PAC07 - List of Keywords (impedance)

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impedance

Paper	Title	Other Keywords	Page
MOPAN007	A Non-intercepting Beam Current Monitor for the ISAC-II SC-linac	ion, pick-up, linac, vacuum	155
	W. R. Rawnsley R. E. Laxdal, A. K. Mitra TRIUMF, Vancouver
	A personnel protection system will monitor the ion beam current into the experimental hall from the ISAC-II SC-linac. It will use continuous self-test and redundancy and have an accuracy of ±10% from 1 to 200enA. The system, based on an Atlas design, will use capacitive pickups with rf resonators and buffer amplifiers. Ion charge, velocity and bunch width will affect the sensitivity so periodic calibration with dc Faraday cups will be needed. The signal from each 13cm long, 5cm diameter pickup tube will pass through a vacuum feedthrough to a helical resonator. An AD8075 IC with an input impedance of 87kΩ at 35MHz will allow a high coil tap. The ISAC beam, bunched at 11.8MHz, is injected into the ISAC-II SC-linac via a 25m long transfer line. Monitors will be placed in the transfer line and downstream of the linac before the experimental hall. A 35MHz and a 70MHz coil (3 and 6 harmonic) have loaded Q's of 600. A test in the transfer line of the 35MHz coil gave a sensitivity 0.09mV/enA from the unity gain buffer using ²⁰Ne⁺⁵ ions at 1.5MeV/u. The background was equivalent to 1enA. The 70MHz coil gave 0.04mV/enA using ²²Ne⁺⁴ ions. System design and test data will be presented.

MOPAN009	Transverse Feedback Development at SOLEIL	feedback, damping, emittance, betatron	161
	R. Nagaoka L. Cassinari, J.-C. Denard, J.-M. Filhol, N. Hubert, M.-P. Level, P. Marchand, C. Mariette, F. Ribeiro, R. Sreedharan SOLEIL, Gif-sur-Yvette K. Kobayashi, T. Nakamura JASRI/SPring-8, Hyogo-ken
	With reduced vertical chamber aperture adopted all around the machine, the transverse impedance for the SOLEIL ring is enhanced both in its resistive-wall and broadband content. The predicted instability threshold currents being significantly low as compared to the nominal current in multibunch and in several single bunch modes, a decision was taken to install a digital bunch by bunch feedback system, with an aim to make it operational since the beginning of the storage ring operation. The system implemented comprises components developed elsewhere, particularly the FPGA processor of SPring-8, chosen among different possible solutions. Using a BPM and a stripline in the diagonal mode, a single unit of the FPGA processor board has shown to successfully suppress resistive-wall and ion induced multibunch instabilities in either one or both transverse planes. On top of the system characteristics, the paper discusses details of the obtained performance, as well as future extensions to overcome the encountered limitations.

MOPAN036	Longitudinal Feedback System for the Photon Factory	feedback, kicker, synchrotron, factory	233
	T. Obina W. X. Cheng, T. Honda, M. Tobiyama KEK, Ibaraki
	In the KEK-PF, longitudinal coupled-bunch instabilities are suppressed by means of the RF phase-modulation technique during the users operation. This method is very effective not only to suppress the instabilities but also to enlarge the beam lifetime. Together with the feasibility study for top-up operation, bunch-by-bunch feedback system have been developed. A two-port longitudinal kicker based on dafne-type cavity were designed and installed in the storage ring in the summer of 2006. FPGA-based signal processing part is under development based on the KEKB design. As an preliminary test of the longitudinal kicker, a simple mode-feedback system which suppress a specific coupled-bunch mode were tested successfully.

MOPAN042	Switching Power Supply for Induction Accelerators	acceleration, induction, power-supply, synchrotron	251
	M. Wake Y. Arakida, K. Koseki, Y. Shimosaki, K. Takayama, K. T. Torikai KEK, Ibaraki W. Jiang, K. Nakahiro Nagaoka University of Technology, Nagaoka, Niigata A. Sugiyama Shindengen Co., Ltd., Tokyo A. Tokuchi Nichicon (Kusatsu) Corporation, Shiga
	A new particle acceleration method using pulsed induction cavities was introduced in the super-bunch project at KEK. Unlike conventional RF acceleration, this acceleration method separates functions of acceleration and confinement As a result, this acceleration method can be applied for accelerating a wide mass range of particles. However, it is necessary to give a very fast pulsed-excitation to the cavity to perform the induction acceleration. Switching power supplies of high voltage output with very fast pulse-operation is one of the most important key technologies for this new acceleration method. We have developed 20ns rise time pulse at continuous repetition rate of 1MHz using MOS-FET's. Induction cavities were modulated through the 200m long transmission lines. Further development using SI- thyristor achieved 1MHz and 2kV switching in a burst mode operation. SiC devices are also studied for the application and some promising results were obtained. Faster operation will make this new acceleration technology available for small accelerator projects.

MOPAN053	Development of Transverse Feedback System and Instabilities Suppress at HLS	feedback, kicker, single-bunch, storage-ring	269
	J. H. Wang J. Cao, L. Ma, J. Yue IHEP Beijing, Beijing Y. B. Chen, L. J. Huang, W. Li, L. Liu, B. Sun, L. Wang, Y. L. Yang, K. Zheng, Z. R. Zhou USTC/NSRL, Hefei, Anhui D. K. Liu, K. R. Ye SINAP, Shanghai
	In order to cure and damp coupled bunch (CB) instabilities, a transverse bunch-by-bunch feedback system is under commission at Hefei Light Source (HLS). In this paper, we introduce the HLS Bunch-by-Bunch measurement system and transverse feedback system. The experiment result in HLS ring is also presented in this paper.

MOPAN082	Four Quadrant 120 A, 10 V Power Converters for LHC	controls, collider, focusing, hadron	347
	Y. Thurel B. Favre, D. Nisbet CERN, Geneva
	The LHC (Large Hadron Collider) particle accelerator makes extensive use of true bipolar power converters, with a regulated high precision output current requirement. A special design and topology is required to permit high performance throughout the converter operating area, including quadrant transition. This paper presents the 120A 10V power converter, well represented in the LHC (300 units). The design is adapted for a wide range of magnet loads [from 10mH to 4 Henry] with stringent EMC requirements. A quick-connect system was applied to the converter modules to allow easy installation and maintenance operations. Discussion of 4 quadrant control and practical results are presented.

MOPAS024	Fast Extraction Kicker for the Accelerator Test Facility	kicker, extraction, simulation, closed-orbit	485
	S. De Santis T. Naito, J. Urakawa KEK, Ibaraki
	Funding: Work supported by the U. S. Department of Energy under Contract No. DE-AC0-05CH11231. We present the final results of a study for the design of a fast extraction kicker to be installed in the Accelerator Test Facility ring at KEK. The purpose of this project is to test the technologies to be used in the design of the extraction kickers for the International Linear Collider damping rings. The kicker's rise and fall times are important parameters in the final configuration of the rings, since they constrain the minimum distance between bunches and ultimately define a lower limit for the rings length. We investigated a stripline kicker composed of several 65-cm long sections, grouped in two different locations in the ATF damping ring. An analytical study of the kicker's parameter and extensive computer simulations using Microwave Studio* point out the ambitious requirements on the pulsers, in order to be able to satisfy the design specifications. We also investigated the use of a single kicker module, together with a close orbit bump near the extraction septum. * http://www.cst.com

MOPAS062	Analysis of the Longitudinal Low-order Mode Beam Dynamics in PEP-II Rings at High Current Beams	klystron, simulation, damping, feedback	575
	T. Mastorides J. D. Fox, C. H. Rivetta, D. Teytelman, D. Van Winkle SLAC, Menlo Park, California
	Funding: Work supported by Department of Energy (USA) under contract # DE-AC02-76SF00515 PEP-II operations will increase the beam currents to 4A for LER and 2.2A for HER to achieve the final goal in luminosity. These magnitudes are challenging in part because they will push toward the limit the longitudinal low-order mode (LOM) beam stability due to beam loading. To analyze the behavior of both rings at high currents and understand the limits in the longitudinal feedback systems a simulation tool has been developed at SLAC. This tool is based on a reduced model of the longitudinal LOM dynamics of the beam interacting with the effective impedance presented by RF station. Simulations and measurements of the longitudinal beam behavior in both rings have been performed to understand the ultimate limit of the system. These studies have defined the impact of control loop parameters in the longitudinal beam dynamics, identified the poor performance of RF devices affecting the optimal performance of the RF stations and quantified the behavior of the longitudinal LOM beam dynamics. Results of sensitivity to parameter variations in the beam dynamics and limits in the maximum current that LER/HER can achieve based on the longitudinal beam stability are reported in this paper.

MOPAS073	700 MHz Low-Loss Electrically-Controlled Fast Ferroelectric Phase Shifter For ERL Application	linac, electron, controls, resonance	599
	V. P. Yakovlev J. L. Hirshfield Omega-P, Inc., New Haven, Connecticut A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio S. Kazakov KEK, Ibaraki E. Nenasheva Ceramics Ltd., St. Petersburg
	Funding: Research supported by the Department of Energy, Division of High Energy Physics A fast, electrically-controlled phase shifter is described with parameters suitable for operation with the SC acceleration structure of the electron cooling system of Relativistic Heavy Ion Collider (RHIC) at BNL. The phase shifter is a key element of the external RF vector modulator that is capable of fast tuning of the cavities against microphonics, Lorentz force and beam instabilities in a way that can possibly lead to an order of magnitude reduction in the required RF power. The phase shifter is based on a shortened low-impendence coaxial line with ferroelectric rings. The dielectric constant of the ferroelectric rings is altered by applying a 4.2 kV voltage that provides an RF phase shift from 0 to 180 deg.

MOPAS105	Analysis and Simulation of Main Magnet Transmission Line Effect	dipole, coupling, simulation, power-supply	673
	W. Zhang I. Marneris, J. Sandberg BNL, Upton, Long Island, New York
	Funding: Wor performed under auspices of U. S. Departemnt of Energy. A main magnet chain forms a pair of transmission lines. Pulse-reflection-caused voltage and current differentiation throughout the magnet chain can have adverse effect on main magnet field quality. This effect is associated with magnet system configuration, coupling efficiency, and parasitic parameters. A better understanding of this phenomenon will help us in new design and existing system upgrade. In this paper, we exam the transmission line effect due to different input functions as well as configuration, coupling, and other parameters.

TUODAB01	Variations of Betatron Tune Spectrum due to Electron Cloud Observed in KEKB	electron, damping, focusing, positron	825
	T. Ieiri H. Fukuma, Y. Ohnishi, M. Tobiyama KEK, Ibaraki
	In order to investigate the characteristics of electron clouds, the wake effects were measured at KEKB using a test bunch placed behind a bunch-train, where there was a rapid decay in the electron cloud density. The current-dependent tune-shift of the test bunch exhibited nonlinear behaviour in the vertical plane [1]. By observing the tune spectrum, we found that the spectrum width expanded and this was accompanied with a large negative tune slope at a low cloud density and at a low bunch current. However, as the cloud density increased, the spectrum width shrunk and this was accompanied with a positive tune slope. These experimental results suggested that a high electron cloud density caused an anti-damping effect in the tune spectrum. We believe that the variations in the tune slope and spectrum width might be related to the wake field in the resonator model, where the wavelength is comparable to the bunch length. [1] T. Ieiri et al., Proc. of EPAC06, Edinburgh, Scotland, 2101 (2006).
	Slides

TUOAC01	Design and Measurements of a Damping Ring Kicker for the ILC	kicker, damping, pulsed-power, optics	846
	M. J. Barnes G. D. Wait TRIUMF, Vancouver
	Funding: Work supported by a contribution from the National Research Council of Canada. The International Linear Collider (ILC) requires ultra fast kickers for the damping ring. One option requires kickers which must produce pulses of 5 kV magnitude, with 6 ns rise and 6 ns fall time into a 50 Ohm, terminated, matched stripline deflector. The pulse must rise and fall within 12 ns. The pulse magnitude must be repeatable to a high accuracy. This paper describes a novel design for a suitable pulse generator for the damping ring kicker, in which 2 stacks of 1kV FETS are combined to generate the fast pulses. The design concept uses 2 parallel 100 Ω drivers combined to provide a 50 Ω driver. The need for 3 MHz burst mode operation for 1 ms at 5 Hz (or 10 Hz) gives an average rep rate of 15 kHz (or 30 kHz). Measurements and calculations are presented on the present state of the TRIUMF prototype pulse generator.
	Slides

TUODC02	Development of 3D Beam-Beam Simulation for the Tevatron	simulation, collider, betatron, dipole	905
	E. G. Stern J. F. Amundson, P. Spentzouris, A. Valishev Fermilab, Batavia, Illinois J. Qiang, R. D. Ryne LBNL, Berkeley, California
	We present status of development of a 3D Beam-Beam simulation code. The essential features of the code are 3D particle-in-cell Poisson solver, multi-bunch beam transport and interaction, chromaticity and machine impedance. The simulations match synchro-betatron oscillations measured at the VEPP-2M collider. The impedance model is compared to analytic expressions for instability growth.
	Slides

TUPMN076	The Fabrication and Characterization of an S-band RF-gun Cavity	coupling, gun, resonance, monitoring	1097
	T.-T. Yang C.-S. Fann, K. T. Hsu, S. Y. Hsu, J.-Y. Hwang, W. K. Lau, A. P. Lee, C. C. Liang, K.-K. Lin, K.-B. Liu, Y.-C. Liu, H. M. Shih, M.-S. Yeh NSRRC, Hsinchu
	A single cell rf-gun cavity is designed and fabricated for the purpose of examining the feasibility of installing a thermionic rf-gun at NSRRC instead of a photocathode rf-gun considered previously. The operating frequency of the rf-gun cavity is set at 2856 MHz in order to utilize the available XK-5 klystron and linac. The fabricated parts of the OFHC copper cavity are brazed together in-house and then the cavity is characterized by rf measurement. It shows that the cavity gives very good character in terms of high quality factor, relaxed tuning range, adequate coupling coefficient, and reasonable reproducibility. The properties of the cavity are further explored by measuring the field profile and its response to an rf pulse in which the filling time is deduced. The measurement results of this brazed cavity are described and summarized in this report.

