SRF2015 - List of Keywords (accelerating-gradient)

Paper	Title	Other Keywords	Page
MOPB069	Superconducting Linac Upgrade Plan for the Second Target Station Project at SNS	cryomodule, cavity, linac, HOM	268
	S.-H. Kim, M. Doleans, J. Galambos, M.P. Howell ORNL, Oak Ridge, Tennessee, USA J.D. Mammosser ORNL RAD, Oak Ridge, Tennessee, USA
	Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE. The beam power of the Linac for the Second Target Station (STS) at the Spallation Neutron Source (SNS) will be doubled to 2.8 MW. For the energy upgrade seven additional cryomodules will be installed in the reserved space at the end of the linac tunnel to produce the linac output energy of 1.3 GeV. The cryomodules for STS will have some changes that do not require changes of overall layout based on the lessons learned from operational experience over the last 10 years and the high beta spare cryomodule developed in house. The average macro-pulse beam current for the STS will be 38 mA that is about 40 % increase from that for the present 1.4 MW operation. Plans for the existing cryomodules to support higher beam current for the STS is also presented in this paper.
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MOPB090	Analysis of Degraded Cavities in Prototype Modules for the European XFEL	cavity, SRF, cryogenics, radiation	355
	S. Aderhold Fermilab, Batavia, Illinois, USA S. Aderhold, D. Kostin, A. Matheisen, A. Navitski, D. Reschke DESY, Hamburg, Germany
	In-between the fabrication and the operation in an accelerator the performance of superconducting RF cavities is typically tested several times. Although the assembly is done under very controlled conditions in a clean room, it is observed from time to time that a cavity with good performance in the vertical acceptance test shows deteriorated performance in the accelerator module afterwards. This work presents the analysis of several such cavities that have been disassembled from modules of the prototype phase for the European XFEL for detailed investigation like additional rf tests, optical inspection and replica.
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MOPB092	Economics of Electropolishing Niobium SRF Cavities in Eco-Friendly Aqueous Electrolytes Without Hydrofluoric Acid	cavity, SRF, niobium, cathode	359
	E.J. Taylor, T.D. Hall, M.E. Inman, S.T. Snyder Faraday Technology, Inc., Clayton, Ohio, USA D. Holmes AES, Medford, New York, USA A.M. Rowe Fermilab, Batavia, Illinois, USA
	A major challenge for industrialization of SRF cavity fabrication and processing is developing a supply chain to meet the high production demands of the ILC prior to establishment of a long term market need. Conventional SRF cavity electropolishing is based on hydrofluoric-sulfuric acid mixtures. In comparison, FARADAYIC® Bipolar EP applies pulse reverse electrolysis in dilute sulfuric acid-water solutions without hydrofluoric acid and offers substantial savings in operating and capital costs. Based on a preliminary economic analysis of the cavity processing requirements associated with the ILC, we project the cost of FARADAYIC® Bipolar EP to be about 27% that of the Baseline EP. In terms of tangible cost savings, the cost per cavity for the FARADAYIC® Bipolar EP and Baseline EP are \1,293 and \4,828, respectively. The “eco-friendly” intangible cost savings are generally accepted although the cost savings in terms of material degradation and maintenance are difficult to quantify at this time. Continued development and validation of FARADAYIC® Bipolar EP on nine cell cavities will contribute greatly to the industrialization of SRF accelerator technology. Work supported by DOE Grant Nos. DE-SC0011235 and DE-SC0011342 and DOE Purchase Order No. 594128.
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MOPB094	Inspection and Repair Techniques for the EXFEL Superconducting 1.3 GHz Cavities at Ettore Zanon S.p.A: Methods and Results	cavity, operation, electron, controls	368
	G. Massaro, G. Corniani, N. Maragno Ettore Zanon S.p.A., Schio, Italy A. Matheisen, A. Navitski DESY, Hamburg, Germany P. Michelato, L. Monaco INFN/LASA, Segrate (MI), Italy
	The quality control of the inner surface of superconducting RF cavities is essential in order to assure high accelerating gradient and quality factor. Ettore Zanon S.p.A. (EZ) has implemented in the serial production an optical system that use an high-resolution camera, in order to detect various types of defects. This system is added to a grinding machine, that was specifically designed and built to repair imperfections of the cavities inner surface. This inspection and repair system is applied to recover performance limited cavities of the 1.3 GHz European XFEL project, where surface irregularities are detected, either by the Obacht inspection system at Desy or the optical system at EZ. The optical system and the grinding procedure are qualified using two series cavities limited in gradient and showing different types of surface defects. The performances of these cavities have been recovered to reach the specifications of the project. Until now, all the series XFEL cavities built by EZ, repaired with this technique, have shown an accelerating gradient well above the EXFEL goal.
	Poster MOPB094 [0.795 MB]
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TUPB001	Progress on Superconducting RF Cavity Development With UK Industry	cavity, niobium, SRF, superconducting-RF	521
	A.E. Wheelhouse, R.K. Buckley, L.S. Cowie, P. Goudket, A.R. Goulden, P.A. McIntosh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom J.R. Everard, N. Shakespeare Shakespeare Engineering, South Woodham Ferrers, Essex, United Kingdom
