This thesis has the aim of describing the design and the applications of the
radio-frequency deflecting cavities. These devices are used to analyze the
properties of the ultra-relativistic electron bunches in the FERMI@Elettra
project, which is a fourth generation light source under development at the
Elettra laboratory. In particular, two travelling wave deflectors will be placed
just before the undulators chains, where the free electron laser occurs, while
another standing wave deflector has been already installed in the first part
of the machine, after the first bunch compressor.
In this work the radio-frequency design of the low energy deflector is
presented with the electron bunch measurements. The measurements have
been performed to investigate the bunch length, the reconstruction of the
longitudinal profile and the slice emittance. Furthermore the radio-frequency
design of the high energy deflectors is discussed, and a new simple theory
which allows the explanation of the energy exchange degradation between
the electromagnetic field and the particles is given. The theory is useful to
describe the mechanical errors in the deflector basic cell realization.
In the last part of this thesis a new algorithm to determine the transversal bunch motion in presence of wakefields in a radio-frequency deflector is
presented. The algorithm is used to evaluate the wakefield effect in the high
energy deflectors and gives the possibility of taking easily in account of every
charge distribution, and of every initial condition of the bunch at the input
section of the cavity. In particular, the errors produced by the transversal wakefields in a bunch length measurement is analyzed with significant
examples.
