07 Accelerator Technology
T06 Room Temperature RF

Paper	Title	Page
WEPVA054	Study of The New Return Yoke for The Upgraded Superconducting Cyclotron of INFN-LNS	3381
	A. Calanna, L. Allegra, L. Calabretta, G. Costa, G. D'Agostino, G. Gallo, D. Rifuggiato, A.D. Russo INFN/LNS, Catania, Italy G. D'Agostino Universita Degli Studi Di Catania, Catania, Italy
	The LNS Superconducting Cyclotron (CS) has been working for 20 years making available a wide range of ions and energies. Its operational diagram is peculiar and many experiment are performed each year. In the near future a major upgrade is planned. This will allow to overcome the major limitation of the CS, which is the beam power limited at 100 W. In the new version of the CS, the extracted beam power will be increased up to a factor 100. This improvement will be reached adding a new extraction line dedicated to a specific set of light ions and energies extracted by stripping. The new design could affect the beam dynamics strongly. Indeed, the iron yoke penetrations don't respect the three folds symmetry of our cyclotron. This inhomogeneity produces unwanted field harmonics, which have to be reduced as much as possible to avoid beam precession or second order effects. Here the study accomplished to minimize the perturbation of the non-three fold field symmetry using the current sheet approximation (CSA) is presented, along with the state-of-art configuration of the updated cyclotron
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA054
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THOBB1	High Power Test Results of the Eli-NP S-Band Gun Fabricated with the New Clamping Technology Without Brazing	3662
	D. Alesini, A. Battisti, M. Bellaveglia, A. Falone, A. Gallo, V.L. Lollo, L. Pellegrino, S. Pioli, S. Tomassini, A. Variola INFN/LNF, Frascati (Roma), Italy F. Cardelli, L. Palumbo University of Rome La Sapienza, Rome, Italy L. Ficcadenti, V. Pettinacci INFN-Roma, Roma, Italy D.T. Palmer Istituto Nazionale di Fisica Nucleare, Milano, Italy L. Piersanti INFN-Roma1, Rome, Italy
	High gradient RF photoguns have been a key development to enable several applications of high quality electron beams. They allow the generation of beams with very high peak current and low transverse emittance, satisfying the tight demands for free-electron lasers, energy recovery Linacs, Compton/Thomson Sources and high-energy linear colliders. A new fabrication technique for this type of structures has been recently developed and implemented at the Laboratories of the National Institute of Nuclear physics in Frascati (LNF-INFN, Italy). It is based on the use of special RF-vacuum gaskets that allow avoiding brazing in the realization process. The S-band gun of the Compton-based ELI-NP gamma beam system (GBS) has been fabricated with this new technique. It operates at 100 Hz with 120 MV/m cathode peak field and long RF pulses to allow the 32 bunch generation foreseen for the GBS. High gradient tests have been performed at full power full repetition rate and have shown the extremely good performances of the structure in term of breakdown rates. In the paper we report and discuss all experimental results with details of the electromagnetic design and mechanical realization processes.
	Slides THOBB1 [6.211 MB]
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THPAB039	Novel Manufacturing Concepts for 12 GHz High Gradient Accelerating Structures	3787
	A. Solodko, S. Atieh, N. Catalán Lasheras, A. Grudiev, S. Lebet, W. Wuensch CERN, Geneva, Switzerland H. Zha TUB, Beijing, People's Republic of China
	CLIC high gradient accelerating structures (AS) work-ing in X-band are made of copper ultra-high precision discs, requiring both milling and turning operations. Discs are then joint together by diffusion bonding. The rest of important technical systems, such as vacuum, cooling and manifolds, to house damping silicon carbide absorbers, are brazed to the bonded disc stack afterwards. This manufacturing technique has been successfully demonstrated but it is very challenging and needs an accurate assembly at every production step. Main issues concern vacuum-tightness, misalignment, deformations during different assembly operations, defects of braz-ing/bonding operations (gaps, a leak of brazing material) etc. Preparation and repairs are time and resource con-suming and increase the final price of the accelerating structure. This paper describes the novel manufacturing concepts for 12 GHz high gradient AS and focuses on new joining techniques as electron beam welding or brazing, new engineering solutions, as rectangular cells or structures made of halves are being considered.
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THPIK001	Copper Accelerating Structure Fabrication With Controled Cu-Ag Joining Conditions	4104
	V. Danielyan, V.S. Avagyan, S.G. Dekhtiarov, T.H. Mkrtchyan, S. Naghdalyan, A.S. Simonyan, V. V. Vardanyan CANDLE SRI, Yerevan, Armenia A.V. Tsakanian HZB, Berlin, Germany
	The paper is devoted to the development of technological processes of copper accelerating structures fabrication from oxygen-free copper. The experimental set-up for vacuum brazing of long accelerating structures with optimal Cu-Ag joining conditions is described. The experimental results of precise machining and subsequent vacuum brazing of Ag-Cu eutectic are presented
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THPIK003	Novel RF Structure for Energy Matching into an RFQ	4111
	V. Zvyagintsev, Z.T. Ang, T. Au, N.V. Avreline, J.J. Keir, R.E. Laxdal, M. Marchetto, B.S. Waraich TRIUMF, Vancouver, Canada A. Cote UBC, Vancouver, Canada
	Funding: National Research Council of Canada The ISAC RFQ at TRIUMF is designed to accelerate ions with A/q<=30 and requires an ion injection energy of 2.04 keV/u (β=0.002) for successful matching. This means that the ions (typically radioactive ions produced via the ISOL method) have to be extracted from a source at a terminal voltage in excess of 60 kV. Presently the ISAC target modules cannot hold more than 54 kV (and some lower than this) so that some of the higher masses cannot be successfully accelerated. A small 3-gap RF structure at 11.8 MHz has been designed to provide an energy matching to the RFQ. The structure operates in pi-mode and provides a maximum effective accelerating voltage of 16 kV to the low energy ions. Beam dynamics considerations, RF and mechanical design will be described. First results of RF tests of the structure will be given.
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THPIK005	RF Conditionning of the Spiral 2 CW RFQ	4114
	O. Piquet, Y. Lussignol CEA/DSM/IRFU, France M. Desmons, A.C. France, P. Galdemard CEA/IRFU, Gif-sur-Yvette, France M. Di Giacomo, R. Ferdinand, J.-M. Lagniel GANIL, Caen, France
	The SPIRAL2 RFQ is designed to accelerate light and heavy ions with A/Q from 1 to 3 at 0.73 MeV/A. The nominal beam intensities are up to 5 mA CW for both proton and deuteron beams and up to 1 mA CW for heavier ions. The four-vane cavity is made with 5 1-meter long sections mechanically assembled, it works at 88 MHz and is powered up to 180 kW CW to achieve the nominal vane voltage of 113.7 kV for A/Q = 3 ions. This paper describes the RF conditioning of the RFQ at GANIL with the setting of its RF systems and cooling system used to tune the cavity resonance frequency.
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THPIK008	Beam Dynamics for the ThomX Linac	4121
SUSPSIK090	use link to see paper's listing under its alternate paper code
	L. Garolfi, C. Bruni, M. El Khaldi, C. Vallerand LAL, Orsay, France
	We report the results of a recent beam dynamics study that has led to promising working points for the split ThomX photoinjector. ThomX is a back-scattering Thomson light source that will use S-band electron Linac with an energy of 50 MeV to produce 45 keV high X-rays flux (1011 - 1013 ph/s), by means of collision between electron bunches and laser pulses, in the energy range from 45 keV to 90 keV. Since Thomx has been conceived to maximise the average X-rays flux in a fixed bandwidth, the high rate electron-photon collisions impose a linear accelerator combined with a storage ring. The high performances of the accelerator are largely affected by the high quality of the electron beam at the interaction point in the ring. Beam specifications should be achieved at the interaction point to the extent that 1 nC, 50 nA average current per bunch with normalised rms transverse emittance less than 5 mm and around 0.3% energy spread, at the end of the linac. The beam dynamics along the linac has been studied to demonstrate the capability of the accelerator to meet the requirements for the high brightness electron beam using an RF photoinjector configuration.
