IPAC2012 - List of Keywords (LLRF)

Paper	Title	Other Keywords	Page
MOOAC01	The European XFEL LLRF System	cavity, cryomodule, klystron, laser	55
	J. Branlard, G. Ayvazyan, V. Ayvazyan, M.K. Grecki, M. Hoffmann, T. Jeżyński, I.M. Kudla, T. Lamb, F. Ludwig, U. Mavrič, S. Pfeiffer, H. Schlarb, Ch. Schmidt, H.C. Weddig, B.Y. Yang DESY, Hamburg, Germany P. Barmuta, S. Bou Habib, L. Butkowski, K. Czuba, M. Grzegrzółka, E. Janas, J. Piekarski, I. Rutkowski, D. Sikora, L. Zembala, M. Żukociński Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland W. Cichalewski, K. Gnidzińska, W. Jałmużna, D.R. Makowski, A. Mielczarek, A. Napieralski, P. Perek, A. Piotrowski, T. Pożniak, K.P. Przygoda TUL-DMCS, Łódź, Poland S. Korolczuk, J. Szewiński The Andrzej Soltan Institute for Nuclear Studies, Centre Świerk, Świerk/Otwock, Poland K. Oliwa, W. Wierba IFJ-PAN, Kraków, Poland
	The European X-ray free electron laser accelerator consists of 800 superconducting cavities grouped in 25 RF stations. The challenges associated with the size and complexity of this accelerator required a high-precision, modular and scalable low level RF (LLRF) system. TheμTCA technology (uTCA) was chosen to support this system and adapted for RF standards. State-of-the-art hardware development in close collaboration with the industry allowed for the system continuity and maintainability. The complete LLRF system design is now in its final phase and the designed hardware was installed and commissioned at FLASH. The uTCA hardware system, measurement results and system performance validation will be shown. Operational strategy and plans for future automation algorithms for performance optimization will also be presented in this paper.
	Slides MOOAC01 [12.188 MB]

MOPPR017	Preliminary Measurement Results of the Upgraded Energy BPM at FLASH	pick-up, electron, controls, FEL	813
	U. Mavrič, M. Felber, C. Gerth, H. Schlarb DESY, Hamburg, Germany W. Jałmużna, A. Piotrowski TUL-DMCS, Łódź, Poland
	The energy beam position monitor in the dispersive section of the two bunch compressors is a valuable instrument for regular operation of FLASH. Recently, an upgrade of the existing instrument to a uTCA form factor has been started. The basic principle of the time-of-flight measurement will remain the same, however the detection of the phases and amplitudes of two pulses has been moved to the programmable gate array. Other changes include different RF frequencies of detection, optimization of the front-end section and integration into the control system. A preliminary version of the system has been tested at FLASH and the results are presented in the paper.

TUOAB01	Timing and Synchronization for the APS Short Pulse X-ray Project	laser, cavity, feedback, storage-ring	1077
	F. Lenkszus, N.D. Arnold, T.G. Berenc, G. Decker, E.M. Dufresne, R.I. Farnsworth, Y.L. Li, R.M. Lill, H. Ma ANL, Argonne, USA J.M. Byrd, L.R. Doolittle, G. Huang, R.B. Wilcox LBNL, Berkeley, California, USA
	Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The Short-Pulse X-ray (SPX) project, which is part of the APS upgrade, will provide intense, tunable, high-repetition-rate picosecond x-ray pulses through the use of deflecting cavities operating at the 8th harmonic of the storage-ring rf. Achieving this picosecond capability while minimizing the impact to other beamlines outside the SPX zone imposes demanding timing and synchronization requirements. For example, the mismatch between the upstream and downstream deflecting cavities' rf field phase is specified to be less than 0.077 degrees root mean squared (rms) at 2815 MHz (~77 femtoseconds). Another stringent requirement is to synchronize beamline pump-probe lasers to the SPX x-ray pulse to 400 femtoseconds rms. To achieve these requirements we have entered into a collaboration with the Beam Technology group at LBNL. They have developed and demonstrated a system for distributing stable rf signals over optical fiber capable of achieving less than 20 femtoseconds rms drift and jitter over 2.2 km over 60 hours. This paper defines the overall timing/synchronization requirements for the SPX and describes the plan to achieve them. R. Wilcox et al. Opt. Let. 34(20), Oct 15, 2009
	Slides TUOAB01 [2.515 MB]

TUPPP054	RF Activation and Preliminary Beam Tests of the X-band Linearizer at the FERMI@Elettra FEL Project	FEL, klystron, linac, emittance	1721
	G. D'Auria, S. Di Mitri, G. Penco, C. Serpico ELETTRA, Basovizza, Italy
	FERMI@Elettra is a fourth generation light source facility presently in commissioning at the Elettra Laboratory in Trieste, Italy. It is based on an S-band (3 GHz), 1.5 GeV normal conducting (NC) linac, that provides ultra short e-bunches with high peak current, using two stages of magnetic compression. To linearize the beam longitudinal phase space and to improve the compression process, a forth harmonic RF structure (12 GHz) has been installed downstream the first magnetic chicane. This paper reports the RF activation of the structure and the preliminary tests performed on the beam.

WEEPPB006	LCLS Femto-second Timing and Synchronization System Update	laser, controls, undulator, EPICS	2176
	G. Huang, J.M. Byrd, R.B. Wilcox LBNL, Berkeley, California, USA A.R. Fry, B.L. Hill SLAC, Menlo Park, California, USA
	Femto second timing and synchronization system has been installed on LCLS operation for 2 years. The requirement of more receiver at different location of the experimental hall urge us to develop a new version of receiver chassis and sync-head. Two sets of the new receiver chassis has been installed to the SXR and CXI end station. To help end user the diagnose the system, a intermediate GUI is developed to show some diagnostic information.

WEPPC023	Status and Progress of RF System for the PLS-II Storage Ring	klystron, cryomodule, SRF, controls	2254
	M.-H. Chun, J.Y. Huang, Y.D. Joo, H.-S. Kang, H.-G. Kim, C.D. Park, H.J. Park, I.S. Park, Y.U. Sohn, I.H. Yu PAL, Pohang, Kyungbuk, Republic of Korea
	Funding: Supported by the Korea Ministry of Science and Technology The RF system for the Pohang Light Source (PLS) storage ring was upgraded for PLS-II project of 3.0GeV/400mA from 2.5GeV/200mA. the RF system is commissioning with five normal conducting(NC) RF cavities at total maximum RF power of 280kW to the cavities with two 300kW klystron and two 75kW klystron amplifiers in 2011. The super conducting(SC) cavities will be installed on August 2012 because of long delivery. Therefore three NC RF cavities will be replaced with two SC cavities with cryomodules, and operated with cryogenics, digital low level, and 300kW klystron high power system. Also we are preparing the third SC cavity stand to increase the storage ring current up to 400mA with all insertion devices operation. This paper describes the present installation, commissioning, operation status, upgrade progress, and future plan of the RF system for the upgraded project of PLS-II storage ring.

WEPPC038	Status of the Short-Pulse X-ray Project at the Advanced Photon Source	cavity, cryomodule, HOM, simulation	2292
	A. Nassiri, N.D. Arnold, T.G. Berenc, M. Borland, B. Brajuskovic, D.J. Bromberek, J. Carwardine, G. Decker, L. Emery, J.D. Fuerst, A.E. Grelick, D. Horan, J. Kaluzny, F. Lenkszus, R.M. Lill, J. Liu, H. Ma, V. Sajaev, T.L. Smith, B.K. Stillwell, G.J. Waldschmidt, G. Wu, B.X. Yang, Y. Yang, A. Zholents ANL, Argonne, USA J.M. Byrd, L.R. Doolittle, G. Huang LBNL, Berkeley, California, USA G. Cheng, G. Ciovati, P. Dhakal, G.V. Eremeev, J.J. Feingold, R.L. Geng, J. Henry, P. Kneisel, K. Macha, J.D. Mammosser, J. Matalevich, A.D. Palczewski, R.A. Rimmer, H. Wang, K.M. Wilson, M. Wiseman JLAB, Newport News, Virginia, USA Z. Li, L. Xiao SLAC, Menlo Park, California, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The Advanced Photon Source Upgrade (APS-U) Project at Argonne will include generation of short-pulse x-rays based on Zholents’* deflecting cavity scheme. We have chosen superconducting (SC) cavities in order to have a continuous train of crabbed bunches and flexibility of operating modes. In collaboration with Jefferson Laboratory, we are prototyping and testing a number of single-cell deflecting cavities and associated auxiliary systems with promising initial results. In collaboration with Lawrence Berkeley National Laboratory, we are working to develop state-of-the-art timing, synchronization, and differential rf phase stability systems that are required for SPX. Collaboration with Advanced Computations Department at Stanford Linear Accelerator Center is looking into simulations of complex, multi-cavity geometries with lower- and higher-order modes waveguide dampers using ACE3P. This contribution provides the current R&D status of the SPX project. * A. Zholents et al., NIM A 425, 385 (1999).

