SRF2023 - List of Keywords (HOM)

Paper	Title	Other Keywords	Page
MOIXA05	Operating Experience of SRF System at High Beam Current in SuperKEKB	cavity, operation, SRF, luminosity	38
	M. Nishiwaki, K. Akai, T. Furuya, S. Mitsunobu, Y. Morita, T. Okada KEK, Ibaraki, Japan
	SuperKEKB aims for high luminosity on the order of 10³⁵ cm^-2s^-1 with beam currents of 2.6 A for electron and 3.6 A for positron to search new physics beyond the Standard Model in the B meson regime. In recent operations, we achieved a new record of luminosity of 4.65×10³⁴ cm^-2s^-1 with 1.1 A for electron and 1.3 A for positron. The SRF system that was designed for KEKB, the predecessor of SuperKEKB, is operating stably with the high beam currents owing to the measures against the large beam powers and the large higher-order-mode (HOM) powers. As a measure against the large beam powers, our SRF cavities have increased a coupling of high-power input couplers during the KEKB operation. As a measure against the large HOM power, newly developed SiC HOM dampers have been installed in the SuperKEKB ring. In addition, we have established the horizontal high-pressure rinse method to recover the cavity performance that has degraded due to vacuum works and accidents in the long-term operation. In this report, we will present our operation experience of SRF system under the high beam currents.
	Slides MOIXA05 [3.450 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOIXA05
About •	Received ※ 19 June 2023 — Revised ※ 21 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 20 July 2023
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MOPMB016	Successful Al₂O₃ Coating of Superconducting Niobium Cavities by Thermal ALD	cavity, niobium, SRF, experiment	104
	G.K. Deyu, W. Hillert, M. Wenskat University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany R.H. Blick, I. González Díaz-Palacio, R. Zierold University of Hamburg, Hamburg, Germany
	Funding: This work is supported by the BMBF under the research Grant 05K19GUB. Al₂O₃ is one of the potential insulator materials in the superconductor-insulator-superconductor (SIS) multilayer coatings of superconducting radio-frequency (SRF) cavities for pushing their performance limits. We report on the successful coating of two 1.3 GHz Tesla-shaped SRF cavities with 18 nm and 36 nm layers of Al₂O₃ deposited by thermal atomic layer deposition (ALD). The coating recipe was developed by thermal atomic layer deposition (ALD). The coating recipe was optimized with respect to different the applied process parameters such as exposure and purge times, substrate temperature and flow rates. After a proof-of-principle Al₂O₃ coating of a cavity, second the cavity maintained its maximum achievable accelerating field of more than 40 MV/m and no deterioration was observed [1]. On the contrary, an improvement of the surface resistance above 10 MV/m has been observed, which is now further under investigation. [1].Wenskat, Marc, et al. "Successful Al₂O₃ coating of superconducting niobium cavities with thermal ALD." Superconductor Science and Technology 36.1 (2022): 015010.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB016
About •	Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 28 June 2023
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MOPMB068	Loading Test of Hom Dampers for Superconducting Cavities for High Current at Superkekb	cavity, SRF, superconducting-cavity, operation	271
	T. Okada, K. Akai, T. Furuya, S. Mitsunobu, Y. Morita, M. Nishiwaki KEK, Ibaraki, Japan
	SuperKEKB is an e⁻e⁺ collider, which is an upgraded accelerator of KEKB with the aim to increase the luminosity by more than one order. The superconducting cavities are used in the electron ring. The superconducting cavities were designed as a HOM-damped structure for KEKB and were operated up to 1.4 A in KEKB. However, the design storage current of the electron ring for SuperKEKB is 2.6 A, which is about twice the achievement current of KEKB. The HOM power is estimated to increase from 16 kW, which is the performance value in KEKB, to over 35 kW. This large load is unacceptable for the ferrite HOM dampers mounted on both sides of the cavity. As a countermeasure, duct type SiC HOM dampers are inserted between the cavities. The HOM damper load tests were performed during normal beam operation with a maximum current of 1.1 A. The load on the downstream ferrite HOM damper decreased due to the HOM power absorbed by the upstream SiC damper. In addition, the load was found to be dependent on the beam filling pattern. We will present the results and discussion of beam tests on the loading of HOM dampers and the dependence on the beam filling pattern in SuperKEKB.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB068
About •	Received ※ 18 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 30 June 2023
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MOPMB078	Design and Prototyping of the Electron Ion Collider Electron Storage Ring SRF Cavity	cavity, simulation, operation, electron	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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TUPTB044	Compact Multicell Superconducting Crab Cavity for ILC	cavity, impedance, dipole, SRF	521
