SRF2015 - Classification: SRF Technology - Ancillaries / G03-Power Coupler

Paper	Title	Page
THBA03	Overview of Recent Advances in Coupler Technology, Fabrication and Conditioning
	W. Kaabi LAL, Orsay, France
	The talk will provide an overview on the latest advances (since SRF2013) of Power Coupler development, production and preparation for SRF applications. The speaker is asked to emphasize issues of design, fabrication and conditioning. Examples from other labs (FRIB, SPIRAL-II, ESS, LCLS-II) should be given that help explain the issues and resolutions including the multipacting free coupler at FRIB and the copper free coupler at FNAL. Details of the speaker's own work with the large scale production of power couplers for XFEL are expected but should occupy <=50% of the talk.
	Slides THBA03 [14.515 MB]
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THPB076	Quality Control of Welding, Brazing Joints and Cu Deposition on EU-XFEL Coupler Parts	1301
	A. Ermakov, D. Kostin, W.-D. Möller DESY, Hamburg, Germany
	In frames of EU-XFEL Project the quality control of fundamental 1.3GHz power couplers is very important task. The power coupler consists of a several number of parts including itself the different types of welding and brazing joints between ceramic, copper and stainless steel components. The quality of these joints is subject to be investigated and controlled according to EU-XFEL Coupler specification taking into account the different coupler manufacturers involved. The quality of Cu deposition on some EU-XFEL coupler parts is also the issue to be qualified according to specs. The number of microscope images of different types of joints and Cu deposition on some EU-XFEL 1.3GHz coupler parts are presented.
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THPB077	Modified TTF3 Couplers for LCLS-II	1306
	C. Adolphsen, K. Fant, Z. Li, C.D. Nantista, G. Stupakov, J. Tice, F.Y. Wang, L. Xiao SLAC, Menlo Park, California, USA I.V. Gonin, K. Premo, N. Solyak Fermilab, Batavia, Illinois, USA
	The LCLS-II 4 GeV SC electron linac will use 280 TESLA cavities and TTF3 couplers, modified for CW operation with input power up to about 7 kW. The coupler modifications include shortening the antenna to achieve higher Qext and thickening the copper plating on the warm section inner conductor to lower the peak temperature. Another change is the use a waveguide transition box that is machined out of a solid piece of aluminum, significantly reducing its cost and improving its fit to the warm coupler window section. This paper describes the changes, simulations of the coupler operation (heat loads and temperatures), rf processing results and CW tests with LCLS-II dressed cavities.
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THPB078	Status of the Power Couplers for the ESS Elliptical Cavity Prototypes	1309
	C. Arcambal CEA/IRFU, Gif-sur-Yvette, France P. Bosland, M. Desmons, G. Devanz, G. Ferrand, A. Hamdi, P. Hardy, H. Jenhani, F. Leseigneur, C. Marchand, F. Peauger, O. Piquet, D. Roudier, C. Servouin CEA/DSM/IRFU, France C. Darve ESS, Lund, Sweden
	In the frame of the European Spallation Source (ESS) project, a linear accelerator composed of a superconducting section is being developed. This accelerator owns two kinds of cavities called “medium beta cavity” (β=0.67) and “high beta cavity” (β= 0.86). These cavities are equipped with RF power couplers whose main characteristics are: fundamental frequency: 704.42MHz, peak RF power: 1.1MW, repetition rate: 14Hz, RF pulse width>3.1ms. These couplers are common to the two cavities. The CEA Saclay is responsible for the design, the manufacture, the preparation and the conditioning of the couplers used for the Elliptical Cavities Cryomodule Technological Demonstrators (ECCTD). This work is performed in collaboration with ESS and the IPNO. This paper describes the coupler architecture, its different components, the main characteristics and the specific features of its elements (RF performance, dissipated power, cooling, coupler box test for the conditioning). The status of the manufacture of each coupler part is also presented.
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THPB079	Improved Capacitive Coupling Type RF Power Couplers for a Cryomodule With Two 9-Cell Cavities	1313
	D.H. Zhuang, P.L. Fan, L.W. Feng, L. Lin, K.X. Liu, S.W. Quan, F. Wang, Z.L. Wang PKU, Beijing, People's Republic of China
	Funding: Work supported by Major State Basic Research Development Program of China(Grant No. 2011CB808302 and 2011CB808304) A capacitive coupling RF power coupler was used for the DC-SRF photoinjector at Peking University. Recently, improved capacitive coupling power couplers, which will be used for a new cryomodule with two 9-cell cavities have been designed and fabricated. The main modifications include enlarging the supporting rods of inner conductors in order to increase heat conduction, moving the bellows from the quarter-wave transformer to the 50 Ω coaxial line to avoid the mismatch during Qext adjusting. Two modified power coupler have already finished RF conditioning up to 10kW, TW, duty factor 30%. In this paper, detailed design based on multi-physics analysis and the conditioning of this improved capacitive coupling RF Power coupler will be presented.
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THPB080	Next Generation Cavity and Coupler Interlock for the European XFEL	1316
	D. Tischhauser, A. Gössel, M. Mommertz DESY, Hamburg, Germany
	The safe operation of cavities and couplers in the European XFEL accelerator environment is secured by a new technical interlock (TIL) design, which is based on the XFEL crate standard (MTCA(TM).4). The new interlock is located inside the accelerator tunnel. Several remote test capabilities ensure the correct operation of sensors for light, temperature and free electrons. Due to the space costs and the very high number of channels, the electronic concept was moved from a conservative, mostly analog electronic approach, with real comparators and thresholds, to a concept, where the digitizing of the signals is done at a very early stage. Filters, thresholds and comparators are moved into the digital part. The usage of an FPGA and an additional watchdog increase the flexibility dramatically, with respect to be as reliable as possible. An overview of the system is shown. MTCA (Micro Telecommunications Computing Architecture) is a standard defined by the PCI Industrial Computer Manufacturers Group (PICMG, www.picmg.org).
	Poster THPB080 [1.123 MB]
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THPB081	FPC and HOM Coupler Test Boxes for HL-LHC Crab Cavities	1321
	A.R.J. Tutte, G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom R. Calaga, A. Macpherson, E. Montesinos CERN, Geneva, Switzerland S.U. De Silva ODU, Norfolk, Virginia, USA Z. Li SLAC, Menlo Park, California, USA B. P. Xiao BNL, Upton, Long Island, New York, USA
