IPAC2017 - Classification: 07 Accelerator Technology / T08 RF Power Sources

Paper	Title	Page
MOOCA1	High Efficiency Klystrons Using the COM Bunching Technique	37
	D.A. Constable Lancaster University, Lancaster, United Kingdom A.Yu. Baikov Moscow University of Finance & Law, Moscow, Russia G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom R.D. Kowalczyk L-3, Williamsport, Pennsylvania, USA I. Syratchev CERN, Geneva, Switzerland
	Future large-scale particle accelerators, for example, the Future Circular Collider (FCC), the Compact Linear Collider (CLIC) and the International Linear Collider (ILC), will require significant RF drive power on the order of 100 MW. Thus, an RF source with high efficiency is preferable to minimise the overall power required. Klystrons represent an attractive RF source, with the current state of the art operating at efficiencies of up to 70%. Such devices feature monotonic bunching, where at the output cavity, a number of electrons will not be in the main bunch, and instead will be present in the anti-bunch, and therefore not contributing to the output power. Therefore, novel bunching methods, such as the Core Oscillation Method (COM), are worthy of investigation. By allowing the core of the electron beam to bunch and de-bunch between successive cavities, the number of electrons contained in the final bunch can increase, and therefore improve the efficiency of the device. Numerical simulation of klystrons featuring COM will be presented, with efficiencies of up to 85% being predicted thus far.
	Slides MOOCA1 [12.765 MB]
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MOPIK098	Techniques for Achieving High Reliability Operation of the Spallation Neutron Source High Power Radio-Frequency System	756
	J. Moss, M.S. Champion ORNL, Oak Ridge, Tennessee, USA
	Funding: *ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. This research was supported by the DOE Office of Science, Basic Energy Science, Scientific User Facilities. The Spallation Neutron Source (SNS) high power radiofrequency (HPRF) system operates with high reliability to support the goals of the SNS user program. In recent operational periods the availability of the HPRF System has exceeded 97 percent while the neutron source availability overall is typically greater than 90 percent. SNS has a unique set of 92 HPRF stations that operate at either 402.5 MHz or 805 MHz with peak output power ranging from 550 kW to 5 MW and average power ranging from 49.5 kW to 450 kW. The HPRF transmitters consist of chassis-mounted power supplies, solid-state amplifiers and other equipment that support the operation of the klystrons that ultimately provide the RF power to the accelerating structures. Management of the operation and maintenance of the HPRF system has increasingly focused on reliability and sustainability in recent years. Techniques for klystron lifetime preservation and optimization of transmitter reliability have been developed and will be described.
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WEZB1	Review and Prospects of RF Solid State Amplifiers for Particle Accelerators	2537
	P. Marchand SOLEIL, Gif-sur-Yvette, France
	Thanks to the growth of high power semiconductor technology, solid state power amplifier (SSPA) systems with several hundred kW RF power are now available for various accelerator fields. Following the successful development at 352 MHz that took place at SOLEIL in the 2000s, the technology was transferred to industry and SSPAs at different frequencies, power levels, and pulse lengths have been widely adopted. In this paper we report about the SOLEIL experience with SSPAs and review the used or planned SSPAs in other accelerator facilities.
	Slides WEZB1 [13.860 MB]
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THPAB127	Development of 1.3 GHz Cavity Combiner for 24 kW CW SSA	4020
SUSPSIK107	use link to see paper's listing under its alternate paper code
	W. Liu, B. Du, G. Huang, L. Lin, L. Shang, W.B. Song USTC/NSRL, Hefei, Anhui, People's Republic of China
	The 24KW CW SSA (Solid-State Amplifier) is being developed to drive the 1.3GHz SC Linac used in a THz light source. The SSA adopts the compact all-in-one combining method ' cavity combiner, which is proposed and developed in recent years. This paper reports the R&D of the cavity combiner. The cavity combiner resonates in TM010 mode, coupling with 24 coaxial-connected 1kW amplifier modules. The cavity's electromagnetic characteristic is calculated by CST, and the mechanical structure including the input and output coupler has been designed.
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THPIK002	Development of a Range of High Peak Power Solid-State Amplifiers for Use in the Heavy Ion Linac at JINR, Dubna	4108
	S.C. Dillon, J.L. Reid Tomco Technologies, Stepney, South Australia, Australia A.V. Butenko JINR, Dubna, Moscow Region, Russia H. Höltermann, H. Podlech, U. Ratzinger BEVATECH, Frankfurt, Germany
	A range of LDMOS based amplifiers rated for up to 340kW peak power and operating at 100.625MHz were developed for use as RF sources for driving cavities in the heavy ion LINAC (HILac) at JINR, Dubna. The final solution had to be compact and competitive while addressing technical challenges such as phase and amplitude stability, long term reliability, reflected power handling and serviceability. Design considerations and performance results are presented.
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THPIK013	Renewal of Bessy Ii Rf System - Solid State Amplifiers and Hom Damped Cavities	4127
	W. Anders, P. Goslawski, A. Heugel, H.-G. Hoberg, H. Hoffmann, A. Jankowiak, J. Knobloch, G. Mielczarek, M. Ries, M. Ruprecht, A. Schälicke, B. Schriefer, H. Stein HZB, Berlin, Germany M. Haucke Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany K. Ludwig BESSY GmbH, Berlin, Germany
	Due to the fact that the klystrons run out of production and due to the aging of the old cavities, a renewal of the RF system was necessary. Solid state based transmitters and HOM damped nc single cell cavities have been installed at the BESSY II storage ring. The parameters of the components, the installation phase and the results to the beam will be presented.
