IPAC2012 - List of Keywords (impedance)

Paper	Title	Other Keywords	Page
MOOBB03	An Alternative 1D Model for CSR with Chamber Shielding	shielding, radiation, vacuum, synchrotron	52
	D. Zhou KEK, Ibaraki, Japan
	An alternative 1D model for modeling the longitudinal coherent synchrotron radiation (CSR) impedance is proposed. The code CSRZ* is used to calculate the CSR impedance with rectangular chamber shielding. Along the beam orbit, which may be formed by multi bends interleaved with drifts, the vacuum chamber is sliced into a series of segments. The low-frequency CSR impedance for each segment, in this case chamber shielding is significant, is obtained by numerical calculations. The high-frequency CSR impedance, in this case chamber shielding is negligible, is estimated by an analytical model*. The wake kick at each segment is computed via inverse Fourier transform of the impedance convolved the the beam spectrum. The most attractive merit of the method for CSR modeling lies in taking into account the realistic chamber shielding. D. Zhou, et al., To be published in Jpn. J. Appl. Phys. ** M. Borland, Phys. Rev. ST Accel. Beams 4, 070701 (2001).
	Slides MOOBB03 [1.856 MB]

MOEPPB007	Studies of eRHIC Coherent Instabilities	proton, simulation, betatron, space-charge	91
	G. Wang, M. Blaskiewicz 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. In the presence of an effective coherent electron cooling, the rms ion bunch length in eRHIC will be kept at 8.4cm, which is about a factor of 3 shorter than the current RHIC rms bunch length. Together with a factor of 2 increase in bunch intensity, coherent instabilities could be a potential limitation for achieving desired machine performance. In this study, we use the tracking code TRANFT to find thresholds and growth rates for various single bunch and coupled bunch instabilities with linear chromaticity and amplitude dependent tune shift taken into account. Based on the simulation results, requirements of machine parameters such as rf voltage, linear chromaticity, and octupole strength are specified to avoid these instabilities.

MOPPC059	Various Approaches to Electromagnetic Field Simulations for RF Cavities	simulation, cavity, electromagnetic-fields, HOM	268
	C. Liu, W. Ackermann, W.F.O. Müller, T. Weiland TEMF, TU Darmstadt, Darmstadt, Germany
	Funding: Work supported by BMBF under contract 05H09RD5. The Superconducting Proton Linac (SPL) cavity is mainly designed and conducted by CERN. It is a part of the planned injector upgrade of the Large Hadron Collider (LHC). The SPL cavity is used to accelerate the ion beam from 160 MeV to 5GeV and served as a driver for neutrino facilities and radioactive beam facilities. In the Superconducting Proton Linac (SPL) cavity, it is very important to calculate the eigenmodes precisely, because many higher-order modes (HOMs) can lead to particle beam instabilities. We used and compared three different ways to calculate the eigenmodes in the SPL cavity: field simulation with hexahedron mesh in frequency domain, field simulation with hexahedron mesh in time domain, and field simulation with tetrahedral mesh and higher order curvilinear elements. In this paper the principles of the three numerical methods will be introduced and compared. Finally the calculated results will be presented.

MOPPC067	Design and Construction of Inductive BPM	simulation, electron, vacuum, resonance	289
	M.Sh. Shafiee, E.E. Ebrahimibasabi, S.A.H. Feghhi, N. Goudarzi sbu, Tehran, Iran M. Jafarzadeh ILSF, Tehran, Iran
	To have a controllable Electron machine, that is required to be able to control beam orbits by knowing the beam position. The basic requirement for detecting the position of electron is calibrating and testing the BPMs. For this purpose wire method is used. Since we hadn't access to accelerator, for having experience at beam diagnostic we used this method for testing our constructed inductive BPM including 4 cm square poly ethylene core with 15 turns coil in each side. In this case study that was tested by a pulsed current (as an electron bunch) produced by a pulse generator. At first Tektronix 2235A oscilloscope was calibrated and used to measure the induced voltage of each coils, then by using of microcontroller, protocol RS232 and GUI induced voltages were read. The electrical center was measured with respect to the mechanical center and wire position was detected with 1mm Resolution. Conversion between the BPM signals and the actual wire position were done. Results were compared and presented.

MOPPC089	CUDA Kernel Design for GPU-based Beam Dynamics Simulations	simulation, acceleration, space-charge, linac	343
	I.V. Pogorelov, K.M. Amyx, J. Balasalle, J. James Tech-X, Boulder, Colorado, USA M. Borland, R. Soliday, Y. Wang ANL, Argonne, USA
	Funding: Work supported by the US DOE Office of Science, Office of Basic Energy Sciences under grant number DE-SC0004585. Efficient implementation of general-purpose particle tracking on GPUs can result in significant performance benefits to large-scale particle tracking and tracking-based accelerator optimization simulations. We present our work on CUDA kernels for transfer maps of single-particle-dynamics and collective-effects beamline elements, to be incorporated into a GPU-accelerated version of the ANL's accelerator code ELEGANT. In particular, we discuss techniques for efficient utilization of the device shared, cache, and local memory in the design of single-particle and collective-effects kernels. We also discuss the use of data-parallel and hardware-assisted approaches (segmented scan and atomic updates) for resolving memory contention issues at the charge deposition stage of algorithms for modeling collective effects. We present and discuss performance results for the CUDA kernels developed and optimized as part of this project.

MOPPD077	Studies for an Alternative LHC Non-Linear Collimation System	collimation, proton, sextupole, betatron	544
	L. Lari, R.W. Assmann, V. Boccone, F. Cerutti, A. Mereghetti, R. Versaci, V. Vlachoudis CERN, Geneva, Switzerland A. Faus-Golfe, L. Lari, J. Resta-López IFIC, Valencia, Spain
	Funding: This work has been carried out through of the European Coordination for Accelerator Research and Development (EuCARD), co-sponsored by EU 7th Framework Program. A LHC nonlinear Betatron cleaning collimation system would allow larger gap for the mechanical jaws, reducing as a consequence the collimator-induced impedance, which may limit the LHC beam intensity. In this paper, the performance of the proposed system is analyzed in terms of beam losses distribution around the LHC ring and cleaning efficiency in stable physics condition at 7TeV for Beam1. Moreover, the energy deposition distribution on the machine elements is compared to the present LHC Betatron cleaning collimation system in the Point 7 Insertion Region (IR).

MOPPP040	Resistive Wall Heating of the Undulator in High Repetition Rate FELs	undulator, electron, wakefield, FEL	652
	J. Qiang, J.N. Corlett, P. Emma LBNL, Berkeley, California, USA J. Wu SLAC, Menlo Park, California, USA
	Funding: Work supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. In next generation high repetition rate FELs, beam energy loss due to resistive wall wakefields will produce significant amount of heat. The heat load for a superconducting undulator (operating at low temperature), must be removed and will be expensive to remove. In this paper, we study this effect in an undulator proposed for a Next Generation Light Source (NGLS) at LBNL. We benchmark our calculations with measurements at the LCLS and carry out detailed parameter studies using beam from a start-to-end simulation. Our preliminary results suggest that the heat load in the undulator is about 2 W/m with an aperture size of 6 mm for nominal NGLS design parameters.

MOPPR006	Surface Waves for Testing of Beam Instrumentation	instrumentation, resonance, induction, electromagnetic-fields	780
	F. Stulle, J.F. Bergoz BERGOZ Instrumentation, Saint Genis Pouilly, France
	The fundamental TM wave can be guided as a surface wave along a single dielectric coated wire. Such a setup is known as a Goubau line. Close to the wire the TM wave resembles closely the radial electric and azimuthal magnetic fields of a charged particle beam moving in an accelerator. Hence, it can be used to test beam instrumentation in the workshop. We introduce the principle, discuss benefits, and compare measurements of a beam instrumentation device performed with a Goubau line to measurements performed with a standard bench testing setup.

MOPPR023	Stripline BPM with Integral In-Vacuo Termination	pick-up, 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.

MOPPR042	Characterization Tests of a Stripline Beam Position Monitor for the CLIC Drive Beam	quadrupole, extraction, simulation, feedback	873
	A. Benot-Morell, A. Faus-Golfe, J.J. García-Garrigós IFIC, Valencia, Spain A. Benot-Morell, L. Søby CERN, Geneva, Switzerland J.M. Nappa, J. Tassan-Viol, S. Vilalte IN2P3-LAPP, Annecy-le-Vieux, France S.R. Smith SLAC, Menlo Park, California, USA
	Funding: FPA2010-21456-C02-01, SEIC-2010-00028 A prototype of a stripline Beam Position Monitor (BPM) with its associated readout electronics has been developed at CERN in collaboration with SLAC, LAPP and IFIC. In this paper, the design and simulations of the BPM with the analog readout chain and the BPM test bench are described, and the results of the first characterization tests are presented. The position resolution and accuracy parameters are expected to be below 2μm and 20μm respectively for a beam with a bunching frequency of 12GHz, an average current of 101A and a machine repetition rate of 50Hz.

TUOBC02	Small-Beta Collimation at SuperKEKB to Stop Beam-Gas Scattered Particles and to Avoid Transverse Mode Coupling Instability	interaction-region, scattering, coupling, simulation	1104
	H. Nakayama, Y. Funakoshi, K. Kanazawa, K. Ohmi, Y. Ohnishi, Y. Suetsugu KEK, Tsukuba, Japan H. Nakano Tohoku University, Graduate School of Science, Sendai, Japan
	At SuperKEKB, beam particles which are Coulomb-scattered by the residual gas molecular change direction and will be eventually lost by hitting beam pipe inner wall. Due to large vertical beta function and small beam pipe radius just before IP, most of Coulomb-scattered particles are lost there and are very dangerous for the Belle-II detector. To stop such particles before the IP, vertical collimators are installed in the ring. However, such vertical collimators should be placed very close (few mm) to the beam and therefore induce transverse mode coupling instability. To avoid beam instability and achieve collimation at the same time, we need to install vertical collimators where vertical beta function is SMALL, since maximum collimator width determined by aperture condition is proportional to β^1/2, and minimum collimator width determined by instability is proportional to β^2/3. We present our strategy to stop beam-gas scattered particles and simulated loss rate in the interaction region. We will also show dedicated vertical collimator design to achieve less instability.
	Slides TUOBC02 [2.196 MB]

TUPPC034	Preparation of SLS for IBS Measurements	emittance, diagnostics, optics, radiation	1233
	N. Milas, M. Böge, A. Streun PSI, Villigen, Switzerland M. Aiba, A. Lüdeke, A. Saa Hernandez Paul Scherrer Institut, Villigen, Switzerland F. Antoniou, Y. Papaphilippou CERN, Geneva, Switzerland
	It is planned to use the SLS for testing damping ring issues related to linear colliders. One aspect is the study of Intra-Beam Scattering (IBS) effects, which are a limiting factor for ultra-low emittance rings. In this paper we present the setup and characterization of a new mode of operation in which the SLS runs at lower energy (1.57 GeV) with a natural emittance of 2.4 nm rad. This is much smaller than that at the nominal energy (2.41 GeV) and should make IBS effects more easily visible. In order to be able to observe IBS a careful setup is required: Optics measurement and correction as well as measurements of the bunch natural energy spread and the onset of turbulent bunch lengthening. Also, a detailed discussion on the available diagnostics and their limitations are shown and finally some preliminary results of beam emittance measurements, in all three planes, as a function of single bunch current are presented.

TUPPD015	Optimization of Muon Capturing in g-2 Ring	kicker, betatron, vacuum, closed-orbit	1440
	A.A. Mikhailichenko CLASSE, Ithaca, New York, USA D.L. Rubin Cornell University, Ithaca, New York, USA
	We describe optimization procedure for muons capturing in g-2 ring under reconstruction at FERMILAB. This procedure includes both the beam dynamics consideration and HV inflector geometry and technique. Some engineering aspects of HV inflector and pulser are presented in detail.

TUPPP031	Modelling the Steady-state CSR Emission in Low Alpha Mode at the Diamond Storage Ring	wakefield, electron, factory, bunching	1677
	I.P.S. Martin, C.A. Thomas Diamond, Oxfordshire, United Kingdom R. Bartolini JAI, Oxford, United Kingdom
	The CSR emitted by short electron bunches can be of a stable or bursting nature, with transition between the two states characterised by a threshold current that depends on various machine parameters. Key to understanding this process is to develop an effective model that describes the way the electron bunch interacts with impedance sources such as the CSR wakefield and surrounding vacuum chamber. In this paper we present the latest results of modelling the equilibrium distribution calculated using the Haissinski equation driven by different impedance models. The bunch lengthening with current, bunch profiles and CSR form factors derived from this model are compared to measured data for both positive and negative momentum compaction factor. Comparisons of the measured bursting thresholds to theoretical predictions are also discussed.

TUPPP038	Electron Beam Collimation for the Next Generation Light Source	collimation, undulator, gun, linac	1695
	C. Steier, P. Emma, H. Nishimura, C. F. Papadopoulos, F. Sannibale LBNL, Berkeley, California, USA
	Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The Next Generation Light Source will deliver high (MHz) repetition rate electron beams to an array of free electron lasers. Because of the significant average current in such a facility, effective beam collimation is extremely important to minimize radiation damage to undulators, prevent quenches of superconducting cavities, limit dose rates outside of the accelerator tunnel and prevent equipment damage. This paper describes the conceptual design of the collimator system, as well as the results of simulations to test its effectiveness.

TUPPP042	Passive Landau Cavity Effects in the NSLS-II Storage Ring	cavity, storage-ring, simulation, wakefield	1701
	G. Bassi, A. Blednykh, S. Krinsky BNL, Upton, Long Island, New York, USA
	Funding: Work supported by DOE contract No: DE-AC02-98CH10886. In new 3rd generation synchrotron light sources with small transverse emittance, higher harmonic cavities (Landau cavities) are installed for bunch lengthening to increase the Touschek lifetime, and to provide Landau damping for beam stability. In this contribution we study the effects of passive Landau cavities in the NSLS-II storage ring for arbitrary fill-patterns with the OASIS tracking code.

TUPPP043	Analysis of Coupled Bunch Instabilities in the NSLS-II Storage Ring with a 7-cell PETRA-III RF Structure	HOM, cavity, damping, simulation	1704
	G. Bassi, A. Blednykh, S. Krinsky, J. Rose BNL, Upton, New York, USA
	Funding: Work supported by DOE contract No: DE-AC02-98CH10886. A 7-cell PETRA-III cavity is considered to be installed for the commissioning Phase 1 in the NSLS-II storage ring at an average current of 25mA. In this contribution we study transverse and longitudinal coupled-bunch instabilities that may be driven by the higher order modes of the 7-cell PETRA-III cavity. The instability thresholds are calculated with the OASIS tracking code, with parameters of the bare lattice (no damping wigglers and Landau cavities). We study multibunch configurations with arbitrary fill-patterns and discuss the slow head-tail effect at positive chromaticity to increase the transverse instability thresholds.

TUPPR015	Choke-Mode Damped Structure Design for the CLIC Main Linac	wakefield, damping, simulation, dipole	1840
	H. Zha, H. Chen, W.-H. Huang, C.-X. Tang TUB, Beijing, People's Republic of China A. Grudiev, J. Shi, W. Wuensch CERN, Geneva, Switzerland
	Choke-mode damped accelerating structures are being studied as an alternative to the CLIC waveguide damped baseline structure. Choke-mode structures hold the potential for much lower pulsed surface heating and reduced cost since no milling is required. We propose a new choke geometry which has significant suppression of higher order dipoles. By impedance matching and detuning of the first dipole pass-band, the wakefield suppression is comparable to the baseline design with waveguide damping. A fully featured choke mode structure with the same accelerating gradient profile and filling time as the nominal CLIC design has been designed. It has the potential to replace the waveguide damped design without changing any of the machine layout or the beam parameters.

TUPPR016	Final Cross Section Design of the Stripline Kicker for the CLIC Damping Rings	damping, kicker, extraction, wakefield	1843
	C. Belver-Aguilar, A. Faus-Golfe IFIC, Valencia, Spain M.J. Barnes CERN, Geneva, Switzerland F. Toral CIEMAT, Madrid, Spain
	Funding: IDC-20101074 and FPA2010-21456-C02-01 The CLIC design relies on the presence of Pre-Damping Rings (PDR) and Damping Rings (DR) to achieve, through synchrotron radiation, the very low emittance needed to fulfill the luminosity requirements. Kicker systems are required to inject and extract the beam from the Pre-Damping and Damping Rings. In order to achieve low beam coupling impedance and reasonable broadband impedance matching to the electrical circuit, striplines have been chosen for the kicker elements. In this paper the final design for the DR kicker is presented, including an optimization of the geometric parameters to achieve the requirements for both characteristic impedance and field homogeneity. In addition, a sensitivity analysis of characteristic impedance and field homogeneity to geometric parameters is reported.

TUPPR018	Beam Impedance Study of the Stripline Kicker for the CLIC Damping Ring	coupling, kicker, damping, simulation	1849
	C. Belver-Aguilar, A. Faus-Golfe IFIC, Valencia, Spain M.J. Barnes CERN, Geneva, Switzerland I. Podadera, F. Toral CIEMAT, Madrid, Spain
	Funding: FPA2010-21456-C02-01 CLIC Pre-Damping (PDR) and Damping Rings (DR) are required for reducing the emittance of the electron and positron beams before being accelerated in the main linac. Several stripline kicker systems are used to inject and extract the beam from the PDR and DR. Wakefields produced by the charged particles when passing through the aperture of the stripline kickers may become an important source of emittance growth; for this reason, simulations of longitudinal and transverse beam impedance in the frequency domain, and their equivalent in the time domain are needed. First analytical approaches, future simulations and tests planned are presented in this paper.

TUPPR025	Higher-Order Modes and Beam Loading Compensation in CLIC Main Linac	coupling, beam-loading, HOM, higher-order-mode	1867
	O. Kononenko, A. Grudiev CERN, Geneva, Switzerland
	Compensation of transient beam loading is one of the major performance issues of the future compact linear collider (CLIC). Recent calculations, which consider only the most important fundamental mode, have shown that the 0.03% limit on the rms relative bunch-to-bunch energy spread in the main beam can be reached by optimizing the RF power pulse shape for the TD26, the CLIC baseline accelerating structure. Here, using HFSS and massively parallel ACE3P codes developed at SLAC, we perform an additional dedicated study of the influence of higher-order modes on the energy spread compensation scheme. It is shown that taking these modes into account in the accelerating structure does not increase the rms energy spread in the main beam above the CLIC specification level. Results of the HFSS and ACE3P simulations are also in a good agreement.

TUPPR090	Analysis of Ferrite Heating of the LHC Injection Kickers and Proposals for Future Reduction of Temperature	kicker, injection, vacuum, coupling	2038
	M.J. Barnes, L. Ducimetière, N. Garrel, B. Goddard, V. Mertens, W.J.M. Weterings CERN, Geneva, Switzerland
	The two LHC injection kicker magnet (MKI) systems produce a kick of 1.3 T-m with a flattop duration variable up to 7860 ns, and rise and fall times of less than 900 ns and 3000 ns, respectively. A beam screen, consisting of a ceramic tube with conductors on the inner wall, is placed in the aperture of the magnets. The conductors provide a path for the image current of the, high intensity, LHC beam and screen the ferrite against wake fields. The conductors initially used gave adequately low beam coupling impedance however inter-conductor discharges occurred during pulsing of the magnet; hence an alternative design was implemented to meet the often conflicting requirements for low beam coupling impedance, fast magnetic field rise-time and good high voltage behaviour. During 2011 the LHC has been operated with high intensity beam, coasting for many hours at a time, resulting in heating of both the ferrite yoke and beam impedance reduction ferrites, of the MKIs. This paper presents an analysis of thermal measurement data and an extrapolation of the heating for future operation; in addition means are discussed for reducing ferrite heating and improving cooling.

TUPPR095	Update on Kicker Development for the NGLS	kicker, controls, status, electron	2053
	G.C. Pappas, S. De Santis, J.E. Galvin, M.V. Orocz, M. Placidi LBNL, Berkeley, California, USA
	The latest requirements for the Next Generation Light Source (NGLS) beam spreader call for a kicker to deflect a 2.4 GeV electron beam by an angle of 3 mrad over a length of 2 meters. The rise and fall time requirements for the integrated B field are <50 ns, the pulse frequency is up to 100 kHz, and both the inter-pulse and pulse to pulse ripple requirements are <0.01% of full scale. These requirements, along with the basic design of the beam spreader are still evolving, and several magnet types and modulator topologies have been considered. This paper will discuss this evolution as it pertains to the kickers, what the current status is of the R&D effort, and the plan to build a full power prototype system.

WEEPPB010	RF Modeling Using Parallel Codes ACE3P for the 400-MHz Parallel-Bar/Ridged-Waveguide Compact Crab Cavity for the LHC HiLumi Upgrade	damping, cavity, HOM, dipole	2185
	Z. Li, L. Ge SLAC, Menlo Park, California, USA J.R. Delayen, S.D. Silva ODU, Norfolk, Virginia, USA
	Funding: Work partially supported by the US DOE through the US LHC Accelerator Research Program (LARP), and by US DOE under contract number DE-AC02-76SF00515. Schemes utilizing crab cavities to achieve head-on beam-beam collisions were proposed for the LHC HiLumi upgrade. These crabbing schemes require that the crab cavities be compact in order to fit into the tight spacing available in the existing LHC beamlines at the location where the crab cavities will be installed. Under the support of US LARP program, Old Dominion University and SLAC have joint efforts to develop a 400-MHz compact superconducting crab cavity to meet the HiLumi upgrade requirements. In this paper, we will present the RF modeling and analysis of a parallel-bar/ridged-waveguide shaped 400-MHz compact cavity design that can be used for both the horizontal and vertical crabbing schemes. We will also present schemes for HOM damping and multipacting analysis for such a design.