	The LHC luminosity upgrade will involve the installation of thirty-two 400 MHz SRF crab cavities. The cavities have two variants known as the RF dipole and double quarter-wave crab cavities. Each cavity has a fundamental power coupler (FPC) at 400 MHz and two or three HOM couplers. Before integration onto the cavities it is necessary to condition the FPC, and to measure the transmission on the HOM couplers at low power to ensure the operate as designed, each requiring a special test box. The FPC test box should provide a high transmission between two couplers without creating high surface fields. The low power HOM test boxes should be terminated to a load such that the natural stop and pass-bands of the couplers are preserved allowing the reflection to me measured and compared to simulations. In addition, due to the possibility of high HOM power in the LHC crab cavities, the concept of creating a broadband high power HOM coupler test box in order to condition and test the couplers at high power has been investigated. The Rf design of all test boxes is presented and discussed.
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THPB082	Design of QWR Power Coupler for the Rare Isotope Science Project in Korea	1326
	I. Shin, M.O. Hyun IBS, Daejeon, Republic of Korea E. Kako KEK, Ibaraki, Japan C.K. Sung Korea University Sejong Campus, Sejong, Republic of Korea
	A power coupler has been designed for the Rare Isotope Science Project (RISP) in Korea. The power couplers will provide 4 kW RF power to 81.25 MHz superconducting quarter wave resonators with β=0.047. The coupler is a coaxial capacitive type with an impedance of 50 ohms using a disc type ceramic window. Design studies of the coupler are presented.
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THPB083	Energetic Copper Coating on Stainless Steel Power Couplers for SRF Application	1330
	I. Irfan, S.F. Chapman, M. Krishnan, K.M. Velas AASC, San Leandro, California, USA W. Kaabi LAL, Orsay, France
	Funding: This research is supported by the US DOE via and SBIR grant: DE-SC0009581 Delivering RF power from the outside (at room temperature) to the inside of SRF cavities (at ~4 K temperature), requires a power coupler to be thermally isolating, while still electrically conducting on the inside. Stainless steel parts that are coated on the insides with a few skin depths of copper can meet these conflicting requirements. The challenge has been the adhesion strength of copper coating on stainless steel coupler parts when using electroplating methods. These methods also require a nickel flash layer that is magnetic and can therefore pose problems. Alameda Applied Sciences Corporation (AASC) uses Coaxial Energetic Deposition (CED) from a cathodic arc plasma to grow copper films directly on stainless steel coupler parts with no Ni layer and no electrochemistry. The vacuum arc plasma consists of ~100 eV Cu ions that penetrate a few monolayers into the stainless steel substrate to promote growth of highly adhesive films with crystalline structure. Adhesion strength and coating quality of copper coatings on complex stainless steel tubes, bellows, mock coupler parts and an actual Tesla Test Facility (TTF) type coupler part, are discussed. * Adhesion and Cu quality testing were done for us by the Fermilab Technical Division, Superconducting RF Development Department
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THPB084	Design of Input Coupler for RIKEN Superconducting Quarter-Wavelength Resonator	1335
	K. Ozeki, O. Kamigaito, H. Okuno, N. Sakamoto, K. Suda, Y. Watanabe, K. Yamada RIKEN Nishina Center, Wako, Japan E. Kako, H. Nakai, K. Umemori KEK, Ibaraki, Japan K. Okihira, K. Sennyu, T. Yanagisawa MHI, Hiroshima, Japan
	In RIKEN Nishina Center, for the purpose of development of elemental technology for the superconducting linear accelerator, the designing and construction of accelerator system based on superconducting quarter-wavelength resonator are carried out. The basic designs of the input coupler are as follows: The resonance frequency of the cavity is 75.5 MHz and assumed beam loading is about 1 kW. Double vacuum windows, which are disk-type, are adopted. A thermal anchor of 40 K is installed near the cold-window. The optimum positions of the cold-window and the thermal anchor depending on the effective RRR of copper-plate are being studied. In this contribution, the details of these designs will be reported. This work was funded by ImPACT Program of Council for Science, Technology and Innovation (Cabinet Office, Government of Japan).
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THPB086	LCLS-II Fundamental Power Coupler Mechanical Integration	1340
	K.S. Premo, T.T. Arkan, Y.O. Orlov, N. Solyak Fermilab, Batavia, Illinois, USA
	Funding: DOE LCLSII is a planned upgrade project for the linear coherent light source (LCLS) at SLAC. The LCLSII linac will consist of thirtyfive 1.3 GHz and two 3.9 GHz superconducting RF continuous wave (CW) cryomodules that Fermilab and Jefferson Lab will assemble in collaboration with SLAC. The LCLSII 1.3 GHz cryomodule design is based on the European XFEL pulsed mode cryomodule design with modifications needed for CW operation. The 1.3 GHz cryomodules for LCLSII will utilize a modified TTF3 syle fundamental power coupler design. Due to CW operation heat removal from the power coupler is critical. This paper presents the details of the mechanical integration of the power coupler into the cryomodule. Details of thermal braids, connections, and other interfaces are discussed.
	Poster THPB086 [1.031 MB]
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THPB087	Design and Simulation of High Power Input Coupler for C-ADS Linac 5-Cell Elliptical Cavities	1343
	K.X. Gu Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China X. Chen, T.M. Huang, Q. Ma, W.M. Pan IHEP, Beijing, People's Republic of China
	Two 650 MHz elliptical cavity sections (elliptical 063, elliptical 082) are chosen to accelerate medium energy protons for China Accelerator Driven sub-critical System (C-ADS) linac. For each 5-cell cavity, RF power up to 150 kW in CW mode is required to be fed by a fundamental power coupler (FPC). A coaxial type coupler is designed to meet the power and RF coupling requirements. This paper presents the RF design, thermal analysis and multipacting simulations of the coupler for C-ADS 5-cell elliptical cavities.
	Poster THPB087 [0.593 MB]
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THPB088	20 kW CW Power Couplers for the APS-U Harmonic Cavity	1346
	M.P. Kelly, A. Barcikowski, Z.A. Conway, D. Horan, M. Kedzie, S.H. Kim, P.N. Ostroumov ANL, Argonne, Illinois, USA S.V. Kutsaev RadiaBeam, Santa Monica, California, USA J. Rathke AES, Medford, New York, USA
