IPAC2016 - List of Keywords (cavity)

Paper	Title	Other Keywords	Page
MOOCA01	R&D of a Super-compact SLED System at SLAC	operation, coupling, impedance, FEL	39
	J.W. Wang, G.B. Bowden, S. Condamoor, Y. Ding, V.A. Dolgashev, J.P. Eichner, M.A. Franzi, A.A. Haase, P. Krejcik, J.R. Lewandowski, S.G. Tantawi, L. Xiao, C. Xu SLAC, Menlo Park, California, USA
	Funding: Work supported by Department of Energy contract DE-AC03-76SF00515. We have successfully designed, fabricated, installed and tested a super-compact X-Band SLED system at SLAC. It is composed of an elegant mode converter/polarizer and a single sphere energy store cavity with high Q of 94000 and diameter less than 12 cm. The available RF peak power of 50 MW can be compressed to peak average power of more than 200 MW in order to double the kick for the electron bunches in a RF transverse deflector system and greatly improve the measurement resolution for both the electron bunch and the x-ray FEL pulse. High power operation has demonstrated the excellent performance of this RF compression system without any problems in RF breakdown, pulse heating and radiation. The design physics and fabrication as well as the measurement results will be presented in detail.
	Slides MOOCA01 [20.278 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOOCA01
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MOOCA02	RFQ Developments at CEA-IRFU	rfq, linac, proton, status	42
	O. Piquet CEA/DSM/IRFU, France
	Vane RFQs are particularly well suited to high intensity proton acceleration, since they offer minimal RF power losses and best accelerating field accuracy. Cea-Irfu is involved in several developments of 4 vane RFQs namely IPHI, Spiral2, Linac4 and ESS. This paper gives an overview of the design flow and tools developed at Irfu in order to design, tune, condition and commission RFQs. SPIRAL2 RFQ will be mainly used to illustrate this design flow. This CW RFQ requires 180 kW to achieve the nominal accelerating voltage. It can accelerate a 5 mA proton or deuteron beam (A/Q=1 and 2) or a 1 mA ion beam with up to A/Q=3 at 0.75 MeV/A. Conditioning and commissioning of this RFQ are actually in progress.
	Slides MOOCA02 [3.712 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOOCA02
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MOPMB005	Study of Short Bunches at the Free Electron Laser CLIO	radiation, electron, gun, simulation	78
	V. Khodnevych, N. Delerue, S. Jenzer LAL, Orsay, France J.P. Berthet, F. Glotin, J.-M. Ortega, R. Prazeres CLIO/ELISE/LCP, Orsay, France V. Khodnevych National Taras Shevchenko University of Kyiv, The Faculty of Physics, Kyiv, Ukraine
	Funding: The authors are grateful for the funding received from the French ANR (contract ANR-12-JS05-0003-01). CLIO is a Free Electron Laser based on a thermionic electron gun. In its normal operating mode it delivers electron 8 pulses but studies are ongoing to shorten the pulses to about 1 ps. We report on simulations showing how the pulse can be shortened and the expected signal yield from several bunch length diagnostics (Coherent Transition Radiation, Coherent Smith Purcell Radiation).
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMB005
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MOPMB032	A New Fault Recovery Mechanism for Superconducting Cavity Failure in C-ADS	FPGA, hardware, space-charge, linac	158
	Z. Xue, J.P. Dai, C. Meng IHEP, Beijing, People's Republic of China
	For proton linear accelerators used in applications such as C-ADS, due to the nature of the operation, it is essential to have beam failures at the rate several orders of magnitude lower than usual performance of similar accelerators. A fault-tolerant mechanism should be mandatorily imposed in order to maintain short recovery time, high uptime and extremely low frequency of beam loss. This paper proposes an innovative and challenging way for compensation and rematch of cavity failure using fast electronic devices and Field Programmable Gate Array (FPGA) instead of embedded computers to complete the computation of beam dynamics. Due to the high arithmetic-computing-speed, good portability and repeatability, it is possible to realize calculation and re-adjustment online. In order to achieve the goal of instantaneous compensation and rematch, an advanced hardware design methodology including high-level synthesis and an improved genetic algorithm will be used.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMB032
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MOPMB040	Design of the Beam Diagnostics System for a New IR-FEL Facility at NSRL	diagnostics, FEL, laser, emittance	181
	J.H. Wei, X.Y. Liu, P. Lu, B.G. Sun, L.L. Tang, F.F. Wu, Y.L. Yang, T.Y. Zhou, Z.R. Zhou USTC/NSRL, Hefei, Anhui, People's Republic of China
	Funding: Work supported by National Natural Science Foundation of China (21327901, 11105141, 11575181) A new IR-FEL has been commissioned at NSRL. This facility provides a final electron energy from 20 to 70 MeV, beam bunch with a macro-pulse length of 5~10 μs and a general micro-pulse repetition rate of 238 MHz, pulsed radiation with up to 100 mJ at about 0.3%~3% FWHM bandwidth. So a diagnostics system is necessary to monitor the performance of the bunch and the character of the FEL radiation, such as the beam position and profile, emittance, energy spread, laser intensity, etc. The beam diagnostics system mainly consists of Flags, a diagnostics beam line, BPMs, pop-in monitors and a FEL monitor system. This paper introduces the construction of this diagnostics system. Corresponding author: ylyang@ustc.edu.cn
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMB040
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MOPMB046	Design and Calculation Error Analysis of a High Order Mode Cavity Bunch Length Monitor	positron, simulation, linac, electron	196
	J.G. Guo, Q. Luo, Z.R. Zhou USTC/NSRL, Hefei, Anhui, People's Republic of China
	Funding: National Science Foundation of China (11375178) and Fundamental Research Funds for the Central Universities (WK2310000046). A two-cavity bunch length monitor for linac of positron source is designed. Fifth harmonic cavity resonates at 14.28 GHz (fifth harmonic of the linac fundamental frequency 2.856 GHz) with mode TM020, as this mode could provide larger cavity radius. Each cavity equipped with a filter to suppress unwanted signal. An improved bunch length calculation method was proposed. A simulation was conducted in CST Particle Studio for beam current from 100-300 mA, bunch length from 5-10 ps. Bunch length was calculated and compared by these two methods
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMB046
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MOPMB049	Beam Experiment of Low Q CBPM Prototype for SXFEL	simulation, HOM, electron, FEL	202
	J. Chen, L.W. Lai, Y.B. Leng, L.Y. Yu, R.X. Yuan SINAP, Shanghai, People's Republic of China
	To meet the high resolution beam position measurement requirement of micron or sub-micron for shanghai soft X-ray free electron laser (SXFEL) under construction, the cavity beam position monitor (CBPM) operating at C-band and the corresponding electronic has been designed by SINAP. In this paper, the design and optimize of the newly low Q cavity BPM is mentioned, the beam test was conducted on the Shanghai Deep ultraviolet free electron laser (SDUV-FEL) facility. CBPM signal processors including broadband oscilloscope and home-made digital BPM processor have been used to evaluate the system performance as well. The beam experimental result, which matched with MAFIA simulation very well, will be presented and discussed in this paper.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMB049
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MOPMB051	Cavity BPM Performance Online Evaluation using PCA Method	experiment, electron, factory, coupling	208
	Y.B. Leng, L.W. Lai, L.Y. Yu, R.X. Yuan SSRF, Shanghai, People's Republic of China J. Chen, Z.C. Chen SINAP, Shanghai, People's Republic of China
	Funding: NSFS 11575282 This article proposes a new test method to evaluate the performance of cavity beam position monitors using the actual beam as the exciting signal. The new method sepa-rates the signals of different modes and improves the measurement accuracy by eliminating unwanted cou-plings from other sources.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMB051
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MOPMB058	Bunch Arrival Time Monitor Test at PAL-XFEL ITF	pick-up, LLRF, simulation, resonance	223
	J.H. Hong, J.H. Han, C. Kim, H. Yang PAL, Pohang, Kyungbuk, Republic of Korea
	Femtosecond resolution electron bunch arrival time monitor (BAM) will be required for the beam-based RF phase feedback during PAL-XFEL operation. Two S-band cavity-type BAMs were manufactured for the test at the PAL-XFEL injector test facility (ITF). The resonance frequencies of the cavities are 2856 MHz and 2826.25 MHz. Electron beam induced signal from the cavities was digitized using a low level RF (LLRF) module. In this paper, the resolution of these cavities are analyzed and a possible improvement for better resolution are discussed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMB058
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MOPMR001	Micro-mover Development and Test in the PAL-XFEL	solenoid, electron, gun, controls	229
	B.G. Oh, J.H. Han, H. Heo, J.H. Hong, H.-S. Kang, C. Kim, D.E. Kim, K.-H. Park, Y.J. Suh PAL, Pohang, Kyungbuk, Republic of Korea
	Two micro-movers, which are able to control the horizontal, vertical and longitudinal positions as well as the yaw and pitch angles remotely, were developed and installed in the PAL-XFEL linac. The solenoid micro-mover in the gun section allows beam-based alignment of an electron beam to the solenoid field and the gun RF field. The X-band cavity micro-mover minimizes the transverse wake field effect caused by transverse misalignment between the beam and X-band cavity. Two micro-movers has similar specifications and the same mechanism, but the sizes are different from each other. In this paper, we present the design, manufacture and test results of the micro-movers.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMR001
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MOPMR017	Design and Simulations of the Cavity BPM Readout Electronics for the ELI-NP Gamma Beam System	electron, electronics, simulation, linac	264
	M. Cargnelutti, B.B. Baricevic I-Tech, Solkan, Slovenia A. Mostacci University of Rome La Sapienza, Rome, Italy S. Pioli, M. Serio, A. Stella, A. Variola INFN/LNF, Frascati (Roma), Italy
	The Extreme Light Infrastructure - Nuclear Physics (ELI-NP) facility will provide a high intensity laser and a very intense gamma beam which will be used in a broad range of experiments. The gamma beam is obtained through incoherent Compton back-scattering of a laser light off a high brightness electron beam provided by a 700MeV warm LINAC. Electrons are accelerated in trains with up to 32 bunches, each one separated by 16ns. In the laser-electron interaction region, every bunch needs to be monitored with a resolution below 1μm RMS. To achieve this performance, a low-Q cavity beam position monitor will be used in combination with a dedicated data acquisition system able to perform bunch-by-bunch beam position measurements with sub-μm resolution. Using fast A/D converters and specific digital filtering, the readout system proposes an alternative measurement concept. The requirements of the system, its design and the results from the simulations will be presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMR017
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MOPMR024	A Versatile Beam Loss Monitoring System for CLIC	electron, quadrupole, beam-losses, background	286
	M. Kastriotou, S. Döbert, W. Farabolini, E.B. Holzer, E. Nebot Del Busto, F. Tecker CERN, Geneva, Switzerland M. Kastriotou, E. Nebot Del Busto, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom M. Kastriotou, C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom
	The design of a potential CLIC beam loss monitoring (BLM) system presents multiple challenges. To successfully cover the 48 km of beamline, ionisation chambers and optical fibre BLMs are under investigation. The former fulfils all CLIC requirements but would need more than 40000 monitors to protect the whole facility. For the latter, the capability of reconstructing the original loss position with a multi-bunch beam pulse and multiple loss locations still needs to be quantified. Two main sources of background for beam loss measurements are identified for CLIC. The two-beam accelerator scheme introduces so-called crosstalk, i.e. detection of losses originating in one beam line by the monitors protecting the other. Moreover, electrons emitted from the inner surface of RF cavities and boosted by the high RF gradients may produce signals in neighbouring BLMs, limiting their ability to detect real beam losses. This contribution presents the results of dedicated experiments performed in the CLIC Test Facility to quantify the position resolution of optical fibre BLMs in a multi-bunch, multi-loss scenario as well as the sensitivity limitations due to crosstalk and electron field emission.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMR024
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MOPMR035	Bunch Length Measurements using a Transverse Deflecting Cavity on VELA	gun, laser, electron, simulation	323
	J.W. McKenzie, S.R. Buckley, L.S. Cowie, P. Goudket, M. Jenkins, B.L. Militsyn, A.J. Moss, A.E. Wheelhouse STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom A. Wolski The University of Liverpool, Liverpool, United Kingdom
	The VELA facility at Daresbury Laboratory in the UK includes a 5 MeV/c 2.5 cell S-band photoinjector gun. This gun operates in the "blow-out" regime with a sub-200 fs length drive laser: the resulting bunch length is determined by space-charge effects. We present measurements made with an S-band transverse deflecting cavity to characterise the bunch length as a function of charge, and as a function of the gun operating phase.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMR035
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MOPMR037	Analysis of Asymmetry Tolerances and Cross-coupling in Cavity BPMs	coupling, alignment, simulation, dipole	331
	E. Yamakawa, S.T. Boogert, A. Lyapin, L.J. Nevay JAI, Egham, Surrey, United Kingdom S. Syme FMB Oxford, Oxford, United Kingdom
	Geometric asymmetries in cavity BPMs result in a coupling between horizontal and vertical signals, which complicates their usage and may affect both the dynamic range and spatial resolution of the system in both directions. Tolerances to several types of geometric asymmetries have been analysed using a 3D electromagnetic field solver (GdfidL). We report on some of the results and discussed the possible impact of the considered geometrical distortions.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMR037
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MOPMR060	C-Band Deflecting Cavity for Bunch Length Measurement of 2.5 MeV Electron Beam	vacuum, electromagnetic-fields, coupling, simulation	386
	J. Jiang, H.B. Chen, J. Shi, P. Wang, L. Zhang, S.X. Zheng TUB, Beijing, People's Republic of China
	The C-band deflecting cavity designed last year is finished. In this paper, the RF measurement of the cavity is introduced. After tuning, it works well at 5.712GHz with a coupling factor degree around 1.05. And we measured the electromagnetic field with bead-pull method. The flatness of the magnetic field is around 0.9, which is not ideal but meet the requirements of the bunch length measurement. And we propose a method of tuning to make sure both frequency and field flatness.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMR060
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MOPMW001	A New Buncher for the ESRF Linac Injector	linac, electron, beam-loading, gun	389
	A.S. Setty, A.S. Chauchat, D. Jousse Thales Communications & Security (TCS), Gennevilliers Cedex, France H. Delamare, J. Jacob, B. Ogier, T.P. Perron, E. Rabeuf, C. Richard, V. Serrière, R. Versteegen ESRF, Grenoble, France
	The electron linac was designed to be able to deliver more than 2.5 A in less than 2 ns at 200 MeV within an energy spread of 1% for positrons production at ESRF . The 200 MeV electron linac was commissioned in 1991. A new gun, a cleaner, a pre-buncher cavity and 4 shielded lenses were tested and installed on the injector in 2008 . Then, a new Buncher for the ESRF electron linac injector was manufactured and commissioned in 2015. Meanwhile, some new settings were performed to reduce the energy spread for both cases: the long pulse mode and the short pulse mode. The simulations and measurements will be presented. D. Tronc et Al. "Electron injector for light source", Proc. EPAC88, Italy, Rome, June 1988. ** T. Perron et Al. "New preinjector for the ESRF booster", Proc. EPAC08, Italy, Genoa, June 2008.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW001
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MOPMW002	Modeling and Simulation of Broadband RF Cavities in PSpice	simulation, coupling, impedance, storage-ring	392
	J. Harzheim, D. Domont-Yankulova, H. Klingbeil, R. Königstein TEMF, TU Darmstadt, Darmstadt, Germany M. Frey, H. Klingbeil GSI, Darmstadt, Germany
	Barrier bucket systems are planned for the SIS100 Synchrotron (part of the future accelerator facility FAIR) and the ESR storage ring to facilitate several longitudinal beam manipulations [9] [15]. In order to achieve a single-sine gap signal of the desired amplitude and quality, effects in the linear and nonlinear region of the RF systems have to be investigated and included in the design of the overall system. Therefore, the cavities and the amplifier stages are to be modeled in PSpice. In this contribution, a cavity model will be presented. In a first step, a model for the magnetic alloy (MA) ring cores, which highly account for the properties of the cavity, has been found based on measurement data. In a second step, the future setup of the cavity is systematically created using the MA ring core models. The model of the cavity allows simulations in frequency domain as well as time domain. The results show good agreement with former measurements.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW002
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MOPMW003	Thermal Simulation of an Energy Feedback Normal Conducting RF Cavity	coupling, simulation, operation, electron	396
	M. Fakhari, K. Flöttmann, S. Pfeiffer, H. Schlarb DESY, Hamburg, Germany J. Roßbach University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany A. Yahaghi CFEL, Hamburg, Germany
	Thermal simulation has been performed for an energy feedback normal conducting RF cavity. The cavity is going to be used as a fast actuator to regulate the arrival time of the electron bunches in fs level in FLASH. By measuring the arrival time jitter of one bunch in a bunch train, the designed cavity apply a correcting accelerating or decelerating voltage to the next bunches. The input power of the cavity is provided by a solid state amplifier and will be coupled to the cavity via a loop on the body. To achieve the fs level precision of the arrival time, the cavity should be able to provide accurate accelerating voltage with a precision of 300 eV. We performed thermal simulation to find out the temperature distribution of the cavity and make sure that heating will not affect its voltage precision. The simulation results show that by using two input loops the coupling constant will vary from 4.11 to 4.13 during the operation of the cavity which effect on the bunchs' arrival time would be less than 0.25 fs. While using just one input loop can lead to an error of about 1 fs.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW003
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MOPMW010	Property Test of the Q-Factor for High Purity Copper at the Temperature of 20K	electron, linac, radiation, cryogenics	417
	A. Iino Sokendai, Ibaraki, Japan K. Endo TOYAMA Co., Ltd., Zama-shi, Kanagawa, Japan S. Yamaguchi KEK, Ibaraki, Japan
	A coherent parametric x-ray radiation (PXR) source based on a cryogenic electron linac has been developed by Toyama Co., Ltd, KEK and Nihon University. This accelerator is a C-band normal-conducting compact linac that requires a high Q factor in the accelerating and de-celerating structures. To obtain a high Q factor, the ac-celerating and decelerating structures are operated around 20 K, and are joined by diffusion bonding and are constructed with high-purity 6N8 copper which has very low resistivity in extremely low temperatures. In this study, we report the measurements and calculation of the residual resistance ratio (RRR) for 6N8 copper and oxy-gen-free copper (Class 1) as well as the Q factor for a pillbox cavity made of 6N8 copper and Class 1. The results of a low-power test of this accelerating structure at low temperature are reported. The Q factor for a 6N8 copper pillbox cavity is not much higher than that of a Class 1 pillbox cavity at low temperatures Moreover, the Q factor is saturated when RRR is greater than 500.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW010
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MOPMW011	The Second Harmonic RF System for J-PARC MR Upgrade	impedance, injection, operation, proton	420
	C. Ohmori, K. Hara, K. Hasegawa, M. Toda, M. Yoshii KEK, Tokai, Ibaraki, Japan M. Nomura, T. Shimada, F. Tamura, M. Yamamoto JAEA/J-PARC, Tokai-mura, Japan
	Power upgrade scenario of J-PARC Main Ring includes replacement of RF cavities with higher field gradient using magnetic alloy cores, FT3L than the present ones. It also need to install the second harmonic RF cavity in the other section where dedicated water system for RF cavities is not available. Installation scenario of the second harmonic RF will be presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW011
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MOPMW012	Study for a 162.5 MHz Window-Type RFQ	rfq, Windows, simulation, dipole	423
	Q. Fu, P.P. Gan, S.L. Gao, F.J. Jia, H.P. Li, J. Liu, Y.R. Lu, Z. Wang, K. Zhu PKU, Beijing, People's Republic of China
	A window type of four vane radio-frequency quadrupole accelerator has been designed to accelerate 50 mA deuteron beam from 50 keV to 1 MeV. It will operate at 162.5 MHz in CW mode. Compared to the traditional four-vane RFQ, the window-type RFQ is more compact and has higher mode separation without π-mode stabilizing loops or dipole rods. A detailed full 3D model including vane modulation was developed. For the purpose of high shunt impedance, high quality factor and low power dissipation, the RF structure design was optimized by using electromagnetic simulations. Following the EM design optimization, an aluminium model of the window-type RFQ was fabricated and tested.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW012
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MOPMW015	Wakefields Studies of High Gradient X-band Accelerating Structure at SINAP	wakefield, impedance, simulation, FEL	429
	X.X. Huang, W. Fang, Q. Gu, M. Zhang, Z.T. Zhao SINAP, Shanghai, People's Republic of China
	Shanghai compact hard x-ray free electron laser (CHXFEL)* is now proposed accompanied with a high-gradient accelerating structure, which is the trend of large scale and compact facility. This structure operated at X-band (11424 MHz) holds the promise to achieve high gradient up to 80 MV/m. However, due to its particular property, a more serious wakefields** will be generated, leading to worse beam instability effects. In this paper, the computation of this case will be carried out with simulation. Moreover, analysis and optimization will be adopted to suppress beam instability. * C. Feng, Z. T. Zhao, Chinese Sci Bull, 2010, 55, 221-227. ** K. Bane, SLAC, NLC-Note 9, Feb. 1995.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW015
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MOPMW023	Optimization of the RF Cavity of a Low-energy Storage Ring for Thomson Scattering X-Ray Source	HOM, storage-ring, coupling, higher-order-mode	438
	L. Ovchinnikova, V.I. Shvedunov SINP MSU, Moscow, Russia A. Ryabov IHEP, Moscow Region, Russia V.I. Shvedunov LEA MSU, Moscow, Russia
	Results of optimization of the RF cavity of a low-energy storage ring for Thomson scattering X-ray source are presented. The geometry of 714 MHz RF cavity was optimized to provide maximum shunt impedance taking into account position of higher order modes (HOMs). The number and position of cooling channels were adjusted to minimize frequency shift due to cavity thermal deformations. The waveguide coupler and frequency tuner were calculated. Special attention was paid to detailed calculations of the HOMs parameter and to study of methods to minimize their influence on the storage ring beam dynamics.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW023
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MOPMW025	Vacuum RF Breakdown of Accelerating Cavities in Multi-Tesla Magnetic Fields	vacuum, operation, Windows, electron	444
	D.L. Bowring, A. Moretti, M.A. Palmer, D.W. Peterson, A.V. Tollestrup, K. Yonehara Fermilab, Batavia, Illinois, USA B.T. Freemire IIT, Chicago, Illinois, USA A.V. Kochemirovskiy University of Chicago, Chicago, Illinois, USA P.G. Lane, Y. Torun Illinois Institute of Technology, Chicago, Illinois, USA
	Funding: Work supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359. Ionization cooling of intense muon beams requires the operation of high-gradient, normal-conducting RF structures within multi-Tesla magnetic fields. The application of strong magnetic fields has been shown to lead to an increase in vacuum RF breakdown. This phenomenon imposes operational (i.e. gradient) limitations on cavities in ionization cooling channels, and has a bearing on the design and operation of other RF structures as well, such as photocathodes and klystrons. We present recent results from Fermilab's MuCool Test Area (MTA), in which 201 and 805 MHz cavities were operated at high power both with and without the presence of multi-Tesla magnetic fields. We present an analysis of damage due to breakdown in these cavities, as well as measurements related to dark current and their relation to a conceptual model describing breakdown phenomena.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW025
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MOPMW026	Resonant Control for Fermilab's PXIE RFQ	rfq, controls, operation, resonance	447
	D.L. Bowring, B.E. Chase, J. Czajkowski, J.P. Edelen, D.J. Nicklaus, J. Steimel, T.J. Zuchnik Fermilab, Batavia, Illinois, USA S. Biedron, A.L. Edelen, S.V. Milton CSU, Fort Collins, Colorado, USA
	Funding: Work supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359. The RFQ for Fermilab's PXIE test program is designed to accelerate a < 10 mA H⁻ CW beam to 2.1 MeV. The RFQ has a four-vane design, with four modules brazed together for a total of 4.45 m in length. The RF power required is < 130 kW at 162.5 MHz. A 3 kHz limit on the maximum allowable frequency error is imposed by the RF amplifiers. This frequency constraint must be managed entirely through differential cooling of the RFQ's vanes and outer body and associated material expansion. Simulations indicate that the body and vane coolant temperature should be controlled to within 0.1 degrees C. We present the design of the cooling network and the resonant control algorithm for this structure, as well as results from initial operation.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW026
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MOPMW027	Design of a Perpendicular Biased 2nd Harmonic Cavity for the Fermilab Booster	booster, Windows, impedance, cathode	451
	C.-Y. Tan, J.E. Dey, K.L. Duel, R.L. Madrak, W. Pellico, E. Prebys, J. Reid, G.V. Romanov, D. Sun, I. Terechkine Fermilab, Batavia, Illinois, USA
	Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. A perpendicular biased 2nd harmonic cavity is currently being designed and built for the Fermilab Booster. The purpose is to flatten the bucket at injection and thus change the longitudinal beam distribution to decrease space charge effects. It can also help with transition crossing. A model cavity has been built to verify various CST Microwave studio and COMSOL results and a test stand has been built to ensure that the Y567 tube is able to operate at twice the Booster fundamental frequencies. Also discussed are the RF windows which are critical to the design.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW027
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MOPMW028	Progress on the MICE RF Module at LBNL	vacuum, operation, coupling, experiment	454
	T.H. Luo, A.J. DeMello, A.R. Lambert, D. Li, T.J. Loew, S. Prestemon, S.P. Virostek, J.G. Wallig LBNL, Berkeley, California, USA T.G. Anderson, A.D. Bross, M.A. Palmer Fermilab, Batavia, Illinois, USA Y. Torun IIT, Chicago, Illinois, USA
	The international Muon Ionization Cooling Experiment aims to demonstrate the transverse cooling of a muon beam by ionization in energy absorbers. The final MICE cooling channel configuration has two RF modules, each housing a 201 MHz RF cavity used to compensate the longitudinal energy loss in the absorbers. The assembly of MICE RF Module is being carried out at LBL. In this paper we will report the recent progress on the assembly work.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW028
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MOPMW029	Analysis of Transverse Field Induced by Curved Beryllium Window in Muon Ionization Cooling Cavity	emittance, Windows, acceleration, focusing	457
	T.H. Luo, D. Li LBNL, Berkeley, California, USA
	The beryllium windows are used in muon ionization cooling cavity to increase the cavity shunt impedance. The windows are curved for predictable thermal deformation. This curvature also introduces transverse field, which will affect the transverse beam emittance. In this paper, we will analyze this transverse field and evaluate its effect on the emittance cooling.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW029
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MOPMW030	High Powered Tests of Dielectric Loaded High Pressure RF Cavities for Use in Muon Cooling Channels	accelerating-gradient, radio-frequency, plasma, experiment	460
	B.T. Freemire IIT, Chicago, Illinois, USA D.L. Bowring, A. Moretti, D.W. Peterson, A.V. Tollestrup, Y. Torun, K. Yonehara Fermilab, Batavia, Illinois, USA A.V. Kochemirovskiy University of Chicago, Chicago, Illinois, USA Y. Torun Illinois Institute of Technology, Chicago, Illlinois, USA
	Funding: This work is supported by the Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359. Bright muon sources require six dimensional cooling to achieve acceptable luminosities. Ionization cooling is the only known method able to do so within the muon lifetime. One proposed cooling channel, the Helical Cooling Channel, utilizes gas filled radio frequency cavities to both mitigate RF breakdown in the presence of strong, external magnetic fields, and provide the cooling medium. Engineering constraints on the diameter of the magnets within which these cavities operate dictate the radius of the cavities be decreased at their nominal operating frequency. To accomplish this, one may load the cavities with a larger dielectric material. Alumina of purities ranging from 96 to 99.8% was tested in a high pressure RF test cell at the MuCool Test Area at Fermilab. The results of breakdown studies with pure nitrogen gas, and oxygen-doped nitrogen gas indicate the peak surface electric field on the alumina ranges between 10 and 15 MV/m. How these results affect the design of a prototype cooling channel cavity will be discussed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW030
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MOPMW031	Beam Test of a Dielectric Loaded High Pressure RF Cavity for Use in Muon Cooling Channels	ion, electron, plasma, accelerating-gradient	463
	B.T. Freemire IIT, Chicago, Illinois, USA D.L. Bowring, A. Moretti, D.W. Peterson, A.V. Tollestrup, K. Yonehara Fermilab, Batavia, Illinois, USA A.V. Kochemirovskiy University of Chicago, Chicago, Illinois, USA Y. Torun Illinois Institute of Technology, Chicago, Illlinois, USA
	Funding: This work is supported by the Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359. Bright muon sources require six dimensional cooling to achieve acceptable luminosities. Ionization cooling is the only known method able to do so within the muon lifetime. One proposed cooling channel, the Helical Cooling Channel, utilizes gas filled radio frequency cavities to both mitigate RF breakdown in the presence of strong, external magnetic fields, and provide the cooling medium. Engineering constraints on the diameter of the magnets within which these cavities operate dictate the radius of the cavities be decreased at their nominal operating frequency. To accomplish this, one may load the cavities with a larger dielectric material. A 99.5% alumina ring was inserted in a high pressure RF test cell and subjected to an intense proton beam at the MuCool Test Area at Fermilab. The results of the performance of this dielectric loaded high pressure RF cavity will be presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW031
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MOPMW032	Study of RF Breakdown in 805MHz Pillbox Modular Cavity in Strong Magnetic Field	operation, radiation, site, pick-up	466
	A.V. Kochemirovskiy University of Chicago, Chicago, Illinois, USA D.L. Bowring, A. Moretti, K. Yonehara Fermilab, Batavia, Illinois, USA B.T. Freemire IIT, Chicago, Illinois, USA Y. Torun Illinois Institute of Technology, Chicago, Illlinois, USA
	RF breakdown has a negative impact on a cavity's performance, especially with the presence of strong magnetic fields. This issue can arise in designs of muon ionization cooling channel, RF guns, klystrons and in many other applications. The MuCool Test Area at Fermilab is the facility that allows us to study the effects of static magnetic field on RF cavity operation. As a part of this research program, we have tested an 805MHz pillbox "modular" cavity in strong external magnetic fields. The design of the cavity allowed for a better control over sources of systematic error. "Modular" structure of the cavity enables easy dismounting of the endplates to perform inspection of inner surfaces after each run as well as swapping endplates to study the effects of various materials on breakdown phenomenon. Coupler design ensures maximum electric field enhancement on cavity axis, thus reducing breakdown probability in the coupler region. The results and analysis from high-power runs with zero and non-zero external magnetic fields will be presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW032
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MOPMW033	Acoustic Localization of RF Cavity Breakdown: Status and Progress	collider, experiment, simulation, status	470
	P.G. Lane, P. Snopok, Y. Torun Illinois Institute of Technology, Chicago, Illinois, USA A.V. Kochemirovskiy University of Chicago, Chicago, Illinois, USA
	Current designs for muon accelerators require high-gradient RF cavities to be placed in solenoidal magnetic fields. These fields help contain and efficiently reduce the phase space volume of source muons in order to create a usable muon beam for collider and neutrino experiments. It has been found that placing normal conducting RF cavities in strong magnetic fields reduces the threshold at which RF cavity breakdown occurs. To aid the effort to study RF cavity breakdown in magnetic fields, it would be helpful to have a diagnostic tool which can localize the source of breakdown sparks inside the cavity. These sparks generate thermal shocks to a small region of the inner cavity wall that can be detected and localized using microphones attached to the outer cavity surface. Presented here are the algorithms for and results from localizing simulated and experimental acoustic data from the Modular Cavity at the MuCool Test Area at Fermilab.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW033
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MOPMW034	Final Commissioning of the MICE RF Module Prototype with Production Couplers	vacuum, operation, coupling, Windows	474
	Y. Torun, P.G. Lane Illinois Institute of Technology, Chicago, Illlinois, USA T.G. Anderson, M. Backfish, D.L. Bowring, A. Moretti, D.V. Neuffer, D.W. Peterson, M. Popovic, K. Yonehara Fermilab, Batavia, Illinois, USA B.T. Freemire IIT, Chicago, Illinois, USA T.L. Hart UMiss, University, Mississippi, USA A.V. Kochemirovskiy University of Chicago, Chicago, Illinois, USA T.H. Luo LBNL, Berkeley, California, USA
	Funding: Supported by the US Department of Energy Office of Science through the Muon Accelerator Program. We report operational experience from the prototype RF module for the Muon Ionization Cooling Experiment (MICE) with final production couplers at Fermilab's MuCool Test Area. This is the last step in fully qualifying the RF modules for operation in the experiment at RAL.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW034
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MOPMW035	Wakefield Excitation in Power Extraction Cavity (PEC) of Co-linear X-band Energy Booster (CXEB) in Time Domain (T3P) with ACE3P	extraction, electron, booster, simulation	477
	T. Sipahi, S. Biedron, S.V. Milton CSU, Fort Collins, Colorado, USA
	In our previous papers we provided the general concept and the design details of our proposed Co-linear X-band Energy Booster (CXEB) as well as more advanced 3D simulations of our system using the frequency domain solvers OMEGA3P and S3P of the ACE3P Suite. Here, using the time domain solver T3P of ACE3P, we provide the single bunch and multiple bunch wakefield excitations resulting from a Gaussian bunch. The related power extraction mechanism for our traveling wave (TW) X-band power extraction cavity (PEC) are also discussed further.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW035
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MOPMW036	Frequency Domain Simulations of Co-linear X-band Energy Booster (CXEB) RF Cavity Structures and Passive RF Components with ACE3P	electron, laser, impedance, extraction	480
	T. Sipahi, S. Biedron, S.V. Milton CSU, Fort Collins, Colorado, USA
	Due to their higher intrinsic shunt impedance X-band accelerating structures offer significant gradients with relatively modest input powers, and this can lead to more compact light sources. At the Colorado State University Accelerator Laboratory (CSUAL) [1] we would like to adapt this technology to our 1.3-GHz, L-band accelerator system using a passively driven 11.7 GHz traveling wave X-band configuration that capitalizes on the high shunt impedances achievable in X-band accelerating structures in order to increase our overall beam energy in a manner that does not require investment in an expensive, custom, high-power X-band klystron system. Here we provide the comparisons of the important parameters achieved using SUPERFISH and OMEGA3P for our Co-linear X-band Energy Booster (XCEB) system that will allow us to achieve our goal of reaching the maximum practical net potential across the X-band accelerating structures while driven solely by the beam from the L-band system.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW036
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MOPMW038	Measurements of Copper RF Surface Resistance at Cryogenic Temperatures for Applications to X-Band and S-Band Accelerators	cryogenics, experiment, electron, coupling	487
	A.D. Cahill, A. Fukasawa, J.B. Rosenzweig UCLA, Los Angeles, California, USA G.B. Bowden, V.A. Dolgashev, M.A. Franzi, S.G. Tantawi, P.B. Welander, C. Yoneda SLAC, Menlo Park, California, USA J. Guo JLab, Newport News, Virginia, USA Y. Higashi OIST, Onna-son, Okinawa, Japan
	Funding: Funding from DOE SCGSR and DOE/SU Contract DE-AC02-76-SF00515 Recent SLAC experiments with cryogenically cooled X-Band standing wave copper accelerating cavities have shown that these structures can operate with accelerating gradients of ~250 MV/m and low breakdown rates. These results prompted us to perform systematic studies of copper rf properties at cryogenic temperatures and low rf power. We placed copper cavities into a cryostat cooled by a pulse tube cryocooler, so cavities could be cooled to 4K. We used different shapes of cavities for the X-Band and S-Band measurements. Properties of the cavities were measured using a network analyzer. We calculated rf surface resistance from measured Q0 and Q external of the cavity at temperatures from 4 K to room temperature. The results were then compared to the theory proposed by Reuter and Sondheimer. These measurements are a part of studies with the goal of reaching very high operational accelerating gradients in normal conducting rf structures.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW038
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MOPMW039	TM01 Mode Launcher for Use in High Brightness Photoguns	quadrupole, gun, electron, impedance	491
	A.D. Cahill UCLA, Los Angeles, California, USA M. Dal Forno, V.A. Dolgashev SLAC, Menlo Park, California, USA
	Funding: DOE SCGSR and DOE/SU Contract DE-AC02-76-SF00515 Photo rf guns are a source of electron beams for X-ray FELs such as LCLS and European XFEL. In existing photoguns power is coupled into the cavity by waveguides through the cell walls, like LCLS, or through coaxial coupling, at the European XFEL. We are considering feeding a gun using a circular waveguide with the TM01 mode. To do that we need a mode launcher, a matched device that couples the rectangular TE01 mode waveguide to a TM01 mode in a circular waveguide. Use of the mode launcher reduces complexity of the gun cavity and increases flexibility of positioning the input waveguide relative to the gun body. Mode launchers have been successfully used at SLAC and elsewhere for X-band high gradient tests. Because the existing mode launchers were not built for high brightness guns, they have a significant quadrupole field component. High brightness rf guns have tight requirements on output beam properties, and this quadrupole component adversely affects the beam. We have designed a mode launcher free of this disadvantage. We present design considerations, methodology, and an example S-band mode launcher.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW039
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MOPMW042	Multi-Dimensional RF Sources Design	klystron, electron, space-charge, gun	501
	M. Dal Forno, A. Jensen, R.D. Ruth, S.G. Tantawi SLAC, Menlo Park, California, USA
	Funding: Work supported by the US DOE under contract DE-AC02-76SF00515. Vacuum electronic devices, such as rf sources for accelerator applications, must provide high rf power with high efficiency. To achieve these requirements, multi-beam klystron and sheet-beam klystron devices have been developed. Multi-beam klystrons, at high frequency employ separate output cavities; hence they have the disadvantage that combining all the rf pulses, generated by all the beams, is challenging. Sheet-beam klystrons have problems with instabilities and with space charge forces that makes the beam not naturally confined. We are proposing an alternative approach that reduces space charge problems, by adopting geometries in which the space charge forces are naturally balanced. An example is when the electron beam is generated by a central source (well) and the electron motion corresponds to the natural expansion of the electron cloud (three-dimensional device). In this paper we will present the design and challenges of a bi-dimensional rf source, a cylindrical klystron, composed by concentric pancake resonant cavities. In this case, space charge forces are naturally balanced in the azimuthal direction.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW042
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MOPMW044	Design of an RF Device to Study the Multipactor Phenomenon	simulation, electron, multipactoring, experiment	507
	D. Amorim Grenoble-INP Phelma, Grenoble, France J.-M. De Conto, Y. Gómez Martínez LPSC, Grenoble Cedex, France
	Multipacting is a parasitic electron avalanche process that may occur in RF devices such as cavities or couplers. As it can be detrimental to the operation of these devices, the accelerator group at LPSC is currently designing a coaxial resonant cavity in order to study this phenomenon. In order to determine the measurable parameters on the cavity, calculations were performed and validated with numerical simulations. In a second time multipacting simulations were conducted to determine if the experiment will allow to observe multipacting.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW044
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MOPMY001	Beam Dynamics Analysis for the Ultra-fast Kicker in Circular Cooler Ring of JLEIC	kicker, electron, emittance, recirculation	510
	Y.L. Huang IMP/CAS, Lanzhou, People's Republic of China R.A. Rimmer, H. Wang, S. Wang JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. An ultra-fast kicker system consist of four quarter wavelength resonator based deflecting cavities was developed that simultaneously resonates at 10 subharmonic modes of the 476.3MHz bunch repetition frequency, thus every 10th bunch in the bunch train will experience a transverse kick while all the other bunches are undisturbed. This fast kicker is developed for the Energy Recovery Linac (ERL) based electron Circular Cooler Ring (CCR) in the proposed Jefferson Lab Electron Ion Collider (JLEIC, previously MEIC). The electron bunches can be reused 10-30 turns thus the beam current in the ERL can be reduced to 1/10 - 1/30 (150mA - 50mA) of the cooling bunch current (1.5A). In this paper, several methods to synthesis such a kicker waveform will be discussed with the comparison of beam dynamics tracking in Elegant.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY001
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MOPMY002	Simulation and Experimental Studies of a 2.45GHz Magnetron Source for an SRF Cavity with Field Amplitude and Phase Controls	controls, LLRF, injection, SRF	514
	H. Wang, T. E. Plawski, R.A. Rimmer JLab, Newport News, Virginia, USA A. Dudas, M.L. Neubauer Muons, Inc, Illinois, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and NP STTR Grant DE-SC0013203. Phase lock to an SRF cavity by using injection signal through output waveguide of a magnetron has been demonstrated [1, 3]. Amplitude control using magnetic field trimming and anode voltage modulation has been studied using MATLAB/Simulink simulations [2]. Based on these, we are planning to use an FPGA based digital LLRF system, which allows applying various types of control algorithms in order to achieve the required accelerating field stability. Since the 1497 MHz magnetron is still in the design stage, the proof of principle measurements of a commercial 2450 MHz magnetron are carried out to characterize the anode I-V curve, output power (the tube electronic efficiency), frequency dependence on the anode current (frequency pushing) and the Rieke diagram (frequency pulling by the reactive load). Based on early Simulink simulation, experimental data and extension of the Adler equation governing injection phase stability by Chen's model, the specification of the new LLRF control chassis for both 2450 and 1497MHz systems are presented in this paper.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY002
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MOPMY003	Transient Beam Loading Effects in RF Systems in JLEIC	electron, klystron, feedback, controls	518
	H. Wang, J. Guo, R.A. Rimmer, S. Wang JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The pulsed electron bunch trains generated from the Continuous Electron Beam Accelerator Facility (CEBAF) linac to inject into the proposed Jefferson Lab Electron Ion Collider (JLEIC) e-ring will produce transient beam loading effects in the Superconducting Radio Frequency (SRF) systems that, if not mitigated, could cause unacceptably large beam energy deviation in the injection capture, exceed the energy acceptance of CEBAF's recirculating arc. In the electron storage ring, the beam abort or ion clearing gaps or uneven bucket filling can cause large beam phase transients in the (S)RF cavity control systems and even beam loss due to Robinson instability. We have first analyzed the beam stability criteria in steady state and estimate the transient effect in Feedforward and Feedback RF controls. Initial analytical models for these effects are shown for the design of the JLEIC e-ring from 3GeV to 12GeV.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY003
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MOPMY005	Study of Pretuning and High Power Test of DTL Iris Waveguide Couplers Using a Single Cell Cavity	DTL, coupling, factory, simulation	522
	S.W. Lee, M.S. Champion, Y.W. Kang ORNL, Oak Ridge, Tennessee, USA
	Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S.DOE. Six drift tube linac (DTL) cavities have been operating successfully at the Spallation Neutron Source (SNS). Each cavity is fed by a tapered ridge waveguide iris input coupler and a waveguide ceramic disk window. The original couplers and cavities have been in service for more than a decade. Design optimization and tuning of the couplers were initially performed prior to installation and commissioning of the cavities. Since each DTL cavity is unique, expensive, and fully utilized for neutron production, none of the cavity structure is available as a test cavity or a spare. Maintaining spares for operations and for future system upgrade, test setup of the iris couplers for precision tuning is needed. Ideally a smaller cavity structure may be used for pretuning and RF conditioning of the iris couplers as a test cavity or a bridge waveguide. In this paper, study of using a single cell cavity for the iris tuning and conditioning is presented along with the 3D simulation results.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY005
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MOPMY007	Mechanical Design and 3-D Coupled RF, Thermal-Structural Analysis of Normal Conducting 704 MHz and 2.1 GHz Cavities for LEReC Linac	simulation, vacuum, software, operation	525
