The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
Igor Syratchev - One of the best experts on this subject based on the ideXlab platform.
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modeling of coupled cell output structures for the Klystrons
IEEE Transactions on Electron Devices, 2019Co-Authors: Igor SyratchevAbstract:High-frequency, high-power Klystrons proved to be significant for application in compact particle accelerators, high-resolution radars, and fast data communication systems. As most of the linear beam devices, the performance of the klystron deteriorates progressively with an increasing operating frequency due to the reduction of individual RF cavity impedances. Coupled cell structures can alleviate such degradation by extending the beam–wave interaction region. The accurate simulation of the klystron with the coupled cell structure relies on the resources and the time-consuming particle-in-cell (PIC) codes. To speed up the klystron design process, the coupled-mode theory was carefully reviewed and extended to facilitate the calculation of the complex spectra of the arbitrarily coupled cavity system and its interaction with the bunched electron beam. These new methods were implemented in the large signal klystron simulation code KlyC. The design and optimization of the Ku -band, low-voltage klystron is explained as a demonstration of the new technique’s effectiveness. The KlyC simulations have been thoroughly benchmarked with the CST PIC code and both codes showed a good (within 1%) agreement, while KlyC is significantly (about 100 times) faster.
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klyc 1 5 d large signal simulation code for Klystrons
IEEE Transactions on Plasma Science, 2019Co-Authors: Igor SyratchevAbstract:The High Efficiency International Klystron Activity (HEIKA) was initiated at CERN in 2014 to evaluate and develop new klystron bunching technologies for high-efficiency Klystrons in application to the large-scale scientific projects such as the Compact Linear Collider (CLIC) and the Future Circular Collider (FCC). The success of such development strongly depends on the availability of the specialized klystron computer codes. Unfortunately, the accurate and efficient 2-D large-signal codes are proprietary and are not freely available to the wide klystron community. The new 1.5-D klystron code called KlyC has been developed as an attempt to bridge the gap between fast, but approximate 1-D models and time/resources consuming particle-in-cell (PIC) codes. KlyC simulates the specific physical processes such as the current emission from the metal surface, the space charge depression along the klystron, and the residual RF current modulation of the spent beam. KlyC internal eigenmode solver allows fast simulations of the 2-D complex electromagnetic (EM) field in the axis-symmetrical cavity with the arbitrary cavity profile. The internal KlyC optimizer module can help the designer to speed up the klystron development process. In this paper, the theoretical model, general review of the code performance, and benchmarking between KlyC, AJDisk/1-D, PIC code MAGIC/2-D, and CST/3-D are presented using FCC Klystrons as an example.
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toward high power Klystrons with rf power conversion efficiency on the order of 90
IEEE Transactions on Electron Devices, 2015Co-Authors: Andrey Yu Baikov, Chiara Marrelli, Igor SyratchevAbstract:The increase in efficiency of RF power generation for future large accelerators is considered a high priority issue. The vast majority of the existing commercial high-power RF Klystrons operates in the electronic efficiency range between 40% and 55%. Only a few Klystrons available on the market are capable of operating with 65% efficiency or above. In this paper, a new method to achieve 90% RF power conversion efficiency in a klystron amplifier is presented. The essential part of this method is a new bunching technique—bunching with bunch core oscillations. Computer simulations confirm that the RF production efficiency above 90% can be reached with this new bunching method. The results of a preliminary study of an $L$ -band, 20-MW peak RF power multibeam klystron for Compact Linear Collider with the efficiency above 85% are presented.
Won Namkung - One of the best experts on this subject based on the ideXlab platform.