TUPMN091	Planned Use of Pulsed Crab Cavities for Short X-ray Pulse Generation at the Advanced Photon Source	storage-ring, photon, single-bunch, damping	1127
	M. Borland J. Carwardine, Y.-C. Chae, P. K. Den Hartog, L. Emery, K. C. Harkay, A. H. Lumpkin, A. Nassiri, V. Sajaev, N. Sereno, G. J. Waldschmidt, B. X. Yang ANL, Argonne, Illinois V. A. Dolgashev SLAC, Menlo Park, California
	Funding: Work supported by the U. S. Department of Energy, Office of Science, Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. In recent years, we have explored application to the Advanced Photon Source (APS) of Zholents'* crab-cavity-based scheme for production of short x-ray pulses. Work concentrated on using superconducting (SC) cavities in order to have a continuous stream of crabbed bunches and flexibility of operating modes. The challenges of the SC approach are related to the size, cost, and development time of the cavities and associated systems. A good case can be made for a pulsed system** using room-temperature cavities. APS has elected to pursue such a system in the near term, with the SC-based system planned for a later date. This paper describes the motivation for the pulsed system and gives an overview of the planned implementation and issues. Among these are overall configuration options and constraints, cavity design options, frequency choice, cavity design challenges, tolerances, instability issues, and diagnostics plans. A. Zholents et al., NIM A 425, 385 (1999).*P. Anfinrud, private communication.

TUPMN102	Electromagnetic Design of the RF Cavity Beam Position Monitor for the LCLS	dipole, coupling, simulation, linac	1153
	G. J. Waldschmidt R. M. Lill, L. H. Morrison ANL, Argonne, Illinois
	Funding: Work supported by the U. S. Department of Energy under Contract Nos DE-AC02-06CH11357 and DE-AC03-76SF00515. A high-resolution X-band cavity beam position monitor (BPM) has been developed for the LCLS in order to achieve micron-level accuracy of the beam position using a dipole mode cavity and a monopole mode reference cavity. The rf properties of the BPM will be discussed in this paper including output power, tuning, and issues of manufacturing. In addition, methods will be presented for improving the isolation of the output ports to differentiate between horizontal/vertical beam motion and to reject extraneous modes from affecting the output signal. The predicted simulation results will be compared to data collected from low-power experimental tests.

TUPMN114	Simulation of the Microbunching Instability in Beam Delivery Systems for Free Electron Lasers	simulation, laser, electron, space-charge	1179
	I. V. Pogorelov J. Qiang, R. D. Ryne, M. Venturini, A. Zholents LBNL, Berkeley, California R. L. Warnock SLAC, Menlo Park, California
	In this paper, we examine the growth of the microbunching instability in the chain of linac sections and bunch compressor chicanes used in the electron beam delivery system of a free electron laser. We compare the results of two sets of simulations, one conducted using a direct Vlasov solver, the other using a particle-in-cell code Impact-Z with the number of simulation macroparticles ranging up to 100 million. The comparison is focused on the values of uncorrelated (slice) energy spread at different points in the lattice. In particular, we discuss the interplay between physical and numerical noise in particle-based simulations, and assess the agreement between the simulation results and theoretical predictions.

TUPMS043	Design of a 2.1 GeV Electron Storage Ring	simulation, emittance, dynamic-aperture, vacuum	1284
	R. A. Bosch
	Funding: This research was supported by National Science Foundation Grant no. DMR-0537588. A 2.1 GeV electron storage ring can serve as a third-generation light source for photon energies of 1-2000 eV. We design a ring with emittance of 1.5 nm-rad, circumference of 215 m, and twelve 5.5 m long straight sections. With a 100 MHz radiofrequency (rf) system, the computed Touschek current-lifetime product is 2800 mA-hr. Two passive fifth-harmonic cavities may be used to suppress parasitic coupled-bunch instabilities while increasing the bunchlength and lifetime by a factor of four. For stable operation with ring currents up to 600 mA, microwave-instability simulations indicate that the reduced longitudinal impedance should not exceed 1.5Ω.

TUPMS057	An Efficient 95-GHz, RF-Coupled Antenna	radiation, undulator, electron, laser	1314
	J. E. Spencer Y. A. Hussein SLAC, Menlo Park, California
	Funding: Work supported by U. S. Dept. of Energy contract DE-AC02-76SF00515. This paper presents an efficient, RF-coupled, 95-GHz undulatory (snake-like) antenna that can be fabricated using IC technology. While there are many uses for directed power at this frequency our interest is in understanding the propagation of the input power through the circuit and its radiative characteristics for comparison to earlier work in the THz range (see PAC05). 95 GHz was chosen because test equipment was available (WR-10 waveguide and HP network analyzer). Different materials, heights and widths of the circuit were considered on a low-loss, 0.10-mm thick quartz substrate e.g. 0.75 microns of elevated gold corresponding to three skin depths. The design is compared to more conventional RF technology using a low energy, high power electron beam and to higher energy, lower power Smith Purcell gratings and free-electron-lasers (FELs). The FDTD results show narrow-band, 80% radiation efficiency with a dipole-like radiation pattern that is enhanced by adding periods. The radiated power was calculated using two different techniques that agreed quite well i.e. by integrating the far-field Poynting vector as well as subtracting the output power from input power.

TUPMS074	Collective Effects in the NSLS-II Storage Ring	emittance, storage-ring, damping, single-bunch	1344
	S. Krinsky J. Bengtsson, J. S. Berg, M. Blaskiewicz, A. Blednykh, W. Guo, N. Malitsky, C. Montag, B. Podobedov, J. Rose, N. A. Towne, L.-H. Yu BNL, Upton, Long Island, New York F. Wang MIT, Middleton, Massachusetts
	Funding: This work was supported by Department of Energy contract DE-AC02-98CH10886. A new high-brightness synchrotron light source (NSLS-II) is under design at BNL. The 3-GeV NSLS-II storage ring has a double-bend achromatic lattice with damping wigglers installed in zero-dispersion straights to reduce the emittance below 1nm. In this note, we present an overview of the impact of collective effects upon the performance of the storage ring. Subjects discussed include Touschek lifetime, intra-beam scattering, instability thresholds due to ring impedance, and use of a third-harmonic Landau cavity.

TUPMS092	GdfidL Simulations of Non-Linear Tapers for ILC Collimators	simulation, emittance, insertion, luminosity	1380
	J. D.A. Smith
	This paper summarises the GdfidL simulations relating to non-linear collimators, which offer the potential for improved wakefield performance at the ILC. Such collimators provide a further method for understanding the performance of simulation software in this challenging regime. Our results are compared with data from ESA at SLAC.

TUPAN056	Fabrication Status of ACS Accelerating Modules of J-PARC Linac	coupling, linac, target, vacuum	1514
	H. Ao K. Hasegawa JAEA, Ibaraki-ken K. Hirano, T. Morishita, A. Ueno JAEA/LINAC, Ibaraki-ken M. Ikegami KEK, Ibaraki V. V. Paramonov RAS/INR, Moscow Y. Yamazaki KEK/JAEA, Ibaraki-Ken
	An ACS (Annular Coupled Structure) cavity has been developed for the J-PARC Linac from 190-MeV to 400-MeV. We fabricated a buncher module with two 5-cell accelerating tanks and one 5-cell bridge tank as the first module. The buncher module is shorter than accelerating module that consists of two 17-cell accelerating tanks and one 9-cell bridge tank. The first buncher module achieved the stable operation of 50 Hz, 600 us, 600 kW in the high-power test, which corresponds to the E0 value of 4.8 MV/m. The second buncher module and three accelerating modules are under fabrication continuously. These results of the frequency tuning and assembling are presented in detail.

TUPAN063	High Power Test of MA Cavity for J-PARC RCS	linac, synchrotron, acceleration, power-supply	1532
	M. Yamamoto S. Anami, E. Ezura, K. Hara, C. Ohmori, A. Takagi, M. Toda, M. Yoshii KEK, Ibaraki K. Hasegawa, M. Nomura, A. Schnase, F. Tamura JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
	We have been testing the RF cavities for the J-PARC RCS, we can operate the cavities without sever problems. Before some MA cores were damaged, then we found such cores have low ribbon resistance. After that we have tested the cavities loaded with improved ribbon resistance.

TUPAN085	LHC Impedance Reduction by Nonlinear Collimation	collimation, insertion, betatron, damping	1571
	J. Resta-Lopez A. Faus-Golfe IFIC, Valencia F. Zimmermann CERN, Geneva
	A nonlinear collimation system can allow larger aperture for the mechanical jaws, and it thereby can help to reduce the collimator impedance, which presently limits the LHC beam intensity. Assuming the nominal LHC beam at 7 TeV, we show how a nonlinear betatronic collimation insertion would reduce considerably the LHC coherent tune shift for the most critical coupled-bunch mode as compared with the conventional baseline linear collimation system of Phase-I. In either case, the tune shifts of the most unstable modes are compared with the stability diagrams for Landau damping.

TUPAN086	An Improved Beam Screen for the LHC Injection Kickers	kicker, coupling, vacuum, injection	1574
	M. J. Barnes F. Caspers, L. Ducimetiere, N. Garrel, T. Kroyer CERN, Geneva
	The two LHC injection kicker magnet systems must 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. Each system is composed of two resonant charging power supplies and four 5 Ω transmission line kicker magnets with matched terminating resistors and pulse forming networks. A beam screen is placed in the aperture of the magnets: the screen consists of a ceramic tube with conductors on the inner wall. 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 impedance however inter-conductor discharges occurred during pulsing of the magnet: an alternative design was discharge free at the nominal operating voltage but the beam impedance was too high for the ultimate LHC beam. This paper presents the results of a new development undertaken to meet the often conflicting requirements for low beam impedance, shielding of the ferrite, fast field rise time and good electrical behaviour. High voltage test results and thermal measurements are also presented.

TUPAN107	Beam Loss Response Measurements with an LHC Prototype Collimator in the SPS	beam-losses, controls, alignment, collimation	1622
	Th. Weiler G. Arduini, R. W. Assmann, C. B. Bracco, H.-H. Braun, B. Dehning, P. Gander, E. B. Holzer, M. Jonker, R. Losito, A. Masi, L. Ponce, S. Redaelli, G. Robert-Demolaize, M. Sobczak, J. Wenninger CERN, Geneva
	Beam tests with an LHC prototype collimator were performed at the SPS in autumn 2006. Applying a new collimator control system many new beam measurements were performed. This contribution presents results on collimator-induced beam loss measurements and their applications to beam-based alignment of collimators and measurements of the beam size and position. Interesting features of the recorded beam loss signals are illustrated and possible impacts for LHC operation are discussed. The measured loss distributions around the full SPS ring are analyzed and compared with simulations.

TUPAN114	RF Design Options for a 180 MeV H^- Linac for Megawatt Beam Facilities	linac, proton, quadrupole, factory	1643
	D. C. Plostinar
	Future projects like a neutrino factory or an advanced spallation neutron source require high power proton accelerators capable of producing beams in the multi-MW range. The quality of the beam delivered to the target is very much dictated by the accelerator front end and by the lower energy linac. Prompted by the Front End Test Stand (FETS) under construction at RAL, a new 180 MeV H^- linac is being considered as a possible replacement for the aging current 70 MeV ISIS injector, and the same linac has also been included in designs for the proton driver for a possible UK Neutrino Factory. In this paper, different RF design options are analysed and a general layout for the new linac is presented based on two accelerating structures to raise the beam energy from 3 to 180 MeV: a 324 MHz Drift Tube Linac (DTL) making use of commercial Toshiba klystrons, followed by Side Coupled Linac (SCL) with a triple frequency jump at the transition between the two structures.

TUPAS058	Electromagnetic Simulations of Linear Proton Accelerator Structures Using Dielectric Wall Accelerators	proton, acceleration, simulation, controls	1784
	S. D. Nelson G. J. Caporaso, B. R. Poole LLNL, Livermore, California
	Funding: This work was performed under the auspices of the U. S. Department of Energy, the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48. Proton accelerator structures for medical applications using Dielectric Wall Accelerator (DWA) technology allows for the utilization of high field gradients on the order of 100 MV/m to accelerate the proton bunch. Medical applications involving cancer therapy treatment usually desire short bunch lengths on the order of hundreds of picoseconds in order to limit the extent of the energy deposited in the tumor site (in 3D space, time, and deposited proton charge). Electromagnetic simulations of the DWA structure, in combination with injections of proton bunches, have been performed using 3D finite difference codes in combination with particle pushing codes. Electromagnetic simulations of DWA structures includes these effects and also includes the details of the switch configuration and how that switch time affects the electric field pulse which accelerates the particle beam. Design trade-offs include the driving switch effects, layer-to-layer coupling analysis and its affect on the pulse rise time.

