SRF2023 - List of Keywords (electron)

Paper	Title	Other Keywords	Page
MOPMB043	Characterization of Dissipative Regions of an N-Doped SRF Cavity	cavity, niobium, radio-frequency, experiment	202
	E.M. Lechner, G. Ciovati JLab, Newport News, Virginia, USA G. Ciovati, A.V. Gurevich, J. Makita ODU, Norfolk, Virginia, USA M. Iavarone, E.M. Lechner, B.D. Oli Temple University, Philadelphia, USA
	Funding: DE-AC05-06OR23177 NSF Award No. 1734075 W911NF-16-2-0189 We report scanning tunneling microscopy measurements on N-doped cavity hot and cold spot cutouts. Analysis of the electron tunneling spectra using a proximity effect theory shows that hot spots have a reduced superconducting gap and a wider distribution of the contact resistance. Alone, these degraded superconducting properties account for a much weaker excess dissipation as compared with the vortex contribution. Based on the correlation between the quasiparticle density of states and temperature mapping, we suggest that degraded superconducting properties may facilitate vortex nucleation or settling of trapped flux during cooling the cavity through the critical temperature.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB043
About •	Received ※ 19 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 13 July 2023
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MOPMB053	Theoretical Study of Thin Noble-Metal Films on the Niobium Surface	niobium, interface, lattice, experiment	230
	C.A. Méndez, T. Arias, M. Liepe, N. Sitaraman Cornell University, Ithaca, New York, USA
	Funding: The Center for Bright Beams, Supported by National Science Foundation award No. PHY-1549132 Recent experiments suggest that noble-metal deposition on niobium metal surfaces can remove the surface oxide and ultimately improve superconducting radio-frequency (SRF) cavities performance. In this preliminary study, we use density-functional theory to investigate the potential for noble-metal passivation of realistic, polycrystalline niobium surfaces for SRF. Specifically, we investigate the stability of gold and palladium monolayers on niobium surfaces with different crystal orientations and evaluate the impact of these impurities on superconducting properties. In particular, our results suggest that gold can grow in thin layers on the niobium surface, whereas palladium rather tends to dissolve into the niobium cavity. These results will help inform ongoing experimental efforts to passivate niobium surfaces of SRF cavities.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB053
About •	Received ※ 22 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 19 August 2023 — Issue date ※ 19 August 2023
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MOPMB078	Design and Prototyping of the Electron Ion Collider Electron Storage Ring SRF Cavity	cavity, simulation, HOM, operation	293
	J. Guo, E.F. Daly, E. Drachuk, R.R. Fernandes, J. Henry, J. Matalevich, G.-T. Park, R.A. Rimmer, D. Savransky JLab, Newport News, Virginia, USA D. Holmes, K.S. Smith, W. Xu, A. Zaltsman BNL, Upton, New York, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177 Among the EIC¿s numerous RF subsystems, the electron storage ring¿s (ESR) 591 MHz fundamental RF system is one of the most challenging. Each cavity in the system will handle up to 2.5 A of beam current and supply up to 600 kW beam power under a wide range of voltage. The EIC R&D plan includes the design, fabrication and testing of such a cavity. In this paper, we will report the latest status and findings of the ongoing design and prototyping of this cavity, including the RF and mechanical/thermal design, fabrication design, and the progress of fabrication.
	Poster MOPMB078 [1.489 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB078
About •	Received ※ 12 June 2023 — Revised ※ 26 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 19 July 2023
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MOPMB080	Dedicate SRF Cryomodule Test Facilities for S3FEL	cryomodule, FEL, linac, SRF	298
	H. Li, C.F. He Institute of Advanced Science Facilities, Shenzhen, People’s Republic of China X.L. Wang, W.M. Yue, W.Q. Zhang IASF, Shenzhen, Guangdong, People’s Republic of China
	Shenzhen Superconducting Soft-X-Ray Free Electron Laser (S3FEL) has been proposed to build a continuous wave (CW) superconducting linear accelerator and produce FEL in the soft X-ray wavelength region. The proposed S3FEL LINAC consists of twenty-eight SRF cryomodules to accelerate beam energy up to 2.5 GeV. Prior to the cryomodules installed in the tunnel, SRF cavities and cryomodules will be conditioned and tested at a delicate SRF Cryomodule Test Facility (SMTF).The SMTF for S3FEL is currently under design which equipped with two vertical cryostats and three horizontal test benches. R&D work for the SMTF and its corresponding cryomodule assembly procedure is now on going. This paper describes the full set of layout design and implementation of the SMTF for S3FEL project as well as its latest status.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB080
About •	Received ※ 19 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 07 July 2023
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TUIAA02	The FLASH 2020+ Upgrade Project	laser, FEL, undulator, operation	354
	M. Vogt, E. Ferrari, C. Gerth, K. Honkavaara, J. Rönsch-Schulenburg, L. Schaper, S. Schreiber, J. Zemella DESY, Hamburg, Germany
	FLASH, the Soft X-Ray and Extreme-UV Free Electron Laser at DESY, is undergoing a substantial upgrade and refurbishment project, called FLASH2020+. The project will finally enable external seeded and SASE FEL operation for a wavelength range down to 4 nm with the EEHG method. A key ingredient of the upgrade was replacing two early TTF-type L-band RF cryo accelerator modules by modern, high-gradient XFEL-type ones. The beam energy range of the injector has been increased by 100 MeV. This was achieved in the first of two long shutdowns from November 2021 to August 2022. The energy increase together with an afterburner APPLE III type undulator for variable circular polarization in the FLASH2 beamline will make it possible to reach the oxygen K-edge (530 eV). This talk will report on the project and the first shutdown with emphasis on the upgraded modules.
	Slides TUIAA02 [15.921 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUIAA02
About •	Received ※ 21 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 07 July 2023
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TUIBA01	A Three-Fluid Model of Dissipation at Surfaces in Superconducting Radiofrequency Cavities	scattering, cavity, niobium, SRF	361
	M.M. Kelley, T. Arias, S. Deyo, D. Liarte, J.P. Sethna, N. Sitaraman Cornell University, Ithaca, New York, USA M. Liepe, T.E. Oseroff Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, 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. Experiments on superconducting cavities have found that under large RF fields the quality factor can improve with increasing field amplitude, a so-called anti-Q slope. We numerically solve the Bogoliubov-de Gennes equations at a superconducting surface in a parallel magnetic field, finding at large fields there are surface quasiparticle states with energies below the bulk superconducting gap that emerge and disappear as the field cycles. Modifying the standard two-fluid model, we introduce a ‘‘three’’-fluid model where we partition the normal fluid to consider continuum and surface quasiparticle states separately. We compute dissipation in a semi-classical theory of conductivity, where we provide physical estimates of elastic scattering times of Bogoliubov quasiparticles with point-like impurities having potential strengths informed from complementary ab initio calculations of impurities in bulk niobium. We show, in this simple yet effective framework, how the relative scattering rates of surface and continuum quasiparticle states can play a role in producing an anti-Q slope while demonstrating how this model naturally includes a mechanism for turning the anti-Q slope on and off. S. Deyo, M. Kelley et al. Phys. Rev. B 106, 104502 (2022)
	Slides TUIBA01 [2.019 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUIBA01
About •	Received ※ 19 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 08 July 2023
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TUPTB004	Progress on Zirconium-Doped Niobium Surfaces	niobium, ECR, vacuum, superconductivity	398
	N. Sitaraman, T. Arias, Z. Baraissov, D.A. Muller Cornell University, Ithaca, New York, USA G. Gaitan, M. Liepe, T.E. Oseroff, Z. Sun Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: This work was supported by the NSF under Award PHY-1549132, the Center for Bright Beams, and in part by CNF (NSF Grant NNCI-2025233), and in part by CCMR (DMR-1719875). The first experimental studies of zirconium-doped surfaces verified that zirconium can enhance the critical temperature of the surface, resulting in a lower BCS resistance than standard-recipe niobium. However, they also produced a disordered oxide layer, resulting in a higher residual resistance than standard-recipe niobium. Here, we show that zirconium-doped surfaces can grow well-behaved thin oxide layers, with a very thin ternary suboxide capped by a passivating ZrO2 surface. The elimination of niobium pentoxide may allow zirconium-doped surfaces to achieve low residual resistance.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB004
About •	Received ※ 30 June 2023 — Revised ※ 26 July 2023 — Accepted ※ 19 August 2023 — Issue date ※ 22 August 2023
