SRF2019 - List of Authors (Grassellino, A.)

Paper	Title	Page
FRTU3	Pushing Bulk Nb Limits (High Q, High Gradient, Reliable SRF Accelerators)
	A. Grassellino Fermilab, Batavia, Illinois, USA
	Superconducting RF technology for particle accelerators have come a long way but still have huge and unexplored potential. SRF technology state of the art cavities have gradients up to 50 MV/m and quality factors exceeding 5·10¹⁰ at 2K, 1.3 GHz, 2·10¹¹ at 1.5K, 2·10¹⁰ at 4.2K (Nb₃Sn). SRF is now at the beginning of a new phase. The next factor of 2-3 will require a strong focus on: Physics of SRF surface (material science tools. As much involvement as possible of superconductivity theory experts with strong ties to technology centers/labs. Long term to focus on: what is the ultimate limit for achievable gradients and Q? Can we go to 100 MV/m or more? We need to understand the ultimate limitations and explore pathways forward.
	Slides FRTU3 [45.661 MB]
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOP026	A Cross-Lab Qualification of Modified 120°C Baked Cavities	90
	M. Wenskat, D. Reschke, J. Schaffran, L. Steder, M. Wiencek DESY, Hamburg, Germany D. Bafia, A. Grassellino, O.S. Melnychuk Fermilab, Batavia, Illinois, USA A.D. Palczewski JLab, Newport News, Virginia, USA M. Wiencek IFJ-PAN, Kraków, Poland
	Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Technologies (MT) Program and by the BMBF under the research grant 05H18GURB1. Within a global effort to understand and standardize the nitrogen-infusion and the low T bake procedure, one large grain and two fine grain single-cell cavity were treated and tested at FNAL and then send to other labs including DESY and JLab for further studies.
	Poster MOP026 [0.813 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP026
About •	paper received ※ 20 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOP031	Investigation of Frequency Behavior Near Tc of Niobium Superconducting Radio-Frequency Cavities	112
SUSP016	use link to see paper's listing under its alternate paper code
	D. Bafia, J. Zasadzinski IIT, Chicago, Illinois, USA D. Bafia, M. Checchin, A. Grassellino, O.S. Melnychuk, A.S. Romanenko, D.A. Sergatskov Fermilab, Batavia, Illinois, USA
	This paper will present a systematic investigation of the resonant frequency behavior of niobium SRF cavities subject to different surface processing (nitrogen doping, nitrogen infusion, 120°C bake, EP, etc.) near the critical transition temperature. We find features occurring in frequency versus temperature (FvsT) data near Tc that seem to vary with surface processing. Emphasis is placed on one of the observed features: a dip in the superconducting resonant frequency below the normal conducting value which is prominent in nitrogen doped cavities and appears to be a signature of nitrogen doping. This gives further insights on the mechanisms responsible for the large increase in performance of cavities subject to this surface treatment. The magnitude of this dip in frequency is studied and related to possible physical parameters such as the concentration of impurities near the surface and the design resonant frequency of the cavity. A possible explanation for the meaning of this dip is discussed, namely, that it is a result of strong coupling between electrons and phonons within the resonator.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP031
About •	paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOP045	The LCLS-II HE High Q and Gradient R&D Program	154
	D. Gonnella, S. Aderhold, A. Burrill, G.R. Hays, T.O. Raubenheimer, M.C. Ross SLAC, Menlo Park, California, USA D. Bafia, M. Checchin, A. Grassellino, M. Martinello, A.S. Romanenko Fermilab, Batavia, Illinois, USA M. Ge, M. Liepe, S. Posen Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA A.D. Palczewski, C.E. Reece JLab, Newport News, Virginia, USA
	Funding: US DOE and the LCLS-II HE Project The LCLS-II HE project is a high energy upgrade to the superconducting LCLS-II linac. It consists of adding twenty additional 1.3 GHz cryomodules to the linac, with cavities operating at a gradient of 20.8 MV/m with a Q₀ of 2.7·10¹⁰. Performance of LCLS-II cryomodules has suggested that operations at this high of a gradient will not be achievable with the existing cavity recipe employed. Therefore a research program was developed between SLAC, Fermilab, Thomas Jefferson National Accelerator Facility, and Cornell University in order to improve the cavity processing method of the SRF cavities and reach the HE goals. This program explores the doping regime beyond what was done for LCLS-II and also has looked to further developed nitrogen-infusion. Here we will summarize the results from this R\&D program, showing significant improvement on both single-cell and 9-cell cavities compared with the original LCLS-II cavity recipe.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP045
About •	paper received ※ 25 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOP092	Overview of LCLS-II Project Status at Fermilab	302
	R.P. Stanek, T.T. Arkan, J.N. Blowers, C.M. Ginsburg, A. Grassellino, C.J. Grimm, B.J. Hansen, E.R. Harms, B.D. Hartsell, J.P. Holzbauer, J.A. Kaluzny, A.L. Klebaner, A. Martinez, T.H. Nicol, Y.O. Orlov, K.S. Premo, N. Solyak, J. Theilacker, G. Wu Fermilab, Batavia, Illinois, USA
	The superconducting RF Continuous-Wave (CW) Linac for the LCLS-II consists of thirty-five 1.3 GHz and two 3.9 GHz cryomodules that Fermilab and Jefferson Lab are jointly producing in collaboration with SLAC. Fermilab¿s scope of work is to build, test, and deliver half the 1.3 GHz and all the 3.9 GHz cryomodules and to design and procure components for the cryogenic distribution system. Fermilab has primary responsibility for delivering a working design. The cryomodule design basis was the European XFEL but several elements evolved to meet CW operation requirements and specifics of the SLAC tunnel. There have been several challenges faced during the design, assembly, testing and transportation of the cryomodules which have required design updates. Success in overcoming these challenges is attributable to the strength of the LCLS-II SRF Collaboration (Fermilab, Jefferson Lab and SLAC with extensive help from DESY and CEA/Saclay). The cryogenic distribution system has progressed relatively well and there are valuable Lessons Learned. An overview of the status, accomplishments, problems encountered, solutions developed, and a summary of Lessons Learned will be presented.
