SRF2019 - List of Keywords (FEL)

Paper	Title	Other Keywords	Page
MOFAA1	LCLS-II: Status, Issues and Plans	cavity, SRF, cryomodule, linac	1
	M.C. Ross SLAC, Menlo Park, California, USA
	Funding: Work supported by Department of Energy contract DE-AC02-76SF00515 The Linac Coherent Light Source II (LCLS-II) project requires the assembly, test, and installation of 37 cryomodules (CM) in order to deliver a 4 GeV CW electron beam to the FEL undulators for production of both hard and soft X-ray pulses at a repetition rate of up to 1 MHz. SRF cavity performance in the 30+ tested CM exceeds gradient and cryogenic dynamic heat-load requirements (set at 16 MV/m and 10 W resp). In this talk we present microphonics, shipping, magnetic-flux exclusion, and field emission performance. The US funding agency, DOE, has recently approved an additional 20 CM for the extension of LCLS-II to 8 GeV. This paper will also include initial cavity and heat-load performance results for the extension project, LCLS-II-HE.
	Slides MOFAA1 [30.146 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOFAA1
About •	paper received ※ 25 June 2019 paper accepted ※ 04 July 2019 issue date ※ 14 August 2019
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MOFAA2	Operation of the European XFEL Towards the Maximum Energy	electron, cavity, operation, MMI	9
	M. Omet, V. Ayvazyan, J. Branlard, S. Choroba, W. Decking, V.V. Katalev, D. Kostin, L. Lilje, P. Morozov, Y. Nachtigal, H. Schlarb, V. Vogel, N. Walker, B. Yildirim DESY, Hamburg, Germany
	After the initial commissioning of the available 25 radio frequency (RF) stations of the European XFEL (RF gun, A1, AH1 and stations A2 through A23) a maximum electron beam energy of 14.5 GeV was achieved, 3 GeV short of the design energy of 17.5 GeV. In order to tackle this problem, the Maximum Gradient Task Force (MGTF) was formed. In the scope of the work of the MGTF, RF stations A6 through A25 (linac L3) were systematically investigated and voltage-limiting factors of the SRF accelerating modules and their RF distribution system were identified and improved. As a result, the design electron beam energy was exceeded at 17.6 GeV on the 18.7.2018. Beside this an overview over the regular RF operation at the European XFEL is given.
	Slides MOFAA2 [5.695 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOFAA2
About •	paper received ※ 21 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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MOP029	N-Doping Studies With Single-Cell Cavities for the SHINE Project	cavity, niobium, SRF, ECR	102
	J.F. Chen, H.T. Hou, Y.F. Liu, D. Wang, Y. Wang SARI-CAS, Pudong, Shanghai, People’s Republic of China Y.W. Huang ShanghaiTech University, Shanghai, People’s Republic of China Z. Wang SINAP, Shanghai, People’s Republic of China
	The SHINE SRF accelerator is designed to operate in CW mode with more than six hundred superconducting cavities. In order to reduce the high cost of construction and operation of the cryogenic system, high-Q cavities with nitrogen-doping technology together with tradition-ally treated large-grain cavities have been considered as two possible options. In this paper, we present N-doping studies on single-cell cavities fabricated with fine-grain and large-grain niobium.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP029
About •	paper received ※ 23 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019
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MOP034	European XFEL: Accelerating Module Repair at DESY	cavity, linac, SRF, operation	127
	D. Kostin, J. Eschke, K. Jensch, N. Krupka, D. Reschke, S. Saegebarth, J. Schaffran, M. Schalwat, P. Schilling, M. Schmökel, S. Sievers, N. Steinhau-Kühl, E. Vogel, H. Weise, M. Wiencek, B. van der Horst DESY, Hamburg, Germany
	The European XFEL is in operation since 2017. The design projected energy of 17.5 GeV was reached, even with the last 4 main linac accelerating modules not yet installed. 2 out of 4 not installed modules did suffer from strong cavity performance degradation, namely increased field emission, and required surface processing. The first of two modules is reassembled and tested. The module test results confirm a successful repair action. The module repair and test steps are described together with cavities performance evolution.
	Poster MOP034 [1.863 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP034
About •	paper received ※ 17 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019
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MOP049	Prototypes Fabrication of 1.3 GHz Superconducting Rf Components for SHINE	cavity, niobium, HOM, SRF	164
	H.T. Hou, J.F. Chen, Z.Y. Ma, J. Shi, Y. Wang SARI-CAS, Pudong, Shanghai, People’s Republic of China F.S. He IHEP, Beijing, People’s Republic of China S.W. Quan PKU, Beijing, People’s Republic of China
	Aiming to high repetition rate hard X-ray facility, con-struction of Shanghai HIgh repetition rate XFEL aNd Extreme light facility (SHINE) project has been ap-proved. During the R & D phase, prototypes fabrication of key components of 1.3GHz superconducting rf system have been proposed, especially 1.3 GHz 9-cell niobium cavities. Here the paper will present the progress of the fabrication status and performance of the prototypes, together with the analysis of not only the quality factor and gradient of the cavities. Consideration of HOM feed-throughs and absorbers are also reported.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP049
About •	paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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MOP054	Fabrication of 3.0-GHz Single-cell Cavities for Thin-film Study	cavity, SRF, MMI, linac	177
	T. Saeki, H. Hayano, H. Inoue, R. Katayama, T. Kubo KEK, Ibaraki, Japan F.E. Hannon, R.A. Rimmer, A-M. Valente-Feliciano JLab, Newport News, Virginia, USA H. Ito Sokendai, Ibaraki, Japan Y. Iwashita, H. Tongu Kyoto ICR, Uji, Kyoto, Japan
	Funding: This work is supported by JSPS KAKENHI JP17H04839, JSPS KAKENHI JP26600142, Japan-US Research Collaboration Program, and the Collaborative Research Program of ICR Kyoto Univ. (2018-13). We fabricated 3.0-GHz single-cell cavities with Cu and Nb materials for testing thin-film creations on the inner surface of the cavities in collaboration between Jefferson Laboratory (JLab) and KEK. The cavity was designed at JLab. According to the design of cavity, the press-forming dies and trimming fixtures for the cavity-cell were also designed and fabricated at JLab. These dies and trimming fixtures were transported to KEK, and the rest of fabrication processes were done at KEK. Finally nine Cu 3.0-GHz single-cell cavities and six Nb 3.0-GHz single-cell cavities were fabricated. Two Cu 3.0-GHz single-cell cavities were mechanically polished at Jlab. All of these cavities will be utilized for the tests of various thin-film creations at JLab and KEK. This presentation describes details of the fabrication of these cavities.
	Poster MOP054 [1.203 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP054
About •	paper received ※ 05 July 2019 paper accepted ※ 13 August 2019 issue date ※ 14 August 2019
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MOP057	Electropolishing of PIP-II Low Beta Cavity Prototypes	cavity, cathode, experiment, linac	194
	M. Bertucci, A. Bosotti, A. D’Ambros, P. Michelato, L. Monaco, C. Pagani, R. Paparella, D. Sertore INFN/LASA, Segrate (MI), Italy A. Gresele, A. Visentin Ettore Zanon S.p.A., Nuclear Division, Schio, Italy C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy D. Rizzetto, M. Rizzi Ettore Zanon S.p.A., Schio, Italy
