SRF2023 - List of Keywords (cathode)

Paper	Title	Other Keywords	Page
MOPMB009	Plasma Electrolytic Polishing Technology Progress Development for Nb and Cu Substrates Preparation	cavity, plasma, experiment, SRF	75
	E. Chyhyrynets, O. Azzolini, R. Caforio, D. Fonnesu, D. Ford, G. Keppel, C. Pira, A. Salmaso, F. Stivanello INFN/LNL, Legnaro (PD), Italy G. Marconato Università degli Studi di Padova, Padova, Italy
	Funding: Work supported by the INFN CSNV experiment SAMARA. Fundings from the EU’s Horizon 2020 Research and Innovation programme under Grant Agreement N 101004730. PNRR MUR project PE0000023-NQSTI. Superconducting radio frequency (SRF) cavity performance is highly dependent on surface preparation. Conventionally, electropolishing (EP) is used to achieve a clean surface and low roughness for both Nb and Cu substrates, but it requires harsh and corrosive solutions like concentrated acids. Plasma Electrolytic Polishing (PEP) is a promising alternative that uses only diluted salt solutions and has several advantages over EP. PEP can replace intermediate steps like mechanical or chemical polishing, thanks to its superior removal rate of up to 2-8 um/min of Nb and 3-30 um/min of Cu. It achieves Ra roughness of 100 nm for both substrates and has a higher smoothing effect than EP. PEP is also suitable for normal conducting cavities and other accelerator components, including couplers. We demonstrate the effectiveness of PEP on SRF substrates and analyse substrate defect evaluation. We demonstrate the application of PEP onto SRF substrates and analyse the substrate’s defect evaluation. The ongoing work includes Nb bulk and Nb on Cu QPR treatments and RF tests in collaboration with HZB.
	Poster MOPMB009 [11.877 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB009
About •	Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 17 July 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPMB013	Influence of the Coating Parameters on the Tc of Nb₃Sn Thin Films on Copper Deposited via DC Magnetron Sputtering	site, niobium, cavity, SRF	92
	D. Fonnesu, O. Azzolini, R. Caforio, E. Chyhyrynets, D. Ford, V.A. Garcia, G. Keppel, C. Pira, A. Salmaso, F. Stivanello INFN/LNL, Legnaro (PD), Italy G. Marconato Università degli Studi di Padova, Padova, Italy
	Funding: The I.FAST project has received funding from the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No 101004730. Work supported by the INFN CSNV experiment SAMARA. The I.FAST collaboration aims at pushing the performance of particle accelerators by developing sustainable innovative technologies. Among its goals, the development of thin film-coated copper elliptical accelerating cavities covers both the optimization of the manufacturing of seamless substrates and the development of functional coatings able to conform to the 3D cavity geometry while delivering the needed performance. For the latter, the optimization of the deposition recipe is central to a successful outcome. The work presented here focuses on the deposition of Nb₃Sn films on flat, small copper samples. The films are deposited via DCMS from a planar stoichiometric Nb₃Sn commercial target. The results of the film characterization are presented here. The observed dependencies between the film properties and, in particular, Tc(90%-10%) = (17.9±0.1)K is reported for Nb₃Sn on sapphire and Tc(90%-10%) = (16.9±0.2)K for Nb₃Sn on copper with a 30 micron thick niobium buffer layer.
	Poster MOPMB013 [1.749 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB013
About •	Received ※ 18 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 02 July 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPMB067	Design of a Cathode Insertion and Transfer System for LCLS-II-HE SRF Gun	gun, SRF, insertion, operation	267
	R. Xiang, A. Arnold, S. Gatzmaga, A. Hoffmann, P. Murcek, R. Steinbrück, J. Teichert HZDR, Dresden, Germany C. Adolphsen, J. Smedley SLAC, Menlo Park, California, USA W. Hartung, S.H. Kim, T.K. Konomi, S.J. Miller, L. Popielarski, K. Saito, T. Xu FRIB, East Lansing, Michigan, USA M.P. Kelly, T.B. Petersen ANL, Lemont, Illinois, USA J.W. Lewellen LANL, Los Alamos, New Mexico, USA