WEXC02	The Impedance Database Computation and Prediction of Single Bunch Instabilities	single-bunch, photon	1996
	Y.-C. Chae
	Funding: Work supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The Impedance Database is a standardized 3D computation of the wake potential generated by a high-intensity beam. The database concept is described and compared to analytical and model-based approaches. The talk will address the computational challenges introduced by tapers, collimators, and very short bunches. Finally, single-bunch instabilities are predicted through tracking and compared to measurements at the Advanced Photon Source and other accelerators.
	Slides

WEOAC02	A New Type of Distributed Enamel Based Clearing Electrode	electron, simulation, vacuum, coupling	2000
	F. Caspers F.-J. Behler Eisenwerke Fried. Wilh. Dueker GmbH & Co. KGaA, Laufach P. P. Hellmold Clausthal, Inst für Nichtmetall. Werkstoffe, Clausthal-Zellerfeld T. Kroyer, E. Metral, F. Zimmermann CERN, Geneva J. Wendel Wendel GmbH, Dillenburg
	A practical technology for implanting thin strip-like enamel structures in metallic beam-pipes, to be used for e-cloud clearing, has been developed. We discuss the technical and technological issues of this method. Parameters of particular interest are the beam coupling impedance as a function of the conductive coating resistivity and also the secondary electron yield. A test-stand for multipactoring measurements on a first prototype using the coaxial resonator method is described.
	Slides

WEOAC03	Transverse Impedance of LHC Collimators	injection, octupole, collimation, insertion	2003
	E. Metral G. Arduini, R. W. Assmann, A. Boccardi, T. Bohl, C. B. Bracco, F. Caspers, M. Gasior, O. R. Jones, K. K. Kasinski, T. Kroyer, S. Redaelli, G. Robert-Demolaize, G. Rumolo, R. J. Steinhagen, Th. Weiler, F. Zimmermann CERN, Geneva F. Roncarolo UMAN, Manchester B. Salvant EPFL, Lausanne
	The transverse impedance in the LHC is expected to be dominated by the numerous collimators, most of which are made of Fibre-Reinforced-Carbon to withstand the impacts of high intensity proton beams in case of failures, and which will be moved very close to the beam, with full gaps of few millimetres, in order to protect surrounding super-conducting equipments. We present an estimate of the transverse resistive-wall impedance of the LHC collimators, the total impedance in the LHC at injection and top energy, the induced coupled-bunch growth rates and tune shifts, and finally the result of the comparison of the theoretical predictions with measurements performed in 2004 and 2006 on a prototype collimator installed in the SPS.
	Slides

WEOAC04	Impedance Minimization by Nonlinear Tapering	simulation	2006
	B. Podobedov I. Zagorodnov DESY, Hamburg
	There exist analytical approximations that express the transverse geometric impedance of tapered transitions in the inductive regime as a functional of the transition boundary and its derivatives. Assuming the initial and final cross-sections and the transition length are fixed, one can minimize these functionals by appropriate choice of the boundary variation with the longitudinal coordinate. In this paper we numerically investigate how well this works for the cases of optimized tapered transitions in circular, elliptical and rectangular geometry by running ABCI, ECHO, and GDFIDL EM field solvers. We show that a significant reduction of impedance for optimized boundary compared to that of a linear taper is indeed possible in some cases, and then we compare this reduction to analytical predictions.
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WEOBC01	Beam Instability Observations and Analysis at SOLEIL	feedback, single-bunch, electron, ion	2019
	R. Nagaoka L. Cassinari, M.-E. Couprie, M. Labat, M.-P. Level, C. Mariette, R. Sreedharan SOLEIL, Gif-sur-Yvette
	Due to reduced vertical chamber aperture around the machine, the impedance was systematically evaluated and optimized 3D-wise at SOLEIL during the design stage, whose budget was then utilized to predict instability thresholds for multi and single bunches. These theoretical calculations are compared with observed instabilities. Transverse multibunch current thresholds are followed as a function of chromaticity, identifying the transition of different head-tail regimes that reflects the broadband impedance spectrum. Although low thresholds due to resistive-wall are basically confirmed, its combined effect with ion-induced instability is found to be significant, exhibiting a strong beam filling pattern dependence. To analyse the involved dynamics, a multibunch tracking code is developed in a structure that allows parallel computations with a cluster of processors. The obtained results are compared with empirical data. Analysis of single bunch instabilities is also made with an aim to identify the enhanced reactive impedance due to NEG coating.
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WEPMN040	MA Cavities for J-PARC with Controlled Q-value by External Inductor	vacuum, resonance, acceleration, controls	2131
	A. Schnase S. Anami, E. Ezura, K. Hara, K. Hasegawa, C. Ohmori, A. Takagi, M. Toda, M. Yoshii KEK, Ibaraki M. Nomura, F. Tamura, M. Yamamoto JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
	The original J-PARC RCS cavity design* used cut-cores to control the Q-value. Adjusting the distance between the C-shaped core parts the optimum Q=2 is reached. Because of problems related to the cut-core surfaces, the "hybrid cavity" was introduced, using tanks with uncut cores (Q=0.6) in parallel to tanks with cut cores with a wider gap (Q=4), resulting in total Q=2. This was successfully tested. The manufacturing procedure for cut-cores involves more steps than for uncut cores. To reduce risks for long-term operation, the RCS cavities will be loaded with uncut cores for day-1 operation. With uncut cores (Q=0.6) the maximum beam power is limited. Therefore we introduce a parallel inductor, placed in the push-pull tube amplifier driving the cavity, to adjust the Q-value to 2. Parallel vacuum capacitors shift the resonance near to 1.7 MHz. Each of the 10 cavity systems for RCS, necessary for day-1 operation, is tested for at least 300 hours to detect initial problems before installation into the RCS tunnel. We report the results of cavity performance tests with external inductor, which simulate 25Hz operation and the optimization of the combined system of cavity and amplifier. * C. Ohmori at. al, "High Field-Gradient Cavity for J-PARC 3 GeV RCS", PAC 2004

WEPMN041	Reduction of RF Skin Loss with Thin Foils	resonance, electromagnetic-fields, controls, linac	2134
	Y. Iwashita H. Fujisawa, M. Ichikawa, Y. Tajima Kyoto ICR, Uji, Kyoto
	Reduction of RF power loss caused by skin effect has been studied. Some measurement results on a coaxial cavity with thin foils are described. Application to another type of RF devices will be discussed.

WEPMN062	HOM Analysis and Design of its Removal System for SRF 3rd Harmonic RF Cavity in PLS	electron, storage-ring, superconducting-RF, vacuum	2179
	Y. U. Sohn J. Choi, M.-H. Chun, J. Y. Huang, I. S. Ko, I. S. Park PAL, Pohang, Kyungbuk
	Funding: Korea Ministry of Science & Technology Pohang Accelerator Laboratory has prepared to SRF 3rd harmonic cavity to increase beam lifetime and to damp orbit instability by lengthening electron bunch in PLS. The SRF cavity was developed and its vertical test was done already with success. Higher order modes were analyzed to optimize its performance in beam orbit. Most of them are not effective to electron beam, while the others have possibility to impact orbit stability. These harmful HOMs can be removed by HOM absorber installed in beam pipe. This paper reports the HOM analysis and design of its removal system.

WEPMN068	Design of the Modulator for the CTF3 Tail Clipper Kicker	kicker, beam-losses, damping, cathode	2185
	M. J. Barnes T. Fowler, G. Ravida CERN, Geneva A. Ueda KEK, Ibaraki
	The goal of the present CLIC test facility (CTF3) is to demonstrate the technical feasibility of specific key issues in the CLIC scheme. The extracted beam from the combiner ring (CR), of 35 A in magnitude and 140 ns duration, is sent to the new CLic EXperimental area (CLEX) facility. A Tail Clipper (TC) is required, in the CR to CLEX transfer line, to allow the duration of the extracted beam pulse to be adjusted. It is proposed to use a stripline kicker for the tail clipper, with each of the deflector plates driven to equal but opposite potential. The tail clipper kick must have a fast rise-time, of not more than 5 ns, in order to minimize uncontrolled beam loss and operate at a rate of up to 50 Hz. Several different options are being investigated to meet the demanding specifications for the modulator of the tail clipper. This paper discusses options considered for the fast, high voltage, semiconductor switches and shows results of initial tests on the switches.

WEPMN069	Low Power Measurements on an AGS Injection Kicker Magnet	kicker, injection, proton, simulation	2188
	M. J. Barnes G. D. Wait TRIUMF, Vancouver
	Funding: Work supported by a contribution from the Canada Foundation for Innovation. The present AGS injection kickers at A5 location were designed for 1.5 GeV proton injection. Recent high intensity runs have pushed the transfer kinetic energy to 1.94 GeV, but with an imperfect matching in transverse phase space. Space charge forces result in both fast and slow beam size growth and beam loss as the size exceeds the AGS aperture. An increase in the AGS injection energy to 2 GeV with adequate kick strength would greatly reduce the beam losses making it possible to increase the intensity from 70 TP (70 * 10¹² protons/s) to 100 TP. R&D studies* have been undertaken by TRIUMF, in collaboration with BNL, to design two new kicker magnets for the AGS A10 location to provide an additional kick of 1.5 mrad to 2 GeV protons. TRIUMF has designed and built a prototype 12.5 Ω transmission line kicker magnet with rise and fall times of 100 ns, 3% to 97% and field uniformity of (±)1% over 85% of the aperture, powered by matched 12.5 Ω pulse-forming lines. This paper describes the results of detailed capacitance and inductance measurements, on the prototype magnet, and compares these with predictions from 2D and 3D electromagnetic simulations. *L. Ahrens, R. B. Armenta, M. J. Barnes, E. W Blackmore, C. J. Gardner, O. Hadary, G. D. Wait, W. Zhang, "Design Concept for AGS Injection Kicker Upgrade to 2 GeV", PAC 2005, Knoxville Tennessee.

WEPMN071	High RF Power Production for CLIC	damping, linac, extraction, simulation	2194
	I. Syratchev E. Adli, D. Schulte, M. Taborelli CERN, Geneva
	The CLIC Power Extraction and Transfer Structure (PETS) is a passive microwave device in which bunches of the drive beam interact with the impedance of the periodically loaded waveguide and excite preferentially the synchronous mode. The RF power produced (several hundred MW) is collected at the downstream end of the structure by means of the Power Extractor and delivered to the main linac structure. The PETS geometry is a result of multiple compromises between beam stability and main linac RF power needs. Another requirement is to provide local RF power termination in case of accelerating structure failure (ON/OFF capability). Surface electric and magnetic fields, power extraction method, HOM damping, ON/OFF capability and fabrication technology were all evaluated to provide a reliable design.

WEPMN077	Impedance Measurements on a Test Bench Model of the ILC Crab Cavity	dipole, coupling, simulation, higher-order-mode	2206
	P. Goudket C. D. Beard, P. A. McIntosh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire G. Burt Cockcroft Institute, Lancaster University, Lancaster N. Chanlek, R. M. Jones UMAN, Manchester A. C. Dexter Cockcroft Institute, Warrington, Cheshire
	Funding: This work was supported by the EC under the FP6 'Research Infrastructure Action - Structuring the European Research Area' EUROTeV DS Project Contract no.011899, RIDS and PPARC. In order to verify detailed impedance simulations, the modes in an aluminium model of the ILC crab cavity were investigated using a bead-pulling technique as well as a stretched-wire frequency domain measurement. The combination of these techniques allow for a comprehensive study of the modes of interest. For the wire measurement, a transverse alignment system was fabricated and rf components were carefully designed to minimize any potential impedance mismatches. The measurements are compared with direct simulations of the stretched-wire experiments using numerical electromagnetic field codes. High impedance modes of particular relevance to the ILC crab cavity are identified and characterized

WEPMN078	RF Cavity Development for FFAG Application on ERLP at Daresbury	klystron, electron, linac, extraction	2209
	E. Wooldridge C. D. Beard, B. D. Fell, P. A. McIntosh, B. Todd STFC/DL/ASTeC, Daresbury, Warrington, Cheshire R. M. Jones, B. Spencer UMAN, Manchester
	Funding for a non-scaling, Fixed Field Alternating Gradient (FFAG) facility has been approved for installation on the Energy Recovery Linac Prototype (ERLP) at Daresbury. The RF system specification for this project requires the development of a high efficiency, 1.3 GHz, normal conducting accelerating structure, capable of delivering the required accelerating voltage, whilst adhering to stringent space limitations imposed by the extremely compact nature of the FFAG ring. We have optimised a cavity design, providing the necessary acceleration and minimising the RF power requirements to match with commercially available power sources.

WEPMN102	A 96 Channel Receiver for the ILCTA LLRF System at Fermilab	controls, target, insertion, linac	2271
	U. Mavric J. Branlard, B. Chase, E. Cullerton, D. W. Klepec Fermilab, Batavia, Illinois
	The present configuration of an ILC Main Linac RF station has 26 nine cell cavities driven from one klystron. With the addition of waveguide power coupler monitors, 96 RF signals will be downconverted and processed. A downconverter chassis is being developed that contains 12 eight channel analog modules and a single upconverter module. This chassis will first be deployed for testing a cryomodule composed of eight cavities located at New Muon Laboratory (NML) - Fermilab. Critical parts of the design for LLRF applications are identified and a detailed description of the circuit with various characteristic measurements is presented. The board is composed of an input band-pass filter centered at 1.3GHz, followed by a mixer, which downconverts the cavity probe signal to a proposed 13 MHz intermediate frequency. Cables with 8 channels per connector and good isolation between channels are being used to interconnect each downconverter module with a digital board. As mixers and power splitters are the most sensitive parts for noise, nonlinearities and cross-talk issues, special attention is given to these parts in the design of the LO port multiplication and distribution.