	A. Lunin, S.A. Belomestnykh, I.V. Gonin, T.N. Khabiboulline, Y.M. Orlov, V. Poloubotko, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	Funding: Work supported by the Fermi National Accelerator Laboratory; managed by Fermi Research Alliance, LLC under Contract No. DEAC02-07CH11359 with the U.S. Department of Energy We propose a novel design of a deflecting cavity for the ILC project with low parasitic HOM losses and preserving the beam emittance, which is critical for operation with high beam current intensity. Multiple electrodes immersed in the hollow waveguide form a trapped-mode resonator. The transverse components of the electromagnetic field of the trapped dipole mode induce a transverse kick and efficiently deflect charged particles passing through the cavity. We present a scalable design of a superconducting Quasi-waveguide Multicell Resonator (QMiR) seamlessly connected with a beam vacuum chamber. The cavity is completely open at both ends, which significantly reduces the maximum loaded quality factor of the higher order modes (HOM), avoids complex HOM couplers and thus simplifies the mechanical design of the cavity. The same port is used to feed RF power to the operating mode and to extract the same order modes (SOM). Finally, we estimate the expected cryogenic losses, HOM impedance limits, RF input power required, and frequency tuning for a QMiR cavity designed to operate at 2.6 GHz.
	Poster TUPTB044 [6.975 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB044
About •	Received ※ 19 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 16 July 2023
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TUPTB046	Development and Performance of RFD Crab Cavity Prototypes for HL-LHC AUP	cavity, impedance, niobium, higher-order-mode	531
	L. Ristori, P. Berrutti, M. Narduzzi Fermilab, Batavia, Illinois, USA A. Castilla JLAB, Newport News, USA S.U. De Silva, J.R. Delayen ODU, Norfolk, Virginia, USA N.A. Huque JLab, Newport News, Virginia, USA Z. Li, A. Ratti SLAC, Menlo Park, California, USA
	Funding: Operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE The US will be contributing to the HL-LHC upgrade at CERN with the fabrication and qualification of RFD crabbing cavities in the framework of the HL-LHC Accelerator Upgrade Project (AUP) managed by Fermilab. AUP received Critical Decision 3 (CD-3) approval by DOE in December 2020 launching the project into the production phase. The electro-magnetic design of the cavity was inherited from the LHC Accelerator Research Program (LARP) but needed to be revised to meet new project requirements and to prevent issues encountered during beam tests performed at CERN in the R&D phase. Two prototype cavities were manufactured in industry and cold tested. Challenges specific to the RFD cavity were the stringent interface tolerances, the pole symmetry and the higher-order-mode impedance spectrum. Chemical processing and heat treatments were performed initially at FNAL/ANL and are now being transferred to industry for the production phase. HOM dampers are manufactured and validated by JLAB. A summary of cold test results with and without HOM dampers is presented.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB046
About •	Received ※ 20 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 11 July 2023
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TUPTB068	EIC 197 MHz Crab Cavity RF Optimization	cavity, multipactoring, GUI, impedance	584
	Z. Li SLAC, Menlo Park, California, USA S.U. De Silva, J.R. Delayen ODU, Norfolk, Virginia, USA R.A. Rimmer JLab, Newport News, Virginia, USA Q. Wu, B.P. Xiao, W. Xu BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under U.S. DOE K No. DE-SC0012704, by Jefferson Science Associates, LLC under U.S. DOE K No. DE-SC0002769, and by DOE K No. DE-AC02-76SF00515. Crab cavities, operating at 197 MHz and 394 MHz respectively, will be used to compensate the loss of luminosity due to a 25 mrad crossing angle at the interaction point in the Electron Ion Collider (EIC). Both crab cavities are of the RF Dipole (RFD) shape. To meet the machine design requirements, there are a few important cavity design considerations that need to be addressed. First, to achieve stable cavity operation at the design voltages, cavity geometry details must be optimized to suppress potential multipacting. Incorporating strong HOM damping in the cavity design is required for the beam stability and quality. Furthermore, due to the finite pole width, the multipole fields, especially the sextupole and the decapole terms, need to be minimized to maintain an acceptable beam dynamic aperture. This paper will present the RF optimization details of the 197 MHz cavity.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB068
About •	Received ※ 16 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 03 July 2023 — Issue date ※ 08 July 2023
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WEPWB047	Higher Order Mode Analysis of a 915 MHz 2-Cell Cavity for a Prototype Industrial Accelerator	cavity, impedance, SRF, higher-order-mode	667
	A. Castilla JLAB, Newport News, USA G. Ciovati, J. Guo, G.-T. Park, R.A. Rimmer, H. Vennekate JLab, Newport News, Virginia, USA
	A possible solution to reduce the complexity posed by the cryogenic systems in a superconducting RF accelerator for industrial applications, is to capitalize on the advances achieved by the Nb₃Sn superconducting RF technology, as well as the feasibility of a reliable 4 K cooling system, based on commercial cryocoolers. Following this philosophy, the conceptual design for a prototype, conduction-cooled, 4 MeV, 20 kW SRF electron linac, is being developed at Jefferson Lab. Such design is based on a 915 MHz two-cell Nb₃Sn cavity. In this contribution, we present the proposed cavity design, including the fundamental power coupler, and the preliminary analysis of the Higher Order Modes, using numerical simulations to estimate the potentially dangerous modes as a starting point to evaluate the requirements for damping for reliable operations with a cryocooler. Finally, different methods to calculate the Higher Order Modes’ Impedances are briefly discussed.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB047
