IPAC2014 - List of Keywords (impedance)

Paper	Title	Other Keywords	Page
MOPRO027	Measurements and Laboratory Tests on a Prototype Stripline Kicker for the CLIC Damping Rings	simulation, coupling, kicker, damping	125
	C. Belver-Aguilar, A. Faus-Golfe IFIC, Valencia, Spain M.J. Barnes, H.A. Day CERN, Geneva, Switzerland F. Toral CIEMAT, Madrid, Spain
	The Pre-Damping Rings (PDRs) and Damping Rings (DRs) of CLIC are required to reduce the beam emittances to the small values required for the main linacs. The injection and extraction, from the PDRs and DRs, are performed by kicker systems. To achieve both low beam coupling impedance and reasonable broadband impedance matching to the electrical circuit, striplines have been chosen for the kicker elements. Prototype striplines have been built: tests and measurements of these striplines have started. The goal of these tests is to characterize, without beam, the electromagnetic response of the striplines. The tests have been carried out at CERN. To study the signal transmission through the striplines, the measured S-parameters have been compared with simulations. In addition, measurements of longitudinal beam coupling impedance, using the coaxial wire method, are reported and compared with simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRO027
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPRO032	Upgrades to the LHC Injection and Beam Dumping Systems for the HL-LHC Project	injection, kicker, dumping, coupling	141
	J.A. Uythoven, M.J. Barnes, B. Goddard, J. Hrivnak, A. Lechner, F.L. Maciariello, A. Mereghetti, A. Perillo Marcone, N.V. Shetty, G.E. Steele CERN, Geneva, Switzerland
	The HL-LHC project will push the performance of the LHC injection and beam dumping systems towards new limits. This paper describes the systems affected and presents the new beam parameters for these systems. It also describes the studies to be performed to determine which sub-components of these systems need to be upgraded to fulfill the new HL-LHC requirements. The results from the preliminary upgrade studies for the injection absorbers TDI are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRO032
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPRO044	Construction and Bench Testing of a Prototype Rotatable Collimator for the LHC	vacuum, collimation, controls, operation	178
	T.W. Markiewicz, E.L. Bong, L. Keller SLAC, Menlo Park, California, USA O. Aberle, A. Bertarelli, P. Gradassi, A. Marsili, S. Redaelli, A. Rossi, B. Salvachua, G. Valentino CERN, Geneva, Switzerland
	Funding: This work partially supported by the U.S. Department of Energy through the US LHC Accelerator Research Program (LARP) and contract DE-AC02-76SF00515. A second generation prototype rotatable collimator has been fabricated at SLAC and delivered to CERN for further vacuum, metrology, function and impedance tests. The design features two cylindrical Glidcop jaws designed to each absorb 12kW of beam in steady state and up to 60kW in transitory beam loss with no damage and minimal thermal distortion. The design is motivated by the use of a radiation resistant high Z low impedance readily available material. A vacuum rotation mechanism using the standard LHC collimation jaw positioning motor system allows each jaw to be rotated to present a new 2cm high surface to the beam if the jaw surface were to be damaged by multiple full intensity beam bunch impacts in a asynchronous beam abort. Design modifications to improve on the first generation prototype, pre-delivery functional tests performed at SLAC and post-delivery test results at CERN are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRO044
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPRO071	Wake Field and Impedance Calculation due to the Beam Position Monitor in the ILSF Storage Ring	vacuum, wakefield, storage-ring, factory	246
	H. Ghasem IPM, Tehran, Iran M. Razazian ILSF, Tehran, Iran
	The Beam Position Monitors (BPMs) are usually used in the particles accelerators to observe position of the beam and to record longitudinal bunch shape. As the vertical beam size demands beam stabilities on the submicron level in the particle accelerators, there must be a sever precision on designing and fabrication of the BPMs. In this paper, we have explored effect of the BPMs on the total impedance and loss factor of the ILSF storage ring.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRO071
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPRO073	Design of Iranian Light Source Facility RF Shielded Bellows	vacuum, storage-ring, wakefield, electron	252
	H. Ghasem IPM, Tehran, Iran J. Etemad Moghadam ILSF, Tehran, Iran
	Total impedance is one of the most effective parameters for proper operation of an accelerator system. This quantity is evaluated with the summation of individual component impedance of the vacuum pipe and is desired to be as low as possible. The bellows have very significant effects on total impedance of the accelerator systems particularly synchrotron light source storage rings. Design of the bellow for Iranian Light Source Facility (ILSF) with a practical approach for fabrication has been down. Minimization of the total impedance budget, loss factor and the resulting wake field due to the passage of 400 mA electron beam is the main goal of our design.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRO073
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPRO116	Mechanical Engineering and Design of Novel Collimators for HL-LHC	operation, proton, experiment, collimation	369
	F. Carra, A. Bertarelli, A. Dallocchio, L. Gentini, P. Gradassi, A. Manousos, N. Mariani, G. Maîtrejean, N. Mounet, E. Quaranta, S. Redaelli, V. Vlachoudis CERN, Geneva, Switzerland
	In view of LHC intensity upgrades, collimator materials may become a limit to the machine performance: the high RF impedance of Carbon-Carbon composites can lead to beam instabilities, while the Tungsten alloy adopted in tertiary collimators exhibits low robustness in case of beam-induced accidents. An R&D program has been pursued to develop new materials overcoming such limitations. Molybdenum-Graphite, in addition to its outstanding thermal conductivity, can be coated with pure molybdenum, reducing collimator impedance by a factor of 10. A new secondary collimator is being designed around this novel composite. New high-melting materials are also proposed to improve the robustness of tertiary collimators. All the new collimators will be equipped with BPMs, significantly enhancing the alignment speed and the beta-star reach. This implies additional constraints of space, as well as detailed static and fatigue calculations on cables and connectors. This paper describes the mechanical design and the engineering calculations of such future collimators, focusing on the study via state-of-the-art numerical methods of interactions between the particle beams and the new materials adopted.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRO116
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPME004	RFQ Solver based on the Method of Moments	rfq, simulation, linac, quadrupole	382
	C. Raucy, C.V.G. Craeye UCL, Louvain-la-Neuve, Belgium D. Vandeplassche SCK•CEN, Mol, Belgium
	Funding: SCK•CEN The aim of this research is to improve the accuracy and the simulation time of solvers devoted to Radio Frequency Quadrupoles (RFQ). The Method of Moments is a full-wave method used to solve scattering problems. Its main advantage over FE or FDTD solvers is that unknowns are limited to the boundaries of the object. The resulting dense system of equations can be solved very rapidly with the help of domain-decomposition approaches (e.g. Macro Basis Functions), especially when the level of detail is very fine compared to the wavelength, which is definitely the case for RFQ’s. Such a method however needs a first regularization method to overcome the low-frequency breakdown in order to compute the Macro Basis Functions. The respective field contributions of different parts of the global structure (e.g. rods vs. stems) can also easily be finely investigated. Numerical results will be presented based on the Myrrha RFQ. The low-frequency breakdown issue due to the very fine mesh will be discussed and a solution based on the so-called Loop-Tree* decomposition will be detailed. * Ozdemir, N.A.; Gonzalez-Ovejero, D.; Craeye, C., IEEE Tr.AP, vol.61, no.4, pp.2088, 2098, April 2013 ** Andriulli, F.P., IEEE Tr.AP, vol.60, no.5, pp.2347, 2356, May 2012
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPME004
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPME009	Numerical Calculation of Electromagnetic Fields in Acceleration Cavities under Precise Consideration of Coupler Structures	cavity, dipole, electromagnetic-fields, HOM	394
	C. Liu, W.A. Ackermann2, W.F.O. Müller, T. Weiland TEMF, TU Darmstadt, Darmstadt, Germany
	Funding: Work supported by BMBF under contract 05H12RD5 During the design phase of superconducting radio frequency (RF) accelerating cavities a challenging and difficult task is to determine the electromagnetic field distribution inside the structure with the help of proper computer simulations. Although dissipation due to lossy materials is neglected in the current work, in reality, because energy transfer appears due to the design of the superconducting cavities, the numerical eigenmode analysis based on real-valued variables is no longer suitable to describe the dissipative acceleration structure. Dissipation can appear with the help of dedicated higher order mode (HOM) couplers, the power coupler as well as the beam tube once the resonance frequency is above the cutoff frequency of the corresponding waveguide. At the Computational Electromagnetics Laboratory (TEMF) a robust parallel eigenmode solver based on complex-valued finite element analysis is available. The eigenmode solver has been applied to the TESLA 1.3 GHz and the third harmonic 3.9 GHz nine-cell cavities to determine the resonance frequency, the quality factor and the corresponding field distribution of eigenmodes.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPME009
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPME070	Investigation of a High Power, Low Impedance Pulse Forming Network based on Ceramic Capacitors	network, simulation, experiment, laser	529
	J. Gao, X.J. Ge, J. He, J. Liu NUDT, Changsha, People's Republic of China
	Solid state is one of the most important development directions for pulsed power technologies. For GW level pulse generators, switches and pulse forming units are difficult to implement with solid state components restricted by high power tolerance and high voltage insulation. Under certain pulse power, operation voltage is decided by impedance of the pulse forming unit, which means that pulse modulation with low impedance method should help improve insulation strength of a pulsed power system. Therefore, a high power, low impedance pulse forming network is developed based on solid components of ceramic capacitors in this research. It is designed that the impedance is 1.6 Ω, the pulse width is about 150 ns, and the output power is above 1 GW. Low impedance is accomplished via several pulse forming units connected in parallel with a circumferential structure, which could reduce the stray inductance due to good symmetrical characteristics. Key factors influencing pulse modulation process are investigated, stray parameters are examined by electromagnetic calculations and preliminary experiments are carried out, with results giving reasonable agreement with the theoretical cases.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPME070
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPME074	High Voltage Performance of the Beam Screen of the LHC Injection Kicker Magnets	injection, kicker, vacuum, operation	541
	M.J. Barnes, P. Adraktas, G. Bregliozzi, S. Calatroni, P. Costa Pinto, H.A. Day, L. Ducimetière, V. Gomes Namora, T. Kramer, V. Mertens, M. Taborelli CERN, Geneva, Switzerland
	The LHC injection kicker magnets include beam screens to shield the ferrite yokes against wakefields resulting from the high intensity beam. The screening is provided by conductors lodged in the inner wall of a ceramic support tube. The design of the beam screen has been upgraded to overcome limitations and permit LHC operation with increasingly higher bunch intensity and short bunch lengths: the new design also significantly reduces the electric field associated with the screen conductors, decreasing the probability of electrical breakdown. The high voltage conditioning process for the upgraded kicker magnets is presented and discussed. In addition a test setup has been utilized to study flashover, on the inner wall of the ceramic tube, as a function of both applied voltage and vacuum pressure: results from the test setup are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPME074
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPME076	Upgrade of the SPS Injection Kicker System for LHC High Luminosity Operation with Heavy Ion Beam	injection, ion, kicker, septum	547
	T. Kramer, J. Borburgh, L. Ducimetière, B. Goddard, L. Sermeus, J.A. Uythoven, F.M. Velotti CERN, Geneva, Switzerland
	In the context of the LHC High Luminosity Upgrade project a performance upgrade for heavy ions is envisaged. One of the performance limitations is the rise time of the present SPS injection kicker system MKP. A reduction of the rise time for lead ions was studied in line with a modification of the whole injection system. This paper briefly describes the different rise time options studied for an initially proposed dedicated ion kicker system MKP-I, focuses however on a cost effective alternative using the presently installed 12 MKPS magnets connected to a new fast pulse forming line. As only 12 out of the 16 injection kicker magnets would be fast enough to be used in an upgraded system, additional deflection has to be provided by the septa. The beam optics for that variant is highlighted and first requirements for the septum elements are stipulated. The paper concludes with a failure analysis of the proposed scheme.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPME076
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPME081	A Stripline Kicker Driver for the Next Generation Light Source	kicker, high-voltage, simulation, coupling	559
	F.M. Niell, N. Butler, M.P.J. Gaudreau, M.K. Kempkes, J. Kinross-Wright Diversified Technologies, Inc., Bedford, Massachusetts, USA
	Funding: US Department of Energy, Award DE-SC00004255 Diversified Technologies, Inc. (DTI) assembled a prototype pulse generator capable of meeting the original specifications for the Next Generation Light Source (NGLS) fast deflector. The ultimate NGLS kicker driver must drive a 50 Ω terminated Transverse Electromagnetic (TEM) deflector blade at 10 kV, with flat-topped pulses and a sustained repetition rate of 100 kHz. Additional requirements of the specification include a 2 ns rise time (10 – 90%), a highly repeatable flattop with pulse width from 5 – 40 ns, and a fall time less than 1 μs (down to 10-4 of the peak value). The driver must also effectively absorb high-order mode signals emerging from the deflector itself. It is envisioned that a scintilla of deflection will be imparted by a symmetric pair of shaped parallel deflection blades, pulsed in opposition at 10 kV. Within the guide, each TEM wave produced by the two pulse generators traverses the guide synchronously with the selected (relativistic) charge packet. The DTI team has designed and demonstrated the key elements of a solid state kicker driver capable of meeting the NGLS requirements, with possible extension to a wide range of fast-pulse applications.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPME081
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPME083	Fast Kicker Systems for ALS-U	kicker, injection, lattice, storage-ring	564
	G.C. Pappas, S. De Santis, J.E. Galvin, L.R. Reginato, C. Steier, C. Sun, H. Tarawneh, W.L. Waldron LBNL, Berkeley, California, USA
	Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 Fast kicker systems are required for the proposed upgrade of ALS to a diffraction-limited light source (ALS-U). The main approach is to have multiple stripline kicker magnets driven by inductive adders. The design details of the kicker structures and the inductive adder options will be discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPME083
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPRI065	The Development of a Low Energy Neutron Accelerator for Rebunching Pulsed Neutrons	neutron, experiment, controls, focusing	751
	S. Imajo Kyoto University, Kyoto, Japan Y. Arimoto KEK, Ibaraki, Japan Y. Iwashita Kyoto ICR, Uji, Kyoto, Japan M. Kitaguchi Kyoto University, Research Reactor Institute, Osaka, Japan Y. Seki RIKEN Nishina Center, Wako, Japan H.M. Shimizu Nagoya University, Nagoya, Japan S. Yamashita ICEPP, Tokyo, Japan T. Yoshioka Kyushu University, Fukuoka, Japan
	Low energy neutrons can be accelerated or decelerated by the technique of AFP-NMR with RF in a gradient magnetic fields. The neutrons have magnetic moments, hence their potential energy are not cancelled before and after passage of magnetic fields and their kinetic energy change finally when their spins are flipped in the fields. Nowadays most measurements of the neutron electric dipole moment (nEDM) are carried out with ultra cold neutrons (UCN), whose kinetic energies are lower than about 300 neV, and with a small storage bottle to reduce the systematic errors. In such experiments highly dense UCNs are desired. The spallation neutron sources generate high-density neutrons at the target, however, the pulsed neutrons with spread velocities are diffused in guide tubes during long beam transport. It is necessary to concentrate UCN temporally upon the bottle by controlling their velocities for nEDM experiments at those facilities. We demonstrated such rebuncher and have been developed the advanced apparatus which makes it possible to handle broader energy range UCN. The design, measured specification of the new rebuncher is described in detail.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI065
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPRI097	Feasibility Studies for the Extraction of both LHC Beams from CERN SPS using a Common Kicker	extraction, kicker, septum, simulation	842
	F.M. Velotti, W. Bartmann, C. Bracco, E. Carlier, K. Cornelis, B. Goddard, V. Kain, M. Meddahi CERN, Geneva, Switzerland
	The CERN Super Proton Synchrotron has to fulfil the demanding intensity specifications for the High Luminosity LHC (HL-LHC) era, with a doubling of the presently achieved operational beam intensity. One of the main problems to be addressed is given by impedance-driven beam instabilities. About 40 % of the total measured SPS impedance is due to the kickers, of which the extraction kickers in two of the SPS straight sections are the largest systems. A potential upgrade is explored which would strongly reduce the number of extraction kickers required in the SPS, by performing non-local extraction. In this scenario LHC Beam 1 would be kicked by the extraction kicker in SPS Long Straight Section 4 (LSS4), normally only used for Beam 2, to be extracted in LSS6. The concept and the expected performance of such a scheme are presented along with detailed simulation results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI097
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUXB01	Recent Progress in 3D Numerical Wakefield Calculations	electron, cavity, insertion, damping	944
	W. Bruns WBFB, Berlin, Germany
	The 3D electromagnetic Field Simulator GdfidL computes Wakepotentials on standard CPUs with a Speed comparable to GPU-Based Implementations. This is achieved via Computing only in interesting Cells, having the FD-Coefficients in compressed Form, traversing the Grid in a Cache-friendly Order and applying a blocked Update Scheme which is NuMA-aware. A Dispersion optimised Scheme is described. Fields in dispersive Materials are computed via solving the Equations of the Electron Hulls of the Material. Moving Mesh Computations have the Grid-generation on the Fly.
	Slides TUXB01 [16.169 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUXB01
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRO017	HL-LHC Performance with a 200 MHz RF System	luminosity, cavity, electron, simulation	1043
	R. Tomás, C.O. Domínguez CERN, Geneva, Switzerland S.M. White BNL, Upton, Long Island, New York, USA
	The HL-LHC performance could considerably benefit from having a 200 MHz RF system. This would allow to inject longer bunches with larger bunch intensity from the SPS and to perform bunch length leveling if required. We also consider the possibility of decreasing the crab cavity frequency to increase both virtual peak luminosity and luminous region. Performance estimates of various configurations are presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRO017
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRO101	Fast Kicker	kicker, vacuum, simulation	1280
	V.V. Gambaryan, A.A. Starostenko BINP SB RAS, Novosibirsk, Russia
	Pulsed deflecting magnet project was worked out in BINP. The kicker design task is: impulsive force value is 1 mT*m, pulse edge is 5 ns, and impulse duration is about 200 ns. The unconventional approach to kicker design was offered. The possibility for set of wires using instead of plates using is considered. This approach allows us to reduce the effective plate surface. In this case we can decrease effects related to induced charges and currents. In the result of modelling optimal construction was developed. It includes 6 wires. The magnet aperture is about 5 cm. Calculated field rise time (about 1.5 ns) satisfies the conditions. Induced current effect reducing idea was confirmed. For configuration with 3 wires pair (with cross section of 2 mm) induced current in one wire is about 10% and in the wall is about 40%. However for design with plates current is about 40% and 20% respectively. Obtained magnet construction allows controlling of high field homogeneity by changing currents magnitudes in wires. In general we demonstrated the method of field optimization. Summary. Optimal kicker design was obtained. Wires using idea was substantiated.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRO101
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPME026	TMCI Thresholds for LHC Single Bunches in the CERN-SPS and Comparison with Simulations	optics, simulation, emittance, kicker	1407
	H. Bartosik, G. Iadarola, Y. Papaphilippou, G. Rumolo, B. Salvant, C. Zannini CERN, Geneva, Switzerland
	At the beginning of 2013 an extensive measurement campaign was carried out at the SPS in order to determine the Transverse Mode Coupling Instability thresholds of LHC-type bunches in a wide range of intensities and longitudinal emittances. The measurements were performed in two different configurations of machine optics (nominal and low gamma transition) with the goal to characterize the differences in behavior and performance. The purpose of this paper is to describe in detail the measurement procedure and results, as well as the comparison of the experimental data with HEADTAIL simulations based on the latest SPS impedance model. Beside the impedances of the resistive wall, the beam position monitors (BPMs), the RF cavities, and the flanges, an advanced model of the impedance of the kicker magnets is included, which are found to play a major role in the definition of the stability region of the LHC-type bunches in the two optics configurations studied.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME026
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPME028	Flat Bunches in the LHC	emittance, operation, luminosity, synchrotron	1413
	E.N. Shaposhnikova, T. Argyropoulos, P. Baudrenghien, J. F. Esteban Müller, T. Mastoridis, G. Papotti, B. Salvant, H. Timko CERN, Geneva, Switzerland C.M. Bhat, A.V. Burov Fermilab, Batavia, Illinois, USA
	A high-harmonic RF system that could serve multiple purposes was proposed for the LHC. Possible applications of the second harmonic RF system include beam stabilisation in the longitudinal plane in the absence of wide-band longitudinal feedback and reduction of bunch peak line-density. Apart from other useful features, flat bunches are expected to produce less beam-induced heating at frequencies below 1 GHz, the frequency region critical for some LHC equipment. The latter, however, can also be achieved by de-populating the bunch centre. This was demonstrated during the dedicated machine development session in the LHC using RF phase modulation. In this paper the results of tests with single bunches and nominal LHC beams are presented and the possible use of this technique in LHC operation is discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME028
