SRF2019 - Classification: Cavities - Fabrication / cavity processing

Paper	Title	Page
FRTU2	Cavity Processing and Cleanroom Techniques
	L. Popielarski FRIB, East Lansing, Michigan, USA
	The "Cavity Processing and Cleanroom Assembly Review of Literature" tutorial will introduce basics for SRF cavity processing and cleanroom techniques based on published processes. The practical applications presented will focus on low beta quarter-wave and half-wave cavities, however there are many publications on elliptical cavity processing and cleanroom assembly available online and in past tutorials. Topics discussed include: SRF coldmass and cavity workflow, SRF cavity receiving and inspection, degreasing, ultra pure water and high pressure rinse, mechanical surface preparation, removal by chemical etching, preparation by electro polishing, safety considerations, heat treatments, cleanroom protocols, and cleanroom assembly techniques.
	Slides FRTU2 [40.595 MB]
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TUP018	New SRF Structures Processed at the ANL Cavity Processing Facility	434
	T. Reid, Z.A. Conway, B.M. Guilfoyle, M. Kedzie, M.P. Kelly, M.K. Ng ANL, Lemont, Illinois, USA
	Argonne National Laboratory (ANL) has extended high quality cavity processing techniques based on those developed for the International Linear Collider to several more complex superconducting RF cavities. Recently, these include a bunch lengthening harmonic cavity, a crabbing rf-dipole cavity, a compact half-wave cavity, and both medium and high frequency elliptical cavities. These systems are an improved version of the one originally developed for 1.3 GHz 9-cell cavities and include a second rotating electrical contact that can support multiple cathodes, necessary for optimum polishing in difficult cavity geometries. All include the possibility for external water cooling.
	Poster TUP018 [4.322 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP018
About •	paper received ※ 28 June 2019 paper accepted ※ 12 July 2019 issue date ※ 14 August 2019
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TUP019	Status of High Temperature Vacuum Heat Treatment Program at IPN Orsay	438
	M. Fouaidy, F. Chatelet, V. Delpech, F. Galet, D. Le Dréan, R. Martret, G. Olry, T. Pépin-Donat Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France M. Baudrier, P. Carbonnier, E. Fayette, X. Hanus, Th. Proslier, D. Roudier, P. Sahuquet, C. Servouin CEA-DRF-IRFU, France E. Cenni, L. Maurice CEA-IRFU, Gif-sur-Yvette, France D. Longuevergne FLUO, Orsay, France
	In the framework of ESS, a vacuum furnace dedicated to High Temperature Heat Treatment under Vacuum (VH2T2) of SRF bulk Nb cavities was developed and commissioned in May 2016. This furnace is currently used for interstitial hydrogen removal (10h00 @ 650 °C) of two type of cavities: 1) the whole series of 26 ESS 352 MHz spoke resonators equipped with their Ti LHe tank well, 2) some prototypes of ESS high beta and medium beta cavities. Up to know IPN Orsay VH2T2 (10h00 @ 650 °C) was successfully applied to more than 16 cavities. In this paper we will first report about these VH2T2 tests. Finally, we have just started testing nitrogen infusion and nitrogen doping processes on samples and 1.3 GHz cavities: the preliminary results will be discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP019
About •	paper received ※ 03 July 2019 paper accepted ※ 04 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	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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TUP021	Effect of Cathode Rotation and Acid Flow in Vertical Electropolishing of 1.3 GHz Niobium Nine-Cell Cavity	448
	V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi MGH, Hyogo-ken, Japan H. Hayano, S. Kato, H. Monjushiro, T. Saeki KEK, Ibaraki, Japan
	We have been carrying out R&D on vertical electropolishing (VEP) technique to establish it as an alternate of the horizontal EP (HEP) technique used for the surface treatment of niobium (Nb) superconducting RF (SRF) cavities. We have earlier reported on a VEP parameter study for 1.3 GHz single and nine-cell Nb cavities. The optimized VEP parameters and a unique rotating cathode yielded uniform removal and a smooth surface in the single cell cavity. The unique cathode and a dual flow mechanism for acid circulation were applied to improve the removal uniformity in the nine-cell cavity. The vertically electropolished single and nine cell cavities achieved the same RF performance as achieved after the HEP processes. We are making efforts to further improve the removal uniformity in the nine-cell cavity. Here, we report on a VEP of the 1.3 GHz Nb nine-cell cavity at a higher cathode rotation speed of 50 rpm. The VEP results reveal that the speed could be considered for improving the uniformity in removal while maintaining the surface smoothness. Required improvements in the VEP facility and acid flow condition for achieving uniform EP and a smooth surface are also described.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP021
