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Jing, C.-J.

Paper Title Page
TPAE016 The Argonne Wakefield Accelerator Facility: Status and Recent Activities 1485
 
  • M.E. Conde, S.P. Antipov, W. Gai, C.-J. Jing, R. Konecny, W. Liu, J.G. Power, H. Wang, Z.M. Yusof
    ANL, Argonne, Illinois
 
  Funding: This work is supported by the U.S. Department of Energy, under contract No. W-31-109-ENG-38.

The Argonne Wakefield Accelerator Facility (AWA) is dedicated to the study of electron beam physics and the development of accelerating structures based on electron beam driven wakefields. In order to carry out these studies, the facility employs a photocathode RF gun capable of generating electron beams with high bunch charges (up to 100 nC) and short bunch lengths. This high intensity beam is used to excite wakefields in the structures under investigation. The wakefield structures presently under development are dielectric loaded cylindrical waveguides with operating frequencies of 7.8 or 15.6 GHz. The facility is also used to investigate the generation and propagation of high brightness electron beams. Presently under investigation, is the use of photons with energies lower than the work function of the cathode surface (Schottky-enabled photoemission), aimed at generating electron beams with low thermal emittance. Novel electron beam diagnostics are also developed and tested at the facility. The AWA electron beam is also used in laboratory-based astrophysics experiments; namely, measurements of microwave Cherenkov radiation and fluorescence of air. We report on the current status of the facility and present recent results.

 
TPAE017 Progress on High Power Tests of Dielectric-Loaded Accelerating Structures 1566
 
  • C.-J. Jing, W. Gai, R. Konecny, J.G. Power
    ANL, Argonne, Illinois
  • S.H. Gold
    NRL, Washington, DC
  • A.K. Kinkead
    ,
 
  Funding: This work was supported by the U.S. Dept of Energy, High Energy Physics Division and Office of Naval Research.

This paper presents a progress report on a series of high-power rf experiments that were carried out to evaluate the potential of the Dielectric-Loaded Accelerating (DLA) structure for high-gradient accelerator operation. Since the last PAC meeting in 2003, we have tested DLA structures loaded with two different ceramic materials: Alumina (Al2O3) and MCT (MgxCa1-xTiO3). The alumina-based DLA experiments have concentrated on the effects of multipactor in the structures under high-power operation, and its suppression using TiN coatings, while the MCT experiments have investigated the dielectric joint breakdown observed in the structures due to local field enhancement. In both cases, physical models have been set up, and the potential engineering solutions are being investigated.

 
TPAE018 34.272 GHz Multilayered Dielectric-Loaded Accelerating Structure 1592
 
  • C.-J. Jing, W. Gai, W. Liu, J.G. Power
    ANL, Argonne, Illinois
  • A. Kanareykin
    Euclid TechLabs, LLC, Solon, Ohio
 
  A scheme of multilayered structure design of 34.272 GHz with alternating dielectric of 38 and 9.7 is presented. The multilayer structure employs the Bragg Fiber concepts where the dielectric layers are used to create multiple reflections in order to confine the accelerating fields, thus greatly reducing the power loss of from external metal wall. The structure will operate at TM03 mode instead of normal TM01 mode. Numerical examples for the 2- and 4-layers 34.272 GHz multilayered structures are presented with detailed analysis of TM (acceleration) modes and HEM (parasitic) modes. We found that the power attenuation of the proposed structure can be lowered from ~ 20 dB/m for a single layer structure to ~ 6 dB/m for 2 -4 layered structure in at 34.272 GHz. We will also present a coupler design for the multilayered dielectric-loaded accelerating structure, which has capability of mode selection and high efficient RF transmission.  
TPAE060 Planned Enhanced Wakefield Transformer Ratio Experiment at Argonne Wakefield Accelerator 3487
 
  • A. Kanareykin
    Euclid TechLabs, LLC, Solon, Ohio
  • P.A. Avrakhov
    LPI, Moscow
  • W. Gai, C.-J. Jing, R. Konecny, J.G. Power
    ANL, Argonne, Illinois
 
  Funding: U.S. Department of Energy.

In this paper, we present a preliminary experimental study of a wakefield accelerating scheme that uses a carefully spaced and current ramped electron pulse train to produce wakefields that increases the transformer ratio much higher than 2. A dielectric structure was designed and fabricated to operate at 13.625 GHz with dielectric constant of 15.7. The structure will be initially excited by two beams with first and second beam charge ratio of 1:3. The expected transformer ratio is 3 and the setup can be easily extend to 4 pulses which leads to a transformer ratio of more than 6. The dielectric structure cold test results show the tube is within the specification. A set of laser splitters was also tested to produce ramped bunch train of 2 - 4 pulses. Overall design of the experiment and initial results will be presented.

 
TPAE065 Development of a 20-MeV Dielectric-Loaded Accelerator Test Facility 3673
 
  • S.H. Gold
    NRL, Washington, DC
  • H. Chen, Y. Hu, Y. Lin, C. Tang
    TUB, Beijing
  • W. Gai, C.-J. Jing, R. Konecny, J.G. Power
    ANL, Argonne, Illinois
  • A.K. Kinkead
    ,
  • C.D. Nantista, S.G. Tantawi
    SLAC, Menlo Park, California
 
  Funding: Work supported by DOE and ONR.

This paper will describe a joint project by the Naval Research Laboratory (NRL) and Argonne National Laboratory (ANL), in collaboration with the Stanford Linear Accelerator Center (SLAC), to develop a dielectric-loaded accelerator (DLA) test facility powered by the high-power 11.424-GHz magnicon that was developed by NRL and Omega-P, Inc. The magnicon can presently produce 25 MW of output power in a 250-ns pulse at 10 Hz, and efforts are in progress to increase this to 50 MW.* The facility will include a 5-MeV electron injector being developed by the Accelerator Laboratory of Tsinghua University in Beijing, China. The DLA test structures are being developed by ANL, and some have undergone testing at NRL at gradients up to ~8 MV/m.** SLAC is developing a means to combine the two magnicon output arms, and to drive an injector and accelerator with separate control of the power ratio and relative phase. The installation and testing of the first dielectric-loaded test accelerator, including injector, DLA structure, and spectrometer, should take place within the next year. The initial goal is to produce a compact 20-MeV dielectric-loaded test accelerator.

*O. A. Nezhevenko et al., Proc. PAC 2003, p. 1128.**S. H. Gold et al., AIP Conf. Proc. 691, p. 282.