SRF2021 - List of Authors (Reece, C.E.)

Paper	Title	Page
SUPTEV011	Nb₃Sn Coating of Twin Axis Cavity for SRF Applications	146
	J.K. Tiskumara, J.R. Delayen ODU, Norfolk, Virginia, USA G.V. Eremeev Fermilab, Batavia, Illinois, USA U. Pudasaini, C.E. Reece JLab, Newport News, Virginia, USA
	The twin axis cavity with two identical accelerating beams has been proposed for energy recovery linac (ERL) applications. Nb₃Sn is a superconducting material with a higher critical temperature and a higher critical field as compared to Nb, which promises a lower operating cost due to higher quality factors. Two niobium twin axis cavities were fabricated at JLab and were proposed to be coated with Nb₃Sn. Due to their more complex geometry, the typical coating process used for basic elliptical cavi-ties needs to be improved to coat these cavities. This development advances the current coating system at JLab for coating complex cavities. Two twin axis cavities were coated recently for the first time. This contribution dis-cusses initial results from coating of twin axis cavities, RF testing and witness sample analysis with an overview of the current challenges towards high performance Nb₃Sn coated twin axis cavities.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPTEV011
About •	Received ※ 22 June 2021 — Revised ※ 19 December 2021 — Accepted ※ 21 February 2022 — Issue date ※ 01 April 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPTEV014	New Improved Horizontal Electropolishing System for SRF Cavities	237
	C.E. Reece, S. Castagnola, P. Denny, A.L.A. Mitchell JLab, Newport News, Virginia, USA
	Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OThR23177. The best performance of niobium SRF accelerating cavities is obtained with surfaces smoothed with electropolishing chemical finishing. Jefferson Lab has recently specified, procured, installed, and commissioned a new versatile production electropolishing (EP) tool. Experience with EP research and operations at JLab as well as vendor interactions and experience guided development of the system specification. Detailed design and fabrication was awarded by contract to Semiconductor Process Equipment Corporation (SPEC). The delivered system was integrated into the JLab chemroom infrastructure and commissioned in 2020. The new EP tool provides much improved heat exchange from the circulating H₂SO₄/HF electrolyte and also the cavity via variable temperature external cooling water flow, resulting in quite uniform cavity wall temperature control and thus improved removal uniformity. With the JLab infrastructure, stabilized process temperature as low as 5 C is available. We describe the system and illustrate operational modes in this contribution.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-MOPTEV014
About •	Received ※ 21 June 2021 — Revised ※ 08 July 2021 — Accepted ※ 19 August 2021 — Issue date ※ 31 March 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPCAV013	LCLS-II-HE Vertical Acceptance Testing Plans	291
	J.T. Maniscalco, S. Aderhold, J.D. Fuerst, D. Gonnella SLAC, Menlo Park, California, USA T.T. Arkan, M. Checchin, J.A. Kaluzny, S. Posen Fermilab, Batavia, Illinois, USA J. Hogan, A.D. Palczewski, C.E. Reece, K.M. Wilson JLab, Newport News, Virginia, USA
	LCLS-II-HE has performance requirements similar to but generally more demanding than those of LCLS-II, with an operating gradient of 21 MV/m (up from 16 MV/m in LCLS-II) and tighter restrictions on field emission and multipacting. In this paper, we outline the requirements for the 1.3 GHz cavities and the plans for qualification of these cavities by vertical test. We discuss lessons learned from LCLS-II and highlight the changes implemented in the vertical test procedure for the new project.
	Poster MOPCAV013 [0.418 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-MOPCAV013