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THPIK023	Concept of the High Power RF Systems for MESA	4147
	R.G. Heine, F. Fichtner IKP, Mainz, Germany
	Funding: work supported by DFG under the cluster od Excellence PRISMA, EXC 1098/2014 The Mainz Energy-recovering Superconducting Accelerator (MESA) is currently designed and built at the Institut für Kernphysik (KPH) at Johannes Gutenberg-Universität Mainz. The main accelerator incorporates four superconducting cavities of the TESLA type, while the preaccelerator MAMBO (Milliampere Booster) is a room temperature linac. The MESA high power RF-systems have to cover a vast power range starting at some 10kW per cavity for the main linac modules and more 50kW per cavity for MAMBO. In this paper we will present the concept of a unified high power RF system for both main accelerator and preaccelertor, based on solid state technology.
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THPIK038	Design of a 100 kW Solid-State RF Pulse Amplifier with a TE011 Mode RF Combiner at 476 MHz	4180
	Y. Otake, T. Asaka, T. Inagaki RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
	Solid-state RF amplifiers, which have long lifetimes and small failures, are the recent current of high-power RF sources for particle accelerators. Hence, we designed a 100 kW solid-state amplifier with a TE011 mode cavity (Q0=100, 000) power combiner with extreme low-loss operated at 476 MHz and a 6 us pulse width. Developing this amplifier is for replacement of a high-power amplifier using an induction output tube, IOT, in the X-ray free-electron laser, SACLA. In SACLA, highly RF phase and amplitude stabilities of less than 0.01 deg. and 10^-4 in rms are necessary to stable lasing within a 10 % intensity fluctuation. The amplifier comprises a drive amplifier, a reentrant cavity RF power divider, 100 final amplifier modules with a 1 kW output each and a TE011 mode cavity combiner. Water-cooling within 10 mK and a DC power supply with a noise of less than -100 dBV at 10 Hz for the amplifier is necessary to realize the previously mentioned stabilities. Based on the experimental results of a test amplifier module and test combiner cavities, possibility to realize the above-mentioned specifications is large. We report the detail and a part of the performance of the 100 kW amplifier.
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THPIK056	Design of a C-Band High-Efficiency Multi-Beam Klystron	4221
	Z.N. Liu, H.B. Chen, M.M. Peng, J. Shi TUB, Beijing, People's Republic of China
	A multi-beam klystron at 5.712GHz has been designed with efficiency of more than 80%. It can generate a pulse with output power of about 3MW and a pulse length of 5 us. Space charge effect and large signal theory, which both increase the accuracy theoretically, are considered in the simulation. A series of parameters of cavities are given after optimizing, including the frequency, R/Q, Q0 and Qe. This paper describes the beam dynamics design of the klystron as well as a preliminary machenical design.
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THPIK065	Reliability Anlysis of 20kw Solid-State Amplifiers for Ciads	4245
	P.H. Gao IMP/CAS, Lanzhou, People's Republic of China
	CIADS will apply the solid-state amplifier. 20KW solid-state amplifiers are the basis of RF systems. This talk model 20KW solid-state amplifiers with reliability block diagram(RBD). Through simulation, we find that the reliability function relative to redundancy approximates logarithm, but cost is linear growth. There is an optimal solution between redundancy and cost.
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THPIK072	Development of High Power RF Amplifier System for the KBSI RFQ	4257
SUSPSIK108	use link to see paper's listing under its alternate paper code
	J. Bahng Kyungpook National University, Daegu, Republic of Korea M.-H. Chun PAL, Pohang, Kyungbuk, Republic of Korea J.G. Hong, B.S. Lee, J.W. Ok Korea Basic Science Institute, Busan, Republic of Korea D.S. Kim DAWONSYS, Ansan-si, Republic of Korea E.-S. Kim Korea University Sejong Campus, Sejong, Republic of Korea
	KBSI (Korean Basic Science Institute) has been developed a compact accelerator system for generation of fast neutron by 2.7 MeV/u of lithium beam. The facility consists of 28 GHz SC-ECR ion source, LEBT, RFQ and DTL. The developed RFQ accelerator provides lithium ion beam from 12 keV/u to 500 keV/u with 98.88 % of high transmission rate at 165 MHz of operation frequency. RF power system for RFQ accelerator has been developed to provide sufficient RF power into RFQ cavity. which consists of LLRF system for control, 5 KW of SSPA as IPA, tetrode tube amplifier as FPA, coaxial transmission line and circulator for protection from reflection power provides 100 kW at operation frequency with CW mode, In this paper, we discuss about development of RF system and performance test in detail.
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THPIK084	Results from the 704 MHz Klystron and Multi-beam IOT Prototypes for the European Spallation Source	4282
	M. Jensen, C. Marrelli ESS, Lund, Sweden
	The European Spallation Source, currently under construction in Lund, Sweden, will contain 155 RF sources for proton beam acceleration. Of these, 120 are at 704 MHz. Each cavity will be powered by individual RF sources. The nominal beam pulse width is 2.86 ms and the RF systems are being specified for a pulse width up to 3.5 ms to allow for ramping and time for regulation. The repetition frequency is 14 Hz which results in 5% duty. The 704 MHz linac is divided into two sections, the medium beta and the high beta cavities. For schedule reasons, the medium beta linac, 36 RF sources, will be based on 1.5 MW pulsed power klystrons and the high beta section, 84 RF sources, is planned to be operated with 1.2 MW multi-beam IOTs. ESS ordered three klystron prototypes designed for the ESS parameters from different supplies and two multi-beam IOT technology demonstrators under two different contracts. We present the specifications for the amplifiers and the results of the klystron prototypes and report the result of the first 1.2 MW multi-beam IOT prototypes.
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THPIK088	A Compact 10 kW Solid-State RF Power Amplifier at 352 MHz	4292