	Funding: Work supported by cooperation project between MSU and HZDR RC113062 from the U.S. Department of Energy Office of Science under Cooperative Agreement DE-AC02-76SF00515. Superconducting radio frequency photo injectors (SRF gun) offer advantages for operating in continuous wave (CW) mode and generating high-brightness and high-current beams. A new SRF gun is designed as a low emittance photo injector for LCLS-II-HE and a prototype gun is currently being developed under collaboration between SLAC, FRIB, HZDR and ANL. The aim is to demonstrate stable CW operation at a cathode gradient of 30 MV/m. One of the crucial component for successful SRF gun operation is the photocathode system. The new SRF gun will adopt the HZDR-type cathode, which includes a cathode holder fixture (cathode stalk) developed by FRIB and a sophisticated cathode exchange system designed by HZDR. This innovative cathode insertion system ensures accurate, particle-free and warm cathode exchanges. A novel alignment process targets the cathode to the stalk axis without touching cathode plug itself. To commission the prototype gun, metallic cathodes will be used. A specifically designed vacuum system ensures vacuum pressure of 10^-9 mbar for transport of a single cathode from the cleanroom to the gun. Thus maintaining cathode quality.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB067
About •	Received ※ 18 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 18 July 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPMB074	Cryomodule Storage for LCLS-II HE	cryomodule, vacuum, controls, cavity	282
	D.A. White, M. Checchin, D. Gonnella, J. Hogan, J.T. Maniscalco, R.D. Porter SLAC, Menlo Park, California, USA
	Funding: U.S. Department of Energy The Linac Coherent Light Source-II High Energy (LCLS-II HE) project will upgrade the superconducting LCLS-II with 23 additional cryomodules, increasing the beam energy from 4 GeV to 8 GeV. Due to the user schedule of the existing linac, Cryomodules arriving at SLAC cannot immediately be installed in the linac. They are scheduled to be stored for up to three years before the 12-month installation window. During this storage period, the risk of damage to Cryomodules prior to installation will be mitigated with procedures and best practices incorporating experience from LCLS-II.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB074
About •	Received ※ 25 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 03 July 2023 — Issue date ※ 10 July 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPTB016	Summary of the FRIB Electropolishing Facility Design and Commissioning, Cavity Processing, and Cavity Test Results	cavity, MMI, power-supply, controls	419
	E.S. Metzgar, B.W. Barker, K. Elliott, J.D. Hulbert, C. Knowles, L. Nguyen, A.R. Nunham, L. Popielarski, A.T. Taylor, T. Xu FRIB, East Lansing, Michigan, USA
	Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics and used resources of the FRIB, which is a DOE Office of Science User Facility, under Award Number DE-SC0000661. Recently, a new Electropolishing (EP) facility was con-structed and commissioned at the Facility for Rare Isotope Beam (FRIB) with the purpose of supporting advanced surface processing techniques for SRF R&D activities. The FRIB production cavities opted for a Buffered Chemical Polish (BCP) method due to its cost effectiveness and was supported by successful outcomes in other facilities with low beta cavities in a similar frequency range. All 324 cavities used in FRIB Linac were processed in-house at MSU using BCP and exhibited satisfactory performance during testing. As part of the FRIB energy upgrade R&D, 5-cell 644 MHz elliptical resonators will be employed, desiring the use of EP and advanced techniques such as nitrogen doping and medium-T baking. The EP facility is designed to accommodate all types of cavities used in FRIB and possesses the capability for performing EP at low temperatures. Here we report the details of design and commissioning of the EP facility, highlights of encountered issues and subsequent improvements, and preliminary results from vertical tests conducted on the cavities.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB016
About •	Received ※ 15 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 14 July 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPTB042	Latest Development of Electropolishing Optimization for 650 MHz Cavity	cavity, SRF, niobium, polarization	512
	V. Chouhan, D.J. Bice, D.A. Burk, S.K. Chandrasekaran, A.T. Cravatta, P.F. Dubiel, G.V. Eremeev, F. Furuta, O.S. Melnychuk, A.V. Netepenko, M.K. Ng, J.P. Ozelis, H. Park, T.J. Ring, G. Wu Fermilab, Batavia, Illinois, USA B.M. Guilfoyle, M.P. Kelly, T. Reid ANL, Lemont, Illinois, USA
	Electropolishing (EP) of 1.3 GHz niobium (Nb) superconducting RF cavities is conducted to achieve a desired smooth and contaminant-free surface that yields good RF performance. Achieving a smooth surface of a large-sized elliptical cavity with the standard EP conditions was found to be challenging. This work aimed to conduct a systematic parametric EP study to understand the effects of various EP parameters on the surface of 650 MHz cavities used in PIP-II linac. Parameters optimized in this study provided a smooth surface of the cavities. The electropolished cavities met the baseline requirement of field gradient and qualified for further surface treatment to improve the cavity quality factor.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB042
