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Paper Title Other Keywords Page
MOP003 Performance of the Control System for the J-PARC Linac linac, vacuum, cavity, klystron 52
  • H. Yoshikawa, H. Sakaki, T. Suzuki
    JAEA, Ibaraki-ken
  • S.F. Fukuta
    MELCO SC, Tsukuba
  • H. Ikeda
    Visual Information Center, Inc., Ibaraki-ken
  • T. Ishiyama
    KEK/JAEA, Ibaraki-Ken
  • Y.I. Itoh, Y. Kato, M. Kawase, H. Sako, G.B. Shen, H. Takahashi
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  • S.S. Sawa
    Total Saport System Corp., Naka-gun, Ibaraki

Linac of J-PARC began to operate in November, 2006, and a achieved an initial performance in January, 2007. Afterwards, the beam supply to RCS begins, and it is operating extremely well with stability up to now. Here, the evaluation for comparison of the design and realities of architecture and performance of the LINAC control system are shown. Especially, the conceptual idea of function arrangement in the hierarchy of the control system architecture is shown. Now, the linac control system is in the second phase for the high power beam and reducing the beam loss, and the analysis of the system response identification for the high precision beam control is started.

MOP012 High Power Test of Room Temperature Spoke Cavities for HINS at Fermilab cavity, vacuum, linac, ion 79
  • W.M. Tam, G. Apollinari, T.N. Khabiboulline, R.L. Madrak, A. Moretti, L. Ristori, G.V. Romanov, J. Steimel, R.C. Webber, D. Wildman
    Fermilab, Batavia
  • W.M. Tam
    IUCF, Bloomington, Indiana

The High Intensity Neutrino Source (HINS) R&D program at Fermilab will build a new 65 MeV test linac to demonstrate new technologies for application in a high intensity hadron linac front-end. The HINS warm section is composed of an ion source, a radio frequency quadrupole, a medium energy beam transport and 16 room temperature Crossbar H-type (RT-CH) cavities that accelerate the beam to 10 MeV (β=0.1422). The RT-CH cavities are separated by superconducting solenoids enclosed in individual cryostats. Beyond 10 MeV, the design uses superconducting spoke resonators. In this paper, we illustrate the completion of four RT-CH cavities and explain latest modifications in the mechanical and radio frequency (RF) designs. Cavities RF measurements and tuning performed at Fermilab are also discussed. Descriptions of the HINS R&D Facility including high power RF, vacuum, cooling and low level RF systems will be given. Finally, the history of RF conditioning and the results of high power tests of RT-CH cavities will be discussed.

MOP014 Status of the LANSCE Refurbishment Project klystron, linac, high-voltage, neutron 85
  • J.L. Erickson, K.W. Jones, M.W. Strevell
    LANL, Los Alamos, New Mexico

The Los Alamos Neutron Science Center (LANSCE) accelerator is an 800 MeV proton linac that drives user facilities for isotope production, proton radiography, ultra-cold neutrons, weapons neutron research and various sciences using neutron scattering. The LANSCE Refurbishment Project (LANSCE-R) is an ambitious project to refurbish key elements of the LANSCE accelerator that are becoming obsolete or nearing end-of-life. The conceptual design phase for the project is funded and underway. The 5 year, $170M (US) project will enable future decades of reliable, high-performance operation. It will replace a substantial fraction of the radio-frequency power systems (gridded tubes and klystrons) with modern systems, completely refurbish the original accelerator control and timing systems, replace obsolete diagnostic devices, and modernize other ancillary systems. An overview of the LANSCE-R project will be presented. The functional and operating requirements will be discussed, the proposed technical solutions presented, and the plan for successful project execution while meeting annual customer expectations for beam delivery will be reviewed.

MOP051 Linac Operations at Fermilab linac, booster, LLRF, ion 190
  • L.J. Allen
    Fermilab, Batavia

Funding: Fermi Research Alliance under contract with the US Department of Energy
In response to increasing beam intensity demands, the Fermilab 400 MeV Linac is operating at high intensity and higher repetition rates than were imagined when it was designed. This is happening at a time when maintenance time is at a premium. This has had an effect on Linac operation, tuning and reliability. Changes in tuning and equipment being made to accommodate the current running scenario along with reliability data will be presented.

MOP103 Artificial Intelligence Research in Particle Accelerator Control Systems for Beam Line Tuning ion, ion-source, beam-losses, feedback 314
  • M. Pieck
    LANL, Los Alamos, New Mexico

Funding: This work has benefited from the use of the LANSCE at LANL. This facility is funded by the US DOE and operated by LANS for NSSA under Contract DE-AC52-06NA25396. LA-UR-08-03585.
Tuning particle accelerators is time consuming and expensive, with a number of inherently non-linear interactions between system components. Conventional control methods have not been successful in this domain, and the result is constant and expensive monitoring of the systems by human operators. This is particularly true for the start-up and conditioning phase after a maintenance period or an unexpected fault. In turn, this often requires a step by step restart of the accelerator. Surprisingly few attempts have been made to apply intelligent accelerator control techniques to help with beam tuning, fault detection, and fault recovery problems. The reason for that might be that accelerator facilities are rare and difficult to understand systems that require detailed expert knowledge about the underlying physics as well as months if not years of experience to understand the relationship between individual components, particularly if they are geographically disjoint. This paper will give an overview about the research effort in the accelerator community that has been dedicated to the use of artificial intelligence methods for accelerator beam line tuning.

MOP111 Control Systems for Linac Test Facilities at Fermilab EPICS, linac, cryomodule, low-level-rf 334
  • J.F. Patrick, S.L. Lackey
    Fermilab, Batavia

Funding: *Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Fermilab* is constructing superconducting rf test facilities for development of technologies to be used in future Linac projects. Two of these facilities, the High Intensity Neutrino Source and the New Muon Laboratory, are proto-type Linacs which will run with beam. The requirements for these facilities vary but all involve collaboration and flexibility for integrating various new instruments. Tight timing requirements and automation are also required. Some facilities require integration into the existing Fermilab Control system. The controls also must be robust so as not to interfere with the main purpose of the facilities. We will outline the plan for accomplishing this task as well as the current status.

MOP112 The DARHT Data Acquisition, Archival, Analysis, and Instrument Control System (DAAAC), and Network Infrastructure diagnostics, monitoring, instrumentation, vacuum 337
  • R.D. Archuleta, L. Sanchez
    LANL, Los Alamos, New Mexico

Funding: This work supported by the US National Nuclear Security Agency and the US Department of Energy under contract DE-AC52-06NA25396
The Dual Axis Radiographic Hydrodynamic Test Facility (DARHT) at Los Alamos National Laboratory is the world's most advanced weapons test facility. DARHT contains two linear accelerators for producing flash radiographs of hydrodynamic experiments. High-speed electronics and optical instrumentation are used for triggering the accelerators and collecting accelerator data. Efficient and effective diagnostics provide basic information needed to routinely tune the accelerators for peak radiographic performance, and to successfully monitor the accelerators performance. DARHT's server and network infrastructure is a key element in providing shot related data storage and retrieval for successfully executing radiographic experiments. This paper will outline the elaborate Data Acquisition, Archival, Analysis, and Instrument Control System (DAAAC), as well as the server and network infrastructure for both accelerators.


