Eighth CW and High Average Power RF Workshop

13 May 2014, 08:00 → 16 May 2014, 18:00 Europe/Zurich

Hotel NH Trieste (Elettra - Sincrotrone Trieste)

Alessandro Fabris (Sincrotrone Trieste), Alireza Nassiri (Argonne National Laboratory - DOE)

This is the eighth in the CWRF workshop series and will be hosted by Elettra - Sincrotrone Trieste S.C.p.A.

CWRF2014 sessions will start on Tuesday morning and will conclude on Friday lunchtime. A visit to Elettra and FERMI will be organized during the workshop.

Workshop web page.

Main areas that will be covered:
- RF Power Sources, Tubes and Solid State Architectures
- High Voltage Power Supplies and Modulators
- RF Power Transmission, Coaxial and Waveguides
- Cavities, Power Couplers and Tuners


ORGANIZING COMMITTEE (OC):

• Alessandro Fabris (Elettra Sincrotrone Trieste) - Workshop Chair
• Alireza Nassiri ( ANL) - Workshop co-Chair)
• Erk Jensen (CERN)
• Morten Jensen (ESS)
• Francis Perez (ALBA - CELLS)
• James Rose (BNL)
• Shigeki Sasaki (SPRing-8)

SCIENTIFIC PROGRAM COMMITTEE SPC):

• Ken Baptiste (LBNL)
• Hans-Rudolf Fitze (PSI)
• Doug Horan (ANL)
• Jörn Jacob (ESRF)
• Yoon Kang (ORNL)
• Patrick Marchand (Synchrotron SOLEIL)
• Eric Montesinos (CERN)
• Richard Nelson (JLAB)
• Daniel Valuch (CERN)

LOCAL ORGANIZING COMMITTEE (LOC)

• Alessandro Fabris (Elettra Sincrotrone Trieste) - Workshop Chair
• Mariella Antonetti (Elettra Sincrotrone Trieste)
• Stefano Deiuri (Elettra Sincrotrone Trieste)
• Paolo Delgiusto (Elettra Sincrotrone Trieste)
• Claudio Serpico (Elettra Sincrotrone Trieste)

Tuesday, 13 May

09:00 → 10:30 Tuesday morning 1

Convener: Dr Alessandro Fabris (Sincrotrone Trieste)

09:00 Workshop opening

Workshop opening, practical information.

Speaker: Dr Alessandro Fabris (Sincrotrone Trieste)

Slides CWRF_2014_opening.pdf CWRF_2014_opening.ppt

09:20 Welcome address by Prof. Giovanni Comelli, vice-president Elettra-Sincrotrone Trieste S.C.p.A.

Welcome address by Prof. Giovanni Comelli, vice-president Elettra-Sincrotrone Trieste S.C.p.A.

09:30 A tribute to Ti Ruan

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Speaker: Robert Lopes (Soleil)

10:00 Elettra and FERMI, The Accelerator Facilities at Elettra Sincrotrone Trieste

Elettra Sincrotrone Trieste is a multidisciplinary international laboratory of excellence, specialized in generating high quality synchrotron and free-electron laser light and applying it in materials science. The main assets of the research center are two advanced light sources, the electron storage ring Elettra and the free-electron laser (FEL) FERMI. This presentation provides an overview of the machines, their development and their operation. Special focus will be dedicated to the RF systems that have been designed and are now in operation both for the storage rings and the linacs.

Speaker: Dr Alessandro Fabris (Sincrotrone Trieste)

Slides MAY13__CWRF2014_AFA.pps

10:30 → 11:00 Coffee break

11:00 → 12:30 Tuesday morning 2

Convener: Dr Alireza Nassiri (Argonne National Laboratory)

11:00 Powering CEBAF’s Extraction Cavities At 12 GeV

CEBAF (Continuous Electron Beam Accelerator Facility) at Jefferson Lab was initially designed to deliver up to a 4 GeV electron beam simultaneously to three experimental halls. The maximum deliverable energy was raised to 6 GeV and CEBAF ran there until May of 2012 after which CEBAF entered an extensive, upgrade shutdown. After the upgrade, scientists plan to use CEBAF to deliver 11 GeV beam to the three original experimental halls and 12 GeV to new hall – Hall D. Delivering beams to multiple halls at the new energy requires increased RF power to drive the separation cavities and adding a 750 MHz beam repetition rate to deliver beam to all halls simultaneously. Doubling the beam energy means doubling field strength in the cavities by quadrupling delivered power. 750 MHz beam repetition rate requires new 750 MHz capable cavities and a frequency change to one of the existing IOT amplifiers powering these cavities, and new 499 MHz SSAs to power four downstream cavities. Topics covered will include: verifying the Cavity’s power capabilities, modifications to the 750 MHz system and new cavities, and the decision process in selecting an amplifier type to power four downstream cavities.

Speaker: Mark Wissmann (J)

11:30 Status and Operating Experience of the ELBE RF System based on 10kW SSPAs

H. Büttig, A. Arnold, A. Büchner, M. Justus, M. Kuntzsch, U. Lehnert, P. Michel, R.Schurig, G. Staats, J.Teichert. Radiation Source ELBE, Helmholtz Zentrum Dresden- Rossendorf, Germany Abstract: In January 2012 the 10 kW klystrons of the CW LINAC ELBE were replaced by pairs of 10kW solid state power amplifiers (SSPA). The talk gives an overview on the SSPA based ELBE RF system. The experience gained during the first two years of operation is reviewed.

