IPAC2016 - Table of Session: WEPMB (Poster Session)

Paper	Title	Page
WEPMB003	Design of the HWR Cavities for SARAF	2119
	G. Ferrand, L. Boudjaoui, D. Chirpaz-Cerbatpresenter, P. Hardy, F. Leseigneur, C. Madec, N. Misiara, N. Pichoff CEA/IRFU, Gif-sur-Yvette, France
	CEA is committed to delivering a Medium Energy Beam Transfer line and a superconducting linac (SCL) for SARAF accelerator in order to accelerate 5mA beam of either protons from 1.3 MeV to 35 MeV or deuterons from 2.6 MeV to 40 MeV. The SCL consists in 4 cryomodules. The first two identical cryomodules host 6 half-wave resonator (HWR) low beta cavities (β = 0.09) at 176 MHz. The last two identical cryomodule will host 7 HWR high-beta cavities (β = 0.18) at 176 MHz. Low-beta and high beta cavities have been optimized to limit electric and magnetic peak fields in the cavity, and to minimize the dissipated power. Manufacturing constraints and helium cooling were taken into consideration to minimize the risk during manufacturing and operation. Preliminary mechanical studies of the cavity and of the tuning system, as well as preliminary studies of the couplers and pick-up antennas were carried out. This work will be presented in this poster.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB003
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WEPMB005	Manufacturing of the IFMIF Series Power Couplers	2122
	H. Jenhani, N. Bazin, N. Berton, G. Devanz, P. Hardy, V.M. Hennion CEA/IRFU, Gif-sur-Yvette, France
	In the framework of the International Fusion Materials Irradiation Facility (IFMIF), which consists of two high power CW accelerator drivers, each delivering a 125 mA deuteron beam at 40 MeV, a Linear IFMIF Prototype Accelerator (LIPAc) is presently under construction for the first phase of the project. Eight power couplers are needed for the cryomodule of LIPAc. After the validation of the two prototypes, the manufacturing of the Series Power Couplers was lunched. This paper will report the status of the manufacturing progress. It will also describe the acceptance tests in addition to the criteria adopted for these critical RF power units. The manufacturing imperfections and some finishing techniques used for the different parts will be also presented and discussed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB005
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WEPMB006	XFEL Couplers RF Conditioning at LAL	2125
	H. Guler, A. Gallas, W. Kaabi, D.J.M. Le Pinvidic, C. Magueur, M. Oublaid, A. Thiebault, A. Verguet LAL, Orsay, France
	The industrialization and the RF conditioning of 800 power couplers for the European XFEL have been performed by LAL-Orsay from fall 2013 to spring 2016. LAL laboratory has in charge the industrial monitoring, the quality control and the RF conditioning of the couplers fabricated by two different suppliers. It was the first experience of coupler production at such scale. The faced challenges, the different issues, and the lessons learned during the mass production will be reported. And finally the huge amount of RF conditioning data will be shown as one of key point on the conditioning process.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB006
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WEPMB007	Error Estimation in Cavity Performance Test for the European XFEL at DESY	2128
	Y. Yamamoto KEK, Ibaraki, Japan W.-D. Möller, D. Reschkepresenter DESY, Hamburg, Germany
	The cavity performance tests, that is, vertical test (V.T.) and cryomodule test (C.T.), in the cavity/cryomodule mass production for XFEL have been done since 2012 at DESY, and is still on-going at present. At the comparatively initial stage of the mass production, the error estimation in the cavity performance tests was done for understanding how precisely those measurements are done at AMTF (Accelerator Module Test Facility). There are two parameters for the error estimation in V.T. One is the cable calibration parameter, and the other is the external Q-value, which is related to the power emitted from cavity. The measurement precision in the external Q-value depends on the measurement of coupling coefficient (β) strongly. Therefore, it is essential not to miss the β measurement for the precise measurement in V.T. On the other hand, as for C.T., the change of parameter (Kt), which is related to the evaluation of accelerating gradient, was used. As the result of the data analysis for Kt, the error was estimated to be 6%, and is related to the cavity performance degradation from V.T. to C.T. In this paper, the detailed data analysis and error estimation will be presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB007
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WEPMB008	ESS DTL Mechanical Design and Prototyping.	2131
	P. Mereu, M. Mezzano INFN-Torino, Torino, Italy D. Castronovo, R. Visintini Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy F. Grespan, A. Pisent, M. Poggi, C. R. Roncolato INFN/LNL, Legnaro (PD), 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. In this paper the DTL mechanical design and simulations are presented, together with the results obtained from the prototypes of three drift tubes, equipped respectively with Permanent Magnet Quadrupole, Steerer and Beam Position Monitor.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB008
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WEPMB009	Status of the Superconducting Cryomodules and Cryogenic System for the Mainz Energy-recovering Superconducting Accelerator MESA	2134
	T. Stengler, K. Aulenbacher, F. Hug, D. Simon, P. Weber IKP, Mainz, Germany F. Schlander ESS, Lund, Sweden N. Wiehl Johannes Gutenberg University Mainz, Institut of Nuclear Chemistry, Mainz, Germany
	Funding: Work supported by the German Research Foundation (DFG) under the Cluster of Excellence "PRISMA" SRF and the cryogenic system are mandatory for the operation of MESA at the Institut für Kernphysik at Johannes Gutenberg-Universität Mainz. The cryomodule production project is running for one year right now and the recent developments and measurements are presented. Further on the cryogenic concept required for the operation of MESA will be discussed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB009
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WEPMB011	ESS Medium and High Beta Cavity Prototypes	2138
	P. Michelato, A. Bellandi, M. Bertucci, A. Bignami, A. Bosotti, J.F. Chenpresenter, L. Monaco, R. Paparella, P. Pierini, D. Sertore INFN/LASA, Segrate (MI), Italy C.G. Maiano DESY, Hamburg, Germany C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy S. Pirani ESS, Lund, Sweden
	In the framework of the ESS activity in progress at INFN-LASA, we are designing and developing 704.42 MHz Medium (β=0.67) and High (β=0.86) beta prototype cavities plug compatible with the ESS cryomodule design. The cells of one Medium and one High beta cavity are fabricated with high quality CBMM Large Grain Niobium (480 mm dia. Ingot, RRR=300, sliced by Heraeus) while a Medium beta cavity is done with Fine Grain material for comparison. The prototype cavities will be produced by the firm Ettore Zanon S.p.A. under the supervision of INFN - LASA group.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB011
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WEPMB012	Production and Investigation of Superconducting 9-Cell Cavity Made of Large Grain Nb in KEK	2141
	T. Dohmae, H. Inoue, K. Umemori, Y. Watanabe, M. Yamanaka KEK, Ibaraki, Japan