	As part of a STFC Industrial Programme Support (IPS) Scheme grant, Daresbury Laboratory and Shakespeare Engineering Ltd have been developing the capability to fabricate, process, and test a 9-cell, 1.3 GHz superconducting RF cavity. The objective of the programme of work is to achieve an accelerating gradient of greater than 20 MV/m at an unloaded quality factor of 1.0 x 10¹⁰ or better. Processes such as the high pressure rinsing and the buffer chemical polishing are being developed at Daresbury Laboratory and the manufacturing of the cavity half cells and beampipes are being optimised by Shakespeare Engineering to enable this target to be achieved. These are discussed in this paper.
	Poster TUPB001 [2.155 MB]
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TUPB038	Superconducting Coatings Synthetized by CVD/PECVD for SRF Cavities	niobium, SRF, plasma, superconductivity	643
	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
	Finding a way to overcome the acceleration gradient limits that bulk niobium cavities can provide is a major challenge, fundamental to allow the accelerator science field to progress. In order to overcome the accelerating gradient limits of bulk niobium and reduce manufacturing and operation costs, the idea of using thin layers of niobium deposited on a copper cavity is being explored. This approach has lower material cost with higher availability and more importantly higher thermal conductivity. Physical vapour deposition (PVD) method is currently the preferred method to coat superconducting cavities, but its lack of conformity renders complicated shapes such as crab cavities very difficult to coat. 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, XRD, and EDX as well as assessing their superconductivity characteristics (RRR and Tc)
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TUPB044	High Quality Factor Studies in SRF Nb3Sn Cavities	cavity, niobium, SRF, radio-frequency	661
	D.L. Hall, B. Clasby, H. Conklin, R.G. Eichhorn, T. Gruber, G.H. Hoffstaetter, J.J. Kaufman, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Work supported by DOE grant DE-SC0008431 and NSF grant PHY-141638 A significant advantage of Nb3Sn coated on niobium over conventional bulk niobium is the substantial reduction in the BCS losses at equal temperatures of the former relative to the latter. The quality factor of a 1.3 GHz Nb3Sn cavity is thus almost entirely dictated by the residual resistance at temperatures at and below 4.2 K, which, if minimised, offers the ability to operate the cavity in liquid helium at atmospheric pressure with quality factors exceeding 4·10¹⁰. In this paper we look at the impact of the cooldown procedure – which is intrinsically linked to the effect of spatial and temporal gradients – and the impact of external ambient magnetic fields on the performance of a Nb3Sn cavity.
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TUPB048	Fermilab Nb3Sn R&D Program	niobium, cavity, SRF, cryogenics	678
	S. Posen, M. Merio, A. Romanenko, Y. Trenikhina Fermilab, Batavia, Illinois, USA
	A substantial program has been initiated at FNAL for R&D on Nb3Sn coated cavities. Since early 2015, design, fabrication, and commissioning has been ongoing on a coating chamber, designed for deposition via vapor diffusion. The volume of the chamber will be large enough to accommodate not just R&D cavities, but full production-style cavities such as TeSLA 9-cells. In this contribution, we overview the development of the chamber and we introduce the R&D program planned for the coming years. We discuss research paths that may yield increased maximum fields and reduced residual resistances as well as new applications that could be explored with larger coated cavities.
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TUPB049	Cutout Study of a Nb3Sn Cavity	cavity, niobium, electron, SRF	681
	S. Posen, O.S. Melnychuk, A. Romanenko, D.A. Sergatskov, Y. Trenikhina Fermilab, Batavia, Illinois, USA D.L. Hall, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	The first 1.3 GHz single cell Nb₃Sn cavity coated at Cornell was shown in RF measurements at Cornell and FNAL to have poor RF performance. Though subsequent cavities showed much higher quality factors, this cavity exhibited Q₀ on the order of 10⁹ caused by strong heating concentrated in one of the half cells. This paper presents an investigation into the source of this excess heating, for the purpose of process improvement, so that similar degradation can be avoided in future coatings. Through the use of temperature mapping both at Cornell and at FNAL, locations with high and low surface resistance were located, cut out from the cavity, and studied with microscopic tools. We present the RF measurements and temperature maps as well as the microscopic analyses, then conclude with plans for continued studies.
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TUPB054	Local Composition and Topography of Nb3Sn Diffusion Coatings on Niobium	niobium, cavity, electron, site	703
	U. Pudasaini, M.J. Kelley The College of William and Mary, Williamsburg, Virginia, USA G.V. Eremeev, M.J. Kelley, C.E. Reece JLab, Newport News, Virginia, USA
	Funding: Co-authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. College of William & Mary supported by U.S. DOE Office of High Energy Physics under grant DE-SC-0014475. The potential for energy savings and for increased gradient continues to bring attention to Nb3Sn-coated niobium as a future SRF cavity technology. We prepared these materials by vapor diffusion coating on polycrystalline and single crystal niobium. The effect of changing substrate preparation, coating parameters and post-treatment were examined by AFM and SEM/EDS. The AFM data were analyzed in terms of power spectral density (PSD). We found little effect of pre-coating topography on the result. The PSD’s show some surprising kinship to those obtained from BCP-treated surfaces. SEM/EDS revealed no composition non-uniformities at the micron scale.