About •	Received ※ 21 June 2021 — Revised ※ 12 July 2021 — Accepted ※ 21 August 2021 — Issue date ※ 02 May 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPFDV002	SIMS Sample Holder and Grain Orientation Effects	401
	J.W. Angle, M.J. Kelley Virginia Polytechnic Institute and State University, Blacksburg, USA M.J. Kelley, E.M. Lechner, A.D. Palczewski, C.E. Reece JLab, Newport News, Virginia, USA F.A. Stevie NCSU AIF, Raleigh, North Carolina, USA
	SIMS analyses for ’N-doped’ materials are becoming increasingly important. A major hurdle to acquiring quantitative SIMS results for these materials is the uncertainty of instrument calibration due to changes in sample height either from sample topography or from the sample holder itself. The CAMECA sample holder design allows for many types of samples to be analyzed. However, the cost is that the holder faceplate can bend, introducing uncertainty into the SIMS results. Here we designed and created an improved sample holder which is reinforced to prevent faceplate deflection and thereby reduce uncertainty. Simulations show that the new design significantly reduces deflection from 10 µm to 5 nm. Measurements show a reduction of calibration (RSF) uncertainty from this source from 4.1% to 0.95%. Grain orientation has long been suspected to affect RSF determination as well. A bicrystal implant standard consisting of [111] and [001] grains were repeatedly rotated 15° in between analyses. It was observed that 20% of the analyses performed on [111] grains exhibited anomalously high RSF values likely due to the changing of the grain normal with respect to the primary Cs+ beam.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUPFDV002
About •	Received ※ 21 June 2021 — Revised ※ 11 July 2021 — Accepted ※ 21 August 2021 — Issue date ※ 05 January 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPFDV004	A SIMS Approach for the Analysis of Furnace Contamination	406
	J.W. Angle, M.J. Kelley Virginia Polytechnic Institute and State University, Blacksburg, USA M.J. Kelley, E.M. Lechner, A.D. Palczewski, C.E. Reece JLab, Newport News, Virginia, USA F.A. Stevie NCSU AIF, Raleigh, North Carolina, USA
	Detection of surface contamination for SRF material is difficult due to the miniscule quantities and near atomic resolution needed. Visual inspection of samples known to have experienced surface contamination were found to have inconsistent nitride coverage after nitrogen doping. EBSD analysis suggest that nitride suppression tends to be most prevalent when deviating from the [111] and [001] zone axes. XPS suggested that tin was present as a contaminant on the surface with SIMS mass spectra also confirming its presence. SIMS depth profiles show a depletion of nitrogen content as well as an increase in car-bon content for contaminated samples.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUPFDV004
About •	Received ※ 22 June 2021 — Revised ※ 11 July 2021 — Accepted ※ 21 August 2021 — Issue date ※ 19 February 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPTEV013	Managing Sn-Supply to Tune Surface Characteristics of Vapor-Diffusion Coating of Nb₃Sn	516
	U. Pudasaini, C.E. Reece JLab, Newport News, Virginia, USA J.K. Tiskumara ODU, Norfolk, Virginia, USA