	Poster MOP092 [0.393 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP092
About •	paper received ※ 20 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUFUA2	Overview of Progress in High Q and High G in Niobium Cavities
	A. Grassellino Fermilab, Batavia, Illinois, USA
	There was no abstract provided by the author.
	Slides TUFUA2 [42.782 MB]
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUFUA4	New Insights on Nitrogen Doping	347
	D. Bafia, J. Zasadzinski IIT, Chicago, Illinois, USA D. Bafia, M. Checchin, A. Grassellino, O.S. Melnychuk, A.S. Romanenko, D.A. Sergatskov Fermilab, Batavia, Illinois, USA
	This paper covers a systematic study of the quench in nitrogen doped cavities: a cavity was sequentially treated/reset with different N-doping recipes which are known to produce different levels of quench field. Analysis of cavity heating profiles using TMAP are used to gain insight on the origins of quench; new recipes demonstrate the possibility to increase quench fields well beyond 30 MV/m. In addition, a new signature of nitrogen doping is explored, namely, a dip in the superconducting resonant frequency below the normal conducting value just below the critical transition temperature, giving further insights on the mechanisms responsible for the large increase in performance of cavities subject to this surface treatment.
	Slides TUFUA4 [3.097 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUFUA4
About •	paper received ※ 23 June 2019 paper accepted ※ 03 July 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUP061	Gradients of 50 MV/m in TESLA Shaped Cavities via Modified Low Temperature Bake	586
	D. Bafia, J. Zasadzinski IIT, Chicago, Illinois, USA D. Bafia, A. Grassellino, O.S. Melnychuk, A.S. Romanenko, Z-H. Sung Fermilab, Batavia, Illinois, USA
	This paper will discuss the 75/120 C modified low temperature bake capable of giving unprecedented accel-erating gradients of above 50 MV/m for 1.3 GHz TESLA-shaped niobium SRF cavities in CW operation. A bifurca-tion in the Q₀ vs E_acc curve is observed after retesting cavities without disassembly in between, yielding per-formance that ranges from exceptional to above state-of-the-art. Atomic Force Microscopy studies on cavity cut-outs gives a possible mechanism responsible for this branching in performance, namely, the dissociation and growth of room temperature niobium nano-hydrides that exist near the RF surface, which are made superconduct-ing only through the proximity effect. In-situ low temper-ature baking of cavity cutouts reveals a dissociation of these room temperature nano-hydrides, which could ex-plain the higher performance of cavities subject to similar in-situ heating in the dewar.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP061
About •	paper received ※ 23 June 2019 paper accepted ※ 03 July 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUP062	New Insights in the Quench Mechanisms in Nitrogen Doped Cavities	592
	D. Bafia, J. Zasadzinski IIT, Chicago, Illinois, USA D. Bafia, D.J. Bice, A. Grassellino, O.S. Melnychuk, A.S. Romanenko, D.A. Sergatskov Fermilab, Batavia, Illinois, USA D. Gonnella SLAC, Menlo Park, California, USA A.D. Palczewski JLab, Newport News, Virginia, USA
	This paper will cover a systematic study of the quench in nitrogen doped cavities: three cavities were sequentially treated/reset with different doping recipes which are known to produce different levels of quench field. Analysis of mean free path and TMAP coupled with sample analysis reveals new insights on the physics of the premature quench in nitrogen doped cavities; new recipes demonstrate the possibility to increase quench fields well beyond 30 MV/m.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP062
About •	paper received ※ 23 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUP085	Operation of an SRF Cavity Tuner Submerged into Liquid He	660
	Y.M. Pischalnikov, D.J. Bice, A. Grassellino, T.N. Khabiboulline, O.S. Melnychuk, R.V. Pilipenko, S. Posen, O.V. Pronitchev, A.S. Romanenko Fermilab, Batavia, Illinois, USA
	To precisely control the resonance of 1.3 GHz SRF cavities during testing at the FNAL’s Vertical Test Facility, we install for the first time a double lever tuner and operate it when submerged into the liquid He bath. Both active components of the tuner: electromechanical actuator (stepper motor) and piezo-actuators are operated inside superfluid helium. Accuracy in controlling the SRF cavity resonance frequency will be presented. Specifics of the tuner operation when submerged into liquid He will be discussed.
	Poster TUP085 [2.164 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP085
About •	paper received ※ 23 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THP014	First Direct Imaging and Profiling TOF-SIMS Studies on Cutouts from Cavities Prepared by State-of-the-Art Treatments	866
	A.S. Romanenko, A. Grassellino, M. Martinello, Y. Trenikhina Fermilab, Batavia, Illinois, USA D. Bafia Illinois Institute of Technology, Chicago, Illinois, USA
	Funding: This work has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. Small amounts of interstitial impurities in the penetra-tion depth of superconducting radio frequency (SRF) cavities have a dramatic effect on the quality factors and maximum accelerating gradients. Here we report the first TOF-SIMS studies of cutouts from cavities prepared by all modern surface treatments, which allow a direct corre-lation of the impurity distribution with the observed cavity performance. Imaging capability of our instrument allows to avoid the possible issues associated with the ‘‘ghost’’ depth profiles appearing as a consequence of particulate surface contamination, which likely caused the inconclusive SIMS results on e.g. oxygen diffusion in the past.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP014
About •	paper received ※ 02 July 2019 paper accepted ※ 04 July 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