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TUPTB020	Surface Properties and RF Performance of Vapor Diffused Nb₃Sn on Nb after Sequential Anneals below 1000 °C	cavity, SRF, ECR, experiment	433
	J.K. Tiskumara, J.R. Delayen ODU, Norfolk, Virginia, USA G.V. Eremeev Fermilab, Batavia, Illinois, USA U. Pudasaini JLab, Newport News, Virginia, USA
	Nb₃Sn is a next-generation superconducting material that can be used for future superconducting radiofrequency (SRF) accelerator cavities, promising better performance, cost reduction, and higher operating temperature than Nb. The Sn vapor diffusion method is currently the most preferred and successful technique to coat niobium cavities with Nb₃Sn. Among post-coating treatments to optimize the coating quality, higher temperature annealing without Sn is known to degrade Nb₃Sn because of Sn loss. We have investigated Nb₃Sn/Nb samples briefly annealed at 800-1000 °C, for 10 and 20 minutes to potentially improve the surface to enhance the performance of Nb₃Sn-coated cavities. Following the sample studies, a coated single-cell cavity was sequentially annealed at 900 °C and tested its performance each time, improving the cavity’s quality factor relatively. This paper summarizes the sample studies and discusses the RF test results from sequentially annealed SRF Nb₃Sn/Nb cavity.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB020
About •	Received ※ 19 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 01 July 2023 — Issue date ※ 07 July 2023
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TUPTB033	On the Way to a 10 MeV, Conduction-Cooled, Compact SRF Accelerator	cavity, SRF, cryogenics, simulation	471
	H. Vennekate, G. Cheng, G. Ciovati, J. Guo, K.A. Harding, J. Henry, U. Pudasaini, R.A. Rimmer JLab, Newport News, VA, USA A. Castilla JLAB, Newport News, USA F.E. Hannon Phase Space Tech, Bjärred, Sweden D.A. Packard GA, San Diego, California, USA J. Rathke TechSource, Los Alamos, New Mexico, USA T. Schultheiss TJS Technologies, Commack, New York, USA
	Funding: The presentation has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. After the success of designing a compact 1 MeV, 1 MW accelerator based on conduction-cooled SRF, Jefferson Lab is now pursuing a concept to provide a tenfold increase of the beam energy. The higher energy significantly extends the range of applications for environmental remediation and industry in general. The obvious challenge for SRF is to move from a single-cell to a multicell cavity while maintaining high efficiency and the ability to operate the machine without a complex cryogenic plant. The contribution presents the latest results of this design study with respect to its centerpiece, a Nb₃Sn coated 915 MHz five-cell cavity and its corresponding RF components, i.e. FPC and HOM absorber, as well as the conduction-cooling concept based on commercially available cryocoolers.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB033
About •	Received ※ 19 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 18 July 2023
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TUPTB060	Reconstruction of Field Emission Pattern for PIP-II LB650 Cavity	cavity, radiation, experiment, site	554
	E. Del Core, M. Bertucci, A. Bosotti, A.T. Grimaldi, L. Monaco, C. Pagani, R. Paparella, D. Sertore INFN/LASA, Segrate (MI), Italy C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy
	Field emission (FE) is a key limiting phenomenon in SRF cavities. An algorithm exploiting a self-consistent model of cavity FE has been developed. This method exploits experimental observables (such as Q value , X-ray endpoint, and dose rate) to reconstruct emitter position and size as well as the field enhancement factor. To demonstrate the model effectiveness, the algorithm has been applied to a data set of the PIP-II LB650 prototype cavity.
	Poster TUPTB060 [0.956 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB060
About •	Received ※ 17 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 28 June 2023
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TUPTB066	Fabrication and Testing of a Prototype RF-Dipole Crabbing Cavity	cavity, dipole, collider, multipactoring	573
	S.U. De Silva, J.R. Delayen ODU, Norfolk, Virginia, USA H. Park Fermilab, Batavia, Illinois, USA
	Crabbing cavities are essential in particle colliders to compensate the luminosity degradation due to beam collision at a crossing angle. The 952.6 MHz 2-cell rf-dipole crabbing cavity system was proposed for the Jef-ferson Lab Electron-Ion Collider to restore the head-on collisions of electron and proton bunches at the interac-tion point. A prototype cavity was designed and devel-oped to demonstrate the performance of multi-cell rf-dipole structures. This paper presents the fabrication pro-cess and cold test results of the first 2-cell rf-dipole proto-type cavity.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB066
About •	Received ※ 18 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 30 June 2023 — Issue date ※ 21 August 2023
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WEPWB049	Multipacting in C75 Cavities	cavity, simulation, SRF, multipactoring	674
	G. Ciovati, P. Dhakal, R.A. Rimmer, H. Wang, S. Wang JLab, Newport News, Virginia, USA
	Funding: This work was supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Cavities for the C75 cryomodule refurbishment program are currently being built, processed, tested and installed in the CEBAF accelerator at Jefferson Lab. They consist of 5-cell, 1497 MHz cavities with waveguide-type power coupler and for higher-order modes. Most of the cavities rf tests in a vertical cryostat at 2.07 K were limited by strong multipacting at accelerating gradients in the range 18 - 23 MV/m. A softer multipacting barrier was sometimes found at 13 - 15 MV/m. An unusual feature of the multipacting was that the barrier often shifted to a lower gradient ~17 MV/m, after multiple quenches at ~20 MV/m. This phenomenon was reproduced in a single-cell cavity of the same shape. The cavity was tested after different amounts of mechanical tuning and residual magnetic field, with no significant impact to the multipacting behavior. This contribution summarizes the experimental results from cavity rf tests, some of which were complemented by additional diagnostic instrumentation. Results from 2D and 3D simulations are also presented, indicating favorable conditions for multipacting at the equator in the range 20 - 29 MV/m.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB049
About •	Received ※ 15 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 01 July 2023
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WEPWB050	Exploring Innovative Pathway for SRF Cavity Fabrication	cavity, SRF, niobium, laser	680
	O. Hryhorenko JLab, Newport News, Virginia, USA C.Z. Antoine Université Paris-Saclay, CEA, Gif-sur-Yvette, France T. Dohmae KEK, Ibaraki, Japan D. Longuevergne Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Funding: ENSAR-2 under grant agreement N° 654002. The U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177. This article shows a study on an alternative pathway for the fabrication of a complete 1.3 GHz SRF cavity, aiming at improving production reliability, reducing the use of chemical polishing (EP or BCP) which is a costly and safety-critical step, and preserving surface quality after forming. Unlike the conventional pathway, the fabrication process is performed after polishing. This point is crucial as the used polishing technology could be applied only to flat geometries. The performed investigation demonstrates that damages during the fabrication process are considered minor, localized, and limited to the near-surface. Moreover, these studies confirm that the damaged layer (100-200 µm) is mainly caused by the rolling process, and not by the subsequent fabrication steps. A laser confocal microscope and SEM-EBSD technique were used to compare samples before and after forming. The preliminary results are discussed and presented in this paper.
	Poster WEPWB050 [2.263 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB050
About •	Received ※ 20 June 2023 — Revised ※ 27 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 01 July 2023
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WEPWB051	Development of a Prototype 197 MHz Crab Cavity for the Electron-Ion Collider at JLab	cavity, GUI, niobium, HOM	685
	N.A. Huque, E.F. Daly, E. Drachuk, J. Henry, M. Marchlik JLab, Newport News, Virginia, USA A. Castilla JLAB, Newport News, USA S.U. De Silva ODU, Norfolk, Virginia, USA B.P. Xiao BNL, Upton, New York, USA
	Thomas Jefferson National Accelerator Facility (JLab) is currently developing a prototype 197 MHz Radio-Frequency Dipole (RFD) crab cavity as part of the Electron-Ion Collider (EIC) to be built at Brookhaven National Laboratory (BNL). Cryomodules containing these cavities will be part of Hadron Storage Ring (HSR) of the EIC. The prototype cavity is constructed primarily of formed niobium sheets of thickness 4.17 mm, with machined niobium parts used as interfaces where tight tolerancing is required. The cavity¿s large size and complex features present a number of challenges in fabrication, tuning, and RF testing. Structural and forming analyses have been carried out to optimize the design and fabricated processes. An overview of the design phase and the current state of fabrication are presented in this paper. Work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB051
About •	Received ※ 17 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 16 July 2023
