Preface

Diffraction radiation appearing in the optical range when charged particles move in vacuum along a periodically deformed surface (grating) was observed for the first time in the early 1950s by S.J. Smith and E.M. Purcell [1]. This radiation was theoretically predicted by I.M. Frank in the early 1940s [2]. In the next two decades, this type of radiation was investigated in detail on beams of nonrelativistic electrons in the centimeter wavelength range. At the same time, theoretical methods were developed for calculating the characteristics of diffraction radiation for various configurations of measuring instruments and various parameters of a beam. A new field appeared in microwave electronics [3] and development of this field actively continues to date [4, 5]. At present, it has been shown that the intensity of visible and ultraviolet diffraction radiation generated by relativistic particles can be comparable with the intensity of transition radiation, which is widely used in high energy physics and accelerator physics. In contrast to transition radiation, diffraction radiation is not accompanied by the direct interaction of beam particles with a target and this circumstance opens prospects for non-invasive diagnostics of beams in modern accelerators. Diffraction radiation can be used to analyze the structure of micron objects for which traditional X–ray methods are ineffective because of the absence of X–ray lenses with the required luminosity. We point to the potentialities of coherent diffraction radiation generated by a beam of moderately relativistic electrons that are grouped into bunches shorter than 1 mm. In this case, the radiation spectrum covers the terahertz range, which is of considerable interest for applied investigations in physics, chemistry, and biology [6]. Diffraction radiation generated by relativistic particles is presented very briefly in modern monographs. Monographs [3] and [4] are completely devoted to diffraction radiation generated in periodic structures by nonrelativistic electrons. Among other problems, some applications of diffraction radiation generated by both nonrelativistic and relativistic particles were considered in monograph [5], but with emphasis on the specific features of microwave instruments (modulation of a beam in the process of its interaction with a target, comparatively low energies of the beam particles, and nonlinearity of physical phenomena), whereas the problems of diffraction radiation itself and modern experimental results in this field remained beyond the scope of