IPAC2016 - List of Keywords (impedance)

Paper	Title	Other Keywords	Page
MOOCA01	R&D of a Super-compact SLED System at SLAC	cavity, operation, coupling, FEL	39
	J.W. Wang, G.B. Bowden, S. Condamoor, Y. Ding, V.A. Dolgashev, J.P. Eichner, M.A. Franzi, A.A. Haase, P. Krejcik, J.R. Lewandowski, S.G. Tantawi, L. Xiao, C. Xu SLAC, Menlo Park, California, USA
	Funding: Work supported by Department of Energy contract DE-AC03-76SF00515. We have successfully designed, fabricated, installed and tested a super-compact X-Band SLED system at SLAC. It is composed of an elegant mode converter/polarizer and a single sphere energy store cavity with high Q of 94000 and diameter less than 12 cm. The available RF peak power of 50 MW can be compressed to peak average power of more than 200 MW in order to double the kick for the electron bunches in a RF transverse deflector system and greatly improve the measurement resolution for both the electron bunch and the x-ray FEL pulse. High power operation has demonstrated the excellent performance of this RF compression system without any problems in RF breakdown, pulse heating and radiation. The design physics and fabrication as well as the measurement results will be presented in detail.
	Slides MOOCA01 [20.278 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOOCA01
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MOPMB025	The Development of 16-Electrode Monitor for Measurement of the Multipole-Moment	quadrupole, injection, coupling, proton	140
	Y. Nakanishi, A. Ichikawa, A. Minamino, K.G. Nakamura, T. Nakaya Kyoto University, Kyoto, Japan T. Koseki, H. Kuboki KEK, Tokai, Ibaraki, Japan T. Toyama J-PARC, KEK & JAEA, Ibaraki-ken, Japan
	Funding: This work was supported by MEXT KAKENHI Grant Number 25105002, Grant-in-Aid for Scientific Research on Innovative Areas titled 'Unification and　Development of the Neutrino Science Frontier' In the J-PARC main ring, the beam intensity is greatly increased to 750 kW or more in near future. Even the beam intensity become higher, the beam loss must be kept at the same level as present. Aiming to make the cause of beam loss clear, we have been developing the beam monitor to measure the beam size. The quadrupole moment is related to the beam size. In principle, monitors with more than four electrodes can measure the quadrupole moment. In addition, two monitors located at the places with different beta functions can measure the emittances and beam sizes, providing the horizontal and vertical beta functions. To obtain more precise quadrupole moment and higher multipoles, we are developing the multi-electrode monitor, tentatively, with 16 electrodes. As a reference of 16-electrode monitor, two 4-electrode BPMs are investigated to measure quadrupole moments. We will present the measurement result of 4-electrode monitors and the status of the development of the 32-electrode monitor.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMB025
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MOPMB038	Development of Shoebox BPM for Xi‘an Proton Application Facility	coupling, simulation, proton, closed-orbit	175
	W. Wang, X. Guan, W.-H. Huang, X.W. Wang, Z. Yang, H.Y. Zhang, S.X. Zheng TUB, Beijing, People's Republic of China M.T. Qiu, Z.M. Wang State Key Laboratory of Intense Pulsed Radiation Simulation and Effect, Northwest Institute of Nuclear Technology, Shannxi, People's Republic of China
	In this paper, development of the Shoebox BPM is presented which can be applied for the measurement of turn-by-turn position data, closed orbit and tune of Xi'an Proton Application Facility (XiPAF). The preliminary design of the physical dimensions including the electrode aperture, the pipe aperture and the gap between the two electrodes is performed by calculating their effects on BPM response respectively with the equivalent circuit model. Furthermore, the mechanical structure of the Shoebox BPM is optimized by CST simulation to achieve better performance. The dependency of the BPM sensitivity and zero offset on the frequency is diminished by adding one isolating ring, which decreases coupling capacitance of electrodes and compensates ground capacitance difference of the two electrodes. Finally one prototype of the Shoebox BPM has been fabricated and tested offline. Results show that relative position measurement error due to frequency dependency of sensitivity is less than 1% and absolute measurement error due to frequency dependency of zero offset is expected to be less than 0.1 mm.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMB038
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MOPMB050	Design of Ultra-wideband Amplifier in RF Front End for Bunch-by-bunch Measurement	power-supply, simulation, experiment, synchrotron-radiation	205
	Y. Yang, Y.B. Leng, Y.B. Yan SSRF, Shanghai, People's Republic of China
	RF front end is one of the key technologies in beam diagnosis, especially in bunch-by-bunch measurement at storage ring. This paper gives the design of ultra-wideband amplifier in RF front end for bunch-by-bunch measurement at SSRF. Simulation have been done to verify the performance of this design.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMB050
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MOPMR019	Beam Tests of a Prototype Stripline Beam Position Monitoring System for the Drive Beam of the CLIC Two-beam Module at CTF3	electronics, pick-up, vacuum, operation	270
	A. Benot-Morell, A. Faus-Golfe IFIC, Valencia, Spain A. Benot-Morell, M. Wendt CERN, Geneva, Switzerland A. Faus-Golfe LAL, Orsay, France J.M. Nappa, S. Vilalte IN2P3-LAPP, Annecy-le-Vieux, France
	Funding: MINECO contract no. FPA2013-47883-C2-1-P. CLIC Collaboration Agreement, contract no. KE2638/BE. FNRA contract no. ANR-11-IDEX-0003-02. In collaboration with LAPP and IFIC, two units of a prototype stripline Beam Position Monitor (BPM) for the CLIC Drive Beam (DB), and its associated readout electronics have been successfully installed and tested in the Two-Beam-Module (TBM) at the CLIC Test Facility 3 (CTF3) at CERN. This paper gives a short overview of the BPM system and presents the performance measured under different Drive Beam configurations.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMR019
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MOPMR038	Design and Simulation Studies of the Novel Beam Arrival Monitor Pickup at Daresbury Laboratory	pick-up, simulation, laser, FEL	334
	A. Kalinin, S.P. Jamison, T.T. Thakker STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom R. Apsimon, G. Burt, A.C. Dexter Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
	We present the novel beam arrival monitor pickup design currently under construction at Daresbury Laboratory, Warrington, UK. The pickup consists of four flat electrodes in a transverse gap. CST Particle Studio simulations have been undertaken for the new pickup design as well as a pickup design from DESY, which is used as a reference for comparison. Simulation results have highlighted two advantages of the new pickup design over the DESY design; the signal bandwidth is 25 GHz, which is half that of the DESY design and the response slope is a factor of 1.6 greater. We discuss optimisation studies of the design parameters in order to maximise the response slope for bandwidths up to 50 GHz and present the final design of the pickup.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMR038
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MOPMW002	Modeling and Simulation of Broadband RF Cavities in PSpice	cavity, simulation, coupling, storage-ring	392
	J. Harzheim, D. Domont-Yankulova, H. Klingbeil, R. Königstein TEMF, TU Darmstadt, Darmstadt, Germany M. Frey, H. Klingbeil GSI, Darmstadt, Germany
	Barrier bucket systems are planned for the SIS100 Synchrotron (part of the future accelerator facility FAIR) and the ESR storage ring to facilitate several longitudinal beam manipulations [9] [15]. In order to achieve a single-sine gap signal of the desired amplitude and quality, effects in the linear and nonlinear region of the RF systems have to be investigated and included in the design of the overall system. Therefore, the cavities and the amplifier stages are to be modeled in PSpice. In this contribution, a cavity model will be presented. In a first step, a model for the magnetic alloy (MA) ring cores, which highly account for the properties of the cavity, has been found based on measurement data. In a second step, the future setup of the cavity is systematically created using the MA ring core models. The model of the cavity allows simulations in frequency domain as well as time domain. The results show good agreement with former measurements.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW002
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MOPMW005	Design of Linac with the New Gaskets Clamping Fabrication Technique	vacuum, coupling, linac, gun	403
	F. Cardelli INFN-Roma1, Rome, Italy D. Alesini INFN/LNF, Frascati (Roma), Italy M. Magi, L. Palumbo University of Rome La Sapienza, Rome, Italy F. Pellegrino, V. Pettinacci INFN-Roma, Roma, Italy
	Recently, a new technique for the realization of high gradient accelerating structures based on the use of gaskets without brazing processes, has been successfully tested at high power on a 1.6 cells RF gun (D. Alesini, et al, PRST 18, 02001, 2015). The new technique developed at the Laboratories of Frascati of the INFN (Italy) in the framework of the SPARC_LAB project has been also adopted for the ELI-NP RF gun. The use of the special gaskets that simultaneously guarantee the vacuum seal and a perfect RF contact allow to avoid the brazing process, strongly reducing the cost, the realization time and the risk of failure. Moreover, without copper annealing due to the brazing process, it is possible, in principle, to decrease the breakdown rate increasing, at the same time, the maximum achievable gradient. The extension of this new fabrication process to complex LINAC structures is the next step on the application of this new technique on particle accelerator. In the paper, we discuss how to extend this process to S-band and C-band Travelling Wave accelerating structures illustrating their electromagnetic design and their mechanical realization.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW005
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MOPMW007	On the Calibration Measurement of Stripline Beam Position Monitor for the ELI-NP Facility	simulation, linac, vacuum, electromagnetic-fields	411
	D. De Arcangelis, F. Cardelli, A. Mostacci, L. Palumbo University of Rome La Sapienza, Rome, Italy
	Stripline Beam Position Monitor (BPM) will be installed in the Compton Gamma Source in construction at the ELI Nuclear Physics facility in Romania. A test bench for the calibration of BPM has been built to characterize the device with stretched wire measurement in order to get the BPM response map. A full S-parameters characterisation is performed as well to measure the electrical offset with the "Lambertson method". This paper discusses the extensive simulations performed with full 3D electromagnetic CAD codes of the above measurements to investigate measurement accuracy, possible measurement artefacts and the beam position reconstruction.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW007
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MOPMW011	The Second Harmonic RF System for J-PARC MR Upgrade	cavity, injection, operation, proton	420
	C. Ohmori, K. Hara, K. Hasegawa, M. Toda, M. Yoshii KEK, Tokai, Ibaraki, Japan M. Nomura, T. Shimada, F. Tamura, M. Yamamoto JAEA/J-PARC, Tokai-mura, Japan
	Power upgrade scenario of J-PARC Main Ring includes replacement of RF cavities with higher field gradient using magnetic alloy cores, FT3L than the present ones. It also need to install the second harmonic RF cavity in the other section where dedicated water system for RF cavities is not available. Installation scenario of the second harmonic RF will be presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW011
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MOPMW015	Wakefields Studies of High Gradient X-band Accelerating Structure at SINAP	wakefield, simulation, cavity, FEL	429
	X.X. Huang, W. Fang, Q. Gu, M. Zhang, Z.T. Zhao SINAP, Shanghai, People's Republic of China
	Shanghai compact hard x-ray free electron laser (CHXFEL)* is now proposed accompanied with a high-gradient accelerating structure, which is the trend of large scale and compact facility. This structure operated at X-band (11424 MHz) holds the promise to achieve high gradient up to 80 MV/m. However, due to its particular property, a more serious wakefields** will be generated, leading to worse beam instability effects. In this paper, the computation of this case will be carried out with simulation. Moreover, analysis and optimization will be adopted to suppress beam instability. * C. Feng, Z. T. Zhao, Chinese Sci Bull, 2010, 55, 221-227. ** K. Bane, SLAC, NLC-Note 9, Feb. 1995.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW015
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MOPMW024	Design of the New Wideband RF System for the CERN PS Booster	electronics, acceleration, booster, controls	441
	M.M. Paoluzzi, S.C.P. Albright, M.E. Angoletta, L. Arnaudon, S. Energico, A. Findlay, M. Haase, M. Jaussi, A.J. Jones, D. Landré, J.C. Molendijk, D. Quartullo, E.N. Shaposhnikova CERN, Geneva, Switzerland
	For the renovation and upgrade of the CERN PS Booster (PSB) RF systems a development project was launched in 2012. The design, based on a new approach, aimed at replacing the existing tuned, narrowband RF systems with wideband, modular, solid-state driven units. A wide range of issues had to be addressed spanning from RF power production, radiation hardness of solid-state devices, active cancellation of beam-induced voltages, dedicated low-level electronics allowing multi-harmonic operation and beam stability. Following a three-year prototyping and testing campaign and two international reviews, the project endorsement came at the end of year 2015. It foresees the complete removal of present h1, h2 and h10 systems and the deployment of a new one covering all the frequency ranges from 1 MHz to 18 MHz. The four PSB rings will be equipped with 144 identical acceleration cells providing 24 kV total RF voltage per ring. This paper describes the design concepts, the retained solutions, the expected performances and includes the procurement and implementation strategies. This activity is part of the LHC Injectors Upgrade project (LIU).
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW024
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MOPMW027	Design of a Perpendicular Biased 2nd Harmonic Cavity for the Fermilab Booster	cavity, booster, Windows, cathode	451
	C.-Y. Tan, J.E. Dey, K.L. Duel, R.L. Madrak, W. Pellico, E. Prebys, J. Reid, G.V. Romanov, D. Sun, I. Terechkine Fermilab, Batavia, Illinois, USA
	Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. A perpendicular biased 2nd harmonic cavity is currently being designed and built for the Fermilab Booster. The purpose is to flatten the bucket at injection and thus change the longitudinal beam distribution to decrease space charge effects. It can also help with transition crossing. A model cavity has been built to verify various CST Microwave studio and COMSOL results and a test stand has been built to ensure that the Y567 tube is able to operate at twice the Booster fundamental frequencies. Also discussed are the RF windows which are critical to the design.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW027
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MOPMW036	Frequency Domain Simulations of Co-linear X-band Energy Booster (CXEB) RF Cavity Structures and Passive RF Components with ACE3P	cavity, electron, laser, extraction	480
	T. Sipahi, S. Biedron, S.V. Milton CSU, Fort Collins, Colorado, USA
	Due to their higher intrinsic shunt impedance X-band accelerating structures offer significant gradients with relatively modest input powers, and this can lead to more compact light sources. At the Colorado State University Accelerator Laboratory (CSUAL) [1] we would like to adapt this technology to our 1.3-GHz, L-band accelerator system using a passively driven 11.7 GHz traveling wave X-band configuration that capitalizes on the high shunt impedances achievable in X-band accelerating structures in order to increase our overall beam energy in a manner that does not require investment in an expensive, custom, high-power X-band klystron system. Here we provide the comparisons of the important parameters achieved using SUPERFISH and OMEGA3P for our Co-linear X-band Energy Booster (XCEB) system that will allow us to achieve our goal of reaching the maximum practical net potential across the X-band accelerating structures while driven solely by the beam from the L-band system.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW036
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MOPMW039	TM01 Mode Launcher for Use in High Brightness Photoguns	quadrupole, gun, electron, cavity	491
	A.D. Cahill UCLA, Los Angeles, California, USA M. Dal Forno, V.A. Dolgashev SLAC, Menlo Park, California, USA
	Funding: DOE SCGSR and DOE/SU Contract DE-AC02-76-SF00515 Photo rf guns are a source of electron beams for X-ray FELs such as LCLS and European XFEL. In existing photoguns power is coupled into the cavity by waveguides through the cell walls, like LCLS, or through coaxial coupling, at the European XFEL. We are considering feeding a gun using a circular waveguide with the TM01 mode. To do that we need a mode launcher, a matched device that couples the rectangular TE01 mode waveguide to a TM01 mode in a circular waveguide. Use of the mode launcher reduces complexity of the gun cavity and increases flexibility of positioning the input waveguide relative to the gun body. Mode launchers have been successfully used at SLAC and elsewhere for X-band high gradient tests. Because the existing mode launchers were not built for high brightness guns, they have a significant quadrupole field component. High brightness rf guns have tight requirements on output beam properties, and this quadrupole component adversely affects the beam. We have designed a mode launcher free of this disadvantage. We present design considerations, methodology, and an example S-band mode launcher.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW039
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MOPMY010	RF Design of Normal Conducting 704 MHz and 2.1 GHz Cavities for LEReC Linac	cavity, HOM, vacuum, simulation	532
	B. P. Xiao, I. Ben-Zvi, M. Blaskiewicz, J.M. Brennan, J.C. Brutus, A.V. Fedotov, H. Hahn, G.T. McIntyre, C. Pai, K.S. Smith, J.E. Tuozzolo, Q. Wu, T. Xin, W. Xu, A. Zaltsman BNL, Upton, Long Island, New York, USA S.A. Belomestnykh Fermilab, Batavia, Illinois, USA S.A. Belomestnykh, I. Ben-Zvi, T. Xin Stony Brook University, Stony Brook, USA V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 and by National Energy Research Scientific Computing Center under contract No. DE-AC02-05CH11231 by US DOE. To improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, the Low Energy RHIC electron Cooler (LEReC) is currently under development at BNL. Two normal conducting cavities, a single cell 704 MHz cavity and a 3 cell 2.1 GHz third harmonic cavity, will be used in LEReC for energy spread correction. Currently these two cavities are under fabrication. In this paper we report the RF design of these two cavities.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY010
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MOPOR002	Impedance Simulations and Measurements for ThomX Storage Ring	simulation, interface, wakefield, storage-ring	586
	A.R. Gamelin, C. Bruni, V. Chaumat, D. Le Guidec, P. Lepercq, R. Marie LAL, Orsay, France
	Funding: Work is supported by ANR-10-EQPX-51, by grants from Région Ile-de-France, IN2P3 and Pheniics Doctoral School ThomX is a compact Compton Backscattering Source (CBS) which is being built at LAL, Orsay, France. ThomX ring has a short circumference of 18 m and a design energy of 50 MeV. Due to the low energy of the beam and in order to avoid beam degradation it is important to evaluate the ring components impedance. A CST Particle Studio impedance simulation of the different components of the ring (BPM, bellows, optical chamber, etc.) is under way. It will be followed by a bench measurement of the longitudinal and transverse impedance using the coaxial wire method. This paper will detail the preliminary results of the ThomX storage ring impedance simulations and the measurement principle we will use.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR002
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MOPOR003	Simulation Studies and Measurements of Beam Instabilities Caused by the Kicker Impedance at High Intensities in the 3-GeV RCS of J-PARC	simulation, kicker, injection, betatron	589
	P.K. Saha, H. Harada, N. Hayashi, H. Hotchi, M. Kinsho, M. Nomura, Y. Shobuda, F. Tamura, N. Tani, Y. Watanabe, M. Yamamoto JAEA/J-PARC, Tokai-mura, Japan
	The transverse impedance of the extraction kickers is a significant beam instability source in the 3-GeV Rapid Cycling Synchrotron of J-PARC. ORBIT code was developed for space charge and beam instability simulations by successfully introducing realistic time dependent machine parameters. The beam instability at high intensities, especially at the designed 1 MW beam power was found be very critical. As there was no practical measure yet to reduce the kicker impedance, a detail simulation studies were done in order to determine realistic machine parameters to suppress the beam instability. The simulation results were found to be very consistent with measurements to successfully accomplish 1 MW beam power. The simulation and beam study results in detail are presented in this paper.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR003
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MOPOR007	Local Impedance Measurements at ALBA from Turn-by-Turn Acquisition	insertion, lattice, vacuum, optics	598
	M. Carlà, G. Benedetti, T.F.G. Günzel, U. Iriso, Z. Martí ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
	A transverse impedance source manifests itself, among other ways, by producing a small defocusing kick which depends on the beam bunch charge. By repeating optics measurements for different bunch charges, it is possible to disentangle the contribution produced by each impedance source from the dominating focusing effects given by the machine optics. But hunting for such faint defocusing effects poses strong requirements on the precision and sensibility of the measurements, and slow machine drifts or different thermal conditions shall be avoided. In this report, we present a novel method to assess in a fast and precise manner machine optics for different bunch charges using BPM turn-by-turn data and hybrid filling patterns. Finally, measurements for different ALBA machine components like scrapers and In-vacuum undulators are compared with simulation results.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR007