	J.C. Brutus, S.A. Belomestnykh, I. Ben-Zvi, M. Blaskiewicz, J.M. Brennan, A.V. Fedotov, M.C. Grau, C. Pai, L. Snydstrup, J.E. Tuozzolo, B. P. Xiao, T. Xin, W. Xu, A. Zaltsman BNL, Upton, Long Island, New York, USA V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE. Two normal conducting cavities operating at 704 MHz and 2.1 GHz will be used for the Low Energy RHIC electron Cooling (LEReC) under development at BNL to improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon. The single cell 704 MHz cavity and the 3-cell 2.1 GHz third harmonic cavity will be used in LEReC to correct the energy spread introduced in the SRF cavity. The successful operation of normal RF cavities has to satisfy both RF and mechanical requirements. 3-D coupled RF-thermal-structural analysis has been performed on the cavities to confirm the structural stability and to minimize the frequency shift resulting from thermal and structural expansion. In this paper, we will present an overview of the mechanical design, results from the RF-thermal-mechanical analysis, progress on the fabrication and schedule for the normal conducting RF cavities for LEReC.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY007
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MOPMY009	HOM Consideration of 704 MHz and 2.1 GHz Cavities for LEReC Linac	HOM, SRF, booster, electron	528
	B. P. Xiao, I. Ben-Zvi, M. Blaskiewicz, J.M. Brennan, J.C. Brutus, A.V. Fedotov, H. Hahn, G.T. McIntyre, C. Pai, K.S. Smith, J.E. Tuozzolo, Q. Wu, T. Xin, W. Xu, A. Zaltsman BNL, Upton, Long Island, New York, USA S.A. Belomestnykh Fermilab, Batavia, Illinois, USA S.A. Belomestnykh, I. Ben-Zvi Stony Brook University, Stony Brook, USA V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 and by National Energy Research Scientific Computing Center under contract No. DE-AC02-05CH11231 by US DOE. To improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, the Low Energy RHIC electron Cooler (LEReC) is currently under development at BNL. The Linac of LEReC is designed to deliver 2 MV to 5 MV electron beam, with rms dp/p less than 5·10^-4. The HOM in this Linac is carefully studied to ensure this specification.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY009
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MOPMY010	RF Design of Normal Conducting 704 MHz and 2.1 GHz Cavities for LEReC Linac	HOM, vacuum, impedance, simulation	532
	B. P. Xiao, I. Ben-Zvi, M. Blaskiewicz, J.M. Brennan, J.C. Brutus, A.V. Fedotov, H. Hahn, G.T. McIntyre, C. Pai, K.S. Smith, J.E. Tuozzolo, Q. Wu, T. Xin, W. Xu, A. Zaltsman BNL, Upton, Long Island, New York, USA S.A. Belomestnykh Fermilab, Batavia, Illinois, USA S.A. Belomestnykh, I. Ben-Zvi, T. Xin Stony Brook University, Stony Brook, USA V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 and by National Energy Research Scientific Computing Center under contract No. DE-AC02-05CH11231 by US DOE. To improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, the Low Energy RHIC electron Cooler (LEReC) is currently under development at BNL. Two normal conducting cavities, a single cell 704 MHz cavity and a 3 cell 2.1 GHz third harmonic cavity, will be used in LEReC for energy spread correction. Currently these two cavities are under fabrication. In this paper we report the RF design of these two cavities.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY010
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MOPMY011	LLRF System Performance during SC Cavity Conditioning at STF KEK	LLRF, controls, feedback, FPGA	536
	S.B. Wibowo Sokendai, Ibaraki, Japan T. Matsumoto, S. Michizono, T. Miura, F. Qiu KEK, Ibaraki, Japan
	High Energy Accelerator Research Organization (KEK) is now developing a digital low-level radio frequency (LLRF) control system based on digital feedback control at superconducting RF test facility (STF). The goal is to achieve the amplitude and phase stability of the accelerating field in the superconducting accelerator. Testing and evaluation of the digital LLRF system were conducted during the cavity conditioning performed between October and December 2015 to determine the level of performance. To enable cavity signal monitoring, direct sampling system was constructed and evaluated.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY011
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MOPMY014	Design Study of RF Section and Cavities for Cepc 650 MHz Klystron	klystron, simulation, electron, bunching	543
	O. Xiao Institute of High Energy Physics (IHEP), People's Republic of China D.D. Dong, S. Fukuda, Z.J. Lu, G. Pei, S.C. Wang, .. Zaib-un-Nisa, Z.S. Zhou IHEP, Beijing, People's Republic of China S. Fukuda KEK, Ibaraki, Japan
	An 800 kW CW klystron operating at 650 MHz is de-veloped for CEPC at Institute of High Energy Physics in China. The conceptual design has been finished and the main parameters are presented in this paper. A 1D large signal disk model code, AJDISK, has been used to design and optimize klystron RF section parameters. In addition, the RF cavities have been designed using SUPERFISH, HFSS and CST.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY014
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MOPMY027	Preliminary Design of High-efficiency Klystron for Pohang Accelerator Laboratory (PAL)	klystron, beam-losses, simulation, operation	557
	S.J. Park, J.Y. Choi, Y.D. Joo, K.R. Kim, W. Namkung, C.D. Park PAL, Pohang, Kyungbuk, Republic of Korea M.-H. Cho, J.H. Hwang, T. Seong POSTECH, Pohang, Kyungbuk, Republic of Korea
	Funding: Supported by the Ministry of Science, ICT and Future Planning of Korea. Klystrons for particle accelerators are typically designed to have narrow bandwidths with center frequencies ranging from several hundreds (e.g., 350) MHz to X-band (11.424 GHz). Output powers are from several tens of kW to ~1 MW for CW klystrons and ~100 MW for pulsed ones. The narrow-bandwidth requirement has enabled them to provide high gain (typically 40 - 50 dB) which greatly simplifies the RF drive system. Recently, especially for large-scale accelerator facilities, the klystron efficiency has become one of the most demanding issues. This is because electricity cost occupies a great portion of their operating budgets and the klystron efficiency is one of the important factors determining the electricity consumption of the whole accelerator system. In this regard, we have designed a high-efficiency klystron for use in the PLS-II and PAL XFEL at PAL. The basic scheme is to re-design the cavity system to include multi-cell output cavity. In this article, we report on our preliminary design work to determine major cavity parameters including cell frequencies, inter-cell distances, and coupling to external circuits (coupling beta).
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY027
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MOPMY033	Effect of Bandwidth of Low Level Radio Frequency System on the Instability of an Electron Beam	feedback, LLRF, synchrotron, electron	570
	Z.K. Liu, L.-H. Chang, M.H. Chang, L.J. Chen, PY. Chen, F.-T. Chung, M.-C. Lin, C.H. Lo, C.L. Tsai, M.H. Tsai, Ch. Wang, M.-S. Yeh, T.-C. Yu NSRRC, Hsinchu, Taiwan
	The analog Low Level Radio Frequency (LLRF) system is used at Taiwan Photon Source (TPS) RF system. It is composed of three feedback loops to control the amplitude and phase of accelerating field and the frequency of RF cavity. Instability of electron beam and accelerating field due to the bandwidth of LLRF system were observed during the TPS commissioning. This effect was studied and the results will be presented in this paper.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY033
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MOPMY035	Theoretical Analysis and Simulation of a Compact Frequency Multiplier for High Power Millimeter and Terahertz Sources	electron, cathode, coupling, space-charge	576
	A.R. Vrielink, S.G. Tantawi, F. Toufexis SLAC, Menlo Park, California, USA
	As the demands on accelerating gradients and the temporal resolution of beam diagnostics and manipulation schemes grow, millimeter-wave and terahertz (THz) accelerator structures may present a natural solution. The recent advent of a radiofrequency undulator and the development of a 0.45 THz accelerator demonstrate growing interest in this frequency regime; however, growth in this area is limited by the lack of efficient, compact high power sources. We present a novel vacuum electronic device featuring an interaction between a radially bunched electron beam and azimuthally traveling waves. The use of an inward traveling radial sheet beam mitigates space charge effects at the low operating energy of 10-30 keV and allows for a high input beam current of approximately 0.5-10 A. Based on preliminary calculations, these devices could operate from 50 GHz to 250 GHz with tens of kiloWatts of output power, while the expected efficiency would scale from 60% at 80 GHz to 15% at 230 GHz. Here we present the underlying theory, possible structure design, and preliminary results from analytical calculations and simulation. Tantawi, S. et al. Phys. Rev. Lett. 112, 164802 (April, 2014) Nanni, E. et al. Nat. Commun. 6, 8486 (October, 2015)
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY035
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MOPMY036	High-harmonic mm-Wave Frequency Multiplication using a Gyrocon-like Device	electron, coupling, vacuum, plasma	579
	F. Toufexis, V.A. Dolgashev, M.V. Fazio, A. Jensen, S.G. Tantawi, A.R. Vrielink SLAC, Menlo Park, California, USA P. Borchard Dymenso LLC, San Francisco, USA
	Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515, and the National Science Foundation. Traditional linear interaction RF sources, such as Klystrons and Traveling Wave Tubes, fail to produce significant power levels at millimeter wavelengths. This is because their critical dimensions are small compared to the wavelength, and the output power scales as the square of the wavelength. We present a vacuum tube technology, where the device size is inherently larger than the operating wavelength. We designed a low–voltage mm–wave source, with an output interaction circuit based on a spherical sector cavity. This device was configured as a phased-locked frequency multiplier. We report the design and cold test results of a proof-of-principle fifth harmonic frequency multiplier with an output frequency of 57.12 GHz.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY036
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MOPOR009	The HL-LHC Impedance Model and Aspects of Beam Stability	impedance, HOM, octupole, focusing	606
	N. Biancacci, K.S.B. Li, E. Métral, B. Salvant CERN, Geneva, Switzerland
	Funding: Research supported by the High Luminosity LHC project The LHC upgrade to the HLLHC foresees new challenging operational scenarios from the beam dynamics point of view. In order to ensure good machine operation and performance, the machine impedance, among other possible sources of instabilities like beam-beam and electron cloud, needs to be carefully quantified profiting also from the current LHC operation. In this work we present the HLLHC impedance model mainly focusing on the contribution of low-impedance collimators and crab cavities: the first reduces the broad-band impedance baseline thanks to the higher jaw material conductivity, the second increases the machine luminosity at the price of increasing the coupled bunch stabilizing octupole current threshold. Other elements like the injection protection absorber (TDI) will be also discussed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR009
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MOPOR012	Study of the Beam-Cavity Interaction in the PS 10 MHz RF System	impedance, simulation, feedback, acceleration	618
	G. Favia, H. Damerau, M. Morvillo, C. Rossi CERN, Geneva, Switzerland M. Migliorati University of Rome "La Sapienza", Rome, Italy
	The eleven main accelerating cavities of the Proton Synchrotron (PS) at CERN consist of two ferrite-loaded coaxial λ/4 resonators each. Both resonators oscillate in phase, as their gaps are electrically connected by short bars. They are in addition magnetically coupled via the bias loop used for cavity tuning. The cavities are equipped with a wide-band feedback system, limiting the beam loading, and a further reduction of the beam induced voltage is achieved by relays which short-circuit each half-resonator gap when the cavity is not in use. Asymmetries of the beam induced voltage observed in the two half-cavities indicate that the coupling between the two resonators is not as tight as expected. The total cavity impedance coupling to the beam may be affected differently by the contributions of both resonators. A dedicated measurement campaign with high-intensity proton beam and numerical simulation have been performed to investigate the beam-cavity interaction. This paper reports the result of the study and the work aiming at the development of a model of the system, including the wide-band feedback, which reproduces this interaction.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR012
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MOPOR013	The PS 10 MHz High Level RF System Upgrade	feedback, impedance, network, beam-loading	622
	G. Favia, H. Damerau, V.D. Desquiens, S. Energico, M. Morvillo, D. Perrelet, C. Rossi CERN, Geneva, Switzerland
	In view of the upgrade of the injectors for the High Luminosity LHC, significantly higher bunch intensity is required for LHC-type beams. In this context an upgrade of the main accelerating RF system of the Proton Synchrotron (PS) is necessary, aiming at reducing the cavity impedance which is the source of longitudinal coupled-bunch oscillations. These instabilities pose as a major limitation for the increase of the beam intensity as planned after LS2. The 10 MHz RF system consists in 11 ferrite loaded cavities, driven by tube-based power amplifiers for reasons of radiation hardness. The cavity-amplifier system is equipped with a wide-band feedback that reduces the beam induced voltage. A further reduction of the beam loading is foreseen by upgrading the feedback system, which can be reasonably achieved by increasing the loop gain of the existing amplification chain. This paper describes the progress of the design of the upgraded feedback system and shows the results of the tests on the new amplifier prototype, installed in the PS during the 2015-16 technical stop. It also reports the first results of its performance with beam, observed in the beginning of the 2016 run.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR013
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MOPOR014	Measurements of the CERN PS Longitudinal Resistive Coupling Impedance	impedance, HOM, coupling, synchrotron	626
	M. Migliorati, N. Biancacci, H. Damerau, G. Sterbini CERN, Geneva, Switzerland M. Migliorati University of Rome "La Sapienza", Rome, Italy M. Migliorati, L. Ventura INFN-Roma1, Rome, Italy S. Persichelli University of Rome La Sapienza, Rome, Italy
	The longitudinal coupling impedance of the CERN PS has been studied in the past years in order to better understand collective effects which could produce beam intensity limitations for the LHC Injectors Upgrade project. By measuring the incoherent quadrupole synchrotron frequency vs beam intensity, the inductive impedance was evaluated and compared with the impedance model obtained by taking into account the contribution of the most important machine devices. In this paper, we present the results of the measurements performed during a dedicated campaign, of the real part of the longitudinal coupling impedance by means of the synchronous phase shift vs beam intensity. The phase shift has been measured by using two different techniques: in one case, we injected in the machine two bunches, one used as a reference with constant intensity, and the second one changing its intensity; in the second case, more conventional, we measured the bunch position with respect to the RF signal of the 40 MHz cavities. The obtained dependence of the synchrotron phase with intensity is then related to the loss factor and the resistive coupling impedance, which is compared to the real part of the PS impedance model.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR014
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MOPOR033	Simulations of Dark Current from the BERLinPro Booster Module	electron, cathode, booster, simulation	671
	M. McAteer, M. Abo-Bakr, B.C. Kuske, A. Neumann HZB, Berlin, Germany
	Funding: Work supported by the German Bundesministerium f\"ur Bildung und Forschung, Land Berlin and grants of Helmholtz Association Dark current emitted from the surface of high-field RF cavities can contribute to radiation levels and cryo budget and can cause damage to sensitive accelerator components such as the photocathode. The superconducting niobium cavities in the booster module of BERLinPro will have surface fields strong enough to produce significant dark current from field emission, so simulations were made using Astra to track the propagation of emitted electrons from the surfaces of the cavities to examine the effects of dark current in the BERLinPro injector. Results of these simulations, including optimization of the layout to reduce propagation of electrons to the cathode and an estimation of power from dark current deposited throughout the injector, are presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR033
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MOPOR038	Implications of Resonantly Driven Higher Order Modes on the ESS Beam	HOM, simulation, linac, emittance	683
	A. Farricker, R.M. Jones, N.Y. Joshi UMAN, Manchester, United Kingdom S. Molloy ESS, Lund, Sweden
	The European Spallation Source (ESS) in Lund, Sweden, will be a facility for fundamental physics studies of atomic structure using a spallation source of unparalleled brightness. To achieve this end, a 2.86 ms long pulsed proton beam will be accelerated up to a final energy of 2 GeV using three suites of superconducting cavities. If a Higher Order Mode (HOM) lies on a harmonic of the bunch frequency the HOM will be resonantly driven. This will dilute the beam quality significantly. Errors in fabricating these cavities are inevitable, and this sets a tolerance on how close the HOM can be within a harmonic of the bunch frequency. The baseline design for ESS requires HOMs to be at least 5 MHz from a machine line. Here we provide details of several finite element electromagnetic simulations on the HOMS anticipated in these ESS cavities. We analyse their impact on the beam emittance using a drift-kick-drift model with the potential for relaxed tolerances.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR038
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MOPOR039	Measurement of Beam Phase at FLASH using HOMs in Accelerating Cavities	HOM, electron, simulation, coupling	686
	L. Shi, R.M. Jones UMAN, Manchester, United Kingdom N. Baboi, L. Shi DESY, Hamburg, Germany N.Y. Joshi University of Manchester, Manchester, United Kingdom
	The beam phase relative to the accelerating field is of vital importance for the quality of photon beams produced in modern Free Electron Lasers based on superconducting (SC) cavities. Normally, the phase is determined by detecting the transient field induced by the beam. In this way the phase of each cavity is checked and adjusted typically every few months. In this paper, we present another means of beam phase determination, based on higher order modes (HOMs) excited in the 2nd monopole band by the beam inside the SC cavities. A circuit model of this HOM band is also presented. Various effects on the resolution have been studied. Circuit model simulations indicate the resolution is strongly dependent on the signal to noise ratio. Preliminary experimental results, based on a broadband setup, reveal an approximately 0.1o RMS resolution. These are in good agreement with simulation results. The work will pave the way for a dedicated system of beam phase monitoring, which is under development for the European XFEL. This will be the first implementation of a dedicated beam phase monitor, based on beam-excited HOMs in accelerating cavities.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR039
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MOPOR043	High-gradient Structures for Proton Energy Boosters	booster, linac, proton, experiment	692
	S.S. Kurennoy, L. Rybarcyk LANL, Los Alamos, New Mexico, USA
	Increasing energy of proton beam at LANSCE from 800 MeV to 3 GeV can improve radiography resolution ~10 times. The best current practice to achieve this energy boost is to employ superconducting (SC) RF cavities with gradients about 15 MV/m after the existing linac, which results in a long and expensive booster. We propose accomplishing the same with a room-sized booster based on high-gradient (100s MV/m) room-temperature RF accelerating structures operating at low duty factors. Such high-gradient (HG) structures at very high RF frequencies have been demonstrated for electrons. However, they have never been used for protons because typical RF wavelengths are smaller than the proton bunch length. This is not a problem for proton radiography (pRad): a train of very short proton bunches with the same total length (10s ps) and charge as the original proton bunch will work as well, i.e., will create one radiography frame. Such a compact HG pRad booster can also be about an order of magnitude cheaper than the SC one. We explore feasibility of HG structures for protons and their application for a compact pRad booster at LANSCE.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR043
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MOPOW026	Status of FELiCHEM, a New IR-FEL in China	FEL, undulator, radiation, electron	774
	H.T. Li, Z.G. He, Q.K. Jia, Q. Luo, L. Wang, S.C. Zhang USTC/NSRL, Hefei, Anhui, People's Republic of China
	FELiChEM is a new experimental facility under construction at University of Science and Technology of China (USTC), whose core device is a FEL oscillator generating middle-infrared and far-infrared laser and covering the spectral range of 2.5-200 μm. It will be a dedicated light source aiming at energy chemistry research, with the photo excitation, photo dissociation and photo detection experimental stations. We present the brief physical and technical design that delivers the required performance for this device and summarize the status of fabrication. Final assembly is scheduled for early in the next year with first light targeted for July 2017.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW026
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MOPOW054	The 4th Harmonic Cavity for Hefei Light Source-II	HOM, storage-ring, synchrotron, operation	837
	C.-F. Wu, S. Dong, G. Huang, D. Jia, K. Jin, C. Li, J.Y. Li, W. Li, J.G. Wang, L. Wang, W. Xu, K. Xuan USTC/NSRL, Hefei, Anhui, People's Republic of China R.A. Bosch UW-Madison/SRC, Madison, Wisconsin, USA G.Y. Kurkin, E. Rotov BINP SB RAS, Novosibirsk, Russia G. Ya Budker Institute of Nuclear Physics, Novosibirsk, Russia
	The 4th harmonic cavity has been firstly used in the storage ring for HLS-II. The paper presents the physics design, developing process and the experimental results for commision. The measurment results show that rf parameters are reasonable. The 4th harmonic cavity efficiently lengthen the bunch and increase the beam life-time. Specially, the beam instablity has been supressed.
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MOPOY001	MedAustron Synchrotron RF Commissioning for Medical Proton Beams	injection, acceleration, synchrotron, proton	844
	C. Schmitzer, F. Farinon, A. Garonna, M. Kronberger, T.K.D. Kulenkampff, C. Kurfürst, S. Myalski, S. Nowak, F. Osmić, L.C. Penescu, M.T.F. Pivi, P. Urschütz, A. Wastl EBG MedAustron, Wr. Neustadt, Austria
	MedAustron is a medical accelerator facility for hadron therapy cancer treatment using protons and carbon ions. The Synchrotron is driven by a 0.47-3.26 MHz Finemet® loaded wideband cavity powered by 12x 1kW solid state amplifiers connected to a digital Low Level RF system. It was developed in collaboration with CERN and put to operation at MedAustron in early 2014. The main Synchrotron RF (sRF )commissioning steps for proton beams involved the setup of the adiabatic capture process, the setup of the frequency and voltage ramps and feedback loops for fast acceleration and the RF jump for extraction. The adiabatic capture process was optimized in terms of energy and voltage mismatch by analyzing longitudinal empty bucket scans after beam injection into the synchrotron. The acceleration ramp optimization was based on calculations using a software tool developed in-house and adapted experimentally to minimize losses at injection and during acceleration. This paper provides an overview of the acceleration system and describes the commissioning process of the sRF system and the related beam commissioning efforts at MedAustron.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOY001
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MOPOY006	Preparations for Upgrading the RF Systems of the PS Booster	impedance, operation, feedback, emittance	853
	S.C.P. Albright, D. Quartullo, E.N. Shaposhnikova CERN, Geneva, Switzerland
	The accelerators of the LHC injector chain need to be upgraded to provide the HL-LHC beams. The PS Booster, the first synchrotron in the LHC injection chain, uses three different RF systems (first, second and up to tenth harmonic) in each of its four rings. As part of the LHC Injector Upgrade the current ferrite RF systems will be replaced with broadband Finemet cavities, increasing the flexibility of the RF system. A Finemet test cavity has been installed in Ring 4 to investigate its effect on machine performance, especially beam stability, during extensive experimental studies. Due to large space charge impedance Landau damping is lost through most of the cycle in single harmonic operation, but is recovered when using the second harmonic and controlled longitudinal emittance blow-up. This paper compares beam parameters during acceleration with and without the Finemet test cavity. Comparisons were made using beam measurements and simulations with the BLonD code based on a full PS Booster impedance model. This work, together with simulations of future operation, have provided input for the decision to adopt a fully Finemet RF system.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOY006
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MOPOY019	Status of the First CH-Cavities for the New Superconducting CW Heavy Ion LINAC@GSI	resonance, linac, operation, ion	886
	M. Basten, M. Amberg, M. Busch, F.D. Dziuba, H. Podlech, M. Schwarz IAP, Frankfurt am Main, Germany K. Aulenbacher IKP, Mainz, Germany K. Aulenbacher, W.A. Barth, V. Gettmann, S. Mickat, M. Miski-Oglu HIM, Mainz, Germany W.A. Barth, M. Heilmann, S. Mickat, S. Yaramyshev GSI, Darmstadt, Germany
	In the field of Super Heavy Elements (SHE) a superconducting (sc) continuous wave (cw) high intensity heavy ion LINAC is highly desirable. Currently a multi-stage R&D program conducted by GSI, HIM and IAP* is in progress. The baseline linac design composes a high performance ion source, a new low energy beam transport line, a (cw) upgraded High Charge State Injector (HLI), and a matching line (1.4 MeV/u) followed by the new sc-DTL LINAC for acceleration up to 7.3 MeV/u. The commissioning of the first CH cavity (Demonstrator), in a horizontal cryo module with beam is a major milestone in 2016*. The advanced demonstrator comprises constant-beta sc Crossbar-H-mode (CH) cavities operated at 217 MHz. Presently, the first two sc CH cavities of the advanced demonstrator are under construction at Research Instruments (RI), Bergisch Gladbach, Germany. A string of cavities and focusing elements build from several short CH-cavities with 8 gaps, without girders is recommended. The new design potentially reduces the overall technical risks during the fabrication and the pressure sensitivity through stiffening brackets. The present status of the first two sc cavities will be presented. W.Barth et al., Further R&D for a new Superconducting cw Heavy Ion LINAC@GSI, IPAC'14 **F.Dziuba et al., Measurements on the Superconducting 217 MHz CH Cavity during the Manufacturing Phase, SRF2015
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOY019
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MOPOY022	Further Upgrade Measures at New GSI cw-Linac Demonstrator Setup	solenoid, linac, ion, heavy-ion	892
	M. Heilmann, W.A. Barth, S. Mickat, S. Yaramyshev GSI, Darmstadt, Germany M. Amberg, M. Basten, F.D. Dziuba, H. Podlech, U. Ratzinger, M. Schwarz IAP, Frankfurt am Main, Germany K. Aulenbacher IKP, Mainz, Germany K. Aulenbacher, W.A. Barth, V. Gettmann, S. Mickat, M. Miski-Oglu HIM, Mainz, Germany
	A new continuous wave (cw) linac is required to deliver high intensity heavy ion beams for Super Heavy Element (SHE) future experiments at GSI Darmstadt, Germany. The presented upgrade measures are dedicated to improve the performance of the cw demonstrator setup. The key component is a cryomodule comprising a superconducting (sc) 217 MHz Crossbar-H-mode (CH) cavity surrounded by two sc 9.3T solenoids with compensation coils. The solenoid coil is made of a Nb3Sn wire; and the compensation coils at both ends of the solenoid comprises NbTi wires. The distance between solenoid lense and CH cavity has to be optimized for ideal beam matching as well as for a minimum rest field inside the cavity below the critical magnetic field. The GSI High Charge State (HLI) injector has to deliver a heavy ion beam with an energy of 1.4 MeV/u. Longitudinal matching to the demonstrator is provided by two 10⁸.4 MHz cw room temperature λ/4 re-buncher cavity installed behind the HLI. In this paper electromagnetic simulations of the field optimization for the solenoids and the re-buncher cavities will be presented as well as first beam experiments at the beam transport line to the demonstrator cavity.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOY022
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MOPOY023	Further Steps Towards the Superconducting CW-LINAC for Heavy Ions at GSI	linac, heavy-ion, ion, target	896
	M. Schwarz, M. Basten, M. Busch, F.D. Dziuba, H. Podlech, U. Ratzinger, R. Tiede IAP, Frankfurt am Main, Germany W.A. Barth, V. Gettmann, M. Heilmann, S. Mickat, M. Miski-Oglu, S. Yaramyshev GSI, Darmstadt, Germany W.A. Barth, V. Gettmann, S. Mickat, M. Miski-Oglu HIM, Mainz, Germany
	Funding: Work supported by BMBF contr. No. 05P15RFRBA For future experiments with heavy ions near the coulomb barrier within the super-heavy element (SHE) research project a multi-stage R&D program of GSI, HIM and IAP is currently in progress. It aims at developing a superconducting (sc) continuous wave (cw) LINAC with multiple CH cavities as key components downstream the upgraded High Charge Injector (HLI) at GSI. The LINAC design is challenging, due to the requirement of intense beams in cw-mode up to a mass-to-charge-ratio of 6 while covering a broad output energy range from 3.5 to 7.3 MeV/u with minimum energy spread. The next milestone will be a full performance beam test of the first expansion stage at GSI, the Demonstrator, comprising two solenoids and a 15-gap CH cavity inside a cryostat.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOY023
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MOPOY025	Electromagnetic Design of β=0.13, f=325 Mhz Half-Wave Resonator for Future High Power, High Intensity Proton Driver at KEK	linac, proton, electron, rfq	902
	G.-T. Park, E. Kako, Y. Kobayashi, T. Koseki, S. Michizono, F. Naito, H. Nakai, K. Umemori, S. Yamaguchi KEK, Ibaraki, Japan T. Maruta KEK/JAEA, Ibaraki-Ken, Japan
	At KEK, a proposal is being prepared for a new linac-based proton driver that can accelerate the proton beam up to 9 GeV with 9 MW beam power and 100 mA peak current. In this report, we present the study on the front end design of the linac, which will accelerate the beam to 1.2 GeV: The baseline layout, the acceleration energy structure, RF characteristics of components, cryomodule configurations, and the detailed design of half-wave resonator 1.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOY025
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MOPOY028	Low Power RF Tuning of the CSNS DTL	DTL, linac, insertion, neutron	913
	H.C. Liu, Q. Chen, M.X. Fan, S. Fu, K.Y. Gong, A.H. Li, J. Peng, S. Wang, X. Wu, F.X. Zhao IHEP, Beijing, People's Republic of China B. Li, P.H. Qu, Y. Wang CSNS, Guangdong Province, People's Republic of China
	The China Spallation Neutron Source (CSNS) is an accelerator-based neutron source being built at dongguan, Guangdong province in China. A conventional 324MHz Alvarez-type Drift tube linac (DTL) is utilized to accelerate an H⁻ ion beam from 3MeV to 80MeV. The RF field tuning of DTL is necessary for compensating the unexpected error caused by manufacturing and assembling. For reasons of RF power saving it is convenient to build a long DTL tank, but this choice involves risks of accelerating field instability. This problem can be fixed by using the resonant coupling stabilization method and equipping DTL cavities with a series of post-couplers. A practical tuning method was proposed, an acceptable field distribution with a good stability was achieved for CSNS DTL-1.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOY028
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MOPOY030	Superconducting Cavity Phase and Amplitude Measurement in Low Energy Accelerating Section	LLRF, linac, beam-transport, superconducting-cavity	919
	C. Meng, H. Geng, F. Yan, Y.L. Zhao IHEP, Beijing, People's Republic of China
	Superconducting linear accelerator is the tendency in linac design with the development of superconducting RF technology. Superconducting cavities used as accelerating section in low energy Hadron linac are more and more common. The 5MeV test stand of CADS accelerator Injector I is composed of an ion source, a LEBT, a 325MHz RFQ, a MEBT, a cryogenic module (CM1) of seven SC spoke cavities (β=0.12) , seven SC solenoids, seven cold BPMs and a beam dump. The phase and amplitude setting of superconducting cavity are very important at the operation of accelerator, so beam based measurement of cavity phase and amplitude is necessary. Beam based phase scan is the most simple and effective method. Because the significant velocity changes in superconducting cavity at low energy section, the effective voltage is changing with cavity phase, meanwhile the synchronous phase is non-linear with LLRF phase. Above two problem make the cavity phase determination difficult. New date fitting method is proposed to solve these problem in this paper. Some measurements of spoke cavities in the CADS CM1 are also presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOY030
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MOPOY033	Design Study on an Injector RFQ for Heavy Ion Accelerator Facility	rfq, simulation, ion, heavy-ion	928
	W. Ma, Y. He, L. Lu, X.B. Xu, Z.L. Zhang, H.W. Zhao IMP/CAS, Lanzhou, People's Republic of China
	A Low Energy Accelerator Facility (LEAF) was launched as a pre-research facility for High Intensity heavy ion Accelerator Facility (HIAF). The LEAF consists of a 2-mA U³⁴⁺ electron cyclotron resonance (ECR) type ion source with 300-kV extraction voltage, a low energy beam transport (LEBT) line with a multi-harmonic buncher (MHB), a CW 81.25MHz radio frequency quad-rupole (RFQ) accelerator which could accelerate heavy ions from 14 keV/u up to 500 keV/u, a triplet magnet for medium energy beam transport and an experimental platform for nuclear physics. After describing the selected structure, an octagonal cavity with π-mode stabilizing loop (PISL) type structure was adopted and simulated. In this paper, the detailed electromagnetic design and ther-mal simulation of the LEAF-RFQ will be reported.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOY033
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MOPOY038	Studies for Tuning Algorithm of Superconducting Cavity Amplitude and Phase in the RAON Accelerator	linac, GUI, simulation, interface	932
	H. Jin, J.-H. Jang IBS, Daejeon, Republic of Korea
	The RAON accelerator utilizes the low energy and high energy superconducting linacs for the acceleration of the stable ion beams and the rare isotope beams. The low energy superconducting linac is composed of the quarter-wave resonator (QWR) and the half-wave resonator (HWR) cavities, and the high energy superconducting linac consists of two kinds of single-spoke resonator (SSR) cavities. In the beam commissioning, the tuning of these superconducting cavities is a significant issue to achieve the targeted beam energy and to avoid the deterioration of the beam quality. In this paper, we will present the tuning program based on the phase scan tuning algorithm for the superconducting cavity amplitude and phase in the RAON accelerator and describe the simulation results.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOY038
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MOPOY039	Progress on Superconducting Linac for the RAON Heavy Ion Accelerator	cryomodule, linac, ion, electron	935
	H.J. Kim, H.C. Jung, W.K. Kim IBS, Daejeon, Republic of Korea
	The RISP (Rare Isotope Science Project) has been proposed as a multi-purpose accelerator facility for providing beams of exotic rare isotopes of various energies. It can deliver ions from proton to uranium. Proton and uranium ions are accelerated upto 600 MeV and 200 MeV/u respectively. The facility consists of three superconducting linacs of which superconducting cavities are independently phased. Requirement of the linac design is especially high for acceleration of multiple charge beams. In this paper, we present the RISP linac design, the prototyping of superconducting cavity and cryomodule.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOY039
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MOPOY042	The Perspective of Jinr Lu-20 Replacement by a Superconducting Linac	linac, simulation, proton, ion	944
	S.M. Polozov, M. Gusarova, T. Kulevoy, M.V. Lalayan, A.V. Samoshin, S.E. Toporkov MEPhI, Moscow, Russia M.A. Baturitski BSU, Minsk, Belarus A.V. Butenko, V. Monchinsky, A.O. Sidorin, G.V. Trubnikov JINR, Dubna, Moscow Region, Russia G. Kropachev, T. Kulevoy ITEP, Moscow, Russia A.A. Marysheva, V.S. Petrakovsky, I.L. Pobol, A.I. Pokrovsky, S.V. Yurevich, A.Yu. Zhuravsky Physical-Technical Institute of the National Academy of Sciences of Belarus, Minsk, Belarus
	The new accelerator complex Nuclotron-based Ion Collider fAcility (NICA) is now under development and construction at JINR. Existing Alvarez-type DTL linac LU-20 is now operates as injector of light ions, polarized protons and deuterons to Nuclotron for LHEP experimental program. It provides proton beam of 20 MeV energy and light ions of 5 MeV/u energy. In 2015 the cascade transformer 800 kV which is pre-accelerator of LU-20 had been replaced by the new RFQ linac (energy 155 keV for ions with Z/A<0.5). The proposal on Alvarez linac LU-20 upgrade by a superconducting light ion linac with energy up to 50 MeV is discussed in this report.
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MOPOY050	Beam Commissioning Plan of the FRIB Superconducting Linac	linac, operation, optics, simulation	961
	Y. Zhang, C.P. Chu, Z.Q. He, M. Ikegami, S.M. Lidia, S.M. Lund, F. Marti, G. Shen, Y. Yamazaki, Q. Zhao FRIB, East Lansing, Michigan, USA
	Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 The FRIB superconducting linac will deliver all heavy ion beams with energy above 200 MeV/u, and beam power on target up to 400 kW for generation of short lived isotopes. Beam commissioning is the first step to prepare and tune the superconducting linac for high power operation. A staged beam commissioning plan of the FRIB linac is developed, and complete beam tuning practices segment by segment through the entire linac are introduced, which include phase scan signature matching of the superconducting cavities, longitudinal beam matching, transverse matching with horizontal-vertical beam coupling, and beam optics corrections of achromatic and isochronous folding segments up to the second order for acceleration and transport of multi charge state beams.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOY050
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MOPOY051	Manufacturing and the LLRF Tests of the SANAEM RFQ	rfq, vacuum, LLRF, simulation	964
	G. Turemen, Y. Akgun, A. Alacakir, A.S. Bolukdemir, I. Kilic, B. Yasatekin TAEK - SANAEM, Ankara, Turkey G. Unel UCI, Irvine, California, USA H. Yildiz Istanbul University, Istanbul, Turkey
	Funding: Turkish Atomic Energy Authority Turkish Atomic Energy Authority is working on building an experimental proton beamline with local resources at the Saraykoy Nuclear Research and Training Center (SANAEM). Manufacturing of the radio frequency quadrupole (RFQ) was started after the beam dynamics and 3D electromagnetic simulation studies were performed. The vanes were machined with a three axis CNC machine. A CMM was used for the acceptance tests of the vanes and also for assembling. Production and assembly results were found acceptable for this cavity, the very first one developed in Turkey. Copper plating was performed by electroplating the aluminum vanes. The plated vanes were bolted and bonded with eight screws, eight pins and two different adhesives. A silver paste was used for RF sealing and a low vapor pressure epoxy was used for vacuum isolation. First LLRF tests of the RFQ were done with a bead-pull setup and a VNA. A N-type RF coupler and a pick-up were used for the LLRF tests. Phase shift method was used for the bead-pull tests. Cavity quality factor was measured with 3dB method for different RF sealing stages. This study summarizes the machining, assembling and the first LLRF tests of the SANAEM RFQ.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOY051
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MOPOY054	Status of the ESS RFQ	rfq, vacuum, status, operation	974
	D. Chirpaz-Cerbat, A. Albéri, A.C. Chauveau, M. Lacroix, N. Misiara, G. Perreu, O. Piquet, H. Przybilski, N. Sellami CEA/IRFU, Gif-sur-Yvette, France N. Berton, G. Bourdelle, M. Desmons, A.C. France, V.M. Hennion, P.-A. Leroy, B. Pottin CEA/DSM/IRFU, France
	The ESS Radio-Frequency Quadrupole (RFQ) is a 4-vanes resonant cavity designed at the frequency of 352.21 MHz. It must accelerate and bunch a 70mA proton beams from 75keV to 3.62MeV with a 4% duty cycle. The RFQ design has already been done, and documented in other papers. This one will present the global status of the RFQ, with technical solutions cho-sen for the main components (for fabrication and op-eration) and the present status of the RFQ fabrication.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOY054
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TUOCA02	APEX Phase-II Commissioning Results at the Lawrence Berkeley National Laboratory	gun, electron, linac, space-charge	1041
	F. Sannibale, J.A. Doyle, J. Feng, D. Filippetto, G.L. Harris, M.J. Johnson, T.D. Kramasz, D. Leitner, C.E. Mitchell, J.R. Nasiatka, H.A. Padmore, H.J. Qian, H. Rasool, J.W. Staples, S.P. Virostek, R.P. Wells, M.S. Zolotorev LBNL, Berkeley, California, USA S.M. Gierman, R.K. Li, J.F. Schmerge, T. Vecchione, F. Zhou SLAC, Menlo Park, California, USA C. Pagani, D. Sertore INFN/LASA, Segrate (MI), Italy
	Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231 Science needs in the last decade have been pushing the accelerator community to the development of high repetition rates (MHz/GHz-class) linac-based schemes capable of generating high brightness electron beams. Examples include X-ray FELs; ERLs for light source, electron cooling and IR to EUV FEL applications; inverse Compton scattering X-ray or gamma sources; and ultrafast electron diffraction and microscopy. The high repetition rate requirement has profound implications on the technology choice for most of the accelerator parts, and in particular for the electron gun. The successful performance of the GHz room-temperature RF photo-injectors running at rates <~ 100 Hz, cannot be scaled up to higher rates because of the excessive heat load that those regimes would impose on the gun cavity. In response to this gun need, we have developed at Berkeley the VHF-Gun, a lower-frequency room-temperature RF photo-gun capable of CW operation and optimized for the performance required by MHz-class X-ray FELs. The Advanced Photo-injector EXperiment (APEX) was funded and built for demonstrating the VHF gun performance, and the results of its last phase of commissioning are presented.
	Slides TUOCA02 [12.015 MB]
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TUOAB03	Transverse Coherent Instabilities in Storage Rings with Harmonic Cavities	synchrotron, radio-frequency, impedance, simulation	1061
	F.J. Cullinan, R. Nagaoka SOLEIL, Gif-sur-Yvette, France G. Skripka, P.F. Tavares MAX IV Laboratory, Lund University, Lund, Sweden
	Many current and future synchrotron light sources employ harmonic cavities to lengthen the electron bunches in order to reduce the emittance dilution caused by intrabeam scattering. In some cases, the harmonic cavities may be tuned to fulfill the flat potential condition. For this condition, a large increase in the threshold currents of transverse coupled-bunch instabilities has been predicted and recently, the physical content behind this stabilization has been better understood. With this in mind, an investigation is made into the effectiveness of harmonic cavities for different machines. Frequency domain computations employing Laclare's eigenvalue method have been used to investigate the influence of several machine parameters and the results are presented.
	Slides TUOAB03 [14.037 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUOAB03
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TUOCB02	Low Secondary Electron Yield of Laser Treated Surfaces of Copper, Aluminium and Stainless Steel	electron, laser, framework, photon	1089
	R. Valizadeh, P. Goudket, O.B. Malyshev, B.S. Sian, S. Wang STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom M.D. Cropper, S. Wang Loughborough University, Loughborough, Leicestershire, United Kingdom P. Goudket Cockcroft Institute, Warrington, Cheshire, United Kingdom B.S. Sian UMAN, Manchester, United Kingdom N. Sykes Micronanics Laser Solution Center, Didcot, United Kingdom
	Funding: STFC Reduction of SEY was achieved by surface engineering through laser ablation with a laser operating at • = 355 nm. It was shown that the SEY can be reduced to near or below 1 on copper, aluminium and 316LN stainless steel. The laser treated surfaces show an increased surface resistance, with a wide variation in resistance found de-pending on the exact treatment details. However, a treated copper surface with similar surface resistance to aluminium was produced.
	Slides TUOCB02 [94.339 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUOCB02
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TUPMB046	The Preliminary Conceptual Design of a 2k Cryogneic System for Circular Electron Positron Collider (CEPC)	cryogenics, collider, booster, cryomodule	1199
	Y.P. Liu, L. Bian, R. Ge, R. Han, S.P. Li, M.J. Sang, L.R. Sun, M.F. Xu, R. Ye, J.Q. Zhang, J.H. Zhang, X.Z. Zhang, Z.Z. Zhang IHEP, Beijing, People's Republic of China
	The Circular Electron Positron Collider (CEPC) is a long-term collider project, which will serve as a Higgs Factory and offer a unique opportunity for direct searches for New Physics in the high-energy range far beyond LHC reach [1]. In the frame of this project, a large 2K cryogenic system will be built to provide coolant for superconducting cavities used in booster ring and collider ring. All the superconducting cavities will be working under 2K. This paper will give a brief introduction to the preliminary considerations of this large cryogenic system, including the general layout, heat load estimation, helium refrigerator, schematic flow diagram as well as the main parameters and working process
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TUPMR011	Development of Optimized RF Cavity in 10 MeV Cyclotron	network, cyclotron, simulation, resonance	1250
	M. Mohamadian, H. Afarideh, M. Salehi AUT, Tehran, Iran J.-S. Chai, M. Ghergherehchi SKKU, Suwon, Republic of Korea
	Cyclotron cavity modelled by an artificial neural net-work, which is trained by our optimized algorithm. The training samples are obtained from simulation results, which are done by MWS CST software for some defined situation and parameters, and also with the conventional BP algorithm. It is shown that the optimized FFN can estimate the cyclotron model parameters with acceptable outputs. Hence, the neural network trained by this algorithm represents the proper estimation and acceptable ability to our structure modelling. The cyclotron cavity parameter modelling illustrate that the neural network trained by this algorithm could be the acceptable method to design parameters.
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TUPMR015	Cooling and Heat Transfer of the IRANCYC-10 Transmission Line	impedance, simulation, cyclotron, factory	1259
	S. Sabounchi, H. Afarideh, M. Mohamadian, M. Salehi AUT, Tehran, Iran J.-S. Chai, M. Ghergherehchi SKKU, Suwon, Republic of Korea
	Heat transfer study for designing RF transmission line in cyclotrons is crucial. Because of enormous amount of surface current on RF transmission line, despite high conductivity of copper, significant amount of heat is being generated, which is enough for altering characteristic impedance and other desirable parameters for transmission line. So, effective cooling system which is nourished by central chiller system is essential. For design of cooling system in RF transmission line suitable mass flow, appropriate geometry and confined temperatures are prominent in order to avoid eroding and impedance changing. In this paper an attempt has been done for accurate analyzing and simulating of heat transfer phenomenon for the 10MeV cyclotron (IRANCYC-10 ) which is under construction at AmirKabir University of Technology. By using Ansys CFX simulation software, the optimum cooling line geometry and mass flow rate of 90 gr/s for cooling water, has been resulted.

