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Vacuum Electronics Conference, 2004. IVEC 2004. Fifth IEEE International

Date 27-29 April 2004

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Displaying Results 1 - 25 of 196
  • Cold electron emission process in CVD diamond films

    Page(s): 251 - 252
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (286 KB) |  | HTML iconHTML  

    The development of robust cold cathodes would provide improved efficiency, lifetime, and design flexibility for a broad range of devices including RF vacuum electronic devices and flat panel displays. Diamond has been identified as a uniquely promising cold cathode material due to the negative electron affinity (NEA) that is present at hydrogenated diamond surfaces. In this study, we investigate the cold electron emission process in CVD diamond using electron transmission spectroscopy. Specifically, we inject electrons into thin CVD diamond films using a 0-20 keV electron gun, and we then detect and analyze the secondary electrons that are transmitted through the films. In particular, the intensity and energy distribution of the transmitted electrons are measured as a function of the incident beam parameters (E0, I0) and analyzed using Monte Carlo simulations. Reflected secondary-electron-emission spectroscopy (SEES) measurements are also used to evaluate the surface properties of the films. View full abstract»

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  • Production and reliability of the VKU-8891M series DBS-MSDC klystron

    Page(s): 340 - 341
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (285 KB) |  | HTML iconHTML  

    With the development of a four-stage depressed collector for air-cooled, permanent-magnet focused, medium-power klystrons, CPI introduced a new generation of high-efficiency klystrons to the satellite-communications market, covering C-, Ku-, and the direct broadcasting satellite (DBS) band. This paper describes the production and over three years of field experience for the VKU-8891M series klystron serving the DBS market. This klystron was the first to utilize the multistage depressed collector (MSDC) in satellite-communications applications. View full abstract»

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  • Non-monochromatic fields in a dispersive electrodynamic line. II. the continuous approximation

    Page(s): 222 - 223
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (362 KB) |  | HTML iconHTML  

    The discrete approximation for evaluation of the non-harmonic fields in a dispersive electrodynamic line with an electron beam has been described in the first part of the paper (ibid., p.220-221). This is universal and wideband approach. However, the normal eigenmode interpolation errors might be excessive, if the number N of the partial eigenmodes is small. Therefore, for regular lines (e.g., a periodic with the period D delay structure or uniform smoothbore waveguide), the continuous approximation, detailed in this paper, might be used. View full abstract»

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  • Spurious reflection of space charge waves in traveling wave structures

    Page(s): 344 - 345
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (257 KB) |  | HTML iconHTML  

    The high gain of traveling wave tube amplifiers makes them particularly sensitive to reflections at output ports and severs. Even small values of reflections can be significant if the reflected waves are regeneratively amplified. Consequently, a great deal of effort is expended in minimizing reflections. One process that complicates the design of devices is the additional reflection that occurs in the presence of the electron beam. The current procedure for minimizing reflections is based on the electrodynamic properties of the cold structure, i.e. in the absence of the electron beam. In the presence of the beam there is an additional reflection due to the beam space charge wave that is induced on the structure. Thus, structures optimized for zero reflection without the beam will have a reflection with the beam. The effect of the space charge wave is illustrated. View full abstract»

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  • University programs in vacuum electronics in Asia

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (169 KB) |  | HTML iconHTML  

    Summary form only given. Various vacuum electronics devices, including klystrons, magnetrons, gyrotrons, and TWTs have been developed in Asian countries for the last several decades. Universities in each country have developed their unique vacuum electronics programs to meet their country's needs. An overview of the vacuum electronics program in Asia is presented. Particularly, the presentation concentrates on vacuum electronics developments in Japan, China, India, Korea and Taiwan. View full abstract»

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  • The electrostatic potential distribution of crossed-field systems

    Page(s): 226 - 229
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (279 KB) |  | HTML iconHTML  

    The research and simulation of crossed-field systems of both classical and inverted construction require together the solution of motion equation, equation of excitation and Poisson's equation. In many problems of vacuum electronics it is necessary to define the distribution of electrostatic potential between electrodes. On the first stage of theoretical research of physical processes we must define the initial and boundary conditions which have an influence on device operation. One of such conditions is the distribution of electrostatic potential in interaction space. Using the Laplace equation solution, and defining unknown coefficients by Fourier methods, it is possible to find electrostatic potential distribution in systems with complex electrode configurations. The offered method may be used to define initial conditions before the simulation such important systems as crossed-field systems. View full abstract»

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  • MAGY simulations of 1.5 MW, 110 GHz MIT gyrotron with non-uniform electron emission