WEPPC012	High Power Tests of CW Input Couplers for cERL Injector Cryomodule	cryomodule, cavity, vacuum, linac	2230
	E. Kako, S. Noguchi, T. Shishido, K. Watanabe, Y. Yamamoto KEK, Ibaraki, Japan
	High power tests of a pair of the prototype input couplers were performed by using a newly developed 300 kW CW klystron. The input couplers were successfully processed up to 100 kW in a pulsed operation with a duty of 10% and 50 kW in a CW operation for 30 minutes. The conditioning was limited by excessive heating at bellows of an inner conductor at a coaxial line locating between a coaxial RF window and a doorknob-type transition. Improvement of a sufficient cooling at the inner conductor is necessary to achieve the required input RF power of 170 kW in a CW operation. Six input couplers to be installed in the injector cryomodule for the cERL project were completed, and they are under preparation for conditioning at a high power test stand.

WEPPC017	Design of a High-Speed Pulsed 324MHz Solid-State Amplifier for Use in a Beam Chopper	resonance, proton, insertion, feedback	2242
	S.C. Dillon, B.S. Nobel, C.P. Schach Tomco Technologies, Stepney, South Australia, Australia
	A 324MHz 30kW high-speed pulsed solid-state amplifier has been designed for use in a beam chopper at the Japan Proton Accelerator Complex (J-PARC). This paper discusses the various design challenges and presents the initial performance test results. In particular, the amplifier achieves pulse rise and fall times of less than 15 nanoseconds, is easily upgradeable in power, and withstands 100% power reflection without damage.

WEPPC028	Slim Elliptical Cavity at 800 MHz for Local Crab Crossing	cavity, coupling, damping, HOM	2263
	L. Ficcadenti, J. Tückmantel CERN, Geneva, Switzerland
	A slim highly eccentric elliptical Crab cavity with vertical deflection at 800 MHz, compatible to beam line distances everywhere in the LHC ring, was designed. It is a good fall-back solution in case of problems with new compact 400 MHz designs. Simulated RF characteristics of the delfecting mode, HOM spectra and damping, tuning and multipacting effects are presented. First the most simple HOM coupling system was investigated. The rejection of the working mode was not sufficient and a notch filter was added. Results of both cases will be presented.

WEPPC037	A Ring-shaped Center Conductor Geometry for a Half-wave Resonator	quadrupole, cavity, linac, ion	2289
	B. Mustapha, Z.A. Conway, P.N. Ostroumov ANL, Argonne, USA
	Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract DE-AC02-06CH11357. Half-wave resonators (HWR) are used and being proposed for the acceleration of high-intensity proton and heavy-ion beams in the 0.1 < β < 0.5 velocity range. The highest performing half-wave resonator geometries use a center conductor with a race-track shaped cross section in the high-electric field region; a feature shared with spoke cavities which are also being proposed for the same velocity regime. We here propose a ring-shaped center conductor instead of the race-track shape. Preliminary studies show that the ring geometry has a similar peak surface electric field as the race-track one, but has several other advantages. In particular, the ring-shaped geometry has: a lower peak surface magnetic field, a much higher Shunt impedance for the same peak fields, and no quadrupole electric field asymmetry which has been observed in the race-track geometry. In a solenoid-based symmetric focusing, the quadrupole component may lead to unnecessary emittance growth which is not acceptable in high-intensity ion linacs. We will present a detailed comparison and a discussion of the two geometries.

WEPPC040	Evaluation of VATSEAL Technology to Seal Waveguide Serving High-field Superconducting RF Cavities	vacuum, SRF, cavity, radio-frequency	2298
	B.K. Stillwell, J.D. Fuerst, J. Liu, G.J. Waldschmidt, G. Wu ANL, Argonne, USA
	Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. A waveguide flange seal serving a high-field, superconducting, radio-frequency (SRF) cavity ideally possesses several characteristics. Seals must generally be ultrahigh-vacuum leak tight. Seals must also bridge the inner surfaces of connecting flanges for optimum transmission and minimal heating due to trapped modes. In addition, if seal contact areas are minimized, flange seals may serve as convenient thermal impedances. Finally, seals must be easily cleanable and not be prone to generate particulate matter during assembly and disassembly. A unique sealing technology known as VATSEAL may neatly address all of the above requirements. In this paper, we describe our evaluation of VATSEAL technology for use in SRF cavity assemblies.

WEPPC042	Low Impedance Bellows for High-current Beam Operations	cryomodule, wakefield, SRF, electron	2303
	G. Wu, K.-J. Kim, A. Nassiri, G.J. Waldschmidt, Y. Yang ANL, Argonne, USA J.J. Feingold, J.D. Mammosser, R.A. Rimmer, H. Wang JLAB, Newport News, Virginia, USA J. Jang, S.H. Kim POSTECH, Pohang, Kyungbuk, Republic of Korea
	Funding: Work Supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract No. DE-AC02-06CH11357 In particle accelerators, bellows are commonly used to connect beamline components. Such bellows are traditionally shielded to lower the beam impedance. Excessive beam impedance can cause overheating in the bellows, especially in high beam current operation. For an SRF-based accelerator, the bellows must also be particulate free. Many designs of shielded bellows incorporate rf slides or fingers that prevent convolutions from being exposed to wakefields. Unfortunately these mechanical structures tend to generate particulates that, if left in the SRF accelerator, can migrate into superconducting cavities, the accelerator's critical components. In this paper, we describe a prototype unshielded bellows that has low beam impedance and no risk of particulate generation.

WEPPC086	Higher Order Modes Damping Analysis for the SPX Deflecting Cavity Cyromodule	cavity, damping, HOM, dipole	2414
	L. Xiao, Z. Li, C.-K. Ng SLAC, Menlo Park, California, USA A. Nassiri, G.J. Waldschmidt, G. Wu ANL, Argonne, USA R.A. Rimmer, H. Wang JLAB, Newport News, Virginia, 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. A single-cell superconducting deflecting cavity operating at 2.812 GHz has been proposed and designed for the Short Pulse X-ray (SPX) project for the Advanced Photon Source upgrade. A cryomodule of 4 such cavities will be needed to produce the required 2-MV deflecting voltage. Each deflecting cavity is equipped with one fundamental power coupler (FPC), one lower order mode (LOM) coupler, and two higher order mode (HOM) couplers to achieve the stringent damping requirements for the unwanted modes. The damping of the HOM/LOM modes below the beampipe cutoff has been analyzed in the single cavity geometry and shown to meet the design requirements. The HOMs above beam pipe cutoff in the 4-cavity cyromodule, however, may result in cross coupling which may affect the HOM damping and potentially trapped modes between the cavities which could produce RF heating to the beamline bellows and even be detrimental to the beam. We have evaluated the HOM damping and trapped modes in the 4-cavity cryomodule using the parallel finite element EM code ACE3P developed at SLAC. We will present the results of the cryomodule analysis in this paper.

WEPPC087	Second Harmonic Cavity Design for Project-X Main Injector	cavity, simulation, dipole, HOM	2417
	L. Xiao, C.-K. Ng SLAC, Menlo Park, California, USA J.E. Dey, I. Kourbanis Fermilab, Batavia, USA
	In order to accelerate the proposed beam intensity for Project-X, a new RF system for Main Injector (MI) will be required. A new 53 MHz first harmonic RF cavity that meets the MI requirements for Project-X has been designed. In order to reduce the peak longitudinal beam density a 10⁶ MHz second harmonic RF system is also needed. The first harmonic RF cavity design is a quarter wave coaxial resonator with a single accelerating gap and a perpendicular biased ferrite tuner. The second harmonic RF cavity baseline design is similar to the fundamental one and scaled down from it. RF simulations and shape optimizations on the second harmonic cavity are carried out to obtain the optimal performance which meets Project-X requirements. The results are discussed and presented in this paper.

WEPPC103	Development of Spoke Cavities for High-velocity Applications	electron, cavity, higher-order-mode, multipole	2456
	C.S. Hopper, J.R. Delayen ODU, Norfolk, Virginia, USA R.G. Olave Old Dominion University, Norfolk, Virginia, USA
	In response to recent interest in alternatives to elliptical cavities for low-frequency, high-velocity applications we have initiated a program for the development of multi-spoke superconducting cavities. We have completed the electromagnetic design for two-spoke cavities operating at 352 and 325 MHz and a design velocity of β = 0.82 and β = 1. We present the results of the optimization, higher order mode (HOM) analysis, multipacting analysis, and an initial multipole expansion study of the fundamental accelerating mode.

WEPPC113	Progress on the High-Current 704 MHz Superconducting RF Cavity at BNL	cavity, HOM, damping, higher-order-mode	2486
	W. Xu, S.A. Belomestnykh, I. Ben-Zvi, H. Hahn, P. Jain BNL, Upton, Long Island, New York, USA C.M. Astefanous, M.D. Cole, J.P. Deacutis, D. Holmes AES, Medford, NY, USA
	Funding: This work was supported by Sotny Brook under contract No. DE-SC0002496 and Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE. The 704 MHz high current superconducting cavity has been designed with consideration of both performance of fundamental mode and damping of higher order modes. A copper prototype cavity was fabricated by AES and delivered to BNL. RF measurements were carried out on this prototype cavity, including fundamental pass-band and HOM spectrum measurements, HOM studies using bead-pull setup, prototyping of antenna-type HOM couplers. The measurements show that the cavity has very good damping for the higher-order modes, which was one of the main goals for the high current cavity design. 3D cavity models were simulated with Omega3P code developed by SLAC to compare with the measurements. The paper describes the cavity design, RF measurement setups for the copper prototype, and presents comparison of the experimental results with computer simulations. The progress with the niobium cavity fabrication will also be described.

WEPPD017	Development of a New RF Finger Concept for Vacuum Beam Line Interconnections	vacuum, linac, higher-order-mode, simulation	2531
	C. Garion, A. Lacroix, H. Rambeau CERN, Geneva, Switzerland
	RF contact fingers are primarily used as a transition element to absorb the thermal expansion of vacuum chambers during bake-out and also to compensate for mechanical tolerances. They have to carry the beam image current to avoid the generation of Higher Order Modes and to reduce beam impedances. They are usually made out of copper beryllium thin sheets and are therefore very fragile and critical components. In this paper, a robust design based on a deformable finger concept is proposed. It allows the compensation of large longitudinal movements and also defaults such as transverse offset, twist or bending. The concept of this new RF fingers is first explained, then the design of the component is presented. The mechanical study based on a highly non linear Finite Element model is shown as well as preliminary tests, including fatigue assessment, carried out on prototypes.

WEPPD021	Optimization of the Ultra-High Vacuum Systems for the 3 GeV TPS Synchrotron Light Source	vacuum, photon, electron, synchrotron	2543
	G.-Y. Hsiung, C.K. Chan, C.-C. Chang, C.L. Chen, J.-R. Chen, C.M. Cheng, Y.T. Cheng, S-N. Hsu, H.P. Hsueh, Huang, Y.T. Huang, I.C. Sheng, L.H. Wu, Y.C. Yang NSRRC, Hsinchu, Taiwan
	The Taiwan Photon Source (TPS), a 3 GeV synchrotron light source, provides an ultra-low emittance of electron beam and the consequent extremely high brightness of photons. The vacuum pressure along the beam duct should be ultra-high vacuum (UHV) and even lower for reduction of the impact to the beam from the gas scattering or ion trapping troubles. Most of the outgas comes from the photon stimulated desorption (PSD) back streaming from downstream absorbers during beam operation and large area surface outgas inside the beam duct as well. Due to the anticipate request of the smallest vertical aperture of beam ducts from various insertion devices and the lowest broadband impedance through all the vacuum chambers of electron storage ring, the inner structure design and the surface treatment of vacuum chambers as well as the constraint of the back stream PSD outgas from distributed absorbers and the pumping locations should be optimized to obtain a high quality UHV system for the high stable synchrotron light source through the long period of operation. The optimized design of the vacuum chambers for the TPS will be described.

WEPPD026	Design and Fabrication of NSLS-II Storage Ring Vacuum Chambers and Components	vacuum, storage-ring, photon, multipole	2558
	H.-C. Hseuh, A.T. Anderson, L. Doom, M.J. Ferreira, C. Hetzel, C. Longo, V. Ravindranath, K. Roy, S.K. Sharma, J.L. Tuozzolo, K. Wilson BNL, Upton, Long Island, New York, USA
	Funding: Work performed under the auspices of U.S. Department of Energy, under contract DE-AC02-98CH10886 The National Synchrotron Light Source II, a 3-GeV, 792-meter circumference, synchrotron radiation facility with ultra-high-flux and brightness, is under construction at Brookhaven National Laboratory. The storage ring vacuum chambers are mainly made of extruded aluminium but with a few made of stainless steel and inconel. The synchrotron radiation from bending magnets is intercepted at discrete photon absorbers made of GlidCop. NEG strips in the ante-chamber provide the distributed pumping, while lumped ion pumps and titanium sublimation pumps at photon absorbers remove the desorbed gas. The complex vacuum system is being assembled and integrated in-house. This paper describes the design and fabrication of both standard and special vacuum chambers, the low impedance RF shielded bellows and the photon absorbers. The vacuum system is now moving into the conditioning, installation and testing phase. Details and experience from the large scale production, testing and lesson learned will also be presented.

WEPPD062	Measurements of the First RF Prototype of the Spiral2 Single Bunch Selector	vacuum, high-voltage, scattering, simulation	2663
	M. Di Giacomo GANIL, Caen, France A.C. Caruso, F. Consoli, G. Gallo, D. Rifuggiato, E. Zappalà INFN/LNS, Catania, Italy A. Longhitano ALTEK, San Gregorio (CATANIA), Italy
	Funding: Work supported by EU commission 7th framework project n. 212692. The single bunch selector of the Spiral2 driver uses 100 Ω travelling wave electrodes driven by fast pulse generators. A 2.5 kV, 1 kW feed-through and a vacuum chamber housing the water cooled electrodes have been designed and built. The paper reviews the whole design and reports the results of first RF and power measurements.

WEPPD063	Construction of Disk-loaded Buncher for S-Band Low Energy TW Electron Linear Accelerator	electron, linac, coupling, cavity	2666
	F. Ghasemi, F. AbbasiDavani, S. Ahmadiannamini, M.Sh. Shafiee sbu, Tehran, Iran M.L. Lamehi Rashti, H. Shaker IPM, Tehran, Iran
	The project of design and construction of Traveling linear electron accelerator is being performed by the Institute for Research in Fundamental Sciences (IPM) and Shahid Beheshti University in Iran. By using the results of the calculations and by dynamic simulation of electron beam in the designed buncher, the dimensions of the designed sample have been obtained. This paper discuss construction of this buncher.

WEPPD066	Design of a Stripline Kicker for Tune Measurement in CSNS RCS	kicker, lattice, cyclotron, wakefield	2675
	X.Y. Yang, S. Fu, T.G. Xu IHEP, Beijing, People's Republic of China
	For CSNS RCS tune measurement, tune value is measured by exciting the bunch with strip-line kicker fed with white noise and using FFT algorithm to the turn-by-turn position of the bunch in the BPM. This article simulates the strip-line kicker in RCS and the efficiency of the kicker is discussed in the MATLAB environment. The parameters of the kicker with arc electrode structure such as wake impedance, thermal state and VSWR are analyzed based on the advantage of this design.

WEPPD070	Automatic Tuner Unit Operation for the Microwave System of the ESS-Bilbao H⁺ Ion Source	plasma, ion-source, ion, controls	2684
	L. Muguira, I. Arredondo, D. Belver, M. Eguiraun, F.J. Fernandez Huerta, J. Feuchtwanger, N. Garmendia, O. González, P.J. González ESS Bilbao, LEIOA, Spain V. Etxebarria, J. Jugo, J. Portilla University of the Basque Country, Faculty of Science and Technology, Bilbao, Spain J. Verdu EPFL, Lausanne, Switzerland
	Funding: The present work is supported by the Basque Government and Spanish Ministry of Science and Innovation. The operation of the waveguide automatic tuner unit (ATU) for optimizing the impedance matching and the RF power coupling in the ESS-Bilbao H⁺ Ion Source (ISHP) is presented. Since the plasma chamber can be considered as a time varying load impedance for the pulsed RF 2.7 GHz high power generator, several approaches have been studied for accurately measuring the load impedance. In the later case, a set of power detectors connected to electric field probes, IQ demodulators and gain/phase detectors connected to dual directional couplers have been integrated. An experimental comparison of these approaches is presented, showing their accuracy, limitations and error-correction methods. Finally, the control system developed for the automatic operation of the triple capacitive post tuner is described, as well as illustrative results.

WEPPD075	A Novel Planar Balun Structure for Continuous Wave 1 kW, 500 MHz Solid-state Amplifier Design	simulation, synchrotron, coupling, HOM	2699
	T.-C. Yu, L.-H. Chang, M.H. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, Y.-H. Lin, C.H. Lo, M.H. Tsai, Ch. Wang, T.-T. Yang, M.-S. Yeh NSRRC, Hsinchu, Taiwan
	In general, the coaxial type balun plays key role in push-pull amplifier design in the increasing high power solid-state technique transmitter design for accelerator application. However, the coaxial baluns not only increase the complexity in manufacturing procedure but also introduce additional tolerance variation between modules. The variation between parallel power modules would decreases combining efficiency and thus increase the operation cost. Here, a novel planar balun has been proposed and successfully implemented on 1kW solid-state amplifier design for continuous operation with newly designed water cooling plates. The long-term CW test has demonstrated the feasibility of the newly designed planar is quite suitable for CW operation with its excellent low loss, balance property and also low tolerance between modules in mass production.

WEPPD079	Measurements of Magnetic Permeability of Soft Steel at High Frequencies	booster, dipole, vacuum, damping	2711
	Y. Tokpanov, V.A. Lebedev, W. Pellico Fermilab, Batavia, USA
	The Fermilab Booster does not have a vacuum chamber which would screen the beam from laminations its dipoles cores. Therefore the booster impedance is mainly driven by the impedance of these dipoles. Recently an analytical model of the laminated dipole impedances was developed. However to match the impedance measurements with calculations one needs an accurate measurement of soft steel magnetic permeability. This paper presents the measurement results of the permeability in a frequency range from ~10 MHz to 1 GHz. Measurements of e.-m. wave propagation in 30 cm long strip line built from soft steel were used to compute the permeability. Measurements were performed in a DC magnetic field to observe the effect of steel saturation on the high frequency permeability. Both real and imaginary parts of the permeability were measured. As expected their values were decreasing with frequency increase from 10 MHz to 1 GHz and with saturation of steel DC permeability. Operated by Fermi Research Alliance, LLC, under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.

WEPPP022	Analysis of a Rectangular Dielectric-lined Accelerating Structure with an Anisotropic Loading	wakefield, radiation, electron, acceleration	2769
	I.L. Sheynman, S. Baturin LETI, Saint-Petersburg, Russia A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio, USA
	Funding: Russian Fund of Basic Research Federal target program "Scientific and scientific and pedagogical personnel of innovative Russia" of the Ministry of Education and Science of Russia. Analysis of Cherenkov radiation generated by high current relativistic electron bunch passing through a rectangular waveguide with anisotropic dielectric loading has been carried out. Some of the materials used for the waveguide loading of accelerating structures (sapphire) possess significant anisotropic properties. In turn, it can influence excitation parameters of the wakefields generated by an electron beam. Using orthogonal eigenmodes decomposition for the rectangular dielectric waveguide, the analytical expressions for the wakefields have been obtained. Numerical modeling of the longitudinal and transverse (deflecting) wakefields has been carried out as well. It is shown that the dielectric anisotropy causes frequency shift in comparison to the dielectric-lined waveguide with the isotropic dielectric loading.

WEPPP064	Design and Simulation of the Stripline Transverse Quadrupole Kicker for HLS II	quadrupole, kicker, dipole, storage-ring	2852
	F.F. Wu, W.B. Li, P. Lu, T.J. Ma, B.G. Sun, Y.Y. Xiao, H. Xu, Y.L. Yang, Z.R. Zhou USTC/NSRL, Hefei, Anhui, People's Republic of China
	In order to investigate the possibility of excite a transverse quadrupole mode oscillation of the electron bunch in the HLS II storage ring, we design a stripline transverse quadrupole kicker. The characteristic impedance of some modes(dipole modes, sum mode, quadrupole mode) of the optimised stripline kicker must match 50Ω characteristic impedance of the external transmission lines so as to reduce the reflected power. We use nonlinear least square method to optimise the kicker and compare characteristic impedances of calculation using 2D Possion code and fitted function of several variables, then we get optimised size with integrated use of Possion code and fitted function of several variables. Using the 2D Poisson code, we simulate the electric field distribution of dipole modes when the horizontal or the vertical electrodes are at opposite unit potentials, and the electric field distribution of quadrupole mode using quadrupole kick. We verified that the designed stripline kicker can excite a transverse quadrupole mode oscillation of the electron bunch.

WEPPP074	Study of a Wideband Feedback Kicker for the SPS	kicker, feedback, cavity, simulation	2882
	S. De Santis, Z. Paret, A. Ratti LBNL, Berkeley, California, USA A. Gallo, F. Marcellini INFN/LNF, Frascati (Roma), Italy
	Funding: Work supported by the US Department of Energy under Contracts DE-AC02-05CH11231 and DE-AC02-76SF00515, and through the US LHC Accelerator Research Program (LARP). The LHC luminosity upgrade currently being planned at CERN depends in large measure on a successful upgrade of its injectors chain. In particular the storing of higher currents in the SPS presents a significant challenge from the point of view of the beam stability. Electron cloud driven and transverse mode-coupled instabilities can disrupt the stored beam to the point of making injection in the LHC impossible. These types of instabilities are characterized by fast growth times and substantial spectral components at high frequency. Therefore a key aspect of any feedback system capable of effectively controlling the instability growth is the development of a suitable kicker with a high frequency response. In this paper we investigate the technologies available for such a kicker and identify a possible solution to be implemented on the SPS. By combining a lower frequency stripline kicker with a high frequency module, such as a damped cavity or a slotted waveguide, it would be possible to provide shunt impedances around 1000 Ω on a bandwidth from DC to 1 GHz. The basic parameters and limits of such a solution are discussed.

