IPAC2011 - Table of Session: MOPC (Poster Session)

Paper	Title	Page
MOPC001	Linac Waveguide Upgrade at the Australian Synchrotron Light Source	62
	R.T. Dowd, G. LeBlanc, K. Zingre ASCo, Clayton, Victoria, Australia
	The Australian Synchrotron Light Source (ASLS) uses a 100 MeV linac as the start of the acceleration chain for the injector. The two main accelerating structures of linac are normally fed by independent pulsed klystrons. A recent upgrade to the waveguide system has allowed for a single klystron to power both accelerating structures. While this operation mode delivers a reduced total beam energy, the operation of only a single klystron results in less wear and enhanced robustness against klystron breakdown. Commissioning results of single klystron operation of the linac are shown and future benefits are detailed.

MOPC002	Flow Induced Vibrations of the CLIC X-band Accelerating Structures	65
	T.K. Charles, K. Ryan Monash University, Melbourne, Australia M.J. Boland ASCo, Clayton, Victoria, Australia G. Riddone CERN, Geneva, Switzerland A. Samoshkin JINR, Dubna, Moscow Region, Russia
	Turbulent cooling water in the Compact Linear Collider (CLIC) accelerating structures will inevitably induce some vibrations. The maximum acceptable amplitude of vibrations is small, as vibrations in the accelerating structure could lead to beam jitter and alignment difficulties. A Finite Element Analysis model is needed to identify the conditions under which turbulent instabilities and significant vibrations are induced. Due to the orders of magnitude difference between the fluid motion and the structure's motion, small vibrations of the structure will not contribute to the turbulence of the cooling fluid. Therefore the resonant conditions of the cooling channels presented in this paper, directly identify the natural frequencies of the accelerating structures to be avoided under normal operating conditions. In this paper a 2D model of the cooling channel is presented finding spots of turbulence being formed from a shear layer instability. This effect is observed through direct visualisation and wavelet analysis.

MOPC004	352.2 MHz HOM Damped Normal Conducting ESRF Cavity: Design and Fabrication	68
	V. Serrière, A.K. Bandyopadhyay, D. Boilot, L. Goirand, J. Jacob, B. Ogier, A. Triantafyllou ESRF, Grenoble, France
	Funding: This work, carried out within the framework of the ESRFUP project, has received research funding from the EU Seventh Framework Programme, FP7. The ongoing ESRF upgrade included an option for an increase of the storage ring current from 200 to 300 mA, which has been tested successfully with the existing RF system. At this current level the HOM tuning of the existing five-cell copper cavities becomes extremely delicate and in view of a future reliable operation in user mode, new HOM free normal conducting cavities were developed at the ESRF. The design is based on the existing BESSY/ALBA cavity. However, several substantial modifications have been implemented and different fabrication processes elaborated to improve the design. Three operational prototypes will be delivered by three manufacturers in the coming months and will be fully tested on the ring. Although the 300 mA option has finally not been retained for the first phase of the ESRF upgrade, the aim is now to validate the new cavity design for a possible later increase in current.

MOPC005	352.2 MHz – 150 kW Solid State Amplifiers at the ESRF	71
	J. Jacob, G. Gautier, M.L. Langlois, J.M. Mercier ESRF, Grenoble, France
	The ESRF has ordered seven 352.2 MHz – 150 kW Solid State Amplifiers (SSA) from the French company ELTA, with a design derived from the existing SSA developed by SOLEIL. The first four SSA will be commissioned by the end of 2011 and will be connected to the two booster cavities in Winter 2012 providing in total 600 kW in 10 Hz cycles. Thanks to anti-flicker capacitor banks with a total of 3 F in the 280 V DC power supply, up to only 350 kW will be drawn from the mains as compared to 1200 kW for the former klystron transmitter. The three remaining SSA will be received in 2012 and will feed three new single cell HOM damped cavities on the storage ring. The analysis of the market had shown that an alternative to klystrons needed to be investigated to guarantee the long term operation of the ESRF. SSA can be operated with a number of RF modules lost and are therefore intrinsically highly redundant. In parallel to the production by industry of this first batch of SSA, the ESRF is developing its own amplifier modules and proposing an alternative way to combine typically hundred RF modules using a single cavity combiner.

MOPC006	A Coupled RFQ-IH Combination for the Neutron Source FRANZ	74
	M. Heilmann, O. Meusel, D. Mäder, U. Ratzinger, A. Schempp IAP, Frankfurt am Main, Germany
	Funding: HIC for FAIR The Frankfurt Neutron Source at the Stern-Gerlach-Zentrum is driven by a 2 MeV proton linac consisting of a 4-rod-radio-frequency-quadrupol (RFQ) and an 8 gap IH-DTL structure. RFQ and IH cavity will be powered by only one radio frequency (RF) amplifier to reduce costs. The RF-amplifier of the RFQ-IH combination is coupled into the RFQ. Internal inductive coupling along the axis connects the RFQ with the IH cavity ensuring the required power transition as well as a fixed phase relation between the two structures. The main acceleration of 120 keV up to 2.03 MeV will be reached by the RFQ-IH combination with 175 MHz and at a total length of 2.3 m. The losses in the RFQ-IH combination are about 200 kW.

MOPC007	Cold Photocathode RF Gun	77
	V. Vogel, K. Flöttmann, S. Schreiber DESY, Hamburg, Germany
	Heating and thermal expansion in the normal conductivity RF-photo electron gun, are the main limitations to achieve high accelerating gradient and consequently a low emittance beam. Some pure materials show a significant increase in thermal conductivity with a small coefficient of temperature expansion at temperatures around 20 degrees Kelvin. Possible materials are Molybdenum, Iridium or Tungsten. However, machining of these materials is very difficult. Therefore we propose a simplified shape for an L-band RF gun. We expect to achieve a significant increase in gradient for similar RF powers as used in the present DESY RF-gun. On the other hand, it would also be possible to increase the duty cycle keeping a moderate gradient. In this report we discuss one possible design of an RF-gun using hard metals and present simulations on thermal properties.

MOPC009	Design of a Pi/2 Mode S-Band Low Energy TW Electron Linear Accelerator	80
	H. Shaker IPM, Tehran, Iran F. Ghasemi sbu, Tehran, Iran H. Shaker CERN, Geneva, Switzerland
	This design is related to a Pi/2 mode S-Band low energy TW electron linear accelerator which is in the construction stage. This project is supported by the school of particles and accelerators, institute for research in fundamental sciences (IPM), Tehran, Iran. This design consists of a buncher and an accelerating structure that are joined and two couplers for the input/output feedings. At each design stage, different methods (analytical or numerical) are used to confirm the results and also to have a better understanding.

MOPC010	Phase-Modulation SLED Operation Mode at Elettra	83
	C. Serpico, P. Delgiusto, A. Fabris, F. Gelmetti, M.M. Milloch, A. Salom, D. Wang ELETTRA, Basovizza, Italy
	FERMI@Elettra is the soft X-ray, fourth generation light source facility at the Elettra Laboratory in Trieste, Italy. It is based on a seeded FEL, driven by a normal conducting linac that is presently expected to operate at 1.5 GeV. The last seven backward traveling wave structures have been equipped with a SLED system. Due to breakdown problems inside the sections, that was the result of high peak fields generated during conventional SLED operation, the sections experienced difficulties in reaching the desired gradients. To lower the peak field and make the compressed pulse “flatter”, phase-modulation of the SLED drive power will be implemented. A description of the phase modulation of the drive power and the results achieved will be reported in the following paper.

MOPC012	Fabrication of the CERN/PSI/ST X-band Accelerating Structures	86
	M.M. Dehler, A. Citterio, R. Zennaro PSI, Villigen, Switzerland S. Atieh, D. Gudkov, S. Lebet, G. Riddone, J. Shi CERN, Geneva, Switzerland G. D'Auria, C. Serpico ELETTRA, Basovizza, Italy
	Within a collaboration between CERN, PSI and Sincrotrone Trieste (ST), a multi- purpose X-band accelerating structure has been designed and fabricated, used for high gradients tests in the CLIC structure testing program and in the FEL projects of PSI and ST. The structure has 72 cells with a phase advance of 5 pi/6 and includes upstream and downstream wakefield monitors to measure the beam alignment. The SLAC mode launcher design is used to feed it with RF power. Following the CERN fabrication procedures for high-gradient structure, diffusion bonding and brazing in hydrogen atmosphere is used to assemble the cells. After tuning, a vacuum bakeout is required before the feedthroughs for the wake field monitors are welded in as a last step. We describe the experiences gained in finishing the first two structures out of a series of four and present the results from the RF tuning and low level RF tests.

MOPC013	Design, Fabrication and High Power RF Test of a C-band Accelerating Structure for Feasibility Study of the SPARC Photo-injector Energy Upgrade	89
	D. Alesini, R. Boni, G. Di Pirro, R. D. Di Raddo, M. Ferrario, A. Gallo, V.L. Lollo, F. Marcellini INFN/LNF, Frascati (Roma), Italy G. Campogiani, A. Mostacci, L. Palumbo, S. Persichelli, V. Spizzo Rome University La Sapienza, Roma, Italy T. Higo, K. Kakihara, S. Matsumoto KEK, Ibaraki, Japan S. Verdú-Andrés TERA, Novara, Italy
	The energy upgrade of the SPARC photo-injector from 170 to 250 MeV will be done by replacing a low gradient 3m S-Band structure with two 1.5m high gradient C-band structures. The structures are traveling wave, constant impedance sections, have symmetric waveguide input couplers and have been optimized to work with a SLED RF input pulse. A prototype with a reduced number of cells has been fabricated and tested at high power in KEK (Japan) giving very good performances in terms of breakdown rates at high accelerating gradient (>50 MV/m). The paper illustrates the design criteria of the structures, the fabrication procedure and the high power RF test results.

MOPC014	RF Processing of L-band RF Gun for KEK-STF	92
	M. Kuriki, H. Iijima, Y.M. Masumoto HU/AdSM, Higashi-Hiroshima, Japan H. Hayano, H. Sugiyama, J. Urakawa, K. Watanabe KEK, Ibaraki, Japan G. Isoyama, R. Kato ISIR, Osaka, Japan S. Kashiwagi Tohoku University, Research Center for Electron Photon Science, Sendai, Japan Y. Takahashi Sokendai, Ibaraki, Japan
	Funding: This work is supported by MEXT Quantum Beam Technology Program, KEK Promotion of collaborative research programs in universitie. KEK STF (Superconducting Test Facility) is established for developing super-conducting accelerator technology for ILC (International Linear Collider). At KEK-STF, accelerator operation with a beam loading is planned in 2013. An electron injector based on L-band Photo-cathode RF gun is now being developed. A L-band RF gun designed by DESY and fabricated by FNAL has been placed in KEK-STF and RF processing was carried out. The results of the RF processing and status of STF injector will be presented.

MOPC015	S-band Vacuum Isolator and Circulator for Injector System of SPring-8 Linac	95
	T. Taniuchi, H. Hanaki, S. Suzuki JASRI/SPring-8, Hyogo-ken, Japan A. Miura, K. Shinohara, S. Tsuruoka Nihon Koshuha Co. Ltd, Yokohama, Japan
	A pressurized sulfur hexafluoride (SF6) waveguide system at an injector section of SPring-8 linac, will be replaced with a vacuum waveguide system in order to renew aged equipments and improve a phase stability. For this renewal, RF isolator and a circulator operated in vacuum, are newly developed. High power RF test for these components were performed and a good result for RF and vacuum characteristics were obtained.

MOPC016	Development of a New RF Accelerating Cavity for J-PARC Ring Accelerator	98
	Y. Morita, T. Kageyama KEK, Ibaraki, Japan J. Kameda ICRR, Chiba, Japan S. Yamashita ICEPP, Tokyo, Japan
	Funding: Japan Society for the Promotion of Science (JSPS) To enhance the beam power delivered by the J-PARC* ring accelerators, upgrading the accelerating cavities is indispensable. In particular, long term stable operation of the present cavities for the RCS is one of the important issues. Currently, the cavities are loaded with FINEMET* cores cooled by water, where every core is coated with glass cloth and epoxy resin for waterproof. However, it was reported that some of the cores were damaged by thermal stress. We are developing a new cavity loaded with multi ring core modules. Each core module consists of three ring cores concentrically arranged and sandwiched between two glass epoxy plates with flow channels grooved. The ring cores without waterproof coating are cooled by the turbulent flow of a chemically inert liquid (Fluorinert), since FINEMET is subject to corrosion in water. We have designed and built a high power prototype cavity loaded with a single core module, then carried out low level measurement and high power test. Finally, the cavity has been stably operated up to an average power loss of 10 kW per core module, which is 1.7 times higher than that for the present RCS cavity. Japan Proton Accelerator Research Complex Rapid-Cycling Synchrotron **FINEMET is an iron-based magnetic alloy produced by Hitachi Metals, Ltd..

MOPC017	Thermal Analyses of an RF Input Coupler for the IFMIF/EVEDA RFQ Linac	101
	S. Maebara JAEA, Ibaraki-ken, Japan
	In the design of prototype RFQ linac for the IFMIF/EVEDA Project, a coupled cavity type of RFQ, which has a longitudinal length of 9.78m, was proposed to accelerate deuteron beam up to 5MeV. The operation frequency of 175MHz was selected to accelerate a large current of 125mA in CW mode. The driving RF power of 1.28 MW by 8 RF input couplers has to be injected to the RFQ cavity. As the RF input coupler design, RF losses including a loop antenna and an RF vacuum window, based on a 6 1/8 inch co-axial waveguide were calculated. In this conference, these results and thermal analysis results in CW operation mode will be presented in details.

MOPC018	Operation Status of C-band High Gradient Accelerator for XFEL/SPring-8 (SACLA)	104
	T. Inagaki, C. Kondo, T. Ohshima, Y. Otake, T. Sakurai, K. Shirasawa RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan T. Shintake RIKEN Spring-8 Harima, Hyogo, Japan
	XFEL project in SPring-8 have constructed a compact XFEL facility. In order to shorten an accelerator length, a C-band (5712 MHz) accelerator was employed due to a higher accelerating gradient than that of an S-band accelerator. Since a C-band accelerating structure generates a gradient of higher than 35 MV/m, the total length of an 8 GeV accelerator fits within 400 m, including 64 C-band RF units, 4 S-band RF units, an injector and three bunch compressors. The accelerator components were carefully installed by September 2010. Then we have performed high power RF conditioning. After 500 hours of the conditioning, the accelerating gradient of each C-band structure was reached up to 35 MV/m without any particular problem. The RF breakdown rate is low enough for an accelerator operation. Since February 2011, we started the beam commissioning for XFEL. The C-band accelerator has accelerated the electron beam up to 8 GeV, with an accelerating gradient of 33-35 MV/m in average. The energy and the trajectory of the electron beam was stable, thanks to the stabilization of a klystron voltage of 350 kV within 0.01% by a high precision high voltage charger. The facility was recently named SACLA (SPring-8 Angstrom Compact free electron LAser).

MOPC019	Condition of MA Cut Cores in the RF Cavities of J-PARC Main Ring after Several Years of Operation	107
	M. Nomura, A. Schnase, T. Shimada, F. Tamura, M. Yamamoto JAEA/J-PARC, Tokai-mura, Japan E. Ezura, K. Hasegawa, K. Takata KEK, Tokai, Ibaraki, Japan K. Hara, C. Ohmori, M. Toda, M. Yoshii KEK/JAEA, Ibaraki-Ken, Japan T. Sato, M. Yamamoto JAEA, Ibaraki-ken, Japan
	J-PARC 3 GeV RCS and 50 GeV Synchrotron (MR) employ RF cavities loaded with Magnetic Alloy (MA) cores to generate a high field gradient. The RF cavities in RCS use MA un-cut cores. On the other hand, the RF cavities in MR employ MA cut cores to increase the Q-value from 0.6 to 26. We observed the impedance reductions of all MR RF cavities during several years operation. Opening the RF cavities, we found that the impedance reductions were resulting from corrosion on the cut and polished surfaces of MA cores. Before installation of the RF cavities, we had 1000 and 2000 hours long tests at a test stand. We didn't observe the impedance reduction related to the corrosion on the MA core cut surfaces at the test stand. The only difference between the test stand and MR is the quality of cooling water. The MR cooling water contains copper ions for example from copper hollow conductors of the main magnets. We report the influence of the copper ions to the corrosion on the MA core cut surface. We also show plans how to solve the issue of MA core cut surface corrosion.

MOPC020	Development of an S-band Multi-cell Accelerating Cavity for RF Gun and Booster Linac	110
	T. Aoki, K. Sakaue, M. Washio RISE, Tokyo, Japan A. Deshpande SAMEER, Mumbai, India M.K. Fukuda, N.K. Kudo, T. Takatomi, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan
	Funding: Work supported by JST Quantum Beam Program We have been developing a photocathode rf gun. The rf gun with multi cell can produce a high energy electron beam, so it may be used for numerous applications such as medicine and industry. At Laser Undulator Compact X-ray source (LUCX), we have developed a compact X-ray source based on inverse Compton scattering. Using a multi cell rf gun will make possible for the X-ray source to use for such applications. S-band 3.5 cell rf electron gun which is 20 cm long can produce more than 10 MeV electron beam. According to the simulation, it is said that the emittance of 3.5 cell rf gun is as low as that of 1.6 cell rf gun. The electromagnetic design has been performed with the code SuperFish, and the particle tracing by Parmela. The new rf gun is already installed and produced a high quality electron beam with energy of more than 10 MeV. As a consequence of the substantial efforts of developing rf cavity, we decide to make a compact RF accelerating structure with more cell for achieving a smaller system. The measurement results of using the 3.5 cell rf gun, the design of 12 cell booster cavity, and current status of 12 cell cavity manufacturing will be presented at the conference.

MOPC021	Design of a Choke-mode Damped Accelerating Structure for CLIC Main Linac	113
	J. Shi, A. Grudiev, W. Wuensch CERN, Geneva, Switzerland H. Chen, W.-H. Huang, C.-X. Tang, H. Zha TUB, Beijing, People's Republic of China
	Choke-mode damped accelerating structures are being studied as an alternative to the CLIC baseline structure by a CERN-Tsinghua collaboration. Choke-mode structures hold the potential for much lower levels of pulsed surface heating and, since milling is not needed, reduced cost. Structures with radial choke attached are simulated in Gdfidl to investigate the damping of the transverse wake. The first pass-band of the dipole modes is well damped, while the higher order dipole modes are possible to be reflected by the choke. Therefore, the geometry of the choke is tuned to minimize the reflection of these higher order dipoles. Based on this damping scheme, an accelerating structure with the same iris dimensions as the nominal CLIC design but with choke-mode damping has been designed. A prototype structure will be manufactured and high power tested in the near future.

MOPC022	Development of a Compact C-band Photocathode RF Gun	116
	X.H. Liu, H. Chen, W.-H. Huang, H.J. Qian, C.-X. Tang, Z. Zhang TUB, Beijing, People's Republic of China
	Funding: This work is supported by National Natural Science Foundation of China and National Basic Research Program of China (973 Program). A C-band photocathode RF gun for a compact electron diffraction facility is developed in Tsinghua University, which is designed to work at the frequency of 5.712GHz. This paper presents the physics and structure design of this C-band RF gun, and the comparison on beam dynamics of S-band and C-band photoinjector has been done. Some new structure design will be adopted in this gun, including the optimized cavity length and elliptical iris, which is helpful to achieve lower emittance and larger mode separation.

MOPC023	Design of a C-band 6 MeV Standing-wave Linear Accelerating Structure	119
	J.H. Shao, H. Chen, Q.Z. Xing TUB, Beijing, People's Republic of China
	We design a C-band standing-wave biperiodic on-axis coupled linear accelerating structure for industrial and medical applications. It’s less than 300mm long; consists of 3 bunching cells and 9 normal cells. It can accelerate electrons to 6MeV and the pulsed beam current is 100mA. The RF power source is a 2.5MW magnetron. We implement 2D cells geometry optimization by SUPERFISH, beam dynamics study by PARMELA and full scale 3D calculations by MAFIA codes.

MOPC024	Construction Status of the CPHS RFQ at Tsinghua University	122
	Q.Z. Xing, Y.J. Bai, J.C. Cai, C. Cheng, L. Du, T. Du, X. Guan, Q. Qiang, X.W. Wang, Z.F. Xiong, S.Y. Yang, H.Y. Zhang, S.X. Zheng TUB, Beijing, People's Republic of China J.H. Billen TechSource, Santa Fe, New Mexico, USA W.Q. Guan, Y. He, J. Li NUCTECH, Beijing, People's Republic of China J. Stovall CERN, Geneva, Switzerland L.M. Young AES, Medford, NY, USA
	Funding: Work supported by the “985 Project” of the Ministry of Education of China. We present, in this paper, the construction status of a Radio Frequency Quadrupole (RFQ) accelerator for the Compact Pulsed Hadron Source (CPHS) at Tsinghua University. The 3-meter-long RFQ will deliver 3 MeV protons to the downstream Drift Tube Linac (DTL) with the peak current of 50 mA, pulse length of 0.5 ms and beam duty factor of 2.5%. The RFQ has been mechanically separated into three sections. A ball-end mill, instead of a forming cutter, is adopted to machine the vane tip due to its varying radius of curvature. The precision of the numerically controlled milling machine has been verified by machining test pieces of aluminum and copper. Fine machining of the vanes was completed in July, 2011. The pre-braze tuning was completed at the beginning of this August.

MOPC026	MA Cavity for HIRFL-CSR	125
	L.R. Mei, Z. Xu, Y.J. Yuan, H.W. Zhao IMP, Lanzhou, People's Republic of China
	To meet the requirements of conducting high energy density physics and plasma physics research at HIRFL-CSR. The higher accelerating gap voltage was required. A magnetic alloy (MA)-core loaded radio frequency (RF) cavity which can provide higher accelerating gap voltage has been studied in Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS), Lanzhou. To select proper MA material to load the RF cavity, measurement for MA cores has been conducted. The MA core with higher shunt impedance and lower than 1 quality factor (Q value) should be selected. The theoretical calculation and simulation for the MA-core loaded RF cavity can be consistent with each other well. Finally 1000kW power was needed to meet 50-kV accelerating gap voltage by calculation.

MOPC028	Beam Acceleration of DPIS RFQ at IMP	128
	Z.L. Zhang, X.H. Guo, Y. He, Y. Liu, S. Sha, A. Shi, L.P. Sun, H.W. Zhao IMP, Lanzhou, People's Republic of China R.A. Jameson, A. Schempp IAP, Frankfurt am Main, Germany M. Okamura BNL, Upton, Long Island, New York, USA
	Beam test of the direct plasma injection scheme (DPIS) is carried out successfully for the first time in China, by setting up a comprehensive test and research platform of RFQ and laser ion source. The C⁶⁺ beam is accelerated successfully, and the peak beam current reaches more than 6mA which is measured by a Faraday cup of unique structure. The RF power coupled into the RFQ cavity is also examined, and results reveal that it is the RF power of about 195kW that can produce the peak beam current.

MOPC029	Development of Injector for Compact FEL Tera-hertz Source in CAEP	131
	W. Bai, M. Li, X. Yang CAEP/IAE, Mianyang, Sichuan, People's Republic of China
	This paper introducs the development of a injector for compact FEL tera-hertz source at Institute of Applied Electronics in China Academy of Engineering Physics (IAE/CAEP). The injector consist of a main accelerator for energy booster section and a multicavity thermionic-cathode rf gun with low back bombardment, with total length no more than one meter. Numerical simulation result shows that the back bombardment power is less for the thermionic-cathode rf gun of the injector and the main accelerator has a good performance, which can provide high quality electron beam with emittance about 10 pi mm mrad, energy about 7 MeV and energy spread about 1%. At present, the preliminary hot test experiment on the injector has been done. The test results indicate that the mainly tested parameters agree well with the theoretical design ones. The process of the preliminary hot test experiment on the injector is present in this paper.

MOPC030	The C-band Traveling-wave Accelerating Structure for Compact XFEL at SINAP*	133
	W. Fang, Q. Gu, Z.T. Zhao SINAP, Shanghai, People's Republic of China D.C. Tong TUB, Beijing, People's Republic of China
	The R&D of C-band accelerating structure has been launched two years ago at Shanghai Institute of Applied Physics, it will be used for the future compact hard X-ray FEL. The 1st C-band traveling-wave accelerating structure is ready for the high power test now. This structure is the preliminary model for the research of the technology of microwave test and tuning, arts and crafts and high power test. This paper presents the process of fabrication, cold test and tuning results.

MOPC031	Performance of a 13 MHz Cavity for an RF Implanter at PEFP*	136
	T.A. Trinh UST, Daejeon, Republic of Korea Y.-S. Cho, J.-H. Jang, D.I. Kim, H.S. Kim, H.-J. Kwon, B.-S. Park, K.T. Seol KAERI, Daejon, Republic of Korea
	Funding: This work is supported by the Ministry of Education, Science and Technology of the Korean Government A 13 MHz - normal conducting cavity for an rf implanter has been successfully developed at PEFP (Proton Engineering Frontier Project). It consists of an inductive coil, accelerating electrodes and a ground electrode for the inductor. Quality factor of 2074 and critical coupling were achieved at resonant frequency of 12.658 MHz. Rf power of 1 kW was forwarded to the cavity without any spark in the cavity. Beam test was then carried out with a 27 keV helium beam generated from a Duoplasmatron ion source. The results showed that the helium beam was accelerated to final energy of 120 keV with energy spread of 1%. Detail experiments and results are addressed in this presentation.

MOPC032	Improvement of the RF System for the PEFP 100 MeV Proton Linac*	139
	K.T. Seol, Y.-S. Cho, H.S. Kim, H.-J. Kwon, Y.-G. Song KAERI, Daejon, Republic of Korea
	Funding: This work is supported by the Ministry of Education, Science and Technology of the Korean Government. The 100 MeV proton linear accelerator of the Proton Engineering Frontier Project (PEFP) has been developed and will be installed in Gyeong-ju site. The 20 MeV accelerator operated in Korea Atomic Energy Research Institute (KAERI) site will be also moved and reinstalled. The LLRF control systems for the 20 MeV accelerator were improved and have been operated within the stability of ±1% in RF amplitude and ±1 degree in RF phase. 7 sets of the extra LLRF control system will be installed with a RF reference system for the 100 MeV accelerator. Waveguide layout was also improved to install HPRF systems for the 100 MeV accelerator. Some of the HPRF components including klystrons, circulators, and RF windows are under purchase. The waveguide sections penetrating into the tunnel, which are fixed in a concrete floor with the bending structure for radiation shielding, were fabricated into a piece of waveguide to prevent the moisture and any foreign debris inside the concrete block. The details of the RF system improvement are presented.

MOPC033	The Status of a 1.6-cell Photocathode RF Gun at PAL	142
	M.S. Chae, J.H. Hong, I.S. Ko, Y.W. Parc POSTECH, Pohang, Kyungbuk, Republic of Korea S.J. Park PAL, Pohang, Kyungbuk, Republic of Korea
	The RF power conditioning of the photocathode RF gun with four holes at the side of the full cell named as 'Pohang gun' is in progress. The first goal of the conditioning is the operation of the gun with RF pulse width of 1.5 μm, repetition rate of 30 Hz, field gradient at the cathode of 130 MV/m. We operated the RF gun successfully with the conditions within last few months. It was first operational experience with such conditions in PAL. Now we have a plan to operate RF gun with higher repetition rate up to 60 Hz.

MOPC034	Design of a 0.6-cell Cell Photocathode RF Gun for FED	145
	Y.W. Parc, M.S. Chae, I.S. Ko POSTECH, Pohang, Kyungbuk, Republic of Korea
	Final goal of this study is the development of single cell radio-frequency (RF) electron gun which is optimized to the femotosecond electron diffraction. This study will open new technology basis for the laboratory research in the femto-second (fs) chemistry at the university. RF electron gun will be fabricated with single cell which will reduce the cost and effort. We will also conduct a simulation study to find an optimized operation condition of the RF gun to provide the best electron beam to the femtosecond electron diffraction experimentalist. In this presentation, we will show the status of the RF gun development. The results with the simulation code PARMELA will be presented to find the optimal operation condition of the single cell RF gun for FED.

MOPC035	Design and Machine Features of 2.2-m C-band Accelerating Structure	148
	C.H. Yi, M.-H. Cho, S.H. Kim, H. Lee POSTECH, Pohang, Kyungbuk, Republic of Korea W. Namkung PAL, Pohang, Kyungbuk, Republic of Korea
	Funding: This work is partly supported by the MEST, Korea and POSTECH BK21 Program. And this work was supported by the Korea Student Aid Foundation (KOSAF) grant funded by the Korea government. A compact linac system is designed using a longer accelerating column in a C-band linac. It reduces the total number of RF units for the given linac beam energy and results in the cost-effective use of RF powers. For the 10 GeV PAL-XFEL project, a C-band accelerating column of 2.2-m long is investigated, which is 22% longer than 1.8-m for the SACLA at SPring-8. The detailed RF and thermal characteristics are presented by an analytic model.

MOPC036	Design of RF Cavity for Compact 9 MeV Cyclotron	151
	H.S. Song, J.-S. Chai, H.W. Kim, B.N. Lee, J.H. Oh SKKU, Suwon, Republic of Korea
	The number of PET facility is rapidly increasing worldwide. To get PET image, circular accelerator such as cyclotron is needed. Compact 9 MeV H-cyclotron, which has a diameter of 1.25m is being designed at Sungkyunkwan University starting from July 2010 for getting F-18. It is expected to be constructed by next year. In this paper, RF system of 9 MeV cyclotron including design processes and detail analysis of result is reported. RF system mainly describes RF cavity design.

MOPC037	Engineering Design and Fabrication of X-band Damped Detuned Structure for the CLIC Study	154
	V. Soldatov, D. Gudkov, A. Samoshkin JINR, Dubna, Moscow Region, Russia S. Atieh, A. D'Elia, A. Grudiev, G. Riddone CERN, Geneva, Switzerland R.M. Jones, V.F. Khan UMAN, Manchester, United Kingdom
	A Damped Detuned Structure (DDS), known as CLIC_DDS_A, has been designed for the Compact Linear Collider (CLIC) study, and is presently under fabrication. The wakefield in DDS structures is damped using a combination of detuning the frequencies of beam-excited higher order modes and by light damping, through slot-coupled manifolds. The broad principles of the design are similar to that used in the NLC/GLC. This serves as an alternative to the present baseline CLIC design which relies on heavy damping. CLIC_DDS_A is conceived to be tested for its capacity to sustain high gradients at CERN. This structure operates with a 120 degrees phase advance per cell. We report on engineering design and fabrication details of the structure consisting of 24 regular cells plus 2 matching cells at both ends, all diffusion bonded together. This design takes into account practical mechanical engineering issues and is the result of several optimizations since the earlier CLIC_DDS designs. V. F. Khan et al., “Recent Progress on a Manifold Damped and Detuned Structure for CLIC”, Proc. of IPAC10, WEPE032, p. 3425 (2010). ** R.M. Jones et al., Phys. Rev. STAB 9, 102001 (2006).

MOPC038	Engineering Design and Fabrication of Tapered Damped X-band Accelerating Structures	157
	A. Solodko, D. Gudkov, A. Samoshkin JINR, Dubna, Moscow Region, Russia S. Atieh, A. Grudiev, G. Riddone, M. Taborelli CERN, Geneva, Switzerland
	The accelerating structures (AS) are one of the main components of the Compact LInear Collider (CLIC), under study at CERN. Each AS contains about 30 copper disks, which form the accelerating cavity. A fully featured AS is very challenging and requires several technologies. Different damping methods, waveguides, vacuum manifolds, slots and choke, result in various design configurations. In the CLIC multibunch AS, called TDS (Tapered Damped Structure), each cell is damped by its four waveguides, which are extended by channels machined in dedicated external vacuum manifolds. The manifolds combine few functions such as damping, vacuum pumping and cooling. Silicon carbide absorbers, fixed inside of each manifold, are required for effective damping of High Order Modes. CERN is producing X-band RF structures in close collaboration with a large number of laboratories taking advantage of their large expertise and test facilities. The fabrication includes several steps from the machining to the final assembly, including quality controls. This paper describes the engineering design and fabrication procedure of the X-band AS with damping material, by focusing on few technical solutions.

MOPC039	Optimization of IH-DTL Resonator for UNDULAC-RF	160
	S.M. Polozov, A.S. Plastun, P.R. Safikanov MEPhI, Moscow, Russia
	The linear undulator accelerator (UNDULAC) was proposed early for ribbon ion beam acceleration. UNDULAC can be realized using two non-synchronous spatial harmonics. One of them must be RF field harmonic and the second can be RF (UNDULAC-RF) or electrostatic (UNDULAC-E). The acceleration mechanism in UNDULAC is similar as inverse free electron laser (IFEL). The beam dynamics in both types of UNDULAC was studied early and the design of UNDUAC-RF resonator was started in . Design of the 150 MHz IH-DTL for UNDULAC-RF will present. The optimization of the longitudinal field distributions will do. The most effective construction will show. Transverse electric field distributions within drift tube will optimize by blending support stems and drift tubes. E.S. Masunov, Sov. Phys. – Tech. Phys. 35(8), 962-965, 1990. ** S. M. Polozov, P. R. Safikanov, Proc. IPAC’10, Kyoto, Japan, p. 3762 (2010).

