Author: Dolgashev, V.A.
Paper Title Page
TUPGW099 Superconducting Crab Cavity Options for Short X-Ray Pulse Generation in SPEAR3 1647
 
  • F. Toufexis, V.A. Dolgashev, X. Huang, Z. Li
    SLAC, Menlo Park, California, USA
 
  Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515.
We are exploring methods to generate short X-ray pulses in SPEAR3 on the order of 1 ps to enable studying ultrafast processes in materials. We are developing a 2-frequency crab cavity scheme with two sets of crab cavities* at the 6th and 6.5th harmonics of the 476 MHz ring RF frequency. In previous work we studied a normal conducting crab cavity for SPEAR3**. In this work we explored two superconducting cavity options: a traditional elliptical cavity and the Quasi-waveguide Resonator***. We found that the Quasi-waveguide Resonator cannot meet our field uniformity specifications due to higher order multipole fields. We then optimized a traditional elliptical cavity with the input, Lower Order Modes, and Higher Order Modes couplers following the Argonne Advanced Photon Source design.
* A. Zholents, et al, Nucl. Instrum. Methods Phys. Res., Sect. A, Vol. 425 (1999), p. 385.
** Z. Li, et al, Proceedings of IPAC17.
*** A. Lunin, et al, Proceedings of HOMSC14.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW099  
About • paper received ※ 11 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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TUPTS077 Design of a High Gradient THz-Driven Electron Gun 2098
SUSPFO127   use link to see paper's listing under its alternate paper code  
 
  • S.M. Lewis, V.A. Dolgashev, A.A. Haase, E.A. Nanni, M. A. K. Othman, A.V. Sy, S.G. Tantawi
    SLAC, Menlo Park, California, USA
  • D. Kim, E.I. Simakov
    LANL, Los Alamos, New Mexico, USA
 
  Funding: This work was supported by Department of Energy contract DE-AC02-76SF00515. This work was also supported by NSF grants PHY-1734015.
We present the design of a high-gradient electron gun. The goal of this gun is to generate relativistic electrons using GV/m accelerating fields. The initial design is a standing-wave field-emission gun operating in the pi-mode with a cavity frequency of 110.08 GHz. A pulsed 110 GHz gyrotron oscillator will be used to drive the structure with power coupled in through a TM01 circular waveguide mode. The gun is machined in two halves which are bonded. This prototype will be used to characterize the electron beam and study RF breakdown at 110 GHz.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS077  
About • paper received ※ 14 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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WEPRB020 Compact Ultra High-Gradient Ka-Band Accelerating Structure for Research, Medical and Industrial Applications 2842
 
  • L. Faillace
    INFN-Milano, Milano, Italy
  • M. Behtouei
    Sapienza University of Rome, Rome, Italy
  • V.A. Dolgashev
    SLAC, Menlo Park, California, USA
  • B. Spataro, A. Variola
    INFN/LNF, Frascati, Italy
  • G. Torrisi
    INFN/LNS, Catania, Italy
 
  Technological advancements are strongly required to fulfil demands for new accelerators devices from the compact or portable devices for radiotherapy to mo-bile cargo inspections and security, biology, energy and environmental applications, and ultimately for the next generation of colliders. In the frame of the collab-oration with INFN-LNF, SLAC (USA) we are working closely on design studies, fabrication and high-power operation of Ka-band accelerating structures. In par-ticular, new manufacturing techniques for hard-copper structures are being investigated in order to determine the maximum sustainable gradients above 150 MV/m and extremely low probability of RF breakdown. In this paper, the preliminary RF and mechanical design as well as beam dynamics estimations for a Ka-Band accelerating structure at 35 GHz are presented together with discussions on practical accelerating gradients and maximum average beam current throughput.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB020  
About • paper received ※ 08 April 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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WEPRB024 Low Power RF Test of a Quadrupole-free X-Band Mode Launcher for High Brightness Applications 2856
 