About •	Received ※ 19 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 06 July 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPTB049	Horizontal Test Results of 1.3 GHz Superconducting RF Gun #2 at KEK	gun, cavity, SRF, laser	540
	T. Konomi, K. Hara, Y. Honda, K. Hosoyama, H. Inoue, E. Kako, Y. Kondo, M. Masuzawa, M. Omet, T. Takatomi, A. Terashima, K. Tsuchiya, R. Ueki, K. Umemori, X. Wang KEK, Ibaraki, Japan
	Superconducting radio-frequency (SRF) electron guns are attractive for delivery of beams at a high bunch repetition rate with a high accelerating field. KEK has been developing the SRF gun to demonstrate basic performance. The SRF gun consists of 1.3 GHz and 1.5 cell SRF gun cavity and K2CsSb photocathode coated on 2K cathode plug. In the vertical test, the surface peak electric field and the surface peak magnetic field reached to 75 MV/m and 170 mT respectively. The SRF gun was installed to horizontal multipurpose cryostat equipped with a superconducting solenoid, photocathode preparation chamber and beam diagnostic line. The results showed the peak surface electric field degraded to 42 MV/m. We suspect that cavity was contaminated during assembly. In this presentation, we will present the high gradient performance in vertical and horizontal test and individual test for each beam line components.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB049
About •	Received ※ 24 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 15 July 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPTB069	Design and Tests of a Cathode Stalk for the LCLS-II-HE Low Emittance Injector SRF Gun	gun, SRF, emittance, operation	589
	T.K. Konomi, W. Hartung, S.H. Kim, S.J. Miller, D.G. Morris, K. Saito, A.T. Taylor, T. Xu, Z.Y. Yin FRIB, East Lansing, Michigan, USA C. Adolphsen, J. Smedley, L. Xiao SLAC, Menlo Park, California, USA S. Gatzmaga, P. Murcek, R. Xiang HZDR, Dresden, Germany M.P. Kelly, T.B. Petersen ANL, Lemont, Illinois, USA J.W. Lewellen LANL, Los Alamos, New Mexico, USA
	A SRF gun can operate CW with a high gradient and ultra-low vacuum for high-quantum efficiency, low MTE photocathodes, useful features for delivery of high-brightness, high-repetition-rate beams. For these reasons, an SRF gun based photoinjector was chosen for a proposed Low Emittance Injector addition to the LCLS-II-HE facility, which will operate CW with bunch rates up to 1 MHz. For this injector, a prototype 185.7 MHz QWR gun is being developed in a collaborative effort among FRIB, HZDR, ANL and SLAC, with the goal of achieving a photocathode gradient of at least 30 MV/m. The photocathode is held by a coaxial fixture (cathode stalk) for thermal isolation from the cavity body. The system must allow for precise alignment of the photocathode, particle-free photocathode exchange, cryogenic (55-70 K) or warm (273-300 K) photocathode operating temperatures, and DC biasing to inhibit multipacting. A prototype cathode stalk has been built and bench tests are underway to validate the design. Measurements include RF power dissipation, DC bias hold-off, multipacting suppression and heat transfer effectiveness. This paper describes the cathode stalk design and the test results.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB069
About •	Received ※ 03 July 2023 — Revised ※ 27 July 2023 — Accepted ※ 19 August 2023 — Issue date ※ 20 August 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEIXA05	Electropolishing Study on Nitrogen-Doped Niobium Surface	cavity, niobium, SRF, radio-frequency	641
	V. Chouhan, T.J. Ring, G. Wu Fermilab, Batavia, Illinois, USA E.A.S. Viklund NU, Evanston, Illinois, USA
	The nitrogen doping (N-doping) process is applied to niobium (Nb) superconducting cavities to enhance their quality factors. The N-doping is followed by an electropolishing process that provides the final surface of the cavities. A controlled EP process is necessary to get the benefit of N-doping and achieve a high accelerating gradient. We have performed electropolishing of N-doped Nb surface under various conditions to understand their impact on the surface. A modified EP process was developed to obtain a smooth pit-free surface.
	Slides WEIXA05 [17.622 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEIXA05
About •	Received ※ 19 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 03 July 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWB113	Evaluation of Photo-Cathode Port Multipacting in the SRF Photo-Injector Cryomodule for the LCLS-II High-Energy Upgrade	simulation, electron, 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
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