FRCAA3	Industrial Cavity Production: Lessons Learned to Push the Boundaries of Nitrogen-Doping	1199
	D. Gonnella, S. Aderhold, A. Burrill, M.C. Ross SLAC, Menlo Park, California, USA E. Daly, G.K. Davis, F. Marhauser, A.D. Palczewski, K.M. Wilson JLab, Newport News, Virginia, USA A. Grassellino, C.J. Grimm, T.N. Khabiboulline, O.S. Melnychuk, S. Posen, D.A. Sergatskov Fermilab, Batavia, Illinois, USA
	Funding: Work supported by US DOE Contract DE-AC02-76SF00515. Nitrogen doping has been proven now in several labs to enhance Q₀ values of 1.3 GHz cavities in the gradient domain favored by CW operation. The choice of doping for the LCLS-II project has given the community a wealth of statistics and experience on the challenge of transferring the doping technology to industry. Overall, industry-produced nitrogen-doped cavities have shown excellent performance, however some technical issues have arisen. This talk focuses on lessons learned from the production of over 300 nitrogen-doped cavities for LCLS-II and how issues were mitigated to further improve performance. Finally, I will discuss pushing the boundaries of nitrogen-doping further by exploring different doping regimes in order to maintain excellent Q₀ performance, while reaching higher quench fields.
	Slides FRCAA3 [16.880 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAA3
About •	paper received ※ 02 July 2019 paper accepted ※ 03 July 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