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MOOCA01

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

operation, coupling, impedance, FEL

39

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

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

Slides MOOCA01 [20.278 MB]

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MOOCA02

RFQ Developments at CEA-IRFU

rfq, linac, proton, status

42

O. Piquet
CEA/DSM/IRFU, France

Vane RFQs are particularly well suited to high intensity proton acceleration, since they offer minimal RF power losses and best accelerating field accuracy. Cea-Irfu is involved in several developments of 4 vane RFQs namely IPHI, Spiral2, Linac4 and ESS. This paper gives an overview of the design flow and tools developed at Irfu in order to design, tune, condition and commission RFQs. SPIRAL2 RFQ will be mainly used to illustrate this design flow. This CW RFQ requires 180 kW to achieve the nominal accelerating voltage. It can accelerate a 5 mA proton or deuteron beam (A/Q=1 and 2) or a 1 mA ion beam with up to A/Q=3 at 0.75 MeV/A. Conditioning and commissioning of this RFQ are actually in progress.

Slides MOOCA02 [3.712 MB]

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MOPMB005

Study of Short Bunches at the Free Electron Laser CLIO

radiation, electron, gun, simulation

78

V. Khodnevych, N. Delerue, S. Jenzer
LAL, Orsay, France
J.P. Berthet, F. Glotin, J.-M. Ortega, R. Prazeres
CLIO/ELISE/LCP, Orsay, France
V. Khodnevych
National Taras Shevchenko University of Kyiv, The Faculty of Physics, Kyiv, Ukraine

Funding: The authors are grateful for the funding received from the French ANR (contract ANR-12-JS05-0003-01).
CLIO is a Free Electron Laser based on a thermionic electron gun. In its normal operating mode it delivers electron 8 pulses but studies are ongoing to shorten the pulses to about 1 ps. We report on simulations showing how the pulse can be shortened and the expected signal yield from several bunch length diagnostics (Coherent Transition Radiation, Coherent Smith Purcell Radiation).

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MOPMB032

A New Fault Recovery Mechanism for Superconducting Cavity Failure in C-ADS

FPGA, hardware, space-charge, linac

158

Z. Xue, J.P. Dai, C. Meng
IHEP, Beijing, People's Republic of China

For proton linear accelerators used in applications such as C-ADS, due to the nature of the operation, it is essential to have beam failures at the rate several orders of magnitude lower than usual performance of similar accelerators. A fault-tolerant mechanism should be mandatorily imposed in order to maintain short recovery time, high uptime and extremely low frequency of beam loss. This paper proposes an innovative and challenging way for compensation and rematch of cavity failure using fast electronic devices and Field Programmable Gate Array (FPGA) instead of embedded computers to complete the computation of beam dynamics. Due to the high arithmetic-computing-speed, good portability and repeatability, it is possible to realize calculation and re-adjustment online. In order to achieve the goal of instantaneous compensation and rematch, an advanced hardware design methodology including high-level synthesis and an improved genetic algorithm will be used.

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MOPMB040

Design of the Beam Diagnostics System for a New IR-FEL Facility at NSRL

diagnostics, FEL, laser, emittance

181

J.H. Wei, X.Y. Liu, P. Lu, B.G. Sun, L.L. Tang, F.F. Wu, Y.L. Yang, T.Y. Zhou, Z.R. Zhou
USTC/NSRL, Hefei, Anhui, People's Republic of China

Funding: Work supported by National Natural Science Foundation of China (21327901, 11105141, 11575181)
A new IR-FEL has been commissioned at NSRL. This facility provides a final electron energy from 20 to 70 MeV, beam bunch with a macro-pulse length of 5~10 μs and a general micro-pulse repetition rate of 238 MHz, pulsed radiation with up to 100 mJ at about 0.3%~3% FWHM bandwidth. So a diagnostics system is necessary to monitor the performance of the bunch and the character of the FEL radiation, such as the beam position and profile, emittance, energy spread, laser intensity, etc. The beam diagnostics system mainly consists of Flags, a diagnostics beam line, BPMs, pop-in monitors and a FEL monitor system. This paper introduces the construction of this diagnostics system.
Corresponding author: ylyang@ustc.edu.cn

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MOPMB046

Design and Calculation Error Analysis of a High Order Mode Cavity Bunch Length Monitor

positron, simulation, linac, electron

196

J.G. Guo, Q. Luo, Z.R. Zhou
USTC/NSRL, Hefei, Anhui, People's Republic of China

Funding: National Science Foundation of China (11375178) and Fundamental Research Funds for the Central Universities (WK2310000046).
A two-cavity bunch length monitor for linac of positron source is designed. Fifth harmonic cavity resonates at 14.28 GHz (fifth harmonic of the linac fundamental frequency 2.856 GHz) with mode TM020, as this mode could provide larger cavity radius. Each cavity equipped with a filter to suppress unwanted signal. An improved bunch length calculation method was proposed. A simulation was conducted in CST Particle Studio for beam current from 100-300 mA, bunch length from 5-10 ps. Bunch length was calculated and compared by these two methods

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MOPMB049

Beam Experiment of Low Q CBPM Prototype for SXFEL

simulation, HOM, electron, FEL

202

J. Chen, L.W. Lai, Y.B. Leng, L.Y. Yu, R.X. Yuan
SINAP, Shanghai, People's Republic of China

To meet the high resolution beam position measurement requirement of micron or sub-micron for shanghai soft X-ray free electron laser (SXFEL) under construction, the cavity beam position monitor (CBPM) operating at C-band and the corresponding electronic has been designed by SINAP. In this paper, the design and optimize of the newly low Q cavity BPM is mentioned, the beam test was conducted on the Shanghai Deep ultraviolet free electron laser (SDUV-FEL) facility. CBPM signal processors including broadband oscilloscope and home-made digital BPM processor have been used to evaluate the system performance as well. The beam experimental result, which matched with MAFIA simulation very well, will be presented and discussed in this paper.

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MOPMB051

Cavity BPM Performance Online Evaluation using PCA Method

experiment, electron, factory, coupling

208

Y.B. Leng, L.W. Lai, L.Y. Yu, R.X. Yuan
SSRF, Shanghai, People's Republic of China
J. Chen, Z.C. Chen
SINAP, Shanghai, People's Republic of China

Funding: NSFS 11575282
This article proposes a new test method to evaluate the performance of cavity beam position monitors using the actual beam as the exciting signal. The new method sepa-rates the signals of different modes and improves the measurement accuracy by eliminating unwanted cou-plings from other sources.

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MOPMB058

Bunch Arrival Time Monitor Test at PAL-XFEL ITF

pick-up, LLRF, simulation, resonance

223

J.H. Hong, J.H. Han, C. Kim, H. Yang
PAL, Pohang, Kyungbuk, Republic of Korea

Femtosecond resolution electron bunch arrival time monitor (BAM) will be required for the beam-based RF phase feedback during PAL-XFEL operation. Two S-band cavity-type BAMs were manufactured for the test at the PAL-XFEL injector test facility (ITF). The resonance frequencies of the cavities are 2856 MHz and 2826.25 MHz. Electron beam induced signal from the cavities was digitized using a low level RF (LLRF) module. In this paper, the resolution of these cavities are analyzed and a possible improvement for better resolution are discussed.

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MOPMR001

Micro-mover Development and Test in the PAL-XFEL

solenoid, electron, gun, controls

229

B.G. Oh, J.H. Han, H. Heo, J.H. Hong, H.-S. Kang, C. Kim, D.E. Kim, K.-H. Park, Y.J. Suh
PAL, Pohang, Kyungbuk, Republic of Korea

Two micro-movers, which are able to control the horizontal, vertical and longitudinal positions as well as the yaw and pitch angles remotely, were developed and installed in the PAL-XFEL linac. The solenoid micro-mover in the gun section allows beam-based alignment of an electron beam to the solenoid field and the gun RF field. The X-band cavity micro-mover minimizes the transverse wake field effect caused by transverse misalignment between the beam and X-band cavity. Two micro-movers has similar specifications and the same mechanism, but the sizes are different from each other. In this paper, we present the design, manufacture and test results of the micro-movers.

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MOPMR017

Design and Simulations of the Cavity BPM Readout Electronics for the ELI-NP Gamma Beam System

electron, electronics, simulation, linac

264

M. Cargnelutti, B.B. Baricevic
I-Tech, Solkan, Slovenia
A. Mostacci
University of Rome La Sapienza, Rome, Italy
S. Pioli, M. Serio, A. Stella, A. Variola
INFN/LNF, Frascati (Roma), Italy

The Extreme Light Infrastructure - Nuclear Physics (ELI-NP) facility will provide a high intensity laser and a very intense gamma beam which will be used in a broad range of experiments. The gamma beam is obtained through incoherent Compton back-scattering of a laser light off a high brightness electron beam provided by a 700MeV warm LINAC. Electrons are accelerated in trains with up to 32 bunches, each one separated by 16ns. In the laser-electron interaction region, every bunch needs to be monitored with a resolution below 1μm RMS. To achieve this performance, a low-Q cavity beam position monitor will be used in combination with a dedicated data acquisition system able to perform bunch-by-bunch beam position measurements with sub-μm resolution. Using fast A/D converters and specific digital filtering, the readout system proposes an alternative measurement concept. The requirements of the system, its design and the results from the simulations will be presented.

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MOPMR024

A Versatile Beam Loss Monitoring System for CLIC

electron, quadrupole, beam-losses, background

286

M. Kastriotou, S. Döbert, W. Farabolini, E.B. Holzer, E. Nebot Del Busto, F. Tecker
CERN, Geneva, Switzerland
M. Kastriotou, E. Nebot Del Busto, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
M. Kastriotou, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom

The design of a potential CLIC beam loss monitoring (BLM) system presents multiple challenges. To successfully cover the 48 km of beamline, ionisation chambers and optical fibre BLMs are under investigation. The former fulfils all CLIC requirements but would need more than 40000 monitors to protect the whole facility. For the latter, the capability of reconstructing the original loss position with a multi-bunch beam pulse and multiple loss locations still needs to be quantified. Two main sources of background for beam loss measurements are identified for CLIC. The two-beam accelerator scheme introduces so-called crosstalk, i.e. detection of losses originating in one beam line by the monitors protecting the other. Moreover, electrons emitted from the inner surface of RF cavities and boosted by the high RF gradients may produce signals in neighbouring BLMs, limiting their ability to detect real beam losses. This contribution presents the results of dedicated experiments performed in the CLIC Test Facility to quantify the position resolution of optical fibre BLMs in a multi-bunch, multi-loss scenario as well as the sensitivity limitations due to crosstalk and electron field emission.

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MOPMR035

Bunch Length Measurements using a Transverse Deflecting Cavity on VELA

gun, laser, electron, simulation

323

J.W. McKenzie, S.R. Buckley, L.S. Cowie, P. Goudket, M. Jenkins, B.L. Militsyn, A.J. Moss, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
A. Wolski
The University of Liverpool, Liverpool, United Kingdom

The VELA facility at Daresbury Laboratory in the UK includes a 5 MeV/c 2.5 cell S-band photoinjector gun. This gun operates in the "blow-out" regime with a sub-200 fs length drive laser: the resulting bunch length is determined by space-charge effects. We present measurements made with an S-band transverse deflecting cavity to characterise the bunch length as a function of charge, and as a function of the gun operating phase.

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MOPMR037

Analysis of Asymmetry Tolerances and Cross-coupling in Cavity BPMs

coupling, alignment, simulation, dipole

331

E. Yamakawa, S.T. Boogert, A. Lyapin, L.J. Nevay
JAI, Egham, Surrey, United Kingdom
S. Syme
FMB Oxford, Oxford, United Kingdom

Geometric asymmetries in cavity BPMs result in a coupling between horizontal and vertical signals, which complicates their usage and may affect both the dynamic range and spatial resolution of the system in both directions. Tolerances to several types of geometric asymmetries have been analysed using a 3D electromagnetic field solver (GdfidL). We report on some of the results and discussed the possible impact of the considered geometrical distortions.

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MOPMR060

C-Band Deflecting Cavity for Bunch Length Measurement of 2.5 MeV Electron Beam

vacuum, electromagnetic-fields, coupling, simulation

386

J. Jiang, H.B. Chen, J. Shi, P. Wang, L. Zhang, S.X. Zheng
TUB, Beijing, People's Republic of China

The C-band deflecting cavity designed last year is finished. In this paper, the RF measurement of the cavity is introduced. After tuning, it works well at 5.712GHz with a coupling factor degree around 1.05. And we measured the electromagnetic field with bead-pull method. The flatness of the magnetic field is around 0.9, which is not ideal but meet the requirements of the bunch length measurement. And we propose a method of tuning to make sure both frequency and field flatness.

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MOPMW001

A New Buncher for the ESRF Linac Injector

linac, electron, beam-loading, gun

389

A.S. Setty, A.S. Chauchat, D. Jousse
Thales Communications & Security (TCS), Gennevilliers Cedex, France
H. Delamare, J. Jacob, B. Ogier, T.P. Perron, E. Rabeuf, C. Richard, V. Serrière, R. Versteegen
ESRF, Grenoble, France

The electron linac was designed to be able to deliver more than 2.5 A in less than 2 ns at 200 MeV within an energy spread of 1% for positrons production at ESRF *. The 200 MeV electron linac was commissioned in 1991. A new gun, a cleaner, a pre-buncher cavity and 4 shielded lenses were tested and installed on the injector in 2008 **. Then, a new Buncher for the ESRF electron linac injector was manufactured and commissioned in 2015. Meanwhile, some new settings were performed to reduce the energy spread for both cases: the long pulse mode and the short pulse mode. The simulations and measurements will be presented.
* D. Tronc et Al. "Electron injector for light source", Proc. EPAC88, Italy, Rome, June 1988.
** T. Perron et Al. "New preinjector for the ESRF booster", Proc. EPAC08, Italy, Genoa, June 2008.

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MOPMW002

Modeling and Simulation of Broadband RF Cavities in PSpice

simulation, coupling, impedance, storage-ring

392

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

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

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MOPMW003

Thermal Simulation of an Energy Feedback Normal Conducting RF Cavity

coupling, simulation, operation, electron

396

M. Fakhari, K. Flöttmann, S. Pfeiffer, H. Schlarb
DESY, Hamburg, Germany
J. Roßbach
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
A. Yahaghi
CFEL, Hamburg, Germany

Thermal simulation has been performed for an energy feedback normal conducting RF cavity. The cavity is going to be used as a fast actuator to regulate the arrival time of the electron bunches in fs level in FLASH. By measuring the arrival time jitter of one bunch in a bunch train, the designed cavity apply a correcting accelerating or decelerating voltage to the next bunches. The input power of the cavity is provided by a solid state amplifier and will be coupled to the cavity via a loop on the body. To achieve the fs level precision of the arrival time, the cavity should be able to provide accurate accelerating voltage with a precision of 300 eV. We performed thermal simulation to find out the temperature distribution of the cavity and make sure that heating will not affect its voltage precision. The simulation results show that by using two input loops the coupling constant will vary from 4.11 to 4.13 during the operation of the cavity which effect on the bunchs' arrival time would be less than 0.25 fs. While using just one input loop can lead to an error of about 1 fs.

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MOPMW010

Property Test of the Q-Factor for High Purity Copper at the Temperature of 20K

electron, linac, radiation, cryogenics

417

A. Iino
Sokendai, Ibaraki, Japan
K. Endo
TOYAMA Co., Ltd., Zama-shi, Kanagawa, Japan
S. Yamaguchi
KEK, Ibaraki, Japan

A coherent parametric x-ray radiation (PXR) source based on a cryogenic electron linac has been developed by Toyama Co., Ltd, KEK and Nihon University. This accelerator is a C-band normal-conducting compact linac that requires a high Q factor in the accelerating and de-celerating structures. To obtain a high Q factor, the ac-celerating and decelerating structures are operated around 20 K, and are joined by diffusion bonding and are constructed with high-purity 6N8 copper which has very low resistivity in extremely low temperatures. In this study, we report the measurements and calculation of the residual resistance ratio (RRR) for 6N8 copper and oxy-gen-free copper (Class 1) as well as the Q factor for a pillbox cavity made of 6N8 copper and Class 1. The results of a low-power test of this accelerating structure at low temperature are reported. The Q factor for a 6N8 copper pillbox cavity is not much higher than that of a Class 1 pillbox cavity at low temperatures Moreover, the Q factor is saturated when RRR is greater than 500.

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MOPMW011

The Second Harmonic RF System for J-PARC MR Upgrade

impedance, injection, operation, proton

420

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

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

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MOPMW012

Study for a 162.5 MHz Window-Type RFQ

rfq, Windows, simulation, dipole

423

Q. Fu, P.P. Gan, S.L. Gao, F.J. Jia, H.P. Li, J. Liu, Y.R. Lu, Z. Wang, K. Zhu
PKU, Beijing, People's Republic of China

A window type of four vane radio-frequency quadrupole accelerator has been designed to accelerate 50 mA deuteron beam from 50 keV to 1 MeV. It will operate at 162.5 MHz in CW mode. Compared to the traditional four-vane RFQ, the window-type RFQ is more compact and has higher mode separation without π-mode stabilizing loops or dipole rods. A detailed full 3D model including vane modulation was developed. For the purpose of high shunt impedance, high quality factor and low power dissipation, the RF structure design was optimized by using electromagnetic simulations. Following the EM design optimization, an aluminium model of the window-type RFQ was fabricated and tested.

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MOPMW015

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

wakefield, impedance, simulation, FEL

429

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

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

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MOPMW023

Optimization of the RF Cavity of a Low-energy Storage Ring for Thomson Scattering X-Ray Source

HOM, storage-ring, coupling, higher-order-mode

438

L. Ovchinnikova, V.I. Shvedunov
SINP MSU, Moscow, Russia
A. Ryabov
IHEP, Moscow Region, Russia
V.I. Shvedunov
LEA MSU, Moscow, Russia

Results of optimization of the RF cavity of a low-energy storage ring for Thomson scattering X-ray source are presented. The geometry of 714 MHz RF cavity was optimized to provide maximum shunt impedance taking into account position of higher order modes (HOMs). The number and position of cooling channels were adjusted to minimize frequency shift due to cavity thermal deformations. The waveguide coupler and frequency tuner were calculated. Special attention was paid to detailed calculations of the HOMs parameter and to study of methods to minimize their influence on the storage ring beam dynamics.

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MOPMW025

Vacuum RF Breakdown of Accelerating Cavities in Multi-Tesla Magnetic Fields

vacuum, operation, Windows, electron

444

D.L. Bowring, A. Moretti, M.A. Palmer, D.W. Peterson, A.V. Tollestrup, K. Yonehara
Fermilab, Batavia, Illinois, USA
B.T. Freemire
IIT, Chicago, Illinois, USA
A.V. Kochemirovskiy
University of Chicago, Chicago, Illinois, USA
P.G. Lane, Y. Torun
Illinois Institute of Technology, Chicago, Illinois, USA

Funding: Work supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359.
Ionization cooling of intense muon beams requires the operation of high-gradient, normal-conducting RF structures within multi-Tesla magnetic fields. The application of strong magnetic fields has been shown to lead to an increase in vacuum RF breakdown. This phenomenon imposes operational (i.e. gradient) limitations on cavities in ionization cooling channels, and has a bearing on the design and operation of other RF structures as well, such as photocathodes and klystrons. We present recent results from Fermilab's MuCool Test Area (MTA), in which 201 and 805 MHz cavities were operated at high power both with and without the presence of multi-Tesla magnetic fields. We present an analysis of damage due to breakdown in these cavities, as well as measurements related to dark current and their relation to a conceptual model describing breakdown phenomena.

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MOPMW026

Resonant Control for Fermilab's PXIE RFQ

rfq, controls, operation, resonance

447

D.L. Bowring, B.E. Chase, J. Czajkowski, J.P. Edelen, D.J. Nicklaus, J. Steimel, T.J. Zuchnik
Fermilab, Batavia, Illinois, USA
S. Biedron, A.L. Edelen, S.V. Milton
CSU, Fort Collins, Colorado, USA

Funding: Work supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359.
The RFQ for Fermilab's PXIE test program is designed to accelerate a < 10 mA H⁻ CW beam to 2.1 MeV. The RFQ has a four-vane design, with four modules brazed together for a total of 4.45 m in length. The RF power required is < 130 kW at 162.5 MHz. A 3 kHz limit on the maximum allowable frequency error is imposed by the RF amplifiers. This frequency constraint must be managed entirely through differential cooling of the RFQ's vanes and outer body and associated material expansion. Simulations indicate that the body and vane coolant temperature should be controlled to within 0.1 degrees C. We present the design of the cooling network and the resonant control algorithm for this structure, as well as results from initial operation.

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MOPMW027

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

booster, Windows, impedance, cathode

451

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

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

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MOPMW028

Progress on the MICE RF Module at LBNL

vacuum, operation, coupling, experiment

454

T.H. Luo, A.J. DeMello, A.R. Lambert, D. Li, T.J. Loew, S. Prestemon, S.P. Virostek, J.G. Wallig
LBNL, Berkeley, California, USA
T.G. Anderson, A.D. Bross, M.A. Palmer
Fermilab, Batavia, Illinois, USA
Y. Torun
IIT, Chicago, Illinois, USA

The international Muon Ionization Cooling Experiment aims to demonstrate the transverse cooling of a muon beam by ionization in energy absorbers. The final MICE cooling channel configuration has two RF modules, each housing a 201 MHz RF cavity used to compensate the longitudinal energy loss in the absorbers. The assembly of MICE RF Module is being carried out at LBL. In this paper we will report the recent progress on the assembly work.

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MOPMW029

Analysis of Transverse Field Induced by Curved Beryllium Window in Muon Ionization Cooling Cavity

emittance, Windows, acceleration, focusing

457

T.H. Luo, D. Li
LBNL, Berkeley, California, USA

The beryllium windows are used in muon ionization cooling cavity to increase the cavity shunt impedance. The windows are curved for predictable thermal deformation. This curvature also introduces transverse field, which will affect the transverse beam emittance. In this paper, we will analyze this transverse field and evaluate its effect on the emittance cooling.

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MOPMW030

High Powered Tests of Dielectric Loaded High Pressure RF Cavities for Use in Muon Cooling Channels

accelerating-gradient, radio-frequency, plasma, experiment

460

B.T. Freemire
IIT, Chicago, Illinois, USA
D.L. Bowring, A. Moretti, D.W. Peterson, A.V. Tollestrup, Y. Torun, K. Yonehara
Fermilab, Batavia, Illinois, USA
A.V. Kochemirovskiy
University of Chicago, Chicago, Illinois, USA
Y. Torun
Illinois Institute of Technology, Chicago, Illlinois, USA

Funding: This work is supported by the Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359.
Bright muon sources require six dimensional cooling to achieve acceptable luminosities. Ionization cooling is the only known method able to do so within the muon lifetime. One proposed cooling channel, the Helical Cooling Channel, utilizes gas filled radio frequency cavities to both mitigate RF breakdown in the presence of strong, external magnetic fields, and provide the cooling medium. Engineering constraints on the diameter of the magnets within which these cavities operate dictate the radius of the cavities be decreased at their nominal operating frequency. To accomplish this, one may load the cavities with a larger dielectric material. Alumina of purities ranging from 96 to 99.8% was tested in a high pressure RF test cell at the MuCool Test Area at Fermilab. The results of breakdown studies with pure nitrogen gas, and oxygen-doped nitrogen gas indicate the peak surface electric field on the alumina ranges between 10 and 15 MV/m. How these results affect the design of a prototype cooling channel cavity will be discussed.

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MOPMW031

Beam Test of a Dielectric Loaded High Pressure RF Cavity for Use in Muon Cooling Channels

ion, electron, plasma, accelerating-gradient

463

B.T. Freemire
IIT, Chicago, Illinois, USA
D.L. Bowring, A. Moretti, D.W. Peterson, A.V. Tollestrup, K. Yonehara
Fermilab, Batavia, Illinois, USA
A.V. Kochemirovskiy
University of Chicago, Chicago, Illinois, USA
Y. Torun
Illinois Institute of Technology, Chicago, Illlinois, USA

Funding: This work is supported by the Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359.
Bright muon sources require six dimensional cooling to achieve acceptable luminosities. Ionization cooling is the only known method able to do so within the muon lifetime. One proposed cooling channel, the Helical Cooling Channel, utilizes gas filled radio frequency cavities to both mitigate RF breakdown in the presence of strong, external magnetic fields, and provide the cooling medium. Engineering constraints on the diameter of the magnets within which these cavities operate dictate the radius of the cavities be decreased at their nominal operating frequency. To accomplish this, one may load the cavities with a larger dielectric material. A 99.5% alumina ring was inserted in a high pressure RF test cell and subjected to an intense proton beam at the MuCool Test Area at Fermilab. The results of the performance of this dielectric loaded high pressure RF cavity will be presented.

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MOPMW032

Study of RF Breakdown in 805MHz Pillbox Modular Cavity in Strong Magnetic Field

operation, radiation, site, pick-up

466

A.V. Kochemirovskiy
University of Chicago, Chicago, Illinois, USA
D.L. Bowring, A. Moretti, K. Yonehara
Fermilab, Batavia, Illinois, USA
B.T. Freemire
IIT, Chicago, Illinois, USA
Y. Torun
Illinois Institute of Technology, Chicago, Illlinois, USA

RF breakdown has a negative impact on a cavity's performance, especially with the presence of strong magnetic fields. This issue can arise in designs of muon ionization cooling channel, RF guns, klystrons and in many other applications. The MuCool Test Area at Fermilab is the facility that allows us to study the effects of static magnetic field on RF cavity operation. As a part of this research program, we have tested an 805MHz pillbox "modular" cavity in strong external magnetic fields. The design of the cavity allowed for a better control over sources of systematic error. "Modular" structure of the cavity enables easy dismounting of the endplates to perform inspection of inner surfaces after each run as well as swapping endplates to study the effects of various materials on breakdown phenomenon. Coupler design ensures maximum electric field enhancement on cavity axis, thus reducing breakdown probability in the coupler region. The results and analysis from high-power runs with zero and non-zero external magnetic fields will be presented.

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MOPMW033

Acoustic Localization of RF Cavity Breakdown: Status and Progress

collider, experiment, simulation, status

470

P.G. Lane, P. Snopok, Y. Torun
Illinois Institute of Technology, Chicago, Illinois, USA
A.V. Kochemirovskiy
University of Chicago, Chicago, Illinois, USA

Current designs for muon accelerators require high-gradient RF cavities to be placed in solenoidal magnetic fields. These fields help contain and efficiently reduce the phase space volume of source muons in order to create a usable muon beam for collider and neutrino experiments. It has been found that placing normal conducting RF cavities in strong magnetic fields reduces the threshold at which RF cavity breakdown occurs. To aid the effort to study RF cavity breakdown in magnetic fields, it would be helpful to have a diagnostic tool which can localize the source of breakdown sparks inside the cavity. These sparks generate thermal shocks to a small region of the inner cavity wall that can be detected and localized using microphones attached to the outer cavity surface. Presented here are the algorithms for and results from localizing simulated and experimental acoustic data from the Modular Cavity at the MuCool Test Area at Fermilab.

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MOPMW034

Final Commissioning of the MICE RF Module Prototype with Production Couplers

vacuum, operation, coupling, Windows

474

Y. Torun, P.G. Lane
Illinois Institute of Technology, Chicago, Illlinois, USA
T.G. Anderson, M. Backfish, D.L. Bowring, A. Moretti, D.V. Neuffer, D.W. Peterson, M. Popovic, K. Yonehara
Fermilab, Batavia, Illinois, USA
B.T. Freemire
IIT, Chicago, Illinois, USA
T.L. Hart
UMiss, University, Mississippi, USA
A.V. Kochemirovskiy
University of Chicago, Chicago, Illinois, USA
T.H. Luo
LBNL, Berkeley, California, USA

Funding: Supported by the US Department of Energy Office of Science through the Muon Accelerator Program.
We report operational experience from the prototype RF module for the Muon Ionization Cooling Experiment (MICE) with final production couplers at Fermilab's MuCool Test Area. This is the last step in fully qualifying the RF modules for operation in the experiment at RAL.

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MOPMW035

Wakefield Excitation in Power Extraction Cavity (PEC) of Co-linear X-band Energy Booster (CXEB) in Time Domain (T3P) with ACE3P

extraction, electron, booster, simulation

477

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

In our previous papers we provided the general concept and the design details of our proposed Co-linear X-band Energy Booster (CXEB) as well as more advanced 3D simulations of our system using the frequency domain solvers OMEGA3P and S3P of the ACE3P Suite. Here, using the time domain solver T3P of ACE3P, we provide the single bunch and multiple bunch wakefield excitations resulting from a Gaussian bunch. The related power extraction mechanism for our traveling wave (TW) X-band power extraction cavity (PEC) are also discussed further.

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MOPMW036

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

electron, laser, impedance, extraction

480

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

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

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MOPMW038

Measurements of Copper RF Surface Resistance at Cryogenic Temperatures for Applications to X-Band and S-Band Accelerators

cryogenics, experiment, electron, coupling

487

A.D. Cahill, A. Fukasawa, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
G.B. Bowden, V.A. Dolgashev, M.A. Franzi, S.G. Tantawi, P.B. Welander, C. Yoneda
SLAC, Menlo Park, California, USA
J. Guo
JLab, Newport News, Virginia, USA
Y. Higashi
OIST, Onna-son, Okinawa, Japan

Funding: Funding from DOE SCGSR and DOE/SU Contract DE-AC02-76-SF00515
Recent SLAC experiments with cryogenically cooled X-Band standing wave copper accelerating cavities have shown that these structures can operate with accelerating gradients of ~250 MV/m and low breakdown rates. These results prompted us to perform systematic studies of copper rf properties at cryogenic temperatures and low rf power. We placed copper cavities into a cryostat cooled by a pulse tube cryocooler, so cavities could be cooled to 4K. We used different shapes of cavities for the X-Band and S-Band measurements. Properties of the cavities were measured using a network analyzer. We calculated rf surface resistance from measured Q0 and Q external of the cavity at temperatures from 4 K to room temperature. The results were then compared to the theory proposed by Reuter and Sondheimer. These measurements are a part of studies with the goal of reaching very high operational accelerating gradients in normal conducting rf structures.

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MOPMW039

TM01 Mode Launcher for Use in High Brightness Photoguns

quadrupole, gun, electron, impedance

491

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

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

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MOPMW042

Multi-Dimensional RF Sources Design

klystron, electron, space-charge, gun

501

M. Dal Forno, A. Jensen, R.D. Ruth, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: Work supported by the US DOE under contract DE-AC02-76SF00515.
Vacuum electronic devices, such as rf sources for accelerator applications, must provide high rf power with high efficiency. To achieve these requirements, multi-beam klystron and sheet-beam klystron devices have been developed. Multi-beam klystrons, at high frequency employ separate output cavities; hence they have the disadvantage that combining all the rf pulses, generated by all the beams, is challenging. Sheet-beam klystrons have problems with instabilities and with space charge forces that makes the beam not naturally confined. We are proposing an alternative approach that reduces space charge problems, by adopting geometries in which the space charge forces are naturally balanced. An example is when the electron beam is generated by a central source (well) and the electron motion corresponds to the natural expansion of the electron cloud (three-dimensional device). In this paper we will present the design and challenges of a bi-dimensional rf source, a cylindrical klystron, composed by concentric pancake resonant cavities. In this case, space charge forces are naturally balanced in the azimuthal direction.

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MOPMW044

Design of an RF Device to Study the Multipactor Phenomenon

simulation, electron, multipactoring, experiment

507

D. Amorim
Grenoble-INP Phelma, Grenoble, France
J.-M. De Conto, Y. Gómez Martínez
LPSC, Grenoble Cedex, France

Multipacting is a parasitic electron avalanche process that may occur in RF devices such as cavities or couplers. As it can be detrimental to the operation of these devices, the accelerator group at LPSC is currently designing a coaxial resonant cavity in order to study this phenomenon. In order to determine the measurable parameters on the cavity, calculations were performed and validated with numerical simulations. In a second time multipacting simulations were conducted to determine if the experiment will allow to observe multipacting.

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MOPMY001

Beam Dynamics Analysis for the Ultra-fast Kicker in Circular Cooler Ring of JLEIC

kicker, electron, emittance, recirculation

510

Y.L. Huang
IMP/CAS, Lanzhou, People's Republic of China
R.A. Rimmer, H. Wang, S. Wang
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
An ultra-fast kicker system consist of four quarter wavelength resonator based deflecting cavities was developed that simultaneously resonates at 10 subharmonic modes of the 476.3MHz bunch repetition frequency, thus every 10th bunch in the bunch train will experience a transverse kick while all the other bunches are undisturbed. This fast kicker is developed for the Energy Recovery Linac (ERL) based electron Circular Cooler Ring (CCR) in the proposed Jefferson Lab Electron Ion Collider (JLEIC, previously MEIC). The electron bunches can be reused 10-30 turns thus the beam current in the ERL can be reduced to 1/10 - 1/30 (150mA - 50mA) of the cooling bunch current (1.5A). In this paper, several methods to synthesis such a kicker waveform will be discussed with the comparison of beam dynamics tracking in Elegant.

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MOPMY002

Simulation and Experimental Studies of a 2.45GHz Magnetron Source for an SRF Cavity with Field Amplitude and Phase Controls

controls, LLRF, injection, SRF

514

H. Wang, T. E. Plawski, R.A. Rimmer
JLab, Newport News, Virginia, USA
A. Dudas, M.L. Neubauer
Muons, Inc, Illinois, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and NP STTR Grant DE-SC0013203.
Phase lock to an SRF cavity by using injection signal through output waveguide of a magnetron has been demonstrated [1, 3]. Amplitude control using magnetic field trimming and anode voltage modulation has been studied using MATLAB/Simulink simulations [2]. Based on these, we are planning to use an FPGA based digital LLRF system, which allows applying various types of control algorithms in order to achieve the required accelerating field stability. Since the 1497 MHz magnetron is still in the design stage, the proof of principle measurements of a commercial 2450 MHz magnetron are carried out to characterize the anode I-V curve, output power (the tube electronic efficiency), frequency dependence on the anode current (frequency pushing) and the Rieke diagram (frequency pulling by the reactive load). Based on early Simulink simulation, experimental data and extension of the Adler equation governing injection phase stability by Chen's model, the specification of the new LLRF control chassis for both 2450 and 1497MHz systems are presented in this paper.