MOPC040	The Measurement of Transversal Shunt Impedance of RF Deflector	163
	A.Yu. Smirnov, M.V. Lalayan, N.P. Sobenin MEPhI, Moscow, Russia A.A. Zavadtsev Nano, Moscow, Russia
	This paper presents the results of transverse shunt impedance measurement performed using field perturbation technique and comparison with numerical MWS simulations. The structure under test is the S-band 3-cell deflecting cavity. The mentioned cavity operates with a dipole TM11-like mode with a phase shift of 120 deg per cell. The analyses were carried out with use of two types of perturbing beads: dielectric beads and metallic rings. The latter type perturbs the on-axis magnetic field much stronger than the electric field, which allows us calculating transversal shunt impedance using on-axis EM fields values.

MOPC041	Cross-Field Multipactor Discharge in the X-Band Cylindrical Cavity	166
	S.V. Kuzikov, E.V. Ilyakov, I.S. Kulagin, A.A. Vikharev IAP/RAS, Nizhny Novgorod, Russia D. Lee NSRRC, Hsinchu, Taiwan
	The paper represents the experimental study of one-sided cross-field multipactor discharge in the copper cavity with the operating mode TM01 in external DC magnetic field. It was shown that discharge is very sensible to magnitudes of the external magnetic field and rf fields as well. At proper fields the multipactor discharge can be developed for 15 ns and the electron concentration can be comparable with critical one for the given rf frequency. As a result of discharging, the cavity changes its own resonant frequency and can play a role of a switch which can substitute full transmission by full reflection. Switching parameters could be controlled by DC magnetic field as well as by additional rf radiation at different frequency than operating frequency. The high rf absorption of multipactor discharge also can be used in electrically controlled powerful loads and attenuators.

MOPC042	RF and Accelerating Structure of 12 MeV UPC Race-track Microtron	169
	Yu.A. Kubyshin, X. Gonzalez Arriola UPC, Barcelona, Spain D. Carrillo, L. García-Tabarés, F. Toral CIEMAT, Madrid, Spain S.J. Mathot CERN, Geneva, Switzerland G. Montoro EPSC, Castelldefels, Spain V.I. Shvedunov MSU, Moscow, Russia
	We describe the design and technical characteristics of a C-band SW accelerating structure of a 12 MeV race-track microtron, which is under construction at the Technical University of Catalonia, and its RF system with a 5712 MHz magnetron as a source. Results of cold tests of the accelerating structure, before and after the brazing, and of high-power tests of the RF system at a special stand are reported. The main features of the magnetron frequency stabilization subsystem are also outlined.

MOPC043	Electromagnetic Simulations of the Input Power Couplers for the ESS-Bilbao RFQ	172
	O. Gonzalez, I. Bustinduy, N. Garmendia, J.L. Munoz, A. Velez ESS Bilbao, Bilbao, Spain F.J. Bermejo Bilbao, Faculty of Science and Technology, Bilbao, Spain V. Etxebarria, J. Portilla University of the Basque Country, Faculty of Science and Technology, Bilbao, Spain
	An input power system is currently being designed at ESS-Bilbao in order to inject the RF power provided by a klystron into the RFQ as part of the linac. In this work, some input power couplers based on a coaxial topology are carefully studied from an electromagnetic point of view. As we will show, the electrical properties of the ceramic window used to ensure the vacuum of the RFQ crucially deteriorates the matching of the devices. To overcome this drawback, a full-wave electromagnetic simulator is used to optimize the coupler dimensions in order to minimize both the return and insertion losses.

MOPC044	Design of the Radiofrequency Quadrupole Coldmodel for the ESS-BILBAO Linear Accelerator	175
	A. Velez, I. Bustinduy, N. Garmendia, O. Gonzalez, J.L. Munoz, D. de Cos ESS Bilbao, Bilbao, Spain F.J. Bermejo Bilbao, Faculty of Science and Technology, Bilbao, Spain V. Etxebarria, J. Portilla University of the Basque Country, Faculty of Science and Technology, Bilbao, Spain
	This work will present the design of the ESS-Bilbao LINAC RFQ cold model. The process goes through the electromagnetic design of the cavity by properly setting the resonant quadrupole and dipole modes, as well as the resonance frequency. The prototype includes the vane modulation designed to accelerate a 75 mA proton beam from 75 keV to 3 MeV, with an operating frequency of 352.2 MHz. To this end, electromagnetic and electrostatic simulations have been performed by means of the commercial software COMSOL. Furthemore, results for the three components of the electrical field distribution will be presented and compared to those calculated by evaluating the 8-term multipole expansion.

MOPC045	Commissioning of the ALBA Storage Ring RF System	178
	F. Pérez, B. Bravo, A. Salom, P. Sanchez CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
	ALBA is a 3 GeV, 400 mA, 3rd generation Synchrotron Light Source that is under commissioning in Cerdanyola, Spain. The RF System has to provide 3.6 MV of accelerating voltage and restore up to 540 kW of power to the electron beam. For that six RF plants, working at 500 MHz, are foreseen. The RF plants include several new developments: DAMPY cavity; the normal conducting HOM damped cavity developed by BESSY and based in the EU design; six are installed. CaCo; a cavity combiner to add the power of two 80 kW IOTs to produce the 160 kW needed for each cavity. WATRAX; a waveguide transition to coaxial, specially designed to feed the DAMPY cavities due to the geometrical and cooling constrains. Digital LLRF; fully designed at ALBA using commercial components. This paper shortly describes these systems and reports their performance during the ALBA commissioning.

MOPC046	CaCo: A Cavity Combiner for IOTs Amplifiers	181
	B. Bravo, F. Mares, F. Pérez, P. Sanchez CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain M.L. Langlois ESRF, Grenoble, France
	The ALBA storage ring uses six room temperature cavities; each one fed by two 80 kW IOTs amplifiers at 499.654 MHz. The power of the pair of transmitters is combined by a cavity combiner, CaCo. One of the design requirements of CaCo was that it continued working safely and with a good efficiency in the case of an IOT failure (asymmetrical mode). During the first asymmetric full power tests, in May 2010, with an active IOT and the other passive, the result was dramatic, the passive IOT broke in two parts after few hours of operation. This paper presents the experimental results and the electromagnetic field simulations of the asymmetrical operation mode of CaCo, i.e. one active IOT and the other passive, and analyze why the ceramic of the output tube of the passive IOT broke during the first performance of this mode. Also, it reports a possible solution to solve this problem.

MOPC047	RF Design of the Re-buncher Cavities for the LIPAC Deuteron Accelerator	184
	A. Lara, I. Podadera, F. Toral CIEMAT, Madrid, Spain
	Funding: Work partially supported by Spanish Ministry of Science and Innovation under project ENE2009-11230. Re-buncher cavities are an essential component of LIPAC (Linear IFMIF Prototype Accelerator), presently being built at Rokkasho (Japan). The deuteron beam exiting from the RFQ (Radio Frequency Quadrupole) structure has to be properly adapted to the superconducting RF (SRF) linac. Re-bunchers are placed in the Medium Energy Beam Transport (MEBT) line and their objective is to longitudinally focus the deuteron beam. IFMIF re-bunchers must provide a 350 kV E0LT at 175 MHz continuous wave (CW). The available length for the re-buncher is limited by the general layout of the MEBT. The high power dissipation derived from the high effective voltage and the short available length is an important design challenge. Four different normal conducting cavity designs were investigated: the pillbox type, double gap coaxial resonators, and multi-gap quarter wave and H resonators. The performance of these cavities was studied with the numerical codes HFSS and ANSYS. The fundamental frequency and field pattern of each re-buncher was investigated in HFSS. This work presents the results of such analyses.

MOPC049	Bead-pull Test Bench for Studying Accelerating Structures at RHUL	187
	S. Molloy ESS, Lund, Sweden R. Ainsworth, G.E. Boorman Royal Holloway, University of London, Surrey, United Kingdom C. Gabor STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom A. Garbayo AVS, Eibar, Gipuzkoa, Spain A.P. Letchford STFC/RAL, Chilton, Didcot, Oxon, United Kingdom A. Lyapin JAI, Egham, Surrey, United Kingdom P. Savage Imperial College of Science and Technology, Department of Physics, London, United Kingdom
	A bead-pull test stand has been constructed at Royal Holloway, University of London (RHUL) with the ability to provide electric field profile measurements along five degrees of freedom using the perturbation method. In this paper, we present example measurements using the test bench which include a field flatness profile of a 324MHz four vane Radio Frequency Quadrupole (RFQ) model designed as part of the Front End Test Stand (FETS) development at Rutherford Appleton Laboratory (RAL). Mechanical and operational details of the apparatus will also be described, as well as future plans for the development and usage of this facility.

MOPC050	Multipacting Analysis for the Superconducting RF Cavity HOM Couplers in ESS	190
	S. Molloy ESS, Lund, Sweden R. Ainsworth Royal Holloway, University of London, Surrey, United Kingdom R.J.M.Y. Ruber Uppsala University, Uppsala, Sweden
	The European Spallation Source (ESS) linac will consist of three families superconducting RF cavities to accelerate protons to the required 5 MW for collision with the target. If it is determined that HOM damping is required to limit the effect of beam induced modes, it is quite likely that HOM couplers will be installed. Multipacting in these couplers is a concern as thermally induced detuning of the fundamental notch filter has limited the achievable gradient in other high power machines. It is therefore important to avoid potential multipacting conditions during the design phase. Presented here are simulations using the Track3P code developed at SLAC. Multipacting regions are highlighted, electron trajectories are shown, and suitability of the proposed HOM coupler design is discussed.

MOPC051	The 100 MHz RF System for the MAX IV Storage Rings	193
	Å. Andersson, E. Elafifi, M. Eriksson, D. Kumbaro, P. Lilja, L. Malmgren, R. Nilsson, H. Svensson, P.F. Tavares MAX-lab, Lund, Sweden J.H. Hottenbacher RI Research Instruments GmbH, Bergisch Gladbach, Germany A. Milan CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain A. Salom ELETTRA, Basovizza, Italy
	The construction of the MAX IV facility has started and user operation is scheduled to commence 2015. The facility is comprised of two storage rings optimized for different wavelength ranges, and a linac-based short pulse facility. In this paper the RF systems for the two storage rings are described. The RF systems will be based on either tetrode or solid state amplifiers working at 100 MHz. Circulators will be used to give isolation between cavity and power amplifier. The main cavities are of normal conducting, entire copper, capacity loaded type, where the present cavities at MAX-lab has served as prototypes. For the MAX IV ring operation it is essential to elongate bunches, in order to minimize the influence of intra beam scattering on beam transverse emittances. For this, 3rd harmonic passive (Landau-) cavities are employed. These are of similar type as the main cavities, mainly because the capacity loaded type has the advantage of pushing higher order modes to relatively high frequencies compared to pill-box cavities. Digital low level RF systems will be used, bearing in mind the possibility of post mortem analysis.

MOPC052	Engineering Design and Fabrication of X-band RF Components	196
	M. Filippova, A. Olyunin, V. Soldatov, A. Solodko JINR, Dubna, Moscow Region, Russia S. Atieh, G. Riddone, I. Syratchev CERN, Geneva, Switzerland
	The CLIC RF frequency has been changed in 2008 from the initial 30 GHz to the European X-band 11.9942 GHz permitting beam independent power production using klystrons for accelerating structure testing. X-band klystron test facilities at 11.424 GHz are operated at SLAC and at KEK, and these facilities are used by CLIC study in the frame of the X-band structure collaboration for testing accelerating structures scaled to that frequency. Generally RF components are used in the transmission and the transformation of radio frequency signals generated by the power supply. The operating range of the devices accommodates the frequencies from 11.424 to 11.9942 GHz. RF components are needed for the Klystron test stand at CERN, and also for the X-FEL projects at PSI and Sincrotrone Trieste. Currently CERN is ordering tens of these companies to industry. The engineering design of the RF components (high power and compact loads, bi-directional couplers, X-band splitters, hybrids, phase shifters, variable power attenuators) and the main fabrication processes are presented here. K.M. Schirm et al., “A 12 GHZ RV Power source for the CLIC study”, Proc. of IPAC’10, THPEB053, p. 3990 (2010).

MOPC053	Mechanical Design and Fabrication Studies for SPL Superconducting RF Cavities	199
	S. Atieh, G. Arnau-Izquierdo, I. Aviles Santillana, O. Capatina, T. Renaglia, T. Tardy, N. Valverde Alonso, W. Weingarten CERN, Geneva, Switzerland
	CERN’s R&D programme on the Superconducting Proton Linac’s (SPL) superconducting radio frequency (SRF) elliptical cavities made from niobium sheets explores new mechanical design and consequently new fabrication methods, where several opportunities for improved optimization were identified. A stainless steel helium vessel is under design rather than a titanium helium vessel using an integrated brazed transition between Nb and the SS helium vessel. Different design and fabrication aspects were proposed and the results are discussed hereafter.

MOPC054	The LHC RF System - Experience with Beam Operation	202
	P. Baudrenghien, M. E. Angoletta, T. Argyropoulos, L. Arnaudon, J. Bento, T. Bohl, O. Brunner, A.C. Butterworth, E. Ciapala, F. Dubouchet, J. Esteban Muller, D.C. Glenat, G. Hagmann, W. Höfle, D. Jacquet, M. Jaussi, S. Kouzue, D. Landre, J. Lollierou, P. Maesen, P. Martinez Yanez, T. Mastoridis, J.C. Molendijk, C. Nicou, J. Noirjean, G. Papotti, A.V. Pashnin, G. Pechaud, J. Pradier, J. Sanchez-Quesada, M. Schokker, E.N. Shaposhnikova, D. Stellfeld, J. Tückmantel, D. Valuch, U. Wehrle, F. Weierud CERN, Geneva, Switzerland
	The LHC RF system commissioning with beam and physics operation for 2010 and 2011 are presented. It became clear in early 2010 that RF noise was not a lifetime limiting factor: the crossing of the much feared 50 Hz line for the synchrotron frequency did not affect the beam. The broadband LHC RF noise is reduced to a level that makes its contribution to beam diffusion in physics well below that of Intra Beam Scattering. Capture losses are also under control, at well below 0.5%. Longitudinal emittance blow-up, needed for ramping of the nominal intensity single bunch, was rapidly commissioned. In 2011, 3.5 TeV/beam physics has been conducted with 1380 bunches at 50 ns spacing, corresponding to 55% of the nominal current. The intensity per bunch (1.3 ·10¹¹ p) is significantly above the nominal 1.15 ·10¹¹. By August 2011 the LHC has accumulated more than 2 fb-1 integrated luminosity, well in excess of the 1 fb-1 target for 2011.

MOPC055	High Power Test of the First PIMS Cavity for Linac4	205
	F. Gerigk, J.-M. Giguet, P. Ugena Tirado, R. Wegner CERN, Geneva, Switzerland
	The PI-Mode Structure (PIMS) accelerates the Linac4 beam from 100 to 160 MeV. Twelve 7-cell cavities will be installed in the linac, with a gradient of ~4 MV/m and operating at a frequency of 352.2 MHz. A full-power prototype has been constructed at CERN in 2010 and was high- power tested in autumn 2010. Peak power tests at the Linac4 duty cycle and high-average power tests at increased duty cycles were completed successful, so that this prototype will be the first of the 12 cavities to be installed in Linac4. This paper reports on the high-power tests and the conditioning experience.

MOPC056	The Linac4 Power Coupler	208
	F. Gerigk, J.-M. Giguet, E. Montesinos, B. Riffaud, P. Ugena Tirado, R. Wegner CERN, Geneva, Switzerland
	Linac4 employs 3 types of accelerating structures after the RFQ: a Drift Tube Linac (DTL), a Cell-Coupled DTL (CCDTL), and a Pi-Mode Structure (PIMS) to accelerate the beam to 160 MeV. The structures are designed for a peak power of 1 MW per coupler, which consists of two parts: a ceramic window, which separates the cavity vacuum from the air in the wave-guides, and a so-called "coupling T", which couples the RF power through an iris to the cavity. In the frame of the Linac4 R&D both devices have been significantly improved with respect to their commonly used design. On the coupler side, the wave-guide short circuit with its matched length has been replaced by a fixed length λ/4 short circuit. The RF matching is done by a simple piston tuner, which allows a quick matching to different cavity quality factors. In the window part, which usually consists of a ceramic disc and 2 pieces of wave-guides with matching elements, the wave-guide sections could be completely suppressed, so that the window became very compact, lightweight, and much simpler to manufacture. In this paper we present electromagnetic simulations, and tests on first prototypes, which were constructed at CERN.

MOPC057	Loss of Landau Damping in the LHC	211
	E.N. Shaposhnikova, T. Argyropoulos, P. Baudrenghien, T. Bohl, A.C. Butterworth, J. Esteban Muller, T. Mastoridis, G. Papotti, J. Tückmantel, W. Venturini Delsolaro, U. Wehrle CERN, Geneva, Switzerland C.M. Bhat Fermilab, Batavia, USA
	Loss of Landau damping leading to a single bunch longitudinal quadrupole instability has been observed in the LHC during the ramp and on the 3.5 TeV flat top for small injected longitudinal emittances. The first measurements are in good agreement with the threshold calculated for the expected longitudinal reactive impedance budget of the LHC as well as with the threshold dependence on beam energy. The cure is a controlled longitudinal emittance blow-up during the ramp which for constant threshold through the cycle should provide an emittance proportional to the square root of energy.

MOPC058	Upgrade of the 200 MHz RF System in the CERN SPS	214
	E.N. Shaposhnikova, E. Ciapala, E. Montesinos CERN, Geneva, Switzerland
	The 200 MHz RF system, used in the SPS to accelerate all beams including those for the LHC, has four travelling wave structure cavities of different length. To stabilize the future higher intensity LHC beams in the SPS a larger (than now) controlled longitudinal emittance blow-up and therefore larger bucket and voltage amplitude will be necessary. However less voltage will be available in the existing system (which has a maximum peak RF power of 1 MW per cavity) due to the increased beam loading, in particular in the long cavities. This issue will be critical for beam acceleration but especially for beam transfer into the 400 MHz RF system of the LHC. The proposed solution is to shorten the two long cavities and use the freed sections together with spare sections to make two extra cavities and install two new power plants of 1.3 MW each. After this upgrade, which is a major part of the more general SPS upgrade for high luminosity LHC to be completed during 2017, the performance of the SPS RF system with high intensity beams will be significantly improved and at the same time the total impedance of the system will be reduced.

MOPC059	The Plane Wave Transformer Linac Development at NSRRC	217
	A. Sadeghipanah, J.-Y. Hwang, W.K. Lau NSRRC, Hsinchu, Taiwan T.H. Chang NTHU, Hsinchu, Taiwan
	A Plane-Wave-Transformer (PWT), standing wave linac operating at S-band frequency (2.9979 GHz) is being developed at NSRRC. This structure offers the advantages of high efficiency, compactness, fabrication simplicity and cost. The PWT prototype at NSRRC consists of three cells with two half-cells at the ends, separated by a set of four flat disks suspended and cooled by four water tubes inside a large cylindrical tank. To fully understand its physical properties, numerical modeling of the PWT prototype has been carried out by using the 2-D code SUPERFISH and 3-D code MAFIA. In this paper, we describe the principle properties of this structure, the electric parameters obtained from numerical simulations, and heat dissipation calculation. The mechanical design for prototype linac is also reported.

MOPC060	Bunching-frequency Multiplication for a THz Pulse-train Photoinjector	220
	Y.-C. Huang, F.H. Chao, C.H. Chen, K.Y. Huang NTHU, Hsinchu, Taiwan
	Funding: This work is supported by National Science Council under Contract NSC 99-2112-M-007 -013 -MY3. A THz-pulse-train photoinjector* employs a THz-pulse-train laser as its driver laser to generate a beam with a bunching frequency in the THz range. However a laser frequency is on the order of a few hundred THz. It is not possible to generate a beam from the pulse-train photoinjector with a bunching frequency exceeding the laser’s carrier frequency. In view of the strong demand for a compact x-ray free-electron laser (FEL), it is highly desirable to multiply the bunching frequency of the beam from a pulse-train injector to the x-ray frequencies. We propose to chirp the energy of the THz electron pulse train in an accelerator and compress the whole beam in a magnet to increase the electron bunching frequency. Our study shows a compression ratio or a bunching-frequency multiplication factor of a few tens is achievable from a properly designed magnetic chicane compressor. The bunching factor, however, is unfortunately degraded due to the energy chirp, emittance growth, and wake-field generation. In the conference, we will show that a bunching factor of a few ppm in the bunch-frequency multiplied beam is sufficient to build up the FEL power from a 10-time length reduced undulator. * Y. C. Huang, “Laser-beat-wave bunched beam for compact superradiance sources,” International Journal of Modern Physics B, Vol. 21 Issue 3/4, p277-286 (2007).

MOPC061	Simulations to Flatten the Field of the FETS RFQ	223
	S.R. Lawrie, A.P. Letchford STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom J.K. Pozimski, P. Savage Imperial College of Science and Technology, Department of Physics, London, United Kingdom
	A high performance Radio Frequency Quadrupole (RFQ) is the next major component to be installed on the Front End Test Stand (FETS) at the Rutherford Appleton Laboratory (RAL) in the UK. The beam dynamics, RF, thermal and mechanical designs of the RFQ are almost complete and so the copper has recently been purchased with a view to start cutting metal near Summer-time. This report summarizes the simulation work performed to ensure the RF design is sound. This includes performance studies of the end-wall dipole suppression fingers, tuning the frequency of the input and output vane end regions and implementing a simple solution to remove modulation induced field tilt.

MOPC062	EMMA RF Comissioning	226
	A.J. Moss, R.K. Buckley, P.A. McIntosh, A.E. Wheelhouse STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	EMMA (Electron Model for Many Applications), the world’s first Non-Scaling Fixed Field Alternating Gradient (NS-FFAG) accelerator is presently in operation at Daresbury Laboratory. The LLRF system is required to synchronize with ALICE (Accelerators and Lasers in Combined Experiments) its injector, which operates at 1.3GHz, and to produce an offset frequency of (+1.5 MHz to -4 MHz) to probe the longitudinal beam dynamics and to also maintain the phase and amplitude of the 19 copper RF cavities of the EMMA machine. The design, commissioning and results of the EMMA RF system is presented.

MOPC064	Upgrade and Commissioning of the 88-Inch Cyclotron Final Power Amplifier	229
	M. Kireeff Covo, D.F. Byford, P.W. Casey, A. Hodgkinson, S. Kwiatkowski, C.M. Lyneis, L. Phair, A. Ratti, C.P. Reiter LBNL, Berkeley, California, USA
	Funding: This work was supported by the Director, Office of Science, Office of High Energy and Nuclear Physics, Division of Nuclear Physics, U.S. Department of Energy under Contract DE-AC02-05CH11231. The RF system of the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory is a resonant system based on the quarter-wave cantilever type resonating structure. Power is fed to the Dee from the anode of the 500 kW RCA 6949 tetrode tube operating in grounded cathode configuration, which is capacitively coupled to the side of the Dee stem. The tube is obsolete and makes its continued use impractical. A new final power amplifier was designed and built using the commercially available tube Eimac 4W150,000E. The new amplifier was successfully commissioned and has been reliable and easy to operate. An overview of the system upgrade and details of the commissioning will be presented.

MOPC065	Ion Motion in the Vicinity of Microprotrusions in Accelerating Structures	232
	D.G. Kashyn, T.M. Antonsen, I. Haber, G.S. Nusinovich UMD, College Park, Maryland, USA
	Funding: This work is supported by Office of High Energy Physics of the U.S. Department of Energy. It is known that newly fabricated accelerating structures have almost ideally smooth surface. However, ‘post mortem’ examination of these structures reveals that their surface can be significantly modified after high-gradient operation. This surface modification can be caused by the appearance of microscopic protrusions. One of the factors leading to heating, melting and evaporation of these protrusions (factors resulting in the RF breakdown) is ion bombardment. In our study we analyze ion motion in the vicinity of microprotrusions both analytically and numerically. First, we study the ion motion in the RF electric field magnified by the protrusion in the absence of electron field emitted current and show that most of the ions do not reach the structure surface. Then we add into consideration the interaction of ions with Fowler-Nordheim current emitted from the tip of protrusion (dark current). First, we develop a model describing this interaction and then we supplement it with numerical results using PIC code WARP*. We show that the ions move towards the area occupied by the dark current, but this does not increase the bombardment of micro-protrusions. R.B. Palmer,et al, Phys. Rev ST Accel. Beams 12, 031002 (2009). P. Wilson, AIP Conf. Proc., 877, Melville, New York, 2006, p. 27. *J.-L. Vay, et al, Physics of Plasmas, 11, 2928 (2004).

MOPC067	X-Band Test Station at Lawrence Livermore National Laboratory	235
	R.A. Marsh, F. Albert, S.G. Anderson, C.P.J. Barty, G.K. Beer, R.R. Cross, G.A. Deis, C.A. Ebbers, D.J. Gibson, F.V. Hartemann, T.L. Houck LLNL, Livermore, California, USA C. Adolphsen, A.E. Candel, T.S. Chu, E.N. Jongewaard, Z. Li, C. Limborg-Deprey, T.O. Raubenheimer, S.G. Tantawi, A.E. Vlieks, F. Wang, J.W. Wang, F. Zhou SLAC, Menlo Park, California, USA
	Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. An X-band multi-bunch test station is being built at LLNL to investigate the science and technology paths required to boost the current mono-energetic gamma-ray (MEGa-Ray) brightness by orders of magnitude. The test station will consist of a 5.5 cell X-band RF photoinjector, single accelerator section, and beam diagnostics. Beam quality must be exceedingly high in order to produce narrow-bandwidth gamma-rays, requiring a robust state of the art photoinjector. The photoinjector will be a high gradient (200 MV/m peak surface field on the cathode) standing wave structure, featuring a dual feed racetrack coupler, elliptical irises, and an optimized first cell length. A solid-state Scandinova modulator will power a single SLAC XL4 11.424 GHz 50 MW klystron. RF distribution will allow for full powering of the photoinjector with the balance of the RF powering a single accelerator section so that the electron parameters can be measured. The status of the facility will be presented including commissioning schedule and first experiment plans. Future experimental programs pertinent to Compton scattering R&D, high gradient structure testing, and light source development will be discussed.

MOPC068	LANSCE RF System Improvements for Current and Future Programs*	238
	D. Rees, J.L. Erickson, R.W. Garnett, J.T.M. Lyles, L. Rybarcyk LANL, Los Alamos, New Mexico, USA
	The Los Alamos Neutron Science Center (LANSCE) is in the midst of an upgrade of the RF systems. This project will return LANSCE to its historical operating capability and sustain facility operations into the next decade. The LANSCE accelerator provides pulsed protons and spallation neutrons for defense and civilian applications. This project involves replacing all the existing 201 MHz RF stations and 805 MHz klystrons. LANSCE is also currently in the conceptual design phase of a program called the Material Test Station (MTS) to establish a 1 MW target station to irradiate fast reactor fuels and materials. A pre conceptual design is also in progress to extend the capabilities of MTS to a 2 MW target that will enable the first in a new generation of scientific facilities for the materials community. The emphasis of this new facility is "Matter-Radiation Interactions in Extremes" (MaRIE) which will be used to discover and design the advanced materials needed to meet 21st century national security and energy security challenges. The design and test results of the new RF systems will be presented as well as the RF system changes required to support the new missions.

MOPC071	Status of High Power Tests of Normal Conducting Short Standing Wave Structures*	241
	V.A. Dolgashev, Z. Li, S.G. Tantawi, A.D. Yeremian SLAC, Menlo Park, California, USA Y. Higashi KEK, Ibaraki, Japan B. Spataro INFN/LNF, Frascati (Roma), Italy
	Funding: Work Supported by Doe Contract No. DE-AC02-76SF00515 We report results of continuing high power tests of short standing wave structures. These tests are part of an experimental and theoretical study of basic physics of rf breakdown in 11.4 GHz, normal conducting structures. The goal of this study is to determine the accelerating gradient capability of normal conducting rf powered particle accelerators. We have tested structures of different geometries, cell joining techniques, and materials. We found that the breakdown rate dependence on peak magnetic fields is stronger than on peak surface electric fields for cylindrically symmetric structures powered via a TM01 mode launcher. We report test results for structures powered by side-coupled rectangular waveguides. We found that increased rf magnetic field due to the side-coupling increases the breakdown rate as compared to the same accelerating gradient in cylindrically symmetric structures.

MOPC072	Design of an RF Feed System for Standing-wave Accelerator Structures	244
	J. Neilson, V.A. Dolgashev, S.G. Tantawi SLAC, Menlo Park, California, USA
	Travelling wave (TW) accelerator structures are known to suffer from several deficiencies. A breakdown in one of the cells propagates towards the source. This results in damage to upstream cells in addition to the cell where the breakdown was initiated. The deficiencies of TW accelerator structures can be overcome by using standing wave (SW) cells that are fed in parallel. An RF breakdown is contained to the cell where it originates. This eliminates upstream cell damage and the resulting changes in phase shift between cells. In addition the feed structure can provide a high conductance port for vacuum pumping. We have completed the design of a parallel fed SW structure with a directional coupler for each cell and serpentine waveguide connection between couplers. This design approach improves isolation between the cells resulting in the maximum increase in the operational robustness of the accelerator structure. The design uses four feed arms spaced uniformly around the cell circumference to suppress dipole modes and improve damping of low order wakefields. Construction of a test structure in now underway and is scheduled for testing in October of this year.

MOPC073	A Dual-mode Accelerating Cavity to Test RF Breakdown Dependence on RF Magnetic Fields	247
	A.D. Yeremian, V.A. Dolgashev, J. Neilson, S.G. Tantawi SLAC, Menlo Park, California, USA
	Funding: * Work Supported by Doe Contract No. DE-AC02-76SF00515 RF Breakdown experiments on short accelerating structures at SLAC have shown that increased rf magnetic fields increase the probability of rf breakdowns. Moreover, the breakdown rate is highly correlated with the peak pulse-heating in soft-copper single-cell standing-wave structures of disk-loaded waveguide type. In these geometries the rf electric and magnetic fields are highly correlated. To separate effects of rf magnetic and electric fields on the rf breakdown rate, we have designed an X-band cavity with a geometry as close to that of a standing-wave accelerator cell as practically possible. This cavity supports two modes: an accelerating TM mode and a TE mode with no-surface-electric field but with a strong magnetic field. The cavity will be constructed and tested at the Accelerator Structure Test Area (ASTA) at SLAC.

MOPC077	Commissioning of Multibunch Feedback Systems at the Fast Ramping Stretcher Ring ELSA	250
	A. Roth, F. Frommberger, N. Heurich, W. Hillert, M. Schedler, R. Zimmermann ELSA, Bonn, Germany
	Funding: Supported by German Research Foundation through SFB/TR 16 and by Helmholtz Alliance through HA-10¹. At the Electron Stretcher Facility ELSA of Bonn University, an external beam of either unpolarized or polarized electrons is supplied to hadron physics experiments. The ELSA stretcherring operates in the energy range of 1.2 to 3.5 GeV and achieves a duty cycle of up to 80% using a fast energy ramp of 4 GeV/s. Under these conditions, an increase of the internal beam current from an actual value of 20 mA up to 200 mA is planned. Such an upgrade is mainly limited by the excitation of multibunch instabilities. As one active counteraction, we have installed state-of-the-art bunch-by-bunch feedback systems for the longitudinal, as well as for both transverse planes. The detailed setup with all main components and first results of the commissioning of the systems will be presented. In particular, the performance of the longitudinal feedback with a stabilized synchrotron frequency during the fast energy ramp will be discussed.

MOPC078	Operation of Superconducting Cavities in a Fast Ramping Electron Storage Ring	253
	A. Roth, W. Hillert ELSA, Bonn, Germany
	Funding: Supported by German Research Foundation through SFB/TR 16. The achievable maximum energy of a medium-sized electron accelerator is mainly limited by the accelerating voltage. Using superconducting (sc) cavities, the energy limitation can be shifted considerably. However, the operation of sc multi-cell cavities in a fast ramping storage ring causes additional problems which were investigated at the 3.5 GeV Electron Stretcher Accelerator ELSA. We studied the use of two 500 MHz sc cavities providing the necessary resonator voltage of up to 14 MV and replacing the normal conducting cavities of PETRA type. A large cavity coupling factor is required, so that using the existing 250 kW klystron, an internal beam of 50 mA can be accelerated up to 5 GeV. In addition, a fast detuning of the resonance frequency of the cavities must be implemented during beam injection and the energy ramp of 4 GeV/s. An appropriate 500 MHz structure is given by a five-cell cavity constructed for the JAERI-FEL-LINAC. Based on this geometry, HOM have been calculated from a numerical simulation. Since all monopole and a larger number of dipole HOM are well above the multibunch instabilities threshold, further studies about beam instabilities damping are essential.

