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ABSTRACT: A compact periodic permanent magnet focused 9290 MHz klystron is described that produces 2.7 MW of output power with 52 dB of gain and 43% efficiency. Three klystrons have been manufactured that exhibited a high degree of repeatability and robustness with all meeting the performance requirements. The goal of a first-time-through design success was met through the use of extensive multidimensional modeling of all aspects of the klystron. Agreement between simulated and measured performance was very good.
IEEE Transactions on Plasma Science 07/2010; · 1.17 Impact Factor
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ABSTRACT: Communications and Power Industries, Inc., has designed and manufactured two versions of a 10-MW-peak high-efficiency multiple-beam klystron (MBK) operating at 1300 MHz. This type of klystron is favored for large particle accelerator projects such as the European X-ray Free-Electron Laser at the Deutsches Elektronen Synchrotron (DESY). Two klystrons have been made for DESY. The first-generation MBK was a vertically oriented prototype using a six-cavity design with higher order mode input and output cavities and conventional intermediate cavities. For cost and performance reasons, the second-generation MBK, designated VKL-8301B, utilized seven coaxial fundamental-mode cavities and is an “industrialized” horizontally oriented klystron. The klystron was designed and optimized using state-of-the-art multidimensional design codes to ensure that all performance requirements are exceeded. Agreement between the simulated and measured performances is good. The VKL-8301B prototype achieved a peak saturated RF output power of 10.4 MW and 67.8% efficiency. The data were measured at the full 1.5% duty and with 1.5-ms pulse width. The klystron satisfied all required operating conditions, including stable operation into an output mismatch of 1.2:1 voltage standing wave ratio at various phases. The prototype has been shipped to DESY and has been successfully tested by a customer.
IEEE Transactions on Plasma Science 07/2010; · 1.17 Impact Factor
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T. Habermann,
A. Balkcum,
R. Begum,
H. Bohlen,
M. Cattelino,
E. Cesca,
L. Cox,
E. Eisen,
S. Forrest,
D. Gajaria,
T. Kimura,
J. Ramirez-Aldana,
A. Staprans, B. Stockwell,
L. Zitelli
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ABSTRACT: Large particle accelerator projects like the European X-ray Free Electron LASER (XFEL), which is under construction at DESY in Hamburg (Germany), or like the planned International Linear Collider (ILC) favor MBKs for their ability to generate high rf output powers at moderate electron beam energies. For the XFEL, Deutsches Electronen Synchrotron (DESY) ordered a prototype of a horizontally oriented, high-power MBK operating at 1300 MHz. This is CPGammas second generation 10 MW, L-band MBK, designated the VKL-8301B. The klystron is required to provide at least 65% efficiency at 10 MW peak rf output and more than 3 MHz instantaneous -l dB bandwidth. Average power and rf pulse length are 150 kW and 1.5 ms, respectively. Our design uses six off-axis electron beams for low cathode current density and thus longer cathode life. For the rf cavities we are utilizing fundamental-mode ring resonators. This ensures sufficient beam separation while still keeping the overall diameter of the device small in order to reduce cost. A more in-depth report on our design process and the tools we used was presented at the 2008 ICOPS. At the time of submission of this paper, initial rf hot test data were taken at reduced duty and pulse width while operating into well-matched output loads. At 0.42% rf duty, a peak rf output power as high as 11.2 MW was achieved, which corresponds to a 74% efficiency. The electron beam interception at and close to saturation was fairly high. Preliminary measurements of body power and the high efficiency indicate that mostly low-energy electrons past the output cavity gaps are involved in the klystron body interception in that operating condition. Initial optimization of the electromagnet for lower interception resulted in a 70% reduction of the rf body current, but this was accompanied by a noticeable drop in rf output power, efficiency (down to 67%) and gain. The klystron performance was stable for all operating conditions encountered so far. Further optim-
ization of the magnetic field balance still has to be carried out for low body current and high efficiency at all required operating conditions, including operation into an output mismatch up to 1.2:1 VSWR. A more complete set of data taken after optimization and tuning will be presented at the conference.