Speaker: Hartmut Büttig (Helmholtz Zentrum Dresden-Rossendorf)

Slides cwrrf14neu_HB.pdf

12:00 Early Commissioning Results of the NSLS-II High Power RF Systems

The NSLS-II has completed early commissioning with the booster synchrotron utilizing a 80 kW IOT transmitter powering a 7-cell “PETRA” like cavity and the storage ring a 300 kW klystron transmitter powering an identical cavity. The 7-cell cavity in the storage ring will be replaced with a “CESR-B” like superconducting cavity during the May 2014 shutdown. Both the klystron and IOT transmitters use switching HV power supplies with redundant switches and programmable switching algorithms that can suppress AC power line harmonics. Early results are presented.

Speaker: Mr James Rose (Brookhaven)

Slides CWRF2014.pdf

12:30 → 14:00 Lunch

14:00 → 15:30 Tuesday afternoon 1

Conveners: Francis PEREZ (CELLS), Dr Francis Perez (ALBA Synchrotron), Francis Perez (A)

14:00 High Power RF System Status and Experience for the PLS-II Storage Ring

The RF system of the Pohang Light Source-II (PLS-II) storage ring is operating at the 3.0 GeV/300 mA with three superconducting RF (SRF) cavities. PLS-II RF system was upgraded to 3.0 GeV/400 mA(max.) beam storage from 2.5 GeV/ 200mA of PLS. Each high power RF (HPRF) station is composed of a 300 kW klystron with power supply unit, transmission components including a 350 kW circulator and load, and water cooling system. Also three digital type LLRFs, three cryomodules with SRF cavities, and a cryogenic system are operating with HPRF system for the PLS-II storage ring. This paper describes the present operation status of 300 kW HPRF system and experiences of the former PLS 75 kW HPRF system. *Supported by the Ministry of Science, ICT and Future Planning in Korea **mhchun@postech.ac.kr

Speaker: Myunghwan CHUN (PAL(Pohang Accelerator Laboratory)/POSTECH)

Slides

• CWRF2014-CHUN-HPRF_System_for_the_PLS-II_SR-final-0513.pdf
• CWRF2014-CHUN-HPRF_System_for_the_PLS-II_SR-final-0513.pdf
• CWRF2014-CHUN-HPRF_System_for_the_PLS-II_SR-final-0513.ppt

14:30 Precision manufacturing considerations of 200 MHz LINAC amplifier

Tubes remain the most effective solution for 200 MHz Final Power Amplifier (FPA) design. An overview of design and manufacturing considerations of a 201.25 MHz FPA, built to Los Alamos Neutron Science Center (LANCE) specifications, will be presented. Precision manufacturing and assembly of amplifier components is critical for optimizing performance of advanced tube design, such as the Thales TH628 Diacrode®. Topics to be presented include an update on system performance at LANCE of their newly designed and manufactured Diacrode Amplifiers, the importance of select raw materials used in manufacturing, and special devices required for heating, component assembly and alignment. Additional system components required such as High Voltage Power Supplies and liquid and air cooling of components will also be presented.

Speakers: Mr Kerry Cozad (Continental Electronics Corporation), Michael Troje (Continentaql Electronics Corp)

Paper Production_considerations_for_LANCE_FPA.pdf

Slides CWRF2014_CEC-LANL_Final.pdf

15:00 Impact of RF Source Efficiency on RF Accelerator Sustainability

RF accelerator electrical energy consumption at the U.S. DOE laboratories was 1 TW-hr in FY2012, and is projected to rise to 1.5 TW-hr by 2018. A major fraction of this energy is used to produce RF power (e.g. this fraction is >50% at SLAC, which is ~40% of the total site energy usage). Although it has long been recognized that improving the efficiency of RF sources would improve sustainability and reduce accelerator program operating costs, developing and implementing higher efficiency systems is typically beyond the means of the programs at individual labs. With the encouragement of the new DOE Accelerator Stewardship program, we have performed a complex-wide survey of RF sources to identify upgrades that could impact multiple lab programs, potentially enabling new sustainability improvement opportunities.

Speaker: Craig Burkhart (S)

Slides Impact_of_RF_Source_Efficiency_-_Burkhart.pdf Impact_of_RF_Source_Efficiency_-_Burkhart.pptx

15:30 → 16:00 Coffee break

16:00 → 17:30 Tuesday afternoon 2

Convener: Dr Erk Jensen (CERN)

16:00 RF System Conceptual Design for the LCLS-II CW, SCRF Linac

At SLAC, a 4 GeV, 1.3 GHz, CW, SCRF linac will be constructed for the LCLS-II project. About 7 kW of rf power will be required per cavity, which will allow operation at 16 MV/m with up to 300 uA beam currents. In the rf system design presented in the project CDR, each cavity in the upstream portion of the machine is powered by a solid state amplifier, while the bulk of the cavities are powered in groups of 48 by 300 kW klystrons. This paper describes these design choices and their related operations issues.

