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Paper Title Other Keywords Page
MOP053 Testing of Super Conducting Low-beta 704 MHz Cavities at 50 Hz Pulse Repetition Rate in View of SPL - First Results* cavity, klystron, feedback, simulation 175
 
  • W. Höfle, M. Hernandez Flano, J. Lollierou, D. Valuch
    CERN, Geneva
  • S. Chel, M. Desmons, G. Devanz, O. Piquet
    CEA, Gif-sur-Yvette
  • R. Paparella, P. Pierini
    INFN/LASA, Segrate (MI)
 
 

In the framework of the preparatory phase for the luminosity upgrade of the LHC (SLHC-PP ) it is foreseen to characterize two superconducting RF cavities and demonstrate compliance of the required SPL field stability in amplitude and phase using a prototype LLRF system. We report on the preparation for testing of two super-conducting low-beta cavities at 50 Hz pulse repetition rate including the setting-up of the low level RF control system to evaluate the performance of the piezo-tuning system and cavity field stability in amplitude and phase. Results from tests with 50 Hz pulse repetition rate are presented. Simulations of the RF system are used to predict the necessary specifications for power and bandwidth to control the cavity field and derive specifications for the RF system and its control.


This project has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under the Grant Agreement no 212114

 
MOP064 R&D of C Band Accelerating Structure at SINAP simulation, electron, linac, FEL 199
 
  • W. Fang, Q. Gu, Z.T. Zhao
    SINAP, Shanghai
  • D.C. Tong
    TUB, Beijing
 
 

A compact hard X-ray FEL facility is on plan now at Shanghai Institute of Applied Physics (SINAP). This facility will be located close to Shanghai Synchrotron Radiation Facility(SSRF) which is a 3rd generation light source in China, in order to control the overall length less than 650m, this facility asks a compact linac with high gradient accelerating structure. C-band (5712MHz) accelerating structure is a compromised and good option for this compact facility. R&D of a C-band (5712MHz) high gradient traveling-wave accelerating structure has been in progress at Shanghai Institute of Applied Physics (SINAP). The structure is consisted of 53 regular disk-loaded cells and two waveguide couplers, and its length is about one meter. This paper introduces the study of the accelerating structure design method, its experimental model and the preliminary results of the RF cold test of the model structure.

 
MOP082 Low Level Radio-frequency Developments toward a Fault-tolerant Linac Scheme for an Accelerator Driven System cavity, LLRF, linac, simulation 244
 
  • F.B. Bouly, J.-L. Biarrotte, C. Joly
    IPN, Orsay
 
 

An Accelerator Driven System (ADS) for transmutation of nuclear waste requires a high power proton beam (several MWs) to reach the necessary spallation efficiency. Due to the induced thermal stress to the subcritical core, the high-power proton linac will have to fulfil stringent reliability requirements to minimise the number of unwanted beam trips (> 1 sec.) per operation cycle. In view of the construction of the MYRRHA ADS demonstrator, in Mol (Belgium), beam dynamic analyses were carried out to evaluate the fault tolerant capability of the superconducting linac, in the particular case of a radiofrequency (RF) cavity failure. This analysis was coupled with simulations on the RF behaviour of 700 MHz superconducting cavitiy as well as its tuning and feedback loop systems. Such considerations led to the development of a prototypical digital Low Level RF (LLRF) system to control the cavity phase and accelerating field, especially in the case of fast cavity retuning for failure compensation. In this paper we summarize the work which has been performed so far toward the development of such a fault-tolerant RF linac.

 
MOP083 LLRF Design for the HINS-SRF Test Facility at Fermilab cavity, LLRF, resonance, SRF 247
 
  • J. Branlard, B. Chase, E. Cullerton, P.W. Joireman, V. Tupikov
    Fermilab, Batavia
 
 

The High Intensity Neutrino Source (HINS) R&D program requires super conducting single spoke resonators operating at 325 MHz. After coupler installation, these cavities are tested at the HINS-SRF facility at Fermilab. The LLRF requirements for these tests include support for continuous wave and pulsed mode operations, with the ability to track the resonance frequency of the tested cavity. Real-time measurement of the cavity loaded Q and Q0 are implemented using gradient decay techniques, allowing for Q0 versus Eacc plots. A real time cavity simulator was also developed to test the LLRF system and verify its functionality.

 
MOP084 A Vector Control and Data Acquisition System for the Multicavity LLRF System for Cryomodule1 at Fermilab cavity, LLRF, cryomodule, feedback 250
 
  • P. Varghese, B. Barnes, J. Branlard, B. Chase, E. Cullerton, P.W. Joireman, V. Tupikov
    Fermilab, Batavia
 
 

A LLRF control and data acquisition system for the 8-cavity Cryo-Module 1 at the ILCTA has been implemented using three , 33-channel MFC boards in a VXI mainframe. One card each is dedicated for the cavity probes for vector control , forward power and reverse power measurements. The system is scalable to 24 cavities or more with the commissioning of Cryo-Modules 2 and 3 without additional hardware. The signal processing and vector control of the cavities is implemented in a FPGA and a high speed data acquisition system with upto 100 channels stores data in external SDRAM memory. The system supports both pulsed and CW modes with a pulse rate of 5Hz. Acquired data is transferred between pulses to auxiliary systems such as the piezo controller through the slot0 controller. The design of the system is described and the performance of the vector control system is evaluated.

 
MOP086 Stability Evaluation for Long FB Loop Delay in the ACS Cavity Field Control for the J-PARC Linac 400-MeV Upgrade cavity, linac, klystron, simulation 253
 
  • T. Kobayashi
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
 
 

For 400-MeV upgrade of the J-PARC Linac, ACS (Annular Coupled Structure) cavities, which are driven by 972-MHz RF, will be installed. The ACS cavity has complicated structure. Its Q-value is very low and the operation frequency is tree times higher in comparison with that of the SDTL cavity. So the stabilizing control of the ACS accelerating field will be more difficult than present 324-MHz RF system. Further more the chopped beam loading compensation is required. Especially, the debuncher will be located very far from the klystron, then the feedback loop delay will be about 1.5 us. This presentation will show the simulation results of the feedback control of the ACS cavity field including long loop delay and the effect of the chopped beam loading.

