NAPAC2019 - List of Keywords (accelerating-gradient)

Paper	Title	Other Keywords	Page
MOYBB3	Progress in Nb₃Sn SRF Cavities at Cornell University	cavity, SRF, site, superconductivity	37
	R.D. Porter, H. Hu, M. Liepe, N.A. Stilin, Z. Sun, M.J. Tao Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Niobium-3 Tin (NbSn) is the most promising alternative material for next-generation SRF cavities. The material can obtain high quality factors (> 10¹⁰) at 4.2 K and could theoretically support ~ 96 MV/m operation of a TESLA elliptical style cavity. Current Nb₃Sn cavities made at Cornell University achieve high quality factors but are limited to about 17 MV/m in CW operation due to the presence of a surface defect. Here we examine recent results on studying the quench mechanism and propose that surface roughness is a major limiter for accelerating gradients. Furthermore, we discuss recent work on reducing the surface roughness including chemical polishing, modification of material growth, and tin electroplating.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBB3
About •	paper received ※ 02 September 2019 paper accepted ※ 12 September 2019 issue date ※ 08 October 2019
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WEPLM52	Recent Developments of Nb₃Sn at Jefferson Lab for SRF Accelerator Application	cavity, SRF, cryomodule, factory	713
	U. Pudasaini, M.J. Kelley The College of William and Mary, Williamsburg, Virginia, USA G.V. Eremeev, M.J. Kelley, C.E. Reece JLab, Newport News, Virginia, USA
	Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics. The desire to reduce the construction and operating costs of future SRF accelerators motivates the search for alternative, higher-performing materials. Nb₃Sn (Tc ~ 18.3 K and Hsh ~ 425 mT) is the front runner. However, tests of early Nb₃Sn-coated cavities encountered strong Q-slopes limiting the performance. Learnings from studies of coated materials related to cavity performance prompted significant changes to the coating process. It is now possible to routinely produce slope-free single-cell cavities having Q₀ ≥ 2×10¹⁰ at 4 K and > 4×10¹⁰ at 2 K up to the accelerating gradient in excess of 15 MV/m at its best. Obtaining similar results in five-cell cavities is a current goal to test them under an accelerator environment. This contribution discusses recent developments at Jefferson Lab.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM52
About •	paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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WEPLM62	First Cold Test Results of a Medium-Beta 644 MHz Superconducting 5-Cell Elliptical Cavity for the FRIB Energy Upgrade	cavity, target, pick-up, linac	731
	K.E. McGee, B.W. Barker, K. Elliott, A. Ganshyn, W. Hartung, S.H. Kim, P.N. Ostroumov, J.T. Popielarski, A. Taylor, C. Zhang FRIB, East Lansing, Michigan, USA M.P. Kelly, T. Reid ANL, Lemont, Illinois, USA
	Funding: Work supported by Michigan State University. The superconducting linac for the Facility for Rare Isotope Beams (FRIB) will accelerate ions to 200 MeV per nucleon, with the possibility of a future energy upgrade to 400 MeV per nucleon via additional cavities. A 5-cell superconducting β = 0.65 elliptical cavity was designed for this purpose. Two unjacketed 5-cell niobium cavities were fabricated; the first of these was Dewar tested in February 2019. The surface preparation was bulk electropolishing (EP, 150 µm), hydrogen degassing (600°C, 10 hours), light EP (20 µm), clean-room high-pressure water rinsing, and in-situ baking (120°C, 48 hours). We achieved Q₀ = 2·10¹⁰, equivalent to Rs = 10 nΩ, at the design gradient of 17.5 MV/m. The cavity was tested in a newly refurbished FRIB test Dewar, equipped with a variable input coupler.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM62
About •	paper received ※ 02 September 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019
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WEPLM67	Optimization of a Single-Cell Accelerating Structure for Rf Breakdown Test With Short Rf Pulses	acceleration, experiment, collider, linear-collider	747
	M.M. Peng, J. Shi TUB, Beijing, People’s Republic of China M.E. Conde, G. Ha, C.-J. Jing, W. Liu, J.G. Power, J. Seok, J.H. Shao, E.E. Wisniewski ANL, Lemont, Illinois, USA C.-J. Jing Euclid TechLabs, LLC, Solon, Ohio, USA
	RF breakdown is one of the major limitations to achieve high gradient acceleration for future structure-based normal conducting linear colliders. Previous statistic research shows that the breakdown rate is proportional to E_a³⁰ * t_p⁵, which indicates that the accelerating gradient E_a could be improved by using shorter RF pulses (t_p). An X-band 11.7~GHz metallic single-cell structure has been designed for RF breakdown study up to 273~MV/m using short pulses (~3ns) generated by a 400~MW power extractor at Argonne Wakefield Accelerator (AWA) facility. The structure has also been scaled to 11.424~GHz for the long pulse (100-1500~ns) breakdown study driven by a klystron and a pulse compressor at Tsinghua X-band High Power Test-stand (TPoT-X), with the gradient up to 246~MV/m with 200~MW input power.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM67
About •	paper received ※ 05 September 2019 paper accepted ※ 26 November 2019 issue date ※ 08 October 2019
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WEPLM68	Design of a Dielectric-Loaded Accelerator for Short Pulse High Gradient Research	acceleration, wakefield, simulation, experiment	751
	M.M. Peng, J. Shi TUB, Beijing, People’s Republic of China M.E. Conde, G. Ha, C.-J. Jing, W. Liu, J.G. Power, J. Seok, J.H. Shao, E.E. Wisniewski ANL, Lemont, Illinois, USA C.-J. Jing Euclid TechLabs, LLC, Solon, Ohio, USA
	The short-pulse two-beam acceleration approach is a promising candidate to meet the cost and luminosity requirements for future linear colliders. Dielectric-loaded structure has been intensely investigated for this approach because of its low fabrication cost, low RF loss, and potential to withstand GV/m gradient. An X-band 11.7~GHz dielectric-loaded accelerator (DLA) has been designed for high power test with short RF pulses (3~ns) generated from a power extractor driven by high charge bunches at Argonne Wakefield Accelerator (AWA) facility. The gradient is expected to be over 100~MV/m with the maximum input power of 400~MW.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM68
About •	paper received ※ 05 September 2019 paper accepted ※ 27 November 2019 issue date ※ 08 October 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Other Keywords