	Funding: Authored by Jefferson Science Associates under contract no. DE¬AC05¬06OR23177 Nb₃Sn promises better RF performance (Q and E_acc) than niobium at any given temperature because of superior superconducting properties. Nb₃Sn-coated SRF cavities are now produced routinely by growing a few microns thick Nb₃Sn films inside Nb cavities via the tin vapor diffusion technique. Sn evaporation and consumption during the growth process notably affect the quality of the coating. Aiming at favorable surface characteristics that could enhance the RF performance, many coatings were produced by varying Sn sources and temperature profiles. Coupon samples were examined using different material characterization techniques, and a selected few sets of coating parameters were used to coat 1.3 GHz single-cell cavities for RF testing. The Sn supply’s careful tuning is essential to manage the microstructure, roughness, and overall surface characteristics of the coating. We summarize the material analysis of witness samples and discuss the performance of several Nb₃Sn-coated single-cell cavities linked to Sn-source characteristics and observed Sn consumption during the film growth process.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUPTEV013
About •	Received ※ 21 June 2021 — Revised ※ 09 October 2021 — Accepted ※ 15 December 2021 — Issue date ※ 22 February 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPFDV003	SIMS Investigation of Furnace-Baked Nb	761
	E.M. Lechner, M.J. Kelley, A.D. Palczewski, C.E. Reece JLab, Newport News, Virginia, USA J.W. Angle, M.J. Kelley Virginia Polytechnic Institute and State University, Blacksburg, USA F.A. Stevie NCSU AIF, Raleigh, North Carolina, USA
	Funding: U.S. DOE Contract No. DE-AC05-06OR23177 Results recently published by Ito et al. showed that "furnace baking" Nb SRF cavities after electropolishing yields high quality factors and anti-Q-slopes resembling that of N doped cavities. Small Nb samples were prepared following the recipe outlined by Ito. These samples were measured by SIMS to examine impurity contributions to the RF penetration layer. These diffusion profiles are modeled, and their consequences on RF properties discussed.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPFDV003
About •	Received ※ 22 June 2021 — Accepted ※ 24 November 2021 — Issue date ※ 15 May 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPCAV008	Results From the Proton Power Upgrade Project Cavity Quality Assurance Plan	801
	J.D. Mammosser, B.E. Robertson ORNL RAD, Oak Ridge, Tennessee, USA R. Afanador, M.S. Champion, M.N. Greenwood, M.P. Howell, S.-H. Kim, S.E. Stewart, D.J. Vandygriff ORNL, Oak Ridge, Tennessee, USA A. Bitter, K.B. Bolz, A. Navitski, L. Zweibäumer RI Research Instruments GmbH, Bergisch Gladbach, Germany E. Daly, G.K. Davis, P. Dhakal, D. Forehand, K. Macha, C.E. Reece, K.M. Wilson JLab, Newport News, Virginia, USA
	Funding: UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE) The Proton Power Upgrade (PPU) Project at Oak Ridge National Lab’s Spallation Neutron Source (SNS) is currently under construction. The project will double the beam power from 1.4 to 2.8 MW. This is accomplished by increasing the beam current and adding seven new Superconducting Radio Frequency (SRF) cryomodules. Each new cryomodule will contain four six-cell, beta 0.81, PPU style cavities. A quality assurance plan was developed and implemented for the procurement of 32 PPU cavities. As part of this plan, reference cavities were qualified and sent to Research Instruments Co. for the development and verification of process steps. Here we present the results from this plan to date.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPCAV008
About •	Received ※ 04 June 2021 — Accepted ※ 06 September 2021 — Issue date ※ 16 May 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPCAV009	Statistical Modeling of Peak Accelerating Gradients in LCLS-II and LCLS-II-HE	804
	J.T. Maniscalco, S. Aderhold, J.D. Fuerst, D. Gonnella SLAC, Menlo Park, California, USA T.T. Arkan, M. Checchin, J.A. Kaluzny, S. Posen Fermilab, Batavia, Illinois, USA J. Hogan, A.D. Palczewski, C.E. Reece, K.M. Wilson JLab, Newport News, Virginia, USA