 
MOP087 Beam Test of Chopped Beam Loading Compensation for the J-PARC Linac 400-MeV Upgrade cavity, beam-loading, linac, LLRF 256
 
  • T. Kobayashi
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  • M. Ikegami
    KEK, Ibaraki
 
 

The function of the chopped beam loading compensation was implemented into the digital feedback/feed-forward control system of the J-PARC Linac LLRF system to stabilize the ACS cavity fields for the 400-MeV upgrade. The beam test of the chopped beam loading compensation was performed with the present 324-MHz cavity sysmte. Consequently the chopped beam loading was successfully compensated and that this system is valid.

 
MOP088 Spallation Neutron Source LLRF Temperature Dependence and Solution LLRF, neutron, DTL, klystron 259
 
  • M.T. Crofford, T.W. Hardek, S.W. Lee, M.F. Piller
    ORNL, Oak Ridge, Tennessee
  • J.A. Ball, T.L. Davidson
    ORNL RAD, Oak Ridge, Tennessee
 
 

The Spallation Neutron Source (SNS) has been operating since the first neutrons were produced on April 29, 2006. During the last several years the beam energy has been methodically ramped-up and outlying issues solved to improve system reliability. During the beam studies a temperature dependence has been discovered with the Low-Level RF systems. The effect is small but readily observable as increased beam losses. The temperature dependence has been studied both in the accelerator and in the laboratory and the sensitive components identified. A prototype solution that replaces the temperature dependent components of the Low-Level RF System has been designed and is in initial testing. Preliminary results of the laboratory tests have been encouraging. Accelerator tests are planned after installation during the December 2010 maintenance cycle.

 
MOP089 Spallation Neutron Source High-Power Protection Module Test Stand neutron, LLRF, linac, cavity 262
 
  • S.W. Lee, J.A. Ball, T.L. Davidson, S.L. Jones
    ORNL RAD, Oak Ridge, Tennessee
  • M.T. Crofford, T.W. Hardek
    ORNL, Oak Ridge, Tennessee
 
 

The Spallation Neutron Source (SNS) High-Power Protection Module (HPM) provided interlocks and fast shutdown for the RF system to protect the accelerating structures and high power RF (HPRF) Distribution System. The HPM has required some functionality upgrades since the start of beam operations and an upgrade to the HPM test stand was required to support these added features. The HPM test stand currently verifies functionality, RF channel calibration, and measurement of the speed of shutdown to ensure the specifications are meet. The upgraded test stand was implemented in a single FPGA to allow for future growth and flexibility. Work is currently progressing on automation of the test stand to better perform the required module calibration schedule.

 
MOP090 Design and Testing of the TRIUMF ISACII High-B RF Control System cavity, TRIUMF, linac, cryomodule 265
 
  • M.P. Laverty, K. Fong, R.E. Laxdal, Q. Zheng
    TRIUMF, Vancouver
  • G. Dennison
    UBC & TRIUMF, Vancouver, British Columbia
 
 

The rf control system for the twenty 141 MHz TRIUMF quarter wave superconducting cavities is a hybrid analogue/digital design. It is based in part on an earlier design developed for the 106MHz 1/4 wave superconducting cavities of the ISACII linac. This design has undergone several iterations in the course of its development. In the current version, a value-engineering approach was used to reduce the cost and simplify the hardware. The result is a single C-size VXI module that incorporates all the required low-level rf functions - amplitude/phase control, tuning control, and control of the rf coupler. It accomplishes these functions at a substantially lower cost than the previous two-module solution. It also includes support for field upgrade of the DSP/PLD hardware and firmware. Some early test results of the system operating in the linac are outlined, and conclusions are summarized.

 
MOP091 A Digital Low Level RF Control System for the S-DALINAC cavity, low-level-rf, superconducting-cavity, electron 268
 
  • M. Konrad, U. Bonnes, C. Burandt, R. Eichhorn, N. Pietralla
    TU Darmstadt, Darmstadt
 
 

The superconducting cavities of the S-DALINAC have a high loaded quality factor and are very susceptible to microphonics. To stabilize the amplitude and phase of the cavities' fields an analog control system has been used for 20 years. To improve the stability and the availability of the low level RF control system it is currently replaced by a digital one. The 3 GHz signals coming from the cavities are converted down to the base band using hardware I/Q demodulators. The base band signals are digitized by ADCs and fed into an FPGA. This FPGA contains a custom CPU which executes the code implementing the control algorithm. The computed control signal is I/Q modulated before it is send to the cavity again. The superconducting cavities are operated with a self-excited loop algorithm whereas a generator driven algorithm is used for the low Q normal conducting bunching cavities. A 6 GHz RF board allows the operation of a new 2f buncher. Parameters can be adjusted via an EPICS IOC running on a standard PC. All signals from the FPGA can be monitored in realtime by the operator.

 
MOP092 LINAC Subsystems for Better Beam Control LLRF, brilliance, linac, FEL 271
 
  • G. Jug, C.J. Bocchetta, A. Kosicek
    I-Tech, Solkan
 
 

Control of bunch arrival time, energy and trajectory of particle beams in linear accelerators is mandatory to reach performance goals and is carried out using different sub-systems. For optimal control and especially for accelerators aiming at the highest level of performance, for example FELs, these systems should be considered as a whole and work together. At Instrumentation Technologies such systems have been developed and tested on the field. Precise control of amplitude and phase of the accelerating felds is performed with the Libera LLRF, a digital RF stabilization system that is couple to Libera SYNC a very low jiiter master oscillator distribution system. The Libera Brilliance Single Pass system provides high resolution position information that allows accurate control of trajectories through critical machine sections such as bunch compression modules and FEL modulators and radiators. These systems are described in detail in the paper with examples from field measurements.