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Preliminary design of high-efficiency klystron for pohang accelerator laboratory
IPAC 2016 - Proceedings of the 7th International Particle Accelerator Conference, 2016Co-Authors: S.-j. Park, Y.d. Joo, Won Namkung, M. H. Cho, K. R. Kim, C.d. Park, J Y Choi, J. H. Hwang, T.s. SeongAbstract:Copyright © 2016 CC-BY-3.0 and by the respective authors. Klystrons for particle accelerators are typically designed to have narrow bandwidths with the centre frequencies ranging from several hundred (e.g., 350) MHz to X-band (11.424 GHz). Output powers are from several tens of kW to ∼1 MW for CW Klystrons and ∼100 MW for pulsed ones. The narrow-bandwidth requirement has enabled them to provide high gain (typically 40-50 dB) which greatly simplifies the RF drive system. Recently, especially for large-scale accelerator facilities, the klystron efficiency has become one of the most demanding issues. This is because electricity cost occupies a great portion of their operating budgets and the klystron efficiency is one of the important factors determining the electricity consumption of the whole accelerator system. In this regard, we have designed a high-efficiency klystron for use in the PLS-II and PAL XFEL at PAL. The basic scheme is to re-design the cavity system to include multi-cell output cavity. In this article, we report on our preliminary design work to determine major cavity parameters including cell frequencies, inter-cell distances, and coupling to external circuits (coupling beta).
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Stability Analysis of C-band 500-kW Klystron with Multi-cell Output cavity
arXiv preprint arXiv, 2016Co-Authors: Jihyun Hwang, Sung Ju Park, Won NamkungAbstract:© 2016, The Korean Physical Society.A prototype 5-GHz 500-kW CW klystron (model E3762 provided by Toshiba Electron Tubes & Devices Co. Ltd.) has been operating as the RF source for the lower hybrid current drive (LHCD) system in the KSTAR tokamak. A cavity design study is being carried out with a simulation code based on the main klystron’s operation parameters in order to investigate how the efficiency of the 5-GHz 500-kW CW klystron prototype can be enhanced. This is being done by simulating the klystron’s performances for various cavity parameters, including the number of cavities, the inter-cavity distance, and the cavity’s tuning frequencies. The simulation has been done with the FCI (field charge interaction) code aided by a matlab script for scanning input parameters. The initial set of scan parameters was obtained by benchmarking the E3762 klystron, and we are able to obtain optimized design parameters for a cavity system with better efficiency by adopting a multi-cell output cavity. However, the multi-cell output cavity is prone to self-oscillations due to the prolonged (several half RF periods) beam-field interaction along its multiple gaps. We have checked the feasibility of the optimization by evaluating the stability of the output cavity system. The stability is given by the ratio of a beam-loading conductance to the circuit conductance.
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200 MW modulator for 80 MW klystron in PLS electron linac
IEEE International Pulsed Power Conference - Digest of Technical Papers, 1993Co-Authors: J S Oh, S.h. Nam, M. H. Cho, S.s Park, Won NamkungAbstract:The Pohang Light Source (PLS) 2.0 GeV electron linac employs 80 MW Klystrons with matching 200 MW modulators as RF sources. To gain a good stability in the electron beam energy, fine regulations in the klystron beam voltage and thus RF output phase are required. For the good energy stability, a pulse-to-pulse klystron beam voltage amplitude variation of less than ±0.5% and its pulse-top flatness of less than ±0.5% are required. The required regulation is achieved by using a SCR phase controller with active feedbacks in a high voltage (HV) DC power supply and also with a de-Q'ing circuit in the modulator charging network. A klystron beam voltage is stabilized to ±0.20%. The ±0.43% flatness of pulse is tuned by variable inductors of a pulse forming network (PFN).
Claudio Paoloni - One of the best experts on this subject based on the ideXlab platform.
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Periodically allocated reentrant cavity klystron
IEEE Transactions on Electron Devices, 2014Co-Authors: Claudio PaoloniAbstract:A novel klystron topology is proposed to overcome the frequency limits of conventional Klystrons. In contrast to the conventional klystron approach, where the distance between the cavities placed along the drift tube is a function of the plasma frequency wavelength, the new configuration exploits the interaction property of a sequence of numerous cavities allocated at fixed short distance along the drift tube. The remarkable advantage is to obtain good performance by the use of cavities with low R/Q, as in the case of high-frequency and high-order mode operation. A frequency operation up to 136 GHz with 20-dB gain and an output power up to a few tens of watts are demonstrated. The promising performance of the periodically allocated reentrant cavity klystron makes it attractive for millimeter-wave applications.