WEPPC060	A High-power 650 MHz CW Magnetron Transmitter for Intensity Frontier Superconducting Accelerators	controls, proton, linac, injection	2351
	G.M. Kazakevich, G. Flanagan, R.P. Johnson, F. Marhauser, M.L. Neubauer Muons, Inc, Batavia, USA B. Chase, S. Nagaitsev, R.J. Pasquinelli, V.P. Yakovlev Fermilab, Batavia, USA T.A. Treado CPI, Beverley, Massachusetts, USA
	A concept of a 650 MHz CW magnetron transmitter with fast control in phase and power, based on two-stage injection-locked CW magnetrons, has been proposed to drive Superconducting Cavities (SC) for intensity-frontier accelerators. The concept is based on a theoretical model considering a magnetron as a forced oscillator and experimentally verified with a 2.5 MW pulsed magnetron. To fulfill fast control of phase and output power requirements of SC accelerators, both two-stage injection-locked CW magnetrons are combined with a 3-dB hybrid. Fast control in output power is achieved by varying the input phase of one of the magnetrons. For output power up to 250 kW we expect the output/input power ratio to be about 35 to 40 dB in CW or quasi-CW mode with long pulse duration. All magnetrons of the transmitter should be based on commercially available models to decrease the cost of the system. An experimental model using 1 kW, CW, S-band, injection-locked magnetrons with a 3-dB hybrid combiner has been developed and built for study. A description of the model, simulations, and experimental results are presented and discussed in this work.

WEPPC093	Commissioning and Operation of the CEBAF 100 MeV Cryomodules	cavity, cryomodule, controls, klystron	2432
	C. Hovater, T.L. Allison, R. Bachimanchi, G.K. Davis, M.A. Drury, L. Harwood, J. Hogan, A.J. Kimber, G.E. Lahti, W. Merz, R.M. Nelson, T. E. Plawski, D.J. Seidman, M. Spata, M.J. Wilson JLAB, Newport News, Virginia, USA
	Funding: This manuscript has been authored by Jefferson Science Associates, under U.S. DOE Contract No. DE-AC05-06OR23177. The Continuous Electron Beam Accelerator Facility (CEBAF) energy upgrade from 6 GeV to 12 GeV includes the installation of ten new 100 MeV cryomodules and RF systems. The superconducting RF cavities are designed to be operated CW at a maximum accelerating gradient of 19.2 MV/m. To support the higher gradients and higher QL (~ 3x107), a new RF system has been developed and is being installed to power and control the cavities. The RF system employs digital control and 13 kW klystrons. Recently, two of these cryomodules and associated RF hardware and software have been installed and commissioned in the CEBAF accelerator. Electrons at currents up to 150 μA have been successfully accelerated and used for nuclear physics experiments. This paper reports on the commissioning and operation of the RF system and cryomodules.

WEPPC107	RF Distribution System for High Power Test of the SNS Cryomodule	controls, cryomodule, EPICS, cavity	2468
	S.W. Lee, M. Broyles, M.T. Crofford, X. Geng, Y.W. Kang, S.-H. Kim, R.C. Peglow, C.L. Phibbs, W.H. Strong, A.V. Vassioutchenko ORNL, Oak Ridge, Tennessee, USA
	Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. A four-way waveguide RF power distribution system for testing the SNS multi-cavity cryomodule to investigate the collective behavior has been developed. A single klystron operating at 805MHz in 60Hz 8% duty cycle powers the 4-way waveguide splitter to deliver up to 600 kW to Individual cavities. Each cavity is fed through a waveguide vector modulator at each splitter output with magnitude and phase control. Waveguide vector modulator consists of two quadrature hybrids and two motorized waveguide phase shifters. The phase shifters and the assembled waveguide vector modulators were individually tested and characterized for low power and high pulsed RF power in the SNS RF test facility. Precise calibrations of magnitude and phase are done to generate the look up tables (LUTs) to provide operation references during the cryomodule test. An IQ demodulator board was developed and utilized to generate 2-port magnitude and phase LUTs. PLC units were developed for mechanical control of the phase shifters. Labview software was programmed for the measurements and the system operation. LUT based operation algorithm was implemented into EPICS control for the cryomodule test stand.

WEPPD048	Laser Synchronization at REGAE using Phase Detection at an Intermediate Frequency	laser, electron, controls, feedback	2624
	M. Felber, M. Hoffmann, U. Mavrič, H. Schlarb, S. Schulz DESY, Hamburg, Germany W. Jałmużna TUL-DMCS, Łódź, Poland
	A new linear accelerator is being set up for electron diffraction experiments at DESY. This machine, called REGAE (Relativistic Electron Gun for Atomic Exploration) is composed of a photo-cathode gun and a buncher cavity. It uses a single laser system for both, the generation of the electron bunches and for pump-probe experiments. The required timing jitter between the electron bunches and the laser pulses at the experiment is in the order of 10 fs rms. The conventional method for laser synchronization using RF technique to measure phase-jitter in the baseband is susceptible to distortions caused by ground-loops and electro-magnetic interference. At REGAE a new scheme for an RF-based laser synchronization is deployed. It uses a down-converter which mixes a higher harmonic of the laser repetition rate down to an intermediate frequency (IF). The IF is digitized and its phase calculated. This information is used for the feedback controller keeping the laser and the RF synchronized.

WEPPD049	Characterization of the Engineered Photodiode-based Fiber Link Stabilization Scheme for Optical Synchronization Systems	laser, FEL, optics, controls	2627
	T. Lamb, M.K. Bock, M. Felber, F. Ludwig, H. Schlarb, S. Schulz DESY, Hamburg, Germany S. Jabłoński Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
	Pulsed optical synchronization systems are used in modern FELs like FLASH and will be used in the upcoming European XFEL. Their purpose is to distribute synchronization signals with femtosecond stability throughout the machine. Optical fibers are used to transport the pulses carrying the timing information to their end-stations. These fibers have to be continuously delay stabilized in order to achieve the desired precision. In this paper, a photodiode-based detector to measure the drifts of the fiber delay and allows their active correction is presented. Promising results from a first prototype setup of a photodiode-stabilized optical fiber link were the starting point for an engineering of this concept. An enclosure with free-space optics, fiber optics and integrated electronics for the detector, operating at 9.75 GHz, was designed. This unit includes all required parts to stabilize four fiber links. It allows to investigate the temperature sensitivity of the detector. Furthermore, results from drift measurements carried out with a two channel engineered detector are presented in this paper.

WEPPP093	Time and Phase Synchronisation at ESS	controls, neutron, cavity, target	2927
	A.J. Johansson Lund University, Lund, Sweden R. Zeng ESS, Lund, Sweden
	ESS is a next generation spallation source to be built in Lund, Sweden. It is a green field laboratory, and as such it has the opportunity to establish one central timing reference for all systems, from control systems through reference phases for the Linac RF generators to the scientific instruments at the detector. We will here present the proposed architecture for this timing and phase reference system.