	We present the upgrade of the EP facility for the surface treatment of PIP-II low beta cavities. The main process parameters, such as voltage, treatment time, acid throughput and cathode geometry, already optimized on the previous experience of 1.3 GHz Tesla-shape cavities, are discussed taking into account the different cavity size and geometry. The first surface treatments have been performed at Ettore Zanon SpA on single cell cavity prototypes in order to reach good final surface finishing and the required thickness removal. In the meantime, the upgrade of the system for the treatment of multicell PIP-II prototype cavities is presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP057
About •	paper received ※ 23 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019
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MOP082	Measurement of the Vibration Response of the EXFEL RF Coupler and Comparison With Simulated Data (Finite Element Analyses)	cryomodule, acceleration, interface, resonance	273
	S. Barbanotti, C. Engling, K. Jensch DESY, Hamburg, Germany
	The coupler is one of the main and most sensitive components of the European X-ray Free Electron Laser (EXFEL) superconducting cryomodule. More than 800 couplers were transported for more than 800 km assembled in a cryomodule during the assembly phase of the EXFEL without any visible damage. However, in a different project, a very similar coupler design showed a week point in one of the bellows when transported over a similar distance with a comparable transport set up. Therefore we decided to further study the coupler behaviour: we investigated the frequency response of the coupler on a vibration table in a controlled environment for different road and loading conditions and compared the data with simulated ones. This paper present the work performed so far and our conclusions.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP082
About •	paper received ※ 18 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019
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MOP084	A Simple Variable Coupler for the Cryogenic Test of SRF Cavities	cavity, SRF, cryogenics, coupling	282
	G. Ciovati, L. Turlington JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The cryogenic rf tests of SRF cavities in vertical cryostats is typically carried out using fixed-length antennae to couple rf power into the cavity and to probe the energy stored into the cavity. Although variable couplers have been designed, built and used in the past, they are often a complex, costly, not very reliable auxiliary component to the cavity test. In this contribution we present the design and implementation of a simple variable rf antenna which has about 50 mm travel, allowing to obtain about four orders of magnitude variation in Q_ext -value. The motion of the antenna is driven by a motorized linear feedthrough outside of the cryostat. The antenna can easily be mounted on the most common type of cavity flanges.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP084
About •	paper received ※ 18 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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TUFUA7	Review of Muon Spin Rotation Studies of SRF Materials	SRF, niobium, cavity, experiment	360
	T. Junginger Lancaster University, Lancaster, United Kingdom R.E. Laxdal TRIUMF, Vancouver, Canada
	Muons spin rotate in magnetic fields and emit a positron preferentially in spin direction after decay. These properties enable muon spin rotation (muSR) as a precise probe for local magnetism. muSR has been used to characterize SRF materials since 2010. At TRIUMF a so called surface beam implants muons at a material dependent depth of about 150 µm in the bulk. A dedicated spectrometer was developed for field of first vortex penetration and pinning strength measurements of SRF materials in parallel magnetic fields of up to 300 mT. A low energy beam available at PSI implants muons at variable depth in the London layer allowing for direct measurements of the London penetration depth from which the lower critical field and the superheating field can be calculated. This facility is limited to parallel magnetic fields of up to 25 mT. Here, surface and low energy muSR results on SRF materials are reviewed and cross-correlated to each other and to further results from additional experiments. Finally, we present the status of a new facility based on the similar beta-NMR technique enabling measurements in the London layer of SRF materials exposed to parallel magnetic fields above 200 mT.
	Slides TUFUA7 [4.063 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUFUA7
About •	paper received ※ 01 July 2019 paper accepted ※ 12 July 2019 issue date ※ 14 August 2019
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TUP020	Statistical Analysis of the 120°C Bake Procedure of Superconducting Radio Frequency Cavities	cavity, accelerating-gradient, SRF, niobium	444
	L. Steder, D. Reschke DESY, Hamburg, Germany
	DESY is and was very active in R&D related to SRF cavities. Many single and nine cell cavities with different surface treatment histories were tested vertically. Results of these cold tests are accelerating gradient and quality factor of the cavities. Using the large number of available datasets the parameters of the 120°C bake procedure, which is applied to avoid high-field Q-slope, are analysed. The impact of different durations and temperatures on accelerating gradient, quality factor and residual resistance is studied in detail and is compared to results obtained with the recently proposed procedure of modified low temperature bake. For this procedure additional four hours at temperatures around 75°C are implemented before the standard bake at about 120°C. Since the claim is, that cavities treated with such a modified procedure achieve extra-ordinary large accelerating gradients it is a very interesting research field for the European XFEL continuous wave mode upgrade. For this purpose cavities with high quality factors are needed, but in addition large maximal accelerating fields are required to maintain high energies in the pulsed operation mode of the accelerator.
	Poster TUP020 [0.747 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP020
About •	paper received ※ 21 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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TUP023	Experience of LCLS-II Cavities Radial Tuning at DESY	cavity, HOM, SRF, linac	456
	A. Sulimov, J.H. Thie DESY, Hamburg, Germany A. Gresele Ettore Zanon S.p.A., Nuclear Division, Schio, Italy A. Navitski RI Research Instruments GmbH, Bergisch Gladbach, Germany A.D. Palczewski JLab, Newport News, Virginia, USA
	Radial tuning (rolling) was applied to three LCLS-II cavities to prevent that their lengths exceed the technical limits. The cavities have a reduced frequency due to additional material removal during cavity treatment well beyond the baseline recipe. The mechanical condition of the cavities was relatively soft because of the thermal history and the niobium manufacture requirement of an optimal flux expulsion. The niobium was highly recrystallized by 3 hours annealing at 900°C and 975°C respectively. Each cavity received an inner surface treatment of 200 µm electro-polishing (EP) and an external 30 µm buffered chemical polishing (BCP) as part of the baseline recipe. Each cavity received an addition ~100 µm of chemical removal along with a second annealing treatment before the radial tuning process. Detailed information about the accuracy and homogeneity of LCLS-II cavities rolling is presented as well as results of field distribution analysis for TM011 zero-mode with a comparison to standard cavities.
	Poster TUP023 [0.521 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP023
About •	paper received ※ 23 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019
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TUP024	Radial Tuning Devices for 1.3 GHz TESLA Shape Cavities	cavity, SRF, HOM, niobium	459
	A. Sulimov, J.H. Thie DESY, Hamburg, Germany