 
MOP093 Design of Low Level RF Control System for Accelerator cavity, LLRF, superconducting-cavity, emittance 274
 
  • Y.S. Lee, J.-S. Chai
    SKKU, Suwon
  • K.R. Kim, K.-H. Park
    PAL, Pohang, Kyungbuk
 
 

The low level RF (LLRF) control system for PLS is being upgraded to improve the performance of the system. The LLRF control system under development consists of FPGA, and high speed ADC and DAC as well as analog front-end devices which process the signal from cavity and to RF high power system. In addition, it utilizes digital signal processing technology based on FPGA. In order to optimize the accelerating electric field in the cavity, it is required to maintain field stability less than ±1% in amplitude and 1° in phase. And the resonance condition of the cavity should be monitored and controlled. The various digital signal processing theories such as digital filters, Cordic, PI control enable to meet these requirements and to control the feedback signal less than a microsecond. The LLRF control system is also equipped with the Ethernet by the cPCI. The preliminary design study on the LLRF control system for PLS superconducting cavity will be described in this paper.

 
MOP094 Cavity Control Algorithms cavity, feedback, LLRF, radio-frequency 277
 
  • T. E. Plawski, C. Hovater
    JLAB, Newport News, Virginia
 
 

A digital low level radio frequency (RF) system typically incorporates either a heterodyne or direct sampling technique, followed by fast ADCs, then an FPGA, and finally a transmitting DAC. This universal platform opens up the possibilities for a variety of control algorithm implementations. The foremost concern for an RF control system is cavity field stability, and to meet the required quality of regulation, the chosen control system needs to have sufficient feedback gain. In this paper we will investigate the effectiveness of the regulation for three basic control system algorithms: I&Q (In-phase and Quadrature), Amplitude & Phase and digital SEL (Self Exciting Loop) along with the example of the Jefferson Lab 12 GeV cavity field control system.

 
MOP095 Status of the CEBAF Energy Upgrade RF Control System cavity, LLRF, interlocks, EPICS 280
 
  • C. Hovater, T.L. Allison, R. Bachimanchi, G.E. Lahti, J. Musson, T. E. Plawski, C. Seaton, D.J. Seidman
    JLAB, Newport News, Virginia
 
 

To support the CEBAF energy upgrade from 6 GeV to 12 GeV, the RF control system is being modernized to control the high gradient high QL superconducting cavities. The new system incorporates a heterodyne transceiver along with I&Q sampling to measure and control magnitude and phase. A low-cost Altera FPGA is used to digitally implement the cavity control algorithms. One of the features of the system is a digital self excited loop to track the cavity over large Lorentz detuning (800 Hz) during turn on. The system has successfully completed preliminary development and is now moving into the production stage of the project. This paper discusses the design, modeling, testing and production of the new RF control system and associated peripheral systems (cavity interlocks, and resonance control).

 
MOP106 Implementation of Multilayered Conductor Structures on RF Cavity Surfaces cavity, resonance, vacuum, linac 310
 
  • Y. Iwashita
    Kyoto ICR, Uji, Kyoto
 
 

Multilayered conductor structures on RF cavity surfaces have been discussed these years. Although a real implementation was succeeded on a coaxial cavity at room temperature by measuring Q-value, it may not be a practical example. Application of the multilayered conductor structure on superconducting cases came out recently and is studied by some groups. Possible thoughts on the further implementation at room temperature will be discussed including a consideration on the superconducting case.

 
MOP108 Planned Machine Protection System for the Facility for Rare Isotope Beams at Michigan State University beam-losses, linac, diagnostics, monitoring 313
 
  • S. Assadi, W. Hartung, M.J. Johnson, T.L. Mann, E. Pozdeyev, E. Tanke, X. Wu, R.C. York, Q. Zhao
    FRIB, East Lansing, Michigan
  • M. Doleans, F. Marti
    NSCL, East Lansing, Michigan
 
 

The Facility for Rare Isotope Beams (FRIB) at Michigan State University will utilize a 400 kW, heavy-ion linear accelerator to produce rare isotopes in support of a rich program of fundamental research. In the event of operating failures, it is extremely important to shut off the beam in a prompt manner to control the beam losses that may damage the accelerator components such as superconducting cavities. FRIB has adapted the residual beam loss activation limit at 30 cm to be equivalent to 1W/m of operating beam losses. We are designing FRIB MPS to be flexible but redundant in safety to accommodate both commissioning and operations. It is also dependent upon the operational mode of the accelerator and the beam dump in use. The operational mode is distributed via a finite state machine to all critical devices that have multiple hardware checkpoints and comparators. It is important to note that FRIB is a cw machine and MPS status is continuously being monitored by 'device mode change' and real time data link. In this paper, we present FRIB Machine Protection architecture, plans and implementation.

 
TU203 Plans for the ESS Linac cavity, linac, cryomodule, emittance 367
 
  • S. Peggs, M. Eshraqi, H. Hahn, A. Jansson, M. Lindroos, A. Ponton, K. Rathsman, C.G. Trahern
    ESS, Lund
  • S. Bousson
    IPN, Orsay
  • R. Calaga
    BNL, Upton, Long Island, New York
  • H. Danared
    MSL, Stockholm
  • G. Devanz, R.D. Duperrier
    CEA, Gif-sur-Yvette
  • J. Eguia
    Fundación TEKNIKER, Eibar (Gipuzkoa)
  • S. Gammino
    INFN/LNS, Catania
  • S.P. Møller
    ISA, Aarhus
  • C. Oyon
    SPRI, Bilbao
  • R.J.M.Y. Ruber
    Uppsala University, Uppsala
  • T. Satogata
    JLAB, Newport News, Virginia
 
 

Following selection of Lund as the site for the long-pulse ESS (European Spallation Source), a team of accelerator and target experts has been working on an update of the 2003 ESS linac design. Improvements to the 2003 design will be summarised, and the latest designs for the linac will be presented.

