| Paper | Title | Page |
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| TPAE018 | 34.272 GHz Multilayered Dielectric-Loaded Accelerating Structure | 1592 |
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| 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. | ||
| TPAE033 | Experimental and Numerical Studies of Particle Acceleration by an Active Microwave Medium | 2275 |
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| There has been considerable theoretical work on the so-called PASER concept, in which a particle beam is accelerated directly by absorbing energy from an active medium, analogous to the amplification of an optical signal in a laser. Use of an active microwave (maser) medium would have the advantage of requiring relaxed beam quality (mm vs. nm characteristic beam dimensions). Recent work using electron paramagnetic resonance (EPR) techniques has demonstrated activity in the microwave regime (i.e. negative imaginary part of the magnetic susceptibility) for a class of organic compounds. A solution of fullerene (C60) in a liquid crystal solvent has been reported in the literature to possess a maser transition in the X-band region. An external DC magnetic field is required to obtain the effect; the frequency of the maser transition is adjustable by varying the magnetic field strength. We will report on the development of numerical and laboratory tools to evaluate the use of this material for accelerator applications, and evaluate the feasibility of an accelerating structure based on an active microwave medium. | ||
| TPAE060 | Planned Enhanced Wakefield Transformer Ratio Experiment at Argonne Wakefield Accelerator | 3487 |
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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. |
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| TPAE061 | Experimental Investigation of an X-Band Tunable Dielectric Accelerating Structure | 3529 |
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Funding: U.S. Department of Energy. Experimental study of a new scheme to tune the resonant frequency for dielectric based accelerating structure (driven either by the wakefield of a beam or an external rf source) is underway. The structure consists of a single layer of conventional dielectric surrounded by a very thin layer of ferroelectric material situated on the outside. Carefully designed electrodes are attached to a thin layer of ferroelectric material. A DC bias can be applied to the electrodes to change the permittivity of the ferroelectric layer and therefore, the dielectric overall resonant frequency can be tuned. In this paper, we present the test results for an 11.424 GHz rectangular DLA prototype structure that the ferroelectric material's dielectric constant of 500 and show that a frequency tuning range of 2% can be achieved. If successful, this scheme would compensate for structure errors caused by ceramic waveguide machining tolerances and dielectric constant heterogeneity. |
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| WPAT094 | Traveling Wave Accelerating Structure for a Superconducting Accelerator | 4296 |
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| We are presenting a superconducting traveling wave accelerating structure (STWA) concept, which may prove to be of crucial importance to the International Linear Collider. Compared to the existing design of a TESLA cavity, the traveling wave structure can provide ~20-40% higher accelerating gradient for the same aperture and the same peak surface magnetic RF field. The recently achieved SC structure gradient of 35 MV/m can be increased up to ~50 MV/m with the new STWA structure design. The STWA structure is supposed to be installed into the superconducting resonance ring and is fed by the two couplers with appropriate phase advance to excite a traveling wave inside the structure. The system requires two independent tuners to be able to adjust the cavity and feedback waveguide frequencies and hence to reduce the unwanted backward wave. In this presentation we discuss the structure design, optimization of the parameters, tuning requirements and plans for further development. | ||
| WPAT095 | Low-Loss Ferroelectric for Accelerator Application | 4305 |
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Funding: U.S. Department of Energy. Ferroelectric ceramics have an electric field-dependent dielectric permittivity that can be altered by applying a bias voltage. Ferroelectrics have unique intrinsic properties that makes them attractive for high-energy accelerator applications: very small response time of ~ 10-11 sec, considerably high breakdown limit of more than 100 kV/cm, good vacuum properties. Because of these features, bulk ferroelectrics may be used as active elements of tunable accelerator structures,* or in fast, electrically - controlled switches and phase shifters in pulse compressors or power distribution circuits of future linear colliders.** One of the most critical requirements for ferroelectric ceramic in these applications is the dielectric loss factor. In this paper, the new bulk ferroelectric ceramic is presented. The new composition shows a loss tangent of 4× 10-3 at 35 GHz. The ceramics have high tunability factor: the bias voltage of 50 kV/cm was enough to reduce the permittivity from 500 to 400. The material chemical compound, features of the technology process, and mechanical and electrical properties are discussed. The ways of BST ferrolectric parameters further improvement are discussed as well. *A. Kanareykin, W. Gai, J. Power, E. Sheinman, and A. Altmark, AIP Conf. Proc. 647, Melville, N.Y., 2002, p. 565. **V.P. Yakovlev, O.A. Nezhevenko, J.L. Hirshfield, and A.D. Kanareykin, AIP Conf. Proc. 691, Melville, N.Y., 2003, p.187. |