IPAC2012 - List of Keywords (pick-up)

Paper	Title	Other Keywords	Page
MOEPPB015	Excitation of Intra-bunch Vertical Motion in the SPS - Implications for Feedback Control of Ecloud and TMCI Instabilities	resonance, feedback, betatron, synchrotron	112
	J.D. Fox, J.M. Cesaratto, M.T.F. Pivi, C.H. Rivetta, O. Turgut, S. Uemura SLAC, Menlo Park, California, USA W. Höfle, U. Wehrle CERN, Geneva, Switzerland
	Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research Program (LARP). Electron cloud and transverse mode coupled-bunch instabilities (TMCI) limit the bunch intensity in the CERN SPS. Intra-bunch fast feedback systems are a possible method to control these effects. This paper presents experimental measurements of single-bunch motion in the SPS driven by a GHz bandwidth vertical excitation system. The primary goal is to quantify the change in internal bunch dynamics as instability thresholds are approached, and quantify the frequencies of internal modes as Ecloud effects become significant. The beam response is sampled at 20 GS/sec. in response to arbitrary excitation patterns, with data in 2011 taken at 3 bunch intensities. We show the excitation of barycentric, head-tail and higher vertical modes. The beam motion is analyzed in the time domain, via animated presentations of the sampled vertical signals, and in the frequency domain, via spectrograms showing the modal frequencies vs. time. The demonstration of the excitation of selected internal modes is a significant step in development of the feedback control techniques. "A 4 GS/Sec. Synchronized Vertical Excitation System for SPS Studies - Steps Towards Wideband Feedback," these proceedings.

MOPPC036	Influence of Intense Beam in High Pressure Hydrogen Gas Filled RF Cavities	cavity, electron, plasma, proton	208
	K. Yonehara, M.R. Jana, M.A. Leonova, A. Moretti, M. Popovic, T.A. Schwarz, A.V. Tollestrup Fermilab, Batavia, USA M. Chung Handong Global University, Pohang, Republic of Korea M.G. Collura Politecnico di Torino, Torino, Italy G. Flanagan, R.P. Johnson, M. Notani Muons, Inc, Batavia, USA B.T. Freemire, Y. Torun IIT, Chicago, Illinois, USA
	Funding: This work is supported by US DOE under contract DE-AC02-07CH11359. Breakdown plasma in a high-pressure hydrogen gas filled RF cavity has been studied from a time domain spectroscopic light analysis. The observed breakdown plasma temperature and density reached 21,000 K and 10²⁰ cm^-3, respectively. The electron recombination rate has been evaluated from the decay of plasma density in various gas pressures. The recombination mechanism in dense plasma will be discussed. Finally, the similarity and difference of the breakdown processes between the high-pressure hydrogen gas filled RF cavity and a vacuum RF one will be discussed.

MOPPD005	Stochastic Cooling of Antiprotons in the Collector Ring at FAIR	antiproton, kicker, simulation, ion	376
	C. Dimopoulou, A. Dolinskii, F. Nolden, C. Peschke, M. Steck GSI, Darmstadt, Germany
	In order to reach the required luminosities for the experiments at FAIR, the hot secondary beams (antiprotons or rare isotopes) emerging from the production targets will be efficiently collected and phase-space cooled in the large-acceptance Collector Ring (CR), which is equipped with pertinent stochastic cooling systems. Simulations of the system performance are underway in parallel with the finalization of the system design. After an overview of the CR stochastic cooling systems, simulation results for antiproton cooling in the bandwidth 1-2 GHz are presented. The CERN Fokker-Planck code is used for momentum cooling and an analytical model based on "rms" theory for the simultaneous betatron cooling. In the focus is the comparison between the time of flight and the notch filter momentum cooling methods. The results are essential for system optimization as well as input for the users of the CR-precooled beams i.e. the HESR.

MOPPD008	RF and Stochastic Cooling System of the HESR	accumulation, controls, coupling, kicker	385
	R. Stassen, F.J. Etzkorn, G. Schug, H. Stockhorst FZJ, Jülich, Germany T. Katayama GSI, Darmstadt, Germany L. Thorndahl CERN, Geneva, Switzerland
	The High Energy Storage Ring HESR (1.5-15 GeV/c) for antiprotons at the FAIR complex (Facility for Antiprotons and Ion Research) in Darmstadt (GSI) will have a dedicated stochastic cooling system not only during the experiments to fulfill the beam requirements, but also during the accumulation due to the postponed RESR. Here the cooperation of stochastic cooling with different Barrier-Bucket configurations is necessary for an high accumulation efficiency. The latest hardware configurations and recent tests results of both the RF-system with air-cooled cavities and the stochastic cooling based on slot-ring couplers will be presented.

MOPPR017	Preliminary Measurement Results of the Upgraded Energy BPM at FLASH	LLRF, 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.

MOPPR018	Beam Halo Monitor for FLASH and the European XFEL	electron, diagnostics, free-electron-laser, laser	816
	A. Ignatenko, N. Baboi, O. Hensler, M. Schmitz, K. Wittenburg DESY, Hamburg, Germany H.M. Henschel, W. Lange, W. Lohmann DESY Zeuthen, Zeuthen, Germany A. Ignatenko BTU, Cottbus, Germany S. Schuwalow Uni HH, Hamburg, Germany
	The Beam Halo Monitor for Free-electron Laser in Hamburg (FLASH) based on pCVD diamond and monocrystalline artificial sapphire sensors has been successfully commissioned in September 2009. It is a part of the beam dump diagnostics and ensures safe beam dumping. Its description and the experience gained during its operation are given. The ideas on the design and aspects of operation of the similar systems at FLASH II and the European XFEL are presented.

MOPPR020	An Improved Cryogenic Current Comparator for FAIR	shielding, cryogenics, niobium, ion	822
	R. Geithner, W. Vodel HIJ, Jena, Germany R. Geithner, R. Neubert, P. Seidel FSU Jena, Jena, Germany F. Kurian, H. Reeg, M. Schwickert GSI, Darmstadt, Germany
	Online monitoring of low intensity (below 1 μA) charged particle beams without disturbing the beam and its environment is crucial for any accelerator facility. For the upcoming FAIR project a beam monitor based on the Cryogenic Current Comparator principle with an enhanced resolution was developed. The main focus of research was on the low temperature properties of the ferromagnetic core material of the superconducting pickup coil. The pickup coil transforms the magnetic field of the beam into a current that is detected by a high performance low temperature dc Superconducting QUantum Interference Device (LTS-DC-SQUID). The penetration of the pickup coil by interfering magnetic fields is highly attenuated by a meander shaped superconducting shielding. The Cryogenic Current Comparator is able to measure DC beam currents, e.g. as required for slow extraction from a synchrotron, as well as bunched beams. In this contribution we present first results of the improved Cryogenic Current Comparator working in a laboratory environment.

MOPPR023	Stripline BPM with Integral In-Vacuo Termination	impedance, vacuum, quadrupole, coupling	828
	A. Stella, A. Ghigo, V.L. Lollo, F. Marcellini, M. Serio INFN/LNF, Frascati (Roma), Italy
	We report the design and realization of a stripline type beam position monitor to be used in the SPARC LAB transfer lines. While the directional properties provided by matched termination at the downstream end are not strictly required in a transfer line, yet matched loads at the end of the stripline electrodes are preferable to reduce the loss factor and to avoid unwanted reflection to the detection electronic. The Integration of a matched resistive load inside the vacuum chamber allows to halve the number of UHV feedthroughs.