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPME029	Identification of High-frequency Resonant Impedance in the CERN SPS	simulation, vacuum, damping, resonance	1416
	E.N. Shaposhnikova, T. Argyropoulos, T. Bohl, J.V. Campelo, F. Caspers, J. F. Esteban Müller, A. Lasheen, B. Salvant, H. Timko CERN, Geneva, Switzerland
	The spectrum of long bunches injected into the ring with RF switched off has been used in the SPS in the past to probe the longitudinal coupling impedance. After a large campaign of shielding of 800 inter-magnet vacuum ports in 1999 - 2001, the microwave instability threshold was significantly increased and the high-frequency spectrum of the beam became practically flat, apart from a prominent peak at around 1.4 GHz. As corresponding high-frequency impedance could potentially lead to microwave instability of high intensity bunches observed now at high energies in the SPS, a search of the source of this impedance was launched. Using a combination of impedance simulations and measurements, vacuum flanges that are present in a large quantity in the machine have been identified as a main source of impedance at this frequency. Particle simulations based on the SPS impedance model, which includes this previously unknown impedance, are able to reproduce the characteristics of the bunch spectrum and amplitude growth rates and hence, confirm that the impedance of the vacuum flanges is responsible for the observed spectral peak.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME029
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPME038	Wakefield excitation via a metasurface-loaded waveguide	wakefield, coupling, simulation, radiation	1437
	E. Sharples Cockcroft Institute, Lancaster University, Lancaster, United Kingdom R. Letizia Lancaster University, Lancaster, United Kingdom
	Funding: Work supported by STFC Quota Studentship grant ST/K520133/1 A metallic waveguide loaded with layers of complementary split ring resonator (CSRR) based metasurface is presented for accelerator and coherent source applications. This structure presents left handed behaviour arising from the strong electrical response of CSRRs which form the metasurface and the transverse field confined between the closely positioned metasurface layers. The loaded waveguide structure is known to have a TM-like mode at 5.47GHz suitable for acceleration. In this paper, the results of wakefield simulations are presented and a narrow band excitation identified around the frequency of the TM-like mode, indicating strong coupling between the beam and the field of this mode.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME038
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI021	Impedance Calculation and Simulation of Microwave Instability for the Main Rings of SuperKEKB	simulation, cavity, vacuum, kicker	1600
	D. Zhou, T. Abe, T. Ishibashi, Y. Morita, K. Ohmi, K. Shibata, Y. Suetsugu, M. Tobiyama KEK, Ibaraki, Japan
	The SuperKEKB B-factory is now under construction. The designs of the components for the SuperKEKB have mostly been finished. This paper summarises the updated results of longitudinal impedance calculations for various components of the main rings. By summing up all available impedances, a pseudo-Green wake function with bunch length of σ_z=0.5 mm is constructed as an impedance model for consequent studies of collective effects. The results of these studies are also reported in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI023	Simulation of Debunching for Slow Extraction in J-PARC MR	cavity, beam-loading, resonance, simulation	1606
	M. Yamamoto, M. Nomura, T. Shimada, F. Tamura JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan E. Ezura, K. Hara, K. Hasegawa, C. Ohmori, A. Takagi, K. Takata, M. Toda, M. Yoshii KEK, Ibaraki, Japan A. Schnase GSI, Darmstadt, Germany
	The J-PARC MR delivers a proton beam for nuclear physics experiments with slow extraction. The beam is debunched at flat top to obtain a coasting beam by turning off the rf voltage. The controlled emittance blow-up before the flat top has been investigated to mitigate the microwave instability. Beam loading effect can disturb the uniformity of the debunching at the flat top. We describe the results of the particle tracking simulation whole acceleration cycle including the controlled emittance blow-up and the beam loading effect.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI023
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI030	Beam Coupling Impedance of the New Beam Screen of the LHC Injection Kicker Magnets	coupling, kicker, injection, operation	1627
	H.A. Day, M.J. Barnes, F. Caspers, E. Métral, B. Salvant, J.A. Uythoven CERN, Geneva, Switzerland
	The LHC injection kicker magnets experienced significant beam induced heating of the ferrite yoke, with high intensity beam circulating for many hours, during operation of the LHC in 2011 and 2012. The causes of this beam coupling impedance were studied in depth and an improved beam screen implemented to reduce the impedance. Results of measurements and simulations of the new beam screen design are presented in this paper: these are used to predict power loss and temperature of the ferrite yoke for operation after long shutdown 1 and for proposed HL-LHC operational parameters.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI030
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI037	Some Features of Wave Distribution in the Thin-Wall Waveguide	vacuum, undulator, shielding, radiation	1641
	M. Ivanyan, L.V. Hovakimyan, A. Sargsyan CANDLE SRI, Yerevan, Armenia
	In this report we derive rigorous and approximate dispersion relations for the round resistive thin-wall waveguide. The features of the distributions of dispersion curves of the waveguide axisymmetric TM modes are obtained. Cases of splitting and degeneracy of modes under consideration are detected and regularities of their behaviours are established.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI037
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI041	Study of Collective Beam Instabilities for Sirius	vacuum, undulator, operation, feedback	1653
	F.H. de Sá, H.O.C. Duarte, L. Liu, N. Milas, X.R. Resende LNLS, Campinas, Brazil
	In this paper we present the on going work of construction of the Sirius impedance budget and instability threshold estimates for several machine operation scenarios.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI041
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI042	Numerical Study of the Microbunching Instability at UVSOR-III: Influence of the Resistive and Inductive Impedances	electron, wakefield, synchrotron, simulation	1656
	E. Roussel, S. Bielawski, C. Evain, C. Szwaj PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France M. Adachi, M. Katoh, S.I. Kimura, T. Konomi UVSOR, Okazaki, Japan M. Hosaka, Y. Takashima, N. Yamamoto Nagoya University, Nagoya, Japan K.S. Ilin, J. Raasch, A. Scheuring, M. Siegel, P. Thoma KIT, Karlsruhe, Germany H. Zen Kyoto University, Kyoto, Japan
	At high charge, relativistic electron bunches circulating in storage rings undergo an instability, the so-called microbunching or the CSR (Coherent Synchrotron Radiation) instability. This instability is due to the interaction of the electrons with their own radiation and leads to the formation of microstructures (at millimeter scale) in the longitudinal phase space. Thanks to a new type of detector, based on superconducting thin film YBCO, it is now possible to observe directly these microstructures and follow their temporal evolution. These experimental observations open a new way to make severe comparisons with theory. Here we present results of the modeling of the dynamics at UVSOR-III using a one dimensional Vlasov-Fokker-Planck equation. We show that to obtain a relatively good agreement between numerical simulations and experiments, we have to take into account several types of impedance such as the shielded CSR impedance but also the resistive and inductive impedances. First Direct, Real Time, Recording of the CSR Pulses Emitted During the Microbunching Instability, using Thin Film YBCO Detectors at UVSOR-III, IPAC2014
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI042
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI043	Analysis of Coupled Bunch Instabilities in BESSY-VSR	HOM, cavity, feedback, damping	1659
	M. Ruprecht, P. Goslawski, A. Jankowiak, M. Ries, A. Schälicke, G. Wüstefeld HZB, Berlin, Germany T. Weis DELTA, Dortmund, Germany
	BESSY-VSR, a scheme where 1.5 ps and 15 ps long bunches (rms) can be stored simultaneously in the BESSY II storage ring has recently been proposed. The strong longitudinal bunch focusing is achieved by superconducting high gradient RF cavities. This paper presents investigations of coupled bunch instabilities driven by HOMs of superconducting multi cell cavities in BESSY-VSR. Analytical calculations and tracking simulations in time domain are performed in the longitudinal and the transverse planes and factors that influence the threshold currents are being discussed. Suitable candidates of cavities which are presently available or in the phase of design are compared with respect to their instability thresholds. G. Wüstefeld, A. Jankowiak, J. Knobloch, M. Ries, Simultaneous Long and Short Electron Bunches in the BESSY II Storage Ring, Proceedings of IPAC2011, San Sebastián, Spain
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI043
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI045	Beam Coupling Impedance Simulation in the Frequency Domain for the SIS100 Synchrotron	coupling, space-charge, dipole, synchrotron	1665
	U. Niedermayer, O. Boine-Frankenheim TEMF, TU Darmstadt, Darmstadt, Germany O. Boine-Frankenheim GSI, Darmstadt, Germany
	For the quantification of intensity thresholds due to coherent instabilities and beam induced heating in the FAIR synchrotron SIS100 a detailed knowledge of transverse and longitudinal beam coupling impedance is required. Due to the rather long proton and heavy-ion bunches, the relevant spectrum is below 100MHz. For the computation of beam coupling impedances in the low frequency regime, frequency domain methods are more advantageous than (explicit) time domain methods. We show the setup of a 2D finite element code that allows to compute the impedance for arbitrary longituninally homogeneous beam and structure shapes. Perfectly conducting pipes, a dispersive ferrite tube, and thin resistive beam pipe serve as test cases. The influence of the beam velocity on the coupling impedance is studied.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI045
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI047	Electromagnetic Modeling of Open Cell Conductive Foams for High Synchrotron Radiation Rings	synchrotron, coupling, synchrotron-radiation, radiation	1671
	S. Petracca, A. Stabile U. Sannio, Benevento, Italy A. Stabile INFN-Salerno, Baronissi, Salerno, Italy
	Open cell conductive foams (OCMF) have been recently suggested as an alternative to perforated metal patches for efficiently handling gas desorption from the beam pipe wall due to intense synchrotron radiation, yielding superior performance in terms of residual gas concentration and beam shielding. Experimental work is ongoing to assess their properties, including secondary emission yields and beam coupling impedances. In this communication we attempt a review of the Literature about electromagnetic modeling of OCMF, and outline a general framework for computing the surface impedance of OCMF walls and deriving the longitudinal and transverse beam coupling impedances thereof, based on effective medium theory and electromagnetic reciprocity. A critical analysis of the relevant modeling approximations is included.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI047
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI049	Geometric Beam Coupling Impedance of LHC Secondary Collimators	factory, simulation, HOM, wakefield	1677
	O. Frasciello, S. Tomassini, M. Zobov INFN/LNF, Frascati (Roma), Italy A. Grudiev, N. Mounet, B. Salvant CERN, Geneva, Switzerland
	Funding: Work supported by European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404 The High Luminosity LHC project is aimed at increasing the LHC luminosity by an order of magnitude. One of the key ingredients to achieve the luminosity goal is the beam intensity increase. In order to keep under control beam instabilities and to avoid excessive power losses a careful design of new vacuum chamber components and an improvement of the present LHC impedance model are required. Collimators are the main impedance contributors. Measurements with beam have revealed that the betatron coherent tune shifts were by about a factor of 2 higher with respect to the theoretical predictions based on the current model. Up to now the resistive wall impedance has been considered as the major impedance contribution for collimators. By carefully simulating their geometric impedance we show that for the graphite collimators with half-gaps higher than 10 mm the geometric impedance exceeds the resistive wall one. In turn, for the tungsten collimators the geometric impedance dominates for all used gap values. Hence, including the geometric collimator impedance into the LHC impedance model enabled us to reach a better agreement between the measured and simulated collimator tune shifts.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI049
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI051	Comparison between Measurements and Orbit Code Simulations for Beam Instabilities due to Kicker Impedance in the 3-GeV RCS of J-PARC	simulation, injection, kicker, acceleration	1683
	P.K. Saha, H. Harada, N. Hayashi, H. Hotchi, Y. Shobuda, F. Tamura, M. Yamamoto JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	The transverse impedance of the extraction kicker magnets is the most dominant beam instability source in the 3-GeV Rapid Cycling Synchrotron of J-PARC. The instability occurs when chromaticity is fully corrected during acceleration but on the other hand no instabilities are observed for a full chromatic correction only at the injection energy even for a beam power up to 500 kW. However, the situation may change for a beam power of 1 MW and also for the upgraded injection beam energy from the present 181 MeV to the 400 MeV, as space charge effect in the non-relativistic region is believed to suppress the growth rate of beam instability. In order to study the kicker impedance in detail, recently we have introduced measured time dependent impedance source in the ORBIT simulation code in a realistic manner. The ORBIT code itself has also been well upgraded and given realistic features for application to synchrotrons. We have also carried out a systematic experimental study for a maximum beam power of 500 kW. In this paper, a detail comparison between measurements and corresponding simulations including 1 MW simulation results are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI051
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI052	Analysis of Single Bunch Measurements at the ALBA Storage Ring	synchrotron, vacuum, undulator, simulation	1686
	T.F.G. Günzel, U. Iriso, F. Pérez CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain E. Koukovini-Platia, G. Rumolo CERN, Geneva, Switzerland
	Measurements of the vertical single bunch mode detuning and the TMCI threshold at zero chromaticity were carried out and their results were compared to the theoretical expectation. Around 65% of the found mode detuning can be explained by a developed transverse impedance model. A good bunch length parametrisation with current contributed essentially to this result. The analysis of single bunch measurements at non-zero chromaticity will also be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI052
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI053	Transverse Beam Instabilities in the MAX IV 3 GeV ring	emittance, damping, operation, storage-ring	1689
	G. Skripka, P.F. Tavares MAX-lab, Lund, Sweden M. Klein, R. Nagaoka SOLEIL, Gif-sur-Yvette, France
	Collective effects in MAX IV 3 GeV storage ring are strongly enhanced by the combination of low emittance, high current and small effective aperture. Three passive harmonic cavities (HC) are introduced to lengthen the bunches, by which beam stabilization is anticipated via decoupling to high frequency wakes, along with Landau damping. The role of the ransverse impedance budget of the MAX IV 3 GeV storage ring as a source of collective beam instabilities was determined. With the help of the macroparticle multi-bunch tracking code mbtrack that directly uses the former as input, we studied the influence of geometric and resistive wall impedance in both transverse planes, as well as that of chromaticity shifting. A fully dynamic treatment of the passive harmonic cavities developed for this study allowed us to evaluate their effectiveness under varying beam conditions.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI053
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI054	FEM Analysis of Beam-coupling Impedance and RF Contacts Criticality on the LHC UA9 Piezo Goniometer	simulation, resonance, experiment, coupling	1692
	A. Danisi, R. Losito, A. Masi, A. Passarelli, B. Salvant, C. Zannini CERN, Geneva, Switzerland
	The UA9 piezo-goniometer has been designed to guarantee micro-radians-accuracy angular positioning of a silicon crystal for a crystal collimation experiment in the LHC, and to minimize the impact on the LHC beam-coupling impedance. This paper presents a Finite Element Method (FEM) study of the device, in both parking and operational positions, to evaluate its impact on the LHC impedance budget. The study has been a progressive simulation work, started from the simplification of the original detailed design, and aimed at highlighting the effect of single details (e.g. objects in confining chambers) on the longitudinal and transverse components of beam-coupling impedance. In addition, the shielding contribution of the RF gaskets has been carefully evaluated, with the objective to assess the consequences for operation in case of their failure. Sensitivity analyses to simulation parameters are also performed, in order to test the FEM model robustness. A final word is drawn on the overall device impedance criticality.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI054
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI055	Theoretical Analysis of Metamaterial Insertions for Resistive-wall Beam-coupling Impedance Reduction	insertion, coupling, vacuum, interface	1695
	A. Danisi, R. Losito, A. Masi, B. Salvant, C. Zannini CERN, Geneva, Switzerland
	Resistive-wall impedance usually constitutes a significant percentage of the total beam-coupling impedance budget of many accelerator structures (e.g. for LHC, it can be more than 50%). Reduction techniques for resistive-wall components entail high electrical-conductivity coatings. This paper proposes the use of metamaterials, having negative values of magnetic permeability or dielectric permittivity (or both), for sensibly reducing or theoretically nearly cancelling the resistive-wall component of beam-coupling impedance. The proposed approach is developed by means of an equivalent transmission-line model, whose results show the potential reduction of both longitudinal and transverse impedance when using metamaterial insertions. The effects on the real and imaginary part have been singled out. The effectiveness of such materials is discussed both for negative-permittivity and for negative-permeability cases, which actually show different impacts and can be then target of proper engineering. This first-stage study opens the possibility of considering metamaterials for impedance mitigation or for setting up proper experimental setups.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI055
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI056	Beam Measurements of the LHC Impedance and Validation of the Impedance Model	emittance, damping, synchrotron, simulation	1698
	J.F. Esteban Müller, T. Argyropoulos, T. Bohl, N. Mounet, E.N. Shaposhnikova, H. Timko CERN, Geneva, Switzerland
	Different measurements of the longitudinal impedance of the LHC done with single bunches with various intensities and longitudinal emittances during measurement sessions in 2011-2012 are compared with particle simulations based on the existing LHC impedance model. The very low reactive impedance of the LHC, with Im(Z/n) around 0.1 Ohm, is not easy to measure. The most sensitive observation is the loss of Landau damping during acceleration, which shows at which energy bunches become unstable depending on their parameters. In addition, the synchrotron frequency shift due to the reactive impedance was estimated following two methods. Firstly, it was obtained from the peak-detected Schottky spectrum. Secondly, a sine modulation in the RF phase was applied to the bunches with different intensities and the modulation frequency was scanned. In both cases, the synchrotron frequency shift was of the order of the measurement precision.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI056
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI057	Review of the Transverse Impedance Budget for the CLIC Damping Rings	damping, wiggler, simulation, operation	1701
	E. Koukovini-Platia, G. Rumolo CERN, Geneva, Switzerland
	Single bunch instability thresholds and the associated coherent tune shifts have been evaluated in the transverse plane for the damping rings (DR) of the Compact Linear Collider (CLIC). A multi-kick version of the HEADTAIL code was used to study the instability thresholds in the case where different impedance contributions are taken into account such as the broad-band resonator model in combination with the resistive wall contribution from the arcs and the wigglers of the DR. Simulations performed for positive values of chromaticity showed that higher order bunch modes can be potentially dangerous for the beam stability.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI057
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI058	Impedance Studies of the Dummy Septum for CERN PS Multi-turn Extraction	extraction, septum, simulation, synchrotron	1704
	S. Persichelli, O.E. Berrig, M. Giovannozzi, J. Herbst, J. Kuczerowski, M. Migliorati, B. Salvant CERN, Geneva, Switzerland
	A protection septum has been installed in the CERN PS section 15 in order to mitigate irradiation of the magnetic septum 16 for fast extractions towards the SPS. Impedance studies have been performed, showing that beams circulating in the septum during extraction generate sharp resonances in the coupling impedance. Impedance measurements with the wire technique have been performed, showing a good agreement with simulations. Instability rise times of trapped modes have been evaluated and compared to extraction duration. Solutions for reducing the impact on the stability of the beam have been considered.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI058
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI059	The Proton Synchrotron Transverse impedance model	simulation, kicker, space-charge, proton	4096
	S. Persichelli, N. Biancacci, S.S. Gilardoni, M. Migliorati, E. Métral, B. Salvant CERN, Geneva, Switzerland
	The current knowledge of the transverse impedance of the CERN Proton Synchrotron (PS) has been established by theoretical computations, electromagnetic simulations and beam-based measurements at different energies. The transverse coherent tune and phase advance shifts as a function of intensity have been measured in order to evaluate the total effective transverse impedance and its distribution in the accelerator. In order to understand the beam dynamics, the frequency dependence of the impedance budget has also been evaluated considering the individual contribution of several machine devices. 3D models of many PS elements have been realized to perform accurate impedance simulations, while resistive wall and indirect space charge impedances have been evaluated with theoretical and numerical computations. Finally comparisons between the total budget and the measurement results are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI059
