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Vacuum Electronics Conference, 2000. Abstracts. International

Date 2-4 May 2000

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  • The future of klystrons

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    Summary form only given, as follows. The klystron is the oldest of the microwave tubes, but continues to be essential to a number of user communities, principally that of experimental physics, which was also responsible for its invention. The advent of traveling-wave tubes and of the transistor has limited the uses of the klystron to applications requiring a high pf/sup 2/ product. For those applications, it remains the amplifier of choice, particularly if cost is considered. The paper describes some new klystron configurations and their potential future. These include multi-beam and sheet-beam klystrons, PPM klystrons, and millimeter-wave klystrons, mass-produced with lithographic techniques. View full abstract»

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  • Development of a high-power klystron for the Spallation Neutron Source

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    Summary form only given. The Spallation Neutron Source (SNS) will provide an intense beam of neutrons for scattering experiments. The SNS will be comprised of an ion source, a 1 GeV H/sup -/ linear accelerator, an accumulator ring, a target for neutron production, and an area for the scattering experiments. It is anticipated that anywhere from 36 high-power klystrons up to 160 lower-power klystrons operating at 805 MHz will be required, depending on the final design. In addition, 7-8 klystrons operating at 402.5 MHz will be required. Characteristics of the 805 MHz klystron are given. View full abstract»

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  • Recent progress in CW and long-pulse klystrons at CPI

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    The need for long-pulse and super-power CW klystrons for particle accelerators has been growing.. The key requirements for these devices are high efficiency and reliability. The authors describe the features of four klystons produced for particle accelerators. View full abstract»

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  • Permanent magnet focused, multi-stage depressed collector klystron amplifiers for satellite communications

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    A new line of high-efficiency multi-stage depressed collector (MSDC) klystron amplifiers has been developed by Communications and Power Industries Microwave Power Products (CPI/MPP) for use in satellite communications and scientific applications market. These klystrons are air-cooled with permanent magnet focusing. The first products are designed to service the satellite uplink and terrestrial repeater markets. MSDC technology for these applications can reduce power consumption by as much as 60%. A general discussion about the benefits of MSDC technology for these applications, as well as two examples of their use, are presented. CPI/MPP has developed the VKU-8891M series klystrons which provide 2.4 kW CW tunable in the frequency range from 17.3 to 18.4 GHz with instantaneous bandwidths up to 85 MHz. The klystron is designed with a 4-stage MSDC which has increased the saturated efficiency of the device from 24% to 40% A detailed discussion of the design, as well as a comparison between simulation and experiment, is presented. CPI/MPP is also developing the VKS-7964M klystron in the frequency range from 2.1 to 2.4 GHz, with instantaneous bandwidths up to 8 MHz. This klystron has a 4-stage MSDC. The simulated efficiency of this klystron approaches 60%. We predict the measured efficiency. A detailed discussion of the design, as well as a comparison between simulation and experiment, is presented. View full abstract»

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  • The klystrino: a high power W-band amplifier

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    High average power millimeter wave sources are being developed in a collaboration between SLAC and CPI. CPI has developed a number of high-power, broadband, millimeter-wave, CCTWT amplifiers. The coupled cavity technology is now approaching the limits for generating power at millimeter wave frequencies. To generate significant increases in power, other technologies need to be considered. At SLAC, compact, lightweight, PPM-focused, klystrons, nicknamed 'klystrinos' are being developed, using lithographic fabrication methods (LIGA). These devices will operate at 100 kW peak power and 1 kW average power at 95 GHz. Two design areas are critical to the success of the klystrino. First is the electron beam optics and beam focusing. A beam tester is being built to evaluate the electron gun and the PPM focusing system. Results of the beam tests are presented. CPI has analyzed the electron gun and is investigating the addition of a control electrode for improved modulator efficiency. The second significant design area is the modeling of the klystrino. The combination of the rectangular LIGA structure and the multiple gap output section make modeling the klystrino difficult. MAFIA and MAGIC have been used to develop an equivalent 2D model of the 3D LIGA circuit. Thermal capacity of the circuit is also investigated at CPI using the ANSYS 3D FEA code. The analysis included both the expected RF losses and beam interception. The calculations include both transient response and steady state. The thermal analysis is used to predict the maximum allowable beam interception and duty cycle that the circuit can withstand without major problems. View full abstract»