About •	Received ※ 25 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 04 July 2023 — Issue date ※ 16 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, electron	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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WEPWB054	In Situ Plasma Processing of Superconducting Cavities at JLab, 2023 Update	cavity, plasma, cryomodule, radiation	701
	T. Powers, N.C. Brock, T.D. Ganey JLab, Newport News, Virginia, USA
	Jefferson Lab has an ongoing R&D program in plasma processing which just completed a round of production processing in the CEBAF accelerator. Plasma processing is a common technique for removing hydrocarbons from surfaces, which increases the work function and reduces the secondary emission coefficient. Unlike helium processing which relies on ion bombardment of the field emitters, plasma processing uses free oxygen produced in the plasma to break down the hydrocarbons on the surface of the cavity. The initial focus of the effort was processing C100 cavities by injecting RF power into the HOM coupler ports. Results from processing cryomodules in the CEBAF accelerator as well as vertical test results will be presented. The goal will be to improve the operational gradients and the energy margin of the linacs. This work will describe the systems and methods used at JLAB for processing cavities using an argon-oxygen gas mixture as well as a helium-oxygen gas mixture. Before and after plasma processing results will also be presented. Funding provided by SC Nuclear Physics Program through DOE SC Lab funding announcement DE-FOA-0002670.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB054
About •	Received ※ 18 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 01 July 2023
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WEPWB057	Refurbishment of an Elbe-Type Cryomodule for Coated HOM-Antenna Tests for MESA	cavity, cryomodule, electron, 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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WEPWB061	Pre-Installation Performance of the RHIC 56 MHz Superconducting System	cryomodule, operation, coupling, cavity	718
	Z.A. Conway, R. Anderson, J.C. Brutus, K. Hernandez, D. Holmes, K. Mernick, G. Narayan, S. Polizzo, S.K. Seberg, F. Severino, M. Sowinski, R. Than, Q. Wu, B.P. Xiao, W. Xu, A. Zaltsman BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under contract No. DE-SC0012704 with the U.S. Department of Energy. Pre-installation test results for the RHIC 56 MHz superconducting RF system are presented here. The 56 MHz quarter-wave resonator achieved a stable accelerating potential of 1.1 MV with 13 W of RF loss at 4.5 K demonstrating its viability for increasing the luminosity of sPHENIX collisions. The new 120 kW travelling wave fundamental mode damper and dual 6 kW combined-function fundamental power couplers perform as expected at 3 kW but remain to be operated with the expected ~40 times greater power achievable with the RHIC sPHENIX beams.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB061
About •	Received ※ 15 June 2023 — Revised ※ 26 June 2023 — Accepted ※ 02 July 2023 — Issue date ※ 17 July 2023
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WEPWB103	Simulations and First RF Measurements of Coaxial HOM Coupler Prototypes for PERLE SRF Cavities	cavity, damping, coupling, simulation	831
	C. Barbagallo, P. Duchesne, W. Kaabi, G. Olivier, G. Olry, S. Roset, Z.F. Zomer Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France B.S. Barriere, C.S. Clement, R.L.A. Gerard, F. Gerigk, P.M. Maurin CERN, Meyrin, Switzerland J. Henry, S.A. Overstreet, G.-T. Park, R.A. Rimmer, H. Wang JLab, Newport News, Virginia, USA
	Superconducting Radio-Frequency (SRF) linac cryomodules are foreseen for the high-current multi-turn energy recovery linac PERLE (Powerful Energy Recovery Linac for Experiments). Coaxial higher order mode (HOM) couplers are the primary design choice to absorb beam-induced power and avoid beam instabilities. We have used 3D-printed and copper-coated HOM couplers for the prototyping and bench RF measurements on the copper PERLE cavities. We have started a collaboration with JLab and CERN on this effort. This paper presents electromagnetic simulations of the cavity HOM-damping performance on those couplers. Bench RF measurements of the HOMs on an 801.58 MHz 2-cell copper cavity performed at JLab are detailed. The results are compared to eigenmode simulations in CST to confirm the design. RF-thermal simulations are conducted to investigate if the studied HOM couplers undergo quenching.
	Poster WEPWB103 [1.533 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB103
About •	Received ※ 18 June 2023 — Revised ※ 26 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 02 July 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, electron, 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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THIAA02	RF Performance Results of RF Double Quarter Wave Resonators for LHC High Luminosity Project	cavity, luminosity, vacuum, radiation	925