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MOPOR008	Beam Induced RF Heating in LHC in 2015	operation, injection, vacuum, monitoring	602
	B. Salvant, O. Aberle, M. Albert, R. Alemany-Fernandez, G. Arduini, J. Baechler, M.J. Barnes, P. Baudrenghien, O.E. Berrig, N. Biancacci, G. Bregliozzi, J.V. Campelo, F. Carra, F. Caspers, P. Chiggiato, A. Danisi, H.A. Day, M. Deile, D. Druzhkin, J. F. Esteban Müller, S. Jakobsen, J. Kuczerowski, A. Lechner, R. Losito, A. Masi, N. Minafra, E. Métral, A.A. Nosych, A. Perillo Marcone, D. Perini, S. Redaelli, F. Roncarolo, G. Rumolo, E.N. Shaposhnikova, J.A. Uythoven, C. Vollinger, A.J. Välimaa, N. Wang, M. Wendt, J. Wenninger, C. Zannini CERN, Geneva, Switzerland M. Bozzo INFN Genova, Genova, Italy J.F. Esteban Müller EPFL, Lausanne, Switzerland N. Wang IHEP, Beijing, People's Republic of China
	Following the recurrent beam induced RF issues that perturbed LHC operation during LHC Run 1, a series of actions were put in place to minimize the risk that similar issues would occur in LHC Run 2: longitudinal impedance reduction campaign and/or improvement of cooling for equipment that were problematic or at the limit during Run 1, stringent constraints enforced on new equipment that would be installed in the machine, tests to control the bunch length and longitudinal distribution, additional monitoring of temperature, new monitoring tools and warning chains. This contribution reports the outcome of these actions, both successes as well as shortcomings, and details the lessons learnt for the future runs.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR008
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MOPOR009	The HL-LHC Impedance Model and Aspects of Beam Stability	HOM, octupole, cavity, focusing	606
	N. Biancacci, K.S.B. Li, E. Métral, B. Salvant CERN, Geneva, Switzerland
	Funding: Research supported by the High Luminosity LHC project The LHC upgrade to the HLLHC foresees new challenging operational scenarios from the beam dynamics point of view. In order to ensure good machine operation and performance, the machine impedance, among other possible sources of instabilities like beam-beam and electron cloud, needs to be carefully quantified profiting also from the current LHC operation. In this work we present the HLLHC impedance model mainly focusing on the contribution of low-impedance collimators and crab cavities: the first reduces the broad-band impedance baseline thanks to the higher jaw material conductivity, the second increases the machine luminosity at the price of increasing the coupled bunch stabilizing octupole current threshold. Other elements like the injection protection absorber (TDI) will be also discussed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR009
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MOPOR010	Impedance Measurements and Simulations on the TCTP and TDI LHC Collimators	HOM, simulation, embedded, operation	610
	N. Biancacci, F. Caspers, A. Grudiev, J. Kuczerowski, I. Lamas Garcia, A. Lechner, E. Métral, A. Passarelli, A. Perillo Marcone, B. Salvant, J.A. Uythoven CERN, Geneva, Switzerland O. Frasciello, M. Zobov INFN/LNF, Frascati (Roma), Italy A. Mostacci Rome University La Sapienza, Roma, Italy N. Mounet EPFL, Lausanne, Switzerland
	The LHC collimation system is a critical element for the safe operation of the LHC machine and is subject to continuous performance monitoring, hardware upgrade and optimization. In this work we will address the impact on impedance of the upgrades performed on the TDI injection protection collimator, where the absorber material has been changed to mitigate the device heating observed in machine operation, and on selected secondary (TCS) and tertiary (TCT) collimators, where beam position monitors (BPM) have been embedded for faster jaw alignment. Concerning the TDI, we will present the RF measurements performed before and after the upgrade, comparing the result to heating and tune shift beam measurements. For the TCTs, we will study how the higher order modes (HOM) introduced by the BPM addition have been cured by means of ferrite placement in the device. The impedance mitigation campaign has been supported by RF measurements whose results are in good agreement with GdfidL and CST simulations. The presence of undamped low frequency modes is proved not to be detrimental to the safe LHC operation.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR010
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MOPOR011	Impedance Localization Measurements using AC Dipoles in the LHC	dipole, quadrupole, betatron, optics	614
	N. Biancacci, L.R. Carver, G. Papotti, T. Persson, B. Salvant, R. Tomás CERN, Geneva, Switzerland
	The knowledge of the LHC impedance is of primary importance to predict the machine performance and allow for the HL-LHC upgrade. The developed impedance model can be benchmarked with beam measurements in order to assess its validity and limit. This is routinely done, for example, moving the LHC collimator jaws and measuring the induced tune shift. In order to localize possible unknown impedance sources, the variation of phase advance with intensity between beam position monitors can be measured. In this work we will present the impedance localization measurements performed at injection in the LHC using AC dipoles as exciter as well as the underlying theory.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR011
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MOPOR012	Study of the Beam-Cavity Interaction in the PS 10 MHz RF System	cavity, simulation, feedback, acceleration	618
	G. Favia, H. Damerau, M. Morvillo, C. Rossi CERN, Geneva, Switzerland M. Migliorati University of Rome "La Sapienza", Rome, Italy
	The eleven main accelerating cavities of the Proton Synchrotron (PS) at CERN consist of two ferrite-loaded coaxial λ/4 resonators each. Both resonators oscillate in phase, as their gaps are electrically connected by short bars. They are in addition magnetically coupled via the bias loop used for cavity tuning. The cavities are equipped with a wide-band feedback system, limiting the beam loading, and a further reduction of the beam induced voltage is achieved by relays which short-circuit each half-resonator gap when the cavity is not in use. Asymmetries of the beam induced voltage observed in the two half-cavities indicate that the coupling between the two resonators is not as tight as expected. The total cavity impedance coupling to the beam may be affected differently by the contributions of both resonators. A dedicated measurement campaign with high-intensity proton beam and numerical simulation have been performed to investigate the beam-cavity interaction. This paper reports the result of the study and the work aiming at the development of a model of the system, including the wide-band feedback, which reproduces this interaction.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR012
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MOPOR013	The PS 10 MHz High Level RF System Upgrade	cavity, feedback, network, beam-loading	622
	G. Favia, H. Damerau, V.D. Desquiens, S. Energico, M. Morvillo, D. Perrelet, C. Rossi CERN, Geneva, Switzerland
	In view of the upgrade of the injectors for the High Luminosity LHC, significantly higher bunch intensity is required for LHC-type beams. In this context an upgrade of the main accelerating RF system of the Proton Synchrotron (PS) is necessary, aiming at reducing the cavity impedance which is the source of longitudinal coupled-bunch oscillations. These instabilities pose as a major limitation for the increase of the beam intensity as planned after LS2. The 10 MHz RF system consists in 11 ferrite loaded cavities, driven by tube-based power amplifiers for reasons of radiation hardness. The cavity-amplifier system is equipped with a wide-band feedback that reduces the beam induced voltage. A further reduction of the beam loading is foreseen by upgrading the feedback system, which can be reasonably achieved by increasing the loop gain of the existing amplification chain. This paper describes the progress of the design of the upgraded feedback system and shows the results of the tests on the new amplifier prototype, installed in the PS during the 2015-16 technical stop. It also reports the first results of its performance with beam, observed in the beginning of the 2016 run.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR013
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MOPOR014	Measurements of the CERN PS Longitudinal Resistive Coupling Impedance	HOM, coupling, synchrotron, cavity	626
	M. Migliorati, N. Biancacci, H. Damerau, G. Sterbini CERN, Geneva, Switzerland M. Migliorati University of Rome "La Sapienza", Rome, Italy M. Migliorati, L. Ventura INFN-Roma1, Rome, Italy S. Persichelli University of Rome La Sapienza, Rome, Italy
	The longitudinal coupling impedance of the CERN PS has been studied in the past years in order to better understand collective effects which could produce beam intensity limitations for the LHC Injectors Upgrade project. By measuring the incoherent quadrupole synchrotron frequency vs beam intensity, the inductive impedance was evaluated and compared with the impedance model obtained by taking into account the contribution of the most important machine devices. In this paper, we present the results of the measurements performed during a dedicated campaign, of the real part of the longitudinal coupling impedance by means of the synchronous phase shift vs beam intensity. The phase shift has been measured by using two different techniques: in one case, we injected in the machine two bunches, one used as a reference with constant intensity, and the second one changing its intensity; in the second case, more conventional, we measured the bunch position with respect to the RF signal of the 40 MHz cavities. The obtained dependence of the synchrotron phase with intensity is then related to the loss factor and the resistive coupling impedance, which is compared to the real part of the PS impedance model.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR014
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MOPOR016	Impedance Study with Single Bunch Beam at Taiwan Photon Source	photon, storage-ring, synchrotron, vacuum	630
	C.-C. Kuo, P.J. Chou, K.T. Hsu, K.H. Hu, C.C. Liang, C.Y. Liao, Z.K. Liu, H.-J. Tsai, F.H. Tseng NSRRC, Hsinchu, Taiwan
	The impedance at Taiwan Photon Source was investigated. The effects of bunch current such as a tune change, a synchronous phase shift and a bunch lengthening under operation conditions at various stages were measured; the machine impedances were deduced. This report presents the results with insertion devices in various configurations.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR016
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MOPOR018	Single Bunch Instability Studies at Diamond Light Source	simulation, coupling, synchrotron, betatron	637
	E. Koukovini-Platia, M. Apollonio, R. Bartolini, R.T. Fielder, I.P.S. Martin DLS, Oxfordshire, United Kingdom R. Bartolini JAI, Oxford, United Kingdom
	Single bunch instability thresholds, the associated coherent tune shifts and the bunch lengthening have been studied at Diamond light source for nominal optics. Measurements were taken under different settings of chromaticity, radio-frequency (RF) voltage and aperture of the insertion devices (IDs). The macro-particle code sbtrack was used to evaluate the instability thresholds and bunch lengthening where different impedance contributions are taken into account such as the resistive wall impedance, a broad-band resonator model and inductive impedance for the longitudinal plane. A comparison of simulation using the developed model impedance with measurements is shown for all cases.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR018
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MOPOY006	Preparations for Upgrading the RF Systems of the PS Booster	cavity, operation, feedback, emittance	853
	S.C.P. Albright, D. Quartullo, E.N. Shaposhnikova CERN, Geneva, Switzerland
	The accelerators of the LHC injector chain need to be upgraded to provide the HL-LHC beams. The PS Booster, the first synchrotron in the LHC injection chain, uses three different RF systems (first, second and up to tenth harmonic) in each of its four rings. As part of the LHC Injector Upgrade the current ferrite RF systems will be replaced with broadband Finemet cavities, increasing the flexibility of the RF system. A Finemet test cavity has been installed in Ring 4 to investigate its effect on machine performance, especially beam stability, during extensive experimental studies. Due to large space charge impedance Landau damping is lost through most of the cycle in single harmonic operation, but is recovered when using the second harmonic and controlled longitudinal emittance blow-up. This paper compares beam parameters during acceleration with and without the Finemet test cavity. Comparisons were made using beam measurements and simulations with the BLonD code based on a full PS Booster impedance model. This work, together with simulations of future operation, have provided input for the decision to adopt a fully Finemet RF system.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOY006
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MOPOY011	Estimating the Transverse Impedance in the Fermilab Recycler	proton, quadrupole, dipole, vacuum	867
	R. Ainsworth, P. Adamson, A.V. Burov, I. Kourbanis, M.-J. Yang Fermilab, Batavia, Illinois, USA
	Impedance could represent a limitation of running high intensity bunches in the Fermilab recycler. With high intensity upgrades foreseen, it is important to quantify the impedance. To do this, studies have been performed measuring the tune shift as a function of bunch intensity allowing the transverse impedance to be derived.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOY011
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MOPOY013	Modeling Longitudinal Dynamics in the Fermilab Booster Synchrotron	booster, emittance, synchrotron, simulation	873
	J.-F. Ostiguy, C.M. Bhat, V.A. Lebedev Fermilab, Batavia, Illinois, USA
	Funding: Work performed under U.S. Government contract DE-AC02-07CH11359 The PIP-II project will replace the existing 400 MeV linac with a new, CW-capable, 800 MeV superconducting one. With respect to current operations, a 50% increase in beam intensity in the rapid cycling Booster synchrotron is expected. Booster batches are combined in the Recycler ring; this process limits the allowed longitudinal emittance of the extracted Booster beam. To suppress eddy currents, the Booster has no beam pipe; magnets are evacuated, exposing the beam to core laminations and this has a substantial impact on the longitudinal impedance. Noticeable longitudinal emittance growth is already observed at transition crossing. Operation at higher intensity will likely necessitate mitigation measures. We describe systematic efforts to construct a predictive model for current operating conditions. A longitudinal only code including a laminated wall impedance model, space charge effects, and feedback loops is developed. Parameter validation is performed using detailed measurements of relevant beam, rf and control parameters. An attempt is made to benchmark the code at operationally favorable machine settings.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOY013
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MOPOY020	Prototype Design of a Newly Revised CW RFQ for the High Charge State Injector at GSI	rfq, simulation, operation, resonance	889
	D. Koser, H. Podlech IAP, Frankfurt am Main, Germany P. Gerhard, L. Groening, O.K. Kester GSI, Darmstadt, Germany
	Within the scope of the FAIR project (Facility for Antiproton and Ion Research) at GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, the front end of the existing High Charge State Injector (HLI) is planned to be upgraded for cw operation. The required newly revised 4-Rod RFQ structure is currently being designed at the Institute for Applied Physics (IAP) of the Goethe University of Frankfurt. It will be operated with a 100 kW power amplifier at 108 MHz. At first instance a dedicated 4-stem prototype, which is based on the RFQ design for MYRRHA* and FRANZ*, is planned to be manufactured in order to validate the simulated RF performance, thermal behavior and mechanical characteristics in continuous operation. The RF simulations as well as basic thermal simulations are done using CST Studio Suite. In order to prevent oscillations of the electrodes mechanical eigenmodes are analyzed using ANSYS Multiphysics. In addition the ANSYS software allows more sophisticated simulations regarding the cooling capability by considering fluid dynamics in water cooling channels, thus providing a more detailed thermal analysis. C. Zhang, H. Podlech, New Reference Design of the European ADS RFQ Accelerator For MYRRHA, IPAC2014 **M. Heilmann et al., A Coupled RFQ-IH Cavity for the Neutron Source FRANZ, IPAC2013
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOY020
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MOPOY058	Removing Known SPS Intensity Limitations for High Luminosity LHC Goals	vacuum, simulation, emittance, shielding	989
	E.N. Shaposhnikova, T. Argyropoulos, T. Bohl, P. Cruikshank, B. Goddard, T. Kaltenbacher, A. Lasheen, J. Perez Espinos, J. Repond, B. Salvant, C. Vollinger CERN, Geneva, Switzerland
	In preparation of the SPS as an LHC injector its impedance was significantly reduced in 1999 - 2000. A new SPS impedance reduction campaign is planned now for the High Luminosity (HL)-LHC project, which requires bunch intensities twice as high as the nominal one. One of the known intensity limitations is a longitudinal multi-bunch instability with a threshold 3 times below this operational intensity. The instability is presently cured using the 4th harmonic RF system and controlled emittance blow-up, but reaching the HL-LHC parameters cannot be assured without improving the machine impedance. Recently the impedance sources responsible for this instability were identified and implementation of their shielding and damping is foreseen during the next long shutdown (2019 - 2020) in synergy with two other important upgrades: amorphous carbon coating of (part of) the vacuum chamber against the e-cloud effect and rearrangement of the 200 MHz RF system. In this paper the strategy of impedance reduction is presented together with beam intensity achievable after its realisation. The potential effect of other proposals on remaining limitations is also considered.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOY058
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TUOAB03	Transverse Coherent Instabilities in Storage Rings with Harmonic Cavities	synchrotron, radio-frequency, cavity, simulation	1061
	F.J. Cullinan, R. Nagaoka SOLEIL, Gif-sur-Yvette, France G. Skripka, P.F. Tavares MAX IV Laboratory, Lund University, Lund, Sweden
	Many current and future synchrotron light sources employ harmonic cavities to lengthen the electron bunches in order to reduce the emittance dilution caused by intrabeam scattering. In some cases, the harmonic cavities may be tuned to fulfill the flat potential condition. For this condition, a large increase in the threshold currents of transverse coupled-bunch instabilities has been predicted and recently, the physical content behind this stabilization has been better understood. With this in mind, an investigation is made into the effectiveness of harmonic cavities for different machines. Frequency domain computations employing Laclare's eigenvalue method have been used to investigate the influence of several machine parameters and the results are presented.
	Slides TUOAB03 [14.037 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUOAB03
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TUPMR015	Cooling and Heat Transfer of the IRANCYC-10 Transmission Line	simulation, cyclotron, factory, cavity	1259
	S. Sabounchi, H. Afarideh, M. Mohamadian, M. Salehi AUT, Tehran, Iran J.-S. Chai, M. Ghergherehchi SKKU, Suwon, Republic of Korea
	Heat transfer study for designing RF transmission line in cyclotrons is crucial. Because of enormous amount of surface current on RF transmission line, despite high conductivity of copper, significant amount of heat is being generated, which is enough for altering characteristic impedance and other desirable parameters for transmission line. So, effective cooling system which is nourished by central chiller system is essential. For design of cooling system in RF transmission line suitable mass flow, appropriate geometry and confined temperatures are prominent in order to avoid eroding and impedance changing. In this paper an attempt has been done for accurate analyzing and simulating of heat transfer phenomenon for the 10MeV cyclotron (IRANCYC-10 ) which is under construction at AmirKabir University of Technology. By using Ansys CFX simulation software, the optimum cooling line geometry and mass flow rate of 90 gr/s for cooling water, has been resulted.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMR015
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TUPMW011	Current Status of Instability Threshold Measurements in the LHC at 6.5 TeV	octupole, damping, simulation, electron	1434
	L.R. Carver, J. Barranco, N. Biancacci, X. Buffat, W. Höfle, G. Kotzian, T. Lefèvre, T.E. Levens, E. Métral, T. Pieloni, B. Salvant, C. Tambasco CERN, Geneva, Switzerland N. Wang IHEP, Beijing, People's Republic of China M. Zobov INFN/LNF, Frascati (Roma), Italy
	Throughout 2015, many measurements of the minimum stabilizing octupole current required to prevent coherent transverse instabilities have been performed. These measurements allow the LHC impedance model at flat top to be verified and give good indicators of future performance and limitations. The results are summarized here, and compared to predictions from the simulation code DELPHI.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW011
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TUPMW021	Roman Pot Insertions in High-Intensity Beams for the CT-PPS Project at LHC	insertion, proton, luminosity, vacuum	1473
	M. Deile, R. Bruce, A. Mereghetti, D. Mirarchi, S. Redaelli, B. Salvachua, B. Salvant, G. Valentino CERN, Geneva, Switzerland