	Funding: This work supported by the U.S. DOE, Office of Nuclear Physics, Contract No. DE-AC02-06CH11357. This research used resources of ANL’s ATLAS facility, which is a DOE Office of Science User Facility. A pair of 20 kW CW adjustable RF power couplers optimized for 1.4 GHz have been designed and are being built as part of the APS-U bunch lengthening system. The system uses one superconducting RF cavity to be installed into the APS Upgrade electron storage ring and will provide a tremendous practical benefit to the majority of users by increasing the beam lifetime by 2-3 times. The 80 mm diameter, 50 Ω coaxial couplers include 4 cm (~20 dB) of adjustability. This allows optimization of bunch lengthening for a range of storage ring beam currents and fill patterns while, simultaneously, maintaining the required 0.84 MV harmonic cavity voltage. To provide bunch lengthening, the cavity/coupler system must extract RF power (up to 32 kW) from the beam. Each coupler will transmit roughly half of the total extracted power to external water-cooled loads. The design extends upon on a well-tested ANL two RF window concept, using a pair of simple rugged 80 mm diameter alumina disks. A new feature is the ‘hourglass-shaped’ inner conductor chosen to maximize transmission at 1.4 GHz. Results of electromagnetic and thermal simulations, as well as, prototyping and initial RF testing are presented.
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THPB091	Mechanical Design of a High Power Coupler for the PIP-II 325 MHz SSR1 RF Cavity	1354
	O.V. Pronitchev, S. Kazakov Fermilab, Batavia, Illinois, USA
	The Project X Injector Experiment (PXIE) at Fermilab will include one cryomodule with eight 325 MHz single spoke superconductive cavities (SSR1). Each cavity requires approximately 2 kW CW RF power for 1 mA beam current operation. A future upgrade will require up to 8 kW RF power per cavity. Fermilab has designed and procured ten production couplers for the SSR1 type cavities. Status of the 325 MHz main coupler development for PXIE SSR1 cryomodule is reported.
	Poster THPB091 [1.821 MB]
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THPB092	Mechanical Design of a High Power Coupler for the PIP-II 162.5 MHz RF Quadrupole	1357
	O.V. Pronitchev, S. Kazakov Fermilab, Batavia, Illinois, USA
	PXIE is a prototype front end system for the proposed PIP-II accelerator upgrade at Fermilab. An integral component of the front end is a 162.5 MHz, normal conducting, continuous wave (CW), radiofrequency quadrupole (RFQ) cavity. Two identical couplers will deliver approximately 100 kW total CW RF power to the RFQ. Fermilab has designed and procured main couplers for the CW RFQ accelerating cavity. The mechanical design of the coupler, along with production status, is presented below.
	Poster THPB092 [0.476 MB]
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THPB093	A 1.3 GHz Waveguide to Coax Coupler for Superconducting Cavities With a Minimum Kick	1360
	J.A. Robbins, C. Egerer, R.G. Eichhorn, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Transversal forces as a result of asymmetric field generated by the fundamental power couplers have become a concern for low emittance beam in future accelerators. In pushing for smallest emittances, Cornell has finished a physics design for a symmetric coupler for superconducting accelerating cavities. This coupler consists of a rectangular waveguide that transforms into a coaxial line inside the beam pipe, eventually feeding the cavity. We will report on the RF design yielding to the extremely low transversal kick. In addition, heating, heat transfer and thermal stability of this coupler has been evaluated.
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THPB094	Status of the Fundamental Power Coupler Production for the European XFEL Accelerator	1364
	S. Sierra, G. Garcin, C. Lievin, G. Vignette TED, Velizy, France A. Gallas, W. Kaabi LAL, Orsay, France M. Knaak, M. Pekeler, L. Zweibaeumer RI Research Instruments GmbH, Bergisch Gladbach, Germany
	For the XFEL accelerator, Thales, RI Research Instrument and LAL are working on the manufacturing, assembly and conditioning of fundamental power couplers. 670 couplers have to be manufactured according to strict specifications. The paper describes the full production activity from the program starting to the currentphase with main measurements for the coupler characteristic: copper and TiN coating characteristics. The status of the production is given with an output rate of 8 couplers per week. The status for more than 500 couplers manufactured and conditionned is presented.
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THPB095	Automatic RF Conditioning Test Bench of Fundamental Power Couplers for the European XFEL Accelerator	1367
	S. Sierra, C. Lievin, P. Rouillon TED, Velizy, France H. Guler, W. Kaabi, A. Verguet LAL, Orsay, France
	In order to perform the RF conditioning of the fundamental coupler for the XFEL accelerator, Thales and LAL developed together a test bench being able to make the automatic RF conditioning. The capability of this test bench is of 4 pairs of coupler at the same time with automatic sequences of increasing the RF power. The test bench is composed of the overall RF station providing up to 5 MW peak power at 1.3 GHz. The waveguide distribution allows 4 individual RF lines for conditionning,and the automatic sequence applied to the couplers in respect with all signals monitored and controlled during the RF process. The paper will also provide some examples of such process.
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THPB096	Lesson Learned on the Manufacturing of Fundamental Power Couplers for the European XFEL Accelerator	1370
	S. Sierra, G. Garcin, C. Lievin, G. Vignette TED, Velizy, France M. Knaak, M. Pekeler RI Research Instruments GmbH, Bergisch Gladbach, Germany
	In this paper we described lesson learned during the production of Fundamental Power Couplerfor the European XFEL accelerator and different steps necessaries for obtaining a rate of 8 couplers a week. From the manufacturing of individual components up to the RF conditioning. This paper also propose some possible ways to be optimized for a future mass production of such components. With comparison of processes and adaptation which could benefit to an increase rate or a more secure program. Some of them which could be studies from the coupler definition to the manufacturing process in order to obtain a stable and possible increased rate or lower cost of production by decreasing the risks on programs. This analysis is based on a current production of more than 500 couplers
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THPB097	New Possible Configuration of 3.9 GHz Coupler	1373
	S. Kazakov Fermilab, Batavia, Illinois, USA
