IPAC2015 - Classification: 7: Accelerator Technology / T07

Paper	Title	Page
MOYGB2	High Q Developments
	A. Grassellino Fermilab, Batavia, Illinois, USA
	This presentation will cover recent breakthroughs in the SRF field that have revolutionized the achievable quality factors in bulk niobium cavities. It will cover two main breakthroughs: one involving the controlled nitrogen doping of the niobium cavity surface, and second the efficient magnetic flux expulsion from the niobium walls via controlled cavity cooling though transition temperature. The talk will give an overview from the discovery of these effects at FNAL to the development into a cryomodule ready technology by the partner labs Cornell, Jlab, FNAL and SLAC for implementation in the LCLS-2 accelerator. New results will be presented from surface analysis, cavity diagnostics tools and very high Q obtained in dressed cavities in cryomodule environment.
	Slides MOYGB2 [11.862 MB]
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOBD2	Design and Prototyping of HL-LHC Double Quarter Wave Crab Cavities for SPS Test	64
	S. Verdú-Andrés, S.A. Belomestnykh, I. Ben-Zvi, J. Skaritka, Q. Wu, B. P. Xiao BNL, Upton, Long Island, New York, USA L. Alberty, K. Artoos, R. Calaga, O. Capatina, T. Capelli, F. Carra, N. Kuder, R. Leuxe, C. Zanoni CERN, Geneva, Switzerland S.A. Belomestnykh, I. Ben-Zvi Stony Brook University, Stony Brook, USA Z. Li SLAC, Menlo Park, California, USA A. Ratti LBNL, Berkeley, California, USA
	Funding: Work supported by US DOE via US LARP program, through BSA LLC contract No.DE-AC02-98CH10886 and by EU FP7 HiLumi LHC grant No.284404. Used NERSC resources by US DOE contract No.DE-AC02-05CH11231. The LHC high luminosity project envisages the use of the crabbing technique for increasing and levelling the LHC luminosity. Double-Quarter Wave (DQW) resonators are compact cavities especially designed to meet the technical and performance requirements for LHC beam crabbing. A couple of DQW crab cavities are under preparation and will be tested with beam in the Super Proton Synchrotron (SPS) of CERN by 2017. This paper describes the design and prototyping of DQW crab cavities for the SPS test.
	Slides MOBD2 [6.909 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOBD2
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA010	First Test Results of the BERLinPro 2-cell Booster Cavities	2765
	A. Burrill, W. Anders, A. Frahm, J. Knobloch, A. Neumann HZB, Berlin, Germany G. Ciovati, W.A. Clemens, P. Kneisel, L. Turlington JLab, Newport News, Virginia, USA
	The BERLinPro Energy Recovery Linac (ERL) is currently being built at Helmholtz-Zentrum Berlin in order to study the physics of operating a high current, a 100 mA, 50 MeV ERL utilizing all SRF cavity technology. This machine will utilize three unique SRF cryomodules for the photoinjector, booster and linac cryomodules respectively. The focus of this paper will be on the cavities contained within the booster cryomodule. Here there will be three 2-cell SRF cavities, based on the original design by Cornell University, but optimized to meet the needs of the project. All of the cavity fabrication, processing and testing was carried out at Jefferson Laboratory where 4 cavities were produced and the 3 cavities with the best RF performance were fitted with helium vessels for installation in the cryomodule. This paper will report on the test results of the cavities as measured in the vertical testing dewar at JLab after fabrication and again after outfitting with the helium vessels.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA010
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA011	First Horizontal Test Results of the HZB SRF Photoinjector for BERLinPro	2768
	A. Burrill, W. Anders, A. Frahm, J. Knobloch, A. Neumann HZB, Berlin, Germany G. Ciovati, W.A. Clemens, P. Kneisel, L. Turlington JLab, Newport News, Virginia, USA
	The BERLinPro project, a small superconducting RF (SRF) c.w. energy recovery linac (ERL) is being built at Helmholtz-Zentrum Berlin in order to develop the technology required for operation of a high current, 100 mA, 50 MeV ERL. The electron source for the accelerator is a 1.4 cell SRF photoinjector fitted with a multi-alkali photocathode. As part of the HZB photoinjector development program three different SRF photoinjectors will be fabricated and tested. The photoinjector described herein is the second cavity that has been fabricated, and the first photoinjector designed for use with a multi-alkali photocathode. The photoinjector has been built and tested at JLab and subsequently shipped to HZB for testing in the horizontal test cryostat HoBiCaT prior to installation in the photoinjector cryomodule. This cryomodule will be used to measure the photocathode operation in a dedicated experiment called GunLab, the precursor to installation in the BERLinPro hall. This paper will report on the final results of the cavity installed in the helium vessel in the vertical testing dewar at Jefferson Lab as well as the first horizontal test in HoBiCaT
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA011
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA012	High-Q Cavity Operation: Study on the Thermoelectrically Induced Contribution to RF Surface Resistance	2771
	J.M. Köszegi, J. Knobloch, O. Kugeler, A. Neumann, A.V. Vélez HZB, Berlin, Germany
	We present a study concerning the operation of a superconducting RF cavity (non-doped niobium) in horizontal testing with the focus on understanding the thermoelectrically induced contribution to the surface resistance. Starting in 2009, we suggested a means of reducing the residual resistance by warming up a cavity after initial cooldown to about 20K and cooling it down again. In subsequent studies we used this technique to manipulate the residual resistance by more than a factor of 2. We postulated that thermocurrents during cooldown generate additional trapped magnetic flux that impacts the cavity quality factor. Since several questions remained open, we present here a more extensive study including measurement of two additional passband modes of the 9-cell cavity that confirms the effect. We also discuss simulations that substantiate the claim. While the layout of the cavity LHe tank system is cylindrically symmetric, we show that the temperature dependence of the material parameters result in a non-symmetric current distribution. Hence a significant amount of magnetic flux can be generated at the RF surface resulting in an increased surface resistance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA012
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA013	Hom Damping Optimization Design Studies for BESSY VSR Cavities	2774
	A.V. Vélez, H.-W. Glock, J. Knobloch, A. Neumann HZB, Berlin, Germany
	The BESSY VSR project is a future upgrade of the 3rd generation BESSY II light source. By using the same "standard" user optics, simultaneously long (ca. 15ps) and short (ca. 1.5ps) bunches will be stored. Thus, superconducting higher harmonic cavities of the fundamental 500 MHz at two frequencies need to be installed in the BESSY II storage ring. This work describes the optimizations studies for the Waveguide-based HOM dampers and the adjustable fundamental power coupler for the 1.5 GHz first SRF cavity prototype.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA013
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA026	Higher Order Mode Propagation and Damping Studies on Axisymmetric Superconducting Multicell RF-Resonators	2812
	B.D. Isbarn, B. Riemann, M. Sommer, T. Weis DELTA, Dortmund, Germany
	Funding: Work supported by the BMBF under contract no. 05K13PEB Higher order mode (HOM) propagation and damping is a major concern in feasibility studies regarding the upcoming upgrade of BESSY II, named BESSY-VSR, which involves the utilization of superconducting multicell RF-resonators in a storage ring while maintaining a reasonably high beam current typical for third generation synchrotron radiation facilities. In addition to the computation of the typical figures of merit, we focus on studies of the mode propagation in axisymmetric structures. Due to the focus on axisymmetric studies we are able to use 2D codes to investigate in eigenmodes with substantial higher frequencies than usually considered with full 3D codes in parametric studies. In this work we present preliminary studies involving mode propagation in superconducting elliptical multicell cavities. G. Wüstefeld et al., Proc. of IPAC'11, San Sebastián, THPC014
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA026
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA035	Low- and High-Beta SRF Elliptical Cavity Stiffening	2835
	E.N. Zaplatin FZJ, Jülich, Germany A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio, USA V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	Elliptical SRF cavities are the main accelerating structures in many accelerators worldwide. Different types of external loads on the resonator walls predetermine the main working conditions of the SC cavities. The most important of them are very high electromagnetic fields that result in strong Lorentz forces and the pressure on cavity walls from the helium tank that also deforms the cavity shape. Also mechanical eigen resonances of cavities are the main source of the microphonics. To withstand any kind of external loads on the resonator walls different schemes of the cavity stiffening were applied. In the paper we report the basic investigations of the cavity stiffening using FNAL 650 MHz β=0.92 and 0.61 as an example. The single-cell investigation results were used as the reference to develop the ultimate scheme of the helium vessel structure to ensure the best resonator stability.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA035
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA036	Double-Cell Notch Filter for SRF Gun Investigations	2838
	E.N. Zaplatin FZJ, Jülich, Germany A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio, USA J. Knobloch, A. Neumann HZB, Berlin, Germany V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	Some projects of SRF guns apply the design where the cathode can be easily and quickly removed. One of the disadvantages of this design is the RF power leakage from the accelerating gun cavity cells to the cathode housing that results in the excessive cathode heating. To minimize the RF power leak different kinds of choke filters are used to protect the cathode structure. These choke filters represent resonant circuits with a zero input impedance and installed at the entrance of the cathode structure that shunt the cathode housing. Still, since the choke filter frequency shift under working conditions is bigger than its bandwidth a filter tuning during assembly only in the warm stage seems insufficient and requires also fine-tuning during operation. To eliminate the problems of the choke filter fine-tuning and hence ensure its stability during operation, a combination of the resonance choke elements can be implemented. In the paper we demonstrate advantages of the double-cell notch filter using BERLinPro SRF gun cavity as an example with its simple design modifications.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA036
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA037	Manufacturing and First Test Results of Euclid SRF Conical Half-wave Resonator	2841
	E.N. Zaplatin FZJ, Jülich, Germany C.H. Boulware, T.L. Grimm, A. Rogacki Niowave, Inc., Lansing, Michigan, USA A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio, USA V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	Funding: This Work is supported by the DOE SBIR Program, contract # DE-SC0006302. Euclid TechLabs has developed a superconducting conical half-wave resonator (162.5 MHz β=v/c=0.11) for the high-intensity proton accelerator complex proposed at Fermi National Accelerator Laboratory. The main objective of this project is to provide a resonator design with high mechanical stability based on an idea of the balancing cavity frequency shifts caused by external loads. A unique cavity side-tuning option has been successfully implemented. Niowave, Inc. proposed a complete cavity production procedure including preparation of technical drawings, processing steps and resonator high-gradient tests. During manufacturing a series of cavity and helium vessel modifications to simplify their manufacturing were proposed. Following standard buffered chemical polish surface treatment and high-pressure rinse, a vertical test was carried out at Niowave’s facilities. Here we present the status of the project and the first high-gradient results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA037
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA041	1.3 GHz SRF Cryomodules for the Mainz Energy-recovering Superconducting Accelerator MESA	2853
	F. Schlander, K. Aulenbacher, R.G. Heine, D. Simon, T. Stengler IKP, Mainz, Germany
	Funding: Work supported by the German Federal Ministery of Education and Research (BMBF) and German Research Foundation (DFG) under the Cluster of Excellence "PRISMA" The Mainz Energy-recovering Superconducting Accelerator MESA requires superconducting RF systems that provide sufficient energy of 50 MeV per turn to an electron beam. The ordering process of two Rossendorf-type cryomodules, containing two 9-cell 1.3 GHz XFEL-like cavities each, is in progress. Besides an overview of the adaptations required for the multipass and high current beam operation of the cryomodules, details about challenges regarding the installation of the cryomodules on the premises of the Institut für Kernphysik at Universität Mainz are given.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA041
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA046	Studies on Innovative Production methods of HOM Coupler for SRF 9-cell Cavity	2869
	K. Nohara, N. Kawabata, K. Miyajima, M. Shinohara SPS, Funabashi-shi, Japan H. Hayano, S. Kato, T. Saeki, A. Yamamoto, M. Yamanaka KEK, Ibaraki, Japan
	Pure Nb as the material of SRF cavity bears hard workability in general. This is why both the inner and outer conductors of HOM coupler for 9-cell cavity have been conventionally produced by full machining, backward extrusion accompanied with annealing and so on. However, in the mass production of 9-cell cavities in ILC, further cost reduction is required. We produced both the inner and outer conductors of HOM coupler for 9-cell cavity in the advanced press forming methods aiming at cost reduction. Press forming of a pure Nb sheet for the outer conductor of HOM coupler was performed with fewer processes free from intermediate annealing and primary machining. For the inner conductor of HOM coupler, water jet cutting and press cold-forging of a plate was performed. The above advanced press forming methods showed favored results, leading to a possibility of simple mass-production of components and cost reduction. The vertical test on a 9-cell cavity with the press formed HOM couplers achieved 36 MV/m that is beyond ILC qualification. The R＆D works are ongoing for further improvement.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA046
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA048	Development for Mass Production of Superconducting Cavity by MHI	2876
	T. Yanagisawa, H. Hara, K. Kanaoka, K. Okihira, K. Sennyu MHI, Hiroshima, Japan
	Mitsubishi Heavy Industries (MHI) have developed manufacturing process of superconducting cavitis for a long time. In this presentation, recent progress will be reported.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA048
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA053	Multipactor Simulations in 325 MHz Superconducting Spoke Cavity for an Electron Accelerator	2892
	T. Kubo, T. Saeki KEK, Ibaraki, Japan E. Cenni, Y. Iwashita, H. Tongu Kyoto ICR, Uji, Kyoto, Japan R. Hajima, M. Sawamura JAEA, Ibaraki-ken, 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 with the laser-Compton scattering, a 325MHz superconducting spoke cavity for an electron accelerator operated at 4K is under development. After design-optimizations of the first cavity, we started fabrication process. In this paper, multipactor analyses carried out as parts of the design-optimization efforts are briefly summarized. Relations between cavity geometries and averaged secondary electron emission yield are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA053
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA054	A Disturbance-Observer-based Controller for LLRF Systems	2895
	F. Qiu, D.A. Arakawa, Y. Honda, H. Katagiri, T. Matsumoto, S. Michizono, T. Miura, T. Obina KEK, Ibaraki, Japan S.B. Wibowo Sokendai, Ibaraki, Japan
	Digital low-level radio frequency (LLRFs) systems have been developed and evaluated in the compact energy recovery linac (cERL) at KEK. The required RF stabilities are 0.1% rms in amplitude and 0.1° rms in phase. These requirements are satisfied by applying digital LLRF systems. To further enhance the control system and make it robust to disturbances such as large power supply (PS) ripples and high-intensity beams, we have designed and developed a disturbance observer (DOB)-based control method. This method utilizes the RF system model, which can be acquired using modern system identification methods. Experiments show that the proposed DOB-based controller is more effective in the presence of high disturbances compared with the conventional proportional and integral (PI) controller. In this paper, we present the preliminary results based on the experiments with DOB-based controller.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA054
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA056	Development of Superconducting Spoke Cavities for Laser Compton Scattered X-ray Sources	2902
	R. Hajima, M. Sawamura JAEA, Ibaraki-ken, Japan E. Cenni, Y. Iwashita, H. Tongu Kyoto ICR, Uji, Kyoto, Japan T. Kubo, T. Saeki KEK, Ibaraki, Japan
	Funding: This study is supported by Photon and Quantum Basic Research Coordinated Development Program of MEXT, Japan. A 5-year research program on the development of superconducting spoke cavities for electron accelerators has been funded by MEXT, Japan since 2013. The purpose of our program is establishing design and fabrication processes of superconducting spoke cavity optimized for compact X-ray sources based on laser Compton scattering. The spoke cavity is expected to realize a compact industrial-use X-ray source with a reasonable cost and easy operation. We have chosen a cavity frequency at 325 MHz due to possible operation at 4 K and carried out cavity shape optimization in terms of electromagnetic and mechanical properties. Production of press-forming dies is also in progress. In this paper, we present overview and up-to-date status of the research program.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA056
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA060	The Development of Cavity Frequency Tracking Type RF Control System for SRF-TEM	2914
	N. Higashi The University of Tokyo, Graduate School of Science, Tokyo, Japan A. Enomoto, Y. Funahashi, T. Furuya, X.J. Jin, Y. Kamiya, S. Michizono, M. Nishiwaki, H. Sakai, M. Sawabe, K. Ueno, M. Yamamoto KEK, Ibaraki, Japan M. Kuriki HU/AdSM, Higashi-Hiroshima, Japan S. Yamashita ICEPP, Tokyo, Japan
	Superconducting accelerating cavities used in high-energy accelerators can generate high electric fields of several 10 MV/m by supplying radio frequency waves (RF) with frequencies matched with resonant frequencies of the cavities. Generally, frequencies of input RFs are fixed, and resonant frequencies of cavities that are fluctuated by Lorentz force detuning and Microphonics are corrected by feedbacks of cavity frequency tuners and input RF power. Now, we aim to develop the cavity frequency tracking type RF control system where the frequency of input RF is not fixed and consistently modulated to match the varying resonant frequency of the cavity. In KEK (Tsukuba, Japan), we are developing SRF-TEM that is a new type of transmission electron microscope using special-shaped superconducting cavity. By applying our new RF control system to the SRF-TEM, it is expected to obtain stable accelerating fields so that we can acquire good spatial resolution. In this presentation, we will explain the required stabilities of accelerating fields for SRF-TEM and the feasibility of SRF-TEM in the case of applying the cavity frequency tracking type RF control system.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA060
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN012	Cathode Stalk Optimization for a 325 MHz Superconducting QWR Electron Gun	2940
	P.L. Fan, Y.M. Li, L. Lin, K.X. Liu, S.W. Quan, F. Zhu PKU, Beijing, People's Republic of China
	Funding: Work supported by National Basic Research Project (No. 2011CB808302) The structure of cathode stalk is very important for the performance of a superconducting QWR (Quarter Wave Resonator) gun. With improper design, RF power dissipation on the surface of cathode stalk and its surrounding tube can lead to a serious decrease of quality factor for superconducting QWR injector. We present here an optimized design of the cathode stalk for the 325 MHz superconducting QWR gun and special considerations are taken to minimize the power dissipation. The details of microwave simulation, beam dynamic simulation of the cavity with cathode stalks in different length, diameter and position are presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN012
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN013	Development of DC-SRF Injector at Peking University	2944
	J.K. Hao, J.E. Chen, P.L. Fan, L.W. Feng, S. Huang, L. Lin, K.X. Liu, S.W. Quan, F. Wang, Zh.W. Wang, X.D. Wen, H.M. Xie, K. Zhao, F. Zhu PKU, Beijing, People's Republic of China
	DC-SRF electron injector, which combines a DC Pierce gun and a 3.5 cell 1.3 GHz superconductor cavity in a cryomodule, has been developed at Peking University. Based on the improvements of beam line, LLRF system and 2K cryogenic system, stable operation of the DC-SRF injector has been carried out recently. Electron beams with 3.4 MeV energy and the currents of ~1mA in a macro-pulse mode was obtained. As the first application of this DC-SRF injector, THz radiation produced with a 10 period undulator was also detected. The description of the experiment process and results will be presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN013
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN024	Exploration of Multi-fold Symmetry Element-loaded Superconducting Radio Frequency Structure for Reliable Acceleration of Low- & Medium-Beta Ion Species	2978
	S.C. Huang IMP/CAS, Lanzhou, People's Republic of China R.L. Geng JLab, Newport News, Virginia, USA
	Reliable acceleration of low- to medium-beta proton or heavy ion species is needed for future high current superconducting radio frequency accelerators. Due to the high-Q nature of a superconducting RF resonator, it is sensitive to many factors such as loading variation (from either the accelerated beam or from parasitic field emitted electrons), mechanical vibration, and liquid helium bath pressure fluctuation etc. To increase the stability against those factors, a mechanically strong and stable RF structure is desirable. Guided by this consideration, multi-fold symmetry element-loaded superconducting radio frequency structures, cylindrical tanks with multiple (n>=3) rod-shaped radial elements, are being explored. The top goal of its optimization is to improve mechanical stability. A natural consequence of this structure is a lowered ratio of the peak surface electromagnetic field to the acceleration gradient as compared to the traditional spoke cavity. A disadvantage of this new structure is an increased size for a fixed resonant frequency and optimal beta. This paper describes the optimization of EM design and preliminary mechanical analysis for such structures.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN024
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN030	Testing Procedures for Fast Frequency Tuners of XFEL Cavities	2991
	K.P. Przygoda, W. Cichalewski, T. Pożniak TUL-DMCS, Łódź, Poland J. Branlard, O. Hensler, H. Schlarb, Ch. Schmidt DESY, Hamburg, Germany K. Kasprzak IFJ-PAN, Kraków, Poland
	The XFEL accelerator will be equipped with 100 accelerating modules. Each accelerating module will host 8 superconducting cavities. Every single cavity will be equipped with a mechanical tuner. Coarse tuning will be supported by a step motor; fine tuning will be handled by double piezoelectric elements installed inside a single mechanical support, providing actuator and sensor functionality or redundancy. Before the main linac installation, all its subcomponents need to be tested and verified. The AMTF (Accelerator Module Test Facility) has been built at DESY to test all XFEL cryomodules. In total 1600 piezos need to be tested. Test procedures for fast frequency tuners have been developed to check their basic performance in cryogenic conditions (tuning range, polarity, acting and sensing abilities). High level applications perform fully automated tests including report generation. After the successful completion of the acceptance tests, the cryomodules will be prepared for tunnel installation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN030
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN031	Automated Quench Limit Test Procedure for Serial Production of XFEL RF Cavities	2994
	K. Kasprzak, D. Konwisorz, K. Krzysik, S. Myalski, J. Świerbleski, K. Turaj, M. Wiencek, A. Zwozniak IFJ-PAN, Kraków, Poland D. Kostin, K.P. Przygoda DESY, Hamburg, Germany
	In the Accelerator Module Test Facility (AMTF) at DESY in Hamburg RF cavities and accelerating cryomodules are tested for the European X-ray Free Electron Laser (XFEL). Measurements are done by a team of physicists, engineers and technicians from The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences in Kraków, Poland, as a part of Polish in-kind contribution to the XFEL. The testing procedures providing information about maximum available gradient and heat loads measurement are performed for the high gradients (up to 31MV/m). During these tests the cavity deformation caused by the Lorentz force is compensated by piezo (fast) tuners. For this purpose automated high level software was developed. This paper describes a method used to tune automatically the cavities during the RF tests. It was validated with the XFEL cryomodules. This improvement was implemented into the testing software and it is successfully used for testing of serial production cavities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN031
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN034	Electron Emission from Surface Roughness on Cavity in Low Temperature	3003
	H. Kim, H.J. Cha, S. Choi, W.K. Kim, G.-T. Park IBS, Daejeon, Republic of Korea Y. Chang Hanshin University, Kyungki, Republic of Korea
	Electron emission phenomenon from surface roughness on cavity is investigated. The distribution of the electric field from the surface roughness can be obtained on cavity surface. The field emission is calculated from the electric field distribution. The generalized electron emission from electric field and temperature effect is also calculated on the surface roughness of the cavity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN034
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN039	RF Accelerating Voltage of PLS-II Superconducting RF System for Stable Top-up Operation with Beam Current of 400 mA	3015
	Y.D. Joo, M.-H. Chun, T. Ha, I. Hwang, B.-J. Lee, I.S. Park, S. Shin, Y.U. Sohn, I.H. Yu PAL, Pohang, Kyungbuk, Republic of Korea
	During the beam store test up to 400 mA in the storage ring, it was observed that the vacuum pressure around the RF window of the superconducting cavity rapidly increases over the interlock level limiting the availability of the maximum beam current storing. We investigated the cause of the window vacuum pressure increment by studying the changes in the electric field distribution at the superconducting cavity and waveguide according to the beam current. An equivalent physical modeling was developed using a finite-difference time-domain (FDTD) simulation and it revealed that the electric field amplitude at the RF window is exponentially increased as the beam current increases, thus this high electric field amplitude causes a RF breakdown at the RF window.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN039
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN042	400 mA Beam Store with Superconducting RF Cavities at PLS-II	3021
	Y.U. Sohn, M.-H. Chun, T. Ha, M.S. Hong, Y.D. Joo, H.-S. Kang, H.-G. Kim, K.R. Kim, T.-Y. Lee, C.D. Park, H.J. Park, I.S. Park, S. Shin, I.H. Yu, J.C. Yun PAL, Pohang, Kyungbuk, Republic of Korea
	Funding: Minister of Science, ICT and Future Planning Three superconducting RF cavities were commissioned with electron beam in way of one by one during the last 3 years, and now PLS-II is in user service on the way of beam current to 400mA, the target of PLS-II. The cavities and cryomodules were prepared with SRF standard technology and procedures, then vertical test, windows conditioning, cryogenic test in each cryomodule, horizontal power test, conditioning, and commissioning without and with beam at PLS-II tunnel by collaboration with industries. All the cavities showed stable performances as good as not-observing any RF instability from cavities, couplers and windows up to 400 mA beam store, but observing several cavity quenches and minor vacuum bursts by abrupt power with control and human errors. The initial beam current for user run were recorded as 150 mA with one cavity, 280 mA with two cavities and 320 mA with three cavities. The 400 mA beam was also achieved with two cavities by decay mode and also with three cavities by top-up mode. The stabilities of RF amplitude and phase are good enough not to induce beam instabilities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN042
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN043	The RF Stability of PLS-II Storage Ring RF System	3024
	I.H. Yu, M.-H. Chun, M.H. Jeong, Y.D. Joo, H.-S. Kang, H.-G. Kim, H.J. Park, I.S. Park, Y.U. Sohn PAL, Pohang, Kyungbuk, Republic of Korea Y.S. Lee SKKU, Suwon, Republic of Korea
	Funding: Minister of Science, ICT and Future Planing The RF system for the Pohang Light Source (PLS) storage ring was greatly upgraded for PLS-II project of 400mA, 3.0GeV from 200mA, 2.5GeV. Three superconducting RF cavities with each 300kW maximum klystron amplifier were commissioned with electron beam in way of one by one during the last 3 years for beam current of 400mA to until March 2014. The RF system is designed to provide stable beam through precise RF phase and amplitude requirements to be less than 0.3% in amplitude and 0.3° in phase deviations. This paper describes the RF system configuration, design details and test results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN043
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN046	Compassion of Higher Order Modes Damping Techniques for Superconducting 9-Cell Structure	3030
	Ya.V. Shashkov, A.A. Mitrofanov, N.P. Sobenin MEPhI, Moscow, Russia V. Zvyagintsev TRIUMF, Vancouver, Canada
	Funding: Work supported by Ministry of Education and Science grant 3.245.2014/r Modern types of accelerators, such as Energy recovery linacs, require low values of higher order modes (HOM) Qext. In accelerators with high current HOM could lead to high losses for the modes excitation, beam instability and beam break up. HOM couplers and waveguides are often used in such structures for HOM damping. Unfortunately they could lead to a violation of the axial symmetry of the accelerating field and negatively affect the beam emittance. Also these devices are subject for multipactor discharge and could be difficult in maintaining and fabrication. In this paper we examine several ways of HOM damping with ridged, fluted and corrugated drift tubes which are devoid of the above-mentioned drawbacks. The influence of the parameters of the drift tube on the HOM damping and on the parameters of the fundamental wave were analyzed. Higher order modes, ERL, SRF