About •	paper received ※ 23 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019
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TUP022	Fermilab EP Facility Improvement	453
	F. Furuta, D.J. Bice, A.C. Crawford, T.J. Ring Fermilab, Batavia, Illinois, USA
	Electro-chemical Polishing (EP) is one of the key technologies of surface treatments for niobium superconducting cavities. We have established a single-cell scale horizontal electro-polishing facility at Fermilab and routinely processed the niobium cavities with the frequencies of 1.3 GHz to 3.9 GHz. The precise control of EP parameters, especially the temperatures of cavity outside wall, allows the uniform removal over the cell with the variation of ±15%. Here we report the details of our EP process and recent improvements on our EP facility at Fermilab.
	Poster TUP022 [1.711 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP022
About •	paper received ※ 10 July 2019 paper accepted ※ 17 August 2019 issue date ※ 14 August 2019
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TUP023	Experience of LCLS-II Cavities Radial Tuning at DESY	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	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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TUP026	Vibro-tumbling as an Alternative to Standard Mechanical Polishing Techniques for SRF Cavities	464
	E. Chyhyrynets, O. Azzolini, V.A. Garcia, G. Keppel, C. Pira, F. Stivanello, L. Zanotto INFN/LNL, Legnaro (PD), Italy
	Funding: Work supported by the INFN V group experiment TEFEN, Agreement N. KE2722/BE/FCC and from the European Union’s H₂020 Framework Programme under grant agreement no. 764879 (EASITrain) Centrifugal Barrel Polishing (CBP) is a common tool in the Nb bulk SC cavities production, prior to elec-tropolishing (EP). Indeed, the mechanical polishing is fun-damental also in the superconducting thin film resonant cavities in which one of the main issues that limits the per-formances is the surface preparation. A promising vi-bro-tumbling technique is being studied and implemented with a possibility to replace or improve mechanical treat-ment steps (grinding, barrel polishing). The simplic-ity of the technology allows it to adapt to any cavity geom-etry, both for Nb and Cu materials. The presented work contains last results on 6 GHz cavities obtained at LNL-INFN, both Nb bulk and Cu cavities.
	Poster TUP026 [5.584 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP026
About •	paper received ※ 21 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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TUP027	Vertical Electropolishing of Niobium Nine-Cell Cavity with a Cavity Flipping System for Uniform Removal	467
	K.N. Nii, V. Chouhan, Y.I. Ida, T.Y. Yamaguchi MGH, Hyogo-ken, Japan H. Hayano, S. Kato, H. Monjushiro, T. Saeki KEK, Ibaraki, Japan
	Marui Galvanizing Co., Ltd. has been developing vertical electropolishing (VEP) technology for single and nine-cell niobium superconducting radio frequency cavities using a unique cathode namely Ninja cathode in collaboration with KEK. The VEP process usually results in non-uniform removal with a large asymmetry along the cavity length. In order to suppress the asymmetry in removal, we are making different approaches. Flipping of the cavity during the VEP process is one of the approaches applied so far. A unique VEP setup, which allows the flipping of a multi-cell cavity, has been developed as reported earlier. Here, we report the improvement in the setup with automation for cavity flipping. VEP experiments were conducted with the improved system. VEP parameters were studied and the VEP results including the removal trend are discussed in detail.
	Poster TUP027 [1.347 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP027
About •	paper received ※ 24 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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TUP028	Development of Vertical Electropolishing Facility for Nb 9-Cell Cavity (3)	470
	Y.I. Ida, V. Chouhan, K.N. Nii MGH, Hyogo-ken, Japan T. Akabori, G. Mitoya, K. Miyano HKK, Morioka, Japan Y. Anetai, F. Takahashi WING. Co.Ltd, Iwate-ken, Japan H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe KEK, Ibaraki, Japan