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WEPWB053	Simulation of the Dynamics of Gas Mixtures during Plasma Processing in the C75 Cavity	cavity, plasma, simulation, SRF	696
	N.K. Raut, P. Dhakal, T.D. Ganey, T. Powers JLab, Newport News, Virginia, USA
	Funding: The work is supported by SC Nuclear Physics Program through DOE SC Lab funding announcement DE-FOA-0002670 & is authored by JSA, LLC under U.S. DOE Contract No. DE-AC05- 06OR23177 Plasma processing using a mixture of noble gas and oxygen is a technique that is currently being used to reduce field emission and multipacting in accelerating cavities. Plasma is created inside the cavity when the gas mixture is exposed to an electromagnetic field that is generated by applying RF power through the fundamental power or higher-order mode couplers. Oxygen ions and atomic oxygen are created in the plasma which breaks down the hydrocarbons on the surface of the cavity and the residuals from this process are removed as part of the process gas flow. Removal of hydrocarbons from the surface increases the work function and reduces the secondary emission coefficient. This work describes the initial results of plasma simulation, which provides insight into the ignition process, distribution of different species, and interactions of free oxygen and oxygen ions with the cavity surfaces. The simulations have been done with an Ar/¿2 plasma using COMSOL® multiphysics. These simulations help in understanding the dynamics and control of plasma inside the cavity and the exploration of different gas mixtures.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB053
About •	Received ※ 16 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 29 June 2023
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WEPWB057	Refurbishment of an Elbe-Type Cryomodule for Coated HOM-Antenna Tests for MESA	HOM, cavity, cryomodule, niobium	709
	P.S. Plattner, F. Hug, T. Stengler KPH, Mainz, Germany
	Funding: The work received funding by BMBF through 05H21UMRB1. The Mainz Energy-Recovering Superconducting Accelerator (MESA), an energy-recovering (ER) LINAC, is currently under construction at the university Mainz. In the ER mode a continues wave (CW) beam is accelerated from 5 MeV up to 10⁵ MeV with a beam current of up to 1 mA. This current is accelerated and decelerated twice within a cavity. For future experiments, the beam current limit has to be pushed up to 10 mA. An analysis of the MESA cavities has shown that the HOM antennas quench at such high beam currents due to the extensive power deposition and the resulting heating of the HOM coupler. To avoid quenching it is necessary to use superconducting materials with higher critical temperature. For this purpose, the HOM antennas will be coated with NbTiN and Nb3SN and their properties will be investigated. For use in the accelerator, the HOM antennas will be installed in the cavities of a former ALICE cryomodule, kindly provided by STFC Daresburry. This paper will show both the status of the refurbishment of the ALICE module to suit MESA, and the coating of the HOM antennas. The authors would like to express their sincere gratitude to STFC Daresbury for the donation of the ALICE module, which strongly supports SRF research in Mainz.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB057
About •	Received ※ 18 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 09 July 2023
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WEPWB064	Performance Analysis from ESS Cryomodule Testing at CEA	cavity, cryomodule, controls, 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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WEPWB084	The Interaction among Interstitial C/N/O/H and Vacancy in Niobium via First-Principles Calculation	niobium, lattice, site, cavity	778
	H. Liu, J.K. Hao, Z.T. Yang PKU, Beijing, People’s Republic of China
	We calculate the interaction among zero dimensional defects in niobium lattice through first-principles calculation. And we compare the trapping effect of hydrogen among carbon, nitrogen, and oxygen as well as the trapping effect of interstitial atoms by vacancy. We find that the interstitial C/N/O have similar effect of trapping interstitial hydrogen in niobium lattice, and the vacancy can trap interstitial C/N/O/H in adjacent protocells and strengthen their chemical bond with Nb. These calculations give some explanation for improving superconducting performance of niobium cavities through medium temperature baking.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB084
About •	Received ※ 15 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 03 July 2023
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WEPWB089	Theoretical Model of External Q Tuning for an SRF Cavity with Waveguide Tuner	cavity, GUI, SRF, operation	794
	W. Xu, Z.A. Conway, K.S. Smith, A. Zaltsman BNL, Upton, New York, USA E.F. Daly, J. Guo, R.A. Rimmer JLab, Newport News, Virginia, USA
	Funding: The work is supported by by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE. A wide range of electron beam energies (5 ¿ 18 GeV) and beam currents (0.2 ¿ 2.5 A) in EIC Electron Storage Ring (ESR) operating scenarios requires a capability of adjusting coupling factor up to a factor of 20 for the 591 MHz Superconducting Radio Frequency (SRF) cavities, which contains two fundamental power couplers (FPC) delivering continuous wave (CW) 800 kW RF power to the beam. Currently, adjusting external Q of a SRF cavity is done by varying protrusion of FPC¿s inner conductor in beam pipe or using three stub tuner to adjust external Q value, which either has limit on tuning range or limit on operating power. This paper presents a method of tuning the FPC external Q by a multiple-waveguide tuner, which allows for high power, wide tuning range operations. The theoretical model of matching beam impedance with waveguide tuner and detailed matching conditions and limits will be presented. Follow the theoretical model, a preliminary design of a 3D waveguide tuner will be presented. The work is supported by by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
	Poster WEPWB089 [1.269 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB089
About •	Received ※ 26 June 2023 — Revised ※ 27 June 2023 — Accepted ※ 19 August 2023 — Issue date ※ 22 August 2023
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WEPWB102	Recent Progress of Fundamental Power Couplers for the SHINE Project	FEL, vacuum, cryomodule, cavity	827
	Z.Y. Ma, J.F. Chen, H.T. Hou, B. Liu, Y. Liu, S. Sun, D. Wang, L. Yin, M. Zhang, S.J. Zhao, Y.B. Zhao, Z.T. Zhao, X. Zheng SARI-CAS, Pudong, Shanghai, People’s Republic of China
	Funding: Project supported by Shanghai Municipal Science and Technology Major Project (Grant No.2017SHZDZX02). The superconducting radio-frequency electron linear accelerator of the Shanghai HIgh repetition rate XFEL aNd Extreme light facility (SHINE) contains 610 1.3 GHz fundamental power couplers which are assembled in 77 superconducting cryomodules used for beam acceleration, and 16 3.9 GHz fundamental power couplers, which are assembled in two third harmonic superconducting cryomodules used for linearizing the longitudinal phase space. The first batch of 26 1.3 GHz coupler prototypes and two 3.9 GHz coupler prototypes have been fabricated from three domestic manufacturers for basic research. Several key manufacturing processes have been developed and qualified, including high residual resistivity ratio (RRR) copper plating, vacuum brazing of ceramic windows, electron beam welding and titanium nitride coating. All the 1.3 GHz coupler prototypes have been power conditioned with 14 kW travelling wave (TW) and 7 kW standing wave (SW) RF in continuous-wave (CW) mode. Even higher power levels have been demonstrated with 20 kW TW and 10 kW SW RF, which indicates their robustness. Both 3.9 GHz coupler prototypes have been power conditioned with 2.2 kW TW and 2 kW SW RF in CW mode.
	Poster WEPWB102 [2.361 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB102
About •	Received ※ 16 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 05 July 2023
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WEPWB104	RF Conditioning of MYRRHA Couplers at IJCLab	vacuum, cavity, FEL, multipactoring	835
	N. ElKamchi, S. Berthelot, P. Duchesne, C. Joly, W. Kaabi, C. Magueur Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France Y. Gómez Martínez LPSC, Grenoble Cedex, France C. Lhomme IJCLab, ORSAY, France
	Multi-purpose hYbrid Research Reactor for High-tech Applications (MYRRHA) is an experimental accelerator-driven system in development at SCK•CEN. It will allow fuel developments, material developments for GEN IV systems, material developments for fusion reactors and radioisotope production for medical and industrial applications1. The IJCLab has in charge the industrial monitoring, the quality control and the RF conditioning of the power couplers up to 80KW at 352Mhz. This paper presents the conditioning bench adapted from the successful experience of IJCLab in the conditioning of the XFEL couplers2. The results of the conditioning of prototype couplers are described and discussed. 1. Abderrahim, P. MYRRHA a multi-purpose hybrid research reactor for high-tech applications. United States: N. p., 2012. Web 2. H. Guler, Proceedings of IPAC2016, Busan, Korea
	Poster WEPWB104 [0.875 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB104
About •	Received ※ 26 June 2023 — Revised ※ 27 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 08 August 2023