	The LCLS-II superconducting accelerator supposedly will use 3.9 GHz (3-d harmonic) superconductive cavities. A new possible configuration of 3.9 GHz main coupler is presented in the papar. This configuration contains two coaxial ceramic windows, a cold and a warm one. Inner conductors of windows are connected through the capacitive gap and have no mechanical no thermal contacts. It allows to avoid using bellows and thus avoid the problem of heating and cooling. The windows have shields protecting shields against the electron, and this prevents the window ceramics from charging. Results of computer simulation of the new coupler are posted.
	Poster THPB097 [1.036 MB]
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THPB098	Testing of 325 MHz Couplers at Test Stand in Resonance Mode	1376
	S. Kazakov, B.M. Hanna, O.V. Pronitchev Fermilab, Batavia, Illinois, USA
	The linear accelerator for the PIP-II program utilizes two types of 325 MHz Single Spoke resonator cavities: SSR-I and SSR-II. Operating power of SSR-II is about 17 kW and requires input couplers which can reliably work at power levels > 20 kW with full reflection at any reflected phase. Currently only one 10 kW RF amp is available for coupler testing. To increase testing power, a special resonance configuration were used. This configuration allows us to raise RF power approximately 3 times. The testing scheme and results are discussed in the paper.
	Poster THPB098 [1.600 MB]
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THPB100	Nb Coatings on Bellows Used in SRF Accelerators	1379
	S.F. Chapman, I. Irfan, M. Krishnan, K.M. Velas AASC, San Leandro, California, USA
	Funding: This research is supported by the US DOE via SBIR grant: DE-SC0007678 Alameda Applied Sciences Corporation (AASC) is developing bellows with the strength and flexibility of stainless steel and the low surface impedance of a superconductor. Such unique bellows would enable alignment of SRF cavity sections with greatly reduced RF losses. To that end, we grow Nb thin films via Coaxial Energetic Deposition (CED) from a cathodic arc plasma. Films of Nb were grown on stainless steel bellows, with and without an intermediate layer of Cu deposited via the same technique, to produce a working bellows with a well adhered superconducting inner layer. The Nb coated bellows have undergone tests conducted by our collaborators to evaluate their RF performance.
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THPB101	High Power Input Couplers for C-ADS	1383
	T.M. Huang, X. Chen, H.Y. Lin, Q. Ma, F. Meng, W.M. Pan, G.W. Wang, X.Y. Zhang IHEP, Beijing, People's Republic of China K.X. Gu Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
	High power input couplers are key components of the superconducting system for China Accelerator Driven sub-critical System (C-ADS) project. For the first phase, C-ADS includes four types of superconducting cavities (SCCs) of two frequencies, 162.5 MHz HWR SCC and 325 MHz Spoke SCC up to the energy of 25 MeV. All input couplers for the SCCs are developed in IHEP. This paper will describe the development status of the high power input couplers for C-ADS.
	Poster THPB101 [0.430 MB]
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THPB102	RF Conditioning of the XFEL Power Couplers at the Industrial Scale	1387
	H. Guler, A. Gallas, W. Kaabi, D.J.M. Le Pinvidic, C. Magueur, M. Oublaid, A. Thiebault, A. Verguet LAL, Orsay, France
	LAL has in charge the production monitoring and the RF conditioning of 800 power couplers to equip 100 XFEL cryomodules. The conditioning process and all the preceding preparation steps are performed in a 70m2 clean room. This infrastructure, its equipment and the RF station are designed to allow the treatment of 8 couplers in the same time, after a ramp-up phase. Clean room process and conditioning results are presented and discussed.
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THPB103	High Power Coupler Test for ARIEL SC Cavities	1390
	Y. Ma, P.R. Harmer, D. Lang, R.E. Laxdal, B.S. Waraich, V. Zvyagintsev TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
	TRIUMF ARIEL[1](The Advanced Rare Isotope Laboratory) project employs five 1.3 GHz 9-cell superconducting elliptical cavities[2] for acceleration of 10 mA electron beam up to energy of 50 MeV. 100 kW CW RF power will be delivered into each cavity by means of pair of Power Couplers: 50 kW per each coupler. Before installing the power couplers with the cavities, they have to be assembled on Power Coupler Test Stand(PCTS) and conditioned with a 30 kW IOT. Six couplers have been conditioned at room temperature and four of them have been installed to the cavities and tested during beam commissioning. Test results of the power couplers will be described and discussed in this paper. #mayanyun@triumf.ca
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THPB104	Higher Order Modes Simulation and Measurements for 2400 MHz Cavity	1394
	Ya.V. Shashkov, D.S. Bazyl, R.V. Donetskiy, M.V. Lalayan, N.P. Sobenin MEPhI, Moscow, Russia R. Calaga CERN, Geneva, Switzerland A.A. Zavadtsev Nano, Moscow, Russia M. Zobov INFN/LNF, Frascati (Roma), Italy
	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 LHC upgrade program an application of additional harmonic cavities operating at multiples of the main RF system frequency of 400 MHz is currently under discussion. The 800 MHz superconducting cavities with grooved beam pipes were suggested for implementation. A scaled aluminum prototype with a frequency of the operational mode of 2400 MHz was manufactured for testing the results of simulations. The load reflection coefficient measurements were performed as well as the Qload measurements for cavities with the load. Here we discuss the prototype design and report the obtained measurement results. Higher order modes, superconducting cavities, srf*
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THPB105	Demonstration of Coaxial Coupling Scheme at 26 MV/m for 1.3 GHz Tesla-Type SRF Cavities	1397
	Y. Xie, A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio, USA T.N. Khabiboulline, A. Lunin, V. Poloubotko, A.M. Rowe, N. Solyak, V.P. Yakovlev Fermilab, Batavia, Illinois, USA J. Rathke AES, Medford, New York, USA
	Superconducting ILC-type cavities have an rf input coupler that is welded on. A detachable input coupler will reduce conditioning time (can be conditioned separately), reduce cost and improve reliability. The problem with placing an extra flange in the superconducting cavity is about creating a possible quench spot at the seal place. Euclid Techlabs LLC has developed a coaxial coupler which has an on the surface with zero magnetic field (hence zero surface current). By placing a flange in that area we are able to avoid disturbing surface currents that typically lead to a quench. The coupler is optimized to preserve the axial symmetry of the cavity and rf field. The surface treatments and rf test of the proto- type coupler with a 1.3 GHz ILC-type single-cell cavity at Fermilab will be reported and discussed.
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Paper