	The 1st report was delivered in May, 2018 at the IPAC 18 in Vancouver, Canada. The 2nd report was delivered in September, 2018 at the LINAC 18 in Beijing, China. We will make our 3rd report in July, 2019 at the SRF-19 in Dresden, Germany. There will be two main points this time. The first is that by using our improved Ninja Electrode Premium, we can out-perform our number one and number two competitors in terms of uniform electropolishing of the interior of the 9-cell cavity. The second point is that we can remove hydrogen gas, reacted during electropolishing, from the cavity chambers in a manner that has not been successfully achieved by 1st report, May 2018 and 2nd report, September 2018. We will report our 9-cell vertical polishing revolver-type unit that solves the above two problems.
	Poster TUP028 [0.444 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP028
About •	paper received ※ 24 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019
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TUP029	An Experimental Analysis of Effective EP Parameters for Low-Frequency Cylindrical Nb Cavities	472
	C.E. Reece JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Work supported by the U.S. DoE, Office of Science, Office of Basic Energy Sciences. While the basic process of electropolishing niobium with 1:9 HF:H₂SO₄ electrolyte has been well characterized, the specific process parameters used to electropolish different superconducting radio frequency (SRF) cavity geometries requires thoughtful attention. One seeks to realize confidently local diffusion-limited polishing at each point on the surface while maximizing uniformity of removal rate. Since the reaction rate is temperature dependent, this implies that one must manage the cavity surface temperature during polishing. Too-high applied voltage aggravates temperature and thus removal non-uniformity, but too-low applied voltage risks placing the large-diameter locations "off the current plateau," yielding etching rather than polishing. The majority of recent experience has been with elliptical L-band SRF cavities and some half-wave cavities at ANL. Lower frequency cavities with increased surface area and larger cathode-to-equator distance require fresh analysis and optimization. In preparation for SNS PPU project, JLab performed some EP process development runs with SNS high beta cavities to help identify viable parameter regimes for communication to cavity vendors. Results from this study are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP029
About •	paper received ※ 23 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019
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TUP031	Heat Treatment for Jacketed Half-wave Resonator Cavity	482
	Y. Jung, B.H. Choi, D.H. Gil, M.O. Hyun, H. Kim, J.W. Kim, M.S. Kim, D.Y. Lee, J. Lee, S. Lee IBS, Daejeon, Republic of Korea
	Vertical tests of a prototype half-wave resonator cavity are being tested. The performance of the cavities, such as quality factor and accelerating electrical field, are measured and compared to the target design value. In previous study, we reported the effect of the heat treatment on a prototype bare HWR cavity. We baked a jacketed HWR cavity to improve a performance for 10 h at 650°C. In this study, we will report the effect of the heat treatment on the jacketed HWR cavity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP031
About •	paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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TUP050	A Multi-layered SRF Cavity for Conduction Cooling Applications	538
	G. Ciovati, G. Cheng, E. Daly, G.V. Eremeev, J. Henry, R.A. Rimmer JLab, Newport News, Virginia, USA I.P. Parajuli ODU, Norfolk, Virginia, USA U. Pudasaini The College of William and Mary, Williamsburg, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Some of the work was supported by the 2008 PECASE Award of G. Ciovati. I. Parajuli is supported by NSF Grant PHYS-100614-010 Industrial application of SRF technology would favor the use of cryocoolers to conductively cool SRF cavities for particle accelerators, operating at or above 4.3 K. In order to achieve a lower surface resistance than Nb at 4.3 K, a superconductor with higher critical temperature should be used, whereas a metal with higher thermal conductivity than Nb should be used to conduct the heat to the cryocoolers. A standard 1.5 GHz bulk Nb single-cell cavity has been coated with a ~2 µm thick layer of Nb₃Sn on the inner surface and with a 5 mm thick Cu layer on the outer surface for conduction cooled applications. The cavity performance has been measured at 4.3 K and 2.0 K in liquid He. The cavity reached a peak surface magnetic field of ~40 mT with a quality factor of 6×10⁹ and 3.5×10⁹ at 4.3 K, before and after applying the thick Cu layer, respectively.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP050
About •	paper received ※ 21 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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TUP093	Summary of FRIB Cavity Processing in the SRF Coldmass Processing Facility and Lessons Learned	680