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THPIK014	Travelling Wave Accelerating Structure for Areal 50 MeV Energy Upgrade	4130
	A. Vardanyan, V. Danielyan, S.G. Dekhtiarov, B. Grigoryan, L. Hakobyan, T. Markosyan, A.S. Simonyan CANDLE SRI, Yerevan, Armenia W. Ackermann TEMF, TU Darmstadt, Darmstadt, Germany A.V. Tsakanian HZB, Berlin, Germany
	AREAL facility development implies energy upgrade to 50 MeV in order to drive a THz free electron laser. To reach this goal, the installation of two 1.6 m long S-Band travelling wave accelerating sections, with nominal accel-erating gradient of 15 MV/m, are foreseen. In this paper the design study of accelerating sections along with the matching performance of RF couplers are presented. The simulations are performed using the CST Microwave Studio. The first results of the accelerating structure proto-type fabrication are discussed.
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THPIK015	Prototype Results of the ESR Barrier-Bucket System	4133
	M. Frey, P. Hülsmann, H. Klingbeil GSI, Darmstadt, Germany D. Domont-Yankulova, K. Groß, J. Harzheim, H. Klingbeil TEMF, TU Darmstadt, Darmstadt, Germany
	The experimental storage ring (ESR), operated at the GSI facility in Darmstadt, Germany, allows experiments with a variety of ion species. In combination with the existing electron cooler, its RF cavities have been used to demonstrate longitudinal beam accumulation in order to increase the beam intensity. Limitations of the existing narrow-band cavities led to the development of a magnetic alloy (MA) based broad-band cavity for the generation of Barrier-Bucket signals. The application of a pre-distortion method demands high linearity of the driver amplifier and highlights the importance of its selection process. In this contribution, the cavity and amplifier system design is described and data measured at a prototype system are presented.
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THPIK016	Status of the SIS100 RF Systems	4136
	H. Klingbeil, R. Balß, M. Frey, P. Hülsmann, A. Klaus, H.G. König, U. Laier, D.E.M. Lens, K.-P. Ningel GSI, Darmstadt, Germany
	Four different types of RF cavities are realized for the heavy-ion synchrotron SIS100 which is built in the scope of the FAIR (Facility for Antiproton and Ion Research) project. The standard acceleration is performed by ferrite cavities. Barrier bucket cavities will allow a pre-compression of the beam by means of moving barriers. Bunch compressor cavities are used to realize a rotation in longitudinal phase space by 90 degrees, thereby reducing the bunch length. Finally, a longitudinal feedback system reduces undesired beam oscillations. In contrast to the ferrite-loaded accelerating cavities, the last-mentioned three cavity types are based on magnetic alloy (MA) material. Depending on the type of the cavity system, the realization is done by - or in close collaboration with - different industrial companies and institutions. In this contribution, the realization status of all these synchrotron RF systems is summarized.
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THPIK017	Field Uniformity Preservation Strategies for the ESS DTL: Approach and Simulations	4139
	G.S. Mauro, F. Grespan, A. Palmieri, A. Pisent INFN/LNL, Legnaro (PD), Italy P. Mereu, M. Mezzano, C. Mingioni, M. Nenni INFN-Torino, Torino, Italy
	The Drift Tube Linac (DTL) of the European Spallation Source (ESS) is designed to operate at 352.2 MHz with a duty cycle of 4 % (3 ms pulse length, 14 Hz repetition period) and will accelerate a proton beam of 62.5 mA pulse peak current from 3.62 to 90 MeV. This paper presents the approach taken in order to preserve field flatness of DTL Tanks. This strategy required a set of simulations and consequent choices about RF design of DTL cells, RF coupler tuning and compensation, cooling of the DTL cells. Outcomes of these simulations and the experimental verifications of this approach are then explained.
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THPIK021	Structural Mechanical Analysis of 4-Rod RFQ Structures in View of a Newly Revised CW RFQ for the HLI at GSI	4142
SUSPSIK091	use link to see paper's listing under its alternate paper code
	D. Koser, H. Podlech IAP, Frankfurt am Main, Germany P. Gerhard, L. Groening GSI, Darmstadt, Germany O.K. Kester TRIUMF, Vancouver, Canada
	Funding: BMBF Contr. No. 05P15RFRBA The High Charge State Injector (HLI) at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, serves as one of the two injector linacs for the UNILAC as well as dedicated injector for the upcoming cw linac project for super heavy element research. As the front end of the HLI is planned to be upgraded for cw operation a newly revised cw capable RFQ structure with an operating frequency of 108 MHz is required. The existent 4-rod structure, which was commissioned at the HLI in 2010, suffers from severe modulated rf power reflections originating from mechanical oscillations of the electrodes that both limit the achievable performance and impede stable operation*. Besides preceding vibration measurements that were done by GSI using a laser vibrometer**, the structural mechanical behavior of the 4-rod geometry was extensively analyzed using ANSYS Workbench. Thereby the crucial mechanical eigenmodes could be identified and their impact on the rf properties was investigated by simulations using CST MWS. A completely newly revised 4-rod RFQ design with optimized structural rigidity was developed of which a 6-stem prototype is currently being manufactured. *P. Gerhard et al., Experience With a 4-Rod CW Radio Frequency Quadrupole, LINAC12, THPLB07 **P. Gerhard et al., In Situ Measurements of Mechanical Vibrations of a 4-Rod RFQ at GSI, LINAC14, TUPP057
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THPIK029	THE RF CAVITY FOR THE INDUS-2 STORAGE RING	4154
	C. P. Pasotti, M. Bocciai, P. Pittana, M. Rinaldi Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	A new Elettra-type cavity has been delivered to the Raja Ramanna Centre for Advanced Technology (RRCAT) Indus-2 facility. This cavity is the very same of those already installed several years ago with some optimization of the cooling channels. It is the Elettra-type cavity, normal conducting copper single cell but resonating at 505.8 MHz. The cavity description, the full characterization of the accelerating mode (L0) and high order modes (HOM) and the acceptance tests are presented in this paper.
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THPIK030	THE RF CAVITY FOR THE SESAME FACILITY	4158
	C. P. Pasotti, M. Bocciai, M. Rinaldi Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy D.S. Foudeh, E. Huttel SESAME, Allan, Jordan
	SESAME is a 2.5 GeV Synchrotron Light Source under commissioning in Allan (Jordan). It will be the first inter-national research centre in the Middle East [1]. It is a cooperative venture with support provided by several international organizations and scientific laboratories. Elettra-Sincrotrone Trieste (Italy) is among them. In the framework of the collaboration agreement among SESAME (Jordan), INFN (Italy) and Elettra-Sincrotrone Trieste, four 500 MHz normal conducting (NC) copper cavities have been built and commissioned at Elettra and then successfully installed in the SESAME storage ring. The cavities properties, their fabrication process, their characterization at low and high RF power is presented here.