THEPPB014	LLRF Testing of Superconducting Cryomodules for the European XFEL	cavity, cryomodule, controls, feedback	3263
	J. Branlard, V. Ayvazyan, T. Jeżyński, H. Schlarb DESY, Hamburg, Germany W. Cichalewski, W. Jałmużna, A. Piotrowski TUL-DMCS, Łódź, Poland
	During the installation phase of the European XFEL (2014), an average of one superconducting cryomodule per week will be tested and validated before being installed into the XFEL tunnel. Extensive tests will be carried in order to assess the RF performance of each cryomodule. A series of low level RF (LLRF) tests are planned as part of this validation phase, and will assess the cryomodule effective operating gradient, tuning range, compensation of Lorentz force detuning and microphonic behavior. These tests will be carried at DESY, in the Cryomodule Test Bench (CMTB) during the early stage of cryomodule production, and later at the Accelerating Module Test Facility (AMTF). Due to the pace and quantity of the modules to be tested, these tests have to be fully automated. This contribution presents the LLRF tests for the XFEL cryomodule validation, the challenges associated with automation, along with the first experimental results obtained on pre-series cryomodules tested at CMTB.

THPPC054	Installation and Tests of the X-Band Power Plant for the FERMI@Elettra Project	klystron, FEL, vacuum, power-supply	3410
	G. D'Auria, P. Delgiusto, F. Gelmetti, M.M. Milloch, A. Milocco, F. Pribaz, C. Serpico, N. Sodomaco, M. Svandrlik, R. Umer, L. Veljak ELETTRA, Basovizza, Italy
	FERMI@Elettra, the fourth generation light source facility at the Elettra Laboratory in Trieste, Italy, foresees an X-band accelerating section downstream the first bunch compressor to linearize the beam longitudinal phase space. The RF power for the structure is produced by the SLAC XL5 klystron, a scaled version of the XL4 tube, operating at the European frequency of 11.992 GHz. The 50 Hz klystron modulator is based on a standard pulse forming network (PFN) design, with thyratron and pulse transformer, for which there is already an extensive experience at the Elettra laboratory. We report about the installation and tests of the first high power RF station.

THPPC058	S-band Low-level RF System for 10 GeV PAL-XFEL	klystron, FEL, controls, linac	3422
	W.H. Hwang, J.Y. Huang, H.-S. Kang, H.-S. Lee, W.W. Lee PAL, Pohang, Kyungbuk, Republic of Korea
	In PAL, We are constructing a 10GeV PxFEL project. The output power of the klystron is 80 MW at the pulse width of 4 ㎲ and the repetition rate of 120 Hz. And the specifications of the rf phase and amplitude stability are 0.05 degrees(rms) and 0.01%(rms) respectively. We achieved the stability of 0.03 degrees(p-p) at low power rf output using a phase amplitude detection system(PAD) and phase amplitude control(PAC) system. This paper describes the microwave system and the PAD and PAC system for the PxFEL.

THPPC071	The Use of a Solid State Analog Television Transmitter as a Superconducting Electron Gun Power Amplifier	cavity, gun, electron, controls	3452
	J.G. Kulpin, K.J. Kleman UW-Madison/SRC, Madison, Wisconsin, USA R.A. Legg JLAB, Newport News, Virginia, USA
	Funding: The electron gun program is supported by DOE award DE-SC0005264, and the University of Wisconsin, Madison. A solid state analog television transmitter designed for 200 MHz operation is being commissioned as a radio frequency power amplifier on the Wisconsin superconducting electron gun cavity. The amplifier consists of three separate radio frequency power combiner cabinets and one monitor and control cabinet. The transmitter employs rugged field effect transistors built into one kilowatt drawers that are individually hot swappable at maximum continuous power output. The total combined power of the transmitter system is 33 kW at 200 MHz, output through a standard coaxial transmission line. A low level radio frequency system is employed to digitally synthesize the 200 MHz signal and precisely control amplitude and phase.

THPPC077	Resonance Control of Superconducting Cavities at Heavy Beam Loading Conditions	cavity, controls, beam-loading, resonance	3467
	M.K. Grecki, S. Pfeiffer DESY, Hamburg, Germany
	Funding: The research leading to these results has received funding from the European Commission under the EuCARD FP7 Research Infrastructures grant agreement no. 227579 The SC cavities operated at high Q level need to be precisely tuned to the RF frequency. Well tuned cavities assure the good field stability and require minimum level of RF power to reach the operating gradient level. The TESLA cavities at FLASH are tuned with the help of slow (step motors) and fast (piezo) tuners driven by the control system. The goal of this control system is to keep the detuning of the cavity as close to zero as possible in the presence of disturbing effects (Lorentz force detuning and microphonics). The detuning of the cavity can be determined using a few measurement methods. The most common is to measure detuning from the phase derivative at the end of the RF pulse. In order to calculate the detuning during the whole RF pulse the cavity equation must be solved taking into account all the driving forces (RF power delivered to the cavity and beam contribution). This in not the trivial task, particularly in the heavy beam conditions, since all signals must be precisely calibrated. This work presents the methods and algorithms to evaluate and control the detuning of the superconducting cavities in the heavy beam loading conditions adequate for ILC operation. Grecki M., Piezo operation experience at FLASH, LLRF-2011, DESY, 09.2011 ** Grecki M. et al. Piezo Control for Lorentz Force Detuned SC Cavities of DESY FLASH, IPAC'10, Kyoto, Japan, pp.1452-1454

THPPC079	Prototype Performance of Digital LLRF Control System for SuperKEKB	controls, cavity, pick-up, feedback	3470
	T. Kobayashi, K. Akai, K. Ebihara, A. Kabe, K. Nakanishi, M. Nishiwaki, J.-I. Odagiri KEK, Ibaraki, Japan H. Deguchi, K. Harumatsu, K. Hayashi, J. Nishio, M. Ryoshi Mitsubishi Electric TOKKI Systems, Amagasaki, Hyogo, Japan
	For the SuperKEKB project, a new LLRF control system has been developed to realize high accuracy and flexibility. It is an FPGA-based digital RF feedback control system using 16-bit ADC's, which works on the μTCA platform. In this μTCA-module, the Linux-OS runs then it performs as the EPICS-IOC. This LLRF system is available to both of normal-conducting cavity and super-conducting cavity. A prototype of the LLRF control system for the SuperKEKB was produced. The feedback control stability, temperature characteristics and cavity-tuner control performance are evaluated. The evaluation results and future issue for the operation will be presented in this report. The amplitude and phase stability in the feedback control is 0.03% and 0.02 degrees, respectively. It is sufficiently stable for the SuperKEKB. However, the temperature dependency is not small for the required stability. Its countermeasures are under consideration.

THPPC080	The Development of LLRF System at PAL	controls, cavity, simulation, radio-frequency	3473
	K.-H. Park, H.S. Han, Y.-G. Jung, D.E. Kim, H.-G. Lee, H.S. Suh PAL, Pohang, Kyungbuk, Republic of Korea J.-S. Chai, H.W. Kim, Y.S. Lee SKKU, Suwon, Republic of Korea B.-K. Kang POSTECH, Pohang, Kyungbuk, Republic of Korea
	The Super Conducting Radio Frequency (SCRF) systems will be installed for PLS-II. The PAL has been carrying out the design of the low level radio frequency (LLRF) system for the SCRF control using the digital technologies. The requirements of the LLRF system are to maintain the field stability in a cavity within ±0.75% in amplitude and 0.35° in phase. The LLRF system includes the analog front-end, analog and digital board (ADC, DAC, DSP, FPGA, etc.), clock generation and distribution, and so on. The control algorithm will be implemented by the VHDL. The hardware design of the LLRF for PLS-II, simulation and test results were described in the paper.

THPPC082	Control Performance Improvement by Using Feedforward in LLRF	controls, klystron, feedback, cavity	3476
	R. Zeng, D.P. McGinnis, S. Molloy ESS, Lund, Sweden A.J. Johansson Lund University, Lund, Sweden
	The LLRF design is ongoing at ESS (European Spallation Source). One major task of LLRF is to overcome a variety of perturbations such as klystron droop and ripple, Lorentz detuning and beam loading. These perturbations can be well suppressed by classical PI (proportional-integral) controller in feedback loop, but at a cost of raising risk of instability and consuming power overhead for overshoot. Since ESS is a green project focusing on energy efficiency, we will hence investigate in this paper some feedforward and advanced adaptive algorithms to deal with these perturbations, so as to improve the control performance and reduce the power overhead.