MOPC079	Status of the Low Beta 0.07 Cryomodules for SPIRAL2	256
	P. Bosland, P. Carbonnier, F. Eozénou, P. Galdemard, O. Piquet CEA/DSM/IRFU, France M. Anfreville, C. Madec, L. Maurice CEA/IRFU, Gif-sur-Yvette, France P.-E. Bernaudin, R. Ferdinand GANIL, Caen, France Y. Gomez-Martinez LPSC, Grenoble Cedex, France A. Pérolat CEA, Gif-sur-Yvette, France
	The status of the low beta cryomodules for SPIRAL2, supplied by the Irfu institute of CEA Saclay, is reported in this paper. We summarise in three parts the RF tests performed on the cavities in vertical cryostat, the RF power tests of the qualifying cryomodule performed in 2010 and the RF power tests performed in 2011 on the first cryomodule of the series

MOPC080	First Considerations Concerning an Optimized Cavity Design for the Main Linac of BERLinPro	259
	B. Riemann, T. Weis DELTA, Dortmund, Germany W. Anders, J. Knobloch, A. Neumann HZB, Berlin, Germany H.-W. Glock, C. Potratz, U. van Rienen Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany F. Marhauser JLAB, Newport News, Virginia, USA
	Funding: work supported by BMBF under contracts 05K10PEA and 05K10HRC The Berlin Energy Recovery Linac Project (BERLinPro) is designed to develop and demonstrate CW linac technology and expertise required to drive next-generation Energy Recovery Linacs. Strongly HOM-damped multicell 1.3 GHz cavities are required for the main linac. The optimization of the cavities presented here is primarily based on the CEBAF 1.5 GHz 5-cell high-current cavity design, including HOM waveguide couplers. The cavity was scaled to 1.3 GHz and extended to 7 cells. Modifications to the end group design have also been studied. An effort was also made to reduce the ratio Epk/Eacc while still permitting HOMs to propagate.

MOPC081	Pulsed Mode Operation and Longitudinal Parameter Measurement of the Rossendorf SRF Gun	262
	J. Teichert, A. Arnold, H. Büttig, M. Justus, U. Lehnert, P. Michel, P. Murcek, Ch. Schneider, R. Schurig, R. Xiang HZDR, Dresden, Germany T. Kamps, J. Rudolph, M. Schenk HZB, Berlin, Germany I. Will MBI, Berlin, Germany
	Funding: The European Community-Research Infrastructure Activity under the FP7 program (EuCARD, contract number 227579) the German Federal Ministry of Education and Research grant 05 ES4BR1/8. The Rossendorf SRF gun with a 3 1/2 cell cavity has been operated since 2007. It has produced CW beam with the electron energy of 3 MeV and the average current up to 16 μA. The electron beam of the gun has successfully injected the ELBE superconducting linac since 2010. The Nb cavity has shown constant quality during the operation and for the Cs2Te photocathode life time of months could be obtained. Recently the gun started to run in the pulsed mode with higher gradient. The longitudinal parameters have been measured in this mode. The dark current arose from the high gradient is studied. The main field emission source has been found to be the half cell. Meanwhile, two modified 3+1/2 cell niobium cavities have been fabricated and tested in Jlab. In this paper the new status of the SRF gun will be presented, and the latest results of the beam experiments will be discussed.

MOPC082	Status of the 325 MHz SC CH-Cavity at IAP Frankfurt	265
	M. Busch, F.D. Dziuba, H. Podlech, U. Ratzinger IAP, Frankfurt am Main, Germany M. Amberg, K. Aulenbacher HIM, Mainz, Germany W.A. Barth, S. Mickat GSI, Darmstadt, Germany
	Funding: BMBF contract no. 06FY161I At the Institute for Applied Physics (IAP), University of Frankfurt, a s.c. 325 MHz CH-Cavity is under development for future beam tests at GSI UNILAC, Darmstadt. The cavity with 7 accelerating cells has a geometrical beta of 0.15 corresponding to 11.4 AMeV. The design gradient is 5 MV/m. The geometry of this resonator was optimized with respect to a compact design, low peak fields, surface processing, power coupling and tuning. Furthermore a new tuning system based on bellow tuners inside the resonator will control the frequency during operation. After rf tests in Frankfurt the cavity will be tested with a 10 mA, 11.4 AMeV beam delivered by the GSI UNILAC. In this paper rf simulations, multipacting analysis as well as thermal calculations will be presented.

MOPC083	Structural Mechanics of Superconducting CH Cavities	268
	M. Amberg, K. Aulenbacher HIM, Mainz, Germany W.A. Barth, S. Mickat GSI, Darmstadt, Germany M. Busch, F.D. Dziuba, H. Podlech, U. Ratzinger IAP, Frankfurt am Main, Germany
	The superconducting CH-structure (Crossbar-H-mode) is a multi-cell drift tube cavity for the low and medium energy range operated in the H21-mode, which has been developed at the Institute for Applied Physics (IAP) of Frankfurt University. With respect to different high power applications two types of superconducting CH-structures (f = 325 MHz, β = 0.16, seven cells and f = 217 MHz, β = 0.059, 15 cells) are presently under construction and accordingly under development. The structural mechanical simulation is a very important aspect of the cavity design. Furthermore, several simulations with ANSYS Workbench have been performed to predict the deformation of the cavity walls due to the cavity cool-down, pressure effects and mechanical vibrations. To readjust the fast frequency changes in consequence of the cavity shape deformation, a new concept for the dynamic frequency tuning has been investigated, including a novel type of bellow-tuner.

MOPC084	The Superconducting cw LINAC Demonstrator for GSI	271
	F.D. Dziuba, M. Busch, H. Podlech, U. Ratzinger IAP, Frankfurt am Main, Germany M. Amberg, K. Aulenbacher HIM, Mainz, Germany W.A. Barth, S. Mickat GSI, Darmstadt, Germany
	Funding: BMBF Contr. No. 06FY9089I, Helmholtz Institut Mainz At GSI a new, superconducting (sc) continuous wave (cw) LINAC is under design in cooperation with the Institute for Applied Physics (IAP) of Frankfurt University and the Helmholtz Institut Mainz (HIM). This proposed LINAC is highly requested by a broad community of future users to fulfill the requirements of nuclear chemistry, nuclear physics, and especially in the research field of Super Heavy Elements (SHE). In this context the preliminary layout of the LINAC has been carried out by IAP. The main acceleration of up to 7.3 AMeV will be provided by nine sc Crossbar-H-mode (CH) cavities operated at 217 MHz. Currently, a prototype of the cw LINAC as a demonstrator is under development. The demonstrator comprises a sc CH-cavity embedded between two sc solenoids mounted in a horizontal cryomodule. A full performance test of the demonstrator in 2013/14 by injecting and accelerating a beam from the GSI High Charge Injector (HLI) is one important milestone of the project. The status of the demonstrator is presented.

MOPC085	Quality Assessment for Industrially Produced High-Gradient Superconducting Cavities	274
	F. Schlander, S. Aderhold, E. Elsen, D. Reschke, M. Wenskat DESY, Hamburg, Germany
	Funding: This work is supported by the Commission of the European Communities under the 7th Framework Programme “Construction of New Infrastructures – Preparatory Phase”, contract number 206711. A series of some 600 superconducting 1.3 GHz cavities will start being delivered to DESY by industry in early 2012. Although a considerably smaller gradient satisfies the needs for the European XFEL the electro-polished cavities (50% of the delivery) are deemed to be suitable for gradients in excess of 35 MV/m, the performance goal of the International Linear Collider (ILC). Specifically 24 cavities will be supplied without helium tank to enable further investigations. The results may serve to improve overall performance; limitations such as field emission and thermal breakdown of superconductivity ("quench") are still under investigation. For this matter the DESY ILC group has developed tools to monitor aspects of the cavity fabrication. An automated optical mapping system (OBACHT) is being commissioned and will be complemented by software for automated cavity surface feature recognition. For cold RF tests a Second Sound setup for locating the positions of the thermal breakdown is routinely used. These diagnostic tools will give guidance on post-processing cavities for best performance. The current status of these projects will be described.

MOPC086	Description and First Experience with the RF Measurement Procedure for the European XFEL SC Cavity Production	277
	A.A. Sulimov, Th. Buettner, A. Gössel, D. Kostin, G. Kreps, W.-D. Möller, D. Reschke, J.H. Thie, K. Twarowski DESY, Hamburg, Germany
	Cavity production for the European XFEL was recently started with first Nb sheets arriving. From this stage to the accelerating module being ready for the linac installation, many critical RF measurements are necessary. During the mechanical cavity fabrication the cavity half-cells, dumb-bells and end-groups are measured and sorted. The cavity spectrum and field profiles are measured and tuned. The HOM (Higher Oder Modes) couplers filter tuning, vertical cavity RF tests, cavity checks during the string assembly and final cavity performance measurements in the module as well as the fundamental mode and HOM RF spectra measurements complete the sequence. We present the procedures of the RF measurements and discuss the first results for the XFEL prototype modules with special attention for the cavity tuning.
	Poster MOPC086 [0.515 MB]

MOPC088	Bead-pull Measurement using Phase-Shift Technique in Multi-cell Elliptical Cavity	280
	S. Ghosh, A. Mandal, S. Seth, S.S. Som DAE/VECC, Calcutta, India
	The project on the development of high-beta multi-cell elliptical shape superconducting rf linac cavity at around 704 MHz has been funded at VECC, Kolkata, India. A full-scale copper prototype cavity has been designed and fabricated. There are 5 distinct modes exist in the cavity and the accelerating mode is pi-mode in which each cell operates at same frequency with phase difference of 180 degrees between two neighboring cells. A fully automated bead-pull measurement setup has been developed for analyzing these modes and field profile distribution at different modes in such type of linac cavity. A special measurement method inside the cavity using phase-shift technique is proposed in this paper, which describes the development of mechanical setup comprising pulleys and stepper motor–gear arrangement, PC-based control system for precise movement of bead using stepper motor, measurement using VNA, development of software for data acquisition & automation and measurement results for the 5-cell copper prototype cavity.

MOPC089	RF Simulations for the QWR Cavities of PIAVE-ALPI	283
	M. Comunian, F. Grespan, A. Palmieri INFN/LNL, Legnaro (PD), Italy
	The PIAVE-ALPI linac is composed of several families of QWR cavities. In order to have a thorough description of the accelerator in terms of beam dynamics, a detailed field mapping of the accelerating cavities is necessary, including non-linear behavior of the off-axis fields, as well as the steering and dispersion effects due to transverse components. For such a purpose, a set of RF simulation was accomplished, with the codes HFSS and COMSOL. The details about these simulations and the main outcomes and results will be described in this article.

MOPC090	Tuner Performance in the S1-global Cryomodule	286
	R. Paparella, A. Bosotti, C. Pagani INFN/LASA, Segrate (MI), Italy C. Albrecht, K. Jensch, L. Lilje DESY, Hamburg, Germany S. Barbanotti, Y.M. Pischalnikov, W. Schappert Fermilab, Batavia, USA H. Hayano, E. Kako, S. Noguchi, N. Ohuchi, Y. Yamamoto KEK, Ibaraki, Japan
	S1-Global is a collaborative effort of INFN, DESY, FNAL, SLAC and KEK, in the framework of the ILC global collaboration. For this project two cryomodules, 6 meter long and hosting four SC cavities each, were realized and successfully cold tested at KEK-STF. Three different cavity tuning systems, provided with fast tuning capability through piezoelectric actuators (piezo), were installed, and fully characterized in static and dynamic operation: Blade Tuner from INFN/FNAL, Saclay Tuner from DESY, Slide Jack Tuner from KEK. Finally, Lorenz Force Detuning (LFD) active compensation has been successfully achieved during high power cavity tests in pulsed RF regime, where active control of the LFD disturbance up to Hz-level residual detuning has been achieved with each type of tuning system up to the maximum gradient of each cavity. The installation procedures, together with the relevant results and their analyses are summarized in the paper.

MOPC091	Status of the XFEL 3.9 GHz Injector Section	289
	P. Pierini, M. Bonezzi, A. Bosotti, M. Fusetti, P.M. Michelato, L. Monaco, R. Paparella, D. Sertore INFN/LASA, Segrate (MI), Italy E. Vogel DESY, Hamburg, Germany
	The European XFEL will use a superconducting third harmonic section to achieve the necessary beam quality for the FEL process. The concept has been successfully proven at the FLASH linac in DESY, with a 4 cavity superconducting module contributed by FNAL. The design of the third harmonic system at the XFEL injector is being finalized and prototypes of the components (cavities and couplers) have been fabricated and are currently in the testing stage. The paper will provide a status of the activities.

MOPC092	Effect of Current Densities on Sulfur Generation at Electropolished Niobium Surface	292
	P.V. Tyagi Sokendai, Ibaraki, Japan H. Hayano, S. Kato, M. Nishiwaki, T. Noguchi, T. Saeki, M. Sawabe KEK, Ibaraki, Japan
	We conducted a series of electropolishing (EP) experiments in aged EP acid with high (≈50 mA/cm²) and low (≈30 mA/cm²) current densities on Nb surfaces. The experiments were carried out both for laboratory coupons and a real Nb single cell cavity with six witness samples located at three typical positions (equator, iris and beam pipe). All the samples surface were investigated by XPS (x-ray photoelectron spectroscopy), SEM (scanning electron microscope) and EDX (energy dispersive x-ray spectroscopy). The surface analysis showed the EP with a high current density produced a huge amount sulfate particles at Nb surface whereas the EP with a low current density is very helpful to mitigate sulfate at Nb surface in both the experiments.

MOPC093	Novel Field Emission Scanner for Surface Study of Niobium SRF Cavity	295
	S. Kato, M. Nishiwaki, T. Noguchi KEK, Ibaraki, Japan V. Chouhan GUAS, Kanagawa, Japan P.V. Tyagi Sokendai, Ibaraki, Japan
	It is mandatory to investigate field emission on Nb SRF cavity systematically since strong field emission often limits the cavity performance. The field emission strength and the number of emission sites strongly depend on Nb surface properties which are determined by its surface treatment and handling. Field emission scanner (FES) developed allows us to measure a distribution of the field emitting sites over a sample surface at a given field strength along with its FE-SEM observation and energy dispersive x-ray analysis. FES consists of an anode needle driven by precise 3D stepping motors and an eucentric sample stage. The compact scanner was installed into the space between the object lens and the SEM sample holder. In addition, this system was newly equipped with a sample load-lock system for existing UHV suitcases. Therefore a sample coupon to be observed is hardly exposed to contaminants and dust particles during the transportation. In-situ heating of a sample coupon can be done during an experiment to simulate a baking process of a SRF cavity. This article describes development of the field emission scanner and its preliminary results of the application to niobium samples.

MOPC095	Superconducting Cavity R&D for ILC at MHI	298
	H. Hitomi, H. Hara, F. Inoue, K. Kanaoka, K. Sennyu, T. Yanagisawa MHI, Kobe, Japan
	We have developed and manufactured some superconducting RF cavity for STF project in KEK. In recent vertical test in KEK, the MHI-#12 cavity which is one of cavities for STF phase 2 project reached ILC specification(max Eacc was about 40MV/m). So techniques for manufacturing cavity is making steady progress in MHI. To be realized ILC project, we also try to decrease the manufacturing cost by using some new techniques, for example Laser Beam Welding, deep drawing, seamless dumbbell, etc. In this meeting, we will report recent MHI's activities for ILC.

MOPC096	Design and Fabrication of a 5-Cell High Current Superconducting Cavity	301
	Y.M. Li, K.X. Liu, S.W. Quan, F. Zhu PKU/IHIP, Beijing, People's Republic of China R. Nassiri ANL, Argonne, USA
	Funding: National High Technology Research and Development program 863 (2009AA03Z206) Energy recovery linacs (ERL) is promising to achieve high average current with superior beam quality. The key component for accelerating such high current beams is the superconducting radio frequency (SRF) cavity. The design of a 1.3 GHz 5-cell high current superconducting cavity has been carried out under the cooperation between Peking University (PKU) and Argonne National Laboratory (ANL). RF properties, damping of the HOMs, multipacting and mechanical features of this cavity have been discussed and the final design is presented.

MOPC097	LLRF Control System for PKU DC-SC Photocathode Injector	304
	H. Zhang, Y.M. Li, K.X. Liu, F. Wang, B.C. Zhang PKU/IHIP, Beijing, People's Republic of China
	A 1.3 GHz 3.5 Cell LG niobium cavity is installed for the new PKU DC-SC injector as its accelerating cavity with working temperature is 2K. High amplitude and phase stability is required for the updated SRF photocathode injector. This paper describes the design of Low Level RF control system based on FPGA, including hardware and software,and the communication function is realized by Tri-State Ethernet. The system should be operated on the precision with the amplitude of ±0.1% and phase stability of ±0.1°.

MOPC101	Vertical Test of PEFP Prototype SRF Cavity	307
	H.S. Kim, Y.-S. Cho, H.-J. Kwon KAERI, Daejon, Republic of Korea
	Funding: This work was supported by Ministry of Education, Science and Technology of the Korean Government. The PEFP Proton linac is a 100-MeV machine which consists of a proton injector, a 3-MeVRFQ and 100-MeV DTL. For the extension of the machine beyond 100 MeV, SRF technology is under consideration. As a prototyping activity, a superconducting RF cavity with a geometrical beta of 0.42 and a resonant frequency of 700 MHz has been designed, fabricated and tested. The cavity is an elliptical shape with 5 cells stiffened by double-ring structure. A design accelerating gradient is 8.0 MV/m at the operating temperature of 4.2 K and maximum duty factor is 9%. For the vertical test of the cavity, a cryostat with a vacuum jacket and multi-layer insulation was prepared. The RF system for driving the cavity is based on PLL to track the resonant frequency. In case of lack of RF power, a two-way RF power combiner based on splitted coaxial transmission line is considered. The details of the vertical test setup and test results will be presented in this paper.

MOPC102	RF and Surface Properties of Superconducting Samples	310
	T. Junginger, W. Weingarten CERN, Geneva, Switzerland T. Junginger MPI-K, Heidelberg, Germany R. Seviour Lancaster University, Lancaster, United Kingdom C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: Work supported by the German Doctoral Students program of the Federal Ministry of Education and Research (BMBF) The surface resistance Rs of superconducting cavities can be obtained from the unloaded quality factor Q0. Since Rs varies strongly over the cavity surface its value must be interpreted as averaged over the whole cavity surface. A more convenient way to investigate the surface resistance of superconducting materials is therefore to examine small samples, because they can be manufactured cheaply, duplicated easily and used for further surface analyses. At CERN a compact Quadrupole Resonator has been developed for the RF characterization of superconducting samples at different frequencies. In this contribution, results from measurements on bulk niobium and niobium film on copper samples are presented. It is shown how different contributions to the surface resistance depend on temperature, applied RF magnetic field and frequency. Furthermore, measurements of the maximum RF magnetic field as a function of temperature and frequency in pulsed and CW operation are presented. The study is accompanied by measurements of the surface properties of the samples by various techniques.

MOPC103	Cryostat for Testing HIE-ISOLDE Superconducting RF Cavities	313
	O. Capatina, J.P. Brachet, G. Cuccuru, M. Pasini, T. Renaglia, M. Therasse, B. Vullierme CERN, Geneva, Switzerland
	The High Intensity and Energy ISOLDE (HIE-ISOLDE) project is a major upgrade of the existing ISOLDE and REX-ISOLDE facilities at CERN [1], with the objective of increasing the energy and the intensity of the delivered radioactive ion beams (RIB). This project aims to fill the request for a more energetic post accelerated beam by means of a new superconducting (SC) linac based on Quarter Wave Resonators (QWRs). A research and development program looking at all different aspects of the SC linac has started in 2008 and continued throughout 2010. In particular the R&D effort has focused on the development of the high β cavity (β = 10.3%), for which it has been decided to adopt the Nb sputtered on Cu substrate technology. Two prototype cavities were manufactured and are undergoing RF cold tests. The pre-series cavity fabrication is under way using 3D forged Cu billets. A single vacuum cryostat was designed and built to test these cavities at liquid helium temperatures. The paper details the main design concepts of the test cryostat as well as the results of the cryogenic behavior of the complete set-up including the cryostat, the RF cavity, the tuner and the main coupler.

MOPC104	HIE-ISOLDE SRF Development Activities at CERN	316
	M. Therasse, O. Brunner, S. Calatroni, J.K. Chambrillon, B. Delaup, M. Pasini CERN, Geneva, Switzerland
	The HIE-ISOLDE project has initiated a new development phase on the SRF domain at CERN. In particular, the HIE-ISOLDE project aims at the construction of the 32 Quarter Wave Resonators (QWRs) using the Nb on Cu sputtering technology. The paper describes the refurbishment of the test infrastructure and the activities from the cavity production to the cold test, including quality assurance procedure for the correct handling of the resonators.

MOPC105	Design of the High Beta Cryomodule for the HIE-ISOLDE Upgrade at CERN	319
	L.R. Williams, A.P. Bouzoud, N. Delruelle, J. Gayde, Y. Leclercq, M. Pasini, J.Ph. G. L. Tock, G. Vandoni CERN, Geneva, Switzerland
	The major upgrade of the energy and intensity of the radioactive ion beams of the existing ISOLDE and REX-ISOLDE facilities at CERN will, in the long term, require downstream of the existing machine, the installation of four high-β and two low-β cryo-modules. The first stage of this upgrade, involving the design, construction, installation and commissioning of two high-β cryo-modules is approved and design work is underway at CERN. The high-β cryo-module houses five high-β superconducting cavities and one superconducting solenoid. As well as providing optimum conditions for physics, where the internal active components must remain aligned within tight tolerances, the cryo-modules need to function under stringent common vacuum and cryogenic conditions. To preserve the RF cavity performance their assembly and sub-system testing will need to be carried out using specifically designed tooling in a class 100 clean-room. We present the determining factors constraining the design of the high-β cryo-module together with the design choices that these factors have imposed.

MOPC106	Study of the Variation of Transverse Voltage in the 4 Rod Crab Cavity for LHC	322
	B.D.S. Hall, P.K. Ambattu, G. Burt, C. Lingwood Cockcroft Institute, Lancaster University, Lancaster, United Kingdom P. Goudket, C. Hill STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	The planned high luminosity upgrade to LHC will utilise crab cavities to rotate the beam in order to increase the luminosity in the presence of a finite crossing angle. A compact design is required in order for the cavities to fit between opposing beam-lines. In this paper we discuss we discuss one option for the LHC crab cavity based on a 4 rod TEM deflecting cavity. Due to the large transverse size of the LHC beam the cavity is required to have a large aperture while maintaining a constant transverse voltage across the aperture. The cavity has been optimised to minimise the variation of the transverse voltage while keeping the peak surface electric and magnetic fields low for a given kick. This is achieved while fitting within the strict design space of the LHC. The variation of deflecting voltage across the aperture has been studied numerically and compared with numerical and analytical estimates of other deflecting cavity types. Performance measurements an aluminium prototype of this cavity are presented and compared to the simulated design.

MOPC107	HOM and FP Coupler Design for the NLSF High Gradient SC Cavity	325
	R.M. Jones, N. Juntong UMAN, Manchester, United Kingdom
	The design of both higher order mode (HOM) and fundamental power (FP) couplers for the New Low Surface Field (NLSF) cavity* is presented. Here we study using the ILC baseline couplers for this new superconducting cavity. A Balleyguier method** of calculating external quality factor is used and the results validated using both Microwave studio and HFSS. * N. Juntong and R.M. Jones, SRF2009, THPPO024, 2009. ** P. Balleyguier, LINAC98, MO4037, 1998

MOPC108	Cornell SRF New Materials Program*	328
	S. Posen, M. Liepe, Y. Xie CLASSE, Ithaca, New York, USA
	Funding: Work supported by NSF Career award PHY-0841213, DOE award ER41628, and the Alfred P. Sloan Foundation The SRF group at Cornell has recently pioneered an extensive program to investigate alternative materials for superconducting cavities. We have developed facilities to fabricate Nb3Sn, a superconductor which will theoretically be able to reach more than twice the maximum accelerating field of Nb in a cavity under the same operating conditions. In addition, with the critical temperature of Nb3Sn being twice that of Nb, Nb3Sn would allow operation of SRF cavities with a much higher cryogenic efficiency. We have also manufactured two TE cavities that measure the RF properties of small, flat samples, ideal for material fabrication methods in development. This paper presents an overview of the materials research program. First results from tests of Nb3Sn samples are presented.

MOPC109	Suppression of Coupler Kicks in 7-Cell Main Linac Cavities for Cornell's ERL	331
	N.R.A. Valles, M. Liepe, V.D. Shemelin CLASSE, Ithaca, New York, USA
	Funding: Supported by NSF award DMR-0807731 Cornell is developing a 5 GeV Energy Recovery Linac operating at 100 mA with very small emittances (~30 pm at 77 pC bunch charge) in the horizontal and vertical directions. We investigate the effect of the fundamental RF power couplers of the main linac SRF cavities on the beam using the ACE3P software package. The cavities in the ERL main linac will be operated at very high loaded quality factors of up to 6.5·10⁷, corresponding to a full bandwidth of only 20 Hz. Cavity microphonics will detune the cavities by more than one bandwidth during operation, thereby causing a time dependent change of the coupler kick in addition to its fast oscillation at the RF frequency. In order to investigate the dependence of the coupler kick on the cavity frequency, we calculate the coupler kick given to the beam for the case of a detuned RF cavity. We show that a compensation stub geometry located opposite to the input coupler port can be optimized to reduce the overall kick given to the beam and the emittace growth caused by its time dependence.

MOPC111	Progress of ILC High Gradient SRF Cavity R&D at Jefferson Lab	334
	R.L. Geng, J. Dai, G.V. Eremeev, A.D. Palczewski JLAB, Newport News, Virginia, USA
	Funding: US Department of Energy Latest progress of ILC high gradient SRF cavity R&D at Jefferson Lab will be presented. 9 out of 10 real 9-cell cavities reached an accelerating gradient of more than 38 MV/m at a unloaded quality factor of more than 8·10⁹. New understandings of quench limitation in 9-cell cavities are obtained through instrumented studies of cavities at cryogenic temperatures. Our data have shown that present limit reached in 9-cell cavities is predominantly due to localized defects, suggesting that the fundamental material limit of niobium is not yet reached in 9-cell cavities and further gradient improvement is still possible. Some examples of quench-causing defects will be given. Possible solutions to pushing toward the fundamental limit will be described.

MOPC112	Fabrication and Testing Status of CEBAF 12 GeV Upgrade Cavities	337
	F. Marhauser, A. Burrill, G.K. Davis, D. Forehand, C. Grenoble, J. Hogan, R.B. Overton, A.V. Reilly, R.A. Rimmer, M. Stirbet JLAB, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The 12 GeV upgrade of the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Laboratory (JLab) is under way. All cavities have been built by industry and are presently undergoing post-processing and final low and high power qualification before cryomodule assembly. The status is reported including fabrication-related experiences, observations and issues throughout production, post-processing and qualification.

MOPC113	Results of Cavity Series Fabrication at Jefferson Laboratory for the Cryomodule “R100”	340
	F. Marhauser, W.A. Clemens, M.A. Drury, D. Forehand, J. Henry, S. Manning, R.B. Overton, R.S. Williams JLAB, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. A series production of eight superconducting RF cavities for the cryomodule R100 was conducted at JLab in 2010. The cavities underwent chemical post-processing prior to vertical high power testing and routinely exceeded the envisaged performance specifications. After cryomodule assembly, cavities were successfully high power acceptance tested. In this paper, we present the achievements paving the way for the first demonstration of 100 MV (and beyond) in a single cryomodule to be operated at CEBAF.

MOPC114	Design, Fabrication and Testing of Medium-Beta 650 MHz SRF Cavity Prototypes for Project-X	343
	F. Marhauser, W.A. Clemens, J. Henry, P. Kneisel, R. Martin, R.A. Rimmer, G. Slack, L. Turlington, R.S. Williams JLAB, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. A new type of superconducting radio frequency (SRF) cavity shape with a shallow equator dome to reduce electron impact energies for suppressing multipacting barriers has been proposed. The shape is in consideration for the first time in the framework of Project-X to design a potential multi-cell cavity candidate for the medium-beta section of the SRF proton CW linac operating at 650 MHz. Rationales covering the design of the multi-cell cavity, the manufacture, post-processing and high power testing of two single-cell prototypes are presented.

MOPC115	JLab SRF Cavity Fabrication Errors, Consequences and Lessons Learned	346
	F. Marhauser JLAB, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 Today, elliptical superconducting RF (SRF) cavities are preferably made from deep-drawn niobium sheets as pursued at Jefferson Laboratory (JLab). The fabrication of a cavity incorporates various cavity cell machining, trimming and electron beam welding (EBW) steps as well as surface chemistry that add to forming errors creating geometrical deviations of the cavity shape from its design. An analysis of in-house built cavities over the last years revealed significant errors in cavity production. Past fabrication flaws are described and lessons learned applied successfully to the most recent in-house series production of multi-cell cavities.

MOPC116	Development of Nb and Alternative Material Thin Films Tailored for SRF Applications	349
	A-M. Valente-Feliciano, H.L. Phillips, C.E. Reece, J.K. Spradlin, B. Xiao, X. Zhao JLAB, Newport News, Virginia, USA H. Baumgart, D. Gu ODU, Norfolk, Virginia, USA D. Beringer, R.A. Lukaszew The College of William and Mary, Williamsburg, USA K.I. Seo NSU, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S.DOE Contract No. DE-AC05-06OR23177. Over the years, Nb/Cu technology, despite its shortcomings due to the commonly used magnetron sputtering, has positioned itself as an alternative route for the future of superconducting structures used in accelerators. Recently, significant progress has been made in the development of energetic vacuum deposition techniques, showing promise for the production of thin films tailored for SRF applications. JLab is pursuing energetic condensation deposition via techniques such as Electron Cyclotron Resonance and High Power Impulse Magnetron Sputtering. As part of this project, the influence of the deposition energy on the material and RF properties of the Nb thin film is investigated with the characterization of their surface, structure, superconducting properties and RF response. It has been shown that the film RRR can be tuned from single digits to values greater than 400. This paper presents results on surface impedance measurements correlated with surface and material characterization for Nb films produced on various substrates, monocrystalline and polycrystalline as well as amorphous. A progress report on work on NbTiN and AlN based multilayer structures will also be presented.

MOPC117	Advance in Vertical Buffered Electropolishing on Niobium for Particle Accelerators*	352
	A.T. Wu, S. Jin, J.D. Mammosser, C.E. Reece, R.A. Rimmer JLAB, Newport News, Virginia, USA L. Lin, X.Y. Lu, K. Zhao PKU/IHIP, Beijing, People's Republic of China
	Funding: The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes. Niobium (Nb) is the most popular material that has been employed for making superconducting radio frequency (SRF) cavities to be used in various particle accelerators over the last couple of decades. One of the most important steps in fabricating Nb SRF cavities is the final chemical removal of 150 μm of Nb from the inner surfaces of the SRF cavities. This is usually done by either buffered chemical polishing (BCP) or electropolishing (EP). Recently a new Nb surface treatment technique called buffered electropolishing (BEP) has been developed at Jefferson Lab. It has been demonstrated that BEP can produce the smoothest surface finish on Nb ever reported in the literature while realizing a Nb removal rate as high as 10 μm/min that is more than 25 and 5 times quicker than those of EP and BCP(112) respectively. In this contribution, recent advance in optimizing and understanding BEP treatment technique is reviewed. Latest results from RF measurements on BEP treated Nb single cell cavities by our unique vertical polishing system will be reported. Authored by The Southeastern Universities Research Association, Inc. under U.S. DOE Contract No. DE-AC05-84ER40150.

MOPC118	Effects of the Thickness of Niobium Surface Oxide Layers on Field Emission*	355
	A.T. Wu, S. Jin, J.D. Mammosser, R.A. Rimmer JLAB, Newport News, Virginia, USA X.Y. Lu, K. Zhao PKU/IHIP, Beijing, People's Republic of China
	Funding: The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes. Field emission on the inner surfaces of niobium superconducting radio frequency cavities is still one of the major obstacles for reaching high accelerating gradients for SRF community. Our previous experimental results* seemed to imply that the threshold of field emission was related to the thickness of Nb surface oxide layers. In this contribution, a more detailed study on the influences of the surface oxide layers on the field emission on Nb surfaces will be reported. By anodization technique, the thickness of the surface pentoxide layer was artificially fabricated from 3 nm up to 460 nm. A home-made scanning field emission microscope was employed to perform the scans on the surfaces. Emitters were characterized using a scanning electron microscope together with an energy dispersive x-ray analyzer. The SFEM experimental results were analyzed in terms of surface morphology and oxide thickness of Nb samples and chemical composition and geographic shape of the emitters. A model based on the classic electromagnetic theory was developed trying to understand the experimental results. Possibly implications for Nb SRF cavity applications from this study will be discussed. * A.T. Wu et al., Proc. of IPAC 2010, Kyoto, Japan, WEPEC081, p. 3067 (2010). Authored by The Southeastern Universities Research Association, Inc. under U.S. DOE Contract No. DE-AC05-84ER40150.