Title

Page

THBA03

Overview of Recent Advances in Coupler Technology, Fabrication and Conditioning

W. Kaabi
LAL, Orsay, France

The talk will provide an overview on the latest advances (since SRF2013) of Power Coupler development, production and preparation for SRF applications. The speaker is asked to emphasize issues of design, fabrication and conditioning. Examples from other labs (FRIB, SPIRAL-II, ESS, LCLS-II) should be given that help explain the issues and resolutions including the multipacting free coupler at FRIB and the copper free coupler at FNAL. Details of the speaker's own work with the large scale production of power couplers for XFEL are expected but should occupy <=50% of the talk.

Slides THBA03 [14.515 MB]

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THPB076

Quality Control of Welding, Brazing Joints and Cu Deposition on EU-XFEL Coupler Parts

1301

A. Ermakov, D. Kostin, W.-D. Möller
DESY, Hamburg, Germany

In frames of EU-XFEL Project the quality control of fundamental 1.3GHz power couplers is very important task. The power coupler consists of a several number of parts including itself the different types of welding and brazing joints between ceramic, copper and stainless steel components. The quality of these joints is subject to be investigated and controlled according to EU-XFEL Coupler specification taking into account the different coupler manufacturers involved. The quality of Cu deposition on some EU-XFEL coupler parts is also the issue to be qualified according to specs. The number of microscope images of different types of joints and Cu deposition on some EU-XFEL 1.3GHz coupler parts are presented.

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THPB077

Modified TTF3 Couplers for LCLS-II

1306

C. Adolphsen, K. Fant, Z. Li, C.D. Nantista, G. Stupakov, J. Tice, F.Y. Wang, L. Xiao
SLAC, Menlo Park, California, USA
I.V. Gonin, K. Premo, N. Solyak
Fermilab, Batavia, Illinois, USA

The LCLS-II 4 GeV SC electron linac will use 280 TESLA cavities and TTF3 couplers, modified for CW operation with input power up to about 7 kW. The coupler modifications include shortening the antenna to achieve higher Qext and thickening the copper plating on the warm section inner conductor to lower the peak temperature. Another change is the use a waveguide transition box that is machined out of a solid piece of aluminum, significantly reducing its cost and improving its fit to the warm coupler window section. This paper describes the changes, simulations of the coupler operation (heat loads and temperatures), rf processing results and CW tests with LCLS-II dressed cavities.

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THPB078

Status of the Power Couplers for the ESS Elliptical Cavity Prototypes

1309

C. Arcambal
CEA/IRFU, Gif-sur-Yvette, France
P. Bosland, M. Desmons, G. Devanz, G. Ferrand, A. Hamdi, P. Hardy, H. Jenhani, F. Leseigneur, C. Marchand, F. Peauger, O. Piquet, D. Roudier, C. Servouin
CEA/DSM/IRFU, France
C. Darve
ESS, Lund, Sweden

In the frame of the European Spallation Source (ESS) project, a linear accelerator composed of a superconducting section is being developed. This accelerator owns two kinds of cavities called “medium beta cavity” (β=0.67) and “high beta cavity” (β= 0.86). These cavities are equipped with RF power couplers whose main characteristics are: fundamental frequency: 704.42MHz, peak RF power: 1.1MW, repetition rate: 14Hz, RF pulse width>3.1ms. These couplers are common to the two cavities. The CEA Saclay is responsible for the design, the manufacture, the preparation and the conditioning of the couplers used for the Elliptical Cavities Cryomodule Technological Demonstrators (ECCTD). This work is performed in collaboration with ESS and the IPNO. This paper describes the coupler architecture, its different components, the main characteristics and the specific features of its elements (RF performance, dissipated power, cooling, coupler box test for the conditioning). The status of the manufacture of each coupler part is also presented.

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THPB079

Improved Capacitive Coupling Type RF Power Couplers for a Cryomodule With Two 9-Cell Cavities

1313

D.H. Zhuang, P.L. Fan, L.W. Feng, L. Lin, K.X. Liu, S.W. Quan, F. Wang, Z.L. Wang
PKU, Beijing, People's Republic of China

Funding: Work supported by Major State Basic Research Development Program of China(Grant No. 2011CB808302 and 2011CB808304)
A capacitive coupling RF power coupler was used for the DC-SRF photoinjector at Peking University. Recently, improved capacitive coupling power couplers, which will be used for a new cryomodule with two 9-cell cavities have been designed and fabricated. The main modifications include enlarging the supporting rods of inner conductors in order to increase heat conduction, moving the bellows from the quarter-wave transformer to the 50 Ω coaxial line to avoid the mismatch during Qext adjusting. Two modified power coupler have already finished RF conditioning up to 10kW, TW, duty factor 30%. In this paper, detailed design based on multi-physics analysis and the conditioning of this improved capacitive coupling RF Power coupler will be presented.

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THPB080

Next Generation Cavity and Coupler Interlock for the European XFEL

1316

D. Tischhauser, A. Gössel, M. Mommertz
DESY, Hamburg, Germany

The safe operation of cavities and couplers in the European XFEL accelerator environment is secured by a new technical interlock (TIL) design, which is based on the XFEL crate standard (MTCA(TM).4). The new interlock is located inside the accelerator tunnel. Several remote test capabilities ensure the correct operation of sensors for light, temperature and free electrons. Due to the space costs and the very high number of channels, the electronic concept was moved from a conservative, mostly analog electronic approach, with real comparators and thresholds, to a concept, where the digitizing of the signals is done at a very early stage. Filters, thresholds and comparators are moved into the digital part. The usage of an FPGA and an additional watchdog increase the flexibility dramatically, with respect to be as reliable as possible. An overview of the system is shown.
MTCA (Micro Telecommunications Computing Architecture) is a standard defined by the PCI Industrial Computer Manufacturers Group (PICMG, www.picmg.org).