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WEPWB105	Improved Study of the Multipactor Phenomenon for the MYRRHA 80 kW CW RF Couplers	multipactoring, coupling, linac, cavity	838
	Y. Gómez Martínez, P.-O. Dumont LPSC, Grenoble Cedex, France P. Duchesne, N. ElKamchi, C. Joly, W. Kaabi Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France C. Lhomme IJCLab, ORSAY, France C. Lhomme ACS, Orsay, France
	MYRRHA (Multi Purpose Hybrid Reactor for High Tech Applications) is an Accelerator Driven System (ADS) project. Its superconducting linac will provide a 600 MeV - 4 mA proton beam. The first project phase based on a 100 MeV linac is launched. The Radio-Frequency (RF) couplers have been designed to handle 80 kW CW (Continuous Wave) at 352.2 MHz. This paper describes the multipactor studies on the coupler when it does not work in the nominal configuration without reflected power.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB105
About •	Received ※ 18 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 12 July 2023
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WEPWB113	Evaluation of Photo-Cathode Port Multipacting in the SRF Photo-Injector Cryomodule for the LCLS-II High-Energy Upgrade	cathode, simulation, SRF, experiment	859
	Z.Y. Yin, W. Hartung, S.H. Kim, T. Konomi, T. Xu FRIB, East Lansing, Michigan, USA
	The high-energy upgrade of the Linac Coherent Light Source (LCLS-II-HE) will increase the photon energy and brightness. A low-emittance injector (LEI) was proposed to increase the photon flux for high X-ray energies. FRIB, HZDR, Argonne, and SLAC are developing a 185.7 MHz superconducting radio-frequency photo-injector (SRF-PI) cryomodule for the LEI. The photo-cathode system requirements are challenging, as cathodes must be maintained at the desired temperature, precisely aligned, and operated without multipacting (MP); to avoid field emission, cathode exchange must be particulate-free. A support stalk has been designed to hold the cathode in position under these requirements. A DC bias is used to inhibit MP. We simulated MP for various surface conditions and bias levels. An RF/DC test was developed to evaluate the cathode stalk performance as a subsystem and to identify and correct issues before assembly into the full cryomodule. The RF/DC test makes use of a resonant coaxial line to generate an RF magnetic field similar to that of the cathode-in-SRF-PI-cavity case. High-power test results will be presented and compared to the MP simulations. * Work supported by the Department of Energy Contract DE-AC02-76SF00515
	Poster WEPWB113 [1.410 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB113
About •	Received ※ 20 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 26 July 2023
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WEPWB116	The Influence of Sample Preparation, Soak Time, and Heating Rate on Measured Recrystallization of Deformed Polycrystalline Niobium	cavity, ECR, niobium, SRF	863
	Z.L. Thune MSU, East Lansing, USA T.R. Bieler Michigan State University, East Lansing, Michigan, USA
	Funding: DOE/OHEP (Grant Number: DE-SC0009960) Improving accelerator performance relies on consistent production of high-purity niobium superconducting radiofrequency (SRF) cavities. Current production uses an 800 °C 3 hr heat treatment, but 900-1000 °C can improve cavity performance via recrystallization (Rx) and grain growth. As Rx is thermally activated, increasing the temperature and/or the heating rate could facilitate a reduction in geometrically necessary dislocation (GND) density that is associated with the degradation of cavity performance via trapped magnetic flux. Recent work shows that increasing the annealing temperature increased the Rx fraction in cold-rolled polycrystalline niobium. However, the influence of heating rate on the extent of Rx was minimal with a 3 hr soak time. To further assess the influence of heating rate on measured Rx, as well as the effects of sample preparation, electron backscatter diffraction (EBSD) was used to quantify the extent of Rx on samples annealed at a single temperature with different soak times. Comparing samples with different surface preparation shows that pinned grain boundaries on the free surface reveal a much smaller grain size than below the surface. * Z.L. Thune et al., "The Influence of Strain Path and Heat Treatment Variations on Recrystallization in Cold-Rolled High-Purity Niobium Polycrystals," doi: 10.1109/TASC.2023.3248533.
	Poster WEPWB116 [1.312 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB116
About •	Received ※ 23 June 2023 — Revised ※ 26 June 2023 — Accepted ※ 20 August 2023 — Issue date ※ 21 August 2023
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WEPWB127	Investigation of Coupler Breakdown Thresholds for Plasma Processing of FRIB Quarter-Wave Resonators with Fundamental and Higher-Order Modes	cavity, plasma, HOM, simulation	893
	P.R. Tutt, W. Hartung, S.H. Kim, T. Xu FRIB, East Lansing, Michigan, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics and used resources of the Facility for Rare Isotope Beams (FRIB) under Award Number DE-SC0000661. FRIB is developing plasma processing techniques for in-situ recovery of cavity performance in linac cryomodules during long-term user operation. While plasma processing has been shown to be effective for high-frequency (0.8 - 1.5 GHz) elliptical cavities, one of the challenges for FRIB is to avoid plasma breakdown in the fundamental input coupler (FPC), which has relatively weak coupling strength (Q_ext ranging from 2E6 to 1E7). FRIB cavities are not equipped with higher-order-mode (HOM) couplers; however, in preliminary tests, we found that HOMs are suitable for plasma processing of FRIB Quarter-Wave Resonators (QWRs) driven via the FPC. In this study, we investigated plasma breakdown thresholds in the fundamental and the first 2 HOMs for the FRIB β = 0.085 QWRs. Electric field distributions in the FPC region and cavity region were calculated for the room-temperature case using CST Microwave Studio’s frequency domain solver (FDS). Simulation results will be presented, with comparison of breakdown thresholds inferred from the RF modeling to the experimental results.
	Poster WEPWB127 [5.068 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB127
About •	Received ※ 19 June 2023 — Revised ※ 27 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 11 August 2023
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THIAA01	Development of 3.9 GHz 9-Cell Cavities at SHINE	cavity, linac, FEL, laser	921
	X.W. Wu Zhangjiang Lab, Shanghai, People’s Republic of China J.F. Chen, P.C. Dong, Y.F. Liu, X.H. Ouyang, S. Sun, J.N. Wu, S. Xing, Y.X. Zhang, S.J. Zhao, Y.L. Zhao SARI-CAS, Pudong, Shanghai, People’s Republic of China X. Huang, Z. Wang, Y. Zong SINAP, Shanghai, People’s Republic of China Y.W. Huang, R.Z. Xia ShanghaiTech University, Shanghai, People’s Republic of China
	The Shanghai high-repetition-rate XFEL and extreme light facility (SHINE) Linac requires two 3.9~GHz crymodules to linearize energy distribution before the bunch compressor. As a key component to the project, studies of 3.9~GHz cavities were conducted in the past few years. The first 3.9~GHz 9-cell prototype cavity has been fabricated, tested, and qualified. It reached Q₀=3.5×10⁹ at 13.1~MV/m and a maximum accelerating gradient of 25.0~MV/m during the vertical test of the bare cavity. The prototype has been helium tank integrated and reached Q₀=2.9×10⁹ at 13.1~MV/m in the vertical test, with a large margin with respect to the SHINE specification. The second prototype has been fabricated and is planned to be tested in 2023. This paper will cover the fabrication, surface treatment, and RF test of the 3.9~GHz cavities.
	Slides THIAA01 [7.573 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-THIAA01
About •	Received ※ 19 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 18 July 2023
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FRIBA02	Instrumentation for High Performance Cavities and Cryomodule Field Emission Analysis	cavity, radiation, neutron, simulation	978
	G. Devanz CEA-IRFU, Gif-sur-Yvette, France M. Baudrier, E. Cenni, L. Maurice, O. Piquet CEA-DRF-IRFU, France
	Field emission (FE) is one of the main reasons for the degradation of accelerator cryomodules, as field emitted current tends to become more severe during the beam operation. It is essential to better understand how this phenomenon is generated and evolves from the SRF cavity preparation in the clean room, through their assembly in the cryomodule until their final test and operation. Due to the shielding environment of a cavity in its vertical test stand, or the architecture of a cryomodule, the more faint radiation occurring at the FE onset remains undetected. More precise diagnostic and analysis tools are required to gain more information. We present the developpement of dedicated time-resolved detectors for the FE radiation which aim at improving its coverage in terms of solid angle and lower energy threshold sensitivity. We approach this topic through detailed simulation based on the Geant4 toolkit in order to analyse the interaction of FE radiation with the cavity environement and optimize the detectors with respect to their application in cryomodule or vertical test stands. We illustrate by analysing recent cryomodule experimental test data.
	Slides FRIBA02 [9.606 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-FRIBA02
About •	Received ※ 27 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 05 July 2023 — Issue date ※ 09 July 2023
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Paper

