SRF2023 - List of Keywords (controls)

Paper	Title	Other Keywords	Page
MOIAA05	Commissioning of the Second JLAB C75 Cryomodule & Performance Evaluation of Installed C75 Cavities	cavity, cryomodule, SRF, plasma	14
	M.D. McCaughan, G. Ciovati, G.K. Davis, M.A. Drury, T. Powers, A.V. Reilly JLab, Newport News, Virginia, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177. JLAB has long been a hub of SRF technology with the CEBAF accelerator as one of its first large scale adopters. As SRF technology has advanced, the C50 and C100 programs have allowed for the extension of CEBAF’s total energy to 6 GeV and nearly 12 GeV respectively. Along with the increase in energy reach, rates of accelerating gradient degradation have been extracted for these cryomodule designs. A plan to mitigate these losses & maintain robust gradient headroom to deliver the 12 GeV program ¿ the CEBAF Performance Plan¿ established a multi-year effort of cryomodule refurbishments and replacements. Part of this plan included a cost optimization of the C50 program with more modern processing techniques and the replacement of existing cavities with larger grain boundary cavities produced from ingot Niobium (dubbed C75 for 75 MeV gain). Reports have been made on the prototype pair of C75 cavities installed in a C50 cryomodule and the first full C75 cryomodule installed in 2017 and 2021. This paper reports on the results from the qualification of the cavities for the second C75 module in both a vertical cryostat and the commissioning results of the cryomodule in the CEBAF tunnel.
	Slides MOIAA05 [1.810 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOIAA05
About •	Received ※ 19 June 2023 — Revised ※ 27 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 02 July 2023
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MOIXA02	PIP-II Project Overview and Status	linac, cryomodule, cavity, SRF	19
	R.P. Stanek, C. Boffo, S.K. Chandrasekaran, S.J. Dixon, E.R. Harms, L. Kokoska, I. Kourbanis, J.R. Leibfritz, O. Napoly, D. Passarelli, E. Pozdeyev, A.M. Rowe Fermilab, Batavia, Illinois, USA
	Funding: Prepared by PIP-II Project using resources of the Fermi National Accelerator Laboratory, a U.S. DOE facility, managed by Fermi Research Alliance, LLC, acting under Contract No. DE-AC02-07CH11359. The Proton Improvement Plan II (PIP-II) project is an essential upgrade to Fermilab’s particle accelerator complex to enable the world’s most intense neutrino beam for LBNF/DUNE and a broad particle physics program for many decades to come. PIP-II will deliver 1.2 MW of proton beam power from the Main Injector, upgradeable to multi-MW capability. The central element of PIP-II is an 800 MeV superconducting radio frequency (SRF) linac, which comprises a room temperature front end followed by an SRF section. The SRF section consists of five different flavors of cavities/cryomodules, including Half Wave Resonators (HWR), Single Spoke and elliptical resonators operating at, or above, state-of-the-art parameters. The first two PIP-II cryomodules, Half Wave Resonator (HWR) and Single Spoke Resonator 1 (SSR1) were installed in the PIP-II Injector Test facility (PIP2IT) and have accelerated beam to above 17 MeV. PIP-II is the first U.S. accelerator project that will be constructed with significant contributions from international partners, including India, Italy, France, United Kingdom and Poland. The project was baselined in April 2022, and the construction phase is underway.
	Slides MOIXA02 [3.353 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOIXA02
About •	Received ※ 07 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 16 July 2023
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MOPMB006	SIMS Characterization of Nitrogen Doping of LCLS-II-HE Production Cavities	cavity, SRF, niobium, vacuum	67
	C.E. Reece, M.J. Kelley, E.M. Lechner JLab, Newport News, Virginia, USA J.W. Angle Virginia Polytechnic Institute and State University, Blacksburg, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177 and Office of High Energy Physics grant DE-SC-0014475. The thermal diffusion of nitrogen into the surface of niobium has been shown to yield superior low-loss SRF performance. An effective solution was identified and promptly employed in the production of cryomodules for LCLS-II. With added experience and R&D, a modified process was chosen for use in the upgrade for LCLS-II-HE. Largely motivated by this circumstance, supporting research has significantly refined the technique for making calibrated secondary ion mass spectrometry (SIMS) measurements of the N concentration depth profiles produced by production processes. Standardized reference samples were included with four HE production cavities in their N-doping furnace runs. We report the calibrated dynamic SIMS depth profiles of N, C, and O for these samples, together with the cryogenic acceptance test performance of the associated cavities. Interpretation and comparison with similar samples acquired in other furnaces highlights the importance of intentional process quality control of furnace conditions.
	Poster MOPMB006 [1.380 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB006
About •	Received ※ 16 June 2023 — Revised ※ 26 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 18 July 2023
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MOPMB010	Analysis of Semiconductor Components as Temperature Sensors for Cryogenic Investigation of SRF Materials	cavity, cryogenics, experiment, SRF	80
	A. Cierpka, S. Keckert, J. Knobloch, F. Kramer, O. Kugeler HZB, Berlin, Germany
	Temperature mapping systems have been used for many years to detect local heating in an SRF cavity surface or materials sample. They require a large number of temperature sensors. Most often, low-cost Allen-Bradley resistors are used for this purpose. Since they have poor sensitivity and reproducibility above 4 K, sensor alternatives that combine the precision of Cernox sensors with the low-cost of Allen-Bradley resistors would be highly desirable. In this work various semiconductor components that exhibit a temperature dependent electrical response, such as diodes and LEDs were analyzed with respect to sensitivity, reproducibility and response speed in a temperature range between 6.5 K and 22 K. In this range, many diodes and LEDs were found to be more sensitive than Cernox sensors. However, in some components the response time was slow - possibly due to poor thermal contact.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB010
About •	Received ※ 08 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 17 July 2023
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MOPMB015	Development of a Plasma-Enhanced Chemical Vapor Deposition System for High-Performance SRF Cavities	cavity, SRF, plasma, vacuum	100
	G. Gaitan, A.T. Holic, W.I. Howes, G. Kulina, P. Quigley, J. Sears, Z. Sun Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA M. Liepe Cornell University, Ithaca, New York, USA B.W. Wendland University of Minnesota, Minnesota, USA
	Funding: This work was supported by the U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams Next-generation, thin-film surfaces employing Nb₃Sn, NbN, NbTiN, or other compound superconductors are essential for reaching enhanced RF performance levels in SRF cavities. However, optimized, advanced deposition processes are required to enable high-quality films of such materials on large and complex-shaped cavities. For this purpose, Cornell University is developing a plasma-enhanced chemical vapor deposition (CVD) system that facilitates coating on complicated geometries with a high deposition rate. This system is based on a high-temperature tube furnace with a high-vacuum, gas, and precursor delivery system, and uses plasma to significantly reduce the required processing temperature and promote precursor decomposition. Here we present an update on the development of this system, including final system design, safety considerations, assembly, and commissioning.
	Poster MOPMB015 [1.951 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB015
About •	Received ※ 16 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 01 July 2023 — Issue date ※ 16 July 2023
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MOPMB022	Recent mid-T Single-Cell Treatments R&D at DESY	cavity, niobium, SRF, vacuum	129
	C. Bate, D. Reschke, J. Schaffran, L. Steder, L. Trelle, H. Weise DESY, Hamburg, Germany
	The challenge of improving the performance of SRF cavities is being faced worldwide. One approach is to modify the superconducting surface properties through certain baking procedures. Recently a niobium retort furnace placed directly under an ISO4 clean room has been refurbished at DESY. Thanks to an inter-vacuum chamber and cryopumps, with high purity values in the mass spectrum it is working in the UHV range of 2·10^-8 mbar. The medium temperature (mid-T) heat treatments around 300°C are promising and successfully deliver reproducible very high Q₀ values of 2-5·10¹⁰ at medium field strengths of 16 MV/m. Since the first DESY and ZRI mid-T campaign yielded promising results, further results of 1.3 GHz single-cell cavities are presented here after several modified treatments of the mid-T recipe. In addition, samples were added to each treatment, the RRR value change was examined, and surface analyses were subsequently performed. The main focus of the sample study is the precise role of the changes in the concentration of impurities on the surface. In particular, the change in oxygen content due to diffusion processes is suspected to be the cause of enhancing the performance.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB022
About •	Received ※ 18 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 01 July 2023
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MOPMB023	Magnetic Flux Expulsion in TRIUMF’s Multi-Mode Coaxial Cavities	cavity, simulation, SRF, experiment	135
	R.R. Gregory, T. Junginger, M.W. McMullin UVIC, Victoria, Canada T. Junginger, P. Kolb, R.E. Laxdal, M.W. McMullin, Z.Y. Yao TRIUMF, Vancouver, Canada
	The external magnetic flux sensitivity of SRF cavities is an important characteristic of SRF accelerator design. Previous studies have shown that n-doped elliptical cavities are very sensitive to external fields, resulting in stringent requirements for residual field and cavity cool-down speed. Few such studies have been done on HWRs and QWRs. The impact of applied field direction and cool-down speed of flux expulsion for these cavities is poorly understood. This study explores the effect of these cool-down characteristics on TRIUMF¿s QWR using COMSOL ® simulations and experimental results. This study seeks to maximize the flux expulsion that occurs when a cavity is cooled down through its superconducting temperature. Flux expulsion is affected by the cool-down speed, temperature gradient, and orientation of the cavity relative to an applied magnetic field. It was found that for a vertically applied magnetic field the cool-down speed and temperature gradient did not have a significant effect on flux expulsion. Contrarily, a horizontal magnetic field can be nearly completely expelled by a fast, high temperature gradient cool-down.