WEPPR002	Intensity Thresholds for Transverse Coherent Instabilities During Proton and Heavy-Ion Operation in SIS100	space-charge, proton, synchrotron, simulation	2934
	V. Kornilov, O. Boine-Frankenheim GSI, Darmstadt, Germany
	The SIS100 synchrotron is the central accelerator of the projected FAIR complex. It should deliver high intensity proton and heavy-ion beams to the different FAIR experiments. Coherent transverse instabilities are a potential intensity-limiting factor in SIS100. In this contribution we give a summary of the different transverse coherent effects in intense bunched beams that can be expected in the SIS100. Some of the main concerns are unstable head-tail modes, the transverse mode coupling instability, and the beam break-up instability. Space charge is an important effect that leads to Landau damping of the head-tail eigenmodes and modifies the transverse mode coupling. The growth times and thresholds for instabilities will be calculated on the basis of the present SIS100 impedance model whose main components are the resistive wall, the kickers, and the broad-band contribution. The corresponding experience from the CERN injector complex will be used for comparisons.

WEPPR003	Longitudinal Dynamics of Intense Heavy-Ion Bunches in SIS-100	space-charge, ion, heavy-ion, beam-loading	2937
	M. Mehler, O. Boine-Frankenheim, O. Chorniy, O.K. Kester GSI, Darmstadt, Germany
	In the SIS-100 highest heavy-ion intensities have to be accelerated to deliver beam to the FAIR experiments. In the projected SIS-100 synchrotron the heavy ion bunches will be strongly affected by the longitudinal space charge force. Due to the limited RF bucket area all mechanisms which might cause longitudinal phase space dilution must be understood and controlled. Space charge effects, like the reduction in the RF voltage and the loss of Landau damping, have already been part of elaborate studies. It has been shown that cavity beam loading can deform the flattened bunch shape in the dual rf bucket. Among the different counter measures an inductive insert has been proposed in order to partially compensate the longitudinal space charge impedance. Optimized settings for the difference between the two rf phases in a dual rf bucket might be an option to reduce the effect of beam loading. In this contribution we will analyse the matched bunch distribution for SIS-100 parameters in single and dual rf buckets. Analytical and numerical studies of the interplay of longitudinal space charge, cavity beam loading and an inductive insert will be presented.

WEPPR054	Calculation of Coherent Wiggler Radiation using Eigenfunction Expansion Method	wiggler, radiation, damping, space-charge	3048
	D. Zhou, Y.H. Chin, K. Ohmi KEK, Ibaraki, Japan G.V. Stupakov SLAC, Menlo Park, California, USA
	An analytic method originated by Y. H. Chin* was extended to calculate the electromagnetic fields and the longitudinal impedance due to coherent wiggler radiation (CWR) in a rectangular chamber. The method used dyadic Green functions based on eigenfunction expansion method in electromagnetic theory and was rigorous for the case of straight chamber. We re-derived the theory and did find the full expressions for the longitudinal impedance of a wiggler with finite length. With shielding of chamber, the CWR impedance indicated resonant properties which were not seen in the theory for CWR in free space. * Y.H. Chin, LBL-29981, 1990.

WEPPR056	Reproduction of Ceramic Chamber Impedances with Electric and Magnetic Polarities of the Ceramics	dipole, vacuum, synchrotron, proton	3051
	Y. Shobuda, M. Kinsho JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	In proton synchrotron, ceramic chambers are used as vacuum chambers to avoid the effect on magnetic fields from eddy current excited by the magnetic fields. One of the standard methods of the derivation of the impedances of the ceramic chamber is the field matching technique. In this report, we reproduce the formulae of the ceramic chamber impedance in terms of electric and magnetic polarities. When the beam passes through the chamber, the impedance is mainly excited by the electric polarity of the ceramic.

WEPPR057	On the Single Bunch Longitudinal Collective Effects in BEPCII	electron, storage-ring, collective-effects, controls	3054
	D. Wang, Z. Duan, J. Gao, Y. Li, L. Wang, L. Wang, N. Wang IHEP, Beijing, People's Republic of China
	Funding: National Natural Science Foundation of China,project 11175192. In order to study the single bunch longitudinal instability in BEPCII, experiments on the bunch lengthening phenomenon were made. By analyzing the experimental data based on the Gao’s theory, the longitudinal loss factor for the bunch are obtained. Also, the total wake potential and the inductance of the machine are estimated.

WEPPR058	The Vertical Impedance Distribution Measurement Using Response Matrix Method at BEPCII BPR	kicker, feedback, injection, betatron	3057
	Y. Wei, D. Ji IHEP, Beijing, People's Republic of China
	Funding: Work supported by the Chinese National Foundation of Natural Sciences, contract 111100512108. In the last run of BEPCII, the single bunch current is limited to about 8mA by the beam-beam effect. To obtain the design luminosity, larger number of bunches are necessary. But higher total current may be limited by the collective effects. A good understanding of the transverse impedance distribution around the BEPCII storage ring is required. Response matrix method has been applied successfully in BEPCII to fit the quadrupole errors and restore the optics. We can also calculate the variation of betatron phase advance around the ring with different single bunch current using the response matrix method and the transverse impedance distribution is thus deduced. In this paper, the first measurement of transverse impedance in BEPCII is presented.

WEPPR061	Thresholds of Longitudinal Single Bunch Instability in Single and Double RF Systems in the CERN SPS	simulation, damping, synchrotron, emittance	3066
	T. Argyropoulos, T. Bohl, J. Esteban Muller, E.N. Shaposhnikova, H. Timko CERN, Geneva, Switzerland C.M. Bhat Fermilab, Batavia, USA
	A fourth harmonic RF system is used in the SPS as a Landau cavity, in order to stabilize the high intensity LHC proton beam against the longitudinal instabilities. Numerous studies proved that operating the two RF systems, through the whole cycle, in bunch shortening mode is necessary to provide a good quality beam at extraction to the LHC. Furthermore, it was shown that the choice of RF parameters as voltage amplitude ratio and relative phase are critical for the beam stability. This paper presents the results of single bunch measurements performed in single and double RF systems with various RF settings and compares them with the results of macroparticle simulations for the SPS impedance model.

WEPPR062	The Mode Matching Method Applied to Beam Coupling Impedance Calculations of Finite Length Devices	coupling, simulation, cavity, resonance	3069
	N. Biancacci, E. Métral, B. Salvant CERN, Geneva, Switzerland M. Migliorati, L. Palumbo URLS, Rome, Italy V.G. Vaccaro Naples University Federico II and INFN, Napoli, Italy
	The infinite length approximation is often used to simplify the calculation of the beam coupling impedance of accelerator elements. This is expected to be a reasonable assumption for devices whose length is greater than the transverse dimension but may be less accurate approximation for segmented devices. This contribution presents the study of the beam coupling impedance in the case of a finite length device: a cylindrical cavity loaded with a toroidal slab of material. In order to take into account the finite length we will decompose the field in the cavity and in the beam pipe into a set of orthonormal modes and apply the mode matching method to obtain the impedance. To validate our method, we will present comparisons between analytical formulas and 3D electromagnetic CST simulations as well as applications to the impedance of short beam pipe inserts, where the longitudinal and transverse dimensions are difficult to model in numerical simulations.

WEPPR064	Very Short Range Wake in Strongly Tapered Disk Loaded Waveguide Structures	simulation, wakefield, linac, FEL	3072
	A. Grudiev CERN, Geneva, Switzerland
	Electron bunches are very short, both in linear collider and in X-FEL projects. Furthermore, typical disk-loaded waveguide structures used for particle acceleration are tapered. For example in CLIC, in order to achieve high accelerating gradient, the structure is only 26 cells long, which results in strong tapering. In this paper, very short range wake is investigated in the regime where the number of cells needed to arrive at steady state is much larger than the number of cells in a single tapered structure. In this case the very short range wake is dominated by the wake from the smallest aperture. The results of an analytical model and numeric solutions are compared.

WEPPR065	Electromagnetic Simulations of the Impedance of the LHC Injection Protection Collimator	simulation, injection, vacuum, wakefield	3075
	B. Salvant, V. Baglin, B. Goddard, A. Grudiev, E. Métral, M.A. Timmins CERN, Geneva, Switzerland
	During the 2011 LHC run, significant vacuum and temperature increase were observed at the location of the LHC injection protection collimators (TDI) during the physics fills. Besides, measurements of the LHC transverse tune shift while changing the TDI gap showed that the impedance of the TDI was significantly higher than the LHC impedance model prediction based on multilayer infinite length theory. This contribution details the electromagnetic simulations performed with a full 3D model of the TDI to obtain both longitudinal and transverse impedances and their comparison with measured observables.

WEPPR069	Measurements and Simulations of Transverse Coupled-Bunch Instability Rise Times in the LHC	simulation, injection, octupole, feedback	3087
	N. Mounet, R. Alemany-Fernandez, W. Höfle, D. Jacquet, V. Kain, E. Métral, L. Ponce, S. Redaelli, G. Rumolo, R. Suykerbuyk, D. Valuch CERN, Geneva, Switzerland
	In the current configuration of the LHC, multibunch instabilities due to the beam-coupling impedance would be in principle a critical limitation if they were not damped by the transverse feedback. For the future operation of the machine, in particular at higher bunch intensities and/or higher number of bunches, one needs to make sure the coupled-bunch instability rise times are still manageable by the feedback system. Therefore, in May 2011 experiments were performed to measure those rise times and compare them with the results obtained from the LHC impedance model and the HEADTAIL wake fields simulation code. At injection energy, agreement turns out to be very good, while a larger discrepancy appears at top energy.

WEPPR070	Beam Coupling Impedance Simulations of the LHC TCTP Collimators	simulation, cavity, coupling, vacuum	3090
	H.A. Day, R.M. Jones UMAN, Manchester, United Kingdom F. Caspers, A. Dallocchio, L. Gentini, A. Grudiev, E. Métral, B. Salvant CERN, Geneva, Switzerland
	As part of an upgrade to the LHC collimation system, 8 TCTP and 1 TCSG collimators are proposed to replace existing collimators in the collimation system. In an effort to review all equipment placed in the accelerator complex for potential side effects due to collective effects and beam-equipment interactions, beam coupling impedance simulations are carried out in both the time-domain and frequency-domain of the full TCTP design. Particular attention is paid to trapped modes that may induce beam instabilities and beam-induced heating due to cavity modes of the device.

WEPPR071	Evaluation of the Beam Coupling Impedance of New Beam Screen Designs for the LHC Injection Kicker Magnets	kicker, coupling, simulation, injection	3093
	H.A. Day, R.M. Jones UMAN, Manchester, United Kingdom M.J. Barnes, F. Caspers, H.A. Day, E. Métral, B. Salvant CERN, Geneva, Switzerland
	During the 2011 run of the LHC there was a measured temperature increase in the LHC Injection Kicker Magnets (LHC-MKI) during operation with 50ns bunch spacing. This was suspected to be due to increased beam-induced heating of the magnet due to beam impedance. Due to concerns about future heating with the increased total intensity to nominal and ultimate luminosities a review of the impedance reduction techniques within the magnet was required. A number of new beam screen designs are proposed and their impedance evaluated. Heating estimates are also given with a particular attention paid to future intensity upgrades to ultimate and HL-LHC parameters.

WEPPR073	Effects of an Asymmetric Chamber on the Beam Coupling Impedance	simulation, kicker, wakefield, synchrotron	3099
	C. Zannini, K.S.B. Li, G. Rumolo CERN, Geneva, Switzerland C. Zannini EPFL, Lausanne, Switzerland
	The wake function of an accelerator device appears to have a constant term if the geometry of the device is asymmetric or when the beam passes off axis in a symmetric geometry. Its contribution can be significant and has to be taken into account. In this paper a generalized definition of the impedance/wake is presented to take into account also this constant term. An example of a device where the constant term appears is analyzed. Moreover, the impact of a constant wake on the beam dynamics is discussed and illustrated by a HEADTAIL simulation.

WEPPR074	Effect of the TEM Mode on the Kicker Impedance	kicker, coupling, simulation, vacuum	3102
	C. Zannini, G. Rumolo, V.G. Vaccaro CERN, Geneva, Switzerland C. Zannini EPFL, Lausanne, Switzerland
	The kickers are major contributors to the CERN SPS beam coupling impedance. As such, they may represent a limitation to increasing the SPS bunch current in the frame of a luminosity upgrade of the LHC. The C-Magnet supports a transverse electromagnetic (TEM) mode due to the presence of two conductors. Due to the finite length of the structure this TEM mode affects the impedance below a certain frequency (when the penetration depth in the ferrite becomes comparable to the magnetic circuit length). A theoretical model was developed to take into account also the impedance contribution due to the TEM mode. The model is found to be in good agreement with CST 3D electromagnetic (EM) simulations. It allows for generic terminations in the longitudinal direction. An example of kicker is analyzed taking into account also the external cables.

WEPPR081	The Collective Effects of the Short Pulsed X-Ray (SPX) System in the Advanced Photon Source Upgrade	cavity, simulation, emittance, collective-effects	3117
	Y.-C. Chae, M. Borland ANL, Argonne, 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 Advanced Photon Source is a 7-GeV hard x-ray synchrotron light source. The APS Upgrade specifies a short-pulse x-ray (SPX) as well as additional beamlines delivering higher brightness and flux. In order to achieve this goal we plan to use S-band superconducting cavities. The performance of such a system based on the zero-current simulation is well established; here, we included the effect of wakefields generated by the SPX system. While the SPX system is off, we are interested in how much current we can store in the single bunch, because the SPX contributes a significant amount of broadband impedance to the ring. With the SPX system on, we are interested in how much vertical emittance will increase, which in turn will enlarge the x-ray pulse length. We report the results of both cases when the SPX system is installed in the ring for the APS Upgrade.

WEPPR082	The Collective Effects of Long Straight Sections (LSSs) in the Advanced Photon Source Upgrade	undulator, storage-ring, collective-effects, injection	3120
	Y.-C. Chae, L.H. Morrison ANL, Argonne, 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 Advanced Photon Source is a 7-GeV hard x-ray synchrotron light source. The APS Upgrade specifies additional beamlines delivering higher brightness and flux as well as for the short-pulse x-ray (SPX). In order to fulfill these demands we plan to provide long straight sections (LSS), for which the total length of the insertion devices is increased to 7.7m. The long straight section also helps in implementing the SPX scheme without removing insertion devices. However, the impedance of the LSS may reduce the single-bunch current of 16 mA per bunch delivered to the users during hybrid fill. We estimate the effect of LSS impedance on the bunched beam current and propose an impedance optimization of the undulator chamber with a small gap.

WEPPR083	New Sector 37 Chamber Design and Installation for High-Current Operation of the APS Storage Ring	vacuum, cavity, storage-ring, HOM	3123
	Y.-C. Chae, R. Bechtold, W. Berg, L. Erwin, M. Givens, J.E. Hoyt, L.H. Morrison, K.M. Schroeder, R. Soliday, J.B. Stevens, G.J. Waldschmidt ANL, Argonne, 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 Advanced Photon Source is a 7-GeV hard x-ray synchrotron light source consisting of 40 sectors. Sector 37 accommodates four radio-frequency cavities followed by a short straight section, which is set aside for the future installation of a diagnostic device. The 60-cm-long section of spool pieces can be isolated by two gate valves and has an independent vacuum pump. The spool pieces are normally under high vacuum condition when the total current is below 100 mA. However, at the higher current required for the APS Upgrade, rf heating causes an unacceptable rise in temperature. We analyzed this situation by wakefield simulation, which led to a new chamber design. Proper fabrication and careful installation with twelve thermocouples ensured a temperature rise under 40-50 degrees Celsius at 100 mA. A brief thermal analysis shows that the present observed temperature rise in the new chamber is mainly due to the resistive wall.

WEPPR086	Computed Wake Field Effects from Measured Surface Roughness in the Walls of the Cornell ERL	wakefield, vacuum, scattering, undulator	3132
	M.G. Billing, G.H. Hoffstaetter, C.E. Mayes, K.W. Smolenski, H.A. Williams CLASSE, Ithaca, New York, USA
	Funding: Work supported by the NSF ERL Phase 1B Cooperative Agreement (DMR-0807731) Wake fields arise from the discontinuities in a smooth vacuum chamber and will cause energy spread in the passing bunch. In an energy recovery linac (ERL), the spent bunches are decelerated before they are dumped to reuse the beam’s energy for the acceleration of new bunches. While the energy spread accumulated from wakes before deceleration is small compared to the beam’s energy after full acceleration, it becomes more important relatively as the beam’s energy decreases.* Thus, in an ERL wake fields can produce very significant energy spread in the beam as it is decelerated to the energy of the beam dump. We report on calculations of wake fields due to the roughness of the surface of the vacuum chamber walls as it affects the Cornell ERL design. These calculations include the effects from the measured roughness for real vacuum chamber wall surfaces. * M. Billing, “Effect of Wake Fields in an Energy Recovery Linac”, PAC’09, Vancouver, BC, Canada, 4-8 May 2009.

WEPPR093	Impedance Budget for Crab Cavity in MEIC Electron Ring	electron, cavity, collider, ion	3153
	S. Ahmed, G.A. Krafft, B.C. Yunn JLAB, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The Medium Energy Electron-Ion Collider (MEIC) at Jefferson Lab has been envisioned as a first stage high energy particle accelerator beyond the 12 GeV upgrade of CEBAF. The estimate of impedance budget is important from the view point of beam stability and matching with other accelerator components driving currents. The detailed study of impedance budget for electron ring has been performed by considering the current design parameters of the e-ring. A comprehensive picture of the calculations involved in this study has been illustrated in the paper.

WEPPR095	Radial Eigenmodes for a Toroidal Waveguide with Rectangular Cross Section	electron, resonance, wakefield, synchrotron	3159
	R. Li JLAB, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. In applying mode expansion to solve the CSR impedance for a section of toroidal vacuum chamber with rectangular cross section, we identify the eigenvalue problem for the radial eigenmodes which is different from that for cylindrical structures. In this paper, we present the general expressions of the radial eigenmodes, and discuss the properties of the eigenvalues on the basis of the Sturm-Liouville theory.

WEPPR098	Two Dimensional Impedance Analysis of Segmented IVU	vacuum, undulator, simulation, storage-ring	3168
	A. Blednykh, G. Bassi, J. Bengtsson, O.V. Chubar, C.A. Kitegi, T. Tanabe BNL, Upton, Long Island, New York, USA
	Funding: Work supported by DOE contract No: DE-AC02-98CH10886 Segmented Adaptive-Gap In-Vacuum Undulator (IVU) with variable magnetic gap along z-axis is considered as an alternative to the Constant Gap IVU (7mm gap) for the NSLS-II storage ring. The length of the Constant Gap IVU for a given minimum gap is limited by the beam stay clear aperture. With the new conceptual design of IVU the magnetic gap can be varied along z-axis and its minimum gap can be reduced down to 5.25mm in the center of the structure for the same stay clear aperture. Beam impedance becomes an important issue since the new design consists of several magnet gaps. Wakepotentials and impedances have been analyzed for a new type of IVU and the results compared with data for the reference geometry which is the Constant Gap IVU.

THYB03	Collective Effects in the LHC and its Injector Complex	emittance, luminosity, linac, injection	3218
	E. Métral CERN, Geneva, Switzerland
	Operation during 4-8 hours at a constant luminosity of five times the nominal one (with “leveling”) is required for the CERN HL-(High Luminosity)-LHC project to be able to reach integrated luminosities of ~ 250 fb-1 per year and ~ 3 ab-1 twelve years after the upgrade. This means that the potential peak luminosity should be at least two times larger than the leveled one, i.e. a factor more than ten compared to the nominal case is contemplated. Even though the LHC had a bold beginning, reaching one third of the nominal peak luminosity at the end of the 2011 run, a factor more than thirty remains to be gained, which will be achieved only if all the collective effects are deeply understood and mastered both in the LHC and its injectors. The observations made during the 2010-2011 runs are first reviewed and compared to predictions to try and identify possible bottlenecks. The lessons learned and the possible solutions and/or mitigation measures to implement in the HL-LHC and the LHC Injectors Upgrade (LIU) projects are then discussed.
	Slides THYB03 [34.295 MB]

THPPC003	Development of a Broad-band Magnetic Alloy Cavity at GSI	cavity, coupling, storage-ring, ion	3275
	T.S. Mohite, U. Ratzinger IAP, Frankfurt am Main, Germany R. Balß, P. Hülsmann GSI, Darmstadt, Germany
	FINEMET, a Magnetic Alloy material, is often used to build a broad-band cavity for an accelerator or a storage ring. A research on the broad-band FINEMET cavity is of prime importance not only for the present accelerator facility but also for the future storage rings and synchrotron in upcoming FAIR facility alongside the GSI, Darmstadt. In several measurements, high intensity rare-isotope beams, with lower life time, are demanded at injection energy in Experimental Storage Ring (ESR) at GSI. A longitudinal beam stacking of such beams by means of using a special barrier-bucket RF cavity is found appropriate to serve this purpose. Additionally, this cavity is supposed to provide the compressed bunches at lower energies for HITRAP, an ion-trap facility for experiments with highly charged ions, in FAIR. Several measurements are being performed, along with the theoretical analysis, to achieve the designed parameters for the planned barrier-bucket cavity. 60 FINEMET ring cores have been tested to confirm their designed electrical properties. Some of these ring cores are then loaded, in steps, in a test cavity, which will further be used as the barrier-bucket cavity for the ESR. C. Dimopoulou et al., JACoW Proceedings of COOL 2007, Bad Kreuznach, Germany

THPPC005	Design of Magnetic Alloy Resonant System (MARS) Cavity for J-PARC MR	cavity, beam-loading, acceleration, status	3278
	C. Ohmori, K. Hara, K. Hasegawa, M. Toda, M. Yoshii KEK, Ibaraki, Japan M. Nomura, A. Schnase, T. Shimada, F. Tamura, M. Yamamoto JAEA/J-PARC, Tokai-mura, Japan
	The Magnetic Alloy Resonant System (MARS) cavity is a new type of Magnetic Alloy (MA) cavity using an external energy storage system. It is proposed as a back-up system of the present J-PARC high-Q MA cavity using cut cores. MARS consists of un-cut core loaded wideband MA cavities combined with an energy storage system using high-impedance, FT3L, cut cores. The main cavities are water-cooled and already established at J-PARC RCS. The energy storage system will be relatively high-Q (>100) to be stable under heavy beam loading. It also has a higher impedance than the main cavity and is air-cooled. The design of this cavity system will be presented.