WEPMN112	Multichannel Vector Field Control Module for LLRF Control of Superconducting Cavities	controls, klystron, diagnostics, feedback	2298
	P. Varghese B. Barnes, J. Branlard, B. Chase, P. W. Joireman, D. W. Klepec, U. Mavric, V. Tupikov Fermilab, Batavia, Illinois
	The field control of multiple superconducting RF cavities with a single Klystron, such as the proposed RF scheme for the ILC, requires high density (number of RF channels) signal processing hardware so that vector control may be implemented with minimum group delay. The MFC (Multichannel Field Control) module is a 33-channel, FPGA based downconversion and signal processing board in a single VXI slot, with 4 channels of high speed DAC outputs. An LO input of upto 1.6 GHz can be divided down to provide 8 clock signals through a clock distribution chip. A 32-bit, 400MHz floating point DSP provides additional computational capability for calibration and implementation of more complex control algorithms. Both the FPGA and DSP have external SDRAM memory for diagnostic data and nonvolatile Flash memory for program and configuration storage. Multiple high speed serial transceivers on the front panel and the backplane bus allow a flexible architecture for inter-module real time data exchanges. An interface CPLD supports the VXI bus protocol for communication to a Slot0 CPU, with Ethernet connections for remote in system programming of the FPGA and DSP as well as for data acquisition.

WEPMS001	Application of Induction Module for Energy Perturbations in the University of Maryland Electron Ring	induction, space-charge, electron, simulation	2322
	B. L. Beaudoin S. Bernal, I. Haber, R. A. Kishek, P. G. O'Shea, M. Reiser, J. C.T. Thangaraj, K. Tian, M. Walter, C. Wu UMD, College Park, Maryland
	Funding: Work supported by the U. S. Department of Energy grant numbers: DE-FG02-94ER40855 and DE-FG02-92ER54178, ONR and Joint Technology Office The University of Maryland Electron Ring (UMER) is a scaled storage ring using low-energy electrons to inexpensively model beams with high-space-charge. With the ability to inject such beams comes the problem of longitudinal end erosion of both the head and tail. It is important therefore to apply suitably designed longitudinal focusing forces to confine the beam and prevent it from its normal expansion. This paper presents the design and prototyping of an induction cell for this purpose. Successful operation of the induction cell would push the achievable number of turns and also enable us to perform studies of the longitudinal physics of such highly space-charge dominated beams. The pulsed voltage requirements for such a system on UMER would require ear-fields that switch 3kV in about 8ns or so for the most intense flat-top rectangular beam injected into the ring. This places a considerable challenge on the electronics used to deliver ideal waveforms with a compact module. Alternate waveforms are also being explored for other various injected beam shapes into UMER.

WEPMS004	Deflecting Cavity for Beam Diagnostics in ERL Injector	diagnostics, gun, emittance, electromagnetic-fields	2331
	S. A. Belomestnykh V. D. Shemelin, K. W. Smolenski, V. Veshcherevich CLASSE, Ithaca
	Funding: Work is supported by the National Science Foundation grant PHY 0131508. A 1300 MHz deflecting cavity will be used for beam slice emittance measurements, and to study the temporal response of negative electron affinity photocathodes in the ERL injector currently under construction at Cornell University. A single-cell TM110-mode cavity was designed to deflect the beam vertically. The paper describes the cavity shape optimization procedure, its mechanical design and performance at low RF power.

WEPMS012	Low Loss and High Gradient SC Cavities with Different Wall Slope Angles	superconductivity, coupling	2352
	V. D. Shemelin
	Funding: NSF The introduction of reentrant shape for superconducting cavities has made it possible to achieve record high gradients. In this paper it is shown that lowest losses in the cavities are also achievable employing the reentrant shape. Influence of the cavity wall slope angle on the extreme gradient and losses is analyzed.

WEPMS013	High Power Tests of First Input Couplers for Cornell ERL Injector Cavities	vacuum, coupling, superconductivity, linac	2355
	V. Veshcherevich S. A. Belomestnykh, P. Quigley, J. J. Reilly, J. Sears CLASSE, Ithaca W.-D. Moller DESY, Hamburg
	Funding: Work is supported by the National Science Foundation grant PHY 0131508 First RF power couplers for the ERL injector, currently under construction at Cornell University, have been fabricated. The couplers were assembled in pairs in the liquid nitrogen cryostat, built for their tests. A 15 kW CW IOT transmitter was available for coupler tests. A resonant ring was used for additional increase of the power. The couplers were successfully tested up to the goal power level of 50 kW CW. However, the first pair of couplers showed excessive temperature rise in some points. Therefore, minor changes in the design have been done to improve cooling.

WEPMS023	Progress on New High Power RF System for LANSCE DTL	power-supply, linac, controls, injection	2382
	J. T.M. Lyles S. Archuletta, D. Baca, J. Davis, D. Rees, P. A. Torrez LANL, Los Alamos, New Mexico
	Funding: Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE-AC52-06NA25396 A new 200 MHz RF system is being developed for the LANSCE proton drift tube linac (DTL). A planned upgrade will replace parts of the DTL RF system with new generation components. When installed for the LANSCE-R project, the new system will reduce the total number of electron power tubes from twenty-four to seven in the DTL plant. The 3.4 MW final power amplifier will use a Thales TH628 Diacrode. This state-of-the-art device eliminates the large anode modulator of the present triode system, and will be driven by a new tetrode intermediate power amplifier. In this mode of operation, this intermediate stage will provide 150 kW of peak power. The first DTL tank requires up to 400 kW of RF power, which will be provided by the same tetrode driver amplifier. A prototype system is being constructed to test components, using some of the infrastructure from previous RF projects. High voltage DC power became available through innovative re-engineering of an installed system. A summary of the design and construction of the intermediate power amplifier will be presented and test results will be summarized.

WEPMS026	Improved Tuning Methods for Converter-Modulators	feedback, linear-collider, collider, operational-performance	2391
	W. Reass R. F. Gribble LANL, Los Alamos, New Mexico
	Funding: This work is supported by the office of Basic Energy Sciences and the Office of Science of the Department of Energy The converter-modulator is a resonant power conditioning configuration that is optimized for a particular load impedance or parameter space. Although traction motor IGBT's are typically used for hard-switching application in the 1 kHz regime, the present use of high-power (10 - 15 MW) converter-modulators have used a 20 kHz resonant switching topology. This presents design challenges to maintain efficient and reliable switching characteristics for the IGBT's. Improved tuning methods and circuit topological changes now offer a significant reduction in IGBT switching losses as compared to those used with the Spallation Neutron Source (SNS) design (perhaps by 10). These circuit and topology changes should also permit Pulse Width Modulation (PWM) of the modulator output voltage to provide a regulated voltage without anomalous IGBT switching characteristics. This paper will review the results of this investigation based on models developed from the SNS converter-modulator operational data.

WEPMS028	Converter-Modulator Design and Operations for the ILC L-band Test Stand	klystron, linear-collider, collider	2397
	W. Reass C. Adolphsen, T. G. Beukers, C. Burkhart, R. L. Cassel, M. N. Nguyen, G. C. Pappas, R. Swent, A. C. de Lira SLAC, Menlo Park, California D. E. Anderson ORNL, Oak Ridge, Tennessee
	Funding: This work supported by Stanford Linear Accelerator Center, Oak Ridge National Laboratory, and the Department of Energy. To facilitate a rapid response to the International Linear Collider (ILC) L-Band development program at SLAC, a spare converter-modulator was shipped from Los Alamos. This modulator was to be a spare for the Spallation Neutron Source (SNS) accelerator at ORNL. The ILC application requires a 33% higher peak output power (15 MW) and output current (130 Amp). This presents significant design challenges to modify the existing hardware and yet maintain switching parameters and thermal cycling within the semiconductor component ratings. To minimize IGBT commutation and free-wheeling diode currents, a different set of optimizations, as compared to the SNS design, were used to tune the resonant switching networks. Additional complexities arose as nanocrystalline cores with different performance characteristics (as compared to SNS), were used to fabricate the resonant "boost" transformers. This paper will describe the electrical design, system modifications, modeling efforts, and resulting electrical performance as implemented for the ILC L-band test stand.

WEPMS038	RF Design of Normal Conducting Deflecting Structures for the Advanced Photon Source	damping, photon, electron, gun	2427
	V. A. Dolgashev M. Borland, G. J. Waldschmidt ANL, Argonne, Illinois
	Use of normal conducting deflecting structures for production of short x-ray pulses is now being implemented at the Advanced Photon Source (APS). The structures have to produce up to 6 MV maximum deflection per structure at a 1kHz repetition rate. At the same time, the nominal beam quality must be maintained throughout the APS ring. Following these requirements, we proposed 2815 MHz standing wave deflecting structure with heavy wakefield damping. In this paper, we discuss the design considerations and present our current results.

WEPMS039	High Power Tests of Normal Conducting Single-Cell Structures	klystron, vacuum, radiation, acceleration	2430
	V. A. Dolgashev Y. Higashi, T. Higo KEK, Ibaraki C. D. Nantista, S. G. Tantawi SLAC, Menlo Park, California
	Funding: This work was supported by the U. S. Department of Energy contract DE-AC02-76SF00515. We report results of the first high power tests of single-cell traveling-wave and standing-wave accelerating structures. These tests are part of an experimental and theoretical study of RF breakdown in normal conducting structures at 11.4 GHz. The goal of this study is to determine the gradient potential of normal conducting, RF powered particle beam accelerators. The test setup consists of reusable mode converters and short test structures powered by SLAC?s XL-4 klystron. This setup was created for economic testing of different cell geometries, cell materials and preparation techniques with short turn-around time. The mode launchers and structures were manufactured at SLAC and KEK and tested in the klystron test laboratory at SLAC. V. A. Dolgashev et al., "RF Breakdown In Normal Conducting Single-Cell Structures," SLAC-PUB-11707, Particle Accelerator Conference (PAC 05), Knoxville, Tennessee, 16-20 May 2005, pp. 595- 599.

WEPMS047	Selecting RF Amplifiers for Impedance Controlled LLRF Systems - Nonlinear Effects and System Implications	controls, klystron, simulation, feedback	2451
	J. D. Fox T. Mastorides, C. H. Rivetta, D. Van Winkle SLAC, Menlo Park, California
	Funding: Work supported by the U. S. Department of Energy under contract #DE-AC02-76SF00515 Several high-current accelerators use feedback techniques in the accelerating RF systems to control the impedances seen by the circulating beam. These Direct and Comb Loop architectures put the high power klystron and LLRF signal processing components inside feedback loops, and the ultimate behavior of the systems depends on the individual sub-component properties. Imperfections and non-idealities in the signal processing leads to reduced effectiveness in the impedance controlled loops. In the PEP-II LLRF systems non-linear effects have been shown to reduce the achievable beam currents, increase low-mode longitudinal growth rates and reduce the margins and stability of the LLRF control loops. We present measurements of the driver amplifiers used in the PEP-II systems, and present measurement techniques needed to quantify the small-signal gain, linearity, transient response and image frequency generation of these amplifiers. Results are presented from measurements of 5 different types of amplifiers, and the trade-offs in selecting between them highlighted.

WEPMS070	Simulation and Measurements of a Heavily HOM-Damped Multi-cell SRF Cavity Prototype	simulation, dipole, damping, coupling	2496
	H. Wang F. Marhauser JLAB, Newport News, Virginia R. A. Rimmer Jefferson Lab, Newport News, Virginia
	Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U. S. DOE Contract No. DE-AC05-06OR23177, and by The Office of Naval Research under contract to the Dept. of Energy. After initial cavity shape optimization* and cryomodule development** for an Ampere-class FEL, we have simulated the whole 5-cell high-current (HC) cavity structure with six waveguide couplers for HOM damping and fundamental power coupling. The time-domain wakefield method using MAFIA is primarily used for calculation of the broadband impedance. Microwave Studio and Omega-3P are also used for the calculation of external Q (Qext) of individual HOMs. A half scale (1497MHz) single-cell model and a 5-cell copper cavity including dummy HOM waveguide loads were fabricated. Details of measurement results on these prototypes including HOM Qext spectrum, bead-pull data, data analysis technique and comparison to the simulations will be presented. * H. Wang et. al., "Elliptical Cavity Shape Optimization for Acceleration and HOM Damping," Proc. PAC 05, Knoxville TN, USA, 2005* R. A.Rimmer et al.; EPAC 2006, paper MOPCH182

WEPMS075	Development and Testing of High Power RF Vector Modulators	controls, klystron, simulation, linac	2508
	Y. W. Kang M. S. Champion, T. W. Hardek, S.-H. Kim, M. P. McCarthy, A. V. Vassioutchenko, J. L. Wilson ORNL, Oak Ridge, Tennessee
	Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U. S. Department of Energy. High power vector modulators can allow a fan-out RF power distribution system that can power many accelerating cavities from a single high-power klystron amplifier. The configuration enables independent control of amplitudes and phases of RF voltages at the cavities. A vector modulator employs either one or two hybrids with two fast phase shifters. Prototype high power RF vector modulators employing a hybrid and two fast ferrite phase shifters in coaxial TEM transmission lines for 402.5 MHz and 805 MHz are built and tested. RF properties of the design and result of high power testing are presented.