Speaker: Chris Adolphsen (SLAC)

Slides Adolphsen_LCLSII_RF_System_CWRF14_05_13_14.pdf

16:30 RF Operation, HOM Damped Cavities and 150 kW Solid State Amplifiers at the ESRF

In the frame of the ongoing ESRF upgrade phase 1, a new RF section has been recently commissioned with three strongly HOM damped cavities powered by three 150 kW Solid State Amplifiers (SSAs). On the booster, four 150 kW SSAs are replacing the former klystron transmitter since April 2012. Twelve additional HOM damped cavities have been ordered at the end of 2013 for the projected low emittance ring that will replace the existing machine at the end of this decade. The status of RF operation, the commissioning of the new SSAs and the HOM damped cavities and the RF system for the new machine will be presented.

Speaker: Dr Jorn Jacob (ESRF)

Slides Jacob-_CWRF_Elettra_2014.pdf Jacob-_CWRF_Elettra_2014.pptx

17:00 Operational experience of high-power RF at Diamond Light Source

Diamond Light Source is a synchrotron light source facility that has been providing beam for users since January 2007. Diamond consists of a 3 GeV storage ring powered by two 300 kW amplifiers each containing four IOTs, a full energy booster also driven by an IOT-based amplifier and a 100 MeV linac using pulsed klystrons. RF performance and reliability are reviewed for all three accelerators and current operating and conditioning procedures are presented. Efforts to minimise the RF-related disturbance of user beam are detailed and plans for possible future upgrades are presented, including an upgrade of beam current towards an ultimate goal of 500 mA from the present 300 mA and the introduction of a third superconducting cavity to the storage ring.

Speakers: Mr Alun Watkins (Diamond Light Source), Chris Christou (D), Dr Pengda Gu (Diamond Light Source)

Slides Diamond_RF.pdf Diamond_RF.pptx

Wednesday, 14 May

09:00 → 10:30 Wednesday morning 1

Convener: Dr Jorn Jacob (ESRF)

09:00 Operation and Developments of High Power RF Systems at ORNL Spallation Neutron Source (SNS)

SNS has been operating successfully and ramping beam power steadily to 1.4 MW the design power at 1.0 GeV beam energy. Availability of RF systems has been improved to ~ 95% over the years since commissioning of SNS. Improvements have been made in operation of accelerating structures, RF windows and couplers, and high voltage converter modulators (HVCM) for klystrons for powering nearly 100 cavity structures: Radio frequency quadrupole (RFQ), drift tube linac (DTL), coupled cavity linac (CCL) and superconducting cavity linac (SCL). New waveguide RF windows have been built and tested for improved reliability and future beam power and energy upgrades of SNS. A new spare RFQ also has been manufactured and delivered to SNS for more robust performance of the linac front-end system aiming the future upgrades. The four vane RFQ with octagonal cross section and end-wall dipole rods operates at 402.5 MHz. Integrated Test Station Facility (ITSF) is being setup to allow full beam test with H- Ion Source together with the RFQ. High power RF tests are performed for performance acceptance and RF conditioning of the RFQ and systems. The results of high power tests and performance of the RF systems and the components are presented.

Speaker: Dr Yoon Kang (Oak Ridge National Laboratory)

09:30 Gallium Nitride Transistor in continuous wave RF applications

Gallium nitride (GaN) RF transistors have higher power handling capacity, higher efficiency and higher operation frequency compared with silicon RF transistors, which makes GaN device a better choice for continuous wave (CW) RF applications. Due to low yield in device fabrication, GaN transistors used to have a much higher price than silicon ones. As a result, high power RF source using GaN devices is only seen in the most demanding applications. Development in GaN transistor fabrication technology in the last 5 years largely reduced the price of GaN devices. Nowadays, cost of L-Band GaN devices are at about the same level as the silicon equivalents, which makes GaN CW RF design an economically competitive solution. In this paper a design using GaN transistors is presented for the proposed LCLS-II RF source. Capital cost and operational cost of both GaN and Si designs are compared. The estimation suggests a reduction of 32% in both capital and operational cost by adopting the GaN technology. GaN solution also enables amplifier topology with high efficiency, which will reduced the operational cost by 47% compared with solution using Si devices.

Speaker: Tao Tang (S)

Slides CWRF_GaN_ver_4.pdf

10:00 The Advanced Photon Source RF Systems -- Performance and Upgrades, 2012-2014

Technical performance of the Advanced Photon Source rf systems from May 2012 to May 2014 is discussed. Significant hardware problems and failures affecting rf system reliability, and approaches taken to resolve them, are described in detail. System upgrades to enhance performance and reliability are described. The design and construction details of a 5kW S-band cw amplifier developed for the APS Upgrade effort will be presented.

Speaker: Mr Douglas Horan (Argonne National Laboratory)

Slides CWRF2014_HORAN.pdf

10:30 → 11:00 Coffee break

11:00 → 12:30 Wednesday morning 2

Convener: Mr Doug Horan (Argonne National Laboratory)

11:00 20 years of high average Fundamental Power Coupler designs at CERN

Description of high average Fundamental Power Coupler designed at CERN over the last 20 years. Main difficulties and power limitations. Some tips to propose better designs.