	For CW operation of superconducting cavity, reduction of heat load at cavity surface is one of important topics, since generated heat load is much higher than that of pulse wave. Using Large Grain (LG) Nb for superconducting cavity has possibility to reach higher Q0 than using Fine Grain Nb, which reduces heat load to 2K Helium. KEK Cavity Fabrication Facility(CFF) group had successfully produced superconducting 1-cell cavity made of LG Nb in 2013, and reached high Q0 at the vertical test (maximum field of 45 MV/m). Then, KEK CFF group started producing first superconducting 9-cell LG cavity in 2015, which will be completed in the end of December 2015. Whole processes of producing this cavity from sliced Nb are done in KEK. In this report, process flow and strategies of producing 9-cell cavity and results of vertical test will be presented in detail.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB012
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WEPMB013	Long Term Cavity Performance in Compact-ERL Injector Cryomodule	2145
	E. Kako, T. Konomi, T. Miura, H. Sakai, K. Umemori KEK, Ibaraki, Japan
	Degradation of cavity performance due to heavy field emission was observed in three 2-cell cavities after beam operation at 5 MeV for 2 years.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB013
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WEPMB014	Cavity Performance of the Prototype KEK Superconducting RF Gun	2148
	T. Konomi, E. Kakopresenter, E. Kakopresenter, Y. Kobayashi, Y. Kobayashi, K. Umemori, K. Umemori, S. Yamaguchi KEK, Ibaraki, Japan R. Matsuda Mitsubishi Heavy Industries Ltd. (MHI), Takasago, Japan T. Yanagisawa MHI, Hiroshima, Japan
	A superconducting RF (SRF) gun can generate a high current and high energy beam. It has a possibility to achieve requirement from high performance ERL and high repetition FEL. Target values of the L-band KEK SRF gun are that beam repetition is 1.3 GHz, beam current is 100 mA, beam energy is 2 MeV, emittance is 1 mm mrad or less. The number of cell is 1.5. Accelerating energy of 2 MeV corresponds to 42 MV/m of maximum surface field. The photocathode is designed to be illuminated by excitation laser from backside. The SRF gun cavity consists of the 1.5 cell accelerating cavity, cathode plug and choke filter for protecting the heating of cathode plug. To evaluate these parts individually, these parts are added step by step. High gradient test of the accelerating cell without cathode plug and choke filter was done. The surface peak electric field reached 66 MV/m, and this meet the target value 42 MV/m sufficiently. Next high gradient test will be done after adding the choke filter. The choke filter is designed to be simple to wash choke cell easier. In this conference, we will report the design, fabrication and high gradient performance of the SRF gun cavity with choke filter.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB014
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WEPMB015	Construction and 2K Cooling Test of Horizontal Test Cryostat at KEK	2151
	K. Umemori, K. Hara, E. Kakopresenter, Y. Kobayashi, Y. Kondo, H. Nakai, H. Sakai, S. Yamaguchi KEK, Ibaraki, Japan
	A horizontal test cryostat was designed and constructed at AR East building on KEK. Main purposes of test stand are improvement of module assembly technique and effective development of module components. Diameter of vacuum chamber is 1 m and its length is 3 m, which is enough to realize performance test of L-band 9-cell cavity with full assembly, including input couplers, HOM dampers/couplers and frequency tuners. On the sides, several ports are prepared to access to components, such as coupler and tuners. A cold box is placed on the top of the chamber. Liquid He is filled in a 4K-pod and 2K He is supplied through a J-T valve. A He pumping system is prepared. Inside of the chamber was covered with 80K shield, which is cooled by Liquid nitrogen. A cavity is supported on 5K table, which is also used as 5K thermal anchors. After cooling down to 80K using liquid Nitrogen, 4K He was stored and pumped down to 2K. The cooling test was successful. In this presentation, details of design and construction of the horizontal test cryostat is described and results of the cooling tests are shown. High power tests will be realized in near future.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB015
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WEPMB016	Vertical Test Results of Nitrogen Doped SRF Cavities at KEK	2154
	K. Umemori, H. Inoue, E. Kakopresenter, T. Konomi, T. Kubo, H. Sakai, H. Shimizu, M. Yamanaka KEK, Ibaraki, Japan H. Hara, K. Sennyu, T. Yanagisawa MHI-MS, Kobe, Japan
	Recently Nitrogen doping(N-doping) technique was proposed and drastic improvements of Q-values were reported. Since high-Q operation of SRF cavities are very attractive for CW machine, we started investigation on performance of Nitrogen doped SRF cavities. Nitrogen doping systems were prepared on two vacuum furnaces, which have been used for annealing of SRF cavities. Two fine grain single cell cavities have been used for the study. After 800 degree, 3 hours annealing, N-doping were carried out under several Pa of Nitrogen pressure and followed by post annealing. Three kind of different conditions, pressure and duration time, were attempted. After applying EP-2, cavity performances were evaluated by vertical tests. Against our expectations, we observed lower Q-values, at every measurements, than those measured without N-doping. In this presentation, we describe details about N-doping system and parameters and results obtained by vertical tests. Some discussions are also given against our results.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB016
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WEPMB017	High Gradient Cavity Performance in STF-2 Cryomodule for the ILC at KEK	2158
	Y. Yamamoto, T. Honma, E. Kakopresenter, Y. Kojima, T. Matsumoto, H. Nakai, T. Shishido KEK, Ibaraki, Japan
	The high power test for STF-2 cryomodule has completed successfully in 2015. Before cooldown of cryomodule, at first, the input coupler conditioning at room temperature is done with detuned cavities. After cooldown, the cavity conditioning, which is the main part in the performance test, is done by monitoring the radiation level measured at three locations around the cryomodule, and the heating and RF output at two HOM (Higher Order Mode) couplers. Consequently, it became clear the average accelerating gradient is 30 MV/m for STF-2 cryomodule (39 MV/m at max. and 15 MV/m at min.), and the second cavity string with four cavities had the significant performance degradation by heavy field emission due to the additional clean room work in the STF tunnel. As the following next steps, there are the LFD (Lorenz Force Detuning) measurement, LFD compensation by piezo, and long run for check of stable operation at high gradient. In the long run around 32 MV/m, each cavity without degradation showed the stable operation with the successful LFD compensation by piezo and RF feedback system. In this paper, the detailed test result will be presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB017
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WEPMB018	Multipactor Simulations in 650 MHz Superconducting Spoke Cavity for an Electron Accelerator	2161
	T. Kubo, T. Saeki KEK, Ibaraki, Japan E. Cenni CEA/IRFU, Gif-sur-Yvette, France R. Hajima, M. Sawamura JAEA, Ibaraki-ken, Japan H. Hokonohara, Y. Iwashita, H. Tongu Kyoto ICR, Uji, Kyoto, Japan
	Funding: The work is supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan. In order to realize a compact industrial-use X-ray source based on the laser-Compton scattering, a superconducting spoke cavity for an electron accelerator operated at 4K is under development. While the initially proposed operating frequency was 325MHz considering the 4K operation, we decided to start from the half scale model at 650MHz to accumulate our production experience of spoke cavity within our limited resources. In the present contribution, procedures and results of multipactor simulations for 650MHz spoke cavities are briefly introduced.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB018