	D.S. Dancila, A. Rydberg Uppsala University, Department of Engineering Sciences, Uppsala, Sweden A.E.T. Hjort, L. Hoang Duc, M.H. Holmberg, M. Jobs, R.J.M.Y. Ruber Uppsala University, Uppsala, Sweden
	A compact 10 kW RF power amplifier at 352 MHz was developed at FREIA for the European Spallation Source, ESS. The specifications of ESS for the conception of amplifiers are related to its pulsed operation: 3.5 ms pulse length and a duty cycle of 5\%. The realized amplifier is composed of eight kilowatt level modules, combined using a planar Gysel 8-way combiner. The combiner has a low insertion loss of only 0.2 dB, measured at 10 kW peak power. Each module is built around a commercially available LDMOS transistor in a single-ended architecture. During the final measurements, a total output peak power of 10.5 kW was measured.
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THPIK090	352 MHz Tetrode RF Stations for Superconducting Spoke Cavities	4296
	M. Jobs, K.J. Gajewski, V.A. Goryashko, H. Li, R.J.M.Y. Ruber, R. Wedberg Uppsala University, Uppsala, Sweden
	Two 352 MHz tetrode based RF stations for pulsed operation have been developed at the FREIA Laboratory, Uppsala University to validate the design and performance as RF source for the Spoke cavities in the first superconductive stage of the European Spallation Source(ESS) linear accelerator. The stations use dual TH595 tetrodes rated at 210 kW peak-power to provide a total power of 400 kW with a maximum pulse duration of 3.5 ms at 14 Hz repetition rate. Each tetrode is fed by a 10 kW solid state amplifier and the station is monitored by an internal control system with complete remote access. Extensive measurements have been performed on the RF performance, the power supplies as well as on the interlock systems. To conform to the specifications, special attention must be given for the response time of the tetrode power-supplies to acquire good quality RF output pulses. For the interlock system any shut-down condition due to tube malfunctioning or other sources must switch off the station in a controlled manner with minimal damage to any internal circuitry or to the tube itself whilst at the same time provide a fast discharge and cut-off of all relevant power supplies.
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THPIK095	High Power X-Band Generation Using Multiple Klystrons and Pulse Compression	4311
	B.J. Woolley, T. Argyropoulos, N. Catalán Lasheras, G. McMonagle, S.F. Rey, I. Syratchev, W. Wuensch CERN, Geneva, Switzerland D. Esperante Pereira IFIC, Valencia, Spain J. Tagg National Instruments Switzerland, Ennetbaden, Switzerland M. Volpi The University of Melbourne, Melbourne, Victoria, Australia
	CERN has constructed and is operating a new X-band test stand containing two pairs of 12 GHz, 6 MW klystrons. By power combination through hybrid couplers and the use of pulse compressors, up to 45 MW of peak power can be sent to any of 4 test slots at pulse repetition rates up to 400 Hz. The test stand is dedicated to RF conditioning and testing of high gradient accelerating structures for the CLIC study and also future X-band FELs. Operations have been ongoing for a few months, with initial operation dedicated to control algorithm development. Significant progress has been made in understanding the unique challenges of high power RF combination and phase switching using RF hybrids.
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THPIK096	Jitter Measurement to 10ppm Level for Pulsed RF Power Amplifiers 3 - 12GHz	4314
	C.H. Gough, S. Dordevic, M. Paraliev PSI, Villigen PSI, Switzerland
	Linacs for FEL applications require a low jitter RF path from RF source through pulsed amplifiers, klystron / modulators and cavities. For the SwissFEL project, pulsed solid state power amplifiers of the 500W / 3us class for driving the klystrons were required. For these amplifiers, a stable and reliable interferometer system was developed to measure the residual RF jitter levels to <10 ppm (parts per million) and <10 urad (0.6mdeg) rms. This paper describes the system and gives some measurement results for 3GHz, 5.7GHz and 12GHz amplifiers.
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THPIK101	Quarter Wavelength Combiner for an 8.5kW Solid-State Amplifier and Conceptual Study of Hybrid Combiners	4324
	T.-C. Yu, F.Y. Chang, L.-H. Chang, M.H. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, Z.K. Liu, C.H. Lo, C.L. Tsai, Ch. Wang, M.-S. Yeh NSRRC, Hsinchu, Taiwan
	Experimental results to combine ten 900 W solid-state amplifier modules based on typical quarter wavelength 10-way combiners are described for a total of 8.5 kW RF power output at 500 MHz. The power gain and phase distribution among the ten modules are measured and calculated to sense the combination efficiency. The combination efficiency of 100 modules differing in power gain and phase distribution is theoretically analysed. Groups of 5, 10, 25, 50 and 100 units are used in 4, 3, 2, and 1-stage power combination for total 100 units and the characteristics are calculated and investigated, including bandwidth, efficiency and even redundancy under various output VSWR levels. To simplify combining complexity and to eliminate the drawbacks of single stage combiners, a multi-way 2-stage coaxial to waveguide combiner is thus proposed as an expandable power combiner.
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THPIK109	The RF Distribution System for the ESS	4352
	T.R. Edgecock, N. Turner University of Huddersfield, Huddersfield, United Kingdom P. Aden, D. Naeem, R. Smith STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom A. Sunesson, R.A. Yogi ESS, Lund, Sweden
	The RF distribution system for the European Spallation Source will be one of the largest systems ever built. It will distribute the power from 146 power sources to the two types of ESS cavity at two different frequencies and will use one line per cavity for resilience. It will consist of a total of around 3.5 km of waveguide and coaxial line and over 1500 hundred bends. It is designed to transport this RF power over a distance of up to 40m per line, while minimising losses, avoiding reflections and allowing the monitoring of performance. This contribution will give an overview of the design of the system and its status. Installation is due to start in September 2017.