Title

Other Keywords

Page

MOPMB043

Characterization of Dissipative Regions of an N-Doped SRF Cavity

cavity, niobium, radio-frequency, experiment

202

E.M. Lechner, G. Ciovati
JLab, Newport News, Virginia, USA
G. Ciovati, A.V. Gurevich, J. Makita
ODU, Norfolk, Virginia, USA
M. Iavarone, E.M. Lechner, B.D. Oli
Temple University, Philadelphia, USA

Funding: DE-AC05-06OR23177 NSF Award No. 1734075 W911NF-16-2-0189
We report scanning tunneling microscopy measurements on N-doped cavity hot and cold spot cutouts. Analysis of the electron tunneling spectra using a proximity effect theory shows that hot spots have a reduced superconducting gap and a wider distribution of the contact resistance. Alone, these degraded superconducting properties account for a much weaker excess dissipation as compared with the vortex contribution. Based on the correlation between the quasiparticle density of states and temperature mapping, we suggest that degraded superconducting properties may facilitate vortex nucleation or settling of trapped flux during cooling the cavity through the critical temperature.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB043

About •

Received ※ 19 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 13 July 2023

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MOPMB053

Theoretical Study of Thin Noble-Metal Films on the Niobium Surface

niobium, interface, lattice, experiment

230

C.A. Méndez, T. Arias, M. Liepe, N. Sitaraman
Cornell University, Ithaca, New York, USA

Funding: The Center for Bright Beams, Supported by National Science Foundation award No. PHY-1549132
Recent experiments suggest that noble-metal deposition on niobium metal surfaces can remove the surface oxide and ultimately improve superconducting radio-frequency (SRF) cavities performance. In this preliminary study, we use density-functional theory to investigate the potential for noble-metal passivation of realistic, polycrystalline niobium surfaces for SRF. Specifically, we investigate the stability of gold and palladium monolayers on niobium surfaces with different crystal orientations and evaluate the impact of these impurities on superconducting properties. In particular, our results suggest that gold can grow in thin layers on the niobium surface, whereas palladium rather tends to dissolve into the niobium cavity. These results will help inform ongoing experimental efforts to passivate niobium surfaces of SRF cavities.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB053

About •

Received ※ 22 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 19 August 2023 — Issue date ※ 19 August 2023

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MOPMB078

Design and Prototyping of the Electron Ion Collider Electron Storage Ring SRF Cavity

cavity, simulation, HOM, operation

293

J. Guo, E.F. Daly, E. Drachuk, R.R. Fernandes, J. Henry, J. Matalevich, G.-T. Park, R.A. Rimmer, D. Savransky
JLab, Newport News, Virginia, USA
D. Holmes, K.S. Smith, W. Xu, A. Zaltsman
BNL, Upton, New York, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177
Among the EIC¿s numerous RF subsystems, the electron storage ring¿s (ESR) 591 MHz fundamental RF system is one of the most challenging. Each cavity in the system will handle up to 2.5 A of beam current and supply up to 600 kW beam power under a wide range of voltage. The EIC R&D plan includes the design, fabrication and testing of such a cavity. In this paper, we will report the latest status and findings of the ongoing design and prototyping of this cavity, including the RF and mechanical/thermal design, fabrication design, and the progress of fabrication.

Poster MOPMB078 [1.489 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB078

About •

Received ※ 12 June 2023 — Revised ※ 26 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 19 July 2023

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MOPMB080

Dedicate SRF Cryomodule Test Facilities for S3FEL

cryomodule, FEL, linac, SRF

298

H. Li, C.F. He
Institute of Advanced Science Facilities, Shenzhen, People’s Republic of China
X.L. Wang, W.M. Yue, W.Q. Zhang
IASF, Shenzhen, Guangdong, People’s Republic of China

Shenzhen Superconducting Soft-X-Ray Free Electron Laser (S3FEL) has been proposed to build a continuous wave (CW) superconducting linear accelerator and produce FEL in the soft X-ray wavelength region. The proposed S3FEL LINAC consists of twenty-eight SRF cryomodules to accelerate beam energy up to 2.5 GeV. Prior to the cryomodules installed in the tunnel, SRF cavities and cryomodules will be conditioned and tested at a delicate SRF Cryomodule Test Facility (SMTF).The SMTF for S3FEL is currently under design which equipped with two vertical cryostats and three horizontal test benches. R&D work for the SMTF and its corresponding cryomodule assembly procedure is now on going. This paper describes the full set of layout design and implementation of the SMTF for S3FEL project as well as its latest status.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB080

About •

Received ※ 19 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 07 July 2023

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TUIAA02

The FLASH 2020+ Upgrade Project

laser, FEL, undulator, operation

354

M. Vogt, E. Ferrari, C. Gerth, K. Honkavaara, J. Rönsch-Schulenburg, L. Schaper, S. Schreiber, J. Zemella
DESY, Hamburg, Germany

FLASH, the Soft X-Ray and Extreme-UV Free Electron Laser at DESY, is undergoing a substantial upgrade and refurbishment project, called FLASH2020+. The project will finally enable external seeded and SASE FEL operation for a wavelength range down to 4 nm with the EEHG method. A key ingredient of the upgrade was replacing two early TTF-type L-band RF cryo accelerator modules by modern, high-gradient XFEL-type ones. The beam energy range of the injector has been increased by 100 MeV. This was achieved in the first of two long shutdowns from November 2021 to August 2022. The energy increase together with an afterburner APPLE III type undulator for variable circular polarization in the FLASH2 beamline will make it possible to reach the oxygen K-edge (530 eV). This talk will report on the project and the first shutdown with emphasis on the upgraded modules.

Slides TUIAA02 [15.921 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUIAA02

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Received ※ 21 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 07 July 2023

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TUIBA01

A Three-Fluid Model of Dissipation at Surfaces in Superconducting Radiofrequency Cavities

scattering, cavity, niobium, SRF

361

M.M. Kelley, T. Arias, S. Deyo, D. Liarte, J.P. Sethna, N. Sitaraman
Cornell University, Ithaca, New York, USA
M. Liepe, T.E. Oseroff
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, 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.
Experiments on superconducting cavities have found that under large RF fields the quality factor can improve with increasing field amplitude, a so-called anti-Q slope. We numerically solve the Bogoliubov-de Gennes equations at a superconducting surface in a parallel magnetic field, finding at large fields there are surface quasiparticle states with energies below the bulk superconducting gap that emerge and disappear as the field cycles. Modifying the standard two-fluid model, we introduce a ‘‘three’’-fluid model where we partition the normal fluid to consider continuum and surface quasiparticle states separately. We compute dissipation in a semi-classical theory of conductivity, where we provide physical estimates of elastic scattering times of Bogoliubov quasiparticles with point-like impurities having potential strengths informed from complementary ab initio calculations of impurities in bulk niobium. We show, in this simple yet effective framework, how the relative scattering rates of surface and continuum quasiparticle states can play a role in producing an anti-Q slope while demonstrating how this model naturally includes a mechanism for turning the anti-Q slope on and off.
S. Deyo, M. Kelley et al. Phys. Rev. B 106, 104502 (2022)

Slides TUIBA01 [2.019 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUIBA01

About •

Received ※ 19 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 08 July 2023

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TUPTB004

Progress on Zirconium-Doped Niobium Surfaces

niobium, ECR, vacuum, superconductivity

398

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

Funding: This work was supported by the NSF under Award PHY-1549132, the Center for Bright Beams, and in part by CNF (NSF Grant NNCI-2025233), and in part by CCMR (DMR-1719875).
The first experimental studies of zirconium-doped surfaces verified that zirconium can enhance the critical temperature of the surface, resulting in a lower BCS resistance than standard-recipe niobium. However, they also produced a disordered oxide layer, resulting in a higher residual resistance than standard-recipe niobium. Here, we show that zirconium-doped surfaces can grow well-behaved thin oxide layers, with a very thin ternary suboxide capped by a passivating ZrO2 surface. The elimination of niobium pentoxide may allow zirconium-doped surfaces to achieve low residual resistance.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB004

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Received ※ 30 June 2023 — Revised ※ 26 July 2023 — Accepted ※ 19 August 2023 — Issue date ※ 22 August 2023