MOPC119	Fastest Electropolishing Technique on Niobium for Particle Accelerators*	358
	A.T. Wu, S. Jin, R.A. Rimmer JLAB, Newport News, Virginia, USA X.Y. Lu, K. Zhao PKU/IHIP, Beijing, People's Republic of China
	Funding: The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes. Field emission on the inner surfaces of niobium (Nb) superconducting radio frequency (SRF) cavities is still one of the major obstacles for reaching high accelerating gradients for SRF community. Our previous experimental results [1] seemed to imply that the threshold of field emission was related to the thickness of Nb surface oxide layers. In this contribution, a more detailed study on the influences of the surface oxide layers on the field emission on Nb surfaces will be reported. By anodization technique, the thickness of the surface pentoxide layer was artificially fabricated from 3nm up to 460nm. A home-made scanning field emission microscope (SFEM) was employed to perform the scans on the surfaces. Emitters were characterized using a scanning electron microscope together with an energy dispersive x-ray analyzer. The experimental results could be understood by a simple model calculation based on classic electromagnetic theory as shown in Ref.1. Possibly implications for Nb SRF cavity applications from this study will be discussed. Authored by The Southeastern Universities Research Association, Inc. under U.S. DOE Contract No. DE-AC05-84ER40150.

MOPC120	Design of Superconducting Parallel-bar Deflecting/Crabbing Cavities	361
	J.R. Delayen, S.U. De Silva ODU, Norfolk, Virginia, USA
	The superconducting parallel-bar cavity is a deflecting/crabbing cavity with attractive properties, compared to other conventional designs, that is being considered for a number of applications. We present an analysis of several designs of parallel-bar cavities and their electromagnetic properties.

MOPC121	Design of Low-frequency Superconducting Spoke Cavities for High-velocity Applications	364
	J.R. Delayen, C.S. Hopper ODU, Norfolk, Virginia, USA R.G. Olave Old Dominion University, Norfolk, Virginia, USA
	Superconducting single- and multi-spoke cavities have been designed to-date for particle velocities from β~0.15 to β~0.65. Superconducting spoke cavities may also be of interest for higher-velocity, low-frequency applications, either for hadrons or electrons. We present the design of 325 and 352 MHz spoke cavities optimized for β=0.8 and β=1.

MOPC122	Etching of Niobium Sample Placed on Superconducting Radio Frequency Cavity Surface in Ar/CL2 Plasma	367
	J. Upadhyay, M. Nikolić, S. Popović, L. Vušković ODU, Norfolk, Virginia, USA H.L. Phillips, A-M. Valente-Feliciano JLAB, Newport News, Virginia, USA
	Plasma based surface modification is a promising alternative to wet etching of superconducting radio frequency (SRF) cavities. It has been proven with flat samples that the bulk Niobium (Nb) removal rate and the surface roughness after the plasma etchings are equal to or better than wet etching processes. To optimize the plasma parameters, we are using a single cell cavity with 20 sample holders symmetrically distributed over the cell. These holders serve the purpose of diagnostic ports for the measurement of the plasma parameters and for the holding of the Nb sample to be etched. The plasma properties at RF (100 MHz) and MW (2.45 GHz) frequencies are being measured with the help of electrical and optical probes at different pressures and RF power levels inside of this cavity. The niobium coupons placed on several holders around the cell are being etched simultaneously. The etching results will be presented at this conference.

MOPC123	Temperature Dependent Microphonics in the BNL Electron Cooler*	370
	P. Jain Stony Brook University, Stony Brook, USA I. Ben-Zvi, C. Schultheiss BNL, Upton, Long Island, New York, USA
	An R&D Energy Recovery Linac (ERL), to be used in the BNL electron cooler, has been operational in a developmental setting. The ERL requires a cryogenic system to supply cooling to a superconducting RF gun and the 5-cell superconducting RF cavity system that is kept cold at 2K. The 2K superfluid bath is produced by pumping on the bath using a sub-atmospheric warm compression system. During a test run in October 2010, a resonance peak corresponding to a noise of 30 Hz was observed at 1.88K. This noise peak, present at all temperatures below 2K, is assumed to be of mechanical origin from the vibration of the cryopump. Another resonance noise peak of 16 Hz, characteristic of the system, was observed at 1.98K, which shifted towards the 30 Hz peak as the temperature of the cryostat varied from 1.98K to 1.88K. The 16 Hz resonance peak upon hitting the 30 Hz resonance peak, sets a resonance condition, thereby the 30 Hz peak getting amplified by more than five times. In this paper we explore the origin of the temperature dependent 16 Hz resonance peak and give a physical explanation of the resonance.

MOPC126	High Power RF System for TRIUMF E-Linac Injector	373
	A.K. Mitra, Z.T. Ang, S. Calic, S.R. Koscielniak, R.E. Laxdal, R.W. Shanks, Q. Zheng TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
	TRIUMF has been funded to build the first stage of an electron linac with a final energy of 50 MeV and 500 kW beam power. The e-linac consists of an injector section with electron gun with 650 MHz rf modulated grid, a room temperature 1.3 GHz buncher cavity, and injector cryomodule, and two main-linac cryomodules for the accelerating section to be installed sequentially. The injector module has one 9 cell cavity whereas each of the accelerating cryomodules contains two 9-cell SC cavities. The injector cryomodule will be fed by a 30 kW cw Inductive Output Tube (IOT)and the accelerating cryomodule will be powered by a cw klystron. A first goal is a beam test of the e-Linac injector to 10MeV in 2012. Installation and full rated output power tests of the IOT on a 50 ohms load have been carried out. The IOT is purchased from CPI, USA while the transmitter is sourced from Bruker BioSpin. A power coupler conditioning station utilizes the same IOT. The buncher cavity is driven from a Bruker 600W amplifier. In this paper, the conceptual design of the e-Linac rf system will be summarized and the high power rf system for the injector including IOT measurement results will be presented. SC stands for superconducting

MOPC127	Development of High RF Power Solid State Amplifiers at SOLEIL	376
	P. Marchand, M.E. El Ajjouri, R. Lopes, F. Ribeiro, T. Ruan SOLEIL, Gif-sur-Yvette, France
	In SOLEIL, 5 solid state amplifiers provide the required 352 MHz RF power: 1 x 35 kW for the booster (BO) cavity and 4 x 190 kW for the 4 superconducting cavities of the storage ring (SR). Based on a design fully developed in house, they consist in a combination of a large number of 330W elementary modules (1 x 147 in the BO and 4 x 724 in the SR) with MOSFET transistors, integrated circulators and individual power supplies. After 5 years of operation, this innovative design has proved itself and demonstrated that it was an attractive alternative to the vacuum tube amplifiers, featuring an outstanding reliability and a MTBF > 1 year. In the meantime, thanks to the acquired expertise and the arrival of the 6th generation transistors, SOLEIL has carried out developments which led to doubling the power of the elementary module (700 W at 352 MHz and 500 MHz), while improving the performance in terms of gain, efficiency and thermal stress. This approach was also extended to frequencies from the FM to L band. The increasing interest for this technology has led SOLEIL to collaborate with several other laboratories and conclude a transfer of know-how with the French company, ELTA-AREVA.

MOPC128	16 kW Upgrade of the 1.3 GHz ELBE RF-system (CW) with Solid State Amplifiers	379
	H. Büttig, A. Arnold, A. Büchner, M. Justus, M. Kuntzsch, U. Lehnert, P. Michel, R. Schurig, G.S. Staats, J. Teichert HZDR, Dresden, Germany
	The superconducting CW- LINAC of the radiation source ELBE is in permanent operation since May 2001. In 2011 an upgrade program of ELBE is in progress to support additional applications. One part of the program is to double the RF-power per cavity to at least 16 kW. We first tested a 30 kW IOT-based amplifier (Bruker /CPI) at a cavity, later two 10 kW solid state amplifiers in parallel. The best solution found is based on 10 kW Solid State Power Amplifiers (SSPA) developed by Bruker BioSpin. The poster gives an overview on the status, the activities around this RF-upgrade project and the technical specification of the “turnkey” SSPA , designed for 10 kW, 1.3 GHz and full CW-operation.

MOPC129	Compact Solid State RF-Modules for Direct Drive RF-linacs	382
	R. Irsigler, M. Back, R. Baumgartner, O. Heid, T.J.S. Hughes, M. Kaspar, T. Kluge, J. Sirtl, K. Weidner, M. Zerb Siemens AG, Erlangen, Germany
	We present a modular RF power source concept based on solid state RF-modules with novel SiC transistors. The concept offers lower cost, better reliability and reduced maintenance compared to traditional RF-source technology. No circulators are required, which makes the RF-module very compact and reliable. The SiC power transistor has a very low input capacitance and was optimized for low gate resistance to enable fast switching in the VHF range. It delivers a maximum pulsed drain saturation current of 65 A. The transistor provides at 350 V supply voltage and 150 MHz an output power of 5,6 kW at a gain of 15,8 dB. It is essential to avoid high parasitic source inductances at RF and good thermal conductivity is required for operation at high duty cycle. We have built very compact 75 x 90 mm ceramic amplifier modules using a planar interconnect technology (SIPLIT) to connect the bare die transistors to the DCB substrate. The modules have a fully symmetric push-pull topology (circlotron) with four transistors in parallel in each leg. The RF-modules delivered at 150 MHz an impressive RF output power in the range of 40 kW. Further tests at 324 MHz are planned and will be presented.

MOPC130	High Power Solid State RF Amplifier Proposal for Iran Light Source Facility (ILSF)	385
	R. safian IPM, Tehran, Iran M. Jafarzadeh ILSF, Tehran, Iran
	Solid state RF amplifiers are being considered for an increasing number of accelerator applications. Their capabilities extend from a few kW of power to several hundred kilo watts and from frequencies less than 100 MHz to above 1 GHz. This paper describes the proposed general scheme for the high power solid state RF generator of the Iran light source facility (ILSF). The maximum expected power of the generator is 200 KW which is used for driving the storage ring cavities. Similar RF generator with lower output power can be used for driving the booster cavities.

MOPC132	Influences of the Inner-conductor on Microwave Characteristics in an L-band Relativistic Backward-wave Oscillator*	388
	X.J. Ge, L. Liu, B.L. Qian, J. Zhang, H.H. Zhong National University of Defense Technology, Changsha, Kaifu District, People's Republic of China
	Funding: College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073, People’s Republic of China. gexingjun230230@yahoo.com.cn* The influences of the inner-conductor on microwave characteristics in an L-band relativistic backward-wave oscillator (RBWO) are investigated theoretically and experimentally. The numerical results show that the resonance frequency decreases obviously with the increase in the inner-conductor radius. To verify the above conclusions, an L-band coaxial RBWO is investigated in detail with particle-in-cell (PIC) code. It is shown that the frequency is lowered from 1.63 GHz to 1.51 GHz when the inner-conductor radius increases from 0.5 cm to 2.5 cm. And the efficiency varies in the range of 35.4-27.7%. Furthermore, experiments are carried out at the Torch-01 accelerator. When the diode voltage is 887.6 kV and the current is 7.65 kA, the radiated microwave with frequency of 1.61 GHz, power of 2.13 GW and efficiency of 31.3% is generated. It is found that the frequency decreases from 1.64 GHz to 1.58 GHz when the inner-conductor radius increases from 0.5 cm to 1.5 cm. And the efficiency varies in the range of 31.3-29.8%.

MOPC134	Multifrequency High Power Microwave Electric-vacuum Devices	391
	K.G. Simonov, A.A. Borisov, A.V. Galdetsky, A.N. Korolev, A.V. Mamontov ISTOK, Moscow Region, Russia O.A. Morozov Research and Production Co. "MAGRATEP", Fryazino, Russia
	A new approach for the design of the multifrequency high power microwave vacuum devices is proposed. These devices provide simultaneously some output phased signals with operating frequencies ω, 2 ω, , nω while input frequency is ω. For example, it is possible obtain output power at frequencies ω and 2ω by using of double-gap output resonator tuned on two modes – sinphased mode at 2ω and antiphased mode at frequency ω. It is possible obtain power at four frequencies ω, 2ω, 3ω and 6ω by using of the two double-gap output resonators placed one inside the other. It is possible obtain power at multiple frequencies by using of the special coaxial resonator. A microwave vacuum device has been fabricated in which power was extracted at nine multiple frequencies simultaneously. The output signal has form of pulses with ultrashort duration and superhigh repetition frequency equal to the input signal frequency ω. Multifrequency high power microwave vacuum devices can be used for the development of compact accelerators of charged particles.

MOPC135	IFMIF-EVEDA RF Power System	394
	D. Regidor, A. Arriaga, J.C. Calvo, A. Ibarra, I. Kirpitchev, J. Molla, P. Méndez, A. Salom, M. Weber CIEMAT, Madrid, Spain M. Abs, B. Nactergal IBA, Louvain-la-Neuve, Belgium P.-Y. Beauvais, M. Desmons, A. Mosnier CEA/DSM/IRFU, France P. Cara Fusion for Energy, Garching, Germany S.J. Ceballos, J. de la Cruz Greenpower Technologies, Sevilla, Spain Z. Cvetkovic, Z. Golubicic, C. Mendez TTI, Santander, Spain J.M. Forteza, J.M. González, C.R. Isnardi Indra Sistemas, San Fernando de Henares, Spain D. Vandeplassche SCK-CEN, Mol, Belgium
	The IFMIF/EVEDA Accelerator Prototype will be a 9 MeV, 125 mA CW deuteron accelerator to validate the technical options for the IFMIF accelerator design. The Radiofrequency Quadrupole (RFQ), buncher cavities and Superconducting Radiofrequency Linac (SRF Linac) require continuous wave RF power at 175 MHz with an accuracy of ±1% in amplitude and ±1° in phase. Also the IFMIF/EVEDA RF Power System has to work under pulsed mode operation (during the accelerator commissioning). The IFMIF/EVEDA RF Power System is composed of 18 RF power generators feeding the eight RFQ couplers (200 kW), the two buncher cavities (10⁵ kW) and the eight superconducting half wave resonators of the SRF Linac (10⁵ kW). The main components of each RF power chain are the Low Level Radio Frequency system (LLRF), three amplification stages and a circulator with its load. For obvious standardization and scale economies reasons, the same topology has been chosen for the 18 RF power chains: all of them use the same main components which can be individually tuned to provide different RF output powers up to 200 kW. The studies and the current design of the IFMIF/EVEDA RF Power System are presented in this contribution.

MOPC136	The RF Power Source for the High Beta Elliptical Cavities of the ESS Linac	397
	K. Rathsman, H. Danared, R. Zeng ESS, Lund, Sweden A.J. Johansson Lund University, Lund, Sweden C. Lingwood Cockcroft Institute, Lancaster University, Lancaster, United Kingdom R.J.M.Y. Ruber Uppsala University, Uppsala, Sweden C. de Almeida Martins IST-UTL, Lisbon, Portugal
	The European Spallation Source is an intergovernmental project building a multidisciplinary research laboratory based upon the world’s most powerful neutron source. The main facility will be built in Lund, Sweden. Construction is expected to start around 2013 and the first neutrons will be produced in 2019. The ESS linac delivers 5 MW of power to the target at 2.5 GeV, with a nominal current of 50 mA. The 120 high beta elliptical cavities, which operate at a frequency of 704 MHz and accelerate protons from 600 MeV to 2.5 GeV, account for more than half of the total number of rf cavities in the ESS linac and three quarter of the total beam power needed. Because of the large number of rf power sources and the high power level needed, all the design and development efforts for the rf power source have so far been focused on this part of the accelerator. The design and development status of the rf power source is reported in this paper with emphasis on reliability, maintainability, safety, power efficiency, investment cost and production capacity.

MOPC137	Medium Power 352 MHz Solid State Pulsed RF Amplifiers for the CERN Linac4 Project	400
	J.C. Broere, J. Marques Balula CERN, Geneva, Switzerland Y. Gomez LPSC, Grenoble Cedex, France M. Rossi DBE, Padova, Italy
	Economic, modular and highly linear pulsed RF amplifiers have recently been developed to be used for the three Buncher cavities in the CERN Linac4. The amplifiers are water cooled and can provide up to 33 kW pulsed RF power, 1.5 msec pulse length and 50 Hz repetition rate. Furthermore a 60 kWatt unit is under construction to provide the required RF Power for the Debuncher cavity. The concept is based on 1.2 kW RF power modules using the latest 6th generation LDMOS technology. For integration into the CERN control environment the amplifiers have an internal industrial controller, which will provide easy control and extended diagnostic functions. This paper describes the construction, performance, including linearity, phase stability and EMC compliance tests.

MOPC138	Practical Test of the Linac4 RF Power System	403
	N. Schwerg, O. Brunner CERN, Geneva, Switzerland
	Linac4 is a linear accelerator for negative Hydrogen ions which will replace the old Linac2 as injector for the CERN accelerators. Its higher energy of 160 MeV will increase the beam intensity in the downstream machines. The normal-conducting accelerating structures are housed in a 100 m long tunnel which will be connected to the existing chain of accelerators and can be extended into a new injector chain. The high RF power for the Linac4 accelerating structures will be generated by thirteen 1.3 MW klystrons, previously used for the CERN LEP accelerator, and six new klystrons of 2.8 MW all operating at a frequency of 352.2 MHz. The re-use of existing LEP equipment, space limitations in the installation and tight phase and amplitude constraints pose a number of challenges for the integration of the RF power system. The power distribution scheme features a folded magic-tee feeding the power from a 2.8 MW klystron to two LEP circulators. We present first results from the Linac4 test place, validating the approach and the used components as well as reporting on the klystron re-tuning activities.

MOPC140	Phase and Frequency Locked Magnetrons for SRF Sources	406
	M.L. Neubauer, M.A.C. Cummings, A. Dudas, R.P. Johnson, R. Sah Muons, Inc, Batavia, USA A. Moretti, M. Popovic Fermilab, Batavia, USA
	Typically, high power sources for accelerator applications are multi-megawatt microwave tubes that may be combined together to form ultra-high-power localized power stations. The RF power is then distributed to multiple strings of cavities through high power waveguide systems which are problematic in terms of expense, efficiency, and reliability. Magnetrons are the lowest cost microwave source in dollars/kW, and they have the highest efficiency (typically greater than 85%). However, the frequency stability and phase stability of magnetrons are not adequate, when magnetrons are used as power sources for accelerators. Novel variable frequency cavity techniques have been developed which will be utilized to phase and frequency lock magnetrons, allowing their use for either individual cavities, or cavity strings. Ferrite or YIG (Yttrium Iron Garnet) materials will be attached in the regions of high magnetic field of radial-vaned, π−mode structures of a selected ordinary magnetron. The microwave characteristics of several materials have been tested with magnetic fields to control the frequency of the magnetron. These results will be presented and an optimum material chosen.

MOPC142	25 Year Performance Review of the SLAC 5045 S-Band Klystron	409
	A. Jensen, A.S. Beebe, M.V. Fazio, A.A. Haase, E.N. Jongewaard, C. Pearson, D.W. Sprehn, A.E. Vlieks, L.E. Whicker SLAC, Menlo Park, California, USA
	Funding: This work was supported by the U.S. Department of Energy under contract DE-AC03-76SF00515. The SLAC 5045 S-band klystron has proven to be a remarkably reliable high peak power tube. Originally developed in the 1980’s as an upgraded RF power source for the Stanford Linear Collider, it has continually powered the SLAC linac in support of numerous programs in particle physics and photon science. The large number of tubes built and operated (more than 800) coupled with accumulated running statistics over the last 25+ years represents an unprecedented wealth of operational experience for high pulse power klystrons in accelerator applications. Mean time between failures has continued to rise during this period and is frequently in excess of 100,000 hours during the last several years. Lifetime statistics as well as some important failure modes are presented and examined here.

MOPC143	A Reduced Gradient Output Design for SLAC's XL4 X-Band Klystron	412
	A. Jensen, C. Adolphsen, A.E. Candel, M.V. Fazio, E.N. Jongewaard, D.W. Sprehn, A.E. Vlieks, F. Wang SLAC, Menlo Park, California, USA
	Funding: This work was supported by the U.S. Department of Energy under contract DE-AC03-76SF00515. X-band klystron work began at SLAC in the mid to late 1980's to develop high frequency (4 times the SLAC S-band klystron), high power RF sources for the linear collider designs under consideration at that time. This work culminated in the current workhorse X-band RF source, the XL4. To date 26 XL4 tubes have been built. The XL4 4-cell disk loaded traveling wave output structure has a high operating gradient. A new 6-cell structure has been designed to reduce breakdown and to further improve the klystron's robustness. Initial simulations show the 6-cell design reduces the gradient roughly 25% and that the structure is stable. A physical XL4 will be retrofitted with the new output cavity and hot tested in the near future.

MOPC144	Autocorrelation Function and Power Spectrum of a Train of Quasiperiodic Sequence of Pulses	415
	E.M. Laziev, B. Grigoryan, V.M. Tsakanov CANDLE, Yerevan, Armenia M. Movsisyan, D.L. Oganesyan YSU, Yerevan, Armenia
	The statistical relationship of the autocorrelation function and spectrum of a train of quasi-periodic sequence of pulses having a time jitter of the repetition rate is obtained. Presented the accordance of autocorrelation function as well as power spectrum of the bounded quasi-periodic sequence of pulses and timing jitter of their repetition rate. The results can be used at the measurements of timing jitter of a train of electron bunches.

MOPC145	Recent Progress on the Technical Realization of the Bunch Phase Timing System BuTiS	418
	B. Zipfel, P. Moritz GSI, Darmstadt, Germany
	A high precision phase synchronous clock distribution system is mandatory for generating local RF reference signals in an accelerator complex. The dedicated Bunch Timing System (BuTiS) at GSI performs this function. The accuracy of the realized installation under rough ambient conditions is presented. Procedures for calibration and standardization aspects of system modules are pointed out. Hardware as well as software interfaces of the system are described. The interfacing between GPS and BuTiS are explained.

MOPC146	Development of Timing Distribution System with Femto-second Stability	421
	T. Naito, K. Ebihara, S. Nozawa, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan M. Amemiya AIST, Tsukuba, Japan
	A timing distribution system with femto-second stability has been developed for the RF synchronization of accelerator and the laser synchronization of the pump-probe experiments. The system uses a phase stabilized optical fiber(PSOF) and an active fiber length stabilization. The PSOF has 5 ps/km/degC of the temperature coefficient. The active fiber length stabilization uses the phase detection of the round-trip sinusoidal wave and the fiber stretcher for the compensation of the fiber length. In this paper, we present the test results on a 500 m long signal distribution. The preliminary results of the timing stability are 20 fs at several minutes and 100 fs at four days, respectively.

MOPC147	Timing System for MedAustron Based on Off-The-Shelf MRF Transport Layer	424
	R. Tavcar, J. Dedič, Z. Kroflic, R. Štefanič Cosylab, Ljubljana, Slovenia J. Gutleber CERN, Geneva, Switzerland
	MedAustron is a new particle accelerator-based ion beam research and therapy centre under construction in Wiener Neustadt, Austria. The timing system for its synchrotron-based accelerator is being developed in close collaboration with Cosylab. We have usedμResearch Finland (MRF) transfer layer and designed and implemented a generic, reusable high-level logic above transport layer inside the generator and receiver FPGA to fulfill machine specific requirements which exceed MRF's original high-level logic capabilities. The new timing system is suitable for small to mid-size accelerators. Its functionalities include support for virtual accelerators and a rich selection of event response mechanisms. The timing system uses a combination of a real-time link for downstream events and a non-real-time link for upstream messaging and non time-critical communication. This article explains the benefits of building a timing system on a proven, stable timing transport layer and describes the high-level services provided by MedAustron timing system.

MOPC148	Optical Clock Distribution System at the ALICE Energy Recovery Linac	427
	T.T. Ng, S.P. Jamison STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Highly stable clock distribution across future light sources is important for the synchronisation of beam generation, manipulation and diagnostics with photon experiments. Optical fibre technology can be used to combat the stability challenges in distributing clock signals over long distances with coaxial cable. We report here on the status of the optical clock distribution system installed on the ALICE energy recovery linac which uses the propagation of ultra-short optical pulses to carry the clock signal. We also present the characterisation of a beam arrival monitor suitable using <40 pC bunch charges and 7 mW, sub-100 fs distributed clock pulses.

MOPC150	High Charge PHIN Photo Injector at CERN with Fast Phase Switching within the Bunch Train for Beam Combination	430
	M. Divall Csatari, A. Andersson, B. Bolzon, E. Bravin, E. Chevallay, A.E. Dabrowski, S. Döbert, V. Fedosseev, C. Heßler, T. Lefèvre, S. Livesley, R. Losito, O. Mete, M. Olvegård, M. Petrarca, A. Rabiller CERN, Geneva, Switzerland A. Drozdy BUTE, Budapest, Hungary D. Egger EPFL, Lausanne, Switzerland
	The high charge PHIN photo-injector was developed within the frame of the European CARE program to provide an alternative to the drive beam thermionic gun in CTF3 (CLIC Test Facility) at CERN. In PHIN 1908 bunches are delivered with bunch spacing of 1.5 GHz and 2.33 nC charge per bunch. Furthermore the drive beam generated by CTF3 requires several fast 180 deg phase-shifts with respect to the 1.5 GHz bunch repetition frequency in order to allow the beam combination scheme developed at CTF3. A total of 8 sub-trains, each 140 ns long and shifted in phase with respect to each other, have to be produced with very high phase and amplitude stability. A novel fiber modulator based phase-switching technique developed on the laser system provides this phase-shift between two consecutive pulses much faster and cleaner than the base line scheme, where a thermionic electron gun and sub-harmonic bunching are used. The paper describes the fiber-based switching system and the measurements verifying the scheme. Stability measurements are presented for the phase-coded system. The paper also discusses the latest 8nC charge production and cathode life-time studies on Cs2Te.

MOPC151	Design and Commissioning of a Multi-frequency Digital Low Level RF Control System*	433
	M. Konrad, U. Bonnes, C. Burandt, J. Conrad, R. Eichhorn, J. Enders, P.N. Nonn, N. Pietralla TU Darmstadt, Darmstadt, Germany
	Funding: Work supported by DFG through CRC 634 and by the BMBF under 06 DA 9024 I. Triggered by the need to control the superconducting cavities of the S-DALINAC, which have a high loaded quality factor and are thus very susceptible to microphonics, the development of a digital low level RF control system was started. The chosen design proved to be very flexible since other frequencies than the original 3 GHz may be adapted easily: The system converts the RF signal coming from the cavity (e. g. 3 GHz) down to the base band using a hardware I/Q demodulator. The base band signals are digitized by ADCs and fed into a FPGA where the control algorithm is implemented. The resulting signals are I/Q modulated before they are sent back to the cavity. The superconducting cavities are operated with a self-excited loop algorithm whereas a generator-driven algorithm is used for the low Q normal-conducting bunching cavities. A 6 GHz RF front end allows the synchronous operation of a new 2f buncher at the S-DALINAC. Meanwhile, a 325 MHz version has been built to control a pulsed prototype test stand for the p-LINAC at FAIR. We will present the architecture of the RF control system as well as results obtained during operation.

Paper

Title

Page

Linac Waveguide Upgrade at the Australian Synchrotron Light Source

62

R.T. Dowd, G. LeBlanc, K. Zingre
ASCo, Clayton, Victoria, Australia

The Australian Synchrotron Light Source (ASLS) uses a 100 MeV linac as the start of the acceleration chain for the injector. The two main accelerating structures of linac are normally fed by independent pulsed klystrons. A recent upgrade to the waveguide system has allowed for a single klystron to power both accelerating structures. While this operation mode delivers a reduced total beam energy, the operation of only a single klystron results in less wear and enhanced robustness against klystron breakdown. Commissioning results of single klystron operation of the linac are shown and future benefits are detailed.

MOPC002

Flow Induced Vibrations of the CLIC X-band Accelerating Structures

65

T.K. Charles, K. Ryan
Monash University, Melbourne, Australia
M.J. Boland
ASCo, Clayton, Victoria, Australia
G. Riddone
CERN, Geneva, Switzerland
A. Samoshkin
JINR, Dubna, Moscow Region, Russia

Turbulent cooling water in the Compact Linear Collider (CLIC) accelerating structures will inevitably induce some vibrations. The maximum acceptable amplitude of vibrations is small, as vibrations in the accelerating structure could lead to beam jitter and alignment difficulties. A Finite Element Analysis model is needed to identify the conditions under which turbulent instabilities and significant vibrations are induced. Due to the orders of magnitude difference between the fluid motion and the structure's motion, small vibrations of the structure will not contribute to the turbulence of the cooling fluid. Therefore the resonant conditions of the cooling channels presented in this paper, directly identify the natural frequencies of the accelerating structures to be avoided under normal operating conditions. In this paper a 2D model of the cooling channel is presented finding spots of turbulence being formed from a shear layer instability. This effect is observed through direct visualisation and wavelet analysis.

MOPC004

352.2 MHz HOM Damped Normal Conducting ESRF Cavity: Design and Fabrication

68

V. Serrière, A.K. Bandyopadhyay, D. Boilot, L. Goirand, J. Jacob, B. Ogier, A. Triantafyllou
ESRF, Grenoble, France

Funding: This work, carried out within the framework of the ESRFUP project, has received research funding from the EU Seventh Framework Programme, FP7.
The ongoing ESRF upgrade included an option for an increase of the storage ring current from 200 to 300 mA, which has been tested successfully with the existing RF system. At this current level the HOM tuning of the existing five-cell copper cavities becomes extremely delicate and in view of a future reliable operation in user mode, new HOM free normal conducting cavities were developed at the ESRF. The design is based on the existing BESSY/ALBA cavity. However, several substantial modifications have been implemented and different fabrication processes elaborated to improve the design. Three operational prototypes will be delivered by three manufacturers in the coming months and will be fully tested on the ring. Although the 300 mA option has finally not been retained for the first phase of the ESRF upgrade, the aim is now to validate the new cavity design for a possible later increase in current.

MOPC005

352.2 MHz – 150 kW Solid State Amplifiers at the ESRF

71

J. Jacob, G. Gautier, M.L. Langlois, J.M. Mercier
ESRF, Grenoble, France

The ESRF has ordered seven 352.2 MHz – 150 kW Solid State Amplifiers (SSA) from the French company ELTA, with a design derived from the existing SSA developed by SOLEIL. The first four SSA will be commissioned by the end of 2011 and will be connected to the two booster cavities in Winter 2012 providing in total 600 kW in 10 Hz cycles. Thanks to anti-flicker capacitor banks with a total of 3 F in the 280 V DC power supply, up to only 350 kW will be drawn from the mains as compared to 1200 kW for the former klystron transmitter. The three remaining SSA will be received in 2012 and will feed three new single cell HOM damped cavities on the storage ring. The analysis of the market had shown that an alternative to klystrons needed to be investigated to guarantee the long term operation of the ESRF. SSA can be operated with a number of RF modules lost and are therefore intrinsically highly redundant. In parallel to the production by industry of this first batch of SSA, the ESRF is developing its own amplifier modules and proposing an alternative way to combine typically hundred RF modules using a single cavity combiner.

MOPC006

A Coupled RFQ-IH Combination for the Neutron Source FRANZ

74

M. Heilmann, O. Meusel, D. Mäder, U. Ratzinger, A. Schempp
IAP, Frankfurt am Main, Germany

Funding: HIC for FAIR
The Frankfurt Neutron Source at the Stern-Gerlach-Zentrum is driven by a 2 MeV proton linac consisting of a 4-rod-radio-frequency-quadrupol (RFQ) and an 8 gap IH-DTL structure. RFQ and IH cavity will be powered by only one radio frequency (RF) amplifier to reduce costs. The RF-amplifier of the RFQ-IH combination is coupled into the RFQ. Internal inductive coupling along the axis connects the RFQ with the IH cavity ensuring the required power transition as well as a fixed phase relation between the two structures. The main acceleration of 120 keV up to 2.03 MeV will be reached by the RFQ-IH combination with 175 MHz and at a total length of 2.3 m. The losses in the RFQ-IH combination are about 200 kW.

MOPC007

Cold Photocathode RF Gun

77

V. Vogel, K. Flöttmann, S. Schreiber
DESY, Hamburg, Germany

Heating and thermal expansion in the normal conductivity RF-photo electron gun, are the main limitations to achieve high accelerating gradient and consequently a low emittance beam. Some pure materials show a significant increase in thermal conductivity with a small coefficient of temperature expansion at temperatures around 20 degrees Kelvin. Possible materials are Molybdenum, Iridium or Tungsten. However, machining of these materials is very difficult. Therefore we propose a simplified shape for an L-band RF gun. We expect to achieve a significant increase in gradient for similar RF powers as used in the present DESY RF-gun. On the other hand, it would also be possible to increase the duty cycle keeping a moderate gradient. In this report we discuss one possible design of an RF-gun using hard metals and present simulations on thermal properties.