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN046
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN047	Suppression of Higher Order Modes in an Array of Cavities Using Waveguides	3033
	Ya.V. Shashkov, N.P. Sobenin MEPhI, Moscow, Russia M. Zobov INFN/LNF, Frascati (Roma), Italy
	Funding: Work is supported by Ministry of Education and Science grant 3.245.2014/r и and by the EU FP7 HiLumi LHC - Grant Agreement 284404 In the frameworks of the High Luminosity LHC upgrade program an application of additional harmonic cavities operating at multiplies of the main RF system frequency of 400 MHz is currently under discussion. A structure consisting of two 800 MHz single cell superconducting cavities with grooved beam pipes coupled by drift tubes has been suggested for implementation. However, it is desirable to increase the number of single cells installed in one cryomodule in order to decrease the number of transitions between “warm” and “cold” parts of the collider vacuum chamber. Unfortunately it can lead to the appearance of higher order modes (HOM) trapped between the cavities. In order to solve this problem the methods of HOM damping with rectangular waveguides connected to the drift tubes were investigated and compared. In this paper we describe the results obtained for arrays of 2, 4 and 8 cavities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN047
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN052	A New RF Laboratory for Developing Accelerator Cavities at the University of Huelva	3046
	I. Martel, C. Bonțoiu, J.A. Dueñas, D. Gordo-Yáñez, A.K. Orduz, J. Sanchez-Segovia University of Huelva, Huelva, Spain
	The University of Huelva is presently involved in R&D projects for developing RF accelerator cavities. Two types of cavities are presently under design, a prototype of room temperature RFQ injector and a quarter-wave resonator for high intensity heavy-ion linear accelerators. The laboratory is equipped with dedicated test-bench for RF measurements, which includes high-power RF generators, network analyzer, amplifiers and power meters. A clean room is also available having a dedicated space for high-precision mechanical metrology and cavity mounting, together with a vertical cryostat for superconducting cavity test.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN052
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN065	Progress at the FREIA Laboratory	3072
	M. Olvegård, A.K. Bhattacharyya, T.J.C. Ekelöf, J. Eriksson, K. Fransson, K.J. Gajewski, V.A. Goryashko, L. Hermansson, M. Holz, M. Jacewicz, M. Jobs, Å. Jönsson, H. Li, T. Lofnes, H. Nicander, R.J.M.Y. Ruber, R. Santiago Kern, R. Wedberg, V.G. Ziemann Uppsala University, Uppsala, Sweden D.S. Dancila, A. Rydberg Uppsala University, Department of Engineering Sciences, Uppsala, Sweden R.A. Yogi ESS, Lund, Sweden
	The FREIA Facility for Research Instrumentation and Accelerator Development at Uppsala University, Sweden, has reached the stage where the testing of superconducting cavities for the European Spallation Source (ESS) is starting. The new helium liquefaction plant has been commissioned and now supplies a custom-made, versatile horizontal cryostat, HNOSS, with liquid helium at up to 140 l/h. The cryostat has been designed and built to house up to two accelerating cavities, or, later on, other superconducting equipment such as magnets or crab cavities. A prototype cavity for the spoke section of the ESS linac will arrive mid 2015 for high-power testing in the horizontal cryostat. Two tetrode-based commercial RF power stations will deliver 400 kW peak power each, at 352 MHz, to the cavity through an RF distribution line developed at FREIA. In addition, significant progress has been made with in-house development of solid state amplifier modules and power combiners for future use in particle accelerators. We report here on these and other ongoing activities at the FREIA laboratory.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN065
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPHA013	The Assembly Experience of the First Cryo-module for HIE-ISOLDE at CERN	3131
	Y. Leclercq, G. Barlow, J.A. Bousquet, A. Chrul, P. Demarest, J-B. Deschamps, J.A. Ferreira Somoza, J. Gayde, M. Gourragne, A. Harrison, G. Kautzmann, D. Mergelkuhl, V. Parma, M. Struik, M. Therasse, L.R. Williams CERN, Geneva, Switzerland J. Dequaire Intitek, Lyon, France
	The HIE ISOLDE project aims at increasing the energy of the radioactive ion beams of the existing REX ISOLDE facility from the present 3 MeV/u up to 10 MeV/u for A/q to 4.5. The upgrade includes the installation of a superconducting linac in successive phases, for a final layout containing two low-β and four high-β cryo-modules. The first phase involves the installation of two high-B cryo-modules, each housing five high- β superconducting cavities and one superconducting solenoid, aligned within tight tolerances. After having designed and procured the cryo-module components, the first units is now being assembled at CERN, in a dedicated facility including class100 (ISO5) clean rooms equipped with specific tooling. The assembly is foreseen to be ultimate and the cryo-module cold tested by May 2015. In this paper, after a brief description of the main design features of the cryo-module , we present the assembly of the first unit, including the methodology, special tools, assembly procedures and quality assurance aspects. We report on the experience from this first assembly, including tests results, and present prospects for the next-coming cryo-module assemblies.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA013
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPHA021	Status of HIE-ISOLDE SC Linac Upgrade	3151
	A. Sublet, L. Alberty, K. Artoos, S. Calatroni, O. Capatina, M.A. Fraser, N.M. Jecklin, Y. Kadi, P. Maesen, G.J. Rosaz, K.M. Schirm, M. Taborelli, M. Therasse, W. Venturini Delsolaro, P. Zhang CERN, Geneva, Switzerland
	The HIE-ISOLDE upgrade project at CERN aims at increasing the energy of radioactive beams from 3MeV/u up to 10 MeV/u with mass-to-charge ratio in the range 2.5-4.5. The objective is obtained by replacing part of the existing normal conducting linac with superconducting Nb/Cu cavities. The new accelerator requires the production of 32 superconducting cavities in three phases: 10 high-beta cavities for phase 1 (2016), 10 high-beta cavities for phase 2 (2017) and possibly 12 low-beta cavities for phase 3 (2020). Half of the phase 1 production is completed with 5 quarter-wave superconducting cavities ready to be installed in the first cryomodule. The status of the cavity production and the RF performance are presented. The optimal linac working configuration to minimize cryogenic load and maximize accelerating gradient is discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPHA022	Characterization of Nb Coating in HIE-ISOLDE QWR Superconducting Accelerating Cavities by means of SEM-FIB and TEM	3155
	B. Bártová, S. Calatroni, A. Sublet, M. Taborelli CERN, Geneva, Switzerland A.B. Aebersold, D.T.L. Alexander, M. Cantoni EPFL, Lausanne, Switzerland
	The Quarter Wave Resonators (QWR) high-β cavities (0.3m diameter and 0.9m height) are made from OFE 3D-forged copper and are coated by DC-bias diode sputtering with a thin superconducting layer of niobium. The Nb film thickness, morphology, purity and quality are critical parameters for RF performances of the cavity. They have been investigated in a detailed material study. The coating structure at different positions along a test cavity was observed by cross-section imaging using SEM-FIB instrument. The samples from the top of the cavity showed presence of unexpected porosities, whose volume was investigated using FIB tomography. TEM lamella was prepared for two samples (top part and inner conductor of the cavity) to study in detail the grain orientation in the coating, its chemical composition and structure. The 14-layer structure in thick coating was indeed evidenced by the TEM analysis. Chemical mapping revealed the presence of a few nm in size copper precipitates close to the Nb/Cu interface and a passivating oxide layer of 10 nm thickness on top of the coating and around porosities. However no impurities or interface layer along the coating profile were present.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA022
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPHA045	Design and Construction of the RF Electronic System at Taiwan Photon Source	3215
	F.-T. Chung, L.-H. Chang, M.H. Chang, L.J. Chen, PY. Chen, M.-C. Lin, Z.K. Liu, C.H. Lo, C.L. Tsai, M.H. Tsai, Ch. Wang, M.-S. Yeh, T.-C. Yu NSRRC, Hsinchu, Taiwan
	The RF electronic system at NSRRC was made fully in house by the RF group from design through construction to completion. The first RF electronic system includes an analogue LLRF system, a step motor, and an ARC module of a Petra cavity. It was successfully integrated with a 100-kW RF transmitter, high-power RF transfer system, and a cooling system and applied to the booster of TPS. Two duplicated RF electronic system were then applied to the storage ring but integrated with the 300-KW transmitters. With these RF systems, the TPS storage ring achieved beam current 100 mA on 2015 March 26.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA045
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPHA052	Test Cavity and Cryostat for SRF Thin Film Evaluation	3232
	O.B. Malyshev, P. Goudket, L. Gurran, D.O. Malyshev, S.M. Pattalwar, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom G. Burt, L. Gurran Cockcroft Institute, Lancaster University, Lancaster, United Kingdom P. Goudket, O.B. Malyshev, S.M. Pattalwar, R. Valizadeh Cockcroft Institute, Warrington, Cheshire, United Kingdom T.J. Jones, E.S. Jordan STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
	In developing superconducting coatings for SRF cavities, the coated samples are tested using various techniques such as resistance measurements, AC and DC magnetometry which provide information about the superconducting properties of the films such as RRR, Hc1, Hc2 and vortex dynamics. However, these results do not allow the prediction of the superconducting properties at RF frequencies. A dedicated RF cavity was designed to evaluate surface resistive losses on a flat sample. The cavity contains two parts: a half-elliptical cell made of bulk Nb and a flat Nb disc. The two parts can be thermally and electrically isolated via a vacuum gap, whereas the electromagnetic fields are constrained through the use of RF chokes. Both parts are conduction cooled hence the system is cryogen free. The flat disk can be replaced with a sample, such as a Cu disc coated with Nb film. The RF test provide the cavity Q-factor and thermometrical measurements of the losses on the sample. The design advantages are that the sample disc can be easily installed and replaced; installing a new sample requires no brazing/welding/vacuum or RF seal, so the sample preparation is simple and inexpensive.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA052
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPHA058	Superconducting Coatings Synthesized by CVD/PECVD for SRF Cavities	3246
	P. Pizzol, P. Chalker, T. Heil The University of Liverpool, Liverpool, United Kingdom A.N. Hannah, O.B. Malyshev, S.M. Pattalwar, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom G.B.G. Stenning STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	Funding: STFC Bulk niobium cavities are widely employed in particle accelerators to create high accelerating gradient despite their high material and operation cost. In order to reduce this cost, thin layer of niobium are deposited on a copper cavity, which has lower material cost with higher availability and more importantly higher thermal conductivity. The coating of superconducting cavities currently is synthesized by physical vapour deposition (PVD) method which suffers from lack of conformity. By using chemical vapour deposition (CVD) and plasma enhanced chemical vapour deposition (PECVD) it is possible to deposit thin Nb layers uniformly with density very close to bulk material. This project explores the use of PECVD / CVD techniques to deposit metallic niobium on copper using NbCl5 as precursor and hydrogen as a coreagent. The samples obtained were then characterized via SEM, TEM, SAD, XRD, XPS, and EDX as well as assessing their superconductivity characteristics (RRR and Tc) All the samples deposited are superconductive and polycrystalline; the sample obtained with CVD measured RRR=31 and Tc=7.9 K, while the sample obtained with PECVD exhibited RRR=9 and Tc= 9.4 K. In both cases the films grew in a (100) preferred orientation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA058
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPHA059	Physical Vapour Deposition of Thin Films for Use in Superconducting RF Cavities	3249
	S. Wilde, B. Chesca Loughborough University, Loughborough, Leicestershire, United Kingdom A.N. Hannah, D.O. Malyshev, O.B. Malyshev, S.M. Pattalwar, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom G.B.G. Stenning STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	The production of superconducting coatings for radio frequency cavities is a rapidly developing field that should ultimately lead to acceleration gradients greater than those obtained by bulk Nb RF cavities. Optimizing superconducting properties of Nb thin-films is therefore essential. Nb films were deposited by magnetron sputtering in pulsed DC mode onto Si (100) and MgO (100) substrates and also by high impulse magnetron sputtering (HiPIMS) onto Si (100), MgO (100) and polycrystalline Cu. The films were characterised using scanning electron microscopy, x-ray diffraction and DC SQUID magnetometry.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA059
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY008	Superconducting Harmonic Cavity for the Advanced Photon Source Upgrade	3267
	M.P. Kelly, A. Barcikowski, J. Carwardine, Z.A. Conway, D. Horan, S.H. Kim, P.N. Ostroumov, G.J. Waldschmidt ANL, Argonne, Illinois, USA J. Rathke, T. Schultheiss AES, Medford, New York, USA
	A new bunch lengthening cryomodule using a single-cell ‘higher-harmonic’ superconducting cavity (HHC) based on the TESLA shape and operating at the 4th harmonic (1408 MHz) of the main RF is under development at Argonne. The system will be used to improve the Touschek lifetime and increase the single-bunch current limit in the upgraded multibend achromat lattice of the Advanced Photon Source electron storage ring. The 4 K cryomodule will fit within one half of a straight section, ~2.5 meters, of the ring. The system will use a pair of moveable 20 kW (each) CW RF power couplers to adjust the loaded Q and extract power from the beam. This will provide the flexibility to adjust the impedance presented to the beam and run at various beam currents. Higher-order modes (HOMs) induced by the circulating electron beam will be extracted along the beam axis and damped using a pair of room temperature beam line absorbers. Engineering designs and the prototyping status for the cavity, power couplers and HOM absorbers are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY008
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY009	Preservation of Quality Factor of Half Wave Resonator during Quenching in the Presence of Solenoid Field	3270
	S.H. Kim, D.M. Caldwell, Z.A. Conway, S.M. Gerbick, M. Kedzie, M.P. Kelly, S.W.T. MacDonald, P.N. Ostroumov, T. Reid ANL, Argonne, Illinois, USA
	Funding: This work was supported by the U.S. Department of energy, Offices of High-Energy Physics and Nuclear Physics, under Contract No. DE-AC02-76-CH03000 and DE-AC02-06CH11357. The Proton Improvement Plan II at FNAL relies upon a 162.5 MHz superconducting half-wave resonator cryomodule to accelerate H⁻ beams from 2.1 to 10 MeV. This cryomodule contains 8 resonators with 8 superconducting solenoid magnets interspersed between them. X-Y steering coils are integrated with a package of the superconducting solenoid magnets. The center of the solenoids is located within ~50 cm of the high surface magnetic field of the half-wave resonators and in this study we assess whether or not magnetic flux generated by this magnet is trapped into the half-wave resonators niobium surface and increases the RF losses to liquid helium. To test this we assembled a solenoid with a 162.5 MHz half-wave resonator spaced as they will be in the cryomodule. We measured the quality factor of the cavity before and after the cavity quenched as a function of field level in the coils. No measurable change in the quality factor was observed. In this paper, we will present details of the measurements and discuss the magnetic field map.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY009
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY010	Electropolishing for Low-Beta and Quasi-Waveguide SRF Cavities	3273
	T. Reid, Z.A. Conway, S.M. Gerbick, M. Kedzie, M.P. Kelly, P.N. Ostroumov ANL, Argonne, Illinois, USA
	Argonne National Laboratory (ANL) has extended high quality electropolishing techniques based on those developed for the International Linear Collider to several more complex superconducting RF cavities. These include the co-axial TEM-mode quarter-wave and half-wave cavities as well as a 2.8 GHz quasi-waveguide structure intended for beam bunch rotation. This system is an improved version of the one developed for 1.3 GHz 9-cell cavities and includes easy provision for direct water cooling using the helium jacket. The performance of these SRF cavities both in terms of RF fields and losses equals or exceeds that of most 9-cell elliptical cavities built and tested today.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY010
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY016	RF Modeling of a Helical Kicker for Fast Chopping	3293
	M.H. Awida, A.Z. Chen, T.N. Khabiboulline, G.W. Saewert, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	High intensity proton particle accelerators that supports several simultaneous physics experiments requires sharing the beam. A bunch by bunch beam chopper system located after the Radio Frequency Quadrupole (RFQ) is required in this case to structure the beam in the proper bunch format required by the several experiments. The unused beam will need to be kicked out of the beam path and is disposed in a beam dumb. In this paper, we report on the RF modeling results of a proposed helical kicker. Two beam kickers constitutes the proposed chopper. The beam sequence is formed by kicking in or out the beam bunches from the streamline. The chopper was developed for Project X Injection Experiment (PXIE).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY016
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY017	Development of 650 MHz β=0.9 5-cell Elliptical Cavities for PIP-II	3296
	M.H. Awida, M.H. Foley, I.V. Gonin, C.J. Grimm, T.N. Khabiboulline, A. Lunin, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	5-cell 650 MHz elliptical cavities are being developed for the Proton Improvement Plan II (PIP-II) of Fermilab. The cavities are designed to accelerate protons of relative group velocity β=0.9 at the high energy part of the linear particle accelerator. In this paper, we report the status of these cavities and summarize the results of the quality control measurements performed on four initial prototypes.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY017
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY018	Analysis of a Quasi-waveguide Multicell Resonator for SPX	3299
	M.H. Awida, I.V. Gonin, T.N. Khabiboulline, A. Lunin, V.P. Yakovlev Fermilab, Batavia, Illinois, USA A. Zholents ANL, Argonne, Ilinois, USA
	A compact deflecting cavity is needed for the Short Pulse X-rays (SPX) at the Advanced Photon Source (APS) of Argonne national laboratory. The deflecting cavity has to quite efficient providing a 2 MV kick voltage and satisfying stringent requirements on aperture size and total cavity length. Meanwhile, the cavity should allow operation up to 100 mT peak surface magnetic field before quenching. In this paper, we report on the latest analysis carried out on the cavity structure to investigate frequency sensitivity to pressure fluctuations, frequency sensitivity to tuning forces, modal frequency, and wakefield losses.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY018
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY019	Transverse Field Perturbation For PIP-II SRF Cavities	3302
	P. Berrutti, T.N. Khabiboulline, V.A. Lebedev, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	Funding: Work supported by D.O.E. Contract No. DE-AC02-07CH11359 Proton Improvement Plan II (PIP-II) consists in a plan for upgrading the Fermilab proton accelerator complex to a beam power capability of at least 1 MW delivered to the neutrino production target. A room temperature section accelerates H⁻ ions to 2.1 MeV and creates the desired bunch structure for injection into the superconducting (SC) linac. Five cavity types, operating at three different frequencies 162.5, 325 and 650 MHz, provide acceleration to 800 MeV. This paper presents the studies on transverse field perturbation on particle dynamic for all the superconducting cavities in the linac. The effects studied include quadrupole defocusing for coaxial resonators, and dipole kick due to couplers for elliptical cavities. A multipole expansion has been performed for each of the cavity designs including effects up to octupole.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY021	Origin of Trapped Flux Caused by Quench in Superconducting Niobium Cavities	3309
	M. Checchin, A. Grassellino, M. Martinello, O.S. Melnychuk, A. Romanenko, D.A. Sergatskov Fermilab, Batavia, Illinois, USA M. Checchin, M. Martinello Illinois Institute of Technology, Chicago, Illlinois, USA
	Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. In this study we prove that the mechanism at the basis of quality factor degradation due to quench involves the entrapment of ambient magnetic field. The cavity quench in the absence of magnetic field does not introduce any extra losses, and a clear trend between the external field and the extra losses introduced by the quench was observed. It is demonstrated that the quality factor can be totally recovered by quenching in zero applied magnetic field. A dependence of the amount of quality factor degradation on the orientation of the magnetic field with respect to the cavity was also found.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY022	Modifications of Superconducting Properties of Niobium Caused by Nitrogen Doping Recipes for High Q Cavities	3312
	A. Vostrikov, M. Checchin, A. Grassellino, A. Romanenko Fermilab, Batavia, Illinois, USA Y.K. Kim, A. Vostrikov University of Chicago, Chicago, Illinois, USA
	Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. Discovery at Fermilab of a drastic effect of nitrogen doping leading to unprecedented high Q values in niobium cavities * motivated a strong interest in revealing the physics underlying the effect. In this contribution we present new results obtained by DC magnetometry, AC susceptibility, resistivity and thermal properties measurements on nitrogen doped samples prepared by different recipes/doping levels, which shed light on the possible origin of the effect. * A. Grassellino et al, 2013 Supercond. Sci. Technol. 26 102001
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY022
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY034	T-map Studies on Gradient-limiting Mechanism in Nitrogen Doped Cavities	3348
	M. Martinello, M. Checchin, A. Grassellino, A. Romanenko Fermilab, Batavia, Illinois, USA
	Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. Nitrogen doping * results in ultra-high quality factors in SRF niobium cavities but currently achievable gradients in doped cavities are, on average, somewhat lower than in EP/120C baked cavities. The origin of this difference is explored in the reported work by detailed temperature mapping studies on several single cell nitrogen doped cavities. * A. Grassellino et al, 2013 Supercond. Sci. Technol. 26 102001
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY034
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY035	Design and Test of the Compact Tuner for Narrow Bandwidth SRF Cavities	3352
	Y.M. Pischalnikov, E. Borissov, I.V. Gonin, J.P. Holzbauer, T.N. Khabiboulline, W. Schappert, S.J. Smith, J.C. Yun Fermilab, Batavia, Illinois, USA
	Funding: Fermi Research Alliance, LLC under Contract N. DE-AC02-07CH11359 with U.S. Department of Energy. The design of the compact tuner for 1.3 GHz 9-cell elliptical cavity will be presented. This compact tuner is designed for future accelerators that will operate in CW and pulsed RF-power modes. The major design features include highly reliable active components (electromechanical actuators and piezo-actuators) and the ability to replace tuner active components through designated ports in the cryomodule vacuum vessel. Results of tuner testing with cold cavity will also be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY035
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY036	Progress at FNAL in the Field of the Active Resonance Control for Narrow Bandwidth SRF Cavities.	3355
	W. Schappert, J.P. Holzbauer, Y.M. Pischalnikov Fermilab, Batavia, Illinois, USA
	Funding: Fermi Research Alliance, LLC under Contract N. DE-AC02-07CH11359 with U.S. Department of Energy. Recent efforts at FNAL to actively compensate microphonics in narrow bandwidth cavities are discussed. Feed-forward compensation of Lorentz force detuning in combination with feedback of the forward/probe phase difference to a piezo actuator successfully stabilized the resonance of a 325 MHz spoke resonator to within 11 mHz of the frequency of the open-loop CW RF drive over a two hour interval.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY036
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY060	Virtual Welding as a Tool for Superconducting Cavity Coarse Tuning	3412
	A. Facco, C. Compton, J. Popielarski, G.J. Velianoff FRIB, East Lansing, Michigan, USA
	Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 Reaching the final frequency in the construction of Superconducting Half-Wave Resonators (HWR), either coaxial or spoke, is often a painful and time consuming process which requires several intermediate frequency tests and parts machining between subsequent welding steps. In spite of that, the final frequency error after final welding is often far from the target due to difficult to predict material contraction and cavity deformation induced by electron beam welding (EBW). Final coarse tuning is required by plastic deformation or differential etching. In coaxial HWR, both can decrease the cavity frequency but are not easily suitable to increase it. A novel method developed at MSU is “virtual” welding, i.e. deformation of the cavity shape by applying systematically EBW on the cavity outer surface to induce controlled Nb material contraction in strategic positions. This technique allows to increase the cavity frequency with excellent precision and predictability, thus simplifying and making less expensive and more reliable HWR coarse tuning. Method and experimental results will be described and discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY060
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY062	Multipactor Breakdown Modelling Using an Averaged Version of Furman's SEY Model	3419
	S.A. Rice, J.P. Verboncoeur Michigan State University, East Lansing, Michigan, USA
	Funding: Work supported by a MSU Strategic Partnership Grant. Furman's seconday electron yield model is commonly used for the simulation of multipactor in accelerating cavities and other resonant structures. While accurate, the stochastic model requires many Monte Carlo simulations in order to characterize susceptibility to multipactor. This paper generalizes our previous research in characterizing a reduced-order Furman model, in which we replace the stochastic Furman model with a deterministic model based upon the Furman model's underlying statistics. Favorable comparisons between the full Furman model and the reduced-order Furman model are shown for multipactor simulations in a coaxial cavity, and the results are expected to generalize to other geometries.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY062
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY066	T-Maps Taken During Cool-down of an SRF cavity: a Tool to Understand Flux Trapping	3431
	R.G. Eichhorn, F. Furuta, G.M. Ge Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	During the past years the impact of cool-down procedures on the flux trapping properties of superconducting cavities have been under investigation. We have measured temperature distributions of a multi-cell cavity using a T-map set-up to understand the transition to superconductivity in detail. We will report how the spatial disorder is affected by the cool-down speed and relate our findings to data on flux pinning.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY066
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY067	Thermal and Mechanical Analysis of a Waveguide to Coax Symmetric Coupler for Superconducting Cavities	3434
	R.G. Eichhorn, J.A. Robbins, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	As kicks from fundamental power couplers become a concern for low emittance future accelerators, a design for a symmetric coupler for superconducting accelerating cavities has been started. In this coupler, a rectangular waveguide transforms into a coaxial line inside the beam pipe to feed the cavity. So far the RF design revealed an extremely low transversal kick but concerns about cooling and the thermal stability of the coaxial transition line remained. Our contribution will address this. We will calculate heating, heat transfer and thermal stability of this coupler and evaluate the risk of quenching due to particle losses on the coupler.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY067
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY068	Asymmetric Thermo-currents Diminishing SRF Cavity Performance	3437
	R.G. Eichhorn, J. May-Mann Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Over the past years it became evident that the quality factor of a superconducting cavity is not only determined by its surface preparation procedure, but is also influenced by the way the cavity is cooled down. In this paper we will present results from numerical field calculations of magnetic fields produced by thermo-currents, driven by temperature gradients and material transitions. We will show how they can impact the quality factor of a cavity by producing a magnetic field at the RF surface of the cavity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY068
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY069	Complection of the Cornell High Q CW Full Linac Cryo-module	3440
	R.G. Eichhorn, B. Bullock, B. Clasby, J.V. Conway, B. Elmore, F. Furuta, G.M. Ge, G.H. Hoffstaetter, M. Liepe, T.I. O'Connel, P. Quigley, D.M. Sabol, J. Sears, E.N. Smith, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA Y. He Fermilab, Batavia, Illinois, USA
	Cornell University has finished building a 10 m long superconducting accelerator module as a prototype of the main linac of a proposed ERL facility. This module houses 6 superconducting cavities- operated at 1.8 K in continuous wave (CW) mode - with individual HOM absorbers and one magnet/ BPM section. In pushing the limits, a high quality factor of the cavities (2x10¹⁰) and high beam currents (100 mA accelerated plus 100 mA decelerated) were targeted. We will review the design shortly and present the results of the components tested before the assembly. This includes data of the quality-factors of all 6 cavities that we produced and treated in-house, the HOM absorber performance measured with beam on a test set-up as well as testing of the couplers and the tuners.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY069
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY072	Update on Nitrogen-doped 9-cell Cavity Performance in the Cornell Horizontal Test Cryomodule	3446