FRIBA07	Status of the SLAC/MSU SRF Gun Development Project	cryomodule, SRF, cavity, alignment	1003
	S.J. Miller, Y. Al-Mahmoud, W. Chang, Y. Choi, C. Compton, X.J. Du, K. Elliott, W. Hartung, J.D. Hulbert, S.H. Kim, T. Konomi, D.G. Morris, M.S. Patil, L. Popielarski, K. Saito, A. Taylor, B.P. Tousignant, J. Wei, J.D. Wenstrom, K. Witgen, T. Xu FRIB, East Lansing, Michigan, USA C. Adolphsen, R. Coy, F. Ji, M.J. Murphy, J. Smedley, L. Xiao SLAC, Menlo Park, California, USA A. Arnold, S. Gatzmaga, P. Murcek, J. Teichert, R. Xiang HZDR, Dresden, Germany M.P. Kelly, T.B. Petersen, P. Piot ANL, Lemont, Illinois, USA J.W. Lewellen LANL, Los Alamos, New Mexico, USA
	Funding: Work supported by the Department of Energy under Contract DE-AC02-76SF00515 The Linac Coherent Light Source II High Energy (LCLS-II-HE) Project at SLAC includes the construction of a low-emittance injector (LEI) and a superconducting quarter-wave resonator (QWR) at 185.7 MHz. Several alternatives to a superconducting radio frequency (SRF) QWR gun were considered for the LEI, including nor-mal-conducting RF guns evolved from the LCLS-II gun design. Compared to normal-conducting designs, the combination of an intrinsically outstanding vacuum environment (for cathode lifetime), and the potential for a larger ultimate performance envelope, led to the deci-sion to pursue development of the QWR-SRF gun. A prototype gun is currently being designed and fabricated at the Facility for Rare Isotope Beams (FRIB) at Michi-gan State University (MSU). This paper presents perfor-mance goals for the new gun design, an overview of the prototype development effort, status, and future plans including fabrication.
	Slides FRIBA07 [9.655 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-FRIBA07
About •	Received ※ 15 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 11 July 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Other Keywords