FRCAB7	Plasma Processing to Reduce Field Emission in LCLS-II 1.3 GHz SRF Cavities	1231
SUSP022	use link to see paper's listing under its alternate paper code
TUP067	use link to see paper's listing under its alternate paper code
	B. Giaccone, J. Zasadzinski IIT, Chicago, Illinois, USA P. Berrutti, B. Giaccone, A. Grassellino, M. Martinello Fermilab, Batavia, Illinois, USA M. Doleans ORNL, Oak Ridge, Tennessee, USA D. Gonnella, G. Lanza, M.C. Ross SLAC, Menlo Park, California, USA
	Plasma cleaning for LCLS-II 9-cell 1.3 GHz cavities is under study at Fermilab. Starting from ORNL method, we have developed a new technique for plasma ignition using HOMs. Plasma processing is being applied to contaminated and field emitting cavities, here are discussed the first results in terms of Q and radiation vs E measured before and after treatment. Further studies are ongoing to optimize plasma parameters and to acquire statistics on plasma cleaning effectiveness.
	Slides FRCAB7 [14.701 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB7
About •	paper received ※ 23 June 2019 paper accepted ※ 04 July 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

FRTU3

Pushing Bulk Nb Limits (High Q, High Gradient, Reliable SRF Accelerators)

A. Grassellino
Fermilab, Batavia, Illinois, USA

Superconducting RF technology for particle accelerators have come a long way but still have huge and unexplored potential. SRF technology state of the art cavities have gradients up to 50 MV/m and quality factors exceeding 5·10¹⁰ at 2K, 1.3 GHz, 2·10¹¹ at 1.5K, 2·10¹⁰ at 4.2K (Nb₃Sn). SRF is now at the beginning of a new phase. The next factor of 2-3 will require a strong focus on: Physics of SRF surface (material science tools. As much involvement as possible of superconductivity theory experts with strong ties to technology centers/labs. Long term to focus on: what is the ultimate limit for achievable gradients and Q? Can we go to 100 MV/m or more? We need to understand the ultimate limitations and explore pathways forward.

Slides FRTU3 [45.661 MB]

Export •

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

MOP026

A Cross-Lab Qualification of Modified 120°C Baked Cavities

90

M. Wenskat, D. Reschke, J. Schaffran, L. Steder, M. Wiencek
DESY, Hamburg, Germany
D. Bafia, A. Grassellino, O.S. Melnychuk
Fermilab, Batavia, Illinois, USA
A.D. Palczewski
JLab, Newport News, Virginia, USA
M. Wiencek
IFJ-PAN, Kraków, Poland

Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Technologies (MT) Program and by the BMBF under the research grant 05H18GURB1.
Within a global effort to understand and standardize the nitrogen-infusion and the low T bake procedure, one large grain and two fine grain single-cell cavity were treated and tested at FNAL and then send to other labs including DESY and JLab for further studies.

