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Goal of the Continuous Wave and High Average Power RF Workshop is to share the experience and ideas on applications which utilize high-power klystrons, gridded tubes, combined solid-state architectures, high-voltage power supplies, high-voltage modulators, high-power combiners, circulators, cavities, power couplers and tuners. New ideas on upgrading the high-power RF system and novel ways of the RF power generation and distribution will also be discussed.
Tenth workshop will be hosted by the National Synchrotron Radiation Research Center (NSRRC) in Hsinchu, Taiwan from June 26 to 29, 2018. More details can be found at the workshop Website:
http://www.nsrrc.org.tw/cwrf2018/
This CERN Indico site is used to manage the abstracts, presentations and archive the contributions.
Introduction to NSRRC, place holder
The injector 2 cyclotron is the second accelerator stage of the high intensity proton accelerator (HIPA) at PSI. In this cyclotron protons are accelerated from 870keV to 72MeV. The beam current is up to 2.4mA DC. The injector 2 is built as a separated sector cyclotron with 4 sector magnets and 4 sections for cavities. The main acceleration is done by two 50MHz cavities. From the initial design two cavities on the 3rd harmonic frequency for flat-toping are installed. Now day those flattop cavities are used as additional accelerating cavities.
Several years ago an upgrade program started to replace the 150MHz cavities by 50MHz for a higher energy gain per turn. This will lead to lower extraction losses and some freedom for higher beam currents. On the other hand the 40 years old LLRF and amplifier systems will be replaced by this upgrade.
During the shutdown this year the first new cavity was installed as vacuum chamber. Until the next shutdown in 2019 the new LLRF and amplifier system will be built and commissioned, to operate the new cavity. This talk will give an overview of the ongoing project with a closer look at the cavity test results.
A homemade KEKB-type 500 MHz superconducting cavity for BEPCII has been developed and operated with beam successfully at IHEP. The unloaded Q value of the cavity is about 2.5e9 at the routine operation voltage of 1.5 MV and the maximum measured voltage is 2.17 MV with a Q0 of 5.8e8. A brief introduction on the cavity’s fabrication, vertical test, horizontal test and beam operation will be presented.
Beam loading improvements were performed to the RHIC landau damping cavity, with the addition of an external loading network. The improvement is required to achieve a beam intensity of 3.0x10^9 Au Ions/bunch.
A status update of the 200MeV drift tube linac pulse width upgrade will be discussed. The increased RF pulse width from .6mS to 1.1mS results in drift tube spring ring failure.
In a steady-state nuclear fusion reactor of the tokamak type, energetic neutral beam injectors and high-power CW RF systems should be employed. These systems are needed to heat the plasma up to the required temperatures of 10-20 keV and to drive a non-inductive plasma-current which is required for the plasma confinement. This paper overviews at first the aforementioned systems and emphasizes on those operating at the Ion Cyclotron and Lower Hybrid Range of Frequencies (ICRF~50MHz, and LHRF~5GHz) as well as on their particularities.
In particular, the paper details the three newly developed megawatt-range CW ICRF antennas of the WEST tokamak. These antennas are based on the internal conjugate-T concept which allows the antennas to be intrinsically immune to the quasi-periodic variations of the plasma loading. The pre-qualifications tests which are conducted to accelerate the commissioning of these antennas on plasma are also reported. Furthermore, the paper discusses the security systems which insure the WEST ICRF system’s safety, in particular the arc detection systems.
The paper then discusses the megawatt-range CW LHRF antennas of WEST which are based on the intrinsically immune multi-junction concept. The paper finally presents the development of a low-power prototype LHRF antenna based on the Slotted-Waveguide Antenna concept and its tests on the COMPASS tokamak.
RF Solid-state technology has emerged in accelerator application in recently years due to the fast development of semiconductor as well as the communication industry and the reduction of vacuum tube market. To generate RF power in scientific application is an useful and interesting topic, some efforts have been made to build solid-state amplifier technology from circuit components, thermal management to the property of systematic power combination in NSRRC, including round planar balun, cooling effects by numerous materials and the the power combination efficiency by various nature spread of the amplifier modules. The results of studies would be demonstrated by a 20-way power combination test stand.