	Radial tuning devices at DESY can be applied to any TESLA shape 1.3 GHz cavity to reduce its elongation due to excessive additional material removal (>300 µm) or to compensate critical manufacturing uncertainties. Radial deformation of cavity cells can be provided by a special chain or a rolling device with three rollers. The chain distributes the radial forces on the equator area around the cell. The rollers are moving radially in relation to the rotating cavity and provide an equator diameter reduction. Both devices have the contour close to the cell shape at the equator area. The required equator radius deviation depends on the tuning target and usually varies between (0.02…0.60) mm. Different aspects of the tuning procedure and material properties are described using the example of cavity rolling.
	Poster TUP024 [0.252 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP024
About •	paper received ※ 23 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019
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TUP033	Modal Analysis of the EXFEL 1.3 GHz Cavity and Cryomodule Main Components and Comparison with Measured Data	cavity, cryomodule, vacuum, linac	488
	S. Barbanotti, A. Bellandi, J. Branlard, K. Jensch DESY, Hamburg, Germany
	Future upgrades of the European X-ray Free Electron Laser (EXFEL) may require driving the linac at higher duty factor, possibly extending to Continuous Wave (CW) mode. An R&D program has started at DESY, to prepare for a CW upgrade. Cryomodules are being tested in CW mode in our CryoModule Test Bench (CMTB) to study the performance and main issues for such an operation mode. Sensitivity to vibration causing microphonics is one of the main concerns for the CW operation in mode. Therefore a detailed analysis is being performed to evaluate the frequency spectrum of the EXFEL cryomodule main components: the cavity itself, the cavity string, the cold mass and the vacuum vessel. Finite Element Modal Analyses have been performed and the results compared with data measured at the CMTB. This paper summarizes the main results and conclusions of such a study.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP033
About •	paper received ※ 18 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019
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TUP057	Study of Flux Trapping Variability between Batches of Tokyo Denkai Niobium used for the LCLS-II Project and Subsequent 9-cell RF Loss Distribution between the Batches	cavity, niobium, SRF, superconductivity	570
	A.D. Palczewski JLab, Newport News, Virginia, USA D. Gonnella SLAC, Menlo Park, California, USA O.S. Melnychuk, D.A. Sergatskov Fermilab, Batavia, Illinois, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. During the LCLS-II project a second batch of niobium was procured from Tokyo Denkai Co Ltd in order to make additional cavities. The original production material came from Two vendors Tokyo Denkai Co., Ltd. (TD) and Ningxia Orient Tantalum Industry Co., Ltd. (OTIC/NX)). It was found TD niobium required a lower annealing temperature (900°C) to obtain satisfactory flux expulsion characteristics compared to NX which required a slightly higher annealing temperature (950°-975°C). In order to ensure the new TD material performed equivalent to the niobium produced 4 year before after 900°C annealing; each heat lot of niobium had its flux expulsion characteristics parametrized and custom thermal treatments developed for each lot. Subsequent pure heat lot 9 cell cavities were made and tested. We will look at the flux expulsion characteristics of each lot, and RF loss of the 9-cell cavities produced using the individual heat lots.
	Poster TUP057 [1.446 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP057
About •	paper received ※ 25 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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TUP073	Superconducting Thin Films Characterization at HZB with the Quadrupole Resonator	cavity, SRF, quadrupole, niobium	616
	D.B. Tikhonov, S. Keckert, J. Knobloch, O. Kugeler, Y. Tamashevich HZB, Berlin, Germany A-M. Valente-Feliciano JLab, Newport News, Virginia, USA
	Funding: EASITrain - European Advanced Superconductivity Innovation and Training. This Marie Sklodowska-Curie Action Innovative Training Networks founded by H₂020 under Grant Agreement no. 764879 Superconducting thin films have great potential as post-Nb material for use in SRF applications in future accelerators and industry. To test the RF-performance of such films in practice, would require the building and coating of a full RF cavity. Deposition of thin films on such scales in test facilities are challenging, in particular when curved surfaces have to be coated. This greatly complicates their systematic research. In this contribution we report on the method we use to characterize small and flat thin film samples (Deposited onto both Nb and Cu substrates) in an actual cavity named the Quadrupole Resonator (QPR). We also summarize the latest measurement results of NbTiN thin films. The Quadrupole Resonator at HZB is a tool that is able to perform SRF characterizations at frequencies ~415, 847, 1300 MHz with RF fields using an RF-DC power compensation technique.
	Poster TUP073 [2.318 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP073
About •	paper received ※ 23 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019
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TUP079	Deposition of Nb₃Sn Films by Multilayer Sequential Sputtering for SRF Cavity Application	cavity, SRF, site, niobium	637
	Md.N. Sayeed, H. Elsayed-Ali ODU, Norfolk, Virginia, USA M.C. Burton, G.V. Eremeev, C.E. Reece, A-M. Valente-Feliciano JLab, Newport News, Virginia, USA U. Pudasaini The College of William and Mary, Williamsburg, Virginia, USA
	Nb₃Sn is considered as an alternative of Nb for SRF accelerator cavity application due to its potential to obtain higher quality factors and higher accelerating gradients at a higher operating temperature. Magnetron sputtering is one of the effective techniques that can be used to fabricate Nb₃Sn on SRF cavity surface. We report on the surface properties of Nb₃Sn films fabricated by sputtering multiple layers of Nb and Sn on sapphire and niobium substrates followed by annealing at 950°C for 3 h. The crystal structure, film microstructure, composition and surface roughness were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and atomic force microscopy (AFM). The RF performance of the Nb₃Sn coated Nb substrates were measured by a surface impedance characterization system. We also report on the design of a multilayer sputter deposition system to coat a single-cell SRF cavity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP079
About •	paper received ※ 22 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019
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TUP099	Particulate Sampling and Analysis During Refurbishment of Prototype European XFEL Cryomodule	cavity, SRF, cryomodule, superconductivity	701
	N. Krupka, C. Bate, D. Reschke, S. Saegebarth, M. Schalwat, P. Schilling, S. Sievers DESY, Hamburg, Germany
	Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Tech-nologies (MT) Program. The cryomodule PXFEL3₁ is one of three prototype cryomodules for the European XFEL. In preparation of the series module assembly it was used for the qualification of infrastructure and personnel at CEA Saclay. After transport and tests at DESY the cryomodule was stored for several years. Last year we decided to refurbish this module with new cavities for the installation in the FLASH accelerator. During the disassembly of the cavity string in the clean room at DESY we took several particulate samples for analysis. Optical and laser optical microscopy give us an insight on the quantity and type of the particulates. We expect to get hints where the particulates come from and how they are transported through the cavity string during transport and operation.