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WEPMB019	Magnetic Fields in Bulk, Film, and Multilayer Superconductors in Front of a Multi-turn Coil	2164
	T. Kubo KEK, Ibaraki, Japan
	Funding: JSPS Young Scientists(B) #26800157, JSPS Challenging Exploratory Research #26600142, MEXT Photon and Quantum Basic Research Coordinated Development Program The magnetic field distribution formulae in a bulk superconductor, a superconducting film, and an SIS multilayer structure in front of a multi-turn coil are derived, which may be useful for a detailed analysis in a vortex field measurement by using the third harmonic method. * See for example the invited oral presentation by T. Kubo, "Theory of multilayer coating for proof-of-concept experiments", at SRF2015 ** C.Z.Antoine et al., Appl. Phys. Lett. 102, 102603 (2013)
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB019
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WEPMB021	Construction of Measurement System for Superconducting Characteristics on Thin-film Samples at KEK	2167
	T. Saeki, H. Hayano, T. Kubo KEK, Ibaraki, Japan Y. Iwashita Kyoto ICR, Uji, Kyoto, Japan H. Oikawa Utsunomiya University, Utsunomiya, Japan
	We set up a measurement system for superconducting characteristics on thin-film samples at KEK. The system includes small-sized and middle-sized cryostats, where critical temperature, critical magnetic field, Residual Resistiviy Ratio (RRR), Superconducting RF (SRF) resistivity can be measured on thin-film samples. A small-sized cryostat has a compact refrigerator to cool down samples for the measurements of critical temperature and RRR. On the other had, we can cool down various setups with a middle-sized cryostat by using liquid helium. A thin-film sample is set into a mushroom cavity and the SRF characteristics of the thin-film sample can be measured. In another setup, a sample is set with a small coil and the third harmonic measurement is done on the sample around the critical temperature. Finally, a thin-film sample is set into the bore-center of superconducting magnet and the magnetization of sample is measured with external magnetic field around the critical temperature. This article presents the details of the system and some measurements of samples by the system.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB021
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WEPMB023	Hydroforming SRF Three-cell Cavity from Seamless Niobium Tube	2170
	M. Yamanaka, T. Dohmae, H. Inoue, G.-T. Park, K. Umemori KEK, Ibaraki, Japan A. Hocker Fermilab, Batavia, Illinois, USA T. Tajima LANL, Los Alamos, New Mexico, USA
	We are developing the manufacturing method for superconducting radio frequency (SRF) cavities by using a hydroforming instead of using conventional electron beam welding. We expect higher reliability and reduced cost with hydroforming. For successful hydroforming, high-purity seamless niobium tubes with good formability as well as advancing the hydroforming technique are necessary. Using a seamless niobium tube from ATI Wah Chang, we were able to successfully hydroform a 1.3 GHz three-cell TESLA-like cavity and obtained an Eacc of 32 MV/m. A barrel polishing process was omitted after the hydroforming. The vertical test was carried out with very rough inside surface. We got amazing and interesting result.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB023
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WEPMB024	Study on Nondestructive Inspections for Super-conducting Cavity	2174
	H. Tongu, H. Hokonohara, Y. Iwashitapresenter Kyoto ICR, Uji, Kyoto, Japan R. Hajima, M. Sawamura JAEA, Ibaraki-ken, Japan H. Hayano, T. Kubo, T. Saeki, Y. Yamamoto KEK, Ibaraki, Japan
	Funding: The work is supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan. We have been studying nondestructive inspections for super-conducting spoke cavities. The temperature mapping (T-map) and X-ray mapping (X-map) are powerful inspection methods to locate a hot spot during the vertical RF tests. There would be a defect under the hot spot and the defect may be the cause of a quench. Our XT-map system (a combined system of T-map and X-map) has a high resolution in space. Because the huge amount of sensor signals are multiplexed at a hi-speed scanning rate in the vicinity of the sensors, the small number of signal lines makes the installation process easy and reduces the system complexity. Our XT-map got useful results on finding a defect in vertical RF tests of International Linear collider super-conducting cavity. The XT-map system is useful as low cost nondestructive inspections for superconducting spoke cavity. The study will be reported. progresses will be reported.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB024
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WEPMB025	Fabrication of Superconducting Spoke Cavity for Laser Compton Scattered Photon Sources	2177
	M. Sawamura, R. Hajimapresenter QST, Tokai, Japan H. Hokonohara, Y. Iwashita, H. Tongu Kyoto ICR, Uji, Kyoto, Japan T. Kubo, T. Saeki KEK, Ibaraki, Japan
	Funding: The work is supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan. We have launched a 5-year research program to develop superconducting spoke cavity for laser Compton scattered (LCS) photon sources. For realizing a wide use of LCS X-ray and γ-ray sources in academic and industrial applications, we adopt the super-conducting spoke cavity to electron beam drivers. The spoke cavity has advantages such as relative compactness in comparison with an elliptical cavity of the same frequency, robustness with respect to manufacturing inaccuracy due to its strong cell-to-cell coupling, the better packing in a linac to install couplers on outer conductor. On the other hand the spoke cavity has disadvantage of more complicated structure than an elliptical cavity. Though our proposal design for the photon source consists of the 325 MHz spoke cavities in 4K operation, we have begun to fabricate the half scale model of 650 MHz spoke cavity in order to accumulate our cavity production experience by effective utilization of our limited resources. In this paper, we present our fabrication status.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB025
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WEPMB026	MHI-MS's Production Activities of Superconducting Cavity	2180
	H. Hara, A. Miyamoto, K. Sennyu, T. Yanagisawa MHI-MS, Kobe, Japan E. Kako, T. Konomi, H. Nakai, K. Umemori KEK, Ibaraki, Japan
	Mitsubishi Heavy Industries Mechatronics Systems, Ltd. (MHI-MS), a subsidiary of MHI, took over MHI's accelerator business on October 1, 2015, and has been developing the business since that time. MHI-MS has developed manufacturing process of superconducting cavities continuously. In this presentation, recent progress will be reported.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB026
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WEPMB028	High HOM Damping Structure Study for CEPC	2183
	Z.C. Liu, J. Gao, S. Jin, Y. Wangpresenter, H.J. Zheng IHEP, Beijing, People's Republic of China
	Both large circular collider such as CEPC and high current ERL facility need high HOM damping superconducting cavity. The slotted cavity is an option for such applications. It has three slotted waveguides which can highly damp the HOM and extract high HOM power out. However, the HOM absorbers for such facility are usually put outside of the cryomodule to decrease the influence of HOM power on the cryogenic system. Large slot waveguide need to make smaller transition structure to adapt this situation. A rectangular waveguide to coaxial waveguide structure was designed to the slotted cavity. In this paper, we will show the cavity HOM damping design scheme with this structure.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB028