THPPC084	LHC One-turn Delay Feedback Commissioning	cavity, feedback, klystron, beam-loading	3482
	T. Mastoridis, P. Baudrenghien, J.C. Molendijk CERN, Geneva, Switzerland
	The 1-turn delay feedback is an FPGA based feedback system part of the LHC cavity controller, which produces gain only around the revolution frequency harmonics. As such, it helps reduce the transient beam loading and effective cavity impedance. Consequently, it increases the stability margin for Longitudinal Coupled Bunch Instabilities driven by the cavity impedance at the fundamental and allows reliable operation at higher beam currents. The 1-turn delay feedback was commissioned on all sixteen cavities in mid-October 2011 and was used in operation for the rest of the run. The commissioning procedure and algorithms for setting-up are presented. The resulting improvements in transient beam loading, beam stability, and required klystron power are analyzed. The commissioning of the 1-turn delay feedback reduced the cavity voltage phase modulation from approximately six degrees peak-to-peak to below one degree at 400 MHz.

THPPC087	Software Firmware Infrastructure for LLRF4 Based System	controls, EPICS, low-level-rf, status	3485
	G. Huang, L.R. Doolittle, C. Serrano LBNL, Berkeley, California, USA
	LLRF4 is a successfully designed FPGA based low noise llrf signal process board. The board has been used in server accelerator as low level RF control and timing system. The complexity of maintain and support different version of software and firmware increase as the application increase. This paper describe our attempt to abstract the software and firmware layer. In the software side, the infrastructure support original rgui like GUI and also provide EPICS IOC driver. From the firmware side, the infrastructure separate board hardware dependent driver, the common algorithm implementation and project specific DSP, it also reserved the capability to expend to UDP based communication and next generation llrf board.

THPPC088	LLRF Control Algorithm for APEX	cavity, controls, laser, monitoring	3488
	G. Huang, K.M. Baptiste, J.M. Byrd, L.R. Doolittle, F. Sannibale LBNL, Berkeley, California, USA
	Advanced photo-cathode experiment is an ongoing experiment of a high repetition rate low emittance VHF band gun experiment. A low level RF control and monitor subsystem is developed base on the 5 LLRF4 board. One of them is used for low level RF control and the other 4 are used as interlock and RF monitor at different point of the system. The laser is also controlled by the system to be synced to the RF system. This paper we summarize the control algorithm used in the system firmware.

THPPC089	LLRF Control for SPX @ APS Demonstration Experiment	cavity, controls, low-level-rf, resonance	3491
	G. Huang, J.M. Byrd, K. Campbell, L.R. Doolittle, J.B. Greer LBNL, Berkeley, California, USA N.D. Arnold, T.G. Berenc, F. Lenkszus, H. Ma ANL, Argonne, USA
	The SPX experiment at APS is part of the APS upgrade project, using two deflecting cavity to chirp the electron pulse and then generate short pulse x-ray. To minimize the influence to other users on the storage ring, the phase synchronization of the two deflecting cavity are required to be better then 77 femto-second. A LLRF4 board based system is designed to demonstrate the capability of meeting this requirement. This paper discuss the hardware and firmware design of the demo experiment including the cavity emulator, frequency reference generation and LLRF control algorithm.

THPPC090	Robust Control of a Two-Input Two-Output (TITO) Multistate Cavity RF System ith Mismatched Uncertainty	cavity, controls, feedback, simulation	3494
	S. Kwon, M.S. Prokop, A. Scheinker LANL, Los Alamos, New Mexico, USA
	A RF cavity is well modeled as a linear two input two output (TITO) system in the Inphase/Quadrature (IQ) coordinates and is both controllable and observable. Whether it is due to the beam loading or Lorentz force detuning of a superconducting cavity, a cavity frequency detuning can be modeled as a matched uncertainty. The cavity field of a TITO cavity system with a matched uncertainty is controlled by output feedback or state feedback, whose error bound is made arbitrary small. Because of the building cost of the RF system, the single RF source (single klystron)-multicavity structure is sometimes used. This structure is described as a two-input multiple-output (TIMO) system. The control problem is not a simple extension of the single TITO system. Though the controllability and observability are preserved, the matched uncertainty of the TITO cavity system caused by cavity detuning becomes a mismatched uncertainty. The error bound of outputs is made arbitrary small by a control, only boundedness of the cavity fields of each TITO subsystem is guaranteed. In this paper, the properties of the TITO and the TIMO cavity RF systems are investigated.

THPPD081	Droop Compensation for the High Voltage Converter Modulators at the Spallation Neutron Source	high-voltage, controls, klystron, cathode	3704
	G. Patel, D.E. Anderson, D.J. Solley, M. Wezensky ORNL, Oak Ridge, Tennessee, USA
	Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725 The Spallation Neutron Source (SNS) has been in operation since 2006 and has demonstrated up to 1 MW of beam power. At 1MW, the High Voltage Converter Modulators (HVCMs) are delivering 11MW pulsed power to the Klystrons for 1185us at 60 Hz. The pulsed output of the modulator has a substantial voltage droop. The future operational goals of the accelerator involve delivering 1.4 MW to the target. This implies an increase in the output pulse width of the HVCM, resulting in loss of RF control from inadequate control margin for LLRF systems due to modulator voltage reduction at the end of pulse. Initially, the HVCM was designed with a pulse width modulation scheme for droop compensation but early operations revealed this technique unreliable for full power operation. Increasing the output voltage of the modulator would likely compromise system reliability. This paper proposes the use of alternate modulation schemes to address the voltage droop. The effect of frequency modulation and phase shift modulation on output pulse is studied and concludes by selecting an optimum modulation algorithm to be implemented. Experimental results will also be presented.

THPPP022	Coalescing at 8 GeV in the Fermilab Main Injector	simulation, emittance, synchrotron, space-charge	3779
	D.J. Scott, D. Capista, I. Kourbanis, K. Seiya, M.-J. Yang Fermilab, Batavia, USA
	For Project X, it is planned to inject a beam of 3 10¹¹ particles per bunch into the Main Injector. To prepare for this by studying the effects of higher intensity bunches in the Main Injector it is necessary to perform coalescing at 8 GeV. The results of a series of experiments and simulations of 8 GeV coalescing are presented. To increase the coalescing efficiency adiabatic reduction of the 53 MHz RF is required, resulting in ~70% coalescing efficiency of 5 initial bunches. Data using wall current monitors has been taken to compare previous work and new simulations for 53 MHz RF reduction, bunch rotations and coalescing, good agreement between experiment and simulation was found. Possible schemes to increase the coalescing efficiency and generate even higher intensity bunches are discussed. These require improving the timing resolution of the low level RF and/or tuning the adiabatic voltage reduction of the 53 MHz.

THPPP097	Diagnostic Pulse for Single-particle-like Beam Position Measurements During Accumulation/Production Mode in the Los Alamos Proton Storage Ring	diagnostics, injection, linac, betatron	3960
	J.S. Kolski, S.A. Baily, E. Björklund, G.O. Bolme, M.J. Hall, S. Kwon, M.P. Martinez, M.S. Prokop, F.E. Shelley, P.A. Torrez LANL, Los Alamos, New Mexico, USA
	Beam position monitors (BPMs) are the primary diagnostic in the Los Alamos Proton Storage Ring (PSR). Injecting one turn, the transverse motion is approximated as a single particle with initial betatron position and angle (x0 and x0'). With single-turn injection, we fit the betatron tune, closed orbit (CO), and injection offset (x0 and x0' at the injection point) to the turn-by-turn beam position. In production mode, we accumulate multiple turns, the transverse phase space fills after 5 injections (horizontal and vertical fractional betatron tunes ~0.2) resulting in no coherent betatron motion, and only the CO may be measured. The injection offset, which determines the accumulated beam size and is very sensitive to steering upstream of the ring, is not measurable in production mode. We describe our approach and ongoing efforts to measure the injection offset during production mode by injecting a ‘‘diagnostic'' pulse ~50 us after the accumulated beam is extracted. We also study the effects of increasing the linac RF gate length to accommodate the diagnostic pulse on the production beam position, transverse size, and loss.

