07 Accelerator Technology
T06 Room Temperature RF

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.
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 CLICDDSA*, 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. CLICDDSA 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 CLICDDS 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.
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).
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.
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.
THOBB02	High Gradient Magnetic Alloy Cavities for J-PARC Upgrade	2885
	C. Ohmori, O. Araoka, E. Ezura, K. Hara, K. Hasegawa, A. Koda, Y. Makida, Y. Miyake, R. Muto, K. Nishiyama, T. Ogitsu, H. Ohhata, K. Shimomura, A. Takagi, K. Takata, K.H. Tanaka, M. Toda, M. Yoshii KEK, Tokai, Ibaraki, Japan T. Minamikawa University of Fukui, Fukui, Japan M. Nomura, A. Schnase, T. Shimada, F. Tamura, M. Yamamoto JAEA/J-PARC, Tokai-mura, Japan
	Magnetic alloy cavities are used for both MR and RCS synchrotrons. Both cavity systems operate successfully and they generate a higher voltage than could be achieved by an ordinary ferrite cavity system. For the future upgrade of J-PARC, a higher RF voltage is needed. A new RF cavity system using the material, FT3L, is designed to achieve this higher field gradient. A large production system using an old cyclotron magnet was constructed to anneal 85-cm size FT3L cores in the J-PARC Hadron Experiment Hall. The muSR (Muon Spin Rotation/Relaxation/Resonance) Experiments were also carried out to study the magnetic alloy. The status of development on the J-PARC site and a new RF system design will be reported.
	Slides THOBB02 [2.729 MB]