Sharif Digital Repository

Problems regarding simulation of field emitter array (FEA) electron guns are discussed. A simple method is proposed to significantly reduce computational requirements such as computation power, system memory, and time of FEA electron gun simulation and modeling. The method can be applied to any numerical solver regardless of its meshing technique. In order to extract field emission parameter from any experimental cathode I-V curve, a partly numerical algorithm, which uses the presented truncation method at the heart of its solver, is proposed. The proposed method and algorithm are applied to a number of examples, including a double-gated FEA problem, and its effectiveness in terms of error... 

Faraday cups (FCs) have been used to measure charged particle beams currents for a wide variety of experiments since the early days of particle accelerators. The major error source in FC performance is the escape of ejected electrons produced by energetic particles striking with interior metal surfaces of the FC. To avoid this problem, electrostatic and magnetic guard rings are used. Some kinds of non-symmetrical electrostatic FC with superior performance than traditional cylindrically symmetric FC have been reported. Here, we propose a novel non-symmetrical electrostatic FC structure, and a method to compare different non-symmetrical FCs. The purpose of this design is to recapture energetic... 

Indium tin oxide (ITO) thin films have been deposited using RF sputtering technique at different pressures, RF powers, and substrate temperatures. Variations in surface morphology, optical properties, and film resistances were measured and analyzed. It is shown that a very low value of sheet resistance (1.96 ω/sq.) can be achieved with suitable arrangement of the deposition experiments. First, at constant RF power, deposition at different pressure values is done, and the condition for achieving minimum sheet resistance (26.43 ω/sq.) is found. In the next step, different values of RF powers are tried, while keeping the pressure fixed on the previously found minimum point (1-2 Pa). Finally,... 

The need for antennas with improved characteristics for communication and radar applications has resulted in an ever-increasing demand for research in the field of high impedance surfaces, which can work as an artificial magnetic conductor. One method in fabrication of these surfaces is formation of a metamaterial by patterning a metallic surface in the shape of space filling curves (e.g. Hilbert or Peanu Curves). In this paper, we present a novel semi-analytical solution to the problem of plasmonic propagation on these surfaces. The method is based on a previously presented Green's function formalism, which has been reported in an earlier paper of ours. We have modified and improved the...