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TUPTB020

Surface Properties and RF Performance of Vapor Diffused Nb₃Sn on Nb after Sequential Anneals below 1000 °C

cavity, SRF, ECR, experiment

433

J.K. Tiskumara, J.R. Delayen
ODU, Norfolk, Virginia, USA
G.V. Eremeev
Fermilab, Batavia, Illinois, USA
U. Pudasaini
JLab, Newport News, Virginia, USA

Nb₃Sn is a next-generation superconducting material that can be used for future superconducting radiofrequency (SRF) accelerator cavities, promising better performance, cost reduction, and higher operating temperature than Nb. The Sn vapor diffusion method is currently the most preferred and successful technique to coat niobium cavities with Nb₃Sn. Among post-coating treatments to optimize the coating quality, higher temperature annealing without Sn is known to degrade Nb₃Sn because of Sn loss. We have investigated Nb₃Sn/Nb samples briefly annealed at 800-1000 °C, for 10 and 20 minutes to potentially improve the surface to enhance the performance of Nb₃Sn-coated cavities. Following the sample studies, a coated single-cell cavity was sequentially annealed at 900 °C and tested its performance each time, improving the cavity’s quality factor relatively. This paper summarizes the sample studies and discusses the RF test results from sequentially annealed SRF Nb₃Sn/Nb cavity.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB020

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Received ※ 19 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 01 July 2023 — Issue date ※ 07 July 2023

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TUPTB033

On the Way to a 10 MeV, Conduction-Cooled, Compact SRF Accelerator

cavity, SRF, cryogenics, simulation

471

H. Vennekate, G. Cheng, G. Ciovati, J. Guo, K.A. Harding, J. Henry, U. Pudasaini, R.A. Rimmer
JLab, Newport News, VA, USA
A. Castilla
JLAB, Newport News, USA
F.E. Hannon
Phase Space Tech, Bjärred, Sweden
D.A. Packard
GA, San Diego, California, USA
J. Rathke
TechSource, Los Alamos, New Mexico, USA
T. Schultheiss
TJS Technologies, Commack, New York, USA

Funding: The presentation has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
After the success of designing a compact 1 MeV, 1 MW accelerator based on conduction-cooled SRF, Jefferson Lab is now pursuing a concept to provide a tenfold increase of the beam energy. The higher energy significantly extends the range of applications for environmental remediation and industry in general. The obvious challenge for SRF is to move from a single-cell to a multicell cavity while maintaining high efficiency and the ability to operate the machine without a complex cryogenic plant. The contribution presents the latest results of this design study with respect to its centerpiece, a Nb₃Sn coated 915 MHz five-cell cavity and its corresponding RF components, i.e. FPC and HOM absorber, as well as the conduction-cooling concept based on commercially available cryocoolers.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB033

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Received ※ 19 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 18 July 2023

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TUPTB060

Reconstruction of Field Emission Pattern for PIP-II LB650 Cavity

cavity, radiation, experiment, site

554

E. Del Core, M. Bertucci, A. Bosotti, A.T. Grimaldi, L. Monaco, C. Pagani, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy

Field emission (FE) is a key limiting phenomenon in SRF cavities. An algorithm exploiting a self-consistent model of cavity FE has been developed. This method exploits experimental observables (such as Q value , X-ray endpoint, and dose rate) to reconstruct emitter position and size as well as the field enhancement factor. To demonstrate the model effectiveness, the algorithm has been applied to a data set of the PIP-II LB650 prototype cavity.

Poster TUPTB060 [0.956 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB060

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Received ※ 17 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 28 June 2023

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TUPTB066

Fabrication and Testing of a Prototype RF-Dipole Crabbing Cavity

cavity, dipole, collider, multipactoring

573

S.U. De Silva, J.R. Delayen
ODU, Norfolk, Virginia, USA
H. Park
Fermilab, Batavia, Illinois, USA

Crabbing cavities are essential in particle colliders to compensate the luminosity degradation due to beam collision at a crossing angle. The 952.6 MHz 2-cell rf-dipole crabbing cavity system was proposed for the Jef-ferson Lab Electron-Ion Collider to restore the head-on collisions of electron and proton bunches at the interac-tion point. A prototype cavity was designed and devel-oped to demonstrate the performance of multi-cell rf-dipole structures. This paper presents the fabrication pro-cess and cold test results of the first 2-cell rf-dipole proto-type cavity.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB066

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Received ※ 18 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 30 June 2023 — Issue date ※ 21 August 2023

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WEPWB049

Multipacting in C75 Cavities

cavity, simulation, SRF, multipactoring

674

G. Ciovati, P. Dhakal, R.A. Rimmer, H. Wang, S. Wang
JLab, Newport News, Virginia, USA

Funding: This work was supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Cavities for the C75 cryomodule refurbishment program are currently being built, processed, tested and installed in the CEBAF accelerator at Jefferson Lab. They consist of 5-cell, 1497 MHz cavities with waveguide-type power coupler and for higher-order modes. Most of the cavities rf tests in a vertical cryostat at 2.07 K were limited by strong multipacting at accelerating gradients in the range 18 - 23 MV/m. A softer multipacting barrier was sometimes found at 13 - 15 MV/m. An unusual feature of the multipacting was that the barrier often shifted to a lower gradient ~17 MV/m, after multiple quenches at ~20 MV/m. This phenomenon was reproduced in a single-cell cavity of the same shape. The cavity was tested after different amounts of mechanical tuning and residual magnetic field, with no significant impact to the multipacting behavior. This contribution summarizes the experimental results from cavity rf tests, some of which were complemented by additional diagnostic instrumentation. Results from 2D and 3D simulations are also presented, indicating favorable conditions for multipacting at the equator in the range 20 - 29 MV/m.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB049

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Received ※ 15 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 01 July 2023

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WEPWB050

Exploring Innovative Pathway for SRF Cavity Fabrication

cavity, SRF, niobium, laser

680

O. Hryhorenko
JLab, Newport News, Virginia, USA
C.Z. Antoine
Université Paris-Saclay, CEA, Gif-sur-Yvette, France
T. Dohmae
KEK, Ibaraki, Japan
D. Longuevergne
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Funding: ENSAR-2 under grant agreement N° 654002. The U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
This article shows a study on an alternative pathway for the fabrication of a complete 1.3 GHz SRF cavity, aiming at improving production reliability, reducing the use of chemical polishing (EP or BCP) which is a costly and safety-critical step, and preserving surface quality after forming. Unlike the conventional pathway, the fabrication process is performed after polishing. This point is crucial as the used polishing technology could be applied only to flat geometries. The performed investigation demonstrates that damages during the fabrication process are considered minor, localized, and limited to the near-surface. Moreover, these studies confirm that the damaged layer (100-200 µm) is mainly caused by the rolling process, and not by the subsequent fabrication steps. A laser confocal microscope and SEM-EBSD technique were used to compare samples before and after forming. The preliminary results are discussed and presented in this paper.

Poster WEPWB050 [2.263 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB050

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Received ※ 20 June 2023 — Revised ※ 27 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 01 July 2023

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WEPWB051

Development of a Prototype 197 MHz Crab Cavity for the Electron-Ion Collider at JLab

cavity, GUI, niobium, HOM

685

N.A. Huque, E.F. Daly, E. Drachuk, J. Henry, M. Marchlik
JLab, Newport News, Virginia, USA
A. Castilla
JLAB, Newport News, USA
S.U. De Silva
ODU, Norfolk, Virginia, USA
B.P. Xiao
BNL, Upton, New York, USA

Thomas Jefferson National Accelerator Facility (JLab) is currently developing a prototype 197 MHz Radio-Frequency Dipole (RFD) crab cavity as part of the Electron-Ion Collider (EIC) to be built at Brookhaven National Laboratory (BNL). Cryomodules containing these cavities will be part of Hadron Storage Ring (HSR) of the EIC. The prototype cavity is constructed primarily of formed niobium sheets of thickness 4.17 mm, with machined niobium parts used as interfaces where tight tolerancing is required. The cavity¿s large size and complex features present a number of challenges in fabrication, tuning, and RF testing. Structural and forming analyses have been carried out to optimize the design and fabricated processes. An overview of the design phase and the current state of fabrication are presented in this paper.
Work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB051

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Received ※ 17 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 16 July 2023

