SRF2023 - List of Keywords (coupling)

Paper	Title	Other Keywords	Page
MOPMB001	Development and Testing of Split 6 GHz Cavities With Niobium Coatings	cavity, SRF, target, site	51
	N.L. Leicester, G. Burt, H.S. Marks Cockcroft Institute, Lancaster University, Lancaster, United Kingdom E. Chyhyrynets, C. Pira INFN/LNL, Legnaro (PD), Italy J.A. Conlon, O.B. Malyshev, B.S. Sian, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom D.J. Seal Lancaster University, Lancaster, United Kingdom
	Superconducting thin-films on a copper substrate are used in accelerator RF cavities as an alternative to bulk Nb due to the high thermal conductivity of copper and the lower production costs. Although thin-film coated RF cavities can match, or even exceed the performance of bulk Nb, there are some challenges around the deposition. The RF cavities are often produced as two half-cells with a weld across the centre where the RF surface current is highest, which could reduce cavity performance. To avoid this, a cavity can be produced in 2 longitudinally split halves, with the join parallel to the surface current. As the current doesn’t cross the join a simpler weld can be performed far from the fields, simplifying the manufacturing process, and potentially improving the cavities performance. This additionally allows for different deposition techniques and coating materials to be used, as well as easier post-deposition quality control. This paper discusses the development and testing of 6 GHz cavities that have been designed and coated at the Cockcroft Institute, using low temperature RF techniques to characterise cavities with different substrate preparations and coating techniques.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB001
About •	Received ※ 18 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 04 July 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPMB008	In-Situ Quality Factor Measurements of SRF Cavities at S-DALINAC	cavity, linac, SRF, resonance	70
	R. Grewe, M. Arnold, A. Brauch, M. Dutine, L.E. Jürgensen, N. Pietralla, F. Schließmann, D. Schneider TU Darmstadt, Darmstadt, Germany
	Funding: Work supported by DFG (GRK 2128) and the State of Hesse within the Research Cluster ELEMENTS (Project ID 500/10.006) The Superconducting Darmstadt Linear Accelerator (S-DALINAC) is a thrice recirculating electron accelerator wich can be operated in a multi-turn energy recovery mode. The design parameters for kinetic energy and beam current are up to 130 MeV and up to 20 uA respectively. The injector consists of a six-cell capture cavity and two 20-cell srf cavities. The main linac consists of eight 20-cell cavities. The cavities are operated at a temperature of 2 K with a frequency of 2.9972(1) GHz. Monitoring of the srf cavities is important for the overall performance of the accelerator. A key parameter for the rating of the srf cavity performance is the intrinsic quality factor Q. At the S-DALINAC it is measured for selected cavities during the yearly maintenance procedures. The unique design of the rf input coupler allows for a wide tuning range for the input coupling strength. This makes in-situ quality factor measurements using the decay time measurement method* possible. The contribution illustrates the principal design of the input couplers and the benefits it yields for Q measurements. Recent results including the progression of the quality factors over time will be presented. Felix Schliessmann et al., Nat. Phys. 19, 597-602 (2023). *Tom Powers, Proc. of SRF’05, Cornell University, Ithaca, New York, USA, 2005, p.40.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB008
About •	Received ※ 19 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 04 August 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPMB029	Exploring the Dynamics of Transverse Inter-Planar Coupling in the Superconducting Section of the PIP-II Linac	space-charge, linac, lattice, quadrupole	155
	A. Pathak Fermilab, Batavia, Illinois, USA E. Pozdeyev JLab, Newport News, USA
	This study investigates the crucial role that an accurate understanding of inter-planar coupling in the transverse plane plays in regulating charged particle dynamics in a high-intensity linear accelerator and minimizing foil/septum impacts during injection from the linac to a ring. We in-depth analyze the emergence and evolution of transverse inter-planar coupling through multiple active lattice elements, taking into account space charge and field nonlinearities in the superconducting section of the PIP-II linac. The article compares various analytical, numerical, and experimental techniques for measuring transverse coupling using beam and lattice matrices and provides insight into effective strategies for its mitigation prior to ring injectio
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB029
About •	Received ※ 21 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 05 July 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWB061	Pre-Installation Performance of the RHIC 56 MHz Superconducting System	cryomodule, operation, cavity, HOM	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
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWB096	Testing of PIP-II Pre-production 650 MHz Couplers in Warm Test Stand and Cryomodule	vacuum, cavity, cryomodule, resonance	812