 

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TUP002 FERMI@Elettra: Installation and Commissioning of the S-Band RF System linac, LLRF, klystron, gun 395
 
  • A. Fabris, P. Craievich, P. Delgiusto, F. Gelmetti, M.M. Milloch, A. Milocco, F. Pribaz, A. Rohlev, C. Serpico, N. Sodomaco, R. Umer, L. Veljak, D. Wang
    ELETTRA, Basovizza
 
 

FERMI@Elettra is a single-pass FEL user-facility covering the wavelength range from 100 nm (12 eV) to 4 nm (310 eV) and is located next to the third-generation synchrotron radiation facility Elettra in Trieste, Italy. The first electron beam from the photocathode electron rf gun and injector system was extracted in August 2009. Commissioning and installation of the remaining linac and linac systems are continuing and will alternate through this year . The linac is based on normal conducting S-band technology. It uses fifteen 3 GHz 45 MW peak RF power plants powering the gun, the accelerating structures, and the RF deflectors, and when completed will be able to deliver greater than 1.5 GeV electron beams to the FEL undulator system. This paper provides a summary of the installation activities and discusses the performances results of the main subassemblies both during the initial checkouts and through the commissioning of the accelerator.

 
TUP014 Construction of Injector System for SPring-8 X-FEL cavity, gun, emittance, klystron 425
 
  • H. Hanaki, T. Asaka, H. Ego, H. Kimura, T. Kobayashi, S. Suzuki, M. Yamaga
    JASRI/SPring-8, Hyogo-ken
  • T. Fukui, T. Inagaki, N. Kumagai, Y. Otake, T. Shintake, K. Togawa
    RIKEN/SPring-8, Hyogo
 
 

The injector of the 8 GeV linac generates an electron beam of 1 nC, accelerates it up to 30 MeV, and compresses its bunch length down to 20 ps. Even slight RF instability in its multi-stage bunching section fluctuates the bunch width and the peak current of an electron beam and it accordingly results in unstable laser oscillation in the undulator section. The acceptable instabilities of the RF fields in the cavities, which permit 10% rms variation of the peak beam current, are only about 0.01% rms in amplitude and 120 fs rms in phase according to beam simulation. The long-term RF variations can be compensated by feedback control of the RF amplitude and phase, the short-term or pulse-to-pulse variations, however, have to be reduced as much as possible by improving RF equipment such as amplifiers. Thus we have carefully designed and manufactured the RF cavities, amplifiers and control systems, giving the highest priority to the stabilization of the short-term variations. Components of the injector will be completed by the end of the May 2010, and the injector will be perfected in the summer 2010. We will present the performance of the completed devices in the conference.

 
TUP017 The Resonant Method of Stabilization for Plane of Deflection in the Disk Loaded Deflecting Structures cavity, coupling, polarization, linac 434
 
  • V.V. Paramonov, L.V. Kravchuk
    RAS/INR, Moscow
 
 

The hybrid HE11 mode in the cylindrical disk loaded deflectors is twice degenerated. To ensure operational performance and stabilize the position for the plane of deflection, the dispersion curve for modes with perpendicular field polarization must be shifted in frequency with respect to the curve for modes with operating polarization. A lot of decisions, based on the deterioration of the axial symmetry of the structure, are known for this purpose. The resonant method of stabilization is proposed. Resonant elements ' slots, coupled only with modes of perpendicular polarization, are placed in the disks. Two created branches of dispersion curve for composed slot - structure modes are generated and placed symmetrically with respect to the non perturbed dispersion curve for operating modes. In the plane stabilization it provides qualitative advantage with respect a simple frequency shift, because cancels, in the first order, the influence of modes with perpendicular field polarization on the plane of deflection. The criteria for the slots definition are presented. The example of application for the traveling wave S-band deflector is described as well.

 
TUP021 100MeV Proton Accelerator Components Tests by Using 20 MeV Linac linac, LLRF, site, klystron 443
 
  • H.-J. Kwon, Y.-S. Cho, J.-H. Jang, D.I. Kim, H.S. Kim, K.T. Seol, Y.-G. Song
    KAERI, Daejon
 
 

A 100MeV proton accelerator is developed by the Proton Engineering Frontier Project (PEFP). As a front part, a 20MeV linac has been installed and operated at Korea Atomic Energy Research Institute (KAERI) site. Among the components for the 100MeV accelerator, some parts were installed and tested by using 20MeV linac. One modulator for a 100MeV linac was installed to drive two klystrons simultaneously which were used for a 20MeV linac. Various operating parameters such as a long term voltage fluctuation and control performance are checked during operation. Also a LLRF system for 100MeV linac which was modified from the 20MeV system was installed and tested. In this paper, the operation characteristics of the 20MeV linac are presented especially from the viewpoint of the newly installed components such as a modulator and LLRF system.

 
TUP038 Matter-Radiation Interactions in Extremes linac, electron, proton, klystron 485
 
  • R.W. Garnett, M.S. Gulley
    LANL, Los Alamos, New Mexico
 
 

LANSCE has been the centerpiece of large-scale science at Los Alamos National Laboratory for many decades. Recently, funding has been obtained to ensure continued reliable operation of the LANSCE linac and to allow planning to enable the first in a new generation of scientific facilities for the materials community. The emphasis of this new facility is "Matter-Radiation Interactions in Extremes" (MaRIE) which will be used to discover and design the advanced materials needed to meet 21st century national security and energy security challenges. MaRIE will provide the tools scientists need to develop next-generation materials that will perform predictably and on-demand for currently unattainable lifetimes in extreme environments. The MaRIE facility is based on a high-power upgrade to the existing LANSCE proton linac, a new electron linac and associated X-ray FEL to provide additional probe beams, and new experimental areas. A conceptual description of this new facility and its requirements will be presented.