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THPIK117	High Efficiency High Power Resonant Cavity Amplifier for Accelerator Applications	4374
	M.P.J. Gaudreau, D.B. Cope, E.G. Johnson, M.K. Kempkes, J. Kinross-Wright, R.E. Simpson Diversified Technologies, Inc., Bedford, Massachusetts, USA
	Funding: Work supported by US Department of Energy under contract DE-SC0015780 Diversified Technologies, Inc. (DTI) has designed and built a unique integrated resonant-cavity combined solid-state amplifier. The design radically simplifies solid-state transmitters to create favorable and straightforward scaling to high power levels. A crucial innovation is demonstration of an inherently reliable soft-failure mode of operation; a failure in one or several of these myriad combined transistors has negligible performance impact. In addition, this design couples the transistor drains directly to the cavity without first transforming to 50 Ohms, avoiding the otherwise-necessary multitude of circulators, cables, and connectors. A conventional amplifier has a complete set of electrical and cooling connections for every stage, resulting in many hundreds of connections for a high power transmitter'in some DTI designs, there are as few as four. This construction both reduces the cost and increases the power level at which it is cost-effective to employ a solid-state transmitter. The prototype has demonstrated multiple-transistor combining from 300 MHz to 1300 MHz, at powers up to 5 kW. This prototype is scalable to several hundred kW at these frequencies.
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THPIK121	Eddy Current Analysis for a 1.495 GHz Injection-Locked Magnetron	4383
	S.A. Kahn, A. Dudas, R.P. Johnson, M.L. Neubauer Muons, Inc, Illinois, USA R.A. Rimmer, H. Wang JLab, Newport News, Virginia, USA
	Funding: U.S. DOE SBIR/STTR grant DE-SC0013203 An injection-locked amplitude modulated magnetron is being developed as a reliable, efficient RF source that could replace klystrons used in particle accelerators. A trim magnetic coil is used to alter the magnetic field in conjunction with the anode voltage to maintain an SRF cavity voltage while the cavity is experiencing microphonics and changing beam loading. The microphonic noise modes have frequencies in the range 10-100 Hz. The changing magnetic field will induce transient eddy currents in the copper anode of the magnetron which will buck the field in the interaction region. This paper will describe the calculation and handling of the eddy currents in the magnetron.
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THPIK122	Methods of Phase and Power Control in Magnetron Transmitters for Superconducting Accelerators	4386
	G.M. Kazakevich, R.P. Johnson, M.L. Neubauer Muons, Inc, Illinois, USA V.A. Lebedev, W. Schappert, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	Various methods of phase and power control in magnetron RF sources of superconducting accelerators intended for ADS-class projects were recently developed and studied with conventional 2.45 GHz, 1 kW, CW magnetrons operating in pulsed and CW regimes. Magnetron trans-mitters excited by a resonant (injection-locking) phase-modulated signal can provide phase and power control with the rates required for precise stabilization of phase and amplitude of the accelerating field in Superconducting RF (SRF) cavities of the intensity-frontier accelerators. An innovative technique that can significantly increase the magnetron transmitter efficiency at the wide-range power control required for superconducting accelerators was developed and verified with the 2.45 GHz magnetrons operating in CW and pulsed regimes. High efficiency magnetron transmitters of this type can significantly reduce the capital and operation costs of the ADS-class accelerator projects.
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THPIK123	Magnetron Design for Amplitude Modulation	4389
	M.L. Neubauer, A. Dudas, S.A. Kahn Muons, Inc, Illinois, USA R.A. Rimmer, H. Wang JLab, Newport News, Virginia, USA
	The amplitude modulation (AM) of a magnetron is accomplished by varying the magnetic field which changes the current to the anode and the output power of the injection locked magnetron. The purpose of the AM is to compensate for microphonics in super conducting cavities by maintaining a constant gradient. The frequency range for the microphones is below 200 Hz. At these frequencies, eddy currents are encountered in the magnetron anode that reduce the effectiveness of the varying magnetic field on the magnetron current. A novel anode design is described which minimizes eddy currents and a method for manufacturing this novel magnetron anode is presented
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THPVA114	Status of High-Efficiency Klystron Development for the PLS-II and PAL-XFEL	4726
	S.J. Park, H.S. Han, W.H. Hwang, S.D. Jang, Y.D. Joo, K.R. Kim, C.D. Park, Y.J. Park PAL, Pohang, Kyungbuk, Republic of Korea J.H. Hwang, S.S. Jang POSTECH, Pohang, Kyungbuk, Republic of Korea S.Y. Hyun, H.S. Seo, D.H. Yu Vitzrotech Co., Ltd., Ansan City, Kyunggi-Do, Republic of Korea
	Funding: This work was supported by the National R&D program (grant number: 2016R1A6B2A01016828) through the National Research Foundation of Korea (NRF). We are developing a high-efficiency klystron for use in the PLS-II(Pohang Light Source II) and the PAL-XFEL in the Pohang Accelerator Laboratory. Since the PLS-II and the PAL-XFEL are already running with ~70 klystron modulator systems, newly developed klystrons should be designed to fit into existing installation spaces and power supplies, and their overall lengths(< 2 m) and beam perveances(2 upervs) should not be changed. In order to achieve the high efficiency with aforementioned boundary conditions, we are going to adopt a multi-cell output cavity in which, unlike those of the the SLAC X-band and KEK C-band klystrons, the cell frequencies are independently tuned to provide maximum beam-to-rf power conversion. In this article we report on our physics and engineering design efforts to achieve the high efficiency with minimum instabilities.
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Paper