    Page(s): 348 - 349
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (261 KB) |  | HTML iconHTML  

    We present simulation results from the code MAGY of a 110 GHz, 1.5 MW gyrotron which is currently in short pulse operation at MIT. The experimental peak power is 1.44 MW at 37 % efficiency, when operating in the TE22,6 mode, with a velocity ratio (v/v||) of 1.43. The MAGY simulations are done for triplet mode excitation (TE21,6, TE22,6 and TE23,6), and include both velocity spread and the azimuthal nonuniform charge density of the electron beam. For a velocity spread of 5.5 % and the measured value of beam emission nonuniformity, the MAGY simulations are in good agreement with the measured experimental results. View full abstract»

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  • Millimeter wave vacuum technology

    Page(s): 6 - 7
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (303 KB) |  | HTML iconHTML  

    Summary form only given. This paper explores the current state of vacuum technology, specifically in the millimeter wavelength regime. A view of the market priorities and technology development is described. Current applications utilizing millimeter devices are characterized. Areas of interest are industrial microwave heating, satellite communications, and radar. Finally, new applications and research in the areas of millimeter wavelengths are discussed. View full abstract»

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  • IOTs step into L-band: 20 kW CW at 1.3 GHz

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (237 KB) |  | HTML iconHTML  

    IOTs have been broadly used in the UHF range for broadcast, science and industrial applications. It was initially thought that IOTs would not be able to maintain their well-appreciated properties, such as efficiency and linearity, while operating at frequencies above 1 GHz due to the transit time limit. However, since a growing number of particle accelerators requests 1.3 GHz amplifiers as RF power sources, an investigation was conducted to determine the possibility of manufacturing L-band IOTs. Detailed operating parameters of prototype and beta version will be presented in the paper. View full abstract»

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  • Peer-peer phase-locking of two L-band industrial heating magnetrons

    Page(s): 230 - 231
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (253 KB) |  | HTML iconHTML  

    We demonstrate the peer-peer phase-locked operation of two matched industrial heating magnetrons. Two commercial off-the-shelf California Tube Laboratory model CWM-75L industrial heating magnetrons were "cherry picked" for identical operating voltage (17.5 kV), current (5.0 A), operating frequency (915 MHz), and output power (75 kW). Their microwave power outputs were cross-coupled by means of a four-port branch wall directional coupler and phase shifter. Coupling as low as -20 dB of each other's output powers was sufficient to create mutual locked operation between both magnetrons. These results suggest more than two matched magnetrons may be driven in a phased-locked condition. View full abstract»

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  • 3D analysis of helical slow-wave structures for space TWTs: critical comparison of Ansoft HFSS and CST Microwave Studio

    Page(s): 352 - 353
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (305 KB) |  | HTML iconHTML  

    3D EM simulators allow to model any type of 3D structure without analytical approximations or experimental errors. The objective of this study is to evaluate the capabilities of two of these simulators (based on finite element and finite difference approaches) and to perform a critical comparison (in terms of CPU-time and accuracy) for a typical space helix TWT in Ku-band. Two commercially available simulators were used for this study: Ansoft-HFSS, and CST Microwave Studio. View full abstract»

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  • Effects of a finite axial magnetic field on the beam loading on a cavity [klystron cavity example]

    Page(s): 218 - 219
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (257 KB) |  | HTML iconHTML  

    The beam loading of a cavity is mostly computed under the assumption of an infinite axial magnetic field. In practice, a finite focusing magnetic field is almost always present. In this paper, we extend Branch's classic paper (IEEE Trans. Electron Devices, vol.8, p.193, 1961) on ballistic bunching in that both the conductive and reactive components of the beam-loaded admittance are computed, and for general values of axial magnetic field. Also included is a comparison of the analytic formulation with a 2D particle-in-cell simulation. This work suggests that the finite axial magnetic field used in linear beam tubes (typically exceeding 1.5 times the Brillouin field) would modify the beam-loaded admittance by about 20%, or less, from that computed under the assumptions of an infinite axial magnetic field. View full abstract»

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  • Grid control for electron guns

    Page(s): 242 - 243
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (338 KB) |  | HTML iconHTML  

    This report provides a basis for selecting the optimum beam control configuration for a given device requirement. Many configurations exist for switching thermionic cathode emission on and off, but no single method can satisfy every tube specification. This report will provide a side-by-side comparison of the appropriate parameter ranges for each of the available grid control solutions, facilitating a choice of the optimal approach for a given device requirement. The report will include geometric configurations and performance characteristics of the different designs. View full abstract»

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  • Influence of ion effects on relativistic field-emission-limited diodes