MOPC009

Design of a Pi/2 Mode S-Band Low Energy TW Electron Linear Accelerator

80

H. Shaker
IPM, Tehran, Iran
F. Ghasemi
sbu, Tehran, Iran
H. Shaker
CERN, Geneva, Switzerland

This design is related to a Pi/2 mode S-Band low energy TW electron linear accelerator which is in the construction stage. This project is supported by the school of particles and accelerators, institute for research in fundamental sciences (IPM), Tehran, Iran. This design consists of a buncher and an accelerating structure that are joined and two couplers for the input/output feedings. At each design stage, different methods (analytical or numerical) are used to confirm the results and also to have a better understanding.

MOPC010

Phase-Modulation SLED Operation Mode at Elettra

83

C. Serpico, P. Delgiusto, A. Fabris, F. Gelmetti, M.M. Milloch, A. Salom, D. Wang
ELETTRA, Basovizza, Italy

FERMI@Elettra is the soft X-ray, fourth generation light source facility at the Elettra Laboratory in Trieste, Italy. It is based on a seeded FEL, driven by a normal conducting linac that is presently expected to operate at 1.5 GeV. The last seven backward traveling wave structures have been equipped with a SLED system. Due to breakdown problems inside the sections, that was the result of high peak fields generated during conventional SLED operation, the sections experienced difficulties in reaching the desired gradients. To lower the peak field and make the compressed pulse “flatter”, phase-modulation of the SLED drive power will be implemented. A description of the phase modulation of the drive power and the results achieved will be reported in the following paper.

MOPC012

Fabrication of the CERN/PSI/ST X-band Accelerating Structures

86

M.M. Dehler, A. Citterio, R. Zennaro
PSI, Villigen, Switzerland
S. Atieh, D. Gudkov, S. Lebet, G. Riddone, J. Shi
CERN, Geneva, Switzerland
G. D'Auria, C. Serpico
ELETTRA, Basovizza, Italy

Within a collaboration between CERN, PSI and Sincrotrone Trieste (ST), a multi- purpose X-band accelerating structure has been designed and fabricated, used for high gradients tests in the CLIC structure testing program and in the FEL projects of PSI and ST. The structure has 72 cells with a phase advance of 5 pi/6 and includes upstream and downstream wakefield monitors to measure the beam alignment. The SLAC mode launcher design is used to feed it with RF power. Following the CERN fabrication procedures for high-gradient structure, diffusion bonding and brazing in hydrogen atmosphere is used to assemble the cells. After tuning, a vacuum bakeout is required before the feedthroughs for the wake field monitors are welded in as a last step. We describe the experiences gained in finishing the first two structures out of a series of four and present the results from the RF tuning and low level RF tests.

MOPC013

Design, Fabrication and High Power RF Test of a C-band Accelerating Structure for Feasibility Study of the SPARC Photo-injector Energy Upgrade

89

D. Alesini, R. Boni, G. Di Pirro, R. D. Di Raddo, M. Ferrario, A. Gallo, V.L. Lollo, F. Marcellini
INFN/LNF, Frascati (Roma), Italy
G. Campogiani, A. Mostacci, L. Palumbo, S. Persichelli, V. Spizzo
Rome University La Sapienza, Roma, Italy
T. Higo, K. Kakihara, S. Matsumoto
KEK, Ibaraki, Japan
S. Verdú-Andrés
TERA, Novara, Italy

The energy upgrade of the SPARC photo-injector from 170 to 250 MeV will be done by replacing a low gradient 3m S-Band structure with two 1.5m high gradient C-band structures. The structures are traveling wave, constant impedance sections, have symmetric waveguide input couplers and have been optimized to work with a SLED RF input pulse. A prototype with a reduced number of cells has been fabricated and tested at high power in KEK (Japan) giving very good performances in terms of breakdown rates at high accelerating gradient (>50 MV/m). The paper illustrates the design criteria of the structures, the fabrication procedure and the high power RF test results.

MOPC014

RF Processing of L-band RF Gun for KEK-STF

92

M. Kuriki, H. Iijima, Y.M. Masumoto
HU/AdSM, Higashi-Hiroshima, Japan
H. Hayano, H. Sugiyama, J. Urakawa, K. Watanabe
KEK, Ibaraki, Japan
G. Isoyama, R. Kato
ISIR, Osaka, Japan
S. Kashiwagi
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
Y. Takahashi
Sokendai, Ibaraki, Japan

Funding: This work is supported by MEXT Quantum Beam Technology Program, KEK Promotion of collaborative research programs in universitie.
KEK STF (Superconducting Test Facility) is established for developing super-conducting accelerator technology for ILC (International Linear Collider). At KEK-STF, accelerator operation with a beam loading is planned in 2013. An electron injector based on L-band Photo-cathode RF gun is now being developed. A L-band RF gun designed by DESY and fabricated by FNAL has been placed in KEK-STF and RF processing was carried out. The results of the RF processing and status of STF injector will be presented.

MOPC015

S-band Vacuum Isolator and Circulator for Injector System of SPring-8 Linac

95

T. Taniuchi, H. Hanaki, S. Suzuki
JASRI/SPring-8, Hyogo-ken, Japan
A. Miura, K. Shinohara, S. Tsuruoka
Nihon Koshuha Co. Ltd, Yokohama, Japan

A pressurized sulfur hexafluoride (SF6) waveguide system at an injector section of SPring-8 linac, will be replaced with a vacuum waveguide system in order to renew aged equipments and improve a phase stability. For this renewal, RF isolator and a circulator operated in vacuum, are newly developed. High power RF test for these components were performed and a good result for RF and vacuum characteristics were obtained.

MOPC016

Development of a New RF Accelerating Cavity for J-PARC Ring Accelerator

98

Y. Morita, T. Kageyama
KEK, Ibaraki, Japan
J. Kameda
ICRR, Chiba, Japan
S. Yamashita
ICEPP, Tokyo, Japan

Funding: Japan Society for the Promotion of Science (JSPS)
To enhance the beam power delivered by the J-PARC* ring accelerators, upgrading the accelerating cavities is indispensable. In particular, long term stable operation of the present cavities for the RCS** is one of the important issues. Currently, the cavities are loaded with FINEMET*** cores cooled by water, where every core is coated with glass cloth and epoxy resin for waterproof. However, it was reported that some of the cores were damaged by thermal stress. We are developing a new cavity loaded with multi ring core modules. Each core module consists of three ring cores concentrically arranged and sandwiched between two glass epoxy plates with flow channels grooved. The ring cores without waterproof coating are cooled by the turbulent flow of a chemically inert liquid (Fluorinert), since FINEMET is subject to corrosion in water. We have designed and built a high power prototype cavity loaded with a single core module, then carried out low level measurement and high power test. Finally, the cavity has been stably operated up to an average power loss of 10 kW per core module, which is 1.7 times higher than that for the present RCS cavity.
*Japan Proton Accelerator Research Complex
**Rapid-Cycling Synchrotron
***FINEMET is an iron-based magnetic alloy produced by Hitachi Metals, Ltd..

MOPC017

Thermal Analyses of an RF Input Coupler for the IFMIF/EVEDA RFQ Linac

101

S. Maebara
JAEA, Ibaraki-ken, Japan

In the design of prototype RFQ linac for the IFMIF/EVEDA Project, a coupled cavity type of RFQ, which has a longitudinal length of 9.78m, was proposed to accelerate deuteron beam up to 5MeV. The operation frequency of 175MHz was selected to accelerate a large current of 125mA in CW mode. The driving RF power of 1.28 MW by 8 RF input couplers has to be injected to the RFQ cavity. As the RF input coupler design, RF losses including a loop antenna and an RF vacuum window, based on a 6 1/8 inch co-axial waveguide were calculated. In this conference, these results and thermal analysis results in CW operation mode will be presented in details.

MOPC018

Operation Status of C-band High Gradient Accelerator for XFEL/SPring-8 (SACLA)

104

T. Inagaki, C. Kondo, T. Ohshima, Y. Otake, T. Sakurai, K. Shirasawa
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
T. Shintake
RIKEN Spring-8 Harima, Hyogo, Japan

XFEL project in SPring-8 have constructed a compact XFEL facility*. In order to shorten an accelerator length, a C-band (5712 MHz) accelerator was employed due to a higher accelerating gradient than that of an S-band accelerator. Since a C-band accelerating structure generates a gradient of higher than 35 MV/m, the total length of an 8 GeV accelerator fits within 400 m, including 64 C-band RF units, 4 S-band RF units, an injector and three bunch compressors. The accelerator components were carefully installed by September 2010. Then we have performed high power RF conditioning. After 500 hours of the conditioning, the accelerating gradient of each C-band structure was reached up to 35 MV/m without any particular problem. The RF breakdown rate is low enough for an accelerator operation. Since February 2011, we started the beam commissioning for XFEL. The C-band accelerator has accelerated the electron beam up to 8 GeV, with an accelerating gradient of 33-35 MV/m in average. The energy and the trajectory of the electron beam was stable, thanks to the stabilization of a klystron voltage of 350 kV within 0.01% by a high precision high voltage charger.
*The facility was recently named SACLA (SPring-8 Angstrom Compact free electron LAser).

MOPC019

Condition of MA Cut Cores in the RF Cavities of J-PARC Main Ring after Several Years of Operation

107

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

J-PARC 3 GeV RCS and 50 GeV Synchrotron (MR) employ RF cavities loaded with Magnetic Alloy (MA) cores to generate a high field gradient. The RF cavities in RCS use MA un-cut cores. On the other hand, the RF cavities in MR employ MA cut cores to increase the Q-value from 0.6 to 26. We observed the impedance reductions of all MR RF cavities during several years operation. Opening the RF cavities, we found that the impedance reductions were resulting from corrosion on the cut and polished surfaces of MA cores. Before installation of the RF cavities, we had 1000 and 2000 hours long tests at a test stand. We didn't observe the impedance reduction related to the corrosion on the MA core cut surfaces at the test stand. The only difference between the test stand and MR is the quality of cooling water. The MR cooling water contains copper ions for example from copper hollow conductors of the main magnets. We report the influence of the copper ions to the corrosion on the MA core cut surface. We also show plans how to solve the issue of MA core cut surface corrosion.

MOPC020

Development of an S-band Multi-cell Accelerating Cavity for RF Gun and Booster Linac

110

T. Aoki, K. Sakaue, M. Washio
RISE, Tokyo, Japan
A. Deshpande
SAMEER, Mumbai, India
M.K. Fukuda, N.K. Kudo, T. Takatomi, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan

Funding: Work supported by JST Quantum Beam Program
We have been developing a photocathode rf gun. The rf gun with multi cell can produce a high energy electron beam, so it may be used for numerous applications such as medicine and industry. At Laser Undulator Compact X-ray source (LUCX), we have developed a compact X-ray source based on inverse Compton scattering. Using a multi cell rf gun will make possible for the X-ray source to use for such applications. S-band 3.5 cell rf electron gun which is 20 cm long can produce more than 10 MeV electron beam. According to the simulation, it is said that the emittance of 3.5 cell rf gun is as low as that of 1.6 cell rf gun. The electromagnetic design has been performed with the code SuperFish, and the particle tracing by Parmela. The new rf gun is already installed and produced a high quality electron beam with energy of more than 10 MeV. As a consequence of the substantial efforts of developing rf cavity, we decide to make a compact RF accelerating structure with more cell for achieving a smaller system. The measurement results of using the 3.5 cell rf gun, the design of 12 cell booster cavity, and current status of 12 cell cavity manufacturing will be presented at the conference.

MOPC021

Design of a Choke-mode Damped Accelerating Structure for CLIC Main Linac

113

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

Choke-mode damped accelerating structures are being studied as an alternative to the CLIC baseline structure by a CERN-Tsinghua collaboration. Choke-mode structures hold the potential for much lower levels of pulsed surface heating and, since milling is not needed, reduced cost. Structures with radial choke attached are simulated in Gdfidl to investigate the damping of the transverse wake. The first pass-band of the dipole modes is well damped, while the higher order dipole modes are possible to be reflected by the choke. Therefore, the geometry of the choke is tuned to minimize the reflection of these higher order dipoles. Based on this damping scheme, an accelerating structure with the same iris dimensions as the nominal CLIC design but with choke-mode damping has been designed. A prototype structure will be manufactured and high power tested in the near future.

MOPC022

Development of a Compact C-band Photocathode RF Gun

116

X.H. Liu, H. Chen, W.-H. Huang, H.J. Qian, C.-X. Tang, Z. Zhang
TUB, Beijing, People's Republic of China

Funding: This work is supported by National Natural Science Foundation of China and National Basic Research Program of China (973 Program).
A C-band photocathode RF gun for a compact electron diffraction facility is developed in Tsinghua University, which is designed to work at the frequency of 5.712GHz. This paper presents the physics and structure design of this C-band RF gun, and the comparison on beam dynamics of S-band and C-band photoinjector has been done. Some new structure design will be adopted in this gun, including the optimized cavity length and elliptical iris, which is helpful to achieve lower emittance and larger mode separation.

MOPC023

Design of a C-band 6 MeV Standing-wave Linear Accelerating Structure

119

J.H. Shao, H. Chen, Q.Z. Xing
TUB, Beijing, People's Republic of China

We design a C-band standing-wave biperiodic on-axis coupled linear accelerating structure for industrial and medical applications. It’s less than 300mm long; consists of 3 bunching cells and 9 normal cells. It can accelerate electrons to 6MeV and the pulsed beam current is 100mA. The RF power source is a 2.5MW magnetron. We implement 2D cells geometry optimization by SUPERFISH, beam dynamics study by PARMELA and full scale 3D calculations by MAFIA codes.

MOPC024

Construction Status of the CPHS RFQ at Tsinghua University

122

Q.Z. Xing, Y.J. Bai, J.C. Cai, C. Cheng, L. Du, T. Du, X. Guan, Q. Qiang, X.W. Wang, Z.F. Xiong, S.Y. Yang, H.Y. Zhang, S.X. Zheng
TUB, Beijing, People's Republic of China
J.H. Billen
TechSource, Santa Fe, New Mexico, USA
W.Q. Guan, Y. He, J. Li
NUCTECH, Beijing, People's Republic of China
J. Stovall
CERN, Geneva, Switzerland
L.M. Young
AES, Medford, NY, USA

Funding: Work supported by the “985 Project” of the Ministry of Education of China.
We present, in this paper, the construction status of a Radio Frequency Quadrupole (RFQ) accelerator for the Compact Pulsed Hadron Source (CPHS) at Tsinghua University. The 3-meter-long RFQ will deliver 3 MeV protons to the downstream Drift Tube Linac (DTL) with the peak current of 50 mA, pulse length of 0.5 ms and beam duty factor of 2.5%. The RFQ has been mechanically separated into three sections. A ball-end mill, instead of a forming cutter, is adopted to machine the vane tip due to its varying radius of curvature. The precision of the numerically controlled milling machine has been verified by machining test pieces of aluminum and copper. Fine machining of the vanes was completed in July, 2011. The pre-braze tuning was completed at the beginning of this August.

MOPC026

MA Cavity for HIRFL-CSR

125

L.R. Mei, Z. Xu, Y.J. Yuan, H.W. Zhao
IMP, Lanzhou, People's Republic of China

To meet the requirements of conducting high energy density physics and plasma physics research at HIRFL-CSR. The higher accelerating gap voltage was required. A magnetic alloy (MA)-core loaded radio frequency (RF) cavity which can provide higher accelerating gap voltage has been studied in Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS), Lanzhou. To select proper MA material to load the RF cavity, measurement for MA cores has been conducted. The MA core with higher shunt impedance and lower than 1 quality factor (Q value) should be selected. The theoretical calculation and simulation for the MA-core loaded RF cavity can be consistent with each other well. Finally 1000kW power was needed to meet 50-kV accelerating gap voltage by calculation.

MOPC028

Beam Acceleration of DPIS RFQ at IMP

128

Z.L. Zhang, X.H. Guo, Y. He, Y. Liu, S. Sha, A. Shi, L.P. Sun, H.W. Zhao
IMP, Lanzhou, People's Republic of China
R.A. Jameson, A. Schempp
IAP, Frankfurt am Main, Germany
M. Okamura
BNL, Upton, Long Island, New York, USA

Beam test of the direct plasma injection scheme (DPIS) is carried out successfully for the first time in China, by setting up a comprehensive test and research platform of RFQ and laser ion source. The C⁶⁺ beam is accelerated successfully, and the peak beam current reaches more than 6mA which is measured by a Faraday cup of unique structure. The RF power coupled into the RFQ cavity is also examined, and results reveal that it is the RF power of about 195kW that can produce the peak beam current.

MOPC029

Development of Injector for Compact FEL Tera-hertz Source in CAEP

131

W. Bai, M. Li, X. Yang
CAEP/IAE, Mianyang, Sichuan, People's Republic of China

This paper introducs the development of a injector for compact FEL tera-hertz source at Institute of Applied Electronics in China Academy of Engineering Physics (IAE/CAEP). The injector consist of a main accelerator for energy booster section and a multicavity thermionic-cathode rf gun with low back bombardment, with total length no more than one meter. Numerical simulation result shows that the back bombardment power is less for the thermionic-cathode rf gun of the injector and the main accelerator has a good performance, which can provide high quality electron beam with emittance about 10 pi mm mrad, energy about 7 MeV and energy spread about 1%. At present, the preliminary hot test experiment on the injector has been done. The test results indicate that the mainly tested parameters agree well with the theoretical design ones. The process of the preliminary hot test experiment on the injector is present in this paper.

MOPC030

The C-band Traveling-wave Accelerating Structure for Compact XFEL at SINAP*

133

W. Fang, Q. Gu, Z.T. Zhao
SINAP, Shanghai, People's Republic of China
D.C. Tong
TUB, Beijing, People's Republic of China

The R&D of C-band accelerating structure has been launched two years ago at Shanghai Institute of Applied Physics, it will be used for the future compact hard X-ray FEL. The 1st C-band traveling-wave accelerating structure is ready for the high power test now. This structure is the preliminary model for the research of the technology of microwave test and tuning, arts and crafts and high power test. This paper presents the process of fabrication, cold test and tuning results.

MOPC031

Performance of a 13 MHz Cavity for an RF Implanter at PEFP*

136

T.A. Trinh
UST, Daejeon, Republic of Korea
Y.-S. Cho, J.-H. Jang, D.I. Kim, H.S. Kim, H.-J. Kwon, B.-S. Park, K.T. Seol
KAERI, Daejon, Republic of Korea

Funding: This work is supported by the Ministry of Education, Science and Technology of the Korean Government
A 13 MHz - normal conducting cavity for an rf implanter has been successfully developed at PEFP (Proton Engineering Frontier Project). It consists of an inductive coil, accelerating electrodes and a ground electrode for the inductor. Quality factor of 2074 and critical coupling were achieved at resonant frequency of 12.658 MHz. Rf power of 1 kW was forwarded to the cavity without any spark in the cavity. Beam test was then carried out with a 27 keV helium beam generated from a Duoplasmatron ion source. The results showed that the helium beam was accelerated to final energy of 120 keV with energy spread of 1%. Detail experiments and results are addressed in this presentation.

MOPC032

Improvement of the RF System for the PEFP 100 MeV Proton Linac*

139

K.T. Seol, Y.-S. Cho, H.S. Kim, H.-J. Kwon, Y.-G. Song
KAERI, Daejon, Republic of Korea

Funding: This work is supported by the Ministry of Education, Science and Technology of the Korean Government.
The 100 MeV proton linear accelerator of the Proton Engineering Frontier Project (PEFP) has been developed and will be installed in Gyeong-ju site. The 20 MeV accelerator operated in Korea Atomic Energy Research Institute (KAERI) site will be also moved and reinstalled. The LLRF control systems for the 20 MeV accelerator were improved and have been operated within the stability of ±1% in RF amplitude and ±1 degree in RF phase. 7 sets of the extra LLRF control system will be installed with a RF reference system for the 100 MeV accelerator. Waveguide layout was also improved to install HPRF systems for the 100 MeV accelerator. Some of the HPRF components including klystrons, circulators, and RF windows are under purchase. The waveguide sections penetrating into the tunnel, which are fixed in a concrete floor with the bending structure for radiation shielding, were fabricated into a piece of waveguide to prevent the moisture and any foreign debris inside the concrete block. The details of the RF system improvement are presented.

MOPC033

The Status of a 1.6-cell Photocathode RF Gun at PAL

142

M.S. Chae, J.H. Hong, I.S. Ko, Y.W. Parc
POSTECH, Pohang, Kyungbuk, Republic of Korea
S.J. Park
PAL, Pohang, Kyungbuk, Republic of Korea

The RF power conditioning of the photocathode RF gun with four holes at the side of the full cell named as 'Pohang gun' is in progress. The first goal of the conditioning is the operation of the gun with RF pulse width of 1.5 μm, repetition rate of 30 Hz, field gradient at the cathode of 130 MV/m. We operated the RF gun successfully with the conditions within last few months. It was first operational experience with such conditions in PAL. Now we have a plan to operate RF gun with higher repetition rate up to 60 Hz.

MOPC034

Design of a 0.6-cell Cell Photocathode RF Gun for FED

145

Y.W. Parc, M.S. Chae, I.S. Ko
POSTECH, Pohang, Kyungbuk, Republic of Korea

Final goal of this study is the development of single cell radio-frequency (RF) electron gun which is optimized to the femotosecond electron diffraction. This study will open new technology basis for the laboratory research in the femto-second (fs) chemistry at the university. RF electron gun will be fabricated with single cell which will reduce the cost and effort. We will also conduct a simulation study to find an optimized operation condition of the RF gun to provide the best electron beam to the femtosecond electron diffraction experimentalist. In this presentation, we will show the status of the RF gun development. The results with the simulation code PARMELA will be presented to find the optimal operation condition of the single cell RF gun for FED.

MOPC035

Design and Machine Features of 2.2-m C-band Accelerating Structure

148

C.H. Yi, M.-H. Cho, S.H. Kim, H. Lee
POSTECH, Pohang, Kyungbuk, Republic of Korea
W. Namkung
PAL, Pohang, Kyungbuk, Republic of Korea

Funding: This work is partly supported by the MEST, Korea and POSTECH BK21 Program. And this work was supported by the Korea Student Aid Foundation (KOSAF) grant funded by the Korea government.
A compact linac system is designed using a longer accelerating column in a C-band linac. It reduces the total number of RF units for the given linac beam energy and results in the cost-effective use of RF powers. For the 10 GeV PAL-XFEL project, a C-band accelerating column of 2.2-m long is investigated, which is 22% longer than 1.8-m for the SACLA at SPring-8. The detailed RF and thermal characteristics are presented by an analytic model.

MOPC036

Design of RF Cavity for Compact 9 MeV Cyclotron

151

H.S. Song, J.-S. Chai, H.W. Kim, B.N. Lee, J.H. Oh
SKKU, Suwon, Republic of Korea

The number of PET facility is rapidly increasing worldwide. To get PET image, circular accelerator such as cyclotron is needed. Compact 9 MeV H-cyclotron, which has a diameter of 1.25m is being designed at Sungkyunkwan University starting from July 2010 for getting F-18. It is expected to be constructed by next year. In this paper, RF system of 9 MeV cyclotron including design processes and detail analysis of result is reported. RF system mainly describes RF cavity design.

MOPC037

Engineering Design and Fabrication of X-band Damped Detuned Structure for the CLIC Study

154

V. Soldatov, D. Gudkov, A. Samoshkin
JINR, Dubna, Moscow Region, Russia
S. Atieh, A. D'Elia, A. Grudiev, G. Riddone
CERN, Geneva, Switzerland
R.M. Jones, V.F. Khan
UMAN, Manchester, United Kingdom

A Damped Detuned Structure (DDS), known as CLIC_DDS_A*, has been designed for the Compact Linear Collider (CLIC) study, and is presently under fabrication. The wakefield in DDS structures is damped using a combination of detuning the frequencies of beam-excited higher order modes and by light damping, through slot-coupled manifolds. The broad principles of the design are similar to that used in the NLC/GLC**. This serves as an alternative to the present baseline CLIC design which relies on heavy damping. CLIC_DDS_A is conceived to be tested for its capacity to sustain high gradients at CERN. This structure operates with a 120 degrees phase advance per cell. We report on engineering design and fabrication details of the structure consisting of 24 regular cells plus 2 matching cells at both ends, all diffusion bonded together. This design takes into account practical mechanical engineering issues and is the result of several optimizations since the earlier CLIC_DDS designs.
* V. F. Khan et al., “Recent Progress on a Manifold Damped and Detuned Structure for CLIC”, Proc. of IPAC10, WEPE032, p. 3425 (2010).
** R.M. Jones et al., Phys. Rev. STAB 9, 102001 (2006).

MOPC038

Engineering Design and Fabrication of Tapered Damped X-band Accelerating Structures

157

A. Solodko, D. Gudkov, A. Samoshkin
JINR, Dubna, Moscow Region, Russia
S. Atieh, A. Grudiev, G. Riddone, M. Taborelli
CERN, Geneva, Switzerland

The accelerating structures (AS) are one of the main components of the Compact LInear Collider (CLIC), under study at CERN. Each AS contains about 30 copper disks, which form the accelerating cavity. A fully featured AS is very challenging and requires several technologies. Different damping methods, waveguides, vacuum manifolds, slots and choke, result in various design configurations. In the CLIC multibunch AS, called TDS (Tapered Damped Structure), each cell is damped by its four waveguides, which are extended by channels machined in dedicated external vacuum manifolds. The manifolds combine few functions such as damping, vacuum pumping and cooling. Silicon carbide absorbers, fixed inside of each manifold, are required for effective damping of High Order Modes. CERN is producing X-band RF structures in close collaboration with a large number of laboratories taking advantage of their large expertise and test facilities. The fabrication includes several steps from the machining to the final assembly, including quality controls. This paper describes the engineering design and fabrication procedure of the X-band AS with damping material, by focusing on few technical solutions.

MOPC039

Optimization of IH-DTL Resonator for UNDULAC-RF

160

S.M. Polozov, A.S. Plastun, P.R. Safikanov
MEPhI, Moscow, Russia

The linear undulator accelerator (UNDULAC) was proposed early for ribbon ion beam acceleration*. UNDULAC can be realized using two non-synchronous spatial harmonics. One of them must be RF field harmonic and the second can be RF (UNDULAC-RF) or electrostatic (UNDULAC-E). The acceleration mechanism in UNDULAC is similar as inverse free electron laser (IFEL). The beam dynamics in both types of UNDULAC was studied early and the design of UNDUAC-RF resonator was started in **. Design of the 150 MHz IH-DTL for UNDULAC-RF will present. The optimization of the longitudinal field distributions will do. The most effective construction will show. Transverse electric field distributions within drift tube will optimize by blending support stems and drift tubes.
* E.S. Masunov, Sov. Phys. – Tech. Phys. 35(8), 962-965, 1990.
** S. M. Polozov, P. R. Safikanov, Proc. IPAC’10, Kyoto, Japan, p. 3762 (2010).

MOPC040

The Measurement of Transversal Shunt Impedance of RF Deflector

163

A.Yu. Smirnov, M.V. Lalayan, N.P. Sobenin
MEPhI, Moscow, Russia
A.A. Zavadtsev
Nano, Moscow, Russia

This paper presents the results of transverse shunt impedance measurement performed using field perturbation technique and comparison with numerical MWS simulations. The structure under test is the S-band 3-cell deflecting cavity. The mentioned cavity operates with a dipole TM11-like mode with a phase shift of 120 deg per cell. The analyses were carried out with use of two types of perturbing beads: dielectric beads and metallic rings. The latter type perturbs the on-axis magnetic field much stronger than the electric field, which allows us calculating transversal shunt impedance using on-axis EM fields values.

MOPC041

Cross-Field Multipactor Discharge in the X-Band Cylindrical Cavity

166

S.V. Kuzikov, E.V. Ilyakov, I.S. Kulagin, A.A. Vikharev
IAP/RAS, Nizhny Novgorod, Russia
D. Lee
NSRRC, Hsinchu, Taiwan

The paper represents the experimental study of one-sided cross-field multipactor discharge in the copper cavity with the operating mode TM01 in external DC magnetic field. It was shown that discharge is very sensible to magnitudes of the external magnetic field and rf fields as well. At proper fields the multipactor discharge can be developed for 15 ns and the electron concentration can be comparable with critical one for the given rf frequency. As a result of discharging, the cavity changes its own resonant frequency and can play a role of a switch which can substitute full transmission by full reflection. Switching parameters could be controlled by DC magnetic field as well as by additional rf radiation at different frequency than operating frequency. The high rf absorption of multipactor discharge also can be used in electrically controlled powerful loads and attenuators.

MOPC042

RF and Accelerating Structure of 12 MeV UPC Race-track Microtron

169

Yu.A. Kubyshin, X. Gonzalez Arriola
UPC, Barcelona, Spain
D. Carrillo, L. García-Tabarés, F. Toral
CIEMAT, Madrid, Spain
S.J. Mathot
CERN, Geneva, Switzerland
G. Montoro
EPSC, Castelldefels, Spain
V.I. Shvedunov
MSU, Moscow, Russia

We describe the design and technical characteristics of a C-band SW accelerating structure of a 12 MeV race-track microtron, which is under construction at the Technical University of Catalonia, and its RF system with a 5712 MHz magnetron as a source. Results of cold tests of the accelerating structure, before and after the brazing, and of high-power tests of the RF system at a special stand are reported. The main features of the magnetron frequency stabilization subsystem are also outlined.

MOPC043

Electromagnetic Simulations of the Input Power Couplers for the ESS-Bilbao RFQ

172

O. Gonzalez, I. Bustinduy, N. Garmendia, J.L. Munoz, A. Velez
ESS Bilbao, Bilbao, Spain
F.J. Bermejo
Bilbao, Faculty of Science and Technology, Bilbao, Spain
V. Etxebarria, J. Portilla
University of the Basque Country, Faculty of Science and Technology, Bilbao, Spain

An input power system is currently being designed at ESS-Bilbao in order to inject the RF power provided by a klystron into the RFQ as part of the linac. In this work, some input power couplers based on a coaxial topology are carefully studied from an electromagnetic point of view. As we will show, the electrical properties of the ceramic window used to ensure the vacuum of the RFQ crucially deteriorates the matching of the devices. To overcome this drawback, a full-wave electromagnetic simulator is used to optimize the coupler dimensions in order to minimize both the return and insertion losses.

MOPC044

Design of the Radiofrequency Quadrupole Coldmodel for the ESS-BILBAO Linear Accelerator

175

A. Velez, I. Bustinduy, N. Garmendia, O. Gonzalez, J.L. Munoz, D. de Cos
ESS Bilbao, Bilbao, Spain
F.J. Bermejo
Bilbao, Faculty of Science and Technology, Bilbao, Spain
V. Etxebarria, J. Portilla
University of the Basque Country, Faculty of Science and Technology, Bilbao, Spain

This work will present the design of the ESS-Bilbao LINAC RFQ cold model. The process goes through the electromagnetic design of the cavity by properly setting the resonant quadrupole and dipole modes, as well as the resonance frequency. The prototype includes the vane modulation designed to accelerate a 75 mA proton beam from 75 keV to 3 MeV, with an operating frequency of 352.2 MHz. To this end, electromagnetic and electrostatic simulations have been performed by means of the commercial software COMSOL. Furthemore, results for the three components of the electrical field distribution will be presented and compared to those calculated by evaluating the 8-term multipole expansion.

MOPC045

Commissioning of the ALBA Storage Ring RF System

178

F. Pérez, B. Bravo, A. Salom, P. Sanchez
CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain

ALBA is a 3 GeV, 400 mA, 3rd generation Synchrotron Light Source that is under commissioning in Cerdanyola, Spain. The RF System has to provide 3.6 MV of accelerating voltage and restore up to 540 kW of power to the electron beam. For that six RF plants, working at 500 MHz, are foreseen. The RF plants include several new developments: DAMPY cavity; the normal conducting HOM damped cavity developed by BESSY and based in the EU design; six are installed. CaCo; a cavity combiner to add the power of two 80 kW IOTs to produce the 160 kW needed for each cavity. WATRAX; a waveguide transition to coaxial, specially designed to feed the DAMPY cavities due to the geometrical and cooling constrains. Digital LLRF; fully designed at ALBA using commercial components. This paper shortly describes these systems and reports their performance during the ALBA commissioning.

