IPAC2021 - List of Authors (Liepe, M.)

Paper	Title	Page
MOPAB391	Conduction Cooling Methods for Nb₃Sn SRF Cavities and Cryomodules	1192
	N.A. Stilin, A.T. Holic, M. Liepe, R.D. Porter, J. Sears, Z. Sun Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Rapid progress in the performance of Nb₃Sn SRF cavities during the last few years has made Nb₃Sn an energy efficient alternative to traditional Nb cavities, thereby initiating a fundamental shift in SRF technology. These Nb₃Sn cavities can operate at significantly higher temperatures than Nb cavities while simultaneously requiring less cooling power. This critical property enables the use of new, robust, turn-key style cryogenic cooling schemes based on conduction cooling with commercial cryocoolers. Cornell University has developed and tested a 2.6 GHz Nb₃Sn cavity assembly which utilizes such cooling methods. These tests have demonstrated stable RF operation at 10 MV/m and the measured thermal dynamics match what is found in numerical simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB391
About •	paper received ※ 20 May 2021 paper accepted ※ 10 June 2021 issue date ※ 17 August 2021
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TUPAB338	Surface Roughness Reduction of Nb₃Sn Thin Films via Laser Annealing for Superconducting Radio-Frequency Cavities	2283
	Z. Sun, M. Ge, M. Liepe, T.E. Oseroff, R.D. Porter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA A.B. Connolly, M.O. Thompson Cornell University, Ithaca, USA
	Superconducting radio frequency (SRF) cavities, a key component of particle accelerators, await new SRF materials beyond the state-of-the-art niobium. Nb₃Sn is one of the most competitive candidates, since it increases the superheating field, allows the operation temperature up to 4K, and improves cavity efficiency. Surface roughness and grain boundaries, however, significantly affect the RF performance of current Nb₃Sn cavities. Here, we explore a post laser annealing technique to reduce the surface roughness. In doing so, we deposited a TiN laser-absorber on Nb₃Sn and Nb surfaces, and then annealed the samples by laser scanning via different laser systems. The Nb₃Sn surface roughness was minimized to 101 nm (Ra) by laser annealing via 308 nm, 35 ns pulses. Surface imaging and Fourier analysis revealed laser annealing is able to remove sharp edges and <1 um wavelength features.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB338
About •	paper received ※ 20 May 2021 paper accepted ※ 09 June 2021 issue date ※ 19 August 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Conduction Cooling Methods for Nb₃Sn SRF Cavities and Cryomodules

1192

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

Rapid progress in the performance of Nb₃Sn SRF cavities during the last few years has made Nb₃Sn an energy efficient alternative to traditional Nb cavities, thereby initiating a fundamental shift in SRF technology. These Nb₃Sn cavities can operate at significantly higher temperatures than Nb cavities while simultaneously requiring less cooling power. This critical property enables the use of new, robust, turn-key style cryogenic cooling schemes based on conduction cooling with commercial cryocoolers. Cornell University has developed and tested a 2.6 GHz Nb₃Sn cavity assembly which utilizes such cooling methods. These tests have demonstrated stable RF operation at 10 MV/m and the measured thermal dynamics match what is found in numerical simulations.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB391

About •

paper received ※ 20 May 2021 paper accepted ※ 10 June 2021 issue date ※ 17 August 2021

Export •

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

TUPAB338

Surface Roughness Reduction of Nb₃Sn Thin Films via Laser Annealing for Superconducting Radio-Frequency Cavities

2283

Z. Sun, M. Ge, M. Liepe, T.E. Oseroff, R.D. Porter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
A.B. Connolly, M.O. Thompson
Cornell University, Ithaca, USA

Superconducting radio frequency (SRF) cavities, a key component of particle accelerators, await new SRF materials beyond the state-of-the-art niobium. Nb₃Sn is one of the most competitive candidates, since it increases the superheating field, allows the operation temperature up to 4K, and improves cavity efficiency. Surface roughness and grain boundaries, however, significantly affect the RF performance of current Nb₃Sn cavities. Here, we explore a post laser annealing technique to reduce the surface roughness. In doing so, we deposited a TiN laser-absorber on Nb₃Sn and Nb surfaces, and then annealed the samples by laser scanning via different laser systems. The Nb₃Sn surface roughness was minimized to 101 nm (Ra) by laser annealing via 308 nm, 35 ns pulses. Surface imaging and Fourier analysis revealed laser annealing is able to remove sharp edges and <1 um wavelength features.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB338

About •

paper received ※ 20 May 2021 paper accepted ※ 09 June 2021 issue date ※ 19 August 2021

Export •

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