	D. Gonnella, R.G. Eichhorn, F. Furuta, G.M. Ge, D.L. Hall, Y. He, K.M.V. Ho, G.H. Hoffstaetter, M. Liepe, J.T. Maniscalco, T.I. O'Connel, S. Posen, P. Quigley, J. Sears, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA A. Grassellino, C.J. Grimm, O.S. Melnychuk, A. Romanenko Fermilab, Batavia, Illinois, USA
	Funding: U.S. Department of Energy The Linac Coherent Light Source-II (LCLS-II) is a new x-ray source that is planned to be constructed in the existing SLAC tunnel. To meet the quality factor specifications (2.7x 10¹⁰ at 2.0 K and 16 MV/m), nitrogen-doping has been proposed as a preparation method for the SRF cavities. In order to demonstrate the feasibility of these goals, four 9-cell cavity tests have been completed in the Cornell Horizontal Test Cryomodule (HTC), which serves as a test bench for the full LCLS-II cryomodule. Here we report on the most recent two cavity tests in the HTC: one cavity nitrogen-doped at Cornell and tested with high Q input coupler and then again tested with high power LCLS-II input coupler. Transition to test in horizontal cryomodule resulted in no degradation in Q0 from vertical test. Additionally, increased dissipated power due to the high power input coupler was small and in good agreement with simulations. These results represent a crucial step on the way to demonstrating technical readiness for LCLS-II.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY072
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY073	Update on Nitrogen Doping: Quench Studies and Sample Analysis	3450
	D. Gonnella, F. Furuta, G.M. Ge, J.J. Kaufman, M. Liepe, J.T. Maniscalco Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: U.S. Department of Energy, NSF Recently, nitrogen-doping of niobium has emerged as a promising preparation method for SRF cavities to reach higher intrinsic quality factors than can be reached with typical cavity preparation. Nitrogen-doped cavities prepared at Cornell have shown quality factors higher than 4x10¹⁰ at 2.0 K and 16 MV/m. While Q results have been very exciting, a reduced quench field currently limits nitrogen-doped cavities with quench typically occurring between 15 and 25 MV/m. Here we report on recent results from Cornell on single-cell and 9-cell cavities, focusing on new preparations and maximum and critical fields. First we discuss results from over-doping niobium with nitrgoen, baking nitrogen-doped cavities at 120C, and doping with Argon. For a subset of these cavities we show results from quench studies that have been completed using temperature mapping. Finally, we present the first measurements of the higher critical field, Hc2, for nitrogen-doped niobium samples.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY073
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY074	Recent Studies on the Current Limitations of State-of-the-Art Nb3Sn Cavities	3454
	D.L. Hall, M. Liepe, J.T. Maniscalco, S. Posen Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA Th. Proslier ANL, Argonne, Illinois, USA
	Funding: NSF PHY-1305500 PHY-14116318 DOE ER41802 Recent advances in the study of Nb3Sn at Cornell University have yielded single-cell cavities that show excellent performance without the limiting Q-slope seen in previous work. This performance has been shown to be repeatable across multiple cavities. However, they are still limited by a quench field of approximately 16 MV/m, as well as residual resistance. In this work we present results quantifying the impact of ambient magnetic fields on Nb3Sn cavities, as well as discuss the impact of cavity cooldown procedures on cavity performance. Finally, we will briefly discuss XRD results that shed light on the composition of the Nb3Sn layer and how this relates to the current limits of these cavities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY074
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY075	Hc2 Measurements of Nb3Sn and Nitrogen-doped Niobium using Physical Property Measurement System	3458
	J.T. Maniscalco, D. Gonnella, D.L. Hall, M. Liepe, S. Posen Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	The measurement of the upper critical field of a type-2 superconductor, Hc2, is an important step in determining its superconducting properties, and therefore its suitability as a material in SRF cavities. However, measuring Hc2 directly can be challenging, as performing electrical measurements causes changes in the very properties one seeks to measure. We present a method for extracting Hc2 from resistivity measurements made near the transition temperature for varied applied fields and excitation currents. We also present results of these measurements made on Nb3Sn and nitrogen-doped niobium.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY075
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY076	RF Performance Studies of Thin-Film Superconductors Using a Sample Host Cavity	3462
	J.T. Maniscalco, D.L. Hall, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Thin-film superconductors have the potential for reduced cost and for improved SRF performance over traditional bulk niobium superconducting cavities. Materials such as Nb3Sn, multilayer NbN/MgO, and thin-film Nb are currently under investigation for cost reduction or possible improvements in RF losses and accelerating gradients. Due to the complex geometries of traditional RF cavities, it is preferable to use a sample host cavity to study flat samples of the novel materials. The Cornell sample host cavity has been commissioned and has now reached peak magnetic surface fields of 100 mT. We present updates on the recent performance of the cavity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY076
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY077	On Quench Propagation, Quench Detection, and Second Sound in SRF Cavities	3464
	S.R. Markham, R.G. Eichhorn Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	The detection of a second sound wave, excited by a quench, has become a valuable tool in diagnosing hot spots and performance limitations of superconducting cavities. Several years ago, Cornell developed an oscillating super-leak transducer (OST) for these waves that nowadays are used world-wide. In a usual set-up, several OSTs surround the cavity, and the quench location is determined by triangulation of the different OST signals. Convenient as the method is there is a small remaining mystery: taking the well-known velocity of the second sound wave, the quench seems to come from a place slightly above the cavity’s outer surface. We will present a model based on numerical quench propagation simulations and analytic geometrical calculations that help explain the discrepancy.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY077
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY078	High Q0 at Medium Fields in Nb3Sn SRF Cavities at 4.2 K	3467
	S. Posen, D.L. Hall, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA Th. Proslier ANL, Argonne, Illinois, USA
	Nb3Sn has proven itself to be a very promising alternative SRF material. With twice the critical temperature of niobium cavities, 1.3 GHz Nb3Sn cavities can achieve quality factors on the order of 10¹⁰ even at 4.2 K, significantly reducing cryogenic infrastructure and operational costs. In addition, its large predicted superheating field may allow for maximum accelerating gradients up to twice that of niobium for high energy applications. In this work, we report on new cavity results from the Cornell Nb3Sn SRF program demonstrating a significant improvement in the maximum field achieved with high Q0 in a Nb3Sn cavity. At 4.2 K, accelerating gradients above 16 MV/m were obtained with Q0 of 8x10⁹, showing the potential of this material for future applications. In addition to this result, current limitations are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY078
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY082	High Gradient Testing of the Five-cell Superconducting RF Module with a PBG Coupler Cell	3471
	S. Arsenyev, W.B. Haynes, D.Y. Shchegolkov, E.I. Simakov, T. Tajima LANL, Los Alamos, New Mexico, USA C.H. Boulware, T.L. Grimm, A. Rogacki Niowave, Inc., Lansing, Michigan, USA
	We report results of high-gradient testing of the first 5- cell superconducting radio frequency (SRF) module with a photonic band gap cell (PBG). Higher order mode (HOM) damping is vital for preserving the quality of high-current electron beams in novel SRF accelerators. Because HOMs are not confined by the PBG array, they can be effectively damped in order to raise the current threshold for beam instabilities. The PBG design increases the real-estate gradient of the linac because both HOM damping and the fundamental power coupling can be done through the PBG cell instead of via the beam pipe at the ends of the cavity. A superconducting multi-cell cavity with a PBG damping cell is therefore an attractive option for high-current linacs. The first-ever SRF multi-cell cavity incorporating a PBG cell was designed a LANL and built at Niowave Inc. The cavity was tuned to a desired gradient profile and underwent surface treatment at Niowave. A vertical test (VTS) was then performed at LANL, demonstrating an abnormally low cavity quality factor in the accelerating mode of 1.6*10⁶. Future tests are proposed to determine the source of the losses and resolve the problem.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY082
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY083	Five-cell Superconducting RF Module with a PBG Coupler Cell: Design and Cold Testing of the Copper Prototype	3475
	S. Arsenyev, D.Y. Shchegolkov, E.I. Simakov LANL, Los Alamos, New Mexico, USA C.H. Boulware, T.L. Grimm, A. Rogacki Niowave, Inc., Lansing, Michigan, USA
	We report the design and experimental data for a copper prototype of a superconducting radio-frequency (SRF) accelerator module. The five-cell module has an incorporated photonic band gap (PBG) cell with couplers. The purpose of the PBG cell is to achieve better higher order mode (HOM) damping which is vital for preserving the quality of highcurrent electron beams. Better HOM damping raises the current threshold for beam instabilities in novel SRF accelerators. The PBG design also increases the real-estate gradient of the linac because both HOM damping and the fundamental power coupling can be done through the PBG cell instead of on the beam pipe via complicated end assemblies. First, we will discuss the design and accelerating properties of the structure. The five-cell module was optimized to provide good HOM damping while maintaining the same accelerating properties as conventional elliptical-cell modules. We will then discuss the process of tuning the structure to obtain the desired accelerating gradient profile. Finally, we will list measured quality factors for the accelerating mode and the most dangerous HOMs.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY083
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI004	FPC and Hi-Pass Filter HOM Coupler Design for the RF Dipole Crab Cavity for the LHC HiLumi Upgrade	3492
	Z. Li SLAC, Menlo Park, California, USA S.U. De Silva, J.R. Delayen, R.G. Olave, H. Park ODU, Norfolk, Virginia, USA
	Funding: Work partially supported by the US DOE through the US LHC Accelerator Research Program (LARP), and by US DOE under contract number DE-AC02-76SF00515. A 400-MHz compact RF dipole (RFD) crab cavity design was jointly developed by Old Dominion University and SLAC under the support of US LARP program for the LHC HiLumi upgrade. The RFD cavity design is consisted of a rounded-square tank and two ridged deflecting poles, operating with a TE11-like dipole mode, which is the lowest mode of the cavity. A prototype RFD cavity is being manufactured and will be tested on the SPS beam line at CERN. The coaxial fundamental Power Coupler (FPC) of the prototype cavity was re-optimized to minimizing the power heating on the coupler internal antenna. A hi-pass filter HOM damping coupler was developed to achieve the required wakefield damping while maintaining a compact size to fit into the beam line space. In this paper, we will discuss the details of the RF optimization and tolerance analyses of the FPC and HOM couplers.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI004
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI007	TTF3 Power Coupler Thermal Analysis for LCLS-II CW Operation	3503
	L. Xiao, C. Adolphsen, Z. Li, C.D. Nantista, T.O. Raubenheimer SLAC, Menlo Park, California, USA I.V. Gonin, N. Solyak Fermilab, Batavia, Illinois, USA
	The TESLA 9-cell SRF cavity design has been adopted for use in the LCLS-II SRF Linac. Its TTF3 coaxial Fundamental Power Coupler (FPC), developed for pulsed operation in the European XFEL and ILC, requires modest changes to make it suitable for LCLS-II CW operation, in which it must be able to handle up to 7 kW of average power with the maximum temperature rise not to exceed 150 C. In order to improve TTF3 FPC cooling, an increased copper plating thickness will be used on the inner and outer conductor stainless steel RF surfaces. Fully 3D FPC thermal analysis with copper plating was performed using the SLAC developed parallel finite element code suite ACE3P with integrated electromagnetic, thermal and mechanical multi-physics simulation capabilities. In this paper, we present TTF3 FPC thermal analysis simulation results obtained using ACE3P as well as a comparison with measurement results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI007
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI009	Nitrogen Doping Study in Ingot Niobium Cavities	3506
	P. Dhakal, G. Ciovati, P. Kneisel, G.R. Myneni JLab, Newport News, Virginia, USA J. Makita ODU, Norfolk, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 Thermal diffusion of nitrogen in superconducting radio frequency cavities at temperatures around 800C has resulted in the increase in quality factor with a low-field Q-rise. However, the maximum accelerating gradients of these doped cavities often reduces below the values achieved by standard treatments. In this contribution, we present the results of the nitrogen diffusion into ingot niobium cavities subjected to successive material removal from the inner cavity surface by electropolishing in an effort to explore the underlying cause for the gradient degradation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI009
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI010	Results from the First Single Cell Nb3Sn Cavity Coatings at JLab	3509
	G.V. Eremeev JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Nb3Sn is a promising superconducting material for SRF applications and has the potential to exceed the limitations of niobium. We have used the recently commissioned Nb3Sn coating system to investigate Nb3Sn coatings on several single cell cavities by applying the same coating procedure on several different single cells with different history and pre-coating surface preparation. We report on our findings with four 1.5 GHz CEBAF-shape single cell and one 1.3 GHz ILC-shape single cavities that were coated, inspected, and tested.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI010
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI011	Commissioning Results of Nb3Sn Cavity Vapor Diffusion Deposition System at JLab	3512
	G.V. Eremeev, W.A. Clemens, K. Macha, H. Park, R.S. Williams JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Nb3Sn as a BCS superconductors with a superconducting critical temperature higher than that of niobium offers potential benefit in lower surface resistance at the same temperature and frequency for SRF cavities. A Nb3Sn vapor diffusion deposition system was built and commissioned at Jefferson Lab. As the part of the commissioning a single cell 1.5 GHz CEBAF-shaped cavity was coated in the built system. The cavity exhibited the superconducting transition at about 17.9 K. The low field quality factor was about 5x10⁹ at 4 K and 7x10⁹ at 2 K dropping with field to about 10⁹ at both temperatures at about 8 MV/m.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI011
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI012	First Attempt of At-cavity X-ray Detection in a CEBAF Cryomodule for Field Emission Monitoring	3515
	R.L. Geng, E. Daly, M.A. Drury, A.D. Palczewski JLab, Newport News, Virginia, USA
	We report on the first result of at-cavity X-ray detection in a CEBAF cryomodule for field emission monitoring. In the 8-cavity cryomodule F100, two silicon diodes were installed near the end flange of each cavity. Each cavity was individually tested during the cryomodule test in JLab’s cryomodule test facility. The behaviors of these at-cavity cryogenic X-ray detectors were compared with those of the standard “in air” Geiger-Muller tubes. Our initial experiments establish correlation between X-ray response of near diodes and the field emission source cavity in the 8-cavity string. For two out of these eight cavities, we also carried out at-cavity X-ray detection experiment during their vertical testing. The aim is to track field emission behavior uniquely from vertical cavity testing to horizontal cavity testing in the cryomodule.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI012
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI013	New Results of Development on High Efficiency High Gradient Superconducting RF Cavities	3518
	R.L. Geng JLab, Newport News, Virginia, USA C. Adolphsen, Z. Li SLAC, Menlo Park, California, USA J.K. Hao, K.X. Liu PKU, Beijing, People's Republic of China H.Y. Zhao Ningxia Orient Tantalum Industry Co., Ltd., Dawukou District, Shizuishan city, People's Republic of China
	We report on the latest results of development on high efficiency high gradient superconducting radio frequency (SRF) cavities. Several 1-cell cavities made of large-grain niobium (Nb) were built, processed and tested. Two of these cavities are of the Low Surface Field (LSF) shape. Series of tests were carried out following controlled thermal cycling. Experiments toward zero-field cooling were carried out. The best experimentally achieved results are Eacc = 41 MV/m at Q0 = 6.5×10¹⁰ at 1.4 K by a 1-cell 1.3 GHz large-grain Nb TTF shape cavity and Eacc = 49 MV/m at Q0 = 1.5×1010 at 1.8 K by a 1-cell 1.5 GHz large-grain Nb CEBAF upgrade low-loss shape cavity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI013
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI015	BNL 56 MHz HOM Damper Prototype Fabrication at JLab	3521
	N.A. Huque, W.A. Clemens, E. Daly JLab, Newport News, Virginia, USA S. Bellavia, G.T. McIntyre, S.K. Seberg, Q. Wu BNL, Upton, Long Island, New York, USA
	A prototype Higher-Order Mode (HOM) Damper was fabricated at JLab for the Relativistic Heavy-Ion Collider’s (RHIC) 56 MHz cavity at Brookhaven National Laboratory (BNL). Primarily constructed from high RRR Niobium and Sapphire, the coaxial damper presented significant challenges in electron-beam welding (EBW), brazing and machining via acid etching. The results of the prototype operation brought about changes in the damper design, due to overheating braze alloys and possible multi-pacting. Five production HOM dampers are currently being fabricated at JLab. This paper outlines the challenges faced in the fabrication process, and the solutions put in place.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI015
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI016	Investigation of Differential Surface Removal due to Electropolishing at JLab	3525
	F. Marhauser, J. Follkie, C.E. Reece JLab, Newport News, Virginia, USA
	Surface chemistry carried out for Superconducting Radio Frequency (SRF) cavities such as Buffered Chemical Polishing (BCP) and Electropolishing (EP) aims to uniformly remove the internal surface of a cavity along the entire structure and within each cell from equator to iris in order to obtain an equally etched surface. A uniform removal however is not readily achievable due to the complex fluid flow and varying temperatures of the acid mixture, which can lead to differential etching. This needs to be considered when envisaging a certain surface damage removal throughout the interior. The process-specific differential etching influences the target frequency set at the manufacturing stage as well as the field flatness and length of the as-built cavity. We report on analyses of JLab's present EP system using experimental data for six nine-cell cavities that have been processed recently in the frame of the LCLS-II high-Q development plan. In conjunction with numerical simulations, the differential etching and the impact on field flatness is assessed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI016
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI019	Quench Studies of Six High Temperature Nitrogen Doped 9 Cell Cavities for Use in the LCLS-II Baseline Prototype Cryo-module at Jefferson Laboratory	3528
	A.D. Palczewski, G.V. Eremeev, R.L. Geng, C.E. Reece JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Jefferson Lab (JLab) processed six nine-cell cavities as part of a small-scale production for LCLS-II cavity processing development utilizing the promising nitrogen-doping process. [1] Various nitrogen-doping recipes have been scrutinized to optimize process parameters with the aim to guarantee an unloaded quality factor (Q 0) of 2.7·10¹⁰ at an accelerating field (Eacc) of 16 MV/m at 2.0 K in the cryomodule. During the R&D phase the characteristic Q0 vs. Eacc performance curve of the cavities has been measured in JLab’s vertical test area at 2 K. The findings showed the characteristic rise of the Q0 with Eacc as expected from nitrogen-doping. Initially, five cavities achieved an average Q0 of 3.3·10¹⁰ at the limiting Eacc averaging to 16.8 MV/m, while one cavity experienced an early quench accompanied by an unusual Q 0 vs. Eacc curve. The project accounts for a cavity performance loss from the vertical dewar test (with or without the helium vessel) to the horizontal performance in a cryomodule, such that these results leave no save margin to the cryomodule specification. Consequently, a refinement of the nitrogen-doping has been initiated to guarantee an average quench field above 20 MV/m without impeding the Q 0. This paper covers the refinement work performed for each cavity, which depends on the initial results, as well as a quench analysis carried out before and after the rework during the vertical RF tests as far as applicable.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI021	An Analysis of the Temperature and Field Dependence of the RF Surface Resistance of Nitrogen-Doped Niobium SRF Cavities with Respect to Existing Theoretical Models	3532
	C.E. Reece, A.D. Palczewski JLab, Newport News, Virginia, USA B. P. Xiao BNL, Upton, Long Island, New York, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177 Recent progress with the reduction of rf surface resistance (Rs) of niobium SRF cavities via the use of high temperature surface doping by nitrogen has opened a new regime for energy efficient accelerator applications. For particular doping conditions one observes dramatic decreases in Rs with increasing surface magnetic fields. The observed variations as a function of temperature may be analyzed in the context of recent theoretical treatments in hopes of gaining insight into the underlying beneficial mechanism of the nitrogen treatment. Systematic data sets of Q0 vs. Eacc vs. temperature acquired during the high Q0 R&D work of the past year will be compared with theoretical model predictions. * * B. P. Xiao et al., Physica C: Superconductivity 490 (0), 26-31 (2013) and A. Gurevich, PRL 113 (8), 087001 (2014)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI022	RF System Requirements for a Medium-Energy Electron-Ion Collider (MEIC) at JLab	3536
	R.A. Rimmer, J. Guo, J. Henry, H. Wang, S. Wang JLab, Newport News, Virginia, USA Y.L. Huang IMP/CAS, Lanzhou, People's Republic of China
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 JLab is studying options for a medium energy electron-ion collider that could fit on the JLab site and use CEBAF as a full-energy electron injector. A new ion source, linac and booster would be required, together with collider storage rings for the ions and electrons. In order to achieve the maximum luminosity these will be high current storage rings with many bunches. We present the high level RF system requirements for the storage rings, ion booster ring and high-energy ion beam cooling system, and describe the technology options under consideration to meet them. We also present options for staging that might reduce the initial capital cost while providing a smooth upgrade path to a higher final energy. The technologies under consideration may also be useful for other proposed storage ring colliders or ultimate light sources.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI022
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI030	Injector Cavities Fabrication, Vertical Test Performance and Primary Cryomodule Design	3551
	H. Wang, G. Cheng, W.A. Clemens, G.K. Davis, K. Macha, R.B. Overton, D. Spell JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. After the electromagnetic design * and the mechanical design ** of a β=0.6, 2-cell elliptical SRF cavity, the cavity has been fabricated. Then both 2-cell and 7-cell cavities have been bench tuned to the target values of frequency, coupling external Q and field flatness. After buffer chemistry polishing (BCP) and high pressure rinses (HPR), Vertical 2K cavity test results have been satisfied the specifications and ready for the string assembly. We will report the cavity performance including Lorenz Force Detuning (LFD) and Higher Order Modes (HOM) damping data. Its integration with cavity tuners to the cryomodule design will be reported. * H. Wang, etc., Proceeding of IPAC2013, Shanghai, China, WEPWO073. ** G. Cheng, etc., Proceeding of PAC2013, Pasadena, CA, WEPAC47.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI030
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI032	Mechanical Properties of Niobium Cavities	3554
	G. Ciovati, P. Dhakal, J. Matalevich, G.R. Myneni JLab, Newport News, Virginia, USA
	Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 The mechanical stability of bulk Nb cavity is an important aspect to be considered in relation to cavity material, geometry and treatments. Mechanical properties of Nb are typically obtained from uniaxial tensile tests of small samples. In this contribution we report the results of measurements of the resonant frequency and local strain along the contour of single-cell cavities made of ingot and fine-grain Nb of different purity subjected to increasing uniform differential pressure, up to 6 atm. Measurements have been done on cavities subjected to different heat treatments. Good agreement between finite element analysis simulations and experimental data in the elastic regime was obtained with a single set of values of Young’s modulus and Poisson’s ratio. The experimental results indicate that the yield strength of medium-purity ingot Nb cavities is higher than that of fine-grain, high-purity Nb.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI032
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI034	Effects of Crab Cavities' Multipole Content in an Electron-Ion Collider	3561
	A. Castilla, J.R. Delayen, T. Satogata ODU, Norfolk, Virginia, USA A. Castilla, J.R. Delayen, V.S. Morozov, T. Satogata JLab, Newport News, Virginia, USA A. Castilla DCI-UG, León, Mexico
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The impact on the beam dynamics of the Medium Energy Electron-Ion Colider (MEIC) due to the multipole content of the 750 MHz crab cavity was studied using thin multipole elements for 6D phase space particle tracking in ELEGANT. Target values of the sextupole component for the cavity’s field expansion were used to perform preliminary studies on the proton beam stability when compared to the case of pure dipole content of the rf kicks. Finally, important effects on the beam sizes due to non-linear components of the crab cavities’ fields were identified and some criteria for their future study were proposed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI034
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI035	Beam Dynamics Studies of 499 MHz Superconducting RF-Dipole Deflecting Cavity System	3564
	S.U. De Silva, K.E. Deitrick, J.R. Delayen, H. Park ODU, Norfolk, Virginia, USA
	A 499 MHz deflecting cavity has been designed as a three-way beam spreader to separate an electron beam into 3 beams. The rf tests carried out on the superconducting rf-dipole cavity have demonstrated that a transverse voltage of 4.2 MV can be achieved with a single cavity. This paper discusses the beam dynamics on a deflecting structure operating in continuous-wave mode with a relativistic beam. The study includes the analysis on emittance growth, energy spread, and change in bunch size including effects due to field non-uniformities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI035
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI036	Design and Prototyping of a 400 MHz RF-dipole Crabbing Cavity for the LHC High-Luminosity Upgrade	3568
	S.U. De Silva, J.R. Delayen, H. Park ODU, Norfolk, Virginia, USA Z. Li SLAC, Menlo Park, California, USA T.H. Nicol Fermilab, Batavia, Illinois, USA
	LHC High Luminosity Upgrade is in need of two crabbing systems that deflects the beam in both horizontal and vertical planes. The 400 MHz rf-dipole crabbing cavity system is capable of crabbing the proton beam in both planes. At present we are focusing our efforts on a complete crabbing system in the horizontal plane. Prior to LHC installation the crabbing system will be installed for beam test at SPS. The crabbing system consists of two rf-dipole cavities in the cryomodule. This paper discusses the electromagnetic design and mechanical properties of the rf-dipole crabbing system for SPS beam test.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI036
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI037	Imperfection and Tolerance Analysis of HOM Couplers for ODU/SLAC 400 MHz Crabbing Cavity	3572
	S.U. De Silva, J.R. Delayen, H. Park ODU, Norfolk, Virginia, USA Z. Li SLAC, Menlo Park, California, USA R.G. Olave Old Dominion University, Norfolk, Virginia, USA
	In preparation for the LHC High Luminosity upgrade, a 400 MHz crab cavity has been developed jointly at ODU/SLAC, including two higher order mode couplers designed to dampen the wakefields in order to comply with the impedance budget specified for the LHC system. During fabrication, assembly, and processing of the couplers, a number of imperfections may arise that could modify the higher order mode spectrum and the associated impedance for each mode. We present here a detailed study of the imperfections of the horizontal- and vertical- HOM couplers, and the associated allowed tolerances for manufacture, assembly and processing.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI037
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI038	Temperature Mapping of Nitrogen-doped Niobium Superconducting Radiofrequency Cavities	3575
	J. Makita ODU, Norfolk, Virginia, USA G. Ciovati, P. Dhakal JLab, Newport News, Virginia, USA
	It was recently shown that diffusing nitrogen on the inner surface of superconducting radiofrequency (SRF) cavities at high temperature can improve the quality factor of the niobium cavity. However, a reduction of the quench field is also typically found. To better understand the location of rf losses and quench, we used a thermometry system to map the temperature of the outer surface of ingot Nb cavities after nitrogen doping and electropolishing. Surface temperature of the cavities was recorded while increasing the rf power and also during the quenching. The results of thermal mapping showed no precursor heating on the cavities and quenching to be ignited near the equator where the surface magnetic field is maximum. Hot-spots at the equator area during multipacting were also detected by thermal mapping.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI038
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI039	Engineering Study of Crab Cavity HOM Couplers for LHC High Luminosity Upgrade	3578