MOPPR030	Various Methods to Measure the Betatron Tune of the Synchrotoron	betatron, closed-orbit, synchrotron, injection	843
	S. Hatakeyama JAEA/J-PARC, Tokai-mura, Japan
	Generally in the synchrotron, the frequency of transverse oscillation of the bunched beam for each single turn (usually called betatron tune or just "tune") is one of fundamental controllable knobs to avoid the instability of the accelerator. In this report, it is not mentioned about the effect to the beam instability but it is focused to various methods to measure the betatron tune by using bunch-by-bunch transverse beam position. The following items will be presented, (1) least square fitting to the time-domain beam position at specific location. (2) peak finding of the frequency-domain beam position at specific location. (3) phase space analysis of the beam position at specific location.(4) frequency-domain analysis of the beam position in the normalized coordinate at many locations in the ring orbit. For the application to the real accelerator, data of the J-PARC (Japan Proton Accelerator Research Complex) will be shown.

MOPPR041	Design and Measurements of the Stripline BPM System of the ESS-BILBAO	controls, EPICS, diagnostics, monitoring	870
	D. Belver, J. Feuchtwanger, N. Garmendia, P.J. González, L. Muguira, S. Varnasseri ESS Bilbao, LEIOA, Spain F.J. Bermejo Bilbao, Faculty of Science and Technology, Bilbao, Spain V. Etxebarria, J. Jugo, J. Portilla University of the Basque Country, Faculty of Science and Technology, Bilbao, Spain
	A new design for the Beam Position Monitors (BPMs) diagnostics of ESS-Bilbao, consisting of a whole block of stripline sensors, has been designed and manufactured. The design is based on travelling wave principles to detect the position of the beam in the vacuum chamber. The length of the stripline is 200 mm and the coverage angle is 0.952 rad. The position of the internal tube simulating the beam can be changed with respect to the outer tube within a range of 20 mm approximately for both X and Y axis, with a resolution less than 10 μm. The characteristics of the block with and without beam are measured and evaluated at frequencies of 175 and 352 MHz, using the electronics system developed for the BPM capacitive pick-ups. This electronics system is divided in an Analog Front-End (AFE) unit, where the signals are conditioned and converted to baseband, and a Digital Unit (DU) to sample them and calculate the position and phase of the beam. In this contribution, the performed tests will be fully described and the results also discussed.

MOPPR060	Calibration of the EMMA Beam Position Monitors: Position, Charge and Accuracy	injection, quadrupole, simulation, diagnostics	921
	I.W. Kirkman The University of Liverpool, Liverpool, United Kingdom J.S. Berg BNL, Upton, Long Island, New York, USA G. Cox STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom A. Kalinin STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom D.J. Kelliher, S. Machida STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
	The accurate determination of transverse beam position is essential to understanding the performance of an accelerator system, and this is particularly the case with non-scaling FFAG machines such as EMMA, where, due to fundamental principles of design, the beam may deviate widely from the central beampipe axis. This paper describes the various modelling approaches taken for the three different button pickup assemblies used in EMMA, and the subsequent methods of calibration (‘mappings’) which allow beam position and charge to be deduced from the processed BPM signals. The use and validity of the modelling and mapping approach adopted is described, and the contributions to positional and bunch charge uncertainty arising from these procedures is discussed.

MOPPR061	Computing Bunch Charge, Position, and BPM Resolution in Turn-by-Turn EMMA BPMs	EPICS, injection, controls, quadrupole	924
	A. Kalinin, J.K. Jones STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom R.G. Borrell WareWorks Ltd, Manchester, United Kingdom G. Cox STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom D.J. Kelliher, S. Machida STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom I.W. Kirkman Cockcroft Institute, Warrington, Cheshire, United Kingdom
	The NS-FFAG electron model ‘EMMA’ and its Injection and Extraction Lines are equipped with a total of 53 EPICS VME BPMs. In the BPMs, each opposite button signal pair is time-domain-multiplexed into one channel as a pulse doublet. The recording of turn-by-turn data into the BPM memory is triggered by the bunch itself on each of its passages. For each accelerating cycle, the BPMs deliver a snapshot of a turn-by-turn trajectory measured in each of 42 cells. Additional BPMs (two pairs) are used to obtain a Poincare map. We describe the EPICS architecture, and a set of Python data processing algorithms that are used to automatically set a BPM intensity range, to eliminate an error due to tails of the doublet pulses, to calculate the bunch charge and position, and, for a set of injections, to find the BPM resolution. We use three types of button pickup mappings* that allow: to eliminate bunch charge signal dependence on offset, to get a linear offset response, and to eliminate ‘quadrupole’ signal dependence on offset as well (which is used in resolution calculation). We present beam measurement results collected in 2011 runs. * A. Kalinin et al., Proc. of IPAC’10, MOPE068, p. 1134, (2010. ** I. Kirkman, these proceedings.

TUPPC082	Non-linear Beam Dynamics Tests at the CERN PS in the Framework of the Multi-turn Extraction	synchrotron, extraction, coupling, betatron	1365
	M. Giovannozzi, G. Arduini, J.M. Belleman, S.S. Gilardoni, C. Hernalsteens, A. Lachaize, G. Métral, Y. Papaphilippou CERN, Geneva, Switzerland
	In the framework of the CERN PS Multi-Turn Extraction several campaigns of measurements probing the non-linear beam dynamics have been carried out. These measurements range from the measurement of non-linear chromaticity to phase space portraits, de-coherence and re-coherence measurements, secondary island tune etc. In this paper these measurements will be reviewed and the results presented and discussed in details.

TUPPD021	Orbit Correction in the EMMA Non-scaling FFAG – Simulation and Experimental Results	closed-orbit, quadrupole, betatron, target	1455
	D.J. Kelliher, S. Machida, S.L. Sheehy STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom J.S. Berg BNL, Upton, Long Island, New York, USA J.K. Jones, B.D. Muratori STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom E. Keil Honorary CERN Staff Member, Berlin, Germany I.W. Kirkman The University of Liverpool, Liverpool, United Kingdom
	The non-scaling FFAG EMMA (Electron Model for Many Applications) is currently in operation at Daresbury Laboratory, UK. Since the lattice is made up solely of linear elements, the betatron tune varies strongly over the momentum range according to the natural chromaticity. Orbit correction is complicated by the resulting variation in response to corrector magnet settings. We consider a method to optimise correction over a range of fixed momenta and discuss experimental results. Measurements of the closed orbit and response matrix are included.

TUPPR032	Beam Stability at CTF3	feedback, klystron, cavity, linac	1888
	T. Persson, P.K. Skowroński CERN, Geneva, Switzerland
	The two beam acceleration tested in CTF3 imposes very tight tolerances on the drive beam stability. A description of the specialized monitoring tool developed to identify the drifts and jitter in the machine is presented. It compares all the relevant signals in an on-line manner for helping the operator to identify drifts or to log data for off-line analysis. The main sources for the drifts of the drive beam were identified and their causes are described. Feedbacks applied to the RF were implemented to reduce the effects. It works by changing the waveform for the pulse compression to compensate for the drifts.