MOP113 The Dual Axis Radiographic Hydrodynamic Test (DARHT) Facility Personnel Safety System (PSS) Control System radiation, interlocks, status, monitoring 340
  • E.B. Jacquez
    LANL, Los Alamos, New Mexico

Funding: This work supported by the US National Nuclear Security Agency and the US Department of Energy under contract DE-AC52-06NA25396
The mission of the Dual Axis Radiograph Hydrodynamic Test (DARHT) Facility is to conduct experiments on dynamic events of extremely dense materials. The PSS control system is designed specifically to prevent personnel from becoming exposed to radiation and explosive hazards during machine operations and/or the firing site operation. This paper will outline the Radiation Safety System (RSS) and the High Explosive Safety System (HESS) which are computer-controlled sets of positive interlocks, warning devices, and other exclusion mechanisms that together form the PSS.

TU302 Control, Stability and Staging in Laser Wakefield Accelerators laser, linac, wakefield, plasma 379
  • D. Panasenko
    LBNL, Berkeley, California

Laser driven plasma wakefields have recently accelerated electron beams with quasi-monoenergetic energy distributions and with gradients of ~100 GV/m. Stabilization and optimization of beam quality are now essential. Recent LBNL experiments have demonstrated control of self trapping, resulting in reproducible bunches at 0.5 GeV. Further optimization has been demonstrated using plasma density gradients to control trapping, producing beams with very low absolute momentum spread at low energies. Simulations indicate that use of these beams as an injector greatly improves accelerator performance and experiments are now underway to demonstrate such staging, which will be a crucial technology for laser driven linacs. This talk will cover recent progress in LWFAs to obtain more reproducible, higher quality beams and also cover staging prospects for high energy laser linacs.


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TUP001 Status and Upgrade Plan of 250 MeV Linac at CLS linac, storage-ring, injection, vacuum 380
  • X. Shen, L.O. Dallin, R.M. Silzer, T. Summers, M.S. de Jong
    CLS, Saskatoon, Saskatchewan

Funding: CLS supports the upgrade of the 250 MeV linac.
The Canadian Light Source (CLS) 250 MeV linac, originally constructed in the 1960's, serves as the injector for the 2.9 GeV synchrotron radiation facility[1] located on the University of Saskatchewan campus. The linac has operated reasonably well for routine operation of the light source. However, the long-term goal of operating the CLS storage ring in top-up mode will place increased demands on the linac for stability and availability that cannot be met with the existing system. Consequently, an upgrade is planned over the next two years to get higher beam stability, reliability and reproducibility. In this paper, the existing linac system will be described and the planned upgrade will be reported.

TUP009 Development of Timing and Control Systems for Fast Beam Switch at KEK 8 GeV Linac linac, EPICS, positron, injection 404
  • K. Furukawa, M. Satoh, T. Suwada
    KEK, Ibaraki
  • A. Kazakov
    GUAS/AS, Ibaraki
  • T. Kudou, S. Kusano
    MELCO SC, Tsukuba
  • G. Lei, G.X. Xu
    IHEP Beijing, Beijing

The 8 GeV Linac at KEK provides electrons and positrons to Photon Factory (PF) and B-Factory (KEKB). Simultaneous top-up injections have been considered for both PF and KEKB rings in order to improve the injection efficiency and the stability. Fast beam-switching mechanisms are being implemented, upgrading the timing and control systems. While the present system provides precise timing signals for 150 devices, many of the signals will be dynamically switched using an event system. A new scheme has been developed and tested to enable double-fold synchronization between rf signals. Fast controls of low-level rf, beam instrumentation, a kicker, a gun, and beam operation parameters will also be upgraded.

TUP021 Digitally Controlled High Availability Power Supply power-supply, linear-collider, collider, diagnostics 437
  • D.J. MacNair
    SLAC, Menlo Park, California

Funding: US DOE
This paper reports the design and test results on novel topology, high-efficiency, and low operating temperature, 1,320-watt power modules for high availability power supplies. The modules permit parallel operation for N+1 redundancy with hot swap capability. An embedded DSP provides intelligent start-up and shutdown, output regulation, general control and fault detection. PWM modules in the DSP drive the FET switches at 20 to 100 kHz. The DSP also ensures current sharing between modules, synchronized switching, and soft start up for hot swapping. The module voltage and current have dedicated ADCs (>200 kS/sec) to provide pulse-by-pulse output control. A Dual CAN bus interface provides for low cost redundant control paths. Over-rated module components provide high reliability and high efficiency at full load. Low on-resistance FETs replace conventional diodes in the buck regulator. Saturable inductors limit the FET reverse diode current during switching. The modules operate in a two-quadrant mode, allowing bipolar output from complimentary module groups. Controllable, low resistance FETs at the input and output provide fault isolation and allow module hot swapping.

TUP022 RF Control and Longitudinal Beam Stability in Energy Recovery Linacs linac, beam-loading, cavity, injection 440
  • A. Neumann, M. Abo-Bakr, J. Knobloch
    BESSY GmbH, Berlin

Funding: Work partially funded by the European Commission in the Sixth Framework Program, contract no. 011935 EUROFEL-DS5, BMBF and Land Berlin.
Most concepts for next generation light sources base on linear accelerators (linac) due to their excellent beam properties. In case of high electron energies and extreme average currents Energy Recovery Linacs (ERL) are mandatory. In this paper we investigate the rf field stability in a generic superconducting, cw operated ERL. By using rf control cavity simulations and longitudinal beam dynamics the influence of rf field stability on the energy recovery process is analyzed. Since the ERL aims for a small net beam loading cavities are operated at a high loaded quality factor. Therefore they are operated at a low bandwidth and are very susceptible to microphonics detuning. We considered the field stability under the influence of limited rf power, mechanical cavity detuning, varying beamloading, synchronization deviations and varying bunch parameters at injection into the linac. The resulting temporal and energy jitter at the linac end will be transformed in the return arc and leads to rf phase deviations on the return path. Implications of varying beam loading on the ERL performance are examined.

TUP034 Status of the 3rd Harmonic Systems for FLASH and XFEL in Summer 2008 cavity, klystron, linac, electron 471
  • E. Vogel, W. Decking, M. Dohlus, M.G. Hoffmann, M. Hüning, J. Iversen, K. Jensch, G. Kreps, T. Limberg, A. Matheisen, W.-D. Möller, K. Rehlich, A. Schmidt, J.K. Sekutowicz, W. Singer
    DESY, Hamburg
  • A. Bosotti, P. Pierini, D. Sertore
    INFN/LASA, Segrate (MI)
  • H.T. Edwards, E.R. Harms, T.N. Khabiboulline
    Fermilab, Batavia

Ultra short bunches with high peak current are required for the creation of high brilliance coherent light in the VUV and X-ray range in undulators. At the Free Electron Laser in Hamburg (FLASH) and the European X-ray free electron laser (XFEL) they are obtained by a two stage bunch compression scheme based on acceleration off the rf field crest and transverse magnetic chicanes. The deviation of the rf field's sine shape from a straight line leads to long bunch tails and reduces the peak current. This effect can be eliminated by adding a third harmonic rf system. The paper gives an overview on the actual status of the beam dynamical examinations and as well on the development of the third harmonic sub-systems like modules, cavities and radio frequency systems for FLASH and the XFEL.