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WEPMB029	Research of Nitrogen Doping at IHEP	2186
	P. Sha Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China J.P. Daipresenter IHEP, Beijing, People's Republic of China F. Jiao PKU, Beijing, People's Republic of China
	Funding: Work funded by National Natural Science Foundation of China, Grant No. 11505197 Recently, nitrogen doping (N-doping) technology has been proved to increase Q0 of superconducting cavity obviously, which lowers the BCS surface resistance. After N-doping, Q0 of 9-cell 1.3 GHz cavity can be increased to 310¹⁰ at Eacc = 16 MV/m, while 1.51010 without N-doping [1]. Since 2013, there have been over 60 cavities nitrogen doped at FNAL, JLAB and Cornell. The Circular Electron Collider (CEPC) has been proposed by IHEP in China, while requests Q0=4e10@Eacc=15.5 MV/m for 650 MHz cavity. It's hard to achieve without N-doping. So research of N-doping was begun in cooperation with Peking University in early 2015. Experiments of niobium samples have showed that nitrogen concentration at niobium surface increased a lot after N-doping. After then, several single-cell 1.3 GHz cavities completed vertical tests, but there're no successful test results of Q0 increasing, yet.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB029
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WEPMB030	Design Study of a Compact Deflecting Cavity at IHEP	2188
	J.P. Dai, B. Ni, J.Y. Zhai, J.R. Zhang IHEP, Beijing, People's Republic of China
	For the XFEL project proposed by IHEP, a sophisticated beam spreader is required to separate a single beam into multiple beams. One of the deflecting cavities used in the spreader has been investigated and optimized. It is a 325 MHz, compact RF-dipole superconducting cavity, with the transverse R/Q of 2900Ω, geometrical factor G of 88.5 Ω, and the Helium pressure sensitivity df/dp of 3.4 Hz/mbar. At the nominal deflecting voltage of 7MV, the peak electric field Epeak is 41 MV/m and peak magnetic field Bpeak is 48 mT. This paper will present the detailed RF and mechanical designs.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB030
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WEPMB031	Post Processing of Spoke Type Superconducting Cavities at Institute of High Energy Physics	2191
	J. Dai, J.P. Daipresenter, F.S. He, X. Huang, L.H. Li, Z.Q. Li, H.Y. Lin, Z.C. Liu, B. Ni, W.M. Pan, P. Sha, G.W. Wang, Q.Y. Wang, Z. Xue, X.Y. Zhang, G.Y. Zhao IHEP, Beijing, People's Republic of China
	Funding: Work supported by Chinese Academy of Science strategic Priority Research Program-Future Advanced Nuclear Fission Energy. After upgrading the post-processing system, several superconducting cavities were RF tested at Institute of High Energy Physics (IHEP) in China recently. The test results of 14 spoke 012 cavities and 6 spoke 021 cavities which used at China ADS injector I and linac all exceeds our design objective. Moreover, a spoke 040, a 650MHz elliptical cavity and a 325MHz HWR cavity are also vertical tested and the test results are all significantly surpass our design value. The post processing of these cavities including Buffered Chemical Polishing (BCP), high temperature heat treatment and High Pressure water Rinsing (HPR) is presented here. daijin@pku.edu.cn
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB031
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WEPMB032	Fabrication and Testing Status of IHEP03	2194
	T.X. Zhao, J. Gao, S. Jin, Z.Q. Li, Y.L. Liu, Z.C. Liu, Y. Wangpresenter, J.Y. Zhai, H.J. Zheng IHEP, Beijing, People's Republic of China M. Asano, E. Kako KEK, Ibaraki, Japan H. Yu, H. Yuan BIAM, Beijing, People's Republic of China
	After the successful development of the IHEP01 and IHEP02 1.3GHz 9cell superconducting cavity, we developed a 1.3GHz Tesla-Like 9cell superconducting cavities in collaboration with KEK. The cavity was made by niobium material produced in OTIC, Ningxia, China. After completeing welding, leakage check, BCP, HPR, we sent the cavity to KEK and used the standard procedures of ILC cavity for processing. These include electron polishing, vacuum furnace outgassing, tuning for field flatness and frequency, light EP, baking and vertical test. We target to have a high Q0 cavity for this experiment. In this paper, we will report the experimental status of the IHEP03 cavity.
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WEPMB034	Analysis of Niobium Quality Control for SRF Cavity	2197
	M.J. Joung IBS, Daejeon, Republic of Korea
	Funding: the Ministry of Science, ICT and Future Planning (MSIP) and the National Research Foundation (NRF) of the Republic of Korea under Contract 2013M7A1A1075764. Clean and smooth surface is important to get low sur-face resistance for superconducting material. SRF (Super-conducting Radio Frequency) cavity made of niobium which is superconducting material and also one of the rare metal. The procedure of niobium quality control was set up to get high performance SRF cavity. The procedure consists of three parts; certificates check, Nb specification verification, and surface inspection and measurements of thickness, roughness, flatness. Three important properties which are RRR value, chemical composition and me-chanical properties were verified to conform Nb specifica-tion. The range of thickness, roughness and flatness for niobium as SRF cavity raw material were obtained by measurement.
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WEPMB035	SRF Cavities for RAON	2200
	H.C. Jung, J. Joo, J. Lee IBS, Daejeon, Republic of Korea R.E. Laxdal, Z.Y. Yao TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
	SRF cavities of superconducting linear accelerators in RAON are developed and tested at 2K/4K. 1st Quarter Wave Resonator (QWR) and Half Wave Resonator (HWR) are fabricated by a domestic vender and tested in the TRIUMF's facility. The measured Q factors are above the required values at the operating gradients. And the predicted multipacting phenomena are observed in the test and easily conditioned. The Q factors decreased after a slow cooldown and enhanced at 4K tests by a low temperature baking. Based on these tests, modified bare cavities are newly developed, jacketed and will be tested with tuners and power couplers.
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WEPMB036	High Pressure Rinsing for Niobium Superconducting Cavity	2202
	Y. Jung, M.J. Joung, M. Lee IBS, Daejeon, Republic of Korea J. Lee, J. Seo Vitzrotech Co., Ltd., Ansan City, Kyunggi-Do, Republic of Korea
	Niobium superconducting cavity is treated with high pressure rinsing to clean the inner surface of the cavity. Either organic or inorganic residues on the inner surface of the cavity can cause serious problems during the cavity operation. A thermal quenching - superconducting material loses its superconductivity - is a typical phenomenon brought out by harmful defects by increasing critical temperature. We have performed high pressure rinsing experiments to check out a prototype HPR machine. HPR experiments were performed with a simplified cavity structure, and analyzed as a function of the pressure, the distance from a nozzle, and the sizes of defects on the niobium surface. In this presentation, we will discuss the performance of the prototype HPR machine.
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WEPMB039	Operation Techniques for HWR1 Cryomodule	2205
	H. Kim, J.W. Choi, Y.W. Jo, W.K. Kim, Y. Kim, M. Lee IBS, Daejeon, Republic of Korea
