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Jing, C.-J.

Paper Title Page
WEPMS086 Design of a 26 GHz Wakefield Power Extractor 2535
 
  • C.-J. Jing, A. Kanareykin
    Euclid TechLabs, LLC, Solon, Ohio
  • W. Gai, F. Gao, R. Konecny
    ANL, Argonne, Illinois
  • S. Kazakov
    KEK, Ibaraki
 
  High frequency, high output power, and high efficiency RF sources have compelling applications in accelerators for high energy physics. The 26 GHz RF power extractor proposed in this paper provides a practical approach for generating high power RF in this particular frequency range. The extractor is designed to couple out RF power generated from the high charge electron bunch train at the Argonne Wakefield Accelerator (AWA) facility traversing dielectric loaded or corrugated waveguides. In this paper we evaluate two different techniques for extracting the beam energy at the AWA: one is based on a completely metallic corrugated waveguide and coupler; and the other is based on a dielectric lined circular waveguide and coupler. Designs for both RF power extractors will be presented including parameter optimization, the electromagnetic modeling of structures and RF couplers, and the analysis of beam dynamics.  
THPMN088 C-Band High Power RF Generation and Extraction Using a Dielectric Loaded Waveguide 2912
 
  • F. Gao, M. E. Conde, W. Gai, R. Konecny, W. Liu, J. G. Power, Z. M. Yusof
    ANL, Argonne, Illinois
  • C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio
  • T. Wong
    Illinois Institute of Technology, Chicago, Illinois
 
  Funding: Department of Energy

We report on the fabrication, simulation, and high-power testing of a C-band RF power extractor recently conducted at the Argonne Wakefield Accelerator (AWA) facility. Dielectric loaded accelerating (DLA) structures can be used for high-power RF generation [*,**] when a high-current electron beam passes through a DLA structure and loses energy into the modes of the structure due to self-wakefields. The AWA generates high charge (up to 100nC), short bunch length (1.5mm~2.5mm) electron beams, which is ideal for high-power RF generation. The generated RF power can be subsequently extracted with a properly designed extraction coupler in order to accelerate a second beam, or for other high power purposes. In this paper, the detailed design of a 7.8 GHz DLA power extractor, MAFIA simulations, and results of the high-power test are presented. Simulation predictions of an 79 MW, 2.2 ns long RF pulse (generated by a single 100 nC electron bunch) and a longer RF pulse of the same power (obtained from a 35 nC periodic bunch train) will be compared to experimental results.

* W. Gai, et al, Experimental Demonstration of Two Beam Acceleration Using Dielectric Step-up Transformer, PAC01, pp.1880-1882.** D. Yu, et al, 21GHz Ceramic RF Power Extractor, AAC02, pp.484-505.

 
THPMS073 Progress towards a Gap Free Dielectric-Loaded Accelerator 3151
 
  • C.-J. Jing, A. Kanareykin
    Euclid TechLabs, LLC, Solon, Ohio
  • S. H. Gold
    NRL, Washington, DC
  • S. Kazakov
    KEK, Ibaraki
  • R. Konecny, J. G. Power
    ANL, Argonne, Illinois
 
  One of the major concerns in the development of Dielectric-Loaded Accelerating (DLA) structures is the destructive breakdown at dielectric joints caused by a local electric field enhancement induced by the discontinuity of the dielectric constant on the surface of the joint gap. Our previous X-band traveling wave DLA structure design*, for example, incorporated two separate impedance matching sections with at least two dielectric joints. In this paper, we present a new design to avoid this problem. This scheme is based on a coaxial type coupler which is able to implement mode conversion and impedance matching at the same time and therefore to eliminate joint gap induced breakdown. The new structure is under construction; bench test results will be presented

* C. Jing, W. Gai, J. Power, R. Konecny, S. Gold, W. Liu and A. Kinkead, IEEE, Trans. PS, vol.33 No.4, Aug. 2005, pp.1155-1160.