	E.S. Metzgar, B.W. Barker, K. Elliott, W. Hartung, L. Popielarski, G.V. Simpson, D.R. Victory, J.D. Whaley FRIB, East Lansing, Michigan, USA
	Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 and the National Science Foundation under Cooperative Agreement PHY-1102511. Baseline coldmass production for the linear particle accelerator at the Facility for Rare Isotope Beams (FRIB) is nearing completion. This paper will review the processing of cavities through the FRIB superconducting radio frequency (SRF) coldmass production facility focusing on chemical processing and high-pressure rinsing. Key processing data will be compiled and correlations between processing variables and cavity RF testing results will be examined.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP093
About •	paper received ※ 22 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019
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FRCAB1	HF-Free Bi-Polar Electropolishing for Application on Multi-Cell Elliptical Cavities
	H. Tian, M. Lester, J. Musson, H.L. Phillips, C.E. Reece JLab, Newport News, Virginia, USA T.D. Hall, M.E. Inman, R. Radhakrishnan, E.J. Taylor Faraday Technology, Inc., Clayton, Ohio, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05₀6OR23177 Pulse reversed electropolishing of niobium SRF cavities, using a dilute aqueous H₂SO4 electrolyte without HF yields equivalent RF performance with traditional EP. A pulse reversed electropolishing (BPEP) system has been implemented at Jefferson lab, and applied to single cells, a 7-cell CEBAF C100 cavity, and to 9-cell TESLA-style cavities with upgraded pulse system recently. A systematically mechanistic characterization and understanding of the BPEP process through bench top coupons study and cavities directs a system and operational parameter refinement for BPEP. We present process parameters, removal characterization, and rf performance of the processed cavities. This is the fruit of collaborative work between Jefferson Lab and Faraday Technology, Inc., directed toward the routine commercialization/industrialization of niobium cavity processing.
	Slides FRCAB1 [4.394 MB]
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FRCAB3	The Design of an Automated High-Pressure Rinsing System for SRF Cavity and the Outlook for Future Automated Cleanroom on Strings Assembly	1216
	H. Guo, Q.W. Chu, Y. He, C.L. Li, Y.K. Song, T. Tan, Z.M. You IMP/CAS, Lanzhou, People’s Republic of China
	High-pressure rinsing (HPR) and cavity assembly are two critical steps in cavity post-processing. Traditionally, high-pressure rinsing processing is based on ultra pure water system, pump, rinsing wand and simple-functional control system; cavity assembly processing is based on simple fixtures, wrenches, bolts and nuts. Beside the equipments, at least two operators are required in either of these two processing. Operators and their actions could bring mistakes and cause extra airborne particle contamination in cleanroom. To avoid the risk from labors, a robot has been introduced in IMP cleanroom for HPR assisting and assembly assisting. Labor cost and cavity RF test results are compared between the circumstances with and without robot assisting. In this work, an automated HPR system that has been designed and will be installed in IMP cleanroom will be presented. In addition, a future automated cleanroom on strings assembly will be discussed as well.
	Slides FRCAB3 [6.203 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB3
About •	paper received ※ 03 July 2019 paper accepted ※ 12 July 2019 issue date ※ 14 August 2019
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FRCAB7	Plasma Processing to Reduce Field Emission in LCLS-II 1.3 GHz SRF Cavities	1231
SUSP022	use link to see paper's listing under its alternate paper code
TUP067	use link to see paper's listing under its alternate paper code
	B. Giaccone, J. Zasadzinski IIT, Chicago, Illinois, USA P. Berrutti, B. Giaccone, A. Grassellino, M. Martinello Fermilab, Batavia, Illinois, USA M. Doleans ORNL, Oak Ridge, Tennessee, USA D. Gonnella, G. Lanza, M.C. Ross SLAC, Menlo Park, California, USA
	Plasma cleaning for LCLS-II 9-cell 1.3 GHz cavities is under study at Fermilab. Starting from ORNL method, we have developed a new technique for plasma ignition using HOMs. Plasma processing is being applied to contaminated and field emitting cavities, here are discussed the first results in terms of Q and radiation vs E measured before and after treatment. Further studies are ongoing to optimize plasma parameters and to acquire statistics on plasma cleaning effectiveness.
	Slides FRCAB7 [14.701 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB7
About •	paper received ※ 23 June 2019 paper accepted ※ 04 July 2019 issue date ※ 14 August 2019
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Paper