High power solid-state amplifiers at 162.5 MHz and 325MHz were developed for a 25MeV superconducting proton linear accelerator system, consists of two 80kW 162.5 MHz amplifiers for RFQ, two 162.5 MHz 12kW amplifiers for buncher cavities, twelve 12kW 162.5 MHz amplifiers, five 20kW 162.5 MHz amplifiers and six 25kW 325MHz amplifiers for SC cavities.
In this talk, commissioning and operating experiences on the solid-state amplifiers systems will be presented along with the latest progress.
Recent developments in the design and performance of a prototype 352-MHz/12kW solid state rf system utilizing a combining cavity will be discussed. Re-tuning 352-MHz/1MW cw klystrons for re-purpose will be discussed.
In 2014, Ampegon presented a novel 500MHz, 65kW CW Solid State RF Amplifier, developed in cooperation with Paul Scherrer Institute (PSI) in Switzerland [1]. Since then, Ampegon has developed this system into a second generation, focussing particularly on standardization, simplicity, scalability, efficiency, robustness, and maintainability. This resulted in an economical system optimized both for the scientific research community, specifically for accelerator labs, as well as for industry and market segments outside scientific research labs. This second-generation 500MHz Solid State Amplifier System is based on a double RF power module and a scalable RF cavity combiner providing up to 80kW nominal and 96kW peak output power per cabinet. The power modules have been designed to follow an automated production process, which provides the same high-quality standard expected of industrialized products and reduced costs of production. This presentation will highlight the amplifier topology based on the latest 500MHz Solid State Amplifier versions (60kW and 80kW CW) for Diamond Light Source (DLS) and show the impressive performance indicators and efficiency measurements. It also addresses system performance improvements over the first generation, presented previously, and the detail of the OEM components.
We report here about the upgrades, which were recently brought in the Soleil RF systems as well as contributions to other projects.
High Energy Photon Source (HEPS) is a 6 GeV synchrotron light source with ultra-low electron beam emittance and a kilometer scale circumference. It has been proposed by IHEP and is planned to be built in Beijing from late 2018. Six PETRA-type 5-cell 500 MHz copper cavities will be used in the booster ring to provide 8 MV RF voltage and 60 kW of beam power. Each cavity will be powered by a 100 kW solid-state amplifier. For the storage ring, a double-frequency RF system has been adopted with 166.6 MHz as the fundamental while 499.8 MHz as the third harmonic. Five 166.6 MHz superconducting cavities will provide the required 5.5 MV RF voltage and 900 kW of beam power. Each cavity will be driven by a 250 kW solid-state amplifier using one single-window coaxial-type fundamental power coupler. The harmonic cavity, on the other hand, is planned to use single-cell 500 MHz elliptical SRF cavity, while its power amplifier will also make use of solid-state technology but its power is to be determined depending on whether an active or a passive harmonic system will be used. This paper describes the high power RF system for the HEPS project.
The CiADS (China initiative Accelerator Driven System) plans to build the 500MeV SC Linac (2018-2024)，loading CW 5mA proton beam. 160 Solid State Amplifiers will be employed to drive the RFQ, buncher, and SC cavity. Along the linac, the operating frequency of SSAs rises up from 162.5 MHz to 325MHz and 650MHz, the level of output power rang from 10kW to 100kW. This report will introduce the design of SSAs, including the RF and mechanical structure, considerations of the RF power’s uniformity, redundancy and feasibility for future update.
I will present the status of the RF systems at the Advanced Light Source (ALS) and the progress made in commissioning the new Storage Ring RF system.
Additionally, I will report on the conceptional design of the ALS-U accumulator RF system and the VHF solid state amplifier for the LCLS-II Gun B collaboration.