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  • Crossed-field devices: where are we and options for the future

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    Summary form only given, as follows. The industry sale of vacuum electron devices worldwide during 1999 was approximately $488M. The share of this in the crossed-field device (CFD) industry was about $105M, or 21%. The US industry sale of vacuum electron devices during the same time was around $251M with approximately $34M, or 14%, in the CFD industry. There are currently two dominant manufacturers of CFDs in the US and one additional dominant company in the world market. The US industrial sales trend in the recent past for CFDs has been a downward slope. This presentation identifies two concerns facing the US CFD industry and probably the world wide industry: (1) A large number of different organizations (especially in the US Department of Defense) that purchase CFDs, and (2) the limited vertical integration into microwave systems houses by the CFD industry. Both of these concerns are discussed and some suggestions for the industry presented. View full abstract»

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  • Development and production of the SFD-268 CFA for the Aegis AN/SPY-1D(V) radar

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    The SFD-268 is a high duty, low noise, low jitter version of the CFA used in the AN/SPY-1 radar. It has been developed in a cooperative effort with NSWC Crane. The objective of this program was to increase CFA performance while maintaining the same form, fit, function, and life as the previous version of this CFA, known as the SFD-262. This paper describes the design improvements and development process of the SFD-268 CFA. Opportunities for future design enhancements are also discussed. View full abstract»

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  • The structure of noise in crossed-field amplifiers

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    Summary form only given, as follows. The results of a series of detailed tests on a pulsed forward wave CFA show that its noise output is highly structured in the frequency domain. The noise structure results from the CFA acting as a delay-line oscillator while it is amplifying the normal drive signal. The CFA oscillations occur at frequencies that are multiples of the reciprocal group delay through the tube. Typical spectrograms of the structured noise are shown as plots of spectral amplitudes as a function of time and frequency. They illustrate the following features. The noise is concentrated in a series of lines evenly spaced around the drive frequency. The lines are noisy in amplitude and phase. The locations of noise lines as the drive frequency is tuned over a few hundred megahertz is shown. The locations of the lines are constant as the drive frequency is changed. A diagram of a CFA model is shown. To achieve a low noise CFA, the conditions necessary for causing delay line oscillations must be removed. This requires that the electronic (active) and electric feedback (passive) paths have sufficient attenuation to prevent oscillation over the entire band where the CFA has small signal gain. The parameters of these feedback paths require considerable attention during the initial design of the CFA. View full abstract»

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  • Cold cathodes for CFAs

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    Summary form only given. Application of cold cathode technology for use in crossed-field amplifiers (CFAs) has been limited by the characteristics of the materials, usually platinum (Pt) or beryllium (Be/BeO), used as the emitter. A case in point is the L-4717, used as the second stage amplifier (baby Amplitron) in the SPS-48-C/E transmitters. This tube, which uses a thermionic emitter, is characterized by short life and high noise. Attempts to use a platinum emitter were not successful because of unacceptable mode boundary separation at rated drive. Similarly, beryllium was found to be unsuitable because the emitter was too active, causing lower mode boundary interference at the rated operating current. A metal alloy cathode (MAC) material, palladium/ barium (Pd/Ba), was evaluated for use in an experimental L-4717 CFA. This tube, using a standard body, and Pd/Ba material developed at Istok, Moscow, Russia, is designated L-4870. Test results are very encouraging. Two tubes demonstrated satisfactory operation in the SPS-48-C and SPS-48-E test beds at ITT Gilfillan, Van Nuys, CA. One of these is currently under evaluation in the SPS-48-E transmitter at Dam Neck, VA. A third tube has been used as an in-plant driver in the Litton SPS-48-E test set. The Pd/Ba material has been evaluated in other experimental tubes to determine whether it is a suitable replacement for beryllium, again with promising results. Both the L-4806 (TPS-63) and the L-4808 (AN/SPY I-B/D) were equipped with Pd/Ba emitters and showed satisfactory operating characteristics. This paper presents test results and gives a description of Pd/Ba emitter assembly techniques. View full abstract»