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THPIK032	Installation and Low Power Test of IFMIF-EVEDA RFQ at Rokkasho Site	4162
	E. Fagotti, L. Antoniazzi, A. Baldo, A. Battistello, L. Bellan, P. Bottin, M. Comunian, A. Conte, L. Ferrari, M.G. Giacchini, F. Grespan, M. Montis, A. Palmieri, A. Pisent, D. Scarpa INFN/LNL, Legnaro (PD), Italy D. Agguiaro, A.G. Colombo INFN- Sez. di Padova, Padova, Italy F. Borotto Dalla Vecchia, G. Dughera, G. Giraudo, P. Mereu, R. Panero INFN-Torino, Torino, Italy P. Cara, R. Heidinger Fusion for Energy, Garching, Germany M. Furini, C. Gessi INFN-Bologna, Bologna, Italy D. Gex F4E, Germany R. Ichimiya, Y. Ikeda, A. Kasugai, K. Kondo, S. O'hira, K. Sakamoto, T. Shinya, M. Sugimoto QST, Aomori, Japan J. Knaster, A. Marqueta, G. Pruneri, F. Scantamburlo IFMIF/EVEDA, Rokkasho, Japan
	The IFMIF-EVEDA RFQ is composed of 18 modules for a total length of 9.8 m and is designed to accelerate the 125 mA D+ beam up to 5 MeV at the frequency of 175 MHz. The RFQ is subdivided into three Super-Modules of six modules each. The Super-Modules were shipped to Rokkasho (Japan) at the beginning of 2016, pre-assembled 3 m far from the final location and tuned to reach target field flatness requirements. Just after conclusion of injector commissioning, the tuned RFQ was disassembled, moved and reassembled in the final location. After confirmation that field flatness was not affected by this movement, high power couplers were installed and tuned and all the structure was baked. Assembling, tuning and coupling results will be presented.
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THPIK033	RF-Mechanical Design and Prototyping of the SPES RFQ	4166
	L. Ferrari, A. Palmieri, A. Pisent INFN/LNL, Legnaro (PD), Italy
	The SPES RFQ is designed in order to accelerate beams in CW with A/q ratios from 3 to 7 from the Charge Breeder through the MRMS and the selection and injection lines up to the MEBT. RFQ is composed of 6 modules about 1.2 m long each. Each module is basically composed of a Stainless Steel Tank and four OFE Copper Electrodes (obtained by brazing of two subassemblies in order to spare material). A copper layer is electrodeposited on the tank inner surface and a spring joint between tank and electrode is used in order to seal the RF. In this paper the main result of the design of the RFQ (with particular focus on the RF-mechanical aspects and thermo-structural calculations), the RFQ prototyping strategy as well as the construction and assembly procedure of RFQ modules are described.
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THPIK035	Rf Properties of a 175 MHz High-Q Load Circuit	4169
	S. Maebara, M. Sugimoto QST, Aomori, Japan
	For an RF input coupler test, a 175MHz high-Q load circuit based on a 6 1/8 in. co-axial waveguide was developed. This circuit consists of the RF input coupler, a trombone-type phase shifter and a stub tuner. The coupler with a loop antenna and the stub tuner are located in edges of the circuit, the loop antenna and the tuner work for a short plate. When RF input power is injected into the circuit, a high-voltage standing wave is excited by adjusting the tuner. The power of standing wave required for the tests is also accumulated due to its low resistive loss. At the operation frequency of 175 MHz, the resistive loss of 0.046ohm is measured and an equivalent RF power of 200 kW is accumulated by the RF input power of 740 W. In this circuit, the bandwidth is narrow to be ±5 kHz in S11 parameter of less -20 dB, but the equivalent RF power of 200 kW-14 sec CW could be achieved after sufficient RF aging. Using this high-Q load circuit, all the fabricated 9 couplers were successfully tested for RF contact defects, unnecessary low-Q value and extraordinary outgassing. This article describes these RF properties in detail.
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THPIK036	Design Study of Damped Accelerating Cavity Based on the TM020-Mode and HOM Couplers for the KEK Light Source Project	4172
	T. Takahashi, S. Sakanaka, N. Yamamoto KEK, Ibaraki, Japan
	A novel damped-cavity scheme was recently proposed by Ego et al.*. In this design, TM020 resonant mode is used for beam acceleration. Power of higher-order (or lower-order) modes are extracted through cylindrical slots which are placed at the position where the magnetic fields of HOMs are strong while that of TM020 mode is zero. Extracted powers are absorbed by lossy ferrites. In this scheme, excellent HOM damping is possible while occupying less space of the straight section in storage rings. We propose in this paper an alternative design which is based on the same TM020 mode but with rod-type HOM couplers. The rod-type HOM couplers are placed where the electric fields of HOMs are strong while that of TM020 mode is zero. In this scheme, openings needed for HOM extraction can be made smaller, which is desirable for stiffening the mechanical structure of the cavity. Potential use of lossy dielectric materials is another merit. We present external Q-values of HOMs that can be achieved in this scheme, as well as an effect of HOM couplers on the TM020 mode. Our current study is directed to a 1.5 GHz higher-harmonic cavity for the proposed KEK Light Source project**. * H. Ego et al., in Proceedings of the 11-th Annual Meeting of Particle Accelerator Society of Japan, Aug. 9-11, 2014, MOOL14 [in Japanese]. ** K. Harada et al., IPAC2016, THPMB012.
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THPIK037	Simulation Study of Normal-Conducting Double RF System for the 3-GeV KEK Light Source Project	4176
	N. Yamamoto, S. Sakanaka, T. Takahashi KEK, Ibaraki, Japan
	For the proposed 3-GeV KEK Light Source (KEK-LS) project*, a double RF system using 500-MHz accelerating and 1.5-GHz third-harmonic cavities is under consideration. To mitigate intrabeam scattering due to ultra-low emittance, the bunch length will be elongated using the harmonic cavities which is based on the TM020 resonant mode. An accelerating cavity based on this mode was first proposed by Ego et al.**, and we found it very suitable for the harmonic cavities due to the following reasons: 1) it has high unloaded-Q and high stored electromagnetic energy which result in the reduction of transient beam-loading effect due to bunch gaps, and 2) efficient damping of higher (or lower) order modes is possible. Our investigations based on numerical simulations predicted the bunch elongation by a factor of 3.1 when realistic bunch-gaps were assumed. To improve the bunch elongation further, we also proposed to compensate the transient beam loading with two realistic measures: 1) compensation of rf voltages due to feedforward technique, and 2) compensation using a separate rf cavity. We will present our study on the double rf system based on numerical simulations. * K. Harada et al., IPAC2016, THPMB012. ** H. Ego et al., Proceedings of the 11-th Annual Meeting of Particle Accelerator Society of Japan, Aug. 9-11, 2014, MOOL14 [in Japanese].
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THPIK039	Multipactor Problem of J-PARC SDTL	4184
	T. Ito, T. Morishita, J. Tamura JAEA/J-PARC, Tokai-mura, Japan K. Nanmo, T. Sugimura KEK, Ibaraki, Japan
	We have suffered from multipactor problem of some SDTL after the Great East Japan Earthquake. As a designed operating rf power of the SDTL is in the multipactor region, we had to operate at higher power of the designed one. From the result of the simulation and the observation of the SDTL cavity, it became clear that the multipactor occurred on the inner surface of the cavity. We think that one of the cause of the maultipactor is the contamination on the inner surface of the cavity, we performed the cleaning of the inner surface of the cavity by using acetone. The cleaning was very effective and the multipactor region was reduced dramatically or disappeared. The multipactor problem has not occurred since then.
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THPIK041	The RF System of the SESAME Storage Ring	4187
	D.S. Foudeh, E. Huttel, N.Kh. Sawai SESAME, Allan, Jordan
	SESAME the Synchrotron Radiation Light Source in Allan (Jordan) consists of a 22 MeV Microtron, an 800 MeV Booster Synchrotron (originally from BESSY I, Berlin, Germany) and a 2.5 GeV Storage Ring (new de-sign). The RF system consists of four 500 MHz ELET-TRA cavities powered by four 80 kW Solid State Ampli-fiers whereas the first amplifier is produced by SOLEIL and the other three are produced by SIGMA-PHI. The RF plant is controlled by the digital Low Level Electronics from DIMTEL. The system has been installed end of 2016. This report describes the setup of the facility and the results of the commissioning.