	Poster MOPMB023 [2.191 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB023
About •	Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 30 July 2023
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MOPMB055	CEA Contribution to the PIP-II Linear Accelerator	cryomodule, cavity, SRF, linac	234
	N. Bazin, S. Berry, J. Drant, M. Fontaine, P. Garin, H. Jenhani, A. Raut, P. Sahuquet, C. Simon CEA-DRF-IRFU, France J. Belorgey, Q. Bertrand, P. Brédy, E. Cenni, C. Cloué, R. Cubizolles, S. Ladegaillerie, A. Le Baut, A. Moreau, O. Piquet, J. Plouin CEA-IRFU, Gif-sur-Yvette, France
	The Proton Improvement Plan II (PIP-II) that will be installed at Fermilab is the first U.S. accelerator project that will have significant contributions from international partners. CEA joined the international collaboration in 2018 and will deliver 10 low-beta cryomodules as In-Kind Contributions to the PIP-II project, with cavities supplied by LASA-INFN (Italy) and VECC-DAE (India), and power couplers and tuning systems supplied by Fermilab. An important milestone was reached in March 2023 with the Final Design Review of the cryomodule, launching the pre-production phase. This paper presents the status CEA activities on the design, manufacturing, assembly and tests of the cryomodules and the upgrade of the existing infrastructures to the PIP-II requirements.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB055
About •	Received ※ 25 June 2023 — Revised ※ 26 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 03 July 2023
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MOPMB074	Cryomodule Storage for LCLS-II HE	cryomodule, vacuum, cavity, cathode	282
	D.A. White, M. Checchin, D. Gonnella, J. Hogan, J.T. Maniscalco, R.D. Porter SLAC, Menlo Park, California, USA
	Funding: U.S. Department of Energy The Linac Coherent Light Source-II High Energy (LCLS-II HE) project will upgrade the superconducting LCLS-II with 23 additional cryomodules, increasing the beam energy from 4 GeV to 8 GeV. Due to the user schedule of the existing linac, Cryomodules arriving at SLAC cannot immediately be installed in the linac. They are scheduled to be stored for up to three years before the 12-month installation window. During this storage period, the risk of damage to Cryomodules prior to installation will be mitigated with procedures and best practices incorporating experience from LCLS-II.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB074
About •	Received ※ 25 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 03 July 2023 — Issue date ※ 10 July 2023
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MOPMB076	Surface Characterization Studies of Gold-Plated Niobium	niobium, cavity, site, radio-frequency	290
	S.G. Seddon-Stettler, M. Liepe, T.E. Oseroff, Z. Sun Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA N. Sitaraman Cornell University, Ithaca, New York, USA
	Funding: The National Science Foundation, Grant No. PHY-1549132 The native niobium oxide layer present on niobium has been shown to affect the performace of superconducting RF cavities. Extremely thin layers of gold on the surface of niobium have the potential to suppress surface oxidation and improve cavity performance. However, depositing uniform layers of gold at the desired thickness (sub-nm) is difficult, and different deposition methods may have different effects on the gold surface, on the niobium surface, and on the interface between the two. In particular, the question of whether gold deposition actually passivates the niobium oxide is extremely relevant for assessing the potential of gold deposition to improve RF performance. This work builds on previous research studying the RF performance of gold/niobium bilayers with different gold layer thicknesses. We here consider alternative methods to characterize the composition and chemical properties of gold/niobium bilayers to supplement the previous RF study.
	Poster MOPMB076 [1.536 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB076
About •	Received ※ 25 June 2023 — Revised ※ 27 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 03 July 2023
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MOPMB093	Optimizing Growth of Niobium-3 Tin Through Pre-nucleation Chemical Treatments	site, niobium, cavity, SRF	337
	S.G. Arnold, G. Gaitan, M. Liepe, L. Shpani, Z. Sun Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA T. Arias, N. Sitaraman Cornell University, Ithaca, New York, USA
	Funding: This work was supported by the U.S. National Science Foundation under award PHY-1549132, the Center for Bright Beams. Nb₃Sn is a promising alternative material for SRF cavities that is close to reaching practical applications. To date, one of the most effective growth methods for this material is vapor diffusion, yet further improvement is needed for Nb₃Sn to reach its full potential. The major issues faced by vapor diffusion are tin depleted regions and surface roughness, both of which lead to impaired performance. Literature has shown that the niobium surface oxide plays an important role in the binding of tin to niobium. In this study, we performed various chemical treatments on niobium samples pre-nucleation to enhance tin nucleation. We quantify the effect that these various treatments had through scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). These methods reveal information on tin nucleation density and uniformity, and a thin tin film present on most samples, even in the absence of nucleation sites. We present our findings from these surface characterization methods and introduce a framework for quantitatively comparing the samples. We plan to apply the most effective treatment to a cavity and conduct an RF test soon.
	Poster MOPMB093 [1.118 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB093
About •	Received ※ 21 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 26 July 2023
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TUCXA01	Study of the Dynamics of Flux Trapping in Different SRF Materials	experiment, cavity, ECR, niobium	380
	F. Kramer, S. Keckert, J. Knobloch, O. Kugeler HZB, Berlin, Germany J. Knobloch University of Siegen, Siegen, Germany T. Kubo KEK, Ibaraki, Japan
	A dedicated experimental setup to measure magnetic flux dynamics and trapped flux in samples is used to precisely map out how trapped flux is influenced by different parameters. The setup allows for rapid thermal cycling of the sample so that effects of cooldown parameters can be investigated in detail. We show how temperature gradient, cooldown rate, and the magnitude of external field influence trapped flux in large grain, fine grain and coated niobium samples. The detailed measurements show unexpected results, namely that too fast cooldowns increase trapped flux, large grain material traps flux only when the external field is larger than a temperature gradient dependent threshold field, and the measured dependence of trapped flux on temperature gradient does not agree with an existing model. Therefore, a new model is presented which agrees better with the measured results.
	Slides TUCXA01 [3.180 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUCXA01
About •	Received ※ 17 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 26 June 2023
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TUPTB002	Modelling Trapped Flux in Niobium	ECR, experiment, cavity, niobium	393
	F. Kramer, S. Keckert, J. Knobloch, O. Kugeler HZB, Berlin, Germany J. Knobloch University of Siegen, Siegen, Germany T. Kubo KEK, Ibaraki, Japan
	Detailed measurements of magnetic flux dynamics and trapped magnetic flux in niobium samples were conducted with a new experimental setup that permits precise control of the cooldown parameters. With this setup the dependency of trapped flux on the temperature gradient, external magnetic field, and cooldown rate can be mapped out in more detail compared to cavity measurements. We have obtained unexpected results, and an existing model describing trapped flux in dependence of temperature gradient does not agree with the measured data. Therefore, a new model is developed which describes the magnitude of trapped flux in dependence of the temperature gradient across the sample during cooldown. The model describes the amount of trapped flux lines with help of a density distribution function of the pinning forces of pinning centers and the thermal force which can de-pin flux lines from pinning centers. The model shows good agreement with the measured data and correctly predicts trapped flux at different external flux densities.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB002
About •	Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 13 July 2023
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TUPTB006	Materials Design for Superconducting RF Cavities: Electroplating Sn, Zr, and Au onto Nb and and Chemical Vapor Deposition	cavity, SRF, plasma, niobium	401
	Z. Sun, M. Liepe, T.E. Oseroff Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA Z. Baraissov, D.A. Muller, M.O. Thompson Cornell University, Ithaca, New York, USA
	Funding: This work was supported by the U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams. Materials scientists seek to contribute to the development of next-generation superconducting radio-frequency (SRF) accelerating cavities. Here, we summarize our achievements and learnings in designing advanced SRF materials and surfaces, including Nb₃Sn [1¿3], ZrNb(CO) [4, 5], and Au/Nb surface design [6,7]. Our efforts involve electrochemical synthesis, phase transformation, and surface chemistry, which are closely coupled with superconducting properties, SRF performance, and engineering considerations. We develop electrochemical processes for Sn, Zr, and Au on the Nb surface, an essential step in our investigation for producing high-quality Nb₃Sn, ZrNb(CO), and Au/Nb structures. Additionally, we design a custom chemical vapor deposition system to offer additional growth options. Notably, we find the second-phase NbC formation in ZrNb(CO) and in ultra-high-vacuum baked or nitrogen-processed Nb. We also identify low-dielectric-loss ZrO2 on Nb and NbZr(CO) surfaces. These advancements provide materials science approaches dealing with fundamental and technical challenges to build high-performance, multi-scale, robust SRF cavities for particle accelerators and quantum applications.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB006
About •	Received ※ 30 June 2023 — Revised ※ 11 August 2023 — Accepted ※ 20 August 2023 — Issue date ※ 21 August 2023