	Poster TUP099 [2.599 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP099
About •	paper received ※ 23 June 2019 paper accepted ※ 03 July 2019 issue date ※ 14 August 2019
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TUP101	LCLS-II Cryomodules Production Experience and Lessons Learned at Fermilab	cryomodule, vacuum, cavity, linac	709
	T.T. Arkan, J.N. Blowers, C.M. Ginsburg, C.J. Grimm, J.A. Kaluzny, T.H. Nicol, Y.O. Orlov, K.S. Premo, R.P. Stanek, G. Wu Fermilab, Batavia, Illinois, USA
	LCLS-II is a planned upgrade project for the linear coherent light source (LCLS) at SLAC. The LCLS-II Linac will consist of thirty-five 1.3 GHz and two 3.9 GHz superconducting RF continuous wave (CW) cryomodules that Fermilab and Jefferson Lab are currently producing in collaboration with SLAC. The LCLS-II 1.3 GHz cryomodule design is based on the European XFEL pulsed-mode cryomodule design with modifications needed for CW operation. Two prototype cryomodules had been assembled and tested. After prototype cryomodule tests, both laboratories have increased their cryomodule production rate to meet the challenging LCLS-II project installation schedule requirements of approximately one cryomodule per month per laboratory. To date, Fermilab has completed the assembly and testing of sixteen 1.3 GHz cryomodules. Fermilab has successfully shipped five CMs to SLAC and will continue to ship with a two-week throughput. The first 3.9 GHz cryomodule assembly is scheduled to start in June 2019; production readiness verifications are in progress. This paper presents LCLS-II cryomodule assembly and production experience, emphasizing the challenges, the mitigations and lessons learned
	Poster TUP101 [0.834 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP101
About •	paper received ※ 20 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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THP050	Measurement of the Magnetic Field Penetration into Superconducting Thin Films	experiment, solenoid, SRF, cavity	978
	I.H. Senevirathne, G. Ciovati, J.R. Delayen ODU, Norfolk, Virginia, USA G. Ciovati, J.R. Delayen JLab, Newport News, Virginia, USA
	The magnetic field at which first flux penetrates is a fundamental parameter characterizing superconducting materials for SRF cavities. Therefore, an accurate technique is needed to measure the penetration of the magnetic field directly. The conventional magnetometers are inconvenient for thin superconducting film measurements because these measurements are strongly influenced by orientation, edge and shape effects. In order to measure the onset of field penetration in bulk, thin films and multi-layered superconductors, we have designed, built and calibrated a system combining a small superconducting solenoid capable of generating surface magnetic field higher than 500 mT and Hall probe to detect the first entry of vortices. This setup can be used to study various promising alternative materials to Nb, especially SIS multilayer coatings on Nb that have been recently proposed to delay the vortex penetration in Nb surface. In this paper, the system will be described and calibration will be presented.
	Poster THP050 [1.201 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP050
About •	paper received ※ 20 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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THP073	Advanced LLRF System Setup Tool for RF Field Regulation of SRF Cavities	controls, cavity, feedback, electron	1063
	S. Pfeiffer, J. Branlard, M. Hoffmann, Ch. Schmidt DESY, Hamburg, Germany
	Feedback operation at the European XFEL ensures an amplitude and phase stability of 0.01% and 0.01 deg, respectively. To reach such high RF field stability, model-based approaches for RF field system characterization and RF field controller design are in use. High demand on this system modelling is set especially to the characterization of additional passband modes for small bandwidth SRF cavities operated in pulsed mode and vector-sum regulation. This contribution discusses the developed "Advanced system setup tool" using a graphical user implementation in Matlab® for the RF field system characterization and the multiple-input-multiple-output feedback controller setup. Examples and current limitations will be presented.
	Poster THP073 [0.873 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP073
About •	paper received ※ 19 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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THP092	Status of Cryomodule Testing at CMTB for CW R&D	cavity, cryomodule, operation, linac	1129
	J. Branlard, V. Ayvazyan, A. Bellandi, J. Eschke, C. Gümüş, D. Kostin, K.P. Przygoda, H. Schlarb, J.K. Sekutowicz DESY, Hamburg, Germany
	Cryo Module Test Bench (CMTB) is a facility to perform tests on European XFEL like superconducting accelerating modules. The 120 kW Inductive Output Tube (IOT) installed in the facility allows driving the eight superconducting cavities inside the module under test in a vector-sum or single cavity control fashion with average Continuous Wave (CW) gradients higher than 20 MV/m. The scope of these tests is to evaluate the feasibility of upgrading European XFEL to CW operation mode. Following the successful tests done on a prototype module XM-3 the initial performance results on the production module XM50 will be presented in this paper. Because of European XFEL requirements, XM50 is equipped with modified couplers that allow a variable Loaded Quality factor(QL) to values higher than 4x10⁷. A cost relevant open question is the maximum QL that can be reached while maintaining the system within the European XFEL field stability specifications of 0.01 % in amplitude and 0.01 deg in phase. Because of this, the LLRF system capability of rejecting microphonic and RF disturbances, as well as Lorentz Force Detuning (LFD) related effects in open and closed loop is of prime interest.
	Poster THP092 [1.514 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP092
About •	paper received ※ 25 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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THP100	Insight into DESY’s Test Laboratory for Niobium Raw Material and Semi-finished Products	cavity, niobium, SRF, controls	1157
	J.I. Iversen, A. Brinkmann, A. Ermakov, A. Muhs, J. Ziegler DESY, Hamburg, Germany
	DESY has started setting up a test laboratory for niobium more than 20 years ago. The initial application was to assure required surface quality of niobium sheets before its forming to half cells for the 1.3 GHz SRF Tesla shape cavities. As a first test equipment DESY developed a basic eddy current test device which was refined continuously. Since that time the laboratory grew with the requirements on R&D activities for niobium raw material and its semi-finished products. To be able to assure the Quality of niobium products needed for the European XFEL series cavity production, the Lab¿s infrastructure was updated significantly. Now the capabilities of the test laboratory cover the investigation of the fundamental physical properties of various materials including for example mechanical properties, surface, microstructure and chemical composition analysis. The Quality Assurance for the European XFEL was performed successfully on an outstanding level and in the meantime the laboratory was used for several other projects like LCLS-II and ESS. We present DESY’s test infrastructure as well as applied methods for the Quality Assurance and R&D activities and we report about experiences.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP100
About •	paper received ※ 25 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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Paper