TUPPR064	Time-resolved Shielded-Pickup Measurements and Modeling of Beam Conditioning Effects on Electron Cloud Buildup at CesrTA	vacuum, electron, photon, simulation	1966
	J.A. Crittenden, Y. Li, X. Liu, M.A. Palmer, S. Santos, J.P. Sikora CLASSE, Ithaca, New York, USA S. Calatroni, G. Rumolo CERN, Geneva, Switzerland S. Kato KEK, Ibaraki, Japan
	Funding: Work supported by the US National Science Foundation PHY-0734867, PHY-1002467, and the U.S. Department of Energy DE-FC02-08ER41538. The Cornell Electron Storage Ring Test Accelerator program includes investigations into electron cloud buildup in vacuum chambers with various coatings. Two 1.1-m-long sections located symmetrically in the east and west arc regions are equipped with BPM-like pickup detectors shielded against the direct beam-induced signal. They detect cloud electrons migrating through an 18-mm-diameter pattern of holes in the top of the chamber. A digitizing oscilloscope is used to record the signals, providing time-resolved information on cloud development. We present new measurements of the effect of beam conditioning on a newly-installed amorphous carbon coated chamber, as well as on a diamond-like carbon coating. The ECLOUD modeling code is used to quantify the sensitivity of these measurements to model parameters, differentiating between photoelectron and secondary-electron production processes.

TUPPR083	Kink Instability Suppression with Stochastic Cooling Pickup and Kicker	ion, electron, feedback, kicker	2017
	Y. Hao, M. Blaskiewicz, V. Litvinenko, V. Ptitsyn BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The kink instability is one of the major beam dynamics issues of the linac-ring based electron ion collider. This head-tail type instability arises from the oscillation of the electron beam inside the opposing ion beam. It must be suppressed to achieve the desired luminosity. There are various ways to suppress the instability, such as tuning the chromaticity in the ion ring or by a dedicated feedback system of the electron beam position at IP, etc. However, each method has its own limitation. In this paper, we will discuss an alternative opportunity of suppressing the kink instability of the proposed eRHIC at BNL using the existing pickup-kicker system of the stochastic cooling system in RHIC.

WEOBA03	Beam Tests of a High Pressure Gas-Filled Cavity for a Muon Collider	cavity, electron, ion, collider	2131
	T.A. Schwarz, M.A. Leonova, A. Moretti, M. Popovic, A.V. Tollestrup, K. Yonehara Fermilab, Batavia, USA M. Chung Handong Global University, Pohang, Republic of Korea B.T. Freemire, P.M. Hanlet, Y. Torun IIT, Chicago, Illinois, USA R.P. Johnson Muons, Inc, Batavia, USA
	Funding: US DOE under contract DE-AC02-07CH11359. One of the greatest challenges in constructing a Muon Collider is cooling the hot muons into a focused beam after their production. Because the beam must be cooled quickly before the muons decay, compact cooling designs require high gradient cavities inside strong magnetic fields. Unfortunately, due to focused field emission, an external magnetic field degrades the performance of the cavity below what is required for a muon collider. High-pressure gas inside the cavity has been proposed to both mitigate this effect, as well as serve as an absorber for transversely cooling the muon beam. A prototype of a high pressure gas-filled cavity is currently being studied at the Muon Test Area at Fermilab. The experimental setup as well as several measurements of the physics and performance of the apparatus while operating in a 400-MeV proton beam will be discussed.
	Slides WEOBA03 [6.912 MB]

WEPPC015	Construction of Injector Cryomodule for cERL at KEK	cryomodule, HOM, cavity, linac	2239
	E. Kako, S. Noguchi, T. Shishido, K. Watanabe, Y. Yamamoto KEK, Ibaraki, Japan
	The cERL injector cryomodule includes three 2-cell cavities, and each cavity has 2 input couplers and 5 HOM couplers. Three 2-cell cavities for cERL has already completed. Vertical test of the three cavities has been going on. The first cavity have achieved Eacc of 30 MV/m. Vertical tests will be carried out twice in each cavity, till the end of December, 2011. Six cw input couplers for cERL has already completed. RF processing at the high-power test stand with a cw 300kW-klystron will be carried out in Jan.-Feb., 2012. After the cavities were covered with a He jacket, assembly of the cERL injector cryomodule will be carried out in March-April, 2012. The first cool-down of the cryomodule is scheduled in June 2012.

WEPPC082	First Results on Cornell TE-type Sample Host Cavities	cavity, niobium, coupling, vacuum	2402
	Y. Xie, M. Liepe CLASSE, Ithaca, New York, USA
	Funding: Work supported by NSF and Alfred P. Sloan Foundation. In order to measure surface resistance of new materials other than niobium such as Nb3Sn and MgB2, two sample host niobium cavities operating at TE modes have been developed at Cornell University. The first one is a 6GHz pillbox TE011 cavity modified from an older vision enabling testing 2.75'' diameter flat sample plates. The second one is an optimized mushroom-shape niobium cavity operating at both 5GHz TE012 and 6GHz TE013 modes for 3.75'' diameter flat sample plates . First results from the commissioning of the two TE cavities will be reported.

WEPPC102	Design and Development of Superconducting Parallel-bar Deflecting/Crabbing Cavities	cavity, HOM, luminosity, damping	2453
	S.U. De Silva, J.R. Delayen ODU, Norfolk, Virginia, USA S.U. De Silva JLAB, Newport News, Virginia, USA
	The superconducting parallel-bar cavity is a deflecting/crabbing cavity with attractive properties that is being considered for a number of applications. We present the designs of a 499 MHz deflecting cavity developed for the Jefferson Lab 12 GeV Upgrade and a 400 MHz crabbing cavity for the LHC High Luminosity Upgrade. Prototypes of these two cavities are now under development and fabrication.

WEPPP060	A Robust Transverse Feedback System	feedback, kicker, status, optics	2843
	M. Alhumaidi, A.M. Zoubir TU Darmstadt, Darmstadt, Germany
	Transverse feedback systems use pickups signals to measure the beam instabilities and kickers to correct the beam. The correction signal is calculated according to the transfer matrices between the pickups and the kickers. However, errors due to magnetic field imperfections and magnets misalignments lead to deviations in the transfer matrices from their nominal values, which affects the feedback quality in a negative manner. In this work we address a new concept for robust feedback system against optics errors or uncertainties. A kicker and multiple pickups are used for each transversal direction. We introduce perturbation terms to the transfer matrices between the kicker and the pickups. Consequently, the Extended Kalman Filter is used to estimate the feedback signal and the perturbation terms by means of the measurements from the pickups. Finally results for the heavy ions synchrotron SIS 18 at the GSI are shown.

WEPPP076	Analysis of Numerical Noise in Particle-In-Cell Simulations of Single-Bunch Transverse Instabilities and Feedback in the CERN SPS	simulation, feedback, emittance, kicker	2888
	R. Secondo, J.-L. Vay, M. Venturini LBNL, Berkeley, California, USA
	Funding: Work supported by the US-DOE and the US-LHC Accelerator Research Program LARP under Contract DE-AC02-05CH11231. Used resources of NERSC and the Lawrencium cluster at LBNL The operation at high current of the SPS at CERN is limited by transverse Single-Bunch instabilities generated by the effect of electron clouds. A model of a high bandwidth feedback control system has been implemented in the macro-particle code WARP to study bunch dynamics and identify system requirements for the efficient damping of single-bunch transverse instability. We analyze the effect of numerical noise and choice of simulation parameters on the modeling of beam dynamics, focusing in particular on the investigation of the feedback system requirements of minimum power to damp the instability and frequency bandwidth given a fixed gain. We report on simulation results and discuss the plans for the future improvements of the feedback model.