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MOOAC01

The European XFEL LLRF System

cavity, cryomodule, klystron, laser

55

J. Branlard, G. Ayvazyan, V. Ayvazyan, M.K. Grecki, M. Hoffmann, T. Jeżyński, I.M. Kudla, T. Lamb, F. Ludwig, U. Mavrič, S. Pfeiffer, H. Schlarb, Ch. Schmidt, H.C. Weddig, B.Y. Yang
DESY, Hamburg, Germany
P. Barmuta, S. Bou Habib, L. Butkowski, K. Czuba, M. Grzegrzółka, E. Janas, J. Piekarski, I. Rutkowski, D. Sikora, L. Zembala, M. Żukociński
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
W. Cichalewski, K. Gnidzińska, W. Jałmużna, D.R. Makowski, A. Mielczarek, A. Napieralski, P. Perek, A. Piotrowski, T. Pożniak, K.P. Przygoda
TUL-DMCS, Łódź, Poland
S. Korolczuk, J. Szewiński
The Andrzej Soltan Institute for Nuclear Studies, Centre Świerk, Świerk/Otwock, Poland
K. Oliwa, W. Wierba
IFJ-PAN, Kraków, Poland

The European X-ray free electron laser accelerator consists of 800 superconducting cavities grouped in 25 RF stations. The challenges associated with the size and complexity of this accelerator required a high-precision, modular and scalable low level RF (LLRF) system. TheμTCA technology (uTCA) was chosen to support this system and adapted for RF standards. State-of-the-art hardware development in close collaboration with the industry allowed for the system continuity and maintainability. The complete LLRF system design is now in its final phase and the designed hardware was installed and commissioned at FLASH. The uTCA hardware system, measurement results and system performance validation will be shown. Operational strategy and plans for future automation algorithms for performance optimization will also be presented in this paper.

Slides MOOAC01 [12.188 MB]

MOPPR017

Preliminary Measurement Results of the Upgraded Energy BPM at FLASH

pick-up, electron, controls, FEL

813

U. Mavrič, M. Felber, C. Gerth, H. Schlarb
DESY, Hamburg, Germany
W. Jałmużna, A. Piotrowski
TUL-DMCS, Łódź, Poland

The energy beam position monitor in the dispersive section of the two bunch compressors is a valuable instrument for regular operation of FLASH. Recently, an upgrade of the existing instrument to a uTCA form factor has been started. The basic principle of the time-of-flight measurement will remain the same, however the detection of the phases and amplitudes of two pulses has been moved to the programmable gate array. Other changes include different RF frequencies of detection, optimization of the front-end section and integration into the control system. A preliminary version of the system has been tested at FLASH and the results are presented in the paper.

TUOAB01

Timing and Synchronization for the APS Short Pulse X-ray Project

laser, cavity, feedback, storage-ring

1077

F. Lenkszus, N.D. Arnold, T.G. Berenc, G. Decker, E.M. Dufresne, R.I. Farnsworth, Y.L. Li, R.M. Lill, H. Ma
ANL, Argonne, USA
J.M. Byrd, L.R. Doolittle, G. Huang, R.B. Wilcox
LBNL, Berkeley, California, USA

Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Short-Pulse X-ray (SPX) project, which is part of the APS upgrade, will provide intense, tunable, high-repetition-rate picosecond x-ray pulses through the use of deflecting cavities operating at the 8th harmonic of the storage-ring rf. Achieving this picosecond capability while minimizing the impact to other beamlines outside the SPX zone imposes demanding timing and synchronization requirements. For example, the mismatch between the upstream and downstream deflecting cavities' rf field phase is specified to be less than 0.077 degrees root mean squared (rms) at 2815 MHz (~77 femtoseconds). Another stringent requirement is to synchronize beamline pump-probe lasers to the SPX x-ray pulse to 400 femtoseconds rms. To achieve these requirements we have entered into a collaboration with the Beam Technology group at LBNL. They have developed and demonstrated a system for distributing stable rf signals over optical fiber capable of achieving less than 20 femtoseconds rms drift and jitter over 2.2 km over 60 hours*. This paper defines the overall timing/synchronization requirements for the SPX and describes the plan to achieve them.
* R. Wilcox et al. Opt. Let. 34(20), Oct 15, 2009

Slides TUOAB01 [2.515 MB]

TUPPP054

RF Activation and Preliminary Beam Tests of the X-band Linearizer at the FERMI@Elettra FEL Project

FEL, klystron, linac, emittance

1721

G. D'Auria, S. Di Mitri, G. Penco, C. Serpico
ELETTRA, Basovizza, Italy

FERMI@Elettra is a fourth generation light source facility presently in commissioning at the Elettra Laboratory in Trieste, Italy. It is based on an S-band (3 GHz), 1.5 GeV normal conducting (NC) linac, that provides ultra short e-bunches with high peak current, using two stages of magnetic compression. To linearize the beam longitudinal phase space and to improve the compression process, a forth harmonic RF structure (12 GHz) has been installed downstream the first magnetic chicane. This paper reports the RF activation of the structure and the preliminary tests performed on the beam.

WEEPPB006

LCLS Femto-second Timing and Synchronization System Update

laser, controls, undulator, EPICS

2176

G. Huang, J.M. Byrd, R.B. Wilcox
LBNL, Berkeley, California, USA
A.R. Fry, B.L. Hill
SLAC, Menlo Park, California, USA

Femto second timing and synchronization system has been installed on LCLS operation for 2 years. The requirement of more receiver at different location of the experimental hall urge us to develop a new version of receiver chassis and sync-head. Two sets of the new receiver chassis has been installed to the SXR and CXI end station. To help end user the diagnose the system, a intermediate GUI is developed to show some diagnostic information.

WEPPC023

Status and Progress of RF System for the PLS-II Storage Ring

klystron, cryomodule, SRF, controls

2254

M.-H. Chun, J.Y. Huang, Y.D. Joo, H.-S. Kang, H.-G. Kim, C.D. Park, H.J. Park, I.S. Park, Y.U. Sohn, I.H. Yu
PAL, Pohang, Kyungbuk, Republic of Korea

Funding: Supported by the Korea Ministry of Science and Technology
The RF system for the Pohang Light Source (PLS) storage ring was upgraded for PLS-II project of 3.0GeV/400mA from 2.5GeV/200mA. the RF system is commissioning with five normal conducting(NC) RF cavities at total maximum RF power of 280kW to the cavities with two 300kW klystron and two 75kW klystron amplifiers in 2011. The super conducting(SC) cavities will be installed on August 2012 because of long delivery. Therefore three NC RF cavities will be replaced with two SC cavities with cryomodules, and operated with cryogenics, digital low level, and 300kW klystron high power system. Also we are preparing the third SC cavity stand to increase the storage ring current up to 400mA with all insertion devices operation. This paper describes the present installation, commissioning, operation status, upgrade progress, and future plan of the RF system for the upgraded project of PLS-II storage ring.

WEPPC038

Status of the Short-Pulse X-ray Project at the Advanced Photon Source

cavity, cryomodule, HOM, simulation

2292

A. Nassiri, N.D. Arnold, T.G. Berenc, M. Borland, B. Brajuskovic, D.J. Bromberek, J. Carwardine, G. Decker, L. Emery, J.D. Fuerst, A.E. Grelick, D. Horan, J. Kaluzny, F. Lenkszus, R.M. Lill, J. Liu, H. Ma, V. Sajaev, T.L. Smith, B.K. Stillwell, G.J. Waldschmidt, G. Wu, B.X. Yang, Y. Yang, A. Zholents
ANL, Argonne, USA
J.M. Byrd, L.R. Doolittle, G. Huang
LBNL, Berkeley, California, USA
G. Cheng, G. Ciovati, P. Dhakal, G.V. Eremeev, J.J. Feingold, R.L. Geng, J. Henry, P. Kneisel, K. Macha, J.D. Mammosser, J. Matalevich, A.D. Palczewski, R.A. Rimmer, H. Wang, K.M. Wilson, M. Wiseman
JLAB, Newport News, Virginia, USA
Z. Li, L. Xiao
SLAC, Menlo Park, California, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Advanced Photon Source Upgrade (APS-U) Project at Argonne will include generation of short-pulse x-rays based on Zholents’* deflecting cavity scheme. We have chosen superconducting (SC) cavities in order to have a continuous train of crabbed bunches and flexibility of operating modes. In collaboration with Jefferson Laboratory, we are prototyping and testing a number of single-cell deflecting cavities and associated auxiliary systems with promising initial results. In collaboration with Lawrence Berkeley National Laboratory, we are working to develop state-of-the-art timing, synchronization, and differential rf phase stability systems that are required for SPX. Collaboration with Advanced Computations Department at Stanford Linear Accelerator Center is looking into simulations of complex, multi-cavity geometries with lower- and higher-order modes waveguide dampers using ACE3P. This contribution provides the current R&D status of the SPX project.
* A. Zholents et al., NIM A 425, 385 (1999).