Paper

Title

Page

MOYGB2

High Q Developments

A. Grassellino
Fermilab, Batavia, Illinois, USA

This presentation will cover recent breakthroughs in the SRF field that have revolutionized the achievable quality factors in bulk niobium cavities. It will cover two main breakthroughs: one involving the controlled nitrogen doping of the niobium cavity surface, and second the efficient magnetic flux expulsion from the niobium walls via controlled cavity cooling though transition temperature. The talk will give an overview from the discovery of these effects at FNAL to the development into a cryomodule ready technology by the partner labs Cornell, Jlab, FNAL and SLAC for implementation in the LCLS-2 accelerator. New results will be presented from surface analysis, cavity diagnostics tools and very high Q obtained in dressed cavities in cryomodule environment.

Slides MOYGB2 [11.862 MB]

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOBD2

Design and Prototyping of HL-LHC Double Quarter Wave Crab Cavities for SPS Test

64

S. Verdú-Andrés, S.A. Belomestnykh, I. Ben-Zvi, J. Skaritka, Q. Wu, B. P. Xiao
BNL, Upton, Long Island, New York, USA
L. Alberty, K. Artoos, R. Calaga, O. Capatina, T. Capelli, F. Carra, N. Kuder, R. Leuxe, C. Zanoni
CERN, Geneva, Switzerland
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA
Z. Li
SLAC, Menlo Park, California, USA
A. Ratti
LBNL, Berkeley, California, USA

Funding: Work supported by US DOE via US LARP program, through BSA LLC contract No.DE-AC02-98CH10886 and by EU FP7 HiLumi LHC grant No.284404. Used NERSC resources by US DOE contract No.DE-AC02-05CH11231.
The LHC high luminosity project envisages the use of the crabbing technique for increasing and levelling the LHC luminosity. Double-Quarter Wave (DQW) resonators are compact cavities especially designed to meet the technical and performance requirements for LHC beam crabbing. A couple of DQW crab cavities are under preparation and will be tested with beam in the Super Proton Synchrotron (SPS) of CERN by 2017. This paper describes the design and prototyping of DQW crab cavities for the SPS test.

Slides MOBD2 [6.909 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOBD2

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA010

First Test Results of the BERLinPro 2-cell Booster Cavities

2765

A. Burrill, W. Anders, A. Frahm, J. Knobloch, A. Neumann
HZB, Berlin, Germany
G. Ciovati, W.A. Clemens, P. Kneisel, L. Turlington
JLab, Newport News, Virginia, USA

The BERLinPro Energy Recovery Linac (ERL) is currently being built at Helmholtz-Zentrum Berlin in order to study the physics of operating a high current, a 100 mA, 50 MeV ERL utilizing all SRF cavity technology. This machine will utilize three unique SRF cryomodules for the photoinjector, booster and linac cryomodules respectively. The focus of this paper will be on the cavities contained within the booster cryomodule. Here there will be three 2-cell SRF cavities, based on the original design by Cornell University, but optimized to meet the needs of the project. All of the cavity fabrication, processing and testing was carried out at Jefferson Laboratory where 4 cavities were produced and the 3 cavities with the best RF performance were fitted with helium vessels for installation in the cryomodule. This paper will report on the test results of the cavities as measured in the vertical testing dewar at JLab after fabrication and again after outfitting with the helium vessels.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA010

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA011

First Horizontal Test Results of the HZB SRF Photoinjector for BERLinPro

2768

A. Burrill, W. Anders, A. Frahm, J. Knobloch, A. Neumann
HZB, Berlin, Germany
G. Ciovati, W.A. Clemens, P. Kneisel, L. Turlington
JLab, Newport News, Virginia, USA

The BERLinPro project, a small superconducting RF (SRF) c.w. energy recovery linac (ERL) is being built at Helmholtz-Zentrum Berlin in order to develop the technology required for operation of a high current, 100 mA, 50 MeV ERL. The electron source for the accelerator is a 1.4 cell SRF photoinjector fitted with a multi-alkali photocathode. As part of the HZB photoinjector development program three different SRF photoinjectors will be fabricated and tested. The photoinjector described herein is the second cavity that has been fabricated, and the first photoinjector designed for use with a multi-alkali photocathode. The photoinjector has been built and tested at JLab and subsequently shipped to HZB for testing in the horizontal test cryostat HoBiCaT prior to installation in the photoinjector cryomodule. This cryomodule will be used to measure the photocathode operation in a dedicated experiment called GunLab, the precursor to installation in the BERLinPro hall. This paper will report on the final results of the cavity installed in the helium vessel in the vertical testing dewar at Jefferson Lab as well as the first horizontal test in HoBiCaT

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA011

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA012

High-Q Cavity Operation: Study on the Thermoelectrically Induced Contribution to RF Surface Resistance

2771

J.M. Köszegi, J. Knobloch, O. Kugeler, A. Neumann, A.V. Vélez
HZB, Berlin, Germany

We present a study concerning the operation of a superconducting RF cavity (non-doped niobium) in horizontal testing with the focus on understanding the thermoelectrically induced contribution to the surface resistance. Starting in 2009, we suggested a means of reducing the residual resistance by warming up a cavity after initial cooldown to about 20K and cooling it down again. In subsequent studies we used this technique to manipulate the residual resistance by more than a factor of 2. We postulated that thermocurrents during cooldown generate additional trapped magnetic flux that impacts the cavity quality factor. Since several questions remained open, we present here a more extensive study including measurement of two additional passband modes of the 9-cell cavity that confirms the effect. We also discuss simulations that substantiate the claim. While the layout of the cavity LHe tank system is cylindrically symmetric, we show that the temperature dependence of the material parameters result in a non-symmetric current distribution. Hence a significant amount of magnetic flux can be generated at the RF surface resulting in an increased surface resistance.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA012