	N. Solyak, S.K. Chandrasekaran, B.M. Hanna, J. Helsper, J.P. Holzbauer, S. Kazakov, A.I. Sukhanov Fermilab, Batavia, Illinois, USA
	650 MHz fundamental power couplers were developed for PIP-II project to deliver RF power for low-beta and high-beta elliptical cavities. Few prototypes were built and tested and after some modification we built 8 pre-production couplers (with three spares for vacuum side) for ppHB650 cryomodule. All couplers were successfully tested in pulse mode (up to 100kW) and in CW mode (up to 50kW) in test stand at full reflection at 8 phases. In baseline configuration with DC bias we do not see any multipactoring activity after short processing. We also tested power processing without bias for uncoated and TiN coated ceramic window. Results of these studies presented in this paper. One of the coupler was assembled on LB650 cavity and tested at cryogenic environment in STC cryostat at ~30kW power with full reflection at different reflection phase. We also demonstrated good result from power processing without bias for warm and cold cavity. Six couplers were assembled on HB650 cavities in pre-production cryomodule. Test results from cryomodule qualification is discussing in this paper.
	Poster WEPWB096 [2.748 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB096
About •	Received ※ 19 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 17 July 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWB097	Testing and Processing of Pre-production 325 MHz Single Spoke Resonator Power Couplers for PIP-II Project	vacuum, cavity, SRF, pick-up	816
	N. Solyak, B.M. Hanna, J. Helsper, S. Kazakov, D. Passarelli Fermilab, Batavia, Illinois, USA S. Wallon Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
	Fundamental 325 MHz power couplers are designed, built and tested for SSR cavities in PIP-II project [1]. Couplers should work in CW mode at power level 7.5kW w/o beam and ~15 kW with the 2 mA beam. At pre-production stage we built and tested 6 couplers, produced by CPI (FNAL) and PMB (IJCLab) and 4 more couplers will be tested soon. Two of tested cou-plers had TiN coated ceramic window. In warm test stand two couplers were mounted on the coupling chamber and tested in SW regime at full reflection with phase controlled by position of short and reflection insert. Couplers were tested at pulse mode (up to 25kW) and cw mode (12kW) with HV bias or without bias. Test results demonstrated that 3.5 kV DC bias completely suppresses multipactor in coupler. Vacuum activity in coupler was controlled by e-pickups and build-in vacuum gauges, located near the vacuum side of window. Power processing without DC bias was done for several couplers with and without TiN coating on ceramic window. Test results are presented and discussing in paper.
	Poster WEPWB097 [2.439 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB097
About •	Received ※ 19 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 29 June 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWB103	Simulations and First RF Measurements of Coaxial HOM Coupler Prototypes for PERLE SRF Cavities	HOM, cavity, damping, 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
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWB105	Improved Study of the Multipactor Phenomenon for the MYRRHA 80 kW CW RF Couplers	multipactoring, electron, 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
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWB108	Update on Cornell High Pulsed Power Sample Host Cavity	cavity, SRF, pulsed-power, simulation	841
	N.M. Verboncoeur, A.T. Holic, M. Liepe, T.E. Oseroff, R.D. Porter, J. Sears, L. Shpani Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA R.D. Porter SLAC, Menlo Park, California, USA
	The Cornell High Pulsed Power Sample Host Cavity (CHPPSHC) is designed to measure the temperature-dependent superheating fields of future SRF materials and thereby gain insights into the ultimate limits of their performance. Theoretical estimation of the superheating fields of SRF materials is challenging and mostly has been done for temperatures near the critical temperature or in the infinite kappa limit. Experimental data currently available is incomplete, and often impacted by material defects and their resulting thermal heating, preventing finding the fundamental limits of theses materials. The CHPPSHC system allows reaching RF fields in excess of half a Tesla within microseconds on material samples by utilizing high pulsed power, thereby outrunning thermal effects. We are principally interested in the superheating field of Nb₃Sn, a material of interest for the SRF community, and present here the current fabrication and assembly status of the CHPPSHC as well as early results.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB108
About •	Received ※ 27 June 2023 — Revised ※ 20 July 2023 — Accepted ※ 20 August 2023 — Issue date ※ 22 August 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THIXA01	Investigation of Plasma Processing for Coaxial Resonators	plasma, cavity, SRF, HOM	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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Paper