WEPPP078	Status of the Mixed-signal Active Feedback Damper System for Controlling Electron-proton Instabilities for the Spallation Neutron Source	feedback, damping, kicker, proton	2894
	Z.P. Xie, M.J. Schulte UW-Madison, Madison, Wisconsin, USA C. Deibele ORNL, Oak Ridge, Tennessee, USA
	Funding: Work supported by Oak Ridge National Laboratory, which is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy As the beam intensity at the Spallation Neutron Source (SNS) in Oak Ridge National Laboratory (ORNL) is leveled up, it becomes necessary to have greater control over the electron-proton (e-p) instability. This paper presents an updated design of a mixed-signal transverse feedback system for active damping of the e-p instability. It describes the design, features and results of this feedback damper and reviews several experimental studies to understand the system performance and its limitations. The updated mixed-signal feedback damper system employs power amplifiers (PAs), analog-to-digital converters (ADCs), multiple field programmable gate array (FPGA) chips, and digital-to-analog converters (DACs) to provide feedback damping and system monitoring. Unlike existing analog damping systems, FPGA-based feedback damping systems offer programmability while maintaining high performance. The system gain, delay and digital signal processing components can be programmed during the fly to perform timing adjustments, correct for ring harmonics, and equalize magnitude and phase dispersions.

WEPPP082	Stochastic Cooling in RHIC	kicker, emittance, luminosity, simulation	2900
	J.M. Brennan, M. Blaskiewicz, K. Mernick BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Stochastic cooling is used in the Relativistic Heavy Ion Collider to increase the integrated luminosity of ion collisions by a factor of two. The cooling system has been assembled incrementally over the past several years, starting with longitudinal cooling only, then adding cooling in the vertical planes, and recently completed with cooling systems in all three phase space planes of both rings. The system operates from 6 to 9 GHz in the longitudinal planes and from 4.7 to 7.8 GHz in the transverse planes, yielding a cooling rate that overcomes Intra-Beam Scattering at the beginning of a store and reaches equilibrium with a factor of 2 reduction of emittances. The system’s components and mode of operation will be presented along with measurements of the beam parameters during stores with stochastic cooling in operation.

WEPPR010	Comparison between Electron Cloud Build-Up Measurements and Simulations at the CERN PS	electron, simulation, extraction, vacuum	2955
	G. Iadarola Naples University Federico II, Science and Technology Pole, Napoli, Italy F. Caspers, S.S. Gilardoni, G. Iadarola, E. Mahner, G. Rumolo, C. Yin Vallgren CERN, Geneva, Switzerland
	The build up of an Electron Cloud (EC) has been observed at the CERN Proton Synchrotron (PS) during the last stages of the LHC high intensity beam preparation, especially after the bunch shortening before extraction. A dedicated EC experiment, equipped with two button pick-ups, a pressure gauge, a clearing electrode, and a small dipole magnet, is available in one of the straight sections of the machine. A measurement campaign has been carried out in order to scan the EC build-up of LHC-type beams with different bunch spacing, bunch intensity, and bunch length. Such information, combined with the results from build up simulations, is of relevance for the characterization in terms of Secondary Emission Yield (SEY) of the chamber inner surface. The interest is twofold: this will enable us to predict the EC build up distribution in the PS for higher intensity beams in the frame of the upgrade program, and it will provide validation of the EC simulation models and codes.

WEPPR084	Measurement of Coherent Damping Rate of the APS Storage Ring	damping, feedback, kicker, storage-ring	3126
	C. Yao, K.C. Harkay, H. Shang, C.-X. Wang ANL, Argonne, USA
	Funding: Work supported by U.S. Department of Energy, Offices of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The APS storage ring is a 7-GeV electron storage ring with a single-bunch current of up to 16 mA during normal user operations. To overcome beam instability we employ both chromatic correction and bunch-by- bunch feedback system. Typically we run a chromaticity of 4 for a 24-single fill pattern and 9 for a hybrids fill pattern in both planes with the feedback system loops closed. The APS upgrade (APS-U) calls for a beam current of 150 mA and installation of vertical deflecting cavities for short X-ray (SPX) production. In order to estimate whether the current chromatic correction and feedback system are adequate for the upgrade, we performed coherent damping rate measurements with two methods: kicking the beam with a kicker pulse and exciting the beam with the feedback system. We conclude that with a chromaticity of 4 in both planes, we can achieve a damping rate of 3 kHz in the x- plane and 2 kHz in the y-plane with feedback loops closed. Similar damping rates can also be achieved with chromatic correction alone. A special fitting program was developed to perform the damping rate analysis. This report presents the measurement data and results of the analysis.

THPPC021	A Microwave Paraphoton and Axion Detection Experiment with 300 dB Electromagnetic Shielding at 3 GHz	cavity, photon, shielding, coupling	3320
	M. Betz, F. Caspers CERN, Geneva, Switzerland
	Funding: Work supported by the Wolfgang-Gentner-Programme of the Bundesministerium für Bildung und Forschung (BMBF). For the microwave equivalent of "light shining through the wall" (LSW) experiments, a sensitive microwave detector and very high electromagnetic shielding is required. The screening attenuation between the axion-generating cavity and the nearby detection-cavity should be greater than 300 dB, in order to push beyond the presently existing exclusion limits. To achieve these goals in practice, a "box in a box" concept was utilized for shielding the detection-cavity, while a vector signal analyzer was used as a microwave receiver with a very narrow resolution bandwidth in the order of a few micro-Hz. This contribution will present the experimental layout and show the results to date.

THPPC079	Prototype Performance of Digital LLRF Control System for SuperKEKB	controls, cavity, LLRF, 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.

THPPD002	The First Magnetic Field Control (B-Train) to Optimize the Duty Cycle of a Synchrotron in Clinical Operation	controls, synchrotron, feedback, extraction	3503
	E. Feldmeier, R. Cee, M. Galonska, Th. Haberer, A. Peters, S. Scheloske HIT, Heidelberg, Germany
	In December 2011 the Heidelberg Ion Therapy Center started to use the magnetic field feedback control for its clinical operation. Therewith the magnetic field deviation of the ramped magnets in the synchrotron depending on eddy currents and hysteresis are no longer in effect. Waiting times on the flattop and the "chimney" in the recovery phase of the synchrotron cycle are no longer necessary. The efficiency of the accelerator is increased by more than 20\% and the treatment time shortens accordingly. The core of the magnetic feedback system is a real time measuring system of the magnetic field with extremely high precision.

THPPD017	Mu2e AC Dipole 300 kHz and 5.1 MHz Tests and Comparison of Nickel-Zinc Ferrites	dipole, proton, impedance, target	3533
	L. Elementi, K.R. Bourkland, D.J. Harding, V.S. Kashikhin, A.V. Makarov, H. Pfeffer, G. Velev Fermilab, Batavia, USA
	To suppress any background events coming from the inter-bunch proton interactions during the muon transport and decay window for the Mu2e experiment, a beam extinction scheme based on two dipoles running at ~300 kHz and 5.1 MHz is considered. The effective field of these magnets is synchronized to the proton bunch spacing in such a way that the bunches are transported at the sinus nodes. Two types Ni-Zn ferrites are considered for these dipoles. Ferrites, their characteristics and ferrites selection is herein discussed through measurements performed under conditions close to operational. The excitation system and the measurement of some characteristics of the magnetic field and field shape and measurement mechanism are also presented.