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TUPB077	The Influence of Cooldown Conditions at Transition Temperature on the Quality Factor of Niobium Sputtered Quarter-Wave Resonators for HIE-ISOLDE	cavity, niobium, linac, cathode	765
	P. Zhang, G.J. Rosaz, A. Sublet, M. Therasse, W. Venturini Delsolaro CERN, Geneva, Switzerland
	Funding: This work has been supported partly by a Marie Curie Early Initial Training Network Fellowship of the European Community’s 7th Programme under contract number PITN-GA-2010-264330-CATHI. Superconducting quarter-wave resonators (QWRs) are to be used in the ongoing linac upgrade of the ISOLDE facility at CERN. The cavities are made of niobium sputtered on copper substrates. They will be operated at 101.28 MHz at 4.5 K providing 6 MV/m accelerating gradient with 10 W power dissipation. In recent measurements, we found the thermal gradient along the cavity during the niobium superconducting transition has an impact on the cavity quality factor. On the other hand, the speed of the cooling down through the superconducting transition turned out to have no influence on the cavity Q-factor.
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TUPB083	Test Characterization of Superconducting Spoke Cavities at Uppsala University	cavity, cryogenics, superconductivity, pick-up	791
	H. Li, A.K. Bhattacharyya, V.A. Goryashko, L. Hermansson, R.J.M.Y. Ruber, R. Santiago Kern Uppsala University, Uppsala, Sweden D.S. Dancila Uppsala University, Department of Engineering Sciences, Uppsala, Sweden G. Olry IPN, Orsay, France
	As part of the development of the ESS spoke linac, the FREIA Laboratory at Uppsala University, Sweden, has been equipped with a superconducting cavity test facility. The cryogenic tests of a single and double spoke cavity developed by IPN Orsay have been performed in the new HNOSS horizontal cryostat system. The cavities are equipped with a low power input antenna and a pick-up antenna. Different measurement methods were investigated to measure the RF signal coupling from the cavity. Results from the tests confirm the possibility to transport the cavities from France to Sweden without consequences. We present the methods and preliminary study results of the cavity performance.
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WEA1A02	Surface Resistance Study on Low Frequency (Low Beta) Cavities	cavity, niobium, superconductivity, SRF	923
	D. Longuevergne, F. Chatelet, G. Michel, G. Olry, F. Rabehasy, L. Renard IPN, Orsay, France
	Additional RF tests and temperature treatments (120°C baking, 100K soaking, …) have been carried out on Spiral2 quarter-wave cavities and ESS double spoke cavities. For each test, residual resistance and BCS resistance have been evaluated by testing the cavities between 4.2K and 1.5K. This talk will summarize the main results and try to highlight the main differences with high frequency cavities.
	Slides WEA1A02 [15.993 MB]
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WEBA05	Achieving High Peak Fields and Low Residual Resistance in Half-Wave Cavities	cavity, niobium, cryomodule, vacuum	973
	Z.A. Conway, A. Barcikowski, G.L. Cherry, R.L. Fischer, S.M. Gerbick, C.S. Hopper, M. Kedzie, M.P. Kelly, S.H. Kim, S.W.T. MacDonald, B. Mustapha, P.N. Ostroumov, T. Reid ANL, Argonne, USA
	Funding: Work supported by the U.S. Department of Energy Office of Science, Office of Nuclear Physics contract number DE-AC02-06CH11357, and the Office of High Energy Physics contract number DE-AC02-76CH03000. We have designed, fabricated and tested two new half-wave resonators following the successful development of a series of niobium superconducting quarter-wave cavities. The half-wave resonators are optimized for β = 0.11 ions, operate at 162.5 MHz and are intended to provide up to 2 MV effective voltage for particles with the optimal velocity. Testing of the first two half-wave resonators is complete with both reaching accelerating voltages greater than 3.5 MV with low-field residual resistances of 1.7 and 2.3 nΩ respectively. The intention of this paper is to provide insight into how Argonne achieves low-residual resistances and high surface fields in low-beta cavities by describing the cavity design, fabrication, processing and testing.
	Slides WEBA05 [2.927 MB]
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THPB001	Propagation of the High Frequency Fields in the Chain of the Superconducting Cavities	cavity, wakefield, electromagnetic-fields, resonance	1049
	A. Novokhatski SLAC, Menlo Park, California, USA
	Funding: Work supported by the Department of Energy. Contract no.DOE-AC03-76SF00515. Combination with the very high repetion rate requires to use the superconducting cavities to accelerate very short bunches for the FEL operation.. In the cavities these bunches excite very high frequency electromagnetic fields. There are severe concerns, that these fields will remain inside the structure for a long time, bring additional heating or even break up the Cooper pairs. We present results of the simulation of the transient dynamics of wake fields of very short bunches. We show how much of the energy is vanishing through the beam pipes immediately and how much energy is staying in the cavity for a long time.
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THPB011	Superconducting Travelling Wave Accelerating Structure Development	cavity, status, feedback, operation	1085