	The CMS-TOTEM Precision Proton Spectrometer (CT-PPS) at the LHC IP5 aims at exploring diffractive physics at high luminosity in standard LHC fills. It is based on 14 Roman Pots (RPs), designed to host tracking and time-of-flight detectors for measuring the kinematics of leading protons. To reach the physics goals, the RPs will finally have to approach the beams to distances of 15 beam σs (i.e. ~1.5 mm) or closer. After problems with showers and impedance heating in first high-luminosity RP insertions in 2012, the LS1 of LHC was used for upgrades in view of impedance minimisation and for adding new collimators to intercept RP-induced showers. In 2015 the effectiveness of these improvements was shown by successfully inserting the RPs in all LHC beam intensity steps to a first-phase distance of ~25 σs. This contribution reviews the measurements of debris showers and impedance effects, i.e. the data from Beam Loss Monitors, beam vacuum gauges and temperature sensors. The dependences of the observables on the luminosity are shown. Extrapolations to L=10³⁴ cm^-2 s^-1 and smaller distances to the beam do not indicate any fundamental problems. The plans for 2016 are outlined.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW021
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TUPMW034	A 200 MHz SC-RF System for the HL-LHC	cavity, emittance, injection, luminosity	1513
	R. Calaga, R. Tomás CERN, Geneva, Switzerland
	Funding: Research supported by the High Luminosity LHC project A quarter wave β=1 superconducting cavity at 200 MHz is proposed for the LHC as an alternative to the present 400 MHz RF system. The primary motivation of such a system would be to accelerate higher intensity and longer bunches with improved capture efficiency. Advantages related to minimizing electron cloud effects, intra-beam scattering, heating and the possibility of luminosity levelling with bunch length are described. Some considerations related to cavity optimization, beam loading and technological challenges are addressed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW034
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TUPOR001	Lifetime Improvements with a Harmonic RF System for the ESRF EBS	cavity, storage-ring, simulation, electron	1644
	N. Carmignani, L. Farvacque, J. Jacob, S.M. Liuzzo, B. Nash, T.P. Perron, P. Raimondi, R. Versteegen, S.M. White ESRF, Grenoble, France
	A third-harmonic RF system to increase the Touschek lifetime is under study for the European Synchrotron Radiation Facility (ESRF) Extremely Brilliant Source (EBS) storage ring, in particular for modes with high current per bunch. Multi-particle simulations have been done to study the bunch lengthening and shape in presence of inductive impedance and a third-harmonic RF system.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR001
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TUPOR004	Calculation of Transverse Coupled Bunch Instabilities in Electron Storage Rings Driven By Quadrupole Higher Order Modes	HOM, quadrupole, dipole, damping	1655
	M. Ruprecht, P. Goslawski, M. Ries, G. Wüstefeld HZB, Berlin, Germany
	This paper presents a formula that estimates the growth rate of a transverse coupled bunch instability driven by quadrupole higher order modes (HOMs) in electron storage rings. Thus far, quadrupole HOMs are usually ignored in HOM driven instability studies for electron storage rings due to their weak nature compared to the lower orders. However, they may become relevant when high gradient SC multi-cell cavities with their potentially strong impedance spectrum are operated at high currents in a third generation or future synchrotron light source. An example is BESSY VSR, a scheme where 1.7 ps and 15 ps long bunches (rms) can be stored simultaneously in the BESSY II storage ring[]. With the presented formula, instability thresholds are discussed for a recent BESSY VSR cavity model and different beam parameters. A. Jankowiak, J. Knobloch, P. Goslawski, and N. Neumann, eds., BESSY VSR - Technical Design Study, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 2015.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR004
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TUPOR008	Effect of the Various Impedances on Longitudinal Beam Stability in the CERN SPS	HOM, simulation, vacuum, operation	1666
	A. Lasheen, T. Argyropoulos, J. Repond, E.N. Shaposhnikova CERN, Geneva, Switzerland
	The High Luminosity (HL)-LHC project at CERN aims at a luminosity increase by a factor ten and one of the necessary ingredients is doubling the bunch intensity to 2.4x10¹¹ ppb for beams with 25 ns bunch spacing. Many improvements are already foreseen in the frame of the LHC Injector Upgrade (LIU) project, but probably this intensity would still not be reachable in the SPS due to longitudinal instabilities. Recently a lot of effort went into finding the impedance sources of the instabilities. Particle simulations based on the latest SPS impedance model are now able to reproduce the measured instability thresholds and were used to determine the most critical impedance sources by removing them one by one from the model. It was found that impedance of vacuum flanges and of the already damped 630 MHz HOM of the main RF system gave for 72 bunches the comparable intensity thresholds. Possible intensity gains are defined for realistic impedance modifications and for various beam configurations (number of bunches, longitudinal emittances) and RF programs (single and double RF). The results of this study are used as a guideline for planning of a new campaign of the SPS impedance reduction.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR008
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TUPOR009	Single Bunch Longitudinal Instability in the CERN SPS	simulation, flattop, synchrotron, emittance	1670
	A. Lasheen, T. Bohl, S. Hancock, T. Roggen, E.N. Shaposhnikova CERN, Geneva, Switzerland E. Radvilas Gediminas Technical University, Vilnius, Lithuania
	The longitudinal single bunch instability observed in the SPS leads to uncontrolled emittance blow-up and limits the quality of high intensity beams required for the High Luminosity LHC and AWAKE projects at CERN. The present SPS impedance model developed from a thorough survey of machine elements was used in macro-particle simulations (with the code BLonD) of the bunch behavior through the acceleration cycle. Comparison of simulations with measurements of the synchrotron frequency shift, performed on the SPS flat bottom to probe the impedance, show a reasonable agreement. During extensive experimental studies various beam and machine parameters (bunch intensity, longitudinal emittance, RF voltage, with single and double RF systems) were scanned in order to further benchmark the SPS impedance model with measurements and to better understand the mechanism behind the instability. It was found that the dependence of instability threshold on longitudinal emittance and beam energy has an unexpected non-monotonic behavior, leading to islands of (in)stability. The results of this study are presented and can be used to define possible parameter settings for the future CERN projects.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR009
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TUPOR010	Simulation of Instability at Transition Energy with a New Impedance Model for CERN PS	simulation, emittance, proton, synchrotron	1674
	N. Wang IHEP, Beijing, People's Republic of China S. Aumon, N. Biancacci, M. Migliorati, G. Sterbini, N. Wang CERN, Geneva, Switzerland M. Migliorati INFN-Roma1, Rome, Italy S. Persichelli University of Rome La Sapienza, Rome, Italy
	Instabilities driven by the transverse impedance are proven to be one of the limitations for the high intensity reach of the CERN PS. Since several years, fast single bunch vertical instability at transition energy has been observed with the high intensity bunch serving the neu-tron Time-of-Flight facility (n-ToF). In order to better understand the instability mechanism, a dedicated meas-urement campaign took place. The results were compared with macro-particle simulations with PyHEADTAIL based on the new impedance model developed for the PS. Instability threshold and growth rate for different longitu-dinal emittances and beam intensities were studied.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR010
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TUPOR011	Study of Microwave Instability for SLS-2	vacuum, storage-ring, emittance, simulation	1678
	H.S. Xu, P. Craievich, M.M. Dehler, L. Stingelin PSI, Villigen PSI, Switzerland
	An ultra-low emittance electron storage ring is under development for the Upgrade of Swiss Light Source (SLS-2). An antechamber scheme consisting of round beam channel with 10 mm inner radius is considered to accommodate the required strong quadrupole and sextupole magnets, achieve the ultra-high vacuum, and absorb the undesired synchrotron radiation. However, the small size of vacuum chamber increases the susceptibility of the beam to the impedance induced collective instabilities. We will present the preliminary study of the microwave instability for SLS-2 storage ring considering the longitudinal Resistive-Wall (RW) impedance due to three different options for the beam chamber. The microwave instability thresholds are calculated under the conditions of two possible RF frequencies (100 MHz and 500 MHz) and three different materials (aluminum, copper, and stainless steel). The influences of third-harmonic cavities are also studied.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR011
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TUPOR012	THz Coherent Synchrotron Radiation from Ultra-low Alpha Operating Mode at Diamond Light Source	simulation, storage-ring, radiation, electron	1682
	T. Chanwattana, M. Atay, R. Bartolini JAI, Oxford, United Kingdom R. Bartolini, G. Cinque, M. Frogley, E. Koukovini-Platia, I.P.S. Martin DLS, Oxfordshire, United Kingdom
	Diamond Light Source is regularly operated in low-alpha mode to provide THz coherent synchrotron radiation (CSR) and short X-ray pulses for users. In order to maintain the wide frequency range of the coherent radiation whilst improving the signal to noise ratio, an ultra-low alpha mode has been considered to shorten the bunch length even further. In order to study this mode, the analysis of single bunch dynamics resulting from a variety of wakefield sources has been investigated using a single bunch multiparticle tracking code. These results are compared with measurements recorded using a Fourier transform infrared (FTIR) interferometer on the MIRIAM beam-line at Diamond.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR012
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TUPOR013	Analysis of Multi-bunch Instabilities at the Diamond Storage Ring	damping, wakefield, storage-ring, simulation	1685
	R. Bartolini, R.T. Fielder, G. Rehm DLS, Oxfordshire, United Kingdom V.V. Smaluk BNL, Upton, Long Island, New York, USA
	We present recent results of analytical, numerical and experimental analysis of multi-bunch instabilities at the Diamond storage ring. The works compares the impedance estimates from numerical modelling with the analysis of the growth rates of the excited multi-bunch modes in different machine configurations. The contribution of a number of wakefield sources has been identified with very high precision thanks to high quality data provided by the existing Transverse multi-bunch feedback diagnostics
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR013
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TUPOW022	Hybrid Electron Linac With Standing and Travelling Wave Accelerating Sections	focusing, linac, coupling, electron	1791
	S.V. Matsievskiy, A.V. Bulanov, V.I. Kaminskiy, E.A. Savin, N.P. Sobenin MEPhI, Moscow, Russia R.Yu. Alekhanov NRNU, Moscow, Russia
	Hybrid electron linacs with standing and travelling wave accelerating sections are not well described in literature. Limited number of studies have shown that application of these systems makes it possible to develop a compact linac with high efficiency and simpler power system. Typically, these systems use well-studied bi-periodical accelerating structure (BAS) cells for a standing wave section and disc-loaded waveguides (DLW) for a traveling wave section. This paper describes the development of such system using DLW cells with magnetic coupling (DLW-M). Here BAS appears as an absorbing load connected to the DLW-M accelerating structure by rectangular waveguide allowing to have theoretical zero reflection at RF input. Such system also provides possibility of plain beam output energy adjustment. Studies of the structure were carried out using equivalent circuits methods and numerical 3D-modeling. Beam dynamics was calculated.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW022
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WEPMB041	Design of RF Power Coupler for RISP Half Wave Resonator	simulation, cavity, vacuum, electron	2208
	S. Lee, E.-S. Kim Korea University Sejong Campus, Sejong, Republic of Korea I. Shin IBS, Daejeon, Republic of Korea
	RF power couplers for half wave resonators are under development for the Rare Isotope Science Project (RISP) in Korea. It is required to deliver up to 6 kW RF power at 162.5 MHz to the HWR in CW mode. The RF coupler is a coaxial capacitive type using a disc type ceramic window. Design studies of 2nd prototype HWR RF coupler are presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB041
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WEPMR037	Wakefield Analysis of the 56 MHz SRF Cavity	cavity, HOM, wakefield, SRF	2354
	Q. Wu, Y. Hao BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The 56 MHz SRF cavity is a superconducting quarter-wave resonator installed in the common section of RHIC. Both beams share the cavity in an interwoven pattern over the entire store. The wake field excited in the cavity is the superposition of the two opposing bunches. This paper will discuss the wake field excited by both beams, and the higher order mode power as a result of the excited field.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR037
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WEPMW031	Towards Optimum Material Choices for the HL-LHC Collimator Upgrade	collimation, beam-losses, luminosity, simulation	2498
	E. Quaranta, A. Bertarelli, N. Biancacci, R. Bruce, F. Carra, E. Métral, S. Redaelli, A. Rossi, B. Salvant CERN, Geneva, Switzerland F. Carra Politecnico di Torino, Torino, Italy
	The first years of operation at the LHC showed that collimator material-related concerns might limit the performance. In addition, the HL-LHC upgrade will bring the accelerator beyond the nominal performance through more intense and brighter proton beams. A new generation of collimators based on advanced materials is needed to match present and new requirements. After several years of R&D on collimator materials, studying the behaviour of novel composites with properties that address different limitations of the present collimation system, solutions have been found to fulfil various upgrade challenges. This paper describes the proposed staged approach to deploy new materials in the upgraded HL-LHC collimation system. Beam tests at the CERN HiRadMat facility were also performed to benchmark simulation methods and constitutive material models.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW031
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WEPMW039	JLEIC SRF Cavity RF Design	cavity, HOM, electron, damping	2522
	S. Wang, J. Guo, R.A. Rimmer, H. Wang JLab, Newport News, Virginia, USA
	The initial design of a low higher order modes (HOM) impedance superconducting RF (SRF) cavity is presented in this paper. The design of this SRF cavity is for the proposed Jefferson Lab Electron Ion Collider (JLEIC). The electron ring of JLEIC will operate with electrons of 3 to 10 GeV energy. The ion ring of JLEIC will operate with protons of up to 100 GeV energy. The bunch lengths in both rings are ~12 mm (RMS). In order to maintain the short bunch length in the ion ring, SRF cavities are adopted to provide large enough gradient. In the first phase of JLEIC, the PEP II RF cavities will be reused in the electron ring to lower the initial cost. The frequency of the SRF cavities is chosen to be the second harmonic of PEP II cavities, 952.6 MHz. In the second phase of JLEIC, the same frequency SRF cavities may replace the normal conducting PEP II cavities to achieve higher luminosity at high energy. At low energies, the synchrotron radiation damping effect is quite weak, to avoid the coupled bunch instability caused by the intense closely-spaced electron bunches, low HOM impedance of the SRF cavities combined with longitudinal feedback system will be necessary.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW039
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WEPMW042	Trapped Modes Study and BBU Analysis in the 5-Cell 650 MHz Cavity	HOM, cavity, electron, damping	2529
	C. Xu, I. Ben-Zvi, Y. Hao, V. Ptitsyn, W. Xu BNL, Upton, Long Island, New York, USA I. Petrushina SUNY SB, Stony Brook, New York, USA
	Funding: This work is supported by LDRD program of Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE. #chenxu@bnl.gov eRHIC project is a future electron-hadron collider proposed at BNL. The proposed electron accelerator will generate up to 20 GeV polarized electrons which will collide with proton beams with energy up to 250 GeV. The proposed collider will deliver electron-nucleon luminosity of 10³³- 10³⁴ cm^-2 ses⁻¹. A superconducting RF (SRF) 5-cell elliptical cavity will be utilized in electron accelerator. This paper presents a study of higher-order modes (HOM) for this 647 MHz SRF cavity. Different types of HOM modes and their BBU instabilities were investigated for frequencies up to 3.2 GHz. Threshold current values of beam breakup are estimated by GBBU code. Further improvement on this threshold current has been explored and discussed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW042
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WEPMY037	Cold Model Cavity for 20-K Cryocooled C-band Photocathode RF Gun	simulation, cavity, gun, coupling	2635
	T. Tanaka, M. Inagaki, R. Nagashima, K. Nakao, K. Nogami, T. Sakai, K. Takatsuka LEBRA, Funabashi, Japan M.K. Fukuda, T. Takatomi, N. Terunuma, J. Urakawa, M. Yoshida KEK, Ibaraki, Japan D. Satoh TIT, Tokyo, Japan
	Funding: Work supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT). A cryocooled 2.6-cell C-band photocathode RF gun is under development at Nihon University in collaboration with KEK. The RF characteristics of a pillbox-type 2.6-cell C-band RF cavity at 20 K were in agreement with the theoretical predictions. The result of the cold test for a cavity with the input coupler confirmed the same characteristics. Based on these results a refined cold model of the 20-K cryocooled photocathode RF gun has been designed using SUPERFISH and CST-STUDIO. The separation between the TM01 pi and the TM01 half-pi modes has been increased from 20 MHz to 52 MHz by extending the diameter of the cavity iris and reducing the disk thickness. The 2.6-cell structure has been modified from pillbox to ellipsoid-like type. The end-plate of the 0.6-cell cavity has a center hole for bead-pull measurements of the on-axis electric filed through the entire structure. Mounting of a photocathode assembly in the end-plate has not been considered, since the purpose is solely to measure the low-power and low-temperature RF characteristics. A new design for the input coupler has been employed. The cavity will be completed early in 2016.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY037
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WEPOW036	Bunch Length Measurements with Passive Harmonic Cavities for Uniform Fill Patterns in a 100 MHz RF System	storage-ring, simulation, cavity, lattice	2914
	T. Olsson, S.C. Leemann, P. Lilja MAX IV Laboratory, Lund University, Lund, Sweden
	The MAX IV facility includes two storage rings operated at 1.5 GeV and 3 GeV. Both rings make use of a 100 MHz RF system and are designed to operate with a uniform multibunch fill pattern as well as employ passive harmonic cavities to damp instabilities and increase Touschek lifetime. Recently, a discussion on timing modes at the MAX IV storage rings has been initiated by the user community. This implies operating the rings with other fill patterns than the originally planned multibunch mode and therefore detailed studies of the performance of the harmonic cavities are of interest. This paper presents bunch length measurements at the 100 MHz MAX II storage ring for uniform fill patterns. The purpose of the measurements was to evaluate the employed measurement method and simulation codes for future studies of fill patterns in the MAX IV storage rings.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOW036
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WEPOW052	Multimodal Interaction in the ALS Longitudinal Feedback Kicker RF Cavity	cavity, kicker, feedback, resonance	2965
	S. De Santis, K.M. Baptiste, J.M. Byrd, S. Kwiatkowski, T.H. Luo, E.R. Sanmateo, C. Steier, C.A. Swenson LBNL, Berkeley, California, USA F. Marcellini PSI, Villigen PSI, Switzerland
	Funding: The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. RF cavities are essential components in particle accelerators not only for beam acceleration, but also for control purposes (bunch lengthening/shortening, deflecting and crabbing, transverse and longitudinal kickers) and for beam diagnostics (BPM). Normally, only a single resonating mode is actively used, although other modes can be excited by the circulating beam. Cavities used as feedback longitudinal kickers are designed with an axial mode which, appropriately excited, provides a kick to the circulating bunches for maintaining beam stability. To provide the necessary bandwidth this mode has to be strongly damped resulting in quality factors of just a few units. In the longitudinal feedback kicker cavity just installed on the ALS we have detected a second axial mode which, although a few hundreds of MHz below the 1.4 GHz design mode, is also strongly damped and has a shunt impedance high enough to be appreciably excited by the feedback amplifier coupling to the first mode. In this paper we show bench measurements on the cavity and with beam during its commissioning and discuss the interaction of the two modes resulting in a modulation of shunt impedance and phase response.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOW052
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WEPOY045	Benchmarking the Beam Longitudinal Dynamics Code BLonD	simulation, synchrotron, feedback, injection	3094
	H. Timko, J. F. Esteban Müller, A. Lasheen, D. Quartullo CERN, Geneva, Switzerland
	The relatively recent Beam Longitudinal Dynamics code BLonD has already been applied to a wide range of studies for all present CERN synchrotrons. Its application area ranges from studies of RF manipulations, over single and multi-bunch interactions with impedance, to the action of feedback loops and RF noise. In this paper, we present benchmarks and comparisons with measurements, theory, or other codes, which have increased greatly the trust in the code. Tests related to bunch-to-bucket transfer, feedback loops, diffusion due to noise injection, as well as collective effects, are presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY045