FRXCB01	Review of Microwave Schottky Beam Diagnostics	proton, antiproton, diagnostics, ion	4175
	R.J. Pasquinelli Fermilab, Batavia, USA
	Non-intercepting beam diagnostics for detection of the incoherent motion of the finite number of beam particles, i.e. Schottky beam monitors, have been proven as extremely useful to characterize tune, chromaticity, and momentum spread in circular accelerators and colliders. This beam instrument, based on advanced microwave techniques, operates successfully in Recycler and Tevatron, and was recently implemented in the Large Hadron Collider. This presentation should review the technology of Schottky beam diagnostics systems with an emphasis on initial deployment at the Tevatron, concluding with the latest measurement results from the LHC and an outlook of possible improvements and extensions of the diagnostics.
	Slides FRXCB01 [22.518 MB]

Paper

Title

Other Keywords

Page

Excitation of Intra-bunch Vertical Motion in the SPS - Implications for Feedback Control of Ecloud and TMCI Instabilities

resonance, feedback, betatron, synchrotron

112

J.D. Fox, J.M. Cesaratto, M.T.F. Pivi, C.H. Rivetta, O. Turgut, S. Uemura
SLAC, Menlo Park, California, USA
W. Höfle, U. Wehrle
CERN, Geneva, Switzerland

Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research Program (LARP).
Electron cloud and transverse mode coupled-bunch instabilities (TMCI) limit the bunch intensity in the CERN SPS. Intra-bunch fast feedback systems are a possible method to control these effects. This paper presents experimental measurements of single-bunch motion in the SPS driven by a GHz bandwidth vertical excitation system*. The primary goal is to quantify the change in internal bunch dynamics as instability thresholds are approached, and quantify the frequencies of internal modes as Ecloud effects become significant. The beam response is sampled at 20 GS/sec. in response to arbitrary excitation patterns, with data in 2011 taken at 3 bunch intensities. We show the excitation of barycentric, head-tail and higher vertical modes. The beam motion is analyzed in the time domain, via animated presentations of the sampled vertical signals, and in the frequency domain, via spectrograms showing the modal frequencies vs. time. The demonstration of the excitation of selected internal modes is a significant step in development of the feedback control techniques.
* "A 4 GS/Sec. Synchronized Vertical Excitation System for SPS Studies - Steps Towards Wideband Feedback," these proceedings.

MOPPC036

Influence of Intense Beam in High Pressure Hydrogen Gas Filled RF Cavities

cavity, electron, plasma, proton

208

K. Yonehara, M.R. Jana, M.A. Leonova, A. Moretti, M. Popovic, T.A. Schwarz, A.V. Tollestrup
Fermilab, Batavia, USA
M. Chung
Handong Global University, Pohang, Republic of Korea
M.G. Collura
Politecnico di Torino, Torino, Italy
G. Flanagan, R.P. Johnson, M. Notani
Muons, Inc, Batavia, USA
B.T. Freemire, Y. Torun
IIT, Chicago, Illinois, USA

Funding: This work is supported by US DOE under contract DE-AC02-07CH11359.
Breakdown plasma in a high-pressure hydrogen gas filled RF cavity has been studied from a time domain spectroscopic light analysis. The observed breakdown plasma temperature and density reached 21,000 K and 10²⁰ cm^-3, respectively. The electron recombination rate has been evaluated from the decay of plasma density in various gas pressures. The recombination mechanism in dense plasma will be discussed. Finally, the similarity and difference of the breakdown processes between the high-pressure hydrogen gas filled RF cavity and a vacuum RF one will be discussed.

MOPPD005

Stochastic Cooling of Antiprotons in the Collector Ring at FAIR

antiproton, kicker, simulation, ion

376

C. Dimopoulou, A. Dolinskii, F. Nolden, C. Peschke, M. Steck
GSI, Darmstadt, Germany

In order to reach the required luminosities for the experiments at FAIR, the hot secondary beams (antiprotons or rare isotopes) emerging from the production targets will be efficiently collected and phase-space cooled in the large-acceptance Collector Ring (CR), which is equipped with pertinent stochastic cooling systems. Simulations of the system performance are underway in parallel with the finalization of the system design. After an overview of the CR stochastic cooling systems, simulation results for antiproton cooling in the bandwidth 1-2 GHz are presented. The CERN Fokker-Planck code is used for momentum cooling and an analytical model based on "rms" theory for the simultaneous betatron cooling. In the focus is the comparison between the time of flight and the notch filter momentum cooling methods. The results are essential for system optimization as well as input for the users of the CR-precooled beams i.e. the HESR.

MOPPD008

RF and Stochastic Cooling System of the HESR

accumulation, controls, coupling, kicker

385

R. Stassen, F.J. Etzkorn, G. Schug, H. Stockhorst
FZJ, Jülich, Germany
T. Katayama
GSI, Darmstadt, Germany
L. Thorndahl
CERN, Geneva, Switzerland

The High Energy Storage Ring HESR (1.5-15 GeV/c) for antiprotons at the FAIR complex (Facility for Antiprotons and Ion Research) in Darmstadt (GSI) will have a dedicated stochastic cooling system not only during the experiments to fulfill the beam requirements, but also during the accumulation due to the postponed RESR. Here the cooperation of stochastic cooling with different Barrier-Bucket configurations is necessary for an high accumulation efficiency. The latest hardware configurations and recent tests results of both the RF-system with air-cooled cavities and the stochastic cooling based on slot-ring couplers will be presented.

MOPPR017

Preliminary Measurement Results of the Upgraded Energy BPM at FLASH

LLRF, 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.

MOPPR018

Beam Halo Monitor for FLASH and the European XFEL

electron, diagnostics, free-electron-laser, laser

816

A. Ignatenko, N. Baboi, O. Hensler, M. Schmitz, K. Wittenburg
DESY, Hamburg, Germany
H.M. Henschel, W. Lange, W. Lohmann
DESY Zeuthen, Zeuthen, Germany
A. Ignatenko
BTU, Cottbus, Germany
S. Schuwalow
Uni HH, Hamburg, Germany

The Beam Halo Monitor for Free-electron Laser in Hamburg (FLASH) based on pCVD diamond and monocrystalline artificial sapphire sensors has been successfully commissioned in September 2009. It is a part of the beam dump diagnostics and ensures safe beam dumping. Its description and the experience gained during its operation are given. The ideas on the design and aspects of operation of the similar systems at FLASH II and the European XFEL are presented.

MOPPR020

An Improved Cryogenic Current Comparator for FAIR

shielding, cryogenics, niobium, ion

822

R. Geithner, W. Vodel
HIJ, Jena, Germany
R. Geithner, R. Neubert, P. Seidel
FSU Jena, Jena, Germany
F. Kurian, H. Reeg, M. Schwickert
GSI, Darmstadt, Germany

Online monitoring of low intensity (below 1 μA) charged particle beams without disturbing the beam and its environment is crucial for any accelerator facility. For the upcoming FAIR project a beam monitor based on the Cryogenic Current Comparator principle with an enhanced resolution was developed. The main focus of research was on the low temperature properties of the ferromagnetic core material of the superconducting pickup coil. The pickup coil transforms the magnetic field of the beam into a current that is detected by a high performance low temperature dc Superconducting QUantum Interference Device (LTS-DC-SQUID). The penetration of the pickup coil by interfering magnetic fields is highly attenuated by a meander shaped superconducting shielding. The Cryogenic Current Comparator is able to measure DC beam currents, e.g. as required for slow extraction from a synchrotron, as well as bunched beams. In this contribution we present first results of the improved Cryogenic Current Comparator working in a laboratory environment.

MOPPR023

Stripline BPM with Integral In-Vacuo Termination

impedance, vacuum, quadrupole, coupling

828

A. Stella, A. Ghigo, V.L. Lollo, F. Marcellini, M. Serio
INFN/LNF, Frascati (Roma), Italy

We report the design and realization of a stripline type beam position monitor to be used in the SPARC LAB transfer lines. While the directional properties provided by matched termination at the downstream end are not strictly required in a transfer line, yet matched loads at the end of the stripline electrodes are preferable to reduce the loss factor and to avoid unwanted reflection to the detection electronic. The Integration of a matched resistive load inside the vacuum chamber allows to halve the number of UHV feedthroughs.

