Author: Grassellino, A.
Paper Title Page
MOPMB032 The Collaborative Effects of Intrinsic and Extrinsic Impurities in Low RRR SRF Cavities 162
SUSPB012   use link to see paper's listing under its alternate paper code  
 
  • K. Howard, Y.K. Kim
    University of Chicago, Chicago, Illinois, USA
  • D. Bafia, A. Grassellino
    Fermilab, Batavia, Illinois, USA
 
  Funding: This manuscript 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.
The SRF community has shown that introducing certain impurities into high-purity niobium can improve quality factors and accelerating gradients. We question why some impurities improve RF performance while others hinder it. The purpose of this study is to characterize the impurity profile of niobium coupons with a low residual resistance ratio (RRR) and correlate these impurities with the RF performance of low RRR cavities so that the mechanism of impurity-based improvements can be better understood and improved upon. The combination of RF testing and material analysis reveals a microscopic picture of why low RRR cavities experience low BCS resistance behavior more prominently than their high RRR counterparts. We performed surface treatments, low temperature baking and nitrogen-doping, on low RRR cavities to evaluate how the intentional addition of oxygen and nitrogen to the RF layer further improves performance through changes in the mean free path and impurity profile. The results of this study have the potential to unlock a new understanding on SRF materials and enable the next generation of high Q/high gradient surface treatments.
 
poster icon Poster MOPMB032 [1.444 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB032  
About • Received ※ 21 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 23 July 2023
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MOPMB037 Exploration of Parameters that Affect High Field Q-Slope 178
SUSPB013   use link to see paper's listing under its alternate paper code  
 
  • K. Howard, Y.K. Kim
    University of Chicago, Chicago, Illinois, USA
  • D. Bafia, A. Grassellino
    Fermilab, Batavia, Illinois, USA
 
  Funding: This manuscript 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.
The onset of high field Q-slope (HFQS) around 25 MV/m prevents cavities in electropolished (EP) condition from reaching high quality factors at high gradients due to the precipitation of niobium hydrides during cooldown. These hydrides are non-superconducting at 2 K, and contribute to losses such as Q disease and HFQS. We are interested in exploring the parameters that affect the behavior of HFQS. We study a high RRR cavity that received an 800 C by 3 hour bake and EP treatment to observe HFQS. First, we explore the effect of trapped magnetic flux. The cavity is tested after cooling slowly through Tc while applying various levels of ambient field. We observe the onset of the HFQS and correlate this behavior with the amount of trapped flux. Next, we investigate the effect of the size/concentration of hydrides. The cavity is tested after holding the temperature at 100 K for 12 hours during the cooldown to promote the growth of hydrides. We can correlate the behavior of the HFQS with the increased hydride concentration. Our results will help further the understanding of the mechanism of HFQS.
 
poster icon Poster MOPMB037 [1.648 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB037  
About • Received ※ 12 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 19 August 2023
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THIXA06
Dark Matter and Gravitational Waves Experiments with SRF Cavities  
 
  • B. Giaccone, A. Grassellino, S. Posen, A.S. Romanenko
    Fermilab, Batavia, Illinois, USA
 
  Funding: This material is based upon work supported by the U.S. DOE, SC, National QIS Research Centers, Superconducting Quantum Materials and Systems Center (SQMS) under contract n. DE-AC02-07CH11359
Recent efforts have shown that the SRF technology developed for accelerators can be successfully applied to new applications, including quantum computing, dark matter searches and beyond the standard model physics. The ultra-high quality factor of SRF cavities can allow to achieve unprecedented sensitivity in fields outside of the usual accelerator applications, for examples in dark photon and axion searches (both as dark matter candidates and lab-produced particles). Applications of SRF cavities for gravitational waves searches are also being investigated. The SQMS Physics and Sensing thrust is leveraging SRF cavities and QIS to search for new particles and BSM physics. This talk will highlight experiments where SRF cavities have already set experimental bounds on new physics.
 
slides icon Slides THIXA06 [5.984 MB]  
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