Author: 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  
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