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| TUPMA039 | Comparison of Codes for Smith-Purcell FEL | simulation, electron, free-electron-laser, laser | 166 | ||
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Smith-Purcell FELs using low energy electron beam are being seen as attractive option for a compact source of coherent Terahertz ratiation. Recently, Kumar and Kim [1] have performed numerical simulation of Smith-Purcell free-electron lasers (SP-FELs) based on a computer code using Maxwell-Lorent equations. Li et al. [2], and Dounhue et al. [3] have performed calculations using PIC codes. In this paper, we present a comparision of these methods and compare results obtained using different codes.
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1. V. Kumar et al., Phys. Rev. E 73, 026501 (2006). 2. D. Li et al., Phys. Rev. ST Accel. Beams 9, 040701 (2006). 3. J. T. Donohue et al., Phys. Rev. ST Accel. Beams 9, 060701 (2006). |
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| TUPMA113 | Design of High Current RF Ion Source for Micromachining Applications | ion, ion-source, electron, extraction | 262 | ||
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Liquid Metal Ion Source (LMIS) and Gas Field Emission Ion Source (GFEIS) are the major ones in micromachining applications so far. They have limitations of contaminations and low throughput respectively. Plasma based ion sources can produce heavier ions for higher throughput, lighter ions for fabrication of higher resolution structures, ions for doping, ion assisted direct writing of metallic, oxide, nitride and carbide layers and lines. Considering wide range of applications, a 13.56 MHz inductive coupled plasma (ICP) ion source for producing high brightness ion beams with very low energy spread has been developed. It is a very compact ion source with external helical antenna wound around a 30 mm quartz tube. 1 mA of Argon and 0.5 mA of proton ion beams have been extracted from 2 mm dia aperture in plasma electrode at 3.5 kV extraction potential and ~200W of RF power. Using LabView software and field point modules, an automated plasma diagnostic system has been designed and used to measure the plasma parameters. This paper describes the features of the ion source, ion beams produced, some results of the plasma diagnostics.
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| TUPMA115 | Simulations of Non-uniform High Density Electronegative Plasma for Optimization of H- ions and their Extraction | ion, electron, ion-source, simulation | 265 | ||
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Numerical simulations of radio frequency multi-cusp volume type H- ion source have been performed under non-uniform electronegative plasma equilibrium conditions in order to understand the physics of formation of various ion species (H+, H-, e- etc.) and for optimization of H- ion formation and extraction. Coupled momentum balance equations along with continuity equations were solved in a cylindrical geometry to obtain the density profile of various ion species. The relevant cross-section data available in the literature as a function of temperature has been used in the computation. The hydrodynamic model of plasma in equilibrium with background neutral gas has been used. Low degree of ionization ( ~1%) has been assumed. The collision less sheath formation, penetration of electric and magnetic field and power requirement to sustain the plasma has been worked out numerically. An effort has been made to give a self-consistent numerical scheme for the solution of inductively coupled plasma (ICP) in equilibrium, and the results obtained have been presented
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| TUPMA116 | Periodic Ion Current Burst in 6.4 GHz ECR Source | ion, electron, ion-source, cyclotron | 268 | ||
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We studied the enhancement in extracted ion current in the 6.4 GHz ECR ion source at VECC, Kolkata by inserting a negatively biased disc in the main stripping stage. In addition to the expected increase in current, we observed a sudden jump in the current at some low bias voltage. The jump amplitude is larger for higher charge states. In order to understand the origin of the jump, we recently measured the time spectra of high charge state ion current for neon. The time spectra revealed the presence of a burst frequency in the kilohertz range. This frequency shows a correlated jump with the ion current described above. Another feature is that the observed burst frequency shows a good linear correlation with the extracted ion current. This may signify that current per burst is a constant factor, higher current means that there are more number of bursts.
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| TUPMA123 | Electron Acceleration in the Wake Field Excited by 200TW Femto Second Laser in Underdense Plasma | electron, laser, scattering, acceleration | 277 | ||
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Laser-plasama acceleration experiment has been carried out using 200TW, 30fs Ti:Sapphire laser pulses focused on helium gas-jets with F/8.75 optics. Intense mono-energetic electron beams have been produced by controlling plasma length and density precisely. Energy spectral oscillations in respect to ejection angle have been also observed. Measurements of images from Thomson scattering and fluorescence side scattering from plasma indicate highly relativistic effects such as a long self-channeling, hosing instability and filamentation. It seems that these nonlinear phenomena strongly disturb high energy gain acceleration and high quality beam generation.
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| WEPMA144 | High Power Microwave Generation From Coaxial Virtual Cathode Oscillator | cathode, electron, impedance, space-charge | 523 | ||
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A coaxial virtual cathode oscillator (VIRCATOR) has been designed to generate Relativistic Electron Beams and High Power Microwaves. Coaxial virtual cathode oscillators are known for better efficiency compared to the axial virtual cathode oscillators. This Coaxial VIRCATOR has been designed for the KALI-5000 (1MeV, 60kA, 100 ns) pulse power system. Provision for a large anode cathode gap has been kept to avoid the prepulse effect during the electron beam generation from the KALI-5000 system. Experimental studies are carried out to generate and characterize Relativistic Electron Beams and High Power Microwaves. Relativistic Electron Beams are generated by the Coaxial Explosively emitted graphite cathodes. Electron beam voltage has been measured by a copper sulphate voltage divider and beam current by a B-dot probe. High Power Microwaves are detected by the glow of neon lamps placed closed to the output window.