A second X-ray free electron laser facility, LCLS-II, is being constructed at SLAC. LCLS-II is based on a 1.3 GHz, 4 GeV, continuous-wave (CW) superconducting linear accelerator, to be installed in the first kilometer of the SLAC tunnel. Multiple types of high power RF (HPRF) sources will be used to power different systems. The main 1.3 GHz linac will be powered by 280 1.3 GHz, 3.8 kW solid state amplifier (SSA) sources. The normal conducting buncher in the injector will use four such SSAs. Two 185.7 MHz, 60 kW sources will power the photocathode dual-feed RF gun. A third harmonic linac section, included for linearizing the bunch energy spread before the first bunch compressor, will require sixteen 3.9 GHz sources at about 1 kW CW. A description and an update on all the HPRF sources of LCLS-II and their implementation is the subject of this presentation.
*Work supported by DoE, Contract No. DE-AC02-76SF00515
The NSLS-II has been operating for four years with two CESRb type SRF cavities powered by 300 kW klystron transmitters. As the operating current is raised from 375 mA operations today to the design value of 500mA, and additional insertion devices increase the energy loss per turn we will reach a limit in installed RF power by 2020. A new project to add a third SRF system to provide power for the additional synchrotron radiation losses has been started. A third niobium cavity which was part of the original project construction has been BCP processed at Cornell including a new N2 doping which has resulted in a record Qzero in vertical test. The processed cavity is being integrated with the industry produced cryomodule by the RF group in our clean room facilities at NSLS-II. A contract has been awarded for commercial production of a 310 kW transmitter and the liquid helium valve box and distribution piping. A description of the system design and project status will be described.
Design features and test results of a multibeam inductive output tube (MB-IOT) that produces over 1.2 MW peak power at 704 MHz with over 65% efficiency will be presented. This is a collaborative effort between Thales Electron Devices and Communications & Power Industries to design and fabricate a new RF source for the European Spallation Source (ESS). The first prototype has been designed and built. The device contains 10 beams generated by 10 gridded guns, focused by a single solenoid and deposited in 10 isolated collectors. The beam-wave interaction takes place inside a coaxial cavity. An input circuit evenly distributes the single input drive power to the individual guns. Initial test at CERN demonstrated output power of 1.2 MW peak, efficiency of 69.8%, and gain of 21.4 dB at 1 ms operation, with 45 kV cathode voltage and with 98% beam transmission. Efficiency was also maintained above 60% down to 680 kW reduced power level. When the pulse length was increased to 4 ms, instability in the RF output pulse developed as the result of a mechanical contact issue in the output window. An improved design has been assembled on to the tube and the repaired prototype has been shipped back to CERN. Subsequent testing is expected in September 2018 to demonstrate full compliance to the ESS requirements.
A critical component of most accelerators is the source of high power RF. Klystrons have often the go-to choice, especially for high power and high frequency. CEBAF has accumulated over 25 years of operation using 420 installed klystrons to meet the goals and provide RF for its physics program. Numerous devices have failed and can be expected to continue doing so, and likely with ever increasing frequency as tubes continue to age. Overall life has far exceeded the original specification requested of vendors. This talk will discuss the history, performance, failures, remediation, monitoring, and life of these devices, plus look at what is expected for the next 20 years of operation. Upgrades have increased maximum accelerator gradient from 4 to 6 to 12 GeV and along with it placed additional stresses and demands on already mature systems.
In SSRF, there are one 180kW klystron, three 300kW klystrons and their high power supplies and waveguide systems in SSRF. From 2009, when the SSRF has been open for user, all the transmitters work well inspite of some problems. This presentation will show the operation status of all the high power sources. Also all the problems and process methods will be shown.
The ESRF's 6 GeV storage ring (SR), commissioned in 1992 and known as the world's first third-generation light source, will be shut down in December 2018 after more than 24 years of reliable user operation. Within one year it will be replaced by an ultra-low emittance 6 GeV ring, which will provide the ESRF with the first Extremely Brilliant Source (EBS) for hard X-rays. Almost all of the parts for the new ring have been delivered and the complete assembly of subsystems is progressing as planned. This will allow a short installation phase ready for commissioning to start in November 2019.