THPPC006	Status of the J-PARC Ring RF Systems	cavity, synchrotron, proton, beam-loading	3281
	M. Yoshii, E. Ezura, K. Hara, K. Hasegawa, C. Ohmori, A. Takagi, K. Takata, M. Toda KEK, Tokai, Ibaraki, Japan M. Nomura, A. Schnase, T. Shimada, F. Tamura, M. Yamamoto JAEA/J-PARC, Tokai-mura, Japan
	Due to the 11th march earthquakes, J-PARC was forced to stop operation. The restoration is following the schedule so that J-PARC is restarted in December. Before the earthquake, we had considerable success in the 400 kW equivalent proton beam in the RCS. Multi-harmonic RF feedforward was established, which contributes to the reduction of beam loss and stable acceleration in RCS. The MR synchrotron achieved stable 150 kW beam operation for the T2K experiment. This summer, we installed two new RF systems in MR. Eight RF systems in total allow a more stable beam acceleration and flexible bunch shape manipulation. Also, we prepare the RF feedforward to compensate beam loading in MR. To achieve a beam power in excess of 1 MW in MR, it is considered to double the MR repetition rate. We developed an annealing scheme for large magnetic alloy cores while inside a DC B-field that results in higher core impedance, and have succeeded in producing large FT3L cores in this summer. With such cores we can almost double the accelerating voltage without re-designing the existing RF sources. For the near future, we plan to replace the existing RF cavities with upgraded cavities using the FT3L cores.

THPPC012	Impedance Computation of Main Components in CSNS/RCS	cavity, simulation, extraction, vacuum	3299
	Y. Li, L. Huang, Z.P. Li, Y.D. Liu, N. Wang, S. Wang IHEP, Beijing, People's Republic of China
	The rapid cycling synchrotron (RCS) of the China spallation neutron source (CSNS) is a high intensity proton accelerator. The study on the coupling impedance in the ring plays an important role in the stability of the beam. The impedance of the main vacuum components in the RCS ring, such as RF cavities, bellows, ports of vacuum pumps, collimator etc, was calculated by using numerical methods. Meantime, RF shielding of bellows, collimators and ports of vacuum pumps are considered. The impact of the busbar configuration on RF cavities and beams was estimated by impedance calculation.

THPPC020	Accurate Measurement of Ferrite Garnets to be used for Fast-tuned Ferrite Loaded Cavities in the Range of 20-40 MHz	cavity, resonance, vacuum, dipole	3317
	C. Vollinger, F. Caspers CERN, Geneva, Switzerland
	For the implementation of ferrite-tuned cavities with perpendicular biased ferrites in the frequency range of 20 to 40 MHz, different types of ferrite garnets were evaluated in terms of their electromagnetic properties. We describe a precision measurement method applicable to small-sized ferrite samples of 1-square-inch surface and 2 mm thickness in the given frequency range. During measurement, these samples are exposed to varying magnetic bias fields of different orientations. Two different techniques for the determination of the real and the imaginary part of the permeability are required to achieve sufficiently accurate results. We present a detailed description of these methods as well as results obtained.

THPPC024	Design, Construction and Power Conditioning of the First C-band Test Accelerating Structure for SwissFEL	cavity, klystron, linac, vacuum	3329
	R. Zennaro, J. Alex, H. Blumer, M. Bopp, A. Citterio, T. Kleeb, L. Paly, J.-Y. Raguin Paul Scherrer Institut, Villigen, Switzerland
	The SwissFEL C-band linac will consist of 26 RF modules with a total acceleration voltage of 5.4 GV. Each module will be composed of a single 50 MW klystron and its solid-state modulator feeding a pulse compressor and four two-meter long accelerating structures. PSI has launched a vigorous R&D program of development of the accelerating structures including structure design, production and high-power RF tests. The baseline design is based on ultra-precise cup machining to avoid dimple tuning. The first test structure is a constant impedance structure composed of eleven double-rounded cups. We report here on the structure design, production, low-level RF measurements, high-power conditioning and breakdown analysis.

THPPC026	A Transverse Deflecting Cavity for the Measurement of Short Low Energy Bunches at EBTF	cavity, coupling, electron, simulation	3335
	G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom S.R. Buckley, P. Goudket, C. Hill, P.A. McIntosh, J.W. McKenzie, A.E. Wheelhouse STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	The Electron Beam Test Facility (EBTF) at Daresbury Laboratory will deliver low energy (5/6 MeV) short bunches (~40 fs) to a number of industrial experimental stations and for scientific research. In order to measure the longitudinal profile of the bunch an S-band transverse deflecting cavity will be inserted into the beamline. A transverse kick of around 5 MV is required hence a 9 cell design has been chosen. The design of the transverse deflecting cavity has been influence by the competing demands of high RF efficiency and minimising the unwanted transverse kick at the entrance and exit of the cavity which cause the electrons to be displaced while traversing the cavity. This has led to a shortened end cell structure design to minimise the kick applied at the entrance and exit to the cavity. In order to minimise the impact of the input coupler a dummy waveguide has been placed on the opposing side of the cavity to minimise the monopole component of the RF fields in the coupling cell. The coupler is located at the central cell of the cavity to avoid exciting the nearby modes. Tracking of the beam is performed in GPT including space charge, due to the low energy of the electrons.

THPPC027	Measurement of the Dynamic Response of the CERN DC Spark System and Preliminary Estimates of the Breakdown Turn-on Time	simulation, vacuum, cathode, radio-frequency	3338
	N.C. Shipman, R.M. Jones UMAN, Manchester, United Kingdom S. Calatroni, W. Wuensch CERN, Geneva, Switzerland
	The new High Rep Rate (HRR) CERN DC Spark System has been used to investigate the current and voltage time structure of a breakdown. Simulations indicate that vacuum breakdowns develop on ns timescales or even less. An experimental benchmark for this timescale is critical for comparison to simulations. The fast rise time of breakdown may provide some explanation of the particularly high gradients achieved by low group velocity, and narrow bandwidth, accelerating structures such as the T18 and T24. Voltage and current measurements made with the previous system indicated that the transient responses measured were dominated by the inherent capacitances and inductances of the DC spark system itself. The bandwidth limitations of the HRR system are far less severe allowing rise times of around 12ns to be measured.

THPPC039	Study of RF Breakdown in Normal Conducting Cryogenic Structure	cryogenics, klystron, lattice, accelerating-gradient	3368
	V.A. Dolgashev, J.R. Lewandowski, D.W. Martin, S.G. Tantawi, S.P. Weathersby, A.D. Yeremian SLAC, Menlo Park, California, USA
	Funding: *Work supported by DoE, Contract No. DE-AC02-76SF00515. RF Breakdown experiments on short accelerating structures at SLAC have shown that properties of rf breakdown probability are reproducible for structures of the same geometry. At a given rf power and pulse shape, the rf breakdown triggers continuously and independently at a constant average rate. Hypotheses describing the properties of the rf breakdown probabilities involve defects of metal crystal lattices that move under forces caused by rf electric and magnetic fields. The dynamics of the crystal defects depend on the temperature of the structure. To study the dependence we designed and built an experimental setup that includes a cryogenically cooled single-cell, standing-wave accelerating structure. This cavity will be high power tested at the SLAC Accelerator Structure Test Area (ASTA).

THPPC044	Development of the Dual Slot Resonance Linac	linac, coupling, cavity, resonance	3383
	N. Barov, X. Chang, R.H. Miller, D.J. Newsham Far-Tech, Inc., San Diego, California, USA
	Funding: Work supported by DOE Grant DE-FG02-08ER85034 We report the status of the Dual Slot Resonance (DSR) linac under development by FAR-TECH. In this linac type, cell-to-cell coupling is provided by a pair of close-coupled resonant slots, resulting in very strong coupling vs. a typical side-coupled linac design, as well as a much more compact radial space requirement. We discuss the status of the structure fabrication, the RF distribution system, and installation and testing at the UCLA Pegasus facility.

THPPC050	Effects of Grids in Drift Tubes	beam-transport, proton, linac, DTL	3401
	M. Okamura BNL, Upton, Long Island, New York, USA H. Yamauchi Time Corporation, Hiroshima, Japan
	In 2011, we upgraded a 200 MHz buncher in the proton injector for the AGS – RHIC complex. In the buncher we installed four grids made of tungsten to improve a transit time factor of the buncher. The grid installed drift tubes have 32 mm of inner diameter and the each grid consists of four quadrants. The quadrants were cut out precisely from 1mm thick tungsten plates by a CNC wire cutting EDM. In the conference the 3D electric field design and performance of the grid will be discussed. Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.

THPPC056	Development of 12kW RF Power Supply for CYCHU-10 Cyclotron	power-supply, cavity, cyclotron, feedback	3416
	D. Li, T. Hu, J. Huang, K.F. Liu, B. Qin, J. Yang, L. Yang Huazhong University of Science and Technology (HUST), Wuhan, People's Republic of China
	One 12kW RF power supply has been developed for CYCHU-10, which is a 10 MeV cyclotron developed in Huazhong University of Science and Technology (HUST). A high performance DDS chip AD9859 is used to synthesize RF signal in this power supply, which is easy to change the output frequency. The centre frequency is 101MHz, and the frequency bandwidth is more than 1MHz. The RF power supply could operate in fine searching mode, coarse searching mode, tracking mode, and so on. It could search the resonant frequency of cavity with the frequency control loop. The final stage amplifier using a triode 3CW20,000H7 operates in grounded grid configuration, which is stable and reliable. The performance test using a 50Ω resistor load has finished, and major results are shown in this paper.

THPPC074	High Frequency High Power RF Generation using a Relativistic Electron Beam	wakefield, electron, extraction, damping	3458
	C.-J. Jing, S.P. Antipov, A. Kanareykin, P. Schoessow Euclid TechLabs, LLC, Solon, Ohio, USA H. Chen, Y. Yang TUB, Beijing, People's Republic of China M.E. Conde, W. Gai, J.G. Power ANL, Argonne, USA
	High frequency, high power rf sources are required for many applications. Benefiting from the ~10 GW beam power provided by the high current linac at the Argonne Wakefield Accelerator facility, we propose to develop a series of high power rf sources based on the extraction of coherent Cherenkov radiation from the relativistic electron beam. The frequencies cover from C-band up to W-band with different structures. Simulations show that ~1 GW 20 ns rf pulse can be generated for an 11.7 GHz structure, ~400 MW for a 26 GHz structure, and ~14 MW for a 91 GHz structure.

THPPD017	Mu2e AC Dipole 300 kHz and 5.1 MHz Tests and Comparison of Nickel-Zinc Ferrites	pick-up, dipole, proton, 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.

THPPD052	Operation and Current Status of Injection, Extraction, Kicker Magnet and the Power Supply for J-PARC 3 GeV RCS	kicker, extraction, power-supply, injection	3629
	M. Watanabe, N. Hayashi, Y. Shobuda, K. Suganuma, T. Takayanagi, T. Togashi JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan T. Toyama J-PARC, KEK & JAEA, Ibaraki-ken, Japan
	3-GeV RCS (Rapid Cycling Synchrotron) at High Intensity Proton Accelerator Facility (J-PARC) have started for 24-hour operation with repetition rate of 25 pps in February, 2009. Kicker power supply system which uses thyratrons switches is used for extraction of the proton beam. There were many troubles for unstable operation of the thyratrons just after beam commissioning started. Recently, however, the operations were improved and the failure rate was reduced to approximately 0.1 % in October 2010. After the earthquake on March 11, 2011, the injection and extraction magnets, power supplies, the cables and the bus-duct have been checked. Insulation resistance test, impedance test were performed. Reflected wave measurements by the low-level and high-power pulse of the kicker magnets were performed. Visual checks by a fiber endoscope were also performed in the kicker magnets. The results of the measurements and the checks were all not in the problem.

THPPD058	Reduction of Conductive EMI Noise Resulted from the Commercial Power Supply	power-supply, high-voltage, vacuum, coupling	3644
	C.S. Chen, C.K. Chan, J.-C. Chang, Y.L. Chu, K.H. Hsu, C.Y. Kuo, Y.-H. Liu, C.S. Yang NSRRC, Hsinchu, Taiwan
	Almost every electronic equipment must be connected to power system. Because of the complexity of power lines, the reduction of conductive electro-magnetic interference (C-EMI) plays an important role in precise measurements. In this paper, a line impedance stabilization network (LISN) was built up to get the spectrum from power lines. After several measurements by some commercial power supplies, it is found that some of these power supplies induce effectively C-EMI into power lines, even if a passive filter is bound in power line. These noises may influence numerous equipments in a local area near the sources. Therefore, how to choose a suitable filter is a decisive factor to reduce the magnitude of C-EMI.

THPPD061	Optimal Design for Resonant Power Transformer	power-supply, controls, factory	3650
	C.-Y. Liu, D.-G. Huang, J.C. Huang NSRRC, Hsinchu, Taiwan
	The energy and dc to dc conversion of the resonant transformer are required to achieve optimal design and working condition of the resonant region frequency. To meet this requirement, the core loss will be checked first by data book for calculation. Using a reliable precise instrument is needed to scan the resonant cure of the resonant transformer as we designed the resonant cure. We calculated the conduction loss in second design step. We design a resonant transformer which the conduction loss equal core loss does not meet optima design, because the core loss is very high when the transformer works in resonant frequency. Thus, we only reduce the conduction loss is optima design aspect.

THPPD072	Performance Optimization of the Stacked-Blumlein	simulation, coupling, high-voltage, induction	3680
	L.W. Zhang, J. Li, W.D. Wang CAEP/IFP, Mainyang, Sichuan, People's Republic of China Y. Li CAEP, Mainyang, Sichuan, People's Republic of China
	Funding: This work was supported by the National Natural Science Foundation of China (11035004) For the applications of the Dielectric Wall Accelerator (DWA), the stacked Blumlein pulse generator comprised of parallel-plate transmission lines is being developed. The peak output voltage of the stacked Blumlein will be much lower than expected due to the parasitic coupling among the individual pulse forming lines of the Blumlein stack. The finite difference time domain method is used to model the stacked Blumlein structure and determine the outputs. We present the optimization of a 20-Blumleins-stack in this paper. The results for different structures are discussed.

THPPP003	Coupling Impedance Study of the New Injection Kicker Magnets of the JPARC Main Ring	kicker, coupling, simulation, vacuum	3725
	K. Fan, S. Fukuoka, H. Matsumoto, T. Sugimoto, T. Toyama KEK, Ibaraki, Japan
	New lumped inductance kicker magnets have been developed for the J-PARC main ring injection system. For high intensity beam operation, the beam coupling impedance of the new kickers is a critical issue, which not only generates significant heating inside the ferrite impairing the performance of the kickers, but also drives beam instability. Numerical simulations based on CST studio have been studied during the design stage to optimize the kicker structure. Impedance measurements based on wire method have been carried out. The measured results agree well with the simulation results.

THPPP004	Design and Test of Injection Kicker Magnets for the JPARC Main Ring	kicker, coupling, injection, proton	3728
	K. Fan, S. Fukuoka, K. Ishii, H. Matsumoto, H. Someya, T. Sugimoto, T. Toyama KEK, Ibaraki, Japan
	The present injection kicker magnets of the JPARC main ring consists of three transmission type kickers. To overcome the operational problems, four lumped inductance kicker magnets have been developed for the simplicity and the high reliability. The tight requirements on the rise and fall time create difficulties for the new design. Magnetic field measurements, coupling impedance measurements and have been carried out. The measurement results show that the new kicker magnets can satisfy the requirements of beam injection.

THPPP011	Studies on a Wideband, Solid-state Driven RF System for the CERN PS Booster	feedback, cavity, acceleration, booster	3749
	M.M. Paoluzzi, L. Arnaudon, N. Chritin, M. Haase, K. Hanke, B. Mikulec, T. Tardy CERN, Geneva, Switzerland
	In the framework of the LHC Injectors Upgrade project (LIU) the PS Booster (PSB) RF systems will undergo in depth consolidation and upgrade programs. The aim is increasing the extraction energy to 2 GeV and allowing reliable operations during next 25 years. Substantial improvements could come from the replacement of the existing narrowband, tuned systems covering the h=1 and h=2 frequency ranges (0.6 / 1.8 MHz and 1.2 / 3.6 MHz respectively) with wideband (0.5 / 4 MHz) Finemet® loaded cavities. The new system would be modular, allow multi-harmonic operation, use solid-state power stages and include fast RF feedback to compensate beam loading effects to some extent. A prove of principle system providing ≈3.0 kV accelerating voltage has been designed, constructed and installed in one of the PSB rings. This paper provides details on the design and measurements as well as information on the project status.

THPPP034	Optimization of a CW RFQ Prototype	rfq, simulation, linac, DTL	3809
	U. Bartz, J. Gerbig, H.C. Lenz, A. Schempp IAP, Frankfurt am Main, Germany
	A short RFQ prototype was built for RF-tests of high power RFQ structures. We studied thermal effects to determine critical points of the design. HF-simulations with CST Microwave Studio and measurements were done. The cw-tests with 20 kW/m RF-power and simulations of thermal effects with ALGOR were finished successfully. The optimization of some details of the RF design is on focus now. Results and the status of the project will be presented

THPPP039	Simulations for a Buncher-Cavity at GSI	simulation, cavity, resonance, induction	3821
	P.L. Till, B. Koubek, A. Schempp, J.S. Schmidt IAP, Frankfurt am Main, Germany
	Buncher cavities can be used to bunch and rebunch or re-accelerate particle beams. A special form of these buncher cavities is a spiral structure. one of its main features is the easy adjustable frequency. A two-gap structure for the GSI has been simulated and will be build at the University of Frankfurt. This structure shall replace an existing buncher at GSI. It is designed to an frequency of 36 MHz. Also general simulations of spiral bunchers will be presented.

THPPP069	Double-Gap Rebuncher Cavity Design of SNS MEBT	cavity, DTL, simulation, linac	3898
	K.R. Shin ORNL RAD, Oak Ridge, Tennessee, USA A.E. Fathy University of Tennessee, Knoxville, Tennessee, USA Y.W. Kang ORNL, Oak Ridge, Tennessee, USA
	A double-gap rebuncher cavity has been studied through design and analysis with computer simulations. This cavity shape is a two cell abridged form of drift tube linac (DTL), instead an omega form of existing single gap elliptical cavity. The cavity operates in TM010 mode, likewise the commonly used single-gap cavities in some medium energy beam transport (MEBT) line of proton accelerators. The new cavity is more power efficient even with slightly lower Q factor because of utilization of two interactive gaps. The breakdown field can be lowered with adjustment of gap and tube length ratio. Electromagnetic, beam envelope, and thermal simulations are presented with comparison to the properties of the conventional elliptical cavity.

THPPP081	Status of Injection Energy Upgrade for J-PARC RCS	power-supply, injection, quadrupole, kicker	3921
	N. Hayashi, H. Harada, H. Hotchi, J. Kamiya, P.K. Saha, Y. Shobuda, T. Takayanagi, N. Tani, M. Watanabe, Y. Watanabe, K. Yamamoto, M. Yamamoto, Y. Yamazaki, M. Yoshimoto JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan T. Toyama J-PARC, KEK & JAEA, Ibaraki-ken, Japan
	The injection energy upgrade for J-PARC RCS is planed in 2013. This includes the power supplies upgrade of injection pulsed magnet system, suppression for leakage field, quadrupole correction magnets, reduction of kicker impedance effect and improvements of beam diagnostic instrumentation. The paper reports the present status.

THPPP082	RF Feedforward System for Beam Loading Compensation in the J-PARC MR	cavity, injection, beam-loading, proton	3924
	F. Tamura, M. Nomura, A. Schnase, T. Shimada, M. Yamamoto JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan K. Hara, K. Hasegawa, C. Ohmori, M. Yoshii KEK, Tokai, Ibaraki, Japan M. Toda KEK/JAEA, Ibaraki-Ken, Japan
	For acceleration of high intensity proton beams in the J-PARC MR, beam loading compensation is important. In the MA-loaded RF cavity in the MR, which has a Q-value in the order of 20, the wake voltage consists of the accelerating harmonic (h=9) and the neighbor harmonics (h=8, 10). We employ the RF feedforward method for the beam loading compensation, like in the J-PARC RCS, in which the impedance seen by the beam is greatly reduced by the feedforward. The full-digital feedforward system developed for the MR has a similar architecture to that of the RCS. The system compensates the beam loading of the important three harmonics (h=8, 9, 10). We present the structure of the RF feedforward system. Also, we report the preliminary results of the beam tests.