WEPMS092	A Simplified Approach to Analyze and Model Inductive Voltage Adder	simulation, kicker, linac, pulsed-power	2553
	W. Zhang W. Eng, C. Pai, J. Sandberg, Y. Tan, Y. Tian BNL, Upton, Long Island, New York
	Funding: Work performed under auspices of U. S. Departemnt of Energy. We have recently developed a simplified model and a set of simple formulas for inductive voltage adder design. This model reveals the relationship of output waveform parameters and hardware designs. A computer simulation has demonstrated that parameter estimation based on this approach is accurate as compared to an actual circuit. This approach can be used in early stages of project development to assist feasibility study, geometry selection in engineering design, and parameter selection of critical components. In this paper, we give the deduction of a simplified model. Among the estimation formulas we present are those for pulse rise time, system impedance, and number of stages. Examples are used to illustrate the advantage of this approach. This approach is also applicable to induction LINAC design.

THOBKI01	Development of a Movable Collimator with Low Beam Impedance	radiation, vacuum, simulation, collider	2587
	Y. Suetsugu K. Shibata KEK, Ibaraki
	A movable collimator (mask) with low beam impedance was proposed for high-intensity accelerators. The collimator head is supported by a ceramic rod with a thin metal coating, instead of a metal block or rod so far. Owing to the ceramic rod, beams hardly see the head, and thus the beam impedance decreases. The thin metal coating prevents the head from unwanted charge up. The head is also made of ceramic, but coated by copper to mitigate the Joule heating by beams. The SiC blocks are prepared close to the head to absorb trapped modes. Impedances and loss factors were calculated by simulation codes, and then the growth rates of coupled bunch instabilities were estimated. A trial model was designed based on the calculation, and installed in the KEK B-factory (KEKB) positron ring. The head had a cross section of 5 mm X 4 mm, and a length of 90 mm, which corresponded to about one radiation length. The performance of the trial model was investigated with beams. The temperatures of components near to the collimator were also measured, which was an indication of the intensity of excited HOM.
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THPMS050	Designing Photonic Bandgap Fibers for Particle Acceleration	lattice, acceleration, vacuum, emittance	3103
	R. J. Noble E. R. Colby, B. M. Cowan, C. M.S. Sears, R. Siemann, J. E. Spencer SLAC, Menlo Park, California
	Funding: Supported by U. S. Dept. of Energy contract DE-AC02-76SF00515 Photonic bandgap (PBG) fibers with hollow core defects have been suggested for use as laser driven accelerator structures. The modes of a periodic PBG fiber lie in a set of allowed bands. A fiber with a central vacuum defect can support so-called defect modes with frequencies in the bandgap and electromagnetic fields confined spatially near the central defect. A defect mode suitable for relativistic particle acceleration must have a longitudinal electric field in the central defect and a phase velocity near the speed of light (SOL). We explore the design of the defect geometry to support well-confined accelerating modes in such PBG fibers. The details of the surface boundary separating the defect from the surrounding matrix are found to be the critical ingredients for optimizing the accelerating mode properties. We give examples of improved accelerating modes in fiber geometries with modified defect surfaces.

THPMS073	Progress towards a Gap Free Dielectric-Loaded Accelerator	coupling, vacuum, simulation, acceleration	3151
	C.-J. Jing S. H. Gold NRL, Washington, DC A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio S. Kazakov KEK, Ibaraki R. Konecny, J. G. Power ANL, Argonne, Illinois
	One of the major concerns in the development of Dielectric-Loaded Accelerating (DLA) structures is the destructive breakdown at dielectric joints caused by a local electric field enhancement induced by the discontinuity of the dielectric constant on the surface of the joint gap. Our previous X-band traveling wave DLA structure design, for example, incorporated two separate impedance matching sections with at least two dielectric joints. In this paper, we present a new design to avoid this problem. This scheme is based on a coaxial type coupler which is able to implement mode conversion and impedance matching at the same time and therefore to eliminate joint gap induced breakdown. The new structure is under construction; bench test results will be presented C. Jing, W. Gai, J. Power, R. Konecny, S. Gold, W. Liu and A. Kinkead, IEEE, Trans. PS, vol.33 No.4, Aug. 2005, pp.1155-1160.

THPMS075	High Power Testing of a Fused Quartz-based Dielectric-loaded Accelerating Structure	plasma, klystron, vacuum, coupling	3157
	C.-J. Jing V. A. Dolgashev, S. G. Tantawi SLAC, Menlo Park, California W. Gai, R. Konecny, J. G. Power, Z. M. Yusof ANL, Argonne, Illinois S. H. Gold NRL, Washington, DC A. K. Kinkead LET
	We report on the most recent results from a series of high power tests being carried out on RF-driven dielectric-loaded accelerating (DLA) structures. The purpose of these tests is to determine the viability of the DLA as a traveling-wave accelerator and is a collaborative effort between Argonne National Laboratory (ANL), Naval Research Laboratory (NRL), and Stanford Linear Accelerator Center (SLAC). In this paper, we report on the recent high power tests of a fused quartz-based DLA structure that was carried out at incident powers of up to 12 MW at NRL and 37 MW at SLAC. We report experimental details of the RF conditioning process and make comparison of our multipactor model to the experiment, including tests of geometrical scaling laws and the time evolution of multipactor. Finally, we discuss future plans for the program including a planned test of new quartz-based DLA with a different geometry to both reach higher accelerating gradients and to continue the parametric study of multipactor.

THPMS076	Development of Dual Layered Dielectric-Loaded Accelerating Structure	simulation, vacuum, coupling, RF-structure	3160
	C.-J. Jing A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio S. Kazakov KEK, Ibaraki
	Funding: DOE SBIR Phase I, DOE Grant No. DE-FG02-05ER84356 Due to the high magnetic field-induced surface currents on its conducting sleeve, a conventional single layer Dielectric-Loaded Accelerating (DLA) structure exhibits a relatively high RF loss. One possible way to solve this problem is to use multilayered DLA structures. In these devices, the RF power attenuation is reduced by making use of the Bragg Fiber concept: the EM fields are well confined by multiple reflections from multiple dielectric layers. This paper presents the design of an X-band dual layer DLA structure as well as the results of bench tests of the device. We will also present results on the design, numerical modeling, and fabrication of structures for coupling RF into multilayer DLAs such as a novel TM03 mode launcher and a TM01-TM03 mode converter using dielectric-loaded corrugated waveguide. C. Jing, W. Liu, W. Gai, J. G. Power, and T. Wong, Nucl. Instr. Meth. Phy. Res. A 539 (2005) 445-454.

THPMS077	Progress towards Development of a Diamond-Based Cylindrical Dielectric Accelerating Structure	plasma, acceleration, vacuum, controls	3163
	A. Kanareykin M. E. Conde, W. Gai ANL, Argonne, Illinois R. Gat Coating Technology Solution, Inc., Somerville C.-J. Jing, P. Schoessow Euclid TechLabs, LLC, Solon, Ohio
	Funding: This research is supported by the US Department of Energy In this talk, we present our recent developments on a high gradient diamond-based cylindrical dielectric loaded accelerator (DLA). The final goal of this research is to achieve a record accelerating gradient (~ 600 MV/m) in a demonstration of the structure at high power and with accelerated beam. We discuss here a new technology for the development of cylindrical diamond-based waveguides and the design, fabrication and high power testing of a cylindrical diamond-based DLA accelerating structure. The electrical and mechanical properties of diamond make it an ideal candidate material for use in dielectric accelerators: high RF breakdown level, extremely low dielectric losses and the highest thermoconductive coefficient available. Multipacting of the CVD diamond can be suppressed by diamond surface dehydrogenation. A plasma supported Chemical Vapor Deposition (CVD) technology to produce low loss high quality cylindrical diamond layers is presented. Special attention is devoted to the numerical optimization of the coupling section, where the surface magnetic and electric fields are minimized relative to the accelerating gradient and within known metal surface breakdown limits.

THPMS081	Proposed Few-cycle Laser-particle Accelerator Structure	laser, electron, vacuum, coupling	3175
	T. Plettner R. L. Byer, P. P. Lu Stanford University, Stanford, Califormia
	We describe a proposed transparent dielectric grating accelerator structure that is designed for ultra-short laser pulse operation. The structure is not a waveguide, but rather it is based on the principle of periodic field reversal to achieve phase synchronicity for relativistic particles. To preserve ultra-short pulse operation it does not resonate the laser field in the vacuum channel. The geometry of the structure appears well suited for application with high average power lasers and high thermal loading. It shows potential for an unloaded gradient of several GeV/m with 10 fsec laser pulses and the possibility to accelerate high bunch charges. The fabrication procedure and proposed near-term experiments with this accelerator structure are presented.

THPAN011	Non Linear Space Charge Effects on Transverse Beam Stability	simulation, space-charge, betatron, damping	3247
	J. J. Espinosa J. F. Cardona UNAL, Bogota D. C
	Funding: This work is funded by DINAIN, Division Nacional de Investigacion, Universidad Nacional de Colombia, Bogota - Colombia. Simbad code is used to study the combined effect of external non linearities and space charge non linearities on the beam stability using a simple FODO lattice. Gaussian and parabolic particle distribution are used for these simulations and results are compared with Mohl and Metral theoretical results.

THPAN018	Stability Thresholds for Transverse Dipole Modes with Nonlinear Space Charge, Chromaticity and Octupoles	space-charge, octupole, simulation, damping	3262
	V. Kornilov O. Boine-Frankenheim, I. Hofmann GSI, Darmstadt
	Funding: Work supported by EU design study (contract 515873 -DIRACsecondary-Beams) Transverse stability due to combinations of chromaticity effect, nonlinear space charge and octupoles of different polarities plays an important role in the determination of the impedance budget for the FAIR synchrotrons. Different analytic approaches [,,etc.] have been suggested, for which no direct comparison has been made so far. In order to clarify this issue we perform numerical investigations employing the particle tracking code PATRIC and compare results of simulation scans with predictions of a dispersion relation. Space charge effects within self-consistent and 'frozen' models are used for comparisons, connection to beam transfer function studies is addressed. D. Moehl, CERN/PS 95-08 (DI), (1995)** M. Blaskiewicz, Phys. Rev. ST Accel. Beams 4, 044202, (2001)

THPAN036	ABCI Progresses and Plans: Parallel Computing and Transverse Napoly-Shobuda Integral	dipole, vacuum	3306
	Y. H. Chin Y. Shobuda JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken K. Takata KEK, Ibaraki
	In this paper, we report the recent progress and future plans of ABCI. First, ABCI now supports parallel processing in OpenMP for a shared memory system, such as a PC with multiple CPUs or a CPU with multiple cores. The new ABCI also supports the dynamic memory allocation for nearly all arrays for field calculations so that the amount of memory needed for a run is determined dynamically during runtime. A user can use any number of mesh points as far as the total allocated memory is within a physical memory of his PC. As a important progress of the features, the transverse extension of Napoly integral (derived by Shobuda) has been implemented to the new ABCI: it permits calculations of wake potentials in structures extending to the inside of the beam tube radius or having unequal tube radii at the two sides not only for longitudinal but also for transverse cases, and still the integration path can be confined to a finite length, by having the integration contour beginning and ending on the beam tubes. The future upgrade plans will be also discussed. The new ABCI is available as a Windows stand-alone executable module so that no installation of the program is necessary.

THPAN048	Numerical Solver with CIP Method for Fokker Planck Equation of Stochastic Cooling	simulation, pick-up, kicker, feedback	3336
	T. Kikuchi T. Katayama CNS, Saitama S. Kawata Utsunomiya University, Utsunomiya
	A Fokker Planck equation for a Stochastic cooling* is solved by using the CIP method*. The Fokker Planck equation can be described in a convection-diffusion equation as a function of time and energy. The equation is a non linear form and the evolution of the distribution function should be numerically solved. The CIP method, which is an effective scheme to solve the convection term numerically, is applied to the Fokker Planck equation of the Stochastic cooling. By using the CIP method for the numerical solver, we can effectively calculate the time-dependent Fokker Planck equation in more few computational costs. The developed numerical solver can give us the energy spectrum of the particle distribution during the beam cooling. The simulation results show the good agreements compared with the experimental results. S. Van der Meer, CERN/PS/AA/78-22, 1978.** T. Yabe and T. Aoki, Comp. Phys. Commun. 66 (1991) 219.

THPAN078	An Elementary Analysis of Coupled-Bunch Instabilities	simulation, coupling, damping, storage-ring	3399
	K. M. Hock A. Wolski Liverpool University, Science Faculty, Liverpool
	We reconsider the equations of motion of wakefield coupled bunches in the light of recent developments in Delay Differential Equations. In the case of uniform resistive wall in a circular accelerator, we demonstrate an alternative way to obtain the growth rates. For each Fourier mode of bunch displacements, we show that multiple time domain modes can arise from an exact solution of the equation of motion. The growth rate as it is commonly defined corresponds to only one of them. The amplitude of each Fourier mode can therefore evolve with time in a way is not simply exponential. This is a result that has been observed in simulations of wakefield coupled bunches.

THPAN090	Fourier Spectral Simulation for Wake Field in Conducting Cavities	simulation, vacuum, coupling, electromagnetic-fields	3432
	M. Min Y.-C. Chae, P. F. Fischer, K.-J. Kim ANL, Argonne, Illinois Y. H. Chin KEK, Ibaraki
	Recent demand of short-bunch beams poses high-order computational tools for investigating beam dynamics in order to improve the beam quality. We have studied a new computational approach with spectrally accurate high-order approximation for wake field calculations. The technique employs the standard Fourier basis combined with a post-processing procedure for noise reduction by Gegenbauer reconstruction. We integrate this scheme into the existing 2D wake field calculation code ABCI and investigate possible enhancemance of its performance on the same grid base. We will demontrate 2D wake potential simulations for various cylindrically symmetric structures with the quality improvement in comparison to the conventional lower-order method.