 
TUP050 Vacuum Brazing of the New RFQ for the J-PARC Linac vacuum, cavity, rfq, linac 521
 
  • T. Morishita, K. Hasegawa, Y. Kondo
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  • H. Baba, Y. Hori, H. Kawamata, H. Matsumoto, F. Naito, Y. Saito, M. Yoshioka
    KEK, Ibaraki
 
 

The J-PARC RFQ (length 3.1m, 4-vane type, 324 MHz) accelerates a negative hydrogen beam from 0.05MeV to 3MeV toward the following DTL. We started the preparation of a new RFQ as a backup machine. The new cavity is divided by three unit tanks in the longitudinal direction. The unit tank consists of two major vanes and two minor vanes. A one-step vacuum brazing of a unit tank has been chosen to unite these four vanes together with the flanges and ports. In this presentation we will report the results of the vacuum brazing with the dimension accuracy and an RF property.

 
TUP052 Preliminary Concept for the Project X CW Radio-frequency Quadrupole (RFQ) rfq, cavity, vacuum, quadrupole 524
 
  • S.P. Virostek, M.D. Hoff, D. Li, J.W. Staples
    LBNL, Berkeley, California
 
 

Project X is a proposed multi-MW proton facility at Fermi National Accelerator Laboratory. It is the key element for future accelerator complex development intended to support world-leading High Energy Physics (HEP) programs. The Project X front-end would consist of H- ion source(s), a low-energy beam transport (LEBT), radio-frequency quadrupole (RFQ) accelerator(s), and a medium-energy beam transport (MEBT). To support current and future HEP experiments at Fermilab, a CW RFQ is required. One of the chosen RFQ designs has a resonant frequency at 325 MHz. The RFQ provides bunching of the 10 mA H- beam with acceleration up to 2.5 MeV and wall power losses of less than 250 kW. LBNL is currently developing the early designs for various components in the Project X front-end. The RFQ design concept and the preliminary RF and thermal analyses are presented here.

 
TUP060 Possibility of Thermal Instability for 4-vane RFQ Operation with High Heat Loading cavity, rfq, linac, coupling 545
 
  • V.V. Paramonov
    RAS/INR, Moscow
 
 

Due to dispersion properties 4-vane RFQ cavity without resonant coupling is a thermally unstable structure. With deterioration of balance for local detuning there is a possibility for runaway in the field distribution and related thermal effects. It can results, in principle, in irreversible plastic deformations and cavity frequency shift. Both the increment and the threshold of instability are proportional to the average dissipated RF power. This possibility is more probable for long RFQ cavities. Also particularities for the cavity ends design are important. Some general features of this effect are discussed qualitatively and illustrated with simulations.

 
TUP079 SS Helium Vessel Development for 1.3 GHz SRF Cavities at Fermilab cavity, niobium, simulation, SRF 596
 
  • N. Dhanaraj, S. Barbanotti, J.S. Brandt, H. Carter, M.H. Foley, J. Grimm, T.N. Khabiboulline, R. Wands
    Fermilab, Batavia
 
 

Fermilab is currently focusing its efforts toward the development of Stainless Steel (SS) helium vessels for its 1.3 GHz SRF cavities. The objective is to transition towards the concept of using SS helium vessels to dress the bare SRF cavities, thereby paving way for significant cost reduction and efficient production techniques for future accelerators. The biggest challenge has been to design a reliable interface between the niobium cavity end group and the stainless steel end flange that encloses the helium vessel. Fermilab has been pursuing a brazed joint design to allow this transition. Additional design challenges associated with this transition are ensuring proper cooling of the cavity, compensating for the difference in thermal contraction between the SS helium vessel and niobium cavities, and also modification of the tuning procedure and ensuring the safety and reliability of the blade and piezo tuners. Current efforts on the qualification of the niobium-SS braze joint, finite element simulations of the thermal design aspects, bench testing of actual cavity displacements, and study of the effects on the tuners will be presented.

 
TUP092 The ISAC II Current Monitor System ISAC, pick-up, rfq, linac 623
 
  • M. Marchetto, J. Aoki, K. Langton, R.E. Laxdal, W.R. Rawnsley, J.E. Richards
    TRIUMF, Vancouver
 
 

The post acceleration section of the ISAC radioactive ion beam (RIB) facility is composed of a radio frequency quadrupole (RFQ) followed by a drift tube linac (DTL), both room temperature machines, that serve a medium energy experimental area up to 1.8 MeV/u, and a superconducting linac (SCLINAC) that serves a high energy experimental area. This SCLINAC, composed of forty quarter wave resonators housed in eight cryomodules, is capable of a total accelerating voltage of circa 40 MV. Since each cavity is phased independently at the maximum operational voltage, the final energy depends on the mass to charge ratio of the accelerated species. In order to deliver energies higher than 5 MeV/u we need to monitor the beam current as mandated by our operating license. The current monitor system (CMS) is composed of two non intercepting and one partially intercepting monitor. The signals from these three monitors are processed in a single control system that provides a go signal to the Safety system enabling beam delivery. The CMS system allows to exploit the SCLINAC to its full potential. In this paper we will present both hardware configuration and software control of the CMS.