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  • A new way reduce control electrode current in DC operated CFAs

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    This paper describes a new method to reduce control electrode (CE) current in DC operated CFAs. The method-which has a patent pending-involves the introduction of an auxiliary electrode behind the traditional CE. When the gap between the cathode and CE is properly designed, current in the rotating hub of the CFA can be diverted into this gap and collected on the auxiliary electrode-which is at anode potential. We have demonstrated that up to 50% of the current that would have normally been collected on the CE, can be diverted and collected on the auxiliary electrode-substantially reducing the CE current. Since the auxiliary electrode is at ground or anode potential, no additional power supplies are required to operate the CFA. There are two embodiments of this idea that have been tested at CPI. In the first, the gap between the auxiliary electrode and the cathode forms a cutoff magnetron so that all electrons entering the gap get collected on the auxiliary electrode. In the second embodiment, the gap is not cutoff but the gap is tapered to produce an axial electric field component that pulls electrons in an axial direction, parallel to the magnetic lines, and into the auxiliary electrode. This second method is required if a cutoff gap would be too small for reliable DC voltage standoff. View full abstract»

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  • Development of ultra-linear traveling wave tubes for telecommunications applications

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    Traveling wave tubes (TWT) intended for telecommunications applications are increasingly required to have high linearity, good intermodulation performance, and high power levels; especially for use as modern multi-carrier power amplifiers (MCPA) and in systems that use digital signal encryption. The linearity of the TWT is greatly improved by optimization of the taper of the helix circuit to reduce the gain compression and phase shift of the output signal as the drive level is increased, and by operation of the tube significantly backed off from saturation in the linear region of the AM/AM and AM/PM transfer curves. However, backed off operation at a given output power level requires increased beam current and power handling capabilities compared to a design operating at saturation, and also results in a greatly reduced efficiency of the TWT. At Hughes, we have developed L-band and S-band TWTs for telecommunication applications that provide good intermodulation performance and high efficiency compared to solid-state amplifiers. The L-band model TWT normally operates 8 dB backed off from 1600 W at saturation, and produces over 250 W of continuous output power with an 8-tone continuous-random-phase signal intermodulation level of -28 dBc and an efficiency of over 25%. The S-band model TWT normally operates 6 dB backed off from 2000 W at saturation, and has produced over 500 W of continuous output power at an efficiency of over 35%. View full abstract»

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  • A high power TWT for military satcom

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    In 1994, a contract was received for the Heavy Terminal, (HT), Program. The award was from the U.S. Army / Harris Corporation to build a 2 1/4 kW X-band helix vacuum electron device (VED), to be used in a military satellite communications terminal. The VED needed to be of an air-cooled variety. The contract was awarded as a result of competing with other suppliers of VEDs and successfully qualifying the unit. A second hurdle was to qualify the VED in the MCL INC. power supply to be sure the VED and the power supply were compatible. The qualifications for the VED came under two headings: 1) electrical tests, and 2) environmental tests. These are discussed. The device lifetime is also discussed. View full abstract»

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  • 45 GHz TWT-recent advancements

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    Summary form only given, as follows. The latest advancements at Hughes Electron Dynamics regarding the development of 45 GHz traveling wave tubes (TWTs) are presented. The major topics are higher power operation, backward wave suppression, thermal management, and related design issues. TWT performance is shown. These TWTs are designed to produce in excess of 120 watts of CW RF power across the frequency band of 43.5 to 45.5 GHz. The basic design incorporates a BeO supported helix with low loss coating, heat shrunk into a conventional pole piece barrel, and focused with PPM magnets. The electron gun operates at 13.5 kV, with 100 mA of beam current. The gun has an isolated focus electrode and a positive anode. The collector is now a two-stage design. The package is conduction cooled. View full abstract»

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  • 94 GHz TWT for military radar applications