Poster THPB080 [1.123 MB]

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THPB081

FPC and HOM Coupler Test Boxes for HL-LHC Crab Cavities

1321

A.R.J. Tutte, G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
R. Calaga, A. Macpherson, E. Montesinos
CERN, Geneva, Switzerland
S.U. De Silva
ODU, Norfolk, Virginia, USA
Z. Li
SLAC, Menlo Park, California, USA
B. P. Xiao
BNL, Upton, Long Island, New York, USA

The LHC luminosity upgrade will involve the installation of thirty-two 400 MHz SRF crab cavities. The cavities have two variants known as the RF dipole and double quarter-wave crab cavities. Each cavity has a fundamental power coupler (FPC) at 400 MHz and two or three HOM couplers. Before integration onto the cavities it is necessary to condition the FPC, and to measure the transmission on the HOM couplers at low power to ensure the operate as designed, each requiring a special test box. The FPC test box should provide a high transmission between two couplers without creating high surface fields. The low power HOM test boxes should be terminated to a load such that the natural stop and pass-bands of the couplers are preserved allowing the reflection to me measured and compared to simulations. In addition, due to the possibility of high HOM power in the LHC crab cavities, the concept of creating a broadband high power HOM coupler test box in order to condition and test the couplers at high power has been investigated. The Rf design of all test boxes is presented and discussed.

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THPB082

Design of QWR Power Coupler for the Rare Isotope Science Project in Korea

1326

I. Shin, M.O. Hyun
IBS, Daejeon, Republic of Korea
E. Kako
KEK, Ibaraki, Japan
C.K. Sung
Korea University Sejong Campus, Sejong, Republic of Korea

A power coupler has been designed for the Rare Isotope Science Project (RISP) in Korea. The power couplers will provide 4 kW RF power to 81.25 MHz superconducting quarter wave resonators with β=0.047. The coupler is a coaxial capacitive type with an impedance of 50 ohms using a disc type ceramic window. Design studies of the coupler are presented.

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THPB083

Energetic Copper Coating on Stainless Steel Power Couplers for SRF Application

1330

I. Irfan, S.F. Chapman, M. Krishnan, K.M. Velas
AASC, San Leandro, California, USA
W. Kaabi
LAL, Orsay, France

Funding: This research is supported by the US DOE via and SBIR grant: DE-SC0009581
Delivering RF power from the outside (at room temperature) to the inside of SRF cavities (at ~4 K temperature), requires a power coupler to be thermally isolating, while still electrically conducting on the inside. Stainless steel parts that are coated on the insides with a few skin depths of copper can meet these conflicting requirements. The challenge has been the adhesion strength of copper coating on stainless steel coupler parts when using electroplating methods. These methods also require a nickel flash layer that is magnetic and can therefore pose problems. Alameda Applied Sciences Corporation (AASC) uses Coaxial Energetic Deposition (CED) from a cathodic arc plasma to grow copper films directly on stainless steel coupler parts with no Ni layer and no electrochemistry. The vacuum arc plasma consists of ~100 eV Cu ions that penetrate a few monolayers into the stainless steel substrate to promote growth of highly adhesive films with crystalline structure. Adhesion strength and coating quality of copper coatings on complex stainless steel tubes, bellows, mock coupler parts and an actual Tesla Test Facility (TTF) type coupler part, are discussed.
* Adhesion and Cu quality testing were done for us by the Fermilab Technical Division, Superconducting RF Development Department

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THPB084

Design of Input Coupler for RIKEN Superconducting Quarter-Wavelength Resonator

1335

K. Ozeki, O. Kamigaito, H. Okuno, N. Sakamoto, K. Suda, Y. Watanabe, K. Yamada
RIKEN Nishina Center, Wako, Japan
E. Kako, H. Nakai, K. Umemori
KEK, Ibaraki, Japan
K. Okihira, K. Sennyu, T. Yanagisawa
MHI, Hiroshima, Japan

In RIKEN Nishina Center, for the purpose of development of elemental technology for the superconducting linear accelerator, the designing and construction of accelerator system based on superconducting quarter-wavelength resonator are carried out. The basic designs of the input coupler are as follows: The resonance frequency of the cavity is 75.5 MHz and assumed beam loading is about 1 kW. Double vacuum windows, which are disk-type, are adopted. A thermal anchor of 40 K is installed near the cold-window. The optimum positions of the cold-window and the thermal anchor depending on the effective RRR of copper-plate are being studied. In this contribution, the details of these designs will be reported. This work was funded by ImPACT Program of Council for Science, Technology and Innovation (Cabinet Office, Government of Japan).

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THPB086

LCLS-II Fundamental Power Coupler Mechanical Integration

1340

K.S. Premo, T.T. Arkan, Y.O. Orlov, N. Solyak
Fermilab, Batavia, Illinois, USA

Funding: DOE
LCLSII is a planned upgrade project for the linear coherent light source (LCLS) at SLAC. The LCLSII linac will consist of thirtyfive 1.3 GHz and two 3.9 GHz superconducting RF continuous wave (CW) cryomodules that Fermilab and Jefferson Lab will assemble in collaboration with SLAC. The LCLSII 1.3 GHz cryomodule design is based on the European XFEL pulsed mode cryomodule design with modifications needed for CW operation. The 1.3 GHz cryomodules for LCLSII will utilize a modified TTF3 syle fundamental power coupler design. Due to CW operation heat removal from the power coupler is critical. This paper presents the details of the mechanical integration of the power coupler into the cryomodule. Details of thermal braids, connections, and other interfaces are discussed.

Poster THPB086 [1.031 MB]

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THPB087

Design and Simulation of High Power Input Coupler for C-ADS Linac 5-Cell Elliptical Cavities

1343

K.X. Gu
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
X. Chen, T.M. Huang, Q. Ma, W.M. Pan
IHEP, Beijing, People's Republic of China

Two 650 MHz elliptical cavity sections (elliptical 063, elliptical 082) are chosen to accelerate medium energy protons for China Accelerator Driven sub-critical System (C-ADS) linac. For each 5-cell cavity, RF power up to 150 kW in CW mode is required to be fed by a fundamental power coupler (FPC). A coaxial type coupler is designed to meet the power and RF coupling requirements. This paper presents the RF design, thermal analysis and multipacting simulations of the coupler for C-ADS 5-cell elliptical cavities.