 
TUP100 Measuring the Longitudinal Bunch Profile at CTF3 pick-up, single-bunch, monitoring, linac 647
 
  • A.E. Dabrowski, E. Adli, S. Bettoni, R. Corsini, S. Döbert, D. Egger, T. Lefèvre, A. Rabiller, P.K. Skowronski, L. Søby, F. Tecker
    CERN, Geneva
  • H.-H. Braun
    PSI, Villigen
  • H. Shaker
    IPM, Tehran
  • M. Velasco
    NU, Evanston
 
 

The CLIC Test Facility 3 (CTF3) is being built and commissioned by an international collaboration in order to test the feasibility of the proposed Compact Linear Collider (CLIC) two-beam acceleration scheme. The monitoring and control of the bunch length throughout the CTF3 complex is important since this affects the efficiency and the stability of the RF power production process. Bunch length diagnostics therefore form an essential component of the beam instrumentation at CTF3. This paper presents and compares longitudinal profile measurements based on transverse RF deflectors, Streak camera and non-destructive microwave spectrometry techniques.

 
THP010 Exploiting New Electrochemical Understanding of Niobium Electropolishing for Improved Performance of SRF Cavities for CEBAF cavity, niobium, cathode, impedance 779
 
  • C.E. Reece, H. Tian
    JLAB, Newport News, Virginia
 
 

Recent incorporation of analytic electrochemistry into the development of protocols for electropolishing niobium SRF cavities has yielded new insights for optimizing this process for consistent, high-performance results. Use of reference electrodes in the electrolyte, electrochemical impedance spectroscopy (EIS), rotating disk electrodes (RDE), and controlled sample temperatures has greatly clarified the process dynamics over the empirical understanding developed via years of practice. Minimizing rf losses at high operational gradients is very valuable for CW linacs. Jefferson Lab is applying these new insights to the low-loss 7-cell cavity design developed for the CEBAF 12 GeV Upgrade. Together with controlled cleaning and assembly techniques to guard against field-emission causing particulates, the resulting process is yielding consistent cavity performance that exceeds project requirements. Cavity tests show BCS-limited Q well above 30 MV/m. Detailed process data, interpretation, and resulting rf performance data will be presented.

 
THP013 Testing of Niobium Material for the European XFEL Pre-series Production niobium, cavity, superconductivity, vacuum 788
 
  • A. Brinkmann, M. Lengkeit, W. Singer, X. Singer
    DESY, Hamburg
 
 

For the XFEL cavity production a rather large quantity of niobium sheets from partially new niobium vendors has to be delivered according to the XFEL Cavity Specification. It is of high importance that the material monitoring of this niobium has to be done within the production process to ensure a high performance of the cavities. The quality assurance program includes electrical measurements, mechanical, structural and chemical material analysis. For the surface investigations two eddy current scanning devices have been fabricated on the basis of our specification and experience. The scanning process and evaluation of test result can now be done in a few minutes per sheet. We describe the material test methods and the scanning machine. Measured results of the pre-series niobium will be compared to older material tests results.

 
THP023 Developments and Test of a 700 MHz Prototypical Cryomodule for the MYRRHA ADS Proton Linear Accelerator cavity, cryomodule, cryogenics, linac 809
 
  • F.B. Bouly, J.-L. Biarrotte, S. Bousson, C. Commeaux, C. Joly, J. Lesrel
    IPN, Orsay
  • A. Bosotti, P.M. Michelato, R. Paparella, P. Pierini, D. Sertore
    INFN/LASA, Segrate (MI)
 
 

Accelerator Driven systems (ADS) are being considered for their potential use in the transmutation of nuclear waste. Because of the induced thermal stress to the subcritical core, the high-power proton LINAC will have to fulfill stringent reliability requirements and to minimize the number of unwanted beam trips per operation cycle. It is forseen to build an ADS demonstrator (MYRRHA) in Mol (Belgium). Such a device will be piloted by a 600 MeV / 4mA superconducting linac. IPN Orsay and INFN Milano are in charge of the realisation and tests of a prototypical cryomodule for the high energy section of the accelerator, equipped with a 5-cell superconducting cavity. Developed at INFN, this RF cryogenic accelerating device is tested for the first time at IPN. We will describe the status of the R&D activities on this device. The first low power tests of the 5-cell superconducting cavity in its prototypical cryomodule will be reviewed. Those tests aim to evaluate the cavity performances after installation in the module (16MV/m in vertical test) but also to measure the tuning systems behaviors in view of reliability considerations for 'fast fault-recovery scenarios'.

 
THP029 Operating Experience with CC2 at Fermilab's SRF Beam Test Facility cavity, LLRF, resonance, acceleration 818
 
  • E.R. Harms, J. Branlard, G.I. Cancelo, K. Carlson, B. Chase, E. Cullerton, A. Hocker, P.W. Joireman, T. Kubicki, J.R. Leibfritz, A. Martinez, M.W. McGee, Y.M. Pischalnikov, J. Reid, W. Schappert, K.R. Treptow, V. Tupikov, P. Varghese, T.J. Zmuda
    Fermilab, Batavia
 
 

Capture Cavity II is the first operational component at the SRF Beam Test Facility now under construction at Fermilab. This 9-cell 1.3 GHz cavity, previously operated in another venue on the Fermilab site, was transported to this facility in early 2009. We will summarize its transport and operation in its new (permanent) home compared to previous performance and also present results of studies, particularly Low Level RF, microphonics/vibration, and Lorentz force de-tuning compensation that have been recently carried out with it.

 
THP031 First High Gradient Test Results of a Dressed 325 MHz Superconducting Single Spoke Resonator at Fermilab cavity, cryogenics, LLRF, solenoid 821
 
  • R.C. Webber, T.N. Khabiboulline, R.L. Madrak, T.H. Nicol, L. Ristori, W.M. Soyars, R.L. Wagner
    Fermilab, Batavia
 
 

A new superconducting RF cavity test facility has been commissioned at Fermilab in conjunction with first tests of a 325 MHz, β = 0.22 superconducting single-spoke cavity dressed with a helium jacket and prototype tuner. The facility is described and results of full gradient, CW cavity tests with a high Qext drive coupler are reported. Sensitivities to Q disease and externally applied magnetic fields were investigated. Results are compared to bare cavity results obtained prior to hydrogen degassing and welding into the helium jacket.