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Micro reentrant cavity for 100 GHz klystron
2012 IEEE 13th International Vacuum Electronics Conference IVEC 2012, 2012Co-Authors: Mauro Mineo, Claudio PaoloniAbstract:A micro reentrant rectangular cavity for Klystrons operating at 100 GHz is proposed. The cavity is designed for higher order mode operation. This permits relative larger dimensions compatible with a realization by mechanical micromachining or high-aspect ratio lithographic fabrication process. Three-dimensional electromagnetic simulations demonstrate the properties of the cavity suitable to be used in a 100 GHz klystron.
G Caryotakis - One of the best experts on this subject based on the ideXlab platform.
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latest results in slac 75 mw ppm Klystrons
Prepared for 7th Workshop on High Energy Density and High Power RF Kalamata Greece 13-17 Jun 2005, 2006Co-Authors: Daryl Sprehn, Erik Jongewaard, L. Le Laurent, G Caryotakis, A Haase, C Pearson, R PhillipsAbstract:75 MW X-band Klystrons utilizing Periodic Permanent Magnet (PPM) focusing have been undergoing design, fabrication and testing at the Stanford Linear Accelerator Center (SLAC) for almost nine years. The klystron development has been geared toward realizing the necessary components for the construction of the Next Linear Collider (NLC). The PPM devices built to date which fit this class of operation consist of a variety of 50 MW and 75 MW devices constructed by SLAC, KEK (Tsukuba, Japan) and industry. All these tubes follow from the successful SLAC design of a 50 MW PPM klystron in 1996. In 2004 the latest two Klystrons were constructed and tested with preliminary results reported at EPAC2004. The first of these two devices was tested to the full NLC specifications of 75 MW, 1.6 microseconds pulse length, and 120 Hz. This 14.4 kW average power operation came with a tube efficiency >50%. The most recent testing of these last two devices will be presented here. Design and manufacturing issues of the latest klystron, due to be tested by the Fall of 2005, are also discussed.
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high power Klystrons theory and practice at the stanford linear accelerator centerpart i
2004Co-Authors: G CaryotakisAbstract:This is Part I of a two-part report on design and manufacturing methods used at SLAC to produce accelerator Klystrons. Chapter 1 begins with the history and applications for Klystrons, in both of which Stanford University was extensively involved. The remaining chapters review the theory of klystron operation, derive the principal formulae used in their design, and discuss the assumptions that they involve. These formulae are subsequently used in small-signal calculations of the frequency response of a particular klystron, whose performance is also simulated by two different computer codes. The results of calculations and simulations are compared to the actual performance of the klystron.
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the future of Klystrons
International Vacuum Electronics Conference, 2000Co-Authors: G CaryotakisAbstract: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.
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periodic permanent magnet development for linear collider x band Klystrons
High energy density microwaves, 1999Co-Authors: Daryl Sprehn, Erik Jongewaard, G Caryotakis, R PhillipsAbstract:The Stanford Linear Accelerator Center (SLAC) klystron group is currently designing, fabricating and testing 11.424 GHz Klystrons with peak output powers from 50 to 75 MW at 1 to 2 μs rf pulsewidths as part of an effort to realize components necessary for the construction of the Next Linear Collider (NLC). In order to eliminate the projected operational-year energy bill for klystron solenoids, Periodic Permanent Magnet (PPM) focusing has been employed on our latest X-band klystron designs. A PPM beam tester has operated at the same repetition rate, voltage and average beam power required for a 75-MW NLC klystron. Prototype 50 and 75-MW PPM Klystrons were built and tested during 1996 and 1997 which operate from 50 to 70 MW at efficiencies greater than 55%. Construction and testing of 75-MW research Klystrons will continue while the design and reliability is perfected. This paper will discuss the design of these PPM Klystrons and the results of testing to date along with future plans for the development of ...