Page

MOPMB009

Plasma Electrolytic Polishing Technology Progress Development for Nb and Cu Substrates Preparation

cavity, plasma, experiment, SRF

75

E. Chyhyrynets, O. Azzolini, R. Caforio, D. Fonnesu, D. Ford, G. Keppel, C. Pira, A. Salmaso, F. Stivanello
INFN/LNL, Legnaro (PD), Italy
G. Marconato
Università degli Studi di Padova, Padova, Italy

Funding: Work supported by the INFN CSNV experiment SAMARA. Fundings from the EU’s Horizon 2020 Research and Innovation programme under Grant Agreement N 101004730. PNRR MUR project PE0000023-NQSTI.
Superconducting radio frequency (SRF) cavity performance is highly dependent on surface preparation. Conventionally, electropolishing (EP) is used to achieve a clean surface and low roughness for both Nb and Cu substrates, but it requires harsh and corrosive solutions like concentrated acids. Plasma Electrolytic Polishing (PEP) is a promising alternative that uses only diluted salt solutions and has several advantages over EP. PEP can replace intermediate steps like mechanical or chemical polishing, thanks to its superior removal rate of up to 2-8 um/min of Nb and 3-30 um/min of Cu. It achieves Ra roughness of 100 nm for both substrates and has a higher smoothing effect than EP. PEP is also suitable for normal conducting cavities and other accelerator components, including couplers. We demonstrate the effectiveness of PEP on SRF substrates and analyse substrate defect evaluation. We demonstrate the application of PEP onto SRF substrates and analyse the substrate’s defect evaluation. The ongoing work includes Nb bulk and Nb on Cu QPR treatments and RF tests in collaboration with HZB.

Poster MOPMB009 [11.877 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB009

About •

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

Cite •

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

MOPMB013

Influence of the Coating Parameters on the Tc of Nb₃Sn Thin Films on Copper Deposited via DC Magnetron Sputtering

site, niobium, cavity, SRF

92

D. Fonnesu, O. Azzolini, R. Caforio, E. Chyhyrynets, D. Ford, V.A. Garcia, G. Keppel, C. Pira, A. Salmaso, F. Stivanello
INFN/LNL, Legnaro (PD), Italy
G. Marconato
Università degli Studi di Padova, Padova, Italy

Funding: The I.FAST project has received funding from the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No 101004730. Work supported by the INFN CSNV experiment SAMARA.
The I.FAST collaboration aims at pushing the performance of particle accelerators by developing sustainable innovative technologies. Among its goals, the development of thin film-coated copper elliptical accelerating cavities covers both the optimization of the manufacturing of seamless substrates and the development of functional coatings able to conform to the 3D cavity geometry while delivering the needed performance. For the latter, the optimization of the deposition recipe is central to a successful outcome. The work presented here focuses on the deposition of Nb₃Sn films on flat, small copper samples. The films are deposited via DCMS from a planar stoichiometric Nb₃Sn commercial target. The results of the film characterization are presented here. The observed dependencies between the film properties and, in particular, Tc(90%-10%) = (17.9±0.1)K is reported for Nb₃Sn on sapphire and Tc(90%-10%) = (16.9±0.2)K for Nb₃Sn on copper with a 30 micron thick niobium buffer layer.

Poster MOPMB013 [1.749 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB013

About •

Received ※ 18 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 02 July 2023

Cite •

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

MOPMB067

Design of a Cathode Insertion and Transfer System for LCLS-II-HE SRF Gun

gun, SRF, insertion, operation

267

R. Xiang, A. Arnold, S. Gatzmaga, A. Hoffmann, P. Murcek, R. Steinbrück, J. Teichert
HZDR, Dresden, Germany
C. Adolphsen, J. Smedley
SLAC, Menlo Park, California, USA
W. Hartung, S.H. Kim, T.K. Konomi, S.J. Miller, L. Popielarski, K. Saito, T. Xu
FRIB, East Lansing, Michigan, USA
M.P. Kelly, T.B. Petersen
ANL, Lemont, Illinois, USA
J.W. Lewellen
LANL, Los Alamos, New Mexico, USA

Funding: Work supported by cooperation project between MSU and HZDR RC113062 from the U.S. Department of Energy Office of Science under Cooperative Agreement DE-AC02-76SF00515.
Superconducting radio frequency photo injectors (SRF gun) offer advantages for operating in continuous wave (CW) mode and generating high-brightness and high-current beams. A new SRF gun is designed as a low emittance photo injector for LCLS-II-HE and a prototype gun is currently being developed under collaboration between SLAC, FRIB, HZDR and ANL. The aim is to demonstrate stable CW operation at a cathode gradient of 30 MV/m. One of the crucial component for successful SRF gun operation is the photocathode system. The new SRF gun will adopt the HZDR-type cathode, which includes a cathode holder fixture (cathode stalk) developed by FRIB and a sophisticated cathode exchange system designed by HZDR. This innovative cathode insertion system ensures accurate, particle-free and warm cathode exchanges. A novel alignment process targets the cathode to the stalk axis without touching cathode plug itself. To commission the prototype gun, metallic cathodes will be used. A specifically designed vacuum system ensures vacuum pressure of 10^-9 mbar for transport of a single cathode from the cleanroom to the gun. Thus maintaining cathode quality.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB067