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA013

Hom Damping Optimization Design Studies for BESSY VSR Cavities

2774

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

The BESSY VSR project is a future upgrade of the 3rd generation BESSY II light source. By using the same "standard" user optics, simultaneously long (ca. 15ps) and short (ca. 1.5ps) bunches will be stored. Thus, superconducting higher harmonic cavities of the fundamental 500 MHz at two frequencies need to be installed in the BESSY II storage ring. This work describes the optimizations studies for the Waveguide-based HOM dampers and the adjustable fundamental power coupler for the 1.5 GHz first SRF cavity prototype.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA013

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA026

Higher Order Mode Propagation and Damping Studies on Axisymmetric Superconducting Multicell RF-Resonators

2812

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

Funding: Work supported by the BMBF under contract no. 05K13PEB
Higher order mode (HOM) propagation and damping is a major concern in feasibility studies regarding the upcoming upgrade of BESSY II, named BESSY-VSR*, which involves the utilization of superconducting multicell RF-resonators in a storage ring while maintaining a reasonably high beam current typical for third generation synchrotron radiation facilities. In addition to the computation of the typical figures of merit, we focus on studies of the mode propagation in axisymmetric structures. Due to the focus on axisymmetric studies we are able to use 2D codes to investigate in eigenmodes with substantial higher frequencies than usually considered with full 3D codes in parametric studies. In this work we present preliminary studies involving mode propagation in superconducting elliptical multicell cavities.
* G. Wüstefeld et al., Proc. of IPAC'11, San Sebastián, THPC014

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA026

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA035

Low- and High-Beta SRF Elliptical Cavity Stiffening

2835

E.N. Zaplatin
FZJ, Jülich, Germany
A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Elliptical SRF cavities are the main accelerating structures in many accelerators worldwide. Different types of external loads on the resonator walls predetermine the main working conditions of the SC cavities. The most important of them are very high electromagnetic fields that result in strong Lorentz forces and the pressure on cavity walls from the helium tank that also deforms the cavity shape. Also mechanical eigen resonances of cavities are the main source of the microphonics. To withstand any kind of external loads on the resonator walls different schemes of the cavity stiffening were applied. In the paper we report the basic investigations of the cavity stiffening using FNAL 650 MHz β=0.92 and 0.61 as an example. The single-cell investigation results were used as the reference to develop the ultimate scheme of the helium vessel structure to ensure the best resonator stability.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA035

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA036

Double-Cell Notch Filter for SRF Gun Investigations

2838

E.N. Zaplatin
FZJ, Jülich, Germany
A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
J. Knobloch, A. Neumann
HZB, Berlin, Germany
V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Some projects of SRF guns apply the design where the cathode can be easily and quickly removed. One of the disadvantages of this design is the RF power leakage from the accelerating gun cavity cells to the cathode housing that results in the excessive cathode heating. To minimize the RF power leak different kinds of choke filters are used to protect the cathode structure. These choke filters represent resonant circuits with a zero input impedance and installed at the entrance of the cathode structure that shunt the cathode housing. Still, since the choke filter frequency shift under working conditions is bigger than its bandwidth a filter tuning during assembly only in the warm stage seems insufficient and requires also fine-tuning during operation. To eliminate the problems of the choke filter fine-tuning and hence ensure its stability during operation, a combination of the resonance choke elements can be implemented. In the paper we demonstrate advantages of the double-cell notch filter using BERLinPro SRF gun cavity as an example with its simple design modifications.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA036

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA037

Manufacturing and First Test Results of Euclid SRF Conical Half-wave Resonator

2841

E.N. Zaplatin
FZJ, Jülich, Germany
C.H. Boulware, T.L. Grimm, A. Rogacki
Niowave, Inc., Lansing, Michigan, USA
A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Funding: This Work is supported by the DOE SBIR Program, contract # DE-SC0006302.
Euclid TechLabs has developed a superconducting conical half-wave resonator (162.5 MHz β=v/c=0.11) for the high-intensity proton accelerator complex proposed at Fermi National Accelerator Laboratory. The main objective of this project is to provide a resonator design with high mechanical stability based on an idea of the balancing cavity frequency shifts caused by external loads. A unique cavity side-tuning option has been successfully implemented. Niowave, Inc. proposed a complete cavity production procedure including preparation of technical drawings, processing steps and resonator high-gradient tests. During manufacturing a series of cavity and helium vessel modifications to simplify their manufacturing were proposed. Following standard buffered chemical polish surface treatment and high-pressure rinse, a vertical test was carried out at Niowave’s facilities. Here we present the status of the project and the first high-gradient results.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA037

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA041

1.3 GHz SRF Cryomodules for the Mainz Energy-recovering Superconducting Accelerator MESA

2853

F. Schlander, K. Aulenbacher, R.G. Heine, D. Simon, T. Stengler
IKP, Mainz, Germany

Funding: Work supported by the German Federal Ministery of Education and Research (BMBF) and German Research Foundation (DFG) under the Cluster of Excellence "PRISMA"
The Mainz Energy-recovering Superconducting Accelerator MESA requires superconducting RF systems that provide sufficient energy of 50 MeV per turn to an electron beam. The ordering process of two Rossendorf-type cryomodules, containing two 9-cell 1.3 GHz XFEL-like cavities each, is in progress. Besides an overview of the adaptations required for the multipass and high current beam operation of the cryomodules, details about challenges regarding the installation of the cryomodules on the premises of the Institut für Kernphysik at Universität Mainz are given.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA041

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA046

Studies on Innovative Production methods of HOM Coupler for SRF 9-cell Cavity

2869

K. Nohara, N. Kawabata, K. Miyajima, M. Shinohara
SPS, Funabashi-shi, Japan
H. Hayano, S. Kato, T. Saeki, A. Yamamoto, M. Yamanaka
KEK, Ibaraki, Japan

Pure Nb as the material of SRF cavity bears hard workability in general. This is why both the inner and outer conductors of HOM coupler for 9-cell cavity have been conventionally produced by full machining, backward extrusion accompanied with annealing and so on. However, in the mass production of 9-cell cavities in ILC, further cost reduction is required. We produced both the inner and outer conductors of HOM coupler for 9-cell cavity in the advanced press forming methods aiming at cost reduction. Press forming of a pure Nb sheet for the outer conductor of HOM coupler was performed with fewer processes free from intermediate annealing and primary machining. For the inner conductor of HOM coupler, water jet cutting and press cold-forging of a plate was performed. The above advanced press forming methods showed favored results, leading to a possibility of simple mass-production of components and cost reduction. The vertical test on a 9-cell cavity with the press formed HOM couplers achieved 36 MV/m that is beyond ILC qualification. The R＆D works are ongoing for further improvement.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA046

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA048

Development for Mass Production of Superconducting Cavity by MHI

2876

T. Yanagisawa, H. Hara, K. Kanaoka, K. Okihira, K. Sennyu
MHI, Hiroshima, Japan

Mitsubishi Heavy Industries (MHI) have developed manufacturing process of superconducting cavitis for a long time. In this presentation, recent progress will be reported.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA048

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA053

Multipactor Simulations in 325 MHz Superconducting Spoke Cavity for an Electron Accelerator

2892

T. Kubo, T. Saeki
KEK, Ibaraki, Japan
E. Cenni, Y. Iwashita, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan
R. Hajima, M. Sawamura
JAEA, Ibaraki-ken, 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 with the laser-Compton scattering, a 325MHz superconducting spoke cavity for an electron accelerator operated at 4K is under development. After design-optimizations of the first cavity, we started fabrication process. In this paper, multipactor analyses carried out as parts of the design-optimization efforts are briefly summarized. Relations between cavity geometries and averaged secondary electron emission yield are discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA053

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA054

A Disturbance-Observer-based Controller for LLRF Systems

2895

F. Qiu, D.A. Arakawa, Y. Honda, H. Katagiri, T. Matsumoto, S. Michizono, T. Miura, T. Obina
KEK, Ibaraki, Japan
S.B. Wibowo
Sokendai, Ibaraki, Japan

Digital low-level radio frequency (LLRFs) systems have been developed and evaluated in the compact energy recovery linac (cERL) at KEK. The required RF stabilities are 0.1% rms in amplitude and 0.1° rms in phase. These requirements are satisfied by applying digital LLRF systems. To further enhance the control system and make it robust to disturbances such as large power supply (PS) ripples and high-intensity beams, we have designed and developed a disturbance observer (DOB)-based control method. This method utilizes the RF system model, which can be acquired using modern system identification methods. Experiments show that the proposed DOB-based controller is more effective in the presence of high disturbances compared with the conventional proportional and integral (PI) controller. In this paper, we present the preliminary results based on the experiments with DOB-based controller.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA054

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA056

Development of Superconducting Spoke Cavities for Laser Compton Scattered X-ray Sources

2902

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

Funding: This study is supported by Photon and Quantum Basic Research Coordinated Development Program of MEXT, Japan.
A 5-year research program on the development of superconducting spoke cavities for electron accelerators has been funded by MEXT, Japan since 2013. The purpose of our program is establishing design and fabrication processes of superconducting spoke cavity optimized for compact X-ray sources based on laser Compton scattering. The spoke cavity is expected to realize a compact industrial-use X-ray source with a reasonable cost and easy operation. We have chosen a cavity frequency at 325 MHz due to possible operation at 4 K and carried out cavity shape optimization in terms of electromagnetic and mechanical properties. Production of press-forming dies is also in progress. In this paper, we present overview and up-to-date status of the research program.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA056

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMA060

The Development of Cavity Frequency Tracking Type RF Control System for SRF-TEM

2914

N. Higashi
The University of Tokyo, Graduate School of Science, Tokyo, Japan
A. Enomoto, Y. Funahashi, T. Furuya, X.J. Jin, Y. Kamiya, S. Michizono, M. Nishiwaki, H. Sakai, M. Sawabe, K. Ueno, M. Yamamoto
KEK, Ibaraki, Japan
M. Kuriki
HU/AdSM, Higashi-Hiroshima, Japan
S. Yamashita
ICEPP, Tokyo, Japan

Superconducting accelerating cavities used in high-energy accelerators can generate high electric fields of several 10 MV/m by supplying radio frequency waves (RF) with frequencies matched with resonant frequencies of the cavities. Generally, frequencies of input RFs are fixed, and resonant frequencies of cavities that are fluctuated by Lorentz force detuning and Microphonics are corrected by feedbacks of cavity frequency tuners and input RF power. Now, we aim to develop the cavity frequency tracking type RF control system where the frequency of input RF is not fixed and consistently modulated to match the varying resonant frequency of the cavity. In KEK (Tsukuba, Japan), we are developing SRF-TEM that is a new type of transmission electron microscope using special-shaped superconducting cavity. By applying our new RF control system to the SRF-TEM, it is expected to obtain stable accelerating fields so that we can acquire good spatial resolution. In this presentation, we will explain the required stabilities of accelerating fields for SRF-TEM and the feasibility of SRF-TEM in the case of applying the cavity frequency tracking type RF control system.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA060

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN012

Cathode Stalk Optimization for a 325 MHz Superconducting QWR Electron Gun

2940

P.L. Fan, Y.M. Li, L. Lin, K.X. Liu, S.W. Quan, F. Zhu
PKU, Beijing, People's Republic of China

Funding: Work supported by National Basic Research Project (No. 2011CB808302)
The structure of cathode stalk is very important for the performance of a superconducting QWR (Quarter Wave Resonator) gun. With improper design, RF power dissipation on the surface of cathode stalk and its surrounding tube can lead to a serious decrease of quality factor for superconducting QWR injector. We present here an optimized design of the cathode stalk for the 325 MHz superconducting QWR gun and special considerations are taken to minimize the power dissipation. The details of microwave simulation, beam dynamic simulation of the cavity with cathode stalks in different length, diameter and position are presented in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN012

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN013

Development of DC-SRF Injector at Peking University

2944

J.K. Hao, J.E. Chen, P.L. Fan, L.W. Feng, S. Huang, L. Lin, K.X. Liu, S.W. Quan, F. Wang, Zh.W. Wang, X.D. Wen, H.M. Xie, K. Zhao, F. Zhu
PKU, Beijing, People's Republic of China

DC-SRF electron injector, which combines a DC Pierce gun and a 3.5 cell 1.3 GHz superconductor cavity in a cryomodule, has been developed at Peking University. Based on the improvements of beam line, LLRF system and 2K cryogenic system, stable operation of the DC-SRF injector has been carried out recently. Electron beams with 3.4 MeV energy and the currents of ~1mA in a macro-pulse mode was obtained. As the first application of this DC-SRF injector, THz radiation produced with a 10 period undulator was also detected. The description of the experiment process and results will be presented in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN013

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN024

Exploration of Multi-fold Symmetry Element-loaded Superconducting Radio Frequency Structure for Reliable Acceleration of Low- & Medium-Beta Ion Species

2978

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

Reliable acceleration of low- to medium-beta proton or heavy ion species is needed for future high current superconducting radio frequency accelerators. Due to the high-Q nature of a superconducting RF resonator, it is sensitive to many factors such as loading variation (from either the accelerated beam or from parasitic field emitted electrons), mechanical vibration, and liquid helium bath pressure fluctuation etc. To increase the stability against those factors, a mechanically strong and stable RF structure is desirable. Guided by this consideration, multi-fold symmetry element-loaded superconducting radio frequency structures, cylindrical tanks with multiple (n>=3) rod-shaped radial elements, are being explored. The top goal of its optimization is to improve mechanical stability. A natural consequence of this structure is a lowered ratio of the peak surface electromagnetic field to the acceleration gradient as compared to the traditional spoke cavity. A disadvantage of this new structure is an increased size for a fixed resonant frequency and optimal beta. This paper describes the optimization of EM design and preliminary mechanical analysis for such structures.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN024

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN030

Testing Procedures for Fast Frequency Tuners of XFEL Cavities

2991

K.P. Przygoda, W. Cichalewski, T. Pożniak
TUL-DMCS, Łódź, Poland
J. Branlard, O. Hensler, H. Schlarb, Ch. Schmidt
DESY, Hamburg, Germany
K. Kasprzak
IFJ-PAN, Kraków, Poland

The XFEL accelerator will be equipped with 100 accelerating modules. Each accelerating module will host 8 superconducting cavities. Every single cavity will be equipped with a mechanical tuner. Coarse tuning will be supported by a step motor; fine tuning will be handled by double piezoelectric elements installed inside a single mechanical support, providing actuator and sensor functionality or redundancy. Before the main linac installation, all its subcomponents need to be tested and verified. The AMTF (Accelerator Module Test Facility) has been built at DESY to test all XFEL cryomodules. In total 1600 piezos need to be tested. Test procedures for fast frequency tuners have been developed to check their basic performance in cryogenic conditions (tuning range, polarity, acting and sensing abilities). High level applications perform fully automated tests including report generation. After the successful completion of the acceptance tests, the cryomodules will be prepared for tunnel installation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN030

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN031

Automated Quench Limit Test Procedure for Serial Production of XFEL RF Cavities

2994

K. Kasprzak, D. Konwisorz, K. Krzysik, S. Myalski, J. Świerbleski, K. Turaj, M. Wiencek, A. Zwozniak
IFJ-PAN, Kraków, Poland
D. Kostin, K.P. Przygoda
DESY, Hamburg, Germany

In the Accelerator Module Test Facility (AMTF) at DESY in Hamburg RF cavities and accelerating cryomodules are tested for the European X-ray Free Electron Laser (XFEL). Measurements are done by a team of physicists, engineers and technicians from The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences in Kraków, Poland, as a part of Polish in-kind contribution to the XFEL. The testing procedures providing information about maximum available gradient and heat loads measurement are performed for the high gradients (up to 31MV/m). During these tests the cavity deformation caused by the Lorentz force is compensated by piezo (fast) tuners. For this purpose automated high level software was developed. This paper describes a method used to tune automatically the cavities during the RF tests. It was validated with the XFEL cryomodules. This improvement was implemented into the testing software and it is successfully used for testing of serial production cavities.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN031

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN034

Electron Emission from Surface Roughness on Cavity in Low Temperature

3003

H. Kim, H.J. Cha, S. Choi, W.K. Kim, G.-T. Park
IBS, Daejeon, Republic of Korea
Y. Chang
Hanshin University, Kyungki, Republic of Korea

Electron emission phenomenon from surface roughness on cavity is investigated. The distribution of the electric field from the surface roughness can be obtained on cavity surface. The field emission is calculated from the electric field distribution. The generalized electron emission from electric field and temperature effect is also calculated on the surface roughness of the cavity.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN034

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN039

RF Accelerating Voltage of PLS-II Superconducting RF System for Stable Top-up Operation with Beam Current of 400 mA

3015

Y.D. Joo, M.-H. Chun, T. Ha, I. Hwang, B.-J. Lee, I.S. Park, S. Shin, Y.U. Sohn, I.H. Yu
PAL, Pohang, Kyungbuk, Republic of Korea

During the beam store test up to 400 mA in the storage ring, it was observed that the vacuum pressure around the RF window of the superconducting cavity rapidly increases over the interlock level limiting the availability of the maximum beam current storing. We investigated the cause of the window vacuum pressure increment by studying the changes in the electric field distribution at the superconducting cavity and waveguide according to the beam current. An equivalent physical modeling was developed using a finite-difference time-domain (FDTD) simulation and it revealed that the electric field amplitude at the RF window is exponentially increased as the beam current increases, thus this high electric field amplitude causes a RF breakdown at the RF window.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN039

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN042

400 mA Beam Store with Superconducting RF Cavities at PLS-II

3021

Y.U. Sohn, M.-H. Chun, T. Ha, M.S. Hong, Y.D. Joo, H.-S. Kang, H.-G. Kim, K.R. Kim, T.-Y. Lee, C.D. Park, H.J. Park, I.S. Park, S. Shin, I.H. Yu, J.C. Yun
PAL, Pohang, Kyungbuk, Republic of Korea

Funding: Minister of Science, ICT and Future Planning
Three superconducting RF cavities were commissioned with electron beam in way of one by one during the last 3 years, and now PLS-II is in user service on the way of beam current to 400mA, the target of PLS-II. The cavities and cryomodules were prepared with SRF standard technology and procedures, then vertical test, windows conditioning, cryogenic test in each cryomodule, horizontal power test, conditioning, and commissioning without and with beam at PLS-II tunnel by collaboration with industries. All the cavities showed stable performances as good as not-observing any RF instability from cavities, couplers and windows up to 400 mA beam store, but observing several cavity quenches and minor vacuum bursts by abrupt power with control and human errors. The initial beam current for user run were recorded as 150 mA with one cavity, 280 mA with two cavities and 320 mA with three cavities. The 400 mA beam was also achieved with two cavities by decay mode and also with three cavities by top-up mode. The stabilities of RF amplitude and phase are good enough not to induce beam instabilities.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN042

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN043

The RF Stability of PLS-II Storage Ring RF System

3024

I.H. Yu, M.-H. Chun, M.H. Jeong, Y.D. Joo, H.-S. Kang, H.-G. Kim, H.J. Park, I.S. Park, Y.U. Sohn
PAL, Pohang, Kyungbuk, Republic of Korea
Y.S. Lee
SKKU, Suwon, Republic of Korea

Funding: Minister of Science, ICT and Future Planing
The RF system for the Pohang Light Source (PLS) storage ring was greatly upgraded for PLS-II project of 400mA, 3.0GeV from 200mA, 2.5GeV. Three superconducting RF cavities with each 300kW maximum klystron amplifier were commissioned with electron beam in way of one by one during the last 3 years for beam current of 400mA to until March 2014. The RF system is designed to provide stable beam through precise RF phase and amplitude requirements to be less than 0.3% in amplitude and 0.3° in phase deviations. This paper describes the RF system configuration, design details and test results.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN043

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN046

Compassion of Higher Order Modes Damping Techniques for Superconducting 9-Cell Structure

3030

Ya.V. Shashkov, A.A. Mitrofanov, N.P. Sobenin
MEPhI, Moscow, Russia
V. Zvyagintsev
TRIUMF, Vancouver, Canada

Funding: Work supported by Ministry of Education and Science grant 3.245.2014/r
Modern types of accelerators, such as Energy recovery linacs, require low values of higher order modes (HOM) Qext. In accelerators with high current HOM could lead to high losses for the modes excitation, beam instability and beam break up. HOM couplers and waveguides are often used in such structures for HOM damping. Unfortunately they could lead to a violation of the axial symmetry of the accelerating field and negatively affect the beam emittance. Also these devices are subject for multipactor discharge and could be difficult in maintaining and fabrication. In this paper we examine several ways of HOM damping with ridged, fluted and corrugated drift tubes which are devoid of the above-mentioned drawbacks. The influence of the parameters of the drift tube on the HOM damping and on the parameters of the fundamental wave were analyzed.
Higher order modes, ERL, SRF

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN046

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN047

Suppression of Higher Order Modes in an Array of Cavities Using Waveguides

3033

Ya.V. Shashkov, N.P. Sobenin
MEPhI, Moscow, Russia
M. Zobov
INFN/LNF, Frascati (Roma), Italy

Funding: Work is supported by Ministry of Education and Science grant 3.245.2014/r и and by the EU FP7 HiLumi LHC - Grant Agreement 284404
In the frameworks of the High Luminosity LHC upgrade program an application of additional harmonic cavities operating at multiplies of the main RF system frequency of 400 MHz is currently under discussion. A structure consisting of two 800 MHz single cell superconducting cavities with grooved beam pipes coupled by drift tubes has been suggested for implementation. However, it is desirable to increase the number of single cells installed in one cryomodule in order to decrease the number of transitions between “warm” and “cold” parts of the collider vacuum chamber. Unfortunately it can lead to the appearance of higher order modes (HOM) trapped between the cavities. In order to solve this problem the methods of HOM damping with rectangular waveguides connected to the drift tubes were investigated and compared. In this paper we describe the results obtained for arrays of 2, 4 and 8 cavities.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN047