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI060	Impedance Studies for the PS Finemet® Loaded Longitudinal Damper	simulation, cavity, kicker, synchrotron	1708
	S. Persichelli, M. Migliorati, M.M. Paoluzzi, B. Salvant CERN, Geneva, Switzerland
	The impedance of the Finemet® loaded longitudinal damper cavity, installed in the CERN Proton Synchrotron straight section 02 during the Long Shutdown 2013-2014, has been evaluated. Time domain simulations with CST Particle Studio have been performed in order to get the longitudinal and transverse impedance of the device and make a comparison with the longitudinal impedance that was measured for a single cell prototype.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI060
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI061	Power Loss Calculation in Separated and Common Beam Chambers of the LHC	electron, coupling, simulation, cryogenics	1711
	C. Zannini, G. Iadarola, G. Rumolo CERN, Geneva, Switzerland G. Iadarola Naples University Federico II, Science and Technology Pole, Napoli, Italy
	The performance of 25 ns beams in the LHC is strongly limited by the electron cloud. To determine the amount electron cloud in the cold sections of the machine, it is very important to be able to disentangle the beam induced heating due to the beam coupling impedance from that attributable to electron cloud. This paper will focus on the calculation of the first contribution. First, the impedance model used for the calculation of the beam induced power loss is briefly discussed. Then, the methods for the calculation of the beam induced power loss in regions with one or two beams are also described. Finally, the calculated power loss is compared with the measured heat loads for both 25 and 50 ns beams in both the LHC arcs and in the inner triplets (ITs).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI061
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI062	The Mode Matching Technique Applied to the Transverse Beam Coupling Impedance Calculation of Azimuthally Symmetric Devices of Finite Length	cavity, coupling, simulation, vacuum	1714
	N. Biancacci, E. Métral, B. Salvant, C. Zannini CERN, Geneva, Switzerland M. Migliorati, L. Palumbo URLS, Rome, Italy V.G. Vaccaro Naples University Federico II and INFN, Napoli, Italy
	The infinite length approximation is often used to simplify the calculation of the beam coupling impedance of accelerator elements. This is expected to be a reasonable assumption for devices whose length is greater than the transverse dimension but may be a less accurate approximation for segmented devices. In this contribution we present the extension of the study of the beam coupling impedance of a finite length device to the transverse plane. In order to take into account the finite length, we decompose the fields in the cavity and in the beam pipe into a set of orthonormal modes and apply the Mode Matching method to obtain the impedance. To validate our method, we will present comparisons between analytical formulas and 3D electromagnetic CST simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI062
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI063	Electromagnetic Simulations for Non-ultrarelativistic Beams and Application to the CERN Low Energy Machines	coupling, simulation, space-charge, vacuum	1718
	C. Zannini, N. Biancacci, T.L. Rijoff, G. Rumolo CERN, Geneva, Switzerland T.L. Rijoff TU Darmstadt, Darmstadt, Germany
	In the framework of the PS-Booster upgrade project an accurate impedance model is needed in order to determine the effect on the beam stability and assess the impact of the new devices to be installed in the machine. CST 3-D EM simulations are widely used to estimate the impedance contribution of the different devices along the CERN accelerator complex. Unlike the highly relativistic case, in which the reliability of the EM solver has been proved in many specific cases by comparing simulations with analytical results, the nonrelativistic case has been so far not yet benchmarked. In order to use systematically CST 3-D EM simulations for the PS-Booster, or even lower energy machines like the antiproton decelerator ELENA, a validation campaign has been carried out. The main complication to single out the beam coupling impedance, as resulting from the interaction of the beam with the surroundings, consisted of removing reliably the strong contribution of the direct space charge of the source bunch, which is included in the EM calculation. The simulation results were then benchmarked with the analytical results for the case of a PEC cylindrical tube and of a ferrite loaded kicker.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI063
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI070	Analysis of Coupled-bunch Instabilities in the NSLS-II Storage Ring	HOM, cavity, storage-ring, damping	1727
	G. Bassi, A. Blednykh, F. Gao, J. Rose BNL, Upton, Long Island, New York, USA
	We discuss coupled-bunch instabilities thresholds for the NSLS-II Storage Ring. In particular, we analyze thresholds from the High Order Modes (HOMs) of the PETRA-III 7-cell cavity. Beam dynamics simulations with the code OASIS, using the measured HOMs, will be compared with machine studies.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI070
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI071	Transverse Impedance Measurement in RHIC and the AGS	injection, betatron, proton, luminosity	1730
	N. Biancacci CERN, Geneva, Switzerland M. Blaskiewicz, Y. Dutheil, C. Liu, K. Mernick, M.G. Minty, S.M. White BNL, Upton, Long Island, New York, USA
	The RHIC luminosity upgrade program aims for an increase of the polarized proton luminosity by a factor 2. To achieve this goal a significant increase in the beam intensity is foreseen. The beam coupling impedance represents a source of detrimental effects for beam quality and stability at high bunch intensities. In this paper, we evaluate a new global transverse impedance in both RHIC and the AGS with recent measurements of tune shift as a function of bunch intensity. The results are compared to past measurements and present impedance model.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI071
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI087	A Wideband Slotted Kicker Design for SPS Transverse Intra-bunch Feedback	kicker, feedback, coupling, interface	1772
	J.M. Cesaratto, J.D. Fox, C.H. Rivetta SLAC, Menlo Park, California, USA D. Alesini, A. Gallo, M. Zobov INFN/LNF, Frascati (Roma), Italy S. De Santis LBNL, Berkeley, California, USA W. Höfle CERN, Geneva, Switzerland
	Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research Program (LARP) and by the EU FP7 HiLumi LHC - Grant Agreement 284404. In order for the SPS to meet the beam intensity demands for the HL-LHC upgrade, control and mitigation of transverse beam instabilities caused by electron cloud and TMCI will be essential. For this purpose a wideband intra-bunch feedback method has been proposed, based on a 4 GS/s front end data acquisition and processing, and on a back end frequency response extending to at least 1 GHz. A slotted type kicker, similar to those used for stochastic cooling, as well as an array of stripline kickers have been considered as the terminal elements of the feedback system. A slotted TEM type kicker has been designed fulfilling the bandwidth and kick strength requirements for the SPS application. In this paper we present an updated version of the design and electromagnetic characteristics, leading into the mechanical design and construction of the kicker occurring later this year.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI087
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPRO016	Injection/Extraction Kicker for the ALS-U Project	kicker, injection, extraction, coupling	1977
	S. De Santis, W. Barry, S. Kwiatkowski, T.H. Luo, G.C. Pappas, L.R. Reginato, D. Robin, C. Steier, C. Sun, H. Tarawneh, W.L. Waldron LBNL, Berkeley, California, USA
	Funding: Work supported by the US Department of Energy under Contract no. DEAC02-05CH11231 The ALS-II proposal consists in the upgrade of the existing Advanced Light Source at LBNL to a new ultra-low emittance lattice for production of diffraction-limited soft x-rays. In order to compensate for the reduced beam lifetime we intend to operate the machine in continuous top-off mode, where one of several bunch trains is extracted every 30-60 seconds and swapped with a fresh train from the accumulator ring, which is injected on axis without perturbing the circulating beam. In this paper we present a possible design for the injection/extraction kicker based on matched stripline electrodes. The main parameters of such a kicker are discussed in reference to the minimum gap between trains, the storage ring lattice, and the characteristics of a suitable pulser. We also present results from 3D electromagnetic modeling of the proposed kicker performed to evaluate its rise and fall time and field uniformity characteristics.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRO016
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPRO064	Recent Results of the HESR RF System	operation, cavity, electron, accumulation	2094
	R. Stassen, F.J. Etzkorn, R. Greven, T. Katayama, R. Maier, G. Schug, H. Stockhorst FZJ, Jülich, Germany
	The FAIR complex (Facility for Antiprotons and Ion Research) will be built in different stages. Due to the postponed RESR in the first stage, both RF-cavities of the HESR have to operate in different modes to achieve the required beam quantity and quality. The RF-system of the HESR will now consists of two identical cavities with a common low-level RF control (LLRF). Both cavities will be driven by low noise solid state amplifiers. Each cavity contains of one gap and two tanks operating in push-pull mode and each tank will house 6 ring cores wound of modern magnetic nano-alloy ribbon. Meanwhile all ring cores were delivered and first results at low power and at high power will be presented. The construction of the new air cooling concept is now in the final stage.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRO064
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPME007	Multi-Bunch Generator Cavity	cavity, electron, cathode, coupling	2267
	E.A. Savin, S.V. Matsievskiy, Ya.V. Shashkov, N.P. Sobenin MEPhI, Moscow, Russia A.A. Zavadtsev Nano, Moscow, Russia
	The concept of the six bunch generator cell for the washers and diaphragm loaded structure (Moscow Meson Factory) power supply is proposed. The required power is 0.8 MW on the 991 MHz frequency. The high-voltage electron gun produces electron bunches and puts them into the cylindrical resonator tuned to TE02 mode and operating frequency. Bunches produces RF field that takes energy from the following bunches and then energy transfer to the accelerating structure throw the tuned coupling system.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME007
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPME008	72 MHz Solid-state Amplifier Power Test	operation, cavity, cyclotron, controls	2270
	A.Yu. Smirnov, E.V. Ivanov, A.A. Krasnov, S.A. Polikhov, I. Řežanov Siemens Research Center, Moscow,, Russia G.B. Sharkov Siemens LLC, Moscow, Russia
	In this paper, we present the performance of 72 MHz 18 kW RF power source developed for cyclotrons. The machine is equipped with 9 class-AB power amplifier modules (each with up to 2 kW output) based on highly reliable LDMOS transistors. The whole system is arranged inside a single 19" cabinet and has coaxial 50 Ω output. The test environment and high power measurement results are described.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME008
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPME012	Solid-State Amplifier Development at FREIA	operation, cryomodule, network, vacuum	2282
	D.S. Dancila, A. Rydberg Uppsala University, Department of Engineering Sciences, Uppsala, Sweden A. Eriksson, V.A. Goryashko, L.F. Haapala, R.J.M.Y. Ruber, R. Wedberg, R.A. Yogi, V.G. Ziemann Uppsala University, Uppsala, Sweden
	The FREIA laboratory is a Facility for REsearch Instrumentation and Accelerator development at Uppsala University, Sweden, constructed recently to test and develop superconducting accelerating cavities and their high power RF sources. FREIA's activity target initially the European Spallation Source (ESS) requirements for testing spoke cavities and RF power stations, typically 400 kW per cavity. Different power stations will be installed at the FREIA laboratory. The first one is based on vacuum tubes and the second on a combination of solid state modules. In this context, we investigate different related aspects, such as power generation and power combination. For the characterization of solid-state amplifier modules in pulsed mode, at ESS specifications, we implemented a Hot S-parameters measurement set-up, allowing in addition the measurement of different parameters, such as gain and efficiency. We developed also a new solid-state amplifier module at 352 MHz, using commercially available LDMOS transistors. Preliminary results show a drain efficiency of 71% at 1300 W pulsed output power.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME012
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPME019	Heat Distribution Analysis of Planar Baluns for 1kW Solid-state Amplifiers and Power Combining for 1.8kW	operation, storage-ring, booster, controls	2294
	T.-C. Yu, L.-H. Chang, M.H. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, Y.-H. Lin, Z.K. Liu, C.H. Lo, M.H. Tsai, Ch. Wang, T.-T. Yang, M.-S. Yeh NSRRC, Hsinchu, Taiwan
	Solid-state transmitter for booster and storage ring in synchrotron would be composed of hundreds of amplifier modules. The amplifier module is biased at class AB and constructed in push-pull operation. Recent trend of amplifier module design features higher power up to 800 Watts and equipped planar balun (balance-unbalance converter) for push-pull operation. In NSRRC, the exclusive round planar design has encounter high temperature situation at kW range. Therefore, further study on this thermal condition is carried out in this study. Four types of planar balun design and two laminate materials are used for heat analysis. The typical coaxial balun is also applied on actual amplifier design. The results bring the better design with proper laminate choice and leads to acceptable thermal distribution with 1kW output power at 500MHz. Besides, for a more compact module with higher output power, the combination of two chips on the same circuit reaching 1.8kW is also presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPME033	Search for New e-cloud Mitigator Materials for High Intensity Particle Accelerators	electron, experiment, vacuum, embedded	2332
	R. Cimino, S.T. O'connor, A.L. Romano INFN/LNF, Frascati (Roma), Italy V. Baglin, G. Bregliozzi, R. Cimino CERN, Geneva, Switzerland M.R. Masullo INFN-Napoli, Napoli, Italy S. Petracca, A. Stabile INFN-Salerno, Baronissi, Salerno, Italy
	Electron cloud is an ubiquitous effect in positively charged particle accelerators and has been observed to induce unwanted detrimental impacts on beam quality, stability, vacuum etc. A great effort has been recently devoted to the search of new material morphology and/or coatings which can intrinsically mitigate beam instabilities deriving from electron cloud effects. In this context, we present some characterization of Cu foams, available from the market, and their qualification in terms of their vacuum behavior, impedance, secondary electron yield, gas desorption etc. More experimental effort is required to finally qualify foams as a mature technology to be integrated in accelerator environments. But, our preliminary results suggests that, when compatible with geometrical constrains, Cu foams can be utilized when low desorption yields are required and as e-cloud moderator in future particles accelerators.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME033
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPME050	High Frequency Electromagnetic Characterization of NEG properties for the CLIC Damping Rings	simulation, damping, network, experiment	2384
	E. Koukovini-Platia, G. Rumolo, C. Zannini CERN, Geneva, Switzerland
	Coating materials will be used in the CLIC damping rings (DR) to suppress two-stream effects. In particular, NEG coating is necessary to suppress fast beam ion instabilities in the electron damping ring (EDR). The electromagnetic (EM) characterization of the material properties up to high frequencies is required for the impedance modeling of the CLIC DR components. The EM properties for frequencies of few GHz are determined with the waveguide method, based on a combination of experimental measurements of the complex transmission coefficient S21 and CST 3D EM simulations. The results obtained from a NEG coated copper (Cu) waveguide are presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME050
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPME064	Comparison of an Analytical Model for Lossy Transmission Lines with Measurement Data	LLRF, radio-frequency, feedback, network	2424
	N. Schmitt TEMF, TU Darmstadt, Darmstadt, Germany H. Klingbeil GSI, Darmstadt, Germany
	This paper deals with the analytical modeling of lossy coaxial transmission lines in the frequency range from 100 kHz to 50 MHz with focus on corrugated coaxial lines with polyethylene foam as dielectric. The considered transmission lines are used in low-level radio frequency (LLRF) systems (< 5 MHz) at GSI. These applications require a high precision in amplitude and phase for the transmitted signals where a detailed knowledge of the line properties is of significant interest. As the corresponding data sheets do not provide appropriate data, the necessary data have been computed. The obtained results from the purely analytical model were then compared with previous measurements for validation purposes.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME064
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPME078	Experimental Test of the Prototype LLRF Systems for PAL-XFEL	LLRF, klystron, target, feedback	2462
	J. Hu, H. Heo, J.H. Hong, W.H. Hwang, H.-S. Kang, H.-S. Lee, C.-K. Min PAL, Pohang, Kyungbuk, Republic of Korea
	Two prototype LLRF systems were developed in collaboration with Pohang Accelerator Laboratory(PAL) and domestic companies. They are focused on the control of single klystron system to obtain mainly analogue performance. The low power test of the developed LLRF showed good performance previously. We experimentally tested LLRF in the klystron systems to see performance in the high power situation. They showed performance around the prototype specification for short time and relatively long time. During test some bugs are discovered and fixed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME078
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPRI008	First Cavity Design Studies for the BESSY-VSR Upgrade Proposal	cavity, HOM, damping, coupling	2493
	A. Neumann, A. Burrill, P. Goslawski, A. Jankowiak, J. Knobloch, M. Ries, M. Ruprecht, A.V. Vélez, G. Wüstefeld HZB, Berlin, Germany
	Funding: Work supported by German Bundesministerium für Bildung und Forschung and Land Berlin Recently HZB proposed an upgrade of the 3rd generation synchrotron light source BESSY II allowing simultanous long and short pulse operation. For this scheme to work superconducting higher harmonic cavities of the fundamental 500 MHz at two frequencies need to be installed in the BESSY II storage ring. Given an appropiate choice of the higher harmonics the resulting gradient leads to a beating effect of the effective longitudinal focussing voltage at the stable fix points resulting in different bunch lengths in subsequent buckets. This project places stringent requirements on the cavity performance, as high accelerating fields, excellent HOM damping capabilities and high reliability as they will operate in a 300 mA 24/7 user facility. In this paper we describe the requirements for the cavity design and first designs steps. G. Wüstefeldt et al., Simultaneous Long and Short Electron Bunches in the BESSY II Storage Ring, Proc. of IPAC'11, San Sebástian, Spain
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI008
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPRI049	Optimization of Window Position on Diamond SCRF Cavities	cavity, operation, coupling, simulation	2592
	S.A. Pande, C. Christou DLS, Oxfordshire, United Kingdom
	The Diamond storage ring uses CESR type superconducting cavities. These cavities have a fixed coupling resulting in fixed Qext which is considerably higher than the optimum. We use 3 stub tuners to match the cavities under these non-optimum conditions. Diamond Cavity-1 will soon be refurbished. This opportunity could be used to lower the Qext on the cavity. One of the options is to modify the coupling tongue geometry along with a matching section. This may require cutting off the beam tube with the coupler for rework or it may need to be newly fabricated. We investigated another option to lower the Qext of the cavity by optimising the location of the window with respect to the cavity, maintaining the same coupling tongue geometry. The height of the waveguide on the vacuum side of the window differs from that of the coupling waveguide on the cavity resulting in a step. The location of window with respect to the cavity makes a significant difference to the ultimate Qext obtained after putting the window in place. In this paper we present the results of our numerical simulations comparing the present and the proposed window position under different operating conditions.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI049
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPRI050	Development and Test Results of a Quasi-waveguide Multi-cell Resonator	cavity, niobium, cathode, HOM	2595
	Z.A. Conway, A. Barcikowski, S.M. Gerbick, M. Kedzie, M.P. Kelly, J.S. Kerby, S.H. Kim, S.V. Kutsaev, R.C. Murphy, A. Nassiri, P.N. Ostroumov, T. Reid, T.L. Smith, A. Zholents ANL, Argonne, Illinois, USA
	Funding: Work supported by the U.S. Department of Energy, Offices of Nuclear Physics and Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. This paper reports the successful fabrication and test results of a novel 2815 MHz superconducting deflecting cavity operating in a TE-mode trapped in a quasi-waveguide structure with extremely high shunt impedance. The waveguide structure of this cavity allows for the free propagation of all higher order modes (HOMs) out of the cavity via the beam ports, eliminating the need for HOM dampers inside the cavity when operated with high beam current. The absence of HOM dampers greatly simplifies the cavity fabrication and operation at cryogenic temperatures. This cavity with its high shunt impedance is ideal for the spatial rotation of short bunches in a small physical space, a requirement for the generation of sub-picosecond short pulse x-rays in electron storage rings or luminosity upgrades of colliders. Results characterizing the fabrication accuracy and precision, the RF performance at 2 K, and frequency tuning considerations will be discussed here.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI050
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPRI073	High Order Modes Survey and Mitigation of the CEBAF C100 Cryomodules	HOM, cavity, cryomodule, survey	2660
	J. Guo, M. Stirbet, H. Wang, S. Wang JLab, Newport News, Virginia, USA
	Funding: Funding Agency: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 Ten new C100 cryomodules have been installed for the CEBAF 12GeV upgrade in the last few years. The high order modes (HOM) of these cryomodules need to be controlled to avoid beam breakup (BBU) instability. We surveyed the HOM for all the 80 cavities of the C100 modules in both the JLab cryomodule test facility (CMTF) and the CEBAF tunnel. Additional measures such as waveguide filters were applied to bring down out of spec modes. In this paper, we will present the HOM survey setup and results. The mitigation measures and their effects will also be discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI073
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THYA01	Control and Application of Beam Microbunching in High Brightness Linac-driven Free Electron Lasers	laser, FEL, electron, radiation	2789