TUP076 Design of a Beam Halo Monitor with a High Dynamic Range laser, photon, radiation, storage-ring 570
  • J. Egberts, S.T. Artikova, C.P. Welsch
    MPI-K, Heidelberg
  • E. Bravin, T. Lefèvre
    CERN, Geneva
  • T. Chapman, M.J. Pilon
    Thermo, Liverpool, New York

A thorough understanding of halo formation and its possible control is highly desirable for essentially all particle accelerators. Limiting the number of particles in the halo region of a beam would allow for minimizing beam losses and maximizing beam transmission, i.e. the experimental output. Measurements based on either optical transition radiation (OTR) or synchrotron radiation (SR) provide an interesting opportunity for high dynamic range measurements of the transverse beam profile, since the signal is linear with the beam charge over a wide range and is routinely used in many diagnostic applications. In this contribution, first results on beam halo measurements obtained from a flexible core masking technique and an innovative CID camera system are summarized.

TUP078 Development of Integrator Circuit for Charge Monitoring linac, injection, storage-ring, electron 576
  • K. Yanagida, H. Hanaki, S. Suzuki
    JASRI/SPring-8, Hyogo-ken

At the SPring-8 1 GeV linac, a beam current or charge is measured by means of an integrator circuit. A signal from a current transformer is processed into an integrated voltage. The Fast Gated Integrator and Boxcar Averager Module (Stanford Research Systems) is presently used as the integrator. However we plan to expand a dynamic range and an integration time of the integrator. Because the noise level of the present integrator becomes too large for the expansion, we developed a low-noise and high-resolution integrator. Both the present and developed integrators have the same functions such as signal gating, accumulation of analog signal and sample hold. The principal noise of the integrator was found to be a switching noise of the gate switch. To reduce the switching noise a GaAs transfer switch SW-283-PIN (M/A-COM) was adopted as the gate switch. The experimental data of the developed integrator showed 1/10 of the noise level of the present integrator.

TUP079 Operational Performance of a New Beam-Charge Interlock System for Radiation Safety at the KEKB Injector Linac injection, linac, positron, radiation 579
  • T. Suwada, K. Furukawa, E. Kadokura, M. Satoh
    KEK, Ibaraki

A new beam-charge interlock system has been developed for radiation safety and machine protection at the KEKB injector linac. Although the previous software-based interlock system was working, it was replaced by the new hardware-based one. The new interlock system restricts the integrated amount of beam charges delivered to four different storage rings (KEKB e+, KEKB e-, PF, PF-AR) at six locations along the linac. When the integrated amount of beam charges exceeds a certain threshold level prescribed at each location, the beam-abort requests are directly sent through a twisted hardwire cable to the safety control system of the linac. The new interlock system boosted its reliability in comparison with the previous system. The full-scale operation of the new interlock system has been started since the end of March 2008. In this report we describe the operational performance of the new beam-charge interlock system.

WE105 RF Control of High QL Superconducting Cavities cavity, feedback, resonance, linac 704
  • C. Hovater
    JLAB, Newport News, Virginia

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
In the last 20 years the requirements for rf control has increased as the target use has broadened from electron/ion accelerators for Nuclear and Particle Physics to light sources such as Free Electron Lasers. The increasing requirement of cavity field control to meet the spectral and jitter performance specifications for light sources has led system designers to a more rigorous approach in designing the rf controls. Design attention must be applied not only to the hardware and control algorithms but also to the overall accelerating system to meet performance and cost requirements. As an example, cavity QL in Energy Recovery Linacs (ERL) must be optimized such that the rf controls can accommodate the lowest possible rf power given the background cavity microphonics. This paper presents the status and future directions of high QL superconducting rf control systems.


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THP002 The 1.3 GHz Superconducting RF Program at TRIUMF cavity, linac, TRIUMF, ISAC 774
  • R.E. Laxdal, K. Fong, A. Grassellino, A.K. Mitra, I. Sekachev, V. Zvyagintsev
    TRIUMF, Vancouver
  • R.S. Orr, W. Trischuk
    University of Toronto, Toronto, Ontario

TRIUMF is proposing to build a 50 MeV electron linac as a driver to produce radioactive ion beams through photofission. The present design calls for the use of nine-cell 1.3 GHz Tesla type cavities. A 1.3 GHz Superconducting RF (SRF) program has been initiated with the goal to produce and test one nine cell cavity by the end of 2009. The program will utilize the existing clean room and SRF test facilities that support the ISAC-II heavy ion superconducting linac. A vertical cryostat has been modified with a new insert to allow single cell testing. Pumps for 2 K sub-atmospheric operation have been tested. A single cell fabrication program is being initiated with a local company. A RRR measurement program is on-going to test cavity welds. The goal of the 1.3 GHz upgrade is to not only produce cavities for the in house project but to broaden TRIUMF's technical base for future potential collaborations. The paper will report the progress and plans of the 1.3 GHz SRF program.


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THP010 Influence of Piezo-Hysteresis and Resolution on Cavity Tuning cavity, feedback, resonance, linac 795
  • O. Kugeler, W. Anders, J. Knobloch, A. Neumann
    BESSY GmbH, Berlin

Funding: Work partially funded by the EU Commission in the sixth framework programme, contract no 011935 EURO-FEL-DS5, BMBF and Land Berlin.
All mechanical tuning systems are subject to hysteresis effects: For coarse tuning with a stepper motor, the exercised forces lead to a visco-elastic deformation of the tuner body. In piezo-based fine tuning, even if the smaller deformations of tuner and cavity can be regarded as fully elastic, the piezo-actuators themselves suffer from remanent polarization effects. The extent of these nonlinearities has been measured in three different tuning systems (Saclay I, Saclay II and Blade Tuner) utilizing high-voltage as well as low-voltage piezo actuators. An estimate of the resulting tuner-resolution and performance degradation with respect to microphonics compensation is given. Experiments were performed in the HoBiCaT facility at BESSY.

THP012 Nondestructive Testing of Niobium Sheets for SRF Cavities Using Eddy-current and SQUID Flaw Detection niobium, cavity, superconductivity, neutron 800
  • A. Brinkmann, W. Singer
    DESY, Hamburg

For more than 10 years DESY has been operating a high resolution eddy-current scanning installation with rotating table for nondestructive flaw detection on niobium sheets for SRF cavities. More than 2000 sheets have been examined up to now, several types of defects have been detected and identified using different supplementary methods such as EDX, X-ray fluorescence, neutron activation analysis etc. In order to scan Nb-sheets needed for XFEL-cavity production, new scanning devices have to be build. One option of the eddy-current installations could be an application of SQUID-sensors due to much higher sensitivity instead of conventional probes. A SQUID based scanner system was built and is in evaluation at DESY. A status report will be given.

