Author: Maxson, J.M.
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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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MOPOTK027 Characterization of Various GaN Samples for Photoinjectors 500
 
  • M.B. Andorf, I.V. Bazarov, S.J. Levenson, J.M. Maxson
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • J. Encomendero, D. Jena, V.V. Protasenko, H.G. Xing
    Cornell University, Ithaca, New York, USA
 
  Funding: DOE-HEP DESC0021002 DOE-NP DE-SC0021425
Photoemission properties (quantum efficiency, spectral response, and lifetime) of various GaN based photocathodes are summarized, including p-doped samples in its hexagonal phase, cubic GaN and a more exotic 2-D hole gas sample. The 2-D hole contains no dopant impurity but achieves high conductivity via polarization fields produced at the heterojunction of GaN and AlN. For efficient electron production, cesium is used to achieve Negative Electron Affinity.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOTK027  
About • Received ※ 08 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 26 June 2022
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MOPOMS004 Optimizing Activation Recipe with Cs, Te, O for GaAs-Based Photocathodes 628
 
  • J. Bae, M.B. Andorf, I.V. Bazarov, A. Galdi, J.M. Maxson
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • L. Cultrera
    BNL, Upton, New York, USA
 
  Funding: Department of Energy (DOE) DE-SC0021039.
GaAs-based photocathodes are the most popular electron sources for producing highly spin-polarized electron beams in accelerator physics and condensed matter physics. Spin-polarized photoemission requires activation to achieve Negative Electron Affinity (NEA). Conventional NEA surfaces such as CS-O/NF3 are extremely vacuum sensitive, and this results in rapid QE degradation. In this work, we activated GaAs with various recipes using Cs, Te, and oxygen. We demonstrate NEA activation on GaAs surfaces. Among Cs-Te activated samples, the oxidized sample showed the highest QE and longest lifetime at 780 nm.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS004  
About • Received ※ 04 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 24 June 2022
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WEPOMS030 A Path-Length Stability Experiment for Optical Stochastic Cooling at the Cornell Electron Storage Ring 2311
SUSPMF077   use link to see paper's listing under its alternate paper code  
 
  • S.J. Levenson, M.B. Andorf, I.V. Bazarov, V. Khachatryan, J.M. Maxson, D.L. Rubin, S. Wang
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Funding: This work was supported by the U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams and NYSTAR award C150153.
To achieve sufficient particle delay with respect to the optical path in order to enable high gain amplification, the design of the Optical Stochastic Cooling (OSC) experiment in the Cornell Electron Storage Ring (CESR) places the pickup (PU) and kicker (KU) undulators approximately 80 m apart. The arrival times at the KU of particles and the light they produce in the PU must be synchronized to an accuracy of less than an optical wavelength, which for this experiment is 780 nm. To test this synchronization, a planned demonstration of the stability of the bypass in CESR is presented where, in lieu of undulators, an interference pattern formed with radiation from two dipoles flanking the bypass is used. In addition to demonstrating stability, the fringe visibility of the pattern is related to the cooling ranges, a critical parameter needed for OSC. We present progress on this stabilization experiment including the design of a second-order isochronous bypass, as well as optimizations of the Dynamic Aperture (DA) and injection efficiency.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOMS030  
About • Received ※ 08 June 2022 — Revised ※ 17 June 2022 — Accepted ※ 23 June 2022 — Issue date ※ 26 June 2022
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WEPOMS031 Light Path Construction for an Optical Stochastic Cooling Stability Test at the Cornell Electron Storage Ring 2315
 
  • S.J. Levenson, M.B. Andorf, I.V. Bazarov, D.C. Burke, J.M. Maxson, D.L. Rubin, S. Wang
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Funding: This work was supported by the U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams and NYSTAR award C150153.
An experiment at the Cornell Electron Storage Ring (CESR) to test the optical path-length stability of a bypass suitable for Optical Stochastic Cooling (OSC) is being pursued. The approximately 80 m light path for this experiment has been assembled, and synchrotron light has been successfully propagated from both sources. A feedback system based on an Electro-Optic Modulator (EOM) to correct the path-error accumulated in both the light and particle path has been table-top tested. We present on the design and construction of the light optics for the OSC stability experiment at CESR.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOMS031  
About • Received ※ 08 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 21 June 2022 — Issue date ※ 03 July 2022
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THPOPT066 Helical Wiggler Design for Optical Stochastic Cooling at CESR 2751
 
  • V. Khachatryan, M.B. Andorf, I.V. Bazarov, J.A. Crittenden, S.J. Levenson, J.M. Maxson, D.L. Rubin, J.P. Shanks, S. Wang
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • W.F. Bergan
    BNL, Upton, New York, USA
 
  Funding: The authors thank the Center for Bright Beams, NSF award PHY-1549132; W.F.B. was supported by the NSF Graduate Research Fellowship Program under grant number DGE-1650441.
A helical wiggler with parameter kund=4.35 has been designed for the Optical Stochastic Cooling (OSC) experiment in the Cornell Electron Storage Ring (CESR). We consider four Halbach arrays, which dimensions are optimized to get the required helical field profile, as well as, to get the best Dynamic Aperture (DA) in simulations. The end poles are designed with different dimensions to minimize the first and second field integrals to avoid the need of additional correctors for the beam orbit. The design is adopted to minimize the risks for the magnet blocks demagnetization. To quantify the tolerances, we simulated the effects of different types of geometrical and magnetic field errors on the OSC damping rates. In addition, to understand the challenges for the construction, as well as, to validate the model field calculations, we prototyped a small two period version. The prototype field is compared to the model, and the results are presented in this work.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOPT066  
About • Received ※ 07 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 14 June 2022
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THPOMS036 HERACLES: A High Average Current Electron Beamline for Lifetime Testing of Novel Photocathodes 3041
 
  • M.B. Andorf, J. Bae, A.C. Bartnik, I.V. Bazarov, J.M. Maxson
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • L. Cultrera
    BNL, Upton, New York, USA
 
  Funding: DOE-NP DE-SC0021425 NSF PHY 1549132
We report on the building and commissioning of a high current beamline dedicated to testing novel photocathodes for high current and spin-polarized electron applications. The main features of the beamline are a 200 keV DC electron gun and a beam dump capable of handling 75 kW of beam power. In this report, a Cs3Sb photocathode is used to demonstrate the facilities high current capabilities.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOMS036  
About • Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 30 June 2022
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