Related papers: Wake potentials and impedances of charged beams in…
We evaluate longitudinal resistive wakefields for cylindrical beam pipes numerically and compare the results with existing approximate formul\ae. We consider an ultra-relativistic bunch traversing a cylindrical, metallic tube for a model in…
In particle accelerators, pumping holes in a vacuum chamber can be a source of unwanted broadband coupling impedance, leading to beam instabilities. Analytical methods have been previously developed to estimate the impedance of holes in…
In the first part of the paper a generalized theoretical approach towards beam coupling impedances and stretched-wire measurements is introduced. Applied to a circular symmetric setup, this approach allows to estimate the systematic…
The concepts of wake fields and impedance are introduced to describe the electromagnetic interaction of a bunch of charged particles with its environment in an particle accelerator. The wake fields can act back on the beam and lead to…
The suppression of transverse wakefield effects using transversely elliptical drive beams in a planar structure is studied with a simple analytical model that unveils the geometric nature of this phenomenon. By analyzing the suggested model…
We present the wakefield conformal mapping technique that can be readily applied to the analysis of the radiation generated by an ultra-relativistic particle in the step transition and a collimator. We derive simple analytical expressions…
As a charged particle beam moves through perfectly conducting structures with varying cross-sectional boundaries - such as RF cavities, tapers, bellows, kickers, ... - it induces both longitudinal and transverse electromagnetic fields…
In a companion report, we have derived a method for finding the impedance at high frequencies of vacuum chamber transitions that are short compared to the catch-up distance, in a frequency regime that (in analogy to geometric optics for…
Dielectric lined waveguides are under extensive study as accelerating structures that can be excited by electron beams. Rectangular dielectric structures are used both in proof of principle experiments for new accelerating schemes and for…
After a general introduction, the basic principles of wake-field and beamcoupling- impedance computations are explained. This includes time domain, frequency domain, and methods that do not include excitations by means of a particle beam.…
In many cases beam coupling impedances or wake fields are calculated with computer simulator such as CST Studio Suite, GdfidL Electromagnetic Field Simulator and so on. But evaluation with the stretched-wire method is still very useful by…
A systematic exposition of the basic concepts of wakes and impedances is given for relativistic beams in accelerators.
Relativistic charged-particle beams which generate intense longitudinal fields in accelerating structures also inherently couple to transverse modes. The effects of this coupling may lead to beam break-up instability, and thus must be…
The wakefields of a relativistic electron beam passing through a waveguide loaded with an active medium with weak resonant dispersion have been considered. For the calculations in this paper the parameters of the medium are those of a…
In this paper we suggest an analytic model, and derive simple formulas, for the beam dynamics in a wakefield structure of arbitrary cross-section. The results could be applied to estimate an upper limit of the projected beam size in devices…
Coaxial wire measurements have provided a simple and effective way to measure the beam coupling impedance of accelerator structures for a number of years. It has been known how to measure the longitudinal and dipolar transverse impedance…
Recently, the experimental discovery of a new type of wakefield effect, the "skewed wake effect", has been reported. We provide an explanation of the nature of the skewed wake effect based on a simple three-particle model that we have…
We consider the calculation of electromagnetic fields generated by an electron bunch passing through a vacuum chamber structure that, in general, consists of an entry pipe, followed by some kind of transition or cavity, and ending in an…
The beam coupling impedances of small obstacles protruding inside the vacuum chamber of an accelerator are calculated analytically at frequencies for which the wavelength is large compared to a typical size of the obstacle. Simple formulas…
The active impedance is a fundamental parameter for characterizing the behavior of large, uniform phased array antennas. However, its conventional calculation via the mutual impedance matrix (or the scattering matrix) offers limited…