	R.A. Kostin, P.V. Avrakhov, A.D. Didenko, A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio, USA T.N. Khabiboulline, Y.M. Pischalnikov, N. Solyak, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	Funding: Work supported by US Department of Energy # DE-SC0006300 The 3 cell superconducting TW accelerating structure was developed to experimentally demonstrate and to study tuning issues for a new experimental device - the superconducting traveling wave accelerator (STWA), a technology that may prove of crucial importance to the high energy SRF linacs by raising the effective gradient and therefore reducing the overall cost. Recently, a STWA structure with a feedback waveguide has been suggested. The structure was optimized and has phase advance per cell of 105° which provide 24% higher accelerating gradient than in SW cavities. Also STWA structure has no strong sensitivity of the field flatness and its length may be much longer than SW structure. With this presentation, we discuss the current status of a 3-cell L-band SC traveling wave along with the analysis of its tuning issues. Special attention will be paid to feedback loop operation with the two-coupler feed system. We also report on the development and fabrication of a niobium prototype 3-cell SC traveling wave structure to be tested at 2°K in fall 2015.
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THPB015	Design of a Medium Beta Half-Wave SC Prototype Cavity at IMP	cavity, operation, linac, electromagnetic-fields	1097
	A.D. Wu, Y. He, T.C. Jiang, Y.M. Li, F.F. Wang, R.X. Wang, L.J. Wen, W.M. Yue, C. Zhang, S.H. Zhang, S.X. Zhang, H.W. Zhao IMP/CAS, Lanzhou, People's Republic of China
	A superconducting half-wave resonator has been designed with frequency of 325 MHz and beta of 0.51. The geometry parameters and the three shapes of inner conductors (racetrack, ring-shape and elliptical-shape) were studied in details to decrease the peak electromagnetic fields to obtain higher accelerating gradients and minimize the dissipated power on the RF walls. To suppress the operation frequency shift caused by the helium pressure fluctuations and maximize the tuner ranges, the frequency shifts and mechanical characters were simulated in the electric and magnetic areas separately. At the end, the helium vessel was also designed to keep stability as possible. The fabrication and test of the prototype will be complete at the beginning of 2016.
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THPB023	The Statistics of Industrial XFEL Cavities Fabrication at E.ZANON	cavity, target, niobium, controls	1119
	A. Gresele, M. Giaretta, A. Visentin Ettore Zanon S.p.A., Nuclear Division, Schio, Italy A.A. Sulimov, J.H. Thie DESY, Hamburg, Germany
	Serial production of superconducting cavities for European-XFEL will be completed at E.ZANON by the end of 2015. For that reason we can summarize the results and present the statistics of industrial cavity fabrication. Many parameters have been traced during different steps of cavity production. The most interesting of them, as cavity length, frequency, field flatness and eccentricity, are presented and discussed.
	Poster THPB023 [3.227 MB]
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THPB030	Fabrication and Evaluation of Low RRR Large Grain 1-Cell Cavity	cavity, niobium, SRF, electron	1146
	H. Shimizu, H. Inoue, E. Kako, T. Saeki, K. Umemori, Y. Watanabe, M. Yamanaka KEK, Ibaraki, Japan
	Successive R&D studies of SRF cavities are ongoing at KEK by using existing facilities of Cavity Fabrication Facility (CFF) and other equipment of Superconducting Test facility (STF). Recently, there are studies on the low RRR of niobium material with high and uniform concentration of tantalum which could be used for the fabrication of high performance SRF cavity, and hence it could reduce the fabrication cost of cavities [1]. In order to confirm the advantage of the material, a large-grain single-cell cavity was fabricated at CFF/KEK with sheets sliced from a low RRR niobium ingot with high and uniform concentration of tantalum. The resistivity measurement of sample from sliced sheet showed the RRR value of 100, whereas it is about 400 for the nominal qualification of fine-grain sheets at KEK. The low RRR large-grain single-cell cavity was already fabricated at CFF/KEK. The quality control of the fabrication processes are well under control. Then several vertical tests of the cavity were done at STF/KEK. In this presentation, the results of the vertical tests are shown. The potential of the low RRR niobium material for SRF cavity are discussed. *P.Kneisel et al, NIM A774(2015)133
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THPB041	Hydroforming SRF Cavities from Seamless Niobium Tubes	cavity, niobium, SRF, superconductivity	1176
	M. Yamanaka, H. Inoue, H. Shimizu, K. Umemori KEK, Ibaraki, Japan A. Hocker Fermilab, Batavia, Illinois, USA T. Tajima LANL, Los Alamos, New Mexico, USA
	The authors are developing the manufacturing method for super conducting radio frequency (SRF) cavities by using a hydroforming instead of an electron beam welding, which is the major manufacturing method. We expect a cost reduction by hiring the hydroforming. To realize this development, getting a high-purity seamless niobium tube with good forming ability and an advancement of hydroforming technique are necessary. We got the seamless niobium tube made by ATI Wah Chang with the cooperation of Fermilab, and succeeded to manufacture the 1-cell cavity by hydroforming. The accelerating gradient attained to 36 MV/m, and we confirmed it was available to use as the SRF cavity.
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Paper