	Control systems such as PLC and EPICS are developed for a half-wave resonator (HWR) cryomodule. PLC rack is fabricated for the HWR1 cryomodule. The PLC controls pumps, heaters and valves. The PLC communicates with temperature monitors through Ethernet. HMI of PLC and EPICS controls and monitors pumps, heaters, valves and temperature sensors through switching hub. The PLC HMI is developed and EPICS is also developed. The CSS of EPICS consists of control, monitor, parameter set-up, alarm and data browser screen.
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WEPMB041	Design of RF Power Coupler for RISP Half Wave Resonator	2208
	S. Lee, E.-S. Kim Korea University Sejong Campus, Sejong, Republic of Korea I. Shin IBS, Daejeon, Republic of Korea
	RF power couplers for half wave resonators are under development for the Rare Isotope Science Project (RISP) in Korea. It is required to deliver up to 6 kW RF power at 162.5 MHz to the HWR in CW mode. The RF coupler is a coaxial capacitive type using a disc type ceramic window. Design studies of 2nd prototype HWR RF coupler are presented.
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WEPMB044	Development of RF Conditioning System for RISP RF Power Couplers	2211
	C.K. Sung, E.-S. Kim Korea University Sejong Campus, Sejong, Republic of Korea S. Lee, I. Shin IBS, Daejeon, Republic of Korea
	RF power coupler prototypes have been conditioned for a heavy ion accelerator of the Rare Isotope Science Project (RISP) in Korea. The RF couplers operate for 162.5 MHz half-wave resonators at 6 kW RF power. The RF couplers are a 50-Ohm coaxial structure with a disk type ceramic window at room temperature. The control system using Labview software supported automatic process for RF conditioning, data acquisition and interlock system. The conditioning system and the result of conditioning of RF coupler are presented in this paper.
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WEPMB045	Measurement of Higher Order Modes Electrodynamic Characteristics for Array of Two 2400 MHz Cavities	2214
	Ya.V. Shashkov, R.V. Donetskiy, M.V. Lalayan, N.P. Sobenin MEPhI, Moscow, Russia A. Orlov NRNU, Moscow, Russia
	Funding: Work supported by Ministry of Education and Science grant 3.245.2014/r and the EU FP7 HiLumi LHC ' Grant Agreement 284404 In the frameworks of the High Luminosity Large hadron collider (HL-LHC) upgrade program an application of additional superconducting harmonic cavities operating at 800 MHz is currently under discussion. As a candidate, the two cavities with grooved beam pipes connected by the drift tube were suggested. In this article of measurements of Qload are performed for the aluminum model of array of two cavities connected by drift tube. Field distribution of Fundamental Mode (FM) and Higher Order Modes (HOM) were measured for aluminum prototype with a frequency of the operational mode of 2400 MHz, and their comparison with the simulation results. Higher order modes*
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WEPMB047	Higher Order Modes Couplers for 800 MHz Harmonic Cavity	2217
	Ya.V. Shashkov, R.V. Donetskiy, M. Gusarova, N.P. Sobenin MEPhI, Moscow, Russia
	Funding: Work supported by Ministry of Education and Science grant 3.245.2014/r For the higher order modes damping (HOM) in the 800 MHz superconducting single cell cavity the HOM coupler was developed. Several versions of the coupler design were shown. For the chain of two cavities with couplers the calculations of external Q-factor are presented. The calculations of multipactor discharge of cavity were also conducted. Higher order modes, Tesla, couplers*
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WEPMB048	Macros for Identification of Higher Order Modes Types, Their Transverse Shunt Impedance and Kick Factor	2220
	Ya.V. Shashkov MEPhI, Moscow, Russia A. Orlov NRNU, Moscow, Russia
	Funding: Work supported by Ministry of Education and Science grant 3.245.2014/r During the design studies of accelerating cavities one of the most time-consuming tasks is classification of the higher order modes (HOM) types. To automate the process of identification of HOM types special macros for CST Microwave studio was written. This article describes the programs algorithm of mode recognition and the results of the analysis on the example of single cell and 9 cell cavities. Macros for the calculation of the HOM transverse shunt impedance upon Q-factor values and kick-factor was also written. Higher order modes, electrodynamic characteristics, macros*
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WEPMB049	Transverse Defocusing Study in LPWA Channel for Linear and Bubble Modes	2224
	S.M. Polozov, V.I. Rashchikov, Ya.V. Shashkovpresenter MEPhI, Moscow, Russia
	Laser plasma wakefield acceleration (LPWA) is one of most popular novel trends of acceleration. The LPWA has two serous disadvantages as very high energy spread and low part of electrons capturing into acceleration. The waveguide and klystron type beam pre-modulation schemes was proposed , * to growth capturing and to limit the energy spectrum of 2-3 % for 200-300 MeV beam. One interesting effect was detected due to numerical simulation of beam dynamics in plasma channel. Not captured electrons are escape to the channel border fast and this effect should be explained. It was shown that such effect is caused by effective potential function which forms very high defocusing transverse field after its trailing edge. The results of such explanation verified by numerical simulations are discussed in report for linear and bubble LPWA modes. * S.M. Polozov. NIM A, 729, p.517-521, 2013 ** S.M. Polozov. Problems of Atomic Science and Technology. Series: Nuclear Physics Investigations, 6 (88), p. 29- 34, 2013
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WEPMB050	RF Test of ESS Superconducting Spoke Cavities at Uppsala University	2227
	H. Li, A.K. Bhattacharyya, V.A. Goryashko, L. Hermansson, R.J.M.Y. Ruber, R. Santiago Kern Uppsala University, Uppsala, Sweden N. Gandolfo, G. Olry IPN, Orsay, France
	The European Spallation Source (ESS) is an accelerator-driven neutron spallation source built in Sweden. It will deliver the first protons to a rotating tungsten target by 2019 and will reach the full 5 MW average beam power in the following years. The superconducting Spoke cavities are considered compact structures at low frequencies and having an excellent RF performance in both low and medium velocity regimes, therefore ESS will include a total of 26 double-spoke cavities. The testing of the double-spoke prototype cavity at high power has been conceded to Uppsala University, Sweden, where the Facility for Research Instrumentation and Accelerator development (FREIA) has been equipped with superconducting cavity test facility. A bare spoke cavity has been tested at the FREIA Laboratory with a self-exited loop at low power level to confirm its vertical test performance at IPNO. Similar test results as IPNO's previous test were obtained with FREIA system. In this paper we present the methods and preliminary study results of the cavity performance.
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WEPMB051	HIE-ISOLDE: First Commissioning Experience	2230
	W. Venturini Delsolaro, E. Bravin, N. Delruelle, M. Elias, J.A. Ferreira Somoza, M.A. Fraser, J. Gayde, Y. Kadi, G. Kautzmann, F. Klumb, Y. Leclercq, M. Martino, V. Parma, J.A. Rodriguez, S. Sadovich, E. Siesling, D. Smekens, L. Valdarno, D. Valuch, P. Zhang CERN, Geneva, Switzerland
	The HIE ISOLDE project [1] reached a major milestone in October 2015, with the start of the first physics run with radioactive ion beams. This achievement was the culminating point of intense months during which the first cryomodule of the HIE ISOLDE superconducting Linac and its high-energy beam transfer lines were first installed and subsequently brought into operation. Hardware commissioning campaigns were conducted in order to define the envelope of parameters within which the machine could be operated, to test and validate software and controls, and to investigate the limitations preventing the systems to reach their design performance. Methods and main results of the first commissioning of HIE ISOLDE post accelerator, including the performance of the superconducting cavities with beam, will be reviewed in this contribution.