	G.V. Stupakov SLAC, Menlo Park, California, USA
	The remarkable properties of coherent radiation from free-electron lasers (FELs) are due to the current modulation in the beam with the modulation period equal to the radiation wavelength. This modulation is developed as a result of a beam instability when the beam propagates in a long FEL undulator, and requires a beam with a high-peak current, small emittance and a small energy spread. Unfortunately the same beam qualities make it a subject to a so-called microbunching instability at a much longer scale than the radiation wavelength. It is driven by the space charge and CSR impedances in the machine and develops during the beam acceleration in the linac, compression, and transport to the undulator. If not controlled, the microbunching instability influences dramatically the FEL performance and in the worst case can even ruin the lasing. In the presentation we will review the mechanism behind the microbunching instability, the suppression methods used in existing facilities as well as possible future developments and concepts.
	Slides THYA01 [5.631 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THYA01
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME012	Results of the High Power Test of the 325 MHz 4-Rod RFQ Prototype	rfq, linac, proton, dipole	3235
	B. Koubek, H. Podlech, A. Schempp, J.S. Schmidt IAP, Frankfurt am Main, Germany
	For the FAIR proton linac at GSI a 325 MHz 4-rod RFQ prototype has been built. On this prototype RF measure- ments have been carried out. After low power conditioning in cw mode the structure was high power tested in pulsed mode. During the performance tests the 6 stem prototype was optimized and has shown the feasibility of a dipole free 4-rod RFQ at high frequencies and was testet up to 120 kW per meter. In this tests the input power and the electrode voltage was observed using gamma spectroskopy. From this the shunt impedance was calculated and compared to other methods of measurements. The power test results are presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME012
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME062	Status of the J-PARC Ring RF Systems	cavity, operation, proton, extraction	3376
	M. Yoshii, M. Nomura, T. Shimada, F. Tamura, M. Yamamoto KEK/JAEA, Ibaraki-Ken, Japan E. Ezura, K. Hara, K. Hasegawa, C. Ohmori, K. Takata, M. Toda KEK, Ibaraki, Japan A. Schnase GSI, Darmstadt, Germany
	The high intensity proton accelerator complex (J-PARC) consists of the Linac, the 25Hz rapid cycling synchrotron (RCS) and the 50GeV main synchrotron (MR). During the long shutdown of 2013, the Linac energy was upgraded from 181MeV to the design value of 400MeV. In the RCS, we have installed the last 12th RF system. In operation from January 2014, beam commissioning aimed at 1 MW operation will be started. In the MR, the upgrade plan of the beam power, realizing by raising the repetition, has been started. For this reason the accelerating voltage must be increased, and all MR RF systems will be replaced with more efficient systems. A new magnetic alloy material (FT3L) has been developed. Manufacturing of the FT3L accelerating cavities has proceeded. It becomes possible to increase the accelerating voltage from 280 kV to 540 kV, using the new cavities in combination with the existing RF power supplies. We have started the developments of a 2nd harmonic system loaded with air-cooled FT3L cores and a high-Q VHF cavity system, too. Both systems are used for longitudinal dilution increase the bunching factor of the circulating high intensity proton beam.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME062
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME065	Beam Test of the CERN PSB Wide-band RF System Prototype in the J-PARC MR	feedback, cavity, beam-loading, extraction	3385
	F. Tamura JAEA/J-PARC, Tokai-mura, Japan K. Hasegawa, C. Ohmori, M. Yoshii KEK, Tokai, Ibaraki, Japan M.M. Paoluzzi CERN, Geneva, Switzerland
	In the framework of the LHC Injectors Upgrade project (LIU), a complete replacement of the existing narrow-band rf systems of CERN PSB with wide-band magnetic alloy (MA) loaded rf systems is in progress. A single gap MA loaded rf system prototype, which uses solid-state power amplifier and includes fast rf feedback for beam loading compensation, has been installed in the J-PARC MR to investigate the system behavior with high intensity proton beams. We report the wake voltage measurement results with and without fast rf feedback. In addition to the fast feedback, the rf feedforward method is under consideration to compensate the heavy beam loading more effectively. Preliminary beam test results with feedforward are also presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME065
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME080	Reflective Streak Camera Bunch Length Measurements at the Australian Synchrotron	cavity, optics, storage-ring, synchrotron	3421
	M.J. Boland, Y.E. Tan SLSA, Clayton, Australia T.M. Mitsuhashi KEK, Ibaraki, Japan
	The bunch length of the 3 GeV electron storage ring at the Australian Synchrotron has been measured using reflective input optics feeding a streak camera. An Offner optical design was employed to reduce the chromatic broadening of the input optics of the streak camera. Using the reflective input optics the bunch length is measured to be 15% shorter than with the refractive input optics. The measured bunch length is now in good agreement with the model of the storage ring and the values are being used for calibration, monitoring and optimisation of the machine. The results of studies to characterise the streak camera shall also be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME080
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME096	Goubau Line Beam Instrumentation Testing, The Benefits	instrumentation, resonance, electromagnetic-fields, electronics	3462
	F. Stulle, J.F. Bergoz BERGOZ Instrumentation, Saint Genis Pouilly, France J. Musson JLab, Newport News, Virginia, USA
	At JLab and Bergoz Instrumentation Goubau lines are used for beam instrumentation testing. A Goubau line differs fundamentally from standard bench testing techniques in the way it produces the electromagnetic fields which interact with the DUT. This allows to acquire complementary information about DUT characteristics. Consequently, we improve our knowledge about the DUT. At JLab BPM responses have been successfully mapped and at Bergoz Instrumentation high frequency behavior of current transformers is under study. We present results, highlight benefits and outline ideas for future studies of additional accelerator components.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME096
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME100	The Mechanical Design of the BPM Inter-tank Section for P-linac at FAIR	linac, cavity, proton, pick-up	3474
	M.H. Almalki, R. M. Brodhage, P. Forck, W. Kaufmann, O.K. Kester, P. Kowina, T. Sieber GSI, Darmstadt, Germany M.H. Almalki, R. M. Brodhage, O.K. Kester IAP, Frankfurt am Main, Germany M.H. Almalki KACST, Riyadh, Kingdom of Saudi Arabia J. Balaguer CEA/IRFU, Gif-sur-Yvette, France P. Girardot, C.S. Simon CEA/DSM/IRFU, France
	At the planned Proton LINAC at the FAIR facility, four-fold button Beam Position Monitor (BPM) will be installed at 14 locations along the 30 m long FAIR p-LINAC. The LINAC comprises of crossbar H-mode (CH) cavity to accelerate a 70 mA proton beam up to 70 MeV at frequency of 325 MHz. At four locations, the BPMs will be an integral part of the inter-tank section between the CCH and CH cavities within an evacuated housing. As the BPM centre is only 48 mm apart from the upstream cavity boundary, the rf-background at the BPM position, generated by the cavity must be evaluated. In this paper the mechanical design of the BPM for the inter-tank section is presented and the rf-noise at the BPM location is discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME100
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME101	Considerations for a Cavity-Based Position-Sensitive Heavy Ion Detector for the CR at FAIR	cavity, ion, heavy-ion, simulation	3477
	X. Chen, P. Hülsmann, Yu.A. Litvinov, F. Nolden, M.S. Sanjari, M. Steck, T. Stöhlker GSI, Darmstadt, Germany X. Chen Heidelberg University, Heidelberg, Germany Yu.A. Litvinov MPI-K, Heidelberg, Germany J. Piotrowski AGH University of Science and Technology, Kraków, Poland T. Stöhlker HIJ, Jena, Germany
	Funding: Work funded by the European Commission (PITN-GA-2011-289485), the Alliance Program of the Helmholtz Association (HA216/EMMI), the Helmholtz-CAS Joint Research Group (HCJRG-108), the BMBF (05E12CD2). The Facility for Antiproton and Ion Research (FAIR) is a complex yet ongoing project which will allow for a broad range of experimental physics programs as well as a variety of material and medical applications. Being a heavy ion storage ring at FAIR, the Collector Ring (CR) is perfectly suitable for scientific investigations on fundamental properties – such as masses and lifetimes – of short-lived radioactive nuclei when it operates in isochronous mode. To fulfill stringent experimental requirements, a compatible heavy ion detector sensitive to beam intensities and positions is highly demanded. In this paper we present a conceptual design of cavity-based Schottky noise pickup to achieve non-destructive detections of stored particles. Computer-aided simulations follow immediately to justify the feasibility of such a design.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME101
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME131	A Multi-conductor Transmission Line Model for the BPMs	pick-up, beam-transport, induction, framework	3550
	T. Toyama J-PARC, KEK & JAEA, Ibaraki-ken, Japan
	We have developed an accurate and efficient analysis method with a multi-conductor transmission line model for beam position monitors (BPMs). This method combines the two-dimensional electrostatic analysis including beams in the transverse plane and the transmission line analysis in the longitudinal direction. The loads are also included in the boundary condition of the transmission line analysis. Calculation of 2D electrostatic fields can be easily performed with the boundary element method. The BPM response to a beam is compared with that to a stretched wire.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME131
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME144	Stripline Beam Position Monitor for THz Source Based FEL	brilliance, electronics, linac, controls	3590
	J. Xu, L. Li, J. Liu, P. Lu, Y.J. Pei, B.G. Sun, K. Tang, J.G. Wang, F.F. Wu, H. Xu, Y.L. Yang, Z.R. Zhou, J.Y. Zou USTC/NSRL, Hefei, Anhui, People's Republic of China
	A 14MeV Linac with both the micro-pulse repetition rate 2856MHz and the macro-pulse width 6us for the THz Source Based FEL was proposed. In order to measure the beam position, a stripline beam position monitor (BPM) was designed, and a commercial BPM electronics Libera Brilliance Single Pass was adopted. As the input carrier frequency of the BPM electrode signal is 2856MHz, but the operating frequency of the Libera Brilliance Single Pass is 500MHz, so a front-end electronics was needed before the electrode signals feed into Libera Brilliance Single Pass. The front-end electronics was designed to make the BPM electrode signals of 2856MHz convert to 500MHz.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME144
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME145	BPM Signal Channel Characterization Test based on TDR for HLS II Storage Ring	storage-ring, pick-up, simulation, electron	3593
	J.J. Zheng, C. Cheng, P. Lu, Q. Luo, B.G. Sun, Y.L. Yang, Z.R. Zhou USTC/NSRL, Hefei, Anhui, People's Republic of China
	A new BPM system on the upgraded Hefei light source (HLSII) storage ring is installed. Before the machine commissioning, the BPM system should be carefully tested, such as the conductivity and integrity of BPM signal channels from button electrodes to digital beam position processors (pickups, cables and connectors). This paper presents an experience of signal channel test based on time domain reflection (TDR) for HLS II storage ring BPM system. Basing on the wave propagation method, an analytic expression for the signal from TDR on BPM signal channel is briefly introduced. The conductivity and integrity of the BPM signal channels can be verified by comparing the TDR waveform to theory signal. All the BPM signal channels are tested by the TDR in order to verify electronic characteristic and the usability. And some breakdowns are analysed and handled.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME145
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME172	Experimental Results from the Characterization of Diamond Particle Detectors with a High Intensity Electron Beam	detector, electron, experiment, radiation	3671
	F. Burkart, R. Schmidt, O. Stein, D. Wollmann CERN, Geneva, Switzerland E. Griesmayer CIVIDEC Instrumentation, Wien, Austria
	Understanding the sources of ultra-fast failures, with durations of less than 3 LHC turns, is important for a safe operation of the LHC, as only passive protection is possible in these time scales. Diamond particle detectors with bunch-by-bunch resolution and high dynamic range have been successfully used to improve the understanding of some new ultra-fast loss mechanisms discovered in the LHC. To fully exploit their potential, diamond detectors were characterized with a high-intensity electron beam (10⁵ to 1010 electrons per shot). For the first time their efficiency and linearity has been measured in such a wide range of intensities. In this paper the experimental setup will be described and the signals of the different detectors will be discussed. Finally, future applications of these detectors in high-radiation applications will be discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME172
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME182	Precise Instruments for Bunch Charge Measurement	pick-up, resonance, monitoring, vacuum	3703
	A. Kalinin STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	For the pulse charge q injected into a capacitor of a parallel resonating circuit, the oscillation voltage V on a series resistor R is V=qwRexp(wt/2Q)sin(wt–1/2Q), t>τ, where w is the resonance frequency, Q>>1 is the quality factor and τ<<1/w is the pulse length. Of the two main parameters, R is known, and w can be found directly from the signal above. The quality factor contribution is low, and its rough estimation is sufficient to retain voltage accuracy. The observations above open a possibility of precise bunch charge measurement. We describe a bunch charge monitor that is a cavity with a lump capacitor as a low impedance coaxial line connected to a gap in the vacuum pipe. An LC electronic circuit is also presented. It integrates the single bunch current delivered by a Faraday Cup, or a Wall Current Monitor, or a Fast Current Transformer. The circuit has w~30MHz, Q~20, and with a Faraday Cup, the lower range is 10pC/V and the noise floor is about 20fC. Several such circuits are in use on the VELA injector in Daresbury Laboratory.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME182
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPRI040	Study of Geometrical Parameters and their Tolerances in Optimization of Accelerating Cells of Side Coupled Linac	cavity, linac, simulation, electron	3850
	S. Zarei Nuclear Science and Technology Research, InstituteRadiation Application School, Tehran, Iran F. AbbasiDavani, S. Ahmadiannamin, F. Ghasemi sbu, Tehran, Iran M. Lamehi Rashti IPM, Tehran, Iran
	After choosing the suitable geometry for accelerating cavity, evaluation of geometrical parameters effects on radio frequency characteristics is essential. In this paper after study of priority of geometrical parameters in optimization of accelerating cells of Side Coupled Linac, according to obtained results, new design of s-band accelerating cavity is suggested. By frequency sensitivity study of new dimensions, we can choose best technique to tune the accelerating cavity during magnetic coupling-hole adjustment.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRI040
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPRI046	Air-cooled Magnetic Alloy Cavity for J-PARC Doubled Rep.-rate Scenario	cavity, injection, acceleration, ion	3869
	C. Ohmori, K. Hara, K. Hasegawa, K. Takata, M. Toda, M. Yoshii KEK, Ibaraki, Japan M. Nomura, A. Schnase, T. Shimada, F. Tamura, M. Yamamoto JAEA/J-PARC, Tokai-mura, Japan
	The upgrade project of the J-PARC MR (Main Ring) is in progress to deliver the beam power of 750 kW based on doubled repetition-rate scenario. The present RF section will be occupied by 9 sets of new magnetic alloy, FT3L, cavity using the direct water cooling scheme. The direct water cooling requires dedicated high-quality cooling water. These cavities will be used for the fundamental RF for acceleration. The second harmonic RF is necessary to increase the bunch length. This allows to enlarge the beam current, and to relax the space charge effects during the injection. Thanks to the high impedance FT3L, the power loss in the second harmonic RF system becomes moderate. The air cooled cavity is designed to fit in any space in the MR where the dedicated water is not available. This paper reports the design of the second RF system, technical issues to produce the magnetic alloy cores to fit the air cooling, and construction of the system.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRI046
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPRI048	Design of an Accelerating Tube for a Standing-wave Accelerator based on Genetic Algorithm’s Optimal Calculation	electron, coupling, simulation, radiation	3875
	Z.X. Tang USTC, Hefei, Anhui, People's Republic of China Y.J. Pei USTC/NSRL, Hefei, Anhui, People's Republic of China
	A compact medical standing-wave (SW) electron accelerating tube has been designed that operating frequency is 2998MHz, operating mode is π/2, final energy is 6MeV and beam current is 100mA based on genetic algorithm (GA)’s optimal calculation. It employed a bi-periodic structure with nose cone shape. We performed the simulation experiment which proved that GA was feasible and gave a set of geometric parameter with higher shunt impedance. We performed tuning of the whole tube by CST MICROWAVE STUDIO and SUPERFISH and calculation of beam dynamics by ASTRA and Parmela in this paper. The total length of the tube is less than 300mm.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRI048
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPRI049	Engineering Design of the RF Input Couplers for C-ADS RFQ	rfq, cavity, linac, operation	3878
	L.P. Sun, Y. He, A. Shi, C. Zhang, Z.L. Zhang IMP, Lanzhou, People's Republic of China
	A new coupler with the special ceramic window has been developed at IMP, CAS (Institute of Modern Physics, Chinese Academy of Sciences), operating at 30 kW/162.5 MHz in CW mode for an one-meter prototype cavity, which can provide all kinds of experiences to the real four-meter cavity including EM simulation, power conditioning, cooling consideration and so on. Now, the beam experiments on prototype cavity have been completed and the results show the simulation and the measurements of coupler were in the good agreement. The special bowl-type ceramic window can promote S parameter and reduce sparking risk for beam commissioning stably. A detailed electromagnetic design and measured results of the coupler will be presented in the paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRI049
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPRI053	Ferrite Material Characterization in a Static Bias Field for the Design of a Tunable Cavity	simulation, cavity, electromagnetic-fields, solenoid	3890
	J. Eberhardt, F. Caspers, C. Vollinger CERN, Geneva, Switzerland
	During the development of ferrite-loaded accelerating cavities, the electromagnetic properties of the dispersive ferrite material need to be known. We describe a coaxial short-circuit measurement technique to measure the complex permeability of toroidal-shaped samples (127mm outer and 70mm inner diameter) that are exposed to an external magnetic bias field. The external magnetic bias field is applied perpendicular to the RF magnetic field. With this method it is possible to characterize the frequency dependence of the permeability for a frequency range of 1-100MHz. The dependence of the permeability on the external magnetic bias is presented for the ferrite G-510 from Trans-Tech Inc. and the material characterization is shown in the same frequency range. The measurement results are verified by simulations of the measurement set-up.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRI053
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPRI054	Permittivity and Permeability Measurement Methods for Particle Accelerator Related Materials	simulation, resonance, cavity, HOM	3893
	C. Vollinger, F. Caspers, E. Jensen CERN, Geneva, Switzerland
	For the special requirements related to particle accelerators, knowledge of the different material parameters of dielectrics and other materials are needed in order to carry out simulations during the design process of accelerator components. This includes also properties of magnetically biased ferrites of which usually little information is available about material characteristics, especially in magnetic bias fields. Several methods of measurement are discussed and compared of which some require delicate sample preparation whereas others can work with unmodified material shapes that makes those methods also suited for acceptance checks on incoming materials delivered by industry. Applications include characterization of different materials, as absorbers in which dielectric losses play an increasing role, as well as low frequency measurements on ferrites that are used for tunable cavities. We present results obtained from both broadband and resonant measurements on different materials determined in the same sample holder. Where possible, the results were confirmed with alternative methods.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRI054
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPRI055	The New 118 MHz Normal Conducting RF Cavity for SIAM Photon Source at SLRI	cavity, storage-ring, electron, HOM	3896
	N. Juntong, S. Krainara SLRI, Nakhon Ratchasima, Thailand
	The Siam Photon Source (SPS) is the 1.2 GeV second generation light source in Thailand. It is managed by the Synchrotron Light Research Institute (SLRI). The institute is located inside the campus of Suranaree University of Technology (SUT), which is approximately 20 km from the city of Nakhon Ratchasima (or normally called Korat). Korat is 250 km north-east of Bangkok. Two insertion devices (IDs) have been installed in the SPS storage ring during June to August 2013. These IDs require additional electrical field energy from RF cavity to compensate electron energy loss in the storage ring. The existing RF cavity has been pushed to its maximum capability and the new RF cavity is in the procurement process. The design and study of the new RF cavity will be presented. Electromagnetic fields of the cavity are studied together with the effects to electron beam instabilities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRI055
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPRI066	Design of a 1.3 GHz Two-cell Buncher for APEX	cavity, HOM, dipole, vacuum	3924
	H.J. Qian, K.M. Baptiste, J.A. Doyle, D. Filippetto, S. Kwiatkowski, C. F. Papadopoulos, D. Patino, F. Sannibale, J.W. Staples, S.P. Virostek, R.P. Wells LBNL, Berkeley, California, USA
	Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231 The design of a 1.3 GHz buncher cavity for the APEX project, a MHz repetition rate high-brightness photoinjector, is presented. The buncher cavity operates at 240 kV in CW mode, and it compresses the 750 keV beam from APEX gun through ballistic compression. Compared with a single cell design, a two-cell cavity doubles the shunt impedance to 7.8 MΩ, which greatly relaxes the requirements for both RF amplifier and cavity cooling. Coupler design, multipacting analysis, HOM analysis and thermal analysis will be presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRI066
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Other Keywords