	K. Turaj, J. Bastard, R. Calaga, S.J. Calvo, O. Capatina, A. Castilla, M. Chiodini, C. Duval, A.V. Edwards, L.M.A. Ferreira, M. Gourragne, P. Kohler, E. Montesinos, C. Pasquino, G. Pechaud, N. Stapley, N. Valverde Alonso, J.D. Walker CERN, Meyrin, Switzerland A. Castilla JLAB, Newport News, USA A.V. Edwards Lancaster University, Lancaster, United Kingdom
	The LHC High Luminosity (HL-LHC) project includes, among other key items, the installation of superconducting crab cavities in the LHC machine. The Double Quarter Wave (DQW) crab cavity will be utilised to compensate for the effects of the vertical crossing angle. Two bare DQW series cavities were manufactured in Germany by RI Research Instruments and validated successfully at CERN through a cold test at 2K. Two DQW series cavities were produced in-house at CERN, integrated into a titanium helium tank, and equipped with RF ancillaries. This paper addresses the cavities preparation processes and summarizes the results of cryogenic tests of DQW cavities at CERN
	Slides THIAA02 [10.840 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-THIAA02
About •	Received ※ 16 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 01 July 2023
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THIXA01	Investigation of Plasma Processing for Coaxial Resonators	plasma, cavity, SRF, coupling	960
	W. Hartung, W. Chang, K. Elliott, S.H. Kim, T. Konomi, K. Saito, P.R. Tutt, T. Xu FRIB, East Lansing, Michigan, USA
	Plasma processing has been investigated by several facilities as a method to mitigate degradation of SRF cavity performance. It provides an alternative to removal and disassembly of cryomodules for refurbishment of each cavity via repeat etching and rinsing. Promising results have been obtained by several groups. Studies of plasma processing for quarter-wave resonators (QWRs) and half-wave resonators (HWRs) were undertaken at FRIB, where a total of 324 such resonators are presently in operation. Plasma ignition and optimization measurements were done with room-temperature-matched input couplers. Plasma cleaning tests were done on several QWRs using the fundamental power coupler (FPC) to drive the plasma. We investigated the usefulness of higher-order modes (HOMs) to drive the plasma. HOMs allow for less mismatch at the FPC and hence lower field in the coupler relative to the cavity. Before-and-after cold tests showed a significant reduction in field emission X-rays with judicious application of plasma processing.
	Slides THIXA01 [2.060 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-THIXA01
About •	Received ※ 01 September 2023 — Accepted ※ 02 September 2023 — Issue date ※ 02 September 2023
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FRIBA03	Heavily Damped Crab Cavities for High Luminosity Collisions	cavity, GUI, impedance, collider	986
	B.P. Xiao BNL, Upton, New York, USA S.U. De Silva ODU, Norfolk, Virginia, USA
	Funding: Work supported by BSA under U.S. DOE contract No. DE-SC0012704, by JSA under U.S. DOE Contract No. DE-SC0002769, and by DOE Contract No. DE-AC02-76SF00515. Next generation colliders require crab cavities to mitigate parasitic collisions caused by finite crossing angle for luminosity leveling and detector data pile up reduction. The Electron Ion Collider (EIC) crab cavity designs will be introduced as an example to fulfill the geometrical constraints, crabbing voltages, multipole components, Higher Order Mode (HOM) power and impedance budgets. Operational challenges such as tuning, high gain low delay control loop, amplitude and phase noises control will be discussed.
	Slides FRIBA03 [3.666 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-FRIBA03
About •	Received ※ 19 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 06 July 2023
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FRIBA04	Crab Cavities for ILC	cavity, SRF, operation, impedance	990
	P.A. McIntosh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom S.A. Belomestnykh, I.V. Gonin, T.N. Khabiboulline, A. Lunin, Y.M. Orlov, V.P. Yakovlev Fermilab, Batavia, Illinois, USA G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom R. Calaga CERN, Meyrin, Switzerland S.U. De Silva JLab, Newport News, Virginia, USA J.R. Delayen ODU, Norfolk, Virginia, USA T. Okugi, A. Yamamoto KEK, Ibaraki, Japan S. Verdú-Andrés, B.P. Xiao BNL, Upton, New York, USA
	For the 14 mrad crossing angle proposed, crab cavity systems are fundamentally anticipated for the viable operation of the International Linear Collider (ILC), in order to maximise its luminosity performance. Since 2021, a specialist development team have been defining optimum crab cavity technologies which can fulfil the operational requirements for ILC, both for its baseline centre-of-mass energy of 250 GeV, but also extending those requirements out to higher beam collision intensities. Five design teams have established crab cavity technology solutions, which have the capability to also operate up to 1 TeV centre-of-mass. This presentation showcases the key performance capabilities of these designs and their associated benefits for both manufacture and integration into the ILC Interaction Region. The recommended outcome of the recently conducted crab cavity technology down-selection, will also be highlighted.
	Slides FRIBA04 [2.526 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-FRIBA04
About •	Received ※ 19 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 20 July 2023
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Paper