THP015 Open 120C Bake in Argon Atmosphere: A Simplified Approach for Q-Drop Removal cavity, vacuum, niobium, superconducting-cavity 809
  • D. Reschke, J. Ziegler
    DESY, Hamburg

The removal of the Q-drop without field emission by a low temperature (app. 120C) bake procedure is essential in order to achieve the full performance in both electropolished (EP) and chemically etched (BCP) high gradient SCRF Nb accelerator cavities. A simplified procedure applying an open 120C bake out in an Argon atmosphere is presented. First results are compared to the well-established bake-out procedure under vacuum conditions.

THP017 Use of Piezoelectric Actuator to Frequency Lock Superconducting Quarter Wave Resonator niobium, linac, high-voltage, resonance 815
  • B.K. Sahu, G.K. Chowdhury, S. Ghosh, D. Kanjilal, D.S. Mathuria, R. Mehta, A. Pandey, P. Patra, A. Rai, A. Roy, K. Singh
    IUAC, New Delhi

The frequency control of the superconducting quarter wave resonator at IUAC is currently accomplished by mechanical and electronic tuners which are operated in the time scale of seconds and hundreds of milliseconds to a few tens of microseconds respectively. Due to presence of microphonics, input rf power in the range 200-300 W was required to control the resonator for a typical field of 3-5 MV/m achieved with 6 watts dissipation. Implementation of a novel idea to damp the mechanical vibration with the help of SS-balls has helped to reduce rf power below 100 W. Though resonators are working fine at this power level, we are investigating whether further reduction of rf power is possible using a piezo actuator to control the drift of frequency. The piezo tuner working in hundreds of milli seconds range with the dynamic phase control scheme will share a substantial load from the electronic tuner. As a result, the resonator's phase lock loop will remain locked for less rf power. The initial test results of the piezo tuner will be presented.

THP021 Development of Inspection Systems for Superconducting Cavities cavity, superconducting-cavity, accelerating-gradient, cryogenics 824
  • Y. Iwashita
    Kyoto ICR, Uji, Kyoto
  • H. Hayano, K. Watanabe
    KEK, Ibaraki

Inspections of superconducting rf cavities seem essential in achieving high achieving gradient. The inspection of interior surface of a superconducting rf cavity with high enough resolution to find defects more than several tens microns is achieved by our high resolution camera system. This system revealed undiscovered defects at just inner sides of the locations predicted by passband-mode and thermometry measurements. This system will help to improve cavity fabrication processs and their yield. This system will be delivered world wide for that purpose. We are planning to widen our activity in this field: developments of new termometry system with easy installation and less cabling and high sensitivity Eddy Current Surface Inspection system for bare niobium sheets. The detailed systems and some preliminary data obtained from the systems will be presented.

THP026 Surface Processing Facilities for Superconducting RF Cavities at ANL cavity, linac, cathode, niobium 839
  • M.P. Kelly, S.M. Gerbick
    ANL, Argonne
  • D.R. Olis, A.M. Rowe
    Fermilab, Batavia

New SRF cavity processing systems at ANL, including those for electropolishing (EP), high-pressure water rinsing (HPR), and single-cavity clean room assembly have been developed and operated at ANL for use with cavities for a range of electron and ion linac applications. Jointly with FNAL, systems for 1.3 GHz single- and multi-cell elliptical cavities for the linear collider effort have been developed. New systems for use with low-beta TEM-class cavities have also been built and used to process a set of new quarter-wave resonators as part of an upgrade to the ATLAS heavy-ion accelerator at ANL. All of the new hardware is located in a 200 m2 joint ANL/FNAL Superconducting Cavity Surface Process Facility (SCSPF) consisting of two separate chemical processing rooms, a clean anteroom, and a pair of class 10 and 100 clean rooms for HPR and clean assembly. Results of first cold tests for elliptical and TEM-class cavities processed in these facilities are presented.

THP034 CW RF Systems of the Cornell ERL Injector cavity, LLRF, klystron, cryogenics 857
  • S.A. Belomestnykh, Z.A. Conway, J. Dobbins, R.P.K. Kaplan, M. Liepe, P. Quigley, J.J. Reilly, J.P. Sikora, C.R. Strohman, V. Veshcherevich
    CLASSE, Ithaca, New York

Funding: Work is supported by the National Science Foundation grant PHY 0131508.
Two high power 1300 MHz rf systems have been developed for the Cornell University ERL Injector. The first system, based on a 16 kWCW IOT transmitter, is to provide rf power to a buncher cavity. The second system employs five 120 kWCW klystrons to feed 2-cell superconducting cavities of the injector cryomodule. The sixth, spare klystron is used to power a deflecting cavity in a pulsed mode for beam diagnostics. A digital LLRF control stem was designed and implemented for precise regulation of the cavities' field amplitudes and phases. All components of these systems have been recently installed and commissioned. The first operational experience with the systems is discussed.

THP048 RF Power Amplifiers for the SPIRAL2 Driver: Requirements and Status cavity, rfq, linac, LLRF 897
  • M. Di Giacomo, B. Ducoudret
    GANIL, Caen

The SPIRAL2 project uses an RFQ, normal conducting rebunchers and a superconducting linac to accelerate high intensity beams of protons, deuterons and heavier ions. All cavities work at 88 MHz, are independently phased and powered by amplifiers whose power ranges from a few kW to 250 kW. The paper describes the amplifier requirements, the proposed solutions and their status.

THP053 The Status of Nextef; The X-band Test Facility in KEK klystron, linear-collider, collider, status 906
  • S. Matsumoto, M. Akemoto, S. Fukuda, T. Higo, N. Kudoh, H. Matsushita, H. Nakajima, T. Shidara, K. Yokoyama, M. Yoshida
    KEK, Ibaraki

Nextef is a new X-band (11.4GHz) test facility in KEK. All of the key devices of this facility are from our old X-band Test Facility(XTF). By combining the power from two klystrons, 100 MW maximum X-band rf power is produced and 75MW is available in the bunker where the high power test of the high gradient accelerator structures will be done. The commissioning of the facility for the structure testing has almost done. The status of the facilityis is reported.

THP054 Status of RF Sources in Super-Conducting RF Test Facility (STF) at KEK cavity, LLRF, cryomodule, klystron 909
  • S. Fukuda, M. Akemoto, H. Hayano, H. Honma, H. Katagiri, S. Kazakov, S. Matsumoto, T. Matsumoto, S. Michizono, H. Nakajima, K. Nakao, T. Shidara, T. Takenaka, Y. Yano, M. Yoshida
    KEK, Ibaraki

Phase 0.5 and Phase 1.0 of the Superconducting RF Test Facility (STF) have been developed since 2005 in KEK. We have completed the two rf-sources and they have been used for the evaluation for the components of power distribution system (PDS) and couplers which were installed in the 5m-cryomodules. We have developed some rf components which is used in the power distribution system(PDS). Phase 1.0 have been conducted now and we attempt the R&D of PDS required in ILC project. This report describes the recent status of the rf source of STF in KEK including the modulator, PDS and LLRF.