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN052

A New RF Laboratory for Developing Accelerator Cavities at the University of Huelva

3046

I. Martel, C. Bonțoiu, J.A. Dueñas, D. Gordo-Yáñez, A.K. Orduz, J. Sanchez-Segovia
University of Huelva, Huelva, Spain

The University of Huelva is presently involved in R&D projects for developing RF accelerator cavities. Two types of cavities are presently under design, a prototype of room temperature RFQ injector and a quarter-wave resonator for high intensity heavy-ion linear accelerators. The laboratory is equipped with dedicated test-bench for RF measurements, which includes high-power RF generators, network analyzer, amplifiers and power meters. A clean room is also available having a dedicated space for high-precision mechanical metrology and cavity mounting, together with a vertical cryostat for superconducting cavity test.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN052

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMN065

Progress at the FREIA Laboratory

3072

M. Olvegård, A.K. Bhattacharyya, T.J.C. Ekelöf, J. Eriksson, K. Fransson, K.J. Gajewski, V.A. Goryashko, L. Hermansson, M. Holz, M. Jacewicz, M. Jobs, Å. Jönsson, H. Li, T. Lofnes, H. Nicander, R.J.M.Y. Ruber, R. Santiago Kern, R. Wedberg, V.G. Ziemann
Uppsala University, Uppsala, Sweden
D.S. Dancila, A. Rydberg
Uppsala University, Department of Engineering Sciences, Uppsala, Sweden
R.A. Yogi
ESS, Lund, Sweden

The FREIA Facility for Research Instrumentation and Accelerator Development at Uppsala University, Sweden, has reached the stage where the testing of superconducting cavities for the European Spallation Source (ESS) is starting. The new helium liquefaction plant has been commissioned and now supplies a custom-made, versatile horizontal cryostat, HNOSS, with liquid helium at up to 140 l/h. The cryostat has been designed and built to house up to two accelerating cavities, or, later on, other superconducting equipment such as magnets or crab cavities. A prototype cavity for the spoke section of the ESS linac will arrive mid 2015 for high-power testing in the horizontal cryostat. Two tetrode-based commercial RF power stations will deliver 400 kW peak power each, at 352 MHz, to the cavity through an RF distribution line developed at FREIA. In addition, significant progress has been made with in-house development of solid state amplifier modules and power combiners for future use in particle accelerators. We report here on these and other ongoing activities at the FREIA laboratory.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN065

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPHA013

The Assembly Experience of the First Cryo-module for HIE-ISOLDE at CERN

3131

Y. Leclercq, G. Barlow, J.A. Bousquet, A. Chrul, P. Demarest, J-B. Deschamps, J.A. Ferreira Somoza, J. Gayde, M. Gourragne, A. Harrison, G. Kautzmann, D. Mergelkuhl, V. Parma, M. Struik, M. Therasse, L.R. Williams
CERN, Geneva, Switzerland
J. Dequaire
Intitek, Lyon, France

The HIE ISOLDE project aims at increasing the energy of the radioactive ion beams of the existing REX ISOLDE facility from the present 3 MeV/u up to 10 MeV/u for A/q to 4.5. The upgrade includes the installation of a superconducting linac in successive phases, for a final layout containing two low-β and four high-β cryo-modules. The first phase involves the installation of two high-B cryo-modules, each housing five high- β superconducting cavities and one superconducting solenoid, aligned within tight tolerances. After having designed and procured the cryo-module components, the first units is now being assembled at CERN, in a dedicated facility including class100 (ISO5) clean rooms equipped with specific tooling. The assembly is foreseen to be ultimate and the cryo-module cold tested by May 2015. In this paper, after a brief description of the main design features of the cryo-module , we present the assembly of the first unit, including the methodology, special tools, assembly procedures and quality assurance aspects. We report on the experience from this first assembly, including tests results, and present prospects for the next-coming cryo-module assemblies.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA013

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPHA021

Status of HIE-ISOLDE SC Linac Upgrade

3151

A. Sublet, L. Alberty, K. Artoos, S. Calatroni, O. Capatina, M.A. Fraser, N.M. Jecklin, Y. Kadi, P. Maesen, G.J. Rosaz, K.M. Schirm, M. Taborelli, M. Therasse, W. Venturini Delsolaro, P. Zhang
CERN, Geneva, Switzerland

The HIE-ISOLDE upgrade project at CERN aims at increasing the energy of radioactive beams from 3MeV/u up to 10 MeV/u with mass-to-charge ratio in the range 2.5-4.5. The objective is obtained by replacing part of the existing normal conducting linac with superconducting Nb/Cu cavities. The new accelerator requires the production of 32 superconducting cavities in three phases: 10 high-beta cavities for phase 1 (2016), 10 high-beta cavities for phase 2 (2017) and possibly 12 low-beta cavities for phase 3 (2020). Half of the phase 1 production is completed with 5 quarter-wave superconducting cavities ready to be installed in the first cryomodule. The status of the cavity production and the RF performance are presented. The optimal linac working configuration to minimize cryogenic load and maximize accelerating gradient is discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPHA022

Characterization of Nb Coating in HIE-ISOLDE QWR Superconducting Accelerating Cavities by means of SEM-FIB and TEM

3155

B. Bártová, S. Calatroni, A. Sublet, M. Taborelli
CERN, Geneva, Switzerland
A.B. Aebersold, D.T.L. Alexander, M. Cantoni
EPFL, Lausanne, Switzerland

The Quarter Wave Resonators (QWR) high-β cavities (0.3m diameter and 0.9m height) are made from OFE 3D-forged copper and are coated by DC-bias diode sputtering with a thin superconducting layer of niobium. The Nb film thickness, morphology, purity and quality are critical parameters for RF performances of the cavity. They have been investigated in a detailed material study. The coating structure at different positions along a test cavity was observed by cross-section imaging using SEM-FIB instrument. The samples from the top of the cavity showed presence of unexpected porosities, whose volume was investigated using FIB tomography. TEM lamella was prepared for two samples (top part and inner conductor of the cavity) to study in detail the grain orientation in the coating, its chemical composition and structure. The 14-layer structure in thick coating was indeed evidenced by the TEM analysis. Chemical mapping revealed the presence of a few nm in size copper precipitates close to the Nb/Cu interface and a passivating oxide layer of 10 nm thickness on top of the coating and around porosities. However no impurities or interface layer along the coating profile were present.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA022

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPHA045

Design and Construction of the RF Electronic System at Taiwan Photon Source

3215

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

The RF electronic system at NSRRC was made fully in house by the RF group from design through construction to completion. The first RF electronic system includes an analogue LLRF system, a step motor, and an ARC module of a Petra cavity. It was successfully integrated with a 100-kW RF transmitter, high-power RF transfer system, and a cooling system and applied to the booster of TPS. Two duplicated RF electronic system were then applied to the storage ring but integrated with the 300-KW transmitters. With these RF systems, the TPS storage ring achieved beam current 100 mA on 2015 March 26.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA045

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPHA052

Test Cavity and Cryostat for SRF Thin Film Evaluation

3232

O.B. Malyshev, P. Goudket, L. Gurran, D.O. Malyshev, S.M. Pattalwar, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G. Burt, L. Gurran
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
P. Goudket, O.B. Malyshev, S.M. Pattalwar, R. Valizadeh
Cockcroft Institute, Warrington, Cheshire, United Kingdom
T.J. Jones, E.S. Jordan
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

In developing superconducting coatings for SRF cavities, the coated samples are tested using various techniques such as resistance measurements, AC and DC magnetometry which provide information about the superconducting properties of the films such as RRR, Hc1, Hc2 and vortex dynamics. However, these results do not allow the prediction of the superconducting properties at RF frequencies. A dedicated RF cavity was designed to evaluate surface resistive losses on a flat sample. The cavity contains two parts: a half-elliptical cell made of bulk Nb and a flat Nb disc. The two parts can be thermally and electrically isolated via a vacuum gap, whereas the electromagnetic fields are constrained through the use of RF chokes. Both parts are conduction cooled hence the system is cryogen free. The flat disk can be replaced with a sample, such as a Cu disc coated with Nb film. The RF test provide the cavity Q-factor and thermometrical measurements of the losses on the sample. The design advantages are that the sample disc can be easily installed and replaced; installing a new sample requires no brazing/welding/vacuum or RF seal, so the sample preparation is simple and inexpensive.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA052

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPHA058

Superconducting Coatings Synthesized by CVD/PECVD for SRF Cavities

3246

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

Funding: STFC
Bulk niobium cavities are widely employed in particle accelerators to create high accelerating gradient despite their high material and operation cost. In order to reduce this cost, thin layer of niobium are deposited on a copper cavity, which has lower material cost with higher availability and more importantly higher thermal conductivity. The coating of superconducting cavities currently is synthesized by physical vapour deposition (PVD) method which suffers from lack of conformity. By using chemical vapour deposition (CVD) and plasma enhanced chemical vapour deposition (PECVD) it is possible to deposit thin Nb layers uniformly with density very close to bulk material. This project explores the use of PECVD / CVD techniques to deposit metallic niobium on copper using NbCl5 as precursor and hydrogen as a coreagent. The samples obtained were then characterized via SEM, TEM, SAD, XRD, XPS, and EDX as well as assessing their superconductivity characteristics (RRR and Tc) All the samples deposited are superconductive and polycrystalline; the sample obtained with CVD measured RRR=31 and Tc=7.9 K, while the sample obtained with PECVD exhibited RRR=9 and Tc= 9.4 K. In both cases the films grew in a (100) preferred orientation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA058

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPHA059

Physical Vapour Deposition of Thin Films for Use in Superconducting RF Cavities

3249

S. Wilde, B. Chesca
Loughborough University, Loughborough, Leicestershire, United Kingdom
A.N. Hannah, D.O. Malyshev, O.B. Malyshev, S.M. Pattalwar, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G.B.G. Stenning
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

The production of superconducting coatings for radio frequency cavities is a rapidly developing field that should ultimately lead to acceleration gradients greater than those obtained by bulk Nb RF cavities. Optimizing superconducting properties of Nb thin-films is therefore essential. Nb films were deposited by magnetron sputtering in pulsed DC mode onto Si (100) and MgO (100) substrates and also by high impulse magnetron sputtering (HiPIMS) onto Si (100), MgO (100) and polycrystalline Cu. The films were characterised using scanning electron microscopy, x-ray diffraction and DC SQUID magnetometry.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA059

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY008

Superconducting Harmonic Cavity for the Advanced Photon Source Upgrade

3267

M.P. Kelly, A. Barcikowski, J. Carwardine, Z.A. Conway, D. Horan, S.H. Kim, P.N. Ostroumov, G.J. Waldschmidt
ANL, Argonne, Illinois, USA
J. Rathke, T. Schultheiss
AES, Medford, New York, USA

A new bunch lengthening cryomodule using a single-cell ‘higher-harmonic’ superconducting cavity (HHC) based on the TESLA shape and operating at the 4th harmonic (1408 MHz) of the main RF is under development at Argonne. The system will be used to improve the Touschek lifetime and increase the single-bunch current limit in the upgraded multibend achromat lattice of the Advanced Photon Source electron storage ring. The 4 K cryomodule will fit within one half of a straight section, ~2.5 meters, of the ring. The system will use a pair of moveable 20 kW (each) CW RF power couplers to adjust the loaded Q and extract power from the beam. This will provide the flexibility to adjust the impedance presented to the beam and run at various beam currents. Higher-order modes (HOMs) induced by the circulating electron beam will be extracted along the beam axis and damped using a pair of room temperature beam line absorbers. Engineering designs and the prototyping status for the cavity, power couplers and HOM absorbers are discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY008

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY009

Preservation of Quality Factor of Half Wave Resonator during Quenching in the Presence of Solenoid Field

3270

S.H. Kim, D.M. Caldwell, Z.A. Conway, S.M. Gerbick, M. Kedzie, M.P. Kelly, S.W.T. MacDonald, P.N. Ostroumov, T. Reid
ANL, Argonne, Illinois, USA

Funding: This work was supported by the U.S. Department of energy, Offices of High-Energy Physics and Nuclear Physics, under Contract No. DE-AC02-76-CH03000 and DE-AC02-06CH11357.
The Proton Improvement Plan II at FNAL relies upon a 162.5 MHz superconducting half-wave resonator cryomodule to accelerate H⁻ beams from 2.1 to 10 MeV. This cryomodule contains 8 resonators with 8 superconducting solenoid magnets interspersed between them. X-Y steering coils are integrated with a package of the superconducting solenoid magnets. The center of the solenoids is located within ~50 cm of the high surface magnetic field of the half-wave resonators and in this study we assess whether or not magnetic flux generated by this magnet is trapped into the half-wave resonators niobium surface and increases the RF losses to liquid helium. To test this we assembled a solenoid with a 162.5 MHz half-wave resonator spaced as they will be in the cryomodule. We measured the quality factor of the cavity before and after the cavity quenched as a function of field level in the coils. No measurable change in the quality factor was observed. In this paper, we will present details of the measurements and discuss the magnetic field map.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY009

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY010

Electropolishing for Low-Beta and Quasi-Waveguide SRF Cavities

3273

T. Reid, Z.A. Conway, S.M. Gerbick, M. Kedzie, M.P. Kelly, P.N. Ostroumov
ANL, Argonne, Illinois, USA

Argonne National Laboratory (ANL) has extended high quality electropolishing techniques based on those developed for the International Linear Collider to several more complex superconducting RF cavities. These include the co-axial TEM-mode quarter-wave and half-wave cavities as well as a 2.8 GHz quasi-waveguide structure intended for beam bunch rotation. This system is an improved version of the one developed for 1.3 GHz 9-cell cavities and includes easy provision for direct water cooling using the helium jacket. The performance of these SRF cavities both in terms of RF fields and losses equals or exceeds that of most 9-cell elliptical cavities built and tested today.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY010

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY016

RF Modeling of a Helical Kicker for Fast Chopping

3293

M.H. Awida, A.Z. Chen, T.N. Khabiboulline, G.W. Saewert, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

High intensity proton particle accelerators that supports several simultaneous physics experiments requires sharing the beam. A bunch by bunch beam chopper system located after the Radio Frequency Quadrupole (RFQ) is required in this case to structure the beam in the proper bunch format required by the several experiments. The unused beam will need to be kicked out of the beam path and is disposed in a beam dumb. In this paper, we report on the RF modeling results of a proposed helical kicker. Two beam kickers constitutes the proposed chopper. The beam sequence is formed by kicking in or out the beam bunches from the streamline. The chopper was developed for Project X Injection Experiment (PXIE).

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY016

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY017

Development of 650 MHz β=0.9 5-cell Elliptical Cavities for PIP-II

3296

M.H. Awida, M.H. Foley, I.V. Gonin, C.J. Grimm, T.N. Khabiboulline, A. Lunin, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

5-cell 650 MHz elliptical cavities are being developed for the Proton Improvement Plan II (PIP-II) of Fermilab. The cavities are designed to accelerate protons of relative group velocity β=0.9 at the high energy part of the linear particle accelerator. In this paper, we report the status of these cavities and summarize the results of the quality control measurements performed on four initial prototypes.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY017

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY018

Analysis of a Quasi-waveguide Multicell Resonator for SPX

3299

M.H. Awida, I.V. Gonin, T.N. Khabiboulline, A. Lunin, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA
A. Zholents
ANL, Argonne, Ilinois, USA

A compact deflecting cavity is needed for the Short Pulse X-rays (SPX) at the Advanced Photon Source (APS) of Argonne national laboratory. The deflecting cavity has to quite efficient providing a 2 MV kick voltage and satisfying stringent requirements on aperture size and total cavity length. Meanwhile, the cavity should allow operation up to 100 mT peak surface magnetic field before quenching. In this paper, we report on the latest analysis carried out on the cavity structure to investigate frequency sensitivity to pressure fluctuations, frequency sensitivity to tuning forces, modal frequency, and wakefield losses.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY018

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY019

Transverse Field Perturbation For PIP-II SRF Cavities

3302

P. Berrutti, T.N. Khabiboulline, V.A. Lebedev, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Funding: Work supported by D.O.E. Contract No. DE-AC02-07CH11359
Proton Improvement Plan II (PIP-II) consists in a plan for upgrading the Fermilab proton accelerator complex to a beam power capability of at least 1 MW delivered to the neutrino production target. A room temperature section accelerates H⁻ ions to 2.1 MeV and creates the desired bunch structure for injection into the superconducting (SC) linac. Five cavity types, operating at three different frequencies 162.5, 325 and 650 MHz, provide acceleration to 800 MeV. This paper presents the studies on transverse field perturbation on particle dynamic for all the superconducting cavities in the linac. The effects studied include quadrupole defocusing for coaxial resonators, and dipole kick due to couplers for elliptical cavities. A multipole expansion has been performed for each of the cavity designs including effects up to octupole.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY019

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY021

Origin of Trapped Flux Caused by Quench in Superconducting Niobium Cavities

3309

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

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
In this study we prove that the mechanism at the basis of quality factor degradation due to quench involves the entrapment of ambient magnetic field. The cavity quench in the absence of magnetic field does not introduce any extra losses, and a clear trend between the external field and the extra losses introduced by the quench was observed. It is demonstrated that the quality factor can be totally recovered by quenching in zero applied magnetic field. A dependence of the amount of quality factor degradation on the orientation of the magnetic field with respect to the cavity was also found.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY022

Modifications of Superconducting Properties of Niobium Caused by Nitrogen Doping Recipes for High Q Cavities

3312

A. Vostrikov, M. Checchin, A. Grassellino, A. Romanenko
Fermilab, Batavia, Illinois, USA
Y.K. Kim, A. Vostrikov
University of Chicago, Chicago, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Discovery at Fermilab of a drastic effect of nitrogen doping leading to unprecedented high Q values in niobium cavities * motivated a strong interest in revealing the physics underlying the effect. In this contribution we present new results obtained by DC magnetometry, AC susceptibility, resistivity and thermal properties measurements on nitrogen doped samples prepared by different recipes/doping levels, which shed light on the possible origin of the effect.
* A. Grassellino et al, 2013 Supercond. Sci. Technol. 26 102001

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY022

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY034

T-map Studies on Gradient-limiting Mechanism in Nitrogen Doped Cavities

3348

M. Martinello, M. Checchin, A. Grassellino, A. Romanenko
Fermilab, Batavia, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Nitrogen doping * results in ultra-high quality factors in SRF niobium cavities but currently achievable gradients in doped cavities are, on average, somewhat lower than in EP/120C baked cavities. The origin of this difference is explored in the reported work by detailed temperature mapping studies on several single cell nitrogen doped cavities.
* A. Grassellino et al, 2013 Supercond. Sci. Technol. 26 102001

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY034

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY035

Design and Test of the Compact Tuner for Narrow Bandwidth SRF Cavities

3352

Y.M. Pischalnikov, E. Borissov, I.V. Gonin, J.P. Holzbauer, T.N. Khabiboulline, W. Schappert, S.J. Smith, J.C. Yun
Fermilab, Batavia, Illinois, USA

Funding: Fermi Research Alliance, LLC under Contract N. DE-AC02-07CH11359 with U.S. Department of Energy.
The design of the compact tuner for 1.3 GHz 9-cell elliptical cavity will be presented. This compact tuner is designed for future accelerators that will operate in CW and pulsed RF-power modes. The major design features include highly reliable active components (electromechanical actuators and piezo-actuators) and the ability to replace tuner active components through designated ports in the cryomodule vacuum vessel. Results of tuner testing with cold cavity will also be presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY035

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY036

Progress at FNAL in the Field of the Active Resonance Control for Narrow Bandwidth SRF Cavities.