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WEPMB052	System Integration and Beam Commissioning of the 500-MHz RF Systems for Taiwan Photon Source	2234
	Ch. Wang, L.-H. Chang, M.H. Chang, C.-T. Chen, L.J. Chen, F.-T. Chungpresenter, M.-C. Lin, Z.K. Liu, C.H. Lo, G.-H. Luo, C.L. Tsai, H.H. Tsai, M.H. Tsai, M.-S. Yeh, T.-C. Yu NSRRC, Hsinchu, Taiwan
	The accelerator complex of the Taiwan Photon Source (TPS) consists of two 500-MHz RF systems: one RF system with two KEKB-type single-cell SRF modules is operated for the 3-GeV storage ring of circumference 518 m, and the other with one five-cell Petra cavity at room temperature is for the concentric full-energy booster synchrotron. This report overviews the installation, system integration, commissioning, and initial operation of the 500-MHz RF systems for the TPS with emphasis on our solution to approach the highly reliable SRF operation at its maximum design beam current of 500-mA. Lessons learned during the project are reviewed.
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WEPMB053	Study of Third Harmonic Cavity for Taiwan Photon Source	2237
	Z.K. Liu, L.-H. Chang, M.H. Chang, L.J. Chen, PY. Chen, F.-T. Chungpresenter, M.-C. Lin, C.H. Lo, C.L. Tsai, M.H. Tsai, Ch. Wang, M.-S. Yeh, T.-C. Yu NSRRC, Hsinchu, Taiwan
	Taiwan Photon Source (TPS) is a modern light source with 3 GeV electron energy and low emittance. The bunch length is about 3 mm at designed beam current of 500 mA and operating gap voltage of 3.2 MV. The short bunch length results in short Touschek lifetime and high parasitic loss of insertion device (ID). Some of the undulators are operated in vacuum at TPS, therefore the head load become an important issue. To install higher harmonic cavity is a solution for improving the Touschek lifetime and the heat load by lengthening the bunch length. The effect of installing 3rd harmonic cavity for TPS is investigated. The expected maximum elongation factor for bunch lengthening, as well as the effect on the Touschek lifetime and heat load of ID are presented in this paper.
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WEPMB056	CVD Deposition of Nb Based Materials for SRF Cavities	2241
	P. Pizzol, P. Chalker, T. Heil The University of Liverpool, Liverpool, United Kingdom O.B. Malyshev, S.M. Pattalwar, R. Valizadehpresenter STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom G.B.G. Stenning STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	Bulk niobium cavities are widely employed in particle accelerators to create high accelerating gradient despite their high material and operation cost. Advancements in technology have taken bulk niobium close to its theoretical operational limits, pushing the research to explore novel materials, such as niobium based alloys. Nitrides of niobium offer such an alternative, exhibiting a higher Tc compared to bulk niobium. Replacing then the niobium with a material with better thermal conductivity, such as copper, coated with thin films of nitrides in a multilayer S-I-S would lead to improved performance at reduced cost. Physical vapour deposition (PVD) is currently used to produce these coatings, but it suffers from lack of conformity. This issue can be resolved by using chemical vapour deposition (CVD), which is able to produce high quality coatings over surfaces with a high aspect ratio. This project explores the use of CVD techniques to deposit NbN thin films starting from their chlorinated precursors. The samples obtained are characterized via SEM, FIB, XRD, and EDX.
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WEPMB057	First Results of Magnetic Field Penetration Measurements on Multilayer S-I-S Structures	2245
	O.B. Malyshev, K.D. Dumbell, L. Gurran, N. Pattalwar, S.M. Pattalwar, R. Valizadehpresenter STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom A.V. Gurevich ODU, Norfolk, Virginia, USA L. Gurran Lancaster University, Lancaster, United Kingdom L. Gurran Cockcroft Institute, Lancaster University, Lancaster, United Kingdom O.B. Malyshev, S.M. Pattalwar, R. Valizadehpresenter Cockcroft Institute, Warrington, Cheshire, United Kingdom
	The performance of superconducting RF cavities made of bulk Nb is limited by a breakdown field of Bp=~200 mT, close to the superheating field for Nb. A potentially promising solution to enhance the breakdown field of the SRF cavities beyond the intrinsic limits of Nb is a multilayer coating suggested in [1]. In the simplest case, such a multilayer may be a superconductor-insulator-superconductor (S-I-S) coating, for example, bulk niobium (S) coated with a thin film of insulator (I) followed by a thin layer of another superconductor (S) which could be e.g. dirty niobium [2]. Here we report the first results of our measurements of field penetration in Nb thin films and Nb-AlN-Nb multilayer samples at 4.2 K using the magnetic field penetration facility designed, built and tested in ASTeC.
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WEPMB058	LHC Crab Cavity Coupler Test Boxes	2248
	J.A. Mitchell Lancaster University, Lancaster, United Kingdom R. Apsimonpresenter, G. Burt, A.R.J. Tutte Cockcroft Institute, Lancaster University, Lancaster, United Kingdom R. Calaga, A. Macpherson, E. Montesinos CERN, Geneva, Switzerland S.D. Silva ODU, Norfolk, Virginia, USA B. P. Xiao BNL, Upton, Long Island, New York, USA
	The LHC double quarter wave (DQW) crab cavities have two different types of Higher Order Mode (HOM) couplers in addition to a fundamental power coupler (FPC). The FPC requires conditioning, so to achieve this we have designed a radio-frequency (RF) quarter wave resonator to provide high transmission between two opposing FPCs. For the HOM couplers we must ensure that the stop-band filter is positioned at the cavity frequency and that peak transmission occurs at the same frequencies as the strongest HOMs. We have designed two test boxes which preserve the cavity spectral response in order to test the couplers.
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WEPMB060	Modifications to the Pump Out Box to Lower the Qext of Diamond SCRF Cavities	2251
	S.A. Pande, C. Christou, P. Gu DLS, Oxfordshire, United Kingdom G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
	Diamond's CESR-B cavities are iris coupled and have fixed Qext. For reliability, the cavities are operated at lower voltages. This results in the optimum condition for beam loading being satisfied at a much lower power typically about 100 kW. For operation at 300 mA with two cavities, the RF power needed per system exceeds 200 kW. Consequently, the cavities need to be operated under-coupled. To lower the Qext and move the optimum operating point nearer to 200kW, 3 stub tuners are used in the waveguide feed line. The difference in the height of the coupling waveguide on cavity and that of the vacuum side waveguide on the window assembly results in a step transition which affects the Qext. The present window/step location results in Qext higher than that without the window. The Qext can be lowered by re-locating the RF window or by shifting the step change in the waveguide cross-section from its present location. This needs modification to the Pump Out box. The pros and cons of the proposed modification to the pump out box in terms of standing waves and multipacting characteristics studied with CST Studio are discussed in this paper.
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Paper