Title

Page

FRTU2

Cavity Processing and Cleanroom Techniques

L. Popielarski
FRIB, East Lansing, Michigan, USA

The "Cavity Processing and Cleanroom Assembly Review of Literature" tutorial will introduce basics for SRF cavity processing and cleanroom techniques based on published processes. The practical applications presented will focus on low beta quarter-wave and half-wave cavities, however there are many publications on elliptical cavity processing and cleanroom assembly available online and in past tutorials. Topics discussed include: SRF coldmass and cavity workflow, SRF cavity receiving and inspection, degreasing, ultra pure water and high pressure rinse, mechanical surface preparation, removal by chemical etching, preparation by electro polishing, safety considerations, heat treatments, cleanroom protocols, and cleanroom assembly techniques.

Slides FRTU2 [40.595 MB]

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TUP018

New SRF Structures Processed at the ANL Cavity Processing Facility

434

T. Reid, Z.A. Conway, B.M. Guilfoyle, M. Kedzie, M.P. Kelly, M.K. Ng
ANL, Lemont, Illinois, USA

Argonne National Laboratory (ANL) has extended high quality cavity processing techniques based on those developed for the International Linear Collider to several more complex superconducting RF cavities. Recently, these include a bunch lengthening harmonic cavity, a crabbing rf-dipole cavity, a compact half-wave cavity, and both medium and high frequency elliptical cavities. These systems are an improved version of the one originally developed for 1.3 GHz 9-cell cavities and include a second rotating electrical contact that can support multiple cathodes, necessary for optimum polishing in difficult cavity geometries. All include the possibility for external water cooling.

Poster TUP018 [4.322 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP018

About •

paper received ※ 28 June 2019 paper accepted ※ 12 July 2019 issue date ※ 14 August 2019

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TUP019

Status of High Temperature Vacuum Heat Treatment Program at IPN Orsay

438

M. Fouaidy, F. Chatelet, V. Delpech, F. Galet, D. Le Dréan, R. Martret, G. Olry, T. Pépin-Donat
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
M. Baudrier, P. Carbonnier, E. Fayette, X. Hanus, Th. Proslier, D. Roudier, P. Sahuquet, C. Servouin
CEA-DRF-IRFU, France
E. Cenni, L. Maurice
CEA-IRFU, Gif-sur-Yvette, France
D. Longuevergne
FLUO, Orsay, France

In the framework of ESS, a vacuum furnace dedicated to High Temperature Heat Treatment under Vacuum (VH2T2) of SRF bulk Nb cavities was developed and commissioned in May 2016. This furnace is currently used for interstitial hydrogen removal (10h00 @ 650 °C) of two type of cavities: 1) the whole series of 26 ESS 352 MHz spoke resonators equipped with their Ti LHe tank well, 2) some prototypes of ESS high beta and medium beta cavities. Up to know IPN Orsay VH2T2 (10h00 @ 650 °C) was successfully applied to more than 16 cavities. In this paper we will first report about these VH2T2 tests. Finally, we have just started testing nitrogen infusion and nitrogen doping processes on samples and 1.3 GHz cavities: the preliminary results will be discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP019

About •

paper received ※ 03 July 2019 paper accepted ※ 04 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

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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TUP021

Effect of Cathode Rotation and Acid Flow in Vertical Electropolishing of 1.3 GHz Niobium Nine-Cell Cavity

448

V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi
MGH, Hyogo-ken, Japan
H. Hayano, S. Kato, H. Monjushiro, T. Saeki
KEK, Ibaraki, Japan

We have been carrying out R&D on vertical electropolishing (VEP) technique to establish it as an alternate of the horizontal EP (HEP) technique used for the surface treatment of niobium (Nb) superconducting RF (SRF) cavities. We have earlier reported on a VEP parameter study for 1.3 GHz single and nine-cell Nb cavities. The optimized VEP parameters and a unique rotating cathode yielded uniform removal and a smooth surface in the single cell cavity. The unique cathode and a dual flow mechanism for acid circulation were applied to improve the removal uniformity in the nine-cell cavity. The vertically electropolished single and nine cell cavities achieved the same RF performance as achieved after the HEP processes. We are making efforts to further improve the removal uniformity in the nine-cell cavity. Here, we report on a VEP of the 1.3 GHz Nb nine-cell cavity at a higher cathode rotation speed of 50 rpm. The VEP results reveal that the speed could be considered for improving the uniformity in removal while maintaining the surface smoothness. Required improvements in the VEP facility and acid flow condition for achieving uniform EP and a smooth surface are also described.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP021