Poster MOP026 [0.813 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP026

About •

paper received ※ 20 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

Export •

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

MOP031

Investigation of Frequency Behavior Near Tc of Niobium Superconducting Radio-Frequency Cavities

112

SUSP016

use link to see paper's listing under its alternate paper code

D. Bafia, J. Zasadzinski
IIT, Chicago, Illinois, USA
D. Bafia, M. Checchin, A. Grassellino, O.S. Melnychuk, A.S. Romanenko, D.A. Sergatskov
Fermilab, Batavia, Illinois, USA

This paper will present a systematic investigation of the resonant frequency behavior of niobium SRF cavities subject to different surface processing (nitrogen doping, nitrogen infusion, 120°C bake, EP, etc.) near the critical transition temperature. We find features occurring in frequency versus temperature (FvsT) data near Tc that seem to vary with surface processing. Emphasis is placed on one of the observed features: a dip in the superconducting resonant frequency below the normal conducting value which is prominent in nitrogen doped cavities and appears to be a signature of nitrogen doping. This gives further insights on the mechanisms responsible for the large increase in performance of cavities subject to this surface treatment. The magnitude of this dip in frequency is studied and related to possible physical parameters such as the concentration of impurities near the surface and the design resonant frequency of the cavity. A possible explanation for the meaning of this dip is discussed, namely, that it is a result of strong coupling between electrons and phonons within the resonator.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP031

About •

paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

Export •

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

MOP045

The LCLS-II HE High Q and Gradient R&D Program

154

D. Gonnella, S. Aderhold, A. Burrill, G.R. Hays, T.O. Raubenheimer, M.C. Ross
SLAC, Menlo Park, California, USA
D. Bafia, M. Checchin, A. Grassellino, M. Martinello, A.S. Romanenko
Fermilab, Batavia, Illinois, USA
M. Ge, M. Liepe, S. Posen
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
A.D. Palczewski, C.E. Reece
JLab, Newport News, Virginia, USA

Funding: US DOE and the LCLS-II HE Project
The LCLS-II HE project is a high energy upgrade to the superconducting LCLS-II linac. It consists of adding twenty additional 1.3 GHz cryomodules to the linac, with cavities operating at a gradient of 20.8 MV/m with a Q₀ of 2.7·10¹⁰. Performance of LCLS-II cryomodules has suggested that operations at this high of a gradient will not be achievable with the existing cavity recipe employed. Therefore a research program was developed between SLAC, Fermilab, Thomas Jefferson National Accelerator Facility, and Cornell University in order to improve the cavity processing method of the SRF cavities and reach the HE goals. This program explores the doping regime beyond what was done for LCLS-II and also has looked to further developed nitrogen-infusion. Here we will summarize the results from this R\&D program, showing significant improvement on both single-cell and 9-cell cavities compared with the original LCLS-II cavity recipe.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP045

About •

paper received ※ 25 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

Export •

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

MOP092

Overview of LCLS-II Project Status at Fermilab

302

R.P. Stanek, T.T. Arkan, J.N. Blowers, C.M. Ginsburg, A. Grassellino, C.J. Grimm, B.J. Hansen, E.R. Harms, B.D. Hartsell, J.P. Holzbauer, J.A. Kaluzny, A.L. Klebaner, A. Martinez, T.H. Nicol, Y.O. Orlov, K.S. Premo, N. Solyak, J. Theilacker, G. Wu
Fermilab, Batavia, Illinois, USA

The superconducting RF Continuous-Wave (CW) Linac for the LCLS-II consists of thirty-five 1.3 GHz and two 3.9 GHz cryomodules that Fermilab and Jefferson Lab are jointly producing in collaboration with SLAC. Fermilab¿s scope of work is to build, test, and deliver half the 1.3 GHz and all the 3.9 GHz cryomodules and to design and procure components for the cryogenic distribution system. Fermilab has primary responsibility for delivering a working design. The cryomodule design basis was the European XFEL but several elements evolved to meet CW operation requirements and specifics of the SLAC tunnel. There have been several challenges faced during the design, assembly, testing and transportation of the cryomodules which have required design updates. Success in overcoming these challenges is attributable to the strength of the LCLS-II SRF Collaboration (Fermilab, Jefferson Lab and SLAC with extensive help from DESY and CEA/Saclay). The cryogenic distribution system has progressed relatively well and there are valuable Lessons Learned. An overview of the status, accomplishments, problems encountered, solutions developed, and a summary of Lessons Learned will be presented.

Poster MOP092 [0.393 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP092

About •

paper received ※ 20 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

Export •

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

TUFUA2

Overview of Progress in High Q and High G in Niobium Cavities

A. Grassellino
Fermilab, Batavia, Illinois, USA

There was no abstract provided by the author.