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MOPMY003

Transient Beam Loading Effects in RF Systems in JLEIC

electron, klystron, feedback, controls

518

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

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The pulsed electron bunch trains generated from the Continuous Electron Beam Accelerator Facility (CEBAF) linac to inject into the proposed Jefferson Lab Electron Ion Collider (JLEIC) e-ring will produce transient beam loading effects in the Superconducting Radio Frequency (SRF) systems that, if not mitigated, could cause unacceptably large beam energy deviation in the injection capture, exceed the energy acceptance of CEBAF's recirculating arc. In the electron storage ring, the beam abort or ion clearing gaps or uneven bucket filling can cause large beam phase transients in the (S)RF cavity control systems and even beam loss due to Robinson instability. We have first analyzed the beam stability criteria in steady state and estimate the transient effect in Feedforward and Feedback RF controls. Initial analytical models for these effects are shown for the design of the JLEIC e-ring from 3GeV to 12GeV.

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MOPMY005

Study of Pretuning and High Power Test of DTL Iris Waveguide Couplers Using a Single Cell Cavity

DTL, coupling, factory, simulation

522

S.W. Lee, M.S. Champion, Y.W. Kang
ORNL, Oak Ridge, Tennessee, USA

Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S.DOE.
Six drift tube linac (DTL) cavities have been operating successfully at the Spallation Neutron Source (SNS). Each cavity is fed by a tapered ridge waveguide iris input coupler and a waveguide ceramic disk window. The original couplers and cavities have been in service for more than a decade. Design optimization and tuning of the couplers were initially performed prior to installation and commissioning of the cavities. Since each DTL cavity is unique, expensive, and fully utilized for neutron production, none of the cavity structure is available as a test cavity or a spare. Maintaining spares for operations and for future system upgrade, test setup of the iris couplers for precision tuning is needed. Ideally a smaller cavity structure may be used for pretuning and RF conditioning of the iris couplers as a test cavity or a bridge waveguide. In this paper, study of using a single cell cavity for the iris tuning and conditioning is presented along with the 3D simulation results.

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MOPMY007

Mechanical Design and 3-D Coupled RF, Thermal-Structural Analysis of Normal Conducting 704 MHz and 2.1 GHz Cavities for LEReC Linac

simulation, vacuum, software, operation

525

J.C. Brutus, S.A. Belomestnykh, I. Ben-Zvi, M. Blaskiewicz, J.M. Brennan, A.V. Fedotov, M.C. Grau, C. Pai, L. Snydstrup, J.E. Tuozzolo, B. P. Xiao, T. Xin, W. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, USA
V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
Two normal conducting cavities operating at 704 MHz and 2.1 GHz will be used for the Low Energy RHIC electron Cooling (LEReC) under development at BNL to improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon. The single cell 704 MHz cavity and the 3-cell 2.1 GHz third harmonic cavity will be used in LEReC to correct the energy spread introduced in the SRF cavity. The successful operation of normal RF cavities has to satisfy both RF and mechanical requirements. 3-D coupled RF-thermal-structural analysis has been performed on the cavities to confirm the structural stability and to minimize the frequency shift resulting from thermal and structural expansion. In this paper, we will present an overview of the mechanical design, results from the RF-thermal-mechanical analysis, progress on the fabrication and schedule for the normal conducting RF cavities for LEReC.

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MOPMY009

HOM Consideration of 704 MHz and 2.1 GHz Cavities for LEReC Linac

HOM, SRF, booster, electron

528

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

Funding: Work supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 and by National Energy Research Scientific Computing Center under contract No. DE-AC02-05CH11231 by US DOE.
To improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, the Low Energy RHIC electron Cooler (LEReC) is currently under development at BNL. The Linac of LEReC is designed to deliver 2 MV to 5 MV electron beam, with rms dp/p less than 5·10^-4. The HOM in this Linac is carefully studied to ensure this specification.

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MOPMY010

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

HOM, vacuum, impedance, simulation

532

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

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

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MOPMY011

LLRF System Performance during SC Cavity Conditioning at STF KEK

LLRF, controls, feedback, FPGA

536

S.B. Wibowo
Sokendai, Ibaraki, Japan
T. Matsumoto, S. Michizono, T. Miura, F. Qiu
KEK, Ibaraki, Japan

High Energy Accelerator Research Organization (KEK) is now developing a digital low-level radio frequency (LLRF) control system based on digital feedback control at superconducting RF test facility (STF). The goal is to achieve the amplitude and phase stability of the accelerating field in the superconducting accelerator. Testing and evaluation of the digital LLRF system were conducted during the cavity conditioning performed between October and December 2015 to determine the level of performance. To enable cavity signal monitoring, direct sampling system was constructed and evaluated.

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MOPMY014

Design Study of RF Section and Cavities for Cepc 650 MHz Klystron

klystron, simulation, electron, bunching

543

O. Xiao
Institute of High Energy Physics (IHEP), People's Republic of China
D.D. Dong, S. Fukuda, Z.J. Lu, G. Pei, S.C. Wang, .. Zaib-un-Nisa, Z.S. Zhou
IHEP, Beijing, People's Republic of China
S. Fukuda
KEK, Ibaraki, Japan

An 800 kW CW klystron operating at 650 MHz is de-veloped for CEPC at Institute of High Energy Physics in China. The conceptual design has been finished and the main parameters are presented in this paper. A 1D large signal disk model code, AJDISK, has been used to design and optimize klystron RF section parameters. In addition, the RF cavities have been designed using SUPERFISH, HFSS and CST.

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MOPMY027

Preliminary Design of High-efficiency Klystron for Pohang Accelerator Laboratory (PAL)

klystron, beam-losses, simulation, operation

557

S.J. Park, J.Y. Choi, Y.D. Joo, K.R. Kim, W. Namkung, C.D. Park
PAL, Pohang, Kyungbuk, Republic of Korea
M.-H. Cho, J.H. Hwang, T. Seong
POSTECH, Pohang, Kyungbuk, Republic of Korea

Funding: Supported by the Ministry of Science, ICT and Future Planning of Korea.
Klystrons for particle accelerators are typically designed to have narrow bandwidths with center frequencies ranging from several hundreds (e.g., 350) MHz to X-band (11.424 GHz). Output powers are from several tens of kW to ~1 MW for CW klystrons and ~100 MW for pulsed ones. The narrow-bandwidth requirement has enabled them to provide high gain (typically 40 - 50 dB) which greatly simplifies the RF drive system. Recently, especially for large-scale accelerator facilities, the klystron efficiency has become one of the most demanding issues. This is because electricity cost occupies a great portion of their operating budgets and the klystron efficiency is one of the important factors determining the electricity consumption of the whole accelerator system. In this regard, we have designed a high-efficiency klystron for use in the PLS-II and PAL XFEL at PAL. The basic scheme is to re-design the cavity system to include multi-cell output cavity. In this article, we report on our preliminary design work to determine major cavity parameters including cell frequencies, inter-cell distances, and coupling to external circuits (coupling beta).

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MOPMY033

Effect of Bandwidth of Low Level Radio Frequency System on the Instability of an Electron Beam

feedback, LLRF, synchrotron, electron

570

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

The analog Low Level Radio Frequency (LLRF) system is used at Taiwan Photon Source (TPS) RF system. It is composed of three feedback loops to control the amplitude and phase of accelerating field and the frequency of RF cavity. Instability of electron beam and accelerating field due to the bandwidth of LLRF system were observed during the TPS commissioning. This effect was studied and the results will be presented in this paper.

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MOPMY035

Theoretical Analysis and Simulation of a Compact Frequency Multiplier for High Power Millimeter and Terahertz Sources

electron, cathode, coupling, space-charge

576

A.R. Vrielink, S.G. Tantawi, F. Toufexis
SLAC, Menlo Park, California, USA

As the demands on accelerating gradients and the temporal resolution of beam diagnostics and manipulation schemes grow, millimeter-wave and terahertz (THz) accelerator structures may present a natural solution. The recent advent of a radiofrequency undulator and the development of a 0.45 THz accelerator demonstrate growing interest in this frequency regime; however, growth in this area is limited by the lack of efficient, compact high power sources. We present a novel vacuum electronic device featuring an interaction between a radially bunched electron beam and azimuthally traveling waves. The use of an inward traveling radial sheet beam mitigates space charge effects at the low operating energy of 10-30 keV and allows for a high input beam current of approximately 0.5-10 A. Based on preliminary calculations, these devices could operate from 50 GHz to 250 GHz with tens of kiloWatts of output power, while the expected efficiency would scale from 60% at 80 GHz to 15% at 230 GHz. Here we present the underlying theory, possible structure design, and preliminary results from analytical calculations and simulation.
Tantawi, S. et al. Phys. Rev. Lett. 112, 164802 (April, 2014)
Nanni, E. et al. Nat. Commun. 6, 8486 (October, 2015)

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MOPMY036

High-harmonic mm-Wave Frequency Multiplication using a Gyrocon-like Device

electron, coupling, vacuum, plasma

579

F. Toufexis, V.A. Dolgashev, M.V. Fazio, A. Jensen, S.G. Tantawi, A.R. Vrielink
SLAC, Menlo Park, California, USA
P. Borchard
Dymenso LLC, San Francisco, USA

Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515, and the National Science Foundation.
Traditional linear interaction RF sources, such as Klystrons and Traveling Wave Tubes, fail to produce significant power levels at millimeter wavelengths. This is because their critical dimensions are small compared to the wavelength, and the output power scales as the square of the wavelength. We present a vacuum tube technology, where the device size is inherently larger than the operating wavelength. We designed a low–voltage mm–wave source, with an output interaction circuit based on a spherical sector cavity. This device was configured as a phased-locked frequency multiplier. We report the design and cold test results of a proof-of-principle fifth harmonic frequency multiplier with an output frequency of 57.12 GHz.

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MOPOR009

The HL-LHC Impedance Model and Aspects of Beam Stability

impedance, HOM, octupole, focusing

606

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

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

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MOPOR012

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

impedance, simulation, feedback, acceleration

618

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

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

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MOPOR013

The PS 10 MHz High Level RF System Upgrade

feedback, impedance, network, beam-loading

622

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

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

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MOPOR014

Measurements of the CERN PS Longitudinal Resistive Coupling Impedance

impedance, HOM, coupling, synchrotron

626

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

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

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MOPOR033

Simulations of Dark Current from the BERLinPro Booster Module

electron, cathode, booster, simulation

671

M. McAteer, M. Abo-Bakr, B.C. Kuske, A. Neumann
HZB, Berlin, Germany

Funding: Work supported by the German Bundesministerium f\"ur Bildung und Forschung, Land Berlin and grants of Helmholtz Association
Dark current emitted from the surface of high-field RF cavities can contribute to radiation levels and cryo budget and can cause damage to sensitive accelerator components such as the photocathode. The superconducting niobium cavities in the booster module of BERLinPro will have surface fields strong enough to produce significant dark current from field emission, so simulations were made using Astra to track the propagation of emitted electrons from the surfaces of the cavities to examine the effects of dark current in the BERLinPro injector. Results of these simulations, including optimization of the layout to reduce propagation of electrons to the cathode and an estimation of power from dark current deposited throughout the injector, are presented.

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MOPOR038

Implications of Resonantly Driven Higher Order Modes on the ESS Beam

HOM, simulation, linac, emittance

683

A. Farricker, R.M. Jones, N.Y. Joshi
UMAN, Manchester, United Kingdom
S. Molloy
ESS, Lund, Sweden

The European Spallation Source (ESS) in Lund, Sweden, will be a facility for fundamental physics studies of atomic structure using a spallation source of unparalleled brightness. To achieve this end, a 2.86 ms long pulsed proton beam will be accelerated up to a final energy of 2 GeV using three suites of superconducting cavities. If a Higher Order Mode (HOM) lies on a harmonic of the bunch frequency the HOM will be resonantly driven. This will dilute the beam quality significantly. Errors in fabricating these cavities are inevitable, and this sets a tolerance on how close the HOM can be within a harmonic of the bunch frequency. The baseline design for ESS requires HOMs to be at least 5 MHz from a machine line. Here we provide details of several finite element electromagnetic simulations on the HOMS anticipated in these ESS cavities. We analyse their impact on the beam emittance using a drift-kick-drift model with the potential for relaxed tolerances.

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MOPOR039

Measurement of Beam Phase at FLASH using HOMs in Accelerating Cavities

HOM, electron, simulation, coupling

686

L. Shi, R.M. Jones
UMAN, Manchester, United Kingdom
N. Baboi, L. Shi
DESY, Hamburg, Germany
N.Y. Joshi
University of Manchester, Manchester, United Kingdom

The beam phase relative to the accelerating field is of vital importance for the quality of photon beams produced in modern Free Electron Lasers based on superconducting (SC) cavities. Normally, the phase is determined by detecting the transient field induced by the beam. In this way the phase of each cavity is checked and adjusted typically every few months. In this paper, we present another means of beam phase determination, based on higher order modes (HOMs) excited in the 2nd monopole band by the beam inside the SC cavities. A circuit model of this HOM band is also presented. Various effects on the resolution have been studied. Circuit model simulations indicate the resolution is strongly dependent on the signal to noise ratio. Preliminary experimental results, based on a broadband setup, reveal an approximately 0.1o RMS resolution. These are in good agreement with simulation results. The work will pave the way for a dedicated system of beam phase monitoring, which is under development for the European XFEL. This will be the first implementation of a dedicated beam phase monitor, based on beam-excited HOMs in accelerating cavities.

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MOPOR043

High-gradient Structures for Proton Energy Boosters

booster, linac, proton, experiment

692

S.S. Kurennoy, L. Rybarcyk
LANL, Los Alamos, New Mexico, USA

Increasing energy of proton beam at LANSCE from 800 MeV to 3 GeV can improve radiography resolution ~10 times. The best current practice to achieve this energy boost is to employ superconducting (SC) RF cavities with gradients about 15 MV/m after the existing linac, which results in a long and expensive booster. We propose accomplishing the same with a room-sized booster based on high-gradient (100s MV/m) room-temperature RF accelerating structures operating at low duty factors. Such high-gradient (HG) structures at very high RF frequencies have been demonstrated for electrons. However, they have never been used for protons because typical RF wavelengths are smaller than the proton bunch length. This is not a problem for proton radiography (pRad): a train of very short proton bunches with the same total length (10s ps) and charge as the original proton bunch will work as well, i.e., will create one radiography frame. Such a compact HG pRad booster can also be about an order of magnitude cheaper than the SC one. We explore feasibility of HG structures for protons and their application for a compact pRad booster at LANSCE.

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MOPOW026

Status of FELiCHEM, a New IR-FEL in China

FEL, undulator, radiation, electron

774

H.T. Li, Z.G. He, Q.K. Jia, Q. Luo, L. Wang, S.C. Zhang
USTC/NSRL, Hefei, Anhui, People's Republic of China

FELiChEM is a new experimental facility under construction at University of Science and Technology of China (USTC), whose core device is a FEL oscillator generating middle-infrared and far-infrared laser and covering the spectral range of 2.5-200 μm. It will be a dedicated light source aiming at energy chemistry research, with the photo excitation, photo dissociation and photo detection experimental stations. We present the brief physical and technical design that delivers the required performance for this device and summarize the status of fabrication. Final assembly is scheduled for early in the next year with first light targeted for July 2017.

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MOPOW054

The 4th Harmonic Cavity for Hefei Light Source-II

HOM, storage-ring, synchrotron, operation

837

C.-F. Wu, S. Dong, G. Huang, D. Jia, K. Jin, C. Li, J.Y. Li, W. Li, J.G. Wang, L. Wang, W. Xu, K. Xuan
USTC/NSRL, Hefei, Anhui, People's Republic of China
R.A. Bosch
UW-Madison/SRC, Madison, Wisconsin, USA
G.Y. Kurkin, E. Rotov
BINP SB RAS, Novosibirsk, Russia
G. Ya
Budker Institute of Nuclear Physics, Novosibirsk, Russia

The 4th harmonic cavity has been firstly used in the storage ring for HLS-II. The paper presents the physics design, developing process and the experimental results for commision. The measurment results show that rf parameters are reasonable. The 4th harmonic cavity efficiently lengthen the bunch and increase the beam life-time. Specially, the beam instablity has been supressed.

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MOPOY001

MedAustron Synchrotron RF Commissioning for Medical Proton Beams

injection, acceleration, synchrotron, proton

844

C. Schmitzer, F. Farinon, A. Garonna, M. Kronberger, T.K.D. Kulenkampff, C. Kurfürst, S. Myalski, S. Nowak, F. Osmić, L.C. Penescu, M.T.F. Pivi, P. Urschütz, A. Wastl
EBG MedAustron, Wr. Neustadt, Austria

MedAustron is a medical accelerator facility for hadron therapy cancer treatment using protons and carbon ions. The Synchrotron is driven by a 0.47-3.26 MHz Finemet® loaded wideband cavity powered by 12x 1kW solid state amplifiers connected to a digital Low Level RF system. It was developed in collaboration with CERN and put to operation at MedAustron in early 2014. The main Synchrotron RF (sRF )commissioning steps for proton beams involved the setup of the adiabatic capture process, the setup of the frequency and voltage ramps and feedback loops for fast acceleration and the RF jump for extraction. The adiabatic capture process was optimized in terms of energy and voltage mismatch by analyzing longitudinal empty bucket scans after beam injection into the synchrotron. The acceleration ramp optimization was based on calculations using a software tool developed in-house and adapted experimentally to minimize losses at injection and during acceleration. This paper provides an overview of the acceleration system and describes the commissioning process of the sRF system and the related beam commissioning efforts at MedAustron.

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MOPOY006

Preparations for Upgrading the RF Systems of the PS Booster

impedance, operation, feedback, emittance

853

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

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

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MOPOY019

Status of the First CH-Cavities for the New Superconducting CW Heavy Ion LINAC@GSI

resonance, linac, operation, ion

886

M. Basten, M. Amberg, M. Busch, F.D. Dziuba, H. Podlech, M. Schwarz
IAP, Frankfurt am Main, Germany
K. Aulenbacher
IKP, Mainz, Germany
K. Aulenbacher, W.A. Barth, V. Gettmann, S. Mickat, M. Miski-Oglu
HIM, Mainz, Germany
W.A. Barth, M. Heilmann, S. Mickat, S. Yaramyshev
GSI, Darmstadt, Germany

In the field of Super Heavy Elements (SHE) a superconducting (sc) continuous wave (cw) high intensity heavy ion LINAC is highly desirable. Currently a multi-stage R&D program conducted by GSI, HIM and IAP* is in progress. The baseline linac design composes a high performance ion source, a new low energy beam transport line, a (cw) upgraded High Charge State Injector (HLI), and a matching line (1.4 MeV/u) followed by the new sc-DTL LINAC for acceleration up to 7.3 MeV/u. The commissioning of the first CH cavity (Demonstrator), in a horizontal cryo module with beam is a major milestone in 2016**. The advanced demonstrator comprises constant-beta sc Crossbar-H-mode (CH) cavities operated at 217 MHz. Presently, the first two sc CH cavities of the advanced demonstrator are under construction at Research Instruments (RI), Bergisch Gladbach, Germany. A string of cavities and focusing elements build from several short CH-cavities with 8 gaps, without girders is recommended. The new design potentially reduces the overall technical risks during the fabrication and the pressure sensitivity through stiffening brackets. The present status of the first two sc cavities will be presented.
* W.Barth et al., Further R&D for a new Superconducting cw Heavy Ion LINAC@GSI, IPAC'14
**F.Dziuba et al., Measurements on the Superconducting 217 MHz CH Cavity during the Manufacturing Phase, SRF2015

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MOPOY022

Further Upgrade Measures at New GSI cw-Linac Demonstrator Setup

solenoid, linac, ion, heavy-ion

892

M. Heilmann, W.A. Barth, S. Mickat, S. Yaramyshev
GSI, Darmstadt, Germany
M. Amberg, M. Basten, F.D. Dziuba, H. Podlech, U. Ratzinger, M. Schwarz
IAP, Frankfurt am Main, Germany
K. Aulenbacher
IKP, Mainz, Germany
K. Aulenbacher, W.A. Barth, V. Gettmann, S. Mickat, M. Miski-Oglu
HIM, Mainz, Germany

A new continuous wave (cw) linac is required to deliver high intensity heavy ion beams for Super Heavy Element (SHE) future experiments at GSI Darmstadt, Germany. The presented upgrade measures are dedicated to improve the performance of the cw demonstrator setup. The key component is a cryomodule comprising a superconducting (sc) 217 MHz Crossbar-H-mode (CH) cavity surrounded by two sc 9.3T solenoids with compensation coils. The solenoid coil is made of a Nb3Sn wire; and the compensation coils at both ends of the solenoid comprises NbTi wires. The distance between solenoid lense and CH cavity has to be optimized for ideal beam matching as well as for a minimum rest field inside the cavity below the critical magnetic field. The GSI High Charge State (HLI) injector has to deliver a heavy ion beam with an energy of 1.4 MeV/u. Longitudinal matching to the demonstrator is provided by two 10⁸.4 MHz cw room temperature λ/4 re-buncher cavity installed behind the HLI. In this paper electromagnetic simulations of the field optimization for the solenoids and the re-buncher cavities will be presented as well as first beam experiments at the beam transport line to the demonstrator cavity.

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MOPOY023

Further Steps Towards the Superconducting CW-LINAC for Heavy Ions at GSI

linac, heavy-ion, ion, target

896

M. Schwarz, M. Basten, M. Busch, F.D. Dziuba, H. Podlech, U. Ratzinger, R. Tiede
IAP, Frankfurt am Main, Germany
W.A. Barth, V. Gettmann, M. Heilmann, S. Mickat, M. Miski-Oglu, S. Yaramyshev
GSI, Darmstadt, Germany
W.A. Barth, V. Gettmann, S. Mickat, M. Miski-Oglu
HIM, Mainz, Germany

Funding: Work supported by BMBF contr. No. 05P15RFRBA
For future experiments with heavy ions near the coulomb barrier within the super-heavy element (SHE) research project a multi-stage R&D program of GSI, HIM and IAP is currently in progress. It aims at developing a superconducting (sc) continuous wave (cw) LINAC with multiple CH cavities as key components downstream the upgraded High Charge Injector (HLI) at GSI. The LINAC design is challenging, due to the requirement of intense beams in cw-mode up to a mass-to-charge-ratio of 6 while covering a broad output energy range from 3.5 to 7.3 MeV/u with minimum energy spread. The next milestone will be a full performance beam test of the first expansion stage at GSI, the Demonstrator, comprising two solenoids and a 15-gap CH cavity inside a cryostat.

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MOPOY025

Electromagnetic Design of β=0.13, f=325 Mhz Half-Wave Resonator for Future High Power, High Intensity Proton Driver at KEK

linac, proton, electron, rfq

902

G.-T. Park, E. Kako, Y. Kobayashi, T. Koseki, S. Michizono, F. Naito, H. Nakai, K. Umemori, S. Yamaguchi
KEK, Ibaraki, Japan
T. Maruta
KEK/JAEA, Ibaraki-Ken, Japan

At KEK, a proposal is being prepared for a new linac-based proton driver that can accelerate the proton beam up to 9 GeV with 9 MW beam power and 100 mA peak current. In this report, we present the study on the front end design of the linac, which will accelerate the beam to 1.2 GeV: The baseline layout, the acceleration energy structure, RF characteristics of components, cryomodule configurations, and the detailed design of half-wave resonator 1.

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MOPOY028

Low Power RF Tuning of the CSNS DTL

DTL, linac, insertion, neutron

913

H.C. Liu, Q. Chen, M.X. Fan, S. Fu, K.Y. Gong, A.H. Li, J. Peng, S. Wang, X. Wu, F.X. Zhao
IHEP, Beijing, People's Republic of China
B. Li, P.H. Qu, Y. Wang
CSNS, Guangdong Province, People's Republic of China

The China Spallation Neutron Source (CSNS) is an accelerator-based neutron source being built at dongguan, Guangdong province in China. A conventional 324MHz Alvarez-type Drift tube linac (DTL) is utilized to accelerate an H⁻ ion beam from 3MeV to 80MeV. The RF field tuning of DTL is necessary for compensating the unexpected error caused by manufacturing and assembling. For reasons of RF power saving it is convenient to build a long DTL tank, but this choice involves risks of accelerating field instability. This problem can be fixed by using the resonant coupling stabilization method and equipping DTL cavities with a series of post-couplers. A practical tuning method was proposed, an acceptable field distribution with a good stability was achieved for CSNS DTL-1.

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MOPOY030

Superconducting Cavity Phase and Amplitude Measurement in Low Energy Accelerating Section

LLRF, linac, beam-transport, superconducting-cavity

919

C. Meng, H. Geng, F. Yan, Y.L. Zhao
IHEP, Beijing, People's Republic of China

Superconducting linear accelerator is the tendency in linac design with the development of superconducting RF technology. Superconducting cavities used as accelerating section in low energy Hadron linac are more and more common. The 5MeV test stand of CADS accelerator Injector I is composed of an ion source, a LEBT, a 325MHz RFQ, a MEBT, a cryogenic module (CM1) of seven SC spoke cavities (β=0.12) , seven SC solenoids, seven cold BPMs and a beam dump. The phase and amplitude setting of superconducting cavity are very important at the operation of accelerator, so beam based measurement of cavity phase and amplitude is necessary. Beam based phase scan is the most simple and effective method. Because the significant velocity changes in superconducting cavity at low energy section, the effective voltage is changing with cavity phase, meanwhile the synchronous phase is non-linear with LLRF phase. Above two problem make the cavity phase determination difficult. New date fitting method is proposed to solve these problem in this paper. Some measurements of spoke cavities in the CADS CM1 are also presented.

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MOPOY033

Design Study on an Injector RFQ for Heavy Ion Accelerator Facility

rfq, simulation, ion, heavy-ion

928

W. Ma, Y. He, L. Lu, X.B. Xu, Z.L. Zhang, H.W. Zhao
IMP/CAS, Lanzhou, People's Republic of China

A Low Energy Accelerator Facility (LEAF) was launched as a pre-research facility for High Intensity heavy ion Accelerator Facility (HIAF). The LEAF consists of a 2-mA U³⁴⁺ electron cyclotron resonance (ECR) type ion source with 300-kV extraction voltage, a low energy beam transport (LEBT) line with a multi-harmonic buncher (MHB), a CW 81.25MHz radio frequency quad-rupole (RFQ) accelerator which could accelerate heavy ions from 14 keV/u up to 500 keV/u, a triplet magnet for medium energy beam transport and an experimental platform for nuclear physics. After describing the selected structure, an octagonal cavity with π-mode stabilizing loop (PISL) type structure was adopted and simulated. In this paper, the detailed electromagnetic design and ther-mal simulation of the LEAF-RFQ will be reported.

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MOPOY038

Studies for Tuning Algorithm of Superconducting Cavity Amplitude and Phase in the RAON Accelerator

linac, GUI, simulation, interface

932

H. Jin, J.-H. Jang
IBS, Daejeon, Republic of Korea

The RAON accelerator utilizes the low energy and high energy superconducting linacs for the acceleration of the stable ion beams and the rare isotope beams. The low energy superconducting linac is composed of the quarter-wave resonator (QWR) and the half-wave resonator (HWR) cavities, and the high energy superconducting linac consists of two kinds of single-spoke resonator (SSR) cavities. In the beam commissioning, the tuning of these superconducting cavities is a significant issue to achieve the targeted beam energy and to avoid the deterioration of the beam quality. In this paper, we will present the tuning program based on the phase scan tuning algorithm for the superconducting cavity amplitude and phase in the RAON accelerator and describe the simulation results.

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MOPOY039

Progress on Superconducting Linac for the RAON Heavy Ion Accelerator

cryomodule, linac, ion, electron

935

H.J. Kim, H.C. Jung, W.K. Kim
IBS, Daejeon, Republic of Korea

The RISP (Rare Isotope Science Project) has been proposed as a multi-purpose accelerator facility for providing beams of exotic rare isotopes of various energies. It can deliver ions from proton to uranium. Proton and uranium ions are accelerated upto 600 MeV and 200 MeV/u respectively. The facility consists of three superconducting linacs of which superconducting cavities are independently phased. Requirement of the linac design is especially high for acceleration of multiple charge beams. In this paper, we present the RISP linac design, the prototyping of superconducting cavity and cryomodule.

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MOPOY042

The Perspective of Jinr Lu-20 Replacement by a Superconducting Linac

linac, simulation, proton, ion

944

S.M. Polozov, M. Gusarova, T. Kulevoy, M.V. Lalayan, A.V. Samoshin, S.E. Toporkov
MEPhI, Moscow, Russia
M.A. Baturitski
BSU, Minsk, Belarus
A.V. Butenko, V. Monchinsky, A.O. Sidorin, G.V. Trubnikov
JINR, Dubna, Moscow Region, Russia
G. Kropachev, T. Kulevoy
ITEP, Moscow, Russia
A.A. Marysheva, V.S. Petrakovsky, I.L. Pobol, A.I. Pokrovsky, S.V. Yurevich, A.Yu. Zhuravsky
Physical-Technical Institute of the National Academy of Sciences of Belarus, Minsk, Belarus

The new accelerator complex Nuclotron-based Ion Collider fAcility (NICA) is now under development and construction at JINR. Existing Alvarez-type DTL linac LU-20 is now operates as injector of light ions, polarized protons and deuterons to Nuclotron for LHEP experimental program. It provides proton beam of 20 MeV energy and light ions of 5 MeV/u energy. In 2015 the cascade transformer 800 kV which is pre-accelerator of LU-20 had been replaced by the new RFQ linac (energy 155 keV for ions with Z/A<0.5). The proposal on Alvarez linac LU-20 upgrade by a superconducting light ion linac with energy up to 50 MeV is discussed in this report.

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MOPOY050

Beam Commissioning Plan of the FRIB Superconducting Linac

linac, operation, optics, simulation

961

Y. Zhang, C.P. Chu, Z.Q. He, M. Ikegami, S.M. Lidia, S.M. Lund, F. Marti, G. Shen, Y. Yamazaki, Q. Zhao
FRIB, East Lansing, Michigan, USA

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
The FRIB superconducting linac will deliver all heavy ion beams with energy above 200 MeV/u, and beam power on target up to 400 kW for generation of short lived isotopes. Beam commissioning is the first step to prepare and tune the superconducting linac for high power operation. A staged beam commissioning plan of the FRIB linac is developed, and complete beam tuning practices segment by segment through the entire linac are introduced, which include phase scan signature matching of the superconducting cavities, longitudinal beam matching, transverse matching with horizontal-vertical beam coupling, and beam optics corrections of achromatic and isochronous folding segments up to the second order for acceleration and transport of multi charge state beams.

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MOPOY051

Manufacturing and the LLRF Tests of the SANAEM RFQ

rfq, vacuum, LLRF, simulation

964

G. Turemen, Y. Akgun, A. Alacakir, A.S. Bolukdemir, I. Kilic, B. Yasatekin
TAEK - SANAEM, Ankara, Turkey
G. Unel
UCI, Irvine, California, USA
H. Yildiz
Istanbul University, Istanbul, Turkey

Funding: Turkish Atomic Energy Authority
Turkish Atomic Energy Authority is working on building an experimental proton beamline with local resources at the Saraykoy Nuclear Research and Training Center (SANAEM). Manufacturing of the radio frequency quadrupole (RFQ) was started after the beam dynamics and 3D electromagnetic simulation studies were performed. The vanes were machined with a three axis CNC machine. A CMM was used for the acceptance tests of the vanes and also for assembling. Production and assembly results were found acceptable for this cavity, the very first one developed in Turkey. Copper plating was performed by electroplating the aluminum vanes. The plated vanes were bolted and bonded with eight screws, eight pins and two different adhesives. A silver paste was used for RF sealing and a low vapor pressure epoxy was used for vacuum isolation. First LLRF tests of the RFQ were done with a bead-pull setup and a VNA. A N-type RF coupler and a pick-up were used for the LLRF tests. Phase shift method was used for the bead-pull tests. Cavity quality factor was measured with 3dB method for different RF sealing stages. This study summarizes the machining, assembling and the first LLRF tests of the SANAEM RFQ.

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MOPOY054

Status of the ESS RFQ

rfq, vacuum, status, operation

974

D. Chirpaz-Cerbat, A. Albéri, A.C. Chauveau, M. Lacroix, N. Misiara, G. Perreu, O. Piquet, H. Przybilski, N. Sellami
CEA/IRFU, Gif-sur-Yvette, France
N. Berton, G. Bourdelle, M. Desmons, A.C. France, V.M. Hennion, P.-A. Leroy, B. Pottin
CEA/DSM/IRFU, France

The ESS Radio-Frequency Quadrupole (RFQ) is a 4-vanes resonant cavity designed at the frequency of 352.21 MHz. It must accelerate and bunch a 70mA proton beams from 75keV to 3.62MeV with a 4% duty cycle. The RFQ design has already been done, and documented in other papers. This one will present the global status of the RFQ, with technical solutions cho-sen for the main components (for fabrication and op-eration) and the present status of the RFQ fabrication.

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TUOCA02

APEX Phase-II Commissioning Results at the Lawrence Berkeley National Laboratory

gun, electron, linac, space-charge

1041

F. Sannibale, J.A. Doyle, J. Feng, D. Filippetto, G.L. Harris, M.J. Johnson, T.D. Kramasz, D. Leitner, C.E. Mitchell, J.R. Nasiatka, H.A. Padmore, H.J. Qian, H. Rasool, J.W. Staples, S.P. Virostek, R.P. Wells, M.S. Zolotorev
LBNL, Berkeley, California, USA
S.M. Gierman, R.K. Li, J.F. Schmerge, T. Vecchione, F. Zhou
SLAC, Menlo Park, California, USA
C. Pagani, D. Sertore
INFN/LASA, Segrate (MI), Italy

Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231
Science needs in the last decade have been pushing the accelerator community to the development of high repetition rates (MHz/GHz-class) linac-based schemes capable of generating high brightness electron beams. Examples include X-ray FELs; ERLs for light source, electron cooling and IR to EUV FEL applications; inverse Compton scattering X-ray or gamma sources; and ultrafast electron diffraction and microscopy. The high repetition rate requirement has profound implications on the technology choice for most of the accelerator parts, and in particular for the electron gun. The successful performance of the GHz room-temperature RF photo-injectors running at rates <~ 100 Hz, cannot be scaled up to higher rates because of the excessive heat load that those regimes would impose on the gun cavity. In response to this gun need, we have developed at Berkeley the VHF-Gun, a lower-frequency room-temperature RF photo-gun capable of CW operation and optimized for the performance required by MHz-class X-ray FELs. The Advanced Photo-injector EXperiment (APEX) was funded and built for demonstrating the VHF gun performance, and the results of its last phase of commissioning are presented.

Slides TUOCA02 [12.015 MB]

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TUOAB03

Transverse Coherent Instabilities in Storage Rings with Harmonic Cavities

synchrotron, radio-frequency, impedance, simulation

1061

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

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

Slides TUOAB03 [14.037 MB]

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TUOCB02

Low Secondary Electron Yield of Laser Treated Surfaces of Copper, Aluminium and Stainless Steel

electron, laser, framework, photon

1089

R. Valizadeh, P. Goudket, O.B. Malyshev, B.S. Sian, S. Wang
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
M.D. Cropper, S. Wang
Loughborough University, Loughborough, Leicestershire, United Kingdom
P. Goudket
Cockcroft Institute, Warrington, Cheshire, United Kingdom
B.S. Sian
UMAN, Manchester, United Kingdom
N. Sykes
Micronanics Laser Solution Center, Didcot, United Kingdom

Funding: STFC
Reduction of SEY was achieved by surface engineering through laser ablation with a laser operating at • = 355 nm. It was shown that the SEY can be reduced to near or below 1 on copper, aluminium and 316LN stainless steel. The laser treated surfaces show an increased surface resistance, with a wide variation in resistance found de-pending on the exact treatment details. However, a treated copper surface with similar surface resistance to aluminium was produced.

Slides TUOCB02 [94.339 MB]

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TUPMB046

The Preliminary Conceptual Design of a 2k Cryogneic System for Circular Electron Positron Collider (CEPC)

cryogenics, collider, booster, cryomodule

1199

Y.P. Liu, L. Bian, R. Ge, R. Han, S.P. Li, M.J. Sang, L.R. Sun, M.F. Xu, R. Ye, J.Q. Zhang, J.H. Zhang, X.Z. Zhang, Z.Z. Zhang
IHEP, Beijing, People's Republic of China

The Circular Electron Positron Collider (CEPC) is a long-term collider project, which will serve as a Higgs Factory and offer a unique opportunity for direct searches for New Physics in the high-energy range far beyond LHC reach [1]. In the frame of this project, a large 2K cryogenic system will be built to provide coolant for superconducting cavities used in booster ring and collider ring. All the superconducting cavities will be working under 2K. This paper will give a brief introduction to the preliminary considerations of this large cryogenic system, including the general layout, heat load estimation, helium refrigerator, schematic flow diagram as well as the main parameters and working process

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TUPMR011

Development of Optimized RF Cavity in 10 MeV Cyclotron

network, cyclotron, simulation, resonance

1250

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

Cyclotron cavity modelled by an artificial neural net-work, which is trained by our optimized algorithm. The training samples are obtained from simulation results, which are done by MWS CST software for some defined situation and parameters, and also with the conventional BP algorithm. It is shown that the optimized FFN can estimate the cyclotron model parameters with acceptable outputs. Hence, the neural network trained by this algorithm represents the proper estimation and acceptable ability to our structure modelling. The cyclotron cavity parameter modelling illustrate that the neural network trained by this algorithm could be the acceptable method to design parameters.

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TUPMR015

Cooling and Heat Transfer of the IRANCYC-10 Transmission Line

impedance, simulation, cyclotron, factory

1259

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

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

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TUPMR016

Research and Development of a Compact Superconducting Cyclotron SC200 for Proton Therapy

cyclotron, proton, simulation, extraction

1262

G.A. Karamysheva, S. Gurskiy, O. Karamyshev, S.A. Kostromin, N.A. Morozov, E.V. Samsonov, G. Shirkov
JINR, Dubna, Moscow Region, Russia
Y.F. Bi, G. Chen, K.Z. Ding, Y. Song
ASIPP, Hefei, People's Republic of China

According to the agreement between the Institute of Plasma Physics (IPP) of the Chinese Academy of Sciences in Hefei (China) and Joint Institute for Nuclear Research, Dubna, (Russia), the development of a superconducting isochronous cyclotron for proton therapy SC200 is started. The cyclotron will provide acceleration of protons up to 200 MeV with maximum beam current of 1 μA. We plan to manufacture in China two cyclotrons: one will operate in Hefei cyclotron medical center the other will replace Phasotron in Medico-technical Center JINR Dubna and will be used for further research and development of cancer therapy by protons. Now we present main parameters of cyclotron and simulation results of magnetic, accelerating and extraction systems.

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TUPMR030

Progress on RFQ Fabrication for RISP Accelerator

rfq, vacuum, alignment, laser

1308

B.-S. Park, B.H. Choi, I.S. Hong
IBS, Daejeon, Republic of Korea

The 81.25MHz Radio Frequency Quadrupole(RFQ), which was designed to accelerate various ion beams from the energy of 10 keV/u to 500 keV/u, is under development for the Rare Isotope Science Project(RISP). The 5 meter long RFQ consists of 9 sections and the total weight is roughly 16 tons. Each sections of RFQ aligned and installed by using a laser tracker on a supporter system. In this paper, the fabrication status of the RISP RFQ and the scheme of installation were described in detail.
This work was supported by the RISP of IBS funded by the Ministry of Science, ICT and Future Planning(MSIP) and the National Research Foundation(NRF) of Korea(2013M7A1A1075764).