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    Summary form only given, as follows. For future military radar applications high frequency, light weight TWTs become more and more important. To cover this market, TTE (Thomson Tubes Electroniques) started the development of a 94 GHz TWT. The goal of this program was a TWT (double comb delay line structure) in the 94 GHz frequency range with an instantaneous bandwidth greater 500 MHz (tunable within 1 GHz) and an output peak power greater 200 W in the center of the band (150 W over the band) for a duty cycle of max. 10%. In a second mode (different operating point) the goal for the output power was more than 100 W peak over the band and a duty cycle of max. 20%. Further parameters were the delay line voltage below 22 kV, a grid voltage swing of max. 400 V and mass smaller 1300 grams. The technical base of this program was TTE's experience in development and production of TWTs in the 30, 35 and 60 GHz frequency range. From there we started with the modification and adaptation of the standard technologies and TWT design, to be applicable for the special requirements in the 94 GHz range, concerning the small mechanical dimensions and allowed tolerances. The basic design and main test results of the 94 GHz TWT are the content of this paper. View full abstract»

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  • Wide bandwidth, high average power EIKs drive new radar concepts

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    Millimeter wave radar and communications capability can be significantly enhanced using improvements to the extended interaction klystron (EIK). This presentation describes the performance resulting from various programs undertaken at CPI (Communications & Power Industries) to increase the bandwidth and power capability of the EIK. This presentation describes the design simulation and corresponding performance results at various frequencies from 27 GHz to 220 GHz. View full abstract»

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  • Experience and application of high power RF sources at the Frascati Laboratory particle accelerator DA/spl Phi/NE

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    After a brief description of the particle accelerators at Frascati National Laboratory, the paper discusses the use of klystrons as power sources. View full abstract»

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  • 700 MHz HOM-IOT: design and first test results

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    IOTs (inductive output tubes) are relatively novel vacuum electron devices that have established their position as reliable and highly efficient UHF amplifiers, predominantly in the television transmitter service. In this application, they reach output power levels equivalent to about 50 kW CW. Scientific applications, like proton accelerators, require UHF amplifiers with considerably higher output power capability. Super power klystrons are available for this service; however, IOTs offer some advantages over klystrons in terms of efficiency: higher basic efficiency; power regulation possible at full output power (no saturation); inconsequential drop of efficiency at reduced output power. Higher order mode IOTs (IOM-IOTs) possess the added advantage of lower operational voltage and smaller size. Based on these expectations, a development of a 700 MHz HOM-IOT, sponsored by the Los Alamos National Laboratory, has been carried out by CPI. The development attention was paid to the suppression of both unwanted modes and stray radiation from the space between electron gun and body. Focusing the electron beam was another issue that required high modeling effort. View full abstract»

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  • Performance characteristics of an MSDC IOT amplifier

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    CPI EIMAC has provided inductive output tube (IOT) amplifier systems for the television broadcast market since 1988. The key performance advantage IOT amplifiers achieve over other high power UHF amplifier technologies are superior DC to RF power conversion efficiency. Efforts continue to further improve the power conversion efficiency of IOT amplifiers by employing multi-staged depressed collector (MSDC) technology. EIMAC has developed such an amplifier based on the well established K2D60 IOT slated for the digital television service. The MSDC collector design utilizes principles evolved from the VKP-7990 MSDC klystron development program. The purpose of this proposed paper is to illustrate EIMAC's development efforts and provide test performance results of a MSDC IOT amplifier (K3D60). View full abstract»

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  • Ka-band klystron amplifiers for satellite communications and scientific applications

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    A new line of Ka-band klystron amplifiers is under development at the Microwave Power Products Division of Communications and Power Industries, Inc. (CPI/MPP), for use in industrial and scientific applications, as well as satellite communications. These amplifiers are air-cooled, permanent magnet focused and will be both fixed (VKA-7934A) and channel tuned (VKA-7934T). A detailed description of both development efforts is discussed. View full abstract»

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  • An extended interaction oscillator based on a complex resonant structure