3355

W. Schappert, J.P. Holzbauer, Y.M. Pischalnikov
Fermilab, Batavia, Illinois, USA

Funding: Fermi Research Alliance, LLC under Contract N. DE-AC02-07CH11359 with U.S. Department of Energy.
Recent efforts at FNAL to actively compensate microphonics in narrow bandwidth cavities are discussed. Feed-forward compensation of Lorentz force detuning in combination with feedback of the forward/probe phase difference to a piezo actuator successfully stabilized the resonance of a 325 MHz spoke resonator to within 11 mHz of the frequency of the open-loop CW RF drive over a two hour interval.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY036

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY060

Virtual Welding as a Tool for Superconducting Cavity Coarse Tuning

3412

A. Facco, C. Compton, J. Popielarski, G.J. Velianoff
FRIB, East Lansing, Michigan, USA

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
Reaching the final frequency in the construction of Superconducting Half-Wave Resonators (HWR), either coaxial or spoke, is often a painful and time consuming process which requires several intermediate frequency tests and parts machining between subsequent welding steps. In spite of that, the final frequency error after final welding is often far from the target due to difficult to predict material contraction and cavity deformation induced by electron beam welding (EBW). Final coarse tuning is required by plastic deformation or differential etching. In coaxial HWR, both can decrease the cavity frequency but are not easily suitable to increase it. A novel method developed at MSU is “virtual” welding, i.e. deformation of the cavity shape by applying systematically EBW on the cavity outer surface to induce controlled Nb material contraction in strategic positions. This technique allows to increase the cavity frequency with excellent precision and predictability, thus simplifying and making less expensive and more reliable HWR coarse tuning. Method and experimental results will be described and discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY060

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY062

Multipactor Breakdown Modelling Using an Averaged Version of Furman's SEY Model

3419

S.A. Rice, J.P. Verboncoeur
Michigan State University, East Lansing, Michigan, USA

Funding: Work supported by a MSU Strategic Partnership Grant.
Furman's seconday electron yield model is commonly used for the simulation of multipactor in accelerating cavities and other resonant structures. While accurate, the stochastic model requires many Monte Carlo simulations in order to characterize susceptibility to multipactor. This paper generalizes our previous research in characterizing a reduced-order Furman model, in which we replace the stochastic Furman model with a deterministic model based upon the Furman model's underlying statistics. Favorable comparisons between the full Furman model and the reduced-order Furman model are shown for multipactor simulations in a coaxial cavity, and the results are expected to generalize to other geometries.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY062

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY066

T-Maps Taken During Cool-down of an SRF cavity: a Tool to Understand Flux Trapping

3431

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

During the past years the impact of cool-down procedures on the flux trapping properties of superconducting cavities have been under investigation. We have measured temperature distributions of a multi-cell cavity using a T-map set-up to understand the transition to superconductivity in detail. We will report how the spatial disorder is affected by the cool-down speed and relate our findings to data on flux pinning.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY066

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY067

Thermal and Mechanical Analysis of a Waveguide to Coax Symmetric Coupler for Superconducting Cavities

3434

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

As kicks from fundamental power couplers become a concern for low emittance future accelerators, a design for a symmetric coupler for superconducting accelerating cavities has been started. In this coupler, a rectangular waveguide transforms into a coaxial line inside the beam pipe to feed the cavity. So far the RF design revealed an extremely low transversal kick but concerns about cooling and the thermal stability of the coaxial transition line remained. Our contribution will address this. We will calculate heating, heat transfer and thermal stability of this coupler and evaluate the risk of quenching due to particle losses on the coupler.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY067

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY068

Asymmetric Thermo-currents Diminishing SRF Cavity Performance

3437

R.G. Eichhorn, J. May-Mann
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Over the past years it became evident that the quality factor of a superconducting cavity is not only determined by its surface preparation procedure, but is also influenced by the way the cavity is cooled down. In this paper we will present results from numerical field calculations of magnetic fields produced by thermo-currents, driven by temperature gradients and material transitions. We will show how they can impact the quality factor of a cavity by producing a magnetic field at the RF surface of the cavity.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY068

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY069

Complection of the Cornell High Q CW Full Linac Cryo-module

3440

R.G. Eichhorn, B. Bullock, B. Clasby, J.V. Conway, B. Elmore, F. Furuta, G.M. Ge, G.H. Hoffstaetter, M. Liepe, T.I. O'Connel, P. Quigley, D.M. Sabol, J. Sears, E.N. Smith, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
Y. He
Fermilab, Batavia, Illinois, USA

Cornell University has finished building a 10 m long superconducting accelerator module as a prototype of the main linac of a proposed ERL facility. This module houses 6 superconducting cavities- operated at 1.8 K in continuous wave (CW) mode - with individual HOM absorbers and one magnet/ BPM section. In pushing the limits, a high quality factor of the cavities (2x10¹⁰) and high beam currents (100 mA accelerated plus 100 mA decelerated) were targeted. We will review the design shortly and present the results of the components tested before the assembly. This includes data of the quality-factors of all 6 cavities that we produced and treated in-house, the HOM absorber performance measured with beam on a test set-up as well as testing of the couplers and the tuners.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY069

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY072

Update on Nitrogen-doped 9-cell Cavity Performance in the Cornell Horizontal Test Cryomodule

3446

D. Gonnella, R.G. Eichhorn, F. Furuta, G.M. Ge, D.L. Hall, Y. He, K.M.V. Ho, G.H. Hoffstaetter, M. Liepe, J.T. Maniscalco, T.I. O'Connel, S. Posen, P. Quigley, J. Sears, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
A. Grassellino, C.J. Grimm, O.S. Melnychuk, A. Romanenko
Fermilab, Batavia, Illinois, USA

Funding: U.S. Department of Energy
The Linac Coherent Light Source-II (LCLS-II) is a new x-ray source that is planned to be constructed in the existing SLAC tunnel. To meet the quality factor specifications (2.7x 10¹⁰ at 2.0 K and 16 MV/m), nitrogen-doping has been proposed as a preparation method for the SRF cavities. In order to demonstrate the feasibility of these goals, four 9-cell cavity tests have been completed in the Cornell Horizontal Test Cryomodule (HTC), which serves as a test bench for the full LCLS-II cryomodule. Here we report on the most recent two cavity tests in the HTC: one cavity nitrogen-doped at Cornell and tested with high Q input coupler and then again tested with high power LCLS-II input coupler. Transition to test in horizontal cryomodule resulted in no degradation in Q0 from vertical test. Additionally, increased dissipated power due to the high power input coupler was small and in good agreement with simulations. These results represent a crucial step on the way to demonstrating technical readiness for LCLS-II.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY072

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY073

Update on Nitrogen Doping: Quench Studies and Sample Analysis

3450

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

Funding: U.S. Department of Energy, NSF
Recently, nitrogen-doping of niobium has emerged as a promising preparation method for SRF cavities to reach higher intrinsic quality factors than can be reached with typical cavity preparation. Nitrogen-doped cavities prepared at Cornell have shown quality factors higher than 4x10¹⁰ at 2.0 K and 16 MV/m. While Q results have been very exciting, a reduced quench field currently limits nitrogen-doped cavities with quench typically occurring between 15 and 25 MV/m. Here we report on recent results from Cornell on single-cell and 9-cell cavities, focusing on new preparations and maximum and critical fields. First we discuss results from over-doping niobium with nitrgoen, baking nitrogen-doped cavities at 120C, and doping with Argon. For a subset of these cavities we show results from quench studies that have been completed using temperature mapping. Finally, we present the first measurements of the higher critical field, Hc2, for nitrogen-doped niobium samples.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY073

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY074

Recent Studies on the Current Limitations of State-of-the-Art Nb3Sn Cavities

3454

D.L. Hall, M. Liepe, J.T. Maniscalco, S. Posen
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
Th. Proslier
ANL, Argonne, Illinois, USA

Funding: NSF PHY-1305500 PHY-14116318 DOE ER41802
Recent advances in the study of Nb3Sn at Cornell University have yielded single-cell cavities that show excellent performance without the limiting Q-slope seen in previous work. This performance has been shown to be repeatable across multiple cavities. However, they are still limited by a quench field of approximately 16 MV/m, as well as residual resistance. In this work we present results quantifying the impact of ambient magnetic fields on Nb3Sn cavities, as well as discuss the impact of cavity cooldown procedures on cavity performance. Finally, we will briefly discuss XRD results that shed light on the composition of the Nb3Sn layer and how this relates to the current limits of these cavities.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY074

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY075

Hc2 Measurements of Nb3Sn and Nitrogen-doped Niobium using Physical Property Measurement System

3458

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

The measurement of the upper critical field of a type-2 superconductor, Hc2, is an important step in determining its superconducting properties, and therefore its suitability as a material in SRF cavities. However, measuring Hc2 directly can be challenging, as performing electrical measurements causes changes in the very properties one seeks to measure. We present a method for extracting Hc2 from resistivity measurements made near the transition temperature for varied applied fields and excitation currents. We also present results of these measurements made on Nb3Sn and nitrogen-doped niobium.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY075

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY076

RF Performance Studies of Thin-Film Superconductors Using a Sample Host Cavity

3462

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

Thin-film superconductors have the potential for reduced cost and for improved SRF performance over traditional bulk niobium superconducting cavities. Materials such as Nb3Sn, multilayer NbN/MgO, and thin-film Nb are currently under investigation for cost reduction or possible improvements in RF losses and accelerating gradients. Due to the complex geometries of traditional RF cavities, it is preferable to use a sample host cavity to study flat samples of the novel materials. The Cornell sample host cavity has been commissioned and has now reached peak magnetic surface fields of 100 mT. We present updates on the recent performance of the cavity.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY076

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY077

On Quench Propagation, Quench Detection, and Second Sound in SRF Cavities

3464

S.R. Markham, R.G. Eichhorn
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

The detection of a second sound wave, excited by a quench, has become a valuable tool in diagnosing hot spots and performance limitations of superconducting cavities. Several years ago, Cornell developed an oscillating super-leak transducer (OST) for these waves that nowadays are used world-wide. In a usual set-up, several OSTs surround the cavity, and the quench location is determined by triangulation of the different OST signals. Convenient as the method is there is a small remaining mystery: taking the well-known velocity of the second sound wave, the quench seems to come from a place slightly above the cavity’s outer surface. We will present a model based on numerical quench propagation simulations and analytic geometrical calculations that help explain the discrepancy.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY077

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY078

High Q0 at Medium Fields in Nb3Sn SRF Cavities at 4.2 K

3467

S. Posen, D.L. Hall, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
Th. Proslier
ANL, Argonne, Illinois, USA

Nb3Sn has proven itself to be a very promising alternative SRF material. With twice the critical temperature of niobium cavities, 1.3 GHz Nb3Sn cavities can achieve quality factors on the order of 10¹⁰ even at 4.2 K, significantly reducing cryogenic infrastructure and operational costs. In addition, its large predicted superheating field may allow for maximum accelerating gradients up to twice that of niobium for high energy applications. In this work, we report on new cavity results from the Cornell Nb3Sn SRF program demonstrating a significant improvement in the maximum field achieved with high Q0 in a Nb3Sn cavity. At 4.2 K, accelerating gradients above 16 MV/m were obtained with Q0 of 8x10⁹, showing the potential of this material for future applications. In addition to this result, current limitations are discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY078

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY082

High Gradient Testing of the Five-cell Superconducting RF Module with a PBG Coupler Cell

3471

S. Arsenyev, W.B. Haynes, D.Y. Shchegolkov, E.I. Simakov, T. Tajima
LANL, Los Alamos, New Mexico, USA
C.H. Boulware, T.L. Grimm, A. Rogacki
Niowave, Inc., Lansing, Michigan, USA

We report results of high-gradient testing of the first 5- cell superconducting radio frequency (SRF) module with a photonic band gap cell (PBG). Higher order mode (HOM) damping is vital for preserving the quality of high-current electron beams in novel SRF accelerators. Because HOMs are not confined by the PBG array, they can be effectively damped in order to raise the current threshold for beam instabilities. The PBG design increases the real-estate gradient of the linac because both HOM damping and the fundamental power coupling can be done through the PBG cell instead of via the beam pipe at the ends of the cavity. A superconducting multi-cell cavity with a PBG damping cell is therefore an attractive option for high-current linacs. The first-ever SRF multi-cell cavity incorporating a PBG cell was designed a LANL and built at Niowave Inc. The cavity was tuned to a desired gradient profile and underwent surface treatment at Niowave. A vertical test (VTS) was then performed at LANL, demonstrating an abnormally low cavity quality factor in the accelerating mode of 1.6*10⁶. Future tests are proposed to determine the source of the losses and resolve the problem.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY082

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTY083

Five-cell Superconducting RF Module with a PBG Coupler Cell: Design and Cold Testing of the Copper Prototype

3475

S. Arsenyev, D.Y. Shchegolkov, E.I. Simakov
LANL, Los Alamos, New Mexico, USA
C.H. Boulware, T.L. Grimm, A. Rogacki
Niowave, Inc., Lansing, Michigan, USA

We report the design and experimental data for a copper prototype of a superconducting radio-frequency (SRF) accelerator module. The five-cell module has an incorporated photonic band gap (PBG) cell with couplers. The purpose of the PBG cell is to achieve better higher order mode (HOM) damping which is vital for preserving the quality of highcurrent electron beams. Better HOM damping raises the current threshold for beam instabilities in novel SRF accelerators. The PBG design also increases the real-estate gradient of the linac because both HOM damping and the fundamental power coupling can be done through the PBG cell instead of on the beam pipe via complicated end assemblies. First, we will discuss the design and accelerating properties of the structure. The five-cell module was optimized to provide good HOM damping while maintaining the same accelerating properties as conventional elliptical-cell modules. We will then discuss the process of tuning the structure to obtain the desired accelerating gradient profile. Finally, we will list measured quality factors for the accelerating mode and the most dangerous HOMs.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY083

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI004

FPC and Hi-Pass Filter HOM Coupler Design for the RF Dipole Crab Cavity for the LHC HiLumi Upgrade

3492

Z. Li
SLAC, Menlo Park, California, USA
S.U. De Silva, J.R. Delayen, R.G. Olave, H. Park
ODU, Norfolk, Virginia, USA

Funding: Work partially supported by the US DOE through the US LHC Accelerator Research Program (LARP), and by US DOE under contract number DE-AC02-76SF00515.
A 400-MHz compact RF dipole (RFD) crab cavity design was jointly developed by Old Dominion University and SLAC under the support of US LARP program for the LHC HiLumi upgrade. The RFD cavity design is consisted of a rounded-square tank and two ridged deflecting poles, operating with a TE11-like dipole mode, which is the lowest mode of the cavity. A prototype RFD cavity is being manufactured and will be tested on the SPS beam line at CERN. The coaxial fundamental Power Coupler (FPC) of the prototype cavity was re-optimized to minimizing the power heating on the coupler internal antenna. A hi-pass filter HOM damping coupler was developed to achieve the required wakefield damping while maintaining a compact size to fit into the beam line space. In this paper, we will discuss the details of the RF optimization and tolerance analyses of the FPC and HOM couplers.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI004

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI007

TTF3 Power Coupler Thermal Analysis for LCLS-II CW Operation

3503

L. Xiao, C. Adolphsen, Z. Li, C.D. Nantista, T.O. Raubenheimer
SLAC, Menlo Park, California, USA
I.V. Gonin, N. Solyak
Fermilab, Batavia, Illinois, USA

The TESLA 9-cell SRF cavity design has been adopted for use in the LCLS-II SRF Linac. Its TTF3 coaxial Fundamental Power Coupler (FPC), developed for pulsed operation in the European XFEL and ILC, requires modest changes to make it suitable for LCLS-II CW operation, in which it must be able to handle up to 7 kW of average power with the maximum temperature rise not to exceed 150 C. In order to improve TTF3 FPC cooling, an increased copper plating thickness will be used on the inner and outer conductor stainless steel RF surfaces. Fully 3D FPC thermal analysis with copper plating was performed using the SLAC developed parallel finite element code suite ACE3P with integrated electromagnetic, thermal and mechanical multi-physics simulation capabilities. In this paper, we present TTF3 FPC thermal analysis simulation results obtained using ACE3P as well as a comparison with measurement results.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI007

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI009

Nitrogen Doping Study in Ingot Niobium Cavities

3506

P. Dhakal, G. Ciovati, P. Kneisel, G.R. Myneni
JLab, Newport News, Virginia, USA
J. Makita
ODU, Norfolk, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
Thermal diffusion of nitrogen in superconducting radio frequency cavities at temperatures around 800C has resulted in the increase in quality factor with a low-field Q-rise. However, the maximum accelerating gradients of these doped cavities often reduces below the values achieved by standard treatments. In this contribution, we present the results of the nitrogen diffusion into ingot niobium cavities subjected to successive material removal from the inner cavity surface by electropolishing in an effort to explore the underlying cause for the gradient degradation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI009

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI010

Results from the First Single Cell Nb3Sn Cavity Coatings at JLab

3509

G.V. Eremeev
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Nb3Sn is a promising superconducting material for SRF applications and has the potential to exceed the limitations of niobium. We have used the recently commissioned Nb3Sn coating system to investigate Nb3Sn coatings on several single cell cavities by applying the same coating procedure on several different single cells with different history and pre-coating surface preparation. We report on our findings with four 1.5 GHz CEBAF-shape single cell and one 1.3 GHz ILC-shape single cavities that were coated, inspected, and tested.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI010

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI011

Commissioning Results of Nb3Sn Cavity Vapor Diffusion Deposition System at JLab

3512

G.V. Eremeev, W.A. Clemens, K. Macha, H. Park, R.S. Williams
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Nb3Sn as a BCS superconductors with a superconducting critical temperature higher than that of niobium offers potential benefit in lower surface resistance at the same temperature and frequency for SRF cavities. A Nb3Sn vapor diffusion deposition system was built and commissioned at Jefferson Lab. As the part of the commissioning a single cell 1.5 GHz CEBAF-shaped cavity was coated in the built system. The cavity exhibited the superconducting transition at about 17.9 K. The low field quality factor was about 5x10⁹ at 4 K and 7x10⁹ at 2 K dropping with field to about 10⁹ at both temperatures at about 8 MV/m.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI011

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI012

First Attempt of At-cavity X-ray Detection in a CEBAF Cryomodule for Field Emission Monitoring

3515

R.L. Geng, E. Daly, M.A. Drury, A.D. Palczewski
JLab, Newport News, Virginia, USA

We report on the first result of at-cavity X-ray detection in a CEBAF cryomodule for field emission monitoring. In the 8-cavity cryomodule F100, two silicon diodes were installed near the end flange of each cavity. Each cavity was individually tested during the cryomodule test in JLab’s cryomodule test facility. The behaviors of these at-cavity cryogenic X-ray detectors were compared with those of the standard “in air” Geiger-Muller tubes. Our initial experiments establish correlation between X-ray response of near diodes and the field emission source cavity in the 8-cavity string. For two out of these eight cavities, we also carried out at-cavity X-ray detection experiment during their vertical testing. The aim is to track field emission behavior uniquely from vertical cavity testing to horizontal cavity testing in the cryomodule.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI012

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI013

New Results of Development on High Efficiency High Gradient Superconducting RF Cavities

3518

R.L. Geng
JLab, Newport News, Virginia, USA
C. Adolphsen, Z. Li
SLAC, Menlo Park, California, USA
J.K. Hao, K.X. Liu
PKU, Beijing, People's Republic of China
H.Y. Zhao
Ningxia Orient Tantalum Industry Co., Ltd., Dawukou District, Shizuishan city, People's Republic of China

We report on the latest results of development on high efficiency high gradient superconducting radio frequency (SRF) cavities. Several 1-cell cavities made of large-grain niobium (Nb) were built, processed and tested. Two of these cavities are of the Low Surface Field (LSF) shape. Series of tests were carried out following controlled thermal cycling. Experiments toward zero-field cooling were carried out. The best experimentally achieved results are Eacc = 41 MV/m at Q0 = 6.5×10¹⁰ at 1.4 K by a 1-cell 1.3 GHz large-grain Nb TTF shape cavity and Eacc = 49 MV/m at Q0 = 1.5×1010 at 1.8 K by a 1-cell 1.5 GHz large-grain Nb CEBAF upgrade low-loss shape cavity.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI013

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI015

BNL 56 MHz HOM Damper Prototype Fabrication at JLab

3521

N.A. Huque, W.A. Clemens, E. Daly
JLab, Newport News, Virginia, USA
S. Bellavia, G.T. McIntyre, S.K. Seberg, Q. Wu
BNL, Upton, Long Island, New York, USA

A prototype Higher-Order Mode (HOM) Damper was fabricated at JLab for the Relativistic Heavy-Ion Collider’s (RHIC) 56 MHz cavity at Brookhaven National Laboratory (BNL). Primarily constructed from high RRR Niobium and Sapphire, the coaxial damper presented significant challenges in electron-beam welding (EBW), brazing and machining via acid etching. The results of the prototype operation brought about changes in the damper design, due to overheating braze alloys and possible multi-pacting. Five production HOM dampers are currently being fabricated at JLab. This paper outlines the challenges faced in the fabrication process, and the solutions put in place.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI015

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI016

Investigation of Differential Surface Removal due to Electropolishing at JLab

3525

F. Marhauser, J. Follkie, C.E. Reece
JLab, Newport News, Virginia, USA

Surface chemistry carried out for Superconducting Radio Frequency (SRF) cavities such as Buffered Chemical Polishing (BCP) and Electropolishing (EP) aims to uniformly remove the internal surface of a cavity along the entire structure and within each cell from equator to iris in order to obtain an equally etched surface. A uniform removal however is not readily achievable due to the complex fluid flow and varying temperatures of the acid mixture, which can lead to differential etching. This needs to be considered when envisaging a certain surface damage removal throughout the interior. The process-specific differential etching influences the target frequency set at the manufacturing stage as well as the field flatness and length of the as-built cavity. We report on analyses of JLab's present EP system using experimental data for six nine-cell cavities that have been processed recently in the frame of the LCLS-II high-Q development plan. In conjunction with numerical simulations, the differential etching and the impact on field flatness is assessed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI016

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI019

Quench Studies of Six High Temperature Nitrogen Doped 9 Cell Cavities for Use in the LCLS-II Baseline Prototype Cryo-module at Jefferson Laboratory

3528

A.D. Palczewski, G.V. Eremeev, R.L. Geng, C.E. Reece
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Jefferson Lab (JLab) processed six nine-cell cavities as part of a small-scale production for LCLS-II cavity processing development utilizing the promising nitrogen-doping process. [1] Various nitrogen-doping recipes have been scrutinized to optimize process parameters with the aim to guarantee an unloaded quality factor (Q 0) of 2.7·10¹⁰ at an accelerating field (Eacc) of 16 MV/m at 2.0 K in the cryomodule. During the R&D phase the characteristic Q0 vs. Eacc performance curve of the cavities has been measured in JLab’s vertical test area at 2 K. The findings showed the characteristic rise of the Q0 with Eacc as expected from nitrogen-doping. Initially, five cavities achieved an average Q0 of 3.3·10¹⁰ at the limiting Eacc averaging to 16.8 MV/m, while one cavity experienced an early quench accompanied by an unusual Q 0 vs. Eacc curve. The project accounts for a cavity performance loss from the vertical dewar test (with or without the helium vessel) to the horizontal performance in a cryomodule, such that these results leave no save margin to the cryomodule specification. Consequently, a refinement of the nitrogen-doping has been initiated to guarantee an average quench field above 20 MV/m without impeding the Q 0. This paper covers the refinement work performed for each cavity, which depends on the initial results, as well as a quench analysis carried out before and after the rework during the vertical RF tests as far as applicable.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI019