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TUPTB014	Development of Nb₃Sn Coating System and RF Measurement Results at KEK	cavity, SRF, radio-frequency, accelerating-gradient	414
	H. Ito, H. Sakai, K. Umemori, T. Yamada KEK, Ibaraki, Japan K. Takahashi Sokendai, Ibaraki, Japan
	We have constructed an Nb₃Sn cavity coating system based on the Sn vapor diffusion method. After the construction, improvement of our coating system and environment has been conducted through sample and cavity coating research. Our cavity achieves a Q-value above 1E10 at 4 K after improvement. We will report on the detail of improvement on our coating system and RF measurement results of single-cell Nb₃Sn cavity.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB014
About •	Received ※ 18 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 28 June 2023
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TUPTB016	Summary of the FRIB Electropolishing Facility Design and Commissioning, Cavity Processing, and Cavity Test Results	cavity, cathode, MMI, power-supply	419
	E.S. Metzgar, B.W. Barker, K. Elliott, J.D. Hulbert, C. Knowles, L. Nguyen, A.R. Nunham, L. Popielarski, A.T. Taylor, T. Xu FRIB, East Lansing, Michigan, USA
	Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics and used resources of the FRIB, which is a DOE Office of Science User Facility, under Award Number DE-SC0000661. Recently, a new Electropolishing (EP) facility was con-structed and commissioned at the Facility for Rare Isotope Beam (FRIB) with the purpose of supporting advanced surface processing techniques for SRF R&D activities. The FRIB production cavities opted for a Buffered Chemical Polish (BCP) method due to its cost effectiveness and was supported by successful outcomes in other facilities with low beta cavities in a similar frequency range. All 324 cavities used in FRIB Linac were processed in-house at MSU using BCP and exhibited satisfactory performance during testing. As part of the FRIB energy upgrade R&D, 5-cell 644 MHz elliptical resonators will be employed, desiring the use of EP and advanced techniques such as nitrogen doping and medium-T baking. The EP facility is designed to accommodate all types of cavities used in FRIB and possesses the capability for performing EP at low temperatures. Here we report the details of design and commissioning of the EP facility, highlights of encountered issues and subsequent improvements, and preliminary results from vertical tests conducted on the cavities.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB016
About •	Received ※ 15 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 14 July 2023
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TUPTB018	MgB₂ Coating Parameter Optimization Using a 1.3-GHz 1-Cell Cavity	cavity, SRF, experiment, vacuum	425
	T. Tajima, T.P. Grumstrup, J.D. Thompson LANL, Los Alamos, New Mexico, USA H. Ito, E. Kako, T. Okada, H. Sakai, K. Umemori KEK, Ibaraki, Japan
	Funding: DOE Office of Science, Office of High Energy Physics We have started parameter optimization for the coating of MgB₂ using a 1-cell 1.3-GHz elliptical cavity with holes for small samples. Our coating method is based on a 2-step technique, i.e., coat a B layer by flowing diborane gas in the first step and react it with Mg vapor in the 2nd step. Three 6 mm x 6 mm B-coated flat samples are attached at inlet, outlet beam pipes, and at a cell equator and reacted with Mg vapor with different parameters and conditions. We started to see the superconducting transitions on samples but Tc is still lower than our goal of >35 K. We will present our current status of B-Mg reaction tests and construction of B coating system.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB018
About •	Received ※ 06 July 2023 — Revised ※ 26 July 2023 — Accepted ※ 02 September 2023 — Issue date ※ 03 September 2023
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TUPTB029	Measurement of Particulates under Slow Pumping after High Pressure Rinsing of Superconducting Cavity by Using Modified Slow Pumping System	cavity, vacuum, cryomodule, SRF	458
	H. Sakai, E. Kako, R. Katayama, K. Umemori KEK, Ibaraki, Japan
	Funding: This research was partially supported by the research fund from Ministry of Education, Culture, Sports, Science and Technology (MEXT). Slow pumping system was used for particle free vacuum pumping in Superconducting rf accelerator. In KEK, recently slow pumping system was developed for the cryomodule assembly work for STF 9-cell cavities and worked well to reduce the particulates movements under pumping. However, this slow pumping system want to be used for preparation of vertical test. Before assembly work in clean room for vertical test, we normally apply high pressure rinsing. There were many waters in the cavity. Therefore, we kept one night to dry inside cavity in clean room. Unfortunately, there were some waters in the cavity even though we kept drying in clean room for one night. This water might make some icing under pumping and stop pumping in mass flow meter, which used for slow pumping to control the mass flow. Therefore, we modify the slow pumping system to be robust under slow pumping even when water exists in the cavity. In this paper, we present the modified slow pumping system in KEK and the results of the vacuum trend through slow pumping of 9-cell superconducting cavity. Under slow pumping, we measure the particulates after high pressure rinsing by using vacuum particle monitor.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB029
About •	Received ※ 16 June 2023 — Revised ※ 26 June 2023 — Accepted ※ 21 August 2023 — Issue date ※ 22 August 2023
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TUPTB030	Development of Automatic Cleaning and Assembly Systems in Clean Room at KEK	cavity, gun, operation, monitoring	463
	Y. Yamamoto, T. Dohmae, M.H. Hiraki, H. Sakai, K. Umemori, T. Yamada KEK, Ibaraki, Japan
	At KEK, new clean work systems including vertical auto cleaning system, replacement system between blank flange and bellows, and robot arm have been developed and installed since 2020 under the collaboration between Japan and France. The main purpose is unmanned and dust-free operation in clean room to avoid performance degradation with field emission in vertical test and cryomodule test. The vertical auto cleaning system and the replacement system between blank flange and bellows have been operated successfully in 2021-2022. Currently, clean work studies related to auto cleaning and assembly is under progress by combining the blank-bellows replacement system and a robot arm. In this report, the recent status of clean works at KEK will be presented.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB030
About •	Received ※ 17 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 30 June 2023
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TUPTB037	Refurbishment and Reactivation of a Niobium Retort Furnace at DESY	cavity, vacuum, niobium, target	485
	L. Trelle, C. Bate, H. Remde, D. Reschke, J. Schaffran, L. Steder, H. Weise DESY, Hamburg, Germany
	Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Technologies (MT) Program. For research in the field of heat treatments of supercon-ducting cavities, a niobium ultra-high vacuum furnace built in 1992 - originally used for the titanization of 1.3 GHz nine-cell cavities - and later shut down was recently refurbished and reactivated. A significant upgrade is the ability to run the furnace in partial pressure mode with nitrogen. The furnace is connected directly to the ISO4 area of the clean room for cavity handling. At room temperature vacuum values of around 3×10^-8 mbar are achieved. The revision included the replacement of the complete control system and a partial renewal of the pump technology. The internal mounting structures are optimized for single-cell operation including tandem operation (two single-cell cavities at once) and corresponding accessories such as witness-samples and caps for the cavities. The installation of additional thermocouples for a detailed monitoring of the temperature curves is also possible at the mounting structure. Due to the furnace design, its location and the strict routines in handling, very high purity levels are achieved in comparison to similar setups and hence provide a mighty tool for SRF cavity R&D at DESY.
	Poster TUPTB037 [0.404 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB037
About •	Received ※ 18 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 01 July 2023
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TUPTB047	The Evaluation of Mechanical Properties of LB650 Cavities	cavity, cryomodule, niobium, SRF	536
	G. Wu, S.D. Adams, D.J. Bice, S.K. Chandrasekaran, I.V. Gonin, C.J. Grimm, J.P. Holzbauer, T.N. Khabiboulline, C.S. Narug, J.P. Ozelis, H. Park, G.V. Romanov, R. Thiede, R. Treece, A.D. Wixson Fermilab, Batavia, Illinois, USA K.E. McGee FRIB, East Lansing, Michigan, USA
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC, under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. The 650 MHz cavities have a stronger requirement of niobium mechanical properties because of the geometric shape of the cavity due to reduced beta. The mechanical property of the niobium half-cell was measured following various heat treatments. The 5-cell cavities were tested in a controlled drop test fashion and the real-world road test. The result showed that the 900C heat treatment was compatible with cavity handling and transportation during production. The test provides the bases of the transportation specification and shipping container design guidelines.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB047
About •	Received ※ 19 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 14 July 2023
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TUPTB059	INFN LASA Experimental Activities for the PIP-II Project	cavity, SRF, experiment, diagnostics	549
	M. Bertucci, M. Bonezzi, A. Bosotti, D. Cardelli, E. Del Core, F. Fiorina, A.T. Grimaldi, L. Monaco, C. Pagani, R. Paparella, D. Sertore, G.M. Zaggia INFN/LASA, Segrate (MI), Italy
	INFN LASA is upgrading its vertical test facility to allow high-Q measurements of the PIP-II LB650 SRF cavities. Such facility is equipped with a wide set of diagnostics for quench, field emission and magnetic flux expulsion studies and will offer a better understanding of cavity performance. At the same time, R&D on LB650 cavity prototypes is ongoing, in order to optimize the overall processing as well as the cavity Jacketing in view of the forthcoming series production with industry. This paper reports on the overall status of these experimental activities.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB059
About •	Received ※ 18 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 18 July 2023