Page

MOPRO027

Measurements and Laboratory Tests on a Prototype Stripline Kicker for the CLIC Damping Rings

simulation, coupling, kicker, damping

125

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

The Pre-Damping Rings (PDRs) and Damping Rings (DRs) of CLIC are required to reduce the beam emittances to the small values required for the main linacs. The injection and extraction, from the PDRs and DRs, are performed by kicker systems. To achieve both low beam coupling impedance and reasonable broadband impedance matching to the electrical circuit, striplines have been chosen for the kicker elements. Prototype striplines have been built: tests and measurements of these striplines have started. The goal of these tests is to characterize, without beam, the electromagnetic response of the striplines. The tests have been carried out at CERN. To study the signal transmission through the striplines, the measured S-parameters have been compared with simulations. In addition, measurements of longitudinal beam coupling impedance, using the coaxial wire method, are reported and compared with simulations.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRO027

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPRO032

Upgrades to the LHC Injection and Beam Dumping Systems for the HL-LHC Project

injection, kicker, dumping, coupling

141

J.A. Uythoven, M.J. Barnes, B. Goddard, J. Hrivnak, A. Lechner, F.L. Maciariello, A. Mereghetti, A. Perillo Marcone, N.V. Shetty, G.E. Steele
CERN, Geneva, Switzerland

The HL-LHC project will push the performance of the LHC injection and beam dumping systems towards new limits. This paper describes the systems affected and presents the new beam parameters for these systems. It also describes the studies to be performed to determine which sub-components of these systems need to be upgraded to fulfill the new HL-LHC requirements. The results from the preliminary upgrade studies for the injection absorbers TDI are presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRO032

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPRO044

Construction and Bench Testing of a Prototype Rotatable Collimator for the LHC

vacuum, collimation, controls, operation

178

T.W. Markiewicz, E.L. Bong, L. Keller
SLAC, Menlo Park, California, USA
O. Aberle, A. Bertarelli, P. Gradassi, A. Marsili, S. Redaelli, A. Rossi, B. Salvachua, G. Valentino
CERN, Geneva, Switzerland

Funding: This work partially supported by the U.S. Department of Energy through the US LHC Accelerator Research Program (LARP) and contract DE-AC02-76SF00515.
A second generation prototype rotatable collimator has been fabricated at SLAC and delivered to CERN for further vacuum, metrology, function and impedance tests. The design features two cylindrical Glidcop jaws designed to each absorb 12kW of beam in steady state and up to 60kW in transitory beam loss with no damage and minimal thermal distortion. The design is motivated by the use of a radiation resistant high Z low impedance readily available material. A vacuum rotation mechanism using the standard LHC collimation jaw positioning motor system allows each jaw to be rotated to present a new 2cm high surface to the beam if the jaw surface were to be damaged by multiple full intensity beam bunch impacts in a asynchronous beam abort. Design modifications to improve on the first generation prototype, pre-delivery functional tests performed at SLAC and post-delivery test results at CERN are presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRO044

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPRO071

Wake Field and Impedance Calculation due to the Beam Position Monitor in the ILSF Storage Ring

vacuum, wakefield, storage-ring, factory

246

H. Ghasem
IPM, Tehran, Iran
M. Razazian
ILSF, Tehran, Iran

The Beam Position Monitors (BPMs) are usually used in the particles accelerators to observe position of the beam and to record longitudinal bunch shape. As the vertical beam size demands beam stabilities on the submicron level in the particle accelerators, there must be a sever precision on designing and fabrication of the BPMs. In this paper, we have explored effect of the BPMs on the total impedance and loss factor of the ILSF storage ring.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRO071

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPRO073

Design of Iranian Light Source Facility RF Shielded Bellows

vacuum, storage-ring, wakefield, electron

252

H. Ghasem
IPM, Tehran, Iran
J. Etemad Moghadam
ILSF, Tehran, Iran

Total impedance is one of the most effective parameters for proper operation of an accelerator system. This quantity is evaluated with the summation of individual component impedance of the vacuum pipe and is desired to be as low as possible. The bellows have very significant effects on total impedance of the accelerator systems particularly synchrotron light source storage rings. Design of the bellow for Iranian Light Source Facility (ILSF) with a practical approach for fabrication has been down. Minimization of the total impedance budget, loss factor and the resulting wake field due to the passage of 400 mA electron beam is the main goal of our design.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRO073

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPRO116

Mechanical Engineering and Design of Novel Collimators for HL-LHC

operation, proton, experiment, collimation

369

F. Carra, A. Bertarelli, A. Dallocchio, L. Gentini, P. Gradassi, A. Manousos, N. Mariani, G. Maîtrejean, N. Mounet, E. Quaranta, S. Redaelli, V. Vlachoudis
CERN, Geneva, Switzerland

In view of LHC intensity upgrades, collimator materials may become a limit to the machine performance: the high RF impedance of Carbon-Carbon composites can lead to beam instabilities, while the Tungsten alloy adopted in tertiary collimators exhibits low robustness in case of beam-induced accidents. An R&D program has been pursued to develop new materials overcoming such limitations. Molybdenum-Graphite, in addition to its outstanding thermal conductivity, can be coated with pure molybdenum, reducing collimator impedance by a factor of 10. A new secondary collimator is being designed around this novel composite. New high-melting materials are also proposed to improve the robustness of tertiary collimators. All the new collimators will be equipped with BPMs, significantly enhancing the alignment speed and the beta-star reach. This implies additional constraints of space, as well as detailed static and fatigue calculations on cables and connectors. This paper describes the mechanical design and the engineering calculations of such future collimators, focusing on the study via state-of-the-art numerical methods of interactions between the particle beams and the new materials adopted.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRO116

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPME004

RFQ Solver based on the Method of Moments

rfq, simulation, linac, quadrupole

382

C. Raucy, C.V.G. Craeye
UCL, Louvain-la-Neuve, Belgium
D. Vandeplassche
SCK•CEN, Mol, Belgium

Funding: SCK•CEN
The aim of this research is to improve the accuracy and the simulation time of solvers devoted to Radio Frequency Quadrupoles (RFQ). The Method of Moments is a full-wave method used to solve scattering problems. Its main advantage over FE or FDTD solvers is that unknowns are limited to the boundaries of the object. The resulting dense system of equations can be solved very rapidly with the help of domain-decomposition approaches (e.g. Macro Basis Functions*), especially when the level of detail is very fine compared to the wavelength, which is definitely the case for RFQ’s. Such a method however needs a first regularization method to overcome the low-frequency breakdown in order to compute the Macro Basis Functions. The respective field contributions of different parts of the global structure (e.g. rods vs. stems) can also easily be finely investigated. Numerical results will be presented based on the Myrrha RFQ. The low-frequency breakdown issue due to the very fine mesh will be discussed and a solution based on the so-called Loop-Tree** decomposition will be detailed.
* Ozdemir, N.A.; Gonzalez-Ovejero, D.; Craeye, C., IEEE Tr.AP, vol.61, no.4, pp.2088, 2098, April 2013
** Andriulli, F.P., IEEE Tr.AP, vol.60, no.5, pp.2347, 2356, May 2012

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPME004

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPME009

Numerical Calculation of Electromagnetic Fields in Acceleration Cavities under Precise Consideration of Coupler Structures

cavity, dipole, electromagnetic-fields, HOM

394

C. Liu, W.A. Ackermann2, W.F.O. Müller, T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany

Funding: Work supported by BMBF under contract 05H12RD5
During the design phase of superconducting radio frequency (RF) accelerating cavities a challenging and difficult task is to determine the electromagnetic field distribution inside the structure with the help of proper computer simulations. Although dissipation due to lossy materials is neglected in the current work, in reality, because energy transfer appears due to the design of the superconducting cavities, the numerical eigenmode analysis based on real-valued variables is no longer suitable to describe the dissipative acceleration structure. Dissipation can appear with the help of dedicated higher order mode (HOM) couplers, the power coupler as well as the beam tube once the resonance frequency is above the cutoff frequency of the corresponding waveguide. At the Computational Electromagnetics Laboratory (TEMF) a robust parallel eigenmode solver based on complex-valued finite element analysis is available. The eigenmode solver has been applied to the TESLA 1.3 GHz and the third harmonic 3.9 GHz nine-cell cavities to determine the resonance frequency, the quality factor and the corresponding field distribution of eigenmodes.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPME009

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPME070

Investigation of a High Power, Low Impedance Pulse Forming Network based on Ceramic Capacitors

network, simulation, experiment, laser

529

J. Gao, X.J. Ge, J. He, J. Liu
NUDT, Changsha, People's Republic of China

Solid state is one of the most important development directions for pulsed power technologies. For GW level pulse generators, switches and pulse forming units are difficult to implement with solid state components restricted by high power tolerance and high voltage insulation. Under certain pulse power, operation voltage is decided by impedance of the pulse forming unit, which means that pulse modulation with low impedance method should help improve insulation strength of a pulsed power system. Therefore, a high power, low impedance pulse forming network is developed based on solid components of ceramic capacitors in this research. It is designed that the impedance is 1.6 Ω, the pulse width is about 150 ns, and the output power is above 1 GW. Low impedance is accomplished via several pulse forming units connected in parallel with a circumferential structure, which could reduce the stray inductance due to good symmetrical characteristics. Key factors influencing pulse modulation process are investigated, stray parameters are examined by electromagnetic calculations and preliminary experiments are carried out, with results giving reasonable agreement with the theoretical cases.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPME070

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPME074

High Voltage Performance of the Beam Screen of the LHC Injection Kicker Magnets

injection, kicker, vacuum, operation

541

M.J. Barnes, P. Adraktas, G. Bregliozzi, S. Calatroni, P. Costa Pinto, H.A. Day, L. Ducimetière, V. Gomes Namora, T. Kramer, V. Mertens, M. Taborelli
CERN, Geneva, Switzerland

The LHC injection kicker magnets include beam screens to shield the ferrite yokes against wakefields resulting from the high intensity beam. The screening is provided by conductors lodged in the inner wall of a ceramic support tube. The design of the beam screen has been upgraded to overcome limitations and permit LHC operation with increasingly higher bunch intensity and short bunch lengths: the new design also significantly reduces the electric field associated with the screen conductors, decreasing the probability of electrical breakdown. The high voltage conditioning process for the upgraded kicker magnets is presented and discussed. In addition a test setup has been utilized to study flashover, on the inner wall of the ceramic tube, as a function of both applied voltage and vacuum pressure: results from the test setup are presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPME074

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPME076

Upgrade of the SPS Injection Kicker System for LHC High Luminosity Operation with Heavy Ion Beam

injection, ion, kicker, septum

547

T. Kramer, J. Borburgh, L. Ducimetière, B. Goddard, L. Sermeus, J.A. Uythoven, F.M. Velotti
CERN, Geneva, Switzerland

In the context of the LHC High Luminosity Upgrade project a performance upgrade for heavy ions is envisaged. One of the performance limitations is the rise time of the present SPS injection kicker system MKP. A reduction of the rise time for lead ions was studied in line with a modification of the whole injection system. This paper briefly describes the different rise time options studied for an initially proposed dedicated ion kicker system MKP-I, focuses however on a cost effective alternative using the presently installed 12 MKPS magnets connected to a new fast pulse forming line. As only 12 out of the 16 injection kicker magnets would be fast enough to be used in an upgraded system, additional deflection has to be provided by the septa. The beam optics for that variant is highlighted and first requirements for the septum elements are stipulated. The paper concludes with a failure analysis of the proposed scheme.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPME076

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPME081

A Stripline Kicker Driver for the Next Generation Light Source

kicker, high-voltage, simulation, coupling

559

F.M. Niell, N. Butler, M.P.J. Gaudreau, M.K. Kempkes, J. Kinross-Wright
Diversified Technologies, Inc., Bedford, Massachusetts, USA

Funding: US Department of Energy, Award DE-SC00004255
Diversified Technologies, Inc. (DTI) assembled a prototype pulse generator capable of meeting the original specifications for the Next Generation Light Source (NGLS) fast deflector. The ultimate NGLS kicker driver must drive a 50 Ω terminated Transverse Electromagnetic (TEM) deflector blade at 10 kV, with flat-topped pulses and a sustained repetition rate of 100 kHz. Additional requirements of the specification include a 2 ns rise time (10 – 90%), a highly repeatable flattop with pulse width from 5 – 40 ns, and a fall time less than 1 μs (down to 10-4 of the peak value). The driver must also effectively absorb high-order mode signals emerging from the deflector itself. It is envisioned that a scintilla of deflection will be imparted by a symmetric pair of shaped parallel deflection blades, pulsed in opposition at 10 kV. Within the guide, each TEM wave produced by the two pulse generators traverses the guide synchronously with the selected (relativistic) charge packet. The DTI team has designed and demonstrated the key elements of a solid state kicker driver capable of meeting the NGLS requirements, with possible extension to a wide range of fast-pulse applications.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPME081

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPME083

Fast Kicker Systems for ALS-U

kicker, injection, lattice, storage-ring

564

G.C. Pappas, S. De Santis, J.E. Galvin, L.R. Reginato, C. Steier, C. Sun, H. Tarawneh, W.L. Waldron
LBNL, Berkeley, California, USA

Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
Fast kicker systems are required for the proposed upgrade of ALS to a diffraction-limited light source (ALS-U). The main approach is to have multiple stripline kicker magnets driven by inductive adders. The design details of the kicker structures and the inductive adder options will be discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPME083

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPRI065

The Development of a Low Energy Neutron Accelerator for Rebunching Pulsed Neutrons

neutron, experiment, controls, focusing

751

S. Imajo
Kyoto University, Kyoto, Japan
Y. Arimoto
KEK, Ibaraki, Japan
Y. Iwashita
Kyoto ICR, Uji, Kyoto, Japan
M. Kitaguchi
Kyoto University, Research Reactor Institute, Osaka, Japan
Y. Seki
RIKEN Nishina Center, Wako, Japan
H.M. Shimizu
Nagoya University, Nagoya, Japan
S. Yamashita
ICEPP, Tokyo, Japan
T. Yoshioka
Kyushu University, Fukuoka, Japan

Low energy neutrons can be accelerated or decelerated by the technique of AFP-NMR with RF in a gradient magnetic fields. The neutrons have magnetic moments, hence their potential energy are not cancelled before and after passage of magnetic fields and their kinetic energy change finally when their spins are flipped in the fields. Nowadays most measurements of the neutron electric dipole moment (nEDM) are carried out with ultra cold neutrons (UCN), whose kinetic energies are lower than about 300 neV, and with a small storage bottle to reduce the systematic errors. In such experiments highly dense UCNs are desired. The spallation neutron sources generate high-density neutrons at the target, however, the pulsed neutrons with spread velocities are diffused in guide tubes during long beam transport. It is necessary to concentrate UCN temporally upon the bottle by controlling their velocities for nEDM experiments at those facilities. We demonstrated such rebuncher and have been developed the advanced apparatus which makes it possible to handle broader energy range UCN. The design, measured specification of the new rebuncher is described in detail.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI065

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPRI097

Feasibility Studies for the Extraction of both LHC Beams from CERN SPS using a Common Kicker

extraction, kicker, septum, simulation

842

F.M. Velotti, W. Bartmann, C. Bracco, E. Carlier, K. Cornelis, B. Goddard, V. Kain, M. Meddahi
CERN, Geneva, Switzerland

The CERN Super Proton Synchrotron has to fulfil the demanding intensity specifications for the High Luminosity LHC (HL-LHC) era, with a doubling of the presently achieved operational beam intensity. One of the main problems to be addressed is given by impedance-driven beam instabilities. About 40 % of the total measured SPS impedance is due to the kickers, of which the extraction kickers in two of the SPS straight sections are the largest systems. A potential upgrade is explored which would strongly reduce the number of extraction kickers required in the SPS, by performing non-local extraction. In this scenario LHC Beam 1 would be kicked by the extraction kicker in SPS Long Straight Section 4 (LSS4), normally only used for Beam 2, to be extracted in LSS6. The concept and the expected performance of such a scheme are presented along with detailed simulation results.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI097

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUXB01

Recent Progress in 3D Numerical Wakefield Calculations

electron, cavity, insertion, damping

944

W. Bruns
WBFB, Berlin, Germany

The 3D electromagnetic Field Simulator GdfidL computes Wakepotentials on standard CPUs with a Speed comparable to GPU-Based Implementations. This is achieved via Computing only in interesting Cells, having the FD-Coefficients in compressed Form, traversing the Grid in a Cache-friendly Order and applying a blocked Update Scheme which is NuMA-aware. A Dispersion optimised Scheme is described. Fields in dispersive Materials are computed via solving the Equations of the Electron Hulls of the Material. Moving Mesh Computations have the Grid-generation on the Fly.

Slides TUXB01 [16.169 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUXB01

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRO017

HL-LHC Performance with a 200 MHz RF System

luminosity, cavity, electron, simulation

1043

R. Tomás, C.O. Domínguez
CERN, Geneva, Switzerland
S.M. White
BNL, Upton, Long Island, New York, USA

The HL-LHC performance could considerably benefit from having a 200 MHz RF system. This would allow to inject longer bunches with larger bunch intensity from the SPS and to perform bunch length leveling if required. We also consider the possibility of decreasing the crab cavity frequency to increase both virtual peak luminosity and luminous region. Performance estimates of various configurations are presented in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRO017

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRO101

Fast Kicker

kicker, vacuum, simulation

1280

V.V. Gambaryan, A.A. Starostenko
BINP SB RAS, Novosibirsk, Russia

Pulsed deflecting magnet project was worked out in BINP. The kicker design task is: impulsive force value is 1 mT*m, pulse edge is 5 ns, and impulse duration is about 200 ns. The unconventional approach to kicker design was offered. The possibility for set of wires using instead of plates using is considered. This approach allows us to reduce the effective plate surface. In this case we can decrease effects related to induced charges and currents. In the result of modelling optimal construction was developed. It includes 6 wires. The magnet aperture is about 5 cm. Calculated field rise time (about 1.5 ns) satisfies the conditions. Induced current effect reducing idea was confirmed. For configuration with 3 wires pair (with cross section of 2 mm) induced current in one wire is about 10% and in the wall is about 40%. However for design with plates current is about 40% and 20% respectively. Obtained magnet construction allows controlling of high field homogeneity by changing currents magnitudes in wires. In general we demonstrated the method of field optimization. Summary. Optimal kicker design was obtained. Wires using idea was substantiated.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRO101

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPME026

TMCI Thresholds for LHC Single Bunches in the CERN-SPS and Comparison with Simulations

optics, simulation, emittance, kicker

1407

H. Bartosik, G. Iadarola, Y. Papaphilippou, G. Rumolo, B. Salvant, C. Zannini
CERN, Geneva, Switzerland

At the beginning of 2013 an extensive measurement campaign was carried out at the SPS in order to determine the Transverse Mode Coupling Instability thresholds of LHC-type bunches in a wide range of intensities and longitudinal emittances. The measurements were performed in two different configurations of machine optics (nominal and low gamma transition) with the goal to characterize the differences in behavior and performance. The purpose of this paper is to describe in detail the measurement procedure and results, as well as the comparison of the experimental data with HEADTAIL simulations based on the latest SPS impedance model. Beside the impedances of the resistive wall, the beam position monitors (BPMs), the RF cavities, and the flanges, an advanced model of the impedance of the kicker magnets is included, which are found to play a major role in the definition of the stability region of the LHC-type bunches in the two optics configurations studied.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME026

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPME028

Flat Bunches in the LHC

emittance, operation, luminosity, synchrotron

1413

E.N. Shaposhnikova, T. Argyropoulos, P. Baudrenghien, J. F. Esteban Müller, T. Mastoridis, G. Papotti, B. Salvant, H. Timko
CERN, Geneva, Switzerland
C.M. Bhat, A.V. Burov
Fermilab, Batavia, Illinois, USA

A high-harmonic RF system that could serve multiple purposes was proposed for the LHC. Possible applications of the second harmonic RF system include beam stabilisation in the longitudinal plane in the absence of wide-band longitudinal feedback and reduction of bunch peak line-density. Apart from other useful features, flat bunches are expected to produce less beam-induced heating at frequencies below 1 GHz, the frequency region critical for some LHC equipment. The latter, however, can also be achieved by de-populating the bunch centre. This was demonstrated during the dedicated machine development session in the LHC using RF phase modulation. In this paper the results of tests with single bunches and nominal LHC beams are presented and the possible use of this technique in LHC operation is discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME028