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI021

An Analysis of the Temperature and Field Dependence of the RF Surface Resistance of Nitrogen-Doped Niobium SRF Cavities with Respect to Existing Theoretical Models

3532

C.E. Reece, A.D. Palczewski
JLab, Newport News, Virginia, USA
B. P. Xiao
BNL, Upton, Long Island, New York, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177
Recent progress with the reduction of rf surface resistance (Rs) of niobium SRF cavities via the use of high temperature surface doping by nitrogen has opened a new regime for energy efficient accelerator applications. For particular doping conditions one observes dramatic decreases in Rs with increasing surface magnetic fields. The observed variations as a function of temperature may be analyzed in the context of recent theoretical treatments in hopes of gaining insight into the underlying beneficial mechanism of the nitrogen treatment. Systematic data sets of Q0 vs. Eacc vs. temperature acquired during the high Q0 R&D work of the past year will be compared with theoretical model predictions. *
* B. P. Xiao et al., Physica C: Superconductivity 490 (0), 26-31 (2013) and
A. Gurevich, PRL 113 (8), 087001 (2014)

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI022

RF System Requirements for a Medium-Energy Electron-Ion Collider (MEIC) at JLab

3536

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

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
JLab is studying options for a medium energy electron-ion collider that could fit on the JLab site and use CEBAF as a full-energy electron injector. A new ion source, linac and booster would be required, together with collider storage rings for the ions and electrons. In order to achieve the maximum luminosity these will be high current storage rings with many bunches. We present the high level RF system requirements for the storage rings, ion booster ring and high-energy ion beam cooling system, and describe the technology options under consideration to meet them. We also present options for staging that might reduce the initial capital cost while providing a smooth upgrade path to a higher final energy. The technologies under consideration may also be useful for other proposed storage ring colliders or ultimate light sources.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI022

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI030

Injector Cavities Fabrication, Vertical Test Performance and Primary Cryomodule Design

3551

H. Wang, G. Cheng, W.A. Clemens, G.K. Davis, K. Macha, R.B. Overton, D. Spell
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
After the electromagnetic design * and the mechanical design ** of a β=0.6, 2-cell elliptical SRF cavity, the cavity has been fabricated. Then both 2-cell and 7-cell cavities have been bench tuned to the target values of frequency, coupling external Q and field flatness. After buffer chemistry polishing (BCP) and high pressure rinses (HPR), Vertical 2K cavity test results have been satisfied the specifications and ready for the string assembly. We will report the cavity performance including Lorenz Force Detuning (LFD) and Higher Order Modes (HOM) damping data. Its integration with cavity tuners to the cryomodule design will be reported.
* H. Wang, etc., Proceeding of IPAC2013, Shanghai, China, WEPWO073.
** G. Cheng, etc., Proceeding of PAC2013, Pasadena, CA, WEPAC47.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI030

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI032

Mechanical Properties of Niobium Cavities

3554

G. Ciovati, P. Dhakal, J. Matalevich, G.R. Myneni
JLab, Newport News, Virginia, USA

Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
The mechanical stability of bulk Nb cavity is an important aspect to be considered in relation to cavity material, geometry and treatments. Mechanical properties of Nb are typically obtained from uniaxial tensile tests of small samples. In this contribution we report the results of measurements of the resonant frequency and local strain along the contour of single-cell cavities made of ingot and fine-grain Nb of different purity subjected to increasing uniform differential pressure, up to 6 atm. Measurements have been done on cavities subjected to different heat treatments. Good agreement between finite element analysis simulations and experimental data in the elastic regime was obtained with a single set of values of Young’s modulus and Poisson’s ratio. The experimental results indicate that the yield strength of medium-purity ingot Nb cavities is higher than that of fine-grain, high-purity Nb.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI032

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI034

Effects of Crab Cavities' Multipole Content in an Electron-Ion Collider

3561

A. Castilla, J.R. Delayen, T. Satogata
ODU, Norfolk, Virginia, USA
A. Castilla, J.R. Delayen, V.S. Morozov, T. Satogata
JLab, Newport News, Virginia, USA
A. Castilla
DCI-UG, León, Mexico

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The impact on the beam dynamics of the Medium Energy Electron-Ion Colider (MEIC) due to the multipole content of the 750 MHz crab cavity was studied using thin multipole elements for 6D phase space particle tracking in ELEGANT. Target values of the sextupole component for the cavity’s field expansion were used to perform preliminary studies on the proton beam stability when compared to the case of pure dipole content of the rf kicks. Finally, important effects on the beam sizes due to non-linear components of the crab cavities’ fields were identified and some criteria for their future study were proposed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI034

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI035

Beam Dynamics Studies of 499 MHz Superconducting RF-Dipole Deflecting Cavity System

3564

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

A 499 MHz deflecting cavity has been designed as a three-way beam spreader to separate an electron beam into 3 beams. The rf tests carried out on the superconducting rf-dipole cavity have demonstrated that a transverse voltage of 4.2 MV can be achieved with a single cavity. This paper discusses the beam dynamics on a deflecting structure operating in continuous-wave mode with a relativistic beam. The study includes the analysis on emittance growth, energy spread, and change in bunch size including effects due to field non-uniformities.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI035

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI036

Design and Prototyping of a 400 MHz RF-dipole Crabbing Cavity for the LHC High-Luminosity Upgrade

3568

S.U. De Silva, J.R. Delayen, H. Park
ODU, Norfolk, Virginia, USA
Z. Li
SLAC, Menlo Park, California, USA
T.H. Nicol
Fermilab, Batavia, Illinois, USA

LHC High Luminosity Upgrade is in need of two crabbing systems that deflects the beam in both horizontal and vertical planes. The 400 MHz rf-dipole crabbing cavity system is capable of crabbing the proton beam in both planes. At present we are focusing our efforts on a complete crabbing system in the horizontal plane. Prior to LHC installation the crabbing system will be installed for beam test at SPS. The crabbing system consists of two rf-dipole cavities in the cryomodule. This paper discusses the electromagnetic design and mechanical properties of the rf-dipole crabbing system for SPS beam test.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI036

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI037

Imperfection and Tolerance Analysis of HOM Couplers for ODU/SLAC 400 MHz Crabbing Cavity

3572

S.U. De Silva, J.R. Delayen, H. Park
ODU, Norfolk, Virginia, USA
Z. Li
SLAC, Menlo Park, California, USA
R.G. Olave
Old Dominion University, Norfolk, Virginia, USA

In preparation for the LHC High Luminosity upgrade, a 400 MHz crab cavity has been developed jointly at ODU/SLAC, including two higher order mode couplers designed to dampen the wakefields in order to comply with the impedance budget specified for the LHC system. During fabrication, assembly, and processing of the couplers, a number of imperfections may arise that could modify the higher order mode spectrum and the associated impedance for each mode. We present here a detailed study of the imperfections of the horizontal- and vertical- HOM couplers, and the associated allowed tolerances for manufacture, assembly and processing.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI037

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI038

Temperature Mapping of Nitrogen-doped Niobium Superconducting Radiofrequency Cavities

3575

J. Makita
ODU, Norfolk, Virginia, USA
G. Ciovati, P. Dhakal
JLab, Newport News, Virginia, USA

It was recently shown that diffusing nitrogen on the inner surface of superconducting radiofrequency (SRF) cavities at high temperature can improve the quality factor of the niobium cavity. However, a reduction of the quench field is also typically found. To better understand the location of rf losses and quench, we used a thermometry system to map the temperature of the outer surface of ingot Nb cavities after nitrogen doping and electropolishing. Surface temperature of the cavities was recorded while increasing the rf power and also during the quenching. The results of thermal mapping showed no precursor heating on the cavities and quenching to be ignited near the equator where the surface magnetic field is maximum. Hot-spots at the equator area during multipacting were also detected by thermal mapping.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI038

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI039

Engineering Study of Crab Cavity HOM Couplers for LHC High Luminosity Upgrade

3578

H. Park, S.U. De Silva, J.R. Delayen, R.G. Olave
ODU, Norfolk, Virginia, USA
T. Capelli
CERN, Geneva, Switzerland
S.U. De Silva, J.R. Delayen, H. Park
JLab, Newport News, Virginia, USA
Z. Li
SLAC, Menlo Park, California, USA
T.H. Nicol
Fermilab, Batavia, Illinois, USA
N. Templeton
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

The LHC is planning to employ crab cavities for the high luminosity upgrade. Old Dominion University and SLAC National Laboratory are developing the crab cavity completed with the HOM damping couplers. The HOM couplers are coaxial type and perform over broad band up to 2 GHz. The amount of extracted power requires active cooling using liquid helium. The electromagnetic study has provided expected power dissipation on the coupler. Correlations between the fabrication tolerance and its damping performance have been studied and the results are providing guidelines on how to manufacture the HOM couplers. This paper summarizes the engineering studies; mechanical strength as a part of pressure system, thermal stability, and fabrication method to ensure the required tolerance.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI039

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI040

Experiment and Results on Plasma Etching of SRF Cavities

3581

J. Upadhyay, J.J. Peshl, S. Popović, L. Vušković
ODU, Norfolk, Virginia, USA
D.S. Im
Old Dominion University, Norfolk, Virginia, USA
H.L. Phillips, A-M. Valente-Feliciano
JLab, Newport News, Virginia, USA

The inner surfaces of SRF cavities are currently chemically treated (etched or electro polished) to achieve the state of the art RF performance. We designed an apparatus and developed a method for plasma etching of the inner surface for SRF cavities. The process parameters (pressure, power, gas concentration, diameter and shape of the inner electrode, temperature and positive dc bias at inner electrode) are optimized for cylindrical geometry. The etch rate non-uniformity has been overcome by simultaneous translation of the gas point-of-entry and the inner electrode during the processing. A single cell SRF cavity has been centrifugally barrel polished, chemically etched and RF tested to establish a baseline performance. This cavity is plasma etched and RF tested afterwards. The effect of plasma etching on the RF performance of this cavity will be presented and discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI040

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI045

Status of Superconducting Traveling Wave Cavity for High Gradient Linac

3591

R.A. Kostin, P.V. Avrakhov, A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
T.N. Khabiboulline, Y.M. Pischalnikov, N. Solyak, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

The use of a travelling wave (TW) accelerating structure with a small phase advance per cell instead of standing wave may provide a significant increase of accelerating gradient in a superconducting linear accelerator. The TW section achieves an accelerating gradient 1.2-1.4 times larger than TESLA-shaped standing wave cavities for the same surface electric and magnetic fields. The final stage of a 3-cell superconducting travelling wave cavity development is presented. This cavity will be tested in travelling wave regime at cryogenic temperature.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI045

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI046

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

3594

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

Funding: Work sponsored by DOE SBIR Grant DE-SC0002479.
We will report the first successful rf test of a detachable coaxial coupler by Euclid Techlabs and Fermilab SRF development department. The coaxial coupling method has vast advantages compared with ordinary welded-on couplers. It totally eliminates coupler kicks and it is detachable and easy to clean. We reached 26 MV/m (no hard quench limit) with a quarter-wave detachable coaxial coupler. This is also a demonstration of the highest field gradient ever reached with a superconducting joint.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI046

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI049

Commissioning of the 112 MHz SRF Gun and 500 MHz Bunching Cavities for the CeC PoP Linac

3597

S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, V. Litvinenko, G. Narayan, P. Orfin, I. Pinayev, T. Rao, J. Skaritka, K.S. Smith, R. Than, J.E. Tuozzolo, E. Wang, Q. Wu, B. P. Xiao, W. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko, T. Xin
Stony Brook University, Stony Brook, USA
P.A. McIntosh, A.J. Moss, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
The Coherent electron Cooling Proof-of-Principle (CeC PoP) experiment at BNL includes a short electron linac. During Phase I a 112 MHz superconducting RF photoemission gun and two 500 MHz normal conducting bunching cavities were installed and commissioned. The paper describes the Phase I linac layout and presents commissioning results for the cavities and associated RF, cryogenic and other sub-systems.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI049

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI050

SRF and RF Systems for LEReC Linac

3600

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

Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
The Low Energy RHIC electron Cooling (LEReC) is under development at BNL to improve RHIC luminosity at low energies. It will consist of a short electron linac and two cooling sections, one for blue and one for yellow beams. For the first stage of the project, LEReC-1, we will to install a 704 MHz superconducting RF cavity and two normal conducting cavities operating at 704 MHz and 2.1 GHz. The SRF cavity will boost the electron beam energy up to 2 MeV. The warm cavities will be used to correct the energy spread introduced in the SRF cavity. The paper describes layouts of the SRF and RF systems, their parameters and status.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI050

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI051

Update on the CeC POP 704 MHz 5-Cell Cavity Cryomodule Design and Fabrication

3603

J.C. Brutus, S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko, I. Pinayev, J. Skaritka, L. Snydstrup, R. Than, J.E. Tuozzolo, W. Xu
BNL, Upton, Long Island, New York, USA
S.M. Gerbick, M.P. Kelly, T. Reid
ANL, Argonne, USA
T.L. Grimm, R. Jecks, J.A. Yancey
Niowave, Inc., Lansing, Michigan, USA
Y. Huang
Fermilab, Batavia, Illinois, USA

Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
A 5-cell SRF cavity operating at 704 MHz will be used for the Coherent Electron Cooling Proof of Principle (CeC PoP) system currently under development for the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. The CeC PoP experiment will demonstrate the ability of relativistic electrons to cool a single bunch of heavy ions in RHIC. The cavity will accelerate 2 MeV electrons from a 112 MHz SRF gun up to 22 MeV. Novel mechanical designs, including the helium vessel, vacuum vessel, tuner mechanism, and FPC are presented. This paper provides an overview of the design, the project status and schedule of the 704 MHz 5-cell SRF for the CeC PoP experiment.
.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI051

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI052

Commissioning and Early Operation Experience of the NSLS-II Storage Ring RF System

3606

F. Gao, J. Cupolo, P. Davila, T. Dilgen, W.K. Gash, B. Holub, J.G. Kulpin, J. Papu, G. Ramirez, V. Ravindranath, B. Rose, J. Rose, R. Sikora, J. Tagger, M. Yeddulla
BNL, Upton, Long Island, New York, USA

The National Synchrotron Light Source II (NSLS-II) is a 3 GeV X-ray user facility commissioned in 2014. The storage ring RF system, essential for replenishing energy loss per turn of the electrons, consists of digital low level RF controllers, 310 kW CW klystron transmitters, CESR-B type superconducting cavities, as well as a supporting cryogenic system. Here we will report on RF commissioning and early operation experience of the system for beam current up to 200 mA.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI052

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI059

Higher Order Mode Filter Design for Double Quarter Wave Crab Cavity for the LHC High Luminosity Upgrade

3627

B. P. Xiao, S.A. Belomestnykh, I. Ben-Zvi, J. Skaritka, S. Verdú-Andrés, Q. Wu
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA
G. Burt, B.D.S. Hall
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
G. Burt
Lancaster University, Lancaster, United Kingdom
R. Calaga, O. Capatina
CERN, Geneva, Switzerland
T.J. Jones
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

Funding: Work partly supported by US LARP, by US DOE under contract No. DE-AC02-05CH11231 and through BSA under contract No. DE-AC02-98CH10886. Research supported by EU FP7 HiLumi LHC - Grant Agreement 284404.
A double quarter wave crab cavity (DQWCC) was designed for the Large Hadron Collider (LHC) luminosity upgrade. A compact Higher Order Mode (HOM) filter with wide stop band at the deflecting mode is developed for this cavity. Multi-physics finite element simulation results are presented. The integration of this design to the cavity cryomodule is described.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI059

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI060

Cryogenic Test of Double Quarter Wave Crab Cavity for the LHC High Luminosity Upgrade

3630

B. P. Xiao, S.A. Belomestnykh, I. Ben-Zvi, C. Cullen, L.R. Hammons, C. Marques, J. Skaritka, S. Verdú-Andrés, Q. Wu
BNL, Upton, Long Island, New York, USA
L. Alberty, R. Calaga, O. Capatina
CERN, Geneva, Switzerland
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA
Z. Li
SLAC, Menlo Park, California, USA

Funding: Work partly supported by US LARP, by US DOE under contract No. DE-AC02-05CH11231 and through BSA under contract No. DE-AC02-98CH10886. Research supported by EU FP7 HiLumi LHC - Grant Agreement 284404.
A Proof-of-Principle (PoP) Double Quarter Wave Crab Cavity (DQWCC) was designed and fabricated for the Large Hadron Collider (LHC) luminosity upgrade. A vertical cryogenic test has been done at Brookhaven National Lab (BNL). The cavity achieved 4.5 MV deflecting voltage with a quality factor above 3×10⁹. We report the test results of this design.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI060

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THXB1

CEBAF SRF Performance during Initial 12 GeV Commissioning

3638

R. Bachimanchi, T.L. Allison, E. Daly, M.A. Drury, C. Hovater, G.E. Lahti, C.I. Mounts, R.M. Nelson, T. E. Plawski
JLab, Newport News, Virginia, USA

The Continuous Electron Beam Accelerator Facility (CEBAF) energy upgrade from 6 GeV to 12 GeV includes the installation of eleven new 100 MV cryomodules (88 cavities). The superconducting RF cavities are designed to operate CW at an accelerating gradient of 19.3 MV/m with a QL of 3×107. Not all the cavities were operated at the minimum gradient of 19.3 MV/m with the beam. Though the initial 12 GeV milestones were achieved during the initial commissioning of CEBAF, there are still some issues to be addressed for long term reliable operation of these modules. This paper reports the operational experiences during the initial commissioning and the path forward to improve the performance of C100 (100 MV) modules.

Slides THXB1 [5.595 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-THXB1

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THXB2

Crab Cavities: Past, Present, and Future of a Challenging Device

3643

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

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with LARP and the U.S. Department of Energy and EU FP7 HiLumi LHC - Grant Agreement 284404
In two-ring facilities operating with a crossing angle collision scheme, the luminosity can be limited due to incomplete overlap of the colliding bunches. Crab cavities are introduced to restore head-on collisions by providing destined opposite deflection to the head and tail of the bunch. Luminosity increase has been demonstrated at KEKB with global crab crossing, and the Large Hardron Collider (LHC) at CERN is currently designing local crab crossing for the Hi-Lumi upgrade. Future colliders may investigate both approaches. This paper reviews the challenges in the technology and implementation of crab cavities, discusses experience in past colliders, ongoing R&D and proposed implementations for future facilities such as HL-LHC, CLIC, ILC, and eRHIC/MEIC.

Slides THXB2 [4.307 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-THXB2

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THZMS1

A New Class of Superconducting Structures for the Deflection and Crabbing of Particle Beams

S.U. De Silva
ODU, Norfolk, Virginia, USA

Recently, superconducting deflecting and crabbing cavities for particle accelerators and colliders have been an area of intense research. The future colliders pushing the energy and luminosity frontiers and particle accelerators with multi-experimental stations have expanded the need of deflecting/crabbing cavities. The current applications in need of such cavities operate at low frequencies and have also specifications with strict dimensional constraints, high operating transverse gradients, and tight impedance budgets. At low operating frequencies the use of standard cavities operating in TM110-like modes has been very challenging. A new type of superconducting deflecting/crabbing structure has been designed that has a wide range of applications. The new rf-dipole cavity operates in a TE11-like mode where several cavities have been fabricated, and tested. The rf performance shows that these structures are capable of operating at high transverse gradients and will be a very attractive deflecting/crabbing cavity for many current applications. At present, a 400 MHz rf-dipole crabbing cavity system is under development to be tested at SPS at LHC as part of the LHC High Luminosity Upgrade.

Slides THZMS1 [1.861 MB]

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THZMS3

Superconducting RF (SRF) Accelerators Enter a Golden Age

H. Padamsee
Fermilab, Batavia, Illinois, USA

Spectacular breakthroughs in SRF cavity performance have launched major successes in SRF-based particle accelerators at major national laboratories. Both the gradient and the Q values of SRF structures have made remarkable strides in the last two decades. When completed, the newly installed accelerators will triple the total installed SRF voltage. The biggest accelerator is the X-ray Free Electron Laser (XFEL) now under construction in Hamburg Germany, based on 800 Niobium. Jefferson Laboratory in Newport News, Va just upgraded the energy of CEBAF by a factor of two using one hundred new cavities. SLAC is upgrading its Linac Coherent Light Source using nearly 300 SRF cavities in 35 cryomodules, half to be constructed at Fermilab and half at Jefferson Lab. Low velocity accelerators for heavy ions are expanding. Argonne has installed record performance upgrade cryomodules. TRIUMF is constructing ARIEL. Spiral II in France is nearing completion and HI-ISOLDE at CERN is getting ready. Michigan Stage University is constructing an accelerator for Nuclear Astrophysics based on 350 low-beta cavities. High intensity proton accelerators are spreading. Starting with the 1.4 Megawatt Spallation Neutron Source at Oak Ridge the European Spallation Source (ESS) has been launched aiming eventually for 5 MW. Fermilab is carrying out R&D on the Proton-Improvement-Plan PIP-II to provide a one MW proton beam with 125 cavities. China and India are planning and protoyping Accelerator Driven Systems (ADS) for Transmutation of Nuclear Waste and power generation from Thorium via non-critical reactors. These and other upcoming projects around the world have launched the “Golden Age of SRF”. Excitement continues about the “800 lb guerrilla” - the International Linear Collider - which will need 16,000 cavities, if built. The next two years will decide its future.

Slides THZMS3 [6.801 MB]

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)