WEPPC060

A High-power 650 MHz CW Magnetron Transmitter for Intensity Frontier Superconducting Accelerators

controls, proton, linac, injection

2351

G.M. Kazakevich, G. Flanagan, R.P. Johnson, F. Marhauser, M.L. Neubauer
Muons, Inc, Batavia, USA
B. Chase, S. Nagaitsev, R.J. Pasquinelli, V.P. Yakovlev
Fermilab, Batavia, USA
T.A. Treado
CPI, Beverley, Massachusetts, USA

A concept of a 650 MHz CW magnetron transmitter with fast control in phase and power, based on two-stage injection-locked CW magnetrons, has been proposed to drive Superconducting Cavities (SC) for intensity-frontier accelerators. The concept is based on a theoretical model considering a magnetron as a forced oscillator and experimentally verified with a 2.5 MW pulsed magnetron. To fulfill fast control of phase and output power requirements of SC accelerators, both two-stage injection-locked CW magnetrons are combined with a 3-dB hybrid. Fast control in output power is achieved by varying the input phase of one of the magnetrons. For output power up to 250 kW we expect the output/input power ratio to be about 35 to 40 dB in CW or quasi-CW mode with long pulse duration. All magnetrons of the transmitter should be based on commercially available models to decrease the cost of the system. An experimental model using 1 kW, CW, S-band, injection-locked magnetrons with a 3-dB hybrid combiner has been developed and built for study. A description of the model, simulations, and experimental results are presented and discussed in this work.

WEPPC093

Commissioning and Operation of the CEBAF 100 MeV Cryomodules

cavity, cryomodule, controls, klystron

2432

C. Hovater, T.L. Allison, R. Bachimanchi, G.K. Davis, M.A. Drury, L. Harwood, J. Hogan, A.J. Kimber, G.E. Lahti, W. Merz, R.M. Nelson, T. E. Plawski, D.J. Seidman, M. Spata, M.J. Wilson
JLAB, Newport News, Virginia, USA

Funding: This manuscript has been authored by Jefferson Science Associates, under U.S. DOE Contract No. DE-AC05-06OR23177.
The Continuous Electron Beam Accelerator Facility (CEBAF) energy upgrade from 6 GeV to 12 GeV includes the installation of ten new 100 MeV cryomodules and RF systems. The superconducting RF cavities are designed to be operated CW at a maximum accelerating gradient of 19.2 MV/m. To support the higher gradients and higher QL (~ 3x107), a new RF system has been developed and is being installed to power and control the cavities. The RF system employs digital control and 13 kW klystrons. Recently, two of these cryomodules and associated RF hardware and software have been installed and commissioned in the CEBAF accelerator. Electrons at currents up to 150 μA have been successfully accelerated and used for nuclear physics experiments. This paper reports on the commissioning and operation of the RF system and cryomodules.

WEPPC107

RF Distribution System for High Power Test of the SNS Cryomodule

controls, cryomodule, EPICS, cavity

2468

S.W. Lee, M. Broyles, M.T. Crofford, X. Geng, Y.W. Kang, S.-H. Kim, R.C. Peglow, C.L. Phibbs, W.H. Strong, A.V. Vassioutchenko
ORNL, Oak Ridge, Tennessee, USA

Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
A four-way waveguide RF power distribution system for testing the SNS multi-cavity cryomodule to investigate the collective behavior has been developed. A single klystron operating at 805MHz in 60Hz 8% duty cycle powers the 4-way waveguide splitter to deliver up to 600 kW to Individual cavities. Each cavity is fed through a waveguide vector modulator at each splitter output with magnitude and phase control. Waveguide vector modulator consists of two quadrature hybrids and two motorized waveguide phase shifters. The phase shifters and the assembled waveguide vector modulators were individually tested and characterized for low power and high pulsed RF power in the SNS RF test facility. Precise calibrations of magnitude and phase are done to generate the look up tables (LUTs) to provide operation references during the cryomodule test. An IQ demodulator board was developed and utilized to generate 2-port magnitude and phase LUTs. PLC units were developed for mechanical control of the phase shifters. Labview software was programmed for the measurements and the system operation. LUT based operation algorithm was implemented into EPICS control for the cryomodule test stand.

WEPPD048

Laser Synchronization at REGAE using Phase Detection at an Intermediate Frequency

laser, electron, controls, feedback

2624

M. Felber, M. Hoffmann, U. Mavrič, H. Schlarb, S. Schulz
DESY, Hamburg, Germany
W. Jałmużna
TUL-DMCS, Łódź, Poland

A new linear accelerator is being set up for electron diffraction experiments at DESY. This machine, called REGAE (Relativistic Electron Gun for Atomic Exploration) is composed of a photo-cathode gun and a buncher cavity. It uses a single laser system for both, the generation of the electron bunches and for pump-probe experiments. The required timing jitter between the electron bunches and the laser pulses at the experiment is in the order of 10 fs rms. The conventional method for laser synchronization using RF technique to measure phase-jitter in the baseband is susceptible to distortions caused by ground-loops and electro-magnetic interference. At REGAE a new scheme for an RF-based laser synchronization is deployed. It uses a down-converter which mixes a higher harmonic of the laser repetition rate down to an intermediate frequency (IF). The IF is digitized and its phase calculated. This information is used for the feedback controller keeping the laser and the RF synchronized.

WEPPD049

Characterization of the Engineered Photodiode-based Fiber Link Stabilization Scheme for Optical Synchronization Systems

laser, FEL, optics, controls

2627

T. Lamb, M.K. Bock, M. Felber, F. Ludwig, H. Schlarb, S. Schulz
DESY, Hamburg, Germany
S. Jabłoński
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland

Pulsed optical synchronization systems are used in modern FELs like FLASH and will be used in the upcoming European XFEL. Their purpose is to distribute synchronization signals with femtosecond stability throughout the machine. Optical fibers are used to transport the pulses carrying the timing information to their end-stations. These fibers have to be continuously delay stabilized in order to achieve the desired precision. In this paper, a photodiode-based detector to measure the drifts of the fiber delay and allows their active correction is presented. Promising results from a first prototype setup of a photodiode-stabilized optical fiber link were the starting point for an engineering of this concept. An enclosure with free-space optics, fiber optics and integrated electronics for the detector, operating at 9.75 GHz, was designed. This unit includes all required parts to stabilize four fiber links. It allows to investigate the temperature sensitivity of the detector. Furthermore, results from drift measurements carried out with a two channel engineered detector are presented in this paper.

WEPPP093

Time and Phase Synchronisation at ESS

controls, neutron, cavity, target

2927

A.J. Johansson
Lund University, Lund, Sweden
R. Zeng
ESS, Lund, Sweden

ESS is a next generation spallation source to be built in Lund, Sweden. It is a green field laboratory, and as such it has the opportunity to establish one central timing reference for all systems, from control systems through reference phases for the Linac RF generators to the scientific instruments at the detector. We will here present the proposed architecture for this timing and phase reference system.