    Page(s): 208 - 209
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (255 KB) |  | HTML iconHTML  

    In a previous work, we investigated a relativistic field-emission-limited diode employing a high-transparency mesh anode via a self-consistent approach (M.C. Lin and D.S. Chuu, IVEC 2002, pp. 111-112, 2002, and Appl. Phys. Lett. vol. 80, pp. 4262-4264, 2002). Ionization effects at the high-transparency mesh anode were ignored. However, the ionization effects at the anode cannot be eliminated in the real world, even for the high-transparency mesh anode. It is well known that the emergence of upstream ion current would enhance the space-charge limiting current. In this work, we consider the anode plasma effects on the relativistic field-emission-limiting current. Thus, the previous theory is extended to the bipolar field-emission-limited flow. The ion current has been included in the relativistic Poisson's equation and has been treated as a tuning parameter. View full abstract»

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  • The status of thermionic cathodes: theory and practice

    Page(s): 8 - 9
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (237 KB) |  | HTML iconHTML  

    Summary form only given. Most practical devices rely on the measurement of emission current as the only practical means of evaluating the adequacy of cathode emission. A complete theory of emission is essential for evaluating cathode efficiency. The theories of thermionic emission developed shortly after the discovery of the emission phenomena are incomplete. Part of this paper addresses the inconsistencies of existing theories and shows that these theories can be used to produce a coherent and unified emission theory. Certain vacuum electron devices (VEDs) such as multiple beam klystrons (MBKs) and millimeter wave devices place a demand on electron sources to provide higher current densities. This paper also describes various cathode materials and structures for these high power devices. View full abstract»

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  • Towards estimation of the effects of misalignment of electron beam injected into a high power gyrotron with depressed collector

    Page(s): 202 - 203
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (274 KB) |  | HTML iconHTML  

    The simulation of gyrotron operation starts with the assumption that the axis of the hollow electron beam is perfectly aligned with the axis of the tube into which it is injected. In practice there is likely to be some degree of misalignment between the two. It is desirable to estimate the effects on the operation of the tube vis-a-vis the degree of misalignment. In a tube with depressed collectors, the effects on collector efficiency and on the heat dissipation density profile are of particular interest. When the two axes do not coincide, ideally speaking the simulation of the electron beam trajectories would need a 3D code. However, for small deviations from perfect alignment, it is possible to get an initial estimation of the effects by using an approximation. Results from such an approximation are the subject of this paper. View full abstract»

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  • Progress on development of a 19 kW CW, L-band klystron for CEBAF

    Page(s): 216 - 217
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (231 KB) |  | HTML iconHTML  

    Summary form only given. Calabazas Creek Research is developing a klystron for the upgrade of the RF system of the continuous electron beam accelerator facility (CEBAF) at the Thomas Jefferson National Accelerator Facility. The klystron is designed to produce 19 kW of saturated CW power at 1497 MHz with an efficiency of 59%. The design parameters are outlined in this paper. View full abstract»

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  • Production status of 805-MHz, 550 kW pulsed klystrons for the Spallation Neutron Source

    Page(s): 338 - 339
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (332 KB) |  | HTML iconHTML  

    The Spallation Neutron Source (SNS) is an accelerator-based neutron source. The SNS will provide the most intense pulsed neutron beams in the world for scientific research and industrial development. CRI is supporting the effort by providing 81 pulsed klystrons, model VKP-8291A, for the superconducting portion of the accelerator. The primary output power requirements are 550 kW peak, 49.5 kW average at 805 MHz, with an electron beam-to-rf conversion efficiency of 65%. View full abstract»

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  • Diamond-based sub millimeter backward wave oscillator

    Page(s): 71 - 72
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (316 KB) |  | HTML iconHTML  

    Summary form only given. The diamond-based backward wave oscillator (BWO) provides a miniature, energy efficient, electronically tunable and mass producible signal source in the sub-mm wavelength regime. Fabricated within a shell of chemically vapor deposited (CVD) diamond for mechanical and thermal robustness, the BWO employs a novel biplanar interdigital slow wave circuit. The electron source for the BWO is a Spindt type field emission cathode. The device has been modeled extensively, and preliminary designs of the slow wave circuit, electron gun and collector for operation at 300 and 600 GHz have been completed. Fabrication of the 300 GHz device is in progress. View full abstract»

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  • Seventy percent efficient Ku-band and C-band traveling wave tubes for satellite communications

    Page(s): 266 - 267
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (268 KB) |  | HTML iconHTML  