THP055 Characteristics of Different Materials on High-Gradient Experiments laser, acceleration, status, klystron 912
  • K. Yokoyama, S. Fukuda, Y. Higashi, T. Higo, N. Kudoh, S. Matsumoto, Y. Watanabe
    KEK, Ibaraki

High-gradient experiments have been performed using a narrow waveguide that has a field of approximately 200 MV/m at an rf power of 100 MW. The study investigates the characteristics of different materials at high-gradient rf breakdown. This paper reports the results of high-gradient experiments and observations of the surface of stainless-steel waveguides.


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THP080 Elimination of Parasitic Oscillations in RF Tube Amplifier for High Power Application cavity, linac, ion, simulation 981
  • E. Feldmeier
    HIT, Heidelberg
  • G. Hutter, B. Schlitt, W. Vinzenz
    GSI, Darmstadt

For the heavy ion therapy center HIT in Heidelberg a 1.6 MW power amplifier for 217 MHz was built to supply the 7 MeV/u IH cavity. The inherent parasitic oscillations of the RF tube increases rapidly the anode current until the system switches off. For the elimination of those parasitic oscillations ferrite material is used. The electro magnetic fields are simulated to find an optimal positioning of the ferrite material in the anode cavity such that only the parasitic oscillations are attenuated without affecting the fundamental mode.

THP081 Development of All Solid State Bouncer Compensated Long Pulse Modulators for LEP 1MW Klystrons to be Used for LINAC4 Project at CERN klystron, linac, high-voltage, simulation 984
  • P. Shrivastava, J. Mulchandani, V.C. Sahni
    RRCAT, Indore (M.P.)
  • F. Bordry, C. De Almeida Martins, C. Rossi
    CERN, Geneva

Funding: Department of Atomic Energy, India.
CERN is building a 352.2 MHz, 3 MeV RFQ based Test Stand as first part of LINAC 4. Extending its collaboration with DAE of India, CERN approached us to design and develop a high voltage pulsed modulator for 1 MW LEP klystrons (planning their reuse). Three design schemes were proposed out of which an all solid state bouncer compensated modulator was chosen for follow up development. The main features of the modulator are: no gas tube crow-bar, all solid state construction low rise/fall times and high stability of the flat top. The major specifications are output voltage upto 110 kV, output current upto 24 Amp, pulse duration 800 μs, PRR 2Hz, pulse droop <1% and ripple on pulse top <0.1%. The energy in klystron arc is restricted to 10J. Based on these principles, a modulator has been developed and constructed at CERN and is currently undergoing tests with a klystron while another one with similar development is in the final stages of integration/evaluation at RRCAT. The present paper describes the topology, simulation results, protection strategy and integration aspects of the pulse modulator and would briefly summarize the results.

The work is done under DAE CERN Collaboration under NAT Protocol.

THP087 Quarter-Wave-Stub Resonant Coupler linac, coupling, rfq, cavity 993
  • D.A. Swenson
    Linac Systems, LLC, Albuquerque, New Mexico

Most small proton and other ion linacs involve two different linac structures, namely an RFQ linac section and some other, more efficient, linac structure, such as the Drift Tube Linac (DTL), the interdigital (Wideroe) linac, or the Rf Focused Interdigital (RFI) linac. Such linacs can benefit a lot by being resonantly coupled into a single resonant unit. The resonantly coupled structures can be driven by a single rf power system, through single rf drive loop, at a single rf frequency. The relative phase and relative amplitude of the fields in the two structures are locked by the resonant coupler. Such systems require no control of phase of the rf power. By designing the rf power system to track the resonant frequency of the combined structures, the control of the resonant frequencies of the two structures is greatly simplified. A simple, compact, resonant coupler, based on a quarter-wave-stub, will be described. Models of this resonant couple have been tuned and adjusted, and are scheduled to be tested at operating powers in the early fall (2008).

THP089 High Power L-Band Fast Phase Shifter coupling, resonance, permanent-magnet, cavity 999
  • I. Terechkine, T.N. Khabiboulline, N. Solyak
    Fermilab, Batavia

Following development and testing a prototype waveguide-based high power phase shifter, a design concept of a high power fast phase shifter has been developed. The shifter uses ferrite blocks positioned in a rectangular waveguide. The waveguide cross-section is chosen to suppress most of resonances that could otherwise be a limiting factor for the phase shifter high power performance. Base bias field is created with the use of permanent magnets. Low inductance coils in the same magnetic circuit excite fast (pulsed) bias field component. The waveguide is designed in a way to ensure that the pulsed magnetic field penetrates inside the waveguide with minimum delay while allowing effective heat extraction from the ferrite blocks. This report provides details of the system design, including expected rf behavior and frequency range.

THP090 Marx Bank Technology for Accelerators and Colliders high-voltage, collider, impedance, diagnostics 1002
  • J.A. Casey, F.O. Arntz, R. Ciprian, M.P.J. Gaudreau, M.K. Kempkes, I. Roth
    Diversified Technologies, Inc., Bedford, Massachusetts

Funding: U.S. Department of Energy SBIR Program
Diversified Technologies, Inc. (DTI) has developed high power, solid-state Marx Bank designs for a range of accelerator and collider designs. We estimate the Marx topology can deliver equivalent performance to conventional designs, while reducing acquisition costs by 25-50%. In this paper DTI will describe the application of Marx based technology to two different designs: a long-pulse ILC focused design (140 kV, 160 A, 1.5 ms), and a short-pulse design (500 kV, 265 A, 3 us). These designs span the known requirements for future accelerator modulators. For the ILC design, the primary challenge is minimizing the overall size and cost of the storage capacitors in the modulator. For the short-pulse design, the primary challenge is high speed operation, to limit the energy lost in the pulse rise-time while providing a very tight (± 3%) voltage flattop. Each design demands unique choices in components and controls, including the use of electrolytic capacitors in the ILC Marx design. This paper will review recent progress in the development and testing of both of these prototype Marx designs, being built under two separate DOE Phase II SBIR grants.

THP094 Leveraging the LEDA High Voltage Power Supply Systems for the LANSCE Refurbishment Project klystron, power-supply, high-voltage, status 1008
  • J.T. Bradley III, D. Rees, W. Roybal, K.A. Young
    LANL, Los Alamos, New Mexico

Funding: Work supported by the NNSA, U. S. Department of Energy under contract DE-AC52-06NA25396.
The LANSCE Refurbishment Project (LANSCE-R) will revitalize the LANSCE accelerator infrastructure. Much of the equipment has been in use for over 36 years and is approaching the end of its design lifetime. As obsolescence issues make like-for-like replacements increasingly more expensive, modern systems with lower costs become a reasonable alternative. As part of the LANSCE-R project, four of the seven HV power supplies for the 805 MHz rf klystrons will be replaced. The present and future requirements for these power supplies influence the selection of replacement options. Details of the HV power supply replacement requirements and the different replacement options will be discussed. One option is to use four 95 kV, 21 A dc power supplies originally installed nearby as part of the Low Energy Demonstration Accelerator (LEDA) project. Significant material and labor cost savings can be achieved by leaving these supplies installed where they are and building a HV transport system to bring high voltage power from the existing LEDA facility to the LANSCE facility. The different replacement options will be compared based on material and labor costs as offset by long-term energy savings.