Poster THPB087 [0.593 MB]

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THPB088

20 kW CW Power Couplers for the APS-U Harmonic Cavity

1346

M.P. Kelly, A. Barcikowski, Z.A. Conway, D. Horan, M. Kedzie, S.H. Kim, P.N. Ostroumov
ANL, Argonne, Illinois, USA
S.V. Kutsaev
RadiaBeam, Santa Monica, California, USA
J. Rathke
AES, Medford, New York, USA

Funding: This work supported by the U.S. DOE, Office of Nuclear Physics, Contract No. DE-AC02-06CH11357. This research used resources of ANL’s ATLAS facility, which is a DOE Office of Science User Facility.
A pair of 20 kW CW adjustable RF power couplers optimized for 1.4 GHz have been designed and are being built as part of the APS-U bunch lengthening system. The system uses one superconducting RF cavity to be installed into the APS Upgrade electron storage ring and will provide a tremendous practical benefit to the majority of users by increasing the beam lifetime by 2-3 times. The 80 mm diameter, 50 Ω coaxial couplers include 4 cm (~20 dB) of adjustability. This allows optimization of bunch lengthening for a range of storage ring beam currents and fill patterns while, simultaneously, maintaining the required 0.84 MV harmonic cavity voltage. To provide bunch lengthening, the cavity/coupler system must extract RF power (up to 32 kW) from the beam. Each coupler will transmit roughly half of the total extracted power to external water-cooled loads. The design extends upon on a well-tested ANL two RF window concept, using a pair of simple rugged 80 mm diameter alumina disks. A new feature is the ‘hourglass-shaped’ inner conductor chosen to maximize transmission at 1.4 GHz. Results of electromagnetic and thermal simulations, as well as, prototyping and initial RF testing are presented.

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THPB091

Mechanical Design of a High Power Coupler for the PIP-II 325 MHz SSR1 RF Cavity

1354

O.V. Pronitchev, S. Kazakov
Fermilab, Batavia, Illinois, USA

The Project X Injector Experiment (PXIE) at Fermilab will include one cryomodule with eight 325 MHz single spoke superconductive cavities (SSR1). Each cavity requires approximately 2 kW CW RF power for 1 mA beam current operation. A future upgrade will require up to 8 kW RF power per cavity. Fermilab has designed and procured ten production couplers for the SSR1 type cavities. Status of the 325 MHz main coupler development for PXIE SSR1 cryomodule is reported.

Poster THPB091 [1.821 MB]

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THPB092

Mechanical Design of a High Power Coupler for the PIP-II 162.5 MHz RF Quadrupole

1357

O.V. Pronitchev, S. Kazakov
Fermilab, Batavia, Illinois, USA

PXIE is a prototype front end system for the proposed PIP-II accelerator upgrade at Fermilab. An integral component of the front end is a 162.5 MHz, normal conducting, continuous wave (CW), radiofrequency quadrupole (RFQ) cavity. Two identical couplers will deliver approximately 100 kW total CW RF power to the RFQ. Fermilab has designed and procured main couplers for the CW RFQ accelerating cavity. The mechanical design of the coupler, along with production status, is presented below.

Poster THPB092 [0.476 MB]

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THPB093

A 1.3 GHz Waveguide to Coax Coupler for Superconducting Cavities With a Minimum Kick

1360

J.A. Robbins, C. Egerer, R.G. Eichhorn, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Transversal forces as a result of asymmetric field generated by the fundamental power couplers have become a concern for low emittance beam in future accelerators. In pushing for smallest emittances, Cornell has finished a physics design for a symmetric coupler for superconducting accelerating cavities. This coupler consists of a rectangular waveguide that transforms into a coaxial line inside the beam pipe, eventually feeding the cavity. We will report on the RF design yielding to the extremely low transversal kick. In addition, heating, heat transfer and thermal stability of this coupler has been evaluated.

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THPB094

Status of the Fundamental Power Coupler Production for the European XFEL Accelerator

1364

S. Sierra, G. Garcin, C. Lievin, G. Vignette
TED, Velizy, France
A. Gallas, W. Kaabi
LAL, Orsay, France
M. Knaak, M. Pekeler, L. Zweibaeumer
RI Research Instruments GmbH, Bergisch Gladbach, Germany

For the XFEL accelerator, Thales, RI Research Instrument and LAL are working on the manufacturing, assembly and conditioning of fundamental power couplers. 670 couplers have to be manufactured according to strict specifications. The paper describes the full production activity from the program starting to the currentphase with main measurements for the coupler characteristic: copper and TiN coating characteristics. The status of the production is given with an output rate of 8 couplers per week. The status for more than 500 couplers manufactured and conditionned is presented.

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THPB095

Automatic RF Conditioning Test Bench of Fundamental Power Couplers for the European XFEL Accelerator

1367

S. Sierra, C. Lievin, P. Rouillon
TED, Velizy, France
H. Guler, W. Kaabi, A. Verguet
LAL, Orsay, France

In order to perform the RF conditioning of the fundamental coupler for the XFEL accelerator, Thales and LAL developed together a test bench being able to make the automatic RF conditioning. The capability of this test bench is of 4 pairs of coupler at the same time with automatic sequences of increasing the RF power. The test bench is composed of the overall RF station providing up to 5 MW peak power at 1.3 GHz. The waveguide distribution allows 4 individual RF lines for conditionning,and the automatic sequence applied to the couplers in respect with all signals monitored and controlled during the RF process. The paper will also provide some examples of such process.

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THPB096

Lesson Learned on the Manufacturing of Fundamental Power Couplers for the European XFEL Accelerator

1370

S. Sierra, G. Garcin, C. Lievin, G. Vignette
TED, Velizy, France
M. Knaak, M. Pekeler
RI Research Instruments GmbH, Bergisch Gladbach, Germany

In this paper we described lesson learned during the production of Fundamental Power Couplerfor the European XFEL accelerator and different steps necessaries for obtaining a rate of 8 couplers a week. From the manufacturing of individual components up to the RF conditioning. This paper also propose some possible ways to be optimized for a future mass production of such components. With comparison of processes and adaptation which could benefit to an increase rate or a more secure program. Some of them which could be studies from the coupler definition to the manufacturing process in order to obtain a stable and possible increased rate or lower cost of production by decreasing the risks on programs. This analysis is based on a current production of more than 500 couplers

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THPB097

New Possible Configuration of 3.9 GHz Coupler

1373

S. Kazakov
Fermilab, Batavia, Illinois, USA

The LCLS-II superconducting accelerator supposedly will use 3.9 GHz (3-d harmonic) superconductive cavities. A new possible configuration of 3.9 GHz main coupler is presented in the papar. This configuration contains two coaxial ceramic windows, a cold and a warm one. Inner conductors of windows are connected through the capacitive gap and have no mechanical no thermal contacts. It allows to avoid using bellows and thus avoid the problem of heating and cooling. The windows have shields protecting shields against the electron, and this prevents the window ceramics from charging. Results of computer simulation of the new coupler are posted.