 
THPMS074 High Transformer Ratios in Collinear Wakefield Accelerators 3154
 
  • C.-J. Jing, A. Kanareykin, P. Schoessow
    Euclid TechLabs, LLC, Solon, Ohio
  • M. E. Conde, W. Gai, J. G. Power, Z. M. Yusof
    ANL, Argonne, Illinois
 
  Funding: DOE SBIR Phase II, DE-FG02-02ER83418.

Based on our previous experiment that successfully demonstrated wakefield transformer ratio enhancement in a 13.625 GHz dielectric-loaded collinear wakefield accelerator using the ramped bunch train technique, we present here a redesigned experimental scheme for even higher enhancement of the efficiency of this accelerator. Design of a collinear wakefield device with a transformer ratio R>>2, is presented. Using a ramped bunch train (RBT) rather than a single drive bunch, the enhanced transformer ratio (ETR) technique is able to increase the transformer ratio R above the ordinary limit of 2. To match the wavelength of the fundamental mode of the wakefield with the bunch length (σz=2 mm) of the new Argonne Wakefield Accelerator (AWA) drive gun, where the experiment will be performed, a 26.625 GHz dielectric based accelerating structure is required. This transformer ratio enhancement technique based on our dielectric-loaded waveguide design will result in a compact, high efficiency accelerating structure for future wakefield accelerators.

 
THPMS075 High Power Testing of a Fused Quartz-based Dielectric-loaded Accelerating Structure 3157
 
  • C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio
  • V. A. Dolgashev, S. G. Tantawi
    SLAC, Menlo Park, California
  • W. Gai, R. Konecny, J. G. Power, Z. M. Yusof
    ANL, Argonne, Illinois
  • S. H. Gold
    NRL, Washington, DC
  • A. K. Kinkead
    LET
 
  We report on the most recent results from a series of high power tests being carried out on RF-driven dielectric-loaded accelerating (DLA) structures. The purpose of these tests is to determine the viability of the DLA as a traveling-wave accelerator and is a collaborative effort between Argonne National Laboratory (ANL), Naval Research Laboratory (NRL), and Stanford Linear Accelerator Center (SLAC). In this paper, we report on the recent high power tests of a fused quartz-based DLA structure that was carried out at incident powers of up to 12 MW at NRL and 37 MW at SLAC. We report experimental details of the RF conditioning process and make comparison of our multipactor model to the experiment, including tests of geometrical scaling laws and the time evolution of multipactor. Finally, we discuss future plans for the program including a planned test of new quartz-based DLA with a different geometry to both reach higher accelerating gradients and to continue the parametric study of multipactor.  
THPMS076 Development of Dual Layered Dielectric-Loaded Accelerating Structure 3160
 
  • C.-J. Jing, A. Kanareykin
    Euclid TechLabs, LLC, Solon, Ohio
  • S. Kazakov
    KEK, Ibaraki
 
  Funding: DOE SBIR Phase I, DOE Grant No. DE-FG02-05ER84356

Due to the high magnetic field-induced surface currents on its conducting sleeve, a conventional single layer Dielectric-Loaded Accelerating (DLA) structure exhibits a relatively high RF loss. One possible way to solve this problem is to use multilayered DLA structures*. In these devices, the RF power attenuation is reduced by making use of the Bragg Fiber concept: the EM fields are well confined by multiple reflections from multiple dielectric layers. This paper presents the design of an X-band dual layer DLA structure as well as the results of bench tests of the device. We will also present results on the design, numerical modeling, and fabrication of structures for coupling RF into multilayer DLAs such as a novel TM03 mode launcher and a TM01-TM03 mode converter using dielectric-loaded corrugated waveguide.

* C. Jing, W. Liu, W. Gai, J. G. Power, and T. Wong, Nucl. Instr. Meth. Phy. Res. A 539 (2005) 445-454.