 
THP032 Status of the EP Simulations and Facilities for the SPL cavity, cathode, simulation, niobium 824
 
  • S. Calatroni, L.M.A. Ferreira, M. Leitao Macatrao, A. S. Skala, M. Sosin, Y.L. Withofs
    CERN, Geneva
  • R. De Waele
    KHLim, Diepenbeek
 
 

CERN is assembling a new vertical electropolishing facility in order to process several niobium cavities of beta 1 and beta 0.65 in the context of the HP-SPL R&D programme. Electrochemical simulations are being used in order to define the optimal cathode geometry to process the cavities in a vertical position. Macroscopic properties of fluid dynamics like the Reynolds number and thermodynamics linked to the power dissipated in the process are taken into account to dimension the main system components. All the materials from the different equipments must be compatible with all chemicals within the required working temperature and pressure. To provide safe operating conditions when handling chemicals or processing cavities, specific safety and protection equipment is also foreseen.

 
THP046 CSNS Linac RF System Design and R&D Progress klystron, high-voltage, rfq, resonance 863
 
  • J. Li, J.M. Qiao, X.A. Xu, Y. Yao, Z.H. Zhang, W. Zhou
    IHEP Beijing, Beijing
  • Z.C. Mu
    Institute of High Energy Physics, CAS, Bejing
 
 

China Spallation Neutron Source (CSNS) is determined to be constructed in Dongguan, Guangdong province of south China. Now its design and R&D are in progress in IHEP, Beijing. The 324 MHz rf linac is designed with beam energy of 81 MeV and a peak current of 30 mA. In the klystron gallery, five klystron power sources will be used to power the RFQ and the four DTL tanks, and three solid state RF amplifiers will drive two MEBT bunchers and a LRBT debuncher. Now we have already made some progress with some key technologies for linac RF system. The digital low level RF control prototype was already developed and successfully applied in beam commissioning of the ADS (Accelerator Driven Sub-critical system) 3.5MeV RFQ accelerator at peak beam 44.5mA, beam duty 7.15%. A proposed new type of power supply, 100Hz ac series resonance high voltage power supply, passed acceptance test and a satisfactory test results was obtained. R&D of crowbar and modulator has gotten preliminary performance test data.

 
THP052 RF Power Generation in LINAC4 klystron, linac, DTL, cavity 869
 
  • O. Brunner, E. Ciapala, J.N. Schwerg
    CERN, Geneva
 
 

Linac4 is a linear accelerator for negative Hydrogen ions (H-) which will replace the old Linac2 as linear injector for the CERN accelerators. Its higher energy of 160 MeV will give increased beam intensity in the downstream machines. Linac4 is about 100 m long, normal-conducting, and will be housed in a tunnel about 12 m below ground. The Linac4 tunnel will be connected to the existing chain of accelerators and can be extended to the new injection chain. The high RF power for the Linac4 accelerating structures will be generated by thirteen 1.3 MW klystrons, previously used for the CERN LEP accelerator, and six new 2.8 MW klystrons of all operating at a frequency of 352.2 MHz. The integration of the RF power system in the building is presented. The technical specifications and the performance of the various high-power elements are discussed, with emphasis on the required retuning of the LEP klystrons. The power distribution system including the power splitting requirements are also described.

 
THP056 Development of a 300-Kv Solid State Modulator for an Argonne XFELO Injector* gun, cathode, high-voltage, power-supply 881
 
  • A.R. Cours, G. Trento
    ANL, Argonne
 
 

A solid state Marx-based pulsed voltage supply is being developed at Argonne National Laboratory (ANL) with the capability of providing 300-kV pulses with 0.5-μs rise time, 1-μs fall time, 2-μs pulse flat top, and up to 10-Hz repetition rate. The supply is designed to operate a direct current (DC) thermionic prototype gun producing ≈ 0.1-μm beam emittance, a part of the ANL x-ray free-electron laser oscillator (XFELO) injector feasibility studies. The pulsed supply utilizes isolated gate bipolar transistor (IGBT) devices. Stage switching allows this supply to quickly charge the 200-pF gun capacitance and maintain 300-mA gun current during the pulse flat top. A second string of IGBT switches charges the stage capacitors and acts as a 'crowbar' to quickly remove high voltage from the gun at the pulse's fall time or during load arcing. We present an overview of the design and development of the XFELO injector DC gun pulsed power supply.


* Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH1137.

 
THP061 Towards a Modulator for the XFEL RF Stations: Test Results of the Prototype from Thomson Multimedia klystron, site, cathode, linac 893
 
  • H. Leich, U. Gensch, M. Grimberg, L. Jachmann, W. Köhler, M. Penno, R.W. Wenndorff
    DESY Zeuthen, Zeuthen
  • S. Choroba, H.-J. Eckoldt, T. Grevsmühl
    DESY, Hamburg
 
 

The European XFEL, an X-ray free electron laser, is planned as an European project with a strong connection to the DESY research center in Hamburg. Construction started in summer 2007 and commissioning will begin in 2014. The LINAC of the XFEL will incorporate 27 RF stations to supply the RF power required by the superconducting cavities. In order to generate this power (10MW at 1.3GHz) HV pulse modulators are required. Each modulator has to supply 12kV pulses at 1.6kA for 1.7ms pulse duration and at 10Hz nominal repetition rate. The repetition rate can be increased to 30Hz keeping the average power of the 10Hz operation. Although experience exists for FLASH with modulators constructed and built by one company two additional companies have been selected and contracted to design and to build additional prototypes of modulators according to the XFEL requirements. A test stand setup has been prepared at DESY, Zeuthen Site, in order to test and to operate these protoypes under similar conditions as at the XFEL. The presentation describes the Modulator Test Facility at DESY (Zeuthen Site) and presents and discusses test results of the modulator prototype from Thomson Multimedia.