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TUPMW025

Machine Protection from Fast Crab Cavity Failures in the High Luminosity LHC

collimation, proton, simulation, luminosity

1485

A. Santamaría García, R. Bruce, H. Burkhardt, F. Cerutti, R. Kwee-Hinzmann, A. Lechner, K.N. Sjobak, A. Tsinganis
CERN, Geneva, Switzerland
R. Kwee-Hinzmann
Royal Holloway, University of London, Surrey, United Kingdom

The time constant of a crab cavity (CC) failure can be faster than the reaction time of the active protection system. In such a scenario, the beams cannot be immediately extracted, making the the protection of the machine rely on the passive protection devices. At the same time, the energy stored in the High Luminosity (HL) LHC beams will be doubled with respect to the LHC to more than 700 MJ, which increases the risk of damaging the machine and the experiments in a failure scenario. In this study we estimate the impact that different CC failures have on the collimation system. We also give a first quantitative estimate of the effect of these failures on the elements near the experiments based on FLUKA simulations, using an updated HL-LHC baseline.

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TUPMW034

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

emittance, injection, luminosity, impedance

1513

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

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

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TUPMW038

RHIC Operation with Asymmetric Collisions in 2015

proton, operation, injection, emittance

1527

C. Liu, E.C. Aschenauer, G. Atoian, M. Blaskiewicz, K.A. Brown, D. Bruno, R. Connolly, T. D'Ottavio, K.A. Drees, W. Fischer, C.J. Gardner, X. Gu, T. Hayes, H. Huang, R.L. Hulsart, J.S. Laster, Y. Luo, Y. Makdisi, G.J. Marr, A. Marusic, F. Méot, K. Mernick, R.J. Michnoff, M.G. Minty, C. Montag, J. Morris, G. Narayan, S.K. Nayak, S. Nemesure, P.H. Pile, A. Poblaguev, V.H. Ranjbar, G. Robert-Demolaize, T. Roser, W.B. Schmidke, V. Schoefer, F. Severino, T.C. Shrey, K.S. Smith, D. Steski, S. Tepikian, D. Trbojevic, N. Tsoupas, G. Wang, K. Yip, A. Zaltsman, K. Zeno, S.Y. Zhang
BNL, Upton, Long Island, New York, USA
S.M. White
ESRF, Grenoble, France

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Collisions with beams of highly asymmetric rigidities (proton-Gold and proton-Aluminum) were provided for the RHIC physics programs in 2015. Magnets were moved for the first time in RHIC prior to the run to accommodate the asymmetric beam trajectories during acceleration and at store. A special ramping scheme was designed to keep the revolution frequencies of the beams in the two rings equal. The unique operational experience of the asymmetric run will be reviewed.

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TUPMY002

APF IH-DTL Design for the Muon LINAC in the J-PARC Muon g-2/EDM Experiment

linac, emittance, DTL, acceleration

1539

M. Otani, T. Mibe, M. Yoshida
KEK, Tsukuba, Japan
K. Hasegawa, Y. Kondo
JAEA, Ibaraki-ken, Japan
N. Hayashizaki
RLNR, Tokyo, Japan
Y. Iwashita
Kyoto ICR, Uji, Kyoto, Japan
Y. Iwata
NIRS, Chiba-shi, Japan
R. Kitamura
University of Tokyo, Tokyo, Japan
N. Saito
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

The muon linac for the J-PARC muon g-2/EDM experiment consists of RFQ (324 MHz), IH-DTL (324 MHz), DAW coupled cell linac (1.3 GHz), and disk loaded structure (1.3 GHz). Because muon has finite life time, the muons should be accelerated in a sufficiently short period. To realize fast acceleration, Alternative Phase Focusing (APF) scheme is adopted in IH-DTL in which the muons are accelerated from 0.34 MeV to about 4 MeV. In this poster, the design of the APF IH-DTL for muon acceleraiton with the computer calculation will be presented.

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TUPMY003

Development of Muon LINAC for the Muon g-2/EDM Experiment at J-PARC

rfq, acceleration, linac, background

1543

M. Otani, T. Mibe, F. Naito, N. Saito, M. Yoshida
KEK, Tsukuba, Japan
K. Hasegawa, T. Ito, Y. Kondo
JAEA/J-PARC, Tokai-mura, Japan
N. Hayashizaki
RLNR, Tokyo, Japan
Y. Iwashita
Kyoto ICR, Uji, Kyoto, Japan
Y. Iwata
NIRS, Chiba-shi, Japan
R. Kitamura
University of Tokyo, Tokyo, Japan

Precision measurements of the muon's anomalous magnetic moment (g-2) and electric dipole moment (EDM) are effective ways to cast light on beyond the standard model of elementary particle physics. The J-PARC E34 experiment aims to measure g-2 with a precision of 0.1 ppm and search for EDM with a sensitivity to 10-{-21} e· cm with high intensity proton beam at J-PARC and a novel technique of making a muon beam with small emittance (the ultra-cold muon beam). The ultra-cold muon beam is generated from a surface muon beam by the thermal muonium (30 meV) production followed by the laser ionization, and acceleration to 212 MeV or 300 MeV/c by the muon dedicated LINAC. The muon LINAC consists of RFQ, inter-digital IH, Disk And Washer (DAW) coupled cell and disk loaded structure. The ultra-cold muons will have an extremely small transverse momentum spread of less than 1 % with a normalized transverse emittance of around 1.5 pi mm-mrad. The muon acceleration to 300 MeV/c will be the first case in the world and it will be one of the base technologies of future accelerator programs. In this talk, design and status of the muon LINAC will be reported.

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TUPMY023

Advanced Gabor Lens Lattice for Laser Driven Hadron Therapy and Other Applications

lattice, laser, collimation, ion

1595

J.K. Pozimski, M. Aslaninejad, P.A. Posocco
Imperial College of Science and Technology, Department of Physics, London, United Kingdom

Funding: Funding was provided by the Imperial Confidence in Concept scheme.
The application of laser accelerated ion beams in hadron therapy requires a beam optics with unique features. Due to the spectral and spatial distribution of laser accelerated protons a compact ion optical system with therapy applications, based on Gabor space charge lenses for collecting, focusing and energy filtering the laser produced proton beam, has significant advantages compared with other setups. While a passive momentum selection could improve already the usability of laser driven hadron, we show that an advanced lattice utilizing additional RF cavities not only will deliver a momentum spread smaller than conventional accelerators, but also will increases the dose delivered. Furthermore, a possible near term application in the field of radio nuclide production is presented.

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TUPMY038

Preliminary Measurement of the Transfer Matrix of a TESLA-type Cavity at FAST

simulation, HOM, experiment, focusing

1632

A. Halavanau, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
N. Eddy, D.R. Edstrom, A. Lunin, P. Piot, J. Ruan, J.K. Santucci, J.K. Santucci, N. Solyak
Fermilab, Batavia, Illinois, USA

Funding: US Department of Energy (DOE) under contract DE-SC0011831 with Northern Illinois University. Fermilab is operated by the Fermi Research Alliance LLC under US DOE contract DE-AC02-07CH11359.
Superconducting linacs are capable of producing intense, ultra-stable, high-quality electron beams that have widespread application in Science and Industry. Many current and planned projects employ 1.3-GHz 9-cell superconducting cavities of the TESLA design*. In the present paper we discuss the transverse-focusing properties of such a cavity and non-ideal transverse-map effects introduced by field asymmetries in the vicinity of the input and high-order-mode radiofrequency (RF) couplers**. We especially consider the case of a cavity located downstream of an RF-gun in a setup similar to the photoinjector of the Fermilab Accelerator Science and Technology (FAST) facility. Preliminary experimental measurements of the CC2 cavity transverse matrix were carried out at the FAST facility. The results are discussed and compared with analytical and numerical simulations.
* A. Aunes et al., Phys. Rev.ST Accel. Beams 3, 092001 (2000).
** P. Piot, el. al., Proc. 2005 Part. Accel. Conf., Knoxville, TN, p. 4135 (2005).

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TUPOR001

Lifetime Improvements with a Harmonic RF System for the ESRF EBS

impedance, storage-ring, simulation, electron

1644

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

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

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TUPOR016

A Multi-GeV Recirculating Proton Linac

proton, linac, acceleration, operation

1688

J. Qiang
LBNL, Berkeley, California, USA

A high power GeV proton linac has many scientific applications. Recirculating RF linac as an efficient accelerator has been used and proposed to accelerate both electron and muon beams. In this paper, we propose using a multi-pass recirculating RF linac to attain a multi-GeV high power proton beam. This linac consists of three types of superconducting RF cavities that accelerate the proton beam multiple times from 150 MeV to final multiple GeV energy. Such a recirculating linac can significantly reduce the number of RF cavities in the accelerator and lower the cost of the facility.

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TUPOR017

Beam-beam Simulation of Crab Cavity with Frequence Dependent Noise for LHC Upgrade

luminosity, simulation, emittance, feedback

1691

J. Qiang
LBNL, Berkeley, California, USA
G. Arduini, Y. Papaphilippou, T. Pieloni
CERN, Geneva, Switzerland
J. Barranco
EPFL, Lausanne, Switzerland

High luminosity LHC upgrade will improve the luminosity of the current LHC operation by an order of magnitude. Crab cavity as a critical component for compensating luminosity loss from large crossing angle collision and also providing luminosity leveling for the LHC upgrade is being actively pursued. In this paper, we will report on the study of potential effects of the frequence-dependent crab cavity noise on the beam luminosity lifetime using strong-strong beam-beam simulations.

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TUPOR019

RF Injector Beam Dynamics Optimization and Injected Beam Energy Constraints for LCLS-II

laser, emittance, electron, gun

1699

C.E. Mitchell, H.J. Qian, J. Qiang, F. Sannibale, M. Venturini
LBNL, Berkeley, California, USA
P. Emma, T.O. Raubenheimer, J.F. Schmerge, F. Zhou
SLAC, Menlo Park, California, USA

Funding: Work supported by the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231.
LCLS-II is a proposed high-repetition rate (>1 MHz) Free Electron Laser (FEL) X-ray light source, based on a CW, superconducting linac, to be built at SLAC National Accelerator Laboratory. The injector technology is based on a high-repetition rate RF photoinjector gun developed as part of the Advanced Photoinjector Experiment (APEX) at Lawrence Berkeley National Laboratory. Exploration of the injector design settings is performed using a multiobjective genetic optimizer to optimize the beam quality at the injector exit (~100 MeV). In this paper, we describe the current status of LCLS-II injector design optimization, with a focus on the sensitivity of the optimized solutions to the beam energy at the injector exit, which is constrained by the requirements of the downstream laser heater system.

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TUPOR025

Beam Break-up Measurements at the Recirculating Electron Accelerator S-DALINAC

linac, recirculation, HOM, experiment

1714

T. Kürzeder, M. Arnold, L.E. Jürgensen, J. Pforr, N. Pietralla
TU Darmstadt, Darmstadt, Germany
F. Hug
IKP, Mainz, Germany

Funding: Supported by the German Federal Ministry for Education and Research (BMBF) under Grant No. 05K13RDA
Beam break-up (BBU) instability is an important limitation to the current which can be accelerated in a superconducting linac. In particular recirculating machines and Energy Recovery Linacs have to deal with that problem. Therefore, it is important to find strategies for increasing the threshold currents of these machines. The superconducting accelerator S-DALINAC at the Technische Universität Darmstadt provides electron beams in c.w. for nuclear physics experiments since 1991. It consists of a 10 MeV injector and a 40 MeV main linac where two and eight 20-cell elliptical 3-GHz cavities are operated in a liquid helium bath at 2 K. Using two recirculation beam lines the main accelerator can be used up to 3 times. Operational experiences have shown that the design-beam current of 20 μA could not be reached. One reason is the occurrence of BBU. We will report on measurements of the threshold current at various energy settings of the S-DALINAC. The results of a first test to increase the BBU limit by using skew quadrupole magnets in the first recirculation beam line will be presented.

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TUPOR028

Excitation of Longitudinal Coupled-bunch Oscillations with the Wide-band Cavity in the CERN PS

feedback, synchrotron, LLRF, proton

1724

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

Longitudinal coupled-bunch oscillations in the CERN Proton Synchrotron have been studied in the past years and they have been recognized as one of the major challenges to reach the high brightness beam required by the High Luminosity LHC project. In the frame of the LHC Injectors Upgrade project in 2014 a new wide-band Finemet cavity has been installed in the Proton Synchrotron as a part of the coupled-bunch feedback system. To explore the functionality of the Finemet cavity during 2015 a dedicated measurement campaign has been performed. Coupled-bunch oscillations have been excited with the cavity around each harmonic of the revolution frequency with both a uniform and nominal filling pattern. In the following the measurements procedure and results are presented.

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TUPOW005

Update on Third Harmonic XFEL Activities at INFN LASA

HOM, operation, pick-up, diagnostics

1751

D. Sertore, M. Bertucci, A. Bignami, A. Bosotti, J.F. Chen, P. Michelato, L. Monaco, R. Paparella, P. Pierini
INFN/LASA, Segrate (MI), Italy
C.G. Maiano
DESY, Hamburg, Germany
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy

After the successful installation and beam operation of the first batch of 3.9 GHz cavities into the XFEL Third Harmonic Injector Module, ten more cavities have been tested and delivered to DESY to be assembled into a spare cryomodule. In this paper, we report on the activities related to the cavities fabrication, treatment and vertical testing at INFN LASA.

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TUPOW024

Compact Standing Wave Electron Linac with the Hybrid Accelerating and Power Generation Cell

coupling, electron, Windows, linac

1797

E.A. Savin, S.V. Matsievskiy, N.P. Sobenin, I.D. Sokolov
MEPhI, Moscow, Russia
A.A. Zavadtsev
Nano, Moscow, Russia

Compact electron linear accelerators for small energies are now found their place in the industrial market. Such accelerators are used for cancer treatment, cargo inspection, when one needs higher dose that X-ray source can produce, food and medicaments irradiation etc. Acceleration structures themselves are already developed very well, so the most important issue now ' is to make the whole installation with power supply, RF tracts, cooling system ' as smaller as possible to provide the structure mobility. In this article we present the development how to combine a power supply (usually it is a klystron, IOT, magnetron or solid state amplifier) with the accelerating cell itself, that can decrease installation size at least twice. No RF tracts needed, no reflected power will occur, so no circulator needed. Different power input combinations have been studied, but the smallest and the most efficient one has been manufactured for cold tests at S-band frequency range. In this structure it is very easy to vary accelerating voltage simply changing the generator beam current or the generator beam accelerating voltage.

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TUPOW029

Transverse Cavity Tuning at the Advanced Photon Source

linac, dipole, gun, LabView

1814

G.J. Waldschmidt, L.H. Morrison, T.L. Smith
ANL, Argonne, Ilinois, USA

A 15-cell transverse deflecting cavity based on a SLAC design was fabricated at the Advanced Photon Source and is being prepared for installation into the Injector Test Stand. A beadpull method for tuning was selected in lieu of the nodal position method to minimize the possibility of contamination and surface damage to the irises. The process has been successfully documented for many accelerating mode structures, but there has been limited application to dipole mode structures. In this paper, we will discuss the methodology for tuning and conditioning a 2.8 GHz backward-traveling wave deflecting cavity.

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TUPOW030

A CW Normal Conducting RF Cavity for Fast Chirp Control in the LCLS-II

linac, controls, FEL, wakefield

1817

M.H. Nasr, P. Emma, S.G. Tantawi
SLAC, Menlo Park, California, USA

The LCLS-II is a high repetition-rate Free-Electron Laser (FEL) facility under construction at SLAC. A new 4-GeV continuous wave (CW) superconducting (SC) L-band linac is being built to provide an electron bunch rate of up to 1 MHz, with bunches rapidly switched between two FEL undulators. It is desirable to provide peak current (i.e., pulse length) control in each FEL independently by varying the RF phase (chirp) prior to the first bunch compressor. However, the high-Q, SCRF, with its 1-ms fill-time, cannot be changed within one bunch spacing (1 us). So to provide a small chirp adjustment from bunch to bunch, we propose a short CW copper RF accelerating cavity, located just after the injector, with < 250-ns fill-time designed to adjust the beam chirp at zero-crossing phase. We examined RF cavity designs spanning RF frequencies from L-band to X-band. We considered both SW and TW structures. We found an optimal solution with 2 cm iris diameter, SW RF cavity, operating at C-band with input power of only 10 kW. If one can afford to operate with smaller diameter, from a wakefield point of view, then similar structure at X-band may require only 500 W with 5 mm iris diameter.

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TUPOW033

Status of the BERLinPro Main Linac Module

linac, HOM, simulation, wakefield

1823

H.-W. Glock, A. Frahm, J. Knobloch, A. Neumann
HZB, Berlin, Germany

Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of the Helmholtz Association
Beam operation of the BERLinPro energy recovery linac project, whose construction is under way, will initially start using the photoinjector and booster modules. In a second step the recirculation beam line and the main linac module will be added. Here the current design status of the main linac module is described. Results of wake field simulations are compared for different set ups. We also report on the manufacturing aspects including the design of the waveguide groups needed for HOM damping and the choice of flange-gasket-pairings appropriate for rectangular waveguides. Also mechanical considerations are included.

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TUPOW034

Status Report of the Berlin Energy Recovery Linac Project BERLinPro

gun, SRF, linac, vacuum

1827

M. Abo-Bakr, W. Anders, K.B. Bürkmann-Gehrlein, A.B. Büchel, P. Echevarria, A. Frahm, H.-W. Glock, F. Glöckner, F. Göbel, B.D.S. Hall, S. Heling, H.-G. Hoberg, A. Jankowiak, C. Kalus, T. Kamps, G. Klemz, J. Knobloch, J. Kolbe, G. Kourkafas, J. Kühn, B.C. Kuske, P. Kuske, J. Kuszynski, D. Malyutin, A.N. Matveenko, M. McAteer, A. Meseck, C.J. Metzger-Kraus, R. Müller, A. Neumann, N. Ohm, K. Ott, E. Panofski, F. Pflocksch, J. Rahn, J. Rudolph, M. Schmeißer, O. Schüler, M. Schuster, J. Ullrich, A. Ushakov, J. Völker
HZB, Berlin, Germany

Funding: Work supported by the German Bundesministerium für Bildung und Forschung, Land Berlin and grants of Helmholtz Association
The Helmholtz Zentrum Berlin is constructing the Energy Recovery Linac Prototype BERLinPro at the Berlin Adlershof site. The project is intended to expand the required accelerator physics and technology knowledge mandatory for the design, construction and operation of future synchrotron light sources. The project goal is the generation of a high current (100 mA), high brilliance (norm. emittance below 1 mm mrad) cw electron beam. We report on the project progress: since spring 2015 the building is under construction, ready for occupancy in January 2017. The planning phase for the first project stage is completed for the warm machine parts, the SRF gun and partly for the SRF booster. Most of the components have been ordered and are in fabrication with some already delivered. An update of the status of the various subprojects as well as a summary of future activities will be given. Project milestones and details of the timeline will be reviewed.

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TUPOW035

First LLRF Tests of BERLinPro Gun Cavity Prototype

gun, controls, linac, cathode

1831

P. Echevarria, J. Knobloch, O. Kugeler, A. Neumann, A. Ushakov
HZB, Berlin, Germany
K.P. Przygoda
DESY, Hamburg, Germany

The goal of Berlin Energy Recovery Linac Project (BERLinPro) is the generation of a 50 MeV, 100-mA low emittance (below 1 mm mrad) CW electron beam at 2 ps rms bunch duration or below. Three different types of 1.3 GHz SRF modules will be employed: the electron gun, the booster and the main linac. Precise RF amplitude and phase control are needed due to the beam recovery pro-cess. In this paper we describe the first tests of the Low Level RF control of the first injector prototype at the HoBiCaT facility, implemented in the digital VME-based LLRF controller developed by Cornell University. Tuner movement control by an mTCA.4 system, together with further plans of using this technology will be also presented.

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TUPOW039

Simulation Study of the Beam Halo Formation for Beam Loss Estimation and Mitigation at KEK Compact ERL

simulation, operation, electron, gun

1843

O. Tanaka, T. Miyajima, N. Nakamura, T. Obina, M. Shimada, R. Takai
KEK, Ibaraki, Japan

Funding: Work supported by the "Grant-in-Aid for Creative Scientific Research" of JSPS (KAKENHI 15K04747)
At KEK Compact ERL (cERL) we are aiming to produce high-current and low-emittance electron beams (up to 10 mA) without significant beam loss. We believe that beam halo makes a significant impact into the beam loss. Therefore, we are performing beam loss simulations to meet the results of the beam loss measurements*. In particular, a simulation of the bunch tail originated from the electron gun was performed to understand the mechanisms of the beam halo formation. Since some measured beam profiles demonstrated unexpected halo particles, several factors such as misalignment of beam line elements and kicks from the steering coils were added into the simulation. Simulation study results are compared with the related beam loss and halo measurements here.
* Sakanaka et al., these proceedings

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TUPOW040

UH-FLUX: Compact, Energy Efficient Superconducting Asymmetric Energy Recovery LINAC for Ultra-high Fluxes of X-ray and THz Radiation

HOM, electron, radiation, coupling

1847

I.V. Konoplev, A. Seryi
JAI, Oxford, United Kingdom
R. Ainsworth
Fermilab, Batavia, Illinois, USA
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom

Funding: This work was supported (in part) by The Leverhulme Trust through the International Network Grant IN-2015-012.
The conventional ERLs have limited peak beam current because increasing the beam charge and repetition rate leads to appearance of the beam break-up instabilities. At this stage the highest current, from the SRF ERL, is around 300 mA. A single turn (the beam will be transported through the accelerating section, interaction point and deceleration section of the AERL only once) Asymmetric Energy Recovery LINAC (AERL) is proposed. The RF cells in different sections of the cavity are tuned in such a way that only operating mode is uniform inside all of the cells. The AERL will drive the electron beams with typical energies of 10 - 30 MeV and peak currents above 1 A, enabling the generation of high flux UV/X-rays and high power coherent THz radiation. We aim to build a copper prototype of the RF cavity for a compact AERL to study its EM properties. The final goal is to build AERL based on the superconducting RF cavity. Preliminary design for AERL's cavity has been developed and will be presented. The results of numerical and analytical models and the next steps toward the AERL operation will also be discussed.

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TUPOW046

Development and Upgrade Plan of an X-ray Source Based on Laser Compton Scattering in Laser Undulator Compact X-ray Source(LUCX)

laser, electron, detector, photon

1867

M.K. Fukuda, S. Araki, Y. Honda, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
M. Kageyama, M. Kuribayashi
Rigaku Corporation, XG & Core Technology, Tokyo, Japan
A. Momose, M.P. Olbinado, Y. Wu
Tohoku University, Institute of Multidisciplinary Research for Advanced Materials, Sendai, Japan
K. Sakaue
Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan
M. Washio
RISE, Tokyo, Japan

Funding: This work was supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
We have been developing a compact X-ray source based on Laser Compton scattering(LCS) at Laser Undulator Compact X-ray source(LUCX) accelerator in KEK. Our aim is to obtain a clear X-ray image in a shorter period of times and the target number of X-ray is 1.7x10⁷ photons/pulse with 10% bandwidth. In the accelerator, an electron beam with the energy of 18-24 MeV is generated by an S-band normal conducting accelerator. The beam is collided with a laser pulse stacked in a 4-mirror planar optical cavity and then 6-10 keV X-rays are generated by LCS. Presently, the generation of X-rays with the number of 3x10⁶ photons/pulse at the collision point has been achieved. X-ray imaging test such as refraction contrast images and phase contrast imaging with Talbot interferometer has also started. To increase the intensity of X-rays, we are continuing the tuning of the electron beam and the optical cavity because the exposure time of X-ray imaging is too long now. We are also planning to increase the beam energy by appending the accelerating tube. In this conference, the recent results and upgrade plan in LUCX will be reported.

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TUPOY010

6/9 MeV S-band Standing Wave Accelerating Structure for Container X-ray Inspection System at RTX

electron, linac, gun, radiation

1924

P. Buaphad, H.D. Park, S. Song, S.Y. Yoo
RTX, Daejeon, Republic of Korea
H.K. Cha, S.S. Cha, J.H. Ha, Y. Kim, B.C. Lee
KAERI, Daejon, Republic of Korea

Recently, there is a need of X-ray inspection system around the world to combat terrorism, drug and weapons smuggling, illegal immigration, and trade fraud. A compact standing wave (SW) linear accelerator (linac) for container X-ray inspection system has been produced at Radiation Technology eXcellence (RTX) to meet this growing need. The RF accelerating structure uses standing wave side-coupled structure fed by a 5 MW e2v magnetron with frequency of 2856 MHz. The electrons are accelerated from DC gun with energy of 25 keV to the final energy of 6 or 9 MeV at the X-ray target and generate X-ray with the dose rate of 8 Gy/min at 1 m after X-ray target. In this paper, we describe the design and optimization of side-coupled RF structure operating at π/2 mode. The beam dynamic of particle along the RF structure is also included in this paper by using ASTRA code.

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TUPOY015

Design of Electron Gun and S-Band Structure for Medical Electron Linear Accelerator

electron, gun, cathode, linac

1930

N. Juntong, R. Chimchang
SLRI, Nakhon Ratchasima, Thailand
S. Rimjaem, C. Saisa-ard
Chiang Mai University, Chiang Mai, Thailand

Linear accelerator technology has been widely utilized for cancer treatment in hospital. This radiotherapy utilizes an accelerated electron beam to create the x-ray beam. The idea to fabricate the prototype of medical electron linac with low cost for domestic use in Thailand was proposed and the budget has been granted. In the first phase, the electron beam energy of the machine will be 6 MeV or equivalent to x-ray energy of 6 MV. The electron gun is a diode type for the simple and low cost fabrication. The design and simulation study of diode gun will be presented together with an analysis of an electron beam in this gun. The S-Band 6 MeV side-coupled RF cavity has been designed to be the accelerating structure of the machine. The electromagnetic fields of the structure have been studied. The electron behaviour when they traverse this cavity will be studied using a particle tracking code. Progression of the project is also presented.

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TUPOY025

ProBE - Proton Boosting Extension for Imaging and Therapy

proton, linac, quadrupole, accelerating-gradient

1963

R. Apsimon, G. Burt, S. Pitman
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
H.L. Owen
UMAN, Manchester, United Kingdom

Conventional proton cyclotrons are practically limited by relativistic effects to energies around 250 MeV, sufficient to conduct proton therapy of adults but not for full-body proton tomography. We present an adaptation of the cyclinac scheme for proton imaging, in which a c.250 MeV cyclotron used for treatment feeds a linac that delivers a lower imaging current at up to 350 MeV. Our ProBE cavity design envisages a gradient sufficient to obtain 100 MeV acceleration in 3 metres after focusing is included, suitable for inclusion in the layouts of existing proton therapy centres such as the UK centre under construction at Christie Hospital. In this paper, we present the results of design studies on the linac optics and RF cavity parameters. We detail particle transmission studies and tracking simulation studies.

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TUPOY040

Advancements in Single-shot Electron Diffraction on VELA at Daresbury Laboratory

electron, laser, gun, cathode

1988

J.W. McKenzie, S.L. Mathisen, M.D. Roper, M. Surman
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
D.M.P. Holland
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
J.G. Underwood
UCL, London, United Kingdom

Electron diffraction on VELA at Daresbury Laboratory was first demonstrated in 2014. Since then, we have studied the machine parameter optimisation for single-shot diffraction patterns from single-crystal gold and silicon samples at bunch charges down to 60 fC. We present bunch length measurements for electron diffraction setups determined with a transverse deflecting cavity. We also discuss the current limitations of VELA for electron diffraction and the improvements to be made.

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TUPOY050

Microtron-based Intense Neutron Source

microtron, neutron, cathode, electron

2014

G.M. Kazakevich, R.J. Abrams, R.P. Johnson, S.A. Kahn
Muons, Inc, Illinois, USA
M.A.C. Cummings
Northern Illinois University, DeKalb, Illinois, USA

Funding: Funded by DOE SBIR grant DE-SC0013795
An L-Band 7.7-9.8 MeV CW relatively inexpensive microtron with a warm accelerating cavity for multi-purpose applications in nuclear medicine and radiation industry is proposed. The microtron with a photo-neutron converter is intended to serve as an intense source of photo-neutrons with yield up to 4·10¹² n/s for nuclear medicine or/and producing of short lived isotopes, as a source of gamma-radiation with dose rates up to 130 kR/min·m with a heavy bremsstrahlung target, and as a source of the electron beam with total energy of 9.8 MeV at the average current up to 4.4 mA for various radiation treatments.

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TUPOY055

Study on Electro-polishing of Nb Surface by Periodic Reverse Current Method with Sodium Hydroxide Solution

experiment, operation, SRF, cathode

2020

J. Taguchi, A. Namekawa
Nomura Plating Co, Ltd., Osaka, Japan
H. Hayano, T. Saeki
KEK, Ibaraki, Japan
C.E. Reece, H. Tian
JLab, Newport News, Virginia, USA

Electropolishing is one of the best methods of Nb surface finishing of the superconducting cavity to obtain high accelerating gradient. Mixed solution of hydrofluoric acid and sulfuric acid is generally used in the electropolishing of Nb. But this solution is very dangerous and because the corrosion of the metal occurs by hydrofluoric acid, all equipment must be made of high density polyethylene or fluorocarbon resin. This causes the expensive cost of electropolishing instrument. In addition, this solution produces sulfur compound on the Nb surface in the electropolishing reaction. This sulfur compound can be field emission sources on the inner surface of cavity and degrades acceleration performance. In this poster, we report noble electropolishing method using periodic reverse current and sodium hydroxide solution. The reaction produces no sulfur content and the equipment is less expensive because the instrument can be made of usual plastic material. As the result of experiments with Nb-coupon samples, we found that the surface roughness is equivalent to the conventional electropolishing method.

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WEYA01

Beam Physics and Technical Challenges of the FRIB Driver Linac

linac, solenoid, ion, focusing

2039

Y. Yamazaki, H. Ao, N.K. Bultman, F. Casagrande, C. Compton, K.D. Davidson, A. Facco, F. Feyzi, P.E. Gibson, T. Glasmacher, Z.Q. He, L.T. Hoff, K. Holland, M. Ikegami, S.M. Lidia, Z. Liu, G. Machicoane, F. Marti, S.J. Miller, D. Morris, J. Popielarski, L. Popielarski, G. Pozdeyev, T. Russo, K. Saito, S. Shanab, G. Shen, S. Stark, H. Tatsumoto, R.C. Webber, J. Wei, T. Xu, Y. Zhang, Q. Zhao, Z. Zheng
FRIB, East Lansing, Michigan, USA
K. Dixon, V. Ganni
JLab, Newport News, Virginia, USA
A. Facco
INFN/LNL, Legnaro (PD), Italy
K. Hosoyama, M. Masuzawa, K. Tsuchiya
KEK, Ibaraki, Japan
M.P. Kelly, P.N. Ostroumov
ANL, Argonne, Illinois, USA
R.E. Laxdal
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661.
The FRIB driver linac accelerates all the stable ion beams including uranium over 200 MeV/u with a CW beam power of 400 kW in order to produce isotopes as rare as possible. Except for 0.5 MeV/u RFQ, the linac is making use of superconducting (SC) RF technology. The beam power, which is an order of 2.5 as high as those of existing SC heavy ion linac, gives rise to many technical challenges as well as beam physics related ones. In particular, the uranium beam loss power density is approximately 30 times as high as the proton one with the same beam energy per nucleon and the same beam power. For this reason, the machine protection system needs a special care. Another example of the technical challenges is to install beam focusing solenoid as close as possible to SC cavities in order to ensure the frequent beam focusing both longitudinally and transversely. The talk reviews all these challenges with development results of their mitigation as well as construction status.

Slides WEYA01 [16.820 MB]

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WEOBA02

Commissioning of the China-ADS Injector-I Testing Facility

rfq, emittance, simulation, proton

2048

F. Yan, J.S. Cao, Y.L. Chi, R. Ge, H. Geng, S. Gu, D.Z. Guo, T.M. Huang, X. Jing, H. Li, R.L. Liu, F. Long, C. Meng, H.F. Ouyang, W.M. Pan, Q.L. Peng, Y.F. Sui, J.L. Wang, S.C. Wang, Z. Xue, Q. Ye, Y.L. Zhao
IHEP, Beijing, People's Republic of China

The 10 MeV accelerator-driven subcritical system (ADS) Injector I test stand at Institute of High Energy Physics (IHEP) is a testing facility dedicated to demonstrate one of the two injector design schemes [Injector Scheme-I, which works at 325 MHz], for the ADS project in China. The ion source was installed since April of 2014, periods of commissioning are regularly scheduled between installation phases of the rest of the injector. 6.05 MeV proton energy has been achieved with average beam current of 10 mA by 7 SC spoke cavities at present. This contribution reports the details of the commissioning results together with the challenges of the CW machine commissioning.

Slides WEOBA02 [5.243 MB]

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WEOAB02

Record Performance of SRF Gun with CsK2Sb Photocathode

cathode, gun, laser, electron

2085

I. Pinayev, Z. Altinbas, S.A. Belomestnykh, I. Ben-Zvi, K.A. Brown, J.C. Brutus, A.J. Curcio, A. Di Lieto, C. Folz, D.M. Gassner, M. Harvey, T. Hayes, R.L. Hulsart, J.P. Jamilkowski, Y.C. Jing, D. Kayran, R. Kellermann, R.F. Lambiase, V. Litvinenko, G.J. Mahler, M. Mapes, W. Meng, K. Mernick, R.J. Michnoff, T.A. Miller, M.G. Minty, G. Narayan, P. Orfin, D. Phillips, T. Rao, J. Reich, T. Roser, B. Sheehy, J. Skaritka, L. Smart, K.S. Smith, L. Snydstrup, V. Soria, Z. Sorrell, R. Than, C. Theisen, J.E. Tuozzolo, E. Wang, G. Wang, B. P. Xiao, T. Xin, W. Xu, A. Zaltsman, Z. Zhao
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
High-gradient CW photo-injectors operating at high ac-celerating gradients promise to revolutionize many sci-ences and applications. They can establish the basis for super-bright monochromatic X-ray and gamma-ray sources, high luminosity hadron colliders, nuclear- waste transmutation or a new generation of microchip produc-tion. In this paper we report on our operation of a super-conducting RF electron gun with a record-high accelerat-ing gradient at the CsK2Sb photocathode (i.e. ~ 20 MV/m) generating a record-high bunch charge (i.e., 2 nC). We briefly describe the system and then detail our experimental results.

Slides WEOAB02 [28.500 MB]

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WEIB06

Industry Role for Advanced Accelerator R&D

emittance, solenoid, plasma, linac

2114

R.P. Johnson
Muons, Inc, Illinois, USA

Besides large research institutes which typically focus on fundamental research, industrial companies can also contribute to the development of advanced applications of accelerators as well as to fundamental accelerator technology. The funding of advanced or fundamental R&D, which is usually high-risk but potentially high-reward, is difficult to obtain for any organization, especially smaller industrial companies. As an example of one funding approach, I discuss the role of industrial companies in the field of accelerators and present several examples from my own experience of advanced R&D performed by industry under the United States Department of Energy Small Business Innovation and Small Business Technology Transfer Research (SBIR-STTR) Grant programs.

Slides WEIB06 [6.226 MB]

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WEPMB003

Design of the HWR Cavities for SARAF

cryomodule, linac, pick-up, simulation

2119

G. Ferrand, L. Boudjaoui, D. Chirpaz-Cerbat, P. Hardy, F. Leseigneur, C. Madec, N. Misiara, N. Pichoff
CEA/IRFU, Gif-sur-Yvette, France

CEA is committed to delivering a Medium Energy Beam Transfer line and a superconducting linac (SCL) for SARAF accelerator in order to accelerate 5mA beam of either protons from 1.3 MeV to 35 MeV or deuterons from 2.6 MeV to 40 MeV. The SCL consists in 4 cryomodules. The first two identical cryomodules host 6 half-wave resonator (HWR) low beta cavities (β = 0.09) at 176 MHz. The last two identical cryomodule will host 7 HWR high-beta cavities (β = 0.18) at 176 MHz. Low-beta and high beta cavities have been optimized to limit electric and magnetic peak fields in the cavity, and to minimize the dissipated power. Manufacturing constraints and helium cooling were taken into consideration to minimize the risk during manufacturing and operation. Preliminary mechanical studies of the cavity and of the tuning system, as well as preliminary studies of the couplers and pick-up antennas were carried out. This work will be presented in this poster.

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WEPMB005

Manufacturing of the IFMIF Series Power Couplers

operation, vacuum, interface, cryomodule

2122

H. Jenhani, N. Bazin, N. Berton, G. Devanz, P. Hardy, V.M. Hennion
CEA/IRFU, Gif-sur-Yvette, France

In the framework of the International Fusion Materials Irradiation Facility (IFMIF), which consists of two high power CW accelerator drivers, each delivering a 125 mA deuteron beam at 40 MeV, a Linear IFMIF Prototype Accelerator (LIPAc) is presently under construction for the first phase of the project. Eight power couplers are needed for the cryomodule of LIPAc. After the validation of the two prototypes, the manufacturing of the Series Power Couplers was lunched. This paper will report the status of the manufacturing progress. It will also describe the acceptance tests in addition to the criteria adopted for these critical RF power units. The manufacturing imperfections and some finishing techniques used for the different parts will be also presented and discussed.

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WEPMB007

Error Estimation in Cavity Performance Test for the European XFEL at DESY

cryomodule, accelerating-gradient, HOM, operation

2128

Y. Yamamoto
KEK, Ibaraki, Japan
W.-D. Möller, D. Reschke
DESY, Hamburg, Germany

The cavity performance tests, that is, vertical test (V.T.) and cryomodule test (C.T.), in the cavity/cryomodule mass production for XFEL have been done since 2012 at DESY, and is still on-going at present. At the comparatively initial stage of the mass production, the error estimation in the cavity performance tests was done for understanding how precisely those measurements are done at AMTF (Accelerator Module Test Facility). There are two parameters for the error estimation in V.T. One is the cable calibration parameter, and the other is the external Q-value, which is related to the power emitted from cavity. The measurement precision in the external Q-value depends on the measurement of coupling coefficient (β) strongly. Therefore, it is essential not to miss the β measurement for the precise measurement in V.T. On the other hand, as for C.T., the change of parameter (Kt), which is related to the evaluation of accelerating gradient, was used. As the result of the data analysis for Kt, the error was estimated to be 6%, and is related to the cavity performance degradation from V.T. to C.T. In this paper, the detailed data analysis and error estimation will be presented.

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WEPMB011

ESS Medium and High Beta Cavity Prototypes

HOM, coupling, cryomodule, interface

2138

P. Michelato, A. Bellandi, M. Bertucci, A. Bignami, A. Bosotti, J.F. Chen, L. Monaco, R. Paparella, P. Pierini, D. Sertore
INFN/LASA, Segrate (MI), Italy
C.G. Maiano
DESY, Hamburg, Germany
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy
S. Pirani
ESS, Lund, Sweden

In the framework of the ESS activity in progress at INFN-LASA, we are designing and developing 704.42 MHz Medium (β=0.67) and High (β=0.86) beta prototype cavities plug compatible with the ESS cryomodule design. The cells of one Medium and one High beta cavity are fabricated with high quality CBMM Large Grain Niobium (480 mm dia. Ingot, RRR=300, sliced by Heraeus) while a Medium beta cavity is done with Fine Grain material for comparison. The prototype cavities will be produced by the firm Ettore Zanon S.p.A. under the supervision of INFN - LASA group.

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WEPMB012

Production and Investigation of Superconducting 9-Cell Cavity Made of Large Grain Nb in KEK

SRF, accelerating-gradient, electron, niobium

2141

T. Dohmae, H. Inoue, K. Umemori, Y. Watanabe, M. Yamanaka
KEK, Ibaraki, Japan

For CW operation of superconducting cavity, reduction of heat load at cavity surface is one of important topics, since generated heat load is much higher than that of pulse wave. Using Large Grain (LG) Nb for superconducting cavity has possibility to reach higher Q0 than using Fine Grain Nb, which reduces heat load to 2K Helium. KEK Cavity Fabrication Facility(CFF) group had successfully produced superconducting 1-cell cavity made of LG Nb in 2013, and reached high Q0 at the vertical test (maximum field of 45 MV/m). Then, KEK CFF group started producing first superconducting 9-cell LG cavity in 2015, which will be completed in the end of December 2015. Whole processes of producing this cavity from sliced Nb are done in KEK. In this report, process flow and strategies of producing 9-cell cavity and results of vertical test will be presented in detail.

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WEPMB013

Long Term Cavity Performance in Compact-ERL Injector Cryomodule

cryomodule, operation, radiation, electron

2145

E. Kako, T. Konomi, T. Miura, H. Sakai, K. Umemori
KEK, Ibaraki, Japan

Degradation of cavity performance due to heavy field emission was observed in three 2-cell cavities after beam operation at 5 MeV for 2 years.