THPAN091	Spectral-Element Discontinuous Galerkin Simulations for Wake Potential Calculations: NEKCEM	simulation, coupling, electromagnetic-fields, storage-ring	3435
	M. Min Y.-C. Chae, P. F. Fisher ANL, Argonne, Illinois
	The demand for short bunches of 1 ps or less poses not only technical challenges in order to deliver the beams for leading-edge research but also poses computational challenges when it comes to investigating bunched multi-particle beam dynamics in order to improve the beam quality. We introduce a powerful high-order numerical tool based on spetral-element discretizations with discontinuous Galerkin approximation approach, which includes spectral element time domain solver for Maxwell's equation and electrostatic Poisson solver. We will demonstrate 3D simulations for wakefield and wake potential calculations in conducting cavity structures, as well as meshing and visualization components. We will discuss the overcome of the computational bottleneck by widely-used low-order finite difference programs for calculating wake field excited by 1-ps bunches, provided with performance and accuracy comparison.

THPAN108	TBT Optics and Impedance Measurements at the Fermilab Main Injector	closed-orbit, injection, optics, vacuum	3480
	E. Gianfelice-Wendt Y. Alexahin Fermilab, Batavia, Illinois
	Funding: Work supported by the U. S. Department of Energy under Contract No. DE-AC02-76CH03000. The Main Injector (MI) is a rapid cycling multipurpose accelerator. After completion of the Tevatron Run II, its primary application will be the acceleration of high intensity proton beams for neutrino experiments. To achieve the intensity goal a detailed knowledge of the optics and transverse impedances is necessary which can be obtained from Turn-By-Turn (TBT) beam position measurements. The recent MI Beam Position Monitor system upgrade made it possible to apply the TBT data analysis methods which were successfully used by the authors for the Tevatron. We present the results of MI optics measurements and the impedance estimates obtained from the betatron phase advance dependence on beam current.

THPAS067	Adaptive Impedance Analysis of Grooved Surface Using the Finite Element Method	dipole, electromagnetic-fields, controls, linear-collider	3639
	L. Wang
	Funding: Work supported by the U. S. Department of Energy under contract DE-AC02-76SF00515 Grooved surface is proposed to reduce the secondary emission yield in a dipole and wiggler magnet of International Linear Collider. An analysis of the impedance of the grooved surface based on adaptive finite element is presented in this paper. The performance of the adaptive algorithms, based on an element-element h-refinement technique, is assessed. The features of the refinement indictors, adaptation criteria and error estimation parameters are discussed.

THPAS104	Simulations of RHIC Coherent Stabilities Due To Wakefield and Electron Cooling	electron, simulation, ion, damping	3726
	G. Wang M. Blaskiewicz BNL, Upton, Long Island, New York
	A circulating ion beam in the presence of electron cooling can experience varies instabilities if the electron beam intensity is above a certain threshold. Firstly the electric field generated by the electron beam can introduce two stream instabilities of varies modes; this has already been observed in the Fermilab Recycler ring. Secondly, longitudinal cooling of the momentum spread will reduce the Landau damping efficiency and thus may make the overcooled ion beam unstable. The thresholds and growth rates of varies two stream instability modes are discussed for the existing RHIC electron cooler design. Both simulation and theoretical results are shown for the thresholds of the instabilities caused by overcooling.

FROBC03	Efficient Accelerating Structures for Low-Energy Light Ions	focusing, rfq, quadrupole, linac	3824
	S. S. Kurennoy L. Rybarcyk, T. P. Wangler LANL, Los Alamos, New Mexico
	The radio-frequency quadrupole (RFQ) accelerator is the best structure immediately after an ion source for accelerating light-ion beams with considerable currents. On the other hand, the higher-energy part of the RFQ is known to be not a very efficient accelerator. We consider alternative room-temperature RF accelerating structures for the beam velocities in the range of a few percent of the speed of light - including H-mode cavities and drift-tube linacs - and compare them with respect to their efficiency, compactness, ease of fabrication, and overall cost. Options for the beam transverse focusing in such structures are discussed. Possible applications include a compact deuteron-beam accelerator up to the energy of a few MeV for homeland defense.
	Slides

FRPMN003	Measurements of Impedance and Beam Instabilities at the Australian Synchrotron	single-bunch, diagnostics, synchrotron, storage-ring	3859
	R. T. Dowd M. J. Boland, G. LeBlanc, M. J. Spencer, Y. E. Tan ASP, Clayton, Victoria J. M. Byrd, F. Sannibale LBNL, Berkeley, California
	In this paper we present the first measurements of machine impedance and observed beam instabilities at the Australian Synchrotron. Impedance measurements are made by studying the single bunch behaviour with beam current, using optical and X-ray diagnostic beamlines. An observed coupled-bunch instability, its cause and cure is also discussed.

FRPMN005	Design of Button Beam Position Monitor for the Brazilian Synchrotron Light Source	vacuum, storage-ring, coupling, synchrotron	3871
	S. R. Marques O. R. Bagnato, R. H.A. Farias, M. J. Ferreira, J. B. Gonzalez, C. Rodrigues, P. F. Tavares LNLS, Campinas
	We present the electric and mechanical design of a button beam position monitor (BPM) recently developed and installed in the UVX electron storage ring at the Brazilian Synchrotron Light Laboratory (LNLS). The first commissioning results will also be presented. This development started when we observed strong correlation between false stripline BPM readings and the external temperature of this BPM. Simulations indicate that the temperature gradient in the BPM body can cause deformations that could explain the false readings in some BPMs. The small dimension of the button compared to the stripline and the better thermal isolation between the button and the BPM body should contribute to minimize this problem.

FRPMN014	3D Simulation of Coherent Instabilities in Long Bunches Induced by the Kicker Impedances in the FAIR Synchrotrons	space-charge, damping, simulation, kicker	3919
	O. Boine-Frankenheim V. Kornilov GSI, Darmstadt
	Funding: Work supported by the European Community under the FP6 programme: Structuring the European Research Area - Specific Support Action - DESIGN STUDY (contract 515873 - DIRACsecondary-Beams). 3D simulation studies of the transverse impedance budget for long bunches in the FAIR synchrotrons have been started. Important transverse instability driving sources are the thin resistive wall and the kicker impedances. Major concerns are the required low momentum spreads and the additional loss of Landau damping due to the space charge tune shift. The simulation code PATRIC has been extended in order to predict coherent instability thresholds with space charge and for broadband impedance sources. Examples of code benchmarking using the numerical Schottky noise, analytical stability boundaries and comparisons with other codes will be discussed. The improvement of transverse stability in long bunches relative to a coasting beam is analyzed for different rf wave forms. Conclusions for the impedance budget in the FAIR synchrotrons are drawn.

FRPMN018	Wake Computations for Undulator Vacuum Chambers of PETRA III	vacuum, undulator, synchrotron, insertion	3943
	R. Wanzenberg K. Balewski DESY, Hamburg E. Gjonaj, T. Weiland TEMF, Darmstadt
	At DESY it is planned to convert the PETRA ring into a synchrotron radiation facility, called PETRA III. The wake fields of a tapered transition from the standard vacuum chamber to the small gap chamber of the insertion devices contribute significantly to the impedance budget of PETRA III. The computer codes MAFIA and PBCI have been used to determine the loss and kick parameter of the tapered transition. PBCI is a recently developed parallelized, fully 3D wake field code, which is using a purely explicit, split-operator scheme to solve the Maxwell equation in the time domain.

FRPMN024	Trapped modes analysis for the ELETTRA booster DCCT installation	booster, coupling, vacuum, single-bunch	3970
	P. Craievich C. Bontoiu, G. Ciani, M. Ferianis ELETTRA, Basovizza, Trieste
	In the new Elettra full energy injector, bunch charge measurements will be performed by different types of current transformers (CT), depending on their position (single pass or multi pass sections). In the single pass sections (Linac and Transfer lines) a new type of current transformer (in-flange CT by Bergoz) will be used. Main advantage of this device is a compact and reliable design; they are also specially suited in space critical application. For the booster ring a standard DC current transformer will be used to measure the DC component of the circulating beam current. The housing has been developed in house, including the magnetic shield and the ceramic gap in the vacuum chamber. Furthermore, calculations of the trapped modes in the current monitor housing are described. Longitudinal coupling impedance and loss factors for these resonant modes are estimated and we showed that dissipated power is not critical with ELETTRA booster parameters.

FRPMN025	Review of the Longitudinal Impedance Budget of the ELETTRA Storage Ring	storage-ring, closed-orbit, vacuum, electron	3976
	G. Penco C. Bontoiu, P. Craievich, V. Forchi', E. Karantzoulis ELETTRA, Basovizza, Trieste
	Changes in the longitudinal impedance budget occur due to the changes in the machine structure. In this paper we update the longitudinal impedance budget of Elettra following the installation of the new vacuum chambers in the last three years. The measurements are performed by mapping the horizontal closed orbit deviation in single bunch operation mode, taking full advantage of the newly installed high resolution BPM electrons system. The current results are compared with those of the previous measurements.

FRPMN028	Design and E. M. Analysis of the New DAFNE Interaction Region	simulation, vacuum, coupling, shielding	3988
	F. Marcellini
	A new interaction region (IR) vacuum chamber has been designed for the DAFNE upgrade aimed at testing of the crabbed waist collision scheme. Compared to the existing IR vacuum chamber, the new one has a simplified design and consists essentially of the confluence of straight tubes, having a double Y shape. Sharp discontinuities have been avoided to limit the beam impedance of the structure. However, the study of the electromagnetic interaction with the beam is necessary in order to avoid excessive power loss due to eventual higher order modes (HOM) trapped in the Y-shape chamber. With HFSS the first design of the chamber has been analyzed and HOMs have been found and characterized. On the basis of these results some modifications in the geometry of the IR chamber have been introduced to eliminate or attenuate these trapped resonances. The results of these simulations are presented.

FRPMN041	Study on the Longitudinal Impedance of BPM for KEKB and Super KEKB	resonance, simulation, damping, luminosity	4048
	K. Shibata H. Fukuma, S. Hiramatsu, Y. Suetsugu, M. Tejima, M. Tobiyama KEK, Ibaraki
	The longitudinal impedance of the KEK B-factory (KEKB) button-type beam position monitors (BPMs) was recalculated by MAFIA in preparation for a future plan to increase the beam current. The diameter and the gap of the button electrode were 12 mm and 1 mm, respectively. For High Energy Ring (HER), an asymmetric structure was applied to extract the TE110 mode into the coaxial cable. The Q-value and shunt impedance were estimated at 91 and 17 Ω (at 7.6 GHz) respectively, and the beam current limit for longitudinal multi-bunch instability was 2.6 A. On the other hand, the electrode of Low Energy Ring (LER) BPM had a symmetric structure and the Q-value and shunt impedance were estimated at 133 and 8 Ω (at 7.6 GHz). In this case, the current limit was 1.7 A. Based on the experiences at the KEKB, the new BPM was designed for the Super KEKB, a future high-intensity B-factory at KEK. In order to reduce the impedance the electrode diameter was cut down to 6 mm from 12 mm. The Q-value and shunt impedance were estimated at 23 and 2 Ω (at 13 GHz). The current limit was expected to be about 7 A in full bucket operation (5120 bunches), and more than 10 kA in 4-bucket spacing operation.

FRPMN053	Beam Instability and Correction for "DRAGON-I"	induction, electron, simulation, laser	4114
	W. W. Zhang Y. Li CAEP, Mainyang, Sichuan
	'Dragon-I' is a high current pulse electron linear induction accelerator designed and constructed in IFP/CAEP. It generates a 20MeV, 2.5kA, 60ns pulse electron beam. The whole facility has three parts: injector; accelerator and beam focus system. The accelerator consists of 72 induction cells and 18 connection cells. A solenoid was installed inside each cell forming beam transport sysem. During the initial beam test both high frequency and low frequency oscillation were found. A lot of simulation and experiment investigations were done to get the transverse impedance of the cells and the corkscrew motion of the electron beam. Details of both the simulation and the experimental methods to correct the instability are presented.

FRPMN065	Fast Vertical Single-Bunch Instability at Injection in the CERN SPS - An Update	simulation, space-charge, emittance, injection	4162
	G. Arduini T. Bohl, H. Burkhardt, E. Metral, G. Rumolo CERN, Geneva B. Salvant EPFL, Lausanne
	Following the first observation of a fast vertical instability for a single high-brightness bunch at injection in the SPS in 2003, a series of detailed measurements and simulations has been performed in order to assess the resulting potential intensity limitations for the SPS, as well as possible cures. During the 2006 run, the characteristics of this instability were studied further, extending the intensity range of the measurements, and comparing the experimental data with simulations that take into account the latest measurements of the transverse machine impedance. In this paper, we summarize the outcome of these studies and our understanding of the mechanisms leading to this instability. The corresponding intensity limitations were also determined.