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w band micro fabricated modular Klystrons
Optical Science Engineering and Instrumentation '97, 1997Co-Authors: G Caryotakis, Erik Jongewaard, Glenn Scheitrum, R L Kustom, N C Luhmann, Michael Petelin, A. VlieksAbstract:Conventional CW millimeter amplifiers (coupled-cavity TWTs or gyro-Klystrons) are limited in power by the maximum current hat can be accommodated in a single beam. Cathode current density, beam optics, and the magnetic field necessary to confine the beam, combine to limit beam current and add cost and bulk to the device. If the microwave source is designed as a pulsed klystron operating at a high voltage, larger lateral as well as axial dimensions can be employed. Beam optics become easier and permanent magnet periodic focusing is possible. A higher efficiency also results, because of the low perveance. A number of Klystrons can then be fabricated on single substrate, using a deep- etch lithography technique. They can be water-cooled individually, and operated in parallel. Several such modules can be stacked to form a klystron `brick,' requiring a relatively low voltage for the peak and average power produced. The `brick' can be provided with a single output, or with individual, spatially-combined radiators. The design of a 4 X 10 X 1.5-inch module producing 500 kW peak, 500 W average at 91 GHz, and operating at 120 kV, 10 A, will be described.
S. Fukuda - One of the best experts on this subject based on the ideXlab platform.
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DEVELOPMENT OF THE Klystrons FOR THE HIGH INTENSITY
2020Co-Authors: A. Yano, S. FukudaAbstract:The linac of High Intensity Proton Accelerator Fac ility requires 324MHz Klystrons for the acceleration of less than 200MeV and 972MHz Klystrons for the acceleration from 200MeV to 400MeV. Toshiba has developed a 324MHz klystron (E3740) in collaboration with KEK and manufactured prototypes of the E3740 klystron. In initial test, we confirmed our design of an electron gun and a window, which are the key points of the klystron development. This klystron was tested at the test facility of KEK and showed performance of an output power of 2.5MW at a beam voltage of 106.6kV with an efficiency of 52%. The first tube of the 972MHz klystron (E3766) was completed. This klystron is now under testing at the new test facility of JAERI. At preliminary test, this klystron produced an output power more than 2MW at a beam voltage of 97kV with an efficiency of 52%.
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Recent high-power klystron status at KEK
Journal of Communications Technology and Electronics, 2020Co-Authors: S. FukudaAbstract:At the High-Energy Accelerator Research Organization in Japan (KEK), there are three major projects: KEKB, the Japanese Hadron Facility (JHF), and the Japanese Linear Collider (JLC) project. All of these projects include a linear accelerator; high-power Klystrons are key issues in their development. In the KEKB project, 59 S-band high-power pulsed Klystrons are used and are now under commission. These S-band tubes were developed from previous 30-MW Klystrons and have produced 50-60 MW. JHF is a future plan of KEK and has a 200-MeV proton linear accelerator. We are now developing a UHF klystron (frequency of 324 MHz, peak power of 3 MW, and RF pulse duration of 650 microseconds). In the JLC project, a collaborative project between KEK and the Protvino Branch of the Institute of Nuclear Physics, X-band high-power Klystrons have been developed. Recently, 2D and 3D MAGIC codes have enabled us to design Klystrons more realistically. This report describes these three Klystrons.
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focusing system with permanent magnets for Klystrons
IEEE Transactions on Applied Superconductivity, 2014Co-Authors: Yasuhiro Fuwa, Shinichiro Michizono, Y Iwashita, H Tongu, Ryunosuke Kitahara, Toshihiro Matsumoto, S. FukudaAbstract:Applying permanent magnet technology to beam focusing in Klystrons can reduce power consumption and increase reliability. These features benefit a variety of applications especially for large facilities that use a large number of Klystrons such as the International Linear Collider. The low magnetic field needed for the purpose allows us to use inexpensive ferrite magnets instead of rare earth magnets. In order to evaluate the feasibility of such a focusing system with ferrite magnets, a test model for 750 kW L-band klystron was constructed. As a result of the power test, we attained 94% of the output power compared to an electromagnet.
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rf windows used at s band pulsed Klystrons in the kek linac
Vacuum, 1996Co-Authors: Shinichiro Michizono, K Hayashi, S. Fukuda, Yoshio Saito, S AnamiAbstract:Abstract The breakdown of the alumina RF-windows used in high-power Klystrons is one of the most serious problems in the development of Klystrons. This breakdown results from excess heating of alumina due to multipactor bombardment and/or localized RF dissipation. In order to develop RF windows having high durability for the KEKB Klystrons, several kinds of alumina ceramics are being examined, and the breakdown mechanism of RF windows are being considered. An improved RF window installed in a KEKB klystron is also being tested.