THEPPB014

LLRF Testing of Superconducting Cryomodules for the European XFEL

cavity, cryomodule, controls, feedback

3263

J. Branlard, V. Ayvazyan, T. Jeżyński, H. Schlarb
DESY, Hamburg, Germany
W. Cichalewski, W. Jałmużna, A. Piotrowski
TUL-DMCS, Łódź, Poland

During the installation phase of the European XFEL (2014), an average of one superconducting cryomodule per week will be tested and validated before being installed into the XFEL tunnel. Extensive tests will be carried in order to assess the RF performance of each cryomodule. A series of low level RF (LLRF) tests are planned as part of this validation phase, and will assess the cryomodule effective operating gradient, tuning range, compensation of Lorentz force detuning and microphonic behavior. These tests will be carried at DESY, in the Cryomodule Test Bench (CMTB) during the early stage of cryomodule production, and later at the Accelerating Module Test Facility (AMTF). Due to the pace and quantity of the modules to be tested, these tests have to be fully automated. This contribution presents the LLRF tests for the XFEL cryomodule validation, the challenges associated with automation, along with the first experimental results obtained on pre-series cryomodules tested at CMTB.

THPPC054

Installation and Tests of the X-Band Power Plant for the FERMI@Elettra Project

klystron, FEL, vacuum, power-supply

3410

G. D'Auria, P. Delgiusto, F. Gelmetti, M.M. Milloch, A. Milocco, F. Pribaz, C. Serpico, N. Sodomaco, M. Svandrlik, R. Umer, L. Veljak
ELETTRA, Basovizza, Italy

FERMI@Elettra, the fourth generation light source facility at the Elettra Laboratory in Trieste, Italy, foresees an X-band accelerating section downstream the first bunch compressor to linearize the beam longitudinal phase space. The RF power for the structure is produced by the SLAC XL5 klystron, a scaled version of the XL4 tube, operating at the European frequency of 11.992 GHz. The 50 Hz klystron modulator is based on a standard pulse forming network (PFN) design, with thyratron and pulse transformer, for which there is already an extensive experience at the Elettra laboratory. We report about the installation and tests of the first high power RF station.

THPPC058

S-band Low-level RF System for 10 GeV PAL-XFEL

klystron, FEL, controls, linac

3422

W.H. Hwang, J.Y. Huang, H.-S. Kang, H.-S. Lee, W.W. Lee
PAL, Pohang, Kyungbuk, Republic of Korea

In PAL, We are constructing a 10GeV PxFEL project. The output power of the klystron is 80 MW at the pulse width of 4 ㎲ and the repetition rate of 120 Hz. And the specifications of the rf phase and amplitude stability are 0.05 degrees(rms) and 0.01%(rms) respectively. We achieved the stability of 0.03 degrees(p-p) at low power rf output using a phase amplitude detection system(PAD) and phase amplitude control(PAC) system. This paper describes the microwave system and the PAD and PAC system for the PxFEL.

THPPC071

The Use of a Solid State Analog Television Transmitter as a Superconducting Electron Gun Power Amplifier

cavity, gun, electron, controls

3452

J.G. Kulpin, K.J. Kleman
UW-Madison/SRC, Madison, Wisconsin, USA
R.A. Legg
JLAB, Newport News, Virginia, USA

Funding: The electron gun program is supported by DOE award DE-SC0005264, and the University of Wisconsin, Madison.
A solid state analog television transmitter designed for 200 MHz operation is being commissioned as a radio frequency power amplifier on the Wisconsin superconducting electron gun cavity. The amplifier consists of three separate radio frequency power combiner cabinets and one monitor and control cabinet. The transmitter employs rugged field effect transistors built into one kilowatt drawers that are individually hot swappable at maximum continuous power output. The total combined power of the transmitter system is 33 kW at 200 MHz, output through a standard coaxial transmission line. A low level radio frequency system is employed to digitally synthesize the 200 MHz signal and precisely control amplitude and phase.

THPPC077

Resonance Control of Superconducting Cavities at Heavy Beam Loading Conditions

cavity, controls, beam-loading, resonance

3467

M.K. Grecki, S. Pfeiffer
DESY, Hamburg, Germany

Funding: The research leading to these results has received funding from the European Commission under the EuCARD FP7 Research Infrastructures grant agreement no. 227579
The SC cavities operated at high Q level need to be precisely tuned to the RF frequency*. Well tuned cavities assure the good field stability and require minimum level of RF power to reach the operating gradient level. The TESLA cavities at FLASH are tuned with the help of slow (step motors) and fast (piezo) tuners driven by the control system**. The goal of this control system is to keep the detuning of the cavity as close to zero as possible in the presence of disturbing effects (Lorentz force detuning and microphonics). The detuning of the cavity can be determined using a few measurement methods. The most common is to measure detuning from the phase derivative at the end of the RF pulse. In order to calculate the detuning during the whole RF pulse the cavity equation must be solved taking into account all the driving forces (RF power delivered to the cavity and beam contribution). This in not the trivial task, particularly in the heavy beam conditions, since all signals must be precisely calibrated. This work presents the methods and algorithms to evaluate and control the detuning of the superconducting cavities in the heavy beam loading conditions adequate for ILC operation.
* Grecki M., Piezo operation experience at FLASH, LLRF-2011, DESY, 09.2011
** Grecki M. et al. Piezo Control for Lorentz Force Detuned SC Cavities of DESY FLASH, IPAC'10, Kyoto, Japan, pp.1452-1454

THPPC079

Prototype Performance of Digital LLRF Control System for SuperKEKB

controls, cavity, pick-up, feedback

3470

T. Kobayashi, K. Akai, K. Ebihara, A. Kabe, K. Nakanishi, M. Nishiwaki, J.-I. Odagiri
KEK, Ibaraki, Japan
H. Deguchi, K. Harumatsu, K. Hayashi, J. Nishio, M. Ryoshi
Mitsubishi Electric TOKKI Systems, Amagasaki, Hyogo, Japan

For the SuperKEKB project, a new LLRF control system has been developed to realize high accuracy and flexibility. It is an FPGA-based digital RF feedback control system using 16-bit ADC's, which works on the μTCA platform. In this μTCA-module, the Linux-OS runs then it performs as the EPICS-IOC. This LLRF system is available to both of normal-conducting cavity and super-conducting cavity. A prototype of the LLRF control system for the SuperKEKB was produced. The feedback control stability, temperature characteristics and cavity-tuner control performance are evaluated. The evaluation results and future issue for the operation will be presented in this report. The amplitude and phase stability in the feedback control is 0.03% and 0.02 degrees, respectively. It is sufficiently stable for the SuperKEKB. However, the temperature dependency is not small for the required stability. Its countermeasures are under consideration.

THPPC080

The Development of LLRF System at PAL

controls, cavity, simulation, radio-frequency

3473

K.-H. Park, H.S. Han, Y.-G. Jung, D.E. Kim, H.-G. Lee, H.S. Suh
PAL, Pohang, Kyungbuk, Republic of Korea
J.-S. Chai, H.W. Kim, Y.S. Lee
SKKU, Suwon, Republic of Korea
B.-K. Kang
POSTECH, Pohang, Kyungbuk, Republic of Korea

The Super Conducting Radio Frequency (SCRF) systems will be installed for PLS-II. The PAL has been carrying out the design of the low level radio frequency (LLRF) system for the SCRF control using the digital technologies. The requirements of the LLRF system are to maintain the field stability in a cavity within ±0.75% in amplitude and 0.35° in phase. The LLRF system includes the analog front-end, analog and digital board (ADC, DAC, DSP, FPGA, etc.), clock generation and distribution, and so on. The control algorithm will be implemented by the VHDL. The hardware design of the LLRF for PLS-II, simulation and test results were described in the paper.

THPPC082

Control Performance Improvement by Using Feedforward in LLRF

controls, klystron, feedback, cavity

3476

R. Zeng, D.P. McGinnis, S. Molloy
ESS, Lund, Sweden
A.J. Johansson
Lund University, Lund, Sweden

The LLRF design is ongoing at ESS (European Spallation Source). One major task of LLRF is to overcome a variety of perturbations such as klystron droop and ripple, Lorentz detuning and beam loading. These perturbations can be well suppressed by classical PI (proportional-integral) controller in feedback loop, but at a cost of raising risk of instability and consuming power overhead for overshoot. Since ESS is a green project focusing on energy efficiency, we will hence investigate in this paper some feedforward and advanced adaptive algorithms to deal with these perturbations, so as to improve the control performance and reduce the power overhead.