Title

Other Keywords

Page

MOPMB001

Development and Testing of Split 6 GHz Cavities With Niobium Coatings

cavity, SRF, target, site

51

N.L. Leicester, G. Burt, H.S. Marks
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
E. Chyhyrynets, C. Pira
INFN/LNL, Legnaro (PD), Italy
J.A. Conlon, O.B. Malyshev, B.S. Sian, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
D.J. Seal
Lancaster University, Lancaster, United Kingdom

Superconducting thin-films on a copper substrate are used in accelerator RF cavities as an alternative to bulk Nb due to the high thermal conductivity of copper and the lower production costs. Although thin-film coated RF cavities can match, or even exceed the performance of bulk Nb, there are some challenges around the deposition. The RF cavities are often produced as two half-cells with a weld across the centre where the RF surface current is highest, which could reduce cavity performance. To avoid this, a cavity can be produced in 2 longitudinally split halves, with the join parallel to the surface current. As the current doesn’t cross the join a simpler weld can be performed far from the fields, simplifying the manufacturing process, and potentially improving the cavities performance. This additionally allows for different deposition techniques and coating materials to be used, as well as easier post-deposition quality control. This paper discusses the development and testing of 6 GHz cavities that have been designed and coated at the Cockcroft Institute, using low temperature RF techniques to characterise cavities with different substrate preparations and coating techniques.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB001

About •

Received ※ 18 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 04 July 2023

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPMB008

In-Situ Quality Factor Measurements of SRF Cavities at S-DALINAC

cavity, linac, SRF, resonance

70

R. Grewe, M. Arnold, A. Brauch, M. Dutine, L.E. Jürgensen, N. Pietralla, F. Schließmann, D. Schneider
TU Darmstadt, Darmstadt, Germany

Funding: Work supported by DFG (GRK 2128) and the State of Hesse within the Research Cluster ELEMENTS (Project ID 500/10.006)
The Superconducting Darmstadt Linear Accelerator (S-DALINAC) is a thrice recirculating electron accelerator wich can be operated in a multi-turn energy recovery mode*. The design parameters for kinetic energy and beam current are up to 130 MeV and up to 20 uA respectively. The injector consists of a six-cell capture cavity and two 20-cell srf cavities. The main linac consists of eight 20-cell cavities. The cavities are operated at a temperature of 2 K with a frequency of 2.9972(1) GHz. Monitoring of the srf cavities is important for the overall performance of the accelerator. A key parameter for the rating of the srf cavity performance is the intrinsic quality factor Q. At the S-DALINAC it is measured for selected cavities during the yearly maintenance procedures. The unique design of the rf input coupler allows for a wide tuning range for the input coupling strength. This makes in-situ quality factor measurements using the decay time measurement method** possible. The contribution illustrates the principal design of the input couplers and the benefits it yields for Q measurements. Recent results including the progression of the quality factors over time will be presented.
*Felix Schliessmann et al., Nat. Phys. 19, 597-602 (2023).
**Tom Powers, Proc. of SRF’05, Cornell University, Ithaca, New York, USA, 2005, p.40.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB008

About •

Received ※ 19 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 04 August 2023

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPMB029

Exploring the Dynamics of Transverse Inter-Planar Coupling in the Superconducting Section of the PIP-II Linac

space-charge, linac, lattice, quadrupole

155

A. Pathak
Fermilab, Batavia, Illinois, USA
E. Pozdeyev
JLab, Newport News, USA

This study investigates the crucial role that an accurate understanding of inter-planar coupling in the transverse plane plays in regulating charged particle dynamics in a high-intensity linear accelerator and minimizing foil/septum impacts during injection from the linac to a ring. We in-depth analyze the emergence and evolution of transverse inter-planar coupling through multiple active lattice elements, taking into account space charge and field nonlinearities in the superconducting section of the PIP-II linac. The article compares various analytical, numerical, and experimental techniques for measuring transverse coupling using beam and lattice matrices and provides insight into effective strategies for its mitigation prior to ring injectio