	In this report, we study the vertical test gradient performance and the gradient degradation between vertical test and cryomodule test for the 1.3 GHz LCLS-II cavities. We develop a model of peak gradient statistics, and use our understanding of the LCLS-II results and the changes implemented for LCLS-II-HE to estimate the expected gradient statistics for the new machine. Finally, we lay out a plan to ensure that the LCLS-II-HE cryomodule gradient specifications are met while minimizing cavity disqualification by introducing a variable acceptance threshold for the accelerating gradient.
	Poster THPCAV009 [1.311 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPCAV009
About •	Received ※ 21 June 2021 — Revised ※ 14 September 2021 — Accepted ※ 02 November 2021 — Issue date ※ 23 November 2021
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPTEV012	Substitution of Spring Clamps for Bolts on SRF Cavity Flanges to Minimize Particle Generation	853
	G.H. Biallas Hyperboloid LLC, Yorktown, Virginia, USA E. Daly, K. Macha, C.E. Reece JLab, Newport News, Virginia, USA
	Funding: Funding supplied by US Department of Energy SBIR Grant #DE-SC0019579 Hyperboloid LLC developed and successfully tested a System of High Force Spring Clamps to substitute, one for one, for bolts on the flanges of SRF Cavities. The Clamps are like exceptionally forceful binder clips. The System, that includes the Hydraulic Openers that apply the clamps, minimizes generation of particulates when sealing cavity flanges. Hyperboloid LLC used ANSYS to design the titanium clamps that generate the force to seal the hexagonal cross section, relatively hard aluminum gasket developed for TESLA and used at JLab and other accelerators. The System is developed to be suitable for use in SRF Clean Rooms. Results of particle counter readings during bolt and clamp installation and superfluid helium challenges to the sealed flanges are discussed. Results of a half-size clamp that could seal a soft aluminum gasket and the attempt to seal a gasket made of niobium are also discussed. L. Monaco, P. Michelato, C. Pagani, N. Panzeri, Experimental and Theoretical Analysis of Tesla-like SFRF Cavity Flanges, INFN Milano- LASA, I-20090 Segrate (MI), Italy. Proc. EPAC 2006, Edinburgh, SC
	Poster THPTEV012 [1.404 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPTEV012
About •	Received ※ 21 June 2021 — Revised ※ 16 December 2021 — Accepted ※ 28 April 2022 — Issue date ※ 01 May 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPTEV017	Status of the LCLS-II-HE Project at Jefferson Lab	876
	K.M. Wilson, J. Hogan, M. Laney, A.D. Palczewski, C.E. Reece JLab, Newport News, Virginia, USA
	Funding: This work was supported by the U.S. Department of Energy Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177 (JSA); and for BES under contract DE’AC02’76SF00515 (SLAC). The Linac Coherent Light Source II High Energy (LCLS-II-HE) upgrade at the SLAC National Accelerator Laboratory is being constructed in partnership with the Thomas Jefferson National Accelerator Facility (JLab) and the Fermi National Accelerator Laboratory (FNAL). The cryomodule production scope consists of the design, procurement, construction, and acceptance testing of 24 eight-cavity, 1.3 GHz cryomodules, as well as R&D activities necessary to develop the required technology. To achieve this, JLab and FNAL are also contributing to SLAC’s effort to develop the cavity recipe and production processes necessary to meet the LCLS-II-HE goal of 20.8 MV/m and average Q₀ of 2.7·10¹⁰. This paper details the JLab scope, focusing on the project initiation phase, in particular technology development and prototyping, project development and planning, and implementation of lessons learned from LCLS-II.
	Poster THPTEV017 [1.536 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPTEV017
About •	Received ※ 21 June 2021 — Revised ※ 12 August 2021 — Accepted ※ 02 March 2022 — Issue date ※ 01 May 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