Title

Other Keywords

Page

MOIXA05

Operating Experience of SRF System at High Beam Current in SuperKEKB

cavity, operation, SRF, luminosity

38

M. Nishiwaki, K. Akai, T. Furuya, S. Mitsunobu, Y. Morita, T. Okada
KEK, Ibaraki, Japan

SuperKEKB aims for high luminosity on the order of 10³⁵ cm^-2s^-1 with beam currents of 2.6 A for electron and 3.6 A for positron to search new physics beyond the Standard Model in the B meson regime. In recent operations, we achieved a new record of luminosity of 4.65×10³⁴ cm^-2s^-1 with 1.1 A for electron and 1.3 A for positron. The SRF system that was designed for KEKB, the predecessor of SuperKEKB, is operating stably with the high beam currents owing to the measures against the large beam powers and the large higher-order-mode (HOM) powers. As a measure against the large beam powers, our SRF cavities have increased a coupling of high-power input couplers during the KEKB operation. As a measure against the large HOM power, newly developed SiC HOM dampers have been installed in the SuperKEKB ring. In addition, we have established the horizontal high-pressure rinse method to recover the cavity performance that has degraded due to vacuum works and accidents in the long-term operation. In this report, we will present our operation experience of SRF system under the high beam currents.

Slides MOIXA05 [3.450 MB]

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reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOIXA05

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Received ※ 19 June 2023 — Revised ※ 21 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 20 July 2023

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MOPMB016

Successful Al₂O₃ Coating of Superconducting Niobium Cavities by Thermal ALD

cavity, niobium, SRF, experiment

104

G.K. Deyu, W. Hillert, M. Wenskat
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
R.H. Blick, I. González Díaz-Palacio, R. Zierold
University of Hamburg, Hamburg, Germany

Funding: This work is supported by the BMBF under the research Grant 05K19GUB.
Al₂O₃ is one of the potential insulator materials in the superconductor-insulator-superconductor (SIS) multilayer coatings of superconducting radio-frequency (SRF) cavities for pushing their performance limits. We report on the successful coating of two 1.3 GHz Tesla-shaped SRF cavities with 18 nm and 36 nm layers of Al₂O₃ deposited by thermal atomic layer deposition (ALD). The coating recipe was developed by thermal atomic layer deposition (ALD). The coating recipe was optimized with respect to different the applied process parameters such as exposure and purge times, substrate temperature and flow rates. After a proof-of-principle Al₂O₃ coating of a cavity, second the cavity maintained its maximum achievable accelerating field of more than 40 MV/m and no deterioration was observed [1]. On the contrary, an improvement of the surface resistance above 10 MV/m has been observed, which is now further under investigation.
[1].Wenskat, Marc, et al. "Successful Al₂O₃ coating of superconducting niobium cavities with thermal ALD." Superconductor Science and Technology 36.1 (2022): 015010.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB016

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Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 28 June 2023

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MOPMB068

Loading Test of Hom Dampers for Superconducting Cavities for High Current at Superkekb

cavity, SRF, superconducting-cavity, operation

271

T. Okada, K. Akai, T. Furuya, S. Mitsunobu, Y. Morita, M. Nishiwaki
KEK, Ibaraki, Japan

SuperKEKB is an e⁻e⁺ collider, which is an upgraded accelerator of KEKB with the aim to increase the luminosity by more than one order. The superconducting cavities are used in the electron ring. The superconducting cavities were designed as a HOM-damped structure for KEKB and were operated up to 1.4 A in KEKB. However, the design storage current of the electron ring for SuperKEKB is 2.6 A, which is about twice the achievement current of KEKB. The HOM power is estimated to increase from 16 kW, which is the performance value in KEKB, to over 35 kW. This large load is unacceptable for the ferrite HOM dampers mounted on both sides of the cavity. As a countermeasure, duct type SiC HOM dampers are inserted between the cavities. The HOM damper load tests were performed during normal beam operation with a maximum current of 1.1 A. The load on the downstream ferrite HOM damper decreased due to the HOM power absorbed by the upstream SiC damper. In addition, the load was found to be dependent on the beam filling pattern. We will present the results and discussion of beam tests on the loading of HOM dampers and the dependence on the beam filling pattern in SuperKEKB.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB068

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Received ※ 18 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 30 June 2023

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MOPMB078

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

cavity, simulation, operation, electron

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]