Plasma Science - Abstracts, 2009. ICOPS 2009. IEEE International Conference on; 07/2009
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T. Habermann,
A. Balkcum,
R. Begum,
H. Bohlen,
M. Cattelino,
E. Cesca,
L. Cox,
E. Eisen,
S. Forrest,
D. Gajaria,
T. Kimura,
J. Ramirez-Aldana,
A. Staprans, B. Stockwell,
L. Zitelli
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ABSTRACT: CPI has designed and is currently in the process of building a prototype of a horizontally oriented, ges10 MW, ges65% efficiency multiple beam klystron (MBK) operating at 1300 MHz. The klystron, designated the VKL-8301B, was ordered by DESY for the European XFEL. The klystron was designed using of sate-of-the-art multi-dimensional design codes to ensure that all performance requirements are exceeded. Initial rf hot test data at reduced duty and pulse width produced a peak saturated rf output power in excess of 11 MW and 70% efficiency, which was however accompanied by high beam interception. Operation at full duty and pulse width as well as adjustment of the focusing and retuning the cavity frequencies impacted output power and efficiency. A compromise was found to satisfy all required operating conditions, including operation into a higher output mismatch. Complete test results will be presented at the conference.
Vacuum Electronics Conference, 2009. IVEC '09. IEEE International; 05/2009
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A. Balkcum,
R. Begum,
M. Cattelino,
L. Cox,
S. Forrest,
F. Friedlander,
L. Roeder,
A. Staprans, B. Stockwell,
C. Wu,
L. Zitelli
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ABSTRACT: PPM focusing has been used in a 2.5 MW, 9300 MHz klystron. The design will be discussed and test results for three klystrons presented.
Vacuum Electronics Conference, 2009. IVEC '09. IEEE International; 05/2009
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T. Habermann,
A. Balkcum,
R. Begum,
H. Bohlen,
M. Cattelino,
E. Cesca,
L. Cox,
E. Eisen,
S. Forrest,
D. Gajaria,
A. Staprans, B. Stockwell,
L. Zitelli
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ABSTRACT: CPI's second generation, 10 MW, 1300 MHz multiple beam klystron (MBK), designated the VKL-8301B, has been developed and is being built for the European X-ray free electron laser (XFEL), which is under construction at DESY in Hamburg (Germany). At 10 MW peak rf output the MBK is required to provide at least 65% efficiency and more than 3 MHz instantaneous -1 dB bandwidth. Average power and rf pulse length are 150 kW and 1.5 ms, respectively. MBKs have the advantage of generating high rf output powers at moderate electron beam energies. For our design, six off-axis electron beams enable low cathode current density for longer cathode life. Compared to our first- generation design, where higher-order-mode cylindrical cavities were used, we are utilizing ring resonators operating in the fundamental-mode. This ensures sufficient beam separation while still keeping the overall diameter of the device small in order to reduce cost. Our in-house 1D large-signal rf code (LSCEX) was used to come up with the initial rf design. The 2.5D rf code TESLA enabled us to verify and refine the design. For the cavity design we utilized the commercially available 3D codes MAFIA and HFSS. The baseline beam optics design was created using our in-house 2.5D code XGun. With state-of- the-art 3D modeling software for beam optics (MICHELLE) and magnetics (MagNet) we then validated and optimized the design. Most of the mechanical design is completed. Material for the prototype is currently being procured and we will start building the klystron by the end of February 2008. We are going to present simulated data showing the expected performance of the device. The simulations exceed the requirements by a healthy margin. Measured data will be presented as they become available throughout the assembly process.
Plasma Science, 2008. ICOPS 2008. IEEE 35th International Conference on; 07/2008
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ABSTRACT: After successfully designed and manufactured 40 kW CW/85 kW peak 1.3 GHz inductive output tube (IOT) amplifiers, we have been working on pushing the power of IOT to a new level, 120 kW CW. The challenges are so significant that simple modifications to the lower power version IOT would not be adequate. A complete new design is necessary for increased power level and reliable performance. In this paper, we will describe the tasks conducted for the IOT amplifier design.