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WEPWB064	Performance Analysis from ESS Cryomodule Testing at CEA	cavity, cryomodule, electron, cryogenics	727
	O. Piquet, C. Arcambal, Q. Bertrand, P. Bosland, E. Cenni, G. Devanz, T. Hamelin CEA-IRFU, Gif-sur-Yvette, France P. Sahuquet CEA-DRF-IRFU, France
	CEA Saclay is in charge of the production of 30 elliptical cavities cryomodule as part of the in Kind contribution to the ESS superconducting. The two medium and high beta prototypes and the three first of each type of the series cryomodules have been tested at CEA in slightly different conditions than at ESS (both in terms of cryogenic operation as well as RF conditions). The goal of these tests was to validate the assembly procedure before the delivery of the series to ESS where the final acceptance tests are performed. This paper summarizes the main results obtained during the tests at CEA with a particular attention to the field emission behaviour.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB064
About •	Received ※ 20 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 07 July 2023
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WEPWB065	Impact of Medium Temperature Heat Treatments on the Magnetic Flux Expulsion Behavior of SRF Cavities	cavity, SRF, niobium, experiment	731
	J.C. Wolff, J. Eschke, A. Gössel, K. Kasprzak, D. Reschke, L. Steder, L. Trelle, M. Wiencek DESY, Hamburg, Germany W. Hillert University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Technologies (MT) Program. Medium temperature (mid-T) heat treatments at 300 °C are used to enhance the intrinsic quality factor of superconducting radio frequency (SRF) cavities. Unfortunately, such treatments potentially increase the sensitivity to trapped magnetic flux and consequently the surface resistance of the cavity. For this reason, it is crucial to maximize the expulsion of magnetic flux during the cool down. The flux expulsion behavior is next to the heat treatment mainly determined by the geometry, the niobium grain size and the grain orientation. However, it is also affected by parameters of the cavity performance tests like the cool down velocity, the spatial temperature gradient along the cavity surface and the magnetic flux density during the transition of the critical temperature. To improve the flux expulsion behavior and hence the efficiency of future accelerator facilities, the impact of these adjustable parameters as well as the mid-T heat treatment on 1.3 GHz TESLA-Type single-cell cavities is investigated by a new approach of a magnetometric mapping system. In this contribution first performance test results of cavities before- and after mid-T heat treatment are presented.
	Poster WEPWB065 [3.077 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB065
About •	Received ※ 21 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 13 July 2023
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WEPWB076	Low Particulates Nitrogen Purge and Backfill during Prototype HB650 Cryomodule String Assembly	cavity, vacuum, SRF, cryomodule	765
	T.J. Ring, M.B. Quinlan, G. Wu Fermilab, Batavia, Illinois, USA
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC, under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. A low particulate vacuum and purging system was developed to support PIP-II cryomodule string assembly. The overpressure can be controlled at a precision of 1 mbar above the atmospheric pressure regardless of the cavity or string assembly air volume. The system minimized the risk of uncontrolled nitrogen flow during the string assembly. Design features will be presented.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB076
About •	Received ※ 19 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 09 July 2023
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WEPWB110	Prevention of Dual-Mode Excitation in 9-Cell Cavities for LCLSII-HE	cavity, resonance, feedback, SRF	852
	P.D. Owen JLab, Newport News, Virginia, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177. Dual-Mode Excitation, also referred to as mode-mixing, is a superposition of two pi modes in an SRF cavity. In 9-cell TESLA cavities used for the LCLSII-HE project, the two modes that are commonly excited are the pi mode (1300.2 MHz), and the 7/9 pi mode (1297.8 MHz). During vertical cavity qualification testing, it is regularly observed that emitted power at the frequency of the 7/9 pi mode grows, despite the RF system only driving the pi mode. When this happens, the RF power measurement system is unable to differentiate between the superimposed modes which invalidates any data taken. A new RF control solution prevents the 7/9 pi mode from being excited. A second RF control system is connected to drive the 7/9 pi mode. The loop phase for driving this mode is determined, then shifted by 180 degrees, thus providing a negative feedback to the undesired mode. Because this off-resonance power can be very small, it does not interfere with the high-power measurements of the fundamental pi mode. At Jefferson Lab, we are now able to test a cavity for the LCLSII-HE project with no complications from mode-mixing, which allows for CW processing of high-gradient multipacting.
	Poster WEPWB110 [1.818 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB110
About •	Received ※ 19 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 13 July 2023
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WEPWB121	Niobium Chronicles: Surface Quality Investigation and Recovery During Material Procurement for the PIP-II High Beta 650 MHz Cavities	cavity, niobium, factory, synchrotron	880
	A.D. Shabalina STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
	The surface quality of high-purity niobium for superconducting radiofrequency cavities experienced a sudden and significant decline in 2021. The recovery process and root cause analysis were challenging due to a variety of factors such as COVID-19 travel restrictions, cultural differences, and bureaucratic processes. Effective open communication was crucial to resolving the issue, especially with direct vendor oversight being impossible.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB121
About •	Received ※ 28 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 20 August 2023 — Issue date ※ 20 August 2023
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WEPWB131	Demonstration of Magnetron as an Alternative RF Source for SRF Accelerators	injection, cavity, power-supply, klystron	902
	H. Wang, K. Jordan, R.A. Rimmer JLab, Newport News, Virginia, USA J.P. Anderson, C.P. Moeller, K.A. Thackston GA, San Diego, California, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177, and DOE OS/ARDAP Accelerator Stewardship award 2019-2023. Magnetron has been considered as alternate high-efficiency, low-cost RF sources for linacs and storage rings [1] for national labs and industrial applications. After the demonstration of magnetrons power to drive and combine for a radio frequency cavity at 2450 MHz in CW mode, we have used trim coils adding to a water-cooled magnetron and amplitude modulation feedback to further suppress the side-band noise to -46.7 dBc level. We also demonstrated the phase-locking to an industrial grade cooking magnetron transmitter at 915 MHz with a 75 kW CW power delivered to a water load by using a -26.6 dBc injection signal [2]. The sideband noise from the 3-Phase SCRs DC power supply can be reduced to -16.2 dBc level. Further noise reduction and their power combining scheme using magic-tee and cavity type combiners for higher power application (2x75kW) are to be presented. We intent to use one power station to drive the normal conducting and superconducting RF cavities for the inductrial linac. We also going to demonstarte a vertical SRF cavity test with a high input coupling Q using a 2.45GHz magnetron and comparing with a baseline test result using a solid state amplifier. [1]. doi:10.18429/JACoW-IPAC2015-WEPWI028. [2]. doi:10.18429/JACoW-NAPAC2022-WEZD3.
	Poster WEPWB131 [2.445 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB131
About •	Received ※ 16 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 30 June 2023 — Issue date ※ 19 August 2023
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WEPWB134	Study of Different Piezoelectric Material Stroke Displacement at Different Temperatures Using an SRF Cavity	cavity, SRF, experiment, resonance	911
	C. Contreras-Martinez, Y.M. Pischalnikov, J.C. Yun Fermilab, Batavia, Illinois, USA
	Piezoelectric actuators are used for resonance control in superconducting linacs. The level of frequency compensation depends on the piezoelectric stroke displacement. In this study, the stroke displacement will be measured with a 1.3 GHz SRF cavity by measuring the frequency shift with respect to the voltage applied. The entire system was submerged in liquid helium. This study characterizes the PZT piezoelectric actuator (P-844K093) and a lithium niobate (P-844B0005) piezoelectric actuator. All these actuators were developed at Physik Instrumente (PI). The piezo-electric displacement was measured at different temperatures.
	Poster WEPWB134 [0.776 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB134
About •	Received ※ 16 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 13 July 2023
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THIXA03	Cryocooler Application for Accelerator and Development Status of Powerful Cryocooler at SHI Ltd.	SRF, cavity, interface, operation	968
	T. Ikeda, S. Sasazaki SHI, Tokyo, Japan
	Advances in recent Nb₃Sn cavity development makes possible to operate the cavities with Qo ~ 1xE10 at 4.3 K and to design SRF accelerator in which the cavities are cooled directly with small mechanical cryocoolers instead of using liquid helium. Conduction-cooling with cryocoolers greatly simplify the overall design and also contribute for cost saving of an SRF accelerator, making the SRF technology feasible for industrial accelerators. However, in the case of using current cryocooler systems (like Gifford-McMahon cryocooler, Pulse-Tube cryocooler, etc.) for the conduction-cooling, since the cooling capacity per unit is small, multiple units will be used in combination depending on the required cooling capacity, it will cause problems in terms of power consumption (efficiency), footprint, and maintenance costs. Therefore, SHI have been developing a large-capacity and high-efficiency 4KGM-JT (Gifford-McMahon-Joule-Thomson) cryocooler system in the 10 W class at 4.2 K. This contribution will report the overview of this cryocooler system and its status of development.
	Slides THIXA03 [1.638 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-THIXA03
About •	Received ※ 20 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 04 July 2023
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Paper