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WEPMB014

Cavity Performance of the Prototype KEK Superconducting RF Gun

cathode, target, gun, SRF

2148

T. Konomi, E. Kako, E. Kako, Y. Kobayashi, Y. Kobayashi, K. Umemori, K. Umemori, S. Yamaguchi
KEK, Ibaraki, Japan
R. Matsuda
Mitsubishi Heavy Industries Ltd. (MHI), Takasago, Japan
T. Yanagisawa
MHI, Hiroshima, Japan

A superconducting RF (SRF) gun can generate a high current and high energy beam. It has a possibility to achieve requirement from high performance ERL and high repetition FEL. Target values of the L-band KEK SRF gun are that beam repetition is 1.3 GHz, beam current is 100 mA, beam energy is 2 MeV, emittance is 1 mm mrad or less. The number of cell is 1.5. Accelerating energy of 2 MeV corresponds to 42 MV/m of maximum surface field. The photocathode is designed to be illuminated by excitation laser from backside. The SRF gun cavity consists of the 1.5 cell accelerating cavity, cathode plug and choke filter for protecting the heating of cathode plug. To evaluate these parts individually, these parts are added step by step. High gradient test of the accelerating cell without cathode plug and choke filter was done. The surface peak electric field reached 66 MV/m, and this meet the target value 42 MV/m sufficiently. Next high gradient test will be done after adding the choke filter. The choke filter is designed to be simple to wash choke cell easier. In this conference, we will report the design, fabrication and high gradient performance of the SRF gun cavity with choke filter.

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WEPMB015

Construction and 2K Cooling Test of Horizontal Test Cryostat at KEK

SRF, operation, cryomodule, HOM

2151

K. Umemori, K. Hara, E. Kako, Y. Kobayashi, Y. Kondo, H. Nakai, H. Sakai, S. Yamaguchi
KEK, Ibaraki, Japan

A horizontal test cryostat was designed and constructed at AR East building on KEK. Main purposes of test stand are improvement of module assembly technique and effective development of module components. Diameter of vacuum chamber is 1 m and its length is 3 m, which is enough to realize performance test of L-band 9-cell cavity with full assembly, including input couplers, HOM dampers/couplers and frequency tuners. On the sides, several ports are prepared to access to components, such as coupler and tuners. A cold box is placed on the top of the chamber. Liquid He is filled in a 4K-pod and 2K He is supplied through a J-T valve. A He pumping system is prepared. Inside of the chamber was covered with 80K shield, which is cooled by Liquid nitrogen. A cavity is supported on 5K table, which is also used as 5K thermal anchors. After cooling down to 80K using liquid Nitrogen, 4K He was stored and pumped down to 2K. The cooling test was successful. In this presentation, details of design and construction of the horizontal test cryostat is described and results of the cooling tests are shown. High power tests will be realized in near future.

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WEPMB016

Vertical Test Results of Nitrogen Doped SRF Cavities at KEK

vacuum, SRF, monitoring, operation

2154

K. Umemori, H. Inoue, E. Kako, T. Konomi, T. Kubo, H. Sakai, H. Shimizu, M. Yamanaka
KEK, Ibaraki, Japan
H. Hara, K. Sennyu, T. Yanagisawa
MHI-MS, Kobe, Japan

Recently Nitrogen doping(N-doping) technique was proposed and drastic improvements of Q-values were reported. Since high-Q operation of SRF cavities are very attractive for CW machine, we started investigation on performance of Nitrogen doped SRF cavities. Nitrogen doping systems were prepared on two vacuum furnaces, which have been used for annealing of SRF cavities. Two fine grain single cell cavities have been used for the study. After 800 degree, 3 hours annealing, N-doping were carried out under several Pa of Nitrogen pressure and followed by post annealing. Three kind of different conditions, pressure and duration time, were attempted. After applying EP-2, cavity performances were evaluated by vertical tests. Against our expectations, we observed lower Q-values, at every measurements, than those measured without N-doping. In this presentation, we describe details about N-doping system and parameters and results obtained by vertical tests. Some discussions are also given against our results.

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WEPMB017

High Gradient Cavity Performance in STF-2 Cryomodule for the ILC at KEK

cryomodule, radiation, HOM, accelerating-gradient

2158

Y. Yamamoto, T. Honma, E. Kako, Y. Kojima, T. Matsumoto, H. Nakai, T. Shishido
KEK, Ibaraki, Japan

The high power test for STF-2 cryomodule has completed successfully in 2015. Before cooldown of cryomodule, at first, the input coupler conditioning at room temperature is done with detuned cavities. After cooldown, the cavity conditioning, which is the main part in the performance test, is done by monitoring the radiation level measured at three locations around the cryomodule, and the heating and RF output at two HOM (Higher Order Mode) couplers. Consequently, it became clear the average accelerating gradient is 30 MV/m for STF-2 cryomodule (39 MV/m at max. and 15 MV/m at min.), and the second cavity string with four cavities had the significant performance degradation by heavy field emission due to the additional clean room work in the STF tunnel. As the following next steps, there are the LFD (Lorenz Force Detuning) measurement, LFD compensation by piezo, and long run for check of stable operation at high gradient. In the long run around 32 MV/m, each cavity without degradation showed the stable operation with the successful LFD compensation by piezo and RF feedback system. In this paper, the detailed test result will be presented.

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WEPMB018

Multipactor Simulations in 650 MHz Superconducting Spoke Cavity for an Electron Accelerator

electron, simulation, multipactoring, laser

2161

T. Kubo, T. Saeki
KEK, Ibaraki, Japan
E. Cenni
CEA/IRFU, Gif-sur-Yvette, France
R. Hajima, M. Sawamura
JAEA, Ibaraki-ken, Japan
H. Hokonohara, Y. Iwashita, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan

Funding: The work is supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
In order to realize a compact industrial-use X-ray source based on the laser-Compton scattering, a superconducting spoke cavity for an electron accelerator operated at 4K is under development. While the initially proposed operating frequency was 325MHz considering the 4K operation, we decided to start from the half scale model at 650MHz to accumulate our production experience of spoke cavity within our limited resources. In the present contribution, procedures and results of multipactor simulations for 650MHz spoke cavities are briefly introduced.

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WEPMB021

Construction of Measurement System for Superconducting Characteristics on Thin-film Samples at KEK

solenoid, operation, experiment, SRF

2167

T. Saeki, H. Hayano, T. Kubo
KEK, Ibaraki, Japan
Y. Iwashita
Kyoto ICR, Uji, Kyoto, Japan
H. Oikawa
Utsunomiya University, Utsunomiya, Japan

We set up a measurement system for superconducting characteristics on thin-film samples at KEK. The system includes small-sized and middle-sized cryostats, where critical temperature, critical magnetic field, Residual Resistiviy Ratio (RRR), Superconducting RF (SRF) resistivity can be measured on thin-film samples. A small-sized cryostat has a compact refrigerator to cool down samples for the measurements of critical temperature and RRR. On the other had, we can cool down various setups with a middle-sized cryostat by using liquid helium. A thin-film sample is set into a mushroom cavity and the SRF characteristics of the thin-film sample can be measured. In another setup, a sample is set with a small coil and the third harmonic measurement is done on the sample around the critical temperature. Finally, a thin-film sample is set into the bore-center of superconducting magnet and the magnetization of sample is measured with external magnetic field around the critical temperature. This article presents the details of the system and some measurements of samples by the system.

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WEPMB023

Hydroforming SRF Three-cell Cavity from Seamless Niobium Tube

niobium, accelerating-gradient, SRF, superconductivity

2170

M. Yamanaka, T. Dohmae, H. Inoue, G.-T. Park, K. Umemori
KEK, Ibaraki, Japan
A. Hocker
Fermilab, Batavia, Illinois, USA
T. Tajima
LANL, Los Alamos, New Mexico, USA

We are developing the manufacturing method for superconducting radio frequency (SRF) cavities by using a hydroforming instead of using conventional electron beam welding. We expect higher reliability and reduced cost with hydroforming. For successful hydroforming, high-purity seamless niobium tubes with good formability as well as advancing the hydroforming technique are necessary. Using a seamless niobium tube from ATI Wah Chang, we were able to successfully hydroform a 1.3 GHz three-cell TESLA-like cavity and obtained an Eacc of 32 MV/m. A barrel polishing process was omitted after the hydroforming. The vertical test was carried out with very rough inside surface. We got amazing and interesting result.

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WEPMB024

Study on Nondestructive Inspections for Super-conducting Cavity

cryogenics, survey, interface, radiation

2174

H. Tongu, H. Hokonohara, Y. Iwashita
Kyoto ICR, Uji, Kyoto, Japan
R. Hajima, M. Sawamura
JAEA, Ibaraki-ken, Japan
H. Hayano, T. Kubo, T. Saeki, Y. Yamamoto
KEK, Ibaraki, Japan

Funding: The work is supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
We have been studying nondestructive inspections for super-conducting spoke cavities. The temperature mapping (T-map) and X-ray mapping (X-map) are powerful inspection methods to locate a hot spot during the vertical RF tests. There would be a defect under the hot spot and the defect may be the cause of a quench. Our XT-map system (a combined system of T-map and X-map) has a high resolution in space. Because the huge amount of sensor signals are multiplexed at a hi-speed scanning rate in the vicinity of the sensors, the small number of signal lines makes the installation process easy and reduces the system complexity. Our XT-map got useful results on finding a defect in vertical RF tests of International Linear collider super-conducting cavity. The XT-map system is useful as low cost nondestructive inspections for superconducting spoke cavity. The study will be reported. progresses will be reported.

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WEPMB025

Fabrication of Superconducting Spoke Cavity for Laser Compton Scattered Photon Sources

laser, photon, simulation, linac

2177

M. Sawamura, R. Hajima
QST, Tokai, Japan
H. Hokonohara, Y. Iwashita, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan
T. Kubo, T. Saeki
KEK, Ibaraki, Japan

Funding: The work is supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
We have launched a 5-year research program to develop superconducting spoke cavity for laser Compton scattered (LCS) photon sources. For realizing a wide use of LCS X-ray and γ-ray sources in academic and industrial applications, we adopt the super-conducting spoke cavity to electron beam drivers. The spoke cavity has advantages such as relative compactness in comparison with an elliptical cavity of the same frequency, robustness with respect to manufacturing inaccuracy due to its strong cell-to-cell coupling, the better packing in a linac to install couplers on outer conductor. On the other hand the spoke cavity has disadvantage of more complicated structure than an elliptical cavity. Though our proposal design for the photon source consists of the 325 MHz spoke cavities in 4K operation, we have begun to fabricate the half scale model of 650 MHz spoke cavity in order to accumulate our cavity production experience by effective utilization of our limited resources. In this paper, we present our fabrication status.

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WEPMB026

MHI-MS's Production Activities of Superconducting Cavity

SRF, electron, gun, superconducting-RF

2180

H. Hara, A. Miyamoto, K. Sennyu, T. Yanagisawa
MHI-MS, Kobe, Japan
E. Kako, T. Konomi, H. Nakai, K. Umemori
KEK, Ibaraki, Japan

Mitsubishi Heavy Industries Mechatronics Systems, Ltd. (MHI-MS), a subsidiary of MHI, took over MHI's accelerator business on October 1, 2015, and has been developing the business since that time. MHI-MS has developed manufacturing process of superconducting cavities continuously. In this presentation, recent progress will be reported.

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WEPMB028

High HOM Damping Structure Study for CEPC

HOM, damping, collider, dipole

2183

Z.C. Liu, J. Gao, S. Jin, Y. Wang, H.J. Zheng
IHEP, Beijing, People's Republic of China

Both large circular collider such as CEPC and high current ERL facility need high HOM damping superconducting cavity. The slotted cavity is an option for such applications. It has three slotted waveguides which can highly damp the HOM and extract high HOM power out. However, the HOM absorbers for such facility are usually put outside of the cryomodule to decrease the influence of HOM power on the cryogenic system. Large slot waveguide need to make smaller transition structure to adapt this situation. A rectangular waveguide to coaxial waveguide structure was designed to the slotted cavity. In this paper, we will show the cavity HOM damping design scheme with this structure.

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WEPMB029

Research of Nitrogen Doping at IHEP

niobium, vacuum, experiment, electron

2186

P. Sha
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
J.P. Dai
IHEP, Beijing, People's Republic of China
F. Jiao
PKU, Beijing, People's Republic of China

Funding: Work funded by National Natural Science Foundation of China, Grant No. 11505197
Recently, nitrogen doping (N-doping) technology has been proved to increase Q0 of superconducting cavity obviously, which lowers the BCS surface resistance. After N-doping, Q0 of 9-cell 1.3 GHz cavity can be increased to 3*10¹⁰ at Eacc = 16 MV/m, while 1.5*1010 without N-doping [1]. Since 2013, there have been over 60 cavities nitrogen doped at FNAL, JLAB and Cornell. The Circular Electron Collider (CEPC) has been proposed by IHEP in China, while requests Q0=4e10@Eacc=15.5 MV/m for 650 MHz cavity. It's hard to achieve without N-doping. So research of N-doping was begun in cooperation with Peking University in early 2015. Experiments of niobium samples have showed that nitrogen concentration at niobium surface increased a lot after N-doping. After then, several single-cell 1.3 GHz cavities completed vertical tests, but there're no successful test results of Q0 increasing, yet.

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WEPMB030

Design Study of a Compact Deflecting Cavity at IHEP

dipole, controls, linac, simulation

2188

J.P. Dai, B. Ni, J.Y. Zhai, J.R. Zhang
IHEP, Beijing, People's Republic of China

For the XFEL project proposed by IHEP, a sophisticated beam spreader is required to separate a single beam into multiple beams. One of the deflecting cavities used in the spreader has been investigated and optimized. It is a 325 MHz, compact RF-dipole superconducting cavity, with the transverse R/Q of 2900Ω, geometrical factor G of 88.5 Ω, and the Helium pressure sensitivity df/dp of 3.4 Hz/mbar. At the nominal deflecting voltage of 7MV, the peak electric field Epeak is 41 MV/m and peak magnetic field Bpeak is 48 mT. This paper will present the detailed RF and mechanical designs.

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WEPMB031

Post Processing of Spoke Type Superconducting Cavities at Institute of High Energy Physics

linac, proton, target, SRF

2191

J. Dai, J.P. Dai, F.S. He, X. Huang, L.H. Li, Z.Q. Li, H.Y. Lin, Z.C. Liu, B. Ni, W.M. Pan, P. Sha, G.W. Wang, Q.Y. Wang, Z. Xue, X.Y. Zhang, G.Y. Zhao
IHEP, Beijing, People's Republic of China

Funding: Work supported by Chinese Academy of Science strategic Priority Research Program-Future Advanced Nuclear Fission Energy.
After upgrading the post-processing system, several superconducting cavities were RF tested at Institute of High Energy Physics (IHEP) in China recently. The test results of 14 spoke 012 cavities and 6 spoke 021 cavities which used at China ADS injector I and linac all exceeds our design objective. Moreover, a spoke 040, a 650MHz elliptical cavity and a 325MHz HWR cavity are also vertical tested and the test results are all significantly surpass our design value. The post processing of these cavities including Buffered Chemical Polishing (BCP), high temperature heat treatment and High Pressure water Rinsing (HPR) is presented here.
daijin@pku.edu.cn

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WEPMB032

Fabrication and Testing Status of IHEP03

SRF, superconducting-RF, niobium, status

2194

T.X. Zhao, J. Gao, S. Jin, Z.Q. Li, Y.L. Liu, Z.C. Liu, Y. Wang, J.Y. Zhai, H.J. Zheng
IHEP, Beijing, People's Republic of China
M. Asano, E. Kako
KEK, Ibaraki, Japan
H. Yu, H. Yuan
BIAM, Beijing, People's Republic of China

After the successful development of the IHEP01 and IHEP02 1.3GHz 9cell superconducting cavity, we developed a 1.3GHz Tesla-Like 9cell superconducting cavities in collaboration with KEK. The cavity was made by niobium material produced in OTIC, Ningxia, China. After completeing welding, leakage check, BCP, HPR, we sent the cavity to KEK and used the standard procedures of ILC cavity for processing. These include electron polishing, vacuum furnace outgassing, tuning for field flatness and frequency, light EP, baking and vertical test. We target to have a high Q0 cavity for this experiment. In this paper, we will report the experimental status of the IHEP03 cavity.

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WEPMB034

Analysis of Niobium Quality Control for SRF Cavity

niobium, SRF, controls, radio-frequency

2197

M.J. Joung
IBS, Daejeon, Republic of Korea

Funding: the Ministry of Science, ICT and Future Planning (MSIP) and the National Research Foundation (NRF) of the Republic of Korea under Contract 2013M7A1A1075764.
Clean and smooth surface is important to get low sur-face resistance for superconducting material. SRF (Super-conducting Radio Frequency) cavity made of niobium which is superconducting material and also one of the rare metal. The procedure of niobium quality control was set up to get high performance SRF cavity. The procedure consists of three parts; certificates check, Nb specification verification, and surface inspection and measurements of thickness, roughness, flatness. Three important properties which are RRR value, chemical composition and me-chanical properties were verified to conform Nb specifica-tion. The range of thickness, roughness and flatness for niobium as SRF cavity raw material were obtained by measurement.

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WEPMB035

SRF Cavities for RAON

SRF, TRIUMF, factory, accelerating-gradient

2200

H.C. Jung, J. Joo, J. Lee
IBS, Daejeon, Republic of Korea
R.E. Laxdal, Z.Y. Yao
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

SRF cavities of superconducting linear accelerators in RAON are developed and tested at 2K/4K. 1st Quarter Wave Resonator (QWR) and Half Wave Resonator (HWR) are fabricated by a domestic vender and tested in the TRIUMF's facility. The measured Q factors are above the required values at the operating gradients. And the predicted multipacting phenomena are observed in the test and easily conditioned. The Q factors decreased after a slow cooldown and enhanced at 4K tests by a low temperature baking. Based on these tests, modified bare cavities are newly developed, jacketed and will be tested with tuners and power couplers.

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WEPMB036

High Pressure Rinsing for Niobium Superconducting Cavity

niobium, target, SRF, operation

2202

Y. Jung, M.J. Joung, M. Lee
IBS, Daejeon, Republic of Korea
J. Lee, J. Seo
Vitzrotech Co., Ltd., Ansan City, Kyunggi-Do, Republic of Korea

Niobium superconducting cavity is treated with high pressure rinsing to clean the inner surface of the cavity. Either organic or inorganic residues on the inner surface of the cavity can cause serious problems during the cavity operation. A thermal quenching - superconducting material loses its superconductivity - is a typical phenomenon brought out by harmful defects by increasing critical temperature. We have performed high pressure rinsing experiments to check out a prototype HPR machine. HPR experiments were performed with a simplified cavity structure, and analyzed as a function of the pressure, the distance from a nozzle, and the sizes of defects on the niobium surface. In this presentation, we will discuss the performance of the prototype HPR machine.

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WEPMB041

Design of RF Power Coupler for RISP Half Wave Resonator

simulation, impedance, vacuum, electron

2208

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

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

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WEPMB044

Development of RF Conditioning System for RISP RF Power Couplers

controls, vacuum, ion, heavy-ion

2211

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

RF power coupler prototypes have been conditioned for a heavy ion accelerator of the Rare Isotope Science Project (RISP) in Korea. The RF couplers operate for 162.5 MHz half-wave resonators at 6 kW RF power. The RF couplers are a 50-Ohm coaxial structure with a disk type ceramic window at room temperature. The control system using Labview software supported automatic process for RF conditioning, data acquisition and interlock system. The conditioning system and the result of conditioning of RF coupler are presented in this paper.

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WEPMB045

Measurement of Higher Order Modes Electrodynamic Characteristics for Array of Two 2400 MHz Cavities

HOM, damping, simulation, higher-order-mode

2214

Ya.V. Shashkov, R.V. Donetskiy, M.V. Lalayan, N.P. Sobenin
MEPhI, Moscow, Russia
A. Orlov
NRNU, Moscow, Russia

Funding: *Work supported by Ministry of Education and Science grant 3.245.2014/r and the EU FP7 HiLumi LHC ' Grant Agreement 284404
In the frameworks of the High Luminosity Large hadron collider (HL-LHC) upgrade program an application of additional superconducting harmonic cavities operating at 800 MHz is currently under discussion. As a candidate, the two cavities with grooved beam pipes connected by the drift tube were suggested. In this article of measurements of Qload are performed for the aluminum model of array of two cavities connected by drift tube. Field distribution of Fundamental Mode (FM) and Higher Order Modes (HOM) were measured for aluminum prototype with a frequency of the operational mode of 2400 MHz, and their comparison with the simulation results.
Higher order modes

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WEPMB047

Higher Order Modes Couplers for 800 MHz Harmonic Cavity

HOM, damping, electron, multipactoring

2217

Ya.V. Shashkov, R.V. Donetskiy, M. Gusarova, N.P. Sobenin
MEPhI, Moscow, Russia

Funding: *Work supported by Ministry of Education and Science grant 3.245.2014/r
For the higher order modes damping (HOM) in the 800 MHz superconducting single cell cavity the HOM coupler was developed. Several versions of the coupler design were shown. For the chain of two cavities with couplers the calculations of external Q-factor are presented. The calculations of multipactor discharge of cavity were also conducted.
Higher order modes, Tesla, couplers

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WEPMB048

Macros for Identification of Higher Order Modes Types, Their Transverse Shunt Impedance and Kick Factor

HOM, higher-order-mode, damping, interface

2220

Ya.V. Shashkov
MEPhI, Moscow, Russia
A. Orlov
NRNU, Moscow, Russia

Funding: *Work supported by Ministry of Education and Science grant 3.245.2014/r
During the design studies of accelerating cavities one of the most time-consuming tasks is classification of the higher order modes (HOM) types. To automate the process of identification of HOM types special macros for CST Microwave studio was written. This article describes the programs algorithm of mode recognition and the results of the analysis on the example of single cell and 9 cell cavities. Macros for the calculation of the HOM transverse shunt impedance upon Q-factor values and kick-factor was also written.
Higher order modes, electrodynamic characteristics, macros

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WEPMB050

RF Test of ESS Superconducting Spoke Cavities at Uppsala University

resonance, pick-up, radiation, controls

2227

H. Li, A.K. Bhattacharyya, V.A. Goryashko, L. Hermansson, R.J.M.Y. Ruber, R. Santiago Kern
Uppsala University, Uppsala, Sweden
N. Gandolfo, G. Olry
IPN, Orsay, France

The European Spallation Source (ESS) is an accelerator-driven neutron spallation source built in Sweden. It will deliver the first protons to a rotating tungsten target by 2019 and will reach the full 5 MW average beam power in the following years. The superconducting Spoke cavities are considered compact structures at low frequencies and having an excellent RF performance in both low and medium velocity regimes, therefore ESS will include a total of 26 double-spoke cavities. The testing of the double-spoke prototype cavity at high power has been conceded to Uppsala University, Sweden, where the Facility for Research Instrumentation and Accelerator development (FREIA) has been equipped with superconducting cavity test facility. A bare spoke cavity has been tested at the FREIA Laboratory with a self-exited loop at low power level to confirm its vertical test performance at IPNO. Similar test results as IPNO's previous test were obtained with FREIA system. In this paper we present the methods and preliminary study results of the cavity performance.

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WEPMB051

HIE-ISOLDE: First Commissioning Experience

cryomodule, solenoid, operation, controls

2230

W. Venturini Delsolaro, E. Bravin, N. Delruelle, M. Elias, J.A. Ferreira Somoza, M.A. Fraser, J. Gayde, Y. Kadi, G. Kautzmann, F. Klumb, Y. Leclercq, M. Martino, V. Parma, J.A. Rodriguez, S. Sadovich, E. Siesling, D. Smekens, L. Valdarno, D. Valuch, P. Zhang
CERN, Geneva, Switzerland

The HIE ISOLDE project [1] reached a major milestone in October 2015, with the start of the first physics run with radioactive ion beams. This achievement was the culminating point of intense months during which the first cryomodule of the HIE ISOLDE superconducting Linac and its high-energy beam transfer lines were first installed and subsequently brought into operation. Hardware commissioning campaigns were conducted in order to define the envelope of parameters within which the machine could be operated, to test and validate software and controls, and to investigate the limitations preventing the systems to reach their design performance. Methods and main results of the first commissioning of HIE ISOLDE post accelerator, including the performance of the superconducting cavities with beam, will be reviewed in this contribution.

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WEPMB052

System Integration and Beam Commissioning of the 500-MHz RF Systems for Taiwan Photon Source

SRF, operation, vacuum, storage-ring

2234

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

The accelerator complex of the Taiwan Photon Source (TPS) consists of two 500-MHz RF systems: one RF system with two KEKB-type single-cell SRF modules is operated for the 3-GeV storage ring of circumference 518 m, and the other with one five-cell Petra cavity at room temperature is for the concentric full-energy booster synchrotron. This report overviews the installation, system integration, commissioning, and initial operation of the 500-MHz RF systems for the TPS with emphasis on our solution to approach the highly reliable SRF operation at its maximum design beam current of 500-mA. Lessons learned during the project are reviewed.

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WEPMB053

Study of Third Harmonic Cavity for Taiwan Photon Source

dipole, vacuum, electron, scattering

2237

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

Taiwan Photon Source (TPS) is a modern light source with 3 GeV electron energy and low emittance. The bunch length is about 3 mm at designed beam current of 500 mA and operating gap voltage of 3.2 MV. The short bunch length results in short Touschek lifetime and high parasitic loss of insertion device (ID). Some of the undulators are operated in vacuum at TPS, therefore the head load become an important issue. To install higher harmonic cavity is a solution for improving the Touschek lifetime and the heat load by lengthening the bunch length. The effect of installing 3rd harmonic cavity for TPS is investigated. The expected maximum elongation factor for bunch lengthening, as well as the effect on the Touschek lifetime and heat load of ID are presented in this paper.

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WEPMB057

First Results of Magnetic Field Penetration Measurements on Multilayer S-I-S Structures

SRF, niobium, target, experiment

2245

O.B. Malyshev, K.D. Dumbell, L. Gurran, N. Pattalwar, S.M. Pattalwar, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
A.V. Gurevich
ODU, Norfolk, Virginia, USA
L. Gurran
Lancaster University, Lancaster, United Kingdom
L. Gurran
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
O.B. Malyshev, S.M. Pattalwar, R. Valizadeh
Cockcroft Institute, Warrington, Cheshire, United Kingdom

The performance of superconducting RF cavities made of bulk Nb is limited by a breakdown field of Bp=~200 mT, close to the superheating field for Nb. A potentially promising solution to enhance the breakdown field of the SRF cavities beyond the intrinsic limits of Nb is a multilayer coating suggested in [1]. In the simplest case, such a multilayer may be a superconductor-insulator-superconductor (S-I-S) coating, for example, bulk niobium (S) coated with a thin film of insulator (I) followed by a thin layer of another superconductor (S) which could be e.g. dirty niobium [2]. Here we report the first results of our measurements of field penetration in Nb thin films and Nb-AlN-Nb multilayer samples at 4.2 K using the magnetic field penetration facility designed, built and tested in ASTeC.

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WEPMB058

LHC Crab Cavity Coupler Test Boxes

HOM, luminosity, operation, higher-order-mode

2248

J.A. Mitchell
Lancaster University, Lancaster, United Kingdom
R. Apsimon, G. Burt, A.R.J. Tutte
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
R. Calaga, A. Macpherson, E. Montesinos
CERN, Geneva, Switzerland
S.D. Silva
ODU, Norfolk, Virginia, USA
B. P. Xiao
BNL, Upton, Long Island, New York, USA

The LHC double quarter wave (DQW) crab cavities have two different types of Higher Order Mode (HOM) couplers in addition to a fundamental power coupler (FPC). The FPC requires conditioning, so to achieve this we have designed a radio-frequency (RF) quarter wave resonator to provide high transmission between two opposing FPCs. For the HOM couplers we must ensure that the stop-band filter is positioned at the cavity frequency and that peak transmission occurs at the same frequencies as the strongest HOMs. We have designed two test boxes which preserve the cavity spectral response in order to test the couplers.

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WEPMB060

Modifications to the Pump Out Box to Lower the Qext of Diamond SCRF Cavities

coupling, operation, simulation, electron

2251

S.A. Pande, C. Christou, P. Gu
DLS, Oxfordshire, United Kingdom
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom

Diamond's CESR-B cavities are iris coupled and have fixed Qext. For reliability, the cavities are operated at lower voltages. This results in the optimum condition for beam loading being satisfied at a much lower power typically about 100 kW. For operation at 300 mA with two cavities, the RF power needed per system exceeds 200 kW. Consequently, the cavities need to be operated under-coupled. To lower the Qext and move the optimum operating point nearer to 200kW, 3 stub tuners are used in the waveguide feed line. The difference in the height of the coupling waveguide on cavity and that of the vacuum side waveguide on the window assembly results in a step transition which affects the Qext. The present window/step location results in Qext higher than that without the window. The Qext can be lowered by re-locating the RF window or by shifting the step change in the waveguide cross-section from its present location. This needs modification to the Pump Out box. The pros and cons of the proposed modification to the pump out box in terms of standing waves and multipacting characteristics studied with CST Studio are discussed in this paper.

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WEPMR003

Tailoring Surface Impurity Content to Maximize Q-factors of Superconducting Resonators

superconductivity, niobium, simulation, factory

2258

M. Martinello, M. Checchin, A. Grassellino, O.S. Melnychuk, S. Posen, A. Romanenko, D.A. Sergatskov
Fermilab, Batavia, Illinois, USA
M. Checchin, M. Martinello
Illinois Institute of Technology, Chicago, Illlinois, USA
J. Zasadzinski
IIT, Chicago, Illinois, USA

Funding: Fermilab is operated by Fermi Research Alliance, LLC under contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Quality factor of superconducting radio-frequency (SRF) cavities is degraded whenever magnetic flux is trapped in the cavity walls during the cooldown. In this contribution we study how the trapped flux sensitivity, defined as the trapped flux surface resistance normalized for the amount of flux trapped, depends on the mean free path. A variety of 1.3 GHz cavities with different surface treatments (EP, 120 C bake and different N-doping) were studied in order to cover the largest range of mean free path nowadays achievable, from few to thousands of nanometers. A bell shaped trend appears for the range of mean free path studied. Over doped cavities falls at the maximum of this curve defining the largest values of sensitivity. In addition, we have also studied the trend of the BCS surface resistance contribution as a function of mean free path, revealing that N-doped cavities follow close to the theoretical minimum of the BCS surface resistance as a function of the mean free path. Adding these results together we unveil that optimal N-doping treatment allows to maximize Q-factor at 2 K and 16 MV/m until the magnetic field fully trapped during the cavity cooldown stays below 10 mG.

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WEPMR004

Cryomdoule Test Stand Reduced-Magnetic Support Design at Fermilab

cryomodule, SRF, vacuum, linac

2262

M.W. McGee, S.K. Chandrasekaran, A.C. Crawford, E.R. Harms, J.R. Leibfritz, G. Wu
Fermilab, Batavia, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC, under Contract No. DE-AC02- 07CH11359 with the U.S. Department of Energy
In a partnership with SLAC National Accelerator Laboratory (SLAC) and Jefferson Lab, Fermilab will assemble and test 17 of the 35 total 1.3 GHz cryomodules for the Linac Coherent Light Source II (LCLS-II) Project. These devices will be tested at Fermilab's Cryomodule Test Facility (CMTF) within the Cryomodule Test Stand (CMTS-1) cave. The problem of magnetic pollution became one of major issues during design stage of the LCLS-II cryomodule as the average quality factor of the accelerating cavities is specified to be 2.7 x 10¹⁰. One of the possible ways to mitigate the effect of stray magnetic fields and to keep it below the goal of 5 mGauss involves the application of low permeable materials. Initial permeability and magnetic measurement studies regarding the use of 316L stainless steel material indicated that cold work (machining) and heat affected zones from welding would be acceptable.

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WEPMR005

Investigation of Thermal Acoustic Effects on SRF Cavities within CM1 at Fermilab

cryomodule, operation, cryogenics, acceleration

2265

M.W. McGee, E.R. Harms, A.L. Klebaner, J.R. Leibfritz, A. Martinez, Y.M. Pischalnikov, W. Schappert
Fermilab, Batavia, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC, under Contract No. DE-AC02- 07CH11359 with the U.S. Department of Energy.
Two TESLA-style 8-cavity cryomodules have been operated at Fermilab Accelerator Science and Technology (FAST), formerly the Superconducting Radio Frequency (SRF) Accelerator Test Facility. Operational instabilities were revealed during Radio Frequency (RF) power studies. These observations were complemented by the characterization of thermal acoustic effects on cavity microphonics manifested by apparent noisy boiling of helium involving vapor bubble and liquid vibration. The thermal acoustic measurements also consider pressure and temperature spikes which drive the phenomenon at low and high frequencies.

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WEPMR006

Transport of LCLS-II 1.3 GHz Cryomodule to SLAC

cryomodule, vacuum, acceleration, alignment

2268

M.W. McGee, T.T. Arkan, T.J. Peterson, Z. Tang
Fermilab, Batavia, Illinois, USA
S.R. Boo, M. Carrasco
SLAC, Menlo Park, California, USA
E. Daly, N.A. Huque
JLab, Newport News, Virginia, USA

Funding: Operated by Fermi Research Alliance, LLC, under Contract No. DE-AC02- 07CH11359 with the U.S. Department of Energy.
In a partnership with SLAC National Accelerator Laboratory (SLAC) and Jefferson Lab, Fermilab will assemble and test 17 of the 35 total 1.3 GHz cryomodules for the Linac Coherent Light Source II (LCLS-II) Project. These include a prototype built and delivered by each Lab. Another two 3.9 GHz cryomodules will be built, tested and transported by Fermilab to SLAC. Each assembly will be transported over-the-road from Fermilab or Jefferson Lab using specific routes to SLAC. The transport system consists of a base frame, isolation fixture and upper protective truss. The strongback cryomodule lifting fixture is described along with other supporting equipment used for both over-the-road transport and local (on-site) transport at Fermilab. Initially, analysis of fragile components and stability studies will be performed in order to assess the risk associated with over-the-road transport of a fully assembled cryomodule.

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WEPMR009

Magnetic Flux Expulsion Studies in Niobium SRF Cavities

niobium, cryomodule, background, survey

2277

S. Posen, M. Checchin, A.C. Crawford, A. Grassellino, M. Martinello, O.S. Melnychuk, A. Romanenko, D.A. Sergatskov, Y. Trenikhina
Fermilab, Batavia, Illinois, USA

With the recent discovery of nitrogen doping treatment for SRF cavities, ultra-high quality factors at medium accelerating fields are regularly achieved in vertical RF tests. To preserve these quality factors into the cryomodule, it is important to consider background magnetic fields, which can become trapped in the surface of the cavity during cooldown and cause Q₀ degradation. Building on the recent discovery that spatial thermal gradients during cooldown can significantly improve expulsion of magnetic flux, a detailed study was performed of flux expulsion on two cavities with different furnace treatments that are cooled in magnetic fields amplitudes representative of what is expected in a realistic cryomodule. In this contribution, we summarize these cavity results, in order to improve understanding of the impact of flux expulsion on cavity performance.

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WEPMR011

Simulations and Experimental Studies of Third Harmonic 3.9 Ghz CW Couplers for LCLS-II Project

operation, simulation, cryomodule, linac

2280

N. Solyak, I.V. Gonin, E.R. Harms, S. Kazakov, T.N. Khabiboulline, A. Lunin
Fermilab, Batavia, Illinois, USA

LCLS-II linac is based on SRF technology developed for the XFEL project. The XFEL 3rd harmonic system built by INFN is based on the original designs of cavity and power coupler developed and built by Fermilab for the FLASH facility at DESY. For LCLS-II application both designs of the 3.9 GHz cavity and the power coupler have been modified for an operation in the continuous wave regime up to 2 kW average RF power. In this paper we discuss coupler modifications and the result multiphysics analysis for various operating regimes. For the initial test of a proposed design, we decided to modify two spare warm sections of power couplers, built for the FLASH facility, by shortening both of two inner bellows and making a thicker copper plating. Modification of the existing coupler test stand and the test program are briefly discussed in this paper.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR011

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WEPMR013

Study of LCLS-II Fundamental Power Coupler Heating in HTS Integrated Cavity Tests

resonance, HOM, vacuum, simulation

2286

N. Solyak, I.V. Gonin, A. Grassellino, C.J. Grimm, T.N. Khabiboulline, J.P. Ozelis, K. Premo, O.V. Prokofiev, D.A. Sergatskov, G. Wu
Fermilab, Batavia, Illinois, USA

LCLS-II coupler based on modified design of TTF3 coupler for higher average power was assembled on high Q cavity and tested at HTS as part of integrated cavity test program. Couplers were thermally connected to thermal shields and equipped with diagnostics to control temperature in different locations and provide information about cryogenic heat loads at 2 K, 5 K and 80 K.Three dressed cavities with power couplers were tested in HTS at full specified RF power. Results are summarized in this paper and cross-checked with simulation.

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WEPMR014

RF Design of a High Average Beam-Power SRF Electron Source

electron, SRF, laser, free-electron-laser

2289

N. Sipahi, S. Biedron, S.V. Milton
CSU, Fort Collins, Colorado, USA
I.V. Gonin, R.D. Kephart, T.N. Khabiboulline, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

There is a significant interest in developing high-average power electron sources, particularly in the area of electron sources integrated with Superconducting Radio Frequency (SRF) systems. For these systems, the electron gun and cathode parts are critical components for stable intensity and high-average powers. In this initial design study, we will present the design of a 9-cell accelerator cavity having a frequency of 1.3 GHz and the corresponding field optimization studies.

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WEPMR015

Surface Topography Techniques at Cornell University: Optical Inspection and Surface Replica

SRF, laser, controls, GUI

2292

G.M. Ge, F. Furuta, D. Gonnella, D.L. Hall, G.H. Hoffstaetter, M. Liepe, T.I. O'Connell, J. Sears
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Surface imperfections significantly limit the performance of superconducting radio frequency (SRF) cavities. The development of surface topography techniques aims to locate the surface flaws in an SRF cavity and profile their geometry details. This effort plays an important role of quality control in cavity productions as well as provides contour information of the defects for understanding quench mechanisms. The surface topography techniques at Cornell University include an optical inspection system and surface replica technique. In this paper, we present the details of the techniques and show features found in the SRF cavities at Cornell.

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WEPMR016

Vertical Electropolishing Studies at Cornell with KEK and Marui

cathode, target, SRF, niobium

2295

F. Furuta, G.M. Ge, T. Gruber, J.J. Kaufman, J. Sears
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi
MGH, Hyogo-ken, Japan
H. Hayano, S. Kato, T. Saeki
KEK, Ibaraki, Japan

Cornell's SRF group has developed Vertical Electro-Polishing (VEP) and applied on 1.3GHz Niobium SRF cavities as the primary surface treatment. High-Q and high voltage performances of VEP'ed SRF cavities had been successfully demonstrated at Cornell. In 2014, new VEP R&D collaboration has started between Cornell, KEK, and Marui Galvanizing Co. Ltd. (MGI). MGI and KEK has developed their original VEP cathode named 'i-cathode Ninja'® which has four retractable wing-shape parts per cell for single-/9-cell cavities. We will report the results of VEP process using 'i-cathode Ninja'® on single cell cavity at Cornell.

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WEPMR019

Development of Plasma Cleaning at Cornell University

plasma, SRF, experiment, superconductivity

2302

G.M. Ge, F. Furuta, M. Liepe, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Cornell University is developing the plasma cleaning technology as an alternative cleaning technique for SRF cavity surface preparation. In experiments, we successfully ignited the plasma in a single-cell SRF cavity. However the experiments were limited by the peak electric-fields in the RF coupler. In this paper, we show the analysis of the limitation and propose a new design of the coupler which can eliminate the limitation.