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THPMR031	Turn-by-Turn Measurements for Beam Dynamics at Vepp-5 Damping Ring	damping, betatron, lattice, vacuum	3452
	M.F. Blinov, K.V. Astrelina, V.V. Balakin, O.I. Meshkov, A.A. Starostenko BINP SB RAS, Novosibirsk, Russia V.L. Dorokhov BINP, Novosibirsk, Russia
	Preinjector complex VEPP-5 is being constructed for high rate production and acceleration of electrons and positrons beams up to energy 510 MeV. Both kinds of particles accumulated in the damping ring and after achieving of needed intensity the beams would be transported alternatively to VEPP-3/VEPP-4M or to BEP/VEPP-2000 colliders. At this paper basic parameters of damping ring presented. All measurements were carried out for electron beam with energy 385 MeV. For turn-by-turn measurements 12 beam position monitors were used. In order to improve precision of measured value NAFF algorithm was applied. For measurements of longitudinal beam profile optical phi-dissector was used.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMR031
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THPMR036	Improved Methods for the Measurement and Simulation of the CERN SPS Non-linear Optics	optics, octupole, sextupole, multipole	3464
	H. Bartosik, A. Oeftiger, M. Schenk, F. Schmidt, M. Titze CERN, Geneva, Switzerland
	Good knowledge of the non-linear properties of the SPS lattice is crucial for modelling and optimising the machine performance in the presence of collective effects leading to incoherent tune spreads such as space charge, e-cloud and beam coupling impedance. In view of the LHC injectors upgrade (LIU) project and the future SPS operation in a regime dominated by such collective effects, detailed measurements of the SPS non-linear chromaticity and detuning with amplitude have been performed for the two optics configurations presently available for LHC type beams. The measurement results are used to fit systematic multipole components to the main magnets of the SPS MADX model as a basis for the non-linear machine model that can be used for beam dynamics simulations. The implications for the operation of the SPS with the LIU beam parameters are discussed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMR036
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THPMW003	Prototype Power Supply for SuperKEKB Final Focus Superconducting Corrector Magnets	power-supply, superconducting-magnet, controls, luminosity	3537
	T. Oki, T. Adachi, S. Nakamura, N. Ohuchi, N. Tokuda KEK, Ibaraki, Japan
	A prototype power supply for the SuperKEKB final focus superconducting corrector magnets was developed. The aiming specifications of the power supply are a DC rated output of ± 60 A ± 5 V bipolar, current setting resolution < 1 ppm, current stability < 5 ppm/8 h, temperature coefficient < 1 ppm/degree, and current ripple < 5 ppm, where the assumed magnet inductance and cable resistance are 0.2'8.7 mH and 75 mohms, respectively. High power tests were performed and expected results were obtained.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW003
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THPMW020	Solid-state Compact Kicker Pulsar using Strip-line Type Blumlein with SIC-MOSFET in Spring-8	high-voltage, kicker, operation, storage-ring	3585
	C. Mitsuda, T. Honiden, K. Kobayashi, T. Kobayashi, S. Sasaki JASRI/SPring-8, Hyogo-ken, Japan N. Sekine Sekine Electric Works Co. Ltd, Osaka, Japan
	In the case of handling the electron beam by bunch-by-bunch and turn-by-turn with a kicker at the SPring-8, the performances required to a pulsar are short pulse width (<40ns) and high repetitions (>208kHz). In order to achieve these specifications, the short pulsed high voltage output and the utilization of the solid-state switch is necessary for an inductance load. In order to suppress the supplied voltage as low as as possible, it is an important feature to realize the extremely small-sized pulsar to be set near the kicker. On the basis of the experiences in developing the solid-state pulsar of 400ns/2kV using Si-MOSFET, combination of the SiC-MOSFET and the strip-line type Blumlein pulse forming network (BPFN) was applied to the prototype driver to achieve a shorter pulse and higher power than Si-type driver. The completed pulsar accomplished a compact size (external dimensions; 300(H)x400(W)x400(D)mm). Furthermore, the targeted short-pulsed high voltage output of 123ns/12kV was obtained by 6 BPFNs serial connection to the load inductance of 800 nH. The BPFN detailed design to enable the compact size, high reliability and stability at high repetitions will be reported. C.Mitsuda et al., Proc. of IPAC2013, MOPAWA003
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW020
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THPMW028	High Voltage Performance of Surface Coatings on Alumina Insulators	kicker, high-voltage, injection, vacuum	3603
	A. Adraktas, M.J. Barnes, H.A. Day, L. Ducimetière CERN, Geneva, Switzerland
	Alumina insulators and dielectrics are required for a variety of applications in particle accelerators. Their use in high voltage devices, both pulsed and DC, is well established as both insulation and mechanical support. In accelerator equipment the alumina is usually used in ultra-high vacuum and hence charge accumulation can be an issue, especially when the alumina is near to the beam. To address challenges regarding surface flashover and high secondary electron yield in high intensity accelerators, surface treatments and coatings are being considered. This paper presents predictions of the influence of surface coatings, on alumina insulators, upon electric field.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW028
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THPMW030	Studies of Impedance-related Improvements of the SPS Injection Kicker System	kicker, simulation, coupling, vacuum	3611
	M.J. Barnes, A. Adraktas, M.S. Beck, G. Bregliozzi, H.A. Day, L. Ducimetière, J.A. Ferreira Somoza, B. Goddard, T. Kramer, C. Pasquino, G. Rumolo, B. Salvant, L. Sermeus, J.A. Uythoven, L. Vega Cid, W.J.M. Weterings, C. Zannini CERN, Geneva, Switzerland F.M. Velotti EPFL, Lausanne, Switzerland
	The injection kicker system for the SPS consists of sixteen magnets housed in a total of four vacuum tanks. The kicker magnets in one tank have recently limited operation of the SPS with high-intensity beam: this is due to both beam induced heating in the ferrite yoke of the kicker magnets and abnormally high pressure in the vacuum tank. Furthermore, operation with the higher intensity beams needed in the future for HL-LHC is expected to exacerbate these problems. Hence studies of the longitudinal beam coupling impedance of the kicker magnets have been carried out to investigate effective methods to shield the ferrite yoke from the circulating beam. The shielding must not compromise the field quality or high voltage behaviour of the kicker magnets and should not significantly reduce the beam aperture: results of these studies, together with measurements, are presented. In addition results of tests to identify the causes of abnormal outgassing are presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW030
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THPMW031	Current and Future Beam Thermal Behaviour of the LHC Injection Kicker Magnet	kicker, injection, simulation, coupling	3615
	H.A. Day, M.J. Barnes, L. Ducimetière, L. Vega Cid, W.J.M. Weterings CERN, Geneva, Switzerland
	During Run 1 of the LHC the injection kicker magnets caused occasional operational delays due to beam induced heating with high bunch intensity and short bunch lengths. Significant upgrades were carried out to the injection kicker magnets during long shutdown 1, including a new design of beam screen to reduce the beam induced heating. Nevertheless these kicker magnets may limit the performance of HL-LHC unless additional, mitigating, measures are taken. Hence extensive simulations have been carried out to predict the distribution of the beam induced power deposition within the magnet and detailed thermal analyses carried out to predict the temperature profiles. To benchmark the simulations the predicted temperatures are compared with observables in the LHC. This paper reports on observations of the thermal behaviour of the magnet during run 2 of the LHC, with 25ns beam. In addition the measurement data is used to extrapolate temperature rise for the beam parameters expected for high-luminosity LHC.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW031
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THPMW033	Operational Experience of the Upgraded LHC Injection Kicker Magnets	kicker, injection, vacuum, operation	3623
	M.J. Barnes, A. Adraktas, G. Bregliozzi, S. Calatroni, H.A. Day, L. Ducimetière, B. Goddard, V. Gomes Namora, V. Mertens, B. Salvant, J.A. Uythoven, L. Vega Cid, W.J.M. Weterings, C. Yin Vallgren CERN, Geneva, Switzerland
	During Run 1 of the LHC the injection kicker magnets caused occasional operational delays due to beam induced heating with high bunch intensity and short bunch lengths. In addition, sometimes there were also sporadic issues with microscopic unidentified falling objects, vacuum activity and electrical flashover of the injection kickers. An extensive program of studies was launched and significant upgrades were carried out during long shutdown 1. These upgrades include a new design of a beam screen to both reduce the beam coupling impedance of the kicker magnet, and to significantly reduce the electric field associated with the screen conductors, hence decreasing the probability of electrical breakdown in this region. In addition new cleaning procedures were implemented and equipment adjacent to the injection kickers and various vacuum components were modified. This paper presents operational experience of the injection kicker magnets during Run 2 of the LHC and assesses the effectiveness of the various upgrades.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW033
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THPMW034	Review on the Effects of Characteristic Impedance Mismatching in a Stripline Kicker	kicker, extraction, damping, emittance	3627
	C. Belver-Aguilar, M.J. Barnes, L. Ducimetière CERN, Geneva, Switzerland
	A stripline kicker operates as two coupled transmission lines, with two TEM operating modes, known as odd and even modes. The characteristic impedance of these two modes is generally different, both only tend to the same value either when the electrodes are widely separated or when the electrodes are very close to the beam pipe wall. In all other cases, the even mode characteristic impedance is always higher than the odd mode characteristic impedance. The specifications required for a kicker operating in a low emittance ring are usually very challenging. In this situation it is desirable to match the even mode characteristic impedance of the striplines to the resistance of their termination. However a mismatched odd mode impedance can significantly influence the striplines performance. This paper presents predictions for the influence of the odd mode characteristic impedance upon the contribution of each field component, electric and magnetic, to the deflection angle. In addition, the variation of the characteristic impedance and field homogeneity with frequency are presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW034
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THPMW038	Prototyping of the ALS-U Fast Kickers	kicker, coupling, vacuum, injection	3637
	G.C. Pappas, S. De Santis, J.-Y. Jung, T.H. Luo, C. Steier, C.A. Swenson, W.L. Waldron LBNL, Berkeley, California, USA
	Prototyping of major components for the ALS-U kickers is in progress. A tapered stripline kicker has been built for installation and testing in the ALS, and multiple modulator options to meet the fast rise time required for swap out injection have been considered. High voltage feedthroughs that are matched into the multi GHz range are also being studied. * Pappas et al., "Fast Kicker Systems for ALS-U", Proc. of IPAC'14, Dresden, Germany, MOPME083.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW038
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THPMW042	Overview of Driver Technologies for Nanosecond TEM Kickers	operation, controls, kicker, injection	3645
	A.K. Krasnykh SLAC, Menlo Park, California, USA
	Funding: Work supported in part by US Department of Energy under contract DE-AC02-76SF00515 and in part by US Department of Energy under contract DE-AC02-06CH11357 Overview of modern methods, circuits, and practical realizations for multi MW peak power pulsers will be presented. All used pulser components are manufactured by the US national industry and they are available for design and pulser fabrication. Two concepts will be discussed: (1) an approach is based on assistance of a nonlinear transmission line with ferromagnetic media and (2) an approach is based on assistance of special diodes which are working in a specific mode of operation. In both approaches the nonlinear characteristic of switching media (ferromagnetic and solid state plasma) are employed in final stage of the pulser to form the multi MW level nanosecond pulses.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW042
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THPMW043	Observation of Beam-induced Abort Kicker Ferrite Heating in RHIC	kicker, vacuum, quadrupole, proton	3648
	C. Montag, L. Ahrens, K.A. Drees, H. Hahn, J.-L. Mi, C. Pai, J. Sandberg, T.C. Shrey, P. Thieberger, J.E. Tuozzolo, W. Zhang BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. During the FY 2013 RHIC polarized proton run, deterioration of the abort kicker system was observed. The reduced kicks resulted in quenching the superconducting quadrupole Q4 downstream of the beam dump. Frequent re-tuning of the modulator wave form temporarily mitigated the effect, which worsened during the course of the run. Beam-induced heating of the kicker ferrites was evenutally identified as the root cause of this behavior. We report our observations and discuss modifications to the kickers.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW043
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THPMY006	Analysis and Testing of a New RF Bridge Concept as an Alternative to Conventional Sliding RF Fingers in LHC	vacuum, operation, ion, alignment	3660
	J. Perez Espinos, C. Garion CERN, Geneva, Switzerland
	RF fingers are used as transition elements in beam vacuum line interconnections to ensure the continuity of the vacuum system wall within acceptable beam stability requirements. The RF fingers must absorb and compensate longitudinal, angular and transversal misalignments due to both thermal effects, during bake-out or cooldown processes, and mechanical movements during assembly, alignment, commissioning and operation phases. The new RF bridge concept is based on a deformable thin-walled structure in copper beryllium, which fulfils the above requirements without the need of sliding contacts. Mechanical tests have been carried out to characterize the response and the lifetime of such a component under different loading conditions. In addition, finite element models have been used to estimate the behaviour. The influence of different material grades and heat treatments on the reliability is presented. The paper includes a detailed analysis of the prototyping and testing phases that have led to a final design of the system, qualified on a dedicated test bench, for the collimator vacuum modules of LHC.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMY006
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THPMY009	Coaxial Wire Method Adapted to Weakly Coupled Resonator Mode for LHC RF Fingers Evaluation	resonance, coupling, cavity, vacuum	3670
	C. Vollinger, F. Caspers, T. Kaltenbacher CERN, Geneva, Switzerland
	In high intensity particle accelerators, RF contact fingers are commonly used to carry the beam induced image current. In addition, they reduce beam impedance by shielding the outer bellows required to compensate mechanical displacements between components. In order to assess the resulting beam impedance from a specific bellow/RF finger configuration, RF measurements are routinely carried out. During these measurements, it was observed that cavity modes in the volume between the fingers and the bellow undulation arise. These resonances occur at significantly higher frequencies than the expected frequency range of interest. Due to their broadband nature, the tails of the imaginary part of these resonances reach into the lower frequency range of interest where it contributes to the beam coupling impedance of the device. For proper evaluation of this contribution, a time domain delay technique in TDT (time domain transmissiometry) was used in order to overcome shortcomings that arise if the classical coaxial wire method is applied to these structures. We present the theory of our method and discuss it in view of the data measured on deformable fingers that were studied for the LHC.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMY009
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THPMY019	LHC Injection Protection Devices, Thermo-mechanical Studies through the Design Phase	injection, operation, kicker, proton	3698
	I. Lamas Garcia, N. Biancacci, G. Bregliozzi, M. Calviani, M.I. Frankl, L. Gentini, S.S. Gilardoni, A. Lechner, A. Perillo-Marcone, B. Salvant, N.V. Shetty, J.A. Uythoven CERN, Geneva, Switzerland
	The TDI is a beam intercepting device installed on the two injection lines of the LHC. Its function is to protect the superconducting machine elements during injection in the case of a malfunction of the injection kickers. The TDIS, which will replace the TDI, is foreseen to be installed for high luminosity operation. Due to the higher bunch intensities and smaller beam emittances expected, and following the operational experiences of the TDI, a complete revision of the design of the jaws must be performed, with a main focus on the material selection. Furthermore, the new TDIS will also improve the TDI reliability by means of a robust design of the jaw positioning mechanism, the efficiency of the cooling circuit and by reducing its impedance. A simplified installation procedure and maintenance will also be an important requirement for the new design. This paper introduces the main characteristics of the TDI as LHC injection protection device, showing the needs and requirements for its upgrade. It also discusses the thermo-mechanical simulations that are supporting and guiding the design phase and the material selection, and describes the modifications to be implemented, so far, for this new device.
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THPOR049	Considerations for the Injection and Extraction Kicker Systems of a 100 TeV Centre-of-Mass FCC-hh Collider	kicker, extraction, injection, collider	3901
	T. Kramer, M.J. Barnes, W. Bartmann, F. Burkart, L. Ducimetière, B. Goddard, V. Senaj, T. Stadlbauer, D.G. Woog CERN, Geneva, Switzerland D. Barna Wigner Research Centre for Physics, Institute for Particle and Nuclear Physics, Budapest, Hungary
	A 100 TeV center-of-mass energy frontier proton collider in a new tunnel of ~100 km circumference is a central part of CERN's Future Circular Colliders (FCC) design study. One of the major challenges for such a machine will be the beam injection and extraction. This paper outlines the recent developments on the injection and extraction kicker system concepts. For injection the system requirements and progress on a new inductive adder design will be presented together with first considerations on the injection kicker magnets. The extraction kicker system comprises the extraction kickers itself as well as the beam dilution kickers, both of which will be part of the FCC beam dump system and will have to reliably abort proton beams with stored energies in the range of 8 Gigajoule. First concepts for the beam dump kicker magnet and generator as well as for the dilution kicker system are described and its feasibility for an abort gap in the 1 μs range is discussed. The potential implications on the overall machine and other key subsystems are outlined, including requirements on (and from) dilution patterns, interlocking, beam intercepting devices and insertion design.
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THPOW001	Design of a 4.6-Cell RF Gun for the PHIL accelerator at LAL	gun, emittance, cavity, coupling	3922
	P. Chen, C. Bruni, S. Chancé, L. Garolfi, A. Gonnin, P. Lepercq, T. Vinatier LAL, Orsay, France
	A photo-injector with 4.6-cell and resonate frequency of 2.998 GHz has been designed and studied to replace the 2.5-cell RF gun + booster association. The cavity iris shape and dimensions were simulated systematically to optimize the shunt impedance. In this study, electron beam reaches to 9.7 MeV with a moderate peak accelerat-ing gradient of 80 MV/m. Considering a beam charge of 1 nC/bunch, average transverse emittance of ~ 5.9 πmm mrad and energy spread of ~ 0.8% can be obtained at the exit of the gun. The RF input power is only 10.2 MW due to the high shunt impedance. Asymmetry of the electric field due to the coupling port has also been studied using 3D codes for RF and beam dynamics calculations. We will present the RF design and beam calculations results.
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THPOW009	Optimal Design of a Photocathode Electron Gun with High-brightness and High-repetition Rate Based on Genetic Algorithm	gun, electron, cavity, laser	3947
	Zh. X. Tang, X.M. Yang, W.Q. Zhang DICP, Dalian, People's Republic of China Y.J. Pei, Y. Yu USTC/NSRL, Hefei, Anhui, People's Republic of China
	A low RF frequency of normal conducting photocathode gun with high-brightness and high-repetition rate is designed as an electron source of the Next Generation Light Source (NGLS). In order to optimize the performance of the gun, a genetic multi-objective algorithm has been used. A genetic algorithm is used because of the inherent complexity of the large number of parameters of the cavity geometry available for optimization. On the other hand, the multiplicity of requirements on the beam, which include beam emittance, beam pulse length, energy chirp, as well as pulse shape and peak current, leads to a multi-objective approach for the optimization technique. In this paper, we present the status of the optimization simulations, using the SUPERFISH and PERMELA particle-in-cell code.
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Paper