Title

Other Keywords

Page

MOIAA05

Commissioning of the Second JLAB C75 Cryomodule & Performance Evaluation of Installed C75 Cavities

cavity, cryomodule, SRF, plasma

14

M.D. McCaughan, G. Ciovati, G.K. Davis, M.A. Drury, T. Powers, A.V. Reilly
JLab, Newport News, Virginia, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
JLAB has long been a hub of SRF technology with the CEBAF accelerator as one of its first large scale adopters. As SRF technology has advanced, the C50 and C100 programs have allowed for the extension of CEBAF’s total energy to 6 GeV and nearly 12 GeV respectively. Along with the increase in energy reach, rates of accelerating gradient degradation have been extracted for these cryomodule designs. A plan to mitigate these losses & maintain robust gradient headroom to deliver the 12 GeV program ¿ the CEBAF Performance Plan¿ established a multi-year effort of cryomodule refurbishments and replacements. Part of this plan included a cost optimization of the C50 program with more modern processing techniques and the replacement of existing cavities with larger grain boundary cavities produced from ingot Niobium (dubbed C75 for 75 MeV gain). Reports have been made on the prototype pair of C75 cavities installed in a C50 cryomodule and the first full C75 cryomodule installed in 2017 and 2021. This paper reports on the results from the qualification of the cavities for the second C75 module in both a vertical cryostat and the commissioning results of the cryomodule in the CEBAF tunnel.

Slides MOIAA05 [1.810 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOIAA05

About •

Received ※ 19 June 2023 — Revised ※ 27 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 02 July 2023

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MOIXA02

PIP-II Project Overview and Status

linac, cryomodule, cavity, SRF

19

R.P. Stanek, C. Boffo, S.K. Chandrasekaran, S.J. Dixon, E.R. Harms, L. Kokoska, I. Kourbanis, J.R. Leibfritz, O. Napoly, D. Passarelli, E. Pozdeyev, A.M. Rowe
Fermilab, Batavia, Illinois, USA

Funding: Prepared by PIP-II Project using resources of the Fermi National Accelerator Laboratory, a U.S. DOE facility, managed by Fermi Research Alliance, LLC, acting under Contract No. DE-AC02-07CH11359.
The Proton Improvement Plan II (PIP-II) project is an essential upgrade to Fermilab’s particle accelerator complex to enable the world’s most intense neutrino beam for LBNF/DUNE and a broad particle physics program for many decades to come. PIP-II will deliver 1.2 MW of proton beam power from the Main Injector, upgradeable to multi-MW capability. The central element of PIP-II is an 800 MeV superconducting radio frequency (SRF) linac, which comprises a room temperature front end followed by an SRF section. The SRF section consists of five different flavors of cavities/cryomodules, including Half Wave Resonators (HWR), Single Spoke and elliptical resonators operating at, or above, state-of-the-art parameters. The first two PIP-II cryomodules, Half Wave Resonator (HWR) and Single Spoke Resonator 1 (SSR1) were installed in the PIP-II Injector Test facility (PIP2IT) and have accelerated beam to above 17 MeV. PIP-II is the first U.S. accelerator project that will be constructed with significant contributions from international partners, including India, Italy, France, United Kingdom and Poland. The project was baselined in April 2022, and the construction phase is underway.

Slides MOIXA02 [3.353 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOIXA02

About •

Received ※ 07 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 16 July 2023

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MOPMB006

SIMS Characterization of Nitrogen Doping of LCLS-II-HE Production Cavities

cavity, SRF, niobium, vacuum

67

C.E. Reece, M.J. Kelley, E.M. Lechner
JLab, Newport News, Virginia, USA
J.W. Angle
Virginia Polytechnic Institute and State University, Blacksburg, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177 and Office of High Energy Physics grant DE-SC-0014475.
The thermal diffusion of nitrogen into the surface of niobium has been shown to yield superior low-loss SRF performance. An effective solution was identified and promptly employed in the production of cryomodules for LCLS-II. With added experience and R&D, a modified process was chosen for use in the upgrade for LCLS-II-HE. Largely motivated by this circumstance, supporting research has significantly refined the technique for making calibrated secondary ion mass spectrometry (SIMS) measurements of the N concentration depth profiles produced by production processes. Standardized reference samples were included with four HE production cavities in their N-doping furnace runs. We report the calibrated dynamic SIMS depth profiles of N, C, and O for these samples, together with the cryogenic acceptance test performance of the associated cavities. Interpretation and comparison with similar samples acquired in other furnaces highlights the importance of intentional process quality control of furnace conditions.

Poster MOPMB006 [1.380 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB006

About •

Received ※ 16 June 2023 — Revised ※ 26 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 18 July 2023

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MOPMB010

Analysis of Semiconductor Components as Temperature Sensors for Cryogenic Investigation of SRF Materials

cavity, cryogenics, experiment, SRF

80

A. Cierpka, S. Keckert, J. Knobloch, F. Kramer, O. Kugeler
HZB, Berlin, Germany

Temperature mapping systems have been used for many years to detect local heating in an SRF cavity surface or materials sample. They require a large number of temperature sensors. Most often, low-cost Allen-Bradley resistors are used for this purpose. Since they have poor sensitivity and reproducibility above 4 K, sensor alternatives that combine the precision of Cernox sensors with the low-cost of Allen-Bradley resistors would be highly desirable. In this work various semiconductor components that exhibit a temperature dependent electrical response, such as diodes and LEDs were analyzed with respect to sensitivity, reproducibility and response speed in a temperature range between 6.5 K and 22 K. In this range, many diodes and LEDs were found to be more sensitive than Cernox sensors. However, in some components the response time was slow - possibly due to poor thermal contact.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB010

About •

Received ※ 08 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 17 July 2023

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MOPMB015

Development of a Plasma-Enhanced Chemical Vapor Deposition System for High-Performance SRF Cavities

cavity, SRF, plasma, vacuum

100

G. Gaitan, A.T. Holic, W.I. Howes, G. Kulina, P. Quigley, J. Sears, Z. Sun
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
M. Liepe
Cornell University, Ithaca, New York, USA
B.W. Wendland
University of Minnesota, Minnesota, USA

Funding: This work was supported by the U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams
Next-generation, thin-film surfaces employing Nb₃Sn, NbN, NbTiN, or other compound superconductors are essential for reaching enhanced RF performance levels in SRF cavities. However, optimized, advanced deposition processes are required to enable high-quality films of such materials on large and complex-shaped cavities. For this purpose, Cornell University is developing a plasma-enhanced chemical vapor deposition (CVD) system that facilitates coating on complicated geometries with a high deposition rate. This system is based on a high-temperature tube furnace with a high-vacuum, gas, and precursor delivery system, and uses plasma to significantly reduce the required processing temperature and promote precursor decomposition. Here we present an update on the development of this system, including final system design, safety considerations, assembly, and commissioning.

Poster MOPMB015 [1.951 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB015

About •

Received ※ 16 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 01 July 2023 — Issue date ※ 16 July 2023

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MOPMB022

Recent mid-T Single-Cell Treatments R&D at DESY

cavity, niobium, SRF, vacuum

129

C. Bate, D. Reschke, J. Schaffran, L. Steder, L. Trelle, H. Weise
DESY, Hamburg, Germany

The challenge of improving the performance of SRF cavities is being faced worldwide. One approach is to modify the superconducting surface properties through certain baking procedures. Recently a niobium retort furnace placed directly under an ISO4 clean room has been refurbished at DESY. Thanks to an inter-vacuum chamber and cryopumps, with high purity values in the mass spectrum it is working in the UHV range of 2·10^-8 mbar. The medium temperature (mid-T) heat treatments around 300°C are promising and successfully deliver reproducible very high Q₀ values of 2-5·10¹⁰ at medium field strengths of 16 MV/m. Since the first DESY and ZRI mid-T campaign yielded promising results, further results of 1.3 GHz single-cell cavities are presented here after several modified treatments of the mid-T recipe. In addition, samples were added to each treatment, the RRR value change was examined, and surface analyses were subsequently performed. The main focus of the sample study is the precise role of the changes in the concentration of impurities on the surface. In particular, the change in oxygen content due to diffusion processes is suspected to be the cause of enhancing the performance.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB022

About •

Received ※ 18 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 01 July 2023

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MOPMB023

Magnetic Flux Expulsion in TRIUMF’s Multi-Mode Coaxial Cavities

cavity, simulation, SRF, experiment

135

R.R. Gregory, T. Junginger, M.W. McMullin
UVIC, Victoria, Canada
T. Junginger, P. Kolb, R.E. Laxdal, M.W. McMullin, Z.Y. Yao
TRIUMF, Vancouver, Canada

The external magnetic flux sensitivity of SRF cavities is an important characteristic of SRF accelerator design. Previous studies have shown that n-doped elliptical cavities are very sensitive to external fields, resulting in stringent requirements for residual field and cavity cool-down speed. Few such studies have been done on HWRs and QWRs. The impact of applied field direction and cool-down speed of flux expulsion for these cavities is poorly understood. This study explores the effect of these cool-down characteristics on TRIUMF¿s QWR using COMSOL ® simulations and experimental results. This study seeks to maximize the flux expulsion that occurs when a cavity is cooled down through its superconducting temperature. Flux expulsion is affected by the cool-down speed, temperature gradient, and orientation of the cavity relative to an applied magnetic field. It was found that for a vertically applied magnetic field the cool-down speed and temperature gradient did not have a significant effect on flux expulsion. Contrarily, a horizontal magnetic field can be nearly completely expelled by a fast, high temperature gradient cool-down.