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPME029

Identification of High-frequency Resonant Impedance in the CERN SPS

simulation, vacuum, damping, resonance

1416

E.N. Shaposhnikova, T. Argyropoulos, T. Bohl, J.V. Campelo, F. Caspers, J. F. Esteban Müller, A. Lasheen, B. Salvant, H. Timko
CERN, Geneva, Switzerland

The spectrum of long bunches injected into the ring with RF switched off has been used in the SPS in the past to probe the longitudinal coupling impedance. After a large campaign of shielding of 800 inter-magnet vacuum ports in 1999 - 2001, the microwave instability threshold was significantly increased and the high-frequency spectrum of the beam became practically flat, apart from a prominent peak at around 1.4 GHz. As corresponding high-frequency impedance could potentially lead to microwave instability of high intensity bunches observed now at high energies in the SPS, a search of the source of this impedance was launched. Using a combination of impedance simulations and measurements, vacuum flanges that are present in a large quantity in the machine have been identified as a main source of impedance at this frequency. Particle simulations based on the SPS impedance model, which includes this previously unknown impedance, are able to reproduce the characteristics of the bunch spectrum and amplitude growth rates and hence, confirm that the impedance of the vacuum flanges is responsible for the observed spectral peak.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME029

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPME038

Wakefield excitation via a metasurface-loaded waveguide

wakefield, coupling, simulation, radiation

1437

E. Sharples
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
R. Letizia
Lancaster University, Lancaster, United Kingdom

Funding: Work supported by STFC Quota Studentship grant ST/K520133/1
A metallic waveguide loaded with layers of complementary split ring resonator (CSRR) based metasurface is presented for accelerator and coherent source applications. This structure presents left handed behaviour arising from the strong electrical response of CSRRs which form the metasurface and the transverse field confined between the closely positioned metasurface layers. The loaded waveguide structure is known to have a TM-like mode at 5.47GHz suitable for acceleration. In this paper, the results of wakefield simulations are presented and a narrow band excitation identified around the frequency of the TM-like mode, indicating strong coupling between the beam and the field of this mode.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME038

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI021

Impedance Calculation and Simulation of Microwave Instability for the Main Rings of SuperKEKB

simulation, cavity, vacuum, kicker

1600

D. Zhou, T. Abe, T. Ishibashi, Y. Morita, K. Ohmi, K. Shibata, Y. Suetsugu, M. Tobiyama
KEK, Ibaraki, Japan

The SuperKEKB B-factory is now under construction. The designs of the components for the SuperKEKB have mostly been finished. This paper summarises the updated results of longitudinal impedance calculations for various components of the main rings. By summing up all available impedances, a pseudo-Green wake function with bunch length of σ_z=0.5 mm is constructed as an impedance model for consequent studies of collective effects. The results of these studies are also reported in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI023

Simulation of Debunching for Slow Extraction in J-PARC MR

cavity, beam-loading, resonance, simulation

1606

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

The J-PARC MR delivers a proton beam for nuclear physics experiments with slow extraction. The beam is debunched at flat top to obtain a coasting beam by turning off the rf voltage. The controlled emittance blow-up before the flat top has been investigated to mitigate the microwave instability. Beam loading effect can disturb the uniformity of the debunching at the flat top. We describe the results of the particle tracking simulation whole acceleration cycle including the controlled emittance blow-up and the beam loading effect.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI023

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI030

Beam Coupling Impedance of the New Beam Screen of the LHC Injection Kicker Magnets

coupling, kicker, injection, operation

1627

H.A. Day, M.J. Barnes, F. Caspers, E. Métral, B. Salvant, J.A. Uythoven
CERN, Geneva, Switzerland

The LHC injection kicker magnets experienced significant beam induced heating of the ferrite yoke, with high intensity beam circulating for many hours, during operation of the LHC in 2011 and 2012. The causes of this beam coupling impedance were studied in depth and an improved beam screen implemented to reduce the impedance. Results of measurements and simulations of the new beam screen design are presented in this paper: these are used to predict power loss and temperature of the ferrite yoke for operation after long shutdown 1 and for proposed HL-LHC operational parameters.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI030

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI037

Some Features of Wave Distribution in the Thin-Wall Waveguide

vacuum, undulator, shielding, radiation

1641

M. Ivanyan, L.V. Hovakimyan, A. Sargsyan
CANDLE SRI, Yerevan, Armenia

In this report we derive rigorous and approximate dispersion relations for the round resistive thin-wall waveguide. The features of the distributions of dispersion curves of the waveguide axisymmetric TM modes are obtained. Cases of splitting and degeneracy of modes under consideration are detected and regularities of their behaviours are established.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI037

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI041

Study of Collective Beam Instabilities for Sirius

vacuum, undulator, operation, feedback

1653

F.H. de Sá, H.O.C. Duarte, L. Liu, N. Milas, X.R. Resende
LNLS, Campinas, Brazil

In this paper we present the on going work of construction of the Sirius impedance budget and instability threshold estimates for several machine operation scenarios.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI041

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI042

Numerical Study of the Microbunching Instability at UVSOR-III: Influence of the Resistive and Inductive Impedances

electron, wakefield, synchrotron, simulation

1656

E. Roussel, S. Bielawski, C. Evain, C. Szwaj
PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France
M. Adachi, M. Katoh, S.I. Kimura, T. Konomi
UVSOR, Okazaki, Japan
M. Hosaka, Y. Takashima, N. Yamamoto
Nagoya University, Nagoya, Japan
K.S. Ilin, J. Raasch, A. Scheuring, M. Siegel, P. Thoma
KIT, Karlsruhe, Germany
H. Zen
Kyoto University, Kyoto, Japan

At high charge, relativistic electron bunches circulating in storage rings undergo an instability, the so-called microbunching or the CSR (Coherent Synchrotron Radiation) instability. This instability is due to the interaction of the electrons with their own radiation and leads to the formation of microstructures (at millimeter scale) in the longitudinal phase space. Thanks to a new type of detector, based on superconducting thin film YBCO, it is now possible to observe directly these microstructures and follow their temporal evolution*. These experimental observations open a new way to make severe comparisons with theory. Here we present results of the modeling of the dynamics at UVSOR-III using a one dimensional Vlasov-Fokker-Planck equation. We show that to obtain a relatively good agreement between numerical simulations and experiments, we have to take into account several types of impedance such as the shielded CSR impedance but also the resistive and inductive impedances.
* First Direct, Real Time, Recording of the CSR Pulses Emitted During the Microbunching Instability, using Thin Film YBCO Detectors at UVSOR-III, IPAC2014

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI042

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI043

Analysis of Coupled Bunch Instabilities in BESSY-VSR

HOM, cavity, feedback, damping

1659

M. Ruprecht, P. Goslawski, A. Jankowiak, M. Ries, A. Schälicke, G. Wüstefeld
HZB, Berlin, Germany
T. Weis
DELTA, Dortmund, Germany

BESSY-VSR, a scheme where 1.5 ps and 15 ps long bunches (rms) can be stored simultaneously in the BESSY II storage ring has recently been proposed*. The strong longitudinal bunch focusing is achieved by superconducting high gradient RF cavities. This paper presents investigations of coupled bunch instabilities driven by HOMs of superconducting multi cell cavities in BESSY-VSR. Analytical calculations and tracking simulations in time domain are performed in the longitudinal and the transverse planes and factors that influence the threshold currents are being discussed. Suitable candidates of cavities which are presently available or in the phase of design are compared with respect to their instability thresholds.
* G. Wüstefeld, A. Jankowiak, J. Knobloch, M. Ries, Simultaneous Long and Short Electron Bunches in the BESSY II Storage Ring, Proceedings of IPAC2011, San Sebastián, Spain

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI043

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI045

Beam Coupling Impedance Simulation in the Frequency Domain for the SIS100 Synchrotron

coupling, space-charge, dipole, synchrotron

1665

U. Niedermayer, O. Boine-Frankenheim
TEMF, TU Darmstadt, Darmstadt, Germany
O. Boine-Frankenheim
GSI, Darmstadt, Germany

For the quantification of intensity thresholds due to coherent instabilities and beam induced heating in the FAIR synchrotron SIS100 a detailed knowledge of transverse and longitudinal beam coupling impedance is required. Due to the rather long proton and heavy-ion bunches, the relevant spectrum is below 100MHz. For the computation of beam coupling impedances in the low frequency regime, frequency domain methods are more advantageous than (explicit) time domain methods. We show the setup of a 2D finite element code that allows to compute the impedance for arbitrary longituninally homogeneous beam and structure shapes. Perfectly conducting pipes, a dispersive ferrite tube, and thin resistive beam pipe serve as test cases. The influence of the beam velocity on the coupling impedance is studied.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI045

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI047

Electromagnetic Modeling of Open Cell Conductive Foams for High Synchrotron Radiation Rings

synchrotron, coupling, synchrotron-radiation, radiation

1671

S. Petracca, A. Stabile
U. Sannio, Benevento, Italy
A. Stabile
INFN-Salerno, Baronissi, Salerno, Italy

Open cell conductive foams (OCMF) have been recently suggested as an alternative to perforated metal patches for efficiently handling gas desorption from the beam pipe wall due to intense synchrotron radiation, yielding superior performance in terms of residual gas concentration and beam shielding. Experimental work is ongoing to assess their properties, including secondary emission yields and beam coupling impedances. In this communication we attempt a review of the Literature about electromagnetic modeling of OCMF, and outline a general framework for computing the surface impedance of OCMF walls and deriving the longitudinal and transverse beam coupling impedances thereof, based on effective medium theory and electromagnetic reciprocity. A critical analysis of the relevant modeling approximations is included.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI047

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI049

Geometric Beam Coupling Impedance of LHC Secondary Collimators

factory, simulation, HOM, wakefield

1677

O. Frasciello, S. Tomassini, M. Zobov
INFN/LNF, Frascati (Roma), Italy
A. Grudiev, N. Mounet, B. Salvant
CERN, Geneva, Switzerland

Funding: Work supported by European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404
The High Luminosity LHC project is aimed at increasing the LHC luminosity by an order of magnitude. One of the key ingredients to achieve the luminosity goal is the beam intensity increase. In order to keep under control beam instabilities and to avoid excessive power losses a careful design of new vacuum chamber components and an improvement of the present LHC impedance model are required. Collimators are the main impedance contributors. Measurements with beam have revealed that the betatron coherent tune shifts were by about a factor of 2 higher with respect to the theoretical predictions based on the current model. Up to now the resistive wall impedance has been considered as the major impedance contribution for collimators. By carefully simulating their geometric impedance we show that for the graphite collimators with half-gaps higher than 10 mm the geometric impedance exceeds the resistive wall one. In turn, for the tungsten collimators the geometric impedance dominates for all used gap values. Hence, including the geometric collimator impedance into the LHC impedance model enabled us to reach a better agreement between the measured and simulated collimator tune shifts.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI049

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI051

Comparison between Measurements and Orbit Code Simulations for Beam Instabilities due to Kicker Impedance in the 3-GeV RCS of J-PARC

simulation, injection, kicker, acceleration

1683

P.K. Saha, H. Harada, N. Hayashi, H. Hotchi, Y. Shobuda, F. Tamura, M. Yamamoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

The transverse impedance of the extraction kicker magnets is the most dominant beam instability source in the 3-GeV Rapid Cycling Synchrotron of J-PARC. The instability occurs when chromaticity is fully corrected during acceleration but on the other hand no instabilities are observed for a full chromatic correction only at the injection energy even for a beam power up to 500 kW. However, the situation may change for a beam power of 1 MW and also for the upgraded injection beam energy from the present 181 MeV to the 400 MeV, as space charge effect in the non-relativistic region is believed to suppress the growth rate of beam instability. In order to study the kicker impedance in detail, recently we have introduced measured time dependent impedance source in the ORBIT simulation code in a realistic manner. The ORBIT code itself has also been well upgraded and given realistic features for application to synchrotrons. We have also carried out a systematic experimental study for a maximum beam power of 500 kW. In this paper, a detail comparison between measurements and corresponding simulations including 1 MW simulation results are presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI051

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI052

Analysis of Single Bunch Measurements at the ALBA Storage Ring

synchrotron, vacuum, undulator, simulation

1686

T.F.G. Günzel, U. Iriso, F. Pérez
CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
E. Koukovini-Platia, G. Rumolo
CERN, Geneva, Switzerland

Measurements of the vertical single bunch mode detuning and the TMCI threshold at zero chromaticity were carried out and their results were compared to the theoretical expectation. Around 65% of the found mode detuning can be explained by a developed transverse impedance model. A good bunch length parametrisation with current contributed essentially to this result. The analysis of single bunch measurements at non-zero chromaticity will also be presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI052

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI053

Transverse Beam Instabilities in the MAX IV 3 GeV ring

emittance, damping, operation, storage-ring

1689

G. Skripka, P.F. Tavares
MAX-lab, Lund, Sweden
M. Klein, R. Nagaoka
SOLEIL, Gif-sur-Yvette, France

Collective effects in MAX IV 3 GeV storage ring are strongly enhanced by the combination of low emittance, high current and small effective aperture. Three passive harmonic cavities (HC) are introduced to lengthen the bunches, by which beam stabilization is anticipated via decoupling to high frequency wakes, along with Landau damping. The role of the ransverse impedance budget of the MAX IV 3 GeV storage ring as a source of collective beam instabilities was determined. With the help of the macroparticle multi-bunch tracking code mbtrack that directly uses the former as input, we studied the influence of geometric and resistive wall impedance in both transverse planes, as well as that of chromaticity shifting. A fully dynamic treatment of the passive harmonic cavities developed for this study allowed us to evaluate their effectiveness under varying beam conditions.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI053

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI054

FEM Analysis of Beam-coupling Impedance and RF Contacts Criticality on the LHC UA9 Piezo Goniometer

simulation, resonance, experiment, coupling

1692

A. Danisi, R. Losito, A. Masi, A. Passarelli, B. Salvant, C. Zannini
CERN, Geneva, Switzerland

The UA9 piezo-goniometer has been designed to guarantee micro-radians-accuracy angular positioning of a silicon crystal for a crystal collimation experiment in the LHC, and to minimize the impact on the LHC beam-coupling impedance. This paper presents a Finite Element Method (FEM) study of the device, in both parking and operational positions, to evaluate its impact on the LHC impedance budget. The study has been a progressive simulation work, started from the simplification of the original detailed design, and aimed at highlighting the effect of single details (e.g. objects in confining chambers) on the longitudinal and transverse components of beam-coupling impedance. In addition, the shielding contribution of the RF gaskets has been carefully evaluated, with the objective to assess the consequences for operation in case of their failure. Sensitivity analyses to simulation parameters are also performed, in order to test the FEM model robustness. A final word is drawn on the overall device impedance criticality.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI054

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI055

Theoretical Analysis of Metamaterial Insertions for Resistive-wall Beam-coupling Impedance Reduction

insertion, coupling, vacuum, interface

1695

A. Danisi, R. Losito, A. Masi, B. Salvant, C. Zannini
CERN, Geneva, Switzerland

Resistive-wall impedance usually constitutes a significant percentage of the total beam-coupling impedance budget of many accelerator structures (e.g. for LHC, it can be more than 50%). Reduction techniques for resistive-wall components entail high electrical-conductivity coatings. This paper proposes the use of metamaterials, having negative values of magnetic permeability or dielectric permittivity (or both), for sensibly reducing or theoretically nearly cancelling the resistive-wall component of beam-coupling impedance. The proposed approach is developed by means of an equivalent transmission-line model, whose results show the potential reduction of both longitudinal and transverse impedance when using metamaterial insertions. The effects on the real and imaginary part have been singled out. The effectiveness of such materials is discussed both for negative-permittivity and for negative-permeability cases, which actually show different impacts and can be then target of proper engineering. This first-stage study opens the possibility of considering metamaterials for impedance mitigation or for setting up proper experimental setups.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI055

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI056

Beam Measurements of the LHC Impedance and Validation of the Impedance Model

emittance, damping, synchrotron, simulation

1698

J.F. Esteban Müller, T. Argyropoulos, T. Bohl, N. Mounet, E.N. Shaposhnikova, H. Timko
CERN, Geneva, Switzerland

Different measurements of the longitudinal impedance of the LHC done with single bunches with various intensities and longitudinal emittances during measurement sessions in 2011-2012 are compared with particle simulations based on the existing LHC impedance model. The very low reactive impedance of the LHC, with Im(Z/n) around 0.1 Ohm, is not easy to measure. The most sensitive observation is the loss of Landau damping during acceleration, which shows at which energy bunches become unstable depending on their parameters. In addition, the synchrotron frequency shift due to the reactive impedance was estimated following two methods. Firstly, it was obtained from the peak-detected Schottky spectrum. Secondly, a sine modulation in the RF phase was applied to the bunches with different intensities and the modulation frequency was scanned. In both cases, the synchrotron frequency shift was of the order of the measurement precision.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI056

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI057

Review of the Transverse Impedance Budget for the CLIC Damping Rings

damping, wiggler, simulation, operation

1701

E. Koukovini-Platia, G. Rumolo
CERN, Geneva, Switzerland

Single bunch instability thresholds and the associated coherent tune shifts have been evaluated in the transverse plane for the damping rings (DR) of the Compact Linear Collider (CLIC). A multi-kick version of the HEADTAIL code was used to study the instability thresholds in the case where different impedance contributions are taken into account such as the broad-band resonator model in combination with the resistive wall contribution from the arcs and the wigglers of the DR. Simulations performed for positive values of chromaticity showed that higher order bunch modes can be potentially dangerous for the beam stability.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI057

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI058

Impedance Studies of the Dummy Septum for CERN PS Multi-turn Extraction

extraction, septum, simulation, synchrotron

1704

S. Persichelli, O.E. Berrig, M. Giovannozzi, J. Herbst, J. Kuczerowski, M. Migliorati, B. Salvant
CERN, Geneva, Switzerland

A protection septum has been installed in the CERN PS section 15 in order to mitigate irradiation of the magnetic septum 16 for fast extractions towards the SPS. Impedance studies have been performed, showing that beams circulating in the septum during extraction generate sharp resonances in the coupling impedance. Impedance measurements with the wire technique have been performed, showing a good agreement with simulations. Instability rise times of trapped modes have been evaluated and compared to extraction duration. Solutions for reducing the impact on the stability of the beam have been considered.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI058

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI059

The Proton Synchrotron Transverse impedance model

simulation, kicker, space-charge, proton

4096

S. Persichelli, N. Biancacci, S.S. Gilardoni, M. Migliorati, E. Métral, B. Salvant
CERN, Geneva, Switzerland

The current knowledge of the transverse impedance of the CERN Proton Synchrotron (PS) has been established by theoretical computations, electromagnetic simulations and beam-based measurements at different energies. The transverse coherent tune and phase advance shifts as a function of intensity have been measured in order to evaluate the total effective transverse impedance and its distribution in the accelerator. In order to understand the beam dynamics, the frequency dependence of the impedance budget has also been evaluated considering the individual contribution of several machine devices. 3D models of many PS elements have been realized to perform accurate impedance simulations, while resistive wall and indirect space charge impedances have been evaluated with theoretical and numerical computations. Finally comparisons between the total budget and the measurement results are presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI059

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI060

Impedance Studies for the PS Finemet® Loaded Longitudinal Damper

simulation, cavity, kicker, synchrotron

1708

S. Persichelli, M. Migliorati, M.M. Paoluzzi, B. Salvant
CERN, Geneva, Switzerland

The impedance of the Finemet® loaded longitudinal damper cavity, installed in the CERN Proton Synchrotron straight section 02 during the Long Shutdown 2013-2014, has been evaluated. Time domain simulations with CST Particle Studio have been performed in order to get the longitudinal and transverse impedance of the device and make a comparison with the longitudinal impedance that was measured for a single cell prototype.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI060

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI061

Power Loss Calculation in Separated and Common Beam Chambers of the LHC

electron, coupling, simulation, cryogenics

1711

C. Zannini, G. Iadarola, G. Rumolo
CERN, Geneva, Switzerland
G. Iadarola
Naples University Federico II, Science and Technology Pole, Napoli, Italy

The performance of 25 ns beams in the LHC is strongly limited by the electron cloud. To determine the amount electron cloud in the cold sections of the machine, it is very important to be able to disentangle the beam induced heating due to the beam coupling impedance from that attributable to electron cloud. This paper will focus on the calculation of the first contribution. First, the impedance model used for the calculation of the beam induced power loss is briefly discussed. Then, the methods for the calculation of the beam induced power loss in regions with one or two beams are also described. Finally, the calculated power loss is compared with the measured heat loads for both 25 and 50 ns beams in both the LHC arcs and in the inner triplets (ITs).