Title

Other Keywords

Page

MOFAA1

LCLS-II: Status, Issues and Plans

cavity, SRF, cryomodule, linac

1

M.C. Ross
SLAC, Menlo Park, California, USA

Funding: Work supported by Department of Energy contract DE-AC02-76SF00515
The Linac Coherent Light Source II (LCLS-II) project requires the assembly, test, and installation of 37 cryomodules (CM) in order to deliver a 4 GeV CW electron beam to the FEL undulators for production of both hard and soft X-ray pulses at a repetition rate of up to 1 MHz. SRF cavity performance in the 30+ tested CM exceeds gradient and cryogenic dynamic heat-load requirements (set at 16 MV/m and 10 W resp). In this talk we present microphonics, shipping, magnetic-flux exclusion, and field emission performance. The US funding agency, DOE, has recently approved an additional 20 CM for the extension of LCLS-II to 8 GeV. This paper will also include initial cavity and heat-load performance results for the extension project, LCLS-II-HE.

Slides MOFAA1 [30.146 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOFAA1

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paper received ※ 25 June 2019 paper accepted ※ 04 July 2019 issue date ※ 14 August 2019

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MOFAA2

Operation of the European XFEL Towards the Maximum Energy

electron, cavity, operation, MMI

9

M. Omet, V. Ayvazyan, J. Branlard, S. Choroba, W. Decking, V.V. Katalev, D. Kostin, L. Lilje, P. Morozov, Y. Nachtigal, H. Schlarb, V. Vogel, N. Walker, B. Yildirim
DESY, Hamburg, Germany

After the initial commissioning of the available 25 radio frequency (RF) stations of the European XFEL (RF gun, A1, AH1 and stations A2 through A23) a maximum electron beam energy of 14.5 GeV was achieved, 3 GeV short of the design energy of 17.5 GeV. In order to tackle this problem, the Maximum Gradient Task Force (MGTF) was formed. In the scope of the work of the MGTF, RF stations A6 through A25 (linac L3) were systematically investigated and voltage-limiting factors of the SRF accelerating modules and their RF distribution system were identified and improved. As a result, the design electron beam energy was exceeded at 17.6 GeV on the 18.7.2018. Beside this an overview over the regular RF operation at the European XFEL is given.

Slides MOFAA2 [5.695 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOFAA2

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paper received ※ 21 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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MOP029

N-Doping Studies With Single-Cell Cavities for the SHINE Project

cavity, niobium, SRF, ECR

102

J.F. Chen, H.T. Hou, Y.F. Liu, D. Wang, Y. Wang
SARI-CAS, Pudong, Shanghai, People’s Republic of China
Y.W. Huang
ShanghaiTech University, Shanghai, People’s Republic of China
Z. Wang
SINAP, Shanghai, People’s Republic of China

The SHINE SRF accelerator is designed to operate in CW mode with more than six hundred superconducting cavities. In order to reduce the high cost of construction and operation of the cryogenic system, high-Q cavities with nitrogen-doping technology together with tradition-ally treated large-grain cavities have been considered as two possible options. In this paper, we present N-doping studies on single-cell cavities fabricated with fine-grain and large-grain niobium.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP029

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paper received ※ 23 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019

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MOP034

European XFEL: Accelerating Module Repair at DESY

cavity, linac, SRF, operation

127

D. Kostin, J. Eschke, K. Jensch, N. Krupka, D. Reschke, S. Saegebarth, J. Schaffran, M. Schalwat, P. Schilling, M. Schmökel, S. Sievers, N. Steinhau-Kühl, E. Vogel, H. Weise, M. Wiencek, B. van der Horst
DESY, Hamburg, Germany

The European XFEL is in operation since 2017. The design projected energy of 17.5 GeV was reached, even with the last 4 main linac accelerating modules not yet installed. 2 out of 4 not installed modules did suffer from strong cavity performance degradation, namely increased field emission, and required surface processing. The first of two modules is reassembled and tested. The module test results confirm a successful repair action. The module repair and test steps are described together with cavities performance evolution.

Poster MOP034 [1.863 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP034

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paper received ※ 17 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019

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MOP049

Prototypes Fabrication of 1.3 GHz Superconducting Rf Components for SHINE

cavity, niobium, HOM, SRF

164

H.T. Hou, J.F. Chen, Z.Y. Ma, J. Shi, Y. Wang
SARI-CAS, Pudong, Shanghai, People’s Republic of China
F.S. He
IHEP, Beijing, People’s Republic of China
S.W. Quan
PKU, Beijing, People’s Republic of China

Aiming to high repetition rate hard X-ray facility, con-struction of Shanghai HIgh repetition rate XFEL aNd Extreme light facility (SHINE) project has been ap-proved. During the R & D phase, prototypes fabrication of key components of 1.3GHz superconducting rf system have been proposed, especially 1.3 GHz 9-cell niobium cavities. Here the paper will present the progress of the fabrication status and performance of the prototypes, together with the analysis of not only the quality factor and gradient of the cavities. Consideration of HOM feed-throughs and absorbers are also reported.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP049

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paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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MOP054

Fabrication of 3.0-GHz Single-cell Cavities for Thin-film Study

cavity, SRF, MMI, linac

177

T. Saeki, H. Hayano, H. Inoue, R. Katayama, T. Kubo
KEK, Ibaraki, Japan
F.E. Hannon, R.A. Rimmer, A-M. Valente-Feliciano
JLab, Newport News, Virginia, USA
H. Ito
Sokendai, Ibaraki, Japan
Y. Iwashita, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan

Funding: This work is supported by JSPS KAKENHI JP17H04839, JSPS KAKENHI JP26600142, Japan-US Research Collaboration Program, and the Collaborative Research Program of ICR Kyoto Univ. (2018-13).
We fabricated 3.0-GHz single-cell cavities with Cu and Nb materials for testing thin-film creations on the inner surface of the cavities in collaboration between Jefferson Laboratory (JLab) and KEK. The cavity was designed at JLab. According to the design of cavity, the press-forming dies and trimming fixtures for the cavity-cell were also designed and fabricated at JLab. These dies and trimming fixtures were transported to KEK, and the rest of fabrication processes were done at KEK. Finally nine Cu 3.0-GHz single-cell cavities and six Nb 3.0-GHz single-cell cavities were fabricated. Two Cu 3.0-GHz single-cell cavities were mechanically polished at Jlab. All of these cavities will be utilized for the tests of various thin-film creations at JLab and KEK. This presentation describes details of the fabrication of these cavities.