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB029

About •

Received ※ 21 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 05 July 2023

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWB061

Pre-Installation Performance of the RHIC 56 MHz Superconducting System

cryomodule, operation, cavity, HOM

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

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWB096

Testing of PIP-II Pre-production 650 MHz Couplers in Warm Test Stand and Cryomodule

vacuum, cavity, cryomodule, resonance

812

N. Solyak, S.K. Chandrasekaran, B.M. Hanna, J. Helsper, J.P. Holzbauer, S. Kazakov, A.I. Sukhanov
Fermilab, Batavia, Illinois, USA

650 MHz fundamental power couplers were developed for PIP-II project to deliver RF power for low-beta and high-beta elliptical cavities. Few prototypes were built and tested and after some modification we built 8 pre-production couplers (with three spares for vacuum side) for ppHB650 cryomodule. All couplers were successfully tested in pulse mode (up to 100kW) and in CW mode (up to 50kW) in test stand at full reflection at 8 phases. In baseline configuration with DC bias we do not see any multipactoring activity after short processing. We also tested power processing without bias for uncoated and TiN coated ceramic window. Results of these studies presented in this paper. One of the coupler was assembled on LB650 cavity and tested at cryogenic environment in STC cryostat at ~30kW power with full reflection at different reflection phase. We also demonstrated good result from power processing without bias for warm and cold cavity. Six couplers were assembled on HB650 cavities in pre-production cryomodule. Test results from cryomodule qualification is discussing in this paper.

Poster WEPWB096 [2.748 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB096

About •

Received ※ 19 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 17 July 2023

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWB097

Testing and Processing of Pre-production 325 MHz Single Spoke Resonator Power Couplers for PIP-II Project

vacuum, cavity, SRF, pick-up

816

N. Solyak, B.M. Hanna, J. Helsper, S. Kazakov, D. Passarelli
Fermilab, Batavia, Illinois, USA
S. Wallon
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France

Fundamental 325 MHz power couplers are designed, built and tested for SSR cavities in PIP-II project [1]. Couplers should work in CW mode at power level 7.5kW w/o beam and ~15 kW with the 2 mA beam. At pre-production stage we built and tested 6 couplers, produced by CPI (FNAL) and PMB (IJCLab) and 4 more couplers will be tested soon. Two of tested cou-plers had TiN coated ceramic window. In warm test stand two couplers were mounted on the coupling chamber and tested in SW regime at full reflection with phase controlled by position of short and reflection insert. Couplers were tested at pulse mode (up to 25kW) and cw mode (12kW) with HV bias or without bias. Test results demonstrated that 3.5 kV DC bias completely suppresses multipactor in coupler. Vacuum activity in coupler was controlled by e-pickups and build-in vacuum gauges, located near the vacuum side of window. Power processing without DC bias was done for several couplers with and without TiN coating on ceramic window. Test results are presented and discussing in paper.

Poster WEPWB097 [2.439 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB097

About •

Received ※ 19 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 29 June 2023

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWB103

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

HOM, cavity, damping, 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

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWB105

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

multipactoring, electron, 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

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWB108

Update on Cornell High Pulsed Power Sample Host Cavity

cavity, SRF, pulsed-power, simulation

841

N.M. Verboncoeur, A.T. Holic, M. Liepe, T.E. Oseroff, R.D. Porter, J. Sears, L. Shpani
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
R.D. Porter
SLAC, Menlo Park, California, USA

The Cornell High Pulsed Power Sample Host Cavity (CHPPSHC) is designed to measure the temperature-dependent superheating fields of future SRF materials and thereby gain insights into the ultimate limits of their performance. Theoretical estimation of the superheating fields of SRF materials is challenging and mostly has been done for temperatures near the critical temperature or in the infinite kappa limit. Experimental data currently available is incomplete, and often impacted by material defects and their resulting thermal heating, preventing finding the fundamental limits of theses materials. The CHPPSHC system allows reaching RF fields in excess of half a Tesla within microseconds on material samples by utilizing high pulsed power, thereby outrunning thermal effects. We are principally interested in the superheating field of Nb₃Sn, a material of interest for the SRF community, and present here the current fabrication and assembly status of the CHPPSHC as well as early results.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB108

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Received ※ 27 June 2023 — Revised ※ 20 July 2023 — Accepted ※ 20 August 2023 — Issue date ※ 22 August 2023

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THIXA01

Investigation of Plasma Processing for Coaxial Resonators

plasma, cavity, SRF, HOM

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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