THP095 Progress Towards the LANSCE RF System Refurbishment neutron, klystron, high-voltage, low-level-rf 1011
  • D. Rees, J.T. Bradley III, S. Kwon, J.T.M. Lyles, M.T. Lynch, M.S. Prokop, W. Reass, K.A. Young
    LANL, Los Alamos, New Mexico

The Los Alamos Neutron Science Center (LANSCE) is in the conceptual design phase of a refurbishment project that will sustain reliable facility operations well into the next decade. The LANSCE accelerator was constructed in the late 1960s and early 1970s and is a national user facility that provides pulsed protons and spallation neutrons for defense and civilian research and applications. The refurbishment will focus on systems that are approaching "end of life" and systems where modern upgrades hold the promise for significant operating cost savings. The current baseline consist of replacing all the 201 MHz rf amplifiers, replacing greater than 75% of the 805 MHz rf systems with a combination of high efficiency klystrons and new klystrons of the existing style, replacing four high voltage systems, and replacing all the low level rf cavity field control systems along the accelerator. System designs and requirements will be presented and the project plan will be discussed.

THP097 ILC Marx Modulator Development Program Status klystron, diagnostics, high-voltage, status 1015
  • C. Burkhart, T.G. Beukers, R.S. Larsen, K.J.P. Macken, M.N. Nguyen, J.J. Olsen, T. Tang
    SLAC, Menlo Park, California

Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515
A Marx-topology klystron modulator is under development as an 'Alternative Conceptual Design' for the International Linear Collider project. It is envisioned as a smaller, lower cost, and higher reliability alternative to the present, bouncer-topology, 'Baseline Conceptual Design'. The application requires 120 kV (±0.5%), 140 A, 1.6 ms pulses at a rate of 5 Hz. The Marx constructs the high voltage pulse by combining, in series, a number of lower voltage cells. The Marx employs solid state elements; IGBTs and diodes, to control the charge, discharge and isolation of the cells. The developmental testing of a first generation prototype, P1, is nearing completion. Development of a second generation prototype, P2, is underway. Status updates for both prototypes will be presented.

THP098 RF Vector Control for Efficient Fan-Out Power Distribution cavity, impedance, linac, coupling 1018
  • Y.W. Kang
    ORNL, Oak Ridge, Tennessee

Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
An algorithm for direct high power rf vector control of fan-out rf distribution using reactive circuit elements is presented. In this approach, rf control is performed for the entire fan-out system with many cavities as one system to maximize the rf power efficiency. Control parameters for a set of required rf voltage vectors in the accelerating cavities are determined and maintained for the whole system. Maximizing rf power efficiency with fan-out power distribution can be valuable for large scale SRF accelerators since construction and operation costs can be saved significantly. If a fan-out system employs a fixed power splitter with high power vector modulators in cavity inputs, the optimum power efficiency especially for a SRF system can not be provided since certain rf power headroom is needed for the vector control at each cavity. In the new fan-out vector control approach, a set of required cavity rf voltages is delivered by adjusting the phase delays between the cavities and the reactive loadings at the cavity inputs. The phase shifts and the reactive loadings are realized with high power rf phase shifters.

THP100 Self Tuning Regulator for ISAC 2 Superconducting RF Cavity Tuner Control ISAC, cavity, alignment, feedback 1024
  • K. Fong, M.P. Laverty, Q. Zheng
    TRIUMF, Vancouver

The ISAC 2 superconducting rf cavities use self-excited, phase-locked mode of operation. As such the microphonics are sensitive to the alignment of the phase control loop. Although initial alignments can minimize the effect of microphonics, long term drifts, particularly in the power amplifiers, can cause the control loop to misalign and an increase in sensitivity to microphonics. The ISAC 2 control system monitors several points in the control loop to determine the phase alignment of the power amplifiers as well as the rf resonant cavities. Online adaptive feedbacks using Self Tuning Regulators are employed to bring the different components back into alignment.

THP101 AM-PM Conversion Induced Instability in I/Q Feedback Control Loop booster, cavity, feedback, TRIUMF 1027
  • K. Fong, M.P. Laverty, Q. Zheng
    TRIUMF, Vancouver

Most rf feedback control systems today uses the I/Q demodulation and modulation scheme because of its simplicity. Its performance, however, depends on the alignment of the feedback loops. If the loop contains elements that have a high AM-PM conversion such as a class C amplifier, then the misalignment is dynamic and power dependent. In the extreme case the I/Q loops can become unstable and the system settled into a limit-cycle oscillation.

THP103 LLRF System Requirement Engineering for the European XFEL LLRF, cavity, diagnostics, klystron 1033
  • S. Simrock, G. Ayvazyan, Z. Geng, M.K. Grecki
    DESY, Hamburg
  • B. Aminov
    CRE, Wuppertal

The LLRF system of the European XFEL must fulfill the requirements of various stakeholders: Photon beam users, accelerator operators, rf experts, controls system, beam diagnostics and many others. Besides stabilizing the accelerating fields the system must be easy to operate, to maintain, and to upgrade. Furthermore it must guarantee high availability and it must be well understood. The development, construction, commissioning and operation with an international team requires excellent documentation of the requirements, designs and acceptance test. For the rf control system of the XFEL the new system modeling language SySML has been chosen to facilitate the system engineering and to document the system. SysML uses 9 diagram types to describe the structure and behavior of the system. The hierarchy of the diagrams allows individual task managers to develop detailed subsystem descriptions in a consistent framework. We present the description of functional and non-functional requirements, the system design and the test cases. An attempt of costing the software effort based on the use case point analysis is also presented.

THP104 Low Level RF and Timing System for XFEL/SPring-8 cavity, pick-up, feedback, low-level-rf 1036
  • T. Ohshima, N. Hosoda, H. Maesaka, Y. Otake
    RIKEN/SPring-8, Hyogo
  • M. Musha
    University of electro-communications, Tokyo
  • K. Tamasaku
    RIKEN Spring-8 Harima, Hyogo

Requirement on a Low Level rf (LLRF) system is very tight and allowable jitter is less than several tens femto seconds for the XFEL/SPring-8. To satisfy this requirement, we have developed special components; a low-noise master oscillator, a high precision IQ modulator/demodulator, a high speed DAC/ADC, and a delayed pulse generator with 700 fs jitter to a 5712 MHz reference clock. These components were installed in the SCSS test accelerator and their performance was checked. The standard deviations of the phase and amplitude were less than 0.02 degree and 0.03% for a 238 MHz SHB acceleration cavity. Measured rms jitter of the beam arrival time relative to the reference rf signal was 50 fs, which demonstrated the high performance of the total LLRF system. For the XFEL, the length of reference signal transmission line is long, about 1 km. Therefore an optical system is adopted because of low transmission loss and an ability to keep precise time accuracy using fiber length control, which has 0.2 um/sqrt(Hz) noise floor. Achieved performance of the LLRF and timing system, and development status on the optical transmission system will be presented in this paper.