Poster MOPMB023 [2.191 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB023

About •

Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 30 July 2023

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MOPMB055

CEA Contribution to the PIP-II Linear Accelerator

cryomodule, cavity, SRF, linac

234

N. Bazin, S. Berry, J. Drant, M. Fontaine, P. Garin, H. Jenhani, A. Raut, P. Sahuquet, C. Simon
CEA-DRF-IRFU, France
J. Belorgey, Q. Bertrand, P. Brédy, E. Cenni, C. Cloué, R. Cubizolles, S. Ladegaillerie, A. Le Baut, A. Moreau, O. Piquet, J. Plouin
CEA-IRFU, Gif-sur-Yvette, France

The Proton Improvement Plan II (PIP-II) that will be installed at Fermilab is the first U.S. accelerator project that will have significant contributions from international partners. CEA joined the international collaboration in 2018 and will deliver 10 low-beta cryomodules as In-Kind Contributions to the PIP-II project, with cavities supplied by LASA-INFN (Italy) and VECC-DAE (India), and power couplers and tuning systems supplied by Fermilab. An important milestone was reached in March 2023 with the Final Design Review of the cryomodule, launching the pre-production phase. This paper presents the status CEA activities on the design, manufacturing, assembly and tests of the cryomodules and the upgrade of the existing infrastructures to the PIP-II requirements.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB055

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Received ※ 25 June 2023 — Revised ※ 26 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 03 July 2023

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MOPMB074

Cryomodule Storage for LCLS-II HE

cryomodule, vacuum, cavity, cathode

282

D.A. White, M. Checchin, D. Gonnella, J. Hogan, J.T. Maniscalco, R.D. Porter
SLAC, Menlo Park, California, USA

Funding: U.S. Department of Energy
The Linac Coherent Light Source-II High Energy (LCLS-II HE) project will upgrade the superconducting LCLS-II with 23 additional cryomodules, increasing the beam energy from 4 GeV to 8 GeV. Due to the user schedule of the existing linac, Cryomodules arriving at SLAC cannot immediately be installed in the linac. They are scheduled to be stored for up to three years before the 12-month installation window. During this storage period, the risk of damage to Cryomodules prior to installation will be mitigated with procedures and best practices incorporating experience from LCLS-II.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB074

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Received ※ 25 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 03 July 2023 — Issue date ※ 10 July 2023

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MOPMB076

Surface Characterization Studies of Gold-Plated Niobium

niobium, cavity, site, radio-frequency

290

S.G. Seddon-Stettler, M. Liepe, T.E. Oseroff, Z. Sun
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
N. Sitaraman
Cornell University, Ithaca, New York, USA

Funding: The National Science Foundation, Grant No. PHY-1549132
The native niobium oxide layer present on niobium has been shown to affect the performace of superconducting RF cavities. Extremely thin layers of gold on the surface of niobium have the potential to suppress surface oxidation and improve cavity performance. However, depositing uniform layers of gold at the desired thickness (sub-nm) is difficult, and different deposition methods may have different effects on the gold surface, on the niobium surface, and on the interface between the two. In particular, the question of whether gold deposition actually passivates the niobium oxide is extremely relevant for assessing the potential of gold deposition to improve RF performance. This work builds on previous research studying the RF performance of gold/niobium bilayers with different gold layer thicknesses. We here consider alternative methods to characterize the composition and chemical properties of gold/niobium bilayers to supplement the previous RF study.

Poster MOPMB076 [1.536 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB076

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Received ※ 25 June 2023 — Revised ※ 27 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 03 July 2023

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MOPMB093

Optimizing Growth of Niobium-3 Tin Through Pre-nucleation Chemical Treatments

site, niobium, cavity, SRF

337

S.G. Arnold, G. Gaitan, M. Liepe, L. Shpani, Z. Sun
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
T. Arias, N. Sitaraman
Cornell University, Ithaca, New York, USA

Funding: This work was supported by the U.S. National Science Foundation under award PHY-1549132, the Center for Bright Beams.
Nb₃Sn is a promising alternative material for SRF cavities that is close to reaching practical applications. To date, one of the most effective growth methods for this material is vapor diffusion, yet further improvement is needed for Nb₃Sn to reach its full potential. The major issues faced by vapor diffusion are tin depleted regions and surface roughness, both of which lead to impaired performance. Literature has shown that the niobium surface oxide plays an important role in the binding of tin to niobium. In this study, we performed various chemical treatments on niobium samples pre-nucleation to enhance tin nucleation. We quantify the effect that these various treatments had through scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). These methods reveal information on tin nucleation density and uniformity, and a thin tin film present on most samples, even in the absence of nucleation sites. We present our findings from these surface characterization methods and introduce a framework for quantitatively comparing the samples. We plan to apply the most effective treatment to a cavity and conduct an RF test soon.

Poster MOPMB093 [1.118 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB093

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Received ※ 21 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 26 July 2023

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TUCXA01

Study of the Dynamics of Flux Trapping in Different SRF Materials

experiment, cavity, ECR, niobium

380

F. Kramer, S. Keckert, J. Knobloch, O. Kugeler
HZB, Berlin, Germany
J. Knobloch
University of Siegen, Siegen, Germany
T. Kubo
KEK, Ibaraki, Japan

A dedicated experimental setup to measure magnetic flux dynamics and trapped flux in samples is used to precisely map out how trapped flux is influenced by different parameters. The setup allows for rapid thermal cycling of the sample so that effects of cooldown parameters can be investigated in detail. We show how temperature gradient, cooldown rate, and the magnitude of external field influence trapped flux in large grain, fine grain and coated niobium samples. The detailed measurements show unexpected results, namely that too fast cooldowns increase trapped flux, large grain material traps flux only when the external field is larger than a temperature gradient dependent threshold field, and the measured dependence of trapped flux on temperature gradient does not agree with an existing model. Therefore, a new model is presented which agrees better with the measured results.

Slides TUCXA01 [3.180 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUCXA01

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Received ※ 17 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 26 June 2023

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TUPTB002

Modelling Trapped Flux in Niobium

ECR, experiment, cavity, niobium

393

F. Kramer, S. Keckert, J. Knobloch, O. Kugeler
HZB, Berlin, Germany
J. Knobloch
University of Siegen, Siegen, Germany
T. Kubo
KEK, Ibaraki, Japan

Detailed measurements of magnetic flux dynamics and trapped magnetic flux in niobium samples were conducted with a new experimental setup that permits precise control of the cooldown parameters. With this setup the dependency of trapped flux on the temperature gradient, external magnetic field, and cooldown rate can be mapped out in more detail compared to cavity measurements. We have obtained unexpected results, and an existing model describing trapped flux in dependence of temperature gradient does not agree with the measured data. Therefore, a new model is developed which describes the magnitude of trapped flux in dependence of the temperature gradient across the sample during cooldown. The model describes the amount of trapped flux lines with help of a density distribution function of the pinning forces of pinning centers and the thermal force which can de-pin flux lines from pinning centers. The model shows good agreement with the measured data and correctly predicts trapped flux at different external flux densities.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB002

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Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 13 July 2023

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TUPTB006

Materials Design for Superconducting RF Cavities: Electroplating Sn, Zr, and Au onto Nb and and Chemical Vapor Deposition

cavity, SRF, plasma, niobium

401

Z. Sun, M. Liepe, T.E. Oseroff
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
Z. Baraissov, D.A. Muller, M.O. Thompson
Cornell University, Ithaca, New York, USA

Funding: This work was supported by the U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams.
Materials scientists seek to contribute to the development of next-generation superconducting radio-frequency (SRF) accelerating cavities. Here, we summarize our achievements and learnings in designing advanced SRF materials and surfaces, including Nb₃Sn [1¿3], ZrNb(CO) [4, 5], and Au/Nb surface design [6,7]. Our efforts involve electrochemical synthesis, phase transformation, and surface chemistry, which are closely coupled with superconducting properties, SRF performance, and engineering considerations. We develop electrochemical processes for Sn, Zr, and Au on the Nb surface, an essential step in our investigation for producing high-quality Nb₃Sn, ZrNb(CO), and Au/Nb structures. Additionally, we design a custom chemical vapor deposition system to offer additional growth options. Notably, we find the second-phase NbC formation in ZrNb(CO) and in ultra-high-vacuum baked or nitrogen-processed Nb. We also identify low-dielectric-loss ZrO2 on Nb and NbZr(CO) surfaces. These advancements provide materials science approaches dealing with fundamental and technical challenges to build high-performance, multi-scale, robust SRF cavities for particle accelerators and quantum applications.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB006

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Received ※ 30 June 2023 — Revised ※ 11 August 2023 — Accepted ※ 20 August 2023 — Issue date ※ 21 August 2023