Poster THPB097 [1.036 MB]

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THPB098

Testing of 325 MHz Couplers at Test Stand in Resonance Mode

1376

S. Kazakov, B.M. Hanna, O.V. Pronitchev
Fermilab, Batavia, Illinois, USA

The linear accelerator for the PIP-II program utilizes two types of 325 MHz Single Spoke resonator cavities: SSR-I and SSR-II. Operating power of SSR-II is about 17 kW and requires input couplers which can reliably work at power levels > 20 kW with full reflection at any reflected phase. Currently only one 10 kW RF amp is available for coupler testing. To increase testing power, a special resonance configuration were used. This configuration allows us to raise RF power approximately 3 times. The testing scheme and results are discussed in the paper.

Poster THPB098 [1.600 MB]

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THPB100

Nb Coatings on Bellows Used in SRF Accelerators

1379

S.F. Chapman, I. Irfan, M. Krishnan, K.M. Velas
AASC, San Leandro, California, USA

Funding: This research is supported by the US DOE via SBIR grant: DE-SC0007678
Alameda Applied Sciences Corporation (AASC) is developing bellows with the strength and flexibility of stainless steel and the low surface impedance of a superconductor. Such unique bellows would enable alignment of SRF cavity sections with greatly reduced RF losses. To that end, we grow Nb thin films via Coaxial Energetic Deposition (CED) from a cathodic arc plasma. Films of Nb were grown on stainless steel bellows, with and without an intermediate layer of Cu deposited via the same technique, to produce a working bellows with a well adhered superconducting inner layer. The Nb coated bellows have undergone tests conducted by our collaborators to evaluate their RF performance.

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THPB101

High Power Input Couplers for C-ADS

1383

T.M. Huang, X. Chen, H.Y. Lin, Q. Ma, F. Meng, W.M. Pan, G.W. Wang, X.Y. Zhang
IHEP, Beijing, People's Republic of China
K.X. Gu
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China

High power input couplers are key components of the superconducting system for China Accelerator Driven sub-critical System (C-ADS) project. For the first phase, C-ADS includes four types of superconducting cavities (SCCs) of two frequencies, 162.5 MHz HWR SCC and 325 MHz Spoke SCC up to the energy of 25 MeV. All input couplers for the SCCs are developed in IHEP. This paper will describe the development status of the high power input couplers for C-ADS.

Poster THPB101 [0.430 MB]

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THPB102

RF Conditioning of the XFEL Power Couplers at the Industrial Scale

1387

H. Guler, A. Gallas, W. Kaabi, D.J.M. Le Pinvidic, C. Magueur, M. Oublaid, A. Thiebault, A. Verguet
LAL, Orsay, France

LAL has in charge the production monitoring and the RF conditioning of 800 power couplers to equip 100 XFEL cryomodules. The conditioning process and all the preceding preparation steps are performed in a 70m2 clean room. This infrastructure, its equipment and the RF station are designed to allow the treatment of 8 couplers in the same time, after a ramp-up phase. Clean room process and conditioning results are presented and discussed.

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THPB103

High Power Coupler Test for ARIEL SC Cavities

1390

Y. Ma, P.R. Harmer, D. Lang, R.E. Laxdal, B.S. Waraich, V. Zvyagintsev
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

TRIUMF ARIEL[1](The Advanced Rare Isotope Laboratory) project employs five 1.3 GHz 9-cell superconducting elliptical cavities[2] for acceleration of 10 mA electron beam up to energy of 50 MeV. 100 kW CW RF power will be delivered into each cavity by means of pair of Power Couplers: 50 kW per each coupler. Before installing the power couplers with the cavities, they have to be assembled on Power Coupler Test Stand(PCTS) and conditioned with a 30 kW IOT. Six couplers have been conditioned at room temperature and four of them have been installed to the cavities and tested during beam commissioning. Test results of the power couplers will be described and discussed in this paper.
#mayanyun@triumf.ca

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THPB104

Higher Order Modes Simulation and Measurements for 2400 MHz Cavity

1394

Ya.V. Shashkov, D.S. Bazyl, R.V. Donetskiy, M.V. Lalayan, N.P. Sobenin
MEPhI, Moscow, Russia
R. Calaga
CERN, Geneva, Switzerland
A.A. Zavadtsev
Nano, Moscow, Russia
M. Zobov
INFN/LNF, Frascati (Roma), Italy

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 LHC upgrade program an application of additional harmonic cavities operating at multiples of the main RF system frequency of 400 MHz is currently under discussion. The 800 MHz superconducting cavities with grooved beam pipes were suggested for implementation. A scaled aluminum prototype with a frequency of the operational mode of 2400 MHz was manufactured for testing the results of simulations. The load reflection coefficient measurements were performed as well as the Qload measurements for cavities with the load. Here we discuss the prototype design and report the obtained measurement results.
Higher order modes, superconducting cavities, srf

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THPB105

Demonstration of Coaxial Coupling Scheme at 26 MV/m for 1.3 GHz Tesla-Type SRF Cavities

1397

Y. Xie, A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
T.N. Khabiboulline, A. Lunin, V. Poloubotko, A.M. Rowe, N. Solyak, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA
J. Rathke
AES, Medford, New York, USA

Superconducting ILC-type cavities have an rf input coupler that is welded on. A detachable input coupler will reduce conditioning time (can be conditioned separately), reduce cost and improve reliability. The problem with placing an extra flange in the superconducting cavity is about creating a possible quench spot at the seal place. Euclid Techlabs LLC has developed a coaxial coupler which has an on the surface with zero magnetic field (hence zero surface current). By placing a flange in that area we are able to avoid disturbing surface currents that typically lead to a quench. The coupler is optimized to preserve the axial symmetry of the cavity and rf field. The surface treatments and rf test of the proto- type coupler with a 1.3 GHz ILC-type single-cell cavity at Fermilab will be reported and discussed.

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