MOPC046

CaCo: A Cavity Combiner for IOTs Amplifiers

181

B. Bravo, F. Mares, F. Pérez, P. Sanchez
CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
M.L. Langlois
ESRF, Grenoble, France

The ALBA storage ring uses six room temperature cavities; each one fed by two 80 kW IOTs amplifiers at 499.654 MHz. The power of the pair of transmitters is combined by a cavity combiner, CaCo. One of the design requirements of CaCo was that it continued working safely and with a good efficiency in the case of an IOT failure (asymmetrical mode). During the first asymmetric full power tests, in May 2010, with an active IOT and the other passive, the result was dramatic, the passive IOT broke in two parts after few hours of operation. This paper presents the experimental results and the electromagnetic field simulations of the asymmetrical operation mode of CaCo, i.e. one active IOT and the other passive, and analyze why the ceramic of the output tube of the passive IOT broke during the first performance of this mode. Also, it reports a possible solution to solve this problem.

MOPC047

RF Design of the Re-buncher Cavities for the LIPAC Deuteron Accelerator

184

A. Lara, I. Podadera, F. Toral
CIEMAT, Madrid, Spain

Funding: Work partially supported by Spanish Ministry of Science and Innovation under project ENE2009-11230.
Re-buncher cavities are an essential component of LIPAC (Linear IFMIF Prototype Accelerator), presently being built at Rokkasho (Japan). The deuteron beam exiting from the RFQ (Radio Frequency Quadrupole) structure has to be properly adapted to the superconducting RF (SRF) linac. Re-bunchers are placed in the Medium Energy Beam Transport (MEBT) line and their objective is to longitudinally focus the deuteron beam. IFMIF re-bunchers must provide a 350 kV E0LT at 175 MHz continuous wave (CW). The available length for the re-buncher is limited by the general layout of the MEBT. The high power dissipation derived from the high effective voltage and the short available length is an important design challenge. Four different normal conducting cavity designs were investigated: the pillbox type, double gap coaxial resonators, and multi-gap quarter wave and H resonators. The performance of these cavities was studied with the numerical codes HFSS and ANSYS. The fundamental frequency and field pattern of each re-buncher was investigated in HFSS. This work presents the results of such analyses.

MOPC049

Bead-pull Test Bench for Studying Accelerating Structures at RHUL

187

S. Molloy
ESS, Lund, Sweden
R. Ainsworth, G.E. Boorman
Royal Holloway, University of London, Surrey, United Kingdom
C. Gabor
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
A. Garbayo
AVS, Eibar, Gipuzkoa, Spain
A.P. Letchford
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
A. Lyapin
JAI, Egham, Surrey, United Kingdom
P. Savage
Imperial College of Science and Technology, Department of Physics, London, United Kingdom

A bead-pull test stand has been constructed at Royal Holloway, University of London (RHUL) with the ability to provide electric field profile measurements along five degrees of freedom using the perturbation method. In this paper, we present example measurements using the test bench which include a field flatness profile of a 324MHz four vane Radio Frequency Quadrupole (RFQ) model designed as part of the Front End Test Stand (FETS) development at Rutherford Appleton Laboratory (RAL). Mechanical and operational details of the apparatus will also be described, as well as future plans for the development and usage of this facility.

MOPC050

Multipacting Analysis for the Superconducting RF Cavity HOM Couplers in ESS

190

S. Molloy
ESS, Lund, Sweden
R. Ainsworth
Royal Holloway, University of London, Surrey, United Kingdom
R.J.M.Y. Ruber
Uppsala University, Uppsala, Sweden

The European Spallation Source (ESS) linac will consist of three families superconducting RF cavities to accelerate protons to the required 5 MW for collision with the target. If it is determined that HOM damping is required to limit the effect of beam induced modes, it is quite likely that HOM couplers will be installed. Multipacting in these couplers is a concern as thermally induced detuning of the fundamental notch filter has limited the achievable gradient in other high power machines. It is therefore important to avoid potential multipacting conditions during the design phase. Presented here are simulations using the Track3P code developed at SLAC. Multipacting regions are highlighted, electron trajectories are shown, and suitability of the proposed HOM coupler design is discussed.

MOPC051

The 100 MHz RF System for the MAX IV Storage Rings

193

Å. Andersson, E. Elafifi, M. Eriksson, D. Kumbaro, P. Lilja, L. Malmgren, R. Nilsson, H. Svensson, P.F. Tavares
MAX-lab, Lund, Sweden
J.H. Hottenbacher
RI Research Instruments GmbH, Bergisch Gladbach, Germany
A. Milan
CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
A. Salom
ELETTRA, Basovizza, Italy

The construction of the MAX IV facility has started and user operation is scheduled to commence 2015. The facility is comprised of two storage rings optimized for different wavelength ranges, and a linac-based short pulse facility. In this paper the RF systems for the two storage rings are described. The RF systems will be based on either tetrode or solid state amplifiers working at 100 MHz. Circulators will be used to give isolation between cavity and power amplifier. The main cavities are of normal conducting, entire copper, capacity loaded type, where the present cavities at MAX-lab has served as prototypes. For the MAX IV ring operation it is essential to elongate bunches, in order to minimize the influence of intra beam scattering on beam transverse emittances. For this, 3rd harmonic passive (Landau-) cavities are employed. These are of similar type as the main cavities, mainly because the capacity loaded type has the advantage of pushing higher order modes to relatively high frequencies compared to pill-box cavities. Digital low level RF systems will be used, bearing in mind the possibility of post mortem analysis.

MOPC052

Engineering Design and Fabrication of X-band RF Components

196

M. Filippova, A. Olyunin, V. Soldatov, A. Solodko
JINR, Dubna, Moscow Region, Russia
S. Atieh, G. Riddone, I. Syratchev
CERN, Geneva, Switzerland

The CLIC RF frequency has been changed in 2008 from the initial 30 GHz to the European X-band 11.9942 GHz permitting beam independent power production using klystrons for accelerating structure testing. X-band klystron test facilities at 11.424 GHz are operated at SLAC and at KEK, and these facilities are used by CLIC study in the frame of the X-band structure collaboration for testing accelerating structures scaled to that frequency*. Generally RF components are used in the transmission and the transformation of radio frequency signals generated by the power supply. The operating range of the devices accommodates the frequencies from 11.424 to 11.9942 GHz. RF components are needed for the Klystron test stand at CERN, and also for the X-FEL projects at PSI and Sincrotrone Trieste. Currently CERN is ordering tens of these companies to industry. The engineering design of the RF components (high power and compact loads, bi-directional couplers, X-band splitters, hybrids, phase shifters, variable power attenuators) and the main fabrication processes are presented here.
* K.M. Schirm et al., “A 12 GHZ RV Power source for the CLIC study”, Proc. of IPAC’10, THPEB053, p. 3990 (2010).

MOPC053

Mechanical Design and Fabrication Studies for SPL Superconducting RF Cavities

199

S. Atieh, G. Arnau-Izquierdo, I. Aviles Santillana, O. Capatina, T. Renaglia, T. Tardy, N. Valverde Alonso, W. Weingarten
CERN, Geneva, Switzerland

CERN’s R&D programme on the Superconducting Proton Linac’s (SPL) superconducting radio frequency (SRF) elliptical cavities made from niobium sheets explores new mechanical design and consequently new fabrication methods, where several opportunities for improved optimization were identified. A stainless steel helium vessel is under design rather than a titanium helium vessel using an integrated brazed transition between Nb and the SS helium vessel. Different design and fabrication aspects were proposed and the results are discussed hereafter.

MOPC054

The LHC RF System - Experience with Beam Operation

202

P. Baudrenghien, M. E. Angoletta, T. Argyropoulos, L. Arnaudon, J. Bento, T. Bohl, O. Brunner, A.C. Butterworth, E. Ciapala, F. Dubouchet, J. Esteban Muller, D.C. Glenat, G. Hagmann, W. Höfle, D. Jacquet, M. Jaussi, S. Kouzue, D. Landre, J. Lollierou, P. Maesen, P. Martinez Yanez, T. Mastoridis, J.C. Molendijk, C. Nicou, J. Noirjean, G. Papotti, A.V. Pashnin, G. Pechaud, J. Pradier, J. Sanchez-Quesada, M. Schokker, E.N. Shaposhnikova, D. Stellfeld, J. Tückmantel, D. Valuch, U. Wehrle, F. Weierud
CERN, Geneva, Switzerland

The LHC RF system commissioning with beam and physics operation for 2010 and 2011 are presented. It became clear in early 2010 that RF noise was not a lifetime limiting factor: the crossing of the much feared 50 Hz line for the synchrotron frequency did not affect the beam. The broadband LHC RF noise is reduced to a level that makes its contribution to beam diffusion in physics well below that of Intra Beam Scattering. Capture losses are also under control, at well below 0.5%. Longitudinal emittance blow-up, needed for ramping of the nominal intensity single bunch, was rapidly commissioned. In 2011, 3.5 TeV/beam physics has been conducted with 1380 bunches at 50 ns spacing, corresponding to 55% of the nominal current. The intensity per bunch (1.3 ·10¹¹ p) is significantly above the nominal 1.15 ·10¹¹. By August 2011 the LHC has accumulated more than 2 fb-1 integrated luminosity, well in excess of the 1 fb-1 target for 2011.

MOPC055

High Power Test of the First PIMS Cavity for Linac4

205

F. Gerigk, J.-M. Giguet, P. Ugena Tirado, R. Wegner
CERN, Geneva, Switzerland

The PI-Mode Structure (PIMS) accelerates the Linac4 beam from 100 to 160 MeV. Twelve 7-cell cavities will be installed in the linac, with a gradient of ~4 MV/m and operating at a frequency of 352.2 MHz. A full-power prototype has been constructed at CERN in 2010 and was high- power tested in autumn 2010. Peak power tests at the Linac4 duty cycle and high-average power tests at increased duty cycles were completed successful, so that this prototype will be the first of the 12 cavities to be installed in Linac4. This paper reports on the high-power tests and the conditioning experience.

MOPC056

The Linac4 Power Coupler

208

F. Gerigk, J.-M. Giguet, E. Montesinos, B. Riffaud, P. Ugena Tirado, R. Wegner
CERN, Geneva, Switzerland

Linac4 employs 3 types of accelerating structures after the RFQ: a Drift Tube Linac (DTL), a Cell-Coupled DTL (CCDTL), and a Pi-Mode Structure (PIMS) to accelerate the beam to 160 MeV. The structures are designed for a peak power of 1 MW per coupler, which consists of two parts: a ceramic window, which separates the cavity vacuum from the air in the wave-guides, and a so-called "coupling T", which couples the RF power through an iris to the cavity. In the frame of the Linac4 R&D both devices have been significantly improved with respect to their commonly used design. On the coupler side, the wave-guide short circuit with its matched length has been replaced by a fixed length λ/4 short circuit. The RF matching is done by a simple piston tuner, which allows a quick matching to different cavity quality factors. In the window part, which usually consists of a ceramic disc and 2 pieces of wave-guides with matching elements, the wave-guide sections could be completely suppressed, so that the window became very compact, lightweight, and much simpler to manufacture. In this paper we present electromagnetic simulations, and tests on first prototypes, which were constructed at CERN.

MOPC057

Loss of Landau Damping in the LHC

211

E.N. Shaposhnikova, T. Argyropoulos, P. Baudrenghien, T. Bohl, A.C. Butterworth, J. Esteban Muller, T. Mastoridis, G. Papotti, J. Tückmantel, W. Venturini Delsolaro, U. Wehrle
CERN, Geneva, Switzerland
C.M. Bhat
Fermilab, Batavia, USA

Loss of Landau damping leading to a single bunch longitudinal quadrupole instability has been observed in the LHC during the ramp and on the 3.5 TeV flat top for small injected longitudinal emittances. The first measurements are in good agreement with the threshold calculated for the expected longitudinal reactive impedance budget of the LHC as well as with the threshold dependence on beam energy. The cure is a controlled longitudinal emittance blow-up during the ramp which for constant threshold through the cycle should provide an emittance proportional to the square root of energy.

MOPC058

Upgrade of the 200 MHz RF System in the CERN SPS

214

E.N. Shaposhnikova, E. Ciapala, E. Montesinos
CERN, Geneva, Switzerland

The 200 MHz RF system, used in the SPS to accelerate all beams including those for the LHC, has four travelling wave structure cavities of different length. To stabilize the future higher intensity LHC beams in the SPS a larger (than now) controlled longitudinal emittance blow-up and therefore larger bucket and voltage amplitude will be necessary. However less voltage will be available in the existing system (which has a maximum peak RF power of 1 MW per cavity) due to the increased beam loading, in particular in the long cavities. This issue will be critical for beam acceleration but especially for beam transfer into the 400 MHz RF system of the LHC. The proposed solution is to shorten the two long cavities and use the freed sections together with spare sections to make two extra cavities and install two new power plants of 1.3 MW each. After this upgrade, which is a major part of the more general SPS upgrade for high luminosity LHC to be completed during 2017, the performance of the SPS RF system with high intensity beams will be significantly improved and at the same time the total impedance of the system will be reduced.

MOPC059

The Plane Wave Transformer Linac Development at NSRRC

217

A. Sadeghipanah, J.-Y. Hwang, W.K. Lau
NSRRC, Hsinchu, Taiwan
T.H. Chang
NTHU, Hsinchu, Taiwan

A Plane-Wave-Transformer (PWT), standing wave linac operating at S-band frequency (2.9979 GHz) is being developed at NSRRC. This structure offers the advantages of high efficiency, compactness, fabrication simplicity and cost. The PWT prototype at NSRRC consists of three cells with two half-cells at the ends, separated by a set of four flat disks suspended and cooled by four water tubes inside a large cylindrical tank. To fully understand its physical properties, numerical modeling of the PWT prototype has been carried out by using the 2-D code SUPERFISH and 3-D code MAFIA. In this paper, we describe the principle properties of this structure, the electric parameters obtained from numerical simulations, and heat dissipation calculation. The mechanical design for prototype linac is also reported.

MOPC060

Bunching-frequency Multiplication for a THz Pulse-train Photoinjector

220

Y.-C. Huang, F.H. Chao, C.H. Chen, K.Y. Huang
NTHU, Hsinchu, Taiwan

Funding: This work is supported by National Science Council under Contract NSC 99-2112-M-007 -013 -MY3.
A THz-pulse-train photoinjector* employs a THz-pulse-train laser as its driver laser to generate a beam with a bunching frequency in the THz range. However a laser frequency is on the order of a few hundred THz. It is not possible to generate a beam from the pulse-train photoinjector with a bunching frequency exceeding the laser’s carrier frequency. In view of the strong demand for a compact x-ray free-electron laser (FEL), it is highly desirable to multiply the bunching frequency of the beam from a pulse-train injector to the x-ray frequencies. We propose to chirp the energy of the THz electron pulse train in an accelerator and compress the whole beam in a magnet to increase the electron bunching frequency. Our study shows a compression ratio or a bunching-frequency multiplication factor of a few tens is achievable from a properly designed magnetic chicane compressor. The bunching factor, however, is unfortunately degraded due to the energy chirp, emittance growth, and wake-field generation. In the conference, we will show that a bunching factor of a few ppm in the bunch-frequency multiplied beam is sufficient to build up the FEL power from a 10-time length reduced undulator.
* Y. C. Huang, “Laser-beat-wave bunched beam for compact superradiance sources,” International Journal of Modern Physics B, Vol. 21 Issue 3/4, p277-286 (2007).

MOPC061

Simulations to Flatten the Field of the FETS RFQ

223

S.R. Lawrie, A.P. Letchford
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
J.K. Pozimski, P. Savage
Imperial College of Science and Technology, Department of Physics, London, United Kingdom

A high performance Radio Frequency Quadrupole (RFQ) is the next major component to be installed on the Front End Test Stand (FETS) at the Rutherford Appleton Laboratory (RAL) in the UK. The beam dynamics, RF, thermal and mechanical designs of the RFQ are almost complete and so the copper has recently been purchased with a view to start cutting metal near Summer-time. This report summarizes the simulation work performed to ensure the RF design is sound. This includes performance studies of the end-wall dipole suppression fingers, tuning the frequency of the input and output vane end regions and implementing a simple solution to remove modulation induced field tilt.

MOPC062

EMMA RF Comissioning

226

A.J. Moss, R.K. Buckley, P.A. McIntosh, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

EMMA (Electron Model for Many Applications), the world’s first Non-Scaling Fixed Field Alternating Gradient (NS-FFAG) accelerator is presently in operation at Daresbury Laboratory. The LLRF system is required to synchronize with ALICE (Accelerators and Lasers in Combined Experiments) its injector, which operates at 1.3GHz, and to produce an offset frequency of (+1.5 MHz to -4 MHz) to probe the longitudinal beam dynamics and to also maintain the phase and amplitude of the 19 copper RF cavities of the EMMA machine. The design, commissioning and results of the EMMA RF system is presented.

MOPC064

Upgrade and Commissioning of the 88-Inch Cyclotron Final Power Amplifier

229

M. Kireeff Covo, D.F. Byford, P.W. Casey, A. Hodgkinson, S. Kwiatkowski, C.M. Lyneis, L. Phair, A. Ratti, C.P. Reiter
LBNL, Berkeley, California, USA

Funding: This work was supported by the Director, Office of Science, Office of High Energy and Nuclear Physics, Division of Nuclear Physics, U.S. Department of Energy under Contract DE-AC02-05CH11231.
The RF system of the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory is a resonant system based on the quarter-wave cantilever type resonating structure. Power is fed to the Dee from the anode of the 500 kW RCA 6949 tetrode tube operating in grounded cathode configuration, which is capacitively coupled to the side of the Dee stem. The tube is obsolete and makes its continued use impractical. A new final power amplifier was designed and built using the commercially available tube Eimac 4W150,000E. The new amplifier was successfully commissioned and has been reliable and easy to operate. An overview of the system upgrade and details of the commissioning will be presented.

MOPC065

Ion Motion in the Vicinity of Microprotrusions in Accelerating Structures

232

D.G. Kashyn, T.M. Antonsen, I. Haber, G.S. Nusinovich
UMD, College Park, Maryland, USA

Funding: This work is supported by Office of High Energy Physics of the U.S. Department of Energy.
It is known that newly fabricated accelerating structures have almost ideally smooth surface. However, ‘post mortem’ examination of these structures reveals that their surface can be significantly modified after high-gradient operation. This surface modification can be caused by the appearance of microscopic protrusions*. One of the factors leading to heating, melting and evaporation of these protrusions (factors resulting in the RF breakdown) is ion bombardment**. In our study we analyze ion motion in the vicinity of microprotrusions both analytically and numerically. First, we study the ion motion in the RF electric field magnified by the protrusion in the absence of electron field emitted current and show that most of the ions do not reach the structure surface. Then we add into consideration the interaction of ions with Fowler-Nordheim current emitted from the tip of protrusion (dark current). First, we develop a model describing this interaction and then we supplement it with numerical results using PIC code WARP***. We show that the ions move towards the area occupied by the dark current, but this does not increase the bombardment of micro-protrusions.
* R.B. Palmer,et al, Phys. Rev ST Accel. Beams 12, 031002 (2009).
** P. Wilson, AIP Conf. Proc., 877, Melville, New York, 2006, p. 27.
***J.-L. Vay, et al, Physics of Plasmas, 11, 2928 (2004).

MOPC067

X-Band Test Station at Lawrence Livermore National Laboratory

235

R.A. Marsh, F. Albert, S.G. Anderson, C.P.J. Barty, G.K. Beer, R.R. Cross, G.A. Deis, C.A. Ebbers, D.J. Gibson, F.V. Hartemann, T.L. Houck
LLNL, Livermore, California, USA
C. Adolphsen, A.E. Candel, T.S. Chu, E.N. Jongewaard, Z. Li, C. Limborg-Deprey, T.O. Raubenheimer, S.G. Tantawi, A.E. Vlieks, F. Wang, J.W. Wang, F. Zhou
SLAC, Menlo Park, California, USA

Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
An X-band multi-bunch test station is being built at LLNL to investigate the science and technology paths required to boost the current mono-energetic gamma-ray (MEGa-Ray) brightness by orders of magnitude. The test station will consist of a 5.5 cell X-band RF photoinjector, single accelerator section, and beam diagnostics. Beam quality must be exceedingly high in order to produce narrow-bandwidth gamma-rays, requiring a robust state of the art photoinjector. The photoinjector will be a high gradient (200 MV/m peak surface field on the cathode) standing wave structure, featuring a dual feed racetrack coupler, elliptical irises, and an optimized first cell length. A solid-state Scandinova modulator will power a single SLAC XL4 11.424 GHz 50 MW klystron. RF distribution will allow for full powering of the photoinjector with the balance of the RF powering a single accelerator section so that the electron parameters can be measured. The status of the facility will be presented including commissioning schedule and first experiment plans. Future experimental programs pertinent to Compton scattering R&D, high gradient structure testing, and light source development will be discussed.

MOPC068

LANSCE RF System Improvements for Current and Future Programs*

238

D. Rees, J.L. Erickson, R.W. Garnett, J.T.M. Lyles, L. Rybarcyk
LANL, Los Alamos, New Mexico, USA

The Los Alamos Neutron Science Center (LANSCE) is in the midst of an upgrade of the RF systems. This project will return LANSCE to its historical operating capability and sustain facility operations into the next decade. The LANSCE accelerator provides pulsed protons and spallation neutrons for defense and civilian applications. This project involves replacing all the existing 201 MHz RF stations and 805 MHz klystrons. LANSCE is also currently in the conceptual design phase of a program called the Material Test Station (MTS) to establish a 1 MW target station to irradiate fast reactor fuels and materials. A pre conceptual design is also in progress to extend the capabilities of MTS to a 2 MW target that will enable the first in a new generation of scientific facilities for the materials community. The emphasis of this new facility is "Matter-Radiation Interactions in Extremes" (MaRIE) which will be used to discover and design the advanced materials needed to meet 21st century national security and energy security challenges. The design and test results of the new RF systems will be presented as well as the RF system changes required to support the new missions.

MOPC071

Status of High Power Tests of Normal Conducting Short Standing Wave Structures*

241

V.A. Dolgashev, Z. Li, S.G. Tantawi, A.D. Yeremian
SLAC, Menlo Park, California, USA
Y. Higashi
KEK, Ibaraki, Japan
B. Spataro
INFN/LNF, Frascati (Roma), Italy

Funding: Work Supported by Doe Contract No. DE-AC02-76SF00515
We report results of continuing high power tests of short standing wave structures. These tests are part of an experimental and theoretical study of basic physics of rf breakdown in 11.4 GHz, normal conducting structures. The goal of this study is to determine the accelerating gradient capability of normal conducting rf powered particle accelerators. We have tested structures of different geometries, cell joining techniques, and materials. We found that the breakdown rate dependence on peak magnetic fields is stronger than on peak surface electric fields for cylindrically symmetric structures powered via a TM01 mode launcher. We report test results for structures powered by side-coupled rectangular waveguides. We found that increased rf magnetic field due to the side-coupling increases the breakdown rate as compared to the same accelerating gradient in cylindrically symmetric structures.

MOPC072

Design of an RF Feed System for Standing-wave Accelerator Structures

244

J. Neilson, V.A. Dolgashev, S.G. Tantawi
SLAC, Menlo Park, California, USA

Travelling wave (TW) accelerator structures are known to suffer from several deficiencies. A breakdown in one of the cells propagates towards the source. This results in damage to upstream cells in addition to the cell where the breakdown was initiated. The deficiencies of TW accelerator structures can be overcome by using standing wave (SW) cells that are fed in parallel. An RF breakdown is contained to the cell where it originates. This eliminates upstream cell damage and the resulting changes in phase shift between cells. In addition the feed structure can provide a high conductance port for vacuum pumping. We have completed the design of a parallel fed SW structure with a directional coupler for each cell and serpentine waveguide connection between couplers. This design approach improves isolation between the cells resulting in the maximum increase in the operational robustness of the accelerator structure. The design uses four feed arms spaced uniformly around the cell circumference to suppress dipole modes and improve damping of low order wakefields. Construction of a test structure in now underway and is scheduled for testing in October of this year.

MOPC073

A Dual-mode Accelerating Cavity to Test RF Breakdown Dependence on RF Magnetic Fields

247

A.D. Yeremian, V.A. Dolgashev, J. Neilson, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: * Work Supported by Doe Contract No. DE-AC02-76SF00515
RF Breakdown experiments on short accelerating structures at SLAC have shown that increased rf magnetic fields increase the probability of rf breakdowns. Moreover, the breakdown rate is highly correlated with the peak pulse-heating in soft-copper single-cell standing-wave structures of disk-loaded waveguide type. In these geometries the rf electric and magnetic fields are highly correlated. To separate effects of rf magnetic and electric fields on the rf breakdown rate, we have designed an X-band cavity with a geometry as close to that of a standing-wave accelerator cell as practically possible. This cavity supports two modes: an accelerating TM mode and a TE mode with no-surface-electric field but with a strong magnetic field. The cavity will be constructed and tested at the Accelerator Structure Test Area (ASTA) at SLAC.

MOPC077

Commissioning of Multibunch Feedback Systems at the Fast Ramping Stretcher Ring ELSA

250

A. Roth, F. Frommberger, N. Heurich, W. Hillert, M. Schedler, R. Zimmermann
ELSA, Bonn, Germany

Funding: Supported by German Research Foundation through SFB/TR 16 and by Helmholtz Alliance through HA-10¹.
At the Electron Stretcher Facility ELSA of Bonn University, an external beam of either unpolarized or polarized electrons is supplied to hadron physics experiments. The ELSA stretcherring operates in the energy range of 1.2 to 3.5 GeV and achieves a duty cycle of up to 80% using a fast energy ramp of 4 GeV/s. Under these conditions, an increase of the internal beam current from an actual value of 20 mA up to 200 mA is planned. Such an upgrade is mainly limited by the excitation of multibunch instabilities. As one active counteraction, we have installed state-of-the-art bunch-by-bunch feedback systems for the longitudinal, as well as for both transverse planes. The detailed setup with all main components and first results of the commissioning of the systems will be presented. In particular, the performance of the longitudinal feedback with a stabilized synchrotron frequency during the fast energy ramp will be discussed.

MOPC078

Operation of Superconducting Cavities in a Fast Ramping Electron Storage Ring

253

A. Roth, W. Hillert
ELSA, Bonn, Germany

Funding: Supported by German Research Foundation through SFB/TR 16.
The achievable maximum energy of a medium-sized electron accelerator is mainly limited by the accelerating voltage. Using superconducting (sc) cavities, the energy limitation can be shifted considerably. However, the operation of sc multi-cell cavities in a fast ramping storage ring causes additional problems which were investigated at the 3.5 GeV Electron Stretcher Accelerator ELSA. We studied the use of two 500 MHz sc cavities providing the necessary resonator voltage of up to 14 MV and replacing the normal conducting cavities of PETRA type. A large cavity coupling factor is required, so that using the existing 250 kW klystron, an internal beam of 50 mA can be accelerated up to 5 GeV. In addition, a fast detuning of the resonance frequency of the cavities must be implemented during beam injection and the energy ramp of 4 GeV/s. An appropriate 500 MHz structure is given by a five-cell cavity constructed for the JAERI-FEL-LINAC. Based on this geometry, HOM have been calculated from a numerical simulation. Since all monopole and a larger number of dipole HOM are well above the multibunch instabilities threshold, further studies about beam instabilities damping are essential.

MOPC079

Status of the Low Beta 0.07 Cryomodules for SPIRAL2

256

P. Bosland, P. Carbonnier, F. Eozénou, P. Galdemard, O. Piquet
CEA/DSM/IRFU, France
M. Anfreville, C. Madec, L. Maurice
CEA/IRFU, Gif-sur-Yvette, France
P.-E. Bernaudin, R. Ferdinand
GANIL, Caen, France
Y. Gomez-Martinez
LPSC, Grenoble Cedex, France
A. Pérolat
CEA, Gif-sur-Yvette, France

The status of the low beta cryomodules for SPIRAL2, supplied by the Irfu institute of CEA Saclay, is reported in this paper. We summarise in three parts the RF tests performed on the cavities in vertical cryostat, the RF power tests of the qualifying cryomodule performed in 2010 and the RF power tests performed in 2011 on the first cryomodule of the series

MOPC080

First Considerations Concerning an Optimized Cavity Design for the Main Linac of BERLinPro

259

B. Riemann, T. Weis
DELTA, Dortmund, Germany
W. Anders, J. Knobloch, A. Neumann
HZB, Berlin, Germany
H.-W. Glock, C. Potratz, U. van Rienen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
F. Marhauser
JLAB, Newport News, Virginia, USA

Funding: work supported by BMBF under contracts 05K10PEA and 05K10HRC
The Berlin Energy Recovery Linac Project (BERLinPro) is designed to develop and demonstrate CW linac technology and expertise required to drive next-generation Energy Recovery Linacs. Strongly HOM-damped multicell 1.3 GHz cavities are required for the main linac. The optimization of the cavities presented here is primarily based on the CEBAF 1.5 GHz 5-cell high-current cavity design, including HOM waveguide couplers. The cavity was scaled to 1.3 GHz and extended to 7 cells. Modifications to the end group design have also been studied. An effort was also made to reduce the ratio Epk/Eacc while still permitting HOMs to propagate.

MOPC081

Pulsed Mode Operation and Longitudinal Parameter Measurement of the Rossendorf SRF Gun

262

J. Teichert, A. Arnold, H. Büttig, M. Justus, U. Lehnert, P. Michel, P. Murcek, Ch. Schneider, R. Schurig, R. Xiang
HZDR, Dresden, Germany
T. Kamps, J. Rudolph, M. Schenk
HZB, Berlin, Germany
I. Will
MBI, Berlin, Germany

Funding: The European Community-Research Infrastructure Activity under the FP7 program (EuCARD, contract number 227579) the German Federal Ministry of Education and Research grant 05 ES4BR1/8.
The Rossendorf SRF gun with a 3 1/2 cell cavity has been operated since 2007. It has produced CW beam with the electron energy of 3 MeV and the average current up to 16 μA. The electron beam of the gun has successfully injected the ELBE superconducting linac since 2010. The Nb cavity has shown constant quality during the operation and for the Cs2Te photocathode life time of months could be obtained. Recently the gun started to run in the pulsed mode with higher gradient. The longitudinal parameters have been measured in this mode. The dark current arose from the high gradient is studied. The main field emission source has been found to be the half cell. Meanwhile, two modified 3+1/2 cell niobium cavities have been fabricated and tested in Jlab. In this paper the new status of the SRF gun will be presented, and the latest results of the beam experiments will be discussed.

MOPC082

Status of the 325 MHz SC CH-Cavity at IAP Frankfurt

265

M. Busch, F.D. Dziuba, H. Podlech, U. Ratzinger
IAP, Frankfurt am Main, Germany
M. Amberg, K. Aulenbacher
HIM, Mainz, Germany
W.A. Barth, S. Mickat
GSI, Darmstadt, Germany

Funding: BMBF contract no. 06FY161I
At the Institute for Applied Physics (IAP), University of Frankfurt, a s.c. 325 MHz CH-Cavity is under development for future beam tests at GSI UNILAC, Darmstadt. The cavity with 7 accelerating cells has a geometrical beta of 0.15 corresponding to 11.4 AMeV. The design gradient is 5 MV/m. The geometry of this resonator was optimized with respect to a compact design, low peak fields, surface processing, power coupling and tuning. Furthermore a new tuning system based on bellow tuners inside the resonator will control the frequency during operation. After rf tests in Frankfurt the cavity will be tested with a 10 mA, 11.4 AMeV beam delivered by the GSI UNILAC. In this paper rf simulations, multipacting analysis as well as thermal calculations will be presented.

MOPC083

Structural Mechanics of Superconducting CH Cavities

268

M. Amberg, K. Aulenbacher
HIM, Mainz, Germany
W.A. Barth, S. Mickat
GSI, Darmstadt, Germany
M. Busch, F.D. Dziuba, H. Podlech, U. Ratzinger
IAP, Frankfurt am Main, Germany

The superconducting CH-structure (Crossbar-H-mode) is a multi-cell drift tube cavity for the low and medium energy range operated in the H21-mode, which has been developed at the Institute for Applied Physics (IAP) of Frankfurt University. With respect to different high power applications two types of superconducting CH-structures (f = 325 MHz, β = 0.16, seven cells and f = 217 MHz, β = 0.059, 15 cells) are presently under construction and accordingly under development. The structural mechanical simulation is a very important aspect of the cavity design. Furthermore, several simulations with ANSYS Workbench have been performed to predict the deformation of the cavity walls due to the cavity cool-down, pressure effects and mechanical vibrations. To readjust the fast frequency changes in consequence of the cavity shape deformation, a new concept for the dynamic frequency tuning has been investigated, including a novel type of bellow-tuner.