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TUPTB014

Development of Nb₃Sn Coating System and RF Measurement Results at KEK

cavity, SRF, radio-frequency, accelerating-gradient

414

H. Ito, H. Sakai, K. Umemori, T. Yamada
KEK, Ibaraki, Japan
K. Takahashi
Sokendai, Ibaraki, Japan

We have constructed an Nb₃Sn cavity coating system based on the Sn vapor diffusion method. After the construction, improvement of our coating system and environment has been conducted through sample and cavity coating research. Our cavity achieves a Q-value above 1E10 at 4 K after improvement. We will report on the detail of improvement on our coating system and RF measurement results of single-cell Nb₃Sn cavity.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB014

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Received ※ 18 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 28 June 2023

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TUPTB016

Summary of the FRIB Electropolishing Facility Design and Commissioning, Cavity Processing, and Cavity Test Results

cavity, cathode, MMI, power-supply

419

E.S. Metzgar, B.W. Barker, K. Elliott, J.D. Hulbert, C. Knowles, L. Nguyen, A.R. Nunham, L. Popielarski, A.T. Taylor, T. Xu
FRIB, East Lansing, Michigan, USA

Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics and used resources of the FRIB, which is a DOE Office of Science User Facility, under Award Number DE-SC0000661.
Recently, a new Electropolishing (EP) facility was con-structed and commissioned at the Facility for Rare Isotope Beam (FRIB) with the purpose of supporting advanced surface processing techniques for SRF R&D activities. The FRIB production cavities opted for a Buffered Chemical Polish (BCP) method due to its cost effectiveness and was supported by successful outcomes in other facilities with low beta cavities in a similar frequency range. All 324 cavities used in FRIB Linac were processed in-house at MSU using BCP and exhibited satisfactory performance during testing. As part of the FRIB energy upgrade R&D, 5-cell 644 MHz elliptical resonators will be employed, desiring the use of EP and advanced techniques such as nitrogen doping and medium-T baking. The EP facility is designed to accommodate all types of cavities used in FRIB and possesses the capability for performing EP at low temperatures. Here we report the details of design and commissioning of the EP facility, highlights of encountered issues and subsequent improvements, and preliminary results from vertical tests conducted on the cavities.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB016

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Received ※ 15 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 14 July 2023

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TUPTB018

MgB₂ Coating Parameter Optimization Using a 1.3-GHz 1-Cell Cavity

cavity, SRF, experiment, vacuum

425

T. Tajima, T.P. Grumstrup, J.D. Thompson
LANL, Los Alamos, New Mexico, USA
H. Ito, E. Kako, T. Okada, H. Sakai, K. Umemori
KEK, Ibaraki, Japan

Funding: DOE Office of Science, Office of High Energy Physics
We have started parameter optimization for the coating of MgB₂ using a 1-cell 1.3-GHz elliptical cavity with holes for small samples. Our coating method is based on a 2-step technique, i.e., coat a B layer by flowing diborane gas in the first step and react it with Mg vapor in the 2nd step. Three 6 mm x 6 mm B-coated flat samples are attached at inlet, outlet beam pipes, and at a cell equator and reacted with Mg vapor with different parameters and conditions. We started to see the superconducting transitions on samples but Tc is still lower than our goal of >35 K. We will present our current status of B-Mg reaction tests and construction of B coating system.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB018

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Received ※ 06 July 2023 — Revised ※ 26 July 2023 — Accepted ※ 02 September 2023 — Issue date ※ 03 September 2023

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TUPTB029

Measurement of Particulates under Slow Pumping after High Pressure Rinsing of Superconducting Cavity by Using Modified Slow Pumping System

cavity, vacuum, cryomodule, SRF

458

H. Sakai, E. Kako, R. Katayama, K. Umemori
KEK, Ibaraki, Japan

Funding: This research was partially supported by the research fund from Ministry of Education, Culture, Sports, Science and Technology (MEXT).
Slow pumping system was used for particle free vacuum pumping in Superconducting rf accelerator. In KEK, recently slow pumping system was developed for the cryomodule assembly work for STF 9-cell cavities and worked well to reduce the particulates movements under pumping. However, this slow pumping system want to be used for preparation of vertical test. Before assembly work in clean room for vertical test, we normally apply high pressure rinsing. There were many waters in the cavity. Therefore, we kept one night to dry inside cavity in clean room. Unfortunately, there were some waters in the cavity even though we kept drying in clean room for one night. This water might make some icing under pumping and stop pumping in mass flow meter, which used for slow pumping to control the mass flow. Therefore, we modify the slow pumping system to be robust under slow pumping even when water exists in the cavity. In this paper, we present the modified slow pumping system in KEK and the results of the vacuum trend through slow pumping of 9-cell superconducting cavity. Under slow pumping, we measure the particulates after high pressure rinsing by using vacuum particle monitor.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB029

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Received ※ 16 June 2023 — Revised ※ 26 June 2023 — Accepted ※ 21 August 2023 — Issue date ※ 22 August 2023

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TUPTB030

Development of Automatic Cleaning and Assembly Systems in Clean Room at KEK

cavity, gun, operation, monitoring

463

Y. Yamamoto, T. Dohmae, M.H. Hiraki, H. Sakai, K. Umemori, T. Yamada
KEK, Ibaraki, Japan

At KEK, new clean work systems including vertical auto cleaning system, replacement system between blank flange and bellows, and robot arm have been developed and installed since 2020 under the collaboration between Japan and France. The main purpose is unmanned and dust-free operation in clean room to avoid performance degradation with field emission in vertical test and cryomodule test. The vertical auto cleaning system and the replacement system between blank flange and bellows have been operated successfully in 2021-2022. Currently, clean work studies related to auto cleaning and assembly is under progress by combining the blank-bellows replacement system and a robot arm. In this report, the recent status of clean works at KEK will be presented.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB030

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Received ※ 17 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 30 June 2023

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TUPTB037

Refurbishment and Reactivation of a Niobium Retort Furnace at DESY

cavity, vacuum, niobium, target

485

L. Trelle, C. Bate, H. Remde, D. Reschke, J. Schaffran, L. Steder, H. Weise
DESY, Hamburg, Germany

Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Technologies (MT) Program.
For research in the field of heat treatments of supercon-ducting cavities, a niobium ultra-high vacuum furnace built in 1992 - originally used for the titanization of 1.3 GHz nine-cell cavities - and later shut down was recently refurbished and reactivated. A significant upgrade is the ability to run the furnace in partial pressure mode with nitrogen. The furnace is connected directly to the ISO4 area of the clean room for cavity handling. At room temperature vacuum values of around 3×10^-8 mbar are achieved. The revision included the replacement of the complete control system and a partial renewal of the pump technology. The internal mounting structures are optimized for single-cell operation including tandem operation (two single-cell cavities at once) and corresponding accessories such as witness-samples and caps for the cavities. The installation of additional thermocouples for a detailed monitoring of the temperature curves is also possible at the mounting structure. Due to the furnace design, its location and the strict routines in handling, very high purity levels are achieved in comparison to similar setups and hence provide a mighty tool for SRF cavity R&D at DESY.

Poster TUPTB037 [0.404 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB037

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Received ※ 18 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 01 July 2023

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TUPTB047

The Evaluation of Mechanical Properties of LB650 Cavities

cavity, cryomodule, niobium, SRF

536

G. Wu, S.D. Adams, D.J. Bice, S.K. Chandrasekaran, I.V. Gonin, C.J. Grimm, J.P. Holzbauer, T.N. Khabiboulline, C.S. Narug, J.P. Ozelis, H. Park, G.V. Romanov, R. Thiede, R. Treece, A.D. Wixson
Fermilab, Batavia, Illinois, USA
K.E. McGee
FRIB, East Lansing, Michigan, USA

Funding: This manuscript has been authored by Fermi Research Alliance, LLC, under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
The 650 MHz cavities have a stronger requirement of niobium mechanical properties because of the geometric shape of the cavity due to reduced beta. The mechanical property of the niobium half-cell was measured following various heat treatments. The 5-cell cavities were tested in a controlled drop test fashion and the real-world road test. The result showed that the 900C heat treatment was compatible with cavity handling and transportation during production. The test provides the bases of the transportation specification and shipping container design guidelines.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB047

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Received ※ 19 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 14 July 2023

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TUPTB059

INFN LASA Experimental Activities for the PIP-II Project

cavity, SRF, experiment, diagnostics

549

M. Bertucci, M. Bonezzi, A. Bosotti, D. Cardelli, E. Del Core, F. Fiorina, A.T. Grimaldi, L. Monaco, C. Pagani, R. Paparella, D. Sertore, G.M. Zaggia
INFN/LASA, Segrate (MI), Italy

INFN LASA is upgrading its vertical test facility to allow high-Q measurements of the PIP-II LB650 SRF cavities. Such facility is equipped with a wide set of diagnostics for quench, field emission and magnetic flux expulsion studies and will offer a better understanding of cavity performance. At the same time, R&D on LB650 cavity prototypes is ongoing, in order to optimize the overall processing as well as the cavity Jacketing in view of the forthcoming series production with industry. This paper reports on the overall status of these experimental activities.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB059