A review of recent RF operation experience with the existing five-cell cavities, two prototype HOM damped single cell copper cavities, RF klystrons and solid state power amplifiers (SSPA) will be presented as well as the status of the RF system upgrade for the new EBS ring. The 12 new series fabricated HOM damped cavities for EBS were all successfully conditioned to 750 kV for a nominal working point at 500 kV, even though some technical problems were encountered during the fabrication of the cavities and their auxiliaries. A report will also be made on the successful identification and mitigation of the technological and mechanical issues encountered throughout the process.
The Iranian Light Source Facility project (ILSF) is a third generation light source with a 3GeV ultra low-emittance storage ring. A thermionic-cathode RF gun will provide the electrons for 150MeV Linac based pre-injector. The cold test results of the first fabricated prototype are in good agreement with the simulation results. Motivated by MAX-IV RF system development at lower frequency, similar 100MHz RF system with capacity-loaded cavity has been chosen for the storage ring and booster. Following the cavity electromagnetic and mechanical design, fabrication of a copper prototype is initiated in order to conclude the possibility of in-house cavity development. Adding a mushroom part to an existing 500MHz aluminum pillbox cavity, a capacity-loaded structure is also available to study the HOM characteristics and tuning mechanisms. Three 30kw and five 60kw solid state amplifiers will be probably supplied from domestic companies based on their experiences in manufacturing of FM transmitters. After an overview of the ILSF RF system design, the ongoing R&D activities will be presented.
The European XFEL is a X-ray laser which uses a 17.5GeV electron beam to generate X-ray light of unprecedented properties. The electrons are accelerated by a linear accelerator which uses 808 superconducting cavities at 1.3GHz. 27 RF stations produce RF power up to 10MW each at 1.4ms pulse width and 10Hz repetition rate to accelerate the electrons in the cavities with gradients of average 23.6MV/m. This paper gives an overview of the layout of the HPRF system and summarizes the experience during commissioning and initial operation of the XFEL.
A third-generation light source SPring-8 has been operated for 20 years. Many of high power components and electrical circuits were aged and outdated. We have updated and reconstructed these components and systems for next 20 years operation, in advance of the upgrade project SPring-8-II. The 8 GeV storage ring has four RF stations to generate a voltage of 16 MV at the frequency of 508.58 MHz. Each RF station consists of 8 bell-shaped single cell cavities driven by a 1.2 MW klystron, combined with a low-level RF system. First, we replaced klystron power stations, supplying a high voltage of 90 kV and a current of 20 A with simple and reliable architecture. Next, we have reconstructed the low-level RF system for one of the RF stations, with newly developed Micro-TCA based modules. The new system is remarkably compact, flexible, and conserves high accuracy of the RF amplitude and phase control. In addition, a vacuum system and an interlock system were also replaced to the new systems with PLC and EtherCAT network connection. This presentation reports these upgrade activities.
The Spallation Neutron Source (SNS) is an H-ion accelerator-based neutron source constructed in Oak Ridge National Laboratory (ORNL). The accelerator delivers 1 GeV, 1.4 MW proton beams to Mercury target for delivering pulsed neutron particles for scientific research. The accelerator employs H- plasma ion source, RFQ, MEBT, DTL, CCL, SCL, and accumulator ring. Since commissioning in 2006, SNS RF Systems have been being tuned up steadily toward the 1.4 MW design beam power with the ion source delivering 38 mA peak pulsed H- beam current (26 mA chopped average). Recently the SNS had a long maintenance outage to replace the RFQ for improved system performance. Other RF systems have provided reasonably reliable operational performances for neutron production. The SNS now has the proton power upgrade (PPU) project that will increase the peak beam current to 59 mA (38 mA chopped average), the beam energy to 1.3 GeV, and the total beam power to 2.8 MW. The inclusion of the new RFQ in the SNS linac is an important upgrade in SNS for robust operation with the present beam power requirement as well as the future power upgrade that will need the robustness of the linac injector system. The status and progress of the operations and the development of the RF systems, subsystems, and components in the SNS linac will be presented.
The European Spallation Source (ESS) currently under construction in Lund, Sweden will deliver a 5 MW average beam power. The RF power to the pulsed proton beam of 2.86 ms at a repetition rate of 14 Hz will be achieved with the installation of 155 high power amplifier stations. This talk will provide a status update on the RF systems being procured and will present the high power test results of the two multi-beam IOT technology demonstrators.