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI061

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI062

The Mode Matching Technique Applied to the Transverse Beam Coupling Impedance Calculation of Azimuthally Symmetric Devices of Finite Length

cavity, coupling, simulation, vacuum

1714

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

The infinite length approximation is often used to simplify the calculation of the beam coupling impedance of accelerator elements. This is expected to be a reasonable assumption for devices whose length is greater than the transverse dimension but may be a less accurate approximation for segmented devices. In this contribution we present the extension of the study of the beam coupling impedance of a finite length device to the transverse plane. In order to take into account the finite length, we decompose the fields in the cavity and in the beam pipe into a set of orthonormal modes and apply the Mode Matching method to obtain the impedance. To validate our method, we will present comparisons between analytical formulas and 3D electromagnetic CST simulations.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI062

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI063

Electromagnetic Simulations for Non-ultrarelativistic Beams and Application to the CERN Low Energy Machines

coupling, simulation, space-charge, vacuum

1718

C. Zannini, N. Biancacci, T.L. Rijoff, G. Rumolo
CERN, Geneva, Switzerland
T.L. Rijoff
TU Darmstadt, Darmstadt, Germany

In the framework of the PS-Booster upgrade project an accurate impedance model is needed in order to determine the effect on the beam stability and assess the impact of the new devices to be installed in the machine. CST 3-D EM simulations are widely used to estimate the impedance contribution of the different devices along the CERN accelerator complex. Unlike the highly relativistic case, in which the reliability of the EM solver has been proved in many specific cases by comparing simulations with analytical results, the nonrelativistic case has been so far not yet benchmarked. In order to use systematically CST 3-D EM simulations for the PS-Booster, or even lower energy machines like the antiproton decelerator ELENA, a validation campaign has been carried out. The main complication to single out the beam coupling impedance, as resulting from the interaction of the beam with the surroundings, consisted of removing reliably the strong contribution of the direct space charge of the source bunch, which is included in the EM calculation. The simulation results were then benchmarked with the analytical results for the case of a PEC cylindrical tube and of a ferrite loaded kicker.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI063

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI070

Analysis of Coupled-bunch Instabilities in the NSLS-II Storage Ring

HOM, cavity, storage-ring, damping

1727

G. Bassi, A. Blednykh, F. Gao, J. Rose
BNL, Upton, Long Island, New York, USA

We discuss coupled-bunch instabilities thresholds for the NSLS-II Storage Ring. In particular, we analyze thresholds from the High Order Modes (HOMs) of the PETRA-III 7-cell cavity. Beam dynamics simulations with the code OASIS, using the measured HOMs, will be compared with machine studies.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI070

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI071

Transverse Impedance Measurement in RHIC and the AGS

injection, betatron, proton, luminosity

1730

N. Biancacci
CERN, Geneva, Switzerland
M. Blaskiewicz, Y. Dutheil, C. Liu, K. Mernick, M.G. Minty, S.M. White
BNL, Upton, Long Island, New York, USA

The RHIC luminosity upgrade program aims for an increase of the polarized proton luminosity by a factor 2. To achieve this goal a significant increase in the beam intensity is foreseen. The beam coupling impedance represents a source of detrimental effects for beam quality and stability at high bunch intensities. In this paper, we evaluate a new global transverse impedance in both RHIC and the AGS with recent measurements of tune shift as a function of bunch intensity. The results are compared to past measurements and present impedance model.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI071

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI087

A Wideband Slotted Kicker Design for SPS Transverse Intra-bunch Feedback

kicker, feedback, coupling, interface

1772

J.M. Cesaratto, J.D. Fox, C.H. Rivetta
SLAC, Menlo Park, California, USA
D. Alesini, A. Gallo, M. Zobov
INFN/LNF, Frascati (Roma), Italy
S. De Santis
LBNL, Berkeley, California, USA
W. Höfle
CERN, Geneva, Switzerland

Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research Program (LARP) and by the EU FP7 HiLumi LHC - Grant Agreement 284404.
In order for the SPS to meet the beam intensity demands for the HL-LHC upgrade, control and mitigation of transverse beam instabilities caused by electron cloud and TMCI will be essential. For this purpose a wideband intra-bunch feedback method has been proposed, based on a 4 GS/s front end data acquisition and processing, and on a back end frequency response extending to at least 1 GHz. A slotted type kicker, similar to those used for stochastic cooling, as well as an array of stripline kickers have been considered as the terminal elements of the feedback system. A slotted TEM type kicker has been designed fulfilling the bandwidth and kick strength requirements for the SPS application. In this paper we present an updated version of the design and electromagnetic characteristics, leading into the mechanical design and construction of the kicker occurring later this year.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI087

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPRO016

Injection/Extraction Kicker for the ALS-U Project

kicker, injection, extraction, coupling

1977

S. De Santis, W. Barry, S. Kwiatkowski, T.H. Luo, G.C. Pappas, L.R. Reginato, D. Robin, C. Steier, C. Sun, H. Tarawneh, W.L. Waldron
LBNL, Berkeley, California, USA

Funding: Work supported by the US Department of Energy under Contract no. DEAC02-05CH11231
The ALS-II proposal consists in the upgrade of the existing Advanced Light Source at LBNL to a new ultra-low emittance lattice for production of diffraction-limited soft x-rays. In order to compensate for the reduced beam lifetime we intend to operate the machine in continuous top-off mode, where one of several bunch trains is extracted every 30-60 seconds and swapped with a fresh train from the accumulator ring, which is injected on axis without perturbing the circulating beam. In this paper we present a possible design for the injection/extraction kicker based on matched stripline electrodes. The main parameters of such a kicker are discussed in reference to the minimum gap between trains, the storage ring lattice, and the characteristics of a suitable pulser. We also present results from 3D electromagnetic modeling of the proposed kicker performed to evaluate its rise and fall time and field uniformity characteristics.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRO016

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPRO064

Recent Results of the HESR RF System

operation, cavity, electron, accumulation

2094

R. Stassen, F.J. Etzkorn, R. Greven, T. Katayama, R. Maier, G. Schug, H. Stockhorst
FZJ, Jülich, Germany

The FAIR complex (Facility for Antiprotons and Ion Research) will be built in different stages. Due to the postponed RESR in the first stage, both RF-cavities of the HESR have to operate in different modes to achieve the required beam quantity and quality. The RF-system of the HESR will now consists of two identical cavities with a common low-level RF control (LLRF). Both cavities will be driven by low noise solid state amplifiers. Each cavity contains of one gap and two tanks operating in push-pull mode and each tank will house 6 ring cores wound of modern magnetic nano-alloy ribbon. Meanwhile all ring cores were delivered and first results at low power and at high power will be presented. The construction of the new air cooling concept is now in the final stage.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRO064

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPME007

Multi-Bunch Generator Cavity

cavity, electron, cathode, coupling

2267

E.A. Savin, S.V. Matsievskiy, Ya.V. Shashkov, N.P. Sobenin
MEPhI, Moscow, Russia
A.A. Zavadtsev
Nano, Moscow, Russia

The concept of the six bunch generator cell for the washers and diaphragm loaded structure (Moscow Meson Factory) power supply is proposed. The required power is 0.8 MW on the 991 MHz frequency. The high-voltage electron gun produces electron bunches and puts them into the cylindrical resonator tuned to TE02 mode and operating frequency. Bunches produces RF field that takes energy from the following bunches and then energy transfer to the accelerating structure throw the tuned coupling system.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME007

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPME008

72 MHz Solid-state Amplifier Power Test

operation, cavity, cyclotron, controls

2270

A.Yu. Smirnov, E.V. Ivanov, A.A. Krasnov, S.A. Polikhov, I. Řežanov
Siemens Research Center, Moscow,, Russia
G.B. Sharkov
Siemens LLC, Moscow, Russia

In this paper, we present the performance of 72 MHz 18 kW RF power source developed for cyclotrons. The machine is equipped with 9 class-AB power amplifier modules (each with up to 2 kW output) based on highly reliable LDMOS transistors. The whole system is arranged inside a single 19" cabinet and has coaxial 50 Ω output. The test environment and high power measurement results are described.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME008

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPME012

Solid-State Amplifier Development at FREIA

operation, cryomodule, network, vacuum

2282

D.S. Dancila, A. Rydberg
Uppsala University, Department of Engineering Sciences, Uppsala, Sweden
A. Eriksson, V.A. Goryashko, L.F. Haapala, R.J.M.Y. Ruber, R. Wedberg, R.A. Yogi, V.G. Ziemann
Uppsala University, Uppsala, Sweden

The FREIA laboratory is a Facility for REsearch Instrumentation and Accelerator development at Uppsala University, Sweden, constructed recently to test and develop superconducting accelerating cavities and their high power RF sources. FREIA's activity target initially the European Spallation Source (ESS) requirements for testing spoke cavities and RF power stations, typically 400 kW per cavity. Different power stations will be installed at the FREIA laboratory. The first one is based on vacuum tubes and the second on a combination of solid state modules. In this context, we investigate different related aspects, such as power generation and power combination. For the characterization of solid-state amplifier modules in pulsed mode, at ESS specifications, we implemented a Hot S-parameters measurement set-up, allowing in addition the measurement of different parameters, such as gain and efficiency. We developed also a new solid-state amplifier module at 352 MHz, using commercially available LDMOS transistors. Preliminary results show a drain efficiency of 71% at 1300 W pulsed output power.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME012

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPME019

Heat Distribution Analysis of Planar Baluns for 1kW Solid-state Amplifiers and Power Combining for 1.8kW

operation, storage-ring, booster, controls

2294

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

Solid-state transmitter for booster and storage ring in synchrotron would be composed of hundreds of amplifier modules. The amplifier module is biased at class AB and constructed in push-pull operation. Recent trend of amplifier module design features higher power up to 800 Watts and equipped planar balun (balance-unbalance converter) for push-pull operation. In NSRRC, the exclusive round planar design has encounter high temperature situation at kW range. Therefore, further study on this thermal condition is carried out in this study. Four types of planar balun design and two laminate materials are used for heat analysis. The typical coaxial balun is also applied on actual amplifier design. The results bring the better design with proper laminate choice and leads to acceptable thermal distribution with 1kW output power at 500MHz. Besides, for a more compact module with higher output power, the combination of two chips on the same circuit reaching 1.8kW is also presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME019

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPME033

Search for New e-cloud Mitigator Materials for High Intensity Particle Accelerators

electron, experiment, vacuum, embedded

2332

R. Cimino, S.T. O'connor, A.L. Romano
INFN/LNF, Frascati (Roma), Italy
V. Baglin, G. Bregliozzi, R. Cimino
CERN, Geneva, Switzerland
M.R. Masullo
INFN-Napoli, Napoli, Italy
S. Petracca, A. Stabile
INFN-Salerno, Baronissi, Salerno, Italy

Electron cloud is an ubiquitous effect in positively charged particle accelerators and has been observed to induce unwanted detrimental impacts on beam quality, stability, vacuum etc. A great effort has been recently devoted to the search of new material morphology and/or coatings which can intrinsically mitigate beam instabilities deriving from electron cloud effects. In this context, we present some characterization of Cu foams, available from the market, and their qualification in terms of their vacuum behavior, impedance, secondary electron yield, gas desorption etc. More experimental effort is required to finally qualify foams as a mature technology to be integrated in accelerator environments. But, our preliminary results suggests that, when compatible with geometrical constrains, Cu foams can be utilized when low desorption yields are required and as e-cloud moderator in future particles accelerators.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME033

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPME050

High Frequency Electromagnetic Characterization of NEG properties for the CLIC Damping Rings

simulation, damping, network, experiment

2384

E. Koukovini-Platia, G. Rumolo, C. Zannini
CERN, Geneva, Switzerland

Coating materials will be used in the CLIC damping rings (DR) to suppress two-stream effects. In particular, NEG coating is necessary to suppress fast beam ion instabilities in the electron damping ring (EDR). The electromagnetic (EM) characterization of the material properties up to high frequencies is required for the impedance modeling of the CLIC DR components. The EM properties for frequencies of few GHz are determined with the waveguide method, based on a combination of experimental measurements of the complex transmission coefficient S21 and CST 3D EM simulations. The results obtained from a NEG coated copper (Cu) waveguide are presented in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME050

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPME064

Comparison of an Analytical Model for Lossy Transmission Lines with Measurement Data

LLRF, radio-frequency, feedback, network

2424

N. Schmitt
TEMF, TU Darmstadt, Darmstadt, Germany
H. Klingbeil
GSI, Darmstadt, Germany

This paper deals with the analytical modeling of lossy coaxial transmission lines in the frequency range from 100 kHz to 50 MHz with focus on corrugated coaxial lines with polyethylene foam as dielectric. The considered transmission lines are used in low-level radio frequency (LLRF) systems (< 5 MHz) at GSI. These applications require a high precision in amplitude and phase for the transmitted signals where a detailed knowledge of the line properties is of significant interest. As the corresponding data sheets do not provide appropriate data, the necessary data have been computed. The obtained results from the purely analytical model were then compared with previous measurements for validation purposes.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME064

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPME078

Experimental Test of the Prototype LLRF Systems for PAL-XFEL

LLRF, klystron, target, feedback

2462

J. Hu, H. Heo, J.H. Hong, W.H. Hwang, H.-S. Kang, H.-S. Lee, C.-K. Min
PAL, Pohang, Kyungbuk, Republic of Korea

Two prototype LLRF systems were developed in collaboration with Pohang Accelerator Laboratory(PAL) and domestic companies. They are focused on the control of single klystron system to obtain mainly analogue performance. The low power test of the developed LLRF showed good performance previously. We experimentally tested LLRF in the klystron systems to see performance in the high power situation. They showed performance around the prototype specification for short time and relatively long time. During test some bugs are discovered and fixed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME078

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPRI008

First Cavity Design Studies for the BESSY-VSR Upgrade Proposal

cavity, HOM, damping, coupling

2493

A. Neumann, A. Burrill, P. Goslawski, A. Jankowiak, J. Knobloch, M. Ries, M. Ruprecht, A.V. Vélez, G. Wüstefeld
HZB, Berlin, Germany

Funding: Work supported by German Bundesministerium für Bildung und Forschung and Land Berlin
Recently HZB proposed an upgrade of the 3rd generation synchrotron light source BESSY II allowing simultanous long and short pulse operation*. For this scheme to work superconducting higher harmonic cavities of the fundamental 500 MHz at two frequencies need to be installed in the BESSY II storage ring. Given an appropiate choice of the higher harmonics the resulting gradient leads to a beating effect of the effective longitudinal focussing voltage at the stable fix points resulting in different bunch lengths in subsequent buckets. This project places stringent requirements on the cavity performance, as high accelerating fields, excellent HOM damping capabilities and high reliability as they will operate in a 300 mA 24/7 user facility. In this paper we describe the requirements for the cavity design and first designs steps.
* G. Wüstefeldt et al., Simultaneous Long and Short Electron Bunches in the BESSY II Storage Ring, Proc. of IPAC'11, San Sebástian, Spain

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI008

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPRI049

Optimization of Window Position on Diamond SCRF Cavities

cavity, operation, coupling, simulation

2592

S.A. Pande, C. Christou
DLS, Oxfordshire, United Kingdom

The Diamond storage ring uses CESR type superconducting cavities. These cavities have a fixed coupling resulting in fixed Qext which is considerably higher than the optimum. We use 3 stub tuners to match the cavities under these non-optimum conditions. Diamond Cavity-1 will soon be refurbished. This opportunity could be used to lower the Qext on the cavity. One of the options is to modify the coupling tongue geometry along with a matching section. This may require cutting off the beam tube with the coupler for rework or it may need to be newly fabricated. We investigated another option to lower the Qext of the cavity by optimising the location of the window with respect to the cavity, maintaining the same coupling tongue geometry. The height of the waveguide on the vacuum side of the window differs from that of the coupling waveguide on the cavity resulting in a step. The location of window with respect to the cavity makes a significant difference to the ultimate Qext obtained after putting the window in place. In this paper we present the results of our numerical simulations comparing the present and the proposed window position under different operating conditions.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI049

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPRI050

Development and Test Results of a Quasi-waveguide Multi-cell Resonator

cavity, niobium, cathode, HOM

2595

Z.A. Conway, A. Barcikowski, S.M. Gerbick, M. Kedzie, M.P. Kelly, J.S. Kerby, S.H. Kim, S.V. Kutsaev, R.C. Murphy, A. Nassiri, P.N. Ostroumov, T. Reid, T.L. Smith, A. Zholents
ANL, Argonne, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Offices of Nuclear Physics and Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
This paper reports the successful fabrication and test results of a novel 2815 MHz superconducting deflecting cavity operating in a TE-mode trapped in a quasi-waveguide structure with extremely high shunt impedance. The waveguide structure of this cavity allows for the free propagation of all higher order modes (HOMs) out of the cavity via the beam ports, eliminating the need for HOM dampers inside the cavity when operated with high beam current. The absence of HOM dampers greatly simplifies the cavity fabrication and operation at cryogenic temperatures. This cavity with its high shunt impedance is ideal for the spatial rotation of short bunches in a small physical space, a requirement for the generation of sub-picosecond short pulse x-rays in electron storage rings or luminosity upgrades of colliders. Results characterizing the fabrication accuracy and precision, the RF performance at 2 K, and frequency tuning considerations will be discussed here.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI050

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPRI073

High Order Modes Survey and Mitigation of the CEBAF C100 Cryomodules

HOM, cavity, cryomodule, survey

2660

J. Guo, M. Stirbet, H. Wang, S. Wang
JLab, Newport News, Virginia, USA

Funding: Funding Agency: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
Ten new C100 cryomodules have been installed for the CEBAF 12GeV upgrade in the last few years. The high order modes (HOM) of these cryomodules need to be controlled to avoid beam breakup (BBU) instability. We surveyed the HOM for all the 80 cavities of the C100 modules in both the JLab cryomodule test facility (CMTF) and the CEBAF tunnel. Additional measures such as waveguide filters were applied to bring down out of spec modes. In this paper, we will present the HOM survey setup and results. The mitigation measures and their effects will also be discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI073

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THYA01

Control and Application of Beam Microbunching in High Brightness Linac-driven Free Electron Lasers

laser, FEL, electron, radiation

2789

G.V. Stupakov
SLAC, Menlo Park, California, USA

The remarkable properties of coherent radiation from free-electron lasers (FELs) are due to the current modulation in the beam with the modulation period equal to the radiation wavelength. This modulation is developed as a result of a beam instability when the beam propagates in a long FEL undulator, and requires a beam with a high-peak current, small emittance and a small energy spread. Unfortunately the same beam qualities make it a subject to a so-called microbunching instability at a much longer scale than the radiation wavelength. It is driven by the space charge and CSR impedances in the machine and develops during the beam acceleration in the linac, compression, and transport to the undulator. If not controlled, the microbunching instability influences dramatically the FEL performance and in the worst case can even ruin the lasing. In the presentation we will review the mechanism behind the microbunching instability, the suppression methods used in existing facilities as well as possible future developments and concepts.