 
THP064 Design of the Second-Generation ILC Marx Modulator klystron, diagnostics, status, monitoring 899
 
  • M.A. Kemp, A.L. Benwell, C. Burkhart, R.S. Larsen, D.J. MacNair, M.N. Nguyen, J.J. Olsen
    SLAC, Menlo Park, California
 
 

The SLAC National Accelerator Laboratory is leading an effort to design a prototype Marx modulator to meet the ILC klystron modulator specifications; a 120 kV (± 0.5%), 140A, 1.6 ms pulse at a 5 Hz prf. A first generation prototype, the P1 Marx, has been developed and is undergoing life testing*. The design of a second-generation Marx, P2, has been completed and most sub-systems have been tested**. The P2 advances the Marx topology demonstrated by the P1; eliminating single-point failures, incorporating advanced diagnostics/prognostics, and optimizing engineering margins to improve system availability. The P2 consists of 32 cells, which are individually regulated at an output of up to 4kV. This is in contrast to the P1 Marx which is collectively regulated by a series "Vernier" Marx. The 30 of 32 cell redundancy allows for up to two cell failures without degrading the modulator output. Failed cells can be quickly replaced and remotely-serviced. This paper presents the design of the P2 Marx. Specific topics discussed include the control architecture, mechanical layout, and power electronics design. Experimental results of both a single and array of cells are presented.


* C. Burkhart, et al., "ILC Marx modulator development status," LINAC, 2008.
** K. Macken, et al., "Towards a PEBB-Based Design Approach for a Marx-Topology ILC Klystron Modulator," PAC, 2009.

 
THP065 Magnetrons as SRF Sources cavity, feedback, injection, resonance 902
 
  • M. Popovic, A. Moretti
    Fermilab, Batavia
  • A. Dudas, R.P. Johnson, M.L. Neubauer, R. Sah
    Muons, Inc, Batavia
 
 

Magnetrons are the lowest cost microwave source in dollars/kW, and they have the highest efficiency (typically greater than 85%). However, the frequency stability and phase stability of magnetrons are not adequate when used as power sources for accelerators. Novel variable frequency cavity techniques have been developed to phase and frequency lock the magnetrons, allowing their use for either individual cavities, or cavity strings. Ferrite or YIG (Yttrium Iron Garnet) materials are placed in the regions of high magnetic field of radial-vaned, π−mode structures of a selected ordinary magnetron. A variable external magnetic field that is orthogonal to the magnetic RF field of the magnetron surrounds the magnetron to vary the permeability of the ferrite or YIG material. Measurements of a prototype magnetron will be described.

 
THP088 Simulation Study of Debuncher System for J-PARC Linac Energy Upgrade linac, injection, beam-losses, simulation 947
 
  • G.H. Wei
    KEK/JAEA, Ibaraki-Ken
  • M. Ikegami
    KEK, Ibaraki
 
 

On the beam line after linac in high power proton accelerators, like J-PARC, debuncher system plays an important role for beam injection to the succeeding ring. The debuncher system usually gives two functions, namely, to correct the center energy jitter and to minimize momentum spread and adjust beam energy at the injection. To mitigate the nonlinear effects of RF field, a debuncher system with two debuncher cavities was designed for the 181-MeV operation of J-PARC linac. In this design, the first debuncher is expected to deal with center energy jitter. Then, the second debuncher is utilized to control the injection momentum spread according to the requirements from the ring. Although the debuncher system was originally designed to minimize the momentum spread, beam-commissioning results show a different requirement for the injection momentum spread to minimize the beam loss in the ring. Based on the original design and the experimental findings with 181-MeV operation, we have designed a debuncher system for the energy upgrade of J-PARC linac to 400 MeV. In this paper, the beam dynamics design of the new debuncher system is presented together with some particle simulation results.

 
THP114 H- Ion Source Development for High Performance ion, ion-source, emittance, plasma 1004
 
  • K.F. Johnson, E. Chacon-Golcher, E.G. Geros, R. Keller, G. Rouleau, L. Rybarcyk, J. Stelzer
    LANL, Los Alamos, New Mexico
  • O.A. Tarvainen
    JYFL, Jyvaskyla
 
 

The Los Alamos Neutron Sciene Center (LANSCE) accelerator facility has the capability of accelerating both H+ and H- ion beams. LANSCE H- User Programs rely on the ion source's ability to deliver an appropriate beam current within a given emittance limit. An active H- ion source development program is ongoing with the goal of improving source performance (e.g. reliability, availability, increased out current, etc.) The formation of H- ions in the LANSCE negative ion source occurs on the surface of a negatively biased electrode (converter), exposed to a flux of positive ions incident from a cusp-confined, filament-driven discharge. The source typically delivers a 16 mA pulsed (60 Hz) H- beam with a source lifetime of 35 days. A program to reach 28-35 mA with the LANSCE source is outlined. It includes efforts to improve filament performance, elevating source body temperatures, optimizing converter geometry and location, optimizing converter cooling, and increasing the number of filaments from two to three.

 
THP115 The Development of the H- Ion Source Test Stand for CSNS ion, ion-source, extraction, power-supply 1007
 
  • H.F. Ouyang, Y.L. Chi, W. He, T. Huang, G. Li, Y.M. Liu, Y.H. Lu, X.B. Wu, T.G. Xu, H.S. Zhang, J. S. Zhang, F.X. Zhao
    IHEP Beijing, Beijing
  • D.C. Faircloth
    STFC/RAL, Chilton, Didcot, Oxon
 
 

The type of the H- ion source foe CSNS is a Penning Surface Plasma Source (SPS). The output energy of the source is 50keV and the pulsed current of H- beam is 20mA with a rms. emittance of 0.2π mm.mrad. The construction of H- ion source test stand for CSNS is finished and commissioning of the source is being done. Up to now, stable H- ion beam with a current up to 45mA and energy of 50keV is achieved. Emittance measurements of the beam is also being prepared.