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The wakefield electron acceleration scheme provides effective means of creating high accelerating field gradients in both dielectric-lined waveguide structures and plasma. We have studied the influence of errors in the structure of this scheme on the efficiency of energy transfer from the driving to witness (driven) electron bunches. Deviation of the wakefield frequency from the calculated optimum value leads to a misfit in the mutual positioning of bunches in the driving train and the corresponding decrease in the energy transformer ratio. It is suggested to compensate for the arising misfit by correcting distances between bunches in the driving train, with a resulting increase in the efficiency of energy transfer. Results of calculations are presented for a dielectric-filled 13-GHz structure with parameters of the Argonne Wakefield Accelerator. [ABSTRACT FROM AUTHOR]

The self-consistent transverse dynamics of high-current relativistic electron bunches used for generating wakefields in multiple-bunch schemes of wakefield acceleration, which are applied in dielectric-filled structures, is studied. The flight range of the electron bunch under no-focusing conditions and the energy transferred to the bunch being accelerated in schemes with profiled (nonuniform) and uniform distributions of the charge over a sequence of generator bunches are determined. Requirements are formulated for a focusing system in which the profiled distribution offers an advantage over the uniform distribution for the efficiency of energy transfer from generator bunches to that being accelerated. [ABSTRACT FROM AUTHOR]

We propose criteria for the optimization of a wakefield acceleration scheme in a dielectric-lined waveguide structure, which is aimed at increasing the efficiency of energy transfer from the driving to witness (driven) electron bunches with simultaneous increase in the accelerating field gradient. It is suggested to use a multimode acceleration structure excited by a train of short electron bunches profiled in a special manner. The proposed scheme provides for a maximum energy transformer ratio simultaneously with an increase in the wakefield as compared to the values typical of the traditional linear acceleration scheme. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

The feasibility of the frequency spectrum of Vavilov–Cherenkov radiation being controlled in a wakefield dielectric-filled accelerating structure via an outer ferroelectric layer is studied. The spectrum and amplitude of the field excited in the structure versus the permittivity of the ferroelectric are found. Dielectric losses in the ferroelectric are estimated. It is shown that these losses impose limitations on the ferroelectric layer thickness and the range within which the frequency spectrum of the waveguide can be controlled. The structure under consideration is optimized for the AWA wakefield accelerator. The multilayer construction of the waveguide, in combination with specially shaped ferroelectric-permittivity-controlling electrodes, allows designers to tune the spectrum of the waveguide and suppress electron-bunch-deflecting waveguide modes. Thereby, there appears the possibility of controlling the transverse stability of the beam. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

We have studied the possibility of increasing the efficiency of dielectric-loaded accelerating (DLA) structures. It is shown that the level of losses in DLA structures can be significantly decreased using the Bragg principle of waveguide design for microwave radiation focusing along the axis. The waveguide lining comprises a set of layers with alternating high and low values of permittivity, which decreases the magnetic field intensity in the external metal shell of the accelerating structure. The results of calculations are presented for the TM 03 mode with a frequency of 11.4 GHz in DLA structures of the two types, with two-and four-layer lining, which show a decrease in the level of losses from −14 to −2 dB/m in the case of multilayer dielectric lining. [ABSTRACT FROM AUTHOR]

Dielectric and induction losses in a rectangular multilayer dielectric-filled accelerating waveguide structure are considered. One ceramic layer of the structure possesses ferroelectric properties, which allow the waveguide frequency spectrum to be controlled by varying the permittivity of this ferroelectric layer. The introduction of an additional dielectric layer with a low permittivity between the ferroelectric layer and a metal shell makes possible a decrease in the waveguide energy losses, while retaining the desired control over the spectrum. The results of calculations of the Q value and the group velocity of the accelerating TM01 mode of the proposed tunable rectangular structure are presented. For an increased Q value, the introduction of an additional layer leads to undesired growth in the group velocity of the accelerating mode. [ABSTRACT FROM AUTHOR]

The possibility to control the frequency spectrum of Vavilov-Cherenkov radiation in a waveguide accelerator structure with the aid of an external ferroelectric layer is studied. A decrease in the permittivity of a ferroelectric material under the action of an applied electric field leads to an increase in the frequency of the wake radiation field of a relativistic electron bunch. Parameters of the ferroelectric layer are calculated proceeding from the required interval of control of the wake field frequency and the tolerable power losses in the waveguide system. [ABSTRACT FROM AUTHOR]