Poster MOP054 [1.203 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP054

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paper received ※ 05 July 2019 paper accepted ※ 13 August 2019 issue date ※ 14 August 2019

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MOP057

Electropolishing of PIP-II Low Beta Cavity Prototypes

cavity, cathode, experiment, linac

194

M. Bertucci, A. Bosotti, A. D’Ambros, P. Michelato, L. Monaco, C. Pagani, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
A. Gresele, A. Visentin
Ettore Zanon S.p.A., Nuclear Division, Schio, Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy
D. Rizzetto, M. Rizzi
Ettore Zanon S.p.A., Schio, Italy

We present the upgrade of the EP facility for the surface treatment of PIP-II low beta cavities. The main process parameters, such as voltage, treatment time, acid throughput and cathode geometry, already optimized on the previous experience of 1.3 GHz Tesla-shape cavities, are discussed taking into account the different cavity size and geometry. The first surface treatments have been performed at Ettore Zanon SpA on single cell cavity prototypes in order to reach good final surface finishing and the required thickness removal. In the meantime, the upgrade of the system for the treatment of multicell PIP-II prototype cavities is presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP057

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paper received ※ 23 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019

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MOP082

Measurement of the Vibration Response of the EXFEL RF Coupler and Comparison With Simulated Data (Finite Element Analyses)

cryomodule, acceleration, interface, resonance

273

S. Barbanotti, C. Engling, K. Jensch
DESY, Hamburg, Germany

The coupler is one of the main and most sensitive components of the European X-ray Free Electron Laser (EXFEL) superconducting cryomodule. More than 800 couplers were transported for more than 800 km assembled in a cryomodule during the assembly phase of the EXFEL without any visible damage. However, in a different project, a very similar coupler design showed a week point in one of the bellows when transported over a similar distance with a comparable transport set up. Therefore we decided to further study the coupler behaviour: we investigated the frequency response of the coupler on a vibration table in a controlled environment for different road and loading conditions and compared the data with simulated ones. This paper present the work performed so far and our conclusions.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP082

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paper received ※ 18 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019

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MOP084

A Simple Variable Coupler for the Cryogenic Test of SRF Cavities

cavity, SRF, cryogenics, coupling

282

G. Ciovati, L. Turlington
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The cryogenic rf tests of SRF cavities in vertical cryostats is typically carried out using fixed-length antennae to couple rf power into the cavity and to probe the energy stored into the cavity. Although variable couplers have been designed, built and used in the past, they are often a complex, costly, not very reliable auxiliary component to the cavity test. In this contribution we present the design and implementation of a simple variable rf antenna which has about 50 mm travel, allowing to obtain about four orders of magnitude variation in Q_ext -value. The motion of the antenna is driven by a motorized linear feedthrough outside of the cryostat. The antenna can easily be mounted on the most common type of cavity flanges.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP084

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paper received ※ 18 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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TUFUA7

Review of Muon Spin Rotation Studies of SRF Materials

SRF, niobium, cavity, experiment

360

T. Junginger
Lancaster University, Lancaster, United Kingdom
R.E. Laxdal
TRIUMF, Vancouver, Canada

Muons spin rotate in magnetic fields and emit a positron preferentially in spin direction after decay. These properties enable muon spin rotation (muSR) as a precise probe for local magnetism. muSR has been used to characterize SRF materials since 2010. At TRIUMF a so called surface beam implants muons at a material dependent depth of about 150 µm in the bulk. A dedicated spectrometer was developed for field of first vortex penetration and pinning strength measurements of SRF materials in parallel magnetic fields of up to 300 mT. A low energy beam available at PSI implants muons at variable depth in the London layer allowing for direct measurements of the London penetration depth from which the lower critical field and the superheating field can be calculated. This facility is limited to parallel magnetic fields of up to 25 mT. Here, surface and low energy muSR results on SRF materials are reviewed and cross-correlated to each other and to further results from additional experiments. Finally, we present the status of a new facility based on the similar beta-NMR technique enabling measurements in the London layer of SRF materials exposed to parallel magnetic fields above 200 mT.

Slides TUFUA7 [4.063 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUFUA7

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paper received ※ 01 July 2019 paper accepted ※ 12 July 2019 issue date ※ 14 August 2019

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TUP020

Statistical Analysis of the 120°C Bake Procedure of Superconducting Radio Frequency Cavities

cavity, accelerating-gradient, SRF, niobium

444

L. Steder, D. Reschke
DESY, Hamburg, Germany

DESY is and was very active in R&D related to SRF cavities. Many single and nine cell cavities with different surface treatment histories were tested vertically. Results of these cold tests are accelerating gradient and quality factor of the cavities. Using the large number of available datasets the parameters of the 120°C bake procedure, which is applied to avoid high-field Q-slope, are analysed. The impact of different durations and temperatures on accelerating gradient, quality factor and residual resistance is studied in detail and is compared to results obtained with the recently proposed procedure of modified low temperature bake. For this procedure additional four hours at temperatures around 75°C are implemented before the standard bake at about 120°C. Since the claim is, that cavities treated with such a modified procedure achieve extra-ordinary large accelerating gradients it is a very interesting research field for the European XFEL continuous wave mode upgrade. For this purpose cavities with high quality factors are needed, but in addition large maximal accelerating fields are required to maintain high energies in the pulsed operation mode of the accelerator.

Poster TUP020 [0.747 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP020

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paper received ※ 21 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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TUP023

Experience of LCLS-II Cavities Radial Tuning at DESY

cavity, HOM, SRF, linac

456

A. Sulimov, J.H. Thie
DESY, Hamburg, Germany
A. Gresele
Ettore Zanon S.p.A., Nuclear Division, Schio, Italy
A. Navitski
RI Research Instruments GmbH, Bergisch Gladbach, Germany
A.D. Palczewski
JLab, Newport News, Virginia, USA

Radial tuning (rolling) was applied to three LCLS-II cavities to prevent that their lengths exceed the technical limits. The cavities have a reduced frequency due to additional material removal during cavity treatment well beyond the baseline recipe. The mechanical condition of the cavities was relatively soft because of the thermal history and the niobium manufacture requirement of an optimal flux expulsion. The niobium was highly recrystallized by 3 hours annealing at 900°C and 975°C respectively. Each cavity received an inner surface treatment of 200 µm electro-polishing (EP) and an external 30 µm buffered chemical polishing (BCP) as part of the baseline recipe. Each cavity received an addition ~100 µm of chemical removal along with a second annealing treatment before the radial tuning process. Detailed information about the accuracy and homogeneity of LCLS-II cavities rolling is presented as well as results of field distribution analysis for TM011 zero-mode with a comparison to standard cavities.

