Abstract
Summary form only given, as follows. Propagation of series of short electron bunches substantially differs from the propagation of long beam. The difference is in that every bunch's front induces electromagnetic fields. Namely these fields provide the space charge and self magnetic field neutralization. From the other side these fields interact resonantly with the beam electrons and this interaction results in the beam instability development. In other words the fields induced by beam front serve as an initial perturbation for instability development. These fields increase exponentially and may essentially influence on many aspects of the physics of the system under consideration. Namely these fields form transient processes in the devices. The most significant influence will be in short-pulse systems, (pulsed power devices) where the fields from each front are added up. In present investigation the space structure and development dynamics of the fields induced by beam/bunch front are obtained and analyzed. Actually the initial value problem for the beam/bunch injected into electrodynamic system is solved. Approach is similar to that of classical approach for initial value problem with integral representation of perturbation and dispersion relation in the denominator of the integrand. In presented approach one pays particular attention to most intrinsic peculiarities of the beam instability and singles them out. One of them is the second order pole in beam contribution in dispersion relation. Overlimiting beam current may also be considered by this approach. Obtained space-time structure of the fields is intrinsic for many types of beam instability: Cherenkov-type, cyclotron-type, beam instability in periodical structures.
Published Version
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