Title

Other Keywords

Page

MOPB069

Superconducting Linac Upgrade Plan for the Second Target Station Project at SNS

cryomodule, cavity, linac, HOM

268

S.-H. Kim, M. Doleans, J. Galambos, M.P. Howell
ORNL, Oak Ridge, Tennessee, USA
J.D. Mammosser
ORNL RAD, Oak Ridge, Tennessee, USA

Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
The beam power of the Linac for the Second Target Station (STS) at the Spallation Neutron Source (SNS) will be doubled to 2.8 MW. For the energy upgrade seven additional cryomodules will be installed in the reserved space at the end of the linac tunnel to produce the linac output energy of 1.3 GeV. The cryomodules for STS will have some changes that do not require changes of overall layout based on the lessons learned from operational experience over the last 10 years and the high beta spare cryomodule developed in house. The average macro-pulse beam current for the STS will be 38 mA that is about 40 % increase from that for the present 1.4 MW operation. Plans for the existing cryomodules to support higher beam current for the STS is also presented in this paper.

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MOPB090

Analysis of Degraded Cavities in Prototype Modules for the European XFEL

cavity, SRF, cryogenics, radiation

355

S. Aderhold
Fermilab, Batavia, Illinois, USA
S. Aderhold, D. Kostin, A. Matheisen, A. Navitski, D. Reschke
DESY, Hamburg, Germany

In-between the fabrication and the operation in an accelerator the performance of superconducting RF cavities is typically tested several times. Although the assembly is done under very controlled conditions in a clean room, it is observed from time to time that a cavity with good performance in the vertical acceptance test shows deteriorated performance in the accelerator module afterwards. This work presents the analysis of several such cavities that have been disassembled from modules of the prototype phase for the European XFEL for detailed investigation like additional rf tests, optical inspection and replica.

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MOPB092

Economics of Electropolishing Niobium SRF Cavities in Eco-Friendly Aqueous Electrolytes Without Hydrofluoric Acid

cavity, SRF, niobium, cathode

359

E.J. Taylor, T.D. Hall, M.E. Inman, S.T. Snyder
Faraday Technology, Inc., Clayton, Ohio, USA
D. Holmes
AES, Medford, New York, USA
A.M. Rowe
Fermilab, Batavia, Illinois, USA

A major challenge for industrialization of SRF cavity fabrication and processing is developing a supply chain to meet the high production demands of the ILC prior to establishment of a long term market need. Conventional SRF cavity electropolishing is based on hydrofluoric-sulfuric acid mixtures. In comparison, FARADAYIC® Bipolar EP applies pulse reverse electrolysis in dilute sulfuric acid-water solutions without hydrofluoric acid and offers substantial savings in operating and capital costs. Based on a preliminary economic analysis of the cavity processing requirements associated with the ILC, we project the cost of FARADAYIC® Bipolar EP to be about 27% that of the Baseline EP. In terms of tangible cost savings, the cost per cavity for the FARADAYIC® Bipolar EP and Baseline EP are \1,293 and \4,828, respectively. The “eco-friendly” intangible cost savings are generally accepted although the cost savings in terms of material degradation and maintenance are difficult to quantify at this time. Continued development and validation of FARADAYIC® Bipolar EP on nine cell cavities will contribute greatly to the industrialization of SRF accelerator technology.
Work supported by DOE Grant Nos. DE-SC0011235 and DE-SC0011342 and DOE Purchase Order No. 594128.

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MOPB094

Inspection and Repair Techniques for the EXFEL Superconducting 1.3 GHz Cavities at Ettore Zanon S.p.A: Methods and Results

cavity, operation, electron, controls

368

G. Massaro, G. Corniani, N. Maragno
Ettore Zanon S.p.A., Schio, Italy
A. Matheisen, A. Navitski
DESY, Hamburg, Germany
P. Michelato, L. Monaco
INFN/LASA, Segrate (MI), Italy

The quality control of the inner surface of superconducting RF cavities is essential in order to assure high accelerating gradient and quality factor. Ettore Zanon S.p.A. (EZ) has implemented in the serial production an optical system that use an high-resolution camera, in order to detect various types of defects. This system is added to a grinding machine, that was specifically designed and built to repair imperfections of the cavities inner surface. This inspection and repair system is applied to recover performance limited cavities of the 1.3 GHz European XFEL project, where surface irregularities are detected, either by the Obacht inspection system at Desy or the optical system at EZ. The optical system and the grinding procedure are qualified using two series cavities limited in gradient and showing different types of surface defects. The performances of these cavities have been recovered to reach the specifications of the project. Until now, all the series XFEL cavities built by EZ, repaired with this technique, have shown an accelerating gradient well above the EXFEL goal.