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    Efficiency enhancement was experimentally demonstrated for a Ku-band extended interaction oscillator which features a five-gap interaction cavity with a coaxial section placed between the first and second gaps for ballistic bunching of electrons. Oscillation power of 2.2 kW at 30% electronic efficiency and 41% total efficiency with a depressed collector was achieved. View full abstract»

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  • Three dimensional simulation of cross-field devices and amplifiers

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    Used the electromagnetic-PIC simulation code MAGIC3D to perform simulations on several cross-field devices. These include an industrial heating magnetron, a high-power rising sun magnetron, the superpower Amplitron, and the baby Amplitron. The purpose of this research effort was to develop simulation procedures and techniques that give good qualitative and quantitative measurements of the performance of this class of device. The process has included ensuring that the simulation methods yield the type of engineering measurement that is useful to the designer and production engineer as well as the researcher interested in the more fundamental aspects of the physics. View full abstract»

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  • A time-domain MTL model of the AEGIS CFA circuit for use in the MASK simulation program

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    A time-domain Multiconductor Transmission Line (MTL/sup 2/) model of the stub-supported helix circuit used in the AEGIS CFA has been developed. The stub-supported helix circuit is also commonly employed by emitting sole CFAs operating in S, C, and X frequency bands-so the model has broad applicability. Currently, the circuit model used in MASK is a lumped element /spl pi/ network-first used for CFA simulation by Dombrowski. The /spl pi/ circuit model can match the phase shift per section and the slope of the phase curve at one frequency but can not mimic the circuit dispersion over the entire pass band of the anode circuit. The new MTL circuit model for the stub-supported helix is constructed using elements that have one-to-one correspondence with the physical anode circuit. Consequently, the pass-band characteristic of the MTL model can match the measured circuit dispersion quite closely. In addition, the impedance of the MTL model is also more accurate since the characteristic values used by the model are calculated from the actual circuit cross section geometries. Because of these improvements, it is expected that use of this model in MASK will enhance our ability to predict the /spl pi/ mode transition current and to estimate spurious frequency generation. The time-domain algorithm is advanced using a time-centered leap frog scheme which is consistent with the advancement algorithm used in MASK. The new circuit has been implemented in MASK and some results are presented. View full abstract»

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  • Transient and steady state phase similarity of the AEGIS AN/SPY-1 crossed-field amplifier (CFA) as a function of duty cycle

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    The CFA duty cycle value controls the heating and cooling of the anode vanes, leading to thermal expansion and contraction, and thereby impacting the phase characteristic of the device. CFA phase similarity with respect to duty changes are therefore important for CFAs that are installed in radar systems that use rapid duty cycle changes. Because the AEGIS AN/SPY-1 Radar System operates using rapid duty cycle changes, the AEGIS AN/SPY-1 CFA must maintain (1) transient phase similarity, and (2) steady state phase similarity, both as a function of duty cycle. Until recently, test equipment limitations prevented the transient phase similarity data from being accurately collected. Engineering testing was conducted at Naval Surface Warfare Center to determine the phase similarity characteristics of the AEGIS CFA with respect to duty cycle changes. A sample of AEGIS AN/SPY-1 CFAs were characterized using a new test method, and the data was analyzed to determine how much the phase similarity changed in the device with changes in duty cycle. This paper describes the test equipment used, the testing procedure used, along with the phase similarity data with respect to duty cycle, for the AEGIS AN/SPY-1 CFA. It is believed that this is the first time instantaneous phase response to duty cycle testing has ever been done. View full abstract»

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  • Recent improvements in injection locked magnetrons

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    CPI-Beverly Microwave Division has been engaged in a program to improve the performance of injection locked magnetrons used in a missile seeker application. The principal objectives of this program were: increasing magnetron reliability by decreasing power density inside the device; increasing device lifetime, and ruggedizing device for use in high vibration environments. The injection locked magnetron (ILM) pair developed produces over 800 W peak of coherent power at Ku-band. The average power is high at 100 W which leads to high power densities in this small device. The instantaneous locking bandwidth is around 0.7% for both magnetrons in the chain. View full abstract»

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