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Other Keywords

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MOOBB03

An Alternative 1D Model for CSR with Chamber Shielding

shielding, radiation, vacuum, synchrotron

52

D. Zhou
KEK, Ibaraki, Japan

An alternative 1D model for modeling the longitudinal coherent synchrotron radiation (CSR) impedance is proposed. The code CSRZ* is used to calculate the CSR impedance with rectangular chamber shielding. Along the beam orbit, which may be formed by multi bends interleaved with drifts, the vacuum chamber is sliced into a series of segments. The low-frequency CSR impedance for each segment, in this case chamber shielding is significant, is obtained by numerical calculations. The high-frequency CSR impedance, in this case chamber shielding is negligible, is estimated by an analytical model**. The wake kick at each segment is computed via inverse Fourier transform of the impedance convolved the the beam spectrum. The most attractive merit of the method for CSR modeling lies in taking into account the realistic chamber shielding.
* D. Zhou, et al., To be published in Jpn. J. Appl. Phys.
** M. Borland, Phys. Rev. ST Accel. Beams 4, 070701 (2001).

Slides MOOBB03 [1.856 MB]

MOEPPB007

Studies of eRHIC Coherent Instabilities

proton, simulation, betatron, space-charge

91

G. Wang, M. Blaskiewicz
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.
In the presence of an effective coherent electron cooling, the rms ion bunch length in eRHIC will be kept at 8.4cm, which is about a factor of 3 shorter than the current RHIC rms bunch length. Together with a factor of 2 increase in bunch intensity, coherent instabilities could be a potential limitation for achieving desired machine performance. In this study, we use the tracking code TRANFT to find thresholds and growth rates for various single bunch and coupled bunch instabilities with linear chromaticity and amplitude dependent tune shift taken into account. Based on the simulation results, requirements of machine parameters such as rf voltage, linear chromaticity, and octupole strength are specified to avoid these instabilities.

MOPPC059

Various Approaches to Electromagnetic Field Simulations for RF Cavities

simulation, cavity, electromagnetic-fields, HOM

268

C. Liu, W. Ackermann, W.F.O. Müller, T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany

Funding: Work supported by BMBF under contract 05H09RD5.
The Superconducting Proton Linac (SPL) cavity is mainly designed and conducted by CERN. It is a part of the planned injector upgrade of the Large Hadron Collider (LHC). The SPL cavity is used to accelerate the ion beam from 160 MeV to 5GeV and served as a driver for neutrino facilities and radioactive beam facilities. In the Superconducting Proton Linac (SPL) cavity, it is very important to calculate the eigenmodes precisely, because many higher-order modes (HOMs) can lead to particle beam instabilities. We used and compared three different ways to calculate the eigenmodes in the SPL cavity: field simulation with hexahedron mesh in frequency domain, field simulation with hexahedron mesh in time domain, and field simulation with tetrahedral mesh and higher order curvilinear elements. In this paper the principles of the three numerical methods will be introduced and compared. Finally the calculated results will be presented.

MOPPC067

Design and Construction of Inductive BPM

simulation, electron, vacuum, resonance

289

M.Sh. Shafiee, E.E. Ebrahimibasabi, S.A.H. Feghhi, N. Goudarzi
sbu, Tehran, Iran
M. Jafarzadeh
ILSF, Tehran, Iran

To have a controllable Electron machine, that is required to be able to control beam orbits by knowing the beam position. The basic requirement for detecting the position of electron is calibrating and testing the BPMs. For this purpose wire method is used. Since we hadn't access to accelerator, for having experience at beam diagnostic we used this method for testing our constructed inductive BPM including 4 cm square poly ethylene core with 15 turns coil in each side. In this case study that was tested by a pulsed current (as an electron bunch) produced by a pulse generator. At first Tektronix 2235A oscilloscope was calibrated and used to measure the induced voltage of each coils, then by using of microcontroller, protocol RS232 and GUI induced voltages were read. The electrical center was measured with respect to the mechanical center and wire position was detected with 1mm Resolution. Conversion between the BPM signals and the actual wire position were done. Results were compared and presented.

MOPPC089

CUDA Kernel Design for GPU-based Beam Dynamics Simulations

simulation, acceleration, space-charge, linac

343

I.V. Pogorelov, K.M. Amyx, J. Balasalle, J. James
Tech-X, Boulder, Colorado, USA
M. Borland, R. Soliday, Y. Wang
ANL, Argonne, USA

Funding: Work supported by the US DOE Office of Science, Office of Basic Energy Sciences under grant number DE-SC0004585.
Efficient implementation of general-purpose particle tracking on GPUs can result in significant performance benefits to large-scale particle tracking and tracking-based accelerator optimization simulations. We present our work on CUDA kernels for transfer maps of single-particle-dynamics and collective-effects beamline elements, to be incorporated into a GPU-accelerated version of the ANL's accelerator code ELEGANT. In particular, we discuss techniques for efficient utilization of the device shared, cache, and local memory in the design of single-particle and collective-effects kernels. We also discuss the use of data-parallel and hardware-assisted approaches (segmented scan and atomic updates) for resolving memory contention issues at the charge deposition stage of algorithms for modeling collective effects. We present and discuss performance results for the CUDA kernels developed and optimized as part of this project.

MOPPD077

Studies for an Alternative LHC Non-Linear Collimation System

collimation, proton, sextupole, betatron

544

L. Lari, R.W. Assmann, V. Boccone, F. Cerutti, A. Mereghetti, R. Versaci, V. Vlachoudis
CERN, Geneva, Switzerland
A. Faus-Golfe, L. Lari, J. Resta-López
IFIC, Valencia, Spain

Funding: This work has been carried out through of the European Coordination for Accelerator Research and Development (EuCARD), co-sponsored by EU 7th Framework Program.
A LHC nonlinear Betatron cleaning collimation system would allow larger gap for the mechanical jaws, reducing as a consequence the collimator-induced impedance, which may limit the LHC beam intensity. In this paper, the performance of the proposed system is analyzed in terms of beam losses distribution around the LHC ring and cleaning efficiency in stable physics condition at 7TeV for Beam1. Moreover, the energy deposition distribution on the machine elements is compared to the present LHC Betatron cleaning collimation system in the Point 7 Insertion Region (IR).

MOPPP040

Resistive Wall Heating of the Undulator in High Repetition Rate FELs

undulator, electron, wakefield, FEL

652

J. Qiang, J.N. Corlett, P. Emma
LBNL, Berkeley, California, USA
J. Wu
SLAC, Menlo Park, California, USA

Funding: Work supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
In next generation high repetition rate FELs, beam energy loss due to resistive wall wakefields will produce significant amount of heat. The heat load for a superconducting undulator (operating at low temperature), must be removed and will be expensive to remove. In this paper, we study this effect in an undulator proposed for a Next Generation Light Source (NGLS) at LBNL. We benchmark our calculations with measurements at the LCLS and carry out detailed parameter studies using beam from a start-to-end simulation. Our preliminary results suggest that the heat load in the undulator is about 2 W/m with an aperture size of 6 mm for nominal NGLS design parameters.

MOPPR006

Surface Waves for Testing of Beam Instrumentation

instrumentation, resonance, induction, electromagnetic-fields

780

F. Stulle, J.F. Bergoz
BERGOZ Instrumentation, Saint Genis Pouilly, France

The fundamental TM wave can be guided as a surface wave along a single dielectric coated wire. Such a setup is known as a Goubau line. Close to the wire the TM wave resembles closely the radial electric and azimuthal magnetic fields of a charged particle beam moving in an accelerator. Hence, it can be used to test beam instrumentation in the workshop. We introduce the principle, discuss benefits, and compare measurements of a beam instrumentation device performed with a Goubau line to measurements performed with a standard bench testing setup.

MOPPR023

Stripline BPM with Integral In-Vacuo Termination

pick-up, 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.

MOPPR042

Characterization Tests of a Stripline Beam Position Monitor for the CLIC Drive Beam

quadrupole, extraction, simulation, feedback

873

A. Benot-Morell, A. Faus-Golfe, J.J. García-Garrigós
IFIC, Valencia, Spain
A. Benot-Morell, L. Søby
CERN, Geneva, Switzerland
J.M. Nappa, J. Tassan-Viol, S. Vilalte
IN2P3-LAPP, Annecy-le-Vieux, France
S.R. Smith
SLAC, Menlo Park, California, USA

Funding: FPA2010-21456-C02-01, SEIC-2010-00028
A prototype of a stripline Beam Position Monitor (BPM) with its associated readout electronics has been developed at CERN in collaboration with SLAC, LAPP and IFIC. In this paper, the design and simulations of the BPM with the analog readout chain and the BPM test bench are described, and the results of the first characterization tests are presented. The position resolution and accuracy parameters are expected to be below 2μm and 20μm respectively for a beam with a bunching frequency of 12GHz, an average current of 101A and a machine repetition rate of 50Hz.

TUOBC02

Small-Beta Collimation at SuperKEKB to Stop Beam-Gas Scattered Particles and to Avoid Transverse Mode Coupling Instability

interaction-region, scattering, coupling, simulation

1104

H. Nakayama, Y. Funakoshi, K. Kanazawa, K. Ohmi, Y. Ohnishi, Y. Suetsugu
KEK, Tsukuba, Japan
H. Nakano
Tohoku University, Graduate School of Science, Sendai, Japan

At SuperKEKB, beam particles which are Coulomb-scattered by the residual gas molecular change direction and will be eventually lost by hitting beam pipe inner wall. Due to large vertical beta function and small beam pipe radius just before IP, most of Coulomb-scattered particles are lost there and are very dangerous for the Belle-II detector. To stop such particles before the IP, vertical collimators are installed in the ring. However, such vertical collimators should be placed very close (few mm) to the beam and therefore induce transverse mode coupling instability. To avoid beam instability and achieve collimation at the same time, we need to install vertical collimators where vertical beta function is SMALL, since maximum collimator width determined by aperture condition is proportional to β^1/2, and minimum collimator width determined by instability is proportional to β^2/3. We present our strategy to stop beam-gas scattered particles and simulated loss rate in the interaction region. We will also show dedicated vertical collimator design to achieve less instability.

Slides TUOBC02 [2.196 MB]

TUPPC034

Preparation of SLS for IBS Measurements

emittance, diagnostics, optics, radiation

1233

N. Milas, M. Böge, A. Streun
PSI, Villigen, Switzerland
M. Aiba, A. Lüdeke, A. Saa Hernandez
Paul Scherrer Institut, Villigen, Switzerland
F. Antoniou, Y. Papaphilippou
CERN, Geneva, Switzerland

It is planned to use the SLS for testing damping ring issues related to linear colliders. One aspect is the study of Intra-Beam Scattering (IBS) effects, which are a limiting factor for ultra-low emittance rings. In this paper we present the setup and characterization of a new mode of operation in which the SLS runs at lower energy (1.57 GeV) with a natural emittance of 2.4 nm rad. This is much smaller than that at the nominal energy (2.41 GeV) and should make IBS effects more easily visible. In order to be able to observe IBS a careful setup is required: Optics measurement and correction as well as measurements of the bunch natural energy spread and the onset of turbulent bunch lengthening. Also, a detailed discussion on the available diagnostics and their limitations are shown and finally some preliminary results of beam emittance measurements, in all three planes, as a function of single bunch current are presented.

TUPPD015

Optimization of Muon Capturing in g-2 Ring

kicker, betatron, vacuum, closed-orbit

1440

A.A. Mikhailichenko
CLASSE, Ithaca, New York, USA
D.L. Rubin
Cornell University, Ithaca, New York, USA

We describe optimization procedure for muons capturing in g-2 ring under reconstruction at FERMILAB. This procedure includes both the beam dynamics consideration and HV inflector geometry and technique. Some engineering aspects of HV inflector and pulser are presented in detail.

TUPPP031

Modelling the Steady-state CSR Emission in Low Alpha Mode at the Diamond Storage Ring

wakefield, electron, factory, bunching

1677

I.P.S. Martin, C.A. Thomas
Diamond, Oxfordshire, United Kingdom
R. Bartolini
JAI, Oxford, United Kingdom

The CSR emitted by short electron bunches can be of a stable or bursting nature, with transition between the two states characterised by a threshold current that depends on various machine parameters. Key to understanding this process is to develop an effective model that describes the way the electron bunch interacts with impedance sources such as the CSR wakefield and surrounding vacuum chamber. In this paper we present the latest results of modelling the equilibrium distribution calculated using the Haissinski equation driven by different impedance models. The bunch lengthening with current, bunch profiles and CSR form factors derived from this model are compared to measured data for both positive and negative momentum compaction factor. Comparisons of the measured bursting thresholds to theoretical predictions are also discussed.

TUPPP038

Electron Beam Collimation for the Next Generation Light Source

collimation, undulator, gun, linac

1695

C. Steier, P. Emma, H. Nishimura, C. F. Papadopoulos, F. Sannibale
LBNL, Berkeley, California, USA

Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
The Next Generation Light Source will deliver high (MHz) repetition rate electron beams to an array of free electron lasers. Because of the significant average current in such a facility, effective beam collimation is extremely important to minimize radiation damage to undulators, prevent quenches of superconducting cavities, limit dose rates outside of the accelerator tunnel and prevent equipment damage. This paper describes the conceptual design of the collimator system, as well as the results of simulations to test its effectiveness.

TUPPP042

Passive Landau Cavity Effects in the NSLS-II Storage Ring

cavity, storage-ring, simulation, wakefield

1701

G. Bassi, A. Blednykh, S. Krinsky
BNL, Upton, Long Island, New York, USA

Funding: Work supported by DOE contract No: DE-AC02-98CH10886.
In new 3rd generation synchrotron light sources with small transverse emittance, higher harmonic cavities (Landau cavities) are installed for bunch lengthening to increase the Touschek lifetime, and to provide Landau damping for beam stability. In this contribution we study the effects of passive Landau cavities in the NSLS-II storage ring for arbitrary fill-patterns with the OASIS tracking code.

TUPPP043

Analysis of Coupled Bunch Instabilities in the NSLS-II Storage Ring with a 7-cell PETRA-III RF Structure

HOM, cavity, damping, simulation

1704

G. Bassi, A. Blednykh, S. Krinsky, J. Rose
BNL, Upton, New York, USA

Funding: Work supported by DOE contract No: DE-AC02-98CH10886.
A 7-cell PETRA-III cavity is considered to be installed for the commissioning Phase 1 in the NSLS-II storage ring at an average current of 25mA. In this contribution we study transverse and longitudinal coupled-bunch instabilities that may be driven by the higher order modes of the 7-cell PETRA-III cavity. The instability thresholds are calculated with the OASIS tracking code, with parameters of the bare lattice (no damping wigglers and Landau cavities). We study multibunch configurations with arbitrary fill-patterns and discuss the slow head-tail effect at positive chromaticity to increase the transverse instability thresholds.

TUPPR015

Choke-Mode Damped Structure Design for the CLIC Main Linac

wakefield, damping, simulation, dipole

1840

H. Zha, H. Chen, W.-H. Huang, C.-X. Tang
TUB, Beijing, People's Republic of China
A. Grudiev, J. Shi, W. Wuensch
CERN, Geneva, Switzerland

Choke-mode damped accelerating structures are being studied as an alternative to the CLIC waveguide damped baseline structure. Choke-mode structures hold the potential for much lower pulsed surface heating and reduced cost since no milling is required. We propose a new choke geometry which has significant suppression of higher order dipoles. By impedance matching and detuning of the first dipole pass-band, the wakefield suppression is comparable to the baseline design with waveguide damping. A fully featured choke mode structure with the same accelerating gradient profile and filling time as the nominal CLIC design has been designed. It has the potential to replace the waveguide damped design without changing any of the machine layout or the beam parameters.

TUPPR016

Final Cross Section Design of the Stripline Kicker for the CLIC Damping Rings

damping, kicker, extraction, wakefield

1843

C. Belver-Aguilar, A. Faus-Golfe
IFIC, Valencia, Spain
M.J. Barnes
CERN, Geneva, Switzerland
F. Toral
CIEMAT, Madrid, Spain

Funding: IDC-20101074 and FPA2010-21456-C02-01
The CLIC design relies on the presence of Pre-Damping Rings (PDR) and Damping Rings (DR) to achieve, through synchrotron radiation, the very low emittance needed to fulfill the luminosity requirements. Kicker systems are required to inject and extract the beam from the Pre-Damping and Damping Rings. In order to achieve low beam coupling impedance and reasonable broadband impedance matching to the electrical circuit, striplines have been chosen for the kicker elements. In this paper the final design for the DR kicker is presented, including an optimization of the geometric parameters to achieve the requirements for both characteristic impedance and field homogeneity. In addition, a sensitivity analysis of characteristic impedance and field homogeneity to geometric parameters is reported.

TUPPR018

Beam Impedance Study of the Stripline Kicker for the CLIC Damping Ring

coupling, kicker, damping, simulation

1849

C. Belver-Aguilar, A. Faus-Golfe
IFIC, Valencia, Spain
M.J. Barnes
CERN, Geneva, Switzerland
I. Podadera, F. Toral
CIEMAT, Madrid, Spain

Funding: FPA2010-21456-C02-01
CLIC Pre-Damping (PDR) and Damping Rings (DR) are required for reducing the emittance of the electron and positron beams before being accelerated in the main linac. Several stripline kicker systems are used to inject and extract the beam from the PDR and DR. Wakefields produced by the charged particles when passing through the aperture of the stripline kickers may become an important source of emittance growth; for this reason, simulations of longitudinal and transverse beam impedance in the frequency domain, and their equivalent in the time domain are needed. First analytical approaches, future simulations and tests planned are presented in this paper.

TUPPR025

Higher-Order Modes and Beam Loading Compensation in CLIC Main Linac

coupling, beam-loading, HOM, higher-order-mode

1867

O. Kononenko, A. Grudiev
CERN, Geneva, Switzerland

Compensation of transient beam loading is one of the major performance issues of the future compact linear collider (CLIC). Recent calculations, which consider only the most important fundamental mode, have shown that the 0.03% limit on the rms relative bunch-to-bunch energy spread in the main beam can be reached by optimizing the RF power pulse shape for the TD26, the CLIC baseline accelerating structure. Here, using HFSS and massively parallel ACE3P codes developed at SLAC, we perform an additional dedicated study of the influence of higher-order modes on the energy spread compensation scheme. It is shown that taking these modes into account in the accelerating structure does not increase the rms energy spread in the main beam above the CLIC specification level. Results of the HFSS and ACE3P simulations are also in a good agreement.

TUPPR090

Analysis of Ferrite Heating of the LHC Injection Kickers and Proposals for Future Reduction of Temperature

kicker, injection, vacuum, coupling

2038

M.J. Barnes, L. Ducimetière, N. Garrel, B. Goddard, V. Mertens, W.J.M. Weterings
CERN, Geneva, Switzerland

The two LHC injection kicker magnet (MKI) systems produce a kick of 1.3 T-m with a flattop duration variable up to 7860 ns, and rise and fall times of less than 900 ns and 3000 ns, respectively. A beam screen, consisting of a ceramic tube with conductors on the inner wall, is placed in the aperture of the magnets. The conductors provide a path for the image current of the, high intensity, LHC beam and screen the ferrite against wake fields. The conductors initially used gave adequately low beam coupling impedance however inter-conductor discharges occurred during pulsing of the magnet; hence an alternative design was implemented to meet the often conflicting requirements for low beam coupling impedance, fast magnetic field rise-time and good high voltage behaviour. During 2011 the LHC has been operated with high intensity beam, coasting for many hours at a time, resulting in heating of both the ferrite yoke and beam impedance reduction ferrites, of the MKIs. This paper presents an analysis of thermal measurement data and an extrapolation of the heating for future operation; in addition means are discussed for reducing ferrite heating and improving cooling.

TUPPR095

Update on Kicker Development for the NGLS

kicker, controls, status, electron

2053

G.C. Pappas, S. De Santis, J.E. Galvin, M.V. Orocz, M. Placidi
LBNL, Berkeley, California, USA

The latest requirements for the Next Generation Light Source (NGLS) beam spreader call for a kicker to deflect a 2.4 GeV electron beam by an angle of 3 mrad over a length of 2 meters. The rise and fall time requirements for the integrated B field are <50 ns, the pulse frequency is up to 100 kHz, and both the inter-pulse and pulse to pulse ripple requirements are <0.01% of full scale. These requirements, along with the basic design of the beam spreader are still evolving, and several magnet types and modulator topologies have been considered. This paper will discuss this evolution as it pertains to the kickers, what the current status is of the R&D effort, and the plan to build a full power prototype system.

WEEPPB010

RF Modeling Using Parallel Codes ACE3P for the 400-MHz Parallel-Bar/Ridged-Waveguide Compact Crab Cavity for the LHC HiLumi Upgrade

damping, cavity, HOM, dipole

2185

Z. Li, L. Ge
SLAC, Menlo Park, California, USA
J.R. Delayen, S.D. Silva
ODU, Norfolk, Virginia, USA

Funding: Work partially supported by the US DOE through the US LHC Accelerator Research Program (LARP), and by US DOE under contract number DE-AC02-76SF00515.
Schemes utilizing crab cavities to achieve head-on beam-beam collisions were proposed for the LHC HiLumi upgrade. These crabbing schemes require that the crab cavities be compact in order to fit into the tight spacing available in the existing LHC beamlines at the location where the crab cavities will be installed. Under the support of US LARP program, Old Dominion University and SLAC have joint efforts to develop a 400-MHz compact superconducting crab cavity to meet the HiLumi upgrade requirements. In this paper, we will present the RF modeling and analysis of a parallel-bar/ridged-waveguide shaped 400-MHz compact cavity design that can be used for both the horizontal and vertical crabbing schemes. We will also present schemes for HOM damping and multipacting analysis for such a design.

