Author: Dong, X.W.
Paper Title Page
WEP279 Improvements on the Design of an Ultra-Low Emittance Injector for a Future X-ray FEL Oscillator 2002
 
  • X.W. Dong, K.-J. Kim
    ANL, Argonne, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DEAC02-06CH11357.
The concept of an ultra-low transverse emittance injector for the X-ray Free-Electron Laser Oscillator* was discussed at PAC09**. Two problems come to mind. A dual-frequency rf chopper for reducing the beam rate from 100 MHz to 1 ~ 3 MHz would limit our choice of the beam repetition rate. The electron back-bombardment could be solved by embedding a three-pole wiggler*** in the nose cone of the gun cavity, but that results in increased emittance. Inspired by the concept of a triode gun, the injector now includes a gated 100 MHz rf gun with thermionic cathode to avoid those limitations. The design has been studied and is capable of producing 40 pC bunches with 0.1 micrometer effective transverse rms emittance.
* K.-J. Kim et al., Phys. Rev. Lett. 100, 244802 (2008).
** P.N. Ostroumov et al., Proc. of PAC09, p.461 (2009).
*** M. Borland et al., Proc. of LINAC10, to be published.
 
 
WEP280 Development of an Ultra-Low-Emittance RF PhotoInjector for a Future X-Ray FEL Oscillator 2005
 
  • X.W. Dong, K.-J. Kim, N. Sereno, C.-X. Wang, A. Zholents
    ANL, Argonne, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DEAC02-06CH11357.
The proposed x-ray free-electron laser oscillator* requires continuous electron bunches with ultra-low normalized transverse emittance of less than 0.1 micrometer, a bunch charge of 40 pC, an rms uncorrelated energy spread of less than 1.4 MeV, produced at a rate between 1 MHz to 10 MHz. The bunches are to be compressed to an rms length of ~1 ps and accelerated to the final energy of 7 GeV. In this paper, we discuss a design for an ultra-low-emittance injector based on a 325-MHz room-temperature rf cavity and a Cs2Te photocathode. The results of initial optimizations of the beam dynamics with a focus on extracting and preserving ultra-low emittance will be presented.
* K.-J. Kim et al., Phys. Rev. Lett. 100, 244802 (2008).