THPPC084

LHC One-turn Delay Feedback Commissioning

cavity, feedback, klystron, beam-loading

3482

T. Mastoridis, P. Baudrenghien, J.C. Molendijk
CERN, Geneva, Switzerland

The 1-turn delay feedback is an FPGA based feedback system part of the LHC cavity controller, which produces gain only around the revolution frequency harmonics. As such, it helps reduce the transient beam loading and effective cavity impedance. Consequently, it increases the stability margin for Longitudinal Coupled Bunch Instabilities driven by the cavity impedance at the fundamental and allows reliable operation at higher beam currents. The 1-turn delay feedback was commissioned on all sixteen cavities in mid-October 2011 and was used in operation for the rest of the run. The commissioning procedure and algorithms for setting-up are presented. The resulting improvements in transient beam loading, beam stability, and required klystron power are analyzed. The commissioning of the 1-turn delay feedback reduced the cavity voltage phase modulation from approximately six degrees peak-to-peak to below one degree at 400 MHz.

THPPC087

Software Firmware Infrastructure for LLRF4 Based System

controls, EPICS, low-level-rf, status

3485

G. Huang, L.R. Doolittle, C. Serrano
LBNL, Berkeley, California, USA

LLRF4 is a successfully designed FPGA based low noise llrf signal process board. The board has been used in server accelerator as low level RF control and timing system. The complexity of maintain and support different version of software and firmware increase as the application increase. This paper describe our attempt to abstract the software and firmware layer. In the software side, the infrastructure support original rgui like GUI and also provide EPICS IOC driver. From the firmware side, the infrastructure separate board hardware dependent driver, the common algorithm implementation and project specific DSP, it also reserved the capability to expend to UDP based communication and next generation llrf board.

THPPC088

LLRF Control Algorithm for APEX

cavity, controls, laser, monitoring

3488

G. Huang, K.M. Baptiste, J.M. Byrd, L.R. Doolittle, F. Sannibale
LBNL, Berkeley, California, USA

Advanced photo-cathode experiment is an ongoing experiment of a high repetition rate low emittance VHF band gun experiment. A low level RF control and monitor subsystem is developed base on the 5 LLRF4 board. One of them is used for low level RF control and the other 4 are used as interlock and RF monitor at different point of the system. The laser is also controlled by the system to be synced to the RF system. This paper we summarize the control algorithm used in the system firmware.

THPPC089

LLRF Control for SPX @ APS Demonstration Experiment

cavity, controls, low-level-rf, resonance

3491

G. Huang, J.M. Byrd, K. Campbell, L.R. Doolittle, J.B. Greer
LBNL, Berkeley, California, USA
N.D. Arnold, T.G. Berenc, F. Lenkszus, H. Ma
ANL, Argonne, USA

The SPX experiment at APS is part of the APS upgrade project, using two deflecting cavity to chirp the electron pulse and then generate short pulse x-ray. To minimize the influence to other users on the storage ring, the phase synchronization of the two deflecting cavity are required to be better then 77 femto-second. A LLRF4 board based system is designed to demonstrate the capability of meeting this requirement. This paper discuss the hardware and firmware design of the demo experiment including the cavity emulator, frequency reference generation and LLRF control algorithm.

THPPC090

Robust Control of a Two-Input Two-Output (TITO) Multistate Cavity RF System ith Mismatched Uncertainty

cavity, controls, feedback, simulation

3494

S. Kwon, M.S. Prokop, A. Scheinker
LANL, Los Alamos, New Mexico, USA

A RF cavity is well modeled as a linear two input two output (TITO) system in the Inphase/Quadrature (IQ) coordinates and is both controllable and observable. Whether it is due to the beam loading or Lorentz force detuning of a superconducting cavity, a cavity frequency detuning can be modeled as a matched uncertainty. The cavity field of a TITO cavity system with a matched uncertainty is controlled by output feedback or state feedback, whose error bound is made arbitrary small. Because of the building cost of the RF system, the single RF source (single klystron)-multicavity structure is sometimes used. This structure is described as a two-input multiple-output (TIMO) system. The control problem is not a simple extension of the single TITO system. Though the controllability and observability are preserved, the matched uncertainty of the TITO cavity system caused by cavity detuning becomes a mismatched uncertainty. The error bound of outputs is made arbitrary small by a control, only boundedness of the cavity fields of each TITO subsystem is guaranteed. In this paper, the properties of the TITO and the TIMO cavity RF systems are investigated.

THPPD081

Droop Compensation for the High Voltage Converter Modulators at the Spallation Neutron Source

high-voltage, controls, klystron, cathode

3704

G. Patel, D.E. Anderson, D.J. Solley, M. Wezensky
ORNL, Oak Ridge, Tennessee, USA

Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725
The Spallation Neutron Source (SNS) has been in operation since 2006 and has demonstrated up to 1 MW of beam power. At 1MW, the High Voltage Converter Modulators (HVCMs) are delivering 11MW pulsed power to the Klystrons for 1185us at 60 Hz. The pulsed output of the modulator has a substantial voltage droop. The future operational goals of the accelerator involve delivering 1.4 MW to the target. This implies an increase in the output pulse width of the HVCM, resulting in loss of RF control from inadequate control margin for LLRF systems due to modulator voltage reduction at the end of pulse. Initially, the HVCM was designed with a pulse width modulation scheme for droop compensation but early operations revealed this technique unreliable for full power operation. Increasing the output voltage of the modulator would likely compromise system reliability. This paper proposes the use of alternate modulation schemes to address the voltage droop. The effect of frequency modulation and phase shift modulation on output pulse is studied and concludes by selecting an optimum modulation algorithm to be implemented. Experimental results will also be presented.

THPPP022

Coalescing at 8 GeV in the Fermilab Main Injector

simulation, emittance, synchrotron, space-charge

3779

D.J. Scott, D. Capista, I. Kourbanis, K. Seiya, M.-J. Yang
Fermilab, Batavia, USA

For Project X, it is planned to inject a beam of 3 10¹¹ particles per bunch into the Main Injector. To prepare for this by studying the effects of higher intensity bunches in the Main Injector it is necessary to perform coalescing at 8 GeV. The results of a series of experiments and simulations of 8 GeV coalescing are presented. To increase the coalescing efficiency adiabatic reduction of the 53 MHz RF is required, resulting in ~70% coalescing efficiency of 5 initial bunches. Data using wall current monitors has been taken to compare previous work and new simulations for 53 MHz RF reduction, bunch rotations and coalescing, good agreement between experiment and simulation was found. Possible schemes to increase the coalescing efficiency and generate even higher intensity bunches are discussed. These require improving the timing resolution of the low level RF and/or tuning the adiabatic voltage reduction of the 53 MHz.

THPPP097

Diagnostic Pulse for Single-particle-like Beam Position Measurements During Accumulation/Production Mode in the Los Alamos Proton Storage Ring

diagnostics, injection, linac, betatron

3960

J.S. Kolski, S.A. Baily, E. Björklund, G.O. Bolme, M.J. Hall, S. Kwon, M.P. Martinez, M.S. Prokop, F.E. Shelley, P.A. Torrez
LANL, Los Alamos, New Mexico, USA

Beam position monitors (BPMs) are the primary diagnostic in the Los Alamos Proton Storage Ring (PSR). Injecting one turn, the transverse motion is approximated as a single particle with initial betatron position and angle (x0 and x0'). With single-turn injection, we fit the betatron tune, closed orbit (CO), and injection offset (x0 and x0' at the injection point) to the turn-by-turn beam position. In production mode, we accumulate multiple turns, the transverse phase space fills after 5 injections (horizontal and vertical fractional betatron tunes ~0.2) resulting in no coherent betatron motion, and only the CO may be measured. The injection offset, which determines the accumulated beam size and is very sensitive to steering upstream of the ring, is not measurable in production mode. We describe our approach and ongoing efforts to measure the injection offset during production mode by injecting a ‘‘diagnostic'' pulse ~50 us after the accumulated beam is extracted. We also study the effects of increasing the linac RF gate length to accommodate the diagnostic pulse on the production beam position, transverse size, and loss.