Title

Page

Design of the HWR Cavities for SARAF

2119

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

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

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WEPMB005

Manufacturing of the IFMIF Series Power Couplers

2122

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

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

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WEPMB006

XFEL Couplers RF Conditioning at LAL

2125

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

The industrialization and the RF conditioning of 800 power couplers for the European XFEL have been performed by LAL-Orsay from fall 2013 to spring 2016. LAL laboratory has in charge the industrial monitoring, the quality control and the RF conditioning of the couplers fabricated by two different suppliers. It was the first experience of coupler production at such scale. The faced challenges, the different issues, and the lessons learned during the mass production will be reported. And finally the huge amount of RF conditioning data will be shown as one of key point on the conditioning process.

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WEPMB007

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

2128

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

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

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WEPMB008

ESS DTL Mechanical Design and Prototyping.

2131

P. Mereu, M. Mezzano
INFN-Torino, Torino, Italy
D. Castronovo, R. Visintini
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
F. Grespan, A. Pisent, M. Poggi, C. R. Roncolato
INFN/LNL, Legnaro (PD), 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. In this paper the DTL mechanical design and simulations are presented, together with the results obtained from the prototypes of three drift tubes, equipped respectively with Permanent Magnet Quadrupole, Steerer and Beam Position Monitor.

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WEPMB009

Status of the Superconducting Cryomodules and Cryogenic System for the Mainz Energy-recovering Superconducting Accelerator MESA

2134

T. Stengler, K. Aulenbacher, F. Hug, D. Simon, P. Weber
IKP, Mainz, Germany
F. Schlander
ESS, Lund, Sweden
N. Wiehl
Johannes Gutenberg University Mainz, Institut of Nuclear Chemistry, Mainz, Germany

Funding: Work supported by the German Research Foundation (DFG) under the Cluster of Excellence "PRISMA"
SRF and the cryogenic system are mandatory for the operation of MESA at the Institut für Kernphysik at Johannes Gutenberg-Universität Mainz. The cryomodule production project is running for one year right now and the recent developments and measurements are presented. Further on the cryogenic concept required for the operation of MESA will be discussed.