Title

Page

High Efficiency Klystrons Using the COM Bunching Technique

37

D.A. Constable
Lancaster University, Lancaster, United Kingdom
A.Yu. Baikov
Moscow University of Finance & Law, Moscow, Russia
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
R.D. Kowalczyk
L-3, Williamsport, Pennsylvania, USA
I. Syratchev
CERN, Geneva, Switzerland

Future large-scale particle accelerators, for example, the Future Circular Collider (FCC), the Compact Linear Collider (CLIC) and the International Linear Collider (ILC), will require significant RF drive power on the order of 100 MW. Thus, an RF source with high efficiency is preferable to minimise the overall power required. Klystrons represent an attractive RF source, with the current state of the art operating at efficiencies of up to 70%. Such devices feature monotonic bunching, where at the output cavity, a number of electrons will not be in the main bunch, and instead will be present in the anti-bunch, and therefore not contributing to the output power. Therefore, novel bunching methods, such as the Core Oscillation Method (COM), are worthy of investigation. By allowing the core of the electron beam to bunch and de-bunch between successive cavities, the number of electrons contained in the final bunch can increase, and therefore improve the efficiency of the device. Numerical simulation of klystrons featuring COM will be presented, with efficiencies of up to 85% being predicted thus far.

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MOPIK098

Techniques for Achieving High Reliability Operation of the Spallation Neutron Source High Power Radio-Frequency System

756

J. Moss, M.S. Champion
ORNL, Oak Ridge, Tennessee, USA

Funding: *ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. This research was supported by the DOE Office of Science, Basic Energy Science, Scientific User Facilities.
The Spallation Neutron Source (SNS) high power radiofrequency (HPRF) system operates with high reliability to support the goals of the SNS user program. In recent operational periods the availability of the HPRF System has exceeded 97 percent while the neutron source availability overall is typically greater than 90 percent. SNS has a unique set of 92 HPRF stations that operate at either 402.5 MHz or 805 MHz with peak output power ranging from 550 kW to 5 MW and average power ranging from 49.5 kW to 450 kW. The HPRF transmitters consist of chassis-mounted power supplies, solid-state amplifiers and other equipment that support the operation of the klystrons that ultimately provide the RF power to the accelerating structures. Management of the operation and maintenance of the HPRF system has increasingly focused on reliability and sustainability in recent years. Techniques for klystron lifetime preservation and optimization of transmitter reliability have been developed and will be described.

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WEZB1

Review and Prospects of RF Solid State Amplifiers for Particle Accelerators

2537

P. Marchand
SOLEIL, Gif-sur-Yvette, France

Thanks to the growth of high power semiconductor technology, solid state power amplifier (SSPA) systems with several hundred kW RF power are now available for various accelerator fields. Following the successful development at 352 MHz that took place at SOLEIL in the 2000s, the technology was transferred to industry and SSPAs at different frequencies, power levels, and pulse lengths have been widely adopted. In this paper we report about the SOLEIL experience with SSPAs and review the used or planned SSPAs in other accelerator facilities.

Slides WEZB1 [13.860 MB]

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THPAB127

Development of 1.3 GHz Cavity Combiner for 24 kW CW SSA

4020

SUSPSIK107

use link to see paper's listing under its alternate paper code

W. Liu, B. Du, G. Huang, L. Lin, L. Shang, W.B. Song
USTC/NSRL, Hefei, Anhui, People's Republic of China

The 24KW CW SSA (Solid-State Amplifier) is being developed to drive the 1.3GHz SC Linac used in a THz light source. The SSA adopts the compact all-in-one combining method ' cavity combiner, which is proposed and developed in recent years. This paper reports the R&D of the cavity combiner. The cavity combiner resonates in TM010 mode, coupling with 24 coaxial-connected 1kW amplifier modules. The cavity's electromagnetic characteristic is calculated by CST, and the mechanical structure including the input and output coupler has been designed.

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THPIK002

Development of a Range of High Peak Power Solid-State Amplifiers for Use in the Heavy Ion Linac at JINR, Dubna

4108

S.C. Dillon, J.L. Reid
Tomco Technologies, Stepney, South Australia, Australia
A.V. Butenko
JINR, Dubna, Moscow Region, Russia
H. Höltermann, H. Podlech, U. Ratzinger
BEVATECH, Frankfurt, Germany

A range of LDMOS based amplifiers rated for up to 340kW peak power and operating at 100.625MHz were developed for use as RF sources for driving cavities in the heavy ion LINAC (HILac) at JINR, Dubna. The final solution had to be compact and competitive while addressing technical challenges such as phase and amplitude stability, long term reliability, reflected power handling and serviceability. Design considerations and performance results are presented.

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THPIK013

Renewal of Bessy Ii Rf System - Solid State Amplifiers and Hom Damped Cavities

4127

W. Anders, P. Goslawski, A. Heugel, H.-G. Hoberg, H. Hoffmann, A. Jankowiak, J. Knobloch, G. Mielczarek, M. Ries, M. Ruprecht, A. Schälicke, B. Schriefer, H. Stein
HZB, Berlin, Germany
M. Haucke
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
K. Ludwig
BESSY GmbH, Berlin, Germany

Due to the fact that the klystrons run out of production and due to the aging of the old cavities, a renewal of the RF system was necessary. Solid state based transmitters and HOM damped nc single cell cavities have been installed at the BESSY II storage ring. The parameters of the components, the installation phase and the results to the beam will be presented.