Poster MOPB094 [0.795 MB]

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TUPB001

Progress on Superconducting RF Cavity Development With UK Industry

cavity, niobium, SRF, superconducting-RF

521

A.E. Wheelhouse, R.K. Buckley, L.S. Cowie, P. Goudket, A.R. Goulden, P.A. McIntosh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
J.R. Everard, N. Shakespeare
Shakespeare Engineering, South Woodham Ferrers, Essex, United Kingdom

As part of a STFC Industrial Programme Support (IPS) Scheme grant, Daresbury Laboratory and Shakespeare Engineering Ltd have been developing the capability to fabricate, process, and test a 9-cell, 1.3 GHz superconducting RF cavity. The objective of the programme of work is to achieve an accelerating gradient of greater than 20 MV/m at an unloaded quality factor of 1.0 x 10¹⁰ or better. Processes such as the high pressure rinsing and the buffer chemical polishing are being developed at Daresbury Laboratory and the manufacturing of the cavity half cells and beampipes are being optimised by Shakespeare Engineering to enable this target to be achieved. These are discussed in this paper.

Poster TUPB001 [2.155 MB]

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TUPB038

Superconducting Coatings Synthetized by CVD/PECVD for SRF Cavities

niobium, SRF, plasma, superconductivity

643

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

Finding a way to overcome the acceleration gradient limits that bulk niobium cavities can provide is a major challenge, fundamental to allow the accelerator science field to progress. In order to overcome the accelerating gradient limits of bulk niobium and reduce manufacturing and operation costs, the idea of using thin layers of niobium deposited on a copper cavity is being explored. This approach has lower material cost with higher availability and more importantly higher thermal conductivity. Physical vapour deposition (PVD) method is currently the preferred method to coat superconducting cavities, but its lack of conformity renders complicated shapes such as crab cavities very difficult to coat. 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, XRD, and EDX as well as assessing their superconductivity characteristics (RRR and Tc)

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TUPB044

High Quality Factor Studies in SRF Nb3Sn Cavities

cavity, niobium, SRF, radio-frequency

661

D.L. Hall, B. Clasby, H. Conklin, R.G. Eichhorn, T. Gruber, G.H. Hoffstaetter, J.J. Kaufman, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work supported by DOE grant DE-SC0008431 and NSF grant PHY-141638
A significant advantage of Nb3Sn coated on niobium over conventional bulk niobium is the substantial reduction in the BCS losses at equal temperatures of the former relative to the latter. The quality factor of a 1.3 GHz Nb3Sn cavity is thus almost entirely dictated by the residual resistance at temperatures at and below 4.2 K, which, if minimised, offers the ability to operate the cavity in liquid helium at atmospheric pressure with quality factors exceeding 4·10¹⁰. In this paper we look at the impact of the cooldown procedure – which is intrinsically linked to the effect of spatial and temporal gradients – and the impact of external ambient magnetic fields on the performance of a Nb3Sn cavity.

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TUPB048

Fermilab Nb3Sn R&D Program

niobium, cavity, SRF, cryogenics

678

S. Posen, M. Merio, A. Romanenko, Y. Trenikhina
Fermilab, Batavia, Illinois, USA

A substantial program has been initiated at FNAL for R&D on Nb3Sn coated cavities. Since early 2015, design, fabrication, and commissioning has been ongoing on a coating chamber, designed for deposition via vapor diffusion. The volume of the chamber will be large enough to accommodate not just R&D cavities, but full production-style cavities such as TeSLA 9-cells. In this contribution, we overview the development of the chamber and we introduce the R&D program planned for the coming years. We discuss research paths that may yield increased maximum fields and reduced residual resistances as well as new applications that could be explored with larger coated cavities.

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TUPB049

Cutout Study of a Nb3Sn Cavity

cavity, niobium, electron, SRF

681

S. Posen, O.S. Melnychuk, A. Romanenko, D.A. Sergatskov, Y. Trenikhina
Fermilab, Batavia, Illinois, USA
D.L. Hall, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

The first 1.3 GHz single cell Nb₃Sn cavity coated at Cornell was shown in RF measurements at Cornell and FNAL to have poor RF performance. Though subsequent cavities showed much higher quality factors, this cavity exhibited Q₀ on the order of 10⁹ caused by strong heating concentrated in one of the half cells. This paper presents an investigation into the source of this excess heating, for the purpose of process improvement, so that similar degradation can be avoided in future coatings. Through the use of temperature mapping both at Cornell and at FNAL, locations with high and low surface resistance were located, cut out from the cavity, and studied with microscopic tools. We present the RF measurements and temperature maps as well as the microscopic analyses, then conclude with plans for continued studies.

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TUPB054

Local Composition and Topography of Nb3Sn Diffusion Coatings on Niobium

niobium, cavity, electron, site

703

U. Pudasaini, M.J. Kelley
The College of William and Mary, Williamsburg, Virginia, USA
G.V. Eremeev, M.J. Kelley, C.E. Reece
JLab, Newport News, Virginia, USA

Funding: Co-authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. College of William & Mary supported by U.S. DOE Office of High Energy Physics under grant DE-SC-0014475.
The potential for energy savings and for increased gradient continues to bring attention to Nb3Sn-coated niobium as a future SRF cavity technology. We prepared these materials by vapor diffusion coating on polycrystalline and single crystal niobium. The effect of changing substrate preparation, coating parameters and post-treatment were examined by AFM and SEM/EDS. The AFM data were analyzed in terms of power spectral density (PSD). We found little effect of pre-coating topography on the result. The PSD’s show some surprising kinship to those obtained from BCP-treated surfaces. SEM/EDS revealed no composition non-uniformities at the micron scale.