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

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TUP022

Fermilab EP Facility Improvement

453

F. Furuta, D.J. Bice, A.C. Crawford, T.J. Ring
Fermilab, Batavia, Illinois, USA

Electro-chemical Polishing (EP) is one of the key technologies of surface treatments for niobium superconducting cavities. We have established a single-cell scale horizontal electro-polishing facility at Fermilab and routinely processed the niobium cavities with the frequencies of 1.3 GHz to 3.9 GHz. The precise control of EP parameters, especially the temperatures of cavity outside wall, allows the uniform removal over the cell with the variation of ±15%. Here we report the details of our EP process and recent improvements on our EP facility at Fermilab.

Poster TUP022 [1.711 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP022

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paper received ※ 10 July 2019 paper accepted ※ 17 August 2019 issue date ※ 14 August 2019

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TUP023

Experience of LCLS-II Cavities Radial Tuning at DESY

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

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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TUP026

Vibro-tumbling as an Alternative to Standard Mechanical Polishing Techniques for SRF Cavities

464

E. Chyhyrynets, O. Azzolini, V.A. Garcia, G. Keppel, C. Pira, F. Stivanello, L. Zanotto
INFN/LNL, Legnaro (PD), Italy

Funding: Work supported by the INFN V group experiment TEFEN, Agreement N. KE2722/BE/FCC and from the European Union’s H₂020 Framework Programme under grant agreement no. 764879 (EASITrain)
Centrifugal Barrel Polishing (CBP) is a common tool in the Nb bulk SC cavities production, prior to elec-tropolishing (EP). Indeed, the mechanical polishing is fun-damental also in the superconducting thin film resonant cavities in which one of the main issues that limits the per-formances is the surface preparation. A promising vi-bro-tumbling technique is being studied and implemented with a possibility to replace or improve mechanical treat-ment steps (grinding, barrel polishing). The simplic-ity of the technology allows it to adapt to any cavity geom-etry, both for Nb and Cu materials. The presented work contains last results on 6 GHz cavities obtained at LNL-INFN, both Nb bulk and Cu cavities.

Poster TUP026 [5.584 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP026

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

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TUP027

Vertical Electropolishing of Niobium Nine-Cell Cavity with a Cavity Flipping System for Uniform Removal

467

K.N. Nii, V. Chouhan, Y.I. Ida, T.Y. Yamaguchi
MGH, Hyogo-ken, Japan
H. Hayano, S. Kato, H. Monjushiro, T. Saeki
KEK, Ibaraki, Japan

Marui Galvanizing Co., Ltd. has been developing vertical electropolishing (VEP) technology for single and nine-cell niobium superconducting radio frequency cavities using a unique cathode namely Ninja cathode in collaboration with KEK. The VEP process usually results in non-uniform removal with a large asymmetry along the cavity length. In order to suppress the asymmetry in removal, we are making different approaches. Flipping of the cavity during the VEP process is one of the approaches applied so far. A unique VEP setup, which allows the flipping of a multi-cell cavity, has been developed as reported earlier. Here, we report the improvement in the setup with automation for cavity flipping. VEP experiments were conducted with the improved system. VEP parameters were studied and the VEP results including the removal trend are discussed in detail.