MOPC084

The Superconducting cw LINAC Demonstrator for GSI

271

F.D. Dziuba, M. Busch, H. Podlech, U. Ratzinger
IAP, Frankfurt am Main, Germany
M. Amberg, K. Aulenbacher
HIM, Mainz, Germany
W.A. Barth, S. Mickat
GSI, Darmstadt, Germany

Funding: BMBF Contr. No. 06FY9089I, Helmholtz Institut Mainz
At GSI a new, superconducting (sc) continuous wave (cw) LINAC is under design in cooperation with the Institute for Applied Physics (IAP) of Frankfurt University and the Helmholtz Institut Mainz (HIM). This proposed LINAC is highly requested by a broad community of future users to fulfill the requirements of nuclear chemistry, nuclear physics, and especially in the research field of Super Heavy Elements (SHE). In this context the preliminary layout of the LINAC has been carried out by IAP. The main acceleration of up to 7.3 AMeV will be provided by nine sc Crossbar-H-mode (CH) cavities operated at 217 MHz. Currently, a prototype of the cw LINAC as a demonstrator is under development. The demonstrator comprises a sc CH-cavity embedded between two sc solenoids mounted in a horizontal cryomodule. A full performance test of the demonstrator in 2013/14 by injecting and accelerating a beam from the GSI High Charge Injector (HLI) is one important milestone of the project. The status of the demonstrator is presented.

MOPC085

Quality Assessment for Industrially Produced High-Gradient Superconducting Cavities

274

F. Schlander, S. Aderhold, E. Elsen, D. Reschke, M. Wenskat
DESY, Hamburg, Germany

Funding: This work is supported by the Commission of the European Communities under the 7th Framework Programme “Construction of New Infrastructures – Preparatory Phase”, contract number 206711.
A series of some 600 superconducting 1.3 GHz cavities will start being delivered to DESY by industry in early 2012. Although a considerably smaller gradient satisfies the needs for the European XFEL the electro-polished cavities (50% of the delivery) are deemed to be suitable for gradients in excess of 35 MV/m, the performance goal of the International Linear Collider (ILC). Specifically 24 cavities will be supplied without helium tank to enable further investigations. The results may serve to improve overall performance; limitations such as field emission and thermal breakdown of superconductivity ("quench") are still under investigation. For this matter the DESY ILC group has developed tools to monitor aspects of the cavity fabrication. An automated optical mapping system (OBACHT) is being commissioned and will be complemented by software for automated cavity surface feature recognition. For cold RF tests a Second Sound setup for locating the positions of the thermal breakdown is routinely used. These diagnostic tools will give guidance on post-processing cavities for best performance. The current status of these projects will be described.

MOPC086

Description and First Experience with the RF Measurement Procedure for the European XFEL SC Cavity Production

277

A.A. Sulimov, Th. Buettner, A. Gössel, D. Kostin, G. Kreps, W.-D. Möller, D. Reschke, J.H. Thie, K. Twarowski
DESY, Hamburg, Germany

Cavity production for the European XFEL was recently started with first Nb sheets arriving. From this stage to the accelerating module being ready for the linac installation, many critical RF measurements are necessary. During the mechanical cavity fabrication the cavity half-cells, dumb-bells and end-groups are measured and sorted. The cavity spectrum and field profiles are measured and tuned. The HOM (Higher Oder Modes) couplers filter tuning, vertical cavity RF tests, cavity checks during the string assembly and final cavity performance measurements in the module as well as the fundamental mode and HOM RF spectra measurements complete the sequence. We present the procedures of the RF measurements and discuss the first results for the XFEL prototype modules with special attention for the cavity tuning.

Poster MOPC086 [0.515 MB]

MOPC088

Bead-pull Measurement using Phase-Shift Technique in Multi-cell Elliptical Cavity

280

S. Ghosh, A. Mandal, S. Seth, S.S. Som
DAE/VECC, Calcutta, India

The project on the development of high-beta multi-cell elliptical shape superconducting rf linac cavity at around 704 MHz has been funded at VECC, Kolkata, India. A full-scale copper prototype cavity has been designed and fabricated. There are 5 distinct modes exist in the cavity and the accelerating mode is pi-mode in which each cell operates at same frequency with phase difference of 180 degrees between two neighboring cells. A fully automated bead-pull measurement setup has been developed for analyzing these modes and field profile distribution at different modes in such type of linac cavity. A special measurement method inside the cavity using phase-shift technique is proposed in this paper, which describes the development of mechanical setup comprising pulleys and stepper motor–gear arrangement, PC-based control system for precise movement of bead using stepper motor, measurement using VNA, development of software for data acquisition & automation and measurement results for the 5-cell copper prototype cavity.

MOPC089

RF Simulations for the QWR Cavities of PIAVE-ALPI

283

M. Comunian, F. Grespan, A. Palmieri
INFN/LNL, Legnaro (PD), Italy

The PIAVE-ALPI linac is composed of several families of QWR cavities. In order to have a thorough description of the accelerator in terms of beam dynamics, a detailed field mapping of the accelerating cavities is necessary, including non-linear behavior of the off-axis fields, as well as the steering and dispersion effects due to transverse components. For such a purpose, a set of RF simulation was accomplished, with the codes HFSS and COMSOL. The details about these simulations and the main outcomes and results will be described in this article.

MOPC090

Tuner Performance in the S1-global Cryomodule

286

R. Paparella, A. Bosotti, C. Pagani
INFN/LASA, Segrate (MI), Italy
C. Albrecht, K. Jensch, L. Lilje
DESY, Hamburg, Germany
S. Barbanotti, Y.M. Pischalnikov, W. Schappert
Fermilab, Batavia, USA
H. Hayano, E. Kako, S. Noguchi, N. Ohuchi, Y. Yamamoto
KEK, Ibaraki, Japan

S1-Global is a collaborative effort of INFN, DESY, FNAL, SLAC and KEK, in the framework of the ILC global collaboration. For this project two cryomodules, 6 meter long and hosting four SC cavities each, were realized and successfully cold tested at KEK-STF. Three different cavity tuning systems, provided with fast tuning capability through piezoelectric actuators (piezo), were installed, and fully characterized in static and dynamic operation: Blade Tuner from INFN/FNAL, Saclay Tuner from DESY, Slide Jack Tuner from KEK. Finally, Lorenz Force Detuning (LFD) active compensation has been successfully achieved during high power cavity tests in pulsed RF regime, where active control of the LFD disturbance up to Hz-level residual detuning has been achieved with each type of tuning system up to the maximum gradient of each cavity. The installation procedures, together with the relevant results and their analyses are summarized in the paper.

MOPC091

Status of the XFEL 3.9 GHz Injector Section

289

P. Pierini, M. Bonezzi, A. Bosotti, M. Fusetti, P.M. Michelato, L. Monaco, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
E. Vogel
DESY, Hamburg, Germany

The European XFEL will use a superconducting third harmonic section to achieve the necessary beam quality for the FEL process. The concept has been successfully proven at the FLASH linac in DESY, with a 4 cavity superconducting module contributed by FNAL. The design of the third harmonic system at the XFEL injector is being finalized and prototypes of the components (cavities and couplers) have been fabricated and are currently in the testing stage. The paper will provide a status of the activities.

MOPC092

Effect of Current Densities on Sulfur Generation at Electropolished Niobium Surface

292

P.V. Tyagi
Sokendai, Ibaraki, Japan
H. Hayano, S. Kato, M. Nishiwaki, T. Noguchi, T. Saeki, M. Sawabe
KEK, Ibaraki, Japan

We conducted a series of electropolishing (EP) experiments in aged EP acid with high (≈50 mA/cm²) and low (≈30 mA/cm²) current densities on Nb surfaces. The experiments were carried out both for laboratory coupons and a real Nb single cell cavity with six witness samples located at three typical positions (equator, iris and beam pipe). All the samples surface were investigated by XPS (x-ray photoelectron spectroscopy), SEM (scanning electron microscope) and EDX (energy dispersive x-ray spectroscopy). The surface analysis showed the EP with a high current density produced a huge amount sulfate particles at Nb surface whereas the EP with a low current density is very helpful to mitigate sulfate at Nb surface in both the experiments.

MOPC093

Novel Field Emission Scanner for Surface Study of Niobium SRF Cavity

295

S. Kato, M. Nishiwaki, T. Noguchi
KEK, Ibaraki, Japan
V. Chouhan
GUAS, Kanagawa, Japan
P.V. Tyagi
Sokendai, Ibaraki, Japan

It is mandatory to investigate field emission on Nb SRF cavity systematically since strong field emission often limits the cavity performance. The field emission strength and the number of emission sites strongly depend on Nb surface properties which are determined by its surface treatment and handling. Field emission scanner (FES) developed allows us to measure a distribution of the field emitting sites over a sample surface at a given field strength along with its FE-SEM observation and energy dispersive x-ray analysis. FES consists of an anode needle driven by precise 3D stepping motors and an eucentric sample stage. The compact scanner was installed into the space between the object lens and the SEM sample holder. In addition, this system was newly equipped with a sample load-lock system for existing UHV suitcases. Therefore a sample coupon to be observed is hardly exposed to contaminants and dust particles during the transportation. In-situ heating of a sample coupon can be done during an experiment to simulate a baking process of a SRF cavity. This article describes development of the field emission scanner and its preliminary results of the application to niobium samples.

MOPC095

Superconducting Cavity R&D for ILC at MHI

298

H. Hitomi, H. Hara, F. Inoue, K. Kanaoka, K. Sennyu, T. Yanagisawa
MHI, Kobe, Japan

We have developed and manufactured some superconducting RF cavity for STF project in KEK. In recent vertical test in KEK, the MHI-#12 cavity which is one of cavities for STF phase 2 project reached ILC specification(max Eacc was about 40MV/m). So techniques for manufacturing cavity is making steady progress in MHI. To be realized ILC project, we also try to decrease the manufacturing cost by using some new techniques, for example Laser Beam Welding, deep drawing, seamless dumbbell, etc. In this meeting, we will report recent MHI's activities for ILC.

MOPC096

Design and Fabrication of a 5-Cell High Current Superconducting Cavity

301

Y.M. Li, K.X. Liu, S.W. Quan, F. Zhu
PKU/IHIP, Beijing, People's Republic of China
R. Nassiri
ANL, Argonne, USA

Funding: National High Technology Research and Development program 863 (2009AA03Z206)
Energy recovery linacs (ERL) is promising to achieve high average current with superior beam quality. The key component for accelerating such high current beams is the superconducting radio frequency (SRF) cavity. The design of a 1.3 GHz 5-cell high current superconducting cavity has been carried out under the cooperation between Peking University (PKU) and Argonne National Laboratory (ANL). RF properties, damping of the HOMs, multipacting and mechanical features of this cavity have been discussed and the final design is presented.

MOPC097

LLRF Control System for PKU DC-SC Photocathode Injector

304

H. Zhang, Y.M. Li, K.X. Liu, F. Wang, B.C. Zhang
PKU/IHIP, Beijing, People's Republic of China

A 1.3 GHz 3.5 Cell LG niobium cavity is installed for the new PKU DC-SC injector as its accelerating cavity with working temperature is 2K. High amplitude and phase stability is required for the updated SRF photocathode injector. This paper describes the design of Low Level RF control system based on FPGA, including hardware and software,and the communication function is realized by Tri-State Ethernet. The system should be operated on the precision with the amplitude of ±0.1% and phase stability of ±0.1°.

MOPC101

Vertical Test of PEFP Prototype SRF Cavity

307

H.S. Kim, Y.-S. Cho, H.-J. Kwon
KAERI, Daejon, Republic of Korea

Funding: This work was supported by Ministry of Education, Science and Technology of the Korean Government.
The PEFP Proton linac is a 100-MeV machine which consists of a proton injector, a 3-MeVRFQ and 100-MeV DTL. For the extension of the machine beyond 100 MeV, SRF technology is under consideration. As a prototyping activity, a superconducting RF cavity with a geometrical beta of 0.42 and a resonant frequency of 700 MHz has been designed, fabricated and tested. The cavity is an elliptical shape with 5 cells stiffened by double-ring structure. A design accelerating gradient is 8.0 MV/m at the operating temperature of 4.2 K and maximum duty factor is 9%. For the vertical test of the cavity, a cryostat with a vacuum jacket and multi-layer insulation was prepared. The RF system for driving the cavity is based on PLL to track the resonant frequency. In case of lack of RF power, a two-way RF power combiner based on splitted coaxial transmission line is considered. The details of the vertical test setup and test results will be presented in this paper.

MOPC102

RF and Surface Properties of Superconducting Samples

310

T. Junginger, W. Weingarten
CERN, Geneva, Switzerland
T. Junginger
MPI-K, Heidelberg, Germany
R. Seviour
Lancaster University, Lancaster, United Kingdom
C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: Work supported by the German Doctoral Students program of the Federal Ministry of Education and Research (BMBF)
The surface resistance Rs of superconducting cavities can be obtained from the unloaded quality factor Q0. Since Rs varies strongly over the cavity surface its value must be interpreted as averaged over the whole cavity surface. A more convenient way to investigate the surface resistance of superconducting materials is therefore to examine small samples, because they can be manufactured cheaply, duplicated easily and used for further surface analyses. At CERN a compact Quadrupole Resonator has been developed for the RF characterization of superconducting samples at different frequencies. In this contribution, results from measurements on bulk niobium and niobium film on copper samples are presented. It is shown how different contributions to the surface resistance depend on temperature, applied RF magnetic field and frequency. Furthermore, measurements of the maximum RF magnetic field as a function of temperature and frequency in pulsed and CW operation are presented. The study is accompanied by measurements of the surface properties of the samples by various techniques.

MOPC103

Cryostat for Testing HIE-ISOLDE Superconducting RF Cavities

313

O. Capatina, J.P. Brachet, G. Cuccuru, M. Pasini, T. Renaglia, M. Therasse, B. Vullierme
CERN, Geneva, Switzerland

The High Intensity and Energy ISOLDE (HIE-ISOLDE) project is a major upgrade of the existing ISOLDE and REX-ISOLDE facilities at CERN [1], with the objective of increasing the energy and the intensity of the delivered radioactive ion beams (RIB). This project aims to fill the request for a more energetic post accelerated beam by means of a new superconducting (SC) linac based on Quarter Wave Resonators (QWRs). A research and development program looking at all different aspects of the SC linac has started in 2008 and continued throughout 2010. In particular the R&D effort has focused on the development of the high β cavity (β = 10.3%), for which it has been decided to adopt the Nb sputtered on Cu substrate technology. Two prototype cavities were manufactured and are undergoing RF cold tests. The pre-series cavity fabrication is under way using 3D forged Cu billets. A single vacuum cryostat was designed and built to test these cavities at liquid helium temperatures. The paper details the main design concepts of the test cryostat as well as the results of the cryogenic behavior of the complete set-up including the cryostat, the RF cavity, the tuner and the main coupler.

MOPC104

HIE-ISOLDE SRF Development Activities at CERN

316

M. Therasse, O. Brunner, S. Calatroni, J.K. Chambrillon, B. Delaup, M. Pasini
CERN, Geneva, Switzerland

The HIE-ISOLDE project has initiated a new development phase on the SRF domain at CERN. In particular, the HIE-ISOLDE project aims at the construction of the 32 Quarter Wave Resonators (QWRs) using the Nb on Cu sputtering technology. The paper describes the refurbishment of the test infrastructure and the activities from the cavity production to the cold test, including quality assurance procedure for the correct handling of the resonators.

MOPC105

Design of the High Beta Cryomodule for the HIE-ISOLDE Upgrade at CERN

319

L.R. Williams, A.P. Bouzoud, N. Delruelle, J. Gayde, Y. Leclercq, M. Pasini, J.Ph. G. L. Tock, G. Vandoni
CERN, Geneva, Switzerland

The major upgrade of the energy and intensity of the radioactive ion beams of the existing ISOLDE and REX-ISOLDE facilities at CERN will, in the long term, require downstream of the existing machine, the installation of four high-β and two low-β cryo-modules. The first stage of this upgrade, involving the design, construction, installation and commissioning of two high-β cryo-modules is approved and design work is underway at CERN. The high-β cryo-module houses five high-β superconducting cavities and one superconducting solenoid. As well as providing optimum conditions for physics, where the internal active components must remain aligned within tight tolerances, the cryo-modules need to function under stringent common vacuum and cryogenic conditions. To preserve the RF cavity performance their assembly and sub-system testing will need to be carried out using specifically designed tooling in a class 100 clean-room. We present the determining factors constraining the design of the high-β cryo-module together with the design choices that these factors have imposed.

MOPC106

Study of the Variation of Transverse Voltage in the 4 Rod Crab Cavity for LHC

322

B.D.S. Hall, P.K. Ambattu, G. Burt, C. Lingwood
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
P. Goudket, C. Hill
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

The planned high luminosity upgrade to LHC will utilise crab cavities to rotate the beam in order to increase the luminosity in the presence of a finite crossing angle. A compact design is required in order for the cavities to fit between opposing beam-lines. In this paper we discuss we discuss one option for the LHC crab cavity based on a 4 rod TEM deflecting cavity. Due to the large transverse size of the LHC beam the cavity is required to have a large aperture while maintaining a constant transverse voltage across the aperture. The cavity has been optimised to minimise the variation of the transverse voltage while keeping the peak surface electric and magnetic fields low for a given kick. This is achieved while fitting within the strict design space of the LHC. The variation of deflecting voltage across the aperture has been studied numerically and compared with numerical and analytical estimates of other deflecting cavity types. Performance measurements an aluminium prototype of this cavity are presented and compared to the simulated design.

MOPC107

HOM and FP Coupler Design for the NLSF High Gradient SC Cavity

325

R.M. Jones, N. Juntong
UMAN, Manchester, United Kingdom

The design of both higher order mode (HOM) and fundamental power (FP) couplers for the New Low Surface Field (NLSF) cavity* is presented. Here we study using the ILC baseline couplers for this new superconducting cavity. A Balleyguier method** of calculating external quality factor is used and the results validated using both Microwave studio and HFSS.
* N. Juntong and R.M. Jones, SRF2009, THPPO024, 2009.
** P. Balleyguier, LINAC98, MO4037, 1998

MOPC108

Cornell SRF New Materials Program*

328

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

Funding: Work supported by NSF Career award PHY-0841213, DOE award ER41628, and the Alfred P. Sloan Foundation
The SRF group at Cornell has recently pioneered an extensive program to investigate alternative materials for superconducting cavities. We have developed facilities to fabricate Nb3Sn, a superconductor which will theoretically be able to reach more than twice the maximum accelerating field of Nb in a cavity under the same operating conditions. In addition, with the critical temperature of Nb3Sn being twice that of Nb, Nb3Sn would allow operation of SRF cavities with a much higher cryogenic efficiency. We have also manufactured two TE cavities that measure the RF properties of small, flat samples, ideal for material fabrication methods in development. This paper presents an overview of the materials research program. First results from tests of Nb3Sn samples are presented.

MOPC109

Suppression of Coupler Kicks in 7-Cell Main Linac Cavities for Cornell's ERL

331

N.R.A. Valles, M. Liepe, V.D. Shemelin
CLASSE, Ithaca, New York, USA

Funding: Supported by NSF award DMR-0807731
Cornell is developing a 5 GeV Energy Recovery Linac operating at 100 mA with very small emittances (~30 pm at 77 pC bunch charge) in the horizontal and vertical directions. We investigate the effect of the fundamental RF power couplers of the main linac SRF cavities on the beam using the ACE3P software package. The cavities in the ERL main linac will be operated at very high loaded quality factors of up to 6.5·10⁷, corresponding to a full bandwidth of only 20 Hz. Cavity microphonics will detune the cavities by more than one bandwidth during operation, thereby causing a time dependent change of the coupler kick in addition to its fast oscillation at the RF frequency. In order to investigate the dependence of the coupler kick on the cavity frequency, we calculate the coupler kick given to the beam for the case of a detuned RF cavity. We show that a compensation stub geometry located opposite to the input coupler port can be optimized to reduce the overall kick given to the beam and the emittace growth caused by its time dependence.

MOPC111

Progress of ILC High Gradient SRF Cavity R&D at Jefferson Lab

334

R.L. Geng, J. Dai, G.V. Eremeev, A.D. Palczewski
JLAB, Newport News, Virginia, USA

Funding: US Department of Energy
Latest progress of ILC high gradient SRF cavity R&D at Jefferson Lab will be presented. 9 out of 10 real 9-cell cavities reached an accelerating gradient of more than 38 MV/m at a unloaded quality factor of more than 8·10⁹. New understandings of quench limitation in 9-cell cavities are obtained through instrumented studies of cavities at cryogenic temperatures. Our data have shown that present limit reached in 9-cell cavities is predominantly due to localized defects, suggesting that the fundamental material limit of niobium is not yet reached in 9-cell cavities and further gradient improvement is still possible. Some examples of quench-causing defects will be given. Possible solutions to pushing toward the fundamental limit will be described.

MOPC112

Fabrication and Testing Status of CEBAF 12 GeV Upgrade Cavities

337

F. Marhauser, A. Burrill, G.K. Davis, D. Forehand, C. Grenoble, J. Hogan, R.B. Overton, A.V. Reilly, R.A. Rimmer, M. Stirbet
JLAB, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The 12 GeV upgrade of the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Laboratory (JLab) is under way. All cavities have been built by industry and are presently undergoing post-processing and final low and high power qualification before cryomodule assembly. The status is reported including fabrication-related experiences, observations and issues throughout production, post-processing and qualification.

MOPC113

Results of Cavity Series Fabrication at Jefferson Laboratory for the Cryomodule “R100”

340

F. Marhauser, W.A. Clemens, M.A. Drury, D. Forehand, J. Henry, S. Manning, R.B. Overton, R.S. Williams
JLAB, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
A series production of eight superconducting RF cavities for the cryomodule R100 was conducted at JLab in 2010. The cavities underwent chemical post-processing prior to vertical high power testing and routinely exceeded the envisaged performance specifications. After cryomodule assembly, cavities were successfully high power acceptance tested. In this paper, we present the achievements paving the way for the first demonstration of 100 MV (and beyond) in a single cryomodule to be operated at CEBAF.

MOPC114

Design, Fabrication and Testing of Medium-Beta 650 MHz SRF Cavity Prototypes for Project-X

343

F. Marhauser, W.A. Clemens, J. Henry, P. Kneisel, R. Martin, R.A. Rimmer, G. Slack, L. Turlington, R.S. Williams
JLAB, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
A new type of superconducting radio frequency (SRF) cavity shape with a shallow equator dome to reduce electron impact energies for suppressing multipacting barriers has been proposed. The shape is in consideration for the first time in the framework of Project-X to design a potential multi-cell cavity candidate for the medium-beta section of the SRF proton CW linac operating at 650 MHz. Rationales covering the design of the multi-cell cavity, the manufacture, post-processing and high power testing of two single-cell prototypes are presented.

MOPC115

JLab SRF Cavity Fabrication Errors, Consequences and Lessons Learned

346

F. Marhauser
JLAB, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
Today, elliptical superconducting RF (SRF) cavities are preferably made from deep-drawn niobium sheets as pursued at Jefferson Laboratory (JLab). The fabrication of a cavity incorporates various cavity cell machining, trimming and electron beam welding (EBW) steps as well as surface chemistry that add to forming errors creating geometrical deviations of the cavity shape from its design. An analysis of in-house built cavities over the last years revealed significant errors in cavity production. Past fabrication flaws are described and lessons learned applied successfully to the most recent in-house series production of multi-cell cavities.

MOPC116

Development of Nb and Alternative Material Thin Films Tailored for SRF Applications

349

A-M. Valente-Feliciano, H.L. Phillips, C.E. Reece, J.K. Spradlin, B. Xiao, X. Zhao
JLAB, Newport News, Virginia, USA
H. Baumgart, D. Gu
ODU, Norfolk, Virginia, USA
D. Beringer, R.A. Lukaszew
The College of William and Mary, Williamsburg, USA
K.I. Seo
NSU, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S.DOE Contract No. DE-AC05-06OR23177.
Over the years, Nb/Cu technology, despite its shortcomings due to the commonly used magnetron sputtering, has positioned itself as an alternative route for the future of superconducting structures used in accelerators. Recently, significant progress has been made in the development of energetic vacuum deposition techniques, showing promise for the production of thin films tailored for SRF applications. JLab is pursuing energetic condensation deposition via techniques such as Electron Cyclotron Resonance and High Power Impulse Magnetron Sputtering. As part of this project, the influence of the deposition energy on the material and RF properties of the Nb thin film is investigated with the characterization of their surface, structure, superconducting properties and RF response. It has been shown that the film RRR can be tuned from single digits to values greater than 400. This paper presents results on surface impedance measurements correlated with surface and material characterization for Nb films produced on various substrates, monocrystalline and polycrystalline as well as amorphous. A progress report on work on NbTiN and AlN based multilayer structures will also be presented.

MOPC117

Advance in Vertical Buffered Electropolishing on Niobium for Particle Accelerators*

352

A.T. Wu, S. Jin, J.D. Mammosser, C.E. Reece, R.A. Rimmer
JLAB, Newport News, Virginia, USA
L. Lin, X.Y. Lu, K. Zhao
PKU/IHIP, Beijing, People's Republic of China

Funding: The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes.
Niobium (Nb) is the most popular material that has been employed for making superconducting radio frequency (SRF) cavities to be used in various particle accelerators over the last couple of decades. One of the most important steps in fabricating Nb SRF cavities is the final chemical removal of 150 μm of Nb from the inner surfaces of the SRF cavities. This is usually done by either buffered chemical polishing (BCP) or electropolishing (EP). Recently a new Nb surface treatment technique called buffered electropolishing (BEP) has been developed at Jefferson Lab. It has been demonstrated that BEP can produce the smoothest surface finish on Nb ever reported in the literature while realizing a Nb removal rate as high as 10 μm/min that is more than 25 and 5 times quicker than those of EP and BCP(112) respectively. In this contribution, recent advance in optimizing and understanding BEP treatment technique is reviewed. Latest results from RF measurements on BEP treated Nb single cell cavities by our unique vertical polishing system will be reported.
Authored by The Southeastern Universities Research Association, Inc. under U.S. DOE Contract No. DE-AC05-84ER40150.

MOPC118

Effects of the Thickness of Niobium Surface Oxide Layers on Field Emission*

355

A.T. Wu, S. Jin, J.D. Mammosser, R.A. Rimmer
JLAB, Newport News, Virginia, USA
X.Y. Lu, K. Zhao
PKU/IHIP, Beijing, People's Republic of China

Funding: The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes.
Field emission on the inner surfaces of niobium superconducting radio frequency cavities is still one of the major obstacles for reaching high accelerating gradients for SRF community. Our previous experimental results* seemed to imply that the threshold of field emission was related to the thickness of Nb surface oxide layers. In this contribution, a more detailed study on the influences of the surface oxide layers on the field emission on Nb surfaces will be reported. By anodization technique, the thickness of the surface pentoxide layer was artificially fabricated from 3 nm up to 460 nm. A home-made scanning field emission microscope was employed to perform the scans on the surfaces. Emitters were characterized using a scanning electron microscope together with an energy dispersive x-ray analyzer. The SFEM experimental results were analyzed in terms of surface morphology and oxide thickness of Nb samples and chemical composition and geographic shape of the emitters. A model based on the classic electromagnetic theory was developed trying to understand the experimental results. Possibly implications for Nb SRF cavity applications from this study will be discussed.
* A.T. Wu et al., Proc. of IPAC 2010, Kyoto, Japan, WEPEC081, p. 3067 (2010).
Authored by The Southeastern Universities Research Association, Inc. under U.S. DOE Contract No. DE-AC05-84ER40150.

MOPC119

Fastest Electropolishing Technique on Niobium for Particle Accelerators*

358

A.T. Wu, S. Jin, R.A. Rimmer
JLAB, Newport News, Virginia, USA
X.Y. Lu, K. Zhao
PKU/IHIP, Beijing, People's Republic of China

Funding: The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes.
Field emission on the inner surfaces of niobium (Nb) superconducting radio frequency (SRF) cavities is still one of the major obstacles for reaching high accelerating gradients for SRF community. Our previous experimental results [1] seemed to imply that the threshold of field emission was related to the thickness of Nb surface oxide layers. In this contribution, a more detailed study on the influences of the surface oxide layers on the field emission on Nb surfaces will be reported. By anodization technique, the thickness of the surface pentoxide layer was artificially fabricated from 3nm up to 460nm. A home-made scanning field emission microscope (SFEM) was employed to perform the scans on the surfaces. Emitters were characterized using a scanning electron microscope together with an energy dispersive x-ray analyzer. The experimental results could be understood by a simple model calculation based on classic electromagnetic theory as shown in Ref.1. Possibly implications for Nb SRF cavity applications from this study will be discussed.
Authored by The Southeastern Universities Research Association, Inc. under U.S. DOE Contract No. DE-AC05-84ER40150.

MOPC120

Design of Superconducting Parallel-bar Deflecting/Crabbing Cavities

361

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

The superconducting parallel-bar cavity is a deflecting/crabbing cavity with attractive properties, compared to other conventional designs, that is being considered for a number of applications. We present an analysis of several designs of parallel-bar cavities and their electromagnetic properties.

MOPC121

Design of Low-frequency Superconducting Spoke Cavities for High-velocity Applications

364

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

Superconducting single- and multi-spoke cavities have been designed to-date for particle velocities from β~0.15 to β~0.65. Superconducting spoke cavities may also be of interest for higher-velocity, low-frequency applications, either for hadrons or electrons. We present the design of 325 and 352 MHz spoke cavities optimized for β=0.8 and β=1.

MOPC122

Etching of Niobium Sample Placed on Superconducting Radio Frequency Cavity Surface in Ar/CL2 Plasma

367

J. Upadhyay, M. Nikolić, S. Popović, L. Vušković
ODU, Norfolk, Virginia, USA
H.L. Phillips, A-M. Valente-Feliciano
JLAB, Newport News, Virginia, USA

Plasma based surface modification is a promising alternative to wet etching of superconducting radio frequency (SRF) cavities. It has been proven with flat samples that the bulk Niobium (Nb) removal rate and the surface roughness after the plasma etchings are equal to or better than wet etching processes. To optimize the plasma parameters, we are using a single cell cavity with 20 sample holders symmetrically distributed over the cell. These holders serve the purpose of diagnostic ports for the measurement of the plasma parameters and for the holding of the Nb sample to be etched. The plasma properties at RF (100 MHz) and MW (2.45 GHz) frequencies are being measured with the help of electrical and optical probes at different pressures and RF power levels inside of this cavity. The niobium coupons placed on several holders around the cell are being etched simultaneously. The etching results will be presented at this conference.

MOPC123

Temperature Dependent Microphonics in the BNL Electron Cooler*

370

P. Jain
Stony Brook University, Stony Brook, USA
I. Ben-Zvi, C. Schultheiss
BNL, Upton, Long Island, New York, USA

An R&D Energy Recovery Linac (ERL), to be used in the BNL electron cooler, has been operational in a developmental setting. The ERL requires a cryogenic system to supply cooling to a superconducting RF gun and the 5-cell superconducting RF cavity system that is kept cold at 2K. The 2K superfluid bath is produced by pumping on the bath using a sub-atmospheric warm compression system. During a test run in October 2010, a resonance peak corresponding to a noise of 30 Hz was observed at 1.88K. This noise peak, present at all temperatures below 2K, is assumed to be of mechanical origin from the vibration of the cryopump. Another resonance noise peak of 16 Hz, characteristic of the system, was observed at 1.98K, which shifted towards the 30 Hz peak as the temperature of the cryostat varied from 1.98K to 1.88K. The 16 Hz resonance peak upon hitting the 30 Hz resonance peak, sets a resonance condition, thereby the 30 Hz peak getting amplified by more than five times. In this paper we explore the origin of the temperature dependent 16 Hz resonance peak and give a physical explanation of the resonance.

MOPC126

High Power RF System for TRIUMF E-Linac Injector

373

A.K. Mitra, Z.T. Ang, S. Calic, S.R. Koscielniak, R.E. Laxdal, R.W. Shanks, Q. Zheng
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

TRIUMF has been funded to build the first stage of an electron linac with a final energy of 50 MeV and 500 kW beam power. The e-linac consists of an injector section with electron gun with 650 MHz rf modulated grid, a room temperature 1.3 GHz buncher cavity, and injector cryomodule, and two main-linac cryomodules for the accelerating section to be installed sequentially. The injector module has one 9 cell cavity whereas each of the accelerating cryomodules contains two 9-cell SC cavities. The injector cryomodule will be fed by a 30 kW cw Inductive Output Tube (IOT)and the accelerating cryomodule will be powered by a cw klystron. A first goal is a beam test of the e-Linac injector to 10MeV in 2012. Installation and full rated output power tests of the IOT on a 50 ohms load have been carried out. The IOT is purchased from CPI, USA while the transmitter is sourced from Bruker BioSpin. A power coupler conditioning station utilizes the same IOT. The buncher cavity is driven from a Bruker 600W amplifier. In this paper, the conceptual design of the e-Linac rf system will be summarized and the high power rf system for the injector including IOT measurement results will be presented.
SC stands for superconducting

MOPC127

Development of High RF Power Solid State Amplifiers at SOLEIL

376

P. Marchand, M.E. El Ajjouri, R. Lopes, F. Ribeiro, T. Ruan
SOLEIL, Gif-sur-Yvette, France

In SOLEIL, 5 solid state amplifiers provide the required 352 MHz RF power: 1 x 35 kW for the booster (BO) cavity and 4 x 190 kW for the 4 superconducting cavities of the storage ring (SR). Based on a design fully developed in house, they consist in a combination of a large number of 330W elementary modules (1 x 147 in the BO and 4 x 724 in the SR) with MOSFET transistors, integrated circulators and individual power supplies. After 5 years of operation, this innovative design has proved itself and demonstrated that it was an attractive alternative to the vacuum tube amplifiers, featuring an outstanding reliability and a MTBF > 1 year. In the meantime, thanks to the acquired expertise and the arrival of the 6th generation transistors, SOLEIL has carried out developments which led to doubling the power of the elementary module (700 W at 352 MHz and 500 MHz), while improving the performance in terms of gain, efficiency and thermal stress. This approach was also extended to frequencies from the FM to L band. The increasing interest for this technology has led SOLEIL to collaborate with several other laboratories and conclude a transfer of know-how with the French company, ELTA-AREVA.