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THPIK043	Design and Optimization of a 2MeV X-Band Side Coupled Accelerating Structure	4193
SUSPSIK093	use link to see paper's listing under its alternate paper code
	H. Yuan IHEP, Beijing, People's Republic of China
	An X-band bi-period side-coupled accelerating structure has been designed in this paper. The structure's working frequency is 9.3GHz. '/2 mode is chosen for the structure's stability. There are 11 accelerating cells, the first 5 work as non-light velocity part while the other 6 work as light velocity part. After CST simulation, the coupling constant between accelerating cells and coupling cells is 5%, efficient shunt impedance is 142M'/m. For the beam dynamic analysis, the particle energy is selected to be 2 MeV and the peak current is 60 mA for the radiation dosage limits by national standard. After Pamela optimization, the particle's capture efficiency is more than 30%. To feed power into the structure, a coupler is designed in the middle of the structure and the coupling coefficient is 1.4. The structure is manufactured and the measurement result accords well with designing value.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK043
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THPIK045	Design of a C-band Travelling-wave Accelerating Structure at IHEP	4196
	J.R. Zhang, Y.L. Chi, J. Lei, H. Wang, X. Wang IHEP, Beijing, People's Republic of China S. Shu Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
	A C-band travelling wave accelerating structure has been developed at IHEP. The structure is a constant gra-dient type and operating with a 3'/4 mode. The total length of the structure is 1.8-meters long with 85 regular cells and two coupler cells. 2D program Superfish is used to optimize the cavity shape and the iris size. The wall cells are rounded for it can improved the Q value for about 10%. The cell irises have an elliptical profile to minimize the peak surface electric fields. In order to compatible with the compact of the short-range wake field on the beam dynamics, the average iris radius is 7.15 mm. The group velocity of the designed structure is from 2.8% to 1.4%. Between the rectangular waveguide and the accelerating structure, magnetic coupling is adopted. The coupled cavity is racetrack type in order to minimize the asymmetry in the coupler. Kyhl's method is used to match the input and output coupler.
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THPIK046	Design, Fabrication and Cold Test of a C-Band Barrel Open Cavity Pulse Compressor	4200
	S. Shu Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China M. Hou, S. Pei, N.B. Song, J.R. Zhang, F. Zhao IHEP, Beijing, People's Republic of China
	The first prototype of the C band barrel open cavity (BOC) pulse compressor has been manufactured by the Institute of High Energy Physics (IHEP), Beijing, which is used to test the brazing process and the RF properties of the structure at low power. The whispering gallery mode TM6, 1,1 with an unload Q of 100, 000 was adopt to oscillate in the cavity, and the coupling factor was optimized to achieve the highest power gain. This paper mainly deals with the RF design, mechanical design and cold test of the C band BOC pulse compressor.
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THPIK048	Design of Rapid Tuning System for a Ferrite-Loaded Cavity with Heavy Beam Loading	4203
	X. Li, H. Sun, F.C. Zhao, J.Y. Zhu IHEP, Beijing, People's Republic of China
	A high power, broadband and rapid frequency sweeping RF system was developed to satisfy the demand of China Spallation Neutron source (CSNS)/ Rapid Cycling Synchrotron (RCS). The cavity tuning is the key issue which has great impact on the performance of the whole RF system. In order to satisfy the requirement of cavity dynamic tuning caused by the nonlinear characteristics of the ferrite material, some new technologies were developed and applied. In this paper, the overall design of the tuning system will be introduced. The ensuing discussion will be focused on the choice of different types bias current supplies, the control algorithm of LLRF system and the beam loading compensation issues.
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THPIK049	High Power Conditioning of the DTL-1 for CSNS	4207
	H.C. Liu, Q. Chen, K.Y. Gong IHEP, Beijing, People's Republic of China M.X. Fan, A.H. Li, B. Li, J. Peng, P.H. Qu, Y. Wang, X.L. Wu CSNS, Guangdong Province, People's Republic of China
	The RF tuning of the first DTL tank for the China spalla-tion neutron source was finished leading to a stabilized-uniform accelerating field. After the installation of the DTL-1 in the linac tunnel, the high power conditioning was carried out deliberately. Consequently a peak RF power of 1.6MW with 25Hz repetition rate and 650'sec pulse width was put into the tank stably. A 3MeV H− ion was injected into the DTL-1 and was successfully accel-erated to 21.6MeV with almost 100% transmission. Dur-ing the operation, The DTL-1 tank worked stable in the design power level. The conditioning details will be pre-sented in this paper.
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THPIK050	Measurement and Tuning of the RF Field for the CSNS DTL	4210
	A.H. Li, M.X. Fan, B. Li, J. Peng, P.H. Qu, Y. Wang, X.L. Wu CSNS, Guangdong Province, People's Republic of China Q. Chen, S. Fu, K.Y. Gong, H.C. Liu IHEP, Beijing, People's Republic of China
	The CSNS DTL accelerates negative hydrogen ions from 3MeV to 80MeV with resonant frequency of 324MHz and peak current of 15mA. The CSNS includes four DTL cavities with diameter of 56.6cm and each length of 9 meters. RF properties research and measurement have been done to make sure the design and manufacture validate for beam operation. A new automatic system has been developed for measuring field distribution. The secondary derivation method is used to calculate the amount of the tuners to tune axial field flatness. The tilt of TS curve is used to judge the gap between the post couplers and drift tubes to achieve stability. At last the tanks have good flatness and strong stabilization, the field deviation is 2% with the standard deviation of 0.96%, and the maximum TS parameter is 65%/MHz. After the low power RF tuning experiment, the four tans have been installed in the tunnel, and have gotten good results of high power test and beam acceleration experiment.
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THPIK054	The X-Band Pulse Compressor for Tsinghua Thomson Scattering X-Ray Source	4214
	Y.L. Jiang, H.B. Chen, C. Cheng, W. Gai, J. Shi, P. Wang, X.W. Wu, H. Zha TUB, Beijing, People's Republic of China
	An X-band (11.424 GHz) high-power RF station is being built for Tsinghua Thomson scattering X-ray Source (TTX). The station aims to feed several X-band accelerating structures working at a high gradient of 80 MV/m. An X-band pulse compressor is designed to compress the RF pulse from 1.5 us to 100 ns and to generate more than 250 MW peak power from a 50MW klystron. This pulse compressor implements a resonate cavity housing the HE11-mode as the energy storage cavity, with a high quality factor Q of more than 105. The detailed design of the high-Q cavity as well as the dedicate couplers of this pulse compressor are present in this work.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK054
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THPIK055	Power-Conditioning Cavity Design and Measurement of the Coaxial Coupler for the Injector of XiPAF Project	4218
	Y. Lei, X. Guan, W. Wang, X.W. Wang, Q.Z. Xing, H.Y. Zhang, S.X. Zheng TUB, Beijing, People's Republic of China
	For the RF high power conditioning on coaxial power couplers of the XiPAF (Xi'an Proton Application Facility), the RF high power-conditioning cavity was designed and manufactured. The cavity consists of a rectangular reso-nant cavity with two ports, which one is connected with input coupler from RF power source and the other one is connected with output coupler, and a tuner. The tuning frequency range could cover 325 (+0.5, -9.5) MHz. The measured Q factors are matched with the design results generally. But the S-parameter is not ideal compared to the simulation. This paper will present the design and low power measurement results of the cavity
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK055
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THPIK057	Development of a High-Power X-Band RF Rotary Joint	4224
	J. Liu, H.B. Chen, J. Shi, X.W. Wu, H. Zha TUB, Beijing, People's Republic of China
	RF rotary joints allow the independent movement be-tween the RF power source and the accelerating tube of a linear accelerator (linac). In this paper, the design of a compact X-band (9.3 GHz) high-power RF rotary joint is presented. Simulation results illustrate that RF parameters (the scattering matrix) of this rotary joint keep stable in the arbitrary rotation angle. The maximum return loss is about -30 dB, the insert loss is less than 0.11 dB, and the variance of output phase shifts is below 1 degree while rotating the joint. RF measurement on the rotary joint using Vector-Network analyser is also conducted and presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK057
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THPIK058	Development of a S-Band Pulse Compressor	4227
	P. Wang, H.B. Chen, C. Cheng, J. Shi, X.W. Wu, H. Zha TUB, Beijing, People's Republic of China
	We designed and fabricated a pulse compressor for S-band high power test stand at Tsinghua University. This pulse compressor is made up of a sphere resonant cavity with quality factor of 100000 and a rf polarizer. It has the ability of compressing a pulse from 3.6 us to 300 ns with the power gain of 7. A short description of the pulse compressor is presented, together with the RF design and low level RF measurement.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK058
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THPIK059	Experimental Study on PM-AM Method in Pulse Compression System	4230
	P. Wang, H.B. Chen, C. Cheng, M.M. Peng, J. Shi, X.W. Wu, J. Yang, H. Zha TUB, Beijing, People's Republic of China
	We experimentally demonstrate the PM-AM method (Phase Modulation to Amplitude Modulation) at the S-band high power test stand, which consists of two S-band klystrons, a SLED type pulse compressor and two high power stainless steel RF loads, in Tsinghua University. A LLRF (low level RF) system has been developed to modulate the phases of the two klystrons in real time such that pulse compressor could generate a flat output pulse. Experimental results presents that the efficiency of the pulse compression system is 45% and the power gain is 2.9.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK059
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THPIK060	Tuning of an S-Band 10 MeV Traveling-Wave Accelerating Structure with a Non-uniform Section	4233
	J.H. Shao, H.B. Chen, C. Gong, J. Shi, X.W. Wu, S.X. Zheng TUB, Beijing, People's Republic of China
	A tuning method of nonuniform travelling wave structures has been developed based on non-resonant perturbation measurement at Tsinghua University. The filed distribution is normalized with the shunt impedance and attenuation of each cell. Then their internal reflection can be deduced and corrected by cavity deforming. This method has been applied to an S-band 10 MeV travelling wave structure successfully. In this paper, the detailed tuning method and cold test results will be presented.