  • G. Torrisi, L. Celona, S. Gammino, O. Leonardi, G. Sorbello
    INFN/LNS, Catania, Italy
  • G. Castorina
    Sapienza University of Rome, Rome, Italy
  • V.A. Dolgashev
    SLAC, Menlo Park, California, USA
  • L. Faillace
    INFN-Milano, Milano, Italy
  • G.S. Mauro
    INFN/LNL, Legnaro (PD), Italy
  • G. Sorbello
    University of Catania, Catania, Italy
  • B. Spataro
    INFN/LNF, Frascati, Italy
 
  In this work we present the low power RF characterization of a novel TM01 X-band mode launcher for the new generation of high brightness RF photo-injectors. The proposed mode launcher exploits a fourfold symmetry which minimizes both the dipole and the quadrupole fields in order to mitigate the emittance growth in the early stages of the acceleration process. Two identical aluminum mode launchers have been assembled and measured in back-to-back configurations for three different central waveguide lengths. From the back-to-back results we infer the performance of each mode launcher. The low power RF test, performed at the Istituto Nazionale di Fisica Nucleare Laboratori Nazionali del Sud (INFN-LNS), validate both the numerical simulations and the quality of fabrication. An oxygen-free high-conductivity copper version of the device is being manufactured for high power and ultra high vacuum tests that are planned to be conducted at SLAC  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB024  
About • paper received ※ 09 April 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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THPGW080 Initial Results of High-Gradient Breakdown Tests for W-Band Accelerating Structures 3769
 
  • M. A. K. Othman, V.A. Dolgashev, A.A. Haase, E.A. Nanni, J. Neilson, S.G. Tantawi
    SLAC, Menlo Park, California, USA
  • S. Jawla, J.F. Picard, R.J. Temkin
    MIT/PSFC, Cambridge, Massachusetts, USA
  • S. C. Schaub
    MIT, Cambridge, Massachusetts, USA
  • B. Spataro
    INFN/LNF, Frascati, Italy
 
  Funding: This work was supported by Department of Energy contract DE-AC02-76SF00515 (SLAC) and grant DE-SC0015566 (MIT). This work was also supported by NSF grants PHY-1734015.
Emerging accelerator technology at mm-wave and THz frequencies has recently shown notable progress. Indeed, metallic and dielectric accelerating structures at THz frequencies are plausible candidates toward miniaturization of accelerators. RF breakdown in such structures is a major factor limiting their performance. Therefore, comprehensive analysis of RF breakdown physics in mm-wave accelerating structures is needed, which includes understanding of dependencies of the breakdown rate on geometric, electromagnetic and material properties. In this work we report on high power tests of a 110 GHz single-cell standing wave accelerating structure powered by a 1 MW gyrotron. The RF power is coupled from the gyrotron into the accelerating structure with a Gaussian to TM01 mode converter through a quasi-optical setup. We demonstrate coupling of 10 ns, 100s of kilowatt pulses into the structure using a fast switch and achieving ~150 MV/m accelerating gradients. Measurements of RF signals and field-emitted currents allow for complete comprehensive of the high-gradient behavior of W-band structures, including breakdown probability.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW080  
About • paper received ※ 15 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPTS064 Sub-Picosecond X-Ray Streak Camera using High-Gradient RF Cavities 4256
 
  • F. Toufexis, V.A. Dolgashev
    SLAC, Menlo Park, California, USA
 
  Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515.
We are developing an ultrafast diagnostic system for X-ray beams from Synchrotron Light Sources and Free-Electron Lasers. In this system, the X-ray beam is focused on the photocathode of a high-gradient radio-frequency cavity that accelerates the photo-emitted electrons to a few MeV while preserving their time structure. The accelerated electron beam is streaked by radio-frequency deflectors and then imaged on a screen. This approach will allow orders of magnitude improvement in time resolution over traditional streak cameras and could potentially enable time-resolved diagnostics of sub-100 fs X-ray pulses. We present preliminary beam dynamics simulations of this system and discuss the implementation.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS064  
About • paper received ※ 11 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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