FROFDV02	A Novel Approach to Producing High Gradient and Q₀ Cavities in Non-Ideal Furnaces
	A.D. Palczewski, P. Dhakal, C.E. Reece JLab, Newport News, Virginia, USA D. Gonnella SLAC, Menlo Park, California, USA
	Funding: Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Since the discovery of nitrogen doping in 2014, infusion in 2017, "mid-T bakes in 2018; the reproducibility in both Q₀ and gradient has been proven to be highly variable between facilities and even within the same furnace within a facility. Multiple studies have pointed to possible contamination from pumps, non-Molybdenum frame outgassing within a hot zone, gas purity issues, and cross-contamination between furnace runs. The traditional approach to mitigating these effects is using niobium furnace caps, high-temperature furnace burnout runs, and expensive pump replacements. We will show multiple examples of a novel approach to increasing Q₀ and Q₀+E_acc, using a simple treatment after a furnace treatment or doping + light EP. We will also outline the possible workflows using this new technique in production. Pashupati Dhakal, https://doi.org/10.1016/j.physo.2020.100034, and enclosed citations.
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Nb₃Sn Coating of Twin Axis Cavity for SRF Applications

146

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

The twin axis cavity with two identical accelerating beams has been proposed for energy recovery linac (ERL) applications. Nb₃Sn is a superconducting material with a higher critical temperature and a higher critical field as compared to Nb, which promises a lower operating cost due to higher quality factors. Two niobium twin axis cavities were fabricated at JLab and were proposed to be coated with Nb₃Sn. Due to their more complex geometry, the typical coating process used for basic elliptical cavi-ties needs to be improved to coat these cavities. This development advances the current coating system at JLab for coating complex cavities. Two twin axis cavities were coated recently for the first time. This contribution dis-cusses initial results from coating of twin axis cavities, RF testing and witness sample analysis with an overview of the current challenges towards high performance Nb₃Sn coated twin axis cavities.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPTEV011

About •

Received ※ 22 June 2021 — Revised ※ 19 December 2021 — Accepted ※ 21 February 2022 — Issue date ※ 01 April 2022

Cite •

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

MOPTEV014

New Improved Horizontal Electropolishing System for SRF Cavities

237

C.E. Reece, S. Castagnola, P. Denny, A.L.A. Mitchell
JLab, Newport News, Virginia, USA

Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OThR23177.
The best performance of niobium SRF accelerating cavities is obtained with surfaces smoothed with electropolishing chemical finishing. Jefferson Lab has recently specified, procured, installed, and commissioned a new versatile production electropolishing (EP) tool. Experience with EP research and operations at JLab as well as vendor interactions and experience guided development of the system specification. Detailed design and fabrication was awarded by contract to Semiconductor Process Equipment Corporation (SPEC). The delivered system was integrated into the JLab chemroom infrastructure and commissioned in 2020. The new EP tool provides much improved heat exchange from the circulating H₂SO₄/HF electrolyte and also the cavity via variable temperature external cooling water flow, resulting in quite uniform cavity wall temperature control and thus improved removal uniformity. With the JLab infrastructure, stabilized process temperature as low as 5 C is available. We describe the system and illustrate operational modes in this contribution.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-MOPTEV014

About •

Received ※ 21 June 2021 — Revised ※ 08 July 2021 — Accepted ※ 19 August 2021 — Issue date ※ 31 March 2022

Cite •

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

MOPCAV013

LCLS-II-HE Vertical Acceptance Testing Plans

291

J.T. Maniscalco, S. Aderhold, J.D. Fuerst, D. Gonnella
SLAC, Menlo Park, California, USA
T.T. Arkan, M. Checchin, J.A. Kaluzny, S. Posen
Fermilab, Batavia, Illinois, USA
J. Hogan, A.D. Palczewski, C.E. Reece, K.M. Wilson
JLab, Newport News, Virginia, USA

LCLS-II-HE has performance requirements similar to but generally more demanding than those of LCLS-II, with an operating gradient of 21 MV/m (up from 16 MV/m in LCLS-II) and tighter restrictions on field emission and multipacting. In this paper, we outline the requirements for the 1.3 GHz cavities and the plans for qualification of these cavities by vertical test. We discuss lessons learned from LCLS-II and highlight the changes implemented in the vertical test procedure for the new project.

Poster MOPCAV013 [0.418 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-MOPCAV013

About •

Received ※ 21 June 2021 — Revised ※ 12 July 2021 — Accepted ※ 21 August 2021 — Issue date ※ 02 May 2022

Cite •

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

TUPFDV002

SIMS Sample Holder and Grain Orientation Effects

401

J.W. Angle, M.J. Kelley
Virginia Polytechnic Institute and State University, Blacksburg, USA
M.J. Kelley, E.M. Lechner, A.D. Palczewski, C.E. Reece
JLab, Newport News, Virginia, USA
F.A. Stevie
NCSU AIF, Raleigh, North Carolina, USA