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THPIK061	3D Model Analysis of Cavity for CSNS DTL	4236
	P.H. Qu, M.X. Fan, B. Li, Y. Wang CSNS, Guangdong Province, People's Republic of China Q. Chen, K.Y. Gong, A.H. Li, H.C. Liu, F.X. Zhao IHEP, Beijing, People's Republic of China
	An Alvarez-type Drift tube linac (DTL) was utilized to accelerate an H− ion beam from 3 MeV to 80 MeV of China Spallation neutron source (CSNS). RF field profile is always deviate from the design curve due to errors in fabrication and assembly of the structure cells, thus RF tuning of DTL is necessary. CSNS DTL operates in zero mode and has long tank, so accelerating field of which is unstable, this problem was solved through adding post couplers at the both side of cavity wall. In order to speed up the schedule of DTL low power RF tuning, we analyzed the operating mode, field flatness with slug tuners, field stabilization with post couplers by CST Micro wave studio (MWS) mainly with eigenmode solver in advance. Considering saving the computer memory and increasing the calculation speed, we divided each tank model into three short units. Slug tuner depth and PC-DT gap of DTL-1 and DTL-3 by simulation were shown which improved the efficiency of CSNS DTL RF tuning.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK061
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THPIK063	The RF System of Infrared Free Electron Laser Facility at NSRL	4239
	L. Lin, B. Du, G. Huang, K. Jin, F.F. Wu USTC/NSRL, Hefei, Anhui, People's Republic of China
	Funding: The Natural Science Foundation of China An infrared free electron laser light source (IRFEL) is being constructed at National Synchrotron Radiation Laboratory, which could be used in the study of far infrared detection, light dissociation and light excitation. The accelerator of IRFEL deliver a average current 300 A electron beam at 15~60 MeV, the energy spread is less than 240 keV, and the emittance is less than 30 mm*mrad. IRFEL is consisted of two optical resonator system, which could create 2.5~50 um, 40~200um infrared laser respectively. The design of IRFEL RF system is introduced, the recent progress of prebuncher, buncher, frequency distribution, accelerator and DLLRF system are also present in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK063
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THPIK067	A C-Band Compact Spherical RF Pulse Compressor for the SXFEL Linac Energy Upgrade	4248
SUSPSIK094	use link to see paper's listing under its alternate paper code
	Z.B. Li, W. Fang, Q. Gu, Z.T. Zhao SINAP, Shanghai, People's Republic of China
	A new compact C-band (5712 MHz) spherical RF pulse compressor has been designed for Shanghai Soft X-ray Free Electron Laser (SXFEL) facility energy upgrading at Shanghai Institute of Applied Physics (SINAP), Chinese Academy of Sciences (CAS). This pulse compressor contains one high Q0 spherical RF resonant cavity which works on two TE113 modes and a novel coupler. As there is only one storage cavity, this pulse compressor can be much smaller than the traditional SLED. With the coupling coefficient 4.9, the average power gain can be as high as 3.8. In this paper, the scheme of the C-band spherical pulse compressor and RF design are presented.
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THPIK068	High Power Test of SINAP X-Band Deflector at KEK	4251
	J.H. Tan, W. Fang, Q. Gu, X.X. Huang, Z.B. Li, Z.T. Zhao SINAP, Shanghai, People's Republic of China T. Higo KEK, Ibaraki, Japan D.C. Tong TUB, Beijing, People's Republic of China
	A crucial RF structure used for bunch length measurement for Shanghai X-ray Free Electron Lasers (SXFEL) at the Shanghai Institute of Applied Physics (SINAP), Chinese Academy of Science [1]. The design, fabrication, measurement and tuning have been completed at SINAP [2], and the high power test was carried out at Nextef of KEK with international collaboration. This paper presents the RF conditioning process and test results.
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THPIK070	Localization of RF Breakdown Point in a Coaxially Loaded LINAC Cavity	4254
	Q.S. Chen, T. Hu, B. Qin HUST, Wuhan, People's Republic of China Y.J. Pei USTC/NSRL, Hefei, Anhui, People's Republic of China
	Here we report how the RF breakdown point (RFBP) can be localized in a coaxially loaded linac cavity with just the forward and the reflected power signal. The cavity uses 4 load cells instead of output coupler to absorb remanent power, so no transmitted power signal could be recorded. We propose two methods to analyze the measured signals and localize the RFBP. One method focuses on the time delay of the two signals while the other one focuses on the amplitude. Quantitative analysis showed the two methods were well consistent with each other and indicated the RFBP located at the end of the linac cavity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK070
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THPIK078	1.5 GHz Cavity Design for the CLIC Damping Ring and as Active Third Harmonic Cavity for ALBA	4263
	B. Bravo, J.M. Alvarez, F. Pérez, A. Salom ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
	In a collaboration framework between CERN and ALBA, we are designing a normal conducting active 1.5 GHz cavity which could serve as main RF system for the Damping Ring of CLIC and as an active third harmonic cavity for the ALBA Storage Ring. The third harmonic cavity at ALBA will be used to increase the bunch length in order to improve the beam lifetime and increase the beam stability thresholds. The main advantage of an active third harmonic cavity is that optimum conditions can be reached for any beam current. This paper presents the preliminary design of this cavity: an active, normal conducting cavity tuned at 1.5 GHz based on the 500 MHz European Higher Order Mode (HOM) damped normal conducting with nose cones using ridged circular waveguides for HOM damping. Electromagnetic simulations, mechanical and thermal stress analysis will be presented together with the calculations on beam stability improvement due to the third harmonic system.