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

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

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TUPTB044

Compact Multicell Superconducting Crab Cavity for ILC

cavity, impedance, dipole, SRF

521

A. Lunin, S.A. Belomestnykh, I.V. Gonin, T.N. Khabiboulline, Y.M. Orlov, V. Poloubotko, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Funding: Work supported by the Fermi National Accelerator Laboratory; managed by Fermi Research Alliance, LLC under Contract No. DEAC02-07CH11359 with the U.S. Department of Energy
We propose a novel design of a deflecting cavity for the ILC project with low parasitic HOM losses and preserving the beam emittance, which is critical for operation with high beam current intensity. Multiple electrodes immersed in the hollow waveguide form a trapped-mode resonator. The transverse components of the electromagnetic field of the trapped dipole mode induce a transverse kick and efficiently deflect charged particles passing through the cavity. We present a scalable design of a superconducting Quasi-waveguide Multicell Resonator (QMiR) seamlessly connected with a beam vacuum chamber. The cavity is completely open at both ends, which significantly reduces the maximum loaded quality factor of the higher order modes (HOM), avoids complex HOM couplers and thus simplifies the mechanical design of the cavity. The same port is used to feed RF power to the operating mode and to extract the same order modes (SOM). Finally, we estimate the expected cryogenic losses, HOM impedance limits, RF input power required, and frequency tuning for a QMiR cavity designed to operate at 2.6 GHz.

Poster TUPTB044 [6.975 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB044

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Received ※ 19 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 16 July 2023

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TUPTB046

Development and Performance of RFD Crab Cavity Prototypes for HL-LHC AUP

cavity, impedance, niobium, higher-order-mode

531

L. Ristori, P. Berrutti, M. Narduzzi
Fermilab, Batavia, Illinois, USA
A. Castilla
JLAB, Newport News, USA
S.U. De Silva, J.R. Delayen
ODU, Norfolk, Virginia, USA
N.A. Huque
JLab, Newport News, Virginia, USA
Z. Li, A. Ratti
SLAC, Menlo Park, California, USA

Funding: Operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE
The US will be contributing to the HL-LHC upgrade at CERN with the fabrication and qualification of RFD crabbing cavities in the framework of the HL-LHC Accelerator Upgrade Project (AUP) managed by Fermilab. AUP received Critical Decision 3 (CD-3) approval by DOE in December 2020 launching the project into the production phase. The electro-magnetic design of the cavity was inherited from the LHC Accelerator Research Program (LARP) but needed to be revised to meet new project requirements and to prevent issues encountered during beam tests performed at CERN in the R&D phase. Two prototype cavities were manufactured in industry and cold tested. Challenges specific to the RFD cavity were the stringent interface tolerances, the pole symmetry and the higher-order-mode impedance spectrum. Chemical processing and heat treatments were performed initially at FNAL/ANL and are now being transferred to industry for the production phase. HOM dampers are manufactured and validated by JLAB. A summary of cold test results with and without HOM dampers is presented.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB046

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Received ※ 20 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 11 July 2023

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TUPTB068

EIC 197 MHz Crab Cavity RF Optimization

cavity, multipactoring, GUI, impedance

584

Z. Li
SLAC, Menlo Park, California, USA
S.U. De Silva, J.R. Delayen
ODU, Norfolk, Virginia, USA
R.A. Rimmer
JLab, Newport News, Virginia, USA
Q. Wu, B.P. Xiao, W. Xu
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under U.S. DOE K No. DE-SC0012704, by Jefferson Science Associates, LLC under U.S. DOE K No. DE-SC0002769, and by DOE K No. DE-AC02-76SF00515.
Crab cavities, operating at 197 MHz and 394 MHz respectively, will be used to compensate the loss of luminosity due to a 25 mrad crossing angle at the interaction point in the Electron Ion Collider (EIC). Both crab cavities are of the RF Dipole (RFD) shape. To meet the machine design requirements, there are a few important cavity design considerations that need to be addressed. First, to achieve stable cavity operation at the design voltages, cavity geometry details must be optimized to suppress potential multipacting. Incorporating strong HOM damping in the cavity design is required for the beam stability and quality. Furthermore, due to the finite pole width, the multipole fields, especially the sextupole and the decapole terms, need to be minimized to maintain an acceptable beam dynamic aperture. This paper will present the RF optimization details of the 197 MHz cavity.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB068

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Received ※ 16 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 03 July 2023 — Issue date ※ 08 July 2023

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WEPWB047

Higher Order Mode Analysis of a 915 MHz 2-Cell Cavity for a Prototype Industrial Accelerator

cavity, impedance, SRF, higher-order-mode

667

A. Castilla
JLAB, Newport News, USA
G. Ciovati, J. Guo, G.-T. Park, R.A. Rimmer, H. Vennekate
JLab, Newport News, Virginia, USA