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WEPMR020

First Cool-down of the Cornell ERL Main Linac Cryo-Module

linac, cryomodule, HOM, vacuum

2305

R.G. Eichhorn, J.V. Conway, F. Furuta, G.M. Ge, D. Gonnella, T. Gruber, G.H. Hoffstaetter, J.J. Kaufman, M. Liepe, T.I. O'Connell, P. Quigley, D.M. Sabol, J. Sears, E.N. Smith, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Cornell University has finished building a 10 m long superconducting accelerator module as a prototype of the main linac of a proposed ERL facility. This module houses 6 superconducting cavities- operated at 1.8 K in continuous wave (CW) mode with a design field of 16 MV/m and a Quality factor of 2x10¹⁰. We wil shortly review the design and focus on reporting on the first cool-down of this module. We will giving data for various cool-down scenarios (fast/ slow), uniformity and performance

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WEPMR021

HOM Measurements for Cornell's High-current CW ERL Cryomodule

HOM, cryomodule, simulation, linac

2309

F. Furuta, R.G. Eichhorn, G.M. Ge, D. Gonnella, G.H. Hoffstaetter, M. Liepe, P. Quigley, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

The main linac cryomodule (MLC) for the future energy-recovery linac (ERL) based synchrotron-light facility at Cornell had been designed, fabricated, and tested. It houses 6 SRF cavities with individual higher order-modes (HOMs)absorbers and one magnet/ BPM section. We will report the HOM study on MLC.

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WEPMR022

ERL Main Linac Cryomodule Cavity Performance and Effect of Thermal Cycling

cryomodule, linac, SRF, target

2312

F. Furuta, J. Dobbins, R.G. Eichhorn, G.M. Ge, D. Gonnella, G.H. Hoffstaetter, M. Liepe, T.I. O'Connell, P. Quigley, D.M. Sabol, J. Sears, E.N. Smith, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Cornell has designed, fabricated, and tested a high current (100 mA) CW SRF prototype cryomodule for the future energy-recovery linac (ERL) based synchrotron-light facility at Cornell . It houses six 7-cell SRF cavities with individual HOM absorbers and one magnet/ BPM section. Cavities are targeted to operate with high Qo of 2.0·10¹⁰ at 16.2 MV/m, 1.8 K in continuous wave (CW) mode. We will report the RF test results of 7-cell cavities in this cryomodule after initial cooldown and several thermal cycles with different cooldown method.

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WEPMR023

Surface Analysis Studies of Nb3Sn Thin Films

niobium, SRF, radio-frequency, electron

2316

D.L. Hall, J.J. Kaufman, M. Liepe, J.T. Maniscalco
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

A recent study to optimise the coating of thin-film Nb3Sn cavities has resulted in coating procedures that can fabricate 1.3 GHz cavities capable of reproducibly achieving fields of >16 MV/m with record high Qs >10¹⁰ at 4.2 K. However, the performance of these next generation SRF cavities is as yet well below the theoretical maximum performance expected of Nb3Sn, thus giving ample room for further advancements. Current measurements strongly suggest that the current limits are due to local defects and irregularities in the coated surface. In this paper we analyse, using methods including SEM/EDS, TEM, XRD and EBSD, the surface of both sample coupons and cavity cut-outs, with a view to identifying and understanding the origin of surface non-uniformities that would lead to increased surface resistance and cavity quench.

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WEPMR024

RF Measurements on High Performance Nb3Sn Cavities

niobium, SRF, radio-frequency, accelerating-gradient

2320

D.L. Hall, M. Liepe, J.T. Maniscalco
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

A single-cell 1.3 GHz ILC-shape thin-film Nb3Sn-on-Nb cavity recently achieved accelerating gradients of >16 MV/m with a record Q0 of approx. 2·10¹⁰ at 4.2 K, exceeding the power efficiency seen in the current most efficient niobium cavities. A concurrent study of the coating process has resulted in a coating procedure that is capable of replicating this performance in other single-cell cavities. In this paper we demonstrate the RF performance and behaviour of these next generation SRF cavities, with an emphasis on both the impact from both external magnetic fields and the cavity cool down procedure on cavity performance.

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WEPMR025

Improved N-Doping Protocols for SRF Cavities

simulation, niobium, SRF, radio-frequency

2323

D. Gonnella, R.G. Eichhorn, F. Furuta, G.M. Ge, T. Gruber, G.H. Hoffstaetter, J.J. Kaufman, P.N. Koufalis, M. Liepe, J.T. Maniscalco
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: NSF, DOE
Nitrogen-doping has been shown to consistently produce better quality factors in SRF cavities than is achievable with standard preparation techniques. Unfortunately, nitrogen-doping typically brings with it lower quench fields and higher sensitivities of residual resistance to trapped magnetic flux. Here we present work to understand these effects in hopes of mitigating them while maintaining the high Q desired by future projects. Using a nitrogen diffusion simulation, material parameters of nitrogen-doped cavities can be predicted prior to doping. These simulations results are consistent with SIMS data taken from samples treated with cavities. The nature of doping's effect on quench field has also been studied using CW and pulsed measurements. These results have allowed us to better understand the nature of nitrogen-doping and its effect on cavity performance.

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WEPMR026

RF Losses from Trapped Flux in SRF Cavities

vacuum, SRF, site, niobium

2327

D. Gonnella, J.J. Kaufman, P.N. Koufalis, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: NSF
Previous measurements at Cornell have shown that the sensitivity of residual resistance to trapped magnetic field in SRF cavities is heavily dependent on the mean free path of the RF penetration layer of the niobium. Here we report on a systematic study of ten cavity preparations with different mean free paths and the effect of these preparations on sensitivity to trapped magnetic flux. In the clean limit, longer mean free path leads to a lower sensitivity to trapped magnetic flux while in the dirty limit the opposite is true, shorter mean free path leads to lower sensitivity. These results are also shown to be in good agreement with theoretical predictions of RF losses due to oscillations of vortex lines.

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WEPMR027

Dependence of Surface Resistance on N-Doping Level

niobium, SRF, linac, radio-frequency

2331

D. Gonnella, F. Furuta, G.M. Ge, J.J. Kaufman, P.N. Koufalis, M. Liepe, J.T. Maniscalco
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: NSF, DOE
Nitrogen-doping has become a standard tool for reaching high quality factors in SRF cavities in the medium field region at 2 K. This high Q has been shown to be a result of lowering of the temperature dependent BCS resistance. Here we show that this lowering of the BCS resistance is due to interstitial nitrogen in the niobium lowering the mean free path. The BCS resistance extracted from experimental data is shown to be consistent with theoretical predictions from BCS theory; that there is an optimal doping of which the mean free path is lowered to about half the intrinsic coherence length. These results provide insight into understanding the mechanisms behind nitrogen-doping and allow us to more accurately predict doping parameters to reach optimal cavity performance.

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WEPMR028

Studies on the Field Dependence of the BCS Surface Resistance

SRF, experiment, niobium, radio-frequency

2335

J.T. Maniscalco, D. Gonnella, G.H. Hoffstaetter, P.N. Koufalis, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Experiments have shown that the temperature-dependent portion of the RF surface resistance of SRF materials also exhibits a dependence on the magnitude of the surface field, manifested as a "Q-slope" or "anti-Q-slope" in the medium field region. Recent theoretical work proposes an explanation of the anti-Q-slope in dirty-limit superconductors. In this report, we compare theoretical predictions with the results of systematic experimental studies on the RF field dependence of the surface resistance using 1.3 GHz niobium SRF cavities with a wide range of mean free paths. We find very good agreement between theory and experiment in the dirty limit, with some divergence as the cavities approach the clean limit.

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WEPMR029

New Material Studies in the Cornell Sample Host Cavity

niobium, SRF, superconducting-RF, vacuum

2338

J.T. Maniscalco, D.L. Hall, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
O.B. Malyshev, R. Valizadeh, S. Wilde
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
S. Wilde
Loughborough University, Loughborough, Leicestershire, United Kingdom

Cornell has developed a TE mode sample host microwave cavity in order to study large, flat samples of novel SRF materials. In recent calibration tests, the cavity was shown to reach peak magnetic fields on the sample plate of >100 mT and a quality factor Q₀ greater than 10¹⁰, making it a powerful system to study the performance of superconductors at high RF fields with nOhms sensitivity. In this report we present results of measurements of two samples of thin-film Nb deposited on Cu using HiPIMS at 500 C and at 800 C.

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WEPMR030

Pulsed Field Limits in SRF Cavities

SRF, niobium, klystron, factory

2341

J.T. Maniscalco, D. Gonnella, D.L. Hall, P.N. Koufalis, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

High-power pulsed (HPP) measurements of SRF cavities offer several different avenues of experimentation from standard continuous wave (CW) measurements by probing higher fields and reducing thermal effects. In this paper we report upon recent measurements of N-doped Nb and Nb3Sn cavities, investigating the limitations of the superheating field, flux entry field, and other maximum fields. We also investigate the potential of these materials for operation in a pulsed accelerator, which would partially or fully mitigate the effects of defects (i.e. thermal quenches).

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WEPMR033

Observation of Stable Low Surface Resistance in Large-Grain Niobium SRF Cavities

niobium, SRF, vacuum, site

2344

R.L. Geng
JLab, Newport News, Virginia, USA
S.C. Huang
IMP/CAS, Lanzhou, People's Republic of China

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Low surface resistance, or high unloaded quality factor (Q0), superconducting radio frequency (SRF) cavities are being pursued actively nowadays as their application in large-scale CW SRF accelerators can save capital and operational cost in cryogenics. There are different options in realization of such cavities. One of them is the large-grain (LG) niobium cavity. In this contribution, we present new experimental results in evaluation of LG niobium cavities cooled down in the presence of an external magnetic field. High Q0 values are achieved even with an ambient magnetic field of up to 100 mG. More over, it is observed that these high Q0 values are super-robust against repeated quench, literally not affected at all after the cavity being deliberately quenched for hundreds of times in the presence of an ambient magnetic field of up to 200 mG.

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WEPMR034

Analyses of 476 MHz and 952 MHz Crab Cavities for JLAB Electron Ion Collider

ion, collider, electron, betatron

2348

H. Park, A. Castilla, S.U. De Silva, J.R. Delayen
ODU, Norfolk, Virginia, USA
V.S. Morozov
JLab, Newport News, Virginia, USA

Center for Accelerator Science at ODU has designed, fabricated and successfully tested a crab cavity for MEIC at Jefferson Lab*. This proof of principle cavity was based on the earlier MEIC design which used 748.5 MHz RF system. The updated MEIC design** utilizes the components from PEP-II. It results in the change on the bunch repetition rate of stored beam to 476.3 MHz. The ion ring collider will eventually require 952.6 MHz crab cavity. This paper will present the analyses of crab cavities of both 476 MHz and 952 MHz options. It compares advantages and disadvantages of the options which provides the MEIC design team important technical information for a system down selection.
* Cryogenic Test of a 750 MHz Superconducting RF Dipole Crabbing Cavity, A. castilla et al, IPAC2014
** MEIC Design Summary, S. Abeyratne et al, arXiv:1504.07961

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WEPMR036

Crab Cavities for eRHIC - A Preliminary Design

electron, proton, linac, luminosity

2351

Q. Wu, I. Ben-Zvi, S. Verdú-Andrés, B. P. Xiao
BNL, Upton, Long Island, New York, USA
I. Ben-Zvi
Stony Brook University, Stony Brook, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The proposed eRHIC electron ion collider at BNL must use a relatively large crossing angle between the ion and electron beams for various reasons, including the reduction of long-range beam-beam effects and minimization of synchrotron radiation noise in the detector. To prevent significant loss of the luminosity due to this large crossing angle, the design of the collider requires the use of groups of crab cavities to provide local crabbing for both proton/ion and electron beams. We will base our design for eRHIC crab cavities based on our experience in the design of the 400 MHz double quarter wave crab cavity (DQWCC) for the Hi-Lumi upgrade of the Large Hadron Collider at CERN. This DQWCC design is scaled to different frequencies of a main crab cavity and its higher harmonics for eRHIC. In this paper, we discuss the preliminary designs of the eRHIC crab cavities and their major parameters.

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WEPMR037

Wakefield Analysis of the 56 MHz SRF Cavity

impedance, HOM, wakefield, SRF

2354

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

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

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WEPMR038

Frequency Tuning for a DQW Crab Cavity

operation, simulation, SRF, insertion

2357

S. Verdú-Andrés, I. Ben-Zvi, J. Skaritka, Q. Wu, B. P. Xiao
BNL, Upton, Long Island, New York, USA
K. Artoos, R. Calaga, O. Capatina, R. Leuxe, C. Zanoni
CERN, Geneva, Switzerland
I. Ben-Zvi
Stony Brook University, Stony Brook, USA

Funding: Work supported by US DOE via BSA LLC contract No.DE-AC02-98CH10886, the US LARP program, US DOE contract No. DE-AC02-05CH1123 (NERSC resources) and by HiLumi project.
The nominal operating frequency for the HL-LHC crab cavities is 400.79 MHz within a bandwidth of ±60kHz. Attaining the required cavity tune implies a good understanding of all the processes that influence the cavity frequency from the moment when the cavity parts are being fabricated until the cavity is installed and under operation. Different tuning options will be available for the DQW crab cavity of LHC. This paper details the different steps in the cavity fabrication and preparation that may introduce a shift in the cavity frequency and introduces the different tuning methods foreseen to bring the cavity frequency to meet the specifications.

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WEPMR040

HOM Absorber Study by Photon Diffraction Model

HOM, photon, damping, SRF

2360

C. Xu, I. Ben-Zvi, V. Ptitsyn, P. Takas, W. Xu
BNL, Upton, Long Island, New York, USA
I. Petrushina
SUNY SB, Stony Brook, New York, USA
B. P. Xiao
SBU, Stony Brook, New York, USA

Photon diffraction model (PDM) is one of the most promising candidates to study High Order Mode (HOM) power absorption on absorbing materials for high current SRF cavities. Because at very high frequency (>10GHz), the wavelengths of HOMs are much smaller compared with accelerators dimension, the phase of those HOM will be negligible. Meanwhile, Finite Element Method (FEM) cannot lend a high resolution on evaluation the HOM field patterns due to limited meshing capability. This PDM model utilizes Monte Carlo simulation to trace the ray diffusive reflection in a cavity. This method can directly estimate the power absorption on the cavity and absorber wall. This method will help design the HOM damper setup for eRHIC HOM damper. In this report, we evaluate HOM absorption on the cavity wall with different absorber setup and give a possible solution for power damping scheme for high frequency HOMs.

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WEPMR041

RF and Mechanical Design of 647 MHz 5-Cell BNL4 Cavity for eRHIC ERL

electron, HOM, linac, SRF

2364

W. Xu, I. Ben-Zvi, H. Hahn, G.T. McIntyre, C. Pai, R. Porqueddu, K.S. Smith, J.L. Tuozzolo, J.E. Tuozzolo, A. Zaltsman
BNL, Upton, Long Island, New York, USA
I. Ben-Zvi
Stony Brook University, Stony Brook, USA

Funding: This work is supported by LDRD program of Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
A 647 MHz 5-cell cavity has been designed for the envisioned EIC at BNL which is configured as an eRHIC ERL with a FFAG lattice to achieve the necessary e-p luminosity. The cavity was optimized to allow propagation of all HOMs out of the cavity for high BBU threshold current and low HOM power (loss factor). eRHIC will collide the electron beam over a wide energy range with protons from 40 GeV to 250 GeV, which requires the cavity to tune up to 170 kHz at 2 K. This poses a true challenge to the mechanical design of the SRF cavity. This paper will present the RF and mechanical designs of the 647 MHz 5-cell cavity, and status of the cavity fabrication will be addressed as well.

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WEPMR042

Ridge Waveguide HOM Damping Scheme for High Current SRF Cavity

HOM, linac, damping, SRF

2367

W. Xu, I. Ben-Zvi, Y. Gao, H. Hahn, G.T. McIntyre, R. Porqueddu, V. Ptitsyn, K.S. Smith, R. Than, J.L. Tuozzolo, C. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, USA
I. Ben-Zvi
Stony Brook University, Stony Brook, USA

Funding: This work is supported by LDRD program of Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
HOM damping is a challenge for high-current SRF linacs possibly generating HOM power at a level of 10 KW per cavity. A rectangular waveguide used as a natural high pass filter is a good option as high power, large spectrum HOM damper. However, its size is too big, causing a big challenge for the cooling and cryogenic system. A reliable, compact HOM damping scheme using a ridged waveguide is being developed to damp high power (> 10 kW), large spectrum HOMs ( up to 40 GHz) that may be generated in the 647 MHz 5-cell eRHIC ERL SRF linac. The size of a ridged waveguide is less than a quarter of the regular waveguide, which alleviates the thermal issue. This paper presents the design of a ridged waveguide and estimated HOM damping results using a ridged waveguide. The thermal or cooling design of the ridged waveguide will also be addressed.

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WEPMR053

Technical Overview of Cavity BPM Mover for PAL XFEL

controls, undulator, operation, EPICS

2395

H.-G. Lee, S.-H. Jeong, Y.-G. Jung, H.-S. Kang, D.E. Kim, K.W. Kim, S.B. Lee, D.H. Na, B.G. Oh, K.-H. Park, H.S. Suh, Y.J. Suh
PAL, Pohang, Kyungbuk, Republic of Korea

Pohang Accelerator Laboratory(PAL) has been developing a SASE X-ray Free Electron Laser based on 10 GeV linear accelerator. The cavity BPM mover was developed to be used in the intersections of the Undulator Systems. The main specifications include submicron repeatability for a 50 kg cavity BPM adjusting system within compact dimensions and a ±1.5 mm stroke in the vertical and horizontal direction. Compact linear motion guide based on 5-phase stepping motors have been chosen. A closed-loop control system has been developed to achieve this repeatability. For the feedback, one digital probe sensor for each axis was used. Mechanical switches are used to limit movement. In addition, hard-stops are included for emergency. In this report, we describe the design of the stages used for precise movement and results of mechanical measurements including reproducibility will be reported.

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WEPMW022

Multi-Cell RF-Dipole Deflecting and Crabbing Cavity

dipole, electron, proton, ion

2469

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

Single cell superconducting rf-dipole cavities operating at 400 MHz, 499 MHz and 750 MHz have been designed, fabricated and successfully tested at cryogenic temperatures. These cavities have been shown to have attractive rf properties: high deflecting gradients, low electric and magnetic peak surface fields, and high shunt impedance. The single cell rf-dipole geometry has no lower order modes and has widely separated higher order mode spectrum. In this study we are investigating a multi-cell superconducting rf-dipole cavity operating at 952.6 MHz intended for the Jefferson Lab Energy Electron-Ion Collider. The analysis investigates the dependence of beam aperture variation and other cavity parameters on rf properties including cavity gradient, surface fields, shunt impedance and higher order mode separation.

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WEPMW026

Beam-Beam Simulation With Crab-Cavities for Erhic

proton, electron, dynamic-aperture, luminosity

2479

Y. Luo, Y. Hao, Y.C. Jing, V. Ptitsyn, D. Trbojevic
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
To avoid the luminosity loss due to cross-angle collision, crab cavities are being considered for the electron-ion collider designs at Brookhaven National Laboratory. In this article, we study the effects of crab cavities on the proton beam dynamics without and with beam-beam interactions. Dynamic apertures are to be calculated with various parameters of crab cavities. To minimize the distortion from a single crab cavity, harmonic crab cavities are also considered.

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WEPMW039

JLEIC SRF Cavity RF Design

impedance, HOM, electron, damping

2522

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

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

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WEPMW041

Multiple Bunch HOM Evaluation for eRHIC Main Linac Cavities

HOM, electron, linac, proton

2525

C. Xu, I. Ben-Zvi, M. Blaskiewicz, Y. Hao, V. Ptitsyn
BNL, Upton, Long Island, New York, USA

Funding: This work is supported by LDRD program of Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
High current Superconducting Radiofrequency (SRF) 5-cell cavities are essential for the proposed ERL-based electron-ion collider eRHIC in BNL. The HOM power generated when a single bunch traverses the cavity is estimated by the corresponding loss factor. Multiple re-circulations through the ERL create a specific bunch pattern. In this case the loss factor can be different than the single bunch loss factor. The HOM power generation can be surveyed in the time and frequency domains. We estimate the average HOM power in the eRHIC 5-cell cavity with different ERL bunch patterns using both methods. We also discuss possible solutions to reduce this HOM power.

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WEPMW042

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

HOM, impedance, electron, damping

2529

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

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

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WEPMW043

Frequency Scaling Study of Crab Cavity for Future Colliders with Crab Crossing

luminosity, ion, collider, electron

2532

Y. Hao, V. Ptitsyn
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Crab crossing is an essential concept in the newly proposed colliders or the upgrades. It enables crossing angles to achieve lower β^* without a loss of luminosity. The frequency of the crab cavity shall be chosen with various considerations, including the luminosity degradation, emittance growth due to synchro-beta resonances and RF noises. We use the figure of merits and related simulation to establish the frequency scaling relations with important beam parameters, which guide the choice of crab cavity frequency for new designs.

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WEPMY013

A Spatially Separated Two Frequency RF Gun Design for Beam Brightness Improvement

gun, emittance, laser, brightness

2572

Z. Zhang, C.-X. Tang, Z. Zhang
TUB, Beijing, People's Republic of China
H.J. Qian
LBNL, Berkeley, California, USA

Recent theoretical and experimental studies shows that transverse beam brightness of photoinjector can be improved by cigar beam photoemission, and beam peak current are then increased with a RF buncher following the gun. We apply this concept to a S-band photoinjector by adding a harmonic RF buncher closely to a S-band RF gun, forming a compact spatially separated two frequency RF gun, targeting a 200 pC beam with emittance < 0.2 mm·mrad and 30 A peak current. Both S/X-band and S/C-band combinations are considered, and an optimized solution with 30 A peak current and 0.1 mm·mrad slice emittance are presented.

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WEPMY037

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

simulation, gun, coupling, impedance

2635

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

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

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WEPMY038

Optimization of C-band RF Input Coupler as a Mode Converter for 20-K Cryocooled Photocathode RF Gun

gun, coupling, simulation, insertion

2638

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

Funding: Work supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT).
Development of a cryocooled 2.6-cell C-band photocathode RF gun has been conducted at Nihon University in collaboration with KEK. An RF mode converter from square TE10 to circular TM01 mode has been employed as an RF input coupler that has a coupling coefficient of approximately 20 at 20 K to the 2.6-cell accelerating structure. In the previous design, the circular waveguide in the mode converter formed part of the accelerating cavity. After the cold test of the cavity completed in 2014, the coupler design was modified to work as a pure mode converter with a VSWR of 1 at 5712 MHz. From the design simulation using CST-STUDIO, the insertion loss in the converter is 0.2 %. The TM010 and TM011 modes excited in the circular waveguide were separated by several ten MHz from the accelerating frequency. The simulation has suggested that the amplitude of the transverse electric filed on the axis in the circular waveguide is reduced to approximately 2 % of that in the longitudinal direction.

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WEPMY039

Time Response Measurements for Transmission-Type GaAs/GaAsP Superlattice Photocathodes

electron, laser, brightness, gun

2641

N. Yamamoto, X.J. Jin
KEK, Ibaraki, Japan
M. Hosaka, Y. Takashima, K. Yamaguchi
Nagoya University, Nagoya, Japan
M. Katoh
UVSOR, Okazaki, Japan

Polarized electron beam is essential for future electron-positron colliders and electron-ion colliders. Recently we have developed the strain compensated superlattice (SL) photocathode. In the strain compensated SLs, the equivalent compressive and tensile strains introduced in the well and barrier SL layers so that strain relaxation is effectively suppressed with increasing the SL layer thickness and high crystal quality can be expected. In this study, we fabricated the GaAs/GaAsP strain compensated SLs with the thickness up to 90-pair SL layers. Up to now, the electron spin polarization of 92 % and the quantum efficiency of 1.6 % were simultaneously achieved from 24-pair sample. In this study, to compare the time response performances with the SL thicknesses, the measurements were carried out for conventional and strain compensated SL PCs. We show the measurement results and discuss the physics.

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WEPOR003

Voltage Control for the 4-Th Harmonic Cavity in Hls Storage Ring

controls, feedback, storage-ring, EPICS

2664

K. Xuan, C. Li, J.Y. Li, G. Liu, W. Xu
USTC/NSRL, Hefei, Anhui, People's Republic of China

In order to increase the beam lifetime, a 4th harmonic RF cavity was installed in the HLS-II storage ring. The electrical fields in the principle cavity and high harmonic cavity stretch the beam in the longitudinal direction, and increase the beam volume in phase space, leading to a longer Touschek lifetime. Stable electrical voltage in the high harmonic cavity is essential for steady beam stretching and better beam lifetime. To get a stable high voltage in the high harmonic cavity, we develop a method to maintain steady resonance condition in the cavity using a PID scheme. This paper presents the details of this method. The feedback result is also reported.

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WEPOR008

Development of a High Resolution Beam Position Monitor for NSRRC VUV/THz FEL

dipole, electron, simulation, coupling

2680

P.J. Kung, K.C. Leou
NTHU, Hsinchu, Taiwan
W.K. Lau, A.P. Lee
NSRRC, Hsinchu, Taiwan

Beam position monitors (BPM) have been widely used on linear colliders and free electron lasers for beam-based alignment and feedback systems. A laser driven photo-injector system has been constructed in NSRRC. This injector has the capability to deliver short relativistic electron beam at high peak current for novel light source R&D. A 2.4 GHz BPM that can be used for high precision beam position measurement has been designed. The BPM were modified to separate frequency between the horizontal and vertical dipole signals, as well as a reduction of the monopole signal. The design has been simulated by CST. A prototype has been built for verification of theoretical predictions. Microwave bench measurement has been made to compare with the computer simulation results. The progress of our work will be presented in this paper.

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WEPOR018

Position Monitoring System for HL-LHC Crab Cavities

monitoring, vacuum, radiation, alignment

2704

M. Sosin, T. Dijoud, H. Mainaud Durand
CERN, Geneva, Switzerland
V. Rude
ESGT-CNAM, Le Mans, France

The high luminosity upgrade for the LHC at CERN (HL-LHC project) will extend the discovery potential of the LHC by a factor 10. It relies on key innovative technologies like superconducting cavities for beam rotation, named 'crab cavities'. Two crab cavities will be hosted in a superconducting cryostat working at a cold (<3 K). The position of each cavity will be monitored during the cool-down and the operation in order to comply with the tight alignment tolerances: the misalignment of a cavity axis w.r.t. the other will have to be lower than 0.5 mm and each cavity roll w.r.t. the cryostat axis will have to be lower than 1 mrad. Moreover, the monitoring system will have to be radiation hard (up to 10 MGy) and maintenance free. We propose a solution based on the Frequency Scanning Interferometry to provide the position monitoring of the crab cavities. This paper describes the design and study of such a solution, including the engineering approach, the issues encountered and the lessons learnt.

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WEPOR030

Gas Filled RF Resonator Hadron Beam Monitor for Intense Neutrino Beam Experiments

electron, plasma, radiation, experiment

2733

K. Yonehara, A.V. Tollestrup, R.M. Zwaska
Fermilab, Batavia, Illinois, USA
R.J. Abrams, R.P. Johnson, G.M. Kazakevich
Muons, Inc, Illinois, USA
H.M. Dinkel
University of Missouri, Columbia, Columbia, Missouri, USA
B.T. Freemire
IIT, Chicago, Illinois, USA

Funding: Work supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359 and DOE HEP STTR Grant DE-SC0013795.
MW-class beam facilities are being considered all over the world to produce an intense neutrino beam for fundamental particle physics experiments. A radiation-robust beam monitor system is required to diagnose the primary and secondary beam qualities in high-radiation environments. We have proposed a novel gas-filled RF-resonator hadron beam monitor in which charged particles passing through the resonator produce ionized plasma that changes the permittivity of the gas. The sensitivity of the monitor has been evaluated in numerical simulation. A signal manipulation algorithm has been designed. A prototype system will be constructed and tested by using a proton beam at the MuCool Test Area at Fermilab.

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WEPOR031

Field Emission Radiation Characterization of LCLS-II Cavities

radiation, cryomodule, detector, linac

2736

M. Santana-Leitner, C. Adolphsen, L. Ge, Z. Li, T.O. Raubenheimer, M.C. Ross
SLAC, Menlo Park, California, USA
S. Aderhold, A. Grassellino, O.S. Melnychuk, R.V. Pilipenko, D.A. Sergatskov
Fermilab, Batavia, Illinois, USA

Funding: Work supported by U.S. Department of Energy contract DE-AC02-76SF00515
LCLS-II XFEL facility at the SLAC National Accelerator Laboratory will accelerate CW beams of up to 300 uA to 4 GeV using superconducting radio frequency cavities. Before installation, fully assembled cryomodules will be tested at Fermilab and Jefferson Lab. Besides the basic measurements of cavity gradients and cryogenic heat loads, radiation and dark current levels will be recorded. The latter parameters need to be limited to ensure the safety of the machine and the lifetime of radio-sensitive components installed near the cavities. In this paper we describe the simulation studies being done in preparation of tests, where expected radiation measurements in the different detectors are correlated with field emission and with dark currents in Faraday cups at each end of the cryomodule. This work includes simulations using a detailed model of the cryomodules and detectors, where field emission data generated with Track3P is parsed to the FLUKA radiation transport code.

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WEPOR032

Power Recycling of Burst-mode Laser Pulses for Laser Particle Interactions

laser, resonance, experiment, ion

2739

Y. Liu, A. Rakhman
ORNL, Oak Ridge, Tennessee, USA
A. Rakhman
UTK, Knoxville, Tennessee, USA

Funding: This work has been partially supported by U.S. DOE grant DE-FG02-13ER41967. ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
A number of laser-particle interaction experiments such as the laser assisted hydrogen ion beam stripping or X-/γ-ray generations via inverse-Compton scattering involve light sources operating in a burst mode to match the temporal structure of the particle beam. As the small cross-section in the laser-particle interaction process results in negligible laser power loss, it is desirable to make the interaction inside an optical cavity to recycle the laser power. In many cases, conventional cavity locking techniques will not work since the burst normally has very small duty factor and low repetition rate and it is impossible to generate an effective control signal. In this talk, we report on the development of a doubly-resonant optical cavity scheme and its locking technique that enables a simultaneous resonance of two laser beams with different spectra and/or temporal structures. We demonstrate that such a cavity can be used to recycle burst-mode ultra-violet laser pulses with arbitrary burst lengths and repetition rates. System implementation, technical challenges, experimental results and applications will be described.
* V. Danilov et al., Phys. Rev. ST Accel. Beams 10, 053501 (2007).
** K. Sakaue et al., Rev. Sci. Instrum. 80, 123304 (2009).
*** A. Rakhman, M. Notcutt, and Y. Liu, Opt. Lett. 40, 5562 (2015).

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WEPOR035

MicroTCA.4-Based LLRF System for Spoke Cavities of C-ADS Injector I

LLRF, operation, controls, cryomodule

2749

X. Ma, N. Gan, X. Huang, N. Liu, R.L. Liu, G.W. Wang, Q.Y. Wang
IHEP, Beijing, People's Republic of China
H.Y. Lin
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China

The C-ADS Injector I is being built in IHEP, which includes 14 β=0.12 superconducting single spoke cavities enclosed with two cryomodules under 2 K. The MicroTCA.4-based Low Level RF (LLRF) system provides GDR mode for the operation of the cavities. The LLRF system supports both CW and duty-adjustable pulsed operation modes for the high power source and the cavities. The firmware of the FPGA controller and the EPICS IOC software has been upgraded during the last half year adding feedforward and abnormal detection. The operator interface (OPI) software and automatic operation script are also described. The MicroTCA.4 platform runs well for the beam commissioning of the Injector I. Some gained experiences with stable beam operation are also shown.

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WEPOR036

Design and Commissioning of LLRF System for ADS Project in China

LLRF, controls, operation, proton

2752

R.L. Liu, Y.L. Chi, N. Gan, X. Huang, N. Liu, X. Ma, Z.H. Mi, G.W. Wang, Q.Y. Wang, S.Z. Wang, Z.S. Zhou
IHEP, Beijing, People's Republic of China
H.Y. Lin
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China

This article describes a low-level RF control system for the ADS project at IHEP, which includes control units for an RFQ, 2 Bunchers and 14 spoke superconducting cavities with the reference line distribution. The paper covers system design consideration and implementation for those units. we will also presented some experience and results for the last one year operation of these LLRF systems.

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WEPOR037

Beam Loading Effects in SSRF Storage Ring

feedback, storage-ring, beam-loading, LLRF

2755

Y. Xia, Q. Chang, Z. Li, K. Xu, Zh.G. Zhang, S.J. Zhao, Y.B. Zhao, X. Zheng
SINAP, Shanghai, People's Republic of China

The beam current in the storage ring of Shanghai Synchrotron Radiation Facility (SSRF) is now normally 240 mA and projected to be raised to 300 mA. Heavy beam loading will be serious and associated Robinson instability needs to be compressed. In this paper, the beam loading effects in SSRF storage ring and methods to increase current limit will be discussed. .

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WEPOR039

Development of 200 MHz Digital LLRF System for the 1 MeV/n RFQ at KOMAC

LLRF, controls, rfq, FPGA

2758

H.S. Jeong, T.S. Ahn, Y.-S. Cho, H.S. Kim, S.G. Kim, H.-J. Kwon
Korea Atomic Energy Research Institute (KAERI), Gyeongbuk, Republic of Korea
Y.G. Song
KAERI, Daejon, Republic of Korea

KOMAC (Korea Multi-purpose Accelerator Complex) has a plan to develop the multipurpose ion irradiation system. This system includes the ion source, LEBT, RFQ and MEBT systems to transport ion particles to the target. In particular, the RFQ (Radio Frequency Quadrupole) system should receive 200 MHz RF within 1% amplitude error stability. To supply stable 200 MHz RF signal to the RFQ cavity, the LLRF (Low-Level Radio Frequency) system should be controlled through a control system which implemented using commercial digital board. This 1 MeV/n RFQ LLRF system has a concept to minimize the number of the analog components for minimizing the control error. For this, the FPGA (Field Programmable Gate Array) in the digital board will control the frequency of the output sinusoidal signal. In addition, this LLRF system applied the direct sampling, Non-IQ sampling, direct RF generation and fast IQ set update rate algorithm. In this presentation, the FPGA control logics of the LLRF digital board will be introduced. Also, the LLRF PI control logic test using 200 MHz dummy cavity will be described.

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WEPOR042

LLRF Control of High Loaded-Q Cavities for the LCLS-II

LLRF, controls, feedback, linac

2765

C. Serrano, L.R. Doolittle, G. Huang, A. Ratti
LBNL, Berkeley, California, USA
S. Babel, M. Boyes, B. Hong
SLAC, Menlo Park, California, USA
R. Bachimanchi, C. Hovater
JLab, Newport News, Virginia, USA
B.E. Chase, E. Cullerton, J. Einstein
Fermilab, Batavia, Illinois, USA

Funding: This work was supported by the LCLS-II Project and the U.S. Department of Energy, Contract DE-AC02-76SF00515
The SLAC National Accelerator Laboratory is planning an upgrade (LCLS-II) to the Linear Coherent Light Source with a 4 GeV CW Superconducting Radio Frequency (SCRF) linac. The nature of the machine places stringent requirements in the Low-Level RF (LLRF) system, expected to control the cavity fields within 0.01 degrees in phase and 0.01% in amplitude, which is equivalent to a longitudinal motion of the cavity structure in the nanometer range. This stability has been achieved in the past but never for hundreds of superconducting cavities in Continuous-Wave (CW) operation. The difficulty resides in providing the ability to reject disturbances from the cryomodule, which is incompletely known as it depends on the cryomodule structure itself (currently under development at JLab and Fermilab) and the harsh accelerator environment. Previous experience in the field and an extrapolation to the cavity design parameters (relatively high Q_Lc≈ 4×10⁷ , implying a half-bandwidth of around 16 Hz) suggest the use of strong RF feedback to reject the projected noise disturbances, which in turn demands careful engineering of the entire system.

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WEPOR043

End-to-end FEL Beam Stability Simulation Engine

simulation, linac, software, cryomodule

2768

C. Serrano, L.R. Doolittle
LBNL, Berkeley, California, USA
D.S. Driver, B. Patel, A.F. Queiruga, Z. Zaky
UCB, Berkeley, USA
Q. Llimona
UPF, Barcelona, Spain

Funding: Work supported by U.S. Department of Energy
During the design, commissioning and operation of a linac-driven Free Electron Laser (FEL) it is important to have a good understanding of the implications of accelerator design choices on beam figures of merit. This simulation engine combines a full state-space model of the RF system (High-Power Amplifier, RF cavities, LLRF controllers, etc.), a characterization of beam properties such as energy, bunch length and arrival time as electrons propagate through the Linac and beam-based feedback. The combination of these models with the ability to introduce both correlated and uncorrelated noise sources at any point of the machine, allows for a complete transposition of noise sources to beam performance parameters, including frequency dependence, in order to analyze implications of accelerator design choices in a simulation environment.

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WEPOR044

Fpga Implementation of a Control System for the LANSCE Accelerator

controls, feedback, LLRF, FPGA

2771

S. Kwon, L.J. Castellano, D.J. Knapp, J.T.M. Lyles, M.S. Prokop, D. Rees, A. Scheinker, P.A. Torrez
LANL, Los Alamos, New Mexico, USA

As part of the modernization of the Los Alamos Neutron Science Center (LANSCE), a digital low level RF (LLRF) system was designed. The LLRF control system was implemented in a Field Programmable Gate Array (FPGA) using embedded Experimental Physics and Industrial Control System (EPICS) Input Output Controller (IOC) under the Real-Time Executive for Multiprocessor Systems (RTEMS). Proportional-Integral (PI) feedback controller, static beam feedforward controller, and iterative learning controller are implemented on the FPGA. The closed loop system performance was tested with a 10mA peak current proton beam.

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WEPOR058

Preliminary Study for the HLS Variable Pulse Length Storage Ring by Two Harmonic Cavities

beam-loading, storage-ring, synchrotron, electron

2802

T. Zhang, W. Li, L. Shang, L. Wang, C.-F. Wu
USTC/NSRL, Hefei, Anhui, People's Republic of China

The 4th harmonic cavity is successfully used in HLS II to increase the beam lifetime and suppress the beam instability now. At the future, a scheme of the two higher harmonic cavities may be applied in Hefei light source for a variable electron pulse length storage ring (HLS VSR). With optimal RF system parameters, 45 ps long bunches and 6 ps short bunches may be stored simultaneously in the HLS storage ring. The ratio of the bunch number for 45 ps to the one for 6 ps is 1:2. Particle tracking calculations are performed to simulate the longitudinal phase space of the new system and to track the process of shortening bunches with Elegant Software. Moreover, a tracking simulation code for RF systems is developed in MALAB to study transient beam loading which affects bunch length, phase stability, and longitudinal muti-bunch oscillation for different fill patterns. In the end, the preliminary design of the two harmonic cavities for longitudinal bunch focusing is given.

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WEPOW008

Specific Operation Modes at the Metrology Light Source

operation, electron, emittance, radiation

2829

J. Feikes, P. Goslawski, J. Li, M. Ries, M. Ruprecht, G. Wüstefeld
HZB, Berlin, Germany
A. Hoehl
PTB, Berlin, Germany

The high flexibility of the Metrology Light Source (MLS) allows application of various nonstandard user modes adapted to the specific needs of their users. We report on some of them including a mode for division of the revolution frequency for the user signal and a mode with an adjustable photon pulse delay on the few ps scale.

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WEPOW012

Hardware Upgrades Improve the Reliability at BESSY II

storage-ring, operation, HOM, klystron

2844

A. Schälicke, W. Anders, J. Borninkhof, V. Dürr, P. Goslawski, A. Hellwig, A. Heugel, H.-G. Hoberg, H. Hoffmann, A. Jankowiak, J. Kolbe, P. Kuske, G. Mielczarek, R. Müller, D. Pflückhahn, M. Ries, S. Rotterdam, M. Ruprecht, B. Schriefer, D. Simmering, H. Stein
HZB, Berlin, Germany

The synchrotron light source BESSY II is now in its second decade of operation. Already in 2013 both top-up and fast orbit feedback have been introduced into user operation. Currently, the facility is undergoing significant hardware upgrades in order to fulfill the increasing demands of its user community in terms of reliability, stability and flexibility. These include replacement of the DORIS cavities with EU HOM damped cavities, the upgrade of the RF transmitters to solid state amplifiers, implementation of the shifted waist optics for the new in-vacuum undulator, and refurbishment of the superconducting multi-pole wiggler. In this contribution status of BESSY II operation and the upgrade projects is reported.

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WEPOW035

Commissioning of the Harmonic Cavities in the MAX IV 3 GeV Ring

damping, resonance, storage-ring, synchrotron

2911

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

The MAX IV 3 GeV storage ring operates with beam of high current and ultralow emittance. These beam parameters in combination with the small effective aperture enhance possible collective beam instabilities. Three passive harmonic cavities are installed to introduce bunch lengthening and tune spread, leading to decoupling of the bunch spectrum from the machine effective impedance and mitigating instabilities by Landau damping respectively. In this paper we present the first results of the commissioning of the passive third harmonic cavities in the MAX IV 3 GeV ring. The additional harmonic cavity potential significantly improved the beam lifetime. First observations of the harmonic cavity effect on the damping of collective beam instabilities are discussed.