WEPPC012

High Power Tests of CW Input Couplers for cERL Injector Cryomodule

cryomodule, cavity, vacuum, linac

2230

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

High power tests of a pair of the prototype input couplers were performed by using a newly developed 300 kW CW klystron. The input couplers were successfully processed up to 100 kW in a pulsed operation with a duty of 10% and 50 kW in a CW operation for 30 minutes. The conditioning was limited by excessive heating at bellows of an inner conductor at a coaxial line locating between a coaxial RF window and a doorknob-type transition. Improvement of a sufficient cooling at the inner conductor is necessary to achieve the required input RF power of 170 kW in a CW operation. Six input couplers to be installed in the injector cryomodule for the cERL project were completed, and they are under preparation for conditioning at a high power test stand.

WEPPC017

Design of a High-Speed Pulsed 324MHz Solid-State Amplifier for Use in a Beam Chopper

resonance, proton, insertion, feedback

2242

S.C. Dillon, B.S. Nobel, C.P. Schach
Tomco Technologies, Stepney, South Australia, Australia

A 324MHz 30kW high-speed pulsed solid-state amplifier has been designed for use in a beam chopper at the Japan Proton Accelerator Complex (J-PARC). This paper discusses the various design challenges and presents the initial performance test results. In particular, the amplifier achieves pulse rise and fall times of less than 15 nanoseconds, is easily upgradeable in power, and withstands 100% power reflection without damage.

WEPPC028

Slim Elliptical Cavity at 800 MHz for Local Crab Crossing

cavity, coupling, damping, HOM

2263

L. Ficcadenti, J. Tückmantel
CERN, Geneva, Switzerland

A slim highly eccentric elliptical Crab cavity with vertical deflection at 800 MHz, compatible to beam line distances everywhere in the LHC ring, was designed. It is a good fall-back solution in case of problems with new compact 400 MHz designs. Simulated RF characteristics of the delfecting mode, HOM spectra and damping, tuning and multipacting effects are presented. First the most simple HOM coupling system was investigated. The rejection of the working mode was not sufficient and a notch filter was added. Results of both cases will be presented.

WEPPC037

A Ring-shaped Center Conductor Geometry for a Half-wave Resonator

quadrupole, cavity, linac, ion

2289

B. Mustapha, Z.A. Conway, P.N. Ostroumov
ANL, Argonne, USA

Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract DE-AC02-06CH11357.
Half-wave resonators (HWR) are used and being proposed for the acceleration of high-intensity proton and heavy-ion beams in the 0.1 < β < 0.5 velocity range. The highest performing half-wave resonator geometries use a center conductor with a race-track shaped cross section in the high-electric field region; a feature shared with spoke cavities which are also being proposed for the same velocity regime. We here propose a ring-shaped center conductor instead of the race-track shape. Preliminary studies show that the ring geometry has a similar peak surface electric field as the race-track one, but has several other advantages. In particular, the ring-shaped geometry has: a lower peak surface magnetic field, a much higher Shunt impedance for the same peak fields, and no quadrupole electric field asymmetry which has been observed in the race-track geometry. In a solenoid-based symmetric focusing, the quadrupole component may lead to unnecessary emittance growth which is not acceptable in high-intensity ion linacs. We will present a detailed comparison and a discussion of the two geometries.

WEPPC040

Evaluation of VATSEAL Technology to Seal Waveguide Serving High-field Superconducting RF Cavities

vacuum, SRF, cavity, radio-frequency

2298

B.K. Stillwell, J.D. Fuerst, J. Liu, G.J. Waldschmidt, G. Wu
ANL, Argonne, USA

Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
A waveguide flange seal serving a high-field, superconducting, radio-frequency (SRF) cavity ideally possesses several characteristics. Seals must generally be ultrahigh-vacuum leak tight. Seals must also bridge the inner surfaces of connecting flanges for optimum transmission and minimal heating due to trapped modes. In addition, if seal contact areas are minimized, flange seals may serve as convenient thermal impedances. Finally, seals must be easily cleanable and not be prone to generate particulate matter during assembly and disassembly. A unique sealing technology known as VATSEAL may neatly address all of the above requirements. In this paper, we describe our evaluation of VATSEAL technology for use in SRF cavity assemblies.

WEPPC042

Low Impedance Bellows for High-current Beam Operations

cryomodule, wakefield, SRF, electron

2303

G. Wu, K.-J. Kim, A. Nassiri, G.J. Waldschmidt, Y. Yang
ANL, Argonne, USA
J.J. Feingold, J.D. Mammosser, R.A. Rimmer, H. Wang
JLAB, Newport News, Virginia, USA
J. Jang, S.H. Kim
POSTECH, Pohang, Kyungbuk, Republic of Korea

Funding: Work Supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract No. DE-AC02-06CH11357
In particle accelerators, bellows are commonly used to connect beamline components. Such bellows are traditionally shielded to lower the beam impedance. Excessive beam impedance can cause overheating in the bellows, especially in high beam current operation. For an SRF-based accelerator, the bellows must also be particulate free. Many designs of shielded bellows incorporate rf slides or fingers that prevent convolutions from being exposed to wakefields. Unfortunately these mechanical structures tend to generate particulates that, if left in the SRF accelerator, can migrate into superconducting cavities, the accelerator's critical components. In this paper, we describe a prototype unshielded bellows that has low beam impedance and no risk of particulate generation.

WEPPC086

Higher Order Modes Damping Analysis for the SPX Deflecting Cavity Cyromodule

cavity, damping, HOM, dipole

2414

L. Xiao, Z. Li, C.-K. Ng
SLAC, Menlo Park, California, USA
A. Nassiri, G.J. Waldschmidt, G. Wu
ANL, Argonne, USA
R.A. Rimmer, H. Wang
JLAB, Newport News, Virginia, 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.
A single-cell superconducting deflecting cavity operating at 2.812 GHz has been proposed and designed for the Short Pulse X-ray (SPX) project for the Advanced Photon Source upgrade. A cryomodule of 4 such cavities will be needed to produce the required 2-MV deflecting voltage. Each deflecting cavity is equipped with one fundamental power coupler (FPC), one lower order mode (LOM) coupler, and two higher order mode (HOM) couplers to achieve the stringent damping requirements for the unwanted modes. The damping of the HOM/LOM modes below the beampipe cutoff has been analyzed in the single cavity geometry and shown to meet the design requirements. The HOMs above beam pipe cutoff in the 4-cavity cyromodule, however, may result in cross coupling which may affect the HOM damping and potentially trapped modes between the cavities which could produce RF heating to the beamline bellows and even be detrimental to the beam. We have evaluated the HOM damping and trapped modes in the 4-cavity cryomodule using the parallel finite element EM code ACE3P developed at SLAC. We will present the results of the cryomodule analysis in this paper.

WEPPC087

Second Harmonic Cavity Design for Project-X Main Injector

cavity, simulation, dipole, HOM

2417

L. Xiao, C.-K. Ng
SLAC, Menlo Park, California, USA
J.E. Dey, I. Kourbanis
Fermilab, Batavia, USA

In order to accelerate the proposed beam intensity for Project-X, a new RF system for Main Injector (MI) will be required. A new 53 MHz first harmonic RF cavity that meets the MI requirements for Project-X has been designed. In order to reduce the peak longitudinal beam density a 10⁶ MHz second harmonic RF system is also needed. The first harmonic RF cavity design is a quarter wave coaxial resonator with a single accelerating gap and a perpendicular biased ferrite tuner. The second harmonic RF cavity baseline design is similar to the fundamental one and scaled down from it. RF simulations and shape optimizations on the second harmonic cavity are carried out to obtain the optimal performance which meets Project-X requirements. The results are discussed and presented in this paper.

WEPPC103

Development of Spoke Cavities for High-velocity Applications

electron, cavity, higher-order-mode, multipole

2456

C.S. Hopper, J.R. Delayen
ODU, Norfolk, Virginia, USA
R.G. Olave
Old Dominion University, Norfolk, Virginia, USA

In response to recent interest in alternatives to elliptical cavities for low-frequency, high-velocity applications we have initiated a program for the development of multi-spoke superconducting cavities. We have completed the electromagnetic design for two-spoke cavities operating at 352 and 325 MHz and a design velocity of β = 0.82 and β = 1. We present the results of the optimization, higher order mode (HOM) analysis, multipacting analysis, and an initial multipole expansion study of the fundamental accelerating mode.

WEPPC113

Progress on the High-Current 704 MHz Superconducting RF Cavity at BNL

cavity, HOM, damping, higher-order-mode

2486

W. Xu, S.A. Belomestnykh, I. Ben-Zvi, H. Hahn, P. Jain
BNL, Upton, Long Island, New York, USA
C.M. Astefanous, M.D. Cole, J.P. Deacutis, D. Holmes
AES, Medford, NY, USA

Funding: This work was supported by Sotny Brook under contract No. DE-SC0002496 and Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
The 704 MHz high current superconducting cavity has been designed with consideration of both performance of fundamental mode and damping of higher order modes. A copper prototype cavity was fabricated by AES and delivered to BNL. RF measurements were carried out on this prototype cavity, including fundamental pass-band and HOM spectrum measurements, HOM studies using bead-pull setup, prototyping of antenna-type HOM couplers. The measurements show that the cavity has very good damping for the higher-order modes, which was one of the main goals for the high current cavity design. 3D cavity models were simulated with Omega3P code developed by SLAC to compare with the measurements. The paper describes the cavity design, RF measurement setups for the copper prototype, and presents comparison of the experimental results with computer simulations. The progress with the niobium cavity fabrication will also be described.

WEPPD017

Development of a New RF Finger Concept for Vacuum Beam Line Interconnections

vacuum, linac, higher-order-mode, simulation

2531

C. Garion, A. Lacroix, H. Rambeau
CERN, Geneva, Switzerland

RF contact fingers are primarily used as a transition element to absorb the thermal expansion of vacuum chambers during bake-out and also to compensate for mechanical tolerances. They have to carry the beam image current to avoid the generation of Higher Order Modes and to reduce beam impedances. They are usually made out of copper beryllium thin sheets and are therefore very fragile and critical components. In this paper, a robust design based on a deformable finger concept is proposed. It allows the compensation of large longitudinal movements and also defaults such as transverse offset, twist or bending. The concept of this new RF fingers is first explained, then the design of the component is presented. The mechanical study based on a highly non linear Finite Element model is shown as well as preliminary tests, including fatigue assessment, carried out on prototypes.

WEPPD021

Optimization of the Ultra-High Vacuum Systems for the 3 GeV TPS Synchrotron Light Source

vacuum, photon, electron, synchrotron

2543

G.-Y. Hsiung, C.K. Chan, C.-C. Chang, C.L. Chen, J.-R. Chen, C.M. Cheng, Y.T. Cheng, S-N. Hsu, H.P. Hsueh, Huang, Y.T. Huang, I.C. Sheng, L.H. Wu, Y.C. Yang
NSRRC, Hsinchu, Taiwan

The Taiwan Photon Source (TPS), a 3 GeV synchrotron light source, provides an ultra-low emittance of electron beam and the consequent extremely high brightness of photons. The vacuum pressure along the beam duct should be ultra-high vacuum (UHV) and even lower for reduction of the impact to the beam from the gas scattering or ion trapping troubles. Most of the outgas comes from the photon stimulated desorption (PSD) back streaming from downstream absorbers during beam operation and large area surface outgas inside the beam duct as well. Due to the anticipate request of the smallest vertical aperture of beam ducts from various insertion devices and the lowest broadband impedance through all the vacuum chambers of electron storage ring, the inner structure design and the surface treatment of vacuum chambers as well as the constraint of the back stream PSD outgas from distributed absorbers and the pumping locations should be optimized to obtain a high quality UHV system for the high stable synchrotron light source through the long period of operation. The optimized design of the vacuum chambers for the TPS will be described.

WEPPD026

Design and Fabrication of NSLS-II Storage Ring Vacuum Chambers and Components

vacuum, storage-ring, photon, multipole

2558

H.-C. Hseuh, A.T. Anderson, L. Doom, M.J. Ferreira, C. Hetzel, C. Longo, V. Ravindranath, K. Roy, S.K. Sharma, J.L. Tuozzolo, K. Wilson
BNL, Upton, Long Island, New York, USA

Funding: Work performed under the auspices of U.S. Department of Energy, under contract DE-AC02-98CH10886
The National Synchrotron Light Source II, a 3-GeV, 792-meter circumference, synchrotron radiation facility with ultra-high-flux and brightness, is under construction at Brookhaven National Laboratory. The storage ring vacuum chambers are mainly made of extruded aluminium but with a few made of stainless steel and inconel. The synchrotron radiation from bending magnets is intercepted at discrete photon absorbers made of GlidCop. NEG strips in the ante-chamber provide the distributed pumping, while lumped ion pumps and titanium sublimation pumps at photon absorbers remove the desorbed gas. The complex vacuum system is being assembled and integrated in-house. This paper describes the design and fabrication of both standard and special vacuum chambers, the low impedance RF shielded bellows and the photon absorbers. The vacuum system is now moving into the conditioning, installation and testing phase. Details and experience from the large scale production, testing and lesson learned will also be presented.

WEPPD062

Measurements of the First RF Prototype of the Spiral2 Single Bunch Selector

vacuum, high-voltage, scattering, simulation

2663

M. Di Giacomo
GANIL, Caen, France
A.C. Caruso, F. Consoli, G. Gallo, D. Rifuggiato, E. Zappalà
INFN/LNS, Catania, Italy
A. Longhitano
ALTEK, San Gregorio (CATANIA), Italy

Funding: Work supported by EU commission 7th framework project n. 212692.
The single bunch selector of the Spiral2 driver uses 100 Ω travelling wave electrodes driven by fast pulse generators. A 2.5 kV, 1 kW feed-through and a vacuum chamber housing the water cooled electrodes have been designed and built. The paper reviews the whole design and reports the results of first RF and power measurements.

WEPPD063

Construction of Disk-loaded Buncher for S-Band Low Energy TW Electron Linear Accelerator

electron, linac, coupling, cavity

2666

F. Ghasemi, F. AbbasiDavani, S. Ahmadiannamini, M.Sh. Shafiee
sbu, Tehran, Iran
M.L. Lamehi Rashti, H. Shaker
IPM, Tehran, Iran

The project of design and construction of Traveling linear electron accelerator is being performed by the Institute for Research in Fundamental Sciences (IPM) and Shahid Beheshti University in Iran. By using the results of the calculations and by dynamic simulation of electron beam in the designed buncher, the dimensions of the designed sample have been obtained. This paper discuss construction of this buncher.

WEPPD066

Design of a Stripline Kicker for Tune Measurement in CSNS RCS

kicker, lattice, cyclotron, wakefield

2675

X.Y. Yang, S. Fu, T.G. Xu
IHEP, Beijing, People's Republic of China

For CSNS RCS tune measurement, tune value is measured by exciting the bunch with strip-line kicker fed with white noise and using FFT algorithm to the turn-by-turn position of the bunch in the BPM. This article simulates the strip-line kicker in RCS and the efficiency of the kicker is discussed in the MATLAB environment. The parameters of the kicker with arc electrode structure such as wake impedance, thermal state and VSWR are analyzed based on the advantage of this design.

WEPPD070

Automatic Tuner Unit Operation for the Microwave System of the ESS-Bilbao H⁺ Ion Source

plasma, ion-source, ion, controls

2684

L. Muguira, I. Arredondo, D. Belver, M. Eguiraun, F.J. Fernandez Huerta, J. Feuchtwanger, N. Garmendia, O. González, P.J. González
ESS Bilbao, LEIOA, Spain
V. Etxebarria, J. Jugo, J. Portilla
University of the Basque Country, Faculty of Science and Technology, Bilbao, Spain
J. Verdu
EPFL, Lausanne, Switzerland

Funding: The present work is supported by the Basque Government and Spanish Ministry of Science and Innovation.
The operation of the waveguide automatic tuner unit (ATU) for optimizing the impedance matching and the RF power coupling in the ESS-Bilbao H⁺ Ion Source (ISHP) is presented. Since the plasma chamber can be considered as a time varying load impedance for the pulsed RF 2.7 GHz high power generator, several approaches have been studied for accurately measuring the load impedance. In the later case, a set of power detectors connected to electric field probes, IQ demodulators and gain/phase detectors connected to dual directional couplers have been integrated. An experimental comparison of these approaches is presented, showing their accuracy, limitations and error-correction methods. Finally, the control system developed for the automatic operation of the triple capacitive post tuner is described, as well as illustrative results.

WEPPD075

A Novel Planar Balun Structure for Continuous Wave 1 kW, 500 MHz Solid-state Amplifier Design

simulation, synchrotron, coupling, HOM

2699

T.-C. Yu, L.-H. Chang, M.H. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, Y.-H. Lin, C.H. Lo, M.H. Tsai, Ch. Wang, T.-T. Yang, M.-S. Yeh
NSRRC, Hsinchu, Taiwan

In general, the coaxial type balun plays key role in push-pull amplifier design in the increasing high power solid-state technique transmitter design for accelerator application. However, the coaxial baluns not only increase the complexity in manufacturing procedure but also introduce additional tolerance variation between modules. The variation between parallel power modules would decreases combining efficiency and thus increase the operation cost. Here, a novel planar balun has been proposed and successfully implemented on 1kW solid-state amplifier design for continuous operation with newly designed water cooling plates. The long-term CW test has demonstrated the feasibility of the newly designed planar is quite suitable for CW operation with its excellent low loss, balance property and also low tolerance between modules in mass production.

WEPPD079

Measurements of Magnetic Permeability of Soft Steel at High Frequencies

booster, dipole, vacuum, damping

2711

Y. Tokpanov, V.A. Lebedev, W. Pellico
Fermilab, Batavia, USA

The Fermilab Booster does not have a vacuum chamber which would screen the beam from laminations its dipoles cores. Therefore the booster impedance is mainly driven by the impedance of these dipoles. Recently an analytical model of the laminated dipole impedances was developed. However to match the impedance measurements with calculations one needs an accurate measurement of soft steel magnetic permeability. This paper presents the measurement results of the permeability in a frequency range from ~10 MHz to 1 GHz. Measurements of e.-m. wave propagation in 30 cm long strip line built from soft steel were used to compute the permeability. Measurements were performed in a DC magnetic field to observe the effect of steel saturation on the high frequency permeability. Both real and imaginary parts of the permeability were measured. As expected their values were decreasing with frequency increase from 10 MHz to 1 GHz and with saturation of steel DC permeability.
Operated by Fermi Research Alliance, LLC, under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.

WEPPP022

Analysis of a Rectangular Dielectric-lined Accelerating Structure with an Anisotropic Loading

wakefield, radiation, electron, acceleration

2769

I.L. Sheynman, S. Baturin
LETI, Saint-Petersburg, Russia
A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA

Funding: Russian Fund of Basic Research Federal target program "Scientific and scientific and pedagogical personnel of innovative Russia" of the Ministry of Education and Science of Russia.
Analysis of Cherenkov radiation generated by high current relativistic electron bunch passing through a rectangular waveguide with anisotropic dielectric loading has been carried out. Some of the materials used for the waveguide loading of accelerating structures (sapphire) possess significant anisotropic properties. In turn, it can influence excitation parameters of the wakefields generated by an electron beam. Using orthogonal eigenmodes decomposition for the rectangular dielectric waveguide, the analytical expressions for the wakefields have been obtained. Numerical modeling of the longitudinal and transverse (deflecting) wakefields has been carried out as well. It is shown that the dielectric anisotropy causes frequency shift in comparison to the dielectric-lined waveguide with the isotropic dielectric loading.

WEPPP064

Design and Simulation of the Stripline Transverse Quadrupole Kicker for HLS II

quadrupole, kicker, dipole, storage-ring

2852

F.F. Wu, W.B. Li, P. Lu, T.J. Ma, B.G. Sun, Y.Y. Xiao, H. Xu, Y.L. Yang, Z.R. Zhou
USTC/NSRL, Hefei, Anhui, People's Republic of China

In order to investigate the possibility of excite a transverse quadrupole mode oscillation of the electron bunch in the HLS II storage ring, we design a stripline transverse quadrupole kicker. The characteristic impedance of some modes(dipole modes, sum mode, quadrupole mode) of the optimised stripline kicker must match 50Ω characteristic impedance of the external transmission lines so as to reduce the reflected power. We use nonlinear least square method to optimise the kicker and compare characteristic impedances of calculation using 2D Possion code and fitted function of several variables, then we get optimised size with integrated use of Possion code and fitted function of several variables. Using the 2D Poisson code, we simulate the electric field distribution of dipole modes when the horizontal or the vertical electrodes are at opposite unit potentials, and the electric field distribution of quadrupole mode using quadrupole kick. We verified that the designed stripline kicker can excite a transverse quadrupole mode oscillation of the electron bunch.