Poster TUP023 [0.521 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP023

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paper received ※ 23 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019

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TUP024

Radial Tuning Devices for 1.3 GHz TESLA Shape Cavities

cavity, SRF, HOM, niobium

459

A. Sulimov, J.H. Thie
DESY, Hamburg, Germany

Radial tuning devices at DESY can be applied to any TESLA shape 1.3 GHz cavity to reduce its elongation due to excessive additional material removal (>300 µm) or to compensate critical manufacturing uncertainties. Radial deformation of cavity cells can be provided by a special chain or a rolling device with three rollers. The chain distributes the radial forces on the equator area around the cell. The rollers are moving radially in relation to the rotating cavity and provide an equator diameter reduction. Both devices have the contour close to the cell shape at the equator area. The required equator radius deviation depends on the tuning target and usually varies between (0.02…0.60) mm. Different aspects of the tuning procedure and material properties are described using the example of cavity rolling.

Poster TUP024 [0.252 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP024

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paper received ※ 23 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019

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TUP033

Modal Analysis of the EXFEL 1.3 GHz Cavity and Cryomodule Main Components and Comparison with Measured Data

cavity, cryomodule, vacuum, linac

488

S. Barbanotti, A. Bellandi, J. Branlard, K. Jensch
DESY, Hamburg, Germany

Future upgrades of the European X-ray Free Electron Laser (EXFEL) may require driving the linac at higher duty factor, possibly extending to Continuous Wave (CW) mode. An R&D program has started at DESY, to prepare for a CW upgrade. Cryomodules are being tested in CW mode in our CryoModule Test Bench (CMTB) to study the performance and main issues for such an operation mode. Sensitivity to vibration causing microphonics is one of the main concerns for the CW operation in mode. Therefore a detailed analysis is being performed to evaluate the frequency spectrum of the EXFEL cryomodule main components: the cavity itself, the cavity string, the cold mass and the vacuum vessel. Finite Element Modal Analyses have been performed and the results compared with data measured at the CMTB. This paper summarizes the main results and conclusions of such a study.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP033

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paper received ※ 18 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019

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TUP057

Study of Flux Trapping Variability between Batches of Tokyo Denkai Niobium used for the LCLS-II Project and Subsequent 9-cell RF Loss Distribution between the Batches

cavity, niobium, SRF, superconductivity

570

A.D. Palczewski
JLab, Newport News, Virginia, USA
D. Gonnella
SLAC, Menlo Park, California, USA
O.S. Melnychuk, D.A. Sergatskov
Fermilab, Batavia, Illinois, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
During the LCLS-II project a second batch of niobium was procured from Tokyo Denkai Co Ltd in order to make additional cavities. The original production material came from Two vendors Tokyo Denkai Co., Ltd. (TD) and Ningxia Orient Tantalum Industry Co., Ltd. (OTIC/NX)). It was found TD niobium required a lower annealing temperature (900°C) to obtain satisfactory flux expulsion characteristics compared to NX which required a slightly higher annealing temperature (950°-975°C). In order to ensure the new TD material performed equivalent to the niobium produced 4 year before after 900°C annealing; each heat lot of niobium had its flux expulsion characteristics parametrized and custom thermal treatments developed for each lot. Subsequent pure heat lot 9 cell cavities were made and tested. We will look at the flux expulsion characteristics of each lot, and RF loss of the 9-cell cavities produced using the individual heat lots.

Poster TUP057 [1.446 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP057

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paper received ※ 25 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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TUP073

Superconducting Thin Films Characterization at HZB with the Quadrupole Resonator

cavity, SRF, quadrupole, niobium

616

D.B. Tikhonov, S. Keckert, J. Knobloch, O. Kugeler, Y. Tamashevich
HZB, Berlin, Germany
A-M. Valente-Feliciano
JLab, Newport News, Virginia, USA

Funding: EASITrain - European Advanced Superconductivity Innovation and Training. This Marie Sklodowska-Curie Action Innovative Training Networks founded by H₂020 under Grant Agreement no. 764879
Superconducting thin films have great potential as post-Nb material for use in SRF applications in future accelerators and industry. To test the RF-performance of such films in practice, would require the building and coating of a full RF cavity. Deposition of thin films on such scales in test facilities are challenging, in particular when curved surfaces have to be coated. This greatly complicates their systematic research. In this contribution we report on the method we use to characterize small and flat thin film samples (Deposited onto both Nb and Cu substrates) in an actual cavity named the Quadrupole Resonator (QPR). We also summarize the latest measurement results of NbTiN thin films. The Quadrupole Resonator at HZB is a tool that is able to perform SRF characterizations at frequencies ~415, 847, 1300 MHz with RF fields using an RF-DC power compensation technique.

Poster TUP073 [2.318 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP073

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paper received ※ 23 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019

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TUP079

Deposition of Nb₃Sn Films by Multilayer Sequential Sputtering for SRF Cavity Application

cavity, SRF, site, niobium

637

Md.N. Sayeed, H. Elsayed-Ali
ODU, Norfolk, Virginia, USA
M.C. Burton, G.V. Eremeev, C.E. Reece, A-M. Valente-Feliciano
JLab, Newport News, Virginia, USA
U. Pudasaini
The College of William and Mary, Williamsburg, Virginia, USA

Nb₃Sn is considered as an alternative of Nb for SRF accelerator cavity application due to its potential to obtain higher quality factors and higher accelerating gradients at a higher operating temperature. Magnetron sputtering is one of the effective techniques that can be used to fabricate Nb₃Sn on SRF cavity surface. We report on the surface properties of Nb₃Sn films fabricated by sputtering multiple layers of Nb and Sn on sapphire and niobium substrates followed by annealing at 950°C for 3 h. The crystal structure, film microstructure, composition and surface roughness were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and atomic force microscopy (AFM). The RF performance of the Nb₃Sn coated Nb substrates were measured by a surface impedance characterization system. We also report on the design of a multilayer sputter deposition system to coat a single-cell SRF cavity.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP079

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paper received ※ 22 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019

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TUP099

Particulate Sampling and Analysis During Refurbishment of Prototype European XFEL Cryomodule

cavity, SRF, cryomodule, superconductivity

701

N. Krupka, C. Bate, D. Reschke, S. Saegebarth, M. Schalwat, P. Schilling, S. Sievers
DESY, Hamburg, Germany

Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Tech-nologies (MT) Program.
The cryomodule PXFEL3₁ is one of three prototype cryomodules for the European XFEL. In preparation of the series module assembly it was used for the qualification of infrastructure and personnel at CEA Saclay. After transport and tests at DESY the cryomodule was stored for several years. Last year we decided to refurbish this module with new cavities for the installation in the FLASH accelerator. During the disassembly of the cavity string in the clean room at DESY we took several particulate samples for analysis. Optical and laser optical microscopy give us an insight on the quantity and type of the particulates. We expect to get hints where the particulates come from and how they are transported through the cavity string during transport and operation.