Slides THYA01 [5.631 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THYA01

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME012

Results of the High Power Test of the 325 MHz 4-Rod RFQ Prototype

rfq, linac, proton, dipole

3235

B. Koubek, H. Podlech, A. Schempp, J.S. Schmidt
IAP, Frankfurt am Main, Germany

For the FAIR proton linac at GSI a 325 MHz 4-rod RFQ prototype has been built. On this prototype RF measure- ments have been carried out. After low power conditioning in cw mode the structure was high power tested in pulsed mode. During the performance tests the 6 stem prototype was optimized and has shown the feasibility of a dipole free 4-rod RFQ at high frequencies and was testet up to 120 kW per meter. In this tests the input power and the electrode voltage was observed using gamma spectroskopy. From this the shunt impedance was calculated and compared to other methods of measurements. The power test results are presented in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME012

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME062

Status of the J-PARC Ring RF Systems

cavity, operation, proton, extraction

3376

M. Yoshii, M. Nomura, T. Shimada, F. Tamura, M. Yamamoto
KEK/JAEA, Ibaraki-Ken, Japan
E. Ezura, K. Hara, K. Hasegawa, C. Ohmori, K. Takata, M. Toda
KEK, Ibaraki, Japan
A. Schnase
GSI, Darmstadt, Germany

The high intensity proton accelerator complex (J-PARC) consists of the Linac, the 25Hz rapid cycling synchrotron (RCS) and the 50GeV main synchrotron (MR). During the long shutdown of 2013, the Linac energy was upgraded from 181MeV to the design value of 400MeV. In the RCS, we have installed the last 12th RF system. In operation from January 2014, beam commissioning aimed at 1 MW operation will be started. In the MR, the upgrade plan of the beam power, realizing by raising the repetition, has been started. For this reason the accelerating voltage must be increased, and all MR RF systems will be replaced with more efficient systems. A new magnetic alloy material (FT3L) has been developed. Manufacturing of the FT3L accelerating cavities has proceeded. It becomes possible to increase the accelerating voltage from 280 kV to 540 kV, using the new cavities in combination with the existing RF power supplies. We have started the developments of a 2nd harmonic system loaded with air-cooled FT3L cores and a high-Q VHF cavity system, too. Both systems are used for longitudinal dilution increase the bunching factor of the circulating high intensity proton beam.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME062

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME065

Beam Test of the CERN PSB Wide-band RF System Prototype in the J-PARC MR

feedback, cavity, beam-loading, extraction

3385

F. Tamura
JAEA/J-PARC, Tokai-mura, Japan
K. Hasegawa, C. Ohmori, M. Yoshii
KEK, Tokai, Ibaraki, Japan
M.M. Paoluzzi
CERN, Geneva, Switzerland

In the framework of the LHC Injectors Upgrade project (LIU), a complete replacement of the existing narrow-band rf systems of CERN PSB with wide-band magnetic alloy (MA) loaded rf systems is in progress. A single gap MA loaded rf system prototype, which uses solid-state power amplifier and includes fast rf feedback for beam loading compensation, has been installed in the J-PARC MR to investigate the system behavior with high intensity proton beams. We report the wake voltage measurement results with and without fast rf feedback. In addition to the fast feedback, the rf feedforward method is under consideration to compensate the heavy beam loading more effectively. Preliminary beam test results with feedforward are also presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME065

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME080

Reflective Streak Camera Bunch Length Measurements at the Australian Synchrotron

cavity, optics, storage-ring, synchrotron

3421

M.J. Boland, Y.E. Tan
SLSA, Clayton, Australia
T.M. Mitsuhashi
KEK, Ibaraki, Japan

The bunch length of the 3 GeV electron storage ring at the Australian Synchrotron has been measured using reflective input optics feeding a streak camera. An Offner optical design was employed to reduce the chromatic broadening of the input optics of the streak camera. Using the reflective input optics the bunch length is measured to be 15% shorter than with the refractive input optics. The measured bunch length is now in good agreement with the model of the storage ring and the values are being used for calibration, monitoring and optimisation of the machine. The results of studies to characterise the streak camera shall also be presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME080

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME096

Goubau Line Beam Instrumentation Testing, The Benefits

instrumentation, resonance, electromagnetic-fields, electronics

3462

F. Stulle, J.F. Bergoz
BERGOZ Instrumentation, Saint Genis Pouilly, France
J. Musson
JLab, Newport News, Virginia, USA

At JLab and Bergoz Instrumentation Goubau lines are used for beam instrumentation testing. A Goubau line differs fundamentally from standard bench testing techniques in the way it produces the electromagnetic fields which interact with the DUT. This allows to acquire complementary information about DUT characteristics. Consequently, we improve our knowledge about the DUT. At JLab BPM responses have been successfully mapped and at Bergoz Instrumentation high frequency behavior of current transformers is under study. We present results, highlight benefits and outline ideas for future studies of additional accelerator components.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME096

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME100

The Mechanical Design of the BPM Inter-tank Section for P-linac at FAIR

linac, cavity, proton, pick-up

3474

M.H. Almalki, R. M. Brodhage, P. Forck, W. Kaufmann, O.K. Kester, P. Kowina, T. Sieber
GSI, Darmstadt, Germany
M.H. Almalki, R. M. Brodhage, O.K. Kester
IAP, Frankfurt am Main, Germany
M.H. Almalki
KACST, Riyadh, Kingdom of Saudi Arabia
J. Balaguer
CEA/IRFU, Gif-sur-Yvette, France
P. Girardot, C.S. Simon
CEA/DSM/IRFU, France

At the planned Proton LINAC at the FAIR facility, four-fold button Beam Position Monitor (BPM) will be installed at 14 locations along the 30 m long FAIR p-LINAC. The LINAC comprises of crossbar H-mode (CH) cavity to accelerate a 70 mA proton beam up to 70 MeV at frequency of 325 MHz. At four locations, the BPMs will be an integral part of the inter-tank section between the CCH and CH cavities within an evacuated housing. As the BPM centre is only 48 mm apart from the upstream cavity boundary, the rf-background at the BPM position, generated by the cavity must be evaluated. In this paper the mechanical design of the BPM for the inter-tank section is presented and the rf-noise at the BPM location is discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME100

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME101

Considerations for a Cavity-Based Position-Sensitive Heavy Ion Detector for the CR at FAIR

cavity, ion, heavy-ion, simulation

3477

X. Chen, P. Hülsmann, Yu.A. Litvinov, F. Nolden, M.S. Sanjari, M. Steck, T. Stöhlker
GSI, Darmstadt, Germany
X. Chen
Heidelberg University, Heidelberg, Germany
Yu.A. Litvinov
MPI-K, Heidelberg, Germany
J. Piotrowski
AGH University of Science and Technology, Kraków, Poland
T. Stöhlker
HIJ, Jena, Germany

Funding: Work funded by the European Commission (PITN-GA-2011-289485), the Alliance Program of the Helmholtz Association (HA216/EMMI), the Helmholtz-CAS Joint Research Group (HCJRG-108), the BMBF (05E12CD2).
The Facility for Antiproton and Ion Research (FAIR) is a complex yet ongoing project which will allow for a broad range of experimental physics programs as well as a variety of material and medical applications. Being a heavy ion storage ring at FAIR, the Collector Ring (CR) is perfectly suitable for scientific investigations on fundamental properties – such as masses and lifetimes – of short-lived radioactive nuclei when it operates in isochronous mode. To fulfill stringent experimental requirements, a compatible heavy ion detector sensitive to beam intensities and positions is highly demanded. In this paper we present a conceptual design of cavity-based Schottky noise pickup to achieve non-destructive detections of stored particles. Computer-aided simulations follow immediately to justify the feasibility of such a design.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME101

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME131

A Multi-conductor Transmission Line Model for the BPMs

pick-up, beam-transport, induction, framework

3550

T. Toyama
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

We have developed an accurate and efficient analysis method with a multi-conductor transmission line model for beam position monitors (BPMs). This method combines the two-dimensional electrostatic analysis including beams in the transverse plane and the transmission line analysis in the longitudinal direction. The loads are also included in the boundary condition of the transmission line analysis. Calculation of 2D electrostatic fields can be easily performed with the boundary element method. The BPM response to a beam is compared with that to a stretched wire.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME131

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME144

Stripline Beam Position Monitor for THz Source Based FEL

brilliance, electronics, linac, controls

3590

J. Xu, L. Li, J. Liu, P. Lu, Y.J. Pei, B.G. Sun, K. Tang, J.G. Wang, F.F. Wu, H. Xu, Y.L. Yang, Z.R. Zhou, J.Y. Zou
USTC/NSRL, Hefei, Anhui, People's Republic of China

A 14MeV Linac with both the micro-pulse repetition rate 2856MHz and the macro-pulse width 6us for the THz Source Based FEL was proposed. In order to measure the beam position, a stripline beam position monitor (BPM) was designed, and a commercial BPM electronics Libera Brilliance Single Pass was adopted. As the input carrier frequency of the BPM electrode signal is 2856MHz, but the operating frequency of the Libera Brilliance Single Pass is 500MHz, so a front-end electronics was needed before the electrode signals feed into Libera Brilliance Single Pass. The front-end electronics was designed to make the BPM electrode signals of 2856MHz convert to 500MHz.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME144

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME145

BPM Signal Channel Characterization Test based on TDR for HLS II Storage Ring

storage-ring, pick-up, simulation, electron

3593

J.J. Zheng, C. Cheng, P. Lu, Q. Luo, B.G. Sun, Y.L. Yang, Z.R. Zhou
USTC/NSRL, Hefei, Anhui, People's Republic of China

A new BPM system on the upgraded Hefei light source (HLSII) storage ring is installed. Before the machine commissioning, the BPM system should be carefully tested, such as the conductivity and integrity of BPM signal channels from button electrodes to digital beam position processors (pickups, cables and connectors). This paper presents an experience of signal channel test based on time domain reflection (TDR) for HLS II storage ring BPM system. Basing on the wave propagation method, an analytic expression for the signal from TDR on BPM signal channel is briefly introduced. The conductivity and integrity of the BPM signal channels can be verified by comparing the TDR waveform to theory signal. All the BPM signal channels are tested by the TDR in order to verify electronic characteristic and the usability. And some breakdowns are analysed and handled.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME145

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME172

Experimental Results from the Characterization of Diamond Particle Detectors with a High Intensity Electron Beam

detector, electron, experiment, radiation

3671

F. Burkart, R. Schmidt, O. Stein, D. Wollmann
CERN, Geneva, Switzerland
E. Griesmayer
CIVIDEC Instrumentation, Wien, Austria

Understanding the sources of ultra-fast failures, with durations of less than 3 LHC turns, is important for a safe operation of the LHC, as only passive protection is possible in these time scales. Diamond particle detectors with bunch-by-bunch resolution and high dynamic range have been successfully used to improve the understanding of some new ultra-fast loss mechanisms discovered in the LHC. To fully exploit their potential, diamond detectors were characterized with a high-intensity electron beam (10⁵ to 1010 electrons per shot). For the first time their efficiency and linearity has been measured in such a wide range of intensities. In this paper the experimental setup will be described and the signals of the different detectors will be discussed. Finally, future applications of these detectors in high-radiation applications will be discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME172

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME182

Precise Instruments for Bunch Charge Measurement

pick-up, resonance, monitoring, vacuum

3703

A. Kalinin
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

For the pulse charge q injected into a capacitor of a parallel resonating circuit, the oscillation voltage V on a series resistor R is V=qwRexp(wt/2Q)sin(wt–1/2Q), t>τ, where w is the resonance frequency, Q>>1 is the quality factor and τ<<1/w is the pulse length. Of the two main parameters, R is known, and w can be found directly from the signal above. The quality factor contribution is low, and its rough estimation is sufficient to retain voltage accuracy. The observations above open a possibility of precise bunch charge measurement. We describe a bunch charge monitor that is a cavity with a lump capacitor as a low impedance coaxial line connected to a gap in the vacuum pipe. An LC electronic circuit is also presented. It integrates the single bunch current delivered by a Faraday Cup, or a Wall Current Monitor, or a Fast Current Transformer. The circuit has w~30MHz, Q~20, and with a Faraday Cup, the lower range is 10pC/V and the noise floor is about 20fC. Several such circuits are in use on the VELA injector in Daresbury Laboratory.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME182

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPRI040

Study of Geometrical Parameters and their Tolerances in Optimization of Accelerating Cells of Side Coupled Linac

cavity, linac, simulation, electron

3850

S. Zarei
Nuclear Science and Technology Research, InstituteRadiation Application School, Tehran, Iran
F. AbbasiDavani, S. Ahmadiannamin, F. Ghasemi
sbu, Tehran, Iran
M. Lamehi Rashti
IPM, Tehran, Iran

After choosing the suitable geometry for accelerating cavity, evaluation of geometrical parameters effects on radio frequency characteristics is essential. In this paper after study of priority of geometrical parameters in optimization of accelerating cells of Side Coupled Linac, according to obtained results, new design of s-band accelerating cavity is suggested. By frequency sensitivity study of new dimensions, we can choose best technique to tune the accelerating cavity during magnetic coupling-hole adjustment.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRI040

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPRI046

Air-cooled Magnetic Alloy Cavity for J-PARC Doubled Rep.-rate Scenario

cavity, injection, acceleration, ion

3869

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

The upgrade project of the J-PARC MR (Main Ring) is in progress to deliver the beam power of 750 kW based on doubled repetition-rate scenario. The present RF section will be occupied by 9 sets of new magnetic alloy, FT3L, cavity using the direct water cooling scheme. The direct water cooling requires dedicated high-quality cooling water. These cavities will be used for the fundamental RF for acceleration. The second harmonic RF is necessary to increase the bunch length. This allows to enlarge the beam current, and to relax the space charge effects during the injection. Thanks to the high impedance FT3L, the power loss in the second harmonic RF system becomes moderate. The air cooled cavity is designed to fit in any space in the MR where the dedicated water is not available. This paper reports the design of the second RF system, technical issues to produce the magnetic alloy cores to fit the air cooling, and construction of the system.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRI046

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPRI048

Design of an Accelerating Tube for a Standing-wave Accelerator based on Genetic Algorithm’s Optimal Calculation

electron, coupling, simulation, radiation

3875

Z.X. Tang
USTC, Hefei, Anhui, People's Republic of China
Y.J. Pei
USTC/NSRL, Hefei, Anhui, People's Republic of China

A compact medical standing-wave (SW) electron accelerating tube has been designed that operating frequency is 2998MHz, operating mode is π/2, final energy is 6MeV and beam current is 100mA based on genetic algorithm (GA)’s optimal calculation. It employed a bi-periodic structure with nose cone shape. We performed the simulation experiment which proved that GA was feasible and gave a set of geometric parameter with higher shunt impedance. We performed tuning of the whole tube by CST MICROWAVE STUDIO and SUPERFISH and calculation of beam dynamics by ASTRA and Parmela in this paper. The total length of the tube is less than 300mm.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRI048

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPRI049

Engineering Design of the RF Input Couplers for C-ADS RFQ

rfq, cavity, linac, operation

3878

L.P. Sun, Y. He, A. Shi, C. Zhang, Z.L. Zhang
IMP, Lanzhou, People's Republic of China

A new coupler with the special ceramic window has been developed at IMP, CAS (Institute of Modern Physics, Chinese Academy of Sciences), operating at 30 kW/162.5 MHz in CW mode for an one-meter prototype cavity, which can provide all kinds of experiences to the real four-meter cavity including EM simulation, power conditioning, cooling consideration and so on. Now, the beam experiments on prototype cavity have been completed and the results show the simulation and the measurements of coupler were in the good agreement. The special bowl-type ceramic window can promote S parameter and reduce sparking risk for beam commissioning stably. A detailed electromagnetic design and measured results of the coupler will be presented in the paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRI049

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPRI053

Ferrite Material Characterization in a Static Bias Field for the Design of a Tunable Cavity

simulation, cavity, electromagnetic-fields, solenoid

3890

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

During the development of ferrite-loaded accelerating cavities, the electromagnetic properties of the dispersive ferrite material need to be known. We describe a coaxial short-circuit measurement technique to measure the complex permeability of toroidal-shaped samples (127mm outer and 70mm inner diameter) that are exposed to an external magnetic bias field. The external magnetic bias field is applied perpendicular to the RF magnetic field. With this method it is possible to characterize the frequency dependence of the permeability for a frequency range of 1-100MHz. The dependence of the permeability on the external magnetic bias is presented for the ferrite G-510 from Trans-Tech Inc. and the material characterization is shown in the same frequency range. The measurement results are verified by simulations of the measurement set-up.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRI053

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPRI054

Permittivity and Permeability Measurement Methods for Particle Accelerator Related Materials

simulation, resonance, cavity, HOM

3893

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

For the special requirements related to particle accelerators, knowledge of the different material parameters of dielectrics and other materials are needed in order to carry out simulations during the design process of accelerator components. This includes also properties of magnetically biased ferrites of which usually little information is available about material characteristics, especially in magnetic bias fields. Several methods of measurement are discussed and compared of which some require delicate sample preparation whereas others can work with unmodified material shapes that makes those methods also suited for acceptance checks on incoming materials delivered by industry. Applications include characterization of different materials, as absorbers in which dielectric losses play an increasing role, as well as low frequency measurements on ferrites that are used for tunable cavities. We present results obtained from both broadband and resonant measurements on different materials determined in the same sample holder. Where possible, the results were confirmed with alternative methods.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRI054

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPRI055

The New 118 MHz Normal Conducting RF Cavity for SIAM Photon Source at SLRI

cavity, storage-ring, electron, HOM

3896

N. Juntong, S. Krainara
SLRI, Nakhon Ratchasima, Thailand

The Siam Photon Source (SPS) is the 1.2 GeV second generation light source in Thailand. It is managed by the Synchrotron Light Research Institute (SLRI). The institute is located inside the campus of Suranaree University of Technology (SUT), which is approximately 20 km from the city of Nakhon Ratchasima (or normally called Korat). Korat is 250 km north-east of Bangkok. Two insertion devices (IDs) have been installed in the SPS storage ring during June to August 2013. These IDs require additional electrical field energy from RF cavity to compensate electron energy loss in the storage ring. The existing RF cavity has been pushed to its maximum capability and the new RF cavity is in the procurement process. The design and study of the new RF cavity will be presented. Electromagnetic fields of the cavity are studied together with the effects to electron beam instabilities.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRI055

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPRI066

Design of a 1.3 GHz Two-cell Buncher for APEX

cavity, HOM, dipole, vacuum

3924

H.J. Qian, K.M. Baptiste, J.A. Doyle, D. Filippetto, S. Kwiatkowski, C. F. Papadopoulos, D. Patino, F. Sannibale, J.W. Staples, S.P. Virostek, R.P. Wells
LBNL, Berkeley, California, USA

Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231
The design of a 1.3 GHz buncher cavity for the APEX project, a MHz repetition rate high-brightness photoinjector, is presented. The buncher cavity operates at 240 kV in CW mode, and it compresses the 750 keV beam from APEX gun through ballistic compression. Compared with a single cell design, a two-cell cavity doubles the shunt impedance to 7.8 MΩ, which greatly relaxes the requirements for both RF amplifier and cavity cooling. Coupler design, multipacting analysis, HOM analysis and thermal analysis will be presented in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRI066

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPRI073

Achieving Higher Energies via Passively Driven X-band Structures

cavity, electron, linac, FEL

3933

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

Due to their higher intrinsic shunt impedance X-band accelerating structures significant gradients with relatively modest input powers, and this can lead to more compact particle accelerators. At the Colorado State University Accelerator Laboratory (CSUAL) 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 design details of the X-band structures that will allow us to achieve our goal of reaching the maximum practical net potential across the X-band accelerating structure while driven solely by the beam from the L-band system.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRI073

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPRI075

S-Band Structure Study for the MaRIE Project

wakefield, coupling, dipole, linac

3940

Z. Li, C. Adolphsen, M.V. Fazio, S.G. Tantawi, L. Xiao
SLAC, Menlo Park, California, USA

Funding: Work was supported by the US Department of Energy through the LANL/LDRD Program.
The Matter-Radiation Interactions in Extremes (MaRIE) facility proposed at LANL utilizes a 20-GeV electron linac to drive a 50-keV XFEL. Experimental requirements drive a need for multiple photon bunches over time durations of about 10 microsecond produced by a bunch train of interleaving 0.1 nC very low-emittance bunches with 2-nC electron bunches. The linac is required not only to provide high gradient and high efficient acceleration, but also a controlled wakefield profile to maintain the beam quality. In this paper, we explore the feasibility of using the S-Band technology to meet such acceleration requirements. We will present the design optimization and comparison of S-Band structures based on different design considerations.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRI075

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)