ALBA is a 3 GeV synchrotron light source located in Barcelona and operating with users since May 2012. The RF systems are based in IOT transmitters and a total of thirteen 80 kW IOT amplifiers are used to power the Storage Ring and Booster cavities at 500 MHz. A modular Solid State Power Amplifier (SSPA) has been proposed for an already designed active 3rd Harmonic RF system of the ALBA Storage Ring. This SSPA is aimed to provide up to 20 kW power per cavity in a Continuous Wave (CW) mode at 1.5 GHz nominal frequency. Accordingly, a 250 W power amplifier module, as the primary unit, has been designed and tested. This SSPA system will be composed of modules of 1 kW, combining four primary units. For these modules, a parallel combination array using a 4-way power divider/combiner of microstrip type has been designed and tested. In this poster the design of the primary unit and combination array as well as their test results will be presented.
Results of the specification, procurement and acceptance testing of the 186MHz (2x) 60 kW CW Solid State Amplifier for the LCLS II Gun B system collaboration project will be presented. The two 60 kW CW SSA amplifiers were specified then ordered through a competitive bid process. The selected manufacture delivered a complete turn-key amplifier system designed for high reliability and performance.
The SRF system of the Pohang Light Source-II (PLS-II) storage ring is operating at the 3.0 GeV/400 mA with three superconducting RF (SRF) cavities. PLS-II SRF system was upgraded to 3.0 GeV/400 mA beam storage from 2.5 GeV/ 200 mA of PLS. Each high power RF (HPRF) station is composed of a 300 kW klystron with KSU power supplies, transmission components including a 350 kW circulator and load, and water cooling system. The TH2161B 300 kW klystrons are generally operated as an RF power source with good performances for SRF system of light sources. This paper describes the present operation status and experience of the high power SRF system as well as klystron and LLRF for PLS-II storage ring.
The high power RF (HPRF) systems have been designed for a heavy ion accelerator of Rare Isotope Science Project (RISP). The HPRF system includes SSPAs (160kW for RFQ, 4kW for QWR, 4kW for HWR), high power circulators, high power RF transmission system. The HPRF transmission systems have designed to provide RF power to each accelerator. The HPRF transmission systems for the performance test of RFQ and superconducting cavities have been installed and operated at the SRF test facility.
The CW RF system for the superconducting cavities of 81.25 MHz quarter wave resonators (QWR), 162.5 MHz half wave resonators (HWR), and 325 MHz single spoke Resonators (SSR) has been designed and the prototypes of HPRF system including SSPAs (4kW for QWR, 4kW for HWR), circulators, and the high power RF transmission line components have been fabricated. With the HPRF systems, the SRF cavities and cryomodules have been tested for a heavy ion accelerator of the Rare Isotope Science Project (RISP).
Shanghai Coherent Light Facility (SCLF) is 8GeV superconductivity LINAC, worked in CW operation mode and beam current is 0.2mA. the acceleration architecture of LINAC consists of six hundred 1.3GHz and sixteen 3.9GHz TELSA type cavities. The length of acclerator is 1.2km at 28 meters underground. Solid state amplifier will be employed to drive the 1.3GHz SC. This poster will descript the design of RF station,lists the specification some features of SSA.
The RF (Radio-frequency) system in the RAON (Rare isotope Accelerator complex for On-line experiment) is constructed as an HPRF systems supplying high RF power to the cavity, LLRF systems for controlling HPRF, and reference line system synchronizing every RF systems.
80 kW RF system for RFQ cavity have been designed to supply RF field in the RFQ cavity. In this paper, we will describe details of High power test for RFQ cavity and construct of the 80 kW SSPA.