A possible solution to reduce the complexity posed by the cryogenic systems in a superconducting RF accelerator for industrial applications, is to capitalize on the advances achieved by the Nb₃Sn superconducting RF technology, as well as the feasibility of a reliable 4 K cooling system, based on commercial cryocoolers. Following this philosophy, the conceptual design for a prototype, conduction-cooled, 4 MeV, 20 kW SRF electron linac, is being developed at Jefferson Lab. Such design is based on a 915 MHz two-cell Nb₃Sn cavity. In this contribution, we present the proposed cavity design, including the fundamental power coupler, and the preliminary analysis of the Higher Order Modes, using numerical simulations to estimate the potentially dangerous modes as a starting point to evaluate the requirements for damping for reliable operations with a cryocooler. Finally, different methods to calculate the Higher Order Modes’ Impedances are briefly discussed.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB047

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Received ※ 25 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 04 July 2023 — Issue date ※ 16 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, electron

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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WEPWB054

In Situ Plasma Processing of Superconducting Cavities at JLab, 2023 Update

cavity, plasma, cryomodule, radiation

701

T. Powers, N.C. Brock, T.D. Ganey
JLab, Newport News, Virginia, USA

Jefferson Lab has an ongoing R&D program in plasma processing which just completed a round of production processing in the CEBAF accelerator. Plasma processing is a common technique for removing hydrocarbons from surfaces, which increases the work function and reduces the secondary emission coefficient. Unlike helium processing which relies on ion bombardment of the field emitters, plasma processing uses free oxygen produced in the plasma to break down the hydrocarbons on the surface of the cavity. The initial focus of the effort was processing C100 cavities by injecting RF power into the HOM coupler ports. Results from processing cryomodules in the CEBAF accelerator as well as vertical test results will be presented. The goal will be to improve the operational gradients and the energy margin of the linacs. This work will describe the systems and methods used at JLAB for processing cavities using an argon-oxygen gas mixture as well as a helium-oxygen gas mixture. Before and after plasma processing results will also be presented.
Funding provided by SC Nuclear Physics Program through DOE SC Lab funding announcement DE-FOA-0002670.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB054

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Received ※ 18 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 01 July 2023

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WEPWB057

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

cavity, cryomodule, electron, 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.

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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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WEPWB061

Pre-Installation Performance of the RHIC 56 MHz Superconducting System

cryomodule, operation, coupling, cavity

718

Z.A. Conway, R. Anderson, J.C. Brutus, K. Hernandez, D. Holmes, K. Mernick, G. Narayan, S. Polizzo, S.K. Seberg, F. Severino, M. Sowinski, R. Than, Q. Wu, B.P. Xiao, W. Xu, A. Zaltsman
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under contract No. DE-SC0012704 with the U.S. Department of Energy.
Pre-installation test results for the RHIC 56 MHz superconducting RF system are presented here. The 56 MHz quarter-wave resonator achieved a stable accelerating potential of 1.1 MV with 13 W of RF loss at 4.5 K demonstrating its viability for increasing the luminosity of sPHENIX collisions. The new 120 kW travelling wave fundamental mode damper and dual 6 kW combined-function fundamental power couplers perform as expected at 3 kW but remain to be operated with the expected ~40 times greater power achievable with the RHIC sPHENIX beams.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB061

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Received ※ 15 June 2023 — Revised ※ 26 June 2023 — Accepted ※ 02 July 2023 — Issue date ※ 17 July 2023

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WEPWB103

Simulations and First RF Measurements of Coaxial HOM Coupler Prototypes for PERLE SRF Cavities

cavity, damping, coupling, simulation

831

C. Barbagallo, P. Duchesne, W. Kaabi, G. Olivier, G. Olry, S. Roset, Z.F. Zomer
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
B.S. Barriere, C.S. Clement, R.L.A. Gerard, F. Gerigk, P.M. Maurin
CERN, Meyrin, Switzerland
J. Henry, S.A. Overstreet, G.-T. Park, R.A. Rimmer, H. Wang
JLab, Newport News, Virginia, USA

Superconducting Radio-Frequency (SRF) linac cryomodules are foreseen for the high-current multi-turn energy recovery linac PERLE (Powerful Energy Recovery Linac for Experiments). Coaxial higher order mode (HOM) couplers are the primary design choice to absorb beam-induced power and avoid beam instabilities. We have used 3D-printed and copper-coated HOM couplers for the prototyping and bench RF measurements on the copper PERLE cavities. We have started a collaboration with JLab and CERN on this effort. This paper presents electromagnetic simulations of the cavity HOM-damping performance on those couplers. Bench RF measurements of the HOMs on an 801.58 MHz 2-cell copper cavity performed at JLab are detailed. The results are compared to eigenmode simulations in CST to confirm the design. RF-thermal simulations are conducted to investigate if the studied HOM couplers undergo quenching.