About •

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

Cite •

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

MOPMB074

Cryomodule Storage for LCLS-II HE

cryomodule, vacuum, controls, cavity

282

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

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

DOI •

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

About •

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

Cite •

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

TUPTB016

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

cavity, MMI, power-supply, controls

419

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

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

DOI •

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

About •

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

Cite •

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

TUPTB042

Latest Development of Electropolishing Optimization for 650 MHz Cavity

cavity, SRF, niobium, polarization

512

V. Chouhan, D.J. Bice, D.A. Burk, S.K. Chandrasekaran, A.T. Cravatta, P.F. Dubiel, G.V. Eremeev, F. Furuta, O.S. Melnychuk, A.V. Netepenko, M.K. Ng, J.P. Ozelis, H. Park, T.J. Ring, G. Wu
Fermilab, Batavia, Illinois, USA
B.M. Guilfoyle, M.P. Kelly, T. Reid
ANL, Lemont, Illinois, USA

Electropolishing (EP) of 1.3 GHz niobium (Nb) superconducting RF cavities is conducted to achieve a desired smooth and contaminant-free surface that yields good RF performance. Achieving a smooth surface of a large-sized elliptical cavity with the standard EP conditions was found to be challenging. This work aimed to conduct a systematic parametric EP study to understand the effects of various EP parameters on the surface of 650 MHz cavities used in PIP-II linac. Parameters optimized in this study provided a smooth surface of the cavities. The electropolished cavities met the baseline requirement of field gradient and qualified for further surface treatment to improve the cavity quality factor.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB042

About •

Received ※ 19 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 06 July 2023

Cite •

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

TUPTB049

Horizontal Test Results of 1.3 GHz Superconducting RF Gun #2 at KEK

gun, cavity, SRF, laser

540

T. Konomi, K. Hara, Y. Honda, K. Hosoyama, H. Inoue, E. Kako, Y. Kondo, M. Masuzawa, M. Omet, T. Takatomi, A. Terashima, K. Tsuchiya, R. Ueki, K. Umemori, X. Wang
KEK, Ibaraki, Japan

Superconducting radio-frequency (SRF) electron guns are attractive for delivery of beams at a high bunch repetition rate with a high accelerating field. KEK has been developing the SRF gun to demonstrate basic performance. The SRF gun consists of 1.3 GHz and 1.5 cell SRF gun cavity and K2CsSb photocathode coated on 2K cathode plug. In the vertical test, the surface peak electric field and the surface peak magnetic field reached to 75 MV/m and 170 mT respectively. The SRF gun was installed to horizontal multipurpose cryostat equipped with a superconducting solenoid, photocathode preparation chamber and beam diagnostic line. The results showed the peak surface electric field degraded to 42 MV/m. We suspect that cavity was contaminated during assembly. In this presentation, we will present the high gradient performance in vertical and horizontal test and individual test for each beam line components.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB049

About •

Received ※ 24 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 15 July 2023

Cite •

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

TUPTB069

Design and Tests of a Cathode Stalk for the LCLS-II-HE Low Emittance Injector SRF Gun

gun, SRF, emittance, operation

589

T.K. Konomi, W. Hartung, S.H. Kim, S.J. Miller, D.G. Morris, K. Saito, A.T. Taylor, T. Xu, Z.Y. Yin
FRIB, East Lansing, Michigan, USA
C. Adolphsen, J. Smedley, L. Xiao
SLAC, Menlo Park, California, USA
S. Gatzmaga, P. Murcek, R. Xiang
HZDR, Dresden, Germany
M.P. Kelly, T.B. Petersen
ANL, Lemont, Illinois, USA
J.W. Lewellen
LANL, Los Alamos, New Mexico, USA