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THPIK081	Design and Construction of a High-Gradient RF Lab at IFIC-Valencia	4272
SUSPSIK096	use link to see paper's listing under its alternate paper code
	A. Vnuchenko, T. Argyropoulos, C. Blanch Gutiérrez, D. Esperante Pereira, A. Faus-Golfe, J. Giner Navarro IFIC, Valencia, Spain N. Catalán Lasheras, G. McMonagle, I. Syratchev, W. Wuensch CERN, Geneva, Switzerland A. Faus-Golfe LAL, Orsay, France
	The IFIC High-Gradient (HG) Radio Frequency (RF) laboratory is designed to host a high-power infrastructure for testing HG S-band normal-conducting RF accelerating structures and has been under construction since 2016. The main objective of the facility is to develop HG S-band accelerating structures and to contribute to the study of HG phenomena. A particular focus is RF structures for medical hadron therapy applications. The design of the laboratory has been made through collaboration between the IFIC and the CLIC RF group at CERN. The layout is inspired by the scheme of the Xbox-3 test facility at CERN, and it has been adapted to S-band frequency. In this paper we describe the design and construction status of such a facility.
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THPIK083	Mechanical Fabrication of ESS-Bilbao RFQ	4279
	J.L. Muñoz, I. Bustinduy, J. Martin, A. Ortega, I. Rueda, A. Zugazaga ESS Bilbao, Zamudio, Spain M.A. Carrera, A. Garbayo AVS, Elgoibar, Spain
	The fabrication of the first segment of ESS-Bilbao's RFQ has started in 2016. The segment, of about 800 mm in length, is an assembly of 4 elements: two major vanes and two minor ones. The assembly will be done by making use of carefully-designed vacuum polymeric gaskets instead of brazing. Electron beam welding has been used during fabrication of the vanes. Apart from conventional CAD systems, a home-made tool for vane modulation solid generation has been successfully used. Machining process from copper blocks to final elements is described in detail. Also, the software tools created to assess the quality of the vanes by analyzing the metrology measurements, particularly of the modulation, are described in the paper. In order to test and validate the chosen vacuum strategy, an aluminum model using the same gaskets as the final model was built and tested. Results will also be presented. The fabrication of the first segment is expected to end up in early 2017, so assembly, segment alignment and vacuum tests with the real device will also be included in the paper.
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THPIK086	Design and Implementation of Stripline Feedback Kickers in the MAX IV 3 GeV Ring	4285
	D. Olsson, L. Malmgren, K. Åhnberg MAX IV Laboratory, Lund University, Lund, Sweden
	The commissioning of a bunch-by-bunch feedback system for the MAX IV 3 GeV storage ring was started in early 2016. At date, the actuators are two stripline kickers oriented in the horizontal and in the vertical plane, respectively. Apart from providing feedback in the transverse plane, the horizontal stripline is simultaneously operating as a longitudinal kicker. This is done by upconverting the longitudinal 0 - 50 MHz baseband signal to the 150 MHz - 250 MHz range where the longitudinal shunt impedance of the stripline is higher. This signal is then fed to the stripline electrodes in common-mode. The design of the stripline kickers and the layout of the bunch-by bunch feedback system in the 3 GeV ring are presented in this report. Results from instability studies in this ring are also discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK086
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THPIK087	A Waveguide Overloaded Cavity Kicker for the MAX IV Bunch-by-Bunch Feedback System	4289
	D. Olsson, L. Malmgren, K. Åhnberg MAX IV Laboratory, Lund University, Lund, Sweden
	The higher-order modes (HOMs) in the main and the 3:rd harmonic cavities are driving longitudinal coupled-bunch mode instabilities (CBMIs) in the MAX IV 3 GeV storage ring. This far, negative feedback has been applied in the longitudinal plane by a stripline kicker at lower ring currents. However, the maximum longitudinal feedback voltage provided by the stripline is rather weak, and a waveguide overload cavity was therefore designed in order to suppress CBMIs at higher ring currents as well. Due to the long bunch length in the MAX IV storage rings, a relatively low center frequency of 625 MHz is selected. The new cavity kicker has been manufactured, and will be installed in the 3 GeV ring during the summer shut-down of 2017. In this paper, the RF and mechanical design of the cavity is presented. Simulation results are also compared with measurements of the manufactured cavity.
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THPIK094	Linac4 PIMS Construction and First Operation	4307
	R. Wegner, G. Favre, P. Françon, J.-M. Geisser, F. Gerigk, J.-M. Giguet, J. Hansen, J.-B. Lallement, A.M. Lombardi, S. Papadopoulos, M. Polini, M. Redondas Monteserin, T. Tardy, N. Thaus, M. Vretenar CERN, Geneva, Switzerland W. Behr, M. Pap Forschungszentrum Jülich GmbH, Central Institute of Engineering, Electronics and Analytics, Jülich, Germany G. Brzezinski, P. Krawczyk, L. Kujawinski, M. Marczenko NCBJ, Świerk/Otwock, Poland
	Linac4, CERN's new H− injector Linac uses PI-Mode Structures (PIMS) for the energy range between 103 and 160 MeV. 180 copper elements for 12 PIMS cavities have been fabricated in a collaboration between CERN, NCBJ and FZJ from 2011 to 2016. The cavities have been assembled, RF tuned and validated at CERN. This paper reports on the results as well as the experience with construction, installation, RF conditioning and first operation with beam.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK094
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THPIK097	High Power Tests of a Prototype X-Band Accelerating Structure for CLIC	4318
	R. Zennaro, H. Blumer, M. Bopp, T. Garvey, L. Rivkin PSI, Villigen PSI, Switzerland T. Argyropoulos, D. Esperante Pereira IFIC, Valencia, Spain N. Catalán Lasheras, A. Grudiev, G. McMonagle, A. Solodko, I. Syratchev, R. Wegner, B.J. Woolley, W. Wuensch CERN, Geneva, Switzerland T.G. Lucas, M. Volpi The University of Melbourne, Melbourne, Victoria, Australia
	Funding: Partially funded by SNF FLARE grant 20FL20147463 We present the design, construction and high-power test of an X-band radio-frequency accelerating structure, built as a prototype for the CERN LInear Collider (CLIC) study. X-band structures have been attracting increasing attention in recent years with applications foreseen in the domains of compact free electron lasers, medical accelerators and as diagnostics for ultra-short (femtosecond) electron bunches (when used in deflecting mode). To date, the main motivation for developments in this field has been as accelerating structures for linear colliders such as CLIC. In the context of a CERN/PSI collaboration we have built a prototype structure based on an existing CERN design, but with some modification, and following, as closely as possible, the realization and vacuum brazing techniques employed in the production of the C-band structures for the Swiss Free Electron Laser, SwissFEL. We will present the basic design of the structure and describe the fabrication process. The results of high power conditioning of the structure at CERN on an X-box test stand, to assess conditioning times, accelerating field and measure breakdown rates, will also be presented.