Poster WEPWB103 [1.533 MB]

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reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB103

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Received ※ 18 June 2023 — Revised ※ 26 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 02 July 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, electron, 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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THIAA02

RF Performance Results of RF Double Quarter Wave Resonators for LHC High Luminosity Project

cavity, luminosity, vacuum, radiation

925

K. Turaj, J. Bastard, R. Calaga, S.J. Calvo, O. Capatina, A. Castilla, M. Chiodini, C. Duval, A.V. Edwards, L.M.A. Ferreira, M. Gourragne, P. Kohler, E. Montesinos, C. Pasquino, G. Pechaud, N. Stapley, N. Valverde Alonso, J.D. Walker
CERN, Meyrin, Switzerland
A. Castilla
JLAB, Newport News, USA
A.V. Edwards
Lancaster University, Lancaster, United Kingdom

The LHC High Luminosity (HL-LHC) project includes, among other key items, the installation of superconducting crab cavities in the LHC machine. The Double Quarter Wave (DQW) crab cavity will be utilised to compensate for the effects of the vertical crossing angle. Two bare DQW series cavities were manufactured in Germany by RI Research Instruments and validated successfully at CERN through a cold test at 2K. Two DQW series cavities were produced in-house at CERN, integrated into a titanium helium tank, and equipped with RF ancillaries. This paper addresses the cavities preparation processes and summarizes the results of cryogenic tests of DQW cavities at CERN

Slides THIAA02 [10.840 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-THIAA02

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Received ※ 16 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 01 July 2023

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THIXA01

Investigation of Plasma Processing for Coaxial Resonators

plasma, cavity, SRF, coupling

960

W. Hartung, W. Chang, K. Elliott, S.H. Kim, T. Konomi, K. Saito, P.R. Tutt, T. Xu
FRIB, East Lansing, Michigan, USA

Plasma processing has been investigated by several facilities as a method to mitigate degradation of SRF cavity performance. It provides an alternative to removal and disassembly of cryomodules for refurbishment of each cavity via repeat etching and rinsing. Promising results have been obtained by several groups. Studies of plasma processing for quarter-wave resonators (QWRs) and half-wave resonators (HWRs) were undertaken at FRIB, where a total of 324 such resonators are presently in operation. Plasma ignition and optimization measurements were done with room-temperature-matched input couplers. Plasma cleaning tests were done on several QWRs using the fundamental power coupler (FPC) to drive the plasma. We investigated the usefulness of higher-order modes (HOMs) to drive the plasma. HOMs allow for less mismatch at the FPC and hence lower field in the coupler relative to the cavity. Before-and-after cold tests showed a significant reduction in field emission X-rays with judicious application of plasma processing.

Slides THIXA01 [2.060 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-THIXA01

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Received ※ 01 September 2023 — Accepted ※ 02 September 2023 — Issue date ※ 02 September 2023

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FRIBA03

Heavily Damped Crab Cavities for High Luminosity Collisions

cavity, GUI, impedance, collider

986

B.P. Xiao
BNL, Upton, New York, USA
S.U. De Silva
ODU, Norfolk, Virginia, USA

Funding: Work supported by BSA under U.S. DOE contract No. DE-SC0012704, by JSA under U.S. DOE Contract No. DE-SC0002769, and by DOE Contract No. DE-AC02-76SF00515.
Next generation colliders require crab cavities to mitigate parasitic collisions caused by finite crossing angle for luminosity leveling and detector data pile up reduction. The Electron Ion Collider (EIC) crab cavity designs will be introduced as an example to fulfill the geometrical constraints, crabbing voltages, multipole components, Higher Order Mode (HOM) power and impedance budgets. Operational challenges such as tuning, high gain low delay control loop, amplitude and phase noises control will be discussed.

Slides FRIBA03 [3.666 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-FRIBA03

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Received ※ 19 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 06 July 2023

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FRIBA04

Crab Cavities for ILC

cavity, SRF, operation, impedance

990

P.A. McIntosh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
S.A. Belomestnykh, I.V. Gonin, T.N. Khabiboulline, A. Lunin, Y.M. Orlov, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
R. Calaga
CERN, Meyrin, Switzerland
S.U. De Silva
JLab, Newport News, Virginia, USA
J.R. Delayen
ODU, Norfolk, Virginia, USA
T. Okugi, A. Yamamoto
KEK, Ibaraki, Japan
S. Verdú-Andrés, B.P. Xiao
BNL, Upton, New York, USA

For the 14 mrad crossing angle proposed, crab cavity systems are fundamentally anticipated for the viable operation of the International Linear Collider (ILC), in order to maximise its luminosity performance. Since 2021, a specialist development team have been defining optimum crab cavity technologies which can fulfil the operational requirements for ILC, both for its baseline centre-of-mass energy of 250 GeV, but also extending those requirements out to higher beam collision intensities. Five design teams have established crab cavity technology solutions, which have the capability to also operate up to 1 TeV centre-of-mass. This presentation showcases the key performance capabilities of these designs and their associated benefits for both manufacture and integration into the ILC Interaction Region. The recommended outcome of the recently conducted crab cavity technology down-selection, will also be highlighted.

Slides FRIBA04 [2.526 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-FRIBA04

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Received ※ 19 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 20 July 2023

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