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WEPWB053

Simulation of the Dynamics of Gas Mixtures during Plasma Processing in the C75 Cavity

cavity, plasma, simulation, SRF

696

N.K. Raut, P. Dhakal, T.D. Ganey, T. Powers
JLab, Newport News, Virginia, USA

Funding: The work is supported by SC Nuclear Physics Program through DOE SC Lab funding announcement DE-FOA-0002670 & is authored by JSA, LLC under U.S. DOE Contract No. DE-AC05- 06OR23177
Plasma processing using a mixture of noble gas and oxygen is a technique that is currently being used to reduce field emission and multipacting in accelerating cavities. Plasma is created inside the cavity when the gas mixture is exposed to an electromagnetic field that is generated by applying RF power through the fundamental power or higher-order mode couplers. Oxygen ions and atomic oxygen are created in the plasma which breaks down the hydrocarbons on the surface of the cavity and the residuals from this process are removed as part of the process gas flow. Removal of hydrocarbons from the surface increases the work function and reduces the secondary emission coefficient. This work describes the initial results of plasma simulation, which provides insight into the ignition process, distribution of different species, and interactions of free oxygen and oxygen ions with the cavity surfaces. The simulations have been done with an Ar/¿2 plasma using COMSOL® multiphysics. These simulations help in understanding the dynamics and control of plasma inside the cavity and the exploration of different gas mixtures.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB053

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Received ※ 16 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 29 June 2023

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WEPWB057

Refurbishment of an Elbe-Type Cryomodule for Coated HOM-Antenna Tests for MESA

HOM, cavity, cryomodule, niobium

709

P.S. Plattner, F. Hug, T. Stengler
KPH, Mainz, Germany

Funding: The work received funding by BMBF through 05H21UMRB1.
The Mainz Energy-Recovering Superconducting Accelerator (MESA), an energy-recovering (ER) LINAC, is currently under construction at the university Mainz. In the ER mode a continues wave (CW) beam is accelerated from 5 MeV up to 10⁵ MeV with a beam current of up to 1 mA. This current is accelerated and decelerated twice within a cavity. For future experiments, the beam current limit has to be pushed up to 10 mA. An analysis of the MESA cavities has shown that the HOM antennas quench at such high beam currents due to the extensive power deposition and the resulting heating of the HOM coupler. To avoid quenching it is necessary to use superconducting materials with higher critical temperature. For this purpose, the HOM antennas will be coated with NbTiN and Nb3SN and their properties will be investigated. For use in the accelerator, the HOM antennas will be installed in the cavities of a former ALICE cryomodule, kindly provided by STFC Daresburry. This paper will show both the status of the refurbishment of the ALICE module to suit MESA, and the coating of the HOM antennas.
The authors would like to express their sincere gratitude to STFC Daresbury for the donation of the ALICE module, which strongly supports SRF research in Mainz.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB057

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Received ※ 18 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 09 July 2023

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WEPWB064

Performance Analysis from ESS Cryomodule Testing at CEA

cavity, cryomodule, controls, 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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WEPWB084

The Interaction among Interstitial C/N/O/H and Vacancy in Niobium via First-Principles Calculation

niobium, lattice, site, cavity

778

H. Liu, J.K. Hao, Z.T. Yang
PKU, Beijing, People’s Republic of China

We calculate the interaction among zero dimensional defects in niobium lattice through first-principles calculation. And we compare the trapping effect of hydrogen among carbon, nitrogen, and oxygen as well as the trapping effect of interstitial atoms by vacancy. We find that the interstitial C/N/O have similar effect of trapping interstitial hydrogen in niobium lattice, and the vacancy can trap interstitial C/N/O/H in adjacent protocells and strengthen their chemical bond with Nb. These calculations give some explanation for improving superconducting performance of niobium cavities through medium temperature baking.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB084

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Received ※ 15 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 03 July 2023

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WEPWB089

Theoretical Model of External Q Tuning for an SRF Cavity with Waveguide Tuner

cavity, GUI, SRF, operation

794

W. Xu, Z.A. Conway, K.S. Smith, A. Zaltsman
BNL, Upton, New York, USA
E.F. Daly, J. Guo, R.A. Rimmer
JLab, Newport News, Virginia, USA

Funding: The work is supported by by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
A wide range of electron beam energies (5 ¿ 18 GeV) and beam currents (0.2 ¿ 2.5 A) in EIC Electron Storage Ring (ESR) operating scenarios requires a capability of adjusting coupling factor up to a factor of 20 for the 591 MHz Superconducting Radio Frequency (SRF) cavities, which contains two fundamental power couplers (FPC) delivering continuous wave (CW) 800 kW RF power to the beam. Currently, adjusting external Q of a SRF cavity is done by varying protrusion of FPC¿s inner conductor in beam pipe or using three stub tuner to adjust external Q value, which either has limit on tuning range or limit on operating power. This paper presents a method of tuning the FPC external Q by a multiple-waveguide tuner, which allows for high power, wide tuning range operations. The theoretical model of matching beam impedance with waveguide tuner and detailed matching conditions and limits will be presented. Follow the theoretical model, a preliminary design of a 3D waveguide tuner will be presented.
The work is supported by by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.

Poster WEPWB089 [1.269 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB089

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Received ※ 26 June 2023 — Revised ※ 27 June 2023 — Accepted ※ 19 August 2023 — Issue date ※ 22 August 2023

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WEPWB102

Recent Progress of Fundamental Power Couplers for the SHINE Project

FEL, vacuum, cryomodule, cavity

827

Z.Y. Ma, J.F. Chen, H.T. Hou, B. Liu, Y. Liu, S. Sun, D. Wang, L. Yin, M. Zhang, S.J. Zhao, Y.B. Zhao, Z.T. Zhao, X. Zheng
SARI-CAS, Pudong, Shanghai, People’s Republic of China

Funding: Project supported by Shanghai Municipal Science and Technology Major Project (Grant No.2017SHZDZX02).
The superconducting radio-frequency electron linear accelerator of the Shanghai HIgh repetition rate XFEL aNd Extreme light facility (SHINE) contains 610 1.3 GHz fundamental power couplers which are assembled in 77 superconducting cryomodules used for beam acceleration, and 16 3.9 GHz fundamental power couplers, which are assembled in two third harmonic superconducting cryomodules used for linearizing the longitudinal phase space. The first batch of 26 1.3 GHz coupler prototypes and two 3.9 GHz coupler prototypes have been fabricated from three domestic manufacturers for basic research. Several key manufacturing processes have been developed and qualified, including high residual resistivity ratio (RRR) copper plating, vacuum brazing of ceramic windows, electron beam welding and titanium nitride coating. All the 1.3 GHz coupler prototypes have been power conditioned with 14 kW travelling wave (TW) and 7 kW standing wave (SW) RF in continuous-wave (CW) mode. Even higher power levels have been demonstrated with 20 kW TW and 10 kW SW RF, which indicates their robustness. Both 3.9 GHz coupler prototypes have been power conditioned with 2.2 kW TW and 2 kW SW RF in CW mode.

Poster WEPWB102 [2.361 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB102

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Received ※ 16 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 05 July 2023

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WEPWB104

RF Conditioning of MYRRHA Couplers at IJCLab

vacuum, cavity, FEL, multipactoring

835

N. ElKamchi, S. Berthelot, P. Duchesne, C. Joly, W. Kaabi, C. Magueur
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
Y. Gómez Martínez
LPSC, Grenoble Cedex, France
C. Lhomme
IJCLab, ORSAY, France

Multi-purpose hYbrid Research Reactor for High-tech Applications (MYRRHA) is an experimental accelerator-driven system in development at SCK•CEN. It will allow fuel developments, material developments for GEN IV systems, material developments for fusion reactors and radioisotope production for medical and industrial applications1. The IJCLab has in charge the industrial monitoring, the quality control and the RF conditioning of the power couplers up to 80KW at 352Mhz. This paper presents the conditioning bench adapted from the successful experience of IJCLab in the conditioning of the XFEL couplers2. The results of the conditioning of prototype couplers are described and discussed.
1. Abderrahim, P. MYRRHA a multi-purpose hybrid research reactor for high-tech applications. United States: N. p., 2012. Web
2. H. Guler, Proceedings of IPAC2016, Busan, Korea

Poster WEPWB104 [0.875 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB104

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Received ※ 26 June 2023 — Revised ※ 27 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 08 August 2023

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WEPWB105

Improved Study of the Multipactor Phenomenon for the MYRRHA 80 kW CW RF Couplers

multipactoring, coupling, linac, cavity

838

Y. Gómez Martínez, P.-O. Dumont
LPSC, Grenoble Cedex, France
P. Duchesne, N. ElKamchi, C. Joly, W. Kaabi
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
C. Lhomme
IJCLab, ORSAY, France
C. Lhomme
ACS, Orsay, France