Page

MOYBB3

Progress in Nb₃Sn SRF Cavities at Cornell University

cavity, SRF, site, superconductivity

37

R.D. Porter, H. Hu, M. Liepe, N.A. Stilin, Z. Sun, M.J. Tao
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Niobium-3 Tin (NbSn) is the most promising alternative material for next-generation SRF cavities. The material can obtain high quality factors (> 10¹⁰) at 4.2 K and could theoretically support ~ 96 MV/m operation of a TESLA elliptical style cavity. Current Nb₃Sn cavities made at Cornell University achieve high quality factors but are limited to about 17 MV/m in CW operation due to the presence of a surface defect. Here we examine recent results on studying the quench mechanism and propose that surface roughness is a major limiter for accelerating gradients. Furthermore, we discuss recent work on reducing the surface roughness including chemical polishing, modification of material growth, and tin electroplating.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBB3

About •

paper received ※ 02 September 2019 paper accepted ※ 12 September 2019 issue date ※ 08 October 2019

Export •

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

WEPLM52

Recent Developments of Nb₃Sn at Jefferson Lab for SRF Accelerator Application

cavity, SRF, cryomodule, factory

713

U. Pudasaini, M.J. Kelley
The College of William and Mary, Williamsburg, Virginia, USA
G.V. Eremeev, M.J. Kelley, C.E. Reece
JLab, Newport News, Virginia, USA

Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics.
The desire to reduce the construction and operating costs of future SRF accelerators motivates the search for alternative, higher-performing materials. Nb₃Sn (Tc ~ 18.3 K and Hsh ~ 425 mT) is the front runner. However, tests of early Nb₃Sn-coated cavities encountered strong Q-slopes limiting the performance. Learnings from studies of coated materials related to cavity performance prompted significant changes to the coating process. It is now possible to routinely produce slope-free single-cell cavities having Q₀ ≥ 2×10¹⁰ at 4 K and > 4×10¹⁰ at 2 K up to the accelerating gradient in excess of 15 MV/m at its best. Obtaining similar results in five-cell cavities is a current goal to test them under an accelerator environment. This contribution discusses recent developments at Jefferson Lab.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM52