Poster TUP099 [2.599 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP099

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paper received ※ 23 June 2019 paper accepted ※ 03 July 2019 issue date ※ 14 August 2019

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TUP101

LCLS-II Cryomodules Production Experience and Lessons Learned at Fermilab

cryomodule, vacuum, cavity, linac

709

T.T. Arkan, J.N. Blowers, C.M. Ginsburg, C.J. Grimm, J.A. Kaluzny, T.H. Nicol, Y.O. Orlov, K.S. Premo, R.P. Stanek, G. Wu
Fermilab, Batavia, Illinois, USA

LCLS-II is a planned upgrade project for the linear coherent light source (LCLS) at SLAC. The LCLS-II Linac will consist of thirty-five 1.3 GHz and two 3.9 GHz superconducting RF continuous wave (CW) cryomodules that Fermilab and Jefferson Lab are currently producing in collaboration with SLAC. The LCLS-II 1.3 GHz cryomodule design is based on the European XFEL pulsed-mode cryomodule design with modifications needed for CW operation. Two prototype cryomodules had been assembled and tested. After prototype cryomodule tests, both laboratories have increased their cryomodule production rate to meet the challenging LCLS-II project installation schedule requirements of approximately one cryomodule per month per laboratory. To date, Fermilab has completed the assembly and testing of sixteen 1.3 GHz cryomodules. Fermilab has successfully shipped five CMs to SLAC and will continue to ship with a two-week throughput. The first 3.9 GHz cryomodule assembly is scheduled to start in June 2019; production readiness verifications are in progress. This paper presents LCLS-II cryomodule assembly and production experience, emphasizing the challenges, the mitigations and lessons learned

Poster TUP101 [0.834 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP101

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paper received ※ 20 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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THP050

Measurement of the Magnetic Field Penetration into Superconducting Thin Films

experiment, solenoid, SRF, cavity

978

I.H. Senevirathne, G. Ciovati, J.R. Delayen
ODU, Norfolk, Virginia, USA
G. Ciovati, J.R. Delayen
JLab, Newport News, Virginia, USA

The magnetic field at which first flux penetrates is a fundamental parameter characterizing superconducting materials for SRF cavities. Therefore, an accurate technique is needed to measure the penetration of the magnetic field directly. The conventional magnetometers are inconvenient for thin superconducting film measurements because these measurements are strongly influenced by orientation, edge and shape effects. In order to measure the onset of field penetration in bulk, thin films and multi-layered superconductors, we have designed, built and calibrated a system combining a small superconducting solenoid capable of generating surface magnetic field higher than 500 mT and Hall probe to detect the first entry of vortices. This setup can be used to study various promising alternative materials to Nb, especially SIS multilayer coatings on Nb that have been recently proposed to delay the vortex penetration in Nb surface. In this paper, the system will be described and calibration will be presented.

Poster THP050 [1.201 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP050

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paper received ※ 20 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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THP073

Advanced LLRF System Setup Tool for RF Field Regulation of SRF Cavities

controls, cavity, feedback, electron

1063

S. Pfeiffer, J. Branlard, M. Hoffmann, Ch. Schmidt
DESY, Hamburg, Germany

Feedback operation at the European XFEL ensures an amplitude and phase stability of 0.01% and 0.01 deg, respectively. To reach such high RF field stability, model-based approaches for RF field system characterization and RF field controller design are in use. High demand on this system modelling is set especially to the characterization of additional passband modes for small bandwidth SRF cavities operated in pulsed mode and vector-sum regulation. This contribution discusses the developed "Advanced system setup tool" using a graphical user implementation in Matlab® for the RF field system characterization and the multiple-input-multiple-output feedback controller setup. Examples and current limitations will be presented.

Poster THP073 [0.873 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP073

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paper received ※ 19 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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THP092

Status of Cryomodule Testing at CMTB for CW R&D

cavity, cryomodule, operation, linac

1129

J. Branlard, V. Ayvazyan, A. Bellandi, J. Eschke, C. Gümüş, D. Kostin, K.P. Przygoda, H. Schlarb, J.K. Sekutowicz
DESY, Hamburg, Germany

Cryo Module Test Bench (CMTB) is a facility to perform tests on European XFEL like superconducting accelerating modules. The 120 kW Inductive Output Tube (IOT) installed in the facility allows driving the eight superconducting cavities inside the module under test in a vector-sum or single cavity control fashion with average Continuous Wave (CW) gradients higher than 20 MV/m. The scope of these tests is to evaluate the feasibility of upgrading European XFEL to CW operation mode. Following the successful tests done on a prototype module XM-3 the initial performance results on the production module XM50 will be presented in this paper. Because of European XFEL requirements, XM50 is equipped with modified couplers that allow a variable Loaded Quality factor(QL) to values higher than 4x10⁷. A cost relevant open question is the maximum QL that can be reached while maintaining the system within the European XFEL field stability specifications of 0.01 % in amplitude and 0.01 deg in phase. Because of this, the LLRF system capability of rejecting microphonic and RF disturbances, as well as Lorentz Force Detuning (LFD) related effects in open and closed loop is of prime interest.

Poster THP092 [1.514 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP092

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paper received ※ 25 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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THP100

Insight into DESY’s Test Laboratory for Niobium Raw Material and Semi-finished Products

cavity, niobium, SRF, controls

1157

J.I. Iversen, A. Brinkmann, A. Ermakov, A. Muhs, J. Ziegler
DESY, Hamburg, Germany

DESY has started setting up a test laboratory for niobium more than 20 years ago. The initial application was to assure required surface quality of niobium sheets before its forming to half cells for the 1.3 GHz SRF Tesla shape cavities. As a first test equipment DESY developed a basic eddy current test device which was refined continuously. Since that time the laboratory grew with the requirements on R&D activities for niobium raw material and its semi-finished products. To be able to assure the Quality of niobium products needed for the European XFEL series cavity production, the Lab¿s infrastructure was updated significantly. Now the capabilities of the test laboratory cover the investigation of the fundamental physical properties of various materials including for example mechanical properties, surface, microstructure and chemical composition analysis. The Quality Assurance for the European XFEL was performed successfully on an outstanding level and in the meantime the laboratory was used for several other projects like LCLS-II and ESS. We present DESY’s test infrastructure as well as applied methods for the Quality Assurance and R&D activities and we report about experiences.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP100

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paper received ※ 25 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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