Vacuum Electronics Conference, 2007. IVEC '07. IEEE International; 06/2007
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ABSTRACT: The presentation describes work done under a Navy contract to reduce the life cycle cost of an S-band coupled cavity device. End of life of these devices was determined to be caused primarily by cathode wear-out. Consequently, the thrust of the program has been to re-design the electron gun for longer life.
Vacuum Electronics Conference, 2004. IVEC 2004. Fifth IEEE International; 05/2004
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ABSTRACT: 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.
Vacuum Electronics Conference, 2004. IVEC 2004. Fifth IEEE International; 05/2004
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ABSTRACT: A C-band helix traveling-wave tube (TWT) was modeled using HFSS/CTLSS (3-D electromagnetic codes) to predict the dispersion and impedance characteristics of different sections of the device. This particular TWT consists of two RF sections separated by a sever. As can be seen the input section has distributed loss along the entire length, with a tip loss in the middle; whereas the output section has distributed loss in part of the circuit, with no loss toward the end. The input section has a uniform pitch, whereas the output section has a velocity tapering with a reduction in pitch at the end to improve efficiency. This device operates in the linear region yet producing the desired RF power.
Vacuum Electronics Conference, 2004. IVEC 2004. Fifth IEEE International; 05/2004
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ABSTRACT: This paper presents results from some of the tools currently used at CPI for design of helix TWTs, coupled-cavity TWTs and klystrons. HFSS, a commercial 3D electromagnetic code, and CTLSS, a 3D electromagnetic code, are currently used to predict helix circuit dispersion and impedance characteristics. CTLSS and HFSS are the first tools available that allow us to perform completely cold-test-free helix TWT design. HFSS is also used to predict CC-TWT circuit dispersion characteristics and to design waveguide transformers, windows and severs.
Vacuum Electronics Conference, 2004. IVEC 2004. Fifth IEEE International; 05/2004
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ABSTRACT: Progress to date is reported on the development of a 10 MW, 1300 MHz multiple beam klystron for the TESLA superconducting linear accelerator. A multiple beam klystron will be used because of its ability to produce high rf output powers A moderate electron beam energies. In this device, low cathode current density loading and hence longer cathode life is achieved by the use of off-axis electron beams. Beam bunching occurs in a series of separate fundamental mode klystron cavities whereas drive power input and output power extraction occur in large over-moded cavities for power combination reasons. The essential parameters of the device are 114 kV beam energy, 131 A beam current (21.8 A per beam), 65% efficiency, 50 dB gain and 150 kW of average rf output power.
Plasma Science, 2003. ICOPS 2003. IEEE Conference Record - Abstracts. The 30th International Conference on; 07/2003
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ABSTRACT: In this paper, we reported on the design of a 10 MW, 1300 MHz multiple beam klystron for TESLA superconducting linear accelerator. The multiple beam klystron is used in the accelerator because of its ability to produce high RF output power at moderate electron beam energies. The beam optics design has been verified by fully 3D simulations using the codes Michelle and Mafia. Electron trajectories in the gun region as calculated from Mafia codes.
Vacuum Electronics, 2003 4th IEEE International Conference on; 06/2003
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ABSTRACT: In this paper, we presents the test results of the 805 MHz, 550 kW pulsed klystron for the spallation neutron source. Electrical and mechanical design of electron guns and klystrons are discussed with VKP-8291A transfer curves and bandpass curves. . Modification of the rf circuit performance were implemented with minor modification in klystrons.