About •

paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

Export •

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

WEPLM62

First Cold Test Results of a Medium-Beta 644 MHz Superconducting 5-Cell Elliptical Cavity for the FRIB Energy Upgrade

cavity, target, pick-up, linac

731

K.E. McGee, B.W. Barker, K. Elliott, A. Ganshyn, W. Hartung, S.H. Kim, P.N. Ostroumov, J.T. Popielarski, A. Taylor, C. Zhang
FRIB, East Lansing, Michigan, USA
M.P. Kelly, T. Reid
ANL, Lemont, Illinois, USA

Funding: Work supported by Michigan State University.
The superconducting linac for the Facility for Rare Isotope Beams (FRIB) will accelerate ions to 200 MeV per nucleon, with the possibility of a future energy upgrade to 400 MeV per nucleon via additional cavities. A 5-cell superconducting β = 0.65 elliptical cavity was designed for this purpose. Two unjacketed 5-cell niobium cavities were fabricated; the first of these was Dewar tested in February 2019. The surface preparation was bulk electropolishing (EP, 150 µm), hydrogen degassing (600°C, 10 hours), light EP (20 µm), clean-room high-pressure water rinsing, and in-situ baking (120°C, 48 hours). We achieved Q₀ = 2·10¹⁰, equivalent to Rs = 10 nΩ, at the design gradient of 17.5 MV/m. The cavity was tested in a newly refurbished FRIB test Dewar, equipped with a variable input coupler.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM62

About •

paper received ※ 02 September 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019

Export •

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

WEPLM67

Optimization of a Single-Cell Accelerating Structure for Rf Breakdown Test With Short Rf Pulses

acceleration, experiment, collider, linear-collider

747

M.M. Peng, J. Shi
TUB, Beijing, People’s Republic of China
M.E. Conde, G. Ha, C.-J. Jing, W. Liu, J.G. Power, J. Seok, J.H. Shao, E.E. Wisniewski
ANL, Lemont, Illinois, USA
C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA

RF breakdown is one of the major limitations to achieve high gradient acceleration for future structure-based normal conducting linear colliders. Previous statistic research shows that the breakdown rate is proportional to E_a³⁰ * t_p⁵, which indicates that the accelerating gradient E_a could be improved by using shorter RF pulses (t_p). An X-band 11.7~GHz metallic single-cell structure has been designed for RF breakdown study up to 273~MV/m using short pulses (~3ns) generated by a 400~MW power extractor at Argonne Wakefield Accelerator (AWA) facility. The structure has also been scaled to 11.424~GHz for the long pulse (100-1500~ns) breakdown study driven by a klystron and a pulse compressor at Tsinghua X-band High Power Test-stand (TPoT-X), with the gradient up to 246~MV/m with 200~MW input power.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM67

About •

paper received ※ 05 September 2019 paper accepted ※ 26 November 2019 issue date ※ 08 October 2019

Export •

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

WEPLM68

Design of a Dielectric-Loaded Accelerator for Short Pulse High Gradient Research

acceleration, wakefield, simulation, experiment

751

M.M. Peng, J. Shi
TUB, Beijing, People’s Republic of China
M.E. Conde, G. Ha, C.-J. Jing, W. Liu, J.G. Power, J. Seok, J.H. Shao, E.E. Wisniewski
ANL, Lemont, Illinois, USA
C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA

The short-pulse two-beam acceleration approach is a promising candidate to meet the cost and luminosity requirements for future linear colliders. Dielectric-loaded structure has been intensely investigated for this approach because of its low fabrication cost, low RF loss, and potential to withstand GV/m gradient. An X-band 11.7~GHz dielectric-loaded accelerator (DLA) has been designed for high power test with short RF pulses (3~ns) generated from a power extractor driven by high charge bunches at Argonne Wakefield Accelerator (AWA) facility. The gradient is expected to be over 100~MV/m with the maximum input power of 400~MW.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM68

About •

paper received ※ 05 September 2019 paper accepted ※ 27 November 2019 issue date ※ 08 October 2019

Export •

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