MOPPR030

Various Methods to Measure the Betatron Tune of the Synchrotoron

betatron, closed-orbit, synchrotron, injection

843

S. Hatakeyama
JAEA/J-PARC, Tokai-mura, Japan

Generally in the synchrotron, the frequency of transverse oscillation of the bunched beam for each single turn (usually called betatron tune or just "tune") is one of fundamental controllable knobs to avoid the instability of the accelerator. In this report, it is not mentioned about the effect to the beam instability but it is focused to various methods to measure the betatron tune by using bunch-by-bunch transverse beam position. The following items will be presented, (1) least square fitting to the time-domain beam position at specific location. (2) peak finding of the frequency-domain beam position at specific location. (3) phase space analysis of the beam position at specific location.(4) frequency-domain analysis of the beam position in the normalized coordinate at many locations in the ring orbit. For the application to the real accelerator, data of the J-PARC (Japan Proton Accelerator Research Complex) will be shown.

MOPPR041

Design and Measurements of the Stripline BPM System of the ESS-BILBAO

controls, EPICS, diagnostics, monitoring

870

D. Belver, J. Feuchtwanger, N. Garmendia, P.J. González, L. Muguira, S. Varnasseri
ESS Bilbao, LEIOA, Spain
F.J. Bermejo
Bilbao, Faculty of Science and Technology, Bilbao, Spain
V. Etxebarria, J. Jugo, J. Portilla
University of the Basque Country, Faculty of Science and Technology, Bilbao, Spain

A new design for the Beam Position Monitors (BPMs) diagnostics of ESS-Bilbao, consisting of a whole block of stripline sensors, has been designed and manufactured. The design is based on travelling wave principles to detect the position of the beam in the vacuum chamber. The length of the stripline is 200 mm and the coverage angle is 0.952 rad. The position of the internal tube simulating the beam can be changed with respect to the outer tube within a range of 20 mm approximately for both X and Y axis, with a resolution less than 10 μm. The characteristics of the block with and without beam are measured and evaluated at frequencies of 175 and 352 MHz, using the electronics system developed for the BPM capacitive pick-ups. This electronics system is divided in an Analog Front-End (AFE) unit, where the signals are conditioned and converted to baseband, and a Digital Unit (DU) to sample them and calculate the position and phase of the beam. In this contribution, the performed tests will be fully described and the results also discussed.

MOPPR060

Calibration of the EMMA Beam Position Monitors: Position, Charge and Accuracy

injection, quadrupole, simulation, diagnostics

921

I.W. Kirkman
The University of Liverpool, Liverpool, United Kingdom
J.S. Berg
BNL, Upton, Long Island, New York, USA
G. Cox
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
A. Kalinin
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
D.J. Kelliher, S. Machida
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom

The accurate determination of transverse beam position is essential to understanding the performance of an accelerator system, and this is particularly the case with non-scaling FFAG machines such as EMMA, where, due to fundamental principles of design, the beam may deviate widely from the central beampipe axis. This paper describes the various modelling approaches taken for the three different button pickup assemblies used in EMMA, and the subsequent methods of calibration (‘mappings’) which allow beam position and charge to be deduced from the processed BPM signals. The use and validity of the modelling and mapping approach adopted is described, and the contributions to positional and bunch charge uncertainty arising from these procedures is discussed.

MOPPR061

Computing Bunch Charge, Position, and BPM Resolution in Turn-by-Turn EMMA BPMs

EPICS, injection, controls, quadrupole

924

A. Kalinin, J.K. Jones
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
R.G. Borrell
WareWorks Ltd, Manchester, United Kingdom
G. Cox
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
D.J. Kelliher, S. Machida
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
I.W. Kirkman
Cockcroft Institute, Warrington, Cheshire, United Kingdom

The NS-FFAG electron model ‘EMMA’ and its Injection and Extraction Lines are equipped with a total of 53 EPICS VME BPMs*. In the BPMs, each opposite button signal pair is time-domain-multiplexed into one channel as a pulse doublet. The recording of turn-by-turn data into the BPM memory is triggered by the bunch itself on each of its passages. For each accelerating cycle, the BPMs deliver a snapshot of a turn-by-turn trajectory measured in each of 42 cells. Additional BPMs (two pairs) are used to obtain a Poincare map. We describe the EPICS architecture, and a set of Python data processing algorithms that are used to automatically set a BPM intensity range, to eliminate an error due to tails of the doublet pulses, to calculate the bunch charge and position, and, for a set of injections, to find the BPM resolution. We use three types of button pickup mappings** that allow: to eliminate bunch charge signal dependence on offset, to get a linear offset response, and to eliminate ‘quadrupole’ signal dependence on offset as well (which is used in resolution calculation). We present beam measurement results collected in 2011 runs.
* A. Kalinin et al., Proc. of IPAC’10, MOPE068, p. 1134, (2010.
** I. Kirkman, these proceedings.

TUPPC082

Non-linear Beam Dynamics Tests at the CERN PS in the Framework of the Multi-turn Extraction

synchrotron, extraction, coupling, betatron

1365

M. Giovannozzi, G. Arduini, J.M. Belleman, S.S. Gilardoni, C. Hernalsteens, A. Lachaize, G. Métral, Y. Papaphilippou
CERN, Geneva, Switzerland

In the framework of the CERN PS Multi-Turn Extraction several campaigns of measurements probing the non-linear beam dynamics have been carried out. These measurements range from the measurement of non-linear chromaticity to phase space portraits, de-coherence and re-coherence measurements, secondary island tune etc. In this paper these measurements will be reviewed and the results presented and discussed in details.

TUPPD021

Orbit Correction in the EMMA Non-scaling FFAG – Simulation and Experimental Results

closed-orbit, quadrupole, betatron, target

1455

D.J. Kelliher, S. Machida, S.L. Sheehy
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
J.S. Berg
BNL, Upton, Long Island, New York, USA
J.K. Jones, B.D. Muratori
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
E. Keil
Honorary CERN Staff Member, Berlin, Germany
I.W. Kirkman
The University of Liverpool, Liverpool, United Kingdom

The non-scaling FFAG EMMA (Electron Model for Many Applications) is currently in operation at Daresbury Laboratory, UK. Since the lattice is made up solely of linear elements, the betatron tune varies strongly over the momentum range according to the natural chromaticity. Orbit correction is complicated by the resulting variation in response to corrector magnet settings. We consider a method to optimise correction over a range of fixed momenta and discuss experimental results. Measurements of the closed orbit and response matrix are included.

TUPPR032

Beam Stability at CTF3

feedback, klystron, cavity, linac

1888

T. Persson, P.K. Skowroński
CERN, Geneva, Switzerland

The two beam acceleration tested in CTF3 imposes very tight tolerances on the drive beam stability. A description of the specialized monitoring tool developed to identify the drifts and jitter in the machine is presented. It compares all the relevant signals in an on-line manner for helping the operator to identify drifts or to log data for off-line analysis. The main sources for the drifts of the drive beam were identified and their causes are described. Feedbacks applied to the RF were implemented to reduce the effects. It works by changing the waveform for the pulse compression to compensate for the drifts.