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THPIK023

Concept of the High Power RF Systems for MESA

4147

R.G. Heine, F. Fichtner
IKP, Mainz, Germany

Funding: work supported by DFG under the cluster od Excellence PRISMA, EXC 1098/2014
The Mainz Energy-recovering Superconducting Accelerator (MESA) is currently designed and built at the Institut für Kernphysik (KPH) at Johannes Gutenberg-Universität Mainz. The main accelerator incorporates four superconducting cavities of the TESLA type, while the preaccelerator MAMBO (Milliampere Booster) is a room temperature linac. The MESA high power RF-systems have to cover a vast power range starting at some 10kW per cavity for the main linac modules and more 50kW per cavity for MAMBO. In this paper we will present the concept of a unified high power RF system for both main accelerator and preaccelertor, based on solid state technology.

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THPIK038

Design of a 100 kW Solid-State RF Pulse Amplifier with a TE011 Mode RF Combiner at 476 MHz

4180

Y. Otake, T. Asaka, T. Inagaki
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

Solid-state RF amplifiers, which have long lifetimes and small failures, are the recent current of high-power RF sources for particle accelerators. Hence, we designed a 100 kW solid-state amplifier with a TE011 mode cavity (Q0=100, 000) power combiner with extreme low-loss operated at 476 MHz and a 6 us pulse width. Developing this amplifier is for replacement of a high-power amplifier using an induction output tube, IOT, in the X-ray free-electron laser, SACLA. In SACLA, highly RF phase and amplitude stabilities of less than 0.01 deg. and 10^-4 in rms are necessary to stable lasing within a 10 % intensity fluctuation. The amplifier comprises a drive amplifier, a reentrant cavity RF power divider, 100 final amplifier modules with a 1 kW output each and a TE011 mode cavity combiner. Water-cooling within 10 mK and a DC power supply with a noise of less than -100 dBV at 10 Hz for the amplifier is necessary to realize the previously mentioned stabilities. Based on the experimental results of a test amplifier module and test combiner cavities, possibility to realize the above-mentioned specifications is large. We report the detail and a part of the performance of the 100 kW amplifier.

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THPIK056

Design of a C-Band High-Efficiency Multi-Beam Klystron

4221

Z.N. Liu, H.B. Chen, M.M. Peng, J. Shi
TUB, Beijing, People's Republic of China

A multi-beam klystron at 5.712GHz has been designed with efficiency of more than 80%. It can generate a pulse with output power of about 3MW and a pulse length of 5 us. Space charge effect and large signal theory, which both increase the accuracy theoretically, are considered in the simulation. A series of parameters of cavities are given after optimizing, including the frequency, R/Q, Q0 and Qe. This paper describes the beam dynamics design of the klystron as well as a preliminary machenical design.

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THPIK065

Reliability Anlysis of 20kw Solid-State Amplifiers for Ciads

4245

P.H. Gao
IMP/CAS, Lanzhou, People's Republic of China

CIADS will apply the solid-state amplifier. 20KW solid-state amplifiers are the basis of RF systems. This talk model 20KW solid-state amplifiers with reliability block diagram(RBD). Through simulation, we find that the reliability function relative to redundancy approximates logarithm, but cost is linear growth. There is an optimal solution between redundancy and cost.

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THPIK072

Development of High Power RF Amplifier System for the KBSI RFQ

4257

SUSPSIK108

use link to see paper's listing under its alternate paper code

J. Bahng
Kyungpook National University, Daegu, Republic of Korea
M.-H. Chun
PAL, Pohang, Kyungbuk, Republic of Korea
J.G. Hong, B.S. Lee, J.W. Ok
Korea Basic Science Institute, Busan, Republic of Korea
D.S. Kim
DAWONSYS, Ansan-si, Republic of Korea
E.-S. Kim
Korea University Sejong Campus, Sejong, Republic of Korea

KBSI (Korean Basic Science Institute) has been developed a compact accelerator system for generation of fast neutron by 2.7 MeV/u of lithium beam. The facility consists of 28 GHz SC-ECR ion source, LEBT, RFQ and DTL. The developed RFQ accelerator provides lithium ion beam from 12 keV/u to 500 keV/u with 98.88 % of high transmission rate at 165 MHz of operation frequency. RF power system for RFQ accelerator has been developed to provide sufficient RF power into RFQ cavity. which consists of LLRF system for control, 5 KW of SSPA as IPA, tetrode tube amplifier as FPA, coaxial transmission line and circulator for protection from reflection power provides 100 kW at operation frequency with CW mode, In this paper, we discuss about development of RF system and performance test in detail.

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THPIK084

Results from the 704 MHz Klystron and Multi-beam IOT Prototypes for the European Spallation Source

4282

M. Jensen, C. Marrelli
ESS, Lund, Sweden

The European Spallation Source, currently under construction in Lund, Sweden, will contain 155 RF sources for proton beam acceleration. Of these, 120 are at 704 MHz. Each cavity will be powered by individual RF sources. The nominal beam pulse width is 2.86 ms and the RF systems are being specified for a pulse width up to 3.5 ms to allow for ramping and time for regulation. The repetition frequency is 14 Hz which results in 5% duty. The 704 MHz linac is divided into two sections, the medium beta and the high beta cavities. For schedule reasons, the medium beta linac, 36 RF sources, will be based on 1.5 MW pulsed power klystrons and the high beta section, 84 RF sources, is planned to be operated with 1.2 MW multi-beam IOTs. ESS ordered three klystron prototypes designed for the ESS parameters from different supplies and two multi-beam IOT technology demonstrators under two different contracts. We present the specifications for the amplifiers and the results of the klystron prototypes and report the result of the first 1.2 MW multi-beam IOT prototypes.