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THP105 LLRF Control System of the J-PARC LINAC cavity, linac, feedback, beam-loading 1039
  • Z. Fang, S. Anami, S. Michizono, S. Yamaguchi
    KEK, Ibaraki
  • T. Kobayashi
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  • H. Suzuki
    JAEA, Ibaraki-ken

At the J-PARC 181 MeV proton linac, the rf sources consist of 4 solid-state amplifiers and 20 klystrons with operation frequency of 324 MHz. The rf fields of each rf source are controlled by a digital feedback system installed in a compact PCI (cPCI). A very good stability of the accelerating fields has been successfully achieved about ±0.2% in amplitude and ±0.2 degree in phase, much better than the requirements of ±1% in amplitude and ±1 degree in phase. Besides, the tuning of each accelerator cavity including 3 DTL and 15 SDTL is also controlled by this LLRF system through a cavity tuner. We pre-defined the cavity resonance states with the tuner adjusted to obtain a flat phase during the cavity field decay. The cavity auto-tuning is well controlled to keep the phase of rf fields within ±1 degree. Furthermore, from the amplitude waveform during the cavity field decay, the Q-value of each cavity is calculated in real-time and displayed in the PLC TP of the LLRF control system.

THP106 High Speed Data Acquisition System Using FPGA for LLRF Measurement and Control LLRF, low-level-rf, superconducting-cavity, linear-collider 1042
  • H. Katagiri, S. Fukuda, T. Matsumoto, S. Michizono, T. Miura, Y. Yano, M. Yoshida
    KEK, Ibaraki

Recently, FPGA technology is widely used for the accelerator control owing to its fast digital processing. We have been developing several applications for LLRF control and measurement using commercial and custom-made FPGA board. XtremeDSP(the commercial FPGA board equipped two ADCs and two DACs) is mainly used for the performance evaluation of STF(Superconducting RF Test Facility) LLRF. Installing the custom-made FPGA board equipped with ten ADCs and two DACs is considering for up-grade of the rf driver and rf monitoring system in the injector linac. Development of the high-speed data acquisition system that combines commercial FPGA board ML555 and FastADC(ADS5474 14bit, 400MS/s) is carried out. Result of those data acquisition systems will be summarized.

THP107 Performance of Digital Low-Level RF Control System with Four Intermediate Frequencies cavity, LLRF, feedback, superconducting-cavity 1045
  • T. Matsumoto, S. Fukuda, H. Katagiri, S. Michizono, T. Miura, Y. Yano
    KEK, Ibaraki

In a superconducting accelerator, an FPGA/DSP-based low-level rf (LLRF) system with feedback control is adopted to satisfy the requirement of stability in the accelerating field. An rf probe signal picked up from cavity is down-converted to an intermediate frequency and sampled by an analog-to-digital converter (ADC) in the digital LLRF control system. In order to decrease the number of the ADCs required for vector sum feedback operation, a digital LLRF control system using different intermediate frequencies has been developed. At STF (Superconducting RF Test Facility) in KEK, the digital LLRF system with four intermediate frequencies was operated and the rf field stability under the feedback operation was estimated using a superconducting cavity. The result of the performance will be reported.

THP108 Performance of Digital LLRF System for STF in KEK cavity, LLRF, feedback, klystron 1048
  • S. Michizono, S. Fukuda, H. Katagiri, T. Matsumoto, T. Miura, Y. Yano
    KEK, Ibaraki

RF operation has started at the STF (Superconducting RF Test Facility) in KEK. The digital feedback system, which consists of one FPGA, ten 16-bit ADCs and two 14-bit DACs, was installed in order to satisfy the rf-field regulation requirements of 0.3% rms and 0.3 deg.rms in phase. The rf field stability under various feedback parameters are presented. Various studies were also carried out such as cavity detuning measurements (microphonics, quench detection, etc.). These results will also be summarized.

THP109 Measurements of Feedback-Instability Due to 8/9π and 7/9π Modes at KEK-STF feedback, cavity, klystron, LLRF 1051
  • T. Miura, S. Fukuda, H. Katagiri, T. Matsumoto, S. Michizono, Y. Yano
    KEK, Ibaraki

In the superconducting rf test facility (STF) at KEK, high power tests of the nine-cell superconducting cavity for the international linear collider (ILC) have been performed. Although the cavity was operated in π-mode, the feedback instability due to 8/9π and 7/9π modes was observed in the STF. The intensities of 8/9π and 7/9π modes were measured by changing the feedback loop-delay and stable/unstable region appeared periodically as expected.

THP110 Pulse-by-Pulse Switching of Beam Loading Compensation in J-PARC Linac RF Control linac, beam-loading, LLRF, cavity 1054
  • T. Kobayashi
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  • S. Anami, Z. Fang, S. Michizono, S. Yamaguchi
    KEK, Ibaraki
  • E. Chishiro, H. Suzuki
    JAEA, Ibaraki-ken

For the J-PARC linac low level rf system, in order to compensate beam-loading change by pulses in the operation of 25 Hz repetition, a function that switches the feed-forward control parameters in every pulse were installed into the digital accelerating-field control system. The linac provides a 50 mA peak current proton beam to a 3 GeV rapid-cycling synchrotron (RCS). Then the RCS distributes the 3-GeV beam into a following 50 GeV synchrotron (main ring, MR) and the Materials and Life Science Facility (MLF), which is one of the experimental facilities in the J-PARC. The 500-us long macro pulses from the ion source of the linac should be chopped into medium pulses for injection into the RCS. The duty (width or repetition) of the medium pulse depends on which facility the RCS provides the beam to the MR or MLF. Therefore the beam loading compensation needs to be corrected for the change of the medium pulse duty in the 25 Hz operation.

THP111 LLRF Control System Using a Commercial Board LLRF, cavity, feedback, DTL 1057
  • H.S. Kim, Y.-S. Cho, H.-J. Kwon, K.T. Seol
    KAERI, Daejon

The requirements for the field amplitude and phase stability of the PEFP linac are 1% and 1 degree, respectively. To achieve the requirements, a digital LLRF control system has been developed using a commercial digital board for general purpose(FPGA). The feedback with PI control and feedforward are implemented in the FPGA. The LLRF control systems are currently used for the linac test. In this paper, test results and discussion on the advantage and disadvantage of the LLRF system based on a commercial board are presented.

THP112 Numerical Simulation of the INR DTL A/P Control System cavity, feedback, DTL, vacuum 1060
  • A.I. Kvasha
    RAS/INR, Moscow

Stabilization of amplitude and phase in linear accelerator cavities can be realized by means of control systems, operating both in polar (A/P) and rectangular (I/Q) coordinates. In analyzing of linear control systems, as a rule, transfer functions are used, which, in turn, are the symbolic representation of the linear differential equation, connecting the input and output variables. It's well known that generally in A/P coordinate it is impossible to get two separate linear differential equations for amplitude and phase of rf voltage in a cavity except for estimating of the control system stability in the small near steady state values of variables. Nevertheless, there is a possibility of numerical simulation of nonlinear A/P control system using up-to-date programs. Some results of the simulation are presented.