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TUPB077

The Influence of Cooldown Conditions at Transition Temperature on the Quality Factor of Niobium Sputtered Quarter-Wave Resonators for HIE-ISOLDE

cavity, niobium, linac, cathode

765

P. Zhang, G.J. Rosaz, A. Sublet, M. Therasse, W. Venturini Delsolaro
CERN, Geneva, Switzerland

Funding: This work has been supported partly by a Marie Curie Early Initial Training Network Fellowship of the European Community’s 7th Programme under contract number PITN-GA-2010-264330-CATHI.
Superconducting quarter-wave resonators (QWRs) are to be used in the ongoing linac upgrade of the ISOLDE facility at CERN. The cavities are made of niobium sputtered on copper substrates. They will be operated at 101.28 MHz at 4.5 K providing 6 MV/m accelerating gradient with 10 W power dissipation. In recent measurements, we found the thermal gradient along the cavity during the niobium superconducting transition has an impact on the cavity quality factor. On the other hand, the speed of the cooling down through the superconducting transition turned out to have no influence on the cavity Q-factor.

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TUPB083

Test Characterization of Superconducting Spoke Cavities at Uppsala University

cavity, cryogenics, superconductivity, pick-up

791

H. Li, A.K. Bhattacharyya, V.A. Goryashko, L. Hermansson, R.J.M.Y. Ruber, R. Santiago Kern
Uppsala University, Uppsala, Sweden
D.S. Dancila
Uppsala University, Department of Engineering Sciences, Uppsala, Sweden
G. Olry
IPN, Orsay, France

As part of the development of the ESS spoke linac, the FREIA Laboratory at Uppsala University, Sweden, has been equipped with a superconducting cavity test facility. The cryogenic tests of a single and double spoke cavity developed by IPN Orsay have been performed in the new HNOSS horizontal cryostat system. The cavities are equipped with a low power input antenna and a pick-up antenna. Different measurement methods were investigated to measure the RF signal coupling from the cavity. Results from the tests confirm the possibility to transport the cavities from France to Sweden without consequences. We present the methods and preliminary study results of the cavity performance.

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WEA1A02

Surface Resistance Study on Low Frequency (Low Beta) Cavities

cavity, niobium, superconductivity, SRF

923

D. Longuevergne, F. Chatelet, G. Michel, G. Olry, F. Rabehasy, L. Renard
IPN, Orsay, France

Additional RF tests and temperature treatments (120°C baking, 100K soaking, …) have been carried out on Spiral2 quarter-wave cavities and ESS double spoke cavities. For each test, residual resistance and BCS resistance have been evaluated by testing the cavities between 4.2K and 1.5K. This talk will summarize the main results and try to highlight the main differences with high frequency cavities.

Slides WEA1A02 [15.993 MB]

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WEBA05

Achieving High Peak Fields and Low Residual Resistance in Half-Wave Cavities

cavity, niobium, cryomodule, vacuum

973

Z.A. Conway, A. Barcikowski, G.L. Cherry, R.L. Fischer, S.M. Gerbick, C.S. Hopper, M. Kedzie, M.P. Kelly, S.H. Kim, S.W.T. MacDonald, B. Mustapha, P.N. Ostroumov, T. Reid
ANL, Argonne, USA

Funding: Work supported by the U.S. Department of Energy Office of Science, Office of Nuclear Physics contract number DE-AC02-06CH11357, and the Office of High Energy Physics contract number DE-AC02-76CH03000.
We have designed, fabricated and tested two new half-wave resonators following the successful development of a series of niobium superconducting quarter-wave cavities. The half-wave resonators are optimized for β = 0.11 ions, operate at 162.5 MHz and are intended to provide up to 2 MV effective voltage for particles with the optimal velocity. Testing of the first two half-wave resonators is complete with both reaching accelerating voltages greater than 3.5 MV with low-field residual resistances of 1.7 and 2.3 nΩ respectively. The intention of this paper is to provide insight into how Argonne achieves low-residual resistances and high surface fields in low-beta cavities by describing the cavity design, fabrication, processing and testing.

Slides WEBA05 [2.927 MB]

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THPB001

Propagation of the High Frequency Fields in the Chain of the Superconducting Cavities

cavity, wakefield, electromagnetic-fields, resonance

1049

A. Novokhatski
SLAC, Menlo Park, California, USA

Funding: Work supported by the Department of Energy. Contract no.DOE-AC03-76SF00515.
Combination with the very high repetion rate requires to use the superconducting cavities to accelerate very short bunches for the FEL operation.. In the cavities these bunches excite very high frequency electromagnetic fields. There are severe concerns, that these fields will remain inside the structure for a long time, bring additional heating or even break up the Cooper pairs. We present results of the simulation of the transient dynamics of wake fields of very short bunches. We show how much of the energy is vanishing through the beam pipes immediately and how much energy is staying in the cavity for a long time.