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THPIK102	Commissioning of the SLRI Storage Ring Second RF System	4328
	N. Juntong, S. Boonsuya, S. Cheedket, Ch. Dhammatong, S. Krainara, W. Phacheerak, R.R. Rujanakraikarn, N. Suradet SLRI, Nakhon Ratchasima, Thailand
	The old RF cavity in the storage ring of SIAM Photon Source (SPS), the 1.2 GeV second generation synchrotron light source in Thailand, has been pushed to its maximum capability to compensate electron energy lost in the storage ring. This energy lost is the effect from two additional insertion devices, which have been installed in SPS storage ring during June to August 2013. The new RF system has been planned since 2012, but with some technical and procurement difficulty the new system was successfully commissioning and running in August 2016. The installation, acceptance testing, conditioning and commissioning results of the new RF cavity, RF high power transmitter, and the low level RF system will be presented
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK102
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THPIK103	Six Months of Operation of the New RF Cavity System of SLRI	4331
	N. Juntong, Ch. Dhammatong, P. Sudmuang, N. Suradet SLRI, Nakhon Ratchasima, Thailand
	The new RF cavity system has been installed in the storage ring of SIAM Photon Source (SPS) since August 2016. The RF cavity was designed base on the MAX-IV laboratory capacitive loaded type cavity. The solid-state technology was implemented in the RF high power transmitter. The low-level RF system utilized the digital technology. The system has been successfully commissioned and run with a capability to compensate an energy lost from a full capacity run of insertion devices since August 2016. This paper summarizes the problems and actions of the new RF system and presents an overview of six months of operation of the new RF system in the storage ring of SPS.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK103
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THPIK106	Low Power RF Characterisation of the 400 Hz Photoinjector for CLARA	4342
	L.S. Cowie, P. Goudket, B.L. Militsyn STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom T.J. Jones STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
	The CLARA High Repetition Rate Photoinjector comprises an S-band dual feed cavity and will operate at a repetition rate of up to 400 Hz and is capable of reaching an electric field strength on the cathode of 120 MV/m. The cavity was brazed after tuning and arrived at Daresbury Laboratory in February 2016. Extensive low power RF testing has been performed including measurements of the quality factors and coupling, pass-band mode frequencies, on axis field and RF repeatability of replacement of cathode plug. The dual feed coupler has been tuned and a Magic Tee type splitter installed. The photoinjector is now installed on the VELA beam line for commissioning and characterisation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK106
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THPIK108	Bead Pull Measurements of the FETS RFQ at RAL	4349
	W. Promdee, T.R. Edgecock IIAA, Huddersfield, United Kingdom G.E. Boorman Royal Holloway, University of London, Surrey, United Kingdom G.E. Boorman JAI, Egham, Surrey, United Kingdom T.R. Edgecock, J.K. Pozimski STFC/RAL, Chilton, Didcot, Oxon, United Kingdom A.P. Letchford STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom J.K. Pozimski Imperial College of Science and Technology, Department of Physics, London, United Kingdom
	A Radio Frequency Quadrupole (RFQ) is a part of the Front End Test Stand (FETS) at the Rutherford Appleton Laboratory (RAL), Didcot, UK. The aim of the FETS project is to produce a 60 mA H− beam at 3 MeV. The RFQ is a four-vane type with 4 modules, each of 1 m length, and is designed to accelerate the beam from 65 keV to 3 MeV at 324 MHz. A bead pull system has been designed to measure the field along the RFQ. This will be used in conjunction with 64 tuners to produce a uniform field. In order to optimise the tuning procedure, a model of the RFQ has been creat-ed in COMSOL Multiphysics. This study shows the results from the bead pull measurements and the tuning studies.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK108
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THPIK110	RF Cavity Design for a Low Cost 1 MeV Proton Source	4355
	D. Soriano Guillén, R. Seviour University of Huddersfield, Huddersfield, United Kingdom S. Hunt Alceli Accelerator Technology Ltd., Huddersfield, United Kingdom
	In this paper we present the design for a low-cost RF cavity capable of accelerating protons from 100 keV to 1 MeV. The system is designed to meet the specifications from the proposed Alceli LTD medical proton therapy linac, to deliver a 1 nA proton beam current with a 1 kHz repetition rate. We present a design of an RF normal conducting (NC) re-entrant Cu cavity operating at 40 MHz consisting of a coupled two cavity system, both driven by a single Marx generator. The choice of such a low operating frequency for the cavity system enables us to use a relatively low-cost cost Marx Generator as the RF source. Marx generators work in a similar fashion to a Cockcroft-Walton accelerator (without the expensive components), creating a high-voltage pulse by charging a number of capacitors relatively slowly in parallel, then rapidly discharging in series, via spark gaps. Marx generators can deliver 2.5 GW, 1 ns pulses, with rise times of 200 ps, and (relatively) low jitter.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK110
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THPIK112	Progress With the Diamond Light Source RF Upgrade	4358
	C. Christou, A.G. Day, M.J. Duignan, P. Gu, N.P. Hammond, P.J. Marten, S.A. Pande, D. Spink DLS, Oxfordshire, United Kingdom
	Failure of a superconducting cavity in the Diamond storage ring can lead to extended down-time because of the time required to remove the module from the ring, the inability to access the cavity without removal from the cryostat and the long time to repair of the module. To reduce the risk to storage ring operation, normal conducting cavities are being installed to support operation of the superconducting cavities. Two cavities will be introduced in 2017 and work is progressing with RF amplifiers, transmission lines and low-level RF as well as storage ring engineering and controls. A summary of progress so far is presented and the plan for installation and further RF upgrades is outlined.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK112
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THPIK113	Tuner of a Second Harmonic Cavity of the Fermilab Booster	4362
	I. Terechkine, K.L. Duel, R.L. Madrak, A.V. Makarov, G.V. Romanov, D. Sun, C.-Y. Tan Fermilab, Batavia, Illinois, USA
	Introducing a second harmonic cavity in the accelerating system of the Fermilab Booster promises significant reduction of the particle beam loss during the injection, transition, and extraction stages. To follow the changing energy of the beam during acceleration cycles, the cavity is equipped with a tuner that employs perpendicularly biased AL800 garnet material as the frequency tuning media. The required tuning range of the cavity is from 75.73 MHz at injection to 105.64 MHz at extraction. This large range necessitates the use of a relatively low bias magnetic field at injection, which could lead to high RF loss power density in the garnet, or a strong bias magnetic field at extraction, which could result in high power consumption in the tuner's bias magnet. The required 15 Hz repetition rate of the device and high sensitivity of the local RF power loss to the level of the magnetic field added to the challenges of the bias system design. In this report, the main features of a proposed prototype of the second harmonic cavity tuner are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK113
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THPIK115	Status of the Perpendicular Biased 2nd Harmonic Cavity for the Fermilab Booster	4366
	C.-Y. Tan, J.E. Dey, K.L. Duel, J. Kuharik, R.L. Madrak, A.V. Makarov, W. Pellico, J. Reid, G.V. Romanov, M. Slabaugh, 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. This is a status report on the 2nd harmonic cavity for the Fermilab Booster as part of the Proton Improvement Plan (PIP) for increasing beam transmission efficiency, and thus reducing losses. A set of tuner rings has been procured and is undergoing quality control tests. The Y567 tube for driving the cavity has been successfully tested at both injection and extraction frequencies. A cooling scheme for the tuner and cavity has been developed after a thorough thermal analysis of the system. RF windows have been procured and substantial progress has been made on the mechanical designs of the cavity and the bias solenoid. The goal is to have a prototype cavity ready for testing by the end of 2017.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK115
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THPIK116	Static Magnetization Properties of AL800 Garnet Material	4370
	J. Kuharik, R.L. Madrak, A.V. Makarov, W. Pellico, D. Sun, C.-Y. Tan, I. Terechkine Fermilab, Batavia, Illinois, USA
	A second harmonic tunable RF cavity is being developed for the Fermilab Booster. This device, which promises reduction of the particle beam loss at the injection, transition, and extraction stages, employs perpendicularly biased garnet material for the frequency tuning. The required range of the tuning is significantly wider than in previously built and tested tunable RF devices. As a result, the magnetic field in the garnet becomes fairly close to the gyromagnetic resonance line at the lower end of the frequency range. The chosen design concept of a tuner for the cavity cannot ensure uniform magnetic field in the garnet material; thus it is important to know the static magnetic properties of the material to avoid significant increase in the local RF loss power density. This report summarizes studies performed at Fermilab to understand variations in the magnetic properties of the AL-800 garnet material used to build the tuner of the cavity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK116
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THPIK118	Final Assembly and Testing of MICE RF Modules at LBNL	4377
	T.H. Luo, A.R. Lambert, D. Li, S.P. Virostek, J.G. Wallig LBNL, Berkeley, California, USA T.G. Anderson, A.D. Bross, D.W. Peterson Fermilab, Batavia, Illinois, USA M.A. Palmer BNL, Upton, Long Island, New York, USA Y. Torun Illinois Institute of Technology, Chicago, Illlinois, USA
	Funding: Work supported by the Office of Science, U.S. Department of Energy under DOE contract number DE-AC02-05CH11231 The international Muon Ionization Cooling Experiment aims to demonstrate the transverse cooling of a muon beam by ionization interaction with absorbers and re-acceleration in RF cavities. The final MICE cooling channel configuration has two RF modules, each housing a 201 MHz RF cavity to compensate the longitudinal energy loss in the absorbers. Two RF modules have been assembled and tested at LBNL. This paper reports the final assembly work, as well as the vacuum test and low level RF measurements.
