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In recent years new interest in Cherenkov radiation has arisen based on progress in its new applications like biomedical imaging, photonic structures, metamaterials, and beam physics. These new applications require Cherenkov radiation theory of short bunches to be extended to rather more complicated media and structures than considered originally. We present a new general approach to the analysis of Cherenkov fields and loss factors for relativistic short bunches in arbitrary slow wave guiding systems. This new formalism is obtained by considering a general integral relation that allows calculation of the fields in the vicinity of the charge. The proposed approach dramatically simplifies simulations using analytical fields near the moving source of Cherenkov radiation. [ABSTRACT FROM AUTHOR]

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]

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]