Slides TUFUA2 [42.782 MB]

Export •

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

TUFUA4

New Insights on Nitrogen Doping

347

D. Bafia, J. Zasadzinski
IIT, Chicago, Illinois, USA
D. Bafia, M. Checchin, A. Grassellino, O.S. Melnychuk, A.S. Romanenko, D.A. Sergatskov
Fermilab, Batavia, Illinois, USA

This paper covers a systematic study of the quench in nitrogen doped cavities: a cavity was sequentially treated/reset with different N-doping recipes which are known to produce different levels of quench field. Analysis of cavity heating profiles using TMAP are used to gain insight on the origins of quench; new recipes demonstrate the possibility to increase quench fields well beyond 30 MV/m. In addition, a new signature of nitrogen doping is explored, namely, a dip in the superconducting resonant frequency below the normal conducting value just below the critical transition temperature, giving further insights on the mechanisms responsible for the large increase in performance of cavities subject to this surface treatment.

Slides TUFUA4 [3.097 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUFUA4

About •

paper received ※ 23 June 2019 paper accepted ※ 03 July 2019 issue date ※ 14 August 2019

Export •

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

TUP061

Gradients of 50 MV/m in TESLA Shaped Cavities via Modified Low Temperature Bake

586

D. Bafia, J. Zasadzinski
IIT, Chicago, Illinois, USA
D. Bafia, A. Grassellino, O.S. Melnychuk, A.S. Romanenko, Z-H. Sung
Fermilab, Batavia, Illinois, USA

This paper will discuss the 75/120 C modified low temperature bake capable of giving unprecedented accel-erating gradients of above 50 MV/m for 1.3 GHz TESLA-shaped niobium SRF cavities in CW operation. A bifurca-tion in the Q₀ vs E_acc curve is observed after retesting cavities without disassembly in between, yielding per-formance that ranges from exceptional to above state-of-the-art. Atomic Force Microscopy studies on cavity cut-outs gives a possible mechanism responsible for this branching in performance, namely, the dissociation and growth of room temperature niobium nano-hydrides that exist near the RF surface, which are made superconduct-ing only through the proximity effect. In-situ low temper-ature baking of cavity cutouts reveals a dissociation of these room temperature nano-hydrides, which could ex-plain the higher performance of cavities subject to similar in-situ heating in the dewar.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP061

About •

paper received ※ 23 June 2019 paper accepted ※ 03 July 2019 issue date ※ 14 August 2019

Export •

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

TUP062

New Insights in the Quench Mechanisms in Nitrogen Doped Cavities

592

D. Bafia, J. Zasadzinski
IIT, Chicago, Illinois, USA
D. Bafia, D.J. Bice, A. Grassellino, O.S. Melnychuk, A.S. Romanenko, D.A. Sergatskov
Fermilab, Batavia, Illinois, USA
D. Gonnella
SLAC, Menlo Park, California, USA
A.D. Palczewski
JLab, Newport News, Virginia, USA

This paper will cover a systematic study of the quench in nitrogen doped cavities: three cavities were sequentially treated/reset with different doping recipes which are known to produce different levels of quench field. Analysis of mean free path and TMAP coupled with sample analysis reveals new insights on the physics of the premature quench in nitrogen doped cavities; new recipes demonstrate the possibility to increase quench fields well beyond 30 MV/m.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP062

About •

paper received ※ 23 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019

Export •

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

TUP085

Operation of an SRF Cavity Tuner Submerged into Liquid He

660

Y.M. Pischalnikov, D.J. Bice, A. Grassellino, T.N. Khabiboulline, O.S. Melnychuk, R.V. Pilipenko, S. Posen, O.V. Pronitchev, A.S. Romanenko
Fermilab, Batavia, Illinois, USA

To precisely control the resonance of 1.3 GHz SRF cavities during testing at the FNAL’s Vertical Test Facility, we install for the first time a double lever tuner and operate it when submerged into the liquid He bath. Both active components of the tuner: electromechanical actuator (stepper motor) and piezo-actuators are operated inside superfluid helium. Accuracy in controlling the SRF cavity resonance frequency will be presented. Specifics of the tuner operation when submerged into liquid He will be discussed.