Poster TUP027 [1.347 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP027

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paper received ※ 24 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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TUP028

Development of Vertical Electropolishing Facility for Nb 9-Cell Cavity (3)

470

Y.I. Ida, V. Chouhan, K.N. Nii
MGH, Hyogo-ken, Japan
T. Akabori, G. Mitoya, K. Miyano
HKK, Morioka, Japan
Y. Anetai, F. Takahashi
WING. Co.Ltd, Iwate-ken, Japan
H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
KEK, Ibaraki, Japan

The 1st report was delivered in May, 2018 at the IPAC 18 in Vancouver, Canada. The 2nd report was delivered in September, 2018 at the LINAC 18 in Beijing, China. We will make our 3rd report in July, 2019 at the SRF-19 in Dresden, Germany. There will be two main points this time. The first is that by using our improved Ninja Electrode Premium, we can out-perform our number one and number two competitors in terms of uniform electropolishing of the interior of the 9-cell cavity. The second point is that we can remove hydrogen gas, reacted during electropolishing, from the cavity chambers in a manner that has not been successfully achieved by 1st report, May 2018 and 2nd report, September 2018. We will report our 9-cell vertical polishing revolver-type unit that solves the above two problems.

Poster TUP028 [0.444 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP028

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paper received ※ 24 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019

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TUP029

An Experimental Analysis of Effective EP Parameters for Low-Frequency Cylindrical Nb Cavities

472

C.E. Reece
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Work supported by the U.S. DoE, Office of Science, Office of Basic Energy Sciences.
While the basic process of electropolishing niobium with 1:9 HF:H₂SO₄ electrolyte has been well characterized, the specific process parameters used to electropolish different superconducting radio frequency (SRF) cavity geometries requires thoughtful attention. One seeks to realize confidently local diffusion-limited polishing at each point on the surface while maximizing uniformity of removal rate. Since the reaction rate is temperature dependent, this implies that one must manage the cavity surface temperature during polishing. Too-high applied voltage aggravates temperature and thus removal non-uniformity, but too-low applied voltage risks placing the large-diameter locations "off the current plateau," yielding etching rather than polishing. The majority of recent experience has been with elliptical L-band SRF cavities and some half-wave cavities at ANL. Lower frequency cavities with increased surface area and larger cathode-to-equator distance require fresh analysis and optimization. In preparation for SNS PPU project, JLab performed some EP process development runs with SNS high beta cavities to help identify viable parameter regimes for communication to cavity vendors. Results from this study are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP029

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

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TUP031

Heat Treatment for Jacketed Half-wave Resonator Cavity

482

Y. Jung, B.H. Choi, D.H. Gil, M.O. Hyun, H. Kim, J.W. Kim, M.S. Kim, D.Y. Lee, J. Lee, S. Lee
IBS, Daejeon, Republic of Korea

Vertical tests of a prototype half-wave resonator cavity are being tested. The performance of the cavities, such as quality factor and accelerating electrical field, are measured and compared to the target design value. In previous study, we reported the effect of the heat treatment on a prototype bare HWR cavity. We baked a jacketed HWR cavity to improve a performance for 10 h at 650°C. In this study, we will report the effect of the heat treatment on the jacketed HWR cavity.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP031

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

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TUP050

A Multi-layered SRF Cavity for Conduction Cooling Applications

538

G. Ciovati, G. Cheng, E. Daly, G.V. Eremeev, J. Henry, R.A. Rimmer
JLab, Newport News, Virginia, USA
I.P. Parajuli
ODU, Norfolk, Virginia, USA
U. Pudasaini
The College of William and Mary, Williamsburg, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Some of the work was supported by the 2008 PECASE Award of G. Ciovati. I. Parajuli is supported by NSF Grant PHYS-100614-010
Industrial application of SRF technology would favor the use of cryocoolers to conductively cool SRF cavities for particle accelerators, operating at or above 4.3 K. In order to achieve a lower surface resistance than Nb at 4.3 K, a superconductor with higher critical temperature should be used, whereas a metal with higher thermal conductivity than Nb should be used to conduct the heat to the cryocoolers. A standard 1.5 GHz bulk Nb single-cell cavity has been coated with a ~2 µm thick layer of Nb₃Sn on the inner surface and with a 5 mm thick Cu layer on the outer surface for conduction cooled applications. The cavity performance has been measured at 4.3 K and 2.0 K in liquid He. The cavity reached a peak surface magnetic field of ~40 mT with a quality factor of 6×10⁹ and 3.5×10⁹ at 4.3 K, before and after applying the thick Cu layer, respectively.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP050

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

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TUP093

Summary of FRIB Cavity Processing in the SRF Coldmass Processing Facility and Lessons Learned