Speaker: Eric Montesinos (CERN)

Slides CWRF_2014_CERN_FPC.pdf CWRF_2014_CERN_FPC.pptx

11:30 A Significant Increase of the Efficiency at the Operating Point of Very High Power Solid State RF Amplifiers (50 MHz to 1.3 GHz) by Remote P1 Control

A new technique was developed to increase the efficiency of very high power RF amplifiers (50 MHz to 1.3 GHz) at a freely chosen operating point. This improvement can be achieved for a large range of output power by a remote P1-point control. The choice of the P1-point of an RF amplifier is a compromise between increased efficiency vs. increased harmonics and decreased linearity. Typically, the P1-point power in the operation of particle accelerators is fixed to cover the maximum required output power including a large safety margin and for all operational situations. This safety margin is typically at least 20-30%. As a consequence, the effective efficiency of the amplifier is significantly below the one obtainable with an optimized setting of the P1-point for each required operating power. Using a new modular AC-DC-power supply with a maximum efficiency of 95% and a special amplifier control system, an adjustment of the P1-point over a wide power range can be made possible and thereby an increased effective efficiency of the amplifier at its operating point can be obtained. In addition, the new architecture of the ACDC-distribution results in a very low phase noise level, which is of higher importance for all light sources. A detailed description of the system and the achieved power savings will be presented.

Speaker: Dr Nico Pupeter (Cryoelectra GmbH)

Slides Cryoelectra_Nico_Pupeter_V2.pdf

12:00 Operational Experience with Superconducting RF Cavities at the Canadian Light Source

The Canadian Light Source synchrotron has been using the CESR-B type 500 MHz superconducting cavity for over 10 years. This presentation will discuss operating experience with these cavities to date.

Speaker: Mr Jonathan Stampe (Canadian Light Source)

Slides CLS-CWRF2014_May_13-14.pdf CLS-CWRF2014_May_13-14.pptx

12:30 → 14:00 Lunch

14:00 → 18:30 Visit to Elettra and FERMI

Thursday, 15 May

09:00 → 10:30 Thursday morning 1

Convener: Dr Daniel Valuch (CERN)

09:00 SOLEIL RF SYSTEMS : OPERATIONAL EXPERIENCE, UPGRADES, R&D’S

In the SOLEIL storage ring, two cryomodules provide to the electron beam an accelerating voltage of 3-4 MV and a power of 575 kW at 352 MHz. Each cryomodule contains a pair of superconducting cavities, cooled with liquid Helium at 4.5 K, which is supplied by a single 350 W cryogenic plant. The RF power is provided by four solid state amplifiers (SSA), each delivering up to 180 kW. The parasitic impedances of the high order modes (HOM) are strongly mitigated by means of four coaxial couplers, located on the central pipe connecting the two cavities. We report about the operational experience with this system, its upgrades and more generally about R&D’s, carried out at SOLEIL in the SSA field.

Speaker: Patrick Marchand (Synchrotron SOLEIL)

09:30 Solid State Amplifier using a cavity combiner

A 12 kW amplifier operating at 352 MHz has been designed, developed and built at ESRF. It uses a resonant cavity to combine the power of 18 home made RF modules. This is a prototype for a bigger amplifier which is currently under construction. The main features of this smaller version will be described, together with hopefully interesting considerations on manufacturing. The performances measured with both CW and pulsed test conditions will be given. These data will be completed by a status of the bigger amplifier project.

Speaker: Mr Michel Langlois (ESRF)

Slides ML_CWRF.pdf ML_CWRF.pptx

10:00 Status and Operation of the ALBA RF System

**Status and Operation of the ALBA RF System** *J.Ocampo, B.Bravo, A.Salom, F.Perez* **Abstract** ALBA is a 3 GeV, 400 mA, 3rd generation Synchrotron Light Source in operation for users since May 2012, in Barcelona, Spain. The RF System has to provide 3.6 MV of accelerating voltage and restore up to 540 kW of power to the electron beam. For that six RF plants, working at 500 MHz, are in operation. A RF plant includes a Dampy cavity (HOM damped) which is feed by two 80 kW IOT amplifiers combined via CaCo; a cavity combiner; and a Digital LLRF fully designed at ALBA using commercial components. Operation with a single IOT is also made possible thanks to the CoStub, a Coaxial Short to isolate the non-operational IOT from the CaCo. This presentation shortly describes the actual status of these systems and reports their performance since the start of the ALBA operation. It also covers the commissioning status of the new RF test laboratory, which is powered by a 80kW IOT amplifier and will be capable of testing either the Dampy cavity or the 5 cell cavity of the Booster.

Speaker: Mr Jesús Ramón Ocampo Pérez (CELLS-ALBA)

Slides ALBA_RF_status_and_RF_LAB.pdf ALBA_RF_status_and_RF_LAB.pptx

10:30 → 11:00 Coffee break

11:00 → 12:30 Thursday morning 2

Convener: Shigeki Sasaki (SPring-8/JASRI)

11:00 Almost 40 years of operation with tetrodes in the CERN-SPS

A brief description of the two tetrode power plants of the CERN-SPS. Some statistics accumulated with more than 100 tetrodes over almost 40 years of operation. Some horrors that occured over the period...

Speaker: Eric Montesinos (CERN)

Slides CWRF_2014_CERN_SPS_Amplifiers.pdf CWRF_2014_CERN_SPS_Amplifiers.pptx

11:30 Digital measurement system for the klystron HV modulator

Important HV electrical parameters of the LHC klystron amplifier are monitored by the control system. The currents are measured by external DCCTs on HV cables at ground potential, voltage dividers are isolated by V to f converters. The system performes well, but many components are at the end of their lives and measurement accuracy and access to the data for trouble shooting could be improved. A new, state of the art digital measurement system, which allows to measure all important HV quantities directly at the source in the HV tank (Vcath, Icath, Vma, Vheater, Iheater...) was developed. It provides 3 orders of magnitude improvement in sample rate, 10 fold increase in accuracy and comfort of online observation and post mortem buffers. We have demonstrated, that we can introduce and run a sophisticated electronic devices into the harsh HV environment. They provide reliable data even during very energetic fault scenarios, e.g. crowbar or arcing. A prototype will be installed in the LHC klystron HV modulator for long time testing in the coming run 2.