A SRF gun can operate CW with a high gradient and ultra-low vacuum for high-quantum efficiency, low MTE photocathodes, useful features for delivery of high-brightness, high-repetition-rate beams. For these reasons, an SRF gun based photoinjector was chosen for a proposed Low Emittance Injector addition to the LCLS-II-HE facility, which will operate CW with bunch rates up to 1 MHz. For this injector, a prototype 185.7 MHz QWR gun is being developed in a collaborative effort among FRIB, HZDR, ANL and SLAC, with the goal of achieving a photocathode gradient of at least 30 MV/m. The photocathode is held by a coaxial fixture (cathode stalk) for thermal isolation from the cavity body. The system must allow for precise alignment of the photocathode, particle-free photocathode exchange, cryogenic (55-70 K) or warm (273-300 K) photocathode operating temperatures, and DC biasing to inhibit multipacting. A prototype cathode stalk has been built and bench tests are underway to validate the design. Measurements include RF power dissipation, DC bias hold-off, multipacting suppression and heat transfer effectiveness. This paper describes the cathode stalk design and the test results.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB069

About •

Received ※ 03 July 2023 — Revised ※ 27 July 2023 — Accepted ※ 19 August 2023 — Issue date ※ 20 August 2023

Cite •

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

WEIXA05

Electropolishing Study on Nitrogen-Doped Niobium Surface

cavity, niobium, SRF, radio-frequency

641

V. Chouhan, T.J. Ring, G. Wu
Fermilab, Batavia, Illinois, USA
E.A.S. Viklund
NU, Evanston, Illinois, USA

The nitrogen doping (N-doping) process is applied to niobium (Nb) superconducting cavities to enhance their quality factors. The N-doping is followed by an electropolishing process that provides the final surface of the cavities. A controlled EP process is necessary to get the benefit of N-doping and achieve a high accelerating gradient. We have performed electropolishing of N-doped Nb surface under various conditions to understand their impact on the surface. A modified EP process was developed to obtain a smooth pit-free surface.

Slides WEIXA05 [17.622 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEIXA05

About •

Received ※ 19 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 03 July 2023

Cite •

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

WEPWB113

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

simulation, electron, 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

Cite •

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

FRIBA07

Status of the SLAC/MSU SRF Gun Development Project

cryomodule, SRF, cavity, alignment

1003

S.J. Miller, Y. Al-Mahmoud, W. Chang, Y. Choi, C. Compton, X.J. Du, K. Elliott, W. Hartung, J.D. Hulbert, S.H. Kim, T. Konomi, D.G. Morris, M.S. Patil, L. Popielarski, K. Saito, A. Taylor, B.P. Tousignant, J. Wei, J.D. Wenstrom, K. Witgen, T. Xu
FRIB, East Lansing, Michigan, USA
C. Adolphsen, R. Coy, F. Ji, M.J. Murphy, J. Smedley, L. Xiao
SLAC, Menlo Park, California, USA
A. Arnold, S. Gatzmaga, P. Murcek, J. Teichert, R. Xiang
HZDR, Dresden, Germany
M.P. Kelly, T.B. Petersen, P. Piot
ANL, Lemont, Illinois, USA
J.W. Lewellen
LANL, Los Alamos, New Mexico, USA

Funding: Work supported by the Department of Energy under Contract DE-AC02-76SF00515
The Linac Coherent Light Source II High Energy (LCLS-II-HE) Project at SLAC includes the construction of a low-emittance injector (LEI) and a superconducting quarter-wave resonator (QWR) at 185.7 MHz. Several alternatives to a superconducting radio frequency (SRF) QWR gun were considered for the LEI, including nor-mal-conducting RF guns evolved from the LCLS-II gun design. Compared to normal-conducting designs, the combination of an intrinsically outstanding vacuum environment (for cathode lifetime), and the potential for a larger ultimate performance envelope, led to the deci-sion to pursue development of the QWR-SRF gun. A prototype gun is currently being designed and fabricated at the Facility for Rare Isotope Beams (FRIB) at Michi-gan State University (MSU). This paper presents perfor-mance goals for the new gun design, an overview of the prototype development effort, status, and future plans including fabrication.

Slides FRIBA07 [9.655 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-FRIBA07

About •

Received ※ 15 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 11 July 2023

Cite •

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