MYRRHA (Multi Purpose Hybrid Reactor for High Tech Applications) is an Accelerator Driven System (ADS) project. Its superconducting linac will provide a 600 MeV - 4 mA proton beam. The first project phase based on a 100 MeV linac is launched. The Radio-Frequency (RF) couplers have been designed to handle 80 kW CW (Continuous Wave) at 352.2 MHz. This paper describes the multipactor studies on the coupler when it does not work in the nominal configuration without reflected power.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB105

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Received ※ 18 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 12 July 2023

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WEPWB113

Evaluation of Photo-Cathode Port Multipacting in the SRF Photo-Injector Cryomodule for the LCLS-II High-Energy Upgrade

cathode, simulation, SRF, experiment

859

Z.Y. Yin, W. Hartung, S.H. Kim, T. Konomi, T. Xu
FRIB, East Lansing, Michigan, USA

The high-energy upgrade of the Linac Coherent Light Source (LCLS-II-HE) will increase the photon energy and brightness. A low-emittance injector (LEI) was proposed to increase the photon flux for high X-ray energies. FRIB, HZDR, Argonne, and SLAC are developing a 185.7 MHz superconducting radio-frequency photo-injector (SRF-PI) cryomodule for the LEI. The photo-cathode system requirements are challenging, as cathodes must be maintained at the desired temperature, precisely aligned, and operated without multipacting (MP); to avoid field emission, cathode exchange must be particulate-free. A support stalk has been designed to hold the cathode in position under these requirements. A DC bias is used to inhibit MP. We simulated MP for various surface conditions and bias levels. An RF/DC test was developed to evaluate the cathode stalk performance as a subsystem and to identify and correct issues before assembly into the full cryomodule. The RF/DC test makes use of a resonant coaxial line to generate an RF magnetic field similar to that of the cathode-in-SRF-PI-cavity case. High-power test results will be presented and compared to the MP simulations.
* Work supported by the Department of Energy Contract DE-AC02-76SF00515

Poster WEPWB113 [1.410 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB113

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Received ※ 20 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 26 July 2023

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WEPWB116

The Influence of Sample Preparation, Soak Time, and Heating Rate on Measured Recrystallization of Deformed Polycrystalline Niobium

cavity, ECR, niobium, SRF

863

Z.L. Thune
MSU, East Lansing, USA
T.R. Bieler
Michigan State University, East Lansing, Michigan, USA

Funding: DOE/OHEP (Grant Number: DE-SC0009960)
Improving accelerator performance relies on consistent production of high-purity niobium superconducting radiofrequency (SRF) cavities. Current production uses an 800 °C 3 hr heat treatment, but 900-1000 °C can improve cavity performance via recrystallization (Rx) and grain growth. As Rx is thermally activated, increasing the temperature and/or the heating rate could facilitate a reduction in geometrically necessary dislocation (GND) density that is associated with the degradation of cavity performance via trapped magnetic flux. Recent work shows that increasing the annealing temperature increased the Rx fraction in cold-rolled polycrystalline niobium. However, the influence of heating rate on the extent of Rx was minimal with a 3 hr soak time. To further assess the influence of heating rate on measured Rx, as well as the effects of sample preparation, electron backscatter diffraction (EBSD) was used to quantify the extent of Rx on samples annealed at a single temperature with different soak times. Comparing samples with different surface preparation shows that pinned grain boundaries on the free surface reveal a much smaller grain size than below the surface.
* Z.L. Thune et al., "The Influence of Strain Path and Heat Treatment Variations on Recrystallization in Cold-Rolled High-Purity Niobium Polycrystals," doi: 10.1109/TASC.2023.3248533.

Poster WEPWB116 [1.312 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB116

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Received ※ 23 June 2023 — Revised ※ 26 June 2023 — Accepted ※ 20 August 2023 — Issue date ※ 21 August 2023

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WEPWB127

Investigation of Coupler Breakdown Thresholds for Plasma Processing of FRIB Quarter-Wave Resonators with Fundamental and Higher-Order Modes

cavity, plasma, HOM, simulation

893

P.R. Tutt, W. Hartung, S.H. Kim, T. Xu
FRIB, East Lansing, Michigan, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics and used resources of the Facility for Rare Isotope Beams (FRIB) under Award Number DE-SC0000661.
FRIB is developing plasma processing techniques for in-situ recovery of cavity performance in linac cryomodules during long-term user operation. While plasma processing has been shown to be effective for high-frequency (0.8 - 1.5 GHz) elliptical cavities, one of the challenges for FRIB is to avoid plasma breakdown in the fundamental input coupler (FPC), which has relatively weak coupling strength (Q_ext ranging from 2E6 to 1E7). FRIB cavities are not equipped with higher-order-mode (HOM) couplers; however, in preliminary tests, we found that HOMs are suitable for plasma processing of FRIB Quarter-Wave Resonators (QWRs) driven via the FPC. In this study, we investigated plasma breakdown thresholds in the fundamental and the first 2 HOMs for the FRIB β = 0.085 QWRs. Electric field distributions in the FPC region and cavity region were calculated for the room-temperature case using CST Microwave Studio’s frequency domain solver (FDS). Simulation results will be presented, with comparison of breakdown thresholds inferred from the RF modeling to the experimental results.

Poster WEPWB127 [5.068 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB127

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Received ※ 19 June 2023 — Revised ※ 27 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 11 August 2023

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THIAA01

Development of 3.9 GHz 9-Cell Cavities at SHINE

cavity, linac, FEL, laser

921

X.W. Wu
Zhangjiang Lab, Shanghai, People’s Republic of China
J.F. Chen, P.C. Dong, Y.F. Liu, X.H. Ouyang, S. Sun, J.N. Wu, S. Xing, Y.X. Zhang, S.J. Zhao, Y.L. Zhao
SARI-CAS, Pudong, Shanghai, People’s Republic of China
X. Huang, Z. Wang, Y. Zong
SINAP, Shanghai, People’s Republic of China
Y.W. Huang, R.Z. Xia
ShanghaiTech University, Shanghai, People’s Republic of China

The Shanghai high-repetition-rate XFEL and extreme light facility (SHINE) Linac requires two 3.9~GHz crymodules to linearize energy distribution before the bunch compressor. As a key component to the project, studies of 3.9~GHz cavities were conducted in the past few years. The first 3.9~GHz 9-cell prototype cavity has been fabricated, tested, and qualified. It reached Q₀=3.5×10⁹ at 13.1~MV/m and a maximum accelerating gradient of 25.0~MV/m during the vertical test of the bare cavity. The prototype has been helium tank integrated and reached Q₀=2.9×10⁹ at 13.1~MV/m in the vertical test, with a large margin with respect to the SHINE specification. The second prototype has been fabricated and is planned to be tested in 2023. This paper will cover the fabrication, surface treatment, and RF test of the 3.9~GHz cavities.

Slides THIAA01 [7.573 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-THIAA01

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Received ※ 19 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 18 July 2023

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FRIBA02

Instrumentation for High Performance Cavities and Cryomodule Field Emission Analysis

cavity, radiation, neutron, simulation

978

G. Devanz
CEA-IRFU, Gif-sur-Yvette, France
M. Baudrier, E. Cenni, L. Maurice, O. Piquet
CEA-DRF-IRFU, France

Field emission (FE) is one of the main reasons for the degradation of accelerator cryomodules, as field emitted current tends to become more severe during the beam operation. It is essential to better understand how this phenomenon is generated and evolves from the SRF cavity preparation in the clean room, through their assembly in the cryomodule until their final test and operation. Due to the shielding environment of a cavity in its vertical test stand, or the architecture of a cryomodule, the more faint radiation occurring at the FE onset remains undetected. More precise diagnostic and analysis tools are required to gain more information. We present the developpement of dedicated time-resolved detectors for the FE radiation which aim at improving its coverage in terms of solid angle and lower energy threshold sensitivity. We approach this topic through detailed simulation based on the Geant4 toolkit in order to analyse the interaction of FE radiation with the cavity environement and optimize the detectors with respect to their application in cryomodule or vertical test stands. We illustrate by analysing recent cryomodule experimental test data.

Slides FRIBA02 [9.606 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-FRIBA02

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Received ※ 27 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 05 July 2023 — Issue date ※ 09 July 2023

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