    Boeing Electron Dynamic Devices, Inc. offers fully qualified, production-ready Ku-band and C-band TWTs for space communications with demonstrated efficiencies exceeding 70%. The C-band 8555HX is a 30-100 W class TWT that has been qualified in a conduction-cooled package with a mass of 790 grams (no leads). The 8555HX performs at better than 70% efficiency across 300 MHz. The Ku-band model, 88150HX, is a 100-150 W class TWT which is qualified in a radiation-cooled package. The first two 88150HX builds both performed at better than 70% efficiency across a 1 GHz operating band. These efficiency improvements are only intended as a stepping stone on the way to better performance. View full abstract»

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  • Development of high power Ka-band and Q-band helix-TWTs

    Page(s): 16 - 17
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (247 KB) |  | HTML iconHTML  

    Boeing EDD continues to make advances in its millimeter-wave helix-TWTs by pushing the CW output power capability and increasing the overall efficiency of Ka-band and Q-band devices for communications. The 8921HP, EDD's latest high power Ka-band TWT model, demonstrates 250 W to 300 W CW output power and 47 % minimum overall efficiency with a two-stage collector over 27.5 GHz-31 GHz. In Q-band, the 8925HP, derived from the current production 120 W Q-Band helix-TWT (8905HP), significantly extends the CW output power capability demonstrating 230 W minimum over 43.5 GHz-45.5 GHz. The beam focusing is improved in both the Ka-band and the Q-band TWT models, with RF beam interception well below 1% of the nominal beam current of 95 mA. The above devices are primarily designed for CW operation but can also be operated in pulsed mode by using the focus electrode to cut-off the beam. The electron gun typically requires a focus electrode voltage of -800 V with respect to the cathode for beam cut-off. View full abstract»

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  • High voltage operation of field emission array cathodes

    Page(s): 152 - 153
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (395 KB) |  | HTML iconHTML  

    The goals of the test are as follows: demonstrate that emission current densities in excess of 100 A/cm2 can be achieved from FEA cathodes in a typical vacuum electron devices; demonstrate that duty factors of interest can be achieved without damage or degradation to the FEA. The near term goal will be to demonstrate CW operation of an FEA cathode at a current emission density in excess of 20 A/cm2. The ultimate goal will be to demonstrate CW operation at the 100 A/cm2 for CCR's W-Band TWT development. This presentation will describe the design of the test vehicle and test setup. The presentation will primarily focus on the test results and their implications for incorporation of FEAs in typical vacuum electron devices. View full abstract»

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  • Simulations of a 1 MW, 700 MHz klystron using MAGIC PIC-code

    Page(s): 124 - 125
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (237 KB) |  | HTML iconHTML  

    A KOMAC (Korea Multipurpose Accelerator Complex) klystron tube operating with a maximum output power of 1 MW at 700 MHz is analyzed by the use of 2-D particle-in-cell code, MAGIC in order to validate the design parameters. View full abstract»

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  • Demonstration of a 95 GHz, 100 kW, CW gyrotron oscillator

    Page(s): 63 - 64
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (251 KB) |  | HTML iconHTML  

    Summary form only given. A program to develop a 100 kW power level, continuous wave (cw), 95 GHz gyrotron oscillator for use in a U.S. military system is currently underway at CPI. To date, three W-band gyrotron oscillators have been constructed and demonstrated. The third of the three gyrotrons developed for the program, which showed significant performance improvements over the first two, demonstrated 115 kW total output power for 43 kV cathode-to-collector voltage, 50 kV total accelerating voltage, and 4.8 A beam current for an efficiency of 56%. Pulses up to 18 minutes in duration, significantly beyond the required 6 minute pulse required by the program, were demonstrated at the 115 kW operating point. View full abstract»

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  • Progress on a gridded electron gun for a sheet beam klystron

    Page(s): 212 - 213
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (407 KB) |  | HTML iconHTML  

    Calabazas Creek Research Inc. (CCR) is developing rectangular, gridded, thermionic dispenser-cathode guns for sheet beam devices. The first application is expected to be klystrons for advanced particle accelerators and colliders. The current generation of accelerators typically use klystrons with a cylindrical beam generated by a Pierce-type electron gun. As RF power is pushed to higher levels, space charge forces in the electron beam limit the amount of current that can be transmitted at a given voltage. The options are to increase the beam voltage, leading to problems with X-ray shielding and modulator and power supply design, or to develop new techniques for lowering the space charge forces in the electron beam. The current development program addresses issues related to beam formation at the emitter surface, design and implementation of shadow and control grids in a rectangular geometry, and the high voltage insulator. View full abstract»

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