SIMS analyses for ’N-doped’ materials are becoming increasingly important. A major hurdle to acquiring quantitative SIMS results for these materials is the uncertainty of instrument calibration due to changes in sample height either from sample topography or from the sample holder itself. The CAMECA sample holder design allows for many types of samples to be analyzed. However, the cost is that the holder faceplate can bend, introducing uncertainty into the SIMS results. Here we designed and created an improved sample holder which is reinforced to prevent faceplate deflection and thereby reduce uncertainty. Simulations show that the new design significantly reduces deflection from 10 µm to 5 nm. Measurements show a reduction of calibration (RSF) uncertainty from this source from 4.1% to 0.95%. Grain orientation has long been suspected to affect RSF determination as well. A bicrystal implant standard consisting of [111] and [001] grains were repeatedly rotated 15° in between analyses. It was observed that 20% of the analyses performed on [111] grains exhibited anomalously high RSF values likely due to the changing of the grain normal with respect to the primary Cs+ beam.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUPFDV002

About •

Received ※ 21 June 2021 — Revised ※ 11 July 2021 — Accepted ※ 21 August 2021 — Issue date ※ 05 January 2022

Cite •

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

TUPFDV004

A SIMS Approach for the Analysis of Furnace Contamination

406

J.W. Angle, M.J. Kelley
Virginia Polytechnic Institute and State University, Blacksburg, USA
M.J. Kelley, E.M. Lechner, A.D. Palczewski, C.E. Reece
JLab, Newport News, Virginia, USA
F.A. Stevie
NCSU AIF, Raleigh, North Carolina, USA

Detection of surface contamination for SRF material is difficult due to the miniscule quantities and near atomic resolution needed. Visual inspection of samples known to have experienced surface contamination were found to have inconsistent nitride coverage after nitrogen doping. EBSD analysis suggest that nitride suppression tends to be most prevalent when deviating from the [111] and [001] zone axes. XPS suggested that tin was present as a contaminant on the surface with SIMS mass spectra also confirming its presence. SIMS depth profiles show a depletion of nitrogen content as well as an increase in car-bon content for contaminated samples.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUPFDV004

About •

Received ※ 22 June 2021 — Revised ※ 11 July 2021 — Accepted ※ 21 August 2021 — Issue date ※ 19 February 2022

Cite •

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

TUPTEV013

Managing Sn-Supply to Tune Surface Characteristics of Vapor-Diffusion Coating of Nb₃Sn

516

U. Pudasaini, C.E. Reece
JLab, Newport News, Virginia, USA
J.K. Tiskumara
ODU, Norfolk, Virginia, USA

Funding: Authored by Jefferson Science Associates under contract no. DE¬AC05¬06OR23177
Nb₃Sn promises better RF performance (Q and E_acc) than niobium at any given temperature because of superior superconducting properties. Nb₃Sn-coated SRF cavities are now produced routinely by growing a few microns thick Nb₃Sn films inside Nb cavities via the tin vapor diffusion technique. Sn evaporation and consumption during the growth process notably affect the quality of the coating. Aiming at favorable surface characteristics that could enhance the RF performance, many coatings were produced by varying Sn sources and temperature profiles. Coupon samples were examined using different material characterization techniques, and a selected few sets of coating parameters were used to coat 1.3 GHz single-cell cavities for RF testing. The Sn supply’s careful tuning is essential to manage the microstructure, roughness, and overall surface characteristics of the coating. We summarize the material analysis of witness samples and discuss the performance of several Nb₃Sn-coated single-cell cavities linked to Sn-source characteristics and observed Sn consumption during the film growth process.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUPTEV013

About •

Received ※ 21 June 2021 — Revised ※ 09 October 2021 — Accepted ※ 15 December 2021 — Issue date ※ 22 February 2022