Speaker: Dr Daniel Valuch (CERN)

Slides measurement_system.pdf measurement_system.pptx

12:00 RF Upgrades and Operating Experience at JLab

Designed as a 4 GeV electron machine, CEBAF was run at 6 GeV. Major upgrades implemented over the past several years increased capabilities to12 GeV. 80 CW RF channels of a new design were added to the existing 340 channels to achieve this energy. As previously reported, a new, higher power klystron design, new HV power supplies, plus new controls and interlocks were required. Deliveries of some major components were late, with some requiring working closely with vendors to meet requirements. RF installation is complete and focus has moved to providing operational support for commissioning of the accelerator as well as improving familiarity with the new systems while working to maintain the existing, aging infrastructure. New systems have generally operated well but not without some early glitches. One klystron failure has occurred to date, numerous support electronics (power supplies, interlocks, cabling, and other failures) have surfaced. Learning these new systems for troubleshooting and repair is ongoing. This talk will review the systems, experiences, discuss select issues and failures.

Speaker: Richard Nelson (Jefferson Lab)

Slides Nelson_CWRF2014.pptx

12:30 → 14:00 Lunch

14:00 → 15:30 Thursday afternoon 1

Convener: Patrick Marchand (Synchrotron SOLEIL)

14:00 The High Power RF System of the European XFEL

The European XFEL requires twenty-seven high power RF stations at 1.3GHz capable of a peak RF power of 10MW at 1.37ms pulse duration and 10Hz repetition rate. Twenty-five RF stations supply RF power to one-hundred cryogenic modules each with eight nine-cell superconducting cavities. Two RF stations are reserved for the RF gun and one cryogenic module in the injector of the European XFEL. Each station consists of a HV modulator, pulse cables, pulse transformer, multi beam klystron, waveguide distribution and several other auxiliary components. This presentation describes the layout and status of the RF system for the European XFEL.

Speaker: Stefan Choroba (DESY)

Slides CWRF2014_choroba.pdf

14:30 Improvements to the APS LINAC & SR / Booster klystron high-voltage power supplies and accomplishments of the 352MHz RFTS

Two of the Fiscal Year 2014 Radio Frequency (RF) Group machine operation goals are to maintain mean time between faults at 100 hours or better and maintain injector, storage ring (SR), and x-ray production availability at 97% or better. To continue to meet these goals, an aggressive approach was instigated to combat parts obsolescence and aging of the accelerator systems. The latest improvements to the linac and SR/booster klystron high-voltage power supplies will be highlighted. The APS 352MHz RF Test Stand (RFTS) was constructed to test and condition booster and SR rf cavity components. The adaptation of a pulsed rf conditioning method was introduced and tested. This methodology and performance of the RFTS will be discussed. *Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.

Speaker: Mr Gianfranco Trento (Argonne National Laboratory)

Slides CWRF2014_Trento.pdf CWRF2014_Trento.ppt

15:00 CW RF System for the ATLAS Efficiency and Beam Intensity Upgrade

In order to increase beam transmission efficiency and intensity of ion beams, a major upgrade project has been conducted at Argonne Tandem Linac Accelerator System (ATLAS). A 4-meter long 60.625 MHz CW radio-frequency quadrupole (RFQ) has been developed, built and commissioned with beam in 2012. The RFQ has been used in the regular operation since January, 2013 and is capable of providing 295 keV/u for any ion from proton to uranium. A new cryomodule Booster A consisting of seven 72.75 MHz superconducting (SC) quarter-wave resonators (QWR) has also been developed and installed in 2013. This cryomodule was commissioned in Feb. 2014 and demonstrated acceleration voltage about 3 MV per cavity which exceeded the required performance of maximum 2.5 MV per cavity. Transmission through Booster A is almost 100%. In this paper, the new CW RF system is presented. Two 60 KW electron tube type amplifiers are controlled to provide the power for the 60.625 MHz RFQ. The resonance frequency is regulated to the master oscillator (MO) frequency by adjusting the cooling water temperature. Seven 4 KW solid state amplifiers are used to operate the cryomodule in the overcoupled mode. Circulators and dummy loads are used to protect the amplifiers.

Speaker: Yong Luo

Slides CWRF14_new-RF-system-ATLAS_upload.pdf CWRF14_new-RF-system-ATLAS_upload.pptx

15:30 → 16:30 Poster session: with coffee break

15:30 Test results of feedback control of LLRF system for RAON QWR

TEM-like superconducting quarter wave resonator (QWR) is adopted for the lowest optimum beta (0.047) section of the RAON. For the proper acceleration of heavy ions in QWR, 3 kW, 81.25 MHz RF power is supplied through coaxial couplers. For acceleration of heavy ion beam in the superconducting linear accelerator, the Low-Level RF (LLRF) should have feedback control of accelerating field and resonance frequency in the cavity and protection of High Power RF (HPRF) system. The integrated test of the LLRF prototype for QWR with the QWR, mockup copper cavity is underway. Field stabilities are required within ±1% in amplitude and ±1° in phase, the RF amplitude and phase are controlled within ±0.2% and ±0.05°, respectively. In this paper, the integration test details and results of the LLRF prototype with the QWR are described.