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Other Keywords

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MOOCA01

R&D of a Super-compact SLED System at SLAC

cavity, operation, coupling, FEL

39

J.W. Wang, G.B. Bowden, S. Condamoor, Y. Ding, V.A. Dolgashev, J.P. Eichner, M.A. Franzi, A.A. Haase, P. Krejcik, J.R. Lewandowski, S.G. Tantawi, L. Xiao, C. Xu
SLAC, Menlo Park, California, USA

Funding: Work supported by Department of Energy contract DE-AC03-76SF00515.
We have successfully designed, fabricated, installed and tested a super-compact X-Band SLED system at SLAC. It is composed of an elegant mode converter/polarizer and a single sphere energy store cavity with high Q of 94000 and diameter less than 12 cm. The available RF peak power of 50 MW can be compressed to peak average power of more than 200 MW in order to double the kick for the electron bunches in a RF transverse deflector system and greatly improve the measurement resolution for both the electron bunch and the x-ray FEL pulse. High power operation has demonstrated the excellent performance of this RF compression system without any problems in RF breakdown, pulse heating and radiation. The design physics and fabrication as well as the measurement results will be presented in detail.

Slides MOOCA01 [20.278 MB]

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MOPMB025

The Development of 16-Electrode Monitor for Measurement of the Multipole-Moment

quadrupole, injection, coupling, proton

140

Y. Nakanishi, A. Ichikawa, A. Minamino, K.G. Nakamura, T. Nakaya
Kyoto University, Kyoto, Japan
T. Koseki, H. Kuboki
KEK, Tokai, Ibaraki, Japan
T. Toyama
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

Funding: This work was supported by MEXT KAKENHI Grant Number 25105002, Grant-in-Aid for Scientific Research on Innovative Areas titled 'Unification and　Development of the Neutrino Science Frontier'
In the J-PARC main ring, the beam intensity is greatly increased to 750 kW or more in near future. Even the beam intensity become higher, the beam loss must be kept at the same level as present. Aiming to make the cause of beam loss clear, we have been developing the beam monitor to measure the beam size. The quadrupole moment is related to the beam size. In principle, monitors with more than four electrodes can measure the quadrupole moment. In addition, two monitors located at the places with different beta functions can measure the emittances and beam sizes, providing the horizontal and vertical beta functions. To obtain more precise quadrupole moment and higher multipoles, we are developing the multi-electrode monitor, tentatively, with 16 electrodes. As a reference of 16-electrode monitor, two 4-electrode BPMs are investigated to measure quadrupole moments. We will present the measurement result of 4-electrode monitors and the status of the development of the 32-electrode monitor.

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MOPMB038

Development of Shoebox BPM for Xi‘an Proton Application Facility

coupling, simulation, proton, closed-orbit

175

W. Wang, X. Guan, W.-H. Huang, X.W. Wang, Z. Yang, H.Y. Zhang, S.X. Zheng
TUB, Beijing, People's Republic of China
M.T. Qiu, Z.M. Wang
State Key Laboratory of Intense Pulsed Radiation Simulation and Effect, Northwest Institute of Nuclear Technology, Shannxi, People's Republic of China

In this paper, development of the Shoebox BPM is presented which can be applied for the measurement of turn-by-turn position data, closed orbit and tune of Xi'an Proton Application Facility (XiPAF). The preliminary design of the physical dimensions including the electrode aperture, the pipe aperture and the gap between the two electrodes is performed by calculating their effects on BPM response respectively with the equivalent circuit model. Furthermore, the mechanical structure of the Shoebox BPM is optimized by CST simulation to achieve better performance. The dependency of the BPM sensitivity and zero offset on the frequency is diminished by adding one isolating ring, which decreases coupling capacitance of electrodes and compensates ground capacitance difference of the two electrodes. Finally one prototype of the Shoebox BPM has been fabricated and tested offline. Results show that relative position measurement error due to frequency dependency of sensitivity is less than 1% and absolute measurement error due to frequency dependency of zero offset is expected to be less than 0.1 mm.

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MOPMB050

Design of Ultra-wideband Amplifier in RF Front End for Bunch-by-bunch Measurement

power-supply, simulation, experiment, synchrotron-radiation

205

Y. Yang, Y.B. Leng, Y.B. Yan
SSRF, Shanghai, People's Republic of China

RF front end is one of the key technologies in beam diagnosis, especially in bunch-by-bunch measurement at storage ring. This paper gives the design of ultra-wideband amplifier in RF front end for bunch-by-bunch measurement at SSRF. Simulation have been done to verify the performance of this design.

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MOPMR019

Beam Tests of a Prototype Stripline Beam Position Monitoring System for the Drive Beam of the CLIC Two-beam Module at CTF3

electronics, pick-up, vacuum, operation

270

A. Benot-Morell, A. Faus-Golfe
IFIC, Valencia, Spain
A. Benot-Morell, M. Wendt
CERN, Geneva, Switzerland
A. Faus-Golfe
LAL, Orsay, France
J.M. Nappa, S. Vilalte
IN2P3-LAPP, Annecy-le-Vieux, France

Funding: MINECO contract no. FPA2013-47883-C2-1-P. CLIC Collaboration Agreement, contract no. KE2638/BE. FNRA contract no. ANR-11-IDEX-0003-02.
In collaboration with LAPP and IFIC, two units of a prototype stripline Beam Position Monitor (BPM) for the CLIC Drive Beam (DB), and its associated readout electronics have been successfully installed and tested in the Two-Beam-Module (TBM) at the CLIC Test Facility 3 (CTF3) at CERN. This paper gives a short overview of the BPM system and presents the performance measured under different Drive Beam configurations.

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MOPMR038

Design and Simulation Studies of the Novel Beam Arrival Monitor Pickup at Daresbury Laboratory

pick-up, simulation, laser, FEL

334

A. Kalinin, S.P. Jamison, T.T. Thakker
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
R. Apsimon, G. Burt, A.C. Dexter
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom

We present the novel beam arrival monitor pickup design currently under construction at Daresbury Laboratory, Warrington, UK. The pickup consists of four flat electrodes in a transverse gap. CST Particle Studio simulations have been undertaken for the new pickup design as well as a pickup design from DESY, which is used as a reference for comparison. Simulation results have highlighted two advantages of the new pickup design over the DESY design; the signal bandwidth is 25 GHz, which is half that of the DESY design and the response slope is a factor of 1.6 greater. We discuss optimisation studies of the design parameters in order to maximise the response slope for bandwidths up to 50 GHz and present the final design of the pickup.

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MOPMW002

Modeling and Simulation of Broadband RF Cavities in PSpice

cavity, simulation, coupling, storage-ring

392

J. Harzheim, D. Domont-Yankulova, H. Klingbeil, R. Königstein
TEMF, TU Darmstadt, Darmstadt, Germany
M. Frey, H. Klingbeil
GSI, Darmstadt, Germany

Barrier bucket systems are planned for the SIS100 Synchrotron (part of the future accelerator facility FAIR) and the ESR storage ring to facilitate several longitudinal beam manipulations [9] [15]. In order to achieve a single-sine gap signal of the desired amplitude and quality, effects in the linear and nonlinear region of the RF systems have to be investigated and included in the design of the overall system. Therefore, the cavities and the amplifier stages are to be modeled in PSpice. In this contribution, a cavity model will be presented. In a first step, a model for the magnetic alloy (MA) ring cores, which highly account for the properties of the cavity, has been found based on measurement data. In a second step, the future setup of the cavity is systematically created using the MA ring core models. The model of the cavity allows simulations in frequency domain as well as time domain. The results show good agreement with former measurements.

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MOPMW005

Design of Linac with the New Gaskets Clamping Fabrication Technique

vacuum, coupling, linac, gun

403

F. Cardelli
INFN-Roma1, Rome, Italy
D. Alesini
INFN/LNF, Frascati (Roma), Italy
M. Magi, L. Palumbo
University of Rome La Sapienza, Rome, Italy
F. Pellegrino, V. Pettinacci
INFN-Roma, Roma, Italy

Recently, a new technique for the realization of high gradient accelerating structures based on the use of gaskets without brazing processes, has been successfully tested at high power on a 1.6 cells RF gun (D. Alesini, et al, PRST 18, 02001, 2015). The new technique developed at the Laboratories of Frascati of the INFN (Italy) in the framework of the SPARC_LAB project has been also adopted for the ELI-NP RF gun. The use of the special gaskets that simultaneously guarantee the vacuum seal and a perfect RF contact allow to avoid the brazing process, strongly reducing the cost, the realization time and the risk of failure. Moreover, without copper annealing due to the brazing process, it is possible, in principle, to decrease the breakdown rate increasing, at the same time, the maximum achievable gradient. The extension of this new fabrication process to complex LINAC structures is the next step on the application of this new technique on particle accelerator. In the paper, we discuss how to extend this process to S-band and C-band Travelling Wave accelerating structures illustrating their electromagnetic design and their mechanical realization.

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MOPMW007

On the Calibration Measurement of Stripline Beam Position Monitor for the ELI-NP Facility

simulation, linac, vacuum, electromagnetic-fields

411

D. De Arcangelis, F. Cardelli, A. Mostacci, L. Palumbo
University of Rome La Sapienza, Rome, Italy

Stripline Beam Position Monitor (BPM) will be installed in the Compton Gamma Source in construction at the ELI Nuclear Physics facility in Romania. A test bench for the calibration of BPM has been built to characterize the device with stretched wire measurement in order to get the BPM response map. A full S-parameters characterisation is performed as well to measure the electrical offset with the "Lambertson method". This paper discusses the extensive simulations performed with full 3D electromagnetic CAD codes of the above measurements to investigate measurement accuracy, possible measurement artefacts and the beam position reconstruction.

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MOPMW011

The Second Harmonic RF System for J-PARC MR Upgrade

cavity, injection, operation, proton

420

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

Power upgrade scenario of J-PARC Main Ring includes replacement of RF cavities with higher field gradient using magnetic alloy cores, FT3L than the present ones. It also need to install the second harmonic RF cavity in the other section where dedicated water system for RF cavities is not available. Installation scenario of the second harmonic RF will be presented.

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MOPMW015

Wakefields Studies of High Gradient X-band Accelerating Structure at SINAP

wakefield, simulation, cavity, FEL

429

X.X. Huang, W. Fang, Q. Gu, M. Zhang, Z.T. Zhao
SINAP, Shanghai, People's Republic of China

Shanghai compact hard x-ray free electron laser (CHXFEL)* is now proposed accompanied with a high-gradient accelerating structure, which is the trend of large scale and compact facility. This structure operated at X-band (11424 MHz) holds the promise to achieve high gradient up to 80 MV/m. However, due to its particular property, a more serious wakefields** will be generated, leading to worse beam instability effects. In this paper, the computation of this case will be carried out with simulation. Moreover, analysis and optimization will be adopted to suppress beam instability.
* C. Feng, Z. T. Zhao, Chinese Sci Bull, 2010, 55, 221-227.
** K. Bane, SLAC, NLC-Note 9, Feb. 1995.

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MOPMW024

Design of the New Wideband RF System for the CERN PS Booster

electronics, acceleration, booster, controls

441

M.M. Paoluzzi, S.C.P. Albright, M.E. Angoletta, L. Arnaudon, S. Energico, A. Findlay, M. Haase, M. Jaussi, A.J. Jones, D. Landré, J.C. Molendijk, D. Quartullo, E.N. Shaposhnikova
CERN, Geneva, Switzerland

For the renovation and upgrade of the CERN PS Booster (PSB) RF systems a development project was launched in 2012. The design, based on a new approach, aimed at replacing the existing tuned, narrowband RF systems with wideband, modular, solid-state driven units. A wide range of issues had to be addressed spanning from RF power production, radiation hardness of solid-state devices, active cancellation of beam-induced voltages, dedicated low-level electronics allowing multi-harmonic operation and beam stability. Following a three-year prototyping and testing campaign and two international reviews, the project endorsement came at the end of year 2015. It foresees the complete removal of present h1, h2 and h10 systems and the deployment of a new one covering all the frequency ranges from 1 MHz to 18 MHz. The four PSB rings will be equipped with 144 identical acceleration cells providing 24 kV total RF voltage per ring. This paper describes the design concepts, the retained solutions, the expected performances and includes the procurement and implementation strategies. This activity is part of the LHC Injectors Upgrade project (LIU).

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MOPMW027

Design of a Perpendicular Biased 2nd Harmonic Cavity for the Fermilab Booster

cavity, booster, Windows, cathode

451

C.-Y. Tan, J.E. Dey, K.L. Duel, R.L. Madrak, W. Pellico, E. Prebys, J. Reid, G.V. Romanov, D. Sun, I. Terechkine
Fermilab, Batavia, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
A perpendicular biased 2nd harmonic cavity is currently being designed and built for the Fermilab Booster. The purpose is to flatten the bucket at injection and thus change the longitudinal beam distribution to decrease space charge effects. It can also help with transition crossing. A model cavity has been built to verify various CST Microwave studio and COMSOL results and a test stand has been built to ensure that the Y567 tube is able to operate at twice the Booster fundamental frequencies. Also discussed are the RF windows which are critical to the design.

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MOPMW036

Frequency Domain Simulations of Co-linear X-band Energy Booster (CXEB) RF Cavity Structures and Passive RF Components with ACE3P

cavity, electron, laser, extraction

480

T. Sipahi, S. Biedron, S.V. Milton
CSU, Fort Collins, Colorado, USA

Due to their higher intrinsic shunt impedance X-band accelerating structures offer significant gradients with relatively modest input powers, and this can lead to more compact light sources. At the Colorado State University Accelerator Laboratory (CSUAL) [1] we would like to adapt this technology to our 1.3-GHz, L-band accelerator system using a passively driven 11.7 GHz traveling wave X-band configuration that capitalizes on the high shunt impedances achievable in X-band accelerating structures in order to increase our overall beam energy in a manner that does not require investment in an expensive, custom, high-power X-band klystron system. Here we provide the comparisons of the important parameters achieved using SUPERFISH and OMEGA3P for our Co-linear X-band Energy Booster (XCEB) system that will allow us to achieve our goal of reaching the maximum practical net potential across the X-band accelerating structures while driven solely by the beam from the L-band system.

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MOPMW039

TM01 Mode Launcher for Use in High Brightness Photoguns

quadrupole, gun, electron, cavity

491

A.D. Cahill
UCLA, Los Angeles, California, USA
M. Dal Forno, V.A. Dolgashev
SLAC, Menlo Park, California, USA

Funding: DOE SCGSR and DOE/SU Contract DE-AC02-76-SF00515
Photo rf guns are a source of electron beams for X-ray FELs such as LCLS and European XFEL. In existing photoguns power is coupled into the cavity by waveguides through the cell walls, like LCLS, or through coaxial coupling, at the European XFEL. We are considering feeding a gun using a circular waveguide with the TM01 mode. To do that we need a mode launcher, a matched device that couples the rectangular TE01 mode waveguide to a TM01 mode in a circular waveguide. Use of the mode launcher reduces complexity of the gun cavity and increases flexibility of positioning the input waveguide relative to the gun body. Mode launchers have been successfully used at SLAC and elsewhere for X-band high gradient tests. Because the existing mode launchers were not built for high brightness guns, they have a significant quadrupole field component. High brightness rf guns have tight requirements on output beam properties, and this quadrupole component adversely affects the beam. We have designed a mode launcher free of this disadvantage. We present design considerations, methodology, and an example S-band mode launcher.

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MOPMY010

RF Design of Normal Conducting 704 MHz and 2.1 GHz Cavities for LEReC Linac

cavity, HOM, vacuum, simulation

532

B. P. Xiao, I. Ben-Zvi, M. Blaskiewicz, J.M. Brennan, J.C. Brutus, A.V. Fedotov, H. Hahn, G.T. McIntyre, C. Pai, K.S. Smith, J.E. Tuozzolo, Q. Wu, T. Xin, W. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh
Fermilab, Batavia, Illinois, USA
S.A. Belomestnykh, I. Ben-Zvi, T. Xin
Stony Brook University, Stony Brook, USA
V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 and by National Energy Research Scientific Computing Center under contract No. DE-AC02-05CH11231 by US DOE.
To improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, the Low Energy RHIC electron Cooler (LEReC) is currently under development at BNL. Two normal conducting cavities, a single cell 704 MHz cavity and a 3 cell 2.1 GHz third harmonic cavity, will be used in LEReC for energy spread correction. Currently these two cavities are under fabrication. In this paper we report the RF design of these two cavities.

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MOPOR002

Impedance Simulations and Measurements for ThomX Storage Ring

simulation, interface, wakefield, storage-ring

586

A.R. Gamelin, C. Bruni, V. Chaumat, D. Le Guidec, P. Lepercq, R. Marie
LAL, Orsay, France

Funding: Work is supported by ANR-10-EQPX-51, by grants from Région Ile-de-France, IN2P3 and Pheniics Doctoral School
ThomX is a compact Compton Backscattering Source (CBS) which is being built at LAL, Orsay, France. ThomX ring has a short circumference of 18 m and a design energy of 50 MeV. Due to the low energy of the beam and in order to avoid beam degradation it is important to evaluate the ring components impedance. A CST Particle Studio impedance simulation of the different components of the ring (BPM, bellows, optical chamber, etc.) is under way. It will be followed by a bench measurement of the longitudinal and transverse impedance using the coaxial wire method. This paper will detail the preliminary results of the ThomX storage ring impedance simulations and the measurement principle we will use.

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MOPOR003

Simulation Studies and Measurements of Beam Instabilities Caused by the Kicker Impedance at High Intensities in the 3-GeV RCS of J-PARC

simulation, kicker, injection, betatron

589

P.K. Saha, H. Harada, N. Hayashi, H. Hotchi, M. Kinsho, M. Nomura, Y. Shobuda, F. Tamura, N. Tani, Y. Watanabe, M. Yamamoto
JAEA/J-PARC, Tokai-mura, Japan

The transverse impedance of the extraction kickers is a significant beam instability source in the 3-GeV Rapid Cycling Synchrotron of J-PARC. ORBIT code was developed for space charge and beam instability simulations by successfully introducing realistic time dependent machine parameters. The beam instability at high intensities, especially at the designed 1 MW beam power was found be very critical. As there was no practical measure yet to reduce the kicker impedance, a detail simulation studies were done in order to determine realistic machine parameters to suppress the beam instability. The simulation results were found to be very consistent with measurements to successfully accomplish 1 MW beam power. The simulation and beam study results in detail are presented in this paper.

