Author: Doran, D.S.
Paper Title Page
TUYGBE3 Recent progress of short pulse dielectric two-beam acceleration 640
 
  • J.H. Shao, M.E. Conde, D.S. Doran, W. Gai, W. Liu, N.R. Neveu, J.F. Power, C. Whiteford, E.E. Wisniewski, L.M. Zheng
    ANL, Argonne, Illinois, USA
  • C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio, USA
 
  Two-Beam Acceleration (TBA) is a structure-based wakefield acceleration method with the potential to meet the luminosity and cost requirements of a TeV class linear collider. The Argonne Wakefield Accelerator (AWA) facility is developing a dielectric-based short pulse TBA scheme with the potential to withstand high acceleration gradients and to achieve low fabrication cost. Recently, the dielectric short pulse TBA technology was successfully demonstrated using K-band 26 GHz structures, achieving 55 MW output power from the power extractor and 28 MeV/m gradient in the accelerator. To improve the generated rf power, an X-band 11.7 GHz power extractor has been developed, which obtained 105 MW in the high power test. In addition, a novel dielectric disk accelerator (DDA) is currently under investigation to significantly increase the efficiency of linear colliders based on short pulse TBA. Details of these research will be presented in this paper.  
slides icon Slides TUYGBE3 [2.224 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUYGBE3  
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TUPMF010 A Conceptual Design of a Compact Wakefield Accelerator for a High Repetition Rate Multi User X-ray Free-Electron Laser Facility 1266
 
  • A. Zholents, D.S. Doran, W.G. Jansma, M. Kasa, R. Kustom, J.G. Power, N.O. Strelnikov, K.J. Suthar, E. Trakhtenberg, I. Vasserman, G.J. Waldschmidt, J.Z. Xu
    ANL, Argonne, Illinois, USA
  • S. Baturin
    Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA
  • H. Perez
    IIT, Chicago, Illinois, USA
 
  Funding: Supported by U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357
A preliminary design of a collinear wakefield accelerator is described. It is assumed that the array of such accelerators will play a central role in a free-electron laser-based x-ray user facility under consideration at Argonne National Laborator [1].
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF010  
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TUPMF020 Demonstration of Fast, Single-shot Photocathode QE Mapping Method Using MLA Pattern Beam 1293
 
  • E.E. Wisniewski, M.E. Conde, D.S. Doran, W. Gai, Q. Gao, W. Liu, J.G. Power, C. Whiteford
    ANL, Argonne, Illinois, USA
  • Q. Gao
    TUB, Beijing, People's Republic of China
  • G. Ha
    PAL, Pohang, Republic of Korea
  • A. Halavanau, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • P. Piot
    Fermilab, Batavia, Illinois, USA
 
  Funding: UChicago Argonne, LLC, Operator of Argonne National Laboratory ("Argonne"). Argonne, a U.S.A. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357.
Quantum efficiency (QE) is the chief figure of merit in the characterization of photocathodes. Semiconductor photocathodes, especially when used in high rep-rate photo-injectors, are known to show QE degradation over time and must be replaced. The total QE is the basic diagnostic which is used widely and is easy to obtain. However, a QE map indicating variations of QE across the cathode surface has greater utility. It can quickly diagnose problems of QE inhomogeneity. Most QE mapping techniques require hours to complete and are thus disruptive to a user facility schedule. A fast, single-shot method has been proposed (citation) using a micro-lens array (MLA) generated QE map. In this paper we report the implementation of the method at Argonne Wakefield Accelerator facility. A micro-lens array (MLA) is used to project an array of beamlets onto the photocathode. The resulting photoelectron beam in the form of an array of electron beamlets is imaged at a YAG screen. Four synchronized measurements are made and the results used to produce a QE map of the photocathode.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF020  
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TUPML003 Design of an L-band Accelerating Structure for the Argonne Wakefield Accelerator Facility Witness Beam Line Energy Upgrade 1533
 
  • J.H. Shao, M.E. Conde, D.S. Doran, J.F. Power
    ANL, Argonne, Illinois, USA
  • C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio, USA
 
  The Argonne Wakefield Accelerator (AWA) facility has been devoting much effort to the fundamental R&D of two-beam acceleration (TBA) technology with two parallel L-band beam lines. Beginning from the 70 MeV drive beam line, the high frequency (C-band and above) rf power is extracted from the beam by a decelerating structure (a.k.a. power extractor), transferred to an accelerating structure in the witness beam line, and used to accelerate the 15 MeV main beam. These high frequency accelerating structures usually have a small aperture to obtain high gradient and high efficiency, making it difficult for the low energy main beam to pass. To address this issue, one proposal is to increase the main beam energy to above 30 MeV by replacing the current witness linac. A 9-cell 𝜋-mode L-band standing-wave accelerating structure has therefore been designed to meet the high shunt impedance and low cost requirements. In addition, the single-feed coupling cell has been optimized with additional symmetrical ports to eliminate field distortion. The detailed design of the new accelerating structure will be presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML003  
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TUPML004 Correction of Emittance Growth Due to Quad Components in Solenoids With Quad Correctors at AWA 1536
 