Speaker: Heejin Do (I)

Poster presentation_CWRF2014_HDo.pdf

15:31 RF Development Status at Iranian Light Source Facility

The Iranian Light Source Facility (ILSF) RF system was conceptually designed in accordance with the requirements for ILSF 3GeV storage ring with 400 mA beam current at 500 MHz RF frequency. The development of the solid state amplifiers initiated with the design and fabrication of two amplifier modules based on BLF578 and MRFE6VP1K25HR6 transistors and 670W and 540W stable RF power were delivered respectively. Combining of 8 such modules is under test to achieve 4kW output power as the first stage of the conceptually designed combining network. The measured characteristics are presented in this poster. Motivated by the development of HOM damped cavity with simpler structure at 100MHz at MAX Lab., 100MHz RF system is under exploration as an alternative to 500 MHz at ILSF. In addition to thorough study of the frequency change effects on the beam and machine parameters, the design of a 100MHz cavity based on MAX Lab. design has also been performed. Fabrication of a prototype cavity is planned in order to conclude the possibility of the cavity development in house.

Speaker: Mrs Khorshid Sarhadi (Iranian Light Source Facility (ILSF), Institute for Research in Fundamental Sciences (IPM), Tehran, Iran, P.O. Box 19395-5746)

Poster 2014CWRF_Poster4(upload).pdf

15:32 Overview on high power/high efficiency RF sources development at Thales Electron Devices

Thales ED has an experience of more than fifty years in high power RF tubes design and manufacturing, from klystrons and grid tubes amplifiers to gyrotrons oscillators. This talk presents recent high power / high efficiency solutions (experimental results and designs) which are suited for the next generation of particles accelerators. Namely, one of the future large scale linacs main challenges is to reduce the large electrical power consumption (in the TWh per year order of magnitude). To make these facilities more environmental friendly and power efficient, research and development is encouraged at Thales ED to increase RF sources electrical to RF power conversion. One ultimate goal for the vacuum tubes would be for instance to deliver the required high peak power with a targeted 70% efficiency. The presentation will introduce different tubes solutions comparing parameters such as performance, maturity and lifetime, as well as possible innovations for each technology (klystrons, tetrodes and IOTs), in order to give an overview of Thales ED capability to deliver efficient RF solutions for long pulse and CW applications for the next decade.

Speakers: Mr Rodolphe Marchesin (THALES Electron Devices), Mr Stephane Bethuys (THALES Electron Devices)

Slides CWRF_-_THALES_poster.pdf

15:33 Availability improvements for the LIPAc RF Power System: tetrodes and solid state solutions

The IFMIF/EVEDA Accelerator Prototype (LIPAc) is currently under construction in Rokkasho (Japan). LIPAc will generate a 9 MeV deuteron beam at 125 mA current with a 100% of duty cycle, and it will serve to validate the final IFMIF accelerator concept. The radiofrequency (RF) Power System, which is being integrated by CIEMAT (Spain) and its partner companies and institutes, consists of 18 RF amplifier chains operating at 175 MHz: eight 200 kW chains for the radio-frequency quadrupole (RFQ); two 105kW chains for the re-buncher cavities of the Medium Energy Beam Transport (MEBT); and eight 105 kW chains for the superconducting half-wave resonator (HWR) cavities. It also comprises 12 high voltage power supplies (HVPS), which feed the final amplifiers, 18 coaxial transmission lines to reach the accelerator cavities, and the water cooling system primary circuit. Very high availability, high performance, and easy maintainability are the main objectives for this development. Dealing with such a challenging goals has required successive improvements in the reference design. All the details regarding the different proposals and developments will be described in this paper. *This work has been funded by the Spanish Government (MINECO) under project AIC-A-2011-0654 and the agreement published in BOE (BOE 16/01/2013, pp. 1988).*

Speaker: Dr Cristina de la Morena (Ciemat)

Poster Ciemat CWRF 2014 Poster

15:34 Development of a RF Power Coupler for the Rare Isotope Science Project (RISP) RFQ Prototype

RAON, heavy ion accelerator for rare isotope science, is under development for the Rare Isotope Science Project (RISP) at Institute for Basic Science in South Korea. Radio-Frequency Quadrupole (RFQ), a component of RAON, accelerates heavy ion beams from 10 keV/u up to 500 keV/u at the current of 12 pμA and the frequency of 81.25 MHz. For RISP RFQ prototype, a 15kW CW RF power coupler has been designed using 3D electromagnetic, mechanical computer simulation codes. Here, the test results of the fabricated RF power coupler are presented.

Speaker: Ms Woo-Kyung Han (Institute for Basic Science)

Poster CWRF2014_poster.pdf

15:35 Prototyping of superconducting cavities for RAON the heavy ion accelerator

Four kinds of superconducting resonators (Quarter wave resonator, half wave resonator, and Single spoke resonator type 1, type 2) are designed and developed for the heavy ion accelerator the RAON. Resonators which have extreme high Q-factor 10E9 ~ 10E10, are filled up through coaxial RF power couplers of over coupling at 81.25MHz (QWR), 162.5MHz (HWR), 325MHz (SSR) respectively. Cavities are fabricated from 3mm RRR300 Niobium sheets by the collaboration with domestic vendors. 325MHz 10kWatts RF power couplers are prototyped and will be tested with a dummy cavity in the room temperature.