THP114 New LLRF System for Fermilab 201.25 MHz Linac LLRF, cavity, linac, feedback 1066
  • T.A. Butler, L.J. Allen, J. Branlard, B. Chase, E. Cullerton, P.W. Joireman, M.J. Kucera, V. Tupikov, P. Varghese
    Fermilab, Batavia

The Fermilab Proton Plan, tasked to increase the intensity and reliability of the Proton Source, has identified the Low Level RF (LLRF) system as the critical component to be upgraded in the Linac. The current 201.25 MHz Drift Tube Linac LLRF system was designed and built over 35 years ago and does not meet the higher beam quality requirements under the new Proton Plan. A new VXI based LLRF system has been designed to improve cavity vector regulation and reduce beam losses. The upgrade includes an adaptive feedforward system for beam loading compensation, a new phase feedback system, and a digital phase comparator for cavity tuning. The new LLRF system is phase locked to a temperature stabilized 805 MHz reference line, currently used as frequency standard in the higher energy accelerating section of the Linac. This paper will address the current status of the project, present the advancements in both amplitude and phase stability over the old LLRF system, and discuss commissioning plans.

THP115 Optimizing Cavity Gradients in Pulsed Linacs Using the Cavity Transient Response cavity, linac, beam-loading, klystron 1069
  • G.I. Cancelo, A. Vignoni
    Fermilab, Batavia

Pulsed Linac accelerators are being designed powering a string of cavities from one klystron. A typical low level rf control loop controls the amplitude and the phase of the klystron's rf power; however, the loop cannot dynamically control individual cavity amplitude and phases. The problem is further complicated by the need to obtain the maximum possible acceleration from the rf unit. Proton Linacs (HINS, ProjectX) add extra complexity. A rf unit may need cavities operating at different synchronous phases. Particles travel cavities at increasing velocities, which implies different beam loading conditions. For pulsed proton Linacs amplitude and phase stability are crucial for beam stability. The usual steady state approach determines optimality conditions for minimum generator power as a function of rf parameters. This approach does not provide constant amplitude and phases when the beam is on. In this paper we propose a novel theory using the cavity transient response. The transient response allows setting flat cavity gradients (A and phi) for each cavity in the unit. The optimized rf parameters for the transient response are the cavity coupling parameter and cavity tuning angle.

THP116 Real Time RF Simulator (RTS) and Control cavity, LLRF, beam-loading, simulation 1072
  • G.I. Cancelo, K.R. Treptow, A. Vignoni, T.J. Zmuda
    Fermilab, Batavia
  • C. Armiento
    University of Pisa and INFN, Pisa

A multi cavity real time rf simulator and PID control has been implemented on a Xilinx Virtex-4 FPGA. The rf simulator simulates an entire rf unit with up to 4 cavities connected to a single simulated klystron. Each cavity is allowed to have its own set of parameters, set point gradients, synchronous phases, and beam loadings. The simulator is built based on an interdependent electrical and mechanical model of a cavity. The electrical model is a 1st order differential equation in the complex phase space. The mechanical model is a 2nd order differential equation of the Lorentz force detuning on the cavities. Other spurious effects as microphonics and noises can be added using an external source or a memory table. The simulator has been optimized for size and utilizes only one Xilinx DSP block per cavity. A typical Virtex-4 has of the order of 100 DSP blocks. The simulator bandwidth is 1MHz which is plenty for niobium type superconducting cavities which have a loaded Q of about 3 million and a half bandwidth of about 250 Hz. The Real Time simulator is currently running on hardware comprised by an ESECON LLRF controller* and a Linux based VME processor.

*ESECON, 14 channel LLRF controller, Low Level Radio Frequency Workshop (LLRF07), Knoxville, Tennessee, October 22-25, 2007, presentation 031.

THP117 Design and Evaluation of the Low-Level RF Electronics for the ILC Main LINAC cavity, LLRF, linac, low-level-rf 1075
  • U. Mavric, B. Barnes, J. Branlard, B. Chase, D.W. Klepec, V. Tupikov
    Fermilab, Batavia

Funding: Work supported by Fermi Research Alliance LLC. Under DE-AC02- 07CH11359 with the U.S. DOE
The proposed 30 km long ILC electron/positron collider is pushing the limits not only in basic physics research but also in engineering. For the two main Linacs, the pulsed rf power that is feeding the high number of SCRF cavities (~17,000) must to be regulated to app. 0.1% for amplitude and 0.2 deg for phase. The regulation of phase and amplitude is carried out by the analog/digital electronics also denoted as the low-level rf control system. Besides meeting the regulation specifications, the low-level rf must be reliable, robust and low cost. In the paper we present a possible hardware solution that addresses these issues. We also reveal the main design strategies that allowed us meeting the conflicting demands of the system. The system is evaluated on a cavity emulator implemented on the FPGA, which shows that system performance is within the specifications. Finally, we discuss the obtained results and give some suggestions for future work.

THP118 A Femtosecond-Level Fiber-Optics Timing Distribution System Using Frequency-Offset Interferometry laser, klystron, cavity, feedback 1078
  • J.W. Staples, J.M. Byrd, L.R. Doolittle, G. Huang, R.B. Wilcox
    LBNL, Berkeley, California

Funding: This work was supported by the Office of Science, U. S. Department of Energy, under Contract No. DE-AC02-05CH11231.
A fiber-based frequency and timing distribution system based on the principle of heterodyne interferometry has been in development at LBNL for several years. The temporal fiber drift corrector has evolved from an rf-based to an optical-base system, from mechanical correctors (piezo and optical trombone) to fully electronic, and the electronics from analog to fully digital, all using inexpensive commodity fiber components. Short-term optical phase jitter and long-term phase drift are both in the femtosecond range over distribution paths of 2 km and more. The temperature dependence of group and phase velocity correction is measured and applied. We will discuss the results of field tests, integration into various client subsystems and further applications.


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THP123 Construction of the Magnets and Supports for the Linac Coherent Light Source (LCLS) Undulator System undulator, quadrupole, vacuum, monitoring 1087
  • M. White, J.T. Collins, M.S. Jaski, G. Pile, B.M. Rusthoven, S. Sasaki, S.E. Shoaf, S.J. Stein, E. Trakhtenberg, I. Vasserman, J.Z. Xu
    ANL, Argonne

Funding: Work at Argonne was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No DE-AC02-06CH11357.
The LCLS, now under construction at the Stanford Linear Accelerator Center (SLAC) in California, will be the world's first X-ray free-electron laser when it comes online next year. Design and production of the undulator system is the responsibility of a team from the Advanced Photon Source (APS) at Argonne National Laboratory (ANL). Forty 3.4-m-long high-precision undulators, 37 laminated quadrupole magnets, plus 38 support and motion systems with micron-level adjustability and stability were constructed and delivered to SLAC, where final tuning, fiducialization, and installation are underway. An overview of the undulators and support systems, including achieved results, is presented.