Cite •

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

THPFDV003

SIMS Investigation of Furnace-Baked Nb

761

E.M. Lechner, M.J. Kelley, A.D. Palczewski, C.E. Reece
JLab, Newport News, Virginia, USA
J.W. Angle, M.J. Kelley
Virginia Polytechnic Institute and State University, Blacksburg, USA
F.A. Stevie
NCSU AIF, Raleigh, North Carolina, USA

Funding: U.S. DOE Contract No. DE-AC05-06OR23177
Results recently published by Ito et al. showed that "furnace baking" Nb SRF cavities after electropolishing yields high quality factors and anti-Q-slopes resembling that of N doped cavities. Small Nb samples were prepared following the recipe outlined by Ito. These samples were measured by SIMS to examine impurity contributions to the RF penetration layer. These diffusion profiles are modeled, and their consequences on RF properties discussed.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPFDV003

About •

Received ※ 22 June 2021 — Accepted ※ 24 November 2021 — Issue date ※ 15 May 2022

Cite •

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

THPCAV008

Results From the Proton Power Upgrade Project Cavity Quality Assurance Plan

801

J.D. Mammosser, B.E. Robertson
ORNL RAD, Oak Ridge, Tennessee, USA
R. Afanador, M.S. Champion, M.N. Greenwood, M.P. Howell, S.-H. Kim, S.E. Stewart, D.J. Vandygriff
ORNL, Oak Ridge, Tennessee, USA
A. Bitter, K.B. Bolz, A. Navitski, L. Zweibäumer
RI Research Instruments GmbH, Bergisch Gladbach, Germany
E. Daly, G.K. Davis, P. Dhakal, D. Forehand, K. Macha, C.E. Reece, K.M. Wilson
JLab, Newport News, Virginia, USA

Funding: UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE)
The Proton Power Upgrade (PPU) Project at Oak Ridge National Lab’s Spallation Neutron Source (SNS) is currently under construction. The project will double the beam power from 1.4 to 2.8 MW. This is accomplished by increasing the beam current and adding seven new Superconducting Radio Frequency (SRF) cryomodules. Each new cryomodule will contain four six-cell, beta 0.81, PPU style cavities. A quality assurance plan was developed and implemented for the procurement of 32 PPU cavities. As part of this plan, reference cavities were qualified and sent to Research Instruments Co. for the development and verification of process steps. Here we present the results from this plan to date.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPCAV008

About •

Received ※ 04 June 2021 — Accepted ※ 06 September 2021 — Issue date ※ 16 May 2022

Cite •

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

THPCAV009

Statistical Modeling of Peak Accelerating Gradients in LCLS-II and LCLS-II-HE

804

J.T. Maniscalco, S. Aderhold, J.D. Fuerst, D. Gonnella
SLAC, Menlo Park, California, USA
T.T. Arkan, M. Checchin, J.A. Kaluzny, S. Posen
Fermilab, Batavia, Illinois, USA
J. Hogan, A.D. Palczewski, C.E. Reece, K.M. Wilson
JLab, Newport News, Virginia, USA

In this report, we study the vertical test gradient performance and the gradient degradation between vertical test and cryomodule test for the 1.3 GHz LCLS-II cavities. We develop a model of peak gradient statistics, and use our understanding of the LCLS-II results and the changes implemented for LCLS-II-HE to estimate the expected gradient statistics for the new machine. Finally, we lay out a plan to ensure that the LCLS-II-HE cryomodule gradient specifications are met while minimizing cavity disqualification by introducing a variable acceptance threshold for the accelerating gradient.