Vacuum Electronics, 2003 4th IEEE International Conference on; 06/2003
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ABSTRACT: A high-efficiency, Multiple-Beam Klystron (MBK), designated the VKL-8301, is being manufactured for the DESY Tera Electron volt Superconducting Linear Accelerator (TESLA) in Hamburg, Germany. There are a number of excellent reasons for using an MBK for this application. The primary reasons are reduced size and lower operating voltage with respect to the conventional, single beam counterparts. Once this decision has been made, the class of MBK must now be selected. MBKs can be divided into two categories: Fundamental Mode (FM) and Higher-order Mode (HM) devices, distinguished by the interaction mode of the cavity resonators. Each class has inherent advantages and disadvantages dependent upon end-user requirements. For the 10 MW, 1.3 GHz TESLA application the HM-MBK is the clear choice. The primary factor influencing this choice was operational life, since the accelerator will require approximately 600 MBKs. The advantage of the HM approach is low cathode loading. Our cathode loading design goal of 2 A/cm<sup>2</sup> or less has been achieved. For this application the HM-MBK cathode loading is a factor of four lower than competing FM-MBK designs and a factor of three lower than the SLAC 5045 design. The VKL-8301 will use six off-axis electron beams interacting with a combination of TM<sub>010</sub> and hybrid TM<sub>020</sub> cavities. These six beams are equally spaced on a diameter of approximately 25 centimeters. Because of the large beam-to-beam separation, individual high-area convergence guns can be utilized versus the single multi-emission-site gun used in FM-MBK's. This solution requires a sophisticated focusing system that is relatively difficult to realize, compounded by our use of confined-flow focusing. Newly developed, state-of-the-art three- dimensional electromagnetics codes have been used to design the novel electron-beam-focusing system and microwave cavity geometry. Modeling and simulation results will be presented, hardware will be shown, and a description of the FM- versus HM-MBK selection process will be discussed.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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ABSTRACT: The Spallation Neutron Source (SNS) is an accelerator-based neutron source being built in Oak Ridge, Tennessee, by the U.S. Department of Energy. The SNS will provide the most intense pulsed neutron beams in the world for scientific research and industrial development. CPI is supporting the effort by providing 550 kW pulsed klystrons for the super-conducting 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% and an rf gain of 50 dB. A total of 73 units are on order. Through April 2003, eighteen units have been factory-tested. Performance specifications, computer model predictions, and operating results will be presented.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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A. Balkcum,
E. Wright,
H. Bohlen,
F. Friedlander,
M. Cattelino,
M. Cusick,
L. Cox,
E. Eisen,
S. Lenci, B. Stockwell,
L. Zitelli
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ABSTRACT: A high efficiency multiple beam klystron, designated the VKL-8301, is being developed for the DESY superconducting linear accelerator TESLA in Hamburg, Germany. The accelerator will require 572 klystrons each producing up to 10 MW of rf output power at 1300 MHz. A multiple beam klystron will be used due to its ability to produce large rf output powers using moderate electron beam energies.
Vacuum Electronics Conference, 2002. IVEC 2002. Third IEEE International; 02/2002
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ABSTRACT: Pulsed Airborne and Millimeter Wave TWTs often need very small gridded guns which are difficult to fabricate. Enter the "Negative Grid", which consists of a single grid at a potential near or below that of the cathode. This operating voltage makes the grid non-intercepting and allows close spacing to the cathode surface. This paper will include both simulation data and measured product performance data.
Vacuum Electronics Conference, 2002. IVEC 2002. Third IEEE International; 02/2002
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ABSTRACT: The growing demands in today's communications market have increased the need for a larger variety and a faster development of competitive products. With the VKU-8893UTA klystron, CPI is expanding its medium-power product line within Ku band. This paper describes the development and the pending production of this klystron.
Vacuum Electronics Conference, 2002. IVEC 2002. Third IEEE International; 02/2002
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ABSTRACT: Summary form only given. The Spallation Neutron Source (SNS) is an accelerator-based neutron source being built in Oak Ridge, Tennessee, by the US Department of Energy. The SNS will provide the most intense pulsed neutron beams in the world for scientific research and industrial development. Los Alamos National Laboratory has ordered 65 klystrons for the superconducting portion of the accelerator from CPI. The key klystron components include: cathode-pulsed electron gun; six-cavity RF circuit, including one cavity tuned near the second harmonic of the operating frequency; single output window; collector capable of dissipating the full beam power. The prototype unit of this model, designated VKP-8291A, is schedule to be in testing at the end of March 2002. Performance specifications, computer model predictions, and prototype operating results are presented.
Vacuum Electronics Conference, 2002. IVEC 2002. Third IEEE International; 02/2002