FRPMN068	The 4.8 GHz LHC Schottky Pick-up System	pick-up, emittance, single-bunch, instrumentation	4174
	F. Caspers T. W. Hamerla, A. Jansson, J. R. Misek, R. J. Pasquinelli, P. C. Seifrid, D. Sun, D. G. Tinsley Fermilab, Batavia, Illinois J. M. Jimenez, O. R. Jones, T. Kroyer, VC. Vuitton CERN, Geneva
	Funding: LARP The LHC Schottky observation system is based on traveling wave type high sensitivity pickup structures operating at 4.8 GHz. The choice of the structure and operating frequency is driven by the demanding LHC impedance requirements, where very low impedance is required below 2 GHz, and good sensitivity at the selected band at 4.8 GHz. A sophisticated filtering and triple down-mixing signal processing chain has been designed and implemented in order to achieve the specified 100 dB instantaneous dynamic range without range switching. Detailed design aspects for the complete systems and test results without beam are presented and discussed.

FRPMN069	Longitudinal Coupled-Bunch Instabilities in the CERN PS	emittance, dipole, feedback, brightness	4180
	H. Damerau S. Hancock, C. Rossi, E. N. Shaposhnikova, J. Tuckmantel, J.-L. Vallet CERN, Geneva M. Mehler GSI, Darmstadt
	Funding: Work supported by EU Design Study DIRACsecondary-Beams (contract 515873). Longitudinal coupled bunch instabilities in the CERN PS represent a major limitation to the high brightness beam delivered for the LHC. To identify possible impedance sources for these instabilities, machine development studies have been carried out. The growth rates of coupled bunch modes have been measured, and modes have been identified using mountain range data. Growth rate estimations from coupled bunch mode theory are compared to these results. It is shown that the longitudinal impedance of the broad resonance curve of the main 10 MHz RF system can be identified as the most probable source. Possible methods to improve the beam stability are analyzed together with the performance of a damping system.

FRPMN074	Simulation Study of the Horizontal Head-Tail Instability Observed at Injection of the CERN Proton Synchrotron	coupling, simulation, space-charge, synchrotron	4210
	E. Metral G. Rumolo, R. R. Steerenberg CERN, Geneva B. Salvant EPFL, Lausanne
	For many years, a horizontal head-tail instability has been observed at the CERN Proton Synchrotron during the long 1.2 s injection flat-bottom. This slow instability has been damped using linear coupling only, i.e. with neither octupoles nor feedbacks. Using the nominal machine and beam parameters for LHC, the sixth head-tail mode number is usually observed. Several other modes were also observed in the past by tuning the chromaticity, and these observations were found to be in good agreement with Sacherer's formula. The purpose of this paper is to present the results of assessing the effect of chromaticity and linear coupling on this slow head-tail instability using the HEADTAIL simulation code, and to compare these simulations with both measurements performed over the last few years, and theoretical calculations.

FRPMN075	Resistive-Wall Impedance of an Infinitely Long Multi-Layer Cylindrical Beam Pipe	vacuum, space-charge, proton, collider	4216
	E. Metral B. Salvant EPFL, Lausanne B. Zotter Honorary CERN Staff Member, Grand-Saconnex
	The resistive wall impedance of cylindrical vacuum chambers was first calculated more than forty years ago under some approximations. Since then many papers have been published to extend its range of validity. In the last few years, the interest in this subject has again been revived for the LHC graphite collimators, for which a new physical regime is predicted. The first unstable betatron line in the LHC is at 8 kHz, where the skin depth for graphite is 1.8 cm, which is smaller than the collimator thickness of 2.5 cm. Hence one could think that the resistive thick-wall formula would be about right. It is found that it is not, and that the resistive impedance is about two orders of magnitude lower at this frequency, which is explained by the fact that the skin depth is much larger than the beam pipe radius. Starting from the Maxwell equations and using field matching, a consistent derivation of the transverse resistive wall impedance of an infinitely long cylindrical beam pipe is presented in this paper. The results, which should be valid for any number of layers, beam velocity, frequency, conductivity, permittivity and permeability, have been compared to previous ones.

FRPMN079	Two-Beam Resistive-Wall Wake Field	coupling, collider, proton, vacuum	4237
	F. Zimmermann
	In all storage-ring colliders, two beams propagating in opposite direction share a common beam pipe over parts or all of the ring circumference. The resistive-wall wake field coupling bunches of these two beams is different from the conventional single-beam wake field, as the magnetic force and the longitudinal electric force experienced by a probe bunch invert their sign, while the transverse electric force does not. In addition, the distance between driving and probing bunches is not constant, but the net wake field must be obtained via an integration of the force experienced over the drive-probe distance. We derive the two-beam resistive-wall wake field for a round beam pipe.

FRPMN092	Beam Coupling Impedance Simulations and Laboratory Measurements for the LHC FP420 Detector	simulation, resonance, coupling, proton	4294
	F. Roncarolo R. Appleby, R. M. Jones UMAN, Manchester
	The FP420 collaboration* aims at designing forward proton tagging detectors to be installed in the LHC sectors 420 meters downstream of the ATLAS detector and/or CMS detector. The experiment requires modification of the beam pipe material and geometry with a consequent impact on the LHC impedance budget and the circulating beam stability. This paper describes numerical simulations and laboratory measurements carried out to characterize the coupling impedance (longitudinal and transverse) and the associated loss factor of each insertion. The detectors are located in pockets of the beam tube. We study both single and multi-pocket configurations with a view to characterizing the impact on the beam dynamics. In addition, results are compared to available analytical calculations for the resistive wall impedance. * Cox, Brian et al., "FP420 : An R&D Proposal to Investigate the Feasibility of Installing Proton Tagging Detectors in the 420 m Region of the LHC", CERN-LHCC-2005-025

FRPMN098	Compact PCI/PXI Based High Voltage Cards.	controls, monitoring, coupling, laser	4312
	S. R. Babel
	Funding: BiRa Systems, Albuquerque, New Mexico High voltage power modules find uses in many applications like the Photo multiplier Tubes (PMT), Ionization chambers, CRT systems testing, high voltage biasing for Avalanche Photodiodes, Photo detectors, X-ray tubes, Pulse generators which are used in radars, lasers, EMC testing and other imaging applications. Providing high voltage, to these applications, which can be remotely controlled in a small, confined area, is a problem many laboratories around the world face. The LV and the HV series of high voltage systems from BiRa Systems present experimenters with voltages ranging from several hundreds upto ± 5kV in a rugged CompactPCI / PXI chassis, running National Instruments' LabView. The CompactPCI architecture offers modularity, tight integration and low cost. Apart from that, the deterministic and real time nature of the operating system also allows these modules to be remotely controlled and monitored over the Ethernet. The high voltage cards can be easily custom tailored to a particular voltage and current requirement

FRPMN099	Equilibrium Fluctuations in an N-Particle Coasting Beam: Schottky Noise Effects	collective-effects, plasma, vacuum, longitudinal-dynamics	4318
	G. Bassi J. A. Ellison, K. A. Heinemann UNM, Albuquerque, New Mexico
	Funding: Supported by DOE grant DE-FG02-99ER41104 We discuss the longitudinal dynamics of an unbunched beam with a collective effect due to the vacuum chamber and with the discretness of an N-particle beam (Schottky noise) included. We start with the 2N equations of motion (in angle and energy) with random initial conditions. The 2D phase space density for the N-Particles is a sum of delta functions and satisfies the Klimontovich equation. An arbitrary function of the energy also satisfies the Klimontovich equation and we linearize about a convenient equilibrium density taking the initial conditions to be independent, identically distributed random vaiables with the equilibrium distribution. The linearized equations can be solved using a Laplace transform in time and a Fourier series in angle. The resultant stochastic process for the phase space density is analyzed and compared with a known result. Work is in progress to study the full nonlinear problem. To gain further insight we are studying three alternative approaches: (1) a BBGKY approach, (2) an approach due to Elskens and Escande* and (3) the 'three-level-approach' of Donsker and Varadhan (see "Entropy, Large Deviations and Statistical Mechanics'', by R. S. Ellis). * V. V. Parkhomchuk and D. V. Pestrikov, Sov. Phys. Tech. Phys. 25(7), July 1980 ** "Microscopic Dynamics of Plasmas and Chaos", Y. Elskens and D. Escande, IoP, Series in Plasma Physics, 2003.

FRPMN103	Single-Bunch Instability Estimates for the 1-nm APS Storage Ring Upgrade with a Smaller Vacuum Chamber	storage-ring, lattice, single-bunch, simulation	4330
	Y.-C. Chae Y. Wang, A. Xiao ANL, Argonne, Illinois
	Funding: Work supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. We recently studied a lattice achieving 1-nm emittance at the APS storage ring. The successful design required very strong sextupoles in order to tune the machine to the desired positive chromaticity. A preliminary design of such magnets indicated saturation in the poles unless the vacuum chamber gets smaller by a factor of two compared to the existing APS chamber. Since the resistive wall impedance scales as 1/b3, where b is the radius of the chamber, we questioned how much current we can store in a single bunch at the 1-nm storage ring. In order to answer this question quantitatively, we calculated all wake potentials of impedance elements of the existing APS storage ring with the transverse dimension properly scaled but with the longitudinal dimension kept unchanged. With the newly calculated impedance of a smaller chamber, we estimated the single-bunch current limit. It turned out that the ring with a smaller chamber would not diminish the single-bunch current limit substantially. We present both wake potentials of 1-nm and the existing rings followed by the simulation results carried out for determining the accumulation limit to the ring. A. Xiao, "A 1-nm Lattice for the APS Storage Ring" these proceedings.

FRPMN104	Impedance Database II for the Advanced Photon Source Storage Ring	simulation, storage-ring, single-bunch, photon	4336
	Y.-C. Chae Y. Wang ANL, Argonne, Illinois
	Funding: Work supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The first Impedance Database* constructed at the Advanced Photon Source was successfully used in reproducing the main characteristics of single-bunch instabilities observed in the storage ring. However, the finite bandwidth of the corresponding impedance model was limited to 25 GHz, which happens to be the resolution limit of the density modulation observed in the microwave instability simulation. In order to resolve simulation results never verified in the experiments, we decided to extend the calculated bandwidth of impedance to 50 GHz by recalculating the wake potentials excited by a shorter bunch. Since low-order electromagnetic code requires 20-40 grid points per wavelength, reducing the bunch length required a large number of grids for the 3D structure. We used bunch lengths of 1- and 2-mm in the Gaussian distribution in the Impedance Database II project. For the large-scale computation we used the 3D electromagnetic code GdfidL ** for wake potential calculation at the cluster equipped with 240 GB of memory. The resultant wake potential excited by the short bunch together with application to the storage ring for collective effects is presented in the paper. * Y.-C. Chae, "The Impedance Database and Its Application to the APS Storage Ring" Proc. 2003 PAC, p. 3017.** http://www.gdfidl.de

FRPMN105	The Wakefield Effects of Pulsed Crab Cavities at the Advanced Photon Source for Short-X-ray Pulse Generation	single-bunch, storage-ring, simulation, photon	4339
	Y.-C. Chae V. A. Dolgashev SLAC, Menlo Park, California G. J. Waldschmidt ANL, Argonne, Illinois
	Funding: Work supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. In recent years we have explored the application to the Advanced Photon Source (APS) of Zholents' crab-cavity-based scheme for production of short x-ray pulses. As a near-term project, the APS has elected to pursue a pulsed system using room-temperature cavities. The cavity design has been optimized to heavily damp parasitic modes while maintaining large shunt impedance for the deflecting dipole mode. We evaluated a system consisting of three crab cavities as an impedance source and determined their effect on the single- and multi-bunch instabilities. In the single-bunch instability we used the APS impedance model as the reference system in order to predict the overall performance of the ring when the crab cavities are installed in the future. For multi-bunch instabilities we used a realistic fill pattern, including hybrid-fill, and tracked multiple bunches where each bunch was treated as soft in distribution. To verify the electrical design, the realistic wake potential of the 3D structure was calculated using GdfidL and this wake potential was used in the multi-bunch simulations. M. Borland et al., "Planned Use of Pulsed Crab Cavities at the APS for Short X-ray Pulse Generation," these proceedings.** V. Dolgashev et al., "RF Design of Normal Conducting Deflecting Structures for the APS," these proceedings.

FRPMN108	Coupled-Bunch Instability Study of Multi-cell Deflecting Mode Cavities for the Advanced Photon Source	damping, dipole, photon, feedback	4348
	L. Emery
	Funding: Work supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The short-pulse X-ray project at the Advanced Photon Source (APS) uses three room-temperature nine-cell 2.815 GHz deflecting-mode cavities in a straight section. Undamped, these cavities' higher-order and lower-order resonator modes will cause multi-bunch instabilities in longitudinal and transverse planes for any bunch pattern of a 1'000mA store. Damping of these modes must be part of the design of the cavities. We report calculations of instability growth rates and tracking simulations that were essential in specifying the rf design of the damping structures. We used various operating bunch patterns and scanned levels of damping of the cavities. Because one of the operating bunch patterns is not symmetric, we used a normal mode analysis * implemented in the APS code clinchor. Our calculation included random sampling of resonator frequencies in a reasonable range. We found that staggering of frequencies is only effective for modes that could not be heavily damped. * K. Thompson and R. Ruth, PAC 1989

FRPMN109	200-mA Studies in the APS Storage Ring	storage-ring, kicker, vacuum, injection	4354
	K. C. Harkay Y.-C. Chae, L. Emery, L. H. Morrison, A. Nassiri, G. J. Waldschmidt ANL, Argonne, Illinois
	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 storage ring is normally operated with 100 mA of beam current. A number of high-current studies were carried out to determine the multibunch instability limits. The longitudinal multibunch instability is dominated by the rf cavity higher-order modes (HOMs), and the coupled-bunch instability (CBI) threshold is bunch-pattern dependent. We can stably store 200 mA with 324 bunches, and the CBI threshold is 245 mA. With 24 bunches, several components are approaching temperature limits above 160 mA, including the HOM dampers. We do not see any CBI at this current. The transverse multibunch instabilities are most likely driven by the resistive wall impedance; there is little evidence that the dipole HOMs contribute. Presently, we rely on the chromaticity to stabilize the transverse multibunch instabilities. When we stored beam up to 245 mA, we used high chromaticity, and the beam was transversely stable. The stabilizing chromaticity was studied as a function of current. We can use these experimental results to predict multibunch instability thresholds for various upgrade options, such as smaller-gap or longer ID chambers and the associated increased impedance.