Poster THPCAV009 [1.311 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPCAV009

About •

Received ※ 21 June 2021 — Revised ※ 14 September 2021 — Accepted ※ 02 November 2021 — Issue date ※ 23 November 2021

Cite •

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

THPTEV012

Substitution of Spring Clamps for Bolts on SRF Cavity Flanges to Minimize Particle Generation

853

G.H. Biallas
Hyperboloid LLC, Yorktown, Virginia, USA
E. Daly, K. Macha, C.E. Reece
JLab, Newport News, Virginia, USA

Funding: Funding supplied by US Department of Energy SBIR Grant #DE-SC0019579
Hyperboloid LLC developed and successfully tested a System of High Force Spring Clamps to substitute, one for one, for bolts on the flanges of SRF Cavities. The Clamps are like exceptionally forceful binder clips. The System, that includes the Hydraulic Openers that apply the clamps, minimizes generation of particulates when sealing cavity flanges. Hyperboloid LLC used ANSYS to design the titanium clamps that generate the force to seal the hexagonal cross section, relatively hard aluminum gasket developed for TESLA and used at JLab and other accelerators. The System is developed to be suitable for use in SRF Clean Rooms. Results of particle counter readings during bolt and clamp installation and superfluid helium challenges to the sealed flanges are discussed. Results of a half-size clamp that could seal a soft aluminum gasket and the attempt to seal a gasket made of niobium are also discussed.
L. Monaco, P. Michelato, C. Pagani, N. Panzeri, Experimental and Theoretical Analysis of Tesla-like SFRF Cavity Flanges, INFN Milano- LASA, I-20090 Segrate (MI), Italy. Proc. EPAC 2006, Edinburgh, SC

Poster THPTEV012 [1.404 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPTEV012

About •

Received ※ 21 June 2021 — Revised ※ 16 December 2021 — Accepted ※ 28 April 2022 — Issue date ※ 01 May 2022

Cite •

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

THPTEV017

Status of the LCLS-II-HE Project at Jefferson Lab

876

K.M. Wilson, J. Hogan, M. Laney, A.D. Palczewski, C.E. Reece
JLab, Newport News, Virginia, USA

Funding: This work was supported by the U.S. Department of Energy Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177 (JSA); and for BES under contract DE’AC02’76SF00515 (SLAC).
The Linac Coherent Light Source II High Energy (LCLS-II-HE) upgrade at the SLAC National Accelerator Laboratory is being constructed in partnership with the Thomas Jefferson National Accelerator Facility (JLab) and the Fermi National Accelerator Laboratory (FNAL). The cryomodule production scope consists of the design, procurement, construction, and acceptance testing of 24 eight-cavity, 1.3 GHz cryomodules, as well as R&D activities necessary to develop the required technology. To achieve this, JLab and FNAL are also contributing to SLAC’s effort to develop the cavity recipe and production processes necessary to meet the LCLS-II-HE goal of 20.8 MV/m and average Q₀ of 2.7·10¹⁰. This paper details the JLab scope, focusing on the project initiation phase, in particular technology development and prototyping, project development and planning, and implementation of lessons learned from LCLS-II.

Poster THPTEV017 [1.536 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPTEV017

About •

Received ※ 21 June 2021 — Revised ※ 12 August 2021 — Accepted ※ 02 March 2022 — Issue date ※ 01 May 2022

Cite •

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

FROFDV02

A Novel Approach to Producing High Gradient and Q₀ Cavities in Non-Ideal Furnaces

A.D. Palczewski, P. Dhakal, C.E. Reece
JLab, Newport News, Virginia, USA
D. Gonnella
SLAC, Menlo Park, California, USA

Funding: Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Since the discovery of nitrogen doping in 2014, infusion in 2017, "mid-T bakes in 2018; the reproducibility in both Q₀ and gradient has been proven to be highly variable between facilities and even within the same furnace within a facility*. Multiple studies have pointed to possible contamination from pumps, non-Molybdenum frame outgassing within a hot zone, gas purity issues, and cross-contamination between furnace runs. The traditional approach to mitigating these effects is using niobium furnace caps, high-temperature furnace burnout runs, and expensive pump replacements. We will show multiple examples of a novel approach to increasing Q₀ and Q₀+E_acc, using a simple treatment after a furnace treatment or doping + light EP. We will also outline the possible workflows using this new technique in production.
*Pashupati Dhakal, https://doi.org/10.1016/j.physo.2020.100034, and enclosed citations.

Cite •

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