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MOPOR007

Local Impedance Measurements at ALBA from Turn-by-Turn Acquisition

insertion, lattice, vacuum, optics

598

M. Carlà, G. Benedetti, T.F.G. Günzel, U. Iriso, Z. Martí
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

A transverse impedance source manifests itself, among other ways, by producing a small defocusing kick which depends on the beam bunch charge. By repeating optics measurements for different bunch charges, it is possible to disentangle the contribution produced by each impedance source from the dominating focusing effects given by the machine optics. But hunting for such faint defocusing effects poses strong requirements on the precision and sensibility of the measurements, and slow machine drifts or different thermal conditions shall be avoided. In this report, we present a novel method to assess in a fast and precise manner machine optics for different bunch charges using BPM turn-by-turn data and hybrid filling patterns. Finally, measurements for different ALBA machine components like scrapers and In-vacuum undulators are compared with simulation results.

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MOPOR008

Beam Induced RF Heating in LHC in 2015

operation, injection, vacuum, monitoring

602

B. Salvant, O. Aberle, M. Albert, R. Alemany-Fernandez, G. Arduini, J. Baechler, M.J. Barnes, P. Baudrenghien, O.E. Berrig, N. Biancacci, G. Bregliozzi, J.V. Campelo, F. Carra, F. Caspers, P. Chiggiato, A. Danisi, H.A. Day, M. Deile, D. Druzhkin, J. F. Esteban Müller, S. Jakobsen, J. Kuczerowski, A. Lechner, R. Losito, A. Masi, N. Minafra, E. Métral, A.A. Nosych, A. Perillo Marcone, D. Perini, S. Redaelli, F. Roncarolo, G. Rumolo, E.N. Shaposhnikova, J.A. Uythoven, C. Vollinger, A.J. Välimaa, N. Wang, M. Wendt, J. Wenninger, C. Zannini
CERN, Geneva, Switzerland
M. Bozzo
INFN Genova, Genova, Italy
J.F. Esteban Müller
EPFL, Lausanne, Switzerland
N. Wang
IHEP, Beijing, People's Republic of China

Following the recurrent beam induced RF issues that perturbed LHC operation during LHC Run 1, a series of actions were put in place to minimize the risk that similar issues would occur in LHC Run 2: longitudinal impedance reduction campaign and/or improvement of cooling for equipment that were problematic or at the limit during Run 1, stringent constraints enforced on new equipment that would be installed in the machine, tests to control the bunch length and longitudinal distribution, additional monitoring of temperature, new monitoring tools and warning chains. This contribution reports the outcome of these actions, both successes as well as shortcomings, and details the lessons learnt for the future runs.

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MOPOR009

The HL-LHC Impedance Model and Aspects of Beam Stability

HOM, octupole, cavity, focusing

606

N. Biancacci, K.S.B. Li, E. Métral, B. Salvant
CERN, Geneva, Switzerland

Funding: Research supported by the High Luminosity LHC project
The LHC upgrade to the HLLHC foresees new challenging operational scenarios from the beam dynamics point of view. In order to ensure good machine operation and performance, the machine impedance, among other possible sources of instabilities like beam-beam and electron cloud, needs to be carefully quantified profiting also from the current LHC operation. In this work we present the HLLHC impedance model mainly focusing on the contribution of low-impedance collimators and crab cavities: the first reduces the broad-band impedance baseline thanks to the higher jaw material conductivity, the second increases the machine luminosity at the price of increasing the coupled bunch stabilizing octupole current threshold. Other elements like the injection protection absorber (TDI) will be also discussed.

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MOPOR010

Impedance Measurements and Simulations on the TCTP and TDI LHC Collimators

HOM, simulation, embedded, operation

610

N. Biancacci, F. Caspers, A. Grudiev, J. Kuczerowski, I. Lamas Garcia, A. Lechner, E. Métral, A. Passarelli, A. Perillo Marcone, B. Salvant, J.A. Uythoven
CERN, Geneva, Switzerland
O. Frasciello, M. Zobov
INFN/LNF, Frascati (Roma), Italy
A. Mostacci
Rome University La Sapienza, Roma, Italy
N. Mounet
EPFL, Lausanne, Switzerland

The LHC collimation system is a critical element for the safe operation of the LHC machine and is subject to continuous performance monitoring, hardware upgrade and optimization. In this work we will address the impact on impedance of the upgrades performed on the TDI injection protection collimator, where the absorber material has been changed to mitigate the device heating observed in machine operation, and on selected secondary (TCS) and tertiary (TCT) collimators, where beam position monitors (BPM) have been embedded for faster jaw alignment. Concerning the TDI, we will present the RF measurements performed before and after the upgrade, comparing the result to heating and tune shift beam measurements. For the TCTs, we will study how the higher order modes (HOM) introduced by the BPM addition have been cured by means of ferrite placement in the device. The impedance mitigation campaign has been supported by RF measurements whose results are in good agreement with GdfidL and CST simulations. The presence of undamped low frequency modes is proved not to be detrimental to the safe LHC operation.

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MOPOR011

Impedance Localization Measurements using AC Dipoles in the LHC

dipole, quadrupole, betatron, optics

614

N. Biancacci, L.R. Carver, G. Papotti, T. Persson, B. Salvant, R. Tomás
CERN, Geneva, Switzerland

The knowledge of the LHC impedance is of primary importance to predict the machine performance and allow for the HL-LHC upgrade. The developed impedance model can be benchmarked with beam measurements in order to assess its validity and limit. This is routinely done, for example, moving the LHC collimator jaws and measuring the induced tune shift. In order to localize possible unknown impedance sources, the variation of phase advance with intensity between beam position monitors can be measured. In this work we will present the impedance localization measurements performed at injection in the LHC using AC dipoles as exciter as well as the underlying theory.

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MOPOR012

Study of the Beam-Cavity Interaction in the PS 10 MHz RF System

cavity, simulation, feedback, acceleration

618

G. Favia, H. Damerau, M. Morvillo, C. Rossi
CERN, Geneva, Switzerland
M. Migliorati
University of Rome "La Sapienza", Rome, Italy

The eleven main accelerating cavities of the Proton Synchrotron (PS) at CERN consist of two ferrite-loaded coaxial λ/4 resonators each. Both resonators oscillate in phase, as their gaps are electrically connected by short bars. They are in addition magnetically coupled via the bias loop used for cavity tuning. The cavities are equipped with a wide-band feedback system, limiting the beam loading, and a further reduction of the beam induced voltage is achieved by relays which short-circuit each half-resonator gap when the cavity is not in use. Asymmetries of the beam induced voltage observed in the two half-cavities indicate that the coupling between the two resonators is not as tight as expected. The total cavity impedance coupling to the beam may be affected differently by the contributions of both resonators. A dedicated measurement campaign with high-intensity proton beam and numerical simulation have been performed to investigate the beam-cavity interaction. This paper reports the result of the study and the work aiming at the development of a model of the system, including the wide-band feedback, which reproduces this interaction.

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MOPOR013

The PS 10 MHz High Level RF System Upgrade

cavity, feedback, network, beam-loading

622

G. Favia, H. Damerau, V.D. Desquiens, S. Energico, M. Morvillo, D. Perrelet, C. Rossi
CERN, Geneva, Switzerland

In view of the upgrade of the injectors for the High Luminosity LHC, significantly higher bunch intensity is required for LHC-type beams. In this context an upgrade of the main accelerating RF system of the Proton Synchrotron (PS) is necessary, aiming at reducing the cavity impedance which is the source of longitudinal coupled-bunch oscillations. These instabilities pose as a major limitation for the increase of the beam intensity as planned after LS2. The 10 MHz RF system consists in 11 ferrite loaded cavities, driven by tube-based power amplifiers for reasons of radiation hardness. The cavity-amplifier system is equipped with a wide-band feedback that reduces the beam induced voltage. A further reduction of the beam loading is foreseen by upgrading the feedback system, which can be reasonably achieved by increasing the loop gain of the existing amplification chain. This paper describes the progress of the design of the upgraded feedback system and shows the results of the tests on the new amplifier prototype, installed in the PS during the 2015-16 technical stop. It also reports the first results of its performance with beam, observed in the beginning of the 2016 run.

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MOPOR014

Measurements of the CERN PS Longitudinal Resistive Coupling Impedance

HOM, coupling, synchrotron, cavity

626

M. Migliorati, N. Biancacci, H. Damerau, G. Sterbini
CERN, Geneva, Switzerland
M. Migliorati
University of Rome "La Sapienza", Rome, Italy
M. Migliorati, L. Ventura
INFN-Roma1, Rome, Italy
S. Persichelli
University of Rome La Sapienza, Rome, Italy

The longitudinal coupling impedance of the CERN PS has been studied in the past years in order to better understand collective effects which could produce beam intensity limitations for the LHC Injectors Upgrade project. By measuring the incoherent quadrupole synchrotron frequency vs beam intensity, the inductive impedance was evaluated and compared with the impedance model obtained by taking into account the contribution of the most important machine devices. In this paper, we present the results of the measurements performed during a dedicated campaign, of the real part of the longitudinal coupling impedance by means of the synchronous phase shift vs beam intensity. The phase shift has been measured by using two different techniques: in one case, we injected in the machine two bunches, one used as a reference with constant intensity, and the second one changing its intensity; in the second case, more conventional, we measured the bunch position with respect to the RF signal of the 40 MHz cavities. The obtained dependence of the synchrotron phase with intensity is then related to the loss factor and the resistive coupling impedance, which is compared to the real part of the PS impedance model.

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MOPOR016

Impedance Study with Single Bunch Beam at Taiwan Photon Source

photon, storage-ring, synchrotron, vacuum

630

C.-C. Kuo, P.J. Chou, K.T. Hsu, K.H. Hu, C.C. Liang, C.Y. Liao, Z.K. Liu, H.-J. Tsai, F.H. Tseng
NSRRC, Hsinchu, Taiwan

The impedance at Taiwan Photon Source was investigated. The effects of bunch current such as a tune change, a synchronous phase shift and a bunch lengthening under operation conditions at various stages were measured; the machine impedances were deduced. This report presents the results with insertion devices in various configurations.

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MOPOR018

Single Bunch Instability Studies at Diamond Light Source

simulation, coupling, synchrotron, betatron

637

E. Koukovini-Platia, M. Apollonio, R. Bartolini, R.T. Fielder, I.P.S. Martin
DLS, Oxfordshire, United Kingdom
R. Bartolini
JAI, Oxford, United Kingdom

Single bunch instability thresholds, the associated coherent tune shifts and the bunch lengthening have been studied at Diamond light source for nominal optics. Measurements were taken under different settings of chromaticity, radio-frequency (RF) voltage and aperture of the insertion devices (IDs). The macro-particle code sbtrack was used to evaluate the instability thresholds and bunch lengthening where different impedance contributions are taken into account such as the resistive wall impedance, a broad-band resonator model and inductive impedance for the longitudinal plane. A comparison of simulation using the developed model impedance with measurements is shown for all cases.

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MOPOY006

Preparations for Upgrading the RF Systems of the PS Booster

cavity, operation, feedback, emittance

853

S.C.P. Albright, D. Quartullo, E.N. Shaposhnikova
CERN, Geneva, Switzerland

The accelerators of the LHC injector chain need to be upgraded to provide the HL-LHC beams. The PS Booster, the first synchrotron in the LHC injection chain, uses three different RF systems (first, second and up to tenth harmonic) in each of its four rings. As part of the LHC Injector Upgrade the current ferrite RF systems will be replaced with broadband Finemet cavities, increasing the flexibility of the RF system. A Finemet test cavity has been installed in Ring 4 to investigate its effect on machine performance, especially beam stability, during extensive experimental studies. Due to large space charge impedance Landau damping is lost through most of the cycle in single harmonic operation, but is recovered when using the second harmonic and controlled longitudinal emittance blow-up. This paper compares beam parameters during acceleration with and without the Finemet test cavity. Comparisons were made using beam measurements and simulations with the BLonD code based on a full PS Booster impedance model. This work, together with simulations of future operation, have provided input for the decision to adopt a fully Finemet RF system.

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MOPOY011

Estimating the Transverse Impedance in the Fermilab Recycler

proton, quadrupole, dipole, vacuum

867

R. Ainsworth, P. Adamson, A.V. Burov, I. Kourbanis, M.-J. Yang
Fermilab, Batavia, Illinois, USA

Impedance could represent a limitation of running high intensity bunches in the Fermilab recycler. With high intensity upgrades foreseen, it is important to quantify the impedance. To do this, studies have been performed measuring the tune shift as a function of bunch intensity allowing the transverse impedance to be derived.

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MOPOY013

Modeling Longitudinal Dynamics in the Fermilab Booster Synchrotron

booster, emittance, synchrotron, simulation

873

J.-F. Ostiguy, C.M. Bhat, V.A. Lebedev
Fermilab, Batavia, Illinois, USA

Funding: Work performed under U.S. Government contract DE-AC02-07CH11359
The PIP-II project will replace the existing 400 MeV linac with a new, CW-capable, 800 MeV superconducting one. With respect to current operations, a 50% increase in beam intensity in the rapid cycling Booster synchrotron is expected. Booster batches are combined in the Recycler ring; this process limits the allowed longitudinal emittance of the extracted Booster beam. To suppress eddy currents, the Booster has no beam pipe; magnets are evacuated, exposing the beam to core laminations and this has a substantial impact on the longitudinal impedance. Noticeable longitudinal emittance growth is already observed at transition crossing. Operation at higher intensity will likely necessitate mitigation measures. We describe systematic efforts to construct a predictive model for current operating conditions. A longitudinal only code including a laminated wall impedance model, space charge effects, and feedback loops is developed. Parameter validation is performed using detailed measurements of relevant beam, rf and control parameters. An attempt is made to benchmark the code at operationally favorable machine settings.

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MOPOY020

Prototype Design of a Newly Revised CW RFQ for the High Charge State Injector at GSI

rfq, simulation, operation, resonance

889

D. Koser, H. Podlech
IAP, Frankfurt am Main, Germany
P. Gerhard, L. Groening, O.K. Kester
GSI, Darmstadt, Germany

Within the scope of the FAIR project (Facility for Antiproton and Ion Research) at GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, the front end of the existing High Charge State Injector (HLI) is planned to be upgraded for cw operation. The required newly revised 4-Rod RFQ structure is currently being designed at the Institute for Applied Physics (IAP) of the Goethe University of Frankfurt. It will be operated with a 100 kW power amplifier at 108 MHz. At first instance a dedicated 4-stem prototype, which is based on the RFQ design for MYRRHA* and FRANZ**, is planned to be manufactured in order to validate the simulated RF performance, thermal behavior and mechanical characteristics in continuous operation. The RF simulations as well as basic thermal simulations are done using CST Studio Suite. In order to prevent oscillations of the electrodes mechanical eigenmodes are analyzed using ANSYS Multiphysics. In addition the ANSYS software allows more sophisticated simulations regarding the cooling capability by considering fluid dynamics in water cooling channels, thus providing a more detailed thermal analysis.
*C. Zhang, H. Podlech, New Reference Design of the European ADS RFQ Accelerator For MYRRHA, IPAC2014
**M. Heilmann et al., A Coupled RFQ-IH Cavity for the Neutron Source FRANZ, IPAC2013

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MOPOY058

Removing Known SPS Intensity Limitations for High Luminosity LHC Goals

vacuum, simulation, emittance, shielding

989

E.N. Shaposhnikova, T. Argyropoulos, T. Bohl, P. Cruikshank, B. Goddard, T. Kaltenbacher, A. Lasheen, J. Perez Espinos, J. Repond, B. Salvant, C. Vollinger
CERN, Geneva, Switzerland

In preparation of the SPS as an LHC injector its impedance was significantly reduced in 1999 - 2000. A new SPS impedance reduction campaign is planned now for the High Luminosity (HL)-LHC project, which requires bunch intensities twice as high as the nominal one. One of the known intensity limitations is a longitudinal multi-bunch instability with a threshold 3 times below this operational intensity. The instability is presently cured using the 4th harmonic RF system and controlled emittance blow-up, but reaching the HL-LHC parameters cannot be assured without improving the machine impedance. Recently the impedance sources responsible for this instability were identified and implementation of their shielding and damping is foreseen during the next long shutdown (2019 - 2020) in synergy with two other important upgrades: amorphous carbon coating of (part of) the vacuum chamber against the e-cloud effect and rearrangement of the 200 MHz RF system. In this paper the strategy of impedance reduction is presented together with beam intensity achievable after its realisation. The potential effect of other proposals on remaining limitations is also considered.

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TUOAB03

Transverse Coherent Instabilities in Storage Rings with Harmonic Cavities

synchrotron, radio-frequency, cavity, simulation

1061

F.J. Cullinan, R. Nagaoka
SOLEIL, Gif-sur-Yvette, France
G. Skripka, P.F. Tavares
MAX IV Laboratory, Lund University, Lund, Sweden

Many current and future synchrotron light sources employ harmonic cavities to lengthen the electron bunches in order to reduce the emittance dilution caused by intrabeam scattering. In some cases, the harmonic cavities may be tuned to fulfill the flat potential condition. For this condition, a large increase in the threshold currents of transverse coupled-bunch instabilities has been predicted and recently, the physical content behind this stabilization has been better understood. With this in mind, an investigation is made into the effectiveness of harmonic cavities for different machines. Frequency domain computations employing Laclare's eigenvalue method have been used to investigate the influence of several machine parameters and the results are presented.

Slides TUOAB03 [14.037 MB]

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TUPMR015

Cooling and Heat Transfer of the IRANCYC-10 Transmission Line

simulation, cyclotron, factory, cavity

1259

S. Sabounchi, H. Afarideh, M. Mohamadian, M. Salehi
AUT, Tehran, Iran
J.-S. Chai, M. Ghergherehchi
SKKU, Suwon, Republic of Korea

Heat transfer study for designing RF transmission line in cyclotrons is crucial. Because of enormous amount of surface current on RF transmission line, despite high conductivity of copper, significant amount of heat is being generated, which is enough for altering characteristic impedance and other desirable parameters for transmission line. So, effective cooling system which is nourished by central chiller system is essential. For design of cooling system in RF transmission line suitable mass flow, appropriate geometry and confined temperatures are prominent in order to avoid eroding and impedance changing. In this paper an attempt has been done for accurate analyzing and simulating of heat transfer phenomenon for the 10MeV cyclotron (IRANCYC-10 ) which is under construction at AmirKabir University of Technology. By using Ansys CFX simulation software, the optimum cooling line geometry and mass flow rate of 90 gr/s for cooling water, has been resulted.

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TUPMW011

Current Status of Instability Threshold Measurements in the LHC at 6.5 TeV

octupole, damping, simulation, electron

1434

L.R. Carver, J. Barranco, N. Biancacci, X. Buffat, W. Höfle, G. Kotzian, T. Lefèvre, T.E. Levens, E. Métral, T. Pieloni, B. Salvant, C. Tambasco
CERN, Geneva, Switzerland
N. Wang
IHEP, Beijing, People's Republic of China
M. Zobov
INFN/LNF, Frascati (Roma), Italy

Throughout 2015, many measurements of the minimum stabilizing octupole current required to prevent coherent transverse instabilities have been performed. These measurements allow the LHC impedance model at flat top to be verified and give good indicators of future performance and limitations. The results are summarized here, and compared to predictions from the simulation code DELPHI.