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THPIK088

A Compact 10 kW Solid-State RF Power Amplifier at 352 MHz

4292

D.S. Dancila, A. Rydberg
Uppsala University, Department of Engineering Sciences, Uppsala, Sweden
A.E.T. Hjort, L. Hoang Duc, M.H. Holmberg, M. Jobs, R.J.M.Y. Ruber
Uppsala University, Uppsala, Sweden

A compact 10 kW RF power amplifier at 352 MHz was developed at FREIA for the European Spallation Source, ESS. The specifications of ESS for the conception of amplifiers are related to its pulsed operation: 3.5 ms pulse length and a duty cycle of 5\%. The realized amplifier is composed of eight kilowatt level modules, combined using a planar Gysel 8-way combiner. The combiner has a low insertion loss of only 0.2 dB, measured at 10 kW peak power. Each module is built around a commercially available LDMOS transistor in a single-ended architecture. During the final measurements, a total output peak power of 10.5 kW was measured.

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THPIK090

352 MHz Tetrode RF Stations for Superconducting Spoke Cavities

4296

M. Jobs, K.J. Gajewski, V.A. Goryashko, H. Li, R.J.M.Y. Ruber, R. Wedberg
Uppsala University, Uppsala, Sweden

Two 352 MHz tetrode based RF stations for pulsed operation have been developed at the FREIA Laboratory, Uppsala University to validate the design and performance as RF source for the Spoke cavities in the first superconductive stage of the European Spallation Source(ESS) linear accelerator. The stations use dual TH595 tetrodes rated at 210 kW peak-power to provide a total power of 400 kW with a maximum pulse duration of 3.5 ms at 14 Hz repetition rate. Each tetrode is fed by a 10 kW solid state amplifier and the station is monitored by an internal control system with complete remote access. Extensive measurements have been performed on the RF performance, the power supplies as well as on the interlock systems. To conform to the specifications, special attention must be given for the response time of the tetrode power-supplies to acquire good quality RF output pulses. For the interlock system any shut-down condition due to tube malfunctioning or other sources must switch off the station in a controlled manner with minimal damage to any internal circuitry or to the tube itself whilst at the same time provide a fast discharge and cut-off of all relevant power supplies.

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THPIK095

High Power X-Band Generation Using Multiple Klystrons and Pulse Compression

4311

B.J. Woolley, T. Argyropoulos, N. Catalán Lasheras, G. McMonagle, S.F. Rey, I. Syratchev, W. Wuensch
CERN, Geneva, Switzerland
D. Esperante Pereira
IFIC, Valencia, Spain
J. Tagg
National Instruments Switzerland, Ennetbaden, Switzerland
M. Volpi
The University of Melbourne, Melbourne, Victoria, Australia

CERN has constructed and is operating a new X-band test stand containing two pairs of 12 GHz, 6 MW klystrons. By power combination through hybrid couplers and the use of pulse compressors, up to 45 MW of peak power can be sent to any of 4 test slots at pulse repetition rates up to 400 Hz. The test stand is dedicated to RF conditioning and testing of high gradient accelerating structures for the CLIC study and also future X-band FELs. Operations have been ongoing for a few months, with initial operation dedicated to control algorithm development. Significant progress has been made in understanding the unique challenges of high power RF combination and phase switching using RF hybrids.

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THPIK096

Jitter Measurement to 10ppm Level for Pulsed RF Power Amplifiers 3 - 12GHz

4314

C.H. Gough, S. Dordevic, M. Paraliev
PSI, Villigen PSI, Switzerland

Linacs for FEL applications require a low jitter RF path from RF source through pulsed amplifiers, klystron / modulators and cavities. For the SwissFEL project, pulsed solid state power amplifiers of the 500W / 3us class for driving the klystrons were required. For these amplifiers, a stable and reliable interferometer system was developed to measure the residual RF jitter levels to <10 ppm (parts per million) and <10 urad (0.6mdeg) rms. This paper describes the system and gives some measurement results for 3GHz, 5.7GHz and 12GHz amplifiers.

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THPIK101

Quarter Wavelength Combiner for an 8.5kW Solid-State Amplifier and Conceptual Study of Hybrid Combiners

4324

T.-C. Yu, F.Y. Chang, L.-H. Chang, M.H. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, Z.K. Liu, C.H. Lo, C.L. Tsai, Ch. Wang, M.-S. Yeh
NSRRC, Hsinchu, Taiwan

Experimental results to combine ten 900 W solid-state amplifier modules based on typical quarter wavelength 10-way combiners are described for a total of 8.5 kW RF power output at 500 MHz. The power gain and phase distribution among the ten modules are measured and calculated to sense the combination efficiency. The combination efficiency of 100 modules differing in power gain and phase distribution is theoretically analysed. Groups of 5, 10, 25, 50 and 100 units are used in 4, 3, 2, and 1-stage power combination for total 100 units and the characteristics are calculated and investigated, including bandwidth, efficiency and even redundancy under various output VSWR levels. To simplify combining complexity and to eliminate the drawbacks of single stage combiners, a multi-way 2-stage coaxial to waveguide combiner is thus proposed as an expandable power combiner.

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THPIK109

The RF Distribution System for the ESS

4352

T.R. Edgecock, N. Turner
University of Huddersfield, Huddersfield, United Kingdom
P. Aden, D. Naeem, R. Smith
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
A. Sunesson, R.A. Yogi
ESS, Lund, Sweden

The RF distribution system for the European Spallation Source will be one of the largest systems ever built. It will distribute the power from 146 power sources to the two types of ESS cavity at two different frequencies and will use one line per cavity for resilience. It will consist of a total of around 3.5 km of waveguide and coaxial line and over 1500 hundred bends. It is designed to transport this RF power over a distance of up to 40m per line, while minimising losses, avoiding reflections and allowing the monitoring of performance. This contribution will give an overview of the design of the system and its status. Installation is due to start in September 2017.