  • L.M. Zheng, C.-X. Tang
    TUB, Beijing, People's Republic of China
  • M.E. Conde, D.S. Doran, W. Gai, W. Liu, J.G. Power, J.H. Shao, C. Whiteford, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
 
  An asymmetrical electron beam is observed on the drive beamline at Argonne Wakefield Accelerator (AWA) due to the quad components in the solenoids. An ASTRA simulation shows that the emittance will increase when the electron beam passes through solenoids with quad errors. We use two quad correctors to correct this emittance growth. A preliminary emittance correction result is presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML004  
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TUPML005 Study of a Dielectric Disk Structure for Short Pulse Two-Beam Acceleration 1539
 
  • J.H. Shao, M.E. Conde, D.S. Doran, J.F. Power
    ANL, Argonne, Illinois, USA
  • C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio, USA
 
  Argonne Flexible Linear Collider (AFLC), a proposed 3 TeV electron-positron linear collider based on two-beam acceleration (TBA) scheme, applies a short pulse length (∼20 ns) to obtain a high accelerating gradient (267 MV/m) and a compact footprint (∼18 km). The baseline design of the main accelerator section adopts 26 GHz K-band traveling-wave dielectric-loaded accelerators (DLA) with an rf to beam efficiency 𝜂𝑟𝑓 −𝑏𝑒𝑎𝑚 of 27%. Recently, an alternative structure which is similar to a metallic disk-loaded one but with dielectric disks, noted as dielectric disk accelerator (DDA), has been investigated and optimized, leading to ∼45% improvement in 𝜂𝑟𝑓 −𝑏𝑒𝑎𝑚. To demonstrate the key technologies, an X-band prototype structure has been designed and will be tested at Argonne Wakefield Accelerator (AWA) facility with a 300 MW metallic power extractor. Detailed comparison between K-band DLA and DDA for AFLC main accelerator as well as the preliminary design of the X-band DDA prototype will be presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML005  
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TUPML006 Updates of the Argonne Cathode Test-stand 1542
 
  • J.H. Shao, M.E. Conde, D.S. Doran, W. Gai, W. Liu, J.F. Power, C. Whiteford, E.E. Wisniewski, L.M. Zheng
    ANL, Argonne, Illinois, USA
  • S.P. Antipov, G. Chen, E. Gomez, C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • S.V. Baryshev
    Michigan State University, East Lansing, Michigan, USA
 
  The Argonne Cathode Test-stand (ACT) is a unique testbed to develop cathodes and to conduct fundamental surface study under ultra-high rf field (up to 700 MV/m with pin-shaped cathodes). The test-stand consists of an L-band 1.3 GHz single-cell photocathode rf gun and a field emission (FE) imaging system to locate emitters with a resolution of ∼20 𝜇m. In the recent upgrade, UV laser has been introduced to improve the imaging system and to significantly expand the ACT towards photoemission and laser-assisted field emission research. In addition, a load-lock system has been added to the beam line to expedite the cathode switching period. The paper will present details of the upgrade as well as experiments planned in the near future.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML006  
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TUPML007 Short Pulse High Power RF Generation with an X-Band Dielectric Power Extractor 1546
 
  • J.H. Shao, M.E. Conde, D.S. Doran, W. Gai, W. Liu, N.R. Neveu, J.F. Power, C. Whiteford, E.E. Wisniewski, L.M. Zheng
    ANL, Argonne, Illinois, USA
  • C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio, USA
 
  Short pulse high power rf generation is one of the key technologies for the Argonne Flexible Linear Collider (AFLC), a proposed 3 TeV electron-positron linear collider based on two-beam acceleration (TBA) scheme. Compared with metallic power extractors, dielectric structures have the potential to achieve lower fabrication cost and to withstand higher gradient. Recently, an X-band dielectric power extractor (a.k.a, DPETS) has been developed at the Argonne Wakefield Accelerator (AWA) facility and achieved 105 MW output power when driven by a high charge 8-bunch train separated by 770 ps. The design, the cold test measurement, the preliminary high power test results, and the structure inspection will be presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML007  
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TUPML009 Design and Test Plan for a Prototype Corrugated Waveguide 1550
 
  • G.J. Waldschmidt, D.S. Doran, G. Ha, R. Kustom, A. Nassiri, J.G. Power, A. Zholents
    ANL, Argonne, Illinois, USA
  • A.E. Siy
    UW-Madison/PD, Madison, Wisconsin, USA
 
  A cylindrical, corrugated wakefield accelerating structure with a 1 mm radius bore is being designed to facilitate sub-terahertz Čerenkov radiation produced by an elec-tron bunch propagating along the waveguide. A 220 GHz axial mode for the wakefield is being considered. The waveguide is being optimized to maximize the trailing wakefield potential while maintaining a ratio of the trail-ing potential to the peak decelerating voltage in the bunch, or transformer ratio, of approximately 5 for the door step peak current distribution [1]. In order to evalu-ate the manufacturing tolerances and perform rf and electron beam testing of the waveguide, a 21 GHz proto-type waveguide structure will be built consisting of re-configurable parts allowing modelling of various fabrica-tion errors. Measurements with an electron beam will be performed at the Argonne Wakefield Accelerator (AWA) test facility. Analysis of the experimental layout has been performed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML009  
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