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THPB011

Superconducting Travelling Wave Accelerating Structure Development

cavity, status, feedback, operation

1085

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

Funding: Work supported by US Department of Energy # DE-SC0006300
The 3 cell superconducting TW accelerating structure was developed to experimentally demonstrate and to study tuning issues for a new experimental device - the superconducting traveling wave accelerator (STWA), a technology that may prove of crucial importance to the high energy SRF linacs by raising the effective gradient and therefore reducing the overall cost. Recently, a STWA structure with a feedback waveguide has been suggested. The structure was optimized and has phase advance per cell of 105° which provide 24% higher accelerating gradient than in SW cavities. Also STWA structure has no strong sensitivity of the field flatness and its length may be much longer than SW structure. With this presentation, we discuss the current status of a 3-cell L-band SC traveling wave along with the analysis of its tuning issues. Special attention will be paid to feedback loop operation with the two-coupler feed system. We also report on the development and fabrication of a niobium prototype 3-cell SC traveling wave structure to be tested at 2°K in fall 2015.

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THPB015

Design of a Medium Beta Half-Wave SC Prototype Cavity at IMP

cavity, operation, linac, electromagnetic-fields

1097

A.D. Wu, Y. He, T.C. Jiang, Y.M. Li, F.F. Wang, R.X. Wang, L.J. Wen, W.M. Yue, C. Zhang, S.H. Zhang, S.X. Zhang, H.W. Zhao
IMP/CAS, Lanzhou, People's Republic of China

A superconducting half-wave resonator has been designed with frequency of 325 MHz and beta of 0.51. The geometry parameters and the three shapes of inner conductors (racetrack, ring-shape and elliptical-shape) were studied in details to decrease the peak electromagnetic fields to obtain higher accelerating gradients and minimize the dissipated power on the RF walls. To suppress the operation frequency shift caused by the helium pressure fluctuations and maximize the tuner ranges, the frequency shifts and mechanical characters were simulated in the electric and magnetic areas separately. At the end, the helium vessel was also designed to keep stability as possible. The fabrication and test of the prototype will be complete at the beginning of 2016.

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THPB023

The Statistics of Industrial XFEL Cavities Fabrication at E.ZANON

cavity, target, niobium, controls

1119

A. Gresele, M. Giaretta, A. Visentin
Ettore Zanon S.p.A., Nuclear Division, Schio, Italy
A.A. Sulimov, J.H. Thie
DESY, Hamburg, Germany

Serial production of superconducting cavities for European-XFEL will be completed at E.ZANON by the end of 2015. For that reason we can summarize the results and present the statistics of industrial cavity fabrication. Many parameters have been traced during different steps of cavity production. The most interesting of them, as cavity length, frequency, field flatness and eccentricity, are presented and discussed.

Poster THPB023 [3.227 MB]

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THPB030

Fabrication and Evaluation of Low RRR Large Grain 1-Cell Cavity

cavity, niobium, SRF, electron

1146

H. Shimizu, H. Inoue, E. Kako, T. Saeki, K. Umemori, Y. Watanabe, M. Yamanaka
KEK, Ibaraki, Japan

Successive R&D studies of SRF cavities are ongoing at KEK by using existing facilities of Cavity Fabrication Facility (CFF) and other equipment of Superconducting Test facility (STF). Recently, there are studies on the low RRR of niobium material with high and uniform concentration of tantalum which could be used for the fabrication of high performance SRF cavity, and hence it could reduce the fabrication cost of cavities [1]. In order to confirm the advantage of the material, a large-grain single-cell cavity was fabricated at CFF/KEK with sheets sliced from a low RRR niobium ingot with high and uniform concentration of tantalum. The resistivity measurement of sample from sliced sheet showed the RRR value of 100, whereas it is about 400 for the nominal qualification of fine-grain sheets at KEK. The low RRR large-grain single-cell cavity was already fabricated at CFF/KEK. The quality control of the fabrication processes are well under control. Then several vertical tests of the cavity were done at STF/KEK. In this presentation, the results of the vertical tests are shown. The potential of the low RRR niobium material for SRF cavity are discussed.
*P.Kneisel et al, NIM A774(2015)133

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THPB041

Hydroforming SRF Cavities from Seamless Niobium Tubes

cavity, niobium, SRF, superconductivity

1176

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

The authors are developing the manufacturing method for super conducting radio frequency (SRF) cavities by using a hydroforming instead of an electron beam welding, which is the major manufacturing method. We expect a cost reduction by hiring the hydroforming. To realize this development, getting a high-purity seamless niobium tube with good forming ability and an advancement of hydroforming technique are necessary. We got the seamless niobium tube made by ATI Wah Chang with the cooperation of Fermilab, and succeeded to manufacture the 1-cell cavity by hydroforming. The accelerating gradient attained to 36 MV/m, and we confirmed it was available to use as the SRF cavity.

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