DESY, Hamburg
In this paper we exploit a formalism to describe Edge Radiation, which relies on Fourier Optics techniques, described in another contribution to this conference. First, we apply our method to develop an analytical model to describe Edge Radiation in the presence of a vacuum chamber. Such model is based on the solution of the field equation with a tensor Green's function technique. In particular, explicit calculations for a circular vacuum chamber are reported. Second, we consider the use of Edge Radiation as a tool for electron beam diagnostics. We discuss coherent Edge Radiation, extraction of Edge Radiation by a mirror, and other issues becoming important at high electron energy and long radiation wavelength. Based on this work we also study the impact of Edge Radiation on XFEL setups and we discuss recent results.
DESY, Hamburg
Electron bunch imagers based on incoherent OTR constitute the main device presently available for the characterization of ultrashort electron bunches in the transverse direction. One difficulty to obtain high-resolution images is related with the very peculiar particle-spread function of OTR radiation, which has a large width compared to the usual point-spread function of a point-like source. In this contribution we explore the possibility of using coherent OTR instead of incoherent OTR radiation, by integrating an ORS setup with a high-resolution coherent optical transition radiation imager. Electron bunches are modulated at optical wavelengths in the ORS setup. When these electron bunches pass through a metal foil target, coherent radiation pulses of tens MW power are generated. It is thereafter possible to exploit the large number of available coherent photons. In particular we manipulate the particle spread function of the system, so that the imaging problem can be reduced to the usual (coherent or incoherent) imaging theory for point-like radiators.
DESY, Hamburg
We describe a novel technique to characterize ultrashort electron bunches in X-ray Free-Electron Lasers. Namely, we propose to use coherent Optical Transition Radiation to measure three-dimensional (3D) electron density distributions. Our method relies on the combination of two known diagnostics setups, an Optical Replica Synthesizer (ORS) and an Optical Transition Radiation (OTR) imager. Electron bunches are modulated at optical wavelengths in the ORS setup. When these electron bunches pass through a metal foil target, coherent radiation pulses of tens MW power are generated. It is thereafter possible to exploit advantages of coherent imaging techniques, such as diffractive imaging, Fourier holography and their combinations. The proposed method opens up the possibility of real-time, wavelength-limited, single-shot 3D imaging of an ultrashort electron bunch.
DESY, Hamburg
We formulate a complete theory of Edge Radiation based on a novel method relying on Fourier Optics techniques. Special attention is paid in discussing the validity of approximations upon which the theory is built. Our study makes consistent use of both similarity techniques and comparisons with numerical results from simulation. We discuss both near and far zone. Physical understanding of many asymptotes is discussed. As an example of application we discuss the case of Transition Undulator Radiation, which can be conveniently treated with our formalism. This work forms the theoretical basis for understanding the impact of Edge radiation on XFEL setups, which is discussed in another contribution to this conference.