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Received ※ 18 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 18 July 2023

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WEPWB064

Performance Analysis from ESS Cryomodule Testing at CEA

cavity, cryomodule, electron, cryogenics

727

O. Piquet, C. Arcambal, Q. Bertrand, P. Bosland, E. Cenni, G. Devanz, T. Hamelin
CEA-IRFU, Gif-sur-Yvette, France
P. Sahuquet
CEA-DRF-IRFU, France

CEA Saclay is in charge of the production of 30 elliptical cavities cryomodule as part of the in Kind contribution to the ESS superconducting. The two medium and high beta prototypes and the three first of each type of the series cryomodules have been tested at CEA in slightly different conditions than at ESS (both in terms of cryogenic operation as well as RF conditions). The goal of these tests was to validate the assembly procedure before the delivery of the series to ESS where the final acceptance tests are performed. This paper summarizes the main results obtained during the tests at CEA with a particular attention to the field emission behaviour.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB064

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Received ※ 20 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 07 July 2023

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WEPWB065

Impact of Medium Temperature Heat Treatments on the Magnetic Flux Expulsion Behavior of SRF Cavities

cavity, SRF, niobium, experiment

731

J.C. Wolff, J. Eschke, A. Gössel, K. Kasprzak, D. Reschke, L. Steder, L. Trelle, M. Wiencek
DESY, Hamburg, Germany
W. Hillert
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Technologies (MT) Program.
Medium temperature (mid-T) heat treatments at 300 °C are used to enhance the intrinsic quality factor of superconducting radio frequency (SRF) cavities. Unfortunately, such treatments potentially increase the sensitivity to trapped magnetic flux and consequently the surface resistance of the cavity. For this reason, it is crucial to maximize the expulsion of magnetic flux during the cool down. The flux expulsion behavior is next to the heat treatment mainly determined by the geometry, the niobium grain size and the grain orientation. However, it is also affected by parameters of the cavity performance tests like the cool down velocity, the spatial temperature gradient along the cavity surface and the magnetic flux density during the transition of the critical temperature. To improve the flux expulsion behavior and hence the efficiency of future accelerator facilities, the impact of these adjustable parameters as well as the mid-T heat treatment on 1.3 GHz TESLA-Type single-cell cavities is investigated by a new approach of a magnetometric mapping system. In this contribution first performance test results of cavities before- and after mid-T heat treatment are presented.

Poster WEPWB065 [3.077 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB065

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Received ※ 21 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 13 July 2023

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WEPWB076

Low Particulates Nitrogen Purge and Backfill during Prototype HB650 Cryomodule String Assembly

cavity, vacuum, SRF, cryomodule

765

T.J. Ring, M.B. Quinlan, G. Wu
Fermilab, Batavia, Illinois, USA

Funding: This manuscript has been authored by Fermi Research Alliance, LLC, under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
A low particulate vacuum and purging system was developed to support PIP-II cryomodule string assembly. The overpressure can be controlled at a precision of 1 mbar above the atmospheric pressure regardless of the cavity or string assembly air volume. The system minimized the risk of uncontrolled nitrogen flow during the string assembly. Design features will be presented.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB076

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Received ※ 19 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 09 July 2023

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WEPWB110

Prevention of Dual-Mode Excitation in 9-Cell Cavities for LCLSII-HE

cavity, resonance, feedback, SRF

852

P.D. Owen
JLab, Newport News, Virginia, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
Dual-Mode Excitation, also referred to as mode-mixing, is a superposition of two pi modes in an SRF cavity. In 9-cell TESLA cavities used for the LCLSII-HE project, the two modes that are commonly excited are the pi mode (1300.2 MHz), and the 7/9 pi mode (1297.8 MHz). During vertical cavity qualification testing, it is regularly observed that emitted power at the frequency of the 7/9 pi mode grows, despite the RF system only driving the pi mode. When this happens, the RF power measurement system is unable to differentiate between the superimposed modes which invalidates any data taken. A new RF control solution prevents the 7/9 pi mode from being excited. A second RF control system is connected to drive the 7/9 pi mode. The loop phase for driving this mode is determined, then shifted by 180 degrees, thus providing a negative feedback to the undesired mode. Because this off-resonance power can be very small, it does not interfere with the high-power measurements of the fundamental pi mode. At Jefferson Lab, we are now able to test a cavity for the LCLSII-HE project with no complications from mode-mixing, which allows for CW processing of high-gradient multipacting.

Poster WEPWB110 [1.818 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB110

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Received ※ 19 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 13 July 2023

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WEPWB121

Niobium Chronicles: Surface Quality Investigation and Recovery During Material Procurement for the PIP-II High Beta 650 MHz Cavities

cavity, niobium, factory, synchrotron

880

A.D. Shabalina
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

The surface quality of high-purity niobium for superconducting radiofrequency cavities experienced a sudden and significant decline in 2021. The recovery process and root cause analysis were challenging due to a variety of factors such as COVID-19 travel restrictions, cultural differences, and bureaucratic processes. Effective open communication was crucial to resolving the issue, especially with direct vendor oversight being impossible.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB121

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Received ※ 28 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 20 August 2023 — Issue date ※ 20 August 2023

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WEPWB131

Demonstration of Magnetron as an Alternative RF Source for SRF Accelerators

injection, cavity, power-supply, klystron

902

H. Wang, K. Jordan, R.A. Rimmer
JLab, Newport News, Virginia, USA
J.P. Anderson, C.P. Moeller, K.A. Thackston
GA, San Diego, California, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177, and DOE OS/ARDAP Accelerator Stewardship award 2019-2023.
Magnetron has been considered as alternate high-efficiency, low-cost RF sources for linacs and storage rings [1] for national labs and industrial applications. After the demonstration of magnetrons power to drive and combine for a radio frequency cavity at 2450 MHz in CW mode, we have used trim coils adding to a water-cooled magnetron and amplitude modulation feedback to further suppress the side-band noise to -46.7 dBc level. We also demonstrated the phase-locking to an industrial grade cooking magnetron transmitter at 915 MHz with a 75 kW CW power delivered to a water load by using a -26.6 dBc injection signal [2]. The sideband noise from the 3-Phase SCRs DC power supply can be reduced to -16.2 dBc level. Further noise reduction and their power combining scheme using magic-tee and cavity type combiners for higher power application (2x75kW) are to be presented. We intent to use one power station to drive the normal conducting and superconducting RF cavities for the inductrial linac. We also going to demonstarte a vertical SRF cavity test with a high input coupling Q using a 2.45GHz magnetron and comparing with a baseline test result using a solid state amplifier.
[1]. doi:10.18429/JACoW-IPAC2015-WEPWI028.
[2]. doi:10.18429/JACoW-NAPAC2022-WEZD3.

Poster WEPWB131 [2.445 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB131

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Received ※ 16 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 30 June 2023 — Issue date ※ 19 August 2023

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WEPWB134

Study of Different Piezoelectric Material Stroke Displacement at Different Temperatures Using an SRF Cavity

cavity, SRF, experiment, resonance

911

C. Contreras-Martinez, Y.M. Pischalnikov, J.C. Yun
Fermilab, Batavia, Illinois, USA

Piezoelectric actuators are used for resonance control in superconducting linacs. The level of frequency compensation depends on the piezoelectric stroke displacement. In this study, the stroke displacement will be measured with a 1.3 GHz SRF cavity by measuring the frequency shift with respect to the voltage applied. The entire system was submerged in liquid helium. This study characterizes the PZT piezoelectric actuator (P-844K093) and a lithium niobate (P-844B0005) piezoelectric actuator. All these actuators were developed at Physik Instrumente (PI). The piezo-electric displacement was measured at different temperatures.

Poster WEPWB134 [0.776 MB]

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reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB134

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Received ※ 16 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 13 July 2023

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THIXA03

Cryocooler Application for Accelerator and Development Status of Powerful Cryocooler at SHI Ltd.

SRF, cavity, interface, operation

968

T. Ikeda, S. Sasazaki
SHI, Tokyo, Japan

Advances in recent Nb₃Sn cavity development makes possible to operate the cavities with Qo ~ 1xE10 at 4.3 K and to design SRF accelerator in which the cavities are cooled directly with small mechanical cryocoolers instead of using liquid helium. Conduction-cooling with cryocoolers greatly simplify the overall design and also contribute for cost saving of an SRF accelerator, making the SRF technology feasible for industrial accelerators. However, in the case of using current cryocooler systems (like Gifford-McMahon cryocooler, Pulse-Tube cryocooler, etc.) for the conduction-cooling, since the cooling capacity per unit is small, multiple units will be used in combination depending on the required cooling capacity, it will cause problems in terms of power consumption (efficiency), footprint, and maintenance costs. Therefore, SHI have been developing a large-capacity and high-efficiency 4KGM-JT (Gifford-McMahon-Joule-Thomson) cryocooler system in the 10 W class at 4.2 K. This contribution will report the overview of this cryocooler system and its status of development.

Slides THIXA03 [1.638 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-THIXA03

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Received ※ 20 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 04 July 2023

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