Speaker: Dr Hoechun Jung (Institute for Basic science)

Poster CWRF2014_HCJung_v1.pdf

15:36 Very High Power Solid State Amplifiers in the Range of 50MHz to 1.3GHz of Industrial Design with Very High Efficiency

A new series of solid-state RF amplifiers will be presented, which cover the frequency range from 50MHz to 750MHz with an output power of more than 100kW. The amplifiers are of industrial design regarding their space and maintenance requirements. They have been designed for the operation of Cyclotrons, Synchrotrons, Storage Rings and Linear Accelerators. The specific design of the Cryoelectra Amplifiers can be extended to frequencies of 1.3 GHz and beyond. Their output power is scalable to several hundreds of kW. The new features of these amplifiers are the optimization of their efficiency by a remote adjustment of the P1- operation point to the required output power and an extraordinary low phase noise, which is important for the operation of Storage Rings.

Speaker: Dr Nico Pupeter (Cryoelectra GmbH, Germany)

15:37 New Solid State driver Amplifiers for the CERN-SPS

Summary of the recent purchasing of the new Solid State driver Amplifiers for the LHC Injectors Upgrade programme. Technical Specifications description and offers from suppliers analysis.

Speaker: Eric Montesinos (CERN)

Slides CWRF_2014_CERN_LIU_SPS_Drivers_Eric_Montesinos_poster.pdf CWRF_2014_CERN_LIU_SPS_Drivers_Eric_Montesinos_poster.pptx

15:38 Stability test of 7 kW SSPA for 325 MHz Single Spoke Resonator

the RAON accelerator complex is planned in Korea for nuclear science research, and solid state power amplifiers will be used to provide superconducting cavities with rf power. The RAON main accelerator is composed of a normal conducting injector and a superconducting linac. The SC linac uses 3 types of SC cavities which are QWR, HWR and SSR. The SSR is divided into two families of low and high betas. Each cavity is driven by a SSPA. The SSPA, which is developed in house, is based on a 2 kW module. This 2 kW module employs four units of 600 W transistors including isolatr, which are combined by a 4 way combibner utilizing the Gygel method (Isolated combiner). Four modules are combined again with the same kind combiner to produce 7 kW of rf power. This paper describes the stability test result for 325 MHz, 7 kW SSPA.

Speaker: Jae Eun Han (I)

Poster Stability_test_of_7_kW_SSPA_for_SSR.pdf

15:39 Update on the CERN arc detectors

A new generation of Arc Detectors was developed at CERN for the Linac4. For reliability reasons the detectors do not use optical fibres. Each sensor head is equipped by four independent photo detectors with optional two "blind" sensors for environments with high radiation background. Since the first introduction in 2012 the detector design has been finalised, the housing ruggedised and made compatible with industrial, series production process. The project is supported by the CERN technology transfer group and the detectors are made available as a product for external users. This contribution presents the current status of the Arc Detector project.

Speaker: Dr Daniel Valuch (CERN)

Poster poster_arc_detectors.pptx.pdf

16:30 → 18:00 Thursday afternoon 2

Convener: Dr Yoon Kang (Oak Ridge National Laboratory)

16:30 Status of the rf-system for the high intensity proton accelerator facility at PSI

This year PSI celebrated the 40 years anniversary of the Ring cyclotron. This is the main accelerator of the high intensity proton accelerator facility, where protons are accelerated up to 590 MeV. In several upgrade programs the beam current was increased from the initial design value of 100 µA up to 2.4 mA. The rf-system of this separated sector cyclotron consists of 4 copper cavities running at 50 MHz for the main acceleration. To increase the phase acceptance of the Ring, an aluminium flattop cavity is operated on a gap voltage of 555 kVp at the 3rd harmonic frequency. In 2013 after half a year of regular operation the flattop cavity caused about 3 weeks of unscheduled downtime. Multipactoring discharges overheated the finger contacts on the coupling loop. A description of the observed phenomena and the taken actions will be presented. The Injector 2 cyclotron is the preaccelerator for the Ring. An upgrade program on the rf-system will replace the two flattop cavities (150 MHz) by accelerating cavities (50 MHz). This program includes the replacement of amplifiers, for those the tubes are no longer produced by the supplier. A status report of this project will be given.

Speaker: Markus Schneider (Paul Scherrer Institut)

Slides CWRF2014_Schneider.pdf CWRF2014_Schneider.pptx

17:00 Test of a 500MHz / 65kW Solid State Amplifier

High Power Solid State RF Amplifiers are being pushed in the market. With the latest generation of LDMOS transistors a high RF power per unit can be generated. Many of these RF modules combined in a single system is a serious competitor to the long established tube technology. Several solid state RF systems have already been realized and used very successfully for RF generation at particle accelerators. Ampegon has a long tradition in engineering and in the manufacture of tube-based amplifier systems and transmitters, while solid state technology was, so far, dominant in medium wave transmitters up to 300kW. In collaboration with the Paul Scherrer Institut we have successfully industrialized a PSI development of a solid state RF amplifier for 500MHz. The result is that both technologies could be tested and compared. The presentation will give an overview over our work and give an idea about the peculiarities of each technology.