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TUPMW021

Roman Pot Insertions in High-Intensity Beams for the CT-PPS Project at LHC

insertion, proton, luminosity, vacuum

1473

M. Deile, R. Bruce, A. Mereghetti, D. Mirarchi, S. Redaelli, B. Salvachua, B. Salvant, G. Valentino
CERN, Geneva, Switzerland

The CMS-TOTEM Precision Proton Spectrometer (CT-PPS) at the LHC IP5 aims at exploring diffractive physics at high luminosity in standard LHC fills. It is based on 14 Roman Pots (RPs), designed to host tracking and time-of-flight detectors for measuring the kinematics of leading protons. To reach the physics goals, the RPs will finally have to approach the beams to distances of 15 beam σs (i.e. ~1.5 mm) or closer. After problems with showers and impedance heating in first high-luminosity RP insertions in 2012, the LS1 of LHC was used for upgrades in view of impedance minimisation and for adding new collimators to intercept RP-induced showers. In 2015 the effectiveness of these improvements was shown by successfully inserting the RPs in all LHC beam intensity steps to a first-phase distance of ~25 σs. This contribution reviews the measurements of debris showers and impedance effects, i.e. the data from Beam Loss Monitors, beam vacuum gauges and temperature sensors. The dependences of the observables on the luminosity are shown. Extrapolations to L=10³⁴ cm^-2 s^-1 and smaller distances to the beam do not indicate any fundamental problems. The plans for 2016 are outlined.

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TUPMW034

A 200 MHz SC-RF System for the HL-LHC

cavity, emittance, injection, luminosity

1513

R. Calaga, R. Tomás
CERN, Geneva, Switzerland

Funding: Research supported by the High Luminosity LHC project
A quarter wave β=1 superconducting cavity at 200 MHz is proposed for the LHC as an alternative to the present 400 MHz RF system. The primary motivation of such a system would be to accelerate higher intensity and longer bunches with improved capture efficiency. Advantages related to minimizing electron cloud effects, intra-beam scattering, heating and the possibility of luminosity levelling with bunch length are described. Some considerations related to cavity optimization, beam loading and technological challenges are addressed.

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TUPOR001

Lifetime Improvements with a Harmonic RF System for the ESRF EBS

cavity, storage-ring, simulation, electron

1644

N. Carmignani, L. Farvacque, J. Jacob, S.M. Liuzzo, B. Nash, T.P. Perron, P. Raimondi, R. Versteegen, S.M. White
ESRF, Grenoble, France

A third-harmonic RF system to increase the Touschek lifetime is under study for the European Synchrotron Radiation Facility (ESRF) Extremely Brilliant Source (EBS) storage ring, in particular for modes with high current per bunch. Multi-particle simulations have been done to study the bunch lengthening and shape in presence of inductive impedance and a third-harmonic RF system.

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TUPOR004

Calculation of Transverse Coupled Bunch Instabilities in Electron Storage Rings Driven By Quadrupole Higher Order Modes

HOM, quadrupole, dipole, damping

1655

M. Ruprecht, P. Goslawski, M. Ries, G. Wüstefeld
HZB, Berlin, Germany

This paper presents a formula that estimates the growth rate of a transverse coupled bunch instability driven by quadrupole higher order modes (HOMs) in electron storage rings. Thus far, quadrupole HOMs are usually ignored in HOM driven instability studies for electron storage rings due to their weak nature compared to the lower orders. However, they may become relevant when high gradient SC multi-cell cavities with their potentially strong impedance spectrum are operated at high currents in a third generation or future synchrotron light source. An example is BESSY VSR, a scheme where 1.7 ps and 15 ps long bunches (rms) can be stored simultaneously in the BESSY II storage ring[*]. With the presented formula, instability thresholds are discussed for a recent BESSY VSR cavity model and different beam parameters.
* A. Jankowiak, J. Knobloch, P. Goslawski, and N. Neumann, eds., BESSY VSR - Technical Design Study, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 2015.

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TUPOR008

Effect of the Various Impedances on Longitudinal Beam Stability in the CERN SPS

HOM, simulation, vacuum, operation

1666

A. Lasheen, T. Argyropoulos, J. Repond, E.N. Shaposhnikova
CERN, Geneva, Switzerland

The High Luminosity (HL)-LHC project at CERN aims at a luminosity increase by a factor ten and one of the necessary ingredients is doubling the bunch intensity to 2.4x10¹¹ ppb for beams with 25 ns bunch spacing. Many improvements are already foreseen in the frame of the LHC Injector Upgrade (LIU) project, but probably this intensity would still not be reachable in the SPS due to longitudinal instabilities. Recently a lot of effort went into finding the impedance sources of the instabilities. Particle simulations based on the latest SPS impedance model are now able to reproduce the measured instability thresholds and were used to determine the most critical impedance sources by removing them one by one from the model. It was found that impedance of vacuum flanges and of the already damped 630 MHz HOM of the main RF system gave for 72 bunches the comparable intensity thresholds. Possible intensity gains are defined for realistic impedance modifications and for various beam configurations (number of bunches, longitudinal emittances) and RF programs (single and double RF). The results of this study are used as a guideline for planning of a new campaign of the SPS impedance reduction.

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TUPOR009

Single Bunch Longitudinal Instability in the CERN SPS

simulation, flattop, synchrotron, emittance

1670

A. Lasheen, T. Bohl, S. Hancock, T. Roggen, E.N. Shaposhnikova
CERN, Geneva, Switzerland
E. Radvilas
Gediminas Technical University, Vilnius, Lithuania

The longitudinal single bunch instability observed in the SPS leads to uncontrolled emittance blow-up and limits the quality of high intensity beams required for the High Luminosity LHC and AWAKE projects at CERN. The present SPS impedance model developed from a thorough survey of machine elements was used in macro-particle simulations (with the code BLonD) of the bunch behavior through the acceleration cycle. Comparison of simulations with measurements of the synchrotron frequency shift, performed on the SPS flat bottom to probe the impedance, show a reasonable agreement. During extensive experimental studies various beam and machine parameters (bunch intensity, longitudinal emittance, RF voltage, with single and double RF systems) were scanned in order to further benchmark the SPS impedance model with measurements and to better understand the mechanism behind the instability. It was found that the dependence of instability threshold on longitudinal emittance and beam energy has an unexpected non-monotonic behavior, leading to islands of (in)stability. The results of this study are presented and can be used to define possible parameter settings for the future CERN projects.

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TUPOR010

Simulation of Instability at Transition Energy with a New Impedance Model for CERN PS

simulation, emittance, proton, synchrotron

1674

N. Wang
IHEP, Beijing, People's Republic of China
S. Aumon, N. Biancacci, M. Migliorati, G. Sterbini, N. Wang
CERN, Geneva, Switzerland
M. Migliorati
INFN-Roma1, Rome, Italy
S. Persichelli
University of Rome La Sapienza, Rome, Italy

Instabilities driven by the transverse impedance are proven to be one of the limitations for the high intensity reach of the CERN PS. Since several years, fast single bunch vertical instability at transition energy has been observed with the high intensity bunch serving the neu-tron Time-of-Flight facility (n-ToF). In order to better understand the instability mechanism, a dedicated meas-urement campaign took place. The results were compared with macro-particle simulations with PyHEADTAIL based on the new impedance model developed for the PS. Instability threshold and growth rate for different longitu-dinal emittances and beam intensities were studied.

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TUPOR011

Study of Microwave Instability for SLS-2

vacuum, storage-ring, emittance, simulation

1678

H.S. Xu, P. Craievich, M.M. Dehler, L. Stingelin
PSI, Villigen PSI, Switzerland

An ultra-low emittance electron storage ring is under development for the Upgrade of Swiss Light Source (SLS-2). An antechamber scheme consisting of round beam channel with 10 mm inner radius is considered to accommodate the required strong quadrupole and sextupole magnets, achieve the ultra-high vacuum, and absorb the undesired synchrotron radiation. However, the small size of vacuum chamber increases the susceptibility of the beam to the impedance induced collective instabilities. We will present the preliminary study of the microwave instability for SLS-2 storage ring considering the longitudinal Resistive-Wall (RW) impedance due to three different options for the beam chamber. The microwave instability thresholds are calculated under the conditions of two possible RF frequencies (100 MHz and 500 MHz) and three different materials (aluminum, copper, and stainless steel). The influences of third-harmonic cavities are also studied.

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TUPOR012

THz Coherent Synchrotron Radiation from Ultra-low Alpha Operating Mode at Diamond Light Source

simulation, storage-ring, radiation, electron

1682

T. Chanwattana, M. Atay, R. Bartolini
JAI, Oxford, United Kingdom
R. Bartolini, G. Cinque, M. Frogley, E. Koukovini-Platia, I.P.S. Martin
DLS, Oxfordshire, United Kingdom

Diamond Light Source is regularly operated in low-alpha mode to provide THz coherent synchrotron radiation (CSR) and short X-ray pulses for users. In order to maintain the wide frequency range of the coherent radiation whilst improving the signal to noise ratio, an ultra-low alpha mode has been considered to shorten the bunch length even further. In order to study this mode, the analysis of single bunch dynamics resulting from a variety of wakefield sources has been investigated using a single bunch multiparticle tracking code. These results are compared with measurements recorded using a Fourier transform infrared (FTIR) interferometer on the MIRIAM beam-line at Diamond.

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TUPOR013

Analysis of Multi-bunch Instabilities at the Diamond Storage Ring

damping, wakefield, storage-ring, simulation

1685

R. Bartolini, R.T. Fielder, G. Rehm
DLS, Oxfordshire, United Kingdom
V.V. Smaluk
BNL, Upton, Long Island, New York, USA

We present recent results of analytical, numerical and experimental analysis of multi-bunch instabilities at the Diamond storage ring. The works compares the impedance estimates from numerical modelling with the analysis of the growth rates of the excited multi-bunch modes in different machine configurations. The contribution of a number of wakefield sources has been identified with very high precision thanks to high quality data provided by the existing Transverse multi-bunch feedback diagnostics

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TUPOW022

Hybrid Electron Linac With Standing and Travelling Wave Accelerating Sections

focusing, linac, coupling, electron

1791

S.V. Matsievskiy, A.V. Bulanov, V.I. Kaminskiy, E.A. Savin, N.P. Sobenin
MEPhI, Moscow, Russia
R.Yu. Alekhanov
NRNU, Moscow, Russia

Hybrid electron linacs with standing and travelling wave accelerating sections are not well described in literature. Limited number of studies have shown that application of these systems makes it possible to develop a compact linac with high efficiency and simpler power system. Typically, these systems use well-studied bi-periodical accelerating structure (BAS) cells for a standing wave section and disc-loaded waveguides (DLW) for a traveling wave section. This paper describes the development of such system using DLW cells with magnetic coupling (DLW-M). Here BAS appears as an absorbing load connected to the DLW-M accelerating structure by rectangular waveguide allowing to have theoretical zero reflection at RF input. Such system also provides possibility of plain beam output energy adjustment. Studies of the structure were carried out using equivalent circuits methods and numerical 3D-modeling. Beam dynamics was calculated.

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WEPMB041

Design of RF Power Coupler for RISP Half Wave Resonator

simulation, cavity, vacuum, electron

2208

S. Lee, E.-S. Kim
Korea University Sejong Campus, Sejong, Republic of Korea
I. Shin
IBS, Daejeon, Republic of Korea

RF power couplers for half wave resonators are under development for the Rare Isotope Science Project (RISP) in Korea. It is required to deliver up to 6 kW RF power at 162.5 MHz to the HWR in CW mode. The RF coupler is a coaxial capacitive type using a disc type ceramic window. Design studies of 2nd prototype HWR RF coupler are presented.

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WEPMR037

Wakefield Analysis of the 56 MHz SRF Cavity

cavity, HOM, wakefield, SRF

2354

Q. Wu, Y. Hao
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The 56 MHz SRF cavity is a superconducting quarter-wave resonator installed in the common section of RHIC. Both beams share the cavity in an interwoven pattern over the entire store. The wake field excited in the cavity is the superposition of the two opposing bunches. This paper will discuss the wake field excited by both beams, and the higher order mode power as a result of the excited field.

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WEPMW031

Towards Optimum Material Choices for the HL-LHC Collimator Upgrade

collimation, beam-losses, luminosity, simulation

2498

E. Quaranta, A. Bertarelli, N. Biancacci, R. Bruce, F. Carra, E. Métral, S. Redaelli, A. Rossi, B. Salvant
CERN, Geneva, Switzerland
F. Carra
Politecnico di Torino, Torino, Italy

The first years of operation at the LHC showed that collimator material-related concerns might limit the performance. In addition, the HL-LHC upgrade will bring the accelerator beyond the nominal performance through more intense and brighter proton beams. A new generation of collimators based on advanced materials is needed to match present and new requirements. After several years of R&D on collimator materials, studying the behaviour of novel composites with properties that address different limitations of the present collimation system, solutions have been found to fulfil various upgrade challenges. This paper describes the proposed staged approach to deploy new materials in the upgraded HL-LHC collimation system. Beam tests at the CERN HiRadMat facility were also performed to benchmark simulation methods and constitutive material models.

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WEPMW039

JLEIC SRF Cavity RF Design

cavity, HOM, electron, damping

2522

S. Wang, J. Guo, R.A. Rimmer, H. Wang
JLab, Newport News, Virginia, USA

The initial design of a low higher order modes (HOM) impedance superconducting RF (SRF) cavity is presented in this paper. The design of this SRF cavity is for the proposed Jefferson Lab Electron Ion Collider (JLEIC). The electron ring of JLEIC will operate with electrons of 3 to 10 GeV energy. The ion ring of JLEIC will operate with protons of up to 100 GeV energy. The bunch lengths in both rings are ~12 mm (RMS). In order to maintain the short bunch length in the ion ring, SRF cavities are adopted to provide large enough gradient. In the first phase of JLEIC, the PEP II RF cavities will be reused in the electron ring to lower the initial cost. The frequency of the SRF cavities is chosen to be the second harmonic of PEP II cavities, 952.6 MHz. In the second phase of JLEIC, the same frequency SRF cavities may replace the normal conducting PEP II cavities to achieve higher luminosity at high energy. At low energies, the synchrotron radiation damping effect is quite weak, to avoid the coupled bunch instability caused by the intense closely-spaced electron bunches, low HOM impedance of the SRF cavities combined with longitudinal feedback system will be necessary.

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WEPMW042

Trapped Modes Study and BBU Analysis in the 5-Cell 650 MHz Cavity

HOM, cavity, electron, damping

2529

C. Xu, I. Ben-Zvi, Y. Hao, V. Ptitsyn, W. Xu
BNL, Upton, Long Island, New York, USA
I. Petrushina
SUNY SB, Stony Brook, New York, USA

Funding: This work is supported by LDRD program of Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE. #chenxu@bnl.gov
eRHIC project is a future electron-hadron collider proposed at BNL. The proposed electron accelerator will generate up to 20 GeV polarized electrons which will collide with proton beams with energy up to 250 GeV. The proposed collider will deliver electron-nucleon luminosity of 10³³- 10³⁴ cm^-2 ses⁻¹. A superconducting RF (SRF) 5-cell elliptical cavity will be utilized in electron accelerator. This paper presents a study of higher-order modes (HOM) for this 647 MHz SRF cavity. Different types of HOM modes and their BBU instabilities were investigated for frequencies up to 3.2 GHz. Threshold current values of beam breakup are estimated by GBBU code. Further improvement on this threshold current has been explored and discussed.

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WEPMY037

Cold Model Cavity for 20-K Cryocooled C-band Photocathode RF Gun

simulation, cavity, gun, coupling

2635

T. Tanaka, M. Inagaki, R. Nagashima, K. Nakao, K. Nogami, T. Sakai, K. Takatsuka
LEBRA, Funabashi, Japan
M.K. Fukuda, T. Takatomi, N. Terunuma, J. Urakawa, M. Yoshida
KEK, Ibaraki, Japan
D. Satoh
TIT, Tokyo, Japan

Funding: Work supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT).
A cryocooled 2.6-cell C-band photocathode RF gun is under development at Nihon University in collaboration with KEK. The RF characteristics of a pillbox-type 2.6-cell C-band RF cavity at 20 K were in agreement with the theoretical predictions. The result of the cold test for a cavity with the input coupler confirmed the same characteristics. Based on these results a refined cold model of the 20-K cryocooled photocathode RF gun has been designed using SUPERFISH and CST-STUDIO. The separation between the TM01 pi and the TM01 half-pi modes has been increased from 20 MHz to 52 MHz by extending the diameter of the cavity iris and reducing the disk thickness. The 2.6-cell structure has been modified from pillbox to ellipsoid-like type. The end-plate of the 0.6-cell cavity has a center hole for bead-pull measurements of the on-axis electric filed through the entire structure. Mounting of a photocathode assembly in the end-plate has not been considered, since the purpose is solely to measure the low-power and low-temperature RF characteristics. A new design for the input coupler has been employed. The cavity will be completed early in 2016.

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WEPOW036

Bunch Length Measurements with Passive Harmonic Cavities for Uniform Fill Patterns in a 100 MHz RF System

storage-ring, simulation, cavity, lattice

2914

T. Olsson, S.C. Leemann, P. Lilja
MAX IV Laboratory, Lund University, Lund, Sweden

The MAX IV facility includes two storage rings operated at 1.5 GeV and 3 GeV. Both rings make use of a 100 MHz RF system and are designed to operate with a uniform multibunch fill pattern as well as employ passive harmonic cavities to damp instabilities and increase Touschek lifetime. Recently, a discussion on timing modes at the MAX IV storage rings has been initiated by the user community. This implies operating the rings with other fill patterns than the originally planned multibunch mode and therefore detailed studies of the performance of the harmonic cavities are of interest. This paper presents bunch length measurements at the 100 MHz MAX II storage ring for uniform fill patterns. The purpose of the measurements was to evaluate the employed measurement method and simulation codes for future studies of fill patterns in the MAX IV storage rings.

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WEPOW052

Multimodal Interaction in the ALS Longitudinal Feedback Kicker RF Cavity

cavity, kicker, feedback, resonance

2965

S. De Santis, K.M. Baptiste, J.M. Byrd, S. Kwiatkowski, T.H. Luo, E.R. Sanmateo, C. Steier, C.A. Swenson
LBNL, Berkeley, California, USA
F. Marcellini
PSI, Villigen PSI, Switzerland

Funding: The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
RF cavities are essential components in particle accelerators not only for beam acceleration, but also for control purposes (bunch lengthening/shortening, deflecting and crabbing, transverse and longitudinal kickers) and for beam diagnostics (BPM). Normally, only a single resonating mode is actively used, although other modes can be excited by the circulating beam. Cavities used as feedback longitudinal kickers are designed with an axial mode which, appropriately excited, provides a kick to the circulating bunches for maintaining beam stability. To provide the necessary bandwidth this mode has to be strongly damped resulting in quality factors of just a few units. In the longitudinal feedback kicker cavity just installed on the ALS we have detected a second axial mode which, although a few hundreds of MHz below the 1.4 GHz design mode, is also strongly damped and has a shunt impedance high enough to be appreciably excited by the feedback amplifier coupling to the first mode. In this paper we show bench measurements on the cavity and with beam during its commissioning and discuss the interaction of the two modes resulting in a modulation of shunt impedance and phase response.