TUPPR064

Time-resolved Shielded-Pickup Measurements and Modeling of Beam Conditioning Effects on Electron Cloud Buildup at CesrTA

vacuum, electron, photon, simulation

1966

J.A. Crittenden, Y. Li, X. Liu, M.A. Palmer, S. Santos, J.P. Sikora
CLASSE, Ithaca, New York, USA
S. Calatroni, G. Rumolo
CERN, Geneva, Switzerland
S. Kato
KEK, Ibaraki, Japan

Funding: Work supported by the US National Science Foundation PHY-0734867, PHY-1002467, and the U.S. Department of Energy DE-FC02-08ER41538.
The Cornell Electron Storage Ring Test Accelerator program includes investigations into electron cloud buildup in vacuum chambers with various coatings. Two 1.1-m-long sections located symmetrically in the east and west arc regions are equipped with BPM-like pickup detectors shielded against the direct beam-induced signal. They detect cloud electrons migrating through an 18-mm-diameter pattern of holes in the top of the chamber. A digitizing oscilloscope is used to record the signals, providing time-resolved information on cloud development. We present new measurements of the effect of beam conditioning on a newly-installed amorphous carbon coated chamber, as well as on a diamond-like carbon coating. The ECLOUD modeling code is used to quantify the sensitivity of these measurements to model parameters, differentiating between photoelectron and secondary-electron production processes.

TUPPR083

Kink Instability Suppression with Stochastic Cooling Pickup and Kicker

ion, electron, feedback, kicker

2017

Y. Hao, M. Blaskiewicz, V. Litvinenko, V. Ptitsyn
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The kink instability is one of the major beam dynamics issues of the linac-ring based electron ion collider. This head-tail type instability arises from the oscillation of the electron beam inside the opposing ion beam. It must be suppressed to achieve the desired luminosity. There are various ways to suppress the instability, such as tuning the chromaticity in the ion ring or by a dedicated feedback system of the electron beam position at IP, etc. However, each method has its own limitation. In this paper, we will discuss an alternative opportunity of suppressing the kink instability of the proposed eRHIC at BNL using the existing pickup-kicker system of the stochastic cooling system in RHIC.

WEOBA03

Beam Tests of a High Pressure Gas-Filled Cavity for a Muon Collider

cavity, electron, ion, collider

2131

T.A. Schwarz, M.A. Leonova, A. Moretti, M. Popovic, A.V. Tollestrup, K. Yonehara
Fermilab, Batavia, USA
M. Chung
Handong Global University, Pohang, Republic of Korea
B.T. Freemire, P.M. Hanlet, Y. Torun
IIT, Chicago, Illinois, USA
R.P. Johnson
Muons, Inc, Batavia, USA

Funding: US DOE under contract DE-AC02-07CH11359.
One of the greatest challenges in constructing a Muon Collider is cooling the hot muons into a focused beam after their production. Because the beam must be cooled quickly before the muons decay, compact cooling designs require high gradient cavities inside strong magnetic fields. Unfortunately, due to focused field emission, an external magnetic field degrades the performance of the cavity below what is required for a muon collider. High-pressure gas inside the cavity has been proposed to both mitigate this effect, as well as serve as an absorber for transversely cooling the muon beam. A prototype of a high pressure gas-filled cavity is currently being studied at the Muon Test Area at Fermilab. The experimental setup as well as several measurements of the physics and performance of the apparatus while operating in a 400-MeV proton beam will be discussed.

Slides WEOBA03 [6.912 MB]

WEPPC015

Construction of Injector Cryomodule for cERL at KEK

cryomodule, HOM, cavity, linac

2239

E. Kako, S. Noguchi, T. Shishido, K. Watanabe, Y. Yamamoto
KEK, Ibaraki, Japan

The cERL injector cryomodule includes three 2-cell cavities, and each cavity has 2 input couplers and 5 HOM couplers. Three 2-cell cavities for cERL has already completed. Vertical test of the three cavities has been going on. The first cavity have achieved Eacc of 30 MV/m. Vertical tests will be carried out twice in each cavity, till the end of December, 2011. Six cw input couplers for cERL has already completed. RF processing at the high-power test stand with a cw 300kW-klystron will be carried out in Jan.-Feb., 2012. After the cavities were covered with a He jacket, assembly of the cERL injector cryomodule will be carried out in March-April, 2012. The first cool-down of the cryomodule is scheduled in June 2012.

WEPPC082

First Results on Cornell TE-type Sample Host Cavities

cavity, niobium, coupling, vacuum

2402

Y. Xie, M. Liepe
CLASSE, Ithaca, New York, USA

Funding: Work supported by NSF and Alfred P. Sloan Foundation.
In order to measure surface resistance of new materials other than niobium such as Nb3Sn and MgB2, two sample host niobium cavities operating at TE modes have been developed at Cornell University. The first one is a 6GHz pillbox TE011 cavity modified from an older vision enabling testing 2.75'' diameter flat sample plates. The second one is an optimized mushroom-shape niobium cavity operating at both 5GHz TE012 and 6GHz TE013 modes for 3.75'' diameter flat sample plates . First results from the commissioning of the two TE cavities will be reported.

WEPPC102

Design and Development of Superconducting Parallel-bar Deflecting/Crabbing Cavities

cavity, HOM, luminosity, damping

2453

S.U. De Silva, J.R. Delayen
ODU, Norfolk, Virginia, USA
S.U. De Silva
JLAB, Newport News, Virginia, USA

The superconducting parallel-bar cavity is a deflecting/crabbing cavity with attractive properties that is being considered for a number of applications. We present the designs of a 499 MHz deflecting cavity developed for the Jefferson Lab 12 GeV Upgrade and a 400 MHz crabbing cavity for the LHC High Luminosity Upgrade. Prototypes of these two cavities are now under development and fabrication.

WEPPP060

A Robust Transverse Feedback System

feedback, kicker, status, optics

2843

M. Alhumaidi, A.M. Zoubir
TU Darmstadt, Darmstadt, Germany

Transverse feedback systems use pickups signals to measure the beam instabilities and kickers to correct the beam. The correction signal is calculated according to the transfer matrices between the pickups and the kickers. However, errors due to magnetic field imperfections and magnets misalignments lead to deviations in the transfer matrices from their nominal values, which affects the feedback quality in a negative manner. In this work we address a new concept for robust feedback system against optics errors or uncertainties. A kicker and multiple pickups are used for each transversal direction. We introduce perturbation terms to the transfer matrices between the kicker and the pickups. Consequently, the Extended Kalman Filter is used to estimate the feedback signal and the perturbation terms by means of the measurements from the pickups. Finally results for the heavy ions synchrotron SIS 18 at the GSI are shown.

WEPPP076

Analysis of Numerical Noise in Particle-In-Cell Simulations of Single-Bunch Transverse Instabilities and Feedback in the CERN SPS

simulation, feedback, emittance, kicker

2888

R. Secondo, J.-L. Vay, M. Venturini
LBNL, Berkeley, California, USA

Funding: Work supported by the US-DOE and the US-LHC Accelerator Research Program LARP under Contract DE-AC02-05CH11231. Used resources of NERSC and the Lawrencium cluster at LBNL
The operation at high current of the SPS at CERN is limited by transverse Single-Bunch instabilities generated by the effect of electron clouds. A model of a high bandwidth feedback control system has been implemented in the macro-particle code WARP to study bunch dynamics and identify system requirements for the efficient damping of single-bunch transverse instability. We analyze the effect of numerical noise and choice of simulation parameters on the modeling of beam dynamics, focusing in particular on the investigation of the feedback system requirements of minimum power to damp the instability and frequency bandwidth given a fixed gain. We report on simulation results and discuss the plans for the future improvements of the feedback model.