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| THPMA065 | Theoretical Analysis of the Recovery Times in Low Pressure Sparkgaps - Positive Ion Diffusion Method | ion, electron | 723 | ||
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The recovery characteristics of the low-pressure sparkgaps in the time interval of 300*s to 50ms, for hydrogen, argon and deuterium gases,had shown thatthat the breakdown voltage under second pulse is higher than the breakdown voltage under first pulse along the left hand side of Paschen's characteristics and defined as over recovery (>100% recovery). An attempt has been made to calculate and analyze the recovery times of low pressure sparkgaps based on diffusion of positive ions here. The recovery times are calculated based on the reported data of plasma diffusion rates. The spherical ambipolar and free diffusion recovery times are generally in good agreement with the experimental recovery times at higher pressures. The cylindrical ambipolar and free diffusion recovery times are an order of magnitude lower than spherical diffusion recovery times. The recovery times are not in good agreement for positive polarity experimental recovery times. The theoretical calculation of recovery times, comparison of calculated and experimental recovery times and discussions are presented in this paper.
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| THPMA066 | Theoretical Analysis of the Recovery Times In Low Pressure Sparkgaps- Anode Temperature Decay Method | vacuum, ion | 726 | ||
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The recovery characteristics of the low-pressure sparkgaps in the time interval of 300*s to 50ms, with stainless steel electrodes, in the pressure range of 1 to 40Pa, for gap spacings of 2.5mm and 10mm, have been determined experimentally for hydrogen, argon and deuterium gases. Presently there are no methods ideally suitable for calculation of recovery times of low pressure sparkgaps. However an attempt has been made to analyze the recovery times of low pressure sparkgaps by anode temperature rise and decay method based on liquid and solid vapour phases here. The recovery times are calculated based on the reported data of anode drops. The solid phase recovery times are generally in good agreement with the experimental recovery times with higher load currents. The liquid phase recovery times are an order of magnitude low compared to the experimental recovery times. The recovery times are not in good agreement for positive polarity experimental recovery times due to non-uniformity in the gap. The theoretical calculation of liquid and solid phase recovery times, comparison of calculated / experimental recovery times and discussions are presented in this paper.
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| THPMA073 | Artificial Neural Network Calculates Backward Wave Oscillator Parameters Reliably For Pulsed Accelerators | simulation, electron, controls, radiation | 738 | ||
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A method of quickly and accurately getting the dispersion curves for a slow wave structure filled with plasma is investigated. A universal dispersion equation is derived by utilizing the field theory and expressing the slow wave structure's profile in a finite Fourier series. In principle simulation program takes nearly 6 to 8 hours to generate a single result. A trained Artificial Neural Network, used in this study, calculates the BWO dispersion curve in a fraction of a second accurately and reliably.
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| THPMA089 | Studies of Metallic Ion Beams using ECRIS | ion, ion-source, extraction, background | 770 | ||
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Low energy metallic ion beams find wide applications in various research fields especially in materials science, atomic and molecular physics. Several metallic ion beams have been developed successfully using all permanent magnet 10 GHz electron cyclotron resonance (ECR) ion source based low energy ion beam facility (LEIBF) [*] at IUAC. The most important feature of the facility is that the source and all its peripheral components including electronics and vacuum systems are on a high voltage platform (300 kV).The metallic ion beams were developed by different methods e.g. oven, sputtering, insertion and metal ions using volatile compounds (MIVOC). The ion source has been tuned to get optimum intensities of metallic ion beams. The high intensities of low charge state metallic ion beams are suitable to engineer the materials for optical, electrical and structural properties via ion implantation. For the interest of atomic and molecular physics, the high intensities of highly charged metallic ion beams are produced using gas mixing [**] and bias techniques. The charge state distribution studies of various metallic ion beams and gas mixing effect of different gases are presented.
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[*] P. Kumar et.al., Nucl. Instr. and Meth. B, 440 (2006) 246.[**] A. G. Drentje et.al., Rev. Sci. Instrum. 953 (1996) 67. |
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| FRXMA01 | Progress of the Laser-Plasma Acceleration Research at KERI | laser, electron, acceleration, background | 832 | ||
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There rise great interest worldwide in plasma accelerators driven by ultra-intense lasers or electron beams which make it possible to generate ultra-high gradient acceleration and high quality particle beams in a much more compact size compared with conventional accelerators. A frontier research on laser and plasma accelerators is focused on high energy electron acceleration and ultra-short coherent X-ray and Tera Hertz radiations as their applications. These achievements will provide not only a wide range of sciences with benefits of a table-top accelerator but also a basic science with a tool of ultrahigh energy accelerators probing an unknown extremely microscopic world. Harnessing the recent advance of ultra-intense ultra-short pulse lasers and accelerators, the worldwide research has made a tremendous breakthrough in demonstrating high-energy high-quality particle beams in a compact scale. This talk highlights recent progress of results on laser and plasma based acceleration experiments to quest for physics of acceleration and beam physics in plasma and to present new outlook for applications of laser and plasma accelerators.
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