Poster TUP085 [2.164 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP085

About •

paper received ※ 23 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019

Export •

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

THP014

First Direct Imaging and Profiling TOF-SIMS Studies on Cutouts from Cavities Prepared by State-of-the-Art Treatments

866

A.S. Romanenko, A. Grassellino, M. Martinello, Y. Trenikhina
Fermilab, Batavia, Illinois, USA
D. Bafia
Illinois Institute of Technology, Chicago, Illinois, USA

Funding: This work has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
Small amounts of interstitial impurities in the penetra-tion depth of superconducting radio frequency (SRF) cavities have a dramatic effect on the quality factors and maximum accelerating gradients. Here we report the first TOF-SIMS studies of cutouts from cavities prepared by all modern surface treatments, which allow a direct corre-lation of the impurity distribution with the observed cavity performance. Imaging capability of our instrument allows to avoid the possible issues associated with the ‘‘ghost’’ depth profiles appearing as a consequence of particulate surface contamination, which likely caused the inconclusive SIMS results on e.g. oxygen diffusion in the past.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP014

About •

paper received ※ 02 July 2019 paper accepted ※ 04 July 2019 issue date ※ 14 August 2019

Export •

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

FRCAA3

Industrial Cavity Production: Lessons Learned to Push the Boundaries of Nitrogen-Doping

1199

D. Gonnella, S. Aderhold, A. Burrill, M.C. Ross
SLAC, Menlo Park, California, USA
E. Daly, G.K. Davis, F. Marhauser, A.D. Palczewski, K.M. Wilson
JLab, Newport News, Virginia, USA
A. Grassellino, C.J. Grimm, T.N. Khabiboulline, O.S. Melnychuk, S. Posen, D.A. Sergatskov
Fermilab, Batavia, Illinois, USA

Funding: Work supported by US DOE Contract DE-AC02-76SF00515.
Nitrogen doping has been proven now in several labs to enhance Q₀ values of 1.3 GHz cavities in the gradient domain favored by CW operation. The choice of doping for the LCLS-II project has given the community a wealth of statistics and experience on the challenge of transferring the doping technology to industry. Overall, industry-produced nitrogen-doped cavities have shown excellent performance, however some technical issues have arisen. This talk focuses on lessons learned from the production of over 300 nitrogen-doped cavities for LCLS-II and how issues were mitigated to further improve performance. Finally, I will discuss pushing the boundaries of nitrogen-doping further by exploring different doping regimes in order to maintain excellent Q₀ performance, while reaching higher quench fields.

Slides FRCAA3 [16.880 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAA3

About •

paper received ※ 02 July 2019 paper accepted ※ 03 July 2019 issue date ※ 14 August 2019

Export •

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

FRCAB7

Plasma Processing to Reduce Field Emission in LCLS-II 1.3 GHz SRF Cavities

1231

SUSP022

use link to see paper's listing under its alternate paper code

TUP067

use link to see paper's listing under its alternate paper code

B. Giaccone, J. Zasadzinski
IIT, Chicago, Illinois, USA
P. Berrutti, B. Giaccone, A. Grassellino, M. Martinello
Fermilab, Batavia, Illinois, USA
M. Doleans
ORNL, Oak Ridge, Tennessee, USA
D. Gonnella, G. Lanza, M.C. Ross
SLAC, Menlo Park, California, USA

Plasma cleaning for LCLS-II 9-cell 1.3 GHz cavities is under study at Fermilab. Starting from ORNL method, we have developed a new technique for plasma ignition using HOMs. Plasma processing is being applied to contaminated and field emitting cavities, here are discussed the first results in terms of Q and radiation vs E measured before and after treatment. Further studies are ongoing to optimize plasma parameters and to acquire statistics on plasma cleaning effectiveness.

Slides FRCAB7 [14.701 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB7

About •

paper received ※ 23 June 2019 paper accepted ※ 04 July 2019 issue date ※ 14 August 2019

Export •

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