WEPPP074

Study of a Wideband Feedback Kicker for the SPS

kicker, feedback, cavity, simulation

2882

S. De Santis, Z. Paret, A. Ratti
LBNL, Berkeley, California, USA
A. Gallo, F. Marcellini
INFN/LNF, Frascati (Roma), Italy

Funding: Work supported by the US Department of Energy under Contracts DE-AC02-05CH11231 and DE-AC02-76SF00515, and through the US LHC Accelerator Research Program (LARP).
The LHC luminosity upgrade currently being planned at CERN depends in large measure on a successful upgrade of its injectors chain. In particular the storing of higher currents in the SPS presents a significant challenge from the point of view of the beam stability. Electron cloud driven and transverse mode-coupled instabilities can disrupt the stored beam to the point of making injection in the LHC impossible. These types of instabilities are characterized by fast growth times and substantial spectral components at high frequency. Therefore a key aspect of any feedback system capable of effectively controlling the instability growth is the development of a suitable kicker with a high frequency response. In this paper we investigate the technologies available for such a kicker and identify a possible solution to be implemented on the SPS. By combining a lower frequency stripline kicker with a high frequency module, such as a damped cavity or a slotted waveguide, it would be possible to provide shunt impedances around 1000 Ω on a bandwidth from DC to 1 GHz. The basic parameters and limits of such a solution are discussed.

WEPPR002

Intensity Thresholds for Transverse Coherent Instabilities During Proton and Heavy-Ion Operation in SIS100

space-charge, proton, synchrotron, simulation

2934

V. Kornilov, O. Boine-Frankenheim
GSI, Darmstadt, Germany

The SIS100 synchrotron is the central accelerator of the projected FAIR complex. It should deliver high intensity proton and heavy-ion beams to the different FAIR experiments. Coherent transverse instabilities are a potential intensity-limiting factor in SIS100. In this contribution we give a summary of the different transverse coherent effects in intense bunched beams that can be expected in the SIS100. Some of the main concerns are unstable head-tail modes, the transverse mode coupling instability, and the beam break-up instability. Space charge is an important effect that leads to Landau damping of the head-tail eigenmodes and modifies the transverse mode coupling. The growth times and thresholds for instabilities will be calculated on the basis of the present SIS100 impedance model whose main components are the resistive wall, the kickers, and the broad-band contribution. The corresponding experience from the CERN injector complex will be used for comparisons.

WEPPR003

Longitudinal Dynamics of Intense Heavy-Ion Bunches in SIS-100

space-charge, ion, heavy-ion, beam-loading

2937

M. Mehler, O. Boine-Frankenheim, O. Chorniy, O.K. Kester
GSI, Darmstadt, Germany

In the SIS-100 highest heavy-ion intensities have to be accelerated to deliver beam to the FAIR experiments. In the projected SIS-100 synchrotron the heavy ion bunches will be strongly affected by the longitudinal space charge force. Due to the limited RF bucket area all mechanisms which might cause longitudinal phase space dilution must be understood and controlled. Space charge effects, like the reduction in the RF voltage and the loss of Landau damping, have already been part of elaborate studies. It has been shown that cavity beam loading can deform the flattened bunch shape in the dual rf bucket. Among the different counter measures an inductive insert has been proposed in order to partially compensate the longitudinal space charge impedance. Optimized settings for the difference between the two rf phases in a dual rf bucket might be an option to reduce the effect of beam loading. In this contribution we will analyse the matched bunch distribution for SIS-100 parameters in single and dual rf buckets. Analytical and numerical studies of the interplay of longitudinal space charge, cavity beam loading and an inductive insert will be presented.

WEPPR054

Calculation of Coherent Wiggler Radiation using Eigenfunction Expansion Method

wiggler, radiation, damping, space-charge

3048

D. Zhou, Y.H. Chin, K. Ohmi
KEK, Ibaraki, Japan
G.V. Stupakov
SLAC, Menlo Park, California, USA

An analytic method originated by Y. H. Chin* was extended to calculate the electromagnetic fields and the longitudinal impedance due to coherent wiggler radiation (CWR) in a rectangular chamber. The method used dyadic Green functions based on eigenfunction expansion method in electromagnetic theory and was rigorous for the case of straight chamber. We re-derived the theory and did find the full expressions for the longitudinal impedance of a wiggler with finite length. With shielding of chamber, the CWR impedance indicated resonant properties which were not seen in the theory for CWR in free space.
* Y.H. Chin, LBL-29981, 1990.

WEPPR056

Reproduction of Ceramic Chamber Impedances with Electric and Magnetic Polarities of the Ceramics

dipole, vacuum, synchrotron, proton

3051

Y. Shobuda, M. Kinsho
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

In proton synchrotron, ceramic chambers are used as vacuum chambers to avoid the effect on magnetic fields from eddy current excited by the magnetic fields. One of the standard methods of the derivation of the impedances of the ceramic chamber is the field matching technique. In this report, we reproduce the formulae of the ceramic chamber impedance in terms of electric and magnetic polarities. When the beam passes through the chamber, the impedance is mainly excited by the electric polarity of the ceramic.

WEPPR057

On the Single Bunch Longitudinal Collective Effects in BEPCII

electron, storage-ring, collective-effects, controls

3054

D. Wang, Z. Duan, J. Gao, Y. Li, L. Wang, L. Wang, N. Wang
IHEP, Beijing, People's Republic of China

Funding: National Natural Science Foundation of China,project 11175192.
In order to study the single bunch longitudinal instability in BEPCII, experiments on the bunch lengthening phenomenon were made. By analyzing the experimental data based on the Gao’s theory, the longitudinal loss factor for the bunch are obtained. Also, the total wake potential and the inductance of the machine are estimated.

WEPPR058

The Vertical Impedance Distribution Measurement Using Response Matrix Method at BEPCII BPR

kicker, feedback, injection, betatron

3057

Y. Wei, D. Ji
IHEP, Beijing, People's Republic of China

Funding: Work supported by the Chinese National Foundation of Natural Sciences, contract 111100512108.
In the last run of BEPCII, the single bunch current is limited to about 8mA by the beam-beam effect. To obtain the design luminosity, larger number of bunches are necessary. But higher total current may be limited by the collective effects. A good understanding of the transverse impedance distribution around the BEPCII storage ring is required. Response matrix method has been applied successfully in BEPCII to fit the quadrupole errors and restore the optics. We can also calculate the variation of betatron phase advance around the ring with different single bunch current using the response matrix method and the transverse impedance distribution is thus deduced. In this paper, the first measurement of transverse impedance in BEPCII is presented.

WEPPR061

Thresholds of Longitudinal Single Bunch Instability in Single and Double RF Systems in the CERN SPS

simulation, damping, synchrotron, emittance

3066

T. Argyropoulos, T. Bohl, J. Esteban Muller, E.N. Shaposhnikova, H. Timko
CERN, Geneva, Switzerland
C.M. Bhat
Fermilab, Batavia, USA

A fourth harmonic RF system is used in the SPS as a Landau cavity, in order to stabilize the high intensity LHC proton beam against the longitudinal instabilities. Numerous studies proved that operating the two RF systems, through the whole cycle, in bunch shortening mode is necessary to provide a good quality beam at extraction to the LHC. Furthermore, it was shown that the choice of RF parameters as voltage amplitude ratio and relative phase are critical for the beam stability. This paper presents the results of single bunch measurements performed in single and double RF systems with various RF settings and compares them with the results of macroparticle simulations for the SPS impedance model.

WEPPR062

The Mode Matching Method Applied to Beam Coupling Impedance Calculations of Finite Length Devices

coupling, simulation, cavity, resonance

3069

N. Biancacci, E. Métral, B. Salvant
CERN, Geneva, Switzerland
M. Migliorati, L. Palumbo
URLS, Rome, Italy
V.G. Vaccaro
Naples University Federico II and INFN, Napoli, Italy

The infinite length approximation is often used to simplify the calculation of the beam coupling impedance of accelerator elements. This is expected to be a reasonable assumption for devices whose length is greater than the transverse dimension but may be less accurate approximation for segmented devices. This contribution presents the study of the beam coupling impedance in the case of a finite length device: a cylindrical cavity loaded with a toroidal slab of material. In order to take into account the finite length we will decompose the field in the cavity and in the beam pipe into a set of orthonormal modes and apply the mode matching method to obtain the impedance. To validate our method, we will present comparisons between analytical formulas and 3D electromagnetic CST simulations as well as applications to the impedance of short beam pipe inserts, where the longitudinal and transverse dimensions are difficult to model in numerical simulations.

WEPPR064

Very Short Range Wake in Strongly Tapered Disk Loaded Waveguide Structures

simulation, wakefield, linac, FEL

3072

A. Grudiev
CERN, Geneva, Switzerland

Electron bunches are very short, both in linear collider and in X-FEL projects. Furthermore, typical disk-loaded waveguide structures used for particle acceleration are tapered. For example in CLIC, in order to achieve high accelerating gradient, the structure is only 26 cells long, which results in strong tapering. In this paper, very short range wake is investigated in the regime where the number of cells needed to arrive at steady state is much larger than the number of cells in a single tapered structure. In this case the very short range wake is dominated by the wake from the smallest aperture. The results of an analytical model and numeric solutions are compared.

WEPPR065

Electromagnetic Simulations of the Impedance of the LHC Injection Protection Collimator

simulation, injection, vacuum, wakefield

3075

B. Salvant, V. Baglin, B. Goddard, A. Grudiev, E. Métral, M.A. Timmins
CERN, Geneva, Switzerland

During the 2011 LHC run, significant vacuum and temperature increase were observed at the location of the LHC injection protection collimators (TDI) during the physics fills. Besides, measurements of the LHC transverse tune shift while changing the TDI gap showed that the impedance of the TDI was significantly higher than the LHC impedance model prediction based on multilayer infinite length theory. This contribution details the electromagnetic simulations performed with a full 3D model of the TDI to obtain both longitudinal and transverse impedances and their comparison with measured observables.

WEPPR069

Measurements and Simulations of Transverse Coupled-Bunch Instability Rise Times in the LHC

simulation, injection, octupole, feedback

3087

N. Mounet, R. Alemany-Fernandez, W. Höfle, D. Jacquet, V. Kain, E. Métral, L. Ponce, S. Redaelli, G. Rumolo, R. Suykerbuyk, D. Valuch
CERN, Geneva, Switzerland

In the current configuration of the LHC, multibunch instabilities due to the beam-coupling impedance would be in principle a critical limitation if they were not damped by the transverse feedback. For the future operation of the machine, in particular at higher bunch intensities and/or higher number of bunches, one needs to make sure the coupled-bunch instability rise times are still manageable by the feedback system. Therefore, in May 2011 experiments were performed to measure those rise times and compare them with the results obtained from the LHC impedance model and the HEADTAIL wake fields simulation code. At injection energy, agreement turns out to be very good, while a larger discrepancy appears at top energy.

WEPPR070

Beam Coupling Impedance Simulations of the LHC TCTP Collimators

simulation, cavity, coupling, vacuum

3090

H.A. Day, R.M. Jones
UMAN, Manchester, United Kingdom
F. Caspers, A. Dallocchio, L. Gentini, A. Grudiev, E. Métral, B. Salvant
CERN, Geneva, Switzerland

As part of an upgrade to the LHC collimation system, 8 TCTP and 1 TCSG collimators are proposed to replace existing collimators in the collimation system. In an effort to review all equipment placed in the accelerator complex for potential side effects due to collective effects and beam-equipment interactions, beam coupling impedance simulations are carried out in both the time-domain and frequency-domain of the full TCTP design. Particular attention is paid to trapped modes that may induce beam instabilities and beam-induced heating due to cavity modes of the device.

WEPPR071

Evaluation of the Beam Coupling Impedance of New Beam Screen Designs for the LHC Injection Kicker Magnets

kicker, coupling, simulation, injection

3093

H.A. Day, R.M. Jones
UMAN, Manchester, United Kingdom
M.J. Barnes, F. Caspers, H.A. Day, E. Métral, B. Salvant
CERN, Geneva, Switzerland

During the 2011 run of the LHC there was a measured temperature increase in the LHC Injection Kicker Magnets (LHC-MKI) during operation with 50ns bunch spacing. This was suspected to be due to increased beam-induced heating of the magnet due to beam impedance. Due to concerns about future heating with the increased total intensity to nominal and ultimate luminosities a review of the impedance reduction techniques within the magnet was required. A number of new beam screen designs are proposed and their impedance evaluated. Heating estimates are also given with a particular attention paid to future intensity upgrades to ultimate and HL-LHC parameters.

WEPPR073

Effects of an Asymmetric Chamber on the Beam Coupling Impedance

simulation, kicker, wakefield, synchrotron

3099

C. Zannini, K.S.B. Li, G. Rumolo
CERN, Geneva, Switzerland
C. Zannini
EPFL, Lausanne, Switzerland

The wake function of an accelerator device appears to have a constant term if the geometry of the device is asymmetric or when the beam passes off axis in a symmetric geometry. Its contribution can be significant and has to be taken into account. In this paper a generalized definition of the impedance/wake is presented to take into account also this constant term. An example of a device where the constant term appears is analyzed. Moreover, the impact of a constant wake on the beam dynamics is discussed and illustrated by a HEADTAIL simulation.

WEPPR074

Effect of the TEM Mode on the Kicker Impedance

kicker, coupling, simulation, vacuum

3102

C. Zannini, G. Rumolo, V.G. Vaccaro
CERN, Geneva, Switzerland
C. Zannini
EPFL, Lausanne, Switzerland

The kickers are major contributors to the CERN SPS beam coupling impedance. As such, they may represent a limitation to increasing the SPS bunch current in the frame of a luminosity upgrade of the LHC. The C-Magnet supports a transverse electromagnetic (TEM) mode due to the presence of two conductors. Due to the finite length of the structure this TEM mode affects the impedance below a certain frequency (when the penetration depth in the ferrite becomes comparable to the magnetic circuit length). A theoretical model was developed to take into account also the impedance contribution due to the TEM mode. The model is found to be in good agreement with CST 3D electromagnetic (EM) simulations. It allows for generic terminations in the longitudinal direction. An example of kicker is analyzed taking into account also the external cables.

WEPPR081

The Collective Effects of the Short Pulsed X-Ray (SPX) System in the Advanced Photon Source Upgrade

cavity, simulation, emittance, collective-effects

3117

Y.-C. Chae, M. Borland
ANL, Argonne, 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 Advanced Photon Source is a 7-GeV hard x-ray synchrotron light source. The APS Upgrade specifies a short-pulse x-ray (SPX) as well as additional beamlines delivering higher brightness and flux. In order to achieve this goal we plan to use S-band superconducting cavities. The performance of such a system based on the zero-current simulation is well established; here, we included the effect of wakefields generated by the SPX system. While the SPX system is off, we are interested in how much current we can store in the single bunch, because the SPX contributes a significant amount of broadband impedance to the ring. With the SPX system on, we are interested in how much vertical emittance will increase, which in turn will enlarge the x-ray pulse length. We report the results of both cases when the SPX system is installed in the ring for the APS Upgrade.

WEPPR082

The Collective Effects of Long Straight Sections (LSSs) in the Advanced Photon Source Upgrade

undulator, storage-ring, collective-effects, injection

3120

Y.-C. Chae, L.H. Morrison
ANL, Argonne, 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 Advanced Photon Source is a 7-GeV hard x-ray synchrotron light source. The APS Upgrade specifies additional beamlines delivering higher brightness and flux as well as for the short-pulse x-ray (SPX). In order to fulfill these demands we plan to provide long straight sections (LSS), for which the total length of the insertion devices is increased to 7.7m. The long straight section also helps in implementing the SPX scheme without removing insertion devices. However, the impedance of the LSS may reduce the single-bunch current of 16 mA per bunch delivered to the users during hybrid fill. We estimate the effect of LSS impedance on the bunched beam current and propose an impedance optimization of the undulator chamber with a small gap.

WEPPR083

New Sector 37 Chamber Design and Installation for High-Current Operation of the APS Storage Ring

vacuum, cavity, storage-ring, HOM

3123

Y.-C. Chae, R. Bechtold, W. Berg, L. Erwin, M. Givens, J.E. Hoyt, L.H. Morrison, K.M. Schroeder, R. Soliday, J.B. Stevens, G.J. Waldschmidt
ANL, Argonne, 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 Advanced Photon Source is a 7-GeV hard x-ray synchrotron light source consisting of 40 sectors. Sector 37 accommodates four radio-frequency cavities followed by a short straight section, which is set aside for the future installation of a diagnostic device. The 60-cm-long section of spool pieces can be isolated by two gate valves and has an independent vacuum pump. The spool pieces are normally under high vacuum condition when the total current is below 100 mA. However, at the higher current required for the APS Upgrade, rf heating causes an unacceptable rise in temperature. We analyzed this situation by wakefield simulation, which led to a new chamber design. Proper fabrication and careful installation with twelve thermocouples ensured a temperature rise under 40-50 degrees Celsius at 100 mA. A brief thermal analysis shows that the present observed temperature rise in the new chamber is mainly due to the resistive wall.

WEPPR086

Computed Wake Field Effects from Measured Surface Roughness in the Walls of the Cornell ERL

wakefield, vacuum, scattering, undulator

3132

M.G. Billing, G.H. Hoffstaetter, C.E. Mayes, K.W. Smolenski, H.A. Williams
CLASSE, Ithaca, New York, USA

Funding: Work supported by the NSF ERL Phase 1B Cooperative Agreement (DMR-0807731)
Wake fields arise from the discontinuities in a smooth vacuum chamber and will cause energy spread in the passing bunch. In an energy recovery linac (ERL), the spent bunches are decelerated before they are dumped to reuse the beam’s energy for the acceleration of new bunches. While the energy spread accumulated from wakes before deceleration is small compared to the beam’s energy after full acceleration, it becomes more important relatively as the beam’s energy decreases.* Thus, in an ERL wake fields can produce very significant energy spread in the beam as it is decelerated to the energy of the beam dump. We report on calculations of wake fields due to the roughness of the surface of the vacuum chamber walls as it affects the Cornell ERL design. These calculations include the effects from the measured roughness for real vacuum chamber wall surfaces.
* M. Billing, “Effect of Wake Fields in an Energy Recovery Linac”, PAC’09, Vancouver, BC, Canada, 4-8 May 2009.

WEPPR093

Impedance Budget for Crab Cavity in MEIC Electron Ring

electron, cavity, collider, ion

3153

S. Ahmed, G.A. Krafft, B.C. Yunn
JLAB, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The Medium Energy Electron-Ion Collider (MEIC) at Jefferson Lab has been envisioned as a first stage high energy particle accelerator beyond the 12 GeV upgrade of CEBAF. The estimate of impedance budget is important from the view point of beam stability and matching with other accelerator components driving currents. The detailed study of impedance budget for electron ring has been performed by considering the current design parameters of the e-ring. A comprehensive picture of the calculations involved in this study has been illustrated in the paper.

WEPPR095

Radial Eigenmodes for a Toroidal Waveguide with Rectangular Cross Section

electron, resonance, wakefield, synchrotron

3159

R. Li
JLAB, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
In applying mode expansion to solve the CSR impedance for a section of toroidal vacuum chamber with rectangular cross section, we identify the eigenvalue problem for the radial eigenmodes which is different from that for cylindrical structures. In this paper, we present the general expressions of the radial eigenmodes, and discuss the properties of the eigenvalues on the basis of the Sturm-Liouville theory.

WEPPR098

Two Dimensional Impedance Analysis of Segmented IVU

vacuum, undulator, simulation, storage-ring

3168

A. Blednykh, G. Bassi, J. Bengtsson, O.V. Chubar, C.A. Kitegi, T. Tanabe
BNL, Upton, Long Island, New York, USA

Funding: Work supported by DOE contract No: DE-AC02-98CH10886
Segmented Adaptive-Gap In-Vacuum Undulator (IVU) with variable magnetic gap along z-axis is considered as an alternative to the Constant Gap IVU (7mm gap) for the NSLS-II storage ring. The length of the Constant Gap IVU for a given minimum gap is limited by the beam stay clear aperture. With the new conceptual design of IVU the magnetic gap can be varied along z-axis and its minimum gap can be reduced down to 5.25mm in the center of the structure for the same stay clear aperture. Beam impedance becomes an important issue since the new design consists of several magnet gaps. Wakepotentials and impedances have been analyzed for a new type of IVU and the results compared with data for the reference geometry which is the Constant Gap IVU.

THYB03

Collective Effects in the LHC and its Injector Complex

emittance, luminosity, linac, injection

3218

E. Métral
CERN, Geneva, Switzerland

Operation during 4-8 hours at a constant luminosity of five times the nominal one (with “leveling”) is required for the CERN HL-(High Luminosity)-LHC project to be able to reach integrated luminosities of ~ 250 fb-1 per year and ~ 3 ab-1 twelve years after the upgrade. This means that the potential peak luminosity should be at least two times larger than the leveled one, i.e. a factor more than ten compared to the nominal case is contemplated. Even though the LHC had a bold beginning, reaching one third of the nominal peak luminosity at the end of the 2011 run, a factor more than thirty remains to be gained, which will be achieved only if all the collective effects are deeply understood and mastered both in the LHC and its injectors. The observations made during the 2010-2011 runs are first reviewed and compared to predictions to try and identify possible bottlenecks. The lessons learned and the possible solutions and/or mitigation measures to implement in the HL-LHC and the LHC Injectors Upgrade (LIU) projects are then discussed.