WEPPP078

Status of the Mixed-signal Active Feedback Damper System for Controlling Electron-proton Instabilities for the Spallation Neutron Source

feedback, damping, kicker, proton

2894

Z.P. Xie, M.J. Schulte
UW-Madison, Madison, Wisconsin, USA
C. Deibele
ORNL, Oak Ridge, Tennessee, USA

Funding: Work supported by Oak Ridge National Laboratory, which is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy
As the beam intensity at the Spallation Neutron Source (SNS) in Oak Ridge National Laboratory (ORNL) is leveled up, it becomes necessary to have greater control over the electron-proton (e-p) instability. This paper presents an updated design of a mixed-signal transverse feedback system for active damping of the e-p instability. It describes the design, features and results of this feedback damper and reviews several experimental studies to understand the system performance and its limitations. The updated mixed-signal feedback damper system employs power amplifiers (PAs), analog-to-digital converters (ADCs), multiple field programmable gate array (FPGA) chips, and digital-to-analog converters (DACs) to provide feedback damping and system monitoring. Unlike existing analog damping systems, FPGA-based feedback damping systems offer programmability while maintaining high performance. The system gain, delay and digital signal processing components can be programmed during the fly to perform timing adjustments, correct for ring harmonics, and equalize magnitude and phase dispersions.

WEPPP082

Stochastic Cooling in RHIC

kicker, emittance, luminosity, simulation

2900

J.M. Brennan, M. Blaskiewicz, K. Mernick
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Stochastic cooling is used in the Relativistic Heavy Ion Collider to increase the integrated luminosity of ion collisions by a factor of two. The cooling system has been assembled incrementally over the past several years, starting with longitudinal cooling only, then adding cooling in the vertical planes, and recently completed with cooling systems in all three phase space planes of both rings. The system operates from 6 to 9 GHz in the longitudinal planes and from 4.7 to 7.8 GHz in the transverse planes, yielding a cooling rate that overcomes Intra-Beam Scattering at the beginning of a store and reaches equilibrium with a factor of 2 reduction of emittances. The system’s components and mode of operation will be presented along with measurements of the beam parameters during stores with stochastic cooling in operation.

WEPPR010

Comparison between Electron Cloud Build-Up Measurements and Simulations at the CERN PS

electron, simulation, extraction, vacuum

2955

G. Iadarola
Naples University Federico II, Science and Technology Pole, Napoli, Italy
F. Caspers, S.S. Gilardoni, G. Iadarola, E. Mahner, G. Rumolo, C. Yin Vallgren
CERN, Geneva, Switzerland

The build up of an Electron Cloud (EC) has been observed at the CERN Proton Synchrotron (PS) during the last stages of the LHC high intensity beam preparation, especially after the bunch shortening before extraction. A dedicated EC experiment, equipped with two button pick-ups, a pressure gauge, a clearing electrode, and a small dipole magnet, is available in one of the straight sections of the machine. A measurement campaign has been carried out in order to scan the EC build-up of LHC-type beams with different bunch spacing, bunch intensity, and bunch length. Such information, combined with the results from build up simulations, is of relevance for the characterization in terms of Secondary Emission Yield (SEY) of the chamber inner surface. The interest is twofold: this will enable us to predict the EC build up distribution in the PS for higher intensity beams in the frame of the upgrade program, and it will provide validation of the EC simulation models and codes.

WEPPR084

Measurement of Coherent Damping Rate of the APS Storage Ring

damping, feedback, kicker, storage-ring

3126

C. Yao, K.C. Harkay, H. Shang, C.-X. Wang
ANL, Argonne, USA

Funding: Work supported by U.S. Department of Energy, Offices of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The APS storage ring is a 7-GeV electron storage ring with a single-bunch current of up to 16 mA during normal user operations. To overcome beam instability we employ both chromatic correction and bunch-by- bunch feedback system. Typically we run a chromaticity of 4 for a 24-single fill pattern and 9 for a hybrids fill pattern in both planes with the feedback system loops closed. The APS upgrade (APS-U) calls for a beam current of 150 mA and installation of vertical deflecting cavities for short X-ray (SPX) production. In order to estimate whether the current chromatic correction and feedback system are adequate for the upgrade, we performed coherent damping rate measurements with two methods: kicking the beam with a kicker pulse and exciting the beam with the feedback system. We conclude that with a chromaticity of 4 in both planes, we can achieve a damping rate of 3 kHz in the x- plane and 2 kHz in the y-plane with feedback loops closed. Similar damping rates can also be achieved with chromatic correction alone. A special fitting program was developed to perform the damping rate analysis. This report presents the measurement data and results of the analysis.

THPPC021

A Microwave Paraphoton and Axion Detection Experiment with 300 dB Electromagnetic Shielding at 3 GHz

cavity, photon, shielding, coupling

3320

M. Betz, F. Caspers
CERN, Geneva, Switzerland

Funding: Work supported by the Wolfgang-Gentner-Programme of the Bundesministerium für Bildung und Forschung (BMBF).
For the microwave equivalent of "light shining through the wall" (LSW) experiments, a sensitive microwave detector and very high electromagnetic shielding is required. The screening attenuation between the axion-generating cavity and the nearby detection-cavity should be greater than 300 dB, in order to push beyond the presently existing exclusion limits. To achieve these goals in practice, a "box in a box" concept was utilized for shielding the detection-cavity, while a vector signal analyzer was used as a microwave receiver with a very narrow resolution bandwidth in the order of a few micro-Hz. This contribution will present the experimental layout and show the results to date.

THPPC079

Prototype Performance of Digital LLRF Control System for SuperKEKB

controls, cavity, LLRF, 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.

THPPD002

The First Magnetic Field Control (B-Train) to Optimize the Duty Cycle of a Synchrotron in Clinical Operation

controls, synchrotron, feedback, extraction

3503

E. Feldmeier, R. Cee, M. Galonska, Th. Haberer, A. Peters, S. Scheloske
HIT, Heidelberg, Germany

In December 2011 the Heidelberg Ion Therapy Center started to use the magnetic field feedback control for its clinical operation. Therewith the magnetic field deviation of the ramped magnets in the synchrotron depending on eddy currents and hysteresis are no longer in effect. Waiting times on the flattop and the "chimney" in the recovery phase of the synchrotron cycle are no longer necessary. The efficiency of the accelerator is increased by more than 20\% and the treatment time shortens accordingly. The core of the magnetic feedback system is a real time measuring system of the magnetic field with extremely high precision.

THPPD017

Mu2e AC Dipole 300 kHz and 5.1 MHz Tests and Comparison of Nickel-Zinc Ferrites

dipole, proton, impedance, target

3533

L. Elementi, K.R. Bourkland, D.J. Harding, V.S. Kashikhin, A.V. Makarov, H. Pfeffer, G. Velev
Fermilab, Batavia, USA

To suppress any background events coming from the inter-bunch proton interactions during the muon transport and decay window for the Mu2e experiment, a beam extinction scheme based on two dipoles running at ~300 kHz and 5.1 MHz is considered. The effective field of these magnets is synchronized to the proton bunch spacing in such a way that the bunches are transported at the sinus nodes. Two types Ni-Zn ferrites are considered for these dipoles. Ferrites, their characteristics and ferrites selection is herein discussed through measurements performed under conditions close to operational. The excitation system and the measurement of some characteristics of the magnetic field and field shape and measurement mechanism are also presented.

FRXCB01

Review of Microwave Schottky Beam Diagnostics

proton, antiproton, diagnostics, ion

4175

R.J. Pasquinelli
Fermilab, Batavia, USA

Non-intercepting beam diagnostics for detection of the incoherent motion of the finite number of beam particles, i.e. Schottky beam monitors, have been proven as extremely useful to characterize tune, chromaticity, and momentum spread in circular accelerators and colliders. This beam instrument, based on advanced microwave techniques, operates successfully in Recycler and Tevatron, and was recently implemented in the Large Hadron Collider. This presentation should review the technology of Schottky beam diagnostics systems with an emphasis on initial deployment at the Tevatron, concluding with the latest measurement results from the LHC and an outlook of possible improvements and extensions of the diagnostics.

Slides FRXCB01 [22.518 MB]