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WEPOY045

Benchmarking the Beam Longitudinal Dynamics Code BLonD

simulation, synchrotron, feedback, injection

3094

H. Timko, J. F. Esteban Müller, A. Lasheen, D. Quartullo
CERN, Geneva, Switzerland

The relatively recent Beam Longitudinal Dynamics code BLonD has already been applied to a wide range of studies for all present CERN synchrotrons. Its application area ranges from studies of RF manipulations, over single and multi-bunch interactions with impedance, to the action of feedback loops and RF noise. In this paper, we present benchmarks and comparisons with measurements, theory, or other codes, which have increased greatly the trust in the code. Tests related to bunch-to-bucket transfer, feedback loops, diffusion due to noise injection, as well as collective effects, are presented.

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THPMR031

Turn-by-Turn Measurements for Beam Dynamics at Vepp-5 Damping Ring

damping, betatron, lattice, vacuum

3452

M.F. Blinov, K.V. Astrelina, V.V. Balakin, O.I. Meshkov, A.A. Starostenko
BINP SB RAS, Novosibirsk, Russia
V.L. Dorokhov
BINP, Novosibirsk, Russia

Preinjector complex VEPP-5 is being constructed for high rate production and acceleration of electrons and positrons beams up to energy 510 MeV. Both kinds of particles accumulated in the damping ring and after achieving of needed intensity the beams would be transported alternatively to VEPP-3/VEPP-4M or to BEP/VEPP-2000 colliders. At this paper basic parameters of damping ring presented. All measurements were carried out for electron beam with energy 385 MeV. For turn-by-turn measurements 12 beam position monitors were used. In order to improve precision of measured value NAFF algorithm was applied. For measurements of longitudinal beam profile optical phi-dissector was used.

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THPMR036

Improved Methods for the Measurement and Simulation of the CERN SPS Non-linear Optics

optics, octupole, sextupole, multipole

3464

H. Bartosik, A. Oeftiger, M. Schenk, F. Schmidt, M. Titze
CERN, Geneva, Switzerland

Good knowledge of the non-linear properties of the SPS lattice is crucial for modelling and optimising the machine performance in the presence of collective effects leading to incoherent tune spreads such as space charge, e-cloud and beam coupling impedance. In view of the LHC injectors upgrade (LIU) project and the future SPS operation in a regime dominated by such collective effects, detailed measurements of the SPS non-linear chromaticity and detuning with amplitude have been performed for the two optics configurations presently available for LHC type beams. The measurement results are used to fit systematic multipole components to the main magnets of the SPS MADX model as a basis for the non-linear machine model that can be used for beam dynamics simulations. The implications for the operation of the SPS with the LIU beam parameters are discussed.

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THPMW003

Prototype Power Supply for SuperKEKB Final Focus Superconducting Corrector Magnets

power-supply, superconducting-magnet, controls, luminosity

3537

T. Oki, T. Adachi, S. Nakamura, N. Ohuchi, N. Tokuda
KEK, Ibaraki, Japan

A prototype power supply for the SuperKEKB final focus superconducting corrector magnets was developed. The aiming specifications of the power supply are a DC rated output of ± 60 A ± 5 V bipolar, current setting resolution < 1 ppm, current stability < 5 ppm/8 h, temperature coefficient < 1 ppm/degree, and current ripple < 5 ppm, where the assumed magnet inductance and cable resistance are 0.2'8.7 mH and 75 mohms, respectively. High power tests were performed and expected results were obtained.

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THPMW020

Solid-state Compact Kicker Pulsar using Strip-line Type Blumlein with SIC-MOSFET in Spring-8

high-voltage, kicker, operation, storage-ring

3585

C. Mitsuda, T. Honiden, K. Kobayashi, T. Kobayashi, S. Sasaki
JASRI/SPring-8, Hyogo-ken, Japan
N. Sekine
Sekine Electric Works Co. Ltd, Osaka, Japan

In the case of handling the electron beam by bunch-by-bunch and turn-by-turn with a kicker at the SPring-8, the performances required to a pulsar are short pulse width (<40ns) and high repetitions (>208kHz). In order to achieve these specifications, the short pulsed high voltage output and the utilization of the solid-state switch is necessary for an inductance load. In order to suppress the supplied voltage as low as as possible, it is an important feature to realize the extremely small-sized pulsar to be set near the kicker. On the basis of the experiences in developing the solid-state pulsar of 400ns/2kV using Si-MOSFET*, combination of the SiC-MOSFET and the strip-line type Blumlein pulse forming network (BPFN) was applied to the prototype driver to achieve a shorter pulse and higher power than Si-type driver. The completed pulsar accomplished a compact size (external dimensions; 300(H)x400(W)x400(D)mm). Furthermore, the targeted short-pulsed high voltage output of 123ns/12kV was obtained by 6 BPFNs serial connection to the load inductance of 800 nH. The BPFN detailed design to enable the compact size, high reliability and stability at high repetitions will be reported.
* C.Mitsuda et al., Proc. of IPAC2013, MOPAWA003

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THPMW028

High Voltage Performance of Surface Coatings on Alumina Insulators

kicker, high-voltage, injection, vacuum

3603

A. Adraktas, M.J. Barnes, H.A. Day, L. Ducimetière
CERN, Geneva, Switzerland

Alumina insulators and dielectrics are required for a variety of applications in particle accelerators. Their use in high voltage devices, both pulsed and DC, is well established as both insulation and mechanical support. In accelerator equipment the alumina is usually used in ultra-high vacuum and hence charge accumulation can be an issue, especially when the alumina is near to the beam. To address challenges regarding surface flashover and high secondary electron yield in high intensity accelerators, surface treatments and coatings are being considered. This paper presents predictions of the influence of surface coatings, on alumina insulators, upon electric field.

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THPMW030

Studies of Impedance-related Improvements of the SPS Injection Kicker System

kicker, simulation, coupling, vacuum

3611

M.J. Barnes, A. Adraktas, M.S. Beck, G. Bregliozzi, H.A. Day, L. Ducimetière, J.A. Ferreira Somoza, B. Goddard, T. Kramer, C. Pasquino, G. Rumolo, B. Salvant, L. Sermeus, J.A. Uythoven, L. Vega Cid, W.J.M. Weterings, C. Zannini
CERN, Geneva, Switzerland
F.M. Velotti
EPFL, Lausanne, Switzerland

The injection kicker system for the SPS consists of sixteen magnets housed in a total of four vacuum tanks. The kicker magnets in one tank have recently limited operation of the SPS with high-intensity beam: this is due to both beam induced heating in the ferrite yoke of the kicker magnets and abnormally high pressure in the vacuum tank. Furthermore, operation with the higher intensity beams needed in the future for HL-LHC is expected to exacerbate these problems. Hence studies of the longitudinal beam coupling impedance of the kicker magnets have been carried out to investigate effective methods to shield the ferrite yoke from the circulating beam. The shielding must not compromise the field quality or high voltage behaviour of the kicker magnets and should not significantly reduce the beam aperture: results of these studies, together with measurements, are presented. In addition results of tests to identify the causes of abnormal outgassing are presented.

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THPMW031

Current and Future Beam Thermal Behaviour of the LHC Injection Kicker Magnet

kicker, injection, simulation, coupling

3615

H.A. Day, M.J. Barnes, L. Ducimetière, L. Vega Cid, W.J.M. Weterings
CERN, Geneva, Switzerland

During Run 1 of the LHC the injection kicker magnets caused occasional operational delays due to beam induced heating with high bunch intensity and short bunch lengths. Significant upgrades were carried out to the injection kicker magnets during long shutdown 1, including a new design of beam screen to reduce the beam induced heating. Nevertheless these kicker magnets may limit the performance of HL-LHC unless additional, mitigating, measures are taken. Hence extensive simulations have been carried out to predict the distribution of the beam induced power deposition within the magnet and detailed thermal analyses carried out to predict the temperature profiles. To benchmark the simulations the predicted temperatures are compared with observables in the LHC. This paper reports on observations of the thermal behaviour of the magnet during run 2 of the LHC, with 25ns beam. In addition the measurement data is used to extrapolate temperature rise for the beam parameters expected for high-luminosity LHC.

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THPMW033

Operational Experience of the Upgraded LHC Injection Kicker Magnets

kicker, injection, vacuum, operation

3623

M.J. Barnes, A. Adraktas, G. Bregliozzi, S. Calatroni, H.A. Day, L. Ducimetière, B. Goddard, V. Gomes Namora, V. Mertens, B. Salvant, J.A. Uythoven, L. Vega Cid, W.J.M. Weterings, C. Yin Vallgren
CERN, Geneva, Switzerland

During Run 1 of the LHC the injection kicker magnets caused occasional operational delays due to beam induced heating with high bunch intensity and short bunch lengths. In addition, sometimes there were also sporadic issues with microscopic unidentified falling objects, vacuum activity and electrical flashover of the injection kickers. An extensive program of studies was launched and significant upgrades were carried out during long shutdown 1. These upgrades include a new design of a beam screen to both reduce the beam coupling impedance of the kicker magnet, and to significantly reduce the electric field associated with the screen conductors, hence decreasing the probability of electrical breakdown in this region. In addition new cleaning procedures were implemented and equipment adjacent to the injection kickers and various vacuum components were modified. This paper presents operational experience of the injection kicker magnets during Run 2 of the LHC and assesses the effectiveness of the various upgrades.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW033

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THPMW034

Review on the Effects of Characteristic Impedance Mismatching in a Stripline Kicker

kicker, extraction, damping, emittance

3627

C. Belver-Aguilar, M.J. Barnes, L. Ducimetière
CERN, Geneva, Switzerland

A stripline kicker operates as two coupled transmission lines, with two TEM operating modes, known as odd and even modes. The characteristic impedance of these two modes is generally different, both only tend to the same value either when the electrodes are widely separated or when the electrodes are very close to the beam pipe wall. In all other cases, the even mode characteristic impedance is always higher than the odd mode characteristic impedance. The specifications required for a kicker operating in a low emittance ring are usually very challenging. In this situation it is desirable to match the even mode characteristic impedance of the striplines to the resistance of their termination. However a mismatched odd mode impedance can significantly influence the striplines performance. This paper presents predictions for the influence of the odd mode characteristic impedance upon the contribution of each field component, electric and magnetic, to the deflection angle. In addition, the variation of the characteristic impedance and field homogeneity with frequency are presented.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW034

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THPMW038

Prototyping of the ALS-U Fast Kickers

kicker, coupling, vacuum, injection

3637

G.C. Pappas, S. De Santis, J.-Y. Jung, T.H. Luo, C. Steier, C.A. Swenson, W.L. Waldron
LBNL, Berkeley, California, USA

Prototyping of major components for the ALS-U kickers is in progress. A tapered stripline kicker has been built for installation and testing in the ALS, and multiple modulator options to meet the fast rise time required for swap out injection have been considered. High voltage feedthroughs that are matched into the multi GHz range are also being studied.
* Pappas et al., "Fast Kicker Systems for ALS-U", Proc. of IPAC'14, Dresden, Germany, MOPME083.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW038

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THPMW042

Overview of Driver Technologies for Nanosecond TEM Kickers

operation, controls, kicker, injection

3645

A.K. Krasnykh
SLAC, Menlo Park, California, USA

Funding: Work supported in part by US Department of Energy under contract DE-AC02-76SF00515 and in part by US Department of Energy under contract DE-AC02-06CH11357
Overview of modern methods, circuits, and practical realizations for multi MW peak power pulsers will be presented. All used pulser components are manufactured by the US national industry and they are available for design and pulser fabrication. Two concepts will be discussed: (1) an approach is based on assistance of a nonlinear transmission line with ferromagnetic media and (2) an approach is based on assistance of special diodes which are working in a specific mode of operation. In both approaches the nonlinear characteristic of switching media (ferromagnetic and solid state plasma) are employed in final stage of the pulser to form the multi MW level nanosecond pulses.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW042

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THPMW043

Observation of Beam-induced Abort Kicker Ferrite Heating in RHIC

kicker, vacuum, quadrupole, proton

3648

C. Montag, L. Ahrens, K.A. Drees, H. Hahn, J.-L. Mi, C. Pai, J. Sandberg, T.C. Shrey, P. Thieberger, J.E. Tuozzolo, W. Zhang
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
During the FY 2013 RHIC polarized proton run, deterioration of the abort kicker system was observed. The reduced kicks resulted in quenching the superconducting quadrupole Q4 downstream of the beam dump. Frequent re-tuning of the modulator wave form temporarily mitigated the effect, which worsened during the course of the run. Beam-induced heating of the kicker ferrites was evenutally identified as the root cause of this behavior. We report our observations and discuss modifications to the kickers.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW043

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THPMY006

Analysis and Testing of a New RF Bridge Concept as an Alternative to Conventional Sliding RF Fingers in LHC

vacuum, operation, ion, alignment

3660

J. Perez Espinos, C. Garion
CERN, Geneva, Switzerland

RF fingers are used as transition elements in beam vacuum line interconnections to ensure the continuity of the vacuum system wall within acceptable beam stability requirements. The RF fingers must absorb and compensate longitudinal, angular and transversal misalignments due to both thermal effects, during bake-out or cooldown processes, and mechanical movements during assembly, alignment, commissioning and operation phases. The new RF bridge concept is based on a deformable thin-walled structure in copper beryllium, which fulfils the above requirements without the need of sliding contacts. Mechanical tests have been carried out to characterize the response and the lifetime of such a component under different loading conditions. In addition, finite element models have been used to estimate the behaviour. The influence of different material grades and heat treatments on the reliability is presented. The paper includes a detailed analysis of the prototyping and testing phases that have led to a final design of the system, qualified on a dedicated test bench, for the collimator vacuum modules of LHC.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMY006

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THPMY009

Coaxial Wire Method Adapted to Weakly Coupled Resonator Mode for LHC RF Fingers Evaluation

resonance, coupling, cavity, vacuum

3670

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

In high intensity particle accelerators, RF contact fingers are commonly used to carry the beam induced image current. In addition, they reduce beam impedance by shielding the outer bellows required to compensate mechanical displacements between components. In order to assess the resulting beam impedance from a specific bellow/RF finger configuration, RF measurements are routinely carried out. During these measurements, it was observed that cavity modes in the volume between the fingers and the bellow undulation arise. These resonances occur at significantly higher frequencies than the expected frequency range of interest. Due to their broadband nature, the tails of the imaginary part of these resonances reach into the lower frequency range of interest where it contributes to the beam coupling impedance of the device. For proper evaluation of this contribution, a time domain delay technique in TDT (time domain transmissiometry) was used in order to overcome shortcomings that arise if the classical coaxial wire method is applied to these structures. We present the theory of our method and discuss it in view of the data measured on deformable fingers that were studied for the LHC.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMY009

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THPMY019

LHC Injection Protection Devices, Thermo-mechanical Studies through the Design Phase

injection, operation, kicker, proton

3698

I. Lamas Garcia, N. Biancacci, G. Bregliozzi, M. Calviani, M.I. Frankl, L. Gentini, S.S. Gilardoni, A. Lechner, A. Perillo-Marcone, B. Salvant, N.V. Shetty, J.A. Uythoven
CERN, Geneva, Switzerland

The TDI is a beam intercepting device installed on the two injection lines of the LHC. Its function is to protect the superconducting machine elements during injection in the case of a malfunction of the injection kickers. The TDIS, which will replace the TDI, is foreseen to be installed for high luminosity operation. Due to the higher bunch intensities and smaller beam emittances expected, and following the operational experiences of the TDI, a complete revision of the design of the jaws must be performed, with a main focus on the material selection. Furthermore, the new TDIS will also improve the TDI reliability by means of a robust design of the jaw positioning mechanism, the efficiency of the cooling circuit and by reducing its impedance. A simplified installation procedure and maintenance will also be an important requirement for the new design. This paper introduces the main characteristics of the TDI as LHC injection protection device, showing the needs and requirements for its upgrade. It also discusses the thermo-mechanical simulations that are supporting and guiding the design phase and the material selection, and describes the modifications to be implemented, so far, for this new device.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMY019

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THPOR049

Considerations for the Injection and Extraction Kicker Systems of a 100 TeV Centre-of-Mass FCC-hh Collider

kicker, extraction, injection, collider

3901

T. Kramer, M.J. Barnes, W. Bartmann, F. Burkart, L. Ducimetière, B. Goddard, V. Senaj, T. Stadlbauer, D.G. Woog
CERN, Geneva, Switzerland
D. Barna
Wigner Research Centre for Physics, Institute for Particle and Nuclear Physics, Budapest, Hungary

A 100 TeV center-of-mass energy frontier proton collider in a new tunnel of ~100 km circumference is a central part of CERN's Future Circular Colliders (FCC) design study. One of the major challenges for such a machine will be the beam injection and extraction. This paper outlines the recent developments on the injection and extraction kicker system concepts. For injection the system requirements and progress on a new inductive adder design will be presented together with first considerations on the injection kicker magnets. The extraction kicker system comprises the extraction kickers itself as well as the beam dilution kickers, both of which will be part of the FCC beam dump system and will have to reliably abort proton beams with stored energies in the range of 8 Gigajoule. First concepts for the beam dump kicker magnet and generator as well as for the dilution kicker system are described and its feasibility for an abort gap in the 1 μs range is discussed. The potential implications on the overall machine and other key subsystems are outlined, including requirements on (and from) dilution patterns, interlocking, beam intercepting devices and insertion design.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR049

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THPOW001

Design of a 4.6-Cell RF Gun for the PHIL accelerator at LAL

gun, emittance, cavity, coupling

3922

P. Chen, C. Bruni, S. Chancé, L. Garolfi, A. Gonnin, P. Lepercq, T. Vinatier
LAL, Orsay, France

A photo-injector with 4.6-cell and resonate frequency of 2.998 GHz has been designed and studied to replace the 2.5-cell RF gun + booster association. The cavity iris shape and dimensions were simulated systematically to optimize the shunt impedance. In this study, electron beam reaches to 9.7 MeV with a moderate peak accelerat-ing gradient of 80 MV/m. Considering a beam charge of 1 nC/bunch, average transverse emittance of ~ 5.9 πmm mrad and energy spread of ~ 0.8% can be obtained at the exit of the gun. The RF input power is only 10.2 MW due to the high shunt impedance. Asymmetry of the electric field due to the coupling port has also been studied using 3D codes for RF and beam dynamics calculations. We will present the RF design and beam calculations results.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW001

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THPOW009

Optimal Design of a Photocathode Electron Gun with High-brightness and High-repetition Rate Based on Genetic Algorithm

gun, electron, cavity, laser

3947

Zh. X. Tang, X.M. Yang, W.Q. Zhang
DICP, Dalian, People's Republic of China
Y.J. Pei, Y. Yu
USTC/NSRL, Hefei, Anhui, People's Republic of China

A low RF frequency of normal conducting photocathode gun with high-brightness and high-repetition rate is designed as an electron source of the Next Generation Light Source (NGLS). In order to optimize the performance of the gun, a genetic multi-objective algorithm has been used. A genetic algorithm is used because of the inherent complexity of the large number of parameters of the cavity geometry available for optimization. On the other hand, the multiplicity of requirements on the beam, which include beam emittance, beam pulse length, energy chirp, as well as pulse shape and peak current, leads to a multi-objective approach for the optimization technique. In this paper, we present the status of the optimization simulations, using the SUPERFISH and PERMELA particle-in-cell code.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW009

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