Author: Kim, Y.K.
Paper Title Page
MOPOTK026 Four-Dimensional Emittance Measurements and Correction of UED Optics up to Sextupole Order 496
 
  • W.H. Li, M.B. Andorf, A.C. Bartnik, I.V. Bazarov, C.J.R. Duncan, M. Kaemingk, S.J. Levenson, J.M. Maxson, C.A. Pennington
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • M.A. Gordon, Y.K. Kim
    University of Chicago, Chicago, Illinois, USA
 
  Funding: U.S Department of Energy, grant DE-SC0020144 U.S. National Science Foundation Grant PHY-1549132, the Center for Bright Beams
Ultrafast electron diffraction imposes stringent constraints on the full 6D brightness of the probe electron beam. The desired normalized emittance, often in the few-nanometer regime and below, renders the beam very sensitive to field aberrations and space charge effects. In this proceeding, we report the correction of normal quadrupole, skew quadrupole, and sextupole aberrations in the MEDUSA ultrafast electron micro-diffraction beamline and measurements of the subsequent emittance. This low emittance is enabled by alkali-antimonide photocathodes driven at the photoemission threshold. We demonstrate that the measured emittance is consistent with that of optimized simulations with these cathodes, indicating that low emittance beams from high quality photocathodes can be preserved and used in practical applications.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOTK026  
About • Received ※ 08 June 2022 — Revised ※ 11 June 2022 — Accepted ※ 20 June 2022 — Issue date ※ 27 June 2022
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TUOXSP2 Analysis of Low RRR SRF Cavities 783
SUSPMF110   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. This work was supported by the University of Chicago.
Recent findings in the superconducting radio-frequency (SRF) community have shown that introducing certain impurities into high-purity niobium can improve quality factors and accelerating gradients. Success has been found in nitrogen-doping, diffusion of the native oxide into the niobium surface, and thin films of alternate superconductors atop a niobium bulk cavity. 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 with a low residual resistance ratio (RRR) and correlate these impurities with the RF performance of low RRR cavities so that the mechanism of recent impurity-based improvements can be better understood and improved upon. Additionally, we perform a low temperature bake on the low RRR cavity to evaluate how the intentional addition of oxygen to the RF layer affects performance. We have found that low RRR cavities experience low temperature-dependent BCS resistance behavior more prominently than their high RRR counterparts. The results of this study have the potential to unlock a new understanding on SRF materials.
 
slides icon Slides TUOXSP2 [1.495 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUOXSP2  
About • Received ※ 08 June 2022 — Accepted ※ 11 June 2022 — Issue date ※ 25 June 2022  
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TUPOTK034 Evaluating the Effects of Nitrogen Doping and Oxygen Doping on SRF Cavity Performance 1287
 
  • H. Hu, Y.K. Kim
    University of Chicago, Chicago, Illinois, USA
  • D. Bafia
    Fermilab, Batavia, Illinois, USA
 
  Superconducting radiofrequency (SRF) cavities are resonators with extremely low surface resistance that enable accelerating cavities to have extremely high quality factors (Q0). High Q0 decreases the capital required to keep the accelerators cold by reducing power loss. The performance of SRF cavities is largely governed by the surface composition of the first §I{100}{nm} of the cavity surface. Impurities such as oxygen and nitrogen have been observed to yield high Q0, but their precise roles are still being studied. Here, we compare the performance of cavities doped with nitrogen and oxygen in terms of surface composition and heating behavior with field. A simulation of the diffusion of oxygen into the bulk of the cavity was built using COMSOL Multiphysics software. Simulated results were compared to the actual surface composition of the cavities as determined from secondary ion mass spectrometry analysis. Understanding how these impurities affects performance allows us to have further insight into the underlying mechanisms that enable these surface treatments to yield high Q0.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK034  
About • Received ※ 08 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 12 June 2022 — Issue date ※ 30 June 2022
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THOXGD2 Electron Cooling Experiment for Proton Beams with Intense Space-Charge in IOTA 2395
 
  • N. Banerjee, J.A. Brandt
    Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA
  • M.K. Bossard, Y.K. Kim
    University of Chicago, Chicago, Illinois, USA
  • B.L. Cathey, S. Nagaitsev, G. Stancari
    Fermilab, Batavia, Illinois, USA
 
  Funding: 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 and also the University of Chicago.
Electron cooling as a method of creating intense ion beams has a practical upper limit when it comes to the peak phase space density of ion beams which can be achieved in practice. We describe a new experiment to study electron cooling of 2.5 MeV protons at the intensity limit using the Integrable Optics Test Accelerator (IOTA), which is a storage ring dedicated to beam physics research at Fermilab. This system will enable the study of magnetized electron cooling of a proton beam with transverse incoherent tune shifts approaching -0.5 due to the presence of intense space-charge forces. We present an overview of the hardware design, simulations and specific experiments planned for this project.
 
slides icon Slides THOXGD2 [2.775 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THOXGD2  
About • Received ※ 13 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 24 June 2022
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