MOPC128

16 kW Upgrade of the 1.3 GHz ELBE RF-system (CW) with Solid State Amplifiers

379

H. Büttig, A. Arnold, A. Büchner, M. Justus, M. Kuntzsch, U. Lehnert, P. Michel, R. Schurig, G.S. Staats, J. Teichert
HZDR, Dresden, Germany

The superconducting CW- LINAC of the radiation source ELBE is in permanent operation since May 2001. In 2011 an upgrade program of ELBE is in progress to support additional applications. One part of the program is to double the RF-power per cavity to at least 16 kW. We first tested a 30 kW IOT-based amplifier (Bruker /CPI) at a cavity, later two 10 kW solid state amplifiers in parallel. The best solution found is based on 10 kW Solid State Power Amplifiers (SSPA) developed by Bruker BioSpin. The poster gives an overview on the status, the activities around this RF-upgrade project and the technical specification of the “turnkey” SSPA , designed for 10 kW, 1.3 GHz and full CW-operation.

MOPC129

Compact Solid State RF-Modules for Direct Drive RF-linacs

382

R. Irsigler, M. Back, R. Baumgartner, O. Heid, T.J.S. Hughes, M. Kaspar, T. Kluge, J. Sirtl, K. Weidner, M. Zerb
Siemens AG, Erlangen, Germany

We present a modular RF power source concept based on solid state RF-modules with novel SiC transistors. The concept offers lower cost, better reliability and reduced maintenance compared to traditional RF-source technology. No circulators are required, which makes the RF-module very compact and reliable. The SiC power transistor has a very low input capacitance and was optimized for low gate resistance to enable fast switching in the VHF range. It delivers a maximum pulsed drain saturation current of 65 A. The transistor provides at 350 V supply voltage and 150 MHz an output power of 5,6 kW at a gain of 15,8 dB. It is essential to avoid high parasitic source inductances at RF and good thermal conductivity is required for operation at high duty cycle. We have built very compact 75 x 90 mm ceramic amplifier modules using a planar interconnect technology (SIPLIT) to connect the bare die transistors to the DCB substrate. The modules have a fully symmetric push-pull topology (circlotron) with four transistors in parallel in each leg. The RF-modules delivered at 150 MHz an impressive RF output power in the range of 40 kW. Further tests at 324 MHz are planned and will be presented.

MOPC130

High Power Solid State RF Amplifier Proposal for Iran Light Source Facility (ILSF)

385

R. safian
IPM, Tehran, Iran
M. Jafarzadeh
ILSF, Tehran, Iran

Solid state RF amplifiers are being considered for an increasing number of accelerator applications. Their capabilities extend from a few kW of power to several hundred kilo watts and from frequencies less than 100 MHz to above 1 GHz. This paper describes the proposed general scheme for the high power solid state RF generator of the Iran light source facility (ILSF). The maximum expected power of the generator is 200 KW which is used for driving the storage ring cavities. Similar RF generator with lower output power can be used for driving the booster cavities.

MOPC132

Influences of the Inner-conductor on Microwave Characteristics in an L-band Relativistic Backward-wave Oscillator*

388

X.J. Ge, L. Liu, B.L. Qian, J. Zhang, H.H. Zhong
National University of Defense Technology, Changsha, Kaifu District, People's Republic of China

Funding: College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073, People’s Republic of China. *gexingjun230230@yahoo.com.cn
The influences of the inner-conductor on microwave characteristics in an L-band relativistic backward-wave oscillator (RBWO) are investigated theoretically and experimentally. The numerical results show that the resonance frequency decreases obviously with the increase in the inner-conductor radius. To verify the above conclusions, an L-band coaxial RBWO is investigated in detail with particle-in-cell (PIC) code. It is shown that the frequency is lowered from 1.63 GHz to 1.51 GHz when the inner-conductor radius increases from 0.5 cm to 2.5 cm. And the efficiency varies in the range of 35.4-27.7%. Furthermore, experiments are carried out at the Torch-01 accelerator. When the diode voltage is 887.6 kV and the current is 7.65 kA, the radiated microwave with frequency of 1.61 GHz, power of 2.13 GW and efficiency of 31.3% is generated. It is found that the frequency decreases from 1.64 GHz to 1.58 GHz when the inner-conductor radius increases from 0.5 cm to 1.5 cm. And the efficiency varies in the range of 31.3-29.8%.

MOPC134

Multifrequency High Power Microwave Electric-vacuum Devices

391

K.G. Simonov, A.A. Borisov, A.V. Galdetsky, A.N. Korolev, A.V. Mamontov
ISTOK, Moscow Region, Russia
O.A. Morozov
Research and Production Co. "MAGRATEP", Fryazino, Russia

A new approach for the design of the multifrequency high power microwave vacuum devices is proposed. These devices provide simultaneously some output phased signals with operating frequencies ω, 2 ω, , nω while input frequency is ω. For example, it is possible obtain output power at frequencies ω and 2ω by using of double-gap output resonator tuned on two modes – sinphased mode at 2ω and antiphased mode at frequency ω. It is possible obtain power at four frequencies ω, 2ω, 3ω and 6ω by using of the two double-gap output resonators placed one inside the other. It is possible obtain power at multiple frequencies by using of the special coaxial resonator. A microwave vacuum device has been fabricated in which power was extracted at nine multiple frequencies simultaneously. The output signal has form of pulses with ultrashort duration and superhigh repetition frequency equal to the input signal frequency ω. Multifrequency high power microwave vacuum devices can be used for the development of compact accelerators of charged particles.

MOPC135

IFMIF-EVEDA RF Power System

394

D. Regidor, A. Arriaga, J.C. Calvo, A. Ibarra, I. Kirpitchev, J. Molla, P. Méndez, A. Salom, M. Weber
CIEMAT, Madrid, Spain
M. Abs, B. Nactergal
IBA, Louvain-la-Neuve, Belgium
P.-Y. Beauvais, M. Desmons, A. Mosnier
CEA/DSM/IRFU, France
P. Cara
Fusion for Energy, Garching, Germany
S.J. Ceballos, J. de la Cruz
Greenpower Technologies, Sevilla, Spain
Z. Cvetkovic, Z. Golubicic, C. Mendez
TTI, Santander, Spain
J.M. Forteza, J.M. González, C.R. Isnardi
Indra Sistemas, San Fernando de Henares, Spain
D. Vandeplassche
SCK-CEN, Mol, Belgium

The IFMIF/EVEDA Accelerator Prototype will be a 9 MeV, 125 mA CW deuteron accelerator to validate the technical options for the IFMIF accelerator design. The Radiofrequency Quadrupole (RFQ), buncher cavities and Superconducting Radiofrequency Linac (SRF Linac) require continuous wave RF power at 175 MHz with an accuracy of ±1% in amplitude and ±1° in phase. Also the IFMIF/EVEDA RF Power System has to work under pulsed mode operation (during the accelerator commissioning). The IFMIF/EVEDA RF Power System is composed of 18 RF power generators feeding the eight RFQ couplers (200 kW), the two buncher cavities (10⁵ kW) and the eight superconducting half wave resonators of the SRF Linac (10⁵ kW). The main components of each RF power chain are the Low Level Radio Frequency system (LLRF), three amplification stages and a circulator with its load. For obvious standardization and scale economies reasons, the same topology has been chosen for the 18 RF power chains: all of them use the same main components which can be individually tuned to provide different RF output powers up to 200 kW. The studies and the current design of the IFMIF/EVEDA RF Power System are presented in this contribution.

MOPC136

The RF Power Source for the High Beta Elliptical Cavities of the ESS Linac

397

K. Rathsman, H. Danared, R. Zeng
ESS, Lund, Sweden
A.J. Johansson
Lund University, Lund, Sweden
C. Lingwood
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
R.J.M.Y. Ruber
Uppsala University, Uppsala, Sweden
C. de Almeida Martins
IST-UTL, Lisbon, Portugal

The European Spallation Source is an intergovernmental project building a multidisciplinary research laboratory based upon the world’s most powerful neutron source. The main facility will be built in Lund, Sweden. Construction is expected to start around 2013 and the first neutrons will be produced in 2019. The ESS linac delivers 5 MW of power to the target at 2.5 GeV, with a nominal current of 50 mA. The 120 high beta elliptical cavities, which operate at a frequency of 704 MHz and accelerate protons from 600 MeV to 2.5 GeV, account for more than half of the total number of rf cavities in the ESS linac and three quarter of the total beam power needed. Because of the large number of rf power sources and the high power level needed, all the design and development efforts for the rf power source have so far been focused on this part of the accelerator. The design and development status of the rf power source is reported in this paper with emphasis on reliability, maintainability, safety, power efficiency, investment cost and production capacity.

MOPC137

Medium Power 352 MHz Solid State Pulsed RF Amplifiers for the CERN Linac4 Project

400

J.C. Broere, J. Marques Balula
CERN, Geneva, Switzerland
Y. Gomez
LPSC, Grenoble Cedex, France
M. Rossi
DBE, Padova, Italy

Economic, modular and highly linear pulsed RF amplifiers have recently been developed to be used for the three Buncher cavities in the CERN Linac4. The amplifiers are water cooled and can provide up to 33 kW pulsed RF power, 1.5 msec pulse length and 50 Hz repetition rate. Furthermore a 60 kWatt unit is under construction to provide the required RF Power for the Debuncher cavity. The concept is based on 1.2 kW RF power modules using the latest 6th generation LDMOS technology. For integration into the CERN control environment the amplifiers have an internal industrial controller, which will provide easy control and extended diagnostic functions. This paper describes the construction, performance, including linearity, phase stability and EMC compliance tests.

MOPC138

Practical Test of the Linac4 RF Power System

403

N. Schwerg, O. Brunner
CERN, Geneva, Switzerland

Linac4 is a linear accelerator for negative Hydrogen ions which will replace the old Linac2 as injector for the CERN accelerators. Its higher energy of 160 MeV will increase the beam intensity in the downstream machines. The normal-conducting accelerating structures are housed in a 100 m long tunnel which will be connected to the existing chain of accelerators and can be extended into a new injector chain. The high RF power for the Linac4 accelerating structures will be generated by thirteen 1.3 MW klystrons, previously used for the CERN LEP accelerator, and six new klystrons of 2.8 MW all operating at a frequency of 352.2 MHz. The re-use of existing LEP equipment, space limitations in the installation and tight phase and amplitude constraints pose a number of challenges for the integration of the RF power system. The power distribution scheme features a folded magic-tee feeding the power from a 2.8 MW klystron to two LEP circulators. We present first results from the Linac4 test place, validating the approach and the used components as well as reporting on the klystron re-tuning activities.

MOPC140

Phase and Frequency Locked Magnetrons for SRF Sources

406

M.L. Neubauer, M.A.C. Cummings, A. Dudas, R.P. Johnson, R. Sah
Muons, Inc, Batavia, USA
A. Moretti, M. Popovic
Fermilab, Batavia, USA

Typically, high power sources for accelerator applications are multi-megawatt microwave tubes that may be combined together to form ultra-high-power localized power stations. The RF power is then distributed to multiple strings of cavities through high power waveguide systems which are problematic in terms of expense, efficiency, and reliability. Magnetrons are the lowest cost microwave source in dollars/kW, and they have the highest efficiency (typically greater than 85%). However, the frequency stability and phase stability of magnetrons are not adequate, when magnetrons are used as power sources for accelerators. Novel variable frequency cavity techniques have been developed which will be utilized to phase and frequency lock magnetrons, allowing their use for either individual cavities, or cavity strings. Ferrite or YIG (Yttrium Iron Garnet) materials will be attached in the regions of high magnetic field of radial-vaned, π−mode structures of a selected ordinary magnetron. The microwave characteristics of several materials have been tested with magnetic fields to control the frequency of the magnetron. These results will be presented and an optimum material chosen.

MOPC142

25 Year Performance Review of the SLAC 5045 S-Band Klystron

409

A. Jensen, A.S. Beebe, M.V. Fazio, A.A. Haase, E.N. Jongewaard, C. Pearson, D.W. Sprehn, A.E. Vlieks, L.E. Whicker
SLAC, Menlo Park, California, USA

Funding: This work was supported by the U.S. Department of Energy under contract DE-AC03-76SF00515.
The SLAC 5045 S-band klystron has proven to be a remarkably reliable high peak power tube. Originally developed in the 1980’s as an upgraded RF power source for the Stanford Linear Collider, it has continually powered the SLAC linac in support of numerous programs in particle physics and photon science. The large number of tubes built and operated (more than 800) coupled with accumulated running statistics over the last 25+ years represents an unprecedented wealth of operational experience for high pulse power klystrons in accelerator applications. Mean time between failures has continued to rise during this period and is frequently in excess of 100,000 hours during the last several years. Lifetime statistics as well as some important failure modes are presented and examined here.

MOPC143

A Reduced Gradient Output Design for SLAC's XL4 X-Band Klystron

412

A. Jensen, C. Adolphsen, A.E. Candel, M.V. Fazio, E.N. Jongewaard, D.W. Sprehn, A.E. Vlieks, F. Wang
SLAC, Menlo Park, California, USA

Funding: This work was supported by the U.S. Department of Energy under contract DE-AC03-76SF00515.
X-band klystron work began at SLAC in the mid to late 1980's to develop high frequency (4 times the SLAC S-band klystron), high power RF sources for the linear collider designs under consideration at that time. This work culminated in the current workhorse X-band RF source, the XL4. To date 26 XL4 tubes have been built. The XL4 4-cell disk loaded traveling wave output structure has a high operating gradient. A new 6-cell structure has been designed to reduce breakdown and to further improve the klystron's robustness. Initial simulations show the 6-cell design reduces the gradient roughly 25% and that the structure is stable. A physical XL4 will be retrofitted with the new output cavity and hot tested in the near future.

MOPC144

Autocorrelation Function and Power Spectrum of a Train of Quasiperiodic Sequence of Pulses

415

E.M. Laziev, B. Grigoryan, V.M. Tsakanov
CANDLE, Yerevan, Armenia
M. Movsisyan, D.L. Oganesyan
YSU, Yerevan, Armenia

The statistical relationship of the autocorrelation function and spectrum of a train of quasi-periodic sequence of pulses having a time jitter of the repetition rate is obtained. Presented the accordance of autocorrelation function as well as power spectrum of the bounded quasi-periodic sequence of pulses and timing jitter of their repetition rate. The results can be used at the measurements of timing jitter of a train of electron bunches.

MOPC145

Recent Progress on the Technical Realization of the Bunch Phase Timing System BuTiS

418

B. Zipfel, P. Moritz
GSI, Darmstadt, Germany

A high precision phase synchronous clock distribution system is mandatory for generating local RF reference signals in an accelerator complex. The dedicated Bunch Timing System (BuTiS) at GSI performs this function. The accuracy of the realized installation under rough ambient conditions is presented. Procedures for calibration and standardization aspects of system modules are pointed out. Hardware as well as software interfaces of the system are described. The interfacing between GPS and BuTiS are explained.

MOPC146

Development of Timing Distribution System with Femto-second Stability

421

T. Naito, K. Ebihara, S. Nozawa, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
M. Amemiya
AIST, Tsukuba, Japan

A timing distribution system with femto-second stability has been developed for the RF synchronization of accelerator and the laser synchronization of the pump-probe experiments. The system uses a phase stabilized optical fiber(PSOF) and an active fiber length stabilization. The PSOF has 5 ps/km/degC of the temperature coefficient. The active fiber length stabilization uses the phase detection of the round-trip sinusoidal wave and the fiber stretcher for the compensation of the fiber length. In this paper, we present the test results on a 500 m long signal distribution. The preliminary results of the timing stability are 20 fs at several minutes and 100 fs at four days, respectively.

MOPC147

Timing System for MedAustron Based on Off-The-Shelf MRF Transport Layer

424

R. Tavcar, J. Dedič, Z. Kroflic, R. Štefanič
Cosylab, Ljubljana, Slovenia
J. Gutleber
CERN, Geneva, Switzerland

MedAustron is a new particle accelerator-based ion beam research and therapy centre under construction in Wiener Neustadt, Austria. The timing system for its synchrotron-based accelerator is being developed in close collaboration with Cosylab. We have usedμResearch Finland (MRF) transfer layer and designed and implemented a generic, reusable high-level logic above transport layer inside the generator and receiver FPGA to fulfill machine specific requirements which exceed MRF's original high-level logic capabilities. The new timing system is suitable for small to mid-size accelerators. Its functionalities include support for virtual accelerators and a rich selection of event response mechanisms. The timing system uses a combination of a real-time link for downstream events and a non-real-time link for upstream messaging and non time-critical communication. This article explains the benefits of building a timing system on a proven, stable timing transport layer and describes the high-level services provided by MedAustron timing system.

MOPC148

Optical Clock Distribution System at the ALICE Energy Recovery Linac

427

T.T. Ng, S.P. Jamison
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Highly stable clock distribution across future light sources is important for the synchronisation of beam generation, manipulation and diagnostics with photon experiments. Optical fibre technology can be used to combat the stability challenges in distributing clock signals over long distances with coaxial cable. We report here on the status of the optical clock distribution system installed on the ALICE energy recovery linac which uses the propagation of ultra-short optical pulses to carry the clock signal. We also present the characterisation of a beam arrival monitor suitable using <40 pC bunch charges and 7 mW, sub-100 fs distributed clock pulses.

MOPC150

High Charge PHIN Photo Injector at CERN with Fast Phase Switching within the Bunch Train for Beam Combination

430

M. Divall Csatari, A. Andersson, B. Bolzon, E. Bravin, E. Chevallay, A.E. Dabrowski, S. Döbert, V. Fedosseev, C. Heßler, T. Lefèvre, S. Livesley, R. Losito, O. Mete, M. Olvegård, M. Petrarca, A. Rabiller
CERN, Geneva, Switzerland
A. Drozdy
BUTE, Budapest, Hungary
D. Egger
EPFL, Lausanne, Switzerland

The high charge PHIN photo-injector was developed within the frame of the European CARE program to provide an alternative to the drive beam thermionic gun in CTF3 (CLIC Test Facility) at CERN. In PHIN 1908 bunches are delivered with bunch spacing of 1.5 GHz and 2.33 nC charge per bunch. Furthermore the drive beam generated by CTF3 requires several fast 180 deg phase-shifts with respect to the 1.5 GHz bunch repetition frequency in order to allow the beam combination scheme developed at CTF3. A total of 8 sub-trains, each 140 ns long and shifted in phase with respect to each other, have to be produced with very high phase and amplitude stability. A novel fiber modulator based phase-switching technique developed on the laser system provides this phase-shift between two consecutive pulses much faster and cleaner than the base line scheme, where a thermionic electron gun and sub-harmonic bunching are used. The paper describes the fiber-based switching system and the measurements verifying the scheme. Stability measurements are presented for the phase-coded system. The paper also discusses the latest 8nC charge production and cathode life-time studies on Cs2Te.

MOPC151

Design and Commissioning of a Multi-frequency Digital Low Level RF Control System*

433

M. Konrad, U. Bonnes, C. Burandt, J. Conrad, R. Eichhorn, J. Enders, P.N. Nonn, N. Pietralla
TU Darmstadt, Darmstadt, Germany

Funding: Work supported by DFG through CRC 634 and by the BMBF under 06 DA 9024 I.
Triggered by the need to control the superconducting cavities of the S-DALINAC, which have a high loaded quality factor and are thus very susceptible to microphonics, the development of a digital low level RF control system was started. The chosen design proved to be very flexible since other frequencies than the original 3 GHz may be adapted easily: The system converts the RF signal coming from the cavity (e. g. 3 GHz) down to the base band using a hardware I/Q demodulator. The base band signals are digitized by ADCs and fed into a FPGA where the control algorithm is implemented. The resulting signals are I/Q modulated before they are sent back to the cavity. The superconducting cavities are operated with a self-excited loop algorithm whereas a generator-driven algorithm is used for the low Q normal-conducting bunching cavities. A 6 GHz RF front end allows the synchronous operation of a new 2f buncher at the S-DALINAC. Meanwhile, a 325 MHz version has been built to control a pulsed prototype test stand for the p-LINAC at FAIR. We will present the architecture of the RF control system as well as results obtained during operation.

MOPC152

Digital Control System for Solid State Direct Drive™ RF-Linacs

436

J. Sirtl, M. Back, T. Kluge
Siemens AG, Erlangen, Germany
H. Schröder
ASTRUM IT GmbH, Erlangen, Germany

The Solid State Direct Drive™ concept for RF linacs has previously been introduced*. Due to the different methodology (i.e. solid state based rather than electron tube based) as compared with conventional RF sources a new control system is required to deliver the required LLRF. To support this new technology a fully digital control system for this new concept has been developed. Progresses in Digital – Analogue Converter technology and FPGA technology allows us to create a digital System which works in the 150 Mhz baseband. The complete functionality was implemented in a Virtex 6 FPGA. Dispensing with the PLL allows an excellent jitter-behaviour. For this job, we use three 12 bit ADCs with a Sampling Rate of 1 GS/s and two 16 bit DACs (1 GS/s). The amplitude of the RF source is controlled by dividing the RF modules mounted on the power combiner** into two groups and controlling the relative phase of each group (in effect mimicking an “out-phasing” amplifier). This allows the modules to be operated at their optimum working point and allows a linear amplitude behaviour.
* O. Heid, T. Hughes, Proc. of IPAC10, THPD002, p. 4278, Kyoto, Japan (2010).
** O. Heid, T. Hughes, Proc. of LINAC10, THPD068, Tsukuba, Japan.

MOPC153

Design and Implementation of Automatic Cavity Resonance Frequency Measurement and Tuning Procedure for FLASH and European XFEL Cryogenic Modules

439

V. Ayvazyan, W. Koprek, D. Kostin, G. Kreps
DESY, Hamburg, Germany
Z. Geng
SLAC, Menlo Park, California, USA

The superconducting cavities in FLASH and European XFEL should be tuned to the frequency of 1.3 GHz after cool down and adjusted to initial frequency before warm up by stepper motor tuners. The initial frequency is 300 kHz far from the operating frequency (1.3 GHz) to remove mechanical hysteresis of the tuner. The cavities should be relaxed to initial frequency to avoid a plastically deformation. In framework of digital low level RF and DOOCS control systems we have developed a simple automatic procedure for the remote resonance frequency measurement and simultaneous remote tuning for all cavities which are driven from the single klystron. The basic idea is based on frequency sweeping both for driving klystron and for generation of local oscillator frequency with constant RF frequency from master oscillator. The developed system has been used during FLASH commissioning in spring 2010 and is in use for cavity and cryogenic module test stands for European XFEL at DESY.

MOPC154

RF Photo Gun Stability Measurement at PITZ

442

I.I. Isaev, H.-J. Grabosch, M. Gross, L. Hakobyan, Ye. Ivanisenko, G. Klemz, W. Köhler, M. Krasilnikov, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, S. Rimjaem, F. Stephan, G. Vashchenko, S. Weidinger, R.W. Wenndorff
DESY Zeuthen, Zeuthen, Germany
G. Asova
INRNE, Sofia, Bulgaria
M. Hoffmann, H. Schlarb
DESY, Hamburg, Germany
M.A. Khojoyan
YerPhI, Yerevan, Armenia
D. Richter
HZB, Berlin, Germany
A. Shapovalov
NRNU MEPHI, Moscow, Russia
I.H. Templin, I. Will
MBI, Berlin, Germany

The stability of the RF phase in the RF photo injector gun is one of the most important factors for the successful operation of linac based free-electron lasers. Instabilities in the RF launch phase can significantly reduce the beam quality. Investigation on the dependence of different gun parameters and selection of optimal conditions are required to achieve high RF gun phase stability. The phase stability of the RF field is measured using the phase scan technique. Measurements were performed for different operating conditions at the Photo Injector Test facility at DESY, location Zeuthen (PITZ). Obtained stability measurement results will be presented and discussed.

MOPC155

Performance of the Micro-TCA Digital Feedback Board for DRFS Test at KEK-STF

445

T. Miura, D.A. Arakawa, S. Fukuda, E. Kako, H. Katagiri, T. Matsumoto, S. Michizono, Y. Yano
KEK, Ibaraki, Japan

The test of distributed RF scheme (DRFS) for ILC was carried out at the superconducting RF test facility in KEK (KEK-STF). The LLRF system and two klystron units were installed in the same tunnel as SRF cavities. The vector-sum control for two cavities was done by using the micro-TCA digital feedback board. This board was the same one developed for the compact-ERL at KEK, but the software was changed for pulse operation. The result of the performance will be reported.

MOPC156

Operation Test of Distributed RF System with Circulator-less Waveguide Distribution in S1-Global Project at STF/KEK

448

T. Matsumoto, M. Akemoto, D.A. Arakawa, S. Fukuda, H. Honma, E. Kako, H. Katagiri, S. Matsumoto, H. Matsushita, S. Michizono, T. Miura, H. Nakajima, K. Nakao, T. Shidara, T. Takenaka, Y. Yano, M. Yoshida
KEK, Ibaraki, Japan

Distributed RF System (DRFS) is one candidate for a single main linac tunnel design of International International Linear Collider (ILC). In the DRFS, more than ten 800-kW klystrons having a modulating anode are operated by a common DC power and a modulation anode modulator. Each klystron feeds its power into two superconducting cavities and its waveguide distribution system is configured without circulators. This DRFS consists of four SC cavities, two klystrons and a modulator was demonstrated in S1-Global project. The results of circulator-less operation in the DRFS will be reported.

MOPC157

Performance of LLRF System at S1-Global in KEK*

451

S. Michizono, D.A. Arakawa, S. Fukuda, E. Kako, H. Katagiri, T. Matsumoto, T. Miura, Y. Yano
KEK, Ibaraki, Japan

Vector-sum control was carried out at S1-Global. The rf stabilities of 0.007% in amplitude and 17 mdeg. in phase are obtained. Various diagnostics (such as on-line quench pulse detector, dynamic detuning monitor and so on) is implemented. The IF-mixture system, where 3 intermediate frequencies (IF) are used and the number of ADCs can be reduced, was used as rf waveform monitors. These monitors are used for the performance analysis. Quench phenomena observed at the high-gradient operation are also analyzed from the view point of dynamic change in loaded Q and cavity detuning during rf pulse.

MOPC158

RF Capture of a Beam with Charge-exchanging Multi-turn Injection

454

T. Uesugi, Y. Ishi, Y. Kuriyama, J.-B. Lagrange, Y. Mori, R. Nakano, T. Planche, B. Qin, E. Yamakawa
KURRI, Osaka, Japan
Y. Niwa, K. Okabe, I. Sakai
University of Fukui, Faculty of Engineering, Fukui, Japan

Funding: This work was supported by MEXT of Japan in the framework of a task entitled ”Research and Development for an Accelerator-Driven Sub-critical System Using an FFAG Accelerator”.
In the fixed field alternating gradient (FFAG) synchrotron in Kyoto university research reactor Institute (KURRI), charge exchange injection was adopted since 2011. The charge stripping foil is located on the closed orbit of the injection energy, and no bump orbit system is used. Instead, the injected beam escapes from the stripping foil according to the closed-orbit shift due to acceleration. In this scheme, it is important to minimize the number of foil hitting, which causes emittance growth and foil heating. In this paper, the rf capture is studied by means of simulation.

MOPC160

Digital LLRF for IFMIF-EVEDA

457

A. Salom, A. Arriaga, J.C. Calvo, I. Kirpitchev, P. Méndez, D. Regidor, M. Weber
CIEMAT, Madrid, Spain
A. Mosnier
CEA/IRFU, Gif-sur-Yvette, France
F. Pérez
CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain

The IFMIF-EVEDA project aims to build a prototype accelerator (deuteron, 9MeV, 125mA) to be located at Rokkasho, Japan, for design validation of the IFMIF Accelerator. CIEMAT from Madrid, Spain, is in charge of providing the RF systems for this prototype accelerator. The LLRF will adjust the phase and amplitude of the RF drive and the resonance frequency of the cavities. This paper summarizes its main characteristics and Control System integrated in EPICS. The hardware is based on a commercial FPGA board, an analog front end and a local timing system. Each LLRF system will control and diagnose two RF chains and it will handle the RF fast Interlocks (vacuum, arcs, reflected power and multipacting). A specific LLRF will be developed for the special case of the RFQ cavity, with one Master LLRF and three Slave LLRFs to feed the 8 RF chains of the cavity. The conceptual design and other capabilities of the system like automatic conditioning, frequency tuning for startup and field flatness of the RFQ, etc, will be shown in this paper together with the first low power test results of the LLRF prototype and the performance of the Control System.

MOPC161

Challenges for the Low Level RF Design for ESS

460

A.J. Johansson
Lund University, Lund, Sweden
R. Zeng
ESS, Lund, Sweden

The European Spallation Source (ESS) is a planned neutron source to be built in Lund, Sweden, which is planned to produce the first neutrons in 2019. It will have an average beam power at the target of 5 MW, an average current along the Linac of 50 mA, and a pulse repetition rate and length of 20 Hz and 2 ms, respectively. The Linac will have around 200 LLRF stations employed to control a variety of RF cavities such as RFQ, DTL, spoke and elliptical superconducting cavities. The challenges on LLRF systems are mainly the high demands on energy efficiency on all parts of the facility, an operational goal of 95% availability of the facility and a comparably short time from start of final design to commissioning. Running with long pulses, high current and spoke cavities also brings new challenges on LLRF design. In this paper we will describe the consequences these challenges have on the LLRF system, and the proposed solutions and development projects that have started in order to reach these demands.

MOPC163

Low-level RF Control System for the Taiwan Photon Source

463

M.-S. Yeh
NSRRC, Hsinchu, Taiwan

The low-level RF (LLRF) control system is an essential component of the RF system for Taiwan Photon Source. The LLRF control system will perform various functions including control loops for the cavity gap voltage and the phase feedback, RF system interlock protection and the diagnostics for a machine trip. The LLRF system is manufactured in house using the most recent commercial RF chips. The LLRF system has an analogue architecture similar to that used in the 1.5-GeV Taiwan Light Source (TLS). An overview of the system architecture and its functionality is presented herein.

MOPC164

Upgrade of the ISIS Synchrotron Low Power RF System

466

A. Seville, N.E. Farthing, I.S.K. Gardner, R.J. Mathieson, J.W.G. Thomason
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
D.B. Allen
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom

The ISIS synchrotron at the Rutherford Appleton Laboratory in the UK now routinely uses a dual harmonic RF system to accelerate beam currents in excess of 230 uA to run two target stations simultaneously. In order to give more stable control of the phase of the RF voltage at each of the fundamental (1RF) and second harmonic (2RF) cavities, changes have been made to the low power RF (LPRF) control systems. In addition to this a new FPGA based master oscillator has been commissioned for the first time, and further changes using digital technologies to replace other components of the LPRF system are to be investigated. This paper reports on the LPRF hardware commissioning and reliability.

MOPC165

Digital Low Level RF Development at Daresbury Laboratory

469

P.A. Corlett, L. Ma, A.J. Moss
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Digital LLRF development using Field Programmable Gate Arrays (FPGAs) is a new activity at Daresbury Laboratory. Using the LLRF4 development board, designed by Larry Doolittle of Lawrence Berkeley National Laboratory, a full featured control system incorporating fast feedback loops and a feed-forward system has been developed for use on the ALICE (Accelerators and Lasers in Combined Experiments) energy recovery linac. Technical details of the system are presented, along with experimental measurements.

MOPC166

Low RF Control Feedback and IQ Vector Modulator Compensation Functions

472

M.G. Fedurin, R. Malone, V. Yakimenko
BNL, Upton, Long Island, New York, USA

IQ vector modulator is key element of the gun and linac RF control circuits at Accelerator Test Facility at Brookhaven National Laboratory. IQ modulator calibration procedure was developed to find proper compensation functions in the conversion algorithm to minimize phase-amplitude coupling and setting-reading errors: rms(A_set - A_read )= 0.03dB, rms(Phi_set - Phi_read) = 0.3 deg. Since stabilization of the RF phase and amplitude is become critical for many experiments the slow feedback was developed and applied as well to significantly compensate drifts in RF system.