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THPIK120	The RF and Mechanical Design of a Compact, 2.5 kW, 1.3 GHz Resonant Loop Coupler for the APEX Buncher Cavity	4380
	S.P. Virostek, F. Sannibale, J.W. Staples LBNL, Berkeley, California, USA H.J. Qian DESY Zeuthen, Zeuthen, Germany
	Funding: This work is supported by the Office of Science, United States Department of Energy under DOE contract DE-AC02-05CH11231. The Advanced Photo-injector Experiment (APEX) at the Lawrence Berkeley National Laboratory (LBNL) is an injector system designed to demonstrate the capability of a normal conducting 186 MHz RF gun operating in CW mode to deliver the brightness required by X-ray FEL applications operating at MHz repetition rate, such as LCLS-II. A 240 kV, 1.3 GHz CW buncher cavity design was developed as part of the APEX experiment. The two-cell cavity profile has been optimized to minimize the RF power requirements and to remove multipacting resonances over the full range of operation. In order to excite the cavity stably at pi-mode and remove the dipole-like coupler kick, the two cells are to be independently driven by four, 2.5 kW, coaxial resonant loop couplers with integrated ceramic windows and a matching section in the body of the coupler. The coupler's inner conductor has a single diameter change at a specified distance from the ceramic insulator in order to cancel the wave reflected from the ceramic window, thus comprising the matching section. The details of the RF analysis, mechanical design, fabrication and testing of the coupler are presented here.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK120
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THPIK125	Ultra High Gradient Breakdown Rates in X-Band Cryogenic Normal Conducting Rf Accelerating Cavities	4395
SUSPSIK097	use link to see paper's listing under its alternate paper code
	A.D. Cahill, J.B. Rosenzweig UCLA, Los Angeles, California, USA V.A. Dolgashev, S.G. Tantawi, S.P. Weathersby SLAC, Menlo Park, California, USA
	Funding: Work Supported by DOE/SU Contract DE-AC02-76-SF00515, US NSF Award PHY-1549132, the Center for Bright Beams, and DOE SCGSR Fellowship. RF breakdown is one of the major factors limiting the operating accelerating gradient in rf particle accelerators. We conjecture that the breakdown rate is linked to the movements of crystal defects induced by periodic mechanical stress. Pulsed surface heating possibly creates a major part of this stress. By decreasing crystal mobility and increasing yield strength we hope to reduce the breakdown rate for the same accelerating gradient. We can achieve these properties by cooling a copper accelerating cavity to cryogenic temperatures. We tested an 11.4 GHz cryogenic copper accelerating cavity at high power and observed that the rf and dark current signals are consistent with Q0 changing during rf pulses. To take this change in Q0 into account, we created a non-linear circuit model in which the Q0 is allowed to vary inside the pulse. We used this model to process the data obtained from the high power test of the cryogenic accelerating structure. We present the results of measurements with low rf breakdown rates for surface electric fields near 500 MV/m for a shaped rf pulse with 150 ns of flat gradient.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK125
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THPIK126	Design of a Field-Emission X-Band Gun Driven by Solid-State RF Source	4399
	E.A. Nanni, V.A. Dolgashev, J. Neilson, S.G. Tantawi SLAC, Menlo Park, California, USA B.E. Carlsten, J.W. Lewellen, D.C. Nguyen LANL, Los Alamos, New Mexico, USA M. Othman UCI, Irvine, California, USA
	We present the design of a field-emission X-band gun designed to be powered using a solid-state RF source. The source of the electron beam is a field emission nano-tip array. The RF gun is intended to be a beam source for 1 MeV solid-state driven linac for deployment on a satellite to map magnetic fields in the magnetosphere. The gun has to satisfy strict requirements on both average and peak power consumption, as well as rapid turn on time. In order to achieve low power consumption, the RF gun operates at relatively low accelerating gradient of 2 MeV/m. The beam exit energy is ~20 keV for an RF power 1.5 kW. Each cell of the RF gun is separately powered by commercially available, GaN high electron mobility transistors. In proof of principle experiments we successfully powered a 9.3 GHz accelerating cavity with a 100 W transistor and a 1% duty cycle.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK126
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THPVA062	Fabrication and Tests of a RF Cavity for a Novel Compact Superconducting Cyclotron for Radioisotope Production	4585
	D. Gavela, J. Calero, L. García-Tabarés, P. Gómez, D. López, D. Obradors-Campos, C. Oliver, J.M. Pérez Morales, I. Podadera, F. Toral CIEMAT, Madrid, Spain B. Bravo, R. Fos, J.R. Ocampo, F. Pérez, A. Salom, P. Solans ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
	Funding: Work partially funded by CDTI and supported by the Spanish Ministry of Economy and Competitiveness, under project AMIT, within the subprogram CEN-20101014 The AMIT cyclotron will be a 8.5 MeV, 10 microAmp, CW, H− accelerator for radioisotope production, including a superconducting, weak focusing, 4 T magnet, allowing for a low extraction radius and a compact design. The cavity is a 60 MHz, quarter wave resonator powered by a modular 8 kW solid state amplifier. The design of the cavity dealed with challenging requirements: high electric fields required by a high voltage (60 kV) on a small gap, a small aperture of the magnet leading to high capacitances and thermal losses and a requirement for a low overall size of the cavity. The fabrication process included high precision machining, soft soldering, laser welding and careful metrologies, which are described together with other technical and practical aspects. The low power tests showed a good agreement with the simulations. The conditioning of the cavity was performed with a 1.1 T magnetic field applied on the central region. It was successfully finished regarding to maximum voltage reached, power losses and temperatures. The cavity was also tested at high power with a constant hydrogen flow injected in the central region (as expected in the cyclotron) with success.
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THPVA071	A Method to Design Multi-Cell Accelerator Cavities	4610
	S.S. Kurennoy LANL, Los Alamos, New Mexico, USA
	An efficient method for designing multi-cell accelerator cavities has been developed. It is similar to the approach used by Superfish codes for drift-tube linacs (DTL), where a few single cells at representative beam velocities are tuned in 2D and their geometrical parameters are interpolated to cover the required beam-velocity range. The method is implemented using 3D electromagnetic (EM) modeling with CST MicroWave Studio, which allows its application for various types of resonators, e.g., for H-mode cavities. Interpolating results of 3D EM design of tuned representative single-cell cavities leads to a 3D multi-cell cavity model that can be finalized with just a few small adjustments. As a challenging application example, we design multi-cell resonators of three types - cross-bar (CH) and inter-digital (IH) H-mode, as well as DTL - for accelerating muons in the velocity range of v/c = 0.08-0.3, and compare their performance.
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THPVA085	Design and Construction of 126 MHz Capacity Loaded Aluminium Cavity Prototype	4653
SUSPSIK092	use link to see paper's listing under its alternate paper code
	S. Ahmadiannamin, J. Rahighi, Kh.S. Sarhadi ILSF, Tehran, Iran F. Abbasi Shahid Beheshti University, Tehran, Iran M. Lamehi Rashti IPM, Tehran, Iran
	Iranian light source Facility (ILSF)isa 3 GeV Ultra low emittance synchrotron with 528 meter circumference that will be constructed in the city of Qazvin, located 150km west of Tehran. Motivated by the development of HOM damped cavity with simpler structure at 100 MHz at MAX Lab and also lower costs, 100 MHz RF system is envisaged for ILSF booster and storage ring. An RF cavity prototype was fabricated for better understandingof characteristics of capacity loaded RF cavities by practical investigation. In this paper, design and development of this prototype is presentedwith the simulation and measurement results.
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