680

E.S. Metzgar, B.W. Barker, K. Elliott, W. Hartung, L. Popielarski, G.V. Simpson, D.R. Victory, J.D. Whaley
FRIB, East Lansing, Michigan, USA

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 and the National Science Foundation under Cooperative Agreement PHY-1102511.
Baseline coldmass production for the linear particle accelerator at the Facility for Rare Isotope Beams (FRIB) is nearing completion. This paper will review the processing of cavities through the FRIB superconducting radio frequency (SRF) coldmass production facility focusing on chemical processing and high-pressure rinsing. Key processing data will be compiled and correlations between processing variables and cavity RF testing results will be examined.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP093

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paper received ※ 22 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019

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FRCAB1

HF-Free Bi-Polar Electropolishing for Application on Multi-Cell Elliptical Cavities

H. Tian, M. Lester, J. Musson, H.L. Phillips, C.E. Reece
JLab, Newport News, Virginia, USA
T.D. Hall, M.E. Inman, R. Radhakrishnan, E.J. Taylor
Faraday Technology, Inc., Clayton, Ohio, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05₀6OR23177
Pulse reversed electropolishing of niobium SRF cavities, using a dilute aqueous H₂SO4 electrolyte without HF yields equivalent RF performance with traditional EP. A pulse reversed electropolishing (BPEP) system has been implemented at Jefferson lab, and applied to single cells, a 7-cell CEBAF C100 cavity, and to 9-cell TESLA-style cavities with upgraded pulse system recently. A systematically mechanistic characterization and understanding of the BPEP process through bench top coupons study and cavities directs a system and operational parameter refinement for BPEP. We present process parameters, removal characterization, and rf performance of the processed cavities. This is the fruit of collaborative work between Jefferson Lab and Faraday Technology, Inc., directed toward the routine commercialization/industrialization of niobium cavity processing.

Slides FRCAB1 [4.394 MB]

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FRCAB3

The Design of an Automated High-Pressure Rinsing System for SRF Cavity and the Outlook for Future Automated Cleanroom on Strings Assembly

1216

H. Guo, Q.W. Chu, Y. He, C.L. Li, Y.K. Song, T. Tan, Z.M. You
IMP/CAS, Lanzhou, People’s Republic of China

High-pressure rinsing (HPR) and cavity assembly are two critical steps in cavity post-processing. Traditionally, high-pressure rinsing processing is based on ultra pure water system, pump, rinsing wand and simple-functional control system; cavity assembly processing is based on simple fixtures, wrenches, bolts and nuts. Beside the equipments, at least two operators are required in either of these two processing. Operators and their actions could bring mistakes and cause extra airborne particle contamination in cleanroom. To avoid the risk from labors, a robot has been introduced in IMP cleanroom for HPR assisting and assembly assisting. Labor cost and cavity RF test results are compared between the circumstances with and without robot assisting. In this work, an automated HPR system that has been designed and will be installed in IMP cleanroom will be presented. In addition, a future automated cleanroom on strings assembly will be discussed as well.

Slides FRCAB3 [6.203 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB3

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paper received ※ 03 July 2019 paper accepted ※ 12 July 2019 issue date ※ 14 August 2019

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FRCAB7

Plasma Processing to Reduce Field Emission in LCLS-II 1.3 GHz SRF Cavities

1231

SUSP022

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TUP067

use link to see paper's listing under its alternate paper code

B. Giaccone, J. Zasadzinski
IIT, Chicago, Illinois, USA
P. Berrutti, B. Giaccone, A. Grassellino, M. Martinello
Fermilab, Batavia, Illinois, USA
M. Doleans
ORNL, Oak Ridge, Tennessee, USA
D. Gonnella, G. Lanza, M.C. Ross
SLAC, Menlo Park, California, USA

Plasma cleaning for LCLS-II 9-cell 1.3 GHz cavities is under study at Fermilab. Starting from ORNL method, we have developed a new technique for plasma ignition using HOMs. Plasma processing is being applied to contaminated and field emitting cavities, here are discussed the first results in terms of Q and radiation vs E measured before and after treatment. Further studies are ongoing to optimize plasma parameters and to acquire statistics on plasma cleaning effectiveness.

Slides FRCAB7 [14.701 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB7

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paper received ※ 23 June 2019 paper accepted ※ 04 July 2019 issue date ※ 14 August 2019

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