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WEPOW036

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

storage-ring, simulation, impedance, lattice

2914

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

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

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WEPOW037

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

simulation, storage-ring, beam-loading, feedback

2918

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

The MAX IV facility includes two storage rings operated at 1.5 GeV and 3 GeV, which are both designed to operate with a uniform, multibunch fill pattern. Both rings have a 100 MHz RF system and employ passive harmonic cavities to damp instabilities and increase Touschek lifetime. Recently, a discussion on timing modes at the MAX IV storage rings has been initiated by the user community. Creating opportunities for timing experiments implies operating the rings with other fill patterns than the planned multibunch mode. Such operation can, however, cause transient effects in the passive harmonic cavities which affect the performance of the machine. It is therefore of interest to study the effect on the beam when operating with non-uniform fill patterns. This paper presents bunch length measurements at the 100 MHz MAX II storage ring for fill patterns with gaps. The purpose of the measurements was to evaluate the employed measurement method and simulation codes for future studies of various alternate fill patterns in the MAX IV storage rings.

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WEPOW047

A Hybrid Superconducting/Normal Conducting RF System for the Diamond Light Source Storage Ring

operation, storage-ring, vacuum, HOM

2950

C. Christou, A.G. Day, P. Gu, N.P. Hammond, J. Kay, M. Maddock, P.J. Marten, S.A. Pande, A.F. Rankin, D. Spink
DLS, Oxfordshire, United Kingdom

300 mA beam in the Diamond Light Source storage ring is presently maintained by two 500 MHz superconducting CESR-B cavities. Cavity reliability is acceptable at modest operating voltages up to 1.4 MV per cavity but falls off rapidly beyond this value. The installation of an extra cavity or cavities would reduce the voltage demand on the current superconducting cavities and also the operating power level of the high power amplifiers, with commensurate improvement in machine reliability. Furthermore, two superconducting cavity failures in recent years have resulted in machine down-time and reduced-current operation and repair has proven to be prolonged and expensive. It is therefore planned to install two normal conducting cavities into the ring to support operation of the superconducting cavities and to act as a safeguard against any future superconducting cavity failures. Details are presented in this paper of plans and progress towards the installation of the hybrid RF system.

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WEPOW052

Multimodal Interaction in the ALS Longitudinal Feedback Kicker RF Cavity

kicker, feedback, resonance, impedance

2965

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

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

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WEPOY002

A Time Domain Analysis Method for RF Noise

simulation, experiment, beam-loading, LLRF

2994

L. Lin, B. Du, G. Huang, Y.T. Liu
USTC/NSRL, Hefei, Anhui, People's Republic of China

A time domain analysis method is developed for the calculation of the longitudinal oscillations caused by the RF noise in the storage ring. This method is based on the impulse response model, and it could calculates the change of transient field caused by beam oscillation and RF noise turn by turn. By means of discrete spectrum analysis, the spectrum of the beam is obtained. According to this analysis method, we developed a simulation pro-gram. The synchronous oscillation of the excited by high RF source with a phase modulation is predicted in this program, and the corresponding experimental measure-ments are carried out on HLS II. The fitting results are in agreed with the experimental measurements.

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WEPOY007

Simulation of Electromagnetic Scattering Through the E-XFEL Third Harmonic Cavity Module

simulation, HOM, dipole, factory

3001

N.Y. Joshi, R.M. Jones
UMAN, Manchester, United Kingdom
N. Baboi, L. Shi
DESY, Hamburg, Germany

Funding: The work is part of EuCARD-2, partly funded by the European Commission, GA 31245. N.~Y.~Joshi receives additional funding from The Cockcroft Institute of Science and Technology.
The European-XFEL is being fabricated in Hamburg to serve as an X-ray Free Electron Laser (FEL) light source. The electron beam will be accelerated through linacs consisting of 1.3 GHz superconducting cavities along a length of 2.1 km. In addition, third harmonic cavities will improve the quality of the beam by linearising the field profile and hence reducing the energy spread. There are eight 3.9 GHz cavities within a single module AH1 of E-XFEL. The beam-excited electromagnetic (EM) field in these cavities can be decomposed into a series of eigenmodes. These modes are, in general, not cut-off between one cavity and the next, as they are able to couple to each other throughout the module. Here for the first time, we evaluate components of the scattering matrix for module AH1. This is a computationally expensive system, and hence we employ a Generalized Scattering Matrix (GSM) technique to allow rapid computation with reduced memory requirements. Verification is provided on reduced structures, which are compared to finite element mesh-based codes. The mode spectrum for the dipole bands of interest in an eight-cavity chain have been calculated and external Q factors for the modes are derived.

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WEPOY023

Beam Dynamics Studies for Coherent Electron Cooling Experiment

electron, emittance, linac, SRF

3032

Y.H. Wu, D. Kayran, V. Litvinenko, I. Pinayev
BNL, Upton, Long Island, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Coherent electron Cooling (CeC)* is a proposed advanced beam cooling method that has the potential to reduce the ion beam emittance in significantly shorter time compared to existing cooling methods. The newly constructed linear electron accelerator for the CeC experiment can generate electron beams with the required beam parameters for effective cooling. In this paper, we show simulation studies for the CEC linac by using the PARMELA** and ELEGANT*** beam dynamics tracking codes.
* V.N.Litvinenko and Y.S.Derbenev, PRL 102, 114801 (2009)
** Lloyd M.Young, Parmela manual, Los Alamos National Laboratory
*** M. Borland, Elegant, Argonne National Laboratory (2000)

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WEPOY056

Beam-beam Simulations with Realistic Crab Crossing for the eRhic Ring-Ring Electron Beam

electron, proton, luminosity, hadron

3123

C. Montag
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The 15mrad beam crossing angle in the eRHIC ring-ring interaction region requires crab crossing of the 250GeV proton beam to restore the luminosity. Since the product of the RF voltage and the RF frequency of the crab cavities is constant for a given crossing angle, higher frequencies are preferred in order to limit the require voltage. However, the 20cm RMS proton bunch length provides an upper limit of the useable frequencies due to the significant curvature of the RF waveform over this bunch length. To study the effectof realistic crab cavities with a finite wavelength on electron beam-beamdynamics and to determine the potential need for higher harmonic crab cavities to linearize the kick a simulation code has been developed.

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WEPOY059

Axisymmetric Numerical Studies of Higher Order Mode Damping Techniques using Ring Ferrites for BESSY VSR

damping, HOM, storage-ring, factory

3132

B. Riemann, B.D. Isbarn, M. Sommer, T. Weis
DELTA, Dortmund, Germany

Funding: Work supported by the BMBF under contract no. 05K13PEB.
Utilizing superconducting multicell rf cavities with fundamental frequencies of 1.5 GHz and 1.75 GHz and therefore modulating the rf gradient, the upcoming BESSY II upgrade BESSY VSR aims to provide both short and long electron bunches simultaneously. However, beam induced excitation of higher order modes (HOM) inside those superconducting cavities is a major concern for beam stability in a recirculating accelerator. Thus it is important to develop and apply proper HOM damping techniques. Current design considerations involve HOM coupler which usually introduce discontinuities in the cross section while also breaking the axisymmetry. To circumvent these issues we investigate in a layout with ring ferrites as an alternative or additional HOM damping technique. We also present an alternative superstructure setup that uses two instead of four cavities for VSR.

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WEPOY060

YACS - Progression Towards Isoparametric 2.5D Finite Elements

software, synchrotron-radiation, radiation, experiment

3135

B.D. Isbarn, B. Riemann, M. Sommer, T. Weis
DELTA, Dortmund, Germany

Funding: Work supported by the BMBF under contract no. 05K13PEB.
YACS is a 2.5D finite element method solver capable of solving for the full 3D eigenfrequency spectra of resonant axisymmetric structures while reducing the computational problem to a 2D rotation plane. Prior studies and benchmarks, comparing YACS to well known commercial 3D and 2D applications, already demonstrated its capabilities of performing fast optimizations of geometries, due to its minimal computational overhead. However, because of the first order elements and basis functions used for approximation of the domain and field, this solving speed advantage vastly diminishes when targeting higher accuracies. In order to circumvent these issues, YACS was upgraded to support arbitrary order basis functions and curved meshes, leading to, but not limited to, isoparametric finite elements. This led to distinct performance and convergence improvements, especially when considering curved geometries, ideally representable by a polynomial mapping, e.g. when choosing a cavity geometry parametrization based on splines.

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THOAA02

The Development of C-Band Cavity Beam Position Monitor with a Position Resolution of Nano Meter

dipole, electronics, feedback, operation

3149

S.W. Jang, E.-S. Kim
Korea University Sejong Campus, Sejong, Republic of Korea
P. Bambade, O.R. Blanco-García, S. Wallon
LAL, Orsay, France
N. Blaskovic Kraljevic, T. Bromwich, P. Burrows
JAI, Oxford, United Kingdom
T. Tauchi, N. Terunuma
KEK, Ibaraki, Japan

We developed and tested an C-band beam position monitor with position resolution of nano meter in ATF2. The C-band BPM was developed for the fast beam feedback system at the interaction point of ATF in KEK, which C-band beam position monitor called to IPBPM (Interaction Point Beam Position Monitor). The developed IPBPM was measured 26nm with 30% of nominal beam charge of ATF. From the measured beam position resolution, we can expected to 8nm beam position resolution with nominal ATF beam charge condition. In this talk, we will described about the development of IPBPM and the beam test results of nano meter level beam position resolution.

Slides THOAA02 [4.806 MB]

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THOAA03

MicroTCA.4 based Single Cavity Regulation including Piezo Controls

controls, operation, feedback, electron

3152

K.P. Przygoda, H. Schlarb, Ch. Schmidt
DESY, Hamburg, Germany
P. Echevarria
HZB, Berlin, Germany
R. Rybaniec
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland

We want to summarize the single cavity regulation with MTCA.4 electronics. Presented solution is based on the one MTCA.4 crate integrating both RF field control and piezo tuner control systems. The RF field control electronics consists of RTM for cavity probes sensing and high voltage power source driving, AMC for fast data processing and digital feedback operation. The piezo control system has been setup with high voltage RTM Piezo driver and low cost AMC based FMC carrier. The communication between both control systems is performed using low latency link over the AMC backplane with data throughput up to the 3.125 Gbps. First results from CW operation of the RF field controller and the cavity active resonance control with the piezo tuners are demonstrated and briefly discussed.

Slides THOAA03 [2.693 MB]

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THOBA01

RF Pinger Commissioning and Beam Dynamics Studies at NSLS-II

synchrotron, LLRF, dynamic-aperture, controls

3161

G.M. Wang, B. Holub, Y. Li, J. Rose, T.V. Shaftan, V.V. Smaluk
BNL, Upton, Long Island, New York, USA

Funding: DOE contract DE-SC0012704
NSLS II storage ring RF system has the digital ramp control function, enabling rapid change of the cavity phase and amplitude. This, together with largely overcoupled RF cavity and transmitter geometry, enables the possibility to "ping" the beam in longitudinal phase space. Similar to the pinger commonly used for transverse beam dynamic studies, the RF jump presents with a powerful tool for investigation of the machine longitudinal beam dynamics. During our beam studies, RF phase was jumped within a short interval of time (less than synchrotron period). Using turn-by-turn data from BPMs we measured the machine energy acceptance with and without damping wigglers. This paper presents the beam study results.

Slides THOBA01 [4.365 MB]

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THYB01

Performance of Superconducting Cavities for the European XFEL

cryomodule, operation, SRF, vacuum

3186

D. Reschke
DESY, Hamburg, Germany

The superconducting accelerator of the European XFEL consists of the injector part and the main linac. The injector includes one 1.3 GHz accelerator module and one 3.9 GHz third harmonic module, while the main linac consists of 100 accelerator modules, each housing eight 1.3 GHz TESLA-type cavities, operated at an average design gradient of 23.6 MV/m. The fabrication and surface treatment by industry as well as the vertical and cryomodule RF tests of the required 808 superconducting 1.3GHz cavities are analysed and presented.

Slides THYB01 [3.227 MB]

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THOBB02

Impurity Doping of Superconducting Radio Frequency Cavities

niobium, vacuum, SRF, radio-frequency

3195

P.N. Koufalis, F. Furuta, G.M. Ge, D. Gonnella, J.J. Kaufman, M. Liepe, J.T. Maniscalco
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: NSF PHYS-1416318
Impurity doping of bulk-niobium superconducting radio frequency (SRF) cavities is a relatively new field of study and the underlying physics is not yet fully understood. Previous studies have shown an increase in the intrinsic quality factor and the corresponding decrease of the temperature-dependent component of the surface resistance of nitrogen-doped cavities with increasing accelerating field.* Here we investigate the effects of alternative inert dopants on the surface resistance and thus the intrinsic quality factor of SRF cavities in pursuit of the optimal dopant and doping level.
A. Grassellino et al., Nitrogen and Argon Doping of Niobium for Superconducting Radio Frequency Cavities. Supercond. Sci. Technol., 26(102001), 2013

Slides THOBB02 [4.048 MB]

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THOBB03

Root Causes of Field Emitters in SRF Cavities Placed in CEBAF Tunnel

cryomodule, SRF, vacuum, operation

3198

R.L. Geng
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
It has been suspected that appearance of new field emitters can occur in SRF cavities after their placement in accelerator tunnel for long term beam operation. This apparently has been the case for CEBAF. However, no physical evidence has been shown in the past. In this contribution, we will report on the recent results concerning the root cause of field emitters in SRF cavities placed in CEBAF tunnel. We will discuss these results in the context of high-reliability and low-cryogenic-loss operation of CEBAF.

Slides THOBB03 [3.768 MB]

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THPMB007

Numerical Computation of Transport Matrices of Axisymmetric RF Cavities for Online Beam Dynamics Applications

focusing, linac, transverse-dynamics, linear-dynamics

3233

V. Balandin, W. Decking, N. Golubeva
DESY, Hamburg, Germany

The RF focusing effect plays a considerable role at low particle energies and cannot be neglected in many online beam dynamics applications. Unfortunately, known analytical expressions for the transfer matrix of a cavity typically are applicable only to ultra-relativistic beams and demonstrate notable differences with accurate numerical simulations at low energies. So, in this paper, we present practical numerical algorithm for calculation of the linear transfer matrices of axisymmetric RF cavities which we developed for online modeling of the beam dynamics in the European XFEL linac.

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THPMB011

Beam Based Alignment Methods for Cavities and Solenoids in Photo-Injectors

solenoid, target, linac, experiment

3247

M. Rossetti Conti
Universita' degli Studi di Milano & INFN, Milano, Italy
A. Bacci
Istituto Nazionale di Fisica Nucleare, Milano, Italy

Solenoids are often used as lens-like beam focusing elements in electron linacs, especially in the low energy beam lines aside the Gun solenoid for emittance compensation, a common element of high brightness photo-injectors. There are also many electron linacs worldwide which use the Velocity Bunching beam compression technique, which needs solenoids wrapping the first acceleration cavity. A misalignment between the beam trajectory and the magnetic center of the solenoids produces a decrease in the beam quality and makes it necessary to find a complex steering setting to force the beam on a good orbit. In this proceeding we present a study of two beam based alignment techniques, which are correlated: the first shows a method to find the correct electromagnetic axis of an acceleration cavity, the second shows how to align the solenoids (wrapping the cavity) on this axis. Therefore the study permits to find the best steering setting and the solenoids positions corrections which have to be done. The work is based on real data acquired on the SPARC linac and on a virtual experiment.

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THPMB013

Proposal of 6 GeV Energy Recovery Linac Hybrid Machine

electron, positron, linac, undulator

3254

M. Shimada, K. Yokoya
KEK, Ibaraki, Japan
R. Hajima
JAEA, Ibaraki-ken, Japan
M. Tecimer
University of Hawaii at Manoa, Honolulu, USA

We proposed 6 GeV Energy Recovery Linac (ERL) as an intense gamma-ray source for the polarized positron source of International Linear Collider (ILC)*. In this scheme, Coherent Synchrotron Radiation from quasi-CW 6 GeV electron beam is stacked in optical cavity at middle infrared region, and it is used for inverse Compton scattering to generate 10 MeV polarized gamma-ray. The same 6 GeV superconducting linac accelerates both the electron and positron beams up to 5 GeV for injection to the dumping ring. Furthermore, it is available for X-ray light source by adding another recirculation loop. It can be expected as a diffraction limit light source at 10 keV, and the target of the brilliance is 10^22-23 ph/s/mm²/mrad²/b.w.0.1%.
* M. Shimada, Proceedings of IPAC'13

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THPMB038

Comparing RF-Cavity Phase-Scan Simulations in the ESS Linac Simulator with Measurements Taken in the Spallation Neutron Source Coupled-Cavity Linac

linac, neutron, controls, radio-frequency

3317

E. Laface, Y.I. Levinsen
ESS, Lund, Sweden
I. List
Cosylab, Ljubljana, Slovenia
T.A. Pelaia II
ORNL, Oak Ridge, Tennessee, USA

The ESS Linac Simulator (ELS) is the model that will be used at the European Spallation Source ERIC in Lund, Sweden, to simulate the transport of the beam envelope for the operations. During the machine restart in August 2015 at the Spallation Neutron Source (SNS) in Oak Ridge, USA, we were able to perform the first benchmarking studies of the ELS. In this paper, we present the results of the phase-scans performed in four RF cavities of the coupled-cavity linac at SNS compared with the same scans simulated in the ELS. The phase of the cavity was modified while the phase of the beam was recorded in two BPMs downstream from the cavity. This measurement was repeated for four independent cavities and the results are compared here with the model, which favourably reproduces the BPM response to the cavity scans.

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THPMR003

Failure Modes and Beam Losses Studies in ILC Bunch Compressors and Main Linac

beam-losses, quadrupole, linac, cryomodule

3388

A. Saini, N. Solyak, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Proposed International linear collider (ILC) involves high average beam power. Dealing with high average beam power and smaller beam sizes result in stringent tolerances on beam losses and therefore, extensive studies are required to investigate every possible scenarios that lead to beam losses. In this paper we discuss beam losses due to failure of critical elements in beamline for ILC bunch compressors and main linac.

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THPMR025

Simulation of Beam Behavior Caused by Odd Harmonics of Beam Loading in J-PARC RCS

beam-loading, simulation, acceleration, resonance

3443

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

The J-PARC RCS accelerates 2 bunches at the harmonic number 2. The major Fourier component of the beam current is even harmonics. However, the odd harmonics grow under some conditions even though they are very small amplitude at the beginning. We describe the the particle tracking simulation results for the odd harmonic beam loading effect in the RCS.

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THPMR052

Compact, Microtron-Based Gamma Source

microtron, cathode, electron, injection

3522

R.J. Abrams, M.A.C. Cummings, R.P. Johnson, S.A. Kahn, G.M. Kazakevich
Muons, Inc, Illinois, USA

Funding: This work was supported U.S. DOE SBIR Grant DE-SC0013795.
The conceptual design of a prototype S-band pulsed, 9.5 MeV compact microtron with type-II injection is described. Estimates of parameters such as beam current and cathode lifetime, and comparisons with X-band and C-band parameters are presented. The electron beam can be extracted at various energies up to 9.5 MeV. Estimated yields of gammas produced at 6.5 MeV operation and estimated yields of gammas and neutrons produced at 9.5 MeV are presented.

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THPMW022

The RF Design of a Compact, High Power Pulse Compressor with a Flat Output Pulse

klystron, FEL, flattop, linac

3591

P. Wang, H.B. Chen, J. Shi
TUB, Beijing, People's Republic of China
I. Syratchev, W. Wuensch, H. Zha
CERN, Geneva, Switzerland

An X-band, high-power pulse compressor, which can produce a flat pulse and a power gain of 4.3, has been designed. The device is compact, with the dimensions of within 1m, and is designed for CLIC first energy stage based on klystrons. We also discuss about a two stage pulse compressor with power gain of 9.18, which may be a candidate of the X-FEL using CLIC X-band linacs and klystrons with low peak power.

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THPMW040

Multipactor Discharge in a Resonator as an Active Switch for RF Pulse Compression

multipactoring, plasma, electron, klystron

3640

J.Q. Qiu, S.P. Antipov, C.-J. Jing, A. Kanareykin
Euclid Beamlabs LLC, Bolingbrook, USA
E.V. Ilyakov, I.S. Kulagin, S.V. Kuzikov, A.A. Vikharev
IAP/RAS, Nizhny Novgorod, Russia

Funding: Phase I DOE SBIR
Pulse compression is a method of increasing the peak power of the microwave pulse at the expense of its length. Over the years a number of pulse compressors had been demonstrated with some being bulky but efficient, like the binary pulse compressor and other being compact but less efficient, like SLED-II. An active pulse compressor had been proposed to increase the efficiency and compression ratio which relies on a high power active switch. Currently there are no practical switches that can work reliably with 100 s of megawatts of power. Most of the switches (ferroelectric, plasma-based, semiconductor) are limited by the breakdown strength of various dielectric inserts. In this paper we report on an active switch development which is based on a pure copper resonator and controlled by a single-side multipactor discharge at a metallic wall in the presence of a resonant DC magnetic field and a normal to metal rf field. The discharge is ignited by external rf power produced by inexpensive 2.45 GHz, 1-5 kW magnetrons.

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THPMY002

Fabrication of Ferrite-Copper Block by Spark Plasma Sintering (SPS)

HOM, vacuum, higher-order-mode, plasma

3654

Y. Suetsugu, T. Ishibashi, S. Terui
KEK, Ibaraki, Japan
H. Ishizaki, A. Kimura, T. Sawhata
Metal Technology Co. Ltd., Ibaraki, Japan

A ferrite has been well known as an effective material for absorbing electromagnetic waves. Various types of the ferrite blocks have been actually used in accelerator fields as the higher-order modes (HOMs) absorbers in the vacuum beam pipes. However, one of difficulties in using the ferrite is to bond it to the beam pipes with a sufficient adhesive force, and to assure the contact with a high thermal conductivity in vacuum. The brazing or Hot Isostatic Pressing (HIP) is not so easy owing to a low thermal expansion rate and a relatively low tensile strength of the ferrite. We established a method of fabricating a ferrite block bonded to copper by spark plasma sintering (SPS). The ferrite powders are directly sintered on a copper block in the SPS process together with some metals to relax the thermal stress between them. The sintered ferrite-copper block can be brazed or welded to other metal blocks, or directly on the beam pipes. Here reported are R&D results of the fabrication method, and some experimental results on the properties of the ferrite-copper block.

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THPMY009

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

resonance, impedance, coupling, vacuum

3670

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

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

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THPMY016

Graphene Coating for the Reduction of the Secondary Electron Yield

electron, vacuum, proton, framework

3688

B.S. Sian, G.X. Xia, G.L. Yu
UMAN, Manchester, United Kingdom
I. Kinloch, L. Lin, V. Valles
University of Manchester, Manchester, United Kingdom
O.B. Malyshev, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
O.B. Malyshev, R. Valizadeh, G.X. Xia
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Secondary electron emission is a limiting factor for a performance of many instruments ranging from small gauges and detectors to waveguides and charged particle accelerators. There have been several methods of reducing this effect, e.g. the method of using a material with a low Secondary Electron Yield (SEY) or thin film coating with such a low SEY material. This paper describes the effect of SEY mitigation with graphene coatings on aluminium substrate. The maximum SEY (dmax) was decreased from 2.4 for bare aluminium to 1.4 with a graphene coating. Measurements were taken using an electron gun and a Faraday cup, the electron energies varied between 80 eV and 1 keV with a bias of -18 V on the sample. Other biases of -3, -5, -9, -25, -50 and -75 V were also tested however there was no effect on the SEY.

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THPMY037

Realization of a System to Monitor Water Quality and for Cooling a TPS KEKB Superconducting Cavity CPL/HOM

HOM, superconducting-cavity, monitoring, operation

3740

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

Taiwan Photon Source (TPS) is a 3GeV synchrotron accelerator and is built next to the present Taiwan Light Source (TLS) [1]. The stability of electron beam is pro-vided by Low-level RF control system for keeping Gap voltage and phase to be constant[2]. The Gap voltage for accelerating electron beam is provided by KEKB super-conducting cavity. During routine operation of the super-conducting cavity, water cooling system is necessary for stabilize the accessory components of the cavity to avoid damage or abnormal of the system. This article would introduce the realization and integration of the water quality monitoring and cooling system for TPS supercon-ducting cavity input coupler and high order mode damper (CPL/HOM). Brief description is shown in first section. The detail architecture and function of the designed signal monitoring system will be discussed in 2nd section. The 3rd section will have further description of interlocks for system protection. The final section would summarize the water quality monitoring and cooling system in this article.

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THPMY041

Neodymium and Ytterbium Hybrid Solid Laser of RF Gun for SuperKEKB

laser, electron, linac, polarization

3748

X. Zhou, T. Natsui, Y. Ogawa, M. Yoshida, R. Zhang
KEK, Ibaraki, Japan
T. Shibuya
TIT, Tokyo, Japan

The electrum beam of the repetition rate of 50 Hz double-bunch is requested for injector linac of SuperKEKB. By development of the Yb-doped laser system, more than 5.0 nC and 3.0 nC electron beam with single-bunch has been generated in the 5 Hz and 25 Hz respectively. Also more than 1.0 nC electron with double-bunch has been obtained in 25 Hz. The Yb-doped laser system is already for commissioning for the linac. Next, a new laser system is development to improve the stability and reliability. The laser system starts with a 50 MHz Yb-doped fiber oscillator with the all normal dispersion (ANDi) structure. A transmission grating pair stretcher was employed to expend pulse to ~30 ps and separate the pulse to two parts with the center wavelength of 1030 nm and 1064 nm. Then the two kinds of pulses can be amplified by Yb:YAG and Nd:YAG crystals respectively. The weak pulses were amplified by the Yb-doped fiber amplifier, and reduced repetition rate by a semiconductor optics amplifier (SOA) pulse picker. To obtain the mJ-class pulse energy, a Yb:YAG thin-disk regenerative solid-state amplifier and a Nd:YAG rod regenerative solid-state amplifier were employed.

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THPOR015

CEPC Bunch Lengthening and Cavity HOM Analysis

HOM, resonance, collider, factory

3805

H.J. Zheng, J. Gao, Y. Wang
IHEP, Beijing, People's Republic of China

In this paper we will show the higher order mode (HOM) analysis of the cavity for the Circular Electron-Positron Collider (CEPC) partial double ring (PDR) scheme. In order to study the single bunch longitudinal instability in CEPC, bunch lengthening and energy spread are estimated based on Gao's theory. Different models are used to study the bunch lengthening and energy spread of the ring.

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THPOR024

Electrical Power Budget for FCC-ee

collider, klystron, operation, cryogenics

3828

F. Zimmermann, S. Aull, M. Benedikt, D. Bozzini, O. Brunner, J.-P. Burnet, A.C. Butterworth, R. Calaga, E. Jensen, V. Mertens, A. Milanese, M. Nonis, N. Schwerg, L.J. Tavian, J. Wenninger
CERN, Geneva, Switzerland
A.P. Blondel, M. Koratzinos
DPNC, Genève, Switzerland
Sh. Gorgi Zadeh
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
K. Oide
KEK, Ibaraki, Japan
L. Rinolfi
JUAS, Archamps, France

Funding: Supported by the European Commission under the Capacities 7th Framework Programme project EuCARD-2, grant agreement 312453.
We present a first rough estimate for the electrical power consumption of the FCC-ee lepton collider. This electrical power is dominated by the RF system, which provides the motivation for the ongoing R&D on highly efficient RF power sources. Other contributions come from the warm arc magnets, the cryogenics systems, cooling, ventilation, general services, the particle-physics detectors, and the injector complex.

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THPOR035

Development of a Low-latency, Micrometre-level Precision, Intra-train Beam Feedback System based on Cavity Beam Position Monitors

feedback, kicker, electron, extraction

3862

N. Blaskovic Kraljevic, R.M. Bodenstein, T. Bromwich, P. Burrows, G.B. Christian, M.R. Davis, C. Perry, R.L. Ramjiawan
JAI, Oxford, United Kingdom
D.R. Bett
CERN, Geneva, Switzerland

A low-latency, intra-train, beam feedback system utilising a cavity beam position monitor (BPM) has been developed and tested at the final focus of the Accelerator Test Facility (ATF2) at KEK. A low-Q cavity BPM was utilised with custom signal processing electronics, designed for low latency and optimal position resolution, to provide an input beam position signal to the feedback system. A custom stripline kicker and power amplifier, and a digital feedback board, were used to provide beam correction and feedback control, respectively. The system was deployed in single-pass, multi-bunch mode with the aim of demonstrating intra-train beam stabilisation on electron bunches of charge ~1 nC separated in time by c. 220 ns. The system has been used to demonstrate beam stabilisation to below the 75 nm level. Results of the latest beam tests, aimed at even higher performance, will be presented.

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THPOR037

TW-Structure Design and E-Field Study for CLIC Booster Linac

linac, booster, positron, electron

3868

E. Darvish Roknabadi
IPM, Tehran, Iran
S. Döbert
CERN, Geneva, Switzerland

Using the SUPERFISH code we present a design for a traveling wave (TW) structure of the Booster Linac for CLIC. The structure, consisting of thirty asymmetric cells attached to the beam pipes at two ends, works in 2Pi/3 operating mode at working frequency 2 GHz. The RF field transmitted through the designed cavity is prepared in an RF field data file to be used in the PARMELA code. We will then compare the resultant output PARMELA field with that of the ideal RF field which obtained from the usual method for a traveling wave structure.
* Based on CLIC Note 1051, 2015

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THPOR043

High Power Test of X-band Single Cell HOM-free Choke-mode Damped Accelerating Structure made by Tsinghua University

operation, vacuum, HOM, coupling

3881

X.W. Wu, H.B. Chen, J. Shi
TUB, Beijing, People's Republic of China
T. Abe, T. Higo
KEK, Ibaraki, Japan
W. Wuensch, H. Zha
CERN, Geneva, Switzerland

As an alternative design for CLIC main accelerating structures, X-band choke-mode damped structures had been studied for several years. However, the performance of choke-mode cavity under high power is still in lack of research. Two standing wave single cell choke-mode damped accelerating structures with different choke dimensions which are working at 11.424 GHz were designed, manufactured and bench tested by accelerator group in Tsinghua University. High power test was carried out on it to study the breakdown phenomenon in high gradient. A single cell structure without choke which almost has the same inner dimension as choke-mode cavity will also be tested to make a comparison and study how the choke affects high-gradient properties.

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THPOR044

mm-Wave Standing-Wave Accelerating Structures for High-Gradient Tests

accelerating-gradient, plasma, experiment, RF-structure

3884

E.A. Nanni, M. Dal Forno, V.A. Dolgashev, J. Neilson, S.G. Tantawi
SLAC, Menlo Park, California, USA
S.C. Schaub
MIT, Cambridge, Massachusetts, USA
R.J. Temkin
MIT/PSFC, Cambridge, Massachusetts, USA

We present the design and parameters of single-cell accelerating structures for high-gradient testing at 110 GHz. The purpose of this work is to study the basic physics of ultrahigh vacuum RF breakdown in high-gradient RF accelerators. The accelerating structures consist of pi-mode standing-wave cavities fed with TM01 circular waveguide mode. The geometry and field shape of these accelerating structures is as close as practical to single-cell standing-wave X-band accelerating structures, more than 40 of which were tested at SLAC. This wealth of X-band data will serve as a baseline for these 110 GHz tests. The structures will be powered from a pulsed MW gyrotron oscillator. One MW of RF power from the gyrotron may allow us to reach a peak accelerating gradient of 400 MeV/m.

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THPOW001

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

gun, emittance, impedance, coupling

3922

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

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

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THPOW002

Electromagnetic, Thermal, and Structural Analysis of a THOMX RF Gun Using ANSYS

gun, electron, coupling, simulation

3925

M. El Khaldi, J. Bonis, A. Camara, L. Garolfi, A. Gonnin
LAL, Orsay, France

Photocathode RF guns are used in the first stage of electron beam generation and acceleration. The RF gun of THOMX is a 2.5 cell standing wave copper cavity with resonance frequency of 2998.55 MHz at 30 °C under vacuum. The metal photocathode such as copper or magnesium is inserted into the backplane of the cavity. Due to high repetition rates up to 50 Hz with the average dissipated power into the internal surfaces up to 1.5 kW, causing a heating and deformation of the cavity shape. Therefore, the cooling system of the device has to be well designed to take under control the deformations of the structure, providing a temperature increase as small and uniform as possible. For this purpose a fully coupled electromagnetic-thermal-structural finite element analysis on this gun has been performed with Ansys workbench. Numerical results show that the gun could operate at 3 μs RF pulse length and 50 Hz repetition rate with an average dissipated power of 1.5 kW. The gun average temperature is around 30 °C while the incoming water temperature is around 24°C. Internal speed of water is 2.5 m/s which corresponds to 15 l/min for the incoming water. The total pressure drop is around 0.4 bar

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THPOW004

Pulse Response Measurements of NEA Photocathodes at Different Laser Wavelengths

laser, electron, photon, cathode

3931

M.A. Dehn, K. Aulenbacher, V. Bechthold
IKP, Mainz, Germany

For high average electron beam currents the length of the electron bunches must match the acceptance of the accelerator. At Johannes Gutenberg-University Mainz we are able to measure the longitudinal pulse response of NEA photocathodes (GaAs) under photo excitation of different wavelengths. A time resolution of < 2 ps at a beam energy of 100 keV is achieved, furthermore, a high dynamic range allows to investigate long ranging tails of the response (longitudinal halo). This serves to identify the best possible operation mode for high current photo sources.

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THPOW009

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

gun, impedance, electron, laser

3947

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

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

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THPOW017

VELA Photoinjector Cavity RF Investigations

cathode, simulation, operation, electron

3968

L.S. Cowie, B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
J.A. Mitchell
Lancaster University, Lancaster, United Kingdom
M.D. Roper
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

One of two ALPHA-X photocathode gun cavities, designed and fabricated at the Laboratoire de l'Accélérateur Linéaire, has been in operation on the VELA electron accelerator at Daresbury Laboratory since first beam in April 2013. In this time the maximum beam momentum recorded is 5.06 MeV/c. An investigation of the cavity has been performed with the aim of reconciling the expected momentum of over 6 MeV/c with the measured momentum. RF and beam simulation results are presented along with low power RF measurements of the cavity. One source of momentum loss, the flatness of the cathode face, is identified and rectified.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW017

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THPOW018

Simulations of Field Emitted Dark Current Dynamics in DC Photoinjectors

simulation, gun, electron, space-charge

3971

P.J. Tipping, J.W. McKenzie, B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Field emission is a concern in injectors with DC photoelectron guns because of the constant generation of dark current, which is accelerated down the beam line and can deteriorate the photoemitted bunch quality and lead to hardware damage. Simulations were carried out on the co-propagation of a field emitted, dark current halo and a photoemitted bunch in a typical 350 kV gun as used in an ERL or FEL injector, followed by a single cell buncher cavity. The photoemitted bunch repelled the halo longitudinally, leaving the area in the centre of the bunch with very low dark current, surrounded by two peaks of relatively high current at the front and back of the bunch. The peaks in current occur at all levels of dark current and were about 3.5 times the amplitude of the undisturbed dark current. The buncher caused the dark current to overcompress, forming a 'ghost' pulse an order of magnitude larger than the initial level of dark current, in front of the photoemitted bunch.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW018

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THPOW028

Automated Design for Standing Wave Electron Photoguns: TOPGUN RF Design

gun, toolkit, simulation, coupling

3999

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

Funding: DOE SCGSR and DOE/SU Contract DE-AC02-76-SF00515
Systematic design of RF photoguns involves multiple RF simulations in conjunction with beam dynamic simulations. RF simulations include tuning gun frequency, matching the gun to the feeding RF circuit, balancing the on axis electric fields between gun cells, minimizing surface electric and magnetic fields and power consumption, and optimizing separation of resonant mode frequencies. We created a tool that allows this multiple parameter optimization to be done automatically. We used SUPERFISH to accomplish the RF simulations. We present an example of the rf photogun TOPGUN design using these tools.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW028

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THPOY020

Neural Network Modeling of the PXIE RFQ Cooling System and Resonant Frequency Response

rfq, network, controls, operation

4131

A.L. Edelen, S. Biedron, S.V. Milton
CSU, Fort Collins, Colorado, USA
D.L. Bowring, B.E. Chase, J.P. Edelen, J. Steimel
Fermilab, Batavia, Illinois, USA

As part of the PIP-II Injector Experiment (PXIE) accel-erator, a four-vane radio frequency quadrupole (RFQ) accelerates a 30-keV, 1-mA to 10-mA H' ion beam to 2.1 MeV. It is designed to operate at a frequency of 162.5 MHz with arbitrary duty factor, including continuous wave (CW) mode. The resonant frequency is controlled solely by a water-cooling system. We present an initial neural network model of the RFQ frequency response to changes in the cooling system and RF power conditions during pulsed operation. A neural network model will be used in a model predictive control scheme to regulate the resonant frequency of the RFQ.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOY020

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THPOY028

Operational Status of HLS-II

operation, vacuum, storage-ring, electron

4155

J.Y. Li, G. Huang, W. Wei, W. Xu, K. Xuan, Y.L. Yang, Z.R. Zhou
USTC/NSRL, Hefei, Anhui, People's Republic of China

After a major renovation, the Hefei light source (HLS), renamed HLS_II, was brought into operation in the beginning of 2015. The operational result shows that the HLS-II not only provides much brighter synchrotron radiation beam for various users, but also shows much higher reliability than the old light source. This paper first gives an overview of the HLS-II. The overall performance of the light source is then summarized in this paper. Some measured key parameters of the light source, including emittance, orbit stability, beam lifetime and so on, are also presented.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOY028

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THPOY036

A New Fast RF Trip Diagnostic System in SSRF

diagnostics, vacuum, pick-up, klystron

4182

S.J. Zhao, Q. Chang, H.T. Hou, Z. Li, K. Xu, W.Z. Zhang, Zh.G. Zhang, Y.B. Zhao, X. Zheng
SINAP, Shanghai, People's Republic of China

A RF trip diagnostic system is essential to find out the trip source when a trip happened. In this paper, a fast RF trip diagnostic system, in storage ring RF system of SSRF, is reported. This system includes a synchronous acquisition recorder to sampling the trip data and a trip server to analysis the data. The recorder has more than 100 channels and maximum sampling rate of each channel is up to 60 MSPS. High precision I/Q cards are designed to detect RF signals. Trip server has been developed to process the trip data.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOY036

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THPOY043

Time Scale of Crab Cavity Failures Relevant for High Luminosity LHC

damping, resonance, luminosity, simulation

4196

K.N. Sjobak, R. Bruce, H. Burkhardt, A. Macpherson, A. Santamaría García
CERN, Geneva, Switzerland
R. Kwee-Hinzmann
Royal Holloway, University of London, Surrey, United Kingdom
A. Santamaría García
EPFL, Lausanne, Switzerland

Funding: Research supported by the High Luminosity LHC project
A good knowledge of the effects of the crab cavities, required for the baseline High Luminosity LHC (HL-LHC), is needed before the results of the first tests of crab cavity prototypes in the SPS, planned for 2018, will be available. In case of crab cavity failures, we have to make sure that time scales are long enough so that the beams can be cleanly dumped before damage by beam loss occurs. We discuss our present knowledge and modeling of crab cavity induced beam losses, combined with mechanical deformation. We discuss lower limits on the time scales required for safe operation, and possible failure mitigation methods.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOY043

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THPOY054

An External Synchronization of PHIL to a High Power Femtosecond Laser

electron, laser, timing, gun

4228

N. ElKamchi, V. Chaumat
LAL, Orsay, France

The synchronization accuracy between laser systems and RF wave is a crucial ingredient for the successful operation of any particle accelerator based on photo-emission. In the case of ultra-short highly charged electron accelerator, the beam is highly sensitive to timing jitter. Thus, a high level of synchronization accuracy is needed. In this paper, we describe the current synchronization system of PHIL (electron accelerator at LAL), and a new approach to synchronize PHIL externally with a high power femtosecond laser (LASERIX) . The main goal of the experience is to design and study a compact way to obtain ultra-short electron bunches (few tens to few hundreds of femtoseconds) under high charge levels (hundred pC). We continue with a description of different modifications made on PHIL timing master to adapt it to external synchronization.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOY054

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