ALBA is a 3 GeV synchrotron light source located in Barcelona and operating with users since May 2012. The IOT based transmitter for the booster cavity will be replaced by a Solid State Power Amplifier (SSPA) of 50 kW at 500 MHz in August 2018. The new transmitter is made of 96 active devices, which are divided in 12 modules of 8 transistors each one, all housed in a single 44U rack. The modules are combined in groups of four using the Gysel topology and two hybrid combiners are used for the final combining stage. The design allows the transmitter to provide enough power even when multiple transistor fails occur, in the same module or in different ones, and it also presents power supplies redundancy. These modules can be hot swapped, i.e., the module can be replaced by a spare at any time without affecting the operation of the booster, even when the transmitter is providing power. Some results and performance values made during the design and construction phase are already available, such as maximum power, efficiency, losses, temperatures, failure case study, etc.
The Advanced Rare Isotope Laboratory (ARIEL) project requires a 50 MeV, 10 mA continuous-wave (CW) electron linear accelerator (e-Linac) as a driver accelerator. Now the stage of the 30MeV portion of the e-Linac is under commissioning which includes an injector cryomodule (ICM) with one 9-cell cavity and the 1st accelerator cryomodule (ACM1) with two 9-cell cavities. A single 290kW klystron is used to drive the two ACM1 cavities in vector sum closed control loop. The initial commissioning results of the ACM1 RF system will be present.
30 MeV proton accelerator (cyclotron) facility, RFT-30, is constructed at KAERI (Korea Atomic Energy Research Institute) in Republic of Korea. RFT-30 is based on a 63.96 MHz, 30 MeV, continuous-wave (CW) cyclotron accelerator. The 63.96 MHz cyclotron is powered by 63.96 MHz, 50 kW vacuum tube amplifier source. The normal conducting RF buncher in the injector is used to increase the beam extraction efficiency, and it is powered by 250 W solid state RF amplifier (SSRF). This presentation shows a detailed description and progress on all the HPRF sources of RFT-30.
Two modern light sources, the 1.5 GeV Taiwan Light Source (TLS) and the 3.0 GeV Taiwan Photon Source (TPS), are now routinely operated at NSRRC to service its user community. Both light sources are powered by the superconducting cavities. The SRF module of CESR-III design was selected for the TLS and has been routinely operated since the end of 2004. Two SRF modules of KEKB design were installed for the TPS and have been routinely operated since the autumn of 2015. Here we report the status of SRF operation at NSRRC including the challenge we met and the remedy we are attempting to. The target of pursue is to commit the reliability and availability acceptable for our user community.
The European Spallation Source (ESS) LINAC includes a specific section called “Spoke Section” with a row of accelerating structures designed for high power pulsed operation at 352.21 MHz. They consist in 26 superconducting spoke cavities, each one powered by a single RF power source, the RFPS. The spoke cavity RF power demand ranges between 260 kW to 330 kW depending on the proton beam energy and acceleration pattern. The RFPS nominal power have therefore been standardized to 400 kW. The RFPS is a complete system that operates unmanned, based on a chain and a combination of solid state and tetrode amplification’s stages.
The 26 equivalent 400 kW RFPS units will be provided by Elettra as part of the Italian contribution to ESS. Their construction is going to be assigned to the successful contractor according to the public procurement procedure in the framework of a trilateral agreement among ESS, Elettra and INFN, Elettra in charge for the contract management and the technical execution.
The tender specification, the RFPS main features and requested performances are discussed here as well as the implemented strategy to fulfil the quality standard for this contribution.
The purpose of a radio-frequency system in a high-energy accelerator is to provide energy to the particle beam. A RF coupler is necessary to transfer the high power from a RF generator to the cavity. A coupler of coaxial type is a common choice. With high-power operation, it might suffer from multipacting, which is a resonance phenomenon due to re-emission of secondary electrons. Applying a bias voltage between inner and outer conductors of the coaxial coupler might increase or decrease the strength of the multipacting effect. We studied the effect of a bias voltage on multipacting using numerical simulation to track the motion of the electrons. We will present the simulation results and the experimental experience in TPS operation.
The CWRF workshop started 20 years ago in a pub-pizzeria in Chicago. An informal event grew into a renowned international workshop, hosting the world's leading experts on high power RF systems for particle accelerators.
This talks looks back to the beginning and to the future.