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THPIK117

High Efficiency High Power Resonant Cavity Amplifier for Accelerator Applications

4374

M.P.J. Gaudreau, D.B. Cope, E.G. Johnson, M.K. Kempkes, J. Kinross-Wright, R.E. Simpson
Diversified Technologies, Inc., Bedford, Massachusetts, USA

Funding: Work supported by US Department of Energy under contract DE-SC0015780
Diversified Technologies, Inc. (DTI) has designed and built a unique integrated resonant-cavity combined solid-state amplifier. The design radically simplifies solid-state transmitters to create favorable and straightforward scaling to high power levels. A crucial innovation is demonstration of an inherently reliable soft-failure mode of operation; a failure in one or several of these myriad combined transistors has negligible performance impact. In addition, this design couples the transistor drains directly to the cavity without first transforming to 50 Ohms, avoiding the otherwise-necessary multitude of circulators, cables, and connectors. A conventional amplifier has a complete set of electrical and cooling connections for every stage, resulting in many hundreds of connections for a high power transmitter'in some DTI designs, there are as few as four. This construction both reduces the cost and increases the power level at which it is cost-effective to employ a solid-state transmitter. The prototype has demonstrated multiple-transistor combining from 300 MHz to 1300 MHz, at powers up to 5 kW. This prototype is scalable to several hundred kW at these frequencies.

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THPIK121

Eddy Current Analysis for a 1.495 GHz Injection-Locked Magnetron

4383

S.A. Kahn, A. Dudas, R.P. Johnson, M.L. Neubauer
Muons, Inc, Illinois, USA
R.A. Rimmer, H. Wang
JLab, Newport News, Virginia, USA

Funding: U.S. DOE SBIR/STTR grant DE-SC0013203
An injection-locked amplitude modulated magnetron is being developed as a reliable, efficient RF source that could replace klystrons used in particle accelerators. A trim magnetic coil is used to alter the magnetic field in conjunction with the anode voltage to maintain an SRF cavity voltage while the cavity is experiencing microphonics and changing beam loading. The microphonic noise modes have frequencies in the range 10-100 Hz. The changing magnetic field will induce transient eddy currents in the copper anode of the magnetron which will buck the field in the interaction region. This paper will describe the calculation and handling of the eddy currents in the magnetron.

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THPIK122

Methods of Phase and Power Control in Magnetron Transmitters for Superconducting Accelerators

4386

G.M. Kazakevich, R.P. Johnson, M.L. Neubauer
Muons, Inc, Illinois, USA
V.A. Lebedev, W. Schappert, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Various methods of phase and power control in magnetron RF sources of superconducting accelerators intended for ADS-class projects were recently developed and studied with conventional 2.45 GHz, 1 kW, CW magnetrons operating in pulsed and CW regimes. Magnetron trans-mitters excited by a resonant (injection-locking) phase-modulated signal can provide phase and power control with the rates required for precise stabilization of phase and amplitude of the accelerating field in Superconducting RF (SRF) cavities of the intensity-frontier accelerators. An innovative technique that can significantly increase the magnetron transmitter efficiency at the wide-range power control required for superconducting accelerators was developed and verified with the 2.45 GHz magnetrons operating in CW and pulsed regimes. High efficiency magnetron transmitters of this type can significantly reduce the capital and operation costs of the ADS-class accelerator projects.

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THPIK123

Magnetron Design for Amplitude Modulation

4389

M.L. Neubauer, A. Dudas, S.A. Kahn
Muons, Inc, Illinois, USA
R.A. Rimmer, H. Wang
JLab, Newport News, Virginia, USA

The amplitude modulation (AM) of a magnetron is accomplished by varying the magnetic field which changes the current to the anode and the output power of the injection locked magnetron. The purpose of the AM is to compensate for microphonics in super conducting cavities by maintaining a constant gradient. The frequency range for the microphones is below 200 Hz. At these frequencies, eddy currents are encountered in the magnetron anode that reduce the effectiveness of the varying magnetic field on the magnetron current. A novel anode design is described which minimizes eddy currents and a method for manufacturing this novel magnetron anode is presented

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THPVA114

Status of High-Efficiency Klystron Development for the PLS-II and PAL-XFEL

4726

S.J. Park, H.S. Han, W.H. Hwang, S.D. Jang, Y.D. Joo, K.R. Kim, C.D. Park, Y.J. Park
PAL, Pohang, Kyungbuk, Republic of Korea
J.H. Hwang, S.S. Jang
POSTECH, Pohang, Kyungbuk, Republic of Korea
S.Y. Hyun, H.S. Seo, D.H. Yu
Vitzrotech Co., Ltd., Ansan City, Kyunggi-Do, Republic of Korea

Funding: This work was supported by the National R&D program (grant number: 2016R1A6B2A01016828) through the National Research Foundation of Korea (NRF).
We are developing a high-efficiency klystron for use in the PLS-II(Pohang Light Source II) and the PAL-XFEL in the Pohang Accelerator Laboratory. Since the PLS-II and the PAL-XFEL are already running with ~70 klystron modulator systems, newly developed klystrons should be designed to fit into existing installation spaces and power supplies, and their overall lengths(< 2 m) and beam perveances(2 upervs) should not be changed. In order to achieve the high efficiency with aforementioned boundary conditions, we are going to adopt a multi-cell output cavity in which, unlike those of the the SLAC X-band and KEK C-band klystrons, the cell frequencies are independently tuned to provide maximum beam-to-rf power conversion. In this article we report on our physics and engineering design efforts to achieve the high efficiency with minimum instabilities.

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