Relativistic electron irradiation of thin solid targets is known to generate collimated beams of x-ray photons in the forward direction by a number of different processes. A variety of mechanisms are discussed that share common characteristics in the angular and spectral distributions of the generated photon beams. Some simple physical explanations are offered for the characteristics shared by these processes. Some examples are then given based on experimental results attained at the LLNL electron-positron accelerator. (LEW).

Energetic electromagnetic radiation finds frequent uses in science (e. g. , for expe riments in nuclear and elementary - particle physics), in technology (for materials testing), and in medicine (for medical X-rays). The most common method of genera ting such radiation is via the process of "bremsstrahlung" (a German term coined by A. Sommerfeld, meaning "braking radiation") in which a beam of electrons is direc ted into matter (e. g. , a metal target), losing energy during its collisions with the atoms and releasing this energy in the form of emitted radiation. The character of such radiation may be drastically changed by the use of a tar get with periodic structure (most commonly, a crystal target). The coherent waves emitted from individual crystal atoms interfere with each other, monochromatizing and polarizing the radiation and often increasing its intensity manifold, thereby creating a powerful radiation source of high quality for purposes of scientific and technical applications. This is true both for the well - established "coherent bremsstrahlung" process in which the interfering radiation is emitted while the electrons cross a succession of crystal planes, as well as for the more recently discovered process of "channeling radiation" (generating radiation of even higher intensity, but lower energy) in which the radiation is emitted while the electrons propagate along a crystal plane, or a crystal axis, in an oscillatory fashion.

Periodic magnetic structures (undulators) are widely used in accelerators to generate monochromatic undulator radiation (UR) in the range from far infrared to the hard X-ray region. Another periodic crystalline structure is used to produce quasimonochromatic polarized photon beams via the coherent bremsstrahlung mechanism (CBS). Due to such characteristics as monochromaticity, polarization and adjustability, these types of radiation is of large interest for applied and basic research of accelerator-emitted radiation. The book provides a detailed overview of the fundamental principles behind electromagnetic radiation emitted from accelerated charged particles (e.g. UR, CBS, radiation of fast electrons in Laser flash fields) as well as a unified description of relatively new radiation mechanisms which attracted great interest in recent years. This are the so-called polarization radiation excited by the Coulomb field of incident particles in periodic structures, parametric X-rays, resonant transition radiation and the Smith-Purcell effect. Characteristics of such radiation sources and perspectives of their usage are discussed. The recent experimental results as well as their interpretation are presented.

The purpose of this book is to give a description of the state of the art in theoretical and experimental work achieved in radiation source development. It summarizes clearly and comprehensibly, the basic physical aspects needed to understand the phenomena, and also provides the interested reader with sufficient literature to be able to follow the development in more detail. In addition, it contains a unified view of most theoretical effects and their common properties. The most recent developments as well as references to further work can be found in this volume. In many cases, review articles and textbooks published in specialized areas are also incorporated into the text.

Coherent radiation emitted from a relativistic electron bunch consists of wavelengths longer than or comparable to the bunch length. The intensity of this radiation out-numbers that of its incoherent counterpart, which extends to wavelengths shorter than the bunch length, by a factor equal to the number of electrons in the bunch. In typical accelerators, this factor is about 8 to 11 orders of magnitude. The spectrum of the coherent radiation is determined by the Fourier transform of the electron bunch distribution and, therefore, contains information of the bunch distribution. Coherent transition radiation emitted from subpicosecond electron bunches at the Stanford SUNSHINE facility is observed in the far-infrared regime through a room-temperature pyroelectric bolometer and characterized through the electron bunch-length study. To measure the bunch length, a new frequency-resolved subpicosecond bunch-length measuring system is developed. This system uses a far-infrared Michelson interferometer to measure the spectrum of coherent transition radiation through optical autocorrelation with resolution far better than existing time-resolved methods. Hence, the radiation spectrum and the bunch length are deduced from the autocorrelation measurement. To study the stimulation of coherent transition radiation, a special cavity named BRAICER is invented. Far-infrared light pulses of coherent transition radiation emitted from electron bunches are delayed and circulated in the cavity to coincide with subsequent incoming electron bunches. This coincidence of light pulses with electron bunches enables the light to do work on electrons, and thus stimulates more radiated energy. The possibilities of extending the bunch-length measuring system to measure the three-dimensional bunch distribution and making the BRAICER cavity a broadband, high-intensity, coherent, far-infrared light source are also discussed.

The first of two volumes presenting an overview of the important research areas in which Professor H. Überall has done his life's work and constitutes a festschrift for this distinguished physicist. Each chapter is intended to serve as a bridge between advanced textbooks and the most recent research literature, thereby providing a valuable reference for active researchers as well as for graduate students.