Slides THYB03 [34.295 MB]

THPPC003

Development of a Broad-band Magnetic Alloy Cavity at GSI

cavity, coupling, storage-ring, ion

3275

T.S. Mohite, U. Ratzinger
IAP, Frankfurt am Main, Germany
R. Balß, P. Hülsmann
GSI, Darmstadt, Germany

FINEMET, a Magnetic Alloy material, is often used to build a broad-band cavity for an accelerator or a storage ring. A research on the broad-band FINEMET cavity is of prime importance not only for the present accelerator facility but also for the future storage rings and synchrotron in upcoming FAIR facility alongside the GSI, Darmstadt. In several measurements, high intensity rare-isotope beams, with lower life time, are demanded at injection energy in Experimental Storage Ring (ESR) at GSI. A longitudinal beam stacking of such beams by means of using a special barrier-bucket RF cavity is found appropriate to serve this purpose*. Additionally, this cavity is supposed to provide the compressed bunches at lower energies for HITRAP, an ion-trap facility for experiments with highly charged ions, in FAIR. Several measurements are being performed, along with the theoretical analysis, to achieve the designed parameters for the planned barrier-bucket cavity. 60 FINEMET ring cores have been tested to confirm their designed electrical properties. Some of these ring cores are then loaded, in steps, in a test cavity, which will further be used as the barrier-bucket cavity for the ESR.
* C. Dimopoulou et al., JACoW Proceedings of COOL 2007, Bad Kreuznach, Germany

THPPC005

Design of Magnetic Alloy Resonant System (MARS) Cavity for J-PARC MR

cavity, beam-loading, acceleration, status

3278

C. Ohmori, K. Hara, K. Hasegawa, M. Toda, M. Yoshii
KEK, Ibaraki, Japan
M. Nomura, A. Schnase, T. Shimada, F. Tamura, M. Yamamoto
JAEA/J-PARC, Tokai-mura, Japan

The Magnetic Alloy Resonant System (MARS) cavity is a new type of Magnetic Alloy (MA) cavity using an external energy storage system. It is proposed as a back-up system of the present J-PARC high-Q MA cavity using cut cores. MARS consists of un-cut core loaded wideband MA cavities combined with an energy storage system using high-impedance, FT3L, cut cores. The main cavities are water-cooled and already established at J-PARC RCS. The energy storage system will be relatively high-Q (>100) to be stable under heavy beam loading. It also has a higher impedance than the main cavity and is air-cooled. The design of this cavity system will be presented.

THPPC006

Status of the J-PARC Ring RF Systems

cavity, synchrotron, proton, beam-loading

3281

M. Yoshii, E. Ezura, K. Hara, K. Hasegawa, C. Ohmori, A. Takagi, K. Takata, M. Toda
KEK, Tokai, Ibaraki, Japan
M. Nomura, A. Schnase, T. Shimada, F. Tamura, M. Yamamoto
JAEA/J-PARC, Tokai-mura, Japan

Due to the 11th march earthquakes, J-PARC was forced to stop operation. The restoration is following the schedule so that J-PARC is restarted in December. Before the earthquake, we had considerable success in the 400 kW equivalent proton beam in the RCS. Multi-harmonic RF feedforward was established, which contributes to the reduction of beam loss and stable acceleration in RCS. The MR synchrotron achieved stable 150 kW beam operation for the T2K experiment. This summer, we installed two new RF systems in MR. Eight RF systems in total allow a more stable beam acceleration and flexible bunch shape manipulation. Also, we prepare the RF feedforward to compensate beam loading in MR. To achieve a beam power in excess of 1 MW in MR, it is considered to double the MR repetition rate. We developed an annealing scheme for large magnetic alloy cores while inside a DC B-field that results in higher core impedance, and have succeeded in producing large FT3L cores in this summer. With such cores we can almost double the accelerating voltage without re-designing the existing RF sources. For the near future, we plan to replace the existing RF cavities with upgraded cavities using the FT3L cores.

THPPC012

Impedance Computation of Main Components in CSNS/RCS

cavity, simulation, extraction, vacuum

3299

Y. Li, L. Huang, Z.P. Li, Y.D. Liu, N. Wang, S. Wang
IHEP, Beijing, People's Republic of China

The rapid cycling synchrotron (RCS) of the China spallation neutron source (CSNS) is a high intensity proton accelerator. The study on the coupling impedance in the ring plays an important role in the stability of the beam. The impedance of the main vacuum components in the RCS ring, such as RF cavities, bellows, ports of vacuum pumps, collimator etc, was calculated by using numerical methods. Meantime, RF shielding of bellows, collimators and ports of vacuum pumps are considered. The impact of the busbar configuration on RF cavities and beams was estimated by impedance calculation.

THPPC020

Accurate Measurement of Ferrite Garnets to be used for Fast-tuned Ferrite Loaded Cavities in the Range of 20-40 MHz

cavity, resonance, vacuum, dipole

3317

C. Vollinger, F. Caspers
CERN, Geneva, Switzerland

For the implementation of ferrite-tuned cavities with perpendicular biased ferrites in the frequency range of 20 to 40 MHz, different types of ferrite garnets were evaluated in terms of their electromagnetic properties. We describe a precision measurement method applicable to small-sized ferrite samples of 1-square-inch surface and 2 mm thickness in the given frequency range. During measurement, these samples are exposed to varying magnetic bias fields of different orientations. Two different techniques for the determination of the real and the imaginary part of the permeability are required to achieve sufficiently accurate results. We present a detailed description of these methods as well as results obtained.

THPPC024

Design, Construction and Power Conditioning of the First C-band Test Accelerating Structure for SwissFEL

cavity, klystron, linac, vacuum

3329

R. Zennaro, J. Alex, H. Blumer, M. Bopp, A. Citterio, T. Kleeb, L. Paly, J.-Y. Raguin
Paul Scherrer Institut, Villigen, Switzerland

The SwissFEL C-band linac will consist of 26 RF modules with a total acceleration voltage of 5.4 GV. Each module will be composed of a single 50 MW klystron and its solid-state modulator feeding a pulse compressor and four two-meter long accelerating structures. PSI has launched a vigorous R&D program of development of the accelerating structures including structure design, production and high-power RF tests. The baseline design is based on ultra-precise cup machining to avoid dimple tuning. The first test structure is a constant impedance structure composed of eleven double-rounded cups. We report here on the structure design, production, low-level RF measurements, high-power conditioning and breakdown analysis.

THPPC026

A Transverse Deflecting Cavity for the Measurement of Short Low Energy Bunches at EBTF

cavity, coupling, electron, simulation

3335

G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
S.R. Buckley, P. Goudket, C. Hill, P.A. McIntosh, J.W. McKenzie, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

The Electron Beam Test Facility (EBTF) at Daresbury Laboratory will deliver low energy (5/6 MeV) short bunches (~40 fs) to a number of industrial experimental stations and for scientific research. In order to measure the longitudinal profile of the bunch an S-band transverse deflecting cavity will be inserted into the beamline. A transverse kick of around 5 MV is required hence a 9 cell design has been chosen. The design of the transverse deflecting cavity has been influence by the competing demands of high RF efficiency and minimising the unwanted transverse kick at the entrance and exit of the cavity which cause the electrons to be displaced while traversing the cavity. This has led to a shortened end cell structure design to minimise the kick applied at the entrance and exit to the cavity. In order to minimise the impact of the input coupler a dummy waveguide has been placed on the opposing side of the cavity to minimise the monopole component of the RF fields in the coupling cell. The coupler is located at the central cell of the cavity to avoid exciting the nearby modes. Tracking of the beam is performed in GPT including space charge, due to the low energy of the electrons.

THPPC027

Measurement of the Dynamic Response of the CERN DC Spark System and Preliminary Estimates of the Breakdown Turn-on Time

simulation, vacuum, cathode, radio-frequency

3338

N.C. Shipman, R.M. Jones
UMAN, Manchester, United Kingdom
S. Calatroni, W. Wuensch
CERN, Geneva, Switzerland

The new High Rep Rate (HRR) CERN DC Spark System has been used to investigate the current and voltage time structure of a breakdown. Simulations indicate that vacuum breakdowns develop on ns timescales or even less. An experimental benchmark for this timescale is critical for comparison to simulations. The fast rise time of breakdown may provide some explanation of the particularly high gradients achieved by low group velocity, and narrow bandwidth, accelerating structures such as the T18 and T24. Voltage and current measurements made with the previous system indicated that the transient responses measured were dominated by the inherent capacitances and inductances of the DC spark system itself. The bandwidth limitations of the HRR system are far less severe allowing rise times of around 12ns to be measured.

THPPC039

Study of RF Breakdown in Normal Conducting Cryogenic Structure

cryogenics, klystron, lattice, accelerating-gradient

3368

V.A. Dolgashev, J.R. Lewandowski, D.W. Martin, S.G. Tantawi, S.P. Weathersby, A.D. Yeremian
SLAC, Menlo Park, California, USA

Funding: *Work supported by DoE, Contract No. DE-AC02-76SF00515.
RF Breakdown experiments on short accelerating structures at SLAC have shown that properties of rf breakdown probability are reproducible for structures of the same geometry. At a given rf power and pulse shape, the rf breakdown triggers continuously and independently at a constant average rate. Hypotheses describing the properties of the rf breakdown probabilities involve defects of metal crystal lattices that move under forces caused by rf electric and magnetic fields. The dynamics of the crystal defects depend on the temperature of the structure. To study the dependence we designed and built an experimental setup that includes a cryogenically cooled single-cell, standing-wave accelerating structure. This cavity will be high power tested at the SLAC Accelerator Structure Test Area (ASTA).

THPPC044

Development of the Dual Slot Resonance Linac

linac, coupling, cavity, resonance

3383

N. Barov, X. Chang, R.H. Miller, D.J. Newsham
Far-Tech, Inc., San Diego, California, USA

Funding: Work supported by DOE Grant DE-FG02-08ER85034
We report the status of the Dual Slot Resonance (DSR) linac under development by FAR-TECH. In this linac type, cell-to-cell coupling is provided by a pair of close-coupled resonant slots, resulting in very strong coupling vs. a typical side-coupled linac design, as well as a much more compact radial space requirement. We discuss the status of the structure fabrication, the RF distribution system, and installation and testing at the UCLA Pegasus facility.

THPPC050

Effects of Grids in Drift Tubes

beam-transport, proton, linac, DTL

3401

M. Okamura
BNL, Upton, Long Island, New York, USA
H. Yamauchi
Time Corporation, Hiroshima, Japan

In 2011, we upgraded a 200 MHz buncher in the proton injector for the AGS – RHIC complex. In the buncher we installed four grids made of tungsten to improve a transit time factor of the buncher. The grid installed drift tubes have 32 mm of inner diameter and the each grid consists of four quadrants. The quadrants were cut out precisely from 1mm thick tungsten plates by a CNC wire cutting EDM. In the conference the 3D electric field design and performance of the grid will be discussed.
Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.

THPPC056

Development of 12kW RF Power Supply for CYCHU-10 Cyclotron

power-supply, cavity, cyclotron, feedback

3416

D. Li, T. Hu, J. Huang, K.F. Liu, B. Qin, J. Yang, L. Yang
Huazhong University of Science and Technology (HUST), Wuhan, People's Republic of China

One 12kW RF power supply has been developed for CYCHU-10, which is a 10 MeV cyclotron developed in Huazhong University of Science and Technology (HUST). A high performance DDS chip AD9859 is used to synthesize RF signal in this power supply, which is easy to change the output frequency. The centre frequency is 101MHz, and the frequency bandwidth is more than 1MHz. The RF power supply could operate in fine searching mode, coarse searching mode, tracking mode, and so on. It could search the resonant frequency of cavity with the frequency control loop. The final stage amplifier using a triode 3CW20,000H7 operates in grounded grid configuration, which is stable and reliable. The performance test using a 50Ω resistor load has finished, and major results are shown in this paper.

THPPC074

High Frequency High Power RF Generation using a Relativistic Electron Beam

wakefield, electron, extraction, damping

3458

C.-J. Jing, S.P. Antipov, A. Kanareykin, P. Schoessow
Euclid TechLabs, LLC, Solon, Ohio, USA
H. Chen, Y. Yang
TUB, Beijing, People's Republic of China
M.E. Conde, W. Gai, J.G. Power
ANL, Argonne, USA

High frequency, high power rf sources are required for many applications. Benefiting from the ~10 GW beam power provided by the high current linac at the Argonne Wakefield Accelerator facility, we propose to develop a series of high power rf sources based on the extraction of coherent Cherenkov radiation from the relativistic electron beam. The frequencies cover from C-band up to W-band with different structures. Simulations show that ~1 GW 20 ns rf pulse can be generated for an 11.7 GHz structure, ~400 MW for a 26 GHz structure, and ~14 MW for a 91 GHz structure.

THPPD017

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

pick-up, dipole, proton, 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.

THPPD052

Operation and Current Status of Injection, Extraction, Kicker Magnet and the Power Supply for J-PARC 3 GeV RCS

kicker, extraction, power-supply, injection

3629

M. Watanabe, N. Hayashi, Y. Shobuda, K. Suganuma, T. Takayanagi, T. Togashi
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
T. Toyama
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

3-GeV RCS (Rapid Cycling Synchrotron) at High Intensity Proton Accelerator Facility (J-PARC) have started for 24-hour operation with repetition rate of 25 pps in February, 2009. Kicker power supply system which uses thyratrons switches is used for extraction of the proton beam. There were many troubles for unstable operation of the thyratrons just after beam commissioning started. Recently, however, the operations were improved and the failure rate was reduced to approximately 0.1 % in October 2010. After the earthquake on March 11, 2011, the injection and extraction magnets, power supplies, the cables and the bus-duct have been checked. Insulation resistance test, impedance test were performed. Reflected wave measurements by the low-level and high-power pulse of the kicker magnets were performed. Visual checks by a fiber endoscope were also performed in the kicker magnets. The results of the measurements and the checks were all not in the problem.

THPPD058

Reduction of Conductive EMI Noise Resulted from the Commercial Power Supply

power-supply, high-voltage, vacuum, coupling

3644

C.S. Chen, C.K. Chan, J.-C. Chang, Y.L. Chu, K.H. Hsu, C.Y. Kuo, Y.-H. Liu, C.S. Yang
NSRRC, Hsinchu, Taiwan

Almost every electronic equipment must be connected to power system. Because of the complexity of power lines, the reduction of conductive electro-magnetic interference (C-EMI) plays an important role in precise measurements. In this paper, a line impedance stabilization network (LISN) was built up to get the spectrum from power lines. After several measurements by some commercial power supplies, it is found that some of these power supplies induce effectively C-EMI into power lines, even if a passive filter is bound in power line. These noises may influence numerous equipments in a local area near the sources. Therefore, how to choose a suitable filter is a decisive factor to reduce the magnitude of C-EMI.

THPPD061

Optimal Design for Resonant Power Transformer

power-supply, controls, factory

3650

C.-Y. Liu, D.-G. Huang, J.C. Huang
NSRRC, Hsinchu, Taiwan

The energy and dc to dc conversion of the resonant transformer are required to achieve optimal design and working condition of the resonant region frequency. To meet this requirement, the core loss will be checked first by data book for calculation. Using a reliable precise instrument is needed to scan the resonant cure of the resonant transformer as we designed the resonant cure. We calculated the conduction loss in second design step. We design a resonant transformer which the conduction loss equal core loss does not meet optima design, because the core loss is very high when the transformer works in resonant frequency. Thus, we only reduce the conduction loss is optima design aspect.

THPPD072

Performance Optimization of the Stacked-Blumlein

simulation, coupling, high-voltage, induction

3680

L.W. Zhang, J. Li, W.D. Wang
CAEP/IFP, Mainyang, Sichuan, People's Republic of China
Y. Li
CAEP, Mainyang, Sichuan, People's Republic of China

Funding: This work was supported by the National Natural Science Foundation of China (11035004)
For the applications of the Dielectric Wall Accelerator (DWA), the stacked Blumlein pulse generator comprised of parallel-plate transmission lines is being developed. The peak output voltage of the stacked Blumlein will be much lower than expected due to the parasitic coupling among the individual pulse forming lines of the Blumlein stack. The finite difference time domain method is used to model the stacked Blumlein structure and determine the outputs. We present the optimization of a 20-Blumleins-stack in this paper. The results for different structures are discussed.

THPPP003

Coupling Impedance Study of the New Injection Kicker Magnets of the JPARC Main Ring

kicker, coupling, simulation, vacuum

3725

K. Fan, S. Fukuoka, H. Matsumoto, T. Sugimoto, T. Toyama
KEK, Ibaraki, Japan

New lumped inductance kicker magnets have been developed for the J-PARC main ring injection system. For high intensity beam operation, the beam coupling impedance of the new kickers is a critical issue, which not only generates significant heating inside the ferrite impairing the performance of the kickers, but also drives beam instability. Numerical simulations based on CST studio have been studied during the design stage to optimize the kicker structure. Impedance measurements based on wire method have been carried out. The measured results agree well with the simulation results.

THPPP004

Design and Test of Injection Kicker Magnets for the JPARC Main Ring

kicker, coupling, injection, proton

3728

K. Fan, S. Fukuoka, K. Ishii, H. Matsumoto, H. Someya, T. Sugimoto, T. Toyama
KEK, Ibaraki, Japan

The present injection kicker magnets of the JPARC main ring consists of three transmission type kickers. To overcome the operational problems, four lumped inductance kicker magnets have been developed for the simplicity and the high reliability. The tight requirements on the rise and fall time create difficulties for the new design. Magnetic field measurements, coupling impedance measurements and have been carried out. The measurement results show that the new kicker magnets can satisfy the requirements of beam injection.

THPPP011

Studies on a Wideband, Solid-state Driven RF System for the CERN PS Booster

feedback, cavity, acceleration, booster

3749

M.M. Paoluzzi, L. Arnaudon, N. Chritin, M. Haase, K. Hanke, B. Mikulec, T. Tardy
CERN, Geneva, Switzerland

In the framework of the LHC Injectors Upgrade project (LIU) the PS Booster (PSB) RF systems will undergo in depth consolidation and upgrade programs. The aim is increasing the extraction energy to 2 GeV and allowing reliable operations during next 25 years. Substantial improvements could come from the replacement of the existing narrowband, tuned systems covering the h=1 and h=2 frequency ranges (0.6 / 1.8 MHz and 1.2 / 3.6 MHz respectively) with wideband (0.5 / 4 MHz) Finemet® loaded cavities. The new system would be modular, allow multi-harmonic operation, use solid-state power stages and include fast RF feedback to compensate beam loading effects to some extent. A prove of principle system providing ≈3.0 kV accelerating voltage has been designed, constructed and installed in one of the PSB rings. This paper provides details on the design and measurements as well as information on the project status.

THPPP034

Optimization of a CW RFQ Prototype

rfq, simulation, linac, DTL

3809

U. Bartz, J. Gerbig, H.C. Lenz, A. Schempp
IAP, Frankfurt am Main, Germany

A short RFQ prototype was built for RF-tests of high power RFQ structures. We studied thermal effects to determine critical points of the design. HF-simulations with CST Microwave Studio and measurements were done. The cw-tests with 20 kW/m RF-power and simulations of thermal effects with ALGOR were finished successfully. The optimization of some details of the RF design is on focus now. Results and the status of the project will be presented

THPPP039

Simulations for a Buncher-Cavity at GSI

simulation, cavity, resonance, induction

3821

P.L. Till, B. Koubek, A. Schempp, J.S. Schmidt
IAP, Frankfurt am Main, Germany

Buncher cavities can be used to bunch and rebunch or re-accelerate particle beams. A special form of these buncher cavities is a spiral structure. one of its main features is the easy adjustable frequency. A two-gap structure for the GSI has been simulated and will be build at the University of Frankfurt. This structure shall replace an existing buncher at GSI. It is designed to an frequency of 36 MHz. Also general simulations of spiral bunchers will be presented.

THPPP069

Double-Gap Rebuncher Cavity Design of SNS MEBT

cavity, DTL, simulation, linac

3898

K.R. Shin
ORNL RAD, Oak Ridge, Tennessee, USA
A.E. Fathy
University of Tennessee, Knoxville, Tennessee, USA
Y.W. Kang
ORNL, Oak Ridge, Tennessee, USA

A double-gap rebuncher cavity has been studied through design and analysis with computer simulations. This cavity shape is a two cell abridged form of drift tube linac (DTL), instead an omega form of existing single gap elliptical cavity. The cavity operates in TM010 mode, likewise the commonly used single-gap cavities in some medium energy beam transport (MEBT) line of proton accelerators. The new cavity is more power efficient even with slightly lower Q factor because of utilization of two interactive gaps. The breakdown field can be lowered with adjustment of gap and tube length ratio. Electromagnetic, beam envelope, and thermal simulations are presented with comparison to the properties of the conventional elliptical cavity.

THPPP081

Status of Injection Energy Upgrade for J-PARC RCS

power-supply, injection, quadrupole, kicker

3921

N. Hayashi, H. Harada, H. Hotchi, J. Kamiya, P.K. Saha, Y. Shobuda, T. Takayanagi, N. Tani, M. Watanabe, Y. Watanabe, K. Yamamoto, M. Yamamoto, Y. Yamazaki, M. Yoshimoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
T. Toyama
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

The injection energy upgrade for J-PARC RCS is planed in 2013. This includes the power supplies upgrade of injection pulsed magnet system, suppression for leakage field, quadrupole correction magnets, reduction of kicker impedance effect and improvements of beam diagnostic instrumentation. The paper reports the present status.

THPPP082

RF Feedforward System for Beam Loading Compensation in the J-PARC MR

cavity, injection, beam-loading, proton

3924

F. Tamura, M. Nomura, A. Schnase, T. Shimada, M. Yamamoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
K. Hara, K. Hasegawa, C. Ohmori, M. Yoshii
KEK, Tokai, Ibaraki, Japan
M. Toda
KEK/JAEA, Ibaraki-Ken, Japan

For acceleration of high intensity proton beams in the J-PARC MR, beam loading compensation is important. In the MA-loaded RF cavity in the MR, which has a Q-value in the order of 20, the wake voltage consists of the accelerating harmonic (h=9) and the neighbor harmonics (h=8, 10). We employ the RF feedforward method for the beam loading compensation, like in the J-PARC RCS, in which the impedance seen by the beam is greatly reduced by the feedforward. The full-digital feedforward system developed for the MR has a similar architecture to that of the RCS. The system compensates the beam loading of the important three harmonics (h=8, 9, 10). We present the structure of the RF feedforward system. Also, we report the preliminary results of the beam tests.