 
THPMS077 Progress towards Development of a Diamond-Based Cylindrical Dielectric Accelerating Structure 3163
 
  • A. Kanareykin, C.-J. Jing, P. Schoessow
    Euclid TechLabs, LLC, Solon, Ohio
  • M. E. Conde, W. Gai
    ANL, Argonne, Illinois
  • R. Gat
    Coating Technology Solution, Inc., Somerville
 
  Funding: This research is supported by the US Department of Energy

In this talk, we present our recent developments on a high gradient diamond-based cylindrical dielectric loaded accelerator (DLA). The final goal of this research is to achieve a record accelerating gradient (~ 600 MV/m) in a demonstration of the structure at high power and with accelerated beam. We discuss here a new technology for the development of cylindrical diamond-based waveguides and the design, fabrication and high power testing of a cylindrical diamond-based DLA accelerating structure. The electrical and mechanical properties of diamond make it an ideal candidate material for use in dielectric accelerators: high RF breakdown level, extremely low dielectric losses and the highest thermoconductive coefficient available. Multipacting of the CVD diamond can be suppressed by diamond surface dehydrogenation. A plasma supported Chemical Vapor Deposition (CVD) technology to produce low loss high quality cylindrical diamond layers is presented. Special attention is devoted to the numerical optimization of the coupling section, where the surface magnetic and electric fields are minimized relative to the accelerating gradient and within known metal surface breakdown limits.

 
THPMS096 Development of a Dielectric-Loaded Test Accelerator 3211
 
  • S. H. Gold
    NRL, Washington, DC
  • W. Gai, R. Konecny, J. Long, J. G. Power
    ANL, Argonne, Illinois
  • C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio
  • A. K. Kinkead
    LET
  • C. D. Nantista, S. G. Tantawi
    SLAC, Menlo Park, California
 
  Funding: Work supported by DoE and ONR.

A joint project is underway by the Naval Research Laboratory (NRL) and Argonne National Laboratory (ANL), in collaboration with the Stanford Linear Accelerator Center (SLAC), to develop a compact X-band accelerator for testing dielectric-loaded accelerator (DLA) structures.* The accelerator will use a 5-MeV injector previously developed by the Tsinghua University in Beijing, China, and will accommodate test structures up to 0.5 m in length. Both the injector and the structures will be powered by an 11.4-GHz magnicon amplifier that can produce 25 MW, 200-ns output pulses at up to 10 Hz. The injector will require ~5 MW of rf power, leaving ~20 MW to power the test structures. This paper will present a progress report on the construction and commissioning of the test accelerator, which will be located in a concrete bunker in the Magnicon Facility at NRL.

* S. H. Gold et al., Proc. PAC 2005.

 
FRPMS094 Beam Breakup Instabilities in Dielectric Structures 4300
 
  • A. Kanareykin, C.-J. Jing, A. L. Kustov, P. Schoessow
    Euclid TechLabs, LLC, Solon, Ohio
  • W. Gai, J. G. Power
    ANL, Argonne, Illinois
 
  Funding: This research is supported by the US Department of Energy

We report on the experimental and numerical investigation of beam breakup (BBU) effects in dielectric structures resulting from parasitic wakefields. The experimental program focuses on measurements of BBU in a number of wakefield devices: (a) a 26 GHz power extraction structure; (b) a high gradient dielectric wakefield accelerator; (c) a wakefield structure driven by a high current ramped bunch train for multibunch BBU studies. New beam diagnostics will provide methods for studying parasitic wakefields that are currently unavailable at the AWA facility. The numerical part of this research is based on a particle-Green's function based beam breakup code we are developing that allows rapid, efficient simulation of beam breakup effects in advanced linear accelerators. The goal of this work is to be able to compare the accurate numerical results obtained from the new BBU code with the results of the detailed experimental measurements. An external focusing system for the control of the beam in the presence of strong transverse wakefields is considered.