0.1 T at the center. Experiments and simulations have been performed for single and double anode ring configurations using helium gas discharge, which infer that double ring configuration gives better light emissions in the large volume Penning plasma discharge arrangement. The optical emission spectroscopy measurements are used to complement the observations. The spectral line-ratio technique is utilized to determine the electron plasma density. The estimated electron plasma density in double ring plasma configuration is ∼2 × 1011 cm-3, which is around one order of magnitude larger than that of single ring arrangement. © 2012 American Institute of Physics.

Review of Scientific Instruments

Development of large volume double ring penning plasma discharge source for efficient light emissions

The paper presents a novel feature based indexing scheme for image collections. The scheme presents the extension of distance based hashing to kernel space for generating the indexing structure based on similarity in kernel space. The objective of the scheme is to incorporate multiple features for defining the image indexing space using the concept of multiple kernel learning. However, the indexing problems are defined with unique learning objective; therefore, a novel application of genetic algorithm is presented for the optimization task. The extensive evaluation of the proposed concept is performed for developing word based document indexing application of Devanagari, Bengali, and English scripts. In addition, the efficacy of the proposed concept is shown by experimental evaluations on handwritten digits and natural image collection. © 2012 IEEE.

IEEE Transactions on Multimedia

Feature combination in kernel space for distance based image hashing

In the present work, we report preparation and characterization of silicon carbide (SiC) films obtained by RF magnetron sputtering using a SiC ceramic target. The films were deposited in Ar ambient without external substrate heating. The residual stress of the films was measured as a function of sputtering parameters. The stress of the as-deposited films was observed to be compressive for the entire range of sputtering parameters used in the present work. Postdeposition annealing at 400 °C in N 2ambient was useful in reducing the stress in the films. On sequentially annealing the films at higher temperatures (600 and 800 °C), the nature of the stress changed from low compressive to high tensile. A superhard SiC film with low residual compressive stress (58.7 MPa) was obtained with hardness and Young's modulus values of 49.86 GPa and 363.75 GPa respectively. The x-ray diffraction pattern revealed that the films were either amorphous or nano-crystalline, depending on the deposition parameters and postdeposition annealing temperature. Atomic force microscopy roughness results confirmed good chemical stability of the films in potassium hydroxide and buffered hydrofluoric acid solutions. Several types of micro-structures were fabricated to demonstrate the feasibility and compatibility of these films in MEMS fabrication. © 2012 IOP Publishing Ltd.

Journal of Micromechanics and Microengineering

Mechanical and structural properties of RF magnetron sputter-deposited silicon carbide films for MEMS applications

This paper presents experimental studies for the production and propagation of an electron beam from a single gap pseudospark discharge based plasma cathode electron (PCE) gun. The generated electron beam has been successfully propagated for more than 25 cm in a gaseous environment without application of external guiding magnetic field at different operating conditions. The electron beam losses due to recombination with ions and collision with walls of drift space have been estimated. The electron beam profile has also been analyzed in the drift region of the gun. © Published under licence by IOP Publishing Ltd.