Speaker: Mr Bodo Fritsche (Ampegon AG, Turgi)

Slides CWRF_Trieste_2014_3.pptx

Friday, 16 May

09:00 → 10:30 Friday morning 1

Convener: Morten Jensen (Diamond Light Source)

09:00 RF Related Issues Encountered during over 15years of Operation of SPring-8

Over 15 years of operation of the SPring-8 storage ring, we encountered several troubles in the RF system. Some of them will be picked up for the report. As an example, we experienced the water leakage from the photon absorbers for the synchrotron radiation to protect RF cavities. The cause was found to be the pinholes created by corrosion of the absorber water channel wall by the chemical reactions of the oxigen in the cooling water with the copper water channel wall. The improper structure of the absorber, the photon beam went through the water, made the chemical reaction possible for the copper wall with dissolved oxygen in the cooling water. In addition to the improper structure, we found that the control of the water quality was important. The density of the copper ion has been monitored since then. We encountered also to the water leakage from the output window part of the klystrons. The cause was found to be excess water flow to the cooling channels. In conjunction with the investigation of the cause, control of the quality was important for the water inside the cooling channel during the storage period as backup stockage of the klystrons. The residual components solved in the water might cause damages to the cooling water channel.

Speaker: Dr Shigeki Sasaki (SPring-8/JASRI)

Slides SPring8_Sasaki.pdf SPring8_Sasaki.pptx

09:30 A New 9MHz Cavity Design for RHIC

A new 9MHz RF system operating at 180KV per ring is required to increase the luminosity of low energy gold ion collisions at the Relativistic Heavy Ion Collider. In order to accommodate all planned collision energies each cavity will be required to operate between 8.7MHz and 9.4MHz while continuously providing 60KV of gap voltage. The proposed design includes a new capacitively loaded gap assembly that was specifically designed for this application. All pertinent design considerations and stress analysis performed to this point will be presented and discussed.

Speaker: Salvatore Polizzo (Brookhaven National Lab)

Slides LeRHIC_9MHz_Cavity_Presentation_Slides.pdf LeRHIC_9MHz_Cavity_Presentation_Slides.ppt

10:00 STATUS OF THE RF SYSTEM FOR SESAME

The SESAME ( Synchtrone Light Source For Experimental Since And Applications in The Middle- East) Accelerator consists of a 22 MeV Microtron , and 800Mev Booster and 2.5 GeV storage Ring . Each accelerator has its own RF system. The Microtron RF frequency is 3 GHz generated by 2 MW pulsed Magnetron, including 41KV modulator works as power supply for magnetron , while the Booster and SR have a common 500MHz CW RF source. The Booster RF system consists of DORIS cavity feds by 2 kW CW solid state amplifier, but the storage Ring RF system design based on 4x 500MHz plants , each comprising a Elettra- Type cavity, powerd by 80kW (CW) RF power via WR1800 waveguide lines. This presentation shows the statues of installed Microtron RF system and upgrades for RF system from BESSY І, as well as design SESAME SR high power RF system. Also this presentation shows the progress of collaboration with SOLEIL.

Speaker: Mr NASHAT SAWAI (RF group SESAME)

Slides CWRF2014_SESAME_N.SAWAI.pdf CWRF2014_SESAME_N.SAWAI.pptx

10:30 → 11:00 Coffee break

11:00 → 12:30 Friday morning 2

Convener: Mr James Rose (Brookhaven)

11:00 The ESS RF Systems and the plans for new developments

The European Spallation Source, a 5 MW average power, pulsed proton linac, will accelerate 62.5 mA of protons to an energy of 2 GeV. Each pulse is 2.86 ms and repeats at 14 Hz, resulting in a power-to-beam requirement per pulse of 125 MW of RF power. The split installation schedule means that existing, more mature technology is considered for the first part of the programme but for the later parts of the linac, which contribute approximately 80% of the final beam energy, development of new, high power and high efficiency sources and power supply systems can be investigated. This talk will review some of the key RF sources and new developments being pursued for ESS.

Speaker: Morten Jensen (European Spallation Source)

Slides CWRF14_Morten_Jensen_v1.pdf CWRF14_Morten_Jensen_v1.pptx

11:30 Solid State Thyratron Replacement for the LHC Klystron Crowbar

The counter-rotating proton beams in the Large Hadron Collider (LHC) are captured and accelerated to their final energies by two identical 400 MHz Radio Frequency (RF) systems. The RF power source required for each beam comprises eight 300 kW klystrons. Each unit of four klystrons is powered by a 100kV/40A AC/DC power converter. A fast protection system (crowbar) protects the four klystrons in each of these units. Although the LHC RF system has shown has very good performance, operational experience has shown that the five-gap double-ended thyratrons used in the crowbar system suffer, from time to time, from auto-firing, which result in beam dumps. A solid state solution, based on a stack of thyristors, has been designed for a direct thyratron replacement and has been fully validated and installed in one of the four bunkers in the LHC in September 2012. After five month it has proven to give full satisfaction. Ten thyristors stack based crowbar are under production and tests to equip the three other bunkers, the tests stand and spare part.

Speaker: Dr Daniel Valuch (CERN)

Slides LHC_Crowbar.pdf LHC_Crowbar.pptx

12:00 Workshop summary

Workshop summary

Speakers: Dr Alessandro Fabris (Sincrotrone Trieste), Dr Alireza Nassiri (Argonne National Laboratory), Mr Doug Horan (Argonne National Laboratory)

12:30 → 14:00 Lunch