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WEPMB011

ESS Medium and High Beta Cavity Prototypes

2138

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

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

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WEPMB012

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

2141

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

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

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WEPMB013

Long Term Cavity Performance in Compact-ERL Injector Cryomodule

2145

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

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

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WEPMB014

Cavity Performance of the Prototype KEK Superconducting RF Gun

2148

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

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

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WEPMB015

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

2151

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

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

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WEPMB016

Vertical Test Results of Nitrogen Doped SRF Cavities at KEK

2154

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

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

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WEPMB017

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

2158

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

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

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WEPMB018

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

2161

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

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

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WEPMB019

Magnetic Fields in Bulk, Film, and Multilayer Superconductors in Front of a Multi-turn Coil

2164

T. Kubo
KEK, Ibaraki, Japan

Funding: JSPS Young Scientists(B) #26800157, JSPS Challenging Exploratory Research #26600142, MEXT Photon and Quantum Basic Research Coordinated Development Program
The magnetic field distribution formulae in a bulk superconductor, a superconducting film, and an SIS multilayer structure in front of a multi-turn coil are derived, which may be useful for a detailed analysis in a vortex field measurement by using the third harmonic method.
* See for example the invited oral presentation by T. Kubo, "Theory of multilayer coating for proof-of-concept experiments", at SRF2015
** C.Z.Antoine et al., Appl. Phys. Lett. 102, 102603 (2013)

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WEPMB021

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

2167

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

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

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WEPMB023

Hydroforming SRF Three-cell Cavity from Seamless Niobium Tube

2170

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

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

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WEPMB024

Study on Nondestructive Inspections for Super-conducting Cavity

2174

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

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

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WEPMB025

Fabrication of Superconducting Spoke Cavity for Laser Compton Scattered Photon Sources

2177

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

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

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WEPMB026

MHI-MS's Production Activities of Superconducting Cavity

2180

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

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

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WEPMB028

High HOM Damping Structure Study for CEPC

2183

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

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

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WEPMB029

Research of Nitrogen Doping at IHEP

2186

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

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

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WEPMB030

Design Study of a Compact Deflecting Cavity at IHEP

2188

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

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

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WEPMB031

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

2191

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

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

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WEPMB032

Fabrication and Testing Status of IHEP03

2194

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

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

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WEPMB034

Analysis of Niobium Quality Control for SRF Cavity

2197

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

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

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WEPMB035

SRF Cavities for RAON

2200

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

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

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WEPMB036

High Pressure Rinsing for Niobium Superconducting Cavity

2202

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

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

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WEPMB039

Operation Techniques for HWR1 Cryomodule

2205

H. Kim, J.W. Choi, Y.W. Jo, W.K. Kim, Y. Kim, M. Lee
IBS, Daejeon, Republic of Korea

Control systems such as PLC and EPICS are developed for a half-wave resonator (HWR) cryomodule. PLC rack is fabricated for the HWR1 cryomodule. The PLC controls pumps, heaters and valves. The PLC communicates with temperature monitors through Ethernet. HMI of PLC and EPICS controls and monitors pumps, heaters, valves and temperature sensors through switching hub. The PLC HMI is developed and EPICS is also developed. The CSS of EPICS consists of control, monitor, parameter set-up, alarm and data browser screen.

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WEPMB041

Design of RF Power Coupler for RISP Half Wave Resonator

2208

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

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

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WEPMB044

Development of RF Conditioning System for RISP RF Power Couplers

2211

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

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

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB044

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WEPMB045

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

2214

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

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

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WEPMB047

Higher Order Modes Couplers for 800 MHz Harmonic Cavity

2217

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

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

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB047

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WEPMB048

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

2220

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

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

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB048

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WEPMB049

Transverse Defocusing Study in LPWA Channel for Linear and Bubble Modes

2224

S.M. Polozov, V.I. Rashchikov, Ya.V. Shashkovpresenter
MEPhI, Moscow, Russia

Laser plasma wakefield acceleration (LPWA) is one of most popular novel trends of acceleration. The LPWA has two serous disadvantages as very high energy spread and low part of electrons capturing into acceleration. The waveguide and klystron type beam pre-modulation schemes was proposed *, ** to growth capturing and to limit the energy spectrum of 2-3 % for 200-300 MeV beam. One interesting effect was detected due to numerical simulation of beam dynamics in plasma channel. Not captured electrons are escape to the channel border fast and this effect should be explained. It was shown that such effect is caused by effective potential function which forms very high defocusing transverse field after its trailing edge. The results of such explanation verified by numerical simulations are discussed in report for linear and bubble LPWA modes.
* S.M. Polozov. NIM A, 729, p.517-521, 2013
** S.M. Polozov. Problems of Atomic Science and Technology. Series: Nuclear Physics Investigations, 6 (88), p. 29- 34, 2013

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WEPMB050

RF Test of ESS Superconducting Spoke Cavities at Uppsala University

2227

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

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

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WEPMB051

HIE-ISOLDE: First Commissioning Experience

2230

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

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

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WEPMB052

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

2234

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

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

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WEPMB053

Study of Third Harmonic Cavity for Taiwan Photon Source

2237

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

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

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WEPMB056

CVD Deposition of Nb Based Materials for SRF Cavities

2241

P. Pizzol, P. Chalker, T. Heil
The University of Liverpool, Liverpool, United Kingdom
O.B. Malyshev, S.M. Pattalwar, R. Valizadehpresenter
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G.B.G. Stenning
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

Bulk niobium cavities are widely employed in particle accelerators to create high accelerating gradient despite their high material and operation cost. Advancements in technology have taken bulk niobium close to its theoretical operational limits, pushing the research to explore novel materials, such as niobium based alloys. Nitrides of niobium offer such an alternative, exhibiting a higher Tc compared to bulk niobium. Replacing then the niobium with a material with better thermal conductivity, such as copper, coated with thin films of nitrides in a multilayer S-I-S would lead to improved performance at reduced cost. Physical vapour deposition (PVD) is currently used to produce these coatings, but it suffers from lack of conformity. This issue can be resolved by using chemical vapour deposition (CVD), which is able to produce high quality coatings over surfaces with a high aspect ratio. This project explores the use of CVD techniques to deposit NbN thin films starting from their chlorinated precursors. The samples obtained are characterized via SEM, FIB, XRD, and EDX.

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WEPMB057

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

2245

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

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

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WEPMB058

LHC Crab Cavity Coupler Test Boxes

2248

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

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

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WEPMB060

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

2251

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

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

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB060

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