FRPMS005	The Tevatron AC Dipole System	dipole, emittance, betatron, synchrotron	3868
	R. Miyamoto A. Jansson, M. J. Syphers Fermilab, Batavia, Illinois S. E. Kopp The University of Texas at Austin, Austin, Texas
	The AC dipole is an oscillating dipole magnet which can induce large amplitude oscillations without causing emittance growth. This makes it a good tool to measure optics of a hadron synchrotron. The vertical AC dipole for the Tevatron is powered by an inexpensive high-power audio amplifier since its operating frequency is approximately 20 kHz. The low impedance magnet is incorporated into a parallel resonant system to form an 8 Ω equivalent circuit to maximize the power output of the amplifier. The magnet used is a vertical pinger previously installed in the Tevatron making the cost relatively inexpensive. Recently, the initial system was upgraded with a more powerful amplifier and oscillation amplitudes up to 2-σ beam size were achieved at 980 GeV. The paper discusses details of the resonant circuit. It also shows test results of the system both on the bench and with the beam.

FRPMS010	Electron Cloud in the Fermilab Booster	electron, space-charge, booster, octupole	3895
	K. Y. Ng
	Simulations reveal a substantial build up of electron cloud in the Fermilab Booster ramping cycle, both inside the unshielded combined-function magnets and the beam pipes joining the magnets. The neutralization can be appreciable depending on the second-emission yield of the magnet pole faces and the beam pipe surfaces. The implication of the electron-cloud effects on the beam emittances and collective instabilities is discussed.

FRPMS014	Chromaticity Measurement Using a Continuous Head-Tail Kicking Technique	emittance, betatron, synchrotron, simulation	3916
	C.-Y. Tan V. H. Ranjbar Tech-X, Boulder, Colorado
	Funding: Operated by Universities Research Association Inc. under Contract No. DE-AC02-76CH03000 with the United States Department of Energy. In the classical head-tail chromaticity measurement technique, a single large kick is applied transversely to the beam. The resulting phase difference between the head and the tail is measured and the chromaticity extracted. In the continuous head-tail kicking technique, a very small transverse kick is applied to the beam and the asymptotic phase difference between the head and the tail is found to be a function of chromaticity. The advantage of this method is that since the tune tracker PLL already supplies the small transverse kicks, no extra modulation is required.

FRPMS061	Impedance and Single Bunch Instability Calculations for the ILC Damping Rings	lattice, damping, single-bunch, simulation	4141
	K. L.F. Bane S. A. Heifets, Z. Li, C.-K. Ng, A. Novokhatski, G. V. Stupakov, R. L. Warnock SLAC, Menlo Park, California M. Venturini LBNL, Berkeley, California
	Funding: Work supported by US Department of Energy contract DE-AC02-76SF00515 One of the action items for the damping rings of the International Linear Collider (ILC) is to compute the broad-band impedance and, from it, the threshold to the microwave instability. For the ILC it is essential that the operating current be below threshold. Operating above threshold would mean that the longitudinal emittance of the beam would be increased. More seriously, above threshold there is the possibility of time dependent variation in beam properties (e.g. the "sawtooth" effect) that can greatly degrade collider performance. In this report, we present the status of our study including calculations of: an impedance budget, a pseudo-Green's function suitable for Haissinski equation and instability calculations, and instability calculations themselves.

FRPMS065	Bunch Length Measurements in SPEAR3	optics, single-bunch, diagnostics, radiation	4159
	W. J. Corbett A. S. Fisher, X. Huang, J. A. Safranek, J. J. Sebek SLAC, Menlo Park, California A. H. Lumpkin ANL, Argonne, Illinois W. Y. Mok Life Imaging Technology, Palo Alto, California
	Funding: Work supported by US Department of Energy Contract DE-AC03-76SF00515 and Office of Basic Energy Sciences, Division of Chemical Sciences. In the nominal SPEAR3 storage ring optics, the natural radiation pulse length is 40ps fwhm per bunch. Due to the double-bend achromat lattice configuration, it is relatively straightforward to reduce the momentum compaction factor (α) and hence reduce the bunch length by modest values. In this paper we present streak camera measurements of the bunch length in the nominal optics, and with ~α/20 and α/50 optics as a function of single-bunch current. The results demonstrate <10ps fwhm radiation pulses with up 5x10⁸ particles/bunch (~100μ amp). Radiation pulse power, bunch length scaling and broadband impedance estimates are discussed.

FRPMS069	Simulations of Stretched Wire Measurements of 3.9GHz Cavities for the ILC	simulation, dipole, scattering, coupling	4177
	R. M. Jones G. Burt Cockcroft Institute, Lancaster University, Lancaster N. Chanlek, B. Spencer UMAN, Manchester P. Goudket STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
	We present wake-field simulations on both the main superconducting cavities and on the beam delivery system crab cavities of the ILC. We utilize both finite difference and finite element computer codes to simulate the electromagnetic fields in these cavities in the presence of a stretched wire. This study is intended to both predict the wake-field in experiments on the modal characterisation of 3.9 GHz cavities in progress at the Cockcroft Institute and, to explore practical issues concerning the feasibility of using this stretched wire method to investigate modes in the ILC main cavities. Multi-cell scattering matrices and the modes in infinite periodic structures are calculated with a view to aiding the interpretation of experimental results. A modal convergence study is also included

FRPMS074	Measurements of the Transverse Collimator Wakefields due to Varying Collimator Characteristics	simulation, controls, insertion, feedback	4207
	S. Molloy C. D. Beard, J.-L. Fernandez-Hernando STFC/DL/ASTeC, Daresbury, Warrington, Cheshire A. Bungau UMAN, Manchester S. Seletskiy, M. Woods SLAC, Menlo Park, California J. D.A. Smith Cockcroft Institute, Warrington, Cheshire A. Sopczak Lancaster University, Lancaster N. K. Watson STFC/RAL/ASTeC, Chilton, Didcot, Oxon
	Funding: EUROtev Contract #011899RIDS US DOE Contract DEAC02-76SF00515 We report on measurements of the transverse wakefields induced by collimators of differing characteristics. An apparatus allowing the insertion of different collimator jaws into the path of a beam was installed in End Station A (ESA) in SLAC. Eight comparable collimator geometries were designed, including one that would allow easy comparison with previous results, and were installed in this apparatus. Measurements of the beam kick due to the collimator wakefields were made with a beam energy of 28.5 GeV, and beam dimensions of ~100 microns vertically and a range of 0.5 to 1.5 mm longitudinally. The trajectory of the beam upstream and downstream of the collimator test apparatus was determined from the outputs of ten BPMs (four upstream and six downstream), thus allowing a measurement of the angular kick imparted to the beam by the collimator under test. The transverse wakefield was inferred from the measured kick. The different aperture designs, data collection and analysis, and initial comparison to theoretical and analytic predictions are presented here. * "An Apparatus for the Direct Measurement of Collimator Transverse Wakefields", P. Tenenbaum, PAC '99** "Direct Measurement of the Resistive Wakefield in Tapered Collimators", P Tenenbaum, PAC '04

FRPMS076	A New Q2-Bellows Absorber for the PEP-II SLAC B-Factory	radiation, simulation, dipole, luminosity	4219
	A. Novokhatski S. DeBarger, S. Ecklund, N. Kurita, J. Seeman, M. K. Sullivan, S. P. Weathersby, U. Wienands SLAC, Menlo Park, California
	Funding: Work supported by US DOE contract DE-AC02-76SF00515 A new Q2-bellows absorber will damp only transverse wake fields and will not produce additional beam losses due to Cherenkov radiation. The design is based on the results of the HOM analysis. Geometry of the slots and absorbing tiles was optimized to get maximum absorbing effect.

FRPMS077	High Current Effects in the PEP-II SLAC B-factory	synchrotron, luminosity, optics, vacuum	4225
	A. Novokhatski S. A. Heifets, D. Teytelman SLAC, Menlo Park, California
	Funding: Work supported by US DOE contract DE-AC02-76SF00515. Wake fields defining beam stability affect also the beam optics and beam properties in high current machines. We present observations and analysis of the optical effects in the PEP-II SLAC B-factory, which has the record in achievement of high electron and positron currents. We study the synchronous phase and the bunch length variation along the train of bunches, overall bunch lengthening and effects of the wakes on the tune and on the Twiss parameters. This analysis is being used in upgrades of PEP II and may be applied to future B-factories and damping rings for Linear Colliders.

FRPMS079	SUPPRESSION OF SECONDARY ELECTRON EMISSION USING TRIANGULAR GROOVED SURFACE IN THE ILC DIPOLE AND WIGGLER MAGNETS	electron, dipole, wiggler, simulation	4234
	L. Wang K. L.F. Bane, C. Chen, T. M. Himel, M. Munro, M. T.F. Pivi, T. O. Raubenheimer, G. V. Stupakov SLAC, Menlo Park, California
	Funding: Work supported by the U. S. Department of Energy under contract DE-AC02-76SF00515 The development of an electron cloud in the vacuum chambers of high intensity positron and proton storage rings may limit machine performance. The suppression of electrons in a magnet is a challenge for the positron damping ring of the International Linear Collider (ILC) as well as the Large Hadron Collider. Simulation show that grooved surfaces can significantly reduce the electron yield in a magnet. Some of the secondary electrons emitted from the grooved surface return to the surface within a few gyrations, resulting in a low effective secondary electron yield (SEY) of below 1.0 A triangular surface is an effective, technologically attractive mitigation with a low SEY and a weak dependence on the scale of the corrugations and the external magnetic field. A chamber with triangular grooved surface is proposed for the dipole and wiggler sections of the ILC and will be tested in PEP-II in 2007. The strategy of electron cloud control in ILC and the optimization of the grooved chamber such as the SEY, impedance as well as the manufacturing of the chamber, are also discussed. SLAC-PUB-11933 & NIMA in publication

FRPMS085	Transverse Effect due to Short-range Resistive Wall Wakefield	dipole, vacuum, focusing, electron	4267
	J. Wu A. Chao SLAC, Menlo Park, California J. R. Delayen Jefferson Lab, Newport News, Virginia
	Funding: AWC and JW were supported by US DOE under contract No. DE-AC02-76SF00515. JRD was supported by US DOE under contract No. DE-AC05-84-ER40150 and No. DE-AC05-00-OR22725. For accelerator projects with ultra short electron beam, beam dynamics study has to invoke the short-range wakefield. In this paper, we first obtain the short-range dipole mode resistive wall wakefield. Analytical approach is then developed to study the single bunch transverse beam dynamics due to this short-range resistive wall wake. The results are applied to the LCLS undulator and some other proposed accelerators.

FRPMS102	Preliminary Impedance Budget for the NSLS-II Storage Ring	vacuum, undulator, storage-ring, electron	4321
	A. Blednykh S. Krinsky BNL, Upton, Long Island, New York
	Extensive calculations have been performed of the wakefield and impedance produced by the storage ring components for the rms bunch length of 3mm. Calculated data are presented for the NSLS-II storage ring components such as dipole vacuum chamber, quadrupole vacuum chamber, sextupole vacuum chamber, tapered elliptic vacuum chamber for superconducting undulator, cryo permanent magnet mini-gap undulator, CESR-B RF cavity, beam position monitor, infrared beam extraction chamber and resistive wall. The loss factor, the kick factor and imaginary part of the longitudinal impedance at low frequency divided by harmonic number are given per component and have been entered into a table.

FRPMS103	Coupling Impedance of the CESR-B RF Cavities for the NSLS-II Storage Ring	storage-ring, coupling, vacuum, damping	4327
	A. Blednykh S. Krinsky, J. Rose BNL, Upton, Long Island, New York
	CESR-B type superconducting cavities are under discussion for acceleration of the electron beam in the 3-GeV NSLS-II storage ring. In this paper we present a detailed investigation of longitudinal and transverse impedances of the cavity and transition assembly. Ferrite material is included in impedance analysis. Its effect on the short range wakepotential has been studied using the GdfidL code. Results of loss factors and kick factors are presented for a 3mm rms bunch length.

FRPMS104	Impedance of Electron Beam Vacuum Chambers for the NSLS-II Storage Ring	vacuum, extraction, dipole, storage-ring	4333
	A. Blednykh S. Krinsky BNL, Upton, Long Island, New York
	In this paper we discuss computation of the coupling impedance of the vacuum chambers for the NSLS-II storage ring using the electromagnetic simulator GdfidL. The impedance of the vacuum chambers depends on the geometric dimensions of the cross-section and height of the slot in the chamber wall. Of particular concern is the complex geometry of the infrared extraction chambers to be installed in special large-gap dipole magnets. In this case